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Risposta infiammatoria dopo chirurgia coronarica a cuore battente: confronto tra sternotomia mediana e toracotomia antero-laterale.
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Spectral distributions of structured matrix-sequences: tools and applications.
No full textThis Ph.D. thesis provides a systematic and unifying treatment of the spectral analysis of matrix sequences collecting the state of the art of the research in this field and providing new advanced results which are interesting both from the theoretical and from the algorithmic point of view.
The first part, made up by Chapters 1–5 concerns the description and analysis of the available tools, together with their generalization including the development of new effective tools of analysis. The basic concept of “approximating class of sequences” is introduced and analyzed in depth. Some new results of great interest have been obtained. It is worth citing an extension of a perturbation result concerning the eigenvalues of Hermitian matrix sequences which are perturbed with non-Hermitian perturbations. These results have been applied to Toeplitz sequences, and to the Tilli class. The classes of g-circulant and g-Toeplitz matrix sequences are introduced as well, and their spectral analysis is carried out.
The second part, formed by Chapters 6–8 is addressed to applications. It contains several new and interesting results. A relevant role is played by the preconditioning of g-Toeplitz matrix sequences by means of g-circulant matrices with a specific attention to the regularizing properties which take their importance in the applications concerning image processing, filtering and restoration. Another interesting application concerns two-grid and multi-grid techniques.
A third application concerns the saddle point problem where once again the spectral approximation of a suitable matrix plays a fundamental role
Experimental techniques for deflection and radiation studies with bent crystals
No full textWhat happens when a high energy charged particle crosses an amorphous material? It loses energy by ionization and its trajectory is affected by the multiple Coulomb scattering, being these phenomena originated by uncorrelated collisions with the atoms. If the atoms of the target were distributed according to an ordered scheme, the uncorrelated collisions would turn into a coherent interaction with the whole atomic structure. This is the case of an aligned crystal that, depending on the orientation, is seen as a set of atomic planes or strings by the impinging particles. Planes and strings produce potential wells able to confine the charged particles in a transversal region of the crystal, in the so called channeling condition, so that, bending the crystal, particles are forced to follow the curvature, being deflected.
This simple and powerful idea, dating 1979, is at the basis of many theoretical and experimental studies that have proven its effectiveness, described the possible applications and optimized the deflection performances.
The contribution of this thesis locates itself in this field as an attempt to provide a picture of the experimental techniques and the analysis procedures developed to investigate bent crystals in the last years.
In this period, bent crystal physics has witnessed a tremendous progress characterized by the increase of performances and the discovery of new phenomena. The driving forces of this process have been essentially three: bent crystals have been identified as a possible solution of the LHC collimation problem, bringing considerable resources to their research field; new bending techniques exploiting secondary deformations have been implemented and, finally, the single particle track reconstruction has become the core of the crystal testing procedures, making the measurements faster and more precise.
This thesis is a bridge across two complementary fields, that is the experimental techniques applied in the crystal study and the description of the observed phenomena from the phenomenological point of view as well as from the microscopic theoretical one, resulting in a complete overview on the bent crystal physics.
The bent crystals features are presented in the very beginning of the thesis, with the key elements of the research field described in the first chapter before going to an overview on the most important applications to show how bent crystals can be exploited in accelerator physics.
The last section of the chapter focuses on the microscopic bent crystal behaviour to describe the physics behind the effects induced by the crystal on the charged particles crossing it. The second chapter describes the state of the art of the bent crystals characterization and test. The first section presents the experimental setup, from the inspiring concepts to the description of the single components and procedures. The setup basic idea is that the combination of a silicon microstrip tracking system with a multi-stage goniometer allows to measure the relative alignment between the beam and the crystal as well as the crystal deflection angle.
The second section is dedicated to the analysis methods used to characterize the single crystal behaviour in terms of the channeling and the volume reflection phenomena. The described procedures are applied in a wide range of beam conditions from 13 GeV to 400 GeV of energy with positive and negative particles; all the data have been acquired at CERN on different beamlines during the past three years.
The third chapter explores a different bent crystal aspect, that is the radiation emission.
Coherent interaction with atoms, in fact, does not only mean deflection capabilities but also quasi-periodic trajectories that, in turn, produce an enhancement of the emitted electromagnetic radiation.
The description of the theoretical bases of this phenomenon both in channeling and volume reflection is presented in the first section of the chapter, while the second one is dedicated to the setup and the results obtained with a 120 GeV/c positron beam.
The last chapter goes back to the bent crystals deflection issue; going beyond channelling and volume reflection, it shows innovative bent crystals deflection schemes, developed in the last years in order to enhance the efficiency and the angular acceptance provided by channeling.
This result can be achieved creating a sequence of aligned crystals to increase the deflection angle induced by volume reflection as shown in the first section or exploiting the interaction with a crystalline axis that, as described in the second section, originates new phenomena such as the multi volume reflection in one crystal (MVROC) and the axial channeling able to deflect both positive and negative particles with high efficiency
Gamma-ray pulsars: a multi-band view
No full textThis Thesis is based mainly on the results of the timing analysis applied to the gamma-ray pulsars observed principally by the AGILE satellite and also extended, in some cases, to observations with the Fermi-LAT satellite and the MAGIC Cherenkov telescope. Aim of this extended study of pulsars at the high energies was to characterize their properties based, now, on a more statistically relevant sample, and be able to disentangle useful informations that can be key to explain the emission mechanisms in pulsars.
THE SCIENTIFIC CONTEXT Pulsars are highly-magnetized, rapidly-rotating neutron stars. As explained in Chapter 1, they have been observed in the radio band over the past forty years, due to their highly anisotropic emission, which, when combined with the misalignment between the rotation and the magnetic axis, produces the pulsed emission we observed, also called the ”lighthouse effect”. Pulsars have been observed as gamma-ray emitters as well, but it is only in the past three years that their number hit the double digits and they started to yield their potential as keys to explain the neutron stars mechanisms.
In Chapter 1, the basics of pulsar theory are given. While the phenomenological aspects have been widely studied thanks to extensive radio observations through the years, their electrodynamics represents an articulated field that is difficult to probe. The ”classical” models of magnetosphere predict the presence of regions of particles’ under-density (a ”gap”), inside an overall force-free magnetized area that surrounds the pulsar, where the particles can be accelerated and can produce the observed radiation, after a number of cascade processes. More ”modern” models of magnetosphere, with their roots in old predictions, discuss the hypothesis of a totally force-free magnetosphere. The discussed theories search for a confirmation in our gamma-ray observations, as the gamma-rays are the ones carrying away a good fraction of the rotational energy loss.
THE NEW PERSPECTIVES OPENED BY THE MULTI-BAND OBSERVATIONS
In April 2007 the Italian Space Agency launched the AGILE satellite for gamma-ray astronomy. About one year later, AGILE was joined in the observation of gammarays by the 16 times bigger Fermi-LAT satellite launched by NASA. AGILE and Fermi-LAT, with their wide field of view and large collective area, are particularly suited for the study of pulsars at high energies. Most recently, the window of veryhigh energy observations has opened up to pulsar studies and, in particular, by the MAGIC telescope, with the lowest up to now threshold for ground-based telescopes, at 25 GeV. Its observations are briefly described, together with AGILE and Fermi-LAT’s, in Chapter 2.
The techniques for studying pulsars in the gamma-rays are also explained in Chapter 2, with the fundamental premise about the radio observations which were part of my analysis work, as they constitute the primary basis for the gammaray observations. The advances with respect to the observations of the previous generation gamma-ray instruments are highlighted. In particular, AGILE was able to take into account, for the first time in gamma-ray observations, the timing noise that affects young pulsars. In this way, the observations can be carried out for longer time spans without being affected by sensible light curve smearing. Thus, we could take advantage of the long time span, up to now the longest for gamma-ray observations, to increase the resolution of our light curves and see structures at the sub-millisecond level.
GAMMA-RAY PULSARS AGILE and Fermi-LAT pulsar observations first concentrated on the known gamma-ray pulsars. As shown in Chapter 3, the apparently ”familiar” pulsars actually hid thriving new prospects for pulsar studies, as well as the new pulsars subsequently detected, described in Chapter 4.
In these two Chapters, the properties of the gamma-ray emission ars analyzed for a number of pulsars, mainly using AGILE data, but also with Fermi-LAT and MAGIC observations. The light curves are investigated with increased resolution from previous observations and the spectral properties are addressed. The availability of a statistically significant sample of gamma-ray pulsars led us to draw some lines on the models. The classical polar cap model seems to be failing the test of gamma-ray observations for most of the present sample, and a simple explanation of which can be found in conservation laws arguments discussed in Chapter 4. At the same time it starts getting clear that a model that contemplates a single gap zone does not seem to be feasible to explain the observed pulse profiles. And, possibly, the entire gap theory should be combined with the more physical force-free models.
Episodes of variability in pulsars have been observed and studied in this context. The Vela glitch of August 2007 was observed by AGILE in search for gamma-ray emission. The Crab pulsar could have a contribution to the emission from a newly observed third pulsar peak, that is less significant and much weaker than the canonical two, and could be due to giant pulses. AGILE observed the first gamma-ray millisecond pulsar but its emission only appeared in a restricted time interval, leading to the interesting possibility that pulsar emission might have some intrinsic variability.
HIGH MAGNETIC FIELD PULSARS After the advent of Fermi-LAT, AGILE found its collocation in the gamma-ray astronomy in the characterization of the low-energy gamma-rays (from 30 to 100 MeV), where the collective areas of the two instruments is equivalent, but AGILE deals with much lower background. For this reason, we concentrated on those pulsars that show a low-energy cutoff, which were theorized to emit gamma-ray radiation through the exotic QED process of photon splitting.
A detailed analysis of the two most significant cases is given in Chapter 5. We have found that the concurrence of a high magnetic field and an aligned geometry, could overcome the objections from Chapter 4 against inner magnetosphere emission and be, indeed, dominated by polar cap emission. Interestingly, this phenomenology, that is observed in pulsars that are similar to magnetars, may be observed in objects that are transitioning from pulsar to magnetar.
THE ENVIRONMENT OF PULSARS Young pulsars are known to power a relativistic wind of particles that surrounds the pulsar and is best known as its Pulsar Wind Nebula (PWN). Important phenomena take place in the PWN and they are powered by the pulsar inside it. As discussed in Chapter 6, very high energy emission was already observed from PWN, but high energy emission was missing, in a spectral region where important constraints on the emission processes could be given.
AGILE was the first satellite to detect GeV emission from a PWN apart from Crab, Vela X, and it was also the first to claim the unexpected flux variation in the Crab Nebula which underwent two intense flares in 2010 and 2011. In Chapter 6 we give a description of the events and a possible trail for an interpretation, although no clear picture can yet emerge from the observed events.
CONCLUSIONS AND FUTURE PROSPECTS The multi-band approach that has been used for the observations described in this Thesis has proven valid for the exploitation of new science and the most useful approach for the comprehensive analysis of pulsar phenomena across the electromagnetic spectrum. As a completion to this work, the more comprehensive AGILE Pulsar Catalog is in preparation. It will comprise all the pulsars observed by AGILE and particularly focus on the low-energy tail of them, which present interesting properties that bridge pulsars and magnetars
Identification and characterization of small non-coding RNA molecules transcribed in Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) larvae parasitized by Toxoneuron nigriceps (Viereck) (Hymenoptera: Braconidae).
No full textToxoneuron nigriceps (Hymenoptera, Braconidae) is an endophagous parasitoid of the tobacco budworm, Heliothis virescens (Lepidoptera, Noctuidae). Parasitized larvae show a complex array of pathological symptoms including immune response suppression, largely due to a symbiotic virus, named TnBV, belonging to the family Polydnaviridae (PDV). A striking characteristic of the TnBV, as well as the other PDV genomes sequenced to date, is the large preponderance of non-coding regions, which raises the question of their functional relevance. To start addressing this question, we decided to analyze the small RNA fraction present in haemocytes of parasitized larvae and search for TnBV-derived sequences that might interfere with the host immune response.
To investigate this hypothesis in the case of TnBV, a specialized cDNA library, representative of the small RNA fraction present in haemocytes of parasitized larvae, was prepared. The generated cDNA library was validated by two types of quality control analyses.
Real-time PCR Absolute Quantification was performed using a standard curve method. This analysis essentially allowed me to evaluate the concentration of the library and also to obtain indications on its purity, by assessing the presence and relative abundance of adapter dimers contaminants.
A further quality test was carried out by cloning a small amount of the cDNA products in a plasmid vector and by sequencing through conventional technology few randomly selected clones. Two cloned sequences turned to be microRNA species already known in other organisms, miR-184 and miR-970, evolutionarily conserved from insects to mammals. In Drosophila melanogaster miR-184 is expressed in all developmental stages (Ping Li et al., 2011). Moreover, functional analysis identified a role for this miRNA in the female germline, where it is involved in multiple steps of oogenesis (Iovino et al., 2009).
The presence of authentic miRNA species in our library, as well as the finding of a correct size range (21-27) in our cloned cDNA sequences represented valid quality control criteria, empowering further analysis of the cDNA library by high-throughput sequencing technologies.
Specifically, cDNA sequencing was performed using the Illumina platform and resulted in about 6 million total reads. Sequence alignment with the TnBV genome was then performed using the FAST (Fast Aligning of Short Tags) software developed by the Institute of Applied Genomics of Udine. These preliminary analyses allowed the identification of 52 cDNA sequences, ranging in size between 20 and 27 nucleotides, that align with the viral genome. 46 are present in the viral genome in single copy, while 6 are located in two different positions and are therefore represented twice. These sequences were extensively analyzed by bioinformatical tools, in particular computational methods based on secondary structure prediction to assess the ability of these genomic regions to generate appropriate small RNA precursor molecules. Specific analyses were performed using a web tool, MirEval. 5 sequences were selected as potential miRNA species, deriving from viral genomic regions that show structural features typical of precursor-miRNA (pre-miRNA) molecules. RT-PCR experiments of these genomic regions, aimed at detecting presumptive primary-miRNA (pri-miRNA) species, indicated that these genomic regions are actively transcribed in haemocytes, 6 and 12 hours after parasitization. In parallel, transcriptional profiling of the TnBV genomic regions where the remaining presumptive TnBV small ncRNA sequences were mapped, as well as of randomly selected regions, that do not contain any protein coding genes or any putative small ncRNAs, indicated that the non-coding portion of the TnBV genome is extensively transcribed in host haemocytes. These analyses indicated that most, if not all, of the non-coding portion of the TnBV genome is transcribed in host haemocytes. This unexpected finding raises several questions concerning: 1) the functional meaning of generalized transcription and 2) the possible existance of specific mechanisms acting downstream of transcription to discriminate biologically relevant RNA molecules from “transcriptional noise”.
Functional characterization of the sequences identified as potential microRNAs is expected to shed light on the role played by the non-coding regions of the TnBV genome during parasitization. Furthermore, future work aimed at target identification may disclose the possible involvement of these sequences in the alteration of host immune system. The generated information will be essential for defining a more comprehensive model of the immunosuppression phenomena occurring during parasitization
Cycloisomerization reactions catalyzed by transition metal complexes. Synthesis of oxygen- and nitrogen- containing heterocyclic compounds.
No full textThe increasing need for environmentally responsible means of preparing a wide diversity of chemical products demanded by society drives the quest for synthetic efficiency. Transition metal-catalyzed cyclizations of polyunsaturated system, which are both selective and atomeconomical, represent an important starting point for this long-term goal.
We describe herein four different class of transition metal-catalyzed reactions that provided an atom- and step-economical entry into a range of oxygen- and nitrogen-containing heterocycles: (1) ring-closing metathesis, (2) Pauson-Khand reactions, (3) platinum-, goldand iridium-catalyzed electrophilic activation of alkynes and (4) gold-catalyzed cyclizations of allenes. All these transformations allow for a rapid increase in molecular complexity from relatively simple starting materials. Moreover, since these processes exhibit an excellent chemoselectivity towards C-C ! systems, the cyclized products usually retain different functional groups that can be used for further synthetic transformations.
Manuscripts adding to the scope of transition metal-catalyzed reactions are being published at a rapid rate attesting to their interest in the chemical community. With the development of new asymmetric methodologies, the transformations described in this thesis will continue to occupy, in the next future, a remarkable role in organic synthesis
Prosystemin coordinates multiple responses in tomato.
No full textIn Solanaceae, a family of peptide hormones called Systemins are involved in the activation of defense genes in response to wounding and herbivory. In tomato, Systemin (Sys) is an 18-aa oligopeptide released from a cytosolic precursor protein of 200 aa called prosystemin (ProSys). ProSys involvement in tomato response to chewing insects has long been described, but little is known about its role in modulating defense responses to phloem-feeding insects or other biotic agents such as pathogenic fungi. The aim of this research activity is to shed more light on ProSys involvement in tomato responses against several stress conditions and to evaluate a possible use of this plant hormone as a broad-spectrum defence instrument. For this reason, tomato cv. “Red Setter” was chosen to over-express ProSys gene since this tomato cultivar lacks the dominant allel at Mi locus, a gene involved in resistance against aphids, nematodes and white flies (Rossi et al., 1998). Solanum lycopersicum cv. “Red Setter” was genetically transformed via A. tumefaciens containing the pMZ vector carrying 35S2:prosystemin, already described by Rocco and collaborators (2008). ProSys conferred-resistance to aphids and fungi was underlined by bioassays. Tomato responses were further investigated by time-course transcriptional analysis of untransformed “Red Setter” plants challenged by aphids or fungi. The comparison with the expression profiles of the same genes in ProSys over-expressing plants underlined that ProSys induces most of the genes associated to tomato responses against these pests. In order to get a global vision of ProSys impact on tomato transcriptome, a microarray analysis was carried out underlining many defence-related differentially expressed genes, most of them supporting these biological evidences. The functional analyses of differentially espressed genes indicated that prosystemin affects genes involved in JA-, SA-, ET and auxin pathways. Molecular data were further investigated in silico to predict networks that highlight protein-protein interactions active in the signaling cascade activated by ProSys gene. This work was carried out at the Bioinformatic Department of “Centro de Investigation Principe Felipe” (CIPF, Valencia). The resulted network contained 195 proteins and highlighted some possible novel interactions such as between the ProSys-regulated ERD4 (early responsive to dehydration) and FPS (pharnesyl pyrophosphate synthase), a promising molecular link between abiotic and biotic response
Advanced languages and techniques for trust negotiation.
No full textThe Web is quickly shifting from a document browsing and delivery system to a hugely complex ecosystem of interconnected online applications. A relevant portion of these applications dramatically increase the number of users required to dynamically authenticate themselves and to, on the other hand, to identify the service they want to use. In order to manage interactions among such users/services is required a flexible but powerful mechanism.
Trust management, and in particular trust negotiation techniques, is a reasonable solution.
In this work we present the formalization of the well known trust negotiation framework Trust-X, of a rule-based policy definition language, called X-RNL.
Moreover, we present the extension of both the framework and of the language to provide advanced trust negotiation architectures, namely negotiations among groups.
We also provide protocols to adapt trust negotiations to mobile environments, specifically, we present protocols allowing a trust negotiation to be executed among several, distinct, sessions while still preserving its security properties. Such protocols have also been extended to provides the capability to migrate a ongoing trust negotiation among a set of known, reliable, subjects.
Finally, we present the application of the previously introduced trust negotiation techniques into real world scenarios: online social networks, critical infrastructures and cognitive radio networks
