1,617 research outputs found
Destruction of chain-superconductivity in YBa_2Cu_4O_8 in a weak magnetic field
We report measurements of the temperature dependent components of the
magnetic penetration depth {\lambda}(T) in single crystal samples of
YBa_2Cu_4O_8 using a radio frequency tunnel diode oscillator technique. We
observe a downturn in {\lambda}(T) at low temperatures for currents flowing
along the b and c axes but not along the a axis. The downturn in {\lambda}_b is
suppressed by a small dc field of ~0.25 T. This and the zero field anisotropy
of {\lambda}(T) likely result from proximity induced superconducting on the CuO
chains, however we also discuss the possibility that a significant part of the
anisotropy might originate from the CuO2 planes.Comment: 5 page
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The effect of direct thermal method, temperature and time on microstructure of a cast aluminum alloy
The direct thermal method is used for the creation of globular microstructures suitable for semi-solid metal forming. In this paper both simulation and experimental results using direct thermal method are presented. ProCAST® software was used to estimate temperature distribution inside the aluminium billet. In validation work, molten aluminium A356 was poured into metallic copper tube moulds and cooled down to the semi-solid temperature before being quenched in water at room temperature. The effect of pouring temperatures of 630°C, 650°C, 665°C, 680°C and holding times of 45s and 60s on the microstructure of aluminium A356 alloy were investigated. The simulation results showed that the average temperature rate within the copper mould, from initial pouring temperature to just before quenching, was approximately 1°C/s. Examination of the solidified microstructures showed that the microstructure was more spherical when lower pouring temperatures and holding periods were used. From the micrographs it was found that the most globular and smallest structures were achieved at processing parameters of 630°C and 45s
a systematic review protocol
Introduction Varicella zoster virus (VZV) causes varicella (chicken pox) and
herpes zoster (shingles). Worldwide, these diseases are associated with
significant morbidity. Most of the epidemiological data on VZV come from high
income countries. There are few data on VZV in Africa, where tropical climates
and high HIV/AIDS prevalence rates are expected to impact the epidemiology of
VZV. Safe and effective vaccinations for both varicella and herpes zoster
exist, but are not routinely used in Africa. There are very few data available
on VZV disease burden in Africa to guide the introduction of these vaccines on
the continent. Our aim is to conduct a systematic review of the VZV-associated
morbidity and mortality in Africa, which will provide critical information
that could be used to develop vaccination policies against these diseases in
Africa. Methods and analysis Electronic databases will be searched and all
studies published after 1974 that meet predefined criteria will be assessed.
The primary outcomes for the study are VZV incidence/prevalence,
hospitalisation rates and total death rates. The secondary outcome for this
study is the proportion of VZV hospitalisations and/or deaths associated with
HIV/AIDS. Two reviewers will screen the titles and abstracts, and then
independently review the full texts, to determine if studies are eligible for
inclusion. A risk of bias and quality assessment tool will be used to score
all included studies. Following standardised data extraction, a trend analysis
using R-programming software will be conducted to investigate the trend of
VZV. Depending on the characteristics of included studies, subgroup analyses
will be performed. This review will be reported according to the Preferred
Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.
Ethics and dissemination As this is a protocol for a systematic review, which
will use already published data, no ethics approval is required. Findings will
be disseminated in peer-reviewed journals. Trial registration number
CRD4201502614
The 3D printing of a polymeric electrochemical cell body and its characterisation
An undivided flow cell was designed and constructed using additive manufacturing technology and its mass transport characteristics were evaluated using the reduction of ferricyanide, hexacyanoferrate (III) ions at a nickel surface. The dimensionless mass transfer correlation Sh = aRebScdLee was obtained using the convective-diffusion limiting current observed in linear sweep voltammetry; this correlation compared closely with that reported in the literature from traditionally machined plane parallel rectangular flow channel reactors. The ability of 3D printer technology, aided by computational graphics, to rapidly and conveniently design, manufacture and re-design the geometrical characteristics of the flow cell ishighlighted
Sports review: A content analysis of the International Review for the Sociology of Sport, the Journal of Sport and Social Issues and the Sociology of Sport Journal across 25 years
The International Review for the Sociology of Sport, the Journal of Sport and Social Issues and Sociology of Sport Journal have individually and collectively been subject to a systematic content analysis. By focusing on substantive research papers published in these three journals over a 25-year time period it is possible to identify the topics that have featured within the sociology of sport. The purpose of the study was to identify the dominant themes, sports, countries, methodological frameworks and theoretical perspectives that have appeared in the research papers published in these three journals. Using the terms, identified by the author(s), that appear in the paper’s title, abstract and/or listed as a key word, subject term or geographical term, a baseline is established to reflect on the development of the sub-discipline as represented by the content of these three journals. It is suggested that the findings illustrate what many of the more experienced practitioners in the field may have felt subjectively. On the basis of this systematic, empirical study it is now possible to identify those areas have received extensive coverage and those which are under-researched within the sociology of sport. The findings are used to inform a discussion of the role of academic journals and the recent contributions made by Michael Silk, David Andrews, Michael Atkinson and Dominic Malcolm on the past, present and future of the ‘sociology of sport’
Neutron interferometric measurement of the scattering length difference between the triplet and singlet states of n-He
We report a determination of the n-He scattering length difference
(
(statistical) (systematic)) fm between the triplet and singlet
states using a neutron interferometer. This revises our previous result (-5.610 (statistical) (systematic)
fm obtained using the same technique in 2008. This revision is due to a
re-analysis of the 2008 experiment that includes a more robust treatment of the
phase shift caused by magnetic field gradients near the He cell.
Furthermore, we more than doubled our original data set from 2008 by acquiring
six months of additional data in 2013. Both the new data set and a re-analysis
of the older data are in good agreement. Scattering lengths of low Z isotopes
are valued for use in few-body nuclear effective field theories, provide
important tests of modern nuclear potential models and in the case of He
aid in the interpretation of neutron scattering from quantum liquids. The
difference was determined by measuring the relative phase
shift between two incident neutron polarizations caused by the spin-dependent
interaction with a polarized He target. The target He gas was sealed
inside a small, flat windowed glass cell that was placed in one beam path of
the interferometer. The relaxation of He polarization was monitored
continuously with neutron transmission measurements. The neutron polarization
and spin flipper efficiency were determined separately using He analyzers
and two different polarimetry analysis methods. A summary of the measured
scattering lengths for n-He with a comparison to nucleon interaction models
is given
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