bluuebunny/crossref_metadata_2025_split huggingface dataset:
X‐ray and optical properties of X‐ray sources in the 13hr XMM‐Newton/Chandra deep survey
Authors: Page M.J. , McHardy I.M. , Gunn K.F. , Loaring N.S. , Mason K.O. , Sasseen T. , Newsam A. , Ware A. , Kennea J. , Sekiguchi K. , Takata T. 
Published: February 2003

AbstractThe 13hr XMM‐Newton/Chandra deep survey is the first of two extremely deep XMM‐Newton fields observed by the XMM‐OM consortium. A 120 ks Chandra mosaic, covering 0.2 deg2 , provides sensitive, confusion‐free point source detection with sub‐arcsecond positions, while the 200 ks XMM‐Newton observation provides high quality X‐ray spectroscopy over the same sky area. We have optical spectroscopic identifications for 70 X–ray sources. Of these, 42 are broad emissionline AGN with a wide range of redshifts. The optical counterparts of a further 23 sources are narrow emission line galaxies and absorption line galaxies. These 23 sources all lie at z < 1 and typically have lower X–ray luminosities than the broad‐line AGN. About half of them show significant X–ray absorption and are almost certainly intrinsically absorbed AGN. However some of them have unabsorbed, AGN‐like, power‐law components in their X–ray spectra, but do not show broad emission lines in their optical spectra. These sources may be weak, unobscured AGN in bright galaxies and their existence at low redshifts could be a consequence of the strong cosmological evolution of AGN characteristic luminosities.
Radio observations of the XMM‐Newton/Chandra 13hr deep survey field
Authors: Gunn K.F. , McHardy I.M. , Seymour N. , Newsam A.M. , Page M.J. , Mason K.O. , Loaring N. , Jones L.R. , Muxlow T. , Takata T. , Sekiguchi K. , Sasseen T. 
Published: February 2003

AbstractOur VLA observations of the XMM‐Newton/Chandra 13hr deep survey field (see Page et al., this proceedings) result in one of the two deepest 1.4GHz radio maps ever made. Within the 15′ radius field covered by the deep X‐ray data (0.19 deg2 ), a total of 556 radio sources are detected, down to a 4σ flux limit of 28μJy. Of the 214 Chandra sources, 55 have radio counterparts. The sub‐arcsecond accuracy of the VLA and Chandra positions enable us to determine with high confidence the sources common to both surveys. Here we present the relationship between the X‐ray and radio source populations at the faintest radio flux limits yet probed by such a study. We discuss how the X‐ray/radio relationship differs as a function of optical morphology, ie between unresolved ‘stellar’ objects and well resolved galaxies. We then discuss the origin of the X‐ray and radio emission, ie AGN, starburst or a mixture of both, in these two classes of object.
Optical and near‐infrared observations of hard serendipitous Chandra sources
Authors: Crawford C.S. , Gandhi P. , Fabian A.C. 
Published: February 2003

AbstractWe have been carrying out a successful observational programme targeted at finding the highly obscured quasars that are thought to be the main contributors to the hard X‐ray background. Out of 56 sources so far studied with optical and near‐infrared imaging and spectroscopy, we have found three definite and a further twelve possible Type II quasars. Few sources show significant line emission, suggesting that the line photons are depleted by the large columns of obscuring matter. The redshift distribution of our sources shows a distinct peak at z ∼ 1. The broad‐band colours and magnitudes of the optical/near‐infrared counterparts indicate that the light in these bands is dominated by the continuum of a massive bright galaxy.
A Chandra survey of nearby spiral galaxies
Authors: Kilgard R.E. , Krauss M.I. , Kaaret P. , Prestwich A.H. , Ward M.J. 
Published: February 2003

AbstractWe present results from a Chandra survey of 11 nearby, face‐on spiral galaxies. 24 observations totalling 900 ks of new and archival Chandra data reveal more than 1000 X‐ray point sources associated with the galaxies, diffuse emission, and hundreds of serendipitous sources.We discuss source populations and luminosity functions and show that the slope of the X‐ray luminosity function is correlated with the star formation rate in the galaxies. We also discuss ultraluminous X‐ray sources in comparison with sources within the Milky Way. Finally, we discuss ongoing work on source classification based upon X‐ray colors and spectra, position within the host galaxies, and multiwavelenth counterparts.
Effect of yeast extract on speciation and bioavailability of nickel and cobalt in anaerobic bioreactors
Authors: Gonzalez‐Gil G. , Jansen S. , Zandvoort M. H. , van Leeuwen H. P. 
Published: February 2003

AbstractThe speciation of metals plays an important role in their bioavailability. In the case of anaerobic reactors for the treatment of wastewaters, the ubiquitous presence of sulfide leads to extensive precipitation of metals like nickel and cobalt, which are essential for the metabolism of the anaerobic microorganisms that carry out the mineralization of the pollutants present in the wastewater. In practice, nickel, cobalt, and iron are added in excessive amounts to full‐scale installations. This study is concerned with the complexation of nickel and cobalt with yeast extract and its effect on the biogas production by methanogenic biomass. Adsorptive stripping voltammetry (AdSV) was used to get information about the stability and complexing capacity of the metal–yeast extract complexes formed. Nickel and cobalt form relatively strong organic complexes with yeast extract. The bioavailability of these essential metals in anaerobic batch reactors was dramatically increased by the addition of yeast extract. This is due to the formation of dissolved bioavailable complexes, which favors the dissolution of metals from their sulfides. Trace doses of yeast extract may be effective in keeping additions of essential metals to anaerobic reactors at a minimum. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 134–142, 2003.
Size‐exclusion reaction chromatography (SERC): A new technique for protein PEGylation
Authors: Fee Conan J. 
Published: February 2003

AbstractA new, widely applicable process that combines reaction and separation in a single unit operation is described. The process, size‐exclusion reaction chromatography (SERC), simultaneously allows control of the extent of reactions in which molecular size is altered and the separation of products and reactants. In SERC, a moving reaction zone is formed by injection of reactants onto a size‐exclusion chromatography column. Reactants and products are partitioned differently within the mobile phase, resulting in different linear flow rates through the column. The products are therefore removed selectively from the reaction zone, minimizing their residence time in the reaction zone and allowing their separation in the downstream section of the column. For reactions such as protein PEGylation, in which successive addition of PEG groups to the protein results in significant molecular size increases, SERC potentially offers a method by which a dominant final PEGylated protein size can be produced at high yield. The SERC PEGylation of two model proteins, α‐lactalbumin and β‐lactoglobulin, is demonstrated and results show that simultaneous reaction and separation was obtained. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 200–206, 2003.
Microalgae cultivation in air‐lift reactors: Modeling biomass yield and growth rate as a function of mixing frequency
Authors: Barbosa Maria J. , Janssen Marcel , Ham Nienke , Tramper Johannes , Wijffels René H. 
Published: February 2003

AbstractThe slow development of microalgal biotechnology stems from the failure in the design of large‐scale photobioreactors where light energy is efficiently utilized. Due to the light gradient inside the reactor and depending on the mixing properties, algae are subjected to certain light/dark cycles where the light period is characterized by a light gradient. These light/dark cycles will determine productivity and biomass yield on light energy. Air‐lift reactors can be used for microalgae cultivation and medium‐frequency light/dark cycles will be found in these systems. Light/dark cycles are associated with two basic parameters: first, the light fraction, i.e., the ratio between the light period and the cycle time and second, the frequency of the light/dark cycle. In the present work, light/dark cycles found in air‐lift reactors were simulated taking into account the light gradient during the light period. The effect of medium‐frequency cycle time (10–100 s) and light fraction (0.1–1) on growth rate and biomass yield on light energy of the microalgae Dunaliella tertiolecta was studied. The biomass yield and growth rates were mainly affected by the light fraction, while cycle time had little influence. Response surface methodology was used and a statistical model describing the effect of light fraction and cycle time on growth rate and biomass yield on light energy was developed. The use of the model as a reactor design criterion is discussed. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 170–179, 2003.
The effect of dissolved oxygen on PHB accumulation in activated sludge cultures
Authors: Third Katie A. , Newland Mark , Cord‐Ruwisch Ralf 
Published: February 2003

AbstractNitrogen removal from wastewater is often limited by the availability of reducing power to perform denitrification, especially when treating wastewaters with a low carbon:nitrogen ratio. In the increasingly popular sequencing batch reactor (SBR), bacteria have the opportunity to preserve reducing power from incoming chemical oxygen demand (COD) as poly‐β‐hydroxybutyrate (PHB). The current study uses laboratory experiments and mathematical modeling in an attempt to generate a better understanding of the effect of oxygen on microbial conversion of COD into PHB. Results from a laboratory SBR with acetate as the organic carbon source showed that the aerobic acetate uptake process was oxygen‐dependent, producing higher uptake rates at higher dissolved oxygen (DO) supply rates. However, at the lower DO supply rates (kLa 6 to 16 h−1, 0 mg L−1 DO), a higher proportion of the substrate was preserved as PHB than at higher DO supply rates (kLa 30, 51 h−1, DO >0.9 mg L−1). Up to 77% of the reducing equivalents available from acetate were converted to PHB under oxygen limitation (YPHB/Ac 0.68 Cmol/Cmol), as opposed to only 54% under oxygen‐excess conditions (YPHB/Ac 0.48 Cmol/Cmol), where a higher fraction of acetate was used for biomass growth. It was calculated that, by oxygen management during the feast phase, the amount of PHB preserved (1.4 Cmmol L−1 PHB) accounted for an additional denitrification potential of up to 18 mg L−1 nitrate‐nitrogen. The trends of the effect of oxygen (and hence ATP availability) on PHB accumulation could be reproduced by the simulation model, which was based on biochemical stoichiometry and maximum rates obtained from experiments. Simulated data showed that, at low DO concentrations, the limited availability of adenosine triphosphate (ATP) prevented significant biomass growth and most ATP was used for acetate transport into the cell. In contrast, high DO supply rates provided surplus ATP and hence higher growth rates, resulting in decreased PHB yields. The results suggest that oxygen management is crucial to conserving reducing power during the feast phase of SBR operation, as excessive aeration rates decrease the PHB yield and allow higher biomass growth. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 238–250, 2003.
Immobilization of thermolysin to polyamide nonwoven materials
Authors: Moeschel Klaus , Nouaimi Meryem , Steinbrenner Christa , Bisswanger Hans 
Published: February 2003

AbstractIn the last few years, an increasing number of biotechnological techniques have been applied to the restoration and conservation of works of art, paintings, old maps, and papers or books. Enzymes can solve problems that give restorers difficulties, although for many applications it is not possible to use soluble enzymes; therefore, it is necessary to look for suitable carriers for immobilization. Different methods for covalent immobilization of enzymes to polyamide nonwovens were tested, using thermolysin as an example. Two distinct strategies were pursued: (1) controlled, partial hydrolysis of the polymer and subsequent binding of the enzyme to the released amino and carboxy groups; and (2) attachment of reactive groups directly to the polyamide without disintegrating the polymeric structure (O‐alkylation). Different spacers were used for covalent fixation of the enzyme in both cases. The enzyme was fixed to the released amino groups by glutaraldehyde, either with or without a spacer. Either way, active enzyme could be immobilized to the matrix. However, intense treatment caused severe damage to the stability of the nonwoven fabric, and reduced the mechanical strength. Conditions were investigated to conserve the nonwoven fabric structure while obtaining near‐maximum immobilized enzyme activity. Immobilization of the enzyme to the released carboxy group after acid hydrolysis was performed using dicyclohexylcarbodiimide. In comparison to the enzyme bound via the amino group, the yield of immobilized enzyme activity was slightly lower when benzidine was taken as spacer and still lower with a 1,6‐hexanediamine spacer. O‐alkylation performed with dimethylsulfate caused severe damage to the nonwoven fabric structure. Considerably better results were obtained with triethyloxonium tetrafluoroborate. As the spacers 1,6‐hexanediamine and adipic acid dihydrazide were used, activation for immobilizing thermolysin was performed with glutaraldehyde, adipimidate, and azide. With the exception of azide, all combinations of spacers and activation reagents gave high yields of immobilized enzyme activity. Thermolysin immobilized by this technique showed a remarkably improved stability with respect to elevated temperature, extreme pH values, and reduced polarity. The nonwoven fabric can be stored for weeks without loss of enzyme activity by washing with distilled water and drying. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 82: 190–199, 2003.
Correct assignment of homology is crucial when genomics meets molecular evolution
Authors: Zouine Mohamed , Sculo Quentin , Labedan Bernard 
Published: February 2003

AbstractPertinent evolutionary studies are based on a correct use of homology terms such as paralogues, metalogues and orthologues. Such crucial concepts have been applied to intragenomic and intergenomic analyses. A further requisite is a proper definition of what is a structural segment of homology. Such segments are called modules to reflect that they play a role in the mechanism of combinational construction of a gene from ready‐made basic components. Since identifying a module is operationally equivalent to determining the ancestor to this gene segment, it becomes possible to track back protein history and genome evolution. Such studies underline the importance of two fundamental processes, gene duplication and gene fusion. Moreover, grouping the closest orthologues in families is a pertinent way to reconstruct a genomic tree for all available prokaryotes. Copyright © 2002 John Wiley & Sons, Ltd.
Meeting review: Intelligent Systems for Molecular Biology 2002 (ISMB02)
Authors: Cara Woodwark K. 
Published: February 2003

AbstractThis report profiles the keynote talks given at ISMB02 in Edmonton, Canada, by Michael Ashburner, Barry Honig, Isidore Rigoutsos, Ford Doolittle, Stephen Altschul, Terry Gaasterland, John Reinitz, and the Overton Prize winner, David Baker. Copyright © 2002 John Wiley & Sons, Ltd.
In vivo mapping of fractional plasma volume (fpv) and endothelial transfer coefficient (Kps) in solid tumors using a macromolecular contrast agent: Correlation with histology and ultrastructure
Authors: Marzola Pasquina , Farace Paolo , Calderan Laura , Crescimanno Caterina , Lunati Ernesto , Nicolato Elena , Benati Donatella , Degrassi Anna , Terron Andrea , Klapwijk Jan , Pesenti Enrico , Sbarbati Andrea , Osculati Francesco 
Published: February 2003

AbstractContrast‐enhanced MRI, immunostaining and electron microscopy were used to detect areas of intense angiogenesis in experimental tumors. This work was also aimed at evaluating the possible effect of the surrounding tissues on tumor microvasculature and at studying the penetration of macromolecules in avascular areas. Human colon carcinoma cells were implanted in subcutaneous tissue of nude mice. Dynamic T1‐weigthed 3D pulse sequences were acquired before and after administration of Gd‐DTPA‐albumin to obtain parametric maps of fractional plasma volume (fpv) and transendothelial permeability (Kps). The maps suggested that tumor can be subdivided into 4 zones located in the peripheral rim (zones I–II) or in the core (zones III–IV) of the tumor itself. Significant differences (p<0.001) were found in the values of Kps and fpv of zones I–II with respect to zones III–IV. In the peripheral rim, permeability was significantly higher (p<0.01) in the muscle‐peripheral region (zone I) with respect to the skin‐peripheral region (zone II). In areas with high Kps, histological and ultrastructural examination revealed clusters of newly formed vessels and signs of intense permeability. Numerous vascular vesicular organs were visible in these areas. In the tumoral core, analysis of the microcirculatory parameters revealed regions with mild permeability (zone III) and regions with negligible permeability (zone IV). These 2 zones were discriminated by the average value of Kps (p<0.05), while their fpv was not significantly different. Upon histological examination, the tumoral core exhibited necrotic areas; CD31 immunocytochemistry exhibited that it was diffusely hypovascularized with large avascular areas. Upon ultrastructural examination, capillaries were rarely visible and exhibited signs of endothelial cell damage. The results suggest that segmentation based on microvascular parameters detects in vivo zones characterized by immunocytochemical and ultrastructural aspects of intense angiogenesis. The finding that a certain amount of contrast agent penetrates in the tumoral core suggests that high oncotic and hydrostatic pressure only partially hinders the penetration of macromolecules. © 2003 Wiley‐Liss, Inc.
Prostate cancer and exposure to pesticides in agricultural settings
Authors: Settimi Laura , Masina Alceste , Andrion Alberto , Axelson Olav 
Published: February 2003

AbstractOur study evaluates the association between prostate cancer and exposure to pesticides in agricultural settings in Italy. The data were derived from a hospital‐based multi‐site case‐control study carried out in 5 rural areas between 1990–92. In our study, 124 new cases of prostate cancer were ascertained and interviewed, along with 659 cancer controls. A team of agronomists assessed past exposure to pesticides by using a checklist of 100 chemical families and 217 compounds applied from 1950–85 in the areas considered. The association between prostate cancer and different occupational risk factors was measured by maximum likelihood estimation of the odds ratio, controlling for potential confounders. “Ever been employed in agriculture” was associated with a 40% increased risk (OR = 1.4, 95% CI = 0.9–2.0). Prostate cancer was also related positively to food and tobacco (OR= 2.1, 95% CI = 1.1–4.1), and chemical products (OR = 2.2, 95% CI = 0.7–7.2) industries. The analyses carried out to estimate the association between different types of pesticides and prostate cancer showed increased risks among farmers exposed to organochlorine insecticides and acaricides (OR = 2.5, 95% CI = 1.4–4.2), more specifically to the often contemporary used compounds DDT (OR = 2.1, 95% CI = 1.2–3.8), and dicofol (OR = 2.8, 95% CI = 1.5–5.0), whose effects could not be well separated. © 2003 Wiley‐Liss, Inc.
Usage of the NF‐κB inhibitor sulfasalazine as sensitizing agent in combined chemotherapy of pancreatic cancer
Authors: Müerköster Susanne , Arlt Alexander , Witt Maike , Gehrz André , Haye Sieglinde , March Christina , Grohmann Frauke , Wegehenkel Kai , Kalthoff Holger , Fölsch Ulrich R. , Schäfer Heiner 
Published: February 2003

AbstractSulfasalazine is commonly used as an anti inflammatory agent and is known as a potent inhibitor of NF‐κB. Some pancreatic carcinomas are characterized by a constitutively elevated NF‐κB activity accounting for chemoresistance. To elucidate whether blockade of NF‐κB activity with sulfasalazine is suitable for overcoming this chemoresistance in vivo, we employed a mouse model with subcutaneously xenotransplanted human Capan‐1 pancreatic carcinoma cells. Fourteen days upon tumor inoculation, animals were randomized in 6 groups, receiving no treatment, treatment with gemcitabine or with etoposide, either alone or in combination with sulfasalazine, or with sulfasalazine alone. Two therapy regimens were given with a 7‐day interval in between. Upon treatment with etoposide or gemcitabine alone, tumor sizes were moderately reduced to 65–68% and 50–65%, respectively, as compared to untreated tumors. Sulfasalazine alone only decreased temporarily the tumor sizes. Sulfasalazine in combination with gemcitabine showed only partially higher reduction in tumor sizes than gemcitabine alone, whereas the combination with etoposide reduced significantly the tumor sizes in all experiments (down to 20%). TUNEL‐staining showed higher numbers of apoptotic cells in tumors from the combination groups, in particular with etoposide, and proliferation as indicated by Ki67 staining was strongly reduced. Furthermore, combined treatment of sulfasalazine with the cytostatic drugs led to a decreased blood vessel density. Immunohistochemical staining of the activated p65 subunit showed that sulfasalazine treatment abolished the basal NF‐κB activity in tumor xenografts. These data imply that the well established anti‐inflammatory drug sulfasalazine sensitizes pancreatic carcinoma cells to anti cancer drugs, in particular to etoposide in vivo by inhibition of NF‐κB. This combined chemotherapy offers great potential for improved anti‐tumor responses in pancreatic carcinomas. © 2003 Wiley‐Liss, Inc.
Disulfiram‐mediated inhibition of NF‐κB activity enhances cytotoxicity of 5‐fluorouracil in human colorectal cancer cell lines
Authors: Wang Weiguang , McLeod Howard L. , Cassidy James 
Published: February 2003

Abstract5‐Fluorouracil (5‐FU) is the major chemotherapeutic component for colorectal cancer (CRC) and other types of solid tumours. Resistance of cancer cells to 5‐FU is considered the major obstacle for successful chemotherapy. NF‐κB is a transcription factor. Cancer cells with high NF‐κB nuclear activity demonstrate robust chemo‐ and radio‐resistance. We demonstrated that nuclear NF‐κB activity in CRC cell lines, DLD‐1 and RKOWT, was significantly induced by 5‐FU in a concentration‐ and time‐dependent manner. 5‐FU induced IκBα degradation and promoted both NF‐κB nuclear translocation and its DNA binding activity. 5‐FU treatment did not influence the activities of AP‐1, AP‐2, Oct‐1, SP‐1, CRE‐B and TFIID. Disulfiram (DS), a clinically used anti‐alcoholism drug, strongly inhibited constitutive and 5‐FU‐induced NF‐κB activity in a dose‐dependent manner. DS inhibited both NF‐κB nuclear translocation and DNA binding activity but had no effect on 5‐FU‐induced IκBα degradation. Used in combination, DS significantly enhanced the apoptotic effect of 5‐FU on DLD‐1 and RKOWT cell lines and synergistically potentiated the cytotoxicity of 5‐FU to both cell lines. DS also effectively abolished 5‐FU chemoresistance in a 5‐FU resistant cell line H6305‐FU in vitro. As DS has extensive preclinical and clinical experience, translating its anticancer usage from in vitro study to clinical trials is relatively straightforward. © 2003 Wiley‐Liss, Inc.