Specific Heat of Liquid Helium in Zero Gravity very near the Lambda Point

We report the details and revised analysis of an experiment to measure the specific heat of helium with subnanokelvin temperature resolution near the lambda point. The measurements were made at the vapor pressure spanning the region from 22 mK below the superfluid transition to 4 uK above. The experiment was performed in earth orbit to reduce the rounding of the transition caused by gravitationally induced pressure gradients on earth. Specific heat measurements were made deep in the asymptotic region to within 2 nK of the transition. No evidence of rounding was found to this resolution. The optimum value of the critical exponent describing the specific heat singularity was found to be a = -0.0127+ - 0.0003. This is bracketed by two recent estimates based on renormalization group techniques, but is slightly outside the range of the error of the most recent result. The ratio of the coefficients of the leading order singularity on the two sides of the transition is A+/A- =1.053+ - 0.002, which agrees well with a recent estimate. By combining the specific heat and superfluid density exponents a test of the Josephson scaling relation can be made. Excellent agreement is found based on high precision measurements of the superfluid density made elsewhere. These results represent the most precise tests of theoretical predictions for critical phenomena to date.Comment: 27 Pages, 20 Figure

Should adults with mild head injury who are receiving direct oral anticoagulants undergo computed tomography scanning? A systematic review

Study objective: Patients receiving direct oral anticoagulant medications commonly undergo computed tomography head scanning after mild traumatic brain injury, regardless of symptoms or signs. International guidelines have noted a lack of evidence to support management decisions for such patients. This systematic review aims to identify, appraise, and synthesize the current evidence for the risk of adverse outcome in patients receiving direct oral anticoagulants after mild head injury. Methods: A protocol was registered with PROSPERO and review methodology followed Cochrane Collaboration recommendations. Studies of adult patients with mild head injury (Glasgow Coma Scale score 13 to 15) and who were receiving direct oral anticoagulants that reported the risk of adverse outcome after the head injury were eligible for inclusion. A comprehensive range of bibliographic databases and gray literature was examined with a sensitive search strategy. Selection of eligible studies, data extraction, and risk of bias were evaluated independently by separate reviewers. A random-effects meta-analysis was used to provide a pooled estimate of the risk of adverse outcome. The overall quality of evidence was assessed with the Grading of Recommendations Assessment, Development and Evaluation Working Group approach. Results: A total of 4,886 articles were screened for inclusion, of which 7 cohort studies including 346 patients met inclusion criteria. All studies were at high or unclear risk of bias as a result of selection and information bias. Estimates of adverse outcome (any death, intracranial hematoma, or neurosurgery) ranged from 0.0% to 8.3%. A random-effects meta-analysis showed a weighted composite outcome risk of 3.7% (95% confidence interval 1.7% to 5.8%; I2=3.3%). The overall quality of the body of evidence was low as a result of imprecision, indirectness, and risk of bias. Conclusion: There are limited data available to characterize the risk of adverse outcome in patients receiving direct oral anticoagulants after mild traumatic brain injury. A sufficiently powered prospective cohort study is required to validly define this risk, identify clinical features predictive of adverse outcome, and inform future head injury guidelines

Quorum-sensing blockade as a strategy for enhancing host defences against bacterial pathogens

Conventional antibiotics target the growth and the basal life processes of bacteria leading to growth arrest and cell death. The selective force that is inherently linked to this mode of action eventually selects out antibiotic-resistant variants. The most obvious alternative to antibiotic-mediated killing or growth inhibition would be to attenuate the bacteria with respect to pathogenicity. The realization that Pseudomonas aeruginosa, and a number of other pathogens, controls much of their virulence arsenal by means of extracellular signal molecules in a process denoted quorum sensing (QS) gave rise to a new ‘drug target rush’. Recently, QS has been shown to be involved in the development of tolerance to various antimicrobial treatments and immune modulation. The regulation of virulence via QS confers a strategic advantage over host defences. Consequently, a drug capable of blocking QS is likely to increase the susceptibility of the infecting organism to host defences and its clearance from the host. The use of QS signal blockers to attenuate bacterial pathogenicity, rather than bacterial growth, is therefore highly attractive, particularly with respect to the emergence of multi-antibiotic resistant bacteria