bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractCD25+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.
Adaptive group detection for DS/CDMA systems over frequency‐selective fading channels
Authors: Buzzi Stefano , Lops Marco , Pauciullo Antonio , Ricci Giuseppe 
Published: August 2003

AbstractIn 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

AbstractSince 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

AbstractThe 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

AbstractGate‐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

AbstractComparison 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
Effects of polyacrylamide‐co‐acrylic acid on cellulose production by Acetobacter xylinum
Authors: Joseph Gerard , Rowe Gerald E , Margaritis Argyrios , Wan Wankei 
Published: August 2003

AbstractPolyacrylamide‐co‐acrylic acid (PA) added to shake flask cultures of Acetobacter xylinum at concentrations up to 3 g dm−3 resulted in increased production of bacterial cellulose. For PA concentrations of 0–3 g dm−3, 7‐day cellulose production rose monotonically from 2.7 ± 0.8 to 6.5 ± 0.5 g dm−3 at a shaker speed of 175 rpm, and from 1.7 ± 0.01 to 3.7 ± 0.5 g dm−3 at shaker speed of 375 rpm. Addition of PA also changed the morphology of the biomass from amorphous/stringy forms to spheroidal particles with diameters ≤2 mm. Similarly, bioreactor cultures grown in the absence of PA formed long fibrous masses which deposited on the internals, while those grown in the presence of 1–2 g dm−3 PA formed small discrete particles with diameters ≤0.1 mm. Tests performed with 1 and 2 g dm−3 PA, and stirrer speeds from 500 to 900 rpm, appeared to give the highest cellulose concentration of 5.3 ± 0.7 g dm−3 in 64–68.5 h in the presence of 2 g dm−3 PA at 700 rpm, although this value was statistically indistinguishable from that obtained at 1 g dm−3 PA and 900 rpm. A qualitative model is proposed to describe the mechanisms by which PA affects biomass morphology, resulting in its advantageous formation as small, dispersed, spheroidal pellets. Quantitative analysis of the results gave inverse correlations between both the fraction of fructose carbon going to cellulose synthesis and the specific fructose consumption rate, and the maximum cellulose concentration and the fraction of fructose carbon going to by‐product formation. Since cellulose yield was almost universally improved by higher polyacrylamide concentration, it appears likely that increased viscosity reduces fructose uptake rate by limiting mass transfer. Copyright © 2003 Society of Chemical Industry
Hydrodynamic considerations on optimal design of a three‐phase airlift bioreactor with high solids loading
Authors: Klein Jaroslav , Vicente António A , Teixeira José A 
Published: August 2003

AbstractThe hydrodynamic study of a three‐phase airlift (TPAL) bioreactor with an enlarged gas–liquid dual separator was carried out. Different lengths and diameters of the draft tube were tested to show how the design of the separator zone affects the hydrodynamic performance of the TPAL reactor. Ca‐alginate beads with entrapped yeast biomass at different loadings (0, 7, 14 and 21% v/v) were used in order to mimic the solid phase of conventional high cell density systems, such as those with cells immobilized on carriers or flocculating cells. Important information on multiphase flow and distribution of gas and solid phases in the internal‐loop airlift reactor (ALR) with high solids loading was obtained, which can be used for suggesting optimal hydrodynamic conditions in a TPAL bioreactor with high solids loading. It is finally suggested that the ALR with a dual separator and a downcomer to riser cross‐sectional area ratio (AD/AR) ranging from 1.2 to 2.0 can be successfully applied to batch/continuous high cell density systems, where the uniform distribution of solid phase, its efficient separation of particles from the liquid phase, and an improved residence time of air bubbles inside the reactor are desirable. Copyright © 2003 Society of Chemical Industry
Bacterial biodegradation of phenol and 2,4‐dichlorophenol
Authors: Gallizia Ilaria , McClean Stephen , Banat Ibrahim M 
Published: August 2003

AbstractNine bacterial strains capable of utilising phenol and 2,4‐dichlorophenol (DCP) have been isolated from a mixed culture grown on substrates containing these compounds. One of these strains, a Micrococcus sp, was further investigated under aerobic conditions using phenol and DCP as sole carbon and energy sources at various pH values. Phenol degradation was enhanced under alkaline conditions, and up to 500 mg dm−3 phenol was mineralised within 50 h at pH 10. DCP was more recalcitrant; however up to 883 mg g−1 and 230 mg g−1 were degraded within 10 days, when using initial DCP concentrations of 100 and 200 mg dm−3, respectively. Biomass measurements showed cell growth, proving that both phenol and DCP are used as growth substrates for this isolate. Copyright © 2003 Society of Chemical Industry
Photoelectrocatalytic humic acid degradation kinetics and effect of pH, applied potential and inorganic ions
Authors: Selcuk Huseyin , Sene Jeosadaque J , Anderson Marc A 
Published: August 2003

AbstractThis study addresses the removal of humic acid (HA) dissolved in an aqueous medium by a photoelectrocatalytic process. UV254 removal and the degradation of color (Vis400) followed pseudo‐first order kinetics. Rate constants were 1.1 × 10−1 min−1, 8.3 × 10−2 min−1 and 2.49 × 10−2 min−1 (R2 > 0.97) for UV254 degradation and 1.7 × 10−1 min−1, 6.5 × 10−2 min−1 and 2.0 × 10−2 min−1 for color removal from 5 mg dm−3, 10 mg dm−3 and 25 mg dm−3 HA respectively. Following a 2 h irradiation time, 96% of the color, 98% of the humic acid and 85% of the total organic carbon (TOC) was removed from an initial 25 mg dm−3 HA solution in the photoanode cell. Photocatalytic removal on the same photoanode was also studied in order to compare the two methods of degradation. Results showed that the photoelectrocatalytic method was much more effective than the photocatalytic method especially at high pH values and with respect to UV254 removal. The effect of other important reaction variables, eg pH, external potential and electrolyte concentration, on the photoelectrocatalytic HA degradation was also studied. Copyright © 2003 Society of Chemical Industry
Synthesis of [18F]‐labeled adenosine analogues as potential PET imaging agents
Authors: Alauddin Mian M. , Fissekis John D. , Conti Peter S. 
Published: August 2003

AbstractThe syntheses of adenosine analogues, 2′‐deoxy‐2′‐[18F]fluoro‐9‐β‐D‐arabinofuranosyladenine ([18F]‐FAA) and 3′‐deoxy‐3′‐[18F]fluoro‐9‐β‐D‐xylofuranosyladenine ([18F]‐FXA) are reported. Adenosine (1) was converted to its methoxytrityl derivatives 2 and 3 as a mixture. After separation, these derivatives were converted to their respective triflates 4 and 5. Each triflate was reacted with tetrabutylammonium[18F]fluoride to produce 6b or 7b, which by acidic hydrolysis yielded compounds 8b and 9b. Crude preparations were purified by HPLC to obtain the desired pure products. The radiochemical yields were 10‐18% decay corrected (d. c.) for 8b and 30‐40% (d. c.) for 9b in 4 and 3 runs, respectively. Radiochemical purity was >99% and specific activity was >74 GBq/μmol at the end of synthesis (EOS). The synthesis time was 90‐95 min from the end of bombardment (EOB). Copyright © 2003 John Wiley & Sons, Ltd.
Efficient synthesis of [11C]befloxatone, a selective radioligand for the in vivo imaging of MAO‐A density using PET
Authors: Dollé F. , Bramoullé Y. , Hinnen F. , Demphel S. , George P. , Bottlaender M. 
Published: August 2003

AbstractCarbon‐11 labelled befloxatone ((5R)‐5‐(methoxymethyl)‐3‐[4‐[(3R)‐4,4,4‐trifluoro‐3‐hydroxybutoxy]phenyl]‐2‐oxazolidinone) is a reversible and selective monoamine oxidase‐A (MAO‐A) inhibitor and appears to be a new potent PET tracer for the in vivo imaging of MAO‐A density. In this paper, the radiosynthesis of befloxatone was investigated and orientated towards the preparation of multi milliCuries of radiotracer. Typically, using no‐carrier‐added [11C]phosgene, 150–300 mCi (5.55–11.10 GBq) of [11C]befloxatone was obtained within 20 min of radiosynthesis (including HPLC purification) with specific radioactivities ranging from 500 to 2000 mCi/µmol (18.5–74.0 GBq/µmol). The high efficiency of these radiosyntheses allows for multi‐injection protocols and kinetic approaches for absolute quantification of the tracer. Copyright © 2003 John Wiley & Sons, Ltd.
Regioselective F‐18 radiolabeling of AM694, a CB1 cannabinoid receptor ligand
Authors: Willis Peter G. , Katoch‐Rouse Reeti , Horti Andrew G. 
Published: August 2003

Abstract[18F]AM694, [1‐(5‐[18F]fluoropentyl)‐1H‐indol‐3‐yl]‐(2‐iodophenyl)methanone, 1b, a potential radiotracer for imaging of cerebral cannabinoid receptor (CB1), has been synthesized by no‐carrier‐added regioselective radiofluorination of the corresponding tosylate. [18F]AM694 was obtained in 20% radiochemical yield (non‐decay‐corrected) with a specific activity of 14 500 mCi/µmol, a radiochemical purity of > 99%, and a chemical purity of 95.5%. Copyright © 2003 John Wiley & Sons, Ltd.
3H‐labelled alkyl‐nucleotides, ‐nucleosides and ‐bases for the immunoanalytical quantification of DNA damage and repair
Authors: Drosdziok Wolfgang , Lutze Catrin , Krüger Kai , Glüsenkamp Karl‐Heinz , Rajewsky Manfred F. 
Published: August 2003

AbstractAnalysis of the formation and repair of structurally modified DNA is of particular interest in the study of carcinogenesis, cancer therapy and aging. The quantification of specific DNA lesions by sensitive immunoanalytical methods requires radiotracers with high specific activity. We describe the synthesis of 3H‐labelled adenine‐, cytosine‐, guanine‐ and thymine‐alkyl derivatives by nucleophilic N‐ and O‐alkylation using alkyl halides and diazoalkanes: 3‐alkyl‐[8‐3H]adenine (Alkyl = Me, Et, n‐Bu); O6‐alkyl‐deoxy[1′,2′‐3H]guanosine (Alkyl = Me, Et, i‐Pro, n‐Bu); O6‐ethyl‐deoxyguanosine‐5′‐triphosphate ([2‐3H‐Ethyl]; [8‐3H]); O6‐alkyl‐9‐hydroxyhexyl‐[8‐3H] guanine (Alkyl=Me, Et); 7‐ethyl‐[8,5′‐3H]guanosine‐3′,5′‐cyclic‐phosphate; O2‐andO4‐alkyl‐[methyl, 1′,2′‐3H]thymidine (Alkyl=Me, Et); the conversion of 3H‐labelled thymidine to the corresponding 5‐methylcytidine; the synthesis of three different 8‐oxo‐guanine tracers; and the generation of thymidine glycol (5,6‐dihydroxy‐5,6‐dihydro‐[methyl‐3H]thymidine) from thymidine. All radiotracers were sucessfully employed in competitive radioimmunoassays for the quantification of defined DNA alkylation products in DNA repair analyses. Copyright © 2003 John Wiley & Sons, Ltd.
Efficient in‐loop synthesis of high specific radioactivity [11C]carfentanil
Authors: Studenov Andrei R. , Jivan Salma , Buckley Kenneth R. , Adam Michael J. 
Published: August 2003

AbstractThe synthesis of the precursor for [11C]carfentanil and the precursor labelling with 11C have both been improved. The problem ‘bottleneck’ step in the carfentanil precursor synthesis, due to low chemical yield (14%) of intermediates nitrile into amide conversion, has been solved. Application of a H2O2/K2CO3/DMSO reaction method significantly increased the yield of this chemical transformation (up to 84%). A simple and straight‐forward synthesis of [11C]carfentanil was achieved by combining in‐loop methylation of the ammonia salt of the precursor by [11C]CH3I, using tetrabutylammonium hydroxide as a base, with a previously developed product purification procedure using a C2 extraction disc. A decay corrected yield with respect to [11C]CH3I of [11C]carfentanil was 64±12% (n=6) with the synthesis time of 21 min. The radiochemical purity was >98%. Comparatively high specific radioactivity of [11C]carfentanil [11.2±4.8 Ci/μmol (EOS, n=5)] was partially attributed to the use of [11C]methane target gas for production of carbon‐11 methyl iodide. Copyright © 2003 John Wiley & Sons, Ltd.
‘Mass defect’ tags for biomolecular mass spectrometry
Authors: Hall Michael P. , Ashrafi Siamak , Obegi Imad , Petesch Robert , Peterson Jeffrey N. , Schneider Luke V. 
Published: August 2003

AbstractWe present a new class of ‘mass defect’ tags with utility in biomolecular mass spectrometry. These tags, incorporating element(s) with atomic numbers between 17 (Cl) and 77 (Ir), have a substantially different nuclear binding energy (mass defect) from the elements common to biomolecules. This mass defect yields a readily resolvable mass difference between tagged and untagged species in high‐resolution mass spectrometers. We present the use of a subset of these tags in a new protein sequencing application. This sequencing technique has advantages over existing mass spectral protein identification methodologies: intact proteins are quickly sequenced and unambiguously identified using only an inexpensive, robust mass spectrometer. We discuss the potential broader utility of these tags for the sequencing of other biomolecules, differential display applications and combinatorial methods. Copyright © 2003 John Wiley & Sons, Ltd.
A strategy for liquid chromatography/tandem mass spectrometric assays of intracellular drugs: application to the validation of the triphosphorylated anabolite of antiretrovirals in peripheral blood mononuclear cells
Authors: Becher François , Pruvost Alain , Gale Jane , Couerbe Philippe , Goujard Cécile , Boutet Valerie , Ezan Eric , Grassi Jacques , Benech Henri 
Published: August 2003

AbstractThe pharmacokinetics of intracellular drugs have recently aroused new interest because monitoring a drug's behaviour near the site of action can enhance knowledge of its efficacy and toxicity. Liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) is particularly attractive for intracellular analytes. Very few papers deal precisely with special features encountered in intracellular drug assay or with how closely the assay matches the actual recommendations.Particular problems are encountered mainly because the analytes are located intracellularly. This mainly concerns the handling of biological media, including provision of blank samples using Ficoll gradient separation, cell counts, optimisation of cell lysis, sample extraction, plotting standard curves using either fmol/106 cells or fmol/ml of extract or fmol/sample, the matrix effect as a function of the number of cells, stability before and during cell separation, as well as in storage conditions using clinical samples, biological matrix replacement and interference by endogenous compounds.This paper describes a strategy for the full validation and routine use of an LC/MS/MS assay applied to the simultaneous intracellular determination of the triphosphorylated anabolites of didanosine (2′,3′‐dideoxyadenosine triphosphate or ddA‐TP) and stavudine (2′,3′‐didehydro‐3′‐deoxythymidine triphosphate or d4T‐TP), two nucleoside reverse transcriptase inhibitors of HIV, in human peripheral blood mononuclear cells (PBMCs), as a guide for further LC/MS/MS assay of intracellular drugs. Copyright © 2003 John Wiley & Sons, Ltd.