Fatty acids of sphingomyelin from amniotic fluid of normal and diabetic pregnancies

Amniotic fluid collected from 14 normal and 11 diabetic patients was analyzed for phospholipids, and separated sphingomyelin and lecithin fractions were further studied for their fatty acid composition by gas liquid chromatography. Notable differences in percent fatty acid composition of sphingomyelin were observed for palmitic (16∶0; diabetic < normal), oleic (18∶1; diabetic > normal), behenic (22∶0; diabetic < normal) and arachidic acid (20∶0; absent in diabetics) in the specimens studied. Notable differences were not observed in fatty acids from lecithin fraction. Fatty acid composition of sphingomyelin from amniotic fluid is similar to fatty acid distribution in sphingomyelin from serum and erythrocyte and suggests maternal origin of the lipid. Presented in part at the 67th annual meeting of the Federation of American Societies for Experimental Biology, Chicago, IL 1983. Abstracted from dissertation written by one of the authors (Vicki Brooks) in partial fulfillment for Master of Science degree in Clinical Chemistry, Department of Pathology, LSU Medical Center.     

Preparative and mechanistic studies on unsymmetrical Dimethyl Hydrazine-Red Fuming Nitric Acid Liquid Propellant Gels

Thixotropic gels of unsymmetrical dimethyl hydrazine (UDMH) have been prepared using methyl cellulose (4.48 wt%) and agar-agar (0.64 wt%) chemical gelling agents. Red fuming nitric acid has been gelled by using sodium silicate (4.25 wt%). The effect of various parameters like size of container, particle size of gellants and temperature on gellation time of UDMH gelled system has been investigated. The gellation time of UDMH gel is found to increase with the increase in the internal diameter of the container. Gellation time is found to show direct proportionality with the particle size when methyl cellulose is used as gellant. In case of methyl cellulose, the gellation occurs quickly at higher temperature whereas the reverse trend is observed when agar-agar gellant is used. In order to boost the performance of liquid propellants, the metallized gels of UDMH containing Al (10-40 wt%) and Mg (10-25 wt%) metal powders have been prepared. The density measurements of virgin and metallized gels reveal that there is a maximum gain of 46.72% and 19.3% over virgin gels on incorporation of Al and Mg powders respectively. Efforts have been made to understand the process of gellation using optical and photomicrographic techniques.     

Boiling heat transfer coefficient of R22 and an HFC/HC refrigerant mixture in a fin‐and‐tube evaporator of a window air conditioner

The commonly used refrigerant in unitary type air conditioners is R22 and its phase out schedule in developing countries is to commence from 2015. Many alternatives to R22 are found in published literature in which R407C has similar characteristics to those of R22 except for its zeotropic nature. However, R407C which is an HFC is made compatible with the mineral oil lubricant in the system compressor by the addition of 20% of HC. This HFC/HC mixture called the M20 refrigerant mixture is reported to be a retrofit refrigerant for R22. Though its latent heat value is greater than that of R22, its refrigerating capacity is lower when it is used to retrofit R22 window air conditioners. Hence, a heat transfer analysis was conducted in the evaporator of a room air conditioner, for practically realized heat flux conditions during standard performance testing. The tests were conducted as per the BIS and ASHRAE standards. Kattan–Thome–Favrat maps are used to confirm the flow patterns, which prevail inside the fin‐and‐tube evaporator in the tested operating conditions. It is revealed that the heat transfer coefficient/heat fluxes are poorer for M20 because of the lower mass flow rate and higher vapor fraction at the entry of the evaporator than that of R22 in the prevailing operating conditions. The heat transfer coefficients of the M20 refrigerant mixture under various test conditions are lower in the range of 14% to 56% than those of R22. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/htj.20299     

Low-intensity differential photocapacitance of MOS structures

Some new observations on the phenomenon of photocapacitane on n-type silicon MOS structures under low intensities of illumination are reported. The difference between the illuminated and dark Ccharacteristics is automatically followed as a function of the applied bias thereby obtaining the differential photocapacitance and the resulting characteristics has been termed as the Low Intensity Differential Photocapacitance (LIDP). For an MOS capacitor, the LIDP characteristics is seen to go through a well defined maximum. The phenomenon has been investigated under different ambient conditions like light intensity, temperature, dependance of the frequency of the light etc. and it has been found that the phenomenon is due to a band excband excitation. In this connection, a novel sensitive technique for the measurement of the capacitance based upon following the frequency changes of a tank circuit is also described in some detail. It is also shown that the phenomenon can be understood by a simple theoretical model.     

Role of CeO2/ZrO2 mole ratio and nickel loading for steam reforming of n-butanol using Ni–CeO2–ZrO2–SiO2 composite catalysts: A reaction mechanism

This study presents steam reforming of n-butanol to synthesis gas using high surface area mesoporous Ni–CeO₂–ZrO₂–SiO₂ composite catalysts. The reaction proceeds through a combination of dehydrogenation, dehydration, and cracking reactions with propanal, butanal, and C₂–C₄ hydrocarbons as intermediate compounds. The ceria forms a solid solution with zirconia, promotes dispersion of nickel, and enhances oxygen storage/release capacity. The carbon conversion to synthesis gas (CCSG) and hydrogen yield are thus enhanced with increasing CeO₂/ZrO₂ mole ratio up to 1:2 and decreased slightly for higher mole ratios. The CCSG and hydrogen yield are also boosted by increasing the amount of nickel in the catalyst up to 20 wt%. 1:2 CeO₂/ZrO₂ mole ratio and 20 wt% nickel content are thus deliberated as optimum. The optimum catalyst exhibits stable catalytic performance for about 30 h time-on-stream. The study further presents the effect of temperature and steam/carbon mole ratio on n-butanol steam reforming.     

Studies on the kinetics of catalytic combustion of deuterium using 0.5% platinum loaded on Dixon ring catalyst

When hydrogen isotopes are present in stoichiometric ratio of 2:1 with oxygen in inert gas such as helium, catalytic combustion is the most promising option to reduce the concentration of hydrogen isotopes and to minimize the associated safety hazards. This is the case, when deuterium and oxygen is formed during radiolysis of heavy water in moderator circuit of Pressurized Heavy Water Reactors (PHWR) and mixed with helium in the cover gas system. In order to design the catalytic reactor for recombination of deuterium and oxygen, the data on catalytic combustion kinetics under the similar process conditions are essential. However, the catalytic combustion data is generally reported for combustion of hydrogen in air, where oxygen is available in excess. The studies on the kinetics of catalytic combustion of deuterium where oxygen is present in stoichiometric ratio of 2:1 in an inert gas medium such as helium, is very scarce. In the present study, the multi-step reaction mechanism of catalytic combustion of hydrogen in presence of platinum catalyst is analyzed for the present process conditions. Based on the analysis, a simple rate expression is proposed for the present process conditions of catalytic combustion of deuterium. Further, 0.5% platinum catalyst is prepared on a stainless steel Dixon ring support with an objective to achieve better heat transfer characteristics and lesser reduction in the catalytic activity due to water adsorption. The kinetic data is generated using a differential packed bed reactor operating in a closed loop. The experiments were conducted at different temperatures using a stoichiometric mixture of deuterium and oxygen in helium. The rate constant for the above proposed model is estimated based on the experimental data at different temperatures. Further, the activation energy and frequency factor are determined and the activation energy for the present catalyst is found to be on the lower side in comparison to literature data.     

Integrated battery controller for distributed energy system

In this article, an improved integrated battery energy storage system (BESS) controller for distributed energy system is presented. The BESS is integrated in parallel with the full wave bridge converter into the distributed energy system network. In a normal operating mode, the BESS serves as a power conditioner as well as an active power filter in a distributed power system network. This work presents BESS controller which is designed for regulating the state of charge of the batteries and also to manage the active power in a distributed power system network. The off peak load energy is used to recover the batteries’ state of charge through the BESS controller. In this BESS controller, the constant current-constant voltage (CC-CV) mode is used and it helps to keep the batteries’ state of charge conditions for improving the reliability of the distributed power system system. This control strategy is incorporated into the main converter. The controller helps in managing the phase, amplitude and waveform of the current and voltage on the distributed power system network. The controller ensures the power quality and also assists in improving the power factor with respect to the utility for the intermittent distributed generation as well as the load. In this article, the test results of a prototype system are presented, which validates the proposed controller strategy of BESS in a distributed power system network.     

Control of a Doubly Fed Induction Wind Generator Under Unbalanced Grid Voltage Conditions

Wind energy is often installed in rural, remote areas characterized by weak, unbalanced power transmission grids. In induction wind generators, unbalanced three-phase stator voltages cause a number of problems, such as overcurrent, unbalanced currents, reactive power pulsations, and stress on the mechanical components from torque pulsations. Therefore, beyond a certain amount of unbalance, induction wind generators are switched out of the network. This can further weaken the grid. In doubly fed induction generators (DFIGs), control of the rotor currents allows for adjustable speed operation and reactive power control. This paper presents a DFIG control strategy that enhances the standard speed and reactive power control with controllers that can compensate for the problems caused by an unbalanced grid by balancing the stator currents and eliminating torque and reactive power pulsations     

Upscaling of biohydrogen production process in semi-pilot scale biofilm reactor: Evaluation with food waste at variable organic loads

The present account focuses on upscaling of biohydrogen (H₂) production at semi-pilot scale bioreactor using composite food waste. Experiments were conducted at different organic load (6, 12, 18, 30, 40, 50 and 66 g COD/l) conditions. H₂ production increased with an increasing organic load up to 50 g COD/l (9.67 l/h) followed by 40 g COD/l (6.48 l/h), 30 g COD/l (1.97 l/h), 18 g COD/l (0.90 l/h), 12 g COD/l (0.78 l/h) and 6 g COD/l (0.32 l/h). H₂ production was affected by acidification (pH drop to 3.96) at 66 g COD/l operation due to the excess accumulation of soluble metabolites (5696 mg VFA/l). Variation in organic load of food waste influenced the overall hydrogen production efficiency.     

Pre-fermentation of waste as a strategy to enhance the performance of single chambered microbial fuel cell (MFC)

Functional role of pre-fermentation of food waste (PFW) was studied to enhance the performance of single chambered microbial fuel cell (MFC) (mediatorless; non-catalyzed graphite electrodes; open-air cathode). Significant improvement in power output was noticed after pre-treatment (391 mV; 530 mA/m²) compared to unfermented waste (275 mV; 361 mA/m²). MFC performance was found to depend on applied organic load and nature of substrate in terms of power generation and substrate degradation. The pre-fermentation of waste facilitated lowering of activation losses and in turn increased the bio-electrochemical activity of biocatalyst, leading to an effective MFC performance. Fuel cell behavior with respect to polarization, anode potential and bio-electrochemical behavior also supported the performance of MFC with PFW. PFW operation showed higher catalytic current in voltammograms with fine catalytic peaks supporting the positive role of pre-fermentation in discharging electrons effectively. VFA and pH profiles also correlated well with power generation and substrate degradation pattern.