Search results for "Bond"
showing 10 items of 3527 documents
Estimating the size of the loan sharking market in Italy
2014
In the current economic crisis, the risk is so high that entrepreneurs, commercial activities and even families may turn to the illegal market to obtain liquidity. This article proposes an estimate of the size of the usury credit market in Italy. The estimate is based on the assumption, provided by Guiso1, that before coming to a moneylender the borrower seeks to obtain credit through official channels. The results of our estimates confirm the seriousness of the problem, but provide much lower data than those reported periodically by the media. It is estimated that 372,000 economic activities may have been potentially involved in the usury market in 2012. The volume of loans disbursed in th…
Derivatisation of Pyrogallarenes
2005
Derivatisation of upper-rim hydroxy groups of pyrogallarenes produced completely acylated and tosylated pyrogallarene derivatives. Mesitylation of pyrogallarene, however, resulted in a regioselective derivatisation of hydroxy groups, i.e. eight OH groups out of 12 were mesitylated. Crystal structures of the synthesised pyrogallarene derivatives indicate that completely substituted pyrogallarenes exist in a distorted crown conformation despite of the lack of stabilising intramolecular hydrogen bonds. In contrast, the partially substituted pyrogallarene adopts a boat conformation and has an open cavity for the inclusion of small guest molecules. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinh…
An efficient esterification of pullulan using carboxylic acid anhydrides activated with iodine
2010
Received August 9, 2009Accepted January 12, 2010Published online February 11, 2010Acylation of alcohols (esterification) with anhydride is an important and routinely utilizedtransformation in organic synthesis. Iodine is a cheap and one of the most powerful anhy-dride activating agents for the esterification of alcohols. Therefore, an efficient and cost ef-fective method was developed for the acylation of pullulan polysaccharide by using differentacid anhydrides activated with iodine. A series of organo-soluble pullulan esters were suc-cessfully synthesized, purified and characterized. Under solvent free conditions, it was feasi-ble to fabricate pullulan nonaacetate and pullulan stearate. A…
VALUTAZIONE DELLA RESISTENZA DI ADESIONE E DELLA LUNGHEZZA EFFICACE DI INCOLLAGGIO NEI GIUNTI ADESIVI TRAMITE LE LEGGI DELL’EFFETTO SCALA
2010
In recent years, growing attention has been paid by researchers in structural mechanics to bonded joints in order to provide theoretical and numerical tools for better understanding the interfacial bonding/debonding phenomena. The research efforts in this area regard the formulation of reliable bond-slip models based on experimental data coming from laboratory tests performed on small specimens [1, 2]. As reported in [3], the mechanical quantities characterizing any interface constitutive law can be derived from the results of the experimental pull tests by a simple procedure making use of a schematization of the structural problem. The application to some single lap joint tests, carried ou…
Current dental adhesives systems. A narrative review.
2012
Adhesive dentistry is based on the development of materials which establish an effective bond with the tooth tissues. In this context, adhesive systems have attracted considerable research interest in recent years. Successful adhesive bonding depends on the chemistry of the adhesive, on appropriate clinical handling of the material as well as on the knowledge of the morphological changes caused on dental tissue by different bonding procedures. This paper outlines the status of contemporary adhesive systems, with particular emphasis on chemical characteristics and mode of interaction of the adhesives with enamel and dentinal tissues. Dental adhesives are used for several clinical application…
Buildup of Ultrathin Multilayer Films by a Self-Assembly Process: II. Consecutive Adsorption of Anionic and Cationic Bipolar Amphiphiles and Polyelec…
1991
We have recently reported on the consecutive physisorption of anionic and cationic bipolar amphiphiles onto charged surfaces, adsorbed out of aqueous solutions [1]. Here, we extend our previous concept to multipolar compounds such as polyelectrolytes. In contrast to the bipolar amphiphile system, it is not necessary to separate single charges by a rigid unit, when the polyelectrolyte is adsorbed from sufficiently concentrated solutions. In this case the physisorbed layer does not bind with all ionic groups to the surface and exposes free ionic groups at the new film/solution interface. Therefore a polyelectrolyte layer can replace a layer of bipolar amphiphiles in the consecutive buildup of…
Retention of Vanadium(V), Molybdenum(VI) and Tungsten(VI) by Kaolin
1993
Abstract The ability of kaolin (approximately H2Al2Si2O8 · H2O), a well known clay mineral constituent, to retain V(V) andMo(VI) species from 10−5 and 10−4 M solutions, and W(VI) species from 10−4 M solutions was investigated in the pH range 2–7.5 using a solid/liquid ratio 1:100 (w:v). The equilibration time in the adsorption studies was 72 h, and the shaking time in the desorption studies was 17 h. 0.02 M KCl was used as ionic medium and desorbing liquid. V(V), Mo(VI) and W(VI) were all retained by kaolin to some extent, and the amounts of the elements which could be washed away from kaolin with 0.02 M KCl were very small. The pH dependence of the adsorption was considerable: when added a…
<title>Large-scale computer simulations of metal/oxide interfaces with defects</title>
2003
Ab initio slab simulations have been performed for silver adhesion to the perfect and defective MgO(001) surfaces. For 1/4 Ag monolayer (ML) coverage of perfect substrate, we observe small silver adhesion energies over both O2- and Mg2+ ions on a regular MgO(001) substrate (0.23 and 0.22 eV per Ag atom, respectively), with negligible interfacial charge transfer towards metal atoms. For larger Ag coverages (beginning with 1/2 ML), silver adsorption over regular O2- ions is much more favorable. We demonstrate that point surface defects on a magnesia surface increase markedly the metal adhesion energy and cause a redistribution of the electron density across the interface. The results for elec…
Microscopic Insights into the Fluorite/Water Interfaces from Vibrational Sum Frequency Generation Spectroscopy
2016
Water/mineral interfaces are central to a wide range of environmental and technological processes. In this report we provide a quantitative, molecular-level understanding of the CaF2/water interface using Density Functional Theory-based molecular dynamics simulations. In particular through the comparison of calculated Vibrational Sum Frequency Generation spectra to the experimental ones, we give a structural characterisation of the interface at different pH. At low pH, the surface is positively charged, causing a substantial degree of water ordering. Our results suggest that the surface charge originates from the dissolution of fluoride ions of the topmost layer, rather than from proton ads…
The taboo against group contact: Hypothesis of Gypsy ontologization
2007
The concept of this article is that the symbolic relationships between human beings and animals serve as a model for the relationships between the majority and the ethnic minority. We postulate that there are two representations that serve to organize these relationships between human beings and animals: a domestic and a wild one. If the domestic animal is an index of human culture, the wild animal is an index of nature which man considers himself to share with the animal. With the wild representation, contact with the animal will be taboo, as it constitutes a threat to the anthropological difference. We offer the hypothesis that ontologization of the minority, that is, the substitution of …