bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of an Acid–Base and Redox Molecular Switch: From Bulk to the Single‐Molecule Level
Authors: Al‐Kaysi Rabih O. , Bourdelande José Luis , Gallardo Iluminada , Guirado Gonzalo , Hernando Jordi 
Published: June 2007

AbstractIn this work we investigate a new fluorescent molecular switch based on the interconversion between the fluorescent zwitterionic form (ZW1) and the non‐fluorescent anionic state (MC2) of a spirocyclic Meisenheimer complex of 1,3,5‐trinitrobenzene. Density functional theory molecular orbital calculations reveal that photo‐induced electron transfer from a guanidine group to the trinitrocyclohexadiene fluorophore of the complex quenches the emission from MC2. Protonation, as well as coordination of other Lewis acids to the guanidine group, suppress the quenching mechanism and allow the complex to fluoresce. In agreement with the calculations, reversible on–off fluorescence switching of the ZW1–MC2 bulk system occurs by protonation–deprotonation of the guanidine moiety upon acid–base addition. Interestingly, spectroelectrochemical ensemble measurements show that switching of the ZW1–MC2 pair can also be attained electrochemically, thus unraveling the versatile functioning of this system. The ultimate limit of monitoring the reversible on–off operation of individual switch molecules is reached by means of single‐molecule fluorescence spectroscopy, which demonstrates the potential of the ZW1–MC2 system to be used as a true single‐molecule switch on the nanometer scale.
Mannosylated G(0) Dendrimers with Nanomolar Affinities to Escherichia coli FimH
Authors: Touaibia Mohamed , Wellens Adinda , Shiao Tze Chieh , Wang Qingan , Sirois Suzanne , Bouckaert Julie , Roy René 
Published: June 2007

AbstractPentaerythritol and bis‐pentaerythritol scaffolds were used for the preparation of first generation glycodendrimers bearing aryl α‐D‐mannopyranoside residues assembled using single‐step Sonogashira and click chemistry. The carbohydrate precursors were built with either para‐iodophenyl, propargyl, or 2‐azidoethyl aglycones whereas the pentaerythritol moieties were built with terminal azide or propargyl groups, respectively. Cross‐linking abilities of this series of glycodendrimers were first evaluated with the lectin from Canavalia ensiformis (Concanavalin A). Surface plasmon resonance measurements showed these two families of mannosylated clusters as the best ligands known to date toward Escherichia coli K12 FimH with subnanomolar affinities. Tetramer 4 had a Kd of 0.45 nM. These clusters were 1000 times more potent than mannose for their capacity to inhibit the binding of E. coli to erythrocytes in vitro.
Methodology for the Calculation of the Potential of Mean Force for a Cation–π Complex in Water
Authors: Ghoufi Aziz , Archirel Pierre , Morel Jean‐Pierre , Morel‐Desrosiers Nicole , Boutin Anne , Malfreyt Patrice 
Published: June 2007

AbstractWe report potential of mean force (PMF) calculations on the interaction between the p‐sulfonatocalix[4]arene and a monovalent cation (Cs+). It has been recently shown from microcalorimetry and 133Cs NMR experiments that the association with Cs+ is governed by favourable cation–π interactions and is characterized by the insertion of the cation into the cavity of the macrocycle. We show that the PMF calculation based upon a classical model is not able to reproduce both the thermodynamic properties of association and the insertion of the cation. In order to take into account the different contributions of the cation–π interactions, we develop a new methodology consisting of changing the standard PMF by an additional contribution resulting from quantum calculations. The calculated thermodynamic properties of association are thus in line with the microcalorimetry and 133Cs NMR experiments and the structure of the complex at the Gibbs free‐energy minimum shows the insertion of the cation into the cavity of the calixarene.
Sensitized Emission from Lanthanide‐Doped Nanoparticles Embedded in a Semiconductor Sol–Gel Thin Film
Authors: Sivakumar Sri , van Veggel Frank C. J. M. , Raudsepp Mati 
Published: June 2007

AbstractIn2O3 sol–gel thin films made with LaF3:Ln3+ (Ln=Er, Nd, and Eu) nanoparticles were prepared and showed sensitized emission of the lanthanide ions after In2O3 matrix excitation. The excitation spectra showed an In2O3 absorption band in addition to the excitation peaks of the lanthanide ions, clearly demonstrating that there is energy transfer from the In2O3 matrix to Ln3+ (Er3+, Nd3+, and Eu3+). Similarly, HfO2 and ZrO2 sol–gel thin films made with LaF3:Ln3+ nanoparticles also showed energy transfer from the semiconductor matrix to the lanthanide ions.
The Molecular Orientation of para‐Sexiphenyl on Cu(110) and Cu(110) p(2×1)O
Authors: Oehzelt Martin , Grill Leonhard , Berkebile Stephen , Koller Georg , Netzer Falko P. , Ramsey Michael G. 
Published: June 2007

AbstractControlling the molecular growth of organic semiconductors is an important issue to optimize the performance of organic devices. Conjugated molecules, used as building blocks, have an anisotropic shape and also anisotropic physical properties like charge transport or luminescence. The main challenge is to grow highly crystalline layers with molecules of defined orientation. The higher the crystallinity, the closer these properties reach their full intrinsic potential, while the orientation determines the physical properties of the film. Herein we show that the molecular orientation and growth can be steered by the surface chemistry, which tunes the molecule–substrate interaction. In addition, the oxygen reconstruction of the surface, demonstrates the flexibility of the organic molecules to adopt a given surface corrugation and their unique possibility to release stress by tilting.
Growth and characterization of pure and doped nonlinear optical l‐arginine acetate single crystals
Authors: Gulam Mohamed M. , Vimalan M. , Jesudurai J. G. M. , Madhavan J. , Sagayaraj P. 
Published: June 2007

AbstractSingle crystals of organic nonlinear optical material of pure, Cu2+ and Mg2+ doped L‐arginine acetate (LAA) were successfully grown by slow evaporation method at room temperature. The UV‐Vis‐NIR spectra of pure and doped LAA indicate that these crystals possess a wide optical transmission window from 240‐1600 nm. Non‐linear optical studies reveal that the SHG efficiency of LAA is nearly three times that of KDP. The dielectric response of the samples was studied in the frequency region 100 Hz to 2 MHz and the influence of Cu2+ and Mg2+ substitution on the dielectric behaviour had been investigated. Photoconductivity study proves that both pure and Cu2+ and Mg2+ doped LAA crystal exhibit positive photoconductivity. It is evident from the Vickers hardness study that the hardness of the crystal decreases with increasing load both for pure and doped samples. ESR studies confirmed the incorporation of Cu2+ into LAA and the value of g‐factor was found to be 2.1654. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis, growth and characterization of l‐alaninium oxalate ‐ a novel organic NLO crystal
Authors: Vimalan M. , Ramanand A. , Sagayaraj P. 
Published: June 2007

AbstractNonlinear optical material of L‐alaninium oxalate (LAO) has been synthesized and single crystals are grown by slow evaporation technique. The solubility data of LAO is determined in water. Single crystal X‐ray diffraction study showed that LAO belongs to orthorhombic system with a non‐centrosymmetric space‐group P212121. The functional groups have been identified from FT‐IR spectrum. The UV‐Vis‐NIR spectrum of LAO shows less optical absorption in the entire visible region. The second harmonic generation (SHG) in the material was estimated using Nd:YAG laser. The mechanical properties of the grown crystals are studied using Vickers microhardness tester. The AC and DC conductivity, and dielectric studies are also carried out and reported for the first time. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐dimensional numerical investigation of the effects of an open window on the convective heat transfer of an oxide Czochralski system
Authors: Tavakoli M. H. , Wilke H. 
Published: June 2007

AbstractA three‐dimensional numerical analysis was carried out for a real Czochralski crystal growth furnace containing only gas and without any melt and crystal in order to investigate the effects of a small observation window on the temperature and flow field of the system. For this approach, the induction heating equations, the Navier‐Stokes equation with Boussinesq approximation, the continuity and energy equations have been solved in cylindrical coordinates using the finite element method. It has been found that the flow and thermal fields in the system are obviously three‐dimensional and non‐axisymmetric. The gas enters the system through the window is directed towards the opposite side wall where it is divided into two parts of vertical direction as well as expands in horizontal direction. Consequently, there is a spiral gas flow in the crucible and afterheater which rotates upwards in azimuthal direction along the walls. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nanocrystalline properties of chemically deposited (Cd0.95‐Pb0.05)S:CdCl2, Gd/Dy films
Authors: Bhushan S. , Shrivastava S. 
Published: June 2007

AbstractResults of SEM and XRD studies, optical absorption spectra and photoluminescence emission spectra are presented for the films of (Cd0.95‐Pb0.05)S:CdCl2, Gd/Dy prepared by chemical bath deposition technique and using thiophenol and methanol as capping agents. The deposition of films is based on precipitation followed by condensation on the substrates. SEM studies show existence of irregular distribution of particles alongwith presence of rod/tube type structure. The XRD studies show diffraction lines of CdS, PbS and CdCl2. Blue shift has been observed in absorption spectra showing quantum confinement. Particle sizes determined from XRD studies and absorption spectral studies are found to lie in the nano range. Photoluminescence emission spectra consist of emissions in blue and green‐yellow regions. The observed emissions are related to the combination of defect levels and levels due to rare earths. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal structure and electrochemical property of one‐dimensional complex: [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]2[Cu(mnt)2]
Authors: Sun Yun‐Ming , Dong Feng‐Ying , Dou Jian‐Min , Li Da‐Cheng , Gao Xi‐Ke , Wang Da‐Qi 
Published: June 2007

AbstractOne metalorganic complex [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]2[Cu(mnt)2] (mnt = maleonitriledithiolate) has been obtained by the reaction of dicyclohexyl‐18‐crown‐6 with K2mnt and CuCl2·2H2O. The title complex has been characterized by elementary analysis, FT‐IR, UV‐Vis spectroscopy and x‐ray single crystal diffraction. The title complex crystallizes in the triclinic space group P1 with crystallographic data: a = 10.870(6) Å, b = 11.536(6) Å, c = 12.904(7) Å, α = 101.541(10)°, β = 110.573(9)°, γ = 99.441(9)°, V = 1435.2(13) Å3, Z = 1, Dcalcd = 1.350 g/cm3, F(000) = 615, R1 = 0.0641, wR2 = 0.1475. It displays one‐dimensional chain‐like structure formed by [K(cis‐syn‐cis‐ dicyclohexyl‐18‐crown‐6)]+ complex cations and [Cu(mnt)2]2‐ complex anions through N‐K‐N interactions. Its electrochemical behavior has also been studied by the cyclic voltammetry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Developmental and activity‐dependent regulation of ARMS/Kidins220 in cultured rat hippocampal neurons
Authors: Cortés Rosa Y. , Arévalo Juan Carlos , Magby Jason P. , Chao Moses V. , Plummer Mark R. 
Published: June 2007

AbstractNeurotrophin activation of Trk receptors elicits diverse effects on neuronal survival, differentiation, and synaptic plasticity. One of the central questions is how specificity is encoded in neurotrophin receptor signaling and actions. A unique downstream protein is the Ankyrin‐Repeat Rich Membrane Spanning (ARMS)/Kinase D‐interacting substrate‐220 kDa (Kidins220), a very abundant scaffold protein in the hippocampus. To determine the roles of ARMS/Kidins220 in hippocampal neurons, we have analyzed the effects of synaptic activity upon the regulation and distribution of ARMS/Kidins220. At early times in vitro (<7 DIV), synaptic activity was low and ARMS/Kidins220 levels were high. As synaptic activity and markers for synapse maturation, such as PSD‐95, increased, ARMS/Kidins220 significantly decreased to a plateau by later times in vitro (>12 DIV). Immunocytochemistry showed ARMS/Kidins220 to be concentrated at the tips of growing processes in immature cultures, and more diffusely distributed in older cultures. To examine the apparent inverse relationship between activity and ARMS/Kidins220 levels, neuronal firing was manipulated pharmacologically. Chronic exposure to TTX increased ARMS/Kidins220 levels, whereas bicuculline caused the opposite effect. Moreover, using shRNA to decrease ARMS/Kidins220 levels produced a corresponding increase in synaptic activity. We find that ARMS/Kidins220 may function in neuronal development as an indicator and potentially as a homeostatic regulator of overall synaptic strength in hippocampal neurons. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007
Detection of beeswax adulterations using concentration guide‐values
Authors: Jiménez Juan José , Bernal José Luis , del Nozal María Jesús , Toribio Laura , Bernal José 
Published: June 2007

AbstractThe concentrations of 102 chemical compounds (saturated and unsaturated hydrocarbons, palmitates, total and free acids, total hydroxyacids, total and free alcohols, acidic monoesters and monoesterified 1,2,3‐propanetriols) have been determined by GC/FID on white and yellow comb beeswax of Apis mellifera from different regions of Spain. Guide‐value ranges are proposed for its characterization and to discriminate adulterated foundation beeswax sheets. The concentrations of many compounds resulted to be statistically different for white and yellow beeswaxes, while the observation of concentrations out of normal in some marketed foundation beeswax sheets suggested their adulteration. However, the measurement of anomalous concentrations in foundation beeswax sheets did not imply necessarily their rejection by the bees.
Inhibition of lipid peroxidation in UVA‐treated skin fibroblasts by luteolin and its glucosides
Authors: Rahimuddin Sawsan A. , Khoja Samir M. , Zuhair Marzoki M. , Howell Nazlin K. , Brown Jonathan E. 
Published: June 2007

AbstractUltraviolet A (UVA) radiation causes oxidative damage to human skin cells. This damage may be reduced or prevented using plant compounds as photoprotectants. To investigate the relationship between chemical structure and UVA‐protective activity, three structurally related flavonoids, namely luteolin, luteolin‐7‐O‐glucoside (both present in artichoke) and luteolin‐4'‐O‐glucoside (present in wild carrot), were studied. Human skin fibroblasts exposed to UVA (250 and 500 kJ/m2) were treated with each flavonoid (30 µM) for 18 h prior to irradiation. The extent of lipid peroxidation in the cellular extracts was assessed as lipid peroxides and malondialdehyde (MDA). Luteolin and luteolin‐7‐O‐glucoside both prevented a significant increase in lipid peroxides at 250 kJ/m2, but at 500 kJ/m2 their effectiveness was clearly attenuated. Contrastingly, luteolin‐4'‐O‐glucoside was pro‐oxidant at both radiation doses. Measurements of MDA levels highlighted that luteolin was clearly more effective than the two glucosides at both 250 and 500 kJ/m2. Overall, these results show clear differences between the three flavonoids and suggest that the B ring 3',4'‐dihydroxy group, lacking in luteolin‐4'‐O‐glucoside, may be particularly important. Flavonoid: transition metal ion chelation studies confirmed the influence of the 3',4'‐dihydroxy group, which is also relevant to the quenching of singlet oxygen. These features as well as the greater lipophilic nature of luteolin together explain the superior activity of this flavonoid which may be potentially useful as a supplement in photoprotective skin preparations.
Testing the boolean hypothesis in the non‐convex case when a bounded grain can be assumed
Authors: Chadœuf J. , Bacro J. N. , Thébaud G. , Labonne G. 
Published: June 2007

AbstractSpatial independence of objects is a strong hypothesis when using boolean models. Methods to test it have then been developed, but only when the objects are convex. We propose here to replace this assumption by a bound assumption of the objects which can be more easily assumed when modeling spatial patterns in ecology and agricultural science. A test is then proposed, based on the length of the voids of the intersection between transect lines and a dilation of the original process related to the bound value. Its application is shown to several examples, together with its extension to an epidemiological case on orchards, where this problem comes from. Copyright © 2007 John Wiley & Sons, Ltd.
Does amplitude scaling of ground motion records result in biased nonlinear structural drift responses?
Authors: Luco Nicolas , Bazzurro Paolo 
Published: June 2007

AbstractLimitations of the existing earthquake ground motion database lead to scaling of records to obtain seismograms consistent with a ground motion target for structural design and evaluation. In the engineering seismology community, acceptable limits for ‘legitimate’ scaling vary from one (no scaling allowed) to 10 or more. The concerns expressed by detractors of scaling are mostly based on the knowledge of, for example, differences in ground motion characteristics for different earthquake magnitude–distance (Mw–Rclose) scenarios, and much less on their effects on structures. At the other end of the spectrum, proponents have demonstrated that scaling is not only legitimate but also useful for assessing structural response statistics for Mw–Rclose scenarios. Their studies, however, have not investigated more recent purposes of scaling and have not always drawn conclusions for a wide spectrum of structural vibration periods and strengths. This article
investigates whether scaling of records randomly selected from an Mw–Rclose bin (or range) to a target fundamental‐mode spectral acceleration (Sa) level introduces bias in the expected nonlinear structural drift response of both single‐degree‐of‐freedom oscillators and one multi‐degree‐of‐freedom building. The bias is quantified relative to unscaled records from the target Mw–Rclose bin that are ‘naturally’ at the target Sa level. We consider scaling of records from the target Mw–Rclose bin and from other Mw–Rclose bins. The results demonstrate that scaling can indeed introduce a bias that, for the most part, can be explained by differences between the elastic response spectra of the scaled versus unscaled records. Copyright © 2007 John Wiley & Sons, Ltd.
Sequence stratigraphy of the upper Millstone Grit (Yeadonian, Namurian), North Wales
Authors: Jerrett Rhodri M. , Hampson Gary J. 
Published: June 2007

AbstractThe upper Millstone Grit strata (Yeadonian, Namurian) of North Wales have been studied using sedimentological facies analysis and sequence stratigraphy. These strata comprise two cyclothems, each containing prodelta shales (Holywell Shale) that pass gradationally upwards into delta‐front and delta‐plain deposits (Gwespyr Sandstone Formation). The deltas formed in shallow water (<100 m), were fluvial‐dominated, had elongate and/or sheet geometries and are assigned to highstand systems tracts. Two delta complexes with distinctive sandstone petrographies are identified: (1) a southerly derived, quartzose delta complex sourced locally from the Wales‐Brabant Massif, and (2) a feldspathic delta complex fed by a regional source(s) to the north and/or west. The feldspathic delta complex extended further south in the younger cyclothem. A multistorey braided‐fluvial complex (Aqueduct Grit, c. 25 m thick) is assigned to a lowstand systems tract, and occupies an incised valley that was eroded into the highstand feldspathic delta complex in the younger cyclothem. A candidate incised valley cut into the highstand feldspathic delta complex in the older cyclothem is also tentatively identified. Transgressive systems tracts are thin (<5 m) and contain condensed fossiliferous shales (marine bands). The high‐resolution sequence stratigraphic framework interpreted for North Wales can be readily traced northwards into the Central Province Basin (‘Pennine Basin’), supporting the notion that high‐frequency, high‐magnitude sea‐level changes were the dominant control on stratigraphic architecture. Copyright © 2007 John Wiley & Sons, Ltd.
The demand for statin: the effect of copay on utilization and compliance
Authors: Thiebaud Patrick , Patel Bimal V. , Nichol Michael B. 
Published: June 2007

AbstractIncreasing drug costs in the US have prompted employers and insurers alike to turn to higher drug copays for cost containment. The effect of rising copays on compliance with statins (HMG‐CoA reductase inhibitors) treatment has received surprisingly little attention in the applied literature. This paper uses pharmacy claims data from a commercially insured adult population to determine the effect of copay change on compliance at the individual level. Fixed effect logit and Poisson regressions estimate the effect of copays on monthly likelihood of high compliance and average monthly days of supply respectively. Higher copays reduce compliance among statin users, with less compliant patients responding more strongly to copay change than compliant patients. These results suggest that specific financial incentives given to less compliant patients could improve compliance with statin treatment at a relatively low cost. Copyright © 2007 John Wiley & Sons, Ltd.
Application of a Highly Robust and Efficient Fluorescence‐Resonance‐Energy‐Transfer (FRET) System in DNA
Authors: Clima Lilia , Hirtz‐Haag Caroline , Kienzler Andrea , Bannwarth Willi 
Published: June 2007

AbstractWe report a feasibility study for the application of our newly developed highly efficient and robust fluorescence‐resonance‐energy‐transfer (FRET) system to DNA. A 2′‐oligodeoxynucleotide, 12, equipped with a quinolinone derivative as donor and a (bathophenanthroline)ruthenium(II) complex as acceptor and having a single uridine as potential cleavage site under basic conditions revealed an intensive FRET, which almost vanished after cleavage of the oligonucleotide under basic conditions (Fig. 7). Furthermore, in the arrangement of a molecular beacon (MB) DNA (see 13), a significant decrease of the FRET was observed after hybridization to a target sequence (Fig. 9). Due to the long decay times of the fluorescence of the Ru‐complex, the system allows for highly sensitive time‐gated measurements.
Two New Highly Oxidized Humulane Sesquiterpenes from the Basidiomycete Lactarius mitissimus
Authors: Luo Du‐Qiang , Gao Yuan , Yang Xiao‐Long , Tang Jian‐Guo , Zhao Li‐Yan , Liu Ji‐Kai 
Published: June 2007

AbstractTwo new highly oxidized humulane sesquiterpenes, mitissimols F (1) and G (2), were isolated from the fruiting bodies of Lactarius mitissimus. Their structures were elucidated by using extensive spectroscopic techniques including 1D‐ and 2D‐NMR experiments. The absolute configuration of mitissimol F (1) was determined by 1H‐NMR resolution of its diastereoisomeric α‐methoxy‐α‐(trifluoromethyl)benzeneacetates (MTPA). It was shown to be (1S,3E,6S,8R,9R,10S,11R)‐8,9 : 10,11‐diepoxy‐1,6‐dihydroxyhumul‐3‐en‐5‐one (=(1S,2R,4R,6S,8E,11S,12R)‐6,11‐dihydroxy‐1,6,10,10‐tetramethyl‐3,13‐dioxatricyclo[10.1.0.02,4]tridec‐8‐en‐7‐one).