Composition-dependence of photoconduction band gap in cadmium zinc phosphate glasses

Photoconduction in cadmium zinc phosphate glasses of various compositions has been measured in the spectral energy range 1.5 to 6.2 eV. With the P₂O₅ percentage remaining fixed at 60 mol %, CdO and ZnO contents have been varied between 0 and 40 mol %. Photocurrents start at about 3.85 eV and rise sharply above 4.5 eV. The optical band gap obtained by the extrapolation of the linear region of the photoresponse curve shows a slow decrease with an increase in the applied field. The optical band gap at a particular applied field decreases with increasing ZnO content. The field-dependence of the optical band gap may be explained in terms of an energy band scheme for non-crystalline solids. The composition-dependence may be due some structural changes in the glasses.     

The role of magnetic resonance imaging in the preoperative assessment of anorectal anomalies

Venous ulcers are common in clinical practice. They are due to end stage skin and subcutaneous damage from sustained venous hypertension. The common cause may be post thrombotic syndrome or primary superficial venous insufficiency. This case illustrates the need to think of inherited thrombophilia as a primary cause.     

The automation of electrode kinetics — II. The application to metal deposition

The Zn deposition from NaClO₄ and KCl solution has been investigated by an automated electrode kinetic measurement system and the data is fitted to a reaction model. A value of the standard rate is probably independent of the anion, the bulk concentration, and the real surface area of the metal.     

Influence of calcium chloride fed prepartum on severity of edema and lactational performance of dairy heifers.

Twenty Holstein heifers in a completely randomized design were used to evaluate the effects of prepartum dietary CaCl2 on the development and regression of edema and on subsequent lactational performance. Heifers were assigned to diets containing either 2.17% limestone or 1.5% CaCl2 (DM basis) at 3 wk before expected calving date. Except for the Ca sources, diets were identical. Test diets were only fed prepartum; at calving, all heifers were offered a lactation diet for 3 wk. Severity of edema was evaluated independently by five people daily throughout the experiment; a 10-point rating system was utilized to quantify the severity of edema. Calcium chloride reduced the severity of edema, although this response was most evident during the 1st wk that this salt was fed. The beneficial effects of CaCl2 on edema prepartum disappeared postpartum, when CaCl2 was removed from the diet. Indeed, edema was higher for heifers fed CaCl2 than for those fed limestone at 2 wk postpartum. Calcium chloride reduced DMI prepartum, but, following parturition, a compensatory increase in feed intake occurred. Postpartum daily DMI averaged 1.3 kg higher for heifers fed CaCl2 than for those fed the limestone diet prepartum. Milk yield and composition were somewhat lower for heifers fed CaCl2, although this response was most evident at 1 wk postpartum. Feeding CaCl2 prepartum to prevent milk fever also may reduce the severity of udder edema prepartum and increase feed intake during early lactation.     

Electric-field induced fluctuations in laser generated plasma plume

The effect of an external electric field on laser-generated plasma has been studied. It is observed that the laser-generated plasma can be used for the ignition of a spark in the presence of a low voltage external electric field. An eight-fold emission intensity enhancement in Cu Ⅰ spectral lines are measured as compared to the signal intensity in the absence of an external electric field.The plasma parameters remain the same initially, up to a few microseconds after the generation of plasma, and this feature makes it more interesting for the quantitative analysis of any sample using laser induced breakdown spectroscopy(LIBS). In the presence of an external electric field,fluctuations(contraction and expansion) in the laser-generated plasma are observed which increase the plasma decay time and consequently result in enhanced signal intensity.     

Mass transfer area in a multi-stage high-speed disperser with split packing

In this study, the mean droplet diameter in the cavity zone and the total mass transfer area of a multi-stage highspeed disperser(HSD) reactor with different packing combinations were measured and evaluated. The effects of rotational speed and packing radius, as well as the packing ring radius and numbers, on the mean droplet diameter and the total mass transfer area were evaluated. A model was established to calculate the mass transfer area in the cavity zone in the HSD reactor, and it was found that the packings contribute 61%–82% of the total mass transfer area. A correlation for predicting the mass transfer area in the packing zone was regressed by the dimensionless analysis method. An enhancement factor based on the mass transfer area in the packing zone was proposed to evaluate the effect of packing combination on mass transfer area. Two optimum packing combinations were proposed in consideration of the mean droplet diameter and the enhancement factor.     

Simultaneous thermal and visual imaging of liquid water of the PEM fuel cell flow channels

Water flooding and membrane dry-out are two major issues that could be very detrimental to the performance and/or durability of the proton exchange membrane (PEM) fuel cells. The above two phenomena are well-related to the distributions of and the interaction between the water saturation and temperature within the membrane electrode assembly (MEA). To obtain further insights into the relation between water saturation and temperature, the distributions of liquid water and temperature within a transparent PEM fuel cell have been imaged using high-resolution digital and thermal cameras. A parametric study, in which the air flow rate has been incrementally changed, has been conducted to explore the viability of the proposed experimental procedure to correlate the relation between the distribution of liquid water and temperature along the MEA of the fuel cell. The results have shown that, for the investigated fuel cell, more liquid water and more uniform temperature distribution along MEA at the cathode side are obtained as the air flow rate decreases. Further, the fuel cell performance was found to increase with decreasing air flow rate. All the above results have been discussed.