bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strategic management in the Japanese context: the East Japan Railway Company (JR East) 1987–2002
Authors: Smith Ian B. 
Published: October 2003

Abstract

This paper reviews the operation of the Japanese Railway (JR) Companies since the dissolution and privatization of the Japanese National Railways in 1987 and evaluates the changes in the strategic management approach of the JR Companies in the ensuing period. It focuses on JR East, which operates the largest passenger network in Japan and examines both the changes in the company's operating environment since privatization and its strategic management policy in relation to these developments.
The key strategic and business environment issues identified in the paper are primarily government regulation of railway operations, social change — particularly in terms of the demographic profile — and a changing competitive environment.
The reaction of the company's management to these events may be summarized as little discernible change in the strategic management approach in the first 10 years after privatization, for two principal reasons. During that period Japanese companies continued to observe the strategic targets of revenue growth and market share (rather than profitability) and there continued to be acceptance that the Japanese railway companies were obliged, for social reasons, to run unprofitable services, the closure of which would have boosted the company's profitability.
It appears, however, that the company's strategy over the past five years has become clarified and simplified, with a greater emphasis on profitability targets and shareholder value.

Copyright © 2003 John Wiley & Sons, Ltd.
Tramadol Release from a Delivery System Based on Alginate‐Chitosan Microcapsules
Authors: Acosta Niuris , Aranaz Inmaculada , Peniche Carlos , Heras Angeles 
Published: October 2003

AbstractAlginate‐chitosan microcapsules to control the release of Tramadol‐HCl were prepared using two different methods. In the two‐stage procedure (Variant I) alginate was first pumped into a CaCl2/NaCl solution and then transferred into a chitosan solution. In the one‐stage procedure (Variant II) alginate was directly pumped into a chitosan/CaCl2 solution, and different behavior could be noted in each case. The microcapsules were spherical in both variants and they swelled to a greater extent in a basic medium as compared to an acid one. The drug release profile of Tramadol from microcapsules in simulated gastric fluid and simulated intestinal fluid was also studied. The maximum release of Tramadol at 24 h was 64% and 86% for Variant I and II, respectively, in simulated intestinal fluid. Release was adjusted using the power law of the semi‐empirical Peppas equation in order to gain information about the release mechanism. In both cases the values of the exponent were found to be between 0.53 and 0.84 for swellable microcapsules in simulated gastric and intestinal fluids, respectively, indicating anomalous drug transport for both variants. The good results obtained with alginate‐chitosan microcapsules are comparable to those of the best products so far described in the scientific bibliography and in addition, chitosan is useful in pharmacy.Surface morphology of Tramadol‐loaded microcapsule.magnified imageSurface morphology of Tramadol‐loaded microcapsule.
Present and Future Role of Chitin and Chitosan in Food
Authors: Agulló Enrique , Rodríguez María Susana , Ramos Viviana , Albertengo Liliana 
Published: October 2003

AbstractThe conversion of processed discarded material into valuable by‐products and alternative specialty materials has been identified as a timely challenge for food research and development associated with numerous applications of chitinous products. Chitin, chitosan, calcareous chitin, and chitosan, N‐acetylated chitosan, N‐methylene phosphonic chitosan (NMPC), and N‐lauryl‐N‐methylene phosphonic chitosan (LMPC) are being studied as a result of their broad range of food applications. These biopolymers offer a wide range of unique applications including formation of biodegradable films, immobilization of enzymes, preservation of foods from microbial deterioration, as additives (clarification and deacidification of fruits and beverages, emulsifier agents, thickening and stabilizing agents, color stabilization), and dietary supplements. This review summarizes some of the most important developments in this field.
Effect of Chemical Crosslinking on the Swelling and Shrinking Properties of Thermal and pH‐Responsive Chitosan Hydrogels
Authors: Goycoolea Francisco M. , Heras Angeles , Aranaz Inmaculada , Galed Gemma , Fernández‐Valle María E. , Argüelles‐Monal Waldo 
Published: October 2003

AbstractThe ability to form a gel through the physical or chemical crosslinking of chitosan has been well documented. In an attempt to mimic biological systems, thermal and pH‐sensitive chitosan cylindrical hydrogels were produced by a combination of physical and chemical crosslinking processes. To this end, chitosan hydrogels prepared from alkali chitin were molded in cylinders and, once washed, were further crosslinked with glutaraldehyde at stoichiometric ratios, R (= [CHO]/[NH2]), of 1.61 and 3.22 × 10−2. Variation in swelling as a result of stepwise changes in temperature between 40 and 2 °C at pH values of 7.0, 7.6, and 8.0 revealed that the system responds in markedly different manners dependent upon the pH. At pH 7.0, cooling from 40 to 2 °C results in contraction of the gel network structure. While raising the temperature from 2 to 40 °C leads to a rapid swelling response (i.e., ca. a twofold increase in the amount of solvent uptake). Subsequent cooling to 2 °C is accompanied by a new contraction cycle. At pH ≥ 7.6 the temperature dependence of the swelling–contraction behavior is exactly the opposite of that observed at pH 7.0. Very similar trends were observed for the gels at both degrees of crosslinking. The swelling–shrinking behavior observed in gels of pH ≥ 7.6, is similar in kind to that of uncrosslinked gels and is interpreted in terms of a lower critical solution temperature (LCST) volume phase transition, driven by hydrophobic association, presumably involving residual acetyl groups in the chitin. The results at pH 7.0 suggest that the slight ionization of the NH groups leads to destruction of the hydrophobic hydration thus effectively reversing the negative thermal shrinking.Evolution of the swelling ratio, S, as a function of time and temperature for crosslinked chitosan hydrogels. Circles represent S values recorded at pH 7.0 and triangles those at pH 7.6.magnified imageEvolution of the swelling ratio, S, as a function of time and temperature for crosslinked chitosan hydrogels. Circles represent S values recorded at pH 7.0 and triangles those at pH 7.6.
Recovery of Metal Ions by Chitosan: Sorption Mechanisms and Influence of Metal Speciation
Authors: Navarro Ricardo , Guzmán Javier , Saucedo Imelda , Revilla Javier , Guibal Eric 
Published: October 2003

AbstractChitosan is characterized by a high affinity for metal ions due to its high content of amine groups. The sorption mechanism depends on both the protonation of these amine groups and the speciation of metal ions. Metal cations may be adsorbed at pH close to neutrality by chelation mechanism while metal anions can be adsorbed in acidic solutions through ionic interactions with protonated amine groups. Several examples are considered. The first example focuses on Cd sorption, which proceeds by a chelation mechanism on free non‐protonated amine groups in neutral media. In acidic solutions the protonation of amine groups limits the ability of amine groups to complex Cd. The cross‐linking of chitosan with glutaraldehyde also results in a dramatic decrease of sorption properties due to the decrease in the density of complexation sites available for sorption. The sorption of vanadium(V) and molybdenum(VI) illustrates the high capacity of chitosan for the sorption of oxo‐anions. They are very efficiently sorbed in acidic solutions by ionic interactions. The correlation of sorption capacities with the distribution of metal species shows that the sorbent has a greater affinity for highly charged anionic species. The sorption of complex anionic species such as chloro‐complexes of Pd and Pt; and that of copper complexed with organic ligands have also been studied. The optimum conditions for sorption are obtained when anionic complexes predominate in the solution. The chemical modification of chitosan, obtained by grafting of sulfur compounds, allows modifying the sorption mechanism: the ion‐exchange polymer is transformed to a dual ion‐exchange and chelating polymer.Copper sorption isotherm in presence of sodium citrate (0.004 M) (RNH: fraction of protonated amine groups; ACuC: total fraction of anionic copper complexes; Cu‐FAL: total fraction of copper‐free anionic ligands).magnified imageCopper sorption isotherm in presence of sodium citrate (0.004 M) (RNH: fraction of protonated amine groups; ACuC: total fraction of anionic copper complexes; Cu‐FAL: total fraction of copper‐free anionic ligands).
Controlled Chemical Modifications of Chitosan. Characterization and Investigation of Original Properties
Authors: Auzély Rachel , Rinaudo Marguerite 
Published: October 2003

AbstractThe main techniques developed to characterize chitosan are recalled. The interaction of chitosan with oppositely charged surfactants was investigated giving very important surface activity effects. A few chemical modifications are described and the new properties obtained are mentioned: alkylation gives amphiphilic polymers having interesting thickening behavior; grafting cyclodextrin (chit‐CD) gives a polymer able to include hydrophobic molecules; grafting adamantane gives an amphiphilic polymer able to specifically interact with chit‐CD forming a temporary network with gel‐like behavior.The viscosities of adamantane‐chitosan, cyclodextrin‐chitosan, and unmodified chitosan solutions studied here.magnified imageThe viscosities of adamantane‐chitosan, cyclodextrin‐chitosan, and unmodified chitosan solutions studied here.
Chitosan: An Attractive Biocompatible Polymer for Microencapsulation
Authors: Peniche Carlos , Argüelles‐Monal Waldo , Peniche Hazel , Acosta Niuris 
Published: October 2003

AbstractChitosan is a weak cationic polysaccharide composed essentially of β(1 → 4) linked glucosamine units together with some N‐acetylglucosamine units. It is obtained by extensive deacetylation of chitin, a polysaccharide common in nature. Chitosan is a biocompatible, biodegradable, and nontoxic natural polymer that exhibits excellent film‐forming ability. As a result of its cationic character, chitosan is able to react with polyanions giving rise to polyelectrolyte complexes. Therefore, because of these interesting properties, it has become the subject of numerous scientific reports and patents on the preparation of microspheres and microcapsules. The techniques employed to microencapsulate with chitosan include, among others, ionotropic gelation, spray drying, emulsion phase separation, simple and complex coacervation, and polymerization of a vinyl monomer in the presence of chitosan. The aim of this work is to review some of the more common techniques used and to put forward the results obtained by our research group in preparing chitosan‐based microcapsules: for taste masking and improving the stability of a nutritional oil, the sustained release of drugs, as well as the preparation of chitosan superparamagnetic microcapsules for the immobilization of enzymes.Scanning electron micrograph of some superparamagnetic chitosan particles and magnetic hysteresis loop of the microparticles.magnified imageScanning electron micrograph of some superparamagnetic chitosan particles and magnetic hysteresis loop of the microparticles.
Use of the Interpolyelectrolyte Complexes of Poly(acrylic acid)‐Chitosan as Inductors of Tolerance Against Pathogenic Fungi in Tomato (Lycopersicon esculentum Mill. var. Floradade)
Authors: Ortega‐Ortíz Hortensia , Benavides‐Mendoza Adalberto , Flores‐Olivas Alberto , Ledezma‐Pérez Antonio 
Published: October 2003

AbstractThe interpolyelectrolyte complexes of poly(acrylic acid)‐chitosan were investigated as inductor of systemic resistance potentially useful in the organic production of vegetables. These complexes, which are water soluble, were tested in tomato (Lycopersicon esculentum Mill. var. Floradade). The seed treatments were carried out using solutions consisting of 0.1 vol.‐% of the complex and 5 g · L−1 NaCl in water. The data showed that this treatment produced a higher resistance to the attack by Fusarium oxysporum and Phytophthora capsici pathogens in tomato seedlings.Formation of the interpolyelectrolyte complex of poly(acrylic acid) and chitosan.magnified imageFormation of the interpolyelectrolyte complex of poly(acrylic acid) and chitosan.
UV Spectrophotometry: Improvements in the Study of the Degree of Acetylation of Chitosan
Authors: Pedroni Viviana Isabel , Gschaider María Elena , Schulz Pablo Carlos 
Published: October 2003

AbstractA simple and rapid method for determining the degree of N‐acetylation (DA) of chitosan by ultraviolet spectrophotometry using double beam equipment is proposed. D‐Glucosamine (GlcN) hydrochloride and N‐acetylglucosamine (GlcNAc) were used as model substances, and chitosan solutions in different solvents were studied. The best results were obtained from 0.1 M HCl solutions, with high reproducibility and in good agreement with those given by conductometric titration, FT‐IR, 1H NMR and elemental analysis.Correlation between DA obtained by UV and DA obtained by conductometric titration.magnified imageCorrelation between DA obtained by UV and DA obtained by conductometric titration.
Preparation of Crosslinked Chitosan/Silk Fibroin Blend Films for Drug Delivery System
Authors: Rujiravanit Ratana , Kruaykitanon Sopon , Jamieson Alexander M. , Tokura Seiichi 
Published: October 2003

AbstractCrosslinked chitosan/silk fibroin blend films were prepared by a solution casting technique using glutaraldehyde as crosslinking agent. Drug release characteristics of the blend films with various blend compositions were investigated. Theophylline, diclofenac sodium, amoxicillin trihydrate, and salicylic acid were used as model drugs. The release studies were performed at 37 °C in buffer solutions at pH 2.0, 5.5, and 7.2. It was found that the blend films with 80% chitosan content showed the maximum amount of model drug release at pH 2.0 for all the drugs studied here. This result corresponded to the swelling ability of the blend films. From a swelling study, the maximum degrees of swelling of the drug‐loaded blend films were obtained at this pH and blend composition. The amount of drugs released from the films with 80% chitosan content, from the highest to the lowest values, occurred in the following sequence: salicylic acid > theophylline > diclofenac sodium > amoxicillin.Comparison of the amounts of drug released from chitosan and the blend film with 80% chitosan content at pH 2.0: (filled) chitosan film, and (blank) blend film with 80% chitosan content (SAL = salicylic acid, THEO = theophylline, DFS = diclofenac sodium, AMX = amoxicillin).magnified imageComparison of the amounts of drug released from chitosan and the blend film with 80% chitosan content at pH 2.0: (filled) chitosan film, and (blank) blend film with 80% chitosan content (SAL = salicylic acid, THEO = theophylline, DFS = diclofenac sodium, AMX = amoxicillin).
Methylation of Chitosan with Iodomethane: Effect of Reaction Conditions on Chemoselectivity and Degree of Substitution
Authors: Curti Elisabete , de Britto Douglas , Campana‐Filho Sérgio Paulo 
Published: October 2003

AbstractN,N,N‐trimethylchitosan (TMC) was prepared by reacting purified chitosan with iodomethane, in the presence of sodium hydroxide, water and sodium iodide, at room temperature. The reaction medium was N‐methyl‐2‐pyrrolidone. Different samples of TMC were obtained by adding to the reaction medium a fixed volume (5.5 mL) of aqueous NaOH solutions at different concentrations (15, 20, 30 and 40 wt.‐%) and carrying out the reactions for 9 or 24 h. The features observed in the 1H and 13C NMR spectra of these chitosan derivatives, in respect of the chemical shift, number and relative intensity of the signals, depended strongly on the excess of NaOH and H3CI added to the reaction medium, but when the lowest excess was employed, the characteristics of the derivative were not affected by the reaction time to the same extent. The average degree of quaternization of these N‐methylated derivatives of chitosan ranged from 10.5% to 44.8%, according to the reaction conditions. Increasing the excess of NaOH, in reactions carried out for 9 h, resulted in TMC samples with progressively higher content of trimethylated sites however, the reaction yields were correspondingly lower and O‐alkylation was favored in these cases.1H NMR spectrum of sample [AX]24h dissolved in D2O (Cp = 10 g/L).magnified image1H NMR spectrum of sample [AX]24h dissolved in D2O (Cp = 10 g/L).
Diffusion Through Membranes of the Polyelectrolyte Complex of Chitosan and Alginate
Authors: Cárdenas Adriana , Argüelles‐Monal Waldo , Goycoolea Francisco M. , Higuera‐Ciapara Inocencio , Peniche Carlos 
Published: October 2003

AbstractThe swelling of membranes of the polyelectrolyte complex (PEC) between chitosan and alginate shows a similar pattern to that of other PECs. However, if the swelled membranes are dried, a second swelling process is seen which exhibits Fickian behavior. The apparent activation energy was estimated to be 32.8 kJ · mol−1. The release rate of model solutes was highly dependent on their molecular weight and the pH of the medium.Arrhenius type plot of the temperature dependence of the apparent diffusion coefficients for the membrane of the polyelectrolyte complex between chitosan and alginate in water.magnified imageArrhenius type plot of the temperature dependence of the apparent diffusion coefficients for the membrane of the polyelectrolyte complex between chitosan and alginate in water.
Synthesis and Unusual Swelling Behavior of Combined Cationic/Non‐Ionic Hydrogels Based on Chitosan
Authors: Yazdani‐Pedram Mehrdad , Tapia Cristian , Retuert Jaime , Arias José Luis 
Published: October 2003

AbstractHydrogel‐forming copolymers based on chitosan grafted with different amounts of polyacrylamide were synthesized and its swelling capacity determined in distilled water, sodium chloride solutions, as well as in buffer solutions at pH 1.2 and 8.0. The resulting products are highly efficient as hydrogel‐forming materials with swelling at equilibrium going approximately from 300 to 3 000 times the volume of the dry solid polymer in all the investigated media. The products, different to usual hydrogels, swells considerably more and quickly in electrolyte‐containing solutions compared to in distilled water. This has been attributed to their structure that contains non‐ionic polyacrylamide macromolecules grafted onto the trunk polymer chitosan, which is cationic in nature. In‐vitro drug‐release behavior of formulations containing grafted copolymers have been tested using theophylline as a water‐soluble drug and the results were compared with similar formulations containing unmodified chitosan. It was found that tablets based on formulations containing grafted chitosan show higher erosion and swelling compared with those of the matrix based on unmodified chitosan, leading to a higher fraction of theophylline released. It can be concluded that formulations based on the synthesized copolymers are potentially useful for fluid absorbency and as prolonged drug‐release matrices.The swelling of one of the hydrogels studied here.magnified imageThe swelling of one of the hydrogels studied here.
Drug Delivery Systems Based on Porous Chitosan/Polyacrylic acid Microspheres
Authors: Peniche Carlos , Fernández Mar , Gallardo Alberto , López‐Bravo Antonio , Román Julio San 
Published: October 2003

AbstractPorous microspheres have been prepared by suspension free radical polymerization of acrylic acid (AA) in the presence of chitosan (CHI). The microspheres were characterized by FTIR and environmental SEM. The PAA content of the microspheres was estimated to be in the range 45–50 wt.‐%. The swelling degree of these particles is almost constant in the range 2 < pH < 5, but it increases considerably as the pH is raised from 5 to 10. The release profiles of microspheres loaded with meclofenamic acid (MF) were determined at pH 2, 7.4, and 10. The in vitro release of MF at different pHs was modulated by the solubility of the drug. These microcapsules are biodegradable and presented good biocompatibility and biodegradability during in vivo experiments.ESEM microphotograph of the porous PAA/CHI microspheres.magnified imageESEM microphotograph of the porous PAA/CHI microspheres.
Effect of Chitosan and Temperature on Spore Germination of Aspergillus niger
Authors: Plascencia‐Jatomea Maribel , Viniegra Gustavo , Olayo Roberto , Castillo‐Ortega Maria Monica , Shirai Keiko 
Published: October 2003

AbstractInhibition of radial growth and spore germination of Aspergillus niger in media with added chitosan were detected. The highest radial growth inhibition (73%) was determined at 24 h with 3 g · L−1 of chitosan, and the percent inhibition of spore germination was 40% after 13 h of inoculation. Further, the CC50, that is, the concentration at which spore germination is inhibited by 50%, was estimated by probit analysis (3.5 g · L−1). The activation energies, EA were estimated by an Arrhenius model in control and amended chitosan media, obtaining 35.6 and 36.6 kcal · mol−1, respectively. These values were in the same order of magnitude because chitosan as inhibitor was more effective at low temperature (≤ 18 °C). Hence synergism of temperature and chitosan were only observed at 12 and 18 °C. Therefore, the maximal percentage of germinated spores, Smax was also affected by low temperatures in chitosan‐amended media with estimated values lower than 70% at temperatures < 37 °C whereas in control media Smax reached values close to 100%. Scanning electron micrographs showed that chitosan produced spore aggregation and morphological anomalies affecting swelling, germ tube emergence, and polarization.Germinated spores percentages of Aspergillus niger in Czapeck media at several chitosan concentrations and 30 °C.magnified imageGerminated spores percentages of Aspergillus niger in Czapeck media at several chitosan concentrations and 30 °C.