37,191 research outputs found
The transient response of global-mean precipitation to increasing carbon dioxide levels
The transient response of global-mean precipitation to an increase in atmospheric carbon dioxide levels of 1% yr(-1) is investigated in 13 fully coupled atmosphere-ocean general circulation models (AOGCMs) and compared to a period of stabilization. During the period of stabilization, when carbon dioxide levels are held constant at twice their unperturbed level and the climate left to warm, precipitation increases at a rate of similar to 2.4% per unit of global-mean surface-air-temperature change in the AOGCMs. However, when carbon dioxide levels are increasing, precipitation increases at a smaller rate of similar to 1.5% per unit of global-mean surface-air-temperature change. This difference can be understood by decomposing the precipitation response into an increase from the response to the global surface-temperature increase (and the climate feedbacks it induces), and a fast atmospheric response to the carbon dioxide radiative forcing that acts to decrease precipitation. According to the multi-model mean, stabilizing atmospheric levels of carbon dioxide would lead to a greater rate of precipitation change per unit of global surface-temperature change
Dynamic and static fracture toughness of Ti-6A1-4v
Room temperature dynamic and static fracture toughness tests were conducted on the alloy Ti-6A1-4V in 1-inch thick section. Several conditions of heat treatment were investigated including one in which the material was severely overaged
Non-collinear long-range magnetic ordering in HgCr2S4
The low-temperature magnetic structure of \HG has been studied by
high-resolution powder neutron diffraction. Long-range incommensurate magnetic
order sets in at T22K with propagation vector
\textbf{k}=(0,0,0.18). On cooling below T, the propagation vector
increases and saturates at the commensurate value \textbf{k}=(0,0,0.25). The
magnetic structure below T consists of ferromagnetic layers in the
\textit{ab}-plane stacked in a spiral arrangement along the \textit{c}-axis.
Symmetry analysis using corepresentations theory reveals a point group symmetry
in the ordered magnetic phase of 422 (D), which is incompatible with
macroscopic ferroelectricity. This finding indicates that the spontaneous
electric polarization observed experimentally cannot be coupled to the magnetic
order parameter
Isotropic and Anisotropic Regimes of the Field-Dependent Spin Dynamics in Sr2IrO4: Raman Scattering Studies
A major focus of experimental interest in Sr2IrO4 has been to clarify how the
magnetic excitations of this strongly spin-orbit coupled system differ from the
predictions of anisotropic 2D spin-1/2 Heisenberg model and to explore the
extent to which strong spin-orbit coupling affects the magnetic properties of
iridates. Here, we present a high-resolution inelastic light (Raman) scattering
study of the low energy magnetic excitation spectrum of Sr2IrO4 and doped
Eu-doped Sr2IrO4 as functions of both temperature and applied magnetic field.
We show that the high-field (H>1.5 T) in-plane spin dynamics of Sr2IrO4 are
isotropic and governed by the interplay between the applied field and the small
in-plane ferromagnetic spin components induced by the Dzyaloshinskii-Moriya
interaction. However, the spin dynamics of Sr2IrO4 at lower fields (H<1.5 T)
exhibit important effects associated with interlayer coupling and in-plane
anisotropy, including a spin-flop transition at Hc in Sr2IrO4 that occurs
either discontinuously or via a continuous rotation of the spins, depending
upon the in-plane orientation of the applied field. These results show that
in-plane anisotropy and interlayer coupling effects play important roles in the
low-field magnetic and dynamical properties of Sr2IrO4.Comment: 8 pages, 4 figures, submitte
An Ensemble Kalman-Particle Predictor-Corrector Filter for Non-Gaussian Data Assimilation
An Ensemble Kalman Filter (EnKF, the predictor) is used make a large change
in the state, followed by a Particle Filer (PF, the corrector) which assigns
importance weights to describe non-Gaussian distribution. The weights are
obtained by nonparametric density estimation. It is demonstrated on several
numerical examples that the new predictor-corrector filter combines the
advantages of the EnKF and the PF and that it is suitable for high dimensional
states which are discretizations of solutions of partial differential
equations.Comment: ICCS 2009, to appear; 9 pages; minor edit
CELL TO CELL INTERACTION IN THE IMMUNE RESPONSE : I. HEMOLYSIN-FORMING CELLS IN NEONATALLY THYMECTOMIZED MICE RECONSTITUTED WITH THYMUS OR THORACIC DUCT LYMPHOCYTES
An injection of viable thymus or thoracic duct lymphocytes was absolutely essential to enable a normal or near-normal 19S liemolysin-forming cell response in the spleens of neonatally thymectomized mice challenged with sheep erythrocytes. Syngeneic thymus lymphocytes were as effective as thoracic duct lymphocytes in this system and allogeneic or semiallogeneic cells could also reconstitute their hosts. No significant elevation of the response was achieved by giving either bone marrow cells, irradiated thymus or thoracic duct cells, thymus extracts or yeast. Spleen cells from reconstituted mice were exposed to anti-H2 sera directed against either the donor of the thymus or thoracic duct cells, or against the neonatally thymectomized host. Only isoantisera directed against the host could significantly reduce the number of hemolysin-forming cells present in the spleen cell suspensions. It is concluded that these antibody-forming cells are derived, not from the inoculated thymus or thoracic duct lymphocytes, but from the host. Thoracic duct cells from donors specifically immunologically tolerant of sheep erythrocytes had a markedly reduced restorative capacity in neonatally thymectomized recipients challenged with sheep erythrocytes. These results have suggested that there are cell types, in thymus or thoracic duct lymph, with capacities to react specifically with antigen and to induce the differentiation, to antibody-forming cells, of hemolysin-forming cell precursors derived from a separate cell line present in the neonatally thymectomized hosts
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