2,294 research outputs found

    Experiments on Passive Hypervelocity Boundary-Layer Control Using an Ultrasonically Absorptive Surface

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    Recently performed linear stability analyses suggested that transition could be delayed in hypersonic boundary layers by using an ultrasonically absorptive surface to damp the second mode (Mack mode). Boundary-layer transition experiments were performed on a sharp 5.06-deg half-angle round cone at zero angle of attack in the T5 Hypervelocity Shock Tunnel to test this concept. The cone was constructed with a smooth surface around half the cone circumference (to serve as a control) and an acoustically absorptive porous surface on the other half. Test gases investigated included nitrogen and carbon dioxide at M∞ ≃ 5 with specific reservoir enthalpy ranging from 1.3 to 13.0 MJ/kg and reservoir pressure ranging from 9.0 to 50.0 MPa. Comparisons were performed to ensure that previous results obtained in similar experiments (on a regular smooth surface) were reproduced, and the results were extended to examine the effects of the porous surface. These experiments indicated that the porous surface was highly effective in delaying transition provided that the pore size was significantly smaller than the viscous length scale

    On Blow-up Time and Rate Of The Numerical Solutions of The Semilinear Heat Equation with Reaction Term

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    In this paper, we study the numerical blow-up solutions and times of the semilinear heat equation with reaction term. We compute the blow-up growth rate in the numerical solutions of two numerical experiments, depending on the blow-up solutions and times, those have been computed using a finite difference method.&nbsp

    Calibrated in-vacuum quantum efficiency system for metallic and III-V thin-film photocathodes

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    The construction and calibration of a high vacuum system for thin film growth and in situ quantum efficiency (QE) measurement are described. Surface cleaning by in situ argon ion sputtering and annealing is supported. The QE measurement is based on an external 265 nm LED and in situ positively biased collector grid. The system is applied to two metallic and two semiconducting photocathodes: polycrystalline silver and copper, and single crystal InP and InSb. Surface cleaning protocols are shown to have a dramatic effect on the QE for all of these materials. The maximum QE values achieved for clean InSb and InP are around 8 × 10−5, for Cu 9 × 10−5 and for Ag 2 × 10−4

    Evaluation of the reanalysis wind over the Indian Ocean across the seasonal reversing wind pattern

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    75-84Present study show the similarity as well as contradictory event among the four different wind data based on monthly, seasonally and annual wind pattern over Indian Ocean. All the four reanalysis wind sources exhibit almost similar trend in their annual as well as monthly average wind pattern, however there is no strong similarity at their peak condition in space and time.The statistical analysis, based on Mean Absolute Error (MAE) and correlation coefficient (R), exhibited that the ECMWF and NCMRWF wind shows comparatively good agreement with the moored buoy data than the NCEP/NCAR and NCEP/CFSR wind under the seasonal reversing wind pattern occurs across the consecutive monsoons

    NO-Donating NSAIDs, PPARδ, and Cancer: Does PPARδ Contribute to Colon Carcinogenesis?

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    The chemopreventive NO-donating NSAIDs (NO-NSAIDs; NSAIDs with an NO-releasing moiety) modulate PPARδ and offer the opportunity to revisit the controversial role of PPARδ in carcinogenesis (several papers report that PPARδ either promotes or inhibits cancer). This review summarizes the pharmacology of NO-NSAIDs, PPARδ cancer biology, and the relationship between the two. In particular, a study of the chemopreventive effect of two isomers of NO-aspirin on intestinal neoplasia in Min mice showed that, compared to wild-type controls, PPARδ is overexpressed in the intestinal mucosa of Min mice; PPARδ responds to m- and p-NO-ASA proportionally to their antitumor effect (p- > m-). This effect is accompanied by the induction of epithelial cell death, which correlates with the antineoplastic effect of NO-aspirin; and NO-aspirin's effect on PPARδ is specific (no changes in PPARα or PPARγ). Although these data support the notion that PPARδ promotes intestinal carcinogenesis and its inhibition could be therapeutically useful, more work is needed before a firm conclusion is reached

    The Diagnostic Accuracy of Double-Layer Sign in Detection of Macular Neovascularization Secondary to Central Serous Chorioretinopathy

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    PURPOSE: To investigate the diagnostic value of elevated retinal pigment epithelium (RPE) and double-layer sign (DLS) in identifying macular neovascularization (MNV) secondary to central serous chorioretinopathy (CSCR). DESIGN: Retrospective, cross-sectional study. METHODS: Patients with CSCR underwent optical coherence tomography (OCT) and OCT angiography (OCT-A) scanning at Moorfields Eye Hospital. OCT scans were reviewed to identify the presence/absence of an RPE elevation. The maximum length and maximum height of the elevated RPE were measured. A minimum length of 1000 µm and a maximum height of 150 µm were used to define the "double-layer sign". Other qualitative anatomical features were also graded from OCT scans. OCT-A was examined to confirm the presence/absence of MNV. Binary logistic regression analyses were used to assess the association between OCT features and the detection of MNV on OCT-A. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to assess the diagnostic accuracy. RESULTS: One hundred and sixty-three eyes from 132 patients were included. Elevated RPE was detected in 148 eyes (91%). OCT-A-confirmed MNV was detected in 54 eyes (33%). The sensitivity and specificity of RPE elevation were 100% and 13.8%, respectively. DLS was identified in 95 eyes (58%). The sensitivity and specificity of DLS for detecting MNV were 87% and 56%, respectively. Hyper-reflectivity and non-homogeneity of the sub-RPE space were independently associated with MNV within the DLS (odds ratio, 17.7 and 14.8, p<0.001 and p=0.02, respectively). None of the other demographic or anatomical features associated with MNV. The presence of non-homogeneous hyper-reflective RPE elevation had a sensitivity and specificity of 98% and 67%, with PPV and NPV of 60% and 99%, respectively. CONCLUSIONS: Non-homogeneous and hyper-reflective space under an elevated RPE of any length or height indicates an eye with higher risk of MNV than DLS. OCT-A should at least be performed for these eyes to confirm the presence of MNV and treat accordingly

    Effective action for the field equations of charged black holes

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    In this article, we consistently reduce the equations of motion for the bosonic N = 2 supergravity action, using a multi-centered black hole ansatz for the metric. This reduction is done in a general, non-supersymmetric setup, in which we extend concepts of BPS black hole technology. First of all we obtain a more general form of the black hole potential, as part of an effective action for both the scalars and the vectors in the supergravity theory. Furthermore, we show that there are extra constraints specifying the solution, which we calculate explicitly. In the literature, these constraints have already been studied in the one-center case. We also show that the effective action we obtain for non-static metrics, can be linked to the "entropy function" for the spherically symmetric case, as defined by Sen and Cardoso et al.Comment: 18 pages, (v2: small corrections, version to be published in CQG
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