We report on a search for high-energy counterparts to fast radio bursts (FRBs) with the Fermi Gamma-ray Burst Monitor, Fermi Large Area Telescope, and the Neil Gehrels Swift Observatory Burst Alert ...Telescope. We find no significant associations for any of the 23 FRBs in our sample, but report upper limits to the high-energy fluence for each on timescales of 0.1, 1, 10, and 100 s. We report lower limits on the ratio of the radio to high-energy fluence, fr/fγ, for timescales of 0.1 and 100 s. We discuss the implications of our non-detections on various proposed progenitor models for FRBs, including analogs of giant pulses from the Crab pulsar and hyperflares from magnetars. This work demonstrates the utility of analyses of high-energy data for FRBs in tracking down the nature of these elusive sources.
Assessments for potential impact to human health from environmental exposures were carried out for 44 active pharmaceutical ingredients (APIs) marketed by GlaxoSmithKline (GSK), representing ...approximately 22 general pharmacological classes exhibiting a broad spectrum of therapeutic activities. These assessments use the considerable amount of information available on the human pharmacology and toxicology of the APIs to develop acceptable daily intakes (ADIs) which are believed to be without pharmacological or toxicological effect. With the exception of the anti-cancer drugs and some antibiotics, the minimum dose producing the intended therapeutic effect was typically used as the point of departure for calculation of ADIs. The ADI values were used to generate predicted no effect concentrations from environmental exposure for human health (PNEC
HHs) from drinking water or fish consumption. These PNECs were compared to predicted environmental concentrations (PECs) calculated using the regional assessment models P
hATE™ for North America and GREAT-ER for Europe. Risk was characterized by calculating the ratio of the 90th percentile PECs to the PNEC
HHs. For the APIs reported here, these ratios are less than one for all of the compounds, varying from 7
×
10
−2 to 6
×
10
−11, indicating that based upon currently available data, these compounds do not appear to pose an appreciable risk to human health from potential environmental exposure from drinking water and fish consumption.
We present multiwavelength modeling of the afterglow from the long γ-ray burst (GRB) 160625B using Markov Chain Monte Carlo techniques of the afterglowpy Python package. GRB 160625B is an extremely ...bright burst with a rich set of observations spanning from radio to γ-ray frequencies. These observations range from ∼0.1 days to >1000 days, thus making this event extremely well suited to such modeling. In this work we compare top-hat and Gaussian jet structure types in order to find best-fit values for the GRB jet collimation angle, viewing angle, and other physical parameters. We find that a Gaussian-shaped jet is preferred (2.7 -5.3 ) over the traditional top-hat model. Our estimate for the opening angle of the burst ranges from 1 26 to 3 90, depending on jet-shape model. We also discuss the implications that assumptions on jet shape, viewing angle, and particularly the participation a fraction of electrons have on the final estimation of GRB intrinsic energy release and the resulting energy budget of the relativistic outflow. Most notably, allowing the participation fraction to vary results in an estimated total relativistic energy of ∼1053 erg. This is two orders of magnitude higher than when the total fraction is assumed to be unity; thus, this parameter has strong relevance for placing constraints on long GRB central engines, details of the circumburst media, and host environment.
Using selection criteria based on amplitude, time, and color, we have identified 329 objects as known or candidate cataclysmic variables (CVs) during the first year of testing and operation of the ...Zwicky Transient Facility. Of these, 90 are previously confirmed CVs, 218 are strong candidates based on the shape and color of their light curves obtained during 3-562 days of observation, and the remaining 21 are possible CVs but with too few data points to be listed as good candidates. Almost half of the strong candidates are within 10 deg of the galactic plane, in contrast to most other large surveys that have avoided crowded fields. The available Gaia parallaxes are consistent with sampling the low mass transfer CVs, as predicted by population models. Our follow-up spectra have confirmed Balmer/helium emission lines in 27 objects, with four showing high-excitation He ii emission, including candidates for an AM CVn, a polar, and an intermediate polar. Our results demonstrate that a complete survey of the Galactic plane is needed to accomplish an accurate determination of the number of CVs existing in the Milky Way.
Metrics to ‘green’ chemistry—which are the best? Constable, David J. C.; Curzons, Alan D.; Cunningham, Virginia L.
Green chemistry : an international journal and green chemistry resource : GC,
01/2002, Letnik:
4, Številka:
6
Journal Article
Recenzirano
A considerable amount has been written about the use of metrics to drive business, government and communities towards more sustainable practices. A number of metrics have also been proposed over the ...past 5-10 years to make chemists aware of the need to change the methods used for chemical syntheses and chemical processes. This paper explores several metrics commonly used by chemists and compares and contrasts these metrics with a new metric known as reaction mass efficiency. The paper also uses an economic analysis of four commercial pharmaceutical processes to understand the relationship between metrics and the most important cost drivers in these processes.
High-cadence transient surveys are able to capture supernovae closer to their first light than ever before. Applying analytical models to such early emission, we can constrain the progenitor stars' ...properties. In this paper, we present observations of SN 2018fif (ZTF 18abokyfk). The supernova was discovered close to first light and monitored by the Zwicky Transient Facility (ZTF) and the Neil Gehrels Swift Observatory. Early spectroscopic observations suggest that the progenitor of SN 2018fif was surrounded by relatively small amounts of circumstellar material compared to all previous cases. This particularity, coupled with the high-cadence multiple-band coverage, makes it a good candidate to investigate using shock-cooling models. We employ the SOPRANOS code, an implementation of the model by Sapir & Waxman and its extension to early times by Morag et al. Compared with previous implementations, SOPRANOS has the advantage of including a careful account of the limited temporal validity domain of the shock-cooling model as well as allowing usage of the entirety of the early UV data. We find that the progenitor of SN 2018fif was a large red supergiant with a radius of and an ejected mass of . Our model also gives information on the explosion epoch, the progenitor's inner structure, the shock velocity, and the extinction. The distribution of radii is double-peaked, with smaller radii corresponding to lower values of the extinction, earlier recombination times, and a better match to the early UV data. If these correlations persist in future objects, denser spectroscopic monitoring constraining the time of recombination, as well as accurate UV observations (e.g., with ULTRASAT), will help break the extinction/radius degeneracy and independently determine both.
A human health risk assessment was carried out for environmental exposures to carbamazepine (CBZ) and its major human metabolites, carbamazepine diol (CBZ-DiOH) and carbamazepine
N-glucuronide (CBZ-
...N-Glu). Carbamazepine is an active pharmaceutical ingredient (API) used worldwide as a medicine for treating epileptic seizures and trigeminal neuralgia. Carbamazepine tends to be detected in surface water more frequently, and at relatively higher concentrations, than most other APIs.
Predicted no effect levels (PNECs) for CBZ and its major human metabolites were developed for surface waters to be protective of human health from environmental exposures from drinking water and fish consumption. These PNECs were compared to both measured (MEC) and predicted (PEC) environmental concentrations for North America and Europe. PECs were calculated using the geo-referenced models P
hATE™ for North America and GREAT-ER for Europe.
The combined PNEC for drinking water and fish consumption for CBZ is 226,000
ng/L. Ninetieth percentile MECs ranged from 150 to 220
ng/L, while 90th percentile PECs ranged from 333 to 658
ng/L. Calculated margins of safety (MOS) therefore range from 340 to 1500. MOS for the major metabolites are significantly higher. This assessment indicates that CBZ and its major metabolites have high MOS (≫1) and thus should have no appreciable risk to human health through environmental exposures based on available human data.
The Fermi Gamma-ray Burst Monitor (GBM) triggers on-board in response to∼40 short gamma-ray bursts (SGRBs) per year; however, their large localization regions have made the search for optical ...counterparts a challenging endeavour. We have developed and executed an extensive program with the wide field of view of the Zwicky Transient Facility (ZTF) camera, mounted on the Palomar 48 inch Oschin telescope (P48), to perform target-of-opportunity (ToO) observations on 10Fermi-GBM SGRBsduring 2018 and 2020-2021. Bridging the large sky areas with small field of view optical telescopesin order to track the evolution of potential candidates, we look for the elusive SGRB afterglows andkilonovae (KNe) associated with these high-energy events. No counterpart has yet been found, eventhough more than 10 ground based telescopes, part of the Global Relay of Observatories WatchingTransients Happen (GROWTH) network, have taken part in these efforts. The candidate selectionprocedure and the follow-up strategy have shown that ZTF is an efficient instrument for searchingfor poorly localized SGRBs, retrieving a reasonable number of candidates to follow-up and showingpromising capabilities as the community approaches the multi-messenger era. Based on the medianlimiting magnitude of ZTF, our searches would have been able to retrieve a GW170817-like event upto∼200 Mpc and SGRB afterglows to z = 0.16 or 0.4, depending on the assumed underlying energymodel. Future ToOs will expand the horizon to z = 0.2 and 0.7 respectively.
Aquatic toxicity of triclosan Orvos, David R.; Versteeg, Donald J.; Inauen, Josef ...
Environmental toxicology and chemistry,
July 2002, Letnik:
21, Številka:
7
Journal Article
Recenzirano
The aquatic toxicity of triclosan (TCS), a chlorinated biphenyl ether used as an antimicrobial in consumer products, was studied with activated‐sludge microorganisms, algae, invertebrates, and fish. ...Triclosan, a compound used for inhibiting microbial growth, was not toxic to wastewater microorganisms at concentrations less than aqueous solubility. The 48‐h Daphnia magna median effective concentration (EC50) was 390 μg/L and the 96‐h median lethal concentration values for Pimephales promelas and Lepomis macrochirus were 260 and 370 μg/L, respectively. A no‐observed‐effect concentration (NOEC) and lowest‐observed‐effect concentration of 34.1 μg/L and 71.3 μg/L, respectively, were determined with an early life‐stage toxicity test with Onco‐rhynchus mykiss. During a 96‐h Scenedesmus study, the 96‐h biomass EC50 was 1.4 μg/L and the 96‐h NOEC was 0.69 μg/L. Other algae and Lemna also were investigated. Bioconcentration was assessed with Danio rerio. The average TCS accumulation factor over the five‐week test period was 4,157 at 3 μg/L and 2,532 at 30 μg/L. Algae were determined to be the most susceptible organisms. Toxicity of a TCS‐containing wastewater secondary effluent to P. promelas and Ceriodaphnia was evaluated and no observed differences in toxicity between control and TCS‐treated laboratory units were detected. The neutral form of TCS was determined to be associated with toxic effects. Ionization and sorption will mitigate those effects in the aquatic compartment.
The PhATE (Pharmaceutical Assessment and Transport Evaluation) model presented in this paper was developed as a tool to estimate concentrations of active pharmaceutical ingredients (APIs) in U.S. ...surface waters that result from patient use (or consumption) of medicines. PhATE uses a mass balance approach to model predicted environmental concentrations (PECs) in 11 watersheds selected to be representative of most hydrologic regions of the United States. The model divides rivers into discrete segments. It estimates the mass of API that enters a segment from upstream or from publicly owned treatment works (POTW) and is subsequently lost from the segment via in-stream loss mechanisms or flow diversions (i.e., man-made withdrawals). POTW discharge loads are estimated based on the population served, the API use per capita, the potential loss of the compound associated with human use (e.g., metabolism), and the portion of the API mass removed in the POTW. Simulations using three surrogate compounds show that PECs generated by PhATE are generally within an order of magnitude of measured concentrations and that the cumulative probability distribution of PECs for all watersheds included in PhATE is consistent with the nationwide distribution of measured concentrations of the surrogate compounds. Model simulations for 11 APIs yielded four categories of results. (1) PECs fit measured data for two compounds. (2) PECs are below analytical method detection limits and thus are consistent with measured data for three compounds. (3) PECs are higher than (i.e., not consistent with) measured data for three compounds. However, this may be the consequence of as yet unidentified depletion mechanisms. (4) PECs are several orders of magnitude below some measured data but consistent with most measured data for three compounds. For the fourth category, closer examination of sampling locations suggests that the field-measured concentrations for these compounds do not accurately reflect human use. Overall, these results demonstrate that PhATE may be used to predict screening-level concentrations of APIs and related compounds in the environment as well as to evaluate the suitability of existing fate information for an API.
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