The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a novel transit radio telescope operating across the 400-800 MHz band. CHIME is composed of four 20 m × 100 m semicylindrical paraboloid ...reflectors, each of which has 256 dual-polarization feeds suspended along its axis, giving it a 200 deg2 field of view. This, combined with wide bandwidth, high sensitivity, and a powerful correlator, makes CHIME an excellent instrument for the detection of fast radio bursts (FRBs). The CHIME Fast Radio Burst Project (CHIME/FRB) will search beam-formed, high time and frequency resolution data in real time for FRBs in the CHIME field of view. Here we describe the CHIME/FRB back end, including the real-time FRB search and detection software pipeline, as well as the planned offline analyses. We estimate a CHIME/FRB detection rate of 2-42 FRBs sky-1 day-1 normalizing to the rate estimated at 1.4 GHz by Vander Wiel et al. Likely science outcomes of CHIME/FRB are also discussed. CHIME/FRB is currently operational in a commissioning phase, with science operations expected to commence in the latter half of 2018.
Fast radio bursts (FRBs) are highly dispersed millisecond-duration radio flashes probably arriving from far outside the Milky Way
. This phenomenon was discovered at radio frequencies near 1.4 GHz ...and so far has been observed in one case
at as high as 8 GHz, but not below 700 MHz in spite of significant searches at low frequencies
. Here we report detections of 13 FRBs at radio frequencies as low as 400 MHz, on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) using the CHIME/FRB instrument
. They were detected during a telescope pre-commissioning phase, when our sensitivity and field-of-view were not yet at design specifications. Emission in multiple events is seen down to 400 MHz, the lowest radio frequency to which we are sensitive. The FRBs show various temporal scattering behaviours, with the majority significantly scattered, and some apparently unscattered to within measurement uncertainty even at our lowest frequencies. Of the 13 reported here, one event has the lowest dispersion measure yet reported, implying that it is among the closest yet known, and another has shown multiple repeat bursts, as described in a companion paper
. The overall scattering properties of our sample suggest that FRBs as a class are preferentially located in environments that scatter radio waves more strongly than the diffuse interstellar medium in the Milky Way.
We report on the discovery of eight repeating fast radio burst (FRB) sources found using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. These sources span a dispersion measure ...(DM) range of 103.5-1281 pc cm−3. They display varying degrees of activity: six sources were detected twice, another three times, and one 10 times. These eight repeating FRBs likely represent the bright and/or high-rate end of a distribution of infrequently repeating sources. For all sources, we determine sky coordinates with uncertainties of ∼10′. FRB 180916.J0158+65 has a burst-averaged DM = 349.2 0.3 pc cm−3 and a low DM excess over the modeled Galactic maximum (as low as ∼20 pc cm−3); this source also has a Faraday rotation measure (RM) of −114.6 0.6 rad m−2, which is much lower than the RM measured for FRB 121102. FRB 181030.J1054+73 has the lowest DM for a repeater, 103.5 0.3 pc cm−3, with a DM excess of ∼70 pc cm−3. Both sources are interesting targets for multi-wavelength follow-up due to their apparent proximity. The DM distribution of our repeater sample is statistically indistinguishable from that of the first 12 CHIME/FRB sources that have not yet repeated. We find, with 4 significance, that repeater bursts are generally wider than those of CHIME/FRB bursts that have not repeated, suggesting different emission mechanisms. Many of our repeater events show complex morphologies that are reminiscent of the first two discovered repeating FRBs. The repetitive behavior of these sources will enable interferometric localizations and subsequent host galaxy identifications.
We report the detection of a single burst from the first-discovered repeating fast radio burst (FRB) source, FRB 121102, with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope, ...which operates in the frequency band 400-800 MHz. The detected burst occurred on 2018 November 19 and its emission extends down to at least 600 MHz, the lowest frequency detection of this source yet. The burst, detected with a significance of 23.7 , has fluence 12 3 Jy ms and shows complex time and frequency morphology. The 34 ms width of the burst is the largest seen for this object at any frequency. We find evidence of subburst structure that drifts downward in frequency at a rate of −3.9 0.2 MHz ms−1. Our best fit tentatively suggests a dispersion measure of 563.6 0.5 pc cm−3, which is 1% higher than previously measured values. We set an upper limit on the scattering time at 500 MHz of 9.6 ms, which is consistent with expectations from the extrapolation from higher-frequency data. We have exposure to the position of FRB 121102 for a total of 11.3 hr within the FWHM of the synthesized beams at 600 MHz from 2018 July 25 to 2019 February 25. We estimate on the basis of this single event an average burst rate for FRB 121102 of 0.1-10 per day in the 400-800 MHz band for a median fluence threshold of 7 Jy ms in the stated time interval.
The HeartWare left ventricular assist device (HVAD, HeartWare Inc, Framingham, MA) is the first implantable centrifugal continuous-flow pump approved for use as a bridge to transplantation. An ...infrequent but serious adverse event of LVAD support is thrombus ingestion or formation in the pump. In this study, we analyze the incidence of pump thrombus, evaluate the comparative effectiveness of various treatment strategies, and examine factors pre-disposing to the development of pump thrombus.
The analysis included 382 patients who underwent implantation of the HVAD as part of the HeartWare Bridge to Transplant (BTT) and subsequent Continued Access Protocol (CAP) trial. Descriptive statistics and group comparisons were generated to analyze baseline characteristics, incidence of pump thrombus, and treatment outcomes. A multivariate analysis was performed to assess significant risk factors for developing pump thrombus.
There were 34 pump thrombus events observed in 31 patients (8.1% of the cohort) for a rate of 0.08 events per patient-year. The incidence of pump thrombus did not differ between BTT and CAP. Medical management of pump thrombus was attempted in 30 cases, and was successful in 15 (50%). A total of 16 patients underwent pump exchange, and 2 underwent urgent transplantation. Five patients with a pump thrombus died after medical therapy failed, 4 of whom also underwent a pump exchange. Survival at 1 year in patients with and without a pump thrombus was 69.4% and 85.5%, respectively (p = 0.21). A multivariable analysis revealed that significant risk factors for pump thrombus included a mean arterial pressure > 90 mm Hg, aspirin dose ≤ 81 mg, international normalized ratio ≤ 2, and Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) profile level of ≥ 3 at implant.
Pump thrombus is a clinically important adverse event in patients receiving an HVAD, occurring at a rate of 0.08 events per patient-year. Significant risk factors for pump thrombosis include elevated blood pressure and sub-optimal anti-coagulation and anti-platelet therapies. This suggests that pump thrombus event rates could be reduced through careful adherence to patient management guidelines.
The HeartWare Ventricular Assist System (HeartWare Inc, Framingmam, MA) is a miniaturized implantable, centrifugal design, continuous-flow blood pump. The pivotal bridge to transplant and continued ...access protocols trials have enrolled patients with advanced heart failure in a bridge-to-transplant indication.
The primary outcome, success, was defined as survival on the originally implanted device, transplant, or explant for ventricular recovery at 180 days. Secondary outcomes included an evaluation of survival, functional and quality of life outcomes, and adverse events.
A total of 332 patients in the pivotal bridge to transplant and continued access protocols trial have completed their 180-day primary end-point assessment. Survival in patients receiving the HeartWare pump was 91% at 180 days and 84% at 360 days. Quality of life scores improved significantly, and adverse event rates remain low.
The use of the HeartWare pump as a bridge to transplant continues to demonstrate a high 180-day survival rate despite a low rate of transplant. Adverse event rates are similar or better than those observed in historical bridge-to-transplant trials, despite longer exposure times due to longer survival and lower transplant rates.
Reverse osmosis membranes are becoming increasingly popular for water purification applications that require high salt rejection such as brackish and seawater desalination. However, due to fouling by ...microorganisms, they have been unable to realize their full potential as of yet. Biofouling leads to the use of higher operating pressure, more frequent chemical cleaning, and shorter membrane life. This paper reviews the causes, consequences and control of biofouling in RO membranes used for seawater desalination. After a brief introduction, the fundamentals of biofouling are discussed in some detail: biofilm formation, role of EPS, and sequence of events leading to biofouling. This is followed by a section on consequences of biofouling on membrane processes with particular emphasis on water permeability and salt rejection. The mechanisms of performance degradation are discussed in some detail for both of these parameters. The last section of this paper reviews the different antifouling strategies that have recently gained more attention with special emphasis on membrane surface modification. A brief conclusion with some recommendations and suggestions is presented at the end of the article.
► Comprehensive review of RO membrane biofouling. ► Description of the phenomenon. ► Effects on membrane processes. ► Control and prevention strategies. ► Conclusion with some recommendations.
The discovery of a repeating fast radio burst (FRB) source
, FRB 121102, eliminated models involving cataclysmic events for this source. No other repeating FRB has hitherto been detected despite many ...recent discoveries and follow-ups
, suggesting that repeaters may be rare in the FRB population. Here we report the detection of six repeat bursts from FRB 180814.J0422+73, one of the 13 FRBs detected
by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB project
during its pre-commissioning phase in July and August 2018. These repeat bursts are consistent with originating from a single position on the sky, with the same dispersion measure, about 189 pc cm
. This traces approximately twice the expected Milky Way column density, and implies an upper limit on the source redshift of 0.1, at least a factor of about 2 closer than FRB 121102
. In some of the repeat bursts, we observe sub-pulse frequency structure, drifting, and spectral variation reminiscent of that seen in FRB 121102
, suggesting similar emission mechanisms and/or propagation effects. This second repeater, found among the first few CHIME/FRB discoveries, suggests that there exists-and that CHIME/FRB and other wide-field, sensitive radio telescopes will find-a substantial population of repeating FRBs.
First-line and adjuvant treatment for food-induced anaphylaxis1114 6.3.2. Despite the risk of severe allergic reactions and even death, there is no current treatment for FA: the disease can only be ...managed by allergen avoidance or treatment of symptoms. ...the diagnosis of FA may be problematic, given that nonallergic food reactions, such as food intolerance, are frequently confused with FAs. Due to these concerns, the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, working with more than 30 professional organizations, federal agencies, and patient advocacy groups, led the development of "best practice" clinical guidelines for the diagnosis and management of FA (henceforth referred to as the Guidelines).1 Based on a comprehensive review and objective evaluation of the recent scientific and clinical literature on FA, the Guidelines were developed by and designed for allergists/immunologists, clinical researchers, and practitioners in the areas of pediatrics, family medicine, internal medicine, dermatology, gastroenterology, emergency medicine, pulmonary and critical care medicine, and others. Bronchodilator (β2-agonist): albuterol MDI (child: 4-8 puffs; adult: 8 puffs) or Nebulized solution (child: 1.5 ml; adult: 3 ml) every 20 minutes or continuously as needed H1 antihistamine: diphenhydramine 1 to 2 mg/kg per dose Maximum dose, 50 mg IV or oral (oral liquid is more readily absorbed than tablets) Alternative dosing may be with a less-sedating second generation antihistamine H2 antihistamine: ranitidine 1 to 2 mg/kg per dose Maximum dose, 75 to 150 mg oral and IV Corticosteroids Prednisone at 1 mg/kg with a maximum dose of 60 to 80 mg oral or Methylprednisolone at 1 mg/kg with a maximum dose of 60 to 80 mg IV Vasopressors (other than epinephrine) for refractory hypotension, titrate to effect Glucagon for refractory hypotension, titrate to effect Child: 20-30 μg/kg Adult: 1-5 mg Dose may be repeated or followed by infusion of 5-15 μg/min Atropine for bradycardia, titrate to effect Supplemental oxygen therapy IV fluids in large volumes if patients present with orthostasis, hypotension, or incomplete response to IM epinephrine Place the patient in recumbent position if tolerated, with the lower extremities elevated Therapy for the patient at discharge First-line treatment:
Fibrous dysplasia (FD) is a rare bone disease caused by postzygotic somatic activating mutations in the GNAS gene, which lead to constitutive activation of adenylyl cyclase and elevated levels of ...cyclic AMP, which act on downstream signaling pathways and cause normal bone to be replaced with fibrous tissue and abnormal (woven) bone. The bone disease may occur in one bone (monostotic), multiple bones (polyostotic), or in combination with hyperfunctioning endocrinopathies and hyperpigmented skin lesions (in the setting of McCune–Albright Syndrome). FD is common in the craniofacial skeleton, causing significant dysmorphic features, bone pain, and dental anomalies. This review summarizes the pathophysiology, clinical findings, and treatment of FD, with an emphasis on the craniofacial and oral manifestations of the disease.
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