bluuebunny/crossref_metadata_2025_split huggingface dataset:
4‐(N,N‐Diethylamino) Benzaldehyde Thiosemicarbazone in the Spectrophotometric Determination of Palladium
Authors: Parameshwara P. , Karthikeyan J. , Shetty A. Nityananda , Shetty Prakash 
Published: September 2007

Abstract4‐(N,N‐diethylamino)benzaldehyde thiosemicarbazone(DEABT) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of palladium(II). The reagent reacts with palladium (II) in a potassium hydrogen phthalate‐hydrochloric acid buffer of pH 3.0, to form a yellow complex. Beer's law is obeyed in the concentration range up to 3.60 μgmL‐1. The optimum concentration range for minimum photometric error as determined by Ringbom plot method is 0.36‐3.24 μg mL‐1. The yellow Pd(II)‐DEABT complex shows a maximum absorbance at 408 nm, with molar absorptivity of 3.33 × 104 dm3 mol‐1 cm‐1 and Sandell's sensitivity of the complex from Beer's data, for D=0.001, is 0.0032 μg cm‐2. The composition of the Pd(II)‐DEABT complex is found to be 1:2 (M:L). The interference of various cations and anions in the method were studied. The proposed method was successfully used for the determination of Pd(II) in alloys, catalysts, complexes and model mixtures with a fair degree of accuracy.
Numerical simulation of microdroplet formation in coflowing immiscible liquids
Authors: Hua Jinsong , Zhang Baili , Lou Jing 
Published: August 2007

AbstractMonodisperse microdroplets can be formed when a liquid is injected via a capillary needle nozzle into another immiscible coflowing liquid in a microchannel. Such system has been applied in microfluidic devices to produce monodisperse microdroplets with controllable size. In this article, the drop formation in a coflowing system is simulated numerically using a front tracking/finite volume method to investigate the droplet formation mechanism. This numerical method solves a single set of Navier–Stokes equations for both liquid phases on a fixed Eulerian two‐dimensional cylindrical coordinate mesh to account for the fluid flow dynamics. The front tracking method is applied to track the movement of the interface between the two immiscible liquids as well as the surface tension force. The simulation results demonstrate that the process of droplet formation in the coflowing immiscible liquids can be reasonably predicted. Two droplet generation modes (namely dripping and jetting), which have been observed in experiments, are successfully produced through the numerical simulations under certain flow conditions. Moreover, the effects of the continuous phase flow speed, viscosity, and the interface tension on the droplet size are investigated. The correlation of the nondimensional droplet size (r) with the continuous phase flow parameters such as the Reynolds number (Reo), Weber number (Weo), Capillary number (Cao), and viscosity ratios (μ*) can be obtained as r ∝ Cao−1/2 Reo−1/6 for the dripping mode and as r} ∝ Cao1/3 Weo−1/2 μ*−1/2 for the jetting mode from the current simulations. © 2007 American Institute of Chemical Engineers AIChE J, 2007
Brief communication: New reconstruction of the Taung endocast
Authors: Falk Dean , Clarke Ron 
Published: September 2007

AbstractEarlier reconstructions of the Taung endocast, from the juvenile type specimen for Australopithecus africanus, were achieved without benefit of the advanced computer technology that is available today and before morphological differences were identified that distinguish endocasts of Paranthropus from those of A. africanus. Here, we reconstruct and measure a relatively complete virtual endocast of Taung and provide a new cranial capacity estimate of 382 cm3 and a projected adult capacity of 406 cm3, which are smaller than previous estimates. Linear measurements and ratios were also obtained from an endocast of Sts 5 and five Paranthropus endocasts and compared with those of Taung. A number of previously unrecognized foramina, processes, and canals are identified in the bony material that adheres to the base of the Taung endocast. The newly reconstructed virtual endocast of Taung displays a number of shape features that sort it more closely with gracile than robust australopithecines, including squared‐off frontal lobes in dorsal view, and the shape of the tips of its temporal poles. The Taung endocast also shares some features with Paranthropus endocasts, while other characteristics such as small temporal lobes may be due to its juvenile status. Just how much of Taung's unique morphology is due to its juvenile status may eventually be clarified by comparing its endocast with those from other juvenile australopithecines such as the 3.3‐million‐year‐old juvenile from Dikika, Ethiopia. Am J Phys Anthropol, 2007. © 2007 Wiley‐Liss, Inc.
pH‐responsive semi‐interpenetrating networks hydrogels of poly(acrylic acid‐acrylamide‐methacrylate) and amylose. I. Synthesis and characterization
Authors: Li Shengfang , Yang Yajiang , Li Haibing , Yang Xiangliang , Xu Huibi 
Published: September 2007

AbstractThe semi‐interpenetrating networks gels of hydrophobically‐modified poly(acrylic acid‐acrylamide‐methacrylate) and amylose were prepared using 4,4′‐bis(methacryloylamino) azobenzene as a crosslinker. Investigation of mechanical strength of gels showed that the equilibrium elastic modulus G changed from 12.4 to 32.9 g/cm2 with increasing the contents of amylose in the case of low content of crosslinker. The swelling behavior of gels indicated that the aggregation of the hydrophobic groups of hydrogels could be destroyed by expanded amylose and the electrostatic repulsion between the charged COO− groups because of the ionization of the carboxylic groups in pH 7.4 buffer solutions. The hydrophobicity and flexibility of the side chain, the entanglement extent of the amylose, and the ionization of carboxyl groups in the gels greatly affected the swelling rates and swelling ratios. Investigations of swelling/deswelling periodically in pH 2.2 and 7.4 media indicated that the semi‐IPN gel was more pH‐sensitive than the nonsemi‐IPN gel. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Preparation and characterization of novel semi‐interpenetrating 2‐hydroxyethyl methacrylate‐g‐chitosan copolymeric microspheres for sustained release of indomethacin
Authors: Babu V. Ramesh , Sairam M. , Hosamani K. M. , Aminabhavi T. M. 
Published: September 2007

AbstractA novel semi‐interpenetrating (semi‐IPN) graft copolymer of 2‐hydroxyethyl methacrylate (HEMA) with chitosan (CS) has been prepared in the form of microspheres, using water‐in‐oil (W/O) emulsion technique. Microspheres were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X‐ray diffractometry (X‐RD) to confirm the crosslinking and polymorphism of indomethacin (IDM). The X‐RD and DSC techniques indicated a molecular‐level dispersion of IDM in the IPN matrix. Scanning electron micrographs (SEM) taken at the cross section of the microspheres have shown rough surfaces around the microspheres. The sustained release characteristics of the matrices for IDM, an anti‐inflammatory drug, were investigated in pH 7.4 media. Particle size and size distribution of the microspheres were studied by laser light diffraction particle size analyzer. The drug was released in a sustained manner for up to 12 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Chemical resistance, void contents, and morphological properties of Hildegardia fabric/polycarbonate‐toughened epoxy composites
Authors: Guduri B. R. , Rajulu A. V. , Luyt A. S. 
Published: September 2007

AbstractA uniaxial natural fabric of Hildegardia populifolia was used as a reinforcement for a polycarbonate‐toughened epoxy. The Hildegardia fabric was treated with a 5% sodium hydroxide solution for 1 h. The fabric was spray‐coated with a 1% silane‐based coupling agent. The variation of the chemical resistance and void content with different fabric contents and fiber orientations was studied. The morphology of the fractured composites was investigated with scanning electron microscopy (SEM). SEM micrographs indicate that the bonding between the Hildegardia fabric and the matrix was enhanced partially by the alkali treatment. The alkali treatment in the presence of the silane coupling agent gave rise to matrix skin formation on the surface of the fibers, which indicated good bonding between the reinforcement and the matrix. Hildegardia/polycarbonate‐toughened epoxy composites were found to have reasonable chemical and water resistance. The liquid absorption increased when the fabric was treated with an alkali, when the coupling agent was used, and in the presence of water and aqueous solutions. The void content of the composites decreased with increasing fabric content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Synthesis and pressure sensitive adhesive performance of poly (EHA‐co‐AA)/silicate nanocomposite used in transdermal drug delivery
Authors: Rana Pradeep K. , Sahoo Prafulla K. 
Published: September 2007

AbstractThe transdermal drug delivery (TDD) has got main advantage over the conventional oral delivery and maintaining the plasma drug level at a plateau over a long period of time. The phenomenon is taking place at the patch‐skin interface, in particular the adhesion of a polymeric nanoscale pressure sensitive adhesive (PNPSA) film loaded with drug. The major requirements of this PNPSA are they should stick firmly to a difficult substrate (skin) and they should be easily and cleanly removed from the substrate when desired. The PNPSA nanocomposite P(EHA‐co‐AA)/SS is prepared by the emulsion copolymerization of two acrylic monomers, 2‐ethyl hexylacrylate (EHA) and acrylic acid (AA) using a silicone additive like sodium silicate (SS). The TDD patch consists of a nanoscale silicone based polymeric adhesive i.e., P(EHA‐co‐AA)/SS and a drug Cloxacillin sodium an antibiotic. The prepared polymeric nanocomposites can carry drug and these bioactives are entrapped in the polymer matrix as particulates enmesh or bound to the particle surface by physical adsorption. The well characterized novel nanocomposites exhibited significant PSA performance in TDD system. In view of its medical application, the biodegradation study by activated sludge water indicated the nanocomposite to be environmentally friendly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Nanoscale patterning in crosslinked methacrylate copolymer networks: An atomic force microscopy study
Authors: Ye Qiang , Spencer Paulette , Wang Yong 
Published: September 2007

AbstractTo understand the properties of materials, their phase structure must be established. It has been difficult in previous work to visualize the heterogeneous crosslinked structure of methacrylate‐based networks. In this work, nano‐sized phases with worm‐like features were detected in the surfaces of model crosslinked methacrylate copolymer containing hydrophobic/hydrophilic co‐monomers using tapping mode atomic force microscopy/phase imaging technique. The effects of different surface‐contact covers on the height and phase‐contrast images of model resin surfaces were also studied. Based on the experimental data, the identification of phase domains was proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Particle growth behavior of poly(methyl methacrylate) nanoparticles synthesized by the reversible addition fragmentation transfer living radical polymerization reaction
Authors: Kim Jusung , Kwak Juho , Kim Dukjoon 
Published: September 2007

AbstractPMMA nanoparticles with highly mono‐dispersed size distribution were prepared using the RAFT living radical emulsion polymerization technique. A novel sur‐iniferter for the RAFT reaction, DTBA, was synthesized and its chemical structure was identified using several spectroscopic techniques. The relationship between the particle size and the molecular weight of the polymer was investigated measuring the rate of growth of each during formation of particles, and was well explained by the simple random flight molecular conformation model. The particle size increased up to a certain value with decreasing sur‐iniferter concentration and then leveled off, because the surface charge density of the growing particles was not high enough to stabilize the particles in aqueous medium above that value. The core‐shell type di‐block copolymer nanoparticles were also successfully prepared via RAFT reaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Thermal, mechanical, and structural investigation of the effect of electron beam‐irradiation in Bayfol nuclear track detector
Authors: Nouh S. A. , Hegazy T. M. , el Hussieny H. M. , Chaaban Jinane K. 
Published: September 2007

AbstractSamples from sheets of the polymeric material Bayfol have been exposed to electron beam in the dose range 10–100 kGy. The resultant effect of electron beam irradiation on the thermal properties of Bayfol has been investigated using thermogravimetric analysis. The onset temperature of decomposition T0 and activation energy of thermal decomposition Ea were calculated, results indicating that the Bayfol polymer decomposes in one main weight loss stage. Also, the electron irradiation in the dose range 40–100 kGy led to a more compact structure of Bayfol polymer, which resulted in an improvement in its thermal stability with an increase in activation energy of thermal decomposition. The variation of transition temperatures with electron dose has been determined using differential thermal analysis. The results indicate that the electron irradiation in the dose range 40–100 kGy causes crosslinking that destroys the crystalline structure depressing the melting temperature and this is most suitable for applications requiring the molding of this polymer at lower temperatures. In addition, the mechanical and structural properties of Bayfol samples were measured and the results revealed that the tensile strength, elongation at break, yield strength, and intrinsic viscosity were affected by the electron doses. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Closed‐form approximations to the error and complementary error functions and their applications in atmospheric science
Authors: Ren C. , MacKenzie A. R. 
Published: August 2007

AbstractThe error function, as well as related functions, occurs in theoretical aspects of many parts of atmospheric science. This note presents a closed‐form approximation for the error, complementary error, and scaled complementary error functions, with maximum relative errors within 0.8%. Unlike other approximate solutions, this single equation gives answers within the stated accuracy for real variable x ∈ [0∞). The approximation is very useful in solving atmospheric science problems by providing analytical solutions. Examples of the utility of the approximation are: the computation of cirrus cloud physics inside a general circulation model, the cumulative distribution functions of normal and log‐normal distributions, and the recurrence period for risk assessment. Copyright © 2007 Royal Meteorological Society
Anwendung verschiedener Injektionstechniken als Sicherungsmaßnahmen im Zuge der Baumaßnahme Nord‐Süd‐Stadtbahn Köln, Los Nord
Authors: Stelte Manuel 
Published: September 2007

AbstractFür den Bau der Nord‐Süd‐Stadtbahn Köln waren im Los Nord aufgrund der schwierigen geologischen Verhältnisse Sicherungsmaßnahmen mittels Injektionstechnik für die anstehende Bebauung und den Tunnelvortrieb erforderlich. Neben dem Soilfrac®‐Verfahren kamen auch Düsenstrahlverfahren (Soilcrete®) in unterschiedlichster Ausführung zur Anwendung.Das Soilfrac®‐Verfahren wurde im Wesentlichen aus Arbeitsschächten heraus zur Stabilisierung und Ertüchtigung der aufzufahrenden Tunnelbereiche eingesetzt.Die Düsenstrahlverfahren wurden unter extrem beengten Arbeitsverhältnissen unter anderem zur Unterfangung von Gebäuden oder zur Herstellung von Dichtblöcken als Einfahrblöcke der Schildvortriebe eingesetzt.Die Injektionstechniken wurden für verschiedene Bauaufgaben eingesetzt. Im Folgenden werden sieben verschiedene Aufgaben beschrieben.
Hinweise für die Baupreiskalkulation und Arbeitsvorbereitung von Erdbauleistungen beim Einsatz von Geokunststoffbewehrungen
Authors: Biedermann Bernd , Elsing Andreas , Nods Max 
Published: September 2007

AbstractDie Kalkulation von Erdbauleistungen wird neben den Aufwendungen für Beschaffung und Entsorgung von Bodenmassen insbesondere von der Leistung und den Kosten der Baugeräte geprägt. Methodik und Hilfsmittel zur präzisen Ermittlung dieser Kosten sind weit verbreitet und gängige Praxis. Bei der Vorbereitung und Preisermittlung von Bauleistungen, bei denen Geokunststoffe und vor allem deren Verlegung kalkuliert werden müssen, werden jedoch häufig Potentiale für Kosteneinsparungen verschenkt.Der vorliegende Beitrag soll diese Potentiale aufzeigen und Anregungen für eine effektivere Kalkulation und Arbeitsvorbereitung liefern.
ELF‐magnetic flux densities measured in a city environment in summer and winter
Authors: Straume Aksel , Johnsson Anders , Oftedal Gunnhild 
Published: September 2007

AbstractEpidemiological studies have indicated a connection between extremely low frequency magnetic flux densities above 0.4 µT (time weighted average) and childhood leukemia risks. This conclusion is based mainly on indoor exposure measurements. We therefore regarded it important to map outdoor magnetic flux densities in public areas in Trondheim, Norway. Because of seasonal power consumption variations, the fields were measured during both summer and winter. Magnetic flux density was mapped 1.0 m above the ground along 17 km of pavements in downtown Trondheim. The spectrum was measured at some spots and the magnetic flux density emanated mainly from the power frequency of 50 Hz. In summer less than 4% of the streets showed values exceeding 0.4 µT, increasing to 29% and 34% on cold and on snowy winter days, respectively. The average levels were 0.13 µT (summer), 0.85 µT (winter, cold), and 0.90 µT (winter, snow), with the highest recorded value of 37 µT. High spot measurements were usually encountered above underground transformer substations. In winter electric heating of pavements also gave rise to relatively high flux densities. There was no indication that the ICNIRP basic restriction was exceeded. It would be of interest to map the flux density situation in other cities and towns with a cold climate. Bioelectromagnetics 29:20–28, 2008. © 2007 Wiley‐Liss, Inc.
Fluorescence correlation spectroscopy at single molecule level on the Tat–TAR complex and its inhibitors
Authors: Nandi Chayan Kanti , Parui Partha Pratim , Brutschy Bernhard , Scheffer Ute , Göbel Michael 
Published: August 2007

AbstractThe TAR element of HIV and the viral protein Tat form a molecular switch regulating transcriptional efficiency in HIV. We show that fluorescence correlation spectroscopy at the single molecule level is a powerful method to study the association between a Tat‐derived peptide and TAR fragments. We also investigated the inhibition of the peptide–RNA complex by different ligands. Utilizing cross correlation measurements, the dissociation constants (KD) were determined. To demonstrate the important role of the bulge for the binding of Tat, we compared wt‐TAR with three RNA mutants, mainly differing in the bulge region. For the TAR mutants studied at equimolar concentration of RNA and peptide (25 nM), the KD values are 15–35 times larger than that of wt‐TAR. This gives evidence that the bulge region is the most crucial part of the TAR RNA for specific Tat binding. The IC50 values for different inhibitors of the Tat/TAR complex both with wt‐TAR and mutants have been determined. Neamine conjugate proved to be the best inhibitor of the complex formation. Our results are in agreement with earlier published data on this system using alternative biophysical and biochemical methods, respectively. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 17–25, 2008.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley. com
Characterization of the distribution of glucose oxidase in Penicillium sp. CBS 120262 and Aspergillus niger NRRL‐3 cultures and its effect on integrated product recovery
Authors: Johnstone‐Robertson M. , Clarke K.G. , Harrison S.T.L. 
Published: September 2007

AbstractGlucose oxidase (GO) is an important industrial enzyme typically purified from Penicillium and Aspergillus sp. As GO distribution within the cultures influences process design for maximal product recovery, distribution of GO activity in Penicillium sp. CBS 120262 and Aspergillus niger NRRL‐3, during mid‐exponential and stationary phases, is compared. On progression from mid‐exponential to stationary phase, the percentage GO activity in the cytoplasm decreased 1.6‐ and 1.3‐fold in Penicillium sp. and A. niger respectively. In Penicillium sp., a concomitant 1.8‐ and 1.9‐fold decrease in the percentage GO activity in the cell envelope and slime mucilage respectively, translated into a 2.0‐fold increase in the extracellular fluid. In A. niger, decreasing cytoplasmic GO activity was accompanied by 1.3‐fold increases in the cell envelope and slime mucilage, with a 1.3‐fold decrease in the extracellular fluid. Similar trends were observed in specific GO activities. As final GO activity recovered is governed by the purification program, recovery from the extracellular fluid plus cell extract or from the extracellular fluid only were compared through simulating processes of varying complexity. A critical yield for each purification stage was identified above which recovery from the extracellular fluid plus cell extract exceeded that from extracellular fluid alone. These results highlight the influence of microorganism, harvest time and efficiency of downstream process on GO activity delivered. In the systems studied, Penicillium sp. is the organism of choice and should be harvested during stationary phase. The purification process chosen should be informed by both enzyme distribution and individual purification stages yields. Biotechnol. Bioeng. 2008;99: 910–918. © 2007 Wiley Periodicals, Inc.
Factor analysis of spectroelectrochemical reduction of FAD reveals the pKa of the reduced state and the reduction pathway
Authors: Malinowski Edmund R. , Barber Michael J. , Whitaker Graham T. , Smith Eugene T. 
Published: September 2007

AbstractThe free flavin adenine dinucleotide (FAD) cofactor is known to exhibit a pH‐dependent midpoint potential involving a simultaneous two‐electron transfer step (n = 2). Uv‐vis spectroelectrochemical reductions of FAD at constant pH, ranging from 5 to 9, were recorded and analyzed by factor analysis. Principal factor analysis was used to determine the number of species present at each pH. The results indicate that only two composite forms of FAD are present: the oxidized and the reduced forms. Window factor analysis was used to extract the concentration profiles of the controlling species. The oxidized form was found to be a single pH‐independent species, whereas the reduced form consists of two species. The pH‐dependent spectroscopic changes of reduced FAD were best modeled by a single proton transfer step involving two different ionization states with an apparent pKa = 6.3. This value compares favorably with those obtained from NMR and from midpoint potential measurements. At pH 6, the reduction of FAD was found to be first order, whereas at pH 9 the reduction is zero order; these observations are explained in terms of the reaction pathway involving xanthine oxidase, its substrate, and the pH. Copyright © 2007 John Wiley & Sons, Ltd.