bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐Spin Molecules with Magnetic Anisotropy toward Single‐Molecule Magnets
Authors: Oshio Hiroki , Nakano Motohiro
Published: June 2005

High‐spin molecules with easy‐axis magnetic anisotropy show slow magnetic relaxation of spin‐flipping along the axis of magnetic anisotropy and are called single‐molecule magnets (SMMs). SMMs behave as molecular‐size permanent magnets at low temperature and magnetic relaxation occurs by quantum tunneling processes; such molecules are promising candidates for use in quantum devices. We first discuss intramolecular ferromagnetic interactions for preparing high‐spin molecules. Second, we determine the magnetic anisotropy for single metal ions with dn configurations and discuss how molecular anisotropy arises from single‐ion anisotropy of the assembled component metal ions.
Triplet Acetylenes as Synthetic Equivalents of 1,2‐Bicarbenes, Part II: New Supramolecular Scaffolds from Photochemical Cycloaddition of Diarylacetylenes to 1,4‐Cyclohexadienes
Authors: Zeidan Tarek A. , Clark Ronald J. , Ghiviriga Ion , Kovalenko Serguei V. , Alabugin Igor V.
Published: June 2005

1,5‐Diaryl substituted homoquadricyclanes which are readily available through cascade photocycloaddition of diarylacetylenes to 1,4‐cyclohexadienes are useful supramolecular scaffolds with an angle of about 60° formed by the two aromatic rings defining a hydrophobic cavity. These structural features of pyridinyl homoquadricyclanes were applied to the design of composite organic/inorganic materials with topologies depending on the ratio of ligand to metal. The crystal structure of complex 1 (L1/AgNO3 in a 1:1 ratio) shows an alternating ligand–metal polymer in which each of the silver ions in its linear coordination geometry is shared between two L1 molecules. A small change in the crystallization method yields a supramolecular rhomboid (complex 2, L1/AgNO3 3:2 ratio) which has two ligands that occupy opposite corners of the rhomboid and two silver atoms occupy the other two corners. Connection of the rhomboids units through a third molecule forms unique “beads on a string” polymeric chains. In complex 2, the silver ions adopt a distorted tetrahedral geometry with the nitrate anion occupying one of the vertices of the tetrahedron. The crystal packing of the chain of rhomboids generates cavities which are filled with disordered solvent molecules. Non‐symmetrical homoquadricyclane L3 coordinates with silver only through the nitrogen of the pyridine ring but not through the nitrogen of the tetrafluoropyridine ring in which the electron density of the nitrogen lone‐pair is very low. The substituents on the polycyclic moiety of the homoquadricyclane cause restricted rotation of the pyridine rings which suggests that the flexibility of such systems can be fine‐tuned to create a family of supramolecular scaffolds of controlled rigidity.
Characterization of sub‐Gaussian heat kernel estimates on strongly recurrent graphs
Authors: Barlow Martin T. , Coulhoun Thierry , Kumagai Takashi
Published: June 2005

Sub‐Gaussian estimates for random walks are typical of fractal graphs. We characterize them in the strongly recurrent case, in terms of resistance estimates only, without assuming elliptic Harnack inequalities. © 2005 Wiley Periodicals, Inc.
Homogenization and flame propagation in periodic excitable media: The asymptotic speed of propagation
Authors: Caffarelli L. A. , Lee K.‐A. , Mellet A.
Published: June 2005

We study the effect of homogenization on flame propagation in periodic excitable media when the width of the flame is much smaller than the characteristic size of the heterogeneities. © 2005 Wiley Periodicals, Inc.
Molecular Modeling, Design, and Synthesis of Less Lipophilic Derivatives of 3‐(4‐Tetradecyloxybenzyl)‐4H‐1,2,4‐oxadiazol‐5‐one (PMS1062) Specific for Group II Enzyme
Authors: Plocki Stéphanie , Aoun Darina , Ahamada‐Himidi Azali , Tavarès‐Camarinha Fernanda , Dong Chang‐Zhi , Massicot France , Huet Jack , Adolphe‐Pierre Sylvie , Chau François , Godfroid Jean‐Jacques , Gresh Nohad , Ombetta Jean Edouard , Heymans Françoise
Published: June 2005

3‐(4‐Tetradecyloxybenzyl)‐4H‐1,2,4‐oxadiazol‐5‐one (PMS1062 or I) can probably act as a PLA2‐II inhibitor on the acute inflammation model, but its highly lipophilic character could prevent it from being biodistributed effectively. In this work, based on a molecular modeling study, we have proposed a model that may provide compounds retaining both anti‐PLA2 activity and specificity while becoming active per os. Moreover, molecular dynamics and energy minimization enabled us to characterize the lowest‐energy complexes of each derivative. Energy balances taking account of the conformational energy changes of both partners, along with the drug–protein interaction, were performed, and were further completed by single‐point computations of the contributions of solvation/desolvation to the binding. The ordering of the resulting energy balances was found to be fully consistent with the experimentally ascertained ordering of affinities inferred from the IC50 values. The essential role of an indole group partaking in cation–π and hydrophobic interactions, together with the CaII‐chelating oxadiazolone ring, was highlighted for the best binding compound. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Tandem Addition/Cyclization of Alkynylzinc Reagents to Enantiopure 2‐tert‐Butyl‐3,5‐dimethyl‐2,3‐dihydroimidazol‐4‐one N‐Oxide: Potential Precursors of Quaternary α‐Amino Acids
Authors: Cantagrel Frédéric , Pinet Sandra , Gimbert Yves , Chavant Pierre Y.
Published: June 2005

A new enantiopure cyclic nitrone, a potential electrophilic alanine synthon, has been prepared. Its reaction with alkynylzinc reagents led to a tandem addition/cyclization reaction with complete regio‐ and stereoselectivity. The adducts are potential precursors of quaternary α‐amino acids. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
The Preparation of the Last Remaining Acyclic Isomers of Benzene
Authors: Maurer Helmut , Hopf Henning
Published: June 2005

The three acyclic isomers of benzene – 2,3‐hexadien‐5‐yne, 3‐methyl‐1,2‐pentadien‐4‐yne, and 1,2,3,4‐hexatetraene – have been prepared by simple routes from readily available starting materials. The hydrocarbons as well as several side products formed during their synthesis were characterized by their spectroscopic data and typical cycloaddition and isomerization reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Fulicineroside, an Unusual Glycosidic Dibenzofuran Metabolite from the Slime Mold Fuligo cinerea (Schwein.) Morgan
Authors: Řezanka Tomáš , Hanuš Lumír O. , Kujan Petr , Dembitsky Valery M.
Published: June 2005

Fulicineroside, a glycosidic dibenzofuran metabolite from the slime mold Fuligo cinerea collected in the Czech Republic, has been isolated as a new natural product. Its structure was elucidated from UV, IR, MS, 1D and 2D NMR spectroscopic data and chemical degradation. The compound was highly active against Gram‐positive bacteria and crown gall tumors. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Tetraalkylammonium and 1,3‐Dialkylimidazolium Salts with Fluorinated Anions as Recoverable Phase‐Transfer Catalysts in Solid Base‐Promoted Cross‐Aldol Condensations
Authors: Kryshtal Galina V. , Zhdankina Galina M. , Zlotin Sergei G.
Published: June 2005

Tetraalkylammonium and 1,3‐dialkylimidazolium tetrafluoroborates and hexafluorophosphates were employed for the first time as recoverable phase‐transfer catalysts in multiphase reactions of CH‐acids, in particular in solid base‐promoted cross‐aldol condensations. The catalysts retained their catalytic activity over several reaction cycles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Entropy of Activation for Reactions in the Condensed Phase: A Theoretical Study of the SN2 Alkylation of Amines
Authors: Canepa Carlo , Mosso Marco , Maranzana Andrea , Tonachini Glauco
Published: June 2005

A theoretical model for the evaluation of the entropy of activation for organic reactions in the condensed phase is proposed. The required partition functions for solutes are computed taking into account the hindered translation and rotation in the solvent cavity. The activation parameters for the alkylation of 3‐bromopyridine by iodomethane in acetonitrile were obtained by regression of experimentally determined rate constants to the Eyring equation with different reference volumes. While the gas‐phase reference volume affords an entropy of activation of –40.7 cal mol–1 K–1, the corresponding calculated quantity at the MPW1K/CRENBL·6‐311(+)G(d) level of theory is –34.9 cal mol–1 K–1. The condensed‐phase reference volume gives ΔS≠ = –24.1 cal mol–1 K–1, in better agreement with the computed value of –22.6 cal mol–1 K–1. Regressions with all reference volumes give an enthalpy of activation of around 13 kcal mol–1, while the computed potential‐energy barriers lie between 16.8 and 18.4 kcal mol–1. Transition‐state theory, making use of calculated potential‐energy barriers and either gas‐phase or condensed‐phase partition functions, affords second‐order rate constants for the reaction of CH3I with 3‐bromopyridine at least three orders of magnitude below the experimentally observed value. This discrepancy does not appear to be a consequence of a lack of accuracy of the pre‐exponential factor, but might be caused by either overestimated calculated potential‐energy barriers or the functional form of the Eyring equation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Activation of Allyl Alcohols as Allyl Cations, Allyl Anions, and Amphiphilic Allylic Species by Palladium
Authors: Tamaru Yoshinao
Published: June 2005

Palladium/Et3B induces allyl alcohols to undergo electrophilic allylation of soft carbonucleophiles (pKa 5–14), alkyl aldehydes at the α‐position, and amines, indoles, and tryptophan at the 3‐position. The same catalyst, and also Pd/Et2Zn, also effect the generation of allyl anions from allyl alcohols, which react with aromatic and aliphatic aldehydes and imines to furnish homoallyl alcohols and homoallylamines, respectively, in good yields. 2‐Methylenepropane‐1,3‐diol undergoes a sequential amphiphilic activation, generating an allyl cation and an allyl anion, and reacts with aldehydes to furnish 3‐methylenecyclopentanols. The amphiphilic activation has been extended to 1,3‐bis(alkoxy)‐2‐methylenepropanes and vinyl epoxides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Cascade Reactions of β‐Amino‐Substituted α,β‐Unsaturated Fischer Carbene Complexes with 1,5‐Dien‐3‐ynes as a Convenient Access to Ring‐Annelated Benzene Derivatives
Authors: Wu Yao‐Ting , Noltemeyer Mathias , de Meijere Armin
Published: June 2005

Upon heating pentacarbonyl(3‐dimethylamino‐1‐ethoxypropenylidene)chromium complexes 1 with 1,5‐dien‐3‐ynes 2 in pyridine at 80 °C, benzene‐annelated cyclopentenones 8 and their regioisomers 9, resulting from a sequence of cocyclization, 6π‐electrocyclization and hydrolysis, were isolated in 12–75 % yield (13 examples). The more flexible the alkenyl substituents were in the dienynes 2, the longer were the reaction times needed to achieve good chemical yields. This new cascade reaction of Fischer carbene complexes provides a direct route to trindanone analogues under milder conditions than traditional methods, and is compatible with more functionalities. Compounds 14 and 15 with steroid‐like skeletons were thus prepared in 54–77 % yields (4 examples) from complex 1‐iPr and the bicyclic alkyne 2. Hexacycles 17 and 18 were accessible with high diastereoselectivity in the triquinane moiety by the same method in 45 % yield, (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Decoding two‐dimensional polyacrylamide gel electrophoresis complex maps by autocovariance function: A simplified approach useful for proteomics
Authors: Pietrogrande Maria Chiara , Marchetti Nicola , Tosi Azzurra , Dondi Francesco , Righetti Pier Giorgio
Published: June 2005

This paper describes a mathematical approach applied for decoding the complex signal of two‐dimensional polyacrylamide gel electrophoresis maps of protein mixtures. The method is helpful in extracting analytical information since separation of all the proteins present in the sample is still far from being achieved and co‐migrating proteins are generally present in the same spot. The simplified method described is based on the study of the 2‐D autocovariance function (2D‐ACVF) computed on an experimental digitized map. The first part of the 2D‐ACVF allows for the estimation of the number of proteins present in the sample (2D‐ACVF computed at the origin) and of the separation performance (mean spot size). Moreover, the 2D‐ACVF plot is a powerful tool in identifying order in the spot position, and singling it out from the complex separation pattern. This method was validated on synthetic maps obtained by computer simulation to describe 2‐D PAGE real maps and reference maps retrieved from the SWISS‐2DPAGE database. The results obtained are discussed by focusing on specific information relevant in proteomics: sample complexity, separation performance, and identification of spot trains related to post‐translational modifications.
Column chromatographic prefractionation leads to the detection of 543 different gene products in human fetal brain
Authors: Shin Joo‐Ho , Krapfenbauer Kurt , Lubec Gert
Published: June 2005

In a previous publication a large series of proteins were identified in fetal human brain by the use of two‐dimensional electrophoresis (2‐DE) with subsequent matrix‐assisted laser desorption/ionization‐time of flight (MALDI‐TOF) and MALDI‐tandem time‐of‐flight (TOF/TOF) analysis. Further identification of many more different spots by traditional 2‐DE without additional step such as narrow immobilized ph gradient (IPG) strips or prefractionation seems unlikely and we therefore decided to separate extracted brain proteins by ion‐exchange chromatography using a TSK gel DEAE‐5PW column followed by 2‐DE of individual fractions and analysis by MALDI‐TOF/TOF with LIFT technology in fetal brain of the early second trimester. About 1880 protein spots corresponding to 543 different gene products were identified. These proteins included housekeeping, signaling, cytoskeletal, metabolic, antioxidant, and neuron/synaptosomal specific proteins. Among these, 314 gene products (314/543, 57.8%), which have never been detected in traditional 2‐DE of human fetal brain, were observed by this method. This updated map of fetal brain proteins may serve as data base and reference map for fetal brain proteins, and the methodology applied may be used as a valuable analytical tool for the basis of protein expressional studies in health and disease.
Chrispaulia, a new genus of mud star (Asteroidea, Goniopectinidae) from the Cretaceous of England
Authors: Gale Andrew S.
Published: June 2005

The asteroid species Nymphaster radiatus Spencer is redescribed in detail and placed in a new genus, Chrispaulia. Newly collected associated ossicles including ambulacral, adambulacral, marginal, terminal and actinal plates demonstrate that this taxon is a member of the family Goniopectinidae (order Paxillosida, suborder Cribellina), rather than of the Goniasteridae (order Valvatida) as hitherto presumed. This is the first fossil record of the Goniopectinidae, which is a small and rather uncommon family in Recent seas. Living Cribellina are specialized deposit feeders which burrow into muddy substrates in moderately deep marine to abyssal environments. The restriction of C. radiatus to Cretaceous muds and marly chalks, taken in conjunction with morphological evidence, leads to the conclusion that this species had a similar life style. The occurrence of fossil Cribellina is reviewed and the Cretaceous (Campanian) genus Paleoctenodiscus from Mexico is assigned to the Porcellanasteridae. Copyright © 2005 John Wiley & Sons, Ltd.
Rapid and reactive nitric oxide production by astrocytes in mouse neocortical slices
Authors: Buskila Yossi , Farkash Shai , Hershfinkel Michal , Amitai Yael
Published: June 2005

Nitric oxide (NO), a cellular signaling molecule, is produced in the brain by both neurons and astrocytes. While neurons are capable of rapid release of small amounts of NO serving as neurotransmitter, astrocytic NO production has been demonstrated mainly as a slow reaction to various stress stimuli. Little is known about the role of astrocyte‐produced NO. Using the NO indicator 4,5‐diaminofluorescein‐2 diacetate (DAF‐2DA) and acute slices from mouse brain, we distinguished neurons from astrocytes based on their different fluorescence kinetics and pattern, cellular morphology, electrophysiology, and responses to selective nitric oxide synthase (NOS) inhibitors. Typically, astrocytic fluorescence followed neuronal fluorescence with a delay of 1–2 min and was dependent on the inducible NOS isoform (iNOS) activity. Western blot analysis established the presence of functional iNOS in the neocortex. An assay for cell death revealed that most DAF‐2DA‐positive neurons, but not astrocytes, were damaged. Whole cell recordings from astrocytes confirmed that these cells maintained their membrane potential and passive properties during illumination and afterward. Induction of excitotoxicity by brief application of glutamate triggered an immediate and intense astrocytic response, while high‐frequency electrical stimulation failed to do so. The present study demonstrates, for the first time, rapid and massive iNOS‐dependent NO production by astrocytes in situ, which appears to be triggered by acute neuronal death. These data may bear important implications for our theoretical understanding and practical management of acute brain insults. © 2005 Wiley‐Liss, Inc.
Anti‐disialosyl antibodies mediate selective neuronal or Schwann cell injury at mouse neuromuscular junctions
Authors: Halstead Susan K. , Morrison Ian , O'Hanlon Graham M. , Humphreys Peter D. , Goodfellow John A. , Plomp Jaap J. , Willison Hugh J.
Published: June 2005

The human paralytic neuropathy, Miller Fisher syndrome (MFS) is associated with autoantibodies specific for disialosyl epitopes on gangliosides GQ1b, GT1a, and GD3. Since these gangliosides are enriched in synaptic membranes, anti‐ganglioside antibodies may target neuromuscular junctions (NMJs), thereby contributing to disease symptoms. We have shown previously that at murine NMJs, anti‐disialosyl antibodies induce an α‐latrotoxin‐like effect, electrophysiologically characterized by transient massive increase of spontaneous neurotransmitter release followed by block of evoked release, resulting in paralysis of the muscle preparation. Morphologically, motor nerve terminal damage, as well as perisynaptic Schwann cell (pSC) death is observed. The relative contributions of neuronal and pSC injury to the paralytic effect and subsequent repair are unknown. In this study, we have examined the ability of subsets of anti‐disialosyl antibodies to discriminate between the neuronal and glial elements of the NMJ and thereby induce either neuronal injury or pSC death. Most antibodies reactive with GD3 induced pSC death, whereas antibody reactivity with GT1a correlated with the extent of nerve terminal injury. Motor nerve terminal injury resulted in massive uncontrolled exocytosis with paralysis. However, pSC ablation induced no acute (within 1 h) electrophysiological or morphological changes to the underlying nerve terminal. These data suggest that at mammalian NMJs, acute pSC injury or ablation has no major deleterious influence on synapse function. Our studies provide evidence for highly selective targeting of mammalian NMJ membranes, based on ganglioside composition, that can be exploited for examining axonal–glial interactions both in disease states and in normal NMJ homeostasis. © 2005 Wiley‐Liss, Inc.
Olfactory ensheathing cells and olfactory nerve fibroblasts maintain continuous open channels for regrowth of olfactory nerve fibres
Authors: Li Ying , Field Pauline M. , Raisman Geoffrey
Published: June 2005

The ensheathing cells of the olfactory nerves are arranged end‐to‐end to form a continuous channel enclosing the olfactory axons from their origin in the olfactory mucosa to their termination in the olfactory bulb. On their outer surface, the olfactory ensheathing cell channels have a basal lamina and an outer encirclement of olfactory nerve fibroblasts. We present an anatomical model of the ensheathing arrangements for the entire transit of the olfactory axons from the horizontal basal cells of the mucosa through the nerves to the superficial astrocytes of the bulb. We used intracranial section of the olfactory nerves to induce a rapid retrograde loss of olfactory neurons and degeneration of their axons, followed by replacement of the neurons from stem cells in the mucosa and growth of the newly formed axons along the olfactory nerves. The olfactory ensheathing cells survive and play a vital role in this process. Unlike Schwann cells in damaged peripheral nerve, the olfactory ensheathing cells neither divide nor migrate. They are actively phagocytic for removal of the degenerating axons, and provide continuous stable open channels along which adventitious cells such as erythrocytes and macrophages can travel, and along which the newly formed axons can regenerate. We suggest that the persistence of these open channels is an important element in the effectiveness of the regeneration. These properties, which the olfactory ensheathing cells exert in collaboration with olfactory nerve fibroblasts, may also be involved in the reparative effects of these cells when transplanted into lesions of the spinal cord. © 2005 Wiley‐Liss, Inc.
How the turtle forms its shell: a paracrine hypothesis of carapace formation
Authors: Cebra‐Thomas Judith , Tan Fraser , Sistla Seeta , Estes Eileen , Bender Gunes , Kim Christine , Riccio Paul , Gilbert Scott F.
Published: June 2005

We propose a two‐step model for the evolutionary origin of the turtle shell. We show here that the carapacial ridge (CR) is critical for the entry of the ribs into the dorsal dermis. Moreover, we demonstrate that the maintenance of the CR and its ability to attract the migrating rib precursor cells depend upon fibroblast growth factor (FGF) signaling. Inhibitors of FGF allow the CR to degenerate, with the consequent migration of ribs along the ventral body wall. Beads containing FGF10 can rearrange rib migration in the chick, suggesting that the CR FGF10 plays an important role in attracting the rib rudiments. The co‐ordinated growth of the carapacial plate and the ribs may be a positive feedback loop (similar to that of the limbs) caused by the induction of Fgf8 in the distal tips of the ribs by the FGF10‐secreting mesenchyme of the CR. Once in the dermis, the ribs undergo endochrondral ossification. We provide evidence that the ribs act as signaling centers for the dermal ossification and that this ossification is due to bone morphogenetic proteins secreted by the rib. Thus, once the ribs are within the dermis, the ossification of the dermis is not difficult to achieve. This relatively rapid means of carapace formation would allow for the appearance of turtles in the fossil record without obvious intermediates. J. Exp. Zool. (Mol. Dev. Evol.) 304B, 2005. © 2005 Wiley‐Liss, Inc.
Effect of low‐dose irradiation on shelf life and microbiological safety of sliced carrot
Authors: Kamat AS , Ghadge N , Ramamurthy MS , Alur MD
Published: June 2005

Minimally processed non‐irradiated carrots (sliced) exhibited diverse microflora at initial level. During storage, bacterial number increased with the presence of pathogenic bacteria accompanied by a loss of total solids. On the other hand γ‐irradiation at an optimal dose of 2 kGy offered a pathogen‐free, hygienic product with insignificant losses in nutrients such as in sucrose, total carotenes and ascorbic acid content in comparison to controls and 2‐ to 4‐fold increased in shelf‐life at refrigeration temperature. The D10 values of pathogens like Escherichia coli and Yersinia enterocolitica in carrot paste were in a lower range (0.12–0.26 kGy) compared with that of Listeria monocytogenes (0.3–0.5 kGy). The validity of the processing treatment (2 kGy) was challenged by artificially inoculating Listeria monocytogenes in the product. Thus, minimally processed carrots (sliced) are amenable to radiation treatment for extended storage stability and microbial safety. Copyright © 2005 Society of Chemical Industry
Microrobotics and MEMS‐Based Fabrication Techniques for Scaffold‐Based Tissue Engineering
Authors: Zhang Han , Hutmacher Dietmar W. , Chollet Franck , Poo Aun Neow , Burdet Etienne
Published: June 2005

Summary: Scaffold based tissue engineering strategies use cells, biomolecules and a scaffold to promote the repair and regeneration of tissues. Although scaffold‐based tissue engineering approaches are being actively developed, most are still experimental, and it is not yet clear what defines an ideal scaffold/cell construct. Solid free form fabrication (SFF) techniques can precisely control matrix architecture (size, shape, interconnectivity, branching, geometry and orientation). The SFF methods enable the fabrication of scaffolds with various designs and material compositions, thus providing a control of mechanical properties, biological effects and degradation kinetics. This paper reviews the application of micro‐robotics and MEMS‐based fabrication techniques for scaffold design and fabrication. It also presents a novel robotic technique to fabricate scaffold/cell constructs for tissue engineering by the assembly of microscopic building blocks.

Scaffold design for a single step pop‐up assembly.

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Scaffold design for a single step pop‐up assembly.
Cover Picture: Macromol. Biosci. 6/2005
Authors: Zhang Han , Hutmacher Dietmar W. , Chollet Franck , Poo Aun Neow , Burdet Etienne
Published: June 2005

Cover: The fabrication of microparts, as those shown in the figure, for the production of scaffolds by means of robotic microassembly is challenging due to their small size and complex 3‐D shape. To facilitate the microassembly process, another challenge is the requirement that the parts need to be stably fixed on the wafer but at the same time easily removed by the microgripper. Currently, SU‐8, a biocompatible material, is used to test the feasibility of the microassembly. Further details can be found in the Review by H. Zhang, D. W. Hutmacher,* F. Chollet, A. N. Poo, and E. Burdet on page 477.
Luminescent Bis(benzoxazolyl)stilbene as a Molecular Probe for Poly(propylene) Film Deformation
Authors: Pucci Andrea , Bertoldo Monica , Bronco Simona
Published: June 2005

Summary: Poly(propylene) (PP) films containing different concentrations of bis(benzoxazolyl)stilbene (BBS) have been prepared by melt processing. We demonstrate that the emission characteristics of PP films depend on BBS concentration and polymer deformation. A well‐defined excimer band is observed with more than 0.2 wt.‐% of BBS, conferring to the film a green luminescence. During drawing (130 °C) the PP reorganisation breaks the BBS excimer‐type arrangement, leading to the prevalence of the blue emission of the single molecules. We have efficiently applied the photophysics of this commercial stilbene derivative to the production of powerful tools acting as an internal probe for PP deformation.

Picture of oriented PP/BBS‐0.5 film taken under excitation with a long‐range UV lamp (λ = 366 nm). During drawing, the macromolecular chains reorganisation is able to break the BBS excimer‐type arrangement leading to the prevalence of the blue emission of the single molecules.

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Picture of oriented PP/BBS‐0.5 film taken under excitation with a long‐range UV lamp (λ = 366 nm). During drawing, the macromolecular chains reorganisation is able to break the BBS excimer‐type arrangement leading to the prevalence of the blue emission of the single molecules.
Living Ziegler‐Natta Polymerizations: True or False?
Authors: Busico Vincenzo , Talarico Giovanni , Cipullo Roberta
Published: June 2005

Based on the recent literature, the synthesis of novel polyolefin architectures via Ziegler‐Natta chemistry under living conditions appears to be a promising and fast‐growing area. In this paper, the appropriateness of the term “living” as applied to the said context is discussed in mechanistic terms, and the potential and the limitations of the field are outlined with the aid of two paradigmatic case histories (i.e., propene polymerization in the presence of bis(phenoxy‐imine)Ti and bis(phenoxy‐amine)Zr catalysts).
Anionic Polymerization of New Dual‐Functionalized Styrene and α‐Methylstyrene Derivatives Having Styrene or α‐Methylstyrene Moieties
Authors: Hirao Akira , Kitamura Masahiro , Hayashi Mayumi , Loykulnant Surapich , Sugiyama Kenji
Published: June 2005

Anionic polymerizations of four new dual‐functionalized styrene and α‐methylstyrene derivatives, 3‐(4‐(4‐isopropenylphenoxy)butyl)styrene (4), 3‐(4‐(2‐isopropenylphenoxy)butyl)‐α‐methylstyrene (5), 4‐(4‐(4‐isopropenylphenoxy)butyl)‐α‐methylstyrene (6), and 4‐(4‐(2‐vinylphenoxy)butyl)styrene (7), were carried out in THF at ‐78 °C with sec‐BuLi as an initiator. Both 4 and 5 underwent anionic polymerization in a living manner to quantitatively afford functionalized polystyrenes and poly(α‐methylstyrene)s having α‐methylstyrene moiety in each monomer unit and precisely controlled chain lengths. On the other hand, insoluble polymers were obtained by the anionic polymerization of 6 and 7 under the same conditions. The positional effect of substituent on anionic polymerization was discussed.
Trialkylsilyl‐Protected Functional Initiators for Stereospecific Anionic Polymerization of Methacrylates
Authors: Kitayama Tatsuki , Kitaura Takehiro
Published: June 2005

Anionic polymerizations of methyl methacrylate with trialkylsilyl‐protected lithium benzylamides were conducted in the presence of aluminum compounds such as n‐Bu3Al. When the Me3Si‐protected amide was used, the carbonyl attack took place to some extent to form a methacrylamide derivative with slightly lower initiator efficiency (∼0.9). In the case of i‐Pr3Si‐protected amide, the carbonyl addition was completely suppressed. The obtained polymers had narrow molecular weight distribution and carried benzylamino end‐group, as revealed by NMR analysis, which is readily accessible for further chemical transformations such as acylation with acryloyl chloride and debenzylation with H2/Pd‐C. Difuntional initiators with protected groups were also examined.
Anionic Polymerization Chemistry of Epoxides: Electron‐Transfer Processes
Authors: Quirk Roderic P. , Pickel Deanna L. , Hasegawa Hiroaki
Published: June 2005

The reaction of poly(styryl)lithium (PSLi) with styrene oxide (SO) in benzene solution has been investigated. In addition to the functionalized polymer (83.5 wt %) the product mixture consisted of unfunctionalized polymer (9 wt %) and a dimeric product (5.6 wt %). The structure of the dimeric product was determined to be the head‐to‐head dimer. The regiochemistry of the addition reaction was unselective: 53 mol % addition to the methylene carbon and 47 mol % corresponding to addition to the hindered, methine carbon. Based on the formation of the dimer and the lack of regioselectivity, a pathway involving electron transfer from PSLi to SO was proposed. To further investigate the propensity to react via this electron‐transfer mechanism, the SO functionalization of the adduct of PSLi with 1,1‐diphenylethylene was investigated as well as the functionalization of PSLi with 1,1‐diphenylethylene oxide.
Submicron Sized Hollow Polymer Particles: Preparation and Properties
Authors: Pavlyuchenko Valery N. , Sorochinskaya Olga V. , Primachenko Oleg N. , Ivanchev Sergey S.
Published: June 2005

The considered method for obtaining hollow polymer particles is based on the following pathway: (1) preparation of a carboxylated core latex by emulsion copolymerization of acrylic monomers with methacrylic acid, (2) synthesis of a core‐shell latex comprising a styrene (co)polymer shell, (3) neutralization of the core carboxylic groups with a base followed by the core ionization and hydration to a high degree, shell expansion and formation of water‐filled hollows. A number of approaches to improve the hydrophilic core – hydrophobic shell compatibility and enlarge the hollow volume are considered. The synthesized hollow particles are of a submicron size with the relative hollow volume Vhol : Vpart.= 0.43 – 0.64. Methods for cationic hollow particle latex preparation by anionic latex recharging with a cationic surfactant or acidic melamine resin are discussed. Recharging with a melamine resin is shown to afford hollow particles with an external polymer shell providing a high thermal stability of the particles.
Macroporous Silica Monoliths Derived from Glyceroxysilanes: Controlling Gel Formation and Pore Structure
Authors: Zheng Zhang , Chen Yang , Hodgson Richard J. , Brook Michael A. , Brennan John D.
Published: June 2005

Diglycerylsilane (DGS), a member of the family of sugar‐based silanes, is converted into monolithic silica at low temperatures and at mild pH. These materials are suitable for the entrapment of proteins under conditions that generally offer protection against denaturation, particularly when compared to analogous silicas prepared from tetraethoxysilane (TEOS). However, the resulting monoliths did not have sufficient porosity to permit flow and, thus, could not be utilized as monolithic chromatographic supports for frontal affinity chromatography (FAC). It was demonstrated that poly(ethylene oxide) can be used to induce spinodal decomposition of the DGS‐derived sol, prior to gelation, leading to a meso‐ and macroporous silica monolith after cure, as demonstrated by nitrogen sorption analysis. High molecular weight PEO is required for effective phase separation to take place: below 10000 MW, no such phase separation occurs under the conditions employed. The amount and molecular weight of PEO is critical to the timing of gelation. If too much PEO is present, or ionic strength is increased, gelation occurs before it is possible to fill the chromatography column with the sol, while too little results in a lack of macropores. Proteins entrapped in this material are shown to be of comparable stability to those prepared in the absence of PEO, and can be used to chromatographically screen, with MS detection, potential drug candidates by changes in retention resulting from ligand binding.
Simultaneous radiofrequency (RF) heating and magnetic resonance (MR) thermal mapping using an intravascular MR imaging/RF heating system
Authors: Qiu Bensheng , El‐Sharkawy Abdel‐Monem , Paliwal Vaishali , Karmarkar Parag , Gao Fabao , Atalar Ergin , Yang Xiaoming
Published: June 2005

Previous studies have confirmed the possibility of using an intravascular MR imaging guidewire (MRIG) as a heating source to enhance vascular gene transfection/expression. This motivated us to develop a new intravascular system that can perform MR imaging, radiofrequncy (RF) heating, and MR temperature monitoring simultaneously in an MR scanner. To validate this concept, a series of mathematical simulations of RF power loss along a 0.032‐inch MRIG and RF energy spatial distribution were performed to determine the optimum RF heating frequency. Then, an RF generator/amplifier and a filter box were built. The possibility for simultaneous RF heating and MR thermal mapping of the system was confirmed in vitro using a phantom, and the obtained thermal mapping profile was compared with the simulated RF power distribution. Subsequently, the feasibility of simultaneous RF heating and temperature monitoring was successfully validated in vivo in the aorta of living rabbits. This MR imaging/RF heating system offers a potential tool for intravascular MR‐mediated, RF‐enhanced vascular gene therapy. Magn Reson Med 54:226–230, 2005. © 2005 Wiley‐Liss, Inc.
Correction of MR image distortions induced by metallic objects using a 3D cubic B‐spline basis set: Application to stereotactic surgical planning
Authors: Skare S. , Andersson J.L.R.
Published: June 2005

Metallic implants in MRI cause spin‐echo (SE) images to be distorted in the slice and frequency‐encoding directions. Chang and Fitzpatrick (IEEE Trans Med Imaging 1992;11:319–329) proposed a distortion correction method (termed the CF method) based on the magnitude images from two SE acquisitions that differ only in the polarity of the frequency‐encoding and slice‐selection gradients. In the present study we solved some problems with the CF method, primarily by modeling the field inhomogeneities as a single 3D displacement field built by 3D cubic B‐splines. The 3D displacement field was applied in the actual distortion direction in the slice/frequency‐encoding plane. To account for patient head motion, a 3D rigid body motion correction was also incorporated in the model. Experiments on a phantom containing an aneurysm clip showed that the knot spacing between the B‐splines is a very important factor in both the final image quality and the processing speed. Depending on the knot spacing and the image volume size, the number of unknowns range from a few thousands to over 100,000, leading to processing times ranging from minutes to days. Optimal knot spacing, a means of increasing the processing speed, and other parameters are investigated and discussed. Magn Reson Med 54:169–181, 2005. © 2005 Wiley‐Liss, Inc.
Optimizing PRESS localized citrate detection at 3 Tesla
Authors: Trabesinger Andreas H. , Meier Dieter , Dydak Ulrike , Lamerichs Rolf , Boesiger Peter
Published: June 2005

Analytical methods are used to characterize the response of the strongly coupled two‐spin system of citrate to point‐resolved spectroscopy (PRESS)‐based sequences at 3 T. The signal output is analyzed line by line, as well as in the Cartesian product operator basis. Patterns with a periodicity of 80.9 ms are identified. Furthermore, it is shown that at TE = n · 80.9 ms (n ∈ {0,1,2,…}), the spin evolution can be described without direct reference to strong coupling terms. The theoretical results are found to be in good agreement with in vivo experiments. These results can be used to design protocols for prostate MRS and MRSI at 3 T, and give guidelines for optimizing spin‐echo‐based acquisition schemes for detecting two‐spin systems at arbitrary field strengths. Magn Reson Med 54:51–58, 2005. © 2005 Wiley‐Liss, Inc.
Method of generalized projections algorithm for image‐based reduction of artifacts in radial imaging
Authors: Lee K. J. , Paley M. N. J. , Griffiths P. D. , Wild J. M.
Published: June 2005

This work describes the method of generalized projections (MGP) as an image‐based, postprocessing method to correct for phase inconsistencies caused by echo misalignments in radial imaging. Computer simulations show that MGP can correct for echo shifts, constant phase, and amplitude errors, but the accuracy of the correction is limited, and this accuracy is reduced by the addition of more degrees of freedom. In phantom experiments, MGP performed better than magnitude filtered backprojection and anti‐parallel projections correction. Magn Reson Med 54:246–250, 2005. © 2005 Wiley‐Liss, Inc.
Influence of proton T1 on oxymetry using Overhauser enhanced magnetic resonance imaging
Authors: Matsumoto Shingo , Utsumi Hideo , Aravalluvan Thirumaran , Matsumoto Ken‐ichiro , Matsumoto Atsuko , Devasahayam Nallathamby , Sowers Anastasia L. , Mitchell James B. , Subramanian Sankaran , Krishna Murali C.
Published: June 2005

In Overhauser enhanced magnetic resonance imaging (OMRI) for in vivo measurement of oxygen partial pressure (pO2), a paramagnetic contrast agent is introduced to enhance the proton signal through dynamic nuclear polarization. A uniform proton T1 is generally assumed for the entire region of interest for the computation of pO2 using OMRI. It is demonstrated here, by both phantom and in vivo (mice) imaging, that such an assumption may cause erroneous estimate of pO2. A direct estimate of pixel‐wise T1 is hampered by the poor native MR intensities, owing to the very low Zeeman field (15–20 mT) in OMRI. To circumvent this problem, a simple method for the pixel‐wise mapping of proton T1 using the OMRI scanner is described. A proton T1 image of a slice through the center of an SCC tumor in a mouse clearly shows a range of T1 distribution (0.2∼1.6 s). Computation of pO2 images using pixel‐wise T1 values promises oximetry with minimal artifacts by OMRI. Magn Reson Med 54:213–217, 2005. Published 2005 Wiley‐Liss, Inc.
Uncovering of intracellular water in cultured cells
Authors: Galons Jean‐Philippe , Lope‐Piedrafita Silvia , Divijak Joseph L. , Corum Curt , Gillies Robert J. , Trouard Theodore P.
Published: June 2005

The complexity of biologic tissues, with multiple compartments each with its own diffusion and relaxation properties, requires complex formalisms to model water signal in most magnetic resonance imaging or magnetic resonance spectroscopy experiments. In this article, we describe a magnetic susceptibility‐induced shift in the resonance frequency of extracellular water by the introduction of a gadolinium contrast agent to medium perfusing a hollow fiber bioreactor. The frequency shift of the extracellular water (+185 Hz at 9.4 T) uncovers the intracellular water and allows direct measurement of motional and relaxation properties of the intracellular space. The proposed method provides a unique tool for understanding the mechanisms underlining diffusion and relaxation in the intracellular space. Magn Reson Med 54:79–86, 2005. © 2005 Wiley‐Liss, Inc.
High‐resolution relaxation scheme for the two‐dimensional Riemann problems in gas dynamics
Authors: Seaïd Mohammed
Published: June 2005

We present a new relaxation method for the numerical approximation of the two‐dimensional Riemann problems in gas dynamics. The novel feature of the technique proposed here is that it does not require either a Riemann solver or a characteristics decomposition. The high resolution of the method is achieved by using a third‐order reconstruction for the space discretization and a third‐order TVD Runge‐Kutta scheme for the time integration. Numerical experiments, using several configurations of Riemann problems in gas dynamics, are included to confirm the high resolution of the new relaxation scheme. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006
Properties of well‐defined alternating and random copolymers of methacrylates and styrene prepared by controlled/living radical polymerization
Authors: Denizli Betül Kirci , Lutz Jean‐François , Okrasa Lidia , Pakula Tadeusz , Guner Ali , Matyjaszewski Krzysztof
Published: June 2005

The physical properties of well‐defined alternating copolymers poly(methyl methacrylate‐alt‐styrene) and poly(n‐butyl methacrylate‐alt‐styrene), prepared by reversible addition–fragmentation chain transfer polymerization in the presence of Lewis acids, were investigated with differential scanning calorimetry, wide‐angle X‐ray scattering, and dynamic mechanical measurements. The properties were compared with those of random copolymers of the same overall composition and the corresponding homopolymers. Wide‐angle X‐ray scattering data showed that the alternating copolymers possessed a more regular comonomer sequence than the random copolymers. The thermomechanical properties of alternating copolymers and random copolymers were quite similar and typical for amorphous polymers, but in one of the cases studied the glass‐transition temperature for alternating copolymer was remarkably higher than for the random copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3440–3446, 2005
Wavefunction analysis and optical nutation in magnetized semiconductor quantum wires exhibiting multiple valence subbands
Authors: Kapoor Sheetal , Kumar Jitendra , Sen Pranay K.
Published: June 2005

The energy eigenvalues and eigenfunctions have been obtained for a GaAs/AlGaAs quantum wire structure with multiple valence subbands, subjected to an external magnetic field. The hole wavefunctions are calculated by numerical diagonalization of Luttinger Hamiltonian in an appropriately chosen basis. The electron–hole wavefunctions thus obtained are used in conjunction with effective semiconductor Bloch equations for the study of optical coherent transient effects like optical nutation. The results show squeezing of wavefunctions with increasing magnetic field while band mixing effects lead to overlapping of peaks. The corresponding optical nutation curves show an increase in nutation frequency with magnetic field while band mixing effects are revealed through multiple oscillations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and transport properties of coherently strained La2/3Ca1/3MnO3/SrTiO3 superlattices
Authors: Lu Yafeng , Klein J. , Herbstritt F. , Philipp J. B. , Marx A. , Alff L. , Gross R. , Zhang H.
Published: June 2005

The front cover of this issue, taken from the Editor's Choice, displays the structural characterization of coherently strained La2/3Ca1/3MnO3/SrTiO3 superlattices prepared by laser molecular beam epitaxy [1]. The pronounced superlattice Bragg peaks and the Kiessig fringes indicate an excellent superlattice structure. The superlattice modulation period is obtained by fitting sin2 θ ∼ n2 and also specular low‐angle X‐ray reflectivity. The correlated interface roughness is confirmed by offset low‐angle X‐ray reflectivity and low‐angle rocking curve.

First author Yafeng Lu was a PhD student in the group led by Prof. R. Gross. His research interests are magnetic materials, superconducting materials, and surface physics.
A comparative study of fluoxetine, moclobemide, and tianeptine in the treatment of posttraumatic stress disorder following an earthquake
Authors: Önder E. , Tural Ü. , Aker T.
Published: June 2005

Purpose

Although antidepressant drugs have been proven as an effective treatment for posttraumatic stress disorder (PTSD), there are few comparative studies of antidepressants that are acting on different neurotransmitters. The main aim of this study is to compare the efficacy of different class of antidepressant drugs on the PTSD.

Subjects/materials and methods. –

In this open label study, the patients who met DSM-IV criteria for PTSD were randomly assigned to flexible doses of fluoxetine, moclobemide, or tianeptine. After the first assessment, consecutive assessments were performed at the end of weeks 2, 4, 8, and 12 using clinician administered PTSD scale (CAPS) and Clinical Global Impression of Severity (CGI-S). Changes in the total score of CAPS and sub-scale scores of symptom clusters (re-experience, avoidance, and hyperarousal) were the main output of efficacy. All statistics were based on intention-to-treat and last-observation-carried-forward (LOCF) principles.

Results.

Thirty-eight patients were assigned to fluoxetine, 35 patients were assigned to moclobemide, and 30 patients were assigned to tianeptine group. Gender distributions and mean ages of the treatment groups were not significantly different. Drop-out rates due to an adverse events or unknown reasons were not significantly different among fluoxetine (18.4%), moclobemide (14.3%), and tianeptine (20.0%) groups. All three treatments has led to a significant improvement in PTSD severity assessed with CAPS total score (ANOVA P < 0.001). Similarly, total scores of re-experiencing, avoidance, and hyperarousal clusters that are subscales of CAPS were significantly reduced by all three treatments (with ANOVA all P values < 0.001). There was not significant difference in terms of treatment effect between three groups.

Discussion. –

Treatment groups showed very similar improvement on all ratings scales. The findings support that fluoxetine, moclobemide, and tianeptine are all effective in the treatment of PTSD. Different mechanisms of action for these antidepressant drugs might result in the same common neurochemical end point. However, further studies using different classes of antidepressant drugs are needed.