Compton scattering in strong magnetic fields: Spin-dependent influences at the cyclotron resonance

The quantum electrodynamical (QED) process of Compton scattering in strong magnetic fields is commonly invoked in atmospheric and inner magnetospheric models of x-ray and soft gamma-ray emission in high-field pulsars and magnetars. A major influence of the field is to introduce resonances at the cyclotron frequency and its harmonics, where the incoming photon accesses thresholds for the creation of virtual electrons or positrons in intermediate states with excited Landau levels. At these resonances, the effective cross section typically exceeds the classical Thomson value by over 2 orders of magnitude. Near and above the quantum critical magnetic field of 44.13 TeraGauss, relativistic corrections must be incorporated when computing this cross section. This paper presents formalism for the QED magnetic Compton differential cross section valid for both subcritical and supercritical fields, yet restricted to scattered photons that are below pair creation threshold. Calculations are developed for the particular case of photons initially propagating along the field, mathematically simple specializations that are germane to interactions involving relativistic electrons frequently found in neutron star magnetospheres. This exposition of relativistic, quantum, magnetic Compton cross sections treats electron spin dependence fully, since this is a critical feature for describing the finite decay lifetimes of the intermediate states. The formalism employs both the Johnson and Lippmann (JL) wave functions and the Sokolov and Ternov (ST) electron eigenfunctions of the magnetic Dirac equation. The ST states are formally correct for self-consistently treating spin-dependent effects that are so important in the resonances. Relatively compact analytic forms for the cross sections are presented that will prove useful for astrophysical modelers.Comment: 45 pages, 10 figures, accepted for publication in Phys. Rev.

SO ORDERED: A Textual Analysis of United States’ Governors’ Press Release Responses to the COVID-19 Pandemic

The COVID-19 pandemic presents a unique environment from which each individual state, in the United States, has been forced to address their publics. In order to understand how each state has engaged with this pandemic, a textual analysis of each state’s governor’s first press release was conducted; five thematic trends were identified. Through use of the social trust approach to risk communication and the contingency theory of strategic conflict management (using external threat variables), the implications of these press releases are discussed

Deubiquitylating enzymes and disease

Deubiquitylating enzymes (DUBs) can hydrolyze a peptide, amide, ester or thiolester bond at the C-terminus of UBIQ (ubiquitin), including the post-translationally formed branched peptide bonds in mono- or multi-ubiquitylated conjugates. DUBs thus have the potential to regulate any UBIQ-mediated cellular process, the two best characterized being proteolysis and protein trafficking. Mammals contain some 80–90 DUBs in five different subfamilies, only a handful of which have been characterized with respect to the proteins that they interact with and deubiquitylate. Several other DUBs have been implicated in various disease processes in which they are changed by mutation, have altered expression levels, and/or form part of regulatory complexes. Specific examples of DUB involvement in various diseases are presented. While no specific drugs targeting DUBs have yet been described, sufficient functional and structural information has accumulated in some cases to allow their rapid development

Extracellular chloride is required for efficient activation of secondary signalling pathways during platelet aggregation

Anion channels perform a diverse range of functions and have been implicated in ATP release, volume regulation and phosphatidylserine exposure. Platelets have been shown to express several anion channels however their function is incompletely understood. Due to a paucity of specific pharmacological blockers, we investigated the global effect of extracellular chloride substitution on platelet activation using aggregometry and flow cytometry. In the absence of extracellular chloride we observed a modest effect on the maximum aggregation response to thrombin or collagen-related peptide. Although the rate of aggregation was substantially reduced in a manner that was dependent on the extracellular chloride concentration, aggregation in the absence of chloride was noticeably biphasic, indicative of impaired secondary signalling. This was further investigated by targeting secondary agonists with aspirin and apyrase or by blockade of the ADP receptor P2Y12. Under these conditions, the rates of aggregation were comparable to those recorded in the absence of extracellular chloride. Finally, we assessed platelet granule release by flow cytometry and report a chloride-dependent element of alpha, but not dense, granule secretion. Taken together these data support a role for anion channels in the efficient induction of platelet activation, likely via enhancement of secondary signalling pathways

Temporal inabilities and decision-making capacity in depression

We report on an interview-based study of decision-making capacity in two classes of patients suffering from depression. Developing a method of second-person hermeneutic phenomenology, we articulate the distinctive combination of temporal agility and temporal inability characteristic of the experience of severely depressed patients. We argue that a cluster of decision-specific temporal abilities is a critical element of decision-making capacity, and we show that loss of these abilities is a risk factor distinguishing severely depressed patients from mildly/moderately depressed patients. We explore the legal and clinical consequences of this result

Extracellular chloride is required for efficient platelet aggregation.

Anion channels perform a diverse range of functions and have been implicated in ATP release, volume regulation, and phosphatidylserine exposure. Platelets have been shown to express several anion channels but their function is incompletely understood. Due to a paucity of specific pharmacological blockers, we investigated the effect of extracellular chloride substitution on platelet activation using aggregometry and flow cytometry. In the absence of extracellular chloride, we observed a modest reduction of the maximum aggregation response to thrombin or collagen-related peptide. However, the rate of aggregation was substantially reduced in a manner that was dependent on the extracellular chloride concentration and aggregation in the absence of chloride was noticeably biphasic, indicative of impaired secondary signaling. This was further investigated by targeting secondary agonists with aspirin and apyrase or by blockade of the ADP receptor P2Y12. Under these conditions, the rates of aggregation were comparable to those recorded in the absence of extracellular chloride. Finally, we assessed platelet granule release by flow cytometry and report a chloride-dependent element of alpha, but not dense, granule secretion. Taken together these data support a role for anion channels in the efficient induction of platelet activation, likely via enhancement of secondary signaling pathways

Automatic georeferencing of astronaut auroral photography

Astronauts on board the International Space Station (ISS) have taken thousands of high-resolution colour photographs of the aurora, which could be made useful for research if their pointing information could be reconstructed. We describe a method to do this using the star field in the images, and how the reconstructed pointing can then be used to georeference the images to a similar level of accuracy in existing all-sky camera images. We have used this method to make georeferenced auroral images taken from the ISS available and here describe the resulting data set, processing software, and how to access them

Comorbidities and Treatments in United States Youth with Chronic Musculoskeletal Pain

Introduction: Chronic musculoskeletal (MSK) pain has been associated with chronic illnesses and high rates of pain medication use, often in referral centers, European populations, or studies focused on single drug classes. We aimed to characterize patterns of comorbidities and treatments associated with chronic MSK pain in a nationally-representative sample of US youth. Methods: We used the National Ambulatory Medical Care Survey (2002-2015) and National Hospital Ambulatory Medical Care Survey (2002-2011), which contain cross-sectional data for US outpatient visits. The study included all visits for youth age 8-24, excluding those with malignancy or sickle cell disease. We compared comorbidities and drugs ordered in visits for chronic MSK pain with (1) visits for any reason besides MSK pain and (2) visits for acute MSK pain, using chi-square tests and logistic regression, adjusting for several covariates. Results: Chronic non-psychiatric diseases were more common among visits for chronic MSK pain (32.0%) in comparison to both visits for acute MSK pain (17.9%) and visits for other reasons (18.8%). Nonsteroidal anti-inflammatories were less commonly ordered at visits for chronic MSK pain in comparison to acute MSK pain (adjusted odds ratio [aOR]: 0.63, 95% CI 0.50-0.80). Opioids, gabapentinoids, and alternative medicine were each ordered more commonly at visits for chronic MSK pain in comparison to visits for acute MSK pain and other visits. Conclusion: US youth with chronic MSK were more likely to have chronic non-psychiatric medical conditions compared to youth without pain. Additionally, opioids, gabapentinoids, and alternative medicine were ordered more often in chronic MSK visits, which warrants further study