952 resultados para Neutral Re(I) complexes


Relevância:

30.00% 30.00%

Publicador:

Resumo:

La Skopos Theory è una teoria introdotta nel mondo della traduzione dal linguista tedesco Hans Joseph Vermeer. Skopos è una parola di derivazione greca che significa “fine” o “scopo”. La teoria elaborata da Vermeer si basa sull’idea che ogni testo abbia uno skopos che determina i metodi e le strategie secondo le quali esso debba essere tradotto. Oltre alla Skopos Theory, che sarà la base della tesi, i testi a seguire verranno analizzati seguendo altri autori, quali Mona Baker e Laurence Venuti, che si rifanno all’idea di skopos e analizzano molto dettagliatamente la figura del traduttore come de-coder e re-encoder del testo.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Il presente lavoro di tesi si inserisce in un progetto di ricerca volto alla sintesi di nuovi complessi di metalli di transizione per lo sviluppo di catalizzatori bifunzionali metallo-legante da impiegare in reazioni di catalisi omogenea, in particolare in reazioni redox quali idrogenazione e deidrogenazione attraverso il trasferimento di idrogeno. Il mio progetto ha riguardato la messa a punto della sintesi di complessi di Ru(0) che combinano leganti ciclopentadienonici e carbeni N-eterociclici e la sintesi dei corrispondenti complessi cationici per protonazione. Inoltre, è stato sintetizzato e caratterizzato un nuovo complesso cationico attraverso la metilazione del corrispettivo complesso neutro. I complessi sintetizzati sono stati utilizzati come precursori di catalizzatori nella riduzione tramite trasferimento di idrogeno del 4-fluoroacetofenone, valutandone l’attività catalitica in relazione a leganti, additivi e controioni. Allo scopo di delineare qualche ipotesi sul meccanismo di reazione sono stati effettuati diversi studi sulla reattività dei complessi impiegati in catalisi, in particolare usando la piridina come agente di “trapping”. Infine, è stato condotto uno studio preliminare dell’attività catalitica dei complessi sintetizzati nell’ossidazione di benzilalcol a benzaldeide. The present work is part of a research project that involves the study of new ruthenium-based transition metal complexes in order to develop new metal-ligand bifunctional catalysts to employ in homogeneous catalytic systems, in particular in redox reactions such as hydrogenation and dehydrogenation through hydrogen transfer. My project is focused on the optimization of the synthesis of Ru(0) complexes that combines different ligands as tetraphenylcyclopentadienone and N-heterocyclic carbenes and the synthesis of the corresponding cationic complexes by protonation. Furthermore, it is reported the synthesis and characterization of a new cationic complex obtained by methylation of the corresponding neutral complex. All the prepared complexes were employed as catalyst precursors in the transfer hydrogenation of 4-fluoroacetophenone and their performances were investigated in relation to the type of ligands, additives and counterions. The reactivity of these ruthenium complexes was also investigated with the aim of delineate some hypothesis on the reaction mechanism, in particular employing pyridine as a trapping agent. Finally, preliminary studies on the oxidation of benzyl alcohol have been carried out.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

In the modern society, light is mostly powered by electricity which lead to a significant increase of the global energy consumption. In order to reduce it, different kinds of electric lamps have been developed over the years; it is now accepted that phosphorescence-based OLEDs offer many advantages over existing light technologies. Iridium complexes are considered excellent candidates for bright materials by virtue of the possibility to easily tune the wavelength of the emitted radiation, by appropriate modifications of the nature of the ligands. It is important to note that the synthesis of Ir(III) blue-emitting complexes is a very challenging goal, because of wide HOMO-LUMO gaps needed for produce a deep blue emission. During my thesis I planned the synthesis of two different series of new Ir(III) heteroleptic complexes, the C and the N series, using cyclometalating ligands containing an increasing number of nitrogens in inverse and regular position. I successfully performed in the synthesis of the required four ligands, i.e. 1-methyl-4-phenyl-1H-imidazole (2), 4-phenyl-1-methyl-1,2,3-triazole (3), 1-phenyl-1H-1,2,3-triazole (6) and 1-phenyl-1H-tetrazole (7), that differ in the number of nitrogens present in the heterocyclic ring and in the position of the phenyl ring. Therefore the cyclometalation of the obtained ligands to get the corresponding Ir(III)-complexes was attempted. I succeeded in the synthesis of two Ir(III)-complexes of the C series, and I carried out various attempts to set up the appropriate reaction conditions to get the remaining desired derivatives. The work is still in progress, and once all the desired complexes will be synthesized and characterized, a correlation between their structure and their emitting properties could be formulated analysing and comparing the photophysical data of the real compounds.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The PM3 semiempirical quantum-mechanical method was found to systematically describe intermolecular hydrogen bonding in small polar molecules. PM3 shows charge transfer from the donor to acceptor molecules on the order of 0.02-0.06 units of charge when strong hydrogen bonds are formed. The PM3 method is predictive; calculated hydrogen bond energies with an absolute magnitude greater than 2 kcal mol-' suggest that the global minimum is a hydrogen bonded complex; absolute energies less than 2 kcal mol-' imply that other van der Waals complexes are more stable. The geometries of the PM3 hydrogen bonded complexes agree with high-resolution spectroscopic observations, gas electron diffraction data, and high-level ab initio calculations. The main limitations in the PM3 method are the underestimation of hydrogen bond lengths by 0.1-0.2 for some systems and the underestimation of reliable experimental hydrogen bond energies by approximately 1-2 kcal mol-l. The PM3 method predicts that ammonia is a good hydrogen bond acceptor and a poor hydrogen donor when interacting with neutral molecules. Electronegativity differences between F, N, and 0 predict that donor strength follows the order F > 0 > N and acceptor strength follows the order N > 0 > F. In the calculations presented in this article, the PM3 method mirrors these electronegativity differences, predicting the F-H- - -N bond to be the strongest and the N-H- - -F bond the weakest. It appears that the PM3 Hamiltonian is able to model hydrogen bonding because of the reduction of two-center repulsive forces brought about by the parameterization of the Gaussian core-core interactions. The ability of the PM3 method to model intermolecular hydrogen bonding means reasonably accurate quantum-mechanical calculations can be applied to small biologic systems.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We present the first molecular model of the coordination complex formed by Cu(I) and imidazole-epichlorohydrin polymers. Our calculations show that the Cu(I) ion has linear coordination and the whole complex has neutral charge. Our model suggests salt couple pairing as the driving force for the formation of the surface-confined precipitation, which is crucial to obtain flat surfaces in industrial copper deposition processes, required for mass fabrication of state-of-the-art electronic and memory devices.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Species with a wide geographical distribution are often composed of distinct subgroups which may be adapted to their local environment. European trout (Salmo trutta species complex) provide an example of such a complex consisting of several genetically and ecologically distinct forms. However, trout populations are strongly influenced by human activities, and it is unclear to what extent neutral and adaptive genetic differences have persisted. We sampled 30 Swiss trout populations from heterogeneous environments along replicated altitudinal gradients in three major European drainages. More than 850 individuals were genotyped at 18 microsatellite loci which included loci diagnostic for evolutionary lineages and candidate markers associated with temperature tolerance, reproductive timing and immune defence. We find that the phylogeographic structure of Swiss trout populations has not been completely erased by stocking. Distinct genetic clusters corresponding to the different drainages could be identified, although nonindigenous alleles were clearly present, especially in the two Mediterranean drainages. We also still detected neutral genetic differentiation within rivers which was often associated with the geographical distance between populations. Five loci showed evidence of divergent selection between populations with several drainage-specific patterns. Lineage-diagnostic markers, a marker linked to a quantitative trait locus for upper temperature tolerance in other salmonids and a marker linked to the major histocompatibility class I gene were implicated in local adaptation and some patterns were associated with altitude. In contrast, tentative evidence suggests a signal of balancing selection at a second immune relevant gene (TAP2). Our results confirm the persistence of both neutral and potentially adaptive genetic differences between trout populations in the face of massive human-mediated dispersal.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The United States¿ Federal and State laws differentiate between acceptable (or, legal) and unacceptable (illegal) behavior by prescribing restrictive punishment to citizens and/or groups that violate these established rules. These regulations are written to treat every person equally and to fairly serve justice; furthermore, the sanctions placed on offenders seek to reform illegal behavior through limitations on freedoms and rehabilitative programs. Despite the effort to treat all offenders fairly regardless of social identity categories (e.g., sex, race, ethnicity, socioeconomic status, age, ability, and gender and sexual orientation) and to humanely eliminate illegal behavior, the American penal system perpetuates de facto discrimination against a multitude of peoples. Furthermore, soaring recidivism rates caused by unsuccessful re-entry of incarcerated offenders puts economic stress on Federal and State budgets. For these reasons, offenders, policy-makers, and law-abiding citizens should all have a vested interest in reforming the prison system. This thesis focuses on the failure of the United States corrections system to adequately address the gender-specific needs of non-violent female offenders. Several factors contribute to the gender-specific discrimination that women experience in the criminal justice system: 1) Trends in female criminality that skew women¿s crime towards drug-related crimes, prostitution, and property offenses; 2) Mandatory minimum sentences for drug crimes that are disproportionate to the crime committed; 3) So-called ¿gender-neutral¿ educational, vocational, substance abuse, and mental health programming that intends to equally rehabilitate men and women, but in fact favors men; and 4) The isolating nature of prison structures that inhibits smooth re-entry into society. I argue that a shift in the placement and treatment of non-violent female offenders is necessary for effective rehabilitation and for reducing recidivism rates. The first component of this shift is the design and implementation of gender- responsive treatment (GRT) rather than gender-neutral approaches in rehabilitative programming. The second shift is the utilization of alternatives to incarceration, which provide both more humane treatment of offenders and smoother reintegration to society. Drawing on recent scholarship, information from prison advocacy organizations, and research with men in an alternative program, I provide a critical analysis of current policies and alternative programs, and suggest several proposals for future gender- responsive programs in prisons and in place of incarceration. I argue that the expansion of gender-responsive programming and alternatives to incarceration respond to the marginalization of female offenders, address concerns about the financial sustainability of the United States criminal justice system, and tackle high recidivism rates.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

OBJECTIVE: (I) To compare the oral microflora at implant and tooth sites in subjects participating in a periodontal recall program, (II) to test whether the microflora at implant and tooth sites differ as an effect of gingival bleeding (bleeding on probing (BOP)), or pocket probing depth (PPD), and (III) to test whether smoking and gender had an impact on the microflora. MATERIAL AND METHODS: Data were collected from 127 implants and all teeth in 56 subjects. Microbiological data were identified by the DNA-DNA checkerboard hybridization. RESULTS: PPD> or =4 mm were found in 16.9% of tooth, and at 26.6% of implant sites (P<0.01). Tooth sites with PPD> or =4 mm had a 3.1-fold higher bacterial load than implant sites (mean difference: 66%, 95% confidence interval (CI): 40.7-91.3, P<0.001). No differences were found for the red, orange, green, and yellow complexes. A higher total bacterial load was found at implant sites with PPD> or =4 mm (mean difference 35.7 x 10(5), 95% CI: 5.2 (10(5)) to 66.1 (10(5)), P<0.02 with equal variance not assumed). At implant sites, BOP had no impact on bacterial load but influenced the load at tooth sites (P<0.01). CONCLUSION: BOP, and smoking had no impact on bacteria at implant sites but influenced the bacterial load at tooth sites. Tooth sites harbored more bacteria than implant sites with comparable PPD. The 4 mm PPD cutoff level influenced the distribution and amounts of bacterial loads. The subject factor is explanatory to bacterial load at both tooth and implant sites.

Relevância:

30.00% 30.00%

Publicador:

Relevância:

30.00% 30.00%

Publicador:

Resumo:

AIMS: Multiple arrhythmia re-inductions were recently shown in His-Purkinje system (HPS) ventricular tachycardia (VT). We hypothesized that HPS VT was a frequent mechanism of repetitive or incessant VT and assessed diagnostic criteria to select patients likely to have HPS VT. METHODS AND RESULTS: Consecutive patients with clustering VT episodes (>3 sustained monomorphic VT within 2 weeks) were included in the analysis. HPS VT was considered plausible in patients with (i) impaired left ventricular function associated with dilated cardiomyopathy or valvular heart disease; or (ii) ECG during VT similar to sinus rhythm QRS or to bundle-branch block QRS. HPS VT was plausible in 12 of 48 patients and HPS VT was demonstrated in 6 of 12 patients (50%, or 13% of the whole study group). Median VT cycle length was 318 ms (250-550). Catheter ablation was successful in all six patients. CONCLUSION: His-Purkinje system VT is found in a significant number of patients with repetitive or incessant VT episodes, and in a large proportion of patients with predefined clinical or electrocardiographic characteristics. Since it is easily amenable to catheter ablation, our data support the screening of all patients with repetitive VT in this regard and an invasive approach in a selected group of patients.