Science.gov

Sample records for develop transmission dynamics

  1. Dynamically prioritized progressive transmission

    NASA Astrophysics Data System (ADS)

    Blanford, Ronald

    1992-04-01

    Retrieval of image data from a centralized database may be subject to bandwidth limitations, whether due to a low-bandwidth communications link or to contention from simultaneous accesses over a high-bandwidth link. Progressive transmission can alleviate this problem by encoding image data so that any prefix of the data stream approximates the complete image at a coarse level of resolution. The longer the prefix, the finer the resolution. In many cases, as little at 1 percent of the image data may be sufficient to decide whether to discard the image, to permit the retrieval to continue, or to restrict retrieval to a subsection of the image. Our approach treats resolution not as a fixed attribute of the image, but rather as a resource which may be allocated to portions of the image at the direction of a user-specified priority function. The default priority function minimizes error by allocating more resolution to regions of high variance. The user may also point to regions of interest requesting priority transmission. More advanced target recognition strategies may be incorporated at the user's discretion. Multispectral imagery is supported. The user engineering implications are profounded. There is immediate response to a query that might otherwise take minutes to complete. The data is transmitted in small increments so that no single user dominates the communications bandwidth. The user-directed improvement means that bandwidth is focused on interesting information. The user may continue working with the first coarse approximations while further image data is still arriving. The algorithm has been implemented in C on Sun, Silicon Graphics, and NeXT workstations, and in Lisp on a Symbolics. Transmission speeds reach as high as 60,000 baud using a Sparc or 68040 processor when storing data to memory; somewhat less if also updating a graphical display. The memory requirements are roughly five bytes per image pixel. Both computational and memory costs may be reduced

  2. Heterogeneity in schistosomiasis transmission dynamics.

    PubMed

    Mari, Lorenzo; Ciddio, Manuela; Casagrandi, Renato; Perez-Saez, Javier; Bertuzzo, Enrico; Rinaldo, Andrea; Sokolow, Susanne H; De Leo, Giulio A; Gatto, Marino

    2017-11-07

    Simple models of disease propagation often disregard the effects of transmission heterogeneity on the ecological and epidemiological dynamics associated with host-parasite interactions. However, for some diseases like schistosomiasis, a widespread parasitic infection caused by Schistosoma worms, accounting for heterogeneity is crucial to both characterize long-term dynamics and evaluate opportunities for disease control. Elaborating on the classic Macdonald model for macroparasite transmission, we analyze families of models including explicit descriptions of heterogeneity related to differential transmission risk within a community, water contact patterns, the distribution of the snail host population, human mobility, and the seasonal fluctuations of the environment. Through simple numerical examples, we show that heterogeneous multigroup communities may be more prone to schistosomiasis than homogeneous ones, that the availability of multiple water sources can hinder parasite transmission, and that both spatial and temporal heterogeneities may have nontrivial implications for disease endemicity. Finally, we discuss the implications of heterogeneity for disease control. Although focused on schistosomiasis, results from this study may apply as well to other parasitic infections with complex transmission cycles, such as cysticercosis, dracunculiasis and fasciolosis. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  3. Global dynamic modeling of a transmission system

    NASA Technical Reports Server (NTRS)

    Choy, F. K.; Qian, W.

    1993-01-01

    The work performed on global dynamic simulation and noise correlation of gear transmission systems at the University of Akron is outlined. The objective is to develop a comprehensive procedure to simulate the dynamics of the gear transmission system coupled with the effects of gear box vibrations. The developed numerical model is benchmarked with results from experimental tests at NASA Lewis Research Center. The modal synthesis approach is used to develop the global transient vibration analysis procedure used in the model. Modal dynamic characteristics of the rotor-gear-bearing system are calculated by the matrix transfer method while those of the gear box are evaluated by the finite element method (NASTRAN). A three-dimensional, axial-lateral coupled bearing model is used to couple the rotor vibrations with the gear box motion. The vibrations between the individual rotor systems are coupled through the nonlinear gear mesh interactions. The global equations of motion are solved in modal coordinates and the transient vibration of the system is evaluated by a variable time-stepping integration scheme. The relationship between housing vibration and resulting noise of the gear transmission system is generated by linear transfer functions using experimental data. A nonlinear relationship of the noise components to the fundamental mesh frequency is developed using the hypercoherence function. The numerically simulated vibrations and predicted noise of the gear transmission system are compared with the experimental results from the gear noise test rig at NASA Lewis Research Center. Results of the comparison indicate that the global dynamic model developed can accurately simulate the dynamics of a gear transmission system.

  4. Canine echinococcosis in Kyrgyzstan: using prevalence data adjusted for measurement error to develop transmission dynamics models

    PubMed Central

    Ziadinov, I.; Mathis, A.; Trachsel, D.; Rysmukhambetova, A.; Abdyjaparov, T. A.; Kuttubaev, O. T.; Deplazes, P.; Torgerson, P. R.

    2008-01-01

    Echinococcosis is a major emerging zoonosis in central Asia. A cross-sectional study of dogs in four villages in rural Kyrgyzstan was undertaken to investigate the epidemiology and transmission of Echinococcus spp. A total of 466 dogs were examined by arecoline purgation for the presence of Echinococcus granulosus and Echinococcus multilocularis. In addition, a faecal sample from each dog was examined for taeniid eggs. Any taeniid eggs found were investigated using PCR techniques (multiplex and single target PCR) to improve the diagnostic sensitivity by confirming the presence of Echinococcus spp. and to identify E. granulosus strains. A total of 83 (18%) dogs had either E. granulosus adults in purge material and/or E. granulosus eggs in their faeces as confirmed by PCR. Three genotypes of E. granulosus: G1, G4 and the G6/7 complex were shown to be present in these dogs through subsequent sequence analysis. Purge analysis combined with PCR identified 50 dogs that were infected with adult E. multilocularis and/or had E. multilocularis eggs in their faeces (11%). Bayesian techniques were employed to estimate the true prevalence, the diagnostic sensitivity and specificity of the procedures used and the transmission parameters. The sensitivity of arecoline purgation for the detection of echinococcosis in dogs was rather low, with a value of 38% (Credible intervals (CIs) 27–50%) for E. granulosus and 21% (CIs 11–34%) for E. multilocularis. The specificity of arecoline purgation was assumed to be 100%. The sensitivity of coproscopy followed by PCR of the isolated eggs was calculated as 78% (CIs 57–87%) for E. granulosus and 50% (CIs 29–72%) for E. multilocularis with specificity of 93% (CIs 88–96%) and 100% (CIs 97–100), respectively. The 93% specificity of the coprological-PCR for E. granulosus could suggest coprophagia rather than true infections. After adjusting for the sensitivity of the diagnostic procedures, the estimated true prevalence of infection of

  5. EPIFIL: the development of an age-structured model for describing the transmission dynamics and control of lymphatic filariasis.

    PubMed Central

    Norman, R. A.; Chan, M. S.; Srividya, A.; Pani, S. P.; Ramaiah, K. D.; Vanamail, P.; Michael, E.; Das, P. K.; Bundy, D. A.

    2000-01-01

    Mathematical models of transmission dynamics of infectious diseases provide a useful tool for investigating the impact of community based control measures. Previously, we used a dynamic (constant force-of-infection) model for lymphatic filariasis to describe observed patterns of infection and disease in endemic communities. In this paper, we expand the model to examine the effects of control options against filariasis by incorporating the impact of age structure of the human community and by addressing explicitly the dynamics of parasite transmission from and to the vector population. This model is tested using data for Wuchereria bancrofti transmitted by Culex quinquefasciatus in Pondicherry, South India. The results show that chemotherapy has a larger short-term impact than vector control but that the effects of vector control can last beyond the treatment period. In addition we compare rates of recrudescence for drugs with different macrofilaricidal effects. PMID:10982078

  6. Dynamics of a split torque helicopter transmission

    NASA Astrophysics Data System (ADS)

    Rashidi, Majid; Krantz, Timothy

    A high reduction ratio split torque gear train has been proposed as an alternative to a planetary configuration for the final stage of a helicopter transmission. A split torque design allows a high ratio of power-to-weight for the transmission. The design studied in this work includes a pivoting beam that acts to balance thrust loads produced by the helical gear meshes in each of two parallel power paths. When the thrust loads are balanced, the torque is split evenly. A mathematical model was developed to study the dynamics of the system. The effects of time varying gear mesh stiffness, static transmission errors, and flexible bearing supports are included in the model. The model was demonstrated with a test case. Results show that although the gearbox has a symmetric configuration, the simulated dynamic behavior of the first and second compound gears are not the same. Also, results show that shaft location and mesh stiffness tuning are significant design parameters that influence the motions of the system.

  7. Backward bifurcations in dengue transmission dynamics.

    PubMed

    Garba, S M; Gumel, A B; Abu Bakar, M R

    2008-09-01

    A deterministic model for the transmission dynamics of a strain of dengue disease, which allows transmission by exposed humans and mosquitoes, is developed and rigorously analysed. The model, consisting of seven mutually-exclusive compartments representing the human and vector dynamics, has a locally-asymptotically stable disease-free equilibrium (DFE) whenever a certain epidemiological threshold, known as the basic reproduction number(R(0)) is less than unity. Further, the model exhibits the phenomenon of backward bifurcation, where the stable DFE coexists with a stable endemic equilibrium. The epidemiological consequence of this phenomenon is that the classical epidemiological requirement of making R(0) less than unity is no longer sufficient, although necessary, for effectively controlling the spread of dengue in a community. The model is extended to incorporate an imperfect vaccine against the strain of dengue. Using the theory of centre manifold, the extended model is also shown to undergo backward bifurcation. In both the original and the extended models, it is shown, using Lyapunov function theory and LaSalle Invariance Principle, that the backward bifurcation phenomenon can be removed by substituting the associated standard incidence function with a mass action incidence. In other words, in addition to establishing the presence of backward bifurcation in models of dengue transmission, this study shows that the use of standard incidence in modelling dengue disease causes the backward bifurcation phenomenon of dengue disease.

  8. Dynamics of a split torque helicopter transmission

    NASA Technical Reports Server (NTRS)

    Rashidi, Majid; Krantz, Timothy

    1992-01-01

    A high reduction ratio split torque gear train has been proposed as an alternative to a planetary configuration for the final stage of a helicopter transmission. A split torque design allows a high ratio of power-to-weight for the transmission. The design studied in this work includes a pivoting beam that acts to balance thrust loads produced by the helical gear meshes in each of two parallel power paths. When the thrust loads are balanced, the torque is split evenly. A mathematical model was developed to study the dynamics of the system. The effects of time varying gear mesh stiffness, static transmission errors, and flexible bearing supports are included in the model. The model was demonstrated with a test case. Results show that although the gearbox has a symmetric configuration, the simulated dynamic behavior of the first and second compound gears are not the same. Also, results show that shaft location and mesh stiffness tuning are significant design parameters that influence the motions of the system.

  9. Transmission seal development

    NASA Technical Reports Server (NTRS)

    Brien, M.

    1977-01-01

    An experimental evaluation was performed on a high-speed (72.9 m/s, 14,349 ft/min) transmission seal of the synergistic type. During testing of the seal, oil leakage occurred at positive bearing cavity pressures. Modifications were made in an attempt to eliminate the leakage but none were completely successful. Leakage appears to be the result of questionable positioning of the sealing elements resulting in inadequate shaft contact by the oil side sealing element. This condition may be related to the nonsymmetrical shape of the elastomeric retainer and to dimensional changes caused by swelling of the elastomeric retainer from exposure to the sealed fluid. Indications of a speed dependent leakage characteristic were also observed.

  10. Avian Influenza spread and transmission dynamics

    USGS Publications Warehouse

    Bourouiba, Lydia; Gourley, Stephen A.; Liu, Rongsong; Takekawa, John Y.; Wu, Jianhong; Chen, Dongmei; Moulin, Bernard; Wu, Jianhong

    2015-01-01

    The spread of highly pathogenic avian influenza (HPAI) viruses of type A of subtype H5N1 has been a serious threat to global public health. Understanding the roles of various (migratory, wild, poultry) bird species in the transmission of these viruses is critical for designing and implementing effective control and intervention measures. Developing appropriate models and mathematical techniques to understand these roles and to evaluate the effectiveness of mitigation strategies have been a challenge. Recent development of the global health surveillance (especially satellite tracking and GIS techniques) and the mathematical theory of dynamical systems combined have gradually shown the promise of some cutting-edge methodologies and techniques in mathematical biology to meet this challenge.

  11. The dynamics of transmission and the dynamics of networks.

    PubMed

    Farine, Damien

    2017-05-01

    A toy example depicted here highlighting the results of a study in this issue of the Journal of Animal Ecology that investigates the impact of network dynamics on potential disease outbreaks. Infections (stars) that spread by contact only (left) reduce the predicted outbreak size compared to situations where individuals can become infected by moving through areas that previously contained infected individuals (right). This is potentially important in species where individuals, or in this case groups, have overlapping ranges (as depicted on the top right). Incorporating network dynamics that maintain information about the ordering of contacts (central blocks; including the ordering of spatial overlap as noted by the arrows that highlight the blue group arriving after the red group in top-right of the figure) is important for capturing how a disease might not have the opportunity to spread to all individuals. By contrast, a static or 'average' network (lower blocks) does not capture any of these dynamics. Interestingly, although static networks generally predict larger outbreak sizes, the authors find that in cases when transmission probability is low, this prediction can switch as a result of changes in the estimated intensity of contacts among individuals. [Colour figure can be viewed at wileyonlinelibrary.com]. Springer, A., Kappeler, P.M. & Nunn, C.L. (2017) Dynamic vs. static social networks in models of parasite transmission: Predicting Cryptosporidium spread in wild lemurs. Journal of Animal Ecology, 86, 419-433. The spread of disease or information through networks can be affected by several factors. Whether and how these factors are accounted for can fundamentally change the predicted impact of a spreading epidemic. Springer, Kappeler & Nunn () investigate the role of different modes of transmission and network dynamics on the predicted size of a disease outbreak across several groups of Verreaux's sifakas, a group-living species of lemur. While some factors

  12. Development of large rotorcraft transmissions

    NASA Technical Reports Server (NTRS)

    Samanich, N. E.; Drago, R. J.; Mack, J. C.

    1984-01-01

    The U.S. Army Heavy Lift Helicopter (HLH) represents a large rotorcraft which was developed by an American aerospace company. In the early 1970's with the HLH Advanced Technology Components (ATC) program, the development of large rotorcraft transmission and drive systems was started. Failures in the spiral bevel gearing were experienced in tests because the employed method of analysis had not considered the effect of rim bending. Consequently, new gears with strengthened rims were designed and fabricated. For a more accurate prediction of the load capacity of the gears, an extensive Finite Element Method (FEM) system was developed. The U.S. Army's XCH-62 HLH aft rotor transmission was finally successfully tested at full design torque and speed. A description of the test program is provided, and the analytical program is discussed. The analytical phase includes the development of a preprocessing program which aids in the review of calculated FEM stresses.

  13. Trypanosome Transmission Dynamics in Tsetse

    PubMed Central

    Aksoy, Serap; Weiss, Brian L.; Attardo, Geoff M.

    2014-01-01

    Tsetse flies (Diptera:Glossinidae) are vectors of African trypanosomes. Tsetse undergo viviparous reproductive biology, and depend on their obligate endosymbiont (genus Wigglesworthia) for the maintenance of fecundity and immune system development. Trypanosomes establish infections in the midgut and salivary glands of the fly. Tsetse’s resistance to trypanosome infection increases as a function of age. Among the factors that mediate resistance to parasites are antimicrobial peptides (AMPs) produced by the Immune deficiency (Imd) signaling pathway, peptidoglycan recognition protein (PGRP) LB, tsetse-EP protein and the integrity of the midgut peritrophic matrix (PM) barrier. The presence of obligate Wigglesworthia during larval development is essential for adult immune system maturation and PM development. Thus, Wigglesworthia prominently influences the vector competency of it’s tsetse host. PMID:25580379

  14. Dynamics of Mechanical Signal Transmission through Prestressed Stress Fibers

    PubMed Central

    Hwang, Yongyun; Barakat, Abdul I.

    2012-01-01

    Transmission of mechanical stimuli through the actin cytoskeleton has been proposed as a mechanism for rapid long-distance mechanotransduction in cells; however, a quantitative understanding of the dynamics of this transmission and the physical factors governing it remains lacking. Two key features of the actin cytoskeleton are its viscoelastic nature and the presence of prestress due to actomyosin motor activity. We develop a model of mechanical signal transmission through prestressed viscoelastic actin stress fibers that directly connect the cell surface to the nucleus. The analysis considers both temporally stationary and oscillatory mechanical signals and accounts for cytosolic drag on the stress fibers. To elucidate the physical parameters that govern mechanical signal transmission, we initially focus on the highly simplified case of a single stress fiber. The results demonstrate that the dynamics of mechanical signal transmission depend on whether the applied force leads to transverse or axial motion of the stress fiber. For transverse motion, mechanical signal transmission is dominated by prestress while fiber elasticity has a negligible effect. Conversely, signal transmission for axial motion is mediated uniquely by elasticity due to the absence of a prestress restoring force. Mechanical signal transmission is significantly delayed by stress fiber material viscosity, while cytosolic damping becomes important only for longer stress fibers. Only transverse motion yields the rapid and long-distance mechanical signal transmission dynamics observed experimentally. For simple networks of stress fibers, mechanical signals are transmitted rapidly to the nucleus when the fibers are oriented largely orthogonal to the applied force, whereas the presence of fibers parallel to the applied force slows down mechanical signal transmission significantly. The present results suggest that cytoskeletal prestress mediates rapid mechanical signal transmission and allows

  15. The transmission development process at Lucas Western

    NASA Astrophysics Data System (ADS)

    Bossler, Robert B., Jr.

    1989-04-01

    An account is given of the technology development efforts undertaken by a helicopter transmission manufacturer in order to produce hardware to more exacting performance requirements than had been previously considered. The first of the illustrative examples considered is a 5,400 hp propeller drive for a high-speed marine hydrofoil employing a supercavitating rotor. Additional examples are drawn from efforts to develop mechanical drives for hoists deployable aboard helicopters. The technology developments required concerned gear systems, joints, dynamics, component design, and lubrication systems.

  16. Dynamics of a split torque helicopter transmission

    NASA Astrophysics Data System (ADS)

    Krantz, Timothy L.

    1994-06-01

    Split torque designs, proposed as alternatives to traditional planetary designs for helicopter main rotor transmissions, can save weight and be more reliable than traditional designs. This report presents the results of an analytical study of the system dynamics and performance of a split torque gearbox that uses a balance beam mechanism for load sharing. The Lagrange method was applied to develop a system of equations of motion. The mathematical model includes time-varying gear mesh stiffness, friction, and manufacturing errors. Cornell's method for calculating the stiffness of spur gear teeth was extended and applied to helical gears. The phenomenon of sidebands spaced at shaft frequencies about gear mesh fundamental frequencies was simulated by modeling total composite gear errors as sinusoid functions. Although the gearbox has symmetric geometry, the loads and motions of the two power paths differ. Friction must be considered to properly evaluate the balance beam mechanism. For the design studied, the balance beam is not an effective device for load sharing unless the coefficient of friction is less than 0.003. The complete system stiffness as represented by the stiffness matrix used in this analysis must be considered to precisely determine the optimal tooth indexing position.

  17. On dynamic loads in parallel shaft transmissions. 2: Parameter study

    NASA Technical Reports Server (NTRS)

    Lin, Edward Hsiang-Hsi; Huston, Ronald L.; Coy, John J.

    1987-01-01

    Solutions to the governing equations of a spur gear transmission model, developed in NASA TM-100180 (AVSCOM TM-87-C-2), are presented. Factors affecting the dynamic load are identified. It is found that the dynamic load increases with operating speed up to a system natural frequency. At operating speeds beyond the natural frequency the dynamic load decreases dramatically. Also. it is found that the applied load and shaft inertia have little effect on the dynamic load. Damping and friction decrease the dynamic load. Finally, tooth stiffness has a significant effect on dynamic loading; the higher the stiffness, the lower the dynamic loading. Also, the higher the stiffness the higher the rotating speed required for dynamic response.

  18. Complex dynamics of blackouts in power transmission systems.

    PubMed

    Carreras, B A; Lynch, V E; Dobson, I; Newman, D E

    2004-09-01

    In order to study the complex global dynamics of a series of blackouts in power transmission systems a dynamical model of such a system has been developed. This model includes a simple representation of the dynamical evolution by incorporating the growth of power demand, the engineering response to system failures, and the upgrade of generator capacity. Two types of blackouts have been identified, each having different dynamical properties. One type of blackout involves the loss of load due to transmission lines reaching their load limits but no line outages. The second type of blackout is associated with multiple line outages. The dominance of one type of blackout over the other depends on operational conditions and the proximity of the system to one of its two critical points. The model displays characteristics such as a probability distribution of blackout sizes with power tails similar to that observed in real blackout data from North America.

  19. Transport composite fuselage technology: Impact dynamics and acoustic transmission

    NASA Technical Reports Server (NTRS)

    Jackson, A. C.; Balena, F. J.; Labarge, W. L.; Pei, G.; Pitman, W. A.; Wittlin, G.

    1986-01-01

    A program was performed to develop and demonstrate the impact dynamics and acoustic transmission technology for a composite fuselage which meets the design requirements of a 1990 large transport aircraft without substantial weight and cost penalties. The program developed the analytical methodology for the prediction of acoustic transmission behavior of advanced composite stiffened shell structures. The methodology predicted that the interior noise level in a composite fuselage due to turbulent boundary layer will be less than in a comparable aluminum fuselage. The verification of these analyses will be performed by NASA Langley Research Center using a composite fuselage shell fabricated by filament winding. The program also developed analytical methodology for the prediction of the impact dynamics behavior of lower fuselage structure constructed with composite materials. Development tests were performed to demonstrate that the composite structure designed to the same operating load requirement can have at least the same energy absorption capability as aluminum structure.

  20. X-ray transmission movies of spontaneous dynamic events

    SciTech Connect

    Smilowitz, L.; Henson, B. F.; Holmes, M.; Novak, A.; Oschwald, D.; Dolgonos, P.; Qualls, B.

    2014-11-15

    We describe a new x-ray radiographic imaging system which allows for continuous x-ray transmission imaging of spontaneous dynamic events. We demonstrate this method on thermal explosions in three plastic bonded formulations of the energetic material octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. We describe the x-ray imaging system and triggering developed to enable the continuous imaging of a thermal explosion.

  1. X-ray transmission movies of spontaneous dynamic events

    NASA Astrophysics Data System (ADS)

    Smilowitz, L.; Henson, B. F.; Holmes, M.; Novak, A.; Oschwald, D.; Dolgonos, P.; Qualls, B.

    2014-11-01

    We describe a new x-ray radiographic imaging system which allows for continuous x-ray transmission imaging of spontaneous dynamic events. We demonstrate this method on thermal explosions in three plastic bonded formulations of the energetic material octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. We describe the x-ray imaging system and triggering developed to enable the continuous imaging of a thermal explosion.

  2. Inference of seasonal and pandemic influenza transmission dynamics

    PubMed Central

    Yang, Wan; Lipsitch, Marc; Shaman, Jeffrey

    2015-01-01

    The inference of key infectious disease epidemiological parameters is critical for characterizing disease spread and devising prevention and containment measures. The recent emergence of surveillance records mined from big data such as health-related online queries and social media, as well as model inference methods, permits the development of new methodologies for more comprehensive estimation of these parameters. We use such data in conjunction with Bayesian inference methods to study the transmission dynamics of influenza. We simultaneously estimate key epidemiological parameters, including population susceptibility, the basic reproductive number, attack rate, and infectious period, for 115 cities during the 2003–2004 through 2012–2013 seasons, including the 2009 pandemic. These estimates discriminate key differences in the epidemiological characteristics of these outbreaks across 10 y, as well as spatial variations of influenza transmission dynamics among subpopulations in the United States. In addition, the inference methods appear to compensate for observational biases and underreporting inherent in the surveillance data. PMID:25730851

  3. Dynamic Power Flow Controller: Compact Dynamic Phase Angle Regulators for Transmission Power Routing

    SciTech Connect

    2012-01-03

    GENI Project: Varentec is developing compact, low-cost transmission power controllers with fractional power rating for controlling power flow on transmission networks. The technology will enhance grid operations through improved use of current assets and by dramatically reducing the number of transmission lines that have to be built to meet increasing contributions of renewable energy sources like wind and solar. The proposed transmission controllers would allow for the dynamic control of voltage and power flow, improving the grid’s ability to dispatch power in real time to the places where it is most needed. The controllers would work as fail-safe devices whereby the grid would be restored to its present operating state in the event of a controller malfunction instead of failing outright. The ability to affordably and dynamically control power flow with adequate fail-safe switchgear could open up new competitive energy markets which are not possible under the current regulatory structure and technology base.

  4. Nonlinear system guidance in the presence of transmission zero dynamics

    NASA Technical Reports Server (NTRS)

    Meyer, G.; Hunt, L. R.; Su, R.

    1995-01-01

    An iterative procedure is proposed for computing the commanded state trajectories and controls that guide a possibly multiaxis, time-varying, nonlinear system with transmission zero dynamics through a given arbitrary sequence of control points. The procedure is initialized by the system inverse with the transmission zero effects nulled out. Then the 'steady state' solution of the perturbation model with the transmission zero dynamics intact is computed and used to correct the initial zero-free solution. Both time domain and frequency domain methods are presented for computing the steady state solutions of the possibly nonminimum phase transmission zero dynamics. The procedure is illustrated by means of linear and nonlinear examples.

  5. A dynamic transmission model of eastern equine encephalitis virus

    PubMed Central

    Unnasch, Robert S.; Sprenger, Tonya; Katholi, Charles R.; Cupp, Eddie W.; Hill, Geoffrey E.; Unnasch, Thomas R.

    2005-01-01

    Eastern equine encephalitis virus (EEEV) is one of several arthropod-borne viruses (arboviruses) endemic to the United States. Interactions between arthropod (mosquito) vectors and avian amplification host populations play a significant role in the dynamics of arboviral transmission. Recent data have suggested the hypothesis that an increased rate of successful feeding on young-of-the-year (YOY) birds might play a role in the dynamics of EEEV transmission. To test this hypothesis, we developed a model to explore the effect of the interactions of the vectors and avian host populations on EEEV transmission. Sensitivity analyses conducted using this model revealed eleven parameters that were capable of disproportionately affecting the predicted level of EEEV infection in the vertebrate reservoir and vector populations. Of these, four parameters were related to the interaction of the vector with young-of-the-year birds. Furthermore, adult birds could not substitute for young-of-the-year in initiating and maintaining a predicted enzootic outbreak of EEEV. Taken together, the model predicted that young-of-the-year birds play a key role in establishing and maintaining enzootic outbreaks of EEEV. PMID:16501661

  6. Dynamics of Multistage Gear Transmission with Effects of Gearbox Vibrations

    NASA Technical Reports Server (NTRS)

    Choy, F. K.; Tu, Y. K.; Zakrajsek, J. J.; Townsend, Dennis P.

    1990-01-01

    A comprehensive approach is presented in analyzing the dynamic behavior of multistage gear transmission systems with the effects of gearbox induced vibrations and mass imbalances of the rotor. The modal method, with undamped frequencies and planar mode shapes, is used to reduce the degrees of freedom of the gear system for time-transient dynamic analysis. Both the lateral and torsional vibration modes of each rotor-bearing-gear stage as well as the interstage vibrational characteristics are coupled together through localized gear mesh tooth interactions. In addition, gearbox vibrations are also coupled to the rotor-bearing-gear system dynamics through bearing support forces between the rotor and the gearbox. Transient and steady state dynamics of lateral and torsional vibrations of the geared system are examined in both time and frequency domains to develop interpretations of the overall modal dynamic characteristics under various operating conditions. A typical three-stage geared system is used as an example. Effects of mass imbalance and gearbox vibrations on the system dynamic behavior are presented in terms of modal excitation functions for both lateral and torsional vibrations. Operational characteristics and conclusions are drawn from the results presented.

  7. Contrasting the epidemiological and evolutionary dynamics of influenza spatial transmission

    PubMed Central

    Viboud, Cécile; Nelson, Martha I.; Tan, Yi; Holmes, Edward C.

    2013-01-01

    In the past decade, rapid increases in the availability of high-resolution molecular and epidemiological data, combined with developments in statistical and computational methods to simulate and infer migration patterns, have provided key insights into the spatial dynamics of influenza A viruses in humans. In this review, we contrast findings from epidemiological and molecular studies of influenza virus transmission at different spatial scales. We show that findings are broadly consistent in large-scale studies of inter-regional or inter-hemispheric spread in temperate regions, revealing intense epidemics associated with multiple viral introductions, followed by deep troughs driven by seasonal bottlenecks. However, aspects of the global transmission dynamics of influenza viruses are still debated, especially with respect to the existence of tropical source populations experiencing high levels of genetic diversity and the extent of prolonged viral persistence between epidemics. At the scale of a country or community, epidemiological studies have revealed spatially structured diffusion patterns in seasonal and pandemic outbreaks, which were not identified in molecular studies. We discuss the role of sampling issues in generating these conflicting results, and suggest strategies for future research that may help to fully integrate the epidemiological and evolutionary dynamics of influenza virus over space and time. PMID:23382422

  8. Time Resolved Phase Transitions via Dynamic Transmission Electron Microscopy

    SciTech Connect

    Reed, B W; Armstrong, M R; Blobaum, K J; Browning, N D; Burnham, A K; Campbell, G H; Gee, R; Kim, J S; King, W E; Maiti, A; Piggott, W T; Torralva, B R

    2007-02-22

    The Dynamic Transmission Electron Microscope (DTEM) project is developing an in situ electron microscope with nanometer- and nanosecond-scale resolution for the study of rapid laser-driven processes in materials. We report on the results obtained in a year-long LDRD-supported effort to develop DTEM techniques and results for phase transitions in molecular crystals, reactive multilayer foils, and melting and resolidification of bismuth. We report the first in situ TEM observation of the HMX {beta}-{delta} phase transformation in sub-{micro}m crystals, computational results suggesting the importance of voids and free surfaces in the HMX transformation kinetics, and the first electron diffraction patterns of intermediate states in fast multilayer foil reactions. This project developed techniques which are applicable to many materials systems and will continue to be employed within the larger DTEM effort.

  9. Wolbachia transmission dynamics in Formica wood ants

    PubMed Central

    2008-01-01

    Background The role of Wolbachia endosymbionts in shaping the mitochondrial diversity of their arthropod host depends on the effects they have on host reproduction and on the mode of transmission of the bacteria. We have compared the sequence diversity of wsp (Wolbachia surface protein gene) and the host mtDNA in a group of Formica ant species that have diverged approximately 0.5 million years ago (MYA). The aim was to study the relationship of Wolbachia and its ant hosts in terms of vertical and horizontal transmission of the bacteria. Results All studied ant species were doubly infected with two Wolbachia strains (wFex1 and wFex4) all over their geographical distribution area in Eurasia. The most common haplotypes of these strains were identical with strains previously described from a more distantly related Formica ant, with an estimated divergence time of 3.5 – 4 MYA. Some strain haplotypes were associated to the same or closely related mtDNA haplotypes as expected under vertical transmission. However, in several cases the wsp haplotypes coexisted with distant mtDNA haplotypes, a pattern which is more compatible with horizontal transmission of the bacteria. Conclusion Two lines of evidence suggest that the sharing of Wolbachia strains by all F. rufa species is rather due to horizontal than vertical transmission. First, the fact that endosymbiont strains identical to those of F. rufa ants have been found in another species that diverged 3.5–4 MYA strongly suggests that horizontal transfer can and does occur between Formica ants. Second, the frequent sharing of identical Wolbachia strains by distant mitochondrial lineages within the F. rufa group further shows that horizontal transmission has occurred repeatedly. Nevertheless, our dataset also provides some evidence for longer-term persistence of infection, indicating that Wolbachia infection within this host clade has been shaped by both horizontal and vertical transmission of symbionts. The fact that all

  10. Life and dynamic capacity modeling for aircraft transmissions

    NASA Technical Reports Server (NTRS)

    Savage, Michael

    1991-01-01

    A computer program to simulate the dynamic capacity and life of parallel shaft aircraft transmissions is presented. Five basic configurations can be analyzed: single mesh, compound, parallel, reverted, and single plane reductions. In execution, the program prompts the user for the data file prefix name, takes input from a ASCII file, and writes its output to a second ASCII file with the same prefix name. The input data file includes the transmission configuration, the input shaft torque and speed, and descriptions of the transmission geometry and the component gears and bearings. The program output file describes the transmission, its components, their capabilities, locations, and loads. It also lists the dynamic capability, ninety percent reliability, and mean life of each component and the transmission as a system. Here, the program, its input and output files, and the theory behind the operation of the program are described.

  11. Dynamic analysis of multimesh-gear helicopter transmissions

    NASA Technical Reports Server (NTRS)

    Choy, Fred K.; Townsend, Dennis P.; Oswald, Fred B.

    1988-01-01

    A dynamic analysis of multimesh-gear helicopter transmission systems was performed by correlating analytical simulations with experimental investigations. The two computer programs used in this study, GRDYNMLT and PGT, were developed under NASA/Army sponsorship. Parametric studies of the numerical model with variations on mesh damping ratios, operating speeds, tip-relief tooth modifications, and tooth-spacing errors were performed to investigate the accuracy, application, and limitations of the two computer programs. Although similar levels of dynamic loading were predicted by both programs, the computer code GRDYNMLT was found to be superior and broader in scope. Results from analytical work were also compared with experimental data obtained from the U.S. Army's UH-60A Black Hawk 2240-kW (3000-hp) class, twin-engine helicopter transmission tested at the NASA Lewis Research Center. Good correlation in gear stresses was obtained between the analytical model simulated by GRDYNMLT and the experimental measurements. More realistic mesh damping can be predicted through experimental data correlation.

  12. Mapping Biological Transmission: An Empirical, Dynamical, and Evolutionary Approach.

    PubMed

    Merlin, Francesca; Riboli-Sasco, Livio

    2017-06-01

    The current debate over extending inheritance and its evolutionary impact has focused on adding new categories of non-genetic factors to the classical transmission of DNA, and on trying to redefine inheritance. Transmitted factors have been mainly characterized by their directions of transmission (vertical, horizontal, or both) and the way they store variations. In this paper, we leave aside the issue of defining inheritance. We rather try to build an evolutionary conceptual framework that allows for tracing most, if not all forms of transmission and makes sense of their different tempos and modes. We discuss three key distinctions that should in particular be the targets of theoretical and empirical investigation, and try to assess the interplay among them and evolutionary dynamics. We distinguish two channels of transmission (channel 1 and channel 2), two measurements of the temporal dynamics of transmission, respectively across and within generations (durability and residency), and two types of transmitted factors according to their evolutionary relevance (selectively relevant and neutral stable factors). By implementing these three distinctions we can then map different forms of transmission over a continuous space describing the combination of their varying dynamical features. While our aim is not to provide yet another model of inheritance, putting together these distinctions and crossing them, we manage to offer an inclusive conceptual framework of transmission, grounded in empirical observation, and coherent with evolutionary theory. This interestingly opens possibilities for qualitative and quantitative analyses, and is a necessary step, we argue, in order to question the interplay between the dynamics of evolution and the dynamics of multiple forms of transmission.

  13. Transmission dynamics of the amphibian ranavirus Ambystoma tigrinum virus.

    PubMed

    Brunner, J L; Schock, D M; Collins, J P

    2007-09-14

    Transmission is central to pathogen fitness and strongly influences the impact of pathogens on host populations. Particularly important to transmission dynamics is the distinction between direct transmission requiring close physical contact (e.g. bumping, fighting, or coughing) and indirect transmission from environmental sources such as contaminated substrates. We present data from 4 experiments addressing the form, routes, and timing of transmission of Ambystoma tigrinum virus (ATV) among tiger salamanders Ambystoma tigrinum nebulosum. Our data suggest that ATV is efficiently transmitted by direct interactions between live animals (bumping, biting and cannibalism) as well as by necrophagy and indirectly via water and fomites. Determining which form of transmission is most important in nature is essential for understanding transmission at the population level. Our experiments also revealed an important temporal aspect of infectiousness: larval salamanders become infectious soon after exposure to ATV and their propensity to infect others increases with time. These results begin to clarify the mechanisms and dynamics of ATV transmission and lead to key questions that need to be addressed in future research.

  14. Dynamic Responses and Vibration Control of the Transmission Tower-Line System: A State-of-the-Art Review

    PubMed Central

    Chen, Bo; Guo, Wei-hua; Li, Peng-yun; Xie, Wen-ping

    2014-01-01

    This paper presented an overview on the dynamic analysis and control of the transmission tower-line system in the past forty years. The challenges and future developing trends in the dynamic analysis and mitigation of the transmission tower-line system under dynamic excitations are also put forward. It also reviews the analytical models and approaches of the transmission tower, transmission lines, and transmission tower-line systems, respectively, which contain the theoretical model, finite element (FE) model and the equivalent model; shows the advances in wind responses of the transmission tower-line system, which contains the dynamic effects under common wind loading, tornado, downburst, and typhoon; and discusses the dynamic responses under earthquake and ice loads, respectively. The vibration control of the transmission tower-line system is also reviewed, which includes the magnetorheological dampers, friction dampers, tuned mass dampers, and pounding tuned mass dampers. PMID:25105161

  15. Dynamic responses and vibration control of the transmission tower-line system: a state-of-the-art review.

    PubMed

    Chen, Bo; Guo, Wei-hua; Li, Peng-yun; Xie, Wen-ping

    2014-01-01

    This paper presented an overview on the dynamic analysis and control of the transmission tower-line system in the past forty years. The challenges and future developing trends in the dynamic analysis and mitigation of the transmission tower-line system under dynamic excitations are also put forward. It also reviews the analytical models and approaches of the transmission tower, transmission lines, and transmission tower-line systems, respectively, which contain the theoretical model, finite element (FE) model and the equivalent model; shows the advances in wind responses of the transmission tower-line system, which contains the dynamic effects under common wind loading, tornado, downburst, and typhoon; and discusses the dynamic responses under earthquake and ice loads, respectively. The vibration control of the transmission tower-line system is also reviewed, which includes the magnetorheological dampers, friction dampers, tuned mass dampers, and pounding tuned mass dampers.

  16. Alternative parasite development in transmission strategies: how time flies!

    PubMed

    Badets, M; Morrison, C; Verneau, O

    2010-10-01

    Among parasitic platyhelminths with complex life cycles, it has been well documented that transmission opportunities are the main forces shaping the diversity of life-history traits and parasite developmental strategies. While deviations in the development pathway usually involve shortening of life cycles, their extension may also occur following perception of remaining time by parasites. Polystoma gallieni, the monogenean parasite of Hyla meridionalis, is able to trigger two alternative developmental strategies depending on the physiological stage of the tadpoles upon which larvae attach. The distribution and reproductive outputs of both resulting phenotypes were surveyed to address questions about the dynamics of transmission in natural environments. Because modifications in the completion of life cycles can have drawbacks which may perturb the dynamic equilibrium of the resulting host-parasite systems, experimental infestations were also performed to assess parasite-parasite interactions. Our results suggest that the bladder adult phenotype, which involves transmission between frogs and tadpoles, is supplied secondarily by the branchial phenotype which involves transmission between tadpoles and metamorphs. They also support the occurrence of finely tuned trade-offs between hosts and parasites and highlight positive trends behind the extension of direct life cycles, in which host-derived signals account for the remaining time to achieve parasitic transmission.

  17. VECTRI: A new dynamical disease model for malaria transmission

    NASA Astrophysics Data System (ADS)

    Tompkins, A. M.; Ermert, V.; Lowe, R.

    2012-04-01

    In order to better address the role of population dynamics and surface hydrology in the assessment of malaria risk, a new dynamical disease model been developed at ICTP, known as the VECToR borne disease model of ICTP (VECTRI). The model accounts for the temperature impact on the larvae, parasite and adult vector populations in a similar fashion to previous dynamical models, but additionally explicitly accounts for the local population density, allowing for the incorporation of such impacts as bednet useor migration, as well as including a new simple pond model framework for surface hydrology. These additions allow the model to be reasonably run on resolutions down to O(10km), essentially the resolution of the population and climate input data. Results from the model driven by ERAI reanalysis and FEWS/TRMM rainfall for various regions in Africa will be shown which are focus areas of the Healthy Futures and QWeCI project which demonstrate that the model produces a realistic spatial and temporal variability of malaria transmission

  18. Great Plains Wind Energy Transmission Development Project

    SciTech Connect

    Brad G. Stevens, P.E.; Troy K. Simonsen; Kerryanne M. Leroux

    2012-06-09

    In fiscal year 2005, the Energy & Environmental Research Center (EERC) received funding from the U.S. Department of Energy (DOE) to undertake a broad array of tasks to either directly or indirectly address the barriers that faced much of the Great Plains states and their efforts to produce and transmit wind energy at the time. This program, entitled Great Plains Wind Energy Transmission Development Project, was focused on the central goal of stimulating wind energy development through expansion of new transmission capacity or development of new wind energy capacity through alternative market development. The original task structure was as follows: Task 1 - Regional Renewable Credit Tracking System (later rescoped to Small Wind Turbine Training Center); Task 2 - Multistate Transmission Collaborative; Task 3 - Wind Energy Forecasting System; and Task 4 - Analysis of the Long-Term Role of Hydrogen in the Region. As carried out, Task 1 involved the creation of the Small Wind Turbine Training Center (SWTTC). The SWTTC, located Grand Forks, North Dakota, consists of a single wind turbine, the Endurance S-250, on a 105-foot tilt-up guyed tower. The S-250 is connected to the electrical grid on the 'load side' of the electric meter, and the power produced by the wind turbine is consumed locally on the property. Establishment of the SWTTC will allow EERC personnel to provide educational opportunities to a wide range of participants, including grade school through college-level students and the general public. In addition, the facility will allow the EERC to provide technical training workshops related to the installation, operation, and maintenance of small wind turbines. In addition, under Task 1, the EERC hosted two small wind turbine workshops on May 18, 2010, and March 8, 2011, at the EERC in Grand Forks, North Dakota. Task 2 involved the EERC cosponsoring and aiding in the planning of three transmission workshops in the midwest and western regions. Under Task 3, the

  19. MRI dynamic range and its compatibility with signal transmission media

    PubMed Central

    Gabr, Refaat E.; Schär, Michael; Edelstein, Arthur D.; Kraitchman, Dara L.; Bottomley, Paul A.; Edelstein, William A.

    2010-01-01

    As the number of MRI phased array coil elements grows, interactions among cables connecting them to the system receiver become increasingly problematic. Fiber optic or wireless links would reduce electromagnetic interference, but their dynamic range (DR) is generally less than that of coaxial cables. Raw MRI signals, however, have a large DR because of the high signal amplitude near the center of k-space. Here, we study DR in MRI in order to determine the compatibility of MRI multicoil imaging with non-coaxial cable signal transmission. Since raw signal data are routinely discarded, we have developed an improved method for estimating the DR of MRI signals from conventional magnitude images. Our results indicate that the DR of typical surface coil signals at 3 T for human subjects is less than 88 dB, even for three-dimensional acquisition protocols. Cardiac and spine coil arrays had a maximum DR of less than 75 dB and head coil arrays less than 88 dB. The DR derived from magnitude images is in good agreement with that measured from raw data. The results suggest that current analog fiber optic links, with a spurious-free DR of 60–70 dB at 500 kHz bandwidth, are not by themselves adequate for transmitting MRI data from volume or array coils with DR ~90 dB. However, combining analog links with signal compression might make non-coaxial cable signal transmission viable. PMID:19251444

  20. Pulsed Power for a Dynamic Transmission Electron Microscope

    SciTech Connect

    dehope, w j; browning, n; campbell, g; cook, e; king, w; lagrange, t; reed, b; stuart, b; Shuttlesworth, R; Pyke, B

    2009-06-25

    Lawrence Livermore National Laboratory (LLNL) has converted a commercial 200kV transmission electron microscope (TEM) into an ultrafast, nanoscale diagnostic tool for material science studies. The resulting Dynamic Transmission Electron Microscope (DTEM) has provided a unique tool for the study of material phase transitions, reaction front analyses, and other studies in the fields of chemistry, materials science, and biology. The TEM's thermionic electron emission source was replaced with a fast photocathode and a laser beam path was provided for ultraviolet surface illumination. The resulting photoelectron beam gives downstream images of 2 and 20 ns exposure times at 100 and 10 nm spatial resolution. A separate laser, used as a pump pulse, is used to heat, ignite, or shock samples while the photocathode electron pulses, carefully time-synchronized with the pump, function as probe in fast transient studies. The device functions in both imaging and diffraction modes. A laser upgrade is underway to make arbitrary cathode pulse trains of variable pulse width of 10-1000 ns. Along with a fast e-beam deflection scheme, a 'movie mode' capability will be added to this unique diagnostic tool. This talk will review conventional electron microscopy and its limitations, discuss the development and capabilities of DTEM, in particularly addressing the prime and pulsed power considerations in the design and fabrication of the DTEM, and conclude with the presentation of a deflector and solid-state pulser design for Movie-Mode DTEM.

  1. Transmission dynamics of cholera: Mathematical modeling and control strategies

    NASA Astrophysics Data System (ADS)

    Sun, Gui-Quan; Xie, Jun-Hui; Huang, Sheng-He; Jin, Zhen; Li, Ming-Tao; Liu, Liqun

    2017-04-01

    Cholera, as an endemic disease around the world, has generated great threat to human society and caused enormous morbidity and mortality with weak surveillance system. In this paper, we propose a mathematical model to describe the transmission of Cholera. Moreover, basic reproduction number and the global dynamics of the dynamical model are obtained. Then we apply our model to characterize the transmission process of Cholera in China. It was found that, in order to avoid its outbreak in China, it may be better to increase immunization coverage rate and make effort to improve environmental management especially for drinking water. Our results may provide some new insights for elimination of Cholera.

  2. Dynamic simulation for distortion image with turbulence atmospheric transmission effects

    NASA Astrophysics Data System (ADS)

    Du, Huijie; Fei, Jindong; Qing, Duzheng; Zhao, Hongming; Yu, Hong; Cheng, Chen

    2013-09-01

    The imaging through atmospheric turbulence is an inevitable problem encountered by infrared imaging sensors working in the turbulence atmospheric environment. Before light-rays enter the window of the imaging sensors, the atmospheric turbulence will randomly interfere with the transmission of the light waves came from the objects, causing the distribution of image intensity values on the focal plane to diffuse, the peak value to decrease, the image to get blurred, and the pixels to deviate, and making image identification very difficult. Owing to the fact of the long processing time and that the atmospheric turbulent flow field is unknown and hard to be described by mathematical models, dynamic simulation for distortion Image with turbulence atmospheric transmission effects is much more difficult and challenging in the world. This paper discusses the dynamic simulation for distortion Image of turbulence atmospheric transmission effect. First of all, with the data and the optical transmission model of the turbulence atmospheric, the ray-tracing method is applied to obtain the propagation path of optical ray which propagates through the high-speed turbulent flow field, and then to calculate the OPD from the reference wave to the reconverted wave front and obtain the point spread function (PSF). Secondly, infrared characteristics models of typical scene were established according to the theory of infrared physics and heat conduction, and then the dynamic infrared image was generated by OpenGL. The last step is to obtain the distortion Image with turbulence atmospheric transmission effects .With the data of atmospheric transmission computation, infrared simulation image of every frame was processed according to the theory of image processing and the real-time image simulation, and then the dynamic distortion simulation images with effects of blurring, jitter and shifting were obtained. Above-mentioned simulation method can provide the theoretical bases for recovering

  3. On dynamic loads in parallel shaft transmissions. 1: Modelling and analysis

    NASA Technical Reports Server (NTRS)

    Lin, Edward Hsiang-Hsi; Huston, Ronald L.; Coy, John J.

    1987-01-01

    A model of a simple parallel-shaft, spur-gear transmission is presented. The model is developed to simulate dynamic loads in power transmissions. Factors affecting these loads are identified. Included are shaft stiffness, local compliance due to contact stress, load sharing, and friction. Governing differential equations are developed and a solution procedure is outlined. A parameter study of the solutions is presented in NASA TM-100181 (AVSCOM TM-87-C-3).

  4. The Transmission Dynamics of Human Immunodeficiency Virus (HIV)

    NASA Astrophysics Data System (ADS)

    May, R. M.; Anderson, R. M.

    1988-10-01

    The paper first reviews data on HIV infections and AIDS disease among homosexual men, heterosexuals, intravenous (IV) drug abusers and children born to infected mothers, in both developed and developing countries. We survey such information as is currently available about the distribution of incubation times that elapse between HIV infection and the appearance of AIDS, about the fraction of those infected with HIV who eventually go on to develop AIDS, about time-dependent patterns of infectiousness and about distributions of rates of acquiring new sexual or needle-sharing partners. With this information, models for the transmission dynamics of HIV are developed, beginning with deliberately oversimplified models and progressing - on the basis of the understanding thus gained - to more complex ones. Where possible, estimates of the model's parameters are derived from the epidemiological data, and predictions are compared with observed trends. We also combine these epidemiological models with demographic considerations to assess the effects that heterosexually-transmitted HIV/AIDS may eventually have on rates of population growth, on age profiles and on associated economic and social indicators, in African and other countries. The degree to which sexual or other habits must change to bring the `basic reproductive rate', R_0, of HIV infections below unity is discussed. We conclude by outlining some research needs, both in the refinement and development of models and in the collection of epidemiological data.

  5. Global Transmission Dynamics of Measles in the Measles Elimination Era.

    PubMed

    Furuse, Yuki; Oshitani, Hitoshi

    2017-04-16

    Although there have been many epidemiological reports of the inter-country transmission of measles, systematic analysis of the global transmission dynamics of the measles virus (MV) is limited. In this study, we applied phylogeographic analysis to characterize the global transmission dynamics of the MV using large-scale genetic sequence data (obtained for 7456 sequences) from 115 countries between 1954 and 2015. These analyses reveal the spatial and temporal characteristics of global transmission of the virus, especially in Australia, China, India, Japan, the UK, and the USA in the period since 1990. The transmission is frequently observed, not only within the same region but also among distant and frequently visited areas. Frequencies of export from measles-endemic countries, such as China, India, and Japan are high but decreasing, while the frequencies from countries where measles is no longer endemic, such as Australia, the UK, and the USA, are low but slightly increasing. The world is heading toward measles eradication, but the disease is still transmitted regionally and globally. Our analysis reveals that countries wherein measles is endemic and those having eliminated the disease (apart from occasional outbreaks) both remain a source of global transmission in this measles elimination era. It is therefore crucial to maintain vigilance in efforts to monitor and eradicate measles globally.

  6. Uncovering the transmission dynamics of Plasmodium vivax using population genetics

    PubMed Central

    Barry, Alyssa E.; Waltmann, Andreea; Koepfli, Cristian; Barnadas, Celine; Mueller, Ivo

    2015-01-01

    Population genetic analysis of malaria parasites has the power to reveal key insights into malaria epidemiology and transmission dynamics with the potential to deliver tools to support control and elimination efforts. Analyses of parasite genetic diversity have suggested that Plasmodium vivax populations are more genetically diverse and less structured than those of Plasmodium falciparum indicating that P. vivax may be a more ancient parasite of humans and/or less susceptible to population bottlenecks, as well as more efficient at disseminating its genes. These population genetic insights into P. vivax transmission dynamics provide an explanation for its relative resilience to control efforts. Here, we describe current knowledge on P. vivax population genetic structure, its relevance to understanding transmission patterns and relapse and how this information can inform malaria control and elimination programmes. PMID:25891915

  7. Presynaptic strontium dynamics and synaptic transmission.

    PubMed

    Xu-Friedman, M A; Regehr, W G

    1999-04-01

    Strontium can replace calcium in triggering neurotransmitter release, although peak release is reduced and the duration of release is prolonged. Strontium has therefore become useful in probing release, but its mechanism of action is not well understood. Here we study the action of strontium at the granule cell to Purkinje cell synapse in mouse cerebellar slices. Presynaptic residual strontium levels were monitored with fluorescent indicators, which all responded to strontium (fura-2, calcium orange, fura-2FF, magnesium green, and mag-fura-5). When calcium was replaced by equimolar concentrations of strontium in the external bath, strontium and calcium both entered presynaptic terminals. Contaminating calcium was eliminated by including EGTA in the extracellular bath, or by loading parallel fibers with EGTA, enabling the actions of strontium to be studied in isolation. After a single stimulus, strontium reached higher peak free levels than did calcium (approximately 1.7 times greater), and decayed more slowly (half-decay time 189 ms for strontium and 32 ms for calcium). These differences in calcium and strontium dynamics are likely a consequence of greater strontium permeability through calcium channels, lower affinity of the endogenous buffer for strontium, and less efficient extrusion of strontium. Measurements of presynaptic divalent levels help to explain properties of release evoked by strontium. Parallel fiber synaptic currents triggered by strontium are smaller in amplitude and longer in duration than those triggered by calcium. In both calcium and strontium, release consists of two components, one more steeply dependent on divalent levels than the other. Strontium drives both components less effectively than does calcium, suggesting that the affinities of the sensors involved in both phases of release are lower for strontium than for calcium. Thus, the larger and slower strontium transients account for the prominent slow component of release triggered by

  8. Presynaptic strontium dynamics and synaptic transmission.

    PubMed Central

    Xu-Friedman, M A; Regehr, W G

    1999-01-01

    Strontium can replace calcium in triggering neurotransmitter release, although peak release is reduced and the duration of release is prolonged. Strontium has therefore become useful in probing release, but its mechanism of action is not well understood. Here we study the action of strontium at the granule cell to Purkinje cell synapse in mouse cerebellar slices. Presynaptic residual strontium levels were monitored with fluorescent indicators, which all responded to strontium (fura-2, calcium orange, fura-2FF, magnesium green, and mag-fura-5). When calcium was replaced by equimolar concentrations of strontium in the external bath, strontium and calcium both entered presynaptic terminals. Contaminating calcium was eliminated by including EGTA in the extracellular bath, or by loading parallel fibers with EGTA, enabling the actions of strontium to be studied in isolation. After a single stimulus, strontium reached higher peak free levels than did calcium (approximately 1.7 times greater), and decayed more slowly (half-decay time 189 ms for strontium and 32 ms for calcium). These differences in calcium and strontium dynamics are likely a consequence of greater strontium permeability through calcium channels, lower affinity of the endogenous buffer for strontium, and less efficient extrusion of strontium. Measurements of presynaptic divalent levels help to explain properties of release evoked by strontium. Parallel fiber synaptic currents triggered by strontium are smaller in amplitude and longer in duration than those triggered by calcium. In both calcium and strontium, release consists of two components, one more steeply dependent on divalent levels than the other. Strontium drives both components less effectively than does calcium, suggesting that the affinities of the sensors involved in both phases of release are lower for strontium than for calcium. Thus, the larger and slower strontium transients account for the prominent slow component of release triggered by

  9. Large rotorcraft transmission technology development program

    NASA Technical Reports Server (NTRS)

    Mack, J. C.

    1983-01-01

    Testing of a U.S. Army XCH-62 HLH aft rotor transmission under NASA Contract NAS 3-22143 was successfully completed. This test establishes the feasibility of large, high power rotorcraft transmissions as well as demonstrating the resolution of deficiencies identified during the HLH advanced technology programs and reported by USAAMRDLTR-77-38. Over 100 hours of testing was conducted. At the 100% design power rating of 10,620 horsepower, the power transferred through a single spiral bevel gear mesh is more than twice that of current helicopter bevel gearing. In the original design of these gears, industry-wide design methods were employed and failures were experienced which identified problem areas unique to gear size. To remedy this technology shortfall, a program was developed to predict gear stresses using finite element analysis for complete and accurate representation of the gear tooth and supporting structure. To validate the finite element methodology gear strain data from the existing U.S. Army HLH aft transmission was acquired, and existing data from smaller gears were made available.

  10. [Classical dengue transmission dynamics involving mechanical control and prophylaxis].

    PubMed

    Toro-Zapata, Hernán D; Restrepo, Leonardo D; Vergaño-Salazar, Juan G; Muñoz-Loaiza, Aníbal

    2010-12-01

    Dengue fever transmission dynamics were studied in an endemic region considering the use of preventative measures and mechanical control in reducing transmission of the disease. A system of ordinary differential equations was proposed, describing the dynamics and their evolution as determined by numerical simulation. Different mechanical control and prophylaxis strategies were compared to the situation without control. The basic reproduction number R₀ was determined R₀ to show that if R₀ > 1 there would be a risk of an epidemic and otherwise the disease would have low impact levels. The basic reproduction number helps determine the dynamics' future pattern and contrast the results so obtained with those obtained numerically. It was concluded that although prophylaxis and mechanical control alone provide effective results in controlling the disease, if both controls are combined then infection levels become significantly reduced. Around 60 % mechanical control and prevention levels are needed to provide suitable results in controlling dengue outbreaks.

  11. Wireless Power Transmission Technology Development and Demonstrations

    NASA Astrophysics Data System (ADS)

    Steinsiek, F.; Weber, K.-H.; Foth, W.-P.; Foth, H. J.; Schäfer, C.

    2004-12-01

    The Wireless Power Transmission (WPT) technology has been treated to a wide extent in the recent years. A broad variety of applications has been investigated, from earth to orbit, orbit to earth, in-orbit and planetary ones, as for moon and Mars missions. In this course the question to use laser or microwave technology has widely been discussed. Beaming energy to spacecrafts could provide an important space mission-economic potential. It promises significant reduction in the cost of access to space, for scientific and commercial missions, and increases the mission capabilities for in-space systems. For the future enhancement of ISS capabilities and operational efficiency, the use of WPT technology became part of the technology research planning for the ISS. The WPT may have the potential of providing operational benefits, increase of spacecraft systems efficiency for elements like co-orbiting platforms, transfer vehicles or other ISS related in-orbit spacecrafts, and planetary exploration vehicles. The laser technology provides specific technical, operational and economic benefits compared to microwave applications and provides the actual basis for the envisioned wireless power transmission concepts. An outlook in terms of future wireless power perspectives, both for terrestrial as for space-to-space scenarios is given; these applications are part of a technology demonstration roadmap for wireless power transmission key- and supporting technologies, which is characterized by dedicated technology demonstration milestones on ground and in space. The actual technology development philosophy as conceived at EADS-Space Transportation is described and includes main system demonstration missions, as a laboratory test bed employing a small rover system, a scaled airship model demonstration as planned in 2004 and an experiment onboard the International Space Station ISS. These demonstrations represent milestones in terms of technical capability verification on the way to

  12. Modeling the Dynamic Transmission of Dengue Fever: Investigating Disease Persistence

    PubMed Central

    de Castro Medeiros, Líliam César; Castilho, César Augusto Rodrigues; Braga, Cynthia; de Souza, Wayner Vieira; Regis, Leda; Monteiro, Antonio Miguel Vieira

    2011-01-01

    Background Dengue is a disease of great complexity, due to interactions between humans, mosquitoes and various virus serotypes as well as efficient vector survival strategies. Thus, understanding the factors influencing the persistence of the disease has been a challenge for scientists and policy makers. The aim of this study is to investigate the influence of various factors related to humans and vectors in the maintenance of viral transmission during extended periods. Methodology/Principal Findings We developed a stochastic cellular automata model to simulate the spread of dengue fever in a dense community. Each cell can correspond to a built area, and human and mosquito populations are individually monitored during the simulations. Human mobility and renewal, as well as vector infestation, are taken into consideration. To investigate the factors influencing the maintenance of viral circulation, two sets of simulations were performed: (1st) varying human renewal rates and human population sizes and (2nd) varying the house index (fraction of infested buildings) and vector per human ratio. We found that viral transmission is inhibited with the combination of small human populations with low renewal rates. It is also shown that maintenance of viral circulation for extended periods is possible at low values of house index. Based on the results of the model and on a study conducted in the city of Recife, Brazil, which associates vector infestation with Aedes aegytpi egg counts, we question the current methodology used in calculating the house index, based on larval survey. Conclusions/Significance This study contributed to a better understanding of the dynamics of dengue subsistence. Using basic concepts of metapopulations, we concluded that low infestation rates in a few neighborhoods ensure the persistence of dengue in large cities and suggested that better strategies should be implemented to obtain measures of house index values, in order to improve the dengue

  13. Modeling the dynamic transmission of dengue fever: investigating disease persistence.

    PubMed

    de Castro Medeiros, Líliam César; Castilho, César Augusto Rodrigues; Braga, Cynthia; de Souza, Wayner Vieira; Regis, Leda; Monteiro, Antonio Miguel Vieira

    2011-01-11

    Dengue is a disease of great complexity, due to interactions between humans, mosquitoes and various virus serotypes as well as efficient vector survival strategies. Thus, understanding the factors influencing the persistence of the disease has been a challenge for scientists and policy makers. The aim of this study is to investigate the influence of various factors related to humans and vectors in the maintenance of viral transmission during extended periods. We developed a stochastic cellular automata model to simulate the spread of dengue fever in a dense community. Each cell can correspond to a built area, and human and mosquito populations are individually monitored during the simulations. Human mobility and renewal, as well as vector infestation, are taken into consideration. To investigate the factors influencing the maintenance of viral circulation, two sets of simulations were performed: (1(st)) varying human renewal rates and human population sizes and (2(nd)) varying the house index (fraction of infested buildings) and vector per human ratio. We found that viral transmission is inhibited with the combination of small human populations with low renewal rates. It is also shown that maintenance of viral circulation for extended periods is possible at low values of house index. Based on the results of the model and on a study conducted in the city of Recife, Brazil, which associates vector infestation with Aedes aegytpi egg counts, we question the current methodology used in calculating the house index, based on larval survey. This study contributed to a better understanding of the dynamics of dengue subsistence. Using basic concepts of metapopulations, we concluded that low infestation rates in a few neighborhoods ensure the persistence of dengue in large cities and suggested that better strategies should be implemented to obtain measures of house index values, in order to improve the dengue monitoring and control system.

  14. Recasting the theory of mosquito-borne pathogen transmission dynamics and control

    PubMed Central

    Smith, David L.; Perkins, T. Alex; Reiner, Robert C.; Barker, Christopher M.; Niu, Tianchan; Chaves, Luis Fernando; Ellis, Alicia M.; George, Dylan B.; Le Menach, Arnaud; Pulliam, Juliet R. C.; Bisanzio, Donal; Buckee, Caroline; Chiyaka, Christinah; Cummings, Derek A. T.; Garcia, Andres J.; Gatton, Michelle L.; Gething, Peter W.; Hartley, David M.; Johnston, Geoffrey; Klein, Eili Y.; Michael, Edwin; Lloyd, Alun L.; Pigott, David M.; Reisen, William K.; Ruktanonchai, Nick; Singh, Brajendra K.; Stoller, Jeremy; Tatem, Andrew J.; Kitron, Uriel; Godfray, H. Charles J.; Cohen, Justin M.; Hay, Simon I.; Scott, Thomas W.

    2014-01-01

    Mosquito-borne diseases pose some of the greatest challenges in public health, especially in tropical and sub-tropical regions of the world. Efforts to control these diseases have been underpinned by a theoretical framework developed for malaria by Ross and Macdonald, including models, metrics for measuring transmission, and theory of control that identifies key vulnerabilities in the transmission cycle. That framework, especially Macdonald's formula for R0 and its entomological derivative, vectorial capacity, are now used to study dynamics and design interventions for many mosquito-borne diseases. A systematic review of 388 models published between 1970 and 2010 found that the vast majority adopted the Ross–Macdonald assumption of homogeneous transmission in a well-mixed population. Studies comparing models and data question these assumptions and point to the capacity to model heterogeneous, focal transmission as the most important but relatively unexplored component in current theory. Fine-scale heterogeneity causes transmission dynamics to be nonlinear, and poses problems for modeling, epidemiology and measurement. Novel mathematical approaches show how heterogeneity arises from the biology and the landscape on which the processes of mosquito biting and pathogen transmission unfold. Emerging theory focuses attention on the ecological and social context for mosquito blood feeding, the movement of both hosts and mosquitoes, and the relevant spatial scales for measuring transmission and for modeling dynamics and control. PMID:24591453

  15. Recasting the theory of mosquito-borne pathogen transmission dynamics and control.

    PubMed

    Smith, David L; Perkins, T Alex; Reiner, Robert C; Barker, Christopher M; Niu, Tianchan; Chaves, Luis Fernando; Ellis, Alicia M; George, Dylan B; Le Menach, Arnaud; Pulliam, Juliet R C; Bisanzio, Donal; Buckee, Caroline; Chiyaka, Christinah; Cummings, Derek A T; Garcia, Andres J; Gatton, Michelle L; Gething, Peter W; Hartley, David M; Johnston, Geoffrey; Klein, Eili Y; Michael, Edwin; Lloyd, Alun L; Pigott, David M; Reisen, William K; Ruktanonchai, Nick; Singh, Brajendra K; Stoller, Jeremy; Tatem, Andrew J; Kitron, Uriel; Godfray, H Charles J; Cohen, Justin M; Hay, Simon I; Scott, Thomas W

    2014-04-01

    Mosquito-borne diseases pose some of the greatest challenges in public health, especially in tropical and sub-tropical regions of the world. Efforts to control these diseases have been underpinned by a theoretical framework developed for malaria by Ross and Macdonald, including models, metrics for measuring transmission, and theory of control that identifies key vulnerabilities in the transmission cycle. That framework, especially Macdonald's formula for R0 and its entomological derivative, vectorial capacity, are now used to study dynamics and design interventions for many mosquito-borne diseases. A systematic review of 388 models published between 1970 and 2010 found that the vast majority adopted the Ross-Macdonald assumption of homogeneous transmission in a well-mixed population. Studies comparing models and data question these assumptions and point to the capacity to model heterogeneous, focal transmission as the most important but relatively unexplored component in current theory. Fine-scale heterogeneity causes transmission dynamics to be nonlinear, and poses problems for modeling, epidemiology and measurement. Novel mathematical approaches show how heterogeneity arises from the biology and the landscape on which the processes of mosquito biting and pathogen transmission unfold. Emerging theory focuses attention on the ecological and social context for mosquito blood feeding, the movement of both hosts and mosquitoes, and the relevant spatial scales for measuring transmission and for modeling dynamics and control.

  16. A review of malaria transmission dynamics in forest ecosystems

    PubMed Central

    2014-01-01

    Malaria continues to be a major health problem in more than 100 endemic countries located primarily in tropical and sub-tropical regions around the world. Malaria transmission is a dynamic process and involves many interlinked factors, from uncontrollable natural environmental conditions to man-made disturbances to nature. Almost half of the population at risk of malaria lives in forest areas. Forests are hot beds of malaria transmission as they provide conditions such as vegetation cover, temperature, rainfall and humidity conditions that are conducive to distribution and survival of malaria vectors. Forests often lack infrastructure and harbor tribes with distinct genetic traits, socio-cultural beliefs and practices that greatly influence malaria transmission dynamics. Here we summarize the various topographical, entomological, parasitological, human ecological and socio-economic factors, which are crucial and shape malaria transmission in forested areas. An in-depth understanding and synthesis of the intricate relationship of these parameters in achieving better malaria control in various types of forest ecosystems is emphasized. PMID:24912923

  17. Biology as population dynamics: heuristics for transmission risk.

    PubMed

    Keebler, Daniel; Walwyn, David; Welte, Alex

    2013-02-01

    Population-type models, accounting for phenomena such as population lifetimes, mixing patterns, recruitment patterns, genetic evolution and environmental conditions, can be usefully applied to the biology of HIV infection and viral replication. A simple dynamic model can explore the effect of a vaccine-like stimulus on the mortality and infectiousness, which formally looks like fertility, of invading virions; the mortality of freshly infected cells; and the availability of target cells, all of which impact on the probability of infection. Variations on this model could capture the importance of the timing and duration of different key events in viral transmission, and hence be applied to questions of mucosal immunology. The dynamical insights and assumptions of such models are compatible with the continuum of between- and within-individual risks in sexual violence and may be helpful in making sense of the sparse data available on the association between HIV transmission and sexual violence. © 2012 John Wiley & Sons A/S.

  18. Broad patterns in domestic vector-borne Trypanosoma cruzi transmission dynamics: synanthropic animals and vector control.

    PubMed

    Peterson, Jennifer K; Bartsch, Sarah M; Lee, Bruce Y; Dobson, Andrew P

    2015-10-22

    Chagas disease (caused by Trypanosoma cruzi) is the most important neglected tropical disease (NTD) in Latin America, infecting an estimated 5.7 million people in the 21 countries where it is endemic. It is one of the NTDs targeted for control and elimination by the 2020 London Declaration goals, with the first goal being to interrupt intra-domiciliary vector-borne T. cruzi transmission. A key question in domestic T. cruzi transmission is the role that synanthropic animals play in T. cruzi transmission to humans. Here, we ask, (1) do synanthropic animals need to be targeted in Chagas disease prevention policies?, and (2) how does the presence of animals affect the efficacy of vector control? We developed a simple mathematical model to simulate domestic vector-borne T. cruzi transmission and to specifically examine the interaction between the presence of synanthropic animals and effects of vector control. We used the model to explore how the interactions between triatomine bugs, humans and animals impact the number and proportion of T. cruzi-infected bugs and humans. We then examined how T. cruzi dynamics change when control measures targeting vector abundance are introduced into the system. We found that the presence of synanthropic animals slows the speed of T. cruzi transmission to humans, and increases the sensitivity of T. cruzi transmission dynamics to vector control measures at comparable triatomine carrying capacities. However, T. cruzi transmission is amplified when triatomine carrying capacity increases with the abundance of syntathoropic hosts. Our results suggest that in domestic T. cruzi transmission scenarios where no vector control measures are in place, a reduction in synanthropic animals may slow T. cruzi transmission to humans, but it would not completely eliminate transmission. To reach the 2020 goal of interrupting intra-domiciliary T. cruzi transmission, it is critical to target vector populations. Additionally, where vector control measures

  19. Analyzing transmission dynamics of cholera with public health interventions.

    PubMed

    Posny, Drew; Wang, Jin; Mukandavire, Zindoga; Modnak, Chairat

    2015-06-01

    Cholera continues to be a serious public health concern in developing countries and the global increase in the number of reported outbreaks suggests that activities to control the diseases and surveillance programs to identify or predict the occurrence of the next outbreaks are not adequate. These outbreaks have increased in frequency, severity, duration and endemicity in recent years. Mathematical models for infectious diseases play a critical role in predicting and understanding disease mechanisms, and have long provided basic insights in the possible ways to control infectious diseases. In this paper, we present a new deterministic cholera epidemiological model with three types of control measures incorporated into a cholera epidemic setting: treatment, vaccination and sanitation. Essential dynamical properties of the model with constant intervention controls which include local and global stabilities for the equilibria are carefully analyzed. Further, using optimal control techniques, we perform a study to investigate cost-effective solutions for time-dependent public health interventions in order to curb disease transmission in epidemic settings. Our results show that the basic reproductive number (R0) remains the model's epidemic threshold despite the inclusion of a package of cholera interventions. For time-dependent controls, the results suggest that these interventions closely interplay with each other, and the costs of controls directly affect the length and strength of each control in an optimal strategy.

  20. Stationary transmission distribution of random spike trains by dynamical synapses

    NASA Astrophysics Data System (ADS)

    Hahnloser, Richard H.

    2003-02-01

    Many nonlinearities in neural media are strongly dependent on spike timing jitter and intrinsic dynamics of synaptic transmission. Here we are interested in the stationary density of evoked postsynaptic potentials transmitted by depressing synapses for Poisson spike trains of fixed mean rates. We present a nonperturbative iterative method for computing the stationary density over increasing intervals. We conclude by showing how this method generalizes to other types of synapses, such as facilitating and hybrid synapses.

  1. Highly dynamic animal contact network and implications on disease transmission

    PubMed Central

    Chen, Shi; White, Brad J.; Sanderson, Michael W.; Amrine, David E.; Ilany, Amiyaal; Lanzas, Cristina

    2014-01-01

    Contact patterns among hosts are considered as one of the most critical factors contributing to unequal pathogen transmission. Consequently, networks have been widely applied in infectious disease modeling. However most studies assume static network structure due to lack of accurate observation and appropriate analytic tools. In this study we used high temporal and spatial resolution animal position data to construct a high-resolution contact network relevant to infectious disease transmission. The animal contact network aggregated at hourly level was highly variable and dynamic within and between days, for both network structure (network degree distribution) and individual rank of degree distribution in the network (degree order). We integrated network degree distribution and degree order heterogeneities with a commonly used contact-based, directly transmitted disease model to quantify the effect of these two sources of heterogeneity on the infectious disease dynamics. Four conditions were simulated based on the combination of these two heterogeneities. Simulation results indicated that disease dynamics and individual contribution to new infections varied substantially among these four conditions under both parameter settings. Changes in the contact network had a greater effect on disease dynamics for pathogens with smaller basic reproduction number (i.e. R0 < 2). PMID:24667241

  2. HIV Transmission Dynamics among Foreign-born Persons in the United States.

    PubMed

    Valverde, Eduardo E; Oster, Alexandra M; Xu, Songli; Wertheim, Joel O; Hernandez, Angela L

    2017-09-07

    In the United States (U.S.), foreign-born persons are disproportionately affected by HIV and differ epidemiologically from U.S.-born persons with diagnosed HIV infection. Understanding HIV transmission dynamics among foreign-born persons is important to guide HIV prevention efforts for these populations. We conducted molecular transmission network analysis to describe HIV transmission dynamics among foreign-born persons with diagnosed HIV. Using HIV-1 polymerase nucleotide sequences reported to the U.S. National HIV Surveillance System for persons with diagnosed HIV infection during 2001-2013, we constructed a genetic distance based transmission network using HIV-TRACE and examined the birth region of potential transmission partners in this network. Of 77,686 people, 12,064 (16%) were foreign-born. Overall, 28% of foreign-born persons linked to at least one other person in the transmission network. Of potential transmission partners, 62% were born in the United States, 31% were born in the same region as the foreign-born person, and 7% were born in another region of the world. The majority of transmission partners of male foreign-born persons (63%) were born in the United States, whereas the majority of transmission partners of female foreign-born (57%) were born in their same world region. These finding suggests that a majority of HIV infections among foreign-born persons in our network occurred after immigrating to the United States. Efforts to prevent HIV infection among foreign-born persons in the U.S. should include information of the transmission networks in which these individuals acquire or transmit HIV in order to develop more targeted HIV prevention interventions.

  3. X-ray transmission microscope development

    NASA Technical Reports Server (NTRS)

    Kaukler, William F.; Rosenberger, Franz E.

    1995-01-01

    We are developing a hard x-ray microscope for direct observation of solidification dynamics in metal alloys and metal matrix composites. The Fein-Focus Inc. x-ray source was delivered in September and found to perform better than expected. Confirmed resolution of better than 2 micrometers was obtained and magnifications up to 800X were measured. Nickel beads of 30 micrometer diameter were easily detected through 6mm of aluminum. X-ray metallography was performed on several specimens showing high resolution and clear definition of 3-dimensional structures. Prototype furnace installed and tested.

  4. Epidemiologic natural history and clinical management of Human Papillomavirus (HPV) Disease: a critical and systematic review of the literature in the development of an HPV dynamic transmission model.

    PubMed

    Insinga, Ralph P; Dasbach, Erik J; Elbasha, Elamin H

    2009-07-29

    Natural history models of human papillomavirus (HPV) infection and disease have been used in a number of policy evaluations of technologies to prevent and screen for HPV disease (e.g., cervical cancer, anogenital warts), sometimes with wide variation in values for epidemiologic and clinical inputs. The objectives of this study are to: (1) Provide an updated critical and systematic review of the evidence base to support epidemiologic and clinical modeling of key HPV disease-related parameters in the context of an HPV multi-type disease transmission model which we have applied within a U.S. population context; (2) Identify areas where additional studies are particularly needed. Consistent with our and other prior HPV natural history models, the literature review was confined to cervical disease and genital warts. Between October 2005 and January 2006, data were gathered from the published English language medical literature through a search of the PubMed database and references were examined from prior HPV natural history models and review papers. Study design and data quality from individual studies were compared and analyses meeting pre-defined criteria were selected. Published data meeting review eligibility criteria were most plentiful for natural history parameters relating to the progression and regression of cervical intraepithelial neoplasia (CIN) without HPV typing, and data concerning the natural history of HPV disease due to specific HPV types were often lacking. Epidemiologic evidence to support age-dependency in the risk of progression and regression of HPV disease was found to be weak, and an alternative hypothesis concerning the time-dependence of transition rates is explored. No data were found on the duration of immunity following HPV infection. In the area of clinical management, data were observed to be lacking on the proportion of clinically manifest anogenital warts that are treated and the proportion of cervical cancer cases that become

  5. Epidemiologic natural history and clinical management of Human Papillomavirus (HPV) Disease: a critical and systematic review of the literature in the development of an HPV dynamic transmission model

    PubMed Central

    2009-01-01

    Background Natural history models of human papillomavirus (HPV) infection and disease have been used in a number of policy evaluations of technologies to prevent and screen for HPV disease (e.g., cervical cancer, anogenital warts), sometimes with wide variation in values for epidemiologic and clinical inputs. The objectives of this study are to: (1) Provide an updated critical and systematic review of the evidence base to support epidemiologic and clinical modeling of key HPV disease-related parameters in the context of an HPV multi-type disease transmission model which we have applied within a U.S. population context; (2) Identify areas where additional studies are particularly needed. Methods Consistent with our and other prior HPV natural history models, the literature review was confined to cervical disease and genital warts. Between October 2005 and January 2006, data were gathered from the published English language medical literature through a search of the PubMed database and references were examined from prior HPV natural history models and review papers. Study design and data quality from individual studies were compared and analyses meeting pre-defined criteria were selected. Results Published data meeting review eligibility criteria were most plentiful for natural history parameters relating to the progression and regression of cervical intraepithelial neoplasia (CIN) without HPV typing, and data concerning the natural history of HPV disease due to specific HPV types were often lacking. Epidemiologic evidence to support age-dependency in the risk of progression and regression of HPV disease was found to be weak, and an alternative hypothesis concerning the time-dependence of transition rates is explored. No data were found on the duration of immunity following HPV infection. In the area of clinical management, data were observed to be lacking on the proportion of clinically manifest anogenital warts that are treated and the proportion of cervical cancer

  6. Cholera transmission dynamic models for public health practitioners

    PubMed Central

    2014-01-01

    Great progress has been made in mathematical models of cholera transmission dynamics in recent years. However, little impact, if any, has been made by models upon public health decision-making and day-to-day routine of epidemiologists. This paper provides a brief introduction to the basics of ordinary differential equation models of cholera transmission dynamics. We discuss a basic model adapted from Codeço (2001), and how it can be modified to incorporate different hypotheses, including the importance of asymptomatic or inapparent infections, and hyperinfectious V. cholerae and human-to-human transmission. We highlight three important challenges of cholera models: (1) model misspecification and parameter uncertainty, (2) modeling the impact of water, sanitation and hygiene interventions and (3) model structure. We use published models, especially those related to the 2010 Haitian outbreak as examples. We emphasize that the choice of models should be dictated by the research questions in mind. More collaboration is needed between policy-makers, epidemiologists and modelers in public health. PMID:24520853

  7. Sexual partner selectiveness effects on homosexual HIV transmission dynamics.

    PubMed

    Koopman, J; Simon, C; Jacquez, J; Joseph, J; Sattenspiel, L; Park, T

    1988-01-01

    Deterministic simulation models are used to show that HIV transmission dynamics in homosexual populations can be strongly affected by sexual partner selectiveness. The type of selectiveness or biased mixing examined is where individuals with similar new partnership formation rates are more likely to form a pair than would be expected by chance. The effect of such selectiveness could be strong even when the total number and distribution of new sexual partnerships and sex acts remains constant. This means that in order to predict the future course of HIV transmission and identify the populations at highest risk, we must have information not only on the frequency of new sexual partnerships and types of sex acts, but also on who has sex with whom. Given high sexual partner selectiveness, some groups of homosexuals with low rates of sex and new sex partners would take many decades before a single introduction would generate an epidemic. Epidemics in these groups can be markedly accelerated by only modest contact with higher risk groups. Even in very low activity groups, which if isolated would have no epidemic, an important proportion of their members can be infected when they are not selective. The relative risks of AIDS in groups making high numbers of new sexual partnerships compared to groups making low numbers are markedly affected by sexual partner selectiveness. The models developed were examined using information collected in 1984 from the Coping and Change Study in collaboration with the Chicago Multicenter AIDS Cohort Study. This population was divided into activity groups by the rate at which individuals established new sexual partnerships and then a structure of new sexual partnerships between these activity groups was defined consistent with available data. Even without introducing any behavior change in the models, the proportion of the homosexual population infected was seen to level off temporarily at around 50% after several years as a consequence of

  8. Generation and transmission improvements in developing countries

    SciTech Connect

    Hammons, T.J.; Willingham, M.; Mak, K.N.; Da Silva, M.; Morozowski, M.; Blyden, B.K.

    1999-09-01

    This paper discusses new realities in Power Development in Developing Countries as seen by the United Nations, The World Energy Council, Asia, Latin America, and Africa. At the outset, technical assistance given by the United Nations for global sustainability projects is summarized. Power system expansion and interconnection in China, greenhouse gas emission reduction in Egypt, and integrated development of the Arab-Mediterranean Regional and environmental considerations are among the projects that are highlighted. The pressing need of Developing Countries as seen by the World Energy Council to meet energy needs without prejudice to the environment where technological advances in the production, delivery and utilization of electrical energy are central to resolving conflicts between energy and the environment is then discussed. The paper goes on to discuss power system planning in deregulated environments where the Brazilian experience is highlighted. Global dynamics and potential for an integrated African Grid is then examined. Concepts associated with the growing interest in renewable resources in Central and East Africa for domestic, continental and international utilization are synthesized. Current and future energy development proposals are discussed with emphasis on operational reliability as a basis for potential large system design. Given are generalized representations to illustrate hydroelectric potential of the Central and East African regions and the kind of centralized pool that could be developed as a result. Other studies which include the Africa-Europe and Zaire-Egypt initiatives are also discussed.

  9. Acoustic asymmetric transmission based on time-dependent dynamical scattering

    PubMed Central

    Wang, Qing; Yang, Yang; Ni, Xu; Xu, Ye-Long; Sun, Xiao-Chen; Chen, Ze-Guo; Feng, Liang; Liu, Xiao-ping; Lu, Ming-Hui; Chen, Yan-Feng

    2015-01-01

    An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrate a new acoustic frequency conversion process in a time-varying system, consisting of a rotating blade and the surrounding air. The scattered acoustic waves from this time-varying system experience frequency shifts, which are linearly dependent on the blade’s rotating frequency. Such scattering mechanism can be well described theoretically by an acoustic linear time-varying perturbation theory. Combining such time-varying scattering effects with highly efficient acoustic filtering, we successfully develop a tunable acoustic unidirectional device with 20 dB power transmission contrast ratio between two counter propagation directions at audible frequencies. PMID:26038886

  10. Acoustic asymmetric transmission based on time-dependent dynamical scattering

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Yang, Yang; Ni, Xu; Xu, Ye-Long; Sun, Xiao-Chen; Chen, Ze-Guo; Feng, Liang; Liu, Xiao-Ping; Lu, Ming-Hui; Chen, Yan-Feng

    2015-06-01

    An acoustic asymmetric transmission device exhibiting unidirectional transmission property for acoustic waves is extremely desirable in many practical scenarios. Such a unique property may be realized in various configurations utilizing acoustic Zeeman effects in moving media as well as frequency-conversion in passive nonlinear acoustic systems and in active acoustic systems. Here we demonstrate a new acoustic frequency conversion process in a time-varying system, consisting of a rotating blade and the surrounding air. The scattered acoustic waves from this time-varying system experience frequency shifts, which are linearly dependent on the blade’s rotating frequency. Such scattering mechanism can be well described theoretically by an acoustic linear time-varying perturbation theory. Combining such time-varying scattering effects with highly efficient acoustic filtering, we successfully develop a tunable acoustic unidirectional device with 20 dB power transmission contrast ratio between two counter propagation directions at audible frequencies.

  11. Transmission dynamics of two dengue serotypes with vaccination scenarios.

    PubMed

    González Morales, N L; Núñez-López, M; Ramos-Castañeda, J; Velasco-Hernández, J X

    2017-05-01

    In this work we present a mathematical model that incorporates two Dengue serotypes. The model has been constructed to study both the epidemiological trends of the disease and conditions that allow coexistence in competing strains under vaccination. We consider two viral strains and temporary cross-immunity with one vector mosquito population. Results suggest that vaccination scenarios will not only reduce disease incidence but will also modify the transmission dynamics. Indeed, vaccination and cross immunity period are seen to decrease the frequency and magnitude of outbreaks but in a differentiated manner with specific effects depending upon the interaction vaccine and strain type. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Transmission dynamics of oral polio vaccine viruses and vaccine-derived polioviruses on networks.

    PubMed

    Kim, Jong-Hoon; Rho, Seong-Hwan

    2015-01-07

    One drawback of oral polio vaccine (OPV) is the potential reversion to more transmissible, virulent circulating vaccine-derived polioviruses (cVDPVs), which may cause outbreaks of paralytic poliomyelitis. Previous modeling studies of the transmission of cVDPVs assume an unrealistic homogeneous mixing of the population and/or ignore that OPV viruses and cVDPVs compete for susceptibles, which we show is a key to understanding the dynamics of the transmission of cVDPVs. We examined the transmission of OPV viruses and cVDPVs on heterogeneous, dynamic contact networks using differential equation-based and individual-based models. Despite the lower transmissibility, OPV viruses may outcompete more transmissible cVDPVs in the short run by spreading extensively before cVDPVs emerge. If viruses become endemic, however, cVDPVs eventually dominate and force OPV viruses to extinction. This study improves our understanding of the emergence of cVDPVs and helps develop more detailed models to plan a policy to control paralytic polio associated with the continued use of OPV in many countries.

  13. Transmission Dynamics of Methicillin-Resistant Staphylococcus aureus in Pigs

    PubMed Central

    Crombé, Florence; Argudín, M. Angeles; Vanderhaeghen, Wannes; Hermans, Katleen; Haesebrouck, Freddy; Butaye, Patrick

    2013-01-01

    From the mid-2000s on, numerous studies have shown that methicillin-resistant Staphylococcus aureus (MRSA), renowned as human pathogen, has a reservoir in pigs and other livestock. In Europe and North America, clonal complex (CC) 398 appears to be the predominant lineage involved. Especially worrisome is its capacity to contaminate humans in close contact with affected animals. Indeed, the typical multi-resistant phenotype of MRSA CC398 and its observed ability of easily acquiring genetic material suggests that MRSA CC398 strains with an increased virulence potential may emerge, for which few therapeutic options would remain. This questions the need to implement interventions to control the presence and spread of MRSA CC398 among pigs. MRSA CC398 shows a high but not fully understood transmission potential in the pig population and is able to persist within that population. Although direct contact is probably the main route for MRSA transmission between pigs, also environmental contamination, the presence of other livestock, the herd size, and farm management are factors that may be involved in the dissemination of MRSA CC398. The current review aims at summarizing the research that has so far been done on the transmission dynamics and risk factors for introduction and persistence of MRSA CC398 in farms. PMID:23518663

  14. Plasmodium vivax Population Structure and Transmission Dynamics in Sabah Malaysia

    PubMed Central

    Abdullah, Noor Rain; Barber, Bridget E.; William, Timothy; Norahmad, Nor Azrina; Satsu, Umi Rubiah; Muniandy, Prem Kumar; Ismail, Zakiah; Grigg, Matthew J.; Jelip, Jenarun; Piera, Kim; von Seidlein, Lorenz; Yeo, Tsin W.; Anstey, Nicholas M.; Price, Ric N.; Auburn, Sarah

    2013-01-01

    Despite significant progress in the control of malaria in Malaysia, the complex transmission dynamics of P. vivax continue to challenge national efforts to achieve elimination. To assess the impact of ongoing interventions on P. vivax transmission dynamics in Sabah, we genotyped 9 short tandem repeat markers in a total of 97 isolates (8 recurrences) from across Sabah, with a focus on two districts, Kota Marudu (KM, n = 24) and Kota Kinabalu (KK, n = 21), over a 2 year period. STRUCTURE analysis on the Sabah-wide dataset demonstrated multiple sub-populations. Significant differentiation (FST  = 0.243) was observed between KM and KK, located just 130 Km apart. Consistent with low endemic transmission, infection complexity was modest in both KM (mean MOI  = 1.38) and KK (mean MOI  = 1.19). However, population diversity remained moderate (HE  = 0.583 in KM and HE  = 0.667 in KK). Temporal trends revealed clonal expansions reflecting epidemic transmission dynamics. The haplotypes of these isolates declined in frequency over time, but persisted at low frequency throughout the study duration. A diverse array of low frequency isolates were detected in both KM and KK, some likely reflecting remnants of previous expansions. In accordance with clonal expansions, high levels of Linkage Disequilibrium (IAS >0.5 [P<0.0001] in KK and KM) declined sharply when identical haplotypes were represented once (IAS  = 0.07 [P = 0.0076] in KM, and IAS = -0.003 [P = 0.606] in KK). All 8 recurrences, likely to be relapses, were homologous to the prior infection. These recurrences may promote the persistence of parasite lineages, sustaining local diversity. In summary, Sabah's shrinking P. vivax population appears to have rendered this low endemic setting vulnerable to epidemic expansions. Migration may play an important role in the introduction of new parasite strains leading to epidemic expansions, with important implications for malaria

  15. Plasmodium vivax population structure and transmission dynamics in Sabah Malaysia.

    PubMed

    Abdullah, Noor Rain; Barber, Bridget E; William, Timothy; Norahmad, Nor Azrina; Satsu, Umi Rubiah; Muniandy, Prem Kumar; Ismail, Zakiah; Grigg, Matthew J; Jelip, Jenarun; Piera, Kim; von Seidlein, Lorenz; Yeo, Tsin W; Anstey, Nicholas M; Price, Ric N; Auburn, Sarah

    2013-01-01

    Despite significant progress in the control of malaria in Malaysia, the complex transmission dynamics of P. vivax continue to challenge national efforts to achieve elimination. To assess the impact of ongoing interventions on P. vivax transmission dynamics in Sabah, we genotyped 9 short tandem repeat markers in a total of 97 isolates (8 recurrences) from across Sabah, with a focus on two districts, Kota Marudu (KM, n = 24) and Kota Kinabalu (KK, n = 21), over a 2 year period. STRUCTURE analysis on the Sabah-wide dataset demonstrated multiple sub-populations. Significant differentiation (F ST  = 0.243) was observed between KM and KK, located just 130 Km apart. Consistent with low endemic transmission, infection complexity was modest in both KM (mean MOI  = 1.38) and KK (mean MOI  = 1.19). However, population diversity remained moderate (H E  = 0.583 in KM and H E  = 0.667 in KK). Temporal trends revealed clonal expansions reflecting epidemic transmission dynamics. The haplotypes of these isolates declined in frequency over time, but persisted at low frequency throughout the study duration. A diverse array of low frequency isolates were detected in both KM and KK, some likely reflecting remnants of previous expansions. In accordance with clonal expansions, high levels of Linkage Disequilibrium (I A (S) >0.5 [P<0.0001] in KK and KM) declined sharply when identical haplotypes were represented once (I A (S)  = 0.07 [P = 0.0076] in KM, and I A (S) = -0.003 [P = 0.606] in KK). All 8 recurrences, likely to be relapses, were homologous to the prior infection. These recurrences may promote the persistence of parasite lineages, sustaining local diversity. In summary, Sabah's shrinking P. vivax population appears to have rendered this low endemic setting vulnerable to epidemic expansions. Migration may play an important role in the introduction of new parasite strains leading to epidemic expansions, with important implications for

  16. On the Identifiability of Transmission Dynamic Models for Infectious Diseases

    PubMed Central

    Lintusaari, Jarno; Gutmann, Michael U.; Kaski, Samuel; Corander, Jukka

    2016-01-01

    Understanding the transmission dynamics of infectious diseases is important for both biological research and public health applications. It has been widely demonstrated that statistical modeling provides a firm basis for inferring relevant epidemiological quantities from incidence and molecular data. However, the complexity of transmission dynamic models presents two challenges: (1) the likelihood function of the models is generally not computable, and computationally intensive simulation-based inference methods need to be employed, and (2) the model may not be fully identifiable from the available data. While the first difficulty can be tackled by computational and algorithmic advances, the second obstacle is more fundamental. Identifiability issues may lead to inferences that are driven more by prior assumptions than by the data themselves. We consider a popular and relatively simple yet analytically intractable model for the spread of tuberculosis based on classical IS6110 fingerprinting data. We report on the identifiability of the model, also presenting some methodological advances regarding the inference. Using likelihood approximations, we show that the reproductive value cannot be identified from the data available and that the posterior distributions obtained in previous work have likely been substantially dominated by the assumed prior distribution. Further, we show that the inferences are influenced by the assumed infectious population size, which generally has been kept fixed in previous work. We demonstrate that the infectious population size can be inferred if the remaining epidemiological parameters are already known with sufficient precision. PMID:26739450

  17. On the Identifiability of Transmission Dynamic Models for Infectious Diseases.

    PubMed

    Lintusaari, Jarno; Gutmann, Michael U; Kaski, Samuel; Corander, Jukka

    2016-03-01

    Understanding the transmission dynamics of infectious diseases is important for both biological research and public health applications. It has been widely demonstrated that statistical modeling provides a firm basis for inferring relevant epidemiological quantities from incidence and molecular data. However, the complexity of transmission dynamic models presents two challenges: (1) the likelihood function of the models is generally not computable, and computationally intensive simulation-based inference methods need to be employed, and (2) the model may not be fully identifiable from the available data. While the first difficulty can be tackled by computational and algorithmic advances, the second obstacle is more fundamental. Identifiability issues may lead to inferences that are driven more by prior assumptions than by the data themselves. We consider a popular and relatively simple yet analytically intractable model for the spread of tuberculosis based on classical IS6110 fingerprinting data. We report on the identifiability of the model, also presenting some methodological advances regarding the inference. Using likelihood approximations, we show that the reproductive value cannot be identified from the data available and that the posterior distributions obtained in previous work have likely been substantially dominated by the assumed prior distribution. Further, we show that the inferences are influenced by the assumed infectious population size, which generally has been kept fixed in previous work. We demonstrate that the infectious population size can be inferred if the remaining epidemiological parameters are already known with sufficient precision.

  18. Human tissue color as viewed in high dynamic range optical spectral transmission measurements.

    PubMed

    Petrov, Georgi I; Doronin, Alexander; Whelan, Harry T; Meglinski, Igor; Yakovlev, Vladislav V

    2012-09-01

    High dynamic range optical-to-near-infrared transmission measurements for different parts of human body in the spectral range from 650 to 950 nm have been performed. Experimentally measured spectra are correlated with Monte Carlo simulations using chromaticity coordinates in CIE 1976 L*a*b* color space. Both a qualitative and a quantitative agreement have been found, paving a new way of characterizing human tissues in vivo. The newly developed experimental and computational platform for assessing tissue transmission spectra is anticipated to have a considerable impact on identifying favorable conditions for laser surgery and optical diagnostics, while providing supplementary information about tissue properties.

  19. Transmission Dynamics of Rhodesian Sleeping Sickness at the Interface of Wildlife and Livestock Areas.

    PubMed

    Auty, Harriet; Morrison, Liam J; Torr, Stephen J; Lord, Jennifer

    2016-08-01

    Many wilderness areas of East and Southern Africa are foci for Rhodesian sleeping sickness, a fatal zoonotic disease caused by trypanosomes transmitted by tsetse flies. Although transmission in these foci is traditionally driven by wildlife reservoirs, rising human and livestock populations may increase the role of livestock in transmission cycles. Deciphering transmission dynamics at wildlife and livestock interface areas is key to developing appropriate control. Data are lacking for key parameters, including host distributions, tsetse density, and mortality rates, and the relative roles of livestock and wildlife as hosts in fragmented habitats, limiting the development of meaningful models to assist in the assessment and implementation of control strategies. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Development of a Nanoindenter for In Situ Transmission Electron Microscopy.

    PubMed

    Stach, Eric A.; Freeman, Tony; Minor, Andrew M.; Owen, Doug K.; Cumings, John; Wall, Mark A.; Chraska, Tomas; Hull, Robert; Morris, J.W.; Jr, A.; Zettl, Ulrich

    2001-11-01

    In situ transmission electron microscopy is an established experimental technique that permits direct observation of the dynamics and mechanisms of dislocation motion and deformation behavior. In this article, we detail the development of a novel specimen goniometer that allows real-time observations of the mechanical response of materials to indentation loads. The technology of the scanning tunneling microscope is adopted to allow nanometer-scale positioning of a sharp, conductive diamond tip onto the edge of an electron-transparent sample. This allows application of loads to nanometer-scale material volumes coupled with simultaneous imaging of the material's response. The emphasis in this report is qualitative and technique oriented, with particular attention given to sample geometry and other technical requirements. Examples of the deformation of aluminum and titanium carbide as well as the fracture of silicon will be presented.

  1. Development of helicopter transmission seals, task 2

    NASA Technical Reports Server (NTRS)

    Hayden, T. S.; Keller, C. H., Jr.

    1973-01-01

    High speed helicopter transmission seal concepts were designed, fabricated and tested. The concepts were a dual element split ring seal and a circumferential seal. The tests were performed in a rig using an actual input quill assembly. The test conditions were selected to simulate transmission operation and were 230 F oil temperature, and a sliding speed of 9400 ft/min. The split ring seal exhibited gross leakage and was considered unsatisfactory, while the circumferential seal leakage was less than 1 c.c./hour; this leakage is within acceptable limits. The circumferential seal wear was only to .0005 inches during a 100 hour run (40 starts and stops). During a 40 hour contamination test (mesh silica flour) the seal total wear was a maximum of .004 inches. This wear is considered acceptable.

  2. Dynamic characteristic analysis of HIV mother to child transmission in China.

    PubMed

    Wang, Jun-Jie; Reilly, Kathleen Heather; Han, Hua; Peng, Zhi-Hang; Wang, Ning

    2010-10-01

    To explore dynamic characteristics of the HIV mother to child transmission (MTCT) epidemic in China. A deterministic dynamic transmission model was used to determine the effect of key parameters on the likely long-term trends of the HIV MTCT epidemic in China. Matlab 7.0 was used to develop the model. The number of the susceptibles (S), the transmission rate (β), and the screening proportion (α) of HIV positive pregnant women have the greatest impact on the HIV MTCT epidemic in China. The growth of the MTCT epidemic in China could not be controlled only by decreasing the MTCT transmission rate. The prevalence of HIV positive women should be reduced and more pregnant women should be tested for HIV. Prevention of MTCT (PMTCT) should focus not only on the reduction of HIV transmission rates and incidences of HIV among women but also on the increase of HIV testing for pregnant women. The most cost-effective PMTCT means for China should be investigated in future studies. Copyright © 2010 The Editorial Board of Biomedical and Environmental Sciences. Published by Elsevier B.V. All rights reserved.

  3. The dynamics, transmission, and population impacts of avian malaria in native hawaiian birds: A modeling approach

    USGS Publications Warehouse

    Samuel, M.D.; Hobbelen, P.H.F.; Decastro, F.; Ahumada, J.A.; Lapointe, D.A.; Atkinson, C.T.; Woodworth, B.L.; Hart, P.J.; Duffy, D.C.

    2011-01-01

    We developed an epidemiological model of avian malaria (Plasmodium relictum) across an altitudinal gradient on the island of Hawaii that includes the dynamics of the host, vector, and parasite. This introduced mosquito-borne disease is hypothesized to have contributed to extinctions and major shifts in the altitudinal distribution of highly susceptible native forest birds. Our goal was to better understand how biotic and abiotic factors influence the intensity of malaria transmission and impact on susceptible populations of native Hawaiian forest birds. Our model illustrates key patterns in the malaria-forest bird system: high malaria transmission in low-elevation forests with minor seasonal or annual variation in infection;episodic transmission in mid-elevation forests with site-to-site, seasonal, and annual variation depending on mosquito dynamics;and disease refugia in high-elevation forests with only slight risk of infection during summer. These infection patterns are driven by temperature and rainfall effects on parasite incubation period and mosquito dynamics across an elevational gradient and the availability of larval habitat, especially in mid-elevation forests. The results from our model suggest that disease is likely a key factor in causing population decline or restricting the distribution of many susceptible Hawaiian species and preventing the recovery of other vulnerable species. The model also provides a framework for the evaluation of factors influencing disease transmission and alternative disease control programs, and to evaluate the impact of climate change on disease cycles and bird populations. ??2011 by the Ecological Society of America.

  4. Seasonality Impact on the Transmission Dynamics of Tuberculosis.

    PubMed

    Yang, Yali; Guo, Chenping; Liu, Luju; Zhang, Tianhua; Liu, Weiping

    2016-01-01

    The statistical data of monthly pulmonary tuberculosis (TB) incidence cases from January 2004 to December 2012 show the seasonality fluctuations in Shaanxi of China. A seasonality TB epidemic model with periodic varying contact rate, reactivation rate, and disease-induced death rate is proposed to explore the impact of seasonality on the transmission dynamics of TB. Simulations show that the basic reproduction number of time-averaged autonomous systems may underestimate or overestimate infection risks in some cases, which may be up to the value of period. The basic reproduction number of the seasonality model is appropriately given, which determines the extinction and uniform persistence of TB disease. If it is less than one, then the disease-free equilibrium is globally asymptotically stable; if it is greater than one, the system at least has a positive periodic solution and the disease will persist. Moreover, numerical simulations demonstrate these theorem results.

  5. Dynamics of a nanodroplet under a transmission electron microscope

    SciTech Connect

    Leong, Fong Yew; Mirsaidov, Utkur M.; Matsudaira, Paul; Mahadevan, L.

    2014-01-15

    We investigate the cyclical stick-slip motion of water nanodroplets on a hydrophilic substrate viewed with and stimulated by a transmission electron microscope. Using a continuum long wave theory, we show how the electrostatic stress imposed by non-uniform charge distribution causes a pinned convex drop to deform into a toroidal shape, with the shape characterized by the competition between the electrostatic stress and the surface tension of the drop, as well as the charge density distribution which follows a Poisson equation. A horizontal gradient in the charge density creates a lateral driving force, which when sufficiently large, overcomes the pinning induced by surface heterogeneities in the substrate disjoining pressure, causing the drop to slide on the substrate via a cyclical stick-slip motion. Our model predicts step-like dynamics in drop displacement and surface area jumps, qualitatively consistent with experimental observations.

  6. Threshold dynamics of a malaria transmission model in periodic environment

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Teng, Zhidong; Zhang, Tailei

    2013-05-01

    In this paper, we propose a malaria transmission model with periodic environment. The basic reproduction number R0 is computed for the model and it is shown that the disease-free periodic solution of the model is globally asymptotically stable when R0<1, that is, the disease goes extinct when R0<1, while the disease is uniformly persistent and there is at least one positive periodic solution when R0>1. It indicates that R0 is the threshold value determining the extinction and the uniform persistence of the disease. Finally, some examples are given to illustrate the main theoretical results. The numerical simulations show that, when the disease is uniformly persistent, different dynamic behaviors may be found in this model, such as the global attractivity and the chaotic attractor.

  7. Dynamic Model for the Z Accelerator Vacuum Section Based on Transmission Line Code

    NASA Astrophysics Data System (ADS)

    Hu, Yixiang; Qiu, Aici; Wang, Liangping; Huang, Tao; Cong, Peitian; Zhang, Xinjun; Li, Yan; Zeng, Zhengzhong; Sun, Tieping; Lei, Tianshi; Wu, Hanyu; Guo, Ning; Han, Juanjuan

    2011-10-01

    The transmission-line-circuit model of the Z accelerator, developed originally by W. A. STYGAR, P. A. CORCORAN, et al, is revised. The revised model uses different calculations for the electron loss and flow impedance in the magnetically insulated transmission line system of the Z accelerator before and after magnetic insulation is established. By including electron pressure and zero electric field at the cathode, a closed set of equations is obtained at each time step, and dynamic shunt resistance (used to represent any electron loss to the anode) and flow impedance are solved, which have been incorporated into the transmission line code for simulations of the vacuum section in the Z accelerator. Finally, the results are discussed in comparison with earlier findings to show the effectiveness and limitations of the model.

  8. X-Ray Transmission Microscope Development

    NASA Technical Reports Server (NTRS)

    Kaukler, William F.

    1997-01-01

    We have succeeded in meeting the goals set out in the proposal. A cadre of detector technologies is available to suit the requirements of the experiment. Resolutions of both real-time and absolute limits to resolution exceed the initial aspirations. Obtaining sufficient contrast is still a significant limitation but can be overcome by Judicious selection of the specimen composition. This can only take time and trial and error for a successful result. The 4th generation furnace provides the capability of real-time in-situ observations of composite alloy development. A low detection sensitivity however, has still made it difficult to observe dendritic growth, although it has been 'seen' in raw video; it was not a recordable signal. We have examined flight ampoules with XTM to observe particle and thermocouple placement, crucible flaws and cracks in collaboration with the Particle Pushing and Engulfment flight experiment (Dr. Stefanescu, UA, P.I.). The value of an in flight XTM to guard against experiment failure and safety assurance is obvious. Although not attributable to equipment limitations, a quest to observe particle pushing was not successful. We tried at length to prepare specimens that would demonstrate particle pushing. Instead, we were successful in imaging the interface deformation due to the thermal field distortion of a ceramic particle or void and to compare to calculated shapes. In theory, we should have been able to make major inroads to this field if the particles could be pushed and the velocities adjusted to make critical measurements. On the other hand, critical issues of sample preparation for the PEP flight experiment were established, particularly the clustering of particles and trapped voids. In this regard, the XTM did prove very useful so that flight specimens would work as expected and to perform post flight analysis. Although not a clear result, particle pushing of precipitates was observed in an Al-Si-Mn alloy. It may be that to be

  9. Hydrologic variability and the dynamics of West Nile virus transmission

    NASA Astrophysics Data System (ADS)

    Shaman, J. L.

    2011-12-01

    West Nile virus (WNV) first emerged in North America in New York City during 1999 and since that time has spread throughout the continent and settled into a pattern of local endemicity in which outbreaks of variable size develop in some years but not others. Predicting where and when these outbreaks will develop is an issue of considerable public health importance. Spillover transmission of WNV to humans typically occurs when infection rates among vector mosquitoes are elevated. Mosquito infection rates are not constant through time but instead increase when newly emergent mosquitoes can more readily acquire WNV by blood-meal feeding on available, infected animal hosts. Such an increase of vector mosquito infection rates is termed amplification and is facilitated for WNV by intense zoonotic transmission of the virus among vector mosquitoes and avian hosts. Theory, observation and model simulations indicate that amplification is favored when mosquito breeding habitats and bird nesting and roosting habitats overlap. Both vector mosquitoes and vertebrate hosts depend on water resources; mosquitoes are critically dependent on the availability of standing water, as the first 3 stages of the mosquito life cycle, egg, larvae, pupae, are aquatic. Here it is shown that hydrologic variability often determines where and when vector mosquitoes and avian hosts congregate together, and when the amplification of WNV is more likely. Measures of land surface wetness and pooling, from ground observation, satellite observation, or numerical modeling, can provide reliable estimates of where and when WNV transmission hotspots will arise. Examples of this linkage between hydrology and WNV activity are given for Florida, Colorado and New York, and an operational system for monitoring and forecasting WNV risk in space and time is presented for Florida.

  10. Experimental investigation and model development for a harmonic drive transmission.

    SciTech Connect

    Preissner, C.; Shu, D.; Royston, T. J.; Univ. of Illinois at Chicago

    2007-01-01

    Harmonic drive transmissions (HDTs) are compact, low-backlash, high-ratio, high-resolution rotary motion transmissions. One application to benefit from these attributes is the revolute joint robot. Engineers at the Advanced Photon Source (APS) are investigating the use of this type of robot for the positioning of an x-ray detector; understanding the properties of the robot components is crucial to modeling positioner behavior. The robot bearing elements had been investigated previously, leaving the transmission as the missing component. While the benefits of HDTs are well known, the disadvantages, including fluctuating dissipation characteristics and nonlinear stiffness, are not understood as well. These characteristics can contribute uncontrolled dynamics to the overall robot performance. A dynamometer has been constructed at the APS to experimentally measure the HDT's response. Empirical torque and position data were recorded for multiple transmission load cases and input conditions. In turn, a computer model of the dynamometer HDT system was constructed to approximate the observed response.

  11. Modelling inter-human transmission dynamics of Chagas disease: analysis and application.

    PubMed

    Fabrizio, M C; Schweigmann, N J; Bartoloni, N J

    2014-05-01

    Transmission of Trypanosoma cruzi, the causal agent of Chagas disease, has expanded from rural endemic to urban areas due to migration. This so-called urban Chagas is an emerging health problem in American, European, Australian and Japanese cities. We present a mathematical model to analyse the dynamics of urban Chagas to better understand its epidemiology. The model considers the three clinical stages of the disease and the main routes of inter-human transmission. To overcome the complexities of the infection dynamics, the next-generation matrix method was developed. We deduced expressions which allowed estimating the number of new infections generated by an infected individual through each transmission route at each disease stage, the basic reproduction number and the number of individuals at each disease stage at the outbreak of the infection. The analysis was applied to Buenos Aires city (Argentina). We estimated that 94% of the new infections are generated by individuals in the chronic indeterminate stage. When migration was not considered, the infection disappeared slowly and R0 = 0.079, whereas when migration was considered, the number of individuals in each stage of the infection tended to stabilize. The expressions can be used to estimate different numbers of infected individuals in any place where only inter-human transmission is possible.

  12. Modeling the transmission dynamics and control of rabies in China.

    PubMed

    Ruan, Shigui

    2017-04-01

    Human rabies was first recorded in ancient China in about 556 BC and is still one of the major public-health problems in China. From 1950 to 2015, 130,494 human rabies cases were reported in Mainland China with an average of 1977 cases per year. It is estimated that 95% of these human rabies cases are due to dog bites. The purpose of this article is to provide a review about the models, results, and simulations that we have obtained recently on studying the transmission of rabies in China. We first construct a basic susceptible, exposed, infectious, and recovered (SEIR) type model for the spread of rabies virus among dogs and from dogs to humans and use the model to simulate the human rabies data in China from 1996 to 2010. Then we modify the basic model by including both domestic and stray dogs and apply the model to simulate the human rabies data from Guangdong Province, China. To study the seasonality of rabies, in Section 4 we further propose a SEIR model with periodic transmission rates and employ the model to simulate the monthly data of human rabies cases reported by the Chinese Ministry of Health from January 2004 to December 2010. To understand the spatial spread of rabies, in Section 5 we add diffusion to the dog population in the basic SEIR model to obtain a reaction-diffusion equation model and determine the minimum wave speed connecting the disease-free equilibrium to the endemic equilibrium. Finally, in order to investigate how the movement of dogs affects the geographically inter-provincial spread of rabies in Mainland China, in Section 6 we propose a multi-patch model to describe the transmission dynamics of rabies between dogs and humans and use the two-patch submodel to investigate the rabies virus clades lineages and to simulate the human rabies data from Guizhou and Guangxi, Hebei and Fujian, and Sichuan and Shaanxi, respectively. Some discussions are provided in Section 7. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Transmission Dynamics of a Multidrug-Resistant Salmonella Typhimurium Outbreak in a Dairy Farm

    PubMed Central

    Warnick, Lorin D.; James, Karen L.; Wright, Emily M.; Wiedmann, Martin; Gröhn, Yrjo T.

    2010-01-01

    Abstract Cattle are recognized as an important source of foodborne Salmonella causing human illness, particularly for antimicrobial-resistant strains. The transmission dynamics of multidrug-resistant (MDR) Salmonella after the onset of a clinical outbreak in a dairy farm has been rarely monitored. The early transmission of a pathogen influences the outbreak size and persistence of the pathogen at the farm level and, therefore, how long the herd represents a risk for Salmonella zoonotic transmission. The objective of this study was to describe the transmission dynamics of MDR Salmonella Typhimurium after the onset of a clinical outbreak in a dairy herd. For that purpose, fecal shedding and serological response to MDR Salmonella were monitored in a longitudinal study conducted in a dairy herd after a few cases of salmonellosis, and a stochastic transmission model was developed to predict Salmonella persistence at the pen level. The outbreak was limited to five clinical cases, and only 18 animals out of 500 cows shed Salmonella in feces. The longest shedder was culture-positive for Salmonella for at least 68 days. The isolates (n = 27) were represented by four pulsed-field gel electrophoresis patterns; three patterns were similar. With one exception, isolates were resistant to nine or more antimicrobial drugs. Simulations of the transmission model indicated that approximately 50% of the outbreaks were likely to die out within 20 days after the first animal was infected. The simulation studies indicated that salmonellosis outbreaks with few clinical cases were likely due to the extinction of the pathogen in the premises in the early phase of the outbreaks. Small population size and group structure within the farm decrease the on-farm persistence of the pathogen. PMID:19919288

  14. The Epidemiological Characteristics and Dynamic Transmission of Dengue in China, 2013

    PubMed Central

    lu, Liang; Bi, Peng; Lv, Ming; Liu, Qiyong

    2016-01-01

    Background There was a dengue epidemic in several regions of China in 2013. No study has explored the dynamics of dengue transmission between different geographical locations with dengue outbreaks in China. The purpose of the study is to analyze the epidemiological characteristics and to explore the dynamic transmission of dengue in China, 2013. Methodology and Principal Findings Records of dengue cases of 2013 were obtained from the China Notifiable Disease Surveillance System. Full E-gene sequences of dengue virus detected from the outbreak regions of China were download from GenBank. Geographical Information System and heatmaps were used to describe the epidemiological characteristics. Maximum Likelihood phylogenetic and Bayesian phylogeographic analyses were conducted to explore the dengue dynamic transmission. Yunnan Province and Guangdong Province had the highest imported cases in the 2013 epidemic. In the locations with local dengue transmission, most of imported cases occurred from June to November 2013 while local dengue cases developed from July to December, 2013. There were significant variations for the incidences of dengue, in terms of age distributions, among different geographic locations. However, gender differences were identified in Guangzhou, Foshan and Xishuangbanna. DENV 1–3 were detected in all locations with the disease outbreaks. Some genotypes were detected in more than one locations and more than one genotypes have been detected in several locations. The dengue viruses introduced to outbreak areas were predominantly from Southeast Asia. In Guangdong Province, the phylogeographical results indicated that dengue viruses of DENV 1 were transmitted to neighboring cities Foshan and Zhongshan from Guangzhou city, and then transmitted to Jiangmen city. The virus in DENV 3 was introduced to Guangzhou city, Guangdong Province from Xishuangbanna prefecture, Yunnan Province. Conclusions Repeated dengue virus introductions from Southeast Asia and

  15. Analysis of longitudinal multivariate outcome data from couples cohort studies: application to HPV transmission dynamics

    PubMed Central

    Kong, Xiangrong; Wang, Mei-Cheng; Gray, Ronald

    2014-01-01

    We consider a specific situation of correlated data where multiple outcomes are repeatedly measured on each member of a couple. Such multivariate longitudinal data from couples may exhibit multi-faceted correlations which can be further complicated if there are polygamous partnerships. An example is data from cohort studies on human papillomavirus (HPV) transmission dynamics in heterosexual couples. HPV is a common sexually transmitted disease with 14 known oncogenic types causing anogenital cancers. The binary outcomes on the multiple types measured in couples over time may introduce inter-type, intra-couple, and temporal correlations. Simple analysis using generalized estimating equations or random effects models lacks interpretability and cannot fully utilize the available information. We developed a hybrid modeling strategy using Markov transition models together with pairwise composite likelihood for analyzing such data. The method can be used to identify risk factors associated with HPV transmission and persistence, estimate difference in risks between male-to-female and female-to-male HPV transmission, compare type-specific transmission risks within couples, and characterize the inter-type and intra-couple associations. Applying the method to HPV couple data collected in a Ugandan male circumcision (MC) trial, we assessed the effect of MC and the role of gender on risks of HPV transmission and persistence. PMID:26195849

  16. Exploring the dynamics of respiratory syncytial virus (RSV) transmission in children.

    PubMed

    Hogan, Alexandra B; Glass, Kathryn; Moore, Hannah C; Anderssen, Robert S

    2016-08-01

    Respiratory syncytial virus (RSV) is the main cause of lower respiratory tract infections in children. Whilst highly seasonal, RSV dynamics can have either one-year (annual) or two-year (biennial) cycles. Furthermore, some countries show a 'delayed biennial' pattern, where the epidemic peak in low incidence years is delayed. We develop a compartmental model for RSV infection, driven by a seasonal forcing function, and conduct parameter space and bifurcation analyses to document parameter ranges that give rise to these different seasonal patterns. The model is sensitive to the birth rate, transmission rate, and seasonality parameters, and can replicate RSV dynamics observed in different countries. The seasonality parameter must exceed a threshold for the model to produce biennial cycles. Intermediate values of the birth rate produce the greatest delay in these biennial cycles, while the model reverts to annual cycles if the duration of immunity is too short. Finally, the existence of period doubling and period halving bifurcations suggests robust model dynamics, in agreement with the known regularity of RSV outbreaks. These findings help explain observed RSV data, such as regular biennial dynamics in Western Australia, and delayed biennial dynamics in Finland. From a public health perspective, our findings provide insight into the drivers of RSV transmission, and a foundation for exploring RSV interventions.

  17. Transmission dynamics of the monogenean Gyrodactylus salaris under seminatural conditions.

    PubMed

    Hendrichsen, D K; Kristoffersen, R; Gjelland, K Ø; Knudsen, R; Kusterle, S; Rikardsen, A H; Henriksen, E H; Smalås, A; Olstad, K

    2015-06-01

    Tracking individual variation in the dynamics of parasite infections in wild populations is often complicated by lack of knowledge of the epidemiological history of hosts. Whereas the dynamics and development of Gyrodactylus salaris Malmberg, 1957, on Atlantic salmon, Salmo salar L., are known from laboratory studies, knowledge about infection development on individual wild fishes is currently sparse. In this study, the dynamics of an infection of G. salaris on individually marked Atlantic salmon parr was followed in a section of a natural stream. During the 6-week experiment, the prevalence increased from 3.3 to 60.0%, with an average increase in intensity of 4.1% day(-1) . Survival analyses showed an initially high probability (93.6%) of staying uninfected by G. salaris, decreasing significantly to 37% after 6 weeks. The results showed that even at subarctic water temperatures and with an initially low risk of infection, the parasite spread rapidly in the Atlantic salmon population, with the capacity to reach 100% prevalence within a short summer season. The study thus track individual infection trajectories of Atlantic salmon living under near-natural conditions, providing an integration of key population parameters from controlled experiments with the dynamics of the epizootic observed in free-living living populations.

  18. Robust transmission stabilization and dynamic switching in broadband hybrid waveguide systems with nonlinear gain and loss

    NASA Astrophysics Data System (ADS)

    Nguyen, Quan M.; Peleg, Avner; Tran, Thinh P.

    2015-01-01

    We develop a method for transmission stabilization and robust dynamic switching for colliding optical soliton sequences in broadband waveguide systems with nonlinear gain and loss. The method is based on employing hybrid waveguides, consisting of spans with linear gain and cubic loss, and spans with linear loss, cubic gain, and quintic loss. We show that the amplitude dynamics is described by a hybrid Lotka-Volterra (LV) model, and use the model to determine the physical parameter values required for enhanced transmission stabilization and switching. Numerical simulations with coupled nonlinear Schrödinger equations confirm the predictions of the LV model, and show complete suppression of radiative instability and pulse distortion. This enables stable transmission over distances larger by an order of magnitude compared with uniform waveguides with linear gain and cubic loss. Moreover, multiple on-off and off-on dynamic switching events are demonstrated over a wide range of soliton amplitudes, showing the superiority of hybrid waveguides compared with static switching in uniform waveguides.

  19. Estimating enhanced prevaccination measles transmission hotspots in the context of cross-scale dynamics

    PubMed Central

    Becker, Alexander D.; Birger, Ruthie B.; Teillant, Aude; Gastanaduy, Paul A.; Wallace, Gregory S.; Grenfell, Bryan T.

    2016-01-01

    A key question in clarifying human–environment interactions is how dynamic complexity develops across integrative scales from molecular to population and global levels. Apart from its public health importance, measles is an excellent test bed for such an analysis. Simple mechanistic models have successfully illuminated measles dynamics at the city and country levels, revealing seasonal forcing of transmission as a major driver of long-term epidemic behavior. Seasonal forcing ties closely to patterns of school aggregation at the individual and community levels, but there are few explicit estimates of school transmission due to the relative lack of epidemic data at this scale. Here, we use data from a 1904 measles outbreak in schools in Woolwich, London, coupled with a stochastic Susceptible-Infected-Recovered model to analyze measles incidence data. Our results indicate that transmission within schools and age classes is higher than previous population-level serological data would suggest. This analysis sheds quantitative light on the role of school-aged children in measles cross-scale dynamics, as we illustrate with references to the contemporary vaccination landscape. PMID:27872300

  20. Photocathode Optimization for a Dynamic Transmission Electron Microscope: Final Report

    SciTech Connect

    Ellis, P; Flom, Z; Heinselman, K; Nguyen, T; Tung, S; Haskell, R; Reed, B W; LaGrange, T

    2011-08-04

    The Dynamic Transmission Electron Microscope (DTEM) team at Harvey Mudd College has been sponsored by LLNL to design and build a test setup for optimizing the performance of the DTEM's electron source. Unlike a traditional TEM, the DTEM achieves much faster exposure times by using photoemission from a photocathode to produce electrons for imaging. The DTEM team's work is motivated by the need to improve the coherence and current density of the electron cloud produced by the electron gun in order to increase the image resolution and contrast achievable by DTEM. The photoemission test setup is nearly complete and the team will soon complete baseline tests of electron gun performance. The photoemission laser and high voltage power supply have been repaired; the optics path for relaying the laser to the photocathode has been finalized, assembled, and aligned; the internal setup of the vacuum chamber has been finalized and mostly implemented; and system control, synchronization, and data acquisition has been implemented in LabVIEW. Immediate future work includes determining a consistent alignment procedure to place the laser waist on the photocathode, and taking baseline performance measurements of the tantalum photocathode. Future research will examine the performance of the electron gun as a function of the photoemission laser profile, the photocathode material, and the geometry and voltages of the accelerating and focusing components in the electron gun. This report presents the team's progress and outlines the work that remains.

  1. Dynamical Diffraction Simulation of Transmission X-ray Phase Retarders

    NASA Astrophysics Data System (ADS)

    Macrander, A. T.; Lang, J. C.; Srajer, G.

    1996-03-01

    Circularly polarized photons couple with magnetic moments which makes them a useful probe of the magnetic properties of condensed matter. Circularly polarized photon beams can be created from linearly polarized undulator beams at the Advanced Photon Source using thin single-crystal transmission phase retarders. Tests of such phase retarders have been made and have been compared to dynamical diffraction calculations. (J.C. Lang and G. Srajer, Rev. Sci. Instrumen. 66,1540(1995).) In addition, a phase retarder was successfully used in a circular magnetic x-ray dichroism experiment. (J.C. Lang, G. Srajer, C. Detliefs, A.I. Goldman, H. Konig, X. Wang, B.N. Harmon, and R.W. McCallum, Phys. Rev. Lett. 74,4935(1995).) The focus of this talk is on the calculations that were made using matrix techniques. ( D.W. Berreman and A.T. Macrander, Phys. Rev. B 37,6030(1988).) Such calculations are possible because not only the amplitude but also the phase of the fields are calculated. This work supported by the U.S. Dept. of Energy, BES-Materials Sciences, under contract no. W-31-109-ENG-38.

  2. Development of a Taenia ovis transmission model and an assessment of control strategies.

    PubMed

    DeWolf, Bradley D; Poljak, Zvonimir; Peregrine, Andrew S; Jones-Bitton, Andria; Jansen, Jocelyn T; Menzies, Paula I

    2013-11-15

    The metacestode stage of the tapeworm, Taenia ovis, causes cystic lesions in the skeletal and cardiac muscle of sheep, which can result in the condemnation of the entire carcass. In recent years, Canadian farms have seen a marked increase in the number of condemnations due to T. ovis. Mathematical transmission models provide a useful tool for predicting parasite transmission and for evaluating the efficacy of potential control options. To date, no model has been developed exclusively for T. ovis. In the work described here, a compartmental, deterministic transmission model was developed to better understand the transmission dynamics of T. ovis on Canadian sheep farms. The model was intended to be practical, and represent the transmission of infection burdens in lambs that result in carcass condemnation, or transmission to canids. All transmission parameters were obtained from the literature or, when unavailable, expert opinion. The model incorporated each stage of the parasite lifecycle using the most probable transmission route on Canadian sheep farms; including definitive host (guard dogs), intermediate host (pastured lambs), and environment. Based on literature, the model performed as expected, and provided a reasonable estimate of parasite prevalence in lambs. In addition, modeling allowed the efficacy of potential control options to be evaluated and compared. Model simulations suggested that infection risk in market lambs could be eliminated through the regular treatment of guardian dogs every fifth week with an appropriate cestocide, or through eliminating carcass consumption by guardian dogs.

  3. Dynamic Epidemiological Models for Dengue Transmission: A Systematic Review of Structural Approaches

    PubMed Central

    Andraud, Mathieu; Hens, Niel; Marais, Christiaan; Beutels, Philippe

    2012-01-01

    Dengue is a vector-borne disease recognized as the major arbovirose with four immunologically distant dengue serotypes coexisting in many endemic areas. Several mathematical models have been developed to understand the transmission dynamics of dengue, including the role of cross-reactive antibodies for the four different dengue serotypes. We aimed to review deterministic models of dengue transmission, in order to summarize the evolution of insights for, and provided by, such models, and to identify important characteristics for future model development. We identified relevant publications using PubMed and ISI Web of Knowledge, focusing on mathematical deterministic models of dengue transmission. Model assumptions were systematically extracted from each reviewed model structure, and were linked with their underlying epidemiological concepts. After defining common terms in vector-borne disease modelling, we generally categorised fourty-two published models of interest into single serotype and multiserotype models. The multi-serotype models assumed either vector-host or direct host-to-host transmission (ignoring the vector component). For each approach, we discussed the underlying structural and parameter assumptions, threshold behaviour and the projected impact of interventions. In view of the expected availability of dengue vaccines, modelling approaches will increasingly focus on the effectiveness and cost-effectiveness of vaccination options. For this purpose, the level of representation of the vector and host populations seems pivotal. Since vector-host transmission models would be required for projections of combined vaccination and vector control interventions, we advocate their use as most relevant to advice health policy in the future. The limited understanding of the factors which influence dengue transmission as well as limited data availability remain important concerns when applying dengue models to real-world decision problems. PMID:23139836

  4. Dynamic data transmission technology for expendable current profiler based on low-voltage differential signaling

    NASA Astrophysics Data System (ADS)

    Li, Shuhan; Zhang, Qisheng; Zhao, Xiao; Liu, Shenghui; Yuan, Zhenzhong; Zhang, Xinyue

    2017-07-01

    A dynamic data transmission technology for expendable current profilers (XCPs) is proposed in this paper. Two parallel varnished wires are employed as the data transmission medium. By testing the transmission properties of the varnished wires, a baseband transmission system is studied and designed. Modified low-voltage differential signaling (LVDS) is adopted as the physical layer for data transmission. The data transmission protocol is modified and optimized in accordance with the RS-232 protocol, and the Manchester code is superimposed. According to the results of indoor and marine tests, the data transmission distance of the designed system, which employs a 0.1 mm diameter varnished wire, extends to 2 km with high efficiency and accuracy for data transmission, exhibiting excellent performance. Moreover, this data transmission technology could be used for other expendable marine-environment parametric measuring instruments such as an expendable bathythermograph and an expendable conductivity temperature depth profiler.

  5. Dynamic analysis of high speed gears by using loaded static transmission error

    NASA Astrophysics Data System (ADS)

    Özgüven, H. Nevzat; Houser, D. R.

    1988-08-01

    A single degree of freedom non-linear model is used for the dynamic analysis of a gear pair. Two methods are suggested and a computer program is developed for calculating the dynamic mesh and tooth forces, dynamic factors based on stresses, and dynamic transmission error from measured or calculated loaded static transmission errors. The analysis includes the effects of variable mesh stiffness and mesh damping, gear errors (pitch, profile and runout errors), profile modifications and backlash. The accuracy of the method, which includes the time variation of both mesh stiffness and damping is demonstrated with numerical examples. In the second method, which is an approximate one, the time average of the mesh stiffness is used. However, the formulation used in the approximate analysis allows for the inclusion of the excitation effect of the variable mesh stiffness. It is concluded from the comparison of the results of the two methods that the displacement excitation resulting from a variable mesh stiffness is more important than the change in system natural frequency resulting from the mesh stiffness variation. Although the theory presented is general and applicable to spur, helical and spiral bevel gears, the computer program prepared is for only spur gears.

  6. Geared rotor dynamic methodologies for advancing prognostic modeling capabilities in rotary-wing transmission systems

    NASA Astrophysics Data System (ADS)

    Stringer, David Blake

    The overarching objective in this research is the development of a robust, rotor dynamic, physics based model of a helicopter drive train as a foundation for the prognostic modeling for rotary-wing transmissions. Rotorcrafts rely on the integrity of their drive trains for their airworthiness. Drive trains rely on gear technology for their integrity and function. Gears alter the vibration characteristics of a mechanical system and significantly contribute to noise, component fatigue, and personal discomfort prevalent in rotorcraft. This research effort develops methodologies for generating a rotor dynamic model of a rotary-wing transmission based on first principles, through (i) development of a three-dimensional gear-mesh stiffness model for helical and spur gears and integration of this model in a finite element rotor dynamic model, (ii) linear and nonlinear analyses of a geared system for comparison and validation of the gear-mesh model, (iii) development of a modal synthesis technique for potentially providing model reduction and faster analysis capabilities for geared systems, and (iv) extension of the gear-mesh model to bevel and epicyclic configurations. In addition to model construction and validation, faults indigenous to geared systems are presented and discussed. Two faults are selected for analysis and seeded into the transmission model. Diagnostic vibration parameters are presented and used as damage indicators in the analysis. The fault models produce results consistent with damage experienced during experimental testing. The results of this research demonstrate the robustness of the physics-based approach in simulating multiple normal and abnormal conditions. The advantages of this physics-based approach, when combined with contemporary probabilistic and time-series techniques, provide a useful method for improving health monitoring technologies in mechanical systems.

  7. Environmental transmission of Mycobacterium ulcerans drives dynamics of Buruli ulcer in endemic regions of Cameroon

    NASA Astrophysics Data System (ADS)

    Garchitorena, Andrés; Ngonghala, Calistus N.; Texier, Gaëtan; Landier, Jordi; Eyangoh, Sara; Bonds, Matthew H.; Guégan, Jean-François; Roche, Benjamin

    2015-12-01

    Buruli Ulcer is a devastating skin disease caused by the pathogen Mycobacterium ulcerans. Emergence and distribution of Buruli ulcer cases is clearly linked to aquatic ecosystems, but the specific route of transmission of M. ulcerans to humans remains unclear. Relying on the most detailed field data in space and time on M. ulcerans and Buruli ulcer available today, we assess the relative contribution of two potential transmission routes -environmental and water bug transmission- to the dynamics of Buruli ulcer in two endemic regions of Cameroon. The temporal dynamics of Buruli ulcer incidence are explained by estimating rates of different routes of transmission in mathematical models. Independently, we also estimate statistical models of the different transmission pathways on the spatial distribution of Buruli ulcer. The results of these two independent approaches are corroborative and suggest that environmental transmission pathways explain the temporal and spatial patterns of Buruli ulcer in our endemic areas better than the water bug transmission.

  8. Variations in Modeled Dengue Transmission over Puerto Rico Using a Climate Driven Dynamic Model

    NASA Technical Reports Server (NTRS)

    Morin, Cory; Monaghan, Andrew; Crosson, William; Quattrochi, Dale; Luvall, Jeffrey

    2014-01-01

    Dengue fever is a mosquito-borne viral disease reemerging throughout much of the tropical Americas. Dengue virus transmission is explicitly influenced by climate and the environment through its primary vector, Aedes aegypti. Temperature regulates Ae. aegypti development, survival, and replication rates as well as the incubation period of the virus within the mosquito. Precipitation provides water for many of the preferred breeding habitats of the mosquito, including buckets, old tires, and other places water can collect. Because of variations in topography, ocean influences and atmospheric processes, temperature and rainfall patterns vary across Puerto Rico and so do dengue virus transmission rates. Using NASA's TRMM (Tropical Rainfall Measuring Mission) satellite for precipitation input, ground-based observations for temperature input, and laboratory confirmed dengue cases reported by the Centers for Disease Control and Prevention for parameter calibration, we modeled dengue transmission at the county level across Puerto Rico from 2010-2013 using a dynamic dengue transmission model that includes interacting vector ecology and epidemiological components. Employing a Monte Carlo approach, we performed ensembles of several thousands of model simulations for each county in order to resolve the model uncertainty arising from using different combinations of parameter values that are not well known. The top 1% of model simulations that best reproduced the reported dengue case data were then analyzed to determine the most important parameters for dengue virus transmission in each county, as well as the relative influence of climate variability on transmission. These results can be used by public health workers to implement dengue control methods that are targeted for specific locations and climate conditions.

  9. Conceptual Framework and Research Methods for Migration and HIV Transmission Dynamics

    PubMed Central

    Cassels, Susan; Jenness, Samuel M.; Khanna, Aditya

    2014-01-01

    Migration and mobility have had a profound influence on the global HIV epidemic. We propose a network-dyadic conceptual model to interpret previous literature and inform the development of future research with respect to study design, measurement methods, and analytic approach. In this model, HIV transmission is driven by risk behaviors of migrants that emerges and is enabled by mobility, the bridging of sub-epidemics across space and time, and the displacement effects on the primary residential sending community for migrants. To investigate these causal pathways, empirical study designs must measure the relative timing of migratory events, sexual risk behaviors, and incident HIV infections. Network-based mathematical models using empirical data on partnerships help gain insight into the dynamic disease transmission systems. Although the network-dyadic conceptual model and related network methods may not address all questions related to migration and HIV, they provide a unified approach for future research on this important topic. PMID:24257897

  10. Co-infections and transmission dynamics in a tick-borne bacterium community exposed to songbirds.

    PubMed

    Heylen, Dieter; Fonville, Manoj; van Leeuwen, Arieke Docters; Sprong, Hein

    2016-03-01

    We investigated the transmission dynamics of a community of tick-borne pathogenic bacteria in a common European songbird (Parus major). Tick-naïve birds were infested with three successive batches (spaced 5 days apart) of field-collected Ixodes ricinus nymphs, carrying the following tick-borne bacteria: Rickettsia helvetica (16.9%), Borrelia garinii (1.9%), Borrelia miyamotoi (1.6%), Anaplasma phagocytophilum (1.2%) and Candidatus Neoehrlichia mikurensis (0.4%). Fed ticks were screened for the pathogens after moulting to the next developmental phase. We found evidence for early transmission (within 2.75 days after exposure) of R. helvetica and B. garinii, and to a lesser extent of A. phagocytophilum based on the increased infection rates of ticks during the first infestation. The proportion of ticks infected with R. helvetica remained constant over the three infestations. In contrast, the infection rate of B. garinii in the ticks increased over the three infestations, indicating a more gradual development of host tissue infection. No interactions were found among the different bacterium species during transmission. Birds did not transmit or amplify the other bacterial species. We show that individual birds can transmit several pathogenic bacterium species at the same time using different mechanisms, and that the transmission facilitation by birds increases the frequency of co-infections in ticks.

  11. Numerical modeling of the transmission dynamics of drug-sensitive and drug-resistant HSV-2

    NASA Astrophysics Data System (ADS)

    Gumel, A. B.

    2001-03-01

    A competitive finite-difference method will be constructed and used to solve a modified deterministic model for the spread of herpes simplex virus type-2 (HSV-2) within a given population. The model monitors the transmission dynamics and control of drug-sensitive and drug-resistant HSV-2. Unlike the fourth-order Runge-Kutta method (RK4), which fails when the discretization parameters exceed certain values, the novel numerical method to be developed in this paper gives convergent results for all parameter values.

  12. Calculation method of reliability on combine harvester transmission belt by considering dynamic stress

    NASA Astrophysics Data System (ADS)

    Guan, Zhuohuai; Li, Liang; Wu, Chongyou

    2017-06-01

    Transmission belt is one of the most likely to fail parts of combine harvester, which affecting the machine reliability seriously. Dynamic strength occurs along with vibration during the operation and must be taken into account when calculating reliability, especially in harsh working environment like harvesting. However, the existing calculation method of reliability on combine harvester transmission belt didn’t take the dynamic strength into account. In this research, a reliability calculation method was proposed based on the dynamic analysis of transmission belt. The nonlinear dynamic equation was built using string and beam model. Through the equation, relationship between belt speed and dynamic stress was deduced. Considering dynamic stress and regarding uncertain parameters as random uncertain parameters, reliability calculation model was built. Finally, an example was presented and the above mentioned dynamic reliability calculation method was simulated to verify the theoretical analysis in this paper and tested by the Monte-Carlo method.

  13. Development of superconducting transmission cable. CRADA final report

    SciTech Connect

    Hawsey, R.; Stovall, J.P.; Hughey, R.L.; Sinha, U.K.

    1997-10-01

    The purpose of this Cooperative Research and Development Agreement (CRADA) between Oak Ridge National Laboratory (ORNL) and Southwire Company is to develop the technology necessary to proceed to commercialization of high-temperature superconducting (HTS) transmission cables. Power transmission cables are a promising near-term electric utility application for high-temperature superconductivity. Present HTS wires match the needs for a three-phase transmission cable: (1) the wires must conduct high currents in self-field, (2) there are no high forces developed, and (3) the cables may operate at relatively low current density. The commercially-available HTS wires, in 100-m lengths, make construction of a full three-phase, alternating current (ac) transmission cable possible. If completed through the pre-commercialization phase, this project will result in a new capability for electric power companies. The superconducting cable will enable delivery with greater efficiency, higher power density, and lower costs than many alternatives now on the market. Job creation in the US is expected as US manufacturers supply transmission cables to the expanding markets in Asia and to the densely populated European cities where pipe-type cable is prevalent. Finally, superconducting cables may enable delivery of the new, diverse and distributed sources of electricity that will constitute the majority of new installed electrical generation in the world during the coming decades.

  14. Mathematical Model of Three Age-Structured Transmission Dynamics of Chikungunya Virus

    PubMed Central

    Agusto, Folashade B.; Easley, Shamise; Freeman, Kenneth; Thomas, Madison

    2016-01-01

    We developed a new age-structured deterministic model for the transmission dynamics of chikungunya virus. The model is analyzed to gain insights into the qualitative features of its associated equilibria. Some of the theoretical and epidemiological findings indicate that the stable disease-free equilibrium is globally asymptotically stable when the associated reproduction number is less than unity. Furthermore, the model undergoes, in the presence of disease induced mortality, the phenomenon of backward bifurcation, where the stable disease-free equilibrium of the model coexists with a stable endemic equilibrium when the associated reproduction number is less than unity. Further analysis of the model indicates that the qualitative dynamics of the model are not altered by the inclusion of age structure. This is further emphasized by the sensitivity analysis results, which shows that the dominant parameters of the model are not altered by the inclusion of age structure. However, the numerical simulations show the flaw of the exclusion of age in the transmission dynamics of chikungunya with regard to control implementations. The exclusion of age structure fails to show the age distribution needed for an effective age based control strategy, leading to a one size fits all blanket control for the entire population. PMID:27190548

  15. Environmental transmission of Mycobacterium ulcerans drives dynamics of Buruli ulcer in endemic regions of Cameroon

    PubMed Central

    Garchitorena, Andrés; Ngonghala, Calistus N.; Texier, Gaëtan; Landier, Jordi; Eyangoh, Sara; Bonds, Matthew H.; Guégan, Jean-François; Roche, Benjamin

    2015-01-01

    Buruli Ulcer is a devastating skin disease caused by the pathogen Mycobacterium ulcerans. Emergence and distribution of Buruli ulcer cases is clearly linked to aquatic ecosystems, but the specific route of transmission of M. ulcerans to humans remains unclear. Relying on the most detailed field data in space and time on M. ulcerans and Buruli ulcer available today, we assess the relative contribution of two potential transmission routes –environmental and water bug transmission– to the dynamics of Buruli ulcer in two endemic regions of Cameroon. The temporal dynamics of Buruli ulcer incidence are explained by estimating rates of different routes of transmission in mathematical models. Independently, we also estimate statistical models of the different transmission pathways on the spatial distribution of Buruli ulcer. The results of these two independent approaches are corroborative and suggest that environmental transmission pathways explain the temporal and spatial patterns of Buruli ulcer in our endemic areas better than the water bug transmission. PMID:26658922

  16. Transmission dynamics of a zoonotic pathogen within and between wildlife host species.

    PubMed Central

    Begon, M; Hazel, S M; Baxby, D; Bown, K; Cavanagh, R; Chantrey, J; Jones, T; Bennett, M

    1999-01-01

    The transmission dynamics of the cowpox virus infection have been quantified in two mixed populations of bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus), through analyses of detailed time-series of the numbers of susceptible, infectious and newly infected individuals. The cowpox virus is a zoonosis which circulates in these rodent hosts and has been shown to have an adverse effect on reproductive output. The transmission dynamics within species is best described as frequency dependent rather than density dependent, contrary to the 'mass action' assumption of most previous studies, both theoretical and empirical. Estimation of a transmission coefficient for each species in each population also allows annual and seasonal variations in transmission dynamics to be investigated through an analysis of regression residuals. Transmission between host species is found to be negligible despite their close cohabitation. The consequences of this for the combining ability of hosts as zoonotic reservoirs, and for apparent competition between hosts, are discussed. PMID:10584336

  17. Fluid dynamics of heart development.

    PubMed

    Santhanakrishnan, Arvind; Miller, Laura A

    2011-09-01

    The morphology, muscle mechanics, fluid dynamics, conduction properties, and molecular biology of the developing embryonic heart have received much attention in recent years due to the importance of both fluid and elastic forces in shaping the heart as well as the striking relationship between the heart's evolution and development. Although few studies have directly addressed the connection between fluid dynamics and heart development, a number of studies suggest that fluids may play a key role in morphogenic signaling. For example, fluid shear stress may trigger biochemical cascades within the endothelial cells of the developing heart that regulate chamber and valve morphogenesis. Myocardial activity generates forces on the intracardiac blood, creating pressure gradients across the cardiac wall. These pressures may also serve as epigenetic signals. In this article, the fluid dynamics of the early stages of heart development is reviewed. The relevant work in cardiac morphology, muscle mechanics, regulatory networks, and electrophysiology is also reviewed in the context of intracardial fluid dynamics.

  18. Early animal farming and zoonotic disease dynamics: modelling brucellosis transmission in Neolithic goat populations.

    PubMed

    Fournié, Guillaume; Pfeiffer, Dirk U; Bendrey, Robin

    2017-02-01

    Zoonotic pathogens are frequently hypothesized as emerging with the origins of farming, but evidence of this is elusive in the archaeological records. To explore the potential impact of animal domestication on zoonotic disease dynamics and human infection risk, we developed a model simulating the transmission of Brucella melitensis within early domestic goat populations. The model was informed by archaeological data describing goat populations in Neolithic settlements in the Fertile Crescent, and used to assess the potential of these populations to sustain the circulation of Brucella. Results show that the pathogen could have been sustained even at low levels of transmission within these domestic goat populations. This resulted from the creation of dense populations and major changes in demographic characteristics. The selective harvesting of young male goats, likely aimed at improving the efficiency of food production, modified the age and sex structure of these populations, increasing the transmission potential of the pathogen within these populations. Probable interactions between Neolithic settlements would have further promoted pathogen maintenance. By fostering conditions suitable for allowing domestic goats to become reservoirs of Brucella melitensis, the early stages of agricultural development were likely to promote the exposure of humans to this pathogen.

  19. Early animal farming and zoonotic disease dynamics: modelling brucellosis transmission in Neolithic goat populations

    PubMed Central

    Pfeiffer, Dirk U.; Bendrey, Robin

    2017-01-01

    Zoonotic pathogens are frequently hypothesized as emerging with the origins of farming, but evidence of this is elusive in the archaeological records. To explore the potential impact of animal domestication on zoonotic disease dynamics and human infection risk, we developed a model simulating the transmission of Brucella melitensis within early domestic goat populations. The model was informed by archaeological data describing goat populations in Neolithic settlements in the Fertile Crescent, and used to assess the potential of these populations to sustain the circulation of Brucella. Results show that the pathogen could have been sustained even at low levels of transmission within these domestic goat populations. This resulted from the creation of dense populations and major changes in demographic characteristics. The selective harvesting of young male goats, likely aimed at improving the efficiency of food production, modified the age and sex structure of these populations, increasing the transmission potential of the pathogen within these populations. Probable interactions between Neolithic settlements would have further promoted pathogen maintenance. By fostering conditions suitable for allowing domestic goats to become reservoirs of Brucella melitensis, the early stages of agricultural development were likely to promote the exposure of humans to this pathogen. PMID:28386446

  20. Transmission Dynamics of Methicillin-Resistant Staphylococcus aureus in a Medical Intensive Care Unit in India

    PubMed Central

    Christopher, Solomon; Verghis, Rejina Mariam; Antonisamy, Belavendra; Sowmyanarayanan, Thuppal Varadachari; Brahmadathan, Kootallur Narayanan; Kang, Gagandeep; Cooper, Ben Symons

    2011-01-01

    Background Methicillin-resistant Staphylococcus aureus (MRSA) is a global pathogen and an important but seldom investigated cause of morbidity and mortality in lower and middle-income countries where it can place a major burden on limited resources. Quantifying nosocomial transmission in resource-poor settings is difficult because molecular typing methods are prohibitively expensive. Mechanistic statistical models can overcome this problem with minimal cost. We analyse the transmission dynamics of MRSA in a hospital in south India using one such approach and provide conservative estimates of the organism's economic burden. Methods and Findings Fifty months of MRSA infection data were collected retrospectively from a Medical Intensive Care Unit (MICU) in a tertiary hospital in Vellore, south India. Data were analysed using a previously described structured hidden Markov model. Seventy-two patients developed MRSA infections and, of these, 49 (68%) died in the MICU. We estimated that 4.2% (95%CI 1.0, 19.0) of patients were MRSA-positive when admitted, that there were 0.39 MRSA infections per colonized patient month (0.06, 0.73), and that the ward-level reproduction number for MRSA was 0.42 (0.08, 2.04). Anti-MRSA antibiotic treatment costs alone averaged $124/patient, over three times the monthly income of more than 40% of the Indian population. Conclusions Our analysis of routine data provides the first estimate of the nosocomial transmission potential of MRSA in India. The high levels of transmission estimated underline the need for cost-effective interventions to reduce MRSA transmission in hospital settings in low and middle income countries. PMID:21750700

  1. Using optogenetics to interrogate the dynamic control of signal transmission by the Ras/Erk module.

    PubMed

    Toettcher, Jared E; Weiner, Orion D; Lim, Wendell A

    2013-12-05

    The complex, interconnected architecture of cell-signaling networks makes it challenging to disentangle how cells process extracellular information to make decisions. We have developed an optogenetic approach to selectively activate isolated intracellular signaling nodes with light and use this method to follow the flow of information from the signaling protein Ras. By measuring dose and frequency responses in single cells, we characterize the precision, timing, and efficiency with which signals are transmitted from Ras to Erk. Moreover, we elucidate how a single pathway can specify distinct physiological outcomes: by combining distinct temporal patterns of stimulation with proteomic profiling, we identify signaling programs that differentially respond to Ras dynamics, including a paracrine circuit that activates STAT3 only after persistent (>1 hr) Ras activation. Optogenetic stimulation provides a powerful tool for analyzing the intrinsic transmission properties of pathway modules and identifying how they dynamically encode distinct outcomes.

  2. Xenon Implantation in Nanodiamonds: In Situ Transmission Electron Microscopy Study and Molecular Dynamics Simulations

    NASA Astrophysics Data System (ADS)

    Shiryaev, A. A.; Hinks, J.; Marks, N.; Greaves, G.; Donnelly, S.; Fisenko, A. V.; Kiwi, M.

    2016-08-01

    We present results of the first investigation of the Xe implantation process into nanodiamonds of various sizes studied in situ in transmission electron microscope (TEM), complemented by advanced molecular dynamics simulations.

  3. HIV Infection: Transmission, Effects on Early Development, and Interventions.

    ERIC Educational Resources Information Center

    Lowenthal, Barbara

    1997-01-01

    Describes the modes of transmission of HIV and the course of the disease in infants and toddlers. Information is provided on its effects on early development, medical screening and treatments, therapies, psychosocial assistance, and interventions, including nutritional therapy, occupational and physical therapies, and speech and language therapy.…

  4. HIV Infection: Transmission, Effects on Early Development, and Interventions.

    ERIC Educational Resources Information Center

    Lowenthal, Barbara

    1997-01-01

    Describes the modes of transmission of HIV and the course of the disease in infants and toddlers. Information is provided on its effects on early development, medical screening and treatments, therapies, psychosocial assistance, and interventions, including nutritional therapy, occupational and physical therapies, and speech and language therapy.…

  5. Developing cryotherapy to eliminate graft-transmissible pathogens in citrus

    USDA-ARS?s Scientific Manuscript database

    This article summarizes research being conducted as part of a project funded by the California Citrus Research Board to develop cryotherapy (freezing buds in liquid nitrogen, and then recovering them) as a viable method for elimination of graft transmissible pathogens from Citrus. There are current...

  6. Nonlinear dynamics of a friction-limited drive: Application to a chain continuously variable transmission (CVT) system

    NASA Astrophysics Data System (ADS)

    Srivastava, Nilabh; Haque, Imtiaz

    2009-03-01

    Over the past two decades, extensive research has been conducted on developing vehicle transmissions that meet the goals of reduced exhaust emissions and increased vehicle efficiency. A continuously variable transmission is an emerging automotive transmission technology that offers a continuum of gear ratios between desired limits. A chain CVT is a friction-limited drive whose dynamic performance and torque capacity rely significantly on the friction characteristic of the contact patch between the chain and the pulley. Although a CVT helps to maximize the vehicle fuel economy, its complete potential has not been accomplished in a mass-production vehicle. The present research focuses on developing models to analyze friction-induced nonlinear dynamics of a chain CVT drive and identify possible mechanisms that cause degradation of the overall dynamic performance by inducing chaos and self-sustained vibrations in the system. Two different mathematical models of friction, which characterize different operating or loading conditions, are embedded into a detailed planar multibody model of chain CVT in order to capture the various friction-induced effects in the system. Tools such as stick-slip oscillator dynamics, Lyapunov exponents, phase-space reconstruction, and recurrence plotting are incorporated to characterize the nonlinear dynamics of such a friction-limited system. The mathematical models, the computational scheme, and the results corresponding to different loading scenarios are discussed. The results discuss the influence of friction characteristics on the nonlinear dynamics and torque transmitting capacity of a chain CVT drive.

  7. Dynamics of cryocooler development

    SciTech Connect

    Timmerhaus, K.D.

    1995-12-01

    A few of the recent developments and future directions of cryocoolers are summarized. Those that will be covered include Joule-Thomson (J-T) microminiature cryocoolers, modified Stirling refrigerators designated as orifice pulse tube refrigerators (OPTR), and thermal acoustic driver orifice pulse tube refrigerators (TADOPTR) as well as the sorption refrigerators.

  8. Transmission of Hepatitis E Virus in Developing Countries

    PubMed Central

    Khuroo, Mohammad S.; Khuroo, Mehnaaz S.; Khuroo, Naira S.

    2016-01-01

    Hepatitis E virus (HEV), an RNA virus of the Hepeviridae family, has marked heterogeneity. While all five HEV genotypes can cause human infections, genotypes HEV-1 and -2 infect humans alone, genotypes HEV-3 and -4 primarily infect pigs, boars and deer, and genotype HEV-7 primarily infects dromedaries. The global distribution of HEV has distinct epidemiological patterns based on ecology and socioeconomic factors. In resource-poor countries, disease presents as large-scale waterborne epidemics, and few epidemics have spread through person-to-person contact; however, endemic diseases within these countries can potentially spread through person-to-person contact or fecally contaminated water and foods. Vertical transmission of HEV from infected mother to fetus causes high fetal and perinatal mortality. Other means of transmission, such as zoonotic transmission, can fluctuate depending upon the region and strain of the virus. For instance, zoonotic transmission can sometimes play an insignificant role in human infections, such as in India, where human and pig HEV infections are unrelated. However, recently China and Southeast Asia have experienced a zoonotic spread of HEV-4 from pigs to humans and this has become the dominant mode of transmission of hepatitis E in eastern China. Zoonotic HEV infections in humans occur by eating undercooked pig flesh, raw liver, and sausages; through vocational contact; or via pig slurry, which leads to environmental contamination of agricultural products and seafood. Lastly, blood transfusion-associated HEV infections occur in many countries and screening of donors for HEV RNA is currently under serious consideration. To summarize, HEV genotypes 1 and 2 cause epidemic and endemic diseases in resource poor countries, primarily spreading through contaminated drinking water. HEV genotypes 3 and 4 on the other hand, cause autochthonous infections in developed, and many developing countries, by means of a unique zoonotic food

  9. Transmission of Hepatitis E Virus in Developing Countries.

    PubMed

    Khuroo, Mohammad S; Khuroo, Mehnaaz S; Khuroo, Naira S

    2016-09-20

    Hepatitis E virus (HEV), an RNA virus of the Hepeviridae family, has marked heterogeneity. While all five HEV genotypes can cause human infections, genotypes HEV-1 and -2 infect humans alone, genotypes HEV-3 and -4 primarily infect pigs, boars and deer, and genotype HEV-7 primarily infects dromedaries. The global distribution of HEV has distinct epidemiological patterns based on ecology and socioeconomic factors. In resource-poor countries, disease presents as large-scale waterborne epidemics, and few epidemics have spread through person-to-person contact; however, endemic diseases within these countries can potentially spread through person-to-person contact or fecally contaminated water and foods. Vertical transmission of HEV from infected mother to fetus causes high fetal and perinatal mortality. Other means of transmission, such as zoonotic transmission, can fluctuate depending upon the region and strain of the virus. For instance, zoonotic transmission can sometimes play an insignificant role in human infections, such as in India, where human and pig HEV infections are unrelated. However, recently China and Southeast Asia have experienced a zoonotic spread of HEV-4 from pigs to humans and this has become the dominant mode of transmission of hepatitis E in eastern China. Zoonotic HEV infections in humans occur by eating undercooked pig flesh, raw liver, and sausages; through vocational contact; or via pig slurry, which leads to environmental contamination of agricultural products and seafood. Lastly, blood transfusion-associated HEV infections occur in many countries and screening of donors for HEV RNA is currently under serious consideration. To summarize, HEV genotypes 1 and 2 cause epidemic and endemic diseases in resource poor countries, primarily spreading through contaminated drinking water. HEV genotypes 3 and 4 on the other hand, cause autochthonous infections in developed, and many developing countries, by means of a unique zoonotic food

  10. Modelling transmission dynamics of paratuberculosis of red deer under pastoral farming conditions.

    PubMed

    Heuer, C; Mitchell, R M; Schukken, Y H; Lu, Z; Verdugo, C; Wilson, P R

    2012-09-01

    This study aimed to develop a mathematical model describing the dynamics of paratuberculosis (PTB) in red deer (Cervus elaphus) under pastoral farming conditions in New Zealand. The model examined infectivity differences between ovine and bovine strains of Mycobacterium avium subspecies paratuberculosis (MAP) and seasonality of MAP survival. We also evaluate variable use of pasture and the effect of management interventions on the infection prevalence and annual clinical incidence of PTB. A state-transition model was developed and calibrated to observed data on both prevalence of infection and incidence of clinical PTB. To accommodate specific PTB features for deer, the model included a fast and a slow track for progression of infection to disease. MAP on pasture was the source for horizontal transmission and infected dams for vertical transmission. In the presence of a single strain, an infectivity reduction of up to 80% allowed MAP to persist in the herd (R(0)>1). For mixed infection by two strains however, a 30% reduction in infectivity of one strain was sufficient to outcompete a strain with lower infectivity, suggesting that mixed infection of MAP strains with different infectivity may not be common in deer. The model showed that seasonal variation of MAP survival on pasture had little impact on transmission dynamics, and that rotational grazing with pasture spelling vs. permanent grazing of the same paddock reduced both infection prevalence and clinical PTB by about 50%. Based on model outputs, early detection of young deer in a high-shedding state was the most effective means of controlling PTB among the tested scenarios.

  11. Transmission dynamics of the recently-identified BYD virus causing duck egg-drop syndrome.

    PubMed

    Vaidya, Naveen K; Wang, Feng-bin; Zou, Xingfu; Wahl, Lindi M

    2012-01-01

    Baiyangdian (BYD) virus is a recently-identified mosquito-borne flavivirus that causes severe disease in ducks, with extremely rapid transmission, up to 15% mortality within 10 days and 90% reduction in egg production on duck farms within 5 days of infection. Because of the zoonotic nature of flaviviruses, the characterization of BYD virus and its epidemiology are important public health concerns. Here, we develop a mathematical model for the transmission dynamics of this novel virus. We validate the model against BYD outbreak data collected from duck farms in Southeast China, as well as experimental data obtained from an animal facility. Based on our model, the basic reproductive number of BYD virus is high (R(0) = 21) indicating that this virus is highly transmissible, consistent with the dramatic epidemiology observed in BYDV-affected duck farms. Our results indicate that younger ducks are more vulnerable to BYD disease and that ducks infected with BYD virus reduce egg production (to about 33% on average) for about 3 days post-infection; after 3 days infected ducks are no longer able to produce eggs. Using our model, we predict that control measures which reduce contact between mosquitoes and ducks such as mosquito nets are more effective than insecticides.

  12. Transmission Dynamics of the Recently-Identified BYD Virus Causing Duck Egg-Drop Syndrome

    PubMed Central

    Vaidya, Naveen K.; Wang, Feng-bin; Zou, Xingfu; Wahl, Lindi M.

    2012-01-01

    Baiyangdian (BYD) virus is a recently-identified mosquito-borne flavivirus that causes severe disease in ducks, with extremely rapid transmission, up to 15% mortality within 10 days and 90% reduction in egg production on duck farms within 5 days of infection. Because of the zoonotic nature of flaviviruses, the characterization of BYD virus and its epidemiology are important public health concerns. Here, we develop a mathematical model for the transmission dynamics of this novel virus. We validate the model against BYD outbreak data collected from duck farms in Southeast China, as well as experimental data obtained from an animal facility. Based on our model, the basic reproductive number of BYD virus is high (R0 = 21) indicating that this virus is highly transmissible, consistent with the dramatic epidemiology observed in BYDV-affected duck farms. Our results indicate that younger ducks are more vulnerable to BYD disease and that ducks infected with BYD virus reduce egg production (to about 33% on average) for about 3 days post-infection; after 3 days infected ducks are no longer able to produce eggs. Using our model, we predict that control measures which reduce contact between mosquitoes and ducks such as mosquito nets are more effective than insecticides. PMID:22529985

  13. Neodymium neutron transmission and capture measurements and development of a new transmission detector

    NASA Astrophysics Data System (ADS)

    Barry, Devin P.

    to finding improved resolution function parameters, a method was developed to find the 'estimated uncertainty' on these parameters. The 'estimated uncertainty' values for the resolution function parameters were chosen to represent a + or -10% change in the reduced chi-squared value in fits to uranium. This thesis also presents the design, construction, and implementation of a new out-of-beam detector (OBD) system for use in transmission experiments. MCNP modeling was used to validate that the OBD system has less neutron backscatter when compared with the previously used in-beam detector (IBD). This decrease in neutron backscatter offers an overall improvement in resolution function. Experiments were performed with the OBD system using uranium samples and resulting data was used to show this improvement in the resolution function.

  14. Toward dynamic model-based prognostics for transmission gears

    NASA Astrophysics Data System (ADS)

    Wang, Wenyi

    2002-07-01

    This paper presents a novel methodology for the diagnosis and prognosis of crucial gear faults, such as gear tooth fatigue cracking. Currently, an effective detection of tooth cracking can be achieved by using the autoregressive (AR) modeling approach, where the gear vibration signal is modeled by an AR model and gear tooth cracking is detected by identifying the sudden changes in the model's error signal. The model parameters can be estimated under the criteria of minimum power or maximum kurtosis of model errors. However, these model parameters possess no physical meaning about the monitored gear system. It is proposed that the AR model be replaced by a gear dynamics model (GDM) that contains physically meaningful parameters, such as mass, damping and stiffness. By identifying and tracking the changes in the parameters, it is possible to make diagnosis and prognosis of gear faults. For example, a reduction in mesh stiffness may indicate cracking of a gear tooth. Towards physical model-based prognosis, an adaptive (or optimization) strategy has been developed for approximating a gear signal using a simplified gear signal model. Preliminary results show that this strategy provides a feasible adaptive process for updating model parameters based on measured gear signal.

  15. Predicting lymphatic filariasis transmission and elimination dynamics using a multi-model ensemble framework.

    PubMed

    Smith, Morgan E; Singh, Brajendra K; Irvine, Michael A; Stolk, Wilma A; Subramanian, Swaminathan; Hollingsworth, T Déirdre; Michael, Edwin

    2017-03-01

    Mathematical models of parasite transmission provide powerful tools for assessing the impacts of interventions. Owing to complexity and uncertainty, no single model may capture all features of transmission and elimination dynamics. Multi-model ensemble modelling offers a framework to help overcome biases of single models. We report on the development of a first multi-model ensemble of three lymphatic filariasis (LF) models (EPIFIL, LYMFASIM, and TRANSFIL), and evaluate its predictive performance in comparison with that of the constituents using calibration and validation data from three case study sites, one each from the three major LF endemic regions: Africa, Southeast Asia and Papua New Guinea (PNG). We assessed the performance of the respective models for predicting the outcomes of annual MDA strategies for various baseline scenarios thought to exemplify the current endemic conditions in the three regions. The results show that the constructed multi-model ensemble outperformed the single models when evaluated across all sites. Single models that best fitted calibration data tended to do less well in simulating the out-of-sample, or validation, intervention data. Scenario modelling results demonstrate that the multi-model ensemble is able to compensate for variance between single models in order to produce more plausible predictions of intervention impacts. Our results highlight the value of an ensemble approach to modelling parasite control dynamics. However, its optimal use will require further methodological improvements as well as consideration of the organizational mechanisms required to ensure that modelling results and data are shared effectively between all stakeholders.

  16. Typhoid transmission: a historical perspective on mathematical model development.

    PubMed

    Bakach, Iurii; Just, Matthew R; Gambhir, Manoj; Fung, Isaac Chun-Hai

    2015-11-01

    Mathematical models of typhoid transmission were first developed nearly half a century ago. To facilitate a better understanding of the historical development of this field, we reviewed mathematical models of typhoid and summarized their structures and limitations. Eleven models, published in 1971 to 2014, were reviewed. While models of typhoid vaccination are well developed, we highlight the need to better incorporate water, sanitation and hygiene interventions into models of typhoid and other foodborne and waterborne diseases. Mathematical modeling is a powerful tool to test and compare different intervention strategies which is important in the world of limited resources. By working collaboratively, epidemiologists and mathematicians should build better mathematical models of typhoid transmission, including pharmaceutical and non-pharmaceutical interventions, which will be useful in epidemiological and public health practice.

  17. Heterosexual HIV transmission dynamics: implications for prevention and control.

    PubMed

    Chin, James; Bennett, Anthony

    2007-08-01

    Understanding the epidemiologic definition of epidemic versus non-epidemic spread of an infectious disease agent and the different patterns of heterosexual HIV transmission are needed to fully understand the low potential for heterosexual HIV epidemics in most heterosexual populations. Epidemic sexual HIV transmission can occur only in populations where there are large numbers of persons who have unprotected sex with multiple and concurrent sex partners. How high HIV prevalence may reach in these populations depends on the size and overlap of sex networks, and the prevalence of facilitating and protective factors that can greatly increase or limit the amount of infected blood and sexual fluids exchanged during intercourse. The wide difference in potentials for heterosexual HIV epidemics that exists within and between countries must be recognized, accepted and monitored in order to design and focus prevention strategies where they are most needed and most effective.

  18. SSME structural dynamic model development

    NASA Technical Reports Server (NTRS)

    Foley, M. J.; Tilley, D. M.; Welch, C. T.

    1983-01-01

    A mathematical model of the Space Shuttle Main Engine (SSME) as a complete assembly, with detailed emphasis on LOX and High Fuel Turbopumps is developed. The advantages of both complete engine dynamics, and high fidelity modeling are incorporated. Development of this model, some results, and projected applications are discussed.

  19. Developing Dynamic Units for EFL

    ERIC Educational Resources Information Center

    Shin, Joan Kang

    2007-01-01

    "Developing Dynamic Units for EFL" describes how to develop a thematic unit that integrates skills in context, provides opportunities for learner autonomy, and is project-based and experiential. Planning includes identifying curriculum standards, thinking of a meaningful topic, brainstorming tasks, organizing the activities, and making…

  20. Leptin potentiates GABAergic synaptic transmission in the developing rodent hippocampus

    PubMed Central

    Guimond, Damien; Diabira, Diabe; Porcher, Christophe; Bader, Francesca; Ferrand, Nadine; Zhu, Mingyan; Appleyard, Suzanne M.; Wayman, Gary A.; Gaiarsa, Jean-Luc

    2014-01-01

    It is becoming increasingly clear that leptin is not only a hormone regulating energy homeostasis but also a neurotrophic factor impacting a number of brain regions, including the hippocampus. Although leptin promotes the development of GABAergic transmission in the hypothalamus, little is known about its action on the GABAergic system in the hippocampus. Here we show that leptin modulates GABAergic transmission onto developing CA3 pyramidal cells of newborn rats. Specifically, leptin induces a long-lasting potentiation (LLP-GABAA) of miniature GABAA receptor-mediated postsynaptic current (GABAA-PSC) frequency. Leptin also increases the amplitude of evoked GABAA-PSCs in a subset of neurons along with a decrease in the coefficient of variation and no change in the paired-pulse ratio, pointing to an increased recruitment of functional synapses. Adding pharmacological blockers to the recording pipette showed that the leptin-induced LLP-GABAA requires postsynaptic calcium released from internal stores, as well as postsynaptic MAPK/ERK kinases 1 and/or 2 (MEK1/2), phosphoinositide 3 kinase (PI3K) and calcium-calmodulin kinase kinase (CaMKK). Finally, study of CA3 pyramidal cells in leptin-deficient ob/ob mice revealed a reduction in the basal frequency of miniature GABAA-PSCs compared to wild type littermates. In addition, presynaptic GAD65 immunostaining was reduced in the CA3 stratum pyramidale of mutant animals, both results converging to suggest a decreased number of functional GABAergic synapses in ob/ob mice. Overall, these results show that leptin potentiates and promotes the development of GABAergic synaptic transmission in the developing hippocampus likely via an increase in the number of functional synapses, and provide insights into the intracellular pathways mediating this effect. This study further extends the scope of leptin's neurotrophic action to a key regulator of hippocampal development and function, namely GABAergic transmission. PMID:25177272

  1. Measurement and analysis of structural dynamics properties of robotic joint transmission system

    NASA Astrophysics Data System (ADS)

    Huang, Shiuh-Jer; Chen, Chin-Yih

    1993-02-01

    This study utilizes two techniques to identify the structural dynamic characteristics of each joint transmission system of an ITRI-U type robot. The driving system of each joint is modeled as a mass-spring-damper mechanism that has a second-order dynamic mathematical equation.

  2. Wet cells and dry cells: In situ transmission electron microscopy of electrically-driven, dynamical processes

    NASA Astrophysics Data System (ADS)

    White, Edward Robert, IV

    Recent developments in nanofabrication techniques allow thin, wet systems to be imaged with high spatial and temporal resolution in the electron microscope. Coupling this ability with simultaneous, measured, electrical control, we cycle processes in liquid systems representing different electrochemical battery components. Dynamic processes imaged with these techniques, which represent a new state-of-the-art, include nanobubble collapse, dendrite growth, ion diffusion, and graphite intercalation. We also develop a sensitive system for measuring electron beam induced currents (EBIC) in the transmission electron microscope and apply it to graphene-MoS2 heterostructures. This new hybrid material has strong light-matter interactions, and the EBIC measurements map the minority carrier diffusion length, which we observe to decrease with increasing radiation damage. These results have direct implications for the function and service lifetime of solar cells based on molybdenum disulfide.

  3. Practical aspects of monochromators developed for transmission electron microscopy

    PubMed Central

    Kimoto, Koji

    2014-01-01

    A few practical aspects of monochromators recently developed for transmission electron microscopy are briefly reviewed. The basic structures and properties of four monochromators, a single Wien filter monochromator, a double Wien filter monochromator, an omega-shaped electrostatic monochromator and an alpha-shaped magnetic monochromator, are outlined. The advantages and side effects of these monochromators in spectroscopy and imaging are pointed out. A few properties of the monochromators in imaging, such as spatial or angular chromaticity, are also discussed. PMID:25125333

  4. Dynamic control of asymmetric electromagnetic wave transmission by active chiral metamaterial.

    PubMed

    Chen, Ke; Feng, Yijun; Cui, Li; Zhao, Junming; Jiang, Tian; Zhu, Bo

    2017-02-16

    The asymmetric transmission of electromagnetic (EM) wave can be fully manipulated by chiral metamaterials, but little can achieve real-time and high efficient tunability due to challenges in practically deployable solutions. Here, we proposed a new scheme for flexibly and dynamically controlling the asymmetric EM wave transmission at microwave frequencies using planar metamaterial of deep subwavelength thickness incorporated with active components of PIN diodes. The asymmetric transmission of linearly polarized EM wave exhibits a high efficiency and a pronounced real-time continuous tunability controlled by the external stimulation of voltage biasing. In addition, the asymmetric transmission effect can be well preserved at large oblique incident angle up to ±70°. The design principle and EM performance are validated by both full wave simulations and experimental measurements. Such dynamically controllable chiral metamaterial may provide robust and flexible approach to manipulate EM wave propagation, as well as to facilitate EM device integration to create diverse functionalities.

  5. Dynamic control of asymmetric electromagnetic wave transmission by active chiral metamaterial

    NASA Astrophysics Data System (ADS)

    Chen, Ke; Feng, Yijun; Cui, Li; Zhao, Junming; Jiang, Tian; Zhu, Bo

    2017-02-01

    The asymmetric transmission of electromagnetic (EM) wave can be fully manipulated by chiral metamaterials, but little can achieve real-time and high efficient tunability due to challenges in practically deployable solutions. Here, we proposed a new scheme for flexibly and dynamically controlling the asymmetric EM wave transmission at microwave frequencies using planar metamaterial of deep subwavelength thickness incorporated with active components of PIN diodes. The asymmetric transmission of linearly polarized EM wave exhibits a high efficiency and a pronounced real-time continuous tunability controlled by the external stimulation of voltage biasing. In addition, the asymmetric transmission effect can be well preserved at large oblique incident angle up to ±70°. The design principle and EM performance are validated by both full wave simulations and experimental measurements. Such dynamically controllable chiral metamaterial may provide robust and flexible approach to manipulate EM wave propagation, as well as to facilitate EM device integration to create diverse functionalities.

  6. Dynamic control of asymmetric electromagnetic wave transmission by active chiral metamaterial

    PubMed Central

    Chen, Ke; Feng, Yijun; Cui, Li; Zhao, Junming; Jiang, Tian; Zhu, Bo

    2017-01-01

    The asymmetric transmission of electromagnetic (EM) wave can be fully manipulated by chiral metamaterials, but little can achieve real-time and high efficient tunability due to challenges in practically deployable solutions. Here, we proposed a new scheme for flexibly and dynamically controlling the asymmetric EM wave transmission at microwave frequencies using planar metamaterial of deep subwavelength thickness incorporated with active components of PIN diodes. The asymmetric transmission of linearly polarized EM wave exhibits a high efficiency and a pronounced real-time continuous tunability controlled by the external stimulation of voltage biasing. In addition, the asymmetric transmission effect can be well preserved at large oblique incident angle up to ±70°. The design principle and EM performance are validated by both full wave simulations and experimental measurements. Such dynamically controllable chiral metamaterial may provide robust and flexible approach to manipulate EM wave propagation, as well as to facilitate EM device integration to create diverse functionalities. PMID:28202903

  7. The genealogical population dynamics of HIV-1 in a large transmission chain: bridging within and among host evolutionary rates.

    PubMed

    Vrancken, Bram; Rambaut, Andrew; Suchard, Marc A; Drummond, Alexei; Baele, Guy; Derdelinckx, Inge; Van Wijngaerden, Eric; Vandamme, Anne-Mieke; Van Laethem, Kristel; Lemey, Philippe

    2014-04-01

    Transmission lies at the interface of human immunodeficiency virus type 1 (HIV-1) evolution within and among hosts and separates distinct selective pressures that impose differences in both the mode of diversification and the tempo of evolution. In the absence of comprehensive direct comparative analyses of the evolutionary processes at different biological scales, our understanding of how fast within-host HIV-1 evolutionary rates translate to lower rates at the between host level remains incomplete. Here, we address this by analyzing pol and env data from a large HIV-1 subtype C transmission chain for which both the timing and the direction is known for most transmission events. To this purpose, we develop a new transmission model in a Bayesian genealogical inference framework and demonstrate how to constrain the viral evolutionary history to be compatible with the transmission history while simultaneously inferring the within-host evolutionary and population dynamics. We show that accommodating a transmission bottleneck affords the best fit our data, but the sparse within-host HIV-1 sampling prevents accurate quantification of the concomitant loss in genetic diversity. We draw inference under the transmission model to estimate HIV-1 evolutionary rates among epidemiologically-related patients and demonstrate that they lie in between fast intra-host rates and lower rates among epidemiologically unrelated individuals infected with HIV subtype C. Using a new molecular clock approach, we quantify and find support for a lower evolutionary rate along branches that accommodate a transmission event or branches that represent the entire backbone of transmitted lineages in our transmission history. Finally, we recover the rate differences at the different biological scales for both synonymous and non-synonymous substitution rates, which is only compatible with the 'store and retrieve' hypothesis positing that viruses stored early in latently infected cells preferentially

  8. Transmission dynamics and elimination potential of zoonotic tuberculosis in morocco

    PubMed Central

    Justus Bless, Philipp; Crump, Lisa; Lohmann, Petra; Laager, Mirjam; Chitnis, Nakul; Zinsstag, Jakob

    2017-01-01

    Bovine tuberculosis (BTB) is an endemic zoonosis in Morocco caused by Mycobacterium bovis, which infects many domestic animals and is transmitted to humans through consumption of raw milk or from contact with infected animals. The prevalence of BTB in Moroccan cattle is estimated at 18%, and 33% at the individual and the herd level respectively, but the human M. bovis burden needs further clarification. The current control strategy based on test and slaughter should be improved through local context adaptation taking into account a suitable compensation in order to reduce BTB prevalence in Morocco and decrease the disease burden in humans and animals. We established a simple compartmental deterministic mathematical model for BTB transmission in cattle and humans to provide a general understanding of BTB, in particular regarding transmission to humans. Differential equations were used to model the different pathways between the compartments for cattle and humans. Scenarios of test and slaughter were simulated to determine the effects of varying the proportion of tested animals (p) on the time to elimination of BTB (individual animal prevalence of less than one in a thousand) in cattle and humans. The time to freedom from disease ranged from 75 years for p = 20% to 12 years for p = 100%. For p > 60% the time to elimination was less than 20 years. The cumulated cost was largely stable: for p values higher than 40%, cost ranged from 1.47 to 1.60 billion euros with a time frame of 12 to 32 years to reach freedom from disease. The model simulations also suggest that using a 2mm cut off instead of a 4mm cut off in the Single Intradermal Comparative Cervical Tuberculin skin test (SICCT) would result in cheaper and quicker elimination programs. This analysis informs Moroccan bovine tuberculosis control policy regarding time frame, range of cost and levels of intervention. However, further research is needed to clarify the national human-bovine tuberculosis ratio in Morocco

  9. Transmission dynamics and elimination potential of zoonotic tuberculosis in morocco.

    PubMed

    Abakar, Mahamat Fayiz; Yahyaoui Azami, Hind; Justus Bless, Philipp; Crump, Lisa; Lohmann, Petra; Laager, Mirjam; Chitnis, Nakul; Zinsstag, Jakob

    2017-02-01

    Bovine tuberculosis (BTB) is an endemic zoonosis in Morocco caused by Mycobacterium bovis, which infects many domestic animals and is transmitted to humans through consumption of raw milk or from contact with infected animals. The prevalence of BTB in Moroccan cattle is estimated at 18%, and 33% at the individual and the herd level respectively, but the human M. bovis burden needs further clarification. The current control strategy based on test and slaughter should be improved through local context adaptation taking into account a suitable compensation in order to reduce BTB prevalence in Morocco and decrease the disease burden in humans and animals. We established a simple compartmental deterministic mathematical model for BTB transmission in cattle and humans to provide a general understanding of BTB, in particular regarding transmission to humans. Differential equations were used to model the different pathways between the compartments for cattle and humans. Scenarios of test and slaughter were simulated to determine the effects of varying the proportion of tested animals (p) on the time to elimination of BTB (individual animal prevalence of less than one in a thousand) in cattle and humans. The time to freedom from disease ranged from 75 years for p = 20% to 12 years for p = 100%. For p > 60% the time to elimination was less than 20 years. The cumulated cost was largely stable: for p values higher than 40%, cost ranged from 1.47 to 1.60 billion euros with a time frame of 12 to 32 years to reach freedom from disease. The model simulations also suggest that using a 2mm cut off instead of a 4mm cut off in the Single Intradermal Comparative Cervical Tuberculin skin test (SICCT) would result in cheaper and quicker elimination programs. This analysis informs Moroccan bovine tuberculosis control policy regarding time frame, range of cost and levels of intervention. However, further research is needed to clarify the national human-bovine tuberculosis ratio in Morocco.

  10. Thermal transmission at Si/Ge interface: ab initio lattice dynamics calculation

    NASA Astrophysics Data System (ADS)

    Alkurdi, A.; Merabia, S.

    2017-01-01

    We perform lattice dynamics calculations (LD) on silicon/germanium interfaces using ab initio interatomic force constants to predict the interfacial phonon transmission as a function of both phonon frequency and the transmission angle. We carry out a spectral and angular analysis to quantify the contribution of each phonon mode in a given scattering direction. The effect of the interaction range was studied at this interface by taking account of more or less atom layers across the interface. Moreover, we were able to predict the thermal boundary conductance (TBC) as a function of the transmission angle and temperature as well. Our results show that, the thermal energy transmission is highly anisotropic while thermal energy reflection is almost isotropic. In addition, we found that it seems there is a global critical angle of transmission beyond which almost no thermal energy is transmitted. This can be used to device high pass phonon filter via changing the orientation of the interface.

  11. Transmission

    SciTech Connect

    Sugano, K.

    1988-12-27

    A transmission is described which consists of: an input shaft; an output shaft; a first planetary gear set including a first sun gear selectively connectable by a first clutch to the input shaft, a first carrier selectively connectable by a second clutch to the input shaft and a first ring gear connected to the output shaft. The first sun gear selectively held stationary by a first brake, the first carrier is allowed to rotate in the same forward direction as the input shaft when the second clutch is engaged, but prevented from rotating in a reverse direction opposite to the forward direction by a first one-way clutch, the first carrier being selectively held stationary by a second brake; a second planetary gear set including a second sun gear connected to the input shaft, a second carrier connected to the first ring gear and also the the output shaft, and a second ring gear.

  12. Computationally exact methods for stochastic periodic dynamics: Spatiotemporal dispersal and temporally forced transmission.

    PubMed

    Ross, J V

    2010-01-07

    The dynamics of many diseases and populations possess distinct recurring phases. For example, many species breed only during a subset of the year and the infection dynamics of many pathogens have transmission rates that vary with season. Here I investigate computational methods for studying transient and long-term behaviour of stochastic models which have periodic phases-several different potential techniques for studying long-term behaviour will be contrasted. I illustrate the results with two studies: The first is of a spatially realistic metapopulation model of malleefowl (Leipoa ocellata), a species which disperses only during a quarter of the year; this model is used to highlight the advantages and disadvantages of the particular methods presented. The second study is of a model for disease dynamics which incorporates seasonality in both the rate of within-population transmission and also in the rate of transmission effected via aerosol importation. This model has applications to studying disease invasion and persistence in captive-breeding populations. We demonstrate, via comparison to appropriately matched models with constant transmission rates and also no aerosol transmission, that seasonality and aerosol importation may alter control choices, with possibly an increase in the threshold population size for local control surveillance, transfer of importance to limiting aerosol transmission, and the use of temporally targetted surveillance. The methodology presented is the gold-standard for dealing with many phased processes in ecology and epidemiology, but its application is limited to systems of small size.

  13. On transmission errors and profile modifications minimising dynamic tooth loads in multi-mesh gears

    NASA Astrophysics Data System (ADS)

    Velex, Ph.; Chapron, M.; Fakhfakh, H.; Bruyère, J.; Becquerelle, S.

    2016-09-01

    A modular three-dimensional model of multi-mesh gears is used to analyse theoretically the link between dynamic mesh excitations and transmission errors. It is demonstrated that dynamic mesh forces are mostly controlled by the local transmission errors associated with each individual mesh. A design criterion is derived which can be used to define the tooth shape modifications minimising dynamic tooth loads. The results from two examples of application on idler and planetary systems prove that the proposed theory is sound and can be applied to a variety of gear geometries. Finally, the interest and limits of using transmission errors from a single pinion-gear pair in the context of multi-mesh gears are discussed.

  14. Transmission stability and Raman-induced amplitude dynamics in multichannel soliton-based optical waveguide systems

    NASA Astrophysics Data System (ADS)

    Peleg, Avner; Nguyen, Quan M.; Tran, Thinh P.

    2016-12-01

    We study transmission stability and dynamics of pulse amplitudes in N-channel soliton-based optical waveguide systems, taking into account second-order dispersion, Kerr nonlinearity, delayed Raman response, and frequency dependent linear gain-loss. We carry out numerical simulations with systems of N coupled nonlinear Schrödinger (NLS) equations and compare the results with the predictions of a simplified predator-prey model for Raman-induced amplitude dynamics. Coupled-NLS simulations for single-fiber transmission with 2 ≤ N ≤ 4 frequency channels show stable oscillatory dynamics of soliton amplitudes at short-to-intermediate distances, in excellent agreement with the predator-prey model's predictions. However, at larger distances, we observe transmission destabilization due to resonant formation of radiative sidebands, which is caused by Kerr nonlinearity. The presence of linear gain-loss in a single fiber leads to a limited increase in transmission stability. Significantly stronger enhancement of transmission stability is achieved in a nonlinear N-waveguide coupler due to efficient suppression of radiative sideband generation by the linear gain-loss. As a result, the distances along which stable Raman-induced dynamics of soliton amplitudes is observed are significantly larger in the waveguide coupler system compared with the single-fiber system.

  15. Dynamic analysis of flexible gear trains/transmissions - An automated approach

    NASA Technical Reports Server (NTRS)

    Amirouche, F. M. L.; Shareef, N. H.; Xie, M.

    1992-01-01

    In this paper an automated algorithmic method is presented for the dynamic analysis of geared trains/transmissions. These are treated as a system of interconnected flexible bodies. The procedure developed explains the switching of constraints with time as a result of the change in the contacting areas at the gear teeth. The elastic behavior of the system is studied through the employment of three-dimensional isoparametric elements having six degrees-of-freedom at each node. The contact between the bodies is assumed at the various nodes, which could be either a line or a plane. The kinematical expressions, together with the equations of motion using Kane's method, strain energy concepts, are presented in a matrix form suitable for computer implementation. The constraint Jacobian matrices are generated automatically based on the contact information between the bodies. The concepts of the relative velocity at the contacting points at the tooth pairs and the subsequent use of the transmission ratios in the analysis is presented.

  16. Description and stability analysis of nonlinear transmission line type metamaterials using nonlinear dynamics theory

    NASA Astrophysics Data System (ADS)

    Elnaggar, Sameh Y.; Milford, Gregory N.

    2017-03-01

    Nonlinear metamaterials offer a potential technology to realize applications at microwave, terahertz, and optical frequencies. However, due to the strong and controlled nonlinearity, the wave interactions can be quite complex. In the current article, a framework based on nonlinear dynamics theory is developed to describe such complex interactions. This is demonstrated for the case of a harmonically pumped nonlinear left handed transmission line through the use of bifurcation theory, stability analysis, and linearization about the limit cycle to calculate the autonomously generated frequencies and their spatial distributions. Higher order parametric interactions, which can be mediated by the strong nonlinearity, are automatically included in the model. It is demonstrated that autonomous components can be visualized in both the phase and the set of solution spaces. The framework is general in terms of the transmission line configuration, the nature and strength of the nonlinearity, and the number of stages. It also provides accurate results when the autonomous frequencies are in the vicinity of the Bragg frequency.

  17. A model of bi-mode transmission dynamics of hepatitis C with optimal control.

    PubMed

    Imran, Mudassar; Rafique, Hassan; Khan, Adnan; Malik, Tufail

    2014-06-01

    In this paper, we present a rigorous mathematical analysis of a deterministic model for the transmission dynamics of hepatitis C. The model is suitable for populations where two frequent modes of transmission of hepatitis C virus, namely unsafe blood transfusions and intravenous drug use, are dominant. The susceptible population is divided into two distinct compartments, the intravenous drug users and individuals undergoing unsafe blood transfusions. Individuals belonging to each compartment may develop acute and then possibly chronic infections. Chronically infected individuals may be quarantined. The analysis indicates that the eradication and persistence of the disease is completely determined by the magnitude of basic reproduction number R(c). It is shown that for the basic reproduction number R(c) < 1, the disease-free equilibrium is locally and globally asymptotically stable. For R(c) > 1, an endemic equilibrium exists and the disease is uniformly persistent. In addition, we present the uncertainty and sensitivity analyses to investigate the influence of different important model parameters on the disease prevalence. When the infected population persists, we have designed a time-dependent optimal quarantine strategy to minimize it. The Pontryagin's Maximum Principle is used to characterize the optimal control in terms of an optimality system which is solved numerically. Numerical results for the optimal control are compared against the constant controls and their efficiency is discussed.

  18. Mathematical model of Ebola transmission dynamics with relapse and reinfection.

    PubMed

    Agusto, F B

    2017-01-01

    The Ebola virus disease is caused by the Ebola virus which belongs to the filoviridae virus family. The 2014 outbreaks were estimated to have caused over 11,000 fatalities. In this paper, we formulate and analyze a system of ordinary differential equations which incorporates disease relapse and reinfection. The Ebola model with disease relapse and reinfection is locally-asymptotically stable when the basic reproduction number is less than unity. The model exhibits in the presence of disease reinfection, the phenomenon of backward bifurcation, where the stable disease-free equilibrium co-exists with a stable endemic equilibrium when the associated reproduction number is less than unity. The feasibility of backward bifurcation occurring increases with increasing values of both relapse and reinfection. The total number of new cases of Ebola-infected individuals increases with increasing values of the relapse and reinfection parameters. Further simulations show that Ebola transmission models that do not incorporate relapse and reinfection may under-estimate disease burden in the community. Similar under-estimation is observed in models that include only one infected and recovered classes. Using results obtained from sensitivity analysis indicates that Ebola (given disease relapse and reinfection) can be effectively curtailed in the community by using control measures with a high-effectiveness level. This strategy is more effective than either the moderate- or low-effectiveness levels. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Engineering science research issues in high power density transmission dynamics for aerospace applications. [rotorcraft geared rotors

    NASA Technical Reports Server (NTRS)

    Singh, Rajendra; Houser, Donald R.

    1993-01-01

    This paper discusses analytical and experimental approaches that will be needed to understand dynamic, vibro-acoustic and design characteristics of high power density rotorcraft transmissions. Complexities associated with mathematical modeling of such systems will be discussed. An overview of research work planned during the next several years will be presented, with emphasis on engineering science issues such as gear contact mechanics, multi-mesh drive dynamics, parameter uncertainties, vibration transmission through bearings, and vibro-acoustic characteristics of geared rotor systems and housing-mount structures. A few examples of work in progress are cited.

  20. Engineering science research issues in high power density transmission dynamics for aerospace applications. [rotorcraft geared rotors

    NASA Technical Reports Server (NTRS)

    Singh, Rajendra; Houser, Donald R.

    1993-01-01

    This paper discusses analytical and experimental approaches that will be needed to understand dynamic, vibro-acoustic and design characteristics of high power density rotorcraft transmissions. Complexities associated with mathematical modeling of such systems will be discussed. An overview of research work planned during the next several years will be presented, with emphasis on engineering science issues such as gear contact mechanics, multi-mesh drive dynamics, parameter uncertainties, vibration transmission through bearings, and vibro-acoustic characteristics of geared rotor systems and housing-mount structures. A few examples of work in progress are cited.

  1. Dynamics of climate-based malaria transmission model with age-structured human population

    NASA Astrophysics Data System (ADS)

    Addawe, Joel; Pajimola, Aprimelle Kris

    2016-10-01

    In this paper, we proposed to study the dynamics of malaria transmission with periodic birth rate of the vector and an age-structure for the human population. The human population is divided into two compartments: pre-school (0-5 years) and the rest of the human population. We showed the existence of a disease-free equilibrium point. Using published epidemiological parameters, we use numerical simulations to show potential effect of climate change in the dynamics of age-structured malaria transmission. Numerical simulations suggest that there exists an asymptotically attractive solution that is positive and periodic.

  2. Direct observation of the dynamic process underlying allosteric signal transmission.

    PubMed

    Brüschweiler, Sven; Schanda, Paul; Kloiber, Karin; Brutscher, Bernhard; Kontaxis, Georg; Konrat, Robert; Tollinger, Martin

    2009-03-04

    Allosteric regulation is an effective mechanism of control in biological processes. In allosteric proteins a signal originating at one site in the molecule is communicated through the protein structure to trigger a specific response at a remote site. Using NMR relaxation dispersion techniques we directly observe the dynamic process through which the KIX domain of CREB binding protein communicates allosteric information between binding sites. KIX mediates cooperativity between pairs of transcription factors through binding to two distinct interaction surfaces in an allosteric manner. We show that binding the activation domain of the mixed lineage leukemia (MLL) transcription factor to KIX induces a redistribution of the relative populations of KIX conformations toward a high-energy state in which the allosterically activated second binding site is already preformed, consistent with the Monod-Wyman-Changeux (WMC) model of allostery. The structural rearrangement process that links the two conformers and by which allosteric information is communicated occurs with a time constant of 3 ms at 27 degrees C. Our dynamic NMR data reveal that an evolutionarily conserved network of hydrophobic amino acids constitutes the pathway through which information is transmitted.

  3. Transmission intensity and drug resistance in malaria population dynamics: implications for climate change.

    PubMed

    Artzy-Randrup, Yael; Alonso, David; Pascual, Mercedes

    2010-10-26

    Although the spread of drug resistance and the influence of climate change on malaria are most often considered separately, these factors have the potential to interact through altered levels of transmission intensity. The influence of transmission intensity on the evolution of drug resistance has been addressed in theoretical studies from a population genetics' perspective; less is known however on how epidemiological dynamics at the population level modulates this influence. We ask from a theoretical perspective, whether population dynamics can explain non-trivial, non-monotonic, patterns of treatment failure with transmission intensity, and, if so, under what conditions. We then address the implications of warmer temperatures in an East African highland, where, as in other similar regions at the altitudinal edge of malaria's distribution, there has been a pronounced increase of cases from the 1970s to the 1990s. Our theoretical analyses, with a transmission model that includes different levels of immunity, demonstrate that an increase in transmission beyond a threshold can lead to a decrease in drug resistance, as previously shown, but that a second threshold may occur and lead to the re-establishment of drug resistance. Estimates of the increase in transmission intensity from the 1970s to the 1990s for the Kenyan time series, obtained by fitting the two-stage version of the model with an explicit representation of vector dynamics, suggest that warmer temperatures are likely to have moved the system towards the first threshold, and in so doing, to have promoted the faster spread of drug resistance. Climate change and drug resistance can interact and need not be considered as alternative explanations for trends in disease incidence in this region. Non-monotonic patterns of treatment failure with transmission intensity similar to those described as the 'valley phenomenon' for Uganda can result from epidemiological dynamics but under poorly understood assumptions.

  4. Direct and Indirect Effects of Rotavirus Vaccination: Comparing Predictions from Transmission Dynamic Models

    PubMed Central

    Pitzer, Virginia E.; Atchison, Christina J.; Harris, John P.; Shim, Eunha; Galvani, Alison P.; Edmunds, W. John; Viboud, Cécile; Patel, Manish M.; Grenfell, Bryan T.; Parashar, Umesh D.; Lopman, Ben A.

    2012-01-01

    Early observations from countries that have introduced rotavirus vaccination suggest that there may be indirect protection for unvaccinated individuals, but it is unclear whether these benefits will extend to the long term. Transmission dynamic models have attempted to quantify the indirect protection that might be expected from rotavirus vaccination in developed countries, but results have varied. To better understand the magnitude and sources of variability in model projections, we undertook a comparative analysis of transmission dynamic models for rotavirus. We fit five models to reported rotavirus gastroenteritis (RVGE) data from England and Wales, and evaluated outcomes for short- and long-term vaccination effects. All of our models reproduced the important features of rotavirus epidemics in England and Wales. Models predicted that during the initial year after vaccine introduction, incidence of severe RVGE would be reduced 1.8–2.9 times more than expected from the direct effects of the vaccine alone (28–50% at 90% coverage), but over a 5-year period following vaccine introduction severe RVGE would be reduced only by 1.1–1.7 times more than expected from the direct effects (54–90% at 90% coverage). Projections for the long-term reduction of severe RVGE ranged from a 55% reduction at full coverage to elimination with at least 80% coverage. Our models predicted short-term reductions in the incidence of RVGE that exceeded estimates of the direct effects, consistent with observations from the United States and other countries. Some of the models predicted that the short-term indirect benefits may be offset by a partial shifting of the burden of RVGE to older unvaccinated individuals. Nonetheless, even when such a shift occurs, the overall reduction in severe RVGE is considerable. Discrepancies among model predictions reflect uncertainties about age variation in the risk and reporting of RVGE, and the duration of natural and vaccine-induced immunity

  5. Modeling the Epidemiology of Cholera to Prevent Disease Transmission in Developing Countries.

    PubMed

    Mukandavire, Zindoga; Morris, J Glenn

    2015-06-01

    Cholera remains an important global cause of morbidity and mortality, which is capable of causing periodic epidemic disease. A number of mathematical models have been developed to help in understanding the dynamics of cholera outbreaks and for use as a tool in planning interventions, including vaccination campaigns. We have explored the utility of models in assessing the spread of cholera in the recent epidemics in Zimbabwe and Haiti. In both instances, a mathematical model was formulated and fitted to cumulative cholera cases to estimate the basic reproductive number ℛ0, and the partial reproductive numbers reflecting potential differences in environmental-to-human versus human-to-human transmission were quantified. In Zimbabwe, estimated ℛ0 for the epidemic using aggregated data at the national level was 1.15; in Haiti, it was 1.55. However, when calculated at a provincial/departmental level, estimated basic reproductive numbers were highly heterogeneous, with a range of 1.11 to 2.72 in Zimbabwe and 1.06 to 2.63 in Haiti. Our models suggest that the underlying patterns of cholera transmission varied widely from region to region, with a corresponding variation in the amenability of outbreaks to control measures such as immunization. These data underscore the heterogeneity of transmission dynamics, potentially linked to differences in environment, socio-economic conditions, and cultural practices. They also highlight the potential utility of these types of models in guiding development of public health intervention strategies.

  6. Maternal antibodies contribute to sex-based difference in hantavirus transmission dynamics

    PubMed Central

    Kallio, Eva R.; Henttonen, Heikki; Koskela, Esa; Lundkvist, Åke; Mappes, Tapio; Vapalahti, Olli

    2013-01-01

    Individuals often differ in their ability to transmit disease and identifying key individuals for transmission is a major issue in epidemiology. Male hosts are often thought to be more important than females for parasite transmission and persistence. However, the role of infectious females, particularly the transient immunity provided to offspring through maternal antibodies (MatAbs), has been neglected in discussions about sex-biased infection transmission. We examined the effect of host sex upon infection dynamics of zoonotic Puumala hantavirus (PUUV) in semi-natural, experimental populations of bank vole (Myodes glareolus). Populations were founded with either females or males that were infected with PUUV, whereas the other sex was immunized against PUUV infection. The likelihood of the next generation being infected was lower when the infected founders were females, underlying the putative importance of adult males in PUUV transmission and persistence in host populations. However, we show that this effect probably results from transient immunity that infected females provide to their offspring, rather than any sex-biased transmission efficiency per se. Our study proposes a potential contrasting nature of female and male hosts in the transmission dynamics of hantaviruses. PMID:24352416

  7. Dynamics of SI models with both horizontal and vertical transmissions as well as Allee effects.

    PubMed

    Kang, Yun; Castillo-Chavez, Carlos

    2014-02-01

    A general SI (Susceptible-Infected) epidemic system of host-parasite interactions operating under Allee effects, horizontal and/or vertical transmission, and where infected individuals experience pathogen-induced reductions in reproductive ability, is introduced. The initial focus of this study is on the analyses of the dynamics of density-dependent and frequency-dependent effects on SI models (SI-DD and SI-FD). The analyses identify conditions involving horizontal and vertical transmitted reproductive numbers, namely those used to characterize and contrast SI-FD and SI-DD dynamics. Conditions that lead to disease-driven extinction, or disease-free dynamics, or susceptible-free dynamics, or endemic disease patterns are identified. The SI-DD system supports richer dynamics including limit cycles while the SI-FD model only supports equilibrium dynamics. SI models under "small" horizontal transmission rates may result in disease-free dynamics. SI models under with and inefficient reproductive infectious class may lead to disease-driven extinction scenarios. The SI-DD model supports stable periodic solutions that emerge from an unstable equilibrium provided that either the Allee threshold and/or the disease transmission rate is large; or when the disease has limited influence on the infectives growth rate; and/or when disease-induced mortality is low. Host-parasite systems where diffusion or migration of local populations manage to destabilize them are examples of what is known as diffusive instability. The exploration of SI-dynamics in the presence of dispersal brings up the question of whether or not diffusive instability is a possible outcome. Here, we briefly look at such possibility within two-patch coupled SI-DD and SI-FD systems. It is shown that relative high levels of asymmetry, two modes of transmission, frequency dependence, and Allee effects are capable of supporting diffusive instability. Published by Elsevier Inc.

  8. DYNAMICS OF SI MODELS WITH BOTH HORIZONTAL AND VERTICAL TRANSMISSIONS AS WELL AS ALLEE EFFECTS*

    PubMed Central

    Kang, Yun; Castillo-Chavez, Carlos

    2014-01-01

    A general SI (Susceptible-Infected) epidemic system of host-parasite interactions operating under Allee effects, horizontal and/or vertical transmission, and where infected individuals experience pathogen-induced reductions in reproductive ability, is introduced. The initial focus of this study is on the analyses of the dynamics of Density-Dependent and Frequency-Dependent effects on SI models (SI-DD and SI-FD). The analyses identify conditions involving horizontal and vertical transmitted reproductive numbers, namely those used to characterize and contrast SI-FD and SI-DD dynamics. Conditions that lead to disease-driven extinction, or disease-free dynamics, or susceptible-free dynamics, or endemic disease patterns are identified. The SI-DD system supports richer dynamics including limit cycles while the SI-FD model only supports equilibrium dynamics. SI models under “small” horizontal transmission rates may result in disease-free dynamics. SI models under with and inefficient reproductive infectious class may lead to disease-driven extinction scenarios. The SI-DD model supports stable periodic solutions that emerge from an unstable equilibrium provided that either the Allee threshold and/or the disease transmission rate is large; or when the disease has limited influence on the infectives growth rate; and/or when disease-induced mortality is low. Host-parasite systems where diffusion or migration of local populations manage to destabilize them are examples of what is known as diffusive instability. The exploration of SI-dynamics in the presence of dispersal brings up the question of whether or not diffusive instability is a possible outcome. Here, we briefly look at such possibility within two-patch coupled SI-DD and SI-FD systems. It is shown that relative high levels of asymmetry, two modes of transmission, frequency dependence, and Allee effects are capable of supporting diffusive instability. PMID:24389426

  9. Spatiotemporal dynamics of the epidemic transmission in a predator-prey system.

    PubMed

    Su, Min; Hui, Cang; Zhang, Yanyu; Li, Zizhen

    2008-11-01

    Epidemic transmission is one of the critical density-dependent mechanisms that affect species viability and dynamics. In a predator-prey system, epidemic transmission can strongly affect the success probability of hunting, especially for social animals. Predators, therefore, will suffer from the positive density-dependence, i.e., Allee effect, due to epidemic transmission in the population. The rate of species contacting the epidemic, especially for those endangered or invasive, has largely increased due to the habitat destruction caused by anthropogenic disturbance. Using ordinary differential equations and cellular automata, we here explored the epidemic transmission in a predator-prey system. Results show that a moderate Allee effect will destabilize the dynamics, but it is not true for the extreme Allee effect (weak or strong). The predator-prey dynamics amazingly stabilize by the extreme Allee effect. Predators suffer the most from the epidemic disease at moderate transmission probability. Counter-intuitively, habitat destruction will benefit the control of the epidemic disease. The demographic stochasticity dramatically influences the spatial distribution of the system. The spatial distribution changes from oil-bubble-like (due to local interaction) to aggregated spatially scattered points (due to local interaction and demographic stochasticity). It indicates the possibility of using human disturbance in habitat as a potential epidemic-control method in conservation.

  10. Dynamically tunable graphene/dielectric photonic crystal transmission lines

    NASA Astrophysics Data System (ADS)

    Williamson, Ian; Mousavi, S. Hossein; Wang, Zheng

    2015-03-01

    It is well known that graphene supports plasmonic modes with high field confinement and lower losses when compared to conventional metals. Additionally, graphene features a highly tunable conductivity through which the plasmon dispersion can be modulated. Over the years these qualities have inspired a wide range of applications for graphene in the THz and infrared regimes. In this presentation we theoretically demonstrate a graphene parallel plate waveguide (PPWG) that sandwiches a 2D photonic crystal slab. The marriage of these two geometries offers a large two dimensional band gap that can be dynamically tuned over a very broad bandwidth. Our device operates in the low-THz band where the graphene PPWG supports a quasi-TEM mode with a relatively flat attenuation. Unlike conventional photonic crystal slabs, the quasi-TEM nature of the graphene PPWG mode allows the slab thickness to be less than 1/10 of the photonic crystal lattice constant. These features offer up a wealth of opportunities, including tunable metamaterials with a possible platform for large band gaps in 3D structures through tiling and stacking. Additionally, the geometry provides a platform for tunable defect cavities without needing three dimensional periodicity.

  11. Powertrain dynamics and control of a two speed dual clutch transmission for electric vehicles

    NASA Astrophysics Data System (ADS)

    Walker, Paul; Zhu, Bo; Zhang, Nong

    2017-02-01

    The purpose of this paper is to demonstrate the application of torque based powertrain control for multi-speed power shifting capable electric vehicles. To do so simulation and experimental studies of the shift transient behaviour of dual clutch transmission equipped electric vehicle powertrains is undertaken. To that end a series of power-on and power-off shift control strategies are then developed for both up and down gear shifts, taking note of the friction load requirements to maintain positive driving load for power-on shifting. A mathematical model of an electric vehicle powertrain is developed including a DC equivalent circuit model for the electric machine and multi-body dynamic model of the powertrain system is then developed and integrated with a hydraulic clutch control system model. Integral control of the powertrain is then performed through simulations on the develop powertrain system model for each of the four shift cases. These simulation results are then replicated on a full scale powertrain test rig. To evaluate the performance of results shift duration and vehicle jerk are used as metrics to demonstrate that the presented strategies are effective for shift control in electric vehicles. Qualitative comparison of both theoretical and experimental results demonstrates reasonable agreement between simulated and experimental outcomes.

  12. Revealing dynamic processes of materials in liquids using liquid cell transmission electron microscopy.

    PubMed

    Niu, Kai-Yang; Liao, Hong-Gang; Zheng, Haimei

    2012-12-20

    The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted significant interests across the research fields of materials science, physics, chemistry and biology. The key enabling technology is a liquid cell. We fabricate liquid cells with thin viewing windows through a sequential microfabrication process, including silicon nitride membrane deposition, photolithographic patterning, wafer etching, cell bonding, etc. A liquid cell with the dimensions of a regular TEM grid can fit in any standard TEM sample holder. About 100 nanoliters reaction solution is loaded into the reservoirs and about 30 picoliters liquid is drawn into the viewing windows by capillary force. Subsequently, the cell is sealed and loaded into a microscope for in situ imaging. Inside the TEM, the electron beam goes through the thin liquid layer sandwiched between two silicon nitride membranes. Dynamic processes of nanoparticles in liquids, such as nucleation and growth of nanocrystals, diffusion and assembly of nanoparticles, etc., have been imaged in real time with sub-nanometer resolution. We have also applied this method to other research areas, e.g., imaging proteins in water. Liquid cell TEM is poised to play a major role in revealing dynamic processes of materials in their working environments. It may also bring high impact in the study of biological processes in their native environment.

  13. How robust are the natural history parameters used in chlamydia transmission dynamic models? A systematic review

    PubMed Central

    2014-01-01

    Transmission dynamic models linked to economic analyses often form part of the decision making process when introducing new chlamydia screening interventions. Outputs from these transmission dynamic models can vary depending on the values of the parameters used to describe the infection. Therefore these values can have an important influence on policy and resource allocation. The risk of progression from infection to pelvic inflammatory disease has been extensively studied but the parameters which govern the transmission dynamics are frequently neglected. We conducted a systematic review of transmission dynamic models linked to economic analyses of chlamydia screening interventions to critically assess the source and variability of the proportion of infections that are asymptomatic, the duration of infection and the transmission probability. We identified nine relevant studies in Pubmed, Embase and the Cochrane database. We found that there is a wide variation in their natural history parameters, including an absolute difference in the proportion of asymptomatic infections of 25% in women and 75% in men, a six-fold difference in the duration of asymptomatic infection and a four-fold difference in the per act transmission probability. We consider that much of this variation can be explained by a lack of consensus in the literature. We found that a significant proportion of parameter values were referenced back to the early chlamydia literature, before the introduction of nucleic acid modes of diagnosis and the widespread testing of asymptomatic individuals. In conclusion, authors should use high quality contemporary evidence to inform their parameter values, clearly document their assumptions and make appropriate use of sensitivity analysis. This will help to make models more transparent and increase their utility to policy makers. PMID:24476335

  14. Enhanced model of gear transmission dynamics for condition monitoring applications: Effects of torque, friction and bearing clearance

    NASA Astrophysics Data System (ADS)

    Fernandez-del-Rincon, A.; Garcia, P.; Diez-Ibarbia, A.; de-Juan, A.; Iglesias, M.; Viadero, F.

    2017-02-01

    Gear transmissions remain as one of the most complex mechanical systems from the point of view of noise and vibration behavior. Research on gear modeling leading to the obtaining of models capable of accurately reproduce the dynamic behavior of real gear transmissions has spread out the last decades. Most of these models, although useful for design stages, often include simplifications that impede their application for condition monitoring purposes. Trying to filling this gap, the model presented in this paper allows us to simulate gear transmission dynamics including most of these features usually neglected by the state of the art models. This work presents a model capable of considering simultaneously the internal excitations due to the variable meshing stiffness (including the coupling among successive tooth pairs in contact, the non-linearity linked with the contacts between surfaces and the dissipative effects), and those excitations consequence of the bearing variable compliance (including clearances or pre-loads). The model can also simulate gear dynamics in a realistic torque dependent scenario. The proposed model combines a hybrid formulation for calculation of meshing forces with a non-linear variable compliance approach for bearings. Meshing forces are obtained by means of a double approach which combines numerical and analytical aspects. The methodology used provides a detailed description of the meshing forces, allowing their calculation even when gear center distance is modified due to shaft and bearing flexibilities, which are unavoidable in real transmissions. On the other hand, forces at bearing level were obtained considering a variable number of supporting rolling elements, depending on the applied load and clearances. Both formulations have been developed and applied to the simulation of the vibration of a sample transmission, focusing the attention on the transmitted load, friction meshing forces and bearing preloads.

  15. HTS DC Transmission Line for Megalopolis Grid Development

    NASA Astrophysics Data System (ADS)

    Kopylov, S.; Sytnikov, V.; Bemert, S.; Ivanov, Yu; Krivetskiy, I.; Romashov, M.; Shakaryan, Yu; Keilin, V.; Shikov, A.; Patrikeev, V.; Lobyntsev, V.; Shcherbakov, V.

    2014-05-01

    Using of HTS AC and DC cables in electric power grids allows increasing of the transferred power, losses diminishing, decreasing of exclusion zone areas, the enhancement of the environmental conditions and fire/explosion safety of electric power systems. However, the use of DC superconducting cable lines together with converters brings additional advantages as reduction of losses in cables and suitable lowering of refrigerating plant capacity, as well as the realization of the function of short-circuit currents limitation by means of the appropriate setting of converter equipment. Russian Federal Grid Company and its R&D Center started the construction of the DC HTS power transmission line which includes the cable itself, cryogenic equipment, AC/DC converters, terminals and cable coupling boxes. This line will connect two substations in Saint-Petersburg - 330 kV "Centralnaya" and 220 kV "RP-9". The length of this HTS transmission line will be about 2500 meters. Nowadays are developed all the elements of the line and technologies of the cable manufacturing. Two HTS cable samples, each 30 m length, have been made. This paper describes the results of cables tests.

  16. Development of Transmissible Photopletysmography Prototype Sensor Using Polimeric Fiber Optic

    NASA Astrophysics Data System (ADS)

    Vilhegas, Leonardo Zane; Veiga, Michel Robert; Mansano, Ronaldo Domingues; Santos, Josemir Coelho

    2008-04-01

    This paper showed the development of a transmissible prototype sensor using polymer fiber optic, in order to verify that the optic fiber is capable to transmit the signal through the receptor device and thus use it to obtain the needed parameters in small biological areas. The sensor consists one plastic clip with silicon inside, one infrared (940 nmn) LED (Light Emitting Diode) of 3 mm and one polymer fiber optic with 1 mm of diameter. The control device consists one photodetector with anatomic housing to the optic fiber and one circuit to control the LED emition intensity signal. The photodetector encapsulation is a photodiode with integrated transimpedance amplification. The transimpedance amplification is favorable because reject many noise artifacts. The choice to polymer optic fiber is because the same has a great mobility to twist, eletromagnetic interference imunity and small area to actuated. The interface system was done by LabVIEW software and the device sensor communication with the notebook was USB-6009 device, both the National Instruments company. The prototype transmissible sensor had the capability to measure the signal doing pratical diagnosis of pathology in biological areas that have small actuated areas.

  17. Exploring migratory dynamics on HIV transmission: the case of Mexicans in New York City and Puebla, Mexico.

    PubMed

    Ruiz, Yumary; Guilamo-Ramos, Vincent; McCarthy, Katharine; Muñoz-Laboy, Miguel A; de Lourdes Rosas López, Maria

    2014-06-01

    Migration and population movement are increasingly viewed as important factors associated with HIV transmission risk. With growing awareness of the potential impact of migration on HIV transmission, several perspectives have emerged that posit differing dynamics of risk. We considered available data on the role of migration on HIV transmission among Mexican migrants in New York City and Puebla, Mexico. Specifically, we examined 3 distinct models of migratory dynamics of HIV transmission-namely, the structural model, the local contextual model, and the interplay model. In doing so, we reframed current public health perspectives on the role of migration on HIV transmission.

  18. Dynamic vs. static social networks in models of parasite transmission: predicting Cryptosporidium spread in wild lemurs.

    PubMed

    Springer, Andrea; Kappeler, Peter M; Nunn, Charles L

    2017-05-01

    Social networks provide an established tool to implement heterogeneous contact structures in epidemiological models. Dynamic temporal changes in contact structure and ranging behaviour of wildlife may impact disease dynamics. A consensus has yet to emerge, however, concerning the conditions in which network dynamics impact model outcomes, as compared to static approximations that average contact rates over longer time periods. Furthermore, as many pathogens can be transmitted both environmentally and via close contact, it is important to investigate the relative influence of both transmission routes in real-world populations. Here, we use empirically derived networks from a population of wild primates, Verreaux's sifakas (Propithecus verreauxi), and simulated networks to investigate pathogen spread in dynamic vs. static social networks. First, we constructed a susceptible-exposed-infected-recovered model of Cryptosporidium spread in wild Verreaux's sifakas. We incorporated social and environmental transmission routes and parameterized the model for two different climatic seasons. Second, we used simulated networks and greater variation in epidemiological parameters to investigate the conditions in which dynamic networks produce larger outbreak sizes than static networks. We found that average outbreak size of Cryptosporidium infections in sifakas was larger when the disease was introduced in the dry season than in the wet season, driven by an increase in home range overlap towards the end of the dry season. Regardless of season, dynamic networks always produced larger average outbreak sizes than static networks. Larger outbreaks in dynamic models based on simulated networks occurred especially when the probability of transmission and recovery were low. Variation in tie strength in the dynamic networks also had a major impact on outbreak size, while network modularity had a weaker influence than epidemiological parameters that determine transmission and recovery

  19. Correction for dynamic bias error in transmission measurements of void fraction

    SciTech Connect

    Andersson, P.; Sunden, E. Andersson; Svaerd, S. Jacobsson; Sjoestrand, H.

    2012-12-15

    Dynamic bias errors occur in transmission measurements, such as X-ray, gamma, or neutron radiography or tomography. This is observed when the properties of the object are not stationary in time and its average properties are assessed. The nonlinear measurement response to changes in transmission within the time scale of the measurement implies a bias, which can be difficult to correct for. A typical example is the tomographic or radiographic mapping of void content in dynamic two-phase flow systems. In this work, the dynamic bias error is described and a method to make a first-order correction is derived. A prerequisite for this method is variance estimates of the system dynamics, which can be obtained using high-speed, time-resolved data acquisition. However, in the absence of such acquisition, a priori knowledge might be used to substitute the time resolved data. Using synthetic data, a void fraction measurement case study has been simulated to demonstrate the performance of the suggested method. The transmission length of the radiation in the object under study and the type of fluctuation of the void fraction have been varied. Significant decreases in the dynamic bias error were achieved to the expense of marginal decreases in precision.

  20. Correction for dynamic bias error in transmission measurements of void fraction

    NASA Astrophysics Data System (ADS)

    Andersson, P.; Sundén, E. Andersson; Svärd, S. Jacobsson; Sjöstrand, H.

    2012-12-01

    Dynamic bias errors occur in transmission measurements, such as X-ray, gamma, or neutron radiography or tomography. This is observed when the properties of the object are not stationary in time and its average properties are assessed. The nonlinear measurement response to changes in transmission within the time scale of the measurement implies a bias, which can be difficult to correct for. A typical example is the tomographic or radiographic mapping of void content in dynamic two-phase flow systems. In this work, the dynamic bias error is described and a method to make a first-order correction is derived. A prerequisite for this method is variance estimates of the system dynamics, which can be obtained using high-speed, time-resolved data acquisition. However, in the absence of such acquisition, a priori knowledge might be used to substitute the time resolved data. Using synthetic data, a void fraction measurement case study has been simulated to demonstrate the performance of the suggested method. The transmission length of the radiation in the object under study and the type of fluctuation of the void fraction have been varied. Significant decreases in the dynamic bias error were achieved to the expense of marginal decreases in precision.

  1. Fluid transmission line dynamics 1983; Proceedings of the Winter Annual Meeting, Boston, MA, November 13-18, 1983

    NASA Astrophysics Data System (ADS)

    Franke, M. E.; Drzewiecki, T. M.

    1983-11-01

    Various topics on fluid transmission line dynamics are addressed. The subjects discussed include: comparison of theoretical and experimental fluid line responses with source and load impedances; a first-order square root approximation for fluid transmission lines; modal approximations for the fluid dynamics of hydraulic and pneumatic transmission lines; and time domain simulation of fluid transmission lines using minimum order state variable models. Also considered are: the simulation of transmission line dynamics in nonlinear electrohydraulic systems; effect of transmission line dynamics on the response of servovalve-controlled actuators; and acoustic load impedance effects on centrifugal pump pulsations in a water flow loop. For individual items see A84-22297 to A84-22300

  2. Development of Live-working Robot for Power Transmission Lines

    NASA Astrophysics Data System (ADS)

    Yan, Yu; Liu, Xiaqing; Ren, Chengxian; Li, Jinliang; Li, Hui

    2017-07-01

    Dream-I, the first reconfigurable live-working robot for power transmission lines successfully developed in China, has the functions of autonomous walking on lines and accurately positioning. This paper firstly described operation task and object of the robot; then designed a general platform, an insulator replacement end and a drainage plate bolt fastening end of the robot, presented a control system of the robot, and performed simulation analysis on operation plan of the robot; and finally completed electrical field withstand voltage tests in a high voltage hall as well as online test and trial on actual lines. Experimental results show that by replacing ends of manipulators, the robot can fulfill operation tasks of live replacement of suspension insulators and live drainage plate bolt fastening.

  3. Development of Concave Conical Gear Used for Marine Transmissions

    NASA Astrophysics Data System (ADS)

    Komatsubara, Hidenori; Mitome, Ken-Ichi; Ohmachi, Tatsuya

    Conical involute gears used for marine transmissions are mostly helical ones. These gears are available in the form of not only intersecting axis gears but also nonintersecting-nonparallel axis gears. The contact between tooth surfaces of a pair of gears is the point contact. Tooth surface durability is generally low. In order to overcome this weak point, one of the authors invented a new type of conical gear called “Concave conical gear”. Concave conical gear has higher tooth durability than the conventional conical involute gear. In this paper, a method to generate the helical Concave conical gear is newly developed. First, the principle of the generating method is introduced, and the tooth surface is analyzed theoretically. Second, test gears are ground. Tooth surfaces of the test gears are measured and compared with theoretical ones, and good agreement is observed.

  4. Manipulation of host-resource dynamics impacts transmission of trophic parasites.

    PubMed

    Luong, Lien T; Grear, Daniel A; Hudson, Peter J

    2014-09-01

    Many complex life cycle parasites rely on predator-prey interactions for transmission, whereby definitive hosts become infected via the consumption of an infected intermediate host. As such, these trophic parasites are embedded in the larger community food web. We postulated that exposure to infection and, hence, parasite transmission are inherently linked to host foraging ecology, and that perturbation of the host-resource dynamic will impact parasite transmission dynamics. We employed a field manipulation experiment in which natural populations of the eastern chipmunk (Tamias striatus) were provisioned with a readily available food resource in clumped or uniform spatial distributions. Using replicated longitudinal capture-mark-recapture techniques, replicated supplemented and unsupplemented control sites were monitored before and after treatment for changes in infection levels with three gastro-intestinal helminth parasites. We predicted that definitive hosts subject to food supplementation would experience lower rates of exposure to infective intermediate hosts, presumably because they shifted their diet away from the intermediate host towards the more readily available resource (sunflower seeds). As predicted, prevalence of infection by the trophically transmitted parasite decreased in response to supplemental food treatment, but no such change in infection prevalence was detected for the two directly transmitted parasites in the system. The fact that food supplementation only had an impact on the transmission of the trophically transmitted parasite, and not the directly transmitted parasites, supports our hypothesis that host foraging ecology directly affects exposure to parasites that rely on the ingestion of intermediate hosts for transmission. We concluded that the relative availability of different food resources has important consequences for the transmission of parasites and, more specifically, parasites that are embedded in the food web. The broader

  5. Understanding the transmission dynamics of respiratory syncytial virus using multiple time series and nested models

    PubMed Central

    White, L.J.; Mandl, J.N.; Gomes, M.G.M.; Bodley-Tickell, A.T.; Cane, P.A.; Perez-Brena, P.; Aguilar, J.C.; Siqueira, M.M.; Portes, S.A.; Straliotto, S.M.; Waris, M.; Nokes, D.J.; Medley, G.F.

    2007-01-01

    The nature and role of re-infection and partial immunity are likely to be important determinants of the transmission dynamics of human respiratory syncytial virus (hRSV). We propose a single model structure that captures four possible host responses to infection and subsequent reinfection: partial susceptibility, altered infection duration, reduced infectiousness and temporary immunity (which might be partial). The magnitude of these responses is determined by four homotopy parameters, and by setting some of these parameters to extreme values we generate a set of eight nested, deterministic transmission models. In order to investigate hRSV transmission dynamics, we applied these models to incidence data from eight international locations. Seasonality is included as cyclic variation in transmission. Parameters associated with the natural history of the infection were assumed to be independent of geographic location, while others, such as those associated with seasonality, were assumed location specific. Models incorporating either of the two extreme assumptions for immunity (none or solid and lifelong) were unable to reproduce the observed dynamics. Model fits with either waning or partial immunity to disease or both were visually comparable. The best fitting structure was a lifelong partial immunity to both disease and infection. Observed patterns were reproduced by stochastic simulations using the parameter values estimated from the deterministic models. PMID:17335858

  6. Understanding the transmission dynamics of respiratory syncytial virus using multiple time series and nested models.

    PubMed

    White, L J; Mandl, J N; Gomes, M G M; Bodley-Tickell, A T; Cane, P A; Perez-Brena, P; Aguilar, J C; Siqueira, M M; Portes, S A; Straliotto, S M; Waris, M; Nokes, D J; Medley, G F

    2007-09-01

    The nature and role of re-infection and partial immunity are likely to be important determinants of the transmission dynamics of human respiratory syncytial virus (hRSV). We propose a single model structure that captures four possible host responses to infection and subsequent reinfection: partial susceptibility, altered infection duration, reduced infectiousness and temporary immunity (which might be partial). The magnitude of these responses is determined by four homotopy parameters, and by setting some of these parameters to extreme values we generate a set of eight nested, deterministic transmission models. In order to investigate hRSV transmission dynamics, we applied these models to incidence data from eight international locations. Seasonality is included as cyclic variation in transmission. Parameters associated with the natural history of the infection were assumed to be independent of geographic location, while others, such as those associated with seasonality, were assumed location specific. Models incorporating either of the two extreme assumptions for immunity (none or solid and lifelong) were unable to reproduce the observed dynamics. Model fits with either waning or partial immunity to disease or both were visually comparable. The best fitting structure was a lifelong partial immunity to both disease and infection. Observed patterns were reproduced by stochastic simulations using the parameter values estimated from the deterministic models.

  7. Modeling the Impact of Bed-Net Use and Treatment on Malaria Transmission Dynamics

    PubMed Central

    2017-01-01

    We modeled the impact of bed-net use and insecticide treated nets (ITNs), temperature, and treatment on malaria transmission dynamics using ordinary differential equations. To achieve this we formulated a simple model of mosquito biting rate that depends on temperature and usage of insecticides treated bed nets. We conducted global uncertainty and sensitivity analysis using Latin Hypercube Sampling (LHC) and Partial Rank Correlation Coefficient (PRCC) in order to find the most effective parameters that affect malaria transmission dynamics. We established the existence of the region where the model is epidemiologically feasible. We conducted the stability analysis of the disease-free equilibrium by the threshold parameter. We found the condition for the existence of the endemic equilibrium and provided necessary condition for its stability. Our results show that the peak of mosquitoes biting rate occurs at a range of temperature values not on a single value as previously reported in literature. The results also show that the combination of treatment and ITNs usage is the most effective intervention strategy towards control and eradication of malaria transmissions. Sensitivity analysis results indicate that the biting rate and the mosquitoes death rates are the most important parameters in the dynamics of malaria transmission. PMID:28835913

  8. Transmission-speckle correlation for measuring dynamic deformation of liquid surface

    NASA Astrophysics Data System (ADS)

    Liu, Zhanwei; Guo, Jing; Shi, Wenxiong; Huang, Xianfu; Xie, Huimin

    2015-02-01

    In this paper, a method based on transmission-speckle correlation is proposed for measuring static and dynamic deformation of liquid surface. In the method, a high-speed camera placed vertically above the tested liquid surface is used to observe and record a special speckle pattern put in advance at the bottom of liquid. According to the Snell's law, the deformation of liquid surface will lead to the movement of the transmission-speckles. In terms of this, the quantitative relationship between height changes of liquid surface and the in-plane displacement of transmission-speckles can be deduced. Combining with multi-directional Newton iteration algorithm, the dynamic deformation field of liquid surface can be calculated from the in-plane displacement vector field of transmission-speckle images in different moment using speckle correlation method. The sensitivity of the method in measuring height changes of liquid surface is discussed. In this paper, a validation test to measure the surface morphology of a plano-convex lens demonstrates the feasibility and the effectiveness of the method. In addition, the dynamic deformation and propagation process of ripples in the water surface caused by a droplet were investigated.

  9. Mathematical Models of Within-Host and Transmission Dynamics to Determine Effects of Malaria Interventions in a Variety of Transmission Settings

    PubMed Central

    Eckhoff, Philip

    2013-01-01

    A model for Anopheles population dynamics and malaria transmission is combined with a within-host dynamics microsolver to study baseline transmission, the effects of seasonality, and the impact of interventions. The Garki Project is recreated in simulation of the pre-intervention baseline and the different combinations of interventions deployed. Modifications are introduced, and longer project duration, extension of dry-season spraying, and transmission-blocking vaccines together achieve local elimination in some conditions. A variety of interventions are simulated in transmission settings that vary in transmission intensity and underlying seasonality. Adding vaccines to existing vector control efforts extends the ability to achieve elimination to higher baseline transmission and less favorable vector behavior. If one species of the Anopheles gambiae species complex feeds disproportionately outdoors for a given complex average behavior, vector control impacts are less than for a single species. Non-zero dry-season transmission limits seasonal oscillation in parasite dynamics and impact of wet-season interventions. PMID:23589530

  10. Modelling the transmission dynamics of dengue in the presence of Wolbachia.

    PubMed

    Ndii, Meksianis Z; Hickson, R I; Allingham, David; Mercer, G N

    2015-04-01

    Use of the bacterium Wolbachia is an innovative new strategy designed to break the cycle of dengue transmission. There are two main mechanisms by which Wolbachia could achieve this: by reducing the level of dengue virus in the mosquito and/or by shortening the host mosquito's lifespan. However, although Wolbachia shortens the lifespan, it also gives a breeding advantage which results in complex population dynamics. This study focuses on the development of a mathematical model to quantify the effect on human dengue cases of introducing Wolbachia into the mosquito population. The model consists of a compartment-based system of first-order differential equations; seasonal forcing in the mosquito population is introduced through the adult mosquito death rate. The analysis focuses on a single dengue outbreak typical of a region with a strong seasonally-varying mosquito population. We found that a significant reduction in human dengue cases can be obtained provided that Wolbachia-carrying mosquitoes persist when competing with mosquitoes without Wolbachia. Furthermore, using the Wolbachia strain WMel reduces the mosquito lifespan by at most 10% and allows them to persist in competition with non-Wolbachia-carrying mosquitoes. Mosquitoes carrying the WMelPop strain, however, are not likely to persist as it reduces the mosquito lifespan by up to 50%. When all other effects of Wolbachia on the mosquito physiology are ignored, cytoplasmic incompatibility alone results in a reduction in the number of human dengue cases. A sensitivity analysis of the parameters in the model shows that the transmission probability, the biting rate and the average adult mosquito death rate are the most important parameters for the outcome of the cumulative proportion of human individuals infected with dengue. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. Multi-host transmission dynamics of schistosomiasis and its optimal control.

    PubMed

    Ding, Chunxiao; Qiu, Zhipeng; Zhu, Huaiping

    2015-10-01

    In this paper we formulate a dynamical model to study the transmission dynamics of schistosomiasis in humans and snails. We also incorporate bovines in the model to study their impact on transmission and controlling the spread of Schistosoma japonicum in humans in China. The dynamics of the model is rigorously analyzed by using the theory of dynamical systems. The theoretical results show that the disease free equilibrium is globally asymptotically stable if R0 < 1, and if R0 > 1 the system has only one positive equilibrium. The local stability of the unique positive equilibrium is investigated and sufficient conditions are also provided for the global stability of the positive equilibrium. The optimal control theory are further applied to the model to study the corresponding optimal control problem. Both analytical and numerical results suggest that: (a) the infected bovines play an important role in the spread of schistosomiasis among humans, and killing the infected bovines will be useful to prevent transmission of schistosomiasis among humans; (b) optimal control strategy performs better than the constant controls in reducing the prevalence of the infected human and the cost for implementing optimal control is much less than that for constant controls; and

  12. Transcriptome Dynamics during Maize Endosperm Development

    PubMed Central

    Feng, Jiaojiao; Xu, Shutu; Wang, Lei; Li, Feifei; Li, Yibo; Zhang, Renhe; Zhang, Xinghua; Xue, Jiquan; Guo, Dongwei

    2016-01-01

    The endosperm is a major organ of the seed that plays vital roles in determining seed weight and quality. However, genome-wide transcriptome patterns throughout maize endosperm development have not been comprehensively investigated to date. Accordingly, we performed a high-throughput RNA sequencing (RNA-seq) analysis of the maize endosperm transcriptome at 5, 10, 15 and 20 days after pollination (DAP). We found that more than 11,000 protein-coding genes underwent alternative splicing (AS) events during the four developmental stages studied. These genes were mainly involved in intracellular protein transport, signal transmission, cellular carbohydrate metabolism, cellular lipid metabolism, lipid biosynthesis, protein modification, histone modification, cellular amino acid metabolism, and DNA repair. Additionally, 7,633 genes, including 473 transcription factors (TFs), were differentially expressed among the four developmental stages. The differentially expressed TFs were from 50 families, including the bZIP, WRKY, GeBP and ARF families. Further analysis of the stage-specific TFs showed that binding, nucleus and ligand-dependent nuclear receptor activities might be important at 5 DAP, that immune responses, signalling, binding and lumen development are involved at 10 DAP, that protein metabolic processes and the cytoplasm might be important at 15 DAP, and that the responses to various stimuli are different at 20 DAP compared with the other developmental stages. This RNA-seq analysis provides novel, comprehensive insights into the transcriptome dynamics during early endosperm development in maize. PMID:27695101

  13. Does interspecific competition have a moderating effect on Taenia solium transmission dynamics in Southeast Asia?

    PubMed

    Conlan, James V; Vongxay, Khamphouth; Fenwick, Stanley; Blacksell, Stuart D; Thompson, R C Andrew

    2009-09-01

    It is well understood that sociocultural practices strongly influence Taenia solium transmission; however, the extent to which interspecific parasite competition moderates Taenia transmission has yet to be determined. This is certainly the case in Southeast Asia where T. solium faces competition in both the definitive host (people) and the intermediate host (pigs). In people, adult worms of T. solium, T. saginata and T. asiatica compete through density-dependent crowding mechanisms. In pigs, metacestodes of T. solium, T. hydatigena and T. asiatica compete through density-dependent immune-mediated interactions. Here, we describe the biological and epidemiological implications of Taenia competition and propose that interspecific competition has a moderating effect on the transmission dynamics of T. solium in the region. Furthermore, we argue that this competitive ecological scenario should be considered in future research and surveillance activities examining T. solium cysticercosis and taeniasis in Southeast Asia.

  14. Network information analysis reveals risk perception transmission in a behaviour-influenza dynamics system.

    PubMed

    Liao, C-M; You, S-H; Cheng, Y-H

    2015-01-01

    Influenza poses a significant public health burden worldwide. Understanding how and to what extent people would change their behaviour in response to influenza outbreaks is critical for formulating public health policies. We incorporated the information-theoretic framework into a behaviour-influenza (BI) transmission dynamics system in order to understand the effects of individual behavioural change on influenza epidemics. We showed that information transmission of risk perception played a crucial role in the spread of health-seeking behaviour throughout influenza epidemics. Here a network BI model provides a new approach for understanding the risk perception spread and human behavioural change during disease outbreaks. Our study allows simultaneous consideration of epidemiological, psychological, and social factors as predictors of individual perception rates in behaviour-disease transmission systems. We suggest that a monitoring system with precise information on risk perception should be constructed to effectively promote health behaviours in preparation for emerging disease outbreaks.

  15. Transmission dynamics of Ebola virus disease and intervention effectiveness in Sierra Leone.

    PubMed

    Fang, Li-Qun; Yang, Yang; Jiang, Jia-Fu; Yao, Hong-Wu; Kargbo, David; Li, Xin-Lou; Jiang, Bao-Gui; Kargbo, Brima; Tong, Yi-Gang; Wang, Ya-Wei; Liu, Kun; Kamara, Abdul; Dafae, Foday; Kanu, Alex; Jiang, Rui-Ruo; Sun, Ye; Sun, Ruo-Xi; Chen, Wan-Jun; Ma, Mai-Juan; Dean, Natalie E; Thomas, Harold; Longini, Ira M; Halloran, M Elizabeth; Cao, Wu-Chun

    2016-04-19

    Sierra Leone is the most severely affected country by an unprecedented outbreak of Ebola virus disease (EVD) in West Africa. Although successfully contained, the transmission dynamics of EVD and the impact of interventions in the country remain unclear. We established a database of confirmed and suspected EVD cases from May 2014 to September 2015 in Sierra Leone and mapped the spatiotemporal distribution of cases at the chiefdom level. A Poisson transmission model revealed that the transmissibility at the chiefdom level, estimated as the average number of secondary infections caused by a patient per week, was reduced by 43% [95% confidence interval (CI): 30%, 52%] after October 2014, when the strategic plan of the United Nations Mission for Emergency Ebola Response was initiated, and by 65% (95% CI: 57%, 71%) after the end of December 2014, when 100% case isolation and safe burials were essentially achieved, both compared with before October 2014. Population density, proximity to Ebola treatment centers, cropland coverage, and atmospheric temperature were associated with EVD transmission. The household secondary attack rate (SAR) was estimated to be 0.059 (95% CI: 0.050, 0.070) for the overall outbreak. The household SAR was reduced by 82%, from 0.093 to 0.017, after the nationwide campaign to achieve 100% case isolation and safe burials had been conducted. This study provides a complete overview of the transmission dynamics of the 2014-2015 EVD outbreak in Sierra Leone at both chiefdom and household levels. The interventions implemented in Sierra Leone seem effective in containing the epidemic, particularly in interrupting household transmission.

  16. Modeling social transmission dynamics of unhealthy behaviors for evaluating prevention and treatment interventions on childhood obesity.

    PubMed

    Frerichs, Leah M; Araz, Ozgur M; Huang, Terry T-K

    2013-01-01

    Research evidence indicates that obesity has spread through social networks, but lever points for interventions based on overlapping networks are not well studied. The objective of our research was to construct and parameterize a system dynamics model of the social transmission of behaviors through adult and youth influence in order to explore hypotheses and identify plausible lever points for future childhood obesity intervention research. Our objectives were: (1) to assess the sensitivity of childhood overweight and obesity prevalence to peer and adult social transmission rates, and (2) to test the effect of combinations of prevention and treatment interventions on the prevalence of childhood overweight and obesity. To address the first objective, we conducted two-way sensitivity analyses of adult-to-child and child-to-child social transmission in relation to childhood overweight and obesity prevalence. For the second objective, alternative combinations of prevention and treatment interventions were tested by varying model parameters of social transmission and weight loss behavior rates. Our results indicated child overweight and obesity prevalence might be slightly more sensitive to the same relative change in the adult-to-child compared to the child-to-child social transmission rate. In our simulations, alternatives with treatment alone, compared to prevention alone, reduced the prevalence of childhood overweight and obesity more after 10 years (1.2-1.8% and 0.2-1.0% greater reduction when targeted at children and adults respectively). Also, as the impact of adult interventions on children was increased, the rank of six alternatives that included adults became better (i.e., resulting in lower 10 year childhood overweight and obesity prevalence) than alternatives that only involved children. The findings imply that social transmission dynamics should be considered when designing both prevention and treatment intervention approaches. Finally, targeting adults may

  17. Modeling Social Transmission Dynamics of Unhealthy Behaviors for Evaluating Prevention and Treatment Interventions on Childhood Obesity

    PubMed Central

    Frerichs, Leah M.; Araz, Ozgur M.; Huang, Terry T. – K.

    2013-01-01

    Research evidence indicates that obesity has spread through social networks, but lever points for interventions based on overlapping networks are not well studied. The objective of our research was to construct and parameterize a system dynamics model of the social transmission of behaviors through adult and youth influence in order to explore hypotheses and identify plausible lever points for future childhood obesity intervention research. Our objectives were: (1) to assess the sensitivity of childhood overweight and obesity prevalence to peer and adult social transmission rates, and (2) to test the effect of combinations of prevention and treatment interventions on the prevalence of childhood overweight and obesity. To address the first objective, we conducted two-way sensitivity analyses of adult-to-child and child-to-child social transmission in relation to childhood overweight and obesity prevalence. For the second objective, alternative combinations of prevention and treatment interventions were tested by varying model parameters of social transmission and weight loss behavior rates. Our results indicated child overweight and obesity prevalence might be slightly more sensitive to the same relative change in the adult-to-child compared to the child-to-child social transmission rate. In our simulations, alternatives with treatment alone, compared to prevention alone, reduced the prevalence of childhood overweight and obesity more after 10 years (1.2–1.8% and 0.2–1.0% greater reduction when targeted at children and adults respectively). Also, as the impact of adult interventions on children was increased, the rank of six alternatives that included adults became better (i.e., resulting in lower 10 year childhood overweight and obesity prevalence) than alternatives that only involved children. The findings imply that social transmission dynamics should be considered when designing both prevention and treatment intervention approaches. Finally, targeting adults

  18. Global Dynamics of a Virus Dynamical Model with Cell-to-Cell Transmission and Cure Rate.

    PubMed

    Zhang, Tongqian; Meng, Xinzhu; Zhang, Tonghua

    2015-01-01

    The cure effect of a virus model with both cell-to-cell transmission and cell-to-virus transmission is studied. By the method of next generation matrix, the basic reproduction number is obtained. The locally asymptotic stability of the virus-free equilibrium and the endemic equilibrium is considered by investigating the characteristic equation of the model. The globally asymptotic stability of the virus-free equilibrium is proved by constructing suitable Lyapunov function, and the sufficient condition for the globally asymptotic stability of the endemic equilibrium is obtained by constructing suitable Lyapunov function and using LaSalle invariance principal.

  19. Global Dynamics of a Virus Dynamical Model with Cell-to-Cell Transmission and Cure Rate

    PubMed Central

    2015-01-01

    The cure effect of a virus model with both cell-to-cell transmission and cell-to-virus transmission is studied. By the method of next generation matrix, the basic reproduction number is obtained. The locally asymptotic stability of the virus-free equilibrium and the endemic equilibrium is considered by investigating the characteristic equation of the model. The globally asymptotic stability of the virus-free equilibrium is proved by constructing suitable Lyapunov function, and the sufficient condition for the globally asymptotic stability of the endemic equilibrium is obtained by constructing suitable Lyapunov function and using LaSalle invariance principal. PMID:26504489

  20. Assessing the effect of zooprophylaxis on zoonotic cutaneous leishmaniasis transmission: a system dynamics approach.

    PubMed

    Kaabi, Belhassen; Ahmed, Sami Ben-hadj

    2013-12-01

    Capturing or diverting the disease carrying vector from humans can reduce the transmission of vector borne diseases such as leishmaniasis. The use of animals that act as dead-end hosts to relieve the vector (sandfly) bites on humans is called zooprophylaxis. However, as the number of blood meal providers especially domestic animals increases, the sandflies enhanced availability of blood meals will improve its number and survival, thereby countering the impact of diverting bites from humans. Thus, the transmission model exhibits the structure of a feedback loop characterizing complex dynamic systems. In order to rigorously assess the effect of zooprophylaxis, we propose a system dynamic model for zoonotic cutaneous leishmaniasis transmission with 3 blood-meal hosts: domestic animals, humans, and a reservoir (rodents). In this context, a simulation study of the proposed model with a follow-up period of 1000 days was performed. We explored how perturbations in the parameters characterizing the transmission, essentially the vector biting rates and the size of the domestic animal population, affect the zooprophylaxis outcome. The results show that the basic reproductive number R0 and the disease incidence in humans are decreasing function of the relative size of the domestic animal population. The speed of this decrease depends also on the vector biting rates of the different mammal species. The key factors influencing the magnitude of zooprophylaxis are: the sizes of the vector, rodent, and domestic animal populations, as well as, the biting rates which incorporate relative attraction and accessibility of the vectors to the mammalian populations.

  1. Genomics reveals historic and contemporary transmission dynamics of a bacterial disease among wildlife and livestock

    PubMed Central

    Kamath, Pauline L.; Foster, Jeffrey T.; Drees, Kevin P.; Luikart, Gordon; Quance, Christine; Anderson, Neil J.; Clarke, P. Ryan; Cole, Eric K.; Drew, Mark L.; Edwards, William H.; Rhyan, Jack C.; Treanor, John J.; Wallen, Rick L.; White, Patrick J.; Robbe-Austerman, Suelee; Cross, Paul C.

    2016-01-01

    Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (∼3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations. PMID:27165544

  2. Genomics reveals historic and contemporary transmission dynamics of a bacterial disease among wildlife and livestock

    USGS Publications Warehouse

    Kamath, Pauline L.; Foster, Jeffrey T.; Drees, Kevin P.; Luikart, Gordon; Quance, Christine; Anderson, Neil J.; Clarke, P. Ryan; Cole, Eric K.; Drew, Mark L.; Edwards, William H.; Rhyan, Jack C.; Treanor, John J.; Wallen, Rick L.; White, Patrick J.; Robbe-Austerman, Suelee; Cross, Paul C.

    2016-01-01

    Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (B3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations.

  3. Genomics reveals historic and contemporary transmission dynamics of a bacterial disease among wildlife and livestock.

    PubMed

    Kamath, Pauline L; Foster, Jeffrey T; Drees, Kevin P; Luikart, Gordon; Quance, Christine; Anderson, Neil J; Clarke, P Ryan; Cole, Eric K; Drew, Mark L; Edwards, William H; Rhyan, Jack C; Treanor, John J; Wallen, Rick L; White, Patrick J; Robbe-Austerman, Suelee; Cross, Paul C

    2016-05-11

    Whole-genome sequencing has provided fundamental insights into infectious disease epidemiology, but has rarely been used for examining transmission dynamics of a bacterial pathogen in wildlife. In the Greater Yellowstone Ecosystem (GYE), outbreaks of brucellosis have increased in cattle along with rising seroprevalence in elk. Here we use a genomic approach to examine Brucella abortus evolution, cross-species transmission and spatial spread in the GYE. We find that brucellosis was introduced into wildlife in this region at least five times. The diffusion rate varies among Brucella lineages (∼3 to 8 km per year) and over time. We also estimate 12 host transitions from bison to elk, and 5 from elk to bison. Our results support the notion that free-ranging elk are currently a self-sustaining brucellosis reservoir and the source of livestock infections, and that control measures in bison are unlikely to affect the dynamics of unrelated strains circulating in nearby elk populations.

  4. Dynamics of a split torque helicopter transmission. M.S. Thesis - Cleveland State Univ.

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy L.

    1994-01-01

    Split torque designs, proposed as alternatives to traditional planetary designs for helicopter main rotor transmissions, can save weight and be more reliable than traditional designs. This report presents the results of an analytical study of the system dynamics and performance of a split torque gearbox that uses a balance beam mechanism for load sharing. The Lagrange method was applied to develop a system of equations of motion. The mathematical model includes time-varying gear mesh stiffness, friction, and manufacturing errors. Cornell's method for calculating the stiffness of spur gear teeth was extended and applied to helical gears. The phenomenon of sidebands spaced at shaft frequencies about gear mesh fundamental frequencies was simulated by modeling total composite gear errors as sinusoid functions. Although the gearbox has symmetric geometry, the loads and motions of the two power paths differ. Friction must be considered to properly evaluate the balance beam mechanism. For the design studied, the balance beam is not an effective device for load sharing unless the coefficient of friction is less than 0.003. The complete system stiffness as represented by the stiffness matrix used in this analysis must be considered to precisely determine the optimal tooth indexing position.

  5. Determination of the Optimal Fourier Number on the Dynamic Thermal Transmission

    NASA Astrophysics Data System (ADS)

    Bruzgevičius, P.; Burlingis, A.; Norvaišienė, R.

    2016-12-01

    This article represents the result of experimental research on transient heat transfer in a multilayered (heterogeneous) wall. Our non-steady thermal transmission simulation is based on a finite-difference calculation method. The value of a Fourier number shows the similarity of thermal variation in conditional layers of an enclosure. Most scientists recommend using no more than a value of 0.5 for the Fourier number when performing calculations on dynamic (transient) heat transfer. The value of the Fourier number is determined in order to acquire reliable calculation results with optimal accuracy. To compare the results of simulation with experimental research, a transient heat transfer calculation spreadsheet was created. Our research has shown that a Fourier number of around 0.5 or even 0.32 is not sufficient ({≈ }17 % of oscillation amplitude) for calculations of transient heat transfer in a multilayered wall. The least distorted calculation results were obtained when the multilayered enclosure was divided into conditional layers with almost equal Fourier number values and when the value of the Fourier number was around 1/6, i.e., approximately 0.17. Statistical deviation analysis using the Statistical Analysis System was applied to assess the accuracy of the spreadsheet calculation and was developed on the basis of our established methodology. The mean and median absolute error as well as their confidence intervals has been estimated by the two methods with optimal accuracy ({F}_{oMDF}= 0.177 and F_{oEPS}= 0.1633 values).

  6. Inducing Herd Immunity against Seasonal Influenza in Long-Term Care Facilities through Employee Vaccination Coverage: A Transmission Dynamics Model

    PubMed Central

    Wendelboe, Aaron M.; Grafe, Carl; McCumber, Micah; Anderson, Michael P.

    2015-01-01

    Introduction. Vaccinating healthcare workers (HCWs) in long-term care facilities (LTCFs) may effectively induce herd immunity and protect residents against influenza-related morbidity and mortality. We used influenza surveillance data from all LTCFs in New Mexico to validate a transmission dynamics model developed to investigate herd immunity induction. Material and Methods. We adjusted a previously published transmission dynamics model and used surveillance data from an active system among 76 LTCFs in New Mexico during 2006-2007 for model validation. We used a deterministic compartmental model with a stochastic component for transmission between residents and HCWs in each facility in order to simulate the random variation expected in such populations. Results. When outbreaks were defined as a dichotomous variable, our model predicted that herd immunity could be induced. When defined as an attack rate, the model demonstrated a curvilinear trend, but insufficiently strong to induce herd immunity. The model was sensitive to changes in the contact parameter β but was robust to changes in the visitor contact probability. Conclusions. These results further elucidate previous studies' findings that herd immunity may not be induced by vaccinating HCWs in LTCFs; however, increased influenza vaccination coverage among HCWs reduces the probability of influenza infection among residents. PMID:26101542

  7. Dynamical behaviour of nanocrystals in transmission electron microscopy: size, temperature or irradiation effects.

    PubMed

    Buffat, Philippe André

    2003-02-15

    High-resolution transmission electron microscopy shows that metal nanoparticles sinter within a fraction of a second under an electron beam at 'room temperature' as long as classical models of thermal equilibrium apply. Images exhibit crystal planes that change in orientation with time as if the particle was undergoing melting and resolidification processes. We explore whether these dynamical effects are the result of heating or transformation effects in the electron microscope or quantum fluctuations in small systems.

  8. A review of typhoid fever transmission dynamic models and economic evaluations of vaccination

    PubMed Central

    Watson, Conall H.; Edmunds, W. John

    2015-01-01

    Despite a recommendation by the World Health Organization (WHO) that typhoid vaccines be considered for the control of endemic disease and outbreaks, programmatic use remains limited. Transmission models and economic evaluation may be informative in decision making about vaccine programme introductions and their role alongside other control measures. A literature search found few typhoid transmission models or economic evaluations relative to analyses of other infectious diseases of similar or lower health burden. Modelling suggests vaccines alone are unlikely to eliminate endemic disease in the short to medium term without measures to reduce transmission from asymptomatic carriage. The single identified data-fitted transmission model of typhoid vaccination suggests vaccines can reduce disease burden substantially when introduced programmatically but that indirect protection depends on the relative contribution of carriage to transmission in a given setting. This is an important source of epidemiological uncertainty, alongside the extent and nature of natural immunity. Economic evaluations suggest that typhoid vaccination can be cost-saving to health services if incidence is extremely high and cost-effective in other high-incidence situations, when compared to WHO norms. Targeting vaccination to the highest incidence age-groups is likely to improve cost-effectiveness substantially. Economic perspective and vaccine costs substantially affect estimates, with disease incidence, case-fatality rates, and vaccine efficacy over time also important determinants of cost-effectiveness and sources of uncertainty. Static economic models may under-estimate benefits of typhoid vaccination by omitting indirect protection. Typhoid fever transmission models currently require per-setting epidemiological parameterisation to inform their use in economic evaluation, which may limit their generalisability. We found no economic evaluation based on transmission dynamic modelling, and no

  9. A review of typhoid fever transmission dynamic models and economic evaluations of vaccination.

    PubMed

    Watson, Conall H; Edmunds, W John

    2015-06-19

    Despite a recommendation by the World Health Organization (WHO) that typhoid vaccines be considered for the control of endemic disease and outbreaks, programmatic use remains limited. Transmission models and economic evaluation may be informative in decision making about vaccine programme introductions and their role alongside other control measures. A literature search found few typhoid transmission models or economic evaluations relative to analyses of other infectious diseases of similar or lower health burden. Modelling suggests vaccines alone are unlikely to eliminate endemic disease in the short to medium term without measures to reduce transmission from asymptomatic carriage. The single identified data-fitted transmission model of typhoid vaccination suggests vaccines can reduce disease burden substantially when introduced programmatically but that indirect protection depends on the relative contribution of carriage to transmission in a given setting. This is an important source of epidemiological uncertainty, alongside the extent and nature of natural immunity. Economic evaluations suggest that typhoid vaccination can be cost-saving to health services if incidence is extremely high and cost-effective in other high-incidence situations, when compared to WHO norms. Targeting vaccination to the highest incidence age-groups is likely to improve cost-effectiveness substantially. Economic perspective and vaccine costs substantially affect estimates, with disease incidence, case-fatality rates, and vaccine efficacy over time also important determinants of cost-effectiveness and sources of uncertainty. Static economic models may under-estimate benefits of typhoid vaccination by omitting indirect protection. Typhoid fever transmission models currently require per-setting epidemiological parameterisation to inform their use in economic evaluation, which may limit their generalisability. We found no economic evaluation based on transmission dynamic modelling, and no

  10. Effects of gear box vibration and mass imbalance on the dynamics of multistage gear transmission

    NASA Technical Reports Server (NTRS)

    Choy, F. K.; Tu, Y. K.; Zakrajsek, J. J.; Townsend, D. P.

    1991-01-01

    The dynamic behavior of multistage gear transmission system, with the effects of gear-box-induced vibrations and rotor mass-imbalances is analyzed. The model method, using undamped frequencies and planar mode shapes, is used to reduce the degree-of-freedom of the system. The various rotor-bearing stages as well as lateral and torsional vibrations of each individual stage are coupled through localized gear-mesh-tooth interactions. Gear-box vibrations are coupled to the gear stage dynamics through bearing support forces. Transient and steady state dynamics of lateral and torsional vibrations of the geared system are examined in both time and frequency domain. A typical three-staged geared system is used as an example. Effects of mass-imbalance and gear box vibrations on the system dynamic behavior are presented in terms of modal excitation functions for both lateral and torsional vibrations. Operational characteristics and conclusions are drawn from the results presented.

  11. Exploring Migratory Dynamics on HIV Transmission: The Case of Mexicans in New York City and Puebla, Mexico

    PubMed Central

    Guilamo-Ramos, Vincent; McCarthy, Katharine; Muñoz-Laboy, Miguel A.; de Lourdes Rosas López, Maria

    2014-01-01

    Migration and population movement are increasingly viewed as important factors associated with HIV transmission risk. With growing awareness of the potential impact of migration on HIV transmission, several perspectives have emerged that posit differing dynamics of risk. We considered available data on the role of migration on HIV transmission among Mexican migrants in New York City and Puebla, Mexico. Specifically, we examined 3 distinct models of migratory dynamics of HIV transmission—namely, the structural model, the local contextual model, and the interplay model. In doing so, we reframed current public health perspectives on the role of migration on HIV transmission. PMID:24825203

  12. Comparative dynamics, seasonality in transmission, and predictability of childhood infections in Mexico.

    PubMed

    Mahmud, A S; Metcalf, C J E; Grenfell, B T

    2017-02-01

    The seasonality and periodicity of infections, and the mechanisms underlying observed dynamics, can have implications for control efforts. This is particularly true for acute childhood infections. Among these, the dynamics of measles is the best understood and has been extensively studied, most notably in the UK prior to the start of vaccination. Less is known about the dynamics of other childhood diseases, particularly outside Europe and the United States. In this paper, we leverage a unique dataset to examine the epidemiology of six childhood infections - measles, mumps, rubella, varicella, scarlet fever and pertussis - across 32 states in Mexico from 1985 to 2007. This dataset provides us with a spatio-temporal probe into the dynamics of six common childhood infections, and allows us to compare them in the same setting over the same time period. We examine three key epidemiological characteristics of these infections - the age profile of infections, spatio-temporal dynamics, and seasonality in transmission - and compare them with predictions from existing theory and past findings. Our analysis reveals interesting epidemiological differences between the six pathogens, and variations across space. We find signatures of term-time forcing (reduced transmission during the summer) for measles, mumps, rubella, varicella, and scarlet fever; for pertussis, a lack of term-time forcing could not be rejected.

  13. Linear dynamic analysis of multi-mesh transmissions containing external, rigid gears

    NASA Astrophysics Data System (ADS)

    Vinayak, H.; Singh, R.; Padmanabhan, C.

    1995-08-01

    This paper extends the multi-body dynamics modeling strategy for a gear pair [6] to multi-mesh transmissions with external, fixed center, helical or spur gears. Each gear is modeled as a rigid body with six degrees of freedom. A multi-dimensional, position-dependent formulation is used to describe the gear mesh stiffness which is assumed to be distributed along the line of action. A simplified model of the shaft-bearing subsystems is included since the focus of this study is on the gear dynamics. Excitation to the system is considered in the form of either external torque pulsation or internal static transmission error. The governing equations are linearized to yield a formulation with position or time-varying coefficients (LTV). Subsequently, three examples of linearized time-invariant (LTI) transmission systems are solved, and eigensolution predictions of the multi-body dynamics model compare very well with finite element calculations. Then the periodic response of a non-unity gear pair system is studied in depth. New results including a comparison between LTI and LTV models are presented. It has been demonstrated that both time and frequency domain solutions can be efficiently and accurately constructed by using the multi-term harmonic balance method, provided that several shaft and gear mesh harmonics are included.

  14. Impact of combined vector-control and vaccination strategies on transmission dynamics of dengue fever: a model-based analysis.

    PubMed

    Knerer, Gerhart; Currie, Christine S M; Brailsford, Sally C

    2015-06-01

    Dengue fever is a vector-borne disease prevalent in tropical and subtropical regions. It is an important public health problem with a considerable and often under-valued disease burden in terms of frequency, cost and quality-of-life. Recent literature reviews have documented the development of mathematical models of dengue fever both to identify important characteristics for future model development as well as to assess the impact of dengue control interventions. Such reviews highlight the importance of short-term cross-protection; antibody-dependent enhancement; and seasonality (in terms of both favourable and unfavourable conditions for mosquitoes). The compartmental model extends work by Bartley (2002) and combines the following factors: seasonality, age-structure, consecutive infection by all four serotypes, cross-protection and immune enhancement, as well as combined vector-host transmission. The model is used to represent dengue transmission dynamics using parameters appropriate for Thailand and to assess the potential impact of combined vector-control and vaccination strategies including routine and catch-up vaccination strategies on disease dynamics. When seasonality and temporary cross-protection between serotypes are included, the model is able to approximate the observed incidence of dengue fever in Thailand. We find vaccination to be the most effective single intervention, albeit with imperfect efficacy (30.2 %) and limited duration of protection. However, in combination, control interventions and vaccination exhibit a marked impact on dengue fever transmission. This study shows that an imperfect vaccine can be a useful weapon in reducing disease spread within the community, although it will be most effective when promoted as one of several strategies for combating dengue fever transmission.

  15. SSII cancellation in an EAM-based OFDM-IMDD transmission system employing a novel dynamic chirp model.

    PubMed

    Hsu, Dar-Zu; Wei, Chia-Chien; Chen, Hsing-Yu; Lu, Yi-Cheng; Song, Cih-Yuan; Yang, Chih-Chieh; Chen, Jyehong

    2013-01-14

    We develop a novel subcarrier-to-subcarrier intermixing interference (SSII) cancellation technique to estimate and eliminate SSII. For the first time, the SSII cancellation technique is experimentally demonstrated in an electro-absorption modulator- (EAM-) based intensity-modulation-direct-detection (IMDD) multi-band OFDM transmission system. Since the characteristics of SSII are seriously affected by the chirp parameter, a simple constant chirp model, we found, cannot effectively remove the SSII. Therefore, assuming that the chirp parameter linearly depends on the optical power, a novel dynamic chirp model is developed to obtain better estimation and cancellation of SSII. Compared with 23.6% SSII cancellation by the constant chirp model, our experimental results show that incorporating the dynamic chirp model into the SSII cancellation technique can achieve up to 74.4% SSII cancellation and 2.8-dB sensitivity improvement in a 32.25-Gbps OFDM system over 100-km uncompensated standard single-mode fiber.

  16. Basic Reproduction Number and Transmission Dynamics of Common Serogroups of Enterohemorrhagic Escherichia coli

    PubMed Central

    Sanderson, Michael W.; Lee, Chihoon; Cernicchiaro, Natalia; Renter, David G.; Lanzas, Cristina

    2016-01-01

    ABSTRACT Understanding the transmission dynamics of pathogens is essential to determine the epidemiology, ecology, and ways of controlling enterohemorrhagic Escherichia coli (EHEC) in animals and their environments. Our objective was to estimate the epidemiological fitness of common EHEC strains in cattle populations. For that purpose, we developed a Markov chain model to characterize the dynamics of 7 serogroups of enterohemorrhagic Escherichia coli (O26, O45, O103, O111, O121, O145, and O157) in cattle production environments based on a set of cross-sectional data on infection prevalence in 2 years in two U.S. states. The basic reproduction number (R0) was estimated using a Bayesian framework for each serogroup based on two criteria (using serogroup alone [the O-group data] and using O serogroup, Shiga toxin gene[s], and intimin [eae] gene together [the EHEC data]). In addition, correlations between external covariates (e.g., location, ambient temperature, dietary, and probiotic usage) and prevalence/R0 were quantified. R0 estimates varied substantially among different EHEC serogroups, with EHEC O157 having an R0 of >1 (∼1.5) and all six other EHEC serogroups having an R0 of less than 1. Using the O-group data substantially increased R0 estimates for the O26, O45, and O103 serogroups (R0 > 1) but not for the others. Different covariates had distinct influences on different serogroups: the coefficients for each covariate were different among serogroups. Our modeling and analysis of this system can be readily expanded to other pathogen systems in order to estimate the pathogen and external factors that influence spread of infectious agents. IMPORTANCE In this paper we describe a Bayesian modeling framework to estimate basic reproduction numbers of multiple serotypes of Shiga toxin-producing Escherichia coli according to a cross-sectional study. We then coupled a compartmental model to reconstruct the infection dynamics of these serotypes and quantify their risk

  17. Evolutionary Analysis of Inter-Farm Transmission Dynamics in a Highly Pathogenic Avian Influenza Epidemic

    PubMed Central

    Bataille, Arnaud; van der Meer, Frank; Stegeman, Arjan; Koch, Guus

    2011-01-01

    Phylogenetic studies have largely contributed to better understand the emergence, spread and evolution of highly pathogenic avian influenza during epidemics, but sampling of genetic data has never been detailed enough to allow mapping of the spatiotemporal spread of avian influenza viruses during a single epidemic. Here, we present genetic data of H7N7 viruses produced from 72% of the poultry farms infected during the 2003 epidemic in the Netherlands. We use phylogenetic analyses to unravel the pathways of virus transmission between farms and between infected areas. In addition, we investigated the evolutionary processes shaping viral genetic diversity, and assess how they could have affected our phylogenetic analyses. Our results show that the H7N7 virus was characterized by a high level of genetic diversity driven mainly by a high neutral substitution rate, purifying selection and limited positive selection. We also identified potential reassortment in the three genes that we have tested, but they had only a limited effect on the resolution of the inter-farm transmission network. Clonal sequencing analyses performed on six farm samples showed that at least one farm sample presented very complex virus diversity and was probably at the origin of chronological anomalies in the transmission network. However, most virus sequences could be grouped within clearly defined and chronologically sound clusters of infection and some likely transmission events between farms located 0.8–13 Km apart were identified. In addition, three farms were found as most likely source of virus introduction in distantly located new areas. These long distance transmission events were likely facilitated by human-mediated transport, underlining the need for strict enforcement of biosafety measures during outbreaks. This study shows that in-depth genetic analysis of virus outbreaks at multiple scales can provide critical information on virus transmission dynamics and can be used to increase

  18. Vectors and transmission dynamics for Setaria tundra (Filarioidea; Onchocercidae), a parasite of reindeer in Finland

    PubMed Central

    Laaksonen, Sauli; Solismaa, Milla; Kortet, Raine; Kuusela, Jussi; Oksanen, Antti

    2009-01-01

    Background Recent studies have revealed expansion by an array of Filarioid nematodes' into the northern boreal region of Finland. The vector-borne nematode, Setaria tundra, caused a serious disease outbreak in the Finnish reindeer population in 2003–05. The main aim of this study was to understand the outbreak dynamics and the rapid expansion of S. tundra in the sub arctic. We describe the vectors of S. tundra, and its development in vectors, for the first time. Finally we discuss the results in the context of the host-parasite ecology of S. tundra in Finland Results Development of S. tundra to the infective stage occurs in mosquitoes, (genera Aedes and Anopheles). We consider Aedes spp. the most important vectors. The prevalence of S. tundra naturally infected mosquitoes from Finland varied from 0.5 to 2.5%. The rate of development in mosquitoes was temperature-dependent. Infective larvae were present approximately 14 days after a blood meal in mosquitoes maintained at room temperature (mean 21 C), but did not develop in mosquitoes maintained outside for 22 days at a mean temperature of 14.1 C. The third-stage (infective) larvae were elongated (mean length 1411 μm (SD 207), and width 28 μm (SD 2)). The anterior end was blunt, and bore two liplike structures, the posterior end slight tapering with a prominent terminal papilla. Infective larvae were distributed anteriorly in the insect's body, the highest abundance being 70 larvae in one mosquito. A questionnaire survey revealed that the peak activity of Culicidae in the reindeer herding areas of Finland was from the middle of June to the end of July and that warm summer weather was associated with reindeer flocking behaviour on mosquito-rich wetlands. Conclusion In the present work, S. tundra vectors and larval development were identified and described for the first time. Aedes spp. mosquitoes likely serve as the most important and competent vectors for S. tundra in Finland. Warm summers apparently promote

  19. Dynamic Analysis of Spur Gear Transmissions (DANST). PC Version 3.00 User Manual

    NASA Technical Reports Server (NTRS)

    Oswald, Fred B.; Lin, Hsiang Hsi; Delgado, Irebert R.

    1996-01-01

    DANST is a FORTRAN computer program for static and dynamic analysis of spur gear systems. The program can be used for parametric studies to predict the static transmission error, dynamic load, tooth bending stress and other properties of spur gears as they are influenced by operating speed, torque, stiffness, damping, inertia, and tooth profile. DANST performs geometric modeling and dynamic analysis for low- or high-contact-ratio spur gears. DANST can simulate gear systems with contact ratios ranging from one to three. It was designed to be easy to use and it is extensively documented in several previous reports and by comments in the source code. This report describes installing and using a new PC version of DANST, covers input data requirements and presents examples.

  20. Neural field simulator: two-dimensional spatio-temporal dynamics involving finite transmission speed

    PubMed Central

    Nichols, Eric J.; Hutt, Axel

    2015-01-01

    Neural Field models (NFM) play an important role in the understanding of neural population dynamics on a mesoscopic spatial and temporal scale. Their numerical simulation is an essential element in the analysis of their spatio-temporal dynamics. The simulation tool described in this work considers scalar spatially homogeneous neural fields taking into account a finite axonal transmission speed and synaptic temporal derivatives of first and second order. A text-based interface offers complete control of field parameters and several approaches are used to accelerate simulations. A graphical output utilizes video hardware acceleration to display running output with reduced computational hindrance compared to simulators that are exclusively software-based. Diverse applications of the tool demonstrate breather oscillations, static and dynamic Turing patterns and activity spreading with finite propagation speed. The simulator is open source to allow tailoring of code and this is presented with an extension use case. PMID:26539105

  1. Complex Dynamics of the Power Transmission Grid (and other Critical Infrastructures)

    NASA Astrophysics Data System (ADS)

    Newman, David

    2015-03-01

    Our modern societies depend crucially on a web of complex critical infrastructures such as power transmission networks, communication systems, transportation networks and many others. These infrastructure systems display a great number of the characteristic properties of complex systems. Important among these characteristics, they exhibit infrequent large cascading failures that often obey a power law distribution in their probability versus size. This power law behavior suggests that conventional risk analysis does not apply to these systems. It is thought that much of this behavior comes from the dynamical evolution of the system as it ages, is repaired, upgraded, and as the operational rules evolve with human decision making playing an important role in the dynamics. In this talk, infrastructure systems as complex dynamical systems will be introduced and some of their properties explored. The majority of the talk will then be focused on the electric power transmission grid though many of the results can be easily applied to other infrastructures. General properties of the grid will be discussed and results from a dynamical complex systems power transmission model will be compared with real world data. Then we will look at a variety of uses of this type of model. As examples, we will discuss the impact of size and network homogeneity on the grid robustness, the change in risk of failure as generation mix (more distributed vs centralized for example) changes, as well as the effect of operational changes such as the changing the operational risk aversion or grid upgrade strategies. One of the important outcomes from this work is the realization that ``improvements'' in the system components and operational efficiency do not always improve the system robustness, and can in fact greatly increase the risk, when measured as a risk of large failure.

  2. Analysis of a temperature- and rainfall-dependent model for malaria transmission dynamics.

    PubMed

    Okuneye, Kamaldeen; Gumel, Abba B

    2017-05-01

    A new non-autonomous model is designed and used to assess the impact of variability in temperature and rainfall on the transmission dynamics of malaria in a population. In addition to adding age-structure in the host population and the dynamics of immature malaria mosquitoes, a notable feature of the new model is that recovered individuals do not revert to wholly-susceptible class (that is, recovered individuals enjoy reduced susceptibility to new malaria infection). In the absence of disease-induced mortality, the disease-free solution of the model is shown to be globally-asymptotically stable when the associated reproduction ratio is less than unity. The model has at least one positive periodic solution when the reproduction ratio exceeds unity (and the disease persists in the community in this case). Detailed uncertainty and sensitivity analysis, using mean monthly temperature and rainfall data from KwaZulu-Natal province of South Africa, shows that the top three parameters of the model that have the most influence on the disease transmission dynamics are the mosquito carrying capacity, transmission probability per contact for susceptible mosquitoes and human recovery rate. Numerical simulations of the model show that, for the KwaZulu-Natal province, malaria burden increases with increasing mean monthly temperature and rainfall in the ranges ([17-25]°C and [32-110] mm), respectively (and decreases with decreasing mean monthly temperature and rainfall values). In particular, transmission is maximized for mean monthly temperature and rainfall in the ranges [21-25]°C and [95-125] mm. This occurs for a six-month period in KwaZulu-Natal (hence, this study suggests that anti-malaria control efforts should be intensified during this period). It is shown, for the fixed mean monthly temperature of KwaZulu-Natal, that malaria burden decreases whenever the amount of rainfall exceeds a certain threshold value. It is further shown (through sensitivity analysis and

  3. Unexpected Interfarm Transmission Dynamics during a Highly Pathogenic Avian Influenza Epidemic

    PubMed Central

    Tassoni, Luca; Milani, Adelaide; Hughes, Joseph; Salviato, Annalisa; Massi, Paola; Zamperin, Gianpiero; Bonfanti, Lebana; Marangon, Stefano; Cattoli, Giovanni; Monne, Isabella

    2016-01-01

    ABSTRACT Next-generation sequencing technology is now being increasingly applied to study the within- and between-host population dynamics of viruses. However, information on avian influenza virus evolution and transmission during a naturally occurring epidemic is still limited. Here, we use deep-sequencing data obtained from clinical samples collected from five industrial holdings and a backyard farm infected during the 2013 highly pathogenic avian influenza (HPAI) H7N7 epidemic in Italy to unravel (i) the epidemic virus population diversity, (ii) the evolution of virus pathogenicity, and (iii) the pathways of viral transmission between different holdings and sheds. We show a high level of genetic diversity of the HPAI H7N7 viruses within a single farm as a consequence of separate bottlenecks and founder effects. In particular, we identified the cocirculation in the index case of two viral strains showing a different insertion at the hemagglutinin cleavage site, as well as nine nucleotide differences at the consensus level and 92 minority variants. To assess interfarm transmission, we combined epidemiological and genetic data and identified the index case as the major source of the virus, suggesting the spread of different viral haplotypes from the index farm to the other industrial holdings, probably at different time points. Our results revealed interfarm transmission dynamics that the epidemiological data alone could not unravel and demonstrated that delay in the disease detection and stamping out was the major cause of the emergence and the spread of the HPAI strain. IMPORTANCE The within- and between-host evolutionary dynamics of a highly pathogenic avian influenza (HPAI) strain during a naturally occurring epidemic is currently poorly understood. Here, we perform for the first time an in-depth sequence analysis of all the samples collected during a HPAI epidemic and demonstrate the importance to complement outbreak investigations with genetic data to

  4. Dynamics of a feline virus with two transmission modes within exponentially growing host populations.

    PubMed Central

    Berthier, K; Langlais, M; Auger, P; Pontier, D

    2000-01-01

    Feline panleucopenia virus (FPLV) was introduced in 1977 on Marion Island (in the southern Indian Ocean) with the aim of eradicating the cat population and provoked a huge decrease in the host population within six years. The virus can be transmitted either directly through contacts between infected and healthy cats or indirectly between a healthy cat and the contaminated environment: a specific feature of the virus is its high rate of survival outside the host. In this paper, a model was designed in order to take these two modes of transmission into account. The results showed that a mass-action incidence assumption was more appropriate than a proportionate mixing one in describing the dynamics of direct transmission. Under certain conditions the virus was able to control the host population at a low density. The indirect transmission acted as a reservoir supplying the host population with a low but sufficient density of infected individuals which allowed the virus to persist. The dynamics of the infection were more affected by the demographic parameters of the healthy hosts than by the epidemiological ones. Thus, demographic parameters should be precisely measured in field studies in order to obtain accurate predictions. The predicted results of our model were in good agreement with observations. PMID:11416908

  5. Dynamics Analysis of Wind Energy Production Development

    NASA Astrophysics Data System (ADS)

    Berg, V. I.; Zakirzakov, A. G.; Gordievskaya, E. F.

    2017-01-01

    The paper presents the analysis of the introduction experience and dynamics development of the world wind energy production. Calculated the amount of wind energy sources investments and the production capacity growth dynamics of the wind turbines. The studies have shown that the introduction dynamics of new wind energy sources is higher than any other energy source.

  6. The transmission dynamics of groups A and B human respiratory syncytial virus (hRSV) in England & Wales and Finland: seasonality and cross-protection.

    PubMed

    White, L J; Waris, M; Cane, P A; Nokes, D J; Medley, G F

    2005-04-01

    Human respiratory syncytial virus (hRSV) transmission dynamics are inherently cyclical, and the observed genetic diversity (between groups A and B) also appears to have a repeating pattern. A key unknown is the extent to which genetic variants interact immunologically, and thus impact on epidemiology. We developed a novel mathematical model for hRSV transmission including seasonal forcing of incidence and temporary intra- and inter-group partial immunity. Simultaneous model fits to data from two locations (England & Wales, UK, and Turku, Finland) successfully reproduced the contrasting infection dynamics and group A/B dominance patterns. Parameter estimates are consistent with direct estimates. Differences in the magnitude and seasonal variation in contact rate between the two populations alone could account for the variation in dynamics between these populations. The A/B group dominance patterns are explained by reductions in susceptibility to and infectiousness of secondary homologous and heterologous infections. The consequences of the observed dynamic complexity are discussed.

  7. On the dynamic response of pressure transmission lines in the research of helium-charged free piston Stirling engines

    NASA Technical Reports Server (NTRS)

    Miller, Eric L.; Dudenhoefer, James E.

    1989-01-01

    The signal distortion inherent to pressure transmission lines in free-piston Stirling engine research is discussed. Based on results from classical analysis, guidelines are formulated to describe the dynamic response properties of a volume-terminated transmission tube for applications involving the helium-charged free-piston Stirling engines. The underdamped flow regime is described, the primary resonance frequency is derived, and the pressure phase and amplitude distortion are discussed. The scope and limitation of the dynamic response analysis are considered.

  8. Dynamical transmission model of MERS-CoV in two areas

    NASA Astrophysics Data System (ADS)

    Yong, Benny; Owen, Livia

    2016-02-01

    Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is a disease first reported in Saudi Arabia in 2012 and it can be transmitted from human to human. This disease has spread to several other countries, most confirmed cases have displayed symptoms of severe acute respiratory illness and many of these patients have died. This research is aimed to construct a mathematical model for the transmission of MERS-CoV in two areas by separating the human population into two groups; susceptible and infectious groups. The dynamics of the disease is studied by a compartmental model involving ordinary differrential equations. The basic reproductive number of this disease is discussed to control the outbreak of this disease. Sensitivity analysis of this model is performed to determine the relative importance of the model parameters to the MERS-CoV transmission.

  9. Dynamics of electrical transmission at club endings on the Mauthner cells.

    PubMed

    Pereda, Alberto E; Rash, John E; Nagy, James I; Bennett, Michael V L

    2004-12-01

    Identifiable mixed electrical and chemical synapses on Mauthner cells, the club endings, have historically provided a window for the study of electrical transmission in vertebrates because of their accessibility for both physiological and ultrastructural characterization. Recent data show that electrical transmission at these terminals is mediated by connexin35 (Cx35), the fish ortholog of the mammalian neuronal gap junction protein, connexin36 (Cx36). While electrical synapses are still perceived by many as passive intercellular channels that lack modifiability, a wealth of experimental evidence shows that electrical synapses at club endings are very plastic and subject to dynamic regulatory control by several mechanisms. The widespread distribution of connexin35 and connexin36 and the ubiquity of some of the proposed regulatory elements suggest that other electrical synapses may be similarly regulated.

  10. On the dynamic response of pressure transmission lines in the research of helium-charged free piston Stirling engines

    NASA Technical Reports Server (NTRS)

    Miller, Eric L.; Dudenhoefer, James E.

    1989-01-01

    In free piston Stirling engine research the integrity of both amplitude and phase of the dynamic pressure measurements is critical to the characterization of cycle dynamics and thermodynamics. It is therefore necessary to appreciate all possible sources of signal distortion when designing pressure measurement systems for this type of research. The signal distortion inherent to pressure transmission lines is discussed. Based on results from classical analysis, guidelines are formulated to describe the dynamic response properties of a volume-terminated transmission tube for applications involving helium-charged free piston Stirling engines. The scope and limitations of the dynamic response analysis are considered.

  11. Transmission dynamics of Bartonella sp. strain OE 1-1 in Sundevall's jirds (Meriones crassus).

    PubMed

    Morick, Danny; Krasnov, Boris R; Khokhlova, Irina S; Gottlieb, Yuval; Harrus, Shimon

    2013-02-01

    A high prevalence of Bartonella infection is found in many natural systems; however, the transmission dynamics leading to observations of these infections is not fully understood. The capability of Xenopsylla ramesis fleas to serve as competent vectors of Bartonella sp. OE 1-1 (a strain closely related to the zoonotic Bartonella elizabethae) to Meriones crassus jirds was investigated. Naïve X. ramesis fleas were placed for 72 h on naïve jirds or jirds that were either experimentally or naturally infected with Bartonella sp. strain OE 1-1, after which they were placed on naïve jirds. Postfeeding, 69 to 100% of the fleas collected from each Bartonella-positive jird contained Bartonella DNA, and all naïve jirds became positive for Bartonella sp. OE 1-1 after infestation with the infected fleas. In addition, maternal transmission of Bartonella sp. OE 1-1 in jirds was tested by mating 5 Bartonella-positive and 5 naïve female jirds with 10 naïve male jirds in the absence of fleas. Fifteen offspring were delivered by each group. Cultures of blood drawn from all offspring on days 35 and 47 postdelivery were found to be negative for Bartonella. A single spleen sample from the offspring of a Bartonella-positive mother was found molecularly positive for Bartonella sp. OE 1-1. This study demonstrates that X. ramesis fleas are competent vectors of Bartonella sp. OE 1-1 to M. crassus jirds and indicates that maternal transmission is probably not the major transmission route from female jirds to their offspring. We suggest that the dynamics of Bartonella sp. OE 1-1 in the M. crassus jird population in nature is mostly dependent on its vectors.

  12. Theories of AIDS Transmission: Their Development and Implications.

    ERIC Educational Resources Information Center

    Sigelman, Carol; And Others

    This study examined knowledge of AIDS transmission, attitudes toward interacting with people who have AIDS, and concerns about being personally affected by AIDS in childhood and adolescence. Subjects were 188 children and adolescents ranging from 6 to 18 years old. An open-ended interview covering a wide range of AIDS-related topics was conducted…

  13. Study on the dynamics responses of a transmission system made from carbon nanotubes

    SciTech Connect

    Yin, Hang; Cai, Kun Wei, Ning; Qin, Qing-Hua; Shi, Jiao

    2015-06-21

    A rotational transmission system from coaxial carbon nanotubes (CNTs) is investigated using a computational molecular dynamics approach. The system consists of a motor from a single-walled carbon nanotube and a bearing from a double-walled carbon nanotube. The motor has a high fixed rotational frequency and the two ends of the outer tube in the bearing are fixed. The inner tube in the bearing works as a rotor. Because of the interlayer friction in the bearing, configurations of the joint between the adjacent ends of motor and rotor have significant effects on rotational transmission properties. Four factors are considered in simulation, i.e., the bonding types of atoms (sp{sup 1} and sp{sup 2}) on the ends of motor and rotor, the difference between motor and rotor radii, the rotational speed of motor, and the environmental temperature. It is found that the synchronous transmission happens if the sp{sup 1} atoms on the jointed ends of motor and rotor are bonded each other and become new sp{sup 2} atoms. Therefore, the lower difference between radii of motor and rotor, higher temperature of environment leads to synchronous rotational transmission easily. If the environmental temperature is too low (e.g., <150 K), the end of motor adjacent to rotor is easily under buckling and new sp{sup 2} atoms appear, too. With capped CNTs or higher radii difference between rotor and motor at an appropriate temperature, a stable asynchronous rotation of rotor can be generated, and the rotor's frequency varying linearly with motor's frequency between 230 and 270 GHz. A multi-signal transmission device combined with oscillating and rotational motion is proposed for motor and stator shares a same size in radius.

  14. The dynamic process and microscopic mechanism of extraordinary terahertz transmission through perforated superconducting films

    PubMed Central

    Wu, J. B.; Zhang, X.; Jin, B. B.; Liu, H. T.; Chen, Y. H.; Li, Z. Y.; Zhang, C. H.; Kang, L.; Xu, W. W.; Chen, J.; Wang, H. B.; Tonouchi, M.; Wu, P. H.

    2015-01-01

    Superconductor is a compelling plasmonic medium at terahertz frequencies owing to its intrinsic low Ohmic loss and good tuning property. However, the microscopic physics of the interaction between terahertz wave and superconducting plasmonic structures is still unknown. In this paper, we conducted experiments of the enhanced terahertz transmission through a series of superconducting NbN subwavelength hole arrays, and employed microscopic hybrid wave model in theoretical analysis of the role of hybrid waves in the enhanced transmission. The theoretical calculation provided a good match of experimental data. In particular, we obtained the following results. When the width of the holes is far below wavelength, the enhanced transmission is mainly caused by localized resonance around individual holes. On the contrary, when the holes are large, hybrid waves scattered by the array of holes dominate the extraordinary transmission. The surface plasmon polaritions are proved to be launched on the surface of superconducting film and the excitation efficiency increases when the temperature approaches critical temperature and the working frequency goes near energy gap frequency. This work will enrich our knowledge on the microscopic physics of extraordinary optical transmission at terahertz frequencies and contribute to developing terahertz plasmonic devices. PMID:26498994

  15. Dynamics of Fasciola hepatica transmission in the Andean Patagonian valleys, Argentina.

    PubMed

    Kleiman, Florencia; Pietrokovsky, Silvia; Prepelitchi, Lucila; Carbajo, Aníbal E; Wisnivesky-Colli, Cristina

    2007-04-30

    We described the transmission dynamics of Fasciola hepatica at its southern distribution range. Studies of prevalence and egg output in cattle and population dynamics and infection in snails were performed in a farm in the Andean Patagonian valleys, Argentina, between December 1998 and February 2002. Snail surveys were conducted from spring to autumn. Infection was diagnosed coprologically in the whole herd at the beginning and end of the study, and in a cohort of heifers at the beginning and end of 2001. A twice-a-year anthelmintic treatment was implemented in 1999. The relationship of the variables mentioned above with temperature and rainfall was determined. Lymnaea viatrix showed a life-span of about 15 months and an annual pattern of population dynamics. Specimens were frequently found in temporary environments and lagoons, and rarely in streams. Snail abundance and soil-water availability were directly related in temporary environments and inversely related in lagoons. Overall prevalence in L. viatrix was 0.67% (range: 0.9-14%) and infection was detected in summer and autumn. At the beginning of the study, calves were the least infected age group (15%). Prevalences and median egg counts in grazing animals were similar at the beginning (heifers: 81%, 3.3 epg; cows: 60%, 1.3 epg) and end of the study (heifers and cows: around 51%, 1 epg). Likewise, the prevalence in the cohort of heifers remained similar (around 40%) between surveys. Transmission to cattle was highly effective despite of the short activity period and the low infection rate of snails, and the regular anthelminthic treatment. There would be two seasonal transmission peaks, one in summer-autumn, when infected snails were present, and the other in early spring due to overwintering metacercariae. Some recommendations based on the climatic conditions of the region are provided to minimize snail infection and ultimately to reduce the incidence of fasciolosis in cattle.

  16. Recent developments in dynamic testing of materials

    NASA Astrophysics Data System (ADS)

    Gilat, Amos; Seidt, Jeremy D.

    2015-09-01

    New techniques for dynamic characterization of materials that have been developed in the last three years (since the last DYMAT conference in 2012), and results from recent dynamic testing of Inconel 718 are presented. The first development is a dynamic punch test in which three dimensional Digital Image Correlation (DIC) is used to measure the deformation of the rear surface of a specimen as it being penetrated. The second experimental technique that is under development is a dynamic tension experiment in which full-field strain measurement with DIC and full-field temperature measurement are done simultaneously during the test.

  17. Predicting the Impact of Vaccination on the Transmission Dynamics of Typhoid in South Asia: A Mathematical Modeling Study

    PubMed Central

    Pitzer, Virginia E.; Bowles, Cayley C.; Baker, Stephen; Kang, Gagandeep; Balaji, Veeraraghavan; Farrar, Jeremy J.; Grenfell, Bryan T.

    2014-01-01

    Background Modeling of the transmission dynamics of typhoid allows for an evaluation of the potential direct and indirect effects of vaccination; however, relevant typhoid models rooted in data have rarely been deployed. Methodology/Principal Findings We developed a parsimonious age-structured model describing the natural history and immunity to typhoid infection. The model was fit to data on culture-confirmed cases of typhoid fever presenting to Christian Medical College hospital in Vellore, India from 2000–2012. The model was then used to evaluate the potential impact of school-based vaccination strategies using live oral, Vi-polysaccharide, and Vi-conjugate vaccines. The model was able to reproduce the incidence and age distribution of typhoid cases in Vellore. The basic reproductive number (R0) of typhoid was estimated to be 2.8 in this setting. Vaccination was predicted to confer substantial indirect protection leading to a decrease in the incidence of typhoid in the short term, but (intuitively) typhoid incidence was predicted to rebound 5–15 years following a one-time campaign. Conclusions/Significance We found that model predictions for the overall and indirect effects of vaccination depend strongly on the role of chronic carriers in transmission. Carrier transmissibility was tentatively estimated to be low, consistent with recent studies, but was identified as a pivotal area for future research. It is unlikely that typhoid can be eliminated from endemic settings through vaccination alone. PMID:24416466

  18. Cumulative cultural dynamics and the coevolution of cultural innovation and transmission: an ESS model for panmictic and structured populations.

    PubMed

    Lehmann, L; Feldman, M W; Kaeuffer, R

    2010-11-01

    When individuals in a population can acquire traits through learning, each individual may express a certain number of distinct cultural traits. These traits may have been either invented by the individual himself or acquired from others in the population. Here, we develop a game theoretic model for the accumulation of cultural traits through individual and social learning. We explore how the rates of innovation, decay, and transmission of cultural traits affect the evolutionary stable (ES) levels of individual and social learning and the number of cultural traits expressed by an individual when cultural dynamics are at a steady-state. We explore the evolution of these phenotypes in both panmictic and structured population settings. Our results suggest that in panmictic populations, the ES level of learning and number of traits tend to be independent of the social transmission rate of cultural traits and is mainly affected by the innovation and decay rates. By contrast, in structured populations, where interactions occur between relatives, the ES level of learning and the number of traits per individual can be increased (relative to the panmictic case) and may then markedly depend on the transmission rate of cultural traits. This suggests that kin selection may be one additional solution to Rogers's paradox of nonadaptive culture. © 2010 The Authors. Journal Compilation © 2010 European Society For Evolutionary Biology.

  19. Development of a Pfs25-EPA malaria transmission blocking vaccine as a chemically conjugated nanoparticle.

    PubMed

    Shimp, Richard L; Rowe, Christopher; Reiter, Karine; Chen, Beth; Nguyen, Vu; Aebig, Joan; Rausch, Kelly M; Kumar, Krishan; Wu, Yimin; Jin, Albert J; Jones, David S; Narum, David L

    2013-06-19

    Successful efforts to control infectious diseases have often required the use of effective vaccines. The current global strategy for control of malaria, including elimination and eradication will also benefit from the development of an effective vaccine that interrupts malaria transmission. To this end, a vaccine that disrupts malaria transmission within the mosquito host has been investigated for several decades targeting a 25 kDa ookinete specific surface protein, identified as Pfs25. Phase 1 human trial results using a recombinant Pfs25H/Montanide ISA51 formulation demonstrated that human Pfs25 specific antibodies block parasite infectivity to mosquitoes; however, the extent of blocking was likely insufficient for an effective transmission blocking vaccine. To overcome the poor immunogenicity, processes to produce and characterize recombinant Pfs25H conjugated to a detoxified form of Pseudomonas aeruginosa exoprotein A (EPA) have been developed and used to manufacture a cGMP pilot lot for use in human clinical trials. The Pfs25-EPA conjugate appears as a nanoparticle with an average molar mass in solution of approximately 600 kDa by static light scattering with an average diameter 20 nm (range 10-40 nm) by dynamic light scattering. The molar ratio of Pfs25H to EPA is about 3 to 1 by amino acid analysis, respectively. Outbred mice immunized with the Pfs25-EPA conjugated nanoparticle formulated on Alhydrogel(®) had a 75-110 fold increase in Pfs25H specific antibodies when compared to an unconjugated Pfs25H/Alhydrogel(®) formulation. A phase 1 human trial using the Pfs25-EPA/Alhydrogel(®) formulation is ongoing in the United States.

  20. Development of a Pfs25-EPA malaria transmission blocking vaccine as a chemically conjugated nanoparticle

    PubMed Central

    Shimp, Richard L.; Rowe, Christopher; Reiter, Karine; Chen, Beth; Nguyen, Vu; Aebig, Joan; Rausch, Kelly M.; Kumar, Krishan; Wu, Yimin; Jin, Albert J.; Jones, David S.; Narum, David L.

    2013-01-01

    Successful efforts to control infectious diseases have often required the use of effective vaccines. The current global strategy for control of malaria, including elimination and eradication will also benefit from the development of an effective vaccine that interrupts malaria transmission. To this end, a vaccine that disrupts malaria transmission within the mosquito host has been investigated for several decades targeting a 25 kDa ookinete specific surface protein, identified as Pfs25. Phase 1 human trial results using a recombinant Pfs25H/Montanide ISA51 formulation demonstrated that human Pfs25 specific antibodies block parasite infectivity to mosquitoes; however, the extent of blocking was likely insufficient for an effective transmission blocking vaccine. To overcome the poor immunogenicity, processes to produce and characterize recombinant Pfs25H conjugated to a detoxified form of Pseudomonas aeruginosa exoprotein A (EPA) have been developed and used to manufacture a cGMP pilot lot for use in human clinical trials. The Pfs25-EPA conjugate appears as a nanoparticle with an average molar mass in solution of approximately 600 kDa by static light scattering with an average diameter 20 nm (range 10 to 40 nm) by dynamic light scattering. The molar ratio of Pfs25H to EPA is about 3 to 1 by amino acid analysis, respectively. Outbred mice immunized with the Pfs25-EPA conjugated nanoparticle formulated on Alhydrogel® had a 75 to 110 fold increase in Pfs25H specific antibodies when compared to an unconjugated Pfs25H/Alhydrogel® formulation. A phase 1 human trial using the Pfs25-EPA/Alhydrogel® formulation is ongoing in the United States. PMID:23623858

  1. Transmission dynamics of schistosomiasis in Zimbabwe: A mathematical and GIS Approach

    NASA Astrophysics Data System (ADS)

    Ngarakana-Gwasira, E. T.; Bhunu, C. P.; Masocha, M.; Mashonjowa, E.

    2016-06-01

    Temperature and presence of water bodies are known to influence the transmission dynamics of schistosomiasis. In this work, effects of water bodies (taken in context of rainfall patterns) and temperature from 1950 to 2000 are considered in the model. With the aid of Geographic Information System (GIS), the reproduction number is mapped on the Zimbabwean country. Results of the mapping show high reproduction numbers along the Lowveld and the Zambezi valley catchment area. High reproduction numbers suggest high levels of schistosomiasis. This result suggests more control efforts should be targeted in these areas with high reproduction numbers.

  2. Viral kinetics and exhaled droplet size affect indoor transmission dynamics of influenza infection.

    PubMed

    Chen, S C; Chio, C P; Jou, L J; Liao, C M

    2009-10-01

    The purpose of this paper was to investigate the effects of viral kinetics and exhaled droplet size on indoor transmission dynamics of influenza infection. The target cell-limited model with delayed virus production was adopted to strengthen the inner mechanisms of virus infection on human epithelial cell. The particle number and volume involved in the viral kinetics were linked with Wells-Riley mathematical equation to quantify the infection risk. We investigated population dynamics in a specific elementary school by using the seasonal susceptible - exposed - infected - recovery (SEIR) model. We found that exhaled pulmonary bioaerosol of sneeze (particle diameter <10 microm) have 10(2)-fold estimate higher than that of cough. Sneeze and cough caused risk probabilities range from 0.075 to 0.30 and 0.076, respectively; whereas basic reproduction numbers (R(0)) estimates range from 4 to 17 for sneeze and nearly 4 for cough, indicating sneeze-posed higher infection risk. The viral kinetics and exhaled droplet size for sneeze affect indoor transmission dynamics of influenza infection since date post-infection 1-7. This study provides direct mechanistic support that indoor influenza virus transmission can be characterized by viral kinetics in human upper respiratory tracts that are modulated by exhaled droplet size. Practical Implications This paper provides a predictive model that can integrate the influenza viral kinetics (target cell-limited model), indoor aerosol transmission potential (Wells-Riley mathematical equation), and population dynamic model [susceptible - exposed - infected - recovery (SEIR) model] in a proposed susceptible population. Viral kinetics expresses the competed results of human immunity ability with influenza virus generation. By linking the viral kinetics and different exposure parameters and environmental factors in a proposed school setting with five age groups, the influenza infection risk can be estimated. On the other hand, we implicated

  3. On the relationship between meningococcal transmission dynamics and disease: remarks on humoral immunity.

    PubMed

    Guzzetta, Giorgio; Manfredi, Piero; Gasparini, Roberto; Panatto, Donatella; Edmunds, W John

    2009-05-26

    We consider a model for the transmission dynamics of Neisseria meningitidis which incorporates the humoral immunity hypothesis in an explicit way. The "humoral immunity" hypothesis states that individuals will experience significantly different risks of invasive disease depending on whether they are experiencing their first infection episode, or a subsequent one. The model is fitted to the Stonehouse-Danbury carriage data and to UK disease data. For serogroup C (B) the risk of disease during the first infection episode results to be 100 (400) times higher compared to subsequent ones. Moreover the best-fit corresponds to the situation where N. lactamica essentially always confers cross-protection.

  4. Global dynamics of bidirectional associative memory neural networks involving transmission delays and dead zones.

    PubMed

    Sree Hari Rao, V; Phaneendra, Bh R.M.

    1999-04-01

    In this article, a model describing the activation dynamics of bidirectional associative memory (BAM) neural networks involving transmission delays was considered. The concept of BAM networks employed in this work is improved and it includes the earlier notions known in the literature and is applied to a wider class of networks. Further, we introduced a new notion, as a measure of restoring stability and termed it as a dead zone. In this article, the influence of the presence of dead zones on the global asymptotic stability of the equilibrium pattern was investigated. Existence and uniqueness of an equilibrium pattern under fairly general and easily verifiable conditions were also established.

  5. Dynamic transmission of West Nile virus across the United States-Mexican border.

    PubMed

    Mann, Brian R; McMullen, Allison R; Guzman, Hilda; Tesh, Robert B; Barrett, Alan D T

    2013-02-05

    Confirmed clinical and veterinary cases of West Nile virus (WNV) infection in Mexico remain restricted to northern Mexico, supporting a unidirectional transmission model from the US into Mexico. Full-length genomic sequencing of nine WNV isolates obtained from Culex spp. mosquito pools in El Paso, Texas (n=7) and Cuidad Juarez, Mexico (n=2) from 2005 to 2010 demonstrates the co-circulation of three independent genetic groups, two of which belong to the southwestern (SW/WN03) genotype and the other to the North American (NA/WN02) genotype. These results indicate ongoing dynamic circulation of WNV between the United States and Mexico.

  6. Development of a nanoindenter for in-situ transmission electron microscopy

    SciTech Connect

    Stach, Eric A.; Freeman, Tony; Minor, Andrew M.; Owen, Doug K.; Cumings, John; Wall, Mark A.; Chraska, Tomas; Hull, Robert; Morris Jr., J.W.; Zettl, A.; Dahmen, Ulrich

    2001-01-30

    In-situ transmission electron microscopy is an established experimental technique that permits direct observation of the dynamics and mechanisms of dislocation motion and deformation behavior. In this paper, we detail the development of a novel specimen goniometer that allows real time observations of the mechanical response of materials to indentation loads. The technology of the scanning tunneling microscope is adopted to allow nanometer scale positioning of a sharp, conductive diamond tip onto the edge of an electron transparent sample. This allows application of loads to nanometer-scale material volumes couple with simultaneous imaging of the material response. The emphasis in this paper is experimental and descriptive, with particular attention given to sample geometry and other technical requirements. Examples of the deformation of aluminum and titanium carbide as well as the fracture of silicon will be presented.

  7. Development of new high transmission eaPSM for Negative Tone Development process on wafer

    NASA Astrophysics Data System (ADS)

    Adachi, Takashi; Tani, Ayako; Fujimura, Yukihiro; Yoshikawa, Shingo; Hayano, Katsuya; Morikawa, Yasutaka; Miura, Yoichi; Miyashita, Hiroyuki

    2015-07-01

    The retardation of the development of NGL techniques causes the extension of ArF immersion lithography for 1x-nm node. We have been researching the new phase shift mask's (PSM) material for the next generation ArF lithography. In this reports, we developed the low-k, high transmission PSM and evaluate it. The developed new PSM shows good lithographic performance in wafer and high ArF excimer laser durability. The mask processability were confirmed such as the CD performance, the cross section image, the inspection sensitivity and repair accuracy.

  8. Dynamic Modeling, Chaos, and Cognitive Development.

    ERIC Educational Resources Information Center

    Howe, Mark L.; Rabinowitz, F. Michael

    1994-01-01

    Introduces the essential constructs involved in dynamic modeling, in relation to issues in psychological development. Presents several instances of how the principles of dynamic systems can be translated into mathematical formalism. Concludes that transition is a key invariance in development and that single subject, longitudinal designs are…

  9. Dynamic Modeling, Chaos, and Cognitive Development.

    ERIC Educational Resources Information Center

    Howe, Mark L.; Rabinowitz, F. Michael

    1994-01-01

    Introduces the essential constructs involved in dynamic modeling, in relation to issues in psychological development. Presents several instances of how the principles of dynamic systems can be translated into mathematical formalism. Concludes that transition is a key invariance in development and that single subject, longitudinal designs are…

  10. Cost-effectiveness of dengue vaccination in Yucatán, Mexico using a dynamic dengue transmission model.

    PubMed

    Shim, Eunha

    2017-01-01

    The incidence of dengue fever (DF) is steadily increasing in Mexico, burdening health systems with consequent morbidities and mortalities. On December 9th, 2015, Mexico became the first country for which the dengue vaccine was approved for use. In anticipation of a vaccine rollout, analysis of the cost-effectiveness of the dengue vaccination program that quantifies the dynamics of disease transmission is essential. We developed a dynamic transmission model of dengue in Yucatán, Mexico and its proposed vaccination program to incorporate herd immunity into our analysis of cost-effectiveness analysis. Our model also incorporates important characteristics of dengue epidemiology, such as clinical cross-immunity and susceptibility enhancement upon secondary infection. Using our model, we evaluated the cost-effectiveness and economic impact of an imperfect dengue vaccine in Yucatán, Mexico. Our study indicates that a dengue vaccination program would prevent 90% of cases of symptomatic DF incidence as well as 90% of dengue hemorrhagic fever (DHF) incidence and dengue-related deaths annually. We conclude that a dengue vaccine program in Yucatán, Mexico would be very cost-effective as long as the vaccination cost per individual is less than $140 and $214 from health care and societal perspectives, respectively. Furthermore, at an exemplary vaccination cost of $250 USD per individual on average, dengue vaccination is likely to be cost-effective 43% and 88% of the time from health care and societal perspectives, respectively.

  11. Static behavioral effects on gonorrhea transmission dynamics in a MSM population.

    PubMed

    Morin, Benjamin R; Medina-Rios, Liana; Camacho, Erika T; Castillo-Chavez, Carlos

    2010-11-07

    An SIS/SAS model of gonorrhea transmission in a population of highly active men-having-sex-with-men (MSM) is presented in this paper to study the impact of safe behavior on the dynamics of gonorrhea prevalence. Safe behaviors may fall into two categories-prevention and self-awareness. Prevention will be modeled via consistent condom use and self-awareness via STD testing frequency. Stability conditions for the disease free equilibrium and endemic equilibrium are determined along with a complete analysis of global dynamics. The control reproductive number is used as a means for measuring the effect of changes to model parameters on the prevalence of the disease. We also find that appropriate intervention would be in the form of a multifaceted approach at overall risk reduction rather than tackling one specific control individually. Copyright © 2010 Elsevier Ltd. All rights reserved.

  12. Transmission dynamics and economics of rabies control in dogs and humans in an African city.

    PubMed

    Zinsstag, J; Dürr, S; Penny, M A; Mindekem, R; Roth, F; Menendez Gonzalez, S; Naissengar, S; Hattendorf, J

    2009-09-01

    Human rabies in developing countries can be prevented through interventions directed at dogs. Potential cost-savings for the public health sector of interventions aimed at animal-host reservoirs should be assessed. Available deterministic models of rabies transmission between dogs were extended to include dog-to-human rabies transmission. Model parameters were fitted to routine weekly rabid-dog and exposed-human cases reported in N'Djaména, the capital of Chad. The estimated transmission rates between dogs (beta(d)) were 0.0807 km2/(dogs x week) and between dogs and humans (beta(dh)) 0.0002 km2/(dogs x week). The effective reproductive ratio (R(e)) at the onset of our observations was estimated at 1.01, indicating low-level endemic stability of rabies transmission. Human rabies incidence depended critically on dog-related transmission parameters. We simulated the effects of mass dog vaccination and the culling of a percentage of the dog population on human rabies incidence. A single parenteral dog rabies-mass vaccination campaign achieving a coverage of least 70% appears to be sufficient to interrupt transmission of rabies to humans for at least 6 years. The cost-effectiveness of mass dog vaccination was compared to postexposure prophylaxis (PEP), which is the current practice in Chad. PEP does not reduce future human exposure. Its cost-effectiveness is estimated at US $46 per disability adjusted life-years averted. Cost-effectiveness for PEP, together with a dog-vaccination campaign, breaks even with cost-effectiveness of PEP alone after almost 5 years. Beyond a time-frame of 7 years, it appears to be more cost-effective to combine parenteral dog-vaccination campaigns with human PEP compared to human PEP alone.

  13. Cholera Transmission in Ouest Department of Haiti: Dynamic Modeling and the Future of the Epidemic.

    PubMed

    Kirpich, Alexander; Weppelmann, Thomas A; Yang, Yang; Ali, Afsar; Morris, J Glenn; Longini, Ira M

    2015-01-01

    In the current study, a comprehensive, data driven, mathematical model for cholera transmission in Haiti is presented. Along with the inclusion of short cycle human-to-human transmission and long cycle human-to-environment and environment-to-human transmission, this novel dynamic model incorporates both the reported cholera incidence and remote sensing data from the Ouest Department of Haiti between 2010 to 2014. The model has separate compartments for infectious individuals that include different levels of infectivity to reflect the distribution of symptomatic and asymptomatic cases in the population. The environmental compartment, which serves as a source of exposure to toxigenic V. cholerae, is also modeled separately based on the biology of causative bacterium, the shedding of V. cholerae O1 by humans into the environment, as well as the effects of precipitation and water temperature on the concentration and survival of V. cholerae in aquatic reservoirs. Although the number of reported cholera cases has declined compared to the initial outbreak in 2010, the increase in the number of susceptible population members and the presence of toxigenic V. cholerae in the environment estimated by the model indicate that without further improvements to drinking water and sanitation infrastructures, intermittent cholera outbreaks are likely to continue in Haiti.

  14. Cholera Transmission in Ouest Department of Haiti: Dynamic Modeling and the Future of the Epidemic

    PubMed Central

    Kirpich, Alexander; Weppelmann, Thomas A.; Yang, Yang; Ali, Afsar; Morris, J. Glenn; Longini, Ira M.

    2015-01-01

    In the current study, a comprehensive, data driven, mathematical model for cholera transmission in Haiti is presented. Along with the inclusion of short cycle human-to-human transmission and long cycle human-to-environment and environment-to-human transmission, this novel dynamic model incorporates both the reported cholera incidence and remote sensing data from the Ouest Department of Haiti between 2010 to 2014. The model has separate compartments for infectious individuals that include different levels of infectivity to reflect the distribution of symptomatic and asymptomatic cases in the population. The environmental compartment, which serves as a source of exposure to toxigenic V. cholerae, is also modeled separately based on the biology of causative bacterium, the shedding of V. cholerae O1 by humans into the environment, as well as the effects of precipitation and water temperature on the concentration and survival of V. cholerae in aquatic reservoirs. Although the number of reported cholera cases has declined compared to the initial outbreak in 2010, the increase in the number of susceptible population members and the presence of toxigenic V. cholerae in the environment estimated by the model indicate that without further improvements to drinking water and sanitation infrastructures, intermittent cholera outbreaks are likely to continue in Haiti. PMID:26488620

  15. Strain-specific estimation of epidemic success provides insights into the transmission dynamics of tuberculosis

    PubMed Central

    Rasigade, Jean-Philippe; Barbier, Maxime; Dumitrescu, Oana; Pichat, Catherine; Carret, Gérard; Ronnaux-Baron, Anne-Sophie; Blasquez, Ghislaine; Godin-Benhaim, Christine; Boisset, Sandrine; Carricajo, Anne; Jacomo, Véronique; Fredenucci, Isabelle; Pérouse de Montclos, Michèle; Flandrois, Jean-Pierre; Ader, Florence; Supply, Philip; Lina, Gérard; Wirth, Thierry

    2017-01-01

    The transmission dynamics of tuberculosis involves complex interactions of socio-economic and, possibly, microbiological factors. We describe an analytical framework to infer factors of epidemic success based on the joint analysis of epidemiological, clinical and pathogen genetic data. We derive isolate-specific, genetic distance-based estimates of epidemic success, and we represent success-related time-dependent concepts, namely epidemicity and endemicity, by restricting analysis to specific time scales. The method is applied to analyze a surveillance-based cohort of 1,641 tuberculosis patients with minisatellite-based isolate genotypes. Known predictors of isolate endemicity (older age, native status) and epidemicity (younger age, sputum smear positivity) were identified with high confidence (P < 0.001). Long-term epidemic success also correlated with the ability of Euro-American and Beijing MTBC lineages to cause active pulmonary infection, independent of patient age and country of origin. Our results demonstrate how important insights into the transmission dynamics of tuberculosis can be gained from active surveillance data. PMID:28349973

  16. Performance Analysis of Control Signal Transmission Technique for Cognitive Radios in Dynamic Spectrum Access Networks

    NASA Astrophysics Data System (ADS)

    Sakata, Ren; Tomioka, Tazuko; Kobayashi, Takahiro

    When cognitive radio (CR) systems dynamically use the frequency band, a control signal is necessary to indicate which carrier frequencies are currently available in the network. In order to keep efficient spectrum utilization, this control signal also should be transmitted based on the channel conditions. If transmitters dynamically select carrier frequencies, receivers have to receive control signals without knowledge of their carrier frequencies. To enable such transmission and reception, this paper proposes a novel scheme called DCPT (Differential Code Parallel Transmission). With DCPT, receivers can receive low-rate information with no knowledge of the carrier frequencies. The transmitter transmits two signals whose carrier frequencies are spaced by a predefined value. The absolute values of the carrier frequencies can be varied. When the receiver acquires the DCPT signal, it multiplies the signal by a frequency-shifted version of the signal; this yields a DC component that represents the data signal which is then demodulated. The performance was evaluated by means of numerical analysis and computer simulation. We confirmed that DCPT operates successfully even under severe interference if its parameters are appropriately configured.

  17. Complexities in using sentinel pigs to study Taenia solium transmission dynamics under field conditions.

    PubMed

    Devleesschauwer, Brecht; Aryal, Arjun; Tharmalingam, Jayaraman; Joshi, Durga Datt; Rijal, Suman; Speybroeck, Niko; Gabriël, Sarah; Victor, Bjorn; Dorny, Pierre

    2013-03-31

    The transmission dynamics of the pork tapeworm, Taenia solium, remain a matter of research and debate. In a longitudinal field study performed in southeastern Nepal, 18 sentinel pigs were serologically monitored to study the field kinetics of Taenia antigens and anti-T. solium antibodies. At the end of the twelve months' study period, necropsy was performed and suspected lesions were subjected to molecular identification of the Taenia species. The study generated new hypotheses on the transmission dynamics of Taenia spp. and exposed crucial complexities in the use of sentinel pigs in longitudinal field studies. Sentinel pigs can be useful epidemiological tools, but their use should be thoroughly planned before initiating a study and carefully monitored throughout the course of the study. Important aspects to be considered are those affecting the pig's susceptibility to infection, such as passive immunity, age, hormonal levels, and infection with competing Taenia species. In addition, serological test results should be interpreted considering possible cross-reactions and with proper understanding of the significance of a positive test result.

  18. Transmission dynamics of an emerging infectious disease in wildlife through host reproductive cycles

    PubMed Central

    Uchii, Kimiko; Telschow, Arndt; Minamoto, Toshifumi; Yamanaka, Hiroki; Honjo, Mie N; Matsui, Kazuaki; Kawabata, Zen'ichiro

    2011-01-01

    Emerging infectious diseases are major threats to wildlife populations. To enhance our understanding of the dynamics of these diseases, we investigated how host reproductive behavior and seasonal temperature variation drive transmission of infections among wild hosts, using the model system of cyprinid herpesvirus 3 (CyHV-3) disease in common carp. Our main findings were as follows: (1) a seroprevalence survey showed that CyHV-3 infection occurred mostly in adult hosts, (2) a quantitative assay for CyHV-3 in a host population demonstrated that CyHV-3 was most abundant in the spring when host reproduction occurred and water temperature increased simultaneously and (3) an analysis of the dynamics of CyHV-3 in water revealed that CyHV-3 concentration increased markedly in breeding habitats during host group mating. These results indicate that breeding habitats can become hot spots for transmission of infectious diseases if hosts aggregate for mating and the activation of pathogens occurs during the host breeding season. PMID:20740025

  19. ATLAS Phase-II-Upgrade Pixel data transmission development

    NASA Astrophysics Data System (ADS)

    Wensing, M.

    2017-01-01

    The ATLAS tracking system will be replaced by an all-silicon detector in the course of the planned upgrade of the Large Hadron Collider around 2025. The readout of the new pixel system will be most challenging in terms of data rate and readout speed. Simulations of the on-detector electronics based on the currently foreseen trigger rate of 1 MHz indicate that a readout speed of up to 5 Gbit/s per data link is necessary. Due to radiation levels, the first part of transmission has to be implemented electrically. System simulation and test results of cable candidates will be presented.

  20. An agent-based model for the transmission dynamics of Toxoplasma gondii.

    PubMed

    Jiang, Wen; Sullivan, Adam M; Su, Chunlei; Zhao, Xiaopeng

    2012-01-21

    Toxoplasma gondii (T. gondii) is a unicellular protozoan that infects up to one-third of the world's human population. Numerous studies revealed that a latent infection of T. gondii can cause life-threatening encephalitis in immunocompromised people and also has significant effects on the behavior of healthy people and animals. However, the overall transmission of T. gondii has not been well understood although many factors affecting this process have been found out by different biologists separately. Here we synthesize what is currently known about the natural history of T. gondii by developing a prototype agent-based model to mimic the transmission process of T. gondii in a farm system. The present model takes into account the complete life cycle of T. gondii, which includes the transitions of the parasite from cats to environment through feces, from contaminated environment to mice through oocysts, from mice to cats through tissue cysts, from environment to cats through oocysts as well as the vertical transmission among mice. Although the current model does not explicitly include humans and other end-receivers, the effect of the transition to end-receivers is estimated by a developed infection risk index. The current model can also be extended to include human activities and thus be used to investigate the influences of human management on disease control. Simulation results reveal that most cats are infected through preying on infected mice while mice are infected through vertical transmission more often than through infection with oocysts, which clearly suggests the important role of mice during the transmission of T. gondii. Furthermore, our simulation results show that decreasing the number of mice on a farm can lead to the eradication of the disease and thus can lower the infection risk of other intermediate hosts on the farm. In addition, with the assumption that the relation between virulence and transmission satisfies a normal function, we show that

  1. SSME structural dynamic model development

    NASA Technical Reports Server (NTRS)

    Foley, Michael J.

    1989-01-01

    The high pressure fuel turbopump (HPFTP) is a major component of the Space Shuttle Main Engine (SSME) powerhead. The device is a three stage centrifugal pump that is directly driven by a two stage hot gas turbine. The purpose of the pump is to deliver fuel (liquid hydrogen) from the low pressure fuel turbopump (LPFTP) through the main fuel valve (MFV) to the thrust chamber coolant circuits. In doing so, the pump pressurizes the fuel from an inlet pressure of approximately 178 psi to a discharge pressure of over 6000 psi. At full power level (FPL), the pump rotates at a speed of over 37,000 rpm while generating approximately 77,000 horsepower. Obviously, a pump failure at these speeds and power levels could jeopardize the mission. Results are summarized for work in which the solutions obtained from analytical models of the fuel turbopump impellers are compared with the results obtained from dynamic tests.

  2. Injecting epidemiology into population viability analysis: avian cholera transmission dynamics at an arctic seabird colony.

    PubMed

    Iverson, Samuel A; Gilchrist, H Grant; Soos, Catherine; Buttler, Isabel I; Harms, N Jane; Forbes, Mark R

    2016-11-01

    Infectious diseases have the potential to spread rapidly and cause high mortality within populations of immunologically naïve hosts. The recent appearance of avian cholera, a highly virulent disease of birds caused by the bacterium Pasteurella multocida, at remote Arctic seabird colonies is an emerging conservation concern. Determining disease risk to population viability requires a quantitative understanding of transmission potential and the factors that regulate epidemic persistence. Estimates of the basic (R0 ) and real-time (Rt ) reproductive number are critical in this regard - enumerating the number of secondary infections caused by each primary infection in a newly invaded host population and the decline in transmission rate as susceptible individuals are removed via mortality or immunized recovery. Here, we use data collected at a closely monitored common eider (Somateria mollissima) breeding colony located in the Canadian Arctic to examine transmission and host population dynamics. Specifically, we infer epidemic curves from daily mortality observations and use a likelihood-based procedure to estimate changes in the reproductive number over a series of annual outbreaks. These data are interpreted in relation to concurrent changes in host numbers to assess local extinction risk. Consistent with expectations for a novel pathogen invasion, case incidence increased exponentially during the initial wave of exposure (R0  = 2·5; generation time = 6·5 days ± 1·1 SD). Disease conditions gradually abated, but only after several years of smouldering infection (Rt  ≈ 1). In total, 6194 eider deaths were recorded during outbreaks spanning eight consecutive breeding seasons. Breeding pair abundance declined by 56% from the pre-outbreak peak; however, a robust population of >4000 pairs remained intact upon epidemic fade-out. Overall, outbreak patterns were consistent with herd immunity acting as a mitigating factor governing in the extent and duration of

  3. Comparison of transmission dynamics between Streptococcus uberis and Streptococcus agalactiae intramammary infections.

    PubMed

    Leelahapongsathon, Kansuda; Schukken, Ynte Hein; Pinyopummintr, Tanu; Suriyasathaporn, Witaya

    2016-02-01

    parameter and R0 values were not different between both pathogens; however, the duration of infection for Strep. agalactiae was longer than Strep. uberis. These suggest that Strep. uberis may have a different transmission dynamic compared with Strep. agalactiae.

  4. Long-term evolution and transmission dynamics of swine influenza A virus.

    PubMed

    Vijaykrishna, Dhanasekaran; Smith, Gavin J D; Pybus, Oliver G; Zhu, Huachen; Bhatt, Samir; Poon, Leo L M; Riley, Steven; Bahl, Justin; Ma, Siu K; Cheung, Chung L; Perera, Ranawaka A P M; Chen, Honglin; Shortridge, Kennedy F; Webby, Richard J; Webster, Robert G; Guan, Yi; Peiris, J S Malik

    2011-05-26

    Swine influenza A viruses (SwIV) cause significant economic losses in animal husbandry as well as instances of human disease and occasionally give rise to human pandemics, including that caused by the H1N1/2009 virus. The lack of systematic and longitudinal influenza surveillance in pigs has hampered attempts to reconstruct the origins of this pandemic. Most existing swine data were derived from opportunistic samples collected from diseased pigs in disparate geographical regions, not from prospective studies in defined locations, hence the evolutionary and transmission dynamics of SwIV are poorly understood. Here we quantify the epidemiological, genetic and antigenic dynamics of SwIV in Hong Kong using a data set of more than 650 SwIV isolates and more than 800 swine sera from 12 years of systematic surveillance in this region, supplemented with data stretching back 34 years. Intercontinental virus movement has led to reassortment and lineage replacement, creating an antigenically and genetically diverse virus population whose dynamics are quantitatively different from those previously observed for human influenza viruses. Our findings indicate that increased antigenic drift is associated with reassortment events and offer insights into the emergence of influenza viruses with epidemic potential in swine and humans.

  5. Evidence against proteoglycan mediated collagen fibril load transmission and dynamic viscoelasticity in tendon.

    PubMed

    Fessel, Gion; Snedeker, Jess G

    2009-10-01

    The glycosaminoglycan (GAG) dermatan sulfate and chondroitin sulfate side-chains of small leucine-rich proteoglycans have been increasingly posited to act as molecular cross links between adjacent collagen fibrils and to directly contribute to tendon elasticity. GAGs have also been implicated in tendon viscoelasticity, supposedly affecting frictional loss during elongation or fluid flow through the extra cellular matrix. The current study sought to systematically test these theories of tendon structure-function by investigating the mechanical repercussions of enzymatic depletion of GAG complexes by chondroitinase ABC in a reproducible tendon structure-function model (rat tail tendon fascicles). The extent of GAG removal (at least 93%) was verified by relevant spectrophotometric assays and transmission electron microscopy. Dynamic viscoelastic tensile tests on GAG depleted rat tail tendon fascicle were not mechanically different from controls in storage modulus (elastic behavior) over a wide range of strain-rates (0.05, 0.5, and 5% change in length per second) in either the linear or nonlinear regions of the material curve. Loss modulus (viscoelastic behavior) was only affected in the nonlinear region at the highest strain-rate, and even this effect was marginal (19% increased loss modulus, p=0.035). Thus glycosaminoglycan chains of small leucine-rich proteoglycans do not appear to mediate dynamic elastic behavior nor do they appear to regulate the dynamic viscoelastic properties in rat tail tendon fascicles.

  6. In Situ Transmission Electron Microscopy And Spectroscopy Studies Of Rechargeable Batteries Under Dynamic Operating Conditions: A Retrospective And Perspective View

    SciTech Connect

    Wang, Chong M.

    2015-02-14

    Since the advent of the transmission electron microscope (TEM), continuing efforts have been made to image material under native and reaction environments that typically involve liquids, gases, and external stimuli. With the advances of aberration-corrected TEM for improving the imaging resolution, steady progress has been made on developing methodologies that allow imaging under dynamic operating conditions, or in situ TEM imaging. The success of in situ TEM imaging is closely associated with advances in microfabrication techniques that enable manipulation of nanoscale objects around the objective lens of the TEM. This paper summarizes and highlights recent progress involving in situ TEM studies of energy storage materials, especially rechargeable batteries. The paper is organized to cover both the in situ TEM techniques and the scientific discoveries made possible by in situ TEM imaging.

  7. Dynamics of Salmonella transmission on a British pig grower-finisher farm: a stochastic model

    PubMed Central

    HILL, A. A.; SNARY, E. L.; ARNOLD, M. E.; ALBAN, L.; COOK, A. J. C.

    2008-01-01

    SUMMARY Previous modelling studies have estimated that between 1% and 10% of human salmonella infections are attributable to pig meat consumption. In response to this food safety threat the British pig industry have initiated a salmonella monitoring programme. It is anticipated that this programme will contribute to achieving a UK Food Standards Agency target for reducing salmonella levels in pigs at slaughter by 50% within 5 years. In order to better inform the monitoring programme, we have developed a stochastic transmission model for salmonella in a specialist grower-finisher pig herd, where data from a Danish longitudinal study have been used to estimate some of the key model parameters. The model estimates that about 17% of slaughter-age pigs will be infected with salmonella, and that of these infected pigs about 4% will be excreting the organism. In addition, the model shows that the most effective control strategies will be those that reduce between-pen transmission. PMID:17475090

  8. Clocking the anisotropic lattice dynamics of multi-walled carbon nanotubes by four-dimensional ultrafast transmission electron microscopy.

    PubMed

    Cao, Gaolong; Sun, Shuaishuai; Li, Zhongwen; Tian, Huanfang; Yang, Huaixin; Li, Jianqi

    2015-02-12

    Recent advances in the four-dimensional ultrafast transmission electron microscope (4D-UTEM) with combined spatial and temporal resolutions have made it possible to directly visualize structural dynamics of materials at the atomic level. Herein, we report on our development on a 4D-UTEM which can be operated properly on either the photo-emission or the thermionic mode. We demonstrate its ability to obtain sequences of snapshots with high spatial and temporal resolutions in the study of lattice dynamics of the multi-walled carbon nanotubes (MWCNTs). This investigation provides an atomic level description of remarkable anisotropic lattice dynamics at the picosecond timescales. Moreover, our UTEM measurements clearly reveal that distinguishable lattice relaxations appear in intra-tubular sheets on an ultrafast timescale of a few picoseconds and after then an evident lattice expansion along the radial direction. These anisotropic behaviors in the MWCNTs are considered arising from the variety of chemical bonding, i.e. the weak van der Waals bonding between the tubular planes and the strong covalent sp(2)-hybridized bonds in the tubular sheets.

  9. Clocking the anisotropic lattice dynamics of multi-walled carbon nanotubes by four-dimensional ultrafast transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Cao, Gaolong; Sun, Shuaishuai; Li, Zhongwen; Tian, Huanfang; Yang, Huaixin; Li, Jianqi

    2015-02-01

    Recent advances in the four-dimensional ultrafast transmission electron microscope (4D-UTEM) with combined spatial and temporal resolutions have made it possible to directly visualize structural dynamics of materials at the atomic level. Herein, we report on our development on a 4D-UTEM which can be operated properly on either the photo-emission or the thermionic mode. We demonstrate its ability to obtain sequences of snapshots with high spatial and temporal resolutions in the study of lattice dynamics of the multi-walled carbon nanotubes (MWCNTs). This investigation provides an atomic level description of remarkable anisotropic lattice dynamics at the picosecond timescales. Moreover, our UTEM measurements clearly reveal that distinguishable lattice relaxations appear in intra-tubular sheets on an ultrafast timescale of a few picoseconds and after then an evident lattice expansion along the radial direction. These anisotropic behaviors in the MWCNTs are considered arising from the variety of chemical bonding, i.e. the weak van der Waals bonding between the tubular planes and the strong covalent sp2-hybridized bonds in the tubular sheets.

  10. Red alder stand development and dynamics.

    Treesearch

    R.L. Deal

    2006-01-01

    This paper synthesizes information on the development of natural pure red alder stands and dynamics of mixed alder-conifer stands. Early research on red alder growth and yield focused on developing stand volume and normal yield. tables for alder in the Pacific Northwest. Recent site-index estimation and height-growth curves were developed on a 20-year site base age....

  11. Dynamical Systems Approaches to Emotional Development

    ERIC Educational Resources Information Center

    Camras, Linda A.; Witherington, David C.

    2005-01-01

    Within the last 20 years, transitions in the conceptualization of emotion and its development have given rise to calls for an explanatory framework that captures emotional development in all its organizational complexity and variability. Recent attempts have been made to couch emotional development in terms of a dynamical systems approach through…

  12. Dynamics of African swine fever virus shedding and excretion in domestic pigs infected by intramuscular inoculation and contact transmission.

    PubMed

    Guinat, Claire; Reis, Ana Luisa; Netherton, Christopher L; Goatley, Lynnette; Pfeiffer, Dirk U; Dixon, Linda

    2014-09-26

    African swine fever virus (ASFV) is a highly virulent swine pathogen that has spread across Eastern Europe since 2007 and for which there is no effective vaccine or treatment available. The dynamics of shedding and excretion is not well known for this currently circulating ASFV strain. Therefore, susceptible pigs were exposed to pigs intramuscularly infected with the Georgia 2007/1 ASFV strain to measure those dynamics through within- and between-pen transmission scenarios. Blood, oral, nasal and rectal fluid samples were tested for the presence of ASFV by virus titration (VT) and quantitative real-time polymerase chain reaction (qPCR). Serum was tested for the presence of ASFV-specific antibodies. Both intramuscular inoculation and contact transmission resulted in development of acute disease in all pigs although the experiments indicated that the pathogenesis of the disease might be different, depending on the route of infection. Infectious ASFV was first isolated in blood among the inoculated pigs by day 3, and then chronologically among the direct and indirect contact pigs, by day 10 and 13, respectively. Close to the onset of clinical signs, higher ASFV titres were found in blood compared with nasal and rectal fluid samples among all pigs. No infectious ASFV was isolated in oral fluid samples although ASFV genome copies were detected. Only one animal developed antibodies starting after 12 days post-inoculation. The results provide quantitative data on shedding and excretion of the Georgia 2007/1 ASFV strain among domestic pigs and suggest a limited potential of this isolate to cause persistent infection.

  13. The index case is not enough: Variation among individuals, groups and social networks modify bacterial transmission dynamics.

    PubMed

    Keiser, Carl N; Pinter-Wollman, Noa; Ziemba, Michael J; Kothamasu, Krishna S; Pruitt, Jonathan N

    2017-07-10

    The traits of the index case of an infectious disease outbreak, and the circumstances for their aetiology, potentially influence the trajectory of transmission dynamics. However, these dynamics likely also depend on the traits of the individuals with whom the index case interacts. We used the social spider Stegodyphus dumicola to test how the traits of the index case, group phenotypic composition and group size interact to facilitate the transmission of a GFP-labelled cuticular bacterium. We also compared bacterial transmission across experimentally generated "daisy-chain" vs. "star" networks of social interactions. Finally, we compared social network structure across groups of different sizes. Groups of 10 spiders experienced more bacterial transmission events compared to groups of 30 spiders, regardless of groups' behavioural composition. Groups containing only one bold spider experienced the lowest levels of bacterial transmission regardless of group size. We found no evidence for the traits of the index case influencing any transmission dynamics. In a second experiment, bacteria were transmitted to more individuals in experimentally induced star networks than in daisy-chains, on which transmission never exceeded three steps. In both experimental network types, transmission success depended jointly on the behavioural traits of the interacting individuals; however, the behavioural traits of the index case were only important for transmission on star networks. Larger social groups exhibited lower interaction density (i.e. had a low ratio of observed to possible connections) and were more modular, i.e. they had more connections between nodes within a subgroup and fewer connections across subgroups. Thus, larger groups may restrict transmission by forming fewer interactions and by isolating subgroups that interacted with the index case. These findings suggest that accounting for the traits of single exposed hosts has less power in predicting transmission dynamics

  14. Intergenerational Wealth Transmission and the Dynamics of Inequality in Small-Scale Societies*

    PubMed Central

    Mulder, Monique Borgerhoff; Bowles, Samuel; Hertz, Tom; Bell, Adrian; Beise, Jan; Clark, Greg; Fazzio, Ila; Gurven, Michael; Hill, Kim; Hooper, Paul L.; Irons, William; Kaplan, Hillard; Leonetti, Donna; Low, Bobbi; Marlowe, Frank; McElreath, Richard; Naidu, Suresh; Nolin, David; Piraino, Patrizio; Quinlan, Rob; Schniter, Eric; Sear, Rebecca; Shenk, Mary; Smith, Eric Alden; von Rueden, Christopher; Wiessner, Polly

    2009-01-01

    Small-scale human societies range from foraging bands with a strong egalitarian ethos to more economically stratified agrarian and pastoral societies. We explain this variation in inequality using a dynamic model in which a population’s long-run steady-state level of inequality depends on the extent to which its most important forms of wealth are transmitted within families across generations. We estimate the degree of intergenerational transmission of three different types of wealth (material, embodied, and relational) as well as the extent of wealth inequality in 21 historical and contemporary populations. We show that intergenerational transmission of wealth and wealth inequality are substantial among pastoral and small-scale agricultural societies (on a par with or even exceeding the most unequal modern industrial economies) and quite limited among horticultural and foraging peoples (equivalent to the most egalitarian of modern industrial populations). Differences in the technology by which a people derive their livelihood and in the institutions and norms making up the economic system jointly contribute to this pattern. PMID:19900925

  15. Transmission Loss Calculation using A and B Loss Coefficients in Dynamic Economic Dispatch Problem

    NASA Astrophysics Data System (ADS)

    Jethmalani, C. H. Ram; Dumpa, Poornima; Simon, Sishaj P.; Sundareswaran, K.

    2016-04-01

    This paper analyzes the performance of A-loss coefficients while evaluating transmission losses in a Dynamic Economic Dispatch (DED) Problem. The performance analysis is carried out by comparing the losses computed using nominal A loss coefficients and nominal B loss coefficients in reference with load flow solution obtained by standard Newton-Raphson (NR) method. Density based clustering method based on connected regions with sufficiently high density (DBSCAN) is employed in identifying the best regions of A and B loss coefficients. Based on the results obtained through cluster analysis, a novel approach in improving the accuracy of network loss calculation is proposed. Here, based on the change in per unit load values between the load intervals, loss coefficients are updated for calculating the transmission losses. The proposed algorithm is tested and validated on IEEE 6 bus system, IEEE 14 bus, system IEEE 30 bus system and IEEE 118 bus system. All simulations are carried out using SCILAB 5.4 (www.scilab.org) which is an open source software.

  16. Transmission dynamics of malaria in four selected ecological zones of Nigeria in the rainy season.

    PubMed

    Okwa, O O; Akinmolayan, F I; Carter, V; Hurd, H

    2009-01-01

    Two of the problems of malaria parasite vector control in Nigeria are the diversity of Anopheline vectors and large size of the country. Anopheline distribution and transmission dynamics of malaria were therefore compared between four ecotypes in Nigeria during the rainy season. Polymerase chain reaction (PCR) was used in molecular identification after morphological identification microscopically. Enzyme linked immunosorbent assay (ELISA) was used for the blood meal analysis and sporozoite detection. Five species were identified out of 16,410 anophelines collected. An. gambiae s.s made up approximately 29.2%-36.6% of the population in each zone. All five species acted as vectors for P. falciparum. An. gambiae s.s had the highest sporozoite rate. The most infected mosquitoes were found in the rain forest. More blood meals were taken from bovids, except the savannah forest, where 73.3% were on humans and Human Blood index (HBI) was 57.3%. The Entomological inoculation rate (EIR) was a mean of 13.6 ib/p but was highest in the rainforest zone. This study demonstrates the complex distribution of anophelines and the considerable variations in the intensity of malaria transmission in Nigeria. We highlight the need to consider diverse epidemiological situations when planning countrywide control programmes.

  17. Gametocyte Dynamics and the Role of Drugs in Reducing the Transmission Potential of Plasmodium vivax

    PubMed Central

    Douglas, Nicholas M.; Simpson, Julie A.; Phyo, Aung Pyae; Siswantoro, Hadjar; Hasugian, Armedy R.; Kenangalem, Enny; Poespoprodjo, Jeanne Rini; Singhasivanon, Pratap; Anstey, Nicholas M.; White, Nicholas J.; Tjitra, Emiliana; Nosten, Francois; Price, Ric N.

    2013-01-01

    Background. Designing interventions that will reduce transmission of vivax malaria requires knowledge of Plasmodium vivax gametocyte dynamics. Methods. We analyzed data from a randomized controlled trial in northwestern Thailand and 2 trials in Papua, Indonesia, to identify and compare risk factors for vivax gametocytemia at enrollment and following treatment. Results. A total of 492 patients with P. vivax infections from Thailand and 476 patients (162 with concurrent falciparum parasitemia) from Indonesia were evaluable. Also, 84.3% (415/492) and 66.6% (209/314) of patients with monoinfection were gametocytemic at enrollment, respectively. The ratio of gametocytemia to asexual parasitemia did not differ between acute and recurrent infections (P = .48 in Thailand, P = .08 in Indonesia). High asexual parasitemia was associated with an increased risk of gametocytemia during follow-up in both locations. In Thailand, the cumulative incidence of gametocytemia between day 7 and day 42 following dihydroartemisinin + piperaquine (DHA + PIP) was 6.92% vs 29.1% following chloroquine (P < .001). In Indonesia, the incidence of gametocytemia was 33.6% following artesunate + amodiaquine (AS + AQ), 7.42% following artemether + lumefantrine, and 6.80% following DHA + PIP (P < .001 for DHA + PIP vs AS + AQ). Conclusions. P. vivax gametocyte carriage mirrors asexual-stage infection. Prevention of relapses, particularly in those with high asexual parasitemia, is likely the most important strategy for interrupting P. vivax transmission. PMID:23766527

  18. Genetic diversity, transmission dynamics and drug resistance of Mycobacterium tuberculosis in Angola.

    PubMed

    Perdigão, João; Clemente, Sofia; Ramos, Jorge; Masakidi, Pedro; Machado, Diana; Silva, Carla; Couto, Isabel; Viveiros, Miguel; Taveira, Nuno; Portugal, Isabel

    2017-02-23

    Tuberculosis (TB) poses a serious public health problem in Angola. No surveillance data on drug resistance is available and nothing is known regarding the genetic diversity and population structure of circulating Mycobacterium tuberculosis strains. Here, we have genotyped and evaluated drug susceptibility of 89 Mycobacterium tuberculosis clinical isolates from Luanda. Thirty-three different spoligotype profiles corresponding to 24 different Shared International Types (SIT) and 9 orphan profiles were detected. SIT 20 (LAM1) was the most prevalent (n = 16, 18.2%) followed by SIT 42 (LAM9; n = 15, 17.1%). Overall, the M. tuberculosis population structure in this sample was dominated by LAM (64.8%) and T (33.0%) strains. Twenty-four-loci MIRU-VNTR analysis revealed that a total of 13 isolates were grouped in 5 distinct clusters. Drug susceptibility data showed that 22 (24.7%) of the 89 clinical isolates were resistant to one or more antibacillary drugs of which 4 (4.5%) were multidrug resistant. In conclusion, this study demonstrates a high predominance of LAM strains circulating in the Luanda setting and the presence of recent transmission events. The rate and the emergence dynamics of drug resistant TB found in this sample are significant and highlight the need of further studies specifically focused on MDR-TB transmission.

  19. Dynamical tuning between nearly perfect reflection, absorption, and transmission of light via graphene/dielectric structures

    PubMed Central

    Linder, Jacob; Halterman, Klaus

    2016-01-01

    Exerting well-defined control over the reflection (R), absorption (A), and transmission (T) of electromagnetic waves is a key objective in quantum optics. To this end, one often utilizes hybrid structures comprised of elements with different optical properties in order to achieve features such as high R or high A for incident light. A desirable goal would be the possibility to tune between all three regimes of nearly perfect reflection, absorption, and transmission within the same device, thus swapping between the cases R → 1, A → 1, and T → 1 dynamically. We here show that a dielectric interfaced with a graphene layer on each side allows for precisely this: by tuning only the Fermi level of graphene, all three regimes can be reached in the THz regime and below. Moreover, we show that the inclusion of cylindrical defects in the system offers a different type of control of the scattering of electromagnetic waves by means of the graphene layers. PMID:27917886

  20. Modeling dynamic interactions between pre-exposure prophylaxis interventions & treatment programs: predicting HIV transmission & resistance

    PubMed Central

    Supervie, Virginie; Barrett, Meagan; Kahn, James S.; Musuka, Godfrey; Moeti, Themba Lebogang; Busang, Lesogo; Blower, Sally

    2011-01-01

    Clinical trials have recently demonstrated the effectiveness of Pre-Exposure Prophylaxis (PrEP) in preventing HIV infection. Consequently, PrEP may soon be used for epidemic control. We model the dynamic interactions that will occur between treatment programs and potential PrEP interventions in resource-constrained countries. We determine the consequences for HIV transmission and drug resistance. We use response hypersurface modeling to predict the effect of PrEP on decreasing transmission as a function of effectiveness, adherence and coverage. We predict PrEP will increase need for second-line therapies (SLT) for treatment-naïve individuals, but could significantly decrease need for SLT for treatment-experienced individuals. If the rollout of PrEP is carefully planned it could increase the sustainability of treatment programs. If not, need for SLT could increase and the sustainability of treatment programs could be compromised. Our results show the optimal strategy for rolling out PrEP in resource-constrained countries is to begin around the “worst” treatment programs. PMID:22355700

  1. Genetic diversity, transmission dynamics and drug resistance of Mycobacterium tuberculosis in Angola

    PubMed Central

    Perdigão, João; Clemente, Sofia; Ramos, Jorge; Masakidi, Pedro; Machado, Diana; Silva, Carla; Couto, Isabel; Viveiros, Miguel; Taveira, Nuno; Portugal, Isabel

    2017-01-01

    Tuberculosis (TB) poses a serious public health problem in Angola. No surveillance data on drug resistance is available and nothing is known regarding the genetic diversity and population structure of circulating Mycobacterium tuberculosis strains. Here, we have genotyped and evaluated drug susceptibility of 89 Mycobacterium tuberculosis clinical isolates from Luanda. Thirty-three different spoligotype profiles corresponding to 24 different Shared International Types (SIT) and 9 orphan profiles were detected. SIT 20 (LAM1) was the most prevalent (n = 16, 18.2%) followed by SIT 42 (LAM9; n = 15, 17.1%). Overall, the M. tuberculosis population structure in this sample was dominated by LAM (64.8%) and T (33.0%) strains. Twenty-four-loci MIRU-VNTR analysis revealed that a total of 13 isolates were grouped in 5 distinct clusters. Drug susceptibility data showed that 22 (24.7%) of the 89 clinical isolates were resistant to one or more antibacillary drugs of which 4 (4.5%) were multidrug resistant. In conclusion, this study demonstrates a high predominance of LAM strains circulating in the Luanda setting and the presence of recent transmission events. The rate and the emergence dynamics of drug resistant TB found in this sample are significant and highlight the need of further studies specifically focused on MDR-TB transmission. PMID:28230095

  2. Dynamical tuning between nearly perfect reflection, absorption, and transmission of light via graphene/dielectric structures.

    PubMed

    Linder, Jacob; Halterman, Klaus

    2016-12-05

    Exerting well-defined control over the reflection (R), absorption (A), and transmission (T) of electromagnetic waves is a key objective in quantum optics. To this end, one often utilizes hybrid structures comprised of elements with different optical properties in order to achieve features such as high R or high A for incident light. A desirable goal would be the possibility to tune between all three regimes of nearly perfect reflection, absorption, and transmission within the same device, thus swapping between the cases R → 1, A → 1, and T → 1 dynamically. We here show that a dielectric interfaced with a graphene layer on each side allows for precisely this: by tuning only the Fermi level of graphene, all three regimes can be reached in the THz regime and below. Moreover, we show that the inclusion of cylindrical defects in the system offers a different type of control of the scattering of electromagnetic waves by means of the graphene layers.

  3. Intergenerational wealth transmission and the dynamics of inequality in small-scale societies.

    PubMed

    Borgerhoff Mulder, Monique; Bowles, Samuel; Hertz, Tom; Bell, Adrian; Beise, Jan; Clark, Greg; Fazzio, Ila; Gurven, Michael; Hill, Kim; Hooper, Paul L; Irons, William; Kaplan, Hillard; Leonetti, Donna; Low, Bobbi; Marlowe, Frank; McElreath, Richard; Naidu, Suresh; Nolin, David; Piraino, Patrizio; Quinlan, Rob; Schniter, Eric; Sear, Rebecca; Shenk, Mary; Smith, Eric Alden; von Rueden, Christopher; Wiessner, Polly

    2009-10-30

    Small-scale human societies range from foraging bands with a strong egalitarian ethos to more economically stratified agrarian and pastoral societies. We explain this variation in inequality using a dynamic model in which a population's long-run steady-state level of inequality depends on the extent to which its most important forms of wealth are transmitted within families across generations. We estimate the degree of intergenerational transmission of three different types of wealth (material, embodied, and relational), as well as the extent of wealth inequality in 21 historical and contemporary populations. We show that intergenerational transmission of wealth and wealth inequality are substantial among pastoral and small-scale agricultural societies (on a par with or even exceeding the most unequal modern industrial economies) but are limited among horticultural and foraging peoples (equivalent to the most egalitarian of modern industrial populations). Differences in the technology by which a people derive their livelihood and in the institutions and norms making up the economic system jointly contribute to this pattern.

  4. The impact of media coverage on the transmission dynamics of human influenza

    PubMed Central

    2011-01-01

    Background There is an urgent need to understand how the provision of information influences individual risk perception and how this in turn shapes the evolution of epidemics. Individuals are influenced by information in complex and unpredictable ways. Emerging infectious diseases, such as the recent swine flu epidemic, may be particular hotspots for a media-fueled rush to vaccination; conversely, seasonal diseases may receive little media attention, despite their high mortality rate, due to their perceived lack of newness. Methods We formulate a deterministic transmission and vaccination model to investigate the effects of media coverage on the transmission dynamics of influenza. The population is subdivided into different classes according to their disease status. The compartmental model includes the effect of media coverage on reporting the number of infections as well as the number of individuals successfully vaccinated. Results A threshold parameter (the basic reproductive ratio) is analytically derived and used to discuss the local stability of the disease-free steady state. The impact of costs that can be incurred, which include vaccination, education, implementation and campaigns on media coverage, are also investigated using optimal control theory. A simplified version of the model with pulse vaccination shows that the media can trigger a vaccinating panic if the vaccine is imperfect and simplified messages result in the vaccinated mixing with the infectives without regard to disease risk. Conclusions The effects of media on an outbreak are complex. Simplified understandings of disease epidemiology, propogated through media soundbites, may make the disease significantly worse. PMID:21356134

  5. Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

    PubMed Central

    Hermannsdörfer, Justus; de Jonge, Niels

    2017-01-01

    Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline. PMID:28190028

  6. Variation in Malaria Transmission Dynamics in Three Different Sites in Western Kenya

    PubMed Central

    Imbahale, S. S.; Mukabana, W. R.; Orindi, B.; Githeko, A. K.; Takken, W.

    2012-01-01

    The main objective was to investigate malaria transmission dynamics in three different sites, two highland villages (Fort Ternan and Lunyerere) and a lowland peri-urban area (Nyalenda) of Kisumu city. Adult mosquitoes were collected using PSC and CDC light trap while malaria parasite incidence data was collected from a cohort of children on monthly basis. Rainfall, humidity and temperature data were collected by automated weather stations. Negative binomial and Poisson generalized additive models were used to examine the risk of being infected, as well as the association with the weather variables. Anopheles gambiae s.s. was most abundant in Lunyerere, An. arabiensis in Nyalenda and An. funestus in Fort Ternan. The CDC light traps caught a higher proportion of mosquitoes (52.3%) than PSC (47.7%), although not significantly different (P = 0.689). The EIR's were 0, 61.79 and 6.91 bites/person/year for Fort Ternan, Lunyerere and Nyalenda. Site, month and core body temperature were all associated with the risk of having malaria parasites (P < 0.0001). Rainfall was found to be significantly associated with the occurrence of P. falciparum malaria parasites, but not relative humidity and air temperature. The presence of malaria parasite-infected children in all the study sites provides evidence of local malaria transmission. PMID:22988466

  7. Transmission dynamics and control for a brucellosis model in Hinggan League of Inner Mongolia, China.

    PubMed

    Li, Mingtao; Sun, Guiquan; Zhang, Juan; Jin, Zhen; Sun, Xiangdong; Wang, Youming; Huang, Baoxu; Zheng, Yaohui

    2014-10-01

    Brucellosis is one of the major infectious and contagious bacterial diseases in Hinggan League of Inner Mongolia, China. The number of newly infected human brucellosis data in this area has increased dramatically in the last 10 years. In this study, in order to explore effective control and prevention measures we propose a deterministic model to investigate the transmission dynamics of brucellosis in Hinggan League. The model describes the spread of brucellosis among sheep and from sheep to humans. The model simulations agree with newly infected human brucellosis data from 2001 to 2011, and the trend of newly infected human brucellosis cases is given. We estimate that the control reproduction number Rc is about 1.9789 for the brucellosis transmission in Hinggan League and compare the effect of existing mixed cross infection between basic ewes and other sheep or not for newly infected human brucellosis cases. Our study demonstrates that combination of prohibiting mixed feeding between basic ewes and other sheep, vaccination, detection and elimination are useful strategies in controlling human brucellosis in Hinggan League.

  8. Dynamics of malaria transmission under changing ecological scenario in and around Nanak Matta Dam, Uttaranchal, India.

    PubMed

    Shukla, R P; Sharma, S N; Kohli, V K; Nanda, N; Sharma, V P; Subbarao, S K

    2001-01-01

    To understand the transmission dynamics of malaria in three different ecotypes, namely watershed (forest), seepage (Nanak Matta Dam) and plain (non-forest, non-dam) areas of Nainital and Udham Singh Nagar districts of Uttaranchal, entomological and parasitological investigations were carried out from July 1996 to June 1997. In the three ecotypes, average per man hour densities of adult vector species in human dwellings and cattlesheds recorded were high for Anopheles culicifacies from April to September and October to March for An. fluviatilis. Prevalence of both An. culicifacies and An. fluviatilis was higher in the forest area as compared to other two areas. Observations on gonotrophic condition revealed endophilic tendency of both vector species. Higher number of both vector species were found in outdoor than indoor during night human bait collections. Out of 864 specimens of An. fluviatilis dissected, one showed natural infection of sporozoites in salivary glands in the month of November from the forest area only. Sibling species study of An. fluviatilis revealed the presence of species S for the first time in the forest area. Parasitological investigations also depicted high incidence of malaria in the forest area as compared to other two areas. Overall results from the study indicated active malaria transmission in the forest area.

  9. Modeling the effects of relapse in the transmission dynamics of malaria parasites.

    PubMed

    Aguas, Ricardo; Ferreira, Marcelo U; Gomes, M Gabriela M

    2012-01-01

    Often regarded as "benign," Plasmodium vivax infections lay in the shadows of the much more virulent P. falciparum infections. However, about 1.98 billion people are at risk of both parasites worldwide, stressing the need to understand the epidemiology of Plasmodium vivax, particularly under the scope of decreasing P. falciparum prevalence and ecological interactions between both species. Two epidemiological observations put the dynamics of both species into perspective: (1) ACT campaigns have had a greater impact on P. falciparum prevalence. (2) Complete clinical immunity is attained at younger ages for P. vivax, under similar infection rates. We systematically compared two mathematical models of transmission for both Plasmodium species. Simulations suggest that an ACT therapy combined with a hypnozoite killing drug would eliminate both species. However, P. vivax elimination is predicted to be unstable. Differences in age profiles of clinical malaria can be explained solely by P. vivax's ability to relapse, which accelerates the acquisition of clinical immunity and serves as an immunity boosting mechanism. P. vivax transmission can subsist in areas of low mosquito abundance and is robust to drug administration initiatives due to relapse, making it an inconvenient and cumbersome, yet less lethal alternative to P. falciparum.

  10. Modeling dynamic interactions between pre-exposure prophylaxis interventions & treatment programs: predicting HIV transmission & resistance.

    PubMed

    Supervie, Virginie; Barrett, Meagan; Kahn, James S; Musuka, Godfrey; Moeti, Themba Lebogang; Busang, Lesego; Busang, Lesogo; Blower, Sally

    2011-01-01

    Clinical trials have recently demonstrated the effectiveness of Pre-Exposure Prophylaxis (PrEP) in preventing HIV infection. Consequently, PrEP may soon be used for epidemic control. We model the dynamic interactions that will occur between treatment programs and potential PrEP interventions in resource-constrained countries. We determine the consequences for HIV transmission and drug resistance. We use response hypersurface modeling to predict the effect of PrEP on decreasing transmission as a function of effectiveness, adherence and coverage. We predict PrEP will increase need for second-line therapies (SLT) for treatment-naïve individuals, but could significantly decrease need for SLT for treatment-experienced individuals. If the rollout of PrEP is carefully planned it could increase the sustainability of treatment programs. If not, need for SLT could increase and the sustainability of treatment programs could be compromised. Our results show the optimal strategy for rolling out PrEP in resource-constrained countries is to begin around the "worst" treatment programs.

  11. Modelling the transmission dynamics of Theileria annulata: model structure and validation for the Turkish context

    PubMed Central

    SUTTON, A. J.; KARAGENC, T.; BAKIRCI, S.; SARALI, H.; PEKEL, G.; MEDLEY, G. F.

    2012-01-01

    SUMMARY A mathematical model that describes the transmission dynamics of Theileria annulata is proposed that consists of 2 host components: the Hyalomma tick population and a compartmental model of T. annulata infection in the cattle population. The model was parameterized using data describing tick infestation and the infection status of cattle in Turkey from 2006 to 2008. The tick attachment rates are highly seasonal and because of the temporal separation of infectious and susceptible ticks virtually all ticks are infected by carrier cattle, so that annual peaks of disease in cattle do not impact on infection in the Hyalomma tick population. The impact of intervention measures that target the tick population both on the host and in the environment and their impact on the transmission of T. annulata were investigated. Interventions that have a limited ‘one-off’ impact and interventions that have a more permanent impact were both considered. The results from the model show the importance of targeting ticks during the period when they have left their first host as nymphs but have yet to feed on their second host. PMID:22309815

  12. Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy.

    PubMed

    Hermannsdörfer, Justus; de Jonge, Niels

    2017-02-05

    Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

  13. The life cycle and transmission dynamics of the larval stages of Hypoderaeum conoideum.

    PubMed

    Muñoz-Antolí, C; Toledo, R; Esteban, J G

    2000-06-01

    The morphology of the different larval stages and life cycle of Hypoderaeum conoideum (Trematoda: Echinostomatidae) are described. The freshwater snail species Lymnaea peregra (Gastropoda: Lymnaeidae) serves as the natural first intermediate host and this and L. corvus serve as experimental first intermediate hosts. These and other freshwater snails, such as Physella acuta and Gyraulus chinensis, in turn serve as second intermediate hosts. Adult worms were obtained from chicks and ducks, but not from rats, mice and golden hamsters. The morphology of the larval stages is compared with previous work on H. conoideum. Several aspects of the biology of the life history stages are described with emphasis on the transmission dynamics of the free-living stages. Differential suitability of the snail species that may act as first and/or second intermediate hosts is studied and discussed.

  14. Seasonal population dynamics of Draeculacephala minerva (Hemiptera: Cicadellidae) and transmission of Xylella fastidiosa.

    PubMed

    Cabrera-La Rosa, Juan C; Johnson, Marshall W; Civerolo, Edwin L; Chen, Jianchi; Groves, Russell L

    2008-08-01

    The grass sharpshooter, Draeculacephala minerva Ball (Hemiptera: Cicadellidae), is a very common and often abundant grass-feeding leafhopper in California. Its population dynamics and ability to transmit Xylella fastidiosa were monitored over a 2-yr period in California's San Joaquin Valley. Collections of individuals from natural populations in irrigated pastures and alfalfa, Medicago savita L. fields adjacent to X. fastidiosa-infected almond (Prunus spp.) orchards indicated the occurrence of three discrete generations per year that peaked during the summer. Population densities varied significantly among experimental field survey sites. Insects captured on intercepting mesh traps, yellow sticky cards, and UV-light traps indicated local movement of these insects into and surrounding X. fastidiosa-infected, almond orchards. Local movement and seasonal transmission of X. fastidiosa from infected almonds to Catharanthus roseus (L.) G. Don indicated that this insect may be partly responsible for the slow spread of almond leaf scorch now recently observed in California's San Joaquin Valley.

  15. Effect of a preventive vaccine on the dynamics of HIV transmission

    NASA Astrophysics Data System (ADS)

    Gumel, A. B.; Moghadas, S. M.; Mickens, R. E.

    2004-12-01

    A deterministic mathematical model for the transmission dynamics of HIV infection in the presence of a preventive vaccine is considered. Although the equilibria of the model could not be expressed in closed form, their existence and threshold conditions for their stability are theoretically investigated. It is shown that the disease-free equilibrium is locally-asymptotically stable if the basic reproductive number R<1 (thus, HIV disease can be eradicated from the community) and unstable if R>1 (leading to the persistence of HIV within the community). A robust, positivity-preserving, non-standard finite-difference method is constructed and used to solve the model equations. In addition to showing that the anti-HIV vaccine coverage level and the vaccine-induced protection are critically important in reducing the threshold quantity R, our study predicts the minimum threshold values of vaccine coverage and efficacy levels needed to eradicate HIV from the community.

  16. Transmission Dynamics and Final Epidemic Size of Ebola Virus Disease Outbreaks with Varying Interventions.

    PubMed

    Barbarossa, Maria Vittoria; Dénes, Attila; Kiss, Gábor; Nakata, Yukihiko; Röst, Gergely; Vizi, Zsolt

    2015-01-01

    The 2014 Ebola Virus Disease (EVD) outbreak in West Africa was the largest and longest ever reported since the first identification of this disease. We propose a compartmental model for EVD dynamics, including virus transmission in the community, at hospitals, and at funerals. Using time-dependent parameters, we incorporate the increasing intensity of intervention efforts. Fitting the system to the early phase of the 2014 West Africa Ebola outbreak, we estimate the basic reproduction number as 1.44. We derive a final size relation which allows us to forecast the total number of cases during the outbreak when effective interventions are in place. Our model predictions show that, as long as cases are reported in any country, intervention strategies cannot be dismissed. Since the main driver in the current slowdown of the epidemic is not the depletion of susceptibles, future waves of infection might be possible, if control measures or population behavior are relaxed.

  17. Charged nanoparticle dynamics in water induced by scanning transmission electron microscopy.

    PubMed

    White, E R; Mecklenburg, Matthew; Shevitski, Brian; Singer, S B; Regan, B C

    2012-02-28

    Using scanning transmission electron microscopy we image ~4 nm platinum nanoparticles deposited on an insulating membrane, where the membrane is one of two electron-transparent windows separating an aqueous environment from the microscope's high vacuum. Upon receiving a relatively moderate dose of ~10(4) e/nm(2), initially immobile nanoparticles begin to move along trajectories that are directed radially outward from the center of the field of view. With larger dose rates the particle motion becomes increasingly dramatic. These observations demonstrate that, even under mild imaging conditions, the in situ electron microscopy of aqueous environments can produce electrophoretic charging effects that dominate the dynamics of nanoparticles under observation. © 2012 American Chemical Society

  18. Dynamics of soft Nanomaterials captured by transmission electron microscopy in liquid water

    SciTech Connect

    Proetto, Maria T.; Rush, Anthony M.; Chien, Miao-Ping; Abellan Baeza, Patricia; Patterson, Joseph P.; Thompson, Matthew P.; Olson, Norman H.; Moore, Curtis E.; Rheingold, Arnold L.; Andolina, Christopher; Millstone, Jill; Howell, Stephen B.; Browning, Nigel D.; Evans, James E.; Gianneschi, Nathan C.

    2014-01-14

    In this paper we present in situ transmission electron microscopy (TEM) of soft, synthetic nanoparticles with a comparative analysis using conventional TEM methods. This comparison is made with the simple aim of describing what is an unprecedented example of in situ imaging by TEM. However, we contend the technique will quickly become essential in the characterization of analogous systems, especially where dynamics are of interest in the solvated state. In this case, particles were studied which were obtained from the direct polymerization of an oxaliplatin analog, designed for an ongoing program in novel chemotherapeutic delivery systems. The resulting nanoparticles provided sufficient contrast for facile imaging in situ, and point toward key design parameters that enable this new characterization approach for organic nanomaterials. We describe the preparation of the synthetic micellar nanoparticles to- gether with their characterization in liquid water.

  19. Horizontal transmission dynamics of White spot syndrome virus by cohabitation trials in juvenile Penaeus monodon and P. vannamei.

    PubMed

    Tuyen, N X; Verreth, J; Vlak, J M; de Jong, M C M

    2014-11-01

    White spot syndrome virus (WSSV), a rod-shaped double-stranded DNA virus, is an infectious agent causing fatal disease in shrimp farming around the globe. Within shrimp populations WSSV is transmitted very fast, however, the modes and dynamics of transmission of this virus are not well understood. In the current study the dynamics of disease transmission of WSSV were investigated in small, closed populations of Penaeus monodon and Penaeus vannamei. Pair cohabitation experiments using PCR as a readout for virus infection were used to estimate transmission parameters for WSSV in these two species. The mortality rate of contact-infected shrimp in P. monodon was higher than the rate in P. vannamei. The transmission rate parameters for WSSV were not different between the two species. The relative contribution of direct and indirect transmission rates of WSSV differed between the two species. For P. vannamei the direct contact transmission rate of WSSV was significantly lower than the indirect environmental transmission rate, but for P. monodon, the opposite was found. The reproduction ratio R0 for WSSV for these two species of shrimp was estimated to be above one: 2.07 (95%CI 1.53, 2.79) for P. monodon and 1.51 (95%CI 1.12, 2.03) for P. vannamei. The difference in R0 between the two species is due to a lower host mortality and hence a longer infectious period of WSSV in P. monodon.

  20. Preventing mother-to-child transmission of HIV in Vietnam and Indonesia: diverging care dynamics.

    PubMed

    Hardon, Anita Petra; Oosterhoff, Pauline; Imelda, Johanna D; Anh, Nguyen Thu; Hidayana, Irwan

    2009-09-01

    How do women and frontline health workers engage in preventing mother-to-child HIV transmission (PMTCT) in urban areas of Vietnam and Indonesia, where HIV is highly stigmatized and is associated with injecting drug use and sex work? This qualitative study explores local dynamics of care, using a mix of observations, focus group discussions, and interviews. In Indonesia the study was conducted in a community-based PMTCT program run by an NGO, while in Vietnam the study explored the care dynamics in routine PMTCT services, implemented by district and provincial public health facilities. In both of these PMTCT arrangements (the routine provider initiated approach in Vietnam and a more client-oriented system in Indonesia), pregnant women value the provision of HIV tests in antenatal care (ANC). Concerns are raised, however, by the unhappy few who test positive. These women are unsatisfied with the quality of counselling, and the failure to provide antiretroviral treatments. Acceptability of HIV testing in ANC is high, but the key policy issue from the perspective of pregnant women is whether the PMTCT services can provide good quality counselling and the necessary follow-up care. We find local level providers of PMTCT are pleased with the PMTCT program. In Vietnam, the PMTCT program offers health workers protection against HIV, since they can refer women away from the district health service for delivery. In Indonesia, community cadres are pleased with the financial incentives gained by mobilizing clients for the program. We conclude that achieving the global aims of reducing HIV infections in children by 50% requires a tailoring of globally designed public health programs to context-specific gendered transmission pathways of HIV, as well as local opportunities for follow-up care and social support.

  1. Electron beam dynamics in an ultrafast transmission electron microscope with Wehnelt electrode.

    PubMed

    Bücker, K; Picher, M; Crégut, O; LaGrange, T; Reed, B W; Park, S T; Masiel, D J; Banhart, F

    2016-12-01

    High temporal resolution transmission electron microscopy techniques have shown significant progress in recent years. Using photoelectron pulses induced by ultrashort laser pulses on the cathode, these methods can probe ultrafast materials processes and have revealed numerous dynamic phenomena at the nanoscale. Most recently, the technique has been implemented in standard thermionic electron microscopes that provide a flexible platform for studying material's dynamics over a wide range of spatial and temporal scales. In this study, the electron pulses in such an ultrafast transmission electron microscope are characterized in detail. The microscope is based on a thermionic gun with a Wehnelt electrode and is operated in a stroboscopic photoelectron mode. It is shown that the Wehnelt bias has a decisive influence on the temporal and energy spread of the picosecond electron pulses. Depending on the shape of the cathode and the cathode-Wehnelt distance, different emission patterns with different pulse parameters are obtained. The energy spread of the pulses is determined by space charge and Boersch effects, given by the number of electrons in a pulse. However, filtering effects due to the chromatic aberrations of the Wehnelt electrode allow the extraction of pulses with narrow energy spreads. The temporal spread is governed by electron trajectories of different length and in different electrostatic potentials. High temporal resolution is obtained by excluding shank emission from the cathode and aberration-induced halos in the emission pattern. By varying the cathode-Wehnelt gap, the Wehnelt bias, and the number of photoelectrons in a pulse, tradeoffs between energy and temporal resolution as well as beam intensity can be made as needed for experiments. Based on the characterization of the electron pulses, the optimal conditions for the operation of ultrafast TEMs with thermionic gun assembly are elaborated. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. The 1918 influenza pandemic in New York City: age-specific timing, mortality, and transmission dynamics

    PubMed Central

    Yang, Wan; Petkova, Elisaveta; Shaman, Jeffrey

    2014-01-01

    Background The 1918 influenza pandemic caused disproportionately high mortality among certain age groups. The mechanisms underlying these differences are not fully understood. Objectives To explore the dynamics of the 1918 pandemic and to identify potential age-specific transmission patterns. Methods We examined 1915–1923 daily mortality data in New York City (NYC) and estimated the outbreak duration and initial effective reproductive number (Re) for each 1-year age cohort. Results Four pandemic waves occurred from February 1918 to April 1920. The fractional mortality increase (i.e. ratio of excess mortality to baseline mortality) was highest among teenagers during the first wave. This peak shifted to 25- to 29-year-olds in subsequent waves. The distribution of age-specific mortality during the last three waves was strongly correlated (r = 0·94 and 0·86). With each wave, the pandemic appeared to spread with a comparable early growth rate but then attenuate with varying rates. For the entire population, Re estimates made assuming 2-day serial interval were 1·74 (1·27), 1·74 (1·43), 1·66 (1·25), and 1·86 (1·37), respectively, during the first week (first 3 weeks) of each wave. Using age-specific mortality, the average Re estimates over the first week of each wave were 1·62 (95% CI: 1·55–1·68), 1·68 (1·65–1·72), 1·67 (1·61–1·73), and 1·69 (1·63–1·74), respectively; Re was not significantly different either among age cohorts or between waves. Conclusions The pandemic generally caused higher mortality among young adults and might have spread mainly among school-aged children during the first wave. We propose mechanisms to explain the timing and transmission dynamics of the four NYC pandemic waves. PMID:24299150

  3. Professional Development Networks: From Transmission to Co-Construction

    ERIC Educational Resources Information Center

    Ngcoza, Ken; Southwood, Sue

    2015-01-01

    This article offers an extract of a qualitative case study focused on collaborative professional development of science teachers in a transformative continuous professional development (TCPD) network, whose aim is the professional development of science teachers with a view to improving praxis. Teacher narratives generated through an iterative…

  4. Professional Development Networks: From Transmission to Co-Construction

    ERIC Educational Resources Information Center

    Ngcoza, Ken; Southwood, Sue

    2015-01-01

    This article offers an extract of a qualitative case study focused on collaborative professional development of science teachers in a transformative continuous professional development (TCPD) network, whose aim is the professional development of science teachers with a view to improving praxis. Teacher narratives generated through an iterative…

  5. Comprehensive Modeling and Analysis of Rotorcraft Variable Speed Propulsion System With Coupled Engine/Transmission/Rotor Dynamics

    NASA Technical Reports Server (NTRS)

    DeSmidt, Hans A.; Smith, Edward C.; Bill, Robert C.; Wang, Kon-Well

    2013-01-01

    This project develops comprehensive modeling and simulation tools for analysis of variable rotor speed helicopter propulsion system dynamics. The Comprehensive Variable-Speed Rotorcraft Propulsion Modeling (CVSRPM) tool developed in this research is used to investigate coupled rotor/engine/fuel control/gearbox/shaft/clutch/flight control system dynamic interactions for several variable rotor speed mission scenarios. In this investigation, a prototypical two-speed Dual-Clutch Transmission (DCT) is proposed and designed to achieve 50 percent rotor speed variation. The comprehensive modeling tool developed in this study is utilized to analyze the two-speed shift response of both a conventional single rotor helicopter and a tiltrotor drive system. In the tiltrotor system, both a Parallel Shift Control (PSC) strategy and a Sequential Shift Control (SSC) strategy for constant and variable forward speed mission profiles are analyzed. Under the PSC strategy, selecting clutch shift-rate results in a design tradeoff between transient engine surge margins and clutch frictional power dissipation. In the case of SSC, clutch power dissipation is drastically reduced in exchange for the necessity to disengage one engine at a time which requires a multi-DCT drive system topology. In addition to comprehensive simulations, several sections are dedicated to detailed analysis of driveline subsystem components under variable speed operation. In particular an aeroelastic simulation of a stiff in-plane rotor using nonlinear quasi-steady blade element theory was conducted to investigate variable speed rotor dynamics. It was found that 2/rev and 4/rev flap and lag vibrations were significant during resonance crossings with 4/rev lagwise loads being directly transferred into drive-system torque disturbances. To capture the clutch engagement dynamics, a nonlinear stick-slip clutch torque model is developed. Also, a transient gas-turbine engine model based on first principles mean

  6. The role of climate variability and change in the transmission dynamics and geographic distribution of dengue.

    PubMed

    Thai, Khoa T D; Anders, Katherine L

    2011-08-01

    The mounting evidence for anthropogenic changes in global climate raises many pressing questions about the potential effects on biological systems, and in particular the transmission of infectious diseases. Vector-borne diseases, such as dengue, may be particularly sensitive to both periodic fluctuations and sustained changes in global and local climates, because vector biology and viral replication are temperature- and moisture-dependent. This paper reviews the current state of knowledge on the associations between climate variability, climate change and dengue transmission, and the tools being used to quantify these associations. The underlying causes of dengue's recent global expansion are multifactorial and poorly understood, but climatic factors should be considered within the context of the sociodemographic, economic and immunological determinants that have contributed to dengue's spread. These factors may mediate the direct effects of climate on dengue and many may operate at a very local level. Translating theoretical models of dengue transmission based on historical data into predictive models that can inform public health interventions is a critical next step and efforts should be focused on developing and refining models at smaller spatial scales to characterize the relationships between both climatic and non-climatic factors and dengue risk.

  7. Negative Fitness Consequences and Transmission Dynamics of a Heritable Fungal Symbiont of a Parasitic Wasp▿

    PubMed Central

    Gibson, Cara M.; Hunter, Martha S.

    2009-01-01

    Heritable bacterial symbionts are widespread in insects and can have many important effects on host ecology and fitness. Fungal symbionts are also important in shaping their hosts' behavior, interactions, and evolution, but they have been largely overlooked. Experimental tests to determine the relevance of fungal symbionts to their insect hosts are currently extremely rare, and to our knowledge, there have been no such tests for strictly predacious insects. We investigated the fitness consequences for a parasitic wasp (Comperia merceti) of an inherited fungal symbiont in the Saccharomycotina (Ascomycota) that was long presumed to be a mutualist. In comparisons of wasp lines with and without this symbiont, we found no evidence of mutualism. Instead, there were significant fitness costs to the wasps in the presence of the yeast; infected wasps attacked fewer hosts and had longer development times. We also examined the relative competitive abilities of the larval progeny of infected and uninfected mothers, as well as horizontal transmission of the fungal symbiont among larval wasps that shared a single host cockroach egg case. We found no difference in larval competitive ability when larvae whose infection status differed shared a single host. We did find high rates of horizontal transmission of the fungus, and we suggest that this transmission is likely responsible for the maintenance of this infection in wasp populations. PMID:19286783

  8. Infection dynamics of endemic malaria in a wild bird population: parasite species-dependent drivers of spatial and temporal variation in transmission rates.

    PubMed

    Lachish, Shelly; Knowles, Sarah C L; Alves, Ricardo; Wood, Matthew J; Sheldon, Ben C

    2011-11-01

    1. Investigating the ecological context in which host-parasite interactions occur and the roles of biotic and abiotic factors in forcing infection dynamics is essential to understanding disease transmission, spread and maintenance. 2. Despite their prominence as model host-pathogen systems, the relative influence of environmental heterogeneity and host characteristics in influencing the infection dynamics of avian blood parasites has rarely been assessed in the wild, particularly at a within-population scale. 3. We used a novel multievent modelling framework (an extension of multistate mark-recapture modelling) that allows for uncertainty in disease state, to estimate transmission parameters and assess variation in the infection dynamics of avian malaria in a large, longitudinally sampled data set of breeding blue tits infected with two divergent species of Plasmodium parasites. 4. We found striking temporal and spatial heterogeneity in the disease incidence rate and the likelihood of recovery within this single population and demonstrate marked differences in the relative influence of environmental and host factors in forcing the infection dynamics of the two Plasmodium species. 5. Proximity to a permanent water source greatly influenced the transmission rates of P. circumflexum, but not of P. relictum, suggesting that these parasites are transmitted by different vectors. 6. Host characteristics (age/sex) were found to influence infection rates but not recovery rates, and their influence on infection rates was also dependent on parasite species: P. relictum infection rates varied with host age, whilst P. circumflexum infection rates varied with host sex. 7. Our analyses reveal that transmission of endemic avian malaria is a result of complex interactions between biotic and abiotic components that can operate on small spatial scales and demonstrate that knowledge of the drivers of spatial and temporal heterogeneity in disease transmission will be

  9. The role of residence times in two-patch dengue transmission dynamics and optimal strategies.

    PubMed

    Lee, Sunmi; Castillo-Chavez, Carlos

    2015-06-07

    The reemergence and geographical dispersal of vector-borne diseases challenge global health experts around the world and in particular, dengue poses increasing difficulties in the Americas, due in part to explosive urban and semi-urban growth, increases of within and between region mobility, the absence of a vaccine, and the limited resources available for public health services. In this work, a simple deterministic two-patch model is introduced to assess the impact of dengue transmission dynamics in heterogeneous environments. The two-patch system models the movement (e.g. urban versus rural areas residence times) of individuals between and within patches/environments using residence-time matrices with entries that budget within and between host patch relative residence times, under the assumption that only the human budgets their residence time across regions. Three scenarios are considered: (i) resident hosts in Patch i visit patch j, where i≠j but not the other way around, a scenario referred to as unidirectional motion; (ii) symmetric bi-directional motion; and (iii) asymmetric bi-directional motion. Optimal control theory is used to identify and evaluate patch-specific control measures aimed at reducing dengue prevalence in humans and vectors at a minimal cost. Optimal policies are computed under different residence-matrix configurations mentioned above as well as transmissibility scenarios characterized by the magnitude of the basic reproduction number. Optimal patch-specific polices can ameliorate the impact of epidemic outbreaks substantially when the basic reproduction number is moderate. The final patch-specific epidemic size variation increases as the residence time matrix moves away from the symmetric case (asymmetry). As expected, the patch where individuals spend most of their time or in the patch where transmissibility is higher tend to support larger patch-specific final epidemic sizes. Hence, focusing on intervention that target areas where

  10. Contrasting Transmission Dynamics of Co-endemic Plasmodium vivax and P. falciparum: Implications for Malaria Control and Elimination

    PubMed Central

    Noviyanti, Rintis; Coutrier, Farah; Utami, Retno A. S.; Trimarsanto, Hidayat; Tirta, Yusrifar K.; Trianty, Leily; Kusuma, Andreas; Sutanto, Inge; Kosasih, Ayleen; Kusriastuti, Rita; Hawley, William A.; Laihad, Ferdinand; Lobo, Neil; Marfurt, Jutta; Clark, Taane G.; Price, Ric N.; Auburn, Sarah

    2015-01-01

    Background Outside of Africa, P. falciparum and P. vivax usually coexist. In such co-endemic regions, successful malaria control programs have a greater impact on reducing falciparum malaria, resulting in P. vivax becoming the predominant species of infection. Adding to the challenges of elimination, the dormant liver stage complicates efforts to monitor the impact of ongoing interventions against P. vivax. We investigated molecular approaches to inform the respective transmission dynamics of P. falciparum and P. vivax and how these could help to prioritize public health interventions. Methodology/ Principal Findings Genotype data generated at 8 and 9 microsatellite loci were analysed in 168 P. falciparum and 166 P. vivax isolates, respectively, from four co-endemic sites in Indonesia (Bangka, Kalimantan, Sumba and West Timor). Measures of diversity, linkage disequilibrium (LD) and population structure were used to gauge the transmission dynamics of each species in each setting. Marked differences were observed in the diversity and population structure of P. vivax versus P. falciparum. In Bangka, Kalimantan and Timor, P. falciparum diversity was low, and LD patterns were consistent with unstable, epidemic transmission, amenable to targeted intervention. In contrast, P. vivax diversity was higher and transmission appeared more stable. Population differentiation was lower in P. vivax versus P. falciparum, suggesting that the hypnozoite reservoir might play an important role in sustaining local transmission and facilitating the spread of P. vivax infections in different endemic settings. P. vivax polyclonality varied with local endemicity, demonstrating potential utility in informing on transmission intensity in this species. Conclusions/ Significance Molecular approaches can provide important information on malaria transmission that is not readily available from traditional epidemiological measures. Elucidation of the transmission dynamics circulating in a given

  11. Stirling Convertor System Dynamic Model Developed

    NASA Technical Reports Server (NTRS)

    Lewandowski, Edward J.; Regan, Timothy F.

    2005-01-01

    Free-piston Stirling convertors are being developed for potential use on NASA exploration missions. In support of this effort, the NASA Glenn Research Center has developed the Stirling convertor System Dynamic Model (SDM). The SDM models the Stirling cycle thermodynamics; heat flow; gas, mechanical, and mounting dynamics; the linear alternator; and the controller. The SDM s scope extends from the thermal energy input to thermal, mechanical, and electrical energy output, allowing one to study complex system interactions among subsystems. Thermal, mechanical, fluid, magnetic, and electrical subsystems can be studied in one model. The SDM is a nonlinear time-domain model containing sub-cycle dynamics, which simulates transient and dynamic phenomena that other models cannot. The entire range of convertor operation is modeled, from startup to full-power conditions.

  12. In situ observation of dynamic recrystallization in five-nine aluminum by a transmission Laue method

    SciTech Connect

    Yamagata, Hiroshi . R and D Div. 2)

    1994-02-15

    Zone refined aluminum shows regular multipeak stress oscillations during deformation at elevated temperatures. Microstructural observations after compression testing have detected recrystallized grains containing subgrain structures in numerous cases. It is thought, in an accepted theory, that dynamic recrystallization (DRX) does not take place as a restorative process in aluminum because of the high stacking fault energy. Experimental results, however, strongly demonstrate that the stress oscillations are due to DRX. Against this conclusion, McQueen et al. have suggested that the stress oscillation is caused by dynamic grain growth or by friction between a specimen and platens. Moreover, they have the opinion that the observed recrystallized structure is due to static recrystallization after deformation has terminated. It is certain that the recrystallized structure observed after the deformation does not in itself constitute strong evidence for DRX, even if a rapidly cooled specimen is used. Given these standpoints, in situ detection of DRX was undertaken. The diffraction pattern was studied using the transmission Laue method. A pattern change was continuously photographed during a regular multipeak stress oscillation in a 533K compression test.

  13. Dynamic Control over the Optical Transmission of Nanoscale Dielectric Metasurface by Alkali Vapors.

    PubMed

    Bar-David, Jonathan; Stern, Liron; Levy, Uriel

    2017-02-08

    In recent years, dielectric and metallic nanoscale metasurfaces are attracting growing attention and are being used for variety of applications. Resulting from the ability to introduce abrupt changes in optical properties at nanoscale dimensions, metasurfaces enable unprecedented control over light's different degrees of freedom, in an essentially two-dimensional configuration. Yet, the dynamic control over metasurface properties still remains one of the ultimate goals of this field. Here, we demonstrate the optical resonant interaction between a form birefringent dielectric metasurface made of silicon and alkali atomic vapor to control and effectively tune the optical transmission pattern initially generated by the nanoscale dielectric metasurface. By doing so, we present a controllable metasurface system, the output of which may be altered by applying magnetic fields, changing input polarization, or shifting the optical frequency. Furthermore, we also demonstrate the nonlinear behavior of our system taking advantage of the saturation effect of atomic transition. The demonstrated approach paves the way for using metasurfaces in applications where dynamic tunability of the metasurface is in need, for example, for scanning systems, tunable focusing, real time displays, and more.

  14. Epidemiology and transmission dynamics of the 1918-19 pandemic influenza in Florence, Italy.

    PubMed

    Rizzo, Caterina; Ajelli, Marco; Merler, Stefano; Pugliese, Andrea; Barbetta, Ilaria; Salmaso, Stefania; Manfredi, Piero

    2011-07-22

    To investigate the 1918/19 influenza pandemic daily number of new hospitalizations in the only hospital in Florence (Central Italy) were analyzed. In order to describe the transmission dynamics of the 1918/1919 pandemic influenza a compartmental epidemic model was used. Model simulations show a high level of agreement with the observed epidemic data. By assuming both latent and infectious period equal to 1.5 days, the estimated basic reproduction number was R(0)(1) = 1.03 (95% CI: 1.00-1.08) during the summer wave and R(0)(2) = 1.38 (95% CI: 1.32-1.48) during the fall wave. Varying the length of the generation time or the estimation method, R(0)(2) ranges from 1.32 to 1.71. The hospitalization rate was found significantly different between summer and fall waves. Notably, the estimated basic reproductive numbers are lower compared to those observed in other countries, while the age distribution of deaths resulted to be consistent with the patterns generally observed during of the 1918-1919 pandemic. Our knowledge on past pandemics, as for the 1918-19 Spanish influenza, would help improving mathematical modeling accuracy and understanding the mechanisms underlying the dynamics of future pandemics.

  15. High-speed nanoscale characterization of dewetting via dynamic transmission electron microscopy

    SciTech Connect

    Hihath, Sahar; Santala, Melissa K.; Campbell, Geoffrey; Benthem, Klaus van

    2016-08-28

    The dewetting of thin films can occur in either the solid or the liquid state for which different mass transport mechanisms are expected to control morphological changes. Traditionally, dewetting dynamics have been examined on time scales between several seconds to hours, and length scales ranging between nanometers and millimeters. The determination of mass transport mechanisms on the nanoscale, however, requires nanoscale spatial resolution and much shorter time scales. This study reports the high-speed observation of dewetting phenomena for kinetically constrained Ni thin films on crystalline SrTiO{sub 3} substrates. Movie-mode Dynamic Transmission Electron Microscopy (DTEM) was used for high-speed image acquisition during thin film dewetting at different temperatures. DTEM imaging confirmed that the initial stages of film agglomeration include edge retraction, hole formation, and growth. Finite element modeling was used to simulate temperature distributions within the DTEM samples after laser irradiation with different energies. For pulsed laser irradiation at 18 μJ, experimentally observed hole growth suggests that Marangoni flow dominates hole formation in the liquid nickel film. After irradiation with 13.8 μJ, however, the observations suggest that dewetting was initiated by nucleation of voids followed by hole growth through solid-state surface diffusion.

  16. A wearable wireless ECG monitoring system with dynamic transmission power control for long-term homecare.

    PubMed

    Wang, Yishan; Doleschel, Sammy; Wunderlich, Ralf; Heinen, Stefan

    2015-03-01

    This paper presents a wearable wireless ECG monitoring system based on novel 3-Lead electrode placements for long-term homecare. The experiment for novel 3-Lead electrode placements is carried out, and the results show that the distance between limb electrodes can be significantly reduced. Based on the new electrode position, a small size sensor node, which is powered by a rechargeable battery, is designed to detect, amplify, filter and transmit the ECG signals. The coordinator receives the data and sends it to PC. Finally the signals are displayed on the GUI. In order to control the power consumption of sensor node, a dynamic power adjustment method is applied to automatically adjust the transmission power of the sensor node according to the received signal strength indicator (RSSI), which is related to the distance and obstacle between sensor node and coordinator. The system is evaluated when the user, who wears the sensor, is walking and running. A promising performance is achieved even under body motion. The power consumption can be significantly reduced with this dynamic power adjustment method.

  17. Transmission dynamics of two strains of Schistosoma mansoni utilizing novel intermediate and definitive hosts.

    PubMed

    Jones-Nelson, Omari; Thiele, Elizabeth A; Minchella, Dennis J

    2011-09-01

    The intimate host-parasite relationship mandates adaptation to the genetic and phenotypic variability of their counterparts. Here, inbred and outcrossed strains of Schistosoma mansoni were challenged with "local" and "novel" intermediate and definitive hosts to examine effects of genetic variability and novelty on infection success and dynamics. Genetically distinct lines of Biomphalaria glabrata intermediate hosts exposed to inbred and outcrossed S. mansoni larvae were assessed for differences in both snail and parasite life-history parameters. Cercariae from each parasite-snail treatment were used to infect "local" and "novel" Mus musculus definitive hosts to assess parasite infectivity and fitness. Outcrossed parasites significantly reduced snail growth, were more productive, and induced greater host mortality than inbred parasites. Mouse strain did not influence parasite infectivity or reproduction, but parasite and snail host genetic background did, affecting both sex-specific infectivity and parasite productivity. Overall, genetic background of S. mansoni and its intermediate snail host altered life history traits and transmission dynamics of the parasite throughout its life cycle.

  18. Practical Considerations for High Spatial and Temporal Resolution Dynamic Transmission Electron Microscopy

    SciTech Connect

    Armstrong, M; Boyden, K; Browning, N D; Campbell, G H; Colvin, J D; DeHope, B; Frank, A M; Gibson, D J; Hartemann, F; Kim, J S; King, W E; LaGrange, T B; Pyke, B J; Reed, B W; Shuttlesworth, R M; Stuart, B C; Torralva, B R

    2006-05-01

    Although recent years have seen significant advances in the spatial resolution possible in the transmission electron microscope (TEM), the temporal resolution of most microscopes is limited to video rate at best. This lack of temporal resolution means that our understanding of dynamic processes in materials is extremely limited. High temporal resolution in the TEM can be achieved, however, by replacing the normal thermionic or field emission source with a photoemission source. In this case the temporal resolution is limited only by the ability to create a short pulse of photoexcited electrons in the source, and this can be as short as a few femtoseconds. The operation of the photo-emission source and the control of the subsequent pulse of electrons (containing as many as 5 x 10{sup 7} electrons) create significant challenges for a standard microscope column that is designed to operate with a single electron in the column at any one time. In this paper, the generation and control of electron pulses in the TEM to obtain a temporal resolution <10{sup -6} s will be described and the effect of the pulse duration and current density on the spatial resolution of the instrument will be examined. The potential of these levels of temporal and spatial resolution for the study of dynamic materials processes will also be discussed.

  19. High-speed nanoscale characterization of dewetting via dynamic transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Hihath, Sahar; Santala, Melissa K.; Campbell, Geoffrey; van Benthem, Klaus

    2016-08-01

    The dewetting of thin films can occur in either the solid or the liquid state for which different mass transport mechanisms are expected to control morphological changes. Traditionally, dewetting dynamics have been examined on time scales between several seconds to hours, and length scales ranging between nanometers and millimeters. The determination of mass transport mechanisms on the nanoscale, however, requires nanoscale spatial resolution and much shorter time scales. This study reports the high-speed observation of dewetting phenomena for kinetically constrained Ni thin films on crystalline SrTiO3 substrates. Movie-mode Dynamic Transmission Electron Microscopy (DTEM) was used for high-speed image acquisition during thin film dewetting at different temperatures. DTEM imaging confirmed that the initial stages of film agglomeration include edge retraction, hole formation, and growth. Finite element modeling was used to simulate temperature distributions within the DTEM samples after laser irradiation with different energies. For pulsed laser irradiation at 18 μJ, experimentally observed hole growth suggests that Marangoni flow dominates hole formation in the liquid nickel film. After irradiation with 13.8 μJ, however, the observations suggest that dewetting was initiated by nucleation of voids followed by hole growth through solid-state surface diffusion.

  20. Transmission electron microscopy and theoretical analysis of AuCu nanoparticles: atomic distribution and dynamic behavior.

    PubMed

    Ascencio, J A; Liu, H B; Pal, U; Medina, A; Wang, Z L

    2006-07-01

    Though the application of bimetallic nanoparticles is becoming increasingly important, the local atomistic structure of such alloyed particles, which is critical for tailoring their properties, is not yet very clearly understood. In this work, we present detailed study on the atomistic structure of Au-Cu nanoparticles so as to determine their most stable configurations and the conditions for obtaining clusters of different structural variants. The dynamic behavior of these nanoparticles upon local heating is investigated. AuCu nanoparticles are characterized by high resolution transmission electron microscopy (HRTEM) and energy filtering elemental composition mapping (EFECM), which allowed us to study the internal structure and the elemental distribution in the particles. Quantum mechanical approaches and classic molecular dynamics methods are applied to model the structure and to determine the lowest energy configurations, the corresponding electronic structures, and understand structural transition of clusters upon heating, supported by experimental evidences. Our theoretical results demonstrate only the core/shell bimetallic structure have negative heat of formation, both for decahedra and octahedral, and energetically favoring core/shell structure is with Au covering the core of Cu, whose reverse core/shell structure is not stable and may transform back at a certain temperature. Experimental evidences corroborate these structures and their structural changes upon heating, demonstrating the possibility to manipulate the structure of such bimetallic nanoparticles using extra stimulating energy, which is in accordance with the calculated coherence energy proportions between the different configurations. Copyright (c) 2006 Wiley-Liss, Inc.

  1. Impact of dynamical scattering on quantitative contrast for aberration-corrected transmission electron microscope images.

    PubMed

    Wen, C; Smith, David J

    2016-10-01

    Aberration-corrected transmission electron microscope images taken under optimum-defocus conditions or processed offline can correctly reflect the projected crystal structure with atomic resolution. However, dynamical scattering, which will seriously influence image contrast, is still unavoidable. Here, the multislice image simulation approach was used to quantify the impact of dynamical scattering on the contrast of aberration-corrected images for a 3C-SiC specimen with changes in atomic occupancy and thickness. Optimum-defocus images with different spherical aberration (CS) coefficients, and structure images restored by deconvolution processing, were studied. The results show that atomic-column positions and the atomic occupancy for SiC 'dumbbells' can be determined by analysis of image contrast profiles only below a certain thickness limit. This limit is larger for optimum-defocus and restored structure images with negative CS coefficient than those with positive CS coefficient. The image contrast of C (or Si) atomic columns with specific atomic occupancy changes differently with increasing crystal thickness. Furthermore, contrast peaks for C atomic columns overlapping with neighboring peaks of Si atomic columns with varied Si atomic occupancy, which is enhanced with increasing crystal thickness, can be neglected in restored structure images, but the effect is substantial in optimum-defocus images. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Gas mixing system for imaging of nanomaterials under dynamic environments by environmental transmission electron microscopy

    SciTech Connect

    Akatay, M. Cem; Zvinevich, Yury; Ribeiro, Fabio H. E-mail: estach@bnl.gov; Baumann, Philipp; Stach, Eric A. E-mail: estach@bnl.gov

    2014-03-15

    A gas mixing manifold system that is capable of delivering a stable pressure stream of a desired composition of gases into an environmental transmission electron microscope has been developed. The system is designed to provide a stable imaging environment upon changes of either the composition of the gas mixture or upon switching from one gas to another. The design of the system is described and the response of the pressure inside the microscope, the sample temperature, and sample drift in response to flow and composition changes of the system are reported.

  3. Evaluation of power system security and development of transmission pricing method

    NASA Astrophysics Data System (ADS)

    Kim, Hyungchul

    The electric power utility industry is presently undergoing a change towards the deregulated environment. This has resulted in unbundling of generation, transmission and distribution services. The introduction of competition into unbundled electricity services may lead system operation closer to its security boundaries resulting in smaller operating safety margins. The competitive environment is expected to lead to lower price rates for customers and higher efficiency for power suppliers in the long run. Under this deregulated environment, security assessment and pricing of transmission services have become important issues in power systems. This dissertation provides new methods for power system security assessment and transmission pricing. In power system security assessment, the following issues are discussed (1) The description of probabilistic methods for power system security assessment; (2) The computation time of simulation methods; (3) on-line security assessment for operation. A probabilistic method using Monte-Carlo simulation is proposed for power system security assessment. This method takes into account dynamic and static effects corresponding to contingencies. Two different Kohonen networks, Self-Organizing Maps and Learning Vector Quantization, are employed to speed up the probabilistic method. The combination of Kohonen networks and Monte-Carlo simulation can reduce computation time in comparison with straight Monte-Carlo simulation. A technique for security assessment employing Bayes classifier is also proposed. This method can be useful for system operators to make security decisions during on-line power system operation. This dissertation also suggests an approach for allocating transmission transaction costs based on reliability benefits in transmission services. The proposed method shows the transmission transaction cost of reliability benefits when transmission line capacities are considered. The ratio between allocation by transmission line

  4. Spatiotemporal Dynamics of Scrub Typhus Transmission in Mainland China, 2006-2014

    PubMed Central

    Hu, Wen-Biao; Haque, Ubydul; Weppelmann, Thomas A.; Wang, Yong; Liu, Yun-Xi; Li, Xin-Lou; Sun, Hai-Long; Sun, Yan-Song; Clements, Archie C. A.; Li, Shen-Long; Zhang, Wen-Yi

    2016-01-01

    Background Scrub typhus is endemic in the Asia-Pacific region including China, and the number of reported cases has increased dramatically in the past decade. However, the spatial-temporal dynamics and the potential risk factors in transmission of scrub typhus in mainland China have yet to be characterized. Objective This study aims to explore the spatiotemporal dynamics of reported scrub typhus cases in mainland China between January 2006 and December 2014, to detect the location of high risk spatiotemporal clusters of scrub typhus cases, and identify the potential risk factors affecting the re-emergence of the disease. Method Monthly cases of scrub typhus reported at the county level between 2006 and 2014 were obtained from the Chinese Center for Diseases Control and Prevention. Time-series analyses, spatiotemporal cluster analyses, and spatial scan statistics were used to explore the characteristics of the scrub typhus incidence. To explore the association between scrub typhus incidence and environmental variables panel Poisson regression analysis was conducted. Results During the time period between 2006 and 2014 a total of 54,558 scrub typhus cases were reported in mainland China, which grew exponentially. The majority of cases were reported each year between July and November, with peak incidence during October every year. The spatiotemporal dynamics of scrub typhus varied over the study period with high-risk clusters identified in southwest, southern, and middle-eastern part of China. Scrub typhus incidence was positively correlated with the percentage of shrub and meteorological variables including temperature and precipitation. Conclusions The results of this study demonstrate areas in China that could be targeted with public health interventions to mitigate the growing threat of scrub typhus in the country. PMID:27479297

  5. Dynamic Pilot Channel Transmission with Adaptive Receive Filter Configuration for Cognitive Radio System

    NASA Astrophysics Data System (ADS)

    Sakata, Ren; Tomioka, Tazuko; Kobayashi, Takahiro

    When a cognitive radio system dynamically utilizes a frequency band, channel control information must be communicated over the network in order for the currently available carrier frequencies to be shared. In order to keep efficient spectrum utilization, this control information should also be dynamically transmitted through channels such as cognitive pilot channels based on the channel conditions. If transmitters dynamically select carrier frequencies, receivers must receive the control signal without knowledge of its carrier frequencies. A novel scheme called differential code parallel transmission (DCPT) enables receivers to receive low-rate information without any knowledge of the carrier frequency. The transmitter simultaneously transmits two signals whose carrier frequencies are separated by a predefined value. The absolute values of the carrier frequencies can be varied. When the receiver receives the DCPT signal, it multiplies the signal by a frequency-shifted version of itself; this yields a DC component that represents the data signal, which is then demodulated. However, the multiplication process results in the noise power being squared, necessitating high received signal power. In this paper, to realize a bandpass filter that passes only DCPT signals of unknown frequency and that suppresses noise and interference at other frequencies, a DCPT-adaptive bandpass filter (ABF) that employs an adaptive equalizer is proposed. In the training phase, the received signal is the filter input and the frequency-shifted signal is the training input. Then, the filter is trained to pass the higher-frequency signal of the two DCPT signals. The performance of DCPT-ABF is evaluated through computer simulations. We find that DCPT-ABF operates successfully even under strong interference.

  6. The development of a portable, automatic, microwave transmission line test set

    NASA Astrophysics Data System (ADS)

    de La Fuente, Val; Karuschkat, Glenn; Simone, Frederick

    Existing test sets for flightline testing of microwave transmission lines are complex, semiportable systems requiring the piece-part testing of waveguides, antennas, and transmission line components in the aircraft. Moreover, these systems are not fully automated and require a large degree of manual intervention. Therefore, advances in test-set miniaturization and automatic control techniques can now be utilized to develop a fully portable, automatic test set for the flightline functional and diagnostic fault isolation testing of RF avionics and microwave transmission lines. A description is given of the proposed capabilities of such a tester, and the benefits expected to be derived from its use.

  7. Border Malaria Associated with Multidrug Resistance on Thailand-Myanmar and Thailand-Cambodia Borders: Transmission Dynamic, Vulnerability, and Surveillance

    PubMed Central

    Bhumiratana, Adisak; Intarapuk, Apiradee; Sorosjinda-Nunthawarasilp, Prapa; Maneekan, Pannamas; Koyadun, Surachart

    2013-01-01

    This systematic review elaborates the concepts and impacts of border malaria, particularly on the emergence and spread of Plasmodium falciparum and Plasmodium vivax multidrug resistance (MDR) malaria on Thailand-Myanmar and Thailand-Cambodia borders. Border malaria encompasses any complex epidemiological settings of forest-related and forest fringe-related malaria, both regularly occurring in certain transmission areas and manifesting a trend of increased incidence in transmission prone areas along these borders, as the result of interconnections of human settlements and movement activities, cross-border population migrations, ecological changes, vector population dynamics, and multidrug resistance. For regional and global perspectives, this review analyzes and synthesizes the rationales pertaining to transmission dynamics and the vulnerabilities of border malaria that constrain surveillance and control of the world's most MDR falciparum and vivax malaria on these chaotic borders. PMID:23865048

  8. Dynamics of Forest Malaria Transmission in Balaghat District, Madhya Pradesh, India

    PubMed Central

    Singh, Neeru; Chand, Sunil K.; Bharti, Praveen K.; Singh, Mrigendra P.; Chand, Gyan; Mishra, Ashok K.; Shukla, Man M.; Mahulia, Man M.; Sharma, Ravendra K.

    2013-01-01

    Background An epidemiological and entomological study was carried out in Balaghat district, Madhya Pradesh, India to understand the dynamics of forest malaria transmission in a difficult and hard to reach area where indoor residual spray and insecticide treated nets were used for vector control. Methods This community based cross-sectional study was undertaken from January 2010 to December 2012 in Baihar and Birsa Community Health Centres of district Balaghat for screening malaria cases. Entomological surveillance included indoor resting collections, pyrethrum spray catches and light trap catches. Anophelines were assayed by ELISA for detection of Plasmodium circumsporozoite protein. Findings Plasmodium falciparum infection accounted for >80% of all infections. P. vivax 16.5%, P. malariae 0.75% and remaining were mixed infections of P. falciparum, P. vivax and P. malariae. More than, 30% infections were found in infants under 6 months of age. Overall, an increasing trend in malaria positivity was observed from 2010 to 2012 (chi-square for trend  =  663.55; P<0.0001). Twenty five Anopheles culicifacies (sibling species C, D and E) were positive for circumsporozoite protein of P. falciparum (44%) and P. vivax (56%). Additionally, 2 An. fluviatilis, were found positive for P. falciparum and 1 for P. vivax (sibling species S and T). An. fluviatilis sibling species T was found as vector in forest villages for the first time in India. Conclusion These results showed that the study villages are experiencing almost perennial malaria transmission inspite of indoor residual spray and insecticide treated nets. Therefore, there is a need for new indoor residual insecticides which has longer residual life or complete coverage of population with long lasting insecticide treated nets or both indoor residual spray and long lasting bed nets for effective vector control. There is a need to undertake a well designed case control study to evaluate the efficacy of these

  9. Assessing the Potential Impact of Hormonal-Based Contraceptives on HIV Transmission Dynamics Among Heterosexuals.

    PubMed

    Malunguza, Noble J; Hove-Musekwa, Senelani D; Mukandavire, Zindoga

    2017-03-03

    HIV susceptibility linked to hormonal contraception (HC) has been studied before, but with mixed results. Reports from some of the recent findings have prompted the World Health Organisation to encourage women who use HC to concurrently use condoms in order to prevent HIV infection in the light of possible increased HIV risk of infection associated with hormone-based contraceptives. A two-sex HIV model classifying women into three risk groups consisting of individuals who use condoms, natural methods, and hormone-based contraceptives is formulated and analysed to assess the possible effects of various birth control strategies on the transmission dynamics of the disease. Our model results showed that women who use HC could be key drivers of the epidemic and that their increased infectivity may be critical in driving the epidemic. Women who use hormone-based contraceptives potentially act as a core group from which men get infected and in turn transmit the disease to other population groups. We fitted the model to HIV prevalence data for Zimbabwe reported by UNAIDS and Zimbabwe Ministry of Health and Child Care and used the model fit to project HIV prevalence. Predictions using HIV data for Zimbabwe suggest that a hypothesised increase in susceptibility and infectivity of two-, three-, and fourfold would result in a 25, 50, and 100% increase in baseline HIV prevalence projection, respectively, thus suggesting possible increased disease burden even in countries reporting plausible HIV prevalence declines. Although a possible causal relationship between HIV susceptibility and HC use remains subject of continuing scientific probe, its inclusion as part of birth control strategy has been shown in this study, to possibly increase HIV transmission. If proven, HC use may potentially explain the inordinate spread of HIV within the sub-Saharan Africa region and therefore compel for urgent assessment with a view to reorienting birth control methods in use in settings with

  10. THE ROLE OF REEF FISH IN THE TRANSMISSION DYNAMICS OF BLACK-BAND DISEASE IN THE FLORIDA KEYS

    EPA Science Inventory

    Aeby, Greta S. and Deborah L. Santavy. In press. Role of Reef Fish in the Transmission Dynamics of Black-Band Disease in the Florida Keys (Abstract). To be presented at the 10th International Coral Reef Symposium, 28 June-2 July 2004, Okinawa, Japan. 1 p. (ERL,GB R998).

    T...

  11. THE ROLE OF REEF FISH IN THE TRANSMISSION DYNAMICS OF BLACK-BAND DISEASE IN THE FLORIDA KEYS

    EPA Science Inventory

    Aeby, Greta S. and Deborah L. Santavy. In press. Role of Reef Fish in the Transmission Dynamics of Black-Band Disease in the Florida Keys (Abstract). To be presented at the 10th International Coral Reef Symposium, 28 June-2 July 2004, Okinawa, Japan. 1 p. (ERL,GB R998).

    T...

  12. Jobs and Economic Development from New Transmission and Generation in Wyoming Fact Sheet

    SciTech Connect

    2011-05-10

    Wyoming is a significant energy exporter, producing nearly 40% of the nation's coal and 10% of the nation's natural gas. However, opportunities to add new energy exports in the form of power generation are limited by insufficient transmission capacity. This fact sheet summarizes results from a recent analysis conducted by NREL for the Wyoming Infrastructure Authority that estimates jobs and economic development activity that could occur in Wyoming should the market support new investments in power generation and transmission in the state.

  13. Jobs and Economic Development from New Transmission and Generation in Wyoming (Fact Sheet)

    SciTech Connect

    Not Available

    2011-05-01

    Wyoming is a significant energy exporter, producing nearly 40% of the nation's coal and 10% of the nation's natural gas. However, opportunities to add new energy exports in the form of power generation are limited by insufficient transmission capacity. This fact sheet summarizes results from a recent analysis conducted by NREL for the Wyoming Infrastructure Authority (WIA) that estimates jobs and economic development activity that could occur in Wyoming should the market support new investments in power generation and transmission in the state.

  14. Estimating dynamic transmission model parameters for seasonal influenza by fitting to age and season-specific influenza-like illness incidence.

    PubMed

    Goeyvaerts, Nele; Willem, Lander; Van Kerckhove, Kim; Vandendijck, Yannick; Hanquet, Germaine; Beutels, Philippe; Hens, Niel

    2015-12-01

    Dynamic transmission models are essential to design and evaluate control strategies for airborne infections. Our objective was to develop a dynamic transmission model for seasonal influenza allowing to evaluate the impact of vaccinating specific age groups on the incidence of infection, disease and mortality. Projections based on such models heavily rely on assumed 'input' parameter values. In previous seasonal influenza models, these parameter values were commonly chosen ad hoc, ignoring between-season variability and without formal model validation or sensitivity analyses. We propose to directly estimate the parameters by fitting the model to age-specific influenza-like illness (ILI) incidence data over multiple influenza seasons. We used a weighted least squares (WLS) criterion to assess model fit and applied our method to Belgian ILI data over six influenza seasons. After exploring parameter importance using symbolic regression, we evaluated a set of candidate models of differing complexity according to the number of season-specific parameters. The transmission parameters (average R0, seasonal amplitude and timing of the seasonal peak), waning rates and the scale factor used for WLS optimization, influenced the fit to the observed ILI incidence the most. Our results demonstrate the importance of between-season variability in influenza transmission and our estimates are in line with the classification of influenza seasons according to intensity and vaccine matching.

  15. Postnatal development of a segmental switch enables corticospinal tract transmission to spinal forelimb motor circuits.

    PubMed

    Chakrabarty, Samit; Martin, John H

    2010-02-10

    Development of skilled movements and the corticospinal tract (CST) begin prenatally and continue postnatally. Because the CST is required for skilled movements in maturity, it is accepted that motor skills cannot occur until the CST develops a mature organization. We recently showed that the CST plays an essential role in postnatal development of interneurons comprising the spinal circuits it engages. We proposed that CST signals are more effectively transmitted to ventral motor circuits after interneuron maturation, thereby enabling expression of CST motor functions, suggesting development of a segmental switch promoting transmission. We tested this by recording CST-evoked focal synaptic potentials, extracellularly, in the cervical enlargement of cats before and after interneuron maturation [postnatal week 5 (PW5) to PW7]. We compared monosynaptic CST amplitude input to segmental circuits with oligosynaptic ventral horn responses, as a measure of CST-evoked segmental response transmission from input to output. The M1 primary motor cortex was unilaterally inactivated between PW5 and PW7 to determine activity dependence. CST interneuron contacts were identified using confocal microscopy. CST terminals contact diverse interneuron classes. CST stimulation strongly activated ventral motor circuits at the ages when both interneurons and CST spinal terminations have developed a mature phenotype, supporting development of segmental transmission of CST signals. CST activity blockade impeded development of effective segmental transmission by the inactivated CST and created a novel path for transmission from the ipsilateral, unaffected, CST. Our findings show that development of segmental CST signal transmission regulates nascent CST motor control functions and provide insight into systems-level mechanisms for protracted motor skill development.

  16. Strategies & recent development of transmission-blocking vaccines against Plasmodium falciparum

    PubMed Central

    Chaturvedi, Neha; Bharti, Praveen K.; Tiwari, Archana; Singh, Neeru

    2016-01-01

    Transmission blocking malaria vaccines are aimed to block the development and maturity of sexual stages of parasite within mosquitoes. The vaccine candidate antigens (Pfs25, Pfs48/45, Pfs230) that have shown transmission blocking immunity in model systems are in different stages of development. These antigens are immunogenic with limited genetic diversity. Pfs25 is a leading candidate and currently in phase I clinical trial. Efforts are now focused on the cost-effective production of potent antigens using safe adjuvants and optimization of vaccine delivery system that are capable of inducing strong immune responses. This review addresses the potential usefulness, development strategies, challenges, clinical trials and current status of Plasmodium falciparum sexual stage malaria vaccine candidate antigens for the development of transmission-blocking vaccines. PMID:27748294

  17. Transmission Line Jobs and Economic Development Impact (JEDI) Model User Reference Guide

    SciTech Connect

    Goldberg, M.; Keyser, D.

    2013-10-01

    The Jobs and Economic Development Impact (JEDI) models, developed through the National Renewable Energy Laboratory (NREL), are freely available, user-friendly tools that estimate the potential economic impacts of constructing and operating power generation projects for a range of conventional and renewable energy technologies. The Transmission Line JEDI model can be used to field questions about the economic impacts of transmission lines in a given state, region, or local community. This Transmission Line JEDI User Reference Guide was developed to provide basic instruction on operating the model and understanding the results. This guide also provides information on the model's underlying methodology, as well as the parameters and references used to develop the cost data contained in the model.

  18. Development of malaria transmission-blocking vaccines: from concept to product.

    PubMed

    Wu, Yimin; Sinden, Robert E; Churcher, Thomas S; Tsuboi, Takafumi; Yusibov, Vidadi

    2015-06-01

    Despite decades of effort battling against malaria, the disease is still a major cause of morbidity and mortality. Transmission-blocking vaccines (TBVs) that target sexual stage parasite development could be an integral part of measures for malaria elimination. In the 1950s, Huff et al. first demonstrated the induction of transmission-blocking immunity in chickens by repeated immunizations with Plasmodium gallinaceum-infected red blood cells. Since then, significant progress has been made in identification of parasite antigens responsible for transmission-blocking activity. Recombinant technologies accelerated evaluation of these antigens as vaccine candidates, and it is possible to induce effective transmission-blocking immunity in humans both by natural infection and now by immunization with recombinant vaccines. This chapter reviews the efforts to produce TBVs, summarizes the current status and advances and discusses the remaining challenges and approaches. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Parameterization and sensitivity analysis of a complex simulation model for mosquito population dynamics, dengue transmission, and their control.

    PubMed

    Ellis, Alicia M; Garcia, Andres J; Focks, Dana A; Morrison, Amy C; Scott, Thomas W

    2011-08-01

    Models can be useful tools for understanding the dynamics and control of mosquito-borne disease. More detailed models may be more realistic and better suited for understanding local disease dynamics; however, evaluating model suitability, accuracy, and performance becomes increasingly difficult with greater model complexity. Sensitivity analysis is a technique that permits exploration of complex models by evaluating the sensitivity of the model to changes in parameters. Here, we present results of sensitivity analyses of two interrelated complex simulation models of mosquito population dynamics and dengue transmission. We found that dengue transmission may be influenced most by survival in each life stage of the mosquito, mosquito biting behavior, and duration of the infectious period in humans. The importance of these biological processes for vector-borne disease models and the overwhelming lack of knowledge about them make acquisition of relevant field data on these biological processes a top research priority.

  20. Transmission dynamics of parasitic sea lice from farm to wild salmon.

    PubMed

    Krkosek, Martin; Lewis, Mark A; Volpe, John P

    2005-04-07

    Marine salmon farming has been correlated with parasitic sea lice infestations and concurrent declines of wild salmonids. Here, we report a quantitative analysis of how a single salmon farm altered the natural transmission dynamics of sea lice to juvenile Pacific salmon. We studied infections of sea lice (Lepeophtheirus salmonis and Caligus clemensi) on juvenile pink salmon (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) as they passed an isolated salmon farm during their seaward migration down two long and narrow corridors. Our calculations suggest the infection pressure imposed by the farm was four orders of magnitude greater than ambient levels, resulting in a maximum infection pressure near the farm that was 73 times greater than ambient levels and exceeded ambient levels for 30 km along the two wild salmon migration corridors. The farm-produced cohort of lice parasitizing the wild juvenile hosts reached reproductive maturity and produced a second generation of lice that re-infected the juvenile salmon. This raises the infection pressure from the farm by an additional order of magnitude, with a composite infection pressure that exceeds ambient levels for 75 km of the two migration routes. Amplified sea lice infestations due to salmon farms are a potential limiting factor to wild salmonid conservation.

  1. Transmission dynamics of resistant bacteria in a predator-prey system.

    PubMed

    Gao, Xubin; Pan, Qiuhui; He, Mingfeng

    2015-01-01

    This paper discusses the impact on human health caused by the addition of antibiotics in the feed of food animals. We use the established transmission rule of resistant bacteria and combine it with a predator-prey system to determine a differential equations model. The equations have three steady equilibrium points corresponding to three population dynamics states under the influence of resistant bacteria. In order to quantitatively analyze the stability of the equilibrium points, we focused on the basic reproduction numbers. Then, both the local and global stability of the equilibrium points were quantitatively analyzed by using essential mathematical methods. Numerical results are provided to relate our model properties to some interesting biological cases. Finally, we discuss the effect of the two main parameters of the model, the proportion of antibiotics added to feed and the predation rate, and estimate the human health impacts related to the amount of feed antibiotics used. We further propose an approach for the prevention of the large-scale spread of resistant bacteria and illustrate the necessity of controlling the amount of in-feed antibiotics used.

  2. Quantifying Transient States in Materials with the Dynamic Transmission Electron Microscope

    SciTech Connect

    Campbell, G; LaGrange, T; Kim, J; Reed, B; Browning, N

    2009-09-21

    The Dynamic Transmission Electron Microscope (DTEM) offers a means of capturing rapid evolution in a specimen through in-situ microscopy experiments by allowing 15 ns electron micrograph exposure times. The rapid exposure time is enabled by creating a burst of electrons at the emitter by ultraviolet pulsed laser illumination. This burst arrives a specified time after a second laser initiates the specimen reaction. The timing of the two Q-switched lasers is controlled by high-speed pulse generators with a timing error much less than the pulse duration. Both diffraction and imaging experiments can be performed, just as in a conventional TEM. The brightness of the emitter and the total current control the spatial and temporal resolutions. We have demonstrated 7 nm spatial resolution in single 15 ns pulsed images. These single-pulse imaging experiments have been used to study martensitic transformations, nucleation and crystallization of an amorphous metal, and rapid chemical reactions. Measurements have been performed on these systems that are possible by no other experimental approaches currently available.

  3. Economics, cultural transmission, and the dynamics of the sex ratio at birth in China

    PubMed Central

    Lipatov, Mikhail; Li, Shuzhuo; Feldman, Marcus W.

    2008-01-01

    In rural China, the ratio of newborn boys to newborn girls [sex ratio at birth (SRB)] has been rising for several decades, to values significantly above its biological norm. This trend has a number of alarming societal consequences, and has attracted the attention of scholars and politicians. The root of the problem lies in a 2,500-year-old culture of son preference. This culture is intricately linked with the economic reality of each couple's life, so that there are financial and psychological repercussions to parents who have no sons. To bring greater clarity and understanding to this issue, we present a quantitative framework that describes the interaction between economics and cultural transmission. We start with an explicit mechanism by which economic incentives can change cultural beliefs of a given individual, and go on to include a mechanism of cultural inheritance from generation to generation. We then show how economic conditions can affect the dynamics of cultural change in an entire society, and may lead to a decrease in the country's sex ratio at birth. PMID:19047641

  4. The impact of a parkinsonian lesion on dynamic striatal dopamine transmission depends on nicotinic receptor activation.

    PubMed

    Jennings, Katie A; Platt, Nicola J; Cragg, Stephanie J

    2015-10-01

    Dopamine function is disturbed in Parkinson's disease (PD), but whether and how release of dopamine from surviving neurons is altered has long been debated. Nicotinic acetylcholine receptors (nAChRs) on dopamine axons powerfully govern dopamine release and could be critical contributing factors. We revisited whether fundamental properties of dopamine transmission are changed in a parkinsonian brain and tested the potentially profound masking effects of nAChRs. Using real-time detection of dopamine in mouse striatum after a partial 6-hydroxydopamine lesion and under nAChR inhibition, we reveal that dopamine signals show diminished sensitivity to presynaptic activity. This effect manifested as diminished contrast between DA release evoked by the lowest versus highest frequencies. This reduced activity-dependence was underpinned by loss of short-term facilitation of dopamine release, consistent with an increase in release probability (Pr). With nAChRs active, the reduced activity-dependence of dopamine release after a parkinsonian lesion was masked. Consequently, moment-by-moment variation in activity of nAChRs may lead to dynamic co-variation in dopamine signal impairments in PD.

  5. Dynamics of an SIS reaction-diffusion epidemic model for disease transmission.

    PubMed

    Huang, Wenzhang; Han, Maoan; Liu, Kaiyu

    2010-01-01

    Recently an SIS epidemic reaction-diffusion model with Neumann (or no-flux) boundary condition has been proposed and studied by several authors to understand the dynamics of disease transmission in a spatially heterogeneous environment in which the individuals are subject to a random movement. Many important and interesting properties have been obtained: such as the role of diffusion coefficients in defining the reproductive number; the global stability of disease-free equilibrium; the existence and uniqueness of a positive endemic steady; global stability of endemic steady for some particular cases; and the asymptotical profiles of the endemic steady states as the diffusion coefficient for susceptible individuals is sufficiently small. In this research we will study two modified SIS diffusion models with the Dirichlet boundary condition that reflects a hostile environment in the boundary. The reproductive number is defined which plays an essential role in determining whether the disease will extinct or persist. We have showed that the disease will die out when the reproductive number is less than one and that the endemic equilibrium occurs when the reproductive number is exceeds one. Partial result on the global stability of the endemic equilibrium is also obtained.

  6. Modeling methicillin-resistant Staphylococcus aureus in hospitals: transmission dynamics, antibiotic usage and its history.

    PubMed

    Chamchod, Farida; Ruan, Shigui

    2012-06-27

    Methicillin-resistant Staphylococcus aureus (MRSA) is endemic in many hospital settings, posing substantial threats and economic burdens worldwide. We propose mathematical models to investigate the transmission dynamics of MRSA and determine factors that influence the prevalence of MRSA infection when antibiotics are given to patients to treat or prevent infections with either MRSA itself or other bacterial pathogens. Our results suggest that: (i) MRSA always persists in the hospital when colonized and infected patients are admitted; (ii) the longer the duration of treatment of infected patients and the lower the probability of successful treatment will increase the prevalence of MRSA infection; (iii) the longer the duration of contamination of health care workers (HCWs) and the more their contacts with patients may increase the prevalence of MRSA infection; (iv) possible ways to control the prevalence of MRSA infection include treating patients with antibiotic history as quickly and efficiently as possible, screening and isolating colonized and infected patients at admission, and compliance with strict hand-washing rules by HCWs. Our modeling studies offer an approach to investigating MRSA infection in hospital settings and the impact of antibiotic history on the incidence of infection. Our findings suggest important influences on the prevalence of MRSA infection which may be useful in designing control policies.

  7. Modeling methicillin-resistant Staphylococcus aureus in hospitals: Transmission dynamics, antibiotic usage and its history

    PubMed Central

    2012-01-01

    Background Methicillin-resistant Staphylococcus aureus (MRSA) is endemic in many hospital settings, posing substantial threats and economic burdens worldwide. Methods We propose mathematical models to investigate the transmission dynamics of MRSA and determine factors that influence the prevalence of MRSA infection when antibiotics are given to patients to treat or prevent infections with either MRSA itself or other bacterial pathogens. Results Our results suggest that: (i) MRSA always persists in the hospital when colonized and infected patients are admitted; (ii) the longer the duration of treatment of infected patients and the lower the probability of successful treatment will increase the prevalence of MRSA infection; (iii) the longer the duration of contamination of health care workers (HCWs) and the more their contacts with patients may increase the prevalence of MRSA infection; (iv) possible ways to control the prevalence of MRSA infection include treating patients with antibiotic history as quickly and efficiently as possible, screening and isolating colonized and infected patients at admission, and compliance with strict hand-washing rules by HCWs. Conclusion Our modeling studies offer an approach to investigating MRSA infection in hospital settings and the impact of antibiotic history on the incidence of infection. Our findings suggest important influences on the prevalence of MRSA infection which may be useful in designing control policies. PMID:22738359

  8. Transmission of severe acute respiratory syndrome in dynamical small-world networks

    NASA Astrophysics Data System (ADS)

    Masuda, Naoki; Konno, Norio; Aihara, Kazuyuki

    2004-03-01

    The outbreak of severe acute respiratory syndrome (SARS) is still threatening the world because of a possible resurgence. In the current situation that effective medical treatments such as antiviral drugs are not discovered yet, dynamical features of the epidemics should be clarified for establishing strategies for tracing, quarantine, isolation, and regulating social behavior of the public at appropriate costs. Here we propose a network model for SARS epidemics and discuss why superspreaders emerged and why SARS spread especially in hospitals, which were key factors of the recent outbreak. We suggest that superspreaders are biologically contagious patients, and they may amplify the spreads by going to potentially contagious places such as hospitals. To avoid mass transmission in hospitals, it may be a good measure to treat suspected cases without hospitalizing them. Finally, we indicate that SARS probably propagates in small-world networks associated with human contacts and that the biological nature of individuals and social group properties are factors more important than the heterogeneous rates of social contacts among individuals. This is in marked contrast with epidemics of sexually transmitted diseases or computer viruses to which scale-free network models often apply.

  9. Quantifying seasonal population fluxes driving rubella transmission dynamics using mobile phone data.

    PubMed

    Wesolowski, Amy; Metcalf, C J E; Eagle, Nathan; Kombich, Janeth; Grenfell, Bryan T; Bjørnstad, Ottar N; Lessler, Justin; Tatem, Andrew J; Buckee, Caroline O

    2015-09-01

    Changing patterns of human aggregation are thought to drive annual and multiannual outbreaks of infectious diseases, but the paucity of data about travel behavior and population flux over time has made this idea difficult to test quantitatively. Current measures of human mobility, especially in low-income settings, are often static, relying on approximate travel times, road networks, or cross-sectional surveys. Mobile phone data provide a unique source of information about human travel, but the power of these data to describe epidemiologically relevant changes in population density remains unclear. Here we quantify seasonal travel patterns using mobile phone data from nearly 15 million anonymous subscribers in Kenya. Using a rich data source of rubella incidence, we show that patterns of population travel (fluxes) inferred from mobile phone data are predictive of disease transmission and improve significantly on standard school term time and weather covariates. Further, combining seasonal and spatial data on travel from mobile phone data allows us to characterize seasonal fluctuations in risk across Kenya and produce dynamic importation risk maps for rubella. Mobile phone data therefore offer a valuable previously unidentified source of data for measuring key drivers of seasonal epidemics.

  10. Transmission dynamics of West Nile virus in mosquitoes and corvids and non-corvids.

    PubMed

    Abdelrazec, Ahmed; Lenhart, Suzanne; Zhu, Huaiping

    2014-05-01

    There are more than 300 avian species that can transmit West Nile virus (WNv). In general, the corvid and non-corvid families of birds have different responses to the virus, with corvids suffering a higher disease-induced mortality rate. By taking both corvids and non-corvids as the primary reservoir hosts and mosquitoes as vectors; we formulate and study a system of ordinary differential equations to model a single season of the transmission dynamics of WNv in the mosquito-bird cycle. We calculate the basic reproduction number and analyze the existence and stability of the equilibria. The existence of a backward bifurcation gives a further sub-threshold condition beyond the basic reproduction number for the spread of the virus. We also discuss the role of corvids and non-corvids in spreading the virus. We conclude that knowledge of the relative abundance of corvid bird species and other mammals assist us in accurate estimation of the epidemic of WNv.

  11. High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy.

    PubMed

    Tate, Mark W; Purohit, Prafull; Chamberlain, Darol; Nguyen, Kayla X; Hovden, Robert; Chang, Celesta S; Deb, Pratiti; Turgut, Emrah; Heron, John T; Schlom, Darrell G; Ralph, Daniel C; Fuchs, Gregory D; Shanks, Katherine S; Philipp, Hugh T; Muller, David A; Gruner, Sol M

    2016-02-01

    We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80-200 keV electron beams.

  12. Evolutionary and transmission dynamics of reassortant H5N1 influenza virus in Indonesia.

    PubMed

    Lam, Tommy Tsan-Yuk; Hon, Chung-Chau; Pybus, Oliver G; Kosakovsky Pond, Sergei L; Wong, Raymond Tze-Yeung; Yip, Chi-Wai; Zeng, Fanya; Leung, Frederick Chi-Ching

    2008-08-22

    H5N1 highly pathogenic avian influenza (HPAI) viruses have seriously affected the Asian poultry industry since their recurrence in 2003. The viruses pose a threat of emergence of a global pandemic influenza through point mutation or reassortment leading to a strain that can effectively transmit among humans. In this study, we present phylogenetic evidences for the interlineage reassortment among H5N1 HPAI viruses isolated from humans, cats, and birds in Indonesia, and identify the potential genetic parents of the reassorted genome segments. Parsimony analyses of viral phylogeography suggest that the reassortant viruses may have originated from greater Jakarta and surroundings, and subsequently spread to other regions in the West Java province. In addition, Bayesian methods were used to elucidate the genetic diversity dynamics of the reassortant strain and one of its genetic parents, which revealed a more rapid initial growth of genetic diversity in the reassortant viruses relative to their genetic parent. These results demonstrate that interlineage exchange of genetic information may play a pivotal role in determining viral genetic diversity in a focal population. Moreover, our study also revealed significantly stronger diversifying selection on the M1 and PB2 genes in the lineages preceding and subsequent to the emergence of the reassortant viruses, respectively. We discuss how the corresponding mutations might drive the adaptation and onward transmission of the newly formed reassortant viruses.

  13. A Theoretical Model for the Transmission Dynamics of the Buruli Ulcer with Saturated Treatment

    PubMed Central

    Bonyah, Ebenezer; Dontwi, Isaac

    2014-01-01

    The management of the Buruli ulcer (BU) in Africa is often accompanied by limited resources, delays in treatment, and macilent capacity in medical facilities. These challenges limit the number of infected individuals that access medical facilities. While most of the mathematical models with treatment assume a treatment function proportional to the number of infected individuals, in settings with such limitations, this assumption may not be valid. To capture these challenges, a mathematical model of the Buruli ulcer with a saturated treatment function is developed and studied. The model is a coupled system of two submodels for the human population and the environment. We examine the stability of the submodels and carry out numerical simulations. The model analysis is carried out in terms of the reproduction number of the submodel of environmental dynamics. The dynamics of the human population submodel, are found to occur at the steady states of the submodel of environmental dynamics. Sensitivity analysis is carried out on the model parameters and it is observed that the BU epidemic is driven by the dynamics of the environment. The model suggests that more effort should be focused on environmental management. The paper is concluded by discussing the public implications of the results. PMID:25214885

  14. Cost-effectiveness of seasonal quadrivalent versus trivalent influenza vaccination in the United States: A dynamic transmission modeling approach

    PubMed Central

    Brogan, Anita J.; Talbird, Sandra E.; Davis, Ashley E.; Thommes, Edward W.; Meier, Genevieve

    2017-01-01

    ABSTRACT Trivalent inactivated influenza vaccines (IIV3s) protect against 2 A strains and one B lineage; quadrivalent versions (IIV4s) protect against an additional B lineage. The objective was to assess projected health and economic outcomes associated with IIV4 versus IIV3 for preventing seasonal influenza in the US. A cost-effectiveness model was developed to interact with a dynamic transmission model. The transmission model tracked vaccination, influenza cases, infection-spreading interactions, and recovery over 10 y (2012–2022). The cost-effectiveness model estimated influenza-related complications, direct and indirect costs (2013–2014 US$), health outcomes, and cost-effectiveness. Inputs were taken from published/public sources or estimated using regression or calibration. Outcomes were discounted at 3% per year. Scenario analyses tested the reliability of the results. Seasonal vaccination with IIV4 versus IIV3 is predicted to reduce annual influenza cases by 1,973,849 (discounted; 2,325,644 undiscounted), resulting in 12–13% fewer cases and influenza-related complications and deaths. These reductions are predicted to translate into 18,485 more quality-adjusted life years (QALYs) accrued annually for IIV4 versus IIV3. Increased vaccine-related costs ($599 million; 5.7%) are predicted to be more than offset by reduced influenza treatment costs ($699 million; 12.2%), resulting in direct medical cost saving annually ($100 million; 0.6%). Including indirect costs, savings with IIV4 are predicted to be $7.1 billion (5.6%). Scenario analyses predict IIV4 to be cost-saving in all scenarios tested apart from low infectivity, where IIV4 is predicted to be cost-effective. In summary, seasonal influenza vaccination in the US with IIV4 versus IIV3 is predicted to improve health outcomes and reduce costs. PMID:27780425

  15. Combining nanocalorimetry and dynamic transmission electron microscopy for in situ characterization of materials processes under rapid heating and cooling

    SciTech Connect

    Grapes, Michael D.; LaGrange, Thomas; Reed, Bryan W.; Campbell, Geoffrey H.; Friedman, Lawrence H.; LaVan, David A.; Weihs, Timothy P.

    2014-08-15

    Nanocalorimetry is a chip-based thermal analysis technique capable of analyzing endothermic and exothermic reactions at very high heating and cooling rates. Here, we couple a nanocalorimeter with an extremely fast in situ microstructural characterization tool to identify the physical origin of rapid enthalpic signals. More specifically, we describe the development of a system to enable in situ nanocalorimetry experiments in the dynamic transmission electron microscope (DTEM), a time-resolved TEM capable of generating images and electron diffraction patterns with exposure times of 30 ns–500 ns. The full experimental system consists of a modified nanocalorimeter sensor, a custom-built in situ nanocalorimetry holder, a data acquisition system, and the DTEM itself, and is capable of thermodynamic and microstructural characterization of reactions over a range of heating rates (10{sup 2} K/s–10{sup 5} K/s) accessible by conventional (DC) nanocalorimetry. To establish its ability to capture synchronized calorimetric and microstructural data during rapid transformations, this work describes measurements on the melting of an aluminum thin film. We were able to identify the phase transformation in both the nanocalorimetry traces and in electron diffraction patterns taken by the DTEM. Potential applications for the newly developed system are described and future system improvements are discussed.

  16. Combining nanocalorimetry and dynamic transmission electron microscopy for in situ characterization of materials processes under rapid heating and cooling.

    PubMed

    Grapes, Michael D; LaGrange, Thomas; Friedman, Lawrence H; Reed, Bryan W; Campbell, Geoffrey H; Weihs, Timothy P; LaVan, David A

    2014-08-01

    Nanocalorimetry is a chip-based thermal analysis technique capable of analyzing endothermic and exothermic reactions at very high heating and cooling rates. Here, we couple a nanocalorimeter with an extremely fast in situ microstructural characterization tool to identify the physical origin of rapid enthalpic signals. More specifically, we describe the development of a system to enable in situ nanocalorimetry experiments in the dynamic transmission electron microscope (DTEM), a time-resolved TEM capable of generating images and electron diffraction patterns with exposure times of 30 ns-500 ns. The full experimental system consists of a modified nanocalorimeter sensor, a custom-built in situ nanocalorimetry holder, a data acquisition system, and the DTEM itself, and is capable of thermodynamic and microstructural characterization of reactions over a range of heating rates (10(2) K/s-10(5) K/s) accessible by conventional (DC) nanocalorimetry. To establish its ability to capture synchronized calorimetric and microstructural data during rapid transformations, this work describes measurements on the melting of an aluminum thin film. We were able to identify the phase transformation in both the nanocalorimetry traces and in electron diffraction patterns taken by the DTEM. Potential applications for the newly developed system are described and future system improvements are discussed.

  17. Intra-epidemic evolutionary dynamics of a Dengue virus type 1 population reveal mutant spectra that correlate with disease transmission

    PubMed Central

    Hapuarachchi, Hapuarachchige Chanditha; Koo, Carmen; Kek, Relus; Xu, Helen; Lai, Yee Ling; Liu, Lilac; Kok, Suet Yheng; Shi, Yuan; Chuen, Raphael Lee Tze; Lee, Kim-Sung; Maurer-Stroh, Sebastian; Ng, Lee Ching

    2016-01-01

    Dengue virus (DENV) is currently the most prevalent mosquito-borne viral pathogen. DENVs naturally exist as highly heterogeneous populations. Even though the descriptions on DENV diversity are plentiful, only a few studies have narrated the dynamics of intra-epidemic virus diversity at a fine scale. Such accounts are important to decipher the reciprocal relationship between viral evolutionary dynamics and disease transmission that shape dengue epidemiology. In the current study, we present a micro-scale genetic analysis of a monophyletic lineage of DENV-1 genotype III (epidemic lineage) detected from November 2012 to May 2014. The lineage was involved in an unprecedented dengue epidemic in Singapore during 2013–2014. Our findings showed that the epidemic lineage was an ensemble of mutants (variants) originated from an initial mixed viral population. The composition of mutant spectrum was dynamic and positively correlated with case load. The close interaction between viral evolution and transmission intensity indicated that tracking genetic diversity through time is potentially a useful tool to infer DENV transmission dynamics and thereby, to assess the epidemic risk in a disease control perspective. Moreover, such information is salient to understand the viral basis of clinical outcome and immune response variations that is imperative to effective vaccine design. PMID:26940650

  18. In-situ Study of Dynamic Phenomena at Metal Nanosolder Interfaces Using Aberration Corrected Scanning Transmission Electron Microcopy.

    SciTech Connect

    Lu, Ping

    2014-10-01

    Controlling metallic nanoparticle (NP) interactions plays a vital role in the development of new joining techniques (nanosolder) that bond at lower processing temperatures but remain viable at higher temperatures. The pr imary objective of this project is t o develop a fundamental understanding of the actual reaction processes, associated atomic mechanisms, and the resulting microstructure that occur during thermally - driven bond formation concerning metal - metal nano - scale (%3C50nm) interfaces. In this LDRD pr oject, we have studied metallic NPs interaction at the elevated temperatures by combining in - situ transmission electron microscopy (TEM ) using an aberration - corrected scanning transmission electron microscope (AC - STEM) and atomic - scale modeling such as m olecular dynamic (MD) simulations. Various metallic NPs such as Ag, Cu and Au are synthesized by chemical routines. Numerous in - situ e xperiments were carried out with focus of the research on study of Ag - Cu system. For the first time, using in - situ STEM he ating experiments , we directly observed t he formation of a 3 - dimensional (3 - D) epitaxial Cu - Ag core - shell nanoparticle during the thermal interaction of Cu and Ag NPs at elevated temperatures (150 - 300 o C). The reaction takes place at temperatures as low as 150 o C and was only observed when care was taken to circumvent the effects of electron beam irradiation during STEM imaging. Atomic - scale modeling verified that the Cu - Ag core - shell structure is energetically favored, and indicated that this phenomenon is a nano - scale effect related to the large surface - to - volume ratio of the NPs. The observation potentially can be used for developing new nanosolder technology that uses Ag shell as the "glue" that stic ks the particles of Cu together. The LDRD has led to several journal publications and numerous conference presentations, and a TA. In addition, we have developed new TEM characterization techniques and phase

  19. Controlling Complex Systems and Developing Dynamic Technology

    NASA Astrophysics Data System (ADS)

    Avizienis, Audrius Victor

    In complex systems, control and understanding become intertwined. Following Ilya Prigogine, we define complex systems as having control parameters which mediate transitions between distinct modes of dynamical behavior. From this perspective, determining the nature of control parameters and demonstrating the associated dynamical phase transitions are practically equivalent and fundamental to engaging with complexity. In the first part of this work, a control parameter is determined for a non-equilibrium electrochemical system by studying a transition in the morphology of structures produced by an electroless deposition reaction. Specifically, changing the size of copper posts used as the substrate for growing metallic silver structures by the reduction of Ag+ from solution under diffusion-limited reaction conditions causes a dynamical phase transition in the crystal growth process. For Cu posts with edge lengths on the order of one micron, local forces promoting anisotropic growth predominate, and the reaction produces interconnected networks of Ag nanowires. As the post size is increased above 10 microns, the local interfacial growth reaction dynamics couple with the macroscopic diffusion field, leading to spatially propagating instabilities in the electrochemical potential which induce periodic branching during crystal growth, producing dendritic deposits. This result is interesting both as an example of control and understanding in a complex system, and as a useful combination of top-down lithography with bottom-up electrochemical self-assembly. The second part of this work focuses on the technological development of devices fabricated using this non-equilibrium electrochemical process, towards a goal of integrating a complex network as a dynamic functional component in a neuromorphic computing device. Self-assembled networks of silver nanowires were reacted with sulfur to produce interfacial "atomic switches": silver-silver sulfide junctions, which exhibit

  20. Comment on "Dynamics and properties of waves in a modified Noguchi electrical transmission line"

    NASA Astrophysics Data System (ADS)

    Kenmogne, Fabien; Yemélé, David; Marquié, Patrick

    2016-09-01

    A recent paper [Phys. Rev. E 91, 022925 (2015), 10.1103/PhysRevE.91.022925] presents the derivation of the nonlinear equation modeling envelope waves in a specific case of band passed filter discrete nonlinear electrical transmission line (NLTL), called "A modified Noguchi electrical transmission line" according to the authors. Using the reductive perturbation approach in the semidiscrete approximation, they showed that the modulated waves propagating in this NLTL are described by the ordinary nonlinear Schrödinger (NLS) equation. On the basis of their results, the authors claimed that all previous works on the band passed filter NLTL, which considered the vanishing of the dc component of the signal voltage, are incorrect, and this dc term is nonzero. As a consequence, the dispersion and nonlinearity coefficients of the NLS equation are strongly different from those usually obtained, and they found, according to the sign of the product P Q , the existence of one more region (compared to the work of Marquié et al. [Phys. Rev. E 49, 828 (1994)], 10.1103/PhysRevE.49.828) in the dispersion curve that allows the motion of envelope solitons of higher frequency in the system. In this Comment we provide sufficient theoretical and numerical evidence showing that the evidence obtained by the authors otherwise is due to certain terms missed in their mathematical developments when they derived the NLS equation. Our results also suggest that the previous work of Marquié and co-workers correctly predict the fact that the dc term of the signal voltage does not exist and there exist only two regions in the dispersion curve according to the sign of the product P Q .

  1. Experimental pig-to-pig transmission dynamics for African swine fever virus, Georgia 2007/1 strain.

    PubMed

    Guinat, C; Gubbins, S; Vergne, T; Gonzales, J L; Dixon, L; Pfeiffer, D U

    2016-01-01

    African swine fever virus (ASFV) continues to cause outbreaks in domestic pigs and wild boar in Eastern European countries. To gain insights into its transmission dynamics, we estimated the pig-to-pig basic reproduction number (R 0) for the Georgia 2007/1 ASFV strain using a stochastic susceptible-exposed-infectious-recovered (SEIR) model with parameters estimated from transmission experiments. Models showed that R 0 is 2·8 [95% confidence interval (CI) 1·3-4·8] within a pen and 1·4 (95% CI 0·6-2·4) between pens. The results furthermore suggest that ASFV genome detection in oronasal samples is an effective diagnostic tool for early detection of infection. This study provides quantitative information on transmission parameters for ASFV in domestic pigs, which are required to more effectively assess the potential impact of strategies for the control of between-farm epidemic spread in European countries.

  2. Transmission of low-energy oxygen ions through ultrathin rare-gas films: Molecular-dynamics simulation

    NASA Astrophysics Data System (ADS)

    Klein, Peter; Urbassek, Herbert M.; Vicanek, Martin

    1995-02-01

    By use of molecular dynamics we simulate a recent experiment by Sack et al. in which oxygen ions are desorbed by electron impact from a WOx surface, and their transmission through rare-gas films of a few monolayer thickness has been measured. When using only elastic scattering cross sections between O+ and rare-gas atoms in the simulation, we find fair quantitative agreement with the measured transmission yield, and energy, and angular distributions, for Xe and Kr films. The large number of transmitted oxygen ions can be traced back to the small O+ radius. The discrepancy between measured and simulated transmission behavior through Ar films is attributed to either electronically inelastic losses or structural effects in these films. The im pact of this work on the depth of origin of sputtered particles is discussed.

  3. Mitochondrial dynamics and inheritance during cell division, development and disease.

    PubMed

    Mishra, Prashant; Chan, David C

    2014-10-01

    During cell division, it is critical to properly partition functional sets of organelles to each daughter cell. The partitioning of mitochondria shares some common features with that of other organelles, particularly in the use of interactions with cytoskeletal elements to facilitate delivery to the daughter cells. However, mitochondria have unique features - including their own genome and a maternal mode of germline transmission - that place additional demands on this process. Consequently, mechanisms have evolved to regulate mitochondrial segregation during cell division, oogenesis, fertilization and tissue development, as well as to ensure the integrity of these organelles and their DNA, including fusion-fission dynamics, organelle transport, mitophagy and genetic selection of functional genomes. Defects in these processes can lead to cell and tissue pathologies.

  4. Micellar aggregates of saponins from Chenopodium quinoa: characterization by dynamic light scattering and transmission electron microscopy.

    PubMed

    Verza, S G; de Resende, P E; Kaiser, S; Quirici, L; Teixeira, H F; Gosmann, G; Ferreira, F; Ortega, G G

    2012-04-01

    Entire seeds of Chenopodium quinoa Willd are a rich protein source and are also well-known for their high saponin content. Due to their amphiphily quinoa saponins are able to form intricate micellar aggregates in aqueous media. In this paper we study the aggregates formed by self-association of these compounds from two quinoa saponin fractions (FQ70 and FQ90) as well as several distinctive nanostructures obtained after their complexation with different ratios of cholesterol (CHOL) and phosphatidylcholine (PC). The FQ70 and FQ90 fractions were obtained by reversed-phase preparative chromatography. The structural features of their resulting aggregates were determined by Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Novel nanosized spherical vesicles formed by self-association with mean diameter about 100-200 nm were observed in FQ70 aqueous solutions whereas worm-like micelles an approximate width of 20 nm were detected in FQ90 aqueous solutions. Under experimental conditions similar to those reported for the preparation of Quillaja saponaria ISCOM matrices, tubular and ring-like micelles arose from FQ70:CHOL:PC and FQ90:CHOL:PC formulations, respectively. However, under these conditions no cage-like ISCOM matrices were observed. The saponin composition of FQ70 and FQ90 seems to determine the nanosized structures viewed by TEM. Phytolaccagenic acid, predominant in FQ70 and FQ90 fractions, is accountable for the formation of the nanosized vesicles and tubular structures observed by TEM in the aqueous solutions of both samples. Conversely, ring-like micelles observed in FQ90:CHOL:PC complexes can be attributed to the presence of less polar saponins present in FQ90, in particular those derived from oleanolic acid.

  5. Force transmission via axial tendons in undulating fish: a dynamic analysis.

    PubMed

    Long, John H; Adcock, Bruce; Root, Robert G

    2002-12-01

    Sonomicrometrics of in vivo axial strain of muscle has shown that the swimming fish body bends like a homogenous, continuous beam in all species except tuna. This simple beam-like behavior is surprising because the underlying tendon structure, muscle structure and behavior are complex. Given this incongruence, our goal was to understand the mechanical role of various myoseptal tendons. We modeled a pumpkinseed sunfish, Lepomis gibbosus, using experimentally-derived physical and mechanical attributes, swimming from rest with steady muscle activity. Axially oriented muscle-tendons, transverse and axial myoseptal tendons, as suggested by current morphological knowledge, interacted to replicate the force and moment distribution. Dynamic stiffness and damping associated with muscle activation, realistic muscle force generation, and force distribution following tendon geometry were incorporated. The vertebral column consisted of 11 rigid vertebrae connected by joints that restricted bending to the lateral plane and endowed the body with its passive viscoelasticity. In reaction to the acceleration of the body in an inviscid fluid and its internal transmission of moment via the vertebral column, the model predicted the kinematic response. Varying only tendon geometry and stiffness, four different simulations were run. Simulations with only intrasegmental tendons produced unstable axial and lateral tail forces and body motions. Only the simulation that included both intra- and intersegmental tendons, muscle-enhanced segment stiffness, and a stiffened caudal joint produced stable and large lateral and axial forces at the tail. Thus this model predicts that axial tendons function within a myomere to (1) convert axial force to moment (moment transduction), (2) transmit axial forces between adjacent myosepta (segment coupling), and, intersegmentally, to (3) distribute axial forces (force entrainment), and (4) stiffen joints in bending (flexural stiffening). The fact that all

  6. Quantifying aggregation dynamics during Myxococcus xanthus development.

    PubMed

    Zhang, Haiyang; Angus, Stuart; Tran, Michael; Xie, Chunyan; Igoshin, Oleg A; Welch, Roy D

    2011-10-01

    Under starvation conditions, a swarm of Myxococcus xanthus cells will undergo development, a multicellular process culminating in the formation of many aggregates called fruiting bodies, each of which contains up to 100,000 spores. The mechanics of symmetry breaking and the self-organization of cells into fruiting bodies is an active area of research. Here we use microcinematography and automated image processing to quantify several transient features of developmental dynamics. An analysis of experimental data indicates that aggregation reaches its steady state in a highly nonmonotonic fashion. The number of aggregates rapidly peaks at a value 2- to 3-fold higher than the final value and then decreases before reaching a steady state. The time dependence of aggregate size is also nonmonotonic, but to a lesser extent: average aggregate size increases from the onset of aggregation to between 10 and 15 h and then gradually decreases thereafter. During this process, the distribution of aggregates transitions from a nearly random state early in development to a more ordered state later in development. A comparison of experimental results to a mathematical model based on the traffic jam hypothesis indicates that the model fails to reproduce these dynamic features of aggregation, even though it accurately describes its final outcome. The dynamic features of M. xanthus aggregation uncovered in this study impose severe constraints on its underlying mechanisms.

  7. Phylogenetic studies of transmission dynamics in generalized HIV epidemics: An essential tool where the burden is greatest?

    PubMed Central

    Dennis, Ann M.; Herbeck, Joshua T.; Brown, Andrew Leigh; Kellam, Paul; de Oliveira, Tulio; Pillay, Deenan; Fraser, Christophe; Cohen, Myron S.

    2014-01-01

    Efficient and effective HIV prevention measures for generalized epidemics in sub-Saharan Africa have not yet been validated at the population-level. Design and impact evaluation of such measures requires fine-scale understanding of local HIV transmission dynamics. The novel tools of HIV phylogenetics and molecular epidemiology may elucidate these transmission dynamics. Such methods have been incorporated into studies of concentrated HIV epidemics to identify proximate and determinant traits associated with ongoing transmission. However, applying similar phylogenetic analyses to generalized epidemics, including the design and evaluation of prevention trials, presents additional challenges. Here we review the scope of these methods and present examples of their use in concentrated epidemics in the context of prevention. Next, we describe the current uses for phylogenetics in generalized epidemics, and discuss their promise for elucidating transmission patterns and informing prevention trials. Finally, we review logistic and technical challenges inherent to large-scale molecular epidemiological studies of generalized epidemics, and suggest potential solutions. PMID:24977473

  8. Transmission Dynamics of Rift Valley Fever Virus: Effects of Live and Killed Vaccines on Epizootic Outbreaks and Enzootic Maintenance

    PubMed Central

    Chamchod, Farida; Cosner, Chris; Cantrell, R. Stephen; Beier, John C.; Ruan, Shigui

    2016-01-01

    Rift Valley fever virus (RVFV) is an arthropod-borne viral pathogen that causes significant morbidity and mortality in small ruminants throughout Africa and the Middle East. Due to the sporadic and explosive nature of RVF outbreaks, vaccination has proved challenging to reduce RVFV infection in the ruminant population. Currently, there are two available types of vaccines, live and killed, in endemic areas. In this study, two mathematical models have been developed to explore the impact of live and killed vaccines on the transmission dynamics of RVFV. We demonstrate in general that vaccination helps reduce the severity of RVF outbreaks and that less delay in implementation and more vaccination attempts and effective vaccines can reduce the outbreak magnitude and the endemic number of RVFV. However, an introduction of a number of ruminants vaccinated by live vaccines in RVFV-free areas may cause an outbreak and RVFV may become endemic if there is sustained use of live vaccines. Other factors that are the important determinants of RVF outbreaks include: unsustained vaccination programs, recruitment of susceptible ruminants, and the seasonal abundance of mosquitoes. PMID:26869999

  9. The Effect of Antibody-Dependent Enhancement on the Transmission Dynamics and Persistence of Multiple-Strain Pathogens

    NASA Astrophysics Data System (ADS)

    Ferguson, Neil; Anderson, Roy; Gupta, Sunetra

    1999-01-01

    Cross-reactive antibodies produced by a mammalian host during infection by a particular microparasitic strain usually have the effect of reducing the probability of the host being infected by a different, but closely related, pathogen strain. Such cross-reactive immunological responses thereby induce between-strain competition within the pathogen population. However, in some cases such as dengue virus, evidence suggests that cross-reactive antibodies act to enhance rather than restrict the severity of a subsequent infection by another strain. This cooperative mechanism is thought to explain why pre-existing immunity to dengue virus is an important risk factor for the development of severe disease (i.e., dengue shock syndrome and dengue hemorrhagic fever). In this paper, we explore the effect of antibody-dependent enhancement on the transmission dynamics of multistrain pathogen populations. We show that enhancement frequently may generate complex and persistent cyclical or chaotic epidemic behavior. Furthermore, enhancement acts to permit the coexistence of all strains where in its absence only one or a subset would persist.

  10. Development of the Beliefs about Primary Education Scale: Distinguishing a Developmental and Transmissive Dimension

    ERIC Educational Resources Information Center

    Hermans, Ruben; van Braak, Johan; Van Keer, Hilde

    2008-01-01

    In this article the development and validation of the Beliefs about Primary Education Scale (BPES) are described. The BPES is an 18-item scale for assessing primary school teachers' beliefs toward the nature of good education, subdivided in a transmissive dimension (TD) and a developmental dimension (DD). Both dimensions assess beliefs toward the…

  11. Developing a Brief Scale to Measure HIV Transmission Risk Among Injecting Drug Users

    PubMed Central

    Shahesmaeili, Armita; Haghdoost, Ali Akbar; Soori, Hamid

    2015-01-01

    Background: One of the main concerns of policymakers is to measure the impact of harm reduction programs and different interventions on the risk of HIV transmission among Injecting Drug Users (IDUs). Looking simultaneously at multiple factors and conditions that affect the risk of HIV transmission may provide policymakers a better insight into the mixed nature of HIV transmission. Objectives: The present study aimed to design a simple, brief, and multi-dimensional scale for measuring HIV transmission risk among IDUs. Patients and Methods: From October 2013 to March 2014, we conducted face-to-face interviews with 147 IDUs. Eligible participants were individuals 18 years or older who had injected drugs at least once during the last year and had not participated in similar studies within the 2 months before the interview. To design a scale for measuring HIV transmission risk, we specified 11 items, which address different dimensions of HIV risk taking behaviors/situations based on experts’ opinion. We applied exploratory factor analysis (EFA) with principal component extraction to develop scales. Eigen values greater than 1 were used as a criterion for factor extraction. Results: We extracted 7 items based on first factor, which were accounted for 21% of the variations. The final scale contained 7 items: 4 items were related to injecting practice and 3 items related to sexual behaviors. The Cronbach’s α coefficient was 0.66, acceptable for such a brief scale. Conclusions: Applying a simple and brief scale that incorporates the different dimensions of HIV transmission risk may provide policymakers and harm reductionists with a better understanding of HIV transmission in this key group and may be advantageous for evaluating intervention programs. PMID:26870713

  12. Effects of gear box vibration and mass imbalance on the dynamics of multi-stage gear transmissions

    NASA Technical Reports Server (NTRS)

    Choy, Fred K.; Tu, Yu K.; Zakrajsek, James J.; Townsend, Dennis P.

    1991-01-01

    The dynamic behavior of multistage gear transmission system, with the effects of gear-box-induced vibrations and rotor mass-imbalances is analyzed. The model method, using undamped frequencies and planar mode shapes, is used to reduce the degree-of-freedom of the system. The various rotor-bearing stages as well as lateral and torsional vibrations of each individual stage are coupled through localized gear-mesh-tooth interactions. Gear-box vibrations are coupled to the gear stage dynamics through bearing support forces. Transient and steady state dynamics of lateral and torsional vibrations of the geared system are examined in both time and frequency domain. A typical three-staged geared system is used as an example. Effects of mass-imbalance and gear box vibrations on the system dynamic behavior are presented in terms of modal excitation functions for both lateral and torsional vibrations. Operational characteristics and conclusions are drawn from the results presented.

  13. Analysis of Influenza and RSV dynamics in the community using a ‘Local Transmission Zone’ approach

    PubMed Central

    Almogy, Gal; Stone, Lewi; Bernevig, B. Andrei; Wolf, Dana G.; Dorozko, Marina; Moses, Allon E.; Nir-Paz, Ran

    2017-01-01

    Understanding the dynamics of pathogen spread within urban areas is critical for the effective prevention and containment of communicable diseases. At these relatively small geographic scales, short-distance interactions and tightly knit sub-networks dominate the dynamics of pathogen transmission; yet, the effective boundaries of these micro-scale groups are generally not known and often ignored. Using clinical test results from hospital admitted patients we analyze the spatio-temporal distribution of Influenza Like Illness (ILI) in the city of Jerusalem over a period of three winter seasons. We demonstrate that this urban area is not a single, perfectly mixed ecology, but is in fact comprised of a set of more basic, relatively independent pathogen transmission units, which we term here Local Transmission Zones, LTZs. By identifying these LTZs, and using the dynamic pathogen-content information contained within them, we are able to differentiate between disease-causes at the individual patient level often with near-perfect predictive accuracy. PMID:28181554

  14. Analysis of Influenza and RSV dynamics in the community using a ‘Local Transmission Zone’ approach

    NASA Astrophysics Data System (ADS)

    Almogy, Gal; Stone, Lewi; Bernevig, B. Andrei; Wolf, Dana G.; Dorozko, Marina; Moses, Allon E.; Nir-Paz, Ran

    2017-02-01

    Understanding the dynamics of pathogen spread within urban areas is critical for the effective prevention and containment of communicable diseases. At these relatively small geographic scales, short-distance interactions and tightly knit sub-networks dominate the dynamics of pathogen transmission; yet, the effective boundaries of these micro-scale groups are generally not known and often ignored. Using clinical test results from hospital admitted patients we analyze the spatio-temporal distribution of Influenza Like Illness (ILI) in the city of Jerusalem over a period of three winter seasons. We demonstrate that this urban area is not a single, perfectly mixed ecology, but is in fact comprised of a set of more basic, relatively independent pathogen transmission units, which we term here Local Transmission Zones, LTZs. By identifying these LTZs, and using the dynamic pathogen-content information contained within them, we are able to differentiate between disease-causes at the individual patient level often with near-perfect predictive accuracy.

  15. A fuzzy-theory-based method for studying the effect of information transmission on nonlinear crowd dispersion dynamics

    NASA Astrophysics Data System (ADS)

    Fu, Libi; Song, Weiguo; Lo, Siuming

    2017-01-01

    Emergencies involved in mass events are related to a variety of factors and processes. An important factor is the transmission of information on danger that has an influence on nonlinear crowd dynamics during the process of crowd dispersion. Due to much uncertainty in this process, there is an urgent need to propose a method to investigate the influence. In this paper, a novel fuzzy-theory-based method is presented to study crowd dynamics under the influence of information transmission. Fuzzy functions and rules are designed for the ambiguous description of human states. Reasonable inference is employed to decide the output values of decision making such as pedestrian movement speed and directions. Through simulation under four-way pedestrian situations, good crowd dispersion phenomena are achieved. Simulation results under different conditions demonstrate that information transmission cannot always induce successful crowd dispersion in all situations. This depends on whether decision strategies in response to information on danger are unified and effective, especially in dense crowds. Results also suggest that an increase in drift strength at low density and the percentage of pedestrians, who choose one of the furthest unoccupied Von Neumann neighbors from the dangerous source as the drift direction at high density, is helpful in crowd dispersion. Compared with previous work, our comprehensive study improves an in-depth understanding of nonlinear crowd dynamics under the effect of information on danger.

  16. Development of Topical Microbicides to Prevent the Sexual Transmission of HIV

    PubMed Central

    Buckheit, Robert W.; Watson, Karen M.; Morrow, Kathleen M.; Ham, Anthony S.

    2009-01-01

    Women comprise almost 50% of the population of people living with HIV and the majority of these women contracted the virus through sexual transmission in monogamous relationships in the developing world. In these environments, where women are not empowered to protect themselves through the negotiation of condom use, effective means of preventing HIV transmission are urgently needed. In the absence of an approved and effective vaccine, microbicides have become the strategy of choice to provide women with the ability to prevent HIV transmission from their infected partners. Topical microbicides are agents specifically developed and formulated for use in either the vaginal or rectal environment that prevent infection by sexually transmitted infectious organisms, including pathogenic viruses, bacteria and fungi. Although a microbicidal product will have many of the same properties as other anti-infective agents and would be similarly developed through human clinical trials, microbicide development bears its own challenges related to formulation and delivery and the unique environment in which the product must act, as well as the requirement to develop a product that is acceptable to the user. Herein, perspectives based on preclinical and clinical microbicide development experience, which have led to an evolving microbicide development algorithm, will be discussed. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, Vol 85, issue 1, 2010”. PMID:19874851

  17. Development of topical microbicides to prevent the sexual transmission of HIV.

    PubMed

    Buckheit, Robert W; Watson, Karen M; Morrow, Kathleen M; Ham, Anthony S

    2010-01-01

    Women comprise almost 50% of the population of people living with HIV and the majority of these women contracted the virus through sexual transmission in monogamous relationships in the developing world. In these environments, where women are not empowered to protect themselves through the negotiation of condom use, effective means of preventing HIV transmission are urgently needed. In the absence of an approved and effective vaccine, microbicides have become the strategy of choice to provide women with the ability to prevent HIV transmission from their infected partners. Topical microbicides are agents specifically developed and formulated for use in either the vaginal or rectal environment that prevent infection by sexually transmitted infectious organisms, including pathogenic viruses, bacteria and fungi. Although a microbicidal product will have many of the same properties as other anti-infective agents and would be similarly developed through human clinical trials, microbicide development bears its own challenges related to formulation and delivery and the unique environment in which the product must act, as well as the requirement to develop a product that is acceptable to the user. Herein, perspectives based on preclinical and clinical microbicide development experience, which have led to an evolving microbicide development algorithm, will be discussed. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of anti-retroviral drug discovery and development, Vol 85, issue 1, 2010. Copyright 2009 Elsevier B.V. All rights reserved.

  18. Cholera epidemiology in developed and developing countries: new thoughts on transmission, seasonality, and control.

    PubMed

    Miller, C J; Feachem, R G; Drasar, B S

    1985-02-02

    It is hypothesized that geographical regions where cholera is endemic, V. cholerae 01 may be maintained in estuarine environments. Endemic cholera, unlike epedemic cholera, occurs regularly, and sometimes seasonally, in certain geographical areas without evidence of importation. Measures used to control epedemic cholera are not very effective in preventing endemic cholera. Areas of endemic cholera include southeastern US and several African and Asian countries, including Bangladesh. It has previously been suggested that V. cholerae 01 is maintained in these areas between outbreaks by 1) living in nonhuman animals; 2) residing in chronic human carriers, who may not excrete the organism; 3) by continous transmission to individuals who manifest only mild symptoms of the disease; and 4) by living in aquatic environments. The 1st 3 explanations are to supported by available evidence. The 4th explanation, previously thought to be impossible, is now engendering new interest. Recent studies reveal that V. cholerae 01 can survive in warm water with a salinity of 0.25-3.0% and a ph of 8.0 for a considerable length of time. Estuarine environments may be suitable for the organism's survival. It is hypothesized further that outbreaks of primary cases in estuarine environments may be precipatated by eating certain types of raw or inadequately cooked estuarian plants or animals, perhaps on a seasonal basis. In areas where sanitation is poor, the disease will be transmitted to secondary cases, and in areas where sanitation is good, secondary cases will be rare. Primary cases may also develop in areas some distance from the estuarian environment by the importation of estuarian products. Outbreaks of secondary cases in nonestuarian environments may be due to the seasonal movement of estuarian inhabitants through the area. This explanation fits the epidemiological evidence available for the southeastern US and Bangladesh. If this hypothesis is correct, appropriate control measures

  19. Development of an accurate transmission line fault locator using the global positioning system satellites

    NASA Technical Reports Server (NTRS)

    Lee, Harry

    1994-01-01

    A highly accurate transmission line fault locator based on the traveling-wave principle was developed and successfully operated within B.C. Hydro. A transmission line fault produces a fast-risetime traveling wave at the fault point which propagates along the transmission line. This fault locator system consists of traveling wave detectors located at key substations which detect and time tag the leading edge of the fault-generated traveling wave as if passes through. A master station gathers the time-tagged information from the remote detectors and determines the location of the fault. Precise time is a key element to the success of this system. This fault locator system derives its timing from the Global Positioning System (GPS) satellites. System tests confirmed the accuracy of locating faults to within the design objective of +/-300 meters.

  20. Dynamic mapping of normal human hippocampal development.

    PubMed

    Gogtay, Nitin; Nugent, Tom F; Herman, David H; Ordonez, Anna; Greenstein, Deanna; Hayashi, Kiralee M; Clasen, Liv; Toga, Arthur W; Giedd, Jay N; Rapoport, Judith L; Thompson, Paul M

    2006-01-01

    The hippocampus, which plays an important role in memory functions and emotional responses, has distinct subregions subserving different functions. Because the volume and shape of the hippocampus are altered in many neuropsychiatric disorders, it is important to understand the trajectory of normal hippocampal development. We present the first dynamic maps to reveal the anatomical sequence of normal human hippocampal development. A novel hippocampal mapping technique was applied to a database of prospectively obtained brain magnetic resonance imaging (MRI) scans (100 scans in 31 children and adolescents), scanned every 2 yr for 6-10 yr between ages 4 and 25. Our results establish that the structural development of the human hippocampus is remarkably heterogeneous, with significant differences between posterior (increase over time) and anterior (loss over time) subregions. These distinct developmental trajectories of hippocampal subregions may parallel differences in their functional development.

  1. Development of Dynamically Optimized Wireless Transmission System for Wireless Sensor Networks in Highrise Apartment Building Heating Systems / Optimizētas Dinamiskās Bezvadu Sensoru Tīklu Pārraides Risinājuma Izstrāde Daudzstāvu Ēku Apkures Sistēmas Parametru Izgūšanai Un Vadībai

    NASA Astrophysics Data System (ADS)

    Isakovs, V.; Kondratjevs, K.; Kunicina, N.; Freliha, B.; Zabasta, A.

    2015-08-01

    Smart meters will be at the centre of the integrated solutions, including interaction with other networks in the next decade. The developed solution for multi-apartment building ventilation and heating parameter monitoring aims to increase energy efficiency and optimal control of the existing system. Dynamic control of heat and ventilation systems, heat loss detection, calculation and mitigation, and individual heat energy accounting are difficult tasks to accomplish. This article deals with the data transmission system using battery powered ISM band radio transmitters. The temperature measurement sensors with cumulative temperature reading are used as sensor part for this solution. The offered approach to monitoring system is used for overall building and individual apartment monitoring. Data coding and antenna designs are explained for this particular application. Daudzstāvu ēkas, kuras nav sākotnēji plānotas integrācijai ar ēku vadības sistēmām, rada kompleksu problemātisko vidi modernizācijai. Vadu sensoru sistēmu uzstādīšana šādās ēkās kļūst nepraktiska vai pat neiespējama. Šī iemesla dēļ ir nepieciešamas efektīvas bezvadu sensoru sistēmas, kas spētu nodrošināt mērījumu nogādi, ņemot vērā daudzstāvu ēku specifiku. Rakstā tiek piedāvāts bezvadu sensoru tīkla risinājums efektīvai datu pārraidei siltumapgādes sistēmas parametru izgūšanai. Tiek izstrādāta un aprobēta specializētā virziena antena efektīvai radio telegrammu savākšanai no dzīvokļiem, nogādājot mērījumus datu koncentratoros. Ziņojumu telegrammu efektīvai pārraidei tiek piedāvāta datu kodēšanas kumulatīvā metode. Piedāvātais risinājums pielietojams gan jaunām, gan esošām ēkām. Izgūtie dati ir pielietojami siltuma apgādes sistēmas uzraudzībai, regulēšanai, kā arī individuālā siltuma patēriņa tarifikācijai.

  2. Ecological dynamics of influenza A viruses: cross-species transmission and global migration

    PubMed Central

    Ren, Hongguang; Jin, Yuan; Hu, Mingda; Zhou, Jing; Song, Ting; Huang, Zhisong; Li, Beiping; Li, Kaiwu; Zhou, Wei; Dai, Hongmei; Shi, Weifeng; Yue, Junjie; Liang, Long

    2016-01-01

    A comprehensive study of cross-species transmission and inter-regional migration would provide insights into the global ecology of influenza A viruses (IAVs). To this end, we assembled 17,241 non-redundant IAV whole-genome sequences with complete epidemiological information. We hierarchically divided the movements of IAVs into the cross-species transmission in each region and the inter-regional migration driven by each host species. We then systematically identified the potential cross-species transmission and inter-regional migration events. Cross-species transmission networks were obtained for each gene segment of the IAVs. Waterfowl, domestic birds and swine showed higher degrees of connection than did other species in all of the transmission networks. East Asia and Southeast Asia were hot regions for avian-mammal transmissions. Swine and migratory birds were the dominant species for global virus delivery. The importance of swine was reemphasized because it has not only provided an environment for adaptive evolution during the avian-human transmission of IAVs (as incubators) but also served as a key species for the global dissemination of the viruses (as carriers). Therefore, monitoring the global live trade of swine and survey of migratory birds along flyways would be beneficial for the prevention and control of IAVs. PMID:27827462

  3. Mathematical Modeling of the Transmission Dynamics of Clostridium difficile Infection and Colonization in Healthcare Settings: A Systematic Review

    PubMed Central

    Gingras, Guillaume; Guertin, Marie-Hélène; Laprise, Jean-François; Drolet, Mélanie; Brisson, Marc

    2016-01-01

    Background We conducted a systematic review of mathematical models of transmission dynamic of Clostridium difficile infection (CDI) in healthcare settings, to provide an overview of existing models and their assessment of different CDI control strategies. Methods We searched MEDLINE, EMBASE and Web of Science up to February 3, 2016 for transmission-dynamic models of Clostridium difficile in healthcare settings. The models were compared based on their natural history representation of Clostridium difficile, which could include health states (S-E-A-I-R-D: Susceptible-Exposed-Asymptomatic-Infectious-Resistant-Deceased) and the possibility to include healthcare workers and visitors (vectors of transmission). Effectiveness of interventions was compared using the relative reduction (compared to no intervention or current practice) in outcomes such as incidence of colonization, CDI, CDI recurrence, CDI mortality, and length of stay. Results Nine studies describing six different models met the inclusion criteria. Over time, the models have generally increased in complexity in terms of natural history and transmission dynamics and number/complexity of interventions/bundles of interventions examined. The models were categorized into four groups with respect to their natural history representation: S-A-I-R, S-E-A-I, S-A-I, and S-E-A-I-R-D. Seven studies examined the impact of CDI control strategies. Interventions aimed at controlling the transmission, lowering CDI vulnerability and reducing the risk of recurrence/mortality were predicted to reduce CDI incidence by 3–49%, 5–43% and 5–29%, respectively. Bundles of interventions were predicted to reduce CDI incidence by 14–84%. Conclusions Although CDI is a major public health problem, there are very few published transmission-dynamic models of Clostridium difficile. Published models vary substantially in the interventions examined, the outcome measures used and the representation of the natural history of Clostridium

  4. Understanding African Swine Fever infection dynamics in Sardinia using a spatially explicit transmission model in domestic pig farms.

    PubMed

    Mur, L; Sánchez-Vizcaíno, J M; Fernández-Carrión, E; Jurado, C; Rolesu, S; Feliziani, F; Laddomada, A; Martínez-López, B

    2017-03-13

    African swine fever virus (ASFV) has been endemic in Sardinia since 1978, resulting in severe losses for local pig producers and creating important problems for the island's veterinary authorities. This study used a spatially explicit stochastic transmission model followed by two regression models to investigate the dynamics of ASFV spread amongst domestic pig farms, to identify geographic areas at highest risk and determine the role of different susceptible pig populations (registered domestic pigs, non-registered domestic pigs [brado] and wild boar) in ASF occurrence. We simulated transmission within and between farms using an adapted version of the previously described model known as Be-FAST. Results from the model revealed a generally low diffusion of ASF in Sardinia, with only 24% of the simulations resulting in disease spread, and for each simulated outbreak on average only four farms and 66 pigs were affected. Overall, local spread (indirect transmission between farms within a 2 km radius through fomites) was the most common route of transmission, being responsible for 98.6% of secondary cases. The risk of ASF occurrence for each domestic pig farm was estimated from the spread model results and integrated in two regression models together with available data for brado and wild boar populations. There was a significant association between the density of all three populations (domestic pigs, brado, and wild boar) and ASF occurrence in Sardinia. The most significant risk factors were the high densities of brado (OR = 2.2) and wild boar (OR = 2.1). The results of both analyses demonstrated that ASF epidemiology and infection dynamics in Sardinia create a complex and multifactorial disease situation, where all susceptible populations play an important role. To stop ASF transmission in Sardinia, three main factors (improving biosecurity on domestic pig farms, eliminating brado practices and better management of wild boars) need to be addressed.

  5. Vancomycin-resistant enterococci in intensive-care hospital settings: Transmission dynamics, persistence, and the impact of infection control programs

    PubMed Central

    Austin, Daren J.; Bonten, Marc J. M.; Weinstein, Robert A.; Slaughter, Sarah; Anderson, Roy M.

    1999-01-01

    Vancomycin-resistant enterococci (VRE) recently have emerged as a nosocomial pathogen especially in intensive-care units (ICUs) worldwide. Transmission via the hands of health-care workers is an important determinant of spread and persistence in a VRE-endemic ICU. We describe the transmission of nosocomial pathogens by using a micro-epidemiological framework based on the transmission dynamics of vector-borne diseases. By using the concept of a basic reproductive number, R0, defined as the average number of secondary cases generated by one primary case, we show quantitatively how infection control measures such as hand washing, cohorting, and antibiotic restriction affect nosocomial cross-transmission. By using detailed molecular epidemiological surveillance and compliance monitoring, we found that the estimated basic reproductive number for VRE during a study at the Cook County Hospital, Chicago, was approximately 3–4 without infection control and 0.7 when infection control measures were included. The impact of infection control was to reduce the prevalence from a predicted 79% to an observed 36%. Hand washing and staff cohorting are the most powerful control measures although their efficacy depends on the magnitude of R0. Under the circumstances tested, endemicity of VRE was stabilized despite infection control measures, by the constant introduction of colonized patients. Multiple stochastic simulations of the model revealed excellent agreement with observed pattern. In conjunction with detailed microbiological surveillance, a mathematical framework provides a precise template to describe the colonization dynamics of VRE in ICUs and impact of infection control measures. Our analyses suggest that compliance for hand washing significantly in excess of reported levels, or the cohorting of nursing staff, are needed to prevent nosocomial transmission of VRE in endemic settings. PMID:10359812

  6. Development on dynamic nuclear polarized targets.

    SciTech Connect

    Penttila, S. I.

    2002-01-01

    Our interest in understanding the spin content of the nucleon has left its marks on the recent development, of the dynamic nuclear polarized (DNP) targets. This can be seen from the targets developed at CERN and SLAC for the measurement of the polarized spin structure functions in deep inelastic scattering. The results of the experiments indicated that less than 30% of the nucleon spin is carried by the quarks. This unpredicted small value initiated planning of new polarized target experiments to determine the gluon polarization on the nucleon using polarized real photons and polarized 'LiD targets. In several facilities very intense polarized photon beams are available at a wide energy range. During the next few years these photon beanis with DNP targets will be used to test the fundamental GDH sum rule. Other DNP target developments are also discussed.

  7. Deviant socialization mediates transmissible and contextual risk on cannabis use disorder development: a prospective study.

    PubMed

    Tarter, Ralph E; Fishbein, Diana; Kirisci, Levent; Mezzich, Ada; Ridenour, Ty; Vanyukov, Michael

    2011-07-01

    This study examined the contribution of transmissible risk, in conjunction with family and peer contextual factors during childhood and adolescence, on the development of cannabis use disorder in adulthood. The family high-risk design was used to recruit proband fathers with and without substance use disorder and track their sons longitudinally from late childhood to adulthood. The families were recruited under the aegis of the Center for Education and Drug Abuse Research in Pittsburgh, Pennsylvania. The oldest son in the family was studied at ages 10-12, 16, 19 and 22 years. The transmissible liability index (TLI), along with measures of quality of the parent-child relationship, cooperative behavior at home, social attitudes and peer milieu were administered to model the developmental pathway to cannabis use disorder. Affiliation with socially deviant peers and harboring non-normative attitudes (age 16) mediate the association between transmissible risk for substance use disorder (SUD) (age 10-12) and use of illegal drugs (age 19), leading to cannabis use disorder (age 22). Deviant socialization resulting from transmissible risk and poor parent-child relationship is integral to development of cannabis use disorder in young adulthood. © 2011 The Authors, Addiction © 2011 Society for the Study of Addiction.

  8. The biology of sexual development of Plasmodium: the design and implementation of transmission-blocking strategies.

    PubMed

    Sinden, Robert E; Carter, Richard; Drakeley, Chris; Leroy, Didier

    2012-03-16

    A meeting to discuss the latest developments in the biology of sexual development of Plasmodium and transmission-control was held April 5-6, 2011, in Bethesda, MD. The meeting was sponsored by the Bill & Melinda Gates Foundation and the National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIH/NIAID) in response to the challenge issued at the Malaria Forum in October 2007 that the malaria community should re-engage with the objective of global eradication. The consequent rebalancing of research priorities has brought to the forefront of the research agenda the essential need to reduce parasite transmission. A key component of any transmission reduction strategy must be methods to attack the parasite as it passes from man to the mosquito (and vice versa). Such methods must be rationally based on a secure understanding of transmission from the molecular-, cellular-, population- to the evolutionary-levels. The meeting represented a first attempt to draw together scientists with expertise in these multiple layers of understanding to discuss the scientific foundations and resources that will be required to provide secure progress toward the design and successful implementation of effective interventions.

  9. The biology of sexual development of Plasmodium: the design and implementation of transmission-blocking strategies

    PubMed Central

    2012-01-01

    A meeting to discuss the latest developments in the biology of sexual development of Plasmodium and transmission-control was held April 5-6, 2011, in Bethesda, MD. The meeting was sponsored by the Bill & Melinda Gates Foundation and the National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIH/NIAID) in response to the challenge issued at the Malaria Forum in October 2007 that the malaria community should re-engage with the objective of global eradication. The consequent rebalancing of research priorities has brought to the forefront of the research agenda the essential need to reduce parasite transmission. A key component of any transmission reduction strategy must be methods to attack the parasite as it passes from man to the mosquito (and vice versa). Such methods must be rationally based on a secure understanding of transmission from the molecular-, cellular-, population- to the evolutionary-levels. The meeting represented a first attempt to draw together scientists with expertise in these multiple layers of understanding to discuss the scientific foundations and resources that will be required to provide secure progress toward the design and successful implementation of effective interventions. PMID:22424474

  10. Crossing the scale from within-host infection dynamics to between-host transmission fitness: a discussion of current assumptions and knowledge.

    PubMed

    Handel, Andreas; Rohani, Pejman

    2015-08-19

    The progression of an infection within a host determines the ability of a pathogen to transmit to new hosts and to maintain itself in the population. While the general connection between the infection dynamics within a host and the population-level transmission dynamics of pathogens is widely acknowledged, a comprehensive and quantitative understanding that would allow full integration of the two scales is still lacking. Here, we provide a brief discussion of both models and data that have attempted to provide quantitative mappings from within-host infection dynamics to transmission fitness. We present a conceptual framework and provide examples of studies that have taken first steps towards development of a quantitative framework that scales from within-host infections to population-level fitness of different pathogens. We hope to illustrate some general themes, summarize some of the recent advances and-maybe most importantly-discuss gaps in our ability to bridge these scales, and to stimulate future research on this important topic.

  11. Assessing the role of landscape connectivity on Opisthorchis viverrini transmission dynamics.

    PubMed

    Wang, Yi-Chen; Yuen, Roy; Feng, Chen-Chieh; Sithithaworn, Paiboon; Kim, Ick-Hoi

    2016-06-02

    Opisthorchis viverrini (Ov) is one of the most important human parasitic diseases in Southeast Asia. Although the concept of connectivity is widely used to comprehend disease dispersal, knowledge of the influences of landscape connectivity on Ov transmission is still rudimentary. This study aimed to investigate the role of landscape connectivity in Ov transmission between the human and the first intermediate snail hosts. Fieldwork was conducted in three villages respectively in Kamalasai District, Kalasin Province, Phu Wiang District, Khon Kaen Province, and Nong Saeng District, Udon Thani Province. Bithynia snails were collected to examine parasitic infections, water samples were analyzed for fecal contamination, and locations of septic tanks and connections between habitat patches with observable water movement were surveyed. Euclidean distance, topological link and distance, and graph measures were employed to quantify the connectivity between human and snail habitats. The findings showed that snail patches with higher fecal contents were generally located nearer to septic tanks. The statistically significant results for the topological link and distance measures highlighted the importance of water in functionally facilitating Ov transmission. Graph measures revealed differences in landscape connectivity across the sites. The site with the largest landscape component size and the most mutually connected snail patches coincided with the presence of Ov parasite, reinforcing its higher risk for human to snail transmission. The site with the dissected landscape structure potentially limited the transmission. This study underscored the potential effect of landscape connectivity on Ov transmission, contributing to the understanding of the spatial variation of Ov infection risk.

  12. Dynamics of the Solar Wind Electromagnetic Energy Transmission Into Magnetosphere during Large Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Tamara; Laptukhov, Alexej; Petrov, Valery

    Causes of the geomagnetic activity (GA) in the report are divided into temporal changes of the solar wind parameters and the changes of the geomagnetic moment orientation relative directions of the solar wind electric and magnetic fields. Based on our previous study we concluded that a reconnection based on determining role of mutual orientation of the solar wind electric field and geomagnetic moment taking into account effects of the Earth's orbital and daily motions is the most effective compared with existing mechanisms. At present a reconnection as paradigma that has applications in broad fields of physics needs analysis of experimental facts to be developed. In terms of reconnection it is important not only mutual orientation of vectors describing physics of interaction region but and reconnection rate which depends from rate of energy flux to those regions where the reconnection is permitted. Applied to magnetosphere these regions first of all are dayside magnetopause and polar caps. Influence of rate of the energy flux to the lobe magnetopause (based on calculations of the Poyting electromagnetic flux component controlling the reconnection rate along the solar wind velocity Pv) on planetary GA (Dst, Kp indices) is investigated at different phases of geomagnetic storms. We study also the rate of energy flux to the polar caps during storms (based on calculations of the Poyting flux vector component along the geomagnetic moment Pm) and its influence on magnetic activity in the polar ionosphere: at the auroral zone (AU,AL indices). Results allow to evaluate contributions of high and low latitude sources of electromagnetic energy to the storm development and also to clear mechanism of the electromagnetic energy transmission from the solar wind to the magnetosphere. We evaluate too power of the solar wind electromagnetic energy during well-known large storms and compare result with power of the energy sources of other geophysical processes (atmosphere, ocean

  13. Development of a transplantation transmission sentinel network to improve safety and traceability of organ and tissues.

    PubMed

    Strong, D Michael; Seem, Debbie; Taylor, Gloria; Parker, Jory; Stewart, Darren; Kuehnert, Matthew J

    2010-11-01

    The US lags behind other developed countries in creating a system to monitor disease transmission and other complications from human allograft use, despite a pressing need. The risks of transmission are amplified in transplantation, since at least 8 organs and more than 100 tissues can be recovered from a single common organ and tissue donor. Moreover, since many allografts collected in the US are distributed internationally, tissue safety is a global concern. In June 2005, participants of a US government-sponsored workshop concluded that a communication network for the tracking and reporting of disease transmissions for tissues and organs was critically needed. The United Network for Organ Sharing (UNOS) entered into a cooperative agreement with the Centers for Disease Control and Prevention (CDC) in 2006 to develop a system prototype. Over the following 3 years, the Transplantation Transmission Sentinel Network (TTSN) was developed and piloted with the participation of organ procurement organizations, tissue banks and transplant centers. The prototype centered around three elements of data entry: (1) donation, (2) tissue implantation, and (3) adverse event. The pilot proved that a system can be built and operated successfully, but also suggested that users may be hesitant to report adverse events. CDC has requested further input on scope and cost to build a transplant surveillance infrastructure for a fully functional national system. For tissues however, in contrast to organs, tracking from recovery to implantation will be necessary before a system is operable, requiring common identifiers and nomenclature. Until a US sentinel network is operational, future transmission events that are preventable may result nationally and globally due to its absence.

  14. Development of a dynamic pressure calibration technique

    NASA Technical Reports Server (NTRS)

    Vezzetti, C. F.; Hilten, J. S.; Lederer, P. S.

    1975-01-01

    The report deals with work continuing on the development of a method of producing sinusoidally varying pressures of at least 34 kPa zero-to-peak with amplitude variations within plus or minus 5% up to 2 kHz for the dynamic calibration of pressure transducers. Sinusoidally varying pressures of 34 kPa zero-to-peak were produced between 40 Hz and 750 Hz by vibrating a 10-cm column of a dimethyl siloxane liquid at 36gn zero-to-peak. Damping of the liquid column was accomplished by packing the fixture tube with a number of smaller diameter tubes.

  15. Malaria intervention scale-up in Africa: effectiveness predictions for health programme planning tools, based on dynamic transmission modelling.

    PubMed

    Korenromp, Eline; Mahiané, Guy; Hamilton, Matthew; Pretorius, Carel; Cibulskis, Richard; Lauer, Jeremy; Smith, Thomas A; Briët, Olivier J T

    2016-08-18

    Scale-up of malaria prevention and treatment needs to continue to further important gains made in the past decade, but national strategies and budget allocations are not always evidence-based. Statistical models were developed summarizing dynamically simulated relations between increases in coverage and intervention impact, to inform a malaria module in the Spectrum health programme planning tool. The dynamic Plasmodium falciparum transmission model OpenMalaria was used to simulate health effects of scale-up of insecticide-treated net (ITN) usage, indoor residual spraying (IRS), management of uncomplicated malaria cases (CM) and seasonal malaria chemoprophylaxis (SMC) over a 10-year horizon, over a range of settings with stable endemic malaria. Generalized linear regression models (GLMs) were used to summarize determinants of impact across a range of sub-Sahara African settings. Selected (best) GLMs explained 94-97 % of variation in simulated post-intervention parasite infection prevalence, 86-97 % of variation in case incidence (three age groups, three 3-year horizons), and 74-95 % of variation in malaria mortality. For any given effective population coverage, CM and ITNs were predicted to avert most prevalent infections, cases and deaths, with lower impacts for IRS, and impacts of SMC limited to young children reached. Proportional impacts were larger at lower endemicity, and (except for SMC) largest in low-endemic settings with little seasonality. Incremental health impacts for a given coverage increase started to diminish noticeably at above ~40 % coverage, while in high-endemic settings, CM and ITNs acted in synergy by lowering endemicity. Vector control and CM, by reducing endemicity and acquired immunity, entail a partial rebound in malaria mortality among people above 5 years of age from around 5-7 years following scale-up. SMC does not reduce endemicity, but slightly shifts malaria to older ages by reducing immunity in child cohorts reached. Health

  16. Molecular epidemiology and transmission dynamics of Mycobacterium tuberculosis in Northwest Ethiopia: new phylogenetic lineages found in Northwest Ethiopia.

    PubMed

    Tessema, Belay; Beer, Joerg; Merker, Matthias; Emmrich, Frank; Sack, Ulrich; Rodloff, Arne C; Niemann, Stefan

    2013-03-11

    Although Ethiopia ranks seventh among the world's 22 high-burden tuberculosis (TB) countries, little is known about strain diversity and transmission. In this study, we present the first in-depth analysis of the population structure and transmission dynamics of Mycobacterium tuberculosis strains from Northwest Ethiopia. In the present study, 244 M. tuberculosis isolates where analysed by mycobacterial interspersed repetitive unit - variable number tandem repeat 24-loci typing and spoligotyping methods to determine phylogenetic lineages and perform cluster analysis. Clusters of strains with identical genotyping patterns were considered as an indicator for the recent transmission. Of 244 isolates, 59.0% were classified into nine previously described lineages: Dehli/CAS (38.9%), Haarlem (8.6%), Ural (3.3%), LAM (3.3%), TUR (2.0%), X-type (1.2%), S-type (0.8%), Beijing (0.4%) and Uganda II (0.4%). Interestingly, 31.6% of the strains were grouped into four new lineages and were named as Ethiopia_3 (13.1%), Ethiopia_1 (7.8%), Ethiopia_H37Rv like (7.0%) and Ethiopia_2 (3.7%) lineages. The remaining 9.4% of the isolates could not be assigned to the known or new lineages. Overall, 45.1% of the isolates were grouped in clusters, indicating a high rate of recent transmission. This study confirms a highly diverse M. tuberculosis population structure, the presence of new phylogenetic lineages and a predominance of the Dehli/CAS lineage in Northwest Ethiopia. The high rate of recent transmission indicates defects of the TB control program in Northwest Ethiopia. This emphasizes the importance of strengthening laboratory diagnosis of TB, intensified case finding and treatment of TB patients to interrupt the chain of transmission.

  17. Temporal dynamics of rabies in a wildlife host and the risk of cross-species transmission.

    PubMed Central

    Gordon, E. R.; Curns, A. T.; Krebs, J. W.; Rupprecht, C. E.; Real, L. A.; Childs, J. E.

    2004-01-01

    An epidemiological model was developed for rabies, linking the risk of disease in a secondary species (cats) to the temporal dynamics of disease in a wildlife reservoir (raccoons). Data were obtained from cats, raccoons, and skunks tested for rabies in the northeastern United States during 1992-2000. An epizootic algorithm defined a time-series of successive intervals of epizootic and inter-epizootic raccoon rabies. The odds of diagnosing a rabid cat during the first epizootic of raccoon rabies was 12 times greater than for the period prior to epizootic emergence. After the first raccoon epizootic, the risk for cat rabies remained elevated at levels six- to seven-fold above baseline. Increased monthly counts of rabid raccoons and skunks and decreasing human population density increased the probability of cat rabies in most models. Forecasting of the public health and veterinary burden of rabies and assessing the economics of control programmes, requires linking outcomes to dynamic, but predictable, changes in the temporal evolution of rabies epizootics. PMID:15188720

  18. Within-farm transmission dynamics of foot and mouth disease as revealed by the 2001 epidemic in Great Britain.

    PubMed

    Chis Ster, Irina; Dodd, Peter J; Ferguson, Neil M

    2012-08-01

    This paper uses statistical and mathematical models to examine the potential impact of within-farm transmission dynamics on the spread of the 2001 foot and mouth disease (FMD) outbreak in Great Britain. We partly parameterize a simple within farm transmission model using data from experimental studies of FMD pathogenesis, embed this model within an existing between-farm transmission model, and then estimate unknown parameters (such as the species-specific within-farm reproduction number) from the 2001 epidemic case data using Markov Chain Monte-Carlo (MCMC) methods. If the probability of detecting an infected premises depends on farm size and species mix then the within-farm species specific basic reproduction ratios for baseline models are estimated to be 21 (16, 25) and 14 (10, 19) for cattle and sheep, respectively. Alternatively, if detection is independent of farm size, then the corresponding estimates are 49 (41, 61) and 10 (1.4, 21). Both model variants predict that the average fraction of total farm infectiousness accumulated prior to detection of infection on an IP is about 30-50% in cattle or mixed farms. The corresponding estimate for sheep farms depended more on the detection model, being 65-80% if detection was linked to the farms' characteristics, but only 25% if not. We highlighted evidence which reinforces the role of within-farm dynamics in contributing to the long tail of the 2001 epidemic. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Reconstruction of Rift Valley fever transmission dynamics in Madagascar: estimation of force of infection from seroprevalence surveys using Bayesian modelling

    PubMed Central

    Olive, Marie-Marie; Grosbois, Vladimir; Tran, Annelise; Nomenjanahary, Lalaina Arivony; Rakotoarinoro, Mihaja; Andriamandimby, Soa-Fy; Rogier, Christophe; Heraud, Jean-Michel; Chevalier, Veronique

    2017-01-01

    The force of infection (FOI) is one of the key parameters describing the dynamics of transmission of vector-borne diseases. Following the occurrence of two major outbreaks of Rift Valley fever (RVF) in Madagascar in 1990–91 and 2008–09, recent studies suggest that the pattern of RVF virus (RVFV) transmission differed among the four main eco-regions (East, Highlands, North-West and South-West). Using Bayesian hierarchical models fitted to serological data from cattle of known age collected during two surveys (2008 and 2014), we estimated RVF FOI and described its variations over time and space in Madagascar. We show that the patterns of RVFV transmission strongly differed among the eco-regions. In the North-West and Highlands regions, these patterns were synchronous with a high intensity in mid-2007/mid-2008. In the East and South-West, the peaks of transmission were later, between mid-2008 and mid-2010. In the warm and humid northwestern eco-region favorable to mosquito populations, RVFV is probably transmitted all year-long at low-level during inter-epizootic period allowing its maintenance and being regularly introduced in the Highlands through ruminant trade. The RVF surveillance of animals of the northwestern region could be used as an early warning indicator of an increased risk of RVF outbreak in Madagascar. PMID:28051125

  20. The tortoise or the hare? Impacts of within-host dynamics on transmission success of arthropod-borne viruses

    PubMed Central

    Althouse, Benjamin M.; Hanley, Kathryn A.

    2015-01-01

    Arthropod-borne viruses (arboviruses) are maintained in a cycle of alternating transmission between vertebrate hosts and arthropod vectors. Arboviruses possess RNA genomes capable of rapid diversification and adaptation, and the between-host trade-offs inherent to host alternation impose well-documented constraints on arbovirus evolution. Here, we investigate the less well-studied within-host trade-offs that shape arbovirus replication dynamics and transmission. Arboviruses generally establish lifelong infection in vectors but transient infection of variable magnitude (i.e. peak virus concentration) and duration in vertebrate hosts. In the majority of experimental infections of vertebrate hosts, both the magnitude and duration of arbovirus replication depended upon the dose of virus administered, with increasing dose resulting in greater magnitude but shorter duration of viraemia. This pattern suggests that the vertebrate immune response imposes a trade-off between the height and breadth of the virus replication curve. To investigate the impact of this trade-off on transmission, we used a simple modelling approach to contrast the effect of ‘tortoise’ (low magnitude, long duration viraemia) and ‘hare’ (high magnitude, short duration viraemia) arbovirus replication strategies on transmission. This model revealed that, counter to previous theory, arboviruses that adopt a tortoise strategy have higher rates of persistence in both host and vector populations. PMID:26150665

  1. Reconstruction of Rift Valley fever transmission dynamics in Madagascar: estimation of force of infection from seroprevalence surveys using Bayesian modelling.

    PubMed

    Olive, Marie-Marie; Grosbois, Vladimir; Tran, Annelise; Nomenjanahary, Lalaina Arivony; Rakotoarinoro, Mihaja; Andriamandimby, Soa-Fy; Rogier, Christophe; Heraud, Jean-Michel; Chevalier, Veronique

    2017-01-04

    The force of infection (FOI) is one of the key parameters describing the dynamics of transmission of vector-borne diseases. Following the occurrence of two major outbreaks of Rift Valley fever (RVF) in Madagascar in 1990-91 and 2008-09, recent studies suggest that the pattern of RVF virus (RVFV) transmission differed among the four main eco-regions (East, Highlands, North-West and South-West). Using Bayesian hierarchical models fitted to serological data from cattle of known age collected during two surveys (2008 and 2014), we estimated RVF FOI and described its variations over time and space in Madagascar. We show that the patterns of RVFV transmission strongly differed among the eco-regions. In the North-West and Highlands regions, these patterns were synchronous with a high intensity in mid-2007/mid-2008. In the East and South-West, the peaks of transmission were later, between mid-2008 and mid-2010. In the warm and humid northwestern eco-region favorable to mosquito populations, RVFV is probably transmitted all year-long at low-level during inter-epizootic period allowing its maintenance and being regularly introduced in the Highlands through ruminant trade. The RVF surveillance of animals of the northwestern region could be used as an early warning indicator of an increased risk of RVF outbreak in Madagascar.

  2. The dynamic landscape of exceptional language development.

    PubMed

    Peltzer-Karpf, Annemarie

    2012-06-01

    Developmental neurocognitive studies have shown that the brain systems supporting the emergence of sensory and cognitive abilities display different profiles of neuroplasticity. The research question posed here is to what extent sensory deprivation influences the dynamics of language development. The findings reported are grounded in studies with vision-impaired children with sighted peers featured as controls (age range 18 months to 3 years). Their data are matched against findings on advanced language development in blind children (age range: from 6 to 10 years; N = 12) and hearing-impaired and deaf children (age range: from 5 to 11 years; N = 20). The data give evidence that language acquisition in sensory-impaired children follows the same overall developmental path with respect to macrostructural changes and the succession of phase-shifts. System-specific temporal discrepancies expressed in protracted phase-shifts and delayed increases of variability are most evident in the early phases. Self-organizing maps (SOMs) help to visualize individual and group-specific variation. The dynamic framework used (1) shows a higher sensibility to system-specific changes, (2) enhances the informative value of the data assessed, and (3) facilitates reliable prognoses concerning the child's cognitive and linguistic future.

  3. Dynamic epithelia of the developing vertebrate face.

    PubMed

    Choe, Chong Pyo; Crump, J Gage

    2015-06-01

    A segmental series of endoderm-derived pouch and ectoderm-derived cleft epithelia act as signaling centers in the developing face. Their precise morphogenesis is therefore essential for proper patterning of the vertebrate head. Intercellular adhesion and polarity are highly dynamic within developing facial epithelial cells, with signaling from the adjacent mesenchyme controlling both epithelial character and directional migration. Endodermal and ectodermal epithelia fuse to form the primary mouth and gill slits, which involves basement membrane dissolution, cell intercalations, and apoptosis, as well as undergo further morphogenesis to generate the middle ear cavity and glands of the neck. Recent studies of facial epithelia are revealing both core programs of epithelial morphogenesis and insights into the coordinated assembly of the vertebrate head.

  4. Optical transmission versus ac magnetization measurements for monitoring colloidal Ni nanorod rotational dynamics

    NASA Astrophysics Data System (ADS)

    Gratz, M.; Tschöpe, A.

    2017-01-01

    Ni nanorods with an average length < 250 nm and diameter < 30 nm were synthesized using the AAO template method. The magnetization and optical transmission of nanorod colloidal dispersions in alternating magnetic fields were measured and analyzed with the objective of comparing the intrinsic Brownian relaxation times obtained with the two methods. The different physical origin of the measured signal, related to different moments of the orientation distribution function, and the non-linear effects expected for the large magnetic moments of the Ni nanorods at common field amplitudes required a comprehensive modelling. The time-dependent magnetization and optical transmission in ac magnetic fields was derived by numerical solution of the Fokker-Planck equation. The simulated time-dependent magnetization and optical transmission at a given frequency and field amplitude were analyzed analogous to experimental data to determine characteristic relaxation frequencies. Empirical relationships were derived which enabled extraction of the intrinsic Brownian relaxation time from the characteristic frequencies measured in the non-linear regime. Despite large differences in the characteristic frequencies obtained from magnetization and optical transmission measurements, the retrieved intrinsic Brownian relaxation times were found to agree well. The potential of ac magnetic field-dependent optical transmission for biosensing applications was demonstrated by monitoring the adsorption of the protein gelatine on the nanorod labels.

  5. Intergenerational Transmission of Adaptive Functioning: A Test of the Interactionist Model of SES and Human Development

    ERIC Educational Resources Information Center

    Schofield, Thomas J; Martin, Monica J.; Conger, Katherine J.; Neppl, Tricia M.; Donnellan, M. Brent; Conger, Rand D.

    2011-01-01

    The interactionist model (IM) of human development (R. D. Conger & M. B. Donellan, 2007) proposes that the association between socioeconomic status (SES) and human development involves a dynamic interplay that includes both social causation (SES influences human development) and social selection (individual characteristics affect SES). Using a…

  6. Intergenerational Transmission of Adaptive Functioning: A Test of the Interactionist Model of SES and Human Development

    ERIC Educational Resources Information Center

    Schofield, Thomas J; Martin, Monica J.; Conger, Katherine J.; Neppl, Tricia M.; Donnellan, M. Brent; Conger, Rand D.

    2011-01-01

    The interactionist model (IM) of human development (R. D. Conger & M. B. Donellan, 2007) proposes that the association between socioeconomic status (SES) and human development involves a dynamic interplay that includes both social causation (SES influences human development) and social selection (individual characteristics affect SES). Using a…

  7. Towards clinical development of a Pfs48/45-based transmission blocking malaria vaccine.

    PubMed

    Theisen, Michael; Jore, Matthijs M; Sauerwein, Robert

    2017-04-01

    Malaria is a devastating vector-borne disease caused by the Plasmodium parasite, resulting in almost 0.5 million casualties per year. The parasite has a complex life-cycle that includes asexual replication in human red blood cells, causing symptomatic malaria, and sexual stages which are essential for the transmission to the mosquito vector. A vaccine targeting the sexual stages of the parasite and thus blocking transmission will be instrumental for the eradication of malaria. One of the leading transmission blocking vaccine candidates is the sexual stage antigen Pfs48/45. Areas covered: PubMed was searched to review the progress and future prospects for clinical development of a Pfs48/45-based subunit vaccine. We will focus on biological function, naturally acquired immunity, functional activity of specific antibodies, sequence diversity, production of recombinant protein and preclinical studies. Expert commentary: Pfs48/45 is one of the lead-candidates for a transmission blocking vaccine and should be further explored in clinical trials.

  8. Intergenerational Transmission of Maternal Childhood Maltreatment Exposure: Implications for Fetal Brain Development.

    PubMed

    Buss, Claudia; Entringer, Sonja; Moog, Nora K; Toepfer, Philipp; Fair, Damien A; Simhan, Hyagriv N; Heim, Christine M; Wadhwa, Pathik D

    2017-05-01

    Growing evidence suggests the deleterious consequences of exposure to childhood maltreatment (CM) not only might endure over the exposed individual's lifespan but also might be transmitted across generations. The time windows, mechanisms, and targets of such intergenerational transmission are poorly understood. The prevailing paradigm posits that mother-to-child transmission of the effects of maternal CM likely occurs after her child's birth. The authors seek to extend this paradigm and advance a transdisciplinary framework that integrates the concepts of biological embedding of life experiences and fetal origins of health and disease risk. The authors posit that the period of embryonic and fetal life represents a particularly sensitive time for intergenerational transmission; that the developing brain represents a target of particular interest; and that stress-sensitive maternal-placental-fetal biological (endocrine, immune) pathways represent leading candidate mechanisms of interest. The plausibility of this model is supported by theoretical considerations and empirical findings in humans and animals. The authors synthesize several research areas and identify important knowledge gaps that might warrant further study. The scientific and public health relevance of this effort relates to achieving a better understanding of the "when," "what," and "how" of intergenerational transmission of CM, with implications for early identification of risk, prevention, and intervention. Copyright © 2017 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

  9. Toward the development of effective transmission-blocking vaccines for malaria.

    PubMed

    Nikolaeva, Daria; Draper, Simon J; Biswas, Sumi

    2015-05-01

    The continued global burden of malaria can in part be attributed to a complex lifecycle, with both human hosts and mosquito vectors serving as transmission reservoirs. In preclinical models of vaccine-induced immunity, antibodies to parasite sexual-stage antigens, ingested in the mosquito blood meal, can inhibit parasite survival in the insect midgut as judged by ex vivo functional studies such as the membrane feeding assay. In an era of renewed political momentum for malaria elimination and eradication campaigns, such observations have fueled support for the development and implementation of so-called transmission-blocking vaccines. While leading candidates are being evaluated using a variety of promising vaccine platforms, the field is also beginning to capitalize on global '-omics' data for the rational genome-based selection and unbiased characterization of parasite and mosquito proteins to expand the candidate list. This review covers the progress and prospects of these recent developments.

  10. Development of a thyristor valve for next generation 500kV HVDC transmission systems

    SciTech Connect

    Hasegawa, T.; Yamaji, K.; Irokawa, H.; Shirahama, H.; Tanaka, C.; Akabane, K.

    1996-10-01

    A high voltage thyristor valve is the basic component of an HVDC transmission system. Development of a 500kV valve for next generation HVDC transmission systems is described. First, the power loss of the valve is analyzed to decide a reasonable wafer size for the light triggered thyristor. From these results, a six inch diameter wafer size is selected. The light triggered thyristor, with ratings of 8kV and 3.5kA, is developed using the six inch wafer. The designing of the valve employing the thyristor and test results with the prototype valve prove that a 500kV valve can be realized by the design method.

  11. Recent developments of the in situ wet cell technology for transmission electron microscopies

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Li, Chang; Cao, Hongling

    2015-03-01

    In situ wet cells for transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) allow studying structures and processes in a liquid environment with high temporal and spatial resolutions, and have been attracting increasing research interests in many fields. In this review, we highlight the structural and functional developments of the wet cells for TEM and STEM. One of the key features of the wet cells is the sealing technique used to isolate the liquid sample from the TEM/STEM vacuum environments, thus the existing in situ wet cells are grouped by different sealing methods. In this study, the advantages and shortcomings of each type of in situ wet cells are discussed, the functional developments of different wet cells are presented, and the future trends of the wet cell technology are addressed. It is suggested that in the future the in situ wet cell TEM/STEM technology will have an increasing impact on frontier nanoscale research.

  12. Development of a model of an x-ray tube transmission source

    SciTech Connect

    Goda, Joetta M; Ianakiev, Kiril D; Moss, Cal E

    2009-01-01

    In support of the development of an x-ray tube based source for transmission measurements of UF6 gas, we have developed a one-dimensional, spreadsheet-based model of the source. Starting with the spectrum produced by an x-ray tube we apply the linear attenuation coefficients for various notch filters, the aluminum pipe, and UF6 gas. This model allows calculation of the transmitted spectrum based on the type of filter, the thickness of the filter, the x-ray tube high voltage, the Al pipe thickness, and the UF6 gas pressure. The sensitivity of the magnitude of the transmission peak produced by the notch filter to any of these variables can be explored quickly and easily to narrow the choices for experimental measurements. To validate the spreadsheet based model, comparisons have been made to various experimental data.

  13. Estimation of the dynamics and rate of transmission of classical swine fever (hog cholera) in wild pigs.

    PubMed Central

    Hone, J.; Pech, R.; Yip, P.

    1992-01-01

    Infectious diseases establish in a population of wildlife hosts when the number of secondary infections is greater than or equal to one. To estimate whether establishment will occur requires extensive experience or a mathematical model of disease dynamics and estimates of the parameters of the disease model. The latter approach is explored here. Methods for estimating key model parameters, the transmission coefficient (beta) and the basic reproductive rate (RDRS), are described using classical swine fever (hog cholera) in wild pigs as an example. The tentative results indicate that an acute infection of classical swine fever will establish in a small population of wild pigs. Data required for estimation of disease transmission rates are reviewed and sources of bias and alternative methods discussed. A comprehensive evaluation of the biases and efficiencies of the methods is needed. PMID:1582476

  14. Protecting the herd: the remarkable effectiveness of the bacterial meningitis polysaccharide-protein conjugate vaccines in altering transmission dynamics.

    PubMed

    Stephens, David S

    2011-01-01

    Interrupting human-to-human transmission of the agents (Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae) of bacterial meningitis by new capsular polysaccharide-protein conjugate vaccines (PPCVs) has proven to be a remarkable (and unanticipated) contributor to vaccine effectiveness. Herd immunity accounts for ∼50% of the protection by meningococcal serogroup C PPCVs, pneumococcal PPCV7, and H. influenzae b PPCVs. Nasopharyngeal carriage can be reduced ≥75% for vaccine serotypes; the decrease in carriage is correlated with disease reduction in unvaccinated individuals, and the impact of herd immunity lasts for years. Based on these data, models for using herd immunity in vaccine-based prevention strategies are underway for control of meningitis in sub-Saharan Africa. Although the immunologic basis of herd immunity and impact on microbial biology need more study, protecting the unvaccinated by altering pathogen transmission dynamics is a powerful effect of PPCVs and increasingly important in vaccine introduction, implementation, and evaluation strategies.

  15. Development of Radar Navigation and Radio Data Transmission for Microhole Coiled Tubing Bottom Hole Assemblies

    SciTech Connect

    Larry G. Stolarczyk; Gerald L. Stolarczyk; Larry Icerman; John Howard; Hooman Tehrani

    2007-03-25

    This Final Technical Report summarizes the research and development (R&D) work performed by Stolar Research Corporation (Stolar) under U.S. Department of Energy (DOE) Contract Number DE-FC26-04NT15477. This work involved the development of radar navigation and radio data transmission systems for integration with microhole coiled tubing bottom hole assemblies. Under this contract, Stolar designed, fabricated, and laboratory and field tested two advanced technologies of importance to the future growth of the U.S. oil and gas industry: (1) real-time measurement-while-drilling (MWD) for guidance and navigation of coiled tubing drilling in hydrocarbon reservoirs and (2) two-way inductive radio data transmission on coiled tubing for real-time, subsurface-to-surface data transmission. The operating specifications for these technologies are compatible with 3.5-inch boreholes drilled to a true vertical depth (TVD) of 5,000 feet, which is typical of coiled tubing drilling applications. These two technologies (i.e., the Stolar Data Transmission System and Drill String Radar) were developed into pre-commercial prototypes and tested successfully in simulated coiled tubing drilling conditions. Integration of these two technologies provides a real-time geosteering capability with extremely quick response times. Stolar is conducting additional work required to transition the Drill String Radar into a true commercial product. The results of this advanced development work should be an important step in the expanded commercialization of advanced coiled tubing microhole drilling equipment for use in U.S. hydrocarbon reservoirs.

  16. Unsafe injections in the developing world and transmission of bloodborne pathogens: a review.

    PubMed Central

    Simonsen, L.; Kane, A.; Lloyd, J.; Zaffran, M.; Kane, M.

    1999-01-01

    Unsafe injections are suspected to occur routinely in developing countries. We carried out a literature review to quantify the prevalence of unsafe injections and to assess the disease burden of bloodborne infections attributable to this practice. Quantitative information on injection use and unsafe injections (defined as the reuse of syringe or needle between patients without sterilization) was obtained by reviewing the published literature and unpublished WHO reports. The transmissibility of hepatitis B and C viruses and human immunodeficiency virus (HIV) was estimated using data from studies of needle-stick injuries. Finally, all epidemiological studies that linked unsafe injections and bloodborne infections were evaluated to assess the attributable burden of bloodborne infections. It was estimated that each person in the developing world receives 1.5 injections per year on average. However, institutionalized children, and children and adults who are ill or hospitalized, including those infected with HIV, are often exposed to 10-100 times as many injections. An average of 95% of all injections are therapeutic, the majority of which were judged to be unnecessary. At least 50% of injections were unsafe in 14 of 19 countries (representing five developing world regions) for which data were available. Eighteen studies reported a convincing link between unsafe injections and the transmission of hepatitis B and C, HIV, Ebola and Lassa virus infections and malaria. Five studies attributed 20-80% of all new hepatitis B infections to unsafe injections, while three implicated unsafe injections as a major mode of transmission of hepatitis C. In conclusion, unsafe injections occur routinely in most developing world regions, implying a significant potential for the transmission of any bloodborne pathogen. Unsafe injections currently account for a significant proportion of all new hepatitis B and C infections. This situation needs to be addressed immediately, as a political

  17. Study of the kinematic and dynamic characteristics of a wormgear transmission for helicopter applications

    NASA Technical Reports Server (NTRS)

    Sun, D. C.; Yuan, Qin

    1994-01-01

    The first phase of the study of the performance of a wormgear transmission is reported. In this phase the work included the selection of a double-enveloping wormgear type, and its dimensions, suitable for use in helicopter transmissions; the 3-D graphics representation of the selected wormgear using the I-DEAS software; the analysis of the kinematics of meshing; the analysis of load sharing among the meshing teeth; and the implementation of the analyses in a computer program. The report describes the analyses, their results, and the use of the computer programs.

  18. Dynamics of Centrocestus armatus Transmission in Endemic River in Hyogo Prefecture, Japan.

    PubMed

    Komatsu, Shintaro; Kimura, Daisuke; Paller, Vachel Gay V; Uga, Shoji

    2014-03-01

    Centrocestus armatus is an intestinal parasite belonging to the family Heterophyidae. We developed an apparatus for recovering cercariae and clarified the infection dynamics of this parasite. To clarify the circadian rhythm of cercarial shedding in the summer season, we filtrated 30 l of river water every 2 h for 24 h. Cercariae were first detected between 06:00 and 08:00 h, increased over time to reach peak at 16:00 h and decreased thereafter, thus showing a single-peak pattern. In a survey of seasonal change, approximately 200 cercariae were contained in 1 l of river water during the summer season, while none were found during the winter. This cercarial shedding pattern appeared to be related to sunrise/sunset and water/atmosphere temperature. Therefore, we examined whether cercarial shedding was affected by light or temperature changes under laboratory conditions, and confirmed that both light and temperature were important factors for cercarial shedding. Light was a stronger factor than water temperature. Cercarial shedding of C. armatus occurred in response to temperature and light. The change in the number of juvenile metacercariae detected in fish brain corresponded with monthly detection rates of cercariae; however, the incidence of new infections decreased in August. This suggests that Nipponocypris temminkii contains a defense mechanism against new infections that may have hindered the increase in parasite infectivity. These results clarified the smooth infection from the first to the second intermediate host of C. armatus in the endemic river. Throughout the study period, fecal samples were collected from 19 kites, 114 herons, and three unidentified species. However, our results using C. armatus showed a low value of 1% in herons and 5% in kites. The infection dynamics of final host to first intermediate host need to be further investigated.

  19. The improbable transmission of Trypanosoma cruzi to human: the missing link in the dynamics and control of Chagas disease.

    PubMed

    Nouvellet, Pierre; Dumonteil, Eric; Gourbière, Sébastien

    2013-11-01

    Chagas disease has a major impact on human health in Latin America and is becoming of global concern due to international migrations. Trypanosoma cruzi, the etiological agent of the disease, is one of the rare human parasites transmitted by the feces of its vector, as it is unable to reach the salivary gland of the insect. This stercorarian transmission is notoriously poorly understood, despite its crucial role in the ecology and evolution of the pathogen and the disease. The objective of this study was to quantify the probability of T. cruzi vectorial transmission to humans, and to use such an estimate to predict human prevalence from entomological data. We developed several models of T. cruzi transmission to estimate the probability of transmission from vector to host. Using datasets from the literature, we estimated the probability of transmission per contact with an infected triatomine to be 5.8 × 10(-4) (95%CI: [2.6 ; 11.0] × 10(-4)). This estimate was consistent across triatomine species, robust to variations in other parameters, and corresponded to 900-4,000 contacts per case. Our models subsequently allowed predicting human prevalence from vector abundance and infection rate in 7/10 independent datasets covering various triatomine species and epidemiological situations. This low probability of T. cruzi transmission reflected well the complex and unlikely mechanism of transmission via insect feces, and allowed predicting human prevalence from basic entomological data. Although a proof of principle study would now be valuable to validate our models' predictive ability in an even broader range of entomological and ecological settings, our quantitative estimate could allow switching the evaluation of disease risk and vector control program from purely entomological indexes to parasitological measures, as commonly done for other major vector borne diseases. This might lead to different quantitative perspectives as these indexes are well known not to be

  20. The Improbable Transmission of Trypanosoma cruzi to Human: The Missing Link in the Dynamics and Control of Chagas Disease

    PubMed Central

    Nouvellet, Pierre; Dumonteil, Eric; Gourbière, Sébastien

    2013-01-01

    Chagas disease has a major impact on human health in Latin America and is becoming of global concern due to international migrations. Trypanosoma cruzi, the etiological agent of the disease, is one of the rare human parasites transmitted by the feces of its vector, as it is unable to reach the salivary gland of the insect. This stercorarian transmission is notoriously poorly understood, despite its crucial role in the ecology and evolution of the pathogen and the disease. The objective of this study was to quantify the probability of T. cruzi vectorial transmission to humans, and to use such an estimate to predict human prevalence from entomological data. We developed several models of T. cruzi transmission to estimate the probability of transmission from vector to host. Using datasets from the literature, we estimated the probability of transmission per contact with an infected triatomine to be 5.8×10−4 (95%CI: [2.6 ; 11.0]×10−4). This estimate was consistent across triatomine species, robust to variations in other parameters, and corresponded to 900–4,000 contacts per case. Our models subsequently allowed predicting human prevalence from vector abundance and infection rate in 7/10 independent datasets covering various triatomine species and epidemiological situations. This low probability of T. cruzi transmission reflected well the complex and unlikely mechanism of transmission via insect feces, and allowed predicting human prevalence from basic entomological data. Although a proof of principle study would now be valuable to validate our models' predictive ability in an even broader range of entomological and ecological settings, our quantitative estimate could allow switching the evaluation of disease risk and vector control program from purely entomological indexes to parasitological measures, as commonly done for other major vector borne diseases. This might lead to different quantitative perspectives as these indexes are well known not to be

  1. Development of a full-scale transmission testing procedure to evaluate advanced lubricants

    NASA Astrophysics Data System (ADS)

    Lewicki, David G.; Decker, Harry J.; Shimski, John T.

    1992-08-01

    Experimental tests were performed on the OH-58A helicopter main rotor transmission in the NASA Lewis 500-hp Helicopter Transmission Test Stand. The testing was part of a joint Navy/NASA/Army lubrication program. The objective of the program was to develop a separate lubricant for gearboxes and demonstrate an improved performance in life and load-carrying capacity. The goal of the experiments was to develop a testing procedure to fail certain transmission components using a MIL-L-23699 base reference oil, then run identical tests with improved lubricants and demonstrate performance. The tests were directed at failing components that the Navy has had problems with due to marginal lubrication. These failures included mast shaft bearing micropitting, sun gear and planet bearing fatigue, and spiral bevel gear scoring. A variety of tests were performed and over 900 hours of total run time accumulated for these tests. Some success was achieved in developing a testing procedure to produce sun gear and planet bearing fatigue failures. Only marginal success was achieved in producing mast shaft bearing micropitting and spiral bevel gear scoring.

  2. Development of a full-scale transmission testing procedure to evaluate advanced lubricants

    NASA Technical Reports Server (NTRS)

    Lewicki, David G.; Decker, Harry J.; Shimski, John T.

    1992-01-01

    Experimental tests were performed on the OH-58A helicopter main rotor transmission in the NASA Lewis 500-hp Helicopter Transmission Test Stand. The testing was part of a joint Navy/NASA/Army lubrication program. The objective of the program was to develop a separate lubricant for gearboxes and demonstrate an improved performance in life and load-carrying capacity. The goal of the experiments was to develop a testing procedure to fail certain transmission components using a MIL-L-23699 base reference oil, then run identical tests with improved lubricants and demonstrate performance. The tests were directed at failing components that the Navy has had problems with due to marginal lubrication. These failures included mast shaft bearing micropitting, sun gear and planet bearing fatigue, and spiral bevel gear scoring. A variety of tests were performed and over 900 hours of total run time accumulated for these tests. Some success was achieved in developing a testing procedure to produce sun gear and planet bearing fatigue failures. Only marginal success was achieved in producing mast shaft bearing micropitting and spiral bevel gear scoring.

  3. Comparative cost-effectiveness of the quadrivalent and bivalent human papillomavirus vaccines: a transmission-dynamic modeling study.

    PubMed

    Brisson, Marc; Laprise, Jean-François; Drolet, Mélanie; Van de Velde, Nicolas; Franco, Eduardo L; Kliewer, Erich V; Ogilvie, Gina; Deeks, Shelley L; Boily, Marie-Claude

    2013-08-20

    The quadrivalent and bivalent human papillomavirus (HPV) vaccines are now licensed in several countries. We compared the cost-effectiveness of the HPV vaccines to provide evidence for policy decisions. We developed HPV-ADVISE, a multi-type individual-based transmission-dynamic model of HPV infection and disease (anogenital warts, and cervical, anogenital and oropharyngeal cancers). We calibrated the model to sexual behavior and epidemiologic data from Canada, and estimated quality-adjusted life-years (QALYs) lost and costs ($CAN 2010) from the literature. Vaccine-type efficacy was based on a systematic literature review. The analysis was performed from the healthcare provider perspective, and costs and benefits were discounted at 3%. Predictions are presented using the median [10th;90th percentiles] of simulations. Under base-case assumptions (vaccinating 10-year-old girls, 80% coverage, $95/dose), using the quadrivalent and bivalent vaccines is estimated to cost $15,528 [12,056;19,140] and $20,182 [15,531;25,240] per QALY-gained, respectively. At equal price, the quadrivalent vaccine is more cost-effective than bivalent under all scenarios investigated, except when assuming longer duration of protection for the bivalent and minimal anogenital warts burden. Under base-case assumptions, the maximum additional cost per dose for the quadrivalent vaccine to remain more cost-effective than the bivalent is $32 [17;46] (using a $40,000/QALY-gained threshold). Results were most sensitive to discounting, time-horizon, differences in durations of protection and anogenital warts burden. Vaccinating pre-adolescent girls against HPV is predicted to be highly cost-effective. If equally priced, the quadrivalent is the most economically desirable vaccine. However, ultimately, the most cost-effective HPV vaccine will be determined by their relative price. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Rapid Laser Induced Crystallization of Amorphous NiTi Films Observed by Nanosecond Dynamic Transmission Electron Microscopy (DTEM)

    SciTech Connect

    LaGrange, T; Campbell, G H; Browning, N D; Reed, B W; Grummon, D S

    2010-03-01

    The crystallization processes of the as-deposited, amorphous NiTi thin films have been studied in detail using techniques such as differential scanning calorimetry and, in-situ TEM. The kinetic data have been analyzed in terms of Johnson-Mehl-Avrami-Kolomogrov (JMAK) semi-empirical formula. The kinetic parameters determined from this analysis have been useful in defining process control parameters for tailoring microstructural features and shape memory properties. Due to the commercial push to shrink thin film-based devices, unique processing techniques have been developed using laser-based annealing to spatially control the microstructure evolution down to sub-micron levels. Nanosecond, pulse laser annealing is particularly attractive since it limits the amount of peripheral heating and unwanted microstructural changes to underlying or surrounding material. However, crystallization under pulsed laser irradiation can differ significantly from conventional thermal annealing, e.g., slow heating in a furnace. This is especially true for amorphous NiTi materials and relevant for shape memory thin film based microelectromechanical systems (MEMS) applications. There is little to no data on the crystallization kinetics of NiTi under pulsed laser irradiation, primarily due to the high crystallization rates intrinsic to high temperature annealing and the spatial and temporal resolution limits of standard techniques. However, with the high time and spatial resolution capabilities of the dynamic transmission electron microscope (DTEM) constructed at Lawrence Livermore National Laboratory, the rapid nucleation events occurring from pulsed laser irradiation can be directly observed and nucleation rates can be quantified. This paper briefly explains the DTEM approach and how it used to investigate the pulsed laser induced crystallization processes in NiTi and to determine kinetic parameters.

  5. Particle dynamics in the Eastern Mediterranean Sea: A synthesis based on light transmission, PMC, and POC archives (1991 2001)

    NASA Astrophysics Data System (ADS)

    Karageorgis, Aristomenis P.; Gardner, Wilford D.; Georgopoulos, Dimitris; Mishonov, Alexey V.; Krasakopoulou, Evangelia; Anagnostou, Christos

    2008-02-01

    During the last two decades light transmission (LT) data have been collected routinely in the Eastern Mediterranean Sea, within the framework of several research projects. A procedure was developed to obtain beam attenuation coefficient due to particles ( cp) at 660-670 nm adjusted for variations in mid-depth 'clear' water and instrumental drifts. Data from 3146 stations occupied between 1991 and 2001 were converted to a common format for the analysis of particulate matter (PM) temporal and spatial distribution patterns. The data were separated into 'wet' (December-May) and 'dry' (June-November) periods. The horizontal distribution of beam cp at various depths revealed clearly higher values in the surface nepheloid layer (SNL) in the vicinity of river mouths during the 'wet' period, whilst the increase was negligible during the 'dry' period. In contrast, the bottom nepheloid layer (BNL; 1-10 m above bottom) appeared to be turbid throughout the year, particularly on the continental shelves receiving riverine discharge. This feature is attributed to resuspension and advection of recently deposited bottom sediments due to waves and currents. However, the Eastern Mediterranean as a whole is impoverished in PM in the water column, particularly at depths >200 m. The behavior of surface-water cp revealed a strong relationship to mesoscale dynamic features. Cyclonic eddies, which upwell nutrient-rich waters toward the surface, favor primary production, which was identified as elevated beam cp values. Beam cp was correlated with PM concentration (PMC) and particulate organic carbon (POC) concentration obtained by bottle sampling. Although there were regional differences in the correlations, no significant seasonal variations were observed. Two generic equations were generated that can be used for a first-order estimate of PMC and POC from historical LT measurements conducted in the area, provided that data are handled according to the proposed methodology.

  6. Vector dynamics and transmission of dengue virus: implications for dengue surveillance and prevention strategies: vector dynamics and dengue prevention.

    PubMed

    Scott, Thomas W; Morrison, Amy C

    2010-01-01

    Accounting for variation in mosquito vector populations will improve dengue surveillance and prevention. Because Aedes aegypti, the principle dengue virus (DENV) vector, transmit the virus with remarkable efficiency, entomological thresholds are especially low. Assessing risk of human infection based on immature mosquito indices has proven difficult. Greater emphasis should be placed on relative abundance of adult vectors in relation to human serotype-specific herd immunity, introduction of unique viruses, mosquito-human contact and weather. The most appropriate spatial scale for assessing entomological risk is the individual household. The scale for measuring DENV transmission risk has yet to be determined but is clearly larger than the household and likely to exceed several city blocks. Because households are expected to be a primary site for human DENV infection, intradomicile vector control strategies should be a priority, especially when the force of transmission is high. The most effective intervention strategy will combine vector control with vaccine delivery for rapid and sustained disease prevention.

  7. Respiratory virus transmission dynamics determine timing of asthma exacerbation peaks: Evidence from a population-level model

    PubMed Central

    Scott, James G.; Galvani, Alison P.; Meyers, Lauren Ancel

    2016-01-01

    Asthma exacerbations exhibit a consistent annual pattern, closely mirroring the school calendar. Although respiratory viruses—the “common cold” viruses—are implicated as a principal cause, there is little evidence to link viral prevalence to seasonal differences in risk. We jointly fit a common cold transmission model and a model of biological and environmental exacerbation triggers to estimate effects on hospitalization risk. Asthma hospitalization rate, influenza prevalence, and air quality measures are available, but common cold circulation is not; therefore, we generate estimates of viral prevalence using a transmission model. Our deterministic multivirus transmission model includes transmission rates that vary when school is closed. We jointly fit the two models to 7 y of daily asthma hospitalizations in adults and children (66,000 events) in eight metropolitan areas. For children, we find that daily viral prevalence is the strongest predictor of asthma hospitalizations, with transmission reduced by 45% (95% credible interval =41–49%) during school closures. We detect a transient period of nonspecific immunity between infections lasting 19 (17–21) d. For adults, hospitalizations are more variable, with influenza driving wintertime peaks. Neither particulate matter nor ozone was an important predictor, perhaps because of the large geographic area of the populations. The school calendar clearly and predictably drives seasonal variation in common cold prevalence, which results in the “back-to-school” asthma exacerbation pattern seen in children and indirectly contributes to exacerbation risk in adults. This study provides a framework for anticipating the seasonal dynamics of common colds and the associated risks for asthmatics. PMID:26858436

  8. Respiratory virus transmission dynamics determine timing of asthma exacerbation peaks: Evidence from a population-level model.

    PubMed

    Eggo, Rosalind M; Scott, James G; Galvani, Alison P; Meyers, Lauren Ancel

    2016-02-23

    Asthma exacerbations exhibit a consistent annual pattern, closely mirroring the school calendar. Although respiratory viruses--the "common cold" viruses--are implicated as a principal cause, there is little evidence to link viral prevalence to seasonal differences in risk. We jointly fit a common cold transmission model and a model of biological and environmental exacerbation triggers to estimate effects on hospitalization risk. Asthma hospitalization rate, influenza prevalence, and air quality measures are available, but common cold circulation is not; therefore, we generate estimates of viral prevalence using a transmission model. Our deterministic multivirus transmission model includes transmission rates that vary when school is closed. We jointly fit the two models to 7 y of daily asthma hospitalizations in adults and children (66,000 events) in eight metropolitan areas. For children, we find that daily viral prevalence is the strongest predictor of asthma hospitalizations, with transmission reduced by 45% (95% credible interval =41-49%) during school closures. We detect a transient period of nonspecific immunity between infections lasting 19 (17-21) d. For adults, hospitalizations are more variable, with influenza driving wintertime peaks. Neither particulate matter nor ozone was an important predictor, perhaps because of the large geographic area of the populations. The school calendar clearly and predictably drives seasonal variation in common cold prevalence, which results in the "back-to-school" asthma exacerbation pattern seen in children and indirectly contributes to exacerbation risk in adults. This study provides a framework for anticipating the seasonal dynamics of common colds and the associated risks for asthmatics.

  9. Transportation properties of a high-current magnetically insulated transmission line and dynamics of the electrode plasma

    SciTech Connect

    Anan'ev, S. S.; Bakshaev, Yu. L.; Bartov, A. V.; Blinov, P. I.; Dan'ko, S. A.; Zhuzhunashvili, A. I.; Kazakov, E. D.; Kalinin, Yu. G.; Kingsep, A. S.; Korolev, V. D.; Mizhiritskii, V. I.; Smirnov, V. P.; Tkachenko, S. I.; Chernenko, A. S.

    2008-07-15

    Results are presented from experimental studies of a section of a magnetically insulated transmission line (MITL) with a current density of up to 500 MA/cm{sup 2} and linear current density of up to 7 MA/cm (the parameters close to those in a fast-Z-pinch-driven fusion reactor projected at Sandia Laboratories). The experiments were performed in the S-300 facility (3 MA, 0.15 {Omega}, 100 ns). At high linear current densities, the surface of the ohmically heated MITL electrode can explode and a plasma layer can form near the electrode surface. As a result, the MITL can lose its transmission properties due to the shunting of the vacuum gap by the plasma produced. In this series of experiments, the dynamics of the electrode plasma and the dependence of the transmission properties of the MITL on the material and cleanness of the electrode surface were studied. It is shown experimentally that, when the current with a linear density of up to 7 MA/cm begins to flow along a model MITL, the input and output currents differ by less than 10% over a time interval of up to 230 ns for nickel electrodes and up to 350 ns for a line with a gold central electrode. No effect of the oil film present on the electrode surface on the loss of the transmission properties of the line was observed. It is also shown that electron losses insignificantly contribute to the total current balance. The experimental results are compared with calculations of the electrode explosion and the subsequent expansion of the plasma layer. A conclusion is made that the life-time of the model MITL satisfies the requirements imposed on the transmission lines intended for use in the projected thermonuclear reactor.

  10. Dynamic inhibition of excitatory synaptic transmission by astrocyte-derived ATP in hippocampal cultures

    NASA Astrophysics Data System (ADS)

    Koizumi, Schuichi; Fujishita, Kayoko; Tsuda, Makoto; Shigemoto-Mogami, Yukari; Inoue, Kazuhide

    2003-09-01

    Originally ascribed passive roles in the CNS, astrocytes are now known to have an active role in the regulation of synaptic transmission. Neuronal activity can evoke Ca2+ transients in astrocytes, and Ca2+ transients in astrocytes can evoke changes in neuronal activity. The excitatory neurotransmitter glutamate has been shown to mediate such bidirectional communication between astrocytes and neurons. We demonstrate here that ATP, a primary mediator of intercellular Ca2+ signaling among astrocytes, also mediates intercellular signaling between astrocytes and neurons in hippocampal cultures. Mechanical stimulation of astrocytes evoked Ca2+ waves mediated by the release of ATP and the activation of P2 receptors. Mechanically evoked Ca2+ waves led to decreased excitatory glutamatergic synaptic transmission in an ATP-dependent manner. Exogenous application of ATP does not affect postsynaptic glutamatergic responses but decreased presynaptic exocytotic events. Finally, we show that astrocytes exhibit spontaneous Ca2+ waves mediated by extracellular ATP and that inhibition of these Ca2+ responses enhanced excitatory glutamatergic transmission. We therefore conclude that ATP released from astrocytes exerts tonic and activity-dependent down-regulation of synaptic transmission via presynaptic mechanisms.

  11. Training the Next Generation of Scientists: System Dynamics Modeling of Chagas Disease (American Trypanosomiasis) transmission.

    NASA Astrophysics Data System (ADS)

    Goff, P.; Hulse, A.; Harder, H. R.; Pierce, L. A.; Rizzo, D.; Hanley, J.; Orantes, L.; Stevens, L.; Justi, S.; Monroy, C.

    2015-12-01

    A computational simulation has been designed as an investigative case study by high school students to introduce system dynamics modeling into high school curriculum. This case study approach leads users through the forensics necessary to diagnose an unknown disease in a Central American village. This disease, Chagas, is endemic to 21 Latin American countries. The CDC estimates that of the 110 million people living in areas with the disease, 8 million are infected, with as many as 300,000 US cases. Chagas is caused by the protozoan parasite, Trypanosoma cruzi, and is spread via blood feeding insect (vectors), that feed on vertebrates and live in crevasses in the walls and roofs of adobe homes. One-third of the infected people will develop chronic Chagas who are asymptomatic for years before their heart or GI tract become enlarged resulting in death. The case study has three parts. Students play the role of WHO field investigators and work collaboratively to: 1) use genetics to identify the host(s) and vector of the disease 2) use a STELLA™ SIR (Susceptible, Infected, Recovered) system dynamics model to study Chagas at the village scale and 3) develop management strategies. The simulations identify mitigation strategies known as Ecohealth Interventions (e.g., home improvements using local materials) to help stakeholders test and compare multiple optima. High school students collaborated with researchers from the University of Vermont, Loyola University and Universidad de San Carlos, Guatemala, working in labs, interviewing researchers, and incorporating mulitple field data as part of a NSF-funded multiyear grant. The model displays stable equilibria of hosts, vectors, and disease-states. Sensitivity analyses show measures of household condition and presence of vertebrates were significant leverage points, supporting other findings by the University research team. The village-scale model explores multiple solutions to disease mitigation for the purpose of producing

  12. Climatic variables and malaria transmission dynamics in Jimma town, South West Ethiopia

    PubMed Central

    2011-01-01

    Background:- In Ethiopia, malaria is seasonal and unstable, causing frequent epidemics. It usually occurs at altitudes < 2,000 m above sea level. Occasionally, transmission of malaria occurs in areas previously free of malaria, including areas > 2,000 m above sea level. For transmission of malaria parasite, climatic factors are important determinants as well as non-climatic factors that can negate climatic influences. Indeed, there is a scarcity of information on the correlation between climatic variability and malaria transmission risk in Ethiopia in general and in the study area in particular. Therefore, the aim of this study was to determine the level of correlation between meteorological variables and malaria cases. Methods: - Time-series analysis was conducted using data on monthly meteorological variables and monthly total malaria in Jimma town, south west Ethiopia, for the period 2000-2009. All the data were entered and analyzed using SPSS-15 database program. Spearman correlation and linear regression analysis were used to asses association between the variables. Results: - During last ten years (2000-2009), a fluctuating trend of malaria transmission was observed with P.vivax becoming predominant species. Spearman correlation analysis showed that monthly minimum temperature, total rainfall and two measures of relative humidity were positively related with malaria but monthly maximum temperature negatively related. Also regression analysis suggested that monthly minimum (p = 0.008), monthly maximum temperature (p = 0.013) and monthly total rainfall (p = 0.040), at one month lagged effect, were significant meteorological factors for transmission of malaria in the study area. Conclusion: - Malaria incidences in the last decade seem to have a significant association with meteorological variables. In future, prospective and multidisciplinary cooperative research involving researchers from the fields of parasitology, epidemiology, botany, agriculture and

  13. Source coding for transmission of reconstructed dynamic geometry: a rate-distortion-complexity analysis of different approaches

    NASA Astrophysics Data System (ADS)

    Mekuria, Rufael N.; Cesar, Pablo; Bulterman, Dick C. A.

    2014-09-01

    Live 3D reconstruction of a human as a 3D mesh with commodity electronics is becoming a reality. Immersive applications (i.e. cloud gaming, tele-presence) benefit from effective transmission of such content over a bandwidth limited link. In this paper we outline different approaches for compressing live reconstructed mesh geometry based on distributing mesh reconstruction functions between sender and receiver. We evaluate rate-performance-complexity of different configurations. First, we investigate 3D mesh compression methods (i.e. dynamic/static) from MPEG-4. Second, we evaluate the option of using octree based point cloud compression and receiver side surface reconstruction.

  14. Observation of genuine wave vector (k or β) gap in a dynamic transmission line and temporal photonic crystals

    SciTech Connect

    Reyes-Ayona, J. R.; Halevi, P.

    2015-08-17

    By definition, a temporal photonic crystal (TPC) has a permittivity ε(t) that varies periodically with time. We prove that, in the long wavelength limit, a TPC is accurately mimicked by a dynamic transmission line (DTL) having a capacitance (inductance) per unit length equal to ε(t) (μ). Employing a DTL in the microwave region, we measured the photonic band structure, which results to display a genuine wave vector (k or β) gap, in very good agreement with our theoretical model and the equivalent TPC.

  15. Towards development of a fiber optic-based transmission monitoring system

    NASA Astrophysics Data System (ADS)

    Baldwin, Chris S.; Kiddy, Jason S.; Samuel, Paul D.

    2011-06-01

    There is interest in the rotorcraft community to develop health monitoring technologies. Among these technologies is the ability to monitor the transmission planetary gear system. The gearbox environment does not lend itself to traditional sensing technologies due to the harsh environment and crowed space. Traditional vibration-based diagnostics are based on the output from externally mounted sensors, usually accelerometers fixed to the gearbox exterior. This type of system relies on the ability of the vibration signal to travel from the gears through the gearbox housing. These sensors are also susceptible to other interference including electrical magnetic interference (EMI). For these reasons, the development of a fiber optic-based transmission monitoring system represents an appealing alternative to the accelerometer due to their resistance to EMI and other signal corrupting influences. Aither Engineering has been working on integrating the fiber optic sensors into the gearbox environment to measure strain on the ring gear of the planetary gear system. This application utilizes a serial array of wavelength division multiplexed fiber Bragg grating (FBG) sensors. Work in this area has been conducted at both the University of Maryland, College Park and more recently at the NASA Glenn Research Center (NGRC) OH-58 transmission test rig facility. This paper discusses some of the testing results collected from the fiber optic ring gear sensor array. Based on these results, recommendations for system requirements are addressed in terms of the capabilities of the FBG instrumentation.

  16. Development of a new high transmission phase shift mask technology for 10 nm logic node

    NASA Astrophysics Data System (ADS)

    Faure, Thomas; Sakamoto, Yoshifumi; Toda, Yusuke; Badger, Karen; Seki, Kazunori; Lawliss, Mark; Isogawa, Takeshi; Zweber, Amy; Kagawa, Masayuki; Wistrom, Richard; Xu, Yongan; Lobb, Granger; Viswanathan, Ramya; Hu, Lin; Inazuki, Yukio; Nishikawa, Kazuhiro

    2016-05-01

    In this paper we will describe the development of a new 12% high transmission phase shift mask technology for use with the 10 nm logic node. The primary motivation for this work was to improve the lithographic process window for 10 nm node via hole patterning by reducing the MEEF and improving the depth of focus (DOF). First, the simulated MEEF and DOF data will be compared between the 6% and high T PSM masks with the transmission of high T mask blank varying from 12% to 20%. This resulted in selection of a 12% transmission phase shift mask. As part of this work a new 12% attenuated phase shift mask blank was developed. A detailed description and results of the key performance metrics of the new mask blank including radiation durability, dry etch properties, film thickness, defect repair, and defect inspection will be shared. In addition, typical mask critical dimension uniformity and mask minimum feature size performance for 10 nm logic node via level mask patterns will be shown. Furthermore, the results of work to optimize the chrome hard mask film properties to meet the final mask minimum feature size requirements will be shared. Lastly, the key results of detailed lithographic performance comparisons of the process of record 6% and new 12% phase shift masks on wafer will be described. The 12% High T blank shows significantly better MEEF and larger DOF than those of 6% PSM mask blank, which is consistent with our simulation data.

  17. Circuit transmission integrity of plenum cables in a developing fire scenario

    NASA Astrophysics Data System (ADS)

    Arroyo, C. J.; Bursh, T. P.

    This paper presents the preliminary results of a new test program designed to measure the circuit transmission integrity of various cable designs in a fire scenarios. Cables are subjected to a novel yet simple circuit integrity measuring technique, while a localized heat source - simulating the intensity of a developing fire scenario - is applied to the cable. While this investigation only monitored changes in mutual and direct capacitance and capacitance-to-ground, other transmission parameters can be measured as well. The importance of this new test method is cables can be rapidly tested, analyzed and redesigned to withstand increasing fire intensities. Cables designed to withstand these extreme temperature environments should survive long enough to energize a fire alarm system, provide voice communication to various locations or effect an orderly shutdown of plant, as part of an energy and safety control PBX.

  18. Development of a PLC modem for data transmission over a PWM power supply

    NASA Astrophysics Data System (ADS)

    Batard, Christophe; Ginot, Nicolas; Mannah, Marc Anthony; Millet, Christophe; Poitiers, Frédéric

    2014-04-01

    In variable-speed electrical drive and online conditioning monitoring, a feedback loop is required in order to transmit the sensor information from the motor to the controller close to the inverter. Additional cabling is used for signalling. This extra cabling has a significant cost and data transmission may not be reliable. Thus, the use of power line communication (PLC) technology to transmit data in motor drive application is quite interesting. The use of a PLC modem dedicated to the home network in a three-phase inverter-fed motor power cable does not work. Therefore, specific coupling interfaces are developed to transmit data through a pulse-width modulated power supply. Laboratory tests have shown that the couplers are operating properly. They ensure reliable data transmission in a motor drive application.

  19. Some recent developments in the theory of acoustic transmission in tube bundles

    NASA Astrophysics Data System (ADS)

    Heckl, Maria A.; Mulholland, L. S.

    1995-01-01

    A comprehensive theoretical model for acoustic transmission in a tube bundle is presented. The tube bundle is considered as a series of diffraction gratings. Each grating consists of periodically spaced cylindrical tubes which obey the equations of motion of a cylindrical shell. Fluid loading is included. The model can be used for numerical simulations to calculate the sound field at any point in a tube bundle. Various phenomena can be predicted which are of interest for the development of acoustic diagnostics in heat exchangers. These include diffraction of a plane incident wave into several directions, the occurrence of passing and stopping bands in the transmission spectrum, features specific to oblique waves and the effect of dissipative losses. Tube bundles with baffle plates are also examined. The validity of the theoretical model is confirmed by comparison with experimental results.

  20. Transmission blocking effects of neem (Azadirachta indica) seed kernel limonoids on Plasmodium berghei early sporogonic development.

    PubMed

    Tapanelli, Sofia; Chianese, Giuseppina; Lucantoni, Leonardo; Yerbanga, Rakiswendé Serge; Habluetzel, Annette; Taglialatela-Scafati, Orazio

    2016-10-01

    Azadirachta indica, known as neem tree and traditionally called "nature's drug store" makes part of several African pharmacopeias and is widely used for the preparation of homemade remedies and commercial preparations against various illnesses, including malaria. Employing a bio-guided fractionation approach, molecules obtained from A. indica ripe and green fruit kernels were tested for activity against early sporogonic stages of Plasmodium berghei, the parasite stages that develop in the mosquito mid gut after an infective blood meal. The limonoid deacetylnimbin (3) was identified as one the most active compounds of the extract, with a considerably higher activity compared to that of the close analogue nimbin (2). Pure deacetylnimbin (3) appeared to interfere with transmissible Plasmodium stages at a similar potency as azadirachtin A. Considering its higher thermal and chemical stability, deacetylnimbin could represent a suitable alternative to azadirachtin A for the preparation of transmission blocking antimalarials.

  1. Understanding the effects of different HIV transmission models in individual-based microsimulation of HIV epidemic dynamics in people who inject drugs.

    PubMed

    Monteiro, J F G; Escudero, D J; Weinreb, C; Flanigan, T; Galea, S; Friedman, S R; Marshall, B D L

    2016-06-01

    We investigated how different models of HIV transmission, and assumptions regarding the distribution of unprotected sex and syringe-sharing events ('risk acts'), affect quantitative understanding of HIV transmission process in people who inject drugs (PWID). The individual-based model simulated HIV transmission in a dynamic sexual and injecting network representing New York City. We constructed four HIV transmission models: model 1, constant probabilities; model 2, random number of sexual and parenteral acts; model 3, viral load individual assigned; and model 4, two groups of partnerships (low and high risk). Overall, models with less heterogeneity were more sensitive to changes in numbers risk acts, producing HIV incidence up to four times higher than that empirically observed. Although all models overestimated HIV incidence, micro-simulations with greater heterogeneity in the HIV transmission modelling process produced more robust results and better reproduced empirical epidemic dynamics.

  2. The impact of stratified immunity on the transmission dynamics of influenza.

    PubMed

    Yuan, Hsiang-Yu; Baguelin, Marc; Kwok, Kin O; Arinaminpathy, Nimalan; van Leeuwen, Edwin; Riley, Steven

    2017-03-12

    Although empirical studies show that protection against influenza infection in humans is closely related to antibody titres, influenza epidemics are often described under the assumption that individuals are either susceptible or not. Here we develop a model in which antibody titre classes are enumerated explicitly and mapped onto a variable scale of susceptibility in different age groups. Fitting only with pre- and post-wave serological data during 2009 pandemic in Hong Kong, we demonstrate that with stratified immunity, the timing and the magnitude of the epidemic dynamics can be reconstructed more accurately than is possible with binary seropositivity data. We also show that increased infectiousness of children relative to adults and age-specific mixing are required to reproduce age-specific seroprevalence observed in Hong Kong, while pre-existing immunity in the elderly is not. Overall, our results suggest that stratified immunity in an aged-structured heterogeneous population plays a significant role in determining the shape of influenza epidemics. Copyright © 2017. Published by Elsevier B.V.

  3. Transmission or Within-Host Dynamics Driving Pulses of Zoonotic Viruses in Reservoir-Host Populations.

    PubMed

    Plowright, Raina K; Peel, Alison J; Streicker, Daniel G; Gilbert, Amy T; McCallum, Hamish; Wood, James; Baker, Michelle L; Restif, Olivier

    2016-08-01

    Progress in combatting zoonoses that emerge from wildlife is often constrained by limited knowledge of the biology of pathogens within reservoir hosts. We focus on the host-pathogen dynamics of four emerging viruses associated with bats: Hendra, Nipah, Ebola, and Marburg viruses. Spillover of bat infections to humans and domestic animals often coincides with pulses of viral excretion within bat populations, but the mechanisms driving such pulses are unclear. Three hypotheses dominate current research on these emerging bat infections. First, pulses of viral excretion could reflect seasonal epidemic cycles driven by natural variations in population densities and contact rates among hosts. If lifelong immunity follows recovery, viruses may disappear locally but persist globally through migration; in either case, new outbreaks occur once births replenish the susceptible pool. Second, epidemic cycles could be the result of waning immunity within bats, allowing local circulation of viruses through oscillating herd immunity. Third, pulses could be generated by episodic shedding from persistently infected bats through a combination of physiological and ecological factors. The three scenarios can yield similar patterns in epidemiological surveys, but strategies to predict or manage spillover risk resulting from each scenario will be different. We outline an agenda for research on viruses emerging from bats that would allow for differentiation among the scenarios and inform development of evidence-based interventions to limit threats to human and animal health. These concepts and methods are applicable to a wide range of pathogens that affect humans, domestic animals, and wildlife.

  4. Transmission or Within-Host Dynamics Driving Pulses of Zoonotic Viruses in Reservoir–Host Populations

    PubMed Central

    Plowright, Raina K.; Peel, Alison J.; Streicker, Daniel G.; Gilbert, Amy T.; McCallum, Hamish; Wood, James; Baker, Michelle L.; Restif, Olivier

    2016-01-01

    Progress in combatting zoonoses that emerge from wildlife is often constrained by limited knowledge of the biology of pathogens within reservoir hosts. We focus on the host–pathogen dynamics of four emerging viruses associated with bats: Hendra, Nipah, Ebola, and Marburg viruses. Spillover of bat infections to humans and domestic animals often coincides with pulses of viral excretion within bat populations, but the mechanisms driving such pulses are unclear. Three hypotheses dominate current research on these emerging bat infections. First, pulses of viral excretion could reflect seasonal epidemic cycles driven by natural variations in population densities and contact rates among hosts. If lifelong immunity follows recovery, viruses may disappear locally but persist globally through migration; in either case, new outbreaks occur once births replenish the susceptible pool. Second, epidemic cycles could be the result of waning immunity within bats, allowing local circulation of viruses through oscillating herd immunity. Third, pulses could be generated by episodic shedding from persistently infected bats through a combination of physiological and ecological factors. The three scenarios can yield similar patterns in epidemiological surveys, but strategies to predict or manage spillover risk resulting from each scenario will be different. We outline an agenda for research on viruses emerging from bats that would allow for differentiation among the scenarios and inform development of evidence-based interventions to limit threats to human and animal health. These concepts and methods are applicable to a wide range of pathogens that affect humans, domestic animals, and wildlife. PMID:27489944

  5. Trans3D: a free tool for dynamical visualization of EEG activity transmission in the brain.

    PubMed

    Blinowski, Grzegorz; Kamiński, Maciej; Wawer, Dariusz

    2014-08-01

    The problem of functional connectivity in the brain is in the focus of attention nowadays, since it is crucial for understanding information processing in the brain. A large repertoire of measures of connectivity have been devised, some of them being capable of estimating time-varying directed connectivity. Hence, there is a need for a dedicated software tool for visualizing the propagation of electrical activity in the brain. To this aim, the Trans3D application was developed. It is an open access tool based on widely available libraries and supporting both Windows XP/Vista/7(™), Linux and Mac environments. Trans3D can create animations of activity propagation between electrodes/sensors, which can be placed by the user on the scalp/cortex of a 3D model of the head. Various interactive graphic functions for manipulating and visualizing components of the 3D model and input data are available. An application of the Trans3D tool has helped to elucidate the dynamics of the phenomena of information processing in motor and cognitive tasks, which otherwise would have been very difficult to observe. Trans3D is available at: http://www.eeg.pl/.

  6. Power transmission cable development for the Space Station Freedom electrical power system

    NASA Technical Reports Server (NTRS)

    Schmitz, Gregory V.; Biess, John J.

    1989-01-01

    Power transmission cable is presently being evaluated under a NASA Lewis Research Center advanced development contract for application in the Space Station Freedom (SSF) electrical power system (EPS). Evaluation testing has been performed by TRW and NASA Lewis Research Center. The results of this development contract are presented. The primary cable design goals are to provide (1) a low characteristic inductance to minimize line voltage drop at 20 kHz, (2) electromagnetic compatibility control of the 20-kHz ac power current, (3) a physical configuration that minimizes ac resistance and (4) release of trapped air for corona-free operation.

  7. Power transmission cable development for the Space Station Freedom electrical power system

    NASA Technical Reports Server (NTRS)

    Schmitz, Gregory V.; Biess, John J.

    1989-01-01

    Power transmission cable is presently being evaluated under a NASA Lewis Research Center advanced development contract for application in the Space Station Freedom (SSF) electrical power system (EPS). Evaluation testing has been performed by TRW and NASA Lewis Research Center. The results of this development contract are presented. The primary cable design goals are to provide (1) a low characteristic inductance to minimize line voltage drop at 20 kHz, (2) electromagnetic compatibility control of the 20-kHz ac power current, (3) a physical configuration that minimizes ac resistance and (4) release of trapped air for corona-free operation.

  8. Analytical study of dynamics of matter-wave solitons in lossless nonlinear discrete bi-inductance transmission lines.

    PubMed

    Kengne, E; Lakhssassi, A

    2015-03-01

    We consider a lossless one-dimensional nonlinear discrete bi-inductance electrical transmission line made of N identical unit cells. When lattice effects are considered, we use the reductive perturbation method in the semidiscrete limit to show that the dynamics of modulated waves can be modeled by the classical nonlinear Schrödinger (CNLS) equation, which describes the modulational instability and the propagation of bright and dark solitons on a continuous-wave background. Our theoretical analysis based on the CNLS equation predicts either two or four frequency regions with different behavior concerning the modulational instability of a plane wave. With the help of the analytical solutions of the CNLS equation, we investigate analytically the effects of the linear capacitance CS on the dynamics of matter-wave solitons in the network. Our results reveal that the linear parameter CS can be used to manipulate the motion of bright, dark, and kink soliton in the network.

  9. Quantifying the impact of immune escape on transmission dynamics of influenza.

    PubMed

    Park, Andrew W; Daly, Janet M; Lewis, Nicola S; Smith, Derek J; Wood, James L N; Grenfell, Bryan T

    2009-10-30

    Influenza virus evades prevailing natural and vaccine-induced immunity by accumulating antigenic change in the haemagglutinin surface protein. Linking amino acid substitutions in haemagglutinin epitopes to epidemiology has been problematic because of the scarcity of data connecting these scales. We use experiments on equine influenza virus to address this issue, quantifying how key parameters of viral establishment and shedding increase the probability of transmission with genetic distance between previously immunizing virus and challenge virus. Qualitatively similar patterns emerge from analyses based on antigenic distance and from a published human influenza study. Combination of the equine data and epidemiological models allows us to calculate the effective reproductive number of transmission as a function of relevant genetic change in the virus, illuminating the probability of influenza epidemics as a function of immunity.

  10. Development of Novel Methods for the Reduction of Noise and Weight in Helicopter Transmissions

    NASA Astrophysics Data System (ADS)

    Dimofte, Florin; Keith, Theo G., Jr.

    2003-01-01

    Over the 70-year evolution of the helicopter, man's understanding of vibration control has greatly increased. However, in spite of the increased performance, the extent of helicopter vibration problems has not significantly diminished. Crew vibration and noise remains important factors in the design of all current helicopters. With more complex and critical demands being placed on aircrews, it is essential that vibration and noise not impair their performance. A major source of helicopter cabin noise (which has been measured at a sound pressure level of over 100 dB) is the gearbox. Reduction of this noise has been a goal of NASA and the U.S. Army. Gear mesh noise is typically in the frequency range of 1000 to 3000 Hz, a range important for speech. A requirement for U.S. Army/NASA Advanced Rotorcraft Transmission project has been a 10-dB reduction compared to current designs. A combined analytical/experimental effort has been underway, since the end of the 80's, to study effects of design parameters on noise production. The noise generated by the gear mesh can be transmitted to the surrounding media through the bearings that support the gear shaft. Therefore, the use of fluid film bearings instead of rolling element bearings could reduce the transmission noise by 10 dB. In addition, the fluid film bearings that support the gear shaft can change the dynamics of the gear assembly by providing damping to the system and by being softer than rolling element bearings. Wave bearings can attenuate, and filter, the noise generated by a machine component due to the dynamic stiffness and damping coefficients. The attenuation ratio could be as large as 35-40 dB. The noise components at higher frequencies than a synchronous frequency can be almost eliminated.

  11. Development of Novel Methods for the Reduction of Noise and Weight in Helicopter Transmissions

    NASA Technical Reports Server (NTRS)

    Dimofte, Florin; Keith, Theo G., Jr.

    2003-01-01

    Over the 70-year evolution of the helicopter, man's understanding of vibration control has greatly increased. However, in spite of the increased performance, the extent of helicopter vibration problems has not significantly diminished. Crew vibration and noise remains important factors in the design of all current helicopters. With more complex and critical demands being placed on aircrews, it is essential that vibration and noise not impair their performance. A major source of helicopter cabin noise (which has been measured at a sound pressure level of over 100 dB) is the gearbox. Reduction of this noise has been a goal of NASA and the U.S. Army. Gear mesh noise is typically in the frequency range of 1000 to 3000 Hz, a range important for speech. A requirement for U.S. Army/NASA Advanced Rotorcraft Transmission project has been a 10-dB reduction compared to current designs. A combined analytical/experimental effort has been underway, since the end of the 80's, to study effects of design parameters on noise production. The noise generated by the gear mesh can be transmitted to the surrounding media through the bearings that support the gear shaft. Therefore, the use of fluid film bearings instead of rolling element bearings could reduce the transmission noise by 10 dB. In addition, the fluid film bearings that support the gear shaft can change the dynamics of the gear assembly by providing damping to the system and by being softer than rolling element bearings. Wave bearings can attenuate, and filter, the noise generated by a machine component due to the dynamic stiffness and damping coefficients. The attenuation ratio could be as large as 35-40 dB. The noise components at higher frequencies than a synchronous frequency can be almost eliminated.

  12. Time-Scaled Evolutionary Analysis of the Transmission and Antibiotic Resistance Dynamics of Staphylococcus aureus Clonal Complex 398.

    PubMed

    Ward, M J; Gibbons, C L; McAdam, P R; van Bunnik, B A D; Girvan, E K; Edwards, G F; Fitzgerald, J R; Woolhouse, M E J

    2014-12-01

    Staphylococcus aureus clonal complex 398 (CC398) is associated with disease in humans and livestock, and its origins and transmission have generated considerable interest. We performed a time-scaled phylogenetic analysis of CC398, including sequenced isolates from the United Kingdom (Scotland), along with publicly available genomes. Using state-of-the-art methods for mapping traits onto phylogenies, we quantified transitions between host species to identify sink and source populations for CC398 and employed a novel approach to investigate the gain and loss of antibiotic resistance in CC398 over time. We identified distinct human- and livestock-associated CC398 clades and observed multiple transmissions of CC398 from livestock to humans and between countries, lending quantitative support to previous reports. Of note, we identified a subclade within the livestock-associated clade comprised of isolates from hospital environments and newborn babies, suggesting that livestock-associated CC398 is capable of onward transmission in hospitals. In addition, our analysis revealed significant differences in the dynamics of resistance to methicillin and tetracycline related to contrasting historical patterns of antibiotic usage between the livestock industry and human medicine. We also identified significant differences in patterns of gain and loss of different tetracycline resistance determinants, which we ascribe to epistatic interactions between the resistance genes and/or differences in the modes of inheritance of the resistance determinants. Copyright © 2014 Ward et al.

  13. Time-Scaled Evolutionary Analysis of the Transmission and Antibiotic Resistance Dynamics of Staphylococcus aureus Clonal Complex 398

    PubMed Central

    Gibbons, C. L.; McAdam, P. R.; van Bunnik, B. A. D.; Girvan, E. K.; Edwards, G. F.; Fitzgerald, J. R.; Woolhouse, M. E. J.

    2014-01-01

    Staphylococcus aureus clonal complex 398 (CC398) is associated with disease in humans and livestock, and its origins and transmission have generated considerable interest. We performed a time-scaled phylogenetic analysis of CC398, including sequenced isolates from the United Kingdom (Scotland), along with publicly available genomes. Using state-of-the-art methods for mapping traits onto phylogenies, we quantified transitions between host species to identify sink and source populations for CC398 and employed a novel approach to investigate the gain and loss of antibiotic resistance in CC398 over time. We identified distinct human- and livestock-associated CC398 clades and observed multiple transmissions of CC398 from livestock to humans and between countries, lending quantitative support to previous reports. Of note, we identified a subclade within the livestock-associated clade comprised of isolates from hospital environments and newborn babies, suggesting that livestock-associated CC398 is capable of onward transmission in hospitals. In addition, our analysis revealed significant differences in the dynamics of resistance to methicillin and tetracycline related to contrasting historical patterns of antibiotic usage between the livestock industry and human medicine. We also identified significant differences in patterns of gain and loss of different tetracycline resistance determinants, which we ascribe to epistatic interactions between the resistance genes and/or differences in the modes of inheritance of the resistance determinants. PMID:25239891

  14. Dynamic Spatiotemporal Trends of Dengue Transmission in the Asia-Pacific Region, 1955–2004

    PubMed Central

    Banu, Shahera; Hu, Wenbiao; Guo, Yuming; Naish, Suchithra; Tong, Shilu

    2014-01-01

    Background Dengue fever (DF) is one of the most important emerging arboviral human diseases. Globally, DF incidence has increased by 30-fold over the last fifty years, and the geographic range of the virus and its vectors has expanded. The disease is now endemic in more than 120 countries in tropical and subtropical parts of the world. This study examines the spatiotemporal trends of DF transmission in the Asia-Pacific region over a 50-year period, and identified the disease’s cluster areas. Methodology and Findings The World Health Organization’s DengueNet provided the annual number of DF cases in 16 countries in the Asia-Pacific region for the period 1955 to 2004. This fifty-year dataset was divided into five ten-year periods as the basis for the investigation of DF transmission trends. Space-time cluster analyses were conducted using scan statistics to detect the disease clusters. This study shows an increasing trend in the spatiotemporal distribution of DF in the Asia-Pacific region over the study period. Thailand, Vietnam, Laos, Singapore and Malaysia are identified as the most likely clusters (relative risk = 13.02) of DF transmission in this region in the period studied (1995 to 2004). The study also indicates that, for the most part, DF transmission has expanded southwards in the region. Conclusions This information will lead to the improvement of DF prevention and control strategies in the Asia-Pacific region by prioritizing control efforts and directing them where they are most needed. PMID:24586780

  15. Implications of within-farm transmission for network dynamics: Consequences for the spread of avian influenza

    PubMed Central

    Nickbakhsh, Sema; Matthews, Louise; Dent, Jennifer E.; Innocent, Giles T.; Arnold, Mark E.; Reid, Stuart W.J.; Kao, Rowland R.

    2013-01-01

    The importance of considering coupled interactions across multiple population scales has not previously been studied for highly pathogenic avian influenza (HPAI) in the British commercial poultry industry. By simulating the within-flock transmission of HPAI using a deterministic S-E-I-R model, and by incorporating an additional environmental class representing infectious faeces, we tracked the build-up of infectious faeces within a poultry house over time. A measure of the transmission risk (TR) was computed for each farm by linking the amount of infectious faeces present each day of an outbreak with data describing the daily on-farm visit schedules for a major British catching company. Larger flocks tended to have greater levels of these catching-team visits. However, where density-dependent contact was assumed, faster outbreak detection (according to an assumed mortality threshold) led to a decreased opportunity for catching-team visits to coincide with an outbreak. For this reason, maximum TR-levels were found for mid-range flock sizes (~25,000–35,000 birds). When assessing all factors simultaneously using multivariable linear regression on the simulated outputs, those related to the pattern of catching-team visits had the largest effect on TR, with the most important movement-related factor depending on the mode of transmission. Using social network analysis on a further database to inform a measure of between-farm connectivity, we identified a large fraction of farms (28%) that had both a high TR and a high potential impact at the between farm level. Our results have counter-intuitive implications for between-farm spread that could not be predicted based on flock size alone, and together with further knowledge of the relative importance of transmission risk and impact, could have implications for improved targeting of control measures. PMID:23746799

  16. Dynamics of a Delayed Model for the Transmission of Malicious Objects in Computer Network

    PubMed Central

    Yang, Huizhong

    2014-01-01

    An SEIQRS model for the transmission of malicious objects in computer network with two delays is investigated in this paper. We show that possible combination of the two delays can affect the stability of the model and make the model bifurcate periodic solutions under some certain conditions. For further investigation, properties of the periodic solutions are studied by using the normal form method and center manifold theory. Finally, some numerical simulations are given to justify the theoretical results. PMID:25147837

  17. A generating function approach to HIV transmission with dynamic contact rates.

    PubMed

    Romero-Severson, E O; Meadors, G D; Volz, E M

    2014-03-01

    The basic reproduction number, R0, is often defined as the average number of infections generated by a newly infected individual in a fully susceptible population. The interpretation, meaning, and derivation of R0 are controversial. However, in the context of mean field models, R0 demarcates the epidemic threshold below which the infected population approaches zero in the limit of time. In this manner, R0 has been proposed as a method for understanding the relative impact of public health interventions with respect to disease eliminations from a theoretical perspective. The use of R0 is made more complex by both the strong dependency of R0 on the model form and the stochastic nature of transmission. A common assumption in models of HIV transmission that have closed form expressions for R0 is that a single individual's behavior is constant over time. In this paper we derive expressions for both R0 and probability of an epidemic in a finite population under the assumption that people periodically change their sexual behavior over time. We illustrate the use of generating functions as a general framework to model the effects of potentially complex assumptions on the number of transmissions generated by a newly infected person in a susceptible population. We find that the relationship between the probability of an epidemic and R0 is not straightforward, but, that as the rate of change in sexual behavior increases both R0 and the probability of an epidemic also decrease.

  18. The "Cognitive-Affective Filter" in Teacher Development: Transmission-Based and Interpretation-Based Schemas for Change.

    ERIC Educational Resources Information Center

    Pennington, Martha C.

    1996-01-01

    Describes two orientations to the learning process: "transmission," transfer of information from source to receiver; and "interpretation," development of knowledge through the interaction of receiver with source. Transmission- or interpretation-based values are like a cognitive-affective filter because they form a cognitive and…

  19. Development of a critical-angle transmission grating spectrometer for the International X-Ray Observatory

    NASA Astrophysics Data System (ADS)

    Heilmann, Ralf K.; Ahn, Minseung; Bautz, Marshall W.; Foster, Richard; Huenemoerder, David P.; Marshall, Herman L.; Mukherjee, Pran; Schattenburg, Mark L.; Schulz, Norbert S.; Smith, Matthew

    2009-08-01

    We present a high-resolution soft x-ray grating spectrometer concept for the International X-Ray Observatory (IXO) that meets or exceeds the minimum requirements for effective area (> 1, 000 cm2 for E < 1 keV) and spectral resolution (E/▵E > 3, 000). At the heart of the spectrometer is an array of recently developed highefficiency blazed transmission gratings, the so-called critical-angle transmission (CAT) gratings. They combine the advantages of traditional transmission gratings (very low mass, extremely relaxed alignment and flatness tolerances) with those of x-ray reflection gratings (high efficiency due to blazing in the direction of grazing-incidence reflection). In addition, a CAT grating spectrometer is well-suited for co-existence with energy-dispersive highenergy focal plane detectors, since most high-energy x rays are neither absorbed, nor diffracted, and contribute to the effective area at the telescope focus. Since our initial successful x-ray demonstrations of the CAT grating concept with large-period and lower aspect-ratio prototypes, we have now microfabricated 200 nm-period silicon CAT gratings comprised of grating bars with the required dimensions (6 micron tall, 40 nm wide, aspect ratio 150), optimized for the 0.3 to 1.0 keV energy band. Preliminary analysis of recent x-ray tests show blazing behavior up to 1.28 keV in accordance with predictions.

  20. A class of tricyclic compounds blocking malaria parasite oocyst development and transmission.

    PubMed

    Eastman, Richard T; Pattaradilokrat, Sittiporn; Raj, Dipak K; Dixit, Saurabh; Deng, Bingbing; Miura, Kazutoyo; Yuan, Jing; Tanaka, Takeshi Q; Johnson, Ronald L; Jiang, Hongying; Huang, Ruili; Williamson, Kim C; Lambert, Lynn E; Long, Carole; Austin, Christopher P; Wu, Yimin; Su, Xin-Zhuan

    2013-01-01

    Malaria is a deadly infectious disease in many tropical and subtropical countries. Previous efforts to eradicate malaria have failed, largely due to the emergence of drug-resistant parasites, insecticide-resistant mosquitoes and, in particular, the lack of drugs or vaccines to block parasite transmission. ATP-binding cassette (ABC) transporters are known to play a role in drug transport, metabolism, and resistance in many organisms, including malaria parasites. To investigate whether a Plasmodium falciparum ABC transporter (Pf14_0244 or PfABCG2) modulates parasite susceptibility to chemical compounds or plays a role in drug resistance, we disrupted the gene encoding PfABCG2, screened the recombinant and the wild-type 3D7 parasites against a library containing 2,816 drugs approved for human or animal use, and identified an antihistamine (ketotifen) that became less active against the PfABCG2-disrupted parasite in culture. In addition to some activity against asexual stages and gametocytes, ketotifen was highly potent in blocking oocyst development of P. falciparum and the rodent parasite Plasmodium yoelii in mosquitoes. Tests of structurally related tricyclic compounds identified additional compounds with similar activities in inhibiting transmission. Additionally, ketotifen appeared to have some activity against relapse of Plasmodium cynomolgi infection in rhesus monkeys. Further clinical evaluation of ketotifen and related compounds, including synthetic new derivatives, in blocking malaria transmission may provide new weapons for the current effort of malaria eradication.

  1. Dynamic Transmission Economic Evaluation of Infectious Disease Interventions in Low- and Middle-Income Countries: A Systematic Literature Review.

    PubMed

    Drake, Tom L; Devine, Angela; Yeung, Shunmay; Day, Nicholas P J; White, Lisa J; Lubell, Yoel

    2016-02-01

    Economic evaluation using dynamic transmission models is important for capturing the indirect effects of infectious disease interventions. We examine the use of these methods in low- and middle-income countries, where infectious diseases constitute a major burden. This review is comprised of two parts: (1) a summary of dynamic transmission economic evaluations across all disease areas published between 2011 and mid-2014 and (2) an in-depth review of mosquito-borne disease studies focusing on health economic methods and reporting. Studies were identified through a systematic search of the MEDLINE database and supplemented by reference list screening. Fifty-seven studies were eligible for inclusion in the all-disease review. The most common subject disease was HIV/AIDS, followed by malaria. A diverse range of modelling methods, outcome metrics and sensitivity analyses were used, indicating little standardisation. Seventeen studies were included in the mosquito-borne disease review. With notable exceptions, most studies did not employ economic evaluation methods beyond calculating a cost-effectiveness ratio or net benefit. Many did not adhere to health care economic evaluations reporting guidelines, particularly with respect to full model reporting and uncertainty analysis. We present a summary of the state-of-the-art and offer recommendations for improved implementation and reporting of health economic methods in this crossover discipline. © 2016 The Authors. Health Economics published by John Wiley & Sons Ltd.

  2. Dynamic quality of service model for improving performance of multimedia real-time transmission in industrial networks.

    PubMed

    Gopalakrishnan, Ravichandran C; Karunakaran, Manivannan

    2014-01-01

    Nowadays, quality of service (QoS) is very popular in various research areas like distributed systems, multimedia real-time applications and networking. The requirements of these systems are to satisfy reliability, uptime, security constraints and throughput as well as application specific requirements. The real-time multimedia applications are commonly distributed over the network and meet various time constraints across networks without creating any intervention over control flows. In particular, video compressors make variable bit-rate streams that mismatch the constant-bit-rate channels typically provided by classical real-time protocols, severely reducing the efficiency of network utilization. Thus, it is necessary to enlarge the communication bandwidth to transfer the compressed multimedia streams using Flexible Time Triggered- Enhanced Switched Ethernet (FTT-ESE) protocol. FTT-ESE provides automation to calculate the compression level and change the bandwidth of the stream. This paper focuses on low-latency multimedia transmission over Ethernet with dynamic quality-of-service (QoS) management. This proposed framework deals with a dynamic QoS for multimedia transmission over Ethernet with FTT-ESE protocol. This paper also presents distinct QoS metrics based both on the image quality and network features. Some experiments with recorded and live video streams show the advantages of the proposed framework. To validate the solution we have designed and implemented a simulator based on the Matlab/Simulink, which is a tool to evaluate different network architecture using Simulink blocks.

  3. Dynamic Quality of Service Model for Improving Performance of Multimedia Real-Time Transmission in Industrial Networks

    PubMed Central

    Gopalakrishnan, Ravichandran C.; Karunakaran, Manivannan

    2014-01-01

    Nowadays, quality of service (QoS) is very popular in various research areas like distributed systems, multimedia real-time applications and networking. The requirements of these systems are to satisfy reliability, uptime, security constraints and throughput as well as application specific requirements. The real-time multimedia applications are commonly distributed over the network and meet various time constraints across networks without creating any intervention over control flows. In particular, video compressors make variable bit-rate streams that mismatch the constant-bit-rate channels typically provided by classical real-time protocols, severely reducing the efficiency of network utilization. Thus, it is necessary to enlarge the communication bandwidth to transfer the compressed multimedia streams using Flexible Time Triggered- Enhanced Switched Ethernet (FTT-ESE) protocol. FTT-ESE provides automation to calculate the compression level and change the bandwidth of the stream. This paper focuses on low-latency multimedia transmission over Ethernet with dynamic quality-of-service (QoS) management. This proposed framework deals with a dynamic QoS for multimedia transmission over Ethernet with FTT-ESE protocol. This paper also presents distinct QoS metrics based both on the image quality and network features. Some experiments with recorded and live video streams show the advantages of the proposed framework. To validate the solution we have designed and implemented a simulator based on the Matlab/Simulink, which is a tool to evaluate different network architecture using Simulink blocks. PMID:25170768

  4. The dynamics of elderly support. The transmission of solidarity patterns between generations.

    PubMed

    Attias-Donfut, C

    2001-02-01

    This paper analyses the support given to the handicapped elderly by their children on the basis of a large survey done in France where both the elderly and their middle-aged children were interviewed. These data allow us to address such questions as: "Who helps?", "Who receives help?" and "According to what principles?". Besides the principle of need which is at work, the results show that there is also the principle of equity, which functions through reciprocity. This study highlights two main processes in the dynamics of support for the elderly, its redistributive effects (family support mainly benefits the poorest elderly), and its complementarity with the state health care systems (family support is mainly directed towards those who also receive public help). Can we make the deduction that the more generous the welfare state, the more developed family solidarity is? Nevertheless, some difficulties arise: support is mostly given by women. Furthermore there are a small number of people on whose shoulders it falls to take care of everybody else in the family. One sign of these difficulties is that the carers are more often in less good health than the non-carers of the same age. Comparisons from one generation to the other, including the youngest (the children of the middle generation who were also interviewed) shows that the younger generation will not want to be so completely involved in parental care at the expense of their own private time and life. Most probably family involvement will be maintained in the future, but to a lesser extent.

  5. Pandemic H1N1 virus transmission and shedding dynamics in index case households of a prospective Vietnamese cohort☆

    PubMed Central

    Thai, Pham Quang; Mai, Le Quynh; Welkers, Matthijs R.A.; Hang, Nguyen Le Khanh; Thanh, Le Thi; Dung, Vu Tien Viet; Yen, Nguyen Thi Thu; Duong, Tran Nhu; Hoa, Le Nguyen Minh; Thoang, Dang Dinh; Trang, Hoang Thi Huyen; de Jong, Menno D.; Wertheim, Heiman; Hien, Nguyen Tran; Horby, Peter; Fox, Annette

    2014-01-01

    Summary Objectives Influenza household transmission studies are required to guide prevention strategies but most passively recruit index cases that seek healthcare. We investigated A(H1N1)pdm09 transmission in a household-based cohort during 2009. Methods Health-workers visited 270 households weekly, and collected swabs from influenza-like-illness cases. If A(H1N1)pdm09 was RT-PCR-confirmed, all household members had symptoms assessed and swabs collected daily for 10–15 days. Viral RNA was quantified and sequenced and serology performed on pre-pandemic sera. Results Index cases were detected in 20 households containing 81 people. 98.5% lacked A(H1N1)pdm09 neutralizing antibodies in pre-pandemic sera. Eleven (18.6%, 95% CI 10.7–30.4%) of 59 contacts were infected. Virus genetic diversity within households was negligible and less than between households. Index and secondary cases were distributed between mothers, daughters and sons, and had similar virus-RNA shedding and symptom dynamics. Fathers were rarely infected. Five secondary cases (45%) had no apparent symptoms and three shed virus before symptoms. Secondary infection was associated with index case wet cough (OR 1.56, 95% CI 1.22–1.99). Conclusions In this cohort of A(H1N1)pdm09 susceptible persons, virus sequencing was capable of discriminating household from community transmission. Household transmission involved mothers and children but rarely fathers. Asymptomatic or pre-symptomatic shedding was common. PMID:24491598

  6. Enhanced efficiency of female-to-male HIV transmission in core groups in developing countries: the need to target men.

    PubMed

    O'Farrell, N

    2001-02-01

    The spread of heterosexual HIV in developing countries is heterogeneous. Factors that explain the wide diversity of HIV prevalences in different countries are undetermined. International aid organizations currently appear to be focusing activities mainly on women rather than on men. To identify critical determinants contributing to the high rates of heterosexual HIV transmission in developing countries through a review of studies investigating HIV per-act transmission rates, and to discuss how these factors might be prioritized through HIV-prevention interventions. Studies investigating the per-act HIV transmission rate were identified through a MEDLINE search and a review of the abstracts of the Annual International AIDS Conferences. When the summary mean per-act HIV transmission rates were calculated, the ratio of female-to-male HIV transmission in developing countries compared with that in the developed world was 341, whereas that for male-to-female transmission was 2.9. Enhanced female-to-male HIV transmission in male core groups is a critical determinant of high-prevalence HIV epidemics among heterosexuals in developing countries. In addition to condom promotion, there is a need for an increased emphasis on HIV-prevention activities in men to decrease their susceptibility in developing countries, particularly in the countries most affected by the epidemic.

  7. Modeling the transmission of community-associated methicillin-resistant Staphylococcus aureus: a dynamic agent-based simulation

    PubMed Central

    2014-01-01

    Background Methicillin-resistant Staphylococcus aureus (MRSA) has been a deadly pathogen in healthcare settings since the 1960s, but MRSA epidemiology changed since 1990 with new genetically distinct strain types circulating among previously healthy people outside healthcare settings. Community-associated (CA) MRSA strains primarily cause skin and soft tissue infections, but may also cause li