Optimization of gas chromatography–single quadrupole mass spectrometry conditions for multiresidue analysis of pesticides in grapes in compliance to EU-MRLs

A single quadrupole GC–MS method was optimized for multiresidue determination of 47 pesticides in grapes with limit of quantifications of each compound in compliance with the EU-MRL requirements. Sample preparation involved extraction of 10 g sample with 10 ml ethyl acetate (+10 g sodium sulphate) by homogenization at 15,000 rpm followed by centrifugation at 3000 rpm. The supernatant was cleaned by dispersive solid phase extraction with primary secondary amine and acidified with 0.1% formic acid. Residues were estimated in selected ion monitoring mode with programmable temperature vaporizer-large volume injection (8 μl). All the GC and MS parameters were thoroughly optimized to achieve satisfactory linearity (R² > 0.99) within 0.01–0.25 mg kg⁻¹ with minimum matrix interferences. Recoveries at 0.01 and 0.02 mg kg⁻¹ were within 67–120% with associated precision RSD below 19%. The method was successfully applied for analysis of the real world samples for incurred residues.     

Numerical Simulations of the High-Velocity Impact of a Single Polymer Particle During Cold-Spray Deposition

In this paper, deposition of polymer powders was studied numerically for the cold-spray deposition technique. In cold spray, a solid particle is impacted on a substrate at high velocity. The deformation and heating upon impact have been shown to be enough to result in particle deposition and adhesion even without melting the particle. Here, a systematic analysis of a single high-density polyethylene particle impacting a semi-infinite high-density polyethylene substrate was carried out for initial velocities ranging between 150 and 250 m/s using the finite element analysis software ABAQUS Explicit. A series of numerical simulations were performed to study the effect of a number of key parameters on the particle impact dynamics. These key parameters include particle impact velocity, particle temperature, particle diameter, composition of the polyethylene particle, surface composition and the thickness of a polyethylene film on a hard metal substrate. The effect of these parameter variations on the particle impact dynamics were quantified by tracking the particle temperature, deformation, plastic strain and rebound kinetic energy. The trends observed through variation of these parameters provided physical insight into the experimentally observed window of deposition where cold-sprayed particles are mostly likely to adhere to a substrate.     

Scaling up biomass gasifier use: an application-specific approach

Biomass energy accounts for about 11% of the global primary energy supply, and it is estimated that about 2 billion people worldwide depend on biomass for their energy needs. Yet, most of the use of biomass is in a primitive and inefficient manner, primarily in developing countries, leading to a host of adverse implications on human health, environment, workplace conditions, and social well being. Therefore, the utilization of biomass in a clean and efficient manner to deliver modern energy services to the world's poor remains an imperative for the development community. One possible approach to do this is through the use of biomass gasifiers. Although significant efforts have been directed towards developing and deploying biomass gasifiers in many countries, scaling up their dissemination remains an elusive goal. Based on an examination of biomass gasifier development, demonstration, and deployment efforts in India—a country with more than two decades of experiences in biomass gasifier development and dissemination, this article identifies a number of barriers that have hindered widespread deployment of biomass gasifier-based energy systems. It also suggests a possible approach for moving forward, which involves a focus on specific application areas that satisfy a set of criteria that are critical to deployment of biomass gasifiers, and then tailoring the scaling up strategy to the characteristics of the user groups for that application. Our technical, financial, economic and institutional analysis suggests an initial focus on four categories of applications—small and medium enterprises, the informal sector, biomass-processing industries, and some rural areas—may be particularly feasible and fruitful.     

Novel D-ring analogues of podophyllotoxin as potent anti-cancer agents

Insulin is one of the hormonal regulators of leptin synthesis and participates in adipose tissue maintenance. The present study was undertaken to clarify the association of endogenous insulin secretion and mode of therapy with body fat and serum leptin levels in diabetic subjects. We measured the fasting serum C-peptide level, as an estimate of endogenous insulin secretion, and the serum leptin level in 176 Japanese diabetic subjects (79 men and 97 women; age, 55.9+/-14.3 years; body mass index [BMI], 23.8+/-4.1 kg/m2 [mean+/-SD]). Thirty-one subjects were treated with diet therapy alone, 66 with sulfonylurea (SU), and 79 with insulin (including 29 with type I diabetes mellitus). Body fat was analyzed by the impedance method. Serum leptin levels significantly correlated with the BMI and body fat and were higher in women, mainly because of their greater body fat. Serum C-peptide concentrations positively correlated with body fat and serum leptin in subjects treated with diet and SU. In insulin-treated type II diabetic subjects, both serum C-peptide and the daily insulin dose were weakly associated with body fat and serum leptin. In those subjects, despite a lower percent body fat and body fat mass, serum leptin concentrations (10.3+/-8.4 ng/mL) were comparable to the levels in subjects treated with diet (8.8+/-8.5 ng/mL). When compared within the same BMI and body fat groups (BMI 20 to 25 and > 25 kg/m2) including the control subjects matched for age and sex, serum leptin levels were higher in insulin-treated type II diabetic subjects versus the control subjects and diabetic patients treated with diet or SU. Stepwise regression analysis for all of the diabetic subjects showed that both the serum C-peptide level and exogenous insulin administration, as well as the BMI, gender, and age, were determinants of the serum leptin level. In conclusion, endogenous insulin secretion is closely associated with body fat and serum leptin in diabetic subjects treated with diet therapy and SU. In Japanese insulin-treated type II diabetic subjects, both endogenous and exogenous insulin are associated with body fat and serum leptin, which is maintained at levels comparable to or somewhat higher than the levels in control subjects and diabetic patients treated without insulin.     

Magnetic Barkhausen emission study in heat-treated Fe-Nb-Cu-Si-B alloy

Magnetic hysteresis and magnetic Barkhausen emission (MBE) parameters have been studied for as-received and annealed Fe/sub 72/Nb/sub 4.5/Cu/sub 1/Si/sub 13.5/B/sub 9/ alloys. The coercivity rapidly decreased at the initial stage of annealing, in contrast to the slow change of root-mean-square voltage of Barkhausen emissions. The amplitude of the Barkhausen emission signal reduced almost to the background noise level at an intermediate annealing temperature, at which the material exhibited superior soft magnetic properties. Pulse height distribution of the MBE signal showed the existence of a large number of small amplitude pulses at the intermediate range of annealing, an indication that the magnetization process of the system is dominated by the rotation of the magnetization vector within a small volume of nanocrystalline particles. We explain the results by a random anisotropy model, assuming the exchange coupling between the Fe/sub 80/Si/sub 20/ nanograins of higher magnetic moment takes place through the magnetically weaker amorphous matrix.     

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.     

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.