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1
Anagnostopoulos, Marios, Georgios Kambourakis, Panagiotis Kopanos, Georgios Louloudakis, and Stefanos Gritzalis. "DNS amplification attack revisited." Computers & Security 39 (November 2013): 475–85. http://dx.doi.org/10.1016/j.cose.2013.10.001.
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Quadir, Md Abdul, J. Christy Jackson, J. Prassanna, K. Sathyarajasekaran, K. Kumar, H. Sabireen, Shivam Ubarhande, and V. Vijaya Kumar. "An efficient algorithm to detect DDoS amplification attacks." Journal of Intelligent & Fuzzy Systems 39, no. 6 (December 4, 2020): 8565–72. http://dx.doi.org/10.3233/jifs-189173.
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Domain name system (DNS) plays a critical part in the functioning of the Internet. But since DNS queries are sent using UDP, it is vulnerable to Distributed Denial of Service (DDoS) attacks. The attacker can take advantage of this and spoof the source IP address and direct the response towards the victim network. And since the network does not keep track of the number of requests going out and responses coming in, the attacker can flood the network with these unwanted DNS responses. Along with DNS, other protocols are also exploited to perform DDoS. Usage of Network Time Protocol (NTP) is to synchronize clocks on systems. Its monlist command replies with 600 entries of previous traffic records. This response is enormous compared to the request. This functionality is used by the attacker in DDoS. Since these attacks can cause colossal congestion, it is crucial to prevent or mitigate these types of attacks. It is obligatory to discover a way to drop the spoofed packets while entering the network to mitigate this type of attack. Intelligent cybersecurity systems are designed for the detection of these attacks. An Intelligent system has AI and ML algorithms to achieve its function. This paper discusses such intelligent method to detect the attack server from legitimate traffic. This method uses an algorithm that gets activated by excess traffic in the network. The excess traffic is determined by the speed or rate of the requests and responses and their ratio. The algorithm extracts the IP addresses of servers and detects which server is sending more packets than requested or which are not requested. This server can be later blocked using a firewall or Access Control List (ACL).
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Sieklik, Boris, Richard Macfarlane, and William J. Buchanan. "Evaluation of TFTP DDoS amplification attack." Computers & Security 57 (March 2016): 67–92. http://dx.doi.org/10.1016/j.cose.2015.09.006.
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Widagdo, Gede Barkah. "Real-Time Early Detection NTP Amplification Attack." ACMIT Proceedings 3, no. 1 (March 18, 2019): 76–84. http://dx.doi.org/10.33555/acmit.v3i1.29.
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This paper is the initials of DDoS mitigation, the goal of this research is to detect NTP Amplification as early as possible so that the victim have a data to do further eskalation process. We knows that the goal of the attacker using NTP Amplification Attack is to exhaust the bandwidth of the victim, in this research also simulate an NTP amplification scenario and detection method; the scenario is the attacker sends requests with spoofed IP MONLIST victim to the compromised NTP server NTP server then responds the large volumes of traffic (amplified traffic) towards Victim to consume the bandwidth so as the legitimate user could not access the services. We put DDoS detection device side of the victim, we combine several monitoring tools to detect NTP amplification i.e bandwidth gauge and netflow analyzer. Netflow analyzer (flow analysis) conduct analysis IP packet header that is sent by the router as a flow-exporter. In our experiment, we could perform early detection of the NTP amplification less than 2 minute.
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Najafabadi, Maryam M., Taghi M. Khoshgoftaar, and Amri Napolitano. "Detecting Network Attacks Based on Behavioral Commonalities." International Journal of Reliability, Quality and Safety Engineering 23, no. 01 (February 2016): 1650005. http://dx.doi.org/10.1142/s0218539316500054.
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Due to the great increase in the amount of attacks that occur in computer networks, there is an increasing dependence on network intrusion detection systems which monitor and analyze the network data to detect attacks. In recent years, machine learning methods have been used to build predictive models for network intrusion detection. These methods are able to automatically extract patterns from the network data to build detection models. Defining proper features, which help models to better discriminate between normal and attack data, is a critical task. While network attacks vary widely, they share some commonalities. Many attacks, by their nature, are repetitive and exhibit behaviors different from normal traffic. Among these commonalities are self-similarity between attack packets, periodicity and repetition characteristics seen in the attack traffic. In this paper, we study the common behaviors between two different attack types, called RUDY and DNS Amplification attacks, in order to propose new features for building predictive models by using machine learning algorithms. We collected Netflow traffic from an operational ISP network. We introduce a concept called “session” derived from Netflow which incorporates both sides of a network communication to define a network instance. Features are extracted for each session. To demonstrate how the newly defined features work for the task of intrusion detection, we use these features to build intrusion detection models for the detection of RUDY attack, DNS Amplification attack and the combination of these two attacks. To build predictive models we apply four machine learning classification algorithms: two versions of a decision tree algorithm, Naïve Bayes and 5-Nearest Neighbor (5-NN) algorithm. Our results show that the proposed features based on the attack commonalities provide very good prediction results for the detection of two studied attacks on real network traffic.
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Khan, Muhammad Salman, Ken Ferens, and Witold Kinsner. "A Chaotic Complexity Measure for Cognitive Machine Classification of Cyber-Attacks on Computer Networks." International Journal of Cognitive Informatics and Natural Intelligence 8, no. 3 (July 2014): 45–69. http://dx.doi.org/10.4018/ijcini.2014070104.
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Today's evolving cyber security threats demand new, modern, and cognitive computing approaches to network security systems. In the early years of the Internet, a simple packet inspection firewall was adequate to stop the then-contemporary attacks, such as Denial of Service (DoS), ports scans, and phishing. Since then, DoS has evolved to include Distributed Denial of Service (DDoS) attacks, especially against the Domain Name Service (DNS). DNS based DDoS amplification attacks cannot be stopped easily by traditional signature based detection mechanisms because the attack packets contain authentic data, and signature based detection systems look for specific attack-byte patterns. This paper proposes a chaos based complexity measure and a cognitive machine classification algorithm to detect DNS DDoS amplification attacks. In particular, this paper computes the Lyapunov exponent to measure the complexity of a flow of packets, and classifies the traffic as either normal or anomalous, based on the magnitude of the computed exponent. Preliminary results show the proposed chaotic measure achieved a detection (classification) accuracy of about 98%, which is greater than that of an Artificial Neural Network. Also, contrary to available supervised machine learning mechanisms, this technique does not require any offline training. This approach is capable of not only detecting offline threats, but has the potential of being applied over live traffic flows using DNS filters.
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Chen, Hsien-Pu, Muneer Mohammad, and Laszlo B. Kish. "Current Injection Attack against the KLJN Secure Key Exchange." Metrology and Measurement Systems 23, no. 2 (June 1, 2016): 173–81. http://dx.doi.org/10.1515/mms-2016-0025.
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AbstractThe Kirchhoff-law-Johnson-noise (KLJN) scheme is a statistical/physical secure key exchange system based on the laws of classical statistical physics to provide unconditional security. We used the LTSPICE industrial cable and circuit simulator to emulate one of the major active (invasive) attacks, the current injection attack, against the ideal and a practical KLJN system, respectively. We show that two security enhancement techniques, namely, the instantaneous voltage/current comparison method, and a simple privacy amplification scheme, independently and effectively eliminate the information leak and successfully preserve the system’s unconditional security.
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Alfraih Abdulaziz Nasser, A., and Wen Bo Chen. "NTP DRDoS Attack Vulnerability and Mitigation." Applied Mechanics and Materials 644-650 (September 2014): 2875–80. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.2875.
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The Network Time Protocol (NTP) is used to synchronize clocks of various computer devices such as personal computers, tablets, and phones based their set time zones. The network of devices that use these NTP servers form a huge distributed network that attracted a number of attacks from late 2013 towards early 2014. This paper presents a hands-on test of the Distributed Reflection Denial of Service (DRDoS) attack by the monlist command, provides more vulnerability in the protocol, and offers mitigation to these vulnerabilities. A Kali Linux server was used to test the monlist command on its localhost. The results showed that a request with a size of 234 bytes got a response of 4,680 bytes. A busy NTP server can return up to 600 addresses which were theoretically calculated to return approximately 48 kilobytes in 100 packets. Consequently, this results in an amplification factor of 206×. The knowledge of the way the attack can be propagated was an important step in thwarting the attack and mitigating more such threats in the same protocol.
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Malekzadeh, Mina, Moghis Ashrostaghi, and M. H. Shahrokh Abadi. "Amplification-based Attack Models for Discontinuance of Conventional Network Transmissions." International Journal of Information Engineering and Electronic Business 7, no. 6 (November 8, 2015): 15–22. http://dx.doi.org/10.5815/ijieeb.2015.06.03.
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Veeraraghavan, Prakash, Dalal Hanna, and Eric Pardede. "NAT++: An Efficient Micro-NAT Architecture for Solving IP-Spoofing Attacks in a Corporate Network." Electronics 9, no. 9 (September 14, 2020): 1510. http://dx.doi.org/10.3390/electronics9091510.
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The Internet Protocol (IP) version 4 (IPv4) has several known vulnerabilities. One of the important vulnerabilities is that the protocol does not validate the correctness of the source address carried in an IP packet. Users with malicious intentions may take advantage of this vulnerability and launch various attacks against a target host or a network. These attacks are popularly known as IP Address Spoofing attacks. One of the classical IP-spoofing attacks that cost several million dollars worldwide is the DNS-amplification attack. Currently, the availability of solutions is limited, proprietary, expensive, and requires expertise. The Internet is subjected to several other forms of amplification attacks happening every day. Even though IP-Spoofing is one of the well-researched areas since 2005, there is no holistic solution available to solve this problem from the gross-root. Also, every solution assumes that the attackers are always from outside networks. In this paper, we provide an efficient and scalable solution to solve the IP-Spoofing problem that arises from malicious or compromised inside hosts. We use a modified form of Network Address Translation (NAT) to build our solution framework. We call our framework as NAT++. The proposed infrastructure is robust, crypto-free, and easy to implement. Our simulation results have shown that the proposed NAT++ infrastructure does not consume more than the resources required by a simple NAT.
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Joo, Shin Woo, Kyu-Seek Sohn, and Seung Yeob Nam. "Vehicle Remote Key Authentication Scheme based on AP List for Preventing Amplification Attack." Journal of Korean Institute of Communications and Information Sciences 42, no. 10 (October 31, 2017): 2012–21. http://dx.doi.org/10.7840/kics.2017.42.10.2012.
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Lizama-Perez, Luis A., and J. Mauricio López. "Quantum Key Distillation Using Binary Frames." Symmetry 12, no. 6 (June 24, 2020): 1053. http://dx.doi.org/10.3390/sym12061053.
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We introduce a new integral method for Quantum Key Distribution to perform sifting, reconciliation and amplification processes to establish a cryptographic key through the use of binary matrices called frames which are capable to increase quadratically the secret key rate. Since the eavesdropper has no control on Bob’s double matching detection events, our protocol is not vulnerable to the Intercept and Resend (IR) attack nor the Photon Number Splitting (PNS) attack. The method can be implemented with the usual optical Bennett–Brassard ( B B 84 ) equipment allowing strong pulses in the quantum regime.
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Luo, Shi Jie, Yao Feng Liu, and Ning Cao. "Numerical Simulation of Lateral Jet Interaction a Slender Body in Supersonic Flow." Applied Mechanics and Materials 404 (September 2013): 296–301. http://dx.doi.org/10.4028/www.scientific.net/amm.404.296.
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A numerical investigation has been conducted to research the interaction flowfield of lateral jet not in the longitudinal symmetry plane on a slender body with rudders in supersonic flow. The surface and space flow features of jet interaction flowfield with different angles of attack was analyzed. The paper also compared with and without jet interaction flowfield characteristics. As a result, the jet interaction destroys pressure distributions of the slender body, and causes normal and lateral loads. With angle of attack, the pressure distributions of the after body and rudders surfaces are change tempestuously. The results also show that the far-field interference played a major role in the lateral jet interaction. Besides, the force/moment amplification factors present highly nonlinear with angle of attack.
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Chiew, Kang Leng, Jeffrey Soon-Fatt Choo, San Nah Sze, and Kelvin S. C. Yong. "Leverage Website Favicon to Detect Phishing Websites." Security and Communication Networks 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/7251750.
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Phishing attack is a cybercrime that can lead to severe financial losses for Internet users and entrepreneurs. Typically, phishers are fond of using fuzzy techniques during the creation of a website. They confuse the victim by imitating the appearance and content of a legitimate website. In addition, many websites are vulnerable to phishing attacks, including financial institutions, social networks, e-commerce, and airline websites. This paper is an extension of our previous work that leverages the favicon with Google image search to reveal the identity of a website. Our identity retrieval technique involves an effective mathematical model that can be used to assist in retrieving the right identity from the many entries of the search results. In this paper, we introduced an enhanced version of the favicon-based phishing attack detection with the introduction of the Domain Name Amplification feature and incorporation of addition features. Additional features are very useful when the website being examined does not have a favicon. We have collected a total of 5,000 phishing websites from PhishTank and 5,000 legitimate websites from Alexa to verify the effectiveness of the proposed method. From the experimental results, we achieved a 96.93% true positive rate with only a 4.13% false positive rate.
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Mamytova, Elmira, Aliya Kadyrova, Dzhamalbek Turgumbaev, Emir Zholdoshev, and Tugolbai Tagaev. "Risk factors of ischemic stroke/transient ischemic attack in young women: A case report." Biomedicine 41, no. 1 (April 2, 2021): 160–62. http://dx.doi.org/10.51248/.v41i1.555.
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This case report aims to demonstrate the clinical significance of the left internal carotid artery (ICA) hypoplasia in a young woman who received a combined oral contraceptive (COC) and its association with arterial occlusion and the development of a lacunar stroke/lacunar cerebral infarct (LACI). Brain magnetic resonance imaging (MRI) of the left frontal lobe revealed multiple subcortical and periventricular amplification/ischemia foci (49.0×17.0 mm), and lacunar infarct loci (2.0×4.0 mm). Brain magnetic resonance angiography revealed a markedly narrowed lumen of the left ICA (2.0–3.0 mm). MRI diffusion-weighted imaging-fluid attenuated inversion recovery revealed a moderate diffuse wall thickening and reinforcement of the left ICA. The patient was diagnosed with LACI and congenital hypoplasia of the left ICA and underwent antiplatelet drug therapy (aspirin - 100 mg) and a complete withdrawal of COC. A full amelioration of neurological symptoms was observed after one month of treatment.
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Luo, Shi Jie. "Asymmetrical Lateral Jet Interaction on a Slender Body in Supersonic Flow." Applied Mechanics and Materials 565 (June 2014): 107–12. http://dx.doi.org/10.4028/www.scientific.net/amm.565.107.
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The lateral jet interaction on a slender body with rudders in supersonic flow had been investigated by numerical simulation, when the lateral jet is not in the longitudinal symmetry plane. It was called Asymmetrical lateral jet interaction in this paper. The flow features of jet interaction flowfield on the surface of the body or in the space far from the surface at different angles of attack and total pressure of jet was analyzed. As a result, the lateral jet interaction disturbed the pressure distributions of the slender body, and it was divided into near-field interaction near jet and far-field interaction aft-body on the basis of distance to jet. With the variety of the angle of attack and total pressure of jet, the pressure distributions at the aft-body change tempestuously, thereby the normal and lateral load will be from positive to negative, or reverse. The results also showed that the far-field interaction played a major role in the lateral jet interaction on a slender body in supersonic flow. The far-field interaction was caused by the changing of the outflow direction and intensity. Besides, the force/moment amplification factors presented highly nonlinear with the variety of angle of attack and total pressure of jet.
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Safar, Noor Zuraidin Mohd, Noryusliza Abdullah, Hazalila Kamaludin, Suhaimi Abd Ishak, and Mohd Rizal Mohd Isa. "Characterising and detection of botnet in P2P network for UDP protocol." Indonesian Journal of Electrical Engineering and Computer Science 18, no. 3 (June 1, 2020): 1584. http://dx.doi.org/10.11591/ijeecs.v18.i3.pp1584-1595.
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<span>Developments in computer networking have raised concerns of the associated Botnets threat to the Internet security. Botnet is an inter-connected computers or nodes that infected with malicious software and being controlled as a group without any permission of the computer’s owner. <br /> This paper explores how network traffic characterising can be used for identification of botnet at local networks. To analyse the characteristic, behaviour or pattern of the botnet in the network traffic, a proper network analysing tools is needed. Several network analysis tools available today are used for the analysis process of the network traffic. In the analysis phase, <br /> the botnet detection strategy based on the signature and DNS anomaly approach are selected to identify the behaviour and the characteristic of the botnet. In anomaly approach most of the behavioural and characteristic identification of the botnet is done by comparing between the normal and anomalous traffic. The main focus of the network analysis is studied on UDP protocol network traffic. Based on the analysis of the network traffic, <br /> the following anomalies are identified, anomalous DNS packet request, <br /> the NetBIOS attack, anomalous DNS MX query, DNS amplification attack and UDP flood attack. This study, identify significant Botnet characteristic in local network traffic for UDP network as additional approach for Botnet detection mechanism.</span>
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Fotis Sakellariou, Dimitris, Alexander David Nesbitt, Sean Higgins, Sandor Beniczky, Jan Rosenzweig, Panagis Drakatos, Nadia Gildeh, et al. "Co-activation of rhythms during alpha band oscillations as an interictal biomarker of exploding head syndrome." Cephalalgia 40, no. 9 (April 10, 2020): 949–58. http://dx.doi.org/10.1177/0333102420902705.
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Background Exploding head syndrome is a rarely reported benign sensory parasomnia that may nonetheless have significant impact on patients’ quality of life and their perceived well-being. To date, the mechanisms underlying attacks, characterised by a painless perception of abrupt, loud noises at transitional sleep-wake or wake-sleep states, are by and large unclear. Methods and results In order to address the current gap in the knowledge of potential underlying pathophysiology, a retrospective case-control study of polysomnographic recordings of patients presenting to a tertiary sleep disorders clinic with exploding head syndrome was conducted. Interictal (non-attack associated) electroencephalographic biomarkers were investigated by performing macrostructural and event-related dynamic spectral analyses of the whole-night EEG. In patients with exploding head syndrome, additional oscillatory activity was recorded during wakefulness and at sleep/wake periods. This activity differed in its frequency, topography and source from the alpha rhythm that it accompanied. Conclusion Based on these preliminary findings, we hypothesise that at times of sleep-wake transition in patients with exploding head syndrome, aberrant attentional processing may lead to amplification and modulation of external sensory stimuli.
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Mondello, Cristina, Elvira Ventura Spagnolo, Luigi Cardia, Daniela Sapienza, Serena Scurria, Patrizia Gualniera, and Alessio Asmundo. "Membrane Attack Complex in Myocardial Ischemia/Reperfusion Injury: A Systematic Review for Post Mortem Applications." Diagnostics 10, no. 11 (November 2, 2020): 898. http://dx.doi.org/10.3390/diagnostics10110898.
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The complement system has a significant role in myocardial ischemia/reperfusion injury, being responsible for cell lysis and amplification of inflammatory response. In this context, several studies highlight that terminal complement complex C5b-9, also known as the membrane attack complex (MAC), is a significant contributor. The MAC functions were studied by many researchers analyzing the characteristics of its activation in myocardial infarction. Here, a systematic literature review was reported to evaluate the principal features, advantages, and limits (regarding the application) of complement components and MAC in post mortem settings to perform the diagnosis of myocardial ischemia/infarction. The review was performed according to specific inclusion and exclusion criteria, and a total of 26 studies were identified. Several methods studied MAC, and each study contributes to defining better how and when it affects the myocardial damage in ischemic/reperfusion injury. The articles were discussed, focusing on the specificity, sensibility, and post mortem stability of MAC as a marker of myocardial ischemia/infarction, supporting the usefulness in routine post mortem investigations.
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Kok, Jen, and Dominic E. Dwyer. "Diagnosis of influenza following the first wave of pandemic (H1N1) 2009 influenza." Microbiology Australia 31, no. 3 (2010): 122. http://dx.doi.org/10.1071/ma10122.
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Aetiological confirmation of respiratory tract infections in individual patients facilitates appropriate antimicrobial use and infection control procedures. From a public health perspective, influenza confirmation allows assessment of community attack rates and the efficacy of vaccination programs, while assisting in modelling for pandemic preparedness planning. Rapid antigen and immunofluorescent antigen tests are relatively insensitive in detecting pandemic (H1N1) 2009 influenza, and influenza subtype-specific nucleic acid amplification tests should be used as the ?gold standard? for diagnosis. Pathogen-specific serological testing aids the retrospective diagnosis of infection. Although some challenges surrounding diagnostic testing during the first pandemic wave have been resolved, others remain; this may test laboratories again in the second and subsequent pandemic waves.
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Yeh, Chi-An, and Kunihiko Taira. "Resolvent-analysis-based design of airfoil separation control." Journal of Fluid Mechanics 867 (March 26, 2019): 572–610. http://dx.doi.org/10.1017/jfm.2019.163.
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We use resolvent analysis to design active control techniques for separated flows over a NACA 0012 airfoil. Spanwise-periodic flows over the airfoil at a chord-based Reynolds number of$23\,000$and a free-stream Mach number of$0.3$are considered at two post-stall angles of attack of$6^{\circ }$and$9^{\circ }$. Near the leading edge, localized unsteady thermal actuation is introduced in an open-loop manner with two tunable parameters of actuation frequency and spanwise wavelength. To provide physics-based guidance for the effective choice of these control input parameters, we conduct global resolvent analysis on the baseline turbulent mean flows to identify the actuation frequency and wavenumber that provide large perturbation energy amplification. The present analysis also considers the use of a temporal filter to limit the time horizon for assessing the energy amplification to extend resolvent analysis to unstable base flows. We incorporate the amplification and response mode from resolvent analysis to provide a metric that quantifies momentum mixing associated with the modal structure. This metric is compared to the results from a large number of three-dimensional large-eddy simulations of open-loop controlled flows. With the agreement between the resolvent-based metric and the enhancement of aerodynamic performance found through large-eddy simulations, we demonstrate that resolvent analysis can predict the effective range of actuation frequency as well as the global response to the actuation input. We believe that the present resolvent-based approach provides a promising path towards mean flow modification by capitalizing on the dominant modal mixing.
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Yang, Xue, Yong-Jie Qi, Mohamed N. Al-Attala, Zheng-Hui Gao, Xing-Kai Yi, Ai-Fang Zhang, Hao-Yu Zang, Chun-Yan Gu, Tong-Chun Gao, and Yu Chen. "Rapid Detection ofAlternariaSpecies Involved in Pear Black Spot Using Loop-Mediated Isothermal Amplification." Plant Disease 103, no. 12 (December 2019): 3002–8. http://dx.doi.org/10.1094/pdis-01-19-0149-re.
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Alternaria species are the most important fungal pathogens that attack various crops as well as fruit trees such as pear and cause black spot disease. Here, a loop-mediated isothermal amplification (LAMP) assay is developed for the detection of Alternaria species. A. alternata cytochrome b (cyt-b) gene was used to design two pairs of primers and amplified a 229-bp segment of Aacyt-b gene. The results showed that LAMP assay is faster and simpler than polymerase chain reaction (PCR). LAMP assay is highly sensitive method for the detection of about 1 pg of genomic DNA of A. alternata by using optimized concentration of MgCl2(4 mM) in final LAMP reaction. In contrast, the limit of detection was 1 ng of target DNA via conventional PCR. Among the genomic DNA of 46 fungal species, only the tubes containing DNA of Alternaria spp. except A. porri, A. solani, and A. infectoria changed color from orange to yellowish green with SYBR Green I including the main pathogens of pear black spot. The yellowish green color was indicative of DNA amplification. Moreover, LAMP assay was used for testing infected tissues among 22 healthy and diseased pear tissues; the orange color changed to yellowish green for infected tissues only. Altogether, we conclude that cyt-b gene can be used for the detection of Alternaria spp. via LAMP assay, which is involved in pear black spot disease.
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Kok, Jen, David W. Smith, and Dominic E. Dwyer. "Laboratory diagnosis of influenza and the impact of the pandemic (H1N1) 2009 virus." Microbiology Australia 32, no. 1 (2011): 7. http://dx.doi.org/10.1071/ma11007.
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Aetiological confirmation of respiratory tract infections in patients facilitates appropriate antimicrobial use and infection control procedures. From a public health perspective, the laboratory confirmation of influenza allows assessment of circulating viruses, community attack rates and the efficacy of vaccination programs, while assisting modelling as part of pandemic preparedness planning. Rapid antigen and immunofluorescent antigen tests are relatively insensitive in detecting pandemic (H1N1) 2009 influenza compared to seasonal subtypes, and influenza subtype-specific nucleic acid amplification tests should be used as the ?gold-standard? for diagnosis. Pathogen-specific serological testing aids the retrospective diagnosis of infection, and is used in seroprevalence studies. Influenza virus isolation is needed for vaccine assessment and formulation. Although some challenges surrounding diagnostic testing during pandemic (H1N1) 2009 have been resolved, others remain; this may test laboratories again in future pandemics.
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Estevez, Brian, and Xiaoping Du. "New Concepts and Mechanisms of Platelet Activation Signaling." Physiology 32, no. 2 (March 2017): 162–77. http://dx.doi.org/10.1152/physiol.00020.2016.
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Upon blood vessel injury, platelets are exposed to adhesive proteins in the vascular wall and soluble agonists, which initiate platelet activation, leading to formation of hemostatic thrombi. Pathological activation of platelets can induce occlusive thrombosis, resulting in ischemic events such as heart attack and stroke, which are leading causes of death globally. Platelet activation requires intracellular signal transduction initiated by platelet receptors for adhesion proteins and soluble agonists. Whereas many platelet activation signaling pathways have been established for many years, significant recent progress reveals much more complex and sophisticated signaling and amplification networks. With the discovery of new receptor signaling pathways and regulatory networks, some of the long-standing concepts of platelet signaling have been challenged. This review provides an overview of the new developments and concepts in platelet activation signaling.
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Hombach, Andreas A., Ulf Geumann, Christine Günther, Felix G. Hermann, and Hinrich Abken. "IL7-IL12 Engineered Mesenchymal Stem Cells (MSCs) Improve A CAR T Cell Attack Against Colorectal Cancer Cells." Cells 9, no. 4 (April 3, 2020): 873. http://dx.doi.org/10.3390/cells9040873.
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Chimeric antigen receptor (CAR) redirected T cells are efficacious in the treatment of leukemia/lymphoma, however, showed less capacities in eliminating solid tumors which is thought to be partly due to the lack of cytokine support in the tumor lesion. In order to deliver supportive cytokines, we took advantage of the inherent ability of mesenchymal stem cells (MSCs) to actively migrate to tumor sites and engineered MSCs to release both IL7 and IL12 to promote homeostatic expansion and Th1 polarization. There is a mutual interaction between engineered MSCs and CAR T cells; in presence of CAR T cell released IFN-γ and TNF-α, chronic inflammatory Th2 MSCs shifted towards a Th17/Th1 pattern with IL2 and IL15 release that mutually activated CAR T cells with extended persistence, amplification, killing and protection from activation induced cell death. MSCs releasing IL7 and IL12 were superior over non-modified MSCs in supporting the CAR T cell response and improved the anti-tumor attack in a transplant tumor model. Data demonstrate the first use of genetically modified MSCs as vehicles to deliver immuno-modulatory proteins to the tumor tissue in order to improve the efficacy of CAR T cells in the treatment of solid malignancies.
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Donghua, Jiang, Guo Zejian, Chen Xujun, Cheng Zhiqiang, and Zheng Zhong. "Study on tobacco disease resistances mediated by the elicitor gene cryptogein from Phytophthora cryptogea." Chinese Journal of Agricultural Biotechnology 1, no. 2 (August 2004): 125–31. http://dx.doi.org/10.1079/cjb200415.
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AbstractThe cryptogein (Crypt) gene was obtained by PCR amplification of genomic DNA from Phytophthora cryptogea and confirmed by DNA sequencing. A promoter of the rice phenylalanine ammonia-lyase (PAL) gene was used to regulate the expression of Crypt, because this promoter has a low level of constitutive expression, is strongly induced by pathogen infection and is expressed in epidermal tissues. These promoter characteristics may be suitable for potential inhibition of pathogen attack on epidermal tissues. For functional interaction of Crypt with its outer plasma membrane binding sites, Crypt was led by a signal sequence of the extracellular pathogenesis-related protein (PR1b) of tobacco (Nicotiana tabacum). The fused gene was constructed into a binary vector and the final plasmid (CHF-PAL::Crypt) was transformed into tobacco using the Agrobacterium-mediated transformation method. Twenty-two lines of transformants were obtained from selection medium containing 100 mg/l of kanamycin. Results from PCR amplification and Southern blot analysis demonstrated that Crypt was integrated into the tobacco genome. In the assay of pathogen challenge, nearly two-thirds (68.2%) of the transgenic plants showed significantly enhanced resistance against black shank fungal (Phytophthora parasitica var. nicotianae), brown spot fungal (Alternaria alternata) and wild fire bacterial (Pseudomonas syringae pv. tabaci) diseases. This observation indicates that low-level constitutive expression of Crypt gene in tobacco could have potential use in generating broad-spectrum disease-resistant plants.
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YANG, DANG-GUO, ZHAO-LIN FAN, JIANG-QIANG LI, and DAN YAO. "EFFECTS OF BOUNDARY-LAYER THICKNESS ON FLOW OSCILLATIONS INSIDE OPEN CAVITIES AT SUPERSONIC SPEEDS." Modern Physics Letters B 24, no. 04n05 (February 20, 2010): 487–93. http://dx.doi.org/10.1142/s021798491002255x.
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An experiment was conducted in a wind-tunnel to study the internal acoustic field and flow oscillations inside rectangular-box cavities. The length-to-depth ratio of the cavities was 8. The data presented herein was obtained over a Mach number of 1.5 at a Reynolds number of 2.26×107 per meter with different boundary-layer thicknesses of approximately 24 mm and 5.5 mm. The experimental angle of attack, yawing and rolling angles were 0°. The rules were revealed as governing the effects of boundary-layer thickness on flow oscillations and unsteady characteristics by comparing the experimental results with flow oscillation modes predicated by Rossiter's and Heller's modified equation. The results indicate that a decrease in the ratio of boundary-layer thickness to cavity-depth (δ/D) induces flow oscillations amplification, peak oscillation frequency splitting and shifting phenomena of open cavity tones in the low-frequency region.
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Standfuß-Gabisch, Christine, Djamila Al-Halbouni, and Bernd Hofer. "Characterization of Biphenyl Dioxygenase Sequences and Activities Encoded by the Metagenomes of Highly Polychlorobiphenyl-Contaminated Soils." Applied and Environmental Microbiology 78, no. 8 (February 10, 2012): 2706–15. http://dx.doi.org/10.1128/aem.07381-11.
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ABSTRACTTotal extracted DNA from two heavily polychlorobiphenyl-contaminated soils was analyzed with respect to biphenyl dioxygenase sequences and activities. This was done by PCR amplification and cloning of a DNA segment encoding the active site of the enzyme. The translated sequences obtained fell into three similarity clusters (I to III). Sequence identities were high within but moderate or low between the clusters. Members of clusters I and II showed high sequence similarities with well-known biphenyl dioxygenases. Cluster III showed low (43%) sequence identity with a biphenyl dioxygenase fromRhodococcus jostiiRHA1. Amplicons from the three clusters were used to reconstitute and express complete biphenyl dioxygenase operons. In most cases, the resulting hybrid dioxygenases were detected in cell extracts of the recombinant hosts. At least 83% of these enzymes were catalytically active. Several amino acid exchanges were identified that critically affected activity. Chlorobiphenyl turnover by the enzymes containing the prototype sequences of clusters I and II was characterized with 10 congeners that were major, minor, or not constituents of the contaminated soils. No direct correlations were observed between on-site concentrations and rates of productive dioxygenations of these chlorobiphenyls. The prototype enzymes displayed markedly different substrate and product ranges. The cluster II dioxygenase possessed a broader substrate spectrum toward the assayed congeners, whereas the cluster I enzyme was superior in the attack ofortho-chlorinated aromatic rings. These results demonstrate the feasibility of the applied approach to functionally characterize dioxygenase activities of soil metagenomes via amplification of incomplete genes.
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Gjetting, Torben, Timothy L. W. Carver, Leif Skøt, and Michael F. Lyngkjær. "Differential Gene Expression in Individual Papilla-Resistant and Powdery Mildew-Infected Barley Epidermal Cells." Molecular Plant-Microbe Interactions® 17, no. 7 (July 2004): 729–38. http://dx.doi.org/10.1094/mpmi.2004.17.7.729.
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Resistance and susceptibility in barley to the powdery mildew fungus (Blumeria graminis f. sp. hordei) is determined at the single-cell level. Even in genetically compatible interactions, attacked plant epidermal cells defend themselves against attempted fungal penetration by localized responses leading to papilla deposition and reinforcement of their cell wall. This conveys a race-nonspecific form of resistance. However, this defense is not complete, and a proportion of penetration attempts succeed in infection. The resultant mixture of infected and uninfected leaf cells makes it impossible to relate powdery mildew-induced gene expression in whole leaves or even dissected epidermal tissues to resistance or susceptibility. A method for generating transcript profiles from individual barley epidermal cells was established and proven useful for analyzing resistant and successfully infected cells separately. Contents of single epidermal cells (resistant, infected, and unattacked controls) were collected, and after cDNA synthesis and PCR amplification, the resulting sample was hybridized to dot-blots spotted with genes, including some previously reported to be induced upon pathogen attack. Transcripts of several genes, (e.g., PR1a, encoding a pathogenesis related protein, and GLP4, encoding a germin-like protein) accumulated specifically in resistant cells, while GRP94, encoding a molecular chaperone, accumulated in infected cells. Thus, the single-cell method allows discrimination of transcript profiles from resistant and infected cells. The method will be useful for microarray expression profiling for simultaneous analysis of many genes.
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Rasetshwane, Daniel M., David A. Raybine, Judy G. Kopun, Michael P. Gorga, and Stephen T. Neely. "Influence of Instantaneous Compression on Recognition of Speech in Noise with Temporal Dips." Journal of the American Academy of Audiology 30, no. 01 (January 2019): 016–30. http://dx.doi.org/10.3766/jaaa.16165.
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AbstractIn listening environments with background noise that fluctuates in level, listeners with normal hearing can “glimpse” speech during dips in the noise, resulting in better speech recognition in fluctuating noise than in steady noise at the same overall level (referred to as masking release). Listeners with sensorineural hearing loss show less masking release. Amplification can improve masking release but not to the same extent that it does for listeners with normal hearing.The purpose of this study was to compare masking release for listeners with sensorineural hearing loss obtained with an experimental hearing-aid signal-processing algorithm with instantaneous compression (referred to as a suppression hearing aid, SHA) to masking release obtained with fast compression. The suppression hearing aid mimics effects of normal cochlear suppression, i.e., the reduction in the response to one sound by the simultaneous presentation of another sound.A within-participant design with repeated measures across test conditions was used.Participants included 29 adults with mild-to-moderate sensorineural hearing loss and 21 adults with normal hearing.Participants with sensorineural hearing loss were fitted with simulators for SHA and a generic hearing aid (GHA) with fast (but not instantaneous) compression (5 ms attack and 50 ms release times) and no suppression. Gain was prescribed using either an experimental method based on categorical loudness scaling (CLS) or the Desired Sensation Level (DSL) algorithm version 5a, resulting in a total of four processing conditions: CLS-GHA, CLS-SHA, DSL-GHA, and DSL-SHA.All participants listened to consonant-vowel-consonant nonwords in the presence of temporally-modulated and steady noise. An adaptive-tracking procedure was used to determine the signal-to-noise ratio required to obtain 29% and 71% correct. Measurements were made with amplification for participants with sensorineural hearing loss and without amplification for participants with normal hearing.Repeated-measures analysis of variance was used to determine the influence of within-participant factors of noise type and, for participants with sensorineural hearing loss, processing condition on masking release. Pearson correlational analysis was used to assess the effect of age on masking release for participants with sensorineural hearing loss.Statistically significant masking release was observed for listeners with sensorineural hearing loss for 29% correct, but not for 71% correct. However, the amount of masking release was less than masking release for participants with normal hearing. There were no significant differences among the amplification conditions for participants with sensorineural hearing loss.The results suggest that amplification with either instantaneous or fast compression resulted in similar masking release for listeners with sensorineural hearing loss. However, the masking release was less for participants with hearing loss than it was for those with normal hearing.
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Banada, Padmapriya P., Srinidhi Deshpande, Riccardo Russo, Eric Singleton, Darshini Shah, Bhavana Patel, Michele Burday, et al. "Rapid Detection of Bacillus anthracis Bloodstream Infections by Use of a Novel Assay in the GeneXpert System." Journal of Clinical Microbiology 55, no. 10 (July 26, 2017): 2964–71. http://dx.doi.org/10.1128/jcm.00466-17.
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ABSTRACT Bacillus anthracis is a tier 1 select agent with the potential to quickly cause severe disease. Rapid identification of this pathogen may accelerate treatment and reduce mortality in the event of a bioterrorism attack. We developed a rapid and sensitive assay to detect B. anthracis bacteremia using a system that is suitable for point-of-care testing. A filter-based cartridge that included both sample processing and PCR amplification functions was loaded with all reagents needed for sample processing and multiplex nested PCR. The assay limit of detection (LOD) and dynamic range were determined by spiking B. anthracis DNA into individual PCR mixtures and B. anthracis CFU into human blood. One-milliliter blood samples were added to the filter-based detection cartridge and tested for B. anthracis on a GeneXpert instrument. Assay specificity was determined by testing blood spiked with non-anthrax bacterial isolates or by testing blood samples drawn from patients with concurrent non- B. anthracis bacteremia or nonbacteremic controls. The assay LODs were 5 genome equivalents per reaction and 10 CFU/ml blood for both the B. anthracis Sterne and V1B strains. There was a 6-log 10 dynamic range. Assay specificity was 100% for tests of non- B. anthracis bacterial isolates and patient blood samples. Assay time was less than 90 min. This automated system suitable for point-of-care detection rapidly identifies B. anthracis directly from blood with high sensitivity. This assay might lead to early detection and more rapid therapy in the event of a bioterrorism attack.
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Barnett, M. H., A. PD Henderson, and J. W. Prineas. "The macrophage in MS: just a scavenger after all? Pathology and pathogenesis of the acute MS lesion." Multiple Sclerosis Journal 12, no. 2 (April 2006): 121–32. http://dx.doi.org/10.1191/135248506ms1304rr.
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Advances in the neuropathology of multiple sclerosis (MS) have contributed greatly to our understanding of the mechanisms of tissue injury in the condition. Particular interest has focussed on the active MS lesion, defined by macrophage activity in the presence of partially demyelinated axons. This has led to the prevailing consensus that a T-cell dependent, macrophage-mediated, autoimmune attack on constituents in the normal myelin sheath underlies the disease. This hypothesis, which has been largely supported by comparisons with the animal model, experimental allergic encephalomyelitis, has recently been questioned by an analysis of the pathological events preceding myelin phagocytosis in nascent MS lesions. The prephagocytic changes in evolving lesions examined shortly after the onset of an MS relapse raise the possibility that oligodendrocyte cell death and associated changes within the myelin sheath initiate local macrophage scavenger activity, with subsequent amplification of the inflammatory response. The presence of such lesions in patients with a spectrum of pathological changes in nearby or distant active phagocytic plaques suggests that pathological heterogeneity in MS is largely due to evolution of lesional pathology, rather than pathogenic heterogeneity.
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Saito, I., B. Servenius, T. Compton, and R. I. Fox. "Detection of Epstein-Barr virus DNA by polymerase chain reaction in blood and tissue biopsies from patients with Sjogren's syndrome." Journal of Experimental Medicine 169, no. 6 (June 1, 1989): 2191–98. http://dx.doi.org/10.1084/jem.169.6.2191.
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Polymerase chain reaction has been used to detect increased levels of EBV DNA in salivary gland (SG) biopsies and PBL from patients with Sjogren's syndrome (SS). These results suggest that EBV, which has a normal site of latency in a small number of SG epithelial cells, may be reactivated in SS patients and provide a target for immune attack. The great sensitivity of polymerase chain reaction (PCR) and the ability to analyze very small tissue biopsies (37) make this technique well suited for clinical diagnosis. Specific methods to prevent artefactual contamination of tissue biopsy DNA with viral DNA of other samples (i.e., lyophilization of samples before DNA extraction) and the use of an internal positive control (i.e., inclusion of primers for a single copy human gene) during PCR amplification are presented. Since EBV reactivation occurs with markedly increased frequency in patients with lymphoproliferative and immunodeficiency diseases, as well as transplant recipients receiving cyclosporin A (10), rapid methods of viral detection such as PCR may allow better monitoring of medications and early detection of EBV-related lymphomas that may arise in these patients.
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Perrott, Matthew R., Christina J. Sigurdson, Gary L. Mason, and Edward A. Hoover. "Mucosal transmission and pathogenesis of chronic wasting disease in ferrets." Journal of General Virology 94, no. 2 (February 1, 2013): 432–42. http://dx.doi.org/10.1099/vir.0.046110-0.
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Chronic wasting disease (CWD) of cervids is almost certainly transmitted by mucosal contact with the causative prion, whether by direct (animal-to-animal) or indirect (environmental) means. Yet the sites and mechanisms of prion entry remain to be further understood. This study sought to extend this understanding by demonstrating that ferrets exposed to CWD via several mucosal routes developed infection, CWD prion protein (PrPCWD) amplification in lymphoid tissues, neural invasion and florid transmissible spongiform encephalopathy lesions resembling those in native cervid hosts. The ferrets developed extensive PrPCWD accumulation in the nervous system, retina and olfactory epithelium, with lesser deposition in tongue, muscle, salivary gland and the vomeronasal organ. PrPCWD accumulation in mucosal sites, including upper respiratory tract epithelium, olfactory epithelium and intestinal Peyer’s patches, make the shedding of prions by infected ferrets plausible. It was also observed that regionally targeted exposure of the nasopharyngeal mucosa resulted in an increased attack rate when compared with oral exposure. The latter finding suggests that nasal exposure enhances permissiveness to CWD infection. The ferret model has further potential for investigation of portals for initiation of CWD infection.
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Andriyani, Wiwien Mukti, Sumini Sumini, and Zeny Widiastuti. "Analysis of Vannamei shrimp DNA fragment resistant to White Spot Virus Syndrome." IJOTA (Indonesian Journal of Tropical Aquatic) 4, no. 1 (March 1, 2021): 31–40. http://dx.doi.org/10.22219/ijota.v4i1.15839.
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The attack of WSSV in Vannamei shrimp cultivation is still common. Shrimp quality improvement can be made through selection with the help of markers (marker-assisted choice). This study aimed to evaluate the DNA fragment profile of white shrimp that was resistant to WSSV disease. The analysis was performed using the PCR-RAPD method. WSSV challenged four groups of 100 Vannamei shrimp, then DNA was extracted from live and dead shrimp. The results showed that 2 of the 17 primers tested had high potential as markers, namely OP-09 and OPD-2. PCR products with OPC-09 primers had specific DNA bands measuring about 1.2 kb in all post-challenge WSSV resistant shrimp individuals. The amplification results using OPD-02 primers showed a particular band of DNA with a length of about 1.0 kb, with 60 % of the appearance in WSSV-resistant shrimp. In contrast, the WSSV-susceptible shrimp group did not have specific DNA fragments. Thus, the two RAPD primers had a high chance of being used in the selection with the help of markers to produce WSSV resistant shrimp.
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He, W., R. S. Gioria, J. M. Pérez, and V. Theofilis. "Linear instability of low Reynolds number massively separated flow around three NACA airfoils." Journal of Fluid Mechanics 811 (December 15, 2016): 701–41. http://dx.doi.org/10.1017/jfm.2016.778.
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Two- and three-dimensional modal and non-modal instability mechanisms of steady spanwise-homogeneous laminar separated flow over airfoil profiles, placed at large angles of attack against the oncoming flow, have been investigated using global linear stability theory. Three NACA profiles of distinct thickness and camber were considered in order to assess geometry effects on the laminar–turbulent transition paths discussed. At the conditions investigated, large-scale steady separation occurs, such that Tollmien–Schlichting and cross-flow mechanisms have not been considered. It has been found that the leading modal instability on all three airfoils is that associated with the Kelvin–Helmholtz mechanism, taking the form of the eigenmodes known from analysis of generic bluff bodies. The three-dimensional stationary eigenmode of the two-dimensional laminar separation bubble, associated in earlier analyses with the formation on the airfoil surface of large-scale separation patterns akin to stall cells, is shown to be more strongly damped than the Kelvin–Helmholtz mode at all conditions examined. Non-modal instability analysis reveals the potential of the flows considered to sustain transient growth which becomes stronger with increasing angle of attack and Reynolds number. Optimal initial conditions have been computed and found to be analogous to those on a cascade of low pressure turbine blades. By changing the time horizon of the analysis, these linear optimal initial conditions have been found to evolve into the Kelvin–Helmholtz mode. The time-periodic base flows ensuing linear amplification of the Kelvin–Helmholtz mode have been analysed via temporal Floquet theory. Two amplified modes have been discovered, having characteristic spanwise wavelengths of approximately 0.6 and 2 chord lengths, respectively. Unlike secondary instabilities on the circular cylinder, three-dimensional short-wavelength perturbations are the first to become linearly unstable on all airfoils. Long-wavelength perturbations are quasi-periodic, standing or travelling-wave perturbations that also become unstable as the Reynolds number is further increased. The dominant short-wavelength instability gives rise to spanwise periodic wall-shear patterns, akin to the separation cells encountered on airfoils at low angles of attack and the stall cells found in flight at conditions close to stall. Thickness and camber have quantitative but not qualitative effect on the secondary instability analysis results obtained.
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Haidar, Michael A., Mark A. van Buchem, Sigurdur Sigurdsson, John D. Gotal, Vilmundur Gudnason, Lenore J. Launer, and Gary F. Mitchell. "Wave Reflection at the Origin of a First-Generation Branch Artery and Target Organ Protection." Hypertension 77, no. 4 (April 2021): 1169–77. http://dx.doi.org/10.1161/hypertensionaha.120.16696.
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Excessive pressure and flow pulsatility in first-generation branch arteries are associated with microvascular damage in high-flow organs like brain and kidneys. However, the contribution of local wave reflection and rereflection to microvascular damage remains controversial. Aortic flow, carotid pressure, flow and hydraulic power, brain magnetic resonance images, and cognitive scores were assessed in AGES-Reykjavik study participants without history of stroke, transient ischemic attack, or dementia (N=668, 378 women, 69–93 years of age). The aorta-carotid interface was generalized as a markedly asymmetrical bifurcation, with a large parent vessel (proximal aorta) branching into small (carotid) and large (distal aorta) daughter vessels. Local reflection coefficients were computed from aortic and carotid characteristic impedances. The bifurcation reflection coefficient, which determines pressure amplification in both daughter vessels, was low (0.06±0.03). The carotid flow transmission coefficient was low (0.11±0.04) and associated with markedly lower carotid versus aortic flow pulsatility (waveform SD, 7.2±2.0 versus 98.7±21.8 mL/s, P <0.001), pulsatility index (1.8±0.5 versus 4.5±0.6, P <0.001), and pulsatile power percentage (10±4% versus 25±5%, P <0.001). Transmitted as compared to incident pulsatile power (19.0±9.8 versus 35.9±17.8 mW, P <0.001) was further reduced by reflection (−4.3±2.7 mW) and rereflection (−12.5±8.1 mW) within the carotid. Higher carotid flow pulsatility correlated with lower white matter volume (R=−0.130, P <0.001) and lower memory scores (R=−0.161, P <0.001). Marked asymmetry of characteristic impedances at aorta-branch artery bifurcations limits amplification of pressure, markedly reduces absolute and relative pulsatility of transmitted flow and hydraulic power into first-generation branch arteries, and thereby protects the downstream local microcirculation from pulsatile damage.
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Prihatini, Istiana, I. L. G. Nurtjahjaningsih, Farah Aulya Faradilla, and Suranto Suranto. "DETEKSI DAN IDENTIFIKASI Austropuccinia psidii PADA MYRTACEAE DI YOGYAKARTAINDONESIA." Jurnal Pemuliaan Tanaman Hutan 14, no. 2 (December 30, 2020): 101–10. http://dx.doi.org/10.20886/jpth.2020.14.2.101-110.
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Austropuccinia psidii is a pathogenic fungus that causes rust in the Myrtaceae plant. The extensive plantation of the host of this fungus has increased the attack of fungal pathogen, therefore, will increase the threat tothe presence of Myrtaceae species around the globe including in Indonesia. This present study was aiming to detect and identify the presence of this pathogen by morphologicaland molecular observation. Morphological observationrevealed the presence of A. psidii urediniospores onsalam (Syzygium polyanthum) andkayuputih (Melaleuca cajuputi)leaves collected from the arboretum of the Indonesian Center for Forest Biotechnology and Tree Improvement (CFBTI), and the presence of teliospores on young Syzygium leaves. PCR amplification using specific primers of Ppsi1 / Ppsi6 succeeded in detecting the presence of A. psidii fungi Melaleuca and Syzygium showed by DNA amplicon length around 500bp. Efforts to obtain ITS DNA sequences to compare the molecular characteristics of fungi from two different hosts have been carried out, however, the sequencing electropherogram was unreadable, so the comparison can not be performed. This study reported that A. psidii is currently present in Myrtaceae species in Yogyakarta, therefore precaution efforts should be conducted to avoid economic and ecological impact from this pathogen.
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Wisenden, Brain D. "Olfactory assessment of predation risk in the aquatic environment." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 355, no. 1401 (September 29, 2000): 1205–8. http://dx.doi.org/10.1098/rstb.2000.0668.
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The aquatic environment is well suited for the transmission of chemical information. Aquatic animals have evolved highly sensitive receptors for detecting these cues. Here, I review behavioural evidence for the use of chemical cues by aquatic animals for the assessment of predation risk. Chemical cues are released during detection, attack, capture and ingestion of prey. The nature of the cue released depends on the stage of the predation sequence in which cues are released. Predator odours, disturbance pheromones, injury–released chemical cues and dietary cues all convey chemical information to prey. Prey use these cues to minimize their probability of being taken on to the next stage of the sequence. The evolution of specialized epidermal alarm substance cells in fishes in the superorder Ostariophysi represent an amplification of this general phenomenon. These cells carry a significant metabolic cost. The cost is offset by the fitness benefit of the chemical attraction of predators. Attempts of piracy by secondary predators interrupt predation events allowing prey an opportunity for escape. In conclusion, chemical cues are widely used by aquatic prey for risk assessment and this has resulted in the evolution of specialized structures among some taxa.
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Gross, Andreas, and Hermann Fasel. "Active Control of Laminar Separation: Simulations, Wind Tunnel, and Free-Flight Experiments." Aerospace 5, no. 4 (October 30, 2018): 114. http://dx.doi.org/10.3390/aerospace5040114.
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When a laminar boundary layer is subjected to an adverse pressure gradient, laminar separation bubbles can occur. At low Reynolds numbers, the bubble size can be substantial, and the aerodynamic performance can be reduced considerably. At higher Reynolds numbers, the bubble bursting can determine the stall characteristics. For either setting, an active control that suppresses or delays laminar separation is desirable. A combined numerical and experimental approach was taken for investigating active flow control and its interplay with separation and transition for laminar separation bubbles for chord-based Reynolds numbers of Re ≈ 64,200–320,000. Experiments were carried out both in the wind tunnel and in free flight using an instrumented 1:5 scale model of the Aeromot 200S, which has a modified NACA 643-618 airfoil. The same airfoil was also used in the simulations and wind tunnel experiments. For a wide angle of attack range below stall, the flow separates laminar from the suction surface. Separation control via a dielectric barrier discharge plasma actuator and unsteady blowing through holes were investigated. For a properly chosen actuation amplitude and frequency, the Kelvin–Helmholtz instability results in strong disturbance amplification and a “roll-up” of the separated shear layer. As a result, an efficient and effective laminar separation control is realized.
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Zhang, Ying, Xia Wang, Cheng Cheng, Qiuqiang Gao, Jingyun Liu, and Xingqi Guo. "Molecular cloning and characterization of GhNPR1, a gene implicated in pathogen responses from cotton (Gossypium hirsutum L.)." Bioscience Reports 28, no. 1 (February 1, 2008): 7–14. http://dx.doi.org/10.1042/bsr20070028.
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A novel gene, designated as GhNPR1 (Gossypium hirsutum non-expressor of pathogenesis-related genes 1), was isolated from G. hirsutum (cotton) by RT–PCR (reverse transcription–PCR) and RACE (rapid amplification of cDNA ends). The full-length cDNA was 2108 bp long and had an ORF (open reading frame) that putatively encoded a polypeptide of 592 amino acids, with a predicted molecular mass of 66 kDa. Comparison of this protein sequence with that of Arabidopsis thaliana, Brassica juncea and Nicotiana tabacum showed that the amino-acid homology was 52.98, 52.32 and 54.98% respectively. Analysis of the exon–intron structure of the GhNPR1 gene showed that GhNPR1 consisted of four exons and three introns. Southern-blot analysis revealed that the GhNPR1 was a single-copy gene in cotton. Northern-blot analysis indicated that GhNPR1 was constitutively expressed in all tested tissues, including roots, stems and leaves, with the high expression in stems and leaves. In addition, GhNPR1 was also found to be induced by signalling molecules for plant defence responses, such as methyl jasmonate, salicylic acid and ethylene, as well as attack by pathogens, such as Fusarium oxysporum and Xanthomonas campestris. These results suggest that GhNPR1 may play an important role in the response to pathogen infections in cotton plants.
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Dos Santos, C. Vieira, P. Letousey, P. Delavault, and P. Thalouarn. "Defense Gene Expression Analysis of Arabidopsis thaliana Parasitized by Orobanche ramosa." Phytopathology® 93, no. 4 (April 2003): 451–57. http://dx.doi.org/10.1094/phyto.2003.93.4.451.
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The infection of Arabidopsis thaliana roots with the obligate parasite Orobanche ramosa represents a useful model for a study of the molecular events involved in the host plant response to a parasitic plant attack. To avoid analysis problems due to the subterranean development of O. ramosa, we developed two in vitro co-culture systems: O. ramosa seedlings infesting Arabidopsis plantlet roots and callus tissues. We were then able to investigate the expression patterns of some host plant genes selected among genes known to be involved in metabolic pathways and resistance mechanisms activated during several plant-pathogen interactions including ethylene, isoprenoid, phenylpropanoid, and jasmonate biosynthesis pathways, oxidative stress responses, and pathogenesis-related proteins. Molecular analyses were carried out using polymerase chain reaction amplification methods allowing semiquantitative evaluation of transcript accumulation during early (first hours) and late (15 days) stages of infestation, in whole roots or parts close to the parasite attachment site. In A. thaliana, O. ramosa induced most of the general response signaling pathways in a transient manner even before its attachment to A. thaliana roots. However, no salicylic acid-dependent defense is observed because no activation of systemic acquired resistance markers is detectable, whereas genes, co-regulated by jasmonate and ethylene, do display enhanced expression.
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van Schaik, IN, M. Vermeulen, and A. Brand. "Immunomodulation and remyelination: two aspects of human polyclonal immunoglobulin treatment in immune mediated neuropathies?" Multiple Sclerosis Journal 3, no. 2 (April 1997): 98–104. http://dx.doi.org/10.1177/135245859700300208.
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Intravenous immunoglobulin is used in inflammatory demyelinating diseases of the peripheral as well as the central nervous system. It is not known which mechanism(s) accounts for the beneficial effect observed in these diseases. The immunomodulatory effects of IVIg in two different models of T and B cell activation were investigated. IVIg inhibited a predominantly cellular immune response of the Th 1 type, which was partially reversed by addition of Th 1 cytokines. In contrast, in a model, which leads to B cell differentiation and antibody production, a synergistic stimulatory effect of IVIg and Th2 cytokines was observed. The ability of IVIg to interfere with cell proliferation and to manipulate the Th 1/Th2 profile will have consequences for the induction, character, and amplification of an immune response. Apart from the immunomodulatory effects, evidence shows that IVIg promote remyelination not only by abrogation of the auto-immune attack but also by an effect on glial cells. We showed that IVIg induce growth arrest of normal human fibroblasts and Schwann cells. In fibroblasts this growth arrest is accompanied by upregulation of GAS-3/PMP-22 mRNA. The implications of this finding are discussed. Further studies in human Schwann cells are imperative to prove the hypothesis that IVIg directly stimulates remyelination.
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Irsalan, Arif Muhammad, Garret C. Y. Lam, and Randolph C. K. Leung. "Numerical Study of Airfoil Tonal Noise Reduction using Segmented Elastic Panel Configuration." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 4 (August 1, 2021): 2916–29. http://dx.doi.org/10.3397/in-2021-2258.
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In this paper, a novel passive method for airfoil tonal noise reduction is proposed using a configuration of two segmented elastic panels mounted on the airfoil. Numerical investigation using perturbation evolution method is carried out at a low Reynolds number based on airfoil chord of 5x10 and an angle of attack of 5. The passive method of employing a single panel has shown promising tonal noise reduction capabilities where the resonating panel located just ahead of the sharp growth of boundary layer instability within the airfoil separation bubble provided the strongest reduction of instabilities and noise reduction up to 3 dB has been achieved. The idea is extended in the present study by employing a two-panel configuration based on the localized flow characteristics over the airfoil surface. Five different panel configurations are designed and their effectiveness in terms of tonal noise reduction is evaluated and compared with baseline configuration. The azimuth and spectral analyses indicate the different extent of noise reduction for each configuration and even noise amplification in one of them. A significant noise reduction up to 8 dB is observed for the optimum configuration indicating the effectiveness of this novel method for devices operating at low Reynolds number.
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Iyany, N. G., and A. E. Ataga. "Isolation and Molecular Identification of some Fungi Associated with Jatropha curcas (L.)." Nigerian Journal of Biotechnology 37, no. 2 (March 12, 2021): 103–12. http://dx.doi.org/10.4314/njb.v37i2.10.
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Jatropha curcas is a plant of great economic importance that experiences high incidence of fungal attack. Misidentification of the fungal species is bound to occur with the use of traditional cultural methods where organisms are identified morphologically and/or microscopically. This study was carried out to isolate and identify the fungi associated with Jatropha curcas (L.) using both traditional/ cultural techniques and molecular methods. The fungi were isolated from diseased leaves and stems of J. curcas using both Standard Blotter and Potato Dextrose Agar (PDA) methods. DNA was extracted from the fungal isolates using Zymo Fungal/Bacteria DNA MiniPrep Kit. Amplification of the Internal Transcribed Spacer (ITS) regions of the fungal isolates was carried out using fungi universal primer pairs for ITS4 and ITS5. The amplicons were sequenced and the isolates were identified as Penicillium brevicompactum, Aspergillus sp., Botryosphaeria rhodina, Aspergillus nomius, Aspergillus tamarii, Rhizopus oryzae, Penicillium citrinum and Fusarium solani. Phylogenetic analysis was carried out to know the relationship between the isolates and other closely-related species in GenBank. Jatropha curcas is colonized by many fungal species some of which may be pathogenic to the plant, and molecular techniques pose the best alternative for accurate identification of these organisms.
Keywords: Jatropha curcas, fungi, polymerase chain reaction, phylogeny, sequencing
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Hasan, Dana, Rebeen R. Hama Amin, and Masnida Hussin. "Efficient Authentication Mechanism for Defending Against Reflection-Based Attacks on Domain Name System." Kurdistan Journal of Applied Research 5, no. 1 (June 13, 2020): 164–74. http://dx.doi.org/10.24017/science.2020.1.12.
Full textAbstract:
Domain Name System (DNS) is one of few services on the Internet which is allowed through every security barrier. It mostly depends on the User Datagram Protocol (UDP) as the transport protocol, which is a connectionless protocol with no built-in authentication mechanism. On top of that, DNS responses are substantially larger than their corresponding requests. These two key features made DNS a fabulous attacking tool for cybercriminals to reflect and amplify a huge volume of requests to consume their victim's resources. Recent incidents revealed how harsh DNS could be when it is abused with great complexity by attackers. Moreover, these events had proven that any defense mechanism with single point deployment couldn’t accurately and efficiently overcome an attack volume with high dynamicity. In this paper, we proposed the Efficient Distributed-based Defense Scheme (EDDS) to overcome the shortcomings of a centralized-based defense mechanism. By using an authentication message exchange, which is a Challenge-Handshake Authentication Protocol (CHAP)-based authentication mechanism. It is deployed on multiple nodes to determine the legitimacy of the DNS request. Moreover, it significantly reduces the impact of the amplification factor for the fake DNS requests without having any side effects on legitimate ones. Then, a Stateful Packet Inspection (SPI)-based packet filtering is proposed to distinguish legitimate requests from fake ones by considering the results of the authentication procedure. Both authentication-message exchange and SPI-based filtering are introduced to provide detection accuracy without reducing the quality of service for legitimate users. As the simulation results show, the proposed mechanism can efficiently and accurately detect, isolate, and discard the bogus traffic with minimal overhead on the system.
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Busby, P. A., Y. C. Tong, and G. M. Clark. "Underlying Structure of Auditory-Visual Consonant Perception by Hearing-Impaired Children and the Influences of Syllabic Compression." Journal of Speech, Language, and Hearing Research 31, no. 2 (June 1988): 156–65. http://dx.doi.org/10.1044/jshr.3102.156.
Full textAbstract:
The identification of consonants in a/-C-/a/nonsense syllables, using a fourteen-alternative forced-choice procedure, was examined in 4 profoundly hearing-impaired children under five conditions: audition alone using hearing aids in free-field (A),vision alone (V), auditory-visual using hearing aids in free-field (AV1), auditory-visual with linear amplification (AV2), and auditory-visual with syllabic compression (AV3). In the AV2 and AV3 conditions, acoustic signals were binaurally presented by magnetic or acoustic coupling to the subjects' hearing aids. The syllabic compressor had a compression ratio of 10:1, and attack and release times were 1.2 ms and 60 ms. The confusion matrices were subjected to two analysis methods: hierarchical clustering and information transmission analysis using articulatory features. The same general conclusions were drawn on the basis of results obtained from either analysis method. The results indicated better performance in the V condition than in the A condition. In the three AV conditions, the subjects predominately combined the acoustic parameter of voicing with the visual signal. No consistent differences were recorded across the three AV conditions. Syllabic compression did not, therefore, appear to have a significant influence on AV perception for these children. A high degree of subject variability was recorded for the A and three AV conditions, but not for the V condition.
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Clarkson, Joshua J., Zakary L. Tormala, and Derek D. Rucker. "Cognitive and Affective Matching Effects in Persuasion." Personality and Social Psychology Bulletin 37, no. 11 (July 6, 2011): 1415–27. http://dx.doi.org/10.1177/0146167211413394.
Full textAbstract:
Past research suggests that cognitive and affective attitudes are more open to change toward cognitive and affective (i.e., matched) persuasive attacks, respectively. The present research investigates how attitude certainty influences this openness. Although an extensive literature suggests that certainty generally reduces an attitude’s openness to change, the authors explore the possibility that certainty might increase an attitude’s openness to change in the context of affective or cognitive appeals. Based on the recently proposed amplification hypothesis, the authors posit that high (vs. low) attitude certainty will boost the resistance of attitudes to mismatched attacks (e.g., affective attitudes attacked by cognitive messages) but boost the openness of attitudes to matched attacks (e.g., affective attitudes attacked by affective messages). Two experiments provide support for this hypothesis. Implications for increasing the openness of attitudes to both matched and mismatched attacks are discussed.
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Fedorov, Alexander V. "Receptivity of a supersonic boundary layer to solid particulates." Journal of Fluid Mechanics 737 (November 18, 2013): 105–31. http://dx.doi.org/10.1017/jfm.2013.564.
Full textAbstract:
AbstractLaminar–turbulent transition in the boundary layer at supersonic speeds can be initiated by small solid particles present in the free stream. Particulates interacting with the boundary-layer flow generate unstable wavepackets related to Tollmien–Schlichting (TS) waves. The latter grow downstream and ultimately break down to turbulent spots. This scenario of TS-dominated transition is modelled using the Mack amplitude method. A theoretical model describing the receptivity mechanism is developed to predict the initial spectrum of TS waves. With these initial conditions the downstream growth of TS instability is calculated using the linear stability theory. The transition onset is associated with the point where the disturbance amplitude reaches a threshold value. As an example, calculations are carried out for a 14° half-angle sharp wedge flying in the standard atmosphere at altitude 20 km, Mach number 4 and zero angle of attack. It is shown that spherical particles of radius from $10$ to $20~\unicode[.5,0][STIXGeneral,Times]{x03BC} \mathrm{m} $ and density ${\geqslant }1~\mathrm{g} ~{\mathrm{cm} }^{- 3} $ can cause transition onset corresponding to the amplification factor $N= 9{\unicode{x2013}} 10$, which is in the empirical range of flight data. This indicates that atmospheric particulates may be a major source of TS-dominated transition on aerodynamically smooth surfaces at supersonic speeds. The receptivity model provides a foundation for further treatments of different cases associated with transition in dusty environments. It can also be used for predictions of particle-induced transition at subsonic and hypersonic speeds.
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Zhang, Jing-Ren, and Steven J. Norris. "Kinetics and In Vivo Induction of Genetic Variation of vlsE in Borrelia burgdorferi." Infection and Immunity 66, no. 8 (August 1, 1998): 3689–97. http://dx.doi.org/10.1128/iai.66.8.3689-3697.1998.
Full textAbstract:
ABSTRACT The Lyme disease agent, Borrelia burgdorferi, is able to persistently infect humans and animals for months or years in the presence of an active immune response. It is not known how the organisms survive immune attack in the mammalian host.vlsE, a gene localized near one end of linear plasmid lp28-1 and encoding a surface-exposed lipoprotein in B. burgdorferi B31, was shown recently to undergo extensive genetic and antigenic variation within 28 days of initial infection in C3H/HeN mice. In this study, we examined the kinetics of vlsEsequence variation in C3H/HeN mice at 4, 7, 14, 21, and 28 days and at 7 and 12 months postinfection. Sequence changes were detected by PCR amplification and sequence analysis as early as 4 days postinfection and accumulated progressively in both C3H/HeN and CB-17 severe combined immunodeficient (SCID) mice throughout the course of infection. The sequence changes were consistent with sequential recombination of segments from multiple silent vls cassette sites into thevlsE expression site. No vlsE sequence changes were detected in organisms cultured in vitro for up to 84 days. These results indicate that vlsE recombination is induced by a factor(s) present in the mammalian host, independent of adaptive immune responses. The possible inducing conditions appear to be present in various tissue sites because isolates from multiple tissues showed similar degrees of sequence variation. The rate of accumulation of predicted amino acid changes was higher in the immunologically intact C3H/HeN mice than in SCID mice, a finding consistent with immune selection of VlsE variants.