bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards monitoring electrostatics in gas–solid fluidized beds
Authors: Demirbas Birol , Nijenhuis John , Yurteri Caner U. , Ommen J. Ruud van
Published: May 2008

The electrostatic charge distribution in a lab‐scale 2‐D fluidized bed of 900 µm glass beads was determined using arrays of induction probes, and the influence of relative humidity and superficial gas velocity was examined. The bubble presence, relative humidity, and superficial gas velocity were found to influence charge separation. Bipolar charging was observed; the net charge build‐up was found to be negligible. Moreover, the system was monitored by applying the attractor comparison method to the electrostatic charge signals from an induction probe. It was concluded that this approach can indeed be used to monitor changes in the electrostatic behaviour.
Magnetically assisted gas–solid fluidization in a tapered vessel: First report with observations and dimensional analysis
Authors: Hristov Jordan
Published: May 2008

The article presents first experimental results on gas–solid fluidization in a tapered bed in presence of an external transverse magnetic field that creates a novel branch in magnetically assisted fluidization. Phase diagrams similar to those used to describe cylindrical beds have been created to distinguish the bed regimes occurring under the action of two principle macroscopic variables such as field intensity and gas flow rate. A detailed analysis and parallelism to the bed behaviour exhibited by non‐magnetic spouted beds of cohesive particles have been performed. Principle process variables such as bed depth, field intensity, particle size, cone angle have been detected. A dimensional analysis utilizing a “pressure transform” of the initial set of variables has been applied to develop scaling relationships. Examples of scaling experimental data pertinent to the minimum spouting point and involving the magnetic granular Bond number have been developed.
Atmospheric aerosols over two sites in a southeastern region of Texas
Authors: Chiou Paul , Tang Wei , Lin Che‐Jen , Chu Hsing‐Wei , Tadmor Rafael , Ho T. C.
Published: May 2008

Speciated samples of PM2.5 were collected at the Bayland Park and Orange sites in Southeastern Texas by US EPA (Environmental Protection Agency) from July 2003 to August 2005. A total of 256 samples for the Bayland Park site and 293 samples for the Orange site with 52 species were measured; however, 22 species were excluded because of too many below‐detection‐limit data. Among the 22 species excluded, 19 species are common to both sites. The two data sets were analyzed by positive matrix factorization (PMF) to infer the sources of PM observed at the two sites. The analysis identified ten common source‐related factors: sulphate‐rich secondary aerosol I, sulphate‐rich secondary aerosol II, cement/carbon‐rich, wood smoke, motor vehicle/road dust, nitrate‐rich secondary aerosol, metal processing, soil, sea salt, and chloride‐depleted marine aerosol. sulphate and nitrate mainly exist as ammonium salts. The two sulphate‐rich secondary aerosols account for about 59% and 54% of the PM2.5 mass concentration at the two sites, respectively. The factor containing highest concentrations of Cl and Na was attributed to sea salt due to the proximity of the monitoring sites to the Gulf of Mexico. The chloride‐depleted marine aerosol was related to the sea salt aerosol but was identified separately due to the chlorine replacement reactions. Basically, the factor of sulphate, nitrate, and soil at the two sites showed similar chemical composition profiles and seasonal variation that reflect the regional characteristics of these sources. The regional factors showed predominantly low frequency variations, however, the area‐related and local factors showed both high and low frequency variations. Motor vehicle/road dust, sea salt, and chloride‐depleted marine aerosol were likely to be area‐related factors. Cement/carbon‐rich, wood smoke, and metal processing factor were likely to be the local sources.
Kinetic simulation of a compact reactor system for hydrogen production by steam reforming of higher hydrocarbons
Authors: Rakib M. A. , Grace J. R. , Elnashaie S. S. E. H. , Lim C. J. , Bolkan Y. G.
Published: May 2008

A bubbling fluidized bed membrane reactor for steam reforming of higher hydrocarbons is modelled, using n‐heptane as a model component to represent steam reforming of naphtha. The reformer is modelled as a bubbling fluidized bed reactor, consisting of two pseudo phases, a dense phase and a bubble phase, both in plug flow. In situ H2 permselective membranes remove H2 continuously as a pure product, greatly enhancing the H2 yield per mole of heptane fed. A fluidized bed membrane reformer for higher hydrocarbons could give a very compact reactor system combining all the units from the pre‐reformer to the hydrogen purification system in a traditional steam reforming plant into a single unit.
Overview and some issues related to co‐firing biomass and coal
Authors: Dai Jianjun , Sokhansanj Shahab , Grace John R. , Bi Xiaotao , Lim C. Jim , Melin Staffan
Published: May 2008

Low heating values, variable chemical compositions, peculiar physical properties, high investment cost and insecurity of biomass feedstocks supply limit the applications of biomass for energy and other processes. Co‐firing biomass and coal has potential for the development of biomass‐to‐energy capacity with significant economic, environmental, and social benefits. However, co‐firing is not straightforward, and some questions need to be addressed due to the differences in chemical compositions and physical properties of biomass and coal. This paper highlights key issues related to co‐firing, including reactor types, feeding, hydrodynamics, ash sintering, fouling, and corrosion, based on previous studies, as well as calculations and analysis. Direct co‐firing is the most common option for biomass and coal co‐firing currently, mostly due to relatively low investment needed to turn existing coal power plants into co‐firing plants. For direct co‐firing, the physical characteristics and chemical compositions of the fuel entering the combustors or gasifiers are critical to an optimum operation. Any biomass mixed with coal needs to have acceptable physical properties. More research is needed on co‐firing biomass and coal, including work on: preparation, handling, storage, and feeding of biomass feedstocks (e.g. drying, torrefaction, pelletization); co‐firing mechanisms; hydrodynamic analysis of co‐firing combustors and gasifiers; boiler/gasifier capacity, slagging, fouling, corrosion, efficiency, reliability, fuel flexibility; lower emissions and gas cleaning; catalyst poisoning; investment and operating costs.
Synthetic Ca‐based solid sorbents suitable for capturing CO2 in a fluidized bed
Authors: Pacciani R. , Müller C. R. , Davidson J. F. , Dennis J. S. , Hayhurst A. N.
Published: May 2008

Coprecipitation and hydrolysis of CaO have been employed to produce Ca‐based synthetic sorbents suitable for capturing CO2 in a fluidized bed. Their composition, CO2 uptake, volume in small pores (2–200 nm) and resistance to attrition were measured and compared to those of limestone and dolomite. Sorbents produced by hydrolysis showed the highest uptake and resistance to attrition. After 20 cycles of carbonation and calcination, two sorbents exceeded the uptake of both limestone and dolomite, when subjected to the same regimes of reaction. A sorbent's uptake of CO2 was shown to be determined by the volume in pores narrower than ∼200 nm.
Characteristics of anthraquinone hydrogenation catalysts in a liquid‐solid fluidized bed
Authors: Chen Guanqun , Zhou Tao , Li Hongzhong
Published: May 2008

The fluidization characteristics of anthraquinone hydrogenation catalysts were investigated in a liquid–solid fluidized bed. The effects of the initial bed conditions such as particle size, bed depth‐to‐column diameter ratio and liquid density and viscosity on the fluidization behaviour, bed expansion and applicability of the Richardson–Zaki equation were studied. The results reveal a strong particle size effect on the Richardson–Zaki (R‐Z) expansion index which in general decreased as the particle diameter increased. One type of particles exhibited two distinct bed expansion behaviours, depending mainly on the bed depth‐to‐column diameter ratio, with an experimentally established boundary at $h_{\rm b}0/D \approx 1.75$. This behaviour could be attributed to increasing wall friction and a tendency to exhibit slugging. The dependence of the Richardson–Zaki exponent on the liquid dynamic viscosity confirms the classic result $n_{\rm a} = f(1/Re_{t})$.
Multi‐scale CFD simulation of operating diagram for gas–solid risers
Authors: Wang Wei , Lu Bona , Dong Weigang , Li Jinghai
Published: May 2008

Our recently presented multi‐scale computational fluid dynamics (CFD) approach has proven to be able to capture the choking phenomena in a circulating fluidized bed (CFB). However, how to transfer this capability to assist industrial operation remains to be explored. To this end, this paper presents further simulation results over the intrinsic flow regime diagram and the operating diagram for gas–solid risers, showing the variation of flow regimes with gas velocity and solids flux as well as riser height. It is confirmed that the choking in CFB risers, characterized by the saturation carrying capacity and the coexistence of both dense and dilute flows, holds clear‐cut definition in hydrodynamics. In physics, both the choking, non‐choking transitions, and the critical point in‐between are intrinsic nature of gas–solid riser flows; they initiate as functions of gas velocity and solids flux. In engineering operation, however, their appearances vary with the riser height used. As a result, the intrinsic flow regime diagram can be defined by the combination of gas velocity and solids flux, although it is hard to obtain in practice owing to the limitation of riser height. The operating diagram of a CFB should be, accordingly, height‐dependent in practice, demanding the riser height as a parameter besides commonly believed gas velocity and solids flux.
Application of discrete element method simulation for studying fluidization of nanoparticle agglomerates
Authors: Wang X. S. , Rahman F. , Rhodes M. J.
Published: May 2008

The usefulness of discrete element method simulation for studying fluidization of nanoparticle agglomerates is explored. Nanoparticle agglomerates were simulated by using solid particles of equivalent sizes and densities. Validity of the present simulation was assessed through comparisons of simulation results and experimental observations of bed expansion, characteristic fluidization behaviour, and dense‐bed settling. The simulation was then used to investigate initial bed expansion and bed uniformity under particulate fluidization conditions. The role of inter‐agglomerate interparticle force in fluidization of nanoparticle agglomerates was examined. A stability analysis originally developed for addressing the transition from particulate to bubbling fluidization for conventional particles was used for predicting the start of bubbling in fluidized beds of nanoparticle agglomerates.
Postnatal ontogeny of the transcription factor Lmx1b in the mouse central nervous system
Authors: Dai Jin‐Xia , Hu Ze‐Lan , Shi Ming , Guo Chao , Ding Yu‐Qiang
Published: May 2008

The expression profile of Lim homeodomain transcription factor Lmx1b in the mouse brain was investigated at different postnatal stages by immunohistochemistry and in situ hybridization. At postnatal day (P) 7, many Lmx1b‐expressing neurons were found in the posterior hypothalamic area, supramammillary nucleus, ventral premammillary nucleus, and subthalamic nucleus. In the midbrain, numerous Lmx1b‐expressing neurons were present in the substantia nigra pars compacta and ventral tegmental area. In the hindbrain, Lmx1b‐expressing neurons were primarily observed in the raphe nuclei, parabrachial nuclei, principal sensory trigeminal nucleus, nucleus of the solitary tract, and laminae I‐II of the medullary dorsal horn as well as spinal dorsal horn. Although expression levels diminished as postnatal life progressed, persistent expression throughout the first year of life was observed in many of these regions. In contrast, Lmx1b was present in a few brain regions (e.g., principal sensory trigeminal nucleus) only in early life with expression expiring by P60. Lmx1b was observed in dopaminergic neurons in the midbrain and serotonergic neurons in the hindbrain, as determined by double labeling with specific markers. In addition, we found that Lmx1b‐expressing neurons are not GABAergic, and Lmx1b was colocalized with Tlx3 in the parabrachial nuclei, principal sensory trigeminal nucleus, nucleus of the solitary tract. as well as the medullary and spinal dorsal horns, suggesting that Lmx1b‐expressing cells in these areas are excitatory neurons. Our data suggest that Lmx1b is involved in the postnatal maturation of certain types of neurons and maintenance of their normal functions in the adult brain. J. Comp. Neurol. 509:341–355, 2008. © 2008 Wiley‐Liss, Inc.
Nucleation kinetics and growth of nonlinear optical bis (dimethyl sulfoxide) manganese mercury thiocyanate single crystals
Authors: Raghavan C. M. , Sankar R. , Kumar R. Mohan , Jayavel R.
Published: May 2008

Nonlinear optical (NLO) material of bis (dimethyl sulfoxide) manganese mercury thiocyanate (MMTD) was synthesized by two step reaction method. The solubility and metastable zonewidth were experimentally determined in order to optimize the growth parameters. Bulk crystals of MMTD were grown by slow cooling and slow evaporation methods. The structure of the grown crystal was confirmed by X‐ray diffraction analysis. Presence of functional groups and the coordination of Lewis base ligand of dimethyl sulfoxide (DMSO) were confirmed by FT‐IR analysis. Optical transparency of the grown crystals was studied by UV‐Vis spectroscopy. Nonlinear optical property of the grown crystal was confirmed by Kurtz powder method. Etching studies reveal the formation of triangular hillock etch patterns, indicative of 2D nucleation mechanism. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical and structural properties of lead iodide thin films prepared by vacuum evaporation method
Authors: Ghosh T. , Bandyopadhyay S. , Roy K. K. , Kar S. , Lahiri A. K. , Maiti A. K. , Goswami K.
Published: May 2008

Thermally processed lead iodide (PbI2) thin films were prepared by the vacuum evaporation method in a constant ambient. Measured thickness of the film was verified analytically from the optical transmittance data in a wavelength range between 300 and 1600 nm. From the Tauc relation for the non‐direct inter band transition, the optical band gap of the film was found to be 2.58 eV for film thickness 300 nm. X‐ray diffraction analysis confirmed that PbI2 films are polycrystalline, having hexagonal structure. The low fluctuation in Urbach energy indicates that the grain size is quite small. The present findings are in agreement with the other results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Efficient Method for the Synthesis of Benzo[f]quinoline and Benzo[a]phenanthridine Derivatives Catalyzed by Iodine by a Three‐Component Reaction of Arenecarbaldehyde, Naphthalen‐2‐amine, and Cyclic Ketone
Authors: Wang Xiang‐Shan , Li Qing , Yao Chang‐Sheng , Tu Shu‐Jiang
Published: May 2008

A mild, efficient, and general method for the synthesis of benzo[f]quinoline and benzo[a]phenanthridine derivatives by a three‐component reaction of arenecarbaldehyde, naphthalen‐2‐amine, and cyclic ketone using iodine as catalyst is described. A possible reaction mechanism for the formation of the product is proposed based on further experimental results.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Metal‐Containing Ionic Liquids as Efficient Catalysts for Hydroxymethylation in Water
Authors: Bica Katharina , Gaertner Peter
Published: May 2008

The iron‐containing ionic liquid butylmethylimidazolium tetrachloroferrate (bmim‐FeCl4) proved to be an efficient and recyclable catalyst for the hydroxymethylation of β‐keto esters using aqueous formaldehyde and a low catalyst loading of up to 0.1 mol‐% without co‐solvents or additional surfactants. An useful and high‐yielding approach to hydroxymethylated keto esters as well as to 3‐disubstitued butyrolactones via tandem hydroxymethylation–lactonization could thus be established.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Room‐Temperature Electrophilic 5‐endo‐dig Chlorocyclization of Alk‐3‐yn‐1‐ones with the Use of Pool Sanitizer: Synthesis of 3‐Chlorofurans and 5‐Chlorofuropyrimidine Nucleosides
Authors: Sniady Adam , Morreale Marco S. , Wheeler Kraig A. , Dembinski Roman
Published: May 2008

The 5‐endo‐dig chlorocyclization of 1,4‐disubstituted alk‐3‐yn‐1‐ones (propargylic ketones) with the use of trichloro‐s‐triazinetrione (trichloroisocyanuric acid, TCCA; 0.4 equiv.) in toluene, at room temperature, in the absence of base, provides 2,5‐disubstituted 3‐chlorofurans in high yields (79–96 %). The reaction can be accomplished by using commercially available swimming pool sanitizer. Selected 3‐chlorofuran was validated as a substrate for Suzuki–Miyaura coupling. In a similar manner, chlorocyclization of 5‐alkynyl‐2′‐deoxyuridines produces 5‐chlorofuropyrimidine nucleosides (76–83 %), which are analogues of potent anitviral agents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Neurons control the expression of connexin 30 and connexin 43 in mouse cortical astrocytes
Authors: Koulakoff Annette , Ezan Pascal , Giaume Christian
Published: May 2008

A characteristic feature of astrocytes is their high level of intercellular communication mediated by gap junctions. The two main connexins, Cx30 and Cx43, that form these junctions in astrocytes of adult brain display different developmental and regional expression, with a delayed onset of appearance for Cx30. In primary cultures of astrocytes from newborn cerebral cortex, while Cx43 is abundantly expressed, Cx30 is not detectable. In the present report, Western blot and confocal immunofluorescence analysis performed in astrocyte/neuron cocultures demonstrate that neurons upregulate the expression of Cx43 and induce that of Cx30 in subsets of astrocytes preferentially located in close proximity to neuronal soma. In Cx43 lacking astrocytes cocultured with neurons, the induction of Cx30 allows the restoration of dye coupling within islets of Cx30‐positive astrocytes, indicating that intercellular channels formed by Cx30 are functional. The upregulating effect of neurons on the expression of connexins in cortical astrocytes is independent of their electrical activity and requires tight interactions between both cell types. This effect is reversed after neuronal death induced by neurotoxic treatments. Furthermore, excitotoxic treatments triggering neuronal death in vivo lead to a downregulation of both connexins in reactive astrocytes located within the area depleted in neurons. Altogether these observations indicate that the expression of the two main astrocyte connexins is tightly regulated by neurons. © 2008 Wiley‐Liss, Inc.
Beta‐amyloid peptide stimulates endozepine release in cultured rat astrocytes through activation of N‐formyl peptide receptors
Authors: Tokay Tursonjan , Hachem Raya , Masmoudi‐Kouki Olfa , Gandolfo Pierrick , Desrues Laurence , Leprince Jerome , Castel Helene , Diallo Mickael , Amri Mohamed , Vaudry Hubert , Tonon Marie‐Christine
Published: May 2008

Astroglial cells synthesize and release endozepines, a family of neuropeptides derived from diazepam‐binding inhibitor (DBI). The authors have recently shown that β‐amyloid peptide (Aβ) stimulates DBI gene expression and endozepine release. The purpose of this study was to determine the mechanism of action of Aβ in cultured rat astrocytes. Aβ25–35 and the N‐formyl peptide receptor (FPR) agonist N‐formyl‐Met‐Leu‐Phe (fMLF) increased the secretion of endozepines in a dose‐dependent manner with EC50 value of ≈2 μM. The stimulatory effects of Aβ25–35 and the FPR agonists fMLF and N‐formyl‐Met‐Met‐Met (fMMM) on endozepine release were abrogated by the FPR antagonist N‐t‐Boc‐Phe‐Leu‐Phe‐Leu‐Phe. In contrast, Aβ25–35 increased DBI mRNA expression through a FPR‐independent mechanism. Aβ25–35 induced a transient stimulation of cAMP formation and a sustained activation of polyphosphoinositide turnover. The stimulatory effect of Aβ25–35 on endozepine release was blocked by the adenylyl cyclase inhibitor somatostatin, the protein kinase A (PKA) inhibitor H89, the phospholipase C inhibitor U73122, the protein kinase C (PKC) inhibitor chelerythrine and the ATP binding cassette transporter blocker glyburide. Taken together, these data demonstrate for the first time that Aβ25–35 stimulates endozepine release from rat astrocytes through a FPR receptor positively coupled to PKA and PKC. © 2008 Wiley‐Liss, Inc.
Reduced synaptic activity precedes synaptic stripping in vagal motoneurons after axotomy
Authors: Yamada Jun , Hayashi Yoshinori , Jinno Shozo , Wu Zhou , Inoue Kazuhide , Kohsaka Shinichi , Nakanishi Hiroshi
Published: May 2008

Activated microglia, which spread on the motor neurons following nerve injury, engage in the displacement of detached afferent synaptic boutons from the surface of regenerating motor neurons. This phenomenon is known as “synaptic stripping.” The present study attempted to examine whether changes in the synaptic inputs after motor nerve injury correlated with the microglial attachment to the dorsal motor neurons of the vagus (DMV). DMV neurons in Wistar rats could survive after nerve injury, whereas most of injured DMV neurons in the C57BL/6 mice died. At 2 days after nerve injury, a significant decrease was observed in the frequencies of both spontaneous and miniature EPSCs and IPSCs recorded from DMV neurons in the slice preparation but not from the mechanically dissociated neurons in the Wistar rats. At this stage, no direct apposition of microglia on the injured neurons was observed. High‐K+ stimulation restored their frequencies to control levels. Furthermore, PPADS and DPCPX, antagonists of P2 and adenosine receptors, respectively, also stimulated the recovery of their frequencies. In contrast, no significant change was detected in the spontaneous EPSCs frequency recorded from the severely injured DMV neurons in the slice preparation of the C57BL/6 mice. These observations strongly suggest that presynaptic inhibition through glia‐derived ATP and adenosine, thus precedes synaptic stripping in regenerating DMV neurons following nerve injury. © 2008 Wiley‐Liss, Inc.
Hypoxia selects for androgen independent LNCaP cells with a more malignant geno‐ and phenotype
Authors: Butterworth Karl T. , McCarthy Helen O. , Devlin Andrea , Ming Louise , Robson Tracy , McKeown Stephanie R. , Worthington Jenny
Published: May 2008

Hypoxia confers resistance to common cancer therapies, however, it has also has been shown to result in genetic alterations which may allow a survival advantage and increase the tumorigenic properties of cancer cells. Additionally, it may exert a selection pressure, allowing expansion of tumor cells with a more aggressive phenotype. To further assess the role of hypoxia in malignant progression in prostate cancer we exposed human androgen dependent prostate cancer cells (LNCaP) to cycles of chronic hypoxia and isolated a subline, LNCaP‐H1. This article describes the partial characterization of this cell line. The LNCaP‐H1 subline showed altered growth characteristics and exhibited androgen independent growth both in vitro and in vivo. Furthermore, these cells were resistant to mitochondrial‐mediated apoptosis, probably since the endogenous levels of Bax was lower and Bcl‐2 higher than in the parental LNCaP cells. Microarray analysis revealed that a complex array of pathways had differential gene expression between the 2 cell lines, with LNCaP‐H1 cells exhibiting a genetic profile which suggests that they may be more likely metastasize to distant organs, especially bone. This was supported by an in vitro invasion assay, and an in vivo metastasis study. This study shows that hypoxia can select for androgen independent prostate cancer cells which have a survival advantage and are more likely to invade and metastasize. © 2008 Wiley‐Liss, Inc.
P53 mutations in stromal fibroblasts sensitize tumors against chemotherapy
Authors: Lafkas Daniel , Trimis George , Papavassiliou Athanasios G. , Kiaris Hippokratis
Published: May 2008

The efficacy of chemotherapy is usually viewed as the outcome of cancer‐cell‐autonomous processes while the contribution of stroma is being overseen. Here we show that p53 mutations in stromal fibroblasts, a genetic lesion that is detectable in primary breast, prostate and probably other cancers, while they accelerate tumorigenesis they also sensitize tumours against conventional chemotherapy by doxorubicin and cis‐platinum. The mechanism by which p53 of stromal fibroblasts affects the response of a tumour against chemotherapy is likely to involve the induction of senescence in the fibroblasts which in turns results in the production of growth factors acting onto the cancer cells by paracrine mechanisms. Our findings identify stromal fibroblasts as important modulators of the efficacy of anticancer therapy. © 2008 Wiley‐Liss, Inc.
Vitamin E and cancer: An insight into the anticancer activities of vitamin E isomers and analogs
Authors: Constantinou Constantina , Papas Andreas , Constantinou Andreas I.
Published: May 2008

Current observations in the literature suggest that vitamin E may be a suitable candidate for the adjuvant treatment of cancer. Even though historically most research focused on α‐tocopherol, more recent evidence suggests that the other isomers of vitamin E (β‐, γ‐ and δ‐tocopherols and α‐, β‐, γ‐ and δ‐tocotrienols) differ in their proapoptotic potencies. The main focus of this communication is the current understanding of the molecular mechanisms regulated by vitamin E isomers and their analogs during the induction of apoptosis. This review highlights that the mitochondria are the major target for the induction of apoptosis by vitamin E isomers and analogs and that the various signaling pathways regulated by these agents are likely to contribute towards maximizing the intrinsic pathway of apoptosis triggered initially by the mitochondria. Overall, the presentation of recent studies from the literature in this communication allows the drawing of the following important conclusions: (i) no direct link exists between the antioxidant activity of each isomer/derivative and proapoptotic potency, (ii) tocotrienols are more effective proapoptotic agents than tocopherols, (iii) synthetic modifications of the naturally occurring compounds may improve their apoptotic potency and (iv) vitamin E isomers and derivatives regulate caspase‐independent pathways of apoptosis. The latter combined with the evidence presented in this review regarding the additive or synergistic anticarcinogenic effects obtained when vitamin E analogs are used in combination with other cancer chemotherapeutic agents, supports further research to design the most promising vitamin E derivatives and clinically test them in adjuvant chemotherapeutic treatments. © 2008 Wiley‐Liss, Inc.
Fabrication and characterization of functionally graded nano‐micro porous titanium surface by anodizing
Authors: Kim Hyun‐Seung , Yang Yunzhi , Koh Jeong‐Tae , Lee Kyung‐Ku , Lee Doh‐Jae , Lee Kwang‐Min , Park Sang‐Won
Published: May 2008

The purpose of this study was to fabricate and characterize nanotubular structure on machined titanium (MA) and resorbable blast media (RBM) treated titanium by anodizing. The anodized MA and RBM were characterized with scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, energy disperse spectra, X‐ray photoelectron spectra, and nano‐indentation and scratch test. Highly ordered nanotubular layers of individually 100 nm in diameter and 500 nm in length approximately were formed regardless of the substrates. The nanotubular layers consisted mainly of amorphous TiO2 with trace fluorine. The nanotubular surfaces on both the substrates significantly reduced water contact angles and elastic modulus compared with those prior to anodizing. The anodizing treatment significantly increased the surface roughness of the smooth MA, but significantly decreased the surface roughness of the roughened RBM. The critical delamination forces of the nanotubular layer were not obtained due to the limitation of surface roughness. The anodized RBM consisted of a nano‐micro porous graded structure, or a nanotubular amorphous fluoride containing TiO2 layer on top of micro‐roughened titanium surface, which is expected to significantly improve the surface area that can be used to deliver drugs and growth factors and alleviate the interfacial elastic modulus mismatch as to enhance osseointegration when compared with conventional dental and orthopedic implant devices with smooth or acid etched surface. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009
Modification of the CHARMM force field for DMPC lipid bilayer
Authors: Högberg Carl‐Johan , Nikitin Alexei M. , Lyubartsev Alexander P.
Published: May 2008

The CHARMM force field for DMPC lipids was modified in order to improve agreement with experiment for a number of important properties of hydrated lipid bilayer. The modification consists in introduction of a scaling factor 0.83 for 1–4 electrostatic interactions (between atoms separated by three covalent bonds), which provides correct transgauche ratio in the alkane tails, and recalculation of the headgroup charges on the basis of HF/6‐311(d,p) ab‐initio computations. Both rigid TIP3P and flexible SPC water models were used with the new lipid model, showing similar results. The new model in a 75 ns simulation has shown a correct value of the area per lipid at zero surface tension, as well as good agreement with the experiment for the electron density, structure factor, and order parameters, including those in the headgroup part of lipids. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008
A new upper bound for the bipartite Ramsey problem
Authors: Conlon David
Published: May 2008

We consider the following question: how large does n have to be to guarantee that in any two‐coloring of the edges of the complete graph Kn,n there is a monochromatic Kk,k? In the late 1970s, Irving showed that it was sufficient, for k large, that n ≥ 2k − 1 (k − 1) − 1. Here we improve upon this bound, showing that it is sufficient to take

where the log is taken to the base 2. © 2008 Wiley Periodicals, Inc. J Graph Theory 58: 351–356, 2008
Inequalities for the first‐fit chromatic number
Authors: Füredi Zoltán , Gyárfás András , Sárközy Gábor N. , Selkow Stanley
Published: May 2008

The First‐Fit (or Grundy) chromatic number of G, written as χFF(G), is defined as the maximum number of classes in an ordered partition of V(G) into independent sets so that each vertex has a neighbor in each set earlier than its own. The well‐known Nordhaus‐‐Gaddum inequality states that the sum of the ordinary chromatic numbers of an n‐vertex graph and its complement is at most n + 1. Zaker suggested finding the analogous inequality for the First‐Fit chromatic number. We show for n ≥ 10 that ⌊(5n + 2)/4⌋ is an upper bound, and this is sharp. We extend the problem for multicolorings as well and prove asymptotic results for infinitely many cases. We also show that the smallest order of C4‐free bipartite graphs with χFF(G) = k is asymptotically 2k2 (the upper bound answers a problem of Zaker [9]). © 2008 Wiley Periodicals, Inc. J Graph Theory 59: 75–88, 2008
Identification of degradation mechanisms in coatings for supercritical steam applications
Authors: Durham R. N. , Singheiser L. , Quadakkers W. J.
Published: May 2008

The development and qualification of coatings for materials used in modern steam power plants stems from the increased demand for higher efficiency, and hence higher operating temperatures. Within the EU funded project ‘SUPERCOAT’, several coatings, both overlay and diffusion type, were investigated. Seven different coatings are presented in this work. They included two commercially available HVOF coatings (Ni–20Cr and Ni–50Cr), an aluminium‐based slurry coating (IPCOTE), together with two further variations of this slurry coating containing sputter‐coated inter‐layers. An overlay slurry coating consisting of silica particles embedded in a matrix of alumina and chromia was also examined. The final coating to be investigated was a pack‐aluminised sample of P92.

All the coating systems examined showed superior oxidation resistance compared to the 9%Cr steel substrate (P91 or P92) in extended exposures to a steam environment at 650 °C. However, in service component lifetime will be limited by degradation of the coating, therefore it is essential that the mechanisms controlling this behaviour are understood. This paper reviews several degradation mechanisms that have been observed during long‐term exposure of these coatings. The mechanisms that have been observed include depletion of active alloying elements, diffusion of aluminium into the substrate from the coating, formation of Kirkendall porosity and mechanical failure of the coatings. Examples of each of these mechanisms will be presented. Possible processing routes to avoid these degradation mechanisms will also be discussed.
Influence of Molecular Structure and Stereochemistry of the 1,4‐Cyclohexylene Ring on Thermal and Mechanical Behavior of Poly(butylene 1,4‐cyclohexanedicarboxylate)
Authors: Berti Corrado , Celli Annamaria , Marchese Paola , Marianucci Elisabetta , Barbiroli Giancarlo , Di Credico Francesco
Published: May 2008

Poly(butylene 1,4‐cyclohexanedicarboxylate), an aliphatic polyester with favorable properties, such as resistance to weather and potential biodegradability, has been synthesized with different cis/trans ratio of the 1,4‐cyclohexylene ring. The samples show high degradation temperatures, independent of the stereochemistry of the aliphatic ring. Instead, glass transition temperature, crystallization and melting behavior are strongly influenced by the cis/trans ratio. The trans isomer, more rigid and symmetric than the cis, favors higher transition temperatures and crystallizability. The DMTA spectra present two secondary relaxations, attributed to the (CH2) unit and aliphatic ring motions, which can be beneficial for improving impact resistance properties. The physical properties are compared with those of PBT and PCCD.

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Prevalence of cholinesterase inhibitors in subjects with dementia in Europe
Authors: Pariente Antoine , Helmer Catherine , Merliere Yvon , Moore Nicholas , Fourrier‐Réglat Annie , Dartigues Jean‐Francois
Published: May 2008

Purpose

To evaluate the prevalence of cholinesterase inhibitor (ChI) treatment in subjects with dementia in European countries.

Methods

We studied the prevalence of treatment in subjects with dementia among European countries in 2004 (Belgium, France, Germany, Italy, the Netherlands, Poland, Portugal, Spain and the United Kingdom) by using estimates of prevalence of dementia and of ChI treatments according to sales and reimbursement data.

Results

In 2004, estimated prevalence of ChI use among subjects with dementia ranged from 3.0% in the Netherlands to 20.3% in France. It was 17.5% in Spain, 6.7% in the UK and 5.9% in Italy. Donepezil was used by more than 60% of patients using a single ChI and represented almost 50% of reimbursements for patients that had used at least two different ChIs during the year. Galantamine and rivastigmine were respectively used by 22 and 18% of subjects using a single drug and 27 and 23% of reimbursements for patients that had used at least two different ChIs. Nevertheless, different patterns of use were found for individual countries.

Conclusions

Prevalence of treatment by ChIs among subjects with dementia remains weak and varies greatly across Europe. Differences in reimbursement rates and health policies could partly explain these variations, as ChIs could have failed to convince health authorities because the outcomes considered for trials are not used by clinicians in their everyday practice. If donepezil was highly predominant across countries, variations in rivastigmine and galantamine importance could reflect local market specificities. Copyright © 2008 John Wiley & Sons, Ltd.
Hydrolysis of aliphatic naphthalene diimides: effect of charge placement in the side chains
Authors: Kim Michelle B. , Dixon Dabney W.
Published: May 2008

Water‐soluble naphthalene diimides (NDIs) have found uses in a wide variety of applications including as electron acceptors in electron transfer reactions and as molecules that undergo spontaneous organization in aqueous solution. Many studies have looked at their interaction with nucleic acids including work with DNA duplexes, triplexes, quadruplexes, hairpins, and DNA–RNA heteroduplexes. In many of these interactions the NDIs serve as threading intercalators. Herein we describe the reversible hydroxide‐catalyzed hydrolysis of NDIs bearing aliphatic side chains, with ring opening first to the monoimide and then to the diamide. Examples with N‐methylpyrrolidinium groups placed two (1) and three (5) atoms from the central core were studied. The Ka values for the first and second hydrolyses for 1 were 2.5 ± 0.2 × 105 and 2.0 ± 0.1 × 102 M−1, respectively; for 5 they were 1.4 ± 0.1 × 105 and 44 ± 2 M−1, respectively. NDI 1 hydrolyzed 6.8 times faster than 5. The rates for the first and second ring opening of 1 in 100 mM hydroxide measured by stopped‐flow were 17.0 ± 0.2 and 0.53 ± 0.01 s−1, respectively. Capillary electrophoresis in borate buffer showed separation of the diimide and monoimide with the former eluting first. Nuclear magnetic resonance (NMR) showed both the syn and anti isomers of the diamide species. Overall, the rate of hydrolysis of the NDI is increased when the cationic charge is moved closer to the NDI core. Copyright © 2008 John Wiley & Sons, Ltd.
Kinetics study of a Diels‐Alder reaction in mixtures of an ionic liquid with molecular solvents
Authors: Harifi‐Mood Ali Reza , Habibi‐Yangjeh Aziz , Gholami Mohammad Reza
Published: May 2008

The second‐order rate constants for cycloaddition reaction of cyclopentadiene with naphthoquinone were determined spectrophotometrically in various compositions of 1‐(1‐butyl)‐3‐methylimidazolium terafluoroborate ([bmim]BF4) with water and methanol at 25 °C. Rate constants of the reaction in pure solvents are in the order of water > [bmim]BF4 > methanol. Rate constants of the reaction decrease sharply with mole fraction of the ionic liquid in aqueous solutions and increase slightly to a maximum in alcoholic mixtures. Multi‐parameter correlation of logk2 versus solute–solvent interaction parameters demonstrated that solvophobicity parameter (Sp), hydrogen‐bond donor acidity (α) and hydrogen‐bond acceptor basicity (β) of media are the main factors influencing the reaction rate constant. The proposed three‐parameter model shows that the reaction rate constant increases with Sp, α and β parameters. Copyright © 2008 John Wiley & Sons, Ltd.
Locally Resolving Measurements of PSD, Particle Concentration and Particle Velocity by Means of TFS with Dual Beams
Authors: Guo Xiaoai , Riebel Ulrich
Published: May 2008

Transmission fluctuation spectrometry with spatial correlation (TFS‐SC) is based on transmitting two beams of radiation through a flowing suspension, whereby the distance of the beam centers is varied. Thus, the spatial correlation of the transmission fluctuations of the two beams is determined as a function of the beam distance.

By numerical modeling, the transition functions of the correlation are found as a function of beam distance, beam diameters, particle diameter and beam intersection angle.

Experimentally determined spatial correlation spectra can be inverted to obtain the particle concentration and particle size distribution by using the theoretical transition functions for mono‐sized particles. In addition, time correlations can be used to extract information on particle velocity. Some experimental results obtained by TFS‐SC are presented and discussed. This method appears promising for application in the local resolving of measurements of PSD, particle concentration and particle velocity in two‐phase flows, both in the laboratory and in process control.
Nanocrystallites obtained through the pyrosol method
Authors: Dinu E. , Andronescu E. , Ghitulica C. D. , Siebert E. , Djurado E. , Dessemond L.
Published: May 2008

The decrease of particles size from micrometric to the nanometric scale is allowing the development of new materials, with dramatically improved properties. The pyrolysis of aerosols is a very interesting method of production for reactive nanopowders. In this study, the influence of various synthesis parameters on the crystallinity and the composition of calcium phosphate powders were investigated. Firstly, the influence of the chemical nature of the calcium precursor was studied, by using two types of water‐soluble calcium salts: CaCl2·2H2O and Ca(NO3)2. Secondly, the effect of the pyrolysis temperature, in the 600–1000 °C interval was studied. Whatever the temperature of pyrolysis of the aerosol, the apatite structure is recognizable, if the precursor used for the calcium oxide is calcium chloride. If the powders are elaborated starting from calcium nitrate, the only phase identified is β‐calcium phosphate. The synthesized powders have spherical morphology, are highly porous and dimensionally in the nanometric range. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prerequisites of nanocavities for single artificial atom laser
Authors: Nomura M. , Iwamoto S. , Arakawa Y.
Published: May 2008

Prerequisites of nanocavities for single quantum dot laser have been theoretically studied by a fully quantum‐mechanical treatment. Numerical simulations are performed by solving master equations for single four‐level electronic system and single cavity electric field mode. Experimentally obtained parameters are used in the simulations to predict prerequisites of the cavity quality factor Q and allowable range of the relative position control of the cavity and a target quantum dot. In the case of a photonic crystal defect nanocavity with a modal volume of 0.04 μm3, the required Q for lasing is 65,000 assuming the atom‐field coupling strength g = 40 GHz. The dephasing effect is also taken into account in the simulation. The results indicate that the dephasing effect can be negligible when the transverse relaxation time is longer than ∼ 100 ps. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selective growth of InP on localized areas of silicon (100) substrate by molecular beam epitaxy
Authors: Araki K. , Seo J. U. , Hasegawa S. , Asahi H.
Published: May 2008

To use III‐V compound semiconductors as channel materials in the future advanced MISFETs with high performance, it is important to acheive the growth of III‐V‐on‐Insulator structures on Si substrates. As a first step to accomplish this, we propose the selective formation of InP only on localized areas of Si (100) substrate by molecular beam epitaxy (MBE). It was found that InP was selectively grown only on bare Si window areas, while not grown on native silicon oxide areas at elevated substrtate temperatures (500°C). It was also found that by decreasing the window size (0.7×0.7 μm2) only single grain of InP was grown on each bare Si window area. This indicates that the selective MBE growth of InP on Si substrate is possible. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interplay of impurity segregation and lattice mismatch in molecular beam epitaxy of III′–III″–V compounds plus dopant: application to the InGaAs:Sn nanoheterolayer growth
Authors: Chikalova‐Luzina O.
Published: May 2008

A thermodynamic model for molecular beam epitaxy of quaternary solid alloys III′–III″–V plus dopant is developed on a practical example of In1x Gax As:Sn/GaAs heterolayer growth. In the frame of the model, the interplay of surface segregation and strain during epitaxy is analyzed. It is shown Sn atoms, being segregated during the growth in the In–stabilized conditions, act as an efficient surfactant, and Sn doping may be used to improve the surface morphology of strained nanoheterolayers. It is found that high doping level and the low growth temperatures are favourable for achieving a smooth morphology. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron tunneling through single self‐assembled InAs quantum dots coupled to nanogap electrodes
Authors: Shibata K. , Jung M. , Buizert C. , Oiwa A. , Hirakawa K. , Machida T. , Tarucha S.
Published: May 2008

We have investigated electronic properties of self‐assembled InAs quantum dots (QDs) grown on GaAs surfaces by using metallic Au and Al leads with narrow gaps. The fabricated junctions with Au nanogap electrodes show single electron tunneling behaviors. When coupling between electrons in the QDs and the electrodes is strong, Kondo effect with relatively high Kondo temperature TK of 10‐15 K is observed. The samples with superconducting (SC) Al electrodes also exhibit clear Coulomb blockade effects. Furthermore, clear suppression in conductance is observed around VSD = 0 V for a voltage range of 4Δ /e at T = 40 mK, where Δ is the SC energy gap of Al, demonstrating successful fabrication of the SC‐QD‐SC junction in the self‐assembled InAs QD system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tunneling mechanism of GaAs ultrashallow sidewall tunnel junction
Authors: Ohno Takeo , Oyama Yutaka , Sato Shota , Nishizawa Jun‐ichi
Published: May 2008

Conductance‐voltage (G ‐V) and current‐voltage (J ‐V) measurements were applied to reveal the tunneling mechanisms of GaAs ultra‐shallow sidewall tunnel junctions, which were fabricated by molecular layer epitaxy. From the G ‐V results, peaks were detected at 2, 12 and 14 THz at 6 K. In the J ‐V measurements, the fine structure near the peak voltage and a step in the tunneling current in the negative resistance region can also be observed. The tunneling mechanism is discussed in terms of the band transition, deep level and phonon‐assisted tunneling. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved EL characteristics of polyfluorene/PBD‐mixed layer by wet process
Authors: Yamaguchi H. , Komoriya M. , Kamata N.
Published: May 2008

We fabricated poly(9,9‐di‐n ‐octylfluorenyl‐2,7‐dilyl) (PFO) EL devices with PBD as an electron transport material. The PBD/PFO double‐layer, which was spin‐coated sequentially by choosing solvents, and the mixed layer devices were fabricated successfully. Factors of improvement in EL intensity were eight and five for mixed layer (PBD:PFO=7:3) and double layer devices, respectively, when compared with that of the PFO single layer device. The combination of mixed layer device with PMPS:PBD:PFO= 60:35:5 showed further improvement in EL intensity by a factor of 2.5 from the mixed layer device without PMPS. These results are promising for optimizing polymer EL devices based on the wet process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature‐dependent high‐frequency performance of deep submicron AlGaN/GaN HEMTs
Authors: Cuerdo R. , Pei Y. , Recht F. , Fichtenbaum N. , Keller S. , Denbaars S. P. , Calle F. , Mishra U. K.
Published: May 2008

A study of the low temperature DC and RF performance of deep submicron AlGaN/GaN high electron mobility transistors (HEMTs) is reported. From 300 K to 100 K both extrinsic transconductance and drain current increase by ∼30%, mainly due to the lowering of the optical phonon scattering that allows higher electron mobility. Source and drain resistances improve too, which contributes to the 15‐20% increase of ftand fmax. The low temperature small signal model has also been extracted accurately at every 50 K. Inductances and capacitances remain constant in the range of temperatures measured. The intrinsic transconductance can be also considered temperature independent, but the output conductance decreases from 300 K to 100 K indicating a better confinement of the 2DEG. The HEMT performance obtained at 100 K can be reached at room temperature by reducing the parasitic resistances and improving the GaN buffer isolation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)