bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advances in biomaterials, drug delivery, and bionanotechnology
Authors: Langer Robert , Peppas Nicholas A. 
Published: April 2004

AbstractBiomaterials are widely used in numerous medical applications. Chemical engineering has played a central role in this research and development. Polymers as biomaterials, materials and approaches used in drug and protein delivery systems, materials used as scaffolds in tissue engineering, and nanotechnology and microfabrication techniques applied to biomaterials are reviewed.
Heterogeneous batch‐extractive distillation of minimum boiling azeotropic mixtures
Authors: Donis Ivonne Rodríguez , Esquijarosa Jhoany Acosta , Gerbaud Vincent , Joulia Xavier 
Published: April 2004

AbstractFollowing previous studies on heterogeneous batch azeotropic distillation, the use of heterogeneous entrainers for the separation of binary azeotropic mixtures by extractive distillation is evaluated. This process is well suited for systems where the entrainer forms a saddle heteregeneous azeotrope with any one of the original components, such systems being unsuitable for nonextractive heterogeneous batch‐distillation processes. Process feasibility is assessed from the isovolatility curves and the volatility order diagram. It tells us whether the homogeneous original component or the heteroazeotrope is drawn at the column top and establishes the distillation tasks sequence using a batch‐rectifying column. The theoretical insights are validated via rigourous simulation for the separation of the acetonitrile–water mixture with hexylamine or butyl acetate. Finally, the same method is applied for the theoretical analysis of a reported industrial example where water is used for the separation of a binary organic mixture, leading to a complex ternary system with several binary azeotropic points and a homogenous ternary azeotrope.
Feasible products in batch reactive distillation
Authors: Guo Zhe , Ghufran Mudassir , Lee Jae W. 
Published: April 2004

AbstractA systematic feasibility evaluation for batch reactive distillation systems is addressed. In each batch configuration, feasibility criteria are obtained for ternary reactive systems by using residual curve maps (RCMs) and reaction equilibrium manifolds. If one of the reaction products is an unstable node (UN) and is reachable from all distillation regions, a rectifier can be used for producing pure products. Even if this unstable node is only reachable from one specific distillation region, a rectifier can still be used when a part of the reaction equilibrium curve lies within the same distillation region as the product. Symmetric results are conserved for a batch stripper with one stable node (SN) product. Finally, pure products are produced in middle‐vessel columns when the UN and SN products share the same distillation region with a part of the reaction equilibrium curve. Although these criteria are obtained for ternary systems, they can be extended to multicomponent reactive systems.
Dynamics of flow and diffusion of adsorbing gases in Al2O3 and Pd‐Al2O3 pellets
Authors: Dogan Meltem , Dogu Gülsen 
Published: April 2004

AbstractA nonisobaric pulse‐response technique was proposed for the simultaneous analysis of flow and diffusion of adsorbing tracers in porous solids. Relative contributions of viscous flow, Knudsen flow, surface flow, and effective diffusion of adsorbing (hydrogen and carbon dioxide) and inert (helium) tracers in alumina and Pd‐alumina pellets were evaluated. Hydrogen permeability was shown to increase by Pd impregnation into alumina, due to the contribution of surface flow, especially at low temperatures. The tortuosity factor, corresponding to the viscous and Knudsen flow, was found to be less than the tortuosity factors evaluated from effective diffusivities obtained from isobaric pulse‐response experiments.
Characterization of anion‐exchange membranes containing pyridinium groups
Authors: Kang Moon‐Sung , Choi Yong‐Jin , Moon Seung‐Hyeon 
Published: April 2004

AbstractA poly(vinyl chloride) (PVC)/glycidyl methacrylate (GMA)‐divinyl benzene (DVB)‐based membrane was prepared via monomer sorption, and then pyridium or its derivates (that is, 4‐ethyl pyridium, 4‐tetrabutyl pyridium) were introduced into the PVC/poly(GMA‐DVB) base membrane. The effects of pyridinium anion‐exchangeable sites on the water splitting and the electrochemical properties of the membrane were investigated. The electrochemical properties and the water splitting on the anion‐exchange membranes were compared with selected commercial membranes containing quaternary ammonium groups. The pyridium membranes showed good electrochemical properties, comparable to those of the commercial membranes, with electrical resistances of less than 3.0 × 10−4 Ω·m2 in 0.5 mol dm−3 NaCl and high ionic permselectivities (the transport number of Cl− ions being 0.96). Moreover, water splitting indicated by the proton transport numbers of the membranes containing pyridinium or its derivates, were about two or three orders of magnitude lower than those of the commercial membranes (such as AM‐1) at the same current density because the resonance effect in the quaternary pyridinium groups contributed to their molecular stability.
Micellar dissolution and diffusion effects on adsorption dynamics of surfactants
Authors: Liao Ying‐Chih , Basaran Osman A. , Franses Elias I. 
Published: April 2004

AbstractA one‐dimensional (1‐D) model for the diffusion‐controlled dynamic adsorption and surface tension in micellar solutions of nonionic surfactants is developed and tested with experimental data. The micellar dissolution rate for monodisperse micelles is described as being proportional to the micellar concentration and to the concentration difference between the critical micelle concentration (cmc) and the local monomer concentration with a micellar dissolution rate constant k. The Langmuir or Frumkin adsorption isotherms are used in a diffusion‐controlled adsorption model with micellar dissolution. The hydrodynamic effects due to interface generation in the experiments are simplified as resulting in a stagnant layer with an adjustable finite length l. The model is solved rigorously by the finite‐element method with a stretched grid and adaptive time step sizes. From simulations, the micellar dissolution rate is found to be much more important for dynamic adsorption than the micellar diffusion rate. Moreover, the size distribution of micelles is found to be insignificant for dynamic adsorption when a narrow distribution is considered. New equilibrium and dynamic surface‐tension data for a planar interface in a Langmuir trough has been obtained for two nonionic surfactants, straight‐chain alkyl ethylene oxides, C14E6 and C16E6, at concentrations below and above their cmc's. The pre‐cmc data are used to obtain the respective Langmuir isotherm parameters Γm,L and KL and the effective diffusion length l≈0.3 mm. With values of Γm,L, KL, and l determined from pre‐cmc data, the post‐cmc data are fitted fairly well with the micellar dissolution time constant τK≡1/kC* (C* is the cmc), which is 1.2 ms for C14E6 and 4.5 ms for C16E6.
Solubility of hydrogen in heavy n‐alkanes: Experiments and saft modeling
Authors: Florusse L. J. , Peters C. J. , Pàmies J. C. , Vega Lourdes F. , Meijer H. 
Published: April 2004

AbstractNew experimental measurements on the solubility of hydrogen in several normal alkanes, ranging from decane and up to hexatetracontane, are presented. Data cover a temperature range from 280 K to 450 K, and pressures up to 16 MPa were applied. Hydrogen solubilities of up to 30 mol % were measured. These mixtures are described through a molecular‐based equation of state based on the statistical associating fluid theory (SAFT). In the SAFT approach, all the compounds are modeled as homonuclear chains of united‐atom sites interacting through a Lennard‐Jones potential. Optimized values for the chain length, Lennard‐Jones diameter, and dispersive energy characterize the hydrogen molecule. In the case of n‐alkanes, a correlation for these molecular parameters is used. Two additional parameters, independent of the thermodynamic variables, were fitted to the experimental data of a single isopleth for each particular mixture. The agreement between the measured and predicted solubilities is excellent (overall AAD<1.5%) in all the thermodynamic range, and does not significantly worsen as the molecular weight of the compound increases.
Photosensitive poly(urethane acylsemicarbazide)s with azobenzene chromophores in the main chain
Authors: Palanisamy Aruna , Sundar Saimani , Radhakrishnan Ganga 
Published: April 2004

AbstractPoly(urethane acylsemicarbazide)s were synthesized with a two‐step process: (1) the in situ generation of diisocyanate through the thermal decomposition of an azobenzene‐containing precursor diazide and a reaction with ester/ether polyols to form an isocyanate‐terminated prepolymer and (2) chain extension in N,N‐dimethylacetamide with aliphatic or aromatic dihydrazides. Films cast from N,N‐dimethylacetamide solutions were characterized with attenuated total reflection/Fourier transform infrared spectroscopy, and the thermal properties were studied with thermogravimetric analysis and differential scanning calorimetry. The effects of the hard‐segment content and chain extenders on the static and dynamic mechanical properties were investigated. The photoresponsive behavior of the polymers and the effects of variations in the chromophore concentration and chemical composition on the kinetics of photoisomerization were investigated with ultraviolet–visible spectroscopy, which revealed that the rates were independent of the chromophore concentration. The photomechanical behavior, assessed with creep‐recovery measurements, proved that the systems underwent photochemical isomerization upon irradiation with ultraviolet light. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 444–454, 2004
Investigation on the properties of a three‐component copolymer consisting of tris(allylphenoxy) triazine monomer and a diamine‐chain‐extension bismaleimide
Authors: Fang Qiang , Li Guang‐Zhe , Zeng Xuan , Jiang Lu‐Xia 
Published: April 2004

AbstractA new type of modified bismaleimide resin was obtained by copolymerization between tris(allylphenoxy)triazine monomer (TAPT) and an aromatic diamine‐chain‐extension bismaleimide [e.g., 4,4′‐diaminodiphenylmethane (DADPM)‐chain‐extension 4,4′‐bismaleimidodiphenylmethane (BMDPM)]. The new three‐component‐polymer system had good processibility and mechanical properties. Better results were obtained when the weight ratio of TAPT to the DADPM‐chain‐extension BMDPM resin was 30%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 475–480, 2004
Validation of a GC‐MS screening method for anabolizing agents in solid nutritional supplements
Authors: Van Thuyne W. , Delbeke F. T. 
Published: April 2004

AbstractA sensitive and selective method for the screening of 28 different compounds including testosterone and prohormones, nandrolone and prohormones, stanozolol and metandienone in solid nutritional supplements is described and validated. The different substances are extracted from the solid nutritional supplements by liquid–liquid extraction with a mixture of pentane and freshly distilled diethylether (9/1) after dissolving the supplement in NaOH (1 N). The anabolizing agents are derivatized with a mixture of MSTFA/NH4I/ethanethiol (320/1/2), routinely used for the derivatization of anabolic steroids extracted from urine. The TMS‐derivatives are analysed by GC‐MS in the SIM mode. The limits of detection were in the range from 2 to 40 ng/g. One supplement was analysed with this method and was found to contain several forbidden substances according to IOC doping regulations. All detected compounds, except dihydrotestosterone, could be conﬁrmed with GC‐MS2, proving that the proposed method is suitable for the screening of anabolizing agents in solid nutritional supplements. Copyright © 2004 John Wiley & Sons, Ltd.
A simple, rapid and sensitive method for simultaneous determination of rivastigmine and its major metabolite NAP 226‐90 in rat brain and plasma by reversed‐phase liquid chromatography coupled to electrospray ionization mass spectrometry
Authors: Enz Albert , Chappuis Alain , Dattler Andre 
Published: April 2004

AbstractA simple and sensitive reversed‐phase liquid chromatography coupled with electrospray–mass spectrometry was developed and validated for the simultaneous determination of rivastigmine, a cholinesterase inhibitor, and its major metabolite NAP 226‐90 in rat plasma and brain homogenates. Rivastigmine and NAP 226‐90 were extracted from plasma and brain by ethyl acetate and, after drying under nitrogen, re‐dissolved in acetonitrile and separated isocratic by HPLC on a C18 column and quantiﬁed by single ion monitoring mass spectrometer. The mean (±SD) extraction efﬁciency for rivastigmine in plasma and brain was 93 ± 2 and 95 ± 2% (n = 5) of NAP 226‐90 in a drug range of 10–100 pmol/mL or pmol/g. The method proved to be linear within the tested range (regression coefﬁcient, r = 0.9999, n = 5). Intra‐ and inter‐day precision coefﬁcients of variation and accuracy bias were acceptable (within 15%, n = 5) over the entire range for both compounds using plasma or brain samples. The limits of quantiﬁcation were 0.5 pmol/mL plasma and 2.5 pmol/g brain for rivastigmine and 1 pmol/mL plasma and 5 pmol/g brain for NAP 226‐90, respectively. The analytical technique was used to determine the concentrations of rivastigmine and its metabolite NAP 226‐90 in rat plasma and brain after oral drug administration. The concentrations of the parent drug and its major metabolite were compared to a pharmacodynamic parameter, the ex vivo inhibition of acetylcholinesterase. Copyright © 2003 John Wiley & Sons, Ltd.
Identiﬁcation and determination of active anthraquinones in Chinese teas by micellar electrokinetic capillary chromatography
Authors: Zheng Wenjie , Wang Shufang , Chen Xingguo , Hu Zhide 
Published: April 2004

AbstractThe simultaneous determination of emodin, aloe‐emodin and rhein, in Semen Cassiae, Qinghai Wild Dahuang tea, Ningxia Juemingzi tea, Lanzhou Juemingzi tea and Surong Juemingzi tea, has been investigated by micellar electrokinetic capillary chromatography for the ﬁrst time. With an electrolyte containing 15 mm borax, 30 mm SDS, 10% (v/v) ethanol, at pH 9.60 and 20 kV applied voltage, the three analytes were completely separated within 12 min. The effects of the concentration of borax, electrolyte pH, the concentrations of SDS and organic modiﬁer and the applied voltage on electropheoretic behavior and separation were studied. The linear calibration range was 4–120 µg/mL (r = 0.9921) for emodin, 10–200 µg/mL (r = 0.9970) for aloe‐emodin and 2–100 µg/mL (r = 0.9971) for rhein, respectively. Under the optimum conditions, the relative standard deviation (RSD) values (n = 6) of the migration time and the peak area of each peak was 0.59–0.80% and 1.30–3.22%, respectively. The contents of the analytes in Rheum, Qinghai Wild Dahuang tea, Semen Cassiae and three other kinds of teas were easily determined with recoveries ranging from 95.3 to 104.4%. Copyright © 2003 John Wiley & Sons, Ltd.
Effects of therapeutic and toxic doses of levamisole on thyroid hormones and some biochemical parameters in sheep
Authors: Atessahin Ahmet , Karahan Izzet , Pirincci Ibrahim 
Published: April 2004

AbstractThis study was carried out to establish the effects of therapeutic and toxic doses of levamisole on thyroid hormone levels and some biochemical parameters in sheep. Twelve Akkaraman ewes were used. Levamisole was given orally at doses of 7.5 mg kg−1 (group 1) and 40 mg kg−1 (group 2) to the animals. Blood samples were taken from the jugular vein at 2, 4, 8, 24, 48, 96 and 144 h after the administrations. Serum thyroid hormones and some biochemical parameters were determined on these samples. When compared with the control levels, no significant changes were observed in triiodothyronine (T3) and thyroxin (T4) levels in group 1. Although levamisole was found to increase the levels of total T3, it decreased the levels of total T4 in group 2. On the other hand, free T3 and free T4 levels were not changed in either group. While serum alkaline phosphatase (ALP) activities were decreased, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) and creatinine kinase (CK) activities were increased significantly by levamisole. However, it increased the serum albumin and cholesterol levels, but decreased the inorganic phosphate levels in groups 1 and 2. On the other hand, when compared with the control levels, no significant changes were detected in serum sodium, potassium and calcium levels. In conclusion, therapeutic and toxic doses of levamisole were determined to affect thyroid metabolism and some biochemical parameters in sheep. Copyright © 2004 John Wiley & Sons, Ltd.
Catalytic Ionic Hydrogenations
Authors: Bullock R. Morris 
Published: April 2004

AbstractCatalytic ionic hydrogenation of ketones occurs by proton transfer to a ketone from a cationic metal dihydride, followed by hydride transfer from a neutral metal hydride. This contrasts with traditional catalysts for ketone hydrogenation that require binding of the ketone to the metal and subsequent insertion of the ketone into a MH bond. Ionic hydrogenation catalysts based on the inexpensive metals molybdenum and tungsten have been developed based on mechanistic understanding of the individual steps required in the catalytic reaction.
Children's narratives and patterns of cardiac reactivity
Authors: Bar‐Haim Yair , Fox Nathan A. , VanMeenen Kirsten M. , Marshall Peter J. 
Published: April 2004

AbstractThe present study examines the associations between narrative processing, narrative production, and cardiac rate and variability in children. Heart period (HP) and vagal tone (VT) were computed for fifty‐eight 7‐year‐olds (29 males) during a resting baseline and during epochs in which the children listened to and completed a selected set of story‐stems from the MacArthur Story‐Stem Battery (I. Bretherton, D. Oppenheim, H. Buchsbaum, R. N. Emde, & the MacArthur Narrative Group, 1990). Significant decreases in HP and VT were observed between a resting baseline and epochs of story‐stem presentation by the experimenter. In addition, HP was shorter and VT lower during children's narrative production to emotionally laden story‐stems compared with narration to a neutral story‐stem. Furthermore, narrative and cardiac responses to stories containing separation–reunion themes reflected increased emotional and cognitive load compared with responses to stories that did not contain such themes. Finally, children who showed VT suppression in response to emotion‐laden stories produced more coherent and adaptive narratives compared to those of children who did not show VT suppression. The findings suggest interplay between the cognitive‐emotional processes associated with narrative processing and production and cardiac activation patterns. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 44: 238–249, 2004.
Postnatal stress in mice: Does “stressing” the mother have the same effect as “stressing” the pups?
Authors: Moles A. , Rizzi R. , D'Amato F. R. 
Published: April 2004

AbstractShort‐ and long‐term effects of brief maternal separation, maternal exposure to novel male odor, and standard rearing were compared in NMRI mice. The first condition consisted of 15 min of daily exposure of pups to clean bedding (CB), and the second condition consisted of 15 min of mothers' exposure to the odor of strange males (SM), for 14 days after birth starting from postnatal Day 1. Thus, both conditions entailed the same period of maternal separation. A control mother–offspring group was left undisturbed (nonhandled, N‐H). Corticosterone levels of mothers and pups were measured at the end of the last manipulation session. Corticosterone levels were higher in SM mothers, differing from both those of CB and of control dams; CB pups showed the highest corticosterone levels in comparison with the pups belonging to the other groups. Maternal behavior observed as furthest as possible from the daily separation session did not differ among the three groups. The behavioral response to 0.5 mg/kg of apomorphine in 15‐day‐old pups was enhanced in both CB and SM animals, which suggests an alteration of dopaminergic functioning. Finally, adult CB and SM male mice showed an increase in the percentage of time and entries into the open arms of the plus‐maze in comparison to nonhandled males. This study indicates that exposure to ecologically relevant stimuli elicited a stress response in lactating dams. This “social stress” brings about short‐ and long‐term effects in the offspring, even in the absence of any direct manipulation of the pups. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 44: 230–237, 2004.
Study of the Behavior of an EC Mechanism Using Cyclic and Derivative Chronopotentiometric Techniques with Spherical Electrodes
Authors: López‐Tenés Manuela , Molina Juana María , Molina Ángela 
Published: April 2004

AbstractThe theory for an EC mechanism in chronopotentiometric techniques – reversal chronopotentiometry, cyclic chronopotentiometry and reciprocal derivative chronopotentiometry – is developed. The equations of this article are valid for spherical electrodes of any size and present a compact and easy‐to‐manage form. Methods for determining kinetic parameters of the chemical reaction are proposed and the influence of the electrode radius is discussed. We conclude that large errors in the determination of these parameters are committed if electrode sphericity is neglected. Reciprocal derivative chronopotentiometry has been applied in its traditional form (dt/dE vs. E), and in a more recently proposed modality consisting of plotting dt1/2/dE vs. E. These techniques are very convenient for studying an EC mechanism since the response is obtained in the form of peaks which are quantitatively related to the kinetic parameters of the chemical reaction. A comparison of the chronopotentiometric methods analyzed leads us to conclude that working curves based on the dt1/2/dE vs. E curves are more suitable to obtain accurate values of the rate constants of the chemical reaction.
Evaluation of the seismic performance of a three‐story ordinary moment‐resisting concrete frame
Authors: Han Sang Whan , Kwon Oh‐Sung , Lee Li‐Hyung 
Published: April 2004

AbstractThis study focuses on the seismic performance of Ordinary Moment‐Resisting Concrete Frames (OMRCF) designed only for gravity loads. For this purpose, a 3‐story OMRCF was designed in compliance with the minimum design requirements in the American Concrete Institute Building Code ACI 318 (1999). This model frame was a regular structure with flexure‐dominated response. A 1/3‐scale 3‐story model was constructed and tested under quasi‐static reversed cyclic lateral loading. The overall behavior of the OMRCF was quite stable without abrupt strength degradation. The measured base shear strength was larger than the design base shear force for seismic zones 1, 2A and 2B calculated using UBC 1997. Moreover, this study used the capacity spectrum method to evaluate the seismic performance of the frame. The capacity curve was obtained from the experimental results for the specimen and the demand curve was established using the earthquake ground motions recorded at various stations with different soil conditions. Evaluation of the test results shows that the 3‐story OMRCF can resist design seismic loads of zones 1, 2A, 2B, 3 and 4 with soil types SA and SB. For soil type SC, the specimen was satisfactory in seismic zones 1, 2A, 2B and 3. For soil type SD, the OMRCF was only satisfactory for seismic zones 1 and 2A. Copyright © 2004 John Wiley & Sons, Ltd.