bluuebunny/crossref_metadata_2025 huggingface dataset:
Conductometric Studies of Molecular Complexes of Charge Transfer Type Formed between Aza-Aromatics and Haloanils
Authors: Randhawa Harbhajan S. , Lakhani Rajni
Published: April 2003

Electrical conductivity technique has been employed to investigate the molecular interaction of aza-aromatics viz. pyridine, α-pikoline, β-picoline and γ-picoline with haloanils, namely chloranil, bromanil and fluranil. The stoichiometry of the charge transfer (CT) complexes has been established and molar conductivities of the complexes determined employing the method of Gutmann and Keyzer. A model has been proposed for determining the equilibrium constant (K) of 1 : 1 molecular complexes of CT type by conductometric measurements. The model involves the assumption: 1/σ = [(1 + K c0A)/qdK c0A] (1/c0D) + (1/qd c0A), where σ is the conductivity of the molecular complex, qd is the extent of depolarization of the complex, c0A) and c0D) are the initial concentrations of the acceptors and donors, respectively. The values of K and qd follows the expected trend of the conductometric parameters determined by the method of Gutmann and Keyzer as well as ionization potential of donors, thereby substantiating the validity of the model proposed. The observed and theoretical values of thermodynamic parameters for the aza-aromatic-chloranil systems that the interaction of aza-aromatics with haloanils is occurring through the lone pair of nitrogen ring.
Photochemical Transformations of 2,4,4,6-Tetraphenyl-4H-thiopyran-1,1-dioxide and Some Its para-Substituted Derivatives
Authors: Šebek Pavel , Sedmera Petr , Kuthan Josef
Published: April 2003

1,2,4,5-Tetrasubstituted cyclopentadienes VIa-VIf or phenanthrene derivative VIII, respectively, were obtained as the main photoproducts upon irradiation of sulfones Ia-If and II in acetonitrile, methanol or benzene. Bridged isomers Va-Vd were isolated from the reaction of Ia-Id carried out in acetonitrile. Probable course of the investigated photochemical transformations of 4H-thiopyran-1,1-dioxides is discussed.
Intramolecular Cyclization of Steroidal Diketo Aldehydes to Acetals
Authors: Boncza-Tomaszewski Zbigniew , Duddeck Helmuth
Published: April 2003

As an attempt to prepare diketo aldehydes I and II conjugated ketones III and IV were converted to the respective keto diols V and VI, which were treated with periodic acid and independently with lead tetraacetate. However, instead of desired diketo aldehydes I and II, unexpected and interesting cyclized acetals X, XI, and XII were obtained. The structures and some of their chemistry are described in this paper.
Synthesis of Some New Heterocyclic Compounds Based on Thiopyrane-2-thione as Antimicrobial Agents
Authors: Awad Ibrahim M. A. , Abdel Hafez Ali A.
Published: April 2003

Some new derivatives containing both thiopyrane-2-thione (I) and β-lactams, thiazolidinones, triazoles, sulfonamides and tricyclic compound have been previously prepared. Here we attempted to use the compound I, for synthesis of new heterocycles.
Characterization of the Hydrophobic Properties of Amino Acids. II. How Hydrophobic, Hydrophilic and Lipophilic Is Tryptophan?
Authors: Chmelík Josef
Published: April 2003

The model for the characterization of hydrophobicity, hydrophilicity and lipophilicity of compounds is presented. It is based on the vapour-to-solvent coefficients for hydrophilicity and lipophilicity and the partition coefficient for hydrophobicity. It is shown that some apparently contradictory facts can be understood on the basis of this model.
Regio- and Stereoselective Tritiation of the Juvenoid Analog W 328
Authors: Elbert Tomáš , Černý Bohuslav , Wimmer Zdeněk , Sergent Leila
Published: April 2003

The juvenoid analog 2-(4-(2-(ethoxycarbamato)ethoxy)benzyl)-1-cyclohexanone ethylene acetal (I) (W 328) was labelled by 3H in the benzyl position by the CESG method. 3H NMR revealed the stereoselectivity of the labelling. The results are compared with the data published in the literature and discussed in the terms of stereoelectronic requirements.
Nonconventional Friedel-Crafts Chemistry. VII. On Homoannular and Heteroannular Reactions of Ferrocene with Bifunctional Moieties under Friedel-Crafts Conditions
Authors: El-Zohry Maher F.
Published: April 2003

The utilization of ferrocene in the organic synthesis and its uses in Friedel-Crafts chemistry, together with our interest in this area, prompted us to investigate the reaction of ferrocene with halo acid chlorides and α,β-unsaturated acid chlorides under different Friedel-Crafts conditions with the aim to employ these reactions in the syntheses of polycyclic ferrocene derivatives.
The Extraction of Strontium and Barium with a Solution of Bis-1,2-Dicarbollylcobaltate in Nitrobenzene in the Presence of 18-Crown-6
Authors: Vaňura Petr , Makrlík Emanuel
Published: April 2003

A study has been made of the extraction of Sr and Ba in an aqueous solution of perchloric acid-18-crown-6-bis-1,2-dicarbollylcobaltate-nitrobenzene. It was found that the organic phase contains complexes of the ML2+org type ( M = Sr2+, Ba2+) that are converted to ML22+org when the concentration of crown (cL) is greater than the concentration of bis-1,2-dicarbollylcobaltate (cB). The values of the corresponding extraction constants, individual extraction constants and stability constants of the extracted species in the organic phase were determined. The system can be utilized for separation applications at concentrations here cL < cB.
Study of the Conditions for the Extraction of Toxic Organic Bases and Methods for Their Determination. II. Extraction of Ion Associates of 3-Quinuclidinyl Benzilate and Diethyl Lysergamide with Azo Dyes and Sulfophthaleins
Authors: Souček Jan , Belický Ladislav , Havel Josef , Hálová Jaroslava
Published: April 2003

Diethyl lysergamide (LSD) and 3-quinuclidin benzilate (BZ) are both extracted by chloroform in dependence on the pH value of the solution. The protonation constants were determined for both bases and their distribution constants were calculated from their distribution constants in the water-chloroform system. Conditions were studied for the formation of the ion associates with 13 dyes and for their extraction with chloroform.
Effect of Coordination on the Structure of Tris(N,N-Dimethylaminomethyl)phosphine Oxide
Authors: Vojtíšek Pavel , Podlahová Jana , Malý Karel , Hašek Jindřich
Published: April 2003

Crystals of tris(N,N-dimethylaminomethyl)phosphine oxide (tmpo) are hexagonal, space group P63; a = 8.723(5), c = 10.636(5) Å, Z = 2, R = 0.039 for 384 observed reflections. The complex [Co(tmpo)2(H2O)2](ClO4)2, forms orthorhombic crystals, space group Pbca, a = 19.16(1), b = 10.576(2), c = 117.043(4) Å, Z = 4, R = 0.069 for 1 409 observed reflections. The molecule is centrosymmetric, with the Co atom lying in the center. The tmpo is coordinated through the oxygen atom and one of the nitrogen atoms. The coordination of the ligand brings about very small changes in the bond lengths and angles except for the P=O bond. The coordinated water molecules play a major part in the structure of [Co(tmpo)2(H2O)2](ClO4)2.
Franck-Condon Factors and R-Centroids for the Band System a1Π-X1Σ+ of the InH Molecule
Authors: Rajamanickam Narayanan , Murali Thangamariappan , Sakthivel Thangasamy , Fernandez Gomez Manuel , Lopez Gonzalez Juan Jesus
Published: April 2003

The Franck-Condon factors (vibrational transition probabilities) and r-centroids have been evaluated by a numerical integration procedure for the bands of the a3Π1-X1Σ+ system of the InH molecule using a suitable potential.
The Spectrophotometric Determination of Elements with Chromazurol S in the Presence of Cetyltrimethylammonium Bromide and Triton X-100. I. The Determination of the Sum of the Rare Earth Elements
Authors: Preisler Jan , Jančář Luděk , Sommer Lumír
Published: April 2003

The study of the interactions of the rare earth elements (REE) with chromazurol S in the presence of a cationic and noncationic tenside permitted a number of general conclusions to be drawn for the effect of tensides on the chromogenic analytical reaction. The ternary ion associate with chromazurol S and cetyl trimethyl ammonia in the presence of Triton-100 is useful for the sensitive spectrophotometric determination of REE in mixtures and in hydroxide concentrates.
Structure of Dimeric Compounds Obtained from 3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide
Authors: Klinotová Eva , Klinot Jiří , Křeček Václav , Hilgard Stanislav , Buděšínský Miloš , Malát Jan
Published: April 2003

The triterpenoid α-diketone with oxabicyclo[2.2.2]octane system in the ring E (3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (I)) gives isopropylidenedioxy derivative II and dimeric compounds V and IX when submitted to chromatography on silica gel in the presence of acetone. Compounds V and IX were reduced with hydride to hydroxy derivatives VI, X, and XI; on reaction with diazomethane they gave dimeric compounds with spiroepoxide group at the position 21 (compound VII) or 22 (compound XII) which reacted further with diazomethane to give monomeric spiroepoxides VIII, XIII, and XIV. The structure of the compounds obtained was derived from their 1H and 13C NMR, IR, and FAB mass spectra.
Activity Coefficients of Tris(ethylenediamine)cobalt(III) Hexacyanoferrate(III) in Water and Mixed Water-Alcohol Solvents
Authors: Holba Vladislav
Published: April 2003

The solubility of tris(ethylenediamine)cobalt(III) hexacyanoferrate(III) were measured in aqueous solution of NaClO4, NaCl, KCl, KBr, K2SO4, Mg2SO4, (CH3)4NBr, (C2H5)4NBr, (1-C3H7)4NBr, and (1-C4H9)4NBr, as well as in the solution of NaClO4 in mixtures of water with methanol and tert-butyl alcohol. The experimental mean activity coefficients are compared with theoretical ones evaluated with the aid of extended Debye-Huckel relation. From the solubilities in water and in water-alcoholic solvents the thermodynamic transfer functions of the saturating salt were calculated.
5-Aryl-2-furancarbaldehyde Hydrazones and Related Compounds
Authors: Krutošíková Alžbeta , Dandárová Miloslava , Alföldi Juraj
Published: April 2003

A series of 5-aryl-2-furancarbaldehyde 2,6-dialkylphenylhydrazones (Ia - Iv) and dimethylhydrazones (IIa - IIf) as well as related compound benzo[b]furan-2-carbaldehyde dimethylhydrazone (III) were prepared. Compounds Ia - Iv were synthesized by condensing 5-aryl-2-furancarbaldehydes with 2,6-dialkylphenylhydrazines, compounds IIa - IIf were obtained from the same starting compounds and N,N-dimethylhydrazine. The intermediate 5-aryl-2-furancarbaldehydes were prepared by reaction of aryldiazonium chlorides with 2-furancarbaldehyde. The structure of the compounds were proven by 1H, 13C and 15N NMR spectra.
Indication of Odd Number of Equivalent Atoms in an EPR Spectrum by the Fourier Transform
Authors: Dračka Oldřich
Published: April 2003

A numerical criterion is proposed for the indication of odd number of equivalent atoms in an EPR spectrum. Physically, this "oddness" criterion is the relation for the content of negative and positive parts of the imaginary part of the EPR spectrum Fourier transform, provided that the spectrum x-coordinate start is shifted into the spectrum symmetry center. The effect of noise present in the spectrum is analysed and the best limit of Fourier transform noise effect minimalization is proposed. With even numbers of equivalent atoms in EPR spectrum only, the oddnes criterion value for the noiseless spectrum is zero and the deviation from this value is due to the effect of the noise. A criterion value greater than 0.3 indicates the presence of at least one well-resolved component with an odd number of equivalent atoms, with spin 1/2 in the spectrum. A value smaller than 0.3 indicates the absence of such component. However, if this value is greater than 1.0, the presence of either a well resolved component with a single atom with spin 1 or an ill-resolved component with an odd number of equivalent atoms with spin 1/2 is indicated. Application of the proposed criterion to noise-loaded synthetic EPR spectra is exhibited. The possibility of identifying methyl group splitting by a sharp decrease of the proposed criterion value after the spectrum contraction with the proper splitting constant is demonstrated.
Effect of the Molecular Structure of Cyanine Dye on the Electrochemical Corrosion Behaviour of Metallic Copper in Nitric Acid Solution
Authors: Makhlouf Mohamed Th. , Khalil Zarif H.
Published: April 2003

The effect of 2-(2-hydroxystyryl)quinolinium-1-ethyl iodide (I) and 4-(2-hydroxystyryl)quinolinium-1-ethyl iodide (II) cyanide dyes on the corrosion behaviour of copper metal in nitric acid solution has been studied. Weight loss measurement, galvanostatic polarization curves, open-circuit potential variation of copper electrode with time and the cathodic protective current values indicate that cyanine dye I gives better anticorrosive effect than dye II. The inhibition effect in case of the two cyanine dyes is more pronounced in case of the addition of dye to the corrosion medium than that obtained in case of copper metal coated by dye thin film (previously treated in dye solution) before immersion in corrosive medium.
Voltammetric and Potentiometric Determination of Gold in Gold-Plated Electrotechnical Components
Authors: Vytřas Karel , Švancara Ivan , Renger František , Srey Malis , Vaňková Radmila , Hvízdalová Marie
Published: April 2003

Differential pulse voltammetry was used to determine gold in gold-plated electrotechnical components. Samples were dissolved to form tetrachlorourate, which was determined on a carbon paste electrode containing tricresyl phosphate as pasting liquid. A characteristic cathodic peak for tetrachlorourate, whose selective accumulation is based on extraction, is obtained during cathodic scan from +0.8 to -0.5 V vs Ag/AgCl electrode. The accompanying Fe(III) and Cu(II) ions from the matrix are masked by adding EDTA. Gold can be determined in the presence of their thousand-fold excess in the concentration range 1 . 10-5 - 1 . 10-7 mol l-1. The results were confirmed by potentiometric titration with a solution of 1-(ethoxycarbonyl)pentadecyltrimethylammonium bromide (Septonex) by using a coated-wire indicator electrode with a softened plastic membrane.
[5-(Adenin-9-yl)-5-deoxypentofuranosyl]phosphonates - A Novel Type of Nucleotide Analogs Related to HPMPA. I. Derivatives with L-arabino, D-arabino, 2-Deoxy-L-erythro and 2-Deoxy-L-threo Configuration
Authors: Otmar Miroslav , Rosenberg Ivan , Masojídková Milena , Holý Antonín
Published: April 2003

[5-(Adenin-9-yl)-5-deoxypentofuranosyl]phosphonates, a new type of nucleotide analogs with fixed HPMPA structure, have been prepared. The synthesis of compounds of L-arabino (IIa, IIb), D-arabino(XIVa, XIVb), 2-deoxy-L-erythro(IIIa, IIIb) and 2-deoxy-L-threo(IVa, IVb) configuration is based on the Michelis-Arbuzov reaction of the fully protected methyl glycosides with triethyl phosphite and trimethylsilyl triflate which leads to anomeric mixture of diethyl (L-pentofuranosyl) phosphonates. The protected 5-O-tosyl derivatives react with sodium salt of adenine to give N9-substituted products which after total deprotection afforded the tittle nucleotide analogs. The fixation of the partial structure of HPMPA to form five-membered ring leads to a significant decrease, or a total loss, of biological activity.
Optics of Heterogeneous Media. Comparison of Some Light Scattering Model Calculations
Authors: Holoubek Jaroslav
Published: April 2003

Typical dependences of turbidity as a function of diameter of scattering elements and their volume fractions as well as a function of the wavelength of the incident light were calculated, based both on the Lorenz-Mie theory and the fluctuation theory of Debye and Bueche. Such dependences calculated for the polyethylene, polypropylene and polyamide inclusions differing slightly in their reactive index from the surrounding matrix of the same material were compared. The multiple scattering correction of the Lorenz-Mie theory based on the asymmetry factor affects the turbidity similarly as the use of mixing rule for refractive indices of multicomponent systems. A good correspondence between both theories was found only for small scattering inclusions fulfilling the approximate condition for diameter d < 0.3 λ. Only approximate agreement of the turbidity and refractive index fluctuations up to the diameters d < 5 λ can be observed for the present systems using both theories. The results obtained for the solid polymers were compared with model calculations for polystyrene latex under identical conditions: the latter are in a reasonable agreement with the expected trends (more pronounced dispersion and larger turbidity).
A Monte Carlo Study of Flexible Polymer Chain Conformations in Restricted Volumes. I. A Model for Insoluble Blocks Conformations in Swollen Cores of Multimolecular Spherical Block Copolymer Micelles
Authors: Limpouchová Zuzana , Procházka Karel
Published: April 2003

Monte Carlo simulations of chain conformations in a restricted spherical volume at relatively high densities of segments were performed for various numbers of chains, N, and chain lengths (number of segments), L, on a tetrahedral lattice. All chains are randomly end-tethered to the surface of the sphere. A relatively uniform surface density of the tethered ends is guaranteed in our simulations. A simultaneous self-avoiding walk of all chains creates starting conformations for a subsequent equilibration. A modified algorithm similar to that of Siepmann and Frenkel is used for the equilibration of the chain conformations. In this paper, only a geometrical excluded volume effect of segments is considered. Various structural and conformational characteristics, e.g. segment densities gS(r), free end densities gF(r) as functions of the position in the sphere (a distance from the center), distributions of the tethered-to-free end distances, ρTF(rTF), etc. are calculated and their physical meaning is discussed. The model is suitable for studies of chain conformations is swollen cores of multimolecular block copolymer micelles and for interpretation of non-radiative excitation energy migration in polymeric micellar systems.
Effect of the Reaction Temperature on the Polymerization of 2-Ethylhexyl Acrylate Initiated by Lithium Ester Enolate-Lithium tert-Butoxide Complex
Authors: Vlček Petr , Jakeš Jaromír , Otoupalová Jaroslava
Published: April 2003

The effect of reaction temperature in the range from -72 to 0 °C on the course of the anionic polymerization of 2-ethyhexyl acrylate in 9 : 1 (v/v) toluene THF was studied. In the polymerization tert-butyl 2-lithioisobutyrate and Li tert-butoxide were used as initiator and active centre stabilizer, respectively; the alkoxide at two different concentrations. From conversion curves and number-average molecular weights of the polymers, the rate constants of the propagation and autotermination reactions were calculated. The rate constant of autotautomerization rises more rapidly with temperature than that of propagation. Consequently, at temperatures higher than -60 °C polymerization autoterminates before reaching quantitative monomer conversion. The limiting monomer conversion was higher at the higher alkoxide concentration but did not reach 100%.
Effect of Temperature History upon Stability and Melting of Poly(ethylene oxide)
Authors: Sikora Antonín , Porsch Bedřich , Pouchlý Julius
Published: April 2003

The effect of temperature history upon the distribution of molecular weights and melting points has been investigated with high-molecular poly(ethylene oxides). The results obtained by the size exclusion chromatography (SEC) and differential scanning calorimetry (DSC) have shown that a long-term annealing of high-molecular poly(ethylene oxides) results in a distinct degradation of polymeric chains. The change in distribution of molecular weights and the presence of oligomers formed by degradation markedly affect the melting points of poly(ethylene oxide). The diffusion of oligomers from crystalline into amorphous regions is manifested by a time change of melting point and crystallinity degree of poly(ethylene oxide). The degradation is also observed during X-ray measurements.
New Type of Plasticized Poly(vinyl chloride)
Authors: Kolínský Miloslav , Ševčík Stanislav , Lukáš Rudolf
Published: April 2003

Low-molecular-weight plasticizers are commonly used in the production of plasticized PVC. However, they readily migrate to the surface of the product, which results in the deterioration of physical properties and contamination of environment. This drawback is eliminated by polymerizing vinyl chloride in water suspension in the presence of a polyester plasticizer and structure stabilizer such as triallyl isocyanurate or the ethylene/vinyl acetate copolymer. The data obtained from water and heptane extractions demonstrate a low extractability of the plasticizer used. Attention is focused on the explanation of the role of structure stabilizers in the polymerization process, and some properties of this new type of plasticized PVC and its possible application areas are discussed.
Behaviour of Human Blood Serum Orosomucoid (Acid α1-Glycoprotein) in the Presence of Small Aliphatic Alcohols
Authors: Karpenko Vladimír , Šinkorová Ludmila , Janáčková Ludmila
Published: April 2003

The influence of both methanol and ethanol on the stability of orosomucoid molecule was studied over a broad range of alcohol concentrations (volume fraction 0 - 70%) and pH between 7 and 12. The data obtained by optical methods were compared with information from prediction studies which were focused on the structural features and physicochemical parameters of amino acid in the orosomucoid molecule. From this analysis the following conclusions can be drawn: (i) ethanol exerts a more pronounced effect on α-helix formation than methanol does, (ii) at higher pH the electrostatic contribution is the crucial effect in the destabilization of the orosomucoid molecule, (iii) out of 12 phenylalanines in the orosomucoid molecule only 1 - 2 are exposed to the solvent; of the residues which are not subjected to substitution appears to be Phe 141, (iv) its neighbor, Tyr 142, appears to be a key residue, the dissociation of which destabilizes one of two longer helical segments of the orosomucoid molecule, (v) the limits of applicability of the four-derivatives of UV spectra with respect to phenylalanines were examined; analysis of the data is recommended on a more precise mathematical basis, taking into consideration the bandwidth of the spectral peaks.
Synthesis of Luminophoric Derivatives of PBD Based on 2,5-Diaryl Substituted Thiazoles and Oxazoles
Authors: Lhoták Pavel , Kurfürst Antonín
Published: April 2003

The Friedel-Crafts acylation of 2-(biphenyl-4-yl)-5-phenyl-1,3,4-oxadiazole (PBD) with hippuryl chloride has been used to prepare the derivative V which on cyclization with POCl3 or P4S10 gives the respective oxazole (or thiazole) derivative of PBD, XIa or XIb. The reaction of carboxylic acid II with 4-(o-aminoacetyl)biphenyl in the presence of CDI gives N-acyl-α-aminoketone VII; the analogous compound VI has been prepared by acylating of o-aminoacetophenone with acyl chloride III. The cyclization of these compounds gives bifluorophores Xa - Xd.
Determination of Diffusion Coefficients of Gases Through a Flat Polymeric Membrane by the Method of Non-Linear Regression
Authors: Dušek Václav , Šípek Milan , Sunková Pavla
Published: April 2003

Non-linear regression was applied for calculation of diffusion coefficients of gases through a flat polymeric membrane from the experimental data obtained by the flow permeation method with the thermal conductivity detection of composition of gaseous mixture. to verify this method a polyethylene and carbon dioxide was chosen. Diffusion coefficients of carbon dioxide in the low-density polyethylene of two different thickness at the temperature of 25 °C were determined with precision about ±2.5% in agreement with literature.
Electrochemical Reduction of 1-Halo-2-butenes in Dimethylformamide
Authors: Casado Juan , Culleré José R. , Julià Montserrat , Brillas Enrique
Published: April 2003

The electrochemical reduction of 1-bromo-2-butene and 1-chloro-2-butene in DMF at a Hg electrode has been studied by polarography, cyclic voltammetry (CV), a rotating ring-disc electrode and controlled-potential coulometry. A CV study using a gold electrode has also been carried out for these compounds to identify the detected intermediates. Two consecutive one-electron reduction processes are found for 1-bromo-2-butene in polarography and in CV using Hg electrode. The first process is initiated by the irreversible one-electron cleavage of the carbon-bromo bond to give the allyl radical and Br-, which is the rate-determining step. The second one follows a first-order EC mechanism, being initiated by generation of the allylmercury anion via a one-electron reduction of the allylmercury radical, previously formed by reaction of the allyl radical with Hg. A single irreversible two-electron process is found for 1-chloro-2-butene under all voltammetric conditions and for both compounds in CV using a gold electrode. Additional anodic peaks detected in CV, as well as anodic waves found at the rotating Hg ring electrode, are ascribed to oxidation of the allylmercury anion and the allyl anion.
Alkaline Hydrolysis of Substituted Phenyl Acetates Catalyzed by Quaternary Ammonium Salts
Authors: Kulič Jiří , Sussenbek Jiří , Ptáček Aleš
Published: April 2003

Alkaline hydrolysis if the phenyl acetates CH3COOC6H4X (X = 4-NO2, 3-NO2, 3-Cl, H, 4-CH3, 3-CH3, and 4-OCH3) in the presence of hexadecyltris(2-hydroxyethyl)ammonium chloride, bis(2-hydroxyethyl)hexadecyl(methyl)ammonium bromide, and hexadecyltrimethylammonium bromide has been studied. Comparison of the rates of the hydrolysis for the above tenzides showed that the most efficient catalyst is the hexadecyltris(2-hydroxyethyl)ammonium chloride. In all cases, the rate data correlated well with structure effects by the Hammett equation.
New Groups of Potential Antituberculotics: 3-Aryl-2H,4H-benz[e][1,3]oxazine-2,4-diones. Comparison of the Topliss Approach with Regression Analysis
Authors: Waisser Karel , Kubicová Lenka , Klimešová Věra , Odlerová Želmíra
Published: April 2003

3-Phenyl-2H,4H-benz[e][1,3]oxazine-2,4-dione (I) and its derivatives II - XI, substituted on the phenyl ring, can be regarded as a new group of potential antituberculotics. Their activity increases with increasing electron-accepting properties of the substituents. introduction of bromine into the position 6 also positively influences the activity. the compounds are active in vitro against Mycobacterium tuberculosis and M. kansasii. The activity of some of them (VIII, IX0 exceeds that of commercial tuberculostatics used as standards.
Continuity for multi-type branching processes with varying environments
Authors: Dafydd Jones Owen
Published: April 2003

Conditions are derived for the components of the normed limit of a multi-type branching process with varying environments, to be continuous on (0, ∞). The main tool is an inequality for the concentration function of sums of independent random variables, due originally to Petrov. Using this, we show that if there is a discontinuity present, then a particular linear combination of the population types must converge to a non-random constant (Equation (1)). Ensuring this can not happen provides the desired continuity conditions.
Extinction of population-size-dependent branching processes in random environments
Authors: Wang Han-xing
Published: April 2003

We generalize a population-size-dependent branching process to a more general branching model called the population-size-dependent branching process in random environments. For the model where {Zn}n≥0 is associated with the stationary environment ξ− = {ξn}n≥0, let B = {ω : Zn(ω) = for some n}, and q(ξ−) = P(B | ξ−, Z0 = 1). The result is that P(q(̅ξ) = 1) is either 1 or 0, and sufficient conditions for certain extinction (i.e. P(q(ξ−) = 1) = 1) and for non-certain extinction (i.e. P(q(ξ−) < 1) = 1) are obtained for the model.
Stationarity of a stochastic population flow model
Authors: Stadje Wolfgang
Published: April 2003

We consider a classical population flow model in which individuals pass through n strata with certain state-dependent probabilities and at every time t = 0,1,2,…, there is a stochastic inflow of new individuals to every stratum. For a stationary inflow process we prove the convergence of the joint distribution of group sizes and derive the limiting Laplace transform.
On spectral gap estimates of a Markov chain via hitting times and coupling
Authors: Meise Christian
Published: April 2003

Well-known inequalities for the spectral gap of a discrete-time Markov chain, such as Poincaré's and Cheeger's inequalities, do not perform well if the transition graph of the Markov chain is strongly connected. For example in the case of nearest-neighbour random walk on then-dimensional cube Poincaré's and Cheeger's inequalities are off by a factorn. Using a coupling technique and a contraction principle lower bounds on the spectral gap can be derived. Finally, we show that using the contraction principle yields a sharp estimate for nearest-neighbour random walk on then-dimensional cube.
Prediction of shot noise
Authors: Lund Robert B. , Butler Ronald W. , Paige Robert L.
Published: April 2003

Prediction of future values of a shot noise process observed on a discrete lattice of points is considered. The shot magnitudes are assumed to be independent and identically distributed and to arrive via a Poisson process; the effect of each shot dissipates and/or accumulates according to a known shot function. Conditional mean and linear point predictors of future process values are developed. Distributional prediction, obtained through saddlepoint approximation of the conditional distributions of the process, is also explored.
Central limit theorems for multivariate semi-Markov sequences and processes, with applications
Authors: Ball Frank
Published: April 2003

In this paper, central limit theorems for multivariate semi-Markov sequences and processes are obtained, both as the number of jumps of the associated Markov chain tends to infinity and, if appropriate, as the time for which the process has been running tends to infinity. The theorems are widely applicable since many functions defined on Markov or semi-Markov processes can be analysed by exploiting appropriate embedded multivariate semi-Markov sequences. An application to a problem in ion channel modelling is described in detail. Other applications, including to multivariate stationary reward processes, counting processes associated with Markov renewal processes, the interpretation of Markov chain Monte Carlo runs and statistical inference on semi-Markov models are briefly outlined.
The distribution of general final state random variables for stochastic epidemic models
Authors: Ball Frank , O'Neill Philip
Published: April 2003

In this paper we introduce the notion of general final state random variables for generalized epidemic models. These random variables are defined as sums over all ultimately infected individuals of random quantities of interest associated with an individual; examples include final severity. By exploiting a construction originally due to Sellke (1983), exact results concerning the final size and general final state random variables are obtained in terms of Gontcharoff polynomials. In particular, our approach highlights the way in which these polynomials arise via simple probabilistic arguments. For ease of exposition we focus initially upon the single-population case before extending our arguments to multi-population epidemics and other variants of our basic model.
On the time-dependent occupancy and backlog distributions for the GI/G/∞ queue
Authors: Ayhan H. , Limon-Robles J. , Wortman M. A.
Published: April 2003

We consider an infinite server queueing system. An examination of sample path dynamics allows a straightforward development of integral equations having solutions that give time-dependent occupancy (number of customers) and backlog (unfinished work) distributions (conditioned on the time of the first arrival) for the GI/G/∞ queue. These integral equations are amenable to numerical evaluation and can be generalized to characterize GIX/G/∞ queue. Two examples are given to illustrate the results.
On overshoots and hitting times for random walks
Authors: Bertoin Jean
Published: April 2003

Consider an oscillating integer valued random walk up to the first hitting time of some fixed integer x > 0. Suppose there is a fee to be paid each time the random walk crosses the level x, and that the amount corresponds to the overshoot. We determine the distribution of the sum of these fees in terms of the renewal functions of the ascending and descending ladder heights. The proof is based on the observation that some path transformation of the random walk enables us to translate the problem in terms of the intersection of certain regenerative sets.
A new stochastic model of microsatellite evolution
Authors: Durrett Richard , Kruglyak Semyon
Published: April 2003

We introduce a continuous-time Markov chain model for the evolution of microsatellites, simple sequence repeats in DNA. We prove the existence of a unique stationary distribution for our model, and fit the model to data from approximately 106base pairs of DNA from fruit flies, mice, and humans. The slippage rates from the best fit for our model are consistent with experimental findings.
Large deviations for the time of ruin
Authors: Nyrhinen Harri
Published: April 2003

Let {Yn | n=1,2,…} be a stochastic process and M a positive real number. Define the time of ruin by T = inf{n | Yn > M} (T = +∞ if Yn ≤ M for n=1,2,…). We are interested in the ruin probabilities for large M. Define the family of measures {PM | M > 0} by PM(B) = P(T/M ∊ B) for B ∊ ℬ (ℬ = Borel sets of ℝ). We prove that for a wide class of processes {Yn}, the family {PM} satisfies a large deviations principle. The rate function will correspond to the approximation P(T/M ≈ x) ≈ P(Y⌈xM⌉/M ≈ 1) for x > 0. We apply the result to a simulation problem.
Asymptotic distribution of sum and maximum for Gaussian processes
Authors: Ho Hwai-Chung , McCormick William P.
Published: April 2003

Let {Xn, n ≥ 0} be a stationary Gaussian sequence of standard normal random variables with covariance function r(n) = EX0Xn. Let Under some mild regularity conditions on r(n) and the condition that r(n)lnn = o(1) or (r(n)lnn)−1 = O(1), the asymptotic distribution of is obtained. Continuous-time results are also presented as well as a tube formula tail area approximation to the joint distribution of the sum and maximum.
Local risk minimization and numéraire
Authors: Biagini F. , Pratelli M.
Published: April 2003

The ‘change of numéraire’ technique has been introduced by Geman, El Karoui and Rochet for pricing and hedging contingent claims in the case of complete markets. In this paper we study the ‘change of numéraire’ using the ‘locally risk-minimizing approach’, when the market is not complete. We prove that, if the stochastic process which represents the prices is continuous, the l.r.m. strategy is invariant by a change of numéraire (this result is false in the right-continuous case, as is shown by some counterexamples).

We also give an extension of Merton's formula to the case of stochastic volatility.
Heavy traffic analysis of a queueing system with bounded capacity for two types of customers
Authors: Perry David , Stadje Wolfgang
Published: April 2003

We study a service system with a fixed upper bound for its workload and two independent inflows of customers: frequent ‘small’ ones and occasional ‘large’ ones. The workload process generated by the small customers is modelled by a Brownian motion with drift, while the arrival times of the large customers form a Poisson process and their service times are exponentially distributed. The workload process is reflected at zero and at its upper capacity bound. We derive the stationary distribution of the workload and several related quantities and compute various important characteristics of the system.
Minimizing response times and queue lengths in systems of parallel queues
Authors: Koole Ger , Sparaggis Panayotis D. , Towsley Don
Published: April 2003

We consider the problem of routeing customers to one of two parallel queues. Arrivals are independent of the state of the system but otherwise arbitrary. Assuming that queues have infinite capacities and the service times form a sequence of i.i.d. random variables with increasing likelihood ratio (ILR) distribution, we prove that the shortest queue (SQ) policy minimizes various cost functionals related to queue lengths and response times. We give a counterexample which shows that this result is not generally true when the service times have increasing hazard rate but are not increasing in the likelihood rate sense. Finally, we show that when capacities are finite the SQ policy stochastically maximizes the departure process and minimizes the loss counting process.
Swords into Plowshares: Nuclear Weapon Dismantlement, Evaluation, and Maintenance at Pantex
Authors: Kjeldgaard Edwin A. , Jones Dean A. , List George F. , Turnquist Mark A. , Angelo James W. , Hopson Richard D. , Hudson John , Holeman Terry
Published: April 2003

The end of the Cold War changed the missions of facilities in the US nuclear weapons complex. They ceased production of new weapons and focused on dismantling old weapons and maintaining the safety, security, and reliability of those remaining. The Pantex Plant, operated for the US Department of Energy (DOE) by the Mason and Hanger Corporation, is the sole assembly and disassembly facility for dismantlement, evaluation, and maintenance activities for the US nuclear stockpile. We developed a decision support tool, the Pantex Process Model (PPM), to help Pantex plan capacity and deploy resources to meet its new requirements. Using the PPM, Pantex has provided critical input to help the US form and defend positions during arms-control-treaty negotiations. It has changed the way Pantex and the DOE evaluate resource requirements in planning future workloads. It has also led to an innovative cooperative agreement among Pantex, the Transportation Safeguards Division of DOE, and the Department of Defense (DOD) that resulted in Pantex exceeding weapon-dismantlement goals.
OR Helps the Poor in a Controversial Irrigation Project
Authors: Appa Gautam , Sridharan R.
Published: April 2003

In 1991, the World Bank was forced to appoint a team to conduct an independent review of the human and environmental impact of a mega-dam and water-distribution project on the river Narmada in India. The review team asked us to help assess the problems caused by the 75,000-km canal network being built for the project. We combined spreadsheet modeling with insights gained from a rapid rural appraisal to prepare both quantitative and qualitative findings and recommendations, many of which have been vindicated by later research and events. The review team used all our findings in a damning report, which led to the World Bank withdrawing from the project. Taking into account the review team's report, the Supreme Court of India has put a ban on the continuation of the project until it is satisfied that the project authorities have taken care of all the human problems of rehabilitation and resettlement.
TransAlta Redesigns Its Service-Delivery Network
Authors: Erkut Erhan , Myroon Tony , Strangway Kevin
Published: April 2003

TransAlta Utilities (TAU), Canada's largest publicly owned electric utility company, wanted to reduce costs and improve service, establish a call center, and redesign its service-delivery network. To help TAU locate service facilities, determine staffing levels, cluster facilities into call pools, locate equipment, and evaluate the impact of customers performing their own operations and maintenance, we used facility-location and vehicle-routing heuristics, multiple regression, cost/benefit analysis, and a geographical information system. We worked closely with TAU management, and TAU has implemented most of our recommendations.
Supply-Chain Management for Recoverable Manufacturing Systems
Authors: Guide V. Daniel R. , Jayaraman Vaidyanathan , Srivastava Rajesh , Benton W. C.
Published: April 2003

Recoverable manufacturing systems minimize the environmental impact of industry by reusing materials, reducing energy use, and reducing the need to landfill industrial products. These systems are widespread in the United States and are profitable, in addition to contributing to sustainable development. However, the management of supply-chain activities can differ greatly from management activities in traditional manufacturing supply chains. Seven complicating characteristics increase uncertainty. Managers must take actions to reduce uncertainty in the timing and quantity of returns, balance return rates with demand rates, and make material recovery more predictable. Managers must also plan for the collection of products from end-users. The use of information systems with new production-planning and control techniques makes management of these activities more predictable.
Product Recovery at the Norwegian National Insurance Administration
Authors: Rudi Nils , Pyke David F. , Sporsheim Per Olav
Published: April 2003

Technical aid centers (TACs) in Norway supply devices, such as wheelchairs and hearing aids, to people with handicaps. When a device is returned to a TAC, the TAC staff must decide whether to scrap it or to refurbish it so that it can be used again. The Norwegian National Insurance Administration (NNIA) found that decision makers were scrapping units too frequently, basing their decisions mainly on the hours of labor required to refurbish. We developed a more complete decision-support-system model that accounts for the full cost of sending a unit to the landfill, the cost of refurbishing, the value of parts that can be used elsewhere, the benefits of refurbishing, and so on. Our model is quite simple and visual. Early results suggest that acceptance has been widespread and that decisions have changed, leading to fewer units being scrapped and more being refurbished for redistribution.
Sustainability and Performance at Interface, Inc.
Authors: DuBose Jennifer R.
Published: April 2003

Interface, Inc., the world's leader in commercial carpet tile, also manufactures and sells 12-foot broadloom carpet, interior fabrics, access flooring, cushion backing, and specialty chemicals. The company has made a strategic commitment to sustainability and integrated this with a monetary incentive plan. The bonus plan gave concrete direction to the company's sustainability mission and sped up the implementation of projects. The company's progress toward becoming a sustainable corporation is due to a number of key factors, including top leadership, administrative direction, training, outside input, and financial scrutiny. Interface's experience shows that a well-designed incentive program can motivate employees to implement sustainability practices.
Implementing Sustainability in Service Operations at Scandic Hotels
Authors: Goodman Ann
Published: April 2003

The case of Scandic Hotels shows, first, that sustainable strategies and practices can be just as useful in service operations as in manufacturing operations; and second, that such strategies and practices can support a corporate turnaround effort. Scandic Hotels, Nordic Europe's biggest hotel chain, was on the verge of collapse in the early 1990s. A new CEO, Roland Nilsson, turned the company around by introducing two business principles, decentralized management and sustainable development. The company's new value system, embodied in the concept of sustainability, linked customers and employees, who were calling for more environmental responsibility. Through employee-training programs, environmental information systems, and innovative collaborations with suppliers, Scandic was revived within a few years as a profitable corporation well on the road to sustainability.
Supply-Chain Analysis at Volkswagen of America
Authors: Karabakal Nejat , Günal Ali , Ritchie Warren
Published: April 2003

In 1995, Volkswagen of America began a review of its vehicle-distribution system looking for opportunities to improve customer responsiveness and simultaneously reduce system costs. An analytical tool was required to evaluate alternative designs in terms of cost and customer service level, both of which are functions of probabilistic and dynamic elements. These elements include inventory policies, demand seasonality and volume, customer-choice patterns, and transportation delays. By using an innovative combination of simulation and discrete optimization models, we addressed the problem of analyzing a large number of alternatives efficiently. Our analysis indicated opportunities for significant savings in estimated annual transportation costs, and it provided insights on how to implement the proposed system.
Book Reviews
Authors: Lev Benjamin , Pinter Janos D. , Kaiser Mark , Bard Jonathan F. , Tuggle Francis D. , McNaught Ken , Barros Lilian L. , Zilinskas Antanas
Published: April 2003

The range of books reviewed is wide, covering theory and applications in operations research, statistics, management science, econometrics, mathematics, computers, and information systems (no software is reviewed). In addition, we include books in other fields that emphasize technical applications. Publishers who wish to have their books reviewed should send them to Professor Benjamin Lev. We list the books received; not all books received can be reviewed because space and time are limited. Those who would like to review books are urged to send me their names, addresses, and specific areas of expertise. We commission all reviews and do not accept unsolicited book reviews. Readers are encouraged to suggest books that might be reviewed or to ask publishers to send me copies of such books.
Improving Operations and Quoting Accurate Lead Times in a Laminate Plant
Authors: Tayur Sridhar
Published: April 2003

The important requirement of quoting short and accurate lead times to customers in industrial supply chains is a difficult challenge as it requires coordination between purchasing, order-entry, scheduling and inventory-control groups. We meet this challenge at a laminate plant where the customer demands (in timing and quantity) are variable, the production processes have uncertain yield, the variety of products is high, and manufacturing involves significant switch-over costs and times between products—through the use of inventory management with cyclic scheduling, along with many concurrent improvements in supplier management, customer relations, product design, and quality.
A Heuristic Scheduling System for Ceramic Industrial Coatings
Authors: Olson John R. , Schniederjans Marc J.
Published: April 2003

We developed and implemented a heuristic-based scheduling system for Ceramic Industrial Coatings (CIC), a large producer of paint and wood coatings in the Midwest. We experienced implementation issues and problems in the process of developing the heuristic system. The paint coating industry has unique scheduling problems. Results included a 39-percent reduction in manufacturing processing time, a 23-percent reduction in late batches, a 49-percent reduction in scrapped batches, and a 72-percent reduction in scrap cost.
Lessons for Success in OR/MS Practice Gained from Experiences in Indian and US Steel Plants
Authors: Dutta Goutam
Published: April 2003

I worked on modeling integrated steel plants in India (as an analyst) and in the USA (as a doctoral student). The following factors influence the success of OR/MS practice: positioning the OR/MS team in operations, not in research and development; selecting the right problems; emphasizing problem solving, not model building; learning from failures; the right academic and practical training; and experience working on the shop floor of a factory. Universities should teach OR as research into operations and emphasize the process of implementation.