bluuebunny/crossref_metadata_2025 huggingface dataset:
Stellar X‐ray surveys and Galaxy structure
Authors: Micela G.
Published: February 2003

Soft X‐ray surveys are very effective to study low‐mass stellar populations in our Galaxy. Indeed stellar X‐ray counts well complement optical stellar counts since they allow us to study spatial distributions and densities of main sequence stars as function of age. This capability is due to the strong dependence of X‐ray luminosity on stellar age, especially during the main sequence life. As a consequence X‐ray surveys oversample young stars, detectable at large distances, permitting to study the spatial characteristics of these populations and the stellar birthrate in the solar neighborhood in the last billion year. In this context both low and high latitude X‐ray surveys play an important role, since low‐latitude surveys allow us to determine the stellar density as a function of age on the Plane, while high latitude surveys constrain the scale heights of the different populations. The comparison of the results at various latitudes can constrain the recent star formation history in the solar neighborhood. I will discuss which improvements the Chandra and XMM‐Newton surveys can provide in our knowledge of stellar populations, and some preliminary results from new ongoing surveys.
Deep XMM‐Newton survey of M33
Authors: Pietsch W. , Ehle M. , Haberl F. , Misanovic Z. , Trinchieri G.
Published: February 2003

In an XMM‐Newton raster observation of the bright local group spiral galaxy M33 we study the population of X‐ray sources (X‐ray binaries, supernova remnants, super‐shells) down to a 0.5–10 keV luminosity of 1035 erg s–1 – more than a factor of 10 deeper than earlier ROSAT observations. EPIC spectra and hardness ratios are used to distinguish between different source classes.We confirmed the 3.45 d orbital light curve of the X‐ray binaryM33 X7, detected a transient super‐soft source in M33, and searched for short term variability of the brighter sources. We characterize the diffuse X‐ray component that is correlated with the inner disk and spiral arms. We will compare the results with other nearby galaxies.
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

The 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

Our 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

We 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

We 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

The 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

A 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

The 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

Nitrogen 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

In 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

Pertinent 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

This 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

Contrast‐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

Our 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

Sulfasalazine 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

5‐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.
Methylation pattern of HLTF gene in digestive tract cancers
Authors: Hibi Kenji , Nakayama Hiroshi , Kanyama Yasuaki , Kodera Yasuhiro , Ito Katsuki , Akiyama Seiji , Nakao Akimasa
Published: February 2003

Recently, the loss of helicase‐like transcription factor (HLTF) gene expression accompanied by HLTF promoter methylation was identified in colon cancers. We examined HLTF methylation in colorectal, gastric and esophageal carcinomas. Twenty‐five of 76 colorectal cancers (33%), 11 of 65 gastric cancers (17%), and 1 of 40 esophageal cancers (3%) demonstrated abnormal methylation of the HLTF promoter. Abnormal methylation was found in the tumors of patients at all clinical stages, suggesting that these cancers could be methylated from an early stage. These results suggested that HLTF might play a variety of roles depending on the tissue type and could be inactivated at an early stage in the tumorigenic pathway. © 2003 Wiley‐Liss, Inc.
Designs arising from Buekenhout‐Metz unitals
Authors: Aguglia A.
Published: February 2003

An affine 2–(q3,q2, q + 1) design is constructed from a Buekenhout‐Metz unital of the affine plane AG(2,q2), with q > 2. It is also shown that such a design is isomorphic to the point‐plane design of the affine space AG(3,q). © 2003 Wiley Periodicals, Inc. J Combin Designs 11: 79–88, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jcd.10010
Nowhere‐zero 3‐flows in locally connected graphs
Authors: Lai Hong‐Jian
Published: February 2003

Let G be a graph. For each vertex v ∈V(G), Nv denotes the subgraph induces by the vertices adjacent to v in G. The graph G is locally k‐edge‐connected if for each vertex v ∈V(G), Nv is k‐edge‐connected. In this paper we study the existence of nowhere‐zero 3‐flows in locally k‐edge‐connected graphs. In particular, we show that every 2‐edge‐connected, locally 3‐edge‐connected graph admits a nowhere‐zero 3‐flow. This result is best possible in the sense that there exists an infinite family of 2‐edge‐connected, locally 2‐edge‐connected graphs each of which does not have a 3‐NZF. © 2003 Wiley Periodicals, Inc. J Graph Theory 42: 211–219, 2003
Size ramsey numbers of stars versus 4‐chromatic graphs
Authors: Pikhurko Oleg
Published: February 2003

We investigate the asymptotics of the size Ramsey number î(K1,nF), where K1,n is the n‐star and F is a fixed graph. The author 11 has recently proved that r̂(K1,n,F)=(1+o(1))n2 for any F with chromatic number χ(F)=3. Here we show that r̂(K1,n,F)≤ ${\chi (F)(\chi(F)-2)}\over{2}$ n2+o(n2), if χ (F) ≥ 4 and conjecture that this is sharp. We prove the case χ(F)=4 of the conjecture, that is, that r̂(K1,n,F)=(4+o(1))n2 for any 4‐chromatic graph F. Also, some general lower bounds are obtained. © 2003 Wiley Periodicals, Inc. J Graph Theory 42: 220–233, 2003
Kif1Bβ isoform is enriched in motor neurons but does not change in a mouse model of amyotrophic lateral sclerosis
Authors: Conforti Laura , Dell'Agnello Carlotta , Calvaresi Novella , Tortarolo Massimo , Giorgini Andrea , Coleman Michael P. , Bendotti Caterina
Published: February 2003

The kinesin superfamily motor protein Kif1B is expressed in two isoforms, Kif1Bα and Kif1Bβ, with distinct cargo‐binding domains. We examined the mRNA distribution of the two isoforms in adjacent sections of brain and spinal cord of adult mice using in situ hybridization analysis. Kif1Bβ mRNA is enriched in several regions of brain and spinal cord. Its levels are four to five times higher than that of the α isoform, which was barely detectable. The highest mRNA levels of Kif1Bβ were found in the cortex, hippocampus, cerebellum and the grey matter of the spinal cord. At the cellular level the highest signal was found in motor neurons in the motor nuclei of medulla oblongata and the ventral horn of spinal cord. Because expression of other Kif genes is altered in amyotrophic lateral sclerosis (ALS) models, we examined the expression level of Kif1Bβ mRNA in the spinal cord of transgenic mice carrying the SOD1G93A mutation, a model of familial ALS, at presymptomatic and early stages of the disease. No changes were observed in Kif1Bβ mRNA in motor neurons or in other regions of the spinal cord. These findings indicate that Kif1Bα, which modulates the transport of mitochondria, may play a major role in tissues other than the central nervous system. Instead Kif1Bβ, responsible for the transport of synaptic vesicle precursors, seems to play an important role in the nervous system, particularly in the lower motor neurons. The absence of changes of Kif1Bβ mRNA in transgenic SOD1G93A mice suggests that other molecular mechanisms may play a role in the disruption of axonal transport occurring in the motor neurons of these mice. © 2002 Wiley‐Liss, Inc.
Chlamydia pneumoniae infection promotes the transmigration of monocytes through human brain endothelial cells
Authors: MacIntyre A. , Abramov R. , Hammond C.J. , Hudson A.P. , Arking E.J. , Little C.S. , Appelt D.M. , Balin B.J.
Published: February 2003

We have investigated the effects of Chlamydia pneumoniae on human brain endothelial cells (HBMECs) and human monocytes as a mechanism for breaching the blood‐brain barrier (BBB) in Alzheimer's disease (AD). HBMECs and peripheral blood monocytes may be key components in controlling the entry of C. pneumoniae into the human brain. Our results indicate that C. pneumoniae infects blood vessels and monocytes in AD brain tissues compared with normal brain tissue. C. pneumoniae infection stimulates transendothelial entry of monocytes through HBMECs. This entry is facilitated by the up‐regulation of VCAM‐1 and ICAM‐1 on HBMECs and a corresponding increase of LFA‐1, VLA‐4, and MAC‐1 on monocytes. C. pneumoniae infection in HBMECs and THP‐1 monocytes up‐regulates monocyte transmigration threefold in an in vitro brain endothelial monolayer. In this way, C. pneumoniae infection in these cell types may contribute to increased monocyte migration and promote inflammation within the CNS resulting from infection at the level of the vasculature. Thus, infection at the level of the vasculature may be a key initiating factor in the pathogenesis of neurodegenerative diseases such as sporadic AD. © 2002 Wiley‐Liss, Inc.
Altered expression of randomly selected genes in mouse hippocampus after traumatic brain injury
Authors: Long Yan , Zou Linglong , Liu Hao , Lu Holly , Yuan Xiaoqing , Robertson Claudia S. , Yang Keyi
Published: February 2003

Using a cDNA microarray method, we analyzed gene expression profiles in mouse hippocampus after traumatic brain injury (TBI). Of 6,400 randomly selected arrayed genes and expressed sequence tags from a mouse cDNA library, 253 were found to be differentially expressed (106 increased and 147 decreased). Genes involved in cell homeostasis and calcium signaling were primarily up‐regulated while those encoding mitochondrial enzymes, metabolic molecules, and structural proteins were predominantly down‐regulated. Equal numbers of genes related to inflammatory reactions showed increased or decreased expression. Importantly, a large proportion of the dysregulated genes we identified have not been reported as differentially expressed in TBI models. Semiquantitative reverse‐transcriptase polymerase chain reaction (RT‐PCR) analyses of representative genes confirmed the validity of the corresponding microarray findings. Thus, our microarray‐based evaluation of gene expression in traumatically injured hippocampus identified both known and novel genes that respond to TBI. Further investigation of these candidate molecules may suggest new ways to attenuate the traumatic effects of brain injury. © 2002 Wiley‐Liss, Inc.
Differential expression of connexin 43 in the chick tangential vestibular nucleus
Authors: Popratiloff Anastas , Pollack Seth M. , Giaume Christian , Peusner Kenna D.
Published: February 2003

The chick tangential nucleus is a major vestibular nucleus whose principal cells receive convergent inputs from primary vestibular and nonvestibular fibers and participate in the vestibular reflexes. During development, the principal cells gradually acquire the mature firing pattern in part by losing a specific potassium current around hatching (H). Here we focus on characterizing the expression of connexin 43 (Cx43), a gap junction protein found mainly between astrocytes in the mature brain. The astrocytic syncytium plays an important role in maintaining extracellular potassium ion balance in the brain. Accordingly, it is important to characterize the potential of this syncytium to communicate during the critical developmental age of hatching. Using fluorescence immunocytochemistry, we investigated whether Cx43 staining was concentrated in specific cellular compartments at H1 by applying well‐known markers for astrocytes (glial fibrillary acidic protein; GFAP), oligodendrocytes (antimyelin), neurons (microtubule‐associated protein 2), and synaptic terminals (synaptotagmin). GFAP‐positive astrocytes and GFAP‐negative nonneuronal cells around the principal cell bodies were labeled with Cx43, suggesting that Cx43 was expressed exclusively by nonneuronal cells near the neuronal elements. Next, the developmental pattern of expression of Cx43 was studied at embryonic day 16 (E16), H1, and H9. At E16, Cx43 was present weakly as random small clusters in the tangential nucleus, whereas, at H1, overall staining became localized, with increases in size, brightness, and number of immunostained clusters. Finally, at H9, Cx43 staining decreased, but cluster size and location remained unchanged. These results suggest that Cx43 is developmentally regulated with a peak at birth and is associated primarily with astrocytes and nonneuronal cells near the principal cell bodies. © 2003 Wiley‐Liss, Inc.
Einfluss der Werkstoffzähigkeit auf das Festigkeitsverhalten unter mehrachsiger Beanspruchung am Beispiel von Schweißverbindungen aus Stahl und Aluminium
Authors: Sonsino C. M.
Published: February 2003

Das bereits aus Untersuchungen mit duktilen und weniger duktilen Werkstoffen bekannte Festigkeitsverhalten unter mehrachsigen Spannungszuständen mit konstanten und veränderlichen Hauptspannungsrichtungen lässt sich auch auf Schweißverbindungen aus unterschiedlich zähen Werkstoffen übertragen. Hierfür wurden geschweißte Flansch‐Rohr‐Verbindungen aus dem Feinkornbaustahl StE 460 und aus der Aluminiumknetlegierung AlSi1MgMn T6 unter kombinierter Biegung und Torsion untersucht. Bei den Schweißverbindungen aus Stahl bewirkt eine Phasenverschiebung zwischen Biegung und Torsion gegenüber synchroner Beanspruchung eine deutliche Minderung der Lebensdauer durch die Veränderung der Hauptspannungsrichtungen. Bei den Verbindungen aus Aluminium hingegen bleibt die Phasenverschiebung ohne Einfluss auf die Lebensdauer.

Die Bewertung der mehrachsigen phasengleichen und phasenverschobenen Beanspruchungen auf Basis von örtlichen Spannungen führt für die Verbindungen aus Stahl mit der integralen Hypothese der Wirksamen Vergleichsspannung (WVS) zu guten Ergebnissen. Diese Hypothese für den duktilen Werkstoffzustand berücksichtigt den lebensdauerverkürzenden Einfluss der phasenverschobenen Beanspruchung durch die Wechselwirkung der lokalen Schubspannungen, die in den unterschiedlichen Schnittebenen des Werkstoffes vorliegen. Im Gegensatz zu Stahl wird das Lebensdauerverhalten der Schweißverbindungen aus Aluminium mit der Hypothese der maximalen, schnittebenenbezogenen, kombinierten örtlichen Normal‐ und Schubspannungen (KoNoS) gut beschrieben, die für den semi‐duktilen Werkstoffzustand gültig ist.
Chemische Zusammensetzung und Mikrostruktur polymerabgeleiteter Gläser und Keramiken im System Si–C–O. Teil 1: Phasenidentifikation mittels Si‐L2,3‐Ionisationskanten‐Elektronenenergieverlustspektroskopie nach dem Fingerprint‐Verfahren und energiegefilterter Durchstrahlungselektronenmikroskopie
Authors: Gegner J.
Published: February 2003

Polymer‐ oder Prekursorkeramik stellt eine neue Klasse von Hochleistungswerkstoffen dar, die durch gesteuerte Pyrolyse metallorganischer Verbindungen hergestellt werden. Die mit der thermischen Zersetzung verbundene Schwindung und Porosität kann durch Zusätze chemisch reaktiver Füllstoffpulver kompensiert werden. Dieses Verfahren gestattet die maßhaltige Fertigung dichter keramischer Volumenbauteile durch kostengünstige endmaßnahe Formung am vernetzten Grünkörper. Für die Prozesssteuerung ist die Definition des Reaktionsverlaufs der Aktivfüller und somit die genaue Kenntnis der chemischen Zusammensetzung und der Gefügeentwicklung des festen Rückstands während der Pyrolyse der Polymervorstufe erforderlich. Wegen der großen technischen Bedeutung der keramischen Endprodukte und ihrer wirtschaftlichen Verfügbarkeit wurde in der vorliegenden Arbeit die thermische Zersetzung eines Siliconharzes (Polymethylsiloxan) bei Temperaturen zwischen 525 und 1550 °C nanochemisch und mikrostrukturell charakterisiert. In Teil 1 werden die Ergebnisse der quantitativen Phasenidentifikation mittels analytischer Elektronenmikroskopie berichtet. Der Bindungszustand des Siliziums wurde durch Feinstrukturanalyse (Si‐L2,3‐Ionisationskante) des Elektronenenergieverlustspektrums bestimmt und erwies sich stets als überwiegend oxidisch. Mittels energiegefilterter Durchstrahlungselektronenmikroskopie wurden Elementverteilungen im Nanometerbereich aufgenommen. Die Phasentrennung der polymerabgeleiteten Si–C–O‐Matrix in SiO2, C und SiC konnte eindeutig nachgewiesen werden. Die Charakterisierung der Gefügeausbildung durch hochauflösende Abbildungs‐ und Beugungsverfahren erfolgt in Teil 2.
Verhalten gekerbter Biegeproben aus der Aluminiumlegierung AA7075 im Kurzzeitermüdungsbereich
Authors: El‐Magd E. , Mahmoud M.
Published: February 2003

Der Einfluss der Kerbgeometrie auf das Ermüdungsverhalten von Biegeproben aus der Aluminiumlegierung AA7075 wird im LCF‐Bereich untersucht. Neben der kontinuierlichen Aufnahme der Kraft und der Durchbiegung als Zeitfunktionen wird das Risswachstum in den gekerbten Biegeproben mit dem Gleichstrom‐Potentialsondenverfahren (PSV) erfasst. Zur Bestimmung der Spannungs‐ und Dehnungsverteilungen sowie der Dehnschwingbreite im Kerbgrund werden Finite‐Elemente‐Simulationen mittels des nicht‐linearen isotrop‐ kinematischen Modells nach Chaboche und Lemaitre bestimmt. Anhand der FE‐ Rechnungen wird die Anrisslebensdauer nach der effektiven Dehnschwingbreitenhypothese „ASME Boiler and Pressure Vessel Code”︁ abgeschätzt und der plastischen Energiedissipationshypothese gegenübergestellt.
Einfluss der Al2Cu‐Phase auf die Superplastizität der AlCuMn Legierung
Authors: Ryspaev T. , Draugelates U. , Bouaifi B.
Published: February 2003

Die warmfeste AlCuMn Knetlegierung ist auf ihre superplastische Umformbarkeit hin untersucht und optimiert worden, so dass eine maximale Bruchdehnung von ε = 850% bei einer Umformtemperatur von 530°C erreicht wurde.

Voraussetzung für ein superplastisches Umformverhalten und die damit verbundenen großen Bruchdehnungen dieser Aluminiumlegierungen ist ein besonders feinkörniges Gefüge, sowie die Größenreduktion der Al2Cu Phase und ihre gleichmäßige Verteilung im Gefüge. Die superplastische Umformung (SPU) bewirkt eine starke Formänderung der großen Partikel der θ‐Phase, dabei bilden die Partikel dieser Phase Adern entlang den Grenzen benachbarter Körner.

Während der Verformung verlieren die Körner ihre äquiaxiale Form und strecken sich in die Zugrichtung aufgrund von starken Versetzungsgleitbewegungen innerhalb der Körner des Mikrogefüges.

Die Untersuchungen des verformten Gefüges mittels Durchstrahlungsmikroskopie haben eine Versetzungsaufstauung in den Körnern der Aluminiumlegierung aufgezeigt.

Die Korngröße der handelsüblichen Bleche der AlCuMn Knetlegierungen mit einer Dicke von 1 mm ist ungefähr 30 μm, die optimierten Bleche wiesen durch das neue Fertigungsverfahren, welches von der industriellen Fertigung nur geringfügig abweicht, eine Korngrößenreduzierung auf 12 μm bis 5 μm auf.
Prevalence of amyloid‐β deposition in the cerebral cortex in Parkinson's disease
Authors: Mastaglia Frank L. , Johnsen Russell D. , Byrnes Michelle L. , Kakulas Byron A.
Published: February 2003

The pathological basis for the dementia which occurs in 20 to 40% of patients with idiopathic Parkinson's disease (PD) remains uncertain. In the present postmortem study, we compared the prevalence and severity of parenchymal and vascular amyloid‐β (Aβ) deposition in the cerebral cortex in a group of 57 PD brains, including 13 cases with dementia, and in 100 control brains. A higher proportion of PD brains had vascular Aβ deposition, whereas the proportions and severity of parenchymal Aβ were similar in the PD and control groups. There was a poor correlation between Aβ deposition and neurofibrillary tangles which were present in only small numbers in a minority of cases. Cortical Aβ deposition was present in only 6 of the 13 cases with dementia and only 3 fulfilled the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) criteria for definite Alzheimer's disease. The present findings confirm that dementia in PD is only infrequently due to fully established Alzheimer's disease. However, vascular and parenchymal Aβ deposition could still contribute to dementia and cognitive decline when combined with other changes such as α‐synuclein deposition in the cerebral cortex and cortical Lewy bodies.
State of the art review: Molecular diagnosis of inherited movement disorders. Movement Disorders Society task force on molecular diagnosis
Authors: Gasser Thomas , Bressman Susan , Dürr Alexandra , Higgins Joseph , Klockgether Thomas , Myers Richard H.
Published: February 2003

This review is designed to provide practical help for the clinical neurologist to make appropriate use of the possibilities of molecular diagnosis of inherited movement disorders. Huntington's disease, Parkinson's disease and parkinsonian syndromes, ataxias, Wilson disease, essential tremor, dystonias, and other genetic diseases associated with a variety of movement disorders are considered separately.
Respect for the developmentally disabled and forgoing life‐sustaining treatment
Authors: Nelson Lawrence J.
Published: February 2003

A developmentally disabled person should be treated at all times as a unique individual and not as some anonymous “disabled person.” The developmentally disabled should not be subjected to invasive medical treatment that is unduly burdensome or nonbeneficial, or be forced to endure a quality of life not meaningful to them as individuals. They have a right to refuse or accept treatment that a surrogate must exercise on behalf of each individual in a responsible and careful manner. Three cases and a preliminary approach to the ethical analysis of decisions to allow developmentally disabled persons to die by forgoing medical treatment are offered. The “best interests” of a developmentally disabled individual, properly understood, can serve as a useful and ethically defensible standard for determining the ethical propriety of surrogate decision making about forgoing life‐sustaining medical treatment of the disabled. MRDD Research Reviews 2003;9:3–9. © 2003 Wiley‐Liss, Inc.
Disability rights critique of prenatal genetic testing: Reflections and recommendations
Authors: Parens Erik , Asch Adrienne
Published: February 2003

Using prenatal tests to prevent the birth of babies with disabilities seems to be self‐evidently good to many people. Even if the testing will not help bring a healthy baby to term this time, it gives prospective parents a chance to try again to conceive. To others, however, prenatal testing looks rather different. If one thinks about the history of our society's treatment of people with disabilities, it is not hard to see why people identified with the disability rights movement might regard such testing as dangerous. For the members of this movement, living with disabling traits need not be detrimental to an individual's prospects of leading a worthwhile life, or to the families in which they grow up, or to society at large. Although the movement has no one position on prenatal diagnosis, many of its adherents believe that public support for prenatal diagnosis and abortion based on disability contravenes the movement's basic philosophy and goals. MRDD Research Reviews 2003;9:40–47. © 2003 Wiley‐Liss, Inc.
Withdrawing life‐sustaining medical treatment—A physician's personal reflection
Authors: Lin Richard J.
Published: February 2003

The decision to withhold or withdraw artificially provided hydration and nutrition is one which evolves over time and must be made jointly by the medical team and the patient's family. Although withholding nutrition can be argued to be ethical and appropriate for certain clinical scenarios, it is still a decision which can be difficult to make and, because of different social and legal issues, can be difficult to carry out. This is the story of one physician's journey as he worked with the mother and father of a young child who suffered a severe neurological injury and was left in a persistent vegetative state. MRDD Research Reviews 2003;9:10–15. © 2003 Wiley‐Liss, Inc.
Ethical aspects of research into the etiology of autism
Authors: Chen Donna T. , Miller Franklin G. , Rosenstein Donald L.
Published: February 2003

Advances in understanding autism and other developmental neuropsychiatric disorders will come from an integration of various research strategies including phenomenologic, functional neuroimaging, and pharmacologic methods, as well as epidemiologic approaches aimed at identifying genetic and environmental risk factors. The highly heritable nature of autism makes it scientifically valuable to involve parents and siblings as research participants. However, many studies on autism pose ethical challenges because they do not offer the prospect of direct benefit to subjects. In this article, we present an in‐depth ethical analysis of current nontherapeutic research strategies that are common in autism research. The ethical analysis applies a proposed ethical framework for evaluating clinical research focusing on seven ethical requirements: (1) social or scientific value, (2) scientific validity, (3) fair subject selection, (4) favorable risk‐benefit ratio, (5) independent review, (6) informed consent, and (7) respect for potential and enrolled research participants. © 2003 Wiley‐Liss, Inc. MRDD Research Reviews 2003;9:48–53.