bluuebunny/crossref_metadata_2025 huggingface dataset:
A hierarchy of Sturm–Liouville problems
Authors: Binding Paul
Published: February 2003

Sturm–Liouville equations will be considered where the boundary conditions depend rationally on the eigenvalue parameter. Such problems apply to a variety of engineering situations, for example to the stability of rotating axles. Classesof these problems will be isolated with a rather rich spectral structure, for example oscillation, comparison and completeness properties analogous to thoseof the ‘usual’ Sturm–Liouville problem which has constant boundary conditions.In fact it will be shown how these classes can be converted into each other, andinto the ‘usual’ Sturm–Liouville problem, by means of transformations preserving all but finitely many eigenvalues. Copyright © 2003 John Wiley & Sons, Ltd.
Nonisothermal crystallization behavior of syndiotactic polystyrene/montmorillonite nanocomposites
Authors: Wu Tzong‐Ming , Hsu Sung‐Fu , Wu Jeng‐Yue
Published: February 2003

X‐ray diffraction methods and differential scanning calorimetry were used to investigate the crystalline structure and crystallization kinetics of syndiotactic polystyrene (sPS)/clay nanocomposites. X‐ray diffraction data showed the presence of polymorphism in sPS/montmorillonite (MMT) nanocomposites, which was strongly dependent on the processing conditions (premelting temperature and cooling rate) of the sPS/MMT nanocomposites and on the content of MMT in the sPS/MMT nanocomposites. The α‐crystalline form could be transformed into β‐crystalline forms at higher premelting temperatures. The nonisothermal melt‐crystallization kinetics and melting behavior of the sPS/MMT nanocomposites were also studied at various cooling rates. The correlation of the crystallization kinetics, melting behavior, and crystalline structure of the sPS/MMT nanocomposites was examined. The results indicated that the addition of a small amount of MMT to sPS caused a change in the mechanism of nucleation and the crystal growth of the sPS crystallite. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 560–570, 2003
Ionization potentials and vibrational structure in photoelectron spectra by a Green’s function method: t
r
a
n
s-HNNH, c
i
s-HNNH, and 1,1-dihydrodiazine (H2NN)
Authors: von Niessen W. , Domcke W. , Cederbaum L. S. , Kraemer W. P.
Published: February 2003

The ionization potentials of trans-diazene, cis-diazene and 1,1-dihydrodiazine (in its singlet state) have been computed by a many-body Green’s function method. For trans-diazene all calculated ionization potentials are within 0.3 eV of the measured values. Koopmans’ theorem supplies the correct ordering only for trans-diazene, but fails for the other two molecules. The electronic structures of the three molecules differ considerably. The ordering of the ionization potentials is for trans-diazene: n+, π, n−, σ+(NH), σ−(NH), and σ (NN); for cis-diazene: n−, n+, π, σ+(NH), σ−(NH), and σ (NN); and for H2NN: n−, n+, π, σ−(NH), σ+(NH), and σ (NN). The n+/n− splitting is calculated to be 5.3, 3.6, and 5.7 eV, respectively. The vibrational structure in the photoelectron spectrum of trans-diazene and trans-diazene-d2 is computed and compared to the experimental one. Similarly looking bands in the spectra of N2H2 and N2D2 may arise from quite different couplings.
Spectra of centrosymmetric rare earth complexes: Pr3+ (HAPI) single crystal
Authors: Mukhopadhyay Anup Kumar , Chowdhury Mihir
Published: February 2003

Polarized low-temperature absorption spectrum of centrosymmetric Pr3+–antipyrene tri-iodide single crystal has been recorded. Electronic transitions to the 1D2 and 3P0,1,2 states have been found to be forbidden. Associated vibronic lines have been analyzed. Lattice, metal–ligand, and ligand internal (such as C=0) modes appear in the spectrum. Crystal field parameters have been evaluated and found to be large. Participation of π electrons in the bonding has been suggested.
Intermolecular forces in mixtures of helium with the heavier noble gases
Authors: Smith K. M. , Rulis A. M. , Scoles G. , Aziz R. A. , Nain V.
Published: February 2003

Crossed beams differential scattering cross sections have been measured for HeAr, HeKr, and HeXe with a new beam modulation technique at two energies. Interatomic potential functions have been found which describe both scattering and dilute gas bulk properties for these systems. Potential functions independently determined from gas phase bulk properties are shown to give a very good account of the scattering data. The potential well depth is found to be about equal for the three systems, in agreement with Chen et al. [J. Chem. Phys. 59, 601 (1973)], although our values are in average 17% larger than those found in the cited work. Also, the deviations of the three potentials from a common shape are smaller than those found by Chen et al. The ability of combining rules to predict the mixed interaction from a knowledge of the pure gas interactions is tested. In contrast to some of the previous work in the field, we conclude that simple combining rules can be found that give useful predictions.
On the convergence of the Zwanzig perturbation expansion for liquids
Authors: Ausloos M. , Clippe P.
Published: February 2003

The excess free energy of a dense gas is expanded around that of rigid spherical molecules as in Zwanzig’s original approach. The expansion procedure treats the intermolecular pair potential as a perturbation. A general analytical form of the coefficients is given. A convergence criterion is discussed. In particular, it is examined how a truncated expansion can serve in describing available experimental thermodynamic data on argon, xenon, molecular nitrogen, and ethylene. In all cases the expansion does not seem strictly convergent in the whole temperature-density plane. Tables and figures illustrate such results. In an Appendix, the quantum limit (’’point hard sphere’’) case is treated. It suggests that the polynomial form of the ’’convergence criterion’’ is correctly reproduced in the cases hereby examined, i.e., for real systems.
Kinetic characteristics of a powdered photochromic sample
Authors: Simmons E. L. , Pierrus J.
Published: February 2003

The kinetics of photochromic powdered samples which undergo photochemical and/or thermal reverse reactions are treated theoretically. Both infinitely thick samples and monoparticulare samples are treated. Methods are suggested for the measurement of quantum yield and rate constant values. The equation describing the reverse thermal reaction is tested by studying the reaction of 2- (2,4-dinitrobenzyl)pyridine.
Aspherical effects in neutron scattering in CuCl2⋅2D2O
Authors: Kirtane S. M. , Khan D. C.
Published: February 2003

The magnetic form factor of Cu++ in CuCl2⋅2D2O has been calculated using the Trammell method. It is shown that the experimental data can be interpreted very well without the introduction of an ad hoc parameter β as was done by Umebayashi, Frazer, Cox, and Shirane. Aspherical magnetic scattering is shown to be substantial. A 22% contraction of the spherical form factor relative to the free ion case is found. This explains the major part of the 29% contraction of the experimental data.
Energy transfer processes in electron beam excited mixtures of laser dye vapors with rare gases
Authors: Marowsky G. , Cordray R. , Tittel F. , Wilson B. , Keto J. W.
Published: February 2003

The energy transfer mechanisms for electron beam excited N-92 dye vapor in various buffer gas mixtures have been examined. Optimum conditions for achieving intense dye vapor fluorescence with short duration electron pulse excitation are reported.
High pressure optical studies of crystalline anils and related compounds
Authors: Hockert E. N. , Drickamer H. G.
Published: February 2003

High pressure optical studies have been made on a series of crystalline therochromic and photochromic anils and model compounds. Measurements include absorption and emission peak locations and the integrated intensities of various absorption peaks including the uv peak and visible peaks introduced thermally or by irradiation at various temperatures and pressures. Emission yields were also obtained. For the thermochromic compounds there was a large increase in the equilibrium yield of the thermally induced peak with pressure (piezochromism), corresponding to a volume decrease of ∼1.2 cc/mole for 5-bromosalicylidene aniline (5BrSA). The emission peak shifts to lower energy and decreases in intensity primarily because of increased rate of the radiationless conversion. For salicylidene aniline and related photochromic crystals the rate of photochromic conversion varied with both pressure and temperature in a manner which depends on the size of the energy barriers to the forward and reverse processes. The emission yield increases with pressure at low pressure, goes through a maximum, and decreases at high pressure. At low pressure the dominant feature is increase in occupation of the emitting state while at high pressure the increased rate of the radiationless process governs. For 2- (O-hydroxyphenyl) benzoxazole (OHBO) (see Fig. 1), where a keto–enol rearrangement is most probable, the changes in absorption and emission intensity can be related to the same diagram used for the anils. This diagram also describes the behavior of benzilidene aniline (BA), where only a cis–trans isomerization is possible.
Magnetic interactions in halobis(morpholyldithiocarbamato) iron(III). II. Magnetic relaxation phenomena
Authors: Grow J. M. , Robbins G. L. , Wickman H. H.
Published: February 2003

Mössbauer resonance hfs in the 4A ground state of several magnetically ordered solvent adducts or crystal forms of Fe(morpholyldithiocaramato)2X, [Fe(S2CNC4H80)2X], with X=Br− and I−, are analyzed with a stochastic Liouville calculation which includes general orientations of the following terms: axial and rhombic crystal fields, spin–dipolar coupling, electric field gradient, and intermolecular Weiss exchange field. Below about 0.9Tc agreement between theory and experiment is satisfactory. However, the internal fields showed marked departures from Brillouin type behavior. Near and below Tc magnetic and nonmagnetic spectral contributions to the hfs were found. Possible origins of this behavior are discussed.
A proton magnetic resonance study of the motion of NH+4 in dilute solid solutions of NH4Cl in RbCl and KCl
Authors: El Saffar Z. M. , Erhard John
Published: February 2003

The temperature dependence of the proton spin–lattice relaxation times of dilute solid solutions of about 3 mol % NH4Cl in RbCl and KCl are studied in the range 5–300 K. The potential barriers hindering the NH+4 reorientations are found to be extremely small (∼150 cal/mol). The relaxation rates are found to depart significantly from the usual semiclassical values: at 6 K the semiclassical relaxation rates are some 40 times greater than experimental ones. This departure from the semiclassical theory is partly explained by including the effects of symmetry and the quantization of the molecular rotational states.
A target model for interactions which include relatively large asymmetric molecules
Authors: Pesuit David R.
Published: February 2003

The fact that mean molecular speed in a gas phase is an inverse function of the square root of molecular weight has been used to obtain effective collision diameters for relatively large asymmetric molecules in the presence of small molecules. Use of these effective distance force constants within the context of a molecular corresponding states formulation is shown to give significant improvement in mixture thermodynamic properties for such systems, calculated from the properties of pure components alone. The effective diameters are defined in terms of target factors ?2=τ12σ2, where ?2 is an integrated average over the surface of an equivalent ellipsoid and σ2 is a value determined from the critical volume as with spherical molecules σ2∼V1/3c2. Detailed computerized integrations which include the effect of glancing collisions have been used to obtain these factors, but it has been learned that nearly identical values are obtained if only center-to-center collisions are considered and if a unit collision probability is assumed for all angles of attack. For a prolate molecule τ12 = (c/R1/3)  sin−1(1/c), where c2=R2/(R2−1) and R is the known average length–width ratio a/b. The equation is also of use for oblate molecules.
Nucleation in racemic mixtures
Authors: Marvin Dean C.
Published: February 2003

Binary nucleation theory is used to calculate the rate of nucleation in racemic mixtures of menthol enantiomers. It is found that the rate of nucleation is a much more sensitive probe of the nonideality in racemic mixtures than is the vapor pressure. Equations are developed for the nucleation rate and the change in vapor pressure as functions of the magnitude of the nonideal effects.
On the representation matrices of the spin permutation group
Authors: Wilson Stephen
Published: February 2003

A method for the determination of the representation matrices of the spin permutation group (symmetric group) is presented.
Nematic ordering in a two-dimensional fluid of overlapping ellipses
Authors: Parsons J. D.
Published: February 2003

A model is presented of the nematic–isotropic transition in which the mechanism for the transition is the geometrical exclusion effects of long rigid molecules. The molecules are modelled as soft ellipses with a repulsive interaction proportional to the mathematical overlap between them. The properties of the model depend upon the axial ratio κ≳1 of the ellipses and the density n. We show that the ordered state minimizes the energy only when n≳nc, where the critical density nc increases as κ→1. For n<nc the isotropic phase minimizes the energy and therefore a nematic state cannot exist at any temperature. When n≳nc there exists a critical temperature Tc such that for T<Tc the nematic state minimizes the free energy. Tc increases with both n and κ. For κ?1, the critical densities nc are larger than that possible in a liquid, and numerical results indicate that κ≳2 to form a nematic at any temperature. The transition for two dimensions is predicted to be second order except when κ→∞. The model roughly illustrates that orientational order cannot exist in an isotropic liquid except when the molecules are sufficiently anisotropic, and suggests that the attractive forces between molecules play only a minimal role.
Liquid–vapor isotope fractionation factors in argon–krypton binary mixtures
Authors: Lee M. W. , Neufeld P. , Bigeleisen J.
Published: February 2003

An equilibrium isotope effect has been studied as a continuous function of the potential field acting on the atom undergoing isotopic exchange. This has been accomplished through a study of the liquid vapor isotope fractionation factors for both, 36Ar/40Ar and 80Kr/84Kr in a series of binary mixtures which span the range between the pure components at 117.5 °K. The 36Ar/40Ar fractionation factor increases (linearly) from (lnα)2.49×10−3 in pure liquid argon to 2.91×10−3 in an infinitely dilute solution in liquid krypton. Conversely, the 80Kr/84Kr fractionation factor decreases (linearly) from (lnα)0.98×10−3 in pure liquid krypton to 0.64×10−3 in an infinetely dilute solution in pure liquid argon. The mean force constants 〈∇2U〉c on both argon and krypton atoms in the mixtures are derived from the respective isotope fractionation factors. It is shown that the mean force constant on argon atoms in infinitely dilute solution in krypton is equal, within experimental error, to the mean force constant on krypton atoms in infinitely dilute solution in argon. The symmetry of the mixed force constants, 〈∇2Ui〉j=〈∇2Uj〉i indicates that the assumption of additive pair interactions is sufficient to treat 〈∇2U〉 in the liquid along the coexistence line. The latter is mainly a function of U (r) in the range 0.90rmin<r<1.10rmin. The mean force constants for argon and krypton as a function of composition have been calculated by a modified corresponding states theory which uses the pure liquids as input parameters. The modified corresponding states theory reproduces 〈∇2U〉 for Kr over the entire concentration range, but leads to values of 〈∇2U〉 (Ar) which are systematically higher than experiment. The discrepancy is 8% at XAr=0. A systematic set of calculations has been made of 〈∇2U〉 (Ar) and 〈∇2U〉 (Kr) as a function of composition using radial distribution functions generated by the Weeks–Chandler–Anderson perturbation theory. The calculated results for 〈∇2U〉 (Kr) using the Lee–Henderson–Barker, Maitland–Smith, and Lennard-Jones potentials are in good agreement with experiment. None of these potentials give satisfactory agreement with the experimental values of 〈∇2U〉 (Ar) in dilute solution in krypton. The discrepancy is ascribed to failure of the WCA method to predict gAr–Kr, the mixed radial distribution function, with sufficient accuracy close to the triple point of a fluid.
Intermolecular mixing of electronic states in chemically mixed molecular crystals
Authors: Vaida Veronica , Colson Steven D.
Published: February 2003

It is shown that the emission spectra can be used as a simple and direct technique for measuring quasiresonance interactions in chemically mixed crystals. This method is illustrated by the study of the nearly resonant triplet states of p-dichloro- and p-dibromobenzene (DCB and DBB, respectively). The amount of mixing in the compound state is determined by measuring the relative intensities of the two ’’component spectra.’’ The results obtained for the DCB–DBB system give an upper limit for H′ of ∼1 cm−1, which is consistent with the small triplet exciton bandwidths of the pure DCB and DBB crystals.
Nitrogen-14 nuclear quadrupole resonance study of several hydroxypyrimidines
Authors: Subbarao S. N. , Bray P. J.
Published: February 2003

Nitrogen-14 nuclear quadrupole resonance (NQR) spectra of several hydroxypyrimidines of biological and pharmacological importance are reported and analyzed in the framework of the semiempirical Townes and Dailey theory. Included among the compounds are thymine, uracil, uridine, barbituric acid, orotic acid, and cyanuric acid. The results obtained suggest that in all cases the molecules in their ground state exist predominantly in the dilactam tautomeric form. Significant differences have been observed in the NQR spectra of the two nitrogens in barbituric acid which cannot be accounted for by the differences in the hydrogen bond lengths alone.
Boron-11 NMR study of the large angle anisotropic motion of B3H−8 in (CH3)4NB3H8
Authors: Fukushima Eiichi , Paine R. T. , Roeder S. B. W.
Published: February 2003

Steady state nuclear magnetic resonance was performed in powdered (CH3)4NB3H8. The quadrupole coupling e2qQ/2h of boron-11 decreases montonically at a decreasing rate from 70 kHz at 278 K to 16 kHz at 370 K. The birefringence also decreases with increasing temperature in the same temperature range and becomes undetectable at 473 K. We conclude that the B3H−8 anions are undergoing large angle wobbling motion in this phase between 270 and 473 K. The wobbling amplitude gradually increases with temperature until the motion becomes isotropic at an order–disorder phase transition near 473 K.
The equation of state of dense fluid monolayers
Authors: Toxvaerd So/ren
Published: February 2003

The equation of state of a two dimensional fluid of particles, interacting through a pair potential which imitates the potential between parallel carbon chains in dense monolayers, is calculated by the molecular dynamics technique and compared with monolayers of alcohols on water.
Molecular dynamics study of polymer formation
Authors: Synek M. , Schieve W. C. , Harrison H. W.
Published: February 2003

Previous studies of dimer formation by molecular dynamics are extended to trimers, tetramers, and pentamers. The mole fractions of these polymers are obtained as a function of temperature for a square well model of a dilute gas in two dimensions.
Redetermination of the N2(C) and N2(B) branching ratio from the Ar(3P0,2)+N2 reaction
Authors: Kolts J. H. , Brashears H. C. , Setser D. W.
Published: February 2003

The N2(B)  :N2(C) product branching ratio from the Ar(3P0,2)+N2 reaction has been measured as 1.0±0.2 using the Ar(3P2)+Kr as a reference reaction. The experiments consisted of reacting mixtures of N2 and Kr with Ar(3P0,2) atoms in a flowing afterglow apparatus. The intensities of the N2(C–B) and N2(B–A) band systems were independently compared to the intensity of the 760 nm krypton emission.
Use of the RINDO method in spectroscopy. Molecular Rydberg S←S and T←S transitions
Authors: Haque W.
Published: February 2003

The excited AO’s 2sH, 2pH, 3sX, and 3pX  (X=C, N, O, and F) have been included in the basis used in the INDO–MO–CI method. This results in virtual orbitals that are largely a combination of valence-shell AO’s, Rydberg AO’s, or a mixture of the two kinds of AO’s. Then the molecular excited state is described largely as a valence, a Rydberg, or a mixed valence–Rydberg state. Both the singlet←singlet and triplet←singlet Rydberg as well as the valence-shell transitions along with their oscillator strengths have been calculated for a number of prototype molecules. The lowest energy transitions in simple unsaturated organic molecules are essentially valence-shell transitions. However, in the case of saturated molecules these lowest lying transitions have appreciable contribution from the Rydberg configurations. The Rydberg character of the other excited states also are generally correctly brought out. In addition, the singlet–triplet splittings are described in a rather satisfactory manner.
A comparison of solutions to the time dependent Schrödinger equation
Authors: Chang Chi-Ming
Published: February 2003

Various methods providing approximate solutions to the time dependent Schrödinger equation proposed in a previous paper are compared using two examples for which the exact analytic solutions are known. Results show that the new method proposed in the previous paper is better than the traditional method for time dependent parameters.
Rayleigh light scattering in a ternary solution: Polybutadiene-n hexane-n heptane
Authors: Geissler E. , Hecht A. M.
Published: February 2003

The concentration fluctuation modes for a ternary solution, in the special case of a polymer in a mixture of two poor solvents, are analyzed to obtain the Rayleigh light scattering formalism. It is shown that one can extract information concerning the cross terms in the kinetic coefficients. From Rayleigh light scattering measurements in the system polybutadiene-n hexane-n heptane (1:1 by volume) and polybutadiene-n heptane the relative amplitude of the cross terms is deduced. The measurements of the scattered light intensity permit the elastic modulus G to be calculated for the pseudogel formed by the concentrated polymer solutions. An abrupt change in the slope of G as a function of temperature is observed, which is believed to be caused by the onset of rotational freedom of the solvent molecules. The monotonic behavior of the diffusion coefficient with concentration and the nonfree-volume behavior of the macroscopic viscosity distinguish this system from solutions with polystyrene and show the influence of the flexibility of the polymer chain.
Temperature dependence of electron transport and generation in biphenyl
Authors: Burshtein Z. , Williams D. F.
Published: February 2003

Drift mobilities of electrons in biphenyl in the a, b, and c′ crystal directions have been measured by the pulsed photoconductivity method and are 0.42, 1.25, and 0.51 cm2/V sec, respectively, at room temperture. For the a and c′ crystal directions these mobilities show a T−1.0 dependence, and a T−1.25 dependence for the b direction. No hole photocurrents were observed. The mechanisms of carrier transport and generation are discussed in terms of current theories.
Optical spectroscopy of copper clusters: Atom to bulk
Authors: Moskovits M. , Hulse J. E.
Published: February 2003

Copper clusters containing two–five atoms and large colloidal particles of copper were formed within matrices by co-condensing metal vapor with argon, methane, and dodecane onto a low-temperature substrate. The electronic absorption spectra of the resulting solids were recorded and absorptions belonging to individual aggregates of copper identified using a previously published calculation which predicts the cluster distribution within matrices of given metal-to-host ratios. The ’’birth’’ of the band structure of copper is clearly visible on going from the dimer upward, with Cu4 already possessing many of the features of the bulk metal.
Institutions interact with economic actors: plea for a general institutional economics
Authors: Held Martin J. , Nutzinger Hans G.
Published: February 2003

In contrast to traditional welfare economics, new institutional economics has made a major contribution to analyzing institutions as both preconditions and elements of economic activities. By including institutions’ incentives and restrictions on human beings, it has made a significant first step toward the further development of economic science. The usual starting point, however, is a world without uncertainty where so‐called “anomalies” from “rational” behavior cannot occur; but in this world, institutions are not necessary either. Related research demonstrates the relevance of factors like intrinsic motivation, internalization of norms, habit formation, etc., but these characteristics are typically treated in a half‐hearted way as mere anomalies. Instead, it is time to take the full second step and to include the effects of institutions on economic actors as well as to take the third step, namely, to consider the fact that economic agents form institutions. We exemplify these further steps and look on the interaction between institutions and economic actors which leads to a general institutional economics.
Nef-Mediated Disruption of HLA-A2 Transport to the Cell Surface in T Cells
Authors: Kasper Matthew R. , Collins Kathleen L.
Published: February 2003

Human immunodeficiency virus type 1 (HIV-1) Nef is a key pathogenic factor necessary for the development of AIDS. One important function of Nef is to reduce cell surface levels of major histocompatibility complex class I (MHC-I) molecules, thereby protecting HIV-infected cells from recognition by cytotoxic T lymphocytes. The mechanism of MHC-I downmodulation by Nef has not been clearly elucidated, and its reported effect on MHC-I steady-state levels ranges widely, from 2-fold in HeLa cells to 200-fold in HIV-infected primary T cells. Here, we directly compared downmodulation of HLA-A2 in HIV-infected HeLa cells to that in T cells. We found that similar amounts of Nef protein resulted in a much more dramatic downmodulation of HLA-A2 in T cells than in HeLa cells. A comparison of Nef's effects on HLA-A2 endocytosis, recycling, and transport rates indicated that the most prominent effect of Nef on HLA-A2 in T cells was to inhibit transport to the cell surface. The phosphatidylinositol 3-kinase inhibitor, LY294002, previously reported to inhibit Nef-mediated MHC-I downmodulation in astrocytic cells, did not directly affect Nef's ability to block transport of MHC-I to the cell surface in T cells.
Cellular Proteins from Human Monocytes Bind to Dengue 4 Virus Minus-Strand 3′ Untranslated Region RNA
Authors: Yocupicio-Monroy Rosa Martha E. , Medina Fernando , Reyes-del Valle Jorge , del Angel Rosa M.
Published: February 2003

The synthesis of plus and minus RNA strands of several RNA viruses requires as a first step the interaction of some viral regulatory sequences with cellular and viral proteins. The dengue 4 virus genome, a single-stranded, positive-polarity RNA, is flanked by two untranslated regions (UTR) located in the 5′ and 3′ ends. The 3′UTR in the minus-strand RNA [3′UTR (−)] has been thought to function as a promoter for the synthesis of plus-strand RNA. To study the initial interaction between this 3′UTR and cellular and viral proteins, mobility shift assays were performed, and four ribonucleoprotein complexes (I through IV) were formed when uninfected and infected U937 cells (human monocyte cell line) interacted with the 3′UTR (−) of dengue 4 virus. Cross-linking assays with RNAs containing the complete 3′UTR (−) (nucleotides [nt] 101 to 1) or a partial sequence from nt 101 to 45 and nt 44 to 1 resulted in specific binding of some cellular proteins. Supermobility shift and immunoprecipitation assays demonstrated that the La protein forms part of these complexes. To determine the region in the 3′ UTR that interacted with the La protein, two deletion mutants were generated. The mutant (del-96), with a deletion of nt 96 to 101, was unable to interact with the La protein, suggesting that La interacted with the 5′ portion of the 3′UTR (−). Complex I, which was the main ribonucleoprotein complex formed with the 3′UTR (−) and which had the fastest electrophoretic migration, contained proteins such as calreticulin and protein disulfide isomerase, which constitute important components of the endoplasmic reticulum.
Temperature-Dependent Conformational Changes in Herpes Simplex Virus ICP4 That Affect Transcription Activation
Authors: Compel Peter , DeLuca Neal A.
Published: February 2003

The C-terminal 500 amino acids of herpes simplex virus type 1 ICP4 are required for full activator function and viral growth and are known to participate in interactions consistent with the role of ICP4 as an activator of transcription. Oligonucleotide mutagenesis was used to target stretches of amino acids that are conserved with the ICP4 analogs of other alphaherpesviruses and were also predicted to be exposed on the surface of the molecule. Seven mutants were isolated that possessed one to three amino acid changes to the residue alanine in four regions between residues 1000 and 1200. The mutants generated were analyzed first in transfection assays and subsequently after introduction into the viral genome. A number of phenotypes representing different degrees of functional impairment were observed. In transient assays conducted at 37°C, mutant M2 was indistinguishable from wild-type ICP4. Mutants M6 and M7 were marginally impaired. M3, M4, and M5 were more significantly impaired but still able to activate transcription, and M1 was completely impaired. In the context of the viral genome, M1, M3, and M7 were found to be temperature sensitive for growth. All three overproduced immediate-early (IE) proteins at the nonpermissive temperature (NPT). M3 and M7 produced early but not late proteins, and M1 produced neither early nor late proteins, at the NPT. The ICP4 proteins synthesized by all of the mutants tested were able to bind to specific ICP4 binding sites in electrophoretic mobility shift experiments. However, the DNA-protein complexes formed with the ICP4 from M1, M3, or M7 produced at the NPT possessed altered mobility. These complexes were not supershifted by a monoclonal antibody that recognizes an epitope in the C terminus; however, they were supershifted by a monoclonal antibody that recognizes the N terminus. The results suggest that the mutant forms of ICP4, while able to bind to DNA, are conformationally altered at the NPT, thus impairing the ability of the protein to activate transcription to different extents. The complete lack of ICP4 function characteristic of the M1 protein, and the inability of all the mutants to attenuate IE gene expression, suggest that the mutations additionally affect functions of the N terminus to different extents.
The Power of High‐Throughput Experimentation in Homogeneous Catalysis Research for Fine Chemicals
Authors: Vries Johannes G. de , Vries André H.M. de
Published: February 2003

The use of high‐throughput experimentation (HTE) in homogeneous catalysis research for the production of fine be found within a very short time frame. At the same time, a reliable process can be achieved because extensive time‐to‐market constraints, HTE allows catalytic solutions to be found within a very short time frame. At the same time, a reliable process can be achieved because extensive imisation can be undertaken. We give examples of lead generation and optimisation, and of scope determination, based on our basic research program aimed at developing low‐cost aromatic substitution reactions (C−H activation, Heck and Suzuki reactions). We also give an example of HTE in mechanistic research, which stems from our work on asymmetric hydrogenation with low‐cost monodentate phosphoramidite ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Towards the definition and use of a core set of archetypal structures in system dynamics
Authors: Wolstenholme E. F.
Published: February 2003

There has been considerable research in the field of system dynamics over the last decade concerned with defining generic structures and templates by which to classify structures and behavioural insights in dynamic systems. These have appeared both in stock/flow and causal loop terms. This article focuses on generic causal loop structures more commonly known as system archetypes, a profusion of which have now been defined. The purpose of the article is to improve the usefulness of system archetypes both as free standing devices to aid model conceptualisation and as a means of disseminating insights arising from models. In order to achieve this three postulates are made: First, that system archetypes can be usefully condensed down to a more understandable core set of four totally generic archetypes, consisting of the four ways of ordering a pair of reinforcing and balancing feedback loops. These are described, named and current archetypes mapped onto them with specific examples. Second, that for every “problem” archetype there exists a closed loop “solution” archetype. It is suggested that some misunderstandings with current archetypes arise from the fact that they often combine problem and solution links in the same diagram. Third, that each archetype has important characteristics, which are vital to understanding the role of archetypes in assisting systemic thinking. The particular characteristic introduced and highlighted is the concept of organisational boundaries. The article concludes by discussing the importance of the reduced set of archetypes, and organisational boundaries in particular, in explaining some barriers to implementing systemic thinking, using a range of examples encountered by the author in recent consulting practice. Copyright © 2003 John Wiley & Sons, Ltd.
Hopelessness and risk behaviour among adolescents living in high‐poverty inner‐city neighbourhoods
Authors: Bolland John M.
Published: February 2003

Ethnographic literature on inner‐city life argues that adolescents react to their uncertain futures by abandoning hope, leading them to engage in high levels of risk behaviour. However, few quantitative studies demonstrate this relationship. This study tests this relationship using a survey of 2468 inner‐city adolescents, asking them questions about hopelessness, violent and aggressive behaviour, substance use, sexual behaviour, and accidental injury. Nearly 50% of males and 25% of females had moderate or severe feelings of hopelessness. Moreover, hopelessness predicted of each of the risk behaviours considered. These results suggest that effective prevention and intervention programmes aimed at inner‐city adolescents should target hopelessness by promoting skills that allow them to overcome the limitations of hopelessness.
The relationship between total quality management practices and their effects on firm performance
Authors: Kaynak Hale
Published: February 2003

Recent research on total quality management (TQM) has examined the relationships between the practices of quality management and various levels of organizational performance. These studies have produced mixed results, probably because of the nature of the research designs used such as measuring TQM or performance as a single construct. Based on a comprehensive literature review, this study identifies the relationships among TQM practices and examines the direct and indirect effects of these practices on various performance levels. A proposed research model and hypotheses are tested by using cross‐sectional mail survey data collected from firms operating in the US. The test of the structural model supports the proposed hypotheses. The implications of the findings for researchers and practitioners are discussed and further research directions are offered.
The angular momentum, creation, and significance of quantized vortices
Authors: Hirschfelder Joseph O.
Published: February 2003

The flux of probability density corresponding to a complex wavefunction, ψ=ψr+iψi, can form vortices which rotate about a nodal region of ψ, and have integer values of the circulation numbers. For one particle wavefunctions (or for approximate natural spin molecular orbitals), the vortices are either axial or toroidal. The axial vortices have angular momentum dipole moments which are usually quantized only if the wave function is an eigenfunction of Lz. The axial vortices interact with homogeneous magnetic fields whereas the toroidal interact with inhomogeneous magnetic fields. Toroidal vortices are easily created or annihilated by a perturbation which moves the nodal surface of ψi relative to the nodal surface of ψr so that these surfaces intersect or become separated. Thus, toroidal vortices are unstable and may be important only near resonance. However, axial vortices are stable since their creation requires (a) photon absorption or emission, (b) a perturbation (such as a magnetic field) which converts a real into a complex wavefunction, or (c) conversion of a toroidal into an axial vortex by expanding the nodal loop until a part of it reaches the boundary of configuration space. Thus, axial vortices should play an important role in energy transfer, photochemical processes, etc., and their circulation numbers should be good quantum numbers. A method for determining generalized first-order density matrices and natural spin–orbitals for use in scattering problems is proposed.
Molecular shape and volume effects on the orientational ordering of simple liquid crystals
Authors: Baron Barbara A. , Gelbart William M.
Published: February 2003

The parameters characterizing the isotropic–nematic phase transition in liquid crystals have been calculated using a generalized van der Waals theory. The molecules are assumed to have spherocylindrical hard cores, which are treated by scaled particle theory, and to have attractions which go as −Ciso/r6ij −Cancos2ϑij/r6ij, where ϑij is the angle between the long axes of molecules i and j and rij is the distance between their centers. The dependence of phase transition properties on the molecular volume, polarizability, and length-to-width ratio are examined; and the importance of the coupling between hard core repulsions and isotropic dispersional attractions is discussed.
Optical nonlinearities of conjugated molecules. Stilbene derivatives and highly polar aromatic compounds
Authors: Oudar J. L.
Published: February 2003

We have investigated the influence of donor and acceptor substituents on the second and third order hyperpolarizabilities β and γ of large conjugated molecules such as stilbene and styrene derivatives. This was performed by two independent measurements of β and γ using the techniques of dc electric-field induced second-harmonic generation and tunable four-wave mixing in liquids and solutions. For trans−stilbene derivatives, β and γ are typically 10 times larger than for the corresponding benzene compounds, and are strongly correlated with the mesomeric effect of the substituents. A series of disubstituted molecules with strong donor–acceptor intramolecular charge transfer exhibit very large β, and it is shown that this enhancement can be predicted from the basic properties of the first electronic excited state.
Vibrational excitation in H+–H2 collisions. Comparison between experiment and rotationally sudden impact parameter calculations
Authors: Schinke R. , Krüger H. , Hermann V. , Schmidt H. , Linder F.
Published: February 2003

Differential cross section measurements are reported for vibrational excitation in H+–H2 collisions at Ec.m.=15.3 eV and 20 eV and for scattering angles including the rainbow region. The experimental results are compared with theory using an impact parameter approach. Rotational motion is treated in the sudden approximation, whereas the Schrödinger equation for vibrational excitation under the action of the time-dependent force is solved exactly using the Giese and Gentry fit potential surface. Very good agreement is found between theory and experiment indicating that the impact parameter approach is applicable for energies down to Ec.m.=15 eV and for angles up to ϑc.m.=20°.
Sequential analysis by cooperative reactions on copolymers. III. Second-order Markovian chains with arbitrary protection
Authors: González J. J. , Hemmer P. C.
Published: February 2003

We develop an exact theory for the kinetics of reactions on long linear binary copolymers. Both monomer types are assumed to exert specific cooperative effects in the sense that after a unit has reacted, the reactivities of the adjacent two monomer units are changed. Hence the reaction pattern depends upon the sequential structure of the copolymer, here assumed to be a second-order Markov chain. Special results, previously obtained by different methods, including reaction kinetics on homopolymers, are recovered. The limits of the extents of reaction for long times, t→∞,when one monomer type protects completely, are very important for sequential analysis of copolymers. We study them in detail for random, Markovian, and second-order Markovian structures as functions of the partial protection by the other monomer type, of the initial rate constants, and of the structure parameters. Interesting effects appear.
Absolute rate constants for the reaction of OH radicals with allene, 1,3-butadiene, and 3-methyl-1-butene over the temperature range 299–424 °K
Authors: Atkinson R. , Perry R. A. , Pitts J. N.
Published: February 2003

Absolute rate constants for the reaction of OH radicals with allene, 1,3-butadiene, and 3-methyl-l-butene have been determined over the temperature range 299–424 °K, using a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained were k (allene) =5.59×10−12 e(305±300)/RT cm3 molecule−1 sec−1, k (1,3-butadiene) =1.45×10−11 e(930±300)/RT cm3 molecule−1 sec−1, k (3-methyl-1-butene) =5.23×10−12 e(1060±300)/RT cm3 molecule−1 sec −1, with rate constants at room temperature of (9.30±0.93) ×10−12, (6.85±0.69) ×10−11, and (3.10±0.31) ×10−11 cm3 molecule−1 sec−1 for allene, 1,3-butadiene, and 3-methyl-l-butene, respectively.
X-ray photoelectron spectroscopy of S2N2 and the solid state polymerization of S2N2 to metallic (SN)x
Authors: Sharma J. , Downs D. S. , Iqbal Z. , Owens F. J.
Published: February 2003

An x-ray photoelectron spectroscopic (XPS) study of a thin film of S2N2 at −100 °C, involving the valence band, core-level and core-level shakeup, and energy-loss spectra, is reported. The results are analyzed in terms of a molecular orbital model and previous optical data. In addition, the thermally induced solid state polymerization of S2N2 to metallic (SN)x was studied by recording the XPS spectra at −40, 0, and 20 °C. The valence band data show changes of the highest filled molecular orbitals of S2N2, consistent with the process of polymerization to the metallic state.
Genetic Network Analyzer: qualitative simulation of
genetic regulatory networks
Authors: de Jong Hidde , Geiselmann Johannes , Hernandez Céline , Page Michel
Published: February 2003

Motivation: The study of genetic regulatory networks has received a major impetus from the recent development of experimental techniques allowing the measurement of patterns of gene expression in a massively parallel way. This experimental progress calls for the development of appropriate computer tools for the modeling and simulation of gene regulation processes.

Results: We present Genetic Network Analyzer (GNA), a computer tool for the modeling and simulation of genetic regulatory networks. The tool is based on a qualitative simulation method that employs coarse-grained models of regulatory networks. The use of GNA is illustrated by a case study of the network of genes and interactions regulating the initiation of sporulation in Bacillus subtilis.

Availability: GNA and the model of the sporulation network are available at http://www-helix.inrialpes.fr/gna

Contact: Hidde.de-Jong@inrialpes.fr

* To whom correspondence should be addressed.
Redundancy based detection of sequence polymorphisms in expressed sequence tag data using autoSNP
Authors: Barker Gary , Batley Jacqueline , O’ Sullivan Helen , Edwards Keith J. , Edwards David
Published: February 2003

Summary: AutoSNP is a program to detect single nucleotide polymorphisms (SNPs) and insertion/deletion polymorphisms (indels) in expressed sequence tag (EST) data. The program uses d2cluster and cap3 to cluster and align EST sequences, and uses redundancy to differentiate between candidate SNPs and sequence errors. Candidate polymorphisms are identified as occurring in multiple reads within an alignment. For each candidate SNP, two measures of confidence are calculated, the redundancy of the polymorphism at a SNP locus and the co segregation of the candidate SNP with other SNPs in the alignment.

Availability: The program was written in PERL and is freely available to non-commercial users by request from the authors.

Contact: dave.edwards@nre.vic.gov.au

* To whom correspondence should be addressed.
IslandPath: aiding detection of genomic islands in prokaryotes
Authors: Hsiao William , Wan Ivan , Jones Steven J. , Brinkman Fiona S. L.
Published: February 2003

Summary: Genomic islands (clusters of genes of potential horizontal origin in a prokaryotic genome) are frequently associated with a particular adaptation of a microbe that is of medical, agricultural or environmental importance, such as antibiotic resistance, pathogen virulence, or metal resistance. While many sequence features associated with such islands have been adopted separately in applications for analysis of genomic islands, including pathogenicity islands, there is no single application that integrates multiple features for island detection. IslandPath is a network service which incorporates multiple DNA signals and genome annotation features into a graphical display of a bacterial or archaeal genome, to aid the detection of genomic islands.

Availability: This application is available at http://www.pathogenomics.sfu.ca/islandpath and the source code is freely available, under GNU public licence, from the authors.

Contact: brinkman@sfu.ca

Supplementary information: An online help file, which includes analyses of the utility of IslandPath, can be found at http://www.pathogenomics.sfu.ca/islandpath/current/islandhelp.html

* To whom correspondence should be addressed.
Impacting organizational learning: the training and experiences of quality award examiners and assessors
Authors: Leonard Denis , McAdam Rodney
Published: February 2003

Aims to show that developments in the quality award assessment process in organizations can make a contribution, within a wider framework of organizational learning. The underpinning theoretical argument is that quality award models and associated organizational assessment processes can be used to achieve much wider benefits, than that of qualityper se. The quality award assessment process has been applied in organizations since the mid‐1980s until the present. The process uses models such as the Business Excellence Model and the Baldrige model. These models use an interpretation of quality, which is based on the holistic approach of total quality management. In parallel with the development of the assessment process there has been considerable development in the field of organizational learning with an emphasis on developing learning based skills in employees. Shows how the learning experiences and skills developed and enhanced through the assessment process can be applied within an organization’s approaches to learning in other disciplines.