1,060 research outputs found
Time dependence studies on giant magnetoresistive Co/Cu multilayers
Time dependence studies consisting of applying current
steps at fixed applied fields have been carried out on bilinear and biquadratic giant magnetoresistive (GMR) Co/Cu multilayers in a temperature controlled environment. It has been shown that the voltage responses to current steps of these aged multilayers are greater in magnitude before field cycling compared to those made after field cycling. Normalized voltage measurements for
some samples suggest a magnetic viscosity effect due to a current step at zero-field is present and before field cycling. The effect is reduced after field cycling. This behavior suggests that the effect being seen is purely magnetic in origin, as only the field is being
varied. A ln( ) type function has been curve fitted to the zero field voltage response to a current step before field cycling. Voltage measurements made on the Co/Cu films at different field values show that as the applied fields are increased the voltage response has a reduced ln(t) character
Micron-sized atom traps made from magneto-optical thin films
We have produced magnetic patterns suitable for trapping and manipulating
neutral atoms on a m length scale. The required patterns are made in
Co/Pt thin films on a silicon substrate, using the heat from a focussed laser
beam to induce controlled domain reversal. In this way we draw lines and
"paint" shaped areas of reversed magnetization with sub-micron resolution.
These structures produce magnetic microtraps above the surface that are
suitable for holding rubidium atoms with trap frequencies as high as ~1 MHz.Comment: 6 pages, 7 figure
Radiatively Induced Neutrino Masses and Large Higgs-Neutrino Couplings in the Standard Model with Majorana Fields
The Higgs sector of the Standard Model with one right-handed neutrino per
family is systematically analyzed. In a model with intergenerational
independent mixings between families, we can account for very light neutrinos
acquiring Majorana masses radiatively at the first electroweak loop level. We
also find that in such a scenario the Higgs coupling to the light-heavy
neutrinos and to the heavy-heavy ones may be remarkably enhanced with
significant implications for the production of these heavy neutrinos at high
energy colliders.Comment: Making the text of an old paper electronically availabl
Standard Model baryogenesis through four-fermion operators in braneworlds
We study a new baryogenesis scenario in a class of braneworld models with low
fundamental scale, which typically have difficulty with baryogenesis. The
scenario is characterized by its minimal nature: the field content is that of
the Standard Model and all interactions consistent with the gauge symmetry are
admitted. Baryon number is violated via a dimension-6 proton decay operator,
suppressed today by the mechanism of quark-lepton separation in extra
dimensions; we assume that this operator was unsuppressed in the early Universe
due to a time-dependent quark-lepton separation. The source of CP violation is
the CKM matrix, in combination with the dimension-6 operators. We find that
almost independently of cosmology, sufficient baryogenesis is nearly impossible
in such a scenario if the fundamental scale is above 100 TeV, as required by an
unsuppressed neutron-antineutron oscillation operator. The only exception
producing sufficient baryon asymmetry is a scenario involving
out-of-equilibrium c quarks interacting with equilibrium b quarks.Comment: 39 pages, 5 figures v2: typos, presentational changes, references and
acknowledgments adde
A genomic prediction model for racecourse starts in the Thoroughbred horse
Durability traits in Thoroughbred horses are heritable, economically valuable and may affect horse welfare. The aims of this study were to test the hypotheses that (i) durability traits are heritable and (ii) genetic data may be used to predict a horse's potential to have a racecourse start. Heritability for the phenotype ‘number of 2‐ and 3‐year‐old starts’ was estimated to be urn:x-wiley:02689146:media:age12798:age12798-math-0001 = 0.11 ± 0.02 (n = 4499). A genome‐wide association study identified SNP contributions to the trait. The neurotrimin (NTM), opioid‐binding protein/cell adhesion molecule like (OPCML) and prolylcarboxypeptidase (PRCP) genes were identified as candidate genes associated with the trait. NTM functions in brain development and has been shown to have been selected during the domestication of the horse. PRCP is an established expression quantitative trait locus involved in the interaction between voluntary exercise and body composition in mice. We hypothesise that variation at these loci contributes to the motivation of the horse to exercise, which may influence its response to the demands of the training and racing environment. A random forest with mixed effects (RFME) model identified a set of SNPs that contributed to 24.7% of the heritable variation in the trait. In an independent validation set (n = 528 horses), the cohort with high genetic potential for a racecourse start had significantly fewer unraced horses (16% unraced) than did low (27% unraced) potential horses and had more favourable race outcomes among those that raced. Therefore, the information from SNPs included in the model may be used to predict horses with a greater chance of a racecourse start
An Extreme Solar Event of 20 January 2005: Properties of the Flare and the Origin of Energetic Particles
The extreme solar and SEP event of 20 January 2005 is analyzed from two
perspectives. Firstly, we study features of the main phase of the flare, when
the strongest emissions from microwaves up to 200 MeV gamma-rays were observed.
Secondly, we relate our results to a long-standing controversy on the origin of
SEPs arriving at Earth, i.e., acceleration in flares, or shocks ahead of CMEs.
All emissions from microwaves up to 2.22 MeV line gamma-rays during the main
flare phase originated within a compact structure located just above sunspot
umbrae. A huge radio burst with a frequency maximum at 30 GHz was observed,
indicating the presence of a large number of energetic electrons in strong
magnetic fields. Thus, protons and electrons responsible for flare emissions
during its main phase were accelerated within the magnetic field of the active
region. The leading, impulsive parts of the GLE, and highest-energy gamma-rays
identified with pi^0-decay emission, are similar and correspond in time. The
origin of the pi^0-decay gamma-rays is argued to be the same as that of lower
energy emissions. We estimate the sky-plane speed of the CME to be 2000-2600
km/s, i.e., high, but of the same order as preceding non-GLE-related CMEs from
the same active region. Hence, the flare itself rather than the CME appears to
determine the extreme nature of this event. We conclude that the acceleration,
at least, to sub-relativistic energies, of electrons and protons, responsible
for both the flare emissions and the leading spike of SEP/GLE by 07 UT, are
likely to have occurred simultaneously within the flare region. We do not rule
out a probable contribution from particles accelerated in the CME-driven shock
for the leading GLE spike, which seemed to dominate later on.Comment: 34 pages, 14 Postscript figures. Solar Physics, accepted. A typo
corrected. The original publication is available at
http://www.springerlink.co
Minimal Composite Higgs Model with Light Bosons
We analyze a composite Higgs model with the minimal content that allows a
light Standard-Model-like Higgs boson, potentially just above the current LEP
limit. The Higgs boson is a bound state made up of the top quark and a heavy
vector-like quark. The model predicts that only one other bound state may be
lighter than the electroweak scale, namely a CP-odd neutral scalar. Several
other composite scalars are expected to have masses in the TeV range. If the
Higgs decay into a pair of CP-odd scalars is kinematically open, then this
decay mode is dominant, with important implications for Higgs searches. The
lower bound on the CP-odd scalar mass is loose, in some cases as low as
100 MeV, being set only by astrophysical constraints.Comment: 33 pages, latex. Corrections in eqs. 3.21, 3.23, 4.1, 4.5-10. One
figure adde
A Taylor Model Based Description of the proof stress of magnesium AZ31 during hot working
A series of hot-compression tests and Taylor-model simulations were carried out with the intention of developing a simple expression for the proof stress of magnesium alloy AZ31 during hot working. A crude approximation of wrought textures as a mixture of a single ideal texture component and a random background was employed. The shears carried by each deformation system were calculated using a full-constraint Taylor model for a selection of ideal orientations as well as for random textures. These shears, in combination with the measured proof stresses, were employed to estimate the critical resolved shear stresses for basal slip, prismatic slip, ⟨c+a⟩ second-order pyramidal slip, and { } twinning. The model thus established provides a semianalytical estimation of the proof stress (a one-off Taylor simulation is required) and also indicates whether or not twinning is expected. The approach is valid for temperatures between ∼150 °C and ∼450 °C, depending on the texture, strain rate, and strain path
Recommended from our members
Grass burning under our feet: Indigenous enterprise development in a political economy of whiteness
In this article we discuss some of our findings from two research projects that explore opportunities for Indigenous enterprise development in remote locations in Northern and Central Australia. Based on a series of focus groups and in-depth interviews with Indigenous community leaders, Traditional Owners, government officials, Land Council officials and other stakeholders, we discuss barriers to economic development faced by Indigenous communities in remote regions. We argue that many of these barriers are the material effects of discursive practices of ‘whiteness’ in the political economy. We discuss the relationships between institutions and Indigenous communities that constitute the Indigenous political economy and argue that these relationships are informed by discursive practices of whiteness and colonial-capitalist relations of power. We conclude by discussing the implications of our findings for management learning and public policy
- …