2,504 research outputs found
Droplet activation of wet particles: development of the Wet CCN approach
Relationships between critical supersaturation required for activation and
particle dry diameter have been the primary means for experimentally
characterizing cloud condensation nuclei (CCN) activity; however, use of the
dry diameter inherently limits the application to cases where the dry
diameter can be used to accurately estimate solute volume. This study
challenges the requirement and proposes a new experimental approach, Wet
CCN, for studying CCN activity without the need for a drying step. The new
approach directly measures the subsaturated portion of the Köhler
curves. The experimental setup consists of a humidity-controlled
differential mobility analyzer and a CCN counter; wet diameter equilibrated
at known relative humidity is used to characterize CCN activity instead of
the dry diameter. The experimental approach was validated against ammonium
sulfate, glucose, and nonspherical ammonium oxalate monohydrate. Further,
the approach was applied to a mixture of nonspherical iodine oxide
particles. The Wet CCN approach successfully determined the hygroscopicity
of nonspherical particles by collapsing them into spherical, deliquesced
droplets. We further show that the Wet CCN approach offers unique insights
into the physical and chemical impacts of the aqueous phase on CCN activity; a
potential application is to investigate the impact of
evaporation/co-condensation of water-soluble semivolatile species on CCN
activity
Probing nuclear skins and halos with elastic electron scattering
I investigate the elastic electron scattering off nuclei far from the
stability line. The effects of the neutron and proton skins and halos on the
differential cross sections are explored. Examples are given for the charge
distribution in Sn isotopes and its relation to the neutron skin. The neutron
halo in Li and the proton halo in B are also investigated.
Particular interest is paid to the inverse scattering problem and its
dependence on the experimental precision. These studies are of particular
interest for the upcoming electron ion colliders at the GSI and RIKEN
facilities.Comment: 27 pages, 9 figures, accepted for publication in J. Phys.
Study of a Threshold Cherenkov Counter Based on Silica Aerogels with Low Refractive Indices
To identify and in the region of GeV/c, a
threshold Cherenkov counter equipped with silica aerogels has been
investigated. Silica aerogels with a low refractive index of 1.013 have been
successfully produced using a new technique. By making use of these aerogels as
radiators, we have constructed a Cherenkov counter and have checked its
properties in a test beam. The obtained results have demonstrated that our
aerogel was transparent enough to make up for loss of the Cherenkov photon
yield due to a low refractive index. Various configurations for the photon
collection system and some types of photomultipliers, such as the fine-mesh
type, for a read out were also tested. From these studies, our design of a
Cherenkov counter dedicated to separation up to a few GeV/c %in the
momentum range of GeV/c with an efficiency greater than \%
was considered.Comment: 21 pages, latex format (article), figures included, to be published
in Nucl. Instrm. Meth.
Recruitment, augmentation and apoptosis of rat osteoclasts in 1,25-(OH)2D3 response to short-term treatment with 1,25-dihydroxyvitamin D3in vivo
Background
Although much is known about the regulation of osteoclast (OC) formation and activity, little is known about OC senescence. In particular, the fate of of OC seen after 1,25-(OH)2D3 administration in vivo is unclear. There is evidence that the normal fate of OC is to undergo apoptosis (programmed cell death). We have investigated the effect of short-term application of high dose 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on OC apoptosis in an experimental rat model.
Methods
OC recruitment, augmentation and apoptosis was visualised and quantitated by staining histochemically for tartrate resistant acid phosphatase (TRAP), double staining for TRAP/ED1 or TRAP/DAPI, in situ DNA fragmentation end labelling and histomorphometric analysis.
Results
Short-term treatment with high-dose 1,25-(OH)2D3 increased the recruitment of OC precursors in the bone marrow resulting in a short-lived increase in OC numbers. This was rapidly followed by an increase in the number of apoptotic OC and their subsequent removal. The response of OC to 1,25-(OH)2D3 treatment was dose and site dependent; higher doses producing stronger, more rapid responses and the response in the tibiae being consistently stronger and more rapid than in the vertebrae.
Conclusions
This study demonstrates that (1) after recruitment, OC are removed from the resorption site by apoptosis (2) the combined use of TRAP and ED1 can be used to identify OC and their precursors in vivo (3) double staining for TRAP and DAPI or in situ DNA fragmentation end labelling can be used to identify apoptotic OC in vivo
Impact of ultrasound guidance in central venous catheterization by inexperienced trainees: a prospective observational study
Decoherence, fluctuations and Wigner function in neutron optics
We analyze the coherence properties of neutron wave packets, after they have
interacted with a phase shifter undergoing different kinds of statistical
fluctuations. We give a quantitative (and operational) definition of
decoherence and compare it to the standard deviation of the distribution of the
phase shifts. We find that in some cases the neutron ensemble is more coherent,
even though it has interacted with a wider (i.e. more disordered) distribution
of shifts. This feature is independent of the particular definition of
decoherence: this is shown by proposing and discussing an alternative
definition, based on the Wigner function, that displays a similar behavior. We
briefly discuss the notion of entropy of the shifts and find that, in general,
it does not correspond to that of decoherence of the neutron.Comment: 18 pages, 7 figure
A stream of cells migrating from the caudal telencephalon reveals a link between the amygdala and neocortex
SAT-based Explicit LTL Reasoning
We present here a new explicit reasoning framework for linear temporal logic
(LTL), which is built on top of propositional satisfiability (SAT) solving. As
a proof-of-concept of this framework, we describe a new LTL satisfiability
tool, Aalta\_v2.0, which is built on top of the MiniSAT SAT solver. We test the
effectiveness of this approach by demonnstrating that Aalta\_v2.0 significantly
outperforms all existing LTL satisfiability solvers. Furthermore, we show that
the framework can be extended from propositional LTL to assertional LTL (where
we allow theory atoms), by replacing MiniSAT with the Z3 SMT solver, and
demonstrating that this can yield an exponential improvement in performance
The s Process: Nuclear Physics, Stellar Models, Observations
Nucleosynthesis in the s process takes place in the He burning layers of low
mass AGB stars and during the He and C burning phases of massive stars. The s
process contributes about half of the element abundances between Cu and Bi in
solar system material. Depending on stellar mass and metallicity the resulting
s-abundance patterns exhibit characteristic features, which provide
comprehensive information for our understanding of the stellar life cycle and
for the chemical evolution of galaxies. The rapidly growing body of detailed
abundance observations, in particular for AGB and post-AGB stars, for objects
in binary systems, and for the very faint metal-poor population represents
exciting challenges and constraints for stellar model calculations. Based on
updated and improved nuclear physics data for the s-process reaction network,
current models are aiming at ab initio solution for the stellar physics related
to convection and mixing processes. Progress in the intimately related areas of
observations, nuclear and atomic physics, and stellar modeling is reviewed and
the corresponding interplay is illustrated by the general abundance patterns of
the elements beyond iron and by the effect of sensitive branching points along
the s-process path. The strong variations of the s-process efficiency with
metallicity bear also interesting consequences for Galactic chemical evolution.Comment: 53 pages, 20 figures, 3 tables; Reviews of Modern Physics, accepte
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