Actively stabilised diode pumped Tm:YAlO laser

An actively stabilised, continuous-wave, 1.94 /spl mu/m Tm:YAlO laser is presented. Optoelectronic negative feedback stabilisation is utilised to prevent relaxation-oscillation-driven spiking. The amplitude stability of the laser is found to be very robust against cavity perturbation and parasitic radiation back-reflection, making it attractive for practical applications.     

Grain-Size Effects on Diffuse Phase Transitions of Sol-Gel Prepared Barium Titanate Ceramics

Barium titanate ceramic samples, obtained by sol-gel methods, having different grain sizes have been analyzed by diffuse phase transition techniques. We performed a study of the influence of each method on the phase transition interval and on the Landau parameters of the ferroelectric phase transition of these materials. The results show the existence of a relationship between the diffuse character of the transition and the grain size of the sample. The method of fitting dielectric data presented here allows us to compare ceramics with single crystals and then analyze the sol-gel process used to obtain them.     

Measurement of thermal conductivity of polymer melts by the line-source method

An apparatus has been developed for the measurement of thermal conductivity of polymer melts. Based on the transient “line source method,” it is ideally suited to these materials because measurements can be made quickly, before the onset of thermal degradation. Also, little or no sample preparation is required. A number of commercial polymers have been tested, including some glass-fiber filled composites.     

On comparing finite difference schemes applied to a nonlinear multi-region heat and mass transfer problem

 A three-time-level scheme is employed to obtain numerical solutions of heat and mass transfer potentials for the nonlinear Luikov system. Relative errors are examined when the numerical solutions are compared to the analytical solutions for a single layer linear problem using different finite difference techniques. As a final example, comparisons also are made when the numerical schemes are used to solve a two-layer multi-region nonlinear approach, considering that the thermal conductivity and mass conductivity of the material are dependent on temperature and moisture transfer potential respectively. Received 6 September 2000     

Reactor design from batch data by a direct graphical method

A graphical method for reactor design is presented which uses the plot of concentration vs. time. This method can be used to compare stirred tank, plug flow and recycle reactors as well as various reactor combinations. With Monod Kinetics the concept of wash-out can be illustrated. A brief comparison with other graphical methods is made.     

Transesophageal echocardiography on the presurgical and postsurgical evaluation of a coronary arteriovenous fistula

One female patient in twenty-six years old, presents corneal marginal relapsed at the left eye, aphthae of inferior eyelid and aphthous stomatitis in episodically fits repeated at three-four weeks. Also she presents disorders of the intestinal transit and thrombosis of the right inferior limb, fragility of the vessels, thoracic neurodermatitis with presternal erythema; these phenomenon are improvement with cortico and immunomodulator therapy. On insist about present of the marginal, relapsed ulcus in Beh?et disease.     

Ethanol enhancement of Pavlovian conditioning.

60 New Zealand albino rabbits were tested for Pavlovian conditioning and extinction of eye-blink (EB) and heart-rate (HR) responses following water or various doses of oral ethanol (375–2,500 mg/kg). The highest dose suppressed both EB and HR conditioning during training, whereas the lowest dose enhanced HR responses during training and increased EB responses during later extinction in a symmetrically state-dependent manner. An intermediate dose (750 mg/kg) administered during training enhanced HR responses and suppressed EB responses but increased EB responses during later extinction following either ethanol or water. Ethanol treatments also suppressed unconditioned responses (UCRs) to shock and increased locomotor activity; however, these effects differed qualitatively from those that ocurred during Pavlovian training and extinction. Results suggest that very low doses of ethanol can enhance the ability of stimuli to elicit Pavlovian conditioned reflexes and impair the ability to adaptively modify these reflexes when stimulus contingencies later change. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of silver nanoparticle addition,porosity, and processing technique on the mechanical properties of Ba0.3Co4Sb12 skutterudites

The thermoelectric skutterudite Ba_0.3Co₄Sb₁₂ is a promising candidate for waste heat recovery applications. Recently, it was demonstrated that the addition of silver nanoparticles (Ag_NP) to Ba_0.3Co₄Sb₁₂ increases both the thermoelectric figure of merit and electrical conductivity. This study is the first to examine the effect of Ag_NP addition on the material’s mechanical properties. This study also found that the Young’s modulus, E, shear modulus, G, and bulk modulus, B, decreased linearly with increasing volume fraction porosity, P. Resonant ultrasound spectroscopy was employed to measure the elastic moduli, and Vickers indentation was used to determine the hardness, H, and fracture toughness, K _C. Trends in the mechanical properties as a function of grain size, porosity, and the Ag_NP are discussed in terms of the pertinent literature. While K _C was independent of Ag_NP addition, porosity, and grain size, both E and H decreased linearly with increasing porosity. In addition, this study is the first to identify (i) the Ag₃Sb phase formed and (ii) the enhanced densification that occurs when the Ag_NP is sintered with Ba_0.3Co₄Sb₁₂ powders, where both effects are consistent with the eutectic and peritectic reactions observed in the binary phase diagram Ag–Sb. These eutectic/peritectic reactions may also be linked to the enhancement of electrical conductivity previously observed when Ag is added to Ba_0.3Co₄Sb₁₂. Also, similar beneficial eutectic/peritectic reactions may be available for other systems where conductive particles are added to other antimonides or other thermoelectric systems.