1,777 research outputs found
Tuning of competing magnetic and superconducting phase volumes in LaFeAsO$_0.945F_0.055 by hydrostatic pressure
The interplay between magnetism and superconductivity in LaFeAsO_0.945F_0.055
was studied as a function of hydrostatic pressure up to p~2.4GPa by means of
muon-spin rotation (\muSR) and magnetization measurements. The application of
pressure leads to a substantial decrease of the magnetic ordering temperature
T_N and a reduction of the magnetic phase volume and, at the same time, to a
strong increase of the superconducting transition temperature T_c and the
diamagnetic susceptibility. From the volume sensitive \muSR measurements it can
be concluded that the superconducting and the magnetic areas which coexist in
the same sample are inclined towards spatial separation and compete for phase
volume as a function of pressure.Comment: 4 pages, 4 figure
QED peripheral mechanism of pair production at colliders
Cross section of the processes of neutral pion production as well as pairs of
charged fermions and bosons in peripherical interaction of leptons, photons are
calculated in main logarithmical approximation. We investigate the phase
volumes and differential cross sections. The differential cross section of few
neutral pions and a few pairs production are written down explicitly.
Considering the academic problem of summation on the number of pairs for the
case of massless particles we reproduce the known results obtained in seventies
of last century. The possibility to construct the generator for Monte-Carlo
modeling of this processes basing of this results are discussed.Comment: 25 pages, 5 figure
HILIC characterization: estimation of phase volumes and composition for a zwitterionic column
A methodology for the estimation of the different phase volumes in HILIC is presented. For a ZIC-HILIC column the mobile phase volume (hold-up volume) is determined in several acetonitrile- and methanol-water compositions by a Linear Free Energy Relationships (LFER) homologous series approach involving n-alkyl-benzenes, -phenones, and -ketones. We demonstrate that the column works as a HILIC column when the mobile phase contains high and medium proportions of methanol or acetonitrile. However, for acetonitrile contents below 20%, or 40% for methanol, same column works in RPLC. In between, a mixed HILIC-RPLC behavior is observed, and solutes of low molecular volume are retained as in HILIC mode, but the largest ones show RPLC retention. From the homologous series retention data and pycnometric measurements involving the pure organic solvents and their mixtures with water, the mean solvent composition of the water-rich transition layers between column functionalization and the bulk mobile phase, which act as stationary phase, is estimated. Finally, the phase ratio between stationary and mobile phases is also estimated for each eluent composition, allowing the calculation of the corresponding stationary phase volumes. All volumes are strongly dependent on the water content in the eluent, especially when acetonitrile is selected as mobile phase constituent. In HILIC mode, when the water content in the hydroorganic mobile phase increases, the volumes of mobile phase decrease, but the volumes of stationary phase (mainly the water layer adsorbed onto the bonded-phase and the water-enriched interface) increase. However, at high water concentrations, where the column works in RPLC mode, the mobile phase volume increases and the stationary phase (which is now the bonded zwitterion) volume decreases when increasing the water percentage in the mobile phase
Phase Volume Changes in Multicomponent Extraction Systems Containing Diisopropyl Ether
There are appreciable changes in the phase volumes and the
influence of composition and temperature on these changes is very
pronounced. Benzene was used as the inert diluent and pentyl
alcohol was the active component of the mixed solvent. In all the
above mentioned systems, except systems A and B, the third phase
(heavy organic phase) was observed at room temperature. The addition
of alcohols to some systems suppresses the formation of the
third phase
The limit behavior of the evolution of Tsallis entropy in self-gravitating systems
In this letter, we study the limit behavior of the evolution of Tsallis
entropy in self-gravitating systems. The study is carried out under two
different situations, drawing the same conclusion. No matter in the energy
transfer process or in the mass transfer process inside the system, when
nonextensive parameter q is more than unity, the total entropy is bounded; on
the contrary, when this parameter is less than unity, the total entropy is
unbounded. There are proofs in both theory and observation that the q is always
more than unity. So the Tsallis entropy in self-gravitating system generally
exhibits a bounded property. This indicates the existence of global maximum of
Tsallis entropy. It is possible for self-gravitating systems to evolve to
thermodynamically stable states
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