bluuebunny/crossref_metadata_2025 huggingface dataset:
New Conjugated Ladder Polymer Containing Carbazole Moieties
Authors: Patil S.A. , Scherf U. , Kadashchuk A.
Published: August 2003

A new ladder polymer incorporating a polar carbazole group within the main chain, ladder‐type poly(para‐phenylene carbazole), LPPPC, was synthesized and characterized by luminescence techniques. Its properties are compared to that of the well‐known methyl‐substituted ladder‐type poly(para‐phenylene), MeLPPP. The results obtained evidence a very low energetic disorder in this new polymer, presumably due to its near‐perfect intrachain structure and low content of defects. It was found that although the density of states (DOS) distribution for neutral excitations is narrower than in MeLPPP, the manifold of charge‐transporting localized states is substantially more energetically disordered due to important dipolar disorder contributions.
Star‐Shaped Oligothiophenes for Solution‐Processible Organic Field‐Effect Transistors
Authors: Ponomarenko S.A. , Kirchmeyer S. , Elschner A. , Huisman B.‐H. , Karbach A. , Drechsler D.
Published: August 2003

We have designed and successfully synthesized star‐shaped oligothiophenes, which could be used as semiconducting materials for solution‐processible organic field‐effect transistors (FETs). By systematically changing the chemical structure of the star‐shaped oligothiophenes we obtained the structural requirements needed for making working FETs from them. UV‐vis fluorescence measurements showed that a molecule of the star‐shaped compounds under consideration is not a fully conjugated molecule, but it has three independently conjugated oligothienyl‐phenylene blocks. A possible scheme of molecular packing of the star‐shaped oligothiophenes in a lamellar structure was proposed and confirmed by atomic force microscopy (AFM) and X‐ray diffraction (XRD) measurements. Although the star‐shaped semiconductors show a somewhat lower mobility than their linear analogs, they possess better solubility and film‐forming properties, leading to improved spin‐coating processing. The best FETs were made by spin‐coating 1,3,5‐tris(5″‐decyl‐2,2′:5′,2″‐terthien‐5‐yl)benzene from a chloroform solution, which resulted in a mobility of 2 × 10–4 cm2 V –1s–1, a 102 on/off ratio at gate voltages of 0 V and –20 V, and a threshold voltage close to 0 V.
Formation of Thick Porous Anodic Alumina Films and Nanowire Arrays on Silicon Wafers and Glass
Authors: Rabin O. , Herz P.R. , Lin Y.‐M. , Akinwande A.I. , Cronin S.B. , Dresselhaus M.S.
Published: August 2003

A method for the fabrication of thick films of porous anodic alumina on rigid substrates is described. The anodic alumina film was generated by the anodization of an aluminum film evaporated on the substrate. The morphology of the barrier layer between the porous film and the substrate was different from that of anodic films grown on aluminum substrates. The removal of the barrier layer and the electrochemical growth of nanowires within the ordered pores were accomplished without the need to remove the anodic film from the substrate. We fabricated porous anodic alumina samples over large areas (up to 70 cm2), and deposited in them nanowire arrays of various materials. Long nanowires were obtained with lengths of at least 9 μm and aspect ratios as high as 300. Due to their mechanical robustness and the built‐in contact between the conducting substrate and the nanowires, the structures were useful for electrical transport measurements on the arrays. The method was also demonstrated on patterned and non‐planar substrates, further expanding the range of applications of these porous alumina and nanowire assemblies.
Vesicles and Liposomes: A Self‐Assembly Principle Beyond Lipids
Authors: Antonietti M. , Förster S.
Published: August 2003

This Progress Report describes the latest advances in vesicles and liposomes. Recent work on the self‐assembly of complex polymer systems shows that the formation of polymer vesicles or closed hull structures is archetypal, leading to fascinating new possibilities and applications in materials science. A general view of the underlying self‐assembly mechanisms leading to vesicles and the control of size, shape, and other vesicular properties by physicochemical means is presented, as background. This is followed by an overview of the recently described new classes of polymer and supramolecular tectons that make vesicle formation a more general phenomenon going beyond just lipids. Finally, the potential applications of vesicles, including non‐lipid vesicles, are outlined.
Charge Transfer Complex Inimer: A Facile Route to Dendritic Materials
Authors: Wang W. , Yan D. , Bratton D. , Howdle S.M. , Wang Q. , Lecomte P.
Published: August 2003

A versatile approach to the preparation of hyperbranched polymers, in which an inimer is used to assemble a charge transfer complex (CTC) with conventional vinyl monomers, is reported. A novel hyperbranched fluoropolymer (see Figure) has been successfully synthesized through the copolymerization of chlorotrifluoroethylene (CTFE) andp‐(chloromethyl)styrene (CMS) by atom transfer radical polymerization (ATRP).
Organic Semiconductor Nanowires for Field Emission
Authors: Chiu J.‐J. , Kei C.‐C. , Perng T.‐P. , Wang W.‐S.
Published: August 2003

Field emission of organic semiconductor nanowires has been demonstrated for the first time. Tris‐(8‐hydroxyquinoline)aluminum (AlQ3) nanowires were grown on an indium tin oxide coated substrate by vapor condensation. The nanowires exhibit a low turn‐on field of 10.0 V μm–1 and a maximum current density of about ∼ 15 mA cm–2. A stable emission current can be achieved, indicating applications in field emission.
Self‐Assembling Sub‐Micrometer‐Sized Tube Junctions and Dendrites of Conducting Polymers
Authors: Wei Z. , Zhang L. , Yu M. , Yang Y. , Wan M.
Published: August 2003

Sub‐micrometer‐sized tube junctions and dendrites of conducting polyaniline (e.g., see Figure) and polypyrrole have been synthesized through a self‐assembly process for the first time. It is shown that the monomer–dopant micelles act as templates for the self‐assembly of sub‐micrometer‐sized tubes, while the interactions among the polymer chains supply the driving force for micelle aggregation and the formation of junctions and dendrites.
Photochemically Gated Protonation Effected by Intramolecular Hydrogen Bonding: Towards Stable Fluorescence Imaging in Polymer Films
Authors: Kim S. , Park S.Y.
Published: August 2003

A photoacid‐induced non‐destructive fluorescence image in a polymer film is achieved by the photochemically gated protonation of a basic fluorophore (HPQ), effected by the intramolecular hydrogen bond via the controlled basicity of the quinoline ring. The Figure shows a non‐degraded fluorescence image (top, using HPQ) after successive readouts, and, for comparison, a degraded image using the conventional hydrogen‐bond‐free analogue (lower, MPQ).
Aluminum Borate–Boron Nitride Nanocables
Authors: Zhu Y.‐C. , Bando Y. , Ma R.‐Z.
Published: August 2003

Aluminum borate nanowires uniformly coated with boron nitride sheaths (see Figure) have been synthesized via a vapor–solid reaction process from alumina and B–N–O precursors. The nanocables have a length of 2∼3 μm, a diameter of 50∼150 nm, and the suggested formation mechanism involves the simultaneous growth and coating of the nanowires.
Base‐Pair Stacking in Oriented Films of DNA–Surfactant Complex
Authors: Yang C. , Moses D. , Heeger A.J.
Published: August 2003

The sensitivity of DNA base‐pair stacking to water content, as shown here, may be responsible for widely different transport results reported in the literature. Oriented films of a DNA–surfactant complex in which aligned double helices are separated by 4.1 nm, with face‐to‐face base‐pair stacking, bases separated by 0.34 nm, and good π–π overlap, are examined. Dehydration drives the base pairs from parallel planar packing to edge packing with poor π–π overlap (see Figure).
Fabrication and Controlled Magnetic Properties of Ni/ZnO Nanorod Heterostructures
Authors: Jung S.W. , Park W.I. , Yi G.‐C. , Kim M.Y.
Published: August 2003

Ni metal is evaporated onto the tips of ZnO nanorods, creating magnetic‐metal/semiconductor heterostructures (see Figure). Accurate thickness control allows tunable magnetic properties in nanosized magnetic layers on individual nanorods due to a crossover from superparamagnetism to ferromagnetism. These magnetic building blocks have potential as components for nanoscale spin‐valve transistors, spin light‐emitting diodes, and nonvolatile storage and logic devices.
Why a universal population‐level approach to the prevention of child abuse is essential
Authors: Sanders Matthew R. , Cann Warren , Markie‐Dadds Carol
Published: August 2003

This paper argues for the importance of adopting a population‐level approach to promote more effective parenting and to reduce the risk of child maltreatment. Family‐based interventions based on social learning principles have been shown to make a useful contribution in the treatment of child maltreatment. However, typically such programmes have been used to treat parents who have already become involved in the child protection system. We argue that the creation of community‐wide support structures to support positive parenting is needed to reduce the prevalence of child maltreatment. Such an approach requires several criteria to be met. These include having knowledge about the prevalence rates for the targeted child outcomes sought, knowledge about the prevalence of various parenting and family risk factors, evidence that changing family risk factors reduces the prevalence of targeted problems, having culturally appropriate, cost‐effective, evidence‐based interventions available and making these widely accessible. Copyright © 2003 John Wiley & Sons, Ltd.
Formation of a new F.C.C. τ2 phase in rapidly quenched Al55Cu35V10 alloy
Authors: Misra D. K. , Tiwari R. S. , Srivastava O. N.
Published: August 2003

X‐ray diffraction and transmission electron microscopy experiments were carried out to study the structure of rapidly solidified as‐cast and annealed Al55Cu35V10 alloy. The as‐cast Al55Cu35V10 alloy shows the presence of a new f.c.c. τ2 phase (a=0.58nm) along with a b.c.c. (a = 0.89 nm) phase which after subsequent annealing transforms into single f.c.c. phase (a = 0.58 nm). In this paper, it is also reported that these phases are crystalline approximants to an icosahedral phase on the basis of e/a (valence electron per atom) constant line. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies on optical properties of polycrystalline SnO2:Sb thin films prepared using SnCl2 precursor
Authors: Elangovan E. , Ramamurthi K.
Published: August 2003

Optical properties of spray deposited antimony (Sb) doped tin oxide (SnO2) thin films, prepared from SnCl2 precursor, have been studied as a function of antimony doping concentration. The doping concentration was varied from 0‐4 wt.% of Sb. All the films were deposited on microscope glass slides at the optimized substrate temperature of 400 °C. The films are polycrystalline in nature with tetragonal crystal structure. The doped films are degenerate and n‐type conducting. The sheet resistance of tin oxide films was found to decrease from 38.22 Ω/□ for undoped films to 2.17 Ω/□ for antimony doped films. The lowest sheet resistance was achieved for 2 wt.% of Sb doping. To the best of our knowledge, this sheet resistance value is the lowest reported so far, for Sb doped films prepared from SnCl2 precursor. The transmittance and reflectance spectra for the as‐deposited films were recorded in the wavelength range of 300 to 2500 nm. The transmittance of the films was observed to increase from 42 % to 55 % (at 800 nm) on initial addition of Sb and then it is decreased for higher level of antimony doping. This paper investigates the variation of optical and electrical properties of the as‐deposited films with Sb doping. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical absorption spectra and related parameters of ammonium zinc chloride crystal in the antiferroelectric and commensurate phases
Authors: Gaffar M. A. , Abu El‐Fadl A. , Bin Anooz S.
Published: August 2003

Optical absorption along the three crystallographic axes of (NH4)2ZnCl4 single crystals is reported over a temperature range from 276 K to 350 K. Our results clearly confirm the antiferroelectric to commensurate phase transition at 319 K. Analysis reveals that at the absorption edge the type of transition is the indirect allowed one. The indirect band gaps at various temperatures are determined and their temperature dependence is estimated in the antiferroelectric and commensurate phases. Optical parameters related to the temperature dependence of the energy gap are evaluated. The single‐effective oscillator model was used to describe the imaginary part of the dielectric constant, which facilitate calculation of the dipole moment parameters. The steepness parameter is given, its value is used to estimate the temperature dependence of the indirect energy gap and the result is compared with that calculated graphically. In the region of the absorption edge, the absorption coefficient obeys Urbach's rule. Urbach characteristic parameters are determined and their temperature dependence is investigated. Correlation between different parameters is considered. Most of the results confirm the optical isotropic nature of AZC crystals. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FTIR spectroscopic, thermal and growth morphological studies of calcium hydrogen phosphate dihydrate crystals
Authors: Joshi Vimal S. , Joshi Mihir J.
Published: August 2003

Calcium hydrogen phosphate dihydrate (CHPD or DCPD) is found quite frequently in urinary calculi (stones). The CHPD crystals were grown by the single diffusion gel growth technique in sodium metasilicate gel. The crystals were found to be having platelet and broad needle type morphologies. The crystals were analyzed by FTIR spectroscopy. The thermal properties were studied by employing the thermogravimetric analysis. Various kinetic and thermodynamic parameters for dehydration were estimated. The selected platelet was studied by SEM for the growth morphologies indicating that the crystals grew in the form of leaflets having prominent (010) faces. This was in agreement with earlier reported studies. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal and molecular structure of 2,6‐bis(4‐fluorobenzylidene)cyclohexanone
Authors: Ompraba G. , Rafi Z. A. , Yogavel M. , Velmurugan D. , Sekar K. , Karthikeyan E. , Perumal S. , Choudhury A. R. , Guru Row T. N.
Published: August 2003

The title compound, C20H16F2O, crystallizes in triclinic system with $ {\rm P} \bar1 $ space group and the unit cell parameters are: a = 9.700(5), b = 11.834(6), c = 14.315(7) Å, α = 78.464(9), β = 74.394(8), γ = 86.186(9)°, V = 1551.0(1) Å3 and Z = 4. The final R‐factor is 4.8%. The cyclohexanone ring adopts a sofa conformation. The different ways of adjusting to steric repulsion results in significant differences between molecule A and B with respect to torsion angles. The steric repulsion between the aromatic groups and hydrogen atoms on the cyclohexanone ring causes increase of the values of bond angles at the C atoms joining the rings and rotation of the corresponding bond, at the expense of conjugation energy of the system. In addition to the van der Waals interactions, C‐H…O, C‐H…F and C‐H…π interactions stabilize the molecular packing. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CVD on Bacteria Networks
Authors: Pons M. , Baillet F. , Gadelle P. , Schouler M.‐C.
Published: August 2003

A novel CVD submicrometer patterning technique of metals using a bacteria network is described and the suitability of the process to produce metallic islands which can catalyze the deposition of carbon nanotubes is demonstrated. The process for pattering, starting from the deposition of bacteria containing metal oxides, is shown in the Figure.
The Characterization of LiMn2O4 Thin Film Cathode for Lithium Rechargeable Microbattery Prepared by Liquid Source Misted Chemical Deposition
Authors: Kim K.W. , Kim M.R. , Lee S.‐W. , Han K.‐S. , Woo S.I.
Published: August 2003

Liquid source misted chemical deposition was used to fabricate LiMn2O4 film as a cathode for lithium rechargeable microbatteries. The effect of crystallization temperature on the film properties was investigated by X‐ray diffraction (XRD), Raman spectroscopy (RS), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), cyclic voltammetry (CV), and charge/discharge experiments. When the heat treatment for crystallization of the as‐deposited film was carried out at 800 °C in a rapid thermal apparatus (RTA) in an oxygen atmosphere for 5 min, the structural and compositional purity, and the electrochemical activity of the deposited film, were optimized. The LiMn2O4 films prepared by this method exhibited much better electrochemical rechargeability than those deposited by other techniques, such as sputtering, laser ablation, sol–gel coating, etc. The prepared film exhibits an initial discharge capacity of 62.5 μA h cm–2 μm–1 and a low capacity fade of 8.0 % over 100 cycles.
MOCVD of Platinum Films from (CH3)3CH3CpPt and Pt(acac)2: Nanostructure, Conformality, and Electrical Resistivity
Authors: Goswami J. , Wang C.‐G. , Cao W. , Dey S.K.
Published: August 2003

A potentially manufacturable liquid‐source MOCVD process was applied to deposit platinum (Pt) films (12–140 nm) on thermally oxidized Si substrates. The deposition of Pt films was carried out at a substrate temperature of 350 °C by oxygen‐assisted pyrolysis of complex precursors in a low‐pressure, hot‐wall reactor. The effects of two different metal–organic precursors, a) trimethyl methyl cyclopentadienyl platinum [(CH3)3CH3CpPt], and b) platinum acetylacetonate [Pt(acac)2], on the properties of Pt films were studied. Although the polycrystalline Pt films deposited from Pt(acac)2 exhibited a preferred (111) orientation with a X‐ray intensity ratio of I(111)/I(200) = 40, the films deposited from (CH3)3CH3CpPt were highly (111) oriented with I(111)/I(200) = 270. The following properties were typical of Pt films from Pt(acac)2 as compared to Pt films from (CH3)3CH3CpPt: finer grain size (25 nm vs. 50 nm), smaller root mean square (rms) surface roughness (5 nm vs. 15 nm), and better step coverage (95 % vs. 35 %). These experimental findings indicated that growth of Pt films from Pt(acac)2 occurred under the kinetically‐limited regime, whereas the deposition of Pt from (CH3)3CH3CpPt was limited by the mass transport rate. Additionally, the temperature (4.2–293 K) dependence of the electrical resistivities (ρ) of Pt films was measured and the electron mean free paths were estimated. It was observed that ρ(T) deviated from Matthiessen's rule.
Synthesis of Boron Nitride Films Using Electron–Cyclotron Resonance Microwave Plasma and an H2–BF3–N2–Ar–He Gas System
Authors: Chan C.‐Y. , Zhang W. , Chan K.‐M. , Bello I. , Lee S.‐T.
Published: August 2003

Boron nitride (BN) films with high crystallinity and phase purity (>80 %) in the cubic phase were synthesized over large areas using fluorine chemistry and electron–cyclotron resonance (ECR) microwave plasma. Plasma‐enhanced fluorine chemistry was provided by a complex H2–BF3–N2–Ar–He gas mixture. Each component of the mixture was optimized in accordance with its function. Such a procedure allowed the preparation of thick cBN films at a bias voltage as low as –30 V. Micrometer‐thick cBN films exhibiting columnar growth were obtained. However, ion bombardment was still indispensable for the cBN growth. The effects of deposition time and ion bombardment on the phase purity and crystallinity of the cBN films were investigated.
The HIV protease inhibitor Indinavir reduces immature dendritic cell transendothelial migration
Authors: Whelan Kathryn T. , Lin Chen‐Lung , Cella Marina , McMichael Andrew J. , Austyn Jonathan M. , Rowland‐Jones Sarah L.
Published: August 2003

Indinavir (IDV) is a protease inhibitor that successfully suppresses HIV‐1 replication as part of anti‐retroviral therapy. There is evidence to suggest that IDV may also act non‐specifically upon host proteases. In this study we investigated whether IDV could modulate protease‐dependent molecules involved in dendritic cell (DC) migration — a pivotal process in immunoregulation. Human monocyte‐derived DC were exposed to IDV (IDV‐DC) and transendothelial migration (TEM) to inflammatory chemokines was determined. TEM of IDV‐DC was significantly impaired compared to non‐treated DC (p<0.01). Phenotypic analysis revealed that IDV‐DC had reduced DC‐SIGN expression, correlating with reduced adhesion to immobilized ICAM‐2. Nevertheless, the reduction in migration following exposure to IDV could not be fully attributable to DC‐SIGN interactions alone. Investigation of IDV‐DC interactions with the underlying matrix protein, fibronectin, demonstrated that IDV significantly impaired DC binding to immobilized fibronectin (p<0.01). IDV appeared to act upon VLA‐4 and VLA‐5 since addition of antagonist monoclonal antibodies (mAb) similarly reduced adhesion ofnon‐treated DC to fibronectin. Combined blockade of DC using anti‐VLA‐4, VLA‐5 and anti‐DC‐SIGN mAb inhibited TEM to a similar extent as IDV. Our results strongly suggest that IDV inhibits host proteases necessary for DC migration and may, therefore, affect DC immunoregulation in HIV‐1‐infected patients.
B cell activation leads to shedding of complement receptor type II (CR2/CD21)
Authors: Masilamani Madhan , Kassahn Daniela , Mikkat Stefan , Glocker Michael O. , Illges Harald
Published: August 2003

Complement receptor type II (CR2/CD21) is the major receptor for C3d fragments on immune complexes. CD21 also serves as the receptor for Epstein–Barr virus in humans. On mature B cells, CD21 reduces the threshold of BCR signaling together with CD81, Leu13 and CD19, but it also occurs on other cells of the immune system where it performs unknown functions. A soluble form of CD21 (sCD21) is shed from the cell surface and is found in human blood plasma. An as‐yet‐unknown protease is thought to be responsible for this shedding. Altered levels of sCD21 occur in plasma in certain clinical conditions. We show here by mass spectrometry that sCD21 in human plasma of healthy donors is predominantly a short form of CD21 without the exon‐11‐encoded sequences. Whereas the N terminus of sCD21 was found unmodified, the C terminus is truncated, implying that only the extracellular portion of CD21 is shed. Peripheral blood B cells, but not T cells, contribute to the plasma CD21‐pool. CD21 shedding is induced by stimulation with PMA plus Ca2+ ionophore, or by stimulation of the BCR with anti‐IgM+anti‐CD40.
Trypanosoma cruzi infection modulates intrathymic contents of extracellular matrix ligands and receptors and alters thymocyte migration
Authors: Cotta‐de‐Almeida Vinícius , Bonomo Adriana , Mendes‐da‐Cruz Daniella Arêas , Riederer Ingo , de Meis Juliana , Lima‐Quaresma Kátia Regina Ferreira , Vieira‐de‐Abreu Adriana , Villa‐Verde Déa Maria Serra , Savino Wilson
Published: August 2003

Several T cell abnormalities have been described in the course of acute Trypanosoma cruzi infection in mice, including severe effects on the thymus. In the present study, looking at the expression of extracellular matrix ligands in the thymus, we observed that deposits of fibronectin and laminin increased progressively during the course of infection, reaching a maximum at the peak of parasitemia and thymic atrophy. Concomitantly, membrane expression of fibronectin and laminin receptors (VLA‐4, VLA‐5 and VLA‐6) was also enhanced on thymocyte subsets of infected mice. These results correlated with changes in intrathymic thymocyte migration ability during the acute phase of infection, when a higher fibronectin‐dependent transmigratory activity of CD4+CD8+ thymocytes was observed. Strikingly, we detected higher frequency of immature and high VLA‐expressing CD4+CD8+ T cells in the peripheral lymphoid organs of infected mice at thepeak of parasitemia. These cells seemed to be thymus dependent, since significantly lower amounts of them were found in thymectomized mice, and some of them carry “prohibited” Vβ segments of the TCR. Our data suggest an imbalance in the intrathymic cell trafficking following acute T. cruzi infection, likely due to dysregulated extracellular matrix‐dependent interactions.
Pathogenesis of Lyme neuroborreliosis: Borrelia burgdorferi lipoproteins induce both proliferation and apoptosis in rhesus monkey astrocytes
Authors: Ramesh Geeta , Alvarez Alida L. , Roberts E. Donald , Dennis Vida A. , Lasater Barbara L. , Alvarez Xavier , Philipp Mario T.
Published: August 2003

Brain invasion by Borrelia burgdorferi, the agent of Lyme disease, results in an inflammatory and neurodegenerative disorder called neuroborreliosis. In humans, neuroborreliosis has been correlated with enhanced concentration of glial fibrillary acidic protein in the cerebrospinal fluid, a sign of astrogliosis. Rhesus monkeys infected by us with B. burgdorferi showed evidence of astrogliosis, namely astrocyte proliferation and apoptosis. We formulated the hypothesis that astrogliosis could be caused by spirochetal lipoproteins. We established primary cultures of rhesus monkey astrocytes and stimulated the cells with recombinant lipidated outer surface protein A (L‐OspA), a model B. burgdorferi lipoprotein, and tripalmitoyl‐S‐glyceryl‐Cys‐Ser‐Lys4‐OH (Pam3Cys), a synthetic lipopeptide that mimics the structure of the lipoprotein lipid moiety. L‐OspA elicited not only astrocyte proliferation but also apoptosis, two features observed during astrogliosis. Astrocytes produced both IL‐6 and TNF‐α in response to L‐OspA and Pam3Cys. Proliferation induced by L‐OspA was diminished in the presence of an excess of anti‐IL‐6 antibody, and apoptosis induced by this lipoprotein was completely suppressed with anti‐TNF‐α antibody. Hence, IL‐6 contributes to, and TNF‐α determines, astrocyte proliferation and apoptosis, respectively, as elicited by lipoproteins. Our results provide proof of the principle that spirochetal lipoproteins could be key virulence factors in Lyme neuroborreliosis, and that astrogliosis might contribute to neuroborreliosis pathogenesis.
Tissue‐specific regulation of the human acute‐phase serum amyloid A genes, SAA1 and SAA2, by glucocorticoids in hepatic and epithelial cells
Authors: Thorn Caroline F. , Lu Zhi‐Yong , Whitehead Alexander S.
Published: August 2003

The human acute‐phase protein serum amyloid A (A‐SAA), encoded by the SAA1 and SAA2 genes, is dramatically induced by pro‐inflammatory mediators during the acute‐phase response to infection or injury. Circulating A‐SAA is predominantly synthesized by the liver. However, other tissues are the source of locally produced A‐SAA. Here, we establish that the qualitative and kinetic aspects of SAA1 and SAA2 transcription following treatment of HepG2 hepatoma cells and KB epithelial cells with glucocorticoids and cytokines are quite distinct. Untreated HepG2 cells do not express A‐SAA mRNA and glucocorticoids, when administered alone, fail to induce either SAA1 or SAA2. In contrast, untreated KB cells constitutively express SAA1 mRNA. Following cytokine stimulation, both A‐SAA genes are rapidly up‐regulated to similar extents. As in the hepatoma cell line, co‐stimulation of KB cells with glucocorticoids places SAA1 at a transcriptional advantage over SAA2. Interestingly, SAA1 can be significantly induced by glucocorticoids alone in KB cells. The effects of glucocorticoids on SAA1 in both cell lines is glucocorticoid receptor‐dependent. Differential regulation of A‐SAA expression in these cell lines may reflect different temporal and spatial requirements for A‐SAA synthesis in response to different inflammatory challenges.
Cruzipain induces autoantibodies against cardiac muscarinic acetylcholine receptors. Functional and pathological implications
Authors: Sterin‐Borda Leonor , Giordanengo Laura , Joensen Lilian , Gea Susana
Published: August 2003

The goal of this study was to investigate whether cruzipain, a Trypanosoma cruzi immunodominant antigen, was able to induce antibodies reactive to the cardiac M2 muscarinic acetylcholine receptor (M2 mAChR). Immunization with cruzipain that was devoid of enzyme activity triggered IgG antibodies against cardiac M2 mAChR. By radioligand competition assay we proved that the anti‐cruzipain IgG fraction, purified from serum, inhibited binding of the specific M2 mAChR radioligand [3H]quinuclidinyl benzilate. We also demonstrated that anti‐cruzipain IgG reacted against the second extracellular loop of the M2 mAChR. The corresponding affinity‐purified serum anti‐M2e2 IgG (reacting against a synthetic peptide corresponding to this loop in humans) displayed agonist‐like activity associated with specific M2 mAChR activation — increase of cGMP, inositol phosphate accumulation and nitric oxide synthase activity — triggering a decrease in myocardial contractility. Moreover, the same IgG fraction decreased heart frequency, related to inhibition of adenylate cyclase activity. These results imply thatcruzipain plays a role in the production of antibodies against M2 mAChR, which have been related to the pathogenesis of dysautonomic syndrome described in Chagas' disease.
OX40 (CD134) and OX40 ligand interaction plays an adjuvant role during in vivo Th2 responses
Authors: Ishii Naoto , Ndhlovu Lishomwa C. , Murata Kazuko , Sato Takayuki , Kamanaka Masahito , Sugamura Kazuo
Published: August 2003

The role of OX40‐OX40 ligand (OX40L) interaction in Th cell differentiation remains contentious. In vitro studies have revealed a Th2‐biased effect by OX40 signals in T cells. However, in vivo studies demonstrated that OX40‐OX40L interaction is involved in responses either Th1 or Th2, or both, which appears to be dependent on the experimental conditions used. We document in our report Th cell differentiation in OX40L‐deficient and OX40L‐transgenic (Tg) mice in response to protein antigens (Ag) and to Leishmania major (L. major) infection. Upon immunization with protein Ag, we demonstrate the adjuvant effect of OX40 signals during in vivo Th2 responses. However, adjuvant treatment to mice ameliorates the Th2‐specific effect of OX40‐OX40L interaction and rather induces concurrent promotion of both Th1 and Th2 responses via OX40 signals. Thus, previous reports showing promotion of Th1 response by OX40‐OX40L interaction may in actual fact be affected by the adjuvant effects mediated by the various experimental conditions. Indeed, constitutive OX40–OX40L interactions in OX40L‐Tg mice converted the normally resistant C57BL/6 strain, into a susceptible status following L. major infection due to an extraordinary elevated Th2 response. These results provide convincing evidence demonstrating that the OX40‐OX40L interaction is paramount in the development of Th2 responses in vivo.
Aging‐dependent generation of suppressive CD4+CD25–R123loCD103+ T cells in mice
Authors: Shimizu Jun , Moriizumi Eiko
Published: August 2003

Advancing age is associated with significant alterations in immune functions, including a decline in CD4 T cell function, in both mice and humans. In our previous report, we showed that CD4+CD25– T cells in aged (24‐month‐old) mice, especially after in vitro pre‐stimulation of these cells, exhibit hyporesponsive and suppressive properties. We examined here whether the suppressive activity of aged CD4+CD25– T cells is ascribable to a particular population within these cells. In vitro analyses revealed that cell populations rapidly extruding Rhodamine‐123 (R123) (referred to as R123lo cells) in aged CD4+CD25– T cells have a more potent suppressive function compared with R123hi populations.In addition, CD103+ cells in freshly prepared aged CD4+CD25–R123lo T cells had a most potent suppressive activity. Both R123hi and R123lo populations had individually stronger suppressive activity after pre‐stimulation than before pre‐stimulation. Furthermore, the R123lo population in young CD4+CD25– T cells also had different properties from R123hi T cells: low responsiveness, no additive effect in proliferation assays, and the gain of a suppressive function after in vitro pre‐stimulation. Takentogether, these results suggest that CD4+CD25–R123lo T cells are a unique population within whole CD4+CD25– T cells. This population exists in the earlystage of the life span, and the properties in this population become obvious with aging, that is the gain of their suppressive activity.
Activation of Epstein‐Barr virus/C3d receptor (gp140, CR2, CD21) on human cell surface triggers pp60src and Akt‐GSK3 activities upstream and downstream to PI 3‐kinase, respectively
Authors: Barel Monique , Balbo Michelle , Le Romancer Muriel , Frade Raymond
Published: August 2003

We previously demonstrated that CR2 activation on human B lymphocyte surface specifically triggered tyrosine phosphorylation of the 95‐kDa nucleolin, this leading to its binding on SH2 domainsof p85 sub‐unit of PI 3‐kinase and to activation of this enzyme. The specificity of CR2 pathway was clearly demonstrated as neither CD19 nor BCR could induce tyrosine phosphorylation of nucleolin in normal B lymphocytes. These data led us to investigate herein additional molecular events, which were triggered by CR2 activation, upstream and downstream to PI 3‐kinase activation. Upstream, we demonstrated that pp60src, a tyrosine kinase of the src family, was involved in tyrosine phosphorylation of nucleolin, while syk tyrosine kinase was not. We also demonstrated a direct protein‐proteininteraction of pp60src with nucleolin in a CR2‐dependent and CD19‐independent pathway. Downstream, we demonstrated that CR2 activation also triggered Akt and GSK3 enzyme activation, this pathway being under the control of pp60src tyrosine kinase activation. These regulatory functions of activated CR2 were specific as independent of syk tyrosine kinase and of CD19 and BCR activation. Thus, CR2 activation recruits a specific mechanism to activate PI 3‐kinase and its subsequent pathways, this mechanism being different to those recruited by CD19 and BCR.
NK T cells stimulated with a ligand for TLR2 at least partly contribute to liver injury caused by Escherichia coli infection in mice
Authors: Hiromatsu Takashi , Matsuguchi Tetsuya , Shimizu Hideyuki , Yajima Toshiki , Nishimura Hitoshi , Arai Toshiyuki , Nimura Yuji , Yoshikai Yasunobu
Published: August 2003

Fas ligand (Fas L) expression was induced on intrahepatic NK1.1+ T cells in vivo after an intraperitoneal inoculation of Escherichia coli. Liver injury after E. coli infection, as assessed by serum GPT level and histological examination, was significantly reduced in Jα281–/– mice lacking NK1.1+ T cells or in gld/gld mice bearing mutated Fas L, indicating that NK T cells at least partly contribute to E. coli‐induced liver injury in a Fas/Fas L‐dependent manner. Bacterial numbers in organs and cytokine levelsin serum of Jα281–/– mice did not differ from those of Jα281+/+ mice following E. coli infection. Intrahepatic NK1.1+ T cells, which preferentially expressed Toll‐like receptor 2 (TLR2) mRNA, responded in vitro to synthetic lipoprotein, a ligand for TLR2, by inducing Fas L expression on their surface. In a manner analogous to E. coli infection, lipoprotein and LPS could additively induce Fas L expression on NK1.1+ T cells, leading to liver injury in vivo in normal mice but not in gld/gld mice. In conclusion, it is suggested that induction of Fas L on NK T cells in response to bacterial components such as lipoproteins plays an important role in pathogenesis of E. coli‐induced liver injuryin mice.
Contrasting roles for IL‐10 in protective immunity to different life cycle stages of intestinal nematode parasites
Authors: Helmby Helena , Grencis Richard K.
Published: August 2003

Expulsion of the gastro‐intestinal nematode Trichinella spiralis is associated with a pronounced mastocytosis mediated by a T helper (Th) 2 type response involving interleukin (IL)‐4 and IL‐13. Here we demonstrate that IL‐10 is a key regulator of protective immune responses against T. spiralis in vivo. IL‐10 knockout mice or normal mice treated with a neutralizing anti‐IL‐10 receptor antibody are highly susceptible to a primary T. spiralis infection and show significantly delayed adult worm expulsion. Depletion of IL‐10 resulted in elevated Th1 and Th2 cytokine responses but significantly reduced numbers of mucosal mast cells in the jejunum. Interestingly, the increase in IFN‐γ detected in the absence of IL‐10 resulted in increased immunity to larval stages. Hence, IL‐10 has a negative effect on immunity to the tissue dwelling larval stages of T. spiralis but plays a significant biological role as an in vivo regulator of intestinal mast cell responses and is crucially involved in protection against adult stages of intestinal parasites in vivo.
The impaired NK cell cytolytic function in viremic HIV‐1 infection is associated with a reduced surface expression of natural cytotoxicity receptors (NKp46, NKp30 and NKp44)
Authors: De Maria Andrea , Fogli Manuela , Costa Paola , Murdaca Giuseppe , Puppo Francesco , Mavilio Domenico , Moretta Alessandro , Moretta Lorenzo
Published: August 2003

Signals leading to NK cell triggering are primarily mediated by natural cytotoxicity receptors (NCR) upon binding to as‐yet‐undefined cell surface ligand(s) on normal hematopoietic cells, pathogen‐infected cells or tumor cells. In this study we tried to determine whether the decreased NK cell cytolytic function that is observed in HIV‐1‐infected patients may be related to a decreased expression of NCR. In HIV‐1‐infected patients, freshly drawn, purified NK cells expressed significantly decreased surface densities of NKp46 and NKp30 NCR. The low surface density of NKp46, NKp30 and NKp44 was also confirmed in in‐vitro‐activated NK cell populations and NK cell clones derived from HIV‐1 patients compared with uninfected donors. This defective NCR expression in HIV‐1 patients was associated with a parallel decrease of NCR‐mediated killing of different tumor target cells. Thus, the present study indicates that the defective expression of NCR represents at least one of the possible mechanisms leading to the impaired NK cell function in HIV‐1 infection and it can contribute to explain the relatively high frequency of opportunistic tumors reported in cohorts of untreated patients before the occurrence of profound immunosuppression (<200 CD4+ cells/mm3).
Proximal changes in signal transduction that modify CD8+ T cell responsiveness in vivo
Authors: Guillaume Séverine , Tuosto Loretta , Tanchot Corinne , Di Bartolo Vincenzo , Acuto Oreste , Rocha Benedita
Published: August 2003

The antigen dose conditions the functional properties of CD8+ T cells generated after priming. At relatively low antigen doses, efficient memory T cells may be generated, while high antigen doses lead to tolerance. To determine the mechanisms leading to such different functional outcomes, we compared the proximal TCR signal transduction of naive cells, to that of memory or high‐dose tolerant cells generated in vivo. In vivo activation led to the constitutive phosphorylation of CD3ϵ, recruiting Zap70, in both memory and tolerant cells. In tolerant cells, these phenomena were much more marked, the CD3ϵ and ζ chains no longer associated, and the Src kinases p56Lck and p59Fyn were inactive. Therefore, when the antigen load overcomes the capacities of immune control, a new mechanism intervenes to block signal transduction: the recruitment of Zap70 to CD3ϵ becomes excessive, leading to TCR complex destabilization, Src kinase dysfunction, and signal arrest.
A unique subpopulation of CD4+ regulatory T cells controls wasting disease, IL‐10 secretion and T cell homeostasis
Authors: Banz Alice , Peixoto António , Pontoux Christiane , Cordier Corinne , Rocha Benedita , Papiernik Martine
Published: August 2003

CD25+CD4+ regulatory T cells have major roles in controlling immune responses, and use heterogeneous regulatory mechanisms. It is possible that these different activities aremediated by different subsets. Here we show that CD103+CD25+CD4+ T cells (that control inflammatory bowel disease) are highly enriched in gut‐associated lymphoid tissue and have unique functional properties. In vivo, only this subpopulation is able to control wasting disease and peripheral T cell homeostasis. In vitro, only this subpopulation is able to regulate IL‐10 secretion, and it might also mediate infectious suppression. These results demonstrate that regulatory T cells can be divided into discrete subpopulations with defined functional properties and regulatory mechanisms.
Use of Ionic Liquids for the Diels‐Alder Reaction of Oleochemicals
Authors: Behr A. , Naendrup F. , Nave S.
Published: August 2003

Recently, ionic liquids have found increasing attention as new reaction media, especially for homogeneously catalyzed syntheses in liquid‐liquid biphasic systems. Their physical and chemical properties are very attractive and can be tuned by a proper choice of the organic cation as well as of the anion. This report presents the use of ionic liquids as reaction media and catalysts for the derivatization of long‐chain fatty acid esters by Diels‐Alder reaction.
Adaptive group detection for DS/CDMA systems over frequency‐selective fading channels
Authors: Buzzi Stefano , Lops Marco , Pauciullo Antonio , Ricci Giuseppe
Published: August 2003

In this paper we consider the problem of group detection for asynchronous Direct‐Sequence Code Division Multiple Access (DS/CDMA) systems operating over frequency‐selective fading channels. A two‐stage near‐far resistant detection structure is proposed. The first stage is a linear filter, aimed at suppressing the effect of the unwanted user signals, while the second stage is a non‐linear block, implementing a maximum likelihood detection rule on the set of desired user signals. As to the linear stage, we consider both the Zero‐Forcing (ZF) and the Minimum Mean Square Error (MMSE) approaches; in particular, based on the amount of prior knowledge on the interference parameters which is available to the receiver and on the affordable computational complexity, we come up with several receiving structures, which trade system performance for complexity and needed channel state information. We also present adaptive implementations of these receivers, wherein only the parameters from the users to be decoded are assumed to be known. The case that the channel fading coefficients of the users to be decoded are not known a priori is also considered. In particular, based on the transmission of pilot signals, we adopt a least‐squares criterion in order to obtain estimates of these coefficients. The result is thus a fully adaptive structure, which can be implemented with no prior information on the interfering signals and on the channel state. As to the performance assessment, the new receivers are shown to be near‐far resistant, and simulation results confirm their superiority with respect to previously derived detection structures. Copyright © 2003 AEI.
Investigation of the Limiting Processes of a DMFC by Mathematical Modeling
Authors: Siebke A. , Schnurnberger W. , Meier F. , Eigenberger G.
Published: August 2003

Since measured current‐voltage curves do not allow conclusions concerning the limiting processes in a direct methanol fuel cell, a detailed mathematical model was developed to quantify the influence of individual physical and electrochemical effects on overall cell performance. Results of numerical simulations given here show good agreement with experimental current‐voltage curves for various operating conditions. According to simulation results, the limiting electrode depends strongly on operating conditions: when the temperature is increased or the cathode gas is switched from oxygen to air, the limitation in current density is shifted from anode to cathode. Moreover, it has been demonstrated that there is only a small range of operating conditions between drying out and flooding of the cathode.
Performance Comparison Between Planar and Tubular‐Shaped PEM Fuel Cells by Three‐Dimensional Numerical Simulation
Authors: Coursange J.‐F. , Hourri A. , Hamelin J.
Published: August 2003

The results of a numerical simulation of the current distribution of a three‐dimensional, tubular shaped, proton exchange membrane fuel cell model are presented. An integrated flow and current density model to predict current density distributions in two dimensions along the membrane has been developed. The numerical model has a cylindrical geometry that includes diffusion layers on the anode and cathode side, the anode being the inner most electrode, and solves the same primary flow related variables along the channels and the diffusion layers. The simulation was performed with commercial flow solver software where a control volume approach was used and source term equations that characterize the electrochemical aspects of the fuel cell have been added.
Energy in chemical manufacturing processes: gate‐to‐gate information for life cycle assessment
Authors: Kim Seungdo , Overcash Michael
Published: August 2003

Gate‐to‐gate process energy for 86 chemical manufacturing processes is presented. The estimation of the process energy follows design‐based methodology. Results show that the gate‐to‐gate process energy for half of organic chemicals ranges from 0 to 4 MJ per kg, and for half of inorganic chemicals ranges from −1 to 3 MJ per kg. The main energy source in both organic and inorganic processes is steam energy followed by potential recovered energy. In organic chemicals, the fractions of heating oil and electricity use are relatively low, but these fractions are higher in the inorganic chemicals than in the organic chemicals. Furthermore, about 50% of the energy consumed in chemical processes is used for purifying the product, byproduct or recycled stream, which indicates that there are large opportunities for improving the process energy in chemical processes. The information presented in this study is very important for those in the life cycle assessment community in order for them to identify inaccurate information or information not based on actual process design. However, the range for the entire range of chemicals is very substantial and thus reflects the need of the life cycle inventory to separately evaluate the chemistry and degree of purity for chemical products. Copyright © 2003 Society of Chemical Industry
Comparative studies on bioconversion of benzaldehyde to L‐phenylacetylcarbinol (L‐PAC) using calcium alginate‐ and barium alginate‐immobilized cells of Torulaspora delbrueckii
Authors: Shukla Vilas B , Kulkarni Pushpa R
Published: August 2003

Comparison of the production of L‐phenylacetylcarbinol (L‐PAC) from benzaldehyde by cells of Torulaspora delbrueckii immobilized in calcium alginate and barium alginate showed that cells immobilized in calcium alginate beads were usable for up to six cycles compared with nine cycles for barium alginate‐immobilized cells. Barium alginate‐immobilized cells yielded a total of 2.17 g of L‐PAC in nine cycles whereas in the case of calcium alginate‐immobilized cells, a total of 1.17 g of L‐PAC was formed when 400 mg benzaldehyde and 400 mm3 of acetaldehyde were used in each cycle as substrate and co‐substrate respectively. Copyright © 2003 Society of Chemical Industry