Dry Medium Research Articles

Evaluation of Dosimetric Parameters for Various 192Ir Brachytherapy Sources Under Unbounded Phantom Geometry by Monte Carlo Simulation

As per TG-43 dose calculation formalism, it is essential to obtain various dosimetric parameters such as the air-kerma strength, dose rate constant, radial dose function, and anisotropy function, as they account for accurate determination of dose rate distribution around brachytherapy sources. Most of the available reported Monte Carlo simulations were performed in liquid water phantoms with a bounded region of 30-cm diameter. In this context, an attempt was made to report the dosimetric parameters for various commercially available pulsed-dose rate (PDR) and high-dose rate (HDR) sources under unbounded phantom conditions, as the data may be used as input to treatment planning systems (TPSs) for quality control assistance. The air-kerma strength per unit activity, S k /A, was computed for various Iridium-192 ( 192Ir) sources in dry air medium. The air-kerma strength and dose rate constant for old PDR is (9.77 ± 0.03) 10 −8 U/Bq and 1.124 ± 0.001 cGyh −1U −1; for new PDR, the values are (9.96 ± 0.03) 10 −8 U/Bq and 1.124 ± 0.001 cGyh −1U −1; for old MHDR, the values are (9.80 ± 0.01) 10 −8 U/Bq and 1.115 ± 0.001 cGyh −1U −1; for new MHDR, (9.80 ± 0.01) 10 −8 U/Bq and 1.112 ± 0.001cGyh −1U −1; for old VHDR, the values are (10.32 ± 0.01) 10 −8 U/Bq and 1.035 ± 0.002 cGyh −1U −1; for new VHDR, the values are (10.34 ± 0.02) 10 −8 U/Bq and 1.096 ± 0.001 cGyh −1U −1. The computed radial dose function values and anisotropy function values are also in good agreement with available data.

GaClx- or GaAlClx-grafted Si-MCM-41: Highly active and moisture insensitive/stable catalyst for the acylation and benzylation of benzene, naphthalene and substituted benzenes

Abstract GaClx- and GaAlClx-grafted Si-MCM-41 catalysts were prepared by reacting anhydrous GaCl3 and mixed anhydrous GaCl3 and AlCl3, respectively, with the terminal hydroxyl groups of Si-MCM-41 (pore size: 2.5 nm) in a dry non-aqueous reaction medium (CCl4) under reflux. The catalysts showed high activity for both the acylation and benzylation (with benzoyl chloride and benzyl chloride, respectively) of benzene, toluene, p-xylene, cumene, mesitylene, anisole and naphthalene. Both the catalysts are moisture insensitive or less moisture sensitive; the presence of moisture has a beneficial effect in the acylation over both the catalysts. The catalytically active sites of the GaClx-grafted Si-MCM-41 are (–O–)2GaCl (i.e. partially chlorided Ga anchored to Si through –O– linkage) species and the equivalent sites of the GaAlClx-grafted Si-MCM-41 are (–O–)2Ga(or Al)Cl and (–O–)3Ga(or Al) species. The high acylation/benzylation activities of both the catalysts even in the presence of moisture are attributed to their redox properties (Ga3+ → Ga1+) rather than to their Lewis acid properties. After the grafting/chemical bonding, the grafted gallium chloride catalyst showed much higher acylation activity but lower benzylation activity than the physically deposited (on Si-MCM-41) or unsupported GaCl3. The GaAlClx-grafted Si-MCM-41 showed higher acylation activity than the GaClx-grafted Si-MCM-41, due to a synergetic effect of the Ga and Al species. However, the relative benzylation activity of the two catalysts showed strong dependence upon the presence or absence of electron donating group(s) and also upon the electron donating ability of the group(s) attached to the aromatic nucleus.

Alumina supported synthesis of Cassia marginata gum‐g‐poly(acrylonitrile) under microwave irradiation

AbstractIn view of the known advantages of the microwave promoted reactions done in dry medium, the seed gum sourced from Cassia marginata has been graft copolymerized with acrylonitrile in dry medium at neutral alumina support under microwave irradiation. Grafting conditions were optimized and the representative graft copolymer was characterized by Fourier transform‐infrared, Thermo gravimetric analysis, Scanning electron microscopy, and X‐Ray Diffraction (XRD) measurement, taking Cassia marginata gum (CM) as reference. Much higher % grafting and % efficiency could be obtained in the microwave promoted alumina supported grafting as compared to grafting done in aqueous medium (microwave promoted and conventional). Properties of the microwave synthesized Cassia marginata gum‐graft‐poly(acrylonitrile) (CM‐g‐PAN) were studied and compared with the parent seed gum. © 2007 John Wiley & Sons, Ltd.

Verification of Roof snap off as a foam-generation mechanism in porous media at steady state

An extensive microvisual analysis is reported of the hydrodynamics of simultaneous gas and water flow through homogeneous etched silicon micromodels. The object of this work is to prove, or to disprove, the relevance of Roof snap off during steady-state gas and water flow in homogeneous porous media. Significant evidence is found that repeated snap off of gas bubbles at pore throats is relevant to steady-state flow through porous media. Importantly, snap off is shown to be the dominant mechanism for generation of a discontinuous gas phase within this porous medium. Experiments are conducted under steady flow conditions in a relatively dry porous medium at significant capillary pressure. Smoothly constricted pores that exhibit small pore throat to pore body aspect ratios are found to be excellent sites for snap off even for low initial wetting liquid contents.

Modification and Application of the Satellite-Based Land Data Assimilation Scheme for Very Dry Soil Regions Using AMSR-E Images: Model Validation for Mongolia-a CEOP data platform

At climatic time-scales, soil moisture is one of the most important boundary condition controlling fluxes to the atmosphere. Here, we explore the feasibility of synthesizing distributed fields of soil moisture using AMSR-E observations and a novel application of data assimilation within a hydrological model. We modified our existing Land Data Assimilation Scheme (LDAS) by specifically considering: (1) weak constraint assumptions rather than a strong constraint, thus accounting for the existence of model errors; and (2) the effects of volume scattering within the soil medium in the Radiative Transfer Model (RTM). Adopting the “effects of volume scattering within the dry soil medium” in the RTM is a new step for satellite-based data assimilation techniques for the retrieval of soil moisture.This LDAS can be used to assess model parameters and estimate vertical profiles of soil moisture, especially in very dry regions (volumetric soil moisture is equal to or less than 5-15%) as well as soil-surface and canopy temperatures by comparing passive microwave observations using a unique minimization technique termed Very Fast Simulated Annealing (VFSA). To validate our new LDAS, AMSR-E observations, gathered in Mongolia, were assimilated into the Land Surface Model (LSM) via the modified RTM. Observed micrometeorology boundary conditions for Mongolia were drawn from the CEOP database. In studies that simulate 2-week dry periods, the results of the revised LDAS are in better agreement with observational data than the results of open-loop simulations.

Just what is a garden?

Introduction The title of this article will be understood immediately upon consideration of figure I. It shows a cluster of shrubs set off by more or less homogenous irregular masses of herbaceous plants and perennials, similar to what we might see in fields. At least two different types of plants are in bloom. Here and there, parts of the ground seem to have been left bare. Clearly this is a field going fallow, much like we might find anywhere where the soil has been worked and then left on its own, or on sites hampered by a poor, dry growing medium, where the bedrock rises to the surface.

Investigation of gas-sensitivity of sensor structures to carbon monoxide in a wide range of temperature, concentration and humidity of gas medium

Response to CO of seven sensor structures of SnO 2 with various catalytic additives, made by thick-film technology, was investigated in a dry gas medium at a concentration of 200 ppm CO in a temperature range of 100–600 °C. Concentration dependence of four sensors (pure SnO 2 and doped with three catalytic additives: 3% La 2O 3, 1% Sb 2O 5 + 3% La 2O 3 and 1% Pt + 3% Pd) was investigated in a range of 0.5–98 ppm CO of different relative humidity (RH) in a range of 0–100% RH. The response and resistance of the sensors weakly depended on the humidity of gas medium at RH ≥ 10%. These parameters were averaged for each CO concentration in the range of 10–100% RH. Arithmetic mean values of response and resistance were approximated by linear functions of lg( S ma − 1) = B + n lg C and R ma = D + k lg C, respectively. It is shown that the relative error of the arithmetic mean values of resistance sd[( R ma)/ R ma] in long-duration continuous measurements of the concentration dependence can be a criterion of reproducibility of sensor indications. The resistance drift of the sensors in pure air did not depend on the humidity of gas medium and did not exceed 0.4–0.5% h −1 for the best sensors. The response threshold C min in a dry gas medium and the arithmetic mean values in a range of 10–100% RH were determined. Based on the comparative analysis of experimental data (response to CO, reproducibility of indications, influence of humidity on the resistance and response, response threshold and a resistance drift in pure air), the best for CO detection was the sensor SnO 2 + 1% Sb 2O 5 + 3% La 2O 3, working at temperature 450 °C and consuming 210 mW. Formulas for response and resistance of this sensor were presented, which allowed estimation of CO concentration in air based on the measured parameters. The error of calculation of 20 ppm CO in a range of 10–100% RH did not exceed 10–18%. Reproducibility of indications in the range of 0.5–98 ppm CO was within 6–10%. The response threshold was 0.80 ± 0.03 ppm CO in the mentioned range of humidity. The present sensor can be recommended as the primary transducer of CO concentration in air for the gas control devices.

Microwave-assisted Synthesis of Starch Maleate by Dry Method

Starch maleate was prepared by microwave-assisted reactions. Microwave-assisted esterification in a dry medium for 5 min gives a reaction efficiency of 98%. Influences of reaction time, reagent molar ratio and water content of starch on the degree of substitution (DS) of the product and reaction efficiency were investigated. The structure of starch maleate was characterized by FTIR and NMR spectroscopy. Changes in the starch granules before and after modification were studied by scanning electron microscopy (SEM). Compared with the conventional heating synthesis method, microwave-assisted synthesis in a dry medium is rapid and energy saving with high reaction efficiency.

Epoxy nanocomposites curing by microwaves

AbstractIn this work, chemically modified sodium montmorillonite and epoxy monomer were used to prepare nanocomposites in two consecutive stages. In the first stage, dodecylamine, octadecylamine, hexadecylamine, and hexadecyltrimethyl ammonium bromide were used to prepare various organophilic clays. In the second stage, the bisphenol‐A based epoxy monomer and predetermined amounts of organoclay were mixed together and then cured by an aliphatic polyamine for 20 min under microwave at 400 W. Furthermore, α‐ω diacrylate poly(dimethylsiloxane) was added to the mixture before the curing process to modify the toughness of the samples. The mixture was poured into the poly(tetrafluoroethylene) mold; the epoxy resin/curing agent ratio was maintained as 2/1. The clear films formed after microwave irradiation were removed from the mold, cooled, and then stored in a cool and dry medium until characterization. The samples were analyzed by wide angle X‐ray diffraction, differential scanning calorimetry, and mechanical tests. Surfaces of the cold fractured samples were also observed under the scanning electron microscope. The results revealed that microwave curing of the samples of 5% organoclay and 5% siloxane showed improvement in mechanical properties. POLYM. ENG. SCI. 46:1104–1110, 2006. © 2006 Society of Plastics Engineers

Magneto-controlled Quantized Electron Transfer to Surface-confined Redox Units and Metal Nanoparticles

Hydrophobic magnetic nanoparticles (NPs) consisting of undecanoate-cappedmagnetite (Fe3O4, average diameter ca. 5 nm) are used to control quantized electron transferto surface-confined redox units and metal NPs. A two-phase system consisting of anaqueous electrolyte solution and a toluene phase that includes the suspended undecanoate-capped magnetic NPs is used to control the interfacial properties of the electrode surface.The attracted magnetic NPs form a hydrophobic layer on the electrode surface resulting inthe change of the mechanisms of the surface-confined electrochemical processes. Aquinone-monolayer modified Au electrode demonstrates an aqueous-type of theelectrochemical process (2e- 2H+ redox mechanism) for the quinone units in the absence ofthe hydrophobic magnetic NPs, while the attraction of the magnetic NPs to the surfaceresults in the stepwise single-electron transfer mechanism characteristic of a dry non-aqueous medium. Also, the attraction of the hydrophobic magnetic NPs to the Au electrodesurface modified with Au NPs (ca. 1.4 nm) yields a microenvironment with a low dielectricconstant that results in the single-electron quantum charging of the Au NPs.

Model Pile Groups Under Oblique Pullout Loads – an Investigation

Experimental investigations on model pile groups of configuration, 1 × 1(single pile), 3 × 1, 2 × 2 for embedment length to diameter ratio, L/d = 38, were conducted in uniform dry medium dense Ennore sand. The spacing of piles in the groups varied from 3 to 6 pile diameter. Soil–pile friction angles were δ = 16° and 28°. The pile groups were subjected to oblique pulling loads at angles θ = 0°, 30°, 60° and 90° with the vertical central axis of the groups. The load–displacement response, oblique ultimate pulling resistances have been qualitatively and quantitatively studied. The inclinations of the load, at which maximum oblique resistance for the groups were observed, have been reported. Predictions of ultimate resistance of pile groups under uplift, lateral and oblique pulling loads have been carried out respectively by the methods of Patra and Pise (2002) (Electronic Journal of Geotechnical Engineering, 8, Bundle B), Patra and Pise (2001) (Journal of Geotechnical and Geoenvironmental Engineering ASCE, 127(6), 481–487) and Chattopadhyay and Pise (1986c) (Proceedings of IST East Asian Conference on Struct Engineering and Const., Vol. 1, pp. 1632–1641). A comparison of the measured values of the Writers and others with the predicted values showed reasonable agreement.

Scattering of SV waves by a canyon in a fluid-saturated, poroelastic layered half-space, modeled using the indirect boundary element method

The scattering of SV waves by a canyon in a fluid-saturated, poroelastic layered half-space is modeled using the indirect boundary element method in the frequency domain. The free-field responses are calculated to determine the displacements and stresses at the surface of the canyon, and fictitious distributed loads are then applied at the surface of the canyon in the free field to calculate the Green's functions for displacements and stresses. The amplitudes of the fictitious distributed loads are determined from the boundary conditions, and the displacements arising from the waves in the free field and from the fictitious distributed loads are summed to obtain the solution. The effects of fluid saturation, boundary conditions, porosity, and soil layers on the surface displacement amplitudes and phase shifts are discussed, and some useful conclusions are obtained. It is shown that the surface displacement amplitudes due to saturation and boundary conditions, different porosities, or the presence of a soil layer can be very dissimilar, and large phase shifts can be observed. The resulting wavelengths for an undrained saturated poroelastic medium are slightly longer than those for a drained saturated poroelastic medium; and are longer for a drained saturated poroelastic medium than those for a dry poroelastic medium. As porosity increases, the wavelengths become longer; and a layered half-space produces longer wavelengths than a homogeneous half-space.

The electronic factor and related redox processes in oxidation catalysis

Catalysis by oxides concern mild selective oxidation as well as total oxidation reactions. Oxides are all semiconductors, either pure, mixed, doped or supported and the redox reactions they catalyse are all connected with their electronic properties. n-Type semiconductors possess anionic vacancies which, when once or twice ionized, are the real oxidative agent of the oxide catalyst. This is illustrated by the Sn–Sb–O system. p-Type oxide semiconductors have positive holes h + as charge carriers, associated with an excess of anionic oxygen. They are illustrated by the case study of vanadyl-pyrophosphate (VO) 2P 2O 7 able to selectively oxidize butane into maleic anhydride in a single pass. In situ measurements of the electrical conductivity of titania during the catalytic oxidation of CO clearly indicated that the oxidizing agent was O − species. All what is described in thermal catalysis can be transposed to photocatalysis at room temperature, with the simultaneous formation of photoelectrons and holes. In dry medium (gas or liquid phase), selective mild oxidation occur involving a neutral activated species O *, illustrated by the direct oxidation of 4- tert-butyl-toluene into 4- tert-butyl-benzaldehyde.

Application of SO 42−/TiO 2 solid superacid in decontaminating radioactive pollutants

Polyaniline doped with SO 4 2−/TiO 2 superacid shows good conductive ability. When used in a strippable coating film for decontaminating radioactive pollutants, the SO 4 2−/TiO 2 solid superacid replacing HCl exhibits higher electrical conductivity (7.01 s/cm) and a decontamination ratio higher than 97%. Coating and electrolyzing the film in solution or in dry medium were effective methods, the latter was more promising for decontaminating radioactive pollutants which were attached to the surface or within the body of equipments used in nuclear industry.

Comparison of the Compact Dry EC with the Most Probable Number Method (AOAC Official Method 966.24) for Enumeration of Escherichia coli and Coliform Bacteria in Raw Meats: Performance-Tested MethodSM 110402

Compact Dry E. coli/Coliform Count (EC) is a ready-to-use test method for the enumeration of Escherichia coli and coliform bacteria in food. The plates are presterilized and contain culture medium and a cold water-soluble gelling agent. The medium should be rehydrated with 1 mL diluted sample inoculated onto the center of the self-diffusible medium, allowing the solution to diffuse by capillary action. The plate can be incubated at 35 degrees C for 20-24 h and the colonies counted without any further working steps. The Compact Dry EC medium plates were validated as an analysis tool for determining colony-forming units (CFU) of E. coli and coliform bacteria from a variety of raw meats using 5 different types of raw meats. The performance tests were conducted at 35 degrees C. In all studies performed, no apparent differences were observed between the Compact Dry EC method and the AOAC Official Method 966.24 results. For the accuracy claim (n = 75), a correlation factor of r2 = 0.93 (E. coli) and r2 = 0.93 (coliform bacteria) could be assigned, as stated in the application for "Performance-Tested Method."

Synthesis of transparent superhydrophobic polyethylene surfaces

Superhydrophobic surfaces, already present in the nature as observed with leaves of plants (lotus) or feathers of some birds, correspond to hydrophobic surface whose water contact angle is higher than 150°. Before running the synthesis of such surface, one must understand the corresponding phenomenon and define the pertinent characteristics. Most of the techniques already developed lead to surfaces with weak physical properties such as optical and mechanical ones. Here, the synthesis in dry medium (plasma) is proposed leading to stable and transparent polymeric superhydrophobic surfaces. Two routes are possible; the first one corresponds to the one-step synthesis (CF 4 plasma modification of low density polyethylene (LDPE)), the second one to the two steps (O 2 plasma treatment followed by CF 4 plasma onto LDPE). The plasma parameters are defined to optimize the degradation and/or the functionalization and the obtained surface structures are characterized. The O 2 plasma allows to create a variable roughness while CF 4 plasma emphasizes this roughness and creates the apolar layer. By the two-step treatments, several plasma parameters were found to elaborate stable transparent superhydrophobic surfaces with a controlled roughness and whose chemical structure is close to a Teflon-like structure. It has been shown that superhydrophobic surface can be obtained even with a low roughness, around 20 nm.

Response of Malt Barley to Phosphorus Fertilization Under Drought Conditions

ABSTRACT Drought conditions are common in the northern Great Plains of the United States, affecting crop yield and quality. Phosphorus (P) fertilizer applications have been found to increase drought tolerance, although there is a lack of published work in this area. The goal of this study was to determine the effects of P fertilization on drought tolerance in malt barley (Hordeum vulgare). Here, 60 cm tall PVC columns were filled with either a silt loam that had a medium soil test phosphorus (STP) level or with the same soil diluted 1:1 (v/v) with coarse sand (low STP). Monoammonium phosphate was incorporated into the surface soil at rates equating to 0, 7.5, and 25 kg P ha− 1 (in triplicate), seeded with malt barley, and watered to maintain water contents either slightly above –1.5 MPa (dry treatment) or slightly drier than field capacity (wet control). Fertilization with P significantly increased plant biomass, root biomass, grain yield, and water-use efficiency (WUE) in the medium STP soil, but not in the low STP soil. Growth in the low STP, coarse, dry soil was apparently limited by water, not P, based on comparisons with the wet control. Fertilization of the dry medium STP soil with P increased grain yield by at least 20-fold, although this increase was not significant due to high variability. These results suggest that adequate soil P levels can substantially offset the impact of drought on barley growth and grain yield.

Influence of pectin and glucose on growth and polygalacturonase production by Aspergillus niger in solid-state cultivation

The solid-state production of endo- and exo-polygalacturonases (PG) by Aspergillus niger was studied in a media containing wheat bran, salts, and different citric pectin and/or glucose concentrations. Kinetic analysis of the process indicated that the formation of PG and the growth of A. niger are associated processes. By increasing citric pectin from 0 to 16% (w/w), the maximum A. niger concentration (X (m)) was raised from 94 to 121 mg/g dry medium suggesting that pectin can be used by A. niger as a growth substrate besides its role as an inducer. With 16% (w/w) pectin, 281 U exo-PG/gdm and 152 U endo-PG/gdm were obtained. Otherwise, pectin concentrations from 20 to 30% (w/w) hindered both production and growth. A. niger concentrations of 108-113 mg/gdm were achieved in runs with glucose from 5 to 12% (w/w), whereas at 16 and 20% (w/w) glucose, lower X (m) values (ca. 100 mg/gdm) were measured. The addition of glucose to the wheat bran medium, up to 10% (w/w) led to maximum endo-PG titers slightly lower than those found in the absence of glucose. Nevertheless, exo-PG formation in these media was strongly increased and activities over 370 U/gdm were achieved. The results suggest that in experiments with pectin concentrations until 16% (w/w), exo-PG production was repressed by pectin-degradation products although these same substances had favored biomass growth. When glucose concentrations over 10% (w/w) were added to the media, the maximum activities of both enzymes decreased drastically, suggesting that glucose at high concentrations also exerts a repressive effect on PG production.

Using a medium-fill simulation to evaluate the microbial contamination rate for USP medium-risk-level compounding

The estimated microbial contamination rate for complex, multiple-step, medium-risk-level compounding was studied. The results of evaluations of the aseptic technique of pharmacists and technicians in compounding complex USP medium-risk-level sterile preparations were compiled to estimate the microbial contamination rate. The testing took place in 2002 and 2003 at a single institution and involved reconstitution of sterile dry growth medium and a series of complicated transfers of the medium from vials and ampuls to intravenous bags. The bags were incubated at 25-35 degrees C for 14 days and observed for microbial growth. Of 539 evaluations, 28 (5.2%) resulted in preparations that yielded microbial growth. Pharmacists' compounding resulted in a slightly lower contamination rate (4.4%) than that of technicians (6.2%). Inadvertent touch contamination may have been the principal source of the contamination. . A two-year series of 539 evaluations of the aseptic technique of pharmacists and technicians conducted with sterile growth medium and designed to simulate the compounding of USP medium-risk-level sterile preparations yielded an overall contamination rate of 5.2%.

Variation of the thermal neutron diffusion cooling properties of wet rock material (Monte Carlo simulations of the pulsed neutron experiments)

The water content in a rock material can significantly change the thermal neutron diffusion parameters with respect to those of the dry medium. The effect has been studied for dolomite, CaMg(CO3)2, by Monte Carlo simulations of the variable buckling experiments for 10 series of samples. The density-removed diffusion cooling coefficient CM varies hyperbolically by two orders of magnitude with water content in the range of 0–20%.