23,575 research outputs found
Parity-Violating Electron Scattering and Neucleon Structure
The measurement of parity violation in the helicity dependence of
electron-nucleon scattering provides unique information about the basic quark
structure of the nucleons. In this review, the general formalism of
parity-violating electron scattering is presented, with emphasis on elastic
electron-nucleon scattering. The physics issues addressed by such experiments
is discussed, and the major goals of the presently envisioned experimental
program are identified. %General aspects of the experimental technique are
reviewed and A summary of results from a recent series of experiments is
presented and the future prospects of this program are also discussed.Comment: 45 pages, 9 figure
Systems development methods and usability in Norway: An industrial perspective
This is the post-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2007 Springer Berlin HeidelbergThis paper investigates the relationship between traditional systems development methodologies and usability, through a survey of 78 Norwegian IT companies. Building on previous research we proposed two hypotheses; (1) that software companies will generally pay lip service to usability, but do not prioritize it in industrial projects, and (2) that systems development methods and usability are perceived as not being integrated. We find support for both hypotheses. Thus, the use of systems development methods is fairly stable, confirming earlier research. Most companies do not use a formal method, and of those who do, the majority use their own method. Generally, the use of methods is rather pragmatic: Companies that do not use formal methods report that they use elements from such methods. Further, companies that use their own method import elements from standardised methods into their own
Photoinduced melting of superconductivity in the high-Tc superconductor La2-xSrxCuO4 probed by time-resolved optical and THz techniques
Dynamics of depletion and recovery of superconducting state in La2-xSrxCuO_4
thin films is investigated utilizing optical pump-probe and optical pump - THz
probe techniques as a function of temperature and excitation fluence. The
absorbed energy density required to suppress superconductivity is found to be
about 8 times higher than the thermodynamically determined condensation energy
density and nearly temperature independent between 4 and 25 K. These findings
indicate that during the time when superconducting state suppression takes
place (~0.7 ps), a large part (nearly 90%) of the energy is transferred to the
phonons with energy lower than twice the maximum value of of the SC gap and
only 10% is spent on Cooper pair breaking.Comment: 8 pages, 5 figure
Synchrotron Radiation From Radiatively Inefficient Accretion Flow Simulations: Applications to Sgr A*
We calculate synchrotron radiation in three-dimensional pseudo-Newtonian
magnetohydrodynamic simulations of radiatively inefficient accretion flows. We
show that the emission is highly variable at optically thin frequencies, with
order of magnitude variability on time-scales as short as the orbital period
near the last stable orbit; this emission is linearly polarized at the 20-50 %
level due to the coherent toroidal magnetic field in the flow. At optically
thick frequencies, both the variability amplitude and polarization fraction
decrease significantly with decreasing photon frequency. We argue that these
results are broadly consistent with the observed properties of Sgr A* at the
Galactic Center, including the rapid infrared flaring.Comment: Accepted for publication in Ap
11. Premunition in Plasmodium falciparum infection: insights from the epidemiology of multiple infections
Epidemiological studies of multiple clone infections by Plasmodium falciparum in highly endemic areas have demonstrated age dependence in both the multiplicity of infection and the relationships between this multiplicity and the risk of acute illness. We hypothesize that, in infants, host defence against blood-stage infections with P falciparum relies mainly on fever and cytokine activities, and the infections are of short duration. In older children, a high multiplicity of infection is characteristic of low-level chronic parasitaemia. This appears to confer cross-protection against newly inoculated parasites, via partially genotype-specific responses which are short-term, lasting little longer than the infections themselves. This has important implications for our understanding of immunity against P. falciparum, its ecological niche, and the epidemiological impact of interventions against i
2. Genotypes of merozoite surface protein 2 of Plasmodium falciparum in Tanzania
The merozoite surface protein 2 (MSP2) of Plasmodium falciparum is extremely polymorphic: 82 different msp2 alleles were found in 4 studies of molecular epidemiology conducted in Tanzania. This diversity renders msp2 suitable as a marker gene for the genotyping of P. falciparum infections. Amplification of msp2 by the polymerase chain reaction (PCR), and subsequent restriction digests of the PCR product (PCR-restriction fragment length polymorphism genotyping), has proved to be an informative tool for enumerating multiple concurrent infections in a blood sample, and distinguishing individual alleles. Depending on the specific questions asked in a genotyping study, analytical techniques of different degrees of complexity are employed. The restriction fragments resulting from a single HinfI digest generally allow the enumeration of multiple concurrent infections and the determination of their allelic families. When a restriction pattern is too complex to be resolved, owing to the high number of concurrent infections, or due to the appearance of previously undescribed alleles, one or more additional digests (DdeI, RsaI, ScrfI) may be necessary. To determine individual alleles unequivocally, in particular in longitudinal studies, when several consecutive samples need to be compared with each other, a more detailed analysis involving all 3 additional digests is applied. The methodological experience and results gained in 4 epidemiological field studies involving msp2 genotyping are summarized. We also provide the HinfI restriction patterns and some nucleotide sequences of the alleles found so far in our studies in Tanzani
Positron-neutrino correlations in 32Ar and 33Ar Decays: Probes of Scalar weak currents and nuclear isospin mixing
The positron-neutrino correlation in the 0^+ \to 0^+ \beta decay of ^{32}Ar
was measured at ISOLDE by analyzing the effect of lepton recoil on the shape of
the narrow proton group following the superallowed decay. Our result is
consistent with the Standard Model prediction; for vanishing Fierz interference
we find a=0.9989 \pm 0.0052 \pm 0.0036. Our result leads to improved
constraints on scalar weak interactions. The positron-neutrino correlation in
^{33}Ar decay was measured in the same experiment; for vanishing Fierz
interference we find a=0.944 \pm 0.002 \pm 0.003. The ^{32}Ar and ^{33}Ar
correlations, in combination with precision measurements of the half-lives,
superallowed branching ratios and beta endpoint energies, will determine the
isospin impurities of the superallowed transitions. These will provide useful
tests of isospin-violation corrections used in deducing |V_{\rm ud}| which
currently indicates non-unitarity of the KM matrix.Comment: 15 pages, 6 figure
Thermodynamic formalism for the Lorentz gas with open boundaries in dimensions
A Lorentz gas may be defined as a system of fixed dispersing scatterers, with
a single light particle moving among these and making specular collisions on
encounters with the scatterers. For a dilute Lorentz gas with open boundaries
in dimensions we relate the thermodynamic formalism to a random flight
problem. Using this representation we analytically calculate the central
quantity within this formalism, the topological pressure, as a function of
system size and a temperature-like parameter \ba. The topological pressure is
given as the sum of the topological pressure for the closed system and a
diffusion term with a \ba-dependent diffusion coefficient. From the
topological pressure we obtain the Kolmogorov-Sinai entropy on the repeller,
the topological entropy, and the partial information dimension.Comment: 7 pages, 5 figure
The social, cosmopolitanism and beyond
First, this article will outline the metaphysics of âthe socialâ that implicitly and explicitly connects the work of lassical and contemporary cosmopolitan sociologists as different as Durkheim, Weber, Beck and Luhmann. In a second step, I will show that the cosmopolitan outlook of classical sociology is driven by exclusive differences. In understanding human affairs, both classical sociology and contemporary cosmopolitan sociology reflect a very modernist outlook of epistemological, conceptual, methodological and disciplinary rigour that separates the cultural sphere from the natural objects of concern. I will suggest that classical sociology â in order to be cosmopolitan â is forced (1) to exclude non-social and non-human objects as part of its conceptual and methodological rigour, and (2) consequently and methodologically to rule out the non-social and the non-human. Cosmopolitan sociology imagines âthe socialâ as a global, universal explanatory device to conceive and describe the non-social and non-human. In a third and final step the article draws upon the work of the French sociologist Gabriel Tarde and offers a possible alternative to the modernist social and cultural other-logics of social sciences. It argues for a inclusive conception of âthe socialâ that gives the non-social and non-human a cosmopolitan voice as well
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