Detection of a supernova signature associated with GRB 011121

Using observations from an extensive monitoring campaign with the Hubble Space Telescope, we present the detection of an intermediate-time flux excess that is redder in color relative to the afterglow of GRB 011121, currently distinguished as the gamma-ray burst with the lowest known redshift. The red "bump," which exhibits a spectral rollover at ∼7200 A, is well described by a redshifted Type le supernova that occurred approximately at the same time as the gamma-ray burst event. The inferred luminosity is about half that of the bright supernova SN 1998bw. These results serve as compelling evidence for a massive star origin of long-duration gamma-ray bursts. Models that posit a supernova explosion weeks to months preceding the gamma-ray burst event are excluded by these observations. Finally, we discuss the relationship between spherical core-collapse supernovae and gamma-ray bursts

Broadband observations of the afterglow of GRB 000926: Observing the effect of inverse Compton scattering

GRB 000926 has one of the best-studied afterglows to date, with multiple X-ray observations, as well as extensive multifrequency optical and radio coverage. Broadband afterglow observations, spanning from X-ray to radio frequencies, provide a probe of the density structure of the circumburst medium, as well as of the ejecta energetics, geometry, and physical parameters of the relativistic blast wave resulting from the explosion. We present an analysis of Chandra X-Ray Observatory observations of this event, along with Hubble Space Telescope and radio monitoring data. We combine these data with ground-based optical and IR observations and fit the synthesized afterglow light curve using models where collimated ejecta expand into a surrounding medium. We find that we can explain the broadband light curve with reasonable physical parameters if the cooling is dominated by inverse Compton scattering. For this model, an excess due to inverse Compton scattering appears above the best-fit synchrotron spectrum in the X-ray band. No previous bursts have exhibited this component, and its observation would imply that the GRB exploded in a moderately dense (n ∼ 30 cm-3) medium, consistent with a diffuse interstellar cloud environment

GRB 010921: Strong limits on an underlying supernova from the Hubble Space Telescope

GRB 010921 was the first HETE-2 gamma-ray burst (GRB) to be localized via its afterglow emission. The low redshift of the host galaxy, z = 0.451, prompted us to undertake intensive multicolor observations with the Hubble Space Telescope with the goal of searching for an underlying supernova (SN) component. We do not detect any coincident SN to a limit 1.33 mag fainter than SN 1998bw at 99.7% confidence, making this one of the most sensitive searches for an underlying SN. Analysis of the afterglow data allows us to infer that the GRB was situated behind a net extinction (Milky Way and the host galaxy) of Av ∼ 1.8 mag in the observer frame. Thus, had it not been for such heavy extinction, our data would have allowed us to probe for an underlying SN with brightness approaching those of more typical Type Ib/c SNe

Uncovering the heterogeneity and temporal complexity of neurodegenerative diseases with Subtype and Stage Inference

The heterogeneity of neurodegenerative diseases is a key confound to disease understanding and treatment development, as study cohorts typically include multiple phenotypes on distinct disease trajectories. Here we introduce a machine-learning technique\u2014Subtype and Stage Inference (SuStaIn)\u2014able to uncover data-driven disease phenotypes with distinct temporal progression patterns, from widely available cross-sectional patient studies. Results from imaging studies in two neurodegenerative diseases reveal subgroups and their distinct trajectories of regional neurodegeneration. In genetic frontotemporal dementia, SuStaIn identifies genotypes from imaging alone, validating its ability to identify subtypes; further the technique reveals within-genotype heterogeneity. In Alzheimer\u2019s disease, SuStaIn uncovers three subtypes, uniquely characterising their temporal complexity. SuStaIn provides fine-grained patient stratification, which substantially enhances the ability to predict conversion between diagnostic categories over standard models that ignore subtype (p = 7.18 7 10 124 ) or temporal stage (p = 3.96 7 10 125 ). SuStaIn offers new promise for enabling disease subtype discovery and precision medicine

Methyiphenidate vs. amphetamine: Comparative review

This article compares the two most common medications for Attention-Deficit/Hyperactivity Disorder (ADHD), using data from controlled studies. Medline and Psychinfo searches were done for 1984-1996 with the key words methylphenidate (MPH) and amphetamine (AMP); these were supplemented with known prior and recent literature. Of 92 animal studies found, 15 showed clear differences between the two drugs. Ten reports of controlled crossover ADHD clinical trials (three in the same sample) and a dozen other articles comparing the two drugs in humans were found. MPH is a pure re-uptake inhibitor of catecholamines, especially dopamine; AMP also releases catecholamines. Lab animals showed differential interactions with other drugs and with behavioral paradigms. Human response profiles are noncongruent. An ADHD patient who fails on one stimulant should try the other. Of 174 patients in the 6 clearest crossover studies, 48 responded better to AMP, 27 to MPH, and at least 72 to both, which is an 87+% overall response rate if both are tried. All crossovers, except the one with comorbid Tourette's, showed a nonsignificant tendency for AMP superiority in response rate. Summed data suggest suspected differences in side effects (AMP more sleep and appetite loss and exacerbation of tics in comorbid Tourette's, MPH possibly more depression/apathy and stomachaches) and effects on comorbid disorders (AMP better for conduct/oppositional symptoms, MPH for Tourette's and possibly learning disorder (LD). Most of the clinical differences are tendencies rather than statistically significant