bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyoma virus middle‐T‐transformed PECAM‐1 deficient mouse brain endothelial cells proliferate rapidly in culture and form hemangiomas in mice
Authors: Rothermel Terri A. , Engelhardt Britta , Sheibani Nader 
Published: June 2004

AbstractWild‐type mouse brain endothelial (bEND) cells transformed with the polyoma virus middle‐T proliferate rapidly in culture and form hemangiomas in mice. These cells express high levels of platelet/endothelial cell adhesion molecule‐1 (PECAM‐1), a molecule shown to be important during hemangioma formation. In this study, we have examined the ability of polyoma virus middle‐T‐transformed mouse bEND cells prepared from PECAM‐1−/− mice to proliferate in culture and form hemangiomas in mice. We show that these cells express a number of endothelial cell markers and share a similar morphology with PECAM‐1+/+ bEND cells. PECAM‐1−/− bEND cells exhibit a limited ability to form tubes in Matrigel and rapidly form hemangioma when injected into nude mice, very similar to PECAM‐1+/+ bEND cells. These cells, however, have increased proliferation, slower migration, altered endothelial cell adhesion molecule expression, and are less adherent when compared to PECAM‐1+/+ bEND cells. Therefore, lack of PECAM‐1 expression impacts polyoma middle‐T‐transformed endothelial cell proliferative, adhesive, and migratory properties without impacting their ability to rapidly form hemangiomas in mice or poorly organize to capillary‐like structures in Matrigel. © 2005 Wiley‐Liss, Inc.
Kinetics and mechanistic analysis of caustic magnesia hydration
Authors: Rocha Sônia DF , Mansur Marcelo B , Ciminelli Virgínia ST 
Published: June 2004

AbstractThe kinetics of magnesia hydration to produce magnesium hydroxide is crucial for process design and control, and for the production of an Mg(OH)2 powder with desirable particle morphology. In this study, highly pure magnesia has been hydrated in a batch reactor. The effects of the following variables were evaluated experimentally: temperature (308–363 K), reaction time (0.5–5 h), initial slurry density (1–25%wt) and particle size in the ranges −212 + 75 µm and −45 + 38 µm. Experimental data indicate increasing magnesia hydration rates with increasing temperature, as expected. In addition, it has been observed that the hydration of magnesia increases significantly up to about 4–5%wt initial slurry density, stabilising afterwards. On the other hand, the reaction was almost unaffected when magnesia with different particle sizes were hydrated because of similar specific surface areas involved. A reaction mechanism to explain the oxide dissolution and the hydroxide precipitation has been proposed, assuming no significant change in the initial solids size and dissolution rate as the controlling step. The calculated activation energy value of 62.3 kJ mol−1 corroborates the mechanism proposed in this study and compares well with values previously reported in the literature. Copyright © 2004 Society of Chemical Industry
Ozonation of 1,3,6‐naphthalenetrisulfonic acid in presence of heavy metals
Authors: Sánchez‐Polo M , Rivera‐Utrilla J 
Published: June 2004

AbstractA study was conducted of the mechanisms by which heavy metals, commonly present in industrial effluents, increase the purification effectiveness of ozone in the removal of organic contaminants of low biodegradability. For this purpose, the ozonation of 1,3,6‐naphthalenetrisulfonic acid (NTS) in the presence of Ni(II), Fe(II), Mn(II), Zn(II), Sr(II), Cr(III), Cd(II), Hg(II), and Cu(II) was examined. The presence of small amounts of Mn(II), Fe(II), Ni(II), Zn(II), and Cr(III) was observed in the system, increasing the degradation rate of the NTS and transforming the dissolved organic matter into CO2. The mineralization of the organic matter was highly favored, especially in the first minutes of treatment. The results obtained appear to indicate that the activity of the metals in the NTS ozonation process is related to their reduction potential. Thus, metals susceptible to oxidation by ozone are potential promoters of NTS ozonation. The presence of Fe(II) or Mn(II) during NTS ozonation increased its degradation rate by 79% and 72% respectively. Moreover, the reaction kinetics of metal oxidation with ozone controls the increase in the purification effectiveness of these systems. The presence of radical scavengers (tert‐butanol or bicarbonate) in the medium during the promoted ozonation of NTS showed a negative effect on this process, and the NTS degradation rate decreased with an increasing concentration of these inhibitors in the system. These results confirm that the degradation of NTS by ozone in the presence of heavy metals occurs by a radical mechanism. O3/Zn(II) and O3/Fe(II) systems were applied to the decontamination of urban waste waters. The presence of Zn(II) or Fe(II) during the ozonation produced a reduction during the first 5 min of treatment of 20% or 44%, respectively, in the concentration of dissolved organic matter present in the system. These results show that ozonation in the presence of heavy metals is a highly promising system for the purification of waste waters and industrial effluents. Copyright © 2004 Society of Chemical Industry
High‐rate clarification of municipal wastewaters: a brief appraisal
Authors: Imasuen Emmuel , Judd Simon , Sauvignet Philippe 
Published: June 2004

AbstractPilot‐plant studies on the treatment of three wastewaters (biological aerated flooded filter (BAFF) backwash water, post‐primary settling tank effluent and BAFF effluent) have been conducted using a ballasted sedimentation process (ACTIFLO®) coupled with ferric chloride and polyaluminium chloride (PACl) coagulants. The response of the process to shock loads of high solids concentrations was also investigated. Results showed over 80% turbidity, 70% suspended solids, and 50% COD removals to be achievable at rise rates in excess of 80 m h−1 and dose rates of 10–20 mg dm−3 Fe. Slightly improved performance was attained using PACL at half the weight concentration (but about the same molar concentration) as that of Fe. No pH adjustment was necessary and process performance was not significantly influenced by changes in hydraulic loading rate. Effluent quality was largely unaffected by shock organic loads provided coagulant dosing was commensurately increased. Non‐ideal flow through the plant was apparent from the measured residence time, which was ∼25% less than that calculated for plug flow. Clarification data were comparable to those reported for other high‐rate clarification (HRC) processes, with somewhat improved performance in terms of hydraulic retention time and coagulant use. Copyright © 2004 Society of Chemical Industry
Pancyclic arcs and connectivity in tournaments
Authors: Havet F. 
Published: June 2004

AbstractA tournament is an orientation of the edges of a complete graph. An arc is pancyclic in a tournament T if it is contained in a cycle of length l, for every 3 ≤ l ≤ |T|. Let p(T) denote the number of pancyclic arcs in a tournament T. In 4, Moon showed that for every non‐trivial strong tournament T, p(T) ≥ 3. Actually, he proved a somewhat stronger result: for any non‐trivial strong tournament h(T) ≥ 3 where h(T) is the maximum number of pancyclic arcs contained in the same hamiltonian cycle of T. Moreover, Moon characterized the tournaments with h(T) = 3. All these tournaments are not 2‐strong. In this paper, we investigate relationship between the functions p(T) and h(T) and the connectivity of the tournament T. Let pk(n) := min {p(T), T k‐strong tournament of order n} and hk(n) := min{h(T), T k‐strong tournament of order n}. We conjecture that (for k ≥ 2) there exists a constant αk> 0 such that pk(n) ≥ αkn and hk(n) ≥ 2k+1. In this paper, we establish the later conjecture when k = 2. We then characterized the tournaments with h(T) = 4 and those with p(T) = 4. We also prove that for k ≥ 2, pk(n) ≥ 2k+3. At last, we characterize the tournaments having exactly five pancyclic arcs. © 2004 Wiley Periodicals, Inc. J Graph Theory 47: 87–110, 2004
Determination of the Crystal Structure of Syndiotactic 3,4‐Poly(2‐methyl‐1,3‐butadiene) by Molecular Mechanics and X‐Ray Diffraction
Authors: Pirozzi Beniamino , Napolitano Roberto , Petraccone Vittorio , Esposito Simona 
Published: June 2004

AbstractSummary: The crystal structure of syndiotactic 3,4‐poly(2‐methyl‐1,3‐butadiene) has been determined by the joint use of molecular mechanics and X‐ray diffraction. Molecular mechanics calculations have been performed both on the isolated chain and on the crystal by the use of various force fields. The energy minimizations predict a model of the crystal structure. The calculated X‐ray powder diffraction pattern is in good agreement with the experimental one. This model has been refined in order to obtain the best agreement with all the experimental data. The space group is Pbcm and the parameters of the unit cell are a = 6.6 Å, b = 13.2 Å, c = 5.27 Å. The presence of defects in the crystal has been taken into account. Analogies and differences with the crystal structure of syndiotactic 1,2‐poly(1,3‐butadiene) are discussed.X‐ray fiber diffraction pattern of syndiotactic 3,4‐poly(2‐methyl‐1,3‐butadiene).magnified imageX‐ray fiber diffraction pattern of syndiotactic 3,4‐poly(2‐methyl‐1,3‐butadiene).
Aggressive bladder carcinoma in a child
Authors: Lezama‐del Valle Pablo , Jerkins Gerald R. , Rao Bhaskar N. , Santana Victor M. , Fuller Christine , Merchant Thomas E. 
Published: June 2004

AbstractThe brief report describes an unusual case of high grade bladder neoplasm with divergent differentiation in a 31 month‐old child. The presentation included hematuria with tissue fragments and the tumor was confined to the bladder. The tumor behaved aggressively despite radical cystectomy, chemotherapy with agents known to be effective against epithelial and mesenchymal tumors and radiation therapy. Although rare, most malignant bladder neoplasms in children are low grade and present in early stages. Sarcomatoid differentiation in the setting of high‐grade urothelial carcinoma portends a poor prognosis. © 2004 Wiley‐Liss, Inc.
Synthesis and polymerization of anthracene‐based itaconimides
Authors: Grigoras Mircea , Colotin Georgiana , Antonoaia Nicoleta Cristina 
Published: June 2004

AbstractTwo new anthracene‐based itaconimides, ie N‐(1‐ and 2‐anthryl) itaconimides, were synthesized by the reaction of aromatic amines with itaconic anhydride, followed by itaconamic acid imidization. The same reaction failed in the case of anthracene‐ring substitution at the position 9′. Radical and thermal polymerization of N‐(1‐ and 2‐anthryl) itaconimides led to polymers with anthracene pendant groups. No self‐polymerization by Diels–Alder cycloaddition of the itaconic function (dienophile) and anthracene nucleus (diene) was observed, as is the case for N‐(anthryl) maleimides and citraconimides. Copyright © 2004 Society of Chemical Industry
Preparation and evaluation of nanocomposites of polyfuran with Al2O3 and montmorillonite clay
Authors: Ballav Nirmalya , Biswas Mukul 
Published: June 2004

AbstractHigh yield oxidative polymerization of furan was accomplished in CHCl3 solvent at 0 °C. A nanocomposite of polyfuran (PF)–Al2O3 was prepared through polymerization of furan in a suspension of nanodimensional Al2O3 in CHCl3 at 0 °C. High yield polymerization of furan was also achieved in montmorillonite clay (MMT) without any extraneous oxidant. The formation of PF was confirmed by FTIR and elemental analysis. Thermogravimetric analyses revealed the following trends in thermal stability: PF < PF–Al2O3 < Al2O3 and PF < PF–MMT < MMT. Scanning electron microscopy showed the average particles sizes to be ca 51 nm and ca 40 nm for PF–Al2O3 and PF–MMT composites, respectively. The occurrence of a peak at 19.84 Å in the X‐ray diffraction pattern of the PF–MMT composite was indicative of the intercalation of PF in MMT lamellae. Transmission electron microscopic analyses for the PF–MMT composite also showed incorporation of PF moieties in‐between the MMT layers. The dc conductivity values (S cm−1) of PF–FeCl3, PF–Al2O3–FeCl3, PF–MMT and PF–MMT–FeCl3 systems were in the order of 10−6, 10−7, 10−8 and 10−7, respectively, and the values were significantly enhanced compared to the dc conductivity value of PF homopolymers (10−11). Copyright © 2004 Society of Chemical Industry
The morphology and thermal properties of multi‐walled carbon nanotube and poly(hydroxybutyrate‐co‐hydroxyvalerate) composite
Authors: Lai Mingfang , Li Jing , Yang Jun , Liu Jingjiang , Tong Xin , Cheng Huiming 
Published: June 2004

AbstractNanocomposites based on poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) and multi‐walled carbon nanotubes (MWNTs) were prepared by solution processing. Ultrasonic energy was used to uniformly disperse MWNTs in solutions and to incorporate them into composites. Microscopic observation reveals that polymer‐coated MWNTs dispersed homogenously in the PHBV matrix. The thermal properties and the crystallization behavior of the composites were characterized by thermogravimetric analysis, differential scanning calorimetry and wide‐angle X‐ray diffraction, the nucleant effect of MWNTs on the crystallization of PHBV was confirmed, and carbon nanotubes were found to enhanced the thermal stability of PHBV in nitrogen. Copyright © 2004 Society of Chemical Industry
Effect of clay on the morphology of blends of poly(propylene) and polyamide 6/clay nanocomposites
Authors: Feng Meng , Gong Fangling , Zhao Chungui , Chen Guangming , Zhang Shimin , Yang Mingshu 
Published: June 2004

AbstractPP/NPA6 blends composed of poly(propylene) (PP) and polyamide 6/clay nanocomposites (NPA6) were prepared by twin‐screw extrusion and melt‐drawn into ribbons by a ribbon extrusion process. The influence of clay on the morphology of PP/NPA6 ribbons was investigated by means of field‐emission scanning electron microscopy and optical microscopy. The results show that at low clay content (3, 5 wt%), NPA6 exhibited continuous lamellar structure in PP as pristine PA6 did in a PP/PA6 blend, but at a higher clay content (10 wt%) only ellipsoids or elongated ellipsoids were observed. In order to explain the morphological difference, two factors, ie the compatibilization effect and melt rheology, have been taken into consideration. It has been found that both factors, and probably mainly the variation in melt rheology, were responsible for the morphological difference in the PP/NPA6 blends with different clay contents under the extensional flow field. Copyright © 2004 Society of Chemical Industry
Graft copolymerization of methyl acrylate onto cellulose initiated by potassium ditelluratoargentate(III)
Authors: Liu Yinghai , Yang Lanying , Shi Zengqian , Li Junbo 
Published: June 2004

AbstractA novel redox system, potassium ditelluratoargentate(III) (DTA)–cellulose, was employed to initiate the graft copolymerization of methyl acrylate onto cellulose in alkali aqueous solution. Grafting parameters, such as total conversion, grafting efficiency and grafting yield, were evaluated comparatively. The dependence of these parameters on temperature, reaction time, initiator concentration and ratio of monomer to cellulose was also investigated. Graft copolymers with high grafting parameters were obtained, which indicated that the DTA–cellulose redox pair is an efficient initiator for cellulose grafting. The proof of grafting was obtained from gravimetric analysis and infrared spectra. A tentative mechanism involving a two‐step single‐electron‐transfer process of DTA is proposed to explain the generation of radicals and initiation. Thermogravimetry, X‐ray diffraction and scanning electron microscopy were also carried out to study the thermal stability, crystallinity and morphology of the grafted copolymers. Copyright © 2004 Society of Chemical Industry
A unified representation of multiprotein complex data for modeling interaction networks
Authors: Ding Chris , He Xiaofeng , Meraz Richard F. , Holbrook Stephen R. 
Published: June 2004

AbstractThe protein interaction network presents one perspective for understanding cellular processes. Recent experiments employing high‐throughput mass spectrometric characterizations have resulted in large data sets of physiologically relevant multiprotein complexes. We present a unified representation of such data sets based on an underlying bipartite graph model that is an advance over existing models of the network. Our unified representation allows for weighting of connections between proteins shared in more than one complex, as well as addressing the higher level organization that occurs when the network is viewed as consisting of protein complexes that share components. This representation also allows for the application of the rigorous MinMaxCut graph clustering algorithm for the determination of relevant protein modules in the networks. Statistically significant annotations of clusters in the protein–protein and complex–complex networks using terms from the Gene Ontology indicate that this method will be useful for posing hypotheses about uncharacterized components of protein complexes or uncharacterized relationships between protein complexes. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Toward the detection and validation of repeats in protein structure
Authors: Murray Kevin B. , Taylor William R. , Thornton Janet M. 
Published: June 2004

AbstractWe present a method called DAVROS to detect, localize, and validate repeating motifs in protein structure allowing for insertions and deletions. DAVROS uses the score matrix from a structural alignment program (SAP) to search for repeating motifs using an algorithm based on concepts from signal processing and the statistical properties of the alignments. The method was tested against a nonredundant Protein Data Bank, and each chain was assigned a score. For the top 50 chains ranked by score, 70% contain repeating motifs detected without error. These represent 14 types of fold covering α, β, and αβ protein classes. A second data set comprising protein chains in different sequence families for triosephosphate isomerase (TIM) barrel, leucine‐rich repeat (LRR), trefoil, and α–α barrel folds was used to assess the ability of DAVROS to detect all motifs within a specific fold. For the second test set, the percentage of motifs detected was highest for the LRR chains (88.7%) and least for the TIM barrels (60%). This variability results from the regularity of the LRR motif compared to the αβ units of the TIM barrel, which generally have many more indels. These reduce the strength of the repeat signal in the SAP matrix, making repeat detection more difficult. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Ion transit pathways and gating in ClC chloride channels
Authors: Yin Jian , Kuang Zhifeng , Mahankali Uma , Beck Thomas L. 
Published: June 2004

AbstractClC chloride channels possess a homodimeric structure in which each monomer contains an independent chloride ion pathway. ClC channel gating is regulated by chloride ion concentration, pH and voltage. Based on structural and physiological evidence, it has been proposed that a glutamate residue on the extracellular end of the selectivity filter acts as a fast gate. We utilized a new search algorithm that incorporates electrostatic information to explore the ion transit pathways through wild‐type and mutant bacterial ClC channels. Examination of the chloride ion permeation pathways supports the importance of the glutamate residue in gating. An external chloride binding site previously postulated in physiological experiments is located near a conserved basic residue adjacent to the gate. In addition, access pathways are found for proton migration to the gate, enabling pH control at hyperpolarized membrane potentials. A chloride ion in the selectivity filter is required for the pH‐dependent gating mechanism. Proteins © 2004 Wiley‐Liss, Inc.
Charge‐transfer transitions and optical spectra of titanates
Authors: Zenkov A. V. 
Published: June 2004

AbstractIn the framework of the cluster approach, we consider the peculiarities of charge‐transfer (CT) states and CT transitions O 2p → Ti 3d in the octahedral (TiO6)9− complex. We have computed the reduced matrix elements of the electric‐dipole transition operator on many‐electron wave functions – the initial and final states of a CT transition. Using the local approximation, we have parameterized the results obtained and computed the relative intensities of various allowed CT transitions in the absence of mixing of CT configurations having the same symmetry. Using the Tanabe–Sugano technique, we have taken this mixing into account and obtained the energies of many‐electron CT transitions and their actual intensities as well.Modelling the optical spectrum of titanium‐based oxides has yielded a complicated CT band consisting of 42 lines with the main maxima at 6–8 eV and satellites in the range of 1.5–4 eV. The total extent of the CT band is about 7 eV. The model spectrum is in satisfactory agreement with experimental data. Thus, the appearance of the spectrum does not at all resemble the oversimplified one‐ or two‐peaked structure that is usually spoken about when analyzing spectra in terms of CT transitions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence of layered semiconductor GaS doped with Mn
Authors: Shigetomi S. , Sakai K. , Ikari T. 
Published: June 2004

AbstractManganese (Mn)‐doped GaS single crystals were grown by the Bridgman technique. Radiative recombination mechanisms have been investigated using photoluminescence (PL) measurement. The PL spectrum (at 77 K) related to the impurity level is dominated by the new emission band at 2.002 eV. The temperature dependences of the PL intensity, peak energy, and full width at half‐maximum are characterized by the recombination mechanism of the configurational coordinate model. It was found that the 2.002 eV emission band is related to the acceptor–vacancy complex center. Moreover, the concentration of the defect is very high in the Mn‐doped GaS. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Level‐spacing distributions of the Gaussian unitary random matrix ensemble
Authors: Grimm Uwe 
Published: June 2004

AbstractLevel‐spacing distributions of the Gaussian Unitary Ensemble (GUE) of random matrix theory are expressed in terms of solutions of coupled differential equations. Series solutions up to order 50 in the level spacing are obtained, thus providing a very good description of the small‐spacing part of the level‐spacing distribution, which can be used to make comparisons with experimental or numerical data. The level‐spacing distributions can be obtained by solving the system of differential equations numerically. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale simulations of micro‐structure selection in binary alloy solidification
Authors: Emmerich Heike , Jurgk Matthias , Siquieri Ricardo 
Published: June 2004

AbstractWe demonstrate that the competition of dendritic crystals in a solidifying sample gives rise to two qualitatively different micro‐structure solutions depending on the density ρ of crystals in the melt. Here we show for the first time, that there is a non‐steady transition from one to the other. The precise ρ‐dependence of the transition point is determined by the Biot number. Our investigation is based on a scaling analysis for the tip velocity of the dendritic crystals, which we assume to be aligned in an array and to be coupled via the transport of heat. We develop our analytical solutions based upon the asymptotic Kruskal‐Segur reduction to a differential equation in the complex plane. It is supported by numerical simulations of a multiscale model of alloy growth. On the one hand this solution can be used to improve the accuracy of applied solidification simulations. On the other hand it yields additional insight in the universality of diffusion limited crystal growth in the presence of competing micro‐structures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)