784 research outputs found
The Absorption and Elimination of Some Commonly Used Drugs,with Practical Deductions From a Knowledge of the Same.
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USING EXERGY LOSS PROFILES AND ENTHALPY-TEMPERATURE PROFILES FOR THE EVALUATION OF THERMODYNAMIC EFFICIENCY IN DISTILLATION COLUMNS
In this work the temperature-enthalpy profile and the exergy loss profile are used together
to improve thermodynamic efficiency of distillation columns, by identifying possible
benefits of using side exchangers. The method proposed is to compute the exergy loss
profile and to analyse the distribution of the losses across the column stages. The present
work aims at applying the stage-by-stage exergy analysis to the distillation of non-ideal
mixtures, e.g. methanol/water. For these systems the use of thermodynamic excess
properties is required: Gibbs free energy for phase equilibrium and enthalpy of solution
for energy balance. Initial studies showed that the enthalpy of solution has a small effect
on the overall energy balance of the distillation column, but a significant impact on the
exergy loss profiles. Some profiles even showed a violation of the second law of
thermodynamics, with entropy being destroyed on some stages, clearly indicating that a
wrong approach to exergy calculation was being used.A model for exergy calculations of
non-ideal solutions is presented. The exergy values so computed are then checked by a
consistency test, using the reversible column profile. Finally, the exergy procedures are
used to study a typical methanol/water distillation columns, where the exergy profiles are
used to identify scope for intermediate heat exchange
Realtime Photoacoustic Microscopy of Murine Cardiovascular Dynamics
Non-invasive visualization of cardiovascular dynamics in small animals is challenging due to their rapid heart-rates. We present a realtime photoacoustic imaging system consisting of a 30-MHz ultrasound array transducer, receive electronics, a high-repetition-rate laser, and a multicore-computer, and demonstrate its ability to image optically-absorbing structures of the beating hearts of young athymic nude mice at rates of ~50 frames per second with 100 µm×25 µm spatial resolution. To our knowledge this is the first report of realtime photoacoustic imaging of physiological dynamics
Occupational sitting behaviour and its relationship with back pain – A pilot study
AbstractNowadays, working in an office environment is ubiquitous. At the same time, progressively more people suffer from occupational musculoskeletal disorders. Therefore, the aim of this pilot study was to analyse the influence of back pain on sitting behaviour in the office environment.A textile pressure mat (64-sensor-matrix) placed on the seat pan was used to identify the adopted sitting positions of 20 office workers by means of random forest classification. Additionally, two standardised questionnaires (Korff, BPI) were used to assess short and long-term back pain in order to divide the subjects into two groups (with and without back pain). Independent t-test indicated that subjects who registered back pain within the last 24 h showed a clear trend towards a more static sitting behaviour. Therefore, the developed sensor system has successfully been introduced to characterise and compare sitting behaviour of subjects with and without back pain
The formation of ultra-compact dwarf galaxies and nucleated dwarf galaxies
Ultra compact dwarf galaxies (UCDs) have similar properties as massive
globular clusters or the nuclei of nucleated galaxies. Recent observations
suggesting a high dark matter content and a steep spatial distribution within
groups and clusters provide new clues as to their origins. We perform
high-resolution N-body / smoothed particle hydrodynamics simulations designed
to elucidate two possible formation mechanisms for these systems: the merging
of globular clusters in the centre of a dark matter halo, or the massively
stripped remnant of a nucleated galaxy. Both models produce density profiles as
well as the half light radii that can fit the observational constraints.
However, we show that the first scenario results to UCDs that are underluminous
and contain no dark matter. This is because the sinking process ejects most of
the dark matter particles from the halo centre. Stripped nuclei give a more
promising explanation, especially if the nuclei form via the sinking of gas,
funneled down inner galactic bars, since this process enhances the central dark
matter content. Even when the entire disk is tidally stripped away, the nucleus
stays intact and can remain dark matter dominated even after severe stripping.
Total galaxy disruption beyond the nuclei only occurs on certain orbits and
depends on the amount of dissipation during nuclei formation. By comparing the
total disruption of CDM subhaloes in a cluster potential we demonstrate that
this model also leads to the observed spatial distribution of UCDs which can be
tested in more detail with larger data sets.Comment: 8 pages, 8 figures, final version accepted for publication in MNRA
Halo orbits in cosmological disk galaxies : tracers of information history
We analyze the orbits of stars and dark matter particles in the halo of a disk galaxy formed in a cosmological hydrodynamical simulation. The halo is oblate within the inner ∼20 kpc and triaxial beyond this radius. About 43% of orbits are short axis tubes—the rest belong to orbit families that characterize triaxial potentials (boxes, long-axis tubes and chaotic orbits), but their shapes are close to axisymmetric. We find no evidence that the self-consistent distribution function of the nearly oblate inner halo is comprised primarily of axisymmetric short-axis tube orbits. Orbits of all families and both types of particles are highly eccentric, with mean eccentricity �0.6. We find that randomly selected samples of halo stars show no substructure in “integrals of motion” space. However, individual accretion events can clearly be identified in plots of metallicity versus formation time. Dynamically young tidal debris is found primarily on a single type of orbit. However, stars associated with older satellites become chaotically mixed during the formation process (possibly due to scattering by the central bulge and disk, and baryonic processes), and appear on all four types of orbits. We find that the tidal debris in cosmological hydrodynamical simulations experiences significantly more chaotic evolution than in collisionless simulations, making it much harder to identify individual progenitors using phase space coordinates alone. However, by combining information on stellar ages and chemical abundances with the orbital properties of halo stars in the underlying self-consistent potential, the identification of progenitors is likely to be possible
The Role of Dwarf Galaxies in Building Large Stellar Halos
The hierarchical theory of galaxy formation rests on the idea that smaller
galactic structures merge to form the galaxies that we see today. The past
decade has provided remarkable observational support for this scenario, driven
in part by advances in spectroscopic instrumentation. Multi-object spectroscopy
enabled the discovery of kinematically cold substructures around the Milky Way
and M31 that are likely the debris of disrupting satellites. Improvements in
high-resolution spectroscopy have produced key evidence that the abundance
patterns of the Milky Way halo and its dwarf satellites can be explained by
Galactic chemical evolution models based on hierarchical assembly.
These breakthroughs have depended almost entirely on observations of nearby
stars in the Milky Way and luminous red giant stars in M31 and Local Group
dwarf satellites. In the next decade, extremely large telescopes will allow
observations far down the luminosity function in the known dwarf galaxies, and
they will enable observations of individual stars far out in the Galactic halo.
The chemical abundance census now available for the Milky Way will become
possible for our nearest neighbor, M31. Velocity dispersion measurements now
available in M31 will become possible for systems beyond the Local Group such
as Sculptor and M81 Group galaxies. Detailed studies of a greater number of
individual stars in a greater number of spiral galaxies and their satellites
will test hierarchical assembly in new ways because dynamical and chemical
evolution models predict different outcomes for halos of different masses in
different environments.Comment: Astro2010 Decadal Survey White Paper, 8 page
Antenatal care and skilled delivery service utilisation in Somali pastoral communities of Eastern Ethiopia
To assess maternal health care service utilisation and associated factors in Somali pastoral communities of eastern Ethiopia.; Community-based cross-sectional study complemented by qualitative assessments in Adadle district, Somali region, eastern Ethiopia, among 450 women in six kebeles from August to September 2016. Logistic regression was used to assess factors associated with antenatal care use and skilled delivery care use, controlling for confounders.; About 27% [95%CI 22.8-31.2%] of women used antenatal care, and 22.6% [95%CI 18.7-26.5%] received skilled delivery service. None of the respondents reported post-natal care. About 43% reported that they had no knowledge of antenatal care, and 46% did not perceive delivery at a health facility as important. Pastoral lifestyle, husband's educational status, women's attitude towards health care service and financial support from the husband were significantly associated with antenatal care utilisation. Health professionals' attitudes, perceptions of institutional delivery, antenatal care utilisation and information about exemptions from maternal health care fees were associated with skilled delivery service utilisation.; Improving community awareness of antenatal care, employing female health professionals and culturally adapted guidelines could improve skilled delivery utilisation. In a patriarchal society, involving male partners in all maternal health issues is essential to increase use of maternal health services and to decrease maternal mortality
Constraining Cluster Physics with the Shape of X-ray Clusters: Comparison of Local X-ray Clusters versus LCDM Clusters
Simulations of cluster formation have demonstrated that condensation of
baryons into central galaxies during cluster formation can drive the shape of
the gas distribution in galaxy clusters significantly rounder, even at radii as
large as half of the virial radius. However, such simulations generally predict
stellar fractions within cluster virial radii that are ~2 to 3 times larger
than the stellar masses deduced from observations. In this work we compare
ellipticity profiles of clusters simulated with and without baryonic cooling to
the cluster ellipticity profiles derived from Chandra and ROSAT observations in
an effort to constrain the fraction of gas that cools and condenses into the
central galaxies within clusters. We find that the observed ellipticity
profiles are fairly constant with radius, with an average ellipticity of 0.18
+/- 0.05. The observed ellipticity profiles are in good agreement with the
predictions of non-radiative simulations. On the other hand, the ellipticity
profiles of the clusters in simulations that include radiative cooling, star
formation, and supernova feedback (but no AGN feedback) deviate significantly
from the observed ellipticity profiles at all radii. The simulations with
cooling overpredict (underpredict) ellipticity in the inner (outer) regions of
galaxy clusters. By comparing the simulations with and without cooling, we show
that the cooling of gas via cooling flows in the central regions of simulated
clusters causes the gas distribution to be more oblate in the central regions,
but makes the outer gas distribution more spherical. We find that late-time gas
cooling and star formation are responsible for the significantly oblate gas
distributions in cluster cores, but the gas shapes outside of cluster cores are
set primarily by baryon dissipation at high redshift z > 2.Comment: 10 pages, 6 figures, matching the published version in ApJ. Corrected
missing reference in the arxiv versio
Realtime Photoacoustic Microscopy of Murine Cardiovascular Dynamics
Non-invasive visualization of cardiovascular dynamics in small animals is challenging due to their rapid heart-rates. We present a realtime photoacoustic imaging system consisting of a 30-MHz ultrasound array transducer, receive electronics, a high-repetition-rate laser, and a multicore-computer, and demonstrate its ability to image optically-absorbing structures of the beating hearts of young athymic nude mice at rates of ~50 frames per second with 100 µm×25 µm spatial resolution. To our knowledge this is the first report of realtime photoacoustic imaging of physiological dynamics
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