bluuebunny/crossref_metadata_2025 huggingface dataset:
A Biomimetic Artificial Disc with Improved Mechanical Properties Compared to Biological Intervertebral Discs
Authors: Shikinami Y. , Kotani Y. , Cunningham B. W. , Abumi K. , Kaneda K.
Published: November 2004

Patients with serious spinal disc disorders will benefit from a novel artificial disc system that is suitable for clinical use in replacement arthroplasty. The disc is composed of a biomimetic three‐dimensional (3D) fabric with a triaxial fiber alignment that has superior mechanical properties when compared to conventional implants. This disc improves on the constitutional imperfections of biological intervertebral discs by eliminating the risk of rupture and delamination. The fabric bonds firmly to disc bodies, and functions in combination with bioactive bioresorbable pins and scaffolds as a stand‐alone system that maintains the position of the disc and promotes bone growth at the interface. The disc has high biocompatibility and can maintain biomimetic “J‐shaped” stress–strain behavior for up to sixty‐three million alternating stresses, which is the equivalent of natural biological movements for a period of more than 30 years. This technology exemplifies how, in the best biomaterials, biological flexibility may occasionally overcome artificial rigidity.
Extracting Parameters from the Current–Voltage Characteristics of Organic Field‐Effect Transistors
Authors: Horowitz G. , Lang P. , Mottaghi M. , Aubin H.
Published: November 2004

Organic field‐effect transistors were fabricated with vapor‐deposited pentacene on aluminum oxide insulating layers. Several methods are used in order to extract the mobility and threshold voltage from the transfer characteristic of the devices. In all cases, the mobility is found to depend on the gate voltage. The first method consists of deriving the drain current as a function of gate voltage (transconductance), leading to the so‐called field‐effect mobility. In the second method, we assume a power‐law dependence of the mobility with gate voltage together with a constant contact resistance. The third method is the so‐called transfer line method, in which several devices with various channel length are used. It is shown that the mobility is significantly enhanced by modifying the aluminum oxide layer with carboxylic acid self‐assembled monolayers prior to pentacene deposition. The methods used to extract parameters yield threshold voltages with an absolute value of less than 2 V. It is also shown that there is a shift of the threshold voltage after modification of the aluminum oxide layer. These features seem to confirm the validity of the parameter‐extraction methods.
Understanding the Origin of the 535 nm Emission Band in Oxidized Poly(9,9‐dioctylfluorene): The Essential Role of Inter‐Chain/Inter‐Segment Interactions (Adv. Funct. Mater. 2004, 14, 765–781)
Authors: Sims M. , Bradley D. D. C. , Ariu M. , Koeberg M. , Asimakis A. , Grell M. , Lidzey D. G.
Published: November 2004

To view the original paper use http://dx.doi.org/10.1002/adfm.200305149">.
Organosilicon Compounds with Blue Photoluminescence Properties.
Authors: Zheng Guorong , Li Wei , Wang Zixing , Lu Ping
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Synthetic Applicability and in situ Recycling of a B‐Methoxy Oxazaborolidine Catalyst Derived from cis‐1‐Amino‐indan‐2‐ol.
Authors: Gilmore Nathan J. , Jones Simon , Muldowney Mark P.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
First Application of Chiral Ionic Liquids in Asymmetric Baylis—Hillman Reaction.
Authors: Pegot Bruce , Vo‐Thanh Giang , Gori Didier , Loupy Andre
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Tandem Cyclopropanation/Ring‐Closing Metathesis of Dienynes.
Authors: Peppers Brian P. , Diver Steven T.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Prepackaged Ramberg—Baecklund Reagents: Useful Tools for Organic Synthesis.
Authors: Block Eric , Jeon Hak Rim , Putman David , Zhang Shao‐Zhong
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Synthetic Approach to Substituted Cyclopropanes Based on the Coupling Reaction of Lithiated Chloroalkyloxazolines with Fischer Carbene Complexes.
Authors: Florio Saverio , Perna Filippo M. , Luisi Renzo , Barluenga Jose , Rodriguez Felix , Fananas Francisco J.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Asymmetric Aziridination of Chalcones Catalyzed by a Novel Backbone 1,8‐Bisoxazolinylanthracene (AnBOX)‐Copper Complex.
Authors: Xu Jiaxi , Ma Linge , Jiao Peng
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Electrochemical Partial Fluorination of Organic Compounds. Part 74. Efficient Anodic Synthesis of 2‐Fluoro‐ and 2,3‐Difluoro‐2,3‐dihydrobenzofuran Derivatives.
Authors: Dawood Kamal M. , Fuchigami Toshio
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Photochromism of Several Synthesized 1,3‐Diazabicyclo[3.1.0]hex‐3‐ene Derivatives.
Authors: Mahmoodi Nosrat O. , Zanjanchi Mohammad A. , Kiyani Hamzeh
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Synthesis of Novel Condensed Binuclear Heterocycles Based on 1,3‐ and 1,5‐Dicarbonyl Derivatives of 2,2‐Dimethyltetrahydropyran.
Authors: Zyk N. V. , Vatsadze S. Z. , Kostochka M. L. , Lezina V. P. , Vinokurov V. G.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Synthesis and Study of the Properties of 7,8‐Polymethyleneimidazo[4,5‐d]‐1,3,2‐diazaphosphorin‐2‐thiones.
Authors: Nilov D. B. , Kadushkin A. V. , Solov'eva N. P. , Sheinker Yu. N. , Granik V. G.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Tris(pentafluorophenyl)borane Catalyzed Ferrier Azaglycosylation with Sulfonamides and Carbamates.
Authors: Chandrasekhar S. , Reddy Ch. Raji , Chandrashekar G.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Novel Stereoselective Entry to 2′‐β‐Carbon‐Substituted 2′‐Deoxy‐4′‐thionucleosides from 4‐Thiofuranoid Glycals.
Authors: Haraguchi Kazuhiro , Shiina Noriaki , Yoshimura Yuichi , Shimada Hisashi , Hashimoto Kyoko , Tanaka Hiromichi
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Auto‐Organized Nanostructures in the Ti—Al—N Thin Film System
Authors: Hultman Lars , Hoerling Anders
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Extending the Reaction Landscape of the {Pt(μ‐S)2Pt} Core: From Metal Centers to Non‐Metallic Electrophiles
Authors: Gonzalez‐Duarte Pilar , Lledos Agusti , Mas‐Balleste Ruben
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
The Pfitzinger Reaction
Authors: Shvekhgeimer M. G.‐A.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Sulfur‐Containing Heterocycles from Thiocarbonyl Compounds
Authors: Mloston Grzegorz , Heimgartner Heinz
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Synthetic, Structural, and Mechanistic Issues in the Development of a Subtype Selective GABA Partial Agonist Hypnotic Agent
Authors: Ragan John A. , Murry Jerry A. , Castaldi Michael J. , Conrad Alyson K. , Hill Paul D. , Jones Brian P. , Kasthurikrishnan Narasimhan , Li Bryan , Makowski Teresa W. , McDermott Ruth , et al. et al.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Bipyridine Ligands
Authors: Smith A. P. , Fraser C. L.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Generation, Structure, and Reactions of Sulfenic Acid Anions
Authors: O'donnell Jennifer , Schwan Adrian
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Combinatorial Approaches
Authors: Hoveyda Amir H. , Murphy Kerry E.
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Direct Catalytic Asymmetric Aldol Reaction
Authors: Shibasaki Masakatsu , Yoshikawa Naoki , Matsunaga Shigeki
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Genetic Control by a Natural Metabolite‐Responsive Ribozyme
Authors: Micura Ronald
Published: November 2004

For Abstract see ChemInform Abstract in Full Text.
Synthesis and Structural Characterization of Three‐Coordinate MnII, FeII, and ZnII Complexes Containing a Bulky Diamide Ligand [DippN(CH2)3NDipp]2− (Dipp = 2,6‐iPr2C6H3)
Authors: Chai Jianfang , Zhu Hongping , Ma Qingjun , Roesky Herbert W. , Schmidt Hans‐Georg , Noltemeyer Mathias
Published: November 2004

The reaction of DippNH(CH2)3NHDipp (1) (Dipp = 2,6‐iPr2C6H3) with 2 equiv. of MeLi in diethyl ether resulted in the formation of the monomeric dilithium salt [(Dipp)N(CH2)3N(Dipp)][Li(OEt2)]2 (2) in high yield. Further reactions of 2 with MnCl2, FeCl2, and ZnCl2, respectively, afforded the complexes [M2{N(Dipp)(CH2)3N(Dipp)}2] [M = Mn (3), Fe (4), Zn (5)] with three‐coordinate metal centers. Complexes 2−5 were characterized by X‐ray structural analysis. The complexes contain a nonplanar MNMN central core. The diamide ligand in complexes 3−5 displays a boat conformation and is both chelating and bridging, so that one of the nitrogen atoms is three‐coordinate and the other four‐coordinate. Complexes 3−5 are the first examples with diamide ligands in such a bonding mode. The magnetic investigations of compounds 3 and 4 reveal an antiferromagnetic exchange between the metal atoms. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Apparent Allyl Rotation and Pd−N Bond Rupture in Allylpalladium Complexes with N‐Donor Ligands − Evidence of an Associative Mechanism
Authors: Jalón Félix A. , Manzano Blanca R. , Moreno‐Lara Belén
Published: November 2004

The new didentate N‐donor ligands 2‐(4‐methyl‐1H‐pyrazol‐1‐yl)pyrimidine (4Me‐pzpm, 1) and 2‐(4‐bromo‐1H‐pyrazol‐1‐yl)pyrimidine (4Br‐pzpm, 2) have been synthesised and used to obtain the allylpalladium derivatives [Pd(η3‐2Me‐C3H4)(NN′)]X [X = BAr′4−, NN′ = 1 (3), NN′ = 2 (4); X = CF3SO3−, NN′ = 1 (5), NN′ = 2 (6)]. In complexes 3−6 two types of fluxional process have been found: apparent allyl rotation that is observed as Hsyn−Hsyn, Hanti−Hanti interconversions and H4−H6 interchange of the pyrimidine protons that must involve Pd−N(pm) bond rupture. The influence of different factors on both processes — such as the nature of the N‐donor ligand, counterion, solvent, complex concentration and addition of water — has been studied. It has been concluded that the apparent allyl rotation has a lower free energy of activation and in both cases the presence of a species with coordinating ability favours the process. Negative entropies of activation have been found. Associative mechanisms involving participation of five‐coordinate intermediates have been proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
The Hidden Equilibrium in Aqueous Sodium Carbonate Solutions − Evidence for the Formation of the Dicarbonate Anion
Authors: Zeller Klaus‐Peter , Schuler Paul , Haiss Peter
Published: November 2004

Crossover 13C NMR experiments between [13C]carbonate and [18O]carbonate in aqueous solution confirm the combined action of two oxygen‐exchange modes. The isotopomeric carbon dioxides formed in the hydrolysis equilibrium of the labeled carbonate anions react with hydroxide with formation of hydrogencarbonate and with isotopomeric carbonate anions yielding the corresponding dicarbonate species, which, in the back reaction, form carbon dioxide and carbonate anions with distributed oxygen. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Columnar Mesomorphism in Hexacatenar Tetrahedral (2,2′‐Bipyridine)zinc Complexes and Homologous Palladium Derivatives
Authors: Barberio Giovanna , Bellusci Anna , Crispini Alessandra , Ghedini Mauro , Golemme Attilio , Prus Piotr , Pucci Daniela
Published: November 2004

The synthesis and characterisation of novel liquid crystals which display columnar mesomorphism induced upon complexation of a series of nonmesomorphic hexacatenar 4,4′‐disubstituted 2,2′‐bipyridines (Ln) are reported. The introduction of different metal centres (Zn, Pd) causes the appearance of mesomorphism in all complexes regardless of the geometry around the metal ion. We therefore report the first examples of mesomorphism in tetrahedral zinc derivatives. The nature of the columnar phases is related to the self‐assembly of the half‐disc shaped [LnMCl2] (M = Zn, Pd) complexes into full disc‐shaped supramolecules. The molecular organisation in the mesophase is mainly driven by intermolecular attractive interactions, as shown by the crystal structure of the model compound [LPdCl2]. Preliminary measurements of photoconductivity have been performed on samples of [LnMCl2] complexes doped with C60 to increase absorption. Promising results were obtained. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Structural and Photophysical Characterisation of fac‐[Tricarbonyl(chloro)(5,6‐epoxy‐1,10‐phenanthroline)rhenium(I)]
Authors: Martí Angel A. , Mezei Gellert , Maldonado Lorena , Paralitici Giovanni , Raptis Raphael G. , Colón Jorge L.
Published: November 2004

The structural and spectroscopic characterisations of fac‐[Re(phen)(CO)3Cl] (1) (phen = 1,10‐phenanthroline), fac‐[Re(ephen)(CO)3Cl] (3) [ephen = 5,6‐epoxy‐1,10‐phenanthroline (2)] and ephen are reported. The appearance of weak hydrogen bond networks in the crystal lattice of [Re(ephen)(CO)3Cl] and ephen are discussed. Two different isomers of [Re(ephen)(CO)3Cl] were identified by IR and NMR spectroscopy. Coincidental resonances were differentiated for these complexes by temperature‐dependent NMR spectroscopy. Recrystallisation of the crude material allowed the separation of the two isomers. The spectroscopic data permitted the calculation of radiative and nonradiative luminescence rate constants which are consistent with the energy gap law. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Fmoc‐Assisted Synthesis of a 29‐Residue Cystine‐Knot Trypsin Inhibitor Containing a Guaninyl Amino Acid at the P1‐Position
Authors: Avrutina Olga , Schmoldt Hans‐Ulrich , Kolmar Harald , Diederichsen Ulf
Published: November 2004

An Fmoc‐assisted synthesis of a 29 amino acid trypsin inhibitor (McoTI‐29) is presented, which contains a non‐natural guaninyl nucleo amino acid as arginine mimetic at the P1 position. This artificial amino acid functions as a conformational restricted arginine isoster with reduced basicity. The folded cyclotide McoTI‐II open‐chain variant McoTI‐29 has been synthesized from a linear precursor by in situ oxidation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Conformational Analysis of Saturated trans‐Fused 1,3,2‐Benzoxazaphosphinine 2‐Oxides − DFT Calculation of NMR J(P,H) Coupling Constants
Authors: Tähtinen Petri , Bagno Alessandro , Koch Andreas , Pihlaja Kalevi
Published: November 2004

The 3JP,H and 4JP,H spin‐spin coupling constants of a selected test set of organophosphorus compounds, calculated by density functional theory (DFT) methods, were found to correlate well with the experimentally measured coupling constants. The contribution of the spin‐dipole (SD) term to the coupling constants was found to be negligible, and the diamagnetic and paramagnetic spin‐orbit (DSO and PSO) terms cancelled each other, as in the case of JH,H. Calculation solely of the Fermi contact (FC) term was found to be sufficient to provide good estimates of the coupling constants. In the second part of the work, the conformational equilibria and coupling constants in 2‐bis(2‐chloroethyl)amino‐trans‐octahydro‐2H‐1,3,2‐benzoxazaphosphinine 2‐oxide and its 3‐methyl derivative were studied. DFT methods failed in predicting the relative stabilities of the conformations but yielded good geometries and coupling constants. Optimization of the conformations at the Møller‐Plesset second‐order perturbation theory (MP2) level resulted in energy differences compatible with previous experimental observations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Linear Fused Pyran‐Dioxane‐Cyclohexane Tricycles: Synthesis of the Five Linkage Isomers and Ensuing Reactions
Authors: Lichtenthaler Frieder W. , Cuny Eckehard
Published: November 2004

A systematic investigation of the mono‐O‐glycosylation of meso‐, (S,S)‐, and (R,R)‐cyclohexane‐1,2‐diol with the D‐glucose‐derived 2‐ketohexosyl bromide 5 is presented. In each instance, simple Königs−Knorr conditions not only elicit the exclusive formation of the respective β‐2‐ketoglycosides, but also effect their subsequent intramolecular hemiketalization to provide tricycles with a 1,5,10‐trioxa‐perhydroanthracene framework. The linkage geometries of the products − two each from the meso‐ (→ 10, 12) and (S,S)‐diols (→ 16, 17), and only one from the (R,R)‐isomer (→ 26) − are determined in the hemiketalization step by an interplay of the anomeric effect and steric factors, favoring those isomers in which the pyran ring oxygen and the ketal‐OH are in a trans‐diaxial disposition. The most propitious case with respect to uniformity of reaction and yield (87%) turned out to the (R,R)‐diol‐derived cis‐cisoid‐trans‐fused 26 as steric and stereoelectronic factors operate concertedly in the hemiketalization step. In each of these pyran‐dioxane‐cyclohexane tricycles, the acetalic hydroxyl group could be removed by BF3‐mediated reduction with triethylsilane, the 1H NMR spectroscopic data of the respective products 14, 15, 18 and 28 being instrumental in assigning their linkage geometries. Slightly basic conditions (nBu4NOAc in acetonitrile) elicit highly stereoselective rearrangements in the pyran ring, for example 16 → 23 and 26 → 30; the tricycles have the structurally and stereochemically correct framework of a variety of cardenolides, in which a 2‐ketosugar is doubly linked to a steroidal aglycon‐diol. Thus, the methodology elaborated here shows high promise to provide a first, preparatively satisfactory access to this type of cardiac glycosides as well as to spectinomycin type antibiotics. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Why do Electron‐Deficient Dienes React Rapidly in Diels−Alder Reactions with Electron‐Deficient Ethylenes? A Density Functional Theory Analysis
Authors: Domingo Luis R.
Published: November 2004

The Diels−Alder reaction of the electron‐deficient (ED) dimethyl 2,3‐dimethylenesuccinate with two electron‐rich (ER) and two ED ethylenes has been studied at the B3LYP/6‐31G* level of theory. The analysis of the geometry and electronic structure of the transition state of the reaction with the ED dimethyl 2‐methylenemalonate along with the analysis of the global and local electrophilicity indices of the reagents provide an explanation of the participation of this ED diene as nucleophile against powerful electrophiles in polar Diels−Alder reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Modeling environmental data by functional principal component logistic regression
Authors: Escabias M. , Aguilera A. M. , Valderrama M. J.
Published: November 2004

In recent years, many studies have dealt with predicting a response variable based on the information provided by a functional variable. When the response variable is binary, different problems arise, such as multicollinearity and high dimensionality, which prejudice the estimation of the model and the interpretation of its parameters. In this article we address these problems by using functional logistic regression and principal component analysis. In order to obtain a unique solution for the maximum likelihood estimation of the parameter function, quasi‐natural cubic spline interpolation of sample paths on their discrete time observations is proposed. We also introduce a new interpretation of the relationship between the response variable and the functional predictor where the change in the odds of success is evaluated from the estimated parameter function. An analysis of climatological data is finally presented to illustrate the practical performance of the proposed methodologies. Copyright © 2004 John Wiley & Sons, Ltd.
Mammalian cell delivery via aerosol deposition
Authors: Veazey William. S. , Anusavice Kenneth J. , Moore Karen
Published: November 2004

The objective of this study was to test the hypothesis that bovine dermal fibroblasts can survive aerosol delivery via an airbrush with mean cell survival rates greater than 50%. This technology has great implications for burn and other wound therapies, for delivery of genetically altered cells in gene therapies, and for tissue engineering with tissue scaffolds. Bovine dermal fibroblasts were suspended at a concentration of 200,000 cells/mL in Hank's Balanced Salt Solution, and delivered into six‐well tissue culture plates using a Badger 100G airbrush. Cells were delivered through three nozzle diameters (312, 484, and 746 μm) at five different air pressures (41, 55, 69, 96, and 124 kPa). Nine repetitions were performed for each treatment group, and cell viability was measured using trypan blue exclusion assay. Mean cell viability ranged from 37 to 94%, and depended on the combination of nozzle diameter and delivery pressure (p < 0.0001). Linear regression analysis was used to develop a stochastic model of cell delivery viability as a function of nozzle diameter and delivery air pressure. This study demonstrates the feasibility of using an airbrush to deliver viable cells in an aerosol to a substrate. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 72B: 334–338, 2005
Trafficking and localization of platinum complexes in cisplatin‐resistant cell lines monitored by fluorescence‐labeled platinum
Authors: Liang Xing‐Jie , Shen Ding‐Wu , Chen Kevin G. , Wincovitch Stephen M. , Garfield Susan H. , Gottesman Michael M.
Published: November 2004

Cisplatin is a chemotherapeutic agent commonly used in the treatment of a wide variety of malignant tumors. Resistance to cisplatin represents a major obstacle to effective cancer therapy because clinically significant levels of resistance quickly emerge after treatment. Based on previous studies indicating abnormal plasma membrane protein trafficking in cisplatin‐resistant (CP‐r) cells, Fluorescence (Alexa Fluor)‐labeled cisplatin was used to determine whether this defect altered the trafficking and localization of cisplatin by comparing drug sensitive KB‐3‐1 and KB‐CP‐r cells. Alexa Fluor–cisplatin was readily internalized and localized throughout the KB‐3‐1 cells, but overall fluorescence decreased in KB‐CP‐r cells, as detected by flow cytometry (FACS) and confocal microscopy. Only punctate cytoplasmic staining was observed in KB‐CP‐r cells with less fluorescence observed in the nucleus. Colocalization experiments with a Golgi‐selective stain indicate the involvement of Golgi‐like vesicles in initial intracellular processing of Alexa Fluor conjugated cisplatin complexes. As detected using an antibody to Alexa Fluor–cisplatin, cisplatin complex‐binding proteins (CCBPs) were reduced in membrane fractions of single‐step cisplatin‐resistant KB‐CP.5 cells, and increased in the cytoplasm of KB‐CP.5 cells compared to KB‐3‐1 cells. CCBPs localized to lower density fractions in KB‐CP.5 cells than in KB‐3‐1 cells as determined by iodixanol gradient centrifugation. In summary, inappropriate trafficking of CCBPs might explain resistance to cisplatin in cultured cancer cells, presumably because membrane binding proteins for cisplatin are not properly located on the cell surface in these cells, but are instead trapped in low density vesicles within the cytoplasm. © 2004 Wiley‐Liss, Inc.
Exploring polyethylenimine‐mediated DNA transfection and the proton sponge hypothesis
Authors: Akinc Akin , Thomas Mini , Klibanov Alexander M. , Langer Robert
Published: November 2004

Background

The relatively high transfection efficiency of polyethylenimine (PEI) vectors has been hypothesized to be due to their ability to avoid trafficking to degradative lysosomes. According to the proton sponge hypothesis, the buffering capacity of PEI leads to osmotic swelling and rupture of endosomes, resulting in the release of the vector into the cytoplasm.

Methods

The mechanism of PEI‐mediated DNA transfer was investigated using quantitative methods to study individual steps in the overall transfection process. In addition to transfection efficiency, the cellular uptake, local pH environment, and stability of vectors were analyzed. N‐Quaternized (and therefore non‐proton sponge) versions of PEI and specific cell function inhibitors were used to further probe the proton sponge hypothesis.

Results

Both N‐quaternization and the use of bafilomycin A1 (a vacuolar proton pump inhibitor) reduced the transfection efficiency of PEI by approximately two orders of magnitude. Chloroquine, which buffers lysosomes, enhanced the transfection efficiency of N‐quaternized PEIs and polylysine by 2–3‐fold. In contrast, chloroquine did not improve the transfection efficiency of PEI. The measured average pH environment of PEI vectors was 6.1, indicating that they successfully avoid trafficking to acidic lysosomes. Significantly lower average pH environments were observed for permethyl‐PEI (pH 5.4), perethyl‐PEI (pH 5.1), and polylysine (pH 4.6) vectors. Cellular uptake levels of permethyl‐PEI and perethyl‐PEI vectors were found to be 20 and 90% higher, respectively, than that of parent PEI vectors, indicating that the reduction in transfection activity of the N‐quaternized PEIs is due to a barrier downstream of cellular uptake. A polycation/DNA‐binding affinity assessment showed that the more charge dense N‐quaternized PEIs bind DNA less tightly than PEI, demonstrating that poor vector unpackaging was not responsible for the reduced transfection activity of the N‐quaternized PEIs.

Conclusions

The results obtained are consistent with the proton sponge hypothesis and strongly suggest that the transfection activity of PEI vectors is due to their unique ability to avoid acidic lysosomes. Copyright © 2004 John Wiley & Sons, Ltd.
Raman spectroscopic study of non‐catalytic hydrogenation of unsaturated rubbers
Authors: Samran Jareerat , Phinyocheep Pranee , Daniel Philippe , Derouet Daniel , Buzaré Jean‐Yves
Published: November 2004

The non‐catalytic hydrogenation of natural rubber (NR) and two epoxidized NRs (ENRs) i.e. ENR‐22 and ENR‐40 containing 22 and 40 mol% of epoxide, respectively, was carried out using p‐toluenesulfonylhydrazide (TSH) as a hydrogenating agent. A two‐fold molar excess of TSH compared with unsaturated units of the rubber was used. The evidence of hydrogenation is a decrease in the intensity of the characteristic signal of the carbon–carbon double bond stretching vibration of the rubber in both the Raman and FT‐IR spectra. The percentage hydrogenation was successfully determined by Raman spectroscopy since the vibrational mode of the carbon–carbon unsaturation is strongly Raman active. The progress of the hydrogenation could be monitored by means of the techniques mentioned above as a function of reaction time. The maximum degree of hydrogenation of NR is ∼89% whereas in the case of ENR‐22 and ENR‐40 it reaches 94 and 96%, respectively. Solid‐state 13C NMR spectroscopy was also used to confirm the microstructure characteristics of the hydrogenated rubbers. 13C NMR analysis showed that cis–trans isomerization of carbon–carbon unsaturations occur during hydrogenation. Copyright © 2004 John Wiley & Sons, Ltd.
Physical Characterization of Coupled Poly(lactic acid)/Starch/Maleic Anhydride Blends Plasticized by Acetyl Triethyl Citrate
Authors: Zhang Jian‐Feng , Sun Xiuzhi
Published: November 2004

Summary: Acetyl triethyl citrate (ATC) was used as a plasticizer for poly(lactic acid) (PLA)/starch blends coupled with maleic anhydride and an initiator of 2,5‐bis(tert‐butylperoxy)‐2,5‐dimethylhexane (L101). Elongation of the blend at break was markedly increased when the ATC content was above the 8% loading level, which is referred to as the percolation threshold. The extended elongation was achieved at the expense of tensile strength and elastic modulus. Thermal transitions of the blend, including the glass transition temperature (Tg), cold crystallization temperature (Tc) and melting temperature (Tm), decreased with ATC content. Thermally induced ATC migration affected the thermal behavior of the plasticized blends and reduced elongation and tensile strength, whereas the elasticity modulus increased. ATC migration increased with ambient temperature, which was controlled by the activation energy of the blend system. Leaching of ATC was slow at room temperature in distilled water, but significant in boiling water. Additionally, the leaching rate was also directly proportional to the ATC content of the blend.

Glass transition temperatures of PLA/starch/MA/L101 blends with various acetryl triethyl citrate contents.

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Glass transition temperatures of PLA/starch/MA/L101 blends with various acetryl triethyl citrate contents.
High‐Molecular‐Weight Polyketones from Higher α‐Olefins: A General Method
Authors: Pérez‐Foullerat David , Meier Uwe W. , Hild Sabine , Rieger Bernhard
Published: November 2004

Summary: A method to optimize the polymerization conditions in order to favor chain propagation is described for the synthesis of polymers containing low reactive, long, linear 1‐olefins and carbon monoxide (CO). It consists of the use of the olefin monomer as the polymerization solvent, together with the emulsification of a carefully chosen immiscible activator. This is given as a general method applicable to different families of catalyst able to produce 1,4‐polyketones. When the catalyst precursor is [dpppPd(NCCH3)2](BF4)2, which has been extensively studied, the polymerization degrees are the highest published (up to 2.4 × 105 g · mol−1). The influence of parameters like temperature, CO pressure, volume of activator, and catalyst counter ion or ligand substitutions are reported. Some chemical and physical properties of the polymers, such as glass transition temperature, melting processes, and mechanical behavior, are examined and compared with the linear 1‐olefin homologues from C3 to C10. These properties are shown in some cases to be unprecedented.

DSC profiles from the 1st scan for α‐olefin/CO copolymers.

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DSC profiles from the 1st scan for α‐olefin/CO copolymers.
Hybrid particle methods in frictionless impact‐contact problems
Authors: Huang H. , Dyka C. T. , Saigal S.
Published: November 2004

The dual particle dynamic (DPD) methods which employ two sets of particles have been demonstrated to have better accuracy and stability than the co‐locational particle methods, such as the smooth particle hydrodynamics (SPH). The hybrid particle method (HPM) is an extension of the DPD method. Besides the advantages of the DPD method, the HPM possesses features which better facilitate the simulation of large deformations. This paper presents the continued development of the HPM for the numerical solution of two‐dimensional frictionless contact problems. The interface contact force algorithm which employs a modified kinematic constraints method is used to determine the contact tractions. In this method, both the impenetrability condition and the traction condition are simultaneously enforced. In the original kinematic constraints method, only the former condition is satisfied. A new formulation to find stress derivatives at stress‐free corners by imposing stress‐free boundary conditions is also developed. The results for 1‐D and 2‐D contact problems indicate good accuracy for the contact formulation as well as the corner treatment when compared to analytical solutions and explicit finite element results using the commercial code LS‐DYNA. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and polymerization of new self‐polymerizable quinoxaline monomers
Authors: Baek Jong‐Beom , Harris Frank W.
Published: November 2004

Extended self‐polymerizable poly(phenylquinoxaline) monomer mixtures {i.e.,2‐[4‐(4‐hydroxyphenoxy)phenyl]‐3‐phenyl‐6‐chloroquinoxaline and 3‐[4‐(4‐hydroxy phenoxy)phenyl]‐2‐phenyl‐6‐chloroquinoxaline, 2‐[4‐(4‐hydroxyphenoxy)phenyl]‐3‐phenyl‐6‐fluoroquinoxaline and 3‐[4‐(4‐hydroxyphenoxy)phenyl]‐2‐phenyl‐6‐fluoroquinoxaline, and 2‐(4‐fluorophenyl)‐3‐phenyl‐6‐(4‐hydroxyphenoxy)quinoxaline and 3‐(4‐fluorophenyl)‐2‐phenyl‐6‐(4‐hydroxyphenoxy)quinoxaline} more flexible and nucleophilic than a previously reported monomer mixture [i.e., 3‐(4‐hydroxyphenyl)‐2‐phenyl‐6‐fluoroquinoxaline and 2‐(4‐hydroxyphenyl)‐3‐phenyl‐6‐fluoroquinoxaline] were synthesized. The monomer mixtures were then polymerized into high‐molecular‐weight polymers. A sample was obtained, through a chlorine displacement reaction, that was a semicrystalline polymer with an intrinsic viscosity of 1.11 dL/g in m‐cresol at 30 ± 0.1 °C and two melting temperatures at 339 and 377 °C in the first differential scanning calorimetry scan. There was a melting temperature at 328 °C without a detectable glass‐transition temperature (Tg) when the sample was subjected to a second differential scanning calorimetry scan. The samples from fluorine displacement reactions were completely amorphous polymers. They had intrinsic viscosities of 0.53–0.90 dL/g in m‐cresol at 30 ± 0.1 °C and Tg's of 220–224 °C. The polymer samples from fluorine displacement reactions were evaluated with gel permeation chromatography and matrix‐assisted laser desorption/ionization time‐of‐flight analyses, which monitored the existence of certain amounts of cyclic oligomers. The thin films of the polymers had room‐temperature tensile strengths of 97–113 MPa, room‐temperature Young's moduli of 2.30–2.35 GPa, and room‐temperature elongations at break of 40–150%. The melt viscosity decreased from 107 to less than 104 Pa s at 310 °C as the frequency was increased from 10−2 to 102 rad/s. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 78–91, 2005
An Empirical Bayes Process Monitoring Technique for Polytomous Data
Authors: Shiau Jyh‐Jen H. , Chen Chih‐Rung , Feltz Carol J.
Published: November 2004

When a product item is tested, usually one has more information than just pass or fail. Often there are categories of failure modes. The purpose of this paper is to develop a method to monitor the fractions of the tested items falling into different categories of pass/fail modes. Using the multinomial model with Dirichlet prior, we describe the theory underlying an empirical Bayes approach to monitoring polytomous data generated in manufacturing processes. A pseudo maximum likelihood estimator (PMLE) and the method‐of‐moments estimator (MME) of the hyperparameters of the prior distribution are considered and compared by a simulation study. It is found that the PMLE performs slightly better than the MME. A monitoring scheme based on the marginal distributions of the observed pass/fail fractions is proposed. The average run length behavior of the proposed monitoring scheme is investigated. Finally, an example to illustrate the use of the technique is given. Copyright © 2004 John Wiley & Sons, Ltd.
Ultrasound detection of nuchal cord prior to labor induction and the risk of Cesarean section
Authors: Peregrine E. , O'Brien P. , Jauniaux E.
Published: November 2004

Objectives

To investigate the ability of ultrasound to detect the presence of a nuchal cord immediately prior to induction of labor and the association of its presence with delivery by Cesarean section.

Methods

A transabdominal ultrasound scan using gray‐scale and color Doppler imaging was performed immediately prior to induction of labor in 289 women in a prospective study to assess the presence of a nuchal cord. The presence of a nuchal cord was classified as present, absent or uncertain. The outcomes of labor, delivery and the neonates were obtained from the patient notes after delivery.

Results

A nuchal cord was present at 18% of deliveries. The incidence was not affected by parity, fetal position or reduced amniotic fluid volume. The sensitivity of ultrasound in diagnosing a nuchal cord was 37.5%, with specificity, positive and negative predictive values of 80%, 29% and 85%, respectively. The presence of a nuchal cord did not significantly increase the risk of delivery by Cesarean section (35% vs. 28%; relative risk = 1.22; 95% CI, 0.80–1.87), instrumental delivery for fetal distress, an abnormal cardiotocograph in labor or at delivery, an Apgar score < 7 at 1 min, arterial cord pH < 7.1 or neonatal unit admission.

Conclusions

The sensitivity of the ultrasound diagnosis of a nuchal cord is low prior to induction of labor at term. A nuchal cord does not appear to increase the risk of Cesarean section or of poor neonatal outcome. The low ultrasound detection rate of a nuchal cord limits its use in decision making prior to induction of labor in high‐risk pregnancies. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Posttranslational activation, site‐directed mutation and phylogenetic analyses of the lysine biosynthesis enzymes α‐aminoadipate reductase Lys1p (AAR) and the phosphopantetheinyl transferase Lys7p (PPTase) from Schizosaccharomyces pombe
Authors: Guo Shujuan , Bhattacharjee J. K.
Published: November 2004

α‐Aminoadipate reductase (AAR), the signature enzyme for lysine biosynthesis in fungi, catalyses the conversion of α‐aminoadipate to α‐aminoadipate‐semiadehyde in the presence of ATP and NADPH. In Saccharomyces cerevisiae and Candida albicans, the LYS2‐encoded AAR is posttranslationally activated by CoA and the LYS5‐encoded PPTase. The fission yeast Schizosaccharomyces pombe is evolutionarily highly diverged from S. cerevisiae and C. albicans. We report here several unusual activation characteristics of Sz. pombe Lys1p and Lys7p, isofunctional to Lys2p (AAR) and Lys5p (PPTase), respectively. Unlike the Lys2p from S. cerevisiae and C. albicans, the Sz. pombe Lys1p was active when expressed in E. coli and exhibited significant AAR activity without the addition of CoA or the Sz. pombe Lys7p intron free PPTase. Somewhat higher AAR activity was obtained with the addition of CoA and the Sz. pombe Lys7p PPTase. Substitution of G910A, S913T or S913A in the Sz. pombe Lys1p activation domain (IGGHSI) resulted in no AAR activity. Similarly, substitutions of several amino acid residues in the Sz. pombe Lys7p PPTase domain (G79A, R80K and P81A in Core 1; F93W, D94E, F95W and N96D in Core 1a; G124A, V125I and D126E in Core 2; K172R, E173D and K177R in Core 3) also resulted in no activation of Lys1p and no AAR activity. The Sz. pombe Lys1p amino acid sequence showed a high degree of similarity to other fungal Lys2p proteins; however, the Lys7p amino acid sequence showed much less similarity to other bacterial, fungal and animal PPTases representing several phylogenetic groups. Copyright © 2004 John Wiley & Sons, Ltd.
Optimal design of a micro parallel positioning platform. Part I: Kinematic analysis
Authors: Oh Kun-Ku , Liu Xin-Jun , Kang Deuk Soo , Kim Jongwon
Published: November 2004

Using a coarse-and-fine actuator combination (dual stage system), a new design of the three degree-of-freedom (DOF) micro parallel positioning platform with high mobility, high accuracy, and a large working space is proposed. To achieve these three DOFs and implement the dual stage system, there are six possible architectures for the coarse and fine actuators, respectively. This paper is organized in two parts. Part I treats the kinematic analysis of each architecture and the problem of selecting the correct coarse actuator architecture. Inverse kinematics and Jacobian matrices for six types of coarse actuator architectures are derived and one proper coarse actuator architecture is selected based on the mobility (rotational capability) analysis, condition number evaluation of the Jacobian matrix, and manufacturability consideration. Part II on real machine design will follow in the next issue of Robotica.
Kinematics control of redundant manipulators using a CMAC neural network combined with a genetic algorithm
Authors: Li Yangmin , Leong Sio Hong
Published: November 2004

A method is proposed to solve the inverse kinematics and control problems of robot control systems using a cerebellar model articulation controller neural network combined with a genetic algorithm. Computer simulations and experiments with a 7-DOF redundant modular manipulator have demonstrated the effectiveness of the proposed method.
Reports and Surveys
Authors: Rudall B. H.
Published: November 2004

The statistics provided by the United Nations Economic Commission (ECE) and the International Federation of Robotics (IFR) supply us with an up-to-date insight into the world robot market. This joint report tells us a great deal about the technological evolution of industrial robots since their introduction at the end of the 1960s. We know that real prices have declined, and the performance of robots is continuously improving. Robots are now in use in a wide range of applications in countries worldwide.
Finite ky ballooning instability in the near‐Earth magnetotail
Authors: Zhu P. , Bhattacharjee A. , Ma Z. W.
Published: November 2004

Two‐dimensional initial value MHD simulations of the linear ideal MHD ballooning instability in the near‐Earth magnetotail are presented. The configuration of the magnetotail is modeled by the analytic two‐dimensional static equilibrium developed by Voigt. For an intermediate range of plasma β values (∼1–100) at the equatorial plane, the Voigt configuration of the near‐Earth magnetotail is shown to be unstable to ballooning modes with finite ky. (A similar intermediate range of plasma β was also obtained in the stability analyses of ballooning modes in the infinite ky limit.) Such a β dependence of the instability arises because of the stabilizing effect of plasma compression involved in the ballooning displacement of flux tubes in the high‐β regime of the magnetotail. The growth rate of the finite ky ballooning instability is found to increase with the wave number ky, approaching a saturated value in the very large ky limit. The thinning of the current sheet is found to enhance the regime of unstable β as well as the growth rate of the linear ballooning instability of the near‐Earth magnetotail, suggesting a possible scenario for the substorm trigger.
Segmental glomerulosclerosis in IgA nephropathy after renal transplantation: relationship with proteinuria and therapeutic response to enalapril
Authors: Jeong Hyeon Joo , Kim Yu Seun , Kwon Kye Won , Kim Myoung Soo , Kim Soon , Choi Kyu Hun , Lee Ho Yung , Han Dae Suk , Park Kiil
Published: November 2004

Abstract: Introduction:Although graft dysfunction has been increasingly reported in post‐transplant IgA nephropathy (Tx‐IgAN), intragraft morphological changes have been largely overlooked. We evaluated glomerular changes in Tx‐IgAN to identify the histological features pertaining to significant proteinuria and therapeutic response to enalapril.

Materials and methods:Fifty‐four renal allograft biopsies, diagnosed as Tx‐IgAN at a median of 46 months after transplantation, were the subject of the study. In 10 patients, glomerular morphometry was performed. In 14 patients who have been treated with enalapril for more than 12 months, we correlated the therapeutic response to enalapril with allograft histology.

Results:No uniform pattern was found in the glomeruli of Tx‐IgAN. The glomerular mesangium was mostly indistinct. Interstitial fibrosis was negative or mild in 88.9%. By morphometry, the glomerular tuft areas and mesangial areas were significantly larger in Tx‐IgAN than those of the normal native kidney (p < 0.05), but were not different from transplant cases without glomerulonephritis. Proteinuria of ≥1 g/24 h was correlated with glomerulosclerosis, interstitial fibrosis and interstitial inflammation at time of biopsy (p < 0.005). The presence of segmental sclerosis (SS) correlated well with the amount of 24‐h proteinuria (p < 0.001). After treatment with enalapril, the amount of proteinuria reduced in 64.3%. Therapeutic response to enalapril tended to be less effective in patients having SS (28.6 versus 71.4%), but this finding did not reach a statistical significance.

Conclusions:Significant proteinuria was associated with advanced chronic injury, especially with the presence of SS in Tx‐IgAN, but anti‐proteinuric effect of enalapril was not affected by graft histology. It remains to be clarified whether glomerular mesangial expansion plays a role in graft dysfunction in a subset of Tx‐IgAN showing prominent mesangial changes.
RENAL TRANSPLANTATION IN AMYLOIDOSIS: EFFECTS OF HLA MATCHING AND DONOR TYPE ON RECURRENCE OF PRIMARY DISEASE
Authors: Özdemir BH , Demirhan B , Özdemir FN , Turan M , Haberal M
Published: November 2004

The aim of this study was to evaluate the effect of HLA‐matching and donor type on recurrence of amyloidosis after renal transplantation. Thirty patients with systemic amyloidosis who received kidney transplants between 1985 and 2001 were included. Donor source and HLA tissue typing of the donor and recipient were evaluated in each case. Twenty of the 30 patients developed biopsy‐confirmed recurrence of amyloidosis in their allografts. The time from transplantation to diagnosis of amyloidosis in the graft ranged from 18 months to 10 years. Eighteen of the 20 patients with recurrence had received their grafts from living‐related donors (LRDs), and two had received their grafts from cadaveric donors. There was a strong correlation between amyloidosis recurrence and degree of HLA‐DR matching (P<0.05). Further, in the recipients of the LRD grafts, the risk of amyloidosis recurrence was significantly higher when the donor‐recipient pair were HLA‐identical than when they were not perfectly matched (P<0.01). The incidence of amyloidosis recurrence in our cases was significantly higher than the rates reported for other series. Most of the cases in previous reports involved cadaveric grafts. The higher rate of amyloidosis recurrence in our cases may be explained by the high proportion of LRD grafts, and by genetic susceptibility.
Total loss of MHC class I in colorectal tumors can be explained by two molecular pathways: β2‐microglobulin inactivation in MSI‐positive tumors and LMP7/TAP2 downregulation in MSI‐negative tumors
Authors: Cabrera C.M. , Jiménez P. , Cabrera T. , Esparza C. , Ruiz‐Cabello F. , Garrido F.
Published: November 2004

Abstract:  The mechanisms that lead to loss of MHC class I expression in different types of tumors are not yet fully known. Accordingly, we studied colorectal carcinomas to elucidate the specific mechanisms of evasion of the T‐cell immune response. We selected tumors with total loss of MHC class I expression and studied 124 colorectal carcinomas with immunohistochemical staining and anti‐HLA monoclonal antibodies (mAb). Fourteen of 124 (11%) tumors exhibited a phenotype with HLA class I total loss. Microsatellite instability (MSI) analysis was also carried out in the same tumor samples. The expression of β2‐microglobulin (β2m), HLA‐A, B, and C antigens, transporter associated with antigen processing 1 (TAP1), TAP2, low‐molecular‐weight protein 2 (LMP2), and LMP7 were analyzed using reverse‐transcription polymerase chain reaction (RT‐PCR) in microdissected tumor samples. Four of 14 microsatellite instability‐positive (MSI+) and W6/32 mAb‐negative tumors showed biallelic inactivation of β2m and accumulation of HLA class I heavy chain in the cytoplasm. MSI‐negative (MSI–)/W6/32 mAb‐negative tumors presented alterations in the expression of components of the antigen processing machinery (APM). Nine of 10 tumor samples showed LMP7 gene downregulation, and four of 10 presented TAP2 dysregulation. This group apparently expressed normal levels of heavy chain and β2m mRNA. Two major mechanisms in colorectal cancer appear to be responsible for the total loss of MHC surface expression (β2m mutations and LMP7/TAP2 downregulation) that may contribute to the failure of T lymphocyte recognition during an immune response. The precise identification of the molecular defects that underlie HLA class I abnormalities will have important implications for patients receiving T‐cell‐based specific immunotherapy.