A model for predicting the thermal conductivities of bentonite-bonded molding sands at high temperatures

The effective thermal conductivities of bonded molding sands vary with the dry density, binder content, initial moisture content, temperature as well as the types of sand and binder clay. In this study, a theoretical model for predicting the effective thermal conductivities of bentonitebonded molding sands was developed. The results of measurement of the effective thermal conductivities of molding sands at temperatures up to 750°C were used. The binder thermal conductivities of both western bentonite and southern bentonite were suggested as a function of dry density, binder content and initial moisture content and were assumed not to vary with temperature. The radiation model proposed by Vortmeyer was also incorporated. The model developed in this study was proved to predict well the effects of binder content, initial moisture content, dry density and temperature.     

The effects of the growth parameters of the CdS window layer on the photovoltaic properties of MOCVD-grown CdS/CdTe solar cells

This paper forms part of an ongoing study aimed at producing high-efficiency polycrystalline photovoltaic cells by a single integrated process using metal organic chemical vapor deposition (MOCVD). Relationships between CdS growth variables, final microstructure and device performance parameters are established. CdTe grain sizes of 3–5 μm diameter can be achieved using CdS growth temperatures of 275 °C or below, even in the absence of nucleation delay. Short-circuit photocurrent depends on CdS growth temperature and dopant concentration.     

Oral keratinocyte immune responses in HIV-associated candidiasis

Technetium-99m is the most commonly used radionuclide in routine nuclear medicine imaging procedures. Development of 99mTc-labeled receptor-specific imaging agents for studying the central nervous system is potentially useful for evaluation of brain function in normal and disease states. A novel 99mTc-labeled tropane derivative, [99mTc]TRODAT-1, which is useful as a potential CNS dopamine transporter imaging agent, was evaluated and characterized. After i. v. injection into rats, [99mTc]TRODAT-1 displayed specific brain uptake in the rat striatal region (striatum-cerebellum/cerebellum ratio 1.8 at 60 min), where dopamine neurons are concentrated. The specific striatal uptake could be blocked by pretreating rats with a dose of competing dopamine transporter ligand, beta-CIT (or RTI-55, i.v., 1 mg/kg). However, the specific striatal uptake of [99mTc]TRODAT-1 was not affected by co-injection of excess free ligand (TRODAT-1, up to 200 microg per rat) or by pretreating the rats with haloperidol (i.v., 1 mg/kg). The specific uptake in striatal regions of rats that had prior 6-hydroxydopamine lesion in the substantia nigra area showed a dramatic reduction. The radioactive material recovered from the rat striatal homogenates at 60 min after i.v. injection of [99mTc]TRODAT-1 showed primarily the original compound (>95%), a good indication of in vivo stability in brain tissue. Similar and comparable organ distribution patterns and brain regional uptakes of [99mTc]TRODAT-1 were obtained for male and female rats. Ex vivo autoradiography results of rat brain sections further confirmed the high uptake and retention of [99mTc]TRODAT-1 in the striatal region. In vitro binding studies measuring the affinity to dopamine transporters for the free ligand, TRODAT-1, and a nonradioactive rhenium derivative, Re-TRODAT-1, showed Ki values of 9.7 nM and 14.1 nM, respectively. Behavioral studies in rats using the free ligand, TRODAT-1 and Re-TRODAT-1 indicated that, unlike other tropane derivatives, they displayed no effect on locomotor activity, suggesting low toxicity. These results strongly support the conclusions that this novel 99mTc radioligand binds selectively to dopamine transporters in the brain and that is is potentially useful for in vivo assessment of the loss of dopamine neurons in Parkinson's and other neurodegenerative diseases.     

Nitric oxide synthase in neuroepithelial brain tumors

Immunohistochemical investigation of NO-synthase in brain astrocytic tumors revealed intense reaction in many tumor cells as well as direct correlation in the intensity of reaction and the degree of tumor anaplasia. Grade I astrocytomas did not show immunoreactivity in contrast to high anaplastic tumors where many cells had positive reaction with a different degree of intensity. Positive immunoreaction was shown in many giant cells. Small cell glioblastomas and oligodendrogliomas were immunonegative. There was a direct correlation between NO-synthase expression and glial fibrillar acidic protein.     

The effect of carotid sinus denervation on fetal heart rate variation in normoxia, hypoxia and post-hypoxia in fetal sheep

BACKGROUND: Previous reports documented high rates of tobacco use among Alaska Natives (Eskimos, Indians, and Aleuts). In this population, tobacco use is the leading preventable cause of death. Lung cancer is the leading cause of cancer death among Alaska Natives and tobacco is responsible for over one-third of all cancer deaths in this population. Until recently there has been no systematic surveillance of the prevalence of tobacco use in this high-risk population. Data that did exist were not readily available to those primarily responsible for the health care of this population. This is the first time since 1990 that data on Alaska Natives have been collected in one analysis; this permits a more representative evaluation of tobacco use. METHODS: Data on tobacco use were obtained and analyzed from national and state surveys and selected research projects from 1988 to 1993. RESULTS: Alaska Natives have high prevalence of tobacco use, including both cigarettes and smokeless tobacco. Tobacco use prevalence among Alaska Natives exceeds that of Alaska non-Natives, U.S. whites, and American Indians/Alaska Natives in the United States outside of Alaska. Smoking prevalence among Alaska Native women is twice that of non-Native women in Alaska and nearly twice as high among pregnant Alaska Natives than pregnant non-Natives. Overall, prevalence of smokeless tobacco use was four times higher among Alaska Natives than comparative state and national populations. CONCLUSION: Because this population has such high rates of tobacco use, it is important to public health that monitoring and educational programs be in place and that data specific to Alaska Natives be made available.     

Characteristics of acoustic streaming created and measured bypulsed Doppler ultrasound

Self measurement of acoustic streaming by Doppler ultrasound could be used to evaluate properties of fluids such as viscosity or the coagulation of blood. To characterize acoustic streaming caused by pulsed ultrasonic beams, Doppler signal processing was used to measure streaming velocity under a variety of conditions in vitro using blood and water. Velocities as high as 5 mm/s were measured in blood at the diagnostic power levels (3.5 mW) used in 20 MHz catheter velocimetry. It was found that streaming decreases with distance due to absorption and beam spreading, increases with applied acoustic power, and decreases with increased viscosity during blood coagulation. However, the increase in velocity with acoustic power is nonlinear with an exponent of 0.67 for water and 1.42 for blood even though the radiation force as measured by deflection of a suspended transducer is linear with power. The time constant of streaming to a step change in acoustic power is 80 ms in blood and 200 ms in water. It is concluded that streaming is measurable in pulsed Doppler beams, that it could produce artifacts or unintended effects, and that it could be used to characterize fluid properties and to detect coagulation of whole blood