Abstract We present a framework for modeling astrophysical pulses from radio pulsars and fast radio bursts (FRBs). This framework, called fitburst , generates synthetic representations of dynamic ...spectra that are functions of several physical and heuristic parameters; the heuristic parameters can nonetheless accommodate a vast range of distributions in spectral energy. fitburst is designed to optimize the modeling of features induced by effects that are intrinsic and extrinsic to the emission mechanism, including the magnitude and frequency dependence of pulse dispersion and scatter broadening. fitburst removes intrachannel smearing through two-dimensional upsampling, and can account for phase-wrapping of “folded” signals that are typically acquired during pulsar-timing observations. We demonstrate the effectiveness of fitburst in modeling data containing pulsars and FRBs observed with the Canadian Hydrogen Intensity Mapping Experiment telescope.
Abstract
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has become a leading facility for detecting fast radio bursts (FRBs) through the CHIME/FRB backend. CHIME/FRB searches for fast ...transients in polarization-summed intensity data streams that have 24 kHz spectral and 1 ms temporal resolution. The intensity beams are pointed to predetermined locations in the sky. A triggered baseband system records the coherent electric field measured by each antenna in the CHIME array at the time of FRB detections. Here we describe the analysis techniques and automated pipeline developed to process these full-array baseband data recordings. Whereas the real-time FRB detection pipeline has a localization limit of several arcminutes, offline analysis of baseband data yields source localizations with subarcminute precision, as characterized by using a sample of pulsars and one repeating FRB with known positions. The baseband pipeline also enables resolving temporal substructure on a microsecond scale and the study of polarization including detections of Faraday rotation.
Abstract
We present a Monte Carlo–based population synthesis study of fast radio burst (FRB) dispersion and scattering focusing on the first catalog of sources detected with the Canadian Hydrogen ...Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) project. We simulate intrinsic properties and propagation effects for a variety of FRB population models and compare the simulated distributions of dispersion measures and scattering timescales with the corresponding distributions from the CHIME/FRB catalog. Our simulations confirm the results of previous population studies, which suggested that the interstellar medium of the host galaxy alone (simulated based on the NE2001 model) cannot explain the observed scattering timescales of FRBs. We therefore consider additional sources of scattering, namely, the circumgalactic medium (CGM) of intervening galaxies and the circumburst medium whose properties are modeled based on typical Galactic plane environments. We find that a population of FRBs with scattering contributed by these media is marginally consistent with the CHIME/FRB catalog. In this scenario, our simulations favor a population of FRBs offset from their galaxy centers over a population that is distributed along the spiral arms. However, if the models proposing the CGM as a source of intense scattering are incorrect, then we conclude that FRBs may inhabit environments with more extreme properties than those inferred for pulsars in the Milky Way.
This study was conducted to assess the net proteolytic activity of human non-Hodgkin's lymphomas (NHLs). We have compared the extracellular matrix (ECM)-degradative abilities of human NHLs, reactive ...lymphoid hyperplasias, and established lymphoid cell lines using Matrigel invasion and elastin degradation assays. The inhibition studies allowed identification of the classes of proteinases involved in ECM degradation. Our results indicate that lymphocytes and other leukocytes derived from both human NHLs and reactive lymphoid hyperplasias are capable of Matrigel penetration, but only cells derived from the high-grade human NHLs degrade elastin in vitro. Established lymphoid cell lines (both malignant and Epstein-Barr virus immortalized) do not produce MMP-9, do not penetrate the Matrigel, and do not degrade elastin. Moreover, in human NHLs, elastolytic activity is blocked by metalloproteinase inhibitors, while inhibitors of the other classes of proteolytic enzymes have only minor effects. This study identifies metalloproteinases as the most important class of proteinases involved in ECM degradation by NHLs. The previous studies suggest that, within this class, MMP-9 represents the key enzyme that plays a role in the biological aggressiveness of human NHLs.
Portal hypertension due to either prehepatic portal hypertension or cirrhosis is associated with cardiovascular derangement. We aimed to delineate regulatory mechanisms in the brain stem ...cardiovascular nuclei in rat models of prehepatic portal hypertension and cirrhosis. Neuronal activation in the nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM) were assessed by immunohistochemical staining for the immediate-early gene product Fos. In the same sections, catecholaminergic neurons were counted by tyrosine hydroxylase (TH) staining. Ninety minutes after hypotensive hemorrhage (or no volume challenge), the animals were killed for Fos and TH medullary staining. These protocols were repeated after capsaicin administration. The NTS of unchallenged sham-operated rats had scant Fos-positive cells (3.6 +/- 0.4 cells/section), whereas hemorrhage significantly increased Fos staining (91.8 +/- 14). In contrast, the unchallenged portal hypertensive and cirrhotic groups showed increased Fos staining (14.3 +/- 5.8 and 32.8 +/- 2.8, respectively), which hemorrhage did not alter significantly. The numbers of TH-positive cells were similar in the three unchallenged groups; double labeling revealed that approximately 50% of TH-positive cells were activated by hemorrhage in the sham and cirrhotic rats but not the portal hypertensive rats. Similar patterns of Fos and TH staining were observed in the VLM. Capsaicin treatment not only significantly reduced the Fos-positive neuron numbers in portal hypertensive and cirrhotic rats but also attenuated hemorrhage-induced Fos and double-positive cells in both NTS and VLM. These results suggest that disordered trafficking in capsaicin-sensitive nerves and central dysregulation contribute to blunted cardiovascular responsiveness in cirrhosis and prehepatic portal hypertension.
Cardiovascular function in cirrhosis is deranged, with indirect evidence of abnormal central cardiovascular regulation. We aimed to elucidate the role of brainstem cardiovascular nuclei in ...hemodynamic regulation by examining the protein product, Fos, of the immediate‐early gene c‐fos, in cirrhotic rats. Cirrhosis was induced by chronic bile duct ligation (BDL) of 25‐days duration, while controls underwent a sham operation. To examine the effects of jaundice per se in the absence of cirrhosis, a third group of 5‐day BDL rats was also studied. All rats were anesthetized with pentobarbital, and catheters were inserted to measure baseline blood pressure and heart rate. Separate groups were then subjected to volume manipulation by a hypotensive hemorrhage or isotonic saline infusion, or no challenge. Ninety minutes after the volume manipulation, the animals were killed and the medulla sectioned and stained for Fos by immunohistochemisty. The nucleus tractus solitarius (NTS) of the sham‐operated unchallenged rats showed scant Fos immunoreactivity (27.8 ± 3.3 cells), but both hemorrhage and volume infusion significantly increased Fos staining (86.0 ± 3.7 and 95.2 ± 8.5, respectively). In contrast, the unchallenged cirrhotic rats showed markedly increased Fos in the NTS (154.6 ± 27.0), but neither hemorrhage nor volume infusion significantly changed the amount of Fos staining. Fos staining in the ventrolateral medulla (VLM) followed a similar pattern with low staining in the unchallenged sham rats and increased staining in the other groups, but no differences between the unchallenged and the volume‐manipulated cirrhotic groups. The 5‐day BDL jaundiced rats showed no baseline increase in Fos staining, nor any significant increase after hemorrhage. These results showing baseline activation of central neuronal regions responsible for blood pressure homeostasis, but completely blunted responsiveness in cirrhotic rats, confirm a central origin of disordered cardiovascular regulation. The presence of jaundice may also contribute to the central cardiovascular hyporesponsiveness.
We present a Monte Carlo-based population synthesis study of fast radio burst (FRB) dispersion and scattering focusing on the first catalog of sources detected with the Canadian Hydrogen Intensity ...Mapping Experiment Fast Radio Burst (CHIME/FRB) project. We simulate intrinsic properties and propagation effects for a variety of FRB population models and compare the simulated distributions of dispersion measures (DMs) and scattering timescales with the corresponding distributions from the CHIME/FRB catalog. Our simulations confirm the results of previous population studies, which suggested that the interstellar medium of the host galaxy alone (simulated based on the NE2001 model) cannot explain the observed scattering timescales of FRBs. We therefore consider additional sources of scattering, namely, the circumgalactic medium (CGM) of intervening galaxies and the circumburst medium whose properties are modeled based on typical Galactic plane environments. We find that a population of FRBs with scattering contributed by these media is marginally consistent with the CHIME/FRB catalog. In this scenario, our simulations favor a population of FRBs offset from their galaxy centers over a population which is distributed along the spiral arms. However, if the models proposing the CGM as a source of intense scattering are incorrect, then we conclude that FRBs may inhabit environments with more extreme properties than those inferred for pulsars in the Milky Way.
Background Protein supplements are routinely used after a laparoscopic gastric bypass (LGB). The aim of this study was to evaluate the impact of an amino acid supplement on glucose homeostasis and ...hormonal and inflammatory markers after LGB. Study Design Thirty patients undergoing LGB were randomized to receive or not 24 g of an oral supplement containing a leucine metabolite, glutamine, and arginine twice daily. Changes in weight, glucose, insulin, C-peptide, insulin sensitivity, interleukin (IL) 6, C-reactive protein (CRP), leptin, insulin-like growth factor (IGF) 1, ghrelin, and incretins were assessed preoperatively and 2 weeks and 8 weeks postoperatively. Results Thirty patients (96.7% female, age 46.9 ± 8.4 years, body mass index 43.3 ± 4.1 kg/m2 ) were randomized. The experimental (n = 14) and control (n = 16) groups were not significantly different at baseline. Weight loss was similar for the 2 groups. Fasting glucose decreased significantly at 2 and 8 weeks compared with base line (p < 0.0001) with no difference between the experimental and control groups (p = 0.8), but insulin and calculated insulin sensitivity, which were similar at baseline, became significantly worse in the experimental group 8 weeks after surgery (p = 0.02 for insulin; p = 0.04 for the homeostasis model assessment of insulin resistance). CRP and IL-6, which were similar at baseline, were found to be significantly higher at 8 weeks in the experimental group (p = 0.018 and p = 0.05, respectively). Leptin and IGF-1 levels decreased significantly from baseline at 2 and 8 weeks (p < 0.0001), but there was no difference between the 2 groups. No significant changes in GLP-1, ghrelin, or gastric inhibitory polypeptide were noticed after 8 weeks. Conclusions An amino acid supplement had no effect on the early postoperative incretins after LGB. It may have a negative influence on glucose kinetics and degree of inflammation. Future studies are needed to clarify these effects.
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has become a leading facility for detecting fast radio bursts (FRBs) through the CHIME/FRB backend. CHIME/FRB searches for fast transients ...in polarization-summed intensity data streams that have 24-kHz spectral and 1-ms temporal resolution. The intensity beams are pointed to pre-determined locations in the sky. A triggered baseband system records the coherent electric field measured by each antenna in the CHIME array at the time of FRB detections. Here we describe the analysis techniques and automated pipeline developed to process these full-array baseband data recordings. Whereas the real-time FRB detection pipeline has a localization limit of several arcminutes, offline analysis of baseband data yields source localizations with sub-arcminute precision, as characterized by using a sample of pulsars and one repeating FRB with known positions. The baseband pipeline also enables resolving temporal substructure on a micro-second scale and the study of polarization including detections of Faraday rotation.
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