6,360 research outputs found
Jarzynski equation for a simple quantum system: Comparing two definitions of work
The validity of the Jarzynski equation for a very simple, exactly solvable
quantum system is analyzed. The implications of two different definitions of
work proposed in the literature are investigated. The first one derives from
measurements of the system energy at the beginning and at the end of the
process under consideration making the work a classical stochastic variable
with transition probabilities derived from quantum mechanics. In the second
definition an operator of work is introduced and the average in the Jarzynski
equation is a quantum expectation value. For the first definition a general
quantum mechanical version of the Jarzynski equation is known to hold. For the
second one the Jarzynski equation fails to yield the free energy difference at
low temperature.Comment: 5 papes, 1 figure largly rewritten and slightly enlarged versio
Technique for experimental determination of radiation interchange factors in solar wavelengths
Process obtains solar heating data which support analytical design. Process yields quantitative information on local solar exposure of models which are geometrically and reflectively similar to prototypes under study. Models are tested in a shirtsleeve environment
Measurement of the proton light response of various LAB based scintillators and its implication for supernova neutrino detection via neutrino-proton scattering
The proton light output function in electron-equivalent energy of various
scintillators based on linear alkylbenzene (LAB) has been measured in the
energy range from 1 MeV to 17.15 MeV for the first time. The measurement was
performed at the Physikalisch-Technische Bundesanstalt (PTB) using a neutron
beam with continuous energy distribution. The proton light output data is
extracted from proton recoil spectra originating from neutron-proton scattering
in the scintillator. The functional behavior of the proton light output is
described succesfully by Birks' law with a Birks constant kB between (0.0094
+/- 0.0002) cm/MeV and (0.0098 +/- 0.0003) cm/MeV for the different LAB
solutions. The constant C, parameterizing the quadratic term in the generalized
Birks law, is consistent with zero for all investigated scintillators with an
upper limit (95% CL) of about 10^{-7} cm^2/MeV^2. The resulting quenching
factors are especially important for future planned supernova neutrino
detection based on the elastic scattering of neutrinos on protons. The impact
of proton quenching on the supernova event yield from neutrino-proton
scattering is discussed.Comment: 12 pages, 17 figures, 4 tables, updated version for publication in
Eur.Phys.J.
Recombining your way out of trouble: the genetic architecture of hybrid fitness under environmental stress
Hybridization between species is a fundamental evolutionary force that can both promote and delay adaptation. There is a deficit in our understanding of the genetic basis of hybrid fitness, especially in non-domesticated organisms. We also know little about how hybrid fitness changes as a function of environmental stress. Here, we made genetically variable F2 hybrid populations from two divergent Saccharomyces yeast species, exposed populations to ten toxins, and sequenced the most resilient hybrids on low coverage using ddRADseq. We expected to find strong negative epistasis and heterozygote advantage in the hybrid genomes. We investigated three aspects of hybridness: 1) hybridity, 2) interspecific heterozygosity, and 3) epistasis (positive or negative associations between non-homologous chromosomes). Linear mixed effect models revealed strong genotype-by-environment interactions with many chromosomes and chromosomal interactions showing species-biased content depending on the environment. Against our predictions, we found extensive selection against heterozygosity such that homozygous allelic combinations from the same species were strongly overrepresented in an otherwise hybrid genomic background. We also observed multiple cases of positive epistasis between chromosomes from opposite species, confirmed by epistasis- and selection-free simulations, which is surprising given the large divergence of the parental species (~15% genome-wide). Together, these results suggest that stress-resilient hybrid genomes can be assembled from the best features of both parents, without paying high costs of negative epistasis across large evolutionary distances. Our findings illustrate the importance of measuring genetic trait architecture in an environmental context when determining the evolutionary potential of hybrid populations
Comparison of Methods to Determine the Fluence of Monoenergetic Neutrons in the Energy Range from 30 keV to 14.8 MeV
The primary reference instruments for neutron fluence measurements used at
the Physikalisch-Technische Bundesanstalt (PTB) are based on the primary
standard for neutron measurements which is the differential neutron-proton
scattering cross section. Such instruments require considerable effort for
their operation and analysis. Therefore, routine measurements are carried out
using a transfer instrument to facilitate the efficient provision of services
to customers. A series of measurements was conducted to compare the transfer
device to the primary reference instruments and ensure the traceability of
neutron fluence measurements. This resulted in an improved characterization of
the instrument and new analysis procedures
Bulk Observers in Non-Factorizable Geometries
We consider five dimensional non-factorizable geometries where the transverse dimension is bounded and the remaining (parallel) dimensions are not. We study the construction of effective theories at distances much longer than the transverse size. An observer unable to resolve the transverse direction can only measure distances along the parallel dimensions, but the non-factorizable geometry makes the length of a curve along the parallel dimension sensitive to where on the transverse direction the curve lies. We show that long geodesics that differ in their endpoints only by shifts along the transverse direction all have the same length to within the observer's resolution. We argue that this is the correct notion of distance in the effective theory for a bulk observer. This allows us to present a consistent interpretation of what is measured by observers that live either on a brane or in the bulk
Assessing chronic disease management in European health systems. Concepts and approaches
This book comprises two volumes and builds on the findings of the DISMEVAL
project (Developing and validating DISease Management EVALuation methods
for European health care systems), funded under the European Union’s (EU)
Seventh Framework Programme (FP7) (Agreement no. 223277). DISMEVAL
was a three-year European collaborative project conducted between 2009 and
2011. It contributed to developing new research methods and generating
the evidence base to inform decision-making in the field of chronic disease
management evaluation (www.dismeval.eu).
In this book, we report on the findings of the project’s first phase, capturing
the diverse range of contexts in which new approaches to chronic care are being
implemented and evaluating the outcomes of these initiatives using an explicit
comparative approach and a unified assessment framework. In this first volume,
we describe the range of approaches to chronic care adopted in 12 European
countries. By reflecting on the facilitators and barriers to implementation, we
aim to provide policy-makers and practitioners with a portfolio of options to
advance chronic care approaches in a given policy context.
In volume II (available online at http://www.euro.who.int/en/about-us/
partners/observatory/studies), we present detailed overviews of each of the 12
countries reviewed for this work and which informed the overview presented in
the first volume of the book
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