215 research outputs found
The structure of fluid trifluoromethane and methylfluoride
We present hard X-ray and neutron diffraction measurements on the polar
fluorocarbons HCF3 and H3CF under supercritical conditions and for a range of
molecular densities spanning about a factor of ten. The Levesque-Weiss-Reatto
inversion scheme has been used to deduce the site-site potentials underlying
the measured partial pair distribution functions. The orientational
correlations between adjacent fluorocarbon molecules -- which are characterized
by quite large dipole moments but no tendency to form hydrogen bonds -- are
small compared to a highly polar system like fluid hydrogen chloride. In fact,
the orientational correlations in HCF3 and H3CF are found to be nearly as small
as those of fluid CF4, a fluorocarbon with no dipole moment.Comment: 11 pages, 9 figure
An electrostatically defined serial triple quantum dot charged with few electrons
A serial triple quantum dot (TQD) electrostatically defined in a GaAs/AlGaAs
heterostructure is characterized by using a nearby quantum point contact as
charge detector. Ground state stability diagrams demonstrate control in the
regime of few electrons charging the TQD. An electrostatic model is developed
to determine the ground state charge configurations of the TQD. Numerical
calculations are compared with experimental results. In addition, the tunneling
conductance through all three quantum dots in series is studied. Quantum
cellular automata processes are identified, which are where charge
reconfiguration between two dots occurs in response to the addition of an
electron in the third dot.Comment: 12 pages, 9 figure
Spatial inhomogeneities in ionic liquids, charged proteins and charge stabilized colloids from collective variables theory
Effects of size and charge asymmetry between oppositely charged ions or
particles on spatial inhomogeneities are studied for a large range of charge
and size ratios. We perform a stability analysis of the primitive model (PM) of
ionic systems with respect to periodic ordering using the collective variables
based theory. We extend previous studies [A. Ciach et al., Phys. Rev.E
\textbf{75}, 051505 (2007)] in several ways. First, we employ a non-local
approximation for the reference hard-sphere fluid which leads to the
Percus-Yevick pair direct correlation functions for the uniform case. Second,
we use the Weeks-Chandler-Anderson regularization scheme for the Coulomb
potential inside the hard core. We determine the relevant order parameter
connected with the periodic ordering and analyze the character of the dominant
fluctuations along the -lines. We show that the above-mentioned
modifications produce large quantitative and partly qualitative changes in the
phase diagrams obtained previously. We discuss possible scenarios of the
periodic ordering for the whole range of size- and charge ratios of the two
ionic species, covering electrolytes, ionic liquids, charged globular proteins
or nanoparticles in aqueous solutions and charge-stabilized colloids
Non-liftable Calabi-Yau spaces
We construct many new non-liftable three-dimensional Calabi-Yau spaces in
positive characteristic. The technique relies on lifting a nodal model to a
smooth rigid Calabi-Yau space over some number field as introduced by the first
author and D. van Straten.Comment: 16 pages, 5 tables; v2: minor corrections and addition
Care leavers in early adulthood: How do they fare in Britain, Finland and Germany?
In this paper we examine the longer term outcomes of young people who experienced out of home care (OHC) as children, in Britain, Germany and Finland, countries characterised by different welfare regimes. While there is some evidence on immediate transitions after leaving care (up to age 21), there is less evidence on experiences around age 30, a phase of early adulthood. Drawing on existing longitudinal data for general population samples we focus on outcomes related to education, employment, family, health and receipt of welfare benefits for those who were ever in care and those who were not. We find evidence for continuing disadvantage regarding education and employment for those who were in care as children, but also indications of subjective wellbeing and commitment to family life – possibly a reflection of “normality” and efforts to “fit in” as parents. Surprisingly, despite variations in welfare system and differences in the scope and quality of available data, trends were similar in each of the countries, suggesting that none provide adequately for the needs of care experienced young adults. The findings point towards the need for a revised conceptualisation of the notion of “independence” which has to take into account the manifold and changing relationships between individuals and the state. Instead of a “cliff edge” approach there should be support for a more gradual shift from “dependence” to “independence” enabling those with care experience to develop their full potential. In interpreting the findings, limitations of the available data have to be acknowledged, pointing to the need for generating harmonised and longitudinal data on vulnerable subpopulations to enable effective monitoring of needs and provision
Prelaunch performance evaluation of the cometary experiment MUPUS-TP
This paper discusses test results obtained in both laboratory and terrestrial environment conditions for the “Multipurpose Sensors for Surface and Sub-Surface Science” Thermal Probe (MUPUS-TP), which has been developed for the European Space Agency Rosetta cometary rendezvous mission. The probe is intended to provide in situ long-term observations of the thermal evolution of the comet nucleus and will measure a thermal conductivity profile with time in the top 30 cm of the comet nucleus. The basic operating principles of the probe are briefly described, including typical test results gathered in terrestrial snow and soil. The tests in snow provide verification of the probe as a useful tool for monitoring the metamorphism of snow on the Earth. The tests in soil are intended to demonstrate the probe's suitability as an alternative to other methods of energy measurement currently practiced in soil physics research. The tests of the probe in the natural environment of the Earth provide a demonstration of the behavior of the instrument in the presence of complex energy exchange processes before it is used on the comet
Criticality in confined ionic fluids
A theory of a confined two dimensional electrolyte is presented. The positive
and negative ions, interacting by a potential, are constrained to move on
an interface separating two solvents with dielectric constants and
. It is shown that the Debye-H\"uckel type of theory predicts that
the this 2d Coulomb fluid should undergo a phase separation into a coexisting
liquid (high density) and gas (low density) phases. We argue, however, that the
formation of polymer-like chains of alternating positive and negative ions can
prevent this phase transition from taking place.Comment: RevTex, no figures, in press Phys. Rev.
- …