Explore the vast range of titles available.

We explore fitting gamma-ray burst (GRB) spectra with three physically motivated models, and thus revisit the viability of synchrotron radiation as the primary source of GRB prompt emission. We pick a sample of 100 bright GRBs observed by the Fermi Gamma-ray Burst Monitor (GBM), based on their energy flux values. In addition to the standard empirical spectral models used in previous GBM spectroscopy catalogs, we also consider three physically motivated models; (a) a thermal synchrotron model, (b) a Band model with a high-energy cutoff, and (c) a smoothly broken power-law (SBPL) model with a multiplicative broken power law (MBPL). We then adopt the Bayesian information criterion to compare the fits obtained and choose the best model. We find that 42% of the GRBs from the fluence spectra and 23% of GRBs from the peak-flux spectra have one of the three physically motivated models as their preferred one. From the peak-flux spectral fits, we find that the low-energy index distributions from the empirical model fits for long GRBs peak around the synchrotron value of −2/3, while the two low-energy indices from the SBPL+MBPL fits of long GRBs peak close to the −2/3 and −3/2 values expected for a synchrotron spectrum from marginally fast-cooling electrons.

The exceptional atmospheric conditions that have accelerated Greenland Ice Sheet mass loss in recent decades have been repeatedly recognized as a possible dynamical response to Arctic amplification. Here, we present evidence of two potentially synergistic mechanisms linking high-latitude warming to the observed increase in Greenland blocking. Consistent with a prominent hypothesis associating Arctic amplification and persistent weather extremes, we show that the summer atmospheric circulation over the North Atlantic has become wavier and link this wavier flow to more prevalent Greenland blocking. While a concomitant decline in terrestrial snow cover has likely contributed to this mechanism by further amplifying warming at high latitudes, we also show that there is a direct stationary Rossby wave response to low spring North American snow cover that enforces an anomalous anticyclone over Greenland, thus helping to anchor the ridge over Greenland in this wavier atmospheric state.

The Gamma‐ray Burst Monitor (GBM) on the Fermi Gamma‐ray Space Telescope detected 12 intense terrestrial gamma ray flashes (TGFs) during its first year of observation. Typical maximum energies for most of the TGFs are ∼30 MeV, with one TGF having a 38 MeV photon; two of the TGFs are softer and longer than the others. After correcting for instrumental effects, a representative bright TGF is found to have a fluence of ∼0.7 photons cm−2. Pulses are either symmetrical or have faster risetimes than fall times; they are well fit with Gaussian or lognormal functions. The fastest risetime observed was 7 μs, constraining the source radius to be less than about 2 km from the velocity of light. TGFs with multiple pulses separated in time have been known since their discovery; the GBM sample also includes clear cases of partially overlapping pulses. Four TGFs are associated with lightning locations from the World Wide Lightning Location Network. With the several μs absolute time accuracy of GBM, the time order can be confidently identified: one TGF occurred before the lightning, two were simultaneous, and one TGF occurred after the lightning.

The recent discovery of a kilonova from the long-duration gamma-ray burst (GRB) GRB 211211A challenges classification schemes based on temporal information alone. Gamma-ray properties of GRB 211211A reveal an extreme event, which stands out among both short and long GRBs. We find very short variations (few milliseconds) in the lightcurve of GRB 211211A and estimate ∼1000 for the Lorentz factor of the outflow. We discuss the relevance of the short variations in identifying similar long GRBs resulting from compact mergers. Our findings indicate that in future gravitational-wave follow-up campaigns, some long-duration GRBs should be treated as possible strong gravitational-wave counterparts.

A high-resolution pollen record from western Greece shows that the amplitude of millennial-scale oscillations in tree abundance during the last glacial period was subdued, with temperate tree populations surviving throughout the interval. This provides evidence for the existence of an area of relative ecological stability, reflecting the influence of continued moisture availability and varied topography. Long-term buffering of populations from climatic extremes, together with genetic isolation at such refugial sites, may have allowed lineage divergence to proceed through the Quaternary. Such ecologically stable areas may be critical not only for the long-term survival of species, but also for the emergence of new ones.

The pronounced increase in meltwater runoff from the Greenland Ice Sheet in recent decades represents an important source of global sea-level rise. The role of anomalous anticyclonic circulation patterns in facilitating this increase has been widely documented; however, this change in atmospheric circulation has coincided with a rapidly warming Arctic. While amplified Arctic warming has undoubtedly contributed to trends in Greenland's mass loss, the contribution of this shift in background conditions relative to changes in regional circulation patterns has yet to be quantified. Here, we apply the pseudo-global warming method of dynamical downscaling to estimate the contribution of the change in the thermodynamic background state under global warming to observed Greenland Ice Sheet surface mass loss since the turn of the century. Our analysis demonstrates that, had the 2000–2019 sequence of atmospheric circulation occurred under a preindustrial thermodynamic background state, anomalous surface mass loss from the ice sheet would have been reduced by over 62 % relative to observations. We show that the change in the thermodynamic environment under amplified Arctic warming has augmented melt of the ice sheet via longwave radiative effects accompanying an increase in atmospheric water vapor content. Furthermore, the thermodynamic contribution to surface mass loss during the record melt years of 2012 and 2019 was less than half that of the long-term average, suggesting that the pronounced mass loss during those two summers was more a result of the anomalous atmospheric circulation than a direct consequence of the long-term warming trend.

The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest γ-ray duration (20 hours), and one of the largest isotropie energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.

Congressional observers have long been interested in the distinction between legislative “workhorses” and “showhorses.” However, when scholars operationalize this by measuring legislator productivity, they often neglect many realities of modern lawmaking by focusing on the traditional bill sponsorship and passage process. To better align measurement with practice, we compile widely available data on bill sponsorship, cosponsorship, and amendments; we also use text-as-data methods to credit instances of behind-the-scenes lawmaking via text reuse between bills. We weight achievements from each of these lawmaking methods to create the Lawmaking Productivity Metric for House Members of the 101–113th Congresses. Including methods of lawmaking beyond bill sponsorship provides important insights about who the congressional workhorses are. In particular, we find that traditional measures systematically undercount the legislative successes of women and likely Black Members of Congress because they disproportionately legislate in less visible ways.

Background The accuracy with which surgeons can predict outcomes following surgery has not been explored in a systematic way. The aim of this review was to determine how accurately a surgeon's ‘gut feeling’ or perception of risk correlates with patient outcomes and available risk scoring systems. Methods A systematic review was undertaken in accordance with PRISMA guidelines. A narrative synthesis was performed in accordance with the Guidance on the Conduct of Narrative Synthesis In Systematic Reviews. Studies comparing surgeons' preoperative or postoperative assessment of patient outcomes were included. Studies that made comparisons with risk scoring tools were also included. Outcomes evaluated were postoperative mortality, general and operation‐specific morbidity and long‐term outcomes. Results Twenty‐seven studies comprising 20 898 patients undergoing general, gastrointestinal, cardiothoracic, orthopaedic, vascular, urology, endocrine and neurosurgical operations were included. Surgeons consistently overpredicted mortality rates and were outperformed by existing risk scoring tools in six of seven studies comparing area under receiver operating characteristic (ROC) curves (AUC). Surgeons' prediction of general morbidity was good, and was equivalent to, or better than, pre‐existing risk prediction models. Long‐term outcomes were poorly predicted by surgeons, with AUC values ranging from 0·51 to 0·75. Four of five studies found postoperative risk estimates to be more accurate than those made before surgery. Conclusion Surgeons consistently overestimate mortality risk and are outperformed by pre‐existing tools; prediction of longer‐term outcomes is also poor. Surgeons should consider the use of risk prediction tools when available to inform clinical decision‐making. Antecedentes La precisión con la cual los cirujanos pueden predecir los resultados de la cirugía no se ha estudiado de forma sistemática. El objetivo de esta revisión fue determinar con qué precisión la intuición de un cirujano o su percepción del riesgo se correlacionaba con los resultados del paciente y con los sistemas de puntuación del riesgo disponibles. Métodos Se efectuó una revisión sistemática siguiendo las directrices PRISMA. Se realizó una síntesis narrativa de acuerdo con la guía para la realización de síntesis narrativas en revisiones sistemáticas. Se incluyeron los estudios que comparaban las evaluaciones preoperatorias o postoperatorias de los cirujanos respecto a los resultados de los pacientes. También se incluyeron aquellos estudios en los que se hacían comparaciones con herramientas de puntuación de riesgo. Se evaluaron la mortalidad postoperatoria, la morbilidad global y la morbilidad específica de las intervenciones, y los resultados a largo plazo. Resultados Se incluyeron 27 estudios con 20.898 pacientes en los que se realizaron procedimientos de cirugía general, digestiva, cardiotorácica, ortopédica, vascular, urológica, endocrina y neurocirugía. Los cirujanos predijeron consistentemente mayores tasas de mortalidad, siendo superados en precisión por los sistemas de estimación del riesgo existentes en seis de los siete estudios que utilizaron el área bajo la curva (area under curve, AUC) operativa del receptor. La predicción de la morbilidad general por parte de los cirujanos fue buena y era equivalente, incluso mejor, que los modelos de predicción de riesgos preexistentes. La capacidad de los cirujanos para predecir los resultados a largo plazo fue pobre, con una AUC que oscilaba entre 0,51 y 0,75. Cuatro de cinco estudios encontraron que las estimaciones de riesgo postoperatorias fueron más precisas que las realizadas preoperatoriamente. Conclusión Los cirujanos sobrestiman consistentemente el riesgo de mortalidad, siendo superados en precisión por las herramientas preexistentes. La predicción de resultados a largo plazo también es muy pobre. Los cirujanos deberían considerar el uso de herramientas de predicción de riesgo cuando estén disponibles para informar en el proceso de decisión clínica. The aim of this review was to determine how accurately surgeons' perceptions of risk correlate with patient outcomes and available risk scoring systems. An extensive systematic review and narrative synthesis was undertaken. Twenty‐seven studies comprising 20 898 patients were included. Surgeons were outperformed by pre‐existing tools. Gut feeling outperformed by prediction tools