9,173 research outputs found
Transfer of gaseous oxygen from high-pressure containers and the Joule-Thomson inversion
From the experiments performed in study, it was determined that oxygen transferred at ambient temperature and pressures up to 10,000 psig consistently dropped in temperature. All results therefore indicate that gaseous oxygen transferred at ambient temperature does not exhibit Joule-Thomson inversion below 10,000 psig
What went wrong with: "The Interaction of Neutrons With 7Be: "Lack of Standard Nuclear Physics Solution to the "Primordial 7Li Problem"", by M. Gai [arXiv:1812.09914v1]?
We comment here on results of the project aimed at measuring the 7Be(n,x)
reactions at SARAF, Israel, in 2016, posted by M. Gai in [arXiv:1812.09914v1]
without the knowledge of parts of the collaboration and against the explicit
veto of the collaborators and the administration of the Paul Scherrer Institut,
Switzerland. We address both the experimental shortcomings and the drawbacks in
project conduction. M. Gais preprint is labeled as "on behalf of the SARAF
Israel-US-Switzerland Collaboration", the author list is given as a reference
to another unpublished contribution (cited as [27]) to the NPA8 conference in
June 2017 in Catania). However, M. Gai did never have the right to report on
unpublished proprietary data of the entire collaboration, and he was not
authorized to act "on behalf of the collaboration". The contribution is
declared as "accepted for publication", but in fact was retracted during the
refereeing process. After several careful data evaluations, we have to state
that the results of these measurements are not trustworthy and neither the
given experimental data basis nor the corresponding data analysis can be
improved further. Therefore, we requested to retract the posting immediately
[arXiv:1904.03023]. We have to emphasize that, in our opinion, arXiv is not the
appropriate platform for handling frictions in a collaboration. These problems
should have been solved internally before publishing. Unfortunately, with his
single-handed posting against the explicit disagreement of parts of the
collaboration, M. Gai did not leave another possibility. With the present
article, we expressed all our concerns and objections and we consider herewith
the public discussion of this issue as closed.Comment: arXiv admin note: This version has been removed by arXiv
administrators due to copyright infringemen
Modelling metallic discontinuities with the non-orthogonal finite difference time domain method
Numerical electromagnetic models, such as the finite difference time domain (FDTD) method, have many applications. The authors focus on the non-orthogonal FDTD method, which offers an improved geometric flexibility compared to other standard techniques. Results from numerical electromagnetic analysis methods, such as the FDTD method, are often degraded by an error known as numerical dispersion. For metallic structures this dispersion error is often higher than expected from theoretical considerations. The source of this additional error is due to the reciprocal field interpolation scheme used in the non-orthogonal FDTD algorithm. The error is illustrated by means of a microstrip waveguide and a microstrip antenna. Techniques for reducing this error are evaluated; careful construction of the mesh at the metallic boundary being the most reliable solution
Calculation of the Regularized Vacuum Energy in Cavity Field Theories
A novel technique based on Schwinger's proper time method is applied to the
Casimir problem of the M.I.T. bag model. Calculations of the regularized vacuum
energies of massless scalar and Dirac spinor fields confined to a static and
spherical cavity are presented in a consistent manner. While our results agree
partly with previous calculations based on asymptotic methods, the main
advantage of our technique is that the numerical errors are under control.
Interpreting the bag constant as a vacuum expectation value, we investigate
potential cancellations of boundary divergences between the canonical energy
and its bag constant counterpart in the fermionic case. It is found that such
cancellations do not occur.Comment: 14 pages, 4 figures, accepted for publication in Eur.Phys.J.
Rigorous solution of a Hubbard model extended by nearest-neighbor Coulomb and isotropic exchange interaction on a triangle and tetrahedron
In the preprint cond-mat/0701060 we detected a factor two error in the coding
of the Heisenberg term of the Hamiltonian. In the result the exchange term used
in the paper was that of an anisotropic Heisenberg model with and
. Thus all results given for which J=0 was chosen, remain unchanged,
whereas all results containing the exchange parameter remain true for the
extended Hubbard model with anisotropic exchange. That model is of some
interest by itself, due to the relation to the XXZ model. The differing results
for isotropic exchange are given here.Comment: Please print pages 1-8 (article and figures) only, if you do not
intend to use the analytical given eigensystem (110 pages
Vacuum structure of a modified MIT Bag
An alternative to introducing and subsequently renormalizing classical
parameters in the expression for the vacuum energy of the MIT bag for quarks is
proposed in the massless case by appealing to the QCD trace anomaly and scale
separation due to asymptotic freedom. The explicit inclusion of gluons implies
an unrealistically low separation scale.Comment: 5 pages, 2 figure
Interference microscopy delineates cellular proliferations on flat mounted internal limiting membrane specimens.
Aim: To demonstrate that interference microscopy of flat
mounted internal limiting membrane specimens clearly
delineates cellular proliferations at the vitreomacular
interface.
Methods: ILM specimens harvested during vitrectomy
were fixed in glutaraldehyde 0.05% and paraformaldehyde
2% for 24 h (pH 7.4). In addition to interference
microscopy, immunocytochemistry using antibodies
against glial fibrillar acidic protein (GFAP) and neurofilament
(NF) was performed. After washing in phosphatebuffered
saline 0.1 M, the specimens were flat-mounted
on glass slides without sectioning, embedding or any
other technique of conventional light microscopy. A cover
slide and 49,6-diamidino-2-phenylindole (DAPI) medium
were added to stain the cell nuclei.
Results: Interference microscopy clearly delineates
cellular proliferations at the ILM. DAPI stained the cell
nuclei. Areas of cellular proliferation can be easily
distinguished from ILM areas without cells.
Immunocytochemistry can be performed without changing
the protocols used in conventional microscopy.
Conclusion: Interference microscopy of flat mounted ILM
specimens gives new insights into the distribution of
cellular proliferations at the vitreomacular interface and
allows for determination of the cell density at the ILM.
Given that the entire ILM peeled is seen en face, the
techniques described offer a more reliable method to
investigate the vitreoretinal interface in terms of cellular
distribution compared with conventional microscopy
Temperature and light requirements for growth of two diatom species (Bacillariophyceae) isolated from an Arctic macroalga
In the present study, two abundant epiphyticdiatom taxa were isolated from the assimilation hairs ofthe brown macroalga Chordaria flagelliformis collected inthe Arctic Kongsfjorden (Spitsbergen, Norway), establishedas unialgal cultures and their growth rates determinedunder controlled photon fluence rate andtemperature conditions. Using morphological (light andscanning electron microscopy) and SSU rRNA gene databoth isolates (ROS D99 and ROS D125) were identifiedas members of a FragilariaSynedropsis clade. Themolecular data of ROS D99 and ROS D125 were notidentical to any other published sequence. While ROSD99 has been identified as Fragilaria barbararum mainlydue to the SEM characteristics, ROS D125 could not bedefinitely identified although morphological data speakfor Fragilaria striatula. Both diatom species showedsimilar growth rates at all temperatures and photon fluencerates tested. They grew well between 0 and 15Cwithoptimum temperatures of 1214C, but did not survive20C. Therefore, compared to Antarctic diatoms bothtaxa from Kongsfjorden can be characterised as eurythermalorganisms. Increasing photon fluence rates between2 and 15 lmol m2 s1 were accompanied with analmost twofold increase in growth rates, but photon fluencerates >15 lmol m2 s1 did not further enhancegrowth pointing to low light requirements. From thesedata optimum, minimum and maximum photon fluencerates and temperatures for growth can be assessed indicatingthat both diatoms are well acclimated to the fluctuatingenvironmental conditions in the Arctic habitat
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