A mobility analysis of the occupational status of the graduates of the University of Palermo in an economic crisis context

In such a global economic crisis context, our aims are describing the mobility of the Palermitan graduates in the labour market, identifying the variables that influence most their occupational status and finally outlining a transition probability structure among the states: Work, Search for a Job, Study, Other. The availability of a large amount of longitudinal data provided by the surveys carried out by STELLA (Statistics about Graduates and Labour Market) allowed us to analyze the mobility of the graduates of the University of Palermo among the different occupational states in three different times. We analyze data coming from a disproportionate stratified sample of graduates in 2009, interviewed three different times: one year (2010), three years (2012), five years (2014) after the graduation. To achieve our aim, first we provide a brief descriptive analysis of the main characteristics of the graduates gathered by the three different surveys; secondly we fit a time inhomogeneous multi-state Markov model with piecewise constant intensities; eventually implications from the main results are discussed

The Homflypt polynomial and the oriented Thompson group

We show how to construct unitary representations of the oriented Thompson group $\vec{F}$ from oriented link invariants. In particular we show that the suitably normalised HOMFLYPT polynomial defines a positive definite function of $\vec{F}$.Comment: To appear in Quantum Topolog

Scheduling Packets with Values and Deadlines in Size-bounded Buffers

Motivated by providing quality-of-service differentiated services in the Internet, we consider buffer management algorithms for network switches. We study a multi-buffer model. A network switch consists of multiple size-bounded buffers such that at any time, the number of packets residing in each individual buffer cannot exceed its capacity. Packets arrive at the network switch over time; they have values, deadlines, and designated buffers. In each time step, at most one pending packet is allowed to be sent and this packet can be from any buffer. The objective is to maximize the total value of the packets sent by their respective deadlines. A 9.82-competitive online algorithm has been provided for this model (Azar and Levy. SWAT 2006), but no offline algorithms have been known yet. In this paper, We study the offline setting of the multi-buffer model. Our contributions include a few optimal offline algorithms for some variants of the model. Each variant has its unique and interesting algorithmic feature. These offline algorithms help us understand the model better in designing online algorithms.Comment: 7 page

Investigation of a Self-Assembled Monolayer as a Cu Diffusion Barrier for Solar Cell Metallization

Copper diffusion into the silicon bulk is a detrimental obstacle to advanced-CMOS and photovoltaic processes that seek to incorporate copper into the metallization steps because of its deep-level trap nature to carriers. Recent studies have hinted that an organic porphyrin or silane-based self-assembled monolayer (SAM) could be a method of prevention to copper diffusion. Inorganic alternatives using TiO2 or Ni may also present a solution. The self-assembly of 5,10,15,20- Tetrakis(4-hydroxyphenyl)-21H,23H-porphine (OHTPP) over SiO2 has been examined using atomic-force microscopy (AFM), contact angle measurements, and variable angle spectroscopic ellipsometry (VASE). Results indicate that this particular OHTPP chemistry fails to adsorb to the Si02 substrate. Metal- Oxide-Semiconductor (MOS) capacitors with varying dielectric stacks with and without TiO2 over SiO2 or Si3N4 and gate metals varying between Cu and Ni have been fabricated and analyzed via bias-temperature stress (BTS) capacitance-voltage (C-V) tests. Results indicate that Cu-coated TiO2 and Ni MOS stacks with a SiO2 insulator show drastic flat band voltage shifting compared to Cu over SiO2 or with a Si3N4 dielectric over SiO2

A statistical method for removing unbalanced trials with multiple covariates in meta-analysis

In meta-analysis literature, there are several checklists describing the procedures necessary to evaluate studies from a qualitative point of view, whereas preliminary quantitative and statistical investigations on the “combinability” of trials have been neglected. Covariate balance is an important prerequisite to conduct meta-analysis. We propose a method to identify unbalanced trials with respect to a set of covariates, in presence of covariate imbalance, namely when the randomized controlled trials generate a meta-sample that cannot satisfy the requisite of randomization/combinability in meta-analysis. The method is able to identify the unbalanced trials, through four stages aimed at achieving combinability. The studies responsible for the imbalance are identified, and then they can be eliminated. The proposed procedure is simple and relies on the combined Anderson-Darling test applied to the Empirical Cumulative Distribution Functions of both experimental and control meta-arms. To illustrate the method in practice, two datasets from well-known meta-analyses in the literature are used

Random graph model with power-law distributed triangle subgraphs

Clustering is well-known to play a prominent role in the description and understanding of complex networks, and a large spectrum of tools and ideas have been introduced to this end. In particular, it has been recognized that the abundance of small subgraphs is important. Here, we study the arrangement of triangles in a model for scale-free random graphs and determine the asymptotic behavior of the clustering coefficient, the average number of triangles, as well as the number of triangles attached to the vertex of maximum degree. We prove that triangles are power-law distributed among vertices and characterized by both vertex and edge coagulation when the degree exponent satisfies $2<\beta<2.5$; furthermore, a finite density of triangles appears as $\beta=2+1/3$.Comment: 4 pages, 2 figure; v2: major conceptual change

Input-Output Relations in Optical Cavities: a Simple Point of View

In this work we present a very simple approach to input-output relations in optical cavities, limiting ourselves to one- and two-photon states of the field. After field quantization, we derive the non-unitary transformation between {\em Inside} and {\em Outside} annihilation and creation operators. Then we express the most general two-photon state generated by {\em Inside} creation operators, through base states generated by {\em Outside} creation operators. After renormalization of coefficients of inside two-photon state, we calculate the outside photon-number probability distribution in a general case. Finally we treat with some detail the single mode and symmetrical cavity case.Comment: 34 pages, 5 figures jpg, LaTe