Articoli di riviste: "Spread ALOHA"

1

Sasamori, Fumihito, e Fumio Takahata. "Transmission efficiency of spread ALOHA system using unified spread-spectrum code". Electronics and Communications in Japan (Part I: Communications) 79, n. 1 (1996): 107–15. http://dx.doi.org/10.1002/ecja.4410790111.

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Sang Wu Kim. "Stabilization of slotted ALOHA spread-spectrum communication networks". IEEE Journal on Selected Areas in Communications 8, n. 4 (maggio 1990): 555–61. http://dx.doi.org/10.1109/49.54453.

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Gallinaro, Gennaro, Filippo Di Cecca, Maria-Antonietta Marchitti, Riccardo De Gaudenzi e Oscar Del Rio Herrero. "Enhanced spread spectrum ALOHA system level performance assessment". International Journal of Satellite Communications and Networking 32, n. 6 (11 novembre 2013): 485–503. http://dx.doi.org/10.1002/sat.1057.

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De Gaudenzi, Riccardo, Oscar del Rio Herrero e Gennaro Gallinaro. "Enhanced spread Aloha physical layer design and performance". International Journal of Satellite Communications and Networking 32, n. 6 (13 maggio 2014): 457–73. http://dx.doi.org/10.1002/sat.1078.

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Enomoto, Masaru, e Fumio Takahata. "An application of chirp to spread-ALOHA system". Electronics and Communications in Japan (Part I: Communications) 78, n. 1 (gennaio 1995): 72–81. http://dx.doi.org/10.1002/ecja.4410780107.

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6

Kim, Tae-Joong, Jin-Ho Lee, Byeong-Gwon Kang e Keum-Chan Whang. "CLSP with channel clearance for spread slotted ALOHA network". Electronics Letters 33, n. 18 (1997): 1524. http://dx.doi.org/10.1049/el:19971020.

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Makrakis, D., e K. M. S. Murthy. "Spread slotted ALOHA techniques for mobile and personal satellite communication systems". IEEE Journal on Selected Areas in Communications 10, n. 6 (1992): 985–1002. http://dx.doi.org/10.1109/49.144885.

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Toshimitsu, K., T. Yamazato, M. Katayama e A. Ogawa. "A novel spread slotted Aloha system with channel load sensing protocol". IEEE Journal on Selected Areas in Communications 12, n. 4 (maggio 1994): 665–72. http://dx.doi.org/10.1109/49.286673.

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Jamalipour, A., M. Katayama, T. Yamazato e A. Ogawa. "Transmit permission control on spread ALOHA packets in LEO satellite systems". IEEE Journal on Selected Areas in Communications 14, n. 9 (1996): 1748–57. http://dx.doi.org/10.1109/49.545697.

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Andrenacci, Marco, Gaetano Mendola, Florian Collard, Daniele Finocchiaro e Annamaria Recchia. "Enhanced spread spectrum aloha demodulator implementation, laboratory tests and satellite validation". International Journal of Satellite Communications and Networking 32, n. 6 (novembre 2014): 521–33. http://dx.doi.org/10.1002/sat.1086.

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I. A. Jabbar, A. "Applying Direct Sequence Spread Spectrum to Improve the Throughput of Aloha Protocols". AL-Rafdain Engineering Journal (AREJ) 17, n. 5 (28 ottobre 2009): 23–31. http://dx.doi.org/10.33899/rengj.2009.43379.

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Goel, M. K., e Vinod Chandra. "A rural messaging network using spread ALOHA access with VSAT satellite terminals". International Journal of Satellite Communications 10, n. 3 (maggio 1992): 93–103. http://dx.doi.org/10.1002/sat.4600100302.

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Noh, Hong-jun, Hyung-won Park e Jae-sung Lim. "High-Efficiency and Low-Complexity Spread Spectrum ALOHA for Machine-to-Machine Communications". Journal of Korean Institute of Communications and Information Sciences 41, n. 12 (31 dicembre 2016): 1700–1706. http://dx.doi.org/10.7840/kics.2016.41.12.1700.

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Gonzalez, O. A., e R. Kohno. "A spread slotted CDMA/ALOHA system with hybrid ARQ for satellite multiple access". IEEE Journal on Selected Areas in Communications 18, n. 1 (gennaio 2000): 123–31. http://dx.doi.org/10.1109/49.821726.

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Yang, Liu, Pingzhi Fan, Li Hao e Naoki Suehiro. "Joint Delay-Power Multiple Packet Capture Scheme for Spread-Spectrum Slotted ALOHA Packet Radio Networks". Wireless Personal Communications 54, n. 3 (3 giugno 2009): 485–500. http://dx.doi.org/10.1007/s11277-009-9736-x.

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Collard, Florian, e Riccardo De Gaudenzi. "On the Optimum Packet Power Distribution for Spread Aloha Packet Detectors With Iterative Successive Interference Cancelation". IEEE Transactions on Wireless Communications 13, n. 12 (dicembre 2014): 6783–94. http://dx.doi.org/10.1109/twc.2014.2361331.

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Kim, Yi-Kang, e Seung-Yeon Kim. "Success Probability Characterization of Long-Range in Low-Power Wide Area Networks". Sensors 20, n. 23 (30 novembre 2020): 6861. http://dx.doi.org/10.3390/s20236861.

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In low-power wide area networks (LPWAN), a considerable number of end devices (EDs) communicate with the gateway in a certain area, whereas for transmitted data, a low data rate and high latency are allowed. Long-range (LoRa), as one of the LPWAN technologies, considers pure ALOHA and chirp spread spectrum (CSS) in the media access control (MAC) and physical (PHY) layers such that it can improve the energy efficiency while mitigating inter-cell interference (ICI). This paper investigates the system throughput of LoRa networks under the assumption that the interferences between EDs for exclusive regions are ignored using CSS. In order to establish an analytical model for the performance of LoRa, we introduce the pure ALOHA capture model, which is the power threshold model. For this model, we assume that the interfering power is proportional to the length of the time overlapped. In addition, we discuss LoRa gain by comparing the total throughput of LoRa with that of non-CSS.

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Gou, Liang, Dongming Bian, Baogui Dong e Yulei Nie. "Improved Spread Spectrum Aloha Protocol and Beam-Hopping Approach for Return Channel in Satellite Internet of Things". Sensors 23, n. 4 (13 febbraio 2023): 2116. http://dx.doi.org/10.3390/s23042116.

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This paper examines potential performances of the Spread Spectrum-based random access technique and proposes an Improved Spread Spectrum Aloha (ISSA) protocol for the return channel in satellite Internet of Things (IoT) based on the beam-hopping technique. The key design driver and detailed solution of ISSA protocol are presented in this work and it is shown that the proposed protocol achieves high throughput and low collision probability. To match user/traffic distribution, delay requirement and channel condition with beam allocation better, a low-complexity heuristic beam scheduling algorithm and a more effective Maximum-Weighted Clique (MWC) algorithm have been proposed. The heuristic algorithm considers the user/traffic distribution, inter-beam interference, and fairness primarily. However, the MWC algorithm gives considerations not only on above factors, but also on delay requirement and channel condition (path loss and rain attenuation) to maximize system capacity. The beam angle and interference avoidance threshold are proposed to measure the inter-beam interference, and the link propagation loss and rain attenuation are considered meanwhile in the channel condition. In the MWC algorithm, we construct an auxiliary graph to find the maximum-weighted clique and derive the weighting approach to be applied in different application scenarios. The performance evaluation of our ISSA protocol compared with the SSA protocol is presented, which achieves a gain of 16.7%. The simulation of the ISSA protocol combined with round robin, heuristic, and MWC beam scheduling for the return link in beam-hopping satellite IoTs is also provided. The results indicate that the throughput in nonuniform user distribution is much lower than in the uniform case without the beam scheduling algorithm. Through the application of the scheduling algorithm, the throughput performance can approach the uniform distribution. Finally, the degree of user satisfaction with different scheduling approaches is presented, which validates the effectiveness of heuristic and MWC algorithms.

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Kulinič, Vitalij, e Michał Maruta. "ALOHA – modern tool for modeling the risks associated with the spread of volatile pollutants in extraction of hydrocarbons". AGH Drilling, Oil, Gas 33, n. 2 (2016): 315. http://dx.doi.org/10.7494/drill.2016.33.2.315.

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Dlodlo, M. E., Wai Hung Wong e R. Prasad. "Performance of type-II hybrid ARQ in a shadowed Rician fading LEO satellite-based spread slotted ALOHA communication channel". Electronics Letters 33, n. 3 (1997): 186. http://dx.doi.org/10.1049/el:19970123.

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Saloglu, Didem, Halil Dertli, Mandana Mohammadi e Mitra Mohammadi. "Emission rates, ALOHA simulation and Box-Behnken design of accidental releases in butyl acrylate tank - case study". Production Engineering Archives 28, n. 4 (21 ottobre 2022): 346–58. http://dx.doi.org/10.30657/pea.2022.28.43.

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Abstract The leakage of hazardous compounds in chemical industries has always been one of the factors threatening workers, plants, and the environment. Among them, butyl acrylate is one of the most harmful materials that are widely used in chemical plants. In the present study, a butyl acrylate tank located in a real tank farm in Kocaeli-Turkey was analyzed for the examination of emissions and trinitrotoluene (TNT) equivalent explosion model of the vapor cloud. Areal Locations of Hazardous Atmospheres (ALOHA) program was used to define threat zones of butyl acrylate leakage based on different scenarios, such as a leakage from the tank without fire, burning as a jet fire, and also burning as a fireball during Boiling Liquid Expanding Vapor Explosion (BLEVE). In addition, since the most important parameters that enhance the effects of explosion and the spread of volatile organic compounds (VOCs) are wind speed, filling ratio of the tanks, and temperature, the interaction of these parameters on the threat zones and the highest threat zones of explosions were investigated using the Box-Behnken experimental design and one-way Analysis of Variance (ANOVA), respectively. As butyl acrylate, one of the most dangerous chemicals for industrial facilities, and its explosion effects have not been studied so far, it can be safely mentioned that this paper representing the first study in the literature is highly original and novel.

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Arcidiacono, Antonio, Daniele Finocchiaro, Riccardo De Gaudenzi, Oscar del Rio-Herrero, Stefano Cioni, Marco Andrenacci e Riccardo Andreotti. "Is Satellite Ahead of Terrestrial in Deploying NOMA for Massive Machine-Type Communications?" Sensors 21, n. 13 (23 giugno 2021): 4290. http://dx.doi.org/10.3390/s21134290.

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Non-orthogonal multiple access (NOMA) technologies are considered key technologies for terrestrial 5G massive machine-type communications (mMTC) applications. It is less known that NOMA techniques were pioneered about ten years ago in the satellite domain to match the growing demand for mMTC services. This paper presents the key features of the first NOMA-based satellite network, presenting not only the underlying technical solutions and measured performance but also the related deployment over the Eutelsat satellite fleet. In particular, we describe the specific ground segment developments for the user terminals and the gateway station. It is shown that the developed solution, based on an Enhanced Spread ALOHA random access technique, achieves an unprecedented throughput, scalability and service cost and is well matched to several mMTC satellite use cases. The ongoing R&D lines covering both the ground segment capabilities enhancement and the extension to satellite on-board packet demodulation are also outlined. These pioneering NOMA satellite technology developments and in-the-field deployments open up the possibility of developing and exploiting 5G mMTC satellite- and terrestrial-based systems in a synergic and interoperable architecture.

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Polorecka, Maria, Jozef Kubas, Pavel Danihelka, Katarina Petrlova, Katarina Repkova Stofkova e Katarina Buganova. "Use of Software on Modeling Hazardous Substance Release as a Support Tool for Crisis Management". Sustainability 13, n. 1 (5 gennaio 2021): 438. http://dx.doi.org/10.3390/su13010438.

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Today’s modern society offers many new opportunities, but also many risks. Even modernization of companies cannot completely eliminate these dangers. In the smart industry, despite significant technological progress, it is necessary to work with various raw materials, including hazardous substances. It is these raw materials that will continue to pose risks in the future for industrial accidents, which cannot be ruled out. The possible release of hazardous substances can potentially have a negative impact on the environment and safety of the population. In order to deal with certain emergencies, it is necessary to allocate a large amount of funds and resources to them. The paper focuses on risk prevention in industry and the use of modern and new approaches. Specifically, it focuses on the implementation of the prevention of leakage of hazardous substances in the gaseous state from industrial facilities. The aim of the paper is to present a new approach to the prevention of leakage of hazardous substances, which provides more realistic calculations for modeling leaks and thus helps to reduce the cost of prevention. However, security in crisis management is not diminished. ALOHA CAMEO software was used for leak modeling, which the authors commonly use in practical applications and modeling in industrial enterprises in the performance of duties in the field of civil protection and crisis management. ALOHA software is used for such modeling, serving as a support tool for modeling for all crisis managers in Industry 4.0. This paper deals with the modeling of dispersion of hazardous substances with specific properties escaping from technological equipment located inside a building. This concerns the inability of the current dispersion model software to prevent the spread of the next leak inside the building containing the substance. A solution is needed to fix this problem. This issue is well illustrated by a specific example at the end of this article. The mentioned improvement of tools for simulation of industrial accidents influences the possibilities of development also in Industry 4.0. It enables more effective preparation for the management of possible accidents with regard to the appropriate spending of funds for prevention and subsequent response.

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Hwang, Woonyong. "A Study on the Prediction of Damage Ranges by Leakages of Seaport-Stored Substances". Journal of the Korean Society of Hazard Mitigation 21, n. 2 (30 aprile 2021): 23–31. http://dx.doi.org/10.9798/kosham.2021.21.2.23.

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In order to check the risk of hydrogen peroxide leakage from the seaport, the leakage amount was changed from 1.0 ton to 10.0 tons, with the maximum and minimum diffusion distances per month in 2020 being subsequently calculated. A total of 82 scenarios were created to confirm the change in the diffusion distance according to the amount of leakage. The scenario was analyzed based on the distance at which the risk concentration was maintained through the ALOHA Air Dispersion Models. As indicated by the analysis, when the amount of leakage is relatively large, the temperature is also high and the wind speed is fast - resulting in the maximum spread. However, when the amount of leakage was relatively minimal, the temperature was low and the wind speed remained fast - this kept diffusion to the minimum. Concerning characteristics of fast wind speeds, the dispersion length changed based on amounts of leakages where PAC-1 contains 2.0 tons, PAC-2 contains 4.0 tons, and PAC-3 contains 5.0 tons. In addition, when the amount of leakage equaled 10.0 tons, and the wind speed was high, the dispersion length reached up to 10 kms. In light of this, it was confirmed that even adjacent administrative districts were affected. Therefore, it is necessary to establish appropriate measures to prevent damage by utilizing the diffusion distance caused by chemical leakages.

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Anugerahanti, Prima, Shovonlal Roy e Keith Haines. "A perturbed biogeochemistry model ensemble evaluated against in situ and satellite observations". Biogeosciences 15, n. 21 (12 novembre 2018): 6685–711. http://dx.doi.org/10.5194/bg-15-6685-2018.

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Abstract. The dynamics of biogeochemical models are determined by the mathematical equations used to describe the main biological processes. Earlier studies have shown that small changes in the model formulation may lead to major changes in system dynamics, a property known as structural sensitivity. We assessed the impact of structural sensitivity in a biogeochemical model of intermediate complexity by modelling the chlorophyll and dissolved inorganic nitrogen (DIN) concentrations. The model is run at five different oceanographic stations spanning three different regimes: oligotrophic, coastal, and the abyssal plain, over a 10-year timescale to observe the effect in different regions. A 1-D Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration, and Acidification (MEDUSA) ensemble was used with each ensemble member having a combination of tuned function parameterizations that describe some of the key biogeochemical processes, namely nutrient uptake, zooplankton grazing, and plankton mortalities. The impact is quantified using phytoplankton phenology (initiation, bloom time, peak height, duration, and termination of phytoplankton blooms) and statistical measures such as RMSE (root-mean-squared error), mean, and range for chlorophyll and nutrients. The spread of the ensemble as a measure of uncertainty is assessed against observations using the normalized RMSE ratio (NRR). We found that even small perturbations in model structure can produce large ensemble spreads. The range of 10-year mean surface chlorophyll concentration in the ensemble is between 0.14 and 3.69 mg m−3 at coastal stations, 0.43 and 1.11 mg m−3 on the abyssal plain, and 0.004 and 0.16 mg m−3 at the oligotrophic stations. Changing both phytoplankton and zooplankton mortalities and the grazing functions has the largest impact on chlorophyll concentrations. The in situ measurements of bloom timings, duration, and terminations lie mostly within the ensemble range. The RMSEs between in situ observations and the ensemble mean and median are mostly reduced compared to the default model output. The NRRs for monthly variability suggest that the ensemble spread is generally narrow (NRR 1.21–1.39 for DIN and 1.19–1.39 for chlorophyll profiles, 1.07–1.40 for surface chlorophyll, and 1.01–1.40 for depth-integrated chlorophyll). Among the five stations, the most reliable ensembles are obtained for the oligotrophic station ALOHA (for the surface and integrated chlorophyll and bloom peak height), for coastal station L4 (for inter-annual mean), and for the abyssal plain station PAP (for bloom peak height). Overall our study provides a novel way to generate a realistic ensemble of a biogeochemical model by perturbing the model equations and parameterizations, which will be helpful for the probabilistic predictions.

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Hendra, Edwin, e Kim Sung Suk. "Default Spread dan Term Spread sebagai Variabel Proxy Siklus Bisnis pada Model Fama-French". Binus Business Review 6, n. 2 (31 agosto 2015): 283. http://dx.doi.org/10.21512/bbr.v6i2.977.

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This research aims to apply the Fama-French models and test the effect of alternative variable of bond yield spread, default spread (RBBB – RAAA and RAAA – RF), and the term spread (RSUN10-RSUN1), as proxy variables of the business cycle, in IDX stock data during 2005-2010. Four types of asset pricing models tested are Sharpe-Lintner CAPM, Fama-French models, Hwang et al.model, and hybrid model. The results showed that the size effect and value effect has an impact on excess stock returns. Slopes of market beta, SMB, and HML are more sensitive to stock big size and high B / M. Default spreads and term spreads in Hwang et al. model can explain the value effect, and weakly explain the size effect, meanwhile the power of explanation disappeared on Hybrid models. Based on the assessment adjusted R2 and the frequency of rejection of non-zero alpha, is found that the hybrid model is the most suitable model.

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Lin, Zhen, Lianying Miao e Shu-Guang Guo. "Bounds on the $A_{\alpha}$-spread of a graph". Electronic Journal of Linear Algebra 36, n. 36 (22 aprile 2020): 214–27. http://dx.doi.org/10.13001/ela.2020.5137.

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Let $G$ be a simple undirected graph. For any real number $\alpha \in[0,1]$, Nikiforov defined the $A_{\alpha}$-matrix of $G$ as $A_{\alpha}(G)=\alpha D(G)+(1-\alpha)A(G)$, where $A(G)$ and $D(G)$ are the adjacency matrix and the degree diagonal matrix of $G$, respectively. The $A_{\alpha}$-spread of a graph is defined as the difference between the largest eigenvalue and the smallest eigenvalue of the associated $A_{\alpha}$-matrix. In this paper, some lower and upper bounds on $A_{\alpha}$-spread are obtained, which extend the results of $A$-spread and $Q$-spread. Moreover, the trees with the minimum and the maximum $A_{\alpha}$-spread are determined, respectively.

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Ndoh Mbue, Innocent, e Samuel Batambock. "Consequence Modeling and Analysis of Benzene leakage and explosion from a poorly sited gas station in the City of Douala, Cameroon". International Journal of Occupational Safety and Health 13, n. 1 (1 gennaio 2023): 1–18. http://dx.doi.org/10.3126/ijosh.v13i1.43091.

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Introduction: Benzene has long been recognized as highly carcinogenic and the most cytotoxic of all air pollutants released by gas stations. Although several studies have been conducted on accidents in the process industry, very little work has been directed toward the modeling of risks caused by the leakage and explosion of toxic substances in gas stations. This knowledge could aid in predicting the vapor concentration inside gas station office buildings and neighboring infrastructures and in developing corresponding safety measures. The purpose of this study was, therefore, to model the consequences of Benzene dispersion following leakage and explosion from gas stations, taking the city of Douala, Cameroon as an example. Methods: Based on the measured vent emission and meteorological data, the Areal Location of Hazardous Atmosphere (ALOHA v.5.4.7) model was used to predict the hazard radius of leakage and dispersion of benzene from a tank in different seasons. The maps of the toxic and flammable vapor cloud of benzene, evaporation rate from a puddle, and the concentration of toxic and flammable vapor cloud inside and outside of the station were prepared with the aid of MARPLOT and Google Earth software. Results: The results showed that the maximum average sustained release rate of benzene from a tank was 26 kilograms per minute, with an estimated total amount released of 1,340 kilograms per 60 minutes in the dry season. The puddle spread to a diameter of 19.8 meters. The predicted threat zone distance from the station in the dry season, as compared to the rainy season, had an increase in radius of 12, 20, and 83m for the red, orange, and yellow zones, respectively. The worst hazard level extends primarily in the downwind direction and is predicted to be 31 meters in the rainy season in all directions, covering parts of the adjacent settlements and social infrastructure. Conclusion: The potential scenarios of benzene dispersion from a poorly sited gas station in the city of Douala have been modeled and the threat zones estimated. Nearby residences and social infrastructures are significantly exposed, with the predicted threat zones being more hazardous for the employees of the gas station. Further research looking at the impact of combined consequences of gasoline emissions may help determine whether the combined effects of benzene with other chemicals are cumulative or synergistic.

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Mrkic, Branka, Jovan Pavlovic, Thomas Rülicke, Pietro Volpe, Christian J. Buchholz, Dennis Hourcade, John P. Atkinson, Adriano Aguzzi e Roberto Cattaneo. "Measles Virus Spread and Pathogenesis in Genetically Modified Mice". Journal of Virology 72, n. 9 (1998): 7420–27. http://dx.doi.org/10.1128/jvi.72.9.7420-7427.1998.

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Attenuated Edmonston measles virus (MV-Edm) is not pathogenic in standard mice. We show here that MV-Edm inoculated via the natural respiratory route has a limited propagation in the lungs of mice with a targeted mutation inactivating the alpha/beta interferon receptor. A high dose of MV-Edm administered intracerebrally is lethal for about half of these mice. To study the consequences of the availability of a high-affinity receptor for MV propagation, we generated alpha/beta interferon-defective mice expressing human CD46 with human-like tissue specificity. Intranasal infection of these mice with MV-Edm resulted in enhanced spread to the lungs and more prominent inflammatory response. Virus replication was also detected in peripheral blood mononuclear cells, the spleen, and the liver. Moreover, intracerebral inoculation of adult animals with low MV-Edm doses caused encephalitis with almost inevitably lethal outcome. We conclude that in mice alpha/beta interferon controls MV infection and that a high-affinity receptor facilitates, but is not strictly required for, MV spread and pathogenesis.

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WELSH, G. H., S. M. WIGGINS, R. C. ISSAC, E. BRUNETTI, G. G. MANAHAN, M. R. ISLAM, S. CIPICCIA, C. ANICULAESEI, B. ERSFELD e D. A. JAROSZYNSKI. "High resolution electron beam measurements on the ALPHA-X laser–plasma wakefield accelerator". Journal of Plasma Physics 78, n. 4 (27 febbraio 2012): 393–99. http://dx.doi.org/10.1017/s0022377812000220.

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AbstractThe Advanced Laser–Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme at the University of Strathclyde is developing laser–plasma accelerators for the production of ultra-short high quality electron bunches. Focussing such LWFA bunches into an undulator, for example, requires particular attention to be paid to the emittance, electron bunch duration and energy spread. On the ALPHA-X wakefield accelerator beam line, a high intensity ultra-short pulse from a 30 TW Ti:Sapphire laser is focussed into a helium gas jet to produce femtosecond duration electron bunches in the range of 90–220 MeV. Measurements of the electron energy spectrum, obtained using a high resolution magnetic dipole spectrometer, show electron bunch r.m.s. energy spreads down to 0.5%. A pepper-pot mask is used to obtain transverse emittance measurements of a 128 ± 3 MeV mono-energetic electron beam. An average normalized emittance of ϵrms,x,y = 2.2 ± 0.7, 2.3 ± 0.6 π-mm-mrad is measured, which is comparable to that of a conventional radio-frequency accelerator. The best measured emittance of ϵrms,x, = 1.1 ± 0.1 π-mm-mrad corresponds to the resolution limit of the detection system. 3D particle-in-cell simulations of the ALPHA-X accelerator partially replicate the generation of low emittance, low energy spread bunches with charge less than 4 pC and gas flow simulations indicate both long density ramps and shock formation in the gas jet nozzle.

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Cek, Mehmet Emre. "M-Ary Alpha-Stable Noise Modulation in Spread-Spectrum Communication". Fluctuation and Noise Letters 14, n. 03 (29 giugno 2015): 1550022. http://dx.doi.org/10.1142/s0219477515500224.

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In this paper, a spread-spectrum communication system based on a random carrier is proposed which transmits M-ary information. The random signal is considered as a single realization of a random process taken from prescribed symmetric α-stable (SαS) distribution that carries digital M-ary information to be transmitted. Considering the noise model in the channel as additive white Gaussian noise (AWGN), the transmitter sends the information carrying random signal from non-Gaussian density. Alpha-stable distribution is used to encode the M-ary message. Inspired by the chaos shift keying techniques, the proposed method is called M-ary symmetric alpha-stable differential shift keying (M-ary SαS-DSK). The main purpose of preferring non-Gaussian noise instead of conventional pseudo-noise (PN) sequence is to overcome the drawback of self-repeating noise-like sequences which are detectable due to the periodic behavior of the autocorrelation function of PN sequences. Having infinite second order moment in α-stable random carrier offers secrecy of the information due to the non-constant autocorrelation behavior. The bit error rate (BER) performance of the proposed method is illustrated by Monte Carlo simulations with respect to various characteristic exponent values and different data length.

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Valdinocci, Dario, Gary D. Grant, Tracey C. Dickson e Dean L. Pountney. "Epothilone D inhibits microglia-mediated spread of alpha-synuclein aggregates". Molecular and Cellular Neuroscience 89 (giugno 2018): 80–94. http://dx.doi.org/10.1016/j.mcn.2018.04.006.

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Peracaula-Bosch, Marta, Meritxell Estebanell-Minguell, Digna Couso e Juan González-Martínez. "What do pre-service teachers know about computational thinking?" Aloma: Revista de Psicologia, Ciències de l'Educació i de l'Esport 38, n. 1 (19 maggio 2020): 75–86. http://dx.doi.org/10.51698/aloma.2020.38.1.75-86.

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In recent years, interest in Computational Thinking (CT), which is seen as a transversal competence that is necessary in the Knowledge Society, has spread to educational systems around the world. In this context, it has become necessary for training programmes for pre-service teachers to address this topic. In this article, we explore the knowledge, attitudes and expectations regarding CT held by pre-service teachers, prior to receiving training on this field. We use a descriptive analysis of both qualitative and quantitative data obtained via an ad hoc questionnaire, whereby 193 pre-service teachers at the University of Girona were asked about different aspects related to CT. The study shows that the majority of pre-service teachers cannot correctly identify most indicators associated to CT, and that most of them are unaware of the implications of the promotion of CT in terms of developed skills or areas of application. However, their expectations regarding their learning process with regard to this topic are positive. Therefore, it is necessary to more thoroughly define theoretical foundations of the concept in order to take steps to effectively include it in teacher training programmes.

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Goldschmidt, Christina, e Eleonora KreačIć. "The spread of fire on a random multigraph". Advances in Applied Probability 51, n. 01 (marzo 2019): 1–40. http://dx.doi.org/10.1017/apr.2019.2.

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AbstractWe study a model for the destruction of a random network by fire. Suppose that we are given a multigraph of minimum degree at least 2 having real-valued edge lengths. We pick a uniform point from along the length and set it alight; the edges of the multigraph burn at speed 1. If the fire reaches a vertex of degree 2, the fire gets directly passed on to the neighbouring edge; a vertex of degree at least 3, however, passes the fire either to all of its neighbours or none, each with probability ${\textstyle{1 \over 2}}$. If the fire goes out before the whole network is burnt, we again set fire to a uniform point. We are interested in the number of fires which must be set in order to burn the whole network, and the number of points which are burnt from two different directions. We analyse these quantities for a random multigraph having n vertices of degree 3 and α(n) vertices of degree 4, where α(n)/n → 0 as n → ∞, with independent and identically distributed standard exponential edge lengths. Depending on whether $\alpha(n) \gg \sqrt{n}$ or $\alpha(n)=O(\sqrt{n})$, we prove that, as n → ∞, these quantities converge jointly in distribution when suitably rescaled to either a pair of constants or to (complicated) functionals of Brownian motion. We use our analysis of this model to make progress towards a conjecture of Aronson, Frieze and Pittel (1998) concerning the number of vertices which remain unmatched when we use the Karp–Sipser algorithm to find a matching on the Erdős–Rényi random graph.

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Li, Shuang-de, Yuan-jian Liu, Le-ke Lin, Zhong Sheng, Xiang-chen Sun, Zhi-peng Chen e Xiao-jun Zhang. "Channel Measurements and Modeling at 6 GHz in the Tunnel Environments for 5G Wireless Systems". International Journal of Antennas and Propagation 2017 (2017): 1–15. http://dx.doi.org/10.1155/2017/1513038.

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Propagation measurements of wireless channels performed in the tunnel environments at 6 GHz are presented in this paper. Propagation characteristics are simulated and analyzed based on the method of shooting and bouncing ray tracing/image (SBR/IM). A good agreement is achieved between the measured results and simulated results, so the correctness of SBR/IM method has been validated. The measured results and simulated results are analyzed in terms of path loss models, received power, root mean square (RMS) delay spread, Ricean K-factor, and angle of arrival (AOA). The omnidirectional path loss models are characterized based on close-in (CI) free-space reference distance model and the alpha-beta-gamma (ABG) model. Path loss exponents (PLEs) are 1.50–1.74 in line-of-sight (LOS) scenarios and 2.18–2.20 in non-line-of-sight (NLOS) scenarios. Results show that CI model with the reference distance of 1 m provides more accuracy and stability in tunnel scenarios. The RMS delay spread values vary between 2.77 ns and 18.76 ns. Specially, the Poisson distribution best fits the measured data of RMS delay spreads for LOS scenarios and the Gaussian distribution best fits the measured data of RMS delay spreads for NLOS scenarios. Moreover, the normal distribution provides good fits to the Ricean K-factor. The analysis of the abovementioned results from channel measurements and simulations may be utilized for the design of wireless communications of future 5G radio systems at 6 GHz.

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36

Serwin, Karol, Bogusz Aksak-Wąs e Miłosz Parczewski. "Phylodynamic Dispersal of SARS-CoV-2 Lineages Circulating across Polish–German Border Provinces". Viruses 14, n. 5 (24 aprile 2022): 884. http://dx.doi.org/10.3390/v14050884.

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Abstract (sommario):

Introduction: The emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has evolved into a worldwide outbreak, with significant molecular evolution over time. Large-scale phylodynamic studies allow to map the virus spread and inform preventive strategies. Aim: This study investigates the extent of binational dispersal and dynamics of SARS-CoV-2 lineages between seven border provinces of the adjacent countries of Poland and Germany to reconstruct SARS-CoV-2 transmission networks. Methods: Following three pandemic waves from March 2020 to the end of May 2021, we analysed a dataset of 19,994 sequences divided into B.1.1.7|Alpha and non-Alpha lineage groups. We performed phylogeographic analyses using the discrete diffusion models to identify the pathways of virus spread. Results: Based on population dynamics inferences, in total, 673 lineage introductions (95% HPD interval 641–712) for non-Alpha and 618 (95% HPD interval 599–639) for B.1.1.7|Alpha were identified in the area. For non-Alpha lineages, 5.05% binational, 86.63% exclusively German, and 8.32% Polish clusters were found, with a higher frequency of international clustering observed for B.1.1.7|Alpha (13.11% for binational, 68.44% German and 18.45% Polish, p < 0.001). We identified key transmission hubs for the analysed lineages, namely Saxony, West Pomerania and Lower Silesia. Conclusions: Clustering patterns between Poland and Germany reflect the viral variant transmission dynamics at the international level in the borderline area. Tracing the spread of the virus between two adjacent large European countries may provide a basis for future intervention policies in cross-border cooperation efforts against the spread of the pandemics.

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37

Serwin, Karol, Bogusz Aksak-Wąs e Miłosz Parczewski. "Phylodynamic Dispersal of SARS-CoV-2 Lineages Circulating across Polish–German Border Provinces". Viruses 14, n. 5 (24 aprile 2022): 884. http://dx.doi.org/10.3390/v14050884.

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Abstract (sommario):

Introduction: The emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has evolved into a worldwide outbreak, with significant molecular evolution over time. Large-scale phylodynamic studies allow to map the virus spread and inform preventive strategies. Aim: This study investigates the extent of binational dispersal and dynamics of SARS-CoV-2 lineages between seven border provinces of the adjacent countries of Poland and Germany to reconstruct SARS-CoV-2 transmission networks. Methods: Following three pandemic waves from March 2020 to the end of May 2021, we analysed a dataset of 19,994 sequences divided into B.1.1.7|Alpha and non-Alpha lineage groups. We performed phylogeographic analyses using the discrete diffusion models to identify the pathways of virus spread. Results: Based on population dynamics inferences, in total, 673 lineage introductions (95% HPD interval 641–712) for non-Alpha and 618 (95% HPD interval 599–639) for B.1.1.7|Alpha were identified in the area. For non-Alpha lineages, 5.05% binational, 86.63% exclusively German, and 8.32% Polish clusters were found, with a higher frequency of international clustering observed for B.1.1.7|Alpha (13.11% for binational, 68.44% German and 18.45% Polish, p < 0.001). We identified key transmission hubs for the analysed lineages, namely Saxony, West Pomerania and Lower Silesia. Conclusions: Clustering patterns between Poland and Germany reflect the viral variant transmission dynamics at the international level in the borderline area. Tracing the spread of the virus between two adjacent large European countries may provide a basis for future intervention policies in cross-border cooperation efforts against the spread of the pandemics.

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38

Serwin, Karol, Bogusz Aksak-Wąs e Miłosz Parczewski. "Phylodynamic Dispersal of SARS-CoV-2 Lineages Circulating across Polish–German Border Provinces". Viruses 14, n. 5 (24 aprile 2022): 884. http://dx.doi.org/10.3390/v14050884.

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Abstract (sommario):

Introduction: The emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has evolved into a worldwide outbreak, with significant molecular evolution over time. Large-scale phylodynamic studies allow to map the virus spread and inform preventive strategies. Aim: This study investigates the extent of binational dispersal and dynamics of SARS-CoV-2 lineages between seven border provinces of the adjacent countries of Poland and Germany to reconstruct SARS-CoV-2 transmission networks. Methods: Following three pandemic waves from March 2020 to the end of May 2021, we analysed a dataset of 19,994 sequences divided into B.1.1.7|Alpha and non-Alpha lineage groups. We performed phylogeographic analyses using the discrete diffusion models to identify the pathways of virus spread. Results: Based on population dynamics inferences, in total, 673 lineage introductions (95% HPD interval 641–712) for non-Alpha and 618 (95% HPD interval 599–639) for B.1.1.7|Alpha were identified in the area. For non-Alpha lineages, 5.05% binational, 86.63% exclusively German, and 8.32% Polish clusters were found, with a higher frequency of international clustering observed for B.1.1.7|Alpha (13.11% for binational, 68.44% German and 18.45% Polish, p < 0.001). We identified key transmission hubs for the analysed lineages, namely Saxony, West Pomerania and Lower Silesia. Conclusions: Clustering patterns between Poland and Germany reflect the viral variant transmission dynamics at the international level in the borderline area. Tracing the spread of the virus between two adjacent large European countries may provide a basis for future intervention policies in cross-border cooperation efforts against the spread of the pandemics.

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39

Talan, Jamie. "In a Parkinson's Disease Model, Researchers Inhibit Spread of Toxic Alpha-Synuclein". Neurology Today 18, n. 24 (20 dicembre 2018): 1,21–22. http://dx.doi.org/10.1097/01.nt.0000552577.65186.5c.

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40

Mircheva, K., Tz Ivanova, I. Panaiotov, V. Ducel e F. Boury. "Enzymatic proteolysis of alpha gliadin monolayer spread at the air–water interface". Journal of Colloid and Interface Science 347, n. 1 (luglio 2010): 69–73. http://dx.doi.org/10.1016/j.jcis.2010.03.016.

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41

Lee, Byung Uk. "Why Does the SARS-CoV-2 Delta VOC Spread So Rapidly? Universal Conditions for the Rapid Spread of Respiratory Viruses, Minimum Viral Loads for Viral Aerosol Generation, Effects of Vaccination on Viral Aerosol Generation, and Viral Aerosol Clouds". International Journal of Environmental Research and Public Health 18, n. 18 (17 settembre 2021): 9804. http://dx.doi.org/10.3390/ijerph18189804.

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Abstract (sommario):

This study analyzes the reasons the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant of concern (VOC) spreads so rapidly. Novel topics such as universal conditions for the rapid spread of respiratory viruses, minimum viral loads for viral aerosol generation, effects of vaccination on viral aerosol generation, and viral aerosol clouds were studied. The analyses were based on experimental results and analytic model studies. Four universal conditions, namely asymptomatic host, high viral load, stability of viruses in air, and binding affinity of viruses to human cells, need to be satisfied for the rapid spread of respiratory viruses. SARS-CoV-2 and its variants such as the Alpha VOC and Delta VOC satisfy the four fundamental conditions. In addition, there is an original principle of aerosol generation of respiratory viruses. Assuming that the aerosol–droplet cutoff particle diameter for distinguishing potential aerosols from earthbound respiratory particles is 100 μm, the minimum viral load required in respiratory fluids to generate viral aerosols is ~106 copies mL−1, which is within the range of the reported viral loads in the Alpha VOC cases and the Delta VOC cases. The daily average viral loads of the Delta VOC in hosts have been reported to be between ~109 copies mL−1 and ~1010 copies mL−1 during the four days after symptom onset in 1848 cases of the Delta VOC infection. Owing to the high viral load, the SARS-CoV-2 Delta VOC has the potential to effectively spread through aerosols. COVID-19 vaccination can decrease aerosol transmission of the SARS-CoV-2 Alpha VOC by reducing the viral load. The viral load can explain the conundrum of viral aerosol spreading. The SARS-CoV-2 Delta VOC aerosol clouds have been assumed to be formed in restricted environments, resulting in a massive numbers of infected people in a very short period with a high spreading speed. Strong control methods against bioaerosols should be considered in this SARS-CoV-2 Delta VOC pandemic. Large-scale environmental monitoring campaigns of SARS-CoV-2 Delta VOC aerosols in public places in many countries are necessary, and these activities could contribute to controlling the coronavirus disease pandemic.

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Angel, Omer, Abbas Mehrabian e Yuval Peres. "The string of diamonds is nearly tight for rumour spreading". Combinatorics, Probability and Computing 29, n. 2 (4 novembre 2019): 190–99. http://dx.doi.org/10.1017/s0963548319000385.

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AbstarctFor a rumour spreading protocol, the spread time is defined as the first time everyone learns the rumour. We compare the synchronous push&pull rumour spreading protocol with its asynchronous variant, and show that for any n-vertex graph and any starting vertex, the ratio between their expected spread times is bounded by $O({n^{1/3}}{\log ^{2/3}}n)$. This improves the $O(\sqrt n)$ upper bound of Giakkoupis, Nazari and Woelfel (2016). Our bound is tight up to a factor of O(log n), as illustrated by the string of diamonds graph. We also show that if, for a pair α, β of real numbers, there exist infinitely many graphs for which the two spread times are nα and nβ in expectation, then $0 \le \alpha \le 1$ and $\alpha \le \beta \le {1 \over 3} + {2 \over 3} \alpha $; and we show each such pair α, β is achievable.

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43

Syafarina, Inna, Taufiq Wirahman, Syam Budi Iryanto e Arnida Lailatul Latifah. "Epidemic Data Analysis of Three Variants of COVID-19 Spread in Indonesia". Jurnal Ilmu Komputer dan Informasi 15, n. 1 (27 febbraio 2022): 47–54. http://dx.doi.org/10.21609/jiki.v15i1.1055.

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Three variants of COVID-19 had been found in Indonesia. A control strategy may rely on the transmission rate of the variant. This study aims to investigate how the variants spread in Indonesia by computing a basic and effective reproduction number on the national and province scale. The basic reproduction number shows the indicator of initial transmission rate of alpha variant computed by an exponential growth rate model. The effective reproduction number describes the dynamic of the transmission rate estimated based on a Bayesian approach. This study revealed that each variant shows different characteristics. The alpha variant of COVID-19 in Indonesia was mainly initiated from big cities, then it spread to all provinces quickly because the control strategies were not established well at the beginning. A rapid increase of the effective reproduction number about July 2021 showed a novel delta variant, but it could be managed quite well by a large number of testing and stronger restrictions. Before the end of 2021, a novel variant omicron was also shown by the steeper change of the effective reproduction number. Thus, the variant spread rate can be estimated by how steep the effective reproduction number change is.

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44

Wakabayashi, Koichi. "Where and how alpha‐synuclein pathology spreads in Parkinson’s disease:". Neuropathology 40, n. 5 (4 agosto 2020): 415–25. http://dx.doi.org/10.1111/neup.12691.

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45

Robinson, Richard. "‘Seeding’ Alpha-Synuclein Spreads Parkinsonʼs Pathology in Normal Mouse Brain". Neurology Today 13, n. 4 (febbraio 2013): 5–6. http://dx.doi.org/10.1097/01.nt.0000427569.97599.63.

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46

Leavesley, DI, GD Ferguson, EA Wayner e DA Cheresh. "Requirement of the integrin beta 3 subunit for carcinoma cell spreading or migration on vitronectin and fibrinogen". Journal of Cell Biology 117, n. 5 (1 giugno 1992): 1101–7. http://dx.doi.org/10.1083/jcb.117.5.1101.

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Abstract (sommario):

FG human pancreatic carcinoma cells use integrin alpha v beta 5 as their primary vitronectin receptor since they fail to express integrin alpha v beta 3. These cells are unable to form focal contacts, spread, or migrate on vitronectin but readily do so on collagen in a beta 1 integrin-dependent manner. Transfection of FG cells with a cDNA encoding the integrin beta 3 subunit results in the surface expression of a functional integrin alpha v beta 3 heterodimer providing these cells with novel adhesive and biological properties. Specifically, FG cells expressing beta 3 acquire the capacity to attach and spread on vitronectin as well as fibrinogen with beta 3 localization to focal contacts. Moreover, these cells gain the capacity to migrate through a porous membrane in response to either vitronectin or fibrinogen. These results demonstrate that the beta 3 and beta 5 integrin subunits when associated with alpha v, promote distinct cellular responses to a vitronectin extracellular environment.

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Kawaguchi, S., J. M. Bergelson, R. W. Finberg e M. E. Hemler. "Integrin alpha 2 cytoplasmic domain deletion effects: loss of adhesive activity parallels ligand-independent recruitment into focal adhesions." Molecular Biology of the Cell 5, n. 9 (settembre 1994): 977–88. http://dx.doi.org/10.1091/mbc.5.9.977.

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Chinese hamster ovary (CHO) cells transfected with the integrin alpha 2 subunit formed a stable VLA-2 heterodimer that mediated cell adhesion to collagen. Within CHO cells spread on collagen, but not fibronectin, wild-type alpha 2 subunit localized into focal adhesion complexes (FACs). In contrast, alpha 2 with a deleted cytoplasmic domain was recruited into FACs whether CHO cells were spread on collagen or fibronectin. Thus, as previously seen for other integrins, the alpha 2 cytoplasmic domain acts as a negative regulator, preventing indiscriminate integrin recruitment into FACs. Notably, ligand-independent localization of the VLA-2 alpha 2 subunit into FACs was partially prevented if only one or two amino acids were present in the alpha 2 cytoplasmic domain (beyond the conserved GFFKR motif) and was completely prevented by four to seven amino acids. The addition of two alanine residues (added to GFFKR) also partially prevented ligand-independent localization. In a striking inverse correlation, the same mutants showing increased ligand-independent recruitment into FACs exhibited diminished alpha 2-dependent adhesion to collagen. Thus, control of VLA-2 localization may be closely related to the suppression of cell adhesion to collagen. In contrast to FAC localization and collagen adhesion results, VLA-2-dependent binding and infection by echovirus were unaffected by either alpha 2 cytoplasmic domain deletion or exchange with other cytoplasmic domains.

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Wu, C., A. J. Fields, B. A. Kapteijn e J. A. McDonald. "The role of alpha 4 beta 1 integrin in cell motility and fibronectin matrix assembly". Journal of Cell Science 108, n. 2 (1 febbraio 1995): 821–29. http://dx.doi.org/10.1242/jcs.108.2.821.

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Abstract (sommario):

The alpha 4 beta 1 integrin has been suggested to play important roles in embryogenesis and pathogenesis of many diseases which involve both cell adhesion and cell migration. Previous studies using anti-alpha 4 beta 1 antibodies and fibronectin (Fn) fragments have suggested that alpha 4 beta 1 integrins may be involved in cell motility on Fn and vascular cell adhesion molecule-1 (VCAM-1). However, the cells used in these studies also express other Fn integrin receptors including alpha 5 beta 1 integrin, which is known to function in cell motility on Fn. To test whether alpha 4 beta 1 integrins mediate cell motility on Fn and VCAM-1 in the absence of alpha 5 beta 1 integrin, we expressed human alpha 4 integrin in a Chinese hamster ovary (CHO) cell line that is deficient in alpha 5 beta 1 integrin (CHO B2). The parental alpha 5 deficient CHO B2 cells were unable to adhere, spread or migrate on Fn, nor could they assemble a fibrillar Fn matrix. Expression of alpha 4 beta 1 integrin in the CHO B2 cells enabled the cells to adhere, spread and migrate on Fn and on VCAM-1 but not to assemble a fibrillar Fn matrix. The cellular processes mediated by the interaction of alpha 4 beta 1 with Fn or VCAM-1 were inhibited by the CS1 peptide derived from the major alpha 4 beta 1 binding site on Fn. These findings demonstrate that alpha 4 beta 1 integrins not only function as cell adhesion receptors but also as cell motility receptors for Fn and VCAM-1 independent of alpha 5 beta 1. Moreover, they reveal important functional differences between Fn binding integrins. The alpha 4-positive, alpha 5-negative CHO cells described in this report will be useful tools in studying the mechanism of molecular signalling during integrin mediated cellular processes.

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Sip, Viktor, Maxime Guye, Fabrice Bartolomei e Viktor Jirsa. "Computational modeling of seizure spread on a cortical surface". Journal of Computational Neuroscience 50, n. 1 (23 ottobre 2021): 17–31. http://dx.doi.org/10.1007/s10827-021-00802-8.

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Abstract (sommario):

AbstractIn the field of computational epilepsy, neural field models helped to understand some large-scale features of seizure dynamics. These insights however remain on general levels, without translation to the clinical settings via personalization of the model with the patient-specific structure. In particular, a link was suggested between epileptic seizures spreading across the cortical surface and the so-called theta-alpha activity (TAA) pattern seen on intracranial electrographic signals, yet this link was not demonstrated on a patient-specific level. Here we present a single patient computational study linking the seizure spreading across the patient-specific cortical surface with a specific instance of the TAA pattern recorded in the patient. Using the realistic geometry of the cortical surface we perform the simulations of seizure dynamics in The Virtual Brain platform, and we show that the simulated electrographic signals qualitatively agree with the recorded signals. Furthermore, the comparison with the simulations performed on surrogate surfaces reveals that the best quantitative fit is obtained for the real surface. The work illustrates how the patient-specific cortical geometry can be utilized in The Virtual Brain for personalized model building, and the importance of such approach.

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Au, N. H., A. R. Tuite, C. Huber, J. Adams e A. Thomas. "Predicted Global Spread of SARS-CoV-2 Alpha Variant of Concern via Air Travel". International Journal of Infectious Diseases 116 (marzo 2022): S89. http://dx.doi.org/10.1016/j.ijid.2021.12.210.

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