bluuebunny/crossref_metadata_2025 huggingface dataset:
An Analysis of the Reaction Rate for Mercury Vapor and Chlorine
Authors: Wang J. , Anthony E. J.
Published: April 2005

Mercury is emitted into the environment by various anthropogenic and natural activities. Hg reacts with Cl2 even at ambient temperature. While this reaction is a subject of great interest, data for this system is scarce, apparently due to experimental difficulties. In this work, the reported data for the reaction between Hg and Cl2 is reanalyzed, and possible mechanisms and environmental effects are discussed. The results strongly support the hypothesis that the reaction of Hg and Cl2 is a surface reaction, which takes place at the reactor wall.
Assessment of Drop Coalescence and Breakup for Stirred Extraction Columns
Authors: Hasseine A. , Meniai A.‐H. , Lehocine M. B. , Bart H.‐J.
Published: April 2005

This work is a model assessment study considering two major hydrodynamic parameters: the holdup of the dispersed phase and the Sauter diameter. This is done for two different types of extraction columns, namely, the rotating disc contactor (RDC) and the Kühni column, using different drop breakup and coalescence models in a droplet population balance model. Based on the film drainage models for undeformable (spherical drops) and deformable drops with partially mobile interfaces, different simulations have been performed and the results compared with experimental values. The agreement between the experimental observation and the simulation is encouraging and the used models have proven to be suitable to predict holdup and Sauter diameter profiles for the system toluene/water.
A New Kind of Column Packing for Conventional and Reactive Distillation – The Sandwich Packing
Authors: Kashani N. , Siegert M. , Sirch T.
Published: April 2005

Packed columns have become increasingly important for rectification in the past years. Research activities in distillation and in developing distillation equipment have led to high‐capacity packings as well as to the sandwich‐packing. The sandwich packing advantageously combines a number of characteristics of tray and packed columns. This work was aimed at was investigated the fluid dynamic behavior of the sandwich packing experimentally and theoretically.
Use of Specific Functionalised Tips with STM: A New Identification Method of Ester Groups and Their Molecular Structure in Self‐Assembled Overlayers
Authors: Volcke Cedric , Simonis Priscilla , Durant François , Thiry Paul A. , Lambin Philippe , Culot Christine , Humbert Christophe
Published: April 2005

The influence of chemical modification of scanning tunnelling microscopy tips on image contrast is studied. This technique is applied to the identification of an ester functional group, hardly visible otherwise. Self‐assembled overlayers of wax esters [CH3‐(CH2)14‐CO‐O‐(CH2)15‐CH3], adsorbed at the interface between highly oriented pyrolitic graphite and a solution of phenyloctane, are imaged. The gold tips used are chemically modified by 4‐mercaptobenzoic acid and 4‐mercaptotoluene. The stability of the ordered overlayers formed facilitates the reproducible set of images with submolecular resolution. This allows the identification of the layer regular structure and of other features within molecules, which can be unambiguously related to the fingerprints of the COO bond. Moreover, we are interested in finding evidence of molecular motions observed at domain boundaries.
Supramolecular Assemblies of a Series of 2‐Arylbenzimidazoles at the Air/Water Interface: In Situ Coordination, Surface Architecture and Supramolecular Chirality
Authors: Guo Zongxia , Yuan Jing , Cui Yong , Chang Fei , Sun Wenhua , Liu Minghua
Published: April 2005

The spreading behavior and supramolecular assemblies of some arylbenzimidazoles with 2‐substituted aromatic groups such as phenyl, naphthyl, anthryl and pyrenyl on water surface and the subphase containing AgNO3 were investigated. It was observed that although these compounds lack long alkyl chains, they showed surface activity when spread from chloroform solution on water surface and formed the supramolecular assemblies. When AgNO3 was present in the subphase, a coordination between the imidazole group of the compounds and AgI occurred in situ in the spreading film, which was verified by the surface pressure/area (π–A) isotherms and UV/Vis absorption spectra. Both the spreading films from water and the aqueous AgNO3 subphase were transferred onto solid substrates and their surface morphologies as well as properties were characterized by AFM, UV/Vis absorption and CD spectra. Various surface morphologies such as nanoparticles, block domains and nanoutensils were observed depending on the substituted aromatic groups. Interestingly, although all of these compounds were achiral, supramolecular chirality was obtained for some of the arylbenzimidazole films assembled from either the water surface or the subphase containing AgNO3. It was revealed that chiral assemblies could be obtained from water surface for the benzimidazoles which have pyrenyl or α‐naphthyl groups. For benzimidazole derivative with anthryl group, chiral assemblies could be obtained when spreading on the aqueous AgNO3 subphase. For the benzimidazoles with phenyl or β‐naphthyl groups, no chirality was obtained. It was suggested that both the overcrowded stacking of the aromatic groups and the cooperative arrangement of the molecules on water surface or aqueous AgNO3 subphase play a crucial role in forming the chiral supramolecular assemblies.
An Efficient Three‐Step Synthesis of Cyclopenta[b]pyrans via 2‐Donor‐Substituted Fischer Ethenylcarbenechromium Complexes
Authors: de Meijere Armin , Schirmer Heiko , Stein Frank , Funke Frank , Duetsch Michael , Wu Yao‐Ting , Noltemeyer Mathias , Belgardt Thomas , Knieriem Burkhard
Published: April 2005

A wide range of cyclopenta[b]pyrans 4 has been synthesized in a one‐pot reaction by treatment of different 2‐donorsubstituted ethenylcarbenechromium complexes 2 with alkynes in THF in moderate to excellent yields (41–90 % for 14 out of 25 examples). The starting materials 2 are readily available in good to excellent yields (76–99 % for 25 out of 36 examples) by Michael addition of amines, alcohols and thiols, respectively, to the corresponding alkynylcarbenechromium complexes 1. Due to their 10 π‐electrons in a cross‐conjugated bicyclic system, cyclopenta[b]pyrans have been termed pseudoazulenes, as they indeed have similar UV/Vis‐spectroscopic properties.
Metal‐Directed Synthesis and Photophysical Studies of Trinuclear V‐Shaped and Pentanuclear X‐Shaped Ruthenium and Osmium Metallorods and Metallostars Based upon 4′‐(3,5‐Dihydroxyphenyl)‐2,2′:6′,2′′‐terpyridine Divergent Units
Authors: Constable Edwin C. , Handel Robyn W. , Housecroft Catherine E. , Farràn Morales Angeles , Ventura Barbara , Flamigni Lucia , Barigelletti Francesco
Published: April 2005

A new series of V‐shaped trinuclear metallorods and X‐shaped pentanuclear metallostars has been prepared by the reaction of metal complexes bearing pendant phenolic functionalities with complexes containing electrophilic ligands. Specifically, {M(tpy)2} motifs (M=Ru or Os; tpy=2,2′:6′,2′′‐terpyridine) bearing one or two pendant 3,5‐dihydroxyphenyl substituents at the 4‐position of the central ring of the tpy have been reacted with the complexes [Ru(tpy)(Xtpy)]2+ (X=Cl or Br) to form new ether‐linked species. The energy transfer from ruthenium to osmium in these complexes has been investigated in detail and the efficiency of transfer shown to be highly temperature dependent; the energy transfer is highly efficient at low temperature, whereas at room temperature nonradiative and nontransfer deactivation of the excited {Ru(tpy)2}* domains is most significant.
A Dispensable Methoxy Group? Phenyl Fencholate as a Chiral Modifier of n‐Butyllithium
Authors: Goldfuss B. , Steigelmann M. , Löschmann T. , Schilling G. , Rominger F.
Published: April 2005

Phenyl fenchol forms a 3:1 aggregate with n‐butyllithium (3‐BuLi), showing unique lithium–HC agostic interactions both in toluene solution (1H,7Li‐HOESY) and in the solid state (X‐ray analysis). Although methoxy–lithium coordination is characteristic for many mixed aggregates of anisyl fencholates with n‐butyllithium, endo‐methyl coordination to lithium ions compensates for the missing methoxy groups in 3‐BuLi. This gives rise to a different orientation of the fenchane moiety, encapsulating and chirally modifying the butylide unit.
Cover Picture: The First Studies of a Tetrathiafulvalene‐σ‐Acceptor Molecular Rectifier (Chem. Eur. J. 10/2005)
Authors: Ho Gregory , Heath James R. , Kondratenko Mykola , Perepichka Dmitrii F. , Arseneault Karin , Pézolet Michel , Bryce Martin R.
Published: April 2005

The role of diads…︁ in molecular electronics has been investigated with the recently synthesized tetrathiafulvalene‐σ‐trinitrofluorene diad (depicted on the cover). As determined by cyclic voltammetry, the HOMO–LUMO gap of this diad is as low as ∼0.3 eV, close to that of the theoretical Aviram–Ratner TTF‐σ‐TCNQ molecular rectifier. The rectification behavior of this molecule was tested as a function of electrode material (Si/Ti and Au/Hg), alignment, and orientation of the molecules in the junction. For more information, see the paper by J. R. Heath, D. F. Perepichka et al. on page 2914 ff.
Interferon α therapy for patients with essential thrombocythemia
Authors: Saba Rashid , Jabbour Elias , Giles Francis , Cortes Jorge , Talpaz Moshe , O'Brien Susan , Freireich Emil J. , Garcia‐Manero Guillermo , Kantarjian Hagop , Verstovsek Srdan
Published: April 2005

BACKGROUND

In 1986, a Phase II trial of recombinant interferon‐α (IFN‐α) was initiated as therapy for patients with essential thrombocythemia (ET).

METHODS

Patients were treated with subcutaneous IFN‐α at a dose of 5 × 106 units/m2 daily. In responding patients, the therapy lasted at least 3 years.

RESULTS

Twenty‐three patients (14 females and 9 males; median age, 41 years; age range, 20–63 years) with a median platelet count of 1350 × 109/L were treated. After a median follow‐up of 174 months (14.5 years), 15 of 20 evaluable patients (75%) responded, including 14 patients who achieved a complete hematologic response (CHR) (6 of them with bone marrow remission) and 1 patient who demonstrated a partial response. The median time to response was 6 months (range, 0.5–36 months), and the median response duration was 48 months (range, 5–114 months). Seven patients who achieved a CHR and were taken off therapy after they completed 3 years of maintenance therapy sustained their response for a median of 28 months. No symptoms or signs of thrombosis or hemorrhage were observed in responding patients. Eleven of 14 patients (78%) who achieved a CHR developed a recurrence, and 2 of 5 patients with recurrences who were rechallenged with IFN‐α achieved a second response. The treatment was tolerated relatively well.

CONCLUSIONS

IFN‐α was safe and effective therapy for patients with ET, and the ability of IFN‐α to reverse disease pathology and possibly modify the clinical course of patients with ET warrants its investigation in larger, prospective trials. Cancer 2005. © 2005 American Cancer Society.
Immunolocalization of Bex protein in the mouse brain and olfactory system
Authors: Koo Jae Hyung , Saraswati Manda , Margolis Frank L.
Published: April 2005

Bex proteins are expressed from a family of “brain expressed X‐linked genes” that are closely linked on the X‐chromosome. Bex1 and 2 have been characterized as interacting partners of the olfactory marker protein (OMP). Here we report the distribution of Bex1 and Bex2 mRNAs in several brain regions and the development and characterization of an antibody to mouse Bex1 protein that cross‐reacts with Bex2 (but not Bex3), and its use to determine the cellular distribution of Bex proteins in the murine brain. The specificity of the antiserum was characterized by immunoprecipitation and Western blots of tissue and transfected cell extracts and by immunocytochemical analyses of cells transfected with either Bex1 or Bex2. Antibodies preabsorbed with Bex2 still recognize Bex1, while blocking with Bex1 eliminates all immunoreactivity to both Bex1 and Bex2. Bex immunoreactivity (ir) was primarily localized to neuronal cells within several regions of the brain, including the olfactory epithelium, bulb, peri/paraventricular nuclei, suprachiasmatic nucleus, arcuate nucleus, median eminence, lateral hypothalamic area, thalamus, hippocampus, and cerebellum. RT‐PCR and in situ hybridization demonstrated the presence of Bex mRNA in several of these regions. Double‐label immunocytochemistry indicates that Bex‐ir is colocalized with OMP in mature olfactory receptor neurons (ORNs) and in the OMP‐positive subpopulation of neurons in hypothalamus. This is the first anatomical mapping of Bex proteins in the mouse brain and their colocalization with OMP in ORNs and hypothalamus. J. Comp. Neurol. 487:1–14, 2005. © 2005 Wiley‐Liss, Inc.
Analysis of the proepicardium–epicardium transition during the malformation of the RXRα−/− epicardium
Authors: Jenkins Shantae J. , Hutson D. Renée , Kubalak Steven W.
Published: April 2005

The epicardium of the heart originates from a cluster of mesothelial‐derived cells that develop beneath the sinus venosus in the embryonic day (E) 9.0–9.5 mouse. The subsequent proepicardium–epicardium transition that forms the epicardial layer of epithelial cells covering the myocardial surface is nearly complete by E10.0–E10.5 and results in a fully covered heart by E11.0. In this study, we show that an established model of congenital heart disease, the retinoid X receptor alpha knockout (RXRα−/−) embryo, displays a malformed epicardium. At E10.0–E10.5, the RXRα−/− has several large regions of myocardium that remain bare. Furthermore, by E11.5–E12.5, when a complete epithelial layer is formed in the mutant, large regions of the epicardium become distended from the underlying myocardium. Close examination of the E9.5 mutant revealed an elevated apoptosis level within the proepicardial cluster of mesothelial cells. Additionally, among the extracellular matrix proteins analyzed, expression of fibronectin was elevated in the RXRα−/− as assessed by immunostaining in paraffin‐embedded sections and proepicardial explants. We propose that these events contribute to a developmental delay in the formation of the epicardium, which leads to an abnormal epicardium and ultimately contributes to the cardiac malformations seen in the RXRα−/−. Developmental Dynamics 233:1091–1101, 2005. © 2005 Wiley‐Liss, Inc.
Embryonic and posthatching development of the barn owl (Tyto alba): Reference data for age determination
Authors: Köppl Christine , Futterer Eva , Nieder Bärbel , Sistermann Ralf , Wagner Hermann
Published: April 2005

The normal development of the barn owl was documented with the intent of providing a guideline for determining the maturational stage of embryos and posthatching individuals. Embryonic development up to stage 39 could be well described using the well‐known developmental atlas for the chicken (Hamburger and Hamilton [1951] J. Morphol. 88:49–92). For later stages, limb size was established as a suitable indicator. In addition, measuring the egg's vascularized area through candling was found to be a useful, noninvasive method for staging very early embryos, up to stage 25. An average relationship between incubation period and embryonic stage was derived, which showed that development in the barn owl initally lags that in the chicken. For posthatching individuals, skeletal measures (tarsal and ulnar length, skull width and length) were the most reliable parameters for judging maturation, up to 1 month. For older individuals, feather development (e.g., length of primary wing feathers) provided the only cue. Developmental Dynamics 233:1248–1260, 2005. © 2005 Wiley‐Liss, Inc.
Cell lineage of primary and secondary enamel knots
Authors: Matalova E. , Antonarakis G.S. , Sharpe P.T. , Tucker A.S.
Published: April 2005

Recent research indicates that control of cusp morphology involves a signalling center at the heart of the developing tooth germ, known as the enamel knot. The primary enamel knot forms in both incisors and molar tooth germs at the cap stage of tooth development. Secondary and tertiary enamel knots only develop in molar tooth germs. These sit at the sites of future cusp tips from the early bell stage of tooth development. In studies describing the relationship between the primary and secondary enamel knots, it is often assumed that there is a cellular continuity between these structures, such that cells from the primary enamel knot physically contribute to the secondary enamel knots. We have devised a method whereby the developing tooth germ can be cultured in frontal slices with the enamel knot visible. The fate of the primary enamel knot cells can then be followed by 1,1′, di‐octadecyl‐3,3,3′,3′,‐tetramethylindo‐carbocyanine perchlorate (DiI) labeling. Using this method, no cells of the primary enamel knot were seen to move toward the developing secondary enamel knots. Thus, although the primary and secondary enamel knots have a close molecular and functional relationship in molar development, they are not actually derived from the same cells. Developmental Dynamics 233:754–759, 2005 © 2005 Wiley‐Liss, Inc.
Platinum Complexes with the Novel Ligand Diethyl [(Methylsulfinyl)‐methyl]phosphonate (SMP): Solid‐State Characterization of Potassium Trichloro(SMP)platinum(II) which, in Solution, Gives Dichloro(SMP)‐platinum(II) and Potassium Chloride
Authors: Laforgia Mariarita , Margiotta Nicola , Capitelli Francesco , Bertolasi Valerio , Natile Giovanni
Published: April 2005

Phosphonate ligands have been employed in the synthesis of platinum complexes, which are active against bone tumors. The stability of a new compound of this family, [PtCl2(SMP)] {1; SMP = diethyl[(methylsulfinyl)methyl]phosphonate}, has been investigated in water and acetone. The compound is stable in aqueous solution where it undergoes only partial solvolysis that is completely repressed by addition of free chloride ions. However, crystallization of 1 from water/acetone/chloroform (0.2:1:1, v/v/v) containing an equimolar amount of KCl affords a new compound containing monodentate SMP {K[PtCl3(SMP‐S)], 2}. Dissolution of 2 in water or acetone restores 1. The driving force in the formation of 2 appears to be the network of electrostatic interactions between cations and complex anions in the solid state. It is not only the detached P=O oxygen atom, but also the oxygen atom bound to the sulfur atom and a coordinated chloride ligand of the same platinum unit that interact rather strongly with the cation. It is expected that the same reaction (partial detachment of the phosphonate and anchoring of the cation) can take place in hypercalcaemic districts associated to bone tumors. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Synthetic Explorations Towards Sterically Crowded 1,2,3‐Substituted Bis(indenyl)zirconium(IV) Dichlorides
Authors: Möller Andreas C. , Blom Richard , Heyn Richard H. , Swang Ole , Görbitz Carl‐Henrik , Seraidaris Tanja
Published: April 2005

The systematic synthesis of 1,3‐dialkyl‐substituted 2‐silylindenes and their suitability as zirconocene ligands is discussed. Unexpected reactivities rendered a number of substitution patterns unfeasible, especially for alkyl groups other than methyl in 2‐(trimethylsilyl)indene derivatives, and essentially for all derivatives of 2‐(dimethylsilyl)indene. The syntheses of rac/meso‐bis[1‐methyl‐2‐(trimethylsilyl)indenyl]zirconium(IV) dichloride (12) and bis[1,3‐dimethyl‐2‐(trimethylsilyl)indenyl]zirconium(IV) dichloride (13b) are described. The solid‐state structure of the latter displays strong deformations within the ligand framework and an unusually large Cpcentroid‐Zr–Cpcentroid angle. Both, 12/MAO and 13b/MAO, displayed ethene and ethene‐co‐1‐hexene polymerization activity. Curiously, 13b/MAO shows an extraordinary monomer selectivity, which can be rationalized by means of DFT calculations on the active site. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Self‐Assembly of Protonated 1,12‐Dodecanediamine Molecules and Strongly Undulated Uranyl Selenate Sheets in the Structure of Amine‐Templated Uranyl Selenate: (H3O)2[C12H30N2]3[(UO2)4(SeO4)8](H2O)5
Authors: Krivovichev Sergey V. , Kahlenberg Volker , Avdontseva Evgeniya Yu. , Mersdorf Edgar , Kaindl Reinhard
Published: April 2005

The amine‐templated uranyl selenate (H3O)2[C12H30N2]3[(UO2)4(SeO4)8](H2O)5 (1) has been prepared. Its structure [monoclinic, P21/n, a = 11.3437(7), b = 24.8042(12), c = 29.2496(19) Å, β = 96.701(5)o, V = 8173.8(8) Å3, Z = 4, R1 = 0.083] is based upon strongly undulating [(UO2)(SeO4)2]2– sheets consisting of corner‐sharing UO7 bipyramids and SeO42– tetrahedra. The undulations of the adjacent sheets have an anti‐phase character that allows the formation of large eliptical channels that are occupied by rod micelles formed by self‐assembly of protonated 1,12‐dodecanedi‐amine molecules. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Sediment‐induced stratification in turbulent open‐channel flow
Authors: Ghoshal K. , Mazumder B. S.
Published: April 2005

A vertical gradient of suspended sediment concentration exists in a turbulent open channel flow, particularly near the bed where sediment erosion and deposition take place. This shows a remarkable effect on the flow dynamics. The density gradient of sediment‐mixed fluid may become stably stratified, which results in damping of turbulence fluctuations. In this work, theoretical models for mean velocity and concentration distributions have been developed considering the effect of sediment‐induced stratification and the modified mixing length due to high suspension together with viscous and turbulent shear stresses, which are the functions of concentration. The models are compared with comprehensive experimental data sets. The comparison reveals that (i) the calculated velocity and concentration profiles agree well with the observed data, (ii) the model constant due to stratification used for verification is consistent with the measurements in thermally stratified flows, and (iii) the higher the sediment suspension, the better the effect of density stratification and the less the impact of mixing length. Copyright © 2005 John Wiley & Sons, Ltd.
A reference solution for phase change with convection
Authors: Hannoun N. , Alexiades V. , Mai T. Z.
Published: April 2005

A reference solutions for phase change involving convection in the melt is currently missing. In the present study, we focus on the problem of melting of pure tin in a square cavity heated from the side, which is used as a benchmark test problem. The mathematical model used for the simulations is based on the enthalpy formulation. Extensive numerical computations are performed with grids as fine as 800 × 800. The convergence of the numerical solution is demonstrated and its level assessed. Data values and plots are provided for use as a reference solution. Copyright © 2005 John Wiley & Sons, Ltd.
Differential roles of XRCC2 in homologous recombinational repair of stalled replication forks
Authors: Liu Nan , Lim Chang‐Su
Published: April 2005

Homologous recombination is an important mechanism in DNA replication to ensure faithful DNA synthesis and genomic stability. In this study, we investigated the role of XRCC2, a member of the RAD51 paralog family, in cellular recovery from replication arrest via homologous recombination. The protein expression of XRCC2, as well as its binding partner RAD51D, is dramatically increased in S‐ and G2‐phases, suggesting that these proteins function during and after DNA synthesis. XRCC2 mutant irs1 cells exhibit hypersensitivity to hydroxyurea (HU) and are defective in the induction of RAD51 foci after HU treatment. In addition, the HU‐induced chromatin association of RAD51 is deficient in irs1 mutant. Interestingly, irs1 cells are only slightly sensitive to thymidine and able to form intact RAD51 foci in S‐phase cells arrested with thymidine. Irs1 cells showed increased level of chromatin‐bound RAD51 as well as the wild type cells after thymidine treatment. Both HU and thymidine induce γ‐H2AX foci in arrested S‐phase nuclei. These results suggest that XRCC2 is involved in repair of HU‐induced damage, but not thymidine‐induced damage, at the stalled replication forks. Our data suggest that there are at least two sub‐pathways in homologous recombination, XRCC2‐dependent and ‐independent, for repair of stalled replication forks and assembly of RAD51 foci following replication arrest in S‐phase. © 2005 Wiley‐Liss, Inc.
Regulation of androgen receptor levels: Implications for prostate cancer progression and therapy
Authors: Burnstein Kerry L.
Published: April 2005

Androgen deprivation has been the standard therapy for advanced and metastatic prostate cancer for over half a century, as prostate tumors are initially dependent on androgens for growth and survival. Unfortunately, in most patients undergoing androgen ablation, relapse (recurrent tumor growth) eventually occurs. The actions of the principal androgens, testosterone and dihydrotestosterone (DHT), are mediated via androgen receptors (ARs), ligand‐activated transcription factors that belong to the nuclear receptor superfamily. Because of the presence of transcriptionally active ARs in tumors from recurrent or androgen‐independent disease, there is a heightened interest in new therapeutic paradigms that target the AR and its regulatory pathways. The regulation of AR levels is highly complex with control exerted by several pathways and in a cell‐, tissue‐, and developmental‐stage specific manner. Androgens are important regulators of AR mRNA and protein through transcriptional and post‐transcriptional mechanisms. This article reviews the evidence implicating the AR in recurrent prostate cancer and discusses the multiple mechanisms that regulate AR levels in normal and neoplastic cells. The complexity of AR regulation suggests that there will be an ample array of potential new drug targets for modulating levels of this receptor, a key signaling molecule in prostate cancer. © 2005 Wiley‐Liss, Inc.
Major contribution of the multidrug transporter P‐glycoprotein to reduced susceptibility of poly(ADP‐ribose) polymerase‐1 knock‐out cells to doxorubicin action
Authors: Węsierska‐Gądek Józefa
Published: April 2005

Inactivation of poly(ADP‐ribose) polymerase‐1 (PARP‐1) has been shown to potentiate the cytotoxicity of distinct DNA targeting agents including topoisomerase I inhibitors. On the other hand, the PARP‐1 deficient cells exhibited resistance to conventional inhibitors of topoisomerase II such as etoposide or doxorubicin (DOX). Recently, we observed the extreme sensitivity of PARP‐1 knock‐out (KO) cells to C‐1305, a new biologically active triazoloacridone compound. C‐1305 permanently arrested the cells in G2‐phase of the cell‐cycle. These observations prompted us to investigate more thoroughly the susceptibility of PARP‐1 KO cells to DOX and to examine the effect of DOX on the progression of cell‐cycle. We determined the uptake of DOX and P‐glycoprotein (P‐gp) expression in mouse cells and compared it with that in human myeloma 8226/Dox40 cells overexpressing P‐gp. Exposure of mouse cells to DOX revealed a reduced drug uptake in cells lacking PARP‐1. However, combined treatment with verapamil, a potent MDR modulator increased the DOX accumulation. Detailed immunoblotting experiments revealed an approximately threefold higher P‐gp level in PARP‐1 KO cells as compared with normal counterparts. Interestingly, DOX induced in normal fibroblasts very rapidly G2 arrest whereas in PARP‐1 KO cells it blocked primarily the transition between S and G2 resulting in the increase of cells remaining in S‐phase. This coincided with the lack of the site‐specific phosphorylation of CDK2. Simultaneous inhibition of P‐gp in cells lacking PARP‐1 resulted in an accumulation of cells in G2. Exposure of mouse cells to high DOX dose activated significantly caspase‐3/7 in PARP‐1 KO cells. © 2005 Wiley‐Liss, Inc.
Mammalian Groucho homologs: Redundancy or specificity?
Authors: Gasperowicz Malgorzata , Otto Florian
Published: April 2005

The proteins termed TLE in humans, Grg in mice and Groucho in Drosophila constitute a family of transcriptional corepressors. In mammalians there are five different genes encoding an even larger number of proteins. Interactions between these TLE/Grg proteins and an array of transcription factors has been described. But is there any specificity? This review tries to make a case for a non‐redundant function of individual TLE/Grg proteins. The specificity may be brought about by a tightly controlled temporo‐spatial expression pattern, post‐translational modifications, and subtle structural differences leading to distinct preferences for interacting transcription factors. A confirmation of this concept will ultimately need to come from genetic experiments. © 2005 Wiley‐Liss, Inc.
Effects of Electron Donors on Active Sites Distribution of MgCl2‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model
Authors: Wang Qi , Murayama Namiko , Liu Boping , Terano Minoru
Published: April 2005

Summary: The stopped‐flow polymerization of propylene catalyzed by a Ziegler‐Natta catalyst in the presence of internal and external electron donors was carried out. The influence of the electron donors on the active sites of the catalyst was investigated using a multiple active site model. The variation of each group of active sites, such as the concentration and kp of each site at various polymerization times, can be obtained from this model. It was found that an electron donor mainly affects the aspecific active site by reducing its concentration and increasing its kp. The isospecific site is only slightly altered in terms of concentration and its kp because of steric hindrance.

Variation of [C*] of each active site of TiCl4/MgCl2‐AlEt3 at various polymerization times.

image

Variation of [C*] of each active site of TiCl4/MgCl2‐AlEt3 at various polymerization times.
Ternary Thermosetting Blends of Epoxy Resin, Poly(ethylene oxide) and Poly(ε‐caprolactone)
Authors: Yin Minghua , Zheng Sixun
Published: April 2005

Summary:The ternary thermosetting blends composed of epoxy resin, poly(ethylene oxide) (PEO) and poly(ε‐caprolactone) (PCL) were prepared via in situ polymerization of epoxy monomers in the presence of the two crystalline polymers, PEO and PCL. DSC results showed that the binary blends of epoxy with PEO (and/or PCL) are fully miscible in the entire composition in the amorphous state. FTIR indicates that there were interchain specific interactions between the crosslinked epoxy and the linear polymers in the binary blends and the hydrogen bonding interactions between epoxy and PCL are much weaker than those between epoxy and PEO. The difference in the strength of interchain specific interactions gives rise to the competitive hydrogen bonding interactions in the ternary blends of epoxy, PEO and PCL, which were evidenced by the results of FTIR. The results of optical microscopy and DSC showed that in the ternary blends PCL component separated out with inclusion of PEO. The formation of the specific phase structures is ascribed to the competitive interchain specific interactions among the crosslinked epoxy, PEO and PCL.

Phase boundary diagram of epoxy, PEO and PCL ternary blends.

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Phase boundary diagram of epoxy, PEO and PCL ternary blends.
Contributions to Forming and Analytical Investigations of Solutions of Cellulose and Cellulose Derivatives – A Research and Development Topic of the TITK eV
Authors: Kosan Birgit , Michels Christoph , Meister Frank
Published: April 2005

Modification, forming and analytical characterisation of cellulose and cellulose solutions represents one of the most important research topics of the Thuringian Institute for Textiles and Plastics Research (TITK). The presentation provides information on the current capabilities of the institute and on the analytical methods developed in these fields.
Carboxymethyl Ethers of Cellulose and Starch – A Review
Authors: Heinze Thomas , Koschella Andreas
Published: April 2005

This review article deals with the technically important carboxymethyl ethers of cellulose and starch. Recent developments of synthesis, characterization, and application are presented considering adequately own research work in this field. In particular, the structure characterization by means of chromatographic (HPLC) and NMR‐spectroscopic techniques as well as commercially important synthesis paths and alternative methods are described.
Carbamoylation Applied for Structure Determination of Cellulose Derivatives
Authors: Liebert Tim , Pfeiffer Katy , Heinze Thomas
Published: April 2005

Carbamoylation of cellulose esters (CE) and investigation of the mixed derivatives obtained with NMR spectroscopy represents a useful analytical tool for the determination of the degree of substitution (DS) and analysis of the distribution of substituents on the level of the anhydroglucose unit (AGU). Especially the carbethoxymethylcarbamoylation and the ethylcarbamoylation of CE combined with 1H NMR spectroscopy are efficient and inexpensive ways to gain information on the over‐all DS and partial DS values in position 2, 3, and 6 of the AGU. Complete subsequent phenylcarbamoylation can be achieved even for CE with bulky substituents, e.g., adamantanecarboxylic acid esters. In addition to NMR experiments the carbamoylated CE were studied by HPLC after complete chain degradation. Carbethoxymethylcarbamoylation has turned out to be the most useful tool for this path. Chromatograms comparable to carboxymethylated cellulose (CMC) were obtained, which can be exploited to calculate the mole fractions of the basic building units (un‐, mono‐, di‐ and tri‐substituted glucoses) of the polymer. Comparison with statistic calculations gave a first hint on the distribution of substituents along the polymer chain. For a commercial cellulose diacetate a statistic pattern of substitution was determined.
Polymer‐Analogous Preparation of Cellulose Tricarbanilates: Mechanisms of Degradation in Dimethylsulfoxide
Authors: Fischer Martin , Fischer Klaus
Published: April 2005

Two cellulose samples were subject to treatment with phenylisocyanate (PhNCO), both in pyridine and in dimethylsulfoxide (DMSO). In each case, DMSO degraded cellulose in an extent depending on the derivatized cellulose. The formation of dimethylsulfonium ions was recognized as the cause leading to an oxidation of hydroxyl groups. This Pfitzner‐Moffatt type oxidation is dependent on carboxyl groups and therefore occurs most probably in their neighbourhood. It was deduced that formation of oxidised sections along the cellulose chains occurs containing either carbonyl and carboxyl groups in the same anhydroglucose unit (AGU) or singly oxidised AGUs in direct neighbourhood to each other. This leads to much facilitated eliminative degradation.
Structural Changes and Activation of Cellulose by Caustic Soda Solution with Urea
Authors: Kunze Jürgen , Fink Hans‐Peter
Published: April 2005

Investigations on the activation of cellulose by mixed solutions of caustic soda and urea are reported. The structural effects of those solutions on various dissolving pulps are studied by 13C‐CP/MAS‐NMR spectroscopy. In a series of steeping lyes, the concentration of NaOH was varied in a range from 0% to 8% and the urea‐concentration in a range from 15% to 40% at ambient temperature and −25 °C.

Using solely the single NaOH or urea solutions in the concentration ranges given above, no or only minor structural changes were found. In contrast to that, the cellulose I structure was partially or completely destroyed by using the bicomponent solution with urea added to caustic soda. The structural effect of the bicomponent solutions is comparable with the effect of solely caustic soda solutions of approx. 10% to 18% NaOH. However, the 13C‐CP/MAS‐NMR‐spectra from the bicomponent pretreated samples indicate a structure different from the usual ordered structures of sodium cellulose I or II, namely a special urea‐NaOH‐cellulose complex. The results show that for cellulose activation the NaOH concentration of the caustic soda can be remarkably reduced by adding urea. The improved activating effect of an optimized caustic soda solution with added urea was proved to be useful for the synthesis of cellulose carbamate.
Analytical Investigations of Bacterial Cellulose
Authors: Udhardt Ulrike , Hesse Stephanie , Klemm Dieter
Published: April 2005

The cultivation of the bacterium Acetobacter xylinus AX 5 was carried out in the common Hestrin‐Schramm medium containing D‐glucose as C‐source and citric acid as buffer component. HPLC studies proved to be convenient methods to investigate the stability and interactions of these constituents in the starting culture liquid. Within the initial sterilization step and limited by the citric acid, up to 6% of the D‐glucose was partially isomerized to D‐fructose and degraded to dark‐yellow products. In static culture, A. xylinus AX 5 produces cellulose extracellularly on the surface of this medium. Solid‐state NMR spectroscopy represents a suitable analytical method to characterize the supramolecular structure of the bacterial cellulose in never‐dried, air‐dried, and freeze‐dried states. It could be demonstrated that the drying process reduces the degree of crystallinity in the range of about 12% without changes in the Iα/β ratio of these cellulose modifications.
Isolation and Identification of Residual Chromophores in Cellulosic Materials
Authors: Rosenau Thomas , Potthast Antje , Hofinger Andreas , Kosma Paul
Published: April 2005

A general procedure was developed for the isolation of residual chromophores in or on cellulosic material, which were hitherto inaccessible to structure elucidation due to their extremely low content in the ppb concentration scale. It is applicable to cellulosic pulp, cellulosic fibers (viscose, Lyocell) and cellulose derivatives (acetate, carbonyl‐labeled cellulose) as well. The chromophore identification comprises treatment of the cellulosic material with boron trifluoride – acetic acid complex (BF3*2HOAc) containing sulfite, chromatographic separation of the resulting chromophore‐containing mixture, and structure determination of the main constituents by NMR / MS and comparison to authentic samples. Both adsorbed and covalently bound aromatic and quinoid compounds are selectively released by the treatment. Covalent ester, ether and secondary alkyl links between chromophore and cellulose are broken.

Two cellulosic example substrates have been analyzed for their chromophore content: Lyocell fibers and non‐bleached viscose fibers, and up to eleven chromophores per sample have been identified.
The correlativity of positive temperature coefficient effects in conductive silicone rubber
Authors: Zhang Jie , Zhang Shengyou , Feng Shengyu , Jiang Zhigang
Published: April 2005

A thorough study on the positive temperature coefficient (PTC) effects of conductive silicone rubber was made. Various conductive silicone rubbers with apparent differences in PTC anomalies (defined as the ratio of peak resistivity to room temperature resistivity) were chosen. The correlation between the size of the PTC anomaly and both the thermal expansion coefficient of conductive silicone rubber and the interaction between silicone rubber and carbon black (CB) were found. The effects of cross‐linking on the temperature effect of resistivity of conductive silicone rubber were also studied. The results testify the important role of the interaction between silicone rubber and CBs in the temperature effect of resistivity of conductive silicone rubber. Copyright © 2005 Society of Chemical Industry
Polyamide/silver antimicrobials: effect of crystallinity on the silver ion release
Authors: Kumar Radhesh , Münstedt Helmut
Published: April 2005

Polyamide/silver (PA/Ag) composite materials are regarded as potential antimicrobials by virtue of their efficacy to release the Ag+ ions in an aqueous medium. The effects of the matrix crystallinity on the Ag+ ion release characteristics of PA/Ag composites are discussed. It is found that matrix crystallinity is very decisive for the silver ion releasing properties and hence the antimicrobial efficacy of silver‐based antimicrobial polyamides. The crystallinities of the composites were evaluated using differential scanning calorimetry. The silver ion release characteristics of these composites were measured by anode stripping voltammetry. Silver ion release was higher in systems possessing lower degrees of crystallinity. Water‐diffusion characteristics of the composites control the silver ion release. The effect of crystallinity on silver ion release rate depends on the time of soaking of the specimens in water. Copyright © 2005 Society of Chemical Industry
Preparation of ultrafine fibrous zein membranes via electrospinning
Authors: Miyoshi Takanori , Toyohara Kiyotsuna , Minematsu Hiroyoshi
Published: April 2005

Zein is a protein in corn gluten meal. It has been investigated for use as a structural material because it is renewable and biodegradable. Potential applications of zein include use in coating, film and fiber. In this paper, ultrafine fibrous zein membranes were produced by electrospinning of an 80 wt% ethanol aqueous solution. The morphology of fibers was affected by parameters such as polymer concentration and electric field. As the concentration of the solution increased, wrinkled beads became fewer and fibers became thicker. Fibers were mainly generated above a polymer concentration of 21 wt% with an electric field of 15 kV. However, with a 30 kV field fibers were already generated above 18 wt%. Copyright © 2005 Society of Chemical Industry
On activated seed swelling technique
Authors: Zohrehvand Shiva
Published: April 2005

The activated seed swelling technique is one of the promising methods in synthesis of micron‐sized monodispersed polymer particles. However, there are some parameters (eg the interference of acetone residue on particle swelling) that make this method difficult to carry out and even lead to a broad particle‐size distribution. Here, these parameters are studied and how to control them is discussed. The polydisperse seed swelling appeared at lower concentration of acetone and with incomplete evaporation of acetone from the system. The monodisperse swelling and larger particle sizes were achieved at higher concentration of acetone and longer evaporation time using a vacuum pump. These results suggest that the particle size and particle‐size distribution in the activated seed swelling technique can be controlled by the carrier (acetone) and the hydrophobe concentration in aqueous medium before and after the swelling process. Copyright © 2005 Society of Chemical Industry
The effect of compatibilization on the dynamic properties of polypropylene/nylon‐6 blends studied by broad band dielectric spectroscopy
Authors: Laredo E. , Grimau M. , Bello A. , Sánchez F. , Gómez M. A. , Marco C. , Campoy I. , Arribas J. M.
Published: April 2005

Polypropylene (PP) and polyamide‐6 (Ny‐6) blends with a 70/30 composition have been studied by broadband dielectric spectroscopy. The unmodified blends are immiscible, and 10% of PP functionalized with maleic anhydride was added as a compatibilizer. The influence of the compatibilizer on the water sorption and on the molecular dynamics of the Ny‐6 phase is followed by the changes induced in the dielectric loss spectra of these blends in both wet and dry states. The shortest range motions are unaffected by the compatibilizer in the dry state, but a higher water sorption is observed in the unmodified blend. Higher activation energies are found for the β relaxation in the dry blends than for the Ny‐6 homopolymer, showing the existence of constraints on these longer scale motions. During increasing temperature experiments, two segmental modes are recorded, the lower temperature mode corresponding to the plasticized material; as the temperature is raised, a second cooperative mode is found, originating in the dry Ny‐6 amorphous phase, rigidized by the loss of moisture. The comparison of the dielectric strengths of the modes shows that the unmodified blend absorbs more water than the compatibilized blend. The segmental dynamics are unaffected by compatibilization. At high temperatures, the high temperature tail of the segmental mode is much higher in the absence of the compatibilizer. The contribution of a peak due to interfacial polarization is lowered by the presence of the compatibilizer, which makes the interface more diffuse and the trapping of free carriers less effective. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1408–1420, 2005
Morphological change of poly (ε‐caprolactone) with a wide range of molecular weight via formation of inclusion complex with α‐cyclodextrin
Authors: Shin Kyung‐Moo , Dong Tungalag , He Yong , Inoue Yoshio
Published: April 2005

The effect of molecular weight of poly(ε‐caprolactone) (PCL) on the formation and stability of inclusion complexes (ICs) between α‐cyclodextrin (α‐CD) and PCL was investigated by FTIR, WAXD, and DSC measurements. ICs between α‐CD and PCLs with a wide range of number‐average molecular weight, Mn = 1.21 × 104 – 1.79 × 105, were prepared by mixing the aqueous solution of CD and acetone solution of PCL followed by stirring at 60 °C for 1h and at the room temperature for 1 day. FTIR, WAXD, and DSC measurement showed the PCL chains were included into the α‐CD cavity, and the crystallization of PCL was suppressed in the α‐CD cavity. Stoichiometry and yield of each IC varied with the molecular weight of guest PCL, and the effect of IC formation on the crystallization behaviour of guest polymer decreased with the increase of molecular weight of guest polymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1433–1440, 2005
A Method to Evaluate the Tensile Strength and Stress–Strain Relationship of Carbon Nanofibers, Carbon Nanotubes, and C‐Chains
Authors: Márquez‐Lucero Alfredo , Gomez Jorge A. , Caudillo Román , Miki‐Yoshida Mario , José‐Yacaman Miguel
Published: April 2005

A method is introduced to assess the tensile strength of carbon nanofibers, carbon nanotubes (CNTs), and linear chains of carbon atoms (C‐chains) obtained from thin amorphous carbon films by electron irradiation. Transmission electron microscopy images show that the nanofibers undergo a radiation‐induced necking process, characterized by CNT formation and often followed by the formation of a C‐chain. Simulations of the necking process are carried out to determine the tensile stress supported by the nanofiber and CNT neck.
Phase Separation Micromolding: A New Generic Approach for Microstructuring Various Materials
Authors: Vogelaar Laura , Lammertink Rob G. H. , Barsema Jonathan N. , Nijdam Wietze , Bolhuis‐Versteeg Lydia A. M. , van Rijn Cees J. M. , Wessling Matthias
Published: April 2005

Phase separation micromolding (PSμM) is a versatile microfabrication technique that can be used to structure a very broad range of polymers, including block copolymers and biodegradable and conductive polymers without the need for clean‐room facilities. By incorporating a subsequent process step, carbon, ceramic, and metallic microstructures can also be fabricated from a polymeric or hybrid precursor. The replication process is straightforward and cost‐effective. It relies on phase separation of a polymer solution while in contact with a structured mold. Intrinsic shrinkage during the phase separation facilitates the release of the replica from the mold, which increases the reliability of the process even at small feature sizes, thin polymer films, or high aspect ratios. Under suitable circumstances perforation of the polymer film can be obtained, resulting in completely open “through” microstructures. Furthermore, porosity can be introduced in a microstructure, which may result in unknown functionalities.