bluuebunny/crossref_metadata_2025_split huggingface dataset:
The hydration of the uranyl dication: Incorporation of solvent effects in parallel density functional calculations with the program PARAGAUSS
Authors: Fuchs Monika S. K. , Shor Alexey M. , Rösch Notker 
Published: August 2002

AbstractThe parallel density functional program PARAGAUSS has been extended by a tool for computing solvent effects based on the conductor‐like screening model (COSMO). The molecular cavity in the solvent is constructed as a set of overlapping spheres according to the GEPOL algorithm. The cavity tessellation scheme and the resulting set of point charges on the cavity surface comply with the point group symmetry of the solute. Symmetry is exploited to reduce the computational effort of the solvent model. To allow an automatic geometry optimization including solvent effects, care has been taken to avoid discontinuities due to the discretization (weights of tesserae, number of spheres created by GEPOL). In this context, an alternative definition for the grid points representing the tesserae is introduced. In addition to the COSMO model, short‐range solvent effects are taken into account via a force field. We apply the solvent module to all‐electron scalar‐relativistic density functional calculations on uranyl, UO22+, and its aquo complexes in aqueous solution. Solvent effects on the geometry are very small. Based on the model [UO2(H2O)5]2+, the solvation energy of uranyl is estimated to be about −400 kcal/mol, in agreement with the range of experimental data. The major part of the solvation energy, about −250 kcal/mol, is due to a donor–acceptor interaction associated with a coordination shell of five water ligands. One can interpret this large solvation energy also as a compounded effect of an effective reduction of the uranyl moiety plus a solvent polarization. The energetic effect of the structure relaxation in the solution is only about 8 kcal/mol. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Dynamics of the D2 + Ni(100) collision system: Analysis of the reactive and inelastic channels
Authors: Böyükata M. , Güvenç Z. B. , Jackson B. , Jellinek J. 
Published: August 2002

AbstractThe reactive and scattering channels of the D2(v,j)+Ni(100) collision system are studied using quasiclassical molecular dynamics simulations. The interaction between the D2 and the atoms of the surface is modeled by a LEPS (London–Eyring–Polani–Sato) potential energy function. The molecule is aimed at three different impact sites (atop, bridge, and center) of a rigid Ni(100) surface along the normal direction with various collision energies ≤1.0 eV. Dissociative chemisorption probabilities are computed for different rotational states of the molecule. Probability distributions of the final rovibrational states of the ground‐state D2 molecule scattered from those impact sites are also computed as a function of the collision energy. Higher collision energy results in excitation of higher rotational and/or vibrational states of the scattered molecule. At collision energies below 0.1 eV an indirect dissociation mechanism (through molecular adsorption) dominates the reaction. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 48–57, 2001
Quantum coherent control of Coulomb enhancement by two‐color pulseshaping
Authors: Pötz Walter 
Published: August 2002

AbstractPulse shaping based on two‐color optical excitation is shown to provide a versatile coherent control scheme for electron inter(sub)band transitions in semiconductors. In semiconductor heterostructures, this control scheme provides both phase‐sensitive absorption and exciton formation, as well as interwell tunneling of photoexcited charge carriers. Our microscopic analysis shows that this control mechanism is due to a combination of many‐body effects arising from the coherent part of the electron–electron Coulomb interaction and pulse‐shaping arising from the spectral overlap between the two pulses. This control mechanism is applicable to a wide range of semiconductors, both bulk and low‐dimensional structures, and may have a practical application for phase sensitive absorbers and the generation of THz radiation. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Quantal density functional theory of excited states: Application to an exactly solvable model
Authors: Slamet Marlina , Sahni Viraht 
Published: August 2002

AbstractThe quantal density functional theory (Q‐DFT) of excited states is the description of the physics of the mapping from any bound nondegenerate excited state of Schrödinger theory to that of the s‐system of noninteracting Fermions with equivalent density ρk(r), energy Ek, and ionization potential Ik. The s‐system may either be in an excited state with the same configuration as in Schrödinger theory or in a ground state with a consequently different configuration. The Q‐DFT description of the s‐system is in terms of a conservative field ℱk(r), whose electron‐interaction ℰee(r) and correlation‐kinetic 𝒵(r) components are separately representative of electron correlations due to the Pauli exclusion principle and Coulomb repulsion, and correlation‐kinetic effects, respectively. The sources of these fields are expectations of Hermitian operators taken with respect to the system wavefunction. The local electron‐interaction potential vee(r) of the s‐system, representative of all the many‐body correlations, is the work done to move an electron in the force of the field ℱk(r). The electron interaction Eee and correlation‐kinetic Tc components of the total energy Ek may be expressed in integral virial form in terms of their respective fields. The difference between the s‐system in its ground or excited state representation is due entirely to correlation‐kinetic effects. The highest occupied eigenvalue of the s‐system differential equation in either case is minus the ionization potential Ik. In this work we demonstrate the transformation of an excited state of Schrödinger theory, as represented by the first excited singlet state of the exactly solvable Hooke's atom, to that of noninteracting Fermions in their ground state with equivalent excited state density, energy, and ionization potential. To further prove the Fermions are in a ground state, we solve the corresponding singlet s‐system differential equation numerically for the vee(r) determined, and obtain the excited state density from the zero node orbitals generated. The resulting total energy is also the same. In addition, the single eigenvalue determined corresponds to minus the ionization potential of the excited state. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Symmetry and degeneracy in density functional theory
Authors: Katriel Jacob , Zahariev Federico , Burke Kieron 
Published: August 2002

AbstractThe superhamiltonian formalism is used to construct a totally symmetric superdensity for a system whose ground state corresponds to a multidimensional irreducible representation of the symmetry group of the Hamiltonian. A Hohenberg–Kohn theorem is proven and the Levy constrained‐search procedure is adapted. An appropriate generalization allows the application of this procedure to degenerate excited states. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Spectroscopic and quantum chemical study on electronic and geometric properties of free and embedded dithizone molecules
Authors: Schönherr T. , Linder R. , Rosellen U. , Schmid V. 
Published: August 2002

AbstractThe molecular and electronic structure of the three tautomeric forms of dithizone has been calculated by using semiempirical, density functional theory (DFT), and ab initio methods. Comparison of ground‐state energies shows the symmetric form most stabilized, but there is only a small barrier (<3 kcal/mol) for the hydrogen transfer from NH toward HS (enol form). For understanding the origin of the optical transitions intermolecular interactions have to be taken into account. By using the supermolecule method, the absorption band pattern can be rationalized already on the level of the PM3 model. The nuclear magnetic resonance (NMR) solution spectrum is interpreted in terms of an equilibrium between the symmetric and the enol forms of dithizone. The appearance of strong EPR signals only for the solid state reflects a considerable lowering of the triplet state (symmetric form). Experimental features are discussed in view of calculated energies (stabilization), chemical shifts (NMR), and SOMO orbitals (EPR). © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Moving pieces in a proteomic puzzle: mass fingerprinting of toxic fractions from the venom of Tityus serrulatus (Scorpiones, Buthidae)
Authors: Pimenta Adriano M. C. , Stöcklin Reto , Favreau Philippe , Bougis Pierre E. , Martin‐Eauclaire Marie‐France 
Published: August 2002

AbstractScorpion venoms are very complex mixtures of molecules, most of which are peptides that display different kinds of biological activity. These venoms have been studied in the light of their pharmacological targets and their constituents are able to bind specifically to a variety of ionic channels located in prey tissues, resulting in neurotoxic effects. Toxins that modulate Na+, K+, Ca++ and Cl− currents have been described in scorpion venoms. Mass spectrometry was employed to analyze toxic fractions from the venom of the Brazilian scorpion Tityus serrulatus in order to shed light on the molecular composition of this venom and to facilitate the search for novel pharmacologically active compounds. T. serrulatus venom was first subjected to gel filtration to separate its constituents according to their molecular size. The resultant fractions II and III, which account for 90 and 10% respectively of the whole venom toxic effect, were further analyzed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS), on‐line liquid chromatography/electrospray mass spectrometry (LC/ESMS) and off‐line LC/MALDI‐TOFMS in order to establish their mass fingerprints. The molecular masses in fraction II were predominantly between 6500 and 7500 Da. This corresponds to long‐chain toxins that mainly act on voltage‐gated Na+ channels. Fraction III is more complex and predominantly contained molecules with masses between 2500 and 5000 Da. This corresponds to the short‐chain toxin family, most of which act on K+ channels, and other unknown peptides. Finally, we were able to measure the molecular masses of 380 different compounds present in the two fractions investigated. To our knowledge, this is the largest number of components ever detected in the venom of a single animal species. Some of the toxins described previously from T. serrulatus venom could be detected by virtue of their molecular masses. The interpretation of this large set of data has provided us with useful proteomic information on the venom, and the implications of these findings are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Ready‐made matrix‐assisted laser desorption/ionization target plates coated with thin matrix layer for automated sample deposition in high‐density array format
Authors: Miliotis Tasso , Kjellström Sven , Nilsson Johan , Laurell Thomas , Edholm Lars‐Erik , Marko‐Varga György 
Published: August 2002

AbstractThe methodology for ready‐made matrix‐assisted laser desorption/ionization (MALDI) target plates covered with an optimized thin layer consisting of matrix and nitrocellulose has been developed. Piezoelectric microdispensing enabled sample depositions in a high‐density array format of 2000 sample depositions on a conventionally sized target plate (45 × 47 mm). The sample depositions were made reproducibly in a fully automated mode by using an in‐house developed computer‐controlled piezoelectric flow‐through microdispenser. Additionally, the piezoelectric technique facilitated significant analyte enrichment that increased the detection sensitivity. The MS signal was obtained rapidly, generally within ten laser pulses. An airbrush device was used to generate a fine spray of matrix and nitrocellulose dissolved in acetone. The acetone evaporated instantly when reaching the target plate leaving the entire surface with a thin and uniform matrix/nitrocellulose coating consisting of very small crystals of matrix embedded in the nitrocellulose. These crystals acted as a seed‐layer on subsequent analyte depositions, rendering homogeneous sample spots when using α‐cyano‐4‐hydroxycinnamic acid (CHCA) as matrix. The relative standard deviation of the signal intensity between spots was (20–30)% (n = 30). The detection sensitivity was improved by restricting the sample spot diameter to 300 µm. The spot size was affected by the deposition rate and the evaporation rate of the dispensed sample volume. Mass spectra of a 25‐amol peptide mixture deposition were successfully recorded. Copyright © 2001 John Wiley & Sons, Ltd.
Atmospheric pressure laser desorption/chemical ionization mass spectrometry: a new ionization method based on existing themes
Authors: Coon Joshua J. , McHale Kevin J. , Harrison W. W. 
Published: August 2002

AbstractWe have designed and constructed an atmospheric pressure laser desorption/chemical ionization (AP‐LD/CI) source that utilizes a laser pulse to desorb intact neutral molecules, followed by chemical ionization via reagent ions produced by a corona discharge. This source employs a heated capillary atmospheric pressure inlet coupled to a quadrupole ion trap mass spectrometer and allows sampling under normal ambient air conditions. Preliminary results demonstrate that this technique provides ∼150‐fold increase in analyte ions compared to the ion population generated by atmospheric pressure infrared matrix‐assisted laser desorption/ionization (AP‐IR‐MALDI). Copyright © 2002 John Wiley & Sons, Ltd.
Mass spectrometric fragmentation of cyclic peptides belonging to the polymyxin and colistin antibiotics studied by ion trap and quadrupole/orthogonal‐acceleration time‐of‐flight technology
Authors: Govaerts Cindy , Rozenski Jef , Orwa Jennifer , Roets Eugène , Schepdael Ann Van , Hoogmartens Jos 
Published: August 2002

AbstractElectrospray ionization linked to quadrupole/orthogonal‐acceleration time‐of‐flight (Q/oaTOF) and ion trap equipment was used to study the fragmentation behavior of the linear side‐chain cyclized peptides of the polymyxin B and E antibiotics. This study exemplifies both the benefits and the drawbacks of mass spectrometric techniques for the determination of the sequence of such complex linear side‐chain cyclized peptides. Q/oaTOF accurate mass measurements did not help sufficiently to assign the product ions observed in the product ion spectra. An ion trap mass spectrometer providing MSn capability was used to eliminate ambiguities encountered with a single MS/MS approach. The complex fragmentation behavior of these compounds of well‐established structure is described which could be useful for structural characterization of unknown substances related to polymyxin B and E in the future. Copyright © 2002 John Wiley & Sons, Ltd.
Liquid chromatography and electron‐capture dissociation in Fourier transform ion cyclotron resonance mass spectrometry
Authors: Palmblad Magnus , Tsybin Youri O. , Ramström Margareta , Bergquist Jonas , Håkansson Per 
Published: August 2002

AbstractLiquid separation methods in combination with electrospray mass spectrometry as well as the recently introduced fragmentation method electron capture dissociation (ECD) have become powerful tools in proteomics research. This paper presents the results of the first successful attempts to combine liquid chromatography (LC) and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) with ECD in the analysis of a mixture of standard peptides and of a bovine serum albumin tryptic digest. A novel electron injection system provided conditions for ECD sufficient to yield extensive sequence information for the most abundant peptides in the mixtures on the time‐scale of the chromatographic separation. The results suggest that LC/ECD‐FTICRMS can be employed in the characterization of peptides in enzymatic digests of proteins or protein mixtures and identify and localize posttranslational modifications. Copyright © 2002 John Wiley & Sons, Ltd.
Headspace solid‐phase microextraction gas chromatography/mass spectrometry in the analysis of the aroma constituents of ‘Cannonau of Jerzu’ wine
Authors: Begala Michela , Corda Luciana , Podda Gianni , Fedrigo Maria Anna , Traldi Pietro 
Published: August 2002

Abstract“Cannonau of Jerzu” wine is a typical Sardinian product, obtained from only one particular grape variety. Its aroma profile is highly characteristic from the organoleptic point of view but, until now, no analytical investigation of the aroma components has been reported. This aspect has been studied by headspace solid‐phase microextraction coupled with gas chromatography/mass spectrometry (GC/MS). Using this approach, 76 abundant aroma components were identified. The results thus obtained show on one hand that the terpene profile is, as expected, dependent on the quality of the grapes (in terms of selection before vintage), and, on the other, that some components are strongly dependent on the production and ageing method. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluation of low‐pressure gas chromatography linked to ion‐trap tandem mass spectrometry for the fast trace analysis of multiclass pesticide residues
Authors: González‐Rodríguez M. J. , Garrido‐Frenich A. , Arrebola F. J. , Martínez‐Vidal J. L. 
Published: August 2002

AbstractA rapid multiresidue method for the analysis of 72 pesticides has been developed using a single injection with low‐pressure gas chromatography/tandem mass spectrometry (LP‐GC/MS/MS). The LP‐GC/MS/MS method used a short capillary column of 10 m × 0.53 mm i.d. × 0.25 µm film thickness coupled with a 0.6 m × 0.10 mm i.d. restriction at the inlet end. Optimal LP‐GC conditions were determined which achieved the fastest separation in MS/MS detection mode. Also MS/MS conditions were optimized in order to increase sensitivity and selectivity. The analytical parameters of the LP‐GC/MS/MS method were compared with those obtained by GC/MS/MS using a conventional capillary column (30 m × 0.25 mm i.d. × 0.25 µm film thickness). Better precision and sensitivity values were obtained with the LP‐GC/MS/MS approach. The limits of detection (LOD) of the compounds ranged from 0.1 to 14.1 µg L−1 for LP‐GC/MS/MS, lower than those obtained for conventional GC/MS/MS that ranged from 0.1 to 17.5 µg L−1. The peak widths obtained with the short column in LP‐GC are similar to those obtained using conventional capillary GC columns, and the peaks can be successfully identified by MS/MS detection with the conventional scan speed of ion‐trap instruments. In addition, the analysis time was significantly reduced with LP‐GC/MS/MS (32 min) versus GC/MS/MS (72 min), allowing the number of samples analyzed per day in a routine laboratory to be doubled. Copyright © 2002 John Wiley & Sons, Ltd.
Towards a human Lassa fever vaccine
Authors: Fisher‐Hoch S. P. , McCormick J. B. 
Published: August 2002

AbstractArenaviruses, such as Lassa fever, establish chronic infections in rodents, leading to incidental transmission to humans. Lassa fever is a clinically severe disease, yet the absence of second attacks implies life‐long immunity. The aim of this review is to consider whether such immunity could be provided by vaccines. The South American arenaviruses are controlled by neutralising antibody and a clinical trial of live, attenuated vaccine for Argentinian haemorrhagic fever provided 84% protection. In contrast, there is no evidence for protective humoral immunity against Old World arenaviruses which are controlled by cell‐mediated immune responses. Nevertheless, vaccination with Lassa glycoproteins can protect monkeys from disease, implying that protection may be achievable, even though the immunological mechanisms are distinct. Recombinant vaccinia viruses expressing various forms of Lassa glycoproteins can protect both guinea‐pigs and primates, while additional protective responses can be mounted against nucleocapsid genes. However, vaccines based upon vaccinia constructs are no longer tenable for African populations with a high seroprevalence of HIV infection. The scientific challenge now remains to find alternative methods of delivering T‐cell immunity against glycoproteins from Lassa virus in ways which can overcome the local economic and political hurdles to vaccine development. Copyright © 2001 John Wiley & Sons, Ltd.
Kinematics of a new spherical parallel manipulator with three equal legs: The 3‐URC wrist
Authors: Di Gregorio Raffaele 
Published: August 2002

AbstractParallel manipulators are constituted of two rigid bodies, one movable (platform) and the other fixed (base), connected by a number of kinematic chains (legs). Manipulators with all equal legs that have the actuators adjacent to the base allow the use of simplified design procedures and manufacturing processes. Moreover, they are able to reach high performances. Further manufacturing simplifications can be obtained if only revolute pairs and passive cylindrical pairs are used. This article presents a new spherical parallel manipulator, named the 3‐URC wrist. The 3‐URC wrist is not overconstrained. It has three equal legs having only passive cylindrical pairs and revolute pairs with the actuators adjacent to the base. The 3‐URC wrist mounting and manufacturing conditions making spherical motions of the platform possible are defined. Then the position analysis and the mobility analysis of the 3‐URC wrist are solved. Finally, the singularity conditions are written in explicit form and geometrically interpreted. © 2001 John Wiley & Sons, Inc.
Phase transition and finite‐size scaling for the integer partitioning problem
Authors: Borgs Christian , Chayes Jennifer , Pittel Boris 
Published: August 2002

AbstractWe consider the problem of partitioning n randomly chosen integers between 1 and 2m into two subsets such that the discrepancy, the absolute value of the difference of their sums, is minimized. A partition is called perfect if the optimum discrepancy is 0 when the sum of all n integers in the original set is even, or 1 when the sum is odd. Parameterizing the random problem in terms of κ=m/n, we prove that the problem has a phase transition at κ=1, in the sense that for κ<1, there are many perfect partitions with probability tending to 1 as n→∞, whereas for κ>1, there are no perfect partitions with probability tending to 1. Moreover, we show that this transition is first‐order in the sense the derivative of the so‐called entropy is discontinuous at κ=1.We also determine the finite‐size scaling window about the transition point: κn=1−(2n)−1 log2 n+λn/n, by showing that the probability of a perfect partition tends to 1, 0, or some explicitly computable p(λ)∈(0, 1), depending on whether λn tends to −∞, ∞, or λ∈(−∞, ∞), respectively. For λn→−∞ fast enough, we show that the number of perfect partitions is Gaussian in the limit. For λn→∞, we prove that with high probability the optimum partition is unique, and that the optimum discrepancy is Θ(2). Within the window, i.e., if |λn| is bounded, we prove that the optimum discrepancy is bounded. Both for λn→∞ and within the window, we find the limiting distribution of the (scaled) discrepancy. Finally, both for the integer partitioning problem and for the continuous partitioning problem, we find the joint distribution of the k smallest discrepancies above the scaling window. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 19: 247–288, 2001