Screen printed Pb₃O₄ films and their application to photoresponsive and photoelectrochemical devices

A new and simple procedure for the deposition of lead (II, IV) oxide films by screen printing was developed. In contrast to conventional electrochemical methods, films can be also deposited on non-conductive substrates without any specific dimensional restriction, being the only requirement the thermal stability of the substrate in air up to 500 °C to allow for the calcination of the screen printing paste and sintering of the film. In this study, films were exploited for the preparation of both photoresponsive devices and photoelectrochemical cell photoanodes. In both cases, screen printing was performed on FTO (Fluorine-Tin Oxide glass) substrates. The photoresponsive devices were tested with I-V curves in dark and under simulated solar light with different irradiation levels. Responses were evaluated at different voltage biases and under light pulses of different durations. Photoelectrochemical cells were tested by current density⁻voltage (J-V) curves under air mass (AM) 1.5 G illumination, incident photon-to-current efficiency (IPCE) measurements, and electrochemical impedance spectroscopy

The Unemployment Route to Versatility

In this paper we document a common sense idea: When an individual is searching for a new job, the longer it takes the more s/he will be available to adapt her/his skills, often with a worsening in status and/or wage. We used a dataset of administrative source, containing a sample of individuals' working careers in the private sector, in Italy, years 1985-1996. We do not observe directly the search activity of individuals: What we observe is the re-entry time elapsing from the separation from a job spell, to the association to a new one. The information collected about the job spells, however, is quite rich, and allows a thorough analysis of the main features of job changes. If we do not take into account re-entry times into dependent work, the inter-industry mobility we report is relatively limited, even at high levels of disaggregation. Still (roughly) 50% of job changes occurs within the same 3-digit Ateco sectors, and without changing skill/status. If we condition on re-entry times, we find a positive effect on the probabilities of changing sector in the first months of the search, while for longer re-entry times, and of worsening the working status and wage.Job matching; Job changes; Re-entry times; Inter sectoral mobility; Wage dynamics; Linked employer-employee datasets.

Mechanistic study of asymmetric amplification in the Soai autocatalytic reaction

Soai’s discovery of chiral amplification in the autocatalytic alkylation of pyrimidine-5-carbaldehyde with diisopropylzinc is one of the most noteworthy findings of the last decade of the 20th century. This is the first experimental confirmation of an early theoretical rationalisation of autocatalysis as a mechanism for the evolution of biological homochirality from a racemic environment (Frank, 1953). This thesis describes kinetic and spectroscopic investigations that were conducted with the aim of better understanding the mechanism under which chiral amplification is achieved in the Soai system. The methodology used to perform the kinetic studies that are presented in this thesis focuses on the use of reaction calorimetry as in-situ tool coupled with the appropriate analytical technique for enantiomeric excess measurements. Observations of an unusual temperature effect on the reaction rate and a profound induction period are reported together with extensive kinetic investigations. Kinetic experiments were designed and carried out following Reaction Progress Kinetic Analysis methodology, which is described in detail. These experiments were carried out in order to ascertain the concentration dependence of the substrates and the reaction product, and revealed a 1.6 order in pyrimidyl aldehyde, a zero order in diisopropylzinc and a first order in the reaction product. Meticulous NMR studies of the alkoxide product at low temperature demonstrated its tendency to form tetrameric complexes, which could be either directly involved in the autocatalysis or be the precursors of the active catalytic species. Possible mechanisms that involve tetramers formation are proposed and supported by simulations carried out using COPASI simulation software. This thesis also includes a separate Chapter on the MIB mediated alkylation of benzaldehyde with diethylzinc, a system characterised by a marked nonlinear effect. Kinetic studies demonstrate how the high degree of chiral amplification comes at the expense of the reaction rate

Migrants and the diffusion of low marital fertility in Belgium

Abstract in Undetermined Although the diffusion of fertility behavior between different social strata in historical communities has received considerable attention in recent studies, the relationship between the diffusion of fertility behavior and the diffusion of people (migration) during the nineteenth century remains largely underexplored. Evidence from population registers compiled in the Historical Database of the Liège Region, covering the period of 1812 to 1900, reveals that migrant couples in Sart, Belgium, from 1850 to 1874 and from 1875 to 1899 had a reduced risk of conception. The incorporation of geographical mobility, as well as the migrant status of both husbands and wives, into this fertility research sheds light not only on the spread of ideas and behaviors but also on the possible reasons why the ideas and behaviors of immigrants might have been similar to, or different from, those of a native-born population

Effects of Regulatory and Market Constraints on the Capital Structure and Share Value of REITs: Evidence from the Italian Market

In contrast to the US experience, most international (European) real estate investments trusts (REITs) are subject to prudential regulation. This paper investigates the effects of prudential regulation on capital structures and consequently, the REIT share values of major legal and market constraints (i.e. leverage limitations, market discount on net asset value (NAV), tax controls) that affect non-US REITs. Italian market data are used for an empirical analysis. Our hypothesis is that in a constrained environment, the effects on share price significantly depend on the adopted valuation perspective, i.e. if shares are valued by following a NAV or a financial approach. The logic for this hypothesis is that the two valuation methodologies perceive leverage and implied financial risk differently. In particular, we argue that NAV valuation techniques incentivise REITs to maximize leverage regardless of the financial theory which indicates a contrasting impact of debt on the market value of shares. Differences in financial risk perception could also partially explain market price discounts on NAVs.The empirical results seem to support these expectations. Almost all Italian REITs tend to increase debt ratios over time. NAV discounts are significantly related to leverage. The discount effect is largely attributable to NAV increases that result from rising debt levels. On the contrary, share market prices tend to be independent from leverage. The latter result may indicate that the classic capital theory applies and current debt ratios do not imply bankruptcy risk. The results have significant policy implications in terms of an optimal regulatory design.REIT regulation; Leverage; NAV discount; REIT capital structure; REIT valuation

Cooling electrons from 1 K to 400 mK with V-based nanorefrigerators

The fabrication and operation of V-based superconducting nanorefrigerators is reported. Specifically, electrons in an Al island are cooled thanks to hot-quasiparticle extraction provided by tunnel-coupled V electrodes. Electronic temperature reduction down to 400 mK starting from 1 K is demonstrated with a cooling power ~20 pW at 1 K for a junction area of 0.3 micron^2. The present architecture extends to higher temperatures refrigeration based on tunneling between superconductors and paves the way to the implementation of a multi-stage on-chip cooling scheme operating from above 1 K down to the mK regime.Comment: 3+ pages, 4 color figure

Energy harvesting from earthquake for vibration-powered wireless sensors

Wireless sensor networks can facilitate the acquisition of useful data for the assessment and retrofitting of existing structures and infrastructures. In this perspective, recent studies have presented numerical and experimental results about self-powered wireless nodes for structural monitoring applications in the event of earthquake, wherein the energy is scavenged from seismic accelerations. A general computational approach for the analysis and design of energy harvesters under seismic loading, however, has not yet been presented. Therefore, this paper proposes a rational method that relies on the random vibrations theory for the electromechanical analysis of piezoelectric energy harvesters under seismic ground motion. In doing so, the ground acceleration is simulated by means of the Clough-Penzien filter. The considered piezoelectric harvester is a cantilever bimorph modeled as Euler-Bernoulli beam with concentrated mass at the free-end, and its global behavior is approximated by the dynamic response of the fundamental vibration mode only (which is tuned with the dominant frequency of the site soil). Once the Lyapunov equation of the coupled electromechanical problem has been formulated, mean and standard deviation of the generated electric energy are calculated. Numerical results for a cantilever bimorph which piezoelectric layers made of electrospun PVDF nanofibers are discussed in order to understand issues and perspectives about the use of wireless sensor nodes powered by earthquakes. A smart monitoring strategy for the experimental assessment of structures in areas struck by seismic events is finally illustrated

Terminal area guidance along curved paths: A stochastic control approach

Stochastic control theory is applied to the problem of designing a digital flight compensator for terminal guidance along a helical flight path as a prelude to landing. The development of aircraft, wind, and measurement models is discussed along with a control scheme consisting of feedback gains multiplying estimate of the aircraft and wind states obtained from a Kalman one step predictor. Preliminary results are presented which indicate that the compensator performs satisfactorily in the presence of both steady winds and gusts

Laminin receptors in the retina: sequence analysis of the chick integrin alpha 6 subunit. Evidence for transcriptional and posttranslational regulation.

The integrin alpha 6 beta 1 is a prominent laminin receptor used by many cell types. In the present work, we isolate clones and determine the primary sequence of the chick integrin alpha 6 subunit. We show that alpha 6 beta 1 is a prominent integrin expressed by cells in the developing chick retina. Between embryonic days 6 and 12, both retinal ganglion cells and other retinal neurons lose selected integrin functions, including the ability to attach and extend neurites on laminin. In retinal ganglion cells, we show that this is correlated with a dramatic decrease in alpha 6 mRNA and protein, suggesting that changes in gene expression account for the developmental regulation of the interactions of these neurons with laminin. In other retinal neurons the expression of alpha 6 mRNA and protein remains high while function is lost, suggesting that the function of the alpha 6 beta 1 heterodimer in these cells is regulated by posttranslational mechanisms

A stochastic model for financiers

In this work, two models for legal and illegal financiers are presented. The aim of the financiers are different: a bank try to minimize the defalt probabilityof the funded company, while the illegal financier aims to bring the company to bankruptcy and, at the same time, to obtain the maximum level of the firm's guarantee wealth. A couple of stochastic dynamic optimization problems are solved. The illegal case let intervene a numerical analysis of the microeconomic situation of the firm, strating fromreal data and writing new simulation�procedure in Matlab and GAMS. The legal case has been solved in closed-form, by using stochastic control theory.