bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐term clinical and angiographic outcome of patients with occlusive in‐stent restenosis treated with (32P) β‐brachytherapy
Authors: Ortolani Paolo , Marzocchi Antonio , Aquilina Matteo , Gaiba William , Neri Stefano , Bunkheila Feisal , Lombardo Enzo , Pini Stefania , Marrozzini Cinzia , Palmerini Tullio , Taglieri Nevio , Sbarzaglia Paolo , Reggiani Maria Letizia Bacchi , Barbieri Enza , Branzi Angelo
Published: November 2004

The objective of this study was to determine the safety and efficacy of 32P β‐brachytherapy in totally occlusive in‐stent restenosis (ISR). Patients with occlusive ISR were generally excluded from the randomized clinical trials on intracoronary brachytherapy (utilizing either γ‐ or β‐sources) that have shown reductions in restenosis rate and need for revascularization procedures. We analyzed short‐ and long‐term effects of 32P β‐brachytherapy (20 Gy) in 27 patients (28 lesions) with occlusive ISR and 84 (99 lesions) patients with nonocclusive high‐risk ISR. The primary outcome measure was frequency of in‐lesion angiographic binary restenosis at 7 months. Secondary endpoints were rates of major adverse cardiac events (MACE), target vessel revascularization (TVR), clinically driven TVR, and target lesion revascularization (TLR). 32P β‐brachytherapy was feasible and safe and provided similar postprocedural angiographic results in the two clinically comparable groups. However, the 7‐month binary restenosis rate was higher in the occlusive group, as were the MACE and late total occlusion rates. Multivariate logistic analysis of the overall population indicated occlusive pattern to be the only independent predictor of angiographic restenosis. In both groups, recurrent lesions most often showed a focal pattern with significant reduction of length. Although safe and effective in high‐risk ISR, 32P brachytherapy at 20 Gy does not appear to be sufficient to avoid long‐term restenosis in patients with occlusive lesions. Further studies should determine the most suitable source and dosage of brachytherapy for patients with occlusive ISR. Catheter Cardiovasc Interv 2004;63:433–438. © 2004 Wiley‐Liss, Inc.
Selective Complexation of N‐Alkylpyridinium Salts: Binding of NAD+ in Water
Authors: Fokkens Michael , Jasper Christian , Schrader Thomas , Koziol Felix , Ochsenfeld Christian , Polkowska Jolanta , Lobert Matthias , Kahlert Björn , Klärner Frank‐Gerrit
Published: November 2004

A new class of receptor molecules is presented that is highly selective for N‐alkylpyridinium ions and electron‐poor aromatics. Its key feature is the combination of a well‐preorganized molecular clip with an electron‐rich inner cavity and strategically placed, flanking bis‐phosphonate monoester anions. This shape and arrangement of binding sites attracts predominantly flat electron‐poor aromatics in water, binds them mainly by π–cation, π–π, CH–π, and hydrophobic interactions, and leads to their highly efficient desolvation. NAD+ and NADP, the important cofactors of many redox enzymes, are recognized by the new receptor molecule, which embraces the catalytically active nicotinamide site and the adenine unit. Even nucleosides such as adenosine are likewise drawn into the clip's cavity. Complex formation and structures were examined by one‐ and two‐dimensional NMR spectroscopy, Job plot analyses, and isothermal titration microcalorimetric (ITC) measurements, as well as quantum chemical calculations of 1H NMR shifts. The new receptor molecule is a promising tool for controlling enzymatic oxidation processes and for DNA chemistry.
Versatile Self‐Complexing Compounds Based on Covalently Linked Donor–Acceptor Cyclophanes
Authors: Liu Yi , Flood Amar H. , Moskowitz Ross M. , Stoddart J. Fraser
Published: November 2004

A range of covalently linked donor–acceptor compounds which contain 1) a hydroquinone (HQ) unit, 2) a 1,5‐dioxynaphthalene (DNP) ring system, or 3) a tetrathiafulvalene (TTF) unit as the π‐donor, and 4) cyclobis(paraquat‐p‐phenylene) (CBPQT4+) as the π‐accepting tetracationic cyclophane were prepared and shown to operate as simple molecular machines. The π‐donating arms can be included inside the cyclophane in an intramolecular fashion by virtue of stabilizing noncovalent bonding interactions. What amounts to self‐complexing/decomplexing equilibria were shown to be highly temperature dependent when the π‐donating arm contains either an HQ or DNP moiety. The thermodynamic parameters associated with the equilibria have been unraveled by using variable‐temperature1H NMR spectroscopy. The negative ΔH° and ΔS° values account for the fact that the “uncomplexed” conformation becomes the dominant species, since the entropy gain associated with the decomplexation process overcomes the enthalpy loss resulting from the breaking of the donor–acceptor interactions. The arm's in‐and‐out movements with respect to the linked cyclophanes can be arrested by installing a bulky substituent at the end of the arm. In the case of compounds carrying a DNP ring system in their side arm, two diastereoisomeric, self‐complexing conformations are observed below 272 K in hexadeuterioacetone. By contrast, control over the TTF‐containing arm's movement is more or less ineffective through the thermally sensitive equilibrium although it can be realized by chemical and electrochemical ways as a result of TTF's excellent redox properties. Such self‐complexing compounds could find applications as thermo‐ and electroswitches. In addition, the thermochromism associated with the arm's movement could lead to some of the compounds finding uses as imaging and sensing materials.
Acid Zeolites as Alcohol Racemization Catalysts: Screening and Application in Biphasic Dynamic Kinetic Resolution
Authors: Wuyts S. , De Temmerman K. , De Vos D. E. , Jacobs P. A.
Published: November 2004

Acid zeolites were screened as heterogeneous catalysts for racemization of benzylic alcohols. The most promising zeolites appeared to be H‐Beta zeolites, for which the optimal reaction conditions were studied in further detail. The zeolite performance was compared to that of homogeneous acids and acid resins under similar reaction conditions. In a second part of the research, H‐Beta zeolites were applied in dynamic kinetic resolution (DKR) of 1‐phenylethanol, which was conducted by means of a two‐phase approach and which resulted in yields smoothly crossing the 50 % border up to 90 %, with an enantiomeric excess of >99 %. To explore the applicability of this biphasic methodology, several other substrates were examined in the standard racemization reaction and in the biphasic dynamic kinetic resolution.
Appropriateness of breast‐conserving treatment of breast carcinoma in women with germline mutations in BRCA1 or BRCA2
Authors: Robson Mark , Svahn Tiffany , McCormick Beryl , Borgen Patrick , A. Hudis Clifford , Norton Larry , Offit Kenneth
Published: November 2004

BACKGROUND

Although BRCA1 and BRCA2 were identified in 1994 and 1995, respectively, to the authors' knowledge the optimal management of women with BRCA‐associated breast carcinoma remains incompletely defined. The current study evaluates the appropriateness of breast‐conserving therapy (BCT) in women with BRCA mutations.

METHODS

Between May 1992 and October 2003, 87 female participants in genetic testing protocols were identified who 1) were found to have deleterious germline BRCA mutations and 2) reported a history of invasive breast carcinoma that was treated with wide local excision and radiation therapy. Clinical records were reviewed and follow‐up was updated.

RESULTS

The 87 subjects underwent BCT for 95 invasive breast tumors (8 women received BCT for metachronous bilateral tumors). In all 95 treated breasts, the 5‐year and 10‐year probabilities of metachronous ipsilateral breast carcinoma (MIBC) were 11.2% and 13.6%, respectively. Among the 87 subjects, the 5‐year and 10‐year probabilities of metachronous contralateral breast carcinoma (CBC) after treatment of the index tumor were 11.9% and 37.6%. No clinical factors were identified that were associated with either MIBC or CBC, including the use of tamoxifen or chemotherapy.

CONCLUSIONS

Women with BRCA‐associated breast carcinoma who undergo BCT appear to have risks of MIBC that are similar to those reported for young women without known mutations. The indications for unilateral mastectomy in this group of women should be the same as those for women with nonhereditary carcinoma. However, significant risks of CBC and possibly late MIBC may prompt the serious consideration of bilateral mastectomy as a preventive measure. Cancer 2005. © 2004 American Cancer Society.
X‐ray Absorption Spectra of CuII and CuIII Complexes of N,N′‐1,2‐Phenylenebis(2‐mercapto‐2‐methylpropionamide)
Authors: Barone Giampaolo , La Manna Gianfranco , Duca Dario
Published: November 2004

The X‐ray absorption spectra of CuII and CuIII complexes of N,N′‐1,2‐phenylenebis(2‐mercapto‐2‐methylpropionamide) were recorded and analysed in solid phase. The EXAFS spectra of the two samples were refined with full multiple scattering path. Geometry optimisations on the CuII and CuIII complexes were performed by the B3LYP density functional method, with the 6‐31G(d,p) basis set, considering different spin multiplicities. The singlet state of the CuIII complex was shown to be more stable than the triplet state, and a good agreement between the calculated and the corresponding experimental structure was found. Further single‐point calculations on the optimised geometry were carried out at the Hartree−Fock level for obtaining molecular orbital eigenvectors and eigenvalues. The latter were employed as parameters in a new fitting approach to rationalise the shape of the K‐edge of the XAS spectra. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Novel Binary Compounds of Group 15 Elements: Synthesis and Characterisation of [Sb4(PSiMe2Thex)4], [Sb4(AsSiiPr3)4] and [Sb2(PSiPh2tBu)4]
Authors: Nikolova Donna , von Hänisch Carsten
Published: November 2004

The low‐temperature reactions of Me2ThexSiPLi2 (Thex = CMe2iPr) and iPr3SiAsLi2 with SbCl3 in a 3:2 molar ratio yields the cage compounds [Sb4(PSiMe2Thex)4] (1) and [Sb4(AsSiiPr3)4] (2), respectively. The metal salt SbBr3 reacts with tBuPh2SiPLi2 at −70 °C to give the bicyclic compound [Sb2(PSiPh2tBu)4] (3). Compounds 1−3 were characterised by NMR and IR spectroscopy, mass spectrometry, elemental analysis and single‐crystal X‐ray diffraction. The structures of 1 and 2 reveal that the both compounds adopt a structure similar to those of realgar (As4S4). The central structural motif is an Sb4Y4 cage (Y = P, As), consisting of four five‐membered rings with common edges. The bicyclic compound 3 is composed of five‐membered and three‐membered rings sharing a common Sb2 bridgehead. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Temperature‐Controlled Solvothermal Syntheses, Structures and Characterizations of a Novel Class of Zn Complexes Constructed from 1,4‐Bis[2‐(5‐phenyloxazolyl)]benzene
Authors: Chen Shu‐Mei , Lu Can‐Zhong , Zhang Quan‐Zheng , Liu Jiu‐Hui , Wu Xiao‐Yuan
Published: November 2004

Three novel complexes, ZnCl2(H2O)(POPOP)·POPOP) (1), [ZnCl2(POPOP)]n (2), and {Zn2(CH3COO)(POPOP)1.5Cl3}n (3) {POPOP = 1,4‐bis[2‐(5‐phenyloxazolyl)]benzene}, of zinc−POPOP coordination polymers have been obtained from an identical starting mixture using temperature as the only independent variable. Complexes 1−3 all crystallize in the triclinic P$\bar 1$
space group, but their ZnII centers adopt different coordinations. Complex 1 consists of POPOP‐coordinated zinc units and discrete POPOP molecules, 2 features an interesting zigzag chain structure, and 3 consists of unique ladder‐like double‐chains bridged by POPOP units. Furthermore, 1−3 display some different fluorescent emissions based on their different coordination architectures. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
cyclo(β‐Asp‐β3‐hVal‐β3‐hLys) – Solid‐Phase Synthesis and Solution Structure of a Water Soluble β‐Tripeptide. Preliminary Communication
Authors: Büttner Frank , Erdélyi Máté , Arvidsson Per I.
Published: November 2004

The H2O‐soluble cyclic β3‐tripeptide cyclo(β‐Asp‐β3‐hVal‐β3‐hLys) (4) was obtained by on‐resin cyclization of the side‐chain‐anchored β‐peptide 3 (Scheme). In aqueous solution, 4 adopts a structure with uniformly oriented amide bonds and all side chains in lateral positions (Fig. 3).
Synthesis of Novel Chiral Ionic Liquids and Their Phase Behavior in Mixtures with Smectic and Nematic Liquid Crystals
Authors: Tosoni Martin , Laschat Sabine , Baro Angelika
Published: November 2004

Alkylation of 1‐alkyl‐1H‐imidazoles 2a–f with citronellyl bromide 1b opens access to chiral 1H‐imidazolium bromides 3a–f (Scheme 1). A similar strategy yielded the chiral pyridinium ionic liquid 6 (Scheme 2). Dialkylation of 1H‐imidazole (7) gave the C2‐symmetric 1,3‐dicitronellyl‐1H‐imidazolium bromide (8) (Scheme 3). Differential scanning calorimetry and optical polarizing microscopy revealed smectic mesophases for 1‐citronellyl‐3‐tetradecy‐1H‐limidazolium bromide (3e) and 1‐citronellylpyridinium bromide (6) (Table). In binary mixtures with smectic and nematic liquid crystals 9 and 10, 1‐citronellyl‐3‐methyl‐1H‐imidazolium bromide (3a) behaved differently. Increasing quantities of 3a cause a decrease of the smectic‐phase width for the mixture 3a/9 (Fig. 3), whereas the phase width of the nematic phase for 3a/10 remained nearly constant (Fig. 4).
Adenanthusone, a New Ursane Type Nortriterpenoid from Isodon adenanthus
Authors: Xiang Wei , Song Qi‐Shi , Zhang Hong‐Jie , Li Rong‐Tao , Na Zhi , Sun Han‐Dong
Published: November 2004

A new ursane‐type nortriterpenoid, adenanthusone (=(11α,12α)‐4‐demethyl‐11,12‐epoxy‐3,13‐dihydroxy‐2‐oxoursa‐3,20(30)‐diene‐28‐oic acid γ‐lactone; 1) was isolated from Isodon adenanthus. Its structure was determined by NMR spectra and X‐ray crystallographic diffraction analysis. The biogenetic implication of the nortriterpene is discussed.
Four Novel Dihydroisocoumarin (=3,4‐Dihydro‐1H‐2‐benzopyran‐1‐one) Glucosides from the Fungus Cephalosporium sp. AL031
Authors: Bi Yun‐Mei , Bi Xu‐Bin , Zhao Qian‐Rong , Chen Yuan‐Teng , Xie Jin‐Lun
Published: November 2004

Four novel dihydroisocoumarin (=3,4‐dihydro‐1H‐2‐benzopyran‐1‐one) glucosides were isolated from a culture broth of a strain of the fungus Cephalosporium sp. AL031. Their structures were elucidated as (2E,4E)‐5‐[(3S)‐5‐acetyl‐8‐(β‐D‐glucopyranosyloxy)‐3,4‐dihydro‐6‐hydroxy‐1‐oxo‐1H‐2‐benzopyran‐3‐yl]penta‐2,4‐dienal (1), (2E,4E)‐5‐[(3S)‐5‐acetyl‐8‐(β‐D‐glucopyranosyloxy)‐3,4‐dihydro‐6‐methoxy‐1‐oxo‐1H‐2‐benzopyran‐3‐yl]penta‐2,4‐dienal (2), (3S)‐8‐(β‐D‐glucopyranosyloxy)‐3‐[(1E,3E,5E)‐hepta‐1,3,5‐trienyl]‐3,4‐dihydro‐6‐hydroxy‐5‐methyl‐1H‐2‐benzopyran‐1‐one (3), and (3S)‐8‐[(6‐O‐acetyl‐β‐D‐glucopyranosyl)oxy]‐3‐[(1E,3E,5E)‐hepta‐1,3,5‐trienyl]‐3,4‐dihydro‐6‐methoxy‐5‐methyl‐1H‐2‐benzopyran‐1‐one (4) by spectroscopic methods, including 2D‐NMR techniques and chemical methods.
Amphiphilic Dendrimers with Heteroleptic Bis([2,2′: 6′,2″]terpyridine)‐Ruthenium(II) Cores
Authors: Joester Derk , Gramlich Volker , Diederich François
Published: November 2004

A new series of dendrimers was assembled through formation of homo‐ and heteroleptic RuII complexes with [2,2′: 6′,2″]terpyridine ligands bearing hydrophilic and hydrophobic dendrons, with the aim to develop amphiphilic vectors for potential use in gene delivery (Scheme 1). The synthesis started with the preparation of the 4′‐(3,5‐dihalo‐4‐methoxyphenyl)‐[2,2′: 6′,2″]terpyridine ligands 1a,b via the Kröhnke pyridine synthesis (Scheme 2), followed by attachment of dendrons 10a–10f (Fig. 2) by Sonogashira cross‐coupling to give the dendritic ligands 11–16 (Schemes 3 and 4). Ligands were subsequently introduced into the coordination sphere of RuIII to give the stable intermediates [Ru(11)Cl3] (24; Scheme 7) and [Ru(14)Cl3] (27; Scheme 8). These were transformed under reductive conditions into the heteroleptic complexes [Ru(11)(13)](PF6)2 (25) and [Ru(13)(14)](PF6)2 (29). Removal of the (tert‐butoxy)carbonyl (Boc) protecting groups in 25 and 29 then gave the desired amphiphilic dendrimers 26 (Scheme 7) and 30 (Scheme 8) with branchings of generations 0 and 1. Complex formation was analyzed by high‐resolution matrix‐assisted laser‐desorption‐ionization Fourier‐transform ion‐cyclotron‐resonance mass spectrometry (HR‐MALDI‐FT‐ICR‐MS), which provided spectra featuring unique fragment‐ion series and perfectly resolved isotope distribution patterns (Figs. 4 and 5). The preparation of homo‐ and heteroleptic complexes with terpyridine ligands bearing generation‐2 dendrons failed due to steric hindrance by the bulky wedges.
Study of the Fire Performance of Magnesium Hydroxide Sulfate Hydrate Whisker Flame Retardant Polyethylene
Authors: Lu Hongdian , Hu Yuan , Yang Ling , Wang Zhengzhou , Chen Zuyao , Fan Weicheng
Published: November 2004

Summary: Halogen‐free, flame retardant low density polyethylene (LDPE) composites, using magnesium hydroxide sulfate hydrate (MHSH) whiskers as a flame retardant, combined with microencapsulated red phosphorous (MRP) as a synergist, have been prepared using a two‐roll mill. Their fire properties were determined by using the limiting oxygen index (LOI), the UL‐94 test and cone calorimetry. The results showed that MRP was a good synergist in improving the flame retardance of the LDPE/MHSH whisker system. Poly[ethylene‐co‐(vinyl acetate)] (EVA), used as a compatibilizer, increased the fire performance of LDPE/MHSH whisker composites.

HRR curves for LDPE/MHSH whisker composites.

magnified image

HRR curves for LDPE/MHSH whisker composites.
Eigenvalue sensitivity and parametric optimization of the large rotating systems
Authors: Byrtus Miroslav , Zeman Vladimír , Hajžman Michal
Published: November 2004

The contribution presents the modal synthesis method of the mathematical modelling of the large rotating systems. The condensed mathematical model is used for deriving analytical formula for eigenvalue sensitivity calculation. According to the sensitivity analysis suitable design parameters are chosen and the optimization process for the purpose of steady state response minimization in a certain operating speed area is performed. The theory is applied to a simple test‐gearbox. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ein Modell zur Untersuchung des dynamischen Verhaltens von Oberbausystemen
Authors: Hochrainer M. J.
Published: November 2004

Im Eisenbahnwesen basiert die Modellierung und Berechnung von Oberbausystemen auch heute noch hauptsächlich auf der Analyse von elastisch gebetteten Balken und der Formel von Zimmermann. Für dieses Modell wird eine dynamische Erweiterung vorgestellt, welche unter anderem auch die Berücksichtigung einer diskreten Schienenlagerung, unterschiedlicher Oberbausysteme oder bewegter dynamischer Lasten erlaubt. Die numerische Berechnung erfolgt auf Basis einer finiten Elemente Formulierung für bewegte Referenzsysteme und ermöglicht, im Unterschied zu analytischen Lösungen, große Flexibilität in der System‐ und Parameterwahl. Die allgemeine Beschreibung eignet sich unter anderem zur Untersuchung der Fahrzeug‐Fahrweg‐Interaktion für Schotteroberbau, Feste Fahrbahn oder Masse‐Feder‐Systeme, sowie zur Abschätzung der Schwingungsanregung für eine nachfolgende Untersuchung der Erschütterungsausbreitung im Untergrund. Durch den Einsatz von Substrukturmethoden können auch komplexe Fahrzeug‐ und Untergrundmodelle in die Oberbausimulation eingebunden werden. Eine Optimierung der Vertikaldynamik von Oberbausystemen ist für Bahnerhalter, Anrainer und Reisende von Bedeutung, weil dadurch einerseits die mechanische Belastung der Bahnstrecken, die Erhaltungskosten und die Abstrahlung von Lärm und Erschütterungen minimiert und andererseits die Basis für einen erhöhten Reisekomfort geschaffen wird. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stabilizing and destabilizing effect of small velocity‐dependent forceson non‐conservative systems: new results
Authors: Kirillov Oleg
Published: November 2004

A theory of the destabilization paradox in general non‐conservative systems with small dissipative and gyroscopic forces is presented. The problem is investigated by the approach based on the sensitivity analysis of multiple eigenvalues. An explicit asymptotic expression for the critical load as a function of the dissipation and gyroscopic parameters allowing to calculate a jump in the critical load is derived. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of Nonlinear Discrete‐time Control Systems based on Lie‐Groups
Authors: Holl Johann , Schlacher Kurt
Published: November 2004

This contribution is concerned with the observability and accessibility analysis of nonlinear explicit discrete‐time control systems. The presented approach is fundamental based on the fact that the geometric interpretation known from the analysis of continuous‐time systems based on Lie groups is also appropriate in the discrete‐time case. It is shown that by investigation of invariants of Lie groups acting on the solution of the system it is possible to state conditions for local observability and accessibility without calculating the solution. These methods provide tests which can be done by computer algebra. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A modal approach to flatness‐based control of flexible structures
Authors: Meurer Thomas , Zeitz Michael
Published: November 2004

Modal coordinates are used to construct a state and input parameterizing flat output for flexible structures and to design open‐loop controls. This is illustrated for the boundary control of a Timoshenko beam model. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On synchronized solutions of coupled Van‐der‐Pol equations
Authors: Teufel Andreas
Published: November 2004

Two linearly coupled Van‐der‐Pol oscillators are considered in the case of a small frequency detuning of the oscillators as well as weak coupling. The occurring resonant Hopf bifurcation leading to synchronized motions is examined and analytical approximations of the oscillation amplitudes and the synchronous frequency are derived. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Seilkraftoptimierung für redundante Parallelmanipulatoren mit Seilantrieben
Authors: Franitza Daniel , Fang Shiqing
Published: November 2004

Seilgetriebene Parallelkinematiken bieten unter den heute verfügbaren Handhabungssystemen die besten dynamischen Voraussetzungen für schnelle Bewegungen. Allerdings stehen der geringen zu bewegenden Masse restriktive Nebenbedingungen gegenüber, die die übertragbaren Seilkräfte nach oben und unten mit endlichen Werten begrenzen. Für eine vollständige Nutzung von n Freiheitsgraden sind daher m > n Seile zur Anlenkung des Endeffektors nötig, was zu gewollten Verspannungen innerhalb der eingeleiteten Seilkräfte führt. Der Beitrag beschäftigt sich mit einer anwendungsorientierten Formulierung der Seilkraftoptimierung und stellt alternative Konzepte für eine gegebene Plattformbewegung gegenüber. Der Algorithmus wird am einem Prüfstand mit sieben Seilen zur Bewegung einer Plattform mit sechs Freiheitsgraden verifiziert. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ein O(n) Verfahren zum Lösen von starren Mehrkörperketten mit Kontaktbedingungen
Authors: Gattringer Hubert , Bremer Hartmut
Published: November 2004

Bei der Modellierung von Mehrkörperketten (starr oder elastisch), wie das bei Robotern der Fall ist, entstehen sehr große Bewegungsgleichungen. Für deren Simulation ist die explizite Invertierung der Massenmatrix (On3) notwendig. Bei dem in dieser Arbeit vorgestellten On Verfahren, welches die Invertierung der Massenmatrix aufgrund der speziellen Struktur der Bewegungsgleichungen rekursiv durchführt, wird die Rechenzeit deutlich reduziert. Treten bei Mehrkörperketten noch zusätzliche Kontakte auf, so kann dies durch die Hinzunahme eines Lagrangeschen Parameters zur Bewegungsgleichung erfolgen. Zur Berechnung dieser Zwangskraft wäre bei der herkömmlichen Modellierung wieder die inverse Massenmatrix notwendig. Der in dieser Arbeit präsentierte Algorithmus kommt ohne eine explizite Invertierung zur Berechnung des Lagrangeschen Parameters aus. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamische Modellierung hybrider Knickarmroboter unter Berücksichtigung
Authors: Mitterhuber Ralph , Gattringer Hubert , Bremer Hartmut
Published: November 2004

Die dynamische Modellbildung von kettenförmigen Mehrkörpersystemen, bestehend aus starren und elastischen Einzelkörpern, führt mit zunehmender Anzahl von Körpern rasch zu sehr großen, partiellen Bewegungsgleichungen. Unter der Annahme von linearisierbar kleinen elastischen Deformationen kann mittels Ritzansätzen auf eine Beschreibung mit gewöhnlichen Differentialgleichungen übergegangen werden. Bei der Herleitung der Bewegungsgleichungen ist es zielführend, das System geeignet zu strukturieren, um so interpretierbare Zwischenergebnisse zu erhalten. Diese Vorgangsweise führt zur Verwendung der Projektionsgleichung, einer synthetischen Methode, welche Impuls‐ und Drallbeziehungen der Einzelkörper unter Elimination der Zwangskräfte in den Raum der Minimalgeschwindigkeiten projiziert. Unter Berücksichtigung der Struktur des betrachteten Systems lassen sich zudem einzelne Körper zu Gruppen, sogenannten Subsystemen, mit entsprechenden beschreibenden Geschwindigkeiten zusammenfassen. Die Dimensionen der resultierenden Massenmatrix des Gesamtsystems entsprechen der Dimension des Minimalgeschwindigkeitsvektors. Der Rechenaufwand zur Invertierung der Massenmatrix und somit zur numerischen Lösung explodiert förmlich mit der kubischen Ordnung der Freiheitsgrade. Aufgrund der kettenförmigen Struktur des elastischen Mehrkörpersystems lässt sich jedoch ein einfach strukturiertes Verfahren angeben, bei dem nur Matrizen der Dimensionen der Relativfreiheitsgrade der Subsysteme zu invertieren sind. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Relationships between the Shape of the Workspace and GeometricalDimensions of Parallel Manipulators
Authors: Pisla D. , Pisla A.
Published: November 2004

In this paper, a new simulation program for the workspace analysis of parallel robots is presented. The system consists of modules, which enable a complex study of the parallel structures. A special method for generating the workspace of the parallel structures is used. The simulation program offers the possibility to generate automatically the virtual model of the parallel robot using the facilities of a 3D modeling software. The structure geometric parameters, which could be modified within the modeling software, influence the simulation environment. These facilities enable to establish the relationships between the workspace shape, elements links and geometrical parameters of the structure. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Integrated motion measurement of rigid multibody systems
Authors: Wagner Jörg F.
Published: November 2004

During the last years, integrated navigation systems based on gyros, accelerometers, and GPS receivers became powerful devices for the guidance of aircraft and ships. Comparable equipment using especially wheel sensors exists for cars. The kernel of such systems is a Kalman filter estimating the relevant vehicle motion. The filter design in turn requires a kinematical model to settle on the motion components considered and to describe the mechanical meaning of the measurements employed. Until now, usual models consider only one to six degrees of freedom of a single rigid body.

The assumption of a solitary rigid body is not a consequence of the basic concept of integrated navigation; it reflects merely classical navigation requirements. In principle, determining the motion of multibody systems, representing certain vehicle types of varying shape, is possible if appropriate kinematical models and sensor arrangements are available.

Based on the theory of integrated navigation systems, the paper outlines the fundamentals of designing integrated motion measurement systems for rigid multibody structures. The example of a double pendulum with a movable inertial support and with equipment of microelectromechanical inertial sensors and of small radar units illustrates this approach. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generalized inertia forces of rigid and flexible bodies
Authors: Zahariev Evtim V.
Published: November 2004

In the paper a method for deriving the dynamic equations of motion of rigid and flexible multibody systems is presented. Three dimensional matrices are applied for working out the configuration space dynamic equations. Finite elements are used for modeling of flexible systems. Novel generalized Newton‐Euler equations and relations for inertia forces in nodes of flexible elements are proposed. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the dynamics of axially moving strings
Authors: Renezeder Hans C. , Steindl Alois , Troger Hans
Published: November 2004

We investigate an axially moving cable with large sag modelled as string and calculate the steady state solution between two rolls. Alternatively we model the cable as beam with very small bending stiffness and compare this solution with the string solution. The validity of the analytically found boundary layer solution is verified by numerical methods. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rolling contact between agricultural tire and deformable ground
Authors: Wille R. , Böhm F. , Duda A.
Published: November 2004

While external tire mechanics deals with the effect of tires on vehicle behaviour, internal tire mechanics is focused on computation of stress‐strain and heat states in a tire. Analytical and numerical analysis of different level tire substructure is a pre‐condition for a better understanding of tire behaviour and for a suitable choice of practical calculation schemes. The tire is described geometrically non‐linear as a multi‐layered anisotropic torus shell with low transfer shear stiffness. The strains are assumed to be small, however, the cross‐sections of the tire shell will exhibit moderate rotations. In order to reflect energy losses the visco‐elastic behaviour of tire rubber‐cord‐composite is taken into account. Results are used for the determination and improvement of stiffness parameters for external tire models and for Böhm's mass points approach for transient loading of a rolling tire on rigid and deformable ground. This model is modified to the real structure of an agricultural tire with lugs. The soil under the tire is described by different rheological laws of ground surface behaviour in normal and tangential direction. The numerical results of contact calculation are compared with experimental data gained by mechanical multi‐point measurement technique in order to determine the displacements in the inner of a rolling tire. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Computation of Anisotropically Evolving Yield Surfaces Based on Micro‐to‐Macro Transitions
Authors: Gürses Ercan , Becker Martin , Miehe Christian
Published: November 2004

The paper proposes a numerical computation technique for anisotropically evolving yield surfaces based on micro–to–macro transitions. The underlying model of the finite crystal plasticity and the homogenization approach have previously been formulated by Miehe et al. [2]. The technique proposed has the following two central aspects, firstly a criterion for the determination of the macroscopic yield point is introduced which is based on the physically relevant mechanisms on the microscale and secondly, as a key point of the methodology, total unloading is applied to the representative volume element (RVE) before the yield surface for the corresponding microstructure is determined. The explained method is applied to a Taylor type polycrystalline material model. With respect to the validation of the proposed concept different tests are performed for various preloading conditions and comparisons with experimental findings are provided. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The influence of the filler volume fraction on the mechanical behaviour of thermoplastic materials
Authors: Kletschkowski Thomas , Schomburg Uwe , Betram Albrecht
Published: November 2004

Uniaxial experiments clarify that the mechanical behaviour of PTFE compounds depends strongly on the amount of filler particles. In order to describe these dependencies, a finite endochronic viscoplastic material model based on material isomorphisms has been applied to various glass fibre filled PTFE compounds. The model allows to characterize viscoplastic material behaviour with equilibrium hysteresis using a rate‐independent endochronic elastoplastic model in parallel connection with a nonlinear Maxwell model. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ein phänomenologisches Modell für anisotropes Kriechen in Schweißnähten
Authors: Naumenko Konstantin , Altenbach Holm
Published: November 2004

Die Auswertung von experimentellen Ergebnissen für Zugproben, die an unterschiedlichen Stellen in Schweißnähten entnommen wurden, haben gezeigt, dass das entsprechende Kriechverhalten anisotrop ist. Nachfolgend werden erste Überlegungen zur phänomenologischen Modellierung und Simulation vorgestellt. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Eulerian‐Lagrangian Concept for the Numerical Simulation of Flat Steady‐State Hot Rolling Processes
Authors: Synka Josef , Kainz Alexander
Published: November 2004

For the finite element analysis of stationary flat hot rolling processes, a new and efficient mathematical model was developed. The method is based on an intermediary Eulerian‐Lagrangian concept, where an Eulerian coordinate is employed in the rolling direction, while Lagrangian coordinates are used in the direction of the thickness and width of the strip. This approach yields an efficient algorithm, where the time is eliminated as an independent variable in the steady‐state case. Further, the vector of independent field variables consists of a velocity component in Eulerian and of displacement components in Lagrangian directions. Due to this concept, the free surface deformations can be accounted for directly and the problems encountered with pure Eulerian or Lagrangian models now appear with reduced complexity and can thus be tackled more easily. The general formalism was applied to different practical hot rolling situations, ranging from thick slabs to ultra‐thin hot strips. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An algorithm for shakedown analysis of structures with temperature dependent yield stress
Authors: Vu Duc Khoi , Staat Manfred
Published: November 2004

This work is an attempt to answer the question: How to use convex programming in shakedown analysis of structures made of materials with temperature‐dependent properties. Based on recently established shakedown theorems and formulations, a dual relationship between upper and lower bounds of the shakedown limit load is found, an algorithm for shakedown analysis is proposed. While the original problem is neither convex nor concave, the algorithm presented here has the advantage of employing convex programming tools. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Model for Kidney Tissue Damage under High Speed Loading
Authors: Weinberg Kerstin , Colonius Tim , Ortiz Michael
Published: November 2004

In a medical procedure to comminute kidney stones the patient is subjected to hypersonic waves focused at the stone. Unfortunately such shock waves also damage the surrounding kidney tissue. We present here a model for the mechanical response of the soft tissue to such a high speed loading regime.

The material model combines shear induced plasticity with irreversible volumetric expansion as induced, e.g., by cavitating bubbles. The theory is based on a multiplicative decomposition of the deformation gradient and on an internal variable formulation of continuum thermodynamics. By the use of logarithmic and exponential mappings the stress update algorithms are extended from small‐strain to the finite deformation range. In that way the time‐discretized version of the porous‐viscoplastic constitutive updates is described in a fully variational manner.

By numerical experiments we study the shock‐wave propagation into the tissue and analyze the resulting stress states. A first finite element simulation shows localized damage in the human kidney. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Stress Adaptive Bone Remodelling – Towards an IndividualTherapy in Endoprosthetics –
Authors: Ebbecke Bastian , Nackenhorst Udo
Published: November 2004

Computational techniques for the simulation of stress‐adaptive bone‐remodelling have been developed and applied for the analysis of the bio‐mechanical compatibility of hip‐joint endoprosthesis. Numerical simulations are in good agreement with clinical observations and enable parameter studies for the development of optimized prosthesis designs. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling the Intervertebral Disc – A Biomechanical Challenge
Authors: Markert Bernd , Ehlers Wolfgang , Karajan Nils
Published: November 2004

From a microscopic perspective, the intervertebral disc (IVD) as a soft biological tissue is a complex arrangement of mostly ionized water and collagen fibers embedded in a charged extracellular meshwork of protein compounds. The difficulty of describing the physiological properties of the disc on the macroscale lies in the strong interaction of all components contributing to the inhomogeneous tissue micro structure. Therefore, an appropriate macroscopic approach must account for a fiber‐reinforced porous solid, which is saturated by a free movable interstitial fluid. In addition to the solid‐fluid interaction, electrostatic and osmotic effects as well as the intrinsic viscoelasticity of the extracellular matrix must be considered. All these requirements are consistently realized within the well‐founded framework of the Theory of Porous Media (TPM), which moreover enables efficient large strain analyses based on the finite element method (FEM). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Uptake of a prenatal screening test: the role of healthcare professionals' attitudes towards the test
Authors: Dormandy Elizabeth , Marteau Theresa M.
Published: November 2004

Objective

To investigate the association between healthcare professionals' attitudes towards prenatal Down syndrome screening and screening uptake in the women who consult them.

Methods

The attitudes of 71 midwives and 18 obstetricians towards Down syndrome screening and screening uptake in the women who consulted them were assessed at two UK hospitals where uptake rates of Down syndrome screening differed (26 vs 61%).

Results

Healthcare professionals based at the hospital with higher screening uptake had more positive attitudes towards Down syndrome screening than healthcare professionals based at the hospital with lower screening uptake (19 vs 17, p = 0.03). Pooling across hospitals, obstetricians had more positive attitudes than midwives (20 vs 17, p = 0.004). In a sub‐group of women who discussed screening with one healthcare professional, there was no significant association between individual healthcare professionals' attitudes and screening uptake (Spearman correlation coefficient = 0.13, p = 0.51).

Conclusion

In this study powered to detect a correlation of 0.5 and over (i.e. a large effect), healthcare professionals' attitudes towards screening were unrelated to uptake of screening in the women consulting them. It remains to be determined if a smaller effect exists. The observed association between healthcare professionals' attitudes and uptake rates by hospitals raises the question of whether healthcare professionals' attitudes might influence systems of care, not just communication with pregnant women. Copyright © 2004 John Wiley & Sons, Ltd.
Quantitative analysis of cellular fetal hemoglobin gamma chain messenger RNA (HbF‐γ mRNA) in maternal peripheral blood
Authors: Okuda Tomohiro , Kinoshita Yoshiyuki , Tamura Takaya , Kato Chikako , Kojima Hidenori , Watanabe Ai , Honjo Hideo
Published: November 2004

Objective

Fetal cells cross the feto‐maternal barrier and circulate in maternal peripheral blood; thus, this study aimed to show the relationship between clinical evidence in pregnancy and qualitative feto‐maternal barrier changes.

Methods

The expression of fetal hemoglobin gamma chain messenger RNA (HbF‐γ mRNA) was measured by quantitative reverse transcriptase‐polymerase chain reaction (RT‐PCR) in maternal peripheral blood.

Results

HbF‐γ mRNA was detected in all pregnant women after 5 weeks of gestation. In normal pregnancy, there were two peaks at 10 and 40 weeks, and a significant increase 4 weeks prior to the onset of labor. In intrauterine growth restriction (IUGR), preterm delivery and placenta previa, the HbF‐γ mRNA expression was significantly higher than in normal pregnancies.

Conclusion

The expression of HbF‐γ mRNA relative to that of β‐actin mRNA is thought to reflect the real‐time leakage of fetal cells into maternal blood. Copyright © 2004 John Wiley & Sons, Ltd.
Current awareness in prenatal diagnosis
Authors:   John Wiley & Sons, Ltd.
Published: November 2004

In order to keep subscribers up‐to‐date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of prenatal diagnosis. Each bibliography is divided into 17 sections: 1 Books, Reviews & Symposia; 2 General Interest; 3 Normal Fetal Development; 4 Gametogenesis and Pre‐implantation Diagnosis; 5 First Trimester Diagnosis; 6 Second Trimester Diagnosis; 7 Fetal Diagnosis by Ultrasound and Other Imaging; 8 Maternal Screening; 9 Screening for Carriers of Genetic Abnormality; 10 Technological Developments; 11 Confined Placental Mosaicism and Uniparental Disomy; 12 Molecular Cytogenetics; 13 Fetal Cells in Maternal Circulation; 14 Fetal Therapy; 15 Psychosocial Aspects; 16 Epidemiology and Environmental Factors; 17 Developmental Pathology. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted
Polymer crystallization kinetics, master quotients, master curves and Nakamura‐Ozawa‐equations of iPP and PTFE
Authors: Lambrigger Markus
Published: November 2004

Evaluation concepts related to Avrami master curves are described for the analysis of isothermal and non‐isothermal kinetic processes exhibiting topological nucleation and growth characteristics. These evaluation concepts are shown to be helpful for studies focusing on kinetic data of polymer crystallization experiments with iPP (isotactic polypropylene) and PTFE (polytetrafluoroethylene). An apparent m‐order reaction model is discussed with respect to the isokinetic nucleation and growth model of Nakamura as well as to the non‐isothermal crystallization kinetics theory of Ozawa. Thus, the cooling functions χ(T) of iPP and PTFE, obtained by analyzing DSC (differential scanning calorimetry) experiments with constant cooling rates, are calculated in two alternative ways by using clearly different mathematical approaches. Finally, master quotients, theoretical crystallization limits, and further types of master curves are defined. Polym. Eng. Sci. 44:2194–2202, 2004. © 2004 Society of Plastics Engineers.
Fate of erucamide in polyolefin films at elevated temperature
Authors: Shuler Christopher A. , Janorkar Amol V. , Hirt Douglas E.
Published: November 2004

Erucamide is incorporated into polymer films to reduce their coefficient of friction (COF). At elevated temperatures, erucamide may be lost from the film surface to the surroundings, undergo chemical change or decomposition, and/or migrate back into the film. The major objective of this work was to investigate the fate of erucamide upon exposure to a higher temperature (55°C). Trilayer films containing a polyolefin plastomer (POP) as one skin layer and LLDPE as the other two layers with erucamide incorporated in the POP layer were used. Based on ATR‐FTIR spectroscopy, solvent washing, and GC‐MS results it was concluded that, upon exposure to 55°C, the major reduction in erucamide surface concentration was due to migration of erucamide back into the film and a slight reduction was due to the decomposition of erucamide present on the surface of the polymer film. Polym. Eng. Sci. 44:2247–2253, 2004. © 2004 Society of Plastics Engineers.
Experimental studies on radial extrudate swell and velocity profiles of flowing PS melt in an electro‐magnetized die of an extrusion rheometer
Authors: Intawong N‐T. , Sombatsompop N.
Published: November 2004

This article investigates the radial extrudate swell and velocity profiles of polystyrene melt in a capillary die of a constant shear‐rate extrusion rheometer, using a parallel coextrusion technique. An electro‐magnetized capillary die was used to monitor the changes in the radial extrudate swell profiles of the melt, which is relatively novel in polymer processing. The magnetic flux density applied to the capillary die was varied in a parallel direction to the melt flow, and all tests were performed under the critical condition at which sharkskin and melt fracture did not occur in the normal die. The experimental results suggest that the overall extrudate swell for all shear rates increased with increasing magnetic flux density to a maximum value and then decreased at higher densities. The maximum swelling peak of the melt appeared to shift to higher magnetic flux density, and the value of the maximum swell decreased with increasing wall shear rate and die temperature. The effect of magnetic torque on the extrudate swell ratio of PS melt was more pronounced when extruding the melt at low shear rates and low die temperatures. For radial extrudate swell and velocity profiles, the radial swell ratio for a given shear rate decreased with increasing r/R position. There were two regions where the changes in the extrudate swell ratio across the die diameter were obvious with changing magnetic torque and shear rate, one around the duct center and the other around r/R of 0.65–0.85. The changes in the extrudate swell profiles across the die diameter were associated with, and can be explained using, the melt velocity profiles generated during the flow. In summary, the changes in the overall extrudate swell ratio of PS melt in a capillary die were influenced more by the swelling of the melt around the center of the die. Polym. Eng. Sci. 44:2298–2307, 2004. © 2004 Society of Plastics Engineers.
Studies on impact‐modified nylon 6/ABS blends
Authors: Chiu H. T. , Hsiao Y. K.
Published: November 2004

The objective of this research is to study the effect of using maleic anhydride‐grafted polyethylene‐octene elastomer (POE‐g‐MA) as a compatibilizer on nylon 6/acrylonitile‐butadiene‐styrene (ABS) copolymer blends. With POE‐g‐MA, nylon 6/ABS at a blending ratio of 80/20 showed an optimal result in modified impact property. Scanning electron microscopy (SEM) revealed that the particle sizes of ABS in the dispersed phase diminished as the amount of the added compatibilizer (POE‐g‐MA) increased. The compatibilizer reduced the surface tension between nylon 6 and ABS, thus increasing the compatibility of the two phases. Furthermore, studies of the rheological behavior of the system showed that the shear viscosity of nylon 6/ABS blends also increased with the introduction of POE‐g‐MA. Finally, dynamic mechanical analysis (DMA) experiments showed that adding POE‐g‐MA dramatically improved the impact strength of the blends at room temperature and low temperatures. Polym. Eng. Sci. 44:2340–2345, 2004. © 2004 Society of Plastics Engineers.