Relativistic models of the universe with pressure equal to zero and time-dependent uniformity

Zero density and approximate, relativistic models of univers

Updated, expanded, fluid properties handbook

Revised handbook presents quantitative data, in the form of graphs and charts, pertaining to thermodynamic properties of specific cryogenic fluids and several metals. References to sources of data are cited

Spin-orbital phase synchronization in the magnetic field-driven electron dynamics in a double quantum dot

We study the dynamics of an electron confined in a one-dimensional double quantum dot in the presence of driving external magnetic fields. The orbital motion of the electron is coupled to the spin dynamics by spin orbit interaction of the Dresselhaus type. We derive an effective time-dependent Hamiltonian model for the orbital motion of the electron and obtain a synchronization condition between the orbital and the spin dynamics. From this model we deduce an analytical expression for the Arnold tongue and propose an experimental scheme for realizing the synchronization of the orbital and spin dynamics.Comment: 6 figures, 14 page

Strain-induced insulator state in La_0.7Sr_0.3CoO_3

We report on the observation of a strain-induced insulator state in ferromagnetic La_0.7Sr_0.3CoO_3 films. Tensile strain above 1% is found to enhance the resistivity by several orders of magnitude. Reversible strain of 0.15% applied using a piezoelectric substrate triggers huge resistance modulations, including a change by a factor of 10 in the paramagnetic regime at 300 K. However, below the ferromagnetic ordering temperature, the magnetization data indicate weak dependence on strain for the spin state of the Co ions. We interpret the changes observed in the transport properties in terms of a strain-induced splitting of the Co e_g levels and reduced double exchange, combined with a percolation-type conduction in an electronic cluster state

Reversible strain effect on the magnetization of LaCoO3 films

The magnetization of ferromagnetic LaCoO3 films grown epitaxially on piezoelectric substrates has been found to systematically decrease with the reduction of tensile strain. The magnetization change induced by the reversible strain variation reveals an increase of the Co magnetic moment with tensile strain. The biaxial strain dependence of the Curie temperature is estimated to be below 4K/% in the as-grown tensile strain state of our films. This is in agreement with results from statically strained films on various substrates

Peripheral Tolerance of CD8 T Lymphocytes

SummaryWhereas high-avidity recognition of peptide-MHC complexes by developing T cells in the thymus results in deletion and promotes self-tolerance, such recognition by mature T cells in the periphery results in activation and clonal expansion. This dichotomy represents the basis of a dilemma that has stumped immunologists for many years, how are self-specific T cells tolerized in the periphery? There appear to be two important criteria used to achieve this goal. The first is that in the absence of inflammatory pathogens, tolerance is promoted when T cells recognize antigen presented by quiescent dendritic cells (DCs) expressing low levels of costimulatory molecules. A second critical factor that defines “self” and drives tolerance through deletion, anergy, or suppression is the persistence of antigen

Molecular Dynamics Simulations of the O-glycosylated 21-residue MUC1 Peptides

The conformational propensities of the 21-residue peptide and its Oglycosylated analogs were studied by molecular dynamics (MD) simulations. This polypeptide motif comprises the tandem repeat of the human mucin (MUC1) protein core that is differently glycosylated in normal and cancer cells. To evaluate the structural effects of O-glycosylation on the polypeptide backbone, conformations of the nonglycosylated peptide and its glycosylated analogs were monitored during the 1 ns MD simulations. Radius gyration for whole peptide and its fragments, as well as root-mean-square-deviation between coordinate sets of the backbone atoms of starting structures and generated structures, were calculated. It was shown that O-glycosylation promotes and stabilizes the extended conformations of the whole peptide and its central PDTRP fragment. O-glycosylation of the specific Thr residues significantly affects the conformational distributions of the flanking Ser residues. It was also shown that Oglycosylation promoted backbone conformations of the immunodominant region PDTRP that were similar to the structural features of the peptides presented by the major histocompatability complex (MHC) to T-cell receptors Keywords: glycoprotein MUC1, glycopeptides, molecular dynamics, conformations

Design Considerations for an Orbital NonPropulsive Vent System

Minimizing of attitude disturbances during critical maneuvers in space is extremely important to the success of present and future aerospace missions. Thus, a means is needed to ensure that definite attitude positions can be maintained during specific phases of a mission and in some cases indefinitely. To fulfill this requirement, excess or residual propellant vapors and waste gases must be removed with minimum impulse unbalances imparted to the vehicle. The obvious method of accomplishing this is to employ a vent system that dissipates the impulse generated by the various effluents in a nonpropulsive manner. Such nonpropulsive vent (NPV) systems have been designed, installed and flown on several S-IV and S-IVB stages of the Saturn Launch Vehicles. This system was the first of its kind to be tested in orbit, and the data from these flights clearly substantiates the design adequacy of the system. Design considerations and the overall approach in resolving the requirements of this system are discussed in detail