Ground‐based riometers provide an inexpensive means to continuously remote sense the precipitation of electrons in the dynamic auroral region of Earth's ionosphere. The energy‐dependent relationship ...between riometer absorption and precipitating electrons is thus of great importance for understanding the loss of electrons from the Earth's magnetosphere. In this study, statistical and event‐based analyses are applied to determine the energy of electrons to which riometers chiefly respond. Time‐lagged correlation analysis of trapped to precipitating fluxes shows that daily averaged absorption best correlates with ∼60 keV trapped electron flux at zero‐time lag, although large variability is observed across different phases of the solar cycle. High‐time resolution statistical cross‐correlation analysis between signatures observed by riometer stations, and assuming electron motion due to gradient and curvature drift, results in inferred energies of 10–100 keV, with a clear maximum in occurrence for 40–60 keV electrons. One event is considered in detail utilizing riometer absorption signatures obtained from several stations. The mean inferred energies for the initial rise time and peak of the absorption after correction for electric field effects were ∼70 keV and ∼60 keV, respectively. The analyses presented provide a means to characterize the energy of electrons to which riometers are responding in both a statistical sense and during the evolution of individual events.
Key Points
Riometer absorption responds to 10–100 keV with peak response at 40–60 keV
Method for determining precipitation energy statistically and for specific events
CNA has a negligible statistical response to MeV electrons
HIV and pathogenic SIV infection are characterized by mucosal dysfunction including epithelial barrier damage, loss of Th17 cells, neutrophil infiltration, and microbial translocation with ...accompanying inflammation. However, it is unclear how and when these contributing factors occur relative to one another. In order to determine whether any of these features initiates the cycle of damage, we longitudinally evaluated the kinetics of mucosal and systemic T-cell activation, microbial translocation, and Th17 cell and neutrophil frequencies following intrarectal SIV infection of rhesus macaques. We additionally assessed the colon proteome to elucidate molecular pathways altered early after infection. We demonstrate increased T-cell activation (HLA-DR+) beginning 3-14 days post-SIV challenge, reduced peripheral zonulin 3-14 days post-SIV, and evidence of microbial translocation 14 days post-SIV. The onset of mucosal dysfunction preceded peripheral and mucosal Th17 depletion, which occurred 14-28 days post-SIV, and gut neutrophil accumulation was not observed. Proteins involved in epithelial structure were downregulated 3 days post-SIV followed by an upregulation of immune proteins 14 days post-SIV. These data demonstrate that immune perturbations such as Th17 loss and neutrophil infiltration occur after alterations to epithelial structural protein pathways, suggesting that epithelial damage occurs prior to widespread immune dysfunction.
Abstract
We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS ...observations of the source were triggered by the detection of a hard-spectrum GeV flare on 2015 May 15 with the Fermi-Large Area Telescope (LAT). A combined 5 hr VERITAS exposure on May 16 and 18 resulted in a strong 13
σ
detection with a differential photon spectral index, Γ = 3.8 ± 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target-of-opportunity observations with Swift, optical photometry, polarimetry, and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of
τ
obs
= 6.2 ± 0.9 hr, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cutoff. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.
We use observations from five magnetospheric spacecraft in a fortuitous constellation to show that narrow transient plasma flow jets of considerable length formed in the tail can intrude into the ...inner magnetosphere and provide considerable contribution to the total plasma transport. A specific auroral structure, the auroral streamer, accompanied the development of this narrow plasma jet. These observations support the ‘boiling’ plasma sheet model consisting of localized underpopulated plasma tubes (bubbles) moving Earthward at high speeds as a realistic way to resolve the ‘convection crisis’ and to close the global magnetospheric circulation pattern.
Our aim was to test the hypothesis that two plates placed parallel to each other are stronger and stiffer than plates placed perpendicular to each other for fixation of a distal humerus fracture ...model.
We created an artificial distal humeral fracture model by osteotomizing two groups of identical epoxy resin humera. Screw and plate constructs were built to mimic osteosynthesis. In the first group, 3.5-mm reconstruction plates were placed parallel to each other along each of the medial and lateral supracondylar ridges. In the second group, 3.5-mm reconstruction plates were placed perpendicular to each other with a medial supracondylar ridge plate and a posterolateral plate. Stiffness and strength data of the two constructs were obtained by testing to failure with sagittal plane bending forces.
The parallel plate group (n = 7) had a mean stiffness of 214.9 +/- 43.3 N/mm and a mean strength of 304.4 +/- 63.5 N. The perpendicular plate group (n = 8) had a mean stiffness of 138.3 +/- 44.6 N/mm and a mean strength of 214.9 +/- 43.3 N. These differences were significant (Student's t test, P < 0.05).
As theoretically expected, a parallel plate configuration is significantly stronger and stiffer than a perpendicular plate configuration when subjected to sagittal bending forces in a distal humerus fracture model.
Abstract Positron emission tomography (PET) studies have reported an association between reduced striatal dopamine D2/3 receptor availability and higher scores on self-report measures of trait ...impulsivity in healthy adults. However, impulsivity is a multi-faceted construct, and it is unclear which aspect(s) of impulsivity might be driving these associations. The current study aimed to investigate the relationship between limbic (ventral) striatal D2/3 receptor availability and individual components of impulsivity (attentional, motor and non-planning) using the Barratt Impulsiveness Scale (BIS-11) and 11 Craclopride PET in 23 healthy volunteers. A partial correlational analysis showed a significant association between non-planning impulsiveness (lack of forethought or ‘futuring’) and limbic D2/3 receptor availability, which was only apparent after the exclusion of potential dissimulators (indexed by high scores on impression management). Our findings suggest that non-planning impulsiveness is associated with individual variation in limbic striatal D2/3 receptor availability and that different facets of impulsivity may have specific neurochemical correlates. Future studies that combine D2/3 receptor imaging with behavioral measures of impulsivity are required to further elucidate the precise relationship between individual components of trait impulsivity and brain dopaminergic function.
Possible effects of the atypical antipsychotic aripiprazole on the pharmacokinetics of standard antidepressant therapies (ADTs) were assessed in two open-label, non-randomised studies in healthy ...subjects (Studies 1 and 2) and two placebo-controlled studies in patients with major depressive disorder (MDD) (Studies 3 and 4). Healthy subjects received venlafaxine 75 mg/day (Study 1; N = 38) or escitalopram 10 mg/ day (Study 2; N = 25) with the addition of aripiprazole 10—20 mg/day (10 mg/day fixed dose in Study 2) for 14 days. Patients with MDD (N = 498; Studies 3 and 4) received escitalopram (10—20 mg/day), fluoxetine (20—40 mg/day), paroxetine controlled-release (37.5—50 mg/day), sertraline (100—150 mg/day) or venlafaxine extended-release (150—225 mg/day) for 8 weeks plus placebo. Incomplete responders were randomised (1:1) to placebo or adjunctive aripiprazole 2—20 mg/day. Blood samples were collected for pharmacokinetic analysis of ADTs. Plasma concentration—time data from Studies 3 and 4 were combined for statistical analysis. In healthy subjects, point estimates 90% CI for the ratios of geometric means of C max (venlafaxine 1.148 1.083—1.217; escitalopram 1.04 0.99—1.09) and AUCTAU (venlafaxine 1.183 1.130—1.238; escitalopram 1.07 1.04—1.11) indicated no meaningful increase in ADT exposure in the presence of aripiprazole. In patients, point estimates for mean plasma concentration ratios indicated no substantial effect of aripiprazole on any ADT escitalopram 0.970 0.911—1.033, fluoxetine 1.177 1.049—1.321, paroxetine 0.730 0.598—0.892, sertraline 0.958 0.887—1.035 or venlafaxine 0.966 0.887—1.051. Aripiprazole had no meaningful effects on the pharmacokinetics of standard ADTs in either healthy subjects or patients with MDD.
Prospective observational study with a 2- to 3-year follow-up.
To determine whether delayed muscle reflex response to sudden trunk loading is a result of or a risk factor for sustaining a low back ...injury (LBI).
Differences in motor control have been identified in individuals with chronic low back pain and in athletes with a history of LBI when compared with controls. However, it is not known whether these changes are a risk for or a result of LBI.
Muscle reflex latencies in response to a quick force release in trunk flexion, extension, and lateral bending were measured in 303 college athletes. Information was also obtained regarding their personal data, athletic experience, and history of LBI. The data were entered into a binary logistic regression model to identify the predictors of future LBI. RESULTS.: A total of 292 athletes were used for the final analysis (148 females and 144 males). During the follow-up period, 31 (11%) athletes sustained an LBI. The regression model, consisting of history of LBI, body weight, and the latency of muscles shutting off during flexion and lateral bending load releases, predicted correctly 74% of LBI outcomes. The odds of sustaining LBI increased 2.8-fold when a history of LBI was present and increased by 3% with each millisecond of abdominal muscle shut-off latency. On average, this latency was 14 milliseconds longer for athletes who sustained LBI in comparison to athletes who did not sustain LBI (77 36 vs. 63 31). There were no significant changes in any of the muscle response latencies on retest following the injury.
The delayed muscle reflex response significantly increases the odds of sustaining an LBI. These delayed latencies appear to be a preexisting risk factor and not the effect of an LBI.
BAT and XRT observations of two recent well-covered GRBs observed by Swift, GRB 050315 and GRB 050319, clearly show a prompt component joining the onset of the afterglow emission. By fitting a ...power-law form to the g-ray spectrum, we extrapolate the time-dependent fluxes measured by BAT, in the energy band 15-350 keV, into the spectral regime observed by XRT, 0.2-10 keV, and examine the functional form of the rate of decay of the two light curves. We find that the BAT and XRT light curves merge to form a unified curve. There is a period of steep decay up to 6300 s, followed by a flatter decay. The duration of the steep decay, 6100 s in the source frame after correcting for cosmological time dilation, agrees roughly with a theoretical estimate for the deceleration time of the relativistic ejecta as it interacts with circumstellar material. For GRB 050315, the steep decay can be characterized by an exponential form, where the e-folding decay time t sub(e) 24 c 2 s (BAT), and t sub(e) 35 c 2 s (XRT). For GRB 050319, a power-law decay -d ln f/d ln t = n, where n 3 provides a reasonable fit. The early-time X-ray fluxes are consistent with representing the lower energy tail of the prompt emission and provide our first quantitative measure of the decay of the prompt g-ray emission over a large dynamic range in flux. The initial steep decay is expected, due to the delayed high-latitude photons from a curved shell of relativistic plasma illuminated only for a short interval. The overall conclusion is that the prompt phase of GRBs remains observable for hundreds of seconds longer than previously thought.
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