Effect of the addition of Fe2O3 and heat treatment duration on the magnetic susceptibility of V2O5-P2O5-B2O3 glass system

The effect of the addition of Fe₂O₃ and heat treatment duration on the magnetic susceptibility of vanadium borophosphate glass were studied. The magnetic susceptibility of glass samples was found to increase with increasing Fe₂O₃ content, which may be explained by the formation of the FeO₆ group and the change of Fe²⁺ to Fe³⁺ which has higher paramagnetic properties. No detectable changes in the magnetic susceptibility with heat treatment for the samples containing 0.0, 0.5 and 1.0 mol% Fe₂O₃ was observed. The magnetic susceptibility for the heat treated samples containing 2.5, 5.0 and 7.5 mol% Fe₂O₃ decreases sharply with increasing duration of heat treatment up to 6 h and then remains almost constant. The sharp decrease in magnetic susceptibility of 2.5 mol% Fe₂O₃ is attributed to the increase in the number of ferrous ions. The sharp decrease for samples containing 5.0 and 7.5 mol% Fe₂O₃ is attributed to the increase in the number of Fe³⁺ in tetrahedral co-ordination. The rate of crystallization owing to the heat treatment was calculated and was found to increase with increasing iron oxide content. The geometry of crystallization was found to be in three-, two-and one-dimension(s) for samples containing 2.5, 5.0 and 7.5 mol% Fe₂O₃, respectively.     

Multiple Linear Regression Model Approach for Aerosol Dispersion in Ventilated Spaces Using Computational Fluid Dynamics and Dimensional Analysis

Aerosol dispersion in living spaces especially bioaerosols, due to accidents or deliberate acts, is of significant current interest. Computational fluid dynamics (CFD) provides an accurate and detailed platform to study the influence of different parameters on aerosol distribution in indoor spaces. The simulations however are time consuming and site-specific. The work here introduces an approach toward addressing this challenge. During emergencies, an accurate, quicker, and more general model is required to give rapid answers to first responders. Significant parameters influencing aerosol behavior in an office room were identified and through dimensional analysis, nine dimensionless groups were developed. Fractional factorial design was used to build sixteen scenarios to explore the design space. These scenarios were then simulated using a comprehensive CFD model. Large eddy simulation with the Smagorinsky subgrid scale model was applied to compute the airflow. Aerosols were modeled as a dispersed solid phase using the Lagrangian treatment. The influence of the dimensionless groups on the temporal variation of the number of aerosols in the room and the spatial distribution of the particles in the room was analyzed. The results showed that all the identified dimensionless groups were significant. Multiple linear regression models were developed for the prediction of the number of aerosols in the room and their spatial distribution as a function of the significant parameters influencing aerosol transport. The linear models accurately predicted the data on which they were based but did not predict the results of the independent tests as well. The limited predictive ability of the model showed that the relationships between the dimensionless groups are nonlinear and a higher level of experimental design will have to be applied to better explore the design space.     

Particle melting in high temperature supersonic low pressure plasma jets

A numerical model has been developed to predict the temperature history of particles injected into a low pressure dc plasma jet. The temperature and velocity fields of the plasma jet are predicted as a free jet by solving the parabolized compressible Navier-Stokes equations using a spatial marching scheme. Particle trajectories and heat transfer characteristics are calculated using the predicted plasma jet temperature and velocity fields. Correction factors have been introduced to take into account noncontinuum effects encountered in the low pressure environment. The exchange of energy and momentum between the injected particles and plasma flow was treated by considering the source terms in the governing equations. The plasma jet profiles as well as the particle/plasma interactions with different jet pressure ratios (from underexpanded to overexpanded) have been investigated. The effect of particle loading on the resulting jet profiles, particle trajectories, and temperature profiles is presented and discussed. This paper is based on a presentation made in the T.B. King Memorial Symposium on “Physical Chemistry in Metals Processing” presented at the Annual Meeting of The Metallurgical Society, Denver, CO, February, 1987, under the auspices of the Physical Chemistry Committee and the PTD/ISS.     

Structure and physical properties of sodium borate glasses containing nickel oxide

A series of glass samples were prepared from a mixtures of B₂O₃, Na₂O and NiO. The role of nickel oxide in a glass matrix was studied by using infrared spectra, optical absorption, magnetic susceptibility, density, and differential thermal analysis (DTA). It was shown that the addition of nickel oxide at different concentrations to the glass batches causes some deformation in the glass structure. The values of ligand field strength and Racah parameter indicated an increasing degree of covalency. The glass samples exhibited diamagnetic behaviour with NiO content up to 1 g, then paramagnetic behaviour. The densities and glass transition temperatures decreased with increase in the NiO content up to 0.2 g and then increased again. This tendency may be related to changes in the glass structure.     

The hydrochloric acid route for phosphate rock

When phosphate rock is leached with hydrochloric acid, radium can be removed by co-precipitation with Ba_0.4Ca_0.6SO₄ and uranium by extraction with a 5% solution of tributyl phosphate in hexane or Varsol. Phosphoric acid is then separated from calcium chloride solution and other impurities by extraction with undiluted tributyl phosphate. The lanthanides can be precipitated from the raffinate by NH₃, and CaSO₄.2H₂O by H₂SO₄ to regenerate HCl for recycle. The organic phase containing H₃PO₄ can be stripped by NH₃ to yield ammonium phosphate and to regenerate the tributyl phosphate for recycle. Fluorine can be precipitated from the initial leach solution as Na₂SiF₆.     

Simulation and Experimental Studies of Illumination Effects on the Current Transport of Nitridated GaAs Schottky Diode

Semiconductors - In this paper, we studied the electrical characteristic of Schottky diodes based on gold contact on nitridated GaAs substrates. The used (100) GaAs substrate is n-type with...     

Duct-to-duct biliary reconstruction following liver transplantation for primary sclerosing cholangitis

BACKGROUND: Use of non-steroidal anti-inflammatory drugs (NSAIDs) is recognized as an important cause of peptic ulcer complications. The aim of this nested case-control study was to identify risk factors for NSAID-related ulcer complications. METHODS: Cases were consecutive NSAID users admitted with an ulcer complication (n = 118), and controls were a random sample of all NSAID users without ulcer complication identified by a pharmacoepidemiologic database (n = 540). RESULTS: Ninety-four of 118 cases were interviewed, and 324 of 540 controls answered the questionnaire. Analysis showed no difference between included and non-included subjects. Risk factors for patients at start of NSAID therapy were high age: 60-75 years (odds ratio (OR), 3.5 (95% confidence interval (Cl), 1.8-7.1); > 75 years (OR, 8.9 (4.3-18.3)); male sex (OR 1.7 (1.0-3.0)); ulcer history (OR 2.5 (1.2-5.1)); steroid treatment (OR 2.0 (0.8-4.6)); smoking (OR 1.6 (0.9-2.7)); and alcohol use (OR 1.8 (0.9-3.6)). Risk factors for patients receiving NSAID therapy were high age, male sex, ulcer history, smoking and, furthermore, dyspepsia (OR 2.0 (1.0-4.2)), especially NSAID-related dyspepsia (OR 8.7 (4.0-18.9)). Risk was lower for patients treated more than 3 months. CONCLUSION: Risk measured from this design can be shown to correlate strongly with the rate difference, a measure that is more clinically relevant than conventional relative risk estimates. Strong risk factors for NSAID-related ulcer complication are high age, male sex, ulcer history, and dyspepsia related to the NSAID therapy. Avoiding NSAID therapy in these high-risk patients, whenever possible, might prevent many adverse events.