bluuebunny/crossref_metadata_2025 huggingface dataset:
La démocratie : oui, mais laquelle?
Authors: Truchon Michel
Published: July 2012

Cet article illustre les difficultés inhérentes au processus démocratique à partir des résultats d’une consultation tenue à l’Université Laval, dans le cadre de la nomination d’un doyen. Lors de ce scrutin, les votants devaient en principe ordonner tous les candidats, au nombre de quatre. La compilation des résultats s’avérait donc un exercice d’agrégation des ordres (préférences) individuels en ordre (préférence) collectif. L’article emprunte abondamment à la littérature sur la théorie des choix sociaux et constitue en quelque sorte un survol partiel de cette dernière. Il montre d’abord comment des résultats, en apparence si clairs selon la règle de la pluralité, peuvent venir en contradiction avec le principe de la majorité préconisé par Condorcet. Ce dernier veut qu’un candidat, que la majorité des votants placent avant un autre, se retrouve également avant ce dernier dans l’ordre collectif. L’article présente ensuite les procédures de vote pondéré, les plus connues étant celles de la pluralité et de Borda. Il discute des possibilités de manipulation de ces procédures selon le système de pondération choisi. Pour revenir au principe de Condorcet, son application à toutes les paires de candidats peut malheureusement donner des cycles dans les préférences collectives. C’est le fameux paradoxe de Condorcet. Plusieurs méthodes ont été proposées pour briser ces cycles. L’article présente la méthode dite du maximum de vraisemblance comme celle qui se rapproche davantage de l’esprit du principe de Condorcet. Plusieurs exemples sont fournis tout au long de l’article.
Traitement fiscal optimal des familles quand la fécondité est endogène
Authors: Cigno Alessandro , Pettini Anna
Published: July 2012

Les effets et le choix optimal d’instruments de politique destinés aux familles (allocations pour enfants à charge, taxes sur les biens consommés spécifiquement par les enfants, etc.) sont analysés à l’aide d’un modèle économique où les ménages possèdent un choix en matière de fécondité. Quand la fécondité est un facteur endogène, nous obtenons des résultats remarquables si nous considérons simultanément les avantages pour enfants à charge et l’imposition du revenu et de la consommation. Entre autres, les différentes capacités des familles à élever des enfants et, par conséquent, toutes choses étant égales par ailleurs, les variations du nombre d’enfants, peuvent ne pas être pertinentes d’un point de vue fiscal si l’État peut effectuer des transferts forfaitaires (impôts/subventions) personnalisés aux familles. Plus surprenant encore, on peut montrer que, si l’État est dans l’impossibilité de procéder à des transferts forfaitaires personnalisés, mais qu’il est en mesure de distinguer les biens consommés exclusivement par les enfants de ceux qui sont propres aux adultes, il pourrait alors être optimal d’imposer selon le nombre d’enfants et de subventionner les biens propres aux enfants (c’est-à-dire d’aider financièrement les parents de manière à les inciter à dépenser davantage pour chaque enfant mis au monde, plutôt que de les amener à avoir plus d’enfants et à lésiner quand il s’agit de subvenir à leurs besoins).
Analyse de l’effet des règles d’obtention d’un permis de conduire au Québec (1991) sur la sécurité routière
Authors: Dionne Georges , Laberge-Nadeau Claire , Maag Urs , Desjardins Denise , Messier Stéphane
Published: July 2012

La réglementation de la sécurité routière a été l’objet de plusieurs études. Sa principale motivation est reliée aux externalités que certains conducteurs peuvent générer à d’autres individus (conducteurs, piétons) et qui ne peuvent être tarifées directement par différents marchés privés. L’objectif de notre recherche est d’évaluer l’effet des règles d’obtention d’un permis de conduire au Québec (1991) sur les taux d’accidents des nouveaux conducteurs. Il n’est pas toujours évident qu’un changement de réglementation affectera le niveau d’équilibre de prévention routière dans une société. Dans cette recherche, nous vérifions que l’effet de la réforme n’est pas significatif sur les taux d’accidents et ce, ni pour l’ensemble des nouveaux conducteurs, ni pour l’ensemble des nouvelles conductrices, et ni pour chaque groupe d’âge analysé séparément. Par contre, il y a clairement des effets d’âge sur les taux d’accidents. Les nouveaux conducteurs comme les nouvelles conductrices âgés de 20 ans et plus, sont moins à risque d’avoir un accident que ceux et celles âgés de 16 ans à l’obtention du permis. Les nouveaux conducteurs âgés de 17 ans et ceux âgés de 18-19 ans enregistrent des risques semblables aux 16 ans. Ces variations entre les groupes d’âges montrent une grande hétérogénéité des nouveaux conducteurs et conductrices même durant leur première année de conduite alors que la réglementation de 1991 des nouveaux conducteurs et conductrices les considérait comme homogènes. Nous avons également vérifié si l’expérience accumulée durant la première année affecte les taux d’accidents. Nous obtenons que les taux moyens d’accidents observés durant les trois premiers mois chez les femmes et les quatre premiers mois chez les hommes, sont plus élevés que ceux des périodes subséquentes de 30 jours.
Comptabilité générationnelle et vieillissement démographique : les enseignements d’un modèle d’équilibre général calculable calibré pour la Belgique
Authors: Docquier Frédéric , Liégeois Philippe , Stijns Jean-Philippe
Published: July 2012

Dans la plupart des pays développés, un vieillissement démographique important s’annonce. À politique économique inchangée, ce vieillissement générera un accroissement important des charges supportées par les individus jeunes et actifs, présents et à venir, et donc une détérioration de la situation des générations futures. Dans ce débat, lacomptabilité générationnelled’Auerbachet al.(1991, 1994) et Kotlikoff (1992) occupe une place prépondérante. Elle permet, en effet, de comparer le bilan fiscal moyen des générations à venir avec la charge supportée par les générations actuelles.

Nous proposons dans ce papier une extension immédiate de la comptabilité générationnelle d’Auerbachet al., qui consiste à estimer, de manière mécanique, la distribution de la charge léguée entre les générations futures. En supposant que la taxe sur les salaires équilibre le budget de l’État à chaque période, il ressort que ce sont les générations qui atteignent l’âge adulte entre 2020 et 2035 qui supportent la charge la plus forte. Les résultats sont établis sur base de données valables pour la Belgique.

Puis nous comparons les enseignements de cette approche avec les résultats livrés par un modèle d’équilibre général dans lequel les agents ont une durée de vie incertaine. Ce type de modèle restitue un ensemble de grandeurs établies sur base d’hypothèses de comportement rationnel des individus et d’équilibre des marchés. Il nous montre que les écarts entre les charges supportées par les individus actuellement en vie et ceux à naître pourraient être beaucoup plus prononcés que ceux dégagés par une simple extrapolation mécanique. Cet effet est essentiellement dû à un rétrécissement des bases fiscales résultant d’une hausse du taux de taxation des salaires.
L’imposition des revenus de l’investissement en Europe, une hétérogénéité coûteuse
Authors: Gérard Marcel
Published: July 2012

L’imposition des revenus du capital en Europe est caractérisée par l’autonomie de juridictions parcellisées d’une part, l’intégration du marché du capital d’autre part. Cette situation ouvre la voie à une concurrence entre juridictions coûteuse en termes de bien-être, tant du fait des pertes de recettes fiscales qu’elle implique, que des modifications qu’elle induit dans la distribution de la charge des dépenses publiques et l’allocation des dépenses des États. Dans cet article nous commençons par décrire cette situation, ensuite nous en proposons une analyse, lecture selon la grille du discours économique sur les finances publiques, enfin nous discutons quelques pistes pour sortir de cette hétérogénéité coûteuse.
Prudence fiscale, indicateurs d’endettement et évolution de l’état des finances des administrations publiques au Canada
Authors: Paquet Alain
Published: July 2012

Ce texte discute de la mesure, des causes et des conséquences de l’endettement public et revoit divers indicateurs d’endettement, de solvabilité et de prudence fiscale. Après avoir présenté une analyse descriptive et comparative de la situation de la dette publique des gouvernements au Canada et ailleurs dans le monde, nous évaluons la solvabilité des gouvernements au Canada. Finalement, nous construisons des indicateurs de prudence fiscale pour les gouvernements fédéral et québécois qui révèlent dans quelle mesure les politiques financières poursuivies ont été insoutenables.
Smart Metal–Polymer Bionanocomposites as Omnidirectional Plasmonic Black Absorber Formed by Nanofluid Filtration
Authors: Elbahri Mady , Homaeigohar Shahin , Abdelaziz Ramzy , Dai Tianhe , Khalil Rania , Zillohu Ahnaf Usman
Published: July 2012

The first smart plasmonic absorber based on metal‐polymer bionanocomposites performing via conformational changes of the biological functional agent, i.e., a protein, is introduced. Such a progress is done through bridging the gaps between nanofluid filtration, plasmonics, and bioswitching. Initially, a biofunctionalized nanofibrous membrane is developed that could filter out metal nanoparticles (<100 nm) from an aqueous stream with a high separation efficiency (97%). This approach brings about a breakthrough in applicability of the macroporous nanofibrous membranes for rejection of suspended nanosolids and extends the application area beyond microfiltration (MF) to ultrafiltration (UF). This operative filtration in the next step leads to a novel synthesis route for plasmonic materials as formation of a smart free‐standing metal–polymer bionanocomposite able to act as an omnidirectional black absorber.
Preparation and characterization of phosphoric acid composite membrane by radiation induced grafting of 4‐vinylpyridine onto poly(ethylene‐co‐tetrafluoroethylene) followed by phosphoric acid doping
Authors: Nasef Mohamed Mahmoud , Shamsaei Ezzatollah , Saidi Hamdani , Ahmad Arshad , Dahlan Khairul Zaman Mohd
Published: July 2012

Preparation of phosphoric acid composite membranes by radiation induced grafting of 4‐vinylpyridine (4‐VP) onto electron beam irradiated poly(ethylene‐co‐tetrafluoroethylene) film followed by phosphoric acid doping was investigated. The effect of grafting parameters (monomer concentration, absorbed dose, reaction time, and temperature) on the degree of grafting (G%) in the membrane precursor and its relation with the amount of acid doped was studied. The proton conductivity of the obtained membranes was evaluated in correlation with G% and temperature using ac impedance. Fourier transform infrared, thermal gravimetric analysis, X‐ray diffraction, and universal mechanical tester were used to investigate chemical composition, thermal resistance, structure, and mechanical properties of the membranes, respectively. The membranes of 34 and 49% recorded high proton conductivity in the magnitude of 10‐2 S cm‐1 without humidification. The membranes were also found to have reasonable mechanical integrity together with thermal stability up to 160°C. The obtained membranes are suggested to be less‐water dependent and have potential for testing in high temperature polymer electrolyte membrane fuel cell. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Interfacial polymerization of polyaniline and its layer‐by‐layer assembly into polyelectrolytes multilayer thin‐films
Authors: Detsri Ekarat , Dubas Stephan Thierry
Published: July 2012

The layer‐by‐layer (LbL) self assembly deposition technique was used to prepare multilayer thin films of anionic polyaniline‐blend‐poly(sodium 4‐styrenesulfonate) (PANI‐PSS) and cationic poly(diallydimethylammonium chloride) (PDADMAC). Anionic polyaniline was prepared by the interfacial polymerization of aniline monomer in the presence of PSS which acted as template to provide water solubility. The PSS to PANI concentration ratios used in the synthesis step was found to have a major effect on the final PANI‐PSS synthesis, its self assembly and the electrical properties of the prepared films. The optical and electrical properties of the films were measured by ultraviolet‐visible spectroscopy (UV‐Vis) and a 4‐point probe setup, respectively while the thickness of the films was measured by atomic force microscopy (AFM). Results showed that the optimum condition for the film growth and optimal conductivity were obtained with different synthesis conditions. These results suggest that the PSS concentration used for interfacial synthesis of PANI must be finely tuned depending on the type of application aimed by the user. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Polyurethanes from soybean oil, aromatic, and cycloaliphatic diamines by nonisocyanate route
Authors: Javni Ivan , Hong Doo Pyo , Petrović Zoran S.
Published: July 2012

Polyurethanes were prepared via a nonisocyanate route, by reacting carbonated soybean oil (CSBO) with aromatic and cycloaliphatic diamines. Nonisocyanate polyurethanes prepared form CSBO and aliphatic diamines have relatively low tensile strength and one of the possible ways to increase strength and rigidity is to use diamines with rigid aromatic or cyclic structure. The effect of amine structure and amine to carbonate ratio on polyurethane structure and mechanical, physical, and swelling properties was studied. m‐xylylene diamine (m‐XDA), p‐xylylene diamine (p‐XDA), and isophorone diamine were used as the reactants, with amine to carbonate ratios of 0.5 : 1, 1 : 1, and 1 : 2. All amines produced elastomeric polyurethanes with glass transitions between −6° C and 26°C, as measured by differential scanning calorimeter (DSC). Tg was primarily controlled by the amine‐to‐cyclic carbonate ratio, and to a lesser extent by the amine structure. The highest tensile strength was obtained for p‐XDA and the lowest for m‐XDA as a result of differences in hydrogen bonding. Tensile strength and hardness were higher than in aliphatic diamine‐based polyurethanes. Swelling in toluene and water depended on the polarity of polyurethane networks that was dominantly controlled by the amine‐to‐cyclic carbonate ratio. Swelling in toluene was higher at the lower amine to carbonate ratio due to lower polarity of the polyurethane matrix. Swelling in water behaved quite the opposite, the degree of swelling for the more polar polyurethane matrix was higher. Reaction temperatures of 70–100°C were high enough to promote ester group cleavage and along with urethanes, amide formation was always present. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Deblocking of the water‐soluble isophorone diisocyanate blocked by sodium bisulfite and its application
Authors: Zhou Zhengfa , Lv Hongxiang , Wang Xiaowen , Ren Fengmei , Xu Weibing
Published: July 2012

A water‐soluble and low stimulation sodium bisulfite blocked isophorone diisocyanate (IPDI) has been prepared. The blocking and deblocking of the blocked IPDI is observed by hot‐stage Fourier transform infrared (FTIR) spectrophotometer. The experimental results reveal that IPDI is successfully blocked by sodium bisulfite and the blocked IPDI can regenerate isocyanate groups when the temperature is higher than 80°C. Differential scanning calorimetry analysis indicates that blocked IPDI deblocks initially at around 85°C and reaches the maximum deblocking rate at 117°C. The blocked IPDI in liquid and solid states are stable after being stored for 12 months at room temperature. The blocked IPDI is used as curing agent for waterborne hydroxyl polyurethane, which has good adhesive performance and long pot life. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Unexpected visible‐light‐induced free radical photopolymerization at low light intensity and high viscosity using a titanocene photoinitiator
Authors: Kitano Hajime , Ramachandran Karthik , Bowden Ned B. , Scranton Alec B.
Published: July 2012

Most visible‐light photoinitiators are based on electron transfer processes and are comprised of two or more components. These initiators can lose effectiveness in viscous systems because the underlying reactions are diffusion controlled. In this contribution, the visible‐light photoinitiator bis(cyclopentadienyl) bis[2,6‐difluoro‐3‐(1‐pyrryl)phenyl]titanium is characterized for polymerization of viscous systems and low light intensities. This compound absorbs visible light at wavelengths up to 550 nm, and does not rely on diffusion‐controlled electron transfer reactions because it undergoes unimolecular decomposition. In contrast to trends observed for other photoinitiators, the effectiveness of the compound is found to increase markedly with the addition of protonic acids and with increasing system viscosity. For a given concentration of initiator and acid, a remarkably low optimal light intensity for effective polymerization is observed. The origins of these surprising results are discussed in terms of the mechanism of decomposition of the photoinitiator. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
No differences in cancer screening rates in patients with rheumatoid arthritis compared to the general population
Authors: Kim Seoyoung C. , Schneeweiss Sebastian , Myers Jessica A. , Liu Jun , Solomon Daniel H.
Published: July 2012

Objective

Previous study findings have suggested that patients with chronic diseases such as rheumatoid arthritis (RA) do not receive optimal preventive medical services, including cancer screening tests. This study was undertaken to evaluate cancer screening rates in RA patients compared to non‐RA control populations.

Methods

Using data from a large US commercial insurance plan, we examined rates of screening tests for cervical, breast, and colon cancer in patients with RA compared to control subjects without RA (non‐RA controls) or control subjects with hypertension. Individuals were included in the RA cohort if they had at least 2 visits coded for a diagnosis of RA and had received at least 1 prescription for a disease‐modifying antirheumatic drug during the study period. Multivariable Cox proportional hazards models were used to compare the rates of different cancer screening tests between RA patients and non‐RA controls.

Results

RA patients (n = 13,314) and control subjects (non‐RA and hypertension controls) (n = 212,324) were screened, on average, once every 3 years for cervical cancer and once every 2 years for breast cancer during the followup period (mean 2.3 years of followup). In the age‐adjusted Cox regression model, women with RA were more likely to receive ≥1 Papanicolaou smear (hazard ratio [HR] 1.21, 95% confidence interval [95% CI] 1.17–1.24), ≥1 mammogram (HR 1.49, 95% CI 1.45–1.53), and ≥1 colonoscopy (HR 1.69, 95% CI 1.61–1.77) compared to female non‐RA control subjects. Men with RA were also more likely to receive at least 1 colonoscopy (HR 1.52, 95% CI 1.40–1.64) than were male non‐RA control subjects. These results were robust in multivariable analyses adjusted for age, number of physician visits, percentage of visits made to primary care physicians, and the Charlson Comorbidity Index.

Conclusion

Patients with RA did not appear to be at risk for receiving fewer cancer screening tests when compared to individuals without RA. The majority of both RA patients and non‐RA control subjects were screened regularly for cervical, breast, and colon cancer, in accordance with current recommendations.
The effects of acute responsive high frequency stimulation of the subiculum on the intra‐hippocampal kainic acid seizure model in rats
Authors: Huang L. , van Luijtelaar G.
Published: July 2012

The effects of acute responsive high frequency stimulation (HFS) to the subiculum on seizures and interictal spikes were investigated in a semi‐acute kainic acid (KA) induced seizure model in rats. Wistar rats (n = 15) were implanted with an electrode‐cannula complex in the CA3 area, stimulation and recording electrodes in the subiculum and another recording electrode at the contralateral motor cortex. Two weeks later rats were injected repeatedly with KA (0.05 μg/0.1 μL) for 3 days with an interval of 48 h. HFS (125 Hz, 100 μsec) was delivered to the subiculum at a predetermined intensity range (100–500 μA) in the HFS group (n = 7) when seizures were visually detected, while no stimulation was delivered in the sham control group (n = 8). Various severities of seizures were obtained (Stage I–V) and all rats of both groups reached Stage V (Racine's scale) on Day 1. The HFS group had less focal seizures and a longer inter‐focal seizure interval on Day 1. Interictal spike rate was also lower in the HFS group and decreased with injection days. Significant day effects were found for the latency, number of focal seizures, and duration of focal seizures and generalized seizures while differences between groups were no longer present. Responsive HFS did not disrupt ongoing seizures. However, focal seizures and interictal spikes were suppressed by HFS. Such anticonvulsant effects of acute subicular stimulation indicate that the subiculum is involved in seizure generation. The reduction of seizure sensitivity over the injection day reflects an intrinsic anticonvulsant mechanism.
Characterization of recovered walking patterns and motor control after contusive spinal cord injury in rats
Authors: Hansen Christopher N. , Linklater William , Santiago Raquel , Fisher Lesley C. , Moran Stephanie , Buford John A. , Michele Basso D.
Published: July 2012

Currently, complete recovery is unattainable for most individuals with spinal cord injury (SCI). Instead, recovery is typically accompanied by persistent sensory and motor deficits. Restoration of preinjury function will likely depend on improving plasticity and integration of these impaired systems. Eccentric muscle actions require precise integration of sensorimotor signals and are predominant during the yield (E2) phase of locomotion. Motor neuron activation and control during eccentric contractions is impaired across a number of central nervous system (CNS) disorders, but remains unexamined after SCI. Therefore, we characterized locomotor recovery after contusive SCI using hindlimb (HL) kinematics and electromyographic (EMG) recordings with specific consideration of eccentric phases of treadmill (TM) walking. Deficits in E2 and a caudal shift of locomotor subphases persisted throughout the 3‐week recovery period. EMG records showed notable deficits in the semitendinosus (ST) during yield. Unlike other HL muscles, recruitment of ST changed with recovery. At 7 days, the typical dual‐burst pattern of ST was lost and the second burst (ST2) was indistinct. By 21 days, the dual‐burst pattern returned, but latencies remained impaired. We show that ST2 burst duration is highly predictive of open field Basso, Beattie, Bresnahan (BBB) scores. Moreover, we found that simple changes in locomotor specificity which enhance eccentric actions result in new motor patterns after SCI. Our findings identify a caudal shift in stepping kinematics, irregularities in E2, and aberrant ST2 bursting as markers of incomplete recovery. These residual impairments may provide opportunities for targeted rehabilitation.
The transformative potential of marketing from the consumers' point of view
Authors: Heath Teresa Pereira , Chatzidakis Andreas
Published: July 2012

In this article, we explore consumers' perceptions of marketing and the extent to which they believe that marketing can play a positive transformative role in society. Findings from 36 semistructured interviews indicate that consumers typically perceive marketing as having a traditional short‐term, transactional, and ‘company‐focused’ orientation rather than a transformative one. This was reflected in participants' views of marketing, as well as in their choices and comments when they were given two academic definitions of marketing and one description of unethical marketing and asked to choose the one they thought best described marketing. In addition, participants viewed marketing as manipulative, and most held one‐sidedly negative opinions of its transformative potential. The majority did not feel autonomous in their purchase decisions, calling into question marketers' usual defence that consumers are sovereign. In a similar vein, they expressed concerns about the effects of marketing's manipulative and deceptive techniques on vulnerable consumers. These findings are rather worrying given that enhancing the transformative potential of marketing requires a more nuanced understanding of its role and function within society. Accordingly, we argue that successful transformative marketing interventions need to take into account and address consumers' disbelief as to the capacity of marketing to improve social welfare. Copyright © 2012 John Wiley & Sons, Ltd.
Taste lovers versus nutrition fact seekers: How health consciousness and self‐efficacy determine the way consumers choose food products
Authors: Mai Robert , Hoffmann Stefan
Published: July 2012

This article identifies consumer segments that differ in the way they consider health‐related and health‐unrelated food properties when making food choices. The paper makes two assumptions: first, the level of health consciousness determines the quality of the attributes (health related versus health unrelated) these segments consider important; and second, the degree of nutrition‐related self‐efficacy subsequently defines the quantity of health‐related attributes considered important. Two studies measure preferences for food attributes (Study 1: n = 54, 12 attributes, conjoint analysis; Study 2: n = 162, 25 attributes, constant sum scales). In both studies, cluster analysis identifies two major segments (taste lovers and nutrition fact seekers) that are determined by consumers' level of health consciousness. Study 2 demonstrates that nutrition‐related self‐efficacy determines how many health‐related attributes nutrition fact seekers consider important. Consequently, they can be split into ‘heavy’ and ‘soft’ subsegments. The study also identifies a segment that lacks a clear food choice strategy as a result of incompatible beliefs. The paper guides marketers and producers in developing healthy food products tailored to the needs of different target segments. Considering the enormous health expenditures, the studies' results are also beneficial to policy makers and governmental organizations to design social marketing campaigns. Copyright © 2012 John Wiley & Sons, Ltd.
Synthesis and Structural Characterization of New Divanada‐ and Diniobaboranes Containing Chalcogen Atoms
Authors: Roy Dipak Kumar , Bose Shubhankar Kumar , Geetharani K. , Varma Chakrahari Kiran Kumar , Mobin Shaikh M. , Ghosh Sundargopal
Published: July 2012

The reaction of [CpnMCl4−x] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=η5‐C5H5) with LiBH4⋅THF followed by thermolysis in the presence of dichalcogenide ligands E2R2 (E=S, Te; R=2,6‐(tBu)2‐C6H2OH, Ph) and 2‐mercaptobenzothiazole (C7H5NS2) yielded dimetallaheteroboranes [{CpV(μ‐TePh)}2(μ3‐Te)BH⋅thf] (1), [(CpV)2(BH3S)2] (2), [(CpNb)2B4H10S] (3), [(CpNb)2B4H11S(tBu)2C6H2OH] (4), and [(CpNb)2B4H11TePh] (5). In cluster 1, the V2BTe atoms define a tetrahedral framework in which the boron atom is linked to a THF molecule. Compound 2 can be described as a dimetallathiaborane that is built from two edge‐fused V2BS tetrahedron clusters. Cluster 3 can be considered as an edge‐fused cluster in which a trigonal‐bipyramidal unit (Nb2B2S) has been fused with a tetrahedral core (Nb2B2) by means of a common Nb2 edge. In addition, thermolysis of an in‐situ‐generated intermediate that was produced from the reaction of [Cp2VCl2] and LiBH4⋅THF with excess BH3⋅THF yielded oxavanadaborane [(CpV)2B3H8(μ3‐OEt)] (6) and divanadaborane cluster [(CpV)2B5H11] (7). Cluster 7 exhibits a nido geometry with C2v symmetry and it is isostructural with [(Cp*M)2B5H9+n] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=η5‐C5Me5). All of these new compounds have been characterized by 1H NMR, 11B NMR, and 13C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds 1–4, 6, and 7.
Supramolecular Binding Thermodynamics by Dispersion‐Corrected Density Functional Theory
Authors: Grimme Stefan
Published: July 2012

The equilibrium association free enthalpies ΔGa for typical supramolecular complexes in solution are calculated by ab initio quantum chemical methods. Ten neutral and three positively charged complexes with experimental ΔGa values in the range 0 to −21 kcal mol−1 (on average −6 kcal mol−1) are investigated. The theoretical approach employs a (nondynamic) single‐structure model, but computes the various energy terms accurately without any special empirical adjustments. Dispersion corrected density functional theory (DFT‐D3) with extended basis sets (triple‐ζ and quadruple‐ζ quality) is used to determine structures and gas‐phase interaction energies (ΔE), the COSMO‐RS continuum solvation model (based on DFT data) provides solvation free enthalpies and the remaining ro‐vibrational enthalpic/entropic contributions are obtained from harmonic frequency calculations. Low‐lying vibrational modes are treated by a free‐rotor approximation. The accurate account of London dispersion interactions is mandatory with contributions in the range −5 to −60 kcal mol−1 (up to 200 % of ΔE). Inclusion of three‐body dispersion effects improves the results considerably. A semilocal (TPSS) and a hybrid density functional (PW6B95) have been tested. Although the ΔGa values result as a sum of individually large terms with opposite sign (ΔE vs. solvation and entropy change), the approach provides unprecedented accuracy for ΔGa values with errors of only 2 kcal mol−1 on average. Relative affinities for different guests inside the same host are always obtained correctly. The procedure is suggested as a predictive tool in supramolecular chemistry and can be applied routinely to semirigid systems with 300–400 atoms. The various contributions to binding and enthalpy–entropy compensations are discussed.
Dramatic Substituent Effects on the Photoluminescence of Boron Complexes of 2‐(Benzothiazol‐2‐yl)phenols
Authors: Santra Mithun , Moon Hyunsoo , Park Min‐Ho , Lee Tae‐Woo , Kim Young Kook , Ahn Kyo Han
Published: July 2012

Substituents can induce dramatic changes in the photoluminescence properties of N,O‐chelated boron complexes. Specifically, the boron complexes of 2‐(benzothiazol‐2‐yl)phenols become bright deep blue‐ and orange‐red‐emitting materials depending on amino substituents at the 5‐ and 4‐positions of 2‐(benzothiazol‐2‐yl)phenol, respectively. Absorption and emission data show that the resulting boron complexes have little or small overlap between the absorption and emission spectra and, furthermore, X‐ray crystal structures for both the blue and orange‐red complexes indicate the absence of π–π stacking interaction in the crystal‐packing structures. These features endow the boron complexes with bright and strong photoluminescence in the solid state, which distinguishes itself from the typical boron complexes of dipyrromethenes (BODIPYs). A preliminary study indicates that the blue complexes have promising electro‐optical characteristics as dopant in an organic light‐emitting diode (OLED) device and show chromaticity close to an ideal deep blue. The substituent effects on the photoluminescent properties may be used to tune the desired emission wavelength of related boron or other metal complexes.
Symmetry‐Enthalpy Correlations in Diels–Alder Reactions
Authors: Tuvi‐Arad Inbal , Avnir David
Published: July 2012

Woodward–Hoffmann (WH) rules provide strict symmetry selection rules: when they are obeyed, a reaction proceeds; when they are not obeyed, there is no reaction. However, the voluminous experimental literature provides ample evidence that strict compliance to symmetry requirements is not an obstacle for a concerted reaction to proceed, and therefore the idea has developed that it is enough to have a certain degree of the required symmetry to have reactivity. Here we provide quantitative evidence of that link, and show that as one deviates from the desired symmetry, the enthalpy of activation increases, that is, we show that concerted reactions slow down the further they are from the ideal symmetry. Specifically, we study the deviation from mirror symmetry (evaluated with the continuous symmetry measure (CSM)) of the [4+2] carbon skeleton of the transition state of a series of twelve Diels–Alder reactions in seven different solvents (and in the gas phase), in which the dienes are butadiene, cyclopentadiene, cyclohexadiene, and cycloheptadiene; the dienophiles are the 1‐, 1,1‐, and 1,1,2‐cyanoethylene derivatives; the solvents were chosen to sample a range of dielectric constants from heptane to ethanol. These components provide twenty‐four symmetry–enthalpy DFT‐calculated correlation lines (out of which only one case is a relatively mild exception) that show the general trend of increase in enthalpy as symmetry decreases. The various combinations between the dienophiles, cyanoethylenes, and solvents provide all kinds of sources for symmetry deviations; it is therefore remarkable that although the enthalpy of activation is dictated by various parameters, symmetry emerges as a primary parameter. In our analysis we also bisected this overall picture into solvent effects and geometry variation effects to evaluate under which conditions the electronic effects are more dominant than symmetry effects.
The Structural Diversity Triggered by Intermolecular Interactions between AuIS2 Groups: Aurophilia and Beyond
Authors: Azani Mohammad‐Reza , Castillo Oscar , Gallego M. Luz , Parella Teodor , Aullón Gabriel , Crespo Olga , Laguna Antonio , Alvarez Santiago , Mas‐Ballesté Rubén , Zamora Félix
Published: July 2012

The present study is aimed at elucidating the factors that direct the assembly of a specific family of AuI species. The assembly of AuI centers and dithiocarboxylato or xanthato ligands results in a surprising structural diversity observed by single‐crystal X‐ray diffraction. However, in solution, just evidences for discrete bimetallic [Au2L2] species have been observed. Interestingly, when dithiocarboxylato ligands have been used, a reversible supramolecular assembly has been observed forming the supramolecules of formulae [Au2L2]2 and [Au2L2]3. Initial studies on luminescent properties have been carried out at variable temperature. All the compounds show red emissions in the solid state at very similar energies, suggesting that the intramolecular interactions play a more relevant role in the luminescent properties than the intermolecular ones. The computational studies indicate that not only Au⋅⋅⋅Au interactions, but also Au⋅⋅⋅S and S⋅⋅⋅S ones play a role in the structure and energetic of the supramolecular species, as well as for the choice between supramolecular association or intramolecular oligomerization.
Hydrogen‐Bonding Induced Alternate Stacking of Donor (D) and Acceptor (A) Chromophores and their Supramolecular Switching to Segregated States
Authors: Das Anindita , Molla Mijanur Rahaman , Maity Bholanath , Koley Debasis , Ghosh Suhrit
Published: July 2012

This paper reports comprehensive studies on the mixed assembly of bis‐(trialkoxybenzamide)‐functionalized dialkoxynaphthalene (DAN) donors and naphthalene‐diimide (NDI) acceptors due the cooperative effects of hydrogen bonding, charge‐transfer (CT) interactions, and solvophobic effects. A series of DAN as well as NDI building blocks have been examined (wherein the relative distance between the two amide groups in a particular chromophore is the variable structural parameter) to understand the structure‐dependent variation in mode of supramolecular assembly and morphology (organogel, reverse vesicle, etc.) of the self‐assembled material. Interestingly, it was observed that when the amide functionalities are introduced to enhance the self‐assembly propensity, the mode of co‐assembly among the DAN and NDI chromophores no longer remained trivial and was dictated by a relatively stronger hydrogen‐bonding interaction instead of a weak CT interaction. Consequently, in a highly non‐polar solvent like methylcyclohexane (MCH), although kinetically controlled CT‐gelation was initially noticed, within a few hours the system sacrificed the CT‐interaction and switched over to the more stable self‐sorted gel to maximize the gain in enthalpy from the hydrogen‐bonding interaction. In contrast, in a relatively less non‐polar solvent such as tetrachloroethylene (TCE), in which the strength of hydrogen bonding is inherently weak, the contribution of the CT interaction also had to be accounted for along with hydrogen bonding leading to a stable CT‐state in the gel or solution phase. The stability and morphology of the CT complex and rate of supramolecular switching (from CT to segregated state) were found to be greatly influenced by subtle structural variation of the building blocks, solvent polarity, and the DAN/NDI ratio. For example, in a given D–A pair, by introducing just one methylene unit in the spacer segment of either of the building blocks a complete change in the mode of co‐assembly (CT state or segregated state) and the morphology (1D fiber to 2D reverse vesicle) was observed. The role of solvent polarity, structural variation, and D/A ratio on the nature of co‐assembly, morphology, and the unprecedented supramolecular‐switching phenomenon have been studied by detail spectroscopic and microscopic experiments in a gel as well as in the solution state and are well supported by DFT calculations.
Activation and Coordination of Ammonia at [Cp*Ir(H)2]: NMR and Matrix Isolation Studies
Authors: Jungton Ann‐Katrin , Herwig Christian , Braun Thomas , Limberg Christian
Published: July 2012

1H NMR exchange spectroscopy of a reaction mixture of [Cp*Ir(H)4] (1; Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) and ammonia suggests an exchange of hydrogen atoms between the hydrido ligands and ammonia. Treatment of 1 with ND3 led to an H/D exchange between ND3 and the hydrido ligands of 1. Subsequent studies showed that photolysis of 1 isolated in frozen argon matrices leads to the formation of the iridium compounds [Cp*Ir(H)2] (2) and [Cp*Ir(H)3] (4), as it was confirmed by IR spectroscopy. In the presence of water the aqua complex [Cp*Ir(H)2(OH2)] (3) was generated simultaneously. Accordingly, photolysis of 1 in an argon matrix doped with ammonia gave rise to the ammine complex [Cp*Ir(H)2(NH3)] (5). IR assignments were supported by calculations of the gas‐phase IR spectra of 1–5 by DFT methods.
New Tetraphosphorus Ligands for Highly Linear Selective Hydroformylation of Allyl and Vinyl Derivatives
Authors: Cai Chaoxian , Yu Shichao , Cao Bonan , Zhang Xumu
Published: July 2012

New tetraphosphorus ligands have been developed and applied in the rhodium‐catalyzed regioselective hydroformylation of a variety of functionalized allyl and vinyl derivatives. Remarkably high linear selectivity was obtained by these tetraphosphorus ligands. The ligand that bears strong electron‐withdrawing 2,4‐difluorophenyl groups is the most effective one in affording linear aldehydes. The Rh/tetraphosphorus ligand catalyst is highly effective to produce linear aldehydes from functionalized allyl derivatives with heteroatoms or aromatic groups directly adjacent to the allyl group. For vinyl derivatives, the ligand is highly linear selective for acrylic derivatives, styrene, vinyl pyridine, and vinyl phthalimide. Linear to branch ratios of 26:1 and 10:1 were obtained for the hydroformylation of styrene and allyl cyanide, respectively.
Systemic Studies of Tetraphenylethene–Triphenylamine Oligomers and a Polymer: Achieving Both Efficient Solid‐State Emissions and Hole‐Transporting Capability
Authors: Liu Yang , Chen Xihan , Lv Yun , Chen Shuming , W. Y. Lam Jacky , Mahtab Faisal , Kwok Hoi Sing , Tao Xutang , Tang Ben Zhong
Published: July 2012

By employing a new synthetic strategy, a series of oligomers and a polymer composed of different number of tetraphenylethene and triphenylamine units was designed and synthesised. The optical physics properties and electroluminescence behaviours were studied comparatively. All the molecules demonstrate an aggregation‐induced emission (AIE) phenomenon and bear very high quantum yields in the solid state. The emission wavelengths and quantum efficiencies alternate with the change of the molecular configurations and achieve their maximum at the largest oligomer. The thermal stabilities also become higher along with the increase in the molecular weight. The molecules have suitable HOMO levels that match the work function of the indium tin oxide (ITO) anode. They can act as both light‐emitting and hole‐transporting materials in OLEDs. Thus the present strategy combines the intrinsic emissive nature of AIE materials and the good hole‐transport capability of aromatic amines, thereby achieving a win–win for both optical and electrical properties.
Bivalent Enzyme Inhibitors Discovered Using Dynamic Covalent Chemistry
Authors: Clipson Alexandra J. , Bhat Venugopal T. , McNae Iain , Caniard Anne M. , Campopiano Dominic J. , Greaney Michael F.
Published: July 2012

A bivalent dynamic covalent chemistry (DCC) system has been designed to selectively target members of the homodimeric glutathione‐S‐transferase (GST) enzyme family. The dynamic covalent libraries (DCLs) use aniline‐catalysed acylhydrazone exchange between bivalent hydrazides and glutathione‐conjugated aldehydes and the bis‐hydrazides act as linkers to bridge between each glutathione binding site. The resultant DCLs were found to be compatible and highly responsive to templating with different GST isozymes, with the best results coming from the M and Schistosoma japonicum (Sj) class of GSTs, targets in cancer and tropical disease, respectively. The approach yielded compounds with selective, nanomolar affinity (Ki=61 nM for mGSTM1‐1) and demonstrates that DCC can be used to simultaneously interrogate binding sites on different subunits of a dimeric protein.
Stereocontrolled Total Synthesis of (+)‐trans‐Dihydronarciclasine
Authors: Hwang Soonho , Kim Deukjoon , Kim Sanghee
Published: July 2012

A highly stereoselective and efficient total synthesis of trans‐dihydronarciclasine from a readily available chiral starting material was developed. The synthesis defines two of the five stereogenic centers of the natural product by an amino acid ester–enolate Claisen rearrangement. The other three stereogenic centers are created in a highly stereocontrolled fashion via a six‐ring vinylogous ester intermediate, which is generated from the γ,δ‐unsaturated ester functional group of the Claisen rearrangement product in an efficient three‐step sequence. This concise total synthesis exemplifies the use of a highly regioselective Friedel–Crafts‐type cyclization to form the B ring via an isocyanate intermediate derived from an N‐Boc group, which is superior to the conventional method using an imino triflate intermediate. This same N‐Boc group is employed to give high selectivity in the Claisen rearrangement earlier in the sequence.
Enantiomeric Recognition of Racemic 4‐Aryl‐1,4‐dihydropyridine Derivatives via Chiralpak AD‐H Stationary Phases
Authors: Dai Zhi , Pittman Charles U. , Li Tingyu
Published: July 2012

The chromatographic chiral resolution of two new series of racemic 4‐substituted‐1,4‐dihydropyridine derivatives was studied on a commercial Chiralpak AD‐H column. Analytes without 5,5‐dimethyl substituents (1–15) are more efficiently resolved than analytes with 5,5‐dimethyl groups (16–30). The AD‐H column discriminated between enantiomers through both hydrogen bonding attractions and π–π interactions. This interpretation is in accord with plots of the logarithm of separation factors, log(α), versus σ (Hammett–Swain substituent parameter) and σ+ (Brown substituent constant) plots. By elucidating the effects of the remote substituents on these chiral separations, it was shown that the influence of π–π interaction forces increase when steric bulk effects act to decrease the hydrogen bonding attractive forces on the AD‐H column. Chirality 24:854–859, 2012. © 2012 Wiley Periodicals, Inc.
Using smooth particle hydrodynamics to investigate femoral cortical bone remodelling at the Haversian level
Authors: Fernandez J. W. , Das R. , Cleary P. W. , Hunter P. J. , Thomas C. D .L. , Clement J. G.
Published: July 2012

In the neck of the femur, about 70% of the strength is contributed by the cortical bone, which is the most highly stressed part of the structure and is the site where failure is almost certainly initiated. A better understanding of cortical bone remodelling mechanisms can help discern changes at this anatomical site, which are essential if an understanding of the mechanisms by which hips weaken and become vulnerable to fracture is to be gained. The aims of this study were to (i) examine a hypothesis that low strain fields arise because of subject‐specific Haversian canal distributions causing bone resorption and reduced bone integrity and (ii) introduce the use of a meshless particle‐based computational modelling approach SPH to capture bone remodelling features at the level of the Haversian canals. We show that bone remodelling initiated by strain at the Haversian level is highly influenced by the subject‐specific pore distribution, bone density, loading and osteocyte density. SPH is shown to be effective at capturing the intricate bone pore shapes that evolved over time. Copyright © 2012 John Wiley & Sons, Ltd.
A New Glimpse into the CO2‐Philicity of Carbonyl Compounds
Authors: Altarsha Muhannad , Ingrosso Francesca , Ruiz‐Lopez Manuel F.
Published: July 2012

We report a theoretical study on non‐conventional structures of 1:1 complexes between carbon dioxide and carbonyl compounds. These structures have never been reported before but are relevant for understanding the solubility of carbonyl compounds in supercritical CO2. The work is based on the results of ab initio calculations at the MP2 and CCSD(T) levels using aug‐cc‐pVDZ and aug‐cc‐pVTZ basis sets. Investigated systems include aldehydes, ketones and esters, together with some fluorinated derivatives. The results are interpreted in terms of natural bond orbital analyses. Harmonic vibrational frequency calculations have also been done in order to compare them with available experimental data. We show for the first time that complexes where CO2 behaves globally as a Lewis base are stable in the case of ketones and esters, but not in the case of aldehydes, and their stability is similar to that of traditional complexes in which CO2 behaves as a Lewis acid. This finding considerably modifies the concept of CO2‐philicity and may have important ramifications in the development of green reactions in supercritical CO2.
Application of a Versatile Nanoparticle Stabilizer in Phase Transfer and Catalysis
Authors: Biondi Ilaria , Laporte Vincent , Dyson Paul J.
Published: July 2012

Gold and rhodium nanoparticles stabilized by a cationic polymer can be readily modified by anion exchange to afford nanoparticles that may be dispersed in a wide range of organic solvents and ionic liquids. The catalytic activity of the Rh nanoparticle dispersions have been evaluated in the selective hydrogenation of limonene and the nature of the solvent has been shown to play a critical role.