9,509 research outputs found
Implementing the AIFMD: Success or failure? ECMI Commentary No. 34, 28 March 2013
No full textThis commentary considers the implementation of the Alternative Investment Fund Managers Directive (AIFMD) by the European Commission. The AIFMD creates an internal market for asset management and as an endeavour to develop market-based finance is an important piece of legislation for the European economy. The author, Mirzha de Manuel Aramendía, considers the implementation of some of the provisions that raised concern among industry participants. He finds that, on balance, a practical and flexible approach to implementation has been followed that should help secure the success of the framework, which at present is still uncertain. The commentary also considers the remuneration guidelines adopted recently by the European Securities and Markets Authority (ESMA). It encourages EU and national authorities to commit to the success of the AIFMD framework, as part of a broader effort to develop capital markets and reduce the historical reliance of the European economy on bank finance
Qubit molecolari basati su paramagneti metallo-organici: progettazione, proprietà e utilizzo nelle tecnologie quantistiche
No full textSfruttare i qubit per sviluppare nuovi dispositivi è una delle maggiori sfide nelle tecnologie quantistiche (TQ). Tra le diverse tipologie di qubit, molto promettenti risultano le molecole magnetiche, dove la decoerenza è indotta principalmente dal rumore magnetico, controllabile mediante design chimico.
Questa Tesi si concentra principalmente su due nuove famiglie di paramagneti metallo-organici basati su complessi di VO2+ con un singolo elettrone spaiato (S = 1/2), i quali possono mostrare tempi di coerenza (TC) sufficientemente lunghi da agire come qubit rilevanti per le TQ.
Il primo nuovo tipo di qubit è stato ottenuto dal prolegante tetradentato H2L contenente due gruppi β-dichetonici, la cui sintesi e purificazione sono state attentamente ottimizzate. La sua forma doppiamente deprotonata L2− può coordinare metalli di transizione attraverso donatori ossigenati privi di spin nucleare, fornendo complessi neutri e stabili. Inizialmente abbiamo studiato la reazione di L2− con Co2+ e Zn2+, isolando cristalli con struttura dimerica dei composti [Co2L2py4] (2) e [Zn2L2py2] (5) (py = piridina). Esperimenti 1H-NMR, inclusi DOSY e NOESY, hanno però stabilito che sia 2 che 5 diventano monomeri in soluzione. Misure magnetiche in stato solido hanno dimostrato che i due ioni Co2+ ad alto spin in 2 presentano un'anisotropia hard-axis e un rilassamento magnetico lento in campo applicato statico. Il complesso di VO2+ e L2− è stato infine assemblato e isolato in tre diverse fasi cristalline, inclusa una nanoporosa, che contengono sempre molecole dimeriche [(VO)2L2] (7). Esperimenti DOSY e CW-EPR hanno dimostrato che anche 7 diventa monomero in soluzione, mostrando coerenza quantistica di spin in soluzione congelata, con T1 = 14 ms e Tm = 13 μs a 10 K.
Come secondo nuovo tipo di qubit, abbiamo studiato i complessi a lanterna [PtVO(SOCR)4]; neutri e contenenti atomi donatori privi di spin nucleare. Sebbene dimerici in stato solido, i derivati con R = Me o Ph sono solubili, stabili e monomerici in soluzione, come dimostrato da DOSY e CV. Tali derivati forniscono spettri EPR in banda X altamente risolti in soluzione congelata, evidenziando un'interazione superiperfine con il nucleo I = 1/2 dell'isotopo 195Pt. Calcoli DFT attribuiscono la delocalizzazione della densità di spin sullo ione Pt2+ a una combinazione di percorsi π e δ, con il primo predominante. Misure di rilassamento di spin in soluzione congelata a 10 K hanno fornito valori di Tm di 6 μs per R = Me e 11 μs per R = Ph, dimostrando che la prossimità di Pt2+ non è dannosa per le proprietà di coerenza di VO2+. Manipolazioni coerenti dello spin a 70 K sono possibili per entrambi i derivati e per 7, come dimostrato dall’osservazione delle oscillazioni di Rabi negli esperimenti di nutazione. Tali risultati indicano che questi complessi di VO2+ possono essere utilizzati come elementi costitutivi robusti e spin-coerenti nelle TQ.
Il tunneling quantistico tra orientazioni opposte di spin non-Kramers, genera livelli di anti-crossing (LAC) con un'eccellente stabilità contro il rumore magnetico. Codificare un qubit negli stati di sovrapposizione che si formano ai LAC è quindi una strategia alternativa per aumentare il TC. La ricerca condotta durante il periodo all'estero presso l'Università di Barcellona, si è concentrata su nuovi elicati omoleptici a triplo filamento contenenti leganti bis-pirazolilpiridinici e due ioni Ni2+ ottaedrici, che mostrano un gap regolabile tra i due livelli inferiori di spin elettronico. Queste specie possono incapsulare selettivamente guest diversi (Cl−, Br−) e mantenere la loro struttura in soluzione, come dimostrato dalle indagini ESI-MS e NMR multinucleare; aprendo la strada al controllo delle LAC e della spin-dinamica dei centri Ni(II) tramite interazioni host-guest.Exploiting qubits to develop new functional tools and devices is one of the main current challenges in quantum technologies (QT). Among the different physical realizations of qubits, magnetic molecules are a very promising option. In magnetic molecules, decoherence is mainly induced by magnetic noise, which can be controlled by chemical design.
This Thesis mostly focuses on two new families of metal-organic paramagnets based on VO2+ complexes and containing a single unpaired electron (S = 1/2). These systems can exhibit sufficiently long coherence times (CTs) to behave as qubits relevant in QT.
The first new type of qubit was assembled using a tetradentate proligand H2L containing two fused -diketones, whose synthesis and purification were carefully optimized. Its doubly deprotonated form L2− can bind transition metals through nuclear spin-free O donors, affording chemically stable and charge-neutral bis-chelated complexes. As a preliminary step, we investigated the reaction of L2− with Co2+ and Zn2+ and isolated crystals of the compounds [Co2L2py4] (2) and [Zn2L2py2] (5), which have an unexpected dimeric structure (py = pyridine). However, a manifold of 1H-NMR experiments, including DOSY and NOESY, established that both 2 and 5 turn to monomeric in solution. Magnetic measurements in the solid state demonstrated that the two high-spin Co2+ ions in 2 have a hard-axis anisotropy and show slow magnetic relaxation in an applied static field. The VO2+ complex of L2− was finally assembled and isolated in three different crystal phases (including a nanoporous phase), which invariably contain the dimeric molecules [(VO)2L2] (7). CW-EPR and DOSY experiments independently demonstrated that 7 also exists in monomeric form in organic solution. These monomers exhibit quantum spin coherence in frozen solution with T1 = 14 ms and Tm = 13 μs at 10 K.
As a second new type of qubit, we investigated the lantern complexes [PtVO(SOCR)4] which are electrically neutral and contain nuclear spin-free donor atoms. While dimeric in the solid state, the derivative with R = Me or Ph are soluble, stable, and monomeric in organic solvents, as proved by DOSY and CV. Moreover, both complexes give highly resolved X-band EPR spectra in frozen solution, which evidence a measurable superhyperfine interaction with the I = 1/2 nucleus of the 195Pt isotope. DFT calculations ascribe the spin density delocalization on the Pt2+ ion to a combination of π and δ pathways, with the former predominating. Spin relaxation measurements in frozen solution at 10 K yielded Tm values of 6 μs for R = Me and 11 μs for R = Ph, showing that the proximal Pt2+ ion is not detrimental to the coherence properties of VO2+. Coherent spin manipulations at 70 K proved possible in both lanterns and in 7, as demonstrated by Rabi oscillations in nutation experiments. The results indicate that these VO2+ complexes can be used as robust spin-coherent building blocks in QT.
Quantum tunneling between opposite orientations of non-Kramers spins generates level anti-crossings (LAC), which possess excellent stability against magnetic noise. Encoding a qubit in the superposition states that form at LAC is therefore an alternative strategy to increase the CT. Research carried out during the period abroad at the University of Barcelona focused on new homoleptic triple-stranded helicates containing bis-pyrazolylpyridine ligands and two octahedral Ni2+ ions, which show a tunable tunnel splitting between the two lowest electronic spin levels. These species can selectively encapsulate different guests (Cl−, Br−) and retain their structure in solution, as demonstrated by ESI-MS and multinuclear NMR investigation; paving the way to control the LAC and the spin dynamics of the Ni(II) centers via host-guest interactions
Manuel Puig: un destino melodramático
No full textEl trabajo es un extracto de una larga investigación en los archivos del escritor argentino Manuel Puig, la génesis de su producción y su relación con el campo intelectual internacional. En este extracto se presenta un estudio del uso del melodrama en la producción 'espectacular' del autor y la publcación de un inédito que incluí como primicia en 1996 en la revista Orbis Tertius No. 2, Centro de Teoría y Crítica Literaria, UNLP.The work is an extract of one long recherch in the archives of the Argentine writer Manuel Puig, the genesis of its production and its relation with international the intellectual field. In this extract is analyzed the use of the melodrama in “the spectacular” production of the author. The publication of an unpublished is included , published for the first time by me in 1996 in the Orbis Tertius Nº 2, Centro de Teoría y Crítica Literaria, UNLP.Facultad de Humanidades y Ciencias de la Educació
Development of Graphite-Epoxy Composites for Bipolar Plates in PEM Fuel Cells
No full textGraphite-Epoxy composites can be a good alternative to metals and metal alloys to build Bipolar Plates (BPs),1 that are important components of Proton Exchange Membrane Fuel Cells (PEMFC), mainly used in hydrogen-powered electric vehicles. We are currently working2 on the preparation of graphite-epoxy composites, suitable for manufacturing BPs meeting the technical targets for 2025.3
Among the overall properties expected for BPs, we are mainly focussing on conductivity, flexural strength and permeability and we are tuning the preparation steps, i.e. composite formulation, mixing and molding, trying to optimize these properties. We compared different resin to filler ratios, dry and wet mixing, mechanical and magnetic stirring and different temperature and pressure ranges. A two-level full factorial Design Of Experiment (DOE) approach was performed to analyze the molding parameters.
We observed substantial changes in the properties of the composites, depending on the type of graphite, the mixing method, the epoxy resin to filler ratio and the molding pressure, temperature and time. The results of these studies will be presented
Conclusive Insight into the Coordination Complexes of a Flexible Bis(beta-diketonato) Ligand and their Phase-dependent Structure: a Multi-technique Approach
No full textMultichelating ligands with nuclear spin-free donor atoms are of particular interest for creating stable electronic spin qubits based on paramagnetic transition metal ions. We recently focused on the coordinating ability of the bis(beta-diketonato) ligand bdhb2–, featuring two “acac” moieties connected through a 1,3-phenylene bridge (H2bdhb = 1,3-bis(3,5-dioxo-1-hexyl)benzene). The two crystalline complexes of bdhb2– so far isolated and structurally characterized, namely [(VO)2(bdhb)2] (1) and [Co2(bdhb)2(py)4] (2), are dimeric and contain bridging bdhb2– ligands; however, they become mononuclear and quasi-macrocyclic in organic solution. To investigate this unique structural isomerism by high-resolution 1H NMR spectroscopy, we have now synthesized a diamagnetic Zn2+ analogue of 1 and 2, namely [Zn2(bdhb)2(py)2] (3). Although both 2 and 3 are dimeric and contain the same ligands, 3 features only one pyridine molecule per metal ion, whose coordination geometry is square pyramidal rather than tetragonally elongated octahedral. The ESI-MS spectra of 3 in THF and CH2Cl2 contain peaks from both monomeric and dimeric species. However, molecular weight determinations by DOSY and conformational studies based on J-coupling analysis and DFT calculations conclusively prove the rearrangement of 3 into quasi-macrocyclic monomers in THF-d8 and CD2Cl2 solution at room temperature
Letter from Manuel E. Ykari [Ikari] to Wayne M. Collins, May 29, 1953
No full textIn this letter to Mr. Wayne M. Collins, Mr. Manuel E. Ykari [Ikari] explains that he will need to pay Mr. Collins in segments. Mr. Collins is a lawyer in San Francisco.Collection of notes, articles, correspondence, photographs, and term papers collected by Yukio Mochizuki, a student at CSU Dominguez Hills, while researching Japanese American incarceration and Japanese Peruvian internment during World War II
Optoelectronic Properties of A‐π‐D‐π‐A Thiophene‐Based Materials with a Dithienosilole Core: An Experimental and Theoretical Study
No full textTwo A‐π‐D‐π‐A thiophene based small molecules, with a central dithienosilole core and dicyanovinyl end groups were synthesized. These compounds differ only for the presence of alkyl and alkylsulfanyl chains, respectively, on thiophene beta positions. The computational data together with the spectroscopic and electrochemical findings (obtained by means of absorption, steady‐state/time‐resolved emission techniques and cyclic voltammetry) revealed that both molecules possess low electronic and optical band gaps, broad absorption spectra and a good stability both in p and n‐doping states, properties that make them suitable for optoelectronic applications. In either compounds the HOMO‐LUMO transition involves an intramolecular charge transfer from the electron‐donor dithienosilole unit to the two terminal electron‐acceptor DCV groups. A marked positive emission solvatochromism was observed for both molecules and was interpreted on the basis of the symmetry breaking in the S1 excited state. The two synthesized compounds were also compared to their shorter precursors and to similar oligothiophenes to understand how the nature of the building block influences the characteristics of the final materials. Furthermore, it was possible to better understand the contribution of the sulfur atom in modulating the optical properties of the small molecules studied
Oral History Interview with Manuel Medrano, June 18, 2015
No full textInterview with Manuel Medrano, an historian and author from Brownsville, Texas. In his interview, Medrano discusses his family background and childhood, education, experiences with discrimination, political activism, and the Chicano movement
Manuel Muñoz, 38th Annual ODU Literary Festival
No full textManuel Muñoz is the author of a novel, What You See in the Dark, as well as two short-story collections, Zigzagger and The Faith Healer of Olive Avenue, which was shortlisted for the Frank O\u27Connor International Short Story Award. His work has appeared in The New York Times, Glimmer Train and Boston Review and has aired on NPR’s “Selected Shorts. The recipient of an O. Henry Prize and a Whiting Writers\u27 Award, Muñoz lives in Tucson, Ariz., where he is an associate professor at the University of Arizona
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