bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of ring‐opening polymerization of genipin and pH‐dependent cross‐linking reactions between chitosan and genipin
Authors: Mi Fwu‐Long , Shyu Shin‐Shing , Peng Chih‐Kang 
Published: March 2005

AbstractIn this study, a novel chitosan‐based polymeric network was synthesized by crosslinking with a naturally occurring crosslinking agent—genipin. The results showed that the crosslinking reactions were pH‐dependent. Under basic conditions, genipin underwent a ring‐opening polymerization prior to crosslinking with chitosan. The crosslink bridges consisted of polymerized genipin macromers or oligomers (7 ∼ 88 monomer units). This ring‐opening polymerization of genipin was initiated by extracting proton from the hydroxyl groups at C‐1 of deoxyloganin aglycone, followed by opening the dihydropyran ring to conduct an aldol condensation. At neutral and acidic conditions, genipin reacted with primary amino groups on chitosan to form heterocyclic amines. The heterocyclic amines were further associated to form crosslinked networks with short chains of dimmer, trimer, and tetramer bridges. An accompanied reaction of nucleophilic substitution of the ester group on genipin by the primary amine group on chitosan would occur in the presence of an acid catalysis. The extent in which chitosan gels crosslinked with genipin was significantly dependent on the crosslinking pH values: 39.9 ± 3.8% at pH 5.0, 96.0 ± 1.9% at pH 7.4, 45.4 ± 1.8% at pH 9.0, and 1.4 ± 1.0% at pH 13.6 (n = 5, p < 0.05). Owing to the different crosslinking extents and different chain lengths of crosslink bridges, the genipin‐crosslinked chitosan gels showed significant difference in their swelling capability and their resistance against enzymatic hydrolysis, depending on the pH conditions for crosslinking. These results indicated a direct relationship between the mode of crosslinking reaction, and the swelling and enzymatic hydrolysis properties of the genipin‐crosslinked chitosan gels. The ring‐opening polymerization of genipin and the pH‐dependent crosslinking reactions may provide a novel way for the preparation and exploitation of chitosan‐based gels for biomedical applications. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1985–2000, 2005
Reversible addition–fragmentation chain transfer polymerization of methyl methacrylate in suspension
Authors: Biasutti John D. , Davis Thomas P. , Lucien Frank P. , Heuts Johan P. A. 
Published: March 2005

AbstractThe reversible addition–fragmentation chain transfer polymerization of methyl methacrylate mediated by 2‐cyanoprop‐2‐yl dithiobenzoate (CPDB) in bulk (60 and 70 °C) and suspension (70 °C) was studied, and in both polymerization systems, a good control of the molecular weight and polydispersity was observed. Stable suspension polymerizations were carried out over a range of CPDB concentrations, and with increasing CPDB concentration, the particle size and polydispersity index of the produced polymer decreased. The former was ascribed to the lower viscosities of the monomer and polymer droplets at low conversions, which caused easier breakup with the applied shear stresses. Lower polydispersity indices at higher CPDB concentrations were probably caused by a diminished gel effect, which was observed at lower CPDB concentrations at high conversions, causing a broadening of the molecular weight distribution. The livingness of the polymers formed in suspension was proven by successful chain extensions with methyl methacrylate, styrene, and 2‐hydroxyethyl methacrylate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2001–2012, 2005
Synthesis of poly(arylene thioether)s from protected dithiols and aromatic difluorides with an organic base
Authors: In Insik , Kim Sang Youl 
Published: March 2005

AbstractAromatic poly(arylene thioether)s were synthesized from N‐propyl‐S‐carbamate‐protected aromatic dithiols and aromatic difluorides. The deprotection of the protected dithiols with an organic base such as 1,8‐diazabicyclo[5.4.0]‐7‐undecene at room temperature and subsequent polymerization with the difluoride monomers at 120 °C in N‐methyl‐2‐pyrrolidinone produced high molecular weight polymers with intrinsic viscosities as high as 0.45 dL/g. The use of organic bases instead of inorganic bases for the generation of thiophenoxide nucleophile was a convenient way of avoiding metallic impurities in the synthesis of the poly(arylene thioether)s through a nucleophilic aromatic substitution reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2021–2027, 2005
Alkali metal salt‐catalyzed aldol addition of dimethylsilyl enolate on a polyether structure
Authors: Yamamoto Shin‐Ichi , Morita Hidehiko , Hayashi Sachika , Moriya Osamu 
Published: March 2005

AbstractThe aldol addition of dimethylsilyl enolates to aldehydes with alkali metal salt catalysts was examined. Several kinds of polyether derivatives were employed as solid solvents without a liquid one. In the presence of the polymer (Gr) obtained from poly(ethylene glycol) methyl ether methacrylate (PEGMA) or the crosslinked derivatives (GLs) from PEGMA, the aldol addition proceeded efficiently and yielded the product. The effective catalyst was lithium bromide for Gr and potassium bromide for GLs. The crosslinked polyether GLs were easily separated from the reaction mixture by simple filtration, which was preferable to simplifying the treatments of the reaction. The results demonstrated that the presence of polyether structures provided a favorable reaction environment and enabled the reaction under solvent‐free conditions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2075–2084, 2005
Investigation of Rayleigh wave attenuation via annular lenses in acoustic microscopy
Authors: Bouhedja S. , Hadjoub I. , Doghmane A. , Hadjoub Z. 
Published: March 2005

AbstractUsing annular lenses in scanning acoustic microscopy, the attenuation coefficients for several materials were determined from the calculated V(z) interference‐free curves. The dependence of such coefficients on Rayleigh velocities as well as on operating frequencies was then investigated to establish empirical relations between these parameters. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of grain size on reversible and irreversible domain wall displacements in La0.7Sr0.3MnO3 perovskite
Authors: Wang Jinhui , Liu Gongqiang , Jiang Xiaolong , Du Youwei 
Published: March 2005

AbstractIn this work, the permeability spectra of La0.7Sr0.3MnO3 perovskite with mean grain size (D) ranging from 1200 to 45 nm have been investigated at 293 K. The spectra exhibit a typical relaxation, relating to reversible domain wall motions. The quasi‐static permeability (μe) decreases from 87 to 11 with D, while relaxation frequency fr increases from 205 kHz to 231 MHz. As the amplitude of the ac field h0 exceeds the domain wall pinning field hp, irreversible domain wall motions will be activated. The increments of permeability with increasing h0 can be explained using the Rayleigh law. With reducing D from 1200 to 140 nm, hp increases from 1.8 to 2.3 A/m and the Rayleigh constant decreasing from 2.15 × 10–1 to 4.66 × 10–2 (A/m)–1. The grain size dependence of μe and fr has been discussed related to the demagnetizing field induced by distributed air gaps between grains. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect states in CdSe nanocrystalline layers
Authors: Nesheva D. , Reynolds S. , Main C. , Aneva Z. , Levi Z. 
Published: March 2005

AbstractDefect states and recombination processes are investigated in SiOx/nanocrystalline CdSe multilayer and composite films, and CdSe single films, using steady‐state and transient photoconductivity and thermally‐stimulated current measurements. A reduction in mobility‐lifetime product as layer thickness is reduced is assigned to increased deep defect density at the nanocrystal surface. Transient photocurrent falls rapidly at typically 0.1 µs as carriers are trapped in deep states, and then continues to fall as a power law of index close to –1. At elevated temperatures, the transient current in multilayer films falls below the steady‐state dark current. This is explained by the effect of potential barrier profiles on recombination. The density of states distribution obtained is fairly broad in multilayers and composite films while in single layer films it is noticeably peaked. Two defect bands located at 0.55 and 0.7 eV below the conduction band edge are identified, the former associated with the nanocrystal bulk and the latter with the CdSe–CdSe interface. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum cascade lasers based on quantum dot superlattice
Authors: Dmitriev Ivan A. , Suris Robert A. 
Published: March 2005

AbstractA theory of threshold characteristics of novel quantum cascade lasers with an active medium made of a regular array of quantum dots is presented. Very low threshold current density for the room‐temperature operation is predicted. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the annealing temperature on the optical transitions of InGaAsP‐based quantum well structures investigated by photoreflectance spectroscopy
Authors: Podhorodecki A. , Kudrawiec R. , Andrzejewski J. , Misiewicz J. , Wojcik J. , Robinson B. J. , Thompson D. A. , Mascher P. 
Published: March 2005

AbstractPhotoreflectance (PR) and photoluminescence (PL) spectroscopies have been used to study the effect of the rapid thermal annealing (RTA) on InGaAsP‐based quantum wells (QWs) which are the active part of a laser structure tailored at 1.5 µm. In the case of PL, it has been observed that the RTA enhances PL intensity and tunes the emission wavelength of the laser structure to blue. In case of PR due to its absorption character, we were able to study QW transitions related to excited states, besides the fundamental transition observed in PL. In addition, optical transitions related to other part of the laser structure have been observed in PR. It has been shown that there exists a “critical” annealing temperature (720 °C) where the energy shift appears. We have observed a blueshift for both the ground and excited state transitions, but in the case of the ground state transitions the blueshift has been found to be bigger. The magnitude of this blueshift has been found to change linearly from 0 to ∼15 meV with the rise of temperature from 720 to 780 °C. Below 720 °C no significant change in the energy of the QW transitions is observed. In the case of PR transitions related to the other part of the laser structure, i.e., the quaternary InGaAsP barriers, it has been observed that after annealing PR features associated with these layers rather do not shift, they change only their line‐shape. Also, it has been shown that RTA does not destroy the optical quality of the samples. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inhibitory effects of stilbenes in Sophora moorcroftiana BENTH ex BAKER on copper ion‐induced protein oxidative modification of mouse brain homogenate in vitro
Authors: Toda Shizuo , Shirataki Yoshiaki 
Published: March 2005

AbstractWe present the results of an in vitro investigation of the inhibitory effects of sophorastilbene A and (+)‐α‐viniferin isolated from Sophora moorcroftiana BENTH ex BAKER on copper ion‐induced protein oxidative modification. They inhibited copper‐induced protein oxidative modification. The order of these stilbenes and mannitol as a hydroxyl radical scavenger was sophorastilbene A > (+)‐α‐viniferin > mannitol. Copyright © 2005 John Wiley & Sons, Ltd.
Antiallergic and antihistaminic effect of two extracts of Capparis spinosa L. flowering buds
Authors: Trombetta Domenico , Occhiuto Francesco , Perri Daniela , Puglia Carmelo , Santagati Natale A. , Pasquale Anna De , Saija Antonella , Bonina Francesco 
Published: March 2005

AbstractThe antiallergic properties of two lyophilized extracts obtained from Capparis spinosa L. flowering buds (capers) by methanol extraction, carried out at room temperature (CAP‐C) or with heating at 60 °C (CAP‐H), were investigated.The protective effects of CAP‐H and CAP‐C, orally administered (14.28 mg[sol ]kg), were evaluated against Oleaceae antigen challenge‐induced and histamine‐induced bronchospasm in anaesthetized guinea‐pigs. Furthermore, the histamine skin prick test was performed on humans, applying a gel formulation containing 2% CAP‐C (the only extract able to protect against histamine‐induced bronchospasm) on the skin for 1 h before histamine application and monitoring the erythema by reflectance spectrophotometry.The CAP‐H showed a good protective effect against the bronchospasm induced by antigen challenge in sensitized guinea‐pigs; conversely, a significant decrease in the responsiveness to histamine was seen only in CAP‐C pretreated animals. Finally, the CAP‐C gel formulation possessed a marked inhibitory effect (46.07%) against histamine‐induced skin erythema.These two caper extracts displayed marked antiallergic effectiveness; however, the protective effect of CAP‐H was very likely due to an indirect mechanism (for example, inhibition of mediator release from mast cells or production of arachidonic acid metabolites); conversely, CAP‐C is endowed with direct antihistaminic properties. The different mechanisms of action of CAP‐H and CAP‐C may be related to a difference in the extraction procedure and, thus, in their qualitative[sol ]quantitative chemical profile. Copyright © 2005 John Wiley & Sons, Ltd.
Radioprotection by plant products: present status and future prospects
Authors: Arora Rajesh , Gupta Damodar , Chawla Raman , Sagar Ravinder , Sharma Ashok , Kumar Raj , Prasad Jagdish , Singh Surinder , Samanta Namita , Sharma Rakesh Kumar 
Published: March 2005

AbstractThe development of radioprotective agents has been the subject of intense research in view of their potential for use within a radiation environment, such as space exploration, radiotherapy and even nuclear war. However, no ideal, safe synthetic radioprotectors are available to date, so the search for alternative sources, including plants, has been on going for several decades. In Ayurveda, the traditional Indian system of medicine, several plants have been used to treat free radical‐mediated ailments and, therefore, it is logical to expect that such plants may also render some protection against radiation damage. A systematic screening approach can provide leads to identifying potential new candidate drugs from plant sources, for mitigation of radiation injury. This article reviews some of the most promising plants, and their bioactive principles, that are widely used in traditional systems of medicine, and which have rendered significant radioprotection in both in vitro and in vivo model systems. Plants and their constituents with pharmacological activities that may be relevant to amelioration of radiation‐mediated damage, including antiemetic, antiinflammatory, antioxidant, cell proliferative, wound healing and haemopoietic stimulatories are also discussed. Copyright © 2005 John Wiley & Sons, Ltd.
Bioactive triterpenoids from Vochysia pacifica interact with cyclic nucleotide phosphodiesterase isozyme PDE4
Authors: Weniger Bernard , Lobstein Annelise , Um Byung‐Hun , Vonthron‐Sénéchau Catherine , Anton Robert , Usuga Nora Jiménez , Basaran Hélène , Lugnier Claire 
Published: March 2005

AbstractSeveral species of the genus Vochysia (Vochysiaceae) are used by traditional communities in South America to relieve ailments linked to inflammation, such as skin sores, asthma and pulmonary congestion. As the cAMP phosphodiesterase 4 isozyme (PDE4) is currently considered as an intracellular target for new antiinflammatory drugs, several constituents of Vochysia pacifica Cuatrec., an endemic tree from the Western coast of Colombia, were tested for their ability to inhibit PDE4. Purification of the methanol extract of the stem bark of this species led to the isolation of seven known triterpene derivatives: betulinic acid, sericic acid, 24‐hydroxytormentic acid, trachelosperogenin B, 24‐hydroxytormentic acid glucosyl ester, quadranoside I and niga‐ichigoside F1. One triterpene glycoside, quadranoside I, and two triterpenes, betulinic and sericic acids, exhibited mild inhibitory activity on the isolated PDE4 isozyme. Copyright © 2005 John Wiley & Sons, Ltd.
Potential biomedical properties of Pinus massoniana bark extract
Authors: Cui Yingyu , Xie Heng , Wang Jinfa 
Published: March 2005

AbstractThis study examined the potential biomedical properties of a bark extract from Pinus massoniana Lamb (PMBE). Its antioxidant activity, superoxide anion radical scavenging and free radical scavenging activities were examined. The antioxidant activity in a linoleic acid emulsion increased with increasing amounts of PMBE, with 100, 300 and 500 µg PMBE inhibiting 64.7%, 68.6% and 76.6% of peroxidation, respectively. Similarly, the radical scavenging activity by PMBE increased in a dose‐dependent manner, suggesting that there may be a correlation between the antioxidant and scavenging activities. In addition, the effect of PMBE on human hepatocellular carcinoma BEL‐7402 cells and normal liver L‐02 cells was investigated in vitro. PMBE appeared to inhibit selectively the growth of BEL‐7402 and slightly promoted the growth of L‐02. Taken together, the results indicate that PMBE is a natural antioxidant that could potentially be used as a food supplement or as a candidate precursor substance for new anticancer therapeutics. Copyright © 2005 John Wiley & Sons, Ltd.
Reversal of LPS‐induced central and peripheral hyperalgesia by green tea extract
Authors: Kaur Surinder , Anurag A. , Tirkey Naveen , Chopra Kanwaljit 
Published: March 2005

AbstractTea has recently attracted a great deal of attention for its beneficial health effects. Green tea polyphenols inhibit the production of arachidonic acid metabolites and leukotrienes resulting in decreased inflammatory responses. In the present study, the effect of green tea extract (GTE) on lipopolysaccharide (LPS)‐induced thermal and behavioural hyperalgesia in mice and the possible involvement of the cyclooxygenase pathway in this paradigm was evaluated. GTE (25 mg[sol ]kg, i.p.), nimesulide (2 mg[sol ]kg, i.p.) and rofecoxib (2 mg[sol ]kg, i.p.) significantly attenuated LPS‐induced thermal and behavioural hyperalgesia but per se did not modify any of the behavioural effects. Concurrent administration of a subeffective dose of GTE (10 mg[sol ]kg, i.p.) and rofecoxib (2 mg[sol ]kg, i.p.) or nimesulide (2 mg[sol ]kg, i.p.) significantly potentiated the antinociceptive effect of GTE in both LPS‐induced thermal and behavioural hyperalgesia with nimesulide showing a more pronounced enhancing effect. Thus it can be concluded that GTE attenuates LPS‐induced central and peripheral hyperalgesia by selective inhibition of cyclooxygenase‐2 enzyme. Copyright © 2005 John Wiley & Sons, Ltd.
BSSE‐corrected geometry and harmonic and anharmonic vibrational frequencies of formamide–water and formamide–formamide dimers
Authors: Bende A. , Suhai S. 
Published: March 2005

AbstractThe basis set superposition error (BSSE) influence in the geometry structure, interaction energies, and intermolecular harmonic and anharmonic vibrational frequencies of cyclic formamide–formamide and formamide–water dimers have been studied using different basis sets (6‐31G, 6‐31G**, 6‐31++G**, D95V, D95V**, and D95V++**). The a posteriori “counterpoise” (CP) correction scheme has been compared with the a priori “chemical Hamiltonian approach” (CHA) both at the Hartree–Fock (HF) and second‐order Møller–Plesset many‐body perturbation (MP2) levels of theory. The effect of BSSE on geometrical parameters, interaction energies, and intermolecular harmonic vibrational frequencies are discussed and compared with the existing experimental data. As expected, the BSSE‐free CP and CHA interaction energies usually show less deep minima than those obtained from the uncorrected methods at both the HF and MP2 levels. Focusing on the correlated level, the amount of BSSE in the intermolecular interaction energies is much larger than that at the HF level, and this effect is also conserved in the values of the force constants and harmonic vibrational frequencies. All these results clearly indicate the importance of the proper BSSE‐free correlation treatment with the well‐defined basis functions. At the same time, the results show a good agreement between the a priori CHA and a posteriori CP correction scheme; this agreement is remarkable in the case of large and well‐balanced basis sets. The anharmonic frequency correction values also show an important BSSE dependence, especially for hydrogen bond stretching and for low frequencies belonging to the intermolecular normal modes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Amide I IR, VCD, and 2d IR spectra of isotope‐labeled α‐helix in liquid water: Numerical simulation studies
Authors: Choi Jun‐Ho , Hahn Seungsoo , Cho Minhaeng 
Published: March 2005

AbstractAmide I infrared (IR), vibrational circular dichroism (VCD), and two‐dimensional IR (2D IR) spectra of various isotope‐labeled α‐helical polyalanines in liquid water were theoretically calculated by combining semiempirical quantum chemistry calculation, Hessian matrix reconstruction, fragmentation approximation, and molecular dynamics simulation methods. The solvation‐induced amide I frequency shift was found to be about −20 cm−1. Properly taking into account the motional narrowing effect in the ensemble averaging, we show that the simulated IR, VCD, and 2D IR spectra are quantitatively in good agreement with experimental results. Depending on the relative positions of the 13C and/or 13C18O labeled peptides in a given α‐helix, the IR absorption line shape, IR intensity distribution, positive‐negative VCD pattern, and diagonal/off‐diagonal 2D IR echo spectral features were found to change dramatically. It is shown that these different spectroscopic observations can be described in a consistent manner by using the present simulation method. We will show that the properly designed isotopomers and their IR, VCD, and 2D IR spectrum analyses can provide incisive information on the three‐dimensional polypeptide structure and dynamics. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Conformational and vibrational study of di‐n‐propyl and di‐i‐propylphosphonates by MM/QM method
Authors: Carauta Alexandre N. M. , Walkimar de M. Carneiro José , Téllez Soto Claudio A. 
Published: March 2005

AbstractA conformational search by MM/QM methods was realized for the di‐n‐propyl and di‐i‐propylphosphonates. The normal mode frequencies and corresponding vibrational assignments were examined theoretically using the hybrid functional B3LYP and the 6‐31G* basis set, and were compared with the experimental spectra. It was possible to arrive at an accurate spectral assignment without the utilization of scaling factors including the region between 1,200 and 850 cm−1, which is the most complicated spectral region for the assignment. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005