bluuebunny/crossref_metadata_2025_split huggingface dataset:
Five‐ and Four‐Coordinate 1,3‐Diaza‐2‐yttria‐ and 1,3‐Diaza‐2‐scandia‐[3]ferrocenophanes
Authors: Wrackmeyer Bernd , Klimkina Elena V. , Milius Wolfgang 
Published: June 2008

Abstract2‐Chloro‐1,3‐bis(trimethylsilyl)‐1,3‐diaza‐2‐metalla‐[3]ferrocenophanes with M = Y (3) and Sc (4) have been prepared as the dipyridine adducts, starting from YCl3 and ScCl3, respectively, and N,N′‐dilithio‐N,N′‐bis(trimethylsilyl)‐1,1′‐diaminoferrocene (2). The reaction of 3 with sodium pentamethylcyclopentadienide (NaCp*) gave the complex 5, in which the yttrium atom is four‐coordinate, bearing the diamido ligand, Cp* and one pyridine ligand. An ate complex of four‐coordinate yttrium (6) was obtained, when YCl3 was treated with 2 equiv. of 2. In 6a, the lithium atom is threefold coordinated by two of the four amido nitrogen atoms and by pyridine, and addition of an excess of pyridine gave the separated ion pairs (6b) in solution. The molecular structures of 3, 5 and 6a were determined by X‐ray structural analysis, and the solution‐state structures were deduced from consistent NMR spectroscopic data sets (1H, 13C, 29Si, 89Y NMR). The 89Y nuclear magnetic shielding of amido complexes appears to increase with the coordination number (3, 4, 5) of yttrium.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Stereoselective Synthesis of the First Chatt‐Type Bis(dinitrogen)‐Molybdenum(0) Complex with a Tetraphosphane Ligand
Authors: Römer René , Stephan Gerald , Habeck Carsten , Hoberg Christian , Peters Gerhard , Näther Christian , Tuczek Felix 
Published: June 2008

AbstractThe first Chatt‐type Mo0 dinitrogen complex with a tetraphosphane ligand has been prepared and characterized by NMR as well as infrared and Raman spectroscopy. Importantly, the employed reaction route allows the stereospecific synthesis of this complex as trans‐[Mo(N2)2(meso‐prP4)] (prP4 = a tetraphos ligand with a central propylene bridge). The stereoselectivity in the reaction course is induced by the oxido‐iodido‐molybdenum(IV) precursor [Mo(O)I(prP4)]+ which directs both phenyl groups of the bridging P atoms of prP4 into a meso configuration. The paper establishes a general strategy to synthesize mononuclear Mo0 dinitrogen and related molybdenum complexes with multidentate phosphane ligands which has not been possible to date. Moreover, the obtained molybdenum tetraphos N2 complex should exhibit a higher thermodynamic stability in the reactions of the Chatt cycle of synthetic nitrogen fixation than the conventional bis(diphos) complexes, due to the linkage of the two diphosphane units by an alkyl bridge. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
A Dual‐Channel Fluorescence‐Enhanced Sensor for Aluminum Ions Based on Photoinduced Electron Transfer and Excimer Formation
Authors: Lin Weiying , Yuan Lin , Feng Jianbo 
Published: June 2008

AbstractSensor 1 was developed as the first example of a fluorescence‐enhanced Al3+ sensor with unique dual‐channel emissions. The addition of Al3+ to 1 elicits a large fluorescence enhancement by inhibition of a quenching Photoinduced electron‐transfer (PET) channel and also a dramatic fluorescence enhancement due to promotion of an emissive excimer channel formation. The dual‐channel fluorescence‐enhanced response of the sensor contributes to its high sensitivity and selectivity.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Sequential Double Olefination of 2‐(Arylmethylidene)‐2‐phosphonoacetonitrile with Dimsyl Lithium and Aldehydes: A Domino Route to Densely Substituted 1,3‐Butadienes
Authors: Chowdhury Raghunath , Ghosh Sunil K. 
Published: June 2008

AbstractAn efficient and highly stereoselective synthesis of densely substituted 1,3‐dienes has been achieved which entails a sequential double olefination of 2‐(arylmethylidene)‐2‐phosphonoacetonitriles by a one‐pot domino process involving Michael addition of dimsyllithium to 2‐(arylmethylidene)‐2‐phosphonoacetonitrile, Horner–Wadsworth–Emmons reaction of the resulting phosphonate ylide with the added aldehyde followed by base induced methylsulfenoxy elimination. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Oxidative Amidation of Aldehydes and Alcohols with Primary Amines Catalyzed by KI‐TBHP
Authors: Reddy K. Rajender , Maheswari C. Uma , Venkateshwar M. , Kantam M. Lakshmi 
Published: June 2008

AbstractOxidative amidation of aldehydes and alcohols with amines to afford the corresponding amides in excellent yields and ee values over 98 % is achieved by using a catalytic amount of KI in combination with TBHP as the external oxidant. This method avoids the use of expensive and/or air‐sensitive reagents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Electrocatalytic Oxidation of Sulfite on a Nickel Aquapentacyanoferrate Modified Electrode: Application for Simple and Selective Determination
Authors: Kumar S. Senthil , Narayanan S. Sriman 
Published: June 2008

AbstractAn electroactive metal cyanometallate complex, nickel aquapentacyanoferrate (NAPCF) was synthesized and characterized using XRD and UV‐vis spectral studies. The solid complex was then mechanically immobilized on the surface of a paraffin impregnated graphite electrode (PIGE) and the NAPCF modified electrode was characterized using cyclic voltammetry. The dependence of the modified electrode was tested in terms of supporting electrolyte, scan rate and pH of the medium. The electrocatalytic oxidation of sulfite at the modified electrode was investigated by cyclic voltammetry, hydrodynamic voltammetry and chronoamperometry techniques. It was found that the NAPCF modified electrode efficiently exhibited electrocatalytic activity for the oxidation of sulfite with relatively high sensitivity, selectivity and long life of activity. Based on the electrocatalytic oxidation, the NAPCF modified electrode was used as a sensor for the determination of sulfite. The linear working range for the determination of sulfite was 2.78×10−6 M to 3.00×10−3 M with a detection limit of 9.26×10−7 M. The electrode was applied for the determination of sulfite in real samples satisfactorily.
Selective Electrochemical Determination of Uric Acid in the Presence of Ascorbic Acid Using a Carbon Paste Electrode Modified with β‐Cyclodextrin
Authors: Ramírez‐Berriozabal Minerva , Galicia Laura , Gutiérrez‐Granados Silvia , Cortes José Sandoval , Herrasti Pilar 
Published: June 2008

AbstractUric acid (UA) was determined in the presence of ascorbic acid (AA) by using a carbon paste electrode modified superficially by a β‐cyclodextrin film (CPE/β‐CD). The surface carbon paste electrode was prepared applying a 30 cycles potential program and using a 1 M HClO4+0.01 M β‐CD electrolytic solution. The UA and AA solutions were used to evaluate the electrode selectivity and sensitivity by cyclic voltammetric and amperometric methods. In these experiments the detection limit for UA was (4.6±0.01)×10−6 M and the RSD calculated from the amperometric curves was 10%. From the data obtained it was possible to quantify UA in the urine and saliva samples. Selective detection of UA was improved by formation of an inclusion complex between β‐CD and UA. The results show that the CPE/β‐CD is a good candidate due to its selectivity and sensitivity in the UA determination in complex samples like the biological fluids.
Electrochemical Study on DNA Damage Based on the Direct Oxidation of 8‐Hydroxydeoxyguanosine at an Electrochemically Modified Glassy Carbon Electrode
Authors: Zhang Jing‐Jing , Wang Bin , Li Yan‐Fen , Jia Wen‐Li , Cui Hui , Wang Huai‐Sheng 
Published: June 2008

AbstractThe study of DNA damage induced by Fenton reaction (Fe2+/H2O2) in vitro was performed based on the direct electrochemical oxidation of 8‐hydroxydeoxyguanosine (8‐OH‐dG), the biomarker of DNA oxidative damage, at an electrochemically modified glassy carbon electrode (GCE). The effects of antioxidants, such as ascorbic acid, and hydroxyl‐radical scavenger (mannitol) on the DNA damage were also investigated. 8‐OH‐dG, the oxidation product of guanine residues in DNA, has shown significantly oxidative peak on the electrochemically modified GCE. The oxidative peak current of 8‐OH‐dG was linear with the damaged DNA concentration in the range of 10–200 mg/L. The experimental results demonstrate that ascorbic acid has ambivalent effect on DNA oxidative stress. It can promote DNA oxidative damage when ascorbic acid concentration is below 1.5 mM and protect DNA from damage in the range of 1.5–2.5 mM. As a hydroxyl‐radical scavenger, mannitol inhibits significantly DNA oxidative damage. The influence of Fe2+, as reactant, and EDTA as iron chelator in the system were also studied. The proposed electrochemical method can be used for the estimation of DNA oxidative damage from new point of view.
Surface Modification of Gold by Quercetin Monolayer for the Electrochemical Determination of Copper(II)
Authors: Xu Guang‐Ri , Yuan Yong , Kim Sunghyun , Lee Jae‐Joon 
Published: June 2008

AbstractA quercetin monolayer has been prepared on top of the self‐assembled 3‐mercaptopropionic acid (MPA) layer for the copper ion determination. Cu2+ ions are readily accumulated on this modified electrode through the complex formation and electrochemically detected. With a quercetin layer, the redox process of Cu2+ became more reversible than at the MPA‐modified electrode. Complexation sites in MPA and quercetin were occupied within five min when the electrode was immersed in 10 μM Cu2+ solution. The MPA and quercetin layers were stable enough to allow repeated EDTA treatment to remove adsorbed Cu2+ for the surface regeneration. Only 7% decrease was found after ten times regeneration and use. Linear current response was found over the concentration range of 1 nM and 10 μM with detection limit of 0.1 nM. Common interfering ions such as Cd2+, Zn2+, and Fe2+/3+ did not show any electrochemical response in the potential range of Cu2+ determination.
Synthesis of Carbon Nanofibers for Mediatorless Sensitive Detection of NADH
Authors: Liu Yang , Hou Haoqing , You Tianyan 
Published: June 2008

AbstractHighly sensitive amperometric detection of dihydronicotinamide adenine dinucleotide (NADH) by using novel synthesized carbon nanofibers (CNFs) without addition of any mediator has been proposed. The CNFs were prepared by combination of electrospinning technique with thermal treatment method and were applied without any oxidation pretreatment to construct the electrochemical sensor. In amperometric detection of NADH, a linear range up to 11.45 μM with a low detection limit of 20 nM was obtained with the CNF‐modified carbon paste electrode (CNF‐CPE). Good selectivity was exhibited for the simultaneous detection of NADH and its common interferent of ascorbic acid (AA) by differential pulse voltammogram. The attractive electrochemical performance and the versatile preparation process of the CNF‐CPE made it a promising candidate for designing effective NADH sensor.
Adsorptive Stripping Voltammetric Determination of 4‐Hexylresorcinol in Pharmaceutical Products Using Multiwalled Carbon Nanotube Based Electrodes
Authors: Kachoosangi Roohollah Torabi , Wildgoose Gregory G. , Compton Richard G. 
Published: June 2008

AbstractA sensitive electroanalytical method is presented for the determination of 4‐hexylresorcinol using adsorptive stripping voltammetry (AdsSV) at a multiwalled carbon nanotube modified basal plane pyrolytic graphite electrode (MWCNT‐BPPGE). This method is also extended to the use of a MWCNT modified screen‐printed electrode (MWCNT‐SPE), thereby demonstrating that this approach can easily be incorporated into a facile and inexpensive electrochemical sensor.
Searching the genome for our adaptations
Authors: Harris Eugene E. 
Published: June 2008

AbstractThe current genomic revolution represents a turning point in our understanding of human evolution. For the first time, we are able to begin to investigate human evolutionary adaptations by comparing our entire genome with the genomes of other animal species with which we are related by descent. We are also able to begin fully investigating the genetic differences within and among human populations to understand exactly how human populations have evolved and adapted over time.
On the Chebyshev collocation spectral approach to stability of fluid flow in a porous medium
Authors: Makinde O. D. 
Published: June 2008

AbstractIn this paper, the temporal development of small disturbances in a pressure‐driven fluid flow through a channel filled with a saturated porous medium is investigated. The Brinkman flow model is employed in order to obtain the basic flow velocity distribution. Under normal mode assumption, the linearized governing equations for disturbances yield a fourth‐order eigenvalue problem, which reduces to the well‐known Orr–Sommerfeld equation in some limiting cases solved numerically by a spectral collocation technique with expansions in Chebyshev polynomials. The critical Reynolds number Rec, the critical wave number αc, and the critical wave speed cc are obtained for a wide range of the porous medium shape factor parameter S. It is found that a decrease in porous medium permeability has a stabilizing effect on the fluid flow. Copyright © 2008 John Wiley & Sons, Ltd.
Matrix metalloproteinase‐9 interplays with the IGFBP2–IGFII complex to promote cell growth and motility in astrocytomas
Authors: Rorive Sandrine , Berton Alix , D'haene Nicky , Takacs Constantin Nicolae , Debeir Olivier , Decaestecker Christine , Salmon Isabelle 
Published: June 2008

AbstractInsulin‐like growth factor II (IGFII) acts as a potent mitogen for several tumor types and has been reported to positively influence astrocytoma cell growth and motility. In the central nervous system, IGFII bioavailability is mainly modulated by insulin‐like growth factor binding protein 2 (IGFBP2), which sequestrates IGFII and therefore prevents its interaction with the type‐1 IGF receptor (IGF‐IR). Proteolysis of IGFBP2 is the predominant mechanism recognized to reduce the binding affinity of IGFBP2 for IGFII, thus favoring dissociation of IGFII from the IGFBP2–IGFII complex. It is known that certain proteases involved in astrocytoma malignancy, such as matrix metalloproteinase‐7 (MMP‐7), plasmin, and cathepsin D, are able to proteolyze IGFBP2 in vitro. The present study aims to investigate whether other proteases expressed by astrocytomas, specifically MMP‐2, MMP‐9, and membrane‐type 1 matrix metalloprotease (MT1‐MMP), are able to proteolyze the IGFBP2–IGFII complex. Our results show the following: (i) MMP‐9 proteolyzes the IGFBP2–IGFII complex in vitro, while MMP‐2 and MT1‐MMP do not; (ii) this MMP‐9‐induced IGFBP2–IGFII complex proteolysis releases free IGFII, which contributes to enhance the motility and the growth of LN229 astrocytoma cells. Furthermore, this study also highlights that the formation of the IGFBP2–IGFII complex inhibits IGFBP2's cell motility promoting effect by reducing the pool of free IGFBP2. In conclusion, MMP‐9‐induced IGFBP2 proteolysis may be regarded as an important post‐translational event involved in astrocytoma aggressiveness. These new findings support drug targeting of MMP‐9 as an interesting approach in the treatment of astrocytoma. © 2008 Wiley‐Liss, Inc.
The expression of tubulin polymerization promoting protein TPPP/p25α is developmentally regulated in cultured rat brain oligodendrocytes and affected by proteolytic stress
Authors: Goldbaum Olaf , Jensen Poul Henning , Richter‐Landsberg Christiane 
Published: June 2008

AbstractThe tubulin polymerization‐promoting protein (TPPP)/p25α was identified as a brain specific protein, is associated with microtubules (MTs) in vitro and can promote abnormal MT assembly. Furthermore it has aggregation promoting properties and is a constituent in pathological protein deposits of neurodegenerative diseases. In the brain, TPPP/p25α is present in myelinating oligodendrocytes. Here we show, using cultured rat brain oligodendrocytes, that TPPP/p25α expression is increasing during development in culture, and particularly in immature cells is associated with the centrosome. MT binding properties in oligodendrocytes are rather low, however, when MTs are disassembled by nocodazole, TPPP/p25α accumulates in the perinuclear region. Treatment of oligodendrocytes with the proteasomal inhibitor MG‐132 (1 μM; 18 h) caused an increase in the amount of TPPP/p25α by about 40%, a decrease in its solubility, and led to the appearance of TPPP/p25α‐positive cytoplasmic inclusions, which stained with thioflavin S and resembled inclusion bodies. Hence, it might be speculated that acute or chronic malfunction of the proteasomal degradation system, leading to the accumulation of aggregation prone proteins and the pro‐aggregatory protein TPPP/p25α or to the aggregation of TPPP/p25α on its own, is causally related to the protein aggregation process in a variety of neurodegenerative diseases. © 2008 Wiley‐Liss, Inc.
Drought impacts on Canadian prairie wetland snow hydrology
Authors: Fang X. , Pomeroy J. W. 
Published: June 2008

AbstractDroughts affect the Canadian prairies on a regular basis. The drought of 1999–2005 was the most recent one and was the most severe on record for part of the region. It was characterized by lack of precipitation, desiccation of agricultural soils, decline in groundwater tables and depletion of surface water supplies. The effects on wetlands were particularly severe, with many wetlands completely drying out. The physically based cold regions hydrological modelling (CRHM) platform was used to analyse the impacts of this recent drought on water flow to and storage within a small Canadian prairie wetland. Model simulations were conducted for a small closed basin for the drought period of 1999–2005 and the relatively wet period of 2005–2006. The basin consists of a cultivated upland, draining into a glacially formed pothole depression with no outlet. The wetland fills the depression in wet years and is underlain by a heavy glacial till that impedes groundwater exchange. Results from the observations and model outputs showed that much lower precipitation and snow accumulation, shorter snow‐covered duration, enhanced winter evaporation, and much lower discharge to the wetland from basin snowmelt runoff developed in the severe drought years of 1999–2002. As a result, there were only 14·9, 3·7, and 14·4 mm of snowmelt runoff for the springs of 2000, 2001, and 2002, respectively. Compared to the 68·2 mm of melt‐water discharge in the spring of 2006, discharge to the wetland was 78, 95, and 79% less for these years. This is consistent with the observed water level in the wetland, which shows dramatic decline over this period. CRHM was used to investigate the potential impact of snow management as a tool to enhance runoff to the wetland during droughts. Model runs parameterized with suppressed vegetation in the cultivated land surrounding the wetland showed increased blowing snow transport to the wetland from an area exceeding the basin area that resulted in greater snow accumulation in and melt‐water supply to the wetland. Copyright © 2008 John Wiley & Sons, Ltd.
Impacts of nutrient management and decrease in paddy field area on groundwater nitrate concentration: a case study at the Nasunogahara alluvial fan, Tochigi Prefecture, Japan
Authors: Somura Hiroaki , Goto Akira , Matsui Hiroyuki , Ali Musa Elhassan 
Published: June 2008

AbstractIn order to help evaluate the trends in the NO3‐N concentration in groundwater with a view to preventing further degradation in water quality in the future, a distributed groundwater quality model was constructed for the Nasunogahara basin. The best fit for the groundwater table elevations by the flow component of the model was achieved with average mean absolute errors (MAEs) of 0·92 m for the calibration period and 0·83 m for the validation period. Moreover, the best fit for the NO3‐N concentration by the water quality component was achieved with average mean relative errors (MREs) of 29·8% for the calibration period and 30·3% for the validation period. After developing a robust model, various change scenarios were tested; specifically, the effects of effluent load control and a decrease in paddy field area on the NO3‐N concentration in groundwater were predicted. The most intensively farmed area contributed about 40% of the total effluent load because of livestock farming in the basin. When the effluent load from this area was decreased by 50%, the average NO3‐N concentrations at sites S1, S2 and S3 were reduced by about 15%; however, the average concentrations at S4 and S5 were reduced by only 1%. Furthermore, when the total effluent load from the concentrated livestock area was removed completely, the average groundwater NO3‐N concentrations at S1, S2 and S3 were reduced by about 30% as compared with the original calculated results. In contrast, decreasing the area of the paddy fields in the basin did not greatly influence the groundwater NO3‐N concentration. In the case of a 70% reduction in paddy field area, average NO3‐N concentrations increased by about 7% at S1, S2 and S3. Copyright © 2008 John Wiley & Sons, Ltd.
Early findings in comparison of AMSR‐E/Aqua L3 global snow water equivalent EASE‐grids data within situobservations for Eastern Turkey
Authors: Tekeli A. Emre 
Published: June 2008

AbstractMicrowave remote sensing (RS) enables the direct determination of snow water equivalent (SWE), which is an important snow parameter for water resources management. The accuracy of remotely sensed SWE values has always been a concern. Previous studies evaluated global SWE monitoring. However, regional effects such as vegetation, snow grain size, snow density and local meteorological conditions may lead to uncertainties. Thus, regional validation studies that quantify and help to understand these uncertainties and possible error sources are important both for algorithm development and accurate SWE computation.In this study, data of Advanced Microwave Scanning Radiometer (AMSR‐E)/Aqua level 3 global SWE Equal Area Scalable Earth (EASE) Grids are compared with ground measurements for 2002–2003 winter period for Eastern Turkey, which includes the headwaters of the Euphrates and Tigris rivers and is fed largely from snowmelt. Thus, accurate determination of SWE is important in optimum resource management for both Turkey and downstream nations. Analyses indicated that AMSR‐E generally overestimated SWE in early season. As winter progressed, higherin situSWE values with respect to AMSR‐E were observed which led to underestimation by AMSR‐E. The differences between AMSR‐E andin situSWE varied between − 218 and 93 mm.Use ofin situsnow densities lead the correlation coefficient between AMSR‐E andin situSWE to increase from 0·10 to 0·32. Underestimation of SWE by AMSR‐E occurs after some warm periods, while overestimations occur following refreezing. On rainy days or some days after precipitation within the warm periods, zero AMSR‐E SWE values are observed. Copyright © 2008 John Wiley & Sons, Ltd.