12,519 research outputs found
New intensity and visibility aspects of a double loop neutron interferometer
Various phase shifters and absorbers can be put into the arms of a double
loop neutron interferometer. The mean intensity levels of the forward and
diffracted beams behind an empty four plate interferometer of this type have
been calculated. It is shown that the intensities in the forward and diffracted
direction can be made equal using certain absorbers. In this case the
interferometer can be regarded as a 50/50 beam splitter. Furthermore the
visibilities of single and double loop interferometers are compared to each
other by varying the transmission in the first loop using different absorbers.
It can be shown that the visibility becomes exactly 1 using a phase shifter in
the second loop. In this case the phase shifter in the second loop must be
strongly correlated to the transmission coefficient of the absorber in the
first loop. Using such a device homodyne-like measurements of very weak signals
should become possible.Comment: 12 pages, 9 figures, accepted for publication in the Journal of
Optics B - Quantum and Semiclassical Optic
Development of a nucleic acid lateral flow immunoassay for simultaneous detection of Listeria spp. and Listeriamonocytogenes in food
We present a new nucleic acid lateral flow immunoassay (NALFIA) for the assessment of listeria contamination. The detection procedure starts with enrichment of sample in Half Fraser broth (24 h). Following isolation of DNA, a duplex PCR is performed with two labelled primer sets, one generic and directed to a specific sequence of the gene encoding 16S rRNA from Listeria spp. and the other specific and directed to a part of the prfA gene encoding the central virulence gene regulator from the food pathogen Listeria monocytogenes (3.5 h). The PCR solution is directly added to the one-step assay device and the appearance of a grey/black line is indicative of the presence of specific amplicons (max 15 min). In all tests performed, the method correctly identified L. monocytogenes and strains of Listeria spp. PCR material of over 20 food samples was tested by NALFIA. The method proved to be useful for the detection of L. monocytogenes in different kinds of food sample
Comparative survey of dynamic analyses of free-piston Stirling engines
Reported dynamics analyses for evaluating the steady-state response and stability of free-piston Stirling engine (FPSE) systems are compared. Various analytical approaches are discussed to provide guidance on their salient features. Recommendations are made in the recommendations remarks for an approach which captures most of the inherent properties of the engine. Such an approach has the potential for yielding results which will closely match practical FPSE-load systems
SFitter: Reconstructing the MSSM Lagrangian from LHC data
Once supersymmetry is found at the LHC, the question arises what are the
fundamental parameters of the Lagrangian. The answer to this question should
thereby not be biased by assumptions on high-scale models. SFitter is a tool
designed for this task. Taking LHC (and possibly ILC) data as input it scans
the TeV-scale MSSM parameter space using its new weighted Markov chain
technique. Using this scan it determines a list of best-fitting parameter
points. Additionally a log-likelihood map is calculated, which can be reduced
to lower-dimensional Frequentist's profile likelihoods or Bayesian probability
maps.Comment: Submitted for the SUSY07 proceedings, 4 pages, LaTeX, 4 eps figure
Stellar laboratories. V. The Xe VI ultraviolet spectrum and the xenon abundance in the hot DO-type white dwarf RE0503-289
For the spectral analysis of spectra of hot stars with a high resolution and
high signal-to-noise ratio (S/N), advanced non-local thermodynamic equilibrium
(NLTE) model atmospheres are mandatory. These are strongly dependent on the
reliability of the atomic data that are used for their calculation.
Reliable Xe VI oscillator strengths are used to identify Xe lines in the
ultraviolet spectrum of the DO-type white dwarf RE0503-289 and to determine its
photospheric Xe abundance.
We publish newly calculated oscillator strengths that are based on a recently
measured Xe VI laboratory line spectrum. These strengths were used to consider
their radiative and collisional bound-bound transitions in detail in our NLTE
stellar-atmosphere models to analyze Xe VI lines exhibited in high-resolution
and high S/N UV observations of RE0503-289.
We identify three hitherto unknown Xe VI lines in the ultraviolet spectrum of
RE0503-289 and confirm the previously measured photospheric Xe abundance of
this white dwarf (log Xe = -4.2 +/- 0.6).
Reliable measurements and calculations of atomic data are prerequisite for
stellar-atmosphere modeling. Observed Xe VI line profiles in the ultraviolet
spectrum of the white dwarf RE0503-289 were well reproduced with the newly
calculated Xe VI oscillator strengths.Comment: 3 pages, 4 figure
Human capital and entrepreneurial success : a meta-analytical review
The study meta-analytically integrates results from three decades of human capital research in entrepreneurship. Based on 70 independent samples (N = 24,733), we found a significant but small relationship between human capital and success (r(c) = .098). We examined theoretically derived moderators of this relationship referring to conceptualizations of human capital, to context, and to measurement of success. The relationship was higher for outcomes of human capital investments (knowledge/skills) than for human capital investments (education/experience), for human capital with high task-relatedness compared to low task-relatedness, for young businesses compared to old businesses, and for the dependent variable size compared to growth or profitability. Findings are relevant for practitioners (lenders, policy makers, educators) and for future research. Our findings show that future research should pursue moderator approaches to study the effects of human capital on success. Further, human capital is most important if it is task-related and if it consists of outcomes of human capital investments rather than human capital investments; this suggests that research should overcome a static view of human capital and should rather investigate the processes of learning, knowledge acquisition, and the transfer of knowledge to entrepreneurial tasks
Cosmological Conductive/Cooling Fronts as Lyman Alpha Forest Clouds
We propose a simple model for the origin and evolution of \lya clouds based
on cosmological conductive/cooling fronts. In this model the \lya arises in the
interfaces between the IGM and cold clouds that could be tentatively identified
with protogalaxies. Most of the properties of the \lya absorbers are reproduced
with a very restricted number of assumptions. Among these are the correct range
of HI column density, cloud sizes and redshift and HI column density
distributions for the absorbers. Several predictions and implications of the
model are briefly discussed.Comment: 9 pages, plain TeX, 3 figures; ApJ Letters, accepte
First detection of bromine and antimony in hot stars
Bromine (atomic number Z=35) and antimony (Z=51) are extremely difficult to
detect in stars. In very few instances, weak and mostly uncertain
identifications of Br I, Br II, and Sb II in relatively cool, chemically
peculiar stars were successful. Adopted solar abundance values rely on
meteoritic determinations. Here, we announce the first identification of these
species in far-ultraviolet spectra of hot stars (with effective temperatures of
49,500-70,000 K), namely in helium-rich (spectral type DO) white dwarfs. We
identify the Br VI resonance line at 945.96 A. A previous claim of Br detection
based on this line is incorrect because its wavelength position is inaccurate
by about 7 A in atomic databases. Taking advantage of precise laboratory
measurements, we identify this line as well as two other, subordinate Br VI
lines. Antimony is detected by the Sb V resonance doublet at 1104.23/1225.98 A,
as well as two subordinate Sb VI lines. A model-atmosphere analysis reveals
strongly oversolar Br and Sb abundances that are caused by radiative-levitation
dominated atomic diffusion.Comment: Accepted for publication in A&
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