Syntheses, structures and efficient catalysis for C–C coupling of some benzaldehyde thiosemicarbazone complexes of palladium

Reaction of the 4-R-benzaldehyde thiosemicarbazones (denoted in general as L-R; R = OCH(3), CH(3), H, Cl and NO(2)) with trans-[Pd(PPh(3))(2)Cl(2)] afforded a group of mixed-ligand complexes (denoted in general as 1-R) incorporating a N,S-coordinated thiosemicarbazone. a triphenylphosphine and a chloride. Similar reaction with Na(2)[PdCl(4)] afforded a family of bis-thiosemicarbazone complexes (denoted in general as 2-R), where each ligand is N,S-coordinated. Crystal structures of 1-CH(3), 1-NO(2), 2-OCH(3), 2-NO(2) and L-NO(2) have been determined. In all the complexes the thiosemicarbazones are coordinated to the metal center, via dissociation of the acidic proton, as bidentate N,S-donors forming five-membered chelate rings. With reference to the structure of the uncoordinated thiosemicarbazone, this coordination mode is associated with a conformational change around the C=N bond. All the 1-R and 2-R complexes display intense absorptions in the visible region. Catalytic activity of the 1-R and 2-R complexes towards some C-C coupling reactions (e.g. Suzuki, Heck and Sonogashira) has been examined and while both are found to be efficient catalysts, 1-R is much better catalyst than 2-R.

Asymmetric synthesis of peptides

The present invention provides a process comprising substitution of an acceptor molecule comprising a group -XC(O)- wherein X is O, S or NR8, where R8 is C1-6 alkyl, C6-12 aryl or hydrogen, with a nucleophile, wherein the acceptor molecule is cyclised such that said nucleophilic substitution at -XC (O)- occurs without racemisation. This process has particular application for the production of a peptide by extension from the activated carboxy-terminus of an acyl amino acid residue without epimerisation.

Asymmetric synthesis of peptides

The present invention provides a process comprising substitution of an acceptor molecule comprising a group -XC(O)- wherein X is O, S or NR8, where R8 is C1-6 alkyl, C6-12 aryl or hydrogen, with a nucleophile, wherein the acceptor molecule is cyclised such that said nucleophilic substitution at -XC (O)- occurs without racemisation. This process has particular application for the production of a peptide by extension from the activated carboxy-terminus of an acyl amino acid residue without epimerisation.

Asymmetric forcing from stratospheric aerosols impacts Sahelian rainfall

The Sahelian drought of the 1970s–1990s was one of the largest humanitarian disasters of the past 50 years, causing up to 250,000 deaths and creating 10 million refugees1. It has been attributed to natural variability2–5, overgrazing6 and the impact of industrial emissions of sulphur dioxide7,8. Each mechanism can influence the Atlantic sea surface temperature gradient, which is strongly coupled to Sahelian precipitation2,3. We suggest that sporadic volcanic eruptions in the Northern Hemisphere also strongly influence this gradient and cause Sahelian drought. Using de-trended observations from 1900 to 2010, we show that three of the four driest Sahelian summers were preceded by substantial Northern Hemisphere volcanic eruptions. We use a state-ofthe- art coupled global atmosphere–ocean model to simulate both episodic volcanic eruptions and geoengineering by continuous deliberate injection into the stratosphere. In either case, large asymmetric stratospheric aerosol loadings concentrated in the Northern Hemisphere are a harbinger of Sahelian drought whereas those concentrated in the Southern Hemisphere induce a greening of the Sahel. Further studies of the detailed regional impacts on the Sahel and other vulnerable areas are required to inform policymakers in developing careful consensual global governance before any practical solar radiation management geoengineering scheme is implemented.

Asymmetric output gap effects in Phillips Curve and mark-up pricing models: evidence for the US and the UK

A number of studies have found an asymmetric response of consumer price index inflation to the output gap in the US in simple Phillips curve models. We consider whether there are similar asymmetries in mark-up pricing models, that is, whether the mark-up over producers' costs also depends upon the sign of the (adjusted) output gap. The robustness of our findings to the price series is assessed, and also whether price-output responses in the UK are asymmetric.

The ocean's role in polar climate change: asymmetric Arctic and Antarctic responses to greenhouse gas and ozone forcing

In recent decades, the Arctic has been warming and sea ice disappearing. By contrast, the Southern Ocean around Antarctica has been (mainly) cooling and sea-ice extent growing. We argue here that interhemispheric asymmetries in the mean ocean circulation, with sinking in the northern North Atlantic and upwelling around Antarctica, strongly influence the sea-surface temperature (SST) response to anthropogenic greenhouse gas (GHG) forcing, accelerating warming in the Arctic while delaying it in the Antarctic. Furthermore, while the amplitude of GHG forcing has been similar at the poles, significant ozone depletion only occurs over Antarctica. We suggest that the initial response of SST around Antarctica to ozone depletion is one of cooling and only later adds to the GHG-induced warming trend as upwelling of sub-surface warm water associated with stronger surface westerlies impacts surface properties. We organize our discussion around ‘climate response functions’ (CRFs), i.e. the response of the climate to ‘step’ changes in anthropogenic forcing in which GHG and/or ozone-hole forcing is abruptly turned on and the transient response of the climate revealed and studied. Convolutions of known or postulated GHG and ozone-hole forcing functions with their respective CRFs then yield the transient forced SST response (implied by linear response theory), providing a context for discussion of the differing warming/cooling trends in the Arctic and Antarctic. We speculate that the period through which we are now passing may be one in which the delayed warming of SST associated with GHG forcing around Antarctica is largely cancelled by the cooling effects associated with the ozone hole. By mid-century, however, ozone-hole effects may instead be adding to GHG warming around Antarctica but with diminished amplitude as the ozone hole heals. The Arctic, meanwhile, responding to GHG forcing but in a manner amplified by ocean heat transport, may continue to warm at an accelerating rate.

Polymer protected gold nanoparticles: synthesis, characterization and application in catalysis

This review discusses the stabilization of gold nanoparticles (AuNPs) by nonionic, anionic, cationic and amphoteric polymers. The protocols used for synthesis of AuNPs in aqueous and organic solvents are described. Size, shape and morphology of AuNPs are characterized by various physicochemical methods. Application aspects of polymer-protected AuNPs in catalysis are outlined.

Asymmetric organocatalytic synthesis of cyclopentane γ-nitroketones

This paper describes the use of bifunctional thiourea catalysts in the intramolecular reaction of a nitronate with conjugated ketones to generate the corresponding γ-nitroketones. In contrast to our previous studies in this area, we obtained the cis-functionalized systems as the major diastereoisomers in good yields and reasonable selectivities.

Asymmetric information, credit market condition, and entrepreneurial finance

The issue of imperfect information plays a much more important role in financing “informationally opaque” small businesses than in financing large companies.1 This chapter examines the asymmetric information issue in entrepreneurial finance from two perspectives: the effects of relationship lending and the impacts of credit market concentration on entrepreneurial financial behavior. These two perspectives are strongly linked to each other via the asymmetric information issue in entrepreneurial finance. Existing literature has recognized the important role played by relationship lending in alleviating the problem of asymmetric information. However, mixed empirical results have been reported. For example, it has been found that the development of relationship lending can improve the availability of finance for small businesses borrowers (Petersen and Rajan, 1994) and reduce the costs of finance (Berger and Udell, 1995). Meanwhile, with monopoly power, banks may extract rents, in terms of charging higher-than-market interest rates, from small businesscustomers who have very concentrated banking relationships (Ongena and Smith, 2001). In addition, both favorable and unfavorable effects of credit market concentration on financing small businesses have been acknowledged. Small business borrowers may have to pay a higher-than-market price on loans (Degryse and Ongena, 2005) and are more likely to be financially constrained (Cetorelli, 2004) than in competitive markets. On the other hand, empirical studies have shown that market concentration create a strong motive for lenders to invest in private information from small business customers, and therefore a concentrated market is more efficient in terms of private information acquisition (Han et al., 2009b). The objective of this chapter is to investigate, by reviewing existing literature, the role played by relationship lending and the effects of market concentration on financing entrepreneurial businesses that are supposed to be informationally opaque. In the first section we review literature on the important role played by asymmetric information in entrepreneurial finance from two perspectives: asymmetric information and relationship lending, and the theoretical modeling of asymmetric information. Then we examine the relationship between capital market conditions and entrepreneurial finance and attempt to answer two questions: Why is the capital market condition important for entrepreneurial finance? and What are the effects of capital market conditions on entrepreneurial financial behavior in terms of discouraged borrowers, cash holding, and the availability and costs of finance?

Asymmetric oxidation of vinyl- and ethynyl terthiophene ligands in triruthenium complexes

A series of ruthenium(II) complexes [{RuCl(CO)(PMe3)3(–CHvCH–)}nX], 1a–1c (1a: n = 3, X = 3,3’’- dimethyl-2,2’:3’,2’’-terthiophene; 1b: n = 2, X = 2,2’-bithiophene; 1c: n = 2, X = 2,3-bis(3-methylthiophen- 2-yl)benzothiophene) and [{Cp*(dppe)2Ru(–CuC–)}3X], 1d (X = 3,3’’-dimethyl-2,2’:3’,2’’- terthiophene), were prepared and characterized by 1H, 13C and 31P NMR. Their redox, spectroscopic and bonding properties were studied with a range of spectro-electrochemical methods in combination with density functional theory calculations. The first two anodic steps observed for 1a and 1d are largely localized on the lateral frameworks of the molecular triangle, the direct conjugation between them being precluded due to the photostable open form of the dithienyl ethene moiety. The third anodic step is then mainly localized on the centerpiece of the triangular structure, affecting both bithiophene laterals. The experimental IR and UV-vis-NIR spectroelectrochemical data and, largely, also DFT calculations account for this explanation, being further supported by direct comparison with the anodic behavior of reference diruthenium complexes 1b and 1c.

Nanostructured copper thin film used for catalysis

Catalytic properties of copper thin films deposited in small channels and cavities were tested using Raman microscopy and mass spectroscopy (MS) techniques, mainly. The catalytic surface conditions were addressed visually and chemically by optical microscopy and X-ray photoelectron spectroscopy (XPS), respectively. The experimental conditions of present work induced copper oxidation; eventually a number of carbon species and graphite remained on the catalytic surface. Quartz crystal microbalance and mass spectroscopy data support both adsorption and catalysis phenomena. MS showed CO2 formation during n-hexane heating process but not to 2-propanol, probably due to redox reactions. XPS of copper surface present in the cavity after catalysis tests detected Cu2O and a range of possible carbon species. The adsorption and catalytic performance of copper films deposited in cavities and microchannels were quite similar. A simple miniaturized device for microanalysis was proposed. (C) 2007 Elsevier B.V. All rights reserved.

An asymmetric sandpile model with height restriction

We analyze by numerical simulations and mean-field approximations an asymmetric version of the stochastic sandpile model with height restriction in one dimension. Each site can have at most two particles. Single particles are inactive and do not move. Two particles occupying the same site are active and may hop to neighboring sites following an asymmetric rule. Jumps to the right or to the left occur with distinct probabilities. In the active state, there will be a net current of particles to the right or to the left. We have found that the critical behavior related to the transition from the active to the absorbing state is distinct from the symmetrical case, making the asymmetry a relevant field.

The dynamics of cargo driven by molecular motors in the context of asymmetric simple exclusion processes

We consider the dynamics of cargo driven by a collection of interacting molecular motors in the context of ail asymmetric simple exclusion process (ASEP). The model is formulated to account for (i) excluded-volume interactions, (ii) the observed asymmetry of the stochastic movement of individual motors and (iii) interactions between motors and cargo. Items (i) and (ii) form the basis of ASEP models and have already been considered to study the behavior of motor density profile [A. Parmeggiani. T. Franosch, E. Frey, Phase Coexistence in driven one-dimensional transport, Phys. Rev. Lett. 90 (2003) 086601-1-086601-4]. Item (iii) is new. It is introduced here as an attempt to describe explicitly the dependence of cargo movement on the dynamics of motors in this context. The steady-state Solutions Of the model indicate that the system undergoes a phase transition of condensation type as the motor density varies. We study the consequences of this transition to the behavior of the average cargo velocity. (C) 2009 Elsevier B.V. All rights reserved.

Polarization and solvatochromic shift of ortho-betaine in water

Betaine dyes are known to show very large transition energy shifts in different solvents. The ortho-betaine molecule - a simple two-ring prototype of the E-T(30) Reichardt dye - has been investigated theoretically from a combined statistical and quantum mechanics approach. Using sequential Monte Carlo (MC) simulations and MP2/cc-pVDZ calculations the in-water dipole moment of ortho-betaine is obtained as 12.30 +/- 0.05 D. This result shows a considerable increase of 75% compared to the in-vacuum dipole moment. For comparison, the use of a polarizable continuum model using the same MP2/cc-pVDZ leads to an in-water dipole moment of 11.6 D, in good agreement. This large polarization is incorporated in the classical potential for another MC simulation to generate solute-solvent configurations and to obtain the contribution of the polarization effect in the solvatochromic shift. Using statistically uncorrelated configurations and supermolecular INDO/CIS calculations, including the solute and, explicitly, 230 solvent water molecules, the statistically converged calculated shift is obtained here as 6360 cm(-1), in good agreement with the experimental result of 7550 cm(-1). (c) 2007 Elsevier B.V. All rights reserved.

Biomimetic biosensor based on lipidic layers containing tyrosinase and lutetium bisphthalocyanine for the detection of antioxidants

This paper describes the preparation of a biomimetic Langmuir-Blodgett film of tyrosinase incorporated in a lipidic layer and the use of lutetium bisphthalocyanine as an electron mediator for the voltammetric detection of phenol derivatives, which include one monophenol (vanillic acid), two diphenols (catechol and caffeic acid) and two triphenols (gallic acid and pyrogallol). The first redox process of the voltammetric responses is associated with the reduction of the enzymatically formed o-quinone and is favoured by the lutetium bisphthalocyanine because significant signal amplification is observed, while the second is associated with the electrochemical oxidation of the antioxidant and occurs at lower potentials in the presence of an electron mediator. The biosensor shows low detection limit (1.98 x 10(-6)-27.49 x 10(-6) M), good reproducibility, and high affinity to antioxidants (Km in the range of 62.31-144.87 mu M). The excellent functionality of the enzyme obtained using a biomimetic immobilisation method, the selectivity afforded by enzyme catalysis, the signal enhancement caused by the lutetium bisphthalocyanine mediator and the increased selectivity of the curves due to the occurrence of two redox processes make these sensors exceptionally suitable for the detection of phenolic compounds. (C) 2010 Elsevier B.V. All rights reserved.