Implementation of atmospheric proton spectrum in GEANT4 simulations for space applications

A major part of cosmic rays consists of the primary protons, and this portion plays a crucial role in the space applications such as shielding of spacecrafts. In this study, the proton flux values measured at the top of the atmosphere through the BESS-TeV spectrometer in 2004 are introduced into the GEANT4 simulations by using a probability grid that generates the corresponding discrete kinetic energies with a certain discrete probability. The introduced scheme is tested over a set of the shielding materials such as aluminum, polypropylene, Kevlar, polyethylene, and water by computing the total absorbed dose, which is the measure of the cumulative energy deposited in the investigated target volumes by protons per unit mass in Gy. It is shown that the present recipe provides the opportunity to use the discrete energy values together with the experimental flux values, thereby demonstrating a beneficial capability in the GEANT4 simulations for diverse space applications.Comment: 8 pages, 3 figures, 4 table

Influence of the initial chemical conditions on the rational design of silica particles

The influence of the water content in the initial composition on the size of silica particles produced using the Stöber process is well known. We have shown that there are three morphological regimes defined by compositional boundaries. At low water levels (below stoichiometric ratio of water:tetraethoxysilane), very high surface area and aggregated structures are formed; at high water content (>40 wt%) similar structures are also seen. Between these two boundary conditions, discrete particles are formed whose size are dictated by the water content. Within the compositional regime that enables the classical Stöber silica, the structural evolution shows a more rapid attainment of final particle size than the rate of formation of silica supporting the monomer addition hypothesis. The clearer understanding of the role of the initial composition on the output of this synthesis method will be of considerable use for the establishment of reliable reproducible silica production for future industrial adoption

Thermal/epithermal neutron detection via LiO2_{2}-doped fiber bundles: A computational study through GEANT4 simulations

One of the neutron capture processes in lithium or lithium-doped materials leads to the production of secondary alpha-triton pairs. The counts of these secondary charged particle pairs in the presence of thermal/epithermal neutrons indirectly give access to detecting the primary incident neutrons with the aid of the plastic scintillators by reminding that both these secondary alphas and tritons deposit their entire kinetic energy within a short range. In this study, we modify the polystyrene fiber core of Kuraray Y11-200(M) by doping with 10 wt.$\%$ LiO$_{2}$. We investigate a fiber bundle system hinged on 10 wt.$\%$ LiO$_{2}$-doped Kuraray Y11-200(M) fibers via the GEANT4 simulations by targeting the detection of the incident thermal/epithermal neutrons through the generation of the secondary alpha-triton pairs. First, we estimate an optimal number of fiber arrays by using a monoenergetic beam of thermal neutrons with a kinetic energy of 0.025 eV and we count the number of secondary alpha-triton pairs. Subsequently, we insert a pixelated photo-sensor on both ends of the fiber bundle in order to collect the entrapped optical photons. In addition to the thermal neutrons, we also explore the detection of epithermal neutrons with a kinetic energy of 1 eV by utilizing a combination of the 10 wt.$\%$ LiO$_{2}$-doped Kuraray Y11-200(M) fiber bundles and the neutron absorption layers. We demonstrate that the LiO$_{2}$-doped plastic scintillating fiber bundles are instrumental for the detection of thermal/epithermal neutrons in diverse applications.Comment: 9 pages, 6 figures, 2 table

Mudanças nos compostos bioativos e atividade antioxidante de pimentas da região amazônica.

A Embrapa Amazônia Oriental possui um Banco Ativo de Pimenteira com diferentes genótipos do gênero Capsicum, os quais ainda não foram analisados, quanto às suas características funcionais e capacidade antioxidante. Este estudo objetivou determinar os teores de ácido ascórbico, compostos fenólicos, carotenoides totais e a atividade antioxidante total, em frutos imaturos e maduros de genótipos de pimentas Capsicum spp. As concentrações de vitamina C (100,76-361,65 mg 100 g-1 nos frutos imaturos e 36,70-157,76 mg 100 g-1 nos maduros) decresceram com a maturação dos frutos. Carotenoides totais não foram detectados nos frutos imaturos, porém, nos frutos maduros, observaram-se valores de 73,80-1349,97 mg g-1, em função do genótipo. Os teores de compostos fenólicos aumentaram nos frutos maduros (147,40-718,64 mg GAE 100 g-1), para oito dos nove genótipos avaliados. Os frutos de pimenteira apresentaram significativa atividade antioxidante (55,02-92,03 mM trolox g-1 nos frutos imaturos e 39,60-113,08 mM trolox g- 1 nos maduros). Concluiu-se que o grau de maturação dos frutos influenciou nos teores de compostos bioativos dos genótipos estudados. Destacaram-se, como genótipos promissores com potencial para serem utilizados em programas de melhoramento genético, IAN-186301 e IAN-186324, pelos altos teores de carotenoides totais; IAN-186301, IAN-186311, IAN-186312 e IAN-186313, com relação às altas concentrações de ácido ascórbico; IAN-186304 e IAN-186311, pelos altos teores de compostos fenólicos; e IAN-186311, para atividade antioxidante

Electrospun Adsorptive Nanofibrous Membranes from Ion Exchange Polymers to Snare Textile Dyes from Wastewater

Increasing discharges of industrial wastewater, along with ever‐stricter regulations for the protection of natural water sources, have amplified the demand for highly efficient water treatment technologies. Here, electrospun nanofibrous polyimides enhanced with ion exchange properties are proposed as adsorptive membranes for the treatment of dye‐loaded textile wastewater. With the careful selection of monomers, carboxyl‐functionalized porous polyimides are synthesized in a single step and then further decorated with strong cation and anion exchange side groups. Nuclear magnetic resonance spectroscopy and thermal gravimetric analysis are used to investigate the alkylation degree and total exchange capacity of the polymers. The electrospinning conditions are optimized to produce highly flexible membrane mats with a uniform nanofibrous structure. A series of dye sorption experiments on the nanofibrous membranes reveals the adsorption kinetics and the effects of the polyimide backbone, the charged side groups, and the hydrophilicity. A recycling study is conducted to confirm the stability of the adsorbent membranes. The results suggest that nanofibrous polyimide membranes enhanced with ion exchange properties are promising candidates for the treatment of dye‐laden wastewater. Owing to their facile syntheses and unique properties, these membranes show promising potential in environmental applications

Aggregation and disaggregation of red blood cells: Depletion versus bridging

The aggregation of red blood cells (RBCs) is a complex phenomenon that strongly impacts blood flow and tissue perfusion. Despite extensive research for more than 50 years, physical mechanisms that govern RBC aggregation are still under debate. Two proposed mechanisms are based on bridging and depletion interactions between RBCs due to the presence of macromolecules in blood plasma. The bridging hypothesis assumes the formation of bonds between RBCs through adsorbing macromolecules, while the depletion mechanism results from the exclusion of macromolecules from the intercellular space, leading to effective attraction. Existing experimental studies generally cannot differentiate between these two aggregation mechanisms, although several recent investigations suggest concurrent involvement of the both mechanisms. We explore dynamic aggregation and disaggregation of two RBCs using three simulation models: a potential-based model mimicking depletion interactions, a bridging model with immobile bonds, and a new bridging model with mobile bonds that can slide along RBC membranes. Simulation results indicate that dynamic aggregation of RBCs primarily arises from depletion interactions, while disaggregation of RBCs involves both mechanisms. The bridging model with mobile bonds reproduces well the corresponding experimental data, offering insights into the interplay between bridging and depletion interactions and providing a framework for studying similar interactions between other biological cells

Studies on decolorization of reactive blue 19 textile dye by Coprinus plicatilis

Background: Studies were carried on the decolorization of the textile dye reactive blue 19 (RB 19) by a novel isolate of Coprinus plicatilis (C. plicatilis) fungi. We describe an in vitro optimization process for decolorization and its behavior under different conditions of carbon and nitrogen sources, pH, temperature and substrate concentration. Results: The optimal conditions for decolorization were obtained in media containing intermediate concentrations of ammonium oxalate and glucose (10 g/L) as nitrogen and carbon sources, respectively, at 26°C and pH = 5.5. Maximum decolorization efficiency against RB 19 achieved in this study was around 99%. Ultra-violet and visible (UV-vis) spectrophotometric analyses, before and after decolorization, suggest that decolorization was due to biodegradation. Conclusions: This effect was associated with laccase enzyme displaying good tolerance to a wide range of pH values, salt concentrations and temperatures, suggesting a potential role for this organism in the remediation of real dye containing effluents. In conclusion, laccase activity in C. plicatilis was firstly described in this study. © 2014 Akdogan et al.; licensee BioMed Central Ltd

Isolation of oleuropein from olive leaf by effective method and investigation of its antimicrobial properties

215-223Natural products play an important role in the production and development of food and medicine. In olive tree cultivation and olive processing industry, vast amounts of by-products are yielded. Olive leaves constitute the major by-product of olive industry. Olive leaf is potential source of phenolic compounds. Plant polyphenols have attracted great interest due to their antimicrobial activities. It was aimed to isolate the oleuropein compound from olive leaf and to identify its antimicrobial effects in this research. In the first stage, methanol extract was obtained from the olive leaf. After then, ethyl acetate extract (including oleuropein with 93.5% purity) procured from methanol extract. Ethyl acetate extract was subjected to chromatographic technique to obtain oleuropein in high purity (97.6%). The structure of oleuropein was determined by spectroscopic method including 1H and 13C NMR besides comparing isolated oleuropein with the standard commercially obtained. Antimicrobial activity of methanol extract, ethyl acetate extract and oleuropein was investigated on Bacillus subtilis, Candida tropicalis, Lactobacillus brevis, Lactobacillus plantarum, Proteus vulgaris, Saccharomyces cerevisiae, Salmonella enteritidis microorganisms by 96-well microtiter plate method. It was determined that MIC (Minimum Inhibitory Concentration) values of olive leaf products ranged between 1:1 (50 mg/mL) and 1:8 (6.25 mg/mL) for tested microorganisms