Scientific Productivity and Academic Promotion: A Study on French and Italian Physicists

The paper examines the determinants of scientific productivity (number of articles and journals’ impact factor) for a panel of about 3600 French and Italian academic physicists active in 2004-05. Endogeneity problems concerning promotion and productivity are addressed by specifying a generalized Tobit model, in which a selection probit equation accounts for the individual scientist’s probability of promotion to her present rank, and a productivity regression estimates the effects of age, gender, cohort of entry, and collaboration characteristics, conditional on the scientist’s rank. We find that the size and international nature of collaborative projects and co-authors’ past productivity have very significant impacts on current productivity, while age and gender, and past productivity are also influential determinants of both productivity and probability of promotion. Furthermore we show that the stop-and-go policies of recruitment and promotion, typical of the Italian and French centralized academic systems of governance, can leave significant long-lasting cohort effects on research productivity.

Bio-sample environment manipulation using advanced microscopy techniques

2010/2011Under physiological conditions in the brain, molecules are released with high spatial and temporal resolution. A lot of efforts have been done in the last years in order to develop techniques that mimic this situation. Among them, we mention the use of micropipettes for the ejection of fluids, the use of AFM (Atomic Force Microscopy), microfluidic devices and optical manipulation. The latter approach exploits light to manipulate the samples, e.g. to create transient pores in the cell membrane or to move small objects carrying a stimulus. This Thesis concerns with the development of new techniques for the local delivery of molecules based on optical manipulation technologies, and in particular on optical tweezers. Sub-micrometer particles in a compact trap, such as the single-beam gradient or optical tweezers, can be localized within a small fraction of a wavelength of light or moved over long distances of many centimeters without any mechanical contact. A three-dimensional trap is simply created by focusing a laser beam through a microscope objective with high numerical aperture. We studied three types of vectors for local delivery of molecules, which can be optically manipulated: microbeads, micron-sized liposomes and Quantum dots (Qdots). Silica microbeads can be covalently functionalized on their surface with the protein of interest and placed in contact with the desired part of a cell. In order to validate the technique, we functionalized beads with a secretory molecule, the neurotrophin Brain-derived neurotrophic factor (BDNF). BDNF is a key regulator of neuronal development and plasticity. We showed that single BDNF-coated microbeads can be extracted with optical tweezers from small reservoirs and positioned with submicrometric precision to specific sites on the dendrites of cultured hippocampal neurons. Localized contact of microbeads functionalized with BDNF induced focal increase of Calcium signaling in the stimulated dendrite, specific activation of the TrkB receptor pathway and influenced the development of growth cones. Remarkably, a single BDNF-coated bead positioned on a dendrite was found to be enough for TrkB phosphorylation, an efficient and long-lasting activation of Calcium signaling in the soma, and c-Fos signaling in the nucleus, comparable to bath stimulation conditions. Moreover, since BDNF is covalently cross-linked to the bead surface we could demonstrate that activation of some of the TrkB receptor pathway does not necessarily require BDNF endocytosis. In the case of liposomes, the molecules of interest were encapsulated within their lumen. Single liposomes were trapped and transported by means of optical tweezers to the site of stimulation on cultured neurons. Finally, the release of liposome content was induced by application of UV-pulses that broke the liposome membrane. In order to test the effect of the UV-induced release, liposomes with a diameter ranging from 1 to 10 μm (fL to pL volumes), were filled with KCl and tested on neuronal cells. Neuronal cultures, loaded with Ca2+ dye, were monitored by imaging intracellular Ca2+. An efficient release from the liposomes was demonstrated by detectable Calcium signals, indicating induced depolarization of the neuronal cells by KCl. Afterwards, this technique was used to address a biological issue, that is the effect of two proteins (Semaphorin 3A and Netrin-1) on growth cones. The growth cone is an intracellular apparatus located at the tip of the neurite of developing neurons. Its motility governs axonal path-finding and the construction of neuronal networks. Growth cones are highly dynamic structures that respond to external stimuli turning towards or away from the chemical gradient. We were able to demonstrate an attractive effect of Netrin-1 on the growth cones of primary hippocampal neurons. On the contrary, Semaphorin 3A showed a repellant behavior. To correlate the high resolution of vector manipulation with high resolution of imaging we used STimulated Emission Depletion (STED) to investigate the intimate organization of two main cytoskeleton components: actin and tubulin filaments. STED microscopy allowed imaging of actin bundles in the filopodia and organized network in lamellipodia with un-precedent resolution, beyond the diffraction barrier. Lastly, we used liposomes to encapsulate Quantum dots. Qdots are bright and photostable nanocrystals. Due to their small size, similar to that of proteins, Qdots may be endocyted along the receptor-mediated endocytosis pathway, when they are functionalized with the appropriate ligand. As case study we considered the BDNF-TrkB endocytotic pathway. We optimized the protocol for the direct binding of BDNF to Qdots and we demonstrated the possibility of encapsulating and releasing them from liposomes. Concluding, two different approaches for local stimulation of neurons, based on optical manipulation of microvectors, were presented and validated in this thesis. Indirect optical manipulation of nanovectors (Qdots) encapsulated in liposomes has been demonstrated as well. The techniques were then successfully applied to address some biological issues, that in turn required the optimization of other imaging tools (super resolution microscopy and Qdots).XXIV Ciclo198

Organic Light Emitting Transistors: A Platform for the Integration of Innovative Nanophotonic Structures

The focus of this Ph.D. thesis is the investigation of the opto-electronic performances and photonic characteristics of Organic Light Emitting Transistors (OLETs). These promising multifunctional devices unify the switching properties of transistors with the light emission capability of light-emitting diodes. The OLETs that have been studied in this research present a peculiar trilayer configuration, which can allow to obtain high light emission efficiency by reducing the quenching processes inherent to the device structure. For these devices, the exciton formation, the light outcoupling and the mechanisms responsible for light losses were investigated, aiming at fully disclosing the potentiality of OLETs in therm of External Quantum Efficiency (EQE) and brightness. In addition, the possibility to modulate the width of the emission area by the gate voltage up to extension of the entire channel was demonstrated. This result is of unprecedented importance for allowing the implementation of OLETs in lighting and photonic applications. Furthermore, a novel strategy based on the introduction of a non conventional planar photonic structure into the device architecture was used to increment the light emission efficiency. Indeed, a fully-organic multilayer structure, that worked both as Distributed Bragg Reflector (DBR) and as gate dielectric, was iserted into the OLET architecture to turn the gate dielectric into an optically active component, capable of enhancing light extraction in forward direction by reducing total internal reflections processes. Other unidimensional photonic structures for lasing application were designed, fabricated and characterized. In specific, a linear Distributed Feedback structure (DFB) based on silk was used for realizing a biocompatible, biodegradable and edible organic laser. The entire route for extracting, purifying and manufacturing silk was optimized for achieving the best performing photonic component. Moreover, a method for making optically active silk by feeding directly the larvae with lasing dye molecules was introduced; the method is green because it allows to fabricate intrinsically colored silk by eliminating the need of resources as water, energy and organic solvents. These findings may open perspectives for applications of optically active silk in biophotonics and biological sensors, such as the realization of Lab-on-a- Chip devices for the biodiagnostics

DEVELOPMENT AND CHARACTERIZATION OF AN INNOVATIVE LOW-NOISE HIGH-DYNAMIC-RANGE VLSI CHARGE-SENSITIVE PREAMPLIFIER FOR SOLID-STATE DETECTORS EMPLOYED IN NUCLEAR PHYSICS EXPERIMENTS WITH RADIOACTIVE ION BEAMS

The latest experimental results of the multichannel front-end ASIC of TRACE are shown. The device submitted to the foundry in the middle of 2014 and received at the end of the same year has been installed on a dedicated PCB and tested using a pulser. We then designed and realized a preamplifier board with eight ASICs for a total of 32 front channels and one back channel. We connected it to a highly-segmented planar silicon detector and acquired the spectrum of a 241Am-244Cm-239Pu triple alpha source obtaining an overall resolution around 3.5\u2030. The chip comprises four channels specifically designed for hole signals and one channel for electron signals. The power consumption is around 10 mW per channel as required by the specifications of TRACE. The main design goals are low noise and fast rise time. With proper shaping of the signals this device is capable of producing energy spectra with resolution of approximatively 1 keV. An innovative circuit architecture based on a Time-Over-Threshold technique boosts the dynamic range of the CSP by more than one order of magnitude. The rise time of the leading edge of the signals is fast enough to perform pulse-shape analysis of the waveforms. A peculiar feature of this device is the possibility to easily adjust a host of key parameters through an I2C bus. The bandwidth and sensitivity of the preamplifier can so be optimized according to the experimental needs on a case-by-case basis

Freedom, autonomy and responsibility in the design of individual educational path within a university system without boundaries: proposal and discussion of a model.

openObiettivo della presente Tesi è quello di proporre un’idea di sistema di educazione terziaria fondato sui principi di libertà, responsabilità e autonomia. Tali concetti, nel modello qui avanzato, vengono concretizzati nella possibilità fornita agli studenti di personalizzare e auto-direzionare il percorso formativo individuale all’Università, al fine di consentire a tutti e a ciascuno di vivere la vita che desiderano. Nel primo capitolo viene presentato il framework teorico di riferimento costituito, appunto, dall’apprendimento personalizzato e dall’apprendimento auto-diretto che, dato il loro focus sull’auto-determinazione e sulla libertà individuale, vengono messi in relazione con il Capabilities Approach. Nel secondo capitolo sono riassunte alcune esperienze, rintracciabili nella letteratura internazionale, progettate per implementare i costrutti dell’apprendimento personalizzato e dell’apprendimento auto-diretto nei contesti universitari. Nel capitolo terzo vengono sintetizzati la normativa e l’iter attraverso cui, attualmente, vengono definite le attività formative che entrano a far parte del Piano di Studio dei discenti. Gli approfondimenti bibliografici e normativo-procedurali di questi primi tre capitoli, hanno ispirato e permesso di delineare l’idea di sistema universitario avanzata nel quarto capitolo, di cui, nel quinto, viene presentato un esempio concreto. Nel sesto capitolo, infine, è stata svolta un’analisi SWOT del modello grazie al contributo di voci esperte di area pedagogica. L’ipotesi che si intende sostenere con questa Tesi è che sia possibile ampliare i confini di libertà, responsabilità e autonomia all’interno dei contesti di educazione terziaria, attraverso la personalizzazione e l’auto-direzione dell’apprendimento, perseguendo, al contempo, l’obiettivo dell’Università di massa e quello della valorizzazione dei diversi talenti (Giarda, 2006)

Simulation, realization and test of veto systems for the NA62 experiment

Search Simple Search Advanced Search Latest Additions Browse Browse by Author Browse by Subject Browse by Year Browse by Type Browse by Full text availability Info Policy About FAQ Contact us Palladino, Vito (2010) Simulation, realization and test of veto systems for the NA62 experiment. [Tesi di dottorato] (Unpublished) [img] PDF palladino_vito_23.pdf Download (55MB) | Preview Item Type: Tesi di dottorato Language: English Title: Simulation, realization and test of veto systems for the NA62 experiment Creators: Creators Email Palladino, Vito [email protected] Date: 30 November 2010 Number of Pages: 146 Institution: Università degli Studi di Napoli Federico II Department: Scienze fisiche Doctoral School: Scienze fisiche PHD name: Fisica fondamentale ed applicata PHD cycle: 23 PHD Coordinator: name email Marrucci, Lorenzo UNSPECIFIED Tutor: name email Ambrosino, Fabio UNSPECIFIED Date: 30 November 2010 Number of Pages: 146 Uncontrolled Keywords: Kaon NA62 Veto CHANTI LAV MIUR S.S.D.: Area 02 - Scienze fisiche > FIS/01 - Fisica sperimentale Date Deposited: 08 Dec 2010 15:49 Last Modified: 30 Apr 2014 19:45 URI: http://www.fedoa.unina.it/id/eprint/8274 DOI: 10.6092/UNINA/FEDOA/8274 Abstract During my PhD course I have been involved in research activities into the frame of the NA62 experiment, which main goal is the measurement of the branching fraction B(K+ -> pi+ nu anti-nu). NA62 is a very challenging experiment due to ultra rare nature of this decay (BR is about 8e(-11)). The study of the decay K+ -> pi+ nu anti-nu is very important because it allows the first direct measurement of CKM element Vtd. Moreover it could provide signals of physics beyond Standard Model (SM) as that decay is highly sensitive to new physics. The experiment will be located at CERN experimental SPS North Area (hence the acronym NA). It is a fixed target experiment done using a unseparated 75 GeV/c beam of positive hadrons, produced by a 400 GeV/c proton beam. Positive Kaons, although being only 6% of the beam, are produced in a very abundant fashion, and will allow us to collect enough statistics to reach a about 10% relative uncertainty after a 2 years long data taking. To reach such level of uncertainty and to keep signal/background ratio below 10, the apparatus is designed in order to provide both particle identification and kinematical rejection. My work was focused on two veto subsystems with different scope, different architecture and different dimensions: the Large Angle photon Veto (or LAV) and the CHarged ANTIcounter (or CHANTI). The LAV is made of 12 different stations all along the decay region. Each station is ring shaped. The main task of LAV is to veto photons from neutral pions decay with an inefficiency lower than 10e(-4), to reduce background from K+ -> pi+ pi0. In order to choose the best technology to implement the detector we have had an intense R&D program. Three different prototypes were tested and finally a solution that uses lead glass blocks from former OPAL electromagnetic calorimeter was chosen. The prototype used to measure inefficiency was made in Naples and tested at Laboratori Nazionali di Frascati beam test facility with electrons of energy between 300 and 500 MeV/c. Unfortunately the area at CERN where blocks were stored was flooded and all blocks were involved. This major event forced a massive recovering campaign, of which I was responsible. During recovering operations many problems were found and (most of them) solved. However not all flooded blocks may be used for LAV. Part of them were damaged (9%) and an other part showed an abnormal behaviour. During the recovering operation the design of the LAV was refined and construction started. In order to reduce costs we opted for a read-out electronics based on Time over Threshold (ToT) technique. The first station out of 12 was realized and tested at CERN in June-September 2009. It was an important mile stone. The test was intended, basically, as confirmation of ToT usefulness and as check of off-line equalization procedure that each block needes to pass before being mounted. To test ToT, signals were splitted and read on one side by custom ToT electronics and from the other side by a commercial CAEN QDC, in order to produce a ToT versus charge curve. Surprisingly not a unique curve was found. After an accurate data analysis the problem was isolated and a solution proposed, consisting in changing the HV dividers of all blocks. A second module was built with new dividers and tested again at CERN. Preliminary data analysis (still going) is showing that the problem is solved and ToT can be used as read-out solution. The other item I was involved on is the CHANTI project. It is a small detector that will be placed just after last station of incoming Kaon tracking system (called Giga TracKer or GTK). GTK is made of three silicon station hit by the 800 MHz incoming beam of hadrons. About 0.3% of particles crossing the GTK undergo in inelastic collision in which the incoming hadron strongly interacts with a nuclei of GTK station producing many particles, among them pions. If inelastic events involves the third station a signal event could be mimicked if only a pion is detected. CHANTI aims to veto these events detecting the cloud of particles produced together with pion. It is made by a series of guard ring made by X and Y scintillating bars planes. Bars have a triangular shape, thus are naturally staggered. Each bar is read through a Wave Length Shifter fiber coupled to a Silicon PhotoMultiplier (SiPM). A detailed Monte Carlo was adopted to improve geometry design and to estimate the efficiency of CHANTI; moreover neutron fluence, crucial if SiPM are to be used, was estimated. Finally we designed and constructed a first full size prototype. Preliminary results about response and time resolution have been done using cosmic rays

Development of FPGA-based High Speed Serial Links for High Energy Physics Experiments

Ricerca Simple Search Advanced Search Ultime accessioni Browse Browse by Author Browse by Subject Browse by Year Browse by Type Browse by Accessibilità del full-text Informazioni Policy About FAQ Contatti Perrella, Sabrina (2016) Development of FPGA-based High-Speed serial links for High Energy Physics Experiments. [Tesi di dottorato] [img] Text Perrella_Sabrina_28.pdf Download (59MB) | Preview [error in script] [error in script] Item Type: Tesi di dottorato Lingua: English Title: Development of FPGA-based High-Speed serial links for High Energy Physics Experiments Creators: Creators Email Perrella, Sabrina [email protected] Date: 31 March 2016 Number of Pages: 113 Institution: Università degli Studi di Napoli Federico II Department: Fisica Scuola di dottorato: Scienze fisiche Dottorato: Fisica fondamentale ed applicata Ciclo di dottorato: 28 Coordinatore del Corso di dottorato: nome email Velotta, Raffaele [email protected] Tutor: nome email Alviggi, Mariagrazia UNSPECIFIED Giordano, Raffaele UNSPECIFIED Izzo, Vincenzo UNSPECIFIED Date: 31 March 2016 Number of Pages: 113 Uncontrolled Keywords: FPGA; serial links; HEP Settori scientifico-disciplinari del MIUR: Area 02 - Scienze fisiche > FIS/01 - Fisica sperimentale Date Deposited: 14 Apr 2016 20:50 Last Modified: 31 Oct 2016 09:49 URI: http://www.fedoa.unina.it/id/eprint/10696 Abstract High Energy Physics (HEP) experiments generate high volumes of data which need to be transferred over long distance. Then, for data read out, reliable and high-speed links are necessary. Over the years, due to their extreme high bandwidth, serial links (especially optical) have been preferred over the parallel ones. So that, now, high-speed serial links are commonly used in Trigger and Data Acquisition (TDAQ) systems of HEP experiments, not only for data transfer, but also for the distribution of trigger and control systems. Examples of their wide use can be found at CERN, where each of the four big experiments mounted on the Large Hadron Collider (LHC) uses a huge amount of serial links in its read out system. Again at LHC, the Timing, Trigger and Control system (TTC), which broadcasts the timing signals, from the LHC machine to the experiments, uses optical serial link to distribute signals over kilometers of distance (diameter of LHC is 27 Km). Also for upgrades of LHC, physical layer components and protocol chips (ASIC) have been designed and are now under development: the Versatile Link and the GBT protocol (and ASICs) whose peculiarity relies in their radiation hardness. This PhD project is intended to respond to the requests of HEP experiments, developing: - a high-speed self-adapting serial link, which can be easily used in different application fields; - the serial interface of a read out board in the end-cap region of ATLAS Experiment at LHC; - the interface board for the barrel read out system of the ATLAS Experiments. Both the two last projects have required the development of fixed latency, high-speed serial links. In order to take advantage of flexibility, re-programmability and system integration of SRAM-based Field Programmable Gate Array devices (FPGAs), their serializer-deserializer (SERDES) embedded modules have been chosen for the development of the links. However, as a drawback, FPGA embedded SERDESes are typically designed for applications that do not require a deterministic latenc. Then, an accurate study of their architecture has been necessary, in order to find a configuration and a clocking scheme to guarantee a deterministic transmission delay in data transfers. The frequency agile, auto-adaptive serial link is capable to analyze the incoming data stream, by scanning the Unit Interval, and to find the highest transmission line rate, according to a given tolerated Bit Error Ratio (BER). It uses a new feature (RX eye margin analysis) of the RX side of the Xilinx 7 series FPGAs high-speed transceivers (GTX/GTH), in order to measure and display the receiver eye margin after the equalizer. When the new eye scan functionality is running, an additional sampler is activated in the GTX. It acquires a new sample (Offset Sample), with programmable (horizontal and vertical) offsets from the data sample point (Data Sample) used in standard operation. An eye scan measurement run is performed by acquiring a large number of Data Samples (which can range from tens of thousands to 1014 or more) and by counting the number of times the Offset Sample has a different value with respect to the Data Sample; the latter number is often called Error Count. The BER at a specific vertical and horizontal offset is given by the ratio between the Error Count and the Sample Count. By repeating the eye scan measurement for each horizontal and vertical offset in the Unit Interval (or in a part of the U.I.) a 2-D BER map can be produced which is usually called Statistical Eye. The auto-adaptive derail ink is designed around an FPGA-embedded microprocessor, which drives the programmable ports of the GTX, in order to perform a 2-D eye-scan, and takes care of the reconfiguration of the GTX parameters, in order to fully benefit from the available link bandwidth. Xilinx provides a standalone tool that allows performing the Eye Scan Analysis on the receiver side of the GTX/GTH transceiver, using the MicroBlaze Micro Controller System macro; the toolkit also includes the Eye Scan algorithm (providing the C code). Moreover, Xilinx supplies the hardware sources files for the implementation of a link based on the XAUI protocol, in which the GTXs are arranged in a loopback configuration. The original contribution of this work consists in the build-up, design and optimization of a full architecture, on top of the basic Xilinx tool, which: - drives the programmable ports of the GTX in order to modify the line rate of the link; - runs consecutive eye scans for various line rate; - analyses the results of the different scans, in order to find the maximum line rate sustainable by the link; - manages the synchronization between the transmitter and the receiver of the link, that will be needed at each line rate change. The application can be deployed as a monitoring tool in HEP experiments, in order to remotely monitor a transmission system or detect issues in the serial link physical layer. An application example could be some of the many experiments at Large Hadron Collider (LHC) at CERN, which have been intensively using different serial links, both for transmission of TTC signals and for trigger and data readout. Besides, this solution could be easily adapted in wide, different frameworks, as it can be used on top of any user’s existing link, as it has no specific requirement about link specification or protocol. The other two serial interface developed in this project are in the framework of the ATLAS experiment. ATLAS is one of the four detectors installed on the LHC proton-proton collider built at CERN. It was designed to collide two opposing particle beams at an energy of 14 TeV and to reach a luminosity of 1034 cm-2/s. In order to reach the design parameters, the LHC system will be upgraded in several phases. In order to take advantage of the improved LHC operation, the ATLAS detector must be upgraded following the same schedule as the LHC upgrade. The main focus of the Phase-I ATLAS upgrade (to be completed by 2018) is on the Level-1 trigger where upgrades are planned for both the muon and the calorimeter trigger systems. In particular, for the end-cap region of the muon spectrometer, the installation of a new set of precision tracking and trigger detectors was approved, called the ‘New Small Wheels’ (NSW). It will be instrumented with micro-mesh gaseous structure detectors (MM) and small-strip Thin Gap Chambers (sTGC). These detectors will solve two points of particular importance at high luminosity: high rate of fake high-pt level-1 muon triggers, and high L1 muon rate with the current momentum threshold. With the introduction of new detectors, new electronics need to be developed, in particular new trigger electronics for both the MM and sTGC. I was involved in the development of serial interface of the FPGA-based sTGC trigger board that uses information from the coarse sTGC readout pads. The sTGC pad trigger board receives serial information coming from 24 front-end chips at 4.8 Gb/s. On the board, data are deserialised, aligned and analyzed by the trigger algorithm. The trigger logic processes the data and choses two candidates at each Bunch Crossing. The result is then serialised and used for selective fine-grained strip readout. I developed the pad trigger board interface logic. The data format from the front-end chips has been agreed upon, and defines the requirements on the receiver and decoding logic. The number of output lines is 24 and the data are 8B/10B formatted. While the receiver uses the Xilinx Kintex-7 GTX transceivers, the output lines are driven by double data rate (DDR) shift registers at 640 Mb/s. A fixed latency in the sTGC trigger chain was guaranteed through the implementation and configuration of all serialisers and deserialisers. In order to test the project, I also developed a simple microprocessor-based protocol for accessing the board via terminal (rs232). A demonstrator board is now being developed. Another Phase-I Level-1 trigger upgrade consists of a new Muon to Central Trigger Processor Interface (MUCTPI). The MUCTPI receives muon candidate information from each of the muon detectors, selects muon candidates and sends them to the Central Trigger Processor (CTP). In the first runs of ATLAS, the L1 Barrel trigger candidate data were transferred to the MuCTPI via copper cables. In order to cope with the trigger upgrade, serial optical links are necessary. The optical links will provide a much higher bandwidth (up to 6.4 Gb/s) which will be used to transfer additional information from the sector logic modules, for example data for more than two muon candidates. They will also provide a lower transmission latency. I developed the interface board between the new MUCTPI and the Resistive Plate Chambers (RPC) muon trigger, using the Xilinx Artix-7 FPGA GTP transceivers. I took care of the study of feasibility of the new serial optical transmitter and the logic for the new data format. Also in this case, the fixed latency has been a requirement to be fulfilled