Effects of packing materials on the sensitivity of RadFET with HfO2 gate dielectric for electron and photon sources

The radiation sensing field effect transistor (RadFET) with SiO₂ gate oxide has been commonly used as a device component or dosimetry system in the radiation applications such as space research, radiotherapy, and high-energy physics experiments. However, alternative gate oxides and more suitable packaging materials are still demanded for these dosimeters. HfO₂ is one of the most attractive gate oxide materials that are currently under investigation by many researchers. In this study, Monte Carlo simulations of the average deposited energy in RadFET dosimetry systems with different package lid materials for point electron and photon sources were performed with the aim of evaluating the effects of package lids on the sensitivity of the RadFET by using HfO₂ as a gate dielectric material. The RadFET geometry was defined in a PENGEOM package and electron–photon transport was simulated by a PENELOPE code. The relatively higher average deposited energies in the sensitive region (HfO₂ layer) for electron energies of 250?keV–20?MeV were obtained from the RadFET with the Al₂O₃ package lid despite of some deviations from the general tendency. For the photon energies of 20–100?keV, the average amount of energy deposited in RadFET with Al₂O₃ package was higher compared with the other capped devices. The average deposited energy in the sensitive region was quite close to each other at 200?keV for both capped and uncapped devices. The difference in the average deposited energy of the RadFET with different package lid materials was not high for photon energies of 200–1200?keV. The increase in the average deposited energy in the HfO₂ layer of the RadFET with Ta package lid was higher compared with the other device configurations above 3?MeV.     

The synthesis of oligoether-substituted benzimidazolium bromides and their use as ligand precursors for the Pd-catalyzed Heck coupling in water

The oligoether-substituted (CH₃(OCH₂CH₂)_n-; n = 1, 2 or 3) benzimidazolium bromides (3-7) and oligoether-linked (-CH₂(CH₂OCH₂)_nCH₂-, n = 1, 2 or 3) bisbenzimidazolium dibromides (8-13) were prepared by quarternization of N-substituted benzimidazoles (1 and 2) with the bulky benzyl bromides (ArCH₂Br: Ar = C₆H₂(CH₃)₃-2,4,6 and C₆(CH₃)₅). trans-Bis(carbene) palladium(II) complexes 14 and 15 derived from 4 and 6 were synthesized by using Ag complexes as carbene-transfer agents in dichloromethane at ambient temperature. In addition, the reactions of 4 and 6 with Pd(OAc)₂ and NaBr gave the Pd(II) dimers 16 and 17 which can readily be cleaved by triphenylphosphine to afford the benzannulated monocarbene (NHC) monophosphine Pd(II) complexes [PdBr₂(NHC)(PPh₃)] (18 and 19). All compounds have been fully characterized by using elemental analysis, ¹H, ¹³C and ³¹P NMR spectroscopies. X-ray diffraction studies on single crystals of 19a and 19b confirm the cis square planar geometry. In situ formed complexes from Pd(OAc)₂ and benzimidazolium salts (3-13) and preformed Pd(II) complexes 14, 15, 18 and 19 were tested as catalyst for the Heck coupling reaction in water. The influence of the oligoether and benzyl substituents on N atoms and CH₃-substituents on the 5,6-positions of benzimidazole frame were investigated under the same conditions in the Heck coupling reaction. In situ formed catalysts showed better conversions than the isolated Pd(II) complexes. The length of the oligoether spacer significantly increases the activity. The salts with two benzimidazole moieties connected by an oligoether as the spacer 8-13 showed similar catalytic activities in the Heck coupling reaction with the mono salts 3-7 bearing corresponding oligoethers on the N atom.     

Fuzzy capital rationing model

In this paper, we study the fuzzification of Weingartner’s pure capital rationing model and its analysis. We develop a primal–dual pair based on t-norm/t-conorm relation for the constraints and objective function for a fully fuzzified pure capital rationing problem except project selection variables. We define the α$\alpha$-interval under which the weak duality is proved. We perform sensitivity analysis for a change in a budget level or in a cash flow level of a non-basic as well as a basic variable. We analyze the problem based on duality and complementary slackness results. We illustrate the proposed model by computational analysis, and interpret the results.     

Determination of Piribedil in Human Serum, Urine and Pharmaceutical Dosage Form by LC-DAD

A rapid, selective and sensitive reversed-phase liquid chromatographic (LC) method was developed for the determination of piribedil in human serum, urine and pharmaceutical dosage form. LC analysis was carried out using reversed-phase isocratic elution with a C₁₈ column and a mobile phase of 0.01 M phosphate buffer-acetonitrile (50:50, v/v). The chromatograms showed good resolution and sensitivity with no interference of human serum and urine. Piribedil concentrations were determined using diode array detection at 240 nm. Sildenafil citrate was used as internal standard. The limit of quantification (LOQ) and limit of detection (LOD) concentrations were 107.2 and 321.6 pg mL^?1, 96.6 and 290.4 pg mL^?1, 161.7 and 53.9 pg mL^?1 for urine, serum and pharmaceutical dosage forms, respectively. The method was validated for its linearity, precision and accuracy and applied to the tablets, urine and human serum. In addition, the results were compared to those obtained from UV-spectrophotometry.     

Improved self-healing performance of polymeric nanocomposites reinforced with talc nanoparticles (TNPs) and urea-formaldehyde microcapsules (UFMCs)

The present work reports the self-healing performance of the epoxy based polymeric nanocomposite coatings containing different concentrations (1 and 3 wt%) of talc nanoparticles (TNPs) modified with sodium nitrate (NaNO₃), and a fixed amount (5 wt%) of urea-formaldehyde microcapsules (UFMCs) encapsulated with linseed oil (LO). The polymeric nanocomposites were developed, coated on polished steel substrates, and their structural, thermal, and self-healing characteristics were investigated using various techniques. The successful loading (~wt 10%) of NaNO₃ into TNPs, which can be ascribed to the involvement of physio-chemical adsorption mechanism, is validated and proceeds without altering the TNPs parent lamellae structure. The performed tests elucidated that the self-release of the corrosion inhibitor (NaNO₃) from TNPs is sensitive to the pH of the solution and immersion time. In addition, the release of the linseed oil (self-healing agent) from UFMCs in response to the external damage was found to be a time-dependent process. The superior self-healing and corrosion inhibition performance of the protective polymeric nanocomposites coatings containing 3 wt% TNPs and UFMCs/LO are proven using the electrochemical impedance spectroscopy (EIS) studies. A careful selection of smart carriers, inhibitor, and self-healing agent compatible with polymeric matrix has enabled to attain decent self-healing and convincing corrosion inhibition efficiency of 99.9% and 99.5%, respectively, for polymeric nanocomposites coatings containing 3 and 1 wt% TNPs, making them attractive for many industrial applications.     

Nonisocyanate based polyurethane/silica nanocomposites and their coating performance

A series of silica nano-particles with different size were prepared by sol–gel technique, then surface modification by using cyclic carbonate functional organoalkoxysilane (CPS) was performed. Various amounts of carbonated silica particles directly added into carbonated soybean oil (CSBO) and carbonated polypropylene glycol (CPPG) resin mixture to prepare polyurethane–silica nanocomposite coating compositions by nonisocyanate route using an aliphatic diamine as a curing agent. Cupping, gloss, impact, and taber abrasion tests were performed on aluminum panels coated with those nano-composite formulations and tensile tests, thermogravimetric and SEM analyses were conducted on the free films prepared from the same coating formulations. An increase in abrasion resistance of CSBO-CPPG resin combination with the addition of silica was observed. In addition, the maximum weight loss of CSBO-CPPG resin combination was shifted to higher temperatures with incorporation of silica nano-particles The positive effect of modified silica particles on thermal stability of CSBO-CPPG system could be explained in such a way that PPG chains are able to disperse particles in the medium throughout the interactions between ether linkages and silanol groups.     

1H magnetic resonance spectroscopy of the normal testis: preliminary findings

PURPOSE: The purpose of this study was to determine the pre- and postpubertal 1H magnetic resonance spectroscopic characteristics of the normal testis to establish baseline values for further clinical studies. MATERIALS AND METHODS: The subjects consisted of male volunteers, of whom 19 were prepubertal with ages between 7 and 13 years and 24 were postpubertal with ages between 19 and 39 years. Their testes were evaluated at 1.5 T with magnetic resonance spectroscopy; in addition, testis volumes were measured. Major metabolite peaks were identified and their ratios were calculated. Metabolite differences of testis between pre- and postpubertal age were analyzed. RESULTS: Major constituents of spectra were 3.21 ppm choline and 0.9-1.3 ppm lipid peaks. At the echo time (TE) spectrum of 31 ms, choline/lipid ratios ranged from 0.35 to 8.30 (mean=1.87) in postpubertal males and from 0.06 to 5.45 (mean=0.88) in prepubertal males (P<.013). At the TE spectrum of 136 ms, choline/lipid ratios ranged from 0.66 to 15.42 (mean=4.09) in postpubertal males and from 0.05 to 4.91 (mean=0.9) in prepubertal males (P<.016). CONCLUSIONS: Choline/lipid ratio was higher in the postpubertal period. The existence of higher choline peak in that age group should be due to the initiation of spermatogenesis. The decrease in the lipid peak may represent the effect of testosterone on testicular tissue or may be due to histochemical changes initiated by puberty. The significant decrease in choline/lipid ratio noted after puberty could represent the presence of spermatogenesis. This hypothesis should be evaluated by further studies on postpubertal subjects with impaired spermatogenesis.     

A Study on the Vinyl Acetate-co-Butyl Acrylate Latexes in the Presence of N-Methylol Acrylamide and Mixed Type Emulsifiers

Summary: The properties of copolymer latexes depend on the copolymer composition, polymer morphology, initiator, polymerization medium and colloidal characteristics of copolymer particles. Poly(vinyl acetate-co-butyl acrylate) latexes with N-metylol acrylamide were prepared by applying semicontinuous emulsion polymerization. The systems studied were (a) the mixture of anionic sodium lauryl sulfate ether (SELES) with nonionic 30 moles ethoxylated nonyl phenol (NP 30) (50:50), (b) the mixture of anionic sodium lauryl sulfate ether (SELES) with nonionic 30 moles ethoxylated nonyl phenol (NP 30) (70:30), and (c) anionic sodium lauryl sulfate ether (SELES) (100%). The effects of the emulsifier and emulsifier composition on the physicochemical properties of obtained vinyl acetate-co-butyl acrylate latex properties in the presence of N-methylol acrylamide initiated by ammonium persulfate were investigated.     

Improvements to compressible Euler methods for low‐Mach number flows

In the present study improvements to numerical algorithms for the solution of the compressible Euler equations at low Mach numbers are investigated. To solve flow problems for a wide range of Mach numbers, from the incompressible limit to supersonic speeds, preconditioning techniques are frequently employed. On the other hand, one can achieve the same aim by using a suitably modified acoustic damping method. The solution algorithm presently under consideration is based on Roe's approximate Riemann solver [Roe PL. Approximate Riemann solvers, parameter vectors and difference schemes. Journal of Computational Physics 1981; 43 : 357–372] for non‐structured meshes. The numerical flux functions are modified by using Turkel's preconditioning technique proposed by Viozat [Implicit upwind schemes for low Mach number compressible flows. INRIA, Rapport de Recherche No. 3084, January 1997] for compressible Euler equations and by using a modified acoustic damping of the stabilization term proposed in the present study. These methods allow the compressible Euler equations at low‐Mach number flows to be solved, and they are consistent in time. The efficiency and accuracy of the proposed modifications have been assessed by comparison with experimental data and other numerical results in the literature. Copyright © 2000 John Wiley & Sons, Ltd.