bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synergistic effect of a phosphorus–nitrogen flame retardant on engineering plastics
Authors: Leu Tsu‐Shang , Wang Chun‐Shan 
Published: February 2004

AbstractThe novel flame retardant tris(3,5‐dimethyl‐4‐diphenyl phenoxy phosphate)isocyanurate (TDPI) was synthesized from the reaction of diphenyl chlorophosphate and tris(3,5‐dimethyl‐4‐hydroxybenzyl)isocyanurate. The compound was characterized with Fourier transform infrared spectroscopy, elemental analysis, mass spectrometry, 1H‐NMR, and 31P‐NMR. Furthermore, blends of the flame retardant with engineering plastics in various weight ratios were made, and their thermal stability and flame retardancy were determined by thermogravimetric analysis (TGA), UL‐94 vertical testing, and limiting oxygen index (LOI) measurements. The phosphorus–nitrogen synergistic effect on flame retardancy was compared with the effects of commonly used tetraphenyl resorcinol diphosphate and tetrabromobisphenol A. TGA indicated that the TDPI/engineering plastics systems were stable up to 397–503°C at a 5% weight loss in a nitrogen atmosphere with a relatively high char yield (21.0–42.1% at 700°C) and that they a achieved UL‐94 V‐0 rating (with a low flame‐retardant content: P, 0.76 wt %, and N, 0.34 wt %). No fume and toxic gas emissions were observed during the burning test for this system. The LOI values were 31.6–42.2. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 410–417, 2004
Rheological and thermomechanical properties of long‐chain‐branched polyethylene prepared by slurry polymerization with metallocene catalysts
Authors: Kolodka Edward , Wang Wen‐Jun , Zhu Shiping , Hamielec Archie 
Published: February 2004

AbstractA series of polyethylene (PE) samples were prepared in a slurry polymerization with bis(cyclopentadienyl) zirconium dichloride (Cp2ZrCl2)/modified methylaluminoxane (MMAO) using a semibatch reactor. The samples had long‐chain branch densities (LCBDs) of a 0.03–1.0 branch per 10,000 carbons and long‐chain branch frequencies (LCBFs) up to a 0.22 branch per polymer molecule. The rheological and dynamic mechanical behaviors of these long‐chain branched PE samples were evaluated. Increasing the LCBF significantly increased the η0's and enhanced shear thinning. Long‐chain branching (LCB) also influenced the loss modulus and storage modulus. Increasing the LCBF led to enhanced G′ and G″ values at low shear rates and broader relaxation spectrums. The samples exhibited thermorheologically complex behavior. LCB also played a significant role in the dynamic mechanical behavior. Increasing the LCBF increased the stiffness of the polymer and enhanced the damping or energy dissipation. However, LCB had little influence on the crystalline structure of the PE. The α‐ and γ‐relaxations showed little dependence on the LCBF. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 307–316, 2004
Selection of top layer materials for gas–liquid membrane contactors
Authors: Nymeijer D. C. , Folkers B. , Breebaart I. , Mulder M. H. V. , Wessling M. 
Published: February 2004

AbstractGas–liquid membrane contactors frequently suffer from wetting of the microporous membrane. Stabilization layers at the liquid side of the membrane potentially prevent this wetting. We applied such stabilized membranes to the separation of olefins and paraffins using AgNO3 solutions as absorption liquid. The stabilization material requires permeation of olefins at minimum counter transport of water. Appropriate selection of the top layer material is crucial in this application. This report describes the selection of potential top layer materials. Dense films of the selected materials were prepared and used to determine ethylene and ethane permeabilities, to perform pervaporation experiments with water and a 3.5M solution of silver nitrate in water, and to determine the swelling behavior of the dense films in water and in a 3.5M silver nitrate solution. Based on the characterization experiments, ethylene propylenediene terpolymer is the most appropriate candidate with the highest potential for application in a gas–liquid membrane contactor for the separation of paraffins and olefins. It has a relatively high olefin permeability (46.4 Barrer) and a corresponding low water vapor permeability and low swelling tendency in a 3.5M silver nitrate solution (1490 Barrer and 0.14 wt %, respectively). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 323–334, 2004
Powder‐shape analysis and sintering behavior of high‐density polyethylene powders for rotational molding
Authors: Greco Antonio , Maffezzoli Alfonso 
Published: February 2004

AbstractThe quality of rotational molded products is strongly affected by the sintering behavior of the powders used in the process. In turn, for a given material, the sintering behavior of polymer powders is dependent on the size and the shape of particles obtained in the milling apparatus. The quality of powders for rotational molding is usually determined by means of size distribution, dry flow, and bulk density tests. However, these tests do not provide insight into the relationship between the shape of powders, the milling conditions, and the sintering behavior during the rotational molding cycle. Nevertheless, the application of mathematical tools to powder analysis can significantly improve the efficiency of the grinding process, looking not only at the size but also at the shape of the powder. This can in turn result in a higher reliability of rotational molding and in better performances of the products obtained in processes dominated by the sintering behavior of polymer powders. In this work the grinding process of recycled high‐density polyethylene was analyzed using a quantitative approach to the shape and size of the powders. In particular, shape factors, capable of characterizing powders obtained in different milling conditions, were studied. Finally, the influence of the powders' shape and size on sintering behavior was studied by thermomechanical analysis. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 449–460, 2004
Synthesis and characterization of organic–inorganic hybrids based on epoxy resin and 3‐glycidyloxypropyltrimethoxysilane
Authors: Macan J. , Ivankovic H. , Ivankovic M. , Mencer H. J. 
Published: February 2004

AbstractOrganic–inorganic hybrid materials based on diglycidyl ether of bisphenol A (DGEBA) and 3‐glycidyloxypropyltrimethoxysilane (GLYMO) were prepared, using a poly(oxypropylene) diamine Jeffamine D230 as a curing agent. Materials were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared spectroscopy, swelling in tetrahydrofurane (THF), and Soxhlet extraction in THF. A dependence of the final conversion of epoxy groups and the final degree of organic phase crosslinking on inorganic phase content was found. The inorganic phase presents a steric hindrance to full crosslinking of epoxy groups. It also immobilizes the organic chains and improves the temperature stability of hybrid materials. Products of GLYMO hydrolysis together with unreacted organic molecules lower the glass transition temperature of hybrid materials. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 498–505, 2004
The added value of task and ontology‐based markup for information retrieval
Authors: Kabel Suzanne , de Hoog Robert , Wielinga Bob J. , Anjewierden Anjo 
Published: February 2004

AbstractIn this report, we investigate how retrieving information can be improved through task‐related indexing of documents based on ontologies. Different index types, varying from content‐based keywords to structured task‐based indexing ontologies, are compared in an experiment that simulates the task of creating instructional material from a database of source material. To be able to judge the added value of task‐ and ontology‐related indexes, traditional information retrieval performance measures are extended with new measures reflecting the quality of the material produced with the retrieved information. The results of the experiment show that a structured task‐based indexing ontology improves the quality of the product created from retrieved material only to some extent, but that it certainly improves the efficiency and effectiveness of search and retrieval and precision of use.
New Dihydroxy Bis(Oxazoline) Ligands for the Palladium‐Catalyzed Asymmetric Allylic Alkylation: Experimental Investigations of the Origin of the Reversal of the Enantioselectivity
Authors: Aït‐Haddou Hassan , Hoarau Olivier , Cramailére Dimitri , Pezet Frédéric , Daran Jean‐Claude , Balavoine Gilbert G. A. 
Published: February 2004

AbstractThe origin of the reversal of the enantioselectivity in the palladium‐catalyzed allylic alkylation of rac‐1,3‐diphenyl‐2‐propenyl acetate with dimethyl malonate anion using chiral dihydroxy bis(oxazoline) “BO” ligands derived from (1S,2S)‐(+)‐2‐amino‐1‐phenyl‐1,3‐propanediol was investigated. To determine the structural effects of the dihydroxy BO ligand on this unique phenomenon, new homochiral dihydroxy BO ligands were prepared from L‐threonine and L‐serine and were assessed in the transformation. The results obtained with these novel BO ligands, compared with the one obtained by using the dihydroxy BO ligands derived from (1S,2S)‐(+)‐2‐amino‐1‐phenyl‐1,3‐propanediol, reveal that the reversal in the enantioselectivity observed with the dihydroxy BO ligand depends on the structure of the ligand. The effect of different bases used to generate the dimethyl malonate anion was also examined. The results are discussed in terms of the interaction of one hydroxy group in the intermediate π‐allyl palladium complex with the dimethyl malonate anion.
Molecular‐Scale Logic Gates
Authors: de Silva A. Prasanna , McClenaghan Nathan D. 
Published: February 2004

AbstractCurrently available approaches to molecular‐scale logic gates are summarized and compared. These include: chemically‐controlled fluorescent and transmittance‐based switches concerned with small molecules, DNA oligonucleotides with fluorescence readout, oligonucleotide reactions with DNA‐based catalysts, chemically‐gated photochromics, reversibly denaturable proteins, molecular machines with optical and electronic signals, two‐photon fluorophores and multichromophoric transient optical switches. The photochemical principles of electron and energy transfer are involved in several of these approaches. More complex molecular logic systems with reconfigurability and superposability provide contrasts with current semiconductor electronics. Integration of simple logic functions to produce more complex ones is also discussed in terms of recent developments.
Biologically Active Compounds through Catalysis: Efficient Synthesis of N‐(Heteroarylcarbonyl)‐N′‐(arylalkyl)piperazines
Authors: Kumar Kamal , Michalik Dirk , Garcia Castro Ivette , Tillack Annegret , Zapf Alexander , Arlt Michael , Heinrich Timo , Böttcher Henning , Beller Matthias 
Published: February 2004

AbstractA practical route for the synthesis of new biologically active 5‐HT2 A receptor antagonists has been developed. In only three catalytic steps, this class of central nervous system (CNS) active compounds can be synthesized efficiently with high diversity. As the initial step, an anti‐Markovnikov addition of amines to styrenes provides an easy route to N‐(arylalkyl)piperazines, which constitute the core structure of the active molecules. Here, base‐catalyzed hydroamination reactions of styrenes with benzylated piperazine proceeded in high yield even at room temperature. After catalytic debenzylation, the free amines were successfully carbonylated with different aromatic and heteroaromatic halides and carbon monoxide to yield the desired compounds in good to excellent yields. The two key reactions, base‐catalyzed hydroamination of styrenes and palladium‐catalyzed aminocarbonylation of haloarenes/heterocycles, showed tolerance towards various functional groups, thereby demonstrating the potential to synthesize a wide variety of new derivatives of this promising class of pharmaceuticals.
Synthesis and Growth Mechanism of Bi2S3 Nanoribbons
Authors: Liu Zhaoping , Liang Jianbo , Li Shu , Peng Sheng , Qian Yitai 
Published: February 2004

AbstractThis article describes a facile solvothermal method by using mixed solvents for the large‐scale synthesis of Bi2S3 nanoribbons with lengths of up to several millimeters. These nanoribbons were formed by a solvothermal reaction between BiIII–glycerol complexes and various sulfur sources in a mixed solution of aqueous NaOH and glycerol. HRTEM (high‐resolution transmission electron microscopy) and SAED (selective‐area electron diffraction) studies show that the as‐synthesized nanoribbons had predominately grown along the [001] direction. The Bi2S3 nanoribbons prepared by the use of different sulfur sources have a common formation process: the initial formation of NaBiS2 polycrystals, which serve as the precursors to Bi2S3, the decomposition of NaBiS2, and the formation of Bi2S3 seeds in the solution through a homogeneous nucleation process; the growth of Bi2S3 nanoribbons occurs at the expense of NaBiS2 materials. The growth mechanism of millimeter‐scale nanoribbons involves a special solid–solution–solid transformation as well as an Ostwald ripening process. Some crucial factors affect nanoribbon growth, such as, solvothermal temperature, volume ratio of glycerol to water, and the concentration of NaOH; these have also been discussed.
Chemieindustrie: Herausforderungen und Antworten
Authors: Staudigl R. 
Published: February 2004

AbstractDie Chemie ist heute einer der umsatzstärksten Wirtschaftszweige weltweit und auf allen Kontinenten vertreten. Die Unternehmenslandschaft in der Chemie hat sich seit dem Zweiten Weltkrieg völlig verändert. Aus diversifizierten Unternehmen wurden in den meisten Fällen Spezialisten, die auf wenige Geschäftsbereiche konzentriert sind und dort optimale Leistungen bringen können, dafür aber Marktschwankungen stärker ausgesetzt sind. Zukünftig ist abzusehen, dass der europäische Chemiemarkt global weiter an Gewicht verlieren wird. Dem kann nur durch höheres Wirtschaftswachstum und verstärkte Innovationsbemühungen in Europa entgegengewirkt werden. Voraussetzung ist jedoch, dass die Chemieindustrie nicht durch ständig zunehmende Belastungen wie unn�tige Umweltauflagen und steigende Energiepreise weiter in Rückstand gerät und als Konsequenz davon wegen mangelnder Profitabilität an Innovationskraft und Wettbewerbsfähigkeit verliert.
Monomethylfumarate affects polarization of monocyte‐derived dendritic cells resulting in down‐regulated Th1 lymphocyte responses
Authors: Litjens Nicolle H. R. , Rademaker Mirjam , Ravensbergen Bep , Rea Delphine , van der Plas Mariena J. A. , Thio Bing , Walding Andrew , van Dissel Jaap T. , Nibbering Peter H. 
Published: February 2004

AbstractPsoriasis vulgaris, a type‐1 cytokine‐mediated chronic skin disease, can be treated successfully with fumaric acid esters (FAE). Beneficial effects of this medication coincided with decreased production of IFN‐γ. Since dendritic cells (DC) regulate the differentiation of T helper (Th) cells, this study focussed on effects of monomethylfumarate (MMF, bioactive metabolite of FAE) on polarization of monocyte‐derived DC. MMF‐incubated, lipo‐polysaccharide‐stimulated DC (MMF‐DC) produced dramatically (p<0.05) reduced levels of IL‐12p70 and IL‐10 (8±4% and 20±4%, respectively) compared to control DC. MMF‐DC were mature. MMF affected polarization of DC irrespective of polarization factor(s) and ligands for the various Toll‐like receptors used. Coculture of MMF‐DC with naive and primed allogenous Th cells resulted in lymphocytes producing less IFN‐γ, i.e. 59% and 54% of that by the respective Th cells cocultured with control DC. IL‐4 production by primed, but not naive Th cells cocultured with MMF‐DC was decreased as compared to cocultures with control DC. IL‐10 production by naive and primed Th cells cocultured with MMF‐DC and control DC did not differ. In addition, MMF inhibited LPS‐induced NF‐κB activation in DC. Together, beneficial effects of FAE in psoriasis involve modulation of DC polarization by MMF such that these cells down‐regulate IFN‐γ production by Th cells.
Control of Leishmania major in the absence of Tyk2 kinase
Authors: Schleicher Ulrike , Mattner Jochen , Blos Martin , Schindler Heike , Röllinghoff Martin , Karaghiosoff Marina , Müller Mathias , Werner‐Felmayer Gabriele , Bogdan Christian 
Published: February 2004

AbstractIL‐12 is indispensable for the control of many intracellular pathogens, but the components of the signaling pathway that are essential for its function in vivo are incompletely understood. Here, we investigated in the Leishmania major mouse model whether Tyk2 kinase is required for the generation of a protective immune response. Unlike C57BL/6 controls, Tyk2–/–mice developed severe skin lesions after infection that frequently ulcerated, but ultimately healed. NK cell cytotoxicity was absent in infected Tyk2–/– mice, even after IL‐12 pretreatment, which correlated with a STAT4 activation defect. IFN‐α / β, which was still able to activate STAT1 in Tyk2–/– NK cells, reconstituted their cytotoxic activity, but not their IL‐12responsiveness. The IL‐12‐induced production of IFN‐γ by NK cells and CD8+ T cells was strongly suppressed in Tyk2–/– mice at day 1 of infection, but partly regained during the late phase of infection. Tyk2–/– CD4+ T cells developed into Th1 cells (although in a delayed fashion) and infected Tyk2–/– mice expressed normals levels of inducible NO synthase. Thus, Tyk2 is required for the IL‐12 response of NK cells and CD8+ T cells in L. major‐infected mice, but not for the generation of Th1 cells and the ultimate control of the disease.
Subversion of effector CD8+ T cell differentiation in acute hepatitis C virus infection: exploring the immunological mechanisms
Authors: Francavilla Vittorio , Accapezzato Daniele , De Salvo Marietta , Rawson Pisana , Cosimi Olivia , Lipp Martin , Cerino Antonella , Cividini Agostino , Mondelli Mario U. , Barnaba Vincenzo 
Published: February 2004

AbstractHallmark of acute hepatitis C virus (HCV) infection is a severe virus‐specific effector CD8+ T cell dysfunction that seems to be a critical factor in preventing the resolution of infection and in favoring the onset of chronic liver immunopathology. We suggest that this dysfunction is critical in the establishment of HCV persistence, unless it is compensated by multispecific responses, as found in individuals resolving infection. Analyses on purified populations indicate that central memory HCV‐specific CCR7+/CD8+ T cells efficiently proliferate and differentiate in vitro, although the large population of memory effector CCR7– cells found in the peripheral blood of acutely infected patients display poor effector functions ex vivo (semi‐effectors). However, we report strong evidence in support of IL‐2 being capable of pushing semi‐effector CTL to complete their effector cell program. Therefore, IL‐2 deficiency during T cell activation may be responsible for the dichotomy between memory CTL expansion and incomplete effector differentiation shown in patients with acute HCV infection. These data are consistent with the possible therapeutic treatment with IL‐2 to rebuild the effector T cell pool in these patients.
Mini‐review: Regulatory T cells and infection: suppression revisited
Authors: Mittrücker Hans‐Willi , Kaufmann Stefan H. E. 
Published: February 2004

AbstractWithin the last few years, regulatory T cells (Treg cells) have re‐entered the stage of immunology. This astonishing revival is mainly due to recent studies on peripheral tolerance, which demonstrated the existence of Treg cells and allowed the isolation and phenotypic and functional characterization of these cells. However, information on the role of Treg cells in the control of immune responses against infections is still limited, although host defense represents the prime function of the immune system. In this overview, we summarize current knowledge on Treg cells in immunity to infection, discuss potential functions of Treg cells during infection, and finally, point to possible implications of Treg cell functions for our understanding of fundamental aspects of host–pathogen interactions.
Synthesis of 3‐Aryloxy‐2‐iodoemodines by Oxidation of Emodin with (Diacetoxyiodo)arenes
Authors: Daub Katja S. , Habermann Bernd , Hahn Thilo , Teich Lars , Eger Kurt 
Published: February 2004

AbstractHypervalent iodine oxidation of emodin (1) with various (diacetoxyiodo)arenes 2a−f in potassium hydroxide/methanol leading to 3‐aryloxy‐1,8‐dihydroxy‐2‐iodo‐anthraquinones 4a−f is reported. Mechanistic studies showed reaction via iodonium ylides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A [2]Catenane Containing 1,1′‐Binaphthyl Units and 1,10‐Phenanthroline Fragments: Synthesis and Intermolecular Energy Transfer Processes
Authors: Koizumi Masatoshi , Dietrich‐Buchecker Christiane , Sauvage Jean‐Pierre 
Published: February 2004

AbstractA chiral copper(I)‐complexed [2]catenane consisting of two interlocking 38‐membered rings, each ring incorporating a 2,9‐diphenyl‐1,10‐phenanthroline (dpp) and an (S)‐1,1′‐binaphthyl group, has been prepared by means of a transition metal template strategy. Demetalation afforded the corresponding free chiral [2]catenane. The coordination polyhedron of the Cu(dpp)2 core in this chiral copper(I)‐complexed [2]catenane reflects the distortion of the chiral 1,1′‐binaphthyl units, as evidenced by the circular dichroism (CD) measurements. Emission measurements demonstrated that in the two‐chromophore compounds (S)‐6 and (S,S)‐9, efficient energy transfer between the 1,1′‐binaphthyl component and the dpp unit takes place in solution at room temperature. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Fully Stereoselective Nucleophilic Addition to a Novel Chiral Pyrroline N‐Oxide: Total Syntheses of (2S,3R)‐3‐Hydroxy‐3‐methylproline and Its (2R)‐Epimer
Authors: Merino Pedro , Revuelta Julia , Tejero Tomas , Cicchi Stefano , Goti Andrea 
Published: February 2004

AbstractA new total synthesis of (2S,3R)‐3‐hydroxy‐3‐methylproline has been performed via a key intermediate chiral pyrroline N‐oxide, obtained from (R)‐citramalic acid. This nitrone underwent nucleophilic addition of furyllithium with complete stereoselectivity through a preferential attack anti to the methoxymethoxy group. The correct stereochemistry was established through an oxidation−reduction sequence, which allowed inversion of configuration at C‐2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Mild Conditions for Copper‐Catalysed N‐Arylation of Pyrazoles
Authors: Cristau Henri‐Jean , Cellier Pascal P. , Spindler Jean‐Francis , Taillefer Marc 
Published: February 2004

AbstractCopper‐catalysed N‐arylation of pyrazoles with aryl or heteroaryl bromides or iodides, which can include functional substituents, was performed under the mildest conditions yet described, with excellent yields and selectivity, by the use as catalyst of a combination of cuprous oxide with a set of inexpensive, chelating oxime‐type ligands not previously known to promote such reactions. Other original bi‐, tri‐ or tetradentate ligands providing nitrogen and/or oxygen as chelating atoms were also successfully tested in this type of arylation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)