bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simple and Efficient Recyclable Catalytic System for Performing Copper‐Catalysed S‐Arylation Reactions in the Presence of Water
Authors: Carril Mónica , SanMartin Raul , Domínguez Esther , Tellitu Imanol 
Published: March 2007

AbstractA novel protocol for the copper‐catalysed S‐arylation of thiophenol derivatives with aryl halides leading to diaryl sulfides is reported. The reactions were catalysed by a combination of a copper salt and a 1,2‐diamine derivative (acting both as the ligand and as the base) using exclusively water as the solvent. The recovery and successful reutilisation of the aqueous medium containing the active catalyst is described. Furthermore, one example of a “one‐pot” process involving Br/I exchange of an aryl bromide and further S‐arylation is presented.
Intramolecular Spin Alignment in Photomagnetic Molecular Devices: A Theoretical Study
Authors: Ciofini Ilaria , Lainé Philippe P. , Zamboni Marta , Daul Claude A. , Marvaud Valérie , Adamo Carlo 
Published: March 2007

AbstractGround‐ and excited‐state magnetic properties of recently characterized π‐conjugated photomagnetic organic molecules are analyzed by the means of density functional theory (DFT). The systems under investigation are made up of an anthracene (An) unit primarily acting as a photosensitizer (P), one or two iminonitroxyl (IN) or oxoverdazyl (OV) stable organic radical(s) as the dangling spin carrier(s) (SC), and intervening phenylene connector(s) (B). The magnetic behavior of these multicomponent systems, represented here by the Heisenberg–Dirac magnetic exchange coupling (J), as well as the EPR observables (g tensors and isotropic A values), are accurately modeled and rationalized by using our DFT approach. As the capability to quantitatively assess intramolecular exchange coupling J in the excited state makes it possible to undertake rational optimization of photomagnetic systems, DFT was subsequently used to model new compounds exhibiting different connection schemes for their functional components (P, B, SC). We show in the present work that it is worthwhile considering the triplet state of anthracene, that is, P when promoted in its lowest photoexcited state, as a full magnetic site in the same capacity as the remote SCs. This framework allows us to accurately account for the interplay between transient (3An) and persistent (IN, OV) spin carriers, which magnetically couple according to a sole polarization mechanism essentially supported by phenyl connector(s). From our theoretical investigations of photoinduced spin alignment, some general rules are proposed and validated. Relying on the analysis of spin‐density maps, they allow us to predict the magnetic behavior of purely organic magnets in both the ground and the excited states. Finally, the notion of photomagnetic molecular devices (PMMDs) is derived and potential application towards molecular spintronics disclosed.
Photophysics and X‐ray Structure of Crystalline 2‐Aminopurine
Authors: Neely Robert K. , Magennis Steven W. , Parsons Simon , Jones Anita C. 
Published: March 2007

AbstractTo explore the effect of intermolecular interactions on the photophysics of 2‐aminopurine (2AP) in a well‐defined environment, we have investigated the fluorescence properties of single 2AP crystals, having determined their X‐ray structure. In the crystal, 2AP is subject to base‐stacking and hydrogen‐bonding interactions similar to those found in DNA. The crystal shows dual fluorescence: π‐stacked molecules in the bulk of the lattice have redshifted excitation and emission spectra, while molecules at defect sites have spectra similar to those of 2AP in solution or in DNA. Heterogeneous intermolecular interactions in the crystal give rise to multiexponential fluorescence decay characteristics similar to those observed for 2AP‐labelled DNA. The presence of about 13 % of the 7H tautomer in the crystal confirms that 9H–7H tautomerisation of 2AP occurs in the ground state. Long‐wavelength excitation of a 2AP‐labelled oligonucleotide duplex produced redshifted emission similar to that observed in the crystal, indicating that π‐stacking interaction of 2AP with nucleobases gives rise to a low energy excited state.
PI3K/Akt and CREB regulate adult neural hippocampal progenitor proliferation and differentiation
Authors: Peltier Joseph , O'Neill Analeah , Schaffer David V. 
Published: March 2007

AbstractThe phosphoinositide 3‐OH kinase (PI3K)/Akt pathway has been implicated in regulating several important cellular processes, including apoptosis, survival, proliferation, and metabolism. Using both pharmacological and genetic means, we demonstrate here that PI3K/Akt plays a crucial role in the proliferation of adult hippocampal neural progenitor cells. PI3K/Akt transduces intracellular signals from multiple mitogens, including basic fibroblast growth factor (FGF‐2), Sonic hedgehog (Shh), and insulin‐like growth factor 1 (IGF‐1). In addition, retroviral vector‐mediated over‐expression of wild type Akt increased cell proliferation, while a dominant negative Akt inhibited proliferation. Furthermore, wild type Akt over‐expression reduced glial (GFAP) and neuronal (β‐tubulin III) marker expression during differentiation, indicating that it inhibits cell differentiation. We also show that activation of the cAMP response element binding protein (CREB), which occurs in cells stimulated by FGF‐2, is limited when Akt signaling is inhibited, demonstrating a link between Akt and CREB. Over‐expression of wild type CREB increases progenitor proliferation, whereas dominant negative CREB only slightly decreases proliferation. These results indicate that PI3K/Akt signaling integrates extracellular signaling information to promote cellular proliferation and inhibit differentiation in adult neural progenitors. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007.
Neuronal nitric oxide synthase and calbindin delineate sex differences in the developing hypothalamus and preoptic area
Authors: Edelmann Michelle , Wolfe Cory , Scordalakes Elka M. , Rissman Emilie F. , Tobet Stuart 
Published: March 2007

AbstractThroughout the hypothalamus there are several regions known to contain sex differences in specific cellular, neurochemical, or cell grouping characteristics. The current study examined the potential origin of sex differences in calbindin expression in the preoptic area and hypothalamus as related to sources of nitric oxide. Specific cell populations were defined by immunoreactive (ir) calbindin and neuronal nitric oxide synthase (nNOS) in the preoptic area/anterior hypothalamus (POA/AH), anteroventral periventricular nucleus (AVPv), and ventromedial nucleus of the hypothalamus (VMN). The POA/AH of adult mice was characterized by a striking sex difference in the distribution of cells with ir‐calbindin. Examination of the POA/AH of androgen receptor deficient Tfm mice suggests that this pattern was in part androgen receptor dependent, since Tfm males had reduced ir‐calbindin compared with wild‐type males and more similar to wild‐type females. At P0 ir‐calbindin was more prevalent than in adulthood, with males having significantly more ir‐calbindin and nNOS than have females. Cells that contained either ir‐calbindin or ir‐nNOS in the POA/AH were in adjacent cell groups, suggesting that NO derived from the enzymatic activity of nNOS may influence the development of ir‐calbindin cells. In the region of AVPv, at P0, there was a sex difference with males having more ir‐nNOS fibers than have females while ir‐calbindin was not detected. In the VMN, at P0, ir‐nNOS was greater in females than in males, with no significant difference in ir‐calbindin. We suggest that NO as an effector molecule and calbindin as a molecular biomarker illuminate key aspects of sexual differentiation in the developing mouse brain. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007.
Evaluating the implementation of the Nitrates Directive in Denmark and England using an actor‐orientated approach
Authors: Smith Rebecca J. Nimmo , Glegg Gillian A. , Parkinson Rob , Richards Jo P. 
Published: March 2007

AbstractThe Nitrates Directive (91/676/EEC) was adopted to address the issue of water pollution caused by nitrate derived from agricultural practices across the European Union (EU). This study evaluates the implementation of the Nitrates Directive by considering the perspectives of respondents from significant actor groups involved in the policy implementation process in Denmark and England. Structured field interviews were conducted and discovered that Nitrate Vulnerable Zone (NVZ) designation in England was a lengthy and inefficient process compared with that in Denmark. Generally, respondents from both countries considered that whole country designation was a more effective policy instrument than designation of discrete zones. Denmark's Action Programme measures reflected the severity of its water quality problems and go beyond the demands of the Nitrates Directive. The respondents recognized that Denmark's strict measures have led to a reduction in nitrate leaching and a decline in nitrate concentrations in streams from cultivated catchments. England's current Action Programme measures do not demand any substantial changes to farming practice and so have limited potential to reduce nitrate losses. This study concludes that a number of vague and ill prepared guidelines within the Nitrates Directive undermine its ability to protect water quality adequately, and hence current implementation of the Water Framework Directive (WFD) is an opportunity to re‐shape water policy in relation to nitrate. Copyright © 2007 John Wiley & Sons, Ltd and ERP Environment.
Mixed‐Metal Dawson Sandwich Complexes: Synthesis, Spectroscopic Characterization and Electrochemical Behaviour of Na16[MIICo3(H2O)2(P2W15O56)2] (M = Mn, Co, Ni, Zn and Cd) (Eur. J. Inorg. Chem. 11/2007)
Authors: Ruhlmann Laurent , Costa‐Coquelard Claure , Canny Jacqueline , Thouvenot René 
Published: March 2007

AbstractThe cover picture shows the synthesis of the mixed‐metal Dawson sandwich complexes [MCo3(H2O)2(P2W15O56)2]16− by the addition of the transition metal cation M2+ to the “lacunary” sandwich complex [NaCo3(H2O)2(P2W15O56)2]17−. This “lacunary” species is a good precursor for the preparation mixed‐metal sanswich complexes, with promising interesting catalytic, electrocatalytic and magnetic properties. Details of the synthesis and the structural characterization in solution are discussed in the article by L. Ruhlmann and R. Thouvenot on p. 1493 ff.
Amperometric Tyrosinase Biosensor Based on Carbon Nanotube–Titania–Nafion Composite Film
Authors: Lee You‐Jin , Lyu Young‐Ku , Choi Han Nim , Lee Won‐Yong 
Published: March 2007

AbstractA highly sensitive and stable amperometric tyrosinase biosensor has been developed based on multiwalled carbon nanotube (MWCNT) dispersed in mesoporous composite films of sol–gel‐derived titania and perfluorosulfonated ionomer (Nafion). Tyrosinase was immobilized within a thin film of MWCNT–titania–Nafion composite film coated on a glassy carbon electrode. Phenolic compounds were determined by the direct reduction of biocatalytically‐liberated quinone species at −100 mV versus Ag/AgCl (3 M NaCl) without a mediator. The present tyrosinase biosensor showed good analytical performances in terms of response time, sensitivity, and stability compared to those obtained with other biosensors based on different sol–gel matrices. Due to the large pore size of the MWCNT–titania–Nafion composite, the present biosensor showed remarkably fast response time with less than 3 s. The present biosensor responds linearly to phenol from 1.0×10−7 M to 5.0×10−5 M with an excellent sensitivity of 417 mA/M and a detection limit of 9.5×10−8 M (S/N=3). The enzyme electrode retained 89% of its initial activity after 2 weeks of storage in 50 mM phosphate buffer at pH 7.0.
Characterization of Mercury – Humic Acids Interaction by Potentiometric Titration with a Modified Carbon Paste Mercury Sensor
Authors: Gismera M. Jesús , Procopio Jesús R. , Sevilla M. Teresa 
Published: March 2007

AbstractStability constant for mercury binding by commercial and natural humic acids (HA) were determined using a new potentiometric mercury(II) sensor based on dithiosalicylic acid modified carbon paste electrode. The sensor present a high selective and sensitive response to mercury(II) ions, and a low detection limit of 1.8×10−8 M. The potentiometric titrations curves of humic acids against mercury(II) ions were modeled. For 1.00×10−7 to 3.00×10−4 M mercury(II) ion concentration levels the results are consistent with the presence of two different binding sites in the humic acid macromolecule. The strongest binding sites (log K1 ranging from 10.1 to 6.8) are probably due to interaction with carboxylic acid and amine groups in the molecule, whereas weakest binding sites (log K2 ranging from 8.8 to 4.5) can be associated to phenolic groups.
Ultrathin Carbon Nanoparticle Composite Film Electrodes: Distinguishing Dopamine and Ascorbate
Authors: Amiri Mandana , Shahrokhian Saeed , Marken Frank 
Published: March 2007

AbstractUltrathin carbon nanoparticle–poly(diallyldimethylammonium chloride) films (CNP‐PDDAC films) are formed on tin‐doped indium oxide (ITO) electrodes in a layer‐by‐layer electrostatic deposition process employing 9–18 nm diameter carbon particles. Transparent and strongly adhering films of high electrical conductivity are formed and characterized in terms of their electrochemical reactivity. When immersed in aqueous 0.1 M phosphate buffer pH 7, each layer of CNP‐PDDAC (of ca. 5–6 nm average thickness) is adding an interfacial capacitance of ca. 10 μF cm−2. Absorption into the CNP–PDDAC nanocomposite film is dominated by the sites in the PDDAC cationomer and therefore anionic molecules such as indigo carmine are strongly bound and retained within the film (cationic binding sites per layer ca. 150 pmol cm−2). In contrast, cationic redox systems such as ferrocenylmethyltrimethyl‐ammonium+ fail to bind. For solution phase redox systems such as hydroquinone, the rate of electron transfer is dramatically affected by the CNP‐PDDAC film and switched from completely irreversible to highly reversible even with a single layer of carbon nanoparticles. For the mixed redox system ascorbate–dopamine in 0.1 M phosphate buffer pH 7 cyclic voltammograms suggest a rapid and selective temporary poisoning process which causes the ascorbate oxidation to be suppressed in the second potential cycle. This effect is exploited for the detection of micromolar concentrations of dopamine in the presence of millimolar ascorbate.
EQCM Study of Ru and RuO2 Surface Electrochemistry
Authors: Juodkazytė J. , Vilkauskaitė R. , Stalnionis G. , Šebeka B. , Juodkazis K. 
Published: March 2007

AbstractThe present study represents comparative analysis of voltammetric and microgravimetric behavior of active ruthenium (Ru), electrochemically passivated ruthenium (Ru/RuO2) and thermally formed RuO2 electrodes in the solutions of 0.5 M H2SO4 and 0.1 M KOH. It has been found that cycling the potential of active Ru electrode within E ranges 0 V–0.8 V and 0 V–1.2 V in 0.5 M H2SO4 and 0.1 M KOH solutions, respectively, leads to continuous electrode mass increase, while mass changes observed in alkaline medium are considerably smaller than those in acidic one. Microgravimetric response of active Ru electrode in 0.5 M H2SO4 within 0.2 V–0.8 V has revealed reversible character of anodic and cathodic processes. The experimentally found anodic mass gain and cathodic mass loss within 0.2–0.8 V make 2.2–2.7 g F−1, instead of 17 g F−1, which is the theoretically predicted value for Ru(OH)3 formation according to equation: Ru+3H2O⇌Ru(OH)3+3H++3e−. In the case of Ru/RuO2 electrode relatively small changes in mass have been found to accompany the anodic and cathodic processes within E range between 0.4 V and 1.2 V in the solution of 0.5 M H2SO4. Meanwhile cycling the potential of thermally formed RuO2 electrode under the same conditions has lead to continuous decrease in electrode mass, which has been attributed to irreversible dehydration of RuO2 layer. On the basis of microgravimetric and voltammetric study as well as the coulometric analysis of the results conclusions are presented regarding the nature of surface processes taking place on Ru and RuO2 electrodes.
Conservatism in summation rules for closely spaced modes
Authors: Kelly James M. , Sackman Jerome L. 
Published: March 2007

AbstractIt is shown that the method recommended by the Nuclear Regulatory Commission to be used to combine spectral response in the case of closely spaced modes is unnecessarily conservative for certain systems. Closely spaced modes arise in structures from symmetry and where there is a light appendage with a frequency close to one of the natural frequencies of the structure. In the former case, the closely spaced modes do not involve significant interaction between components of the system and the Nuclear Regulatory Commission Guide is reasonable. The latter case, that is when there are closely spaced modes where interaction of components occurs as in the examples of light appendages and torsionally unbalanced buildings, must be treated by consideration of the interacting components. The approach proposed here is that the modes that are not closely spaced be treated by modal analysis and the closely spaced modes, in the case of two closely spaced modes, be treated as a coupled two‐degree‐of‐freedom system. If this is done, the beat phenomenon, the most important characteristic of the interaction, is evident, as is the associated result that the peak response of the coupled system is developed much later than the peak responses obtained in the individual modes. It is shown that the square root of the sum of the squares procedure underestimates, as expected, the response for undamped and very lightly damped systems, but for damped systems the square root of the sum of the squares method can be extremely conservative. It follows that the other methods specified by the Nuclear Regulatory Commission for closely spaced modes must be even more conservative.
Dynamic response of an elastic‐viscoplastic system in modal co‐ordinates
Authors: Lukkunaprasit Panitan , Widartawan Stephen , Karasudhi Pisidhi 
Published: March 2007

AbstractA dynamic analysis of elastic–viscoplastic systems, incorporating the modal co‐ordinate transformation technique, is presented. The formulation results in uncoupled incremental equations of motion with respect to the modal co‐ordinates. The elastic–viscoplastic model adopted allows the analysis not to involve yielding regions and loading/unloading processes. An implicit Runge–Kutta scheme together with the Newton–Raphson method are used to solve the non‐linear constitutive equations. Stability and accuracy of the numerical solution are improved by utilizing a local time step sub‐incrementing procedure.Applications of the analyses to multi‐storey shear buildings show that good results can be obtained for the maximum displacement response by including only a few lower modes in the computation, but the prediction of the ductility factor response tends to underestimate the peak values when too few modes are used. In addition, stable and valid results can be obtained even with a sizable time step increment.
Identification of a one‐dimensional model for a soil‐layer–bedrock system during an earthquake
Authors: Tomizawa Minoru 
Published: March 2007

AbstractThe propriety of adopting a multi‐degree‐of‐freedom lumped mass–spring–dampers system driven by white noise support excitation as a one‐dimensional model for a soil‐layer–bedrock system during an earthquake is investigated by means of statistical system identification of the model with noisy measurement of the earthquake ground velocity. The present discussion also suggests that this model may not be applicable to all observed earthquake records, since the model itself depends on the statistical nature of the earthquake motion. For appropriate earthquake records, the system identification procedure may be accomplished; then dynamical properties of the soil‐layer and the power spectral density for white noise excitation acting upon the bedrock can be estimated as shown in a numerical example.
Resonance capacity method for earthquake response analysis of hysteretic structures
Authors: Yamada Minoru , Kawamura Hiroshi 
Published: March 2007

AbstractThe Resonance Capacity Method is proposed for the earthquake response analysis of hysteretic structures. Resonance Capacity is a physical quantity of structures which is related to the hysteretic energy absorbed by structures in one cycle and is equated to the acceleration, velocity and displacement amplitudes α0, d0 and d0 of earthquake ground motions at resonance.1 According to the idealized trapezoidal approximation of earthquake ground motions in the logarithmic period–velocity plane as proposed by Veletsos and Newmark,8 the Resonance Capacity property applies in each period range, short, medium and long, where α0, v0 and d0 respectively are approximately constant. In the medium range of periods, the energy dissipated in hysteretic loops and the deformation amplitudes of a single‐degree system with elasto–plastic force–deformation relationships are calculated for the case of El Centro 1940, 18 May earthquake, by this Resonance Capacity Method. The result is compared with results from conventional numerical response analyses obtained by Berg and Thomaides,14 Kato and Akiyama12 and Veletsos and Newmark,8 and the general agreement is seen to be good. Therefore, it may be possible to apply this Resonance Capacity Method over the entire range of periods. By means of this method the earthquake response analysis of hysteretic systems can be performed easily, and the hysteretic energy and fatigue characteristics of structures may be taken into account directly, up to the point of fracture.
Seismicity and seismic intensities in Jamaica, West Indies: A problem in risk assessment
Authors: Shepherd John B. , Aspinall W. P. 
Published: March 2007

AbstractA review of the history of earthquake observations in Jamaica is presented; there have been several high‐intensity earthquakes in the last 300 years. The observed seismicity of the Jamaica region is discussed in the context of what is known of regional tectonics, and possible source regions of earthquakes are identified but a comparison between instrumentally determined seismicity and macroseismicity shows that the instrumental data are of insufficient quantity or quality to permit direct assessment of earthquake risk by conventional techniques. An alternative approach has been adopted; consideration of the macroseismic record suggests that the peak acceleration in rock with 90 per cent probability of not being exceeded in any 50‐year period is of order 0.3 g but that there are very significant local variations caused by near‐surface geology. Especially this applies to the capital, Kingston, and envelope response spectra are derived for shallow, intermediate and deep thickness of sediments under the city to demonstate the possibility that localized amplification may occur.A current apparent decline in the seismicity of the Jamaica region is noted but it is shown that the decline in the number of earthquakes of engineering interest is not yet statistically significant.