A fast radio burst localized at detection to a galactic disk using very long baseline interferometry

Fast radio bursts (FRBs) are millisecond-duration, luminous radio transients of extragalactic origin. These events have been used to trace the baryonic structure of the Universe using their dispersion measure (DM) assuming that the contribution from host galaxies can be reliably estimated. However, contributions from the immediate environment of an FRB may dominate the observed DM, thus making redshift estimates challenging without a robust host galaxy association. Furthermore, while at least one Galactic burst has been associated with a magnetar, other localized FRBs argue against magnetars as the sole progenitor model. Precise localization within the host galaxy can discriminate between progenitor models, a major goal of the field. Until now, localizations on this spatial scale have only been carried out in follow-up observations of repeating sources. Here we demonstrate the localization of FRB 20210603A with very long baseline interferometry (VLBI) on two baselines, using data collected only at the time of detection. We localize the burst to SDSS J004105.82+211331.9, an edge-on galaxy at $z\approx 0.177$, and detect recent star formation in the kiloparsec-scale vicinity of the burst. The edge-on inclination of the host galaxy allows for a unique comparison between the line of sight towards the FRB and lines of sight towards known Galactic pulsars. The DM, Faraday rotation measure (RM), and scattering suggest a progenitor coincident with the host galactic plane, strengthening the link between the environment of FRB 20210603A and the disk of its host galaxy. Single-pulse VLBI localizations of FRBs to within their host galaxies, following the one presented here, will further constrain the origins and host environments of one-off FRBs.Comment: 40 pages, 13 figures, submitted. Fixed typo in abstrac

CHIME/FRB Discovery of 25 Repeating Fast Radio Burst Sources

We present the discovery of 25 new repeating fast radio burst (FRB) sources found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1. The sources were found using a new clustering algorithm that looks for multiple events co-located on the sky having similar dispersion measures (DMs). The new repeaters have DMs ranging from $\sim$220 pc cm$^{-3}$ to $\sim$1700 pc cm$^{-3}$, and include sources having exhibited as few as two bursts to as many as twelve. We report a statistically significant difference in both the DM and extragalactic DM (eDM) distributions between repeating and apparently nonrepeating sources, with repeaters having lower mean DM and eDM, and we discuss the implications. We find no clear bimodality between the repetition rates of repeaters and upper limits on repetition from apparently nonrepeating sources after correcting for sensitivity and exposure effects, although some active repeating sources stand out as anomalous. We measure the repeater fraction and find that it tends to an equilibrium of $2.6_{-2.6}^{+2.9}$% over our exposure thus far. We also report on 14 more sources which are promising repeating FRB candidates and which merit follow-up observations for confirmation.Comment: Submitted to ApJ. Comments are welcome and follow-up observations are encouraged

Bone marrow metastasis in Ewing's sarcoma and peripheral primitive neuroectodermal tumor: An immunohistochemical study

Bone marrow metastases from small round cell tumors can present diagnostic difficulties. In this study, we assessed the value of immunohistochemistry, using two monoclonal antibodies to CD99, for the diagnosis of metastatic disease in bone marrow trephine specimens from patients with Ewing's sarcoma or primitive neuroectodermal tumor (PNET). The proportions of specimens showing metastases were 10.3% with routine staining and 20.7% with immunohistochemistry. The specimens that were negative on conventional light microscopy and positive with immunohistochemistry all showed other abnormalities. The results do not support the routine use of immunohistochemistry in specimens that are normal by conventional light microscopy, but indicate that useful information may be gained in cases where marrow histology is obscured by fibrosis, necrosis, or distortion artefact. Neither of the two antibodies tested was superior for this purpose

Immunohistochemical detection of myocardial necrosis in stillbirth and neonatal death

The aims of this study were to determine whether immunohistochemical staining for C9 can demonstrate myocardial necrosis in the fetus and neonate. Hearts from cases of stillbirth or neonatal death with confirmed myocardial necrosis (in neonates) or with ischemic lesions outside the heart (in neonates and stillborns) were stained immunohistochemically with antibodies to C9. All five cases with confirmed myocardial infarction showed positive immunohistochemical staining for C9, largely localized to the infarcted areas. The youngest subject was born at 24 weeks gestation and died at 4 days of age. One of two neonates without myocardial necrosis on H&E staining but with pathological evidence of ischemic lesions elsewhere showed staining of scattered fibers. Six out of ten hearts from macerated stillborn infants showed varying degrees of positive staining. Immunohistochemical staining for C9 detects myocardial necrosis in neonates of a gestational age of 24 weeks or more. C9 is also demonstrable immunohistochemically in macerated stillborns, and this is likely to represent myocardial necrosis. The method is of great potential value in the investigation of cardiac ischemia in the fetal and perinatal period

Primary lymphoma of the gallbladder

A case of primary lymphoma of the gallbladder is described which is rare in the medical literature. A 76 year old man presented with acute cholecystitis and septicaemia. Investigation showed a lung abscess and a gallbladder mass. The mass was thought to be an empyema and cholecystostomy was performed. Biopsy of the gallbladder wall showed high-grade B cell lymphoma. The patient unfortunately succumbed to overwhelming septicaemia in the postoperative period. Postmortem examination confirmed primary lymphoma of the gallbladder without dissemination

Reproducibility and accuracy of MR imaging of the brain after severe birth asphyxia

BACKGROUND AND PURPOSE: MR imaging of the brain can be used to detect cerebral damage after suspected hypoxic-ischemic injury. This study examines the reproducibility and accuracy of MR imaging soon after severe birth asphyxia. METHODS: During a 48-month period, full-term newborn neonates, who died within the first week as a result of severe hypoxic ischemic encephalopathy, were included in the study if they had undergone early (<5 days old) MR imaging and postmortem neuropathologic studies. Two trained observers assessed reproducibility by examining multiple brain regions independently with current criteria and then defining and applying improved criteria. Accuracy of MR findings was tested by comparing the brain regions about which the two imaging raters agreed to those regions about which the two pathologists agreed. RESULTS: Eight neonates, with a median gestational age of 40 weeks (range, 38−40 weeks) and who suffered severe birth asphyxia, were included in the study. In the reproducibility study, MR imaging agreement was moderate when current criteria were used (k = .44). Using the improved criteria, agreement increased considerably (k = .62). Much of this improvement was due to limiting the analyses to the posterior limb of the internal capsule, thalamus, parietal cortex, hippocampus, and medulla. The posterior limb of the internal capsule was the most reliable region analyzed. MR imaging agreement was similar to that achieved by two experienced pathologists reviewing the histologic sections (k = .66). In the accuracy study, MR imaging abnormality was predictive of pathologic abnormality with a sensitivity of .79 and a positive predictive value of 1.0. The predictive value of a single MR imaging abnormality was .79 (95% confidence interval, .61−.96). CONCLUSION: Criteria that provide substantial reproducibility and accuracy for the interpretation of MR imaging findings very early after birth asphyxia can be derived

Reproducibility and accuracy of MR imaging of the brain after severe birth asphyxia

BACKGROUND AND PURPOSE: MR imaging of the brain can be used to detect cerebral damage after suspected hypoxic-ischemic injury. This study examines the reproducibility and accuracy of MR imaging soon after severe birth asphyxia. METHODS: During a 48-month period, full-term newborn neonates, who died within the first week as a result of severe hypoxic ischemic encephalopathy, were included in the study if they had undergone early (<5 days old) MR imaging and postmortem neuropathologic studies. Two trained observers assessed reproducibility by examining multiple brain regions independently with current criteria and then defining and applying improved criteria. Accuracy of MR findings was tested by comparing the brain regions about which the two imaging raters agreed to those regions about which the two pathologists agreed. RESULTS: Eight neonates, with a median gestational age of 40 weeks (range, 38−40 weeks) and who suffered severe birth asphyxia, were included in the study. In the reproducibility study, MR imaging agreement was moderate when current criteria were used (k = .44). Using the improved criteria, agreement increased considerably (k = .62). Much of this improvement was due to limiting the analyses to the posterior limb of the internal capsule, thalamus, parietal cortex, hippocampus, and medulla. The posterior limb of the internal capsule was the most reliable region analyzed. MR imaging agreement was similar to that achieved by two experienced pathologists reviewing the histologic sections (k = .66). In the accuracy study, MR imaging abnormality was predictive of pathologic abnormality with a sensitivity of .79 and a positive predictive value of 1.0. The predictive value of a single MR imaging abnormality was .79 (95% confidence interval, .61−.96). CONCLUSION: Criteria that provide substantial reproducibility and accuracy for the interpretation of MR imaging findings very early after birth asphyxia can be derived