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Auysakul, Jutamanee, He Xu y Vishwanath Pooneeth. "A Hybrid Motion Estimation for Video Stabilization Based on an IMU Sensor". Sensors 18, n.º 8 (17 de agosto de 2018): 2708. http://dx.doi.org/10.3390/s18082708.
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Recorded video data must be clear for accuracy and faster analysis during post-processing, which often requires video stabilization systems to remove undesired motion. In this paper, we proposed a hybrid method to estimate the motion and to stabilize videos by the switching function. This method switched the estimated motion between a Kanade–Lucus–Tomasi (KLT) tracker and an IMU-aided motion estimator. It facilitated the best function to stabilize the video in real-time as those methods had numerous advantages in estimating the motion. To achieve this, we used a KLT tracker to correct the motion for low rotations and an IMU-aided motion estimator for high rotation, owing to the poor performance of the KLT tracker during larger movements. Furthermore, a Kalman filter was used to remove the undesired motion and hence smoothen the trajectory. To increase the frame rate, a multi-threaded approach was applied to execute the algorithm in the array. Irrespective of the situations exposed to the experimental results of the moving camera from five video sequences revealed that the proposed algorithm stabilized the video efficiently.
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Jiang, Xue, Peng Sun y Hui Wang. "An Algorithm for Electronic Image Stabilization". Applied Mechanics and Materials 738-739 (marzo de 2015): 590–93. http://dx.doi.org/10.4028/www.scientific.net/amm.738-739.590.
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In most video systems,the carrier of camera expierences all kinds of motions which make the video ambiguous and unstable.Usually,the gray projection matching algorithm can only stabilize the translation motion between frames,but the rotation motion of frames in a video sequence.By zoning the image into few small regions,the rotation motion could be ignored,then, local movement vector is aqcuired by the grey projection matching method and compensate the movement between frames.Then for the rotation movement,it can be stabilized by the compensation with circle projection matching.
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Wang, Hui, Peng Sun y Xiao Wei Han. "An Electronic Image Stabilizition Algorithm Based on Gray Projection and Circle Projection Matching". Applied Mechanics and Materials 571-572 (junio de 2014): 817–20. http://dx.doi.org/10.4028/www.scientific.net/amm.571-572.817.
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In most video systems,the carrier of camera expierences all kinds of motions which make the video ambiguous and unstable.Usually,the gray projection matching algorithm can only stabilize the translation motion between frames,but the rotation motion of frames in a video sequence.By zoning the image into few small regions,the rotation motion could be ignored,then, local movement vector is aqcuired by the grey projection matching method and compensate the movement between frames.Then for the rotation movement,it can be stabilized by the compensation with circle projection matching.
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Nikolov, Atanas y Dimo Dimov. "2D Video Stabilization for Industrial High-Speed Cameras". Cybernetics and Information Technologies 15, n.º 7 (1 de diciembre de 2015): 23–34. http://dx.doi.org/10.1515/cait-2015-0086.
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Abstract The current research concerns the problem of video stabilization “in a point”, which aims to stabilize all video frames according to one chosen reference frame to produce a new video, as by a static camera. Similar task importance relates providing static background in the video sequence that can be usable for correct measurements in the frames when studying dynamic objects in the video. For this aim we propose an efficient combined approach, called “3×3OF9×9”. It fuses our the previous development for fast and rigid 2D video stabilization [2] with the well-known Optical Flow approach, applied by parts via Otsu segmentation, for eliminating the influence of moving objects in the video. The obtained results are compared with those, produced by the commercial software Warp Stabilizer of Adobe-After-Effects CS6.
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Ji, Shu Jiao, Ming Zhu y Yan Min Lei. "Video Stabilization Algorithm Based on Background Feature Points Matching". Applied Mechanics and Materials 738-739 (marzo de 2015): 690–93. http://dx.doi.org/10.4028/www.scientific.net/amm.738-739.690.
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Global motion estimation between two successive frames is important to the process of video stabilization. In the proposed approach, the estimation of global motion was based on the background feature points (BFPS). First, feature points (FPS) were collected from the input video by FAST operator; second, feature point’s descriptor and matching were based on FREAK operator.The M-SAC is used to classify the BFPS. Last, the six parameters of the affine transform model to calculate the interframe motion estimation vector. The experiment results show that he proposed method can stabilize inter-frame jitter, in the meanwhile, it improve the video quality effectively.
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Rodriguez-Padilla, Isaac, Bruno Castelle, Vincent Marieu y Denis Morichon. "ALTERNATIVE IMAGE STABILIZATION METHOD FOR COASTAL VIDEO MONITORING SYSTEMS". Coastal Engineering Proceedings, n.º 36v (28 de diciembre de 2020): 33. http://dx.doi.org/10.9753/icce.v36v.waves.33.
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The use of shore-based video systems has become a very popular and accessible low-cost tool for coastal monitoring given their capability to deliver continuous and high-resolution temporal data over large enough spatial scales. However, the reliability of the final image products can be compromised by external factors, sometimes overlooked, that can alter the image geometry over time. In particular, unwanted camera movement, produced either by thermal or mechanical effects, can lead to significant geo-rectification errors if not properly corrected. This study addresses an alternative straightforward method to stabilize an either continuous or subsampled image sequence based on state-of-the-art techniques and available routines.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/xX1CrvPQpK8
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Mănescu, Mihai, Luciana Cristea, Barbu Christian Braun y Daniel Ola. "Research on Actuators Optimization via PID Closed Control Algorithm for Video and Photo Cameras Stabilization". Applied Mechanics and Materials 436 (octubre de 2013): 337–44. http://dx.doi.org/10.4028/www.scientific.net/amm.436.337.
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The paper shows how closed-loop control procedure, using the algorithm Proportional Integrative derivative (PID) was applied to improve the photo and video cameras stability correction in real time. The stability system contains an Attitude Heading reference System (AHRS) sensor that is connected to a microcontroller that will make the operations for measuring angles of rotation (roll, pitch and yaw) acquired from a camera displaced on a suspended cable. Closed loop PID algorithm applied to stabilize the system was implemented as programming subroutines dedicated to Atmega162 microcontroller, at which they were recorded and processed in real time as input signals sensor information measured by the AHRS system. Programming based on a closed loop process control through actuators ordered 3 servo-motors for real-time correction of camera rotation angles. In this way it could be provided the positioning cameras error compensation, the errors being caused by different perturbing external factors. The adopted solution has achieved a cost reduction necessary to stabilize the cameras placed in mobile systems. The solution ensures also to increase the stabilization efficiency reported to the case of human operator intervention.
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Neumann, H., M. Raithel y M. Neurath. "Description of a new technique using biopsy forceps to stabilize pedunculated polyps for confocal laser endomicroscopy (with video)". Endoscopy 42, S 02 (julio de 2010): E182. http://dx.doi.org/10.1055/s-0029-1244005.
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Axente, Corneliu, Liviu Coşereanu y Daniel Ioan Suteu. "The Command and Control Software Implementation of a CCD Video 2 Axis Gyrostabilized Payload Used by a Fixed Wing UAV Configuration Platform". Applied Mechanics and Materials 186 (junio de 2012): 46–49. http://dx.doi.org/10.4028/www.scientific.net/amm.186.46.
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The software algorithm is designed to ensure compatibility between the commands given by the operator and the need to stabilize the CCD/IR payload. The implementation was made on a mini-turret with 2 degrees of freedom mounted on a miniUAV. Appropriate command and control functions were developed by programming an Atmel family microcontroller.
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Pathak, Sarthak, Alessandro Moro, Hiromitsu Fujii, Atsushi Yamashita y Hajime Asama. "Spherical Video Stabilization by Estimating Rotation from Dense Optical Flow Fields". Journal of Robotics and Mechatronics 29, n.º 3 (20 de junio de 2017): 566–79. http://dx.doi.org/10.20965/jrm.2017.p0566.
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[abstFig src='/00290003/12.jpg' width='300' text='Spherical video stabilization' ] We propose a method for stabilizing spherical videos by estimating and removing the effect of camera rotation using dense optical flow fields. By derotating each frame in the video to the orientation of its previous frame in two dense approaches, we estimate the complete 3 DoF rotation of the camera and remove it to stabilize the spherical video. Following this, any chosen area on the spherical video (equivalent of a normal camera’s field of view) is unwarped to result in a ‘rotation-less virtual camera’ that can be oriented independent of the camera motion. This can help in perception of the environment and camera motion much better. In order to achieve this, we use dense optical flow, which can provide important information about camera motion in a static environment and can have several advantages over sparse feature-point based approaches. The spatial regularization property of dense optical flow provides more stable motion information as compared to tracking sparse points and negates the effect of feature point outliers. We show superior results as compared to using sparse feature points alone.
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Ma, Biao y Amy Reibman. "Viewing Experience Model of First-Person Videos". Journal of Imaging 4, n.º 9 (31 de agosto de 2018): 106. http://dx.doi.org/10.3390/jimaging4090106.
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First-Person Videos (FPVs) are recorded using wearable cameras to share the recorder’s First-Person Experience (FPE). Ideally, the FPE is conveyed by the viewing experience of the FPV. However, raw FPVs are usually too shaky to watch, which ruins the viewing experience. To solve this problem, we improve the viewing experience of FPVs by modeling it as two parts: video stability and First-Person Motion Information (FPMI). Existing video stabilization techniques can improve the video stability but damage the FPMI. We propose a Viewing Experience (VE) score, which measures both the stability and the FPMI of a FPV by exploring the mechanism of human perception. This enables us to further develop a system that can stabilize FPVs while preserving their FPMI so that the viewing experience of FPVs is improved. Objective tests show that our measurement is robust under different kinds of noise, and our system has competitive performance relative to current stabilization techniques. Subjective tests show that (1) both our stability and FPMI measurements can correctly compare the corresponding attributes of an FPV across different versions of the same content, and (2) our video processing system can effectively improve the viewing experience of FPVs.
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Kevin, Kevin, Nico Gunawan, Mariana Erfan Kristiani Zagoto, Laurentius Laurentius y Amir Mahmud Husein. "Comparison Of Cellular Video Quality For Object Detection Using Neural Network Convolution". SinkrOn 4, n.º 1 (30 de octubre de 2019): 260. http://dx.doi.org/10.33395/sinkron.v4i1.10248.
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Abstract— The purpose of this study is to compare the video quality between the Samsung HP camera and the Xiaomi HP camera. The object of study was UNPRI students who walked through the front yard of the UNPRI SEKIP campus. Here we test how accurate the camera's HP capture capacity is used to take the video. The method used to test this research is the Convolution Neural Network method. Object detection and recognition aim to detect and classify objects that can be applied to various fields such as face, human, pedestrian, vehicle detection (Pedoeem & Huang, 2018), besides the ability to find, identify, track and stabilize objects in various poses and important backgrounds in many real-time video applications. Object detection, tracking, alignment and stabilization have become very interesting fields of research in the vision and recognition of computer patterns due to the challenging nature of several slightly different objects such as object detection, where the algorithm must be precise enough to identify, track and center an object from the others
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Pojskić, Mirza, Vincent Nguyen, Goran Lakičević y Kenan I. Arnautović. "Microsurgical Resection of Brain Stem Ependymoma: 2-Dimensional Operative Video". Operative Neurosurgery 18, n.º 6 (23 de agosto de 2019): E240—E241. http://dx.doi.org/10.1093/ons/opz252.
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Abstract The brainstem is a less-common location for ependymomas than the spinal cord where they are the most common adult intramedullary tumor.1-18 In this first video case report in the peer-reviewed literature, we demonstrate microsurgical resection of a medulla oblongata ependymoma. There are several case reports of medulla oblongata ependymomas1,3,5,6,13 and a few series of spinal cord ependymomas that included cases of ependymomas of the cervicomedullary junction.9,10 The goal of surgery was to stabilize the preoperative neurological function; favorable outcome is achieved in patients with good preoperative statuses and well-defined tumor boundaries.9 Although gross total resection (GTR) provides the best overall outcome, it is most effective for classic grade II tumors, but not grade I (myxopapillary) and ependymomas, which have a lower GTR rate.14,15 A 55-yr-old patient developed 4-extremity weakness and dysphagia. Pre-/postcontrast magnetic resonance imaging (MRI) revealed centrally located brainstem lesion situated at the lower half of the medulla oblongata. Surgery, performed by the senior author, was performed in the prone position with a small suboccipital craniectomy and C1 posterior arch removal, followed by pia opening and posterior midline myelotomy. Tumor was debulked, dissected from the white matter, and resected. Histology revealed ependymoma (World Health Organization grade II). Postoperative pre-/postcontrast MRI revealed total resection. The patient's neurological deficit completely resolved postoperatively. Written consent was obtained from the patient.
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Ohata, Ken, Takashi Muramoto, Yohei Minato, Hideyuki Chiba, Eiji Sakai y Nobuyuki Matsuhashi. "Usefulness of a multifunctional snare designed for colorectal hybrid endoscopic submucosal dissection (with video)". Endoscopy International Open 06, n.º 02 (febrero de 2018): E249—E253. http://dx.doi.org/10.1055/s-0043-124364.
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AbstractSince colorectal endoscopic submucosal dissection (ESD) remains technically difficult, hybrid ESD was developed as an alternative therapeutic option to achieve en bloc resection of relatively large lesions. In this feasibility study, we evaluated the safety and efficacy of hybrid colorectal ESD using a newly developed multifunctional snare. From June to August 2016, we prospectively enrolled 10 consecutive patients with non-pedunculated intramucosal colorectal tumors 20 – 30 mm in diameter. All of the hybrid ESD steps were performed using the “SOUTEN” snare. The knob-shaped tip attached to the loop top helps to stabilize the needle-knife, making it less likely to slip during circumferential incision and enables partial submucosal dissection. All of the lesions were curatively resected by hybrid ESD, with a short mean procedure time (16.1 ± 4.8 minutes). The mean diameters of the resected specimens and tumors were 30.5 ± 4.9 and 26.0 ± 3.5 mm, respectively. No perforations occurred, while delayed bleeding occurred in 1 patient. In conclusion, hybrid ESD using a multifunctional snare enables easy, safe, and cost-effective resection of relatively large colorectal tumors to be achieved.Study registration: UMIN000022545
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Tai, Ying, Yicong Liang, Xiaoming Liu, Lei Duan, Jilin Li, Chengjie Wang, Feiyue Huang y Yu Chen. "Towards Highly Accurate and Stable Face Alignment for High-Resolution Videos". Proceedings of the AAAI Conference on Artificial Intelligence 33 (17 de julio de 2019): 8893–900. http://dx.doi.org/10.1609/aaai.v33i01.33018893.
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In recent years, heatmap regression based models have shown their effectiveness in face alignment and pose estimation. However, Conventional Heatmap Regression (CHR) is not accurate nor stable when dealing with high-resolution facial videos, since it finds the maximum activated location in heatmaps which are generated from rounding coordinates, and thus leads to quantization errors when scaling back to the original high-resolution space. In this paper, we propose a Fractional Heatmap Regression (FHR) for high-resolution video-based face alignment. The proposed FHR can accurately estimate the fractional part according to the 2D Gaussian function by sampling three points in heatmaps. To further stabilize the landmarks among continuous video frames while maintaining the precise at the same time, we propose a novel stabilization loss that contains two terms to address time delay and non-smooth issues, respectively. Experiments on 300W, 300VW and Talking Face datasets clearly demonstrate that the proposed method is more accurate and stable than the state-ofthe-art models.
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Alaya, Bechir. "Payoff-based Dynamic Segment Replication and Graph Classification Method with Attribute Vectors Adapted to Urban VANET". ACM Transactions on Multimedia Computing, Communications, and Applications 17, n.º 3 (31 de agosto de 2021): 1–22. http://dx.doi.org/10.1145/3440018.
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Due to the number of constraints and the dynamic nature of vehicular ad hoc networks (VANET), effective video broadcasting always remains a difficult task. In this work, we proposed a quality of video visualization guarantee model based on a feedback loop and an efficient algorithm for segmenting and replicating video segments using the Payoff-based Dynamic Segment Replication Policy (P-DSR). In the urban VANET environment, P-DSR is defined by taking into account the position of the vehicles, the speed, the direction, the number of neighboring vehicles, and the reputation of each node to stabilize the urban VANET topology. However, the management of various load control parameters between the different components of the urban VANET network remains a problem to be studied. This work uses a multi-objective problem that takes the parameters of our algorithm based on the Graph Classification Method with Attribute Vectors (GCMAV) as input. This algorithm aims to provide an improved class lifetime, an improved video segment delivery rate, a reduced inter-class overload, and an optimization of a global criterion. A scalable algorithm is used to optimize the parameters of the GCMAV. The simulations were carried out using the NetSim simulator and Multi-Objective Evolutionary Algorithms framework to optimize parameters. Experiments were carried out with realistic maps of Open Street Maps and its results were compared with other algorithms such as Seamless and Authorized Multimedia Streaming and P-DSR. The survey suggests that the proposed methodology works well concerning the average lifetime of the inter-classes and the delivery rate of video segments.
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Shah Newaj Bhuiyan, Sharif y Othman O. Khalifa. "Efficient 3D stereo vision stabilization for multi-camera viewpoints". Bulletin of Electrical Engineering and Informatics 8, n.º 3 (1 de septiembre de 2019): 882–89. http://dx.doi.org/10.11591/eei.v8i3.1518.
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In this paper, an algorithm is developed in 3D Stereo vision to improve image stabilization process for multi-camera viewpoints. Finding accurate unique matching key-points using Harris Laplace corner detection method for different photometric changes and geometric transformation in images. Then improved the connectivity of correct matching pairs by minimizing the global error using spanning tree algorithm. Tree algorithm helps to stabilize randomly positioned camera viewpoints in linear order. The unique matching key-points will be calculated only once with our method. Then calculated planar transformation will be applied for real time video rendering. The proposed algorithm can process more than 200 camera viewpoints within two seconds.
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Wu, Qiang, Shi Dong Li, Le Gong Sun y Yu Fei Zhou. "Implementation and Optimization of Tracking System on Dual-DSP". Applied Mechanics and Materials 58-60 (junio de 2011): 2231–36. http://dx.doi.org/10.4028/www.scientific.net/amm.58-60.2231.
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The paper provides a solution of tracking system on dual-DSP(ADSP-BF561, ADP-BF548), and gives the method of implementation and optimization. The system implements the complex tracking algorithm in real time on the high-performance dual-core ADSP -BF561. The multimedia processor ADSP-BF548，which has integrated a pixel composer and many interfaces internally, is used to control the entire operating of the system and complete the task of input and output flexibly. With the help of the code and decode chips ADV7181 and ADV7171, which have strong ability of adaption to varieties of video formats, the system has the features of easy- expansibility, strong adaption, stabilize, function, small size and low consumption.
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Vora, Paras, Nicholas Bell, Romulo Albuquerque, Jooyoung Cho y Gregory Botzet. "2126 Optimizing a technique for visualizing retinal and choroidal blood flow noninvasively". Journal of Clinical and Translational Science 2, S1 (junio de 2018): 22–23. http://dx.doi.org/10.1017/cts.2018.104.
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OBJECTIVES/SPECIFIC AIMS: Diabetic retinopathy is an increasingly prevalent disease, difficult to screen for across the globe. We have developed and began optimizing an innovative technique to visualize and quantify retinal blood flow, to elucidate the role of the choroid in retinal pathologies such as diabetic retinopathy or choroidopathy. METHODS/STUDY POPULATION: Preliminary retinal was obtained from a surgical retina video library (Truvision, Goleta, CA, USA). Videos of different organs were recorded while vessels were occluded via a blood pressure cuff, using consumer-grade digital video cameras (NEX-5T, a7sii; Sony, New York, NY, USA). All other retinal videos were taken using a fundus camera (50×; Topcon, Oxland, NJ, USA) modified to support the above digital video cameras. All videos were processed using experimental software (MATLAB, Mathworks, Natick, MA, USA). RESULTS/ANTICIPATED RESULTS: Video imaging of the retina was optimized for lighting conditions and software requirements. Parameters were defined for the software imaging pipeline, such as frequency range of interest, sampling rate, and noise minimization. Software was developed to stabilize frames, accounting for eye saccades. Use of a biosensor enabled accurate measurement of pulse waveform, increasing signal-to-noise ratio. The optimal light requirements were determined such that adequate exposure of the retina is reproducible yet still comfortable for use in human subjects. DISCUSSION/SIGNIFICANCE OF IMPACT: This novel technique allows for an inexpensive, noninvasive, and reproducible ocular blood flow imaging platform. By optimizing this technique, we can proceed with our future plans for a pilot study to compare our imaging technique with the current standard, paving the way for future clinical studies.
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Kimmatkar, Nisha Vishnupant y B. Vijaya Babu. "Novel Approach for Emotion Detection and Stabilizing Mental State by Using Machine Learning Techniques". Computers 10, n.º 3 (19 de marzo de 2021): 37. http://dx.doi.org/10.3390/computers10030037.
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The aim of this research study is to detect emotional state by processing electroencephalography (EEG) signals and test effect of meditation music therapy to stabilize mental state. This study is useful to identify 12 subtle emotions angry (annoying, angry, nervous), calm (calm, peaceful, relaxed), happy (excited, happy, pleased), sad (sleepy, bored, sad). A total 120 emotion signals were collected by using Emotive 14 channel EEG headset. Emotions are elicited by using three types of stimulus thoughts, audio and video. The system is trained by using captured database of emotion signals which include 30 signals of each emotion class. A total of 24 features were extracted by performing Chirplet transform. Band power is ranked as the prominent feature. The multimodel approach of classifier is used to classify emotions. Classification accuracy is tested for K-nearest neighbor (KNN), convolutional neural network (CNN), recurrent neural network (RNN) and deep neural network (DNN) classifiers. The system is tested to detect emotions of intellectually disable people. Meditation music therapy is used to stable mental state. It is found that it changed emotions of both intellectually disabled and normal participants from the annoying state to the relaxed state. A 75% positive transformation of mental state is obtained in the participants by using music therapy. This research study presents a novel approach for detailed analysis of brain EEG signals for emotion detection and stabilize mental state.
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Pothier, David D., Cian Hughes, Wanda Dillon, Paul J. Ranalli y John A. Rutka. "The Use of Real-Time Image Stabilization and Augmented Reality Eyewear in the Treatment of Oscillopsia". Otolaryngology–Head and Neck Surgery 146, n.º 6 (18 de enero de 2012): 966–71. http://dx.doi.org/10.1177/0194599811434708.
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Objectives/Hypothesis. The symptom of oscillopsia in patients with bilateral vestibular loss (BVL) can be reduced as dynamic visual acuity (DVA), the reduction in visual acuity during head movement, is improved by using real-time image stabilization, delivered by augmented reality eyewear. Setting. Tertiary multidisciplinary neurotology clinic. Study Design. Prospective experimental study. Methods. Immersive virtual reality glasses used in combination with a compact digital video camera were used. A software algorithm was developed that used a center-weighted Lucas-Kanade optical flow method to stabilize video in real time. Six patients with BVL were tested for changes in DVA using the eyewear. The ability to read a Snellen chart during a 2-Hz oscillating head rotation DVA test was measured. Results. For combined scores of vertical and horizontal head rotations, the mean number of lines readable at rest was 7.86, which dropped to 2.77 with head movement (a combination of vertical and horizontal perturbations). This increased to a mean of 6.14 lines with the image stabilization software being activated. This difference was statistically significant ( P < .001). Conclusion. This is the first successful attempt to improve dynamic visual acuity in patients with bilateral vestibular loss. Recent hardware upgrades are promising in improving these results even further.
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Fukushima, Toshihiko, Robert Siddall, Fabian Schwab, Séverine L. D. Toussaint, Greg Byrnes, John A. Nyakatura y Ardian Jusufi. "Inertial Tail Effects during Righting of Squirrels in Unexpected Falls: From Behavior to Robotics". Integrative and Comparative Biology 61, n.º 2 (30 de abril de 2021): 589–602. http://dx.doi.org/10.1093/icb/icab023.
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Abstract Arboreal mammals navigate a highly three dimensional and discontinuous habitat. Among arboreal mammals, squirrels demonstrate impressive agility. In a recent “viral” YouTube video, unsuspecting squirrels were mechanically catapulted off of a track, inducing an initially uncontrolled rotation of the body. Interestingly, they skillfully stabilized themselves using tail motion, which ultimately allowed the squirrels to land successfully. Here we analyze the mechanism by which the squirrels recover from large body angular rates. We analyzed from the video that squirrels first use their tail to help stabilizing their head to visually fix a landing site. Then the tail starts to rotate to help stabilizing the body, preparing themselves for landing. To analyze further the mechanism of this tail use during mid-air, we built a multibody squirrel model and showed the righting strategy based on body inertia moment changes and active angular momentum transfer between axes. To validate the hypothesized strategy, we made a squirrel-like robot and demonstrated a fall-stabilizing experiment. Our results demonstrate that a squirrel’s long tail, despite comprising just 3% of body mass, can inertially stabilize a rapidly rotating body. This research contributes to better understanding the importance of long tails for righting mechanisms in animals living in complex environments such as trees.
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Rodriguez-Padilla, Isaac, Bruno Castelle, Vincent Marieu y Denis Morichon. "A Simple and Efficient Image Stabilization Method for Coastal Monitoring Video Systems". Remote Sensing 12, n.º 1 (24 de diciembre de 2019): 70. http://dx.doi.org/10.3390/rs12010070.
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Fixed video camera systems are consistently prone to importune motions over time due to either thermal effects or mechanical factors. Even subtle displacements are mostly overlooked or ignored, although they can lead to large geo-rectification errors. This paper describes a simple and efficient method to stabilize an either continuous or sub-sampled image sequence based on feature matching and sub-pixel cross-correlation techniques. The method requires the presence and identification of different land-sub-image regions containing static recognizable features, such as corners or salient points, referred to as keypoints. A Canny edge detector ( C E D ) is used to locate and extract the boundaries of the features. Keypoints are matched against themselves after computing their two-dimensional displacement with respect to a reference frame. Pairs of keypoints are subsequently used as control points to fit a geometric transformation in order to align the whole frame with the reference image. The stabilization method is applied to five years of daily images collected from a three-camera permanent video system located at Anglet Beach in southwestern France. Azimuth, tilt, and roll deviations are computed for each camera. The three cameras showed motions on a wide range of time scales, with a prominent annual signal in azimuth and tilt deviation. Camera movement amplitude reached up to 10 pixels in azimuth, 30 pixels in tilt, and 0.4° in roll, together with a quasi-steady counter-clockwise trend over the five-year time series. Moreover, camera viewing angle deviations were found to induce large rectification errors of up to 400 m at a distance of 2.5 km from the camera. The mean shoreline apparent position was also affected by an approximately 10–20 m bias during the 2013/2014 outstanding winter period. The stabilization semi-automatic method successfully corrects camera geometry for fixed video monitoring systems and is able to process at least 90% of the frames without user assistance. The use of the C E D greatly improves the performance of the cross-correlation algorithm by making it more robust against contrast and brightness variations between frames. The method appears as a promising tool for other coastal imaging applications such as removal of undesired high-frequency movements of cameras equipped in unmanned aerial vehicles (UAVs).
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Casey, F., D. Brown, N. Corrigan, B. G. Craig, M. Quinn, B. Mccord, J. Rogers y H. C. Mulholland. "Value of a low-cost telemedicine link in the remote echocardiographic diagnosis of congenital heart defects". Journal of Telemedicine and Telecare 4, n.º 1_suppl (marzo de 1998): 46–48. http://dx.doi.org/10.1258/1357633981931416.
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We established a low-cost telemedicine link from a district general hospital to the regional paediatric cardiology department about 120km away. The link was used to transmit echocardiographic images of newborn infants suspected of having congenital heart disease (CHD) to the referral centre, with simultaneous video and audio contact for consultation. Echocardiograms were transmitted for 61 patients suspected of having CHD, aged from 1 to 42 days. The transmitted images were of adequate quality for the paediatric cardiologist to make a diagnosis in 59 (97%). Congenital heart abnormalities were diagnosed in 38 (64%). Twelve patients (20%) had major CHD diagnosed on the transmitted scan and required transfer to the regional cardiology unit either urgently or electively after initial measures to stabilize the patient. Our findings suggest that, for babies suspected of having CHD, ultrasound images of diagnostic quality can be obtained and transmitted using a low-cost telemedicine system.
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Michel, Jacqueline, Christine Boring y Chris Locke. "RAPID ASSESSMENT PROTOCOLS FOR SMALL VESSEL GROUNDINGS". International Oil Spill Conference Proceedings 2008, n.º 1 (1 de mayo de 2008): 381–86. http://dx.doi.org/10.7901/2169-3358-2008-1-381.
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ABSTRACT Vessel groundings in coral or seagrass habitats can cause significant injury to these benthic communities. Injury assessment requires information on the areal extent and degrees of injury at the grounding site, including the inbound and exit vessel tracks. Scientific divers need to rapidly delineate the boundaries of the impacted areas, map the location of specific points (such as large dislodged coral heads), and record observations along transects underwater. A series of 2–3 page protocols was developed to provide guidance on collection of key ephemeral data after small vessel groundings, particularly where resources are limited and access is difficult. The Initial Assessment protocol outlines the steps to plan and conduct emergency phase surveys to document the physical injuries. Guidance is provided on how to set up the sampling grids, develop site-specific injury categories, and record field parameters. The Live Coral Triage protocol describes how to salvage and stabilize live coral and associated resources in a coral reef or hardbottom habitat that have been physically fractured, dislodged, or overturned. The Underwater Video Mapping protocol describes how to document and provide a permanent video record of the area, type, and degree of physical damage to benthic communities. These protocols for small vessel groundings should assist first responders collect ephemeral data during the emergency phases of a response and start the recovery process.
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Chae, H.-B., C.-H. Kim, J.-H. Kim y S. Rhee. "The effect of shielding gas composition in CO2 laser—gas metal arc hybrid welding". Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 222, n.º 11 (1 de noviembre de 2008): 1315–24. http://dx.doi.org/10.1243/09544054jem944.
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In carbon dioxide (CO2) laser—gas metal arc hybrid welding, a shielding gas is supplied to isolate the molten metal from the ambient air, suppress the laser-induced plasma, remove the plume out of the keyhole, and stabilize the metal transfer. In this study, a shielding gas consisting of helium, argon, and CO2 was used, and its effects on the composition of the welding phenomena, such as behaviours of laser-induced plasma generation, molten pool flow, and droplet transfer in gas metal arc welding, were investigated. High-speed video observation was used to investigate the welding phenomena inside the arc regime. Consequently, helium was found to have a dominant role in suppressing laser-induced plasma; minimum helium content at a laser power of 8 kW was suggested for laser autogenous and hybrid welding. Argon and CO2 govern the droplet transfer and arc stability. A 12 per cent addition of CO2 stabilizes the metal transfer and eliminates undercut caused by insufficient wetting of molten metal.
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Iragorry, J. y Y. X. Tao. "Frost Temperature Relations for Defrosting Sensing System". Journal of Heat Transfer 127, n.º 3 (1 de marzo de 2005): 344–51. http://dx.doi.org/10.1115/1.1860566.
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To develop a better defrosting control system on finned evaporators of a refrigeration system, a study is conducted to better quantify the frosting and defrosting processes by using an infrared thermometer to determine the frost surface temperature. For gradual frost deposition a slow variation in surface emissivity is expected, while the defrosting process is characterized by a sudden change of this property. As an indicator for the defrosting initiation control mechanism, the times at which the IR signals stabilize at different conditions (Reynolds number, cold surface temperature, and ambient temperature) are reported along with the terminal mass concentration of a defined frosting process. On the other hand, the abrupt variation of surface emissivity indicates the termination of the defrosting process. Removable fins are used to measure frost weight, and a video microscope is used to determine the frost thickness. Defrosting initiation time and durations marked by melting, temperature are reported as a function of initial mass concentration and defrosting base surface temperature. The presented results could be used to design a better defrosting control system with better accuracy and energy saving features.
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Joshi, Anand C., Matthew J. Thurtell, Mark F. Walker, Alessandro Serra y R. John Leigh. "Effect of Vergence on Human Ocular Following Response (OFR)". Journal of Neurophysiology 102, n.º 1 (julio de 2009): 513–22. http://dx.doi.org/10.1152/jn.00045.2009.
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The human ocular following response (OFR) is a preattentive, short-latency visual-field–holding mechanism, which is enhanced if the moving stimulus is applied in the wake of a saccade. Since most natural gaze shifts incorporate both saccadic and vergence components, we asked whether the OFR was also enhanced during vergence. Ten subjects viewed vertically moving sine-wave gratings on a video monitor at 45 cm that had a temporal frequency of 16.7 Hz, contrast of 32%, and spatial frequency of 0.17, 0.27, or 0.44 cycle/deg. In Fixation/OFR experiments, subjects fixed on a white central dot on the video monitor, which disappeared at the beginning of each trial, just as the sinusoidal grating started moving up or down. We measured the change in eye position in the 70- to 150-ms open-loop interval following stimulus onset. Group mean downward responses were larger (0.14°) and made at shorter latency (85 ms) than upward responses (0.10° and 96 ms). The direction of eye drifts during control trials, when gratings remained stationary, was unrelated to the prior response. During vergence/OFR experiments, subjects switched their fixation point between the white dot at 45 cm and a red spot at 15 cm, cued by the disappearance of one target and appearance of the other. When horizontal vergence velocity exceeded 15°/s, motion of sinusoidal gratings commenced and elicited the vertical OFR. Subjects showed significantly ( P < 0.001) larger OFR when the moving stimulus was presented during convergence (group mean increase of 46%) or divergence (group mean increase of 36%) compared with following fixation. Since gaze shifts between near and far are common during natural activities, we postulate that the increase of OFR during vergence movements reflects enhancement of early cortical motion processing, which serves to stabilize the visual field as the eyes approach their new fixation point.
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Vujasinović, Stéphane, Stefan Becker, Timo Breuer, Sebastian Bullinger, Norbert Scherer-Negenborn y Michael Arens. "Integration of the 3D Environment for UAV Onboard Visual Object Tracking". Applied Sciences 10, n.º 21 (29 de octubre de 2020): 7622. http://dx.doi.org/10.3390/app10217622.
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Single visual object tracking from an unmanned aerial vehicle (UAV) poses fundamental challenges such as object occlusion, small-scale objects, background clutter, and abrupt camera motion. To tackle these difficulties, we propose to integrate the 3D structure of the observed scene into a detection-by-tracking algorithm. We introduce a pipeline that combines a model-free visual object tracker, a sparse 3D reconstruction, and a state estimator. The 3D reconstruction of the scene is computed with an image-based Structure-from-Motion (SfM) component that enables us to leverage a state estimator in the corresponding 3D scene during tracking. By representing the position of the target in 3D space rather than in image space, we stabilize the tracking during ego-motion and improve the handling of occlusions, background clutter, and small-scale objects. We evaluated our approach on prototypical image sequences, captured from a UAV with low-altitude oblique views. For this purpose, we adapted an existing dataset for visual object tracking and reconstructed the observed scene in 3D. The experimental results demonstrate that the proposed approach outperforms methods using plain visual cues as well as approaches leveraging image-space-based state estimations. We believe that our approach can be beneficial for trafficmonitoring, video surveillance, and navigation.
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Eskesen, I. G., J. Teilmann, B. M. Geertsen, G. Desportes, F. Riget, R. Dietz, F. Larsen y U. Siebert. "Stress level in wild harbour porpoises (Phocoena phocoena) during satellite tagging measured by respiration, heart rate and cortisol". Journal of the Marine Biological Association of the United Kingdom 89, n.º 5 (21 de julio de 2009): 885–92. http://dx.doi.org/10.1017/s0025315408003159.
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During satellite tagging of harbour porpoises (Phocoena phocoena), heart rate, respiration rate and cortisol value were measured to evaluate stress effects during handling and tagging. Respiration rates were obtained using video recordings, heart rates were recorded and serum cortisol levels were analysed from blood samples. Differences in heart rates, respiration rates and cortisol levels before and during the tagging events were investigated. An overall significant decrease of 31.5% in respiration rate was found during the tagging event period, while mature porpoises respired significantly more often than immature individuals. Though significant differences in heart rates were found for some individuals, no general significant change for all animals was detected. We found no correlation between cortisol concentration and either heart rate or respiration rate, nor did we find any relationships between cortisol and month of year, sex and body length. As high individual variations occurred in response to tagging of harbour porpoises, it is not possible to give general advice based on the factors investigated, on how to reduce stress during handling. However, pouring water over the animal and lowering it into the water seem to stabilize a stressed animal. Therefore, general precaution and individual judgement based on experience is essential when handling wild harbour porpoises.
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Boeddeker, Norbert y Jan M. Hemmi. "Visual gaze control during peering flight manoeuvres in honeybees". Proceedings of the Royal Society B: Biological Sciences 277, n.º 1685 (9 de diciembre de 2009): 1209–17. http://dx.doi.org/10.1098/rspb.2009.1928.
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As animals travel through the environment, powerful reflexes help stabilize their gaze by actively maintaining head and eyes in a level orientation. Gaze stabilization reduces motion blur and prevents image rotations. It also assists in depth perception based on translational optic flow. Here we describe side-to-side flight manoeuvres in honeybees and investigate how the bees’ gaze is stabilized against rotations during these movements. We used high-speed video equipment to record flight paths and head movements in honeybees visiting a feeder. We show that during their approach, bees generate lateral movements with a median amplitude of about 20 mm. These movements occur with a frequency of up to 7 Hz and are generated by periodic roll movements of the thorax with amplitudes of up to ±60°. During such thorax roll oscillations, the head is held close to horizontal, thereby minimizing rotational optic flow. By having bees fly through an oscillating, patterned drum, we show that head stabilization is based mainly on visual motion cues. Bees exposed to a continuously rotating drum, however, hold their head fixed at an oblique angle. This result shows that although gaze stabilization is driven by visual motion cues, it is limited by other mechanisms, such as the dorsal light response or gravity reception.
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Boyes, E. D., L. Hanna y P. L. Gai. "Controlled hot-stage experiments in the HREM with active drift compensation and 2Å lattice resolution". Proceedings, annual meeting, Electron Microscopy Society of America 50, n.º 1 (agosto de 1992): 98–99. http://dx.doi.org/10.1017/s0424820100120898.
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An electronic system has been developed to compensate electronically, with <2Å lattice resolution, for the image shift due to specimen and/or stage drift in the HREM. A simple system has been highly effective in compensating for the drift which has long limited many scientifically important but technically demanding applications of TEM in both the physical and biological sciences. It has facilitated controlled hot stage experiments with full HREM resolution.Over an extended period of time (>15s) which is fully adequate to record a high resolution image photographically or electronically, most drift of either the stage or the specimen can be approximated to a constant and relatively slow rate along a straight line path segment. With the new system the drift characteristic is video analyzed and an inverse correction ramp derived from a 12-bit DAC or external analog function generator is applied to existing post-specimen electrical image shift coils to stabilize the image position at the TEM camera. Image stabilization is also necessary for high quality data recording by digital processing of multiple (e.g. 256 or more) TV frames for an equivalent exposure time of several (8.5) seconds. This is the main data recording method for the dynamic experiments and with it low dose techniques can be used to minimize the beam damage effects which otherwise can be a serious problem in many HREM applications.
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Ko, Tianyi, Kazuya Murotani, Ko Yamamoto y Yoshihiko Nakamura. "Whole-Body Compliant Motion by Sensor Integration of an EHA-Driven Humanoid Hydra". International Journal of Humanoid Robotics 18, n.º 01 (febrero de 2021): 2150002. http://dx.doi.org/10.1142/s021984362150002x.
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Joints’ backdrivability is desired for robots that perform tasks contacting the environment, in addition to the high torque and fast response property. The electro-hydrostatic actuator (EHA) is an approach to realize force-sensitive robots. To experimentally confirm the performance of a biped robot driven by EHAs, we developed the fully electro-hydrostatically driven humanoid robot Hydra. In this paper, we evaluate the whole-body control performance realized by integrating encoders, pressure sensors, and IMU through a high-speed communication bus to the distributed whole-body control system. We report the first example of bipedal locomotion by an EHA-driven robot in both position-controlled and torque-controlled approaches. The robot could keep the balance even when the ground condition was changing impulsively and utilize its high joint backdrivability to absorb a disturbance by the null space compliance. We also report practical challenges in implementing compliant control in real hardware with limitations in parameter accuracy, torque, and response. We experimentally confirmed that the resolved viscoelasticity control (RVC), which has indirect feedback of operational space tasks by projecting the operational space feedback gain to the joint space one, was effective to tune a proper gain to stabilize the center-of-mass motion while avoiding joint-level oscillation invoked by the control bandwidth limitation. The attached multimedia file includes the video of all experiments presented in the paper.
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Misiaszek, John E. "Control of Frontal Plane Motion of the Hindlimbs in the Unrestrained Walking Cat". Journal of Neurophysiology 96, n.º 4 (octubre de 2006): 1816–28. http://dx.doi.org/10.1152/jn.00370.2006.
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This study describes the patterns of activity of hip abductor and adductor muscles and relates their activity to the frontal plane motions of the hindlimbs during unrestrained walking in the cat to provide insight into the function of these muscles in maintaining stability during walking. Electromyographic activity was recorded from hindlimb muscles while cats walked across a walkway. Four video cameras were used to record the movement of the animal in three dimensions. To further delineate the role of the hip abductors and adductors in regulating frontal plane movements of the legs, medial-lateral translations of the walking surface were periodically introduced. During walking, the hip abducts throughout much of the stance phase and adducts during swing. Normally, the abductors and adductors are co-active during much of the stance phase and are quiescent during swing. Consequently, the adduction observed during swing is likely the result of passive events. It is argued that the activity of the hip abductors during stance phase plays a prominent role in regulating frontal plane motion of the legs during walking. However, when medial-lateral stability is disturbed, both the hip abductors and adductors respond to stabilize the frontal plane motion of the body mass while also adjusting the frontal plane swing trajectory and subsequent paw placement. The balance corrective reactions observed in the cat after medial-lateral perturbations of the support surface reasonably approximate the reactions observed previously in humans, indicating that the cat is a reasonable model to explore the neural mechanisms of lateral stability during walking.
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Ritter, D. "Epaxial muscle function during locomotion in a lizard (Varanus salvator) and the proposal of a key innovation in the vertebrate axial musculoskeletal system". Journal of Experimental Biology 198, n.º 12 (1 de diciembre de 1995): 2477–90. http://dx.doi.org/10.1242/jeb.198.12.2477.
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The pattern of electromyographic activity in the epaxial muscles of walking and running lizards (water monitors, Varanus salvator) was quantified with high-speed video and synchronized electromyography. Muscle denervation experiments were performed and ground reaction forces were recorded to evaluate hypotheses of muscle function. Water monitors exhibit unilateral, uniphasic activation of the epaxial muscles ipsilateral to rear limb support. The iliocostalis and longissimus dorsi muscles are active throughout the support phase of the rear limb, while the transversospinalis is active only during the second half of the support phase. The timing of muscle activity does not support the presumed locomotor function of the epaxial muscles of lizards (lateral bending of the trunk). Bilateral denervation of the two most lateral epaxial muscles (iliocostalis and longissimus dorsi) caused no significant change in the amplitude of lateral trunk bending. These two epaxial muscles do not appear to be necessary for lateral bending of the trunk, nor do they appear to be involved in resisting lateral bending of the trunk. On the basis of the data reported in this study, as well as a re-evaluation of previously existing data, it is proposed that the locomotor function of the epaxial muscles of lizards is to stabilize the trunk against the vertical component of the ground reaction forces; i.e. the epaxial muscles function in a postural role during locomotion in lizards, as they do in other amniotes. This proposed postural role of the epaxial muscles may represent a key innovation of amniotes, made possible by the loss of an aquatic larval stage in their common ancestor.
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Waters, J. C., R. V. Skibbens y E. D. Salmon. "Oscillating mitotic newt lung cell kinetochores are, on average, under tension and rarely push". Journal of Cell Science 109, n.º 12 (1 de diciembre de 1996): 2823–31. http://dx.doi.org/10.1242/jcs.109.12.2823.
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Experimentally introduced tension on kinetochores and their centromeres has been shown to stabilize kinetochore attachment to microtubules, modify kinetochore directional instability, and regulate cell-cycle progression into anaphase. In mitosis, kinetochore tension and the stretch of centromere chromatin are produced by the movement of sister kinetochores toward opposite poles and astral ejection forces on the chromosome arms. However, newt lung cell kinetochores oscillate between poleward and away from the pole motility states throughout mitosis, indicating kinetochores are not under constant tension. To test whether kinetochores are under net tension while they are oscillating, and how often they are under compression and pushing into the chromosome, we measured the distance between sister kinetochores in newt lung cells using both video-enhanced differential interference contrast microscopy (VE-DIC) and immunofluorescence microscopy. We found that for chromosomes in which sister kinetochores are attached to opposite spindle poles, centromeres are, on average, stretched (2.2 microns in living cells and 1.8 microns in fixed cells) with respect to the inter-kinetochore ‘rest’ length (1.1 microns in living and fixed cells). For chromosomes in which only one kinetochore is attached to the spindle, the centromere chromatin associated with the tethered kinetochore is, on average, stretched to approximately half of the average inter-kinetochore distance measured for chromosomes in which both kinetochores are attached. We conclude that while newt lung cell kinetochores oscillate between states of P and AP movement, they are under tension approximately 90% of the time and under compression less than 6% of the time.
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Luo, Ge, Jianjun Zhu, Huadong Ni, Qinghe Zhou, Yaping Lu, Qihong Shen, Yibing Yao, Qiuli He, Jie Fu y Ming Yao. "Pretreatment with Pectoral Nerve Block II Is Effective for Reducing Pain in Patients Undergoing Thoracoscopic Lobectomy: A Randomized, Double-Blind, Placebo-Controlled Trial". BioMed Research International 2021 (16 de abril de 2021): 1–8. http://dx.doi.org/10.1155/2021/6693221.
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Background. Although video-assisted thoracoscopy has a smaller incision than traditional surgery, the postoperative pain is still severe. Ultrasound-guided pectoral nerve block (PECS) II is a new technique that can reduce pain in patients, and it had not been reported in the analgesia after thoracoscopic lobectomy. Methods. 40 patients scheduled for thoracoscopic lobectomy were randomly divided into two groups. Patients in the PECS II group received 0.5% ropivacaine 25 ml before the general anesthesia, while patients in the placebo group received 0.9% saline. Thirty minutes after the block was performed, a pin-prick test was used to analyze the sense of pain of T2-T6 segments. The primary endpoint was the total consumption of fentanyl. Data were collected in the postanesthesia care unit (PACU) and in the ward within 24 hours after operation. Results. The total consumption of fentanyl and the consumption of fentanyl in the intravenous analgesia pump within 24 hours after the operation were significantly lower in the PECS II group compared to the placebo group ( p < 0.05 ). The implementation rate of rescue analgesia during operation and in PACU in the PECS II group was significantly lower than that in the placebo group ( p < 0.05 ). The numerical rating scale (NRS) in 1 and 4 h after operation was lower in the PECS II group ( p < 0.05 ). Mean arterial pressure (MAP) and heart rate (HR) of the PECS II group at chest entering (T1) were significantly lower than those in the placebo group ( p < 0.05 ). Conclusion. Preconditioning of PECS II can stabilize the intraoperative circulation and significantly reduce pain and the consumption of opioids after operation.
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Sofía, Ceja León Edna, Sánchez Saavedra Ma Guadalupe, Cárdenas Pérez Ricardo, Loeza Lara Pedro Damian y Núñez Oregel Verónica. "Evaluación de aditivos químicos y biológicos en la vida de anaquel de la tortilla de nopal (opuntia ficus-indica)". South Florida Journal of Development 2, n.º 4 (24 de septiembre de 2021): 6133–41. http://dx.doi.org/10.46932/sfjdv2n4-087.
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La tortilla de maíz (Zea mays L.), es la base de la alimentación mexicana, por su alto valor nutricional, no obstante, dado el nivel calórico que presenta se buscan alternativas que disminuyan este contenido. Una opción es adicionarle nopal, lo que disminuye el nivel calórico y proporciona beneficios importantes tales como, buena fuente de fibra dietética, actividad antioxidante, efecto prebiótico y con ello, es una alternativa para prevención de enfermedades crónicas degenerativas. Sin embargo, dada la alta actividad acuosa del nopal disminuye considerablemente la vida de anaquel de la tortilla, ocasionando deterioro significativo en pocos días. Para revertir tal efecto existen conservadores químicos como: el benzoato de sodio y ácido cítrico y conservadores biológicos como: las gomas arábigas, guar, xantana y el quitosano, que favorecen la baja actividad acuosa y permiten estabilizar de manera importante un alimento. Aunado al interés de la población de una disminución del consumo calórico también existe la preocupación de consumir alimentos libres de patógenos y la menor cantidad de aditivos posibles. Por lo anterior, en este trabajo se analizan diferentes conservadores químicos y biológicos con la finalidad de alargar la vida de anaquel de la tortilla de nopal con la mínima dosis posible. Para ello, a 1 kg de masa se agregó el agente conservante en diferentes concentraciones, se homogeneizó y posteriormente se elaboraron las tortillas a partir de 30 g de la masa, se dejó alcanzar la temperatura ambiente, empacaron y almacenaron a 25 °C y 4 °C, se registró diariamente el estado de la tortilla hasta observar cambios desfavorables. Se obtuvieron resultados con una duración de 5 días a temperatura ambiente con aditivos diferentes y de 25 y 37 días a temperatura de 4°C.
Corn tortilla (Zea mays L.) is the basis of Mexican food, due to its high nutritional value; however, given its high caloric content, alternatives are being sought to reduce this content. One option is to add nopal, which reduces the caloric level and provides important benefits such as a good source of dietary fiber, antioxidant activity, prebiotic effect and thus is an alternative for the prevention of chronic degenerative diseases. However, due to the high aqueous activity of nopal, the tortilla's shelf life decreases considerably, causing significant deterioration in a few days. To reverse this effect, there are chemical preservatives such as sodium benzoate and citric acid and biological preservatives such as gums arabic, guar, xanthan and chitosan, which favor the low water activity and can significantly stabilize a food. In addition to the population's interest in reducing caloric intake, there is also the concern of consuming food free of pathogens and the least amount of additives possible. Therefore, in this work, different chemical and biological preservatives are analyzed in order to extend the shelf life of nopal tortillas with the minimum possible dose. For this purpose, the preservative agent was added to 1 kg of dough in different concentrations, homogenized and then the tortillas were made from 30 g of dough, allowed to reach room temperature, packed and stored at 25 °C and 4 °C, and the tortilla condition was recorded daily until unfavorable changes were observed. Results were obtained with a shelf life of 5 days at room temperature with different additives and 25 and 37 days at 4°C.
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Harayev, G. I. y S. N. Shukhanov. "Modernization of a technical means for separating a grain-straw heap". Traktory i sel'hozmashiny 1, n.º 5 (2020): 33–36. http://dx.doi.org/10.31992/0321-4443-2020-5-33-36.
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The successful functioning of agricultural production at the present stage of development pre-supposes the creation of agro-engineering systems operating on innovative principles. In this set of tasks, the technical support of cereal production has a key place. Post-harvest treatment of grain is of paramount importance, including its pre-purification, namely, separation of grain straw heap. Therefore, the solution of the technical task of modernizing the technical means for separation of grain straw heap is a pressing problem. A wide overview of literary sources devoted to this topic, a comprehensive and thoughtful analysis of inventions made it possible to modernize device at the level of patentability. Proposed modernization of apparatus is achieved due to uniform feed, which provides thin-layer stratification with required orientation of particles moved by conical spreader into formed annular air flow. A distinctive feature of the proposed device is a new form of execu-tion of known structural components, namely, the representation of the feeder in the form of a fun-nel-shaped hopper with an outlet slot, as well as a ring-shaped dispenser, the design of a conical spreader equipped with straight blades, including receiving chambers made in the form of a design of circular funnel-shaped working chambers. In addition, a characteristic feature of the proposed apparatus is the presence of a device for directing the air flow in the form of a cone. The hopper of a funnel-shaped design with an outlet slot allows to stabilize the movement of the components of the processed material before they arrive at the ring dispenser. Availability of design features of the proposed apparatus ensures realization of technical result at the level of patentability, which pro-vides an increase of productivity, as well as efficiency of extraction of output components from processed material.
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Neupane, Anuj Kumar, Krithika Gururaj y Sujeet Kumar Sinha. "Higher Asymmetry Ratio and Refixation Saccades in Individuals with Motion Sickness". Journal of the American Academy of Audiology 29, n.º 02 (febrero de 2018): 175–86. http://dx.doi.org/10.3766/jaaa.16175.
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AbstractMotion sickness is a complex autonomic phenomenon caused by the intersensory conflict among the balancing systems, resulting in a mismatch of signals between static physical conditions of the susceptible individual exposed to dynamic environment.The present study was done to assess the sacculocollic reflex pathway and six semicircular canals in individuals susceptible to motion sickness.Standard group comparison was used.A total of 60 participants with an age range of 17–25 yr were included, where group I comprised 30 participants with motion sickness and group II comprised 30 participants without motion sickness. The Motion Sickness Susceptibility Questionnaire–Short was administered to classify the participants into groups with or without motion sickness.The cervical vestibular-evoked myogenic potential (cVEMP) test and video head impulse test (vHIT) were administered to all participants. The Shapiro–Wilk test revealed normal distribution of the data (p > 0.05). Hence a parametric independent sample t test was done to check significant difference in cVEMP and vHIT parameters between the two groups.The present study revealed no significant difference for cVEMP latencies and amplitude in individuals with motion sickness. However, significantly higher cVEMP asymmetry ratio was observed in individuals with motion sickness. Though the vestibulo-ocular reflex (VOR) gain values showed no significant difference between the two groups except for the right anterior left posterior plane, the asymmetry in VOR gain values revealed significant difference between the groups, suggesting asymmetry as a better parameter than absolute VOR gain values. Also, the presence of refixation saccades in 100% of the individuals with motion sickness accorded with various studies reported earlier with vestibular-related pathologies.Presence of higher asymmetry ratio in cVEMP and vHIT test results plus refixation saccades to stabilize the gaze in vHIT can suggest some amount of vestibular anomalies in individuals with motion sickness.
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Sriramarao, P., LR Languino y DC Altieri. "Fibrinogen mediates leukocyte-endothelium bridging in vivo at low shear forces". Blood 88, n.º 9 (1 de noviembre de 1996): 3416–23. http://dx.doi.org/10.1182/blood.v88.9.3416.bloodjournal8893416.
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In addition to preserving hemostasis, fibrinogen assembly on leukocytes mediates inflammatory responses and may aberrantly contribute to vascular injury. In this study, we used real-time intravital video microscopy in exposed rabbit mesentery to investigate the potential role of fibrinogen on leukocyte adherence mechanisms, in vivo. At physiologic concentrations of 0.15 to 0.5 mg/mL, human fibrinogen dose-dependently enhanced by threefold to fivefold the adhesion of chemoattractant-stimulated monocytic HL-60 cells to rabbit mesenteric endothelium, by acting as a bridging molecule between the two types. Fibrinogen-dependent intercellular bridging occurred in venules, but not in arterioles or capillaries (1), was optimal at reduced flow shear forces (range: 0.77 to 2.79 dyne/cm2) (2), and produced a firm attachment of monocytic cells to endothelium, rather than transient rolling (3). Consistent with this model, rabbit fibrinogen failed to support human leukocyte adhesion, while human fibrinogen enhanced monocytic cell attachment to rabbit endothelial cells in vitro, in a reaction indistinguishable from that observed with human endothelium. Antagonists of the recently described association of fibrinogen with intercellular adhesion molecule-1 (ICAM-1), including monoclonal antibodies (MoAbs) LB-2 or 2D5, or the fibrinogen gamma 3 peptide gamma Asn117-Ala133, blocked fibrinogen-dependent leukocyte-endothelium interaction in vitro or in vivo, respectively, while a control nonbinding antibody or the fibrinogen L10 peptide gamma Leu402-Val411 were ineffective. These data suggest that simultaneous assembly of fibrinogen on leukocytes and endothelial ICAM-1 provides a pathway of intercellular adhesion which may act in concert with beta 2 integrins to stabilize firm leukocyte attachment to endothelium, in vivo. Given the recognized role of fibrinogen as a major risk factor for atherosclerosis, this mechanism may directly contribute to thrombus formation and endothelial cell damage in vascular diseases.
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Schwaner, M. Janneke, Grace A. Freymiller, Rulon W. Clark y Craig P. McGowan. "How to Stick the Landing: Kangaroo Rats Use Their Tails to Reorient during Evasive Jumps Away from Predators". Integrative and Comparative Biology 61, n.º 2 (3 de mayo de 2021): 442–54. http://dx.doi.org/10.1093/icb/icab043.
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Synopsis Tails are widespread in the animal world and play important roles in locomotor tasks, such as propulsion, maneuvering, stability, and manipulation of objects. Kangaroo rats, bipedal hopping rodents, use their tail for balancing during hopping, but the role of their tail during the vertical evasive escape jumps they perform when attacked by predators is yet to be determined. Because we observed kangaroo rats swinging their tails around their bodies while airborne following escape jumps, we hypothesized that kangaroo rats use their tails to not only stabilize their bodies while airborne, but also to perform aerial re-orientations. We collected video data from free-ranging desert kangaroo rats (Dipodomys deserti) performing escape jumps in response to a simulated predator attack and analyzed the rotation of their bodies and tails in the yaw plane (about the vertical-axis). Kangaroo rat escape responses were highly variable. The magnitude of body re-orientation in yaw was independent of jump height, jump distance, and aerial time. Kangaroo rats exhibited a stepwise re-orientation while airborne, in which slower turning periods corresponded with the tail center of mass being aligned close to the vertical rotation axis of the body. To examine the effect of tail motion on body re-orientation during a jump, we compared average rate of change in angular momentum. Rate of change in tail angular momentum was nearly proportional to that of the body, indicating that the tail reorients the body in the yaw plane during aerial escape leaps by kangaroo rats. Although kangaroo rats make dynamic 3D movements during their escape leaps, our data suggest that kangaroo rats use their tails to control orientation in the yaw plane. Additionally, we show that kangaroo rats rarely use their tail length at full potential in yaw, suggesting the importance of tail movement through multiple planes simultaneously.
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Kumar, Sachin, Juying Xu, Yi Zheng y Marie-Dominique Filippi. "Rho-GTPase Cdc42 Regulates Neutrophil Polarity Via Crosstalk Between Wiskott Aldrich Syndrome Protein (WASp), Lipid Raft Reorganization, CD11b and Microtubules". Blood 118, n.º 21 (18 de noviembre de 2011): 16. http://dx.doi.org/10.1182/blood.v118.21.16.16.
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Abstract Abstract 16 Neutrophils (PMNs) are the first line of immune defense by moving toward the infection site. A key event of cell migration is the maintenance of a polarized morphology characterized by a single protrusive leading edge (i.e. lamellipodia) and a contractile uropod. Using mice with a conditional Cdc42 (flox) allele, we have previously reported that the small Rho GTPase Cdc42 controls neutrophil polarity via CD11b integrin signaling at the uropod (Szczur; Blood 2009). In the present study, we seek to dissect the mechanism of Cdc42-CD11b axis in neutrophil polarity. We first examined the role of the Cdc42 effector Wiskott Aldrich Syndrome protein (WASp), as WASp−/− neutrophils showed defective neutrophil migration and integrin clustering (Yang; Immunity 2006). A Cdc42 mutant for WASp Binding (Cdc42S71P) was expressed in Cdc42−/− cells using retroviral transduction. Rescue of Cdc42 functions was analyzed compared to WT cells and Cdc42−/− cells transduced with an empty vector, and Cdc42−/− cells transduced with the wild type form of Cdc42 (wtCdc42). While expression of wtCdc42 rescued abnormal polarity and CD11b clustering in Cdc42−/− neutrophils to WT levels, expression of Cdc42S71P did not, suggesting that Cdc42 controls neutrophil polarity via WASp. We further confirmed the involvement of WASp in neutrophil polarity using WASp−/− neutrophils. WASp−/− neutrophils exhibited all characteristics of loss of polarity (ie frequent changes in direction during migration as assessed by video microscopy, multiple F-actin protrusions at the uropod). We next examined how Cdc42/WASp regulates neutrophil polarity and explored the roles of microtubules (MTs), since MTs are oriented toward the uropod in migrating WT neutrophils and Cdc42 is known to regulate MT polarity. Cdc42−/− as well as WASp−/− neutrophils showed loss of MT polarity with cells extending MT towards both the front and the uropod. They also exhibited less stabilized MTs (ie, defect in detyrosinated MT). Interestingly, MTs made contact with CD11b clusters at the uropod in WT, but not in Cdc42−/− and WASp−/− neutrophils. Enforcing CD11b clustering by CD11b antibody crosslinking in Cdc42−/− and WASp−/− neutrophils rescued polarity and MT capture at the plasma membrane to WT levels. Thus, Cdc42 regulates CD11b clustering via WASp, which, in turn, may capture and stabilize MTs at the uropod. To further examine this possibility, we examined in detail the plasma membrane of these cells. Indeed, on activation, the uropod of neutrophils reorganizes into detergent resistant membrane (DRM) domains – something, which is essential for polarity. Immunostaining with the DRM marker cholera toxin indicated loss of DRM assembly at the uropod of Cdc42−/− and WASp−/− neutrophils. Biochemistry analysis showed that DRM fraction of WT cells contained CD11b, WASp, tubulin and the microtubule end-binding protein EB1. In contrast, Cdc42−/− and WASp−/− DRMs had significantly lower amount of CD11b, WASp, tubulin, EB1 and CD11b, tubulin, EB1, respectively. Remarkably, CD11b crosslinking in WASp−/− cells rescued CD11b, tubulin and EB1 whereas CD11b crosslinking in Cdc42−/− cells rescued CD11b, tubulin and EB1 but not WASp, suggesting that Cdc42 and WASp controls DRM formation containing CD11b, and that CD11b recruits EB1 to capture and stabilize microtubules downstream of WASp. Together, our study uncovers a novel mechanism of neutrophil migration in which Cdc42 recruits WASp to the uropod to reorganize the plasma membrane into discrete DRM domains and induce CD11b clustering. CD11b clusters, in turn, capture and stabilize microtubules via EB1 – something that is critical for maintaining neutrophil polarity during directed migration. Our study thus reveals a new function for WASp in the control of neutrophil polarity via crosstalk of DRM/CD11b and microtubules. We used a 3-D migration model that mimics the extravasation cascade ex vivo to show that Cdc42/WASp/CD11b-dependent neutrophil polarity regulates the crawling step of neutrophils toward endothelial cell junction for efficient transmigration on HUVECs. Using a model of LPS-induced acute lung injury, we then show that Cdc42 loss dramatically reduced neutrophil recruitment to lung alveolar cavities as well as lung tissue inflammation – an indication for the patho-physiological importance of this pathway during the neutrophil extravasation cascade and subsequent inflammation in vivo. Disclosures: No relevant conflicts of interest to declare.
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Knyazev, S. V., D. V. Skopich, E. A. Fat’yanova, A. A. Usol’tsev y A. I. Kutsenko. "SOFTWARE AND HARDWARE AUTOMATED SYSTEM OF CASTS DEFECTS NON-DESTRUCTIVE MONITORING". Izvestiya. Ferrous Metallurgy 62, n.º 2 (30 de marzo de 2019): 134–40. http://dx.doi.org/10.17073/0368-0797-2019-2-134-140.
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Introduction of the “Automated system for operational control of casts production (OCCP AS)” makes the basis of an integrated automated production control system (APCS). It performs three main tasks: control and recording (production, products, materials, etc.), improving quality of casts and operational management of technological processes. Solution of these tasks was accomplished through automating data collection in real time for all production operations, recording material flows, creating operational communication channels, as well as centralized collection, processing and representation of data by the process information server. The next step in building an effective automated control system is to stabilize product quality in changing external conditions, for example, quality of materials, and to optimize production (technology change in order to reduce costs for constant or higher product quality). The second stage is based on mathematical processing and analysis of data coming from OCCP AS, it allows to determine optimal ranges of parameters of technological processes – “Automated system for optimization and analysis of production progress (OAPP AS)”. OAPP AS consists of two subsystems: quality analysis and technology management. The first solves the problem of data analysis and modeling, the second – calculation of real-time optimal process parameters and real time prediction. The stages tasks compete for access to different hardware resources. The most critical parameter for OCCP AS is performance of server disk arrays, for OAPP AS it is processor performance. In either case, system scaling is effectively solved by parallelizing operations across different servers, forming a cluster, and across different processors (cores) on the same server. To process defect images and to obtain cause-and-effect characteristics, you can use OpenCV software package, which is an open source computer vision library. In course of processing, Sobel operator, Gauss filter and binarization were used. They are based on processing pixels using matrices. Operations on pixels are independent and can be performed in parallel. The task of clustering is reduced to definition of an expert method or using various mathematical algorithms for defects belonging to a specific cluster (data block) through a set of values of dependent factors. Thus, data blocks are formed by the criterion of the defect cause. Calculation of a data block to which a product defect belongs can be very resource-intensive operation. To increase efficiency of image recognition systems and parallelization ofsearch operations, it makes sense to place data clusters on different servers. As a result, there is a need for a distributed database. This is a special class of DBMS, which requires appropriate software. Generation of OAPPAS based on a multi-node cluster with ApacheCassandra DBMS installed and using Nvidia video cards supporting CUDA technology on each node will be the cheapest and most effective solution. Video card is selected based on required number of graphics processors on the node.
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Klekamp, Jörg, Giorgio Iaconetta, Ulrich Batzdorf y Madjid Samii. "Syringomyelia associated with foramen magnum arachnoiditis". Journal of Neurosurgery: Spine 97, n.º 3 (octubre de 2002): 317–22. http://dx.doi.org/10.3171/spi.2002.97.3.0317.
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Object. Syringomyelia is often linked to pathological lesions of the foramen magnum. The most common cause is hindbrain herniation, usually referred to as Chiari I or II malformation. Foramen magnum arachnoiditis without either Chiari I or II malformation is a rare cause of syringomyelia. The authors undertook a retrospective analysis of 21 patients with foramen magnum arachnoiditis (FMA) and syringomyelia treated between 1978 and 2000 to determine clinical course and optimum management. Methods. In the review of records, 21 patients with FMA and syringomyelia were documented. A stable clinical course was demonstrated in three patients in whom surgery was not performed, and one patient refused surgical intervention. Seventeen patients underwent 23 operations to treat progressive neurological disease. Of these 23 operations, 18 involved opening of the foramen magnum, arachnoid dissection, and placement of a large dural graft. One patient underwent insertion of a ventriculoperitoneal shunt for treatment of accompanying hydrocephalus, one patient received a cystoperitoneal shunt for an accompanying arachnoid cyst; two syringoperitoneal and one syringosubarachnoid shunts were also inserted. Hospital and outpatient files, neuroimaging studies, and intraoperative photographic and video material were analyzed. Additional follow-up information was obtained by telephone interview and questionnaires. Standard and cardiac-gated magnetic resonance imaging studies are the diagnostic procedures of choice in these patients. Sensory disturbances, dysesthesias, and pain were the only symptoms likely to improve after foramen magnum surgery. Motor weakness and gait disturbances, which were severe in a considerable number of patients, and swallowing disorders tended to remain unchanged. As a consequence of the rather severe arachnoid lesions in most patients, clinical recurrences were observed in 57% over a 5-year period. Conclusions. Surgery for FMA and syringomyelia has to provide clear cerebrospinal fluid pathways between the cerebellopontine cisterns, spinal canal, and fourth ventricle. If this can be achieved successfully, the syrinx decreases in size and the clinical course of the patient may even improve. In patients with severe and widespread areas of arachnoiditis, however, multiple operations may be required at least to stabilize the clinical course.
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Groen, Eric, Jelte E. Bos y Bernd de Graaf. "Contribution of the otoliths to the human torsional vestibulo-ocular reflex". Journal of Vestibular Research 9, n.º 1 (1 de febrero de 1999): 27–36. http://dx.doi.org/10.3233/ves-1999-9104.
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The dynamic contribution of the otolith organs to the human ocular torsion response was examined during passive sinusoidal body roll about an earth-horizontal axis (varying otolith inputs) and about an earth-vertical axis (invariant otolith inputs). Torsional eye movements were registered in 5 subjects by means of video-oculography. At a fixed amplitude of 25°, the stimulus frequency was varied from 0.05 to 0.4 Hz. Additionally, at a fixed frequency of 0.2 Hz, the response was also measured at the amplitudes of 12.5° and 50°. The results showed that the gain and phase of the torsional slow component velocity (SCV) did not depend on stimulus amplitude, indicating a linear response. Contribution of the otoliths affected the ocular torsion response in three different ways. First, the gain of the SCV was slightly, but consistently, higher during rotation about an earth-horizontal axis than during rotation about an earth-vertical axis. With invariant otolith inputs the average gain increased from 0.10 at 0.05 Hz to 0.26 at 0.25 Hz. With varying otolith inputs, the average gain increased from 0.14 to 0.37. Second and more substantially, contribution of the otoliths improved the response dynamics by reducing the phase lead at frequencies up to 0.2 Hz. Third, the nystagmus showed considerably less anticompensatory saccades in upright conditions than in supine conditions, even though the SCV gain was lower in the latter. As a consequence, the average excursion of torsional eye position was highest during earth-horizontal rotation. This effect was observed in the entire frequency range. Thus, the otoliths controlled the human torsional VOR not only at low stimulus frequencies by keeping the slow component in phase with head motion, but also in a wider frequency range by modulating the saccadic behavior as to increase the amplitude of ocular torsion. We conclude that the primary concern of the otolith-oculomotor system during head tilt is to stabilize eye position in space, rather than to prevent retinal blur.
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Llorente-Adán, José Ángel y José Félix Ruíz-Tricio. "El desarrollo rural a partir de la gobernanza territorial en tiempos del coronavirus (Ocón, La Rioja, España) / / / \ \ \ Rural development from the territorial governance in times of the coronavirus (Ocón, La Rioja, Spain)". TERRA: Revista de Desarrollo Local, n.º 7 (30 de diciembre de 2020): 72. http://dx.doi.org/10.7203/terra.7.17533.
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Resumen: Con una tendencia demográfica descendente y una pérdida de servicios y de ofertas de consumo durante la segunda mitad del s XX, los pueblos de Ocón (La Rioja) presentaban las mismas características que la mayor parte de zonas rurales del interior peninsular. Durante las dos últimas décadas, Ocón ha conseguido revertir esta situación, con un desarrollo local muy activo y dinámico, como se ha dejado ver en la diversificación de su economía, en la revitalización de sus núcleos de población a través de la ejecución de multitud de proyectos e infraestructuras y en una mayor oferta de servicios, que poco a poco van cubriendo las demandas de la población. Demográficamente, presenta un elevado índice de envejecimiento y ha conseguido estabilizarse. La actual situación de crisis sanitaria vivida por el coronavirus ha hecho plantearse los modos y formas de vida de la población en general y al parecer se comienza a valorar mejor la calidad de vida que ofrecen los pueblos. De cómo se afronte esta situación depende que pueblos pequeños como Ocón pueden salir fortalecidos con una serie de líneas estratégicas que permitan una mejor conexión a Internet y afianzar un progreso sostenible.
Palabras clave: Desarrollo local, ordenación territorial, reto demográfico, virus COVID-19, sostenibilidad.
Abstract: This paper studies the declining demographic tendency and a loss of services and consumption offers during the second half of the XX century, the villages of Ocón (La Rioja, Spain) presented the same characteristics as most of the rural areas of the interior of the peninsula. Over the past two decades, Ocón has managed to reverse this situation, with a very active and dynamic local development, as it can been seen in the diversification of its economy, in the revitalization of its population centers through the execution of a multitude of projects and infrastructures and in a greater offer of services, which little by little are meeting the population’s demands. Demographically, it has a high aging index which has managed to stabilize. The current situation of health crisis caused by the coronavirus has made consider the ways of life of the population in general and it seems that a better appreciation of the quality of life offered by the villages is taking place. Depending on how this situation was dealt with, small towns like Ocón can emerge stronger if a series of strategy lines are carried out to consolidate a sustainable progress, solving the lack of the most urgent services such as the slow Internet connection, a key in the current development of society and teleworking.
Key words: Local development, land-use planning, demographic challenge, virus (COVID-19), sustainability.
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Olmsted, J. B., D. L. Stemple, W. M. Saxton, B. W. Neighbors y J. R. McIntosh. "Cell cycle-dependent changes in the dynamics of MAP 2 and MAP 4 in cultured cells." Journal of Cell Biology 109, n.º 1 (1 de julio de 1989): 211–23. http://dx.doi.org/10.1083/jcb.109.1.211.
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To examine the behavior of microtubule-associated proteins (MAPs) in living cells, MAP 4 and MAP 2 have been derivatized with 6-iodoacetamido-fluorescein, and the distribution of microinjected MAP has been analyzed using a low light level video system and fluorescence redistribution after photobleaching. Within 1 min following microinjection of fluoresceinated MAP 4 or MAP 2, fluorescent microtubule arrays were visible in interphase or mitotic PtK1 cells. After cold treatment of fluorescent MAP 2-containing cells (3 h, 4 degrees C), microtubule fluorescence disappeared, and the only fluorescence above background was located at the centrosomes; microtubule patterns returned upon warming. Loss of microtubule immunofluorescence after nocodozole treatment was similar in MAP-injected and control cells, suggesting that injected fluorescein-labeled MAP 2 did not stabilize microtubules. The dynamics of the MAPs were examined further by FRAP. FRAP analysis of interphase cells demonstrated that MAP 2 redistributed with half-times slightly longer (60 +/- 25 s) than those for MAP 4 (44 +/- 20 s), but both types of MAPs bound to microtubules in vivo exchanged with soluble MAPs at rates exceeding the rate of tubulin turnover. These data imply that microtubules in interphase cells are assembled with constantly exchanging populations of MAP. Metaphase cells at 37 degrees C or 26 degrees C showed similar mean redistribution half-times for both MAP 2 and MAP 4; these were 3-4 fold faster than the interphase rates (MAP 2, t1/2 = 14 +/- 6 s; MAP 4, t1/2 = 17 +/- 5 s). The extent of recovery of spindle fluorescence in MAP-injected cells was to 84-94% at either 26 or 37 degrees C. Although most metaphase tubulin, like the MAPs, turns over rapidly and completely under physiologic conditions, published work shows either reduced rates or extents of turnover at 26 degrees C, suggesting that the fast mitotic MAP exchange is not simply because of fast tubulin turnover. Exchange of MAP 4 bound to telophase midbodies occurred with dynamics comparable to those seen in metaphase spindles (t1/2 = approximately 27 s) whereas midbody tubulin exchange was slow (greater than 300 s). These data demonstrate that the rate of MAP exchange on microtubules is a function of time in the cell cycle.
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Friederich, E., T. E. Kreis y D. Louvard. "Villin-induced growth of microvilli is reversibly inhibited by cytochalasin D". Journal of Cell Science 105, n.º 3 (1 de julio de 1993): 765–75. http://dx.doi.org/10.1242/jcs.105.3.765.
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Villin is an actin-binding protein that is associated with the cytoskeleton of brush border microvilli. In vitro, villin nucleates, caps or severs actin filaments in a Ca(2+)-dependent manner. In the absence of Ca2+, villin organizes microfilaments into bundles. Transfection of a villin-specific cDNA into cultured cells that do not produce this protein results in the growth of long surface microvilli and the reorganization of the underlying actin cytoskeleton. Here we studied the effects of low concentrations of cytochalasin D on the induction of these plasma membrane-actin cytoskeleton specializations. Transfected cells were treated with concentrations of cytochalasin D that prevent the association of actin monomers with the fast-growing end of microfilaments in vitro. In villin-positive cells, cytochalasin D inhibited the growth of microvilli and promoted the formation of rodlet-like actin structures, which were randomly distributed throughout the cytoplasm. The formation of these structures was dependent on large amounts of villin and on the integrity of an actin-binding site located at the carboxy terminus of villin, which is required for microfilament bundling in vitro and for the growth of microvilli in vivo. The effect of cytochalasin D was reversible. The observation of living cells by video-imaging revealed that when cytochalasin D was removed, rapid disassembly of actin rodlets occurred after a lag phase. The present data stress the important role of the plasma membrane in the organization of the actin cytoskeleton and suggest that the extension of the microvillar plasma membrane is dependent on the elongation of microfilaments at their fast-growing end. Inhibition of microfilament elongation near the plasma membrane by cytochalasin D may result in the ‘random’ nucleation of actin filaments throughout the cytoplasm. On the basis of the present data, we propose that villin is involved in the assembly of the microvillar actin bundle by a mechanism that does not prevent monomer association with the preferred end of microfilaments. For instance, villin may stabilize actin filaments by lateral interactions. The functional importance of the carboxy-terminal F-actin binding site in such a mechanism is stressed by the fact that it is required for the formation of F-actin rodlets in cytochalasin D-treated cells. Finally, our data further emphasize the observations that the effects of cytochalasin D in living cells can be modulated by actin-binding proteins.
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Singh, Brajesh K., Andrew L. Hornick, Sateesh Krishnamurthy, Anna C. Locke, Crystal A. Mendoza, Mathieu Mateo, Catherine L. Miller-Hunt, Roberto Cattaneo y Patrick L. Sinn. "The Nectin-4/Afadin Protein Complex and Intercellular Membrane Pores Contribute to Rapid Spread of Measles Virus in Primary Human Airway Epithelia". Journal of Virology 89, n.º 14 (29 de abril de 2015): 7089–96. http://dx.doi.org/10.1128/jvi.00821-15.
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ABSTRACTThe discovery that measles virus (MV) uses the adherens junction protein nectin-4 as its epithelial receptor provides a new vantage point from which to characterize its rapid spread in the airway epithelium. We show here that in well-differentiated primary cultures of airway epithelial cells from human donors (HAE), MV infectious centers form rapidly and become larger than those of other respiratory pathogens: human respiratory syncytial virus, parainfluenza virus 5, and Sendai virus. While visible syncytia do not form after MV infection of HAE, the cytoplasm of an infected cell suddenly flows into an adjacent cell, as visualized through wild-type MV-expressed cytoplasmic green fluorescent protein (GFP). High-resolution video microscopy documents that GFP flows through openings that form on the lateral surfaces between columnar epithelial cells. To assess the relevance of the protein afadin, which connects nectin-4 to the actin cytoskeleton, we knocked down its mRNA. This resulted in more-limited infectious-center formation. We also generated a nectin-4 mutant without the afadin-binding site in its cytoplasmic tail. This mutant was less effective than wild-type human nectin-4 at promoting MV infection in primary cultures of porcine airway epithelia. Thus, in airway epithelial cells, MV spread requires the nectin-4/afadin complex and is based on cytoplasm transfer between columnar cells. Since the viral membrane fusion apparatus may open the passages that allow cytoplasm transfer, we refer to them as intercellular membrane pores. Virus-induced intercellular pores may contribute to extremely efficient measles contagion by promoting the rapid spread of the virus through the upper respiratory epithelium.IMPORTANCEMeasles virus (MV), while targeted for eradication, still causes about 120,000 deaths per year worldwide. The recent reemergence of measles in insufficiently vaccinated populations in Europe and North America reminds us that measles is extremely contagious, but the processes favoring its spread in the respiratory epithelium remain poorly defined. Here we characterize wild-type MV spread in well-differentiated primary cultures of human airway epithelial cells. We observed that viral infection promotes the flow of cytoplasmic contents from infected to proximal uninfected columnar epithelial cells. Cytoplasm flows through openings that form on the lateral surfaces. Infectious-center growth is facilitated by afadin, a protein connecting the adherens junction and the actin cytoskeleton. The viral fusion apparatus may open intercellular pores, and the cytoskeleton may stabilize them. Rapid homogenization of cytoplasmic contents in epithelial infectious centers may favor rapid spread and contribute to the extremely contagious nature of measles.