bluuebunny/crossref_metadata_2025_split huggingface dataset:
Natural‐Product Diversity of the New Caledonian Marine Ecosystem Compared to Other Ecosystems: A Pharmacologically Oriented View
Authors: Laurent Dominique , Pietra Francesco 
Published: April 2004

AbstractIn comparison with other ecosystems, biodiversity and natural‐product diversity of the New Caledonian marine ecosystem, comprising lagoons, barrier reefs, and deep waters in seamount regions, are described here phylogenetically with the aid of molecular drawings and tabulation of data. Admittedly, since the inception of these studies in 1977, the comparison is biased by selection of New Caledonian organisms on the basis of positive pharmacologically oriented bioassays. However, we show that these and other distortions must be accepted to draw any comparison on a regional basis, which, nonetheless, turn out to be useful for the progress of knowledge, particularly in directing future explorations of biodiversity in the search for new pharmacologically active metabolites.
Analysing the Java package/access concepts in Isabelle/HOL
Authors: Schirmer Norbert 
Published: April 2004

AbstractJava access modifiers and packages provide a mechanism to restrict access to members and types, as an additional means of information hiding beyond the purely object‐oriented concept of classes. In this paper we clarify the semantics of access modifiers and packages by adding them to our formal model of Java in the theorem prover Isabelle/HOL. We analyse which properties we can rely on at runtime, provided that the program has passed the static accessibility tests. Copyright © 2004 John Wiley & Sons, Ltd.
Formation of the B Ring in Steroids and Hopanoids from Squalene
Authors: Hess B. Andes 
Published: April 2004

AbstractA theoretical conformational study based on density functional calculations provides evidence that the sterol and nonsterol cyclizations of squalene to triterpenes are controlled by conformational effects as has been previously suggested. It was found that different conformers of a model system of squalene give rise to the chair−boat conformation found in the steroids and the chair−chair conformation of the pentacyclic 3‐deoxytriterpenes for their A and B rings. It is suggested that the enzymes play a key role in holding the substrate in the proper orientation for these cyclizations to occur. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Asymmetric Syntheses of Potent Antitumor Macrolides Cryptophycin B and Arenastatin A
Authors: Ghosh Arun K. , Bischoff Alexander 
Published: April 2004

AbstractEfficient and highly stereoselective syntheses of cryptophycin B and arenastatin A, potent cytotoxic agents, are described. An ester‐derived titanium enolate mediated syn‐aldol reaction was employed to generate the stereocenters C‐5 and C‐6. The route is convergent and provides a convenient access to the synthesis of structural variants of cryptophycins as well as members of its family. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Composition of the essential oils of wild and cultivated Satureja khuzistanica Jamzad from Iran
Authors: Farsam H. , Amanlou M. , Radpour M. R. , Salehinia A. N. , Shaﬁee A. 
Published: April 2004

AbstractThe essential oils of the wild and cultivated Satureja khuzistanica Jamzad (Lamiaceae) from Iran were isolated by hydrodistillation in yields of 0.6% and 1.2% respectively. The chemical composition of the essential oils was examined by GC and GC–MS. Twelve components of the wild plants' oil, representing 98.5% of the total oil, and 21 components of the cultivated plants' oil, representing 99.2%, were identiﬁed. The main components of the wild plants' oil were carvacrol (93.9%), eugenol (1.0%), p‐cymene (0.8%) and thymol (0.6%). The major constituents of the cultivated plants' oil were carvacrol (80.6%), p‐cymene (4.8%), myrcene (1.5%), γ‐terpinene (2.1%) and terpinene‐4‐ol (2.1%). In both the wild and cultivated plants the main component of the oil was carvacrol. Copyright © 2004 John Wiley & Sons, Ltd.
Determination of aromatic descriptors of Touriga Nacional wines by sensory descriptive analysis
Authors: Falqué Elena , Ferreira Antonio Cesar , Hogg Tim , Guedes‐Pinho Paula 
Published: April 2004

AbstractTouriga Nacional wines from the Douro Demarcated Region (northern Portugal) were evaluated by sensory descriptive analysis by 11–13 trained judges. The panel initially identiﬁed 78 attributes. After some sessions of reduction of terms and by using statistical methods, the list was reduced to 16 sensory attributes. Principal component analysis of the sensory data permitted the clear differentiation between Touriga Nacional and Tinta Roriz wines. These wines differed signiﬁcantly for ﬁve sensory attributes. Touriga Nacional wines were characterized by ‘plum brandy’, ‘mulberry’, ‘cherry’, ‘wild fruits’ and ‘dry raisin’ aromas. Copyright © 2004 John Wiley & Sons, Ltd.
Metal‐on‐metal bearing wear with different swing phase loads
Authors: Williams Sophie , Stewart Todd D. , Ingham Eileen , Stone Martin H. , Fisher John 
Published: April 2004

AbstractThere is currently much discussion about the most clinically relevant testing methods for evaluating total hip replacements. This study examined the effect of different swing phase loads, including microseparation, on the wear, friction, and wear particles of metal‐on‐metal (MOM) hip replacements. MOM hip replacements were tested for 5 million cycles with the use of a hip simulator; prostheses were tested with a low (100‐N) and ISO (280‐N) swing phase load, and under microseparation conditions. Increasing the swing phase load from 100 to 280 N in the same hip simulator increased the wear of the MOM hip replacements by over tenfold. Introducing microseparation into the gait cycle increased wear further, and stripe wear was observed on the femoral heads, accompanied by corresponding rim damage on the acetabular cups. No significant difference in wear particle size was observed between wear particles produced by low load and microseparation hip simulator conditions. Introducing microseparation into the hip simulator gait cycle increased the wear of MOM prostheses. Joint laxity and separation may lead to increased wear rates of MOM prostheses in vivo. Additionally elevated positive swing phase loads may also increase wear. Variable swing phase load conditions in vivo may contribute to variations in clinical wear rates. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 70B: 233–239, 2004
A role for lysyl oxidase regulation in the control of normal collagen deposition in differentiating osteoblast cultures
Authors: Hong Hsiang‐Hsi , Pischon Nicole , Santana Ronaldo B. , Palamakumbura Amitha H. , Chase Hermik Babakhanlou , Gantz Donald , Guo Ying , Uzel Mehmet Ilhan , Ma Daniel , Trackman Philip C. 
Published: April 2004

AbstractDifferentiation of phenotypically normal osteoblast cultures leads to formation of a bone‐like extracellular matrix in vitro. Maximum collagen synthesis occurs early in the life of these cultures, whereas insoluble collagen deposition occurs later and is accompanied by a diminished rate of collagen synthesis. The mechanisms that control collagen deposition seem likely to include regulation of extracellular collagen biosynthetic enzymes, but expression patterns of these enzymes in differentiating osteoblasts has received little attention. The present study determined the regulation of lysyl oxidase as a function of differentiation of phenotypically normal murine MC3T3‐E1 cells at the level of RNA and protein expression and enzyme activity. In addition, the regulation of BMP‐1/mTLD mRNA levels that encodes procollagen C‐proteinases was assayed. The role of lysyl oxidase in controlling insoluble collagen accumulation was further investigated in inhibition studies utilizing β‐aminopropionitrile, a specific inhibitor of lysyl oxidase enzyme activity. Results indicate that lysyl oxidase is regulated as a function of differentiation of MC3T3‐E1 cells, and that the maximum increase in lysyl oxidase activity precedes the most efficient phase of insoluble collagen accumulation. By contrast BMP‐1/mTLD is more constitutively expressed. Inhibition of lysyl oxidase in these cultures increases the accumulation of abnormal collagen fibrils, as determined by solubility studies and by electron microscopy. Taken together, these data support that regulation of lysyl oxidase activity plays a key role in the control of collagen deposition by osteoblast cultures. Copyright © 2004 Wiley‐Liss, Inc.
Response to lysophosphatidic acid in Xenopus oocytes and its rapid desensitization: The role of Gq and Go G‐protein families
Authors: Van‐Ham Irit Itzhaki , Lupu‐Meiri Monica , Tayer Maya , Shapira Hagit , Oron Yoram 
Published: April 2004

AbstractNative Xenopus oocytes exhibit dose‐dependent depolarizing current responses to lysophosphatidic acid (LPA), with EC50 = 0.18 μM. Responses to LPA were subject to pronounced rapid desensitization. When oocytes were challenged with 5 nM LPA, the response was <10% of the maximal. Subsequent addition of 0.5 μM LPA resulted in 50–70% desensitization, when compared to naïve controls. Injection of antisense oligodeoxyoligonucleotides (ASODNs) targeted at either of the two endogenous LPA receptors inhibited the LPA response by approximately 50%, but did not alter the degree of rapid desensitization. To study the involvement of G‐proteins in rapid homologous desensitization of responses to LPA, we selectively depleted native G‐proteins by injection of specific ASDONs. Injection of ASDONs targeted at Gαq family mRNAs (mainly Gα11) reduced the response to 0.5 μM LPA by 50%. ASDONs targeted at either Gαo or Gαo1 caused a large decrease in the amount of their cognate mRNAs and the Gαo family proteins, while the response to LPA was inhibited by up to 30%. Injection of ASDONs targeted at Gαo1 mRNA decreased rapid desensitization from 69 to 23%, while pertussis toxin (PTX) completely abolished it. Expression of two dominant negative mutants of the human Gαo family homologs either decreased or virtually abolished rapid desensitization. Microinjection of CaCl2 demonstrated that 50% of rapid desensitization could be attributed to inhibition of Ca2+ activation of chloride channels. We propose that the apparent degenerate coupling of different G‐proteins to LPA receptors in Xenopus oocytes actually serves both the generation of the response (by Gq and Go G‐protein families) and its desensitization (mostly by Go G‐protein family). © 2004 Wiley‐Liss, Inc.
An artificial receptor for glycoproteins
Authors: Gupta Geeta , Lowe Christopher R. 
Published: April 2004

AbstractWe describe the rational design, synthesis and development of a sterilizable biomimetic ligand for the affinity purification of glycoproteins. Based on mimicking the principles of natural carbohydrate recognition, a putative library of 196 glycoprotein‐binding synthetic ligands was designed and synthesized on a polymeric support. Ligand 11/11, based on a triazine scaffold and immobilized on a hydrophilic support, was identified as the ‘lead’ ligand. The carbohydrate recognizing the potential of the ‘lead’ ligand was revealed by reduced binding of a periodate oxidized model glycoprotein, and by ‘sharp’ elution profiles achieved with borate buffer eluents. Specific elution and competitive binding experiments determined the monosaccharide specificity of 11/11 in the order mannoside > glucoside > galactoside. The diastereo‐selective performance of ligand 11/11 was quantified and reaffirmed by analytical affinity chromatography and1H‐NMR, in the order galactoside < glucoside < mannoside with binding affinities (Ka,M−1) in the 63–214 and 20–83 M−1range, respectively. Partition coefficient analysis revealed binding constants towards glycoproteins in the 104 M−1range, that compared favourably with the affinities of carbohydrate binding lectins for glycoproteins, such as concanavalin A. Molecular modelling studies of ligand 11/11 revealed the formation of a pre‐organized apolar ‘tweezer‐like’ cavity, containing complementary nitrogenous hydrogen bond donor and acceptor groups that formed selective interactions with the equatorial 3‐ and 4‐hydroxyl groups of saccharides. Copyright © 2004 John Wiley & Sons, Ltd.
Metal‐containing conjugated oligo‐ and polythiophenes
Authors: Moorlag Carolyn , Clot Olivier , Zhu Yongbao , Wolf Michael O. 
Published: April 2004

AbstractConjugated polymers containing metal groups are an important class of new materials that may find application as sensors, non‐linear optical materials and in molecular electronics. Polythiophenes are an extensively studied class of conjugated polymers, that can be easily modified synthetically, and may be prepared using a variety of methods. Metal groups pendant to polythiophene backbones modulate the electronic, optical and redox properties of the conjugated backbone and can introduce novel structural motifs to these materials. Functionalization of oligo‐ and polythiophenes by Fe, Pd and Ru containing groups is discussed, along with the properties of some of these materials.
Synthesis and physical properties of π‐conjugated metallacycle polymers of cobalt and ruthenium
Authors: Kurashina Masashi , Murata Masaki , Nishihara Hiroshi 
Published: April 2004

AbstractRecent studies on two types of π‐conjugated metallacylce polymers are reviewed. Reaction of CpCo(PPh3)2 with conjugated diacetylenes afford poly(arylene cobaltacyclopentadienylene) and that of CpRuBr(cod) does poly(arylene ruthenacyclopentrienylene)s in ambient conditions. Regioselectivity of the former metallacycling reacion is not perfect (at most 80% of the 2,5‐diaryl selectivity) but that of the latter is satisfactory (∼100% of the 2,5‐diaryl selectivity) for the formation of π‐conjugated structure. Electrochemical oxidation of the cobaltacyclopentadiene polymer and reduction of the ruthenacycle polymer occur facilely and quasi‐reversibly by the contribution of metal d‐orbitals. Physical properties in undoped (neutral) and doped (charged) sates show the behavior of electronic band structure derived from the organic π‐conjugated main chain strongly coupled with the metal d‐orbitals. This affords, for example, photoconductivity in the neutral form of the cobaltacylopentadiene polymer and ferromagnetic interaction in the reduced form of the ruthenacyclopentatriene polymer.
Bisglycine‐substituted ferrocene conjugates
Authors: Kraatz Heinz‐Bernhard 
Published: April 2004

AbstractThe solid state structures of three bissubstituted glycine ferrocene conjugates are described allowing a direct comparison of the structural parameters. Whereas the fully protected glycine ester Fc(Gly‐OEt)2 adopts a 1,3′‐conformation leading exclusively to intermolecular H‐bond formation, the free acid Fc(Gly‐OH)2 adopts the more compact 1,3′‐comformation with intramolecular H‐bonding. The same intramolecular H‐bonding pattern is adopted by the glycine ferrocenophane Fc(Gly‐CSA)2.
Organoiron polynorbornenes with pendent arylazo and hetarylazo dye moieties
Authors: Abd‐El‐Aziz Alaa S. , Okasha Rawda M. , Afifi Tarek H. 
Published: April 2004

AbstractOrganoiron polynorbornene containing arylazo or hetarylazo dye chromophores has been prepared via ring opening metathesis polymerization using Grubbs' catalyst. The obtained polymers were isolated as brightly colored materials and displayed good solubility in polar organic solvents. The colors of these polymers were affected by the nature of the incorporated azo chromophores. Thermogravimetric analysis of these materials showed that the cleavage of the cyclopentadienyliron (CpFe+) moieties was between 225 and 231 °C, while the degradation of the polymer backbones occurred between 400 and 450 °C. UV‐vis studies in DMF showed that the organoiron polymers containing arylazo dyes exhibit wavelength maxima around 425 nm. However, the replacement of these arylazo moieties with hetarylazo dyes displayed substantial bathochromic shifts in the λmax values (≈ 511 nm).
Synthesis and applications of polymers containing metallacyclopentadiene moieties in the main chain
Authors: Tomita Ikuyoshi , Ueda Masahiro 
Published: April 2004

AbstractOrganometallic polymers containing metallacycles in the main chain were prepared by the reactions of diynes with low‐valent organometallic complexes such as CpCo(PPh3)2, CP2Ti(CH2=CHC2H5), and (iPrO)2Ti(CH2=CHCH3). Their polymer reactions involving the conversion of the main chain structures gave rise to polymers containing functional groups in their main chain repeating units. Design and synthesis of organometallic polymers that potentially serve as novel functional materials are also described.
Photochemically degradable polymers containing metal‐metal bonds along their backbones: the effect of stress on the rates of photochemical degradation
Authors: Tyler David R. , Chen Rui 
Published: April 2004

AbstractThe syntheses of polymers that have metal‐metal bonds along their backbones are described. The polymers are photodegradable because the metal‐metal bonds homolyze when irradiated with visible light. The photochemical reactions of the polymers in solution are identical to the photochemical reactions of the discrete metal‐metal bonded dimers. Typical reactions include metal‐metal bond disproportionation and metal radical capture, for example, by chlorine atom abstraction from carbon tetrachloride. The polymers are also photochemically degradable in the solid state; thin films of the polymers degrade when irradiated with visible light in the presence of oxygen or in the absence of oxygen if the polymer backbone has a built‐in radical trap. The origin of tensile stress‐induced rate enhancements in the photodegradation of polymers was studied using the polymers with metal‐metal bonds along their backbones and with built‐in radical traps. By eliminating the need for external oxygen to act as a radical trap, the experimentally challenging problem of diffusion‐controlled oxidation kinetics was avoided. Analysis of plots of quantum yields for degradation vs. stress reveals that stress increases the separation of the radical fragments produced by photolysis. An increased separation leads to less radical‐radical recombination, which increases the efficiency of degradation. Quantitative knowledge of the factors that control polymer degradation rates will eventually allow synthesis of an ideal photodegradable polymer ‐ one that has a tunable onset of degradation and that degrades quickly once degradation has started.
Superelasticity of free‐standing NiTi films depending on the oxygen impurity of the used targets
Authors: Zamponi C. , Rumpf H. , Wehner B. , Frenzel J. , Quandt E. 
Published: April 2004

AbstractOff‐stoichiometric NiTi sputter targets were manufactured by ingot metallurgy in order to produce Ni‐rich NiTi thin films. Crystalline samples, which undergo a martensitic transformation, were fabricated by magnetron sputtering and subsequent thermal treatment. The sacrificial layer technique was applied to obtain free‐standing NiTi films. The stoichiometry of the sputtered film is different to the stoichiometry of the target material. Sputtering targets with a Ti content higher than 49.5 at.% have a typical Ti‐loss rate in the order of 4.3 at.%, whereas at more Ni‐rich targets a Ti loss rate of only 0.5–1.5 at.% is observed. Due to this Ti loss rate target composites of Ti‐53.1Ni‐46.9 at.% and Ti‐53.2Ni‐46.8 at.% were taken. The NiTi films obtained from these two targets were compared. The main difference between the two targets is the impurity content of oxygen and carbon. Auger electron spectroscopy measurements were performed to determine qualitatively the content of oxygen in the free‐standing NiTi films. Transformation temperatures and hysteresis properties of the martensitic transformation were characterised by differential scanning calorimetry. Free‐standing films obtained from the Ti‐53.1Ni‐46.9 at.% and Ti‐53.2Ni‐46.8 at.% sputtering targets revealed superelastic properties at 45 °C as demonstrated by tensile testing. Tensile tests were taken at various temperatures of 40 °C, 45 °C, 50 °C, 55 °C and 60 °C, revealing e.g. a maximum superelastic strain of approximately 5 % at 45 °C.
Damping Factors and Fatigue Notch Factors of Pseudoelastic NiTi‐Shape Memory Alloys
Authors: Predki W. , Knopik A. , Klönne M. 
Published: April 2004

AbstractPseudoelastic NiTi‐ shape memory alloys (SMAs) provide a high damping capacity and can be used in order to achieve a reduction of peak loads being caused by unexpected shock loading. These “pseudoelastic” properties are related to the formation of martensite M from austenite A, which has been induced by stress; they allow to refer to SMAs as functional materials. Furthermore, these functional materials can operate at high stresses and thus, have to withstand severe mechanical loadings like classical structural materials. In combination, these characteristics provide opportunities for technical applications, e.g., to reduce vibrations or to reduce peak loads caused by shock loading. An extensive knowledge of the functional and structural fatigue behaviour of the material is required to design SMA components. NiTi hollow shaft samples and solid shaft samples have been tested under cyclic torsional loading conditions in a load‐controlled mode. By using these two geometries the influence of the sample geometry on the fatigue behaviour can be investigated. In addition, a test programme has been elaborated in order to investigate the behaviour of the material when subjected to bending. The experimental data have been evaluated describing the transformation behaviour induced by stress concerning transformation stress, apparent shear modulus of the austenite GA and apparent stiffness τMs (describing the slope of the shear stress‐strain‐curve in the transformation range GA‐M). These parameters naturally depend on the cycle number, the load amplitude as well as the temperature. Engineering failures are often associated with the presence of notches. In this context, torsion tests on notched samples are planned to be carried out in order to assess the resulting data based on the results obtained from the notch free samples. This will allow to derive simple design rules based on fatigue notch factors, which are needed for engineering design.
Minimizing beam‐on time in cancer radiation treatment using multileaf collimators
Authors: Boland Natashia , Hamacher Horst W. , Lenzen Frank 
Published: April 2004

AbstractIn this article the modulation of intensity matrices arising in cancer radiation therapy using multileaf collimators (MLC) is investigated. It is shown that the problem is equivalent to decomposing a given integer matrix into a positive linear combination of (0, 1) matrices. These matrices, called shape matrices, must have the strict consecutive‐1‐property, together with another property derived from the technological restrictions of the MLC equipment. Various decompositions can be evaluated by their beam‐on time (time during which radiation is applied to the patient) or the treatment time (beam‐on time plus time for setups). We focus on the former, and develop a nonlinear mixed‐integer programming formulation of the problem. This formulation can be decomposed to yield a column generation formulation: a linear program with a large number of variables that can be priced by solving a subproblem. We then develop a network model in which paths in the network correspond to feasible shape matrices. As a consequence, we deduce that the column generation subproblem can be solved as a shortest path problem. Furthermore, we are able to develop two alternative models of the problem as side‐constrained network flow formulations, and so obtain our main theoretical result that the problem is solvable in polynomial time. Finally, a numerical comparison of our exact solutions with those of well‐known heuristic methods shows that the beam‐on time can be reduced by a considerable margin. © 2004 Wiley Periodicals, Inc.