bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of molecular weight and charge density on the performance of polyacrylamide in low‐grade oil sand ore processing
Authors: Li Haihong , Long Jun , Xu Zhenghe , Masliyah Jacob H. 
Published: March 2008

AbstractThe effect of charge density and molecular weight (MW) of partially hydrolyzed polyacrylamide (HPAM) polymers on their performance in processing low‐grade oil sand ores was investigated. Bitumen extraction and tailings settling tests were carried out and an atomic force microscope (AFM) was used to directly measure the bitumen‐solid and solid‐solid interaction forces. It was found that HPAM polymers with a low MW acted as dispersants in the bitumen extraction process, resulting in low bitumen recovery and slow tailings settling but improved froth quality. In contrast, the use of HPAM polymers with a high MW improved both bitumen recovery and tailings settling but deteriorated froth quality. To achieve high bitumen recovery and fast tailings settling, a HPAM polymer must have a low to medium charge density (∼30%) and a high MW (17.5 million Daltons). A stronger clay‐bitumen adhesion force normally resulted in a lower bitumen recovery. Fast tailings settling was achieved in the presence of a strong solid‐solid adhesion force.
Novel polymer aids for low‐grade oil sand ore processing
Authors: Li Haihong , Long Jun , Xu Zhenghe , Masliyah Jacob H. 
Published: March 2008

AbstractIn the present study, a hybrid Al(OH)3‐polyacrylamide (Al‐PAM) was synthesized and used in combination with a partially hydrolyzed polyacrylamide (HPAM) to process a low‐grade oil sand ore. It was found that Al‐PAM was capable to improve bitumen froth quality and tailings settling. But it led to deterioration in bitumen recovery due to the formation of large bitumen lumps during the bitumen extraction process. To resolve this problem, HPAM was added in combination with Al‐PAM as a dual system. The use of the dual system at a low dosage achieved a holistic improvement in bitumen recovery, froth quality, and tailings settling. To understand the role of Al‐PAM and the dual system in the bitumen extraction process, bitumen‐clay, bitumen‐bitumen, and clay‐sand interaction and adhesion forces were directly measured using an atomic force microscope (AFM). The measured forces indicate that bitumen recovery and tailings settling are controlled by the colloidal interaction and adhesion forces between the oil sand components.
Modelling crystal growth between potash particles near contact points during drying processes. Part II: Analysis, results, and comparison with experimental data
Authors: Wang Yan , Evitts Richard W. , Besant Robert W. 
Published: March 2008

AbstractCaking of bulk granular materials is a serious problem that affects many industries including the mineral processing industry. Caking occurs when bulk materials undergo wetting and drying cycles and it has been thought that it occurs due to the formation of new crystal bridges between individual particles. In the first paper in this series a mathematical model is developed for the crystal formation process that occurs at the contact point between two particles. In Part II, numerical simulations of the model are used to determine the effects of changes for several independent parameters in this model: initial moisture content; rate of evaporation of the salt solution from the particle surface; relative size of the contact region compared to the initial film thickness of salt solution; and supersaturation levels near the contact point. Non‐dimensional graphical curves of these simulations are used to compare the effects of each parameter for the deposition of salt crystals near the contact point. These results, when compared to data for cake strength in potash specimens which were obtained for various initial moisture contents, drying rate, and chemical composition of the particle surfaces, show good qualitative agreement even though cake strength and mass recrystallization near a contact point are different physical phenomena. The numerical results show that the mass of crystal deposition near the contact point will increase with increased initial moisture content and decreased evaporation rate. It is also found that variations in the degree of supersaturation near the contact point causes significant variations in the crystal mass deposition near the contact point.
Application of MRI phase‐difference mapping to assessment of vascular concentrations of BMS agent in mice
Authors: Ribot Emeline Julie , Thiaudière Eric , Roulland Richard , Brugières Pierre , Rahmouni Alain , Voisin Pierre , Franconi Jean‐Michel , Miraux Sylvain 
Published: March 2008

AbstractDirect quantitation of contrast agent concentration can be performed using dynamic susceptibility contrast MRI. This method is based on phase imaging and administration of paramagnetic agents such as gadolinium‐chelates. This technique has only been applied on humans or primates. However, numerous research models have been developed on small animals like mice. For this reason, the aim of this work was the application of this MRI technique, allowing the direct quantitation of the contrast agent concentrations in vivo, in the mouse vascular system at high field. For this purpose, Dy–DOTA has been preferred to Gd–DOTA due to a lower T2* effect. Dy‐DOTA shifts in Larmor frequency were measured by phase difference mapping, using fast gradient‐echo imaging at short echo times. Such an acquisition sequence allowed the limitation of susceptibility artifacts at high magnetic fields and phase wrapping. As demonstrated in a phantom oriented parallel to the static magnetic field, it is possible to measure contrast agent concentrations between 0 and 10 mm with an uncertainty of about 100 µm. Finally, the method was applied on living mice at 4.7 T. After the bolus injection, the evolution of contrast agent concentrations was assessed in brain blood vessels parallel to B0. Long‐term disappearance of contrast agent was monitored at high spatial resolution every 15 s. Alternatively, lower resolved images at 0.72 s time‐resolution allowed preliminary assessment of arterial input functions. The feasibility of quantitative bolus‐tracking in small rodents opens the way for comprehensive descriptions of flow and over time‐dependent biological processes, especially in pathological murine models. Copyright © 2008 John Wiley & Sons, Ltd.
Role of endogenous sleep‐wake and analgesic systems in anesthesia
Authors: Lu Jun , Nelson Laura E. , Franks Nick , Maze Mervyn , Chamberlin Nancy L. , Saper Clifford B. 
Published: March 2008

AbstractClassical anesthetics of the γ‐aminobutyric acid type A receptor (GABAA)‐enhancing class (e.g., pentobarbital, chloral hydrate, muscimol, and ethanol) produce analgesia and unconsciousness (sedation). Dissociative anesthetics that antagonize the N‐methyl‐D‐aspartate (NMDA) receptor (e.g., ketamine, MK‐801, dextromethorphan, and phencyclidine) produce analgesia but do not induce complete loss of consciousness. To understand the mechanisms underlying loss of consciousness and analgesia induced by general anesthetics, we examined the patterns of expression of c‐Fos protein in the brain and correlated these with physiological effects of systemically administering GABAergic agents and ketamine at dosages used clinically for anesthesia in rats. We found that GABAergic agents produced predominantly delta activity in the electroencephalogram (EEG) and sedation. In contrast, anesthetic doses of ketamine induced sedation, followed by active arousal behaviors, and produced a faster EEG in the theta range. Consistent with its behavioral effects, ketamine induced Fos expression in cholinergic, monoaminergic, and orexinergic arousal systems and completely suppressed Fos immunoreactivity in the sleep‐promoting ventrolateral preoptic nucleus (VLPO). In contrast, GABAergic agents suppressed Fos in the same arousal‐promoting systems but increased the number of Fos‐immunoreactive neurons in the VLPO compared with waking control animals. All anesthetics tested induced Fos in the spinally projecting noradrenergic A5–7 groups. 6‐hydroxydopamine lesions of the A5–7 groups or ibotenic acid lesions of the ventrolateral periaqueductal gray matter (vlPAG) attenuated antinociceptive responses to noxious thermal stimulation (tail‐flick test) by both types of anesthetics. We hypothesize that neural substrates of sleep‐wake behavior are engaged by low‐dose sedative anesthetics and that the mesopontine descending noradrenergic cell groups contribute to the analgesic effects of both NMDA receptor antagonists and GABAA receptor‐enhancing anesthetics. J. Comp. Neurol. 508:648–662, 2008. © 2008 Wiley‐Liss, Inc.
Point and extended defects in superconductors
Authors: Obaidat I. M. , Goeckner H. P. , Albiss B. A. , Kouvel J. S. 
Published: March 2008

AbstractThe effect of point defects created by γ‐irradiation and extended defects created by Pb‐ion irradiation on the behavior of the critical current density, Jc in several superconductors have been investigated. We have found a limitation of the role of both types of defects on enhancing Jc. We report an explanation of the effect of γ‐irradiation and Pb‐ion irradiation doses on Jc in these materials. The explanation is based on combining several competing mechanisms of irradiation which we believe to take place mainly in the regions of the grain boundaries. The influences of these mechanisms were found to vary with the irradiation dose level. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and luminescence properties of large‐scale zinc oxide nanotetrapods
Authors: Panda S. K. , Singh N. , Hooda J. , Jacob C. 
Published: March 2008

AbstractLarge‐scale zinc oxide (ZnO) nanotetrapods have been grown on p‐type Si (111) substrate by oxidizing zinc pieces in air by thermal evaporation technique without the presence of any catalyst. The size and morphology of the nanostructures was found to depend on experimental parameters. The grown nanostructures were characterized by X‐ray Diffraction (XRD), Photoluminescence (PL), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and analysis of elemental composition was done by Energy Dispersive X‐ray analysis (EDX). The EDX spectrum shows that the grown product contains Zn and O only. The X‐ray diffraction pattern indicates that the microstructure of the obtained products is typical hexagonal wurtzite ZnO. The optical properties were studied using room temperature PL spectroscopy which indicates that the products are of high optical quality and the near band edge UV transition peak intensity increases with decrease in tetrapod size. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystallization features of YBa2Cu3O7‐δ in the Y2BaCuO5‐BaCuO2‐CuO and Y2Cu2O5‐BaCuO2 systems
Authors: Kalanda N. A. , Gurskii L. I. , Saad A. M. , Truhan V. M. , Haliakevich T. V. 
Published: March 2008

AbstractBased on the data of X‐ray phase and microstructure analysis, the sample composition was optimized in order to provide maximum size of the textured macrograins of YBa2Cu3O7‐δ and of the crystallites in the Y2BaCuO5‐BaCuO2‐CuO, Y2Cu2O5‐BaCuO2 systems. The growth rate has been studied and the YBa2Cu3O7‐δ growth activation energy has been calculated for the samples of Y2BaCuO5+3BaCuO2+2.3CuO, Y2BaCuO5+3BaCuO2+0.6CuO, and Y2Cu2O5+3.5BaCuO2 compounds in the temperature range of 1240‐1270K for the case of use of the Y2Cu2O5 and Y2BaCuO5 precursors with an average grain diameter of 10 μm and 1mm. A crystallization mechanism of YBa2Cu3O7‐δ in the Y2BaCuO5‐BaCuO2‐CuO and Y2Cu2O5‐BaCuO2 systems in the case of different sizes of Y2BaCuO5 and Y2Cu2O5 precursor grains was proposed and validated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low temperature EPR spectra of Fe3+ centers in ternary layered TlGaS2 crystal
Authors: Acikgoz M. , Kazan S. , Mikailov F. A. , Kerimova E. , Aktas B. 
Published: March 2008

AbstractThe results of low temperature electron paramagnetic resonance (EPR) study of Fe doped TlGaS2 single crystal in the temperature range of 5‐300 K are presented. Iron was added to the growth mixture in amounts corresponding to a molar ratio Fe/Ga of about 1%. The EPR signal due to Fe3+ centers located at the centers of GaS4 tetrahedrons has been observed. A transformation of EPR spectra has been observed on decreasing the temperature, which is attributed to lowering of the number of resonance lines. The simulation of rotational patterns of the resonance fields exhibits a decrease of the number of centers at low temperatures as a contrary to those of isostructural compounds of TlGaS2. On comparing the EPR spectra of Fe3+ centers in TlGaSe2, it has been revealed that the Tl atoms lose their zigzag alignment observed previously at room temperature and rearranged to equal structural positions on Tl chains on lowering the temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gold nanoparticles induce protein crystallization
Authors: Hodzhaoglu F. , Kurniawan F. , Mirsky V. , Nanev C. 
Published: March 2008

AbstractNucleation of protein crystals by gold nanoparticles was observed. Lysozyme and ferritin were used as model proteins. The effect was established with uncoated gold nanoparticles and with gold nanoparticles coated by 16‐mercaptodecanoic acid. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CFD‐based optimization of aerofoils using radial basis functions for domain element parameterization and mesh deformation
Authors: Morris A. M. , Allen C. B. , Rendall T. C. S. 
Published: March 2008

AbstractA novel domain element shape parameterization method is presented for computational fluid dynamics‐based shape optimization. The method is to achieve two aims: (1) provide a generic ‘wrap‐around’ optimization tool that is independent of both flow solver and grid generation package and (2) provide a method that allows high‐fidelity aerodynamic optimization of two‐ and three‐dimensional bodies with a low number of design variables. The parameterization technique uses radial basis functions to transfer domain element movements into deformations of the design surface and corresponding aerodynamic mesh, thus allowing total independence from the grid generation package (structured or unstructured). Independence from the flow solver (either inviscid, viscous, aeroelastic) is achieved by obtaining sensitivity information for an advanced gradient‐based optimizer (feasible sequential quadratic programming) by finite‐differences.Results are presented for two‐dimensional aerofoil inverse design and drag optimization problems. Inverse design results demonstrate that a large proportion of the design space is feasible with a relatively low number of design variables using the domain element parameterization. Heavily constrained (in lift, volume, and moment) two‐dimensional aerofoil drag optimization has shown that significant improvements over existing designs can be achieved using this method, through the use of various objective functions. Copyright © 2008 John Wiley & Sons, Ltd.
Regulation of prostaglandin E2 synthase expression in activated primary rat microglia: Evidence for uncoupled regulation of mPGES‐1 and COX‐2
Authors: de Oliveira Antonio Carlos Pinheiro , Candelario‐Jalil Eduardo , Bhatia Harsharan S. , Lieb Klaus , Hüll Michael , Fiebich Bernd L. 
Published: March 2008

AbstractProstaglandin E2 (PGE2) is among the most important mediators involved in neuroinflammatory processes. The final step of its synthesis is regulated by enzymes termed prostaglandin E2 synthases (PGES). Three PGES are known, cytosolic (c)PGES, membrane‐associated (m)PGES‐1 and mPGES‐2. The expression of mPGES‐1 is induced by inflammatory stimuli such as lipopolysaccharide (LPS), interleukin (IL)‐1β, and tumor necrosis factor (TNF)‐α. Although some roles of mPGES‐1 have already been suggested, its function in the CNS and the signaling pathways involved in its upregulation are poorly understood. In this study, we examined the regulation of mPGES‐1 in primary rat microglia and the signaling pathways involved in its expression. Whereas the expression of cPGES and mPGES‐2 was not stimulated by LPS, low doses of LPS (0.1–1 ng/mL) sufficiently stimulated mPGES‐1 mRNA expression. A corresponding protein synthesis, however, was obtained only with higher doses (10–100 ng/mL). The LPS‐induced increase of mPGES‐1 was inhibited by different signaling pathway inhibitors, such as SP600125, LY294002, GF109203X, and SC‐514, suggesting the involvement of c‐Jun N‐terminal kinase (JNK), phosphatidylinositol 3‐kinase (PI‐3K)/Akt, protein kinase C (PKC) pathways, and the nuclear factor (NF)‐κB, respectively. In contrast to other reports, LPS‐induced mPGES‐1 synthesis was not invariably coupled to the synthesis of COX‐2, since inhibition of PI‐3K with LY294002 decreased mPGES‐1 but increased COX‐2 levels. This detailed view of the intracellular signaling pathways involved in mPGES‐1 expression in activated microglia opens a new avenue in the search for novel potential therapeutic targets to reduce neuroinflammation, and demonstrates that mPGES‐1 expression is not strictly coupled to the expression of COX‐2. © 2008 Wiley‐Liss, Inc.
HIV‐1‐infected and/or immune‐activated macrophage‐secreted TNF‐α affects human fetal cortical neural progenitor cell proliferation and differentiation
Authors: Peng Hui , Whitney Nicholas , Wu Yumei , Tian Changhai , Dou Huanyu , Zhou You , Zheng Jialin 
Published: March 2008

AbstractNeurogenesis, tied to the proliferation, migration and differentiation of neural progenitor cells (NPC) is affected during neurodegenerative diseases, but how neurogenesis is affected during HIV‐1 associated dementia (HAD) has not been fully addressed. Here we test the hypothesis that HIV‐1‐infected and/or immune‐activated brain macrophages affect NPC proliferation and differentiation through the regulation of cytokines. We showed that human monocyte‐derived macrophages (MDM) conditioned medium (MCM) induces a dose dependant increase in NPC proliferation. Conditioned media from lipopolysaccharide (LPS)‐activated MDM (LPS‐MCM) or HIV‐infected MCM (HIV‐MCM) induced a profound increase in NPC proliferation. HIV‐infected and LPS‐activated MCM (HIV+LPS‐MCM) induced the most robust increase in NPC proliferation. Moreover, LPS‐MCM and HIV+LPS‐MCM decreased β‐III‐tubulin and increased GFAP expression, demonstrating an induction of gliogenesis and inhibition of neurogenesis. The increase of NPC proliferation and gliogenesis correlated with increases in production of TNF‐α by infected/activated MDM. Although both IL‐1β and TNF‐α induced NPC proliferation and gliogenesis, these effects were only partially abrogated by soluble TNF‐α receptors R1 and R2 (TNF‐R1R2), but not by the IL‐1 receptor antagonist (IL‐1ra). This indicated that the HIV‐1‐infected/LPS‐activated MCM‐mediated effects were, in part, through TNF‐α. These observations were confirmed in severe combined immunodeficient (SCID) mice with HIV‐1 encephalitis (HIVE). In these HIVE mice, NPC injected with HIV‐infected MDM showed more astrocyte differentiation and less neuronal differentiation compared to NPC injection alone. These observations demonstrated that HIV‐1‐infected and immune‐activated MDM could affect neurogenesis through induction of NPC proliferation, inhibition of neurogenesis, and activation of gliogenesis. © 2008 Wiley‐Liss, Inc.
Replication of Theiler's virus requires NF‐κB‐activation: Higher viral replication and spreading in astrocytes from susceptible mice
Authors: Kang Min Hyung , So Eui Young , Park Hyesuk , Kim Byung S. 
Published: March 2008

AbstractTo investigate viral replication and cell–cell spreading in astrocytes, recombinant Theiler's murine encephalomyelitis virus (TMEV) expressing green fluorescent protein (GFP) during the replication was generated. GFP and TMEV proteins were processed correctly in infected cells and production of viral proteins could be tracked by fluorescent microscopy. Viral replication of both wild‐type TMEV and GFP‐TMEV was dependent on the activation of NF‐κB and partially MAP kinase, based on chemical inhibition studies. Viral replication was significantly reduced in primary astrocytes from NF‐κB1 (p105)‐deficient mice compared with that from wild‐type control mice, whereas cytokine production was enhanced. These results suggest an association of canonical NF‐κB subunits in viral replication, but not cytokine production. Viral replication was also suppressed in both IKKα and IKKβ‐deficient mouse embryonic fibroblasts (MEFs), compared with that in wild‐type MEF. However, the inhibition was significantly greater in IKKβ‐deficient MEF, suggesting that IKKβ plays a stronger role in supporting viral replication. Interestingly, viral replication and spreading in primary astrocytes from susceptible SJL/J mice were several‐fold higher than those in astrocytes from resistant C57BL/6 mice, suggesting that higher viral replication levels in astrocytes may also contribute to the viral persistence in the central nervous system (CNS) of susceptible SJL/J mice. A relatively higher level of activated NF‐κB was found in the nuclei of virus‐infected SJL astrocytes compared with C57BL/6 astrocytes suggest that the NF‐κB activation level affects on viral replication. © 2008 Wiley‐Liss, Inc.
Modulation of astrocytic metabolic phenotype by proinflammatory cytokines
Authors: Gavillet Mathilde , Allaman Igor , Magistretti Pierre J. 
Published: March 2008

AbstractAstrocytes play an important role in nervous system homeostasis. In particular, they contribute to the regulation of local energy metabolism and to oxidative stress defence. In previous experiments, we showed that long‐term treatment with interleukin 1α (IL‐1α) or tumor necrosis factor‐α (TNFα) alone increases glucose utilization in primary culture of mouse astrocytes. In our study, we report that a combination of IL‐1β and TNFα exerts a synergistic effect on glucose utilization and markedly modifies the metabolic phenotype of astrocytes. Thus, IL‐1β+TNFα treated astrocytes show a marked decrease in glycogen levels, a slight but not significant decrease in lactate release as well as a massive increase in both the pentose phosphate pathway and TCA cycle activities. Glutamate‐stimulated glucose utilization and lactate release, a typical feature of astrocyte energy metabolism, are altered after pretreatment with IL‐1β+TNFα. As far as mechanisms for oxidative stress defence are concerned, we observed that treatment with IL‐1β+TNFα decreases cellular glutathione content and increases glutathione release into the extracellular space while stimulating superoxide anion and nitric oxide production as well as H2O2 release. Interestingly, stimulation of glucose utilization by IL‐1β+TNFα is not affected by the antioxidant N‐acetyl‐L‐cysteine, suggesting that cellular stress does not account for this effect. Finally, the effects of cytokines on glucose utilization appear to involve multiple signaling cascades including the phosphoinositide 3‐kinase and mitogen‐activated protein kinases. Taken together these results establish that a proinflammatory environment such as observed in several neuropathological conditions including Alzheimer's disease, markedly modifies the metabolic phenotype of astrocytes. © 2008 Wiley‐Liss, Inc.