172 research outputs found
Correlation between the Extraordinary Hall Effect and Resistivity
We study the contribution of different types of scattering sources to the
extraordinary Hall effect. Scattering by magnetic nano-particles embedded in
normal-metal matrix, insulating impurities in magnetic matrix, surface
scattering and temperature dependent scattering are experimentally tested. Our
new data, as well as previously published results on a variety of materials,
are fairly interpreted by a simple modification of the skew scattering model
A hepatitis C avidity test for determining recent and past infections in both plasma and dried blood spots
DBS testing has been used successfully to detect HCV antibody positive individuals. Determining how long someone has been infected is important for surveillance initiatives. Antibody avidity is a method that can be used to calculate recency of infection. A HCV avidity assay was evaluated for both plasma and DBS. Study design: To measure antibody avidity a commercial HCV ELISA was modified using 7 M urea. The plasma samples were split into: group 1 (recently infected N = 19), group 2 (chronic carrier N = 300) and group 3 (resolved infection N = 82). Mock DBS made from group 1 (N = 12), group 2 (N = 50), group 3 (N = 25) and two seroconverter panels were evaluated. 133 DBS taken from patients known to have a resolved infection or be a chronic carrier were also tested. The avidity assay cut-off was set at AI ≤ 30 for a recent infection. Using sequential samples the assay could detect a recent infection in the first 4–5 months from the point of infection. Most of the false positive results (AI < 30 among cases known not to have had recent infection) were detected among known resolved infections, in both the plasma and DBS; as a result, a testing algorithm has been designed incorporating both PCR and two dilution factors. The sensitivity and specificity of the assay on plasma was 100% and 99.3%, respectively, while DBS had 100% sensitivity and 98.3% specificity. The HCV avidity assay can be used to distinguish between chronic and recent infection using either plasma or DBS as the sample type
Interface magnetic anisotropy in cobalt clusters embedded in a platinum or niobium matrix
A low concentration of cobalt clusters with a fcc structure and containing
almost one thousand atoms are embedded in two different metallic matrices:
platinum and niobium. Samples have been prepared using a co-deposition
technique. Cobalt clusters preformed in the gas phase and matrix atoms are
simultaneously deposited on a silicon substrate under Ultra High Vacuum
conditions. This original technique allows to prepare nanostructured systems
from miscible elements such as Co/Pt and Co/Nb in which clusters keep a pure
cobalt core surrounded with an alloyed interface. Magnetic measurements
performed using a Vibrating Sample Magnetometer (VSM) reveal large differences
in the magnetic properties of cobalt clusters in Pt and Nb pointing out the key
role of cluster/matrix interfaces.Comment: 7 pages (LaTeX), 12 PostScript figures, 1 PostScript tabl
Magnetic Anisotropy of a Single Cobalt Nanoparticle
Using a new microSQUID set-up, we investigate magnetic anisotropy in a single
1000-atoms cobalt cluster. This system opens new fields in the characterization
and the understanding of the origin of magnetic anisotropy in such
nanoparticles. For this purpose, we report three-dimensional switching field
measurements performed on a 3 nm cobalt cluster embedded in a niobium matrix.
We are able to separate the different magnetic anisotropy contributions and
evidence the dominating role of the cluster surface.Comment: 4 pages, 8 figure
In-field evaluation of Xpert® HCV viral load fingerstick assay in people who inject drugs in Tanzania
Background Although novel hepatitis C (HCV) RNA point-of-care technology has the potential to enhance diagnosis in resource-limited settings, very little real-world validation of their utility exists. We evaluate the performance of HCV RNA quantification using the Xpert® HCV Viral Load Fingerstick assay (Xpert® HCV VL Fingerstick assay) as compared to the WHO pre-qualified plasma Xpert® HCV viral load assay among people who inject drugs (PWID) attending an opioid agonist therapy (OAT) clinic in Dar-es-Salaam, Tanzania. Methods Between December 2018 and February 2019 consecutive HCV seropositive PWID attending the OAT clinic provided paired venous and finger-stick samples for HCV RNA quantification. These were processed on-site using the GeneXpert® platform located at the Central tuberculosis reference laboratory. Results A total of 208 out of 220 anti-HCV positive participants recruited (94.5%) had a valid Xpert® HCV VL result available; 126 (61%; (95% CI 53.8-67.0) had detectable and quantifiable HCV RNA. 188 (85%) had paired plasma and finger-stick whole blood samples; the sensitivity and specificity for the quantification of HCV RNA levels were 99.1% and 98.7% respectively. There was an excellent correlation (R2=0.95) and concordance (mean difference 0.13 IU/mL, (95% CI -0.9 to 0.16 IU/mL) in HCV RNA levels between plasma samples and finger-stick samples. Conclusion This study found excellent performance of the Xpert® HCV VL Fingerstick assay for HCV RNA detection and quantification in an African-field setting. Its clinical utility represents an important watershed in overcoming existing challenges to HCV diagnosis, which should play a crucial role in HCV elimination in Africa
P07-11 LB. Impact of highly active antiretroviral therapy on cell-free and cell-associated HIV-1 in cervicovaginal secretions and blood
Structure and Magnetism of well-defined cobalt nanoparticles embedded in a niobium matrix
Our recent studies on Co-clusters embedded in various matrices reveal that
the co-deposition technique (simultaneous deposition of two beams : one for the
pre-formed clusters and one for the matrix atoms) is a powerful tool to prepare
magnetic nanostructures with any couple of materials even though they are
miscible. We study, both sharply related, structure and magnetism of the Co/Nb
system. Because such a heterogeneous system needs to be described at different
scales, we used microscopic and macroscopic techniques but also local selective
absorption ones. We conclude that our clusters are 3 nm diameter f.c.c
truncated octahedrons with a pure cobalt core and a solid solution between Co
and Nb located at the interface which could be responsible for the magnetically
inactive monolayers we found. The use of a very diluted Co/Nb film, further
lithographed, would allow us to achieve a pattern of microsquid devices in view
to study the magnetic dynamics of a single-Co cluster.Comment: 7 TeX pages, 9 Postscript figures, detailed heading adde
New Speakers and Language Revitalisation: Arpitan and Community (Re)formation
Today, it is uncontroversial to claim that France’s regional (minority) languages (RLs) are in decline. However, revitalisation movements have nonetheless continued to surface, and this chapter considers one by-product of such efforts: the emergence of new speakers in RL contexts. The term ‘new speaker’ refers to individuals who acquire the target language not through traditional transmission contexts (e.g. home, family), but instead as adults through language revitalisation initiatives. The chapter focuses on revitalisation efforts in the context of Francoprovençal, a severely endangered and understudied RL spoken transnationally across French, Italian and Swiss borders. A critical examination of current studies supplemented with recently collected empirical data shows new speakers to be central agents in a movement championing proto-nation-statehood across national borders, reorienting the region’s traditional sociolinguistic field
Exploring contested authenticity among speakers of a contested language: the case of ‘Francoprovençal'
This paper explores the notion of speaker authenticity in the context of obsolescent ‘Francoprovençal’: a highly fragmented grouping of Romance varieties spoken in parts of France, Italy, and Switzerland by less than 1% of the total regional population. While Francoprovençal has long been losing ground to the dominant language(s) with which it is in contact, new speakers have begun to emerge within the context of revitalisation movements and activities geared more favourable language planning policies and increased literacy. The emergence of these new speakers has polarised native-speaker communities, and has blurred the lines associated with the traditional view of sociolinguistic authenticity. Through an analysis of qualitative data collected in 2012, this article argues in particular that it may not be sufficient to simply examine contested authenticities from a native–non-native perspective, but rather it is important to consider how new speakers might themselves form a complex spectrum of speaker types with new sets of tensions as has been argued elsewhere
Comparison of Serum HBsAg Quantitation by Four Immunoassays, and Relationships of HBsAg Level with HBV Replication and HBV Genotypes
BACKGROUND: The decline in hepatitis B virus surface antigen (HBsAg) may be an early predictor of the viral efficacy of Hepatitis B virus (HBV) therapy. The HBsAg levels obtained by different immunoassays now need comparing and the relationships between levels of HBsAg and HBV DNA alongside HBsAg and genotype must be evaluated. METHODOLOGY/PRINCIPAL FINDINGS: HBsAg levels were compared among 80 patients using the Abbott Architect assay, a commercial immunoassay approved for HBsAg detection and quantitation, and three other assays derived from immunoassays approved for HBsAg detection (manufactured by Diasorin, Bio-Rad and Roche). Good correlation was found between the Abbot vs. Diasorin, Bio-Rad and Roche assays with narrow 95% limits of agreement and small mean differences: -0.06 to 0.11, -0.09 log(10) IU/mL; -0.57 to 0.64, -0.04 log(10) IU/mL; -0.09 to 0.45, -0.27 log(10) IU/mL, respectively. These agreements were not affected by genotypes A or D. HBsAg was weakly correlated with HBV DNA, whatever the HBsAg assay used: Abbott, ρ = 0.36 p = 0.001, Diasorin ρ = 0.34, p = 0.002; Bio-Rad ρ = 0.37, p<0.001; or Roche ρ = 0.41, p<0.001. This relationship between levels of HBsAg and HBV DNA seemed to depend on genotypes. Whereas HBsAg (Abbott assay) tended to correlate with HBV DNA for genotype A (ρ = 0.44, p = 0.02), no such correlation was significant for genotypes D (ρ = 0.29, p = 0.15). CONCLUSION/SIGNIFICANCE: The quantitation of HBsAg in routine clinical samples is comparable between the reference assay and the adapted assays with acceptable accuracy limits, low levels of variability and minimum discrepancy. While HBsAg quantitation is not affected by HBV genotype, the observed association between levels of HBsAg and HBV DNA seems genotype dependent
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