514 research outputs found
Trust-based algorithms for fusing crowdsourced estimates of continuous quantities
No full textCrowdsourcing has provided a viable way of gathering information at unprecedented volumes and speed by engaging individuals to perform simple micro–tasks. In particular, the crowdsourcing paradigm has been successfully applied to participatory sensing, in which the users perform sensing tasks and provide data using their mobile devices. In this way, people can help solve complex environmental sensing tasks, such as weather monitoring, nuclear radiation monitoring and cell tower mapping, in a highly decentralised and parallelised fashion. Traditionally, crowdsourcing technologies were primarily used for gathering data for classifications and image labelling tasks. In contrast, such crowd–based participatory sensing poses new challenges that relate to (i) dealing with human–reported sensor data that are available in the form of continuous estimates of an observed quantity such as a location, a temperature or a sound reading, (ii) dealing with possible spatial and temporal correlations within the data and (ii) issues of data trustworthiness due to the unknown capabilities and incentives of the participants and their devices. Solutions to these challenges need to be able to combine the data provided by multiple users to ensure the accuracy and the validity of the aggregated results. With this in mind, our goal is to provide methods to better aid the aggregation process of crowd–reported sensor estimates of continuous quantities when data are provided by individuals of varying trustworthiness. To achieve this, we develop a trust–based in- formation fusion framework that incorporates latent trustworthiness traits of the users within the data fusion process. Through this framework, we develop a set of four novel algorithms (MaxTrust, BACE, TrustGP and TrustLGCP) to compute reliable aggregations of the users’ reports in both the settings of observing a stationary quantity (Max- Trust and BACE) and a spatially distributed phenomenon (TrustGP and TrustLGCP). The key feature of all these algorithm is the ability of (i) learning the trustworthiness of each individual who provide the data and (ii) exploit this latent user’s trustworthiness information to compute a more accurate fused estimate. In particular, this is achieved by using a probabilistic framework that allows our methods to simultaneously learn the fused estimate and the users’ trustworthiness from the crowd reports. We validate our algorithms in four key application areas (cell tower mapping, WiFi networks mapping, nuclear radiation monitoring and disaster response) that demonstrate the practical impact of our framework to achieve substantially more accurate and informative predictions compared to the existing fusion methods. We expect that results of this thesis will allow to build more reliable data fusion algorithms for the broad class of human–centred information systems (e.g., recommendation systems, peer reviewing systems, student grading tools) that are based on making decisions upon subjective opinions provided by their users
Fontana e lo spazio : aspetti innovativi dalle opere ambientali di Lucio Fontana
No full textLa tesi intende sondare gli aspetti innovativi che emergono dall'analisi degli ambienti maggiori di Lucio Fontana costruiti fra il 1949 e il 1968. Attraverso la ricostruzione storico critica si aprono nuove possibilità critiche riguardo la storia dell'environment
Photocurrent generation in peptide-based self-assembled monolayers on gold electrodes
No full textThe photocurrent generation properties of a self-assembled monolayer formed by a helical hexapeptide carrying a pyrene group at the C-terminus and chemisorbed on a gold electrode through a lipoyl chain have been investigated by means of photoelectrochemical experiments. Anodic and cathodic photocurrents have been measured by simply changing the redox-active electrolyte in the electrochemical cell. (c) 2008 Elsevier Ltd. All rights reserved
Solution studies of complexes of the types trans-PtCl2L(1,4-diazine) and trans-LCl2Pt(μ-1,4-diazine)PtCl2L (L=phosphine and C2H4). The X-ray structures of PtCl4L2(2,5-dimethylpyrazine) (L= C2H4 and PEt3) and the relative trans-influence of alkene and tertiary phosphine ligands.
No full textSolution studies of the complexes PtCI,L( 1,4-diazine) and fruns-LCl,Pt( 1,4-diazine)PtCI,L (L = PEt,, PMe2Ph, PMePh,, P-n-Bu,,
C2H4d;ia zine = pyrazine, 2-methylpyrazine, 2,3-, 2,5- and 2,6-dimethylpyrazine, 2,3,5-trimethylpyrazine,2 ,3,5,6-tetramethylpyrazine,
phenazine) have been carried out. It is shown that (a) coordination of the “PtCI,L” fragment does not significantly
weaken the donor capacity of the still uncoordinated nitrogen atom of the heterocycle, (b) these complexes are dynamic in solution,
the ethene complexes being more labile than the corresponding phosphine complexes, and (c) the presence of methyl substituents
near the coordinated nitrogen atom slows down the dynamic process. The X-ray crystal structures of (C2H4)C12Pt(2,5-dimethylpyrazine)
PtCI2(C2H4()E 2ppz) and (PEt3)CI,Pt(2,5-dimethylpyrazine)PtCl2(PEt(A3)2 ppz) were determined. The crystals
of E,ppz are monoclinic and belong to the space group P2,/n with unit cell dimensions u = 7.048 (3) A, b = 13.407 (3) A, c =
9.219 (2) A, /3 = 69.81 (3)O, V = 817.7 A’, and 2 = 2. The structure was refined to R = 0.044. The crystals of A2ppz are
monoclinic and belong to the space group P2,/c with unit cell dimensions a = 12.149 (3) A, b = 8.231 (6) A, c = 15.464 (5)
A, /3 = 108.95 (2)O, V = 1462.6 A’, and Z = 2. The structure was refined to R = 0.038. Each platinum atom shows normal
square-planar geometry with bonding parameters that are typical of the complexes fruns-PtCI,L(N-ligand) (L = alkene, tertiary
phosphine). The differences in Pt-N distances in the two complexes clearly show the higher trans influence of the phosphine relative
to that of the alkene
The vibrational spectrum of Tp(3,5-Me)RhH(2)(H-2) : a computational and inelastic neutron scattering study
No full textWe report extensive density functional theory studies of the structures and vibrational frequencies of Tp(3,5-Me)RhH(2)(H-2) in its ground and various transition states as well as the first direct comparison of observed and calculated inelastic neutron scattering (INS) vibrational spectra on this type of compound. Geometry optimizations produced canted eta(2)-dihydrogen dihydride local minima of C, symmetry, with HH distances for the C-1 minimum energy structure of 0.842 and 0.898 A and barriers to rotation of 0.34 and 0.50 kcal mol (1), respectively for B3LYP/BS1 and BP86/BS1 calculations of Tp(3.5-Me)RhH(2)(H-2). The latter results from one transition state rotated approximately 60degrees away (a second lower energy transition state which is a few hundreds of a kcal mol (- 1) above the C-1 MIN is rotated approximately 30degrees away). With these calculated d(HH) values for the C-1 MIN the previously reported experimental data on the rotation of the dihydrogen ligand yields an experimental barrier to rotation of similar to 1 kcal mol (- 1) and places the torsional transition at 200 cm (- 1) in the INS spectrum. Optimization of the Rh structure, that is analogous to the related Ir(V) C, minimum found for TpIrH(4), generates a high-energy ( > 4 cal mol (- 1)) C-s transition state TpRh(III)H(4) structure with an eta(3)-H-3, ligand. This transition state (C-s TSE) exchanges the hydrogen in the mirror plane between two chiral C-1 MIN structures. Comparisons between observed and computed INS spectra suggests that the experimental INS spectrum be viewed as resulting from a quantum-averaged ground state encompassing at least two of the low energy structures found in our calculations
Fattori di rischio macroeconomici e rendimenti delle strategie di portafoglio: ipotesi teoriche ed evidenza empirica
No full textFrom Fama-French (1993) and Carhart (1997) studies, which identify size, value, and momentum factors in addition to market risk as significant drivers of stock returns, the micro-finance research addressed the measurement of macroeconomic factors’ impacts on returns of portfolio strategies based on these multi-factor models. These analyses could be crucial in explaining the low or negative correlation often found in literature between the returns of such strategies (Cooper-Priestley 2009; Avramov et al. 2012; Asness et al. 2013; Wisniewski-Jackson 2020; Dahlquist-Hasseltoft 2020).
The contribution of this paper is twofold: i) to explain the theoretical foundation of expected impacts of the main macroeconomic factors on the returns of value and momentum strategies regarding equity and bond asset classes; ii) to verify whether these relationships are supported (in terms of sign and statistical significance) by the most recent empirical literature. The analysis shows that: i) univocal hypotheses on the expected links cannot be formulated; the causes of persistent returns of the two strategies, in fact, can be explained by adopting different theoretical perspectives, behavioural vs risk-premium models, which assume different linkages with macroeconomic factors; ii) the empirical findings are mixed; they could be also explained by differences, among studies, in country
samples (Continental Europe, Emerging Markets, UK, Developed Asia, and
USA), time periods, and testing methodology used. Nonetheless, the provided literature review is useful in delineating a comprehensive framework of the expected and empirically observed links
Francisco De Venanzi: Estudio Hemerográfico. En homenaje a los 100 años de su nacimiento (1917-2017)
No full textSe recopila el legado hemerográfico del Dr. Francisco De Venanzi (1917-1987). Se incluye una lista completa de todas sus publicaciones científicas, aparecidas en revistas científicas, tanto nacionales como internacionales, compiladas en su hoja de vida (91 referencias (iniciales IME/UCV) y suman 108 en total). Se incorporan los resultados de 6 nuevos estudios publicados por De Venanzi, entre 1987 y 2006, referidos a sus dos grandes líneas de investigación y de mayor impacto sobre la salud del venezolano. Se incorporan 9 nuevos artículos localizados posterior a su fallecimiento, 6 de ellos postmortem y se agregan 2 trabajos no reseñados anteriormente dentro de la bibliografía existente del autor. (1987-2006). Se contabilizan: (a) 59 artículos (58,41%) área de fósforo (b) 15 publicaciones (14,85%) en Metabolismo del Iodo y el Bocio Endémico; (c) 27 artículos (26,73%) referido a otros temas (especialmente vitaminas). Se comentan algunas referencias y se reseñan algunos premios, reconocimientos y homenajes en su nombre
Looking for a Robust, Synthetic, Fully-Extended (2.05-Helical) Peptide Structure - Effect of Terminal Groups
No full textThe incorporation of alpha-amino acids with a quaternary alpha-carbon atom into a peptide provides a tool to effectively restrict the available range of its backbone conformations. Specifically, under favorable conditions, Calpha,alpha-diethylglycine (Deg) homopeptides are known to preferentially adopt the fully-extended (2.05-helical) structure, which is characterized by the longest possible separation between two adjacent alpha-amino acid Cα atoms. We have investigated the influence of the nature of the N- and/or C-terminal protecting (or blocking) groups on the relative stabilities of the fully-extended conformation vs. the competing, shorter 3(10)-helical structure in a synthetic Deg homopeptide series
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