6,267 research outputs found
The Micro Slit Gas Detector
We describe the first tests with a new proportional gas detector. Its
geometry consists in slits opened in a copper metallized kapton foil with 30
micron anode strips suspended in these openings. In this way the multiplication
process is similar to a standard MSGC. The fundamental difference is the
absence of an insulating substrate around the anode. Also the material budget
is significantly reduced, and the problems related to charging-up or
polarization are removed. Ageing properties of this detector are under study.Comment: 13 pages tex file, 10 figures ep
Absence of a structural transition up to 40 Gpa in MgB2 and the relevance of magnesium non-stoichiometry
We report measurements on MgB2 up to ~40GPa. Increasing pressure yields a
monotonous decrease of the lattice parameters and of the c/a ratio, but no
structural transition down to parameters smaller than those of AlB2. The
transition superconducting temperature also decreases with temperature in a
sample dependent way. The results are explained by an increase of the filling
of the 2D pxy bands with pressure, the Mg stoichiometry determining the
starting position of the Fermi level. Our measurements indicate that these hole
bands are the relevant ones for superconductivity.Comment: submitted March 9th 2001, PRB accepte
Meson mass and confinement force driven by dilaton
Meson spectra given as fluctuations of a D7 brane are studied under the
background driven by the dilaton. This leads to a dual gauge theory with quark
confinement due to the gauge condensate. We find that the effect of the gauge
condensate on the meson spectrum is essential in order to make a realistic
hadron spectrum in the non-supersymmetric case. In the supersymmetric case,
however, only the spectra of the scalars are affected, but they are changed in
an opposite way compared to the non-supersymmetric case.Comment: 11 pages, 2 figure
EVN observations of 6.7-GHz methanol maser polarization in massive star-forming regions II. First statistical results
Magnetic fields have only recently been included in theoretical simulations
of high-mass star formation. The simulations show that magnetic fields play an
important role in the formation and dynamics of molecular outflows. Masers, in
particular 6.7-GHz CH3OH masers, are the best probes of the magnetic field
morphologies around massive young stellar objects on the smallest scales of
10-100 AU. This paper focuses on 4 massive young stellar objects,
IRAS06058+2138-NIRS1, IRAS22272+6358A, S255-IR, and S231, which complement our
previous 2012 sample (the first EVN group). From all these sources, molecular
outflows have been detected in the past. Seven of the European VLBI Network
antennas were used to measure the linear polarization and Zeeman-splitting of
the 6.7-GHz CH3OH masers in the star-forming regions in this second EVN group.
We detected a total of 128 CH3OH masing cloudlets. Fractional linear
polarization (0.8%-11.3%) was detected towards 18% of the CH3OH masers in our
sample. The linear polarization vectors are well ordered in all the massive
young stellar objects. We measured significant Zeeman-splitting in
IRAS06058+2138-NIRS1 (DVz=3.8+/-0.6 m/s) and S255-IR (DVz=3.2+/-0.7 m/s). By
considering the 20 massive young stellar objects towards which the morphology
of magnetic fields was determined by observing 6.7-GHz CH3OH masers in both
hemispheres, we find no evident correlation between the linear distributions of
CH3OH masers and the outflows or the linear polarization vectors. On the other
hand, we present first statistical evidence that the magnetic field (on scales
10-100 AU) is primarily oriented along the large-scale outflow direction.
Moreover, we empirically find that the linear polarization fraction of
unsaturated CH3OH masers is P_l<4.5%.Comment: 13 pages, 8 figures, 7 tables, accepted by Astronomy & Astrophysic
Modelling alcohol-consumption in New Zealand: A Bayesian conditional copula-based regression approach.
Holographic Walking Technicolor and Stability of Techni-Branes
Techni-fermions are added as stacks of D7-anti-D7 techni-branes within the
framework of a holographic technicolor model that has been proposed as a
realization of walking technicolor. The stability of the embedding of these
branes is determined. When a sufficiently low bulk cut-off is provided the
fluctuations remain small. For a longer walking region, as would be required in
any realistic model of electroweak symmetry breaking, a larger bulk cut-off is
needed and in this case the oscillations destabilize.Comment: Latex, 25 pages, 10 figure
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