bluuebunny/crossref_metadata_2025 huggingface dataset:
Real‐time resistivity sounding using a hand‐held broadband electromagnetic sensor
Authors: Huang Haoping , Won I. J.
Published: August 2003

Common situations encountered in geophysical investigations involving environmental and engineering problems call for simple and fast onsite interpretation of the survey data so results can be available in a timely manner for the projects. We have developed a method of interpreting broadband electromagnetic induction (EMI) data using a hand‐held electromagnetic (EM) sensor based on a layered‐earth model. In conductive environments, a hand‐held EM sensor yields sufficient information for shallow resistivity soundings. The result is a conductivity–depth section based on the frequency‐sounding principle. Tests using simulated data show that the method can reasonably recover earth conductivity structures with up to several layers.

We have field tested the method using data obtained with a GEM‐2 broadband EMI sensor. The conductivity–depth section converted from the field data reasonably reflects the known variations in earth conductivity. Because the current GEM‐2 is band‐limited to 48 kHz, the method works mainly in conductive environments. Sample GEM‐2 and GEM‐3 data collected over shallow seawater produced a bathymetric section with a precision of a few centimeters. Application of the method in resistive environments requires a broader bandwidth.
A proven method for acquiring highly repeatable towed streamer seismic data
Authors: Eiken Ola , Haugen Geir Ultveit , Schonewille Michel , Duijndam Adri
Published: August 2003

Seismic reservoir monitoring has become an important tool in the management of many fields. Monitoring subtle changes in the seismic properties of a reservoir caused by production places strong demands on seismic repeatability. A lack of repeatability limits how frequently reservoir changes can be monitored or the applicability of seismic monitoring at all. In this paper we show that towing many streamers with narrow separation, combined with cross‐line interpolation of data onto predefined sail lines, can give highly repeatable marine seismic data.

Results from two controlled zero time lag monitoring experiments in the North Sea demonstrate high sensitivity to changing water level and variations in lateral positions. After corrections by deterministic tidal time shifts and spatial interpolation of the irregularly sampled streamer data, relative rms difference amplitude levels are as low as 12% for a deep, structurally complex field and as low as 6% for a shallow, structurally simple field.

Reducing the degree of nonrepeatability to as low as 6% to 12% allows monitoring of smaller reflectivity changes. In terms of reservoir management this has three important benefits: (1) reservoirs with small seismic changes resulting from production can be monitored, (2) reservoirs with large seismic changes can be monitored more frequently, and (3) monitoring data can be used more quantitatively.
White's model for wave propagation in partially saturated rocks: Comparison with poroelastic numerical experiments
Authors: Carcione José M. , Helle Hans B. , Pham Nam H.
Published: August 2003

We use a poroelastic modeling algorithm to compute numerical experiments of wave propagation in White's partial saturation model. The results are then compared to the theoretical predictions. The model consists of a homogeneous sandstone saturated with brine and spherical gas pockets. White's theory predicts a relaxation mechanism, due to pressure equilibration, causing attenuation and velocity dispersion of the wavefield. We vary gas saturation either by increasing the radius of the gas pocket or by increasing the density of gas bubbles. Despite that the modeling is two dimensional and interaction between the gas pockets is neglected in White's model, the numerical results show the trends predicted by the theory. In particular, we observe a similar increase in velocity at high frequencies (and low permeabilities). Furthermore, the behavior of the attenuation peaks versus water saturation and frequency is similar to that of White's model. The modeling results show more dissipation and higher velocities than White's model due to multiple scattering and local fluid‐flow effects. The conversion of fast P‐wave energy into dissipating slow waves at the patches is the main mechanism of attenuation. Differential motion between the rock skeleton and the fluids is highly enhanced by the presence of fluid/fluid interfaces and pressure gradients generated through them.
Biochemical support for the V-ATPase rotary mechanism: antibody against HA-tagged Vma7p or Vma16p but not Vma10p inhibits activity
Authors: Aviezer-Hagai Keren , Padler-Karavani Vered , Nelson Nathan
Published: August 2003

V-ATPase null mutants in yeast have a distinct, conditionally lethal phenotype that can be obtained through disruption of any one of its subunits. This enables supplementation of this mutant with the relevant subunit tagged with an epitope against which an antibody is available. In this system, the effect of antibody on the activity of the enzyme can be analyzed. Towards this end we used HA to tag subunits Vma7p, Vma10p and Vma16p, which are assumed to represent, respectively, the shaft, stator and turbine of the enzyme, and used them to supplement the corresponding yeast V-ATPase null mutants. The anti-HA epitope antibody inhibited both the ATP-dependent proton uptake and the ATPase activities of the Vma16p-HA and Vma7p-HA containing complexes, in intact vacuoles and in the detergent-solubilized enzyme. Neither of these activities was inhibited by the antibody in Vma10p-HA containing enzyme. These results support the function of Vma10p as part of the stator, while the other tagged subunits are part of the rotor apparatus. The HA-tag was attached to the N terminus of Vma16p; thus the antibody inhibition points to its accessibility outside the vacuolar membrane. This assumption is supported by the supplementation of the yeast mutant by the homologues of Vma16p isolated from Arabidopsis thaliana and lemon fruit c-DNA. Contrary to yeast, which has five predicted helices, the plant subunit Vma16p has only four. Our results confirm a recent report that only four of the yeast Vma16p complexes are actually transmembrane helices.
Comparison of renal and salt gland function in three species of wild ducks
Authors: Bennett Darin C. , Hughes Maryanne R.
Published: August 2003

Three processes central to osmoregulation of marine birds were compared in three species of ducks that differ in habitat affinity, diet and saline tolerance. These processes are filtration of Na+ and water from the plasma by the kidneys, their reabsorption along the renal tubules, and secretion by the salt glands. Barrow's goldeneyes Bucephala islandica, the most marine species, have the highest rates for all three processes and only this species can secrete all the infused salt viathe salt glands. Rates of all three processes are lower in mallards Anas platyrhynchos, the most freshwater species. Following saline acclimation,mallards could excrete all the infused Na+ by a combined Na+ excretion of the kidneys and salt glands. Canvasbacks Aythya valisineria, despite being more saline tolerant than mallards,are unable to excrete all the infused Na+. They produce a large volume of urine (like mallards) that has a low [Na+] (like goldeneyes). Salt gland secretion Na+ concentration did not differ among the three species, but only goldeneyes secrete at a rate sufficient to eliminate all infused Na+via the salt glands. Differences in saline tolerance of these ducks species cannot be fully explained by differences in their filtration, reabsorption and secretion of Na+and water, suggesting that the intestinal tract plays an important role.
Monolith‐ and Silica‐Supported Carboxylate‐Based Grubbs–Herrmann‐Type Metathesis Catalysts
Authors: Krause Jens O. , Lubbad Said , Nuyken Oskar , Buchmeiser Michael R.
Published: August 2003

The synthesis of silica‐ and monolith‐supported Grubbs–Herrmann‐type catalysts is described. Two polymerizable, carboxylate‐containing ligands, exo, exo‐7‐oxanorborn‐2‐ene‐5,6‐dicarboxylic anhydride and 7‐oxanorborn‐2‐ene‐5‐carboxylic acid were surface‐immobilized onto silica‐ and ring‐opening metathesis (ROMP‐) derived monolithic supports using “grafting‐from” techniques. The “1st generation Grubbs catalyst”, RuCl2(CHPh)(PCy3)2, was used for these purposes. In addition, a poly(norborn‐2‐ene‐b‐exo, exo‐norborn‐2‐ene‐5,6‐dicarboxylic anhydride)‐coated silica 60 was prepared. The polymer supported anhydride and carboxylate groups were converted into the corresponding mono‐ and disilver salts, respectively, and reacted with the Grubbs–Herrmann catalyst RuCl2(CHPh)(IMesH2)(PCy3) [IMesH2=1,3‐bis(2,4,6‐trimethylphenyl)‐4,5‐dihydroimidazol‐2‐ylidene]. Heterogenization was accomplished by exchange of one chlorine ligand with the polymeric, immobilized silver carboxylates to yield monolith‐supported catalysts 4, 5, and 6 as well as silica‐supported systems 7, 8 and 9. The actual composition of these heterogenized catalysts was proven by the synthesis of a homogeneous analogue, RuCl[7‐oxanorbornan‐2‐(COOAg)‐3‐COO](CHPh)(IMesH2)(PCy3) (3). All homogeneous and heterogeneous catalysts were used in ring‐closing metathesis (RCM) of diethyl diallylmalonate, 1,7‐octadiene, diallyldiphenylsilane, methyl trans‐3‐pentenoate, diallyl ether, N,N‐diallyltrifluoracetamide and t‐butyl N,N‐diallylcarbamate allowing turnover numbers (TON's) close to 1000. In a flow‐through set‐up, an auxiliary effect of pendant silver carboxylates was observed with catalyst 5, where the silver moiety functions as a (reversible) phosphine scavenger that both accelerates initiation and stabilizes the catalyst by preventing phosphine elution. Detailed catalytic studies were carried out with the monolith‐supported systems 4 and 6 in order to investigate the effects of temperature and chain‐transfer agents (CTA's) such as cis‐1,4‐diacetoxybut‐2‐ene. In all RCM experiments Ru‐leaching was low, resulting in a Ru‐content of the RCM products ≤3.5 μg/g (3.5 ppm).
Lewis Acids as Highly Efficient Catalysts for the Decarboxylative Esterification of Carboxylic Acids with Dialkyl Dicarbonates
Authors: Gooßen L. , Döhring A.
Published: August 2003

Mild Lewis acids such as Mg(ClO4)2 show a new level of catalytic activity for the decarboxylative esterification of carboxylic acids with commercially available dialkyl dicarbonates. In the presence of as little as one mol % Mg(ClO4)2 catalyst, carboxylic acids can thus easily and near quantitatively be protected at room temperature, e.g., as methyl, benzyl, or t‐butyl esters. Only volatile by‐products are released so that the purification of the products is particularly easy. Many sensitive functionalities are tolerated, including even phenol esters, or free hydroxy and BOC groups.
Efficient Osmium/Rhenium‐Catalyzed Dihydroxylation of Olefins with Hydrogen Peroxide under Acidic Conditions
Authors: Éll Alida H. , Closson Adam , Adolfsson Hans , Bäckvall Jan‐E.
Published: August 2003

Simple addition of citric acid confers great stability to the catalytically active osmium and rhenium species involved in a triple catalytic system utilizing aqueous hydrogen peroxide as the terminal oxidant. The resulting system is capable of dihydroxylating traditionally resistant olefins in high yields.
Combinatorial Design of Copper‐Based Mixed Nanoclusters: New Catalysts for Suzuki Cross‐Coupling
Authors: Thathagar Mehul B. , Beckers Jurriaan , Rothenberg Gadi
Published: August 2003

Quantum dots (2–5 nm) of copper and copper/palladium mixtures are found to be good catalysts for Suzuki cross‐coupling. The catalysts are applicable to a wide range of iodo‐ and bromoaryl substrates, and give moderate yields using chloroaryl substrates. Cluster activity and stability is found to depend strongly on the preparation method and the reaction conditions. The mechanism of cluster deactivation and the sensitivity of the cluster‐catalysed reaction to substituent effects are studied and discussed.
Montmorillonite KSF‐Catalyzed One‐Pot, Three‐Component, Aza‐Diels–Alder Reactions of Methylenecyclopropanes with Arenecarbaldehydes and Arylamines
Authors: Shao Li‐Xiong , Shi Min
Published: August 2003

A series of novel quinoline derivatives having a spirocyclopropyl ring can be synthesized by one‐pot, three‐component aza‐Diels–Alder reactions of arenecarbaldehydes, arylamines, and methylenecyclopropanes (MCPs) using a heterogeneous solid acid catalyst, montmorillonite KSF, under mild reaction conditions in good to excellent yields.
Catalyzed Reactions of Enol Ethers with SN1 Active Groups: A Novel Method for the Preparation of α‐Alkylated Ketones
Authors: Gansäuer Andreas , Fielenbach Doris , Stock Christoph , Geich‐Gimbel Daniel
Published: August 2003

The performance of tert‐alkylations, alkoxyalkylations, and aldehyde enolate allylations proceeding with low catalyst loading (0.1 mol %–5 mol %) is described. The reactions are complete within short times and can even be performed without solvent and under ambient conditions. The mechanism of the reaction was investigated by deuterium labeling and cross‐over studies.
A Novel Mesoporous Silica‐Supported Lewis Acid Catalyst for CC Bond Formation Reactions in Water
Authors: Sreekanth Pentlavalli , Kim Sang‐Wook , Hyeon Taegwhan , Kim B. Moon
Published: August 2003

Catalytic allylation of carbonyl compounds in water using tetraallyltin in the presence of lanthanum sulfonate immobilized on mesoporous silica (SBA‐15) has been carried out for the first time. The reaction proceeded smoothly in water and furnished the corresponding homoallylic alcohols in good to excellent yields. The catalyst could be reused without significant loss of catalytic activity.
Practical Short Synthesis of 1β‐Methylcarbapenem Utilizing a New Dehydration Type Ti‐Dieckmann Condensation
Authors: Tanabe Yoo , Manta Naoki , Nagase Ryohei , Misaki Tomoniri , Nishii Yoshinori , Sunagawa Makoto , Sasaki Akira
Published: August 2003

An efficient, practical, and stereocontrolled synthesis of 1β‐methylcarbapenems has been performed utilizing a new dehydration type of Ti‐Dieckmann (intramolecular Ti‐Claisen) condensation. This cyclization reaction has the advantage of direct incorporation of the thiol moiety into the target 1β‐methylcarbapenem, compared with the traditional basic Dieckmann condensation. Another advantage is the use of environmentally benign (low toxicity and safe) reagents (TiCl4 and Et3N or Bu3N).
Polymer‐Supported Lewis Bases for the Baylis–Hillman Reaction
Authors: Huang Jin‐Wen , Shi Min
Published: August 2003

The use of polymer‐supported Lewis bases such as PEG4600‐(PPh2)2 and poly(DMAP) in the Baylis–Hillman reactions of N‐tosylimines (ArCHNTs) 1 or the corresponding arenecarbaldehydes with α,β‐unsaturated ketones has been investigated. The corresponding Baylis–Hillman adducts are obtained in good yields. The polymer‐supported Lewis bases can be easily recovered by filtration and the Lewis base PEG4600‐(PPh2)2 can be reproduced by reduction with LiAlH4 and CeCl3.
Chemie und Biologie des Roseophilins und der Prodigiosin‐Alkaloide: 2500 Jahre im Überblick
Authors: Fürstner Alois
Published: August 2003

Die Pyrrolalkaloide der Prodigiosin‐Familie haben ein ungewöhnliches Kapitel der Alkaloidchemie geschrieben. Aufgrund ihrer charakteristischen roten Farbe können Kolonien der Prodigiosin‐produzierenden Gram‐negativen Bakterien Blutstropfen zum Verwechseln ähneln. Dies hat in der Vergangenheit offenbar für Verwirrung gesorgt und dürfte wohl zahlreiche scheinbar “wundersame” Ereignisse erklären. Seitdem jedoch der Schritt vom Aberglauben zur Naturwissenschaft vollzogen ist, ziehen die Prodigiosine wegen ihrer vielversprechenden physiologischen Eigenschaften einige Aufmerksamkeit auf sich. Besonders relevant sind in diesem Zusammenhang ihre immunsuppressiven Wirkungen, zumal In‐vivo‐Studien einen synergetischen Effekt bei gemeinsamer Verabreichung mit den klinisch eingesetzten Medikamenten Cyclosporin A und FK 506 nachweisen. Des Weiteren wird in diesem Aufsatz die Chemie des mit den Prodigiosinen nahe verwandten, strukturell ungewöhnlichen Alkaloids Roseophilin zusammengefasst, eines cytotoxischen Naturstoffs, der in den letzten Jahren Gegenstand zahlreicher innovativer Totalsynthesen war.
Chemistry and Biology of Roseophilin and the Prodigiosin Alkaloids: A Survey of the Last 2500 Years
Authors: Fürstner Alois
Published: August 2003

The pyrrole alkaloids of the prodigiosin family make up an unusual chapter in the chemistry of natural products. Owing to the characteristic red color of these secondary metabolites, colonies of the Gram‐negative‐producing bacteria may strikingly resemble droplets of blood. This phenomenon caused considerable confusion in the past and was likely responsible for many seemingly miraculous (prodigious) events. After the eventual transition from superstition to science, the prodigiosins started to attract considerable attention because of their promising physiological properties. Most interesting are the immunosuppressive activities at doses that are not cytotoxic, in particular since in vivo studies suggest that the prodigiosins act synergistically with cyclosporine A or FK 506, which are presently the dominant drugs in clinical immunosuppressive regimens. Furthermore, the chemistry of the closely related and structurally rather unique alkaloid roseophilin is summarized, a cytotoxic agent that recently became the focal point of many innovative total syntheses.
Synthesis and characterization of thiol‐terminated poly(ethylene oxide) for chemisorption to gold surface
Authors: Du Ying Jun , Brash John L.
Published: August 2003

Thiol‐terminated poly(ethylene oxide) (PEO) was synthesized using two different approaches: esterification of terminal hydroxyl groups with mercaptoacetic acid and amidation using N‐hydroxysuccinimidyl PEO (NHS–PEO) and cysteine. The reaction of hydroxyl‐terminated PEO with mercaptoacetic acid was carried out in boiling toluene. Different thiolated PEOs, including linear PEOs of varying molecular weights and end‐group types, and star‐type PEOs were synthesized. Nuclear magnetic resonance and infrared spectroscopy were used to characterize the products. The reaction kinetics were also briefly investigated. Gel permeation chromatography was used to investigate the relative amounts of the mono‐ and disubstituted products in the α,ω‐dihydroxy PEOs. NHS–PEO was used both to attach terminal thiol groups via reaction with cysteine and to conjugate other amino acids (and potentially any amino‐containing molecule) to PEO. Reactions using NHS–PEO were carried out at room temperature in water. The chemisorption of these thiolated PEOs to gold was expected to yield surfaces resistant to biofouling, in particular to unwanted protein adsorption. Chemisorption of amino acid–, peptide‐, or protein‐terminated PEOs in addition may yield surfaces having specific biological activity. Work on these aspects will be reported elsewhere. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 594–607, 2003
Viscometric behavior of quaternized polysulfones
Authors: Ghimici Luminita , Avram Ecaterina
Published: August 2003

The effects of the quaternary ammonium group size and the solvent nature and composition on the viscometric behavior of several quaternized polysulfones (PSFs) were investigated. The solution viscosity of the cationic PSFs was determined over a wide concentration range in N,N‐dimethylformamide (DMF). The experimental data were plotted in the terms of the Fedors equation. It was found that the intrinsic viscosity values were strongly dependent on the size of quaternary ammonium groups. The viscosity of PSF quaternized with N,N‐dimethylbutylamine (PSF‐DMBA) was also measured in the mixed solvents consisting of DMF/methanol and DMF/diethylether. Polyelectrolyte behavior was observed for PSF‐DMBA in the mixtures of DMF/methanol for all compositions employed and in the mixtures of DMF/diethylether with the diethylether content as high as 25 vol %. The viscosity decrease and precipitation in the polymer solution with increasing diethylether content was attributed to the dipole–dipole attraction between ion pairs formed in a less polar medium. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 465–469, 2003
Vibrational overtone initiated photopolymerization of acrylonitrile
Authors: Gu Hua , Snavely D. L.
Published: August 2003

Vibrational overtone activated polymerization of acrylonitrile (AN) has been demonstrated using two initiators, benzoyl peroxide (BP), and 2,2′‐(azobis)isobutyronitrile (AIBN). Excitation of the fifth vibrational overtone of the CH stretch of AIBN at 627 nm and BP at 604 nm initiates the reaction. Monomer conversions were monitored by a gravimetric method. In both cases, the wavelength selectivity was investigated by irradiating the monomer/initiator mixtures at the absorption maximum of the initiator, the absorption maximum of the monomer, and at a wavelength (580 nm for AN/AIBN and 625 nm for AN/BP) where neither the initiator nor the monomer absorbs light. For the AN/AIBN mixture, after 48 h the monomer conversion for the irradiation on the peak absorption of AIBN (627 nm) is about twice as large as the irradiation at 580 nm. For the AN/BP mixture, after 48 h the monomer conversion for the irradiation on the peak absorption of BP (604 nm) is about a factor of 2.2 larger than for the irradiation at 625 nm. The overall quantum yields of both polymerizations were estimated. After 48 h the overall quantum yield for the AN/AIBN mixture irradiated at the initiator absorption (Φ627 = 21083) is about 10 times larger than for the sample irradiated at the pure monomer absorption (Φ595 = 1942). For the AN/BP mixture, the 604 nm quantum yield (Φ604 = 1096) is about 2.4 times larger than the 595 nm quantum yield (Φ595 = 448). The influence of the initiator concentration is also presented. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 565–571, 2003
TROPDAD: A New Ligand for the Synthesis of Water‐Stable Paramagnetic [16+1]‐Electron Rhodium and Iridium Complexes
Authors: Breher Frank , Böhler Carsten , Frison Gilles , Harmer Jeffrey , Liesum Lorenz , Schweiger Arthur , Grützmacher Hansjörg
Published: August 2003

The new tetradentate ligand 1,4‐bis(5 H‐dibenzo[a,d]cyclohepten‐5‐yl)‐1,4‐diazabuta‐1,3‐diene (Htropdad) allows the syntheses of the 16‐electron cationic rhodium complexes [M(Htropdad)](O3SCF3) (M=Rh, Ir). The structure of the rhodium complex was determined by X‐ray analysis and points to a description of these as [M+1(Htropdad)0] with short CN bonds (av 1.285 Å) and a long CC bond (1.46 Å) in the diazabutadiene (dad) moiety, that is the M→dad charge‐transfer is negligible. Both [Rh(Htropdad)]+and [Ir(Htropdad)]+are reduced at very low potentials (E11/2= −0.56 V andE11/2=−0.35 V, respectively) which allowed the quantitative synthesis of the neutral paramagnetic complexes [M(Htropdad)]0(M=Rh, Ir) by reacting the cationic precursor complexes simply with zinc powder. The [M(Htropdad)]0complexes are stable against protic reagents in organic solvents. Continuous wave and pulse EPR spectroscopy was used to characterize the paramagnetic species and the hyperfine coupling constants were determined: [Rh(Htropdad)]0:Aiso(14N)=11.9 MHz,Aiso(1H)=14.3 MHz,Aiso(103Rh)= −5.3 MHz; [Ir(Htropdad)]0:Aiso(14N)=11.9 MHz,Aiso(1H)=14.3 MHz. In combination with DFT calculations, the experimentally determinedgand hyperfine matrices could be orientated within the molecular frame and the dominant spin density contributions were determined. These results clearly show that the complexes [M(Htropdad)]0are best described as [M+1(Htropdad).−] with a [16+1] electron configuration.
Thermodynamics and Kinetics of the Hydride‐Transfer Cycles for 1‐Aryl‐1,4‐dihydronicotinamide and Its 1,2‐Dihydroisomer
Authors: Zhu Xiao‐Qing , Cao Lei , Liu Yang , Yang Yuan , Lu Jin‐Yong , Wang Jian‐Shuang , Cheng Jin‐Pei
Published: August 2003

Five 1‐(p‐substituted phenyl)‐1,4‐dihydronicotinamides (GPNAH‐1,4‐H2) and five 1‐(p‐substituted phenyl)‐1,2‐dihydronicotinamides (GPNAH‐1,2‐H2) were synthesized, which were used to mimic NAD(P)H coenzyme and its 1,2‐dihydroisomer reductions, respectively. When the 1,4‐dihydropyridine (GPNAH‐1,4‐H2) and the 1,2‐dihydroisomer (GPNAH‐1,2‐H2) were treated with p‐trifluoromethylbenzylidenemalononitrile (S) as a hydride acceptor, both reactions gave the same products: pyridinium derivative (GPNA+) and carbanion SH− by a hydride one‐step transfer. Thermodynamic analysis on the two reactions shows that the hydride transfer from the 1,2‐dihydropyridine is much more favorable than the hydride transfer from the corresponding 1,4‐dihydroisomer, but the kinetic examination displays that the former reaction is remarkably slower than the latter reaction, which is mainly due to much more negative activation entropy for the former reaction. When the formed pyridinium derivative (GPNA+) was treated with SH−, the major reduced product was the corresponding 1,4‐dihydropyridine along with a trace of the 1,2‐dihydroisomer. Thermodynamic and kinetic analyses on the hydride transfer from SH− to GPNA+ all suggest that the 4‐position on the pyridinium ring in GPNA+ is much easier to accept the hydride than the 2‐position, which indicates that when the 1,4‐dihydropyridine is used the hydride donor to react with S, the formed pyridinium derivative GPNA+ may return to the 1,4‐dihydropyridine by a hydride transfer cycle; but when the 1,2‐dihydropyridine is used as the hydride donor, the formed pyridinium derivative can not return to the 1,2‐dihydropyridine by the hydride reverse transfer from SH− to GPNA+. These results clearly show that the hydride‐transfer cycle is favorable for the 1,4‐dihydronicotinamides, but unfavorable for the corresponding 1,2‐dihydroisomers.
Chemical and Biochemical Sensing with Modified Single Walled Carbon Nanotubes
Authors: Davis Jason J. , Coleman Karl S. , Azamian Bobak R. , Bagshaw Claire B. , Green Malcolm L. H.
Published: August 2003

The nano dimensions, graphitic surface chemistry and electronic properties of single walled carbon nanotubes make such a material an ideal candidate for chemical or biochemical sensing. Carbon nanotubes can be nondestructively oxidized along their sidewalls or ends and subsequently covalently functionalized with colloidal particles or polyamine dendrimers via carboxylate chemistry. Proteins adsorb individually, strongly and noncovalently along nanotube lengths. These nanotube–protein conjugates are readily characterized at the molecular level by atomic force microscopy. Several metalloproteins and enzymes have been bound on both the sidewalls and termini of single walled carbon nanotubes. Though coupling can be controlled, to a degree, through variation of tube oxidative pre‐activation chemistry, careful control experiments and observations made by atomic force microscopy suggest that immobilization is strong, physical and does not require covalent bonding. Importantly, in terms of possible device applications, protein attachment appears to occur with retention of native biological structure. Nanotube electrodes exhibit useful voltammetric properties with direct electrical communication possible between a redox‐active biomolecule and the delocalized π system of its carbon nanotube support.
Coordination Algorithms Control Molecular Architecture: [CuI4(L2)4]4+ Grid Complex Versus [MII2(L2)2X4]y+ Side‐By‐Side Complexes (M=Mn, Co, Ni, Zn; X=Solvent or Anion) and [FeII(L2)3][Cl3FeIIIOFeIIICl3]
Authors: Lan Yanhua , Kennepohl Dietmar K. , Moubaraki Boujemaa , Murray Keith S. , Cashion John D. , Jameson Geoffrey B. , Brooker Sally
Published: August 2003

The synthesis and characterisation of a pyridazine‐containing two‐armed grid ligand L2 (prepared from one equivalent of 3,6‐diformylpyridazine and two equivalents of p‐anisidine) and the resulting transition metal (Zn, Cu, Ni, Co, Fe, Mn) complexes (1–9) are reported. Single‐crystal X‐ray structure determinations revealed that the copper(I) complex had self‐assembled as a [2×2] grid, [CuI4(L2)4][PF6]4⋅(CH3CN)(H2O)(CH3CH2OCH2CH3)0.25 (2⋅(CH3CN)(H2O)(CH3CH2OCH2CH3)0.25), whereas the [Zn2(L2)2(CH3CN)2(H2O)2][ClO4]4⋅CH3CN (1⋅CH3CN), [NiII2(L2)2(CH3CN)4][BF4]4⋅(CH3CH2OCH2CH3)0.25 (5 a⋅(CH3CH2OCH2CH3)0.25) and [CoII2(L2)2(H2O)2(CH3CN)2][ClO4]4⋅(H2O)(CH3CN)0.5 (6 a⋅(H2O)(CH3CN)0.5) complexes adopt a side‐by‐side architecture; iron(II) forms a monometallic cation binding three L2 ligands, [FeII(L2)3][FeIIICl3OCl3FeIII]⋅CH3CN (7⋅CH3CN). A more soluble salt of the cation of 7, the diamagnetic complex [FeII(L2)3][BF4]2⋅2 H2O (8), was prepared, as well as two derivatives of 2, [CuI2(L2)2(NCS)2]⋅H2O (3) and [CuI2(L2)(NCS)2] (4). The manganese complex, [MnII2(L2)2Cl4]⋅3 H2O (9), was not structurally characterised, but is proposed to adopt a side‐by‐side architecture. Variable temperature magnetic susceptibility studies yielded small negative J values for the side‐by‐side complexes: J=−21.6 cm−1 and g=2.17 for S=1 dinickel(II) complex [NiII2(L2)2(H2O)4][BF4]4 (5 b) (fraction monomer 0.02); J=−7.6 cm−1 and g=2.44 for S= 3/2 dicobalt(II) complex [CoII2(L2)2(H2O)4][ClO4]4 (6 b) (fraction monomer 0.02); J=−3.2 cm−1 and g=1.95 for S= 5/2 dimanganese(II) complex 9 (fraction monomer 0.02). The double salt, mixed valent iron complex 7⋅H2O gave J=−75 cm−1 and g=1.81 for the S= 5/2 diiron(III) anion (fraction monomer=0.025). These parameters are lower than normal for FeIIIOFeIII species because of fitting of superimposed monomer and dimer susceptibilities arising from trace impurities. The iron(II) centre in 7⋅H2O is low spin and hence diamagnetic, a fact confirmed by the preparation and characterisation of the simple diamagnetic iron(II) complex 8. Mössbauer measurements at 77 K confirmed that there are two iron sites in 7⋅H2O, a low‐spin iron(II) site and a high‐spin diiron(III) site. A full electrochemical investigation was undertaken for complexes 1, 2, 5 b, 6 b and 8 and this showed that multiple redox processes are a feature of all of them.
Pairing of Isolated Nucleobases: Double Resonance Laser Spectroscopy of Adenine–Thymine
Authors: Plützer Christian , Hünig Isabel , Kleinermanns Karl , Nir Eyal , de Vries Mattanjah S.
Published: August 2003

The vibronic spectrum of the adenine–thymine (A–T) base pair was obtained by one‐color resonant two‐photon ionization (R2PI) spectroscopy in a free jet of thermally evaporated A and T under conditions favorable for formation of small clusters. The onset of the spectrum at 35 064 cm−1 exhibits a large red shift relative to the π–π* origin of 9H‐adenine at 36 105 cm−1. The IR–UV spectrum was assigned to cluster structures with HNH⋅⋅⋅OC/N⋅⋅⋅HN hydrogen bonding by comparison with the IR spectra of A and T monomers and with ab initio calculated vibrational spectra of the most stable A–T isomers. The Watson–Crick A–T base pair is not the most stable base‐pair structure at different levels of ab initio theory, and its vibrational spectrum is not in agreement with the observed experimental spectrum. Experiments with methylated A and T were performed to further support the structural assignment.
Detecting instabilities in flows of viscoelastic fluids
Authors: Fiétier N.
Published: August 2003

There is a growing interest in developing numerical tools to investigate the onset of physical instabilities observed in experiments involving viscoelastic flows, which is a difficult and challenging task as the simulations are very sensitive to numerical instabilities. Following a recent linear stability analysis carried out in order to better understand qualitatively the origin of numerical instabilities occurring in the simulation of flows viscoelastic fluids, the present paper considers a possible extension for more complex flows. This promising method could be applied to track instabilities in complex (i.e. essentially non‐parallel) flows. In addition, results related to transient growth mechanism indicate that it might be responsible for the development of numerical instabilities in the simulation of viscoelastic fluids. Copyright © 2003 John Wiley & Sons, Ltd.
Occurrence of certain mycotoxins in corn and corn‐based products and thermostability of fumonisin B1 during processing
Authors: El‐Sayed A. M. Abd Alla , Soher E. Aly , Sahab A. F.
Published: August 2003

A total of 57 samples of corn and corn‐based products collected from various districts of Egypt were analyzed for Fusarium mycotoxins (T‐2, diacetoxyscripenol (DAS( deoxynivalenol (DON) and fumonisin B1 (FB1) and aflatoxins. FB1 was detected in about 80%, 53.85%, 33.3%, and 28.57% of yellow corn, corn meal, white corn, and popcorn samples, respectively. The levels of FB1 ranged from 10 to 780 μg/kg. T‐2 and DAS were detected in 5% and 10% of yellow corn samples, respectively, and DON was detected in white corn and popcorn samples at levels of 28.8 and 10.1 μg/kg, respectively. Starch samples were found to be free from Fusarium mycotoxins. Baking balady bread at 450°C/min reduced FB1 to 72.4% while baking Franco bread at 250°C/20 min reduced FB1 to 57.4%. Boiling of macaroni and corn in water completely removed FB1 from contaminated samples. On the other side, corn flakes samples were found to be contaminated with aflatoxins B1 and G1 at levels ranging from 6 to 10 ppm, whereas 2.9% of samples were contaminated with aflatoxin B1 > 35 ppm and G1 > 16 ppm.
Effects of different emulsifier types, fat contents, and gum types on retardation of staling of microwave‐baked cakes
Authors: Seyhun Nadide , Sumnu Gülüm , Sahin Serpil
Published: August 2003

The effects of different types of emulsifiers, gums, and fat contents on the retardation of staling of microwave‐baked cakes were investigated. First, different types of emulsifiers (DATEM, Lecigran, and Purawave) at three different fat contents (50%, 25%, and 0%) were added to cake formulations to retard staling of microwave‐baked cakes. Then, three types of gums (guar gum, xanthan gum, and methylcellulose) were added to the optimum formulations chosen. As a control, cakes formulated without any emulsifier or gum addition and baked in an conventional oven at 175°C for 25 min was used. Weight loss, firmness, soluble starch and amylose content of the cakes were used as the indicators of staling criteria. Cakes were baked in a microwave oven for 1.5 min at 100% power. Variation of staling parameters during storage of cakes followed zero‐order kinetics. Use of emulsifiers and gums helped to retard staling of microwave‐baked cakes. Fat content was found to be a significant factor in affecting variation of firmness and weight loss of the cakes during storage. DATEM and Purawave were the most effective emulsifier types. Using gums in combination with emulsifiers gave better moisture retention and softer cakes than using gums alone.
Effect of processing on the protein nutritional value of Canavalia gladiata seeds
Authors: Ekanayake Sagarika , Nair Baboo , Radcliff Jansz Errol , Asp Nils‐Georg
Published: August 2003

Evaluation of protein true digestibility (TD( biological value (BV( and net protein utilization (NPU) of diets containing mature sword bean (Canavalia gladiata( seed flour and grits were carried out with male Sprague‐Dawley rats. The seed flour and grits were processed by soaking, cooking, soaking and cooking, autoclaving, and roasting. The TD of processed flour (cooked (84.8( soaked and cooked (76.2( autoclaved (82.0( roasted grits (64.5( and roasted flour (61.2)) were significantly higher (p < 0.05) than in the raw (51.4) and the soaked only grits (35.8). Soaking the grits decreased the TD. The BV of cooked grits and grits cooked after soaking were significantly higher than that of the other processed samples (p < 0.05). However, the BV of the diets containing cooked and soaked and cooked grits were not significantly different. The NPU of the cooked grits (39.4) and grits cooked after soaking (37.6) were significantly higher (p < 0.05) than that of the other processed samples (autoclaved grits (31.0( roasted grits (19.5( roasted flour (10.8( and soaked only grits (1.6)). The NPU of all the processed samples were significantly lower than the reference casein (p < 0.05). The highest protein nutritional quality was obtained by either cooking the grits or by soaking and cooking the grits. In vitro protein digestibility measurements were not well correlated to the true digestibility.
Application of Bayesian spatial statistical methods to analysis of haplotypes effects and gene mapping
Authors: Molitor John , Marjoram Paul , Thomas Duncan
Published: August 2003

We propose a method to analyze haplotype effects using ideas derived from Bayesian spatial statistics. We assume that two haplotypes that are similar to one another in structure are likely to have similar risks, and define a distance metric to specify the appropriate level of closeness between the two haplotypes. Through the choice of distance metric, varying levels of population genetics theory can be incorporated into the modeling process, including some that allow estimation of the location of the disease causing mutation(s). This location can be estimated, along with the other parameters of the model, using Markov chain Monte Carlo (MCMC) estimation methods. We demonstrate the effectiveness of the model on two real datasets, a well‐known dataset used to fine‐map the gene for cystic fibrosis, and one used to localize the gene for Friedreich's ataxia. Genet Epidemiol 25:95–105, 2003. © 2003 Wiley‐Liss, Inc.
Pedigree disequilibrium tests for multilocus haplotypes
Authors: Dudbridge Frank
Published: August 2003

Association tests of multilocus haplotypes are of interest both in linkage disequilibrium mapping and in candidate gene studies. For case‐parent trios, I discuss the extension of existing multilocus methods to include ambiguous haplotypes in tests of models which distinguish between thecisandtransphase. A likelihood‐ratio test is proposed, using the expectation‐maximization (E‐M) algorithm to account for haplotype ambiguities. Assumptions about the population structure are required, but realistic situations, including population stratification, which violate the assumptions lead to conservative tests. I describe a permutation procedure for the null hypothesis of interest, which controls for violation of the assumptions. For general pedigrees, I describe extensions of the pedigree disequilibrium test to include uncertain haplotypes. The summary statistics are replaced by their expected values over prior distributions of haplotype frequencies. If prior distributions are not available, a valid test is possible by using the E‐M algorithm to estimate the null distribution of haplotype frequencies. Similar methods are available for quantitative traits. Exact permutation tests are difficult to construct in small samples, but an approximate procedure is appropriate in large samples, and can be used to account for dependencies between tests of multiple haplotypes and loci.Genet Epidemiol25:115–121, 2003. © 2003 Wiley‐Liss, Inc.
The employment relationships of foreign workers versus local employees: a field study of organizational justice, job satisfaction, performance, and OCB
Authors: Ang Soon , Van Dyne Linn , Begley Thomas M.
Published: August 2003

Foreign workers seek overseas employment without sponsorship from a firm in their home country and hold temporary work visas in the host country. Despite the rising numbers of foreign workers, there is very little research that examines employment relationships and work behaviors of foreign workers. In this study, we draw on social exchange theory and predict differences in work perceptions, attitudes, and behaviors of foreign versus local employees based on differences in their exchange relationships. We then draw on social comparison theories and propose that these differences in perceptions, attitudes, and behaviors will be accentuated for workers in jobs with high task interdependence. We examined these hypotheses in a field study of 466 ethnic Chinese employees (213 foreign workers from the People's Republic of China and 253 local workers in Singapore with ongoing employment status). Results demonstrate lower distributive justice judgments, performance, and organizational citizenship for foreign versus local employees. Furthermore, results demonstrate that differences in distributive and procedural justice, performance, and organizational citizenship were heightened by task interdependence. We discuss findings and the implications of employing foreign workers. Copyright © 2003 John Wiley & Sons, Ltd.
Perceived organizational membership: an aggregate framework representing the employee–organization relationship
Authors: Masterson Suzanne S. , Stamper Christina L.
Published: August 2003

Organizational scholars have examined the relational ties between employees and organizations, often focusing on specific facets of the relationship. However, this approach has not generated an overall representation of the employee–organization relationship, nor has it facilitated the identification of interrelationships among the concepts. This paper seeks to address these two issues by developing an integrative framework labeled perceived organizational membership. Perceived organizational membership is proposed to be an aggregate multidimensional construct reflecting employees' perceptions of their relationship with their employing organization, and its three underlying dimensions (need fulfillment, mattering, and belonging) offer a framework for categorizing and understanding relational tie concepts, both separately and in combination with one another. Drawing from the community psychology literature (McMillan & Chavis, 1986) as well as Graham's (1991) early work on organizational citizenship, we identify perceived organizational membership's underlying motives and the mechanisms through which they influence the construct, demonstrate how specific relational tie subdimensions fit with the more general construct, and develop propositions regarding relationships among the dimensions and the specific relational tie subdimensions. Finally, we discuss the benefits of the framework, including its ability to allow researchers to better understand both specific relational tie concepts as well as the overall employee–organization relationship. Copyright © 2003 John Wiley & Sons, Ltd.
Psychological contract development during organizational socialization: adaptation to reality and the role of reciprocity
Authors: De Vos Ans , Buyens Dirk , Schalk René
Published: August 2003

Based on the theoretical framework of newcomer sensemaking this study examines factors associated with changes in newcomers' psychological contract perceptions during the socialization process. More specifically, two mechanisms are addressed that could explain changes in newcomers' perceptions of the promises they have exchanged with their employer: (1) unilateral adaptation of perceived promises to reality and (2) adaptation of perceived promises as a function of the reciprocity norm. To test our hypotheses, a four‐wave longitudinal study among 333 new hires has been conducted, covering the first year of their employment relationship. Results show that changes in newcomers' perceptions of the promises they have made to their employer are affected by their perceptions of their own contributions as well as by their perceptions of inducements received from their employer. Changes in newcomers' perceptions of employer promises are affected by their perceptions of employer inducements received, but the impact of perceived employee contributions is less clear. The data provide limited support for the idea that the adaptation of perceived promises to perceived inducements and contributions occurs to a stronger extent during the encounter stage than during the acquisition stage of socialization. Copyright © 2003 John Wiley & Sons, Ltd.
The effects of psychological contract breach and organizational cynicism: not all social exchange violations are created equal
Authors: Johnson Jonathan L. , O'Leary‐Kelly Anne M.
Published: August 2003

This research explored the differential effects on employees of two types of social exchange violations: those that generate perceptions of psychological contract breach and of organizational cynicism. We predicted that psychological contract breach and cynicism would result in differential outcomes because of differences in the person specificity of their underlying social exchange relationships. Using a sample of bank employees, we found that cynicism partially mediated the effects of psychological contract breach on work‐related attitudes (organizational commitment, job satisfaction), but that only psychological contract breach (not cynicism) predicted employees' behavioral responses (performance, absenteeism). Further, affective cynicism fully mediated the relationship between psychological contract breach and emotional exhaustion, suggesting that cynical attitudes have negative consequences for the attitude holder. Copyright © 2003 John Wiley & Sons, Ltd.
The dual commitments of contingent workers: an examination of contingents' commitment to the agency and the organization
Authors: Liden Robert C. , Wayne Sandy J. , Kraimer Maria L. , Sparrowe Raymond T.
Published: August 2003

A model based on social exchange theory was developed to examine antecedents and consequences of contingent workers' commitment to their agencies and their client companies. In terms of antecedents, it was hypothesized that organization (client) procedural justice would be positively related to perceived organizational support (client), which in turn would be positively related to commitment to the client organization. Similarly, we proposed that agency procedural justice would be positively related to perceived agency support, which in turn would be positively related to commitment to the agency. Regarding the consequences, client organization commitment was hypothesized to be positively related to managerial ratings of contingents' altruistic organizational citizenship behaviors (OCBs) and managers' perceptions of contingents' commitment to the client company. Finally, whether agency commitment ‘spills over’ to influence managers' perceptions of contingents' commitment to the client organization was examined. Using a sample of 98 contingent workers with matched data from their managers at the client organization and structural equation modeling analyses, we found support for all of the hypothesized relationships. Copyright © 2003 John Wiley & Sons, Ltd.
Perceived organizational support and psychological contracts: a theoretical integration
Authors: Aselage Justin , Eisenberger Robert
Published: August 2003

Although organizational support theory and psychological contract theory both stress social exchange processes in the establishment and maintenance of the employee–employer relationship, they have focused on different aspects of this relationship. We suggest that, far from being independent, the different parts of the employee–employer association considered by the two theories are mutually interdependent. Further, key processes identified by each theory influence the relationships described by the other theory. To further the understanding of the employee–employer relationship, we provide an integrated account that emphasizes the interdependence of perceived organizational support and the psychological contract. Copyright © 2003 John Wiley & Sons, Ltd.
Empirical study of traffic trunking in Linux‐based MPLS test‐bed
Authors: Rosenbaum G. , Jha S. , Hassan M.
Published: August 2003

The thrust of this study is to construct an MPLS test‐bed using open hardware and software and later use this test‐bed for experimenting with various traffic engineering options available with MPLS. We have constructed a test‐bed using Pentium PCs and Linux and used this test‐bed to try a well‐known MPLS traffic engineering feature of separating flows into multiple trunks. The purpose of this separation is to experimentally assess the quality of service benefits we can expect from MPLS networks. Copyright © 2003 John Wiley &Sons, Ltd.