964 resultados para source and sink


Relevância:

80.00% 80.00%

Publicador:

Resumo:

This article describes the design, implementation, and experiences with AcMus, an open and integrated software platform for room acoustics research, which comprises tools for measurement, analysis, and simulation of rooms for music listening and production. Through use of affordable hardware, such as laptops, consumer audio interfaces and microphones, the software allows evaluation of relevant acoustical parameters with stable and consistent results, thus providing valuable information in the diagnosis of acoustical problems, as well as the possibility of simulating modifications in the room through analytical models. The system is open-source and based on a flexible and extensible Java plug-in framework, allowing for cross-platform portability, accessibility and experimentation, thus fostering collaboration of users, developers and researchers in the field of room acoustics.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The use of organic trace minerals is getting strength and is an alternative to increase production and improve other characteristics such as humoral immunity. The present study was conducted to evaluate the effect of different levels and sources of selenium (Se) on humoral immunity of broilers. A six-week research was conducted using 1440 one-day-old males broiler chickens. The experimental design was randomized with six experimental diets (A: 0.15mg kg(-1) inorganic (inorg.); B: 0.15mg kg(-1) organic; C: 0.15mg kg(-1) inorg. + organic; D: 0.45mg kg(-1) inorganic; E: 0.45mg kg(-1) organic; F: 0.45mg kg(-1) inorg. + organic) calculated to provide the described amount of Se. Each diet was replicated in six box with 40 birds. A 3x2 factorial arrangement was used and the data were analyzed by ANOVA. The immunity was evaluated by means of the reaction against vaccine of Newcastle disease, and a reaction against sheep red blood cells (SRBC). No significant effects were observed at 5% significance level in NewCastle antibody (P >0.05). However at 14 day-old the source factor had p value at 0.0580, that show a trend of inorganic source in prolong the maternal immunity. No effect was observed in the immune response against SRBC (P >0.05). The results showed a immunologic response against Newcastle vaccine and SRBC, but the treatments was not able to induce a significant difference. The source and the level of Se showed no effect on the response against Newcastle vaccine and SRBC.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Objective: Antimicrobial photodynamic therapy (aPDT) has been used to combat local infections, and it consists of the combination of a photosensitizer, a light source, and reactive oxygen species (ROS) to kill microbial cells. In this study, we evaluated the effectiveness of aPDT in the treatment of candidiasis in HIV-infected patients. Methods: Twenty-one patients were divided into three groups. Control group (CG) was treated with the conventional medication for candidiasis (fluconazole 100 mg/day during 14 days). Laser group (LG) was subjected to low-level laser therapy (LLLT), wavelength 660 nm, power of 30 mW, and fluence of 7.5 J/cm(2), in contact with mucosa during 10 sec on the affected point. An aPDT group (aPDTG) was treated with aPDT, that is, combination of a low-power laser and methylene blue 450 mu g/mL. Pre-irradiation time was 1 min. Parameters of irradiation were the same ones as for the LG, and patients were single irradiated. Patients were clinically evaluated and culture analysis was performed before, immediately after, and 7, 15, and 30 days after the treatment. Results: Our results showed that fluconazole was effective; however, it did not prevent the return of the candidiasis in short-term. LLLT per se did not show any reduction on Candida spp. aPDT eradicated 100% of the colonies of this fungus and the patients did not show recurrence of candidiasis up to 30 days after the irradiation. Conclusions: These findings suggest that aPDT is a potential approach to oral candidiasis treatment in HIV-infected patients.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Inspection for corrosion of gas storage spheres at the welding seam lines must be done periodically. Until now this inspection is being done manually and has a high cost associated to it and a high risk of inspection personel injuries. The Brazilian Petroleum Company, Petrobras, is seeking cost reduction and personel safety by the use of autonomous robot technology. This paper presents the development of a robot capable of autonomously follow a welding line and transporting corrosion measurement sensors. The robot uses a pair of sensors each composed of a laser source and a video camera that allows the estimation of the center of the welding line. The mechanical robot uses four magnetic wheels to adhere to the sphere's surface and was constructed in a way that always three wheels are in contact with the sphere's metallic surface which guarantees enough magnetic atraction to hold the robot in the sphere's surface all the time. Additionally, an independently actuated table for attaching the corrosion inspection sensors was included for small position corrections. Tests were conducted at the laboratory and in a real sphere showing the validity of the proposed approach and implementation.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The periodic spectroscopic events in eta Carinae are now well established and occur near the periastron passage of two massive stars in a very eccentric orbit. Several mechanisms have been proposed to explain the variations of different spectral features, such as an eclipse by the wind-wind collision (WWC) boundary, a shell ejection from the primary star or accretion of its wind onto the secondary. All of them have problems explaining all the observed phenomena. To better understand the nature of the cyclic events, we performed a dense monitoring of eta Carinae with five Southern telescopes during the 2009 low-excitation event, resulting in a set of data of unprecedented quality and sampling. The intrinsic luminosity of the He II lambda 4686 emission line (L similar to 310 L-circle dot) just before periastron reveals the presence of a very luminous transient source of extreme UV radiation emitted in the WWC region. Clumps in the primary's wind probably explain the flare-like behavior of both the X-ray and He II lambda 4686 light curves. After a short-lived minimum, He II lambda 4686 emission rises again to a new maximum, when X-rays are still absent or very weak. We interpret this as a collapse of the WWC onto the "surface" of the secondary star, switching off the hard X-ray source and diminishing the WWC shock cone. The recovery from this state is controlled by the momentum balance between the secondary's wind and the clumps in the primary's wind.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Abstract Background Several mathematical and statistical methods have been proposed in the last few years to analyze microarray data. Most of those methods involve complicated formulas, and software implementations that require advanced computer programming skills. Researchers from other areas may experience difficulties when they attempting to use those methods in their research. Here we present an user-friendly toolbox which allows large-scale gene expression analysis to be carried out by biomedical researchers with limited programming skills. Results Here, we introduce an user-friendly toolbox called GEDI (Gene Expression Data Interpreter), an extensible, open-source, and freely-available tool that we believe will be useful to a wide range of laboratories, and to researchers with no background in Mathematics and Computer Science, allowing them to analyze their own data by applying both classical and advanced approaches developed and recently published by Fujita et al. Conclusion GEDI is an integrated user-friendly viewer that combines the state of the art SVR, DVAR and SVAR algorithms, previously developed by us. It facilitates the application of SVR, DVAR and SVAR, further than the mathematical formulas present in the corresponding publications, and allows one to better understand the results by means of available visualizations. Both running the statistical methods and visualizing the results are carried out within the graphical user interface, rendering these algorithms accessible to the broad community of researchers in Molecular Biology.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The motivation for the work presented in this thesis is to retrieve profile information for the atmospheric trace constituents nitrogen dioxide (NO2) and ozone (O3) in the lower troposphere from remote sensing measurements. The remote sensing technique used, referred to as Multiple AXis Differential Optical Absorption Spectroscopy (MAX-DOAS), is a recent technique that represents a significant advance on the well-established DOAS, especially for what it concerns the study of tropospheric trace consituents. NO2 is an important trace gas in the lower troposphere due to the fact that it is involved in the production of tropospheric ozone; ozone and nitrogen dioxide are key factors in determining the quality of air with consequences, for example, on human health and the growth of vegetation. To understand the NO2 and ozone chemistry in more detail not only the concentrations at ground but also the acquisition of the vertical distribution is necessary. In fact, the budget of nitrogen oxides and ozone in the atmosphere is determined both by local emissions and non-local chemical and dynamical processes (i.e. diffusion and transport at various scales) that greatly impact on their vertical and temporal distribution: thus a tool to resolve the vertical profile information is really important. Useful measurement techniques for atmospheric trace species should fulfill at least two main requirements. First, they must be sufficiently sensitive to detect the species under consideration at their ambient concentration levels. Second, they must be specific, which means that the results of the measurement of a particular species must be neither positively nor negatively influenced by any other trace species simultaneously present in the probed volume of air. Air monitoring by spectroscopic techniques has proven to be a very useful tool to fulfill these desirable requirements as well as a number of other important properties. During the last decades, many such instruments have been developed which are based on the absorption properties of the constituents in various regions of the electromagnetic spectrum, ranging from the far infrared to the ultraviolet. Among them, Differential Optical Absorption Spectroscopy (DOAS) has played an important role. DOAS is an established remote sensing technique for atmospheric trace gases probing, which identifies and quantifies the trace gases in the atmosphere taking advantage of their molecular absorption structures in the near UV and visible wavelengths of the electromagnetic spectrum (from 0.25 μm to 0.75 μm). Passive DOAS, in particular, can detect the presence of a trace gas in terms of its integrated concentration over the atmospheric path from the sun to the receiver (the so called slant column density). The receiver can be located at ground, as well as on board an aircraft or a satellite platform. Passive DOAS has, therefore, a flexible measurement configuration that allows multiple applications. The ability to properly interpret passive DOAS measurements of atmospheric constituents depends crucially on how well the optical path of light collected by the system is understood. This is because the final product of DOAS is the concentration of a particular species integrated along the path that radiation covers in the atmosphere. This path is not known a priori and can only be evaluated by Radiative Transfer Models (RTMs). These models are used to calculate the so called vertical column density of a given trace gas, which is obtained by dividing the measured slant column density to the so called air mass factor, which is used to quantify the enhancement of the light path length within the absorber layers. In the case of the standard DOAS set-up, in which radiation is collected along the vertical direction (zenith-sky DOAS), calculations of the air mass factor have been made using “simple” single scattering radiative transfer models. This configuration has its highest sensitivity in the stratosphere, in particular during twilight. This is the result of the large enhancement in stratospheric light path at dawn and dusk combined with a relatively short tropospheric path. In order to increase the sensitivity of the instrument towards tropospheric signals, measurements with the telescope pointing the horizon (offaxis DOAS) have to be performed. In this circumstances, the light path in the lower layers can become very long and necessitate the use of radiative transfer models including multiple scattering, the full treatment of atmospheric sphericity and refraction. In this thesis, a recent development in the well-established DOAS technique is described, referred to as Multiple AXis Differential Optical Absorption Spectroscopy (MAX-DOAS). The MAX-DOAS consists in the simultaneous use of several off-axis directions near the horizon: using this configuration, not only the sensitivity to tropospheric trace gases is greatly improved, but vertical profile information can also be retrieved by combining the simultaneous off-axis measurements with sophisticated RTM calculations and inversion techniques. In particular there is a need for a RTM which is capable of dealing with all the processes intervening along the light path, supporting all DOAS geometries used, and treating multiple scattering events with varying phase functions involved. To achieve these multiple goals a statistical approach based on the Monte Carlo technique should be used. A Monte Carlo RTM generates an ensemble of random photon paths between the light source and the detector, and uses these paths to reconstruct a remote sensing measurement. Within the present study, the Monte Carlo radiative transfer model PROMSAR (PROcessing of Multi-Scattered Atmospheric Radiation) has been developed and used to correctly interpret the slant column densities obtained from MAX-DOAS measurements. In order to derive the vertical concentration profile of a trace gas from its slant column measurement, the AMF is only one part in the quantitative retrieval process. One indispensable requirement is a robust approach to invert the measurements and obtain the unknown concentrations, the air mass factors being known. For this purpose, in the present thesis, we have used the Chahine relaxation method. Ground-based Multiple AXis DOAS, combined with appropriate radiative transfer models and inversion techniques, is a promising tool for atmospheric studies in the lower troposphere and boundary layer, including the retrieval of profile information with a good degree of vertical resolution. This thesis has presented an application of this powerful comprehensive tool for the study of a preserved natural Mediterranean area (the Castel Porziano Estate, located 20 km South-West of Rome) where pollution is transported from remote sources. Application of this tool in densely populated or industrial areas is beginning to look particularly fruitful and represents an important subject for future studies.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Questa tesi di dottorato di ricerca ha come oggetto la nozione di fatto urbano elaborata e presentata da Aldo Rossi nel libro L’architettura della città edito nel 1966. Ne L’architettura della città sono molteplici le definizioni e le forme con cui è enunciata la nozione di fatto urbano. Nel corso della tesi si è indagato come la costruzione nel tempo di questo concetto è stata preceduta da diversi studi giovanili intrapresi dal 1953, poi riorganizzati e sintetizzati a partire dal 1963 in un quaderno manoscritto dal titolo “Manuale di urbanistica”, in diversi appunti e in due quaderni manoscritti. Il lavoro di ricerca ha ricostruito la formulazione della nozione di fatto urbano attraverso gli scritti di Rossi. In questa direzione la rilevazione della partecipazione di Rossi a dibattiti, seminari, riviste, corsi universitari o ricerche accademiche è apparsa di fondamentale importanza, per comprendere la complessità di un lavoro non riconducibile a dei concetti disciplinari, ma alla formazione di una teoria trasmissibile. Il tentativo di comprendere e spiegare la nozione di fatto urbano ha condotto ad esaminare l’accezione con cui Rossi compone L’architettura della città, che egli stesso assimila ad un trattato. L’analisi ha identificato come la composizione del libro non è direttamente riferibile ad un uso classico della stesura editoriale del trattato, la quale ha tra i riferimenti più noti nel passato la promozione di una pratica corretta come nel caso vitruviano o un’impalcatura instauratrice di una nuova categoria come nel caso dell’Alberti. La mancanza di un sistema globale e prescrittivo a differenza dei due libri fondativi e il rimando non immediato alla stesura di un trattato classico è evidente ne L’architettura della città. Tuttavia la possibilità di condurre la ricerca su una serie di documenti inediti ha permesso di rilevare come negli scritti a partire dal 1953, sia maturata una trattazione delle questioni centrali alla nozione di fatto urbano ricca di intuizioni, che aspirano ad un’autonomia, sintetizzate, seppure in modo non sistematico, nella stesura del celebre libro. Si è così cercato di mettere in luce la precisazione nel tempo della nozione di fatto urbano e della sua elaborazione nei molteplici scritti antecedenti la pubblicazione de L’architettura della città, precisando come Rossi, pur costruendo su basi teoriche la nozione di fatto urbano, ne indichi una visione progressiva, ossia un uso operativo sulla città. La ricerca si è proposta come obiettivo di comprendere le radici culturali della nozione di fatto urbano sia tramite un’esplorazione degli interessi di Rossi nel suo percorso formativo sia rispetto alla definizione della struttura materiale del fatto urbano che Rossi individua nelle permanenze e che alimenta nella sua definizione con differenti apporti derivanti da altre discipline. Compito di questa ricerca è stato rileggere criticamente il percorso formativo compiuto da Rossi, a partire dal 1953, sottolinearne gli ambiti innovativi e precisarne i limiti descrittivi che non vedranno mai la determinazione di una nozione esatta, ma piuttosto la strutturazione di una sintesi complessa e ricca di riferimenti ad altri studi. In sintesi la tesi si compone di tre parti: 1. la prima parte, dal titolo “La teoria dei fatti urbani ne L’architettura della città”, analizza il concetto di fatto urbano inserendolo all’interno del più generale contesto teorico contenuto nel libro L’architettura della città. Questo avviene tramite la scomposizione del libro, la concatenazione delle sue argomentazioni e la molteplicità delle fonti esplicitamente citate da Rossi. In questo ambito si precisa la struttura del libro attraverso la rilettura dei riferimenti serviti a Rossi per comporre il suo progetto teorico. Inoltre si ripercorre la sua vita attraverso le varie edizioni, le ristampe, le introduzioni e le illustrazioni. Infine si analizza il ruolo del concetto di fatto urbano nel libro rilevando come sia posto in un rapporto paritetico con il titolo del libro, conseguendone un’accezione di «fatto da osservare» assimilabile all’uso proposto dalla geografia urbana francese dei primi del Novecento. 2. la seconda parte, dal titolo “La formazione della nozione di fatto urbano 1953-66”, è dedicata alla presentazione dell’elaborazione teorica negli scritti di Rossi prima de L’architettura della città, ossia dal 1953 al 1966. Questa parte cerca di descrivere le radici culturali di Rossi, le sue collaborazioni e i suoi interessi ripercorrendo la progressiva definizione della concezione di città nel tempo. Si è analizzato il percorso maturato da Rossi e i documenti scritti fin dagli anni in cui era studente alla Facoltà di Architettura Politecnico di Milano. Emerge un quadro complesso in cui i primi saggi, gli articoli e gli appunti testimoniano una ricerca intellettuale tesa alla costruzione di un sapere sullo sfondo del realismo degli anni Cinquanta. Rossi matura infatti un impegno culturale che lo porta dopo la laurea ad affrontare discorsi più generali sulla città. In particolare la sua importante collaborazione con la rivista Casabella-continuità, con il suo direttore Ernesto Nathan Rogers e tutto il gruppo redazionale segnano il periodo successivo in cui compare l’interesse per la letteratura urbanistica, l’arte, la sociologia, la geografia, l’economia e la filosofia. Seguono poi dal 1963 gli anni di lavoro insieme al gruppo diretto da Carlo Aymonino all’Istituto Universitario di Architettura di Venezia, e in particolare le ricerche sulla tipologia edilizia e la morfologia urbana, che portano Rossi a compiere una sintesi analitica per la fondazione di una teoria della città. Dall’indagine si rileva infatti come gli scritti antecedenti L’architettura della città sviluppano lo studio dei fatti urbani fino ad andare a costituire il nucleo teorico di diversi capitoli del libro. Si racconta così la genesi del libro, la cui scrittura si è svolta nell’arco di due anni, e le aspirazioni che hanno portato quello che era stato concepito come un “manuale d’urbanistica” a divenire quello che Rossi definirà “l’abbozzo di un trattato” per la formulazione di una scienza urbana. 3. la terza parte, dal titolo “La struttura materiale dei fatti urbani: la teoria della permanenza”, indaga monograficamente lo studio della città come un fatto materiale, un manufatto, la cui costruzione è avvenuta nel tempo e del tempo mantiene le tracce. Sul tema della teoria della permanenza è stato importante impostare un confronto con il dibattito vivo negli anni della ricostruzione dopo la guerra intorno ai temi delle preesistenze ambientali nella ricostruzione negli ambienti storici. Sono emersi fin da subito importanti la relazione con Ernesto Nathan Rogers, le discussioni sulle pagine di Casabella-Continuità, la partecipazione ad alcuni dibatti e ricerche. Si è inoltre Rilevato l’uso di diversi termini mutuati dalle tesi filosofiche di alcune personalità come Antonio Banfi e Enzo Paci, poi elaborati dal nucleo redazionale di Casabella-Continuità, di cui faceva parte anche Rossi. Sono così emersi alcuni spostamenti di senso e la formulazione di un vocabolario di termini all’interno della complessa vicenda della cultura architettonica degli anni Cinquanta e Sessanta. 1. Si è poi affrontato questo tema analizzando le forme con cui Rossi presenta la definizione della teoria della permanenza e i contributi desunti da alcuni autori per la costruzione scientifica di una teoria dell’architettura, il cui fine è quello di essere trasmissibile e di offrire strumenti di indagine concreti. Questa ricerca ha permesso di ipotizzare come il lavoro dei geografi francesi della prima metà del XX secolo, e in particolare il contributo più rilevante di Marcel Poëte e di Pierre Lavedan, costituiscono le fonti principali e il campo d’indagine maggiormente esplorato da Rossi per definire la teoria della permanenza e i monumenti. Le permanenze non sono dunque presentate ne L’architettura della città come il “tutto”, ma emergono da un metodo che sceglie di isolare i fatti urbani permanenti, consentendo così di compiere un’ipotesi su “ciò che resta” dopo le trasformazioni continue che operano nella città. Le fonti su cui ho lavorato sono state quelle annunciate da Rossi ne L’architettura della città, e più precisamente i testi nelle edizioni da lui consultate. Anche questo lavoro ha permesso un confronto dei testi che ha fatto emergere ne L’architettura della città l’uso di termini mutuati da linguaggi appartenenti ad altre discipline e quale sia l’uso di concetti estrapolati nella loro interezza. Presupposti metodologici Della formulazione della nozione di fatto urbano si sono indagate l’originalità dell’espressione, le connessioni presunte o contenute negli studi di Rossi sulla città attraverso la raccolta di fonti dirette e indirette che sono andate a formare un notevole corpus di scritti. Le fonti dirette più rilevanti sono state trovare nelle collezioni speciali del Getty Research Institute di Los Angeles in cui sono conservati gli Aldo Rossi Papers, questo archivio comprende materiali inediti dal 1954 al 1988. La natura dei materiali si presenta sotto forma di manoscritti, dattiloscritti, quaderni, documenti ciclostilati, appunti sparsi e una notevole quantità di corrispondenza. Negli Aldo Rossi Papers si trovano anche 32 dei 47 Quaderni Azzurri, le bozze de L’architettura della città e dell’ Autobiografia Scientifica. Per quanto riguarda in particolare L’architettura della città negli Aldo Rossi Papers sono conservati: un quaderno con il titolo “Manuale d’urbanistica, giugno 1963”, chiara prima bozza del libro, degli “Appunti per libro urbanistica estate/inverno 1963”, un quaderno con la copertina rossa datato 20 settembre 1964-8 agosto 1965 e un quaderno con la copertina blu datato 30 agosto 1965-15 dicembre 1965. La possibilità di accedere a questo archivio ha permesso di incrementare la bibliografia relativa agli studi giovanili consentendo di rileggere il percorso culturale in cui Rossi si è formato. E’ così apparsa fondamentale la rivalutazione di alcune questioni relative al realismo socialista che hanno portato a formare un più preciso quadro dei primi scritti di Rossi sullo sfondo di un complesso scenario intellettuale. A questi testi si è affiancata la raccolta delle ricerche universitarie, degli articoli pubblicati su riviste specializzate e degli interventi a dibattiti e seminari. A proposito de L’architettura della città si è raccolta un’ampia letteratura critica riferita sia al testo in specifico che ad una sua collocazione nella storia dell’architettura, mettendo in discussione alcune osservazioni che pongono L’architettura della città come un libro risolutivo e definitivo. Per quanto riguarda il capitolo sulla teoria della permanenza l’analisi è stata svolta a partire dai testi che Rossi stesso indicava ne L’architettura della città rivelando i diversi apporti della letteratura urbanistica francese, e permettendo alla ricerca di precisare le relazioni con alcuni scritti centrali e al contempo colti da Rossi come opportunità per intraprendere l’elaborazione dell’idea di tipo. Per quest’ultima parte si può precisare come Rossi formuli la sua idea di tipo in un contesto culturale dove l’interesse per questo tema era fondamentale. Dunque le fonti che hanno assunto maggior rilievo in quest’ultima fase emergono da un ricco panorama in cui Rossi compie diverse ricerche sia con il gruppo redazionale di Casabella-continuità, sia all’interno della scuola veneziana negli anni Sessanta, ma anche negli studi per l’ILSES e per l’Istituto Nazionale d’Urbanistica. RESEARCH ON THE NOTION OF URBAN ARTIFACT IN THE ARCHITECTURE OF THE CITY BY ALDO ROSSI. Doctoral candidate: Letizia Biondi Tutor: Valter Balducci The present doctoral dissertation deals with the notion of urban artifact that was formulated and presented by Aldo Rossi in his book The Architecture of the City, published in 1966. In The Architecture of the City, the notion of urban artifact is enunciated through a wide range of definitions and forms. In this thesis, a research was done on how the construction of this concept over time was preceded by various studies started in 1953 during the author’s youth, then re-organized and synthesized since 1963 in a manuscript titled “Manual of urban planning” and in two more manuscripts later on. The work of research re-constructed the formulation of the notion of urban artifact through Rossi’s writings. In this sense, the examination of Rossi’s participation in debates, seminars, reviews, university courses or academic researches was of fundamental importance to understand the complexity of a work which is not to be attributed to disciplinary concepts, but to the formulation of a communicable theory. The effort to understand and to explain the notion of urban artifact led to an examination of the meaning used by Rossi to compose The Architecture of the City, which he defines as similar to a treatise. Through this analysis, it emerged that the composition of the book is not directly ascribable to the classical use of editorial writing of a treatise, whose most famous references in the past are the promotion of a correct practice as in the case of Vitruvio’s treatise, or the use of a structure that introduces a new category as in the Alberti case. Contrary to the two founding books, the lack of a global and prescriptive system and the not immediate reference to the writing of a classical treatise are evident in The Architecture of the City. However, the possibility of researching on some unpublished documents allowed to discover that in the writings starting from 1953 the analysis of the questions that are at the core of the notion of urban artifact is rich of intuitions, that aim to autonomy and that would be synthesized, even though not in a systematic way, in his famous book. The attempt was that of highlighting the specification over time of the notion of urban artifact and its elaboration in the various writings preceding the publication of The Architecture of the City. It was also specified that, despite building on theoretical grounds, Rossi indicates a progressive version of the notion of urban artifact, that is a performing use in the city. The present research aims to understand the cultural roots of the notion of urban artifact in two main directions: analyzing, firstly, Rossi’s interests along his formation path and, secondly, the definition of material structure of an urban artifact identified by Rossi in the permanences and enriched by various contributions from other disciplines. The purpose of the present research is to revise the formation path made by Rossi in a critical way, starting by 1953, underlining its innovative aspects and identifying its describing limits, which will never lead to the formulation of an exact notion, but rather to the elaboration of a complex synthesis, enriched by references to other studies. In brief, the thesis is composed of three parts: 1. The first part, titled “The Theory of urban artifacts in The Architecture of the City”, analyzes the concept of urban artifact in the more general theoretical context of the book The Architecture of the City. Such analysis is done by “disassembling” the book, and by linking together the argumentations and the multiplicity of the sources which are explicitly quoted by Rossi. In this context, the book’s structure is defined more precisely through the revision of the references used by Rossi to compose his theoretical project. Moreover, the author’s life is traced back through the various editions, re-printings, introductions and illustrations. Finally, it is specified which role the concept of urban artifact has in the book, pointing out that it is placed in an equal relation with the book’s title; by so doing, the concept of urban artifact gets the new meaning of “fact to be observed”, similar to the use that was suggested by the French urban geography at the beginning of the 20th century. 2. The second part, titled “The formation of the notion of urban artifact 1953-66”, introduces the theoretical elaboration in Rossi’s writings before The Architecture of the City, that is from 1953 to 1966. This part tries to describe Rossi’s cultural roots, his collaborations and his interests, tracing back the progressive definition of his conception of city over time. The analysis focuses on the path followed by Rossi and on the documents that he wrote since the years as a student at the Department of Architecture at the Politecnico in Milan. This leads to a complex scenario of first essays, articles and notes that bear witness to the intellectual research aiming to the construction of a knowledge on the background of the Realism of the 1950s. Rossi develops, in fact, a cultural engagement that leads him after his studies to deal with more general issues about the city. In particular, his important collaboration with the architecture magazine “Casabella-continuità”, with the director Ernesto Nathan Rogers and with the whole redaction staff mark the following period when he starts getting interested in city planning literature, art, sociology, geography, economics and philosophy. Since 1963, Rossi has worked with the group directed by Carlo Aymonino at the “Istituto Universitario di Architettura” (University Institute of Architecture) in Venice, especially researching on building typologies and urban morphology. During these years, Rossi elaborates an analytical synthesis for the formulation of a theory about the city. From the present research, it is evident that the writings preceding The Architecture of the City develop the studies on urban artifacts, which will become theoretical core of different chapters of the book. In conclusion, the genesis of the book is described; written in two years, what was conceived to be an “urban planning manual” became a “treatise draft” for the formulation of an urban science, as Rossi defines it. 3. The third part is titled “The material structure of urban artifacts: the theory of permanence”. This research is made on the study of the city as a material fact, a manufacture, whose construction was made over time, bearing the traces of time. As far as the topic of permanence is concerned, it was also important to draw a comparison with the debate about the issues of environmental pre-existence of re-construction in historical areas, which was very lively during the years of the Reconstruction. Right from the beginning, of fundamental importance were the relationship with Ernesto Nathan Rogers, the discussions on the pages of Casabella-Continuità and the participation to some debates and researches. It is to note that various terms were taken by the philosophical thesis by some personalities such as Antonio Banfi and Enzo Paci, and then re-elaborated by the redaction staff at Casabella-Continuità, which Rossi took part in as well. Through this analysis, it emerged that there were some shifts in meaning and the formulation of a vocabulary of terms within the complex area of the architectonic culture in the 1950s and 1960s. Then, I examined the shapes in which Rossi introduces the definition of the theory of permanence and the references by some authors for the scientific construction of an architecture theory whose aim is being communicable and offering concrete research tools. Such analysis allowed making a hypothesis about the significance for Rossi of the French geographers of the first half of the 20th century: in particular, the work by Marcel Poëte and by Pierre Lavedan is the main source and the research area which Rossi mostly explored to define the theory of permanence and monuments. Therefore, in The Architecture of the City, permanencies are not presented as the “whole”, but they emerge from a method which isolates permanent urban artifacts, in this way allowing making a hypothesis on “what remains” after the continuous transformations made in the city. The sources examined were quoted by Rossi in The Architecture of the City; in particular I analyzed them in the same edition which Rossi referred to. Through such an analysis, it was possible to make a comparison of the texts with one another, which let emerge the use of terms taken by languages belonging to other disciplines in The Architecture of the City and which the use of wholly extrapolated concepts is. Methodological premises As far as the formulation of the notion of urban artifact is concerned, the analysis focuses on the originality of the expression, the connections that are assumed or contained in Rossi’s writings about the city, by collecting direct and indirect sources which formed a significant corpus of writings. The most relevant direct sources were found in the special collections of the Getty Research Institute in Los Angeles, where the “Aldo Rossi Papers” are conserved. This archive contains unpublished material from 1954 to 1988, such as manuscripts, typescripts, notebooks, cyclostyled documents, scraps and notes, and several letters. In the Aldo Rossi Papers there are also 32 out of the 47 Light Blue Notebooks (Quaderni Azzurri), the rough drafts of The Architecture of the City and of the “A Scientific Autobiography”. As regards The Architecture of the City in particular, the Aldo Rossi Papers preserve: a notebook by the title of “Urban planning manual, June, 1963”, which is an explicit first draft of the book; “Notes for urban planning book summer/winter 1963”; a notebook with a red cover dated September 20th, 1964 – August 8th, 1965; and a notebook with a blue cover dated August 30th, 1965 – December 15th, 1965. The possibility of accessing this archive allowed to increase the bibliography related to the youth studies, enabling a revision of the cultural path followed by Rossi’s education. To that end, it was fundamental to re-evaluate some issues linked to the socialist realism which led to a more precise picture of the first writings by Rossi against the background of the intellectual scenario where he formed. In addition to these texts, the collection of university researches, the articles published on specialized reviews and the speeches at debates and seminars were also examined. About The Architecture of the City, a wide-ranging critical literature was collected, related both to the text specifics and to its collocation in the story of architecture, questioning some observations which define The Architecture of the City as a conclusive and definite book. As far as the chapter on the permanence theory is concerned, the analysis started by the texts that Rossi indicated in The Architecture of the City, revealing the different contributions from the French literature on urban planning. This allowed to the present research a more specific definition of the connections to some central writings which, at the same time, were seen by Rossi as an opportunity to start up the elaboration of the idea of type. For this last part, it can be specified that Rossi formulates his idea of type in a cultural context where the interest in this topic was fundamental. Therefore, the sources which played a central role in this final phase emerge from an extensive panorama in which Rossi researched not only with the redaction staff at Casablanca-continuità and within the School of Venice in the 1960s, but also in his studies for the ILSES (Institute of the Region Lombardia for Economics and Social Studies) and for the National Institute of Urban Planning.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

The running innovation processes of the microwave transistor technologies, used in the implementation of microwave circuits, have to be supported by the study and development of proper design methodologies which, depending on the applications, will fully exploit the technology potentialities. After the choice of the technology to be used in the particular application, the circuit designer has few degrees of freedom when carrying out his design; in the most cases, due to the technological constrains, all the foundries develop and provide customized processes optimized for a specific performance such as power, low-noise, linearity, broadband etc. For these reasons circuit design is always a “compromise”, an investigation for the best solution to reach a trade off between the desired performances. This approach becomes crucial in the design of microwave systems to be used in satellite applications; the tight space constraints impose to reach the best performances under proper electrical and thermal de-rated conditions, respect to the maximum ratings provided by the used technology, in order to ensure adequate levels of reliability. In particular this work is about one of the most critical components in the front-end of a satellite antenna, the High Power Amplifier (HPA). The HPA is the main power dissipation source and so the element which mostly engrave on space, weight and cost of telecommunication apparatus; it is clear from the above reasons that design strategies addressing optimization of power density, efficiency and reliability are of major concern. Many transactions and publications demonstrate different methods for the design of power amplifiers, highlighting the availability to obtain very good levels of output power, efficiency and gain. Starting from existing knowledge, the target of the research activities summarized in this dissertation was to develop a design methodology capable optimize power amplifier performances complying all the constraints imposed by the space applications, tacking into account the thermal behaviour in the same manner of the power and the efficiency. After a reminder of the existing theories about the power amplifier design, in the first section of this work, the effectiveness of the methodology based on the accurate control of the dynamic Load Line and her shaping will be described, explaining all steps in the design of two different kinds of high power amplifiers. Considering the trade-off between the main performances and reliability issues as the target of the design activity, we will demonstrate that the expected results could be obtained working on the characteristics of the Load Line at the intrinsic terminals of the selected active device. The methodology proposed in this first part is based on the assumption that designer has the availability of an accurate electrical model of the device; the variety of publications about this argument demonstrates that it is so difficult to carry out a CAD model capable to taking into account all the non-ideal phenomena which occur when the amplifier operates at such high frequency and power levels. For that, especially for the emerging technology of Gallium Nitride (GaN), in the second section a new approach for power amplifier design will be described, basing on the experimental characterization of the intrinsic Load Line by means of a low frequency high power measurements bench. Thanks to the possibility to develop my Ph.D. in an academic spin-off, MEC – Microwave Electronics for Communications, the results of this activity has been applied to important research programs requested by space agencies, with the aim support the technological transfer from universities to industrial world and to promote a science-based entrepreneurship. For these reasons the proposed design methodology will be explained basing on many experimental results.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

In recent years, due to the rapid convergence of multimedia services, Internet and wireless communications, there has been a growing trend of heterogeneity (in terms of channel bandwidths, mobility levels of terminals, end-user quality-of-service (QoS) requirements) for emerging integrated wired/wireless networks. Moreover, in nowadays systems, a multitude of users coexists within the same network, each of them with his own QoS requirement and bandwidth availability. In this framework, embedded source coding allowing partial decoding at various resolution is an appealing technique for multimedia transmissions. This dissertation includes my PhD research, mainly devoted to the study of embedded multimedia bitstreams in heterogenous networks, developed at the University of Bologna, advised by Prof. O. Andrisano and Prof. A. Conti, and at the University of California, San Diego (UCSD), where I spent eighteen months as a visiting scholar, advised by Prof. L. B. Milstein and Prof. P. C. Cosman. In order to improve the multimedia transmission quality over wireless channels, joint source and channel coding optimization is investigated in a 2D time-frequency resource block for an OFDM system. We show that knowing the order of diversity in time and/or frequency domain can assist image (video) coding in selecting optimal channel code rates (source and channel code rates). Then, adaptive modulation techniques, aimed at maximizing the spectral efficiency, are investigated as another possible solution for improving multimedia transmissions. For both slow and fast adaptive modulations, the effects of imperfect channel estimation errors are evaluated, showing that the fast technique, optimal in ideal systems, might be outperformed by the slow adaptive modulation, when a real test case is considered. Finally, the effects of co-channel interference and approximated bit error probability (BEP) are evaluated in adaptive modulation techniques, providing new decision regions concepts, and showing how the widely used BEP approximations lead to a substantial loss in the overall performance.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Array seismology is an useful tool to perform a detailed investigation of the Earth’s interior. Seismic arrays by using the coherence properties of the wavefield are able to extract directivity information and to increase the ratio of the coherent signal amplitude relative to the amplitude of incoherent noise. The Double Beam Method (DBM), developed by Krüger et al. (1993, 1996), is one of the possible applications to perform a refined seismic investigation of the crust and mantle by using seismic arrays. The DBM is based on a combination of source and receiver arrays leading to a further improvement of the signal-to-noise ratio by reducing the error in the location of coherent phases. Previous DBM works have been performed for mantle and core/mantle resolution (Krüger et al., 1993; Scherbaum et al., 1997; Krüger et al., 2001). An implementation of the DBM has been presented at 2D large-scale (Italian data-set for Mw=9.3, Sumatra earthquake) and at 3D crustal-scale as proposed by Rietbrock & Scherbaum (1999), by applying the revised version of Source Scanning Algorithm (SSA; Kao & Shan, 2004). In the 2D application, the rupture front propagation in time has been computed. In 3D application, the study area (20x20x33 km3), the data-set and the source-receiver configurations are related to the KTB-1994 seismic experiment (Jost et al., 1998). We used 60 short-period seismic stations (200-Hz sampling rate, 1-Hz sensors) arranged in 9 small arrays deployed in 2 concentric rings about 1 km (A-arrays) and 5 km (B-array) radius. The coherence values of the scattering points have been computed in the crustal volume, for a finite time-window along all array stations given the hypothesized origin time and source location. The resulting images can be seen as a (relative) joint log-likelihood of any point in the subsurface that have contributed to the full set of observed seismograms.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Das Hauptziel der vorliegenden Arbeit war die Entwicklung eines Experimentaufbaus für die elektrochemische Abscheidung von Transactiniden mit anschließender Detektion. Zu diesem Zweck wurden Experimente mit den Homologen dieser Elemente durchgeführt. Die Elektrodeposition von Tracermengen an Fremdelektroden führt zu einer Elektrodenbedeckung von weniger als einer Monolage. Die erforderlichen Abscheidepotentiale sind häufig positiver, als nach der Nernst’schen Gleichung zu erwarten ist. Dieses Phänomen nennt man Unterpotentialabscheidung. In zahlreichen Versuchen mit Radiotracern wurde die Abscheideausbeute als Funktion des Elektrodenpotentials bestimmt, wobei abzuscheidendes Ion, Elektrodenmaterial und Elektrolyt variiert wurden. Es wurden kritische Potentiale, bei denen eine nennenswerte Abscheidung gerade begann, ermittelt sowie Potentiale für die Abscheidung von 50 % der in der Lösung befindlichen Atome. Diese Werte wurden mit theoretisch vorhergesagten Potentialen und Werten aus der Literatur verglichen. Die Abscheidung von Pb als Homologem von Element 114 funktionierte sehr gut an Elektroden aus Palladium oder palladinierten Nickelelektroden unter Verwendung von 0,1 M HCl als Elektrolyt. Zur Charakterisierung der Unterpotentialabscheidung wurde neben der Radiotracer-Methode auch die Cyclovoltammetrie eingesetzt. Hier findet die Abscheidung der ersten Monolage auf der Elektrode ebenfalls häufig bei positiveren Potentialen statt, als die der Hauptmenge. Die mit beiden Methoden ermittelten Werte wurden einander gegenübergestellt. Die Elektrodeposition von kurzlebigen Isotopen muss sehr schnell erfolgen. Es konnte gezeigt werden, dass eine hohe Temperatur und damit verbunden eine niedrige Viskosität des Elektrolyten die Abscheidung beschleunigt. Ebenfalls wichtig ist ein gutes Rühren der Lösung, um eine kleine Nernst’sche Diffusionsschichtdicke zu erzielen. Das Verhältnis von Elektrodenfläche zu Elektrolytvolumen muss möglichst groß sein. Auf der Grundlage dieser Ergebnisse wurde eine für schnelle Elektrolysen optimierte Elektrolysezelle entwickelt. Unter Einsatz dieser Zelle wurden die Abscheidegeschwindigkeiten für verschiedene Ionen- und Elektrodenkombinationen gemessen. Es wurden Experimente zur Kopplung von Gasjet und Elektrolysezelle durchgeführt, dabei wurde sowohl mit am Reaktor erzeugten Spaltprodukten, mit Pb-Isotopen aus einer emanierenden Quelle und mit am Beschleuniger erzeugten Isotopen gearbeitet. Mit den dort gewonnenen Erkenntnissen wurde ein Experimentaufbau für die kontinuierliche Abscheidung und Detektion von kurzlebigen Isotopen realisiert. Am Beschleuniger wurden u. a. kurzlebige Hg- und Pb-Isotope erzeugt und mit einem Gasjet aus der Targetkammer zum ALOHA-System transportiert. Dort wurden sie in einem quasi-kontinuierlichen Prozess in die wässrige Phase überführt und zu einer Elektrolyszelle transportiert. In dieser erfolgte die Elektrodeposition auf eine bandförmige Elektrode aus Nickel oder palladiniertem Nickel. Nach der Abscheidung wurde das Band zu einer Detektorphalanx gezogen, wo der -Zerfall der neutronenarmen Isotope registriert wurde. Es wurden charakteristische Größen wie die Abscheidegeschwindigkeit und die Gesamtausbeute der Elektrolyse ermittelt. Das System wurde im Dauerbetrieb getestet. Es konnte gezeigt werden, dass der gewählte Aufbau prinzipiell für die Abscheidung von kurzlebigen, am Beschleuniger erzeugten Isotopen geeignet ist. Damit ist eine wichtige Voraussetzung für den zukünftigen Einsatz der Methode zum Studium der chemischen Eigenschaften der superschweren Elemente geschaffen.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Translations, says Gideon Toury, are facts of target cultures – but the perceived status of source texts has a bearing on how these are reflected or refracted in the target language. This proposition is particularly evident in the case of classics: when translators have to work on literary creations occupying a pivotal position in the source/target cultures, they adopt strategies of literalness and ennoblement which betray a quasi-religious awe – on the one hand, a desire to ruffle the surface of the revered original as little as possible; and on the other, a determination to reproduce the supposed “classical qualities” of the classic even when they are not present in the source. In this dissertation, Paola Venturi studies how the “idea of classic” influences translation theory and practice, and substantiates her theoretical observations by looking at Italian translations of eighteenth- and nineteenth-century English classics. A marked – and historically determined – disparity between source and target readerships, and the translators’ reverence for their prestigious originals, conspire to produce Italian versions which are much more “wooden” and “elegant” than their English counterparts.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Die vorliegende Dissertation beschreibt die Realisation des neuartigen Konzepts der Laserionenquellenfalle für die on-line Produktion exotischer Nuklide und für den Nachweis von Spurenisotopen in Proben mit starken Isobarenkontaminationen. Ziel dieser Entwicklung ist eine wesentliche Steigerung der Isobarenselektivität einer herkömmlichen Laserionenquelle, sowie die Erzeugung zeitlich kontrollierter Ionenpulse mit hervorragender Strahlqualität. Es konnte die prizipielle Funktionsfähigkeit des Systems in Kombination mit einem Titan:Saphir-Lasersystem für die Elemente Gallium, Calcium und Nickel demonstriert und Ionenpulse mit einer minimalen Pulslänge von 1 µs erzeugt werden. Nach ersten Abschätzungen ist die Effizienz des Systems etwa einen Faktor 2500 geringer als die einer herkömmlichen Laserionenquelle. Der zweite Teil der Arbeit beschäftigt sich mit dem spurenanalytischen Nachweis von 99-Tc, mit dem Ziel, das Verhalten von 99-Tc in der Umgebung eines möglichen Endlagers für nukleare Abfälle studieren zu können. Hier wurden erste Studien mit dem kurzlebigen Isomer 99m-Tc zur Wechselwirkung von Tc(VII) mit Huminsäure und Kaolinit durchgeführt. Für den Einsatz der Laserionenquellenfalle in der Ultraspurenanalyse, wurde ein effizientes Anregungsschema für Titan:Saphir-Laser entwickelt und 99-Tc in einer herkömmlichen Ionenquelle nachgewiesen. Der letzte Teil der Arbeit beschreibt Machbarkeitsstudien zum Aufbau einer Laserionenquelle auf Basis eines Titan:Sahphir-Lasersystems, die parallel zu oben genannten Entwicklungen am Oak Ridge National Laboratory durchgeführt wurden. Im Rahmen dieser Messungen wurden Anregungsschemata für die resonante Anregung und Ionisation von Kupfer und Palladium für Titan:Saphir-Laser getestet. Dabei konnte zum ersten Mal frequenzvervierfachtes Laserlicht in einer Laserionenquelle eingesetzt werden. Am ORNL wurden Studien zur Zeitstruktur von Laserionenpulsen, sowie Emittanzmessungen von Laser- und Oberflächenionenstrahlen durchgeführt werden.

Relevância:

80.00% 80.00%

Publicador:

Resumo:

Several studies support the use of probiotics for the treatment of minor gastrointestinal problems in infants. Positive effects on newborn colics have been evidenced after administration of Lactobacillus strains, whereas no studies have been reported regarding the use of bifidobacteria for this purpose. This work was therefore aimed at the characterization of Bifidobacterium strains capable of inhibiting the growth of pathogens typical of the infant gastro-intestinal tract and of coliforms isolated from colic newborns. Among the 46 Bifidobacterium strains considered, 16 showed high antimicrobial activity against potential pathogens; these strains were further characterized from a taxonomic point of view, for the presence and transferability of antibiotic resistances, for citotoxic effects and adhesion to non tumorigenic gut epithelium cell lines. Moreover, their ability to stimulate gut health by increasing the metabolic activity and the immune response of epithelial cells was also studied. The examination of all these features allowed to identify 3 B. breve strains and a B. longum subsp. longum strain as potential probiotics for the treatments of enteric disorders in newborns such as infantile colics. The formulation of a synbiotic product with an appropriate prebiotic fiber capable of supporting the growth of the selected Bifidobacterium strains was also considered in this study. In this respect the ability of the 4 selected Bifidobacterium strains to use as the sole carbon source and energy source different polisaccharide fibers was investigated The last phase of the work has been dedicated to the evaluation of the gut microbial diversity in newborns whose mothers has been subjected to antibiotic therapy a few hours before the delivery because of a Streptococcus type B infection. These newborns can represent a possible target for the probiotic strains selected in this work.