968 research outputs found

    Deexcitation nuclear gamma-ray line emission from low-energy cosmic rays in the inner Galaxy

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    Recent observations of high ionization rates of molecular hydrogen in diffuse interstellar clouds point to a distinct low-energy cosmic-ray component. Supposing that this component is made of nuclei, two models for the origin of such particles are explored and low-energy cosmic-ray spectra are calculated which, added to the standard cosmic ray spectra, produce the observed ionization rates. The clearest evidence of the presence of such low-energy nuclei between a few MeV per nucleon and several hundred MeV per nucleon in the interstellar medium would be a detection of nuclear \gamma-ray line emission in the range E_ 0.1 - 10 MeV, which is strongly produced in their collisions with the interstellar gas and dust. Using a recent \gamma-ray cross section compilation for nuclear collisions, \gamma-ray line emission spectra are calculated alongside with the high-energy \gamma-ray emission due to {\pi} 0 decay, the latter providing normalization of the absolute fluxes by comparison with Fermi-LAT observations of the diffuse emission above E \gamma = 0.1 GeV. Our predicted fluxes of strong nuclear \gamma-ray lines from the inner Galaxy are well below the detection sensitivies of INTEGRAL, but a detection, especially of the 4.4-MeV line, seems possible with new-generation \gamma-ray telescopes based on available technology. We predict also strong \gamma-ray continuum emission in the 1-8 MeV range, which in a large part of our model space for low-energy cosmic rays exceeds considerably estimated instrument sensitivities of future telescopes.Comment: 22 pages, 7 figures, accepted for publication in ApJ; figures 6 and 7 replace

    Low power respiration monitoring using wearable 3D knitted helical coils.

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    We demonstrate a novel low power inductive wearable plethysmography system. This consists of ultra-sensitive 3D knitted helical coils integrated in a garment and an oscillator circuit with high quality factor. The low power oscillator is built using two cross coupled FET pairs with low capacitance drawing only 95 μA during operation and with a response time smaller than 10 μs . The sensor system is linear, with negligible hysteresis. The best compromise in sensitivity and power consumption is obtained with a 3D knitted helical coil using jersey knit with elastic yarn, a lower knitting needle size than recommended for the yarn and minimizing both the number of stitches per winding as well as the stitches containing metal. A sensitivity of 2.7 kHz per mm change in circumference with a power consumption of 6.85 mW per 30 ms measurement time is reported. This system can be used for long term breathing monitoring using a garment indistinguishable from everyday clothing

    Spectroscopy of 19^{19}Ne for the thermonuclear 15^{15}O(α,γ\alpha,\gamma)19^{19}Ne and 18^{18}F(p,αp,\alpha)15^{15}O reaction rates

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    Uncertainties in the thermonuclear rates of the 15^{15}O(α,γ\alpha,\gamma)19^{19}Ne and 18^{18}F(p,αp,\alpha)15^{15}O reactions affect model predictions of light curves from type I X-ray bursts and the amount of the observable radioisotope 18^{18}F produced in classical novae, respectively. To address these uncertainties, we have studied the nuclear structure of 19^{19}Ne over Ex=4.05.1E_{x} = 4.0 - 5.1 MeV and 6.17.36.1 - 7.3 MeV using the 19^{19}F(3^{3}He,t)19^{19}Ne reaction. We find the JπJ^{\pi} values of the 4.14 and 4.20 MeV levels to be consistent with 9/29/2^{-} and 7/27/2^{-} respectively, in contrast to previous assumptions. We confirm the recently observed triplet of states around 6.4 MeV, and find evidence that the state at 6.29 MeV, just below the proton threshold, is either broad or a doublet. Our data also suggest that predicted but yet unobserved levels may exist near the 6.86 MeV state. Higher resolution experiments are urgently needed to further clarify the structure of 19^{19}Ne around the proton threshold before a reliable 18^{18}F(p,αp,\alpha)15^{15}O rate for nova models can be determined.Comment: 5 pages, 3 figures, Phys. Rev. C (in press

    KRT5 missense variant in a Cardigan Welsh Corgi with epidermolysis bullosa simplex.

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    Epidermolysis bullosa (EB) is a group of blistering disorders that includes several subtypes, classified according to their level of cleavage. Typical clinical signs are blisters and erosions resulting from minimal trauma. The disease has been described in many mammalian species and pathogenic variants in at least 18 different genes have been identified. In the present study, we investigated a Cardigan Welsh Corgi with congenital clinical signs consistent with epidermolysis bullosa. The puppy had blisters and erosions on the paw pads, and the oral mucosa. Histologic examination demonstrated the typical clefting between the dermis and epidermis and confirmed the clinical suspicion. We obtained whole genome sequencing data from the affected puppy and searched for variants in candidate genes known to cause EB. This revealed a heterozygous missense variant, KRT5:p.(E476K), affecting the highly conserved KLLEGE motif of keratin 5. The mutant allele in the affected puppy arose owing to a de novo mutation event as it was absent from both unaffected parents. Knowledge of the functional impact of KRT5 variants in other species together with the demonstration of the de novo mutation event establishes KRT5:p.(E476K) as causative variant for the observed EBS

    Effect of boron doping on grain boundary cohesion in technically pure molybdenum investigated via meso-scale three-point-bending tests

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    Molybdenum has numerous advantageous functional and high-temperature properties. However, plastic deformation as well as structural applications are limited due to a propensity for brittle, intercrystalline failure, especially at low temperatures. It is well known that oxygen segregations have a detrimental effect, whereas it is assessed that carbon and/or boron have a beneficial effect on grain boundary cohesion. An advanced approach for the improvement of these interfaces is segregation engineering, e.g. the addition of cohesion enhancing elements segregating to the grain boundaries. To investigate early stages of crack formation, three-point bending tests on recrystallized commercially pure and boron micro-doped molybdenum were conducted between −28 \ub0C and room temperature. The tensile-loaded top surface of the specimens was examined post-mortem close to the final fracture area via scanning electron microscopy. The occurring separations of grains are investigated for distinct features and the chemical composition of the interface is complementary measured by atom probe tomography

    Eye-tracking based classification of Mandarin Chinese readers with and without dyslexia using neural sequence models

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    Eye movements are known to reflect cognitive processes in reading, and psychological reading research has shown that eye gaze patterns differ between readers with and without dyslexia. In recent years, researchers have attempted to classify readers with dyslexia based on their eye movements using Support Vector Machines (SVMs). However, these approaches (i) are based on highly aggregated features averaged over all words read by a participant, thus disregarding the sequential nature of the eye movements, and (ii) do not consider the linguistic stimulus and its interaction with the reader’s eye movements. In the present work, we propose two simple sequence models that process eye movements on the entire stimulus without the need of aggregating features across the sentence. Additionally, we incorporate the linguistic stimulus into the model in two ways---contextualized word embeddings and manually extracted linguistic features. The models are evaluated on a Mandarin Chinese dataset containing eye movements from children with and without dyslexia. Our results show that (i) even for a logographic script such as Chinese, sequence models are able to classify dyslexia on eye gaze sequences, reaching state-of-the-art performance, and (ii) incorporating the linguistic stimulus does not help to improve classification performance

    Purification and properties of Methanobacterium thermoautotrophicum DNA photolyase

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    We have purified DNA photolyase from the autotrophic anaerobic archaebacterium Methanobacterium thermoautotrophicum to near homogeneity by a two-column affinity chromatography. The purified enzyme has an Mr = 60,000 and shows near UV absorption peak at 440 nm and a fluorescence emission maximum at 462 nm indicating that it contains 8-hydroxy-5-deazaflavin (coenzyme F420) as an intrinsic chromophore. The photolyase binds with high specificity to thymine dimer in DNA with an equilibrium binding constant, KA = 1.4 x 10(9) M-1, and a dissociation rate constant, koff = 1.4 x 10(-4) s-1 (t1/2 = 43 min). Despite 6-fold higher affinity compared to the folate-containing Escherichia coli photolyase the two enzymes apparently contact the same phosphates around the thymine dimer: the phosphate immediately 5' and the three phosphates immediately 3' to the dimer on the damaged strand and the phosphate across from the dimer in the minor groove on the complementary strand. The absolute action spectrum of the Methanobacterium photolyase in the 400-500-nm region closely matches the absorption of the enzyme-bound F420. The quantum yield (phi) over this region is constant and is approximately 0.2. The value is measurably smaller than the quantum yields reported for other DNA photolyases
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