Positron annihilation signatures associated with the outburst of the microquasar V404 Cygni.

Microquasars are stellar-mass black holes accreting matter from a companion star and ejecting plasma jets at almost the speed of light. They are analogues of quasars that contain supermassive black holes of 10(6) to 10(10) solar masses. Accretion in microquasars varies on much shorter timescales than in quasars and occasionally produces exceptionally bright X-ray flares. How the flares are produced is unclear, as is the mechanism for launching the relativistic jets and their composition. An emission line near 511 kiloelectronvolts has long been sought in the emission spectrum of microquasars as evidence for the expected electron-positron plasma. Transient high-energy spectral features have been reported in two objects, but their positron interpretation remains contentious. Here we report observations of γ-ray emission from the microquasar V404 Cygni during a recent period of strong flaring activity. The emission spectrum around 511 kiloelectronvolts shows clear signatures of variable positron annihilation, which implies a high rate of positron production. This supports the earlier conjecture that microquasars may be the main sources of the electron-positron plasma responsible for the bright diffuse emission of annihilation γ-rays in the bulge region of our Galaxy. Additionally, microquasars could be the origin of the observed megaelectronvolt continuum excess in the inner Galaxy.

Controlled Substance Prescription History among Individuals Who Died of an Accidental Opioid-Involved Drug Overdose in Rhode Island.

Background: Accidental opioid-involved overdose deaths are increasing nationally in the wake of the COVID-19 pandemic, but it is unclear if this reflects a change in populations most at risk. Objective: To determine whether the demographic characteristics and controlled substance prescription history of accidental opioid-involved drug overdose decedents in 2020 differed from prior years. Methods: We identified accidental opioid-involved overdose decedents using Rhode Island (RI) State Medical Examiner's Office data. Decedents were linked to the RI Prescription Drug Monitoring Program database. We compared demographic characteristics and prescription history by year of death. Results: From 2018 to 2020, 763 RI residents died from accidental opioid-involved overdose in RI. From 2018 to 2019, deaths decreased by 7%, but then increased by 31% from 2019 to 2020. Demographic characteristics were similar by year of death (all p > 0.05). The percentage of decedents with a prior opioid prescription and a prior benzodiazepine prescription declined from 2018 to 2020 (p < 0.01 and p = 0.03). Conclusions: We found that opioid-involved overdose deaths in RI are increasing overall, but without significant changes in demographics. While prior exposure to some controlled substances did decline over time, it is not clear if these changes reflect more responsible prescribing practices, or a more concerning pattern such as patient abandonment or decreased healthcare access. More studies are needed to better describe the current trend of increasing opioid-involved deaths while also pursuing current evidence-based interventions.

Transparent thin shield for radio frequency transmit coils.

OBJECTIVE: To identify a shielding material compatible with optical head-motion tracking for prospective motion correction and which minimizes radio frequency (RF) radiation losses at 7 T without sacrificing line-of-sight to an imaging target. MATERIALS AND METHODS: We evaluated a polyamide mesh coated with silver. The thickness of the coating was approximated from the composition ratio provided by the material vendor and validated by an estimate derived from electrical conductivity and light transmission measurements. The performance of the shield is compared to a split-copper shield in the context of a four-channel transmit-only loop array. RESULTS: The mesh contains less than a skin-depth of silver coating (300 MHz) and attenuates light by 15 %. Elements of the array vary less in the presence of the mesh shield as compared to the split-copper shield indicating that the array behaves more symmetrically with the mesh shield. No degradation of transmit efficiency was observed for the mesh as compared to the split-copper shield. CONCLUSION: We present a shield compatible with future integration of camera-based motion-tracking systems. Based on transmit performance and eddy-current evaluations the mesh shield is appropriate for use at 7 T.

Improved reproducibility of unit-cell parameters in macromolecular cryocrystallography by limiting dehydration during crystal mounting.

In macromolecular cryocrystallography unit-cell parameters can have low reproducibility, limiting the effectiveness of combining data sets from multiple crystals and inhibiting the development of defined repeatable cooling protocols. Here, potential sources of unit-cell variation are investigated and crystal dehydration during loop-mounting is found to be an important factor. The amount of water lost by the unit cell depends on the crystal size, the loop size, the ambient relative humidity and the transfer distance to the cooling medium. To limit water loss during crystal mounting, a threefold strategy has been implemented. Firstly, crystal manipulations are performed in a humid environment similar to the humidity of the crystal-growth or soaking solution. Secondly, the looped crystal is transferred to a vial containing a small amount of the crystal soaking solution. Upon loop transfer, the vial is sealed, which allows transport of the crystal at its equilibrated humidity. Thirdly, the crystal loop is directly mounted from the vial into the cold gas stream. This strategy minimizes the exposure of the crystal to relatively low humidity ambient air, improves the reproducibility of low-temperature unit-cell parameters and offers some new approaches to crystal handling and cryoprotection.

An embedded optical tracking system for motion-corrected magnetic resonance imaging at 7T.

OBJECT: Prospective motion correction using data from optical tracking systems has been previously shown to reduce motion artifacts in MR imaging of the head. We evaluate a novel optical embedded tracking system. MATERIALS AND METHODS: The home-built optical embedded tracking system performs image processing within a 7 T scanner bore, enabling high speed tracking. Corrected and uncorrected in vivo MR volumes are acquired interleaved using a modified 3D FLASH sequence, and their image quality is assessed and compared. RESULTS: The latency between motion and correction of the slice position was measured to be (19 ± 5) ms, and the tracking noise has a standard deviation no greater than 10 µm/0.005° during conventional MR scanning. Prospective motion correction improved the edge strength by 16 % on average, even though the volunteers were asked to remain motionless during the acquisitions. CONCLUSION: Using a novel method for validating the effectiveness of in vivo prospective motion correction, we have demonstrated that prospective motion correction using motion data from the embedded tracking system considerably improved image quality.

Pasteurella Multocida Urinary Tract Infection in a Susceptible Patient with Non-Traumatic Feline Contact.

Pasteurella multocida is a part of the normal oral flora of domestic animals. Humans can develop skin and soft tissue infections from P. multocida after traumatic animal contact, usually through bites and scratches from domestic animals. Although rare, there have been documented case reports where P. multocida has been isolated from patients even after minimal casual animal contact. Even rarer, is the isolation of P. multocida from urine. The few documented cases of urine isolation have been described in patients who have underlying medical conditions, particularly those with urologic abnormalities. Here we present a 34-year-old female patient with known congenital neurological and urological anomalies who developed a P. multocida urinary tract infection from casual contact with a household feline, a previously unrecognized risk factor for P. multocida UTI in anatomically susceptible individuals.

Visual cues associated with sweet taste increase short-term eating and grab attention in healthy volunteers.

Most studies that examine responses to food cues use images of actual foods as stimuli. Since foods are rewarding in multiple ways, it then becomes difficult to try and partial out the role of the importance of different aspects of food reward. Here we aimed to evaluate the impact of novel visual cues specifically associated with the immediate sensory reward from a liked sweet taste. In the training phase, one visual cue (CSsweet) was associated with the experience of sweet taste (10%sucrose) and a second, control cue (CSneutral) with a neutral taste (artificial saliva) using a disguised training procedure. In Experiment 1, participants (n = 45) were given an ad libitum snack intake test 30 min post-training, either labelled with CSsweet or CSneutral. Total caloric consumption was significantly higher in the CSsweet (650 ± 47 kcal) than CSneutral (477 ± 45 kcal) condition, but ratings of liking for the snacks did not differ significantly between conditions. In Experiment 2, participants (n = 80) exhibited an overall attentional bias (22.1 ± 9.9 ms) for the CSsweet relative to CSneutral cue (assessed using a dot-probe task), however rated liking for the CSsweet did not change significantly after cue-sweet training. Likewise, measures of expected satiety for drinks labelled with CSsweet did not differ significantly from CSneutral. Overall these two experiments provide evidence that associations between neutral visual cues and the experience of a liked sweet taste leads to cue-potentiated eating in the presence of the CSsweet cue. With no evidence that cue-sweet training altered rated liking for the visual cues, and in keeping with extant literature on the dissociation of hedonic and rewarding properties of food rewards, we propose this potentiation effect to reflect increased incentive salience.

Whether or not to eat: A controlled laboratory study of discriminative cueing effects on food intake in humans.

There is a wealth of data showing a large impact of food cues on human ingestion, yet most studies use pictures of food where the precise nature of the associations between the cue and food is unclear. To test whether novel cues which were associated with the opportunity of winning access to food images could also impact ingestion, 63 participants participated in a game in which novel visual cues signalled whether responding on a keyboard would win (a picture of) chocolate, crisps, or nothing. Thirty minutes later, participants were given an ad libitum snack-intake test during which the chocolate-paired cue, the crisp-paired cue, the non-winning cue and no cue were presented as labels on the food containers. The presence of these cues significantly altered overall intake of the snack foods; participants presented with food labelled with the cue that had been associated with winning chocolate ate significantly more than participants who had been given the same products labelled with the cue associated with winning nothing, and in the presence of the cue signalling the absence of food reward participants tended to eat less than all other conditions. Surprisingly, cue-dependent changes in food consumption were unaffected by participants' level of contingency awareness. These results suggest that visual cues that have been pre-associated with winning, but not consuming, a liked food reward modify food intake consistent with current ideas that the abundance of food associated cues may be one factor underlying the 'obesogenic environment'.

Early 56Ni decay gamma rays from SN2014J suggest an unusual explosion.

Type Ia supernovae result from binary systems that include a carbon-oxygen white dwarf, and these thermonuclear explosions typically produce 0.5 solar mass of radioactive (56)Ni. The (56)Ni is commonly believed to be buried deeply in the expanding supernova cloud. In SN2014J, we detected the lines at 158 and 812 kiloelectron volts from (56)Ni decay (time ~8.8 days) earlier than the expected several-week time scale, only ~20 days after the explosion and with flux levels corresponding to roughly 10% of the total expected amount of (56)Ni. Some mechanism must break the spherical symmetry of the supernova and at the same time create a major amount of (56)Ni at the outskirts. A plausible explanation is that a belt of helium from the companion star is accreted by the white dwarf, where this material explodes and then triggers the supernova event.