bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrode-mediated Wacker oxidation of cyclic and internal olefins
Authors: Miller D. G. , Wayner D. D. M.
Published: May 2006

An improved method for the electrode-mediated oxidations of olefins by palladium(II) is described. Current efficiencies from 80% to 95% were obtained in oxidations of 1-decene, styrene, trans-2-octene, and cyclohexene in which perchloric acid was added to a chloride-free solution of a palladium(II) acetate catalyst. The palladium(0) was reoxidized to palladium(II) by reaction with catalytic amounts of benzoquinone, which was, in turn, regenerated by anodic oxidation. Addition of varying amounts of perchloric acid did not affect the current efficiency but accelerated the oxidation reaction, up to a concentration of approximately 0.15 M. The current efficiency remained high (>80%) over the course of the electrode-mediated oxidations of 1-decene, trans-2-octene, and cyclohexene. At the end of the reactions, when the substrate was depleted, a drastic decrease in the current was observed, indicating that the catalytic cycle leading to product was primarily responsible for the electrochemical reaction. It also was shown that the rates of the electrochemical reactions were generally slower than those of homogeneous reactions in which a stoichiometric amount of benzoquinone was used, indicating that the electrochemical regeneration of benzoquinone was mass transport limited at the highest concentrations of perchloric acid. This is in contrast to other reports in the literature that suggested that the homogeneous (non-electrochemical) reactions were actually slower. Reasons for the discrepancy between these results are discussed.
The negative 7J(CHO, CH3) in 4-methylbenzaldehyde. Ionicity of the carbonyl bond
Authors: Schaefer Ted , Sebastian Rudy
Published: May 2006

The spin–spin coupling constant over seven bonds between the formyl and methyl protons in 4-methylbenzaldehyde is −0.030 Hz in CS2/C6D12/TMS, and (−)0.035 Hz in acetone-d6, solutions at 297 K. This unexpected result is rationalized in terms of a spin–spin coupling mechanism attributed to the importance of a valence bond structure with an ionic carbonyl bond. The result again emphasizes the sensitivity to substituent perturbations of the six-bond coupling constant in quasi-planar benzaldehyde derivatives. It can have either sign and presents a challenge to its computation from first principles.
Coordination chemistry of thioether–pyridazine macrocycles II. Synthesis, structural and spectroscopic studies of dinuclear copper(II) and polynuclear copper(I) and silver(I) complexes of a tetrathiapyridazinophane macrocyclic ligand
Authors: Chen Liqin , Thompson Laurence K. , Bridson John N.
Published: May 2006

The preparation and properties of the thioether–pyridazine macrocycle (L3; C11H16N2S4) containing one pyridazine subunit, and its copper(II), copper(I), and silver(I) complexes are described. Magnetic susceptibility data (5–300 K) for the binuclear complexes [CuL3Cl2]2 (I) and [CuL3Br2]2 (II) have been fitted to the Friedberg magnetization expression with a molecular field correction. Intradimer antiferromagnetic exchange is weak (−2J < 18 cm−1), with even weaker interdimer exchange (−zJ′ < 0.3 cm−1). The complexes [CuL3Cl]x (III) and [AgL3ClO4]x (V) have been characterized by X-ray crystallography. III crystallizes in the triclinic system, space group [Formula: see text], with a = 9.410(2) Å, b = 10.291(2) Å, c = 9.208(2) Å, α = 108.56(1)°, β = 91.82(2)°, γ = 68.04(1)°, V = 780.1(2) Å3, and Z = 2(R = 0.035, Rw = 0.031 for 1856 reflections). The ligand acts as a bidentate, S2, bridge between dinuclear Cu2Cl2 units in a double stranded polymer. III crystallized in the monoclinic system, space group P21/n, with a = 9.382(4) Å, b = 19.274(4) Å, c = 10.190(3) Å, β = 106.35(3)°, V = 1768(1) Å3, and Z = 4 (R = 0.036, Rw = 0.029 for 1776 reflections). The structure consists of a polymeric, two dimensional sheet structure, involving pseudo-tetrahedral silver ions linked by exo-bidentate, S2, ligands and bidentate perchlorates.
The effect of tensioactive agents on the kinetics of hydrogen evolution at a nickel electrode
Authors: Menini Richard , Wrona Piotr K. , Ménard Hugues , Vittori Olivier
Published: May 2006

The effect of tensioactive agents (TSA = SDS, BRIJ35, BRIJ78, BRIJ99, and CTAB) on the kinetics of hydrogen evolution at a rotating nickel electrode in 0.2 M solutions of Na2SO4 was investigated. It was found that at higher concentrations of TSA, their presence inhibited the reaction although their adsorption behaviour at the nickel electrode is different. We concluded that BRIJ35 and CTAB should show better performance in the hydrogenation of organic compounds than SDS.
Stereochemistry of crown ethers, X-ray crystallographic structures, solid phase 13C NMR, and solution conformational equilibria in cis-syn-cis dicyclohexano-15-crown-5 ether and its sodium thiocyanate complex
Authors: Buchanan G W , Mathias S. , Bensimon C. , Charland J. P.
Published: May 2006

The structures of the title materials have been determined via X-ray crystallography. In the free crown ether, there is effectively a plane of symmetry that bisects the molecule. In the NaNCS complex, ring inversion of one of the cyclo-hexane moieties has occurred, giving a distorted pentagonal pyramidal coordination geometry about the sodium ion. For the free crown, two conformers, whose free energies differ by ca. 0.5 kJ / mol in solution can be detected via 13C NMR at 168 K. Limiting low-temperature solution spectra are compared to those which have been obtained in the solid phase using the 13C CPMAS technique.

Key words: crown ethers, stereochemistry, X-ray, NMR.
Synthesis and characterization of dimethyl- and dimethoxyphenylbis(N,N-dialkyldithiocarbamato)tellurium(IV) and chlorodimethyl- and chlorodimethoxyphenyl-(N,N-dialkyldithiocarbamato)tellurium(IV). Crystal structures of Me2Te[S2CNMe2]2 and (p-MeOC6H4)2Te[S2CNMe2]2
Authors: Bailey Jane H. E. , Drake John E.
Published: May 2006

The compounds Me2Te[S2CNR2]2, Me2TeCl[S2CNR2], (p-MeOC6H4)2Te[S2CNR2]2, and (p-MeOC6H4)2TeCl[S2CNR2], where R = Me, Et, have been prepared and characterised primarily by vibrational and NMR spectroscopy. Variable temperature NMR spectroscopy and qualitative time studies indicate that in solution the dimethoxyphenyltellurium derivatives undergo the reductive-elimination noted for analogous phenyl derivatives but the reductive-elimination does not occur with the dimethyl tellurium derivatives. The crystal structures of Me2Te[S2CNMe2]2, 1, and (p-MeOC6H4)2-Te[S2CNMe2]2, 5, were completed. The cell parameters for 1, which crystallizes as monoclinic in space group P21/n, are a = 13.550(2), b = 13.034(2), c = 17.854(2) Å, β = 106.61(1)°, V = 3021.6(7) Å3, Z = 8, R = 0.0368, and Rw = 0.0402 and for 5, which crystallizes as monoclinic in space group C2/c, are a = 35.36(1), b = 11.063(3), c = 12.778(3) Å, β = 96.16(3)°, V = 4963(3) Å3, Z = 8, R = 0.0627, and Rw = 0.0646.
Reaction de méthanation du gaz de synthèse: Influence de la température de calcination des catalyseurs à base de nickel
Authors: Ghazi M. , Barrault J.
Published: May 2006

Due to their important activity and selectivity, nickel catalysts are often used to realize the methanation reaction; however, the usual process based on these catalysts is not fitted for the present economic situation. To raise their stability, three catalysts with similar nickel content but calcinated at different temperatures have been studied for the reaction of methanation. The results obtained show that the catalyst calcinated at the highest temperature (973 K) shows the greatest promise because a great part of its activity and of its stability is preserved even when the reaction conditions are extreme (temperature of 773 K).
A simple quality test for self-consistent-field atomic orbitals
Authors: Desmarais N. , Dancausse G. , Fliszár S.
Published: May 2006

A quality test is proposed for SCF atomic orbitals, [Formula: see text] approximated as finite linear combinations of suitable basis functions [Formula: see text] The key is in a function, readily derived from the Hartree–Fock equation [Formula: see text] which is identically zero for true Hartree–Fock spin orbitals and not so for approximate orbitals. In this way, our test measures how closely approximate orbital descriptions approach the true Hartree–Fock limit and thus provides a quality ordering of orbital bases with respect to one another and with respect to that limit, in a scale uniquely defined by the latter. Moreover, this analysis also holds for atomic subspaces of our choice, e.g., the valence region. Examples are offered for representative collections of Slater- and Gaussian-type orbital expansions.
Ab initio study of the structure of the hydrogen maleate anion
Authors: Ríos Miguel A. , Rodríguez Jesús
Published: May 2006

The hydrogen maleate ion was studied by ab initio methods with complete optimization at the 3-21G, 6-31G, 6-31G**, and 6-31+G(2d,1p) levels. To study the influence of electron correlation, MP2 calculations have been done for the 6-31G** geometry. All calculations at the HF level predicted an asymmetric hydrogen bond with a double minimum potential governing transfer between the two equivalent structures. Moreover, both asymmetry and proton transfer barrier increase systematically with the power of the basis set used, with calculated barrier heights of 0.12 (3-21G), 1.59 (6-31G), 1.64 (6-31G**), and 2.00 kcal/mol (6-31+G). Only the introduction of the electron correlation at the MP2 level seems to predict a single minimum potential.
The chemistry of 5β,6β-epoxy-4,4-dimethylcholest-1-en-3-one. Approaches to the synthesis of 1α,5α-cyclosteroids. Part II
Authors: Georghiou Paris E. , Ren Yi
Published: May 2006

Epoxidation of 4,4-dimethylcholesta-1,5-dien-3-one (9) with MCPBA gives a mixture of the corresponding epimeric 5α,6α and 5β,6β epoxides. The major product is the 5β,6β epimer 6, in contradiction to what has been reported by others. The unambiguous assignment of the structures of these epoxides is based upon NMR NOED experiments. The chemistry of the 5β,6β epoxide is described in the context of unsuccessful attempts at synthesizing the corresponding 1α,5α cyclosteroids. Reductive methods using lithium – liquid ammonia, lithium–ethylamine, or tri-n-butyl- or tri-phenyltin–AIBN gave products in which the α,β-unsaturated carbonyl system and the epoxide were reduced. When 6 was treated with BF3•etherate a B-nor derivative 27 was formed, presumably via a pinacol-type rearrangement.
2′-O-Methyl-cis-adenosine 3′,5′-cyclic methyl monophosphate, a new model system for cAMP. Aspects of structure and reactivity
Authors: Broeders Niek L.H.L. , Heiden Arthur P. van der , Koole Leo H. , Kanters Jan A. , Schouten Arie
Published: May 2006

This study is focussed on 2′-O-methyl-cis-adenosine 3′,5′-cyclic methyl monophosphate (cis-4; cis describes the relationship between OMe (bound to phosphorus) and the adenine base), which is regarded a model for enzyme-bound cyclic adenosine monophosphate (cAMP). In this complex the negative phosphate charge is shielded in part via complexation with cationic sites on the enzyme surface. We report synthesis, crystal structure, solution conformation (400 MHz 1H NMR), and kinetic-mechanistic aspects of the alkaline hydrolysis of cis-4. The methanol solvate of cis-4 crystallizes in the orthorhombic space group P212121 and the cell dimensions are a = 8.170(2) Å, b = 9.249(1) Å, c = 23.699(4) Å; V = 1788.5(6) Å3; Z = 4 molecules per cell. Least-squares refinement converged at R = 0.062 for 2006 observed reflections. The adenine bases are linked via [Formula: see text] and [Formula: see text] hydrogen bonds in such a way that infinite one-dimensional chains are formed. This hydrogen bond scheme is very similar to that observed in the structure of 2′-deoxy-3′,5′-di-O-acetyl adenosine. An additional hydrogen bond is formed between methanol, incorporated in the crystal structure, and the adenine base. The conformational preferences of the cis-4 dissolved in methanol have been determined with 400 MHz 1H NMR. It is found that the conformations observed in the solid and solution states are practically the same. Hydrolysis of the title compound yields two acyclic phosphate diesters (a 3′- and a 5′-phosphate diester). The intermediates formed during the hydrolysis reaction are most likely five-coordinated phosphorus (PV) compounds with a trigonal bipyramidal geometry and an equatorial-axial located 3′,5′-dioxaphosphorinane ring.
Solvent effects on the reactivity of solvated electrons with ammonium and nitrate ions in 1-butanol–water solvents
Authors: Chen Ruzhong , Freeman Gordon R.
Published: May 2006

Values of the rate constants, k2 (106 m3 mol−1 s−1), of solvated electrons,[Formula: see text] with several related salts, in pure water and pure 1-butanol solvents at 298 K are, respectively, as follows: LiNO3, 9.2, 0.19; NH4NO3, 10, 8.3; NH4ClO4, 1.5 × 10−3, 12 in 20 mol% water; LiClO4, 1.0 × 10−4, < 1.0 × 10−4. The value of [Formula: see text] in water solvent is 48 times larger than that in 1-butanol solvent, whereas [Formula: see text] in water is 10−4 times smaller than the value in 1-butanol. This enormous reversal of solvent effects on [Formula: see text] reaction rates is the first observed for ionic reactants. The solvent participates chemically in the [Formula: see text] reaction, and the overall rate constant increases with increasing viscosity and dielectric relaxation time. This unusual behavior is attributed to a greatly increased probability of reaction of an encounter pair with increasing duration of the encounter. Effective reaction radii κRr for [Formula: see text] and [Formula: see text] were estimated with the aid of measured electrical conductances of the salt solutions in all the solvents. Values of κRr are (2–7) × 10−10 m, except for NH4,s+ in 100 and 99 mol% water, which are 2.6 and 2.7 × 10−14 m, respectively. The effective radii of the ions for mutual diffusion increase with increasing butanol content of the solvent, from ~50 pm in water to ~150 pm in 1-butanol, due to the increasing average size of the molecules that solvate the ions.
Photochemistry of lignin model compounds on solid supports
Authors: Hurrell L. , Johnston L.J. , Mathivanan N. , Vong D.
Published: May 2006

The photochemistry of several substituted α-(aryloxy)acetoveratrones that are models for chromophores in lignin has been studied using a combination of laser flash photolysis and product studies in solution and on silica, Na-X zeolite, and cellulose. The lifetimes of the triplet ketones vary substantially with the electron-donating ability of the substituents in the α-aryloxy ring, with values ranging from 30 ns for the 4-methoxy derivative to 5.5 µs for the 4-cyano ketone in acetonitrile. The triplet ketones are considerably longer lived on a silica surface than in solution and do not decay with first-order kinetics; however, they are all shorter lived than triplet acetoveratrone under the same conditions, indicating that β-phenyl quenching and (or) β-cleavage dominate their decay. The same triplets show quite different kinetic behavior in Na-X or cellulose and there is no indication in these systems for the importance of either β-phenyl quenching or β-cleavage in determining the rates of triplet decay. Product studies for α-guaiacoxyacetoveratrone indicate that β-cleavage from the singlet excited state is responsible for product formation; in contrast to solution results, the phenacyl–phenoxyl radical pairs react exclusively by geminate recombination to give rearranged ketones resulting from ortho and para ring coupling of the two radicals. Product formation is very inefficient for this ketone in cellulose, indicating either a low singlet reactivity or efficient geminate recombination of the initial radical pair to regenerate starting material.
Novel quinazolinones and enniatins from Fusarium lateritium Nees
Authors: Tsantrizos Youla S. , Xu Xiao-Jin , Sauriol Françoise , Hynes Rosemary C.
Published: May 2006

Fusarium lateritium Nees is a natural antagonist of the plant pathogen Eutypa armeniacae. In an effort to show that this biological phenomenon is chemically mediated, the bioactive metabolites of F. lateritium were investigated. The cytotoxic alkaloids 2-(1-hydroxyethyl)-4(3H)quinazolinone (1) and 2-acetyl-4(3H)quinazolinone (2), and the three cyclohexadepsipeptides, enniatins B (3), B1 (4), and A1 (5), were isolated and characterized. Metabolites 3, 4, and 5 were found to exhibit strong antifungal activity against E. armeniacae. The structures of the novel metabolites 1 and 2 were elucidated by spectroscopic analysis and that of 2 was confirmed by X-ray crystallography. The absolute stereochemistry of 1 was investigated by 1H and I9F NMR analysis of its Mosher ester derivative.
The E1Σ+–X1Σ+ system of GeS in emission
Authors: Balfour Walter J. , Shetty Belvai J.
Published: May 2006

A new group of bands has been observed in emission in the 500–600 nm region under conditions that generate known systems of GeS. It has been deduced from the appearance and position of the bands, and from their intensity distribution, that these bands constitute the long-wavelength component of the E1Σ+–X1Σ+ system of GeS, which gives rise to strong absorption and emission in the ultraviolet. E–X Franck–Condon factors have been estimated.
Molecular motion of guests trapped in N-methyl-1,3-diaminopropanecadmium(II) tetracyanonickelate(II) host lattices
Authors: Nishikiori Shinichi , Ratcliffe Christopher I. , Ripmeester John A.
Published: May 2006

The molecular motion of guest molecules in Cd(mtn)Ni(CN)4•0.5G clathrates (mtn = N-methyl-1,3-diaminopropane, G = toluene, nitrobenzene, dichloromethane, and chloroform) were studied by using CP/MAS 13C and 2H NMR techniques. At room temperature, application of 13C CP/MAS NMR with dipolar dephasing showed the presence of large amplitude molecular motion in all cases. Temperature dependent 2H NMR spectra for the toluene-d8 clathrate shows that the methyl group rotated at all temperatures down to 77 K. Also, a 2-site in-plane reorientation process of the entire molecule is activated above 180 K, which goes over into axially symmetric in-plane rotation around 450 K. Severely restricted motions were also observed for the nitrobenzene and haloalkane guests. The rather complicated dynamic behaviour of the guest molecules at low and room temperatures can be attributed to the presence of static disorders which disappear at higher temperatures due to time averaging.
Evaluation of organic compounds as new cathode active materials in primary cell systems
Authors: Udhayan R. , Bhatt Devendra P.
Published: May 2006

The performance characteristics of magnesium/trichloroisocyanuric acid (Mg/TCIA) and magnesium/trichloromelamine (Mg/TCM) cells have been reported in this paper. These cells show higher open circuit (>2.5 V) and working voltages (>2.0 V) than known primary organic cells such as magnesium/meta-dinitrobenzene (OCV: 1.5 V; CCV: 1.0 V). The capacity, energy density, and coulombic efficiency of these cells are calculated using the galvanostatic technique and the results are compared with magnesium/dichloroisocyanuric acid (Mg/DCIA) cell.
On the role of hexafluoroisopropanol in Diels–Alder reactions of acid-sensitive reagents
Authors: Cativiela Carlos , García José I. , Mayoral José A. , Salvatella Luis
Published: May 2006

1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP) is described as an excellent solvent for those Diels–Alder reactions in which Lewis-acid-sensitive reagents are used, leading to high yields with good regio- and endo/exo selectivities under very mild conditions.
Fluorimetric measurement of the activity of surface-immobilized monolayers of enzyme using a dual emission probe
Authors: Brennan John D. , Kukavica Vanja , Kallury Krishna M.R. , Krull Ulrich J.
Published: May 2006

A sensitive assay for measurement of the activity of hydrolase enzymes that are immobilized onto quartz and silicon dioxide surfaces was developed. Measurements are based on the changes of the fluorescence properties of the probe carboxy-seminaptharhodafluor-X that are caused by pH variations associated with the reaction of urea with urease. The results indicated a loss of activity in 8 days, and a half-life of 3 days, when urease was immobilized onto quartz surfaces that were first derivatized with a 16-carbon spacer chain.
Interligand interaction in ternary complexes of Zn(II) and Cd(II) with dipeptides and aminoacids
Authors: Vaidyan Alexander Varghese , Bhattacharya Pabitra K.
Published: May 2006

The stability constants of binary and ternary complexes [MA], [Ma2], and [MAL] (where M = Zn(II) or Cd(II); A = glycylglycine, glycyl L-alanine, glycyl L-leucine; L = α-alanine phenylalanine, tyrosine, tryptophan, or L-histidine) in aqueous medium have been determined potentometrically at 25 °C and an ionic strength of 0.2 M NaClO4 (0.2 mol dm−3) using a computer system. It is observed that Δ log K of MAL complexes has low negative or positive values. Probable reasons have been discussed.
Excess enthalpies of some (1-propanol + methyl tert-butyl ether + C6-hydrocarbon) ternary systems at 298.15 K
Authors: Zhu Shemin , Shen Shubao , Benson George C. , Lu Benjamin C.-Y.
Published: May 2006

Calorimetric measurements of excess enthalpies are reported for the three ternary systems (1-propanol + methyl tert-butyl ether + (n-hexane, or 2,3-dimethylbutane, or cyclohexane)) at 298.15 K. Smoothing equations, fitted to the results, were used to construct constant enthalpy contours on a Roozeboom diagram for each of the systems.
Synthesis of tridentate amine Pt(II) complexes and study of their reactions with purine and pyrimidine bases
Authors: Rochon Fernande D. , Laperrière Guylaine
Published: May 2006

Complexes of the type [Pt(L)X] where L is a tridentate N ligand and X = Cl or I, were synthesized and characterized. Three of the ligands are N-derivatives of diethylenetriamine, (2-aminoethyl)(N-dimethyl-2-aminoethyl)amine, (2-aminoethyl)(N-diethyl-2-aminoethyl)amine, and (2-aminoethyl)(N-methyl-2-aminoethyl)N-methylamine. The other two ligands are di(3-amino-propyl)amine and (2-aminoethyl)(3-aminopropyl)amine. A new method for the synthesis of the chloro complexes from the direct reaction of the amine with K2[PtCl4] was developed. The reactions of these five compounds with several purine and pyrimidine bases were studied by NMR techniques. The Pt(II) complexes containing two five-membered chelates were shown to be more reactive than the one containing two six-membered rings, while the complex containing one five- and one six-membered chelates showed intermediate reactivity. For the diethylenetriamine derivatives, the complexes containing ligands with two alkyl groups on the same terminal N atom were more reactive than the one containing one methyl group on a terminal N atom and one methyl group on a non-terminal N atom.
Metal ion complexes of 1,4,7-triazacyclononane and their aminoalkyl derivatives. Analysis of chelate rings fusion and molecular mechanics study
Authors: Pletnev Igor V.
Published: May 2006

Stereochemistry of metal ion complexes of 1,4,7-triazacyclononane, their N,N′,N′′-tris(aminoethyl), tris(aminopropyl), and their N,N′-(4,7-diazadecylene) derivatives is described in terms of the fusion of chelate rings at metal–nitrogen coordination bonds. Molecular mechanics calculations and analysis of the X-ray data confirm that the semi-quantitative analysis is valid and that fusion plays a critical role in the structure of the complexes. Molecular mechanics study of puckering of the ethylenediamine chelate ring, an essential part in this study, is also presented.
Preparation and analysis of some acetosugar esters of abscisic acid and derivatives
Authors: Balsevich J. , Bishop G. , Jacques S.L. , Hogge L.R. , Olson D.J.H. , Laganière N.
Published: May 2006

Racemic abscisic acid (ABA), the cis and trans 1′, 4′-diols (ABA diols) derived from ABA by reduction of the 4′ ketone, and the corresponding 4′-O-acetates were converted into various acetosugar esters by reaction of their cesium salts with the 1-chloroacetosugars derived from glucose, galactose, lactose, and maltose. Analytical separations of the acetosugar esters using high-performance liquid chromatography (LC) on reverse-phase columns were developed. Continuous flow secondary ion mass spectra (CFSIMS) of the various acetosugar esters were obtained and an LC/CFSIMS protocol employing multiple reaction monitoring was used to detect ABA acetoglucose ester in an acetylated extract obtained from plant cells that had been treated with ABA. Key words: abscisic acid, acetosugar esters, synthesis, chromatography, mass spectrometry.
Transition state stabilization by micelles: the hydrolysis of p-nitrophenyl alkanoates in cetyltrimethylammonium bromide micelles
Authors: Tee Oswald S. , Fedortchenko Alexei A.
Published: May 2006

The cleavage of p-nitrophenyl alkanoates (acetate to octanoate) at high pH is modestly catalyzed by micelles formed from cetyltrimethylammonium bromide (CTAB) in aqueous solution. Rate constants exhibit saturation behaviour with respect to [CTAB], consistent with substrate binding in the micelles. The strength of substrate binding and transition state binding to the micelles increases monotonically with the acyl chain length, and with exactly the same sensitivity. As a result, the extent of acceleration (or catalytic ratio) is independent of the ester chain. These and earlier results are consistent with the reaction centre being located in the Stern layer of the micelle, with the acyl chain of the ester being directed into the hydrophobic micellar interior. The chain length dependence of kinetic parameters found in this work is comparable to that found previously for ester cleavage by cyclodextrins and by various enzymes with hydrophobic binding sites, as well as to that observed for other phenomena involving hydrophobic effects. Keywords: catalysis, ester hydrolysis, micelles, transition state.
Using O(
n
) ProxmapSort and O(1) ProxmapSearch to motivate CS2 students (Part I)
Authors: Standish Thomas A. , Jacobson Norman
Published: May 2006

Presenting "cool" algorithms to CS2 students helps convince them that the study of data structures and algorithms is worthwhile. An algorithm is perceived as cool if it is easy to understand,
very
fast on large data sets, uses memory judiciously and has a straightforward, short proof --- or at least a convincing proof sketch --- using accessible mathematics. To illustrate, we discuss two related and relatively unknown algorithms: ProxmapSort, discussed here, and ProxmapSearch, to be discussed in Part II.
Stanislavski and computer science
Authors: Klinger William J.
Published: May 2006

Computer science concepts can be difficult for new students to grasp fully. As educators, we look for ways to give our students not only an understanding of a concept but also insight. In the acting profession, actors face a similar situation where they need to understand their characters in depth. The method of having an actor "become" a character is one that can also be applied to computer science education. This paper explores the method of having computer science students "become" a concept and act out their roles. This method has been very effective in helping students gain insights into computer science concepts.
Development of XML-based tools to support user interaction with algorithm visualization
Authors: Naps Thomas , Rößling Guido , Brusilovsky Peter , English John , Jarc Duane , Karavirta Ville , Leska Charles , McNally Myles , Moreno Andrés , Ross Rockford J. , Urquiza-Fuentes Jaime
Published: May 2006

As a report of a working group at ITiCSE 2005, this paper represents a vision of the use of XML specifications and tools in algorithm visualization, particularly with regard to supporting user interaction. A detailed description is given of how an interesting event to be visualized is decomposed, combined with interactive questions, narratives, control flow code and metadata, and finally rendered into graphical primitive and transformation specifications. The heart of the paper is our discussion of XML specifications for content generation (the object being visualized), interactive questions, and graphical primitives and transformations, with briefer discussions of narratives and metadata. Examples are provided for each in an appendix, with fuller details to be published on an associated website that we hope will become a source of future standards in this area. In conclusion, the approach of the working group is discussed, and important remaining challenges are identified.
University of Washington implementation
Authors: Zosel Mary
Published: May 2006

APL/B5500, as implemented by Computer Science students at the University of Washington, is designed to service eight remote model 33 teletypes on the B5500 while allowing background processing to proceed normally. The implementation uses reserved words for operators. The transliteration chosen (see attached page) omits several obvious characters, including>, <, !,?, because these characters have special control functions on the B5500 remote system at the University of Washington. The execute operator (monadic epsilon) is included in the implementation.
On data structures in associative memories
Authors: Lipovski G. J.
Published: May 2006

This report discusses the capability of an associative memory to search some useful data bases. The report utilizes a simplified cell and a collection of "assembler language" instructions to show how sets and trees can be searched in the memory. An OR rail and an EXCLUSIVE OR rail are discussed in relation to their use to search ordered and unordered sets, strings and tree data structures. Linked data structures are also discussed. This report is oriented towards the software aspects of the associative memory to lead to further research in the design of high level languages that utilize the capability of the rails.
APLISP
Authors: Smillie K. W.
Published: May 2006

This note gives a brief description of a number of APL functions which implement a simple list processor somewhat similar to LISP. As the reader is expected to have some familiarity with LISP, only a few preliminary remarks will be given here. Introductions to LISP may be found, for example, in "List processing" by P. M. Woodward in
Advances in Programming and Non-numerical Computation
by L. Fox (Pergamon, 1966), and in
Recursive Techniques in Programming
by D. W. Barron (Macdonald, 1968).
What’s on Your Hard Drive?
Authors: O'Hanlon Charlene
Published: May 2006

Therefore, it’s no surprise that many of you “roll your own” when what’s available just isn’t cutting it.
Review of "Foundations of Ajax by Ryan Asleson," Nathaniel Schutta, APress, 2005, $39.99 ISBN: 1590595823
Authors: Gittleman Arthur
Published: May 2006

Review of "Foundations of Ajax by Ryan Asleson," Nathaniel Schutta, APress, 2005, $39.99 ISBN: 1590595823
Review of "Switching to VoIP by Ted Wallingford," O’Reilly & Associates, 2005, $39.95 ISBN: 0596008686
Authors: State Radu
Published: May 2006

Review of "Switching to VoIP by Ted Wallingford," O’Reilly & Associates, 2005, $39.95 ISBN: 0596008686
The operational executive sponsor
Authors: Armour Phillip G.
Published: May 2006

The sometimes-missing link in software process change.
Automated data verification in a format-free environment
Authors: Collins Michael , Reynolds Charles , Le Christine , Varol Cihan , Bayrak Coskun
Published: May 2006

Data collection and interpretation are vital for innumerable purposes: both commercial and academic. Sifting through vast mountains of data to separate correct information from incorrect can be expensive both in terms of money and of time. Automation of as much of this process as possible is the key to collecting useful information in an efficient and timely manner. This paper discusses a system designed to automate the comparison of raw collected data to store of previously verified data. This comparison can be used both to estimate the accuracy and the value of the collected data. In addition, it is possible to gauge the efficacy of various collection methods. In this system special attention was paid to accepting a wide range of document formats and to properly handling data sets whose attribute types might be differently organized than those in the reference data.
The high wire balancing act of the IS project director
Authors: Roy Vital , Bernier Carmen , Léveillé Lucie
Published: May 2006

The implementation of a cross-functional enterprise system requires a more sustained and comprehensive change management program than does classical Information System (IS) application development. The tools and techniques used in such projects will presumably differ accordingly, as will the roles and responsibilities of each project contributor. The objective of this exploratory research is to elucidate the main managerial roles played by internal project directors in the implementation of a cross-functional enterprise system. To this effect, we will compare the roles of project directors involved in high organizational transformation projects with project directors participating in IS projects involving little transformation.We found that in order to comply with the allotted budget and schedule, project directors alternately adopt transactional and transformational management styles. In an IS project marked by a high level of organizational change, the transformational roles of the internal project director are more prevalent than in IS projects that entail modest organizational transformation. The impact of this type of project on the organizational culture requires a new breed of project director, capable of mastering both the technological and the organizational complexity of such projects, while at the same time coordinating the involvement of numerous contributors such as end-users, functional managers, software package suppliers and integrators. Conversely, within a low organizational transformation project, the internal project director plays both transformational and transactional roles to differing degrees, yet transactional roles prevail. Contrary to our expectations, however, in high organizational transformation projects, the transactional roles and the transformational roles were manifested to a comparable extent.
Hidden word statistics
Authors: Flajolet Philippe , Szpankowski Wojciech , Vallée Brigitte
Published: May 2006

We consider the sequence comparison problem, also known as “
hidden
” pattern problem, where one searches for a given
subsequence
in a text (rather than a string understood as a sequence of consecutive symbols). A characteristic parameter is the number of occurrences of a given pattern
w
of length
m
as a subsequence in a random text of length
n
generated by a memoryless source. Spacings between letters of the pattern may either be constrained or not in order to define valid occurrences. We determine the mean and the variance of the number of occurrences, and establish a Gaussian limit law and large deviations. These results are obtained via combinatorics on words, formal language techniques, and methods of analytic combinatorics based on generating functions. The motivations to study this problem come from an attempt at finding a reliable threshold for intrusion detections, from textual data processing applications, and from molecular biology.
Toward meaningful computing
Authors: Argamon Shlomo , Olsen Mark
Published: May 2006

Computer science can revolutionize the humanities as it has the hard sciences by revealing and contextualizing the meaning hidden in digital libraries.
Exploiting predicate-window semantics over data streams
Authors: Ghanem Thanaa M. , Aref Walid G. , Elmagarmid Ahmed K.
Published: May 2006

The
continuous sliding-window
query model is used widely in data stream management systems where the focus of a continuous query is limited to a set of the most
recent
tuples. In this paper, we show that an interesting and important class of queries over data streams cannot be answered using the
sliding-window
query model. Thus, we introduce a new model for continuous window queries, termed the
predicate-window
query model that limits the focus of a continuous query to the stream tuples that qualify a certain predicate.
Predicate-window
queries have some distinguishing characteristics, e.g., (1) The window predicate can be defined over any attribute in the stream tuple (ordered or unordered). (2) Stream tuples qualify and disqualify the window predicate in an out-of-order manner. In this paper, we discuss the applicability of the predicate-window query model. We will show how the existing
sliding-window
query models fail to answer some of the
predicate-window
queries. Finally, we discuss the challenges in supporting the
predicate-window
query model in data stream management systems.
Join minimization in XML-to-SQL translation
Authors: Mani Murali , Wang Song , Dougherty Dan , Rundensteiner Elke A.
Published: May 2006

Consider an XML view defined over a relational database, and a user query specified over this view. This user XML query is typically processed using the following steps: (a) our translator maps the XML query to one or more SQL queries, (b) the relational engine translates an SQL query to a relational algebra plan, (c) the relational engine executes the algebra plan and returns SQL results, and (d) our translator translates the SQL results back to XML. However, a straightforward approach produces a relational algebra plan after step (b) that is
inefficient
and has redundant joins. In this paper, we report on our preliminary observations with respect to how joins in such a relational algebra plan can be minimized. Our approach works on the relational algebra plan and optimizes it using novel rewrite rules that consider pairs of joins in the plan and determine whether one of them is redundant and hence can be removed. Our study shows that algebraic techniques achieve effective join minimization, and such techniques are useful and can be integrated into mainstream SQL engines.
Perfect sampling for queues and network models
Authors: Murdoch Duncan J. , Takahara Glen
Published: May 2006

We review Propp and Wilson's [1996] CFTP algorithm and Wilson's [2000] ROCFTP algorithm. We then use these to construct perfect samplers for several queueing and network models: Poisson arrivals and exponential service times, several types of customers, and a trunk reservation protocol for accepting new customers; a similar protocol on a network switching model; a queue with a general arrival process; and a queue with both general arrivals and service times. Our samplers give effective ways to generate random samples from the steady-state distributions of these queues.
What’s on Your Hard Drive?
Authors: O'Hanlon Charlene
Published: May 2006

Pay attention as well to the tools people love. There you’ll often find people raving about some of the smaller or lesser-known developer tools—tools that could be just the thing to make your latest project easier.
Discovery of knowledge flow in science
Authors: Zhuge Hai
Published: May 2006

Recognizing and understanding knowledge flow between scientists is valuable for science. Discovering, managing, and utilizing such knowledge are advanced services of the e-science knowledge grid environment.
Finding 3-shredders efficiently
Authors: Hegde Rajneesh
Published: May 2006

A shredder in an undirected graph is a set of vertices whose removal results in at least three components. A 3-shredder is a shredder of size three. We present an algorithm that, given a 3-connected graph, finds its 3-shredders in time proportional to the number of vertices and edges, when implemented on a RAM (random access machine).
The minimum generalized vertex cover problem
Authors: Hassin Refael , Levin Asaf
Published: May 2006

Let
G
= (
V
,
E
) be an undirected graph, with three numbers
d
0
(
e
) ≥
d
1
(
e
) ≥
d
2
(
e
) ≥ 0 for each edge
e
∈
E
. A solution is a subset
U
⊆
V
and

d
i

(
e
) represents the cost contributed to the solution by the edge
e
if exactly
i
of its endpoints are in the solution. The cost of including a vertex
v
in the solution is
c
(
v
). A solution has cost that is equal to the sum of the vertex costs and the edge costs. The minimum generalized vertex cover problem is to compute a minimum cost set of vertices. We study the complexity of the problem with the costs
d
0
(
e
) = 1,
d
1
(
e
) = α and
d
2
(
e
) = 0 ∀
e
∈
E
and
c
(
v
) = β∀
v
∈
V
, for all possible values of α and β. We also provide 2-approximation algorithms for the general case.
Introduction to the special issue
Authors: Kaeli David , Cohn Robert
Published: May 2006

Welcome to the Workshop on Binary Instrumentation and Applications. Binary instrumentation is a commonly used tool in many areas of computer science and engineering research. By using instrumentation to insert code to observe the dynamic behavior of programs, researchers can model the behavior of memory systems, collect profiles to guide compiler optimization, inject and detect faults in programs, and implement security policies. This workshop is an opportunity for developers and users of binary instrumentation tools to exchange ideas.
Dynamic memory optimization using pool allocation and prefetching
Authors: Zhao Qin , Rabbah Rodric , Wong Weng-Fai
Published: May 2006

Heap memory allocation plays an important role in modern applications. Conventional heap allocators, however, generally ignore the underlying memory hierarchy of the system, favoring instead a low runtime overhead and fast response times. Unfortunately, with little concern for the memory hierarchy, the data layout may exhibit poor spatial locality, and degrade cache performance. In this paper, we describe a dynamic heap allocation scheme called pool allocation. The strategy aims to improve cache performance by inspecting memory allocation requests, and allocating memory from appropriate heap pools as dictated by the requesting context. The advantages are two fold. First, by pooling together data with a common context, we expect to improve spatial locality, as data fetched to the caches will contain fewer items from different contexts. If the allocation patterns are closely matched to the traversal patterns, the end result is faster memory performance. Second, by pooling heap objects, we expect access patterns to exhibit more regularity, thus creating more opportunities for data prefetching. Our dynamic memory optimizer exploits the increased regularity to insert prefetch instructions at runtime. The optimizations are implemented in DynamoRIO, a dynamic optimization framework. We evaluate the work using various bench-marks, and measure a 17% speedup over gcc −03 on an Athlon MP, and a 13% speedup on a Pentium 4.
MonteSim
Authors: Srinivasan Ram , Lubeck Olaf
Published: May 2006

In this paper, we present a predictive Monte Carlo based performance model for in-order microarchitectures that is validated against the Itanium-2 processor. In such architectures, we find that application specific characteristics such as
load
carried dependence and prefetching significantly impact performance. We parametrize these effects and use the PIN instrumentation tool to obtain them. We use Monte Carlo sampling techniques to model the processor core, memory hierarchy and application characteristics. These techniques are widely used in physical simulations but their application to computer architecture performance modeling is atypical and the application parameterization used in this work is also believed to be novel. Preliminary results indicate that the model predicts CPI with a high degree of accuracy as validated against real measurements. Unlike detailed cycle accurate simulation which is computationally infeasible for evaluating realistic scientific applications, the proposed Monte Carlo model converges to a prediction in a few seconds. The accuracy of the model given its simplicity is surprising.
News 2.0
Authors: Stanik John
Published: May 2006

Attackers Set Sights on Macs
The (not so) Hidden Computer
Authors: Coatta Terry
Published: May 2006

Ubiquitous computing may not have arrived yet, but ubiquitous computers certainly have. The sustained improvements wrought by the fulfillment of Moore’s law have led to the use of microprocessors in a vast array of consumer products. A typical car contains 50 to 100 processors. Your microwave has one or maybe more. They’re in your TV, your phone, your refrigerator, your kids’ toys, and in some cases, your toothbrush.
Evolution or Revolution?
Authors: Creeger Mache
Published: May 2006

We work in an industry that prides itself on "changing the world," one that chants a constant mantra of innovation and where new products could aptly be described as "this year’s breakthrough of the century." While there are some genuine revolutions in the technology industry, including cellphones, GPS (global positioning system), quantum computing, encryption, and global access to content, the vast majority of new product introductions are evolutionary, not revolutionary. Real technical breakthroughs are few and far between. Most new products are just a recycling of an earlier idea.
The effects of development team skill on software product quality
Authors: Beaver Justin M. , Schiavone Guy A.
Published: May 2006

This paper provides an analysis of the effect of the skill/experience of the software development team on the quality of the final software product. A method for the assessment of software development team skill and experience is proposed, and was derived from a workforce management tool currently in use by the National Aeronautics and Space Administration. Using data from 26 small-scale software development projects, the team skill measures are correlated to 5 software product quality metrics from the ISO/IEC 9126 Software Engineering Product Quality standard. In the analysis of the results, development team skill is found to be a significant factor in the adequacy of the design and implementation. In addition, the results imply that inexperienced software developers are tasked with responsibilities ill-suited to their skill level, and thus have a significant adverse effect on the quality of the software product.
π-Method
Authors: Oquendo Flavio
Published: May 2006

Software systems have become increasingly complex and are often used in highly dynamic, distributed and mobile environments. Formal development of such software systems in order to guarantee their completeness and correctness is a large research challenge. This article presents the π-Method, a novel formal method that has been designed in the ArchWare European Project to address model-driven development of safe software systems. It is a well-founded theoretically method relying on formal foundations: its formal language for architecture description is based on the π-calculus, for architecture analysis on the μ-calculus, and for architecture transformation and refinement on the rewriting logic. The π-Method, like formal methods such as B, FOCUS, VDM, and Z, aims to provide full support for formal development of software systems. However, unlike these methods that do not provide any architectural support, the π-Method has been built from scratch to formally support architecture-centric component-based model-driven development. Furthermore, a major impetus behind defining formal languages and method is that their formality renders them suitable to be manipulated by software tools. Indeed, a comprehensive toolset supporting formal model-driven engineering has been developed.