827 research outputs found
Antinuclear Antibodies (ANA) in Gordon Setters with Symmetrical Lupoid Onychodystrophy and Black Hair Follicular Dysplasia
Antinuclear antibodies (ANA) were demonstrated in 3 out of 10 Gordon setters with symmetrical lupoid onychodystrophy and in 5 out of 13 Gordon setters with black hair follicular dysplasia. Two dogs showed both symmetrical lupoid onychodystrophy and black hair follicular dysplasia, and one of these was ANA positive. The results suggest that symmetrical lupoid onychodystrophy and black hair follicular dysplasia in the Gordon setter might be autoimmune diseases that are pathogenetically related, which might indicate a common genetic predisposition
Surface Properties of the Half- and Full-Heusler Alloys
Using a full-potential \textit{ab-initio} technique I study the electronic
and magnetic properties of the (001) surfaces of the half-Heusler alloys,
NiMnSb, CoMnSb and PtMnSb and of the full-Heusler alloys CoMnGe, CoMnSi
and CoCrAl. The MnSb terminated surfaces of the half-Heusler compounds
present properties similar to the bulk compounds and, although the
half-metallicity is lost, an important spin-polarisation at the Fermi level. In
contrast to this the Ni terminated surface shows an almost zero net
spin-polarisation. While the bulk CoMnGe and CoMnSi are almost
half-ferromagnetic, their surfaces lose the half-metallic character and the net
spin-polarisation at the Fermi level is close to zero. Contrary to these
compounds the CrAl terminated (001) surface of CoCrAl shows a spin
polarisation of about 84%.Comment: 14 pages, 6 figure
Half-Metallic Ferrimagnetism in Mn_2VAl
We show that Mn_2VAl is a compound for which the generalized gradient
approximation (GGA) to the exchange-correlation functional in density
functional theory makes a qualitative change in predicted behavior compared to
the usual local density approximation (LDA). Application of GGA leads to
prediction of Mn_2VAl being a half-metallic ferrimagnet, with the minority
channel being the conducting one. The electronic and magnetic structure is
analyzed and contrasted with the isostructural enhanced semimetal Fe_2VAl.Comment: 5 pages, Latex, 6 postscript figures. Description and figures of the
(minority) Fermi surfaces have been adde
New High- Half-Heusler Ferromagnets NiMnZ (Z = Si, P, Ge, As)
Based on the first principle calculation, we propose a new class of
high- half-heusler ferromagnets NiMnZ (Z = Si, P, Ge, As). The structural
and magnetic properties are investigated through the calculation of the
electronic structure, phase stability, equilibrium lattice constant, magnetic
exchange interaction and Curie temperature . It is found that all
alloys show half-metallicity and ferromagnetism at temperatures much higher
than room temperature in a wide range of lattice expansion (compression). At
the equilibrium lattice constant, of 715K, 840K, 875K and 1050K are
predicted by Monte Carlo simulation for NiMnP, NiMnAs, NiMnGe and NiMnSi,
respectively. Following these results, these alloys are strongly expected to be
promising candidates for spintronic applications.Comment: 6 pages, 6 figure
Transverse oscillations of flowing prominence threads observed with Hinode
Recent observations with the Hinode Solar Optical Telescope display an active
region prominence whose fine threads oscillate in the vertical direction as
they move along a path parallel to the photosphere. A seismological analysis of
this event is carried out by taking advantage of the small radius of these
structures compared to the total length of magnetic field lines, i.e. by using
the thin tube approximation. This analysis reveals that the oscillatory period
is only slightly modified by the existence of the flow and that the difference
between the period of a flowing thread and a static one is below the error bars
of these observations. Moreover, although it is not possible to obtain values
of the physical parameters, a lower bound for the Alfv\'en speed (ranging
between 120 km s and 350 km s) is obtained for each of the
threads. Such Alfv\'en speeds agree with the intense magnetic fields and large
densities usually found in active region prominences
Near-Limb Zeeman and Hanle Diagnostics
"Weak" magnetic-field diagnostics in faint objects near the bright solar disk
are discussed in terms of the level of non-object signatures, in particular, of
the stray light in telescopes. Calculated dependencies of the stray light
caused by diffraction at the 0.5-, 1.6-, and 4-meter entrance aperture are
presented. The requirements for micro-roughness of refractive and reflective
primary optics are compared. Several methods for reducing the stray light (the
Lyot coronagraphic technique, multiple stages of apodizing in the focal and
exit pupil planes, apodizing in the entrance aperture plane with a special
mask), and reducing the random and systematic errors are noted. An acceptable
level of stray light in telescopes is estimated for the V-profile recording
with a signal-to-noise ratio greater than three. Prospects for the limb
chromosphere magnetic measurements are indicated.Comment: 11 pages, 3 figure
Origin and Properties of the Gap in the Half-Ferromagnetic Heusler Alloys
We study the origin of the gap and the role of chemical composition in the
half-ferromagnetic Heusler alloys using the full-potential screened KKR method.
In the paramagnetic phase the C1_b compounds, like NiMnSb, present a gap.
Systems with 18 valence electrons, Z_t, per unit cell, like CoTiSb, are
semiconductors, but when Z_t > 18 antibonding states are also populated, thus
the paramagnetic phase becomes unstable and the half-ferromagnetic one is
stabilized. The minority occupied bands accommodate a total of nine electrons
and the total magnetic moment per unit cell in mu_B is just the difference
between Z_t and . While the substitution of the transition metal
atoms may preserve the half-ferromagnetic character, substituting the atom
results in a practically rigid shift of the bands and the loss of
half-metallicity. Finally we show that expanding or contracting the lattice
parameter by 2% preserves the minority-spin gap.Comment: 11 pages, 7 figures New figures, revised tex
Slater-Pauling Behavior of the Half-Ferromagnetic Full-Heusler Alloys
Using the full-potential screened Korringa-Kohn-Rostoker method we study the
full-Heusler alloys based on Co, Fe, Rh and Ru. We show that many of these
compounds show a half-metallic behavior, however in contrast to the
half-Heusler alloys the energy gap in the minority band is extremely small.
These full-Heusler compounds show a Slater-Pauling behavior and the total
spin-magnetic moment per unit cell (M_t) scales with the total number of
valence electrons (Z_t) following the rule: M_t=Z_t-24. We explain why the
spin-down band contains exactly 12 electrons using arguments based on the group
theory and show that this rule holds also for compounds with less than 24
valence electrons. Finally we discuss the deviations from this rule and the
differences compared to the half-Heusler alloys.Comment: 10 pages, 8 figures, revised figure 3, new text adde
The Politics of Pleasure: Promenading on the Corniche and Beachgoing
Can the pleasures of young Palestinian women from refugee camps in promenading on the Beirut seaside Corniche on a warm summer evening be political? Or days spent at women-only beaches? If so, how do we understand such pleasure as everyday practices, as a politics of the present moment, or conversely (or simultaneously) as mechanisms of being co-opted into a broader apparatus of consumerist ideology and capitalist complacency? Drawing on ethnographic research over 2 years I argue that these moments of pleasure are caesuras in the massive apparatus of power – welded from strands of work, neoliberal practice, nationalist certitudes and political exclusion – which binds these women. These acts of pleasure cannot easily be categorised as ‘resistance’ but I argue that they should not facilely be considered reinforcements of hegemonic control either. They are momentary and ephemeral recognitions of ordinary life lived in hard times, attempts at clawing back an instant of joy from the drudgery of the everyday, and a surrender to the enjoyment of conviviality in public and urban spaces. If they are at all political, they are so because such conviviality is ever harder to sustain in the calamity of hopelessness that characterises so much politics today
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