An experiment on dissipation in helium film flow

Experiments are reported in a double-bucket system with a view to examining the application to helium film flow of recent predictions regarding the exponential relationship between the superflow speed and the chemical potential gradient driving force. The theory is found to be generally commensurate with our experimental results with a notable exception. One of the parameters, which is predicted to be constant, is experimentally found to have a definite temperature dependence which we give in detail. We report also our evidence with regard to the height dependence of film thickness in the dissipative regime. We find that this thickness appears to be determined by the mean distance to the two bath levels.     

Racial differences in nitric oxide-mediated vasodilator response to mental stress in the forearm circulation

An abnormal hemodynamic response to stressful stimuli has been proposed as a mechanism involved in the higher prevalence of hypertension in blacks. Given the important role of nitric oxide (NO) in the regulation of cardiovascular homeostasis, we investigated the possibility of racial differences in vascular NO activity during mental stress. To test this hypothesis, we compared the forearm blood flow (FBF) response to mental stress in 14 white and 12 black healthy subjects during intra-arterial infusion of either saline or NO synthesis inhibitor N(G)-monomethyl-L-arginine (L-NMMA; 4 micromol/min). We also examined vascular responses of the two groups to intra-arterial infusion of sodium nitroprusside (0.8 to 3.2 microg/min), an exogenous NO donor. During saline infusion, the increase in FBF from baseline induced by mental stress was significantly higher in whites than in blacks (109+/-20% versus 58+/-8%; P=0.03). L-NMMA significantly reduced stress-induced increase in FBF in whites (from 109+/-20% to 54+/-11%; P=0.004) but not in blacks (from 58+/-8% to 42+/-10%; P=0.24); thus, the vasodilator effect of stress testing during L-NMMA was similar in whites and blacks (54+/-11% versus 42+/-10%; P=0.44). The vasodilator response to sodium nitroprusside was also lower in blacks than in whites (maximum flow, 6.9+/-2 versus 11.6+/-3.5 mL x min(-1) x dL(-1); P=0.001) and was not significantly modified by L-NMMA in either group. Our findings indicate that blacks have a reduced NO-dependent vasodilator activity during mental stress. This difference seems related to reduced sensitivity of smooth muscle to the vasodilator effect of NO and may play some role in the increased prevalence of hypertension and its complications in blacks.     

The effect of applied stress on densification of nanostructured zirconia during sinter-forging

Nanoparticles of ZrO₂ (n-ZrO₂) synthesized by the inert gas condensation technique were consolidated by sinter-forging, which is a pressure-assisted sintering process. It was found that there is a threshold stress below which there is only a small contribution to densification by the applied pressure. The value of the threshold stress depends on grain size and the effect is explained on the basis of driving forces for sintering. The grain size in the fully dense n-ZrO₂ samples was 45 nm.     

A skeleton and neural network-based approach for identifyingcosmetic surface flaws

This paper introduces an approach to cosmetic surface flaw identification that is essentially invariant to changes in workpiece orientation and position while being efficient in the use of computer memory. Visual binary images of workpieces are characterized according to the number of pixels in progressive subskeleton iterations. Those subskeletons are constructed using a modified Zhou skeleton transform with disk shaped structuring elements. Two coding schemes are proposed to record the pixel counts of succeeding subskeletons with and without lowpass filtering. The coded pixel counts are on-line fed to a supervised neural network that is previously trained by the backpropagation method using flawed and unflawed simulation patterns. The test workpiece is then identified as flawed or unflawed by comparing its coded pixel counts to associated training patterns. Such off-line trainings using simulated patterns avoid the problems of collecting flawed samples. Since both coding schemes tremendously reduce the representative skeleton image data, significant run time in each epoch is saved in the application of neural networks. Experimental results are reported using six different shapes of workpieces to corroborate the proposed approach.     

Clinical factors useful in predicting aortic valve structure in patients > 40 years of age with isolated valvular aortic stenosis

A number of reports have described the frequency of coronary arterial narrowing in patients with valvular aortic stenosis. No published reports have examined the structure of the stenotic aortic valve in adults and related the valve structure to variables, including coronary arterial narrowing, useful in predicting that structure. One hundred eighty-eight patients having aortic valve replacement for isolated valvular aortic stenosis were studied. All patients were > 40 years of age at the time of aortic valve replacement, all had coronary angiograms preoperatively, and of 182 patients (97%) measurements of serum total cholesterol had been obtained and 184 (98%) had body mass index calculated. The structure of the operatively excised valve was classified as unicuspid or bicuspid (congenitally malformed), or tricuspid aortic valve. A logistic regression model was developed that found 4 factors (age, serum total cholesterol, angiographic coronary artery disease and body mass index) to be predictive of aortic valve structure: (1) Patients with at least 3 or all 4 factors high or present (i.e., age > 65 years, serum total cholesterol > 200 mg/dl, body mass index > 29 kg/m2 and coronary artery disease) had a low probability (10 to 29%) of having a congenitally malformed valve; (2) patients with at least 3 or all 4 factors low or absent (i.e., age < or = 65 years, serum total cholesterol < or = 200 mg/dl, body mass index < or = 29 kg/m2, and no coronary artery disease) had a high probability (72 to 90%) of having a congenitally malformed valve.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dopaminergic activity of some apomorphine analogs

The dopaminergic activity of ten apomorphine analogs was studied in rats lesioned unilaterally with 6-hydroxydopamine in the nigro-striatal system. Of these ten compounds, N,N-dimethyl-5,6-dihydroxy-2-amino-tetralin (M-7), N-methyl-5,6-dihydroxy-2-aminotetralin (M-8) and N,N-dimethyl-4,5-dihydroxy-2-aminoindan (DDAI) exhibited potent dopaminergic stimulant activity by causing the rat to turn to the unoperated side. The turning behavior of apomorphine, M-7, DDAI and d-amphetamine were antagonized by haloperidol. M-7 and DDAI also induced pecking in pigeons and their effects were also blocked by haloperidol. It is concluded that M-7, M-8 and DDAI are direct acting central dopaminergic agents.     

Installation and Performance of the Chicago Lightwave Transmission System

The first lightwave communications system that provides a wide range of telecommunications services to customers has been carrying commercial traffic in the Chicago Loop area since early May, 1977. The exploratory system furnishes POTS (plain old telephone service), analog data, and digital data services from the Franklin central office (CO) to customers in the Brunswick building, over an optical cable approximately 0.6 mi long. Picturephone^®meeting service, a 4-MHz video service, is delivered over an optical cable from the Wabash CO to the Franklin CO, then on to the Brunswick building, a total distance of 1.6 mi. The optical cable was placed inside a small plastic pipe, which had been installed previously along the cable route. The plastic pipe, or innerduct, was used to reduce pulling tensions and provide environmental protection. The optical cable was installed using a novel 2-way installation technique by which the two ends of each section were fed successively in opposite directions from an intermediate manhole toward the splicing manholes. The connectorized optical cable was then spliced in five manholes along the cable route. This paper describes the installation and splicing of the lightguide cable and the transmission characteristics of the installed medium. It also contains a discussion of the manner in which the various telecommunication services are provided and a performance evaluation of the lightwave transmission system to date.