2,691 research outputs found
Organometallic Systems To Sustain A Better Future
Almost all branches of chemistry and material science now interface with Organometallic Chemistry. Organometallics are used extensively in the synthesis of useful compounds on both large and small scales. Industrial processes involving plastics, polymers, electronic materials, and pharmaceuticals all depend on advancements in organometallic chemistry. Many catalytic and non-catalytic stereoselective processes that are key steps in creative and non-conventional synthesis of complex molecules have gained significant advantage from organometallic chemistry. The ISOC series is the most important school on organometallic chemistry at the European level, organized under the auspices of EuCheMS (the European Association for Chemical and Molecular Sciences) and the interdivisional group of organometallic chemistry of the Italian Chemical Society with the aim of encouraging the presence of young researchers and Ph.D. students both from University and Industry, including those not directly involved in organometallic research projects, in order to bring together young researchers and distinguished European scientists as a contribution to the important goal of increasing the transfer of knowledge at a high level between different European countries and different generations of Scientists. The major objective of the ISOC is to promote synergy in organometallic research. The number of participants will be limited to around 120 in order to facilitate maximum interaction among the participants and between them and the lecturers. The 9th edition of ISOC (ISOC 2013) will focus on the relevance of organometallics systems to sustain a better future. The development of advanced methodologies based on the peculiar properties of organometallic compounds may lead to important changes in the approach of organometallic chemists to the field. A full roster of scientifically distinguished speakers will present their reading keys. In fact, fundamental studies on the mechanistic and structural aspects, as well as new experimental methods and investigation techniques, support the use of organometallic compounds in different application areas including Organometallic Catalysis, Bioorganometallic Chemistry in Biology and Medicine, Green Chemistry (energy and sustainable development), Industrial chemistry and Polymers production, Metal-mediated organic synthesis and Activation of small molecules
A precise numerical estimation of the magnetic field generated around recombination
We investigate the generation of magnetic fields from non-linear effects
around recombination. As tight-coupling is gradually lost when approaching
, the velocity difference between photons and baryons starts to
increase, leading to an increasing Compton drag of the photons on the
electrons. The protons are then forced to follow the electrons due to the
electric field created by the charge displacement; the same field, following
Maxwell's laws, eventually induces a magnetic field on cosmological scales.
Since scalar perturbations do not generate any magnetic field as they are
curl-free, one has to resort to second-order perturbation theory to compute the
magnetic field generated by this effect. We reinvestigate this problem
numerically using the powerful second-order Boltzmann code SONG. We show that:
i) all previous studies do not have a high enough angular resolution to reach a
precise and consistent estimation of the magnetic field spectrum; ii) the
magnetic field is generated up to ; iii) it is in practice
impossible to compute the magnetic field with a Boltzmann code for scales
smaller than . Finally we confirm that for scales of a few , this magnetic field is of order , many orders
of magnitude smaller than what is currently observed on intergalactic scales.Comment: 6 pages, 3 figure
Teorie della gravitazione f(R)
Tra tutti i fenomeni naturali osservabili, ne era presente uno particolarmente interessante e con il quale si aveva diretto contatto quotidianamente: la gravità.
Dopo le innumerevoli osservazioni astronomiche effettuate da Galileo, fu Newton nel diciassettesimo secolo a capire che il moto dei pianeti era governato dalle medesime leggi che descrivono la caduta dei gravi sulla Terra e fu quindi lui che ci fornì una prima teoria della gravità con la quale si spiegarono le orbite dei pianeti con ottima precisione.
Grazie al contributo di Einstein, la teoria si rinnovò e si arricchì, ma rimase pur sempre lontana dall' essere completa, tant' è che ancora oggi sono presenti molte domande a cui non siamo in grado di rispondere. In questo articolo ci occuperemo di tali quesiti, provando a formulare una teoria che sia in accordo con le attuali evidenze sperimentali.
Nella prima parte, tratteremo le ragioni che hanno spinto i ricercatori ad introdurre le nuove teorie della gravità f(R); in particolare vedremo la peculiarità delle curve di rotazione delle galassie e perché ci sia il bisogno di tirare in ballo la materia oscura. Discuteremo anche alcuni problemi derivanti dall' evoluzione cosmica e altre incongruenze riguardanti la stabilità delle stelle di neutroni.
In seguito mostreremo come ricavare l' equazione di Einstein partendo dai principi variazionali di Hamilton, e estenderemo tale ragionamento con lo scopo di ottenere un' equazione corrispondente ad una gravità modificata.
Infine, verranno introdotte le teorie della gravità f(R), per mezzo delle quali cercheremo di discutere alcune possibili spiegazioni alle problematiche mosse nella parte introduttiva
Oxidoperoxidomolybdenum(VI) complexes with acylpyrazolonate ligands: synthesis, structure and catalytic properties
Oxidoperoxido–molybdenum(VI) complexes containing acylpyrazolonate ligands were obtained by reaction of [Mo(O)(O)2(H2O)n] with the corresponding acylpyrazolone compounds HQR. Complexes Ph4P[Mo(O)(O2)2(QR)] (R = neopentyl, 1; perfluoroethyl, 2; hexyl, 3; phenyl, 4; naphthyl, 5; methyl, 6; cyclohexyl, 7; ethylcyclopentyl, 8) were obtained if the reaction was carried out with one equivalent of HQR in the presence of Ph4PCl. Alternatively, neutral complexes [Mo(O)(O2)(QR)2] (R = neopentyl, 9; hexyl, 10; cyclohexyl, 11) were formed when two equivalents of HQR were used in the reaction. These complexes were isolated in good yields as yellow or yellow-orange crystalline solids and were spectroscopically (IR, 1H, 13C{1H} and 31P{1H} NMR), theoretically (DFT) and structurally characterised (X-ray for 1, 2, 9 and 10). Compounds 1 and 9 were selected to investigate their catalytic behaviour in epoxidation of selected alkenes and oxidation of selected sulphides, while 10 and 11 were tested as catalyst precursors in the deoxygenation of selected epoxide substrates to alkenes, using PPh3 as the oxygen-acceptor. Complexes Ph4P[Mo(O)(O2)2(QR)] were shown to be poor catalyst precursors in oxidation reactions, while the activity of [Mo(O)(O2)(QR)2] species is good in all the studied reactions and comparable to related oxidoperoxido–molybdenum(VI) complexes. Complex [Mo(O)2(QC6)2], 12, was obtained by treatment of 10 with one equivalent of PPh3, demonstrating that the first step in the epoxide deoxygenation mechanism was the oxygen atom transfer toward the phosphane.Junta de Andalucía (Proyecto de Excelencia, FQM-7079)Universidad de Sevilla (VI Plan Propio
L’ANALISI E LA MISURAZIONE DEL CAPITALE INTELLETTUALE NEGLI ENTI LOCALI
Sulla scia del crescente interesse mostrato dal mondo operativo, istituzionale ed accademico, il presente lavoro si propone di dare un contributo all’analisi e alla misurazione del capitale intellettuale degli enti locali e, in particolare, dei comuni e delle province.
Il metodo di ricerca adottato è essenzialmente di tipo teorico-deduttivo. L’indagine è, inoltre, condotta privilegiando un approccio normativo. Essa, infatti, è volta a:
• contestualizzare il concetto di capitale intellettuale negli enti locali;
• individuare le fasi in cui si dovrebbe articolare il processo di misurazione del capitale intellettuale per finalità gestionali e di comunicazione esterna;
• identificare una dimensione di analisi e un correlato sistema di misurazione che permettano di integrare la performance del capitale intellettuale con la quella globale.
L’obiettivo principale è, quindi, quello di progettare un modello in grado di guidare gli enti locali nella misurazione del capitale intellettuale, così da favorire il conseguimento della performance aziendale che, nelle realtà oggetto di indagine, attiene alla sopravvivenza e allo sviluppo dello strumento-azienda e alla capacità dello stesso di soddisfare, efficacemente ed efficientemente, i bisogni della collettività amministrata
Fault Diagnosis Techniques for Linear Sampled Data Systems and a Class of Nonlinear Systems
This thesis deals with the fault diagnosis design problem both for dynamical continuous time systems whose output signal are affected by fixed point quantization,\ud
referred as sampled-data systems, and for two different applications whose dynamics are inherent high nonlinear: a remotely operated underwater vehicle and a scramjet-powered hypersonic vehicle.\ud
Robustness is a crucial issue. In sampled-data systems, full decoupling of disturbance terms from faulty signals becomes more difficult after discretization.\ud
In nonlinear processes, due to hard nonlinearity or the inefficiency of linearization, the “classical” linear fault detection and isolation and fault tolerant control methods may not be applied.\ud
Some observer-based fault detection and fault tolerant control techniques are studied throughout the thesis, and the effectiveness of such methods are validated with simulations. The most challenging trade-off is to increase sensitivity to faults and robustness to other unknown inputs, like disturbances. Broadly speaking, fault detection filters are designed in order to generate analytical diagnosis functions, called residuals, which should be independent with respect to the system operating state and should be decoupled from disturbances. Decisions on the occurrence of a possible fault are therefore taken on the basis such residual signals
Evolution of interfacial dislocation network during anisothermal high-temperature creep of a nickel-based superalloy
The effect of thermal cycling creep on the dislocation networks at the γ/γ′ interfaces in the MC2 superalloy is investigated. Tensile creep tests were performed under thermal cycling and isothermal conditions at low stress (80 MPa) and high temperature (1150 °C). In these conditions γ′ rafts may dissolve and reprecipitate during thermal cycling creep. The difference between the effects of isothermal and thermal cycling conditions on the γ/γ′ interface dislocation networks, characterized by transmission electron microscopy, is exposed, as well as their evolution during the cycle
Expression and refolding of the protective antigen of Bacillus anthracis: A model for high-throughput screening of antigenic recombinant protein refolding
Bacillus anthracis protective antigen (PA) is a well known and relevant immunogenicprotein that is the basis for both anthrax vaccines and diagnostic methods. Properly foldedantigenic PA is necessary for these applications. In this study a high level of PA was obtained inrecombinant Escherichia coli. The protein was initially accumulated in inclusion bodies, whichfacilitated its efficient purification by simple washing steps; however, it could not be recognizedby specific antibodies. Refolding conditions were subsequently analyzed in a high-throughputmanner that enabled nearly a hundred different conditions to be tested simultaneously. Therecovery of the ability of PA to be recognized by antibodies was screened by dot blot usinga coefficient that provided a measure of properly refolded protein levels with a high degreeof discrimination. The best refolding conditions resulted in a tenfold increase in the intensityof the dot blot compared to the control. The only refolding additive that consistently yieldedgood results was L-arginine. The statistical analysis identified both cooperative and negativeinteractions between the different refolding additives. The high-throughput approach describedin this study that enabled overproduction, purification and refolding of PA in a simple andstraightforward manner, can be potentially useful for the rapid screening of adequate refoldingconditions for other overexpressed antigenic proteins.Fil: Pavan, María Elisa. Biochemiq; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Pavan, Esteban E.. Politecnico di Milano; ItaliaFil: Cairo, Fabian Martin. Biochemiq; ArgentinaFil: Pettinari, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentin
Effect of crumb rubber gradation on a rubberized cold recycled mixture for road pavements
Cold recycling technique represents the most environmental friendly solution for pavement rehabilitation nowadays. In fact, this technique allows the use of the highest percentage of reclaimed asphalt avoiding the energy consumption related to aggregates heating required by the traditional hot mix asphalt design. The mix design represents a key phase of the cold mix production. The study of workability and compactability properties combined with a deep laboratory investigation is required. The idea of introducing crumb rubber in the cold mixtures was developed based on the concept of maximizing the valorization of recycled materials together with the goal of achieving high performance. In the present research project, two different gradations of crumb rubber, processed with the traditional grading method, have been adopted for the production of a cold recycled mixture stabilized with bitumen emulsion and cement. The spring-back effects of the rubber particles, which occur after compaction, together with the Indirect Tensile Strength and the Indirect Tensile Stiffness Modulus have been studied. The results show that the gradation of the adopted crumb rubber sensibly affects the compaction and mechanical properties of the cold recycled mixture
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