bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the Constrained Environment on the Interactions between the Surfactant and Different Polar Solvents Encapsulated within AOT Reverse Micelles
Authors: Durantini Andrés M. , Falcone R. Dario , Silber Juana J. , Correa N. Mariano 
Published: May 2009

AbstractHerein, we report a study of the interactions between different nonaqueous polar solvents, namely, ethylene glycol (EG), propylene glycol (PG), glycerol (GY), dimethylformamide (DMF), and dimethylacetamide (DMA), and the polar heads of sodium 1,4‐bis‐2‐ethylhexylsulfosuccinate (AOT) in nonaqueous AOT/n‐heptane reverse micelles. The goal of our study is to gain insights into the unique reverse‐micelle microenvironment created upon encapsulation of these polar solvents. For the first time, the study is focused on determining which regions of the AOT molecular structure are involved in the interactions with the polar solvents. We use FTIR spectroscopy—a noninvasive technique—to follow the changes in the AOT CO band and the symmetric and asymmetric SO3− vibration modes upon increasing the content of polar solvents in the micelles. The results show that GY interacts through H bonds with the SO3− group, thereby removing the Na+ counterions from the interface remaining in the polar core of the micelles. PG and EG interact through H bonds, mainly with the CO group of AOT, penetrating into the oil side of the interface. Thus, they interact weakly with the Na+ counterion, which seems to be close to the AOT sulfonate group. Finally, DMF and DMA, encapsulated inside the reverse micelles, interact neither with the CO nor with the SO3− groups, but their weakly bulk‐associated structure is broken because of the interactions with Na+. We suggest that DMF and DMA can complex the Na+ ions through their carbonyl and nitrogen groups. Hence, our results do not only give insights into how the constrained environment affects the bulk properties of polar solvents encapsulated within reverse micelles but—more importantly—they also help us to answer the tricky question about which regions of the AOT moiety are involved in the interactions with the polar solvents. We believe that our results show a clear picture of the interactions present at the nonaqueous reverse‐micelle interface; this is important because these media are interesting nanoreactors for heterogeneous chemistry, templates for nanoparticles, and models for membranes.
Nonlinear Optical Spectroscopy of Soft Matter Interfaces
Authors: Roke Sylvie 
Published: May 2009

AbstractMolecular interfacial properties of colloidal soft matter systems (for example vesicle fusion, or particle synthesis) can be investigated without the need of planar model systems or fluorescent labelling. Exclusively observing chemical properties and changes in a molecular layer of a few molecular dimensions thick around a small particle adds a new dimension to the field of surface science (see figure).magnified imageSoft matter consists of complex molecules that can undergo drastic structural transformations under mild changes of chemical and physical conditions. Since a wide variety of chemical, physical and biological processes occur at soft matter interfaces, they can exhibit complex behavior. This is even more so for interfaces of colloidal soft matter since the relative amount of interface material increases by orders of magnitude. Herein, we focus on new developments that enable us to obtain detailed molecular structural changes in the topmost molecular layers of soft matter interfaces composed of complex bio‐molecules. In particular, the possibilities to probe interfaces of colloidal soft matter systems are discussed.
The Role of Oxygen at the Interface between Titanium and Carbon Nanotubes
Authors: Felten Alexandre , Suarez‐Martinez Irene , Ke Xiaoxing , Van Tendeloo Gustaaf , Ghijsen Jacques , Pireaux Jean‐Jacques , Drube Wolfgang , Bittencourt Carla , Ewels Christopher P. 
Published: May 2009

AbstractWe study the interface between carbon nanotubes (CNTs) and surface‐deposited titanium using electron microscopy and photoemission spectroscopy, supported by density functional calculations. Charge transfer from the Ti atoms to the nanotube and carbide formation is observed at the interface which indicates strong interaction. Nevertheless, the presence of oxygen between the Ti and the CNTs significantly weakens the Ti–CNT interaction. Ti atoms at the surface will preferentially bond to oxygenated sites. Potential sources of oxygen impurities are examined, namely oxygen from any residual atmosphere and pre‐existing oxygen impurities on the nanotube surface, which we enhance through oxygen plasma surface pre‐treatment. Variation in literature data concerning Ohmic contacts between Ti and carbon nanotubes is explained via sample pre‐treatment and differing vacuum levels, and we suggest improved treatment routes for reliable Schottky barrier‐free Ti–nanotube contact formation.
Influence of Iodide Concentration on the Efficiency and Stability of Dye‐Sensitized Solar Cell Containing Non‐Volatile Electrolyte
Authors: Zhang Zhipan , Ito Seigo , Moser Jacques‐E. , Zakeeruddin Shaik M. , Grätzel Michael 
Published: May 2009

AbstractDye‐sensitized solar cells based on nanocrystalline TiO2 have been fabricated with an amphiphilic ruthenium sensitizer NaRu(4‐carboxylic acid‐4′‐carboxylate)(4,4′‐dinonyl‐2,2′‐bipyridine)(NCS)2, coded as Z‐907Na, and a series of non‐volatile 3‐methoxyproprionitrile (MPN)‐based electrolytes with different concentration of 1‐methyl‐3‐propylimidazolium iodide (PMII). The short‐circuit photocurrent density increases with increasing iodide concentration until at 1.5 M practically quantitative dye regeneration is achieved as proved by time‐resolved laser experiments. Devices containing 1.0 M PMII electrolyte show excellent stability during long‐time thermal aging at 80 °C and under light soaking at 60 °C.
From Single‐Biomolecule Electrochemistry to Biosensors and Biofuel Cells
Authors: Calvo Ernesto Julio 
Published: May 2009

AbstractThe bioelectrochemistry symposium at the 59th annual meeting of the International Society of Electrochemistry (ISE) covered significant developments in this area—from biomimetics, redox proteins, and enzymes, to biosensors and biofuel‐cell applications. This conference report highlights some of the most important contributions (the picture shows a schematic representation of an amperometric enzyme electrode, courtesy of P.N. Bartlett).magnified image
Inside Cover: Absorption Spectra of 4‐Nitrophenolate Ions Measured in Vacuo and in Solution (ChemPhysChem 8/2009)
Authors: Suhr Kirketerp Maj‐Britt , Åxman Petersen Michael , Wanko Marius , Andres Espinosa Leal Leonardo , Zettergren Henning , Raymo Françisco M. , Rubio Angel , Brøndsted Nielsen Mogens , Brøndsted Nielsen Steen 
Published: May 2009

AbstractThe inside cover picture shows gas‐phase absorption spectra of four p‐nitrophenolates. The ions cover the entire visible spectrum when isolated in vacuo and are located within a narrower region in solution. On p. 1207 A. Rubio, M. Brøndsted Nielsen, S. Brøndsted Nielsen et al. use the gas‐phase absorption maxima to benchmark excitation energy calculations (blue lines).magnified image
Differential amplifier with improved gain‐accuracy and linearity
Authors: Wu R. , Lidgey F. J. , Hayatleh K. , Hart B. L. 
Published: May 2009

AbstractA novel circuit design technique is presented which improves gain‐accuracy and linearity in differential amplifiers. The technique employs negative impedance compensation and results demonstrate a significant performance improvement in precision, lowering sensitivity, and wide dynamic range. A theoretical underpinning is given together with the results of a demonstrator differential input/output amplifier with gain of 12 dB. The simulation results show that, with the novel method, both the gain‐accuracy and linearity can be improved greatly. Especially, the linearity improvement in IMD can get to more than 23 dB with a required gain. Copyright © 2009 John Wiley & Sons, Ltd.
Programmable feedforward linearized CMOS OTA for fully differential continuous‐time filter design
Authors: Szczepanski Stanislaw , Pankiewicz Bogdan , Koziel Slawomir 
Published: May 2009

AbstractIn this paper, a feedforward linearization method for programmable CMOS operational transconductance amplifier (OTA) is described. The proposed circuit technique is developed using simple source‐coupled differential pair transconductors, a feedback‐loop amplifier for self‐adjusting transcoductance (gm) and a linear reference resistor (R). As a result, an efficient linearization of a transfer characteristic of the OTA is obtained. SPICE simulations show that for 0.35µm AMS CMOS process with a single +3V power supply, total harmonic distortion at 1 Vppand temperature range from −30 to +90°C is less than −49.3 dB in comparison with −35.8  dB without linearization. Moreover, the input voltage range of linear operation is increased. Power consumption of the linearized OTA circuit is 0.86 mW. Finally, the OTA is used to design a third‐order elliptic low‐pass filter in high‐frequency range. The cut‐off frequency of the operational transconductance amplifier‐capacitor (OTA‐C) filter is tunable in the range of 322.6 kHz–10 MHz using the feedforward linearized OTAs with the digitally programmable current mirrors. Copyright © 2009 John Wiley & Sons, Ltd.
Ecohydrological controls on snowmelt partitioning in mixed‐conifer sub‐alpine forests
Authors: Molotch Noah P. , Brooks Paul D. , Burns Sean P. , Litvak Marcy , Monson Russell K. , McConnell Joseph R. , Musselman Keith 
Published: May 2009

AbstractWe used co‐located observations of snow depth, soil temperature, and moisture and energy fluxes to monitor variability in snowmelt infiltration and vegetation water use at mixed‐conifer sub‐alpine forest sites in the Valles Caldera, New Mexico (3020 m) and on Niwot Ridge, Colorado (3050 m). At both sites, vegetation structure largely controlled the distribution of snow accumulation with 29% greater accumulation in open versus under‐canopy locations. Snow ablation rates were diminished by 39% in under‐canopy locations, indicating increases in vegetation density act to extend the duration of the snowmelt season. Similarly, differences in climate altered snow‐season duration, snowmelt infiltration and evapotranspiration. Commencement of the growing season was coincident with melt‐water input to the soil and lagged behind springtime increases in air temperature by 12 days on average, ranging from 2 to 33 days under warmer and colder conditions, respectively. Similarly, the timing of peak soil moisture was highly variable, lagging behind springtime increases in air temperature by 42 and 31 days on average at the Colorado and New Mexico sites, respectively. Latent heat flux and associated evaporative loss to the atmosphere was 28% greater for the year with earlier onset of snowmelt infiltration. Given the large and variable fraction of precipitation that was partitioned into water vapour loss, the combined effects of changes in vegetation structure, climate and associated changes to the timing and magnitude of snowmelt may have large effects on the partitioning of snowmelt into evapotranspiration, surface runoff and ground water recharge. Copyright © 2009 John Wiley & Sons, Ltd.
Hydrology and species‐specific effects of Bacopa monnieri and Leersia oryzoides on soil and water chemistry
Authors: Pierce S. C. , Pezeshki S. R. , Larsen D. , Moore M. T. 
Published: May 2009

AbstractIn an 8‐week greenhouse experiment, Bacopa monnieri (water hyssop) and Leersia oryzoides (rice cutgrass) were compared for nutrient assimilation as well as soil and water chemistry under variable flooding regimes using a nutrient solution rich in nitrogen (N) and phosphorus (P). Soil redox potential decreased in flooded treatments; however, mesocosms containing B. monnieri remained aerobic for much of the study, while flooded mesocosms containing L. oryzoides became moderately reduced. Soils containing L. oryzoides were higher in nitrogen. Generally, effluent concentrations of PO43− were higher in B. monnieri mesocosms. B. monnieri immobilization of N and P was significantly less in below‐ground tissues than L. oryzoides. P immobilization in L. oryzoides generally increased in response to flooding, while B. monnieri showed no detectable response. Results indicated that species‐specific flood responses in plant nutrient status are due to differing interactions of B. monnieri and L. oryzoides with the soil environment. Additionally, L. oryzoides demonstrated greater P uptake than B. monnieri across treatments, resulting in decreased concentrations of PO4−3 in effluent. Although N was also affected by flooding and species, generalizations on N allocation within the system are difficult to describe due to the changes in species of N in response to oxidation–reduction gradients and biotic assimilation. Copyright © 2009 John Wiley & Sons, Ltd.
Streamside herbaceous vegetation response to hydrologic restoration on the San Pedro River, Arizona
Authors: Katz Gabrielle L. , Stromberg J. C. , Denslow M. W. 
Published: May 2009

AbstractRecovery of physical conditions and processes is increasingly emphasized in ecosystem restoration. We examined a restoration project aimed at recovery of groundwater levels and base flows on an undammed desert river. We sampled streamside plant communities and hydrology annually (2003–2008) at six restoration sites at two farms (Three Links Farm and H&E Farm) after groundwater pumping was curtailed for restoration purposes, and at six reference sites. Vascular plant cover was recorded, and species were classified into functional groups based on water needs and life history. Synthetic vegetation metrics and community composition were compared between restoration sites and perennial‐flow reference sites representing target conditions. Perennial sites had higher cover, species richness, relative cover of hydric perennials and hydric annuals, and lower wetland indicator scores than non‐perennial sites, but did not differ in relative cover of non‐native species. Perennial sites had distinct species composition and high species constancy among years. Streamside vegetation was similar at Three Links Farm and perennial reference sites, indicating restoration success; streamside vegetation at H&E Farm differed from target conditions according to most measures. Hydrology is a key factor shaping desert streamside plant communities. However, single river sites may respond differently to hydrologic restoration. Contrasts in site response were likely due to differences in hydrogeomorphic context, exacerbated by drought. Understanding the constraints on restoration response is critical for setting realistic restoration goals and anticipating time frames of ecosystem change. Copyright © 2009 John Wiley & Sons, Ltd.
Preparation of Mesoporous Silica and Carbon Materials with Multilength‐Scale Pores and Hydrogen Sorption Application
Authors: Kwon Tae‐Hwan , Jung Suhyun , Kim Hee‐Jin , Park Seongsoon , Kim Sung‐Jin , Huh Seong 
Published: May 2009

AbstractA facile method was developed for the preparation of bimodal mesoporous siliceous materials with nanostructured pores in which a cationic organic template, n‐hexadecyltrimethylammonium hydroxide, was employed as a base catalyst as well as a mesopore structure‐directing agent during the slow condensation of tetraethoxysilane. It was possible to alter the pore orientations of smaller pores by adding neutral auxiliary templates such as Brij76 and P123. A series of biomodal mesoporous carbons was also obtained from the bimodal mesoporous silica materials through a nanocasting process. The resulting bimodal mesoporous carbons exhibited decent hydrogen uptake values at 77 K. The maximum hydrogen uptake was 1.33 wt.‐% for the sample having the narrowest pores, while keeping a relatively large pore volume. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Bis(N‐heterocyclic carbene) Dipalladium Complexes: Synthesis, Solid‐State Conformational Studies and Solution Behaviour
Authors: Willans Charlotte E. , Anderson Kirsty M. , Paterson Martin J. , Junk Peter C. , Barbour Leonard J. , Steed Jonathan W. 
Published: May 2009

AbstractNew palladium(II) bis(N‐heterocyclic carbene) (NHC) complexes have been prepared via metallomacrocyclic AgI ligand transfer agents. Reaction of 1,4‐bis(3‐isopropylimidazolium)xylene (1a) hexafluorophosphate with Ag2O gives a AgI macrocyclic NHC complex in which two silver ions are sandwiched between two dipodal ligands (2a). The NHC moieties adopt a cisoid conformation relative to one another. Upon transfer to palladium to give [{PdCl2(MeCN)}2(bis‐NHC)] (3a) the NHC ligands in the complexes adopt a mixture of cisoid and transoid conformers in the solid state, which have been characterized by X‐ray crystallography. In CD3CN solution the cisoid and transoid conformers interconvert and exhibit resonances for a single averaged form.DFT calculations indicate an interconversion barrier of 56 kJ mol–1. In CDCl3 solution two different isomers are observed which have been assigned to isomers of a chloride‐bridged dimer (4a) following dissociation of the acetonitrile ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Difluorenyl[2]borametallocenophanes of Group 4 Metals: Synthesis and Structure
Authors: Braunschweig Holger , Kupfer Thomas , Mies Jan , Oechsner Andreas 
Published: May 2009

AbstractWe report the synthesis of difluorenyl[2]borametallocenophanes of Zr and Hf. The ligand precursor has been synthesized starting from 1,2‐dibromo‐1,2‐bis(dimethylamino)diborane(4) upon reaction with Li[C13H9]. All compounds have been fully characterized by multinuclear NMR spectroscopy and, in addition, selected examples by X‐ray analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Winheim, Germany, 2009)
Effect of O6‐alkylguanine‐DNA alkyltransferase on genotoxicity of epihalohydrins
Authors: Kalapila Aley G. , Loktionova Natalia A. , Pegg Anthony E. 
Published: May 2009

AbstractThe effect of O6‐alkylguanine‐DNA alkyltransferase (AGT) on the toxicity and mutagenicity of epihalohydrins was studied. AGT is a DNA repair protein that protects cells from agents that produce genotoxic O6‐alkylguanine lesions by transferring the alkyl group to an internal cysteine residue (Cys145 in human AGT) in a single‐step. This cysteine acceptor site is highly reactive and epihalohydrins reacted readily with AGT at this site with a halide order of reactivity of Br > Cl > F. AGT expression in bacterial cells caused a very large increase in the mutagenicity and cytotoxicity of epibromohydrin. The mutations were almost all G:C to A:T transitions. Epichlorohydrin also augmented AGT‐mediated mutagenesis but to a lesser extent than epibromohydrin. In vitro experiments showed that AGT was covalently cross‐linked to DNA in the presence of epibromohydrin and that this conjugation occurred predominantly at Cys145, and to a smaller extent at Cys150, a less reactive residue also located within the active site pocket. Two pathways yielding the AGT–DNA adduct were found to occur. The predominant mechanism results in an AGT‐epihalohydrin intermediate, which, facilitated by the DNA binding properties of AGT, then reacts covalently with DNA. The second pathway involves an initial reactive DNA‐epihalohydrin intermediate that subsequently reacts with AGT. Our results show that the paradoxical AGT‐mediated increase in genotoxicity which has previously been shown to occur with dihaloalkanes, butadiene diepoxide and nitrogen mustards, also occurs with epihalohydrins and is likely to contribute to their toxicity and mutagenicity. Environ. Mol. Mutagen., 2009. © 2009 Wiley‐Liss, Inc.
Arsenate and dimethylarsinic acid in drinking water did not affect DNA damage repair in urinary bladder transitional cells or micronuclei in bone marrow
Authors: Wang Amy , Kligerman Andrew D. , Holladay Steven D. , Wolf Douglas C. , Robertson John L. 
Published: May 2009

AbstractArsenic is a human skin, lung, and urinary bladder carcinogen, and may act as a cocarcinogen in the skin and urinary bladder. Possible modes of action of arsenic carcinogenesis/cocarcinogenesis include oxidative stress induction and inhibition of DNA damage repair. We investigated the effects of arsenic in drinking water on DNA damage repair in urinary bladder transitional cells and on micronucleus formation in bone marrow. F344 rats were given 100 ppm arsenate [As(V)] or dimethylarsinic acid [DMA(V)] in drinking water for 1 week. The in vivo repair of cyclophosphamide (CP)‐induced DNA damage resulting from a single oral gavage of CP, and the in vitro repair of hydrogen peroxide (H2O2)‐ or formaldehyde‐induced DNA damage, resulting from adding H2O2 or formaldehyde into cell medium, were measured by the Comet assay. DMA(V) effects were not observed on either CP‐induced DNA damage induction or on DNA repair. Neither DMA(V) nor As(V) increased the H2O2‐ or formaldehyde‐induced DNA damage, and neither inhibited the repair of H2O2‐induced DNA damage. Neither DMA(V) nor As(V) increased the micronucleus frequency, nor did they elevate micronucleus frequency resulting from CP treatment above the level observed by the treatment with CP alone. These results suggest that arsenic carcinogenesis/cocarcinogenesis in the urinary bladder may not be via DNA damage repair inhibition. To our knowledge this is the first report of arsenic effects on DNA damage repair in the urinary bladder. Environ. Mol. Mutagen. 2009. Published 2009 by Wiley‐Liss, Inc.
Folate deficiency in human peripheral blood lymphocytes induces chromosome 8 aneuploidy but this effect is not modified by riboflavin
Authors: Ni Juan , Lu Lin , Fenech Michael , Wang Xu 
Published: May 2009

AbstractChromosome 8 aneuploidy is a common event in certain cancers but whether folate (F) deficiency induces chromosome 8 aneuploidy is not known. Furthermore the impact of riboflavin (R) deficiency, which may alter activity of a key enzyme in folate metabolism, on these events is unknown. Therefore, the aim of our research was to test the following hypotheses: (a) F deficiency induces chromosome 8 aneuploidy; (b) chromosome 8 aneuploidy is affected by F deficiency to a similar degree as chromosome 17 and (c) R deficiency aggravates the risk of aneuploidy caused by F deficiency. These hypotheses were tested in long‐term cultures of lymphocytes from twenty female healthy volunteers (aged 30–48 years). Lymphocytes were cultured in each of the four possible combinations of low (L) and high (H) F (LF, 20 nmol/L, HF 200 nmol/L, respectively) and L and H R (LR 1 nmol/L, HR 500 nmol/L, respectively) media (LFLR, LFHR, HFLR, HFHR) for 9 days. Chromosomes 8 and 17 aneuploidy was measured in mononucleated (MONO) and cytokinesis‐blocked binucleated (BN) cells using dual‐color fluorescence in situ hybridization (FISH) with fluorescent centromeric probes specific for chromosomes 8 and 17. Culture in LF media (LFLR or LFHR) induced significant and similar increases in frequencies of aneuploidy of chromosomes 8 and 17 (P < 0.001) relative to culture in HF media (HFLR or HFHR). There was no significant effect of R concentration on aneuploidy frequency for either chromosome. We conclude that F deficiency is a possible cause of chromosome 8 aneuploidy. Environ. Mol. Mutagen. 2010. © 2009 Wiley‐Liss, Inc.