3,568 research outputs found
Analysis of total urinary catecholamines by liquid chromatography: methodology, routine experience and clinical interpretations of results
A simple routine method is described for simultaneous assay of total urinary adrenaline, noradrenaline and dopamine. The catecholamines are pre-purified on a small ion-exchange column, separated by reversed phase ion-pair liquid chromatography, and are quantitated by electrochemical detection. The method was routinely applied to 422 urines. Elevated values were found in four urine specimens obtained from patients with histologically proven phaeochromocytomas. Virtually no interference by endogenous or exogenous compounds was found. Values for urinary catecholamines determined by fluorimetric analysis agreed with those obtained by high pressure liquid chromatography with electrochemical detection. Within-day CVs for the compounds ranged from 5.2-11.9%, between-day CVs from 3.3-6.6%. The normal range (95% confidence level) was 20-230 micrograms/24 h for noradrenaline and 1-35 micrograms/24 h for adrenaline
Impact of dust cooling on direct collapse black hole formation
Observations of quasars at suggest the presence of black holes with
a few times . Numerous models have been proposed to
explain their existence including the direct collapse which provides massive
seeds of . The isothermal direct collapse requires a strong
Lyman-Werner flux to quench formation in massive primordial halos. In
this study, we explore the impact of trace amounts of metals and dust
enrichment. We perform three dimensional cosmological simulations for two halos
of with illuminated
by an intense Lyman Werner flux of . Our results show that
initially the collapse proceeds isothermally with K but dust
cooling becomes effective at densities of and
brings the gas temperature down to a few 100-1000 K for . No gravitationally bound clumps are found in cases by the end of our simulations in contrast to the case with . Large inflow rates of are
observed for similar to a zero-metallicity case
while for the inflow rate starts to decline earlier
due to the dust cooling and fragmentation. For given large inflow rates a
central star of may form for .Comment: Accepted for publication in ApJ, comments are still welcom
A timeline for massive star-forming regions via combined observation of o-HD and ND
Context: In cold and dense gas prior to the formation of young stellar
objects, heavy molecular species (including CO) are accreted onto dust grains.
Under these conditions H and its deuterated isotopologues become more
abundant, enhancing the deuterium fraction of molecules such as NH that
are formed via ion-neutral reactions. Because this process is extremely
temperature sensitive, the abundance of these species is likely linked to the
evolutionary stage of the source.
Aims: We investigate how the abundances of o-HD and ND vary
with evolution in high-mass clumps.
Methods: We observed with APEX the ground-state transitions of o-HD
near 372 GHz, and ND(3-2) near 231 GHz for three massive clumps in
different evolutionary stages. The sources were selected within the
G351.77-0.51 complex to minimise the variation of initial chemical conditions,
and to remove distance effects. We modelled their dust continuum emission to
estimate their physical properties, and also modelled their spectra under the
assumption of local thermodynamic equilibrium to calculate beam-averaged
abundances.
Results: We find an anticorrelation between the abundance of o-HD and
that of ND, with the former decreasing and the latter increasing with
evolution. With the new observations we are also able to provide a qualitative
upper limit to the age of the youngest clump of about 10 yr, comparable to
its current free-fall time.
Conclusions: We can explain the evolution of the two tracers with simple
considerations on the chemical formation paths, depletion of heavy elements,
and evaporation from the grains. We therefore propose that the joint
observation and the relative abundance of o-HD and ND can act
as an efficient tracer of the evolutionary stages of the star-formation
process
Optical polarimetry and photometry of comet 17P/Holmes
Comet 17P/Holmes was observed for linear polarisation using the optical
polarimeter mounted on the 1.2m telescope atop Gurushikhar peak near Mt. Abu
during the period November-December 2007. Observations were conducted through
the IHW narrow band (continuum) filters. During the observing run the phase
angle was near at which the comet showed negative polarisation. On
the basis of the observed polarisation data we find comet 17P/Holmes to be a
typical comet with usual dust characteristics. We note that radial rate of
change of brightness in coma in red band is higher than that in blue band; it
has decreased by a factor of 3.6 and 2.5 respectively in red and blue bands
during the November - December run, indicating relative increase in the
abundance of smaller dust particles out ward. Radial brightness variation seen
near the nucleus on November 6 is indicative of the presence of a blob or
shocked region beyond 10" from the nucleus which has gradually smoothened by
December 13. The brightness distribution is found steeper during November 5-7
as compared to on December 13.Comment: 11pages, 7 figures, accepted for publication in MNRA
Tracking Data Relay Satellite System (TDRSS) VHF propagation study
A study performed to investigate the use of the Bent Ionospheric Model in computing corrections to the range and range rate measurements of the TDRSS satellites is documented. Several orbital configurations between the two satellites are discussed as to their effects on total electron content along the radio path between the satellites. Problem areas in the accurate computation of total electron content and range rate corrections are also discussed. The Bent Ionospheric Model gives the electron density versus height profile as a function of latitude, longitude, height, time, season, and solar flux
The formation of the first galaxies and the transition to low-mass star formation
The formation of the first galaxies at redshifts z ~ 10-15 signaled the
transition from the simple initial state of the universe to one of ever
increasing complexity. We here review recent progress in understanding their
assembly process with numerical simulations, starting with cosmological initial
conditions and modelling the detailed physics of star formation. In this
context we emphasize the importance and influence of selecting appropriate
initial conditions for the star formation process. We revisit the notion of a
critical metallicity resulting in the transition from primordial to present-day
initial mass functions and highlight its dependence on additional cooling
mechanisms and the exact initial conditions. We also review recent work on the
ability of dust cooling to provide the transition to present-day low-mass star
formation. In particular, we highlight the extreme conditions under which this
transition mechanism occurs, with violent fragmentation in dense gas resulting
in tightly packed clusters.Comment: 16 pages, 7 figures, appeared in the conference proceedings for IAU
Symposium 255: Low-Metallicity Star Formation: From the First Stars to Dwarf
Galaxies, a high resolution version (highly recommended) can be found at
http://www.ita.uni-heidelberg.de/~tgreif/files/greif08.pd
Анализ и совершенствование системы адаптации персонала на предприятии
Цель работы анализ и совершенствование системы адаптации персонала на предприятии ООО "Суши-Маркет".
В соответствии с поставленной целью, в задачи работы входит:
1) рассмотрение теоретических основ найма и адаптации персонала;
2) проведение анализа действующей системы найма и адаптации персонала в ООО "Суши-Маркет";
3) внесение руководству рассматриваемой компании предложений по улучшению действующей системы найма и адаптации персонала.The purpose of the work is the analysis and improvement of the personnel adaptation system at the Sushi-Market LLC.
In accordance with the goal, the tasks of the work include:
1) consideration of the theoretical principles of recruitment and adaptation of personnel;
2) analysis of the current system of recruitment and adaptation of personnel in LLC "Sushi-Market";
3) submission to the management of the company in question of proposals for improving the current system of recruitment and adaptation of personnel
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