587 research outputs found

    An Ultra-High Time Resolution Cosmic-Ray Detection Mode for the Murchison Widefield Array

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    The radio-wavelength detection of extensive air showers (EASs) initiated by cosmic-ray interactions in the Earth's atmosphere is a promising technique for investigating the origin of these particles and the physics of their interactions. The Low-frequency Array (LOFAR) and the Owens Valley Long Wavelength Array (OVRO-LWA) have both demonstrated that the dense cores of low-frequency radio telescope arrays yield detailed information on the radiation ground pattern, which can be used to reconstruct key EAS properties and infer the primary cosmic-ray composition. Here, we demonstrate a new observation mode of the Murchison Widefield Array (MWA), tailored to the observation of the sub-microsecond coherent bursts of radiation produced by EAS. We first show how an aggregate 30.72MHz bandwidth (3072×10kHz frequency channels) recorded at 0.1ms resolution with the MWA's voltage capture system (VCS) can be synthesized back to the full bandwidth Nyquist resolution of 16.3ns. This process, which involves "inverting"two sets of polyphase filterbanks, retains 90.5% of the signal-to-noise of a cosmic-ray signal. We then demonstrate the timing and positional accuracy of this mode by resolving the location of a calibrator pulse to within 5m. Finally, preliminary observations show that the rate of nanosecond radio-frequency interference (RFI) events is 0.1Hz, much lower than that found at the sites of other radio telescopes that study cosmic rays. We conclude that the identification of cosmic rays at the MWA, and hence with the low-frequency component of the Square Kilometre Array, is feasible with minimal loss of efficiency due to RFI

    The Friedreich's ataxia mutation may originate from a premutation and shows size reduction when transmitted from parent to affected child

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    Most trinucleotide repeat mutations cause dominant or X linked neurological disorders and show progressive increase in size from affected parent to affected child, the basis of phenotypic anticipation. Friedreich's ataxia (FA) is a recessive disorder in which gene dysfunction is due to an expansion of a GAA trinucleotide repeat in intron one which reduces mRNA and protein levels. We confirm that the severity of the disorder in our population depends upon the repeat length of the smaller allele, to a point where those with smaller alleles may be mis-diagnosed with other conditions such as spastic paraparesis. Two brothers were found to be heterozygou1; for the expansion and a point mutation (G to T) which leads to G130V. These patients have an atypical clinical phenotype. From studying 81 transmissions.we demonstrate that the repeat number of the expansion in FA usually decreases in size from parent to affected child, and that this affect is particularly marked in the paternal allele. No expanded alleles were found in the range between 22 and 332 trinucleotides with one important exception, a carrier with an intermediate repeat size of approximately 100. When this allele was transmitted to the affected child, the repeat increased in size either probably to 538 or possible to 1036. Analysis of a sperm sample from this carrier showed a major band for the expanded allele of 320 repeats. These data suggest that there may be a premutation for Friedrelch's ataxia carriers, similar to that demonstrated for FraX-A and that expansion occurs in two stages, the first during meiosis followed by a second mitotic expansion

    The isolation and serology of the "FSA" Brucella melitensis Rev.1 mutant in a flock of sheep

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    A flock of sheep, known to be infected with the "FSA" mutant of Brucella melitensis Rev. 1, was examined serologically and bacteriologically to determine whether any relationship existed which would help in the control of this infection in the field. An attempt was also made to determine whether vertical transmission occurred. Twenty-one out of 62 sheep were bacteriologically positive. The best organs for isolation were the udder, supramammary lymphnodes and uterus. No significant relationship could be shown between the complement fixation test and bacterial isolation. The absence of any relationship between serological and bacteriological results agrees with a short-lived infection. None of the 24 lambs sacrificed at 5 months showed either serological reactions or were bacteriologically positive, thus no vertical transmission could be shown.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.lmchunu2014mn201

    Actinobacillus pleuropneumoniae serovar 8 predominates in England and Wales

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    This work was supported by a Longer and Larger (LoLa) grant from the Biotechnology and Biological Sciences Research Council (BBSRC grant numbers BB/G020744/1, BB/G019177/1, BB/G019274/1 and BB/G018553/1) and Zoetis (formerly Pfizer Animal Health) awarded to the Bacterial Respiratory Diseases of Pigs-1 Technology (BRaDP1T) Consortium

    Foliations of Isonergy Surfaces and Singularities of Curves

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    It is well known that changes in the Liouville foliations of the isoenergy surfaces of an integrable system imply that the bifurcation set has singularities at the corresponding energy level. We formulate certain genericity assumptions for two degrees of freedom integrable systems and we prove the opposite statement: the essential critical points of the bifurcation set appear only if the Liouville foliations of the isoenergy surfaces change at the corresponding energy levels. Along the proof, we give full classification of the structure of the isoenergy surfaces near the critical set under our genericity assumptions and we give their complete list using Fomenko graphs. This may be viewed as a step towards completing the Smale program for relating the energy surfaces foliation structure to singularities of the momentum mappings for non-degenerate integrable two degrees of freedom systems.Comment: 30 pages, 19 figure

    Functional diversity of chemokines and chemokine receptors in response to viral infection of the central nervous system.

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    Encounters with neurotropic viruses result in varied outcomes ranging from encephalitis, paralytic poliomyelitis or other serious consequences to relatively benign infection. One of the principal factors that control the outcome of infection is the localized tissue response and subsequent immune response directed against the invading toxic agent. It is the role of the immune system to contain and control the spread of virus infection in the central nervous system (CNS), and paradoxically, this response may also be pathologic. Chemokines are potent proinflammatory molecules whose expression within virally infected tissues is often associated with protection and/or pathology which correlates with migration and accumulation of immune cells. Indeed, studies with a neurotropic murine coronavirus, mouse hepatitis virus (MHV), have provided important insight into the functional roles of chemokines and chemokine receptors in participating in various aspects of host defense as well as disease development within the CNS. This chapter will highlight recent discoveries that have provided insight into the diverse biologic roles of chemokines and their receptors in coordinating immune responses following viral infection of the CNS

    The Use of Preoperative Prophylactic Systemic Antibiotics for the Prevention of Endopthalmitis in Open Globe Injuries:A Meta-Analysis

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    Topic:This study reports the effect of systemic prophylactic antibiotics (and their route) on the risk of endophthalmitis after open globe injury. Clinical relevance:Endophthalmitis is a major complication of open globe injury, it can lead to rapid sight loss in the affected eye. The administration of systemic antibiotic prophylaxis is common practice in some health care systems, although there is no consensus on their use. PubMed, CENTRAL, Web of Science, CINAHL and Embase were searched. This was completed 6th July 2021 and updated 10th Dec 2022. We included randomised and non-randomised prospective studies which reported the rate of post-open globe injury endophthalmitis, when systemic pre-operative antibiotic prophylaxis (via the oral or intravenous route) was given. The Cochrane Risk of Bias tool and ROBINS-I tool were used for assessing the risk of bias. Where meta-analysis was performed results were reported as odds ratio. PROSPERO registration: CRD42021271271. Three studies were included. One prospective observational study compared outcomes of patients who had received systemic or no systemic pre-operative antibiotics. The endophthalmitis rates reported were 3.75% and 4.91% in the systemic and no systemic pre-operative antibiotics groups, a non-significant difference (p = 0.68). Two randomised controlled trials were included (1,555 patients). The rates of endophthalmitis were 17 events in 751 patients (2.26%) and 17 events in 804 patients (2.11%) in the oral antibiotics and intravenous (+/- oral) antibiotics groups, respectively. Meta-analysis demonstrated no significant differences between groups (OR 1.07 [95% confidence interval 0.54 – 2.12]). The incidences of endophthalmitis after open globe injury were low with and without systemic antibiotic prophylaxis, although high risk cases were excluded in the included studies. When antibiotic prophylaxis is considered, there is moderate evidence that oral antibiotic administration is non-inferior to intravenous

    The Risk of Sympathetic Ophthalmia Associated with Open-Globe Injury Management Strategies:A Meta-analysis

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    Topic: Sympathetic ophthalmia (SO) is a sight-threatening granulomatous panuveitis caused by a sensitizing event. Primary enucleation or primary evisceration, versus primary repair, as a risk management strategy after open-globe injury (OGI) remains controversial.Clinical Relevance: This systematic review was conducted to report the incidence of SO after primary repair compared with that of after primary enucleation or primary evisceration. This enabled the reporting of an estimated number needed to treat.Methods: Five journal databases were searched. This review was registered with International Prospective Register of Systematic Reviews (identifier, CRD42021262616). Searches were carried out on June 29, 2021, and were updated on December 10, 2022. Prospective or retrospective studies that reported outcomes (including SO or lack of SO) in a patient population who underwent either primary repair and primary enucleation or primary evisceration were included. A systematic review and meta-analysis were carried out in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Random effects modelling was used to estimate pooled SO rates and absolute risk reduction (ARR).Results: Eight studies reporting SO as an outcome were included in total. The included studies contained 7500 patients and 7635 OGIs. In total, 7620 OGIs met the criteria for inclusion in this analysis; SO developed in 21 patients with OGI. When all included studies were pooled, the estimated SO rate was 0.12% (95% confidence interval [CI], 0.00%–0.25%) after OGI. Of 779 patients who underwent primary enucleation or primary evisceration, no SO cases were reported, resulting in a pooled SO estimate of 0.05% (95% CI, 0.00%–0.21%). For primary repair, the pooled estimate of SO rate was 0.15% (95% CI, 0.00%–0.33%). The ARR using a random effects model was −0.0010 (in favour of eye removal; 95% CI, −0.0031 [in favor of eye removal] to 0.0011 [in favor of primary repair]). Grading of Recommendations, Assessment, Development, and Evaluations analysis highlighted a low certainty of evidence because the included studies were observational, and a risk of bias resulted from missing data.Discussion: Based on the available data, no evidence exists that primary enucleation or primary evisceration reduce the risk of secondary SO.Financial Disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article

    Multiwavelength studies of MHD waves in the solar chromosphere: An overview of recent results

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    The chromosphere is a thin layer of the solar atmosphere that bridges the relatively cool photosphere and the intensely heated transition region and corona. Compressible and incompressible waves propagating through the chromosphere can supply significant amounts of energy to the interface region and corona. In recent years an abundance of high-resolution observations from state-of-the-art facilities have provided new and exciting ways of disentangling the characteristics of oscillatory phenomena propagating through the dynamic chromosphere. Coupled with rapid advancements in magnetohydrodynamic wave theory, we are now in an ideal position to thoroughly investigate the role waves play in supplying energy to sustain chromospheric and coronal heating. Here, we review the recent progress made in characterising, categorising and interpreting oscillations manifesting in the solar chromosphere, with an impetus placed on their intrinsic energetics.Comment: 48 pages, 25 figures, accepted into Space Science Review
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