bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regioselective Synthesis of 4,5‐Diaryl‐1‐methyl‐1H‐imidazoles Including Highly Cytotoxic Derivatives by Pd‐Catalyzed Direct C‐5 Arylation of 1‐Methyl‐1H‐imidazole with Aryl Bromides
Authors: Bellina Fabio , Cauteruccio Silvia , Di Fiore Annarita , Rossi Renzo 
Published: October 2008

AbstractA general and efficient three‐step procedure for the highly regioselective synthesis of 1‐methyl‐1H‐imidazoles possessing electron‐rich, electron‐neutral, and/or electron‐deficient aryl moieties at their 4‐ and 5‐positions is described. The first step involves the Pd‐catalyzed direct C‐5 arylation of commercially available 1‐methyl‐1H‐imidazole with aryl bromides, and the second and third steps of the sequence involve the selective C‐4 bromination of the resulting 5‐aryl‐1‐methyl‐1H‐imidazoles with NBS, followed by a PdCl2(dppf)‐catalyzed Suzuki‐type reaction between 5‐aryl‐4‐bromo‐1‐methyl‐1H‐imidazoles and arylboronic acids under phase‐transfer conditions. Two 4,5‐diaryl‐1‐methyl‐1H‐imidazoles so prepared, which can be regarded as Z‐restricted analogues of naturally occurring combretastatin A‐4 (CA‐4), proved to be highly cytotoxic against a variety of human tumor cell lines, and one of these derivatives has been shown to be more cytotoxic than CA‐4 and all of the imidazole derivatives investigated in the literature thus far. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TMSOTf‐Promoted Addition of Alkynes to Aldehydes: A Novel Synthesis of Chroman‐4‐ones
Authors: Park Ji Yeon , Ullapu Punna Reddy , Choo Hyunah , Lee Jae Kyun , Min Sun‐Joon , Pae Ae Nim , Kim Youseung , Baek Du‐Jong , Cho Yong Seo 
Published: October 2008

AbstractA novel synthetic method to prepare chalcones 2 and chroman‐4‐ones 3 by TMSOTf‐promoted addition of alkynes 1 to various aldehydes has been developed. The ratios of chalcones 2, chroman‐4‐ones 3 and hydrated products 4 varied depending upon the substituents R (nBu, phenyl, H and TMS) on the alkynes 1. We also describe the transformation of the chalcones 2 to the corresponding chroman‐4‐ones 3 under basic conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Second‐order diagnostics for space‐time point processes with application to seismic events
Authors: Adelfio Giada , Chiodi Marcello 
Published: October 2008

AbstractA diagnostic method for space‐time point process is introduced and used to interpret and assess the goodness of fit of particular models to real data such as the seismic ones. The proposed method is founded on the definition of a weighted process and allows to detect second‐order features of data, like long‐range dependence and fractal behavior, that are not accounted for by the fitted model. Applications to earthquake data are provided. Copyright © 2008 John Wiley & Sons, Ltd.
Determination of shortest distance to voltage instability with particle swarm optimization algorithm
Authors: Chen M. J. , Wu B. , Chen C. 
Published: October 2008

AbstractLoading margin denotes how close the power system is to voltage instability. This paper presents a new technique to obtain the shortest distance to voltage instability, which converts the computation of the closest point of collapse to an optimization problem. Compared with the existing methods, the notable advantage of this technique is the capability of dealing with various constraints such as generation reactive power limits expediently and of finding out the global shortest distance to instability instead of local one, so that the shortest distance obtained corresponds to the practical system operation and then effective measures may be taken to prevent voltage collapse according to the results. A modified particle swarm optimization algorithm is presented to solve this optimization problem. Of the proposed algorithm, local optimum areas are ascertained and further exploring is implemented to find genuine local optima. Recruiting new particles outside the ascertained local optimum areas enhances the global search stability of the proposed algorithm. Details of the optimization problem and the implementation of the proposed optimization method to test systems are presented and the feasibility and validity are demonstrated. Copyright © 2008 John Wiley & Sons, Ltd.
Source encoding with efficient transmission of CSI in multiuser MIMO–OFDMA downlink
Authors: Yi Liu , Hailin Zhang 
Published: October 2008

AbstractThis paper investigates the problem of source encoding in multiuser multiple‐input multiple‐output (MIMO)–orthogonal frequency division multiplexing (OFDMA) downlink with a limited feedback channel. The proposed encoding scheme, including beamforming, subcarrier distribution and rate loading, applies a pre‐designed codebook of beamforming vectors, which is stored at both the transmitter and the receiver. The receiver selects the beamforming vector and user for each subcarrier aiming at SINR maximization and conveys the index of the chosen vector and equivalent gain to the transmitter. At the transmitter, the rate is loaded to each subcarrier using the ‘greedy’ algorithm. The methods of codebook construction and rate loading are discussed in detail. Simulation results show that the scheme decreases the amount of feedback data while maintaining quite a large downlink capacity and the capacity approaches that of perfect CSI with an increase in codebook elements. Copyright © 2008 John Wiley & Sons, Ltd.
A robust cell search scheme for OFDMA systems
Authors: Li Li , Zhou Ping , Hu Honglin , Zhang Xiaodong 
Published: October 2008

AbstractOne essential stage in orthogonal frequency‐division multiple access (OFDMA) downlink is cell search, which is the initialisation for the access of the users to the communication networks. This paper proposes a robust cell search structure for the OFDMA system based on constant amplitude zero auto‐correlation (CAZAC) sequences, namely an orthogonal allocation (OA) scheme. Simulation results show that the cell identification capability has been improved remarkably, especially for the users at the cell boundary. Copyright © 2008 John Wiley & Sons, Ltd.
Seen in der Sahara
Authors: Kröpelin Stefan 
Published: October 2008

AbstractGroße Wasserflächen inmitten der Wüste sind nicht nur ein Naturspektakel, sondern auch ein hochpräzises Umweltarchiv. Die aus ihnen gewonnenen Sedimente dokumentieren die Klimaentwicklung und geben Aufschluss über Staubstürme, Savannenbrände und Vulkanausbrüche. Eine Reise in den Nordosten des Tschad.
Synthesis of Dispersed and Contiguous Nanoparticles in Solid Oxide Fuel Cell Electrodes
Authors: Sholklapper T. Z. , Jacobson C. P. , Visco S. J. , De Jonghe L. C. 
Published: October 2008

AbstractSolid oxide fuel cell (SOFC) electrodes, after their high temperature sintering, may be impregnated (infiltrated) to deposit nanoparticles within their pores. There are two main motivations for modifying the electrodes: (i) to add catalytic function, and (ii) to enhance electronic or ionic conduction pathways, since either or both may not be sufficient within the as‐sintered electrodes. The impregnated particles take on two configurations: dispersed or connected. While dispersed nanoparticles introduce catalysts, connected nanoparticulate networks can add conduction paths in addition to enhancing catalysis. This paper reviews the prevalent SOFC electrode types, the function of the impregnated nanoparticles, and the common impregnation methods. Specific attention is given to the optimal uses of each method, with positives and negatives addressed for each.
Impact of wildfire on source water contributions in Devil Creek, CA: evidence from end‐member mixing analysis
Authors: Jung Helen Y. , Hogue Terri S. , Rademacher Laura K. , Meixner Tom 
Published: October 2008

AbstractA geochemical and end‐member mixing analysis (EMMA) is undertaken in Devil Canyon catchment, located in southern California, to further understanding of watershed behaviour and source water contributions after an acute and extensive wildfire. Physical and chemical transformations in post‐fire watersheds are known to increase overland flow and decrease infiltration, mainly due to formation of a hydrophobic layer at, or near, the soil surface. However, less is known about subsurface flow response in burned watersheds. The current study incorporates EMMA to evaluate and quantify source water contributions before, and after, a catchment affected by wildfires in southern California during the fall of 2003. Pre‐ and post‐fire stream water data were available at several sampling sites within the catchment, allowing the identification of contributing water sources at varying spatial scales. Proposed end‐member observations (groundwater, overland flow, shallow subsurface flow) were also collected to constrain and develop the catchment mixing model. Post‐fire source water changes are more evident in the smaller and faster responding sub‐basin (interior sampling point). Early post‐fire storm events are dominated by overland flow with no significant soil water or groundwater flow contribution. Inter‐storm streamwater in this smaller basin shows an increase in groundwater and a decrease in soil water. In the larger, baseflow‐dominated system, source water components appear less affected by fire. A slight increase in lateral flow is observed with only a slight decrease in baseflow. Changes in the post‐fire flow regimes affect nutrient loading and chemical response of the basin. Relatively rapid recovery of the chaparral ecosystem is evidenced, with active re‐growth and evapotranspiration evidenced by the fourth post‐fire rainy season. Copyright © 2008 John Wiley & Sons, Ltd.
Flow and sediment regimes at tributary junctions on a regulated river: impact on sediment residence time and benthic macroinvertebrate communities
Authors: Svendsen Kristen M. , Renshaw Carl E. , Magilligan Francis J. , Nislow Keith H. , Kaste James M. 
Published: October 2008

AbstractTributaries may either ameliorate or exacerbate the geomorphic and ecologic impacts of flow regulation by altering the flux of water and sediment into the flow‐regulated mainstem. To capture the effects of tributary influences on a flow regulated river, long‐term discharge and cross‐sectional data are used to assess the geomorphic and hydrologic impacts of impoundment. In addition, the use of the short‐lived cosmogenic radioisotope 7Be (half‐life 53·4 days) to link sediment transport dynamics to benthic macroinvertebrate community structure is evaluated. It is found that the 7Be activity of transitional bed load sediment is highly seasonal and reflects both variations in activity of sediment sources and limited sediment residence time within the junction. Benthic communities also exhibit a strong seasonal variability. In the spring, neither the 7Be activity of the sediment, nor benthic communities exhibit clear relationships with sample site location. In contrast, during the late summer the ratio of Ephemeroptera (mayflies)/Trichoptera (caddisflies) decreased significantly below tributary junctions. This decrease in benthic community ratio was driven by increases in caddisfly abundance and was strongly correlated with the presence of recently 7Be tagged transitional bedload sediment. These observations are probably associated with the presence of coarse, stable, and unembedded substrate downstream of tributaries and the rapid turnover of sediment that may also be associated with a rapid flux in nutrients or seston. The results show that tributaries are impacting the flow‐regulated mainstem and that these impacts are reflected in the benthic community structure and in the 7Be activity of transitional bed load sediment. Moreover, the observed reduction in competence and capacity of the mainstem following flood control suggests that these spatial discontinuities may be a consequence of impoundment. Copyright © 2008 John Wiley & Sons, Ltd.
Monitoring drought severity in agriculture through a synthetic index based on dry periods: a case study in the Mediterranean basin
Authors: Salvati Luca , Venezian‐Scarascia Maria‐Elisa , Zitti Marco 
Published: October 2008

AbstractDrought is usually defined as a significant, temporary reduction in water availability below the expected amount for a specified period and for a defined climatic zone. Drought episodes may be described by means of different characteristics, namely drought duration and intensity, considered as the two dimensions of this agro‐climatic phenomenon. Among the several methods proposed for describing drought, the run method appears as suitable to provide an objective characterisation of drought events. A simple drought index, obtained from only two input variables (rainfall and reference evapotranspiration), able to describe different dimensions of drought phenomena (duration, intensity and severity), and to recognise “normal” conditions, both in statistical and ecological terms, is meaningful. Our interest is therefore to develop such a drought index, able to produce information on a detailed geographic and time scale.The procedure we have built up consists in calculating for each day, considered as dry or wet, the length of the present dry spell (LH) and water deficit (DF). The same variables were computed over a six‐month period preceding the evaluation day (LH6 and DF6). For each day to be evaluated we associated each agro‐climatological variable with the corresponding percentile value obtained from the climatology data set. Two partial indicators depicting drought duration (LHS) and intensity (DFS) were introduced. LHS and DFS were computed respectively as the maximum daily value between LH and LH6, and between DF and DF6. A synthetic index of drought severity (DSI) was finally obtained as the geometric mean of LHS and DHS indicators.Using dry spell climatology we estimated duration, intensity and severity of drought on a daily basis over the test period 1988–2003. The most arid period in Italy was recorded during spring–summer 2003, when especially dry conditions occurred in northern and central Italy. DSI correctly indicates a significant increase of drought from March to July 2003 throughout Italy: drought severity reaches the 90 percentile in all the stations from Po plain, Apennines, and coastal areas of central Italy.In conclusion, DSI may be used to assess the agro‐climatic conditions occurring in a certain location through only two input variables. It allows a synthetic description of drought episodes in terms of both dry spell length and water balance. Copyright © 2008 John Wiley & Sons, Ltd.
Correlation of histology and linear and nonlinear microscopy of the living human cornea
Authors: Masters Barry R. 
Published: October 2008

AbstractThe morphology and the function of cellular and non‐cellular structures in the living human cornea can be determined with modern correlative linear and nonlinear optical microscopic techniques and histology. Correlative microscopy is based on the use of different optical techniques to study the same specimen, ideally at the same location within the specimen, in order to increase the functional and/or morphological understanding of the specimen. A case study to assess the effect of overnight lid‐closure on in vivo human corneal morphology is presented to illustrate correlative linear microscopy and optical low‐coherence reflectometry. Nonlinear multiphoton excitation microscopy provides functional information on cellular metabolism based on the intrinsic fluorescence from the reduced pyridine nucleotides and the oxidized flavoproteins. Second‐harmonic generation microscopy, a scattering process that does not deposit net energy into the tissue, provides structural information on corneal collagen organization. Molecular third‐harmonic generation microscopy generates a signal in all materials and it an emerging technique. Coherent anti‐Stokes Raman scattering microscopy provides chemical imaging for biology and medicine. The comparison and limitations of these microscopic modalities, linear and nonlinear microscopy applied to the cornea, and a review of some key findings is analyzed. A correlative integration and correlation of linear and nonlinear microscopies to study corneal function and structure is proposed to validate the clinical interpretation of microscopic images of the cornea. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A theoretical study on fullerene‐dizincocene hybrids
Authors: Gao Guohua , Xu Xiang , Kang Hong Seok 
Published: October 2008

AbstractUsing the density functional theory, we investigated the possible formation of fullerene‐dizincocene hybrids, specifically C60*‐Zn‐Zn‐Cp*, C60*‐Zn‐Zn‐C60*, C70*‐Zn‐Zn‐Cp*, and C70*‐Zn‐Zn‐C70*, where C60*, Cp*, and C70* represent C60(CH3)5, C5(CH3)5, and C70(CH3)5 radicals. Our calculation shows that these hybrids have HOMO‐LUMO gaps which are larger than has been experimentally identified for C60*‐Fe‐Cp. In addition, the strength of the ZnZn bonds is similar to that in Cp*‐Zn‐Zn‐Cp* which was also synthesized recently. Furthermore, heterohybrids, C60*‐Zn‐Zn‐Cp* and C70*‐Zn‐Zn‐Cp* are expected to exist in equilibria with homohybrids, C60*‐Zn‐Zn‐C60* and C70*‐Zn‐Zn‐C70*, in which heterohybrids are much more favored. On the other hand, another hybrid involving Sc3N@C68 as a fullerene unit is not highly probable. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009
Decolorisation of synthetic dyes by crude laccase from Rigidoporus lignosus W1
Authors: Li Li , Dai Wenkui , Yu Peng , Zhao Jian , Qu Yinbo 
Published: October 2008

AbstractBACKGROUND: Effluents from the dyeing process containing dyes are difficult to degrade biologically. Therefore enzymatic dye decolorisation has received considerable attention recently. In this study the dye decolorisation potential of crude laccase from the white rot fungus Rigidoporus lignosus W1 was demonstrated on an anthraquinone dye, Remazol Brilliant Blue R (RBBR), and a triphenylmethane dye, malachite green (MG). Effects of pH, temperature and ionic strength on laccase activity and decolorisation efficiency were investigated.RESULTS: Native polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate PAGE confirmed the decolorisation ability of the crude enzyme on RBBR and MG. A single laccase with a molecular mass of about 40 kDa appeared to be involved in the process. Efficient enzymatic decolorisation without redox mediator was achieved, with 39 mg L−1 MG being removed within 2 h and 160 mg L−1 RBBR within 1 h at 60 °C and pH 4.5. Although the laccase activity was inhibited in the presence of NaCl, it was renatured gradually in low concentrations of NaCl (<0.8 mol L−1), resulting in unusual dye decolorisation kinetics. Surprisingly, unusual storage stability at alkaline pH was observed, with the laccase activity being enhanced 1.5–2‐fold after 3 h of incubation.CONCLUSION: Crude laccase with unusual storage stability from the fungus R. lignosus W1 showed excellent decolorisation ability on RBBR and MG without redox mediator. This laccase would seem to be a good candidate for application in dye decolorisation and textile effluent biotreatment. Copyright © 2008 Society of Chemical Industry
Purification and biochemical characterization of an intracellular lipase by Rhizopus chinensis under solid‐state fermentation and its potential application in the production of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)
Authors: Sun Shu Yang , Xu Yan , Wang Dong 
Published: October 2008

AbstractBACKGROUND: Purification and characterization of an intracellular lipase produced by Rhizopus chinenesis cultured in solid‐state fermentation was investigated. The potential application in concentrating eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil by the pure enzyme was also studied.RESULTS: Through four successive purification steps, the enzyme was purified to homogeneity with an apparent molecular mass of 36 kDa. The lipase was active for pH between 7.0 and 9.0 and temperatures 20–45 °C. Lipase activity was slightly increased in the presence of Ca2+ and Mg2+, but strongly inhibited by Hg2+ and SDS. The pure enzyme was most active on medium chain p‐nitrophenol esters, with the highest activity towards pNP‐caprylate (C8). The enzyme is a non‐specific lipase, because it cleaved not only the 1,3‐positioned ester bonds but also the 2‐positioned bond in triolein. High EPA (17.6%) and DHA (32.9%) contents were achieved using the pure lipase (100 U) within 10 h.CONCLUSION: The enzymatic activity of the lipase on a wide variety of substrates and its stability in the presence of some organic solvents suggest that the lipase should be investigated for a range of commercial applications. The pure lipase was proved to possess potential ability for the production and concentration of EPA and DHA from fish oil. Copyright © 2008 Society of Chemical Industry
Removal of H2S using a new Ce(IV) redox mediator by a mediated electrochemical oxidation process
Authors: Chandrasekara Pillai K. , Raju T. , Chung Sang Joon , Moon Il‐Shik 
Published: October 2008

AbstractBACKGROUND:Hydrogen sulfide (H2S) from industrial activities and anaerobic manure decomposition in commercial livestock animal operations is an offensive malodorous and toxic gas even in small concentrations, causing serious discomfort and health and social problems. The objective of this study was to employ for the first time a novel, attractive, low cost, environmentally benign mediated electrochemical oxidation (MEO) process with Ce(IV) as the redox catalyst for H2S gas removal from an H2S–air feed mixture.RESULTS:The influence of liquid flow rate (QL) from 2–4 L min−1, gas flow rate (QG) from 30–70 L min−1, H2S concentration in the H2S–air feed mixture from 5–15 ppm, and Ce(III) pre‐mediator concentration in the electrochemical cell from 0.1–1 mol L−1on H2S removal efficiency were investigated. Both liquid and gas flow rates influenced the removal efficiencies, but in opposite directions. Nearly 98% H2S removal was achieved when the concentration of Ce(IV) mediator ion in the flowing scrubbing liquid reached 0.08 mol L−1.CONCLUSIONS:The new MEO method proved promising for H2S removal, achieving high removal efficiency. Integration of the electrochemical cell with the scrubber set‐up ensured continuous regeneration of the mediator and its repeated reuse for H2S removal, avoiding use of additional chemicals. Since the process works at room temperature and atmospheric pressure utilizing conventional transition metal oxide electrodes more commonly used in industrial applications, it is also safe and economical. Copyright © 2008 Society of Chemical Industry
The preparation of three new partially deuterated hexadecanethiols for applications in surface chemistry
Authors: Sheepwash Erin E. , Rowntree Paul A. , Schwan Adrian L. 
Published: October 2008

AbstractThe synthesis of three partially deuterated hexadecanethiols has been achieved. Thiols CH3(CH2)7(CD2)8SH, CD3(CD2)7(CH2)8SH and CD3(CH2)15SH were targeted, as these compounds, after formation of self‐assembled monolayers on Au(1 1 1) or Au nanoparticles, can provide mechanistic information pertaining to reactive atom migrations within the assembly. The syntheses of each of these compounds called upon Grignard coupling chemistry, which was activated by Li2CuCl4. Applicable deuterium containing fragments were either commercially obtained or constructed from by way of an inexpensive and efficient ring opening, protection and dimerization of THF‐d8. Sulfur incorporation was by thiolacetate substitution or addition reactions. The protocols presented possess general applicability in a number of syntheses requiring block‐deuterated fattyalkyl sections. Copyright © 2008 John Wiley & Sons, Ltd.