325 research outputs found
Magnetic Phase Control in Monolayer Films by Substrate Tuning
We propose to tailor exchange interactions in magnetic monolayer films by
tuning the adjacent non-magnetic substrate. As an example, we demonstrate a
ferromagnetic-antiferromagnetic phase transition for one monolayer Fe on a
Ta(x)W(1-x)(001) surface as a function of the Ta concentration. At the critical
Ta concentration, the nearest-neighbor exchange interaction is small and the
magnetic phase space is dramatically broadened. Complex magnetic order such as
spin-spirals, multiple-Q, or even disordered local moment states can occur,
offering the possibility to store information in terms of ferromagnetic dots in
an otherwise zero-magnetization state matrix.Comment: after minor changes, 5 pages, 5 figures, revtex
Flux-flow induced giant magnetoresistance in all-amorphous superconductor-ferromagnet hybrids
We present magnetoresistance measurements on all-amorphous ferromagnet (F) /
superconductor (S) heterostructures. The F/S/F trilayers show large
magnetoresistance peaks in a small field range around the coercive field of the
F layers, at temperatures within and below the superconducting transition. This
is interpreted as flux flow of weakly pinned vortices induced by the stray
field of Bloch magnetic domains in the F layers. Bilayers show much smaller
effects, implying that the Bloch walls of the F-layers in the trilayer line up
and focus the stray fields. The data are used to discuss the expected minimum
F-layer thickness needed to nucleate vortices.Comment: 6 pages, 6 figure
Dissemination of information to General Practitioners: a questionnaire survey
BACKGROUND: Early identification of permanent hearing impairment in children enables appropriate intervention which reduces adverse developmental outcomes. The UK Government has introduced a universal hearing screening programme for neonates. All involved health professionals, including those in Primary Care, need to be aware of the service to enable them to offer appropriate support to their patients. A programme of information dissemination within Primary Care was therefore undertaken. The aim of the current study was to determine the extent to which the information had reached General Practitioners (GPs), the GPs' preferred mode of dissemination and the sources from which GPs accessed information METHODS: Postal questionnaire survey of a randomised sample of 1000 GPs in the Phase I pilot sites of the Neonatal Hearing Screening Programme (NHSP). RESULTS: Responses were received from 54.2% of the sample. Just under 50% of those responding had received information, 62.2% of respondents said they would like to receive more information and the preferred methods of dissemination were the written word and web-sites to allow access when needed. Few GPs perceive themselves to have a core role in the delivery of the NHSP and thence a need for knowledge in the subject. Many are keen to delegate detail to a third party, usually the health visitor, who has traditionally had responsibility for hearing screening. CONCLUSIONS: Dissemination efforts for service developments of relevance to GPs should concentrate on advertising a website address via brief but memorable posted literature and/or articles in relevant journals and magazines. The website should be GP-friendly, and have a dedicated area for GPs including information of specific relevance and downloadable information sheets
Anomalous field-dependent specific heat in charge-ordered PrCaMnO and LaCaMnO
We report low temperature specific heat measurements of
PrCaMnO () and
LaCaMnO with and without applied magnetic field. An
excess specific heat, , of non-magnetic origin associated with
charge ordering is found for all the samples. A magnetic field sufficient to
induce the transition from the charge-ordered state to the ferromagnetic
metallic state does not completely remove the contribution. This
suggests that the charge ordering is not completely destroyed by a "melting"
magnetic field. In addition, the specific heat of the
PrCaMnO compounds exhibit a large contribution linear in
temperature () originating from magnetic and charge disorder.Comment: submitted to PRL 5 pages, 3 figures include
The ETTAA study protocol: a UK-wide observational study of 'Effective Treatments for Thoracic Aortic Aneurysm'.
Introduction Chronic thoracic aortic aneurysm (CTAA) affecting the arch or descending aorta is an indolent but life-threatening condition with a rising prevalence as the UK population ages. Treatment may be in the form of open surgical repair (OSR) surgery, endovascular stent grafting (ESG) or best medical therapy (BMT). Currently, there is no consensus on the best management strategy, and no UK-specific economic studies that assess outcomes beyond the chosen procedure, but this is required in the context of greater demand for treatment and limited National Health Service (NHS) resources. Methods and analysis This is a prospective, multicentre observational study with statistical and economic modelling of patients with CTAA affecting the arch or descending aorta. We aim to gain an understanding of how treatments are currently chosen, and to determine the clinical effectiveness and cost-effectiveness of the three available treatment strategies (BMT, ESG and OSR). This will be achieved by: (1) following consecutive patients who are referred to the teams collaborating in this proposal and collecting data regarding quality of life (QoL), medical events and hospital stays over a maximum of 5â
years; (2) statistical analysis of the comparative effectiveness of the three treatments; and (3) economic modelling of the comparative cost-effectiveness of the three treatments. Primary study outcomes are: aneurysm growth, QoL, freedom from reintervention, freedom from death or permanent neurological injury, incremental cost per quality-adjusted life year gained. Ethics and dissemination The study will generate an evidence base to guide patients and clinicians to determine the indications and timing of treatment, as well as informing healthcare decision-makers about which treatments the NHS should provide. The study has achieved ethical approval and will be disseminated primarily in the form of a Health Technology Assessment monograph at its completion
The geography of recent genetic ancestry across Europe
The recent genealogical history of human populations is a complex mosaic
formed by individual migration, large-scale population movements, and other
demographic events. Population genomics datasets can provide a window into this
recent history, as rare traces of recent shared genetic ancestry are detectable
due to long segments of shared genomic material. We make use of genomic data
for 2,257 Europeans (the POPRES dataset) to conduct one of the first surveys of
recent genealogical ancestry over the past three thousand years at a
continental scale. We detected 1.9 million shared genomic segments, and used
the lengths of these to infer the distribution of shared ancestors across time
and geography. We find that a pair of modern Europeans living in neighboring
populations share around 10-50 genetic common ancestors from the last 1500
years, and upwards of 500 genetic ancestors from the previous 1000 years. These
numbers drop off exponentially with geographic distance, but since genetic
ancestry is rare, individuals from opposite ends of Europe are still expected
to share millions of common genealogical ancestors over the last 1000 years.
There is substantial regional variation in the number of shared genetic
ancestors: especially high numbers of common ancestors between many eastern
populations likely date to the Slavic and/or Hunnic expansions, while much
lower levels of common ancestry in the Italian and Iberian peninsulas may
indicate weaker demographic effects of Germanic expansions into these areas
and/or more stably structured populations. Recent shared ancestry in modern
Europeans is ubiquitous, and clearly shows the impact of both small-scale
migration and large historical events. Population genomic datasets have
considerable power to uncover recent demographic history, and will allow a much
fuller picture of the close genealogical kinship of individuals across the
world.Comment: Full size figures available from
http://www.eve.ucdavis.edu/~plralph/research.html; or html version at
http://ralphlab.usc.edu/ibd/ibd-paper/ibd-writeup.xhtm
Reconstructing Roma History from Genome-Wide Data
The Roma people, living throughout Europe and West Asia, are a diverse population linked by the Romani language and culture. Previous linguistic and genetic studies have suggested that the Roma migrated into Europe from South Asia about 1,000â1,500 years ago. Genetic inferences about Roma history have mostly focused on the Y chromosome and mitochondrial DNA. To explore what additional information can be learned from genome-wide data, we analyzed data from six Roma groups that we genotyped at hundreds of thousands of single nucleotide polymorphisms (SNPs). We estimate that the Roma harbor about 80% West Eurasian ancestryâderived from a combination of European and South Asian sourcesâand that the date of admixture of South Asian and European ancestry was about 850 years before present. We provide evidence for Eastern Europe being a major source of European ancestry, and North-west India being a major source of the South Asian ancestry in the Roma. By computing allele sharing as a measure of linkage disequilibrium, we estimate that the migration of Roma out of the Indian subcontinent was accompanied by a severe founder event, which appears to have been followed by a major demographic expansion after the arrival in Europe.OrszaÌgos TudomaÌnyos KutataÌsi Alapprogramok (OTKA K 103983)OrszaÌgos TudomaÌnyos KutataÌsi Alapprogramok (OTKA 73430)National Science Foundation (U.S.) (HOMINID grant 1032255)National Institutes of Health (U.S.) (grant GM100233
The genetic prehistory of southern Africa
Southern and eastern African populations that speak non-Bantu languages with
click consonants are known to harbour some of the most ancient genetic lineages
in humans, but their relationships are poorly understood. Here, we report data
from 23 populations analyzed at over half a million single nucleotide
polymorphisms, using a genome-wide array designed for studying human history.
The southern African Khoisan fall into two genetic groups, loosely
corresponding to the northwestern and southeastern Kalahari, which we show
separated within the last 30,000 years. We find that all individuals derive at
least a few percent of their genomes from admixture with non-Khoisan
populations that began approximately 1,200 years ago. In addition, the east
African Hadza and Sandawe derive a fraction of their ancestry from admixture
with a population related to the Khoisan, supporting the hypothesis of an
ancient link between southern and eastern AfricaComment: To appear in Nature Communication
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