770 research outputs found

    Differences in health symptoms among residents living near illegal dump sites in Los Laureles Canyon, Tijuana, Mexico: a cross sectional survey.

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    Living near landfills is a known health hazard prompting recognition of environmental injustice. The study aim was to compare self-reported symptoms of ill health among residents of four neighborhoods, living in haphazardly constructed settlements surrounded by illegal dumpsites in Tijuana, Mexico. One adult from each of 388 households located in Los Laureles Canyon were interviewed about demographics, health status, and symptoms. Distance from each residence to both the nearest dumpsite and the canyon bottom was assessed. The neighborhoods were selected from locations within the canyon, and varied with respect to proximity to dump sites. Residents of San Bernardo reported significantly higher frequencies of ill-health symptoms than the other neighborhoods, including extreme fatigue (OR 3.01 (95% CI 1.6-5.5)), skin problems/irritations (OR 2.73 (95% CI 1.3-5.9)), stomach discomfort (OR 2.47 (1.3-4.8)), eye irritation/tears (OR 2.02 (1.2-3.6)), and confusion/difficulty concentrating (OR 2.39 (1.2-4.8)). Proximity to dumpsites did not explain these results, that varied only slightly when adjusted for distance to nearest dumpsite or distance to the canyon bottom. Because San Bernardo has no paved roads, we hypothesize that dust and the toxicants it carries is a possible explanation for this difference. Studies are needed to further document this association and sources of toxicants

    Five New Millisecond Pulsars From a Radio Survey of 14 Unidentified Fermi-LAT Gamma-ray Sources

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    We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Fermi-LAT sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephemeris derived from timing observations of PSR J0101-6422 (P =2.57 ms, DM=12 pc cm-3), we have detected {\gamma}-ray pulsations and measured its proper motion. Its {\gamma}-ray spectrum (a power law of {\Gamma} = 0.9 with a cutoff at 1.6 GeV) and efficiency are typical of other MSPs, but its radio and {\gamma}-ray light curves challenge simple geometric models of emission. The high success rate of this survey-enabled by selecting {\gamma}-ray sources based on their detailed spectral characteristics-and other similarly successful searches indicate that a substantial fraction of the local population of MSPs may soon be known.Comment: 6 pages, 3 figures, 2 tables, accepted by ApJ

    Radio Detection of the Fermi LAT Blind Search Millisecond Pulsar J1311-3430

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    We report the detection of radio emission from PSR J1311-3430, the first millisecond pulsar discovered in a blind search of Fermi Large Area Telescope (LAT) gamma-ray data. We detected radio pulsations at 2 GHz, visible for <10% of ~4.5-hrs of observations using the Green Bank Telescope (GBT). Observations at 5 GHz with the GBT and at several lower frequencies with Parkes, Nancay, and the Giant Metrewave Radio Telescope resulted in non-detections. We also report the faint detection of a steep spectrum continuum radio source (0.1 mJy at 5 GHz) in interferometric imaging observations with the Jansky Very Large Array. These detections demonstrate that PSR J1311-3430, is not radio quiet and provides additional evidence that the radio beaming fraction of millisecond pulsars is very large. The radio detection yields a distance estimate of 1.4 kpc for the system, yielding a gamma-ray efficiency of 30%, typical of LAT-detected MSPs. We see apparent excess delay in the radio pulsar as the pulsar appears from eclipse and we speculate on possible mechanisms for the non-detections of the pulse at other orbital phases and observing frequencies.Comment: 6 pages, 4 figures. ApJ Letters, in pres

    PSR J2030+3641: radio discovery and gamma-ray study of a middle-aged pulsar in the now identified Fermi-LAT source 1FGL J2030.0+3641

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    In a radio search with the Green Bank Telescope of three unidentified low Galactic latitude Fermi-LAT sources, we have discovered the middle-aged pulsar J2030+3641, associated with 1FGL J2030.0+3641 (2FGL J2030.0+3640). Following the detection of gamma-ray pulsations using a radio ephemeris, we have obtained a phase-coherent timing solution based on gamma-ray and radio pulse arrival times that spans the entire Fermi mission. With a rotation period of 0.2 s, spin-down luminosity of 3e34 erg/s, and characteristic age of 0.5 Myr, PSR J2030+3641 is a middle-aged neutron star with spin parameters similar to those of the exceedingly gamma-ray-bright and radio-undetected Geminga. Its gamma-ray flux is 1% that of Geminga, primarily because of its much larger distance, as suggested by the large integrated column density of free electrons, DM=246 pc/cc. We fit the gamma-ray light curve, along with limited radio polarimetric constraints, to four geometrical models of magnetospheric emission, and while none of the fits have high significance some are encouraging and suggest that further refinements of these models may be worthwhile. We argue that not many more non-millisecond radio pulsars may be detected along the Galactic plane that are responsible for LAT sources, but that modified methods to search for gamma-ray pulsations should be productive -- PSR J2030+3641 would have been found blindly in gamma rays if only >0.8 GeV photons had been considered, owing to its relatively flat spectrum and location in a region of high soft background.Comment: Accepted for publication in ApJ, 9 pages, 6 figure

    GMRT discovery of PSR J1544+4937, an eclipsing black-widow pulsar identified with a Fermi LAT source

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    Using the Giant Metrewave Radio Telescope (GMRT) we performed deep observations to search for radio pulsations in the directions of unidentified Fermi Large Area Telescope (LAT) gamma-ray sources. We report the discovery of an eclipsing black-widow millisecond pulsar, PSR J1544+4937, identified with the un-cataloged gamma-ray source Fermi J1544.2+4941. This 2.16 ms pulsar is in a 2.9 hours compact circular orbit with a very low-mass companion (Mc > 0.017 Msun). At 322 MHz this pulsar is found to be eclipsing for 13% of its orbit, whereas at 607 MHz the pulsar is detected throughout the low-frequency eclipse phase. Variations in the eclipse ingress phase are observed, indicating a clumpy and variable eclipsing medium. Moreover, additional short-duration absorption events are observed around the eclipse boundaries. Using the radio timing ephemeris we were able to detect gamma-ray pulsations from this pulsar, confirming it as the source powering the gamma-ray emission.Comment: 15 pages, 4 figures, 1 table, accepted for publication in ApJ Letter

    Three Millisecond Pulsars in FERMI LAT Unassociated Bright Sources

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    We searched for radio pulsars in 25 of the non-variable, unassociated sources in the Fermi LAT Bright Source List with the Green Bank Telescope at 820 MHz. We report the discovery of three radio and gamma-ray millisecond pulsars (MSPs) from a high Galactic latitude subset of these sources. All of the pulsars are in binary systems, which would have made them virtually impossible to detect in blind gamma-ray pulsation searches. They seem to be relatively normal, nearby (<=2 kpc) millisecond pulsars. These observations, in combination with the Fermi detection of gamma-rays from other known radio MSPs, imply that most, if not all, radio MSPs are efficient gamma-ray producers. The gamma-ray spectra of the pulsars are power-law in nature with exponential cutoffs at a few GeV, as has been found with most other pulsars. The MSPs have all been detected as X-ray point sources. Their soft X-ray luminosities of ~10^{30-31} erg/s are typical of the rare radio MSPs seen in X-rays.Comment: Accepted for publication in ApJ Letter

    Infrared based saliva screening test for COVID-19

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    Abstract: Severe acute respiratory syndrome coronavirus 2 has resulted in an unprecedented need for diagnostic testing that is critical in controlling the spread of COVID-19. We propose a portable infrared spectrometer with purpose-built transflection accessory for rapid point-of-care detection of COVID-19 markers in saliva. Initially, purified virion particles were characterized with Raman spectroscopy, synchrotron infrared (IR) and AFM-IR. A data set comprising 171 transflection infrared spectra from 29 patients testing positive for SARS-CoV-2 by RT-qPCR and 28 testing negative, was modeled using Monte Carlo Double Cross Validation with 50 randomized test and model sets. The testing sensitivity was 93 % (27/29) with a specificity of 82 % (23/28) that included positive samples on the limit of detection for RT-qPCR. Here, we demonstrate a proof-of-concept high throughput infrared COVID-19 test that is rapid, inexpensive, portable and utilizes sample self-collection thus minimizing the risk to healthcare workers and ideally suited to mass screening

    PSR J2030+364I: Radio Discovery and Gamma-ray Study of a Middle-aged Pulsar in the Now Identified Fermi-LAT Source 1FGL J2030.0+3641

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    In a radio search with the Green Bank Telescope of three unidentified low Galactic latitude Fermi-LAT sources, we have discovered the middle-aged pulsar J2030+3641, associated with IFGL J2030.0+3641 (2FGL J2030.0+3640). Following the detection of gamma-ray pulsations using a radio ephemeris, we have obtained a phase-coherent timing solution based on gamma-ray and radio pulse arrival times that spans the entire Fermi mission. With a rotation period of 0.28, spin-down luminosity of 3 x 10(exp 34) erg/s, and characteristic age of 0.5 Myr, PSR J2030+3641 is a middle-aged neutron star with spin parameters similar to those of the exceedingly gamma-ray-bright and radio-undetected Geminga. Its gamma-ray flux is 1 % that of Geminga, primarily because of its much larger distance, as suggested by the large integrated column density of free electrons, DM = 246 pc/cu cm. We fit the gamma-ray light curve, along with limited radio polarimetric constraints, to four geometrical models of magnetospheric emission, and while none of the fits have high significance some are encouraging and suggest that further refinements of these models may be worthwhile. We argue that not many more non-millisecond radio pulsars may be detected along the Galactic plane that are responsible for LAT sources, but that modified methods to search for gamma-ray pulsations should be productive - PSR J2030+364 I would have been found blindly in gamma rays if only > or approx. 0.8 GeV photons had been considered, owing to its relatively flat spectrum and location in a region of high soft background
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