Surface modification of Hastelloy C-276 by SiC addition and electron beam melting

Electron beam surface melting of Hastelloy C-276 with the SiC addition is carried out to improve the surface properties. The resulted microstructure and non-equilibrium phases are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive system (EDS). The Hastelloy C-276 is successfully surface-hardened by electron beam melting, the surface hardening effect can be attributed to both microstructure refinement and eutectic phases produced by EB. During EB melting the SiC broke into small pieces and spread in the microstructure increasing the surface hardness by thirteen times.     

Velocity-image model for online signature verification.

In general, online signature capturing devices provide outputs in the form of shape and velocity signals. In the past, strokes have been extracted while tracking velocity signal minimas. However, the resulting strokes are larger and complicated in shape and thus make the subsequent job of generating a discriminative template difficult. We propose a new stroke-based algorithm that splits velocity signal into various bands. Based on these bands, strokes are extracted which are smaller and more simpler in nature. Training of our proposed system revealed that low- and high-velocity bands of the signal are unstable, whereas the medium-velocity band can be used for discrimination purposes. Euclidean distances of strokes extracted on the basis of medium velocity band are used for verification purpose. The experiments conducted show improvement in discriminative capability of the proposed stroke-based system.     

SITO High Output Impedance Transadmittance Filter Using FTFNs

FTFN based single input and three outputs transadmittance filter topology supporting simultaneously three filtering signals LP, BP, and HP without any passive component matching conditions is presented. The filter uses three PFTFNs and five passive components and realizes all current signals at high impedances, lending feature of cascadibility to the circuit. The circuit enjoys low sensitivity figures. PSPICE simulation results confirming the theoretical calculations are included.     

A comparison of the trap properties and locations within GaAs fieldeffect transistors measured under different bias conditions

The activation energy and capture cross section of traps found in GaAs field effect transistors (GaAs FETs) have been measured with both ohmic channel and current saturation bias using a variety of transient, frequency dispersion, and noise spectroscopy techniques. With current saturation bias these effects have been seen in both the transconductance and the output conductance. The results for all methods and bias conditions are compared with those found by others. The relative sensitivity of the techniques and the location of the traps are discussed     

Microstructure and hardness studies of the electron beam welded zone of Hastelloy C-276

Electron beam welding (EBW) technique is becoming popular in nuclear, chemical and aerospace industries due to its high penetration depth and fast cooling rate. Samples of Hastelloy C-276 have been welded by electron beam (EB). A scanning electron microscope (SEM) having the attachment of an energy dispersive system (EDS) has been employed to study the resulting microstructure and micro-eutectic phases. The microstructure of the molten zone (MZ) is found to be of fine lamellar type. The hardness of the MZ is found to be 35% higher compared to as-received alloy. The micro-eutectoids are rich in Mo and W. The X-ray diffraction patterns of the MZ show shifting of peaks towards higher angle compared to the diffraction pattern of the as-received alloy. Broadening of the peaks is also observed in the diffraction pattern of the MZ. Formation of the μ-phase was observed in the MZ after a tempering treatment at 950 °C.     

A randomized double-blind comparison of the effects on systemic calcium homeostasis of topical calcitriol (3 micrograms/g) and calcipotriol (50 micrograms/g) in the treatment of chronic plaque psoriasis vulgaris

Calcitriol and calcipotriol are effective treatments for psoriasis, although the two have never been directly compared. We compared the efficacy and toxicity of each agent in 24 patients with moderately extensive chronic plaque psoriasis, who were randomized in double-blind fashion to apply 90 g per week of either calcitriol (3 micrograms/g) ointment or calcipotriol (50 micrograms/g) ointment over an 8-week period. Mean PASI in patients applying calcitriol fell from 13 to 8.8 (p < 0.05) and in patients applying calcipotriol from 14.9 to 4.7 (p < 0.005). The reduction was significantly greater in the calcipotriol-treated group (p < 0.05). There was a small increase in serum ionized calcium in the calcipotriol-treated group (from 1.21 mmol/L to 1.25 mmol/L, p < 0.05) but no effect on calcium homeostasis in the calcitriol group.     

Evidence that Fe-NTA-induced renal prostaglandin F2 alpha is responsible for hyperplastic response in kidney: implications for the role of cyclooxygenase-dependent arachidonic acid metabolism in renal tumor promotion

Oxidative stress in a tissue activates phospholipase A2 which releases free arachidonic acid. In addition, a low grade oxidative tone also stimulates the tissue cyclooxygenase activity. Cyclooxygenase-dependent arachidonic acid metabolites such as PGF 2 alpha are known to play an important role in the development and maintenance of hyperplasia in skin in response to the application of tumor promoters. In this study we show that Fe-NTA, an oxidant renal tumor promoter induces PGF 2 alpha which was maximum at 12 hours after Fe-NTA treatment. However, at all time points studied, the elevated levels of PGF 2 alpha have been observed. As a result of the induction of PGF 2 alpha, the hyperplastic response can also be observed in the histopathology of the tissue. Additionally, an increased incorporation of [3H]thymidine in renal DNA has also been observed. Pretreatment of animals with indomethacin suppresses Fe-NTA-mediated hyperproliferation suggesting a role of cyclooxygenase in Fe-NTA-mediated stimulation of hyperplastic activity. The pretreatment of animals with the chain breaking antioxidants, Vit. E, BHA and BHT were only partially effective in inhibiting Fe-NTA-mediated PGF2 alpha production, further suggesting a role of non-free radical-dependent mechanism in its production. Our data suggest that Fe-NTA-induced PGF2 alpha through the activation of cyclooxygenase is responsible for the development and maintenance of hyperplasia in kidney.     

High speed performance of 1.5 mu m compressive-strained multiquantum-well gain-coupled distributed-feedback lasers

1.5 mu m compressive-strained multiquantum-well gain-coupled distributed-feedback lasers have been fabricated on semi-insulating InP substrates with very low parasitic capacitance for studying the laser dynamic characteristics. A maximum 3 dB bandwidth of 12.8 GHz under small signal modulation, a 20 dB down chirping width of 0.33 nm under modulation, a 20 dB down chirping width of 0.33 nm under 5 Gbit/s NRZ pseudorandom modulation, and a low chirping short pulse of 20 ps under gain switching are obtained.<>     

High grade dysplasia/esophageal adenocarcinoma in short segment Barrett's esophagus

Short segment Barrett's esophagus (SSBE) is a frequent finding in patients having endoscopy, but its clinical significance is not fully understood. With the rising incidence of esophageal adenocarcinoma, a potential role of SSBE has been suggested. Biopsy of such lesions may have to be done when seen on endoscopy.     

Stochastic simulation of fission product activity in primary coolant due to fuel rod failures in typical PWRs under power transients

During normal operation of PWRs, routine fuel rods failures result in release of radioactive fission products (RFPs) in the primary coolant of PWRs. In this work, a stochastic model has been developed for simulation of failure time sequences and release rates for the estimation of fission product activity in primary coolant of a typical PWR under power perturbations. In the first part, a stochastic approach is developed, based on generation of fuel failure event sequences by sampling the time dependent intensity functions. Then a three-stage model based deterministic methodology of the FPCART code has been extended to include failure sequences and random release rates in a computer code FPCART-ST, which uses state-of-the-art LEOPARD and ODMUG codes as its subroutines. The value of the ¹³¹I activity in primary coolant predicted by FPCART-ST code has been found in good agreement with the corresponding values measured at ANGRA-1 nuclear power plant. The predictions of FPCART-ST code with constant release option have also been found to have good agreement with corresponding experimental values for time dependent ¹³⁵I, ¹³⁵Xe and ⁸⁹Kr concentrations in primary coolant measured during EDITHMOX-1 experiments.