Determination of the thixocasting temperatures of AZ91D and other Mg alloys using a quenching method

The thixocasting injection temperature is a crucial processing parameter, frequently unavailable in the literature, especially for newly developed alloys. In this work, a simple and rapid method derived from the quenching method was developed to obtain an acceptable thixocasting injection temperature range for various magnesium alloys: AZ91D, AJ62x, AXJ530, MRI153 and ZAEX10440. Small specimens of each alloy were heated to appropriate temperatures within the semisolid range and quenched. Their microstructure was observed optically and the proportion of phase was measured using quantitative image analysis. The microsegregation was characterized and two different heating cycles prior to quenching were studied. The apparent volume fraction of the primary solid was determined as a function of quenching temperature between liquidus and solidus. These results were found useful to obtain a practical injection temperature range for each alloy and to obtain good quality thixocast parts.La temp\ue9rature d\u2019injection pour la thixocoul\ue9e est un param\ue8tre crucial de proc\ue9d\ue9 qui n\u2019est pas toujours disponible dans la litt\ue9rature et ce, surtout dans le cas de nouveaux alliages d\ue9velopp\ue9s en laboratoire. Dans cet article, une m\ue9thode simple et rapide, d\ue9riv\ue9e de la m\ue9thode de trempe, est propos\ue9e pour estimer un intervalle de temp\ue9rature d\u2019injection d\u2019alliages de magn\ue9sium tels que AZ91D, AJ62x, AXJ530, MRI153 et ZAEX10440. Des sp\ue9cimens de chaque alliage ont \ue9t\ue9 chauff\ue9s \ue0 diff\ue9rentes temp\ue9ratures dans l\u2019intervalle semisolide et tremp\ue9s. Leur microstructure a \ue9t\ue9 observ\ue9e en microscopie optique et analys\ue9e quantitativement par analyse d\u2019image afin de mesurer la proportion de la phase solide primaire. La micros\ue9gr\ue9gation a \ue9galement \ue9t\ue9 mesur\ue9e dans les phases apr\ue8s trempe et deux cycles thermiques diff\ue9rents ont \ue9t\ue9 compar\ue9s. La fraction volumique apparente de la phase solide primaire a \ue9t\ue9 d\ue9termin\ue9e en fonction de la temp\ue9rature de trempe entre le liquidus et le solidus. \uc0 partir de ces r\ue9sultats, un intervalle de temp\ue9rature a \ue9t\ue9 estim\ue9 pour chaque alliage afin d\u2019obtenir par thixocoul\ue9e des pi\ue8ces d\u2019excellente qualit\ue9.NRC publication: Ye

High-frequency bone conduction audiometry using a piezoelectric transducer

NRC publication: Ye

Wavelength scaling of high harmonic generation efficiency

Using longer wavelength laser drivers for high harmonic generation is desirable because the highest extreme ultraviolet frequency scales as the square of the wavelength. Recent numerical studies predict that high harmonic efficiency falls dramatically with increasing wavelength, with a very unfavorable \u3bb-(5-6) scaling. We performed an experimental study of the high harmonic yield over a wavelength range of 800\u20131850 nm. A thin gas jet was employed to minimize phase matching effects, and the laser intensity and focal spot size were kept constant as the wavelength was changed. Ion yield was simultaneously measured so that the total number of emitting atoms was known. We found that the scaling at constant laser intensity is \u3bb-6.3\ub11.1 in Xe and \u3bb-6.5\ub11.1 in Kr over the wavelength range of 800\u20131850 nm, somewhat worse than the theoretical predictions.Peer reviewed: YesNRC publication: Ye

High harmonic generation with long-wavelength few-cycle laser pulses

We report the extension of hollow-core fibre pulse compression to longer wavelengths. High-energy multi-cycle infrared pulses are generated via optical parametric amplification and subsequently broadened in the fibre. 2.5-cycle pulses at the Signal wavelength (1.4 \ub5m) and 1.6-cycle pulses at the Idler wavelength (1.8 \ub5m) in the sub-millijoule regime have been generated. New compression schemes can be applied at 1.8 \ub5m and beyond. In this manner, 1.6-cycle carrier envelope phase stable pulses were generated by linear propagation in the anomalous dispersion regime of bulk glass which surprisingly enables compression below its third-order dispersion limit. Furthermore, a dispersion-free way of controlling the carrier envelope phase is demonstrated. Moreover, we experimentally confirm the increase in high-harmonic cut-off energy with driving laser wavelength and demonstrate the beneficial effect of few-cycle pulses which enable higher saturation intensities on target compared to multi-cycle pulses. It will be an ideal tool for future synthesis of isolated attosecond pulses in the sub-keV regime. With this laser source, we revealed for the first time multi-electron effects in high harmonic generation in xenon.Peer reviewed: YesNRC publication: Ye

Pulse compression of submillijoule few-optical-cycle infrared laser pulses using chirped mirrors

We report generation of 400 \u3bcJ, 13.1 fs, 1425 nm optical parametric amplifier laser pulses. Spectral broadening of a 100 Hz optical parametric amplifier laser source is achieved by self-phase modulation in an argon-filled hollow-core fiber, and dispersion compensation is performed using chirped mirrors. This laser source will be useful for ultrafast time-resolved molecular orbital tomography.Peer reviewed: YesNRC publication: Ye

Intense few-cycle infrared laser pulses at the advanced laser light source

To push the generation of isolated attosecond pulses towards shorter XUV wavelengths (0.3 to 1 keV), intense few-cycle driving pulses are required whose center frequency is significantly red shifted compared to established Ti-Sa technology. A simple route for generating these pulses is demonstrated using an optical parametric amplifier (OPA). Its infrared (IR) multi-cycle laser pulses with millijoule of energy are spectrally broadened by nonlinear propagation in a hollow-core fiber (HCF) filled with Argon. For the OPA Signal wavelength (\u3bb = 1.4 micron), chirped mirrors were used for dispersion compensation with a resulting pulse duration of 13.1 fs. For the OPA Idler wavelength at 1.8 micron, a new compression scheme has been developed with which 11.2 fs laser pulses have been characterized (1 cycle= 6 fs). Here, pulse compression is achieved through the combined effects of self-steepening during nonlinear propagation in the HCF followed by anomalous dispersion during linear propagation in fused silica.Peer reviewed: YesNRC publication: Ye

Helicobacter pylori eradication with a capsule containing bismuth subcitrate potassium, metronidazole, and tetracycline given with omeprazole versus clarithromycin-based triple therapy: a randomised, open-label, non-inferiority, phase 3 trial

BACKGROUND: Helicobacter pylori is associated with benign and malignant diseases of the upper gastrointestinal tract, and increasing antibiotic resistance has made alternative treatments necessary. Our aim was to assess the efficacy and safety of a new, single-capsule treatment versus the gold standard for H pylori eradication. METHODS: We did a randomised, open-label, non-inferiority, phase 3 trial in 39 sites in Europe, comparing the efficacy and safety of 10 days of quadruple therapy with omeprazole plus a single three-in-one capsule containing bismuth subcitrate potassium, metronidazole, and tetracycline (quadruple therapy) versus 7 days of omeprazole, amoxicillin, and clarithromycin (standard therapy) in adults with recorded H pylori infection. Patients were randomly assigned treatment according to a predetermined list independently generated by Quintiles Canada (Ville St-Laurent, QC, Canada). Our study was designed as a non-inferiority trial but was powered to detect superiority. Our primary outcome was H pylori eradication, established by two negative (13)C urea breath tests at a minimum of 28 and 56 days after the end of treatment. Our assessment for non-inferiority was in the per-protocol population, with subsequent assessment for superiority in the intention-to-treat population (ie, all participants randomly assigned treatment). This study is registered with ClinicalTrials.gov, number NCT00669955. FINDINGS: 12 participants were lost to follow-up and 101 were excluded from the per-protocol analysis. In the per-protocol population (n=339), the lower bound of the CI for treatment with quadruple therapy was greater than the pre-established non-inferiority margin of -10% (95% CI 15\ub71-32\ub73; p<0\ub70001). In the intention-to-treat population (n=440), eradication rates were 80% (174 of 218 participants) in the quadruple therapy group versus 55% (123 of 222) in the standard therapy group (p<0\ub70001). Safety profiles for both treatments were similar; main adverse events were gastrointestinal and CNS disorders. INTERPRETATION: Quadruple therapy should be considered for first-line treatment in view of the rising prevalence of clarithromycin-resistant H pylori, especially since quadruple therapy provides superior eradication with similar safety and tolerability to standard therapy.Background: Helicobacter pylori is associated with benign and malignant diseases of the upper gastrointestinal tract, and increasing antibiotic resistance has made alternative treatments necessary. Our aim was to assess the efficacy and safety of a new, single-capsule treatment versus the gold standard for H pylori eradication. Methods: We did a randomised, open-label, non-inferiority, phase 3 trial in 39 sites in Europe, comparing the efficacy and safety of 10 days of quadruple therapy with omeprazole plus a single three-in-one capsule containing bismuth subcitrate potassium, metronidazole, and tetracycline (quadruple therapy) versus 7 days of omeprazole, amoxicillin, and clarithromycin (standard therapy) in adults with recorded H pylori infection. Patients were randomly assigned treatment according to a predetermined list independently generated by Quintiles Canada (Ville St-Laurent, QC, Canada). Our study was designed as a non-inferiority trial but was powered to detect superiority. Our primary outcome was H pylori eradication, established by two negative 13C urea breath tests at a minimum of 28 and 56 days after the end of treatment. Our assessment for non-inferiority was in the per-protocol population, with subsequent assessment for superiority in the intention-to-treat population (ie, all participants randomly assigned treatment). This study is registered with ClinicalTrials.gov, number NCT00669955. Findings: 12 participants were lost to follow-up and 101 were excluded from the per-protocol analysis. In the per-protocol population (n=339), the lower bound of the CI for treatment with quadruple therapy was greater than the pre-established non-inferiority margin of -10% (95% CI 15.1-32.3; p<0.0001). In the intention-to-treat population (n=440), eradication rates were 80% (174 of 218 participants) in the quadruple therapy group versus 55% (123 of 222) in the standard therapy group (p<0.0001). Safety profiles for both treatments were similar; main adverse events were gastrointestinal and CNS disorders. Interpretation: Quadruple therapy should be considered for first-line treatment in view of the rising prevalence of clarithromycin-resistant H pylori, especially since quadruple therapy provides superior eradication with similar safety and tolerability to standard therapy. Funding: Axcan Pharma Inc. \ua9 2011 Elsevier Ltd