71 research outputs found
Improved Laboratory Transition Probabilities for Neutral Chromium and Re-determination of the Chromium Abundance for the Sun and Three Stars
Branching fraction measurements from Fourier transform spectra in conjunction
with published radiative lifetimes are used to determine transition
probabilities for 263 lines of neutral chromium. These laboratory values are
employed to derive a new photospheric abundance for the Sun: log (Cr
I) = 5.640.01 (). These Cr I solar abundances do
not exhibit any trends with line strength nor with excitation energy and there
were no obvious indications of departures from LTE. In addition, oscillator
strengths for singly-ionized chromium recently reported by the FERRUM Project
are used to determine: log (Cr II) = 5.770.03 (). Transition probability data are also applied to the spectra of three
stars: HD 75732 (metal-rich dwarf), HD 140283 (metal-poor subgiant), and CS
22892-052 (metal-poor giant). In all of the selected stars, Cr I is found to be
underabundant with respect to Cr II. The possible causes for this abundance
discrepancy and apparent ionization imbalance are discussed.Comment: 44 pages, 6 figure
High Q^2 Deep Inelastic Scattering at HERA
High Q^2 NC and CC cross-sections as measured at HERA can give information on
two distinct areas of current interest. Firstly, supposing that all the
electroweak parameters are well known, these cross-sections may be used to give
information on parton distributions at high x and high Q^2. Secondly, supposing
that parton distributions are well known, after evolution in Q^2 from the
kinematic regime where they are already measured, these cross-sections can be
used to give information on electroweak parameters in a process where the
exchanged boson is `spacelike' rather than `timelike'. WG1 addressed itself to
clarifying the limits of our present and possible future knowledge on both
these areas.Comment: 26 pages, 12 figures. Uses iopart.cls, iopart12.clo, axodraw.sty.
Report of WG1 of the 3rd UK Phenomenology Workshop on HERA Physics, Durham
1998. To be published in Journal of Physics
Factors contributing to delay in parasite clearance in uncomplicated falciparum malaria in children
Background: Drug resistance in Plasmodium falciparum is common in many endemic and other settings but there
is no clear recommendation on when to change therapy when there is delay in parasite clearance after initiation
of therapy in African children.
Methods: The factors contributing to delay in parasite clearance, defined as a clearance time > 2 d, in falciparum
malaria were characterized in 2,752 prospectively studied children treated with anti-malarial drugs between 1996
and 2008.
Results: 1,237 of 2,752 children (45%) had delay in parasite clearance. Overall 211 children (17%) with delay in
clearance subsequently failed therapy and they constituted 72% of those who had drug failure, i.e., 211 of 291
children. The following were independent risk factors for delay in parasite clearance at enrolment: age less than or
equal to 2 years (Adjusted odds ratio [AOR] = 2.13, 95% confidence interval [CI]1.44-3.15, P < 0.0001), presence of
fever (AOR = 1.33, 95% CI = 1.04-1.69, P = 0.019), parasitaemia >50,000/ul (AOR = 2.21, 95% CI = 1.77-2.75,
P < 0.0001), and enrolment before year 2000 (AOR= 1.55, 95% CI = 1.22-1.96, P < 0.0001). Following treatment,
a body temperature ≥ 38°C and parasitaemia > 20000/μl a day after treatment began, were independent risk
factors for delay in clearance. Non-artemisinin monotherapies were associated with delay in clearance and
treatment failures, and in those treated with chloroquine or amodiaquine, with pfmdr 1/pfcrt mutants. Delay in
clearance significantly increased gametocyte carriage (P < 0.0001).
Conclusion: Delay in parasite clearance is multifactorial, is related to drug resistance and treatment failure in
uncomplicated malaria and has implications for malaria control efforts in sub-Saharan Africa
Interchromosomal Duplications on the Bactrocera oleae Y Chromosome Imply a Distinct Evolutionary Origin of the Sex Chromosomes Compared to Drosophila
BACKGROUND: Diptera have an extraordinary variety of sex determination mechanisms, and Drosophila melanogaster is the paradigm for this group. However, the Drosophila sex determination pathway is only partially conserved and the family Tephritidae affords an interesting example. The tephritid Y chromosome is postulated to be necessary to determine male development. Characterization of Y sequences, apart from elucidating the nature of the male determining factor, is also important to understand the evolutionary history of sex chromosomes within the Tephritidae. We studied the Y sequences from the olive fly, Bactrocera oleae. Its Y chromosome is minute and highly heterochromatic, and displays high heteromorphism with the X chromosome. METHODOLOGY/PRINCIPAL FINDINGS: A combined Representational Difference Analysis (RDA) and fluorescence in-situ hybridization (FISH) approach was used to investigate the Y chromosome to derive information on its sequence content. The Y chromosome is strewn with repetitive DNA sequences, the majority of which are also interdispersed in the pericentromeric regions of the autosomes. The Y chromosome appears to have accumulated small and large repetitive interchromosomal duplications. The large interchromosomal duplications harbour an importin-4-like gene fragment. Apart from these importin-4-like sequences, the other Y repetitive sequences are not shared with the X chromosome, suggesting molecular differentiation of these two chromosomes. Moreover, as the identified Y sequences were not detected on the Y chromosomes of closely related tephritids, we can infer divergence in the repetitive nature of their sequence contents. CONCLUSIONS/SIGNIFICANCE: The identification of Y-linked sequences may tell us much about the repetitive nature, the origin and the evolution of Y chromosomes. We hypothesize how these repetitive sequences accumulated and were maintained on the Y chromosome during its evolutionary history. Our data reinforce the idea that the sex chromosomes of the Tephritidae may have distinct evolutionary origins with respect to those of the Drosophilidae and other Dipteran families
Genomic epidemiology of COVID-19 in care homes in the east of England
Funder: National Institute for Health Research; FundRef: http://dx.doi.org/10.13039/501100000272COVID-19 poses a major challenge to care homes, as SARS-CoV-2 is readily transmitted and causes disproportionately severe disease in older people. Here, 1167 residents from 337 care homes were identified from a dataset of 6600 COVID-19 cases from the East of England. Older age and being a care home resident were associated with increased mortality. SARS-CoV-2 genomes were available for 700 residents from 292 care homes. By integrating genomic and temporal data, 409 viral clusters within the 292 homes were identified, indicating two different patterns – outbreaks among care home residents and independent introductions with limited onward transmission. Approximately 70% of residents in the genomic analysis were admitted to hospital during the study, providing extensive opportunities for transmission between care homes and hospitals. Limiting viral transmission within care homes should be a key target for infection control to reduce COVID-19 mortality in this population
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Structure and sequence of the Cu,Zn Sod gene in the Mediterranean fruit fly, Ceratitis capitata: intron insertion/deletion and evolution of the gene.
We have cloned a 4-kb region encompassing the Cu,Zn superoxide dismutase (Sod) gene from a genomic library of the Mediterranean fruit fly, Ceratitis capitata, using a cDNA probe from Drosophila melanogaster. The coding sequence of 462 bases is equally as long as that in Drosophila species. The rate of amino acid replacement over the past 100 million years is approximately the same in the Diptera and in mammals, thus excluding the hypothesis (proposed to account for an apparent acceleration in rate of evolution of Sod over geological time) that the evolution of the SOD protein is much higher in the mammals than in other organisms. The coding region is interrupted by two introns in Ceratitis, whereas only one occurs in Drosophila. Phylogenetic comparisons indicate that the second intron was present in the common dipteran ancestor, but was lost shortly after the divergence of the Drosophila lineage from other Diptera. Analysis of the exon/intron structure of Sod in various animal phyla, plants, and fungi indicates that intron insertions as well as deletions have occurred in the evolution of the Sod gene
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