Elevated temperature creep properties for selected active metal braze alloys

Active metal braze alloys reduce the number of processes required for the joining of metal to ceramic components by eliminating the need for metallization and/or Ni plating of the ceramic surfaces. Titanium (Ti), V, and Zr are examples of active element additions which have been used successfully in such braze alloys. Since the braze alloy is expected to accommodate thermal expansion mismatch strains between the metal and ceramic materials, a knowledge of its elevated temperature mechanical properties is important. In particular, the issue of whether or not the creep strength of an active metal braze alloy is increased or decreased relative to its non-activated counterpart is important when designing new brazing processes and alloy systems. This paper presents a survey of high temperature mechanical properties for two pairs of conventional braze alloys and their active metal counterparts: (a) the conventional 72Ag-28Cu (Cusil) alloy, and the active braze alloy 62.2Ag- 36.2Cu-1.6Ti (Cusil ABA), and (b) the 82Au-18Ni (Nioro) alloy and the active braze alloy Mu-15.5M-0.75Mo-1.75V (Nioro ABA). For the case of the Cusil/Cusil ABA pair, the active metal addition contributes to solid solution strengthening of the braze alloy, resulting in a higher creep strength as compared to the non-active alloy. In the case of the Nioro/Nioro ABA pair, the Mo and V additions cause the active braze alloy to have a two-phase microstructure, which results in a reduced creep strength than the conventional braze alloy. The Garofalo sinh equation has been used to quantitatively describe the stress and temperature dependence of the deformation behavior. It will be observed that the effective stress exponent in the Garofalo sinh equation is a function of the instantaneous value of the stress argument

Occurrence and extent of hybridisation between the invasive Mallard Duck and native Yellow-billed Duck in South Africa

Hybridisation between invasive and native species represents a significant threat to biodiversity. The Mallard Duck (Anas platyrhynchos) is known to hybridise with numerous closely related Anas species in regions where they have been introduced, threatening the genetic integrity of native ducks and in some instances contributing to their extinction risk. Mallard Ducks were introduced into South Africa in the 1940s and are now naturalised and widespread in the country. It has been speculated that Mallard Ducks are hybridising with native Yellow-billed Ducks (A. undulata) in South Africa, but evidence for this remains observational or purely anecdotal. Here we use data from nuclear microsatellite markers and mitochondrial DNA sequencing to show that hybridisation is indeed occuring between these two species. We found evidence for the occurance of hybridisation, mostly as crosses between Mallard Duck hens and Yellow-billed Duck drakes. Surprisingly, our results suggest that introgressive hybridisation is primarily occuring into the invasive Mallard Duck population (mostly Mallard Duck backcrosses were detected), evidenced by directionally-skewed gene flow and sex-biased mating. Whether these findings reflect true assortative mating or a case of Haldane’s rule remains unknown. We also found evidence of high connectivity between Yellow-billed Duck populations, as far as 1000 km apart, in South Africa. Taken together these results suggest that hybrid genotypes can disperse over vast distances between populations and lead to genetic pollution, even in the absence of invasive Mallard Ducks. Active management of Mallard Duck populations has been met by public resistance in some areas in South Africa, partly because of a lack of evidence showing clear impacts by these birds. This study provides some of the first scientifically-documented evidence for such impacts

Coupling Of Ribosome And tRNA Dynamics During Translation

Interstellar matter and star formatio

On the Origin of the Outgoing Black Hole Modes

The question of how to account for the outgoing black hole modes without drawing upon a transplanckian reservoir at the horizon is addressed. It is argued that the outgoing modes must arise via conversion from ingoing modes. It is further argued that the back-reaction must be included to avoid the conclusion that particle creation cannot occur in a strictly stationary background. The process of ``mode conversion" is known in plasma physics by this name and in condensed matter physics as ``Andreev reflection" or ``branch conversion". It is illustrated here in a linear Lorentz non-invariant model introduced by Unruh. The role of interactions and a physical short distance cutoff is then examined in the sonic black hole formed with Helium-II.Comment: 12 pages, plain latex, 2 figures included using psfig; Analogy to ``Andreev reflection" in superfluid systems noted, references and acknowledgment added, format changed to shorten tex

Disc polarization from both emission and scattering of magnetically aligned grains: the case of NGC 1333 IRAS 4A1

Stars and planetary system

Balloon Measurements of Cosmic Ray Muon Spectra in the Atmosphere along with those of Primary Protons and Helium Nuclei over Mid-Latitude

We report here the measurements of the energy spectra of atmospheric muons and of the cosmic ray primary proton and helium nuclei in a single experiment. These were carried out using the MASS superconducting spectrometer in a balloon flight experiment in 1991. The relevance of these results to the atmospheric neutrino anomaly is emphasized. In particular, this approach allows uncertainties caused by the level of solar modulation, the geomagnetic cut-off of the primaries and possible experimental systematics to be decoupled in the comparison of calculated fluxes of muons to measured muon fluxes. The muon observations cover the momentum and depth ranges of 0.3-40 GeV/c and 5-886 g/cmsquared, respectively. The proton and helium primary measurements cover the rigidity range from 3 to 100 GV, in which both the solar modulation and the geomagnetic cut-off affect the energy spectra at low energies.Comment: 31 pages, including 17 figures, simplified apparatus figure, to appear in Phys. Rev.

Protostellar accretion traced with chemistry. High-resolution C18O and continuum observations towards deeply embedded protostars in Perseus

Interstellar matter and star formatio

Production and Decay of D_1(2420)^0 and D_2^*(2460)^0

We have investigated $D^{+}\pi^{-}$ and $D^{*+}\pi^{-}$ final states and observed the two established $L=1$ charmed mesons, the $D_1(2420)^0$ with mass $2421^{+1+2}_{-2-2}$ MeV/c$^{2}$ and width $20^{+6+3}_{-5-3}$ MeV/c$^{2}$ and the $D_2^*(2460)^0$ with mass $2465 \pm 3 \pm 3$ MeV/c$^{2}$ and width $28^{+8+6}_{-7-6}$ MeV/c$^{2}$. Properties of these final states, including their decay angular distributions and spin-parity assignments, have been studied. We identify these two mesons as the $j_{light}=3/2$ doublet predicted by HQET. We also obtain constraints on {\footnotesize $\Gamma_S/(\Gamma_S + \Gamma_D)$} as a function of the cosine of the relative phase of the two amplitudes in the $D_1(2420)^0$ decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by sending mail to: [email protected]

Safety of elvitegravir, cobicistat, emtricitabine, and tenofovir alafenamide in HIV-1-infected adults with end-stage renal disease on chronic haemodialysis: an open-label, single-arm, multicentre, phase 3b trial

Background: Current treatment for HIV-infected individuals with renal failure on haemodialysis frequently requires complex regimens with multiple pills. A daily single-tablet regimen of coformulated elvitegravir, cobicistat, emtricitabine, and tenofovir alafenamide is approved in Europe, the USA, and in other regions for use in HIV-1-infected individuals with mild-to-moderate chronic kidney disease (creatinine clearance 30–69 mL/min). We aimed to assess the safety, efficacy, and pharmacokinetics of this regimen in HIV-infected adults with end-stage renal disease on chronic haemodialysis. Methods: We did an open-label, single-arm, multicentre, phase 3b trial at 26 outpatient clinics in Austria, France, Germany, and the USA. Participants were HIV-1-infected adults with end-stage renal disease (creatinine clearance <15 mL/min), on chronic haemodialysis for at least 6 months before screening. Virological suppression (ie, plasma HIV-1 RNA <50 copies per mL) on a stable antiretroviral regimen was required for at least 6 months before screening with a CD4 count of at least 200 cells per μL. We switched all participants to coformulated elvitegravir 150 mg, cobicistat 150 mg, emtricitabine 200 mg, and tenofovir alafenamide 10 mg once daily, taken after haemodialysis for up to 96 weeks. We did assessments at study visits at weeks 2, 4, 8, 12, 24, 36, and 48, and every 12 weeks thereafter up to 96 weeks. The primary endpoint was the incidence of treatment-emergent adverse events of grade 3 or higher up to week 48. All participants who received at least one dose of study drug were included in the primary analysis. This study is registered with ClinicalTrials.gov (NCT02600819) and is closed to new participants. Findings: Between Feb 1, and Nov 3, 2016, 55 participants were enrolled and received at least one dose of study drug. Through week 48, 18 of 55 participants (33%, 95% CI 20–45) had an adverse event of grade 3 or higher on study treatment. Treatment-emergent grade 3 or higher adverse events that occurred in more than one participant included anaemia, osteomyelitis, prolonged electrocardiogram QT, fluid overload, hyperkalaemia, hypertension, and hypotension (all n=2). No adverse event of grade 3 or higher was considered by the site investigators to be treatment related. Three participants (5%, 95% CI 0–11) discontinued treatment because of adverse events; one of these (grade 1 allergic pruritus) was considered treatment related. Treatment-related adverse events were reported for six individuals (11%, 95% CI 3–19), the most common of which was nausea (in four individuals [7%]); all treatment-related adverse events were grade 1 or 2 in severity. Interpretation: At 48 weeks, switching to the single-tablet regimen of elvitegravir, cobicistat, emtricitabine, and tenofovir alafenamide was well tolerated. This regimen might provide a tolerable and convenient option for ongoing treatment of HIV-1 infection in adults with end-stage renal disease on chronic haemodialysis. Funding: Gilead Sciences