A CW external-cavity surface-emitting laser

Room temperature, continuous wave (CW) operation of an external-cavity, optically-pumped surface-emitting laser is reported. The device is a resonant-periodic gain (RPG) vertical-cavity surface-emitting laser (VCSEL) with the top mirror stack replaced by an epitaxially grown antireflection (AR) coating. An external mirror having a 50-mm radius of curvature completes the resonator in a near hemispherical configuration. Mode spectra, input-output curves, and polarization properties of the device are presented.     

Increased protein kinase C activity and expression of Ca2+-sensitive isoforms in the failing human heart

BACKGROUND: Increased expression of Ca2+-sensitive protein kinase C (PKC) isoforms may be important markers of heart failure. Our aim was to determine the relative expression of PKC-beta1, -beta2, and -alpha in failed and nonfailed myocardium. METHODS AND RESULTS: Explanted hearts of patients in whom dilated cardiomyopathy or ischemic cardiomyopathy was diagnosed were examined for PKC isoform content by Western blot, immunohistochemistry, enzymatic activity, and in situ hybridization and compared with nonfailed left ventricle. Quantitative immunoblotting revealed significant increases of >40% in PKC-beta1 (P<0.05) and -beta2 (P<0.04) membrane expression in failed hearts compared with nonfailed; PKC-alpha expression was significantly elevated by 70% in membrane fractions (P<0.03). PKC-epsilon expression was not significantly changed. In failed left ventricle, PKC-beta1 and -beta2 immunostaining was intense throughout myocytes, compared with slight, scattered staining in nonfailed myocytes. PKC-alpha immunostaining was also more evident in cardiomyocytes from failed hearts with staining primarily localized to intercalated disks. In situ hybridization revealed increased PKC-beta1 and -beta2 mRNA expression in cardiomyocytes of failed heart tissue. PKC activity was significantly increased in membrane fractions from failed hearts compared with nonfailed (1021+/-189 versus 261+/-89 pmol. mg-1. min-1, P<0.01). LY333531, a selective PKC-beta inhibitor, significantly decreased PKC activity in membrane fractions from failed hearts by 209 pmol. min-1. mg-1 (versus 42.5 pmol. min-1. mg-1 in nonfailed, P<0.04), indicating a greater contribution of PKC-beta to total PKC activity in failed hearts. CONCLUSIONS: In failed human heart, PKC-beta1 and -beta2 expression and contribution to total PKC activity are significantly increased. This may signal a role for Ca2+-sensitive PKC isoforms in cardiac mechanisms involved in heart failure.     

Small intestinal submucosa as a vascular graft: a review

Continuing investigations of vascular graft materials suggest that unacceptable graft complications continue and that the ideal graft material has not yet been found. We have developed and tested a biologic vascular graft material, small intestine submucosa (SIS), in normal dogs. This material, when used as an autograft, allograft, or xenograft has demonstrated biocompatibility and high patency rates in aorta, carotid and femoral arteries, and superior vena cava locations. The grafts are completely endothelialized at 28 days post-implantation. At 90 days, the grafts are histologically similar to normal arteries and veins and contain a smooth muscle media and a dense fibrous connective tissue adventitia. Follow-up periods of up to 5 years found no evidence of infection, intimal hyperplasia, or aneurysmal dilation. One infection-challenge study suggested that SIS may be infection resistant, possibly because of early capillary penetration of the SIS (2 to 4 days after implantation) and delivery of body defenses to the local site. We conclude that SIS is a suitable blood interface material and is worthy of continued investigation. It may serve as a structural framework for the application of tissue engineering technologies in the development of the elusive ideal vascular graft material.     

Influence of long-term sodium exposure on the composition and microstructure of austenitic alloys

Austenitic alloys (Types 304, 316, 321, 347 stainless steel and Incoloy-800) were exposed to flowing sodium in out-of-pile test loops at 704 °C (1300 °F) and 621 °C (1150 °F) for varying times up to 15726 h. Changes in chemical composition and microstructure increased with increasing exposure time. Major alloying elements (Cr, Ni, Mn) were depleted from surface layers up to 130 μm thick. Unstabilized alloys (Types 304 and 316) lost carbon during exposure while stabilized alloys (Types 321, 347 and I-800) tended to gain carbon. Variations in other minor elements with exposure were determined. Changes in microstructure reflected the compositional changes in all the alloys. Specimens were examined by optical, transmission electron and scanning electron microscopy. A ferrite layer formed at the sodium exposed surface of all alloys except Incoloy-800. Sigma phase precipitation increased with exposure time. In the stabilized alloys cavities formed up to 120 μm below the sodium-exposed surface. The subsurface cavities appeared to be connected to surface pits via intergranular channels and were related to a decrease in density observed in the specimens.     

Proactive approaches to assure the structural integrity of Boiling Water Reactor components

Pressure vessel components in operating Boiling Water Reactor (BWR) plants are subjected to a variety of loading and environmental conditions which could lead to degradation over time. The significant damage mechanisms such as fatigue, stress corrosion cracking (SCC) and irradiation embrittlement are considered in the design basis of the reactor components and thus provide adequate structural margins over the operating life of the plant. Nevertheless, when the design basis assumptions are exceeded, e.g., thermal cycles, vibratory loading or chemistry transients, cracking may occur in pressure boundary components. Several proactive measures are being implemented to address this concern and assure the structural margins in BWR plants. These measures include: (i) control of materials and design to mitigate SCC and improvement of the environmental conditions through the implementation of Hydrogen Water Chemistry, (ii) advances in automated ultrasonic inspection of the BWR pressure vessel and piping, (iii) improved monitoring techniques for tracking fatigue usage and SCC effects in the piping and in the core, and (iv) development and qualification of durable repairs and specialized techniques such as use of high purity materials and temper bead repair. This paper describes current progress in implementing these proactive approaches for Boiling Water Reactors.     

Use of semiselective TOCSY and the pearson correlation for the metabonomic analysis of biofluid mixtures: application to urine

The authors recently proposed an approach to the metabonomic analysis of biofluid mixtures based on the use of the selective TOCSY experiment (Sandusky, P.; Raftery, D. Anal. Chem. 2005, 77, 2455). This method has some significant advantages over standard metabonomic analysis. However, when analyzing overlapped components, the selective TOCSY method can suffer from the relatively high likelihood of simultaneous excitation of several spin systems at once. This multiple excitation can cause problems both with the purity of the individual TOCSY peaks observed and with their assignment into specific spin systems. To address this problem, the possibility of using a more selective excitation is initially explored. Unfortunately, in most cases, greater spin system selectivity can only be gained at the expense of sensitivity. This is obviously an unacceptable tradeoff when dealing with biofluid samples. However, the application of the Pearson product moment correlation to the TOCSY peak integral intensities provides a test for individual TOCSY peak purity and allows for the assignment of the peaks into spin systems. The specific application of this two-stage "semiselective" TOCSY method to rat and human urine is presented. Significantly, it is also demonstrated that the use of semiselective TOCSY spectra as data inputs for PCA calculations provides a more sensitive and reliable method of distinguishing small differences in biofluid composition than the standard metabonomic approach using complete 1D proton NMR spectra of urine samples.     

Infrastructure Management as Cooperative Work: Implications for Systems Design

This study looks at the data communicationsnetwork management organization (NMO) within alarge financial institution and appliesconcepts from Computer-Supported CooperativeWork (CSCW) and other domains to developtechniques for describing work within this andother similar organizations. Networkmanagement is one form of infrastructuremanagement, which is comprised of two kinds ofwork: real-time supervisory control work anddesign work. While many studies of group workfocus on the activities of small groups ofpeople engaged in either real-time supervisorycontrol or design work, examinations oforganizations where both kinds of work occurare relatively rare. The focus is on the workpatterns and data forms that are found withinthe NMO. Some of the implications of theanalysis in regard to the design of CSCWsystems are presented and discussed.