bluuebunny/crossref_metadata_2025 huggingface dataset:
Sperm transfer during mating in the pharaoh’s ant, Monomorium pharaonis
Authors: ALLARD D. , BØRGESEN L. , VAN HULLE M. , BOBBAERS A. , BILLEN J. , GOBIN B.
Published: May 2006

Abstract Sperm transfer in the pharaoh’s ant Monomorium pharaonis (L.) is studied by making longitudinal sections through the gasters of mating pairs fixed in copula. Sperm is transferred inside a spermatophore similar to those found in two other ants, Diacamma sp. from Japan and Carebara vidua. Sharp teeth‐ridges are present on the penis valves and, during copulation, these teeth make contact with a thick and soft cuticular layer covering the bursa copulatrix. This ensures an attachment long enough for the successful transfer of the spermatophore to the right position inside the female oviduct. The thick cuticle also protects the queen from serious damage by the male’s sharp claspers. After a first successful copulation, sperm is still present inside the male’s seminal vesicles, suggesting that males can mate multiply. Additional experiments, where single, initially virgin males are presented to several virgin females, confirm this.
Patient experience with, and use of, an electronic monitoring system to assess vaccination responses
Authors: Olmsted Stuart S. , Grabenstein John D. , Jain Arvind K. , Lurie Nicole
Published: May 2006

Objective  To evaluate the user experience and acceptability of an electronic patient monitoring system.

Setting and participants  822 Military and civilian personnel at a health clinic at a major US military headquarters used an Internet and telephone‐based electronic monitoring system to report vaccination‐site responses and symptoms after receiving the smallpox vaccination. Focus groups of vaccinees were conducted to help develop a survey about the experience that was distributed to 379 vaccinees (96% completion rate).

Results  Users of the electronic monitoring system reported that it was fast and easy to use and reported they would use a system like this again and recommend an electronic monitoring system to a friend or relative. Most users (84%) were comfortable with a physician tracking their vaccine reaction using their electronic reports, but only half (51%) were comfortable with eliminating the post‐vaccination follow‐up visit with their health‐care provider based on their electronic reports.

Conclusions  This electronic monitoring system was well received by vaccinees and allowed health‐care providers to track the status of vaccinees. However, vaccinees were not comfortable replacing a physician visit with electronic monitoring, at least for the smallpox vaccination. A monitoring system like this may be useful in public health settings, such as mass vaccination or prophylaxis during a bioterrorism event, a pandemic influenza outbreak, or another public health emergency.
Metabolism of high density lipoprotein apolipoprotein A‐I and cholesteryl ester in insulin resistant dog: a stable isotope study
Authors: Briand F. , Bailhache E. , Nguyen P. , Krempf M. , Magot T. , Ouguerram K.
Published: May 2006

Aims:  In reverse cholesterol transport (RCT), hepatic Scavenger Receptor class B type I (SR‐BI) plays an important role by mediating the selective uptake of high‐density lipoprotein cholesteryl ester (HDL‐CE). However, little is known about this antiatherogenic mechanism in insulin resistance. HDL‐CE selective uptake represents the main process for HDL‐CE turnover in dog, a species lacking cholesteryl ester transfer protein activity. We therefore investigate the effects of diet induced insulin resistance on RCT.

Methods:  Five beagle dogs, in healthy and insulin resistant states, underwent a primed constant infusion of [1,213C2]acetate and [5,5,5‐2H3]leucine, as labelled precursors of CE and apolipoprotein (apo) A‐I, respectively. Data were analysed using modelling methods.

Results:  HDL‐apo A‐I concentration did not change in insulin resistant state but apo A‐I absolute production rate (APR) and fractional catabolic rate (FCR) were both higher (2.2‐ and 2.4‐fold, respectively, p < 0.05). HDL‐CE levels were lower (1.2‐fold, p < 0.05). HDL‐CE APR and FCR were both lower (2.3‐ and 2‐fold, respectively, p < 0.05), as well as selective uptake (2.6‐fold, p < 0.05).

Conclusions:  Lower HDL‐CE selective uptake suggests that RCT is impaired in obese insulin resistant dog.
What was hot at the fourth World Fisheries Congress?*
Authors: Chuenpagdee Ratana , Bundy Alida
Published: May 2006

Given the current crisis in global fisheries, how well are we doing at managing fisheries? This short paper describes as summarises the results of a systematic assessment of the scientific papers presented at the Fourth World Fisheries Congress, the theme of which was ’Reconciling fisheries with conservation’. Over 200 papers were presented, 70% of which were based on natural sciences, focusing on issues such as biodiversity, species at risk, resiliency, ecosystem modelling, and ecosystem indicators. Encouragingly, over 60% of the papers scored medium to high for their potential contribution to reconciling fisheries with conservation. However, although the human dimensions of fisheries were recognized, few studies involved stakeholders beyond their roles of objects to study. Communication of scientific research findings, particularly to the general public, was notably absent and emphasised as one of the key challenges in achieving sustainability and in reconciling fisheries with conservation.
Assessing the Therapeutic Use of Lafoensia pacari St. Hil. Extract (Mangava‐Brava) in the Eradication of Helicobacter pylori: Double‐Blind Randomized Clinical Trial
Authors: Da Mota Menezes Valfredo , Atallah Álvaro Nagib , Lapa Antonio José , Catapani Wilson R.
Published: May 2006

Background:  The eradication of Helicobacter pylori is easily achieved by combining antisecretory agents and antibiotics; however, the cost of these associations is very high for the population of Third World countries, where the prevalence of the infection is even higher and leads to markedly reduced treatment effectiveness. We tested a plant (Lafoensia pacari) that is used in the central region of Brazil. According to previous studies, this plant has high concentrations of ellagic acid, which presents gastric antisecretory and antibacterial actions.

Material and Methods:  One hundred dyspeptic, urease‐positive patients were randomized to receive 500 mg of methanolic extract of L. pacari (n = 55) or placebo (n = 45), for 14 days, in a double‐blind clinical trial. The main variables assessed were the eradication of H. pylori 8 weeks after the intervention and complete symptom relief at the end of the treatment.

Results:  The examinations (urease and histology) showed persistence of H. pylori in 100% of participants. Complete symptom relief was experienced by 42.5% of patients (95% CI: 29.4–55.8) in the intervention group and by 21% (95% CI: 8.8–33.1) in the control group, p = .020. The side‐effects were minimal and similar in both groups.

Conclusions:  The extract of L. pacari as a single agent was not effective to eradicate H. pylori. However, it was well tolerated and many participants reported relief of symptoms. Future studies may test the agent using larger doses and longer periods, in monotherapy or in combination with antibiotics.
Plasma ectonucleotidases prevent desensitization of purinergic receptors in stored platelets: importance for platelet activity during thrombus formation
Authors: Cauwenberghs Sandra , Feijge Marion A.H. , Hageman Geja , Hoylaerts Marc , Akkerman Jan‐Willem N. , Curvers Joyce , Heemskerk Johan W.M.
Published: May 2006

BACKGROUND:  Platelets (PLTs) contain purinergic receptors for ATP (P2X1) and ADP (P2Y1 and P2Y12) that rapidly desensitize upon stimulation with these nucleotides. In vivo, this is antagonized by ectonucleotidases on the surface of endothelial cells and white blood cells (WBCs). The receptor desensitization of ATP‐ and ADP‐induced responses of PLTs stored in plasma without WBCs was investigated.

STUDY DESIGN AND METHODS:  ATP‐ and ADP‐induced PLT shape change (shear‐induced) aggregation and Ca2+ signaling were measured in the presence or absence of plasma. Degradation of nucleotides in plasma was quantified by high‐performance liquid chromatography.

RESULTS:  Washed PLTs became refractory for ATP and ADP in shape change, aggregation, and Ca2+ responses during a 90‐minute incubation at 37°C. The PLT responses mediated by P2X1, P2Y1, and P2Y12 receptors gradually reduced or disappeared. When plasma was present, however, the PLTs persistently showed high responses to ATP and ADP. Heat treatment of plasma abolished this effect. Also under conditions of flow and high shear, PLTs in plasma kept high P2X1 activity, mediating aggregate formation. In isolated plasma, not containing WBCs, nucleotides were degraded in the order of ADP/UDP > ATP/UTP. Degradation of ATP was partly inhibited by blocking the ecto‐NTPDase CD39, whereas degradation of both ATP and ADP was inhibited by blocking ectopyrophosphatase/phosphodiesterase activity. Part of the nucleotide‐degrading activities appeared to be membrane‐bound.

CONCLUSION:  Ectonucleotidases in plasma preserve the functionality of P2X1 and P2Y receptors. Upon PLT storage, these plasma activities are essential to ensure adequate (shear‐dependent) formation of aggregates and thrombi.
Total antioxidant capacity and superoxide dismutase activity levels in serum and gingival crevicular fluid in post‐menopausal women with chronic periodontitis
Authors: Baltacıoğlu Esra , Akalın Ferda Alev , Alver Ahmet , Balaban Fulya , Ünsal Mesut , Karabulut Erdem
Published: May 2006

Objectives: Menopause has been linked with oxidative stress and decreased antioxidant (AO) defence. A connection has been established between menopause and certain periodontal conditions. The objective of this study is to compare serum and gingival crevicular fluid (GCF) total antioxidant capacity (TAOC) and superoxide dismutase (SOD) concentrations in post‐menopausal patients with chronic periodontitis (PMCP) with those of pre‐menopausal chronic periodontitis patients (CP).

Material and Methods: Thirty‐two PMCP patients, 31 CP patients, 25 post‐menopausal periodontally healthy controls (PMPH) and 26 pre‐menopausal controls (PH) were studied. After clinical measurements and samplings, serum and GCF TAOC and SOD concentrations were established in turn using an automated TAOC assay and spectrophotometric end point measurement. The results were analysed statistically.

Results: Serum and GCF TAOC and SOD concentrations were significantly lower in menopause and periodontitis (p<0.05). The lowest values were in the PMCP group, whereas the highest values were in the PH group. While the effect of menopause was more evident in serum antioxidant analysis, the effect of periodontitis was observed to be more apparent in GCF.

Conclusions: A decrease in systemic and local AO defence was observed owing to both menopause and periodontitis. The lowest AO values in the PMCP group suggest that menopause may be a risk factor for periodontitis.
The management of drug‐induced gingival overgrowth
Authors: Mavrogiannis M. , Ellis J. S. , Thomason J. M. , Seymour R. A.
Published: May 2006

Objectives: This review critically evaluates the different therapies that are available to manage drug‐induced overgrowth (DIGO).

Material and Methods: This review is based on literature identified using the online databases MEDLINE and PUB MED. It is not a systematic review, but a conventional review of the relevant literature.

Results: Patients benefit from a non‐surgical approach if this can be delivered before commencement of medication although in many instances this may not be practicable. Systemic antibiotic usage has been evaluated in the management of ciclosporin‐induced gingival overgrowth. Efficacy appears to be equivocal and long‐term use is undesirable. Surgical excision remains the main treatment option especially for patients with severe overgrowth. Few studies have compared different techniques with respect to recurrence rate or post‐operative sequelae.

Conclusion: DIGO is a common clinical problem that often requires intervention. Non‐surgical techniques can limit the occurrence of this unwanted affect, reduce the extent of plaque‐induced gingival inflammation and reduce the rate of recurrence. Wherever possible this management strategy should be adopted first. Surgical treatment is often the most reliable option and scalpel gingivectomy remains the treatment of choice. Further investigations are required to develop appropriate management strategies to prevent recurrence of DIGO.
Use of Miniaturized Protein Arrays for
Escherichia coli
O Serotyping
Authors: Anjum Muna F. , Tucker James D. , Sprigings Katherine A. , Woodward Martin J. , Ehricht Ralf
Published: May 2006

Serological typing of
Escherichia coli
O antigens is a well-established method used for differentiation and identification of O serotypes commonly associated with disease. In this feasibility study, we have developed a novel somatic antibody-based miniaturized microarray chip, using 17 antisera, which can be used to detect bound whole-cell
E. coli
antigen with its corresponding immobilized antibody, to assess the feasibility of this approach. The chip was tested using the related 17 control strains, and the O types found by the microarray chip showed 100% correlation with the O types found by conventional typing. A blind trial was performed in which 100
E. coli
isolates that had been O serotyped previously by the conventional assay were tested by the array approach. Overall, the O serotypes of 88% of isolates were correctly identified by the microarray method. For several isolates, ambiguity of O-type designation by microarray arose due to increased sensitivity of this method, allowing signal intensities of cross-reactions to be quantified. Investigation of discrepancies between conventional and microarray O serotyping indicated that some isolates upon storage had become untypeable and, therefore, gave poor signal intensity when tested by the microarray or retested by conventional means. For all 20 serotype O26 and O157 isolates, the apparent discrepancy in O serotyping was analyzed further by a third independent test, which confirmed the microarray results. Therefore, the use of miniaturized protein arrays increases the speed and efficiency of O serotyping in a cost-effective manner, and these preliminary findings suggest the microarray approach may have a higher accuracy than those of traditional O-serotyping methods.
Unique Posttranslational Modifications of Chitin-Binding Lectins of
Entamoeba invadens
Cyst Walls
Authors: Van Dellen Katrina L. , Chatterjee Anirban , Ratner Daniel M. , Magnelli Paula E. , Cipollo John F. , Steffen Martin , Robbins Phillips W. , Samuelson John
Published: May 2006

Entamoeba histolytica
, which causes amebic dysentery and liver abscesses, is spread via chitin-walled cysts. The most abundant protein in the cyst wall of
Entamoeba invadens
, a model for amebic encystation, is a lectin called EiJacob1. EiJacob1 has five tandemly arrayed, six-Cys chitin-binding domains separated by low-complexity Ser- and Thr-rich spacers.
E. histolytica
also has numerous predicted Jessie lectins and chitinases, which contain a single, N-terminal eight-Cys chitin-binding domain. We hypothesized that
E. invadens
cyst walls are composed entirely of proteins with six-Cys or eight-Cys chitin-binding domains and that some of these proteins contain sugars.
E. invadens
genomic sequences predicted seven Jacob lectins, five Jessie lectins, and three chitinases. Reverse transcription-PCR analysis showed that mRNAs encoding Jacobs, Jessies, and chitinases are increased during
E. invadens
encystation, while mass spectrometry showed that the cyst wall is composed of an ∼30:70 mix of Jacob lectins (cross-linking proteins) and Jessie and chitinase lectins (possible enzymes). Three Jacob lectins were cleaved prior to Lys at conserved sites (e.g., TPSVDK) in the Ser- and Thr-rich spacers between chitin-binding domains. A model peptide was cleaved at the same site by papain and
E. invadens
Cys proteases, suggesting that the latter cleave Jacob lectins in vivo. Some Jacob lectins had
O
-phosphodiester-linked carbohydrates, which were one to seven hexoses long and had deoxysugars at reducing ends. We concluded that the major protein components of the
E. invadens
cyst wall all contain chitin-binding domains (chitinases, Jessie lectins, and Jacob lectins) and that the Jacob lectins are differentially modified by site-specific Cys proteases and
O
-phosphodiester-linked glycans.
Heterocyclic compounds. VIII. Studies on oxazolophenoxazines
Authors: Osman A. M. , Metwally S. A. M. , Youssef M. S. K.
Published: May 2006

5H-Oxazolo[4,5-b]phenoxazine (5) was synthesized by the reaction of 3-amino-2-hydroxyphenoxazine hydrochloride (2) with formamide. A series of styryl-oxazolophenoxazines (9) were prepared by condensation of 2-methyl-5-acetyloxazolo[4,5-b]phenoxazine methiodide (8) with aromatic aldehydes. By contrast, 2-aryl-oxazolophenoxazines (14) were synthesized by reaction of 3-aminophenoxaz-2-one (1) with the appropriate aldehydes in the presence of an acid–base catalyst. The biological activities of some of these compounds were tested.
Asymmetric induction in the Sommelet rearrangement of chiral benzyl sulfonium salts
Authors: Campbell Stewart John , Darwish David
Published: May 2006

The Sommelet rearrangement of (+)-ethylmethyl-p-nitrobenzylsulfonium perchlorate, (+)-1, and (+)-ethylmethyl-p-chlorobenzylsulfonium perchlorate, (+)-2, are described. Elution of (+)-1 through an hydroxide exchange resin generated ethylmethylsulfonium p-nitro-benzylide (+)-3 which decomposed in methanol at room temperature to ethyl 2-methyl-5-nitro-benzyl sulfide, 6, and (+)-methyl α-(2-methyl-5-nitrophenyl)ethyl sulfide, (+)-7, with 18 to 20.3% asymmetric induction. Decomposition of (+)-2 in sodium methoxide solution at 70 °C for 2 h produced ethyl 2-methyl-5-chlorobenzyl sulfide, 8, and (+)-methyl α-(2-methyl-5-nitro-phenyl)ethyl sulfide, (+)-9, with 21 to 25.5% asymmetric induction. The lower estimates of asymmetric induction for each sulfide were made by comparison with specific rotations of authentic samples obtained by synthesis and resolution. The higher estimates were obtained by the use of a chiral lanthanide shift reagent Eu(hfbc)3 with the sulfone derivatives of these chiral sulfides. The ylide (+)-3 reacted with aldehydes in high yield to produce oxiranes with no induction of asymmetry.
Composés carbonylés aromatiques: traitement semi-empirique des influences structurales sur leur basicité
Authors: Beaupère D. , Séguin J. P. , Uzan R. , Doucet J. P.
Published: May 2006

We have calculated the total electron density qt0 at the oxygen atom, to the CNDO II approximation, for twenty-five compounds of the type [Formula: see text] where X = NO2, Cl, H, CH3, OMe, and [Formula: see text] and [Formula: see text] A linear variation of pK as a function of qt0 is shown by a set of four essentially parallel lines; the separation of the lines could be attributed to variations in the solvent effect which depend on the nature of R. A more general treatment of all the results, using a single equation ΔpK = 154Δqt0 + 0.1, allows an evaluation of the effect of structure on the basicity of a carbonyl compound whatever might be the nature of X or R. [Journal translation]
Photochemical rearrangements of substituted thiochromanone sulfoxides
Authors: Still I. W. J. , Arora P. C. , Chauhan M. S. , Kwan M.-H. , Thomas M. T.
Published: May 2006

The photochemical behavior of a number of substituted derivatives of thiochroman-4-one 1-oxide has been examined. In contrast to the analogous sulfones these sulfoxides undergo a variety of photochemical rearrangements. At least three distinct pathways have been recognized; β-hydrogen abstraction or rearrangement to cyclic sulfenates, which then undergo further reaction by homolysis of the S—O bond, appearing to be particularly favorable processes. In a small number of examples, photochemical deoxygenation is observed as a competing reaction. Mechanisms which attempt to account for the influence of structural variations on the particular pathway followed have been proposed.
Studies of the pyrolysis of diethylzinc by the toluene carrier method and of the reaction of ethyl radicals with toluene
Authors: Koski Ahti A. , Price S. James W. , Trudell Barry C.
Published: May 2006

The thermal decomposition of diethylzinc in a toluene carrier system has been studied over the temperature range of 669 to 762 K, and percent decomposition of 3.8 to 97.2%. The decomposition occurs by a two step mechanism, the second step rapidly following the first,[Formula: see text]The overall progress of the reaction was followed by determination of the residual diethylzinc by hydrolysis followed by analysis for zinc by atomic absorption. In selected runs two additional methods were used: (i) measurement and analysis of the gas evolved during the hydrolysis and (ii) full analysis of all pyrolysis products involving the C2H5 group.In the absence of zinc oxide the decomposition is essentially homogeneous and[Formula: see text]or −205 000/19.15T if the activation energy is expressed in joules rather than calories. The presence of zinc oxide causes marked catalysis of the overall decomposition but does not appear to affect reaction 3 or reaction 6.[Formula: see text][Formula: see text]Reaction 6 is in a strongly pressure dependent region and is based on very limited data.
Photoelectron studies on intramolecularly hydrogen-bonded systems. I. The photoelectron spectra of cis- and trans-2-aminocyclopentanol, and cis- and trans-2-(N,N-dimethylamino)cyclopentanol
Authors: Brown R. S.
Published: May 2006

The photoelectron spectra of cis- and trans-2-aminocyclopentanol and cis- and trans-2-(N,N,-dimethylamino)cyclopentanol have been recorded and interpreted. The cis isomers exhibit N lone pair ionizations at higher ionization energy, and O lone pair ionizations at lower ionization energy than their trans isomers.The results are most consistent with the existence and observation of intramolecular hydrogen-bonding in the cis isomers. Infrared data on these systems also show that the cis isomers exist in the intramolecularly hydrogen-bonded state.
Molecular structure effects on electron ranges and mobilities in liquid hydrocarbons: chain branching and olefin conjugation: mobility model
Authors: Dodelet J.-P. , Shinsaka K. , Freeman G. R.
Published: May 2006

The effect of molecular structure on electron behavior in liquids was studied by measuring secondary electron penetration ranges bGP and thermal electron mobilities ue in substituted methanes and ethylenes. The penetration ranges are smaller (energy transfer cross sections are larger) when the alkane molecules are less rigid. It was confirmed that the epithermal electron energy transfer interaction radius in a liquid phase alkane molecule is limited to two C—C bonds in series. This modifies the earlier noted correlation between bGP and the degree of sphericity of the molecules. For example, the density normalized range bGPd in the relatively sphere-like tetraethylmethane (54 × 10−8 g/cm2) is more similar to that in the distinctly nonspherical diethylmethane (n-pentane, 43 × 10−8 g/cm2) than to that in the sphere-like tetramethylmethane (126 × 10−8 g/cm2). Tetraethylmethane is too large for the entire molecule to interact with an electron in the liquid phase, and the possibility of rotations about the C—C bonds in the ethyl groups makes the molecule less rigid. Electrons sense these relatively sphere-like molecules to be similar to those of a n-alkane. Connecting tert-butyl groups to olefinic or acetylenic carbons creates sphere-like quasi neopentyl groups which greatly enhance electron ranges in the unsaturated compounds. In conjugated olefins cis–trans effects are largely overshadowed by the general efficiency of these compounds as electron energy sinks. The earlier noted correlation between bGP and ue contains fine structure. For a given value of bGP, ue increases in the order n-alkane < cyclo or branched alkane < olefin. Electron mobilities are interpreted in terms of a model that contains a Gaussian distribution of solvated electron state energies, a conduction band, and thermally activated transitions between them. The model is a combination of our treatment of electrons in ethers and Schiller's treatment of electrons in hydrocarbons. The percolation model does not provide a sufficiently complete interpretation of electron migration in hydrocarbons.
Use of polymers as protecting groups in organic synthesis. III. Selective functionalization of polyhydroxy alcohols
Authors: Fréchet Jean M. J. , Nuyens Lucy J.
Published: May 2006

Insoluble polymers containing trityl chloride residues were used to block one primary alcohol functional group of several polyhydroxy alcohols. After protecting the remaining hydroxyl groups by benzoylation, the ether linkage between the polymer and the protected alcohol was cleaved in acidic medium. Depending on the reaction conditions and the nature of the starting alcohol, several alcohols or bromides in which only one of the two primary hydroxyls had been esterified, were obtained. In some cases benzoyl migrations were observed. The trityl chloride polymers could be regenerated in one step without degradation or appreciable loss of activity.
The crystal structure of potassium trichloro(2,6-lutidine)platinum(II)
Authors: Melanson R. , Rochon F. D.
Published: May 2006

The molecular and crystal structure of potassium trichloro(2,6-lutidine)platinum(II) has been determined by X-ray diffraction. The complex salt forms monoclinic crystals, a = 6.941, b = 24.301, c = 11.168 Å, β = 141.58°, Z = 4, and space group P21/c. Positional and anisotropic thermal parameters were refined by full matrix least squares calculations to R = 0.038 and Rw = 0.034.The coordination around the platinum atom is planar. The Pt—Cl bond lengths are 2.301, 2.299, and 2.302 Å and the Pt—N bond length is 2.011 Å. The 2,6-lutidine ring lies almost perpendicular to the coordination plane of the platinum atom (81.6°). The PtCl3 moieties are packed around the potassium ions, which are surrounded by four chlorine atoms at distances smaller than 3.15 Å forming a distorted tetrahedron.
Recherches en série hétérocyclique. XXVII. Etude de la condensation de l'azidoacétate d'éthyle sur les thiophènedicarbaldéhydes-2,5, -2,4 et -3,4
Authors: Farnier Michel , Soth Samreth , Fournari Pierre
Published: May 2006

Ethyl azidoacetate reacts with 2,5-, 2,4-, and 3,4-thiophenedialdehydes to yield products of both mono- and dicondensation. Cyclization of the thiophene derivatives thus obtained leads to substituted thienopyrroles, to systems involving two pyrrole rings orthocondensed to one thiophene ring, or to thieno[3,4-c]pyridones and pyridines. The structures of the compounds obtained from various syntheses were established by nmr. [Journal translation]
Urea – boron trihalide adducts. V. Effects of acid strength on restricted rotation in adducts of tetramethylurea and 1,1-bis(dimethylamino)ethylene
Authors: Hartman J. Stephen , Yetman Ronald R.
Published: May 2006

Boron trihalide adducts of tetramethylurea (1) and of 1,1-bis(dimethylamino)ethylene (2) show similar complexation shifts and restricted rotation about the central C—N bonds. Rotation becomes more hindered as the Lewis acid strength increases in the series BF3 < BCl3 < BBr3. A large high-field complexation shift of the CH2 protons of 2 corresponds to loss of the olefinic structure on formation of the BF3 adduct.
Electrochemical reduction of 1,3-diketones in hydroorganic medium. Preparation of 1,2-cyclopropanediols
Authors: Armand Joseph , Boulares Line
Published: May 2006

The electrochemical reduction of 1,3-diketones C6H5—CO—CR1R2—CO—R3 (R1 = H, CH3; R2 = CH3, CH2C6H5; R3 = CH3, C6H5) in an hydroorganic medium corresponds to a bielectronic process and leads to 1,2-cyclopropanediols which, in most cases, are obtained in good yields. The polarographic results are presented and the mechanisms are discussed.
The charge storage and other electrical properties of a series of polyacene quinone radical polymers
Authors: O'Brien R. N. , Lushington K. J.
Published: May 2006

A series of polyacene quinone radical polymers were made. The chemical analysis showed that the severe reaction conditions favored the Scholl (elimination of H2 and H2O) over the Friedel–Crafts reaction. Electron paramagnetic resonance spectra confirmed the presence of a biradical. Conductivity measurements in the ohmic and space charge limited regions showed that large π systems existed and that carrier traps were shallow. The π system structure and absence of quinone structure was confirmed by ir spectrometry which also showed the optical absorption edge to be 0.8 eV. Charge was injected into the polymers forming electrets and thermally stimulated current emission spectra confirmed a shallow trap depth (∼0.4 eV). It is postulated that thermal excitation to a triplet state produces the biradical and conduction is by hopping between adjacent π systems and charge storage is associated with the extensive π systems.
Thermodynamics of the dissociation of trans-cinnamic acid
Authors: Das Rebati Charan , Dash Upendra Nath , Panda Kshama Nidhi
Published: May 2006

The dissociation constant of trans-cinnamic acid in water has been determined at 15, 20, 25, 30, 35, 40, and 45 °C using a cell without liquid junction potential. From the temperature coefficient of the dissociation constant, the standard enthalpy, entropy, and free energy changes of the dissociation process have been calculated.
Chemistry of proximal π-bond systems. Part IV. The structure of 5,6-dimethylenebicyclo[2,2,1]hept-2-ene molybdenum tricarbonyl
Authors: Anderson Bryan F. , Robertson Glen B. , Butler Douglas N.
Published: May 2006

Crystals of 5,6-dimethylenebicyclo[2,2,1]hept-2-ene molybdenum tricarbonyl 1 (M = Mo) are monoclinic, a = 7.4451(3) Å, b = 13.5783(7) Å, c = 11.2691(4) Å, β = 92.593(3)°, Z = 4, space group P21/c. The structure was solved by the 'heavy atom' method and was refined by full-matrix least square procedures to a final R = 0.031. The weighted R factor was 0.051. Experimental bond lengths and angles are close to other reported values for bicyclo[2,2,1]hept-2-ene systems except for three major distortions in the triene ligand namely: the closing of the angles C(2)—C(1)—C(6) and C(3)—C(4)—C(5) by about 5.3°, the bending of the butadiene fragment plane C(8)—C(5)—C(6)—C(9) toward the metal atom by about 20° and the twisting of the terminal methylene hydrogens H(8i) and H(9i) out of the butadiene fragment plane (0.44 and 0.53 Å respectively) away from the molybdenum atom.
Metals intercalated in graphite. III. The reactions of aromatic, olefinic, and acetylenic hydrocarbons with potassium–graphite intercalates
Authors: Lalancette Jean Marc , Roussel Roger
Published: May 2006

Potassium–graphite intercalates (C24K) can act as a catalyst for the reduction of olefins and alkynes. C24K is a very efficient catalyst for the isomerization of cis-stilbene to trans-stilbene. C24K can promote deuterium exchange with hydrogens carried by hydrocarbons having an acidity equal to or higher than that of benzene. C24K can condense benzene to biphenyl and can isomerize 2-alkynes to 1-alkynes at low temperature.
Proton spin–spin coupling constants and intramolecular hydrogen bonding in bromine derivatives of 1,3-dihydroxybenzene
Authors: Schaefer Ted , Rowbotham J. Brian
Published: May 2006

The conformational preferences in CCl4 solution at 32 °C of the hydroxyl groups in bromine derivatives of 1,3-dihydroxybenzene are deduced from the long-range spin–spin coupling constants between hydroxyl protons and ring protons over five bonds. Two hydroxyl groups hydrogen bond to the same bromine substituent in 2-bromo-1,3-dihydroxybenzene but prefer to hydrogen bond to different bromine substituents when available, as in 2,4-dibromo-1,3-dihydroxybenzene. When the OH groups can each choose between two ortho bromine atoms, as in 2,4,6-tribromoresorcinol, they apparently do so in a very nearly statistical manner except that they avoid hydrogen bonding to the common bromine atom.
Kinetic study of formation of nickel (II)-isoquinoline complex in water and nonaqueous solvents
Authors: Chattopadhyay Praphulla Kumar , Kratochvil Byron
Published: May 2006

Rate constants and activation parameters for the formation of the monocomplex of nickel(II) with isoquinoline in water, methanol, dimethylsulfoxide, and N,N-dimethylformamide were obtained from measurements by stopped-flow spectrophotometry. The data are compared with previously reported work by other authors for substitution at nickel(II) with related monodentate and multidentate ligands. The results in all solvents except dimethylsulfoxide are consistent with an Id mechanism. In dimethylsulfoxide substitution at nickel(II) proceeds in a similar way for all monodentate ligands but whether the mechanism is Id or D cannot be ascertained.
Tautomeric equilibrium study of thiazolidine-2-thione. Transition metal complexes of the deprotonated ligand
Authors: Preti Carlo , Tosi Giuseppe
Published: May 2006

not available
Pyrolysis of iodobenzene by the toluene carrier technique and determination of D[C6H5—I]
Authors: Kominar R. John , Krech Michael J. , Price Stanley James W.
Published: May 2006

The pyrolysis of C6H5I has been studied by the toluene carrier technique over the temperature range 861–955 K using contact times of 0.54–3.28 s and total pressures of 2.5–4.13 kPa. Percent decomposition based on analysis for residual C6H5I ranged from 5.6–93.3%. Only trace quantities of I2 were observed and when HI was trapped out the only other gaseous products were small quantities of hydrogen and methane in about a 2:1 ratio. Within the limits of the experimental method the decomposition was found to be homogeneous and first order.[Formula: see text]The Arrhenius equation obtained for reaction 1 is[Formula: see text]Making an approximate correction of the activation energy to 298 K then gives[Formula: see text]
Reactions of tert-C4H9+, tert-C5H11+, and CH3-cy-C5H9+ ions with pentenes
Authors: Collin Guy J.
Published: May 2006

Total reaction rate constants for the disappearance of tert-C4H9+ ions with five C5H10 unsaturated hydrocarbons were determined by comparing the rate of formation of isobutane in the radiolysis of neopentane in the presence of various additives. These rate constants are of the order of 5 to 1.35 × 10−10 cm3 molecule−1 s−1 depending upon the olefin under investigation. The hydride transfer reaction from 3-methyl-1-butene and trans-2-pentene toward the tert-C4H9+ ion was also observed, as was the proton transfer reaction from the tert-C4H9+ ion toward 2-methyl-2-butene and 2-methyl-1-butene. In the latter two cases, a significant isomerization of methylbutene is noticed: an isomerization mechanism based upon the reactions of tert-C5H11+ ions is tentatively suggested. Finally, the transfer reaction of an hydrogen molecule between the CH3-cy-C5H9+ ion and the methylbutenes is observed during the radiolysis of methylcyclopentane.
Synthesis and vibrational spectra of some lead(II) halide adducts with O-, S-, and N-donor atom ligands
Authors: Wharf Ivor , Gramstad Thor , Makhija Ramesh , Onyszchuk Mario
Published: May 2006

Lead(II) halides (PbX2 where X = Cl, Br, and I) formed five types of adducts with monodentate (L) and bidentate (LL) ligands: PbX2•L, PbX2•2L, 2PbX2•L, PbX2•LL, and PbX2•2LL, but not all halides and ligands produced each type. Monodentate ligands were dimethylsulphoxide, N,N-dimethylacetamide, N,N-dimethylthioacetamide, thioacetamide, 2,6-dimethyl-γ-pyrone, N-methyl-2-pyridone, N-methyl-2-pyrollidinone, thiourea, pyridine, piperidine, and aniline, while bidentate ligands were ethylenediamine, tetramethylethylenediamine, 1,10-phenanthroline, and 2,2′-bipyridine. Infrared and Raman spectra are reported together with ligand vibrational frequencies shifted by coordination. Under similar experimental conditions qualitative trends in acceptor and donor abilities appeared to be PbI2 > PbBr2 > PbCl2 and S-donors > O-donors, respectively.
Synthesis of bridged azabicyclic ketones. Solvolysis of enol ether ethylene ketal N-cholramines in acidic medium
Authors: Furstoss Roland , Tadayoni Rahim , Esposito Gilbert , Lacrampe Jean , Heumann Andreas , Waegell Bernard
Published: May 2006

The syntheses of 2-azabicyclo[2.2.2]octanes, 2-azabicyclo[3.2.1]octanes and 2-azabicyclo[3.3.1]nonanes, by means of intramolecular cyclizations of N-chloramines under acidic solvolytic conditions, are described. The cyclization is regioselective for the enol ethers and dioxolanes. The latter reacts in an unsaturated open form. The experimental data lead us to conclude that the reaction mechanism involves an electrophilic chlorination of the enol ether double bond.
The xenon sensitised radiolysls of HBr
Authors: Nagra Surjit S. , Armstrong David Anthony
Published: May 2006

The 60Co γ-radiolysis of mixtures of HBr with Xe bas been investigated at room temperature. Ionisation measurements and hydrogen yields provide strong evidence for energy transfers between the two components. The small but significant decrease in ionisation yields at low HBr:Xe is independent of total pressure and consistent with a competition between HBr and Xe for the Hornbeck–Molnar states of Xe. The increase in ionisation yields at higher HBr:Xe (Z above 0.2) is probably due to collisionally-induced ionisation or chemi-ionisation reactions of highly excited states of HBr.As in previously reported experiments with H2S the hydrogen yields from HBr are strongly enhanced in the presence of Xe. The maximum sensitisation of 4 molecules of H2 per 100 eV can be explained by energy transfer from excited states of Xe (G ∼ 2.5) and subexcitation electrons having energy between 4.3–8.3 eV (G ∼ 1.5) in Xe. The results obtained from thermal electron scavenging with SF6 confirm previous findings that inert gases are inefficient at moderating electrons to thermal energies. At high [SF6]/[HBr], SF6 interferes with hydrogen-forming reactions other than those of electrons.
Conformational analysis of substituted 1,2-oxathiane 2-oxides by 13C and 1H nuclear magnetic resonance spectroscopy
Authors: Buchanan G. W. , Sharma N. K. , Reinach-Hirtzbach F. De , Durst T.
Published: May 2006

1H and 13C nmr results for 1,2-oxathiane 2-oxide and eight derivatives are reported. It is concluded that these molecules have a high preference for chair forms with axial S=O groups, even when a sterically bulky group such as phenyl is substituted in a syn-axial orientation to the exocyclic oxygen.
Chalkogenides of the transition elements. XI. MÖssbauer 57Fe spectrum of the spinel Co2.94Fe0.06S4 between 10 K and room temperature
Authors: Woodhams F. W. D. , Knop Osvald
Published: May 2006

Mössbauer spectra of 57Fe probe atoms in the spinel Co2.94Fe0.06S4 indicate the existence of a magnetic transition at Ttr ≈ 95 K in the parent phase Co3S4. The spectrum observed below Ttr consists of a six-line magnetic spectrum and a two-line quadrupole spectrum. Above Ttr the six-line spectrum collapses to a single line superposed on the two-line quadrupole spectrum. Consideration of the Mossbauer parameters and of the area ratio of the component spectra suggests that the atomic occupancy of the spinel lattice is [Co0.968Fe0.032][Co0.986Fe0.014]2S4, the Fe atoms having preference for the tetrahedrally coordinated cation sites.
An alternative view of unimolecular reaction theory
Authors: Pritchard Huw Owen
Published: May 2006

A primitive form of unimolecular reaction theory is constructed, based on the master equation. Application of the theory depends upon the way in which eigenvalues of large stochastic matrices behave as certain of the matrix elements are varied. Some of the required eigenvalue properties have been deduced by numerical experiment, and others are available from earlier work on diatomic dissociation reactions. Comparison of the results from this primitive approach with those of existing theories of unimolecular reactions suggests some reinterpretation of parameters used in those theories: most interestingly, the number of effective oscillators occurring in Kassel theory (or its Slater-theory equivalent) appears to be the ratio, at infinite pressure, of the total rate to the rate of the only reaction channel which survives at the low-pressure limit.
The cyclic carbamate unit of maytansine
Authors: Edwards Oliver E. , Ho Pak-Tsun
Published: May 2006

An eleven step sequence with control of the relative stereochemistry of four asymmetric centers has converted 3,4-epoxycyclohexene into a highly functionalized model for synthesis of the cyclic carbamate unit of maytansine.
Détermination du mécanisme de dégagement d'hydrogène sur le niobium en milieu alcalin
Authors: Vijayan Cherubala P. , Piron Dominique-Louis
Published: May 2006

The mechanism of the hydrogen evolution reaction on niobium is evaluated in alkaline media at 24 °C. The reaction order of zero, along with the observed Tafel slopes of 120 mV/decade (standard deviation 8 mV/dec.), indicate the Heyrovsky reaction mechanism to be applicable for the hydrogen evolution reaction. The presence of anions such as sulfate and chloride does not influence the mechanism.
The stereochemical dependence of 13C nuclear magnetic resonance chemical shifts and 13C–31P couplings in some dialkylphosphonocyclohexanes
Authors: Buchanan Gerald W. , Bowen John H.
Published: May 2006

13C chemical shifts and 13C–31P couplings are reported for 15 dialkylphosphonocyclohexanes. Data are compared to those for three related hydroxyphosphonates. Both direct and vicinal 13C–31P couplings are useful stereochemical probes. Materials with equatorial phosphorus exhibit one bond couplings larger by ca. 5 Hz than their axial counterparts. Vicinal couplings follow an approximate dihedral angle dependence but are attenuated by OH substitution. In addition to the expected gauche-γ shielding effects, pentavalent phosphorus substituents induce minor (ca. 1 ppm) upfield shifts at carbons to which they bear an anti-periplanar relation.
A study of 3-hydroxy-1,2,3-benzotriazin-4-one and its O-methyl and O-acyl derivatives
Authors: Ahern T. Patrick , Navratil Thomas , Vaughan Keith
Published: May 2006

3-Hydroxy-1,2,3-benzotriazin-4-one, 1, was prepared by diazotization of o-aminob-enz-hydroxamic acid, 2. 3-Methoxy-1,2,3-benzotriazin-4-one, 5a, was obtained by reaction of 1 with dimethyl sulphate and was found to be stable to thermolysis. Acetylation and benzoylation of 1 yielded the N-acetoxy-5b and benzoyloxy-5c derivatives respectively. The N-benzoyloxy derivative 5c is converted into the acetate 5b by a novel 'acyl-exchange' reaction in acetic anhydride. Acid hydrolysis of 1 gives anthranilic acid, and thermolyses of 1 in amyl alcohol and aniline afford amyl anthranilate and N-phenylanthranilamide, respectively. The ketenimine 11 is postulated as an intermediate in the thermal breakdown of 1, and this is confirmed by the isolation of the Diels–Alder adduct 12 from reaction of 1 with phenyl isocyanate. Thermolysis of 1 in inert solvents affords a novel compound, 3-(o-aminobenzoyloxy)-1,2,3-benzotriazin-4-one, 6, which polymerizes when 1 is subjected to prolonged thermolysis in diglyme. 6 resisted methylation and acid hydrolysis, but underwent acyl-oxygen cleavage when diazotization of 6 was attempted and suffered 'acyl-exchange' when acylation was attempted. The formation of 6 from 1 also involves the ketenimine 11. The importance of these observations to an understanding of previously reported reactions of benzotriazinones is discussed. The o-aminobenzoyloxy derivative 6 shows potential as an o-aminobenzoylating agent.
Rules for the quantitative prediction of stereochemistry in the reduction of cyclohexanones by sodium borohydride
Authors: Wigfield Donald C.
Published: May 2006

A procedure is outlined which allows calculation of the stereoselectivity of reduction of cyclohexanones by sodium borohydride under normal conditions (room temperature, 2-propanol as solvent). The procedure rests on incremental enthalpy values of steric hindrance, coupled with known isokinetic relationships to obtain values of ΔΔG≠;thus it delineates quantitatively the steric factors governing stereoselectivity in these reductions.
Studies in solvolysis. Part VIII. An entropy correlation related to the reaction of various nucleophiles with malachite green
Authors: Morris Stephen Harvey , Scott John Marshall William , Steele Frederick
Published: May 2006

The entropies of activation related to the reactions of aqueous malachite green with the nucleophiles water, hydroxide, hydrazine, ammonia, hypochlorite, and sulphite have been calculated from the temperature dependence of the rate constants appropriate to these reactions. The entropies of the transition states for these reactions have been characterized and the transition states shown to be 'reactant like'. A similar correlation, based on data for a series of nucleophiles attacking methyl iodide, suggests that the transition states for the SN2 displacement reactions are also 'reactant like' with respect to the attacking nucleophile. A relationship between two distinct parameters each of which is related to the position of transition states along the reaction coordinate is considered.
High resolution 119Sn nuclear magnetic resonance studies by pulse Fourier transform
Authors: Lassigne C. R. , Wells E. J.
Published: May 2006

The T1's, linewidths (T2's), and chemical shifts of 119Sn nuclei in a variety of tin compounds have been surveyed using pulse Fourier transform techniques. The results span the very large chemical shift range for tin-119 (∼2000 ppm), and indicate rather short T1 values with widely varied T2 relaxation times. Possible mechanisms are discussed for both T1 and T2 relaxation times. Our results show an approximate correlation between T1 (119Sn) and the paramagnetic contribution to the observed shielding of the 119Sn nucleus, indicating that apart from a large scalar contribution in Sn(IV) iodides and bromides, the dominant 119Sn T1 mechanism is spin rotation interaction.
An optically active cyclopropene as a mechanistic probe in cyclopropene photochemistry
Authors: Pincock James A. , Moutsokapas Alexios A.
Published: May 2006

The photochemistry of methyl 1-methyl-2-phenylcyclopropene-3-carboxylate has been examined in both the racemic and optically active forms. In the excited singlet the cyclopropene is converted to 2-methoxy-5-methyl-4-phenylfuran whereas the triplet state dimerizes to a tricyclohexane derivative. Experiments with optically active cyclopropene ester demonstrate that photochemical racemization occurs about 2.5 times as fast as conversion to the furan product indicating that there is an intermediate vinyl carbene on the singlet surface. No racemization is observed in the triplet state.
Nuclear magnetic resonance study of catalyzed intermolecular fluorine exchange in the methyltetrafluorosilicate anion
Authors: Marat Ronald Kirk , Janzen Alexander F.
Published: May 2006

The effect of HF, MeOH, H2O, F−, pyridine, Pr4N+MeSiF4−, and temperature on the rate of intermolecular fluorine exchange in the methyltetrafluorosilicate anion has been studied by the dynamic nuclear magnetic resonance technique. The exchange was found to be catalyzed by HF and, to a lesser extent, MeOH and H2O, but inhibited by F−, pyridine, and Pr4N+ MeSiF4−. The results are analyzed in terms of the coordination model of reaction mechanisms
Coefficients B de viscosité dans les systèmes ternaires aqueux. I. NaCl – alcool tert-butylique – eau et Bu4NBr – alcool tert-butylique – eau à 25 °C
Authors: Palma Marc , Morel Jean-Pierre
Published: May 2006

We have measured the viscosity coefficient B of the electrolytes NaCl and Bu4NBr in aqueous-organic mixtures containing up to 40% by weight of tert-butyl alcohol (TBA), as well as that of the non-electrolyte TBA in aqueous solutions of the salts NaCl and Bu4NBr. The variations of B were compared with those of the thermodynamic quantities ΔHtθ and ΔStθ of the solutes studied in these different media. The contribution of the solute to the free enthalpy of activation of viscosity has also been calculated.