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1
Lao, Li, Constantine Dovrolis, and M. Y. Sanadidi. "The probe gap model can underestimate the available bandwidth of multihop paths." ACM SIGCOMM Computer Communication Review 36, no. 5 (October 10, 2006): 29–34. http://dx.doi.org/10.1145/1163593.1163599.
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Li, J., D. W. Smith, and S. G. Fityus. "The effect of a gap between the access tube and the soil during neutron probe measurements." Soil Research 41, no. 1 (2003): 151. http://dx.doi.org/10.1071/sr02054.
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The neutron probe is a tool employed for the measurement of water content in a soil mass. The presence of a gap between the soil and the neutron probe access tube, filled with either air or water, inevitably introduces a systematic error in neutron probe readings. In this study, experimental investigations and numerical analyses were carried out to evaluate the effects of this gap on neutron probe calibration. The numerical model was developed based on the multigroup neutron diffusion equations and the finite element method. The experiments were conducted in a heavy clay soil. The results show that an air gap of 2.5–30 mm between the soil and a 50-mm-diameter aluminium tube could lead to an underestimation of soil water content by 5–45%, but significant underestimation was apparent for air gaps <10 mm. It is also found that the neutron count is significantly overestimated if the gap around the access tube is filled with water rather than air, but this effect is most significant for larger gaps. The results of this research clearly indicate that a gap between the neutron probe access tube and the soil profile should be avoided during field installation, and that if a gap between the access tube and soil develops during service, a systematic error will be introduced into measurements.
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Hyun, S. Y., S. Y. Kim, and Y. S. Kim. "Finite-difference time-domain model for the feeding gap of coaxial probe driven antennas." IET Microwaves, Antennas & Propagation 3, no. 3 (2009): 501. http://dx.doi.org/10.1049/iet-map.2008.0082.
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Chima, R. V. "Calculation of Tip Clearance Effects in a Transonic Compressor Rotor." Journal of Turbomachinery 120, no. 1 (January 1, 1998): 131–40. http://dx.doi.org/10.1115/1.2841374.
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The flow through the tip clearance region of a transonic compressor rotor (NASA rotor 37) was computed and compared to aerodynamic probe and laser anemometer data. Tip clearance effects were modeled both by gridding the clearance gap and by using a simple periodicity model across the ungridded gap. The simple model was run with both the full gap height, and with half the gap height to simulate a vena-contracta effect. Comparisons between computed and measured performance maps and downstream profiles were used to validate the models and to assess the effects of gap height on the simple clearance model. Recommendations were made concerning the use of the simple clearance model. Detailed comparisons were made between the gridded clearance gap solution and the laser anemometer data near the tip at two operating points. The computed results agreed fairly well with the data but overpredicted the extent of the casing separation and underpredicted the wake decay rate. The computations were then used to describe the interaction of the tip vortex, the passage shock, and the casing boundary layer.
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Beyer, E. C., D. L. Paul, and D. A. Goodenough. "Connexin43: a protein from rat heart homologous to a gap junction protein from liver." Journal of Cell Biology 105, no. 6 (December 1, 1987): 2621–29. http://dx.doi.org/10.1083/jcb.105.6.2621.
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Northern blot analysis of rat heart mRNA probed with a cDNA coding for the principal polypeptide of rat liver gap junctions demonstrated a 3.0-kb band. This band was observed only after hybridization and washing using low stringency conditions; high stringency conditions abolished the hybridization. A rat heart cDNA library was screened with the same cDNA probe under the permissive hybridization conditions, and a single positive clone identified and purified. The clone contained a 220-bp insert, which showed 55% homology to the original cDNA probe near the 5' end. The 220-bp cDNA was used to rescreen a heart cDNA library under high stringency conditions, and three additional cDNAs that together spanned 2,768 bp were isolated. This composite cDNA contained a single 1,146-bp open reading frame coding for a predicted polypeptide of 382 amino acids with a molecular mass of 43,036 D. Northern analysis of various rat tissues using this heart cDNA as probe showed hybridization to 3.0-kb bands in RNA isolated from heart, ovary, uterus, kidney, and lens epithelium. Comparisons of the predicted amino acid sequences for the two gap junction proteins isolated from heart and liver showed two regions of high homology (58 and 42%), and other regions of little or no homology. A model is presented which indicates that the conserved sequences correspond to transmembrane and extracellular regions of the junctional molecules, while the nonconserved sequences correspond to cytoplasmic regions. Since it has been shown previously that the original cDNA isolated from liver recognizes mRNAs in stomach, kidney, and brain, and it is shown here that the cDNA isolated from heart recognizes mRNAs in ovary, uterus, lens epithelium, and kidney, a nomenclature is proposed which avoids categorization by organ of origin. In this nomenclature, the homologous proteins in gap junctions would be called connexins, each distinguished by its predicted molecular mass in kilodaltons. The gap junction protein isolated from liver would then be called connexin32; from heart, connexin43.
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Salehin, Khondaker M., and Roberto Rojas-Cessa. "Scheme for Measuring Queueing Delay of a Router Using Probe-Gap Model: The Single-Hop Case." IEEE Communications Letters 18, no. 4 (April 2014): 696–99. http://dx.doi.org/10.1109/lcomm.2014.030114.132775.
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Li, Bo, Yanquan Geng, and Yongda Yan. "Nano/Microscale Thermal Field Distribution: Conducting Thermal Decomposition of Pyrolytic-Type Polymer by Heated AFM Probes." Nanomaterials 10, no. 3 (March 7, 2020): 483. http://dx.doi.org/10.3390/nano10030483.
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In relevant investigations and applications of the heated atomic force microscope (AFM) probes, the determination of the actual thermal distribution between the probe and the materials under processing or testing is a core issue. Herein, the polyphthalaldehyde (PPA) film material and AFM imaging of the decomposition structures (pyrolytic region of PPA) were utilized to study the temperature distribution in the nano/microscale air gap between heated tips and materials. Different sizes of pyramid decomposition structures were formed on the surface of PPA film by the heated tip, which was hovering at the initial tip–sample contact with the preset temperature from 190 to 220 °C for a heating duration ranging from 0.3 to 120 s. According to the positions of the 188 °C isothermal surface in the steady-state probe temperature fields, precise 3D boundary conditions were obtained. We also established a simplified calculation model of the 3D steady-state thermal field based on the experimental results, and calculated the temperature distribution of the air gap under any preset tip temperature, which revealed the principle of horizontal (<700 nm) and vertical (<250 nm) heat transport. Based on our calculation, we fabricated the programmable nano-microscale pyramid structures on the PPA film, which may be a potential application in scanning thermal microscopy.
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Ghosh, Sudip Kumar, Subhradeep Chakraborty, L. Lolit Kumar Singh, and Sudipta Chattopadhyay. "Modal analysis of probe-fed circular sector microstrip antenna with and without variable air gap: Investigation with modified cavity model." International Journal of RF and Microwave Computer-Aided Engineering 28, no. 1 (September 7, 2017): e21172. http://dx.doi.org/10.1002/mmce.21172.
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Fazli, Norodin, Ali Koochi, Asieh Sadat Kazemi, and Mohamadreza Abadyan. "Influence of electrostatic force and the van der Waals attraction on the pull-in instability of the CNT-based probe–actuator." Canadian Journal of Physics 92, no. 9 (September 2014): 1047–57. http://dx.doi.org/10.1139/cjp-2013-0202.
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In recent years, carbon nanotubes (CNTs) have attracted great attention in the fabrication of probe tips and actuators for scanning microscopes. Herein, the pull-in instability of CNT-based probe is investigated using a nanoscale continuum model. The Euler–Bernoulli beam theory is applied to model the elastic response of the CNT. The van der Waals attraction is computed from the simplified Lennard-Jones potential. Two analytical methods (i.e., Homotopy perturbation method and Adomian decomposition method) are applied to solve the nonlinear governing equation of the system. Furthermore, the obtained results are validated by comparing with experimental results in the literature as well as numerical solutions of the finite difference method. The pull-in parameters are determined and effect of van der Waals force and a geometrical parameter effect on the instability behavior of the CNT is discussed. Moreover, the detachment length and minimum initial gap of the freestanding CNT probe are determined.
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Rettig, L., J. H. Chu, I. R. Fisher, U. Bovensiepen, and M. Wolf. "Coherent dynamics of the charge density wave gap in tritellurides." Faraday Discuss. 171 (2014): 299–310. http://dx.doi.org/10.1039/c4fd00045e.
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The dynamics of the transient electronic structure in the charge density wave (CDW) system RTe3 (R = rare-earth element) is studied using time- and angle-resolved photoemission spectroscopy (trARPES). Employing a three-pulse pump–probe scheme we investigate the effect of the amplitude mode oscillations on the electronic band structure and, in particular, on the CDW energy gap. We observe coherent oscillations in both lower and upper CDW band with opposite phases, whereby two dominating frequencies are modulating the CDW order parameter. This demonstrates the existence of more than one collective amplitude mode, in contrast to a simple Peierls model. Coherent control experiments of the two amplitude modes, which are strongly coupled in equilibrium, demonstrate independent control of the modes suggesting a decoupling of both modes in the transient photoexcited state.
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Frenken, Joost, and Bas Hendriksen. "The Reactor-STM: A Real-Space Probe for Operando Nanocatalysis." MRS Bulletin 32, no. 12 (December 2007): 1015–21. http://dx.doi.org/10.1557/mrs2007.210.
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Abstract“Looking” on the other side of the pressure gap in heterogeneous catalysis is an essential step in identifying and understanding differences and similarities between the behavior of catalysts under actual operation conditions (operando) and under the nearvacuum conditions of traditional laboratory experiments. In this article, we demonstrate that real-space, atomic-scale imaging of active catalyst surfaces is possible under realistic or semirealistic reaction conditions with the reactor-STM, a scanning tunneling microscope that is fully integrated with a miniature flow reactor and housed inside an ultrahigh-vacuum system. This special-purpose instrument combines the merits of standard surface-science methods with operando STM observations of model catalysts in action. We illustrate the strength of this microscope with examples of CO oxidation on platinum surfaces.
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Bian, Xingyuan, Junning Cui, Yesheng Lu, Yamin Zhao, Zhongyi Cheng, and Jiubin Tan. "Quantitative Investigation of Surface Charge Distribution and Point Probing Characteristics of Spherical Scattering Electrical Field Probe for Precision Measurement of Miniature Internal Structures with High Aspect Ratios." Applied Sciences 10, no. 15 (July 30, 2020): 5268. http://dx.doi.org/10.3390/app10155268.
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For precision measurement of miniature internal structures with high aspect ratios, a spherical scattering electrical field probe (SSEP) is proposed based on charge signal detection. The characteristics and laws governing surface charge distribution on the probing ball of the SSEP are analyzed, with the spherical scattering electrical field modeled using a 3D seven-point finite difference method. The model is validated with finite element simulation by comparing with the analysis results of typical situations, in which probing balls of different diameters are used to probe a grounded plane with a probing gap of 0.3 μm. Results obtained with the proposed model and finite element method (FEM) simulation indicate that 31% of the total surface charge on a ϕ1 mm probing ball concentrates in an area that occupies 1% of the total probing ball surface. Moreover, this surface charge concentration remains unchanged when the surface being measured varies in geometry, or when the probing gap varies in sensing range. Based on this, the SSEP has realized approximate point probing capability with a virtual “needle” of electrical effect. Together with its non-contact sensing characteristics and 3D isotropy, it can, therefore, be concluded that the SSEP has great potential to be an ideal solution for precision measurement of miniature internal structures with high aspect ratios.
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Yaras, M. I., and S. A. Sjolander. "Effects of Simulated Rotation on Tip Leakage in a Planar Cascade of Turbine Blades: Part I—Tip Gap Flow." Journal of Turbomachinery 114, no. 3 (July 1, 1992): 652–59. http://dx.doi.org/10.1115/1.2929189.
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The paper presents further results from a continuing study on tip leakage in axial turbines. Rotation has been simulated in a linear cascade test section by using a moving-belt tip wall. Measurements were made inside the tip gap with a three-hole pressure probe for a clearance size of 3.8 percent of the blade chord. Two wall speeds are considered and the results are compared with the case of no rotation. As in other experiments, significant reduction in the gap mass flow rate is observed due to the relative motion. The detailed nature of the measurements allows the dominant physical mechanism by which wall motion affects the tip gap flow to be identified. Based on the experimental observations, an earlier model for predicting the tip gap flow field is extended to the case of relative wall motion. Part II of the paper examines the effect of the relative motion on the downstream flow field and the blade loading.
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Pfau, A., J. Schlienger, D. Rusch, A. I. Kalfas, and R. S. Abhari. "Unsteady Flow Interactions Within the Inlet Cavity of a Turbine Rotor Tip Labyrinth Seal." Journal of Turbomachinery 127, no. 4 (March 1, 2003): 679–88. http://dx.doi.org/10.1115/1.2008973.
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This paper focuses on the flow within the inlet cavity of a turbine rotor tip labyrinth seal of a two stage axial research turbine. Highly resolved, steady and unsteady three-dimensional flow data are presented. The probes used here are a miniature five-hole probe of 0.9 mm head diameter and the novel virtual four sensor fast response aerodynamic probe (FRAP) with a head diameter of 0.84mm. The cavity flow itself is not only a loss producing area due to mixing and vortex stretching, it also adversely affects the following rotor passage through the fluid that is spilled into the main flow. The associated fluctuating mass flow has a relatively low total pressure and results in a negative incidence to the rotor tip blade profile section. The dominating kinematic flow feature in the region between cavity and main flow is a toroidal vortex, which is swirling at high circumferential velocity. It is fed by strong shear and end wall fluid from the pressure side of the stator passage. The static pressure field interaction between the moving rotor leading edges and the stator trailing edges is one driving force of the cavity flow. It forces the toroidal vortex to be stretched in space and time. A comprehensive flow model including the drivers of this toroidal vortex is proposed. This labyrinth seal configuration results in about 1.6% turbine efficiency reduction. This is the first in a series of papers focusing on turbine loss mechanisms in shrouded axial turbines. Additional measurements have been made with variations in seal clearance gap. Initial indications show that variation in the gap has a major effect on flow structures and turbine loss.
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Shi, Yan Ping, and Shu Hua Fan. "Application of Magnetoelastic Effect of Ferromagnetic Material in Stress Measurement." Advanced Materials Research 496 (March 2012): 306–9. http://dx.doi.org/10.4028/www.scientific.net/amr.496.306.
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A new non-contact sensor with three magnetic pole based on magnetoelastic effect was designed, and its operation principle and mathematical model of induced voltage output were given. The output characteristic of the sensor affected by field current intensity, frequency, and the gap between the probe of the sensor and the surface of the material tested was analyzed by testing. The calculation result based on the output model found by the paper accord basically with the test result. The results of the test have showed that the measuring precision and sensitivity of the sensor can meet the demands of the general practical application.
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Furukawa, Shigeto, Katuhiro Maki, Makio Kashino, and Hiroshi Riquimaroux. "Dependency of the Interaural Phase Difference Sensitivities of Inferior Collicular Neurons on a Preceding Tone and Its Implications in Neural Population Coding." Journal of Neurophysiology 93, no. 6 (June 2005): 3313–26. http://dx.doi.org/10.1152/jn.01219.2004.
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This study examined the sensitivities of the neuronal responses in the inferior colliculus (IC) to the interaural phase difference (IPD) of a preceding tone, and explored its implications in the neural-population representation of the IPD. Single-unit responses were recorded from the IC of anesthetized gerbils. The stimulus was a dichotic tone sequence with a common frequency (typically the unit’s best frequency) and level (10–20 dB relative to the threshold), consisting of a conditioner (200 ms) followed by a probe (50 ms) with a silent gap (5–100 ms) between them. The IPDs of the 2 tones were varied independently. The presence of a conditioner generally suppressed the probe-driven responses; the effect size increased as the conditioner IPD approached the unit’s most responsive IPD. The units’ preferred IPDs were relatively invariant with the conditioner IPD. Two types of models were used to evaluate the effects of a conditioner on the IPD representation at the level of IC neural population. One was a version of the population-vector model. The other was the hemispheric-channel model, which assumed that the stimulus IPD is represented by the activities of 2 broadly tuned hemispheric channels. Both models predicted that, in the presence of a conditioner, the IPD representation would shift in a direction away from the conditioner IPD. This appears to emphasize the difference between the conditioner and the probe IPDs. The results indicate that in the IC, neural processes for IPD adapt to the stimulus history to enhance the representational contrast between successive sounds.
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KOOCHI, ALI, ASIEHSADAT KAZEMI, and MOHAMADREZA ABADYAN. "SIMULATING DEFLECTION AND DETERMINING STABLE LENGTH OF FREESTANDING CARBON NANOTUBE PROBE/SENSOR IN THE VICINITY OF GRAPHENE LAYERS USING A NANOSCALE CONTINUUM MODEL." Nano 06, no. 05 (October 2011): 419–29. http://dx.doi.org/10.1142/s1793292011002731.
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Herein, the deflection and instability of a freestanding carbon nanotube (CNT) probe/sensor in the vicinity of the graphene layers are investigated. A nanoscale continuum model is employed to obtain nonlinear constitutive equation of freestanding CNT. The van der Waals attraction is computed from the simplified Lennard-Jones potential for two common engineering cases including large and small number of graphene layers. Four approaches, i.e., approximated function, homotopy perturbation method, lumped parameter model and numerical analysis, are employed to solve the governing equation of CNT. The intermolecular force-induced deflection, minimum initial gap and stable length of freestanding CNT are determined. The analytical results agree well with the numerical solutions.
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Smirnov-Pinchukov, Grigorii V., Dmitry A. Semenov, Vitaly V. Akimkin, and Thomas Henning. "Using HCO+ isotopologues as tracers of gas depletion in protoplanetary disk gaps." Astronomy & Astrophysics 644 (November 24, 2020): A4. http://dx.doi.org/10.1051/0004-6361/202038572.
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Context. The widespread rings and gaps seen in the dust continuum in protoplanetary disks are sometimes accompanied by similar substructures seen in molecular line emission. One example is the outer gap at ~100 au in AS 209, which shows that the H13CO+ and C18O emission intensities decrease along with the continuum in the gap, while the DCO+ emission increases inside the gap. Aims. We aim to study the behavior of DCO+/H13CO+ and DCO+/HCO+ ratios in protoplanetary disk gaps assuming the two scenarios: (A) the gas depletion follows the dust depletion and (B) only the dust is depleted. Methods. We first modeled the physical disk structure using the thermo-chemical model ANDES. This 1+1D steady-state disk model calculates the thermal balance of gas and dust and includes the far ultraviolet, X-rays, cosmic rays, and other ionization sources together with the reduced chemical network for molecular coolants. Afterward, this physical structure was adopted for calculations of molecular abundances with the extended gas-grain chemical network with deuterium fractionation. Ideal synthetic spectra and 0th-moment maps were produced with the LIne Modeling Engine. Results. We are able to qualitatively reproduce the increase in the DCO+ intensity and the decrease in the H13CO+ and C18O intensities inside the disk gap, which is qualitatively similar to what is observed in the outer AS 209 gap. The corresponding disk model (A) assumes that both the gas and dust are depleted in the gap. The model (B) with the gas-rich gap, where only the dust is depleted, produces emission that is too bright in all HCO+ isotopologues and C18O. Conclusions. The DCO+/H13CO+ line ratio can be used to probe gas depletion in dust continuum gaps outside of the CO snow line. The DCO+/C18O line ratio shows a similar, albeit weaker, effect; however, these species can be observed simultaneously with a single (sub)mm interferometer setup.
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Chen, Ying, Rebekah Wu, James Felton, David M. Rocke, and Anu Chakicherla. "A Method to Detect Differential Gene Expression in Cross-Species Hybridization Experiments at Gene and Probe Level." Biomedical Informatics Insights 3 (January 2010): BII.S3846. http://dx.doi.org/10.4137/bii.s3846.
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Motivation Whole genome microarrays are increasingly becoming the method of choice to study responses in model organisms to disease, stressors or other stimuli. However, whole genome sequences are available for only some model organisms, and there are still many species whose genome sequences are not yet available. Cross-species studies, where arrays developed for one species are used to study gene expression in a closely related species, have been used to address this gap, with some promising results. Current analytical methods have included filtration of some probes or genes that showed low hybridization activities. But consensus filtration schemes are still not available. Results A novel masking procedure is proposed based on currently available target species sequences to filter out probes and study a cross-species data set using this masking procedure and gene-set analysis. Gene-set analysis evaluates the association of some priori defined gene groups with a phenotype of interest. Two methods, Gene Set Enrichment Analysis (GSEA) and Test of Test Statistics (ToTS) were investigated. The results showed that masking procedure together with ToTS method worked well in our data set. The results from an alternative way to study cross-species hybridization experiments without masking are also presented. We hypothesize that the multi-probes structure of Affymetrix microarrays makes it possible to aggregate the effects of both well-hybridized and poorly-hybridized probes to study a group of genes. The principles of gene-set analysis were applied to the probe-level data instead of gene-level data. The results showed that ToTS can give valuable information and thus can be used as a powerful technique for analyzing cross-species hybridization experiments. Availability Software in the form of R code is available at http://anson.ucdavis.edu/~ychen/cross-species.html Supplementary Data Supplementary data are available at http://anson.ucdavis.edu/~ychen/cross-species.html
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Eslami Pirharati, Mahmoud, Hans-W. Krauss, Carsten Schilde, and Dirk Lowke. "Effect of Different Shear Rates on Particle Microstructure of Cementitious Materials in a Wide Gap Vane-in-cup Rheometer." Materials 13, no. 9 (April 27, 2020): 2035. http://dx.doi.org/10.3390/ma13092035.
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Rheological properties of cementitious suspensions are affected not only by their mixture composition but also by process-related factors such as shear history. To enable a model-based description, investigations were carried out on the effect of shear history (shear rate variation over time) on the cement paste agglomeration state. Therefore, a Focused Beam Reflectance Measurement (FBRM) system and a wide gap rheometer were coupled to study the relation between shear history and in-situ chord length distribution simultaneously, indicating particle agglomeration. Hence, the effect of average shear rates (resulting from the applied shear profile), as well as shear rate distribution within the gap (local shear rates) on the particle agglomeration state have been investigated. The rheological properties of cement paste were evaluated with the Reiner–Riwlin approach. Furthermore, the agglomeration state of the particles was compared for different average shear rates and local shear rates at various positions of the FBRM probe. The results show that the median chord length increases in all positions when the average shear rate is decreased, indicating increasing particle agglomeration. Moreover, due to variable local shear rates at different FBRM probe positions, different agglomeration states are observed, resulting from two factors, shear rate dependent particle agglomeration and shear-induced particle migration.
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Majzoub, Salam, and Mehmet Aga. "Characterizing the Gap between Accounting Education and Practice: Evidence from Lebanon." International Journal of Business and Management 10, no. 12 (November 19, 2015): 127. http://dx.doi.org/10.5539/ijbm.v10n12p127.
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<p>Over the past few decades, there has been a widening gap between accounting education and accounting practice. In this article, we present a novel framework that aims to understand this gap by analyzing the accounting educational system and profession from the perspective of the International Accounting Education Standards (IAES). We further consider Lebanon as a case study for thoroughly investigating the accounting educational system and characterizing the gap.</p><p> This study is the first of its kind in analyzing the five main groups of stakeholders in this system (fresh graduates, employees, professors, department heads, and employers) and comparing their perspectives about the competencies of accounting graduates. As part of our framework, we introduce a model that captures the interactions between the various stakeholders of the accounting educational and professional system. We then thoroughly probe the various components of this model theoretically, as well as through qualitative and quantitative studies.</p>Our findings show that while, theoretically, the accounting curriculum incorporates the competencies stipulated by the IAES, in practice, there is a large gap in how the various stakeholders assess the proficiencies of fresh accounting graduates in these competencies. Alarmingly, employers believe that accounting graduates lack the required technical competencies for the job market, while professors, department heads, and students believe that fresh graduates have acquired the required competencies by the time of graduation. In this paper, we investigate the reasons for this gap, characterize it in details, and propose recommendations for bridging it.
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Sharan, Alok, M. Ashok Kumar, and N. P. Anusha. "FDTD Modelling of 1D Photonic Crystal comprised of Double Positive and Double Negative Metamaterial for Thermal Masking Application with CPML Absorbing Boundary Condition." Defence Science Journal 67, no. 2 (March 14, 2017): 224. http://dx.doi.org/10.14429/dsj.67.9850.
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<p>Periodic structures of double positive and double negative metamaterial of thickness of λ/4 is designed to stop long-wave infrared and mid-wave infrared frequencies for masking from infrared detection devices. Band-gaps are obtained by calculating reflection and transmission coefficients at probe point close to the front and back faces of the periodic structure. 1D- finite difference time domain method is implemented in Matlab to study the electromagnetic wave propagation which is incident normal to a periodic stack of double positive and double negative metamaterial of having refractive indices of 9 and -6 respectively, at centre wavelength. Drude model is adapted to model double negative medium. Band-gap obtained are compared with the conventional photonic crystal by replacing the double negative medium with a double positive medium with the magnitude of refractive index same as that of double negative medium. Band-gap obtained confirms the presence of Zero-n͂ band-gap in DPS-DNG photonic crystal which is wider than the reflection band in conventional photonic crystal; nearly twice in mid-wave infrared region and five times in long-wave infrared region. A novel and highly efficient convolutional perfectly matched layer absorbing boundary condition is used to terminate the infinite computational finite difference time domain lattices.</p>
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Basu, Rahul, and Tanumoy Mandal. "Graviton Signals in Central Production at the LHC." Advances in High Energy Physics 2013 (2013): 1–17. http://dx.doi.org/10.1155/2013/652714.
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We study central production, in the inclusive case, to look for graviton signals in a large extra dimensional model using dilepton and diphoton channels. We carefully analyze signal and possible standard model background processes and study the feasibility of such new physics searches in a relatively clean environment as in central production where the proton fragments are mostly emitted in the forward direction, and there is a clear rapidity gap between them and the centrally produced system. Our analysis shows that the LHC with 14 TeV center of mass energy and 100 fb−1(300 fb−1) of integrated luminosity can probe the effective gravity scale up to 3.6 TeV (4.4 TeV) in both the dilepton and diphoton channels.
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Sun, Hao, Hong Ma, and Jiancai Leng. "Femtosecond Pump Probe Reflectivity Spectra in CdTe and GaAs Crystals at Room Temperature." Materials 13, no. 1 (January 6, 2020): 242. http://dx.doi.org/10.3390/ma13010242.
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Ultrafast pump probe reflectivity (PPR) signal near band edge is modeled by taking into account band filling (BF) and band gap renormalization (BGR) effects with the carrier density of ~1017/cm3 in GaAs crystal at room temperature. The calculated results indicate that the transient reflectivity ΔR/R is determined by BF and BGR effects. The most interesting feature is that ΔR/R signal experiences a sign change from photo-bleaching (PB) to photo-absorption (PA) due to the competition between BF and BGR effects. We experimentally measured ΔR as a function of photon energy across band edge with carrier density of ~1017/cm3 in GaAs and CdTe crystals, which has a similar trend as that calculated according to our model. In addition, the reflectivity is very sensitive to electron spin orientation, which is well confirmed by the corresponding experiments with 100 fs pump probe reflectivity spectroscopy in bulk CdTe. Our research in this work provides a method to study optoelectronic properties of conventional semiconductors at moderate carrier density excited by ultrafast laser pulse. Importantly, this model can be used for other novel semiconductor materials beyond GaAs and will provide new insights into the underlying spin dependent photophysics properties for new materials.
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Karn-orachai, Kullavadee. "Gap-Dependent Surface-Enhanced Raman Scattering (SERS) Enhancement Model of SERS Substrate–Probe Combination Using a Polyelectrolyte Nanodroplet as a Distance Controller." Langmuir 37, no. 36 (August 31, 2021): 10776–85. http://dx.doi.org/10.1021/acs.langmuir.1c01556.
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Jin, Lan, Yonggui Cheng, Kai Zhang, Zhangna Xue, and Jianlin Liu. "Axisymmetric model of the sealing cylinder in service: analytical solutions." Journal of Mechanics 37 (2021): 404–14. http://dx.doi.org/10.1093/jom/ufab010.
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Abstract The stress state analysis of the sealing cylinder is of great significance for the safe operation of the sealing system. In this study, we probe a sealing system that can be simplified as an axisymmetric problem. In service, the rubber around the central pipe contacts the casing under the action of the axial pressure, and thus the sealing function is realized. The analytical solution of the stress at the sealing interface is derived based on the Love strain function in the axisymmetric configuration. Then, the relationship between the axial pressure and the gap (between the sealing cylinder and the casing) is presented, and the contact pressure at the contact interface is also given. The numerical simulation is performed, which is in agreement with the analytical solutions in the two deformation stages. The obtained results in the current work have also been comprehensively compared with the previous results, to give suggestions for engineering selection. These findings are beneficial to obtain a deep understanding on the mechanism of the sealing process, and provide some inspirations on the new types of sealing tools for mechanical engineering, chemical engineering, petroleum engineering, etc.
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CAMUSSI, R., J. GRILLIAT, G. CAPUTI-GENNARO, and M. C. JACOB. "Experimental study of a tip leakage flow: wavelet analysis of pressure fluctuations." Journal of Fluid Mechanics 660 (August 5, 2010): 87–113. http://dx.doi.org/10.1017/s0022112010002570.
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A wavelet-based conditional analysis of unsteady flow and sound signals highlights the role of intermittent perturbations both in the sound generation and the unsteady field of an aerofoil tip leakage flow experiment. It is shown how the most probable flow perturbations generated at the pressure side tip edge are convected through the gap and swept downstream along the suction side past the trailing edge tip corner, where they radiate sound. The nascent sound sources are identified and localized in the clearance between 40% and 60% of the chord. It is also found that the time dependence of the averaged intermittent structures scales with the inverse of the square root of the mean velocity and a physical interpretation based on a simple potential vortex model is proposed. The data are retrieved from an experiment that has been carried out at low Mach number (Ma < 0.3) in an anechoic test facility. A single motionless instrumented NACA 5510 aerofoil was mounted into the potential core of an open rectangular jet between two plates with an adjustable clearance. The tip leakage flow was ensured by the 5% camber and a 15° angle of attack. A large database obtained by a variety of measurement techniques is thus available for the present analysis. More specifically, the conditional approach is applied to joint far field, wall pressure and particle image velocimetry (PIV) measurements. The wall pressure probes are located along the suction side tip edge and on the tip inside the gap, whereas the PIV plane is parallel to the mid-gap plane. Additional joint wall pressure and single hot-wire anemometry (HWA) measurements are also analysed with a hot-wire probe located near the trailing edge tip corner. The conditional averaging is triggered by high-energy wavelet events selected in a reference signal by setting a threshold to the so-called local intermittency measure.
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Su, M., J. L. Borke, H. J. Donahue, Z. Li, N. M. Warshawsky, C. M. Russell, and J. E. Lewis. "Expression of Connexin 43 in Rat Mandibular Bone and Periodontal Ligament (PDL) Cells during Experimental Tooth Movement." Journal of Dental Research 76, no. 7 (July 1997): 1357–66. http://dx.doi.org/10.1177/00220345970760070501.
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Bone remodeling in response to force requires the coordinated action of osteoblasts, osteoclasts, osteocytes, and periodontal ligament cells. Coordination among these cells may be mediated, in part, by cell-to-cell communication via gap junctions. This study tests the hypothesis that the regulation of expression of connexin 43, a gap junction protein, is part of the transduction mechanism between force as applied to bone during orthodontic tooth movement and bone remodeling. To test this hypothesis, we examined connexin 43 expression in a rat model system of experimental tooth movement. To establish the model, we extracted maxillary first molars to initiate supra-eruption of opposing mandibular molars. The rats were killed at 0, 6, 12, 24, and 48 hrs post-extraction. The mandibles were removed, demineralized, and embedded in paraffin. To localize connexin 43 protein and mRNA, we used a specific antibody for immunohistochemistry and a specific cDNA probe for in situ hybridization. Western and Northern blot analyses were used to assess the specificity of the connexin 43 antibody and cDNA probe, respectively. We found connexin 43 protein expressed by osteoclasts (++++) and periodontal ligament cells (+++) in compression zones, and by osteoblasts (++++) and osteocytes (++++) in tension zones of the periodontal ligament. In addition, connexin 43 mRNA was found in some bone and periodontal ligament cells. Connexin 43 protein was found, by densitometric analysis, to be higher in the periodontal ligament after exposure to force compared with controls (P < 0.001). The number of osteocytes expressing connexin 43 48 hrs after molar extraction was also significantly greater in bone subjected to tension when compared with controls (P < 0.001). The results of this study support the hypothesis that connexin 43 plays a role in the coordination of events during experimentally induced alveolar bone remodeling.
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El-Batsh, Hesham M., and Magdy Bassily Hanna. "An Investigation on the Effect of Endwall Movement on the Tip Clearance Loss Using Annular Turbine Cascade." International Journal of Rotating Machinery 2011 (2011): 1–11. http://dx.doi.org/10.1155/2011/489150.
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The aerodynamic losses in gas turbines are mainly caused by profile loss secondary flow, and tip leakage loss. This study focuses on tip leakage flow of high-pressure turbine stages. An annular turbine cascade was constructed with fixed blades on the casing, and the distance between blade tip and the hub was considered as tip clearance gap. The effect of endwall movement on loss mechanism was investigated by using experimental and numerical techniques. The measurements were obtained while the hub was fixed but the numerical calculations were carried out for both stationary and moving cascades. Upstream and downstream flows were measured by using a calibrated five-hole pressure probe. The steady incompressible turbulent flow was obtained by solving Reynolds averaged Navier-Stokes equations and by employing shear stress transport (SST)k-ωturbulence model. The total pressure loss coefficient obtained from the numerical technique was compared with the experimental measurements, and the comparison showed good agreement. Tip clearance vortices were observed in the tip clearance gap. It was found through this study that end-wall movement reduces tip leakage loss through the cascade.
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Li, Xiaohu, Julia N. Wagner, Andreas Stark, Robert Koos, Martin Landesberger, Michael Hofmann, Guohua Fan, Weimin Gan, and Winfried Petry. "Carbon Redistribution Process in Austempered Ductile Iron (ADI) During Heat Treatment—APT and Synchrotron Diffraction Study." Metals 9, no. 7 (July 16, 2019): 789. http://dx.doi.org/10.3390/met9070789.
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In-situ synchrotron diffraction and atom probe tomography (APT) have been used to study the carbon diffusion and redistribution process in austempered ductile iron (ADI) during austempering. The process of carbon content change in bainitic ferrite during different austempering temperatures has been determined quantitatively. The transformation in ADI is controlled by decarburization of supersaturated ferrite and carbide precipitation and has been found to be divided into three stages based on a model developed for bainitic steels by Takahashi and Bhadeshia. The formation, morphology and composition of carbides and carbon clusters in ferrite after austempering have been identified unequivocally by APT. Finally, the relationships of carbon content in ferrite, carbon gap values, and austempering temperatures in the ADI alloy were expressed using empirical equations.
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Jäck, Berthold, Yonglong Xie, Jian Li, Sangjun Jeon, B. Andrei Bernevig, and Ali Yazdani. "Observation of a Majorana zero mode in a topologically protected edge channel." Science 364, no. 6447 (June 13, 2019): 1255–59. http://dx.doi.org/10.1126/science.aax1444.
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Superconducting proximity pairing in helical edge modes, such as those of topological insulators, is predicted to provide a unique platform for realizing Majorana zero modes (MZMs). We used scanning tunneling microscopy measurements to probe the influence of proximity-induced superconductivity and magnetism on the helical hinge states of bismuth(111) films grown on a superconducting niobium substrate and decorated with magnetic iron clusters. Consistent with model calculations, our measurements revealed the emergence of a localized MZM at the interface between the superconducting helical edge channel and the iron clusters, with a strong magnetization component along the edge. Our experiments also resolve the MZM’s spin signature, which distinguishes it from trivial in-gap states that may accidentally occur at zero energy in a superconductor.
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Ali Mohammed, Hussein. "Structures of vortex in Co-doped BaFe2As2 iron superconductors with different doping level by scanning Hall probe microscopy." Tikrit Journal of Pure Science 22, no. 11 (October 28, 2018): 55. http://dx.doi.org/10.25130/j.v22i11.720.
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The 122 iron arsenide unconventional superconductors are part of a new class of iron-based superconductors. Co-doped BaFe2xCoxAs2 (Ba-122) iron superconductors sample have been examine by scanning Hall probe microscopy (SHPM) technique to find out the magnetic properties of Ba-122 . Has been completed the evolution of profiles of vortices which has well isolated and it is as function of temperature, then utilized suitable technique to extract the temperature depending on penetration depth, .So, this allowed to deduce the temperature dependent on density of superfluid and it has been compared with α-model consequences for a (2-band) of superconductor. When the superfluid density for the BaFe2xCoxAs2 (Over D x= 0.113) sample. As result, the two gap -model has been fitted to the data with Δ1=4.25kTc, Δ2=1.92kTc , =0.708, 1=0.293 then a2=1. However, When values of for the BaFe2-xCoxAs2 (Over D x= 0.075) sample. Result of the superfluid density for BaFe2-xCoxAs2 with parameters are (Δ1=3.9k, Δ2=1.6k), =0.615 for Δ1, and =0.237, =1. Suitable parameters produce refer into the symmetry of the order parameter at hole pockets with the electron, and then the relative supports of the bands to the density of superfluid in the iron-based crystals.
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CHEAH, K. W., T. Y. LEUNG, M. H. CHAN, and S. K. SO. "STUDY OF POROUS SILICON SURFACE PROPERTIES." Surface Review and Letters 03, no. 02 (April 1996): 1235–39. http://dx.doi.org/10.1142/s0218625x96002230.
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Porous silicon is a material with a coral-like structure which has a fractal surface. To study these aspects of porous silicon and its relationship with the luminescence property, we have used atomic force microscopy (AFM). Samples were prepared using either pure HF or HF diluted with ethanol. From the results of AFM, distinct structural difference was observed from samples prepared by these two etchants. If we relate the structures to their respective photoluminescence spectra, it appears that finer structure produced shorter wavelength peak photoluminescence. However, the columns of the samples were too large for one to attribute the luminescence to quantum confinement only. Hence, an alternative model may be required to explain the luminescence mechanism. We have also observed that the composition of the etchant can also affect the evolution of the fractal dimension with respect to etching time. Probing of the surfcace electron states was performed using photothermal deflection spectroscopy (PDS). In order to ensure that only porous silicon layer was probed, free-standing films of various porosity were produced for the PDS measurement. The probe energy range was from 0.56 eV to 2.5 eV so that both the bulk states and the surface states were probed. The results showed that there is a clear blueshift of the energy band gap with respect to porosity, and the absorption coefficient decreases with porosity increase at a fixed photon energy. Overtones of hydrides and fluorides of silicon were also observed.
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Alnoaimi, K. R., C. Duchateau, and A. R. Kovscek. "Characterization and Measurement of Multiscale Gas Transport in Shale-Core Samples." SPE Journal 21, no. 02 (April 14, 2016): 573–88. http://dx.doi.org/10.2118/2014-1920820-pa.
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Summary This work introduces an experimental technique to probe simultaneously flow and diffusion of gas through shale. A core-scale pressure-pulse-decay experiment is used to study the upstream- and downstream-pressure responses of Eagle Ford and Haynesville shale samples. With the aid of numerical models, the pressure histories obtained from the experiments are matched and gas and rock properties are obtained. The experiments are conducted at varying pore pressure and net effective stress to understand the sensitivity of the rock porosity and permeability as well as the gas diffusivity. A dual-porosity model is constructed to examine gas transport through a system of micropores and microcracks. In this sense, the role of the two different-sized pore systems is deconvolved. In some cases, the micropore system carries roughly one-third of the gas flow. The porosity, permeability, and diffusivity obtained assign physical properties to the macroscales and microscales simultaneously. Results bridge the gap between these scales and improve our understanding of how to assign transport physics to the correct pore scale.
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Mathias, R. T., J. L. Rae, and G. J. Baldo. "Physiological properties of the normal lens." Physiological Reviews 77, no. 1 (January 1, 1997): 21–50. http://dx.doi.org/10.1152/physrev.1997.77.1.21.
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The lens is an avascular organ suspended between the aqueous and vitreous humors of the eye. The cellular structure is symmetric about an axis passing through its anterior and posterior poles but asymmetric about a plane passing through its equator. Because of its asymmetric structure, the lens has historically been assumed to perform transport between the aqueous and vitreous humors. Indeed, when anterior and posterior surfaces were isolated in an Ussing chamber, a translens current was measured. However, in the eye, the two surfaces are not isolated. The vibrating probe technique showed the current densities at the surface of a free-standing lens were surprisingly large, about an order of magnitude greater than measured in an Ussing chamber, and were not directed across the lens. Rather, they were inward in the region of either anterior or posterior pole and outward at the equator. This circulating current is the most dramatic physiological property of a normal lens. We believe it is essential to maintain clarity; hence, this review focuses on factors likely to drive and direct it. We review properties and spatial distribution of lens Na+/K+ pumps, ion channels, and gap junctions. Based on these data, we propose a model in which the difference in electromotive potential of surface versus interior cell membranes drives the current, whereas the distribution of gap junctions directs the current in the observed pattern. Although this model is clearly too simple, it appears to quantitatively predict observed currents. However, the model also predicts fluid will move in the same pattern as ionic current. We therefore speculate that the physiological role of the current is to create an internal circulatory system for the avascular lens.
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Pivato, Mattia, Luca Carniello, Daniele Pietro Viero, Chiara Soranzo, Andrea Defina, and Sonia Silvestri. "Remote Sensing for Optimal Estimation of Water Temperature Dynamics in Shallow Tidal Environments." Remote Sensing 12, no. 1 (December 21, 2019): 51. http://dx.doi.org/10.3390/rs12010051.
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Given the increasing anthropogenic pressures on lagoons, estuaries, and lakes and considering the highly dynamic behavior of these systems, methods for the continuous and spatially distributed retrieval of water quality are becoming vital for their correct monitoring and management. Water temperature is certainly one of the most important drivers that influence the overall state of coastal systems. Traditionally, lake, estuarine, and lagoon temperatures are observed through point measurements carried out during field campaigns or through a network of sensors. However, sporadic measuring campaigns or probe networks rarely attain a density sufficient for process understanding, model development/validation, or integrated assessment. Here, we develop and apply an integrated approach for water temperature monitoring in a shallow lagoon which incorporates satellite and in-situ data into a mathematical model. Specifically, we use remote sensing information to constrain large-scale patterns of water temperature and high-frequency in situ observations to provide proper time constraints. A coupled hydrodynamic circulation-heat transport model is then used to propagate the state of the system forward in time between subsequent remote sensing observations. Exploiting the satellite data high spatial resolution and the in situ measurements high temporal resolution, the model may act a physical interpolator filling the gap intrinsically characterizing the two monitoring techniques.
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Dzedzickis, Andrius, Vytautas Bucinskas, Darius Viržonis, Nikolaj Sesok, Arturas Ulcinas, Igor Iljin, Ernestas Sutinys, Sigitas Petkevicius, Justinas Gargasas, and Inga Morkvenaite-Vilkonciene. "Modification of the AFM Sensor by a Precisely Regulated Air Stream to Increase Imaging Speed and Accuracy in the Contact Mode." Sensors 18, no. 8 (August 16, 2018): 2694. http://dx.doi.org/10.3390/s18082694.
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Increasing the imaging rate of atomic force microscopy (AFM) without impairing of the imaging quality is a challenging task, since the increase in the scanning speed leads to a number of artifacts related to the limited mechanical bandwidth of the AFM components. One of these artifacts is the loss of contact between the probe tip and the sample. We propose to apply an additional nonlinear force on the upper surface of a cantilever, which will help to keep the tip and surface in contact. In practice, this force can be produced by the precisely regulated airflow. Such an improvement affects the AFM system dynamics, which were evaluated using a mathematical model that is presented in this paper. The model defines the relationships between the additional nonlinear force, the pressure of the applied air stream, and the initial air gap between the upper surface of the cantilever and the end of the air duct. It was found that the nonlinear force created by the stream of compressed air (aerodynamic force) prevents the contact loss caused by the high scanning speed or the higher surface roughness, thus maintaining stable contact between the probe and the surface. This improvement allows us to effectively increase the scanning speed by at least 10 times using a soft (spring constant of 0.2 N/m) cantilever by applying the air pressure of 40 Pa. If a stiff cantilever (spring constant of 40 N/m) is used, the potential of vertical deviation improvement is twice is large. This method is suitable for use with different types of AFM sensors and it can be implemented practically without essential changes in AFM sensor design.
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GÖPPERT, M., R. BECKER, C. MAIER, M. JÖRGER, A. JOLK, and C. KLINGSHIRN. "INFRARED ABSORPTION BY EXCITONS IN CUPROUS OXIDE." International Journal of Modern Physics B 15, no. 28n30 (December 10, 2001): 3615–18. http://dx.doi.org/10.1142/s0217979201008275.
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We report on the first observation of the 1s to 2p exciton transition in a direct gap semiconductor. Cuprous oxide is well known for its excitonic features which provide a model case for the theory of Wannier excitons. In our pump-probe experiment we measured the infrared transmission of cuprous oxide with the without Ar +-laser illumination. The observed photo-induced absorption line in the differential transmission spectra at 126 meV is assigned to the excitonic transition from 1s to 2p exciton levels i.e. to the analog of the Lyman series in atomic hydrogen. From the dependence of the integrated photo-induced absorption on the pump laser intensity we determine the lifetime of the paraexciton τ p ≈0.3 ms. We also studied the influence of the pump laser on the phonon absorption band in the mid-infrared. Its observed shift to lower energies with increasing pump laser intensity can be explained by heating of the samples.
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Ramachandran, Abhinay, Carissa Livingston, Elise Corbin, Alexia Vite, Alex Bennett, and Kenneth Margulies. "3299 Dynamic Afterload Cardiac Microtissue Model To Examine Molecular Pathways of Heart Failure." Journal of Clinical and Translational Science 3, s1 (March 2019): 9. http://dx.doi.org/10.1017/cts.2019.25.
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OBJECTIVES/SPECIFIC AIMS: This project aims to determine the key molecular pathways that link increased myocardial wall stress to cardiomyocyte hypertrophy and subsequent heart failure. We will use a cardiac microtissue (CMT) model with dynamically tunable cantilever stiffness to examine changes in CMT hypertrophy and electro-mechanical properties in response to increased afterload (cantilever stiffness). Subsequently, we will determine if inhibition of pro-hypertrophic or anti-hypertrophic pathways alter the hypertrophic response to increased afterload. Primary outcomes for this study are static/dynamic force, minimum electric field strength (VT), maximum capture rate (MCR), average cell area, and tissue cross-sectional thickness, and secondary outcomes are degree of myoblast activation and apoptosis. METHODS/STUDY POPULATION: CMT platforms will be fabricated using iron-doped polydimethylsiloxane (PDMS) to create magnetically tunable cantilevers. Cantilever stiffness will be increased with the application of an external magnetic field. Cantilever stiffness will be measured using a capacitance probe, where the force required to deflect both the cantilever and calibration probe is in accordance with Hooke’s Law. Human induced pluripotent stem cell cardiomyocyte (hiPSC-CMs) will be cultured and matured as 3D CMTs. In-vitro static/dynamic force generation will also be calculated by measuring the deflection of the cantilevers and applying Hooke’s law. CMTs will be paced using carbon electrodes to obtain VT and MCR. Structural data will be obtained using immunostaining and confocal microscopy. Finally, we will use pharmacologic inhibitors to inhibit molecular pathways that we identified in prior genetic screens such as ABCC8 (anti-hypertrophic mediator) and C1QTNF9 (pro-hypertrophic mediator). We will examine each of these pathways in low- and high-stiffness conditions. RESULTS/ANTICIPATED RESULTS: We believe increased afterload will cause significant hypertrophy, measured by increases in CMT cross-sectional thickness, cardiac myocyte area, myofibroblast activation, and myocyte apoptosis. In addition, we expect to see increases in static/dynamic force, increased voltage threshold, and decreased maximum capture rate. Preliminary results show a 64.3% increase in force generation when stiffness is increased by approximately 30%, and a 44.4% decrease in force generation when stiffness is decreased by approximately 30%. Finally, we expect that inhibiting a pro- or anti-hypertrophic molecular pathway will weaken or strengthen the hypertrophic response to increased afterload, respectively. DISCUSSION/SIGNIFICANCE OF IMPACT: To our knowledge, our lab is the first to create a dynamically tunable afterload system in the cantilever CMT model. This advance provides us with a robust platform to determine the molecular pathways that cause increased myocardial wall stress to result in cardiomyocyte hypertrophy and heart failure, which remain a critical knowledge gap in our understanding of cardiovascular disease. With more precise understanding of these pathways, we will equip ourselves with the knowledge to develop novel therapeutic agents to prevent the development or progression of heart failure.
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Saxena, Stuti. "Drivers and barriers towards re-using open government data (OGD): a case study of open data initiative in Oman." foresight 20, no. 2 (April 9, 2018): 206–18. http://dx.doi.org/10.1108/fs-10-2017-0060.
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Purpose The purpose of this study is to underscore the significance, drivers and barriers towards re-use of open data sets in the context of Oman’s open government data (OGD) initiative. Design/methodology/approach Following a qualitative framework, the paper invoked a documentary analysis approach to probe the OGD initiative of Oman. Specifically, the national OGD portal of Oman (https://data.gov.om/) is being investigated in the paper. Furthermore, the paper invokes a theoretical model of “citizen engagement” (“Data over the wall”, “Code exchange”, “Civic issue tracker” and “Participatory open data model”) proposed by Sieber and Johnson (2015) to assess the extent to which open data sets may be re-used. Findings As per the theoretical model forwarded by Sieber and Johnson (2015), the OGD initiative of Oman is a cusp between “Data over the wall”, “Code exchange” and “Participatory” models. Oman’s OGD initiative facilitates the re-use of the open data sets. However, there are challenges in re-using the open data sets as well. The paper underlines the prospects of better re-use of data sets by institutionalizing the OGD initiative across all administrative levels of the country. Practical implications This study holds relevance for practitioners and policy-makers in Oman to ensure the re-use of data sets is facilitated for generating public value. Originality/value Hitherto, research has underlined the significance of launching OGD initiatives in the West but studies in developing countries are few. The present study seeks to plug this research gap by underlining the significance of OGD re-usage in Oman’s context.
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Slavin, Moriya, Joanna Zamel, Keren Zohar, Tsiona Eliyahu, Merav Braitbard, Esther Brielle, Leah Baraz, et al. "Targeted in situ cross-linking mass spectrometry and integrative modeling reveal the architectures of three proteins from SARS-CoV-2." Proceedings of the National Academy of Sciences 118, no. 34 (August 9, 2021): e2103554118. http://dx.doi.org/10.1073/pnas.2103554118.
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Atomic structures of several proteins from the coronavirus family are still partial or unavailable. A possible reason for this gap is the instability of these proteins outside of the cellular context, thereby prompting the use of in-cell approaches. In situ cross-linking and mass spectrometry (in situ CLMS) can provide information on the structures of such proteins as they occur in the intact cell. Here, we applied targeted in situ CLMS to structurally probe Nsp1, Nsp2, and nucleocapsid (N) proteins from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and obtained cross-link sets with an average density of one cross-link per 20 residues. We then employed integrative modeling that computationally combined the cross-linking data with domain structures to determine full-length atomic models. For the Nsp2, the cross-links report on a complex topology with long-range interactions. Integrative modeling with structural prediction of individual domains by the AlphaFold2 system allowed us to generate a single consistent all-atom model of the full-length Nsp2. The model reveals three putative metal binding sites and suggests a role for Nsp2 in zinc regulation within the replication–transcription complex. For the N protein, we identified multiple intra- and interdomain cross-links. Our integrative model of the N dimer demonstrates that it can accommodate three single RNA strands simultaneously, both stereochemically and electrostatically. For the Nsp1, cross-links with the 40S ribosome were highly consistent with recent cryogenic electron microscopy structures. These results highlight the importance of cellular context for the structural probing of recalcitrant proteins and demonstrate the effectiveness of targeted in situ CLMS and integrative modeling.
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Hou, Pei Guo, Yue Zhang, Yu Tian Wang, and Jin Zhao. "Study on Optically Powered Hall Current Transformer." Advanced Materials Research 204-210 (February 2011): 522–27. http://dx.doi.org/10.4028/www.scientific.net/amr.204-210.522.
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A hybrid fiber optically powered current transformer with the Hall element is studied and developed in this paper. The sensing probe is the zero-flux current transformer which is based on Hall Effect. The main current can be insulated from the measurement circuit by use of Hall current transformer. Due to the broad bandwidth characteristics and the high linearity between the Hall potential and measured magnetic flux density and the high sensitivity of the Hall current transformer, any changes in the excitation current can be accurately detected without distortion. The three-dimensional model of the Hall current transformer is set up by use of ANSYS software in this paper. The magnetic flux density in the opening air-gap is calculated by nonlinear magnetic analysis method of the three-dimensional finite element. Experimental data shows that the calculation method and results are reliable. At the same time, high power laser power supply is adopted to drive the electronic devices in high potential side, and the reliable insulation between the high potential and low potential is achieved by optical fibers. So the accuracy of this measurement system can be ensured.
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Medjroubi, Mohamed Larbi, Ouarda Brihi, Noudjoud Hamdouni, Ali Boudjada, and Jean Meinnel. "The Crystal Structure of Dibromonitrotoluen (DBNT) C7Br2H5 NO2." Advanced Materials Research 324 (August 2011): 209–12. http://dx.doi.org/10.4028/www.scientific.net/amr.324.209.
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The crystal structure of Dibromonitrotoluen (DBNT) obtained at the ambient temperature 293k from the X-ray diffraction crystallizes in the space group P-1 with 2 molecules by mesh. The crystal growth is made along the a axis. In parallel with this study, a theoretical calculation of molecular conformation from the density functional theory (DFT) carried out using the Gaussian03 chain program in the case of isolated molecule, led to results of Optimization very close to the experiment. The molecular conformation calculations were made from two different functional the B3LYP and MPW1PW91. The values of bond lengths obtained from the functional MPW1PW91 and base set 6-311G are very close to the experiment with a gap of 1.25% (2.14% for the B3LYP) while for bond angles, calculation results are better for functional B3LYP (Lan2DZ) 0.95% and 1.02% for MPW1PW91.In this work a study of internal modes of Dibromonitrotoluen (DBNT) is presented, while comparing the infrared spectroscopic experimental results and the DFT studies of the isolated molecule. This material is a good probe to test the model precision and the calculated methods used to interpret dynamic properties by experimental spectroscopy.
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Prelovšek, P., and Z. Lenarčič. "Charge relaxation and recombination in photo-excited Mott insulators." International Journal of Modern Physics B 30, no. 13 (May 19, 2016): 1642015. http://dx.doi.org/10.1142/s0217979216420157.
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Recent femtosecond pump-probe experiments on Mott insulators reveal charge recombination, which is in picosecond range, i.e., much faster than in clean bandgap semiconductors although excitation gaps in Mott insulators are even larger. The charge response in photo-excited insulators can be generally divided in femtosecond transient relaxation of charge excitations, which are holons and doublons, and a second slower, but still very fast, holon–doublon (HD) recombination. We present a theory of the recombination rate of the excited HD pairs, based on the two-dimensional (2D) model relevant for cuprates, which shows that such fast processes can be explained even quantitatively with the multi-magnon emission. We show that the condition for the exponential decay as observed in the experiment is the existence of the exciton, i.e., the bound HD pair. Its recombination rate is exponentially dependent on the charge gap and on the magnon energy, while the ultrafast process can be traced back to strong charge-spin coupling. We comment also fast recombination times in the one-dimensional (1D) Mott insulators, as e.g., organic salts. The recombination rate in the latter cases can be explained with the stronger coupling with phonon excitations.
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Oosthuizen, P. H., and A. Sheriff. "AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER." Transactions of the Canadian Society for Mechanical Engineering 17, no. 2 (June 1993): 145–60. http://dx.doi.org/10.1139/tcsme-1993-0009.
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Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the “developing” world. The performance so far achieved with such dryers has, however, not proved to be very satisfactory. If this performance is to be improved it is necessary to have an accurate computer model of such dryers to assist in their design. An important element is any dryer model is an accurate equation for the convective heat transfer in the collector. To assist in the development of such an equation, an experimental and numerical study of the collector heat transfer has been undertaken. In the experimental study, the collector was simulated by a 1m long by 1m wide channel with a gap of 4 cm between the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, simulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded thermocouple probe. Local heat transfer rates were then determined from these measured temperature profiles. In the numerical study, the parabolic forms of the governing equations were solved by a forward-marching finite difference procedure.
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Correia, AMO, MR Andrade, JPM Tribst, ALS Borges, and TMF Caneppele. "Influence of Bulk-fill Restoration on Polymerization Shrinkage Stress and Marginal Gap Formation in Class V Restorations." Operative Dentistry 45, no. 4 (April 3, 2020): E207—E216. http://dx.doi.org/10.2341/19-062-l.
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Clinical Relevance Restoring Class V cavities with a regular bulk-fill composite presents a more favorable biomechanical behavior than restoring with a regular nano-filled composite. SUMMARY Purpose: This study evaluated the influence of Class V cavity extension and restorative material on the marginal gap formation, before and after aging, and the theoretical polymerization shrinkage stress distribution in a tooth restoration. Methods and Materials: Class V cavities with the depth of 2 mm, cervical/incisal distance of 4 mm, and margins located in the enamel 1 mm above the cementoenamel junction were prepared in 60 bovine incisors in two mesiodistal dimensions (n=30): 2.9-mm large extension cavities (LE) or 1.4-mm small extension cavities (SE). The cavities' depths were validated using a periodontal probe, while the mesiodistal and cervical/incisal distances were measured using a stereomicroscope. After adhesive application (Clearfil SE Bond), each group was randomly divided into two groups (n=15) according to the restorative material: Filtek Z350 XT (N) or Filtek Bulk Fill Posterior (BF). The marginal gap formation between the tooth structure and the restorative material was evaluated using a stereomicroscope before and after thermocycling for 15,000 cycles (5°C and 55°C). Data were analyzed using repeated-measures analysis of variance (ANOVA) and Tukey test for multiple comparisons (α=0.05). A three-dimensional geometric model with the same dimensions as the experimental test was created for each cavity, and the restorations were modeled for each restorative material. In the analysis software, the finite element mesh was created with tetrahedral quadratic elements, and the polymerization shrinkage was simulated by thermal analogy. The maximum principal stress was used to express the tensile stress in the adhesive interface through colorimetric graphs. Results: For the marginal gap, the repeated-measures ANOVA revealed a significant effect only for the factors composite resin (df=1, F=4.09, p=0.04) and thermal aging (df=1, F=44.35, p<0.001). For all numerical simulations, higher stress concentration occurred at the enamel margin, and the stress peak decreased in the following sequence: LE-N (17.0 MPa) > SE-N (15.0 MPa) > LE-BF (9.1 MPa) > SE-BF (8.2 MPa). Conclusion: Marginal gaps in the specimens fell between approximately 12 and 17 μm; however, the regular bulk-fill composite showed less gap formation and better stress distribution around the cavity margin than the regular nano-filled composite, regardless of the cavity extension.
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Han, X., H. J. H. Franssen, R. Rosolem, R. Jin, X. Li, and H. Vereecken. "Correction of systematic model forcing bias of CLM using assimilation of cosmic-ray Neutrons and land surface temperature: a study in the Heihe Catchment, China." Hydrology and Earth System Sciences 19, no. 1 (January 30, 2015): 615–29. http://dx.doi.org/10.5194/hess-19-615-2015.
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Abstract. The recent development of the non-invasive cosmic-ray soil moisture sensing technique fills the gap between point-scale soil moisture measurements and regional-scale soil moisture measurements by remote sensing. A cosmic-ray probe measures soil moisture for a footprint with a diameter of ~ 600 m (at sea level) and with an effective measurement depth between 12 and 76 cm, depending on the soil humidity. In this study, it was tested whether neutron counts also allow correcting for a systematic error in the model forcings. A lack of water management data often causes systematic input errors to land surface models. Here, the assimilation procedure was tested for an irrigated corn field (Heihe Watershed Allied Telemetry Experimental Research – HiWATER, 2012) where no irrigation data were available as model input although for the area a significant amount of water was irrigated. In the study, the measured cosmic-ray neutron counts and Moderate-Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) products were jointly assimilated into the Community Land Model (CLM) with the local ensemble transform Kalman filter. Different data assimilation scenarios were evaluated, with assimilation of LST and/or cosmic-ray neutron counts, and possibly parameter estimation of leaf area index (LAI). The results show that the direct assimilation of cosmic-ray neutron counts can improve the soil moisture and evapotranspiration (ET) estimation significantly, correcting for lack of information on irrigation amounts. The joint assimilation of neutron counts and LST could improve further the ET estimation, but the information content of neutron counts exceeded the one of LST. Additional improvement was achieved by calibrating LAI, which after calibration was also closer to independent field measurements. It was concluded that assimilation of neutron counts was useful for ET and soil moisture estimation even if the model has a systematic bias like neglecting irrigation. However, also the assimilation of LST helped to correct the systematic model bias introduced by neglecting irrigation and LST could be used to update soil moisture with state augmentation.
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Han, X., H. J. Hendricks Franssen, R. Rosolem, R. Jin, X. Li, and H. Vereecken. "Correction of systematic model forcing bias of CLM using assimilation of cosmic-ray neutrons and land surface temperature: a study in the Heihe catchment, China." Hydrology and Earth System Sciences Discussions 11, no. 7 (July 30, 2014): 9027–66. http://dx.doi.org/10.5194/hessd-11-9027-2014.
Full textAbstract:
Abstract. The recent development of the non-invasive cosmic-ray soil moisture sensing technique fills the gap between point scale soil moisture measurements and regional scale soil moisture measurements by remote sensing. A cosmic-ray probe measures soil moisture for a footprint with a diameter of ~600 m (at sea level) and with an effective measurement depth between 12 and 76 cm, depending on the soil humidity. In this study, it was tested whether neutron counts also allow to correct for a systematic error in the model forcings. Lack of water management data often cause systematic input errors to land surface models. Here, the assimilation procedure was tested for an irrigated corn field (Heihe Watershed Allied Telemetry Experimental Research – HiWATER, 2012) where no irrigation data were available as model input although the area a significant amount of water was irrigated. Measured cosmic-ray neutron counts and Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) products were jointly assimilated into the Community Land Model (CLM) with the Local Ensemble Transform Kalman Filter. Different data assimilation scenarios were evaluated, with assimilation of LST and/or cosmic-ray neutron counts, and possibly parameter estimation of leaf area index (LAI). The results show that the direct assimilation of cosmic-ray neutron counts can improve the soil moisture and evapotranspiration (ET) estimation significantly, correcting for lack of information on irrigation amounts. The joint assimilation of neutron counts and LST could improve further the ET estimation, but the information content of neutron counts exceeded the one of LST. Additional improvement was achieved by calibrating LAI, which after calibration was also closer to independent field measurements. It was concluded that assimilation of neutron counts was useful for ET and soil moisture estimation even if the model has a systematic bias like neglecting irrigation. However, also the assimilation of LST helped to correct the systematic model bias introduced by neglecting irrigation and LST could be used to update soil moisture with state augmentation.
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Sturm, J. A., G. P. Rosotti, and C. Dominik. "Dust dynamics in planet-driven spirals." Astronomy & Astrophysics 643 (November 2020): A92. http://dx.doi.org/10.1051/0004-6361/202038919.
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Context. Protoplanetary disks are known to host spiral features that are observed in scattered light, the ALMA continuum, and more recently in CO gas emission and gas dynamics. However, it is unknown whether spirals in gas and dust trace the same morphology. Aims. We aim to study the morphology and amplitude of dusty spirals as function of the Stokes number and the underlying mechanisms that cause a difference between dusty spirals and gas spirals. We then construct a model to relate the deviation from Keplerian rotation in the gas to a perturbation in surface density of the gas and dust. Methods. We used FARGO-3D with dust implementation to numerically study the spirals, after which the results were interpreted using a semi-analytical model. This model was tested on observational data to predict the perturbation of the spiral in gas dynamics based on the continuum data. Results. We find that the pitch angle of a spiral does not differ significantly between gas and dust. The amplitude of the dust spiral decreases with the Stokes number (St) and starts to fade out at a typical St > 0.1 as the dust becomes decoupled from the gas. The semi-analytical model provides an accurate and fast representation of the difference in the surface density of the spiral in dust and gas. We find a spiral in the TW Hya velocity residual map, never seen before, which is a feature in the vertical velocity and has a kink at the continuum gap, yielding strong evidence for a planet at 99 au. Conclusions. We built a model that gives an estimate of the underlying dynamics of dust in a spiral, which can serve as evidence of the planetary origin of spirals and can be a probe for the Stokes number in the disk.
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Cummings, Kirstie A., and Gabriela K. Popescu. "Glycine-dependent activation of NMDA receptors." Journal of General Physiology 145, no. 6 (May 11, 2015): 513–27. http://dx.doi.org/10.1085/jgp.201411302.
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N-methyl-d-aspartate (NMDA) receptors are the only neurotransmitter receptors whose activation requires two distinct agonists. Heterotetramers of two GluN1 and two GluN2 subunits, NMDA receptors are broadly distributed in the central nervous system, where they mediate excitatory currents in response to synaptic glutamate release. Pore opening depends on the concurrent presence of glycine, which modulates the amplitude and time course of the glutamate-elicited response. Gating schemes for fully glutamate- and glycine-bound NMDA receptors have been described in sufficient detail to bridge the gap between microscopic and macroscopic receptor behaviors; for several receptor isoforms, these schemes include glutamate-binding steps. We examined currents recorded from cell-attached patches containing one GluN1/GluN2A receptor in the presence of several glycine-site agonists and used kinetic modeling of these data to develop reaction schemes that include explicit glycine-binding steps. Based on the ability to match a series of experimentally observed macroscopic behaviors, we propose a model for activation of the glutamate-bound NMDA receptor by glycine that predicts apparent negative agonist cooperativity and glycine-dependent desensitization in the absence of changes in microscopic binding or desensitization rate constants. These results complete the basic steps of an NMDA receptor reaction scheme for the GluN1/GluN2A isoform and prompt a reevaluation of how glycine controls NMDA receptor activation. We anticipate that our model will provide a useful quantitative instrument to further probe mechanisms and structure–function relationships of NMDA receptors and to better understand the physiological and pathological implications of endogenous fluctuations in extracellular glycine concentrations.