bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Singlet–Triplet Exchange Energy in Conjugated Polymers
Authors: Köhler A. , Beljonne D. 
Published: January 2004

AbstractElectron–electron interactions in organic semiconductors split the lowest singlet and triplet states by the exchange energy, ΔEST. Measurement of singlet and triplet emission spectra in a large number of conjugated polymers yield an almost constant ΔEST value close to 0.7 eV. This is in contrast to the situation in molecules, where the exchange energy is found to depend on molecular size and to vary over a wide range. Quantum‐chemical calculations are performed to address the origin of the constant exchange energy in phenylene‐based conjugated polymers. The electron–hole separation in the lowest singlet and triplet excited states is found to be independent of the π‐conjugated backbone, and saturates for chains longer than a few repeating units, resulting in a constant exchange energy. In shorter conjugated oligomers, confinement of the excitations destabilizes the singlet with respect to the triplet through exchange interactions and leads to a larger and size‐dependent singlet–triplet energy separation.
Synthesis of ZSM‐5 Films and Monoliths with Bimodal Micro/Mesoscopic Structures
Authors: Cho S. I. , Choi S. D. , Kim J.‐H. , Kim G.‐J. 
Published: January 2004

AbstractA route to synthesize ZSM‐5 crystals with a bimodal micro/mesoscopic pore system has been developed in this study; the successful incorporation of the mesopores within the ZSM‐5 structure was performed using tetrapropylammonium hydroxide (TPAOH)‐impregnated mesoporous materials containing carbon nanotubes in the pores, which were encapsulated in the ZSM‐5 crystals during a solid rearrangement process within the framework. Such mesoporous ZSM‐5 zeolites can be readily obtained as powders, thin films, or monoliths.
Emission Characteristics and Performance Comparison of Polyfluorene Lasers with One‐ and Two‐Dimensional Distributed Feedback
Authors: Heliotis G. , Xia R. , Turnbull G. A. , Andrew P. , Barnes W. L. , Samuel I. D. W. , Bradley D. D. C. 
Published: January 2004

AbstractWe report the fabrication of optically pumped solid‐state polymer lasers based on the semiconducting polymer poly(9,9‐dioctylfluorene) (PFO) using resonator structures that offer one‐ and two‐dimensional distributed feedback. The lasers are readily fabricated by solution deposition of thin polymer films on top of suitable grating microstructures etched into fused silica substrates. The devices operate in the blue spectral region, are highly efficient (slope efficiencies as high as 7.8 % are demonstrated), and exhibit very low threshold energies for oscillation (0.8 nJ per pulse). The operating characteristics of the lasers are investigated in detail. The transverse mode profiles and divergence of the output beams are measured and correlated with the internal lasing modes and the feedback mechanism present in the resonators. Additionally, broadband tuning of the emission wavelength over a range of ∼ 40 nm is demonstrated by controlling the supported resonant frequency of the laser cavities.
Templated Synthesis of Carbon Nanofibers from Polyacrylonitrile Using Sepiolite
Authors: Fernández‐Saavedra R. , Aranda P. , Ruiz‐Hitzky E. 
Published: January 2004

AbstractCarbon nanofibers of ca. 1 μm by 20 nm dimensions have been successfully prepared by an improved route, consisting of the graphitization of polyacrylonitrile (PAN) previously formed inside the nanosized pores of sepiolite. This natural microfibrous silicate contains structural tunnels extending along the whole fiber, which are able to include acrylonitrile (AN). This is polymerized to give polyacrylonitrile (PAN), which is further thermally treated to form carbon nanofibers inside the pores. We have clearly shown the mechanisms and the role of the structural tunnels of sepiolite in the adsorption, polymerization, and graphitization of AN by applying spectroscopic techniques as FTIR spectroscopy, 13C NMR spectroscopy, in‐situ EIS (electrochemical impedance spectroscopy), and other structural, textural, and analytical tools (powder X‐ray diffraction (PXRD), scanning transmission electron microscopy–energy‐dispersive X‐ray analysis (STEM–EDX), differential thermal analysis (DTA), thermogravimetric analysis (TG), N2 isotherms, etc.). The resulting solids constitute a new class of conductive carbon–clay nanocomposites, useful for applications in diverse electrochemical devices such as lithium batteries, sensors, or electrocatalysts.
Amide Derivatives of [6‐(5‐Methyl‐3‐phenylpyrazole‐1‐yl)‐3(2H)‐pyridazinone‐2‐yl]acetic Acids as Potential Analgesic and Anti‐Inflammatory Compounds
Authors: Banoglu Erden , Akoğlu Çağla , Ünlü Serdar , Küpeli Esra , Yeşilada Erdem , Şahin M. Fethi 
Published: January 2004

AbstractIn this study, amide derivatives of [6‐(5‐methyl‐3‐phenyl‐pyrazole‐1‐yl)‐3(2H)‐pyridazinone‐2‐yl]acetic acid were synthesized and tested for their in vivo analgesic and anti‐inflammatory activity by using the p‐benzoquinone‐induced writhing test and carrageenan‐induced hind paw edema model, respectively. The analgesic and anti‐inflammatory activity of the compounds 6a, 6d, 6e, 6g, 6h and 6m were more potent than that of aspirin as an analgesic and indomethacin as an anti‐inflammatory drug, respectively. The other derivatives generally resulted in comparable activity to reference compounds. Inhibitor activity of the active compounds on cyclooxygenase isoforms was also investigated by using in vitro human whole blood assay and found that these derivatives did not exert their analgesic and anti‐inflammatory activities through COX inhibition and other mechanisms might be involved.
Synthesis and Structure‐Activity Relationships of 4‐Cycloalkylamino‐1, 2, 4‐triazolo[4, 3‐a]quinoxalin‐1‐ one Derivatives as A1 and A3 Adenosine Receptor Antagonists
Authors: Colotta Vittoria , Catarzi Daniela , Varano Flavia , Filacchioni Guido , Martini Claudia , Trincavelli Letizia , Lucacchini Antonio , Colotta Vittoria 
Published: January 2004

AbstractIn a previous paper (Colotta V. et al., J. Med. Chem. 2000, 43, 1158—1164) we reported the synthesis and binding activity of 4‐cycloalkylamino‐1, 2, 4‐triazolo[4, 3‐a]quinoxalin‐1‐one derivatives, differently substituted on the appended 2‐phenyl ring, some of which were potent and selective A1 adenosine receptor (AR) antagonists. In the present paper several 4‐cycloalkylamino‐2‐phenyl‐1, 2, 4‐triazolo[4, 3‐a]quinoxalin‐1‐one derivatives (1—11), bearing simple substituents on the benzofused moiety, are reported. The binding data of bovine A1 and A2A and human A3 AR show that we have obtained highly potent A1 AR antagonists. In particular, the 4‐cyclohexylamino derivatives 1—5 show higher A1 vs A2A selectivity than the parent compound A, which lacks substituents on the benzofused moiety. Moreover, compounds 1—11 display, in general, good A3 AR affinity. Finally, SAR studies provide some new insights about the steric requirements of the A3 receptor pocket, which accommodates the benzofused moiety of our 4‐amino‐triazoloquinoxalin‐1‐one derivatives.
Flow calorimetry and dielectric spectroscopy to control the bacterial conversion of toxic substrates into polyhydroxyalcanoates
Authors: Maskow Thomas , Olomolaiye Dayo , Breuer Uta , Kemp Richard 
Published: January 2004

AbstractThe microbial conversion of toxic substrates into valuable products in continuous culture requires the equivalent of a tight rope walk between formation of the desired product and intoxication of the microbial catalyst. The condition of the latter is reflected immediately by changes in heat flow rate and β‐dispersion in an electrical RF field. Therefore, these were applied to the example of the continuous growth‐associated synthesis of polyhydroxyalcanoates (PHA) from phenol by the bacterial strain Variovorax paradoxus DSM 4065. By controlling the supply of phenol to the chemostat, the rates of degradation, biomass formation, and synthesis of target product, respectively, were increasingly elevated until the onset of poisoning the organisms. The boundary between the maximum rates and the initiation of intoxication coincided with a sudden change in the heat flux. Using this occurrence, it was possible to develop a control strategy and test it successfully for a time period of 80 h. After 40 h the process stabilized at mean values, i.e., at rates of 92% phenol degradation, 100% biomass formation, and 70 – 75% of PHA formation compared with the situation shortly before poisoning the organisms. Using a moving‐average technique to filter the raw dielectric spectroscope data, changes were followed in biomass concentration of approximately 100 mg/L. However, this technique was not sensitive or rapid enough to control the process. © 2004 Wiley Periodicals, Inc.
Milking microalga Dunaliella salina for β‐carotene production in two‐phase bioreactors
Authors: Hejazi M. A. , Holwerda E. , Wijffels R. H. 
Published: January 2004

AbstractA new method was developed for production of β‐carotene from Dunaliella salina. Cells were grown in low light intensity and then transferred to a production bioreactor illuminated at a higher light intensity. It was a two‐phase bioreactor consisting of an aqueous and a biocompatible organic phase. Mixing of the cells and extraction were performed by recirculation of the organic phase. Two experiments were performed. In the first experiment, bioreactors were operated at two different solvent recirculation rates of 150 and 200 mL min−1. The β‐carotene extraction rate increased significantly at the higher recirculation rate, without exerting any influence on cell number and viability. A second experiment was carried out at a recirculation rate (200 mL min−1) appropriate for the study of long‐term production of β‐carotene. The results show that D. salina at high light intensity remained viable for a long period (>47 days) in the presence of a biocompatible organic phase; however, cell growth was very slow. β‐Carotene could be continuously extracted to the organic phase; the cells continued to produce β‐carotene and the extracted molecules were continuously reproduced. As a result, β‐carotene was continuously removed (“milked”) from the cells. β‐Carotene extraction efficiency in this system was >55%, and productivity was 2.45 mg m−2 day−1, much higher than that of commercial plants. © 2004 Wiley Periodicals, Inc.
Rabies virus production in high vero cell density cultures on macroporous microcarriers
Authors: Yokomizo A. Y. , Antoniazzi M. M. , Galdino P. L. , Azambuja N. , Jorge S. A. C. , Pereira C. A. 
Published: January 2004

AbstractThe purpose of the study was to investigate the rabies virus multiplication in Vero cell cultures performed on porous microcarriers, MCs (cellulose–Cytopore and gelatin–Cultispher G), which provide higher available surface area compared with solid (nonporous) MCs (DEAE–Cytodex 1). In a set of experiments performed at the same MC concentration (MCs per milliliter), cell densities regularly obtained in porous MC cultures were comparable, but almost twice as high as those in solid MC cultures. In addition, 41.1 ± 3.9‐, 35.2 ± 2‐, and 19.6 ± 5.8‐fold increases in cell concentration, relative to the initial cell number, along with maximum rabies virus titers of 6.3 ± 0.3 × 104, 5 ± 0.1 × 104, and 4.3 ± 0.2 × 104 FFD50/mL were observed in Cytopore, Cultispher G, and Cytodex 1 MC cultures, respectively. When higher concentrations of MCs were employed, lower performances of virus production and MC‐cell occupation (cells per MC or cells per square millimeter) were observed. Cell attachment to MCs was shown to be faster for Cytopore MCs and Cytodex 1 MCs than for Cultispher G MCs. Concerning the kinetics of cell multiplication on MCs, exponential cell growth, at similar specific cell growth rates, took place on Cytopore, Cultispher G, and Cytodex 1 MCs. In addition, cell densities as high as 2.1 ± 0.2 × 106 cells/mL on Cytopore MCs, 1.8 ± 0.1 × 106 cells/mL on Cultispher G MCs, and 1 ± 0.3 × 106 cells/mL on Cytodex 1 MCs were regularly obtained in batch cultures. Optical as well as scanning and transmission electron microscopy studies carried out to analyze MC structure, MC cell occupation, and cell permissivity to virus infection demonstrated that there was uniform cell distribution in the external and internal areas of the MCs, suggesting an efficiency of virus synthesis. Our results indicate the usefulness of these supports for rabies virus antigen production, as well as possibilities for further optimization. © 2004 Wiley Periodicals, Inc.
Mosquito and mammalian cells grown on microcarriers for four‐serotype dengue virus production: Variations in virus titer, plaque morphology, and replication rate
Authors: Liu Chia‐Chyi , Wu Suh‐Chin 
Published: January 2004

AbstractDengue (DEN) viruses consisting of four distinct serotypes cause diseases such as dengue fever, dengue hemorrhagic fever, and dengue shock syndrome in humans. Most of the dengue viruses can be effectively propagated in some mosquito and mammalian cell lines. In this study, we applied microcarrier cell culture technology to study two relevant aspects involving dengue virus, one on biotechnology of cell growth and virus production, and the other on virus biology concerning genetic variation of a virus population. We investigated the growth of C6/36 mosquito cells and Vero cells grown on Cytodex 1 microcarriers. High‐titer DEN virus production can be achieved in C6/36 and Vero cells infected at low cell inoculation density, in the lag‐phase cell stage, and at low multiplicity of infection (MOI). The maximum titers produced for DEN‐1, DEN‐3, and DEN‐4 viruses were approximately 10‐ to 10,000‐fold lower than for DEN‐2 virus produced in C6/36 and Vero cells grown on microcarriers. The DEN‐2 virus produced in C6/36 cells displayed far more extensive plaque heterogeneity than in Vero cells. Microcarrier C6/36 mosquito cell culture appeared to be the most effective system for four‐serotype DEN virus production. Interestingly, some selected variants of DEN virus may outgrow in Vero cells when using a T‐flask culture. These results may provide useful information for DEN vaccine development. © 2004 Wiley Periodicals, Inc.
Removal of Mn(II) ions from aqueous neutral media by manganese‐oxidizing fungus in the presence of carbon fiber
Authors: Sasaki Keiko , Konno Hidetaka , Endo Mai , Takano Keishi 
Published: January 2004

AbstractA manganese‐oxidizing fungus was isolated from a hot spring in Japan. The fungus was increasingly effective at oxidizing Mn(II) ions as the concentration of organic carbon sources in the growth medium was decreased. The fungus oxidized 50 ppm of Mn(II) ions within 160 h in a pH 7.3 medium at 25°C. The presence of carbon fiber shortened the time to 80 h, and promoted steady oxidation. The oxidation products were identified by XPS and XRD to be poorly crystallized and amorphous MnO2, both with and without the fiber. These results suggest that the fiber participates in kinetically limited oxidation. The fungus was entangled with and clung to the fibers, and the oxidized Mn species accumulated on the fungus. Similarly shaped polyethylene telephthalate fiber did not enhance the oxidation, nor was adhesion of the fungus observed. Although the mechanism is still unknown, the present work shows that removal of Mn from solution through the precipitation and accumulation of Mn‐oxides on the fungus in the presence of carbon fiber is a promising improvement for water treatment. © 2004 Wiley Periodicals, Inc.
Combinatorial formulation of biocatalyst preparations for increased activity in organic solvents: Salt activation of penicillin amidase
Authors: Lindsay John P. , Clark Douglas S. , Dordick Jonathan S. 
Published: January 2004

AbstractA combinatorial experimental technique was used to identify salts and salt mixtures capable of activating penicillin amidase in organic solvents for the transesterification of phenoxyacetate methyl ester with 1‐propanol. Penicillin amidase was lyophilized in the presence of various chloride and acetate salts within 96‐deep‐well plates and catalytic rates measured to determine lead candidates for highly salt‐activated preparations. The kinetics of the most active formulations were then further evaluated. These studies revealed that a formulation consisting of 98% (w/w) of a 1:1 KAc:CsCl salt mixture, 1% (w/w) enzyme, and 1% (w/w) potassium phosphate buffer was ∼35,000‐fold more active than the salt‐free formulation in hexane, as reflected in values of Vmax/Km. This extraordinary activation could be extended to more polar solvents, including tert‐amyl alcohol, and to formulations with lower total salt contents. A correlation was found between the kosmotropic/chaotropic behavior of the salts (as measured by the Jones‐Dole B coefficients) and the observed activation. Strongly chaotropic cations combined with strongly kosmotropic anions yielded the greatest activation, and this is likely due to the influence of the ions on protein–water and protein–salt interactions. © 2004 Wiley Periodicals, Inc.
Thermal and enzymatic pretreatment of sludge containing phthalate esters prior to mesophilic anaerobic digestion
Authors: Gavala Hariklia N. , Yenal Umur , Ahring Birgitte K. 
Published: January 2004

AbstractThe present study aimed at investigating the effect of thermal pretreatment of sludge at 70°C on the anaerobic degradation of three commonly found phthalic acid esters (PAE): di‐ethyl phthalate (DEP), di‐butyl phthalate (DBP), and di‐ethylhexyl phthalate (DEHP). Also, the enzymatic treatment at 28°C with a commercial lipase was studied as a way to enhance PAE removal. Pretreatment at 70°C of the sludge containing PAE negatively influenced the anaerobic biodegradability of phthalate esters at 37°C. The observed reduction of PAE biodegradation rates after the thermal pretreatment was found to be proportional to the PAE solubility in water: the higher the solubility, the higher the percentage of the reduction (DEP > DBP > DEHP). PAE were slowly degraded during the pretreatment at 70°C, yet this was probably due to physicochemical reactions than to microbial/biological activity. Therefore, thermal pretreatment of sludge containing PAE should be either avoided or combined with a treatment step focusing on PAE reduction. On the other hand, enzymatic treatment was very efficient in the removal of PAE. The enzymatic degradation of DBP, DEP, and DEHP could be one to two orders of magnitude faster than under normal mesophilic anaerobic conditions. Moreover, the enzymatic treatment resulted in the shortest half‐life of DEHP in sludge reported so far. Our study further showed that enzymatic treatment with lipases can be applied to raw sludge and its efficiency does not depend on the solids concentration. © 2004 Wiley Periodicals, Inc.
High‐level accumulation of a recombinant antibody fragment in the periplasm of Escherichia coli requires a triple‐mutant (degP prc spr) host strain
Authors: Chen Christina , Snedecor Brad , Nishihara Julie C. , Joly John C. , McFarland Nancy , Andersen Dana C. , Battersby John E. , Champion Kathleen M. 
Published: January 2004

AbstractDuring production of a humanized antibody fragment secreted into the periplasm of Escherichia coli, proteolytic degradation of the light chain was observed. In order to determine which protease(s) were responsible for this degradation, we compared expression of the F(ab′)2 antibody fragment in several E. coli strains carrying mutations in genes encoding periplasmic proteases. Analysis of strains cultured in high cell density fermentations showed that the combination of mutations in degP prc spr was necessary for the cells to produce high levels of the desired recombinant antibody fragment. In order to eliminate the possible effects of mutations in other genes, we constructed E. coli strains with protease mutations in isogenic backgrounds and repeated the studies in high cell density fermentations. Extensive light chain proteolysis persisted in degP strains. However, light chain proteolysis was substantially decreased in prc and prc spr strains, and was further decreased with the introduction of a degP mutation in prc and prc spr mutant strains. These results show that the periplasmic protease Prc (Tsp) is primarily responsible for proteolytic degradation of the light chain during expression of a recombinant antibody fragment in E. coli, and that DegP (HtrA) makes a minor contribution to this degradation as well. The results also show that spr, a suppressor of growth defects in prc strains, is required for a prc mutant to survive throughout high cell density fermentations. © 2004 Wiley Periodicals, Inc.
Inadvertent perforation during rectal cancer resection in Norway
Authors: Eriksen M T , Wibe A , Syse A , Haffner J , Wiig J N 
Published: January 2004

Abstract

Background
Inadvertent perforation of the bowel or tumour is a relatively common complication during resection of rectal cancer. The purpose of this study was to examine intraoperative perforation following the introduction of mesorectal excision as a standard surgical technique in Norway.

Methods
This was a prospective national cohort study of 2873 patients undergoing major resection of rectal carcinoma at 54 Norwegian hospitals from November 1993 to December 1999.

Results
The overall perforation rate was 8·1 per cent (234 of 2873 patients). In a multivariate analysis, the risk of perforation was significantly greater in patients undergoing abdominoperineal resection (odds ratio (OR) 5·6 (95 per cent confidence interval (c.i.) 3·5 to 8·8)) and in those aged 80 years or more (OR 2·0 (95 per cent c.i. 1·2 to 3·5)). The 5-year local recurrence rate was 28·8 per cent following perforation, compared with 9·9 per cent in patients with no perforation (P &lt; 0·001); survival rates were 41·5 and 67·1 per cent respectively (P &lt; 0·001).

Conclusion
The risk of intraoperative perforation was significantly greater in patients with rectal cancer undergoing abdominoperineal resection and in those aged 80 years or more. The high local recurrence rates and reduced survival following perforation call for increased attention to avoid this complication.