51 research outputs found
On the Specific Features of Temperature Evolution in Ultracold Plasmas
A theoretical interpretation of the recent experimental studies of
temperature evolution in the course of time in the freely-expanding ultracold
plasma bunches, released from a magneto-optical trap, is discussed. The most
interesting result is finding the asymptotics of the form T_e ~ t^{-(1.2 +/-
0.1)} instead of t^{-2}, which was expected for the rarefied monatomic gas
during inertial expansion. As follows from our consideration, the substantially
decelerated decay of the temperature can be well explained by the specific
features of the equation of state for the ultracold plasmas with strong
Coulomb's coupling, whereas a heat release due to inelastic processes (in
particular, three-body recombination) does not play an appreciable role in the
first approximation. This conclusion is confirmed both by approximate
analytical estimates, based on the model of "virialization" of the
charged-particle energies, and by the results of "ab initio" numerical
simulation. Moreover, the simulation shows that the above-mentioned law of
temperature evolution is approached very quickly--when the virial criterion is
satisfied only within a factor on the order of unity.Comment: LaTeX + 3 eps figures, 16 pages. Plasma Physics Reports, v.37, in
press (2011
Cosmological expansion and local systems: a Lema\^{i}tre-Tolman-Bondi model
We propose a Lema\^{i}tre-Tolman-Bondi system mimicking a two-body system to
address the problem of the cosmological expansion versus local dynamics. This
system is strongly bound but participates in the cosmic expansion and is
exactly comoving with the cosmic substratum
Cytosolic SYT/SS18 Isoforms Are Actin-Associated Proteins that Function in Matrix-Specific Adhesion
SYT (SYnovial sarcoma Translocated gene or SS18) is widely produced as two isoforms, SYT/L and SYT/S, that are thought to function in the nucleus as transcriptional coactivators. Using isoform-specific antibodies, we detected a sizable pool of SYT isoforms in the cytosol where the proteins were organized into filamentous arrays. Actin and actin-associated proteins co-immunoprecipitated with SYT isoforms, which also co-sedimented and co-localized with the actin cytoskeleton in cultured cells and tissues. The association of SYT with actin bundles was extensive yet stopped short of the distal ends at focal adhesions. Disruption of the actin cytoskeleton also led to a breakdown of the filamentous organization of SYT isoforms in the cytosol. RNAi ablation of SYT/L alone or both isoforms markedly impaired formation of stress fibers and focal adhesions but did not affect formation of cortical actin bundles. Furthermore, ablation of SYT led to markedly impaired adhesion and spreading on fibronectin and laminin-111 but not on collagen types I or IV. These findings indicate that cytoplasmic SYT isoforms interact with actin filaments and function in the ability cells to bind and react to specific extracellular matrices
Identification of metabolomic signatures of macrophages and the implications for atherogenesis
Feedback inactivation of D-serine synthesis by NMDA receptor-elicited translocation of serine racemase to the membrane
D-serine is a physiological coagonist of N-methyl D-aspartate receptors (NMDARs) that plays a major role in several NMDAR-dependent events. In this study we investigate mechanisms regulating D-serine production by the enzyme serine racemase (SR). We now report that NMDAR activation promotes translocation of SR to the plasma membrane, which dramatically reduces the enzyme activity. Membrane-bound SR isolated from rat brain is not extracted from the membrane by high detergent and salt concentration, indicating a strong association. Colocalization studies indicate that most membrane-bound SR is located at the plasma membrane and dendrites, with much less SR observed in other types of membrane. NMDAR activation promotes translocation of the cytosolic SR to the membrane, resulting in reduced D-serine synthesis, and this effect is averted by blockade of NMDARs. In primary neuronal cultures, SR translocation to the membrane is blocked by a palmitoylation inhibitor, indicating that membrane binding is mediated by fatty acid acylation of SR. In agreement, we found that SR is acylated in transfected neuroblastoma cells using [3H]palmitate or [3H]octanoic acid as precursors. In contrast to classical S-palmitoylation of cysteines, acylation of SR occurs through the formation of an oxyester bond with serine or threonine residues. In addition, we show that phosphorylation of Thr-227 is also required for steady-state binding of SR to the membrane under basal, nonstimulated condition. We propose that the inhibition of D-serine synthesis caused by translocation of SR to the membrane provides a fail-safe mechanism to prevent NMDAR overactivation in vicinal cells or synapses
Function of ion transporters in maintaining acid-base homeostasis of the mammary gland and the pathophysiological role in breast cancer
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