197 research outputs found
InAs-AlSb quantum wells in tilted magnetic fields
InAs-AlSb quantum wells are investigated by transport experiments in magnetic
fields tilted with respect to the sample normal. Using the coincidence method
we find for magnetic fields up to 28 T that the spin splitting can be as large
as 5 times the Landau splitting. We find a value of the g-factor of about 13.
For small even-integer filling factors the corresponding minima in the
Shubnikov-de Haas oscillations cannot be tuned into maxima for arbitrary tilt
angles. This indicates the anti-crossing of neighboring Landau and spin levels.
Furthermore we find for particular tilt angles a crossover from even-integer
dominated Shubnikov-de Haas minima to odd-integer minima as a function of
magnetic field
Andreev magnetotransport in low-dimensional proximity structures: Spin-dependent conductance enhancement
We study the excess conductance due to the superconducting proximity effect
in a ballistic two-dimensional electron system subject to an in-plane magnetic
field. We show that under certain conditions the interplay of the Zeeman spin
splitting and the effect of a screening supercurrent gives rise to a
spin-selective Andreev enhancement of the conductance and anomalies in its
voltage, temperature and magnetic field characteristics. The magnetic-field
influence on Andreev reflection is discussed in the context of using
superconducting hybrid junctions for spin detection.Comment: 4 pages, 5 figure
Zero-field spin splitting in InAs-AlSb quantum wells revisited
We present magnetotransport experiments on high-quality InAs-AlSb quantum
wells that show a perfectly clean single-period Shubnikov-de Haas oscillation
down to very low magnetic fields. In contrast to theoretical expectations based
on an asymmetry induced zero-field spin splitting, no beating effect is
observed. The carrier density has been changed by the persistent photo
conductivity effect as well as via the application of hydrostatic pressure in
order to influence the electric field at the interface of the electron gas.
Still no indication of spin splitting at zero magnetic field was observed in
spite of highly resolved Shubnikov- de Haas oscillations up to filling factors
of 200. This surprising and unexpected result is discussed in view of other
recently published data.Comment: 4 pages, 3 figures, submitted to Phys. Rev.
D-SPACE4Cloud: A Design Tool for Big Data Applications
The last years have seen a steep rise in data generation worldwide, with the
development and widespread adoption of several software projects targeting the
Big Data paradigm. Many companies currently engage in Big Data analytics as
part of their core business activities, nonetheless there are no tools and
techniques to support the design of the underlying hardware configuration
backing such systems. In particular, the focus in this report is set on Cloud
deployed clusters, which represent a cost-effective alternative to on premises
installations. We propose a novel tool implementing a battery of optimization
and prediction techniques integrated so as to efficiently assess several
alternative resource configurations, in order to determine the minimum cost
cluster deployment satisfying QoS constraints. Further, the experimental
campaign conducted on real systems shows the validity and relevance of the
proposed method
Comparison of different control strategies for classical swine fever using emergency vaccination and rapid PCR testing by using a Monte-Carlo simulation model
Whenever an outbreak of classical swine fever has occurred in the European Union (EU), the basic control measures have usually been supplemented by preventive culling. This strategy has led to a great number of culled pigs and is discussed by general public and politics from both ethical and economic points of view. Emergency vaccination has been deemed to be an alternative control measure for some time now. PCR testing also provides a possible future strategy, since this method would allow a rapid and reliable testing of pigs in the vicinity of an outbreak farm. In this study, a spatial and temporal Monte-Carlo simulation model was used to compare alternative control strategies based upon these two measures (»Emergency Vaccination«, »Test To Slaughter«, »Test To Control« and »Vaccination in conjunction with Rapid Testing«) with the current control strategy. Two regions for investigation with different farm densities were used in the model. In a region with a low farm density, the basic EU control measures seemed to be sufficient to control an epidemic. In a region with a high farm density, additional measures would be necessary. »Emergency Vaccination« in a 3 km application zone and »Traditional Control« reached the same level of infected farms. Both »Test To Slaughter« and »Test To Control« combined with preventive culling led to a lower number of infected farms compared to the sole preventive culling strategy. The alternative control measures can reduce the number of culled farms significantly compared to »Traditional Control«
Rashba precession in quantum wires with interaction
Rashba precession of spins moving along a one-dimensional quantum channel is
calculated, accounting for Coulomb interactions. The Tomonaga--Luttinger model
is formulated in the presence of spin-orbit scattering and solved by
Bosonization. Increasing interaction strength at decreasing carrier density is
found to {\sl enhance} spin precession and the nominal Rashba parameter due to
the decreasing spin velocity compared with the Fermi velocity. This result can
elucidate the observed pronounced changes of the spin splitting on applied gate
voltages which are estimated to influence the interface electric field in
heterostructures only little.Comment: now replaced by published versio
Strong evidence that the common variant S384F in BRCA2 has no pathogenic relevance in hereditary breast cancer
INTRODUCTION: Unclassified variants (UVs) of unknown clinical significance are frequently detected in the BRCA2 gene. In this study, we have investigated the potential pathogenic relevance of the recurrent UV S384F (BRCA2, exon 10). METHODS: For co-segregation, four women from a large kindred (BN326) suffering from breast cancer were analysed. Moreover, paraffin-embedded tumours from two patients were analysed for loss of heterozygosity. Co-occurrence of the variant with a deleterious mutation was further determined in a large data set of 43,029 index cases. Nature and position of the UV and conservation among species were evaluated. RESULTS: We identified the unclassified variant S384F in three of the four breast cancer patients (the three were diagnosed at 41, 43 and 57 years of age). One woman with bilateral breast cancer (diagnosed at ages 32 and 50) did not carry the variant. Both tumours were heterozygous for the S384F variant, so loss of the wild-type allele could be excluded. Ser384 is not located in a region of functional importance and cross-species sequence comparison revealed incomplete conservation in the human, dog, rodent and chicken BRCA2 homologues. Overall, the variant was detected in 116 patients, five of which co-occurred with different deleterious mutations. The combined likelihood ratio of co-occurrence, co-segregation and loss of heterozygosity revealed a value of 1.4 × 10(-8 )in favour of neutrality of the variant. CONCLUSION: Our data provide conclusive evidence that the S384F variant is not a disease causing mutation
Spintronics: Fundamentals and applications
Spintronics, or spin electronics, involves the study of active control and
manipulation of spin degrees of freedom in solid-state systems. This article
reviews the current status of this subject, including both recent advances and
well-established results. The primary focus is on the basic physical principles
underlying the generation of carrier spin polarization, spin dynamics, and
spin-polarized transport in semiconductors and metals. Spin transport differs
from charge transport in that spin is a nonconserved quantity in solids due to
spin-orbit and hyperfine coupling. The authors discuss in detail spin
decoherence mechanisms in metals and semiconductors. Various theories of spin
injection and spin-polarized transport are applied to hybrid structures
relevant to spin-based devices and fundamental studies of materials properties.
Experimental work is reviewed with the emphasis on projected applications, in
which external electric and magnetic fields and illumination by light will be
used to control spin and charge dynamics to create new functionalities not
feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes
from the published versio
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