Position-sensitive silicon strip detector characterization using particle beams

Silicon strip detectors are fast, cost-effective and have an excellent spatial resolution. They are widely used in many high-energy physics experiments. Modern high energy physics experiments impose harsh operation conditions on the detectors, e.g., of LHC experiments. The high radiation doses cause the detectors to eventually fail as a result of excessive radiation damage. This has led to a need to study radiation tolerance using various techniques. At the same time, a need to operate sensors approaching the end their lifetimes has arisen. The goal of this work is to demonstrate that novel detectors can survive the environment that is foreseen for future high-energy physics experiments. To reach this goal, measurement apparatuses are built. The devices are then used to measure the properties of irradiated detectors. The measurement data are analyzed, and conclusions are drawn. Three measurement apparatuses built as a part of this work are described: two telescopes measuring the tracks of the beam of a particle accelerator and one telescope measuring the tracks of cosmic particles. The telescopes comprise layers of reference detectors providing the reference track, slots for the devices under test, the supporting mechanics, electronics, software, and the trigger system. All three devices work. The differences between these devices are discussed. The reconstruction of the reference tracks and analysis of the device under test are presented. Traditionally, silicon detectors have produced a very clear response to the particles being measured. In the case of detectors nearing the end of their lifefimes, this is no longer true. A new method benefitting from the reference tracks to form clusters is presented. The method provides less biased results compared to the traditional analysis, especially when studying the response of heavily irradiated detectors. Means to avoid false results in demonstrating the particle-finding capabilities of a detector are also discussed. The devices and analysis methods are primarily used to study strip detectors made of Magnetic Czochralski silicon. The detectors studied were irradiated to various fluences prior to measurement. The results show that Magnetic Czochralski silicon has a good radiation tolerance and is suitable for future high-energy physics experiments.

Modified governing equations for gas-particle nozzle flows

A modified set of governing equations for gas-particle flows in nozzles is suggested to include the inertial forces acting on the particle phase. The problem of gas-particle flow through a nozzle is solved using a first order finite difference scheme. A suitable stability condition for the numerical scheme for gas-particle flows is defined. Results obtained from the present set of equations are compared with those of the previous set of equations. It is also found that present set of equations give results which are in good agreement with the experimental observation.

Super-plasticized natural rubber latex modified concretes

Polymeric admixtures to concrete ingredients modify the properties of the processed concrete. Ductility is one such property modification. This investigation deals with the development of a method of incorporating natural rubber latex into concrete ingredients with only marginal effects on the compressive strength of base plain concrete. This retention of the strength has been effected by reducing the water/cement ratio with the aid of a superplasticizer. The quantity of natural rubber latex is expressed as the dry rubber content by percentage of volume of concrete. The compressive and tensile strengths, as well as post peak ductile behaviour have been the basis for comparison with those of unmodified concrete.

Effect of particle size on the dielectric behaviour of double propionates

Introduction Dicalcium strontium propionate (DCSP) undergoes a ferroelectric phase transition at about 28 1.5 K, with the spontaneous polarization occurring along the tetragonal C-axis.1 Takashige et al.2,3 have recently reported ferroelectricity in annealed samples of dicalcium lead propionate (DCLP) in the range 191 K to 331 K. The removal of the inner biasing field by annealing has been known in the case of DCLP3 and DCSP.4 Because of the possible dependence of the inner biasing field on the particle size, a study of the temperature dependence of the dielectric behaviour of the powdered samples of these compounds was undertaken.

Investigations on the melting and bending modulus of polymer grafted bilayers using dissipative particle dynamics

Understanding the influence of polymer grafted bilayers on the physicomechanical properties of lipid membranes is important while developing liposomal based drug delivery systems. The melting characteristics and bending moduli of polymer grafted bilayers are investigated using dissipative particle dynamics simulations as a function of the amount of grafted polymer and lipid tail length. Simulations are carried out using a modified Andersen barostat, whereby the membrane is maintained in a tensionless state. For lipids made up of four to six tail beads, the transition from the low temperature L-beta phase to the L-alpha phase is lowered only above a grafting fraction of G(f)=0.12 for polymers made up of 20 beads. Below G(f)=0.12 small changes are observed only for the HT4 bilayer. The bending modulus of the bilayers is obtained as a function of G(f) from a Fourier analysis of the height fluctuations. Using the theory developed by Marsh Biochim. Biophys. Acta 1615, 33 (2003)] for polymer grafted membranes, the contributions to the bending modulus due to changes arising from the grafted polymer and bilayer thinning are partitioned. The contributions to the changes in kappa from bilayer thinning were found to lie within 11% for the lipids with four to six tail beads, increasing to 15% for the lipids containing nine tail beads. The changes in the area stretch modulus were also assessed and were found to have a small influence on the overall contribution from membrane thinning. The increase in the area per head group of the lipids was found to be consistent with the scalings predicted by self-consistent mean field results. (C) 2010 American Institute of Physics.

Biomimetic synthesis of silver nanoparticles by Citrus limon (lemon) aqueous extract and theoretical prediction of particle size

In the present study silver nanoparticles were rapidly synthesized at room temperature by treating silver ions with the Citrus limon (lemon) extract The effect of various process parameters like the reductant con centration mixing ratio of the reactants and the concentration of silver nitrate were studied in detail In the standardized process 10(-2) M silver nitrate solution was interacted for 411 with lemon Juice (2% citric acid concentration and 0 5% ascorbic acid concentration) in the ratio of 1 4(vol vol) The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance as determined by UV-Visible spectra in the range of 400-500 nm X ray diffraction analysis revealed the distinctive facets (1 1 1 200 220 2 2 2 and 3 1 1 planes) of silver nanoparticles We found that citric acid was the principal reducing agent for the nanosynthesis process FT IR spectral studies demonstrated citric acid as the probable stabilizing agent Silver nanoparticles below 50 nm with spherical and spheroidal shape were observed from transmission electron microscopy The correlation between absorption maxima and particle sizes were derived for different UV-Visible absorption maxima (corresponding to different citric acid concentrations) employing MiePlot v 3 4 The theoretical particle size corresponding to 2% citric acid concentration was corn pared to those obtained by various experimental techniques like X ray diffraction analysis atomic force microscopy and transmission electron microscopy (C) 2010 Elsevier B V All rights reserved

Dynamic response of latex modified concrete machine foundations

New materials in concrete constructions have been widely used to improve various properties such as impact resistance, strength and durability. Polymer modified concrete is one of the new materials which has been developed for potential application in the construction industry. This Paper describes the use of polymer latex for foundation blocks subjected to dynamic loads. Experiments were conducted using ordinary concrete and latex modified concrete footings of three different thicknesses, for three static loads at four excitation levels. Experimental results have revealed that the amplitude of resonance is reduced considerably in the latex modified concrete footings.

Effect of morphology and particle size on the ionic conductivities of composite solid electrolytes

A model incorporating the surface conductivity and morphology of the composite solid electrolytes is envisaged to explain their conduction behaviour. The conductivity data on LinX−50 m/o Al2O3 (X = F−, Cl−, Br−, CO32−, SO42−, PO43−) composites prepared by thermal decomposition of LinX·2nAl(OH)3·mH2O salts and Li2SO4−A (A=Al2O3, CeO2, Y2O3, Yb2O3, Zr2O3, ZrO2 and BaTiO3) composites prepared by mechanical mixing of the components are examined in the light of this model. It is surmised that the particle size of both the dispersoids and the hosts not only influence the ionic conductivity of the host matrix but also affect its bulk properties.

Combustion synthesis and properties of fine-particle rare-earth-metal zirconates, Ln2Zr2O7

Fine-particle rare-earth-metal zirconates, Ln2Zr2O7, where Ln = La, Ce, Pr, Nd, Sm, Gd and Dy having the pyrochlore structure have been prepared using a novel combustion process. The process employs aqueous solutions of the corresponding rare-earth-metal nitrate, zirconium nitrate and carbohydrazide/urea in the required molar ratio. When the solution is rapidly heated to 350–500 °C it boils, foams and burns autocatalytically to yield voluminous oxides. The formation of single-phase Ln2Zr2O7 has been confirmed by powder X-ray diffraction, infrared and fluorescence spectroscopy. The solid combustion products are fine, having surface areas in the range 6–20 m2 g–1. The cold-pressed Pr2Zr2O7 compact when sintered at 1500 °C, 4 h in air, achieved 99% theoretical density.

Combustion Synthesis and Properties of Fine Particle Spinel Manganites

Fine particle spinel manganites have been prepared by thermal decomposition of the precursors N2H5M1/3Mn2/3(N2H3COO)3 · H2O (M = Co and Ni) and M1/3 Mn2/3(N2H3COO)2 · 2H2O (M = Mg and Zn), as well as by the combustion of redox mixtures containing M(II) nitrate (M = Mg, Co, Ni, Cu, and Zn), Mn(II) nitrate, and maleic hydrazide (MH) in the required molar ratio. Both the precursor and redox mixtures undergo self-propagating, gas-producing, exothermic reactions once ignited at 250-375°C to yield corresponding manganites in less than 5 min. Formation of single phase products was confirmed by X-ray powder diffraction patterns. The manganites are of submicrometer size and have surface area in the range 20-76 m2/g.

Hydrazine carboxylate precursors to fine particle titania, zirconia and zirconium titanate

Titanyl hydrazine carboxylate dihydrate, TiO(N2H3COO)2.2H2O, zirconyl hydrazine carboxylate dihydrate, ZrO(N2H3COO)2.2H2O and their solid solution, ZrTiO2(N2H3COO)4.4H2O have been prepared for the first time and investigated as precursors to fine particle TiO2, ZrO2 and ZrTiO4 respectively. Titania(anatase) formed has a very high surface area of 110 m2/g and zirconium titanate showed very low dielectric loss (4 x 10(-4)).

Dense granular flow down an inclined plane A comparison between the hard particle model and soft particle simulations

The granular flow down an inclined plane is simulated using the discrete element (DE) technique to examine the extent to which the dynamics of an unconfined dense granular flow can be well described by a hard particle model First, we examine the average coordination number for the particles in the flow down an inclined plane using the DE technique using the linear contact model with and without friction, and the Hertzian contact model with friction The simulations show that the average coordination number decreases below 1 for values of the spring stiffness corresponding to real materials, such as sand and glass, even when the angle of inclination is only 10 larger than the angle of repose Additional measures of correlations in the system, such as the fraction of particles with multibody contact, the force ratio (average ratio of the magnitudes of the largest and the second largest force on a particle), and the angle between the two largest forces on the particle, show no evidence of force chains or other correlated motions in the system An analysis of the bond-orientational order parameter indicates that the flow is in the random state, as in event-driven (ED) simulations V Kumaran, J Fluid Mech 632, 107 (2009), J Fluid Mech 632, 145 (2009)] The results of the two simulation techniques for the Bagnold coefficients (ratio of stress and square of the strain rate) and the granular temperature (mean square of the fluctuating velocity) are compared with the theory V Kumaran, J Fluid Mech 632, 107 (2009), J Fluid Mech 632, 145 (2009)] and are found to be in quantitative agreement In addition, we also conduct a comparison of the collision frequency and the distribution of the precollisional relative velocities of particles in contact The strong correlation effects exhibited by these two quantities in event-driven simulations V Kumaran, J Fluid Mech 632, 145 (2009)] are also found in the DE simulations (C) 2010 American Institute of Physics doi 10 1063/1 3504660]