5,410 research outputs found
Derivation of Generalized Thomas-Bargmann-Michel-Telegdi Equation for a Particle with Electric Dipole Moment
General classical equation of spin motion is explicitly derived for a
particle with magnetic and electric dipole moments in electromagnetic fields.
Equation describing the spin motion relatively the momentum direction in
storage rings is also obtained.Comment: 7 page
Glass Dynamics at High Strain Rates
We present a shear-transformation-zone (STZ) theoretical analysis of
molecular-dynamics simulations of a rapidly sheared metallic glass. These
simulations are especially revealing because, although they are limited to high
strain rates, they span temperatures ranging from well below to well above the
glass transition. With one important discrepancy, the STZ theory reproduces the
simulation data, including the way in which those data can be made to collapse
onto simple curves by a scaling transformation. The STZ analysis implies that
the system's behavior at high strain rates is controlled primarily by
effective-temperature thermodynamics, as opposed to system-specific details of
the molecular interactions. The discrepancy between theory and simulations
occurs at the lower strain rates for temperatures near the glass transition. We
argue that this discrepancy can be resolved by the same multi-species
generalization of STZ theory that has been proposed recently for understanding
frequency-dependent viscoelastic responses, Stokes-Einstein violations, and
stretched-exponential relaxation in equilibrated glassy materials.Comment: 9 pages, 6 figure
PD-1 signaling promotes control of chronic viral infection by restricting type-I-interferon-mediated tissue damage
Immune responses are essential for pathogen elimination but also cause tissue damage, leading to disease or death. However, it is unclear how the host immune system balances control of infection and protection from the collateral tissue damage. Here, we show that PD-1-mediated restriction of immune responses is essential for durable control of chronic LCMV infection in mice. In contrast to responses in the chronic phase, PD-1 blockade in the subacute phase of infection paradoxically results in viral persistence. This effect is associated with damage to lymphoid architecture and subsequently decreases adaptive immune responses. Moreover, this tissue damage is type I interferon dependent, as sequential blockade of the interferon receptor and PD-1 pathways prevents immunopathology and enhances control of infection. We conclude that PD-1-mediated suppression is required as an immunoregulatory mechanism for sustained responses to chronic viral infection by antagonizing type-I interferon-dependent immunopathology
Path-integral virial estimator for reaction rate calculation based on the quantum instanton approximation
The quantum instanton approximation is a type of quantum transition state
theory that calculates the chemical reaction rate using the reactive flux
correlation function and its low order derivatives at time zero. Here we
present several path-integral estimators for the latter quantities, which
characterize the initial decay profile of the flux correlation function. As
with the internal energy or heat capacity calculation, different estimators
yield different variances (and therefore different convergence properties) in a
Monte Carlo calculation. Here we obtain a virial-type estimator by using a
coordinate scaling procedure rather than integration by parts, which allows
more computational benefits. We also consider two different methods for
treating the flux operator, i.e., local-path and global-path approaches, in
which the latter achieves a smaller variance at the cost of using second-order
potential derivatives. Numerical tests are performed for a one-dimensional
Eckart barrier and a model proton transfer reaction in a polar solvent, which
illustrates the reduced variance of the virial estimator over the corresponding
thermodynamic estimator.Comment: 23 pages, 5 figures, 1 tabl
Commuting difference operators arising from the elliptic C_2^{(1)}-face model
We study a pair of commuting difference operators arising from the elliptic
C_2^{(1)}-face model. The operators, whose coefficients are expressed in terms
of the Jacobi's elliptic theta function, act on the space of meromorphic
functions on the weight space of the C_2 type simple Lie algebra. We show that
the space of functions spanned by the level one characters of the affine Lie
algebra sp(4,C) is invariant under the action of the difference operators.Comment: latex2e file, 19 pages, no figures; added reference
Locally embedded presages of global network bursts
Spontaneous, synchronous bursting of neural population is a widely observed
phenomenon in nervous networks, which is considered important for functions and
dysfunctions of the brain. However, how the global synchrony across a large
number of neurons emerges from an initially non-bursting network state is not
fully understood. In this study, we develop a new state-space reconstruction
method combined with high-resolution recordings of cultured neurons. This
method extracts deterministic signatures of upcoming global bursts in "local"
dynamics of individual neurons during non-bursting periods. We find that local
information within a single-cell time series can compare with or even
outperform the global mean field activity for predicting future global bursts.
Moreover, the inter-cell variability in the burst predictability is found to
reflect the network structure realized in the non-bursting periods. These
findings demonstrate the deterministic mechanisms underlying the locally
concentrated early-warnings of the global state transition in self-organized
networks
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