bluuebunny/crossref_metadata_2025_split huggingface dataset:
Macrocycles, 22
Authors: Kricheldorf Hans R. , Schwarz Gert , Böhme Sigrid , Schultz Claus‐Ludolf , Wehrmann Rolf 
Published: July 2003

AbstractThe phosgenation of bisphenol A with diphosgene in the CH2Cl2/NaOH system was studied using the pseudo‐high‐dilution method either with triethylamine, with triethylbenzyl ammonium chloride (TEBA‐Cl), or with tetraphenylphosphonium chloride as catalyst. For Ph4PCl, only low‐molecular‐weight polycarbonates containing various by‐products were obtained. With the TEBA catalyst, the fraction of cycles and the average molecular weights increased with higher feed ratios of the catalyst. Both the fraction of cycles and the molecular weights steeply decreased at higher temperatures. With triethylamine as catalyst both the fraction of cycles and molecular weight passed through a maximum at low catalyst concentration, when the feed ratio of triethylamine was varied. Higher temperatures favored slightly lower fractions of cycles and lower molecular weights. Samples containing ≥ 95 mol‐% of cycles were obtained. The cycles were identified by matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectrometry up to 22 000 Da in the case of virgin samples, and up to 55 000 Da after fractionation by size exclusion chromatography (SEC). Selected samples were characterized by SEC measurements and evaluated by the triple‐detection method. High polydispersities and a tendency towards a bimodal mass distribution were found, when triethylamine was used as catalyst.MALDI‐TOF mass spectrum of a polycarbonate prepared by triethylamine‐catalyzed phosgenation at 20 °C by the pseudo‐high‐dilution method.magnified imageMALDI‐TOF mass spectrum of a polycarbonate prepared by triethylamine‐catalyzed phosgenation at 20 °C by the pseudo‐high‐dilution method.
Quantitative Correlation between Steric Defects and Thermal Behavior in Highly Syndiotactic Polystyrene: A Study Based on DSC and 13C NMR Spectroscopy
Authors: Abbondanza Luigi , Abis Luigi , Cardi Nicoletta , Garbassi Fabio , Po Riccardo 
Published: July 2003

AbstractSeveral syndiotactic polystyrene (sPS) samples have been synthesized by using different catalytic systems. Their stereochemistry has been determined by 13C NMR spectra in both the aliphatic CH2 and aromatic C1 resonance regions. The observed peaks have been unambiguously assigned to specific hexads and heptads, respectively, and their intensities have been used to draw the percent of defects (meso dyads) in the polymer chains. On the hypothesis that chain defects are at the origin of chain folding and thus determine the thickness of crystalline lamellae, we performed differential scanning calorimetry (DSC) analysis on the same samples, and their thermal parameters were measured. A model was developed to determine the amount of steric defects from the DSC melting‐peak profiles, and the results obtained were compared with the NMR results. A satisfactory agreement was found (correlation factor 0.96) in the explored range of defect concentrations (up to 2.5% of meso dyads). The possible influence of the extraction procedure of the amorphous fraction was found to be negligible. Thus, information on stereochemistry can be obtained from DSC experiments starting from as‐prepared (not extracted) samples.magnified image
TLB: An Experienced Consultant and Broker between Universities and Industry
Authors: Dubs Andreas 
Published: July 2003

AbstractThis section contains news of the macromolecular community all over the world. Articles about, for example, people, projects, and market trends are welcome. Suggestions should be sent to the editorial office of the Macromolecular journals, preferably by E‐mail to macromol@wiley‐vch.de. The editorial office decides which articles will be published.
Semiclassical resolvent estimates for Schrödinger matrix operators with eigenvalues crossing
Authors: Jecko Thierry 
Published: July 2003

AbstractFor semiclassical Schrödinger 2×2–matrix operators, the symbol of which has crossing eigenvalues, we investigate the semiclassical Mourre theory to derive bounds O(h−1) (h being the semiclassical parameter) for the boundary values of the resolvent, viewed as bounded operator on weighted spaces. Under the non–trapping condition on the eigenvalues of the symbol and under a condition on its matricial structure, we obtain the desired bounds for codimension one crossings. For codimension two crossings, we show that a geometrical condition at the crossing must hold to get the existence of a global escape function, required by the usual semiclassical Mourre theory.
On some new properties of the gamma function and the Riemann zeta function
Authors: Liao Liangwen , Yang Chung‐Chung 
Published: July 2003

AbstractIn this paper, we have exhibited, by utilizing value distribution theory, some new properties of the Gamma function Γ(z) and the Riemann zeta function ζ(z). Specifically, we have proved that both of the two functions are prime and the Riemann zeta function, like Γ(z), does not satisfy any algebraic differential equation with coefficients in ℒ︁0. Moreover, the two functions do not satisfy any functional equation of the form P(Γ, ζ, z) ≡ 0, where P(x, y, z) is a nonconstant polynomial in x, y and z.
Local solvability for semilinear Fuchsian equations
Authors: Messina Francesca 
Published: July 2003

AbstractWe consider a semilinear elliptic operator P on a manifold B with a conical singular point. We assume P is Fuchs type in the linear part and has a non–linear lower order therms. Using the Schauder fixed point theorem, we prove the local solvability of P near the conical point in the weighted Sobolev spaces.
On Osgood theorem in Banach spaces
Authors: Shkarin Stanislav 
Published: July 2003

AbstractLet X be a real Banach space, ω : [0, +∞) → ℝ be an increasing continuous function such that ω(0) = 0 and ω(t + s) ≤ ω(t) + ω(s) for all t, s ∈ [0, +∞). According to the infinite dimensional analog of the Osgood theorem if ∫10 (ω(t))−1 dt = ∞, then for any (t0, x0) ∈ ℝ×X and any continuous map f : ℝ×X → X such that ∥f(t, x) – f(t, y)∥ ≤ ω(∥x – y∥) for all t ∈ ℝ, x, y ∈ X, the Cauchy problem $\dot x$(t) = f(t, x(t)), x(t0) = x0 has a unique solution in a neighborhood of t0. We prove that if X has a complemented subspace with an unconditional Schauder basis and ∫10 (ω(t))−1 dt < ∞ then there exists a continuous map f : ℝ × X → X such that ∥f(t, x) – f(t, y)∥ ≤ ω(∥x – y∥) for all (t, x, y) ∈ ℝ × X × X and the Cauchy problem $\dot x$(t) = f(t, x(t)), x(t0) = x0 has no solutions in any interval of the real line.
On the structure of the solution set of a third kind boundary value problem
Authors: Takahasi Sin–Ei , Oka Hirokazu , Miura Takeshi 
Published: July 2003

AbstractWe show that given any closed subset C of a real Banach space E, there is a continuous function f(t, x) which is Lipschitz continuous in its second variable such that the solution set of the corresponding third kind boundary value problem is homeomorphic to C (Theorem 1.1). In the special problem we give the infimum of Lipschitz constants Lf of such functions f(t, x) (Theorem 1.3).
A meta‐analytic investigation of contrast effects in decision making
Authors: Conway Dato‐on Mary , Dahlstrom Robert 
Published: July 2003

AbstractSeveral theoretical perspectives and numerous experiments illustrate the influence of context on social judgment. Debate ensues, however, when researchers attempt to describe mechanisms that lead persons to contrast current decisions with prior judgments. The purpose of this study is to summarize and qualify prior analyses of the influences of context on judgment. Procedural conditions, stimuli type, and priming conditions are implicated as factors that moderate the main effect of extremity on contrastive judgments. Meta‐analytical methods assess the main effect and moderators of contrastive judgments. Discussion of the results focuses on the implications of the study for theory of contrastive judgments and strategy. © 2003 Wiley Periodicals, Inc.
Self‐assembly of metal‐organometallic coordination networks
Authors: Oh Moonhyun , Carpenter Gene B. , Sweigart Dwight A. 
Published: July 2003

AbstractA range of neutral metal‐organometallic coordination networks (MOMNs) containing both backbone and pendant metal sites have been synthesized and characterized. These materials consist of metal ions or metal ion clusters as nodes that are linked by the bifunctional “organometalloligand” (η4‐benzoquinone)Mn(CO)3−, which binds through the quinone oxygen atoms. The resulting MOMNs can be rationally designed to a significant extent based upon a knowledge of the electronic and geometrical requirements of the metal ion nodes, the solvent, organometalloligand substituents, and the presence or absence of organic spacers. An impressive range of architectures have been accessed in this manner, suggesting that the use of π‐organometallics in coordination directed self‐assembly holds much promise.
Synthesis and thermal properties of diblock copolymers utilizing non‐covalent interactions
Authors: Lohmeijer Bas G.G. , Schlaad Helmut , Schubert Ulrich S. 
Published: July 2003

AbstractDiblock copolymers of poly(styrene) and poly(ethylene oxide) were prepared utilizing a bisterpyridine ruthenium complex as non‐covalent interaction for the connection of the two blocks. Apart from the synthesis and characterization of four metallo‐supramolecular block copolymers, first studies on the thermal properties of the block copolymers have been performed. A complex crystallization behavior was observed and is described in a qualitative fashion. The influence of the metal complex on the thermal stability of the metallo‐supramolecular block copolymers remains a question for further investigation.
Precious metal polymers
Authors: Puddephatt Richard J. 
Published: July 2003

AbstractThe synthesis and properties of polymers containing precious metal centres in the backbone are described. Polymers with labile transition metal centres can be prepared by ring‐opening polymerization of macrocycles, and examples are given with silver, gold and palladium as the metal centres. In some cases, the polymers can be further organized by using ligands with hydrogen bonding substituents, and self‐assembly into sheet or network structures can then occur. Secondary bonding between inorganic centres can also lead to ordered self‐assembly. Bicyclic precursors can ring open to form either chains or sheets.
Design, synthesis and structural diversity in coordination polymers
Authors: Abourahma Heba , McManus Gregory J. , Moulton Brian , Bailey Walsh Rosa D. , Zaworotko Michael J. 
Published: July 2003

AbstractThe fundamental precept of crystal engineering is that all the information necessary for the design of a network is already stored in the molecular building blocks used. Coordination polymers represent an example of how crystal engineering has become a paradigm for the synthesis of new architectures and compositions. We report herein ten structures that are supramolecular isomers of one another. The structures are prepared from the same building blocks under mild reaction conditions. The modularity of coordination polymers imparts structural diversity that otherwise would not be possible.
Conformational analysis of siloxane‐based enzyme‐mimic precursors[1]
Authors: Parish Carol A. , Zeldin Martel , Hilson Sean , Pratt Jennifer 
Published: July 2003

AbstractThe conformational flexibility of six hybrid organodisiloxane oligomers were studied using the Low Mode‐Monte Carlo conformational search method with the MM2* force field and the Generalized Born/Surface Area continuum solvent model for water. These systems have enzyme‐like properties as synthetic acyltransferases and contain aminopyridine groups in various states of protonation. An ensemble of low energy structures was generated and used to investigate the dependence of molecular shape and flexibility on protonation, which plays an important role in catalyst solubility and self‐association. The results as measured by the number of unique conformations, end‐to‐end or longest intramolecular distance and radius of gyration of the conformational point cloud indicate that the number of protonated pyridines plays a significant role in the overall molecular shape. A similar study was also carried out on various POSS‐substitutive organodisiloxane oligomers.
Interactions of ferrocenoyl‐peptides in solution and on surfaces
Authors: Kraatz Heinz‐Bernhard 
Published: July 2003

AbstractThe Ferrocenoyl‐peptide‐cystamines, such as [Fc‐Gly‐CSA]2 (Gly = glycine, CSA = cystamine), [Fc‐Ala‐CSA]2 (Ala = alanine) and Fc‐conjugates involving collagen models, such as [Fc‐(Pro2Gly)n‐CSA]2 (Pro = proline, n = 1‐6) are readily prepared by solution methods. In solution and the solid state, these systems exhibit intermolecular hydrogen bonding between adjacent peptide chains. For [Fc‐Gly‐CSA]2 this results in the formation of a supramolecular helicate with two different H‐bonding patterns. Ferrocenoyl‐collagen‐cystamines form assemblies in solution, which melt at elevated tempertures. All systems for monolayers on gold surfaces, which show a well‐behaved ferrocene‐based electrochemistry, which allows the determination of the spatial requirements of the peptides on the surface.
Organoiron polymers containing azo dyes
Authors: Abd‐El‐Aziz Alaa S. , Todd Erin K. , Okasha Rawda M. , Afifi Tarek H. 
Published: July 2003

AbstractThe synthesis of cationic organoiron polymers with azobenzene moieties in their side chains has been accomplished via nucleophilic aromatic substitution and ring‐opening metathesis polymerization (ROMP) reactions. Polyaromatic ethers and thioethers with azobenzene moieties in their side chains were functionalized with different chromophores to yield yellow‐, orange‐ and red‐colored polymers. Polynorbornenes with azobenzene‐containing side chains were isolated following ROMP of their monomeric analogs. All of the organoiron polymers were soluble in polar organic solvents and underwent reversible electrochemical reduction processes. Photobleaching of the azobenzene‐containing polymers was achieved in the presence of hydrogen peroxide. The metallated polymers had glass transition temperatures approximately 50 to 80°C higher than their organic analogs.
Molecular Weight and Long Chain Branch Distributions of Branch‐Block Olefinic Thermoplastic Elastomers
Authors: Nele Márcio , Soares João B. P. 
Published: July 2003

AbstractOlefinic thermoplastic elastomers can be prepared by incorporating semi‐crystalline macromonomers (e.g. isotactic or syndiotactic poly(propylene), high‐density polyethylene) onto amorphous backbones (e.g. atactic poly(propylene), ethylene/α‐olefin copolymers). The macromonomer incorporation reaction can be carried out in semi‐batch reactors by adding previously synthesized macromonomers to the reactor (ex situ approach), or by generating and incorporating the macromonomers in a single step (in situ approach). The differences in the microstructure of copolymers synthesized by in situ and ex situ techniques are explored herein through a mathematical model that can predict the concentration of linear and branched chains, their average molecular weights, polydispersity indices, and molecular weight distributions. In both cases linear chains predominate, but the ex situ approach produces a larger amount of branched chains with thermoplastic elastomer properties. Furthermore, for the in situ strategy, a significant amount of branched chains is only formed after the macromonomer concentration reaches a critical value.Schematic representation of the polymerization mechanism.imageSchematic representation of the polymerization mechanism.
Pifithrin‐α promotes p53‐mediated apoptosis in JB6 cells
Authors: Kaji Akira , Zhang Yiguo , Nomura Masaaki , Bode Ann M. , Ma Wei‐Ya , She Qing‐Bai , Dong Zigang 
Published: July 2003

AbstractRecently, blockage of p53‐dependent transcriptional activation and apoptosis by pifithrin‐α (PFTα) has been reported to be useful for reducing the side effects of cancer therapy and the compound is thus thought to be a specific inhibitor of p53 [Komarov et al., Science 1999;285:1733–1737]. Here, we found that PFTα did not inhibit UVB‐ or doxorubicin (Dox)‐stimulated p53‐mediated transcriptional activation and apoptosis in JB6 cells. Instead, p53‐dependent activation and apoptosis were not only induced by PFTα itself but were also enhanced by a combination of PFTα with UVB or Dox. Furthermore, PFTα‐induced apoptosis was mediated through p53‐dependent and ‐independent signaling pathways. Extracellular signal‐regulated kinases and p38 kinase, but not c‐jun N‐terminal kinases (JNKs), were activated, and these activations were required for phosphorylation and accumulation of p53 in the cellular apoptotic response to PFTα. Thus, we conclude that PFTα is not a specific p53 inhibitor in JB6 cells but is a potential activator of p53‐mediated signaling and apoptosis. © 2003 Wiley‐Liss, Inc.
Functional evaluation of novel single nucleotide polymorphisms and haplotypes in the promoter regions of CYP1B1 and CYP1A1 genes
Authors: Han Weiguo , Pentecost Brian T. , Spivack Simon D. 
Published: July 2003

AbstractInterindividual variation in the expression of the carcinogen‐ and estrogen‐metabolizing enzymes cytochrome P4501B1 and 1A1 (CYP1B1 and CYP1A1) has been detected in human lung. To search for polymorphisms with functional consequences for CYP1B1 and CYP1A1 gene expression, we examined 1.5 kb of the promoter region of each gene. Genomic DNA from 21 Caucasian individuals was amplified by polymerase chain reaction (PCR) for direct cycle sequencing. Eight single nucleotide polymorphisms (SNPs) for CYP1B1 and 13 SNPs for CYP1A1 were found. The majority of polymorphisms occurred as multiSNP combinations for individual subjects. The wild‐type sequences were cloned into a luciferase reporter construct. The most frequent polymorphisms were then recreated by iterative site‐directed mutagenesis, replicating single polymorphisms and multiSNP combinations. These wild‐type and variant constructs were functionally evaluated in transient transfection experiments employing exposures to either the index polycyclic aromatic hydrocarbon (PAH) inducer benzo[a]pyrene (B[a]P), a composite mixture of cigarette smoke extract (CSE), or the repressor chemopreventive agent trans‐3,4,5‐trihydroxystilbene (reseveratrol). Results indicated that all wild‐type and variant constructs responded in qualitatively concordant fashion to the inducers and to the repressor. The CYP1B1 haplotypes and the majority of CYP1A1 haplotypes were shown to have no functional consequence, as compared to those of the wild‐type promoter sequences. Two constructs of composite polymorphisms of CYP1A1 appeared to result in a statistically significant increase in basal promoter activity (1.38‐ and 1.50‐fold, respectively), but the degree of functional impact was judged unlikely to be biologically important in vivo. We conclude that the observed promoter region polymorphisms in these genes are common, but are of unclear functional consequence. © 2003 Wiley‐Liss, Inc.
Translational regulation of a novel testis‐specific RNF4 transcript
Authors: Pero Raffaela , Lembo Francesca , Chieffi Paolo , Del Pozzo Giovanna , Fedele Monica , Fusco Alfredo , Bruni Carmelo B. , Chiariotti Lorenzo 
Published: July 2003

AbstractThe RING‐finger protein SNURF/RNF4, a modulator of both steroid receptor dependent and basal transcription, is expressed at very high levels in testis and at much lower levels in several other tissues. In somatic tissues, the RNF4 gene is expressed as a 3‐kb transcript while an additional shorter sized transcript (1.6 kb) was found in mouse testis. In murine germ cells, RNF4 protein expression is strongly modulated during progression of spermatogonia to spermatids, with a peak in spermatocytes. The expression of 3‐kb transcript correlated with protein levels in the different germ cell populations. Conversely, the 1.6‐kb transcript was abundantly and specifically expressed in spermatids, in which RNF4 protein was detected at very low levels. We have then examined possible mechanisms underlying this discrepancy. Primer extension and RNase protection analyses demonstrated that the 1.6‐ and 3.0‐kb transcripts originate from the same promoter, encode for the same protein and differ in the 3′ UTR. In vitro assays showed that protein degradation is not involved in the regulation of RNF4 protein level. Finally, polysome analysis revealed that only a slight fraction of the testis‐specific transcript is engaged in translation, thus providing a feasible mechanism for the quantitative differences of RNF4 mRNA and protein levels. Present results demonstrate that RNF4 short transcript is poorly translated suggesting that this mechanism could be essential for normal spermatogenesis. Mol. Reprod. Dev. 66: 1–7, 2003. © 2003 Wiley‐Liss, Inc.
Hmga1 is required for normal sperm development
Authors: Liu Jun , Schiltz John F. , Ashar Hena R. , Chada Kiran K. 
Published: July 2003

AbstractThe Hmgi protein family of chromosomal architectural factors is extensively studied for its roles in embryogenesis and its association with benign mesenchymal tumors. Although the biochemical function of Hmga1 has been studied in vitro, to provide in vivo insight into its biological function, a targeted disruption of Hmga1 was initiated. Chimeric founder mice were derived from embryonic stem (ES) cells harboring a targeted mutation in a single Hmga1 allele. These 14 different chimeric founders produced 494 black progeny. Since none of these 494 progeny were agouti, none of them were derived from ES cells. Control injections of the wild‐type ES cell lines resulted in ES cell derived agouti mice, indicating that the ES cells were totipotent. Therefore, our results indicate that one intact Hmga1 allele was not sufficient for germ‐line transmission of the ES cells. Seven chimeric founder mice that were examined histologically demonstrated aberrant regions in their reproductive organs. Aberrant regions of seminiferous tubules were reduced in diameter, demonstrated vacuolated Sertoli cells, and had an absolute deficiency of sperm. While the Hmga1+/− ES cells were shown to contribute to the formation of the epididymides, they did not significantly contribute to the testes of chimeric founder mice. No sperm isolated from any of the Hmga1+/− chimeric mice were shown to arise from the ES cells, as none of them contained the targeted disruption of the Hmga1 gene. Our results suggest that both alleles of Hmga1 are required for normal sperm production in the mouse. Mol. Reprod. Dev. 66: 81–89, 2003. © 2003 Wiley‐Liss, Inc.
Role of apoptosis and Fas/FasL system in the oogenesis of the spotted ray Torpedo marmorata
Authors: Loredana Ricchiari , Barbara D'onghia , Annamaria Liguoro , Stefania Tammaro , Maria Motta Chiara , Silvana Filosa , Piero Andreuccetti , Marina Prisco 
Published: July 2003

AbstractIn the present paper we investigated the role played by apoptosis during oogenesis in the cartilagineous fish Torpedo marmorata. TEM, TUNEL and immunohistochemical techniques were employed to specifically reveal morphological and biochemical hallmarks of apoptosis in specimens from birth to sexual maturity. Data obtained demonstrate that apoptosis occurs in prefollicular oocyte selection, in maintaining the homeostasis of granulosa in healthy growing oocyte and in resorbing atretic follicles. In this respect, the involvement of apoptosis in Torpedo marmorata oogenesis closely parallels that found in mammals, thus confirming that strategies of germ cell selection among vertebrates have been evolutively preserved. Mol. Reprod. Dev. 66: 54–59, 2003. © 2003 Wiley‐Liss, Inc.