bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charge‐Shift Bonding—A Class of Electron‐Pair Bonds That Emerges from Valence Bond Theory and Is Supported by the Electron Localization Function Approach
Authors: Shaik Sason , Danovich David , Silvi Bernard , Lauvergnat David L. , Hiberty Philippe C. 
Published: August 2005

AbstractThis paper deals with a central paradigm of chemistry, the electron‐pair bond. Valence bond (VB) theory and electron‐localization function (ELF) calculations of 21 single bonds demonstrate that along the two classical bond families of covalent and ionic bonds, there exists a class of charge‐shift bonds (CS bonds) in which the fluctuation of the electron pair density plays a dominant role. In VB theory, CS bonding manifests by way of a large covalent‐ionic resonance energy,RECS, and in ELF by a depleted basin population with large variances (fluctuations). CS bonding is shown to be a fundamental mechanism that is necessary to satisfy the equilibrium condition, namely the virial ratio of the kinetic and potential energy contributions to the bond energy. The paper defines the atomic propensity and territory for CS bonding: Atoms (fragments) that are prone to CS bonding are compact electronegative and/or lone‐pair‐rich species. As such, the territory of CS bonding transcends considerations of static charge distribution, and involves: a) homopolar bonds of heteroatoms with zero static ionicity, b) heteropolar σ and π bonds of the electronegative and/or electron‐pair‐rich elements among themselves and to other atoms (e.g., the higher metalloids, Si, Ge, Sn, etc), c) all hypercoordinate molecules. Several experimental manifestations of charge‐shift bonding are discussed, such as depleted bonding density, the rarity of ionic chemistry of silicon in condensed phases, and the high barriers of halogen‐transfer reactions as compared to hydrogen‐transfers.
Two‐Photon Dyes Containing Heterocyclic Rings with Enhanced Photostability
Authors: Kim Hwan Myung , Yang Wen Jun , Kim Chang Ho , Park Won‐Hwa , Jeon Seung‐Joon , Cho Bong Rae 
Published: August 2005

AbstractA series of donor–π–donor derivatives containing phenyl, naphthyl, and anthryl groups as the π‐center and heterocyclic rings as the conjugation bridge have been synthesized and their one‐ and two‐photon spectroscopic properties and photostability were determined. These compounds show bathochromic shifts in the absorption and emission spectra, larger two‐photon cross‐section, and enhanced photostability in comparison to their open‐chain analogues. In addition, a convenient method for the qualitative photostability measurement is proposed.
Organolanthanide‐Mediated Intermolecular Hydroamination of 1,3‐Dienes: Mechanistic Insights from a Computational Exploration of Diverse Mechanistic Pathways for the Stereoselective Hydroamination of 1,3‐Butadiene with a Primary Amine Supported by an ansa‐Neodymocene‐Based Catalyst
Authors: Tobisch Sven 
Published: August 2005

AbstractThe complete catalytic reaction course for the organolanthanide‐mediated intermolecular hydroamination of 1,3‐butadiene and n‐propylamine by an archetypical [Me2Si(η5‐Me4C5)2NdCH(SiMe3)2] precatalyst was critically scrutinized by employing a reliable gradient‐corrected DFT method. A free‐energy profile of the overall reaction is presented that is based on the thorough characterization of all crucial elementary steps for a tentative catalytic cycle. A computationally verified, revised mechanistic scenario is proposed which is consistent with the experimentally derived empirical rate law and accounts for crucial experimental observations. It involves kinetically mobile reactant association/dissociation equilibria and facile, reversible intermolecular diene insertion into the Nd–amido bond, linked to turnover‐limiting protonolysis of the η3‐butenyl–Nd functionality. The computationally predicted effective kinetics (Δ${H{{{\ne}\hfill \atop {\rm tot}\hfill}}}$=11.3 kcal mol−1, Δ${S{{{\ne}\hfill \atop {\rm tot}\hfill}}}$=−35.7 e.u.) are in reasonably good agreement with experimental data for the thoroughly studied hydroamination of alkynes. The thermodynamic and kinetic factors that determine the almost complete regio‐ and stereoselectivity of the mechanistically diverse intermolecular 1,3‐diene hydroamination have been unraveled. The present computational study complements experiments because it allows, first, a more detailed understanding and a consistent rationalization of the experimental results for the hydroamination of 1,3‐dienes and primary amines and, second, enhances the insights into general mechanistic aspects of organolanthanide‐mediated intermolecular hydroamination.
A Photoactive Molecular Triad as a Nanoscale Power Supply for a Supramolecular Machine
Authors: Saha Sourav , Johansson Erik , Flood Amar H. , Tseng Hsian‐Rong , Zink Jeffrey I. , Stoddart J. Fraser 
Published: August 2005

AbstractA tetrathiafulvalene–porphyrin–fullerene (TTF–P–C60) molecular triad, which generates electrical current by harnessing light energy when self‐assembled onto gold electrodes, has been developed. The triad, composed of three unique electroactive components, namely, 1) an electron‐donating TTF unit, 2) a chromophoric porphyrin unit, and 3) an electron‐accepting C60unit, has been synthesized in a modular fashion. A disulfide‐based anchoring group was tagged to the TTF end of the molecule in order to allow its self‐assembly on gold surfaces. The surface coverage by the triad in a self‐assembled monolayer (SAM) was estimated to be 1.4 nm2per molecule, a density which is consistent with hexagonal close‐packing of the spherical C60component (diameter ∼1 nm). In a closed electronic circuit, a triad‐SAM functionalized working‐electrode generates a switchable photocurrent of ∼1.5 μA cm−2when irradiated with a 413 nm Kr‐ion laser, a wavelength which is close to the porphyrin chromophore's absorption maximum peak at 420 nm. The electrical energy generated by the triad at the expense of the light energy is ultimately exploited to drive a supramolecular machine in the form of a [2]pseudorotaxane comprised of a π‐electron‐deficient tetracationic cyclobis(paraquat‐p‐phenylene) (CBPQT4+) cyclophane and a π‐electron‐rich 1,5‐bis[(2‐hydroxyethoxy) ethoxy]naphthalene (BHEEN) thread. The redox‐induced dethreading of the CBPQT4+cyclophane from the BHEEN thread can be monitored by measuring the increase in the fluorescence intensity of the BHEEN unit. A gradual increase in the fluorescence intensity of the BHEEN unit concomitant with the photocurrent generation, even at a potential (0 V) much lower than that required (−300 mV) for the direct reduction of the CBPQT4+unit, confirms that the dethreading process is driven by the photocurrent generated by the triad‐SAM.
Interplay between Intra‐ and Interligand Charge Transfer with Variation of the Axial N‐Heterocyclic Ligand in Osmium(II) Pyridylpyrazolate Complexes: Extensive Color Tuning by Phosphorescent Solvatochromism
Authors: Li Shih‐Wen , Cheng Yi‐Ming , Yeh Yu‐Shan , Hsu Cheng‐Chih , Chou Pi‐Tai , Peng Shie‐Ming , Lee Gene‐Hsiang , Tung Yung‐Liang , Wu Pei‐Chi , Chi Yun , Wu Fang‐Iy , Shu Ching‐Fong 
Published: August 2005

AbstractThe rational design and syntheses of a new series of OsII complexes with formula [Os(fppz)2(CO)(L)] (1: L=4‐dimethylaminopyridine; 2: L=pyridine; 3: L=4,4′‐bipyridine; 4: L=pyridazine; 5: L=4‐cyanopyridine), bearing two (2‐pyridyl)pyrazolate ligands (fppz) together with one carbonyl and one N‐heterocyclic ligand at the axial positions are reported. Single‐crystal X‐ray diffraction studies of, for example, 2 reveal a distorted octahedral geometry in which both fppz ligands reside in the equatorial plane with a trans configuration and adopt a bent arrangement at the metal center with a dihedral angle of ∼23°, while the carbonyl and pyridine ligands are located at the axial positions. Variation of the axial N‐heterocyclic ligand leads to remarkable changes in the photophysical properties as the energy gap and hence the phosphorescence peak wavelength can be tuned. For complexes 1 and 2 the solvent‐polarity‐independent phosphorescence originates from a combination of intraligand 3π–π* (3ILCT) and metal‐to‐ligand charge transfer transitions (3MLCT). In sharp contrast, as supported by cyclic voltammetry measurements and theoretical calculations, complexes 3–‐5 exhibit mainly ligand‐to‐ligand charge transfer (LLCT) transitions, resulting in a large dipolar change. The phosphorescence of complexes 3–‐5 thus exhibits a strong dependence on the polarity of the solvent, being shifted for example, from 560 (in C6H12) to 665 nm (in CH3CN) and from 603 (in C6H12) to 710 nm (in CH3CN) for complexes 3 and 5, respectively. The results clearly demonstrate that a simple, straightforward derivatization of the axial N‐heterocyclic ligand drastically alters the excitation properties per se from intraligand charge transfer (ILCT) to LLCT transitions. The latter exhibit remarkable LLCT phosphorescence solvatochromism so that a broad range of color tunability can be achieved.
Spectral interpolation errors
Authors: Sándor N. , Ondró T. , Schanda J. 
Published: August 2005

AbstractSeveral CIE Technical Committees discussed the advantages and disadvantages of different spectral interpolation methods during the past years. Linear, Lagrange, cubic spline, and Sprague methods were under discussion. We have investigated the colorimetric differences caused by using the different interpolation methods, and showed that Lagrange, cubic spline, and Sprague methods provide very similar results for most well‐behaved spectra. As a further result, we found that the 5‐nm sampling and using the 5 nm tables of the CIE Technical Report “Colorimetry” is almost as good as an interpolation to 1‐nm sampling and colorimetric calculation using the 1‐nm tables of the CIE colorimetric standards. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 348–353, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.
Testing the behavior for metamerism of the new deviate observer (JF‐DO)
Authors: Martínez J. A. , Vega F. J. , Díaz J. A. , Pérez‐Ocón F. , Jiménez J. R. 
Published: August 2005

AbstractRecently,in our laboratories, a set of color‐matching functions (cmfs) has been formulated for small fields by using two groups of real observers: JAM, MM, CF and AY, JR, MR, JL, JA, FP. The measurements of these cmfs have been made using different experimental devices and methods and it has enabled us to propose a New Deviate Observer for small fields (JF‐DO). This new JF‐DO was derived from the average observer of our nine real observers, following the technique used by the CIE to establish the Standard Deviate Observer (CIE‐1989 SDO), which was established for fields of 10°, despite the CIE's assumption that it can be applied to smaller fields. In the present work, we report experimental results of the JF‐DO using metameric reflectances in comparison to the CIE‐1931 Standard Observer and to the CIE‐1989 SDO. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 363–370, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.
Intermolecular Electronic Excitation Transfer in a Confined Space: A First‐Principles Study
Authors: Fois Ettore , Gamba Aldo , Medici Cinzia , Tabacchi Gloria 
Published: August 2005

AbstractThe process of intermolecular electronic excitation transfer (EET) in a monodimensional supramolecular arrangement of molecules in confined space has been modelled and investigated by means of first‐principles molecular dynamics simulations. The chosen model system consists of a wire of chlorine molecules hosted in the noncrossing channels of the zeolite bikitaite. The time evolution of the system in its first excited singlet state has been described by the restricted open shell Kohn–Sham formalism. Simulation results have highlighted that excitation, initially localized on a guest molecule, is transferred to an adjacent moiety in the molecular wire on the picosecond scale via a collision‐induced Dexter‐type short range EET. Analysis of the modifications of the electronic structure of the system brought about by EET has given insight into the microscopic details of the process.
Dual‐Scale Modeling of Benzene Adsorption onto Ni(111) and Au(111) Surfaces in Explicit Water
Authors: Schravendijk Pim , van der Vegt Nico , Delle Site Luigi , Kremer Kurt 
Published: August 2005

AbstractWe present a multiscale modeling approach for studying interactions of organic molecules with metal surfaces in explicit water. The approach is based on combining adsorption energies of isolated molecules on transition metal surfaces calculated by ab initio density functional methods and classical molecular dynamics simulations using atomistically detailed force fields. The interaction of benzene with Ni(111) and Au(111) surfaces was studied. It is shown that a strong affinity of water for the hydrophilic surfaces makes benzene adsorption on Au thermodynamically unfavorable, while on Ni there is no preference. The work presented here serves as a first step in modeling the interactions of larger organic molecules with metal surfaces.
Density of Configurational States from First‐Principles Calculations: The Phase Diagram of Al–Na Surface Alloys
Authors: Borg Mikael , Stampfl Catherine , Mikkelsen Anders , Gustafson Johan , Lundgren Edvin , Scheffler Matthias , Andersen Jesper N. 
Published: August 2005

AbstractThe structural phases of AlxNa1−x surface alloys have been investigated theoretically and experimentally. We describe the system using a lattice‐gas Hamiltonian, determined from density functional theory, together with Monte Carlo (MC) calculations. The obtained phase diagram reproduces the experiment on a quantitative level. From calculation of the (configurational) density of states by the recently introduced Wang–Landau MC algorithm, we derive thermodynamic quantities, such as the free energy and entropy, which are not directly accessible from conventional MC simulations. We accurately reproduce the stoichiometry, as well as the temperature at which an order–disorder phase transition occurs, and demonstrate the crucial role, and magnitude, of the configurational entropy.
Correlation analysis of coupled fitness landscapes
Authors: Hordijk Wim , Kauffman Stuart A. 
Published: August 2005

AbstractThe correlation structure of fitness landscapes is a much used measure to characterize and classify various types of landscapes. However, analyzing the correlation structure of fitness landscapes has so far been restricted to static landscapes only. Here, we investigate the correlation structure of coupled, or dynamic, fitness landscapes. Using the NKC model of coevolution, we apply a correlation analysis on various instances of this model and present the results. One of the main goals of this article is thus to show that a previously introduced correlation analysis can be successfully extended to coupled fitness landscapes. Furthermore, our analysis shows that this provides meaningful and interesting results that can contribute to a better understanding of coevolution in general. © 2005 Wiley Periodicals, Inc. Complexity 10: 41–49, 2005
Improved Understanding of the Nonlinear Properties of Ionization Instabilities in Plasmas
Authors: Bruhn B. , Koch B.‐P. , Wilke C. 
Published: August 2005

AbstractIn this paper we review our experimental and theoretical investigations of ionization waves in a low‐pressure discharge of neon. The main results are connected with the transition between regular and irregular wave motions. The experimental observed stability boundaries can well be understood within the hydrodynamic model. The point is the explanation of the experimentally observed mode transitions by means of a quintic amplitude equation of the Ginzburg‐Landau type. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis and Kinetics of Transient Species in Electrode Near Plasma and Plasma Boundary Sheath of RF Plasmas in Molecular Gases
Authors: Geigl M. , Peters S. , Gabriel O. , Krames B. , Meichsner J. 
Published: August 2005

AbstractModern diagnostic methods are applied for investigation of spatial and temporal behaviour of selected reactive species in oxygen and fluorocarbon rf plasmas. Comprehensive investigations of the spatial distribution of atomic oxygen were done by means of two‐photon absorption laser induced fluorescence spectroscopy. Exemplarily, axial and radial O‐concentrations are shown for an asymmetric capacitively coupled rf plasma in pure oxygen. The time resolved threshold ionization mass spectrometry was applied for investigation of small fluorocarbon radicals. In pulsed CF4/H2 rf plasma the concentrations of the extracted radicals CF2, CF3, C2F5 as well as the intermediate product C2F4 in the plasma on and off phase are presented. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interaction of Partially Ionized Plasmas with Electromagnetic Fields
Authors: Kremp D. , Bornath Th. , Bonitz M. , Semkat D. , Schlanges M. 
Published: August 2005

AbstractThe interaction of partially ionized plasmas with an electromagnetic field is investigated using quantum statistical methods. A general statistical expression for the current density of a plasma in an electromagnetic field is presented and considered in the linear response and the high field regime. Expressions for the collisional absorption (inverse bremsstrahlung) are derived and discussed. In addition, results of molecular dynamics simulations are shown. Further, partially ionized plasmas are considered. Plasma Bloch equations for the description of bound–free transitions are given and the absorption coefficient as well as rate coefficients for multiphoton ionization are presented. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamic Properties of Dense Hydrogen
Authors: Schlanges M. , Bezkrovniy V. , Vorberger J. , Kremp D. , Kraeft W. D. 
Published: August 2005

AbstractThe equation of state of hydrogen is determined theoretically in the limits of the fully ionized plasma and the neutral reacting gas mixture. Analytical results are presented for the fully ionized state and compared to data from quantum simulations. The dense hydrogen gas is dealt with using Reaction Ensemble Monte Carlo and hypernetted chain techniques. The results are compared to other theoretical methods and to experimental findings. Finally, Reaction Ensemble Monte Carlo data are combined with Path Integral Monte Carlo results to give a Hugoniot curve covering the entire pressure range. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic Structure Factor of Dusty and Low‐Dimensional Plasmas
Authors: Wierling A. , Reinholz H. , Röpke G. , Adams J. 
Published: August 2005

AbstractExperiences investigating the dynamic structure factor of dense plasmas are applied to complex plasmas, in particular to dusty plasmas and dimensionally reduced plasmas. Using generalized linear response theory, the dynamical structure factor is obtained from a density response function expressed in terms of equilibrium correlation function. Corrections beyond the RPA approximation are taken into account by evaluating local‐field corrections within the recurrance method. Results for the dynamic structure factor of a Yukawa plasma is compared with molecular dynamics calculations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First Principle Thermodynamic and Dynamic Simulations for Dense Quantum Plasmas
Authors: Bonitz M. , Filinov A. , Golubnychiy V. O. , Bornath Th. , Kraeft W. D. 
Published: August 2005

AbstractWe present a detailed analysis of temperature‐dependent effective quantum pair potentials. These potentials are derived from first‐principle path integral Monte Carlo simulations and are accurate even at strong coupling and partial ionization. They can be efficiently used in molecular‐dynamics (MD) simulations to obtain accurate thermodynamic and dynamic properties of strongly coupled hydrogen down to the temperatures of about 60 000 K. Furthermore, using spin‐dependent pair potentials, dynamic structure factors and spin‐density correlation functions were calculated for different values of coupling and degeneracy. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Isolation and characterization of the laure olfactory behavioral mutant in the zebrafish, Danio rerio
Authors: Vitebsky A. , Reyes R. , Sanderson M.J. , Michel W.C. , Whitlock K. E. 
Published: August 2005

AbstractTo initiate a genetic analysis of olfactory development and function in the zebrafish, Danio rerio, we developed a behavioral genetic screen for mutations affecting the olfactory sensory system. First, we characterized olfactory responses of wild‐type zebrafish to various odors. We found that 3‐day‐old juvenile zebrafish reacted to the amino acid L‐cysteine with an aversive behavioral response. We isolated one mutant, laure (lre), which showed no aversive behavioral response to L‐cysteine at 3 days of development, and carried out a preliminary characterization of this mutant's defects. We found that lre mutant fish were also defective in their response to L‐serine and L‐alanine, but not to taurocholic acid, as young adults. In addition, lre mutant fish had significantly fewer primary olfactory sensory neurons than normal, and the axons of these neurons did not form the characteristic axon termination pattern in the developing olfactory bulb. Nevertheless, the olfactory epithelium of lre mutant fish showed normal or near normal electrophysiological responses to several odorants. Our data suggest that the behavioral defects observed in the lre mutant result from the disruption of the developing olfactory sensory neurons and their axonal connections within the olfactory bulb. The isolation of the lre mutant shows that our behavior‐based screen represents a viable approach for carrying out a genetic dissection of olfactory behaviors in this vertebrate model system. Developmental Dynamics 234:229–242, 2005. © 2005 Wiley‐Liss, Inc.
Induction of apoptosis involving multiple pathways is a primary response to cyclin A1‐deficiency in male meiosis
Authors: Salazar Glicella , Joshi Ayesha , Liu Dong , Wei Hongquan , Persson Jenny Liao , Wolgemuth Debra J. 
Published: August 2005

AbstractThe meiotic arrest in male mice null for the cyclin A1 gene (Ccna1) was associated with apoptosis of spermatocytes. To determine whether the apoptosis in spermatocytes was triggered in response to the arrest at G2/M phase, as opposed to being a secondary response to overall disruption of spermatogenesis, we examined testes during the first wave of spermatogenesis by terminal deoxynucleotidyl transferase–mediated deoxyuridinetriphosphate nick end‐labeling (TUNEL) staining. We observed enhanced apoptosis coinciding with the arrest point in postnatal day 22 tubules, with no overt degeneration. Along with activation of caspase‐3, an increase in the levels and change of subcellular localization of Bax protein was observed in cyclin A1–deficient spermatocytes, which coincided with the detection of apoptosis. As p53 is implicated in the activation of Bax‐mediated cell death, we generated mice lacking both cyclin A1 and p53. Although the absence of p53 did not rescue the meiotic arrest, there was a decrease in the number of apoptotic cells in the double‐mutant testes. This finding suggested that p53 may be involved in the process by which the arrested germ cells are removed from the seminiferous tubules but that other pathways function as well to ensure removal of the arrested spermatocytes. Developmental Dynamics 234:114–123, 2005. © 2005 Wiley‐Liss, Inc.