An analysis of large-area CO J= 3-2 maps from the James Clerk Maxwell Telescope for 12 nearby spiral galaxies reveals low velocity dispersions in the molecular component of the interstellar medium. ...The three lowest luminosity galaxies show a relatively flat velocity dispersion as a function of radius while the remaining nine galaxies show a central peak with a radial fall-off within 0.2-0.4r
25. Correcting for the average contribution due to the internal velocity dispersions of a population of giant molecular clouds, the average cloud-cloud velocity dispersion across the galactic discs is 6.1 ± 1.0 km s−1 (standard deviation of 2.9 km s−1), in reasonable agreement with previous measurements for the Galaxy and M33. The cloud-cloud velocity dispersion derived from the CO data is on average two times smaller than the H i velocity dispersion measured in the same galaxies. The low cloud-cloud velocity dispersion implies that the molecular gas is the critical component determining the stability of the galactic disc against gravitational collapse, especially in those regions of the disc which are H2 dominated. The cloud-cloud velocity dispersion shows a significant positive correlation with both the far-infrared luminosity, which traces the star formation activity, and the K-band absolute magnitude, which traces the total stellar mass. For three galaxies in the Virgo cluster, smoothing the data to a resolution of 4.5 kpc (to match the typical resolution of high-redshift CO observations) increases the measured velocity dispersion by roughly a factor of 2, comparable to the dispersion measured recently in a normal galaxy at z= 1. This comparison suggests that the mass and star formation rate surface densities may be similar in galaxies from z= 0 to 1 and that the high star formation rates seen at z= 1 may be partly due to the presence of physically larger molecular gas discs.
We report the observation of 16 cosmic ray events with a mean energy of 1.5 × 10¹⁹ eV via radio pulses originating from the interaction of the cosmic ray air shower with the Antarctic geomagnetic ...field, a process known as geosynchrotron emission. We present measurements in the 300-900 MHz range, which are the first self-triggered, first ultrawide band, first far-field, and the highest energy sample of cosmic ray events collected with the radio technique. Their properties are inconsistent with current ground-based geosynchrotron models. The emission is 100% polarized in the plane perpendicular to the projected geomagnetic field. Fourteen events are seen to have a phase inversion due to reflection of the radio beam off the ice surface, and two additional events are seen directly from above the horizon. Based on a likelihood analysis, we estimate angular pointing precision of order 2° for the event arrival directions.
ABSTRACT SGR1833-0832 was discovered on 2010 March 19, thanks to the Swift detection of a short hard X-ray burst and follow-up X-ray observations. Since then, it was repeatedly observed with Swift, ...Rossi X-ray Timing Explorer and XMM-Newton. Using these data, which span about 225d, we studied the long-term spectral and timing characteristics of SGR1833-0832. We found evidence for diffuse emission surrounding SGR1833-0832, which is most likely a halo produced by the scattering of the point-source X-ray radiation by dust along the line of sight, and we show that the source X-ray spectrum is well described by an absorbed blackbody, with temperature kT 1.2keV and absorbing column NH= (10.4 ± 0.2) × 1022cm-2, while different or more complex models are disfavoured. The source persistent X-ray emission remained fairly constant at 3.7 × 10-12 erg cm-2s-1 for the first 20d after the onset of the bursting episode, then it faded by a factor of 40 in the subsequent 140d, following a power-law trend with index α-0.5. We obtained a phase-coherent timing solution with the longest baseline (225d) to date for this source which, besides period P= 7.5654084(4)s and period derivative ss-1, includes higher order period derivatives. We also report on our search of the counterpart to the soft gamma-ray repeater (SGR) at radio frequencies using the Australia Telescope Compact Array and the Parkes Radio Telescope. No evidence for radio emission was found, down to flux densities of 0.9mJy (at 1.5 GHz) and 0.09mJy (at 1.4 GHz) for the continuum and pulsed emissions, respectively, consistently with other observations at different epochs. Finally, the analysis of the field of PSRB1830-08 (J1833-0827), which was serendipitously imaged by the XMM-Newton observations, led to the discovery of the X-ray pulsar wind nebula generated by this 85-ms radio pulsar. We discuss its possible association with the unidentified TeV source HESSJ1834-087. PUBLICATION ABSTRACT
The Calorimetric Electron Telescope, CALET, is an astroparticle physics mission installed on the International Space Station, ISS. The primary objective of the mission is studying the details of ...galactic cosmic-ray acceleration and propagation, and searching for the possible nearby sources of high-energy electrons and dark matter signatures. The CALET experiment measure the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma-rays to 10 TeV and nuclei to 1000 TeV. The detector is an all-calorimetric instrument with a total vertical thickness of 30 radiation lengths and fine imaging capability, optimized for the measurement of the electron and positron (all-electron) spectrum well into the TeV energy region. It consists of a charge detector (CHD) with two layers of segmented plastic scintillators for the identification of cosmic-rays via a measurement of their charge over the range Z=1∼40, a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 radiation length thick lead-tungstate calorimeter (TASC). The instrument was launched on August 19, 2015 to the ISS and installed on the Japanese Experiment Module-Exposed Facility. Since the start of operation in October, 2015, CALET has been collecting scientific data without any major interruption for more than eight years. The number of triggered events over 10 GeV is nearly 1.97 billion events as of November 30, 2023. In this paper, we present the results of the CALET mission so far, including the all-electron energy spectrum, the spectra of protons and other nuclei, gamma-ray observations, as well as the characterization of on-orbit performance. Some results on the electromagnetic counterpart search for LIGO/Virgo gravitational wave events and the observations of solar modulation and gamma-ray bursts are also included.
Heparanase, a heparan sulfate (HS)–specific endoglucuronidase, mediates the onset of proteinuria and renal damage during experimental diabetic nephropathy. Glomerular heparanase expression is ...increased in most proteinuric diseases. Herein, we evaluated the role of heparanase in two models of experimental glomerulonephritis, being anti-glomerular basement membrane and lipopolysaccharide-induced glomerulonephritis, in wild-type and heparanase-deficient mice. Induction of experimental glomerulonephritis led to an increased heparanase expression in wild-type mice, which was associated with a decreased glomerular expression of a highly sulfated HS domain, and albuminuria. Albuminuria was reduced in the heparanase-deficient mice in both models of experimental glomerulonephritis, which was accompanied by a better renal function and less renal damage. Notably, glomerular HS expression was preserved in the heparanase-deficient mice. Glomerular leukocyte and macrophage influx was reduced in the heparanase-deficient mice, which was accompanied by a reduced expression of both types 1 and 2 helper T-cell cytokines. In vitro , tumor necrosis factor-α and lipopolysaccharide directly induced heparanase expression and increased transendothelial albumin passage. Our study shows that heparanase contributes to proteinuria and renal damage in experimental glomerulonephritis by decreasing glomerular HS expression, enhancing renal leukocyte and macrophage influx, and affecting the local cytokine milieu.
The CALorimetric Electron Telescope CALET is collecting science data on the International Space Station since October 2015 with excellent and continuous performance. Energy is measured with a deep ...homogeneous calorimeter (1.2 nuclear interaction lengths, 27 radiation lengths) preceded by an imaging pre-shower (3 radiation lengths, 1mm granularity) providing tracking and
electron/proton discrimination. Two independent sub-systems identify the charge
of the incident particle from proton to iron and above (
40). CALET measures the cosmic-ray electron + positron flux up to 20 TeV, gamma rays up to 10 TeV, and nuclei up to the PeV scale. In this paper, we report the on-orbit performance of the instrument and summarize the main results obtained during the first 5 years of operation, including the electron + positron energy spectrum and the individual spectra of protons, heavier nuclei and iron. Solar modulation and gamma-ray observations are also concisely reported, as well as transient phenomena and the search for gravitational wave counterparts.
Pacemakers can automatically identify and catalog atrial high-rate episodes (AHREs). While most AHREs represent true atrial tachyarrhythmia/atrial fibrillation (AT/AF), a review of stored ...electrograms suggests that a substantial proportion do not. As AHREs may lead to the initiation of oral anticoagulation, it is crucial to understand the relationship between AHREs and true AT/AF.
To compare the positive predictive value of AHREs for electrogram-confirmed AT/AF for various atrial rates and episode durations.
By using data from 2580 patients who participated in the ASymptomatic atrial fibrillation and Stroke Evaluation in pacemaker patients and the AF Reduction atrial pacing Trial, all AHREs >6 minutes and >190 beats/min with available electrograms were reviewed to determine whether they represented true AT/AF. The positive predictive value of these AHREs was assessed for episode durations of 6 minutes, 30 minutes, 6 hours, and 24 hours at atrial rates of 190 and 250 beats/min.
Of 5769 AHREs >6 minutes and >190 beats/min, 82.7% were true AT/AF and 17.3% were false positives (predominantly due to repetitive non-re-entrant ventriculoatrial synchrony). False positives dropped to 6.8%, 3.3%, and 1.8% when the threshold duration was increased to 30 minutes, 6 hours, and 24 hours, respectively. Increasing the threshold heart rate to 250 beats/min added little to the positive predictive value when longer threshold durations were used.
By using a cutoff of >6 minutes and >190 beats/min, the rate of false-positive AHREs is 17.3%, making physician review of electrograms essential. For AHREs lasting >6 hours, the rate of false positives is 3.3%, making physician review less crucial.
The relative abundance of nickel with respect to iron is by far larger than all other trans-iron elements, therefore it provides a favourable opportunity for a low background measurement of its ...spectrum. Since nickel, as well as iron, is one of the most stable nuclei, the nickel energy spectrum and its relative abundance with respect to iron provide important information to estimate the abundances at the source and to model the propagation of heavy nuclei. However, only a few direct measurements of cosmic-ray nickel at energy larger than∼3 GeV/n are available at present in the literature and they are affected by strong limitations in both energy reach and statistics. In this paper we present a measurement of the differential energy spectrum of nickel from 8.8 GeV/nto 240 GeV/n, carried out with unprecedented precision by the Calorimetric Electron1 Telescope(CALET) in operation on the International Space Station since 2015. The CALET instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number Z = 40). The particle’s energy is measured by a homogeneous calorimeter (1.2 proton interaction lengths, 27 radiation lengths) preceded by a thin imaging section (3 radiation lengths) providing tracking and energy sampling. This paper follows our previous measurement of the iron spectrum 1 and it extends our investigation on the energy dependence of the spectral index of heavy elements. It reports the analysis of nickel data collected from November 2015 to May 2021 and a detailed assessment of the systematic uncertainties. In the region from 20 GeV/nto 240 GeV/n our present data are compatible within the errors with a single power law with spectral index−2.51±0.07.
Iron and nickel cosmic ray nuclei play a key role in the understanding of the acceleration and propagation mechanisms of charged particles in our Galaxy. In fact, iron and nickel are the most ...abundant nuclei among the heavy elements and provide favorable conditions for a low background measurement thanks to the negligible contamination from spallation of higher mass elements. CALET, operating on the ISS since 2015, has excellent capabilities of charge discrimination up to nickel and can measure the energy of cosmic ray nuclei thanks to a lead tungstate calorimeter providing a direct and precise measurement of heavy charged nuclei spectra. In this contribution, a direct measurement of iron and nickel nuclei spectra in the energy range from 10 GeV/n to 2 TeV/n and from 8.8 GeV/n to 240 GeV/n, respectively is presented. More than five years of data collected by CALET were used. A detailed study of systematic uncertainties is also illustrated. The measured spectra are compared with the ones measured by other experiments and are compatible with a single power law fit in the energy region from 50 GeV/n to 2 TeV/n and from 20 GeV/n to 240 GeV/n for iron and nickel respectively. Also, the ratio between nickel and iron spectra is reported.
We report measurements of record-setting intensities of cosmic-ray nuclei from C to Fe, made with the Cosmic Ray Isotope Spectrometer carried on the Advanced Composition Explorer in orbit about the ...inner Sun-Earth Lagrangian point. In the energy interval from ~70 to ~450 MeV nucleon--1, near the peak in the near-Earth cosmic-ray spectrum, the measured intensities of major species from C to Fe were each 20%-26% greater in late 2009 than in the 1997-1998 minimum and previous solar minima of the space age (1957-1997). The elevated intensities reported here and also at neutron monitor energies were undoubtedly due to several unusual aspects of the solar cycle 23/24 minimum, including record-low interplanetary magnetic field (IMF) intensities, an extended period of reduced IMF turbulence, reduced solar-wind dynamic pressure, and extremely low solar activity during an extended solar minimum. The estimated parallel diffusion coefficient for cosmic-ray transport based on measured solar-wind properties was 44% greater in 2009 than in the 1997-1998 solar-minimum period. In addition, the weaker IMF should result in higher cosmic-ray drift velocities. Cosmic-ray intensity variations at 1 AU are found to lag IMF variations by 2-3 solar rotations, indicating that significant solar modulation occurs inside ~20 AU, consistent with earlier galactic cosmic-ray radial-gradient measurements. In 2010, the intensities suddenly decreased to 1997 levels following increases in solar activity and in the inclination of the heliospheric current sheet. We describe the conditions that gave cosmic rays greater access to the inner solar system and discuss some of their implications.
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