704 research outputs found
The control of a nuclear reactor using helium- 3 gas control elements
Control system for water moderated reactor using helium-3 ga
Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature
Using the guinea pig as a model host, we show that aerosol spread of influenza virus is dependent upon both ambient relative humidity and temperature. Twenty experiments performed at relative humidities from 20% to 80% and 5 °C, 20 °C, or 30 °C indicated that both cold and dry conditions favor transmission. The relationship between transmission via aerosols and relative humidity at 20 °C is similar to that previously reported for the stability of influenza viruses (except at high relative humidity, 80%), implying that the effects of humidity act largely at the level of the virus particle. For infected guinea pigs housed at 5 °C, the duration of peak shedding was approximately 40 h longer than that of animals housed at 20 °C; this increased shedding likely accounts for the enhanced transmission seen at 5 °C. To investigate the mechanism permitting prolonged viral growth, expression levels in the upper respiratory tract of several innate immune mediators were determined. Innate responses proved to be comparable between animals housed at 5 °C and 20 °C, suggesting that cold temperature (5 °C) does not impair the innate immune response in this system. Although the seasonal epidemiology of influenza is well characterized, the underlying reasons for predominant wintertime spread are not clear. We provide direct, experimental evidence to support the role of weather conditions in the dynamics of influenza and thereby address a long-standing question fundamental to the understanding of influenza epidemiology and evolution
Massive orbital metastasis of hepatocellular carcinoma
Federal University of São Paulo Multidisciplinary Oncology Group/Department of PathologyUNIFESP, Multidisciplinary Oncology Group/Department of PathologySciEL
Non-equilibrium dynamics of stochastic point processes with refractoriness
Stochastic point processes with refractoriness appear frequently in the
quantitative analysis of physical and biological systems, such as the
generation of action potentials by nerve cells, the release and reuptake of
vesicles at a synapse, and the counting of particles by detector devices. Here
we present an extension of renewal theory to describe ensembles of point
processes with time varying input. This is made possible by a representation in
terms of occupation numbers of two states: Active and refractory. The dynamics
of these occupation numbers follows a distributed delay differential equation.
In particular, our theory enables us to uncover the effect of refractoriness on
the time-dependent rate of an ensemble of encoding point processes in response
to modulation of the input. We present exact solutions that demonstrate generic
features, such as stochastic transients and oscillations in the step response
as well as resonances, phase jumps and frequency doubling in the transfer of
periodic signals. We show that a large class of renewal processes can indeed be
regarded as special cases of the model we analyze. Hence our approach
represents a widely applicable framework to define and analyze non-stationary
renewal processes.Comment: 8 pages, 4 figure
Soft particles at liquid interfaces: From molecular particle architecture to collective phase behavior
Soft particles such as microgels and core-shell particles can undergo
significant and anisotropic deformations when adsorbed to a liquid interface.
This, in turn, leads to a complex phase behavior upon compression. Here we
develop a multiscale framework to rationally link the molecular particle
architecture to the resulting interfacial morphology and, ultimately, to the
collective interfacial phase behavior, enabling us to identify the key
single-particle properties underlying two-dimensional continuous,
heterostructural, and isostructural solid-solid transitions. Our approach
resolves existing discrepancies between experiments and simulations and thus
provides a unifying framework to describe phase transitions in interfacial
soft-particle systems. We establish proof-of-principle for our rational
approach by synthesizing three different poly(N-isopropylacrylamide)
soft-particle architectures, each of which corresponds to a different targeted
phase behavior. In parallel, we introduce a versatile and highly efficient
coarse-grained simulation method that adequately captures the qualitative key
features of each soft-particle system; the novel ingredient in our simulation
model is the use of auxiliary degrees of freedom to explicitly account for the
swelling and collapse of the particles as a function of surface pressure.
Notably, these combined efforts allow us to establish the first experimental
demonstration of a heterostructural transition to a chain phase in a
single-component system, as well as the first accurate in silico account of the
two-dimensional isostructural transition. Overall, our multiscale framework
provides a bridge between physicochemical soft-particle characteristics at the
molecular- and nanoscale and the collective self-assembly phenomenology at the
macroscale, paving the way towards novel materials with on-demand interfacial
behavior
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