9,007 research outputs found
Continuous-flow electrophoresis: Membrane-associated deviations of buffer pH and conductivity
The deviations in buffer pH and conductivity which occur near the electrode membranes in continuous-flow electrophoresis were studied in the Beckman charged particle electrophoresis system and the Hanning FF-5 preparative electrophoresis instrument. The nature of the membranes separating the electrode compartments from the electrophoresis chamber, the electric field strength, and the flow rate of electrophoresis buffer were all found to influence the formation of the pH and conductivity gradients. Variations in electrode buffer flow rate and the time of electrophoresis were less important. The results obtained supported the hypothesis that a combination of Donnan membrane effects and the differing ionic mobilities in the electrophoresis buffer was responsible for the formation of the gradients. The significance of the results for the design and stable operation of continuous-flow electrophoresis apparatus was discussed
Many-body system with a four-parameter family of point interactions in one dimension
We consider a four-parameter family of point interactions in one dimension.
This family is a generalization of the usual -function potential. We
examine a system consisting of many particles of equal masses that are
interacting pairwise through such a generalized point interaction. We follow
McGuire who obtained exact solutions for the system when the interaction is the
-function potential. We find exact bound states with the four-parameter
family. For the scattering problem, however, we have not been so successful.
This is because, as we point out, the condition of no diffraction that is
crucial in McGuire's method is not satisfied except when the four-parameter
family is essentially reduced to the -function potential.Comment: 8 pages, 4 figure
Anisotropic thermal expansion of Fe1.06Te and FeTe0.5Se0.5 single crystals
Heat capacity and anisotropic thermal expansion was measured for Fe1.06Te and
FeTe0.5Se0.5 single crystals. Previously reported phase transitions are clearly
seen in both measurements. In both cases the thermal expansion is anisotropic.
The uniaxial pressure derivatives of the superconducting transition temperature
in FeTe0.5Se0.5 inferred from the Ehrenfest relation have opposite signs for
in-plane and c-axis pressures. Whereas the Gruneisen parameters for both
materials are similar and only weakly temperature-dependent above ~ 80 K, at
low temperatures (in the magnetically ordered phase) the magnetic contribution
to the Gruneisen parameter in Fe1.06Te is significantly larger than electron
and phonon contributions combined
Lunar particle shadows and boundary layer experiment: Plasma and energetic particles on the Apollo 15 and 16 subsatellites
The lunar particle shadows and boundary layer experiments aboard the Apollo 15 and 16 subsatellites and scientific reduction and analysis of the data to date are discussed with emphasis on four major topics: solar particles; interplanetry particle phenomena; lunar interactions; and topology and dynamics of the magnetosphere at lunar orbit. The studies of solar and interplanetary particles concentrated on the low energy region which was essentially unexplored, and the studies of lunar interaction pointed up the transition from single particle to plasma characteristics. The analysis concentrated on the electron angular distributions as highly sensitive indicators of localized magnetization of the lunar surface. Magnetosphere experiments provided the first electric field measurements in the distant magnetotail, as well as comprehensive low energy particle measurements at lunar distance
Permafrost - physical aspects and carbon cycling, databases and uncertainties
Permafrost is defined as ground that remains below 0°C for at least 2 consecutive years. About 24% of the northern hemisphere land area is underlain by permafrost. The thawing of permafrost has the potential to influence the climate system through the release of carbon (C) from northern high latitude terrestrial ecosystems, but there is substantial uncertainty about the sensitivity of the C cycle to thawing permafrost. Soil C can be mobilized from permafrost in response to changes in air temperature, directional changes in water balance, fire, thermokarst, and flooding. Observation networks need to be implemented to understand responses of
permafrost and C at a range of temporal and spatial scales. The understanding gained from these observation networks needs to be integrated into modeling frameworks capable of representing how the responses of permafrost C will influence the trajectory of climate in the future
VLA Survey of Dense Gas in Extended Green Objects: Prevalence of 25 GHz Methanol Masers
We present resolution Very Large Array (VLA) observations of four
CHOH - 25~GHz transitions (=3, 5, 8, 10) along with 1.3~cm
continuum toward 20 regions of active massive star formation containing
Extended Green Objects (EGOs), 14 of which we have previously studied with the
VLA in the Class~I 44~GHz and Class~II 6.7~GHz maser lines (Cyganowski et al.
2009). Sixteen regions are detected in at least one 25~GHz line (=5), with
13 of 16 exhibiting maser emission. In total, we report 34 new sites of
CHOH maser emission and ten new sites of thermal CHOH emission,
significantly increasing the number of 25~GHz Class I CHOH masers observed
at high angular resolution. We identify probable or likely maser counterparts
at 44~GHz for all 15 of the 25~GHz masers for which we have complementary data,
providing further evidence that these masers trace similar physical conditions
despite uncorrelated flux densities. The sites of thermal and maser emission of
CHOH are both predominantly associated with the 4.5 m emission from
the EGO, and the presence of thermal CHOH emission is accompanied by 1.3~cm
continuum emission in 9 out of 10 cases. Of the 19 regions that exhibit 1.3~cm
continuum emission, it is associated with the EGO in 16 cases (out of a total
of 20 sites), 13 of which are new detections at 1.3~cm. Twelve of the 1.3~cm
continuum sources are associated with 6.7~GHz maser emission and likely trace
deeply-embedded massive protostars
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