34 research outputs found
Recent developments in the characterization of superconducting films by microwaves
We describe and analyze selected surface impedance data recently obtained by
different groups on cuprate, ruthenate and diboride superconducting films on
metallic and dielectric substrates for fundamental studies and microwave
applications. The discussion includes a first review of microwave data on MgB2,
the weak-link behaviour of RABiTS-type YBa2Cu3O7-d tapes, and the observation
of a strong anomalous power-dependence of the microwave losses in MgO at low
temperatures. We demonstrate how microwave measurements can be used to
investigate electronic, magnetic, and dielectric dissipation and relaxation in
the films and substrates. The impact of such studies reaches from the
extraction of microscopic information to the engineering of materials and
further on to applications in power systems and communication technology.Comment: Invited contribution to EUCAS2001, accepted for publication in
Physica C in its present for
In-situ characterization of metal clusters supported on a birefringent substrate using reflectance difference spectroscopy
Accelarated immune ageing is associated with COVID-19 disease severity
Background
The striking increase in COVID-19 severity in older adults provides a clear example of immunesenescence, the age-related remodelling of the immune system. To better characterise the association between convalescent immunesenescence and acute disease severity, we determined the immune phenotype of COVID-19 survivors and non-infected controls.
Results
We performed detailed immune phenotyping of peripheral blood mononuclear cells isolated from 103 COVID-19 survivors 3–5 months post recovery who were classified as having had severe (n = 56; age 53.12 ± 11.30 years), moderate (n = 32; age 52.28 ± 11.43 years) or mild (n = 15; age 49.67 ± 7.30 years) disease and compared with age and sex-matched healthy adults (n = 59; age 50.49 ± 10.68 years). We assessed a broad range of immune cell phenotypes to generate a composite score, IMM-AGE, to determine the degree of immune senescence. We found increased immunesenescence features in severe COVID-19 survivors compared to controls including: a reduced frequency and number of naïve CD4 and CD8 T cells (p < 0.0001); increased frequency of EMRA CD4 (p < 0.003) and CD8 T cells (p < 0.001); a higher frequency (p < 0.0001) and absolute numbers (p < 0.001) of CD28−ve CD57+ve senescent CD4 and CD8 T cells; higher frequency (p < 0.003) and absolute numbers (p < 0.02) of PD-1 expressing exhausted CD8 T cells; a two-fold increase in Th17 polarisation (p < 0.0001); higher frequency of memory B cells (p < 0.001) and increased frequency (p < 0.0001) and numbers (p < 0.001) of CD57+ve senescent NK cells. As a result, the IMM-AGE score was significantly higher in severe COVID-19 survivors than in controls (p < 0.001). Few differences were seen for those with moderate disease and none for mild disease. Regression analysis revealed the only pre-existing variable influencing the IMM-AGE score was South Asian ethnicity (
= 0.174, p = 0.043), with a major influence being disease severity (
= 0.188, p = 0.01).
Conclusions
Our analyses reveal a state of enhanced immune ageing in survivors of severe COVID-19 and suggest this could be related to SARS-Cov-2 infection. Our data support the rationale for trials of anti-immune ageing interventions for improving clinical outcomes in these patients with severe disease
Temperature Dependence of Intermodulation Distortion in YBCO: Understanding Nonlinearity
On the Power Handling Properties of High Temperature Superconducting Microwave Contiguous Duplexer
Distinction between pleural mesothelioma and pulmonary adenocarcinoma using MOC31 in an asbestos sprayer
Phylogenetic diversity and the conservation biogeography of African primates
Aim Phylogenetics has an important role in conservation biogeography.
However, there are few data on the phylogenetic diversity of African primates.
The phylogenetic diversity (PD) of a species is a measure of its taxonomic
distinctness and can be estimated by looking at the phylogenetic relationships
among taxa. Species-specific metrics on PD can then be used to determine
conservation priorities at various biogeographical scales. We used PD metrics to
rank 55 African primate species according to their conservation priorities at the
country level and within six African biogeographical regions. We also addressed
the following question: are there differences in conservation rankings between the
IUCN Red List and our PD metrics?
Location Africa.
Methods We created a consensus phylogeny for all African primate clades based
on genetic studies. Analyses of species distributions were determined using
presence/absence scores at two levels: country and biogeographical region.
A node-based method that standardizes for widespread taxa and endemicity was
used to calculate PD indices. Hierarchical cluster analysis was used to convert one
of the standardized, phylogenetic indices into three clusters that could be ranked
and compared with the main IUCN conservation rankings of endangered,
vulnerable, and lower risk.
Results At the country and region levels, the top-priority species in terms of PD are
Pan paniscus, Macaca sylvanus, Arctocebus calabarensis, Gorilla beringei, Arctocebus
aureus, Allenopithecus nigroviridis, Gorilla gorilla, Procolobus verus, Cercopithecus
solatus, Cercocebus galeritus, Colobus angolensis, Theropithecus gelada, Galagoides
zanzibaricus, Galagoides granti, and Procolobus (Piliocolobus) badius. Geographic
rankings were highest for the Democratic Republic of the Congo (country level) and
Central Africa (region level). Although there were no overall differences between
IUCN conservation ranks and the PD rankings, there were significant differences
between the two systems for vulnerable and endangered primate taxa.
Main conclusions There are few ecological and behavioural data on populations
of some of the African primates that represent the highest levels of phylogenetic
diversity. Studies of primate taxa with high PD rankings should focus on
identifying sites suitable for intensive studies of population densities, feeding
ecology, and reproductive behaviour. We suggest that PD metrics can serve as an
important, complementary data set in the IUCN ranking system for primates