2,670 research outputs found
Oxidation of Transition and Noble Metal Size-Selected Clusters Supported on Epitaxial Graphene
No full textSize-selected clusters have emerged in the past decades for their unique features, which are often very different from their bulk analogues. In a cluster, the electronic and chemical features depends on the exact number of atoms, offering an unmatched playground to look for new properties of matter. However, clusters are hard to handle, due to their high reactivity and mobility when they are deposited on solid surfaces. In particular, understanding the interaction of supported metallic size-selected clusters with simple molecules such as oxygen and their oxidation process in conditions where the mass selection is not compromised is experimentally challenging. During my PhD, I was able to focus on this aspect using ENAC (Exact Number of Atoms in each Cluster), the cluster source designed and built at the Nanoscale Materials Laboratory of the Elettra synchrotron in Trieste. The unique feature of ENAC is that it can be connected it directly to the SuperESCA beamline of the Elettra synchrotron to deposit and study the cluster in situ by means of experimental techniques based on synchrotron radiation, such as X-ray photoelectron spectroscopy (XPS). This offers the opportunity to characterize the clusters in controlled conditions, avoiding critical issues such as the presence of contaminants. In the first part of my research activity, I have been involved in the commissioning and optimization of the cluster source, and in its installation at the SuperESCA beamline. When this crucial goal was accomplished, I participated to the first experiment ever performed with the cluster source at the beamline. We studied the adsorption of size selected Ag on Ru(0001) by means of XPS and with the support of density functional theory calculations. Our results indicate that using different clusters as building blocks, it is possible to form two-dimensional Ag islands on Ru(0001) with different degrees of order that depend on the size of the cluster. This experiment acted as a benchmark to test the capabilities of ENAC, and was instrumental to address our investigation towards more complex studies, i.e., the the oxidation of graphene-supported size-selected clusters. Graphene, which was epitaxially grown on Ru(0001) and Ir(111), is a versatile template, whose corrugated morphology allows to reduce the mobility of the clusters while affecting their properties only in a minor extent. To further reduce the cluster mobility and preserve the mass selection, all the experiments were performed at the temperature of 20 K. The cluster oxidation was achieved by exploiting a method based on the photo-induced dissociation of physisorbed O2, which leads to an efficient production of atomic O in an extremely clean environment. We studied the oxidation of supported Ag, Pt and Fe size-selected clusters by means of XPS and DFT calculations, highlighting similarities and differences with their counterparts at larger scale and discussed the potential technological applications for the oxidized clusters in the light of our new results.Size-selected clusters have emerged in the past decades for their unique features, which are often very different from their bulk analogues. In a cluster, the electronic and chemical features depends on the exact number of atoms, offering an unmatched playground to look for new properties of matter. However, clusters are hard to handle, due to their high reactivity and mobility when they are deposited on solid surfaces. In particular, understanding the interaction of supported metallic size-selected clusters with simple molecules such as oxygen and their oxidation process in conditions where the mass selection is not compromised is experimentally challenging. During my PhD, I was able to focus on this aspect using ENAC (Exact Number of Atoms in each Cluster), the cluster source designed and built at the Nanoscale Materials Laboratory of the Elettra synchrotron in Trieste. The unique feature of ENAC is that it can be connected it directly to the SuperESCA beamline of the Elettra synchrotron to deposit and study the cluster in situ by means of experimental techniques based on synchrotron radiation, such as X-ray photoelectron spectroscopy (XPS). This offers the opportunity to characterize the clusters in controlled conditions, avoiding critical issues such as the presence of contaminants. In the first part of my research activity, I have been involved in the commissioning and optimization of the cluster source, and in its installation at the SuperESCA beamline. When this crucial goal was accomplished, I participated to the first experiment ever performed with the cluster source at the beamline. We studied the adsorption of size selected Ag on Ru(0001) by means of XPS and with the support of density functional theory calculations. Our results indicate that using different clusters as building blocks, it is possible to form two-dimensional Ag islands on Ru(0001) with different degrees of order that depend on the size of the cluster. This experiment acted as a benchmark to test the capabilities of ENAC, and was instrumental to address our investigation towards more complex studies, i.e., the the oxidation of graphene-supported size-selected clusters. Graphene, which was epitaxially grown on Ru(0001) and Ir(111), is a versatile template, whose corrugated morphology allows to reduce the mobility of the clusters while affecting their properties only in a minor extent. To further reduce the cluster mobility and preserve the mass selection, all the experiments were performed at the temperature of 20 K. The cluster oxidation was achieved by exploiting a method based on the photo-induced dissociation of physisorbed O2, which leads to an efficient production of atomic O in an extremely clean environment. We studied the oxidation of supported Ag, Pt and Fe size-selected clusters by means of XPS and DFT calculations, highlighting similarities and differences with their counterparts at larger scale and discussed the potential technological applications for the oxidized clusters in the light of our new results
Do Incentives for Innovation work? Evidence from the Italian Manufacturing Sector
No full textUnderstanding and estimating the impact of fiscal incentives on innovation are crucial elements for policy evaluation. This is so because innovation- be it of the product or the process type- is able to move the production frontier and hence, ultimately, enlarge society’s consumption possibilities (as shown by the endogenous growth literature). However, despite the fact that innovation is the final goal of public policy, most studies look at the relationship between R&D expenses and fiscal policy, perhaps considering that the relationship between innovation and R&D is strong and deterministic. However, there exists evidence that such a relationship is neither strong nor deterministic. In fact, if the innovation is a process to which many factors contribute (including R&D), from our perspective the interesting policy question becomes: do fiscal incentives designed–directly or indirectly (i.e. through R&D) to promote innovation - work?
Hence, the main purpose of this study is to investigate the impact that fiscal incentives have on firms’ innovative performance. For this, we use data from the 7th, 8th and 9th waves of the “Indagine sulle Imprese Manifatturiere Italiane” by Unicredit (previously managed by Capitalia-Mediocredito Centrale), which contains information on both product and process innovation by manufacturing firms, on the amount of resources invested in R&D (if such amount is positive) and it is also informative of the existence of forms of fiscal incentive for R&D and investment in innovative activities. This information is crucial for our study since it permits us to link firms’ innovation (the dependent variable in our exercise) to fiscal incentives.
In our work, we use different techniques. First we look at Average Treatment Effects, under the assumption of “selection on observables”, implying that the econometrician has access to all the variables affecting the likelihood of being treated (i.e. have access to incentives for innovative activities). In this part of the report, we just want to verify whether- everything else remaining constant (i.e. for a given value of the propensity score obtained with the conditioning variables) - there is evidence that firms that have access to fiscal incentives tend to innovate more. In the second part of our study, we cast some doubts on the plausibility of the “selection on observables” assumption and we look in more depth at one specific case of fiscal incentive: the one provided by Law 140/1999 to firms located in “depressed areas” (as defined by the law itself). We focus on this law because it is particularly important from a policy perspective within the Italian dual economy, but also because it allows us a more precise estimate of the treatment effect in a situation where treatment status (i.e. access to the incentive) is likely to depend on the same (unobserved) factors that affect the innovation outcome. In such a situation, OLS estimated are biased and inconsistent and we have to use instrumental variable estimation. We choose to instrument treatment using the eligibility rules for treatment and we find that an endogeneity issue does indeed exist and that its effects are stronger the weaker the impact of the treatment is on the outcome variable.JRC.J.3 - Information Societ
ICT use and learning outcomes: discussing evidence from recent econometric studies
No full textIn this paper we review the econometric literature on ICT use and learning outcomes (including a summary of our recent analysis of PISA 2009
Chronische Graft-versus-Host-Erkrankung am männlichen Genitale: eine unterschätzte Manifestation
No full textnon
Information hidden behind a single peak in the C 1s spectrum of graphene on Ir(111)
No full textThe energy resolution that can be achieved in x-ray photoelectron spectroscopy experiments allows to disen- tangle the contribution arising from the presence of a large variety of surface atoms in non-equivalent config- urations which manifests itself not only with the appearance of different spectral components, but also as unusual lineshape.
In the present work, we show that the fit of the C 1s core level spectrum of graphene grown on Ir(1 1 1) realized using 200 peaks based on ab initio calculations, accounting for the non-equivalent C atoms in the (10 × 10) moir ́e cell, does not improve the fit quality with respect to the use of a single component. On the contrary, the quantitative fit quality can be drastically increased by introducing a dependency of the Lorentzian width on the distance between C and Ir first-layer atoms. This result is associated to the different electronic properties, and in particular to the different density of states of the σ and π bands, of C atoms sitting on TOP (hills) or FCC (valleys) regions of graphene which affect the lifetimes of the core-holes generated during the photoemission process
Does chronic immunosuppressive therapy for autoimmune disease influence the risk of developing active tuberculosis?
No full textHTTP/3 will not Save you from Request Smuggling: A Methodology to Detect HTTP/3 Header (mis)Validations
No full textHTTP/3 will be the new de-facto standard for communication in web applications. Despite its increasing integration into modern browsers, its security properties have not yet been fully investigated. A significant problem is represented by request smuggling attacks, which may constitute a critical issue concerning web applications’ security and privacy, leading to critical consequences such as cache poisoning, session hijacking, and Denial Of Service (DOS). This category of attacks is particularly interesting as it involves abusing the characteristics of the HTTP protocol to manipulate and craft malicious requests that the server will misinterpret, creating desynchronizations between the frontend and the backend. In this paper, we present the first taxonomy of request smuggling attacks in HTTP/3. Specifically, we focus on conversion and validation issues observed in HTTP/2 that can persist in HTTP/3 environments. Since these attacks depend on how proxies parse incoming requests, we also present a methodology to discover possible header validation issues that can cause request smuggling in proxies and frameworks. Finally, we apply this methodology to four proxies and a Python framework, finding various incoherences in their ways to parse malformed requests. Our work aims to underscore the importance of vigilance in current and future applications utilizing HTTP/3 protocols to mitigate potential security risks. Despite the limited availability of libraries and frameworks supporting HTTP/3 at the present moment, its rapid adoption calls for consideration and analysis of its security
Dermatophytosis in a psoriatic patient treated with secukinumab: An underrated adverse effect?
No full text- …
