2,257 research outputs found
A first-principles study of tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) magnetic tunnel junctions
We investigated the spin-dependent transport properties of Fe/MgAl2O4/Fe(001)
magnetic tunneling junctions (MTJs) on the basis of first-principles
calculations of the electronic structures and the ballistic conductance. The
calculated tunneling magnetoresistance (TMR) ratio of a Fe/MgAl2O4/Fe(001) MTJ
was about 160%, which was much smaller than that of a Fe/MgO/Fe(001) MTJ
(1600%) for the same barrier thickness. However, there was an evanescent state
with delta 1 symmetry in the energy gap around the Fermi level of normal spinel
MgAl2O4, indicating the possibility of a large TMR in Fe/MgAl2O4/Fe(001) MTJs.
The small TMR ratio of the Fe/MgAl2O4/Fe(001) MTJ was due to new conductive
channels in the minority spin states resulting from a band-folding effect in
the two-dimensional (2-D) Brillouin zone of the in-plane wave vector (k//) of
the Fe electrode. Since the in-plane cell size of MgAl2O4 is twice that of the
primitive in-plane cell size of bcc Fe, the bands in the boundary edges are
folded, and minority-spin states coupled with the delta 1 evanescent state in
the MgAl2O4 barrier appear at k//=0, which reduces the TMR ratio of the MTJs
significantly.Comment: 5 pages, 6 figures, 1 tabl
Resolution of secondary hemophagocytic lymphohistiocytosis after treatment with the JAK1/2 inhibitor ruxolitinib
A 125GeV Higgs Boson and Muon g-2 in More Generic Gauge Mediation
Recently, the ATLAS and CMS collaborations reported exciting hints of a
Standard Model-like Higgs boson with a mass around 125GeV. A Higgs boson this
heavy is difficult to realize in conventional models of gauge mediation. Here
we revisit the lightest Higgs boson mass in "more generic gauge mediation,"
where the Higgs doublets mix with the messenger doublets. We show that a Higgs
boson mass around 125GeV can be realized in more generic gauge mediation
models, even for a relatively light gluino mass ~1TeV. We also show that the
muon anomalous magnetic moment can be within 1sigma of the experimental value
for these models, even when the Higgs boson is relatively heavy. We also
discuss the LHC constraints and the prospects of discovery.Comment: 28 pages, 7 figures. Corrections and references are adde
Detection of Phase Jumps of Free Core Nutation of the Earth and their Concurrence with Geomagnetic Jerks
We detected phase jumps of the Free Core Nutation (FCN) of the Earth directly
from the analysis of the Very Long Baseline Interferometer (VLBI) observation
of the Earth rotation for the period 1984-2003 by applying the Weighted Wavelet
Z-Transform (WWZ) method and the Short-time Periodogram with the Gabor function
(SPG) method. During the period, the FCN had two significant phase jumps in
1992 and 1998. These epochs coincide with the reported occurrence of
geomagnetic jerks.Comment: 8 pages, 4 figure
Island resort runoff threatens reef ecosystems: an isotopic assessment of the extent and impact of sewage-derived nitrogen across Redang Island, Terengganu, Peninsular Malaysia
The influence of the Lande -factor in the classical general relativistic description of atomic and subatomic systems
We study the electromagnetic and gravitational fields of the proton and
electron in terms of the Einstenian gravity via the introduction of an
arbitrary Lande -factor in the Kerr-Newman solution. We show that at length
scales of the order of the reduced Compton wavelength, corrections from
different values of the -factor are not negligible and discuss the presence
of general relativistic effects in highly ionized heavy atoms. On the other
hand, since at the Compton-wavelength scale the gravitational field becomes
spin dominated rather than mass dominated, we also point out the necessity of
including angular momentum as a source of corrections to Newtonian gravity in
the quantum description of gravity at this scale.Comment: 11 pages, 2 figure
Spectral Dependence of Polarized Radiation due to Spatial Correlations
We study the polarization of light emitted by spatially correlated sources.
We show that in general polarization acquires nontrivial spectral dependence
due to spatial correlations. The spectral dependence is found to be absent only
for a special class of sources where the correlation length scales as the
wavelength of light. We further study the cross correlations between two
spatially distinct points that are generated due to propagation. It is found
that such cross correlation leads to sufficiently strong spectral dependence of
polarization which can be measured experimentally.Comment: 5 pages, 4 figure
Biologic Monitoring to Characterize Organophosphorus Pesticide Exposure among Children and Workers: An Analysis of Recent Studies in Washington State
We examined findings from five organophosphorus pesticide biomonitoring studies conducted in Washington State between 1994 and 1999. We compared urinary dimethylthiophosphate (DMTP) concentrations for all study groups and composite dimethyl alkylphosphate (DMAP) concentrations for selected groups. Children of pesticide applicators had substantially higher metabolite levels than did Seattle children and farmworker children (median DMTP, 25 ÎŒg/L; p < 0.0001). Metabolite levels of children living in agricultural communities were elevated during periods of crop spraying. Median DMTP concentrations for Seattle children and farmworker children did not differ significantly (6.1 and 5.8 ÎŒg/L DMTP, respectively; p = 0.73); however, the DMAP concentrations were higher for Seattle children than for farmworker children (117 and 87 nmol/L DMAP, respectively; p = 0.007). DMTP concentrations of U.S. children 6â11 years of age (1999â2000 National Health and Nutrition Examination Survey population) were higher than those of Seattle children and farmworker children at the 75th, 90th, and 95th percentiles. DMTP concentrations for workers actively engaged in apple thinning were 50 times higher than DMTP concentrations for farmworkers sampled outside of peak exposure periods. We conclude that workers who have direct contact with pesticides should continue to be the focus of public health interventions and that elevated child exposures in agricultural communities may occur during active crop-spraying periods and from living with a pesticide applicator. Timing of sample collection is critical for the proper interpretation of pesticide biomarkers excreted relatively soon after exposure. We surmise that differences in dietary exposure can explain the similar exposures observed among farmworker children, children living in the Seattle metropolitan area, and children sampled nationally
Fe XI emission lines in a high resolution extreme ultraviolet spectrum obtained by SERTS
New calculations of radiative rates and electron impact excitation cross
sections for Fe XI are used to derive emission line intensity ratios involving
3s^23p^4 - 3s^23p^33d transitions in the 180-223 A wavelength range. These
ratios are subsequently compared with observations of a solar active region,
obtained during the 1995 flight Solar EUV Research Telescope and Spectrograph
(SERTS). The version of SERTS flown in 1995 incorporated a multilayer grating
that enhanced the instrumental sensitivity for features in the 170 - 225 A
wavelength range, observed in second-order between 340 and 450 A. This
enhancement led to the detection of many emission lines not seen on previous
SERTS flights, which were measured with the highest spectral resolution (0.03
A) ever achieved for spatially resolved active region spectra in this
wavelength range. However, even at this high spectral resolution, several of
the Fe XI lines are found to be blended, although the sources of the blends are
identified in the majority of cases. The most useful Fe XI electron density
diagnostic line intensity ratio is I(184.80 A)/I(188.21 A). This ratio involves
lines close in wavelength and free from blends, and which varies by a factor of
11.7 between N_e = 10^9 and 10^11 cm^-3, yet shows little temperature
sensitivity. An unknown line in the SERTS spectrum at 189.00 A is found to be
due to Fe XI, the first time (to our knowledge) this feature has been
identified in the solar spectrum. Similarly, there are new identifications of
the Fe XI 192.88, 198.56 and 202.42 A features, although the latter two are
blended with S VIII/Fe XII and Fe XIII, respectively.Comment: 21 pages, 9 gigures, accepted for publication in the Astrophysical
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