La Dalmazia

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Opinione pubblica e democrazia, al tempo dei nuovi media

Come indica il titolo, questo elaborato punta a esaminare l’intreccio fra opinione pubblica, democrazia e nuovi media, mostrando come l’introduzione di Internet e dei suoi dispositivi abbia modificato queste categorie politiche e filosofiche. La tesi è stata divisa in tre capitoli: il primo cerca di chiarire il concetto di “opinione pubblica” attraverso un inquadramento storico e un approfondimento di quelle che sono state le teorie filosofiche e sociologiche più complete al riguardo, il secondo punta a intrecciare queste categorie con la comunicazione mediale tradizionale e introduce al terzo capitolo in cui, attraverso l’analisi di alcuni fatti contemporanei come le cosiddette “Rivoluzioni di Internet”, si fa notare come il potere del web e dei nuovi media non abbia intensificato la partecipazione democratica alla vita politica, ma anzi abbia modificato il concetto di opinione pubblica e i comportamenti del singolo all’interno della collettività, ormai sempre più digitale

NEW PLATE MEDIUM FOR SCREENING AND PRESUMPTIVE IDENTIFICATION OF GRAM-NEGATIVE URINARY-TRACT PATHOGENS

A new selective, differential plating medium to screen the common gram-negative urinary tract pathogens is described. The medium combines adonitol fermentation, phenylalanine deaminase, and P-glucuronidase tests and allows the indole and cytochrome oxidase tests to be performed directly from the plates. High-level agreement with individual conventional tests was recorded in comparative studies with 504 cultures of gram-negative rods. There was 100% agreement, except for the Providencia spp. indole spot test (61.6% agreement). Adonitol fermentation by Providencia species could not be determined. Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Pseudomonas aeruginosa were identified with a high efficiency (100, 85.7, 83.5, and 100% agreement, respectively) without further testing. There was 96% overall agreement for the 267 infected urine samples tested

Advanced Techniques for Future Multicarrier Systems

Future multicarrier systems face the tough challenge of supporting high data-rate and high-quality services. The main limitation is the frequency-selective nature of the propagation channel that affects the received signal, thus degrading the system performance. OFDM can be envisaged as one of the most promising modulation techniques for future communication systems. It exhibits robustness to ISI even in very dispersive environments and its main characteristic is to take advantage of channel diversity by performing dynamic resource allocation. In a multi-user OFDMA scenario, the challenge is to allocate, on the basis of the channel knowledge, different portions of the available frequency spectrum among the users in the systems. Literature on resource allocation for OFDMA systems mainly focused on single-cell systems, where the objective is to assign subcarriers, power and data-rate for each user according to a predetermined criterion. The problem can be formulated with the goal of either maximizing the system sum-rate subject to a constraint on transmitted power or minimizing the overall power consumption under some predetermined constraints on rate per user. Only recently, literature focuses on resource allocation in multi-cell networks, where the goal is not only to take advantage of frequency and multi-user diversity, but also to mitigate MAI, which represents one of the most limiting factor for such problems. We consider a multi-cell OFDMA system with frequency reuse distance equal to one. Allowing all cells to transmit on the whole bandwidth unveils large potential gains in terms of spectral efficiency in comparison with conventional cellular systems. Such a scenario, however, is often deemed unfeasible because of the strong MAI that negatively affects the system performance. In this dissertation we present a layered architecture that integrates a packet scheduler with an adaptive resource allocator, explicitly designed to take care of the multiple access interference. Each cell performs its resource management in a distributed way without any central controller. Iterative resource allocation assigns radio channels to the users so as to minimize the interference. Packet scheduling guarantees that all users get a fair share of resources regardless of their position in the cell. This scheduler-allocator architecture integrates both goals and is able to self adapt to any traffic and user configuration. An adaptive, distributed load control strategy can reduce the cell load so that the iterative procedure always converges to a stable allocation, regardless of the interference. Numerical results show that the proposed architecture guarantees both high spectral efficiency and throughput fairness among flows. In the second part of this dissertation we deal with FBMC communication systems. FBMC modulation is a valid alternative to conventional OFDM signaling as it presents a set of appealing characteristics, such as robustness to narrowband interferers, more flexibility to allocate groups of subchannels to different users/services, and frequency-domain equalization without any cyclic extension. However, like any other multicarrier modulations, FBMC is strongly affected by residual CFOs that have to be accurately estimated. Unlike previously proposed algorithms, whereby frequency is recovered either relying on known pilot symbols multiplexed with the data stream or exploiting specific properties of the multicarrier signal structure following a blind approach, we present and discuss an algorithm based on the ML principle, which takes advantage both of pilot symbols and also indirectly of data symbols through knowledge and exploitation of their specific modulation format. The algorithm requires the availability of the statistical properties of channel fading up to second-order moments. It is shown that the above approach allows to improve on both frequency acquisition range and estimation accuracy of previously published schemes

T-MOD PATHWAY, A REDUCED SEQUENCE FOR IDENTIFICATION OF GRAM-NEGATIVE URINARY-TRACT PATHOGENS

In this paper, we describe a reduced sequence of identification that includes T-mod medium, a selective and differential isolation medium which allows accurate presumptive identification of the most common gramnegative bacteria encountered in urine samples. The present study, performed on bacteria isolated from 1,762 independent urine samples, has shown that a few selected tests (lysine and ornithine decarboxylase, urease and trehalose fermentation tests) improve the identification accuracy of T-mod, making it possible both to identify the less frequent species and to prevent some misidentifications of Klebsiella pneumoniae and Proteus mirabilis. The proposed work flow agreed with conventional identification protocols to a 99.3% extent and allowed identification of 87.4% of the isolates directly from the primary plate, 11.4% after 1 to 3 additional tests, and 1.2% after an identification gallery

Combined Pilot-Aided and Decision-Directed Carrier Synchronization for Filtered Multitone Wireless Systems

This paper focuses on the issue of carrier frequency synchronization for filtered multitone wireless transmission over time-frequency selective fading channels. Rather than either relying only on known pilot symbols multiplexed within the transmitted burst or exploiting the specific signal structure in a blind mode, the estimation algorithm we pursue is derived from the maximum likelihood principle and takes advantage of both pilot symbols and also the unknown information-bearing symbols through specific differential decision-directed processing. When compared to conventional pilot-based methods, the proposed approach improves the frequency acquisition range without degrading estimation accuracy at even lower cost in terms of computational complexity

Business Model and Non-Financial Key Performance Indicator Disclosure

Business model disclosure is proposed as a communication tool for companies to increase the effectiveness of non-financial key performance indicator (NFKPI) disclosure. First, business model enables the identification of indicators that are aligned with strategic objectives. Moreover, it acts as an integrated framework, showing how different capitals are combined to create value