bluuebunny/crossref_metadata_2025_split huggingface dataset:
Does overweight impact on the prognosis of patients with renal cell carcinoma? A single center experience of 683 patients
Authors: Schips Luigi , Lipsky Katja , Zigeuner Richard , Gidaro Stefano , Salfellner Michael , Rehak Peter , Pummer Karl , Hubmer Gerhart 
Published: October 2004

AbstractBackground and ObjectivesAn increased incidence of renal cell carcinoma (RCC) in obese patients has been reported by several authors. We investigated the association of body mass index (BMI) with prognosis of patients with RCC.MethodsFrom January 1994 to December 2000, 693 operations for RCC in 683 consecutive patients were performed at our institution. Patients' BMI at operation was evaluated, overall, tumor‐specific and progression‐free survival was investigated using the Kaplan–Meier method, for multivariate analysis the Cox regression model was used.ResultsFour hundred seventeen patients were males, 266 females. Mean age was 62 years (range 16–88). BMI was available in 609 (89.2%). 371/609 (60.9%) of patients exhibited a BMI greater than 25. After a mean follow‐up of 41.5 months, 86 (12.6%) patients died from metastatic RCC, and 29 (4.3%) were alive with metastatic disease. A significant advantage regarding overall (P = 0.015) and progression‐free (0.017) but not tumor‐specific survival (P = 0.057) was found for patients with a BMI of more than 25 compared to normal‐weight patients. In multivariate analysis, BMI showed no significant association with tumor‐specific survival.ConclusionsPatients with a BMI of more than 25 had a better outcome compared to patients with normal weight in univariate analysis but not multivariate analysis. J. Surg. Oncol. 2004;88:57–61. © 2004 Wiley‐Liss, Inc.
Crystallization and Ring‐Banded Spherulite Morphology of Poly(ethylene oxide)‐block‐Poly(ε‐caprolactone) Diblock Copolymer
Authors: Jiang Shichun , He Chaoliang , An Lijia , Chen Xuesi , Jiang Bingzheng 
Published: October 2004

AbstractSummary:The crystallization behavior of crystalline‐crystalline diblock copolymer containing poly(ethylene oxide) (PEO) and poly(ε‐caprolactone) (PCL), in which the weight fraction of PCL is 0.815, has been studied via differential scanning calorimeter (DSC), wide‐angle X‐ray diffraction (WAXD), and polarized optical microscopy (POM). DSC and WAXD indicated that both PEO and PCL blocks crystallize in the block copolymer. POM revealed a ring‐banded spherulite morphology for the PEO‐b‐PCL diblock copolymer.DSC heating curve for the PEO‐b‐PCL block copolymer.magnified imageDSC heating curve for the PEO‐b‐PCL block copolymer.
Verwertung von PTFE‐Glasfaser‐Compound‐Abfällen – Ergebnisse einer Werkstoffentwicklung
Authors: Lehmann D. , Hupfer B. , Lappan U. , Geißler U. , Reinhardt G. , Kunze K. 
Published: October 2004

AbstractGlasfaserverstärkte PTFE Compounds (PTFE/GF) werden zu Halbzeugen verarbeitet, die anschließend spanend zu entsprechenden Produkten weiterverarbeitet werden. Im Gegensatz zu unmodifizierten PTFE‐Abfällen sind PTFE/GF‐Spanabfälle zur Zeit noch nicht direkt verwertbar und werden entsorgt. Dieser Beitrag beschreibt ein Verfahren und erste Ergebnisse, in dem solche Abfälle zu Werkstoffen verarbeitet werden können. Der erste Schritt ist der strahlenchemische Abbau des PTFE in den PTFE/GF‐Abfällen zu Pulvern mit Glasfaseranteil. In der folgenden Compoundierung mit PA‐6 werden chemisch gekoppelte PTFE‐PA‐6‐Materialien (mit Glasanteil) hergestellt. In tribologischen Untersuchungen weisen diese Compounds nahezu dieselben Eigenschaften auf, als wäre reines PTFE in dieses Verfahren eingesetzt worden. Chemisch gekoppelte PTFE‐PA‐Materialien zeichnen sich durch sehr gute Gleitreibungseigenschaften aus. Die Besonderheit besteht in der sehr hohen Verschleißfestigkeit solcher Materialien im Vergleich zu physikalischen Mischungen.
Lubricants under high local pressure: Liquids act like solids
Authors: Müser M. H. 
Published: October 2004

AbstractA lubricant layer solidifies when it is confined between two walls at large normal pressures. The atomic scale motion that occurs when the two confining surfaces slide past each other induces flow in the lubricant layer that is akin of plastic flow. This results in friction‐velocity relationships similar to Coulomb’s law of friction. Moreover, the lubricant layer does not necessarily melt, even when the two solids are in stick slip motion. In this paper, atomic‐scale details of the plastic flow mechanism are investigated by means of molecular dynamics simulations.
Stabilisierung der Prozessführung bei der Herstellung von Weißblech‐Getränkedosen durch Optimierung des tribologischen Gesamtsystems
Authors: Gade D. , Höhn W. , Sauer R. 
Published: October 2004

AbstractBei der Herstellung von Getränkedosen aus Weißblech kommt der Oberflächenstruktur und der Schmierung der Grundmaterialien eine entscheidende Bedeutung zu. Die Beschaffenheit der ca. 0,5‐0,7 μm dicken Zinnschicht und die Mikrostruktur der darunter liegenden Stahl‐Oberfläche bestimmen die tribologische Qualität des Weißbleches.Die Fertigung der Dosenrümpfe geschieht durch die beiden aufeinander folgenden Prozessschritte Tiefzug und Abstreckzug, deren Prozessrandbedingungen extreme Anforderungen an das Grundmaterial stellen. Zur Vermeidung von Rissen müssen die Umformkräfte und die Verteilung von Inhomogenitäten in der Stahlmatrix sehr genau kontrolliert werden. Weiterhin muss die Prozesstemperatur in der Umformzone unter dem Schmelzpunkt von Zinn (ca. 232 °C) gehalten werden, da ein Aufschmelzen das optische Erscheinungsbild und den Korrosionsschutz der Dosenoberfläche zerstören würde.Es wird anhand von Experimenten gezeigt, dass die Zinnschicht des Weißbleches eine entscheidende Bedeutung für die Schmierung des tribologischen Gesamtsystems hat, sowohl im Tiefzug als auch im Abstreckzug. Die Veränderung der Morphologie und der Oberflächenverteilung dieser Zinnschicht während der einzelnen Prozessschritte wird gezeigt und die Einflüsse von Temperaturverlauf und Werkzeugauslegung werden beleuchtet. Der Einfluss von zusätzlich eingesetzten Kühlmitteln auf die Temperaturverteilung und auf die Reibungsverhältnisse in der Umformzone wird unter spezieller Berücksichtigung des Verschleißes der eingesetzten Abstreckwerkzeuge dargestellt.
Untersuchung von Einflussfaktoren auf das tribologische Verhalten von Werkstoffen gegen Eis
Authors: Albracht F. , Reichel S. , Winkler V. , Kern H. 
Published: October 2004

AbstractZiel der Untersuchungen ist die Bestimmung der Einflussfaktoren auf das tribologische Verhalten verschiedener Werkstoffe auf einer Eisoberfläche. Für Voruntersuchungen wurde ein Stift‐Scheibe‐Tribometer in eine Kältekammer eingebaut. Die zylinderförmigen Proben mit definierter Halbkugeloberfläche wurden auf eine sich drehende Eisscheibe aufgesetzt. Die Abhängigkeiten der Reibungszahl von äußeren Einflussgrößen (Normalkraft, Eistemperatur, Gleitgeschwindigkeit) sowie von der Wärmeleitfähigkeit und der Oberflächentopografie der Probenstifte konnten gemessen werden. Mit der bisherigen Versuchsanordnung war eine gute Reproduzierbarkeit der Messergebnisse nicht gegeben aufgrund der manuellen Präparation der Eisoberfläche. Eine elektronische Datenerfassung während des Versuches war nicht vorhanden. Aus diesen Gründen wurde ein neuartiges Tieftemperatur‐Tribometer konzipiert und aufgebaut.Dieses Computer gestützte Tieftemperatur‐Tribometer besitzt ein rotierendes Messsystem bei feststehender Eisscheibe (temperierbar bis –30 °C). Durch die Möglichkeit der Bewegung in einer Spiralbahn ist immer eine neue Eisoberfläche für die Messung garantiert. Die Reibgeschwindigkeit kann bis max. 9,4 m/s eingestellt werden. Ein Schwerpunkt ist die definierte und reproduzierbare Herstellung der Eis‐ und Probenoberfläche.Erste Messergebnisse aus Reibversuchen mit dem neuartigen Tribometer werden vorgestellt.
Development of Tribologically Optimized Surface Coatings with Micro and Nano Particles
Authors: Xian G. , Walter R. , Haupert F. 
Published: October 2004

AbstractThis paper is focused on the tribological behaviour of epoxy‐based coatings applied to metal substrates. Aramid particles, nanometer‐sized Titanium dioxide (TiO2), graphite and Polytetrafluoroethylene (PTFE) served as filler materials. Under sliding conditions, incorporation of Aramid particles to the graphite and TiO2 filled composites improved the wear resistance significantly, but it slightly increased the coefficient of friction (cof). Under fretting wear conditions, 10 vol.% Aramid particles filled composite showed the lowest wear rate and cof. To further improve the wear performance, PTFE (2 ‐ 6 vol.%) was introduced to the above‐optimized composition (10 vol.% Aramid particles, graphite and TiO2). However, both the sliding and fretting wear resistance was impaired, and cof was increased. Deterioration of the mechanical properties and the friction films were attributed to the unusual trend. Finally, the optimal composition for epoxy‐based coatings was determined as 10 vol.% Aramid particles together with graphite and nano‐TiO2 filled composite.
Tribologische Prüfung von Reibpaarungen für Kfz‐Kupplungen
Authors: Walther G. , Schneider L. , Diemer M. 
Published: October 2004

AbstractDie steigende Antriebsleistung in Kraftfahrzeugen stellt immer höhere Anforderungen an Reibbeläge und Gegenmaterial in Trockenkupplungen. Die wichtigsten Kriterien dafür sind der Reibungskoeffizient, der Verschleiß, das spezifische Gewicht, die Rupf‐ und Geräuschneigung. Die während des Einkuppelns entstehende Reibungswärme führt zu einer hohen Temperaturbelastung der Belagfläche. Bisher werden weltweit bevorzugt organisch gebundene Reibbeläge wegen des guten Komfortverhaltens und des günstigen Preises eingesetzt. Ihre Eigenschaften wurden über jahrzehntelange Entwicklungsarbeit stetig verbessert, jedoch bestehen bezüglich der umsetzbaren Reibleistungen Grenzen. Die Evaluierung alternativer Reibwerkstoffe ist deshalb ein ständiges Ziel der Kupplungshersteller. Für die Tests wurden Teilbelagprüfungen mit Schwungmassensimulation an verschiedenen Materialpaarungen im Trockenlauf durchgeführt. Die einstellbare Massenträgheit des Systems gewährleistet einen definierten Energieeintrag pro Kupplungsvorgang. Dies erlaubt die Auswertung des Reibwertes in Abhängigkeit von der Gleitgeschwindigkeit und Zyklenzahl sowie die Ermittlung des Verschleißvolumens bezogen auf die geleistete Reibungsarbeit. Zusätzlich wurde die Schallemission zur Beurteilung des Komfortverhaltens herangezogen. Die Versuchsergebnisse der Modellprüfung zeigen eine gute Korrelation zu den durchgeführten Prüfstandsversuchen.
Synthesis, characterization, and permeability evaluation of hybrid organic–inorganic films
Authors: José N. M. , Prado L. A. S. A. , Yoshida I. V. P. 
Published: October 2004

AbstractThe preparation and characterization of hybrid organic–inorganic films based on poly(dimethylsiloxane), PDMS, crosslinked with nanoclusters obtained from pentaerythrithol triacrylate (PETA) and 2‐aminoethyl‐3‐aminopropyltrimethoxysilane (AS), are reported. The introduction of silica nanoclusters, obtained from tetraethoxysilane as an additional crosslinker, improved the mechanical stability of the films and also produced a noticeable decrease in the solvent sorption and in the distance between the nodes of the polymeric networks. The performance of these films as membranes for gas separation processes was similar to those reported for commercial PDMS, although they presented polar organic PETA/AS crosslinker nuclei. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4281–4292, 2004
Global secondary structure packing angle bias in proteins
Authors: Platt Daniel E. , Guerra Concettina , Zanotti Giuseppe , Rigoutsos Isidore 
Published: October 2004

AbstractWhile studies of secondary structure interactions have focused on local interacting features, there is a need for a more global characterization of packing‐induced aligned packing of secondary structures. This study presents an analysis of the distribution of globally sampled secondary structures within selected subunits of a selected set of multimeric proteins. Comparisons are made between the distribution of the cosines of angles between triplets of linear segments associated to secondary structures and a theoretically obtained distribution for triplets of random uniformly distributed unit vectors. We show that, among all pairs of helix or strand segments, planar configurations appear more frequently than expected for uniformly distributed vectors, and alignment is strongly preferred compared to that expected for uniformly distributed vector triplets. Among all secondary structure triplets, pairs of angle cosines between helix strand segments deviate from uniformity corresponding to alignment and anti‐alignment. Furthermore, among all helix or strand segments, including non‐interacting secondary structures, the distribution of a single angle cosine indicates a strong preference for alignment and anti‐alignment. Selection for interactive triplets shows results consistent with prior studies. Lastly, angle pairs are not statistically independent, indicating that alignment between two helix or strand segments is more likely if another helix or strand is aligned with either of the first two helices or strands. Selection for interactive segment triplets shows results consistent with prior studies. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Computational detection of the binding‐site hot spot at the remodeled human growth hormone–receptor interface
Authors: Verkhivker Gennady M. , Bouzida Djamal , Gehlhaar Daniel K. , Rejto Paul A. , Freer Stephan T. , Rose Peter W. 
Published: October 2004

AbstractA hierarchical computational approach is used to identify the engineered binding‐site cavity at the remodeled intermolecular interface between the mutants of human growth hormone (hGH) and the extracellular domain of its receptor (hGHbp). Multiple docking simulations are conducted with the remodeled hGH–hGHbp complex for a panel of potent benzimidazole‐containing inhibitors that can restore the binding affinity of the wild‐type complex, and for a set of known nonactive small molecules that contain different heterocyclic motifs. Structural clustering of ligand‐bound conformations and binding free‐energy calculations, using the AMBER force field and a continuum solvation model, can rapidly locate and screen numerous ligand‐binding modes on the protein surface and detect the binding‐site hot spot at the intermolecular interface. Structural orientation of the benzimidazole motif in the binding‐site cavity closely mimics the position of the hot spot residue W104 in the crystal structure of the wild‐type complex, which is recognized as an important structural requirement for restoring binding affinity. Despite numerous pockets on the protein surface of the mutant hGH–hGHbp complex, the binding‐site cavity presents the energetically favorable hot spot for the benzimidazole‐containing inhibitors, whereas for a set of nonactive molecules, the lowest energy ligand conformations do not necessarily bind in the engineered cavity. The results reveal a dominant role of the intermolecular van der Waals interactions in providing favorable ligand–protein energetics in the redesigned interface, in agreement with the experimental and computational alanine scanning of the hGH–hGHbp complex. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Mechanism for the α‐helix to β‐hairpin transition
Authors: Ding Feng , Borreguero Jose M. , Buldyrey Sergey V. , Stanley H. Eugene , Dokholyan Nikolay V. 
Published: October 2004

AbstractThe aggregation of α‐helix‐rich proteins into β‐sheet‐rich amyloid fibrils is associated with fatal diseases, such as Alzheimer's disease and prion disease. During an aggregation process, protein secondary structure elements—α‐helices—undergo conformational changes to β‐sheets. The fact that proteins with different sequences and structures undergo a similar transition on aggregation suggests that the sequence nonspecific hydrogen bond interaction among protein backbones is an important factor. We perform molecular dynamics simulations of a polyalanine model, which is an α‐helix in its native state and observe a metastable β‐hairpin intermediate. Although a β‐hairpin has larger potential energy than an α‐helix, the entropy of a β‐hairpin is larger because of fewer constraints imposed by the hydrogen bonds. In the vicinity of the transition temperature, we observe the interconversion of the α‐helix and β‐sheet states via a random coil state. We also study the effect of the environment by varying the relative strength of side‐chain interactions for a designed peptide—an α‐helix in its native state. For a certain range of side‐chain interaction strengths, we find that the intermediate β‐hairpin state is destabilized and even disappears, suggesting an important role of the environment in the aggregation propensity of a peptide. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Insight into the stability of the hydrophobic binding proteins ofescherichia coli:Assessing the proteins for use as biosensors
Authors: Salopek‐Sondi Branka , Skeels Matthew C. , Swartz Derrick , Luck Linda A. 
Published: October 2004

AbstractSpectroscopic methods were used to monitor the unfolding of the leucine specific (LS) and the leucine‐isoleucine‐valine (LIV) binding proteins. Our studies indicate that ligand‐free protein undergoes a simple two‐state unfolding, whereas the protein‐ligand complex undergoes a three‐state unfolding model. Ligand binding causes significant stabilization of both proteins. There is correlation between ligand hydrophobicity and protein stabilization: the most hydrophobic ligand, isoleucine, causes the most significant stabilization of LIV protein. A disulfide bond present in N‐domain of both proteins makes a large contribution to the protein stability of these periplasmic binding receptors. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Functional motions can be extracted from on‐lattice construction of protein structures
Authors: Doruker Pemra , Jernigan Robert L. 
Published: October 2004

AbstractThe three‐dimensional structure of a 1509‐residue protein‐hemagglutinin is reconstructed on a simple cubic lattice by retaining all lattice sites that fall within close proximity of the X‐ray coordinates. Coarse‐grained normal modes analysis is performed using these lattice sites as the nodes of an elastic network. The collective deformations of the protein can still be extracted from such a structure that just mimics the overall shape of the protein but not its mass distribution. These results emphasize that the overall shape rather than the details of the protein fold determines the dynamical domains in proteins. Thus, low‐resolution protein structures, even those constructed on a regularly spaced lattice, can provide insights about the functionally important global dynamics around the native state. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Prediction of possible sites for posttranslational modifications in human gamma crystallins: Effect of glycation on the structure of human gamma‐b‐crystallin as analyzed by molecular modeling
Authors: Salim Asmat , Bano Asifa , Zaidi Zafar H. 
Published: October 2004

AbstractCrystallins are recognized as one of the long‐lived proteins of lens tissue that might serve as the target for several posttranslational modifications leading to cataract development. We have studied several such sites present in the human γ‐crystallins based either on PROSITE pattern search results or earlier experimental evidences. Their probabilities were examined on the basis of the database analysis of the γ‐crystallin sequences and on their specific locations in the constructed homology models. An N‐glycosylation site in human γD‐crystallin and several phosphorylation sites in all four human γ‐crystallins were predicted by the PROSITE search. Some of these sites were found to be strongly conserved in the γ‐crystallin sequences from different sources. An extensive analysis of these sites was performed to predict their probabilities as potential sites for protein modifications. Glycation studies were performed separately by attaching sugars to the human γB‐crystallin model, and the effect of binding was analyzed. The studies showed that the major effect of αD‐glucose (αD‐G) and αD‐glucose‐6‐phosphate (αD‐G6P) binding was the disruption of charges not only at the surface but also within the molecule. Only a minor alteration in the distances of sulfhydryl groups of cysteines and on their positions in the three‐dimensional models were observed, leading us to assume that glycation alone is not responsible for intra‐ and intermolecular disulfide bond formation. Proteins 2003. © 2003 Wiley‐Liss, Inc.
TOUCHSTONEX: Protein structure prediction with sparse NMR data
Authors: Li Wei , Zhang Yang , Kihara Daisuke , Huang Yuanpeng Janet , Zheng Deyou , Montelione Gaetano T. , Kolinski Andrzej , Skolnick Jeffrey 
Published: October 2004

AbstractTOUCHSTONEX, a new method for folding proteins that uses a small number of long‐range contact restraints derived from NMR experimental NOE (nuclear Overhauser enhancement) data, is described. The method employs a new lattice‐based, reduced model of proteins that explicitly represents Cα, Cβ, and the sidechain centers of mass. The force field consists of knowledge‐based terms to produce protein‐like behavior, including various short‐range interactions, hydrogen bonding, and one‐body, pairwise, and multibody long‐range interactions. Contact restraints were incorporated into the force field as an NOE‐specific pairwise potential. We evaluated the algorithm using a set of 125 proteins of various secondary structure types and lengths up to 174 residues. Using N/8 simulated, long‐range sidechain contact restraints, where N is the number of residues, 108 proteins were folded to a Cα‐root‐mean‐square deviation (RMSD) from native below 6.5 Å. The average RMSD of the lowest RMSD structures for all 125 proteins (folded and unfolded) was 4.4 Å. The algorithm was also applied to limited experimental NOE data generated for three proteins. Using very few experimental sidechain contact restraints, and a small number of sidechain–main chain and main chain–main chain contact restraints, we folded all three proteins to low‐to‐medium resolution structures. The algorithm can be applied to the NMR structure determination process or other experimental methods that can provide tertiary restraint information, especially in the early stage of structure determination, when only limited data are available. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Predicting protein quaternary structure by pseudo amino acid composition
Authors: Chou Kuo‐Chen , Cai Yu‐Dong 
Published: October 2004

AbstractIn the protein universe, many proteins are composed of two or more polypeptide chains, generally referred to as subunits, that associate through noncovalent interactions and, occasionally, disulfide bonds. With the number of protein sequences entering into data banks rapidly increasing, we are confronted with a challenge: how to develop an automated method to identify the quaternary attribute for a new polypeptide chain (i.e., whether it is formed just as a monomer, or as a dimer, trimer, or any other oligomer). This is important, because the functions of proteins are closely related to their quaternary attribute. For example, some critical ligands only bind to dimers but not to monomers; some marvelous allosteric transitions only occur in tetramers but not other oligomers; and some ion channels are formed by tetramers, whereas others are formed by pentamers. To explore this problem, we adopted the pseudo amino acid composition originally proposed for improving the prediction of protein subcellular location (Chou, Proteins, 2001; 43:246–255). The advantage of using the pseudo amino acid composition to represent a protein is that it has paved a way that can take into account a considerable amount of sequence‐order effects to significantly improve prediction quality. Results obtained by resubstitution, jack‐knife, and independent data set tests, have indicated that the current approach might be quite promising in dealing with such an extremely complicated and difficult problem. Proteins 2003. © 2003 Wiley‐Liss, Inc.