A case of Ohtahara syndrome with cytochrome oxidase deficiency

Ohtahara syndrome is a rare cause of epileptic seizures during the neonatal period. This is believed to be the first report of this syndrome with a specific metabolic defect. Defects in respiratory chain function may be more common than previously assumed in patients with this epilepsy syndrome.     

Discrete-Time Analysis of Integrated Voice/Data Multiplexers With and Without Speech Activity Detectors

Discrete-time analysis of two schemes for multiplexing voice and data is presented. In each scheme voice and data are multiplexed using the movable boundary frame allocation scheme. In the first scheme, speech activity detectors (SAD's) are not used, and hence, the variations in the voice traffic are only due to the on/off characteristics of voice. In the second scheme, SAD's are employed so that talker silences can he utilized for transmission of additional voice and/or data. In this scheme, the multiplexer performs digital speech interpolation as well as movable boundary frame allocation. The performance measures considered are probability of loss for voice calls, probability of speech clipping, speech packet rejection ratio, and the expected data message delay. In the case of the multiplexer with SAD, a tradeoff exists between data message delay and speech interpolation advantage. Some numerical examples are presented which illustrate the performance of the two multiplexers.     

A tilting disc valve — component materials and hydraulic function

The component materials used in fabrication of the Chitra heart valve, their choice and screening are described. Further the haemodynamic performance of this valve, which is under development and an equal sized No. 27 Bjork-Shiley valve prosthesis was compared in a left-heart pulse duplicator under similar conditions of flow rates and pressures. They were tested in both the aortic and mitral positions of the duplicator. Regurgitant volumes and transvalvular pressure gradients were measured over flow rates ranging from 2 to 8 LPM. Flow patterns of the fluid flow across the valves were also photographed. The results indicate that the performance of the indigeneous valve is comparable, if not marginally better, to that of the well-established Bjork-Shiley valve. Transvalvular gradients and regurgitant volumes were marginally lower for the Chitra valve. This is attributed to the improved design of the valve disc shape.     

Ozone-mediated polyol synthesis from soybean oil

Polyols from vegetable oils can replace petroleumbased polyols in the preparation of polyurethanes and polyesters in a wide range of applications. However, previous preparation methods are either too costly, inefficient, or yield secondary alcohols, which are less reactive than the desired primary alcohols. The objectives of this study were to prepare primary soy-based polyols by a new catalytic ozonolysis process and to characterize the composition of the product mixture. In this new process, the polyols were prepared by passing ozone through a solution of soybean oil and ethylene glycol in the presence of an alkaline catalyst. Unlike conventional ozonolysis that yields aldehydes and carboxylic acids by spontaneous decomposition of the ozonide intermediates, the ozonides in our method reacted with the hydroxyl group of the glycol to form an ester linkage with a terminal hydroxy group. Statistical analysis of the product mixture indicates that the resulting polyol mixture is more uniform than the original TG mixture, having (2-hydroxy)nonanoate as the major component of the new hydroxyl functional TG. The chemical structure of the polyols produced was further characterized by iodine number and ¹³C NMR and FTIR spectroscopy, which confirmed the cleavage of the double bonds, the presence of hydroxyl groups, and the formation of new ester linkages.     

Monte Carlo simulation of low density flows

The necessity for adopting a kinetic-theoretical approach to obtain aerodynamic characteristics in low density flow past space vehicles is highlighted in this paper; it is shown how long-standing difficulties in theoretically handling such flows can be circumvented by adopting a Monte Carlo technique. The principles underlying the technique are briefly described, and are first illustrated by applying the technique to the evaluation of the drag of cylinders and cones in collisionless flow. The Markoff process underlying the Monte Carlo simulation of the full Boltzmann equation with collisions is then described in detail. Instead of the time-counter strategy of Bird, a theoretically sounder ‘Random Collision Number’ (RCN) strategy has been adopted in the present simulation. In this strategy the number of collisions in each time-step in the computation is a random number drawn from an appropriate distribution. Computer programs using this strategy have been developed for calculating aerodynamic characteristics like drag and heat transfer for a cone in the transition regime between free molecule and continuum flow. The results obtained from these programs show that both time-counter and RCN strategies require almost the same computer time.     

Dynamics of flexible-link mechanisms

Dynamic response of flexible-link mechanism (structure) when subjected to external dynamic load is analyzed. The non-linear equations of motion are discretized using the finite element method (FEM) and Newmark time integration method combined with Newton-Raphson iterative technique is used for solution. From the dynamic response of the structure, the required kinematic characteristics are derived. Typical examples are worked out for illustration.     

Stress corrosion cracking of carbon steel in caustic aluminate solutions—crack propagation studies

Stress corrosion cracking of a commercial 0.19 pct C steel (SA-516 Grade 70) was studied in hot (92 ‡C) caustic solutions of NaOH and NaOH plus aluminate (AlO⁻ ₂) species. Potentiostatically controlled tests were conducted near the active-passive transition, using fracture mechanics testing techniques and fatigue precracked double cantilever beam specimens. Crack propagation rates (Ν) were determined for a range of stress intensities (K _l). In simple NaOH solutions, Region I (K₁-dependent) and Region II (K ₁-independent) cracking behavior were observed. Increasing the concentration of NaOH from2m to8m decreasedK _ISCC and displaced Region I and the onset of Region II to lowerK ₁ levels. The presence of AlO⁻ ₂ produced a comparable effect, with Region II being extended to lowerK _I -Ν levels relative to simple NaOH solutions of similar hydroxyl anion concentration. The overallK _I -Νv behavior and fractography were consistent with a dissolution mechanism of crack advance based on the general principles of the film rupture-dissolution model. The effect of environment composition uponK _I — Ν behavior was attributed to changes in repassivation kinetics. Formerly Graduate Student at the University of British Columbia     

Determination of mixing time in BOF process by a cold model study

Mixing time in a BOF process has been studied using a 1/14 water-air model. The study shows that for a simulated cold model, mixing time is independent of jet Froude number. For a partially simulated model, mixing time was found to be inversely proportional to square root of bath height to diameter ratio. This is in agreement with the similarity condition.     

Nanocolumnar Preferentially Oriented PSZT Thin Films Deposited on Thermally Grown Silicon Dioxide

We report the first instance of deposition of preferentially oriented, nanocrystalline, and nanocolumnar strontium-doped lead zirconate titanate (PSZT) ferroelectric thin films directly on thermal silicon dioxide. No intermediate seed or activation layers were used between PSZT and silicon dioxide. The deposited thin films have been characterised using a combination of diffraction and microscopy techniques.     

Starved air combustion-solidification/stabilization of primary chemical sludge from a tannery

The high concentration of trivalent chromium along with organic/inorganic compounds in tannery sludge causes severe ground water contamination in the case of land disposal and chronic air pollution during incineration. In the present investigation, the sludge was subjected to flow-through column test to evaluate the concentration of leachable organics (tannin, COD and TOC) and heavy metal ions (Cr(3+), Fe(2+)) present in it. The dried sludge was incinerated at 800 degrees C in an incinerator under starved oxygen supply (starved-air combustion) to prevent the conversion of Cr(3+) to Cr(6+). The efficiency of starved air combustion was studied under different loading rates of sludge. The calcined sludge was solidified/stabilized using fly ash and Portland cement/gypsum. The solidified bricks were tested for unconfined compressive strength and heavy metal leaching. Unconfined compressive strength of the blocks was in the range of 83-156 kg/cm(2). The stabilization of chromium (III) in the cement gel matrix was confirmed with scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDX). Leachability studies on solidified bricks were carried out to determine the metal fixation and dissolved organic (as COD) concentration in the leachate.