Radio Astronomy

Contains reports on three research projects.National Aeronautics and Space Administration (Grant NsG-419)National Aeronautics and Space Administration (Contract NSR-22-009-120)Lincoln Laboratory Purchase Order No. 74

Radio Astronomy

Contains research objectives and reports on six research projects.National Aeronautics and Space Administration (Contract NSR-22-009-120)National Aeronautics and Space Administration (Grant NsG-419)Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 36-039-AMC-03200(E

Experience-Dependent Effects of Muscimol-Induced Hippocampal Excitation on Mnemonic Discrimination

Memory requires similar episodes with overlapping features to be represented distinctly, a process that is disrupted in many clinical conditions as well as normal aging. Data from humans have linked this ability to activity in hippocampal CA3 and dentate gyrus (DG). While animal models have shown the perirhinal cortex is critical for disambiguating similar stimuli, hippocampal activity has not been causally linked to discrimination abilities. The goal of the current study was to determine how disrupting CA3/DG activity would impact performance on a rodent mnemonic discrimination task. Rats were surgically implanted with bilateral guide cannulae targeting dorsal CA3/DG. In Experiment 1, the effect of intra-hippocampal muscimol on target-lure discrimination was assessed within subjects in randomized blocks. Muscimol initially impaired discrimination across all levels of target-lure similarity, but performance improved on subsequent test blocks irrespective of stimulus similarity and infusion condition. To clarify these results, Experiment 2 examined whether prior experience with objects influenced the effect of muscimol on target-lure discrimination. Rats that received vehicle infusions in a first test block, followed by muscimol in a second block, did not show discrimination impairments for target-lure pairs of any similarity. In contrast, rats that received muscimol infusions in the first test block were impaired across all levels of target-lure similarity. Following discrimination tests, rats from Experiment 2 were trained on a spatial alternation task. Muscimol infusions increased the number of spatial errors made, relative to vehicle infusions, confirming that muscimol remained effective in disrupting behavioral performance. At the conclusion of behavioral experiments, fluorescence in situ hybridization for the immediate-early genes Arc and Homer1a was used to determine the proportion of neurons active following muscimol infusion. Contrary to expectations, muscimol increased neural activity in DG. An additional experiment was carried out to quantify neural activity in naïve rats that received an intra-hippocampal infusion of vehicle or muscimol. Results confirmed that muscimol led to DG excitation, likely through its actions on interneuron populations in hilar and molecular layers of DG and consequent disinhibition of principal cells. Taken together, our results suggest disruption of coordinated neural activity across the hippocampus impairs mnemonic discrimination when lure stimuli are novel

Social Dominance Orientation, Dispositional Empathy, and Need for Cognitive Closure Moderate the Impact of Empathy-Skills Training, but Not Patient Contact, on Medical Students' Negative Attitudes toward Higher-Weight Patients

Anti-fat bias in healthcare providers and medical students has serious implications for quality of care of higher-weight patients. Studies of interventions aimed at reducing anti-fat attitudes in medical students have generally been disappointing, with little enduring effect. It is possible that some students may be more receptive to prejudice-reducing influences than others, due to underlying differences in their personal characteristics. It is also possible that attitudes toward patients, specifically, may differ from anti-fat attitudes in general, and prejudice-reduction effectiveness on patient-specific attitudes has not yet been evaluated. The present study explored the effect on general and patient-specific anti-fat attitudes of (1) contact with higher-weight individuals prior to and during medical school; and (2) training designed to increase medical students' empathy toward patients by encouraging them to take the patient's perspective during clinical encounters. The moderating role of individual difference factors on effectiveness of contact and student-reported hours of empathy training on patient-specific attitudes was assessed. A total of 3,576 students enrolled across 49 US medical schools completed an online survey at the start of their first year of medical school and at the end of their fourth year. Favorable contact experience with higher-weight patients predicted improved attitudes toward heavier patients after 4 years of medical school, and appeared sufficient to partially offset the effects of dislike of higher-weight individuals at baseline. The impact of favorable contact on general anti-fat attitudes was less strong, highlighting the importance of using target-specific outcome measures. The positive effects of favorable contact on attitudes toward higher-weight patients did not differ based on students' baseline levels of social dominance orientation, dispositional empathy, or need for cognitive closure. In contrast, the effectiveness of training did vary by student characteristics, generally being more effective in students who were more egalitarian and empathic at baseline, with little effect, or even adverse effects in students low in these traits. Overall, however, perspective-taking training produced only small improvements in attitudes toward higher-weight patients

Radio Astronomy

Contains reports on five research projects.National Aeronautics and Space Administration (Grant NsG-419)National Science Foundation (Grant GP-7046)National Aeronautics and Space Administration (Contract NSR-22-009-120)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U, S. Air Force, under Contract DA 28-043-AMC-02536(E)U. S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-000

Fluoroquinolones Protective against Cephalosporin Resistance in Gram-negative Nosocomial Pathogens

In a matched case-control study, we studied the effect of prior receipt of fluoroquinolones on isolation of three third-generation cephalosporin-resistant gram-negative nosocomial pathogens. Two hundred eighty-two cases with a third-generation cephalosporin-resistant pathogen (203 with Enterobacter spp., 50 with Pseudomonas aeruginosa, and 29 with Klebsiella pneumoniae) were matched on length of stay to controls in a 1:2 ratio. Case-patients and controls were similar in age (mean 62 years) and sex (54% male). Variables predicting third-generation cephalosporin resistance were surgery (p = 0.005); intensive care unit stay (p < 0.001); and receipt of a β-lactam/β-lactamase inhibitor (p < 0.001), a ureidopenicillin (p = 0.002), or a third-generation cephalosporin (p < 0.001). Receipt of a fluoroquinolone was protective against isolation of a third-generation cephalosporin-resistant pathogen (p = 0.005). Interventional studies are required to determine whether replacing third-generation cephalosporins with fluoroquinolones will be effective in reducing cephalosporin resistance and the effect of such interventions on fluoroquinolone resistance

Signalling hostility: The relationship between witnessing weight-based discrimination in medical school and medical student wellbeing

Environments that are hostile to one or more marginalised groups are known to have a negative effect on the mental health and wellbeing of both targets and observers. Anti-fat attitudes have been well documented in medical education, including the use of derogatory humour and discriminatory treatment towards higher-weight patients. However, to date, it is not known what effect observing weight stigma and discrimination during medical school has on medical students’ psychological health and wellbeing, sense of belonging, and medical school burnout. The present study surveyed a total of 3,994 students enrolled across 49 US medical schools at the start of their first year and at the end of their fourth year. Participants reported the frequency with which they had observed stigmatising and discriminatory behaviours targeted at both higher-weight patients and higher-weight students during their four years of medical school. Observed weight stigma was prevalent, and was associated with worse psychological and general health, reduced medical school belonging and increased medical school burnout. The indirect effects of observed weight stigma on medical school burnout, via belonging, psychological health, and general health, were statistically significant in the sample as a whole, but were more pronounced in higher-weight students. This effect may be explained, in part, by the relationship between observed stigma and medical school belonging. Higher levels of observed stigma were associated with reduced feelings of belonging in higher-weight but not normative-weight students. Top-down institutional culture change is needed to rectify this situation, which is detrimental to both students and patients

Three red suns in the sky: A transiting, terrestrial planet in a triple M-dwarf system at 6.9 pc

We present the discovery from Transiting Exoplanet Survey Satellite (TESS) data of LTT 1445Ab. At a distance of 6.9 pc, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use MEarth data and results from the Science Processing Operations Center data validation report to determine that the planet transits the primary star in the system. The planet has a radius of ${1.38}_{-0.12}^{+0.13}$ ${R}_{\oplus }$, an orbital period of ${5.35882}_{-0.00031}^{+0.00030}$ days, and an equilibrium temperature of ${433}_{-27}^{+28}$ K. With radial velocities from the High Accuracy Radial Velocity Planet Searcher, we place a 3σ upper mass limit of 8.4 ${M}_{\oplus }$ on the planet. LTT 1445Ab provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. We also present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicate a moderate amount of variability, in agreement with that observed in the TESS light-curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system hints that the entire system may be co-planar, implying that the system may have formed from the early fragmentation of an individual protostellar core.Accepted manuscrip

Low prevalence of significant carotid artery disease in Iranian patients undergoing elective coronary artery bypass

BACKGROUND: Coronary artery bypass grafting ranks as one of the most frequent operations worldwide. The presence of carotid artery stenosis may increase the stroke rate in the perioperative period. Routine preoperative noninvasive assessment of the carotid arteries are recommended in many institutions to reduce the stroke rate. METHODS: 271 consecutive patients undergoing coronary artery bypass grafting at Shaheed Madani hospital of Tabriz, Iran (age, 58.5 Y; 73.1% male) underwent preoperative ultrasonography for assessment of carotid artery wall thickness. RESULTS: Plaque in right common, left common, right internal and left internal carotid arteries was detected in 4.8%, 7.4%, 43.2% and 42.1% of patients respectively. 5 patients (1.8%) had significant (<50%) and 3 (1.1%) patients had critical (<70%) stenosis in internal carotid arteries. Plaque formation in common carotid was not significantly different between two genders but the stenosis of left internal carotid was more frequently seen among men. Patients with plaques in right or left internal carotid arteries were significantly older. CONCLUSION: Consecutive Iranian patients undergoing elective coronary artery bypass surgery show a very low prevalence of significant carotid artery disease

Exploring the atmospheric dynamics of the extreme ultra-hot Jupiter KELT-9b using TESS photometry

We carry out a phase-curve analysis of the KELT-9 system using photometric observations from NASA's Transiting Exoplanet Survey Satellite (TESS). The measured secondary eclipse depth and peak-to-peak atmospheric brightness modulation are $650^{+14}_{-15}$ ppm and $566\pm16$ ppm, respectively. The planet's brightness variation reaches maximum $31\pm5$ minutes before the midpoint of the secondary eclipse, indicating a $5\overset{\circ}{.}2\pm0\overset{\circ}{.}9$ eastward shift in the dayside hot spot from the substellar point. We also detect stellar pulsations on KELT-9 with a period of $7.58695\pm0.00091$ hours. The dayside emission of KELT-9b in the TESS bandpass is consistent with a blackbody brightness temperature of $4600\pm100$ K. The corresponding nightside brightness temperature is $3040\pm100$ K, comparable to the dayside temperatures of the hottest known exoplanets. In addition, we detect a significant phase-curve signal at the first harmonic of the orbital frequency and a marginal signal at the second harmonic. While the amplitude of the first harmonic component is consistent with the predicted ellipsoidal distortion modulation assuming equilibrium tides, the phase of this photometric variation is shifted relative to the expectation. Placing KELT-9b in the context of other exoplanets with phase-curve observations, we find that the elevated nightside temperature and relatively low day-night temperature contrast agree with the predictions of atmospheric models that include H$_{2}$ dissociation and recombination. The nightside temperature of KELT-9b implies an atmospheric composition containing about 50% molecular and 50% atomic hydrogen at 0.1 bar, a nightside emission spectrum that deviates significantly from a blackbody, and a 0.5-2.0 $\mu$m transmission spectrum that is featureless at low resolution.Comment: Published in AJ, updated with proof corrections. 17 pages, 8 figure