4,968 research outputs found
Internal-state thermometry by depletion spectroscopy in a cold guided beam of formaldehyde
We present measurements of the internal state distribution of
electrostatically guided formaldehyde. Upon excitation with continuous tunable
ultraviolet laser light the molecules dissociate, leading to a decrease in the
molecular flux. The population of individual guided states is measured by
addressing transitions originating from them. The measured populations of
selected states show good agreement with theoretical calculations for different
temperatures of the molecule source. The purity of the guided beam as deduced
from the entropy of the guided sample using a source temperature of 150K
corresponds to that of a thermal ensemble with a temperature of about 30 K
Sporopollenin, a natural copolymer, is robust under high hydrostatic pressure
Lycopodium sporopollenin, a natural copolymer, shows exceptional stability under high hydrostatic pressures (10 GPa) as determined by in situ high pressure synchrotron source FTIR spectroscopy. This stability is evaluated in terms of the component compounds of the sporopollenin: p-coumaric acid, phloretic acid, ferulic acid, and palmitic and sebacic acids, which represent the additional n-acid and ndiacid components. This high stability is attributed to interactions between these components, rather than the exceptional stability of any one molecular component. We propose a biomimetic solution for the creation of polymer materials that can withstand high pressures for a multitude of uses in aeronautics, vascular autografts, ballistics and light-weight protective materials
Muon Spin Relaxation Studies of Superconductivity in a Crystalline Array of Weakly Coupled Metal Nanoparticles
We report Muon Spin Relaxation studies in weak transverse fields of the
superconductivity in the metal cluster compound,
Ga[N(SiMe)]-LiBr(thf)2toluene. The temperature and field dependence of the muon spin relaxation
rate and Knight shift clearly evidence type II bulk superconductivity below
K, with T,
T, and weak flux pinning. The data
are well described by the s-wave BCS model with weak electron-phonon coupling
in the clean limit. A qualitative explanation for the conduction mechanism in
this novel type of narrow band superconductor is presented.Comment: 4 figures, 5 page
Electrostatic extraction of cold molecules from a cryogenic reservoir
We present a method which delivers a continuous, high-density beam of slow
and internally cold polar molecules. In our source, warm molecules are first
cooled by collisions with a cryogenic helium buffer gas. Cold molecules are
then extracted by means of an electrostatic quadrupole guide. For ND the
source produces fluxes up to molecules/s with
peak densities up to molecules/cm. For
HCO the population of rovibrational states is monitored by depletion
spectroscopy, resulting in single-state populations up to .Comment: 4 pages, 4 figures, changes to the text, updated figures and
reference
Pion propagation in real time field theory at finite temperature
We describe how the thermal counterpart of a vacuum two-point function may be
obtained in the real time formalism in a simple way by using directly the
matrices that different elements acquire in this formalism. Using
this procedure we calculate the analytic (single component) thermal amplitude
for the pion pole term in the ensemble average of two axial-vector currents to
two loops in chiral perturbation theory. The general expressions obtained for
the effective mass and decay constants of the pion are evaluated in the chiral
and the nonrelativistic limits. We also investigate the effect of massive
states on these effective parameters.Comment: 17 pages TeX and 9 eps figure
De bijdrage van toevoeging van cacao aan tabak aan rookverslaving
In this report the effect of these compounds on the addiction to cigarette smoking was assessed, using currently available information in the literature on psychoactive compounds of cocoa. The investigated psychoactive cocoa compounds were theobromine, caffeine, serotonin, histamine, tryptophan, tryptamine, tyramine, phenylethylamine, octopamine and anandamide. The general conclusion is that the level of these compounds in added cocoa in cigarettes is not sufficient to increase the addiction to cigarette smoking.In dit rapport wordt de mogelijke bijdrage van cacao aan rookverslaving beschreven. Cacao wordt aan tabak toegevoegd om de smaak te verbeteren. Daarnaast bevat cacao tal van psychoactieve stoffen die mogelijk bijdragen aan rookverslaving Dit literatuuronderzoek beschrijft de blootstelling, farmacologie, farmacokinetiek, toxicologie, interacties en verslavende eigenschappen van de tien meest bekende stoffen in cacao. De onderzochte stoffen zijn theobromine, caffeine, serotonine, histamine, tryptofaan, tryptamine, tyramine, fenylethylamine, octopamine en anandamide. Deze stoffen komen ook via dranken en voedsel het lichaam binnen of worden door het lichaam zelf aangemaakt. Dit rapport laat zien dat de aan roken gerelateerde blootstelling aan de psychoactieve stoffen uit cacao gering is ten opzichte van de inname via voeding en dranken en/of de lichaamseigen productie van deze stoffen. Een systemisch effect lijkt derhalve onwaarschijnlijk ook al omdat lichaamseigen stoffen snel worden afgebroken. Daarnaast kunnen deze stoffen, omdat ze geinhaleerd worden, een direct effect op de luchtwegen hebben. Daarmee zou de opname van nicotine beinvloed kunnen worden. De nicotine opname zou bijvoorbeeld kunnen toenemen via luchtwegverwijding door theobromine en cafe6ne of kunnen afnemen door luchtwegvernauwing door histamine. Dit rapport laat zien dat de aan roken gerelateerde blootstelling aan deze stoffen waarschijnlijk te gering is voor een direct effect op de luchtwegen. Verder dient te worden opgemerkt dat de hoeveelheid tryptamine, tyramine en fenylethylamine die via cacao wordt toegevoegd verwaarloosbaar is ten opzichte van de hoeveelheid die in tabak zelf aanwezig is. Tot slot is aandacht besteed aan de verbrandingsproducten van cacao. Amine verbindingen als serotonin, tryptofaan, tyramine, tryptamine en fenylethylamine vormen tijdens het roken stoffen die het enzym mono amine oxidase (MAO) remmen. MAO-remmers hebben een anti-depressieve werking en kunnen op die manier bijdragen aan rookverslaving. De conclusie van dit literatuur onderzoek is dat de afzonderlijke psychoactieve stoffen in tabak als gevolg van toevoeging van cacao niet direct bijdragen aan rookverslaving. De verbrandingsproducten van cacao doen dit, via remming van het enzym mono amine oxidase, mogelijk wel. Ook de smaak van cacao wordt geassocieerd met verslaving. De literatuur biedt geen inzicht in het effect op gezondheid en verslaving van het inhaleren van de combinatie van de 10 onderzochte stoffen uit cacao
Real-time propagators at finite temperature and chemical potential
We derive a form of spectral representations for all bosonic and fermionic
propagators in the real-time formulation of field theory at finite temperature
and chemical potential. Besides being simple and symmetrical between the
bosonic and the fermionic types, these representations depend explicitly on
analytic functions only. This last property allows a simple evaluation of loop
integrals in the energy variables over propagators in this form, even in
presence of chemical potentials, which is not possible over their conventional
form
Inactivation of the Saccharomyces cerevisiae SKY1 gene induces a specific modification of the yeast anticancer drug sensitivity profile accompanied by a mutator phenotype
The therapeutic potential of the highly active anticancer agent cisplatin
is severely limited by the occurrence of cellular resistance. A better
understanding of the molecular pathways involved in cisplatin-induced cell
death could potentially indicate ways to overcome cellular
unresponsiveness to the drug and thus lead to better treatment results. We
used the budding yeast Saccharomyces cerevisiae as a model organism to
identify and characterize novel genes involved in cisplatin-induced cell
kill, and found that SKY1 (SR-protein-specific kinase from budding yeast)
is a cisplatin sensitivity gene whose disruption conferred cisplatin
resistance. In cross-resistance studies, we observed resistance of yeast
sky1 Delta cells (i.e., cells from which the SKY1 gene had been disrupted)
to cisplatin, carboplatin (but not oxaliplatin), doxorubicin and
daunorubicin, and hypersensitivity to cadmium chloride and 5-fluorouracil.
Furthermore, these cells did not display reduced platinum accumulation,
DNA platination or doxorubicin accumulation, indicating that the
resistance is unrelated to decreased drug import or increased drug export.
Based on the modification of the anticancer drug sensitivity profile and
our finding that sky1 Delta cells display a mutator phenotype, we propose
that Sky1p might play a significant role in specific repair and/or
tolerance pathways. Disruption of the S. cerevisiae SKY1 gene would thus
result in deregulation of such mechanisms and, consequently, lead to
altered drug sensitivity
Probing the dynamics of quasicrystal growth using synchrotron live imaging
The dynamics of quasicrystal growth remains an unsolved problem in condensed
matter. By means of synchrotron live imaging, facetted growth proceeding by the
tangential motion of ledges at the solid-melt interface is clearly evidenced
all along the solidification of icosahedral AlPdMn quasicrystals. The effect of
interface kinetics is significant so that nucleation and free growth of new
facetted grains occur in the melt when the solidification rate is increased.
The evolution of these grains is explained in details, which reveals the
crucial role of aluminum rejection, both in the poisoning of grain growth and
driving fluid flow
Renminbi Internationalisation: Precedents and Implications
While it is commonly assumed that there are no known precedents against which to benchmark the internationalisation of the Renminbi (RMB), this paper argues that the PRCs own development experience provides a useful perspective on the internationalisation debate. In particular it indicates that lessons can be learnt from both the successes and the shortcomings of efforts to internationalise the RMB in the 1970s. During this period state-owned banks in Hong Kong played a central role in mobilising finance for foreign trade. Access to Hong Kongâs developed financial institutions allowed the PRC to maximise receipts from foreign trade as well as minimise the risks of undue swings in capital flows. The paper shows that although China no longer faces foreign exchange scarcity, economic reforms have not yet resolved vulnerabilities in Chinaâs financial institutions and as such Hong Kongâs role in mitigating the risk of undue capital swings remains
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