2,727 research outputs found
Superfluidity versus localization in bulk 4He at zero temperature
We present a zero-temperature quantum Monte Carlo calculation of liquid
He immersed in an array of confining potentials. These external potentials
are centered in the lattice sites of a fcc solid geometry and, by modifying
their well depth and range, the system evolves from a liquid phase towards a
progressively localized system which mimics a solid phase. The superfluid
density decreases with increasing order, reaching a value when the Lindemann's ratio of the model equals the experimental
value for solid He.Comment: 5 pages,5 figure
Magnetic Properties of a Two-Dimensional Mixed-Spin System
Using a Langmuir-Blodgett (LB) synthesis method, novel two-dimensional (2D)
mixed-spin magnetic systems, in which each magnetic layer is both structurally
and magnetically isolated, have been generated. Specifically, a 2D Fe-Ni
cyanide-bridged network with a face-centered square grid structure has been
magnetically and structurally characterized. The results indicate the presence
of ferromagnetic exchange interactions between the Fe () and
Ni (S=1) centers.Comment: 2 pages, 3 figs., submitted 23rd International Conference on Low
Temperature Physics (LT-23), Aug. 200
Mechanism for nonequilibrium symmetry breaking and pattern formation in magnetic films
Magnetic thin films exhibit a strong variation in properties depending on
their degree of disorder. Recent coherent x-ray speckle experiments on magnetic
films have measured the loss of correlation between configurations at opposite
fields and at the same field, upon repeated field cycling. We perform finite
temperature numerical simulations on these systems that provide a comprehensive
explanation for the experimental results. The simulations demonstrate, in
accordance with experiments, that the memory of configurations increases with
film disorder. We find that non-trivial microscopic differences exist between
the zero field spin configuration obtained by starting from a large positive
field and the zero field configuration starting at a large negative field. This
seemingly paradoxical beahvior is due to the nature of the vector spin dynamics
and is also seen in the experiments. For low disorder, there is an instability
which causes the spontaneous growth of line-like domains at a critical field,
also in accord with experiments. It is this unstable growth, which is highly
sensitive to thermal noise, that is responsible for the small correlation
between patterns under repeated cycling. The domain patterns, hysteresis loops,
and memory properties of our simulated systems match remarkably well with the
real experimental systems.Comment: 12 pages, 10 figures Added comparison of results with
cond-mat/0412461 and some more discussio
Milk protein-derived peptide inhibitors of angiotensin-I-converting enzyme
peer-reviewedNumerous casein and whey protein-derived angiotensin-I-converting enzyme (ACE) inhibitory
peptides/hydrolysates have been identified. Clinical trials in hypertensive animals and humans
show that these peptides/hydrolysates can bring about a significant reduction in hypertension.
These peptides/hydrolysates may be classified as functional food ingredients and nutraceuticals
due to their ability to provide health benefits i.e. as functional food ingredients in reducing the
risk of developing a disease and as nutraceuticals in the prevention/treatment of disease
Method to Suppress Isobaric and Polyatomic Interferences for Measurements of Highly Siderophile Elements in Desilicified Geological Samples
Sample decomposition using inverse aqua regia at elevated temperatures and pressures (e.g., Carius tube or highāpressure asher) is the most common method used to extract highly siderophile elements (HSEs: Ru, Rh, Pd, Re, Os, Ir, Pt and Au) from geological samples. Recently, it has been recognised that additional HF desilicification is necessary to better recover HSEs, potentially contained within silicate or oxide minerals in mafic samples, which cannot be dissolved solely by inverse aqua regia. However, the abundance of interfering elements tends to increase in the eluent when conventional ionāexchange purification procedures are applied to desilicified samples. In this study, we developed an improved purification method to determine HSEs in desilicified samples. This method enables the reduction of the ratios of isobaric and polyatomic interferences, relative to the measured intensities of HSE isotope masses, to less than a few hundred parts per million. Furthermore, the total procedural blanks are either comparable to or lower than conventional methods. Thus, this method allows accurate and precise HSE measurements in mafic and ultramafic geological samples, without the need for interference corrections. Moreover, the problem of increased interfering elements, such as Zr for Pd and Cr for Ru, is circumvented for the desilicified samples
Adjusting the frequency of mammography screening on the basis of genetic risk: Attitudes among women in the UK.
Purpose
To explore public attitudes towards modifying frequency of mammography screening based on genetic risk.
Methods
Home-based interviews were carried out with a population-based sample of 942 women aged 18ā74 years in the UK. Demographic characteristics and perceived breast cancer (BC) risk were examined as predictors of support for risk-stratified BC screening and of the acceptability of raised or lowered screening frequency based on genetic risk, using multivariate logistic regression.
Results
Over two-thirds of respondents (65.8%) supported the idea of varying screening frequency on the basis of genetic risk. The majority (85.4%) were willing to have more frequent breast screening if they were found to be at higher risk, but fewer (58.8%) were willing to have less frequent screening if at lower risk (t (956) = 15.6, p < 0.001). Ethnic minority status was associated with less acceptability of more frequent screening (OR = 0.40, 95% CI = 0.21ā0.74), but there were no other significant demographic correlates. Higher perceived risk of BC was associated with greater acceptability of more frequent screening (OR = 1.71, 95%CI = 1.27ā2.30).
Conclusion
Women were positive about adjusting the frequency of mammography screening in line with personal genetic risk, but it will be important to develop effective communication materials to minimise resistance to reducing screening frequency for those at lower genetic risk
Survey of public definitions of the term 'overdiagnosis' in the UK
Objectives: To determine how āoverdiagnosisā is currently conceptualised among adults in the United Kingdom (UK) in light of previous research, which has found that the term is difficult for the public to understand and awareness is low. This study aims to add to current debates on healthcare in which overdiagnosis is a prominent issue. Design: An observational, web-based survey was administered by a survey company. Setting: Participants completed the survey at a time and location of their choosing. Participants: 390 consenting UK adults aged 50-70 years. Quota sampling was used to achieve approximately equal numbers in three categories of education. Primary outcome measures: Participants were asked whether they had seen or heard the term āoverdiagnosisā. If they had, they were then invited to explain in a free text field what they understood it to mean. If they had not previously encountered it, they were invited to say what they thought it meant. Responses were coded and interpreted using content analysis and descriptive statistics. Results: Data from 390 participants were analysed. Almost a third (30.0%) of participants reported having previously encountered the term. However, their responses often indicated that they had no knowledge of its meaning. The most prevalent theme consisted of responses related to the diagnosis itself. Subthemes indicated common misconceptions, including an āoverly negative or complicated diagnosisā, āfalse positive diagnosisā or āmisdiagnosisā. Other recurring themes consisted of responses related to testing (i.e. ātoo many testsā), treatment (e.g. āovertreatmentā), and patient psychology (e.g. āoverthinkingā). Responses categorised as consistent with āoverdiagnosisā (defined as detection of a disease that would not cause symptoms or death) were notably rare (n=10; 2.6%). Conclusions: Consistent with previous research, public awareness of āoverdiagnosisā in the UK is low and its meaning is often misunderstood or misinterpreted
Photoinduced Magnetization in a Thin Fe-CN-Co Film
The magnetization of a thin Fe-Co cyanide film has been investigated from 5 K
to 300 K and in fields up to 500 G. Upon illumination with visible light, the
magnetization of the film rapidly increases. The original cluster glass
behavior is further developed in the photoinduced state and shows substantial
changes in critical temperature and freezing temperature.Comment: 2 pages, 2 figures, 1 table, International Conference on Magnetism
200
Identification of a novel angiotensin-I-converting enzyme inhibitory peptide corresponding to a tryptic fragment of bovine Ć-lactoglobulin
peer-reviewedThe angiotensin-I-converting enzyme (ACE) inhibitory activity of a tryptic digest of bovine Ī²-lactoglobulin (Ī²-lg) was investigated. Intact Ī²-lg essentially did not inhibit ACE while the tryptic digest gave an 84.3% inhibition of ACE. Peptide material eluting between 20 and 25% acetonitrile during C18 solid-phase extraction of the Ī²-lg tryptic digest inhibited ACE by 93.6%. This solid-phase extraction fraction was shown by mass spectroscopy to contain Ī²-lg f(142ā148). This peptide had an ACE IC50 value of 42.6 Ī¼mol/l. The peptide was resistant to further digestion with pepsin and was hydrolysed to a very low extent with chymotrypsin. The contribution of specific amino acid residues within the peptide to ACE inhibitory activity and the potential application of this peptide as a nutraceutical is discussed
Magnetodielectric coupling of infrared phonons in single crystal CuOSeO
Reflection and transmission as a function of temperature have been measured
on a single crystal of the magnetoelectric ferrimagnetic compound
CuOSeO utilizing light spanning the far infrared to the visible
portions of the electromagnetic spectrum. The complex dielectric function and
optical properties were obtained via Kramers-Kronig analysis and by fits to a
Drude-Lortentz model. The fits of the infrared phonons show a magnetodielectric
effect near the transition temperature (~K). Assignments to
strong far infrared phonon modes have been made, especially those exhibiting
anomalous behavior around the transition temperature
- ā¦