Demonstration of celiac disease in Cuba

A study performed in 50 children carriers of celiac disease with ages between 8 months and 14 years of age, is presented; diagnosis was proved based on clinical picture, histological changes of jejunal mucosa, intestinal absorption tests and response to the suppression of gluten from the diet, with clinical, histological and biochemical control according to international criteria. It has been insisted on the familial study and the gluten overload test and its incidency in the black race. The development of public health has made it possible to demostrate the existence of this disease in our country.     

Turbulent flow in helically ribbed pipes

Velocity profiles, turbulence intensities and Reynolds stresses were determined in pipes containing three helical ribs equally spaced on the pipe wall. Pitch to diameter ratios of 8 and 11 were used. The fluid considered was air and measurements were made with X wire probes calibrated for pitch and yaw effects. The ribs appeared to affect the axial flow via the tangential component which reached a maximum below the ribs in most cases. Evidence of increases in mixing length near the wall and decreases in the central core was obtained. These are in agreement with recent theoretical predictions of other workers. Turbulence intensities were not significantly altered when normalized with the usual friction velocity.     

Kinetics of thermal degradation and thermo-oxidative degradation of conductive styrene-butadiene rubber-carbon black composites

The kinetics of the thermal degradation and thermo-oxidative degradation of conductive styrene-butadiene rubber (SBR)-carbon black composites were investigated using thermogravimetric analysis both in nitrogen and oxygen atmospheres. Experiments were carried out at heating rates of 5, 10, 15 and 20 °C/min in both the atmospheres. Friedman method, Kissinger method, Flynn–Wall–Ozawa method and Coats–Redfern method have been used to determine the activation energies of degradation. The invariant kinetic parameters using the IKP method were also determined. The results showed that the thermal stability of the composites in pure nitrogen is higher than that in air atmosphere and the increase in filler loading was found to increase the thermal stability in nitrogen atmosphere. The probable degradation mechanisms of the polymer in both the atmospheres were evaluated based on Fourier Transform Infra Red Spectroscopy (FT-IR) studies.     

World literature on thorium research: A scientometric study based on Science Citation Index

Summary This paper attempts to highlight quantitatively the growth and development of world literature on thorium in terms of publication output as per Science Citation Index (1982-2004). During 1982-2004 a total of 3987 papers were published by the scientists in the field 'thorium'. The average number of publications published per year were 173. The highest number of papers 249 were published in 2001. The spurt in the literature output was reported during 1991-2004.There were 94 countries involved in the research in this field. USA is the top producing country with 1000 authorships (21.11%) followed by India with 498 authorships (10.51%). Authorship and collaboration trend was towards multi-authored papers. Intensive collaboration was found during 1990-2004.One paper 'Nuclear Instruments and Methods in Physics Research - A 406 (3) (1998) 411-426' had 64 collaborators. There were 586 international collaborative papers. Bilateral collaboration accounted for 80.55 percent of total collaborative papers. Bhabha Atomic Research Centre (India) topped the list with 153 authorships followed by Los Alamos National Laboratory (USA) with 105 authorships.The most preferred journals by the scientists were: Journal of Radioanalytical Nuclear Chemistry with 181 papers, Radiochimica Acta with 139 papers, Journal of Radioanalytical Nuclear Chemistry -Articles with 127 papers, Geochimica Cosmochimica Acta with 96 papers, Health Physics with 91 papers, Applied Radiation and Isotopes with 88 papers, Journal of Alloys and Compounds with 65 papers, Earth and Planetary Science letters with 59 papers and Chemical Geology, Indian Journal of Chemistry -A, Radiation Protection Dosimetry with 55 papers each. English was the most predominant language used by the scientists for communication. The high frequency keywords were: Thorium (500), Uranium (284), Separation (94), Thorium Isotopes (90), Thorium (IV) (86), Seawater (73), Solvent Extraction (70), and Rare Earth Elements (68).     

Design and development of efficient multipurpose domestic solar cookers/dryers

A truncated pyramid-type solar cooker is designed, fabricated and tested. The truncated pyramid geometry concentrates the incident light radiations towards the bottom and the glazing glass surface on the top facilitates the trapping of energy inside the cooker. One of the salient features of the proposed design is to completely eradicate the need for tracking the sun during cooking, as tracking of sun does not yield better performance. During testing, the highest plate stagnation temperature, under no-load condition, approached 140 °C and under full-load condition, water temperature inside the cooker reached 98.6 °C in 70 min. Two figures of merit, F₁ and F₂, were calculated and their values were 0.117° C m²/W and 0.467 °C l, respectively, meeting the standards prescribed by the Bureau of Indian Standards for solar box-type cookers. Minor modifications in design are recommended to achieve higher temperatures and reduce cooking times. The design also allows trays to be retained for use as a household dryer.     

Properties of GaN epitaxial layers grown on 6H-SiC(0001) by plasma-assisted molecular beam epitaxy

The structural, electrical, and optical properties of GaN grown on 6H-SiC(0001) substrates by molecular beam epitaxy are studied. Suitable substrate preparation and growth conditions are found to greatly improve the structural quality of the films. Threading dislocation densities of about 3×10⁹ cm⁻² for edge dislocations and <1×10⁶ cm⁻² for screw dislocations are achieved in GaN films of 0.8 μm thickness. Mechanisms of dislocation generation and annihilation are discussed. Increasing the Ga to N flux ratio used during growth is found to improve the surface morphology. An unintentional electron concentration in the films of about 5×10¹⁷ cm⁻³ is observed, and is attributed to excess Si in the films due to a Si-cleaning step used in the substrate preparation. Results from optical characterization are correlated with the structural and electronic studies.     

Effect of temperature,pressure, and composition on DC resistivity and AC conductivity of conductive styrene–butadiene rubber–particulate metal alloy nanocomposites

Conductive nanocomposites were prepared using styrene butadiene rubber as the polymer matrix and nanosized powder of copper–nickel (Cu–Ni) alloy as the filler. The filler loading was varied from 0 to 40 phr. The electrical conductivity of filled polymer composites is due to the formation of some continuous conductive networks in the polymer matrix. Atomic force microscopy was used to determine the particle size of the nanofiller and its nature of dispersion in the rubber matrix. The DC volume resistivity was measured against the loading of the nanofiller to check the percolation limit. The effect of temperature, applied pressure, time duration under constant compressive stress on the DC resistivity and AC conductivity of the composites with different filler loading were investigated. The change in DC resistivity and AC conductivity against temperature of these composites exhibited positive coefficient of temperature. With the change in applied pressure and time duration under constant compressive stress the DC resistivity undergoes an exponential decrease. The effect of AC field frequency on the AC conductivity was investigated. POLYM. COMPOS. 28:696–704, 2007. © 2007 Society of Plastics Engineers     

A parameter tree approach to estimating system sensitivities to parameter sets

A post-processing technique for determining relative system sensitivity to groups of parameters and system components is presented. It is assumed that an appropriate parametric model is used to simulate system behavior using Monte Carlo techniques and that a set of realizations of system output(s) is available. The objective of our technique is to analyze the input vectors and the corresponding output vectors (that is, post-process the results) to estimate the relative sensitivity of the output to input parameters (taken singly and as a group) and thereby rank them. This technique is different from the design of experimental techniques in that a partitioning of the parameter space is not required before the simulation. A tree structure (which looks similar to an event tree) is developed to better explain the technique. Each limb of the tree represents a particular combination of parameters or a combination of system components. For convenience and to distinguish it from the event tree, we call it the parameter tree.To construct the parameter tree, the samples of input parameter values are treated as either a “+” or a “−” based on whether or not the sampled parameter value is greater than or less than a specified branching criterion (e.g., mean, median, percentile of the population). The corresponding system outputs are also segregated into similar bins. Partitioning the first parameter into a “+” or a “−” bin creates the first level of the tree containing two branches. At the next level, realizations associated with each first-level branch are further partitioned into two bins using the branching criteria on the second parameter and so on until the tree is fully populated. Relative sensitivities are then inferred from the number of samples associated with each branch of the tree.The parameter tree approach is illustrated by applying it to a number of preliminary simulations of the proposed high-level radioactive waste repository at Yucca Mountain, NV. Using a Total System Performance Assessment Code called TPA, realizations are obtained and analyzed. In the examples presented, groups of five important parameters, one for each level of the tree, are used to identify branches of the tree and construct the bins. In the first example, the five important parameters are selected by more traditional sensitivity analysis techniques. This example shows that relatively few branches of the tree dominate system performance. In another example, the same realizations are used but the most important five-parameter set is determined in a stepwise manner (using the parameter tree technique) and it is found that these five parameters do not match the five of the first example. This important result shows that sensitivities based on individual parameters (i.e. one parameter at a time) may differ from sensitivities estimated based on joint sets of parameters (i.e. two or more parameters at a time).The technique is extended using subsystem outputs to define the branches of the tree. The subsystem outputs used in this example are the total cumulative radionuclide release (TCR) from the engineered barriers, unsaturated zone, and saturated zone over 10,000 yr. The technique is found to be successful in estimating the relative influence of each of these three subsystems on the overall system behavior.     

CFD analysis of flow pattern and heat transfer in direct contact steam condensation

Direct contact steam condensation used in steam jet injectors, and direct contact feed water heaters, has been studied using CFD simulations. Fairly good agreement has been obtained, with the available experimental data of plume length and the profiles of axial and radial temperature. Further, critical analyses have been carried out for all the published semi-empirical models and correlations. In addition, CFD analysis has been extended to examine the role of nozzle diameter and geometry, on heat transfer phenomenon which governs the direct contact steam condensation phenomenon. A new hydrodynamic model has been formulated which estimates the interfacial area available for condensation. A rational correlation has been developed for the estimation of interfacial area, expressed in terms of Nusselt number (Nu), Reynolds number (Re), Prandtl number (Pr) and ratio of viscosity of steam and water.     

Robust transcoding resistant watermarking for H.264 standard

Content in the digital form can be easily copied and distributed without permission of the owner. As a result, it is of paramount importance to protect content and deter illegal distribution using content protection mechanisms like embedding an imperceptible watermark into the content. Given that consumers want access to content from anywhere using any device, it is necessary to transcode content keeping in mind the limitations of the devices in terms of processing power and network connectivity. However, it is important that the watermark embedded in the content is preserved even after transcoding. The proposed approach embeds in a video, an imperceptible yet robust watermark which is resistant to transcoding. This approach focuses on the H.264 codec because of its widespread use in the industry.