Literature data are collated for 38 stripped-envelope core-collapse supernovae (SE SNe; i.e. SNe IIb, Ib, Ic and Ic-BL) that have good light-curve coverage in more than one optical band. Using ...bolometric corrections derived in previous work, the bolometric light curve of each SN is recovered and template bolometric light curves provided. Peak light distributions and decay rates are investigated; SNe subtypes are not cleanly distinguished in this parameter space, although some grouping of types does occur and there is a suggestion of a Phillips-like relation for most SNe Ic-BL. The bolometric light curves are modelled with a simple analytical prescription and compared to results from more detailed modelling. Distributions of the explosion parameters show the extreme nature of SNe Ic-BL in terms of their 56Ni mass and the kinetic energy, however ejected masses are similar to other subtypes. SNe Ib and Ic have very similar distributions of explosion parameters, indicating a similarity in progenitors. SNe IIb are the most homogeneous subtype and have the lowest average values for 56Ni mass, ejected mass, and kinetic energy. Ejecta masses for each subtype and SE SNe as a whole are inconsistent with those expected from very massive stars. The majority of the ejecta mass distribution is well described by more moderately massive progenitors in binaries, indicating these are the dominant progenitor channel for SE SNe.
Protein Condensation Gunton, James D.; Shiryayev, Andrey; Pagan, Daniel L.
09/2007
eBook
The quest to understand the condensation of proteins from solutions is a rapidly evolving field. The purpose of this book is to bring to an interdisciplinary audience the state-of-the-art in current ...research. The first part of the book deals with issues related to the production of high quality protein crystals from solution. Since protein function is determined by structure, high quality protein crystals must be grown in order to determine their structure by X-ray crystallography. The book also discusses diseases that occur due to undesired protein condensation, an increasingly important subject. Examples include sickle cell anemia, cataracts and Alzheimer's disease. Current experimental and theoretical work on these diseases is discussed, which seeks understanding at a fundamental, molecular level, to prevent the undesired condensation from occurring. The book, containing color plate sections, is suitable for graduate students and academic researchers in physics, chemistry, structural biology, protein crystallography and medicine.
Although the proteins BAX and BAK are required for initiation of apoptosis at the mitochondria, how BAX and BAK are activated remains unsettled. We provide in vivo evidence demonstrating an essential ...role of the proteins BID, BIM, and PUMA in activating BAX and BAK. Bid, Bim, and Puma triple-knockout mice showed the same developmental defects that are associated with deficiency of Bax and Bak, including persistent interdigital webs and imperforate vaginas. Genetic deletion of Bid, Bim, and Puma prevented the homo-oligomerization of BAX and BAK, and thereby cytochrome c-mediated activation of caspases in response to diverse death signals in neurons and T lymphocytes, despite the presence of other BH3-only molecules. Thus, many forms of apoptosis require direct activation of BAX and BAK at the mitochondria by a member of the BID, BIM, or PUMA family of proteins.
Whole genome duplication (WGD) is a major factor in the evolution of multicellular eukaryotes, yet by doubling the number of homologs, WGD severely challenges reliable chromosome segregation 1–3, a ...process conserved across kingdoms 4. Despite this, numerous genome-duplicated (polyploid) species persist in nature, indicating early problems can be overcome 1, 2. Little is known about which genes are involved—only one has been molecularly characterized 5. To gain new insights into the molecular basis of adaptation to polyploidy, we investigated genome-wide patterns of differentiation between natural diploids and tetraploids of Arabidopsis arenosa, an outcrossing relative of A. thaliana 6, 7. We first show that diploids are not preadapted to polyploid meiosis. We then use a genome scanning approach to show that although polymorphism is extensively shared across ploidy levels, there is strong ploidy-specific differentiation in 39 regions spanning 44 genes. These are discrete, mostly single-gene peaks of sharply elevated differentiation. Among these peaks are eight meiosis genes whose encoded proteins coordinate a specific subset of early meiotic functions, suggesting these genes comprise a polygenic solution to WGD-associated chromosome segregation challenges. Our findings indicate that even conserved meiotic processes can be capable of nimble evolutionary shifts when required.
People with schizophrenia are enriched for rare coding variants in genes associated with neurodevelopmental disorders, particularly autism spectrum disorders and intellectual disability. However, it ...is unclear if the same changes to gene function that increase risk to neurodevelopmental disorders also do so for schizophrenia. Using data from 3444 schizophrenia trios and 37,488 neurodevelopmental disorder trios, we show that within shared risk genes, de novo variants in schizophrenia and neurodevelopmental disorders are generally of the same functional category, and that specific de novo variants observed in neurodevelopmental disorders are enriched in schizophrenia (P = 5.0 × 10
). The latter includes variants known to be pathogenic for syndromic disorders, suggesting that schizophrenia be included as a characteristic of those syndromes. Our findings imply that, in part, neurodevelopmental disorders and schizophrenia have shared molecular aetiology, and therefore likely overlapping pathophysiology, and support the hypothesis that at least some forms of schizophrenia lie on a continuum of neurodevelopmental disorders.
This review describes a meta-analysis of findings from 50 controlled evaluations of intelligent computer tutoring systems. The median effect of intelligent tutoring in the 50 evaluations was to raise ...test scores 0.66 standard deviations over conventional levels, or from the 50th to the 75th percentile. However, the amount of improvement found in an evaluation depended to a great extent on whether improvement was measured on locally developed or standardized tests, suggesting that alignment of test and instructional objectives is a critical determinant of evaluation results. The review also describes findings from two groups of evaluations that did not meet all of the selection requirements for the meta-analysis: six evaluations with nonconventional control groups and four with flawed implementations of intelligent tutoring systems. Intelligent tutoring effects in these evaluations were small, suggesting that evaluation results are also affected by the nature of control treatments and the adequacy of program implementations.
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