120,180 research outputs found

    How effective is harassment on infalling late-type dwarfs?

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    A new harassment model is presented that models the complex, and dynamical tidal field of a Virgo like galaxy cluster. The model is applied to small, late-type dwarf disc galaxies (of substantially lower mass than in previous harassment simulations) as they infall into the cluster from the outskirts. These dwarf galaxies are only mildly affected by high speed tidal encounters with little or no observable consequences; typical stellar losses are <10%<10\%, producing very low surface brightness streams (μB>31\mu_B > 31 mag arcsec2^{-2}), and a factor of two drop in dynamical mass-to-light ratio. Final stellar discs remain disc-like, and dominated by rotation although often with tidally induced spiral structure. By means of Monte-Carlo simulations, the statistically likely influences of harassment on infalling dwarf galaxies are determined. The effects of harassment are found to be highly dependent on the orbit of the galaxy within the cluster, such that newly accreted dwarf galaxies typically suffer only mild harassment. Strong tidal encounters, that can morphologically transform discs into spheroidals, are rare occurring in <15%<15 \% of dwarf galaxy infalls for typical orbits of sub-structure within Λ\LambdaCDM cluster mass halos. For orbits with small apocentric distances (<<250 kpc), harassment is significantly stronger resulting in complete disruption or heavy mass loss (>90%>90 \% dark matter and >50%> 50 \% stellar), however, such orbits are expected to be highly improbable for newly infalling galaxies due to the deep potential well of the cluster.Comment: 15 pages, 11 figures, 4 table

    How the minuscule can contribute to the big picture: the neutron electric dipole moment project at TRIUMF

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    A permanent electric dipole moment (EDM) of a fundamental particle violates both parity (P) and time (T) reversal symmetry and combined charge and parity (CP) reversal symmetry if the combined reversal of charge, parity \textit{and} time (CPT) is preserved. It is a very promising place to search for physics beyond the Standard Model. Ultracold neutrons (UCN) are the ideal tool to study the neutron electric dipole moment since they can be observed for hundreds of seconds. This article summarizes the current searches for the neutron EDM using UCN and introduces the project to measure the neutron electric dipole moment at TRIUMF using its unique accelerator driven spallation neutron and liquid helium UCN source. The aim is to reach a sensitivity for the neutron EDM of around 1027e10^{-27} \,e \cdotcm.Comment: 12 pages, 6 figures, MENU 2016 Conference, Kyoto, Japa

    Isolation of Cellulolytic Microfungi Involved in Wood-Waste Decomposition: Prospects for Enzymatic Hydrolysis of Cellulosic Wastes

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    Wood-wastes from dump-sites at Okobaba Saw-mills on the western part of the Lagos lagoon were examined for cellulolytic microorganisms. Cellulolytic microfungi were isolated from the wastes using minimal salt agar medium containing 0.2% (w/v) crystalline cellulose, sugarcane pulp, corn cob or saw-dust as sole carbon/energy source. The colonies of cellulolytic microfungi which appeared on the plates increased in size and number as the incubation period (days) increased. Among the fungal isolates were two pathogenic Aspergilli (A flavus and A fumigatus), three different black Aspergilli (herein designated as A.niger I, A.niger II and A.niger III), Botrytis cinerea, Fusarium species and Penicillium species. Cell-free filtrates of 7 – day cultures of A.flavus, A.niger I, A.niger II, B. cinerea and P.species grown on the minimal salt broth supplemented with crystalline cellulose as sole carbon/energy source showed very significant CM–cellulase activity. P. species gave a very high value that was over 4 times the value for the closest organism, A.niger II. There is a good propect for cellulase production using the virgin strain of P. species isolated from the wood-wastes

    Biochemical diagnosis of ventricular dysfunction in elderly patients in general practice: observational study

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    Objective: To investigate the usefulness of measuring plasma concentrations of B type natriuretic peptide in the diagnosis of left ventricular systolic dysfunction in an unselected group of elderly people. Design: Observational study. Setting: General practice with four centres in Poole, Dorset. Participants: 155 elderly patients aged 70 to 84 years. Main outcome measures: Diagnostic characteristics of plasma B type natriuretic peptide measured by radioimmunoassay as a test for left ventricular systolic dysfunction assessed by echocardiography. Results: The median plasma concentration of B type natriuretic peptide was 39.3 pmol/l in patients with left ventricular systolic dysfunction and 15.8 pmol/l in those with normal function. The proportional area under the receiver operator curve was 0.85. At a cut-off point of 18.7 pmol/l the test sensitivity was 92% and the predictive value 18%. Conclusions: Plasma concentration of B type natriuretic peptide could be used effectively as an initial test in a community screening programme and, possibly, using a low cut-off point, as a means of ruling out left ventricular systolic dysfunction. It is, however, not a good test to “rule in” the diagnosis, and access to echocardiography remains essential for general practitioners to diagnose heart failure early

    Acoustic design of the QCSEE propulsion systems

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    Acoustic design features and techniques employed in the Quiet Clean Short-Haul Experimental Engine (QCSEE) Program are described. The role of jet/flap noise in selecting the engine fan pressure ratio for powered lift propulsion systems is discussed. The QCSEE acoustic design features include a hybrid inlet (near-sonic throat velocity with acoustic treatment); low fan and core pressure ratios; low fan tip speeds; gear-driven fans; high and low frequency stacked core noise treatment; multiple-thickness treatment; bulk absorber treatment; and treatment on the stator vanes. The QCSEE designs represent and anticipated acoustic technology improvement of 12 to 16 PNdb relative to the noise levels of the low-noise engines used on current wide-body commercial jet transport aircraft

    The importance of the classical channel in the impurity transport of optimized stellarators

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    In toroidal magnetic confinement devices, such as tokamaks and stellarators, neoclassical transport is usually an order of magnitude larger than its classical counterpart. However, when a high-collisionality species is present in a stellarator optimized for low Pfirsch-Schl\"uter current, its classical transport can be comparable to the neoclassical transport. In this letter, we compare neoclassical and classical fluxes and transport coefficients calculated for Wendelstein 7-X (W7-X) and Large Helical Device (LHD) cases. In W7-X, we find that the classical transport of a collisional impurity is comparable to the neoclassical transport for all radii, while it is negligible in the LHD cases, except in the vicinity of radii where the neoclassical transport changes sign. In the LHD case, electrostatic potential variations on the flux-surface significantly enhance the neoclassical impurity transport, while the classical transport is largely insensitive to this effect in the cases studied.Comment: 10 pages, 2 figure

    Orientation filtering by growth-velocity competition in zone-melting recrystallization of silicon on SiO_2

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    We describe a method of controlling the in-plane directions of grains in (100)-textured silicon films produced by zone-melting recrystallization over amorphous SiO2. Grains having in-plane orientation within a narrow range are able to grow through an orientation filter consisting of a pattern of crystallization barriers, while grains having other orientations are occluded. The results of experiments using an orientation filter, and the parameters which optimize filter performance, are reported

    Prevalence and clinical characteristics of left ventricular dysfunction among elderly patients in general practice setting: cross sectional survey

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    Objective: To assess the prevalence and clinical characteristics of left ventricular dysfunction among elderly patients in the general practice setting by echocardiographic assessment of ventricular function. Design: Cross sectional survey. Setting: Four centre general practice in Poole, Dorset. Subjects: 817 elderly patients aged 70-84 years. Main outcomes: Echocardiographic assessment of left ventricular systolic function including measurement of ejection fraction by biplane summation method where possible, clinical symptoms, and signs of left ventricular dysfunction. Results: The overall prevalence of left ventricular systolic dysfunction was 7.5% (95% confidence interval 5.8% to 9.5%); mild dysfunction (5.0%) was considerably more prevalent than moderate (1.6%) or severe dysfunction (0.7%). Measurement of ejection fraction was possible in 82% of patients (n=667): in patients categorised as having mild, moderate, or severe dysfunction, the mean ejection fraction was 48% (SD 12.0), 38% (8.1), and 26% (7.9) respectively. At all ages the prevalence was much higher in men than in women (odds ratio 5.1, 95% confidence interval 2.6 to 10.1). No clinical symptom or sign was both sensitive and specific. In around half the patients with ventricular dysfunction (52%, 32/61) heart failure had not been previously diagnosed. Conclusions: Unrecognised left ventricular dysfunction is a common problem in elderly patients in the general practice setting. Appropriate treatment with angiotensin converting enzyme inhibitors has the potential to reduce hospitalisation and mortality in these patients, but diagnosis should not be based on clinical history and examination alone. Screening is feasible in general practice, but it should not be implemented until the optimum method of identifying left ventricular dysfunction is clarified, and the cost effectiveness of screening has been shown
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