35 research outputs found
The nature of slow dynamics in a minimal model of frustration-limited domains
We present simulation results for the dynamics of a schematic model based on
the frustration-limited domain picture of glass-forming liquids. These results
are compared with approximate theoretical predictions analogous to those
commonly used for supercooled liquid dynamics. Although model relaxation times
increase by several orders of magnitude in a non-Arrhenius manner as a
microphase separation transition is approached, the slow relaxation is in many
ways dissimilar to that of a liquid. In particular, structural relaxation is
nearly exponential in time at each wave vector, indicating that the mode
coupling effects dominating liquid relaxation are comparatively weak within
this model. Relaxation properties of the model are instead well reproduced by
the simplest dynamical extension of a static Hartree approximation. This
approach is qualitatively accurate even for temperatures at which the mode
coupling approximation predicts loss of ergodicity. These results suggest that
the thermodynamically disordered phase of such a minimal model poorly
caricatures the slow dynamics of a liquid near its glass transition
Prediction of huge X-ray Faraday rotation at the Gd N_4,5 threshold
X-ray absorption spectra in a wide energy range around the 4d-4f excitation
threshold of Gd were recorded by total electron yield from in-plane magnetized
Gd metal films. Matching the experimental spectra to tabulated absorption data
reveals unprecedented short light absorption lengths down to 3 nm. The
associated real parts of the refractive index for circularly polarized light
propagating parallel or antiparallel to the Gd magnetization, determined
through the Kramers-Kronig transformation, correspond to a magneto-optical
Faraday rotation of 0.7 degrees per atomic layer. This finding shall allow the
study of magnetic structure and magnetization dynamics of lanthanide elements
in nanosize systems and dilute alloys.Comment: 4 pages, 2 figures, final version resubmitted to Phys. Rev. B, Brief
Reports. Minor change
Co-immunization with DNA vaccines expressing granulocyte–macrophage colony-stimulating factor and mycobacterial secreted proteins enhances T-cell immunity, but not protective efficacy against Mycobacterium tuberculosis
The development of more effective antituberculosis vaccines would assist in the control of the global problem of infection with Mycobacterium tuberculosis. One recent vaccination strategy is immunization with DNA plasmids encoding individual microbial genes. Using the genes for the M. tuberculosis-secreted proteins, MPT64 (23 000 MW) and Ag85B (30 000 MW) as candidate antigens, we previously prepared DNA vaccines and demonstrated their ability to stimulate T-cell responses and confer protection in a mouse model of aerosol tuberculosis (TB). The protective efficacy of the DNA vaccines was less than that promoted by the current vaccine Mycobacterium bovis bacille Calmette–Guèrin (BCG). To improve the immunogenicity and protective efficacy of these mycobacterial vectors, co-immunization of a plasmid expressing granulocyte–macrophage colony-stimulating factor (GM-CSF) was investigated. Intramuscular immunization with DNA expressing MPT64 or Ag85B and GM-CSF enhanced the antigen-specific cellular immune response, with increased proliferative response and production of interferon-γ (IFN-γ). The titre of antimycobacterial protein immunoglobulin G (IgG) antibodies was unchanged. Mice immunized with DNA vaccines showed reduced pulmonary bacterial load following an aerosol challenge of M. tuberculosis, but codelivery of the plasmid expressing GM-CSF did not increase the protective effect. Therefore, despite modifying the cellular immune response to DNA vaccines, GM-CSF does not improve their protective efficacy at the peak of infection after an aerosol challenge with 100 c.f.u. of M. tuberculosis
Heterogeneous diffuse interfaces: A new mechanism for arrested coarsening in binary mixtures
We discuss the dynamics of binary fluid mixtures in which surface tension density is allowed to become locally negative within the interface, while still preserving positivity of the overall surface tension (heterogeneous diffuse interface). Numerical simulations of two-dimensional Ginzburg-Landau phase field equations implementing such mechanism and including hydrodynamic motion, show evidence of dynamically arrested domain coarsening. Under specific conditions on the functional form of the surface tension density, dynamical arrest can be interpreted in terms of the collective dynamics of metastable, non-linear excitations of the density field, named compactons, as they are localized to finite-size regions of configuration space and strictly zero elsewhere. Aside from compactons, the heterogeneous diffuse interface scenario appears to provide a robust mechanism for the interpretation of many aspects of soft-glassy behaviour in binary fluid mixtures
Preferential Migration of CD62L<sup>+</sup> Cells into the Appendix in Mice with Experimental Chronic Colitis
Galileo at Io: Results from High-Resolution Imaging
During late 1999/early 2000, the solid state imaging experiment on the Galileo spacecraft returned more than 100 high-resolution (5 to 500 meters per pixel) images of volcanically active Io. We observed an active lava lake, an active curtain of lava, active lava flows, calderas, mountains, plateaus, and plains. Several of the sulfur dioxide-rich plumes are erupting from distal flows rather than from the source of the silicate lava (caldera or fissure, often with red pyroclastic deposits). Most of the active flows in equatorial regions are being emplaced slowly beneath insulated crust, but rapidly emplaced channelized flows are also found at all latitudes. There is no evidence for high-viscosity lava, but some bright flows may consist of sulfur rather than mafic silicates. The mountains, plateaus, and calderas are strongly influenced by tectonics and gravitational collapse. Sapping channels and scarps suggest that many portions of the upper ~1 kilometer are rich in volatiles
Granulocyte colony-stimulating factor administration modulates the surface expression of effector cell molecules on human monocytes
Short-term and long-term outcome in low body mass index patients undergoing cardiac surgery
A Unilateral Cervical Spinal Cord Contusion Injury Model in Non-Human Primates ( Macaca mulatta
The development of a non-human primate (NHP) model of spinal cord injury (SCI) based on mechanical and computational modeling is described. We scaled up from a rodent model to a larger primate model using a highly controllable, friction-free, electronically-driven actuator to generate unilateral C6-C7 spinal cord injuries. Graded contusion lesions with varying degrees of functional recovery, depending upon pre-set impact parameters, were produced in nine NHPs. Protocols and pre-operative magnetic resonance imaging (MRI) were used to optimize the predictability of outcomes by matching impact protocols to the size of each animal's spinal canal, cord, and cerebrospinal fluid space. Post-operative MRI confirmed lesion placement and provided information on lesion volume and spread for comparison with histological measures. We evaluated the relationships between impact parameters, lesion measures, and behavioral outcomes, and confirmed that these relationships were consistent with our previous studies in the rat. In addition to providing multiple univariate outcome measures, we also developed an integrated outcome metric describing the multivariate cervical SCI syndrome. Impacts at the higher ranges of peak force produced highly lateralized and enduring deficits in multiple measures of forelimb and hand function, while lower energy impacts produced early weakness followed by substantial recovery but enduring deficits in fine digital control (e.g., pincer grasp). This model provides a clinically relevant system in which to evaluate the safety and, potentially, the efficacy of candidate translational therapies