bluuebunny/crossref_metadata_2025 huggingface dataset:
Precipitation of Calcium Carbonate in Confinement
Authors: Loste E. , Park R. J. , Warren J. , Meldrum F. C.
Published: October 2004

In contrast to the regular morphologies displayed by synthetic single crystals, biogenic single crystals frequently exhibit unusual forms and curved surfaces. Such controlled mineralization in biology occurs within restricted volumes constructed for this purpose and there is significant evidence that some crystals with complex morphologies may form via an amorphous precursor phase. We here investigate morphological control of single crystals, using these biological mechanisms as inspiration. Calcite was precipitated within the cylindrical pores of track‐etch membranes via an amorphous calcium carbonate (ACC) precursor phase. Perfect replication of the pore channel to yield rod‐shaped single crystals of calcite was only achieved when the ACC precursor particles entirely filled the pore channels prior to crystallization, a process dependent on the pore diameter. Misshapen particles were formed in all pore diameters in the absence of an ACC phase. This system provides an ideal opportunity to carry out a systematic study into the effect of pore diameter, and the presence of an ACC precursor phase on crystal growth.
Polyetherols from melamine and alkylene carbonates: Properties and application of foamed polyurethanes
Authors: Kijowska Dorota , Kucharski Mieczysław
Published: October 2004

Some results are presented on the applications of polyetherols obtained in reactions of melamine with alkylene carbonates for preparation of foamed polyurethanes. Physical properties of the polyetherols and the parameters of their use are evaluated. Selected properties of polyurethane foams obtained by using the polyetherols, such as apparent density, uptake volume, linear shrinkage, and flammability, are presented. Thermal properties of the products have been found to be much better than those of traditional polyurethane foams. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2302–2308, 2004
Structure and ionic conductivity of a series of di‐o‐butyrylchitosan membranes
Authors: Wan Ying , Creber Katherine A. M. , Peppley Brant , Bui V. Tam
Published: October 2004

Di‐o‐butyrylchitosan was prepared by reacting chitosan with butyric acid anhydride in the presence of perchloric acid as a catalyst. 13C‐NMR and IR spectra of the modified chitosan suggested that both hydroxyl groups, at the C‐6 and C‐3 positions, in the chitosan molecules were substituted. The maximum degree of substitution was found to be less than 28%. The results of X‐ray diffractograms revealed that, in comparison with the unmodified chitosan membrane, the crystallinity of di‐o‐butyrylchitosan membranes was remarkably decreased. Meanwhile, it was also observed that the swelling indices of modified membranes were increased significantly in direct proportion to the degree of substitution. Thermogravimetric analysis indicated that the modified membranes exhibited a slightly increased thermal stability compared to the unmodified membrane. The ionic conductivity of di‐o‐butyrylchitosan membranes after hydration was investigated using impedance spectroscopy. Compared to the unmodified chitosan membrane, the hydrated di‐o‐butyrylchitosan membrane with a relatively high degree of the substitution showed an increased ionic conductivity of more than one order of magnitude. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2309–2323, 2004
Zerstörungsfreie Ortung von Fehlstellen und Inhomogenitäten in Bauteilen mit der Impuls‐Thermografie
Authors: Arndt Ralf , Hillemeier Bernd , Maierhofer Christiane , Rieck Carsten , Röllig Mathias , Scheel Horst , Walther Andrei
Published: October 2004

Im Rahmen eines von der Deutschen Forschungsgemeinschaft geförderten Forschungsvorhabens wird von der Bundesanstalt für Materialforschung und ‐prüfung (BAM) und der Technischen Universität Berlin (TUB) die Anwendung der Impuls‐Thermografie zur zerstörungsfreien Prüfung von Bauteilen und Bauwerken weiterentwickelt. Zu diesem Zweck werden Messungen zu verschiedenen baupraktischen Fragestellungen durchgeführt. Die Bauteiloberflächen werden mit einer Wärmequelle, die dem Prüfproblem angepaßt ist, erwärmt. Der daran anschließende Abkühlungsvorgang wird mit einer Infrarotkamera beobachtet und aufgenommen. Die anschließende Auswertung der gespeicherten Daten wird im Zeitbereich mittels numerischer Verfahren und im Frequenzbereich mittels Puls‐Phasen‐Thermografie durchgeführt. Die Puls‐Phasen‐Thermografie führt insbesondere zu einer praxisrelevanten Reduzierung des Störeinflusses von Oberflächeninhomogenitäten und ungleichmäßiger Erwärmung.
Erweiterung bestehender Verkehrswege bei erhöhtem Lärmschutz – 6‐ und 8streifiger Ausbau der BAB A9 bei München
Authors: Peiker Gilbert , Wagner Paul , Gier Dieter , Wolf Helmut , Schmidt Jürgen
Published: October 2004

Neben dem Neubau gewinnt die Erweiterung bestehender Verkehrswege in Deutschland immer mehr an Bedeutung. Durch den Umbau der Infrastruktur werden Lärmschutzmaßnahmen in neuen Größenordnungen notwendig. Anhand des Ausbaus der Bundesautobahn A9 bei München wird die Koordination und Planung der Maßnahme bei engen Terminen aufgezeigt. Zwei ausgewählte Lösungen zeigen, daß Schallschutz bei bestehenden Verkehrswegen in beengten Platzverhältnissen effektiv sowie wirtschaftlich und gestalterisch auf hohem Niveau sein kann.
Kavitationserosion von Werkstoffen für Wasserbauten
Authors: Momber Andreas
Published: October 2004

Kurzzeitkavitationserosion mit Beanspruchungszeiten bis hinunter zu zwei Sekunden erzeugt in Gesteinen und Betonen meßbaren Masseverlust. Der Verschleißverlauf wird von der Mineralzusammensetzung bestimmt. Er erfolgt in vielen Fällen, im Beton sogar ausschließlich, intergranular. Die Bruchzähigkeit kann den Widerstand der untersuchten Werkstoffe gegen Kavitationserosion ausdrücken. Darüber hinaus spielt die Verteilungsdichte von Strukturfehlern eine Rolle. Eine allgemeine Beziehung$ \dot M $∼ K–nIcbeschreibt den Zusammenhang zwischen Verschleißrate und Bruchzähigkeit, wobei der Exponent n eine Funktion des R‐Kurven‐Verhaltens der Werkstoffe ist.
Singlet Excited‐State Interactions in Naphthalene–Thymine Dyads
Authors: Encinas Susana , Climent Maria J. , Gil Salvador , Abrahamsson Urban O. , Davidsson Jan , Miranda Miguel A.
Published: October 2004

Two thymidine‐derived nucleosides 1 and 2 were prepared by attaching a chiral naphthalene to the positions 5′ and 3′ of the sugar. The resulting dyads, which contain key substructures present in drugs and nucleic acids, exhibit different spatial arrangements (transoid or cisoid) of the fluorophore relative to the thymine unit. Emission measurements on these compounds in the presence of ROH molecules revealed a remarkable intramolecular fluorescence quenching for dyad 1. The obtained results are consistent with quenching of the singlet excited state of 1 by hydrogen‐bond donor solvents. Thus, a physical deactivation process (vibronically induced internal conversion) would be the pathway responsible for the accelerated decay of 1*, favorably competing with fluorescence and intersystem crossing to the triplet. This effect appears to be strongly dependent on the relative spatial arrangement between the naphthalene and thymine units, together with the hydrogen‐bonding ability of the employed ROH.
A comparison of different methods of assessing the features of eating disorders in post‐gastric bypass patients: a pilot study
Authors: de Zwaan Martina , Mitchell James E. , Swan‐Kremeier Lorraine , McGregor Tasha , Howell Michael L. , Roerig James L. , Crosby Ross D.
Published: October 2004

Objective

Two methods for assessing the features of eating disorders in post‐gastric bypass surgery patients were compared.

Method

A total of 45 participants were administered the Eating Disorder Examination (EDE) Interview and completed the EDE‐Questionnaire (EDE‐Q4).

Results

The EDE and the EDE‐Q4 were significantly correlated on the restraint, eating concern, weight concern and shape concern subscales. However, the mean difference in scores was significant for the restraint and eating concern subscales. The discrepancy between methods was largest for the restraint subscale. There was no agreement with regard to objective bulimic episodes and the agreement on subjective bulimic episodes was poor (kappa 0.276). However, the frequencies of subjective bulimic episodes were significantly correlated and did not differ significantly.

Discussion

The EDE‐Q4 seems suitable in assessing eating‐ related psychopathology (subscales) in post‐surgery patients. However, the questionnaire appears to have limited utility for assessing binge eating in this population. Copyright © 2004 John Wiley & Sons, Ltd and Eating Disorders Association.
‘Theory of mind’ in anorexia nervosa
Authors: Tchanturia Kate , Happé Francesca , Godley Joanne , Treasure Janet , Bara‐Carril Nuria , Schmidt Ulrike
Published: October 2004

The ability to make inferences about others' mental states has been termed ‘theory of mind’ (ToM). It underlies the ability to engage in complex social interaction and is impaired in autism. A subgroup of anorexia nervosa (AN) sufferers has autism‐spectrum disorders/empathy disorders. The aim of the study was to explore whether, even in the absence of clear‐cut autistic features, impairments in their ability to mentalize could be found in AN patients. Twenty patients with AN and 20 female healthy control (HC) subjects were tested using: (1) a story comprehension task (ToM stories and control stories); and (2) a cartoon task (ToM cartoons and control cartoons). Individuals with AN performed worse than HC subjects on ToM and on control tasks. However, there was no evidence of any selective impairment of ToM in AN sufferers. These findings do not support a specific link between impaired ToM and AN. Copyright © 2004 John Wiley & Sons, Ltd and Eating Disorders Association.
Has the United Nations General Assembly Special Session on HIV/AIDS made a difference?
Authors: Massoud Nicole , De Lay Paul , Carael Michel
Published: October 2004

The 2001 Declaration of Commitment on HIV/AIDS by 189 countries serves as a benchmark for global action. Definition of specific and time‐bound targets put pressure on these countries to accelerate program implementation, but the first progress reports indicate a low response rate for some indicators and concern about data quality.
World Bank contribution to building national HIV/AIDS monitoring and evaluation capacity in Africa: Going beyond indicator development and conceptual training
Authors: Wilson David
Published: October 2004

An operational plan for monitoring and evaluation with a detailed budget is an essential step in moving from an indicator set to a functioning monitoring and evaluation system. Experience suggests that this will happen only with appropriate funding incentives.
Intervention research and program evaluation: The need to move beyond monitoring
Authors: Peersman Greet , Rugg Deborah
Published: October 2004

Ineffective public health interventions can cost substantial amounts of money that could be directed to more effective programs. The suffering associated with HIV/AIDS necessitates that we proceed with the best possible evidence in hand.
Impact of the coxsackie and adenovirus receptor (CAR) on glioma cell growth and invasion: Requirement for the C‐terminal domain
Authors: Huang Kuo‐Cheng , Altinoz Meric , Wosik Karolina , Larochelle Nancy , Koty Zafiro , Zhu Lixia , Holland Paul C. , Nalbantoglu Josephine
Published: October 2004

Expression of the coxsackie and adenovirus receptor (CAR) is downregulated in malignant glioma cell lines and is barely detectable in high‐grade primary astrocytoma (glioblastoma multiforme). We determined the effect of forced CAR expression on the invasion and growth of the human glioma cell line U87‐MG, which does not express any CAR. Although retrovirally mediated expression of full‐length CAR in U87‐MG cells did not affect monolayer growth in vitro, it did reduce glioma cell invasion in a 3‐dimensional spheroid model. Furthermore, in xenograft experiments, intracerebral implantation of glioma cells expressing full‐length CAR resulted in tumors with a significantly reduced volume compared to tumors generated by control vector‐transduced U87‐MG cells. In contrast, U87‐MG cells expressing transmembrane CAR with a deletion of the entire cytoplasmic domain (except for the first 2 intracellular juxtamembrane cysteine amino acids) had rates of invasion and tumor growth that were similar to those of the control cells. This difference in behavior between the 2 forms of CAR was not due to improper cell surface localization of the cytoplasmically deleted CAR as determined by comparable immunostaining of unpermeabilized cells, equivalent adenoviral transduction of the cells and similar extent of fractionation into lipid‐rich domains. Taken together, these results suggest that the decrease or loss of CAR expression in malignant glioma may confer a selective advantage in growth and invasion to these tumors. © 2004 Wiley‐Liss, Inc.
Increased expression of prostate‐specific G‐protein‐coupled receptor in human prostate intraepithelial neoplasia and prostate cancers
Authors: Weng Jinsheng , Wang Jianghua , Cai Yi , Stafford Lewis Joe , Mitchell Dianne , Ittmann Michael , Liu Mingyao
Published: October 2004

The G‐protein‐coupled receptors and signal transduction pathways represent important specific targets for a variety of human diseases, ranging from the control of blood pressure, allergic response, hormonal disorders and neurologic diseases to tumorigenesis. Most recently, we and others have identified a novel human prostate‐specific G‐protein coupled receptor (PSGR). To investigate the potential roles of PSGR in human normal prostate and prostate cancers, we examined the expression level of PSGR in 146 human prostate samples with real‐time quantitative reverse transcription‐PCR and in situ hybridization method. We significantly extended previous studies and demonstrated that PSGR is specifically expressed in human prostate tissues, not in any other normal and tumor samples tested. Compared to normal and benign prostatic hyperplasia tissues, the expression of PSGR increased significantly in human prostate intraepithelial neoplasia (PIN) and prostate tumors (approximately 10‐fold), especially in early prostate tumors, suggesting PSGR may play an important role in early prostate cancer development and progression. The sensitivity and specificity estimates for PSGR expression were calculated as the area under the receiver‐operating characteristics curve (0.902), indicating high‐level sensitivity and specificity for discriminating benign prostate tissues from malignant prostate tissues. The association of PSGR expression with clinical parameters (clinical stages, Gleason scores, recurrent status and metastasis) was also investigated in this study. Our data suggest that overexpression of PSGR in human PIN and prostate cancers have the potential for early prostate cancer detection and diagnosis. © 2004 Wiley‐Liss, Inc.
L‐carnitine inhibits hepatocarcinogenesis via protection of mitochondria
Authors: Chang BaoJun , Nishikawa Manabu , Nishiguchi Shuhei , Inoue Masayasu
Published: October 2004

Hepatocellular carcinoma is usually preceded by chronic inflammation. However, the molecular mechanism in hepatocarcinogenesis is not well known. Recently, we reported that mitochondrial dysfunction plays an important role in hepatocarcinogenesis via the production of free radicals. Furthermore, we proved that L‐carnitine effectively protects mitochondrial function in vivo. Therefore, we investigated whether long‐term administration of L‐carnitine could prevent hepatitis and subsequent hepatocellular carcinoma in Long‐Evans Cinnamon rats that are often analyzed as a model of hepatocarcinogenesis. The results indicated that oxidative stress elicited from abnormally accumulated copper increased the amount of free fatty acids, thereby inducing mitochondrial dysfunction, resulting in cell death and enhanced secondary generation of reactive oxygen species, which were significantly inhibited by carnitine treatment. Finally, the occurrence of placental glutathione S‐transferase‐positive foci as a marker for preneoplastic lesions and hepatocarcinogenesis were significantly inhibited by L‐carnitine. These facts suggest that mitochondrial injury plays an essential role in the development of hepatocarcinogenesis and that the clinical use of carnitine has excellent therapeutic potential in individuals with chronic hepatitis. © 2004 Wiley‐Liss, Inc.
Genes upregulated in a metastasizing human colon carcinoma cell line
Authors: Orian‐Rousseau Véronique , Mink Sigrun , Mengwasser Jörg , HogenEsch Harm , Guo Feng , Thies Wolf‐Gerolf , Hofmann Martin , Herrlich Peter , Ponta Helmut
Published: October 2004

Differential gene expression between the metastatic human colon cancer cell line HT29p and its nonmetastatic counterpart HT29‐MTX was revealed by suppression subtractive hybridization. Fifty‐eight individual genes showed increased mRNA levels in HT29p cells. Only 15 of these genes had been related to transformation in previous studies; the majority of genes are new candidates encoding proteins relevant for the metastatic process. Cancer profiling arrays as well as in situ hybridization study revealed that at least some of the genes obtained in the SSH screen are also differentially expressed in human tumors. © 2004 Wiley‐Liss, Inc.
Photoexcited formation of bone apatite‐like coatings on micro‐arc oxidized titanium
Authors: Han Yong , Xu Kewei
Published: October 2004

A novel method to rapidly deposit bone apatite‐like coatings on titanium implants in simulated body fluid (SBF) is proposed in this article. The processing was composed of two steps; for example, micro‐arc oxidation (MAO) of titanium to form titania films, and UV‐light illumination of the titania‐coated titanium in SBF. The morphology, crystalline structure, and bond strength of the MAO films were investigated as a function of the applied voltage (in the range of 250–400 V) by using scanning electron microscopy, transmission electron microscopy, energy‐dispersive X‐ray spectrometry, Fourier transform infrared spectroscopy, adhesion‐tensile test, and scratch test. Results showed that the MAO films were porous and nanocrystalline with pore sizes varying from 1 to 3 μm and grain sizes varying from 10–20 to 70–80 nm; the predominant phase in titania films changed from anatase to rutile, and the bond strength of the films decreased from 43.4 to 32.9 MPa as the applied voltage increased from 250 to 400 V. After UV‐light illumination of the films in SBF for 2 h, bone apatite‐like coating was deposited on the MAO film formed at 250 V. The bond strength of the apatite/titania bilayer was about 44.2 MPa. However, no apatite was observed on the MAO film formed at 400 V after UV‐light illumination. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 608–614, 2004
High‐mobility group protein 1(Y): Metastasis‐associated or metastasis‐inducing?
Authors: Evans Alice , Lennard Thomas W.J. , Davies Barry R.
Published: October 2004

Metastasis is the major cause of mortality and morbidity for patients with cancer. The high‐mobility group protein 1(Y) [HMG‐1(Y)] has a role in the transcription of many genes involved at different steps in the metastatic cascade and has been linked with cancer in human and animal models. This may represent a potential therapeutic target for patients. The following review summarizes and critically appraises the evidence for the role of HMG‐1(Y) in metastasis. J. Surg. Oncol. 2004;88:86–99. © 2004 Wiley‐Liss, Inc.
Postoperative pulmonary complications are associated with worse short‐ and long‐term outcomes after extended esophagectomy
Authors: Kinugasa Shoichi , Tachibana Mitsuo , Yoshimura Hiroshi , Ueda Shuhei , Fujii Toshiyuki , Dhar Dipok Kumar , Nakamoto Takeru , Nagasue Naofumi
Published: October 2004

Background

Risk analysis of pulmonary complications after extended esophagectomy with three‐field lymph node dissection (3FLND) has been little reported in the literature.

Methods

Risk factors of developing postoperative pneumonia after extended esophagectomy and its effects on in‐hospital death and overall long‐term survival were compared between 38 patients who developed pneumonia and 80 patients who did not.

Results

Eight patients died of postoperative complications during the hospital stay after esophagectomy. Seven of those 8 patients developed pneumonia, whereas 31 patients of 110 patients who were discharged from the hospital developed pneumonia (P < 0.01). Pneumonia occurred more frequently in elderly patients (P < 0.01), in heavy smokers (P < 0.05), in patients with preoperative pulmonary obstructive dysfunction (P < 0.05), and in patients who received 3 U or more perioperative blood transfusion (P < 0.05). Five‐year overall survival rate (26.7%) of 38 patients who developed pneumonia was significantly worse than 53.4% who did not develop pneumonia (P < 0.01). Multivariate analysis of prognostic factors for overall survival showed that pathological tumor stage (hazard ratio 5.380, P < 0.01) and pneumonia (hazard ratio 2.369, P < 0.01) were independent risk factors. Postoperative pneumonia is correlated with in‐hospital death and poorer long‐term survival after extended esophagectomy with 3FLND.

Conclusions

Elderly patients with a history of heavy smoking and poor pulmonary function should be regarded as a high‐risk group of patients for developing pneumonia and very careful selection is required before subjecting such patients to extended esophagectomy. J. Surg. Oncol. 2004;88:71–77. © 2004 Wiley‐Liss, Inc.
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

Background and Objectives

An 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.

Methods

From 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.

Results

Four 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.

Conclusions

Patients 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

Summary: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 image

DSC 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

Glasfaserverstärkte 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

A 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

Bei 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

Ziel 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

This 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

Die 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

The 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

While 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

A 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

The 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

Spectroscopic 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

The 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

Crystallins 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

TOUCHSTONEX, 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

In 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.
Exploration of structural features of monomeric helical peptides designed with a genetic algorithm
Authors: Zhang Wuming , Loughran Micheal G. , Kanna Shin‐ichi , Yano Kazuyoshi , Ikebukuro Kazunori , Yokobayashi Yohei , Kuroda Reiko , Karube Isao
Published: October 2004

A genetic algorithm (GA)‐based strategy to dissect the determinants of peptide folding into α‐helix was developed. The structural information of helical peptides was obtained with respect to patterns of sequence variability. In many previously reported studies the intrinsic α‐helical propensities of amino acids although sequence‐dependent are apparently independent of the amino acid position. In this research, monomeric helical peptides selected from possible sequences produced by a GA‐chemical synthesis were analyzed to identify possible influential structural features. These hexadeca‐peptides were obtained after four successive generations. A total of 128 synthetic peptides were evaluated via circular dichroism (CD) measurements in aqueous solution, while the mean ellipticity at 222 nm confirmed the monomeric state of the peptides. The results presented here show that our GA‐based strategy may be useful in the design of proteins with increased α‐helix content. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Efficient minimization of angle‐dependent potentials for polypeptides in internal coordinates
Authors: Wedemeyer William J. , Baker David
Published: October 2004

Angular potentials play an important role in the refinement of protein structures through angle‐dependent restraints (e.g., those determined by cross‐correlated relaxations, residual dipolar couplings, and hydrogen bonds). Analytic derivatives of such angular potentials with respect to the dihedral angles of proteins would be useful for optimizing such restraints and other types of angular potentials (i.e., such as we are now introducing into protein structure prediction) but have not been described. In this article, analytic derivatives are calculated for four types of angular potentials and integrated with the efficient recursive derivative calculation methods of Gō and coworkers. The formulas are implemented in publicly available software and illustrated by refining a low‐resolution protein structure with idealized vector‐angle, dipolar‐coupling, and hydrogen‐bond restraints. The method is now being used routinely to optimize hydrogen‐bonding potentials in ROSETTA. Proteins 2003. © 2003 Wiley‐Liss, Inc.