bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing the effect of processing variables on the mechanical response of polysytrene molded using vibration‐assisted injection molding process
Authors: Kikuchi A. , Coulter J. P. , Gomatam R. R.
Published: December 2005

The present work is focused on the study of vibration‐assisted injection molding (VAIM) process, using polystyrene as a model polymeric system. This recently developed polymer processing operation is based on the concept of using motion of the injection screw to apply mechanical vibration to polymer melt during the injection and packing stages of injection molding process, to control the polymer behavior at a molecular level, which would result in improvements/alterations to the mechanical behavior of molded products. In this study, the afore‐mentioned concept was verified experimentally from monotonic tensile experiments and birefringence measurements of VAIM molded polystyrene in comparison with those of conventional injection molding process. The results of our study indicate that the actual degree of strength improvement depends on at least four parameters, namely, vibration frequency, vibration amplitude, vibration duration, and the delay time between the injection start and the vibration start. Furthermore, when these parameters were optimized, as much as a 28% strength improvement was observed, accompanied by an increase in toughness. Furthermore, birefringence measurements revealed that VAIM processing significantly altered the residual stress distribution throughout final products, but it did not, however, change the material density in the products. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Study of the factors influencing the exfoliation of an organically modified montmorillonite in methyl methacrylate/poly(methyl methacrylate) mixtures
Authors: McAlpine Morven , Hudson Nicholas E. , Liggat John J. , Pethrick Richard A. , Pugh David , Rhoney Ian
Published: December 2005

The factors that affect the dispersion of exfoliated organically modified montmorillonite in a solution of poly(methyl methacrylate) in methyl methacrylate are explored. Exfoliation of montmorillonite in the solution is achieved with the assistance of ultrasound, and rheological measurements indicate a very significant increase in the viscosity, a dramatic shear thinning behavior, and a finite yield stress, all of which are direct consequences of the exfoliated state of the clay platelets. A number of factors, including the sonication power, clay loading, use of a swelling agent, and moisture content of the modified montmorillonite, are found to influence the exfoliation process. The effect of addition of a range of titanate coupling agents (LICA‐01, 12, 38, 44, and 97) on the viscosity of the nanoclay dispersions was investigated. It was found that LICA‐44 had the effect of reducing the viscosity of the exfoliated montmorillonite dispersion without apparently influencing the extent of the exfoliation. Molecular modeling, UV–visible and Fourier transform infrared spectrometry were used to investigate the possible reasons for efficacy of this LICA. The LICA appears to act through a combination of steric effects and the presence of certain charges on the organic molecule. The magnitude of the negative charges on elements of the LICA appears to influence its ability to bind to the clay and also its ability to reduce the viscosity of the nanoclay. This article indicates how the apparently conflicting requirements of achieving a highly exfoliated state and also maintaining a viscosity low enough for processing can be effectively addressed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Compressive properties of soybean oil‐based polymers at quasi‐static and dynamic strain rates
Authors: Song Bo , Chen Weinong , Liu Zengshe , Erhan Sevim Z.
Published: December 2005

Quasi‐static and dynamic compressive properties of three soybean oil‐based polymeric materials, which were made through the reaction of epoxidized soybean oil with diamine compounds, have been determined. Quasi‐static properties were determined with an MTS 810 hydraulically driven testing machine, whereas dynamic experiments were conducted with a split Hopkinson pressure bar (SHPB) modified for low‐impedance material testing. All three materials were capable of deforming to very large strains, with significant nonlinear stress–strain response. Their compressive behaviors were strain‐rate sensitive with distinctive rate sensitivities. On the basis of the experimental results at various strain rates, a compressive one‐dimensional stress–strain material model with strain‐rate effects was developed to describe the experimental results for all three materials under both quasi‐static and dynamic loading conditions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 2006
Cascade model for coupled two‐component polymer gels
Authors: Mao Ching‐Feng , Chen Jia‐Chin
Published: December 2005

A cascade model for the network of coupled two‐component polymer gels is presented. The network formation is assumed to be primarily due to the interaction between the functional groups of two unlike polymers. The gel modulus G versus polymer concentration C curve is constructed using the cascade formalism. The variation of G versus C curves with respect to the concentration ratio r of the two components is found to be the characteristics of mixed gels. The model parameters can be obtained by fitting G versus C curves using a nonlinear least‐squares method (the gel‐modulus approach). The approach is applied to the experimental data for galactomannan/xanthan and glucomannan/xanthan mixed gels. Finally we discuss the gel point predicted by the cascade model. The critical concentration C0 for the gel point is strongly dependent on r and the functionalities for both polymers. The C0 versus r curve is easily obtained by experiment, and can be used to evaluate the model parameters (the gel‐point approach). The experimental data for galactomannan/xanthan mixed gels is tested to demonstrate the validity of the gel‐point approach. The advantages and limitations of both approaches are discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Properties of highly filled polypropylene derivative composites containing calcite and zeolite
Authors: Biswas Jagannath , Kim Hyun , Choe Soonja
Published: December 2005

This work aims to study the effects of high loading (total 50 wt %) of inorganic calcite, zeolite particulates, and calcite/zeolite mixture with structurally different copolymer [CoPP; poly(propylene‐co‐ethylene)] and terpolymer [TerPP; poly(propylene‐co‐ethylene‐co‐1‐butene)] systems. Melt processing is the sole mode of mixing particulates with polymer for making master batch sample throughout this work. Mechanical properties, like the modulus and yield stress, continuously increase up to a critical zeolite ratio in calcite/zeolite mix and then decrease after exceeding the critical concentration. The impact strength of the composites is not improved by replacing the calcite portion from the mix with zeolite. Morphological study was carried out for matrix–filler dispersion observation. The complex melt viscosity, increased for both systems with increasing zeolite content, indicates extra processing difficulties because of high filler volume. Burning properties and thermal stability of CoPP and TerPP composites with 50 wt % filler systems were also studied. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Aging behavior of a hot‐cured epoxy system
Authors: Fata Davis , Possart Wulff
Published: December 2005

The thermal and hydro‐thermal aging of a hot‐cured epoxy system (diglycidylether of bisphenol A (DGEBA) + dicyandiamide (DDA)) in the glassy state is revisited using DSC and IR attenuated total reflection spectroscopy. Because of the diffusion of DDA from the solid particles into the liquid DGEBA matrix, curing produces a highly crosslinked amorphous matrix that contains low crosslinked amorphous regions. After full curing, the network possesses a relatively low molecular mobility and no residual reactive groups. Thermal and hydro‐thermal loading is performed at 60°C, well below the principal glass transition temperature (Tg1 = 171°C). Both aging regimes cause significant chemical and structural changes to the glassy epoxy. It undergoes a phase separation of relatively mobile segments inside the low mobile matrix, providing a second glass transition that shifts from Tg2 = 86–114°C within 108 days of aging. This phase separation is reversible on heating into the viscoelastic state. Hydro‐thermal aging leads to a reversible and a nonreversible plasticizing effect as well. On thermal aging, no chemical changes are observed but hydro‐thermal aging causes significant chemical modifications in the epoxy system. These modifications are identified as a partial degradation of crosslinks produced by the cyano groups of the DDA and correspond to the nonreversible plasticitation. These changes in the cured epoxy should exert an influence on the mechanical properties of an adhesive bond. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Mechanical and acoustic frequency responses in flat hot‐compacted polyethylene and polypropylene panels
Authors: Jenkins M. J. , Hine P. J. , Hay J. N. , Ward I. M.
Published: December 2005

A range of flat hot‐compacted single‐polymer composite panels made from oriented polypropylene and polyethylene with differing dynamic modulus and damping capacity were freely suspended and subjected to mechanical excitation, allowing their acoustic frequency response over the audio bandwidth to be measured. The audio response over selected bands was correlated with the dynamic modulus and damping capacity measured in bending in these materials and compared with the response of a traditional composite material, namely, carbon‐fiber‐reinforced epoxy resin. Low damping and high dynamic modulus were found to result in relatively high output levels from the hot‐compacted flat panels, which contrasted with the results previously measured on a traditional cone‐shaped speaker made from a hot‐compacted polypropylene material, which found high damping to be advantageous. The results of the current study on flat panels are explained in terms of mechanical impedance of the panels and their corresponding efficiency. It was concluded that the best flat‐panel audio response came from compacted polyethylene sheets, which combined high stiffness, low density, and a low level of damping. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Use of bacteria in anti‐cancer therapies
Authors: Ryan Rachel M. , Green Jeffrey , Lewis Claire E.
Published: December 2005

While a number of valid molecular targets have been discovered for tumours over the past decade, finding an effective way of delivering therapeutic genes specifically to tumours has proved more problematic. A variety of viral and non‐viral delivery vehicles have been developed and applied in anti‐cancer gene therapies. However, these suffer from either inefficient and/or short‐lived gene transfer to target cells, instability in the bloodstream and inadequate tumour targeting. Recently, various types of non‐pathogenic obligate anaerobic and facultative anaerobic bacteria have been shown to infiltrate and selectively replicate within solid tumours when delivered systemically. This has prompted the development of cancer gene therapy protocols that use such bacteria as gene delivery vehicles. Here, we review the evidence for the success of these in pre‐clinical models and clinical trials, as single modality treatments and in combination with conventional cancer therapies. BioEssays 28:84–94, 2006. © 2005 Wiley Periodicals, Inc.
Multicellular redox regulation: integrating organismal biology and redox chemistry
Authors: Blackstone Neil W.
Published: December 2005

Early in the 20th century, Charles Manning Child attributed organismal gradients in metabolism to interactions among groups of cells. Metabolic gradients are now firmly grounded in redox chemistry, yet modern work on metabolic signaling has consistently focused on the cellular level. Multicellular redox regulation, however, may occur when redox state is determined by the behavior of a group of cells. For instance, typically an abundance of substrate will shift the redox state of mitochondria in the direction of reduction, leading to increased reactive oxygen species (ROS). These ROS, in turn, may modify the conformation and activity of proteins involved in signaling pathways, resulting in phenotypic changes. In contrast, if substrate triggers the contractions of a muscular structure comprising mitochondrion‐rich cells, the resulting metabolic demand may shift the redox state in the direction of oxidation, with a corresponding decrease of ROS and different phenotypic effects. Indeed, colonial hydroids exemplify this process. Parallel examples may occur whenever mitochondria are concentrated in cells of structures that can respond to environmental perturbations with increased metabolic demand. In these circumstances, predicting the direction of metabolic signaling may require an understanding of events at the organismal level. BioEssays 28:72–77, 2006. © 2005 Wiley Periodicals, Inc.
Hypothesis: transcript‐templated repair of DNA double‐strand breaks
Authors: Trott Deborah A. , Porter Andrew C.G.
Published: December 2005

Two mechanisms are available for the repair of DNA double‐strand breaks (DSBs) in eukaryotic cells: homology directed repair (HDR) and non‐homologous end‐joining (NHEJ). While NHEJ is not restricted to a particular phase of the cell cycle, it is incapable of accurately repairing DBSs that have suffered a loss or gain of nucleotide sequence information. In contrast, HDR achieves accurate repair of such DSBs by use of a sister chromatid as a DNA template, but is restricted to cell cycle phases (S/G2) when such templates are available. In this scheme, G1 cells appear to lack a mechanism for the accurate repair of certain DSBs, and an ability to use alternative templates would be highly advantageous. Considered here, therefore, is the possibility that RNA transcripts are used as templates for HDR. Potential mechanisms for transcript‐templated HDR, and ways in which it might be detected, are presented. BioEssays 28:78–83, 2006. © 2005 Wiley Periodicals, Inc.
Plants on red alert: do insects pay attention?
Authors: Schaefer H. Martin , Rolshausen Gregor
Published: December 2005

Two recent hypotheses have proposed that non‐green plant colouration evolved as a defence against herbivores, either as protective colouration promoting handicap signals indicating plant fitness or by undermining their crypsis. The handicap hypothesis posits a co‐evolutionary process between plants and herbivores, whereas the anti‐crypsis hypothesis suggests that an arms race between insects and plants is the evolutionary mechanism. Both explanations assume that insects are the evolutionary origin causing plants' colouration. Here, we propose a different hypothesis, termed the “Defence Indication hypothesis”. This idea focuses on the multiple protective functions of anthocyanins and carotenoids as pigments, and suggests that plant colouration evolved primarily in response to various stressors. Because pigments and defensive compounds share a common biosynthesis, the production of pigments also provides elevated defensive strengths against herbivores, a process termed priming. In effect, the Defence Indication hypothesis predicts that pleiotropic effects of the pigments and, more generally, plants' shared defence responses, explain why insects might react to plant colouration. BioEssays 28:65–71, 2006. © 2005 Wiley Periodicals, Inc.
Signal transduction in bacterial chemotaxis
Authors: Baker Melinda D. , Wolanin Peter M. , Stock Jeffry B.
Published: December 2005

Motile bacteria respond to environmental cues to move to more favorable locations. The components of the chemotaxis signal transduction systems that mediate these responses are highly conserved among prokaryotes including both eubacterial and archael species. The best‐studied system is that found in Escherichia coli. Attractant and repellant chemicals are sensed through their interactions with transmembrane chemoreceptor proteins that are localized in multimeric assemblies at one or both cell poles together with a histidine protein kinase, CheA, an SH3‐like adaptor protein, CheW, and a phosphoprotein phosphatase, CheZ. These multimeric protein assemblies act to control the level of phosphorylation of a response regulator, CheY, which dictates flagellar motion. Bacterial chemotaxis is one of the most‐understood signal transduction systems, and many biochemical and structural details of this system have been elucidated. This is an exciting field of study because the depth of knowledge now allows the detailed molecular mechanisms of transmembrane signaling and signal processing to be investigated. BioEssays 28:9–22, 2006. © 2005 Wiley Periodicals, Inc.
Controlling the stem cell niche: right time, right place, right strength
Authors: Niemann Catherin
Published: December 2005

Wnt signalling through β‐catenin plays a pivotal role during embryonic pattern formation, cell fate determination and tissue homeostasis in the adult organism. In the skin, as in many other tissues, Wnt/β‐catenin signalling can control lineage determination and differentiation. However, it was not known whether Wnt/β‐catenin signalling is an immediate regulator of the stem cell niche in skin tissue. A recent publication now provides evidence that Wnt/β‐catenin signalling exerts a direct effect on the stem cell compartment by inducing quiescent stem cells to enter the cell cycle during early stages of hair follicle regeneration. In addition, the authors demonstrate that β‐catenin is required for maintenance of the stem cell pool in the tissue.1 The data suggest that a gradient in Wnt/β‐catenin activity levels can induce different responses within distinct cell populations reflected by activation of distinct transcriptional profiles. BioEssays 28:1–5, 2006. © 2005 Wiley Periodicals, Inc.
Resistance and the jumping gene
Authors: ffrench‐Constant Richard , Daborn Philip , Feyereisen Rene
Published: December 2005

Transposons are well‐known architects of genetic change but their role in insecticide resistance has, until recently, only been speculated upon.1 Transposon insertion, or transposon‐mediated transposition, could alter either metabolic enzymes capable of degrading pesticides or could change the functionality of insecticide targets. The recent work of Aminetzach and coworkers2 suggests an exciting alternative, that transposon insertion can cause resistance by altering gene product function. This hypothesis is discussed in the light of other examples in which transposons have been implicated in insecticide resistance. BioEssays 28:6–8, 2006. © 2005 Wiley Periodicals, Inc.
Facilitating safer choices: use of warnings to dissuade viewing of pornography on the internet
Authors: Williams Katherine S.
Published: December 2005

There are many facets of child safety on the internet. Here the interest is in two scenarios: firstly, protection of children using the internet from viewing pornographic images; and secondly, the prevention of damage to children through adults viewing child pornography disseminated via the internet. The aim is to explore whether warnings or informational advice attached to sites would dissuade individuals from visiting them. Consideration will be given to the practicalities of attaching these warnings as well as to their success/failure in other media and across other products before assessing their utility in these scenarios. In essence, their use to protect children against viewing pornography is probably of little value, and may be counterproductive except in helping carers to guide safe use on the internet. Use of informational advice attached to child pornography sites may have more success and be worth pursuing, as might realistic warnings of prosecution. More research needs to be conducted into automatic means of assessing the nature of sites, into the mechanics of successful warnings on the internet and into their effects in this medium and for this material. Copyright © 2005 John Wiley & Sons, Ltd.
Using computer‐assisted self‐interviewing (CASI) questionnaires to facilitate consultation and participation with vulnerable young people
Authors: Davies Murray , Morgan Alun
Published: December 2005

This paper explores computer‐assisted self‐interviewing (CASI) as a methodology for consulting with vulnerable children. The authors provide a brief review of the literature in this area, indicating that computer‐mediated environments for self‐administered questionnaires can be particularly helpful in enabling data to be obtained about sensitive subjects. A case example is provided of Viewpoint Interactive, a CASI application in use in the UK in local authority children's services, education, and in learning disability child care practice. The paper concludes that CASI as a methodology can assist with consultation, and that it may provide a useful additional tool in the complex process of moving beyond consultation alone to the development of increased and more effective participation for vulnerable children in the provision of their care. Copyright © 2005 John Wiley & Sons, Ltd.
Cationic P–S–X cages (X=Br, I)
Authors: Gonsior Marcin , Krossing Ingo , Matern Eberhard
Published: December 2005

The first condensed‐phase preparation of ternary P–Ch–X cations (Ch=O–Te, X=F–I) is reported: [P5S3X2]+, [P5S2X2]+, and [P4S4X]+ (X=Br, I). [P5S3X2]+ is formed from the reaction of the Ag+/PX3 reagent with P4S3. The [P5S3X2]+ ions have a structure that is related to P4S5 by replacing PS by P+X and S in the four‐membered ring by P(X). We provide evidence that the active ingredient of the Ag+/PX3 reagent is the (H2CCl2)Ag–X–PX2+ cation. The latter likely reacts with the HOMO of P4S3 in a concerted HOMO–LUMO addition to give the P5S3X2+ ion as the first species visible in situ in the low‐temperature 31P NMR spectrum. The [P5S3X2]+ ions are metastable at −78 °C and disproportionate at slightly higher temperatures to give [P5S2X2]+ and [P4S4X]+, probably with the extrusion of 1/n (PX)n (X=Br, I). All six new cage compounds have been characterized by multinuclear NMR spectroscopy and, in part, by IR or Raman spectroscopy. The [P5S2X2]+ salts have a nortricyclane skeleton and were also characterized by X‐ray crystallography. The structure of the [P4S4X]+ ion is related to that of P4S5 in that the exo‐cage PS bond is replaced by an isoelectronic P+X moiety.
Discovery and Structure–Activity Relationship Studies of a Unique Class of HIV‐1 Integrase Inhibitors
Authors: Dayam Raveendra , Sanchez Tino , Neamati Nouri
Published: December 2005

HIV‐1 integrase (IN) is an essential enzyme for viral replication and a validated target for the development of drugs against AIDS. Currently there are no approved drugs that target IN. However, new IN inhibitors are under clinical investigation. As more IN inhibitors enter human drug trials, there is a growing need for the design of novel lead compounds with diverse structural scaffolds and promising pharmacokinetic properties to counteract the difficulties observed with first‐generation IN inhibitors. We have identified a novel class of IN inhibitors through the systematic exploration of structure–activity relationships in a series of linomide analogues. The predicted bound conformation of the most active analogues inside the IN active site also supports the observed structure–activity correlation in this new compound class.
Individualizing combination of two antiproliferative immunosuppressants with pharmacodynamic modeling of stimulated lymphocyte responses
Authors: Berry Vishal , Magill Amy , Yost Mary , Janosky Janine , Sindhi Rakesh
Published: December 2005

Background

Unpredictable serious adverse events (SAE) of immunosuppression, e.g. nephrotoxicity, with the nephrotoxic immunosuppressants have fostered interest in alternative regimens, which contain two antiproliferative agents, and individualized therapy. However, titration of such combinations to individual needs is not understood.

Specific Aim

To determine concentration (C) mixtures of mycophenolate mofetil (MMF) and sirolimus (SRL), which produce half‐maximal inhibitory effect (EC50) on human lymphocytes from individual subjects.

Methods

Concentration mixtures of MMF (0–5 μg/ml) and SRL (0–30 ng/ml) were incubated with whole blood from each of five healthy human subjects. The intracellular cytokines IL‐2, TNF‐α, and IFN‐γ were measured in PMA‐ionomycin‐stimulated T‐cells (CD4+), while CD54, CD95, CD86, CD25, CD69, and CD71 were measured in pokeweed mitogen‐stimulated B‐cells, by flow cytometry. Pharmacodynamic (PD) relationships were evaluated using Hill equations modified for single and multidrug regimens, and expressed as EC50 for each target receptor.

Results

No change was seen in the expression of the T‐cell cytokines with either MMF or SRL. Each B‐cell receptor was inhibited with increasing concentrations of either MMF or SRL. Each B‐cell receptor was also inhibited half‐maximally at lower concentrations of MMF in the presence of SRL, than with either agent alone, for the test population of five subjects together, and for each of five individual subjects. However, each subject showed distinctly different amounts of MMF and SRL that needed to be present together, in order to produce an identical inhibitory effect on lymphocyte function.

Conclusions

PD analysis of biological effect can potentially predict optimal concentration mixtures of two immunosuppressants for individual recipients, and enhance rejection prophylaxis and safety. While this holds promise for drug development efforts, clinical application must await correlation of lymphocyte markers with post‐transplant clinical outcomes. © 2005 Wiley‐Liss, Inc.
Systems biology and clinical cytomics: The 10th Leipziger workshop and the 3rd international workshop on slide‐based cytometry
Authors: Tárnok Attila , Valet Günther K. , Emmrich Frank
Published: December 2005

Despite very significant technical and software improvements in flow cytometry (FCM) since the 1980's, the demand for a cytometric technology combining both quantitative cell analysis and morphological documentation in Cytomics became evident. Improvements in microtechnology and computing permit nowadays similar quantitative and stoichiometric single cell‐based high‐throughput analyses by microscopic instruments, like Slide‐Based Cytometry (SBC). SBC and related techniques offer unique tools to perform complex immunophenotyping, thereby enabling diagnostic procedures during early disease stages. Multicolor or polychromatic analysis of cells by SBC is of special importance not only as a cytomics technology platform but also because of low quantities of required reagents and biological material. The exact knowledge of the location of each cell on the slide permits repetitive restaining and reanalysis of specimens. Various separate measurements of the same specimen can be ultimately fused to one database increasing the information obtained per cell. Relocation and optical evaluation of cells as typical SBC feature, can be of integral importance for cytometric analysis, since artifacts can be excluded and morphology of measured cells can be documented.

Progress in cell analytic: In the SBC, new horizons can be opened by the new techniques of structural and functional analysis with the high resolution from intracellular and membrane (confocal microscopy, nanoscopy, total internal fluorescence microscopy (TIRFM), and tissue level (tissomics), to organ and organism level (in vivo cytometry, optical whole body imaging).

Predictive medicine aims at the detection of changes in patient's state prior to the manifestation of the disease or the complication. Such instances concern immune consequences of surgeries or noninfectious posttraumatic shock in intensive care patients or the pretherapeutic identification of high risk patients in cancer cytostatic therapy. Preventive anti‐infectious or anti‐shock therapy as well as curative chemotherapy in combination with stem cell transplantation may provide better survival chances for patient at concomitant cost containment. Predictive medicine‐guided optimization of therapy could lead to individualized medicine that gives significant therapeutic effect and may lower or abrogate potential therapeutic side effects.

The 10th Leipziger Workshop combined with the 3rd International Workshop on SBC aimed to offer new methods in Image‐ and Slide‐Based Cytometry for solutions in clinical research. It moved towards practical applications in the clinics and the clinical laboratory. This development will be continued in 2006 at the upcoming Leipziger Workshop and the International Workshop on Slide‐Based Cytometry. © 2005 International Society for Analytical Cytology
RNA interference reveals a role for TLR2 and TLR3 in the recognition of Leishmania donovani promastigotes by interferon–γ‐primed macrophages
Authors: Flandin Jean‐Frédéric , Chano Frédéric , Descoteaux Albert
Published: December 2005

Leishmania donovani promastigotes evade the induction of a proinflammatory response during their invasion of naive macrophages. However, their entry into IFN‐γ‐primed macrophages is accompanied by the secretion of nitric oxide (NO) and proinflammatory cytokines. In the present study, we addressed the hypothesis that priming with IFN‐γ induces the expression of a receptor that enables mouse macrophages to recognize L. donovani promastigotes. We observed that in IFN‐γ‐primed macrophages, L. donovani promastigotes stimulated Interleukin‐1 receptor‐associated kinase‐1 (IRAK‐1) activity. We next showed that Toll‐like receptor (TLR)3 is barely detectable in naive macrophages but is expressed in IFN‐γ‐treated macrophages. Silencing of TLR3, TLR2, IRAK‐1 and myeloid differentiation factor 88 (MyD88) expression by RNA interference revealed that both TLR are involved in the secretion of NO and TNF‐α induced by L. donovani promastigotes. Using L. donovani mutants, we showed that TLR2‐mediated responses are dependent on Galβ1,4Manα‐PO4‐containing phosphoglycans, whereas TLR3‐mediated responses are independent of these glycoconjugates. Furthermore, our data indicate a participation of TLR2 and TLR3 in the phagocytosis of L. donovani promastigotes and a role for TLR3 in the leishmanicidal activity of the IFN‐γ‐primed macrophages. Collectively, our data are consistent with a model where recognition of L. donovani promastigotes depends on the macrophage activation status and requires the expression of TLR3.
Synthesis and Characterization of Dinuclear Europium Complexes Showing Pure Red Electroluminescence
Authors: Jang Hyosook , Shin Chang‐Hwan , Jung Byung‐Jun , Kim Do‐hyeon , Shim Hong‐Ku , Do Youngkyu
Published: December 2005

Two dinuclear EuIII complexes have been synthesized by employing β‐diketones and 2,2′‐bipyrimidine (bpm) as sensitizing ligands for the Eu ion and a bridging ligand, respectively, and characterized by various means including single‐crystal X‐ray crystallography. The use of dibenzoylmethane (dbm) and trifluorothenoylacetone (tta) as β‐diketones gave [Eu2(dbm)6(bpm)] (1) and [Eu2(tta)6(bpm)] (2). Both show strong intermolecular π–π interactions that may be responsible for their high melting points. The analysis of the absorption, excitation, and emission spectra of the dinuclear complexes along with a comparison with analogous mononuclear complexes containing the same β‐diketone ligands and 1,10‐phenanthroline (phen) suggests that the dinuclear complexes follow the luminescence mechanism of general LnIII complexes. An EL device with the structure ITO/PEDOT/PVK + PBD + 1 10 wt.‐%/LiF/Al shows pure red emission with an efficiency similar to those of mononuclear complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Mechanism of the MeOH/H2O Substitution in a Series of Biomimetic Bimetallo Zinc‐Based H3O2 Complexes
Authors: Jaime Elke , Weston Jennie
Published: December 2005

Small bimetallo biomimetic zinc‐based compounds containing a bridging μ‐OH functionality can be easily hydrated to yield complexes containing an intramolecular Zn–H3O2–Zn bridge. Because such bridges are intrinsically more nucleophilic than the corresponding μ‐OH functionality, this effectively activates the complex. The Zn–H3O2–Zn unit is labile, and one can successively substitute the “water” and the “hydroxide” in the bridge for methanol and methoxide to form metal‐bound HO–H–OMe and MeO–H–OMe functionalities. We have performed an extensive density functional investigation of this substitution mechanism for a series of bimetallo zinc complexes which have been synthesised and investigated by F. Meyer et al. There are two mechanisms for water/methanol exchange – an addition–elimination and a direct exchange mechanism. If the metal ions are coordinatively unsaturated, and their ligand sphere does not sterically hinder the approach of the methanol, both pathways compete with each other. For coordinatively saturated bimetallo complexes with larger ligand spheres, only the direct exchange mechanism is possible. Regardless of the mechanism operating, the exchange is facile and is controlled by the relative thermodynamic stability of the intermediates. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Steric and Catalytic Effects in Tetraruthenated Manganese Porphyrins
Authors: Mayer Ildemar , Nunes Genebaldo S. , Toma Henrique E. , Araki Koiti
Published: December 2005

A new tetraruthenated manganese(III) porphyrin has been obtained and characterized by spectroscopy, electrochemistry, and spectroelectrochemistry. It exhibits a saddle‐shaped, nonplanar structure that conveys interesting catalytic, electrocatalytic, and spectroelectrochemical properties to the molecule. Selective steric influence induced by the peripheral ruthenium complexes has been detected in the catalytic oxidation of cyclohexane and cyclohexene with iodosylbenzene. Films formed by layer‐by‐layer electrostatic assembly with tetraanionic sulfonated copper phthalocyanine exhibit electrocatalytic activity for the oxidation of nitrite and sulfite, thus providing interesting applications in amperometric sensors.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Dissociation of CP20 from Iron(II)(cp20)3: A Pulse Radiolysis Study
Authors: Merkofer Martin , Domazou Anastasia , Nauser Thomas , Koppenol Willem H.
Published: December 2005

Deferiprone (CP20), a hydroxypyridine‐4‐one, is used in iron‐chelation therapy. For the iron(III)‐/(II)(cp20)3 couple, a standard electrode potential of –620 mV was measured by cyclic voltammetry [Templeton et al., Inorg. Chim. Acta 1996, 245, 199; Merkofer et al., Helv. Chim. Acta 2004, 87, 3021]. On the basis of this value and the overall stability constant for the equilibrium of iron(III) and three CP20 molecules, ligand dissociation ought to take place after reduction of the iron(III)(cp20)3 complex. By pulse radiolysis, we show that hydrated electrons reduce the iron(III)(cp20)3 complex with a rate constant of k = (6.4 ± 0.3) × 1010 M–1 s–1, and that the iron(II)(cp20)3 complex aquates rapidly. The dissociation of the first two CP20 molecules takes place within a few μs after the pulse. The dissociation rate constant for the last CP20 ligand is (8 ± 1) × 103 s–1. The observation of a dissociation illustrates that, under dilute conditions, iron(II) is not fully complexed by CP20 and could potentially participate in redox cycling to produce oxyradicals. The CO2·– radical does not reduce iron(III)(cp20)3, which indicates that this complex reacts, as expected, very slowly with inner‐sphere reductants. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis, Structural Characterisation and Reactions of Some Vinylgold(I) Phosphane Complexes
Authors: Mohr Fabian , Falvello Larry R. , Laguna Mariano
Published: December 2005

A series of vinylgold(I) complexes [Au(CR=CHR)L] (R = H, Me; L = PPh3, PPh2Me, PPhMe2) were prepared from the reaction of the Grignard reagents [MgBr(CR=CHR)] (R = H, Me) with the gold(I) phosphane complexes [AuCl(L)] (L = PPh3, PPh2Me, PPhMe2) at low temperature. The complexes were characterised by various spectroscopic techniques and, in the case of [Au(CMe=CHMe)(PPh3)], by a single‐crystal X‐ray structure determination. The gold–carbon bonds of these vinylgold(I) complexes are easily cleaved by acids and, in the presence of potassium permanganate, by species containing acidic protons. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
The Effective Electron‐Transfer Distance in Dinuclear Ruthenium Complexes Containing the Unsymmetrical Bridging Ligand 3,5‐Bis(2‐pyridyl)‐1,2,4‐triazolate
Authors: D’Alessandro Deanna M. , Dinolfo Peter H. , Hupp Joseph T. , Junk Peter C. , Keene F. Richard
Published: December 2005

Electroabsorption (Stark effect) measurements on the intervalence charge‐transfer (IVCT) transitions in the diastereoisomers of [{Ru(bpy)2}2(μ‐bpt–)]4+ [bpy = 2,2′‐bipyridine, bpt– = 3,5‐bis(2‐pyridyl)‐1,2,4‐triazolate] in n‐butyronitrile glass at 77 K reveal effective charge‐transfer distances of 5.92 ± 0.03 Å for the ΔΛ/ΛΔ form and 5.44 ± 0.04 Å for the ΔΔ/ΛΛ form. These values correspond to approximately 95 and 88 %, respectively, of the geometrical metal–metal distance of 6.185(10) Å, obtained from the X‐ray crystal structure of the cation in the related complex (ΔΛ)‐[{Ru(Me2bpy)2}2(μ‐bpt–)](PF6)3. The results are consistent with a localized Class II classification for the mixed‐valence systems [{Ru(pp)2}2(μ‐bpt–)]4+, where pp = bpy, Me2bpy = 4,4′‐dimethyl‐2,2′‐bipyridine. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Facile Enantioselective Ring‐Opening Reaction of meso Epoxides with Anilines Using (S)‐(–)‐BINOL‐Ti Complex as a Catalyst
Authors: Kureshy Rukhsana I. , Singh Surendra , Khan Noor‐ul H. , Abdi Sayed H. R. , Suresh Eringathodi , Jasra Raksh V.
Published: December 2005

The catalytic enantioselective ring‐opening reaction of meso‐stilbene oxide and cyclohexene oxide with anilines was catalyzed by (S)‐(–)‐BINOL‐Ti complexes at ambient temperature to obtain β‐amino alcohols in high yield (95 %) and enantioselectivity (ee, 78 %). The enantiomeric excess (ee) of the product was further improved to 98 % by a single recrystallization step. The absolute configuration of representative β‐amino alcohols was determined by single‐crystal X‐ray diffraction analysis. The catalyst recovered after first use was recycled four times with retention in its performance. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
“On Water”‐Promoted Direct Coupling of Indoles with 1,4‐Benzoquinones without Catalyst
Authors: Zhang Hai‐Bo , Liu Li , Chen Yong‐Jun , Wang Dong , Li Chao‐Jun
Published: December 2005

A highly efficient direct coupling of indole compounds with 1,4‐benzoquinones was developed “on water” in the absence of any catalyst, organic co‐solvent, or additives. The “on‐water” conditions provided the best yields of the corresponding products and the only system to produce bis(coupling) products. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Bioleaching of Heavy Metal Polluted Sediment: Kinetics of Leaching and Microbial Sulfur Oxidation
Authors: Löser C. , Zehnsdorf A. , Görsch K. , Seidel H.
Published: December 2005

Remediation of heavy metal polluted sediment through bioleaching using elemental sulfur (S0) as the leaching agent can be regarded as a two‐step process: firstly, the microbial oxidation of the added S0 to sulfuric acid and, secondly, the reaction of the produced acid with the sediment. Here, both subprocesses were studied in detail independently: oxidized river sediment was either suspended in sulfuric acid of various strengths, or mixed with various amounts of finely ground S0 powder (diameter of the S0 particles between 1 and 175 μm with a Rosin‐Rammler‐Sperling‐Bennet (RRSB) distribution and an average diameter of 35 μm) and suspended in water. The leaching process was observed by repeated analysis of the suspension concerning pH, soluble sulfate and metals, and remaining S0. In the case of abiotic leaching with H2SO4, the reaction between the acid and the sediment resulted in a gradual increase in pH and a solubilization of sediment‐borne heavy metals which required some time; 80 % of the finally solubilized heavy metals was dissolved after 1 h, 90 % after 10 h, and 100 % after 100 h. In the case of bioleaching, the rate of S0 oxidation was maximal at the beginning, gradually diminished with time, and was proportional to the initial amount of S0. Due to its very low solubility in water, S0 is oxidized in a surface reaction catalyzed by attached bacteria. The oxidation let the particles shrink, their surface became smaller and, thus, the S0 oxidation rate gradually decreased. The shrinking rate was time‐invariant and, at 30 °C, amounted to 0.5 μm/day (or 100 μg/cm2/day). Within 21 days, 90 % of the applied S0 was oxidized. Three models with a different degree of complexity have been developed that describe this S0 oxidation, assuming S0 particles of uniform size (I), using a measured particle size distribution (II), or applying an adapted RRSB distribution (III). Model I deviated slightly from the measured data but was easy to handle, Model II fitted the measured data best but its simulation was complicated, and Model III was intermediate. The amount of soluble sulfate was smaller than the amount of H2SO4 added or microbially generated as the H2SO4 reacted with the sediment to form in part poorly soluble sulfates. A model has been developed that describes the pH and the soluble sulfate and metals at equilibrium, depending on the amount of H2SO4 applied or microbially generated, and that is based on the condition of electrical neutrality, a global metal/proton exchange reaction, and a sulfate‐fixation reaction. In suspension, bioleaching with S0 required considerably more time than abiotic leaching with H2SO4, but the final pH and metal solubilization were identical when equimolar amounts of leaching agents were applied.
Kinetic Modeling of Amino Acid Oxidation Catalyzed by a New D‐Amino Acid Oxidase from Arthrobacter protophormiae
Authors: Findrik Z. , Vasić‐Rački D. , Geueke B. , Kuzu M. , Hummel W.
Published: December 2005

Amino acid oxidases, which enantiospecifically catalyze the oxidative deamination of either D‐ or L‐amino acids, belong to the class of oxidoreductases functioning with a tightly bound cofactor. This cofactor favors industrial applications of D‐amino acid oxidases (D‐AAO). Hence, the enzyme is very important for the industrial application in the purification and determination of certain amino acids. In developing the enzyme‐catalyzed reaction for large‐scale production, modeling of the reaction kinetics plays an important role. Therefore, the subject of this study was the kinetics of the oxidative deamination, a very complex reaction system, which is catalyzed by D‐AAO from Arthrobacter protophormiae using its natural substrate D‐methionine and the aromatic amino acid 3,4‐dihydroxyphenyl‐D‐alanine (D‐DOPA). The kinetic parameters determined by the measurement of the initial rate and nonlinear regression were verified in batch reactor experiments by comparing calculated and experimental concentration‐time curves. It was found that the enzyme is highly specific towards D‐methionine (Km = 0.24 mM) and not as specific to D‐DOPA as a substrate (Km = 9.33 mM). The enzyme activity towards D‐methionine ($ V_m^{D-{\rm Met}}$ = 3.01 U/mL) was approx. seven times higher than towards D‐DOPA ($ V_m^{D-{\rm DOPA}} $= 20.01 U/mL). The enzyme exhibited no activity towards L‐methionine and L‐DOPA. Batch and repetitive batch experiments were performed with both substrates in the presence and in the absence of catalase for hydrogen peroxide decomposition. Their comparison made it possible to conclude that hydrogen peroxide has no negative influence on the enzyme activity.
Optimization of Glycoalkaloid Analysis for Use in Industrial Potato Fruit Juice Downstreaming
Authors: Alt V. , Steinhof R. , Lotz M. , Ulber R. , Kasper C. , Scheper T.
Published: December 2005

Annually, within the European Union about 1.7 million tons of starch is produced by processing over 8 million tons of potato tubers, Solanum tuberosum. In recent years, the potato protein content has gained tremendous industrial interest, since these proteins have excellent nutritional value. As naturally occurring, secondary plant metabolites steroidal potato glycoalkaloids are formed in potatoes. The two major glycoalkaloids in potatoes are α‐solanine and α‐chaconine. Because of the significant toxicity of the glycoalkaloids for human and for animal nutrition it was essential to develop efficient extraction processes. The need for an easy, fast, sensitive and reliable glycoalkaloid assay at the very beginning of the production chain is obvious. In this study an efficient analytical assay for potato glycoalkaloids from powdery protein samples under industrially relevant conditions is described: sample extraction, analyte pre‐purification, and final HPLC analysis. An acetic acid extraction/homogenization process was used for glycoalkaloid extraction from potato protein samples. The extracts were purified by means of solid phase extraction cartridges using the different washing steps developed in this study. The final determination was performed through an HPLC method using a Reprosil‐Pur NH2 column. The limit of detection was 5 μg/mL for α‐solanine and α‐chaconine, respectively, corresponding to concentrations of 20 ppm in potato protein powder.
Correlating specific conductivity with total hardness in limestone and dolomite karst waters
Authors: Krawczyk Wiesława Ewa , Ford Derek C.
Published: December 2005

Under field conditions modern digital conductivity meters give standardized, rapid and reproducible measurements. Here we investigate the accuracy of their estimates of the composition of karst waters, as total hardness (TH, as mg/L CaCO3) for limestone and dolomite. These are the fundamental measures of process in carbonate karst geomorphology. PHREEQC theoretical curves for the dissolution of pure calcite/aragonite and dolomite in water at 25 °C are compared with water analyses from karst studies worldwide. Other principal ions encountered are sulphates, nitrates and chlorides (the ‘SNC’ group). From carbonate karsts, 2309 spring, well and stream samples were divided into uncontaminated (SNC < 10%), moderately contaminated (10 < SNC < 20%), and contaminated (SNC > 20%) classes. Where specific conductivity (SpC) is less than 600 µS/cm, a clear statistical distinction can be drawn between waters having little contamination and substantially contaminated waters with SNC > 20%. As sometimes claimed in manufacturers' literature, in ‘clean’ limestone waters TH is close to 1/2SpC, with a standard error of 2–3 mg/L. The slope of the best‐fit line for 1949 samples covering all SNC classes where SpC < 600 µS/cm is 1·86, very close to the 1·88 obtained for clean limestone waters; however, the value of the intercept is ten times higher. The regression line for clean limestone waters where SpC > 600 µS/cm helps to distinguish polluted waters from clean waters with possible endogenic sources of CO2. In the range 250 < SpC < 600 µS/cm, dolomite waters can be readily distinguished from limestone waters. Copyright © 2005 John Wiley & Sons, Ltd.
A coupled boundary element–finite difference model of surface wave motion over a wall turbulent flow
Authors: Jamali Mirmosadegh
Published: December 2005

An effective numerical technique is presented to model turbulent motion of a standing surface wave in a tank. The equations of motion for turbulent boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM–finite difference technique is used to model the wave motion and the corresponding boundary layer flow. A mixing‐length theory is used for turbulence modelling. The model results are in good agreement with previous physical and numerical experiments. Although the technique is presented for a standing surface wave, it can be easily applied to other free surface problems. Copyright © 2005 John Wiley & Sons, Ltd.