bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of process conditions for catalytic alkylation of isomeric cresols with cyclohexene
Authors: Kamruzzaman Mohammad , Rana Ashequl Alam , Saha Manoranjan 
Published: July 2012

Alkylation of isomeric cresols with cyclohexene in presence of perchloric acid as catalyst was studied and cyclohexyl cresols obtained in high yield. The effects of the variation of reaction parameters such as temperature, molar ratio of cresol to cyclohexene, amount of perchloric acid and time of reaction were investigated. The yield of the products increased with the increase of each of the above-mentioned parameters. Optimum yield (97.6% for cyclohexyl m-cresol; 95.4% for 2-cyclohexyl-4-methylphenol and 91.2% for cyclohexyl o-cresol) of the products were obtained under the reaction conditions of a temperature of 140ºC; an 8-6:1 molar ratio of cresol to cyclohexene, a 5% by weight perchloric acid of cresol, a 2 h time of addition of cyclohexene and a 2 h time of stirring of the reaction mixture. Considering the yields of cyclohexyl cresols and ease of purifications, the above mentioned conditions were accounted as optimum for the alkylation of isomeric cresols with cyclohexene in the presence of perchloric acid. DOI: http://dx.doi.org/10.3329/bjsir.v47i2.11446 Bangladesh J. Sci. Ind. Res. 47(2), 153-160, 2012
Characterization of the sand of Brahmaputra river of Bangladesh
Authors: Rahmanb Md Aminur , Biswasb Pradip Kumar , Zamanb Mohammad Nazim , Miah Md Yunus , Hossain Tofazzal , Huq SM Imamul 
Published: July 2012

The aim of this paper is to study on the mineralogy, morphology, magnetic property and composition of the sand of Brahmaputra River, Bangladesh. The sand has been collected from randomly selected seven places and separated by High Intensity Rolling Magnetic Separator into three fractions, viz. magnetic, para-magnetic and non-magnetic parts. The identifications of the valuable heavy minerals existing in these fractions have been performed. The valuable heavy minerals in the separated fractions have been counted under reflected and polarizing microscope and it is found that the magnetic fraction contains ilmenite, magnetite and garnet. The major grain size fraction of the magnetic fraction is 125 - 250 ?m (57.18%). Zircon, rutile, xenotime, monazite, sillimanite etc. have been counted in other two fractions. X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and Isodynamic Separator have been applied for mineral assessment and to quantify the relative proportion of mineral species. DOI: http://dx.doi.org/10.3329/bjsir.v47i2.11448 Bangladesh J. Sci. Ind. Res. 47(2), 167-172, 2012
Effect of antioxidants on stability, nutritional values of refined sunflower oil during accelerated storage and thermal oxidation in frying
Authors: Akhtar H , Tariq I , Mahmood S , Hamid S , Khanum R 
Published: July 2012

Untreated sunflower oil (without antioxidants) was much more affected during long storage as well as by the thermal oxidation in 4 hours frying process. The shelf life of oil was increased both during storage and in frying process at elevated temperature by the addition of synthetic antioxidants. TBHQ (Tertiory butyl hydroquinone) BHT (Butylated hydroxyl toluene) BHA (Butylatd hydroxyl amine) and the mixture of BHA and BHT used in the present study in 0.02, 0.02, 0.02 and 0.01+0.01 amount respectively to observe the stability of refined sunflower when stored at 30°C for 21 weeks in transparent PET bottles. The stored oils (treated and untreated) when underwent in the process of frying at the temperature of 180°C further deterioration of oils happened. The antioxidant activities and protective effects in stabilization of sunflower oils during storage and in frying process measured in terms of POV (peroxide), FFA (free fatty acids), p-AnV (p- Anisidine value), Colour Index, RI (Refractive index), and fatty acid profile. Result indicated that TBHQ exhibited stronger antioxidant activity during storage and gave maximum protection against thermal oxidation when oil subjected in the process of multiple frying for continous four hours at elevated temperature. The results were indicated the effectiveness of antioxidants in the order like TBHQ > BHT > BHA BHA+BHT. DOI: http://dx.doi.org/10.3329/bjsir.v47i2.11458 Bangladesh J. Sci. Ind. Res. 47(2), 223-230, 2012
Production performance of closed water fishery resources in Narayangonj-Narsingdi Irrigation Project
Authors: Hossain Md Motaher , Shafi Mohammed , Ahmed Md Kawser 
Published: August 2012

A survey was conducted both inside (flood?free zone and flooded zone) and outside the embankment of Narayangonj?Narsingdi Irrigation Project, Rupgonj, Narayanganj. All ponds and borrow pits were surveyed from the randomly 10% selected villages by using pre?tested questionnaires. The highest production was in semi?intensive ponds (3,827 and 3,979 kg/ha) in flood?free zone, (3,911 and 4,000 kg/ha) in flooded zone and (3,800 and 4,000 kg/ha) in outside zone, while, the lowest production was found (1,756 and 1,759 kg/ha) in flood?free zone, (1,603 and 1,646 kg/ha) in flooded zone and (1,699 and 1,706 kg/ha) in outside zone in 2003?2004 and 2004?2005, respectively. It was also observed that the production of culturable ponds was higher (959 and 942 kg/ha) in outside, followed by flooded zone (950 and 917 kg/ha) and the lowest production in flood?free zone (400 and 356 kg/ha) in 2003?2004 and 2004?2005. The highest average production of fishes in closed water (ponds and borrow pits) was found in flood?free zone (23,277 and 2,368 kg/ha), followed by flooded zone (2,249 and 2,336 kg/ha) and the lowest average production in outside zone (1,972 and 1,985 kg/ha) in 2003?2004 and 2004?2005, respectively. The higher significant difference (p<0.001) was found between the production of flood?free zone and outside zone in both 2003?2004 and 2004?2005, where no significant difference (p > 0.05) was found between the production of flooded zone and outside zone both in both years.DOI: http://dx.doi.org/10.3329/dujbs.v21i2.11512 Dhaka Univ. J. Biol. Sci. 21(2): 141-152, 2012 (July)
Susceptibility of six varieties of rice to the infestation of rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae)
Authors: Khan Humayun Reza , Halder Polash Kanti 
Published: August 2012

The susceptibility of six varieties of rice, Oryza sativa, viz. Lata, Minicate, Nazersail, Parija, Kalijira and Kataribhog, to the infestation of the rice weevil, Sitophilus oryzae (L.), was studied on the basis of population build up under an ambient condition (28 ± 4ºC and 70 ± 4 % RH) of the laboratory. The mean weights of each grain of the above six rice varieties were 16.9, 16.1, 11.43, 13.87, 6.23 and 9.77 mg, respectively; mean lengths were 6.47, 6.56, 5.37, 5.38, 4.22 and 4.92 mm, respectively; mean widths were 2.45, 2.03, 2.05, 2.17, 1.6 and 1.9 mm, respectively; and moisture contents were 11.55, 10.75, 11.6, 12.71, 11.85, and 12.1 per cents, respectively. As far as the number of emerging adults is concerned, the weevil showed the highest number (695) in Nazersail on the 16th week, Lata (755) on the 18th week, Minicate (654) on the 16th week, Parija (482) on the 20th week, Kalijira (402) on the 20th week, and Kataribhog (456) on the 20th week. The mean numbers of the adult weevils in the above six varieties after 22 weeks of rearing were 425, 410, 351, 387, 357 and 400, respectively and was statistically significant at 5% level. The degree of susceptibility of the rice varieties to the rice weevils from the highest to lowest susceptibility was ? Lata > Nazersail > Minicate > Pariza > Kataribhog > Kalijira.DOI: http://dx.doi.org/10.3329/dujbs.v21i2.11514 Dhaka Univ. J. Biol. Sci. 21(2): 163-168, 2012 (July)
Tuning the Porosity of Bimetallic Nanostructures by a Soft Templating Approach
Authors: Lehoux Anaïs , Ramos Laurence , Beaunier Patricia , Uribe Daniel Bahena , Dieudonné Philippe , Audonnet Fabrice , Etcheberry Arnaud , José‐Yacaman Miguel , Remita Hynd 
Published: July 2012

AbstractHexagonal mesophases made of oil‐swollen surfactant‐stabilized tubes arranged on a triangular lattice in water and doped with metallic salts are used as templates for the radiolytic synthesis of nanostructures. The nanostructures formed in this type of soft matrix are bimetallic palladium‐platinum porous nanoballs composed of 3D‐connected nanowires, of typical thickness 2.5 nm, forming hexagonal cells. Using electron microscopy and small‐angle X‐ray scattering it is demonstrated that the pore size of the nanoballs is directly determined by the diameter of the oil tube of the doped mesophases, which is varied in a controlled fashion from 10 to 55 nm. Bimetallic nanostructures composed of various proportions of palladium and platinum can be synthesized. Their alloy structure is studied using X‐ray photoelectron spectroscopy, energy‐dispersive X‐ray spectroscopy, and high‐angular dark field scanning transmission electron microscopy experiments. The templating approach allows the synthesis of bimetallic nanoballs of tunable porosity and composition.
Femtosecond time‐resolved hot carrier energy distributions of photoexcited semiconductor quantum dots
Authors: Chuang Chi‐Hung , Chen Xiaobo , Burda Clemens 
Published: July 2012

AbstractUsing femtosecond transient absorption spectroscopy, we investigated hot carrier distributions in semiconductor cadmium selenide quantum dots. The relaxation processes represent the behavior of an ensemble of QDs. This concept is applied for analysis with the Fermi‐Dirac distribution and relaxation processes among different electron‐hole pair states. By extracting the experimental hot carrier distribution and fitting with the Fermi‐Dirac function, we resolved the rapid thermalization processes, such as carrier‐carrier and carrier‐phonon interactions was resolved within one picosecond upon photoexcitation. The analysis, using the Fermi‐Dirac distribution modulated by the density of states, provides a general route to understanding the carrier cooling and heat dissipation processes in quantum dot‐based systems.
A comparison of silver‐ and copper‐charged polypropylene feed spacers for biofouling control
Authors: Hausman Richard , Escobar Isabel C. 
Published: July 2012

AbstractImplementation of nanofiltration (NF) and reverse osmosis (RO) processes in treating traditional water sources can provide a steady‐state level of removal that eliminates the need for regeneration of ion exchange resins or granular activated carbon. Moreover, RO can help meet future potable water demands through desalination of seawater and brackish waters. The productivity of membrane filtration is severely lowered by fouling, which is caused by the accumulation of foreign substances on the surface and/or within pores of membranes. Microbial fouling, or biofouling, is the growth of microorganisms on the membrane surface and on the feed spacer as present between the envelopes. The fouling of membranes has demanded and continues to demand considerable attention from industry and research communities. Many of these applications use membranes in a spiral wound configuration that contains a feed spacer. The goal of this project was to develop low‐biofouling polypropylene (PP) spacers through the functionalization of PP by a spacer arm with metal chelating ligands charged with biocidal metal ions, investigate the use of this metal‐charged polypropylene (PP) feed spacers that target biofouling control, and to use some traditional and one novel techniques to autopsy the membranes after filtration to gain a better understanding of the biofouling mechanism and how the modified spacers are affecting it. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Preparation and colorimetric characterization of polymeric nanophotonic structures
Authors: Shamshiri Mohammad Reza , Yousefi Ali Akbar , Ameri Farhad 
Published: July 2012

AbstractA spin‐casting machine was designed and fabricated for preparation of multilayer polymer films from parent polymer solutions together with a polymeric dispersion of nanoparticles. The dispersion consists of polystyrene (PS)‐based core coated with a poly(methyl methacrylate‐co‐butyl acrylate) shell. Multilayer structure of such films was confirmed using a scanning electron microscope A sandwiched dispersed nanoparticles cast from the spin‐casting machine assumed a near to hexagonal arrangement. This structure affected the optical properties of the cast films. The films were characterized using colorimetric methods such as spectrophotometric and goniospectrophotometric techniques. Moreover, a dispersion of styrene‐based nanoparticles is sandwiched between PS and poly(methyl methacrylate) layers. The multilayer sandwiched films illustrated a greenish color shift attributed to the formation of hexagonal structures. The dispersion of styrene‐based nanoparticles within this sandwich restricts the observation of some wavelengths, which could be attributed to changes in the refractive indices of such samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Modelling the effects of reserve size and fishing mortality for Caribbean queen conch Strombus gigas
Authors: Hernandez‐Lamb Jennifer , Dibello Anthony , Lewis Shelley , Mackin Gail , Kirby Kevin , Acosta Charles 
Published: July 2012

ABSTRACT

Overfishing has led to declines in many populations of Caribbean queen conch Strombus gigas, leading to its listing on CITES Appendix II. No‐take marine protected areas (MPA) are increasingly being used as a conservation tool for protecting stocks and sustaining fisheries.
A reaction–diffusion model was developed to study queen conch population responses to various sizes of MPAs, differing spatial and temporal fishing mortalities, and fluctuating recruitment rates. Movement behaviour and demographic data from a protected conch population at Glover's Reef, Belize, were used to parameterize the model and assess simulation results.
The model predicted increases in density ranging from 300% in an MPA encompassing one‐tenth of the total habitat area to 450% in an MPA encompassing half of the habitat, agreeing with field observations.
Queen conch stock in the fishing zone was predicted to decline 6‐40% with MPAs encompassing proportions of 0.1–0.5 of habitat area. Spillover estimated from conch movement was expected to reduce these losses and supplement the fishery by 2–4%.
Sensitivity analysis of fluctuating recruitment showed that larger reserves can sustain population buildup even with lower recruitment rates. Relatively small increases in recruitment rates can potentially reduce fishing losses to 0 from MPA closures.
Opening MPAs to fishing periodically or permanently is expected to rapidly deplete the conch population in a fraction of the time necessary for the initial buildup at the current fishing mortality rate.
These results support those of previous modelling studies but also showed complex dynamics for this case study. While MPAs reduce the stock available to the fishery, spillover can supplement the fishery, and increases in recruitment could increase fishery yield beyond pre‐MPA levels. With high fishing mortality, it would not be prudent to open MPAs to fishing for queen conch in any situation. Copyright © 2012 John Wiley & Sons, Ltd.
Correlation Between Activity and Solubility of Water in Some Aliphatic Alcohols
Authors: Apelblat Alexander 
Published: July 2012

AbstractThe solubility of water in 2‐butanol, iso‐butanol, 2‐pentanol, n‐hexanol, n‐heptanol and n‐octanol as a function of water activity was determined at 25°C. Applying the Gibbs‐Duhem relationship, the activities of alcohols and the excess free energies of mixing were evaluated in the binary alcohol‐water systems.
Selective Adsorption of n‐Fatty Acids (C4–C12–C18) at the Alumina/n‐Heptane Interface: Adsorption Isotherms and Heats of Displacement
Authors: Stradella L. , Venturello G. 
Published: July 2012

AbstractThe isotherms and the heats of selective adsorption of n‐fatty acids (C4, C12, C18) at the alumina/n‐heptane interface have been determined at 313 K. All adsorption isotherms show stepwise trend of the L‐4 type isotherm according to Gile's classification. This behaviour has been interpreted assuming progressive rearrangement in the adsorbed layer with partial formation of dimers of n‐fatty acid molecules in correspondence of high surface coverage. – As the monocarboxylic acid orientation is concerned limiting adsorption from n‐heptane is consistent with the hypothesis of the surface structure made up of symmetric bidentate carboxylate ions, with the molecular symmetry axis rotating away from the perpendicular, orientation. – Studying the effects of the sample outgassing temperature upon the differential heats of adsorption, one may assume that:

At T ≤ 573 K the differential heats are typical of hydrogen bonding between fatty acids' carboxylic group and isolated surface hydroxyls groups.
At higher outgassing temperatures the heats of selective adsorption are representative of dissociative chemisorption on c.u.s. sites.
In correspondence of higher surface coverages aspecific Van der Waals interactions become prevalent. – The differential heats of adsorption for all η‐ and α‐alumina samples decrease as the chain length increases. – α‐Al2O3 differential heats are smaller than η‐Al2O3 adsorption heats.
The Viscosity and the Energies of Activation for Selected Cyclic Compounds at Pressures up to 2 kbar
Authors: Kuss E. 
Published: July 2012

AbstractIn order to investigate the relationship between the viscosity‐pressure behavior and the structure of the molecule the viscosities η of Diphenyl‐methane, Dicyclohexylmethane, Triphenylmethane, Tricyclohexylmethane as well as those of unhydrogenized and hydrogenized Bixylyltoluene and Terxylyltoluene were measured between 25 and 80°C up to 2 kbar. It is found, that in each case the viscosity‐pressure dependence is strongly enhanced by hydrogenation. – Furthermore the pVT‐data of unhydrogenized and hydrogenized Bixylyltoluene were measured and reproduced by the equation of Tait. The lg η‐isotherms as‐function of density ρ, the lg η‐isochors as function of 1/T, the heat of activation Ep and the energy of activation Ev are discussed. Ep is diminished to higher temperatures and is enhanced with increasing pressure. However the ration Ep/Ev is approximately equal to 2, independent of temperature and pressure.
The Dibutylphosphate + Benzene System
Authors: Atrops H. , Kohler Friedrich , Apelblat Alexander 
Published: July 2012

AbstractMelting curves and densities have been determined for this system, from which activity coefficients, excess Gibbs energies and excess volumes were evaluated. The results are interpreted similar to the acetic acid + benzene system, with dibutylphosphate (HDBP) to undergo strong dimerization. But with HDBP + benzene, it seems necessary to consider the size differences of the species.
Magnetism and Hyperfine Interactions in Ti – Mn Intermetallic Hydrides
Authors: Hempelmann R. , Wicke E. , Hilscher G. , Wiesinger G. 
Published: July 2012

AbstractWe have studied the magnetic properties of the C14 Laves phase Ti0.40Mn0.60 (homogeneity range from Ti0.33Mn0.67 to Ti0.45Mn0.55), of the p phase Ti0.46Mn0.54, and of the ϕ phase Ti0.48Mn0.52, as well as the magnetic properties of their hydrides. The investigation includes susceptibility measurements in the temperature range 5 to 360 K, magnetization measurements between 4.2 K and 250 K with fields up to 7.2 T, and Mössbauer effect measurements on 57Fe doped samples at 4.2 K and 295 K. Additionally, low temperature heat capacity measurements have been performed. While the Ti – Mn intermetallic C14, ρ and ϕ phases themselves are paramagnetic with susceptibilities independent of temperature, their hydrides are ferromagnetic with Curie temperatures of about 213 K, 87 and 155 K, respectively. The ρ and ϕ phase hydrides possess a weak itinerant ferromagnetism, whereas the ferromagnetism of the C14 Laves phase hydride is of a more localized type. The susceptibilities above Tc consist of Curie Weiss terms and large temperature independent contributions. The non‐symmetric quadrupole split Mössbauer spectrum at room temperature indicates a distortion of a fraction of the tetrahedrons in the uncharged Ti0.40Mn0.60 Laves phase which is removed by hydrogenation. The onset of ferromagnetism in the Ti – Mn ternary hydrides is due to the volume expansion which causes a narrowing of the d bands and thus increases the density of states at the Fermi level upon hydrogenation.
Electrical and Magnetic Properties of the Molten Tl – CuTlSe2 System
Authors: Uemura Osamu , Takahashi Kazuhiko , Satow Tsuneo 
Published: July 2012

AbstractThe electrical conductivity, the thermoelectric power and the magnetic susceptibility of molten Tl + CuTlSe2 mixtures have been measured up to 950°C. These mixtures exhibit a sharp decrease in electrical conductivity and a change in sign of thermoelectric power around the stoichiometric composition CuTl3Se2. Measurements of magnetic susceptibility also indicate a marked anomaly at this composition. These electronic properties for molten Tl + CuTlSe2 mixtures are discussed in the light of current transport theories employed in the amorphous and liquid semiconductors.
Untersuchungen zum Mechanismus und zur Katalyse der elektrochemischen Salpetersäurereduktion
Authors: Kreysa G. , Breidenbach G. , Müller K. J. 
Published: July 2012

AbstractElectrochemical nitric acid reduction has been investigated on graphite and titanium electrodes obtaining current‐potential‐curves, current‐time‐curves and applying electrochemical mass spectrometry for product analysis. Integral current efficiencies and selectivities for the various products has been determined. On graphite at low reduction potentials only NO is formed. At potentials where thermodynamically hydrogen evolution is possible the main products are H2, NO, N2O, and NH. Under these conditions the reduction is catalysed by Cu2+, Ag+, and Pb2+‐ions which were deposited at the base electrode. These metals strongly influence the product distribution. A general reaction scheme is proposed, and the various electrocatalytic effects are discussed.
A NMR Study of Benzene Adsorbed on Graphitized Carbon Black
Authors: Boddenberg B. , Moreno J. A. 
Published: July 2012

AbstractBy means of pulsed NMR spectroscopy the spin‐lattice (T1) and spin‐spin (T2,T2R) proton relaxation times of benzene adsorbed on the graphitized carbon black Graphon were measured as functions of temperature (80 to 300 K), resonance frequency (4 to 60 MHz), and surface coverage (θ = 0.5 to 2). Using the deuterium dilution technique the intermolecular contributions to the relaxation rates were obtained separately. From the intra‐ and intermolecular relaxation times at low temperatures (<140 K) the following structural and dynamical model was developed. The benzene layer is a two‐dimensional quasi‐solid like layer in registry with the graphite (0001) planes (hexagonal unit cell length 0.56 nm) with the benzene molecular planes being oriented perpendicularly to the support. Reorientational motions occur about a two‐fold molecular symmetry axis in a sixfold potential well structure which is determined by the symmetry of the graphite basal planes. The residence time in a potential well is τ = 4.3 · 10−14exp(1070/T) [s]. – At high temperatures (>140 K) great translational mobility in the adsorbed layer is manifested by the irreversible damping of the Carr‐Purcell spin echoes and by the dispersion region ofT1,inter. The diffusion coefficient on the graphite planes isDtr= 3.2 · 10−8exp(−1365/T) [m2s−1]. The non‐inter spin‐lattice and the spin‐spin relaxation times are determined by the magnetic interactions of the adsorbate protons with delocalized and localized paramagnetic centers of Graphon, theT2data in addition by translational diffusion of the molecules among the faces of the polyhedral shaped particles. Only a fraction of 5 · 10−3of the localized centers is found on the surface of the particles, presumably being located on their edges.