3,983 research outputs found

    Evaluating the impact of active labor programs : results of cross country studies in Europe and Central Asia

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    The objective of this cross country study was to determine if there was any significant difference those individuals who participated in active labor programs (ALP) and similar individuals who did not participate in the programs (the comparison group), with regard to agreed outcome measures of program success (e.g., employment, wage levels) in four countries: the Czech Republic, Poland, Hungary, and Turkey. The study evaluated five different ALPs across the four countries for several categories of program participants, grouped by demographic characteristics and geographic location. The active labor programs studies comprised: retraining, public works or temporary community employment, wage subsidy, self-employment initiatives, and general employment services. All five ALPs evaluated were found to have a significant positive net impact for some population subgroups, a general finding supported by the 1996 OECD review that concluded that there are ALPs that work for most groups of individuals. However, the study found the impact was not significant for some sub-groups, and for some ALPs the impact was negative. The final chapter summarizesthe general trends in findings on the various outcome measures across demographic and regional subgroups.Environmental Economics&Policies,Poverty Impact Evaluation,ICT Policy and Strategies,Health Monitoring&Evaluation,Poverty Monitoring&Analysis

    Conformations of N-Heterocyclic Carbene Ligands in Ruthenium Complexes Relevant to Olefin Metathesis

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    The structure of ruthenium-based olefin metathesis catalyst 3 and model π-complex 5 in solution and in the solid state are reported. The N-tolyl ligands, due to their lower symmetry than the traditional N-mesityl substituents, complicate this analysis, but ultimately provide explanation for the enhanced reactivity of 3 relative to standard catalyst 2. The tilt of the N-tolyl ring provides additional space near the ruthenium center, which is consistent with the enhanced reactivity of 3 toward sterically demanding substrates. Due to this tilt, the more sterically accessible face bears the two methyl substituents of the N-aryl rings. These experimental studies are supported by computational studies of these complexes by DFT. The experimental data provides a means to validate the accuracy of the B3LYP and M06 functionals. B3LYP provides geometries that match X-ray crystal structural data more closely, though it leads to slightly less (0.5 kcal mol^(−1)) accuracy than M06 most likely because it underestimates attractive noncovalent interactions

    Z-Selective Olefin Metathesis on Peptides: Investigation of Side-Chain Influence, Preorganization, and Guidelines in Substrate Selection

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    Olefin metathesis has emerged as a promising strategy for modulating the stability and activity of biologically relevant compounds; however, the ability to control olefin geometry in the product remains a challenge. Recent advances in the design of cyclometalated ruthenium catalysts has led to new strategies for achieving such control with high fidelity and Z selectivity, but the scope and limitations of these catalysts on substrates bearing multiple functionalities, including peptides, remained unexplored. Herein, we report an assessment of various factors that contribute to both productive and nonproductive Z-selective metathesis on peptides. The influence of sterics, side-chain identity, and preorganization through peptide secondary structure are explored by homodimerization, cross metathesis, and ring-closing metathesis. Our results indicate that the amino acid side chain and identity of the olefin profoundly influence the activity of cyclometalated ruthenium catalysts in Z-selective metathesis. The criteria set forth for achieving high conversion and Z selectivity are highlighted by cross metathesis and ring-closing metathesis on diverse peptide substrates. The principles outlined in this report are important not only for expanding the scope of Z-selective olefin metathesis to peptides but also for applying stereoselective olefin metathesis in general synthetic endeavors

    Hypervelocity Stars from the Andromeda Galaxy

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    Hypervelocity stars (HVSs) discovered in the Milky Way (MW) halo are thought to be ejected from near the massive black hole (MBH) at the galactic centre. In this paper we investigate the spatial and velocity distributions of the HVSs which are expected to be similarly produced in the Andromeda galaxy (M31). We consider three different HVS production mechanisms: (i) the disruption of stellar binaries by the galactocentric MBH; (ii) the ejection of stars by an in-spiraling intermediate mass black hole; and (iii) the scattering of stars off a cluster of stellar-mass black holes orbiting around the MBH. While the first two mechanisms would produce large numbers of HVSs in M31, we show that the third mechanism would not be effective in M31. We numerically calculate 1.2*10^6 trajectories of HVSs from M31 within a simple model of the Local Group and hence infer the current distribution of these stars. Gravitational focusing of the HVSs by the MW and the diffuse Local Group medium leads to high densities of low mass (~ solar mass) M31 HVSs near the MW. Within the virialized MW halo, we expect there to be of order 1000 HVSs for the first mechanism and a few hundred HVSs for the second mechanism; many of these stars should have distinctively large approach velocities (< -500 km/s). In addition, we predict ~5 hypervelocity RGB stars within the M31 halo which could be identified observationally. Future MW astrometric surveys or searches for distant giants could thus find HVSs from M31.Comment: 14 pages, 6 figures, changed to match version accepted by MNRA

    Nuclear alpha-clustering, superdeformation, and molecular resonances

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    Nuclear alpha-clustering has been the subject of intense study since the advent of heavy-ion accelerators. Looking back for more than 40 years we are able today to see the connection between quasimolecular resonances in heavy-ion collisions and extremely deformed states in light nuclei. For example superdeformed bands have been recently discovered in light N=Z nuclei such as 36^{36}Ar, 40^{40}Ca, 48^{48}Cr, and 56^{56}Ni by γ\gamma-ray spectroscopy. The search for strongly deformed shapes in N=Z nuclei is also the domain of charged-particle spectroscopy, and our experimental group at IReS Strasbourg has studied a number of these nuclei with the charged particle multidetector array {\sc Icare} at the {\sc Vivitron} Tandem facility in a systematical manner. Recently the search for γ\gamma-decays in 24^{24}Mg has been undertaken in a range of excitation energies where previously nuclear molecular resonances were found in 12^{12}C+12^{12}C collisions. The breakup reaction 24^{24}Mg+12+^{12}C has been investigated at Elab_{lab}(24^{24}Mg) = 130 MeV, an energy which corresponds to the appropriate excitation energy in 24^{24}Mg for which the 12^{12}C+12^{12}C resonance could be related to the breakup resonance. Very exclusive data were collected with the Binary Reaction Spectrometer in coincidence with {\sc Euroball IV} installed at the {\sc Vivitron}.Comment: 10 pages, 4 eps figures included. Invited Talk 10th Nuclear Physics Workshop Marie and Pierre Curie, Kazimierz Dolny Poland, Sep. 24-28, 2003; To be published in International Journal of Modern Physics

    How far and for how much? Evidence on wages and potential travel-to-work distances from a survey of the economically inactive

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    The U.K. government has recently committed itself to an ambitious 80 per cent employment rate target. Recognising that achieving this aspiration will require significant numbers of the economically inactive to (re-)engage with the labour market, the government has enacted various policy reforms seeking to encourage those on the fringes of the labour market to do so. The present paper uses unique survey data to examine three factors relevant to these issues, namely the desire to work, minimum acceptable wages and the distance the inactive are prepared to travel to work for a given minimum acceptable wage offer

    Carboxylate-Assisted C(sp^3)–H Activation in Olefin Metathesis-Relevant Ruthenium Complexes

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    The mechanism of C–H activation at metathesis-relevant ruthenium(II) benzylidene complexes was studied both experimentally and computationally. Synthesis of a ruthenium dicarboxylate at a low temperature allowed for direct observation of the C–H activation step, independent of the initial anionic ligand-exchange reactions. A first-order reaction supports an intramolecular concerted metalation–deprotonation mechanism with ΔG^(‡)_(298K) = 22.2 ± 0.1 kcal·mol^(–1) for the parent N-adamantyl-N′-mesityl complex. An experimentally determined ΔS^(‡) = −5.2 ± 2.6 eu supports a highly ordered transition state for carboxylate-assisted C(sp^3)–H activation. Experimental results, including measurement of a large primary kinetic isotope effect (k_(H)/k_(D) = 8.1 ± 1.7), agree closely with a computed six-membered carboxylate-assisted C–H activation mechanism where the deprotonating carboxylate adopts a pseudo-apical geometry, displacing the aryl ether chelate. The rate of cyclometalation was found to be influenced by both the electronics of the assisting carboxylate and the ruthenium ligand environment

    Synthesis and reactivity of olefin metathesis catalysts bearing cyclic (alkyl) (amino) carbenes

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    All it's CAACed up to be! Cyclic (alkyl)(amino)carbenes (CAACs) can be used as ligands for olefin metathesis catalysis. A dramatic steric effect of the N-aryl group of the CAAC on catalyst activity was observed and utilized to develop a new catalyst with activity comparable to standard commercially available catalysts
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