bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of hydroxyl‐terminated copolymer of styrene and 4‐vinylpyridine via nitroxide‐mediated living radical polymerization
Authors: Chen Zhijun , Wang Yuan , Feng Yan , Jiang Xiqun , Yang Changzheng , Wang Mu 
Published: December 2003

AbstractThe random copolymers of styrene (St) and 4‐vinylpyridine (4‐VP) with hydroxyl end group and low polydispersities were synthesized by nitroxide‐mediated living radical polymerization initiated by azobisisobutyronitrile (AIBN) and 4‐hydroxyl‐2,2,6,6–tetramethylpiperidine‐oxyl (TEMPO‐OH). The experimental results have shown that all synthesized copolymers have narrow molecular weight distribution. The conversion of monomers and the molecular weight of copolymer increased with polymerization time. The copolymerization rate is affected by molar ratios of HTEMPO to AIBN. 1H‐Nuclear magnetic resonance spectra shows that one end of copolymers was capped by TEMPO‐OH moiety. The use of this method permits the copolymer with hydroxyl chain end and controllable molecular weight and molecular weight distribution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1842–1847, 2004
Effect of a natural magnesium silicate treated with a new coupling agent on the properties of ethylene–propylene–diene rubber compounds
Authors: López Valentín J. , Rodríguez Díaz A. , Ibarra Rueda L. , González Hernández L. 
Published: December 2003

AbstractThe behavior of sepiolite (magnesium silicate with a microfibrillar morphology) as a filler in ethylene–propylene–diene compounds was studied. A new coupling agent, meta‐isopropenyl dimethyl benzyl isocyanate, was used. The effect of the filler modified by meta‐isopropenyl dimethyl benzyl isocyanate on the physical properties was improved with respect to other fillers and commercial silane coupling agents under the same conditions. In addition to a smoother surface, the flow behavior of compounds filled with sepiolite, on account of its fibrous morphology, was better than that obtained with other fillers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1489–1493, 2004
Synthesis and characterization of biodegradable low molecular weight aliphatic polyesters and their use in protein‐delivery systems
Authors: Zhou Shaobing , Deng Xianmo , Li Xiaohong , Jia Wenxiang , Liu Li 
Published: December 2003

AbstractPoly(lactic acid) (PLA) and poly(lactic‐co‐GA) (PLGA) with low molecular weights were synthesized by a one‐step polycondensation of lactic acid (LA) with glycolic acid (GA) molecules using stannous octoate as a catalyst at 160°C. A high yield (>80%) of all the polymers was obtained in the study. The PLA and PLGA copolymers were characterized by 1H‐NMR, GPC, and DSC measurements, etc. We elaborated HSA‐loaded microspheres based on PLA and PLGA copolymers with different monomer ratios (LA/GA = 85:15, 75:25, 65:35, and 50:50) by the solvent‐extraction method based on the formation of double w/o/w emulsion. Microspheres were characterized in terms of the morphology, size, and encapsulation efficiency (E.E.). The highest E.E. (69.3%) of HSA was obtained for HSA‐loaded PLGA (65/35) microspheres among all the formulations. In vitro matrix degradation and protein release of these microspheres were performed in phosphate‐buffer saline (PBS; 154 mM, pH 7.4). The degradation profiles were characterized by measuring the loss of the microsphere mass and the decrease of the polymer intrinsic viscosity. The release profiles were investigated from the measurement of the protein presented in the release medium at various intervals. It was shown that the matrix degradation and protein‐release profiles were highly LA/GA ratio‐dependent. It is suggested that these matrix polymers may be optimized as carriers in protein‐ and peptide‐delivery systems for different purposes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1848–1856, 2004
Characterization of ramie yarn treated with sodium hydroxide and crosslinked by 1,2,3,4‐butanetetracarboxylic acid
Authors: Zhou L. M. , Yeung K. W. , Yuen C. W. M. , Zhou X. 
Published: December 2003

AbstractRamie yarns were treated with various concentrations of NaOH at room temperature and subsequently crosslinked with 1,2,3,4‐butanetetracarboxylic acid (BTCA). The microstructure and tensile properties of the treated yarns were characterized. X‐ray diffraction (XRD) and FTIR were used to study the crystalline structure of the resultant ramie yarns. The results showed that the maximum change in the structure of the alkali‐modified ramie took place at 16% NaOH, which would completely transform cellulose I to cellulose II. At the same time, the crystallinity index and fiber orientation decreased to the minimum value while the absorption properties were enhanced. The average degree of polymerization (DP) of the treated ramie yarns slightly decreased after NaOH treatment. Tensile properties including tenacity, breaking elongation, and modulus of the treated yarns were also investigated. Scanning electron microscopy (SEM) was used to investigate the breakage of the treated yarns. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1857–1864, 2004
Infrared spectroscopic studies of poly(methyl methacrylate) doped with a new sulfur‐containing ligand and its cobalt(II) complex during γ‐radiolysis
Authors: Sayyah S. M. , El‐Shafiey Z. A. , Barsoum B. N. , Khaliel A. B. 
Published: December 2003

AbstractInfrared (IR) spectroscopy studies were performed for poly(methyl methacrylate) (PMMA) samples doped with an organic ligand or its cobalt(II) complex after the extraction of the dopant during γ‐radiolysis. There were no drastic changes in the IR absorption band position, but noticeable changes in the intensities were found. The relative transmission of IR absorption bands, such as those at 750, 840, 1065, and 1388 cm−1, were measured according to the transmission of the carbonyl group band at 1717 cm−1. The degradation and recombination mechanism of different groups in the polymeric chain or backbone during radiolysis could be explained by the behavior of the relative transmission data for each group with increasing exposure dose. The tacticity of the PMMA samples was unchanged during radiolysis, and they were found to be syndiotactic. This was confirmed by the IR J values for different PMMA samples before and after irradiation. The protection efficiency of the organic ligand and its cobalt(II) complex was also investigated, and it was found that the organic ligand was more protective than the cobalt(II) complex for PMMA samples against γ‐rays. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1937–1950, 2004
Lignin–polypropylene composites. II. Plasma modification of kraft lignin and particulate polypropylene
Authors: Toriz G. , Ramos J. , Young R. A. 
Published: December 2003

AbstractIndulin kraft lignin and polypropylene were subjected to plasma treatments in a rotating electrodeless plasma reactor at 13.56 MHz radio frequency, with the goal of improving the strength properties of the composites made from these materials. It was shown that efficient surface modification could be achieved by these plasma treatments, avoiding long reaction times and large volumes of reactants for modification by conventional wet chemistry. SiCl4‐plasma treatments of lignin at 100 and 200 W resulted in silicon implantation in the range of 4–10% that depended on the treatment time. However, the effect of power in the treatments was minimal, given that changes in silicon implantation were not observed for changes in this parameter. SiCl4‐plasma treatment of polypropylene at 80 W, 1 and 10 min, resulted in silicon implantation in the order of 10–15%, for the two different treatment times, showing that low power and short treatment times were sufficient to significantly alter the polypropylene surface. However at high power (250 W), the longer treatment time of polypropylene apparently led to formation of oligohalosilanes. Other plasma treatments in the rotating reactor such as plasma‐induced copolymerization of acryloyl chloride on both lignin and polypropylene, and plasma‐state polymerization of acryloyl chloride on polypropylene under pulsing conditions, resulted in thin film depositions. Evaluation of composites from these treated materials is described in the next contribution (Part III) from this series. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1920–1926, 2004
An improved fast encoding algorithm for vector quantization
Authors: Liu Li‐Juan , Shen Xu‐Bang , Zou Xue‐Cheng 
Published: December 2003

AbstractIn the current information age, people have to access various information. With the popularization of the Internet in all kinds of information fields and the development of communication technology, more and more information has to be processed in high speed. Data compression is one of the techniques in information data processing applications and spreading images. The objective of data compression is to reduce data rate for transmission and storage. Vector quantization (VQ) is a very powerful method for data compression. One of the key problems for the basic VQ method, i.e., full search algorithm, is that it is computationally intensive and is difficult for real time processing. Many fast encoding algorithms have been developed for this reason. In this paper, we present a reasonable half‐L2‐norm pyramid data structure and a new method of searching and processing codewords to significantly speed up the searching process especially for high dimensional vectors and codebook with large size; reduce the actual requirement for memory, which is preferred in hardware implementation system, e.g., SOC (system‐on‐chip); and produce the same encoded image quality as full search algorithm. Simulation results show that the proposed method outperforms some existing related fast encoding algorithms.
Metadata‐based modeling of information resources on the Web
Authors: Özel S. Ayse , Altingövde I. Sengör , Ulusoy Özgür , Özsoyoǧlu Gültekin , Özsoyoǧlu Z. Meral 
Published: December 2003

AbstractThis paper deals with the problem of modeling Web information resources using expert knowledge and personalized user information for improved Web searching capabilities. We propose a “Web information space” model, which is composed of Web‐based information resources (HTML/XML [Hypertext Markup Language/Extensible Markup Language] documents on the Web), expert advice repositories (domain‐expert‐specified metadata for information resources), and personalized information about users (captured as user profiles that indicate users' preferences about experts as well as users' knowledge about topics).Expert advice, the heart of the Web information space model, is specified using topics and relationships among topics (called metalinks), along the lines of the recently proposed topic maps. Topics and metalinks constitute metadata that describe the contents of the underlying HTML/XML Web resources. The metadata specification process is semiautomated, and it exploits XML DTDs (Document Type Definition) to allow domain‐expert guided mapping of DTD elements to topics and metalinks. The expert advice is stored in an object‐relational database management system (DBMS).To demonstrate the practicality and usability of the proposed Web information space model, we created a prototype expert advice repository of more than one million topics/metalinks for DBLP (Database and Logic Programming) Bibliography data set. We also present a query interface that provides sophisticated querying facilities for DBLP Bibliography resources using the expert advice repository.
Visible, less visible, and invisible work: Patterns of collaboration in 20th century chemistry
Authors: Cronin Blaise , Shaw Debora , Barre Kathryn La 
Published: December 2003

AbstractWe chronicle the use of acknowledgments in 20th century chemistry by analyzing and classifying over 2,000 specimens covering a 100‐year period. Our results show that acknowledgment has gradually established itself as a constitutive element of academic writing—one that provides a revealing insight into the structural nature of subauthorship collaboration in science. Complementary data on rates of coauthorship are also presented to highlight the growing importance of teamwork and the increasing division of labor in contemporary chemistry. The results of this study are compared with the findings of a parallel study of collaboration in both the social sciences and the humanities.
Does citation reflect social structure?: Longitudinal evidence from the “Globenet” interdisciplinary research group
Authors: White Howard D. , Wellman Barry , Nazer Nancy 
Published: December 2003

AbstractMany authors have posited a social component in citation, the consensus being that the citers and citees often have interpersonal as well as intellectual ties. Evidence for this belief has been rather meager, however, in part because social networks researchers have lacked bibliometric data (e.g., pairwise citation counts from online databases), and citation analysts have lacked sociometric data (e.g., pairwise measures of acquaintanceship). In 1997 Nazer extensively measured personal relationships and communication behaviors in what we call “Globenet,” an international group of 16 researchers from seven disciplines that was established in 1993 to study human development. Since Globenet's membership is known, it was possible during 2002 to obtain citation records for all members in databases of the Institute for Scientific Information. This permitted examination of how members cited each other (intercited) in journal articles over the past three decades and in a 1999 book to which they all contributed. It was also possible to explore links between the intercitation data and the social and communication data. Using network‐analytic techniques, we look at the growth of intercitation over time, the extent to which it follows disciplinary or interdisciplinary lines, whether it covaries with degrees of acquaintanceship, whether it reflects Globenet's organizational structure, whether it is associated with particular in‐group communication patterns, and whether it is related to the cocitation of Globenet members. Results show cocitation to be a powerful predictor of intercitation in the journal articles, while being an editor or coauthor is an important predictor in the book. Intellectual ties based on shared content did better as predictors than content‐neutral social ties like friendship. However, interciters in Globenet communicated more than did noninterciters.
Malformations following methimazole exposure in utero: An open issue
Authors: Ferraris Silvio , Valenzise Mariella , Lerone Margherita , Divizia Maria Teresa , Rosaia Lucia , Blaid Dario , Nemelka Odette , Ferrero Giovanni Battista , Silengo Margherita 
Published: December 2003

AbstractBACKGROUNDIn hyperthyroidism‐complicated pregnancies, medical therapy is necessary to reach an euthyroid condition, and propylthiouracil (PTU) or methimazole (MMI) are used. These drugs are equally effective, but may cause fetal and neonatal hypothyroidism because they freely cross the placenta. Although PTU has not been significantly associated with embryo‐fetal anomalies, it has been suggested that MMI might be responsible for a specific embryopathy.CASE(S)Two cases of major congenital anomalies after MMI exposure during pregnancy are reported.CONCLUSIONSPTU should be the drug of choice, and the use of MMI should be restricted to cases with allergic reactions, intolerance, or poor response to PTU. Birth Defects Research (Part A), 2003. © 2003 Wiley‐Liss, Inc.
Multiple congenital anomalies associated with in utero exposure of phenytoin: Possible hypoxic ischemic mechanism?
Authors: Lyon Helen M. , Holmes Lewis B. , Huang Taosheng 
Published: December 2003

AbstractBACKGROUNDThe characteristics of the phenotype of the malformed phenytoin‐exposed infant can help to clarify the mechanism of the drug's teratogenesis. One postulated mechanism is vascular disruption.CASEAn infant who was exposed to phenytoin as monotherapy throughout pregnancy was born with the following abnormalities: midface hypoplasia, digit hypoplasia with syndactyly in the hands and feet, meningomyelocele, talipes equinovarus, and a long skin pedicle on the back. The mother was also exposed to cigarette smoking and alcohol during the pregnancy.CONCLUSIONSThe malformations of the hands and feet, and the talipes deformity are potential effects of vascular disruption, a postulated fetal effect of both phenytoin and cigarette smoking. The mechanism of the teratogenicity of phenytoin may have included episodes of bradyarrhythmia in the fetus; however, no such episodes were documented. Birth Defects Research (Part A) 67:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Puerto Rican primary physicians' knowledge about folic acid supplementation for the prevention of neural tube defects
Authors: Miranda Ana , Dávila Torres René R. , Gorrín Peralta José J. , Montes De Longo Idalina 
Published: December 2003

AbstractBACKGROUNDWe conducted a study of a group of primary physicians in Puerto Rico to evaluate their knowledge about folic acid supplementation to prevent neural tube defects.METHODThe study design was transverse‐correlational. A total of 66 primary physicians in two hospitals (public and private) participated in the study. The sample was nonrandom and opportunistic, and only those physicians present in the hospitals at the moment of distribution of the questionnaires participated. A self‐administered and anonymous questionnaire was used. Descriptive statistics and cross‐tabular analysis were used to describe the results of this study. Inferential statistics were also used, including Chi square and t‐tests to establish the associations/differences between physician knowledge and the independent variables.RESULTSOf the participants, 87.9% demonstrated an inadequate knowledge about folic acid supplementation for the prevention of neural tube defects as part of preconception care and only 12.1% demonstrated adequate knowledge. Older physicians had greater knowledge about folic acid. Also, women demonstrated greater knowledge about folic acid than did men. Most of the physicians who always recommend supplementation to their patients demonstrated a greater knowledge about folic acid, and all participants with adequate knowledge came from the public hospital.CONCLUSIONSDespite a concerted effort by the Health Department of Puerto Rico to provide education in the importance of folic acid supplementation to reduce the incidence of neural tube defects, primary physicians in two Puerto Rican hospitals generally have not availed themselves of this training and showed a lack of knowledge on this important clinical issue. Birth Defects Research (Part A) 67:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Otto von Guericke und die Kosmologie im 17.?Jahrhundert
Authors: Knobloch Eberhard 
Published: December 2003

AbstractOtto von Guericke's scientific method was based on reason and experimental science. His cosmology was embedded in theology and can be interpreted as a refutation of Descartes's worldview. He used Nicolaus Cusanus's theory of quantities in order to characterize the space. The notion of space has to be distinguished from that of world or heaven. Forces play a crucial role in this respect described by Kircher in his ‘Celestial journey’. Guericke read this work very diligently. In spite of some obvious similarities between Guericke's and Newton's scientific aims and methods there are crucial differences between the scientific convictions and results of these scholars.
In Situ Investigations of Structure–Activity Relationships in Heteropolyoxomolybdates as Partial Oxidation Catalysts
Authors: Wienold Julia , Timpe Olaf , Ressler Thorsten 
Published: December 2003

AbstractThe structural evolution of Keggin‐type heteropolyoxomolybdates (HPOM) during thermal treatment in propene and in propene and oxygen in the temperature range from 300 to 773 K was investigated by in situ X‐ray diffraction (XRD) and in situ X‐ray absorption spectroscopy (XAS) combined with mass spectrometry. During treatment in propene or hydrogen and at reaction temperatures above 673 K, the initially triclinic H3[PMo12O40]⋅13 H2O is transformed quantitatively into a cubic HPOM (Pn$\bar 3$m, a=11.853 Å) exhibiting a long‐range structure similar to that of the corresponding cesium salts. The treatment described constitutes the first readily available preparation route for a cubic HPOM without alkali metal ions in the structure. For both H3[PMo12O40] and Cs2H[PMo12O40] migration of molybdenum from the Keggin ion onto interstitial sites is proposed to occur in propene or hydrogen at temperatures above about 573 K to give thermally stable, partially reduced lacunary Keggin ions. During activation in propene and oxygen the onset of catalytic activity of H3[PMo12O40] and Cs2H[PMo12O40] at about 573 K correlates with partial reduction of Mo and characteristic changes in the local structure of the Keggin ion. The structural changes observed indicate that, similar to the treatment of the HPOM in propene, migration of molybdenum from the Keggin ions onto interstitial sites and formation of lacunary Keggin ions take place. Moreover, the formation of these partially reduced lacunary Keggin ions appears to be a prerequisite for the material to become an active heterogeneous catalyst. Evidently, the undistorted Keggin ion in the as‐prepared HPOM has to be regarded as a precursor of the active catalyst.
Assembled Dendritic Titanium Catalysts for Enantioselective Hetero‐Diels–Alder Reaction of Aldehydes with Danishefsky's Diene
Authors: Ji Baoming , Yuan Yu , Ding Kuiling , Meng Jiben 
Published: December 2003

AbstractA new type of dendritic 2‐amino‐2′‐hydroxy‐1,1′‐binaphthyl (NOBIN)‐derived Schiff‐base ligands have been synthesized and applied to the titanium‐catalyzed hetero‐Diels–Alder reaction of Danishefsky's diene with aldehydes. These reactions afforded the corresponding 2‐substituted 2,3‐dihydro‐4H‐pyran‐4‐ones in quantitative yields and with excellent enantioselectivities (up to 97.2 % ee). The disposition of the dendritic wedges and the dendron size in the ligands were found to have significant impact on the enantioselectivity of the reaction. The recovered dendritic catalyst could be reused without further addition of the Ti source or a carboxylic acid additive for at least three cycles, retaining similar activity and enantioselectivity. The high stability of this type of assembled dendritic titanium catalyst may be attributed to the stabilization effect of large‐sized dendron units in the catalyst molecule. The other important phenomenon observed with this catalyst system is that a higher degree of asymmetric amplification has been achieved by attachment of the dendron unit to the chiral ligand, which represents a new advantage of dendrimer catalysts for asymmetric reactions using chiral ligands of lower optical purity.
Palladium‐Catalyzed Highly Regio‐ and Stereoselective Addition of Organoboronic Acids to Allenes in the Presence of AcOH
Authors: Ma Shengming , Jiao Ning , Ye Longwu 
Published: December 2003

AbstractThe Pd0‐catalyzed regio‐ and stereoselective addition of organoboronic acids to allenes leads to stereodefined tri‐ or tetrasubstituted alkenes. Furthermore, this method shows high substitutent‐loading capability and tolerance of various substitutents. A hydropalladation–Suzuki coupling mechanism, which may account for the regio‐ and stereoselectivity, is proposed.