94 research outputs found

    WISE/NEOWISE Observations of Comet 103P/Hartley 2

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    We report results based on mid-infrared photometry of comet 103P/Hartley 2 taken during 2010 May 4-13 (when the comet was at a heliocentric distance of 2.3 AU, and an observer distance of 2.0 AU) by the Wide-field Infrared Survey Explorer. Photometry of the coma at 22 Ī¼m and data from the University of Hawaii 2.2 m telescope obtained on 2010 May 22 provide constraints on the dust particle size distribution, d log n/d log m, yielding power-law slope values of alpha = ā€“0.97 Ā± 0.10, steeper than that found for the inbound particle fluence during the Stardust encounter of comet 81P/Wild 2. The extracted nucleus signal at 12 Ī¼m is consistent with a body of average spherical radius of 0.6 Ā± 0.2 km (one standard deviation), assuming a beaming parameter of 1.2. The 4.6 Ī¼m band signal in excess of dust and nucleus reflected and thermal contributions may be attributed to carbon monoxide or carbon dioxide emission lines and provides limits and estimates of species production. Derived carbon dioxide coma production rates are 3.5(Ā± 0.9) Ɨ 10^(24) molecules per second. Analyses of the trail signal present in the stacked image with an effective exposure time of 158.4 s yields optical-depth values near 9 Ɨ 10^(ā€“10) at a delta mean anomaly of 0.2 deg trailing the comet nucleus, in both 12 and 22 Ī¼m bands. A minimum chi-squared analysis of the dust trail position yields a beta-parameter value of 1.0 Ɨ 10^(ā€“4), consistent with a derived mean trail-grain diameter of 1.1/Ļ cm for grains of Ļ g cm^(ā€“3) density. This leads to a total detected trail mass of at least 4 Ɨ 10^(10) Ļ kg

    Continental carbonate facies of a Neoproterozoic panglaciation, north-east Svalbard

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    The Marinoan panglaciation (ca 650 to 635 Ma) is represented in north-east Svalbard by the 130 to 175 m thick Wilsonbreen Formation which contains syn-glacial carbonates in its upper 100 m. These sediments are now known to have been deposited under a CO2-rich atmosphere, late in the glaciation, and global climate models facilitate testing of proposed analogues. Precipitated carbonates occur in four of the seven facies associations identified: Fluvial Channel (including stromatolitic and intraclastic limestones in ephemeral stream deposits); Dolomitic Floodplain (dolomite-cemented sand and siltstones, and microbial dolomites); Calcareous Lake Margin (intraclastic dolomite and wave-rippled or aeolian siliciclastic facies); and Calcareous Lake (slump-folded and locally re-sedimented rhythmic/stromatolitic limestones and dolomites associated with ice-rafted sediment). There is no strong cyclicity, and modern analogues suggest that sudden changes in lake level may exert a strong control on facies geometry. Both calcite and dolomite in stromatolites and rhythmites display either primary or early diagenetic replacive growth. Oxygen isotope values (āˆ’12 to +15ā€°VPDB) broadly covary with Ī“13C. High Ī“13C values of +3Ā·5 to +4Ā·5ā€° correspond to equilibration with an atmosphere dominated by volcanically degassed CO2 with Ī“13C of āˆ’6 to āˆ’7ā€°. Limestones have consistently negative Ī“18O values, while rhythmic and playa dolomites preserve intermediate compositions, and dolocretes possess slightly negative to strongly positive Ī“18O signatures, reflecting significant evaporation under hyperarid conditions. Inferred meltwater compositions (āˆ’8 to āˆ’15Ā·5ā€°) could reflect smaller Rayleigh fractionation related to more limited cooling than in modern polar regions. A common pseudomorph morphology is interpreted as a replacement of ikaite (CaCO3Ā·H2O), which may also have been the precursor for widespread replacive calcite mosaics. Local dolomitization of lacustrine facies is interpreted to reflect microenvironments with fluctuating redox conditions. Although differing in (palaeo)latitude and carbonate abundance, the Wilsonbreen carbonates provide strong parallels with the McMurdo Dry Valleys of Antarctica

    Video and Synthetic MRI Pre-training of 3D Vision Architectures for Neuroimage Analysis

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    Transfer learning represents a recent paradigm shift in the way we build artificial intelligence (AI) systems. In contrast to training task-specific models, transfer learning involves pre-training deep learning models on a large corpus of data and minimally fine-tuning them for adaptation to specific tasks. Even so, for 3D medical imaging tasks, we do not know if it is best to pre-train models on natural images, medical images, or even synthetically generated MRI scans or video data. To evaluate these alternatives, here we benchmarked vision transformers (ViTs) and convolutional neural networks (CNNs), initialized with varied upstream pre-training approaches. These methods were then adapted to three unique downstream neuroimaging tasks with a range of difficulty: Alzheimer's disease (AD) and Parkinson's disease (PD) classification, "brain age" prediction. Experimental tests led to the following key observations: 1. Pre-training improved performance across all tasks including a boost of 7.4% for AD classification and 4.6% for PD classification for the ViT and 19.1% for PD classification and reduction in brain age prediction error by 1.26 years for CNNs, 2. Pre-training on large-scale video or synthetic MRI data boosted performance of ViTs, 3. CNNs were robust in limited-data settings, and in-domain pretraining enhanced their performances, 4. Pre-training improved generalization to out-of-distribution datasets and sites. Overall, we benchmarked different vision architectures, revealing the value of pre-training them with emerging datasets for model initialization. The resulting pre-trained models can be adapted to a range of downstream neuroimaging tasks, even when training data for the target task is limited

    WISE/NEOWISE observations of Active Bodies in the Main Belt

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    We report results based on mid-infrared photometry of 5 active main belt objects (AMBOs) detected by the Wide-field Infrared Survey Explorer (WISE) spacecraft. Four of these bodies, P/2010 R2 (La Sagra), 133P/Elst-Pizarro, (596) Scheila, and 176P/LINEAR, showed no signs of activity at the time of the observations, allowing the WISE detections to place firm constraints on their diameters and albedos. Geometric albedos were in the range of a few percent, and on the order of other measured comet nuclei. P/2010 A2 was observed on April 2-3, 2010, three months after its peak activity. Photometry of the coma at 12 and 22 {\mu}m combined with ground-based visible-wavelength measurements provides constraints on the dust particle mass distribution (PMD), dlogn/dlogm, yielding power-law slope values of {\alpha} = -0.5 +/- 0.1. This PMD is considerably more shallow than that found for other comets, in particular inbound particle fluence during the Stardust encounter of comet 81P/Wild 2. It is similar to the PMD seen for 9P/Tempel 1 in the immediate aftermath of the Deep Impact experiment. Upper limits for CO2 & CO production are also provided for each AMBO and compared with revised production numbers for WISE observations of 103P/Hartley 2.Comment: 32 Pages, including 5 Figure

    An economic evaluation of targeted case-finding strategies for identifying postnatal depression: A model-based analysis comparing common case-finding instruments

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    BackgroundHalf of women with postnatal depression (PND) are not identified in routine care. We aimed to estimate the cost-effectiveness of PND case-finding in women with risk factors for PND.MethodsA decision tree was developed to represent the one-year costs and health outcomes associated with case-finding and treatment for PND. The sensitivity and specificity of case-finding instruments, and prevalence and severity of PND, for women with ā‰„1 PND risk factor were estimated from a cohort of postnatal women. Risk factors were history of anxiety/depression, ageĀ ResultsMore than half of the cohort had one or more PND risk factor (57.8Ā %; 95Ā % CI 52.7Ā %-62.7Ā %). The most cost-effective case-finding strategy was the Edinburgh Postnatal Depression Scale with a cut-off of ā‰„10 (EPDS-10). Among high-risk women, there is a high probability that EPDS-10 case-finding for PND is cost-effective compared to no case-finding (78.5Ā % at a threshold of Ā£20,000/QALY), with an ICER of Ā£8146/QALY gained. Universal case-finding is even more cost-effective at Ā£2945/QALY gained (versus no case-finding). There is a greater health improvement with universal rather than targeted case-finding.LimitationsThe model includes costs and health benefits for mothers in the first year postpartum, the broader (e.g. families, societal) and long-term impacts are also important.ConclusionsUniversal PND case-finding is more cost-effective than targeted case-finding which itself is more cost-effective than not case-finding

    The NEOWISE-Discovered Comet Population and the CO+CO_2 production rates

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    The 163 comets observed during the WISE/NEOWISE prime mission represent the largest infrared survey to date of comets, providing constraints on dust, nucleus size, and CO + CO_2 production. We present detailed analyses of the WISE/NEOWISE comet discoveries, and discuss observations of the active comets showing 4.6 Ī¼m band excess. We find a possible relation between dust and CO + CO_2 production, as well as possible differences in the sizes of long and short period comet nuclei

    Modulation of RNA splicing enhances response to BCL2 inhibition in leukemia.

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    Therapy resistance is a major challenge in the treatment of cancer. Here, we performed CRISPR-Cas9 screens across a broad range of therapies used in acute myeloid leukemia to identify genomic determinants of drug response. Our screens uncover a selective dependency on RNA splicing factors whose loss preferentially enhances response to the BCL2 inhibitor venetoclax. Loss of the splicing factor RBM10 augments response to venetoclax in leukemia yet is completely dispensable for normal hematopoiesis. Combined RBM10 and BCL2 inhibition leads to mis-splicing and inactivation of the inhibitor of apoptosis XIAP and downregulation of BCL2A1, an anti-apoptotic protein implicated in venetoclax resistance. Inhibition of splicing kinase families CLKs (CDC-like kinases) and DYRKs (dual-specificity tyrosine-regulated kinases) leads to aberrant splicing of key splicing and apoptotic factors that synergize with venetoclax, and overcomes resistance to BCL2 inhibition. Our findings underscore the importance of splicing in modulating response to therapies and provide a strategy to improve venetoclax-based treatments
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