An Interview with Professor Peter Singer

An interview conducted by Denise Russell with Professor Peter Singer

REPAD: An empirical model of pitch angle distributions for energetic electrons in the Earth\u27s outer radiation belt

Abstract We have recently conducted a statistical survey on pitch angle distributions of energetic electrons trapped in the Earth\u27s outer radiation belt, and a new empirical model was developed based upon survey results. This model - relativistic electron pitch angle distribution (REPAD) - aims to present statistical pictures of electron equatorial pitch angle distributions, instead of the absolute flux levels, as a function of energy, L shell, magnetic local time, and magnetic activity. To quantify and facilitate this statistical survey, we use Legendre polynomials to fit long-term in situ directional fluxes observed near the magnetic equator from three missions: CRRES, Polar, and LANL-97A. As the first of this kind of model, REPAD covers the whole outer belt region, providing not only the mean and median pitch angle distributions in the area but also error estimates of the average distributions. Preliminary verification and validation results demonstrate the reliable performance of this model. Usage of REPAD is mainly to predict the full pitch angle distribution of fluxes along a given magnetic field line, or even on a given drift shell, based upon one single unidirectional or omnidirectional flux measurement anywhere on that field line. This can be particularly useful for data assimilation, which usually has large tolerance on data errors. In addition, relatively small variations in pitch angle distributions measured at L shell between?∼?4 and 5 justify the assumption of fixed pitch angle distributions at GPS equatorial crossings (L?∼?4.2) used in our previous studies

Reduced insular γ‐aminobutyric acid in fibromyalgia

Objective Recent scientific findings have reinvigorated interest in examining the role of γ‐aminobutyric acid (GABA), the major inhibitory central nervous system neurotransmitter, in chronic pain conditions. Decreased inhibitory neurotransmission is a proposed mechanism in the pathophysiology of chronic pain syndromes such as fibromyalgia (FM). The purpose of this study was to test the hypothesis that decreased levels of insular and anterior cingulate GABA would be present in FM patients, and that the concentration of this neurotransmitter would be correlated with pressure–pain thresholds. Methods Sixteen FM patients and 17 age‐ and sex‐matched healthy controls underwent pressure–pain testing and a 3T proton magnetic resonance spectroscopy session in which the right anterior insula, right posterior insula, anterior cingulate, and occipital cortex were examined in subjects at rest. Results GABA levels in the right anterior insula were significantly lower in FM patients compared with healthy controls (mean ± SD 1.17 ± 0.24 arbitrary institutional units versus 1.42 ± 0.32 arbitrary institutional units; P = 0.016). There was a trend toward increased GABA levels in the anterior cingulate of FM patients compared with healthy controls ( P = 0.06). No significant differences between groups were detected in the posterior insula or occipital cortex ( P > 0.05 for all comparisons). Within the right posterior insula, higher levels of GABA were positively correlated with pressure–pain thresholds in the FM patients (Spearman's rho = 0.63; P = 0.02). Conclusion Diminished inhibitory neurotransmission resulting from lower concentrations of GABA within the right anterior insula may play a role in the pathophysiology of FM and other central pain syndromes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90292/1/33339_ftp.pd

THEMIS Observations of Directly-Driven Pi2 Pulsations

The THEMIS tail seasons have provided an unprecedented opportunity to examine the causal relationship between midtail plasma flows and low latitude Pi2 pulsations. We present several events where multiple THEMIS spacecraft observed magnetotail flow bursts which were followed up to several minutes later by ground Pi2 pulsations. We find good agreement with the waveforms of the flow bursts and flank Pi2, in agreement with the hypothesis that Pi2 at low-latitude on the flank are directly-driven by periodic variations in the flow bursts. For at least I event we are able to follow the Pi2 impulses from the periodic flow bursts on the nightside. to ground Pi2 at the flanks, and finally through the dayside magnetosphere as observed by GOES. We further place the physical mechanism generating these Pi2 into the context of sub storm onset. We conclude by discussing the sequence and coupling of events that are necessary to explain the correlation, and the constraints this places on models of transient magnetospheric transport

Event-oriented modelling of magnetic fields and currents during storms

We model the magnetospheric magnetic field during two storms, moderate and intense, using the event-oriented modelling technique which includes the representations of the magnetic field arising from the various magnetospheric current systems. The model free parameters are specified for each time step separately using observations from GOES 8, 9, and 10, Polar, Interball and Geotail satellites and Dst measurements. It is shown that the ring current is most important during intense storms, whereas the near Earth tail currents contribute more to the Dst index than the ring current during moderate storms

Short and user-friendly: The development and validation of the Mini-DBQ

The Driver Behavior Questionnaire (DBQ) is used to measure aberrant driver behavior by asking drivers how often they engage in various aberrant driver behaviors. Since the development of the original DBQ several modified versions have been developed. The difference between the various versions is that new items are added or existing items modified or excluded. However, despite the differences, all versions are relatively long and therefore time-consuming and tiring to answer, which might limit the usability of the instrument. The main purpose of the present study was to develop a mini DBQ version by reducing the 27-item original DBQ to the shortest possible DBQ version. A second aim was to explore the feasibility of a second-order structure within the data, which means that violations, errors and lapses factors load on a higher-order aberrant driver behavior factor. The presence of a second-order structure further indicates the validity of the DBQ and its theoretical structure. Confirmatory factor analysis (CFA) was used to test the fit (i.e., how well the models explain the data) of the original DBQ versus the fit of the shortest possible DBQ as well as the presence of a second-order structure for the DBQ. The results indicated a nine-item Mini-DBQ In addition, a second-order structure was established in the data. These findings indicate that the Mini-DBQ is a valid and useful short measure of aberrant driver behavior

Vasopressin in conjunction with norepinephrine in septic shock: A retrospective cohort study from a low middle-income country

Objectives: Guidelines recommend use of norepinephrine as the first-line treatment for fluid-refractory septic shock and if septic shock persists vasopressin may be initiated. Since there are limited data from low middle-income countries with high disease burden of sepsis, we aimed to compare the outcomes of using vasopressin adjunct to norepinephrine in comparison with norepinephrine alone.Design: Retrospective cohort study.Setting: Aga Khan University Hospital, Karachi, Pakistan.Patients: Six-hundred fifty-three patients diagnosed with septic shock from January 2019 to December 2019, with 498 given norepinephrine only and 155 given norepinephrine-vasopressin combination.Interventions: None.Measurements and main results: Primary outcome was in-hospital mortality. Secondary outcomes were duration of vasopressor used, length of hospital stay, length of ICU stay, and days on ventilatory support. After adjustment by multivariable logistic regression, it was found that mortality was not significantly associated with the norepinephrine-vasopressin combination (adjusted odds ratio, 0.633 [95% CI, 0.370-1.081]). However, Sequential Organ Failure Assessment score at admission (1.100 [1.014-1.193]), lactate at admission (1.167 [1.109-1.227]), duration of vasopressor used (1.481 [1.316-1.666]), and level of care (3.025 [1.682-5.441]) were found to be independently associated with the adjunct usage of norepinephrine and vasopressin.Conclusions: The use of norepinephrine-vasopressin combination has remained debatable in literature. Our study showed that although there was no difference in mortality between the two groups, admission Sequential Organ Failure Assessment scores and admission lactate levels were found to be significantly higher in the norepinephrine-vasopressin group. Hence, physicians from Pakistan used the norepinephrine-vasopressin combination in resistant septic shock patients who were sicker to begin with. Furthermore, duration of vasopressor therapy and ICU admission were also significantly higher in the combination group. Considering the recent hyperinflation of vasopressors costs and that most healthcare expenditure for patients in Pakistan is out-of-pocket, this can consequently lead to unwarranted financial burden for patients and their families