A lanthanide-rich kilonova in the aftermath of a long gamma-ray burst.

Observationally, kilonovae are astrophysical transients powered by the radioactive decay of nuclei heavier than iron, thought to be synthesized in the merger of two compact objects1-4. Over the first few days, the kilonova evolution is dominated by a large number of radioactive isotopes contributing to the heating rate2,5. On timescales of weeks to months, its behaviour is predicted to differ depending on the ejecta composition and the merger remnant6-8. Previous work has shown that the kilonova associated with gamma-ray burst 230307A is similar to kilonova AT2017gfo (ref. 9), and mid-infrared spectra revealed an emission line at 2.15 micrometres that was attributed to tellurium. Here we report a multi-wavelength analysis, including publicly available James Webb Space Telescope data9 and our own Hubble Space Telescope data, for the same gamma-ray burst. We model its evolution up to two months after the burst and show that, at these late times, the recession of the photospheric radius and the rapidly decaying bolometric luminosity (Lbol ∝ t-2.7±0.4, where t is time) support the recombination of lanthanide-rich ejecta as they cool.

A structured jet explains the extreme GRB 221009A.

Long-duration gamma-ray bursts (GRBs) are powerful cosmic explosions, signaling the death of massive stars. Among them, GRB 221009A is by far the brightest burst ever observed. Because of its enormous energy (Eiso ≈ 1055 erg) and proximity (z ≈ 0.15), GRB 221009A is an exceptionally rare event that pushes the limits of our theories. We present multiwavelength observations covering the first 3 months of its afterglow evolution. The x-ray brightness decays as a power law with slope ≈t-1.66, which is not consistent with standard predictions for jetted emission. We attribute this behavior to a shallow energy profile of the relativistic jet. A similar trend is observed in other energetic GRBs, suggesting that the most extreme explosions may be powered by structured jets launched by a common central engine.

Embryonic atrazine exposure elicits proteomic, behavioral, and brain abnormalities with developmental time specific gene expression signatures.

Atrazine (ATZ), the second most commonly used herbicide in the United States, is an endocrine disrupting chemical linked to cancer and a common drinking water contaminant. This study further investigates ATZ-related developmental toxicity by testing the following hypotheses in zebrafish: the effects of embryonic ATZ exposure are dependent on timing of exposure; embryonic ATZ exposure alters brain development and function; and embryonic ATZ exposure changes protein abundance in carcinogenesis-related pathways. After exposing embryos to 0, 0.3, 3, or 30 parts per billion (ppb) ATZ, we monitored the expression of cytochrome P450 family 17 subfamily A member 1 (cyp17a1), glyoxalase I (glo1), ring finger protein 14 (rnf14), salt inducible kinase 2 (sik2), tetratricopeptide domain 3 (ttc3), and tumor protein D52 like 1 (tpd52l1) at multiple embryonic time points to determine normal expression and if ATZ exposure altered expression. Only cyp17a1 had normal dynamic expression, but ttc3 and tpd52l1 had ATZ-related expression changes before 72 h. Larvae exposed to 0.3 ppb ATZ had increased brain length, while larvae exposed to 30 ppb ATZ were hypoactive. Proteomic analysis identified altered protein abundance in pathways related to cellular function, neurodevelopment, and genital-tract cancer. The results indicate embryonic ATZ toxicity involves interactions of multiple pathways. SIGNIFICANCE: This is the first report of proteomic alterations following embryonic exposure to atrazine, an environmentally persistent pesticide and common water contaminant. Although the transcriptomic alterations in larval zebrafish with embryonic atrazine exposure have been reported, neither the time at which gene expression changes occur nor the resulting proteomic changes have been investigated. This study seeks to address these knowledge gaps by evaluating atrazine's effect on gene expression through multiple time points during embryogenesis, and correlating changes in gene expression to pathological alterations in brain length and functional changes in behavior. Finally, pathway analysis of the proteomic alterations identifies connections between the molecular changes and functional outcomes associated with embryonic atrazine exposure.

Use of mental-health services by Australian medical students: a cross-sectional survey.

OBJECTIVE: Medical students have higher rates of mental illness compared to the general population. Little is known about services accessed by medical students for mental-health problems. This study aimed to assess the use of mental-health services by Australian medical students and to identify barriers that may prevent students from using mental-health services. METHOD: A cross-sectional online survey was designed and administered to medical students at the University of Western Australia. Questions focused on self-reported psychological well-being, use of mental-health services, the perceived usefulness of services and barriers to the use of services. RESULTS: The response rate was 41% ( n=286). Sixty-two per cent self-reported experiencing mental-health problems, and of these, 75% had used at least one service. General practitioners and psychiatrists were rated as the most effective service type. The main barriers to seeking help were not enough time, affordability and concerns regarding stigma, including disclosure and peer judgement. CONCLUSION: A high proportion of students with self-reported mental-health problems had accessed services. However, barriers were also identified. Access to mental-health services needs to be improved, and strategies aimed at reducing stigma and raising awareness of mental-health issues should be encouraged by medical faculties.

Benign fibrous histiocytoma of the conjunctiva.

A case is reported on recurrence of a rare conjunctival fibrous histiocytoma (FH) in a 38-year-old man. The lesion was excised and subsequently sent for histopathology and immunostaining resulting in a diagnosis of fibrous histiocytoma (FH). Recurrence was detected 3 months postoperatively requiring a conjunctivosclerokeratomy with cryotherapy and flap. At 6-month followup there was no recurrence detected.