Quantum hydrodynamic models for semiconductors with and without collisions

In dieser Arbeit werden Quantum-Hydrodynamische (QHD) Modelle betrachtet, die ihren Einsatz besonders in der Modellierung von Halbleiterbauteilen finden. Das QHD Modell besteht aus den Erhaltungsgleichungen für die Teilchendichte, das Momentum und die Energiedichte, inklusive der Quanten-Korrekturen durch das Bohmsche Potential. Zu Beginn wird eine Übersicht über die bekannten Ergebnisse der QHD Modelle unter Vernachlässigung von Kollisionseffekten gegeben, die aus ein­em Schrödinger-System für den gemischten-Zustand oder aus der Wigner-Glei­chung hergeleitet werden können. Nach der Reformulierung der eindimensionalen QHD Gleichungen mit linearem Potential als stationäre Schrö­din­ger-Gleichung werden die semianalytischen Fassungen der QHD Gleichungen für die Gleichspannungs-Kurve betrachtet. Weiterhin werden die viskosen Stabilisierungen des QHD Modells be­rück­sich­tigt, sowie die von Gardner vorgeschlagene numerische Viskosität für das {sf upwind} Finite-Differenzen Schema berechnet. Im Weiteren wird das viskose QHD Modell aus der Wigner-Glei­chung mit Fokker-Planck Kollisions-Ope­ra­tor hergeleitet. Dieses Modell enthält die physikalische Viskosität, die durch den Kollision-Operator eingeführt wird. Die Existenz der Lösungen (mit strikt positiver Teilchendichte) für das isotherme, stationäre, eindimensionale, viskose Modell für allgemeine Daten und nichthomogene Randbedingungen wird gezeigt. Die dafür notwendigen Abschätzungen hängen von der Viskosität ab und erlauben daher den Grenzübergang zum nicht-viskosen Fall nicht. Numerische Simulationen der Resonanz-Tunneldiode modelliert mit dem nichtisothermen, stationären, eindimensionalen, viskosen QHD Modell zeigen den Einfluss der Viskosität auf die Lösung. Unter Verwendung des von Degond und Ringhofer entwickelten Quanten-Entropie-Minimierungs-Verfahren werden die allgemeinen QHD-Gleichungen aus der Wigner-Boltzmann-Gleichung mit dem BGK-Kollisions-Operator hergeleitet. Die Herleitung basiert auf der vorsichtige Entwicklung des Quanten-Max­well­ians in Potenzen der skalierten Plankschen Konstante. Das so erhaltene Modell enthält auch vertex-Terme und dispersive Terme für die Ge­schwin­dig­keit. Dadurch bleibt die Gleichspannungs-Kurve für die Re­so­nanz-Tunnel­diode unter Verwendung des allgemeinen QHD Modells in einer Dimension numerisch erhalten. Die Ergebnisse zeigen, dass der dispersive Ge­schwin­dig­keits-Term die Lösung des Systems stabilisiert.

L’iconografia dell’imperatore alato nel contesto della teologia politica bizantina

La presente ricerca di dottorato si propone di esaminare l’evoluzione della teologia politica bizantina e dei suoi riflessi nella propaganda imperiale nel periodo compreso tra il XIII e il XIV secolo, attraverso lo studio delle manifestazioni dell'ideologia nell'iconografia e nella numismatica del periodo in esame. L'intreccio interdisciplinare di questi ambiti di ricerca, iconografia e numismatica - con una metodologia innovativa, i cui risultati si profilano estremamente proficui - permette di comprendere i caratteri concreti, ma forse più reconditi, del realizzarsi dell'ideologia politica e della propaganda imperiale nell'impero bizantino ormai ridotto ad una costellazione di potentati particolari di estensione limitata. Il tema specifico di questo studio ha come oggetto alcune iconografie ritenute inedite, o meno tradizionali, nel panorama numismatico bizantino, emesse, in particolare, dalla zecca di Tessalonica tra XIII e XIV secolo, che vengono qui esaminate in funzione dell’evoluzione della rappresentazione imperiale. Tra di esse emerge l’inedita iconografia dell’imperatore pteroforo per la sua valenza di interscambiabilità semantica con l’immagine arcangelica. Lo studio si è proposto l’obiettivo principale di rintracciare elementi iconologici quanto più possibile comuni tra tutti i soggetti iconografici presi in esame, vagliando il substrato ideologico e propagandistico sotteso alla valenza iconologica per ogni tipologia numismatica.

Project Financing nelle Infrastrutture del Trasporto

L’elaborato ha avuto ad oggetto l’analisi delle sofisticate soluzioni normative proposte dall’ordinamento nazionale in relazione all’evoluzione della finanza di progetto. In particolare, è stata condotto un dettagliato studio delle fasi che compongono il project financing, nonché dei soggetti che, a diverso titolo e ragione, vi partecipano. L’elaborato contiene, poi, recenti esempi concreti di project financing nelle infrastrutture primarie (autostrade) tra cui il progetto di costruzione e la successiva gestione dell’autostrada regionale Medio Padana veneta, dell’autostrada regionale Cispadana, e dell’autostrada “Nogara-mare”. L’ultimo parte della tesi è stata infine incentrata sull’analisi delle più recenti pronunce giurisprudenziali in materia di project financing. In particolare, si ha avuto modo di analizzare il fenomeno dello jus poenitendi dell’amministrazione aggiudicatrice, nonché, più in generale gli eventi che possono negativamente incidere sulla finanza di progetto (mancata aggiudicazione, risoluzione del contratto di gestione, ecc.).

A novel functional renormalization group framework for gauge theories and gravity

In this thesis we develop further the functional renormalization group (RG) approach to quantum field theory (QFT) based on the effective average action (EAA) and on the exact flow equation that it satisfies. The EAA is a generalization of the standard effective action that interpolates smoothly between the bare action for krightarrowinfty and the standard effective action rnfor krightarrow0. In this way, the problem of performing the functional integral is converted into the problem of integrating the exact flow of the EAA from the UV to the IR. The EAA formalism deals naturally with several different aspects of a QFT. One aspect is related to the discovery of non-Gaussian fixed points of the RG flow that can be used to construct continuum limits. In particular, the EAA framework is a useful setting to search for Asymptotically Safe theories, i.e. theories valid up to arbitrarily high energies. A second aspect in which the EAA reveals its usefulness are non-perturbative calculations. In fact, the exact flow that it satisfies is a valuable starting point for devising new approximation schemes. In the first part of this thesis we review and extend the formalism, in particular we derive the exact RG flow equation for the EAA and the related hierarchy of coupled flow equations for the proper-vertices. We show how standard perturbation theory emerges as a particular way to iteratively solve the flow equation, if the starting point is the bare action. Next, we explore both technical and conceptual issues by means of three different applications of the formalism, to QED, to general non-linear sigma models (NLsigmaM) and to matter fields on curved spacetimes. In the main part of this thesis we construct the EAA for non-abelian gauge theories and for quantum Einstein gravity (QEG), using the background field method to implement the coarse-graining procedure in a gauge invariant way. We propose a new truncation scheme where the EAA is expanded in powers of the curvature or field strength. Crucial to the practical use of this expansion is the development of new techniques to manage functional traces such as the algorithm proposed in this thesis. This allows to project the flow of all terms in the EAA which are analytic in the fields. As an application we show how the low energy effective action for quantum gravity emerges as the result of integrating the RG flow. In any treatment of theories with local symmetries that introduces a reference scale, the question of preserving gauge invariance along the flow emerges as predominant. In the EAA framework this problem is dealt with the use of the background field formalism. This comes at the cost of enlarging the theory space where the EAA lives to the space of functionals of both fluctuation and background fields. In this thesis, we study how the identities dictated by the symmetries are modified by the introduction of the cutoff and we study so called bimetric truncations of the EAA that contain both fluctuation and background couplings. In particular, we confirm the existence of a non-Gaussian fixed point for QEG, that is at the heart of the Asymptotic Safety scenario in quantum gravity; in the enlarged bimetric theory space where the running of the cosmological constant and of Newton's constant is influenced by fluctuation couplings.

Il presidente del consiglio dei ministri nell'ordinamento vigente e nelle prospettive di riforma

“Il Presidente del Consiglio dei Ministri nell'ordinamento vigente e nelle proposte di riforma”. La tesi si propone di ricostruire i caratteri propri della figura giuridica del Presidente del Consiglio nell’ordinamento vigente, sino alla analisi delle più recenti proposte di riforma costituzionale in tema. La dimensione analitico-sistematica proposta è stata sviluppata in riferimento alle concrete dinamiche economiche, politiche ed istituzionali, in relazione alle quali si è inteso verificare il tipo di rapporto tra esigenze di stabilizzazione del ciclo economico ed esigenze di stabilizzazione degli esecutivi, dando il dovuto rilievo al processo di integrazione della Unione Europea, come “motore” delle istanze di riforma del sistema economico ed istituzionale. Nel primo capitolo, si sono esplicitate le chiavi metodologiche secondo le quali si è inteso sviluppare il percorso di ricerca. Nel secondo capitolo si è operata una ricostruzione del quadro ordinamentale a base statutaria, come termine iniziale per poter cogliere al meglio la configurazione del ruolo poi assunta nell’ordinamento repubblicano; ciò come premessa necessaria ad una corretta ricostruzione diacronica, di tutti gli elementi rilevanti per poter comprendere la portata delle proposte attuali. Nel terzo capitolo, si è cercato di ricostruire il ruolo del presidente del consiglio, collocandolo nel quadro della dinamica attuazione/inattuazione dell’ordinamento repubblicano e alla luce dei caratteri del sistema politico, in modo da poter coniugare i tratti evolutivi imposti all’inquadramento della figura dalle dinamiche del sistema politico; così da poter conseguentemente cogliere gli elementi genetici di un dibattito politico istituzionale, che genera proposte di riforma organica, mediante l’analisi degli atti delle commissioni Parlamentari per le riforme. Nel quarto capitolo, a partire dalla apertura di una fase di c.d. “transizione”, si ricostruiscono le proposte specificamente finalizzate al riassetto del Presidente del Consiglio prodotte dalle commissioni parlamentari per le riforme, segnando le tappe di un percorso ancora aperto e dall’esito incerto.

I "governi del Presidente"

Gli avvenimenti politico-istituzionali degli ultimi anni hanno determinato un vivace dibattito sulla questione dei cc.dd. “governi del Presidente”, con cui si suole far riferimento ad Esecutivi il cui procedimento di formazione e le cui crisi registrano un interventismo del Presidente della Repubblica superiore a quello richiesto e/o consentito dal dettato costituzionale. Obiettivo dell’elaborato è duplice: fornire un tentativo definitorio della categoria “governi del Presidente”, nonché valutare la compatibilità di questa con la forma di governo parlamentare, soprattutto in considerazione dei recenti sviluppi delle dinamiche politico-istituzionali italiane. Sulla base di questo presupposto, nel presente lavoro si procede a una ricostruzione dell’evoluzione della prassi e delle consuetudini costituzionali in merito all’esercizio dei poteri presidenziali nella gestione delle crisi di governo, con particolare riferimento al procedimento di formazione dell’Esecutivo. La tesi si presenta articolata in due parti, corrispondenti a due differenti periodi storici (cc.dd. Prima e Seconda Repubblica), organizzate per capitoli, relativi alle principali fasi di evoluzione del sistema politico attraversate nel corso della storia della Repubblica. Questa scelta si giustifica in ragione del fatto che il modus operandi del Presidente della Repubblica risulta fortemente condizionato dai mutamenti del contesto politico-istituzionale. Nei singoli paragrafi, dedicati ai presidenti, vengono trattati l’elezione del Presidente, le modalità di formazione dei governi nominati, nonché ulteriori temi la cui disamina è stata ritenuta opportuna allo scopo di fornire una contestualizzazione più adeguata dell’analisi svolta (utilizzo del potere di esternazione e di scioglimento delle Camere, gestione delle attività di politica interna e politica estera, principali avvenimenti dei periodi storici considerati, e così via).

The market manipulation regime in the European Union

Market manipulation is an illegal practice that enables a person can profit from practices that artificially raise or lower the prices of an instrument in the financial markets. Its prohibition is based on the 2003 Market Abuse Directive in the EU. The current market manipulation regime was broadly considered as a big success except for enforcement and supervisory inconsistencies in the Member States at the initial. A review of the market manipulation regime began at the end of 2007, which became quickly incorporated into the wider EU crisis-era reform program. A number of weaknesses of current regime have been identified, which include regulatory gaps caused by the development of trading venues and financial products, regulatory gaps concerning cross-border and cross-markets manipulation (particular commodity markets), legal uncertainty as a result of various implementation, and inefficient supervision and enforcement. On 12 June 2014, a new regulatory package of market abuse, Market Abuse Regulation and Directive on criminal sanctions for market abuse, has been adopted. And several changes will be made concerning the EU market manipulation regime. A wider scope of the regime and a new prohibition of attempted market manipulation will ensure the prevention of market manipulation at large. The AMPs will be subject to strict scrutiny of ESMA to reduce divergences in implementation. In order to enhance efficiency of supervision and enforcement, powers of national competent authorities will be strengthened, ESMA is imposed more power to settle disagreement between national regulators, and the administrative and criminal sanctioning regimes are both further harmonized. In addition, the protection of fundamental rights is stressed by the new market manipulation regime, and some measures are provided to guarantee its realization. Further, the success EU market manipulation regime could be of significant reference to China, helping China to refine its immature regime.

Decomposing Blaschke Products And Polynomials

The goal of this paper is to contribute to the understanding of complex polynomials and Blaschke products, two very important function classes in mathematics. For a polynomial, $f,$ of degree $n,$ we study when it is possible to write $f$ as a composition $f=g\circ h$, where $g$ and $h$ are polynomials, each of degree less than $n.$ A polynomial is defined to be \emph{decomposable }if such an $h$ and $g$ exist, and a polynomial is said to be \emph{indecomposable} if no such $h$ and $g$ exist. We apply the results of Rickards in \cite{key-2}. We show that $$C_{n}=\{(z_{1},z_{2},...,z_{n})\in\mathbb{C}^{n}\,|\,(z-z_{1})(z-z_{2})...(z-z_{n})\,\mbox{is decomposable}\},$$ has measure $0$ when considered a subset of $\mathbb{R}^{2n}.$ Using this we prove the stronger result that $$D_{n}=\{(z_{1},z_{2},...,z_{n})\in\mathbb{C}^{n}\,|\,\mbox{There exists\,}a\in\mathbb{C}\,\,\mbox{with}\,\,(z-z_{1})(z-z_{2})...(z-z_{n})(z-a)\,\mbox{decomposable}\},$$ also has measure zero when considered a subset of $\mathbb{R}^{2n}.$ We show that for any polynomial $p$, there exists an $a\in\mathbb{C}$ such that $p(z)(z-a)$ is indecomposable, and we also examine the case of $D_{5}$ in detail. The main work of this paper studies finite Blaschke products, analytic functions on $\overline{\mathbb{D}}$ that map $\partial\mathbb{D}$ to $\partial\mathbb{D}.$ In analogy with polynomials, we discuss when a degree $n$ Blaschke product, $B,$ can be written as a composition $C\circ D$, where $C$ and $D$ are finite Blaschke products, each of degree less than $n.$ Decomposable and indecomposable are defined analogously. Our main results are divided into two sections. First, we equate a condition on the zeros of the Blaschke product with the existence of a decomposition where the right-hand factor, $D,$ has degree $2.$ We also equate decomposability of a Blaschke product, $B,$ with the existence of a Poncelet curve, whose foci are a subset of the zeros of $B,$ such that the Poncelet curve satisfies certain tangency conditions. This result is hard to apply in general, but has a very nice geometric interpretation when we desire a composition where the right-hand factor is degree 2 or 3. Our second section of finite Blaschke product results builds off of the work of Cowen in \cite{key-3}. For a finite Blaschke product $B,$ Cowen defines the so-called monodromy group, $G_{B},$ of the finite Blaschke product. He then equates the decomposability of a finite Blaschke product, $B,$ with the existence of a nontrivial partition, $\mathcal{P},$ of the branches of $B^{-1}(z),$ such that $G_{B}$ respects $\mathcal{P}$. We present an in-depth analysis of how to calculate $G_{B}$, extending Cowen's description. These methods allow us to equate the existence of a decomposition where the left-hand factor has degree 2, with a simple condition on the critical points of the Blaschke product. In addition we are able to put a condition of the structure of $G_{B}$ for any decomposable Blaschke product satisfying certain normalization conditions. The final section of this paper discusses how one can put the results of the paper into practice to determine, if a particular Blaschke product is decomposable. We compare three major algorithms. The first is a brute force technique where one searches through the zero set of $B$ for subsets which could be the zero set of $D$, exhaustively searching for a successful decomposition $B(z)=C(D(z)).$ The second algorithm involves simply examining the cardinality of the image, under $B,$ of the set of critical points of $B.$ For a degree $n$ Blaschke product, $B,$ if this cardinality is greater than $\frac{n}{2}$, the Blaschke product is indecomposable. The final algorithm attempts to apply the geometric interpretation of decomposability given by our theorem concerning the existence of a particular Poncelet curve. The final two algorithms can be implemented easily with the use of an HTML

Multi-stage ytterbium fiber-amplifier seeded by a gain-switched laser diode

We demonstrated all-fiber amplification of 11 ps pulses from a gain-switched laser diode at 1064 nm. The diode was driven at a repetition rate of 40 MHz and delivered 13 µW of fiber-coupled average output power. For the low output pulse energy of 325 fJ we have designed a multi-stage core pumped pre-amplifier in order to keep the contribution of undesired amplified spontaneous emission as low as possible. By using a novel time-domain approach for determining the power spectral density ratio (PSD) of signal to noise, we identified the optimal working point for our pre-amplifier. After the pre-amplifier we reduced the 40 MHz repetition rate to 1 MHz using a fiber coupled pulse-picker. The final amplification was done with a cladding pumped Yb-doped large mode area fiber and a subsequent Yb-doped rod-type fiber. With our setup we reached a total gain of 73 dB, resulting in pulse energies of >5.6 µJ and peak powers of >0.5 MW. The average PSD-ratio of signal to noise we determined to be 18/1 at the output of the final amplification stage.

Genetic association studies under the population stratification, family pedigree and application to genome-wide association studies

This dissertation has three separate parts: the first part deals with the general pedigree association testing incorporating continuous covariates; the second part deals with the association tests under population stratification using the conditional likelihood tests; the third part deals with the genome-wide association studies based on the real rheumatoid arthritis (RA) disease data sets from Genetic Analysis Workshop 16 (GAW16) problem 1. Many statistical tests are developed to test the linkage and association using either case-control status or phenotype covariates for family data structure, separately. Those univariate analyses might not use all the information coming from the family members in practical studies. On the other hand, the human complex disease do not have a clear inheritance pattern, there might exist the gene interactions or act independently. In part I, the new proposed approach MPDT is focused on how to use both the case control information as well as the phenotype covariates. This approach can be applied to detect multiple marker effects. Based on the two existing popular statistics in family studies for case-control and quantitative traits respectively, the new approach could be used in the simple family structure data set as well as general pedigree structure. The combined statistics are calculated using the two statistics; A permutation procedure is applied for assessing the p-value with adjustment from the Bonferroni for the multiple markers. We use simulation studies to evaluate the type I error rates and the powers of the proposed approach. Our results show that the combined test using both case-control information and phenotype covariates not only has the correct type I error rates but also is more powerful than the other existing methods. For multiple marker interactions, our proposed method is also very powerful. Selective genotyping is an economical strategy in detecting and mapping quantitative trait loci in the genetic dissection of complex disease. When the samples arise from different ethnic groups or an admixture population, all the existing selective genotyping methods may result in spurious association due to different ancestry distributions. The problem can be more serious when the sample size is large, a general requirement to obtain sufficient power to detect modest genetic effects for most complex traits. In part II, I describe a useful strategy in selective genotyping while population stratification is present. Our procedure used a principal component based approach to eliminate any effect of population stratification. The paper evaluates the performance of our procedure using both simulated data from an early study data sets and also the HapMap data sets in a variety of population admixture models generated from empirical data. There are one binary trait and two continuous traits in the rheumatoid arthritis dataset of Problem 1 in the Genetic Analysis Workshop 16 (GAW16): RA status, AntiCCP and IgM. To allow multiple traits, we suggest a set of SNP-level F statistics by the concept of multiple-correlation to measure the genetic association between multiple trait values and SNP-specific genotypic scores and obtain their null distributions. Hereby, we perform 6 genome-wide association analyses using the novel one- and two-stage approaches which are based on single, double and triple traits. Incorporating all these 6 analyses, we successfully validate the SNPs which have been identified to be responsible for rheumatoid arthritis in the literature and detect more disease susceptibility SNPs for follow-up studies in the future. Except for chromosome 13 and 18, each of the others is found to harbour susceptible genetic regions for rheumatoid arthritis or related diseases, i.e., lupus erythematosus. This topic is discussed in part III.

Acute lower gastrointestinal hemorrhage: minimally invasive management with microcatheter embolization

PURPOSE: To evaluate the efficacy of superselective embolization therapy in the management of acute lower gastrointestinal (LGI) hemorrhage, including any bleeding distal to the ligament of Treitz. MATERIALS AND METHODS: Between June and August 2007, 20 patients with acute LGI bleeding underwent superselective transcatheter arterial embolization (TAE) at the authors' institution. The bleeding had different causes. All patients were treated with use of microcatheters. The following embolic agents were used: microcoils (n = 16), polyvinyl alcohol (PVA) particles (n = 2), and a combination of microcoils and PVA particles (n = 2). Outcome measures included technical success (complete cessation of bleeding as documented at completion angiography), clinical success (resolution of signs or symptoms of LGI bleeding within 30 days after TAE), and the rate of major and minor complications. RESULTS: The identified bleeding sources were as follows: jejunal branch, branch of middle colic artery, branch of ileocolic artery, ileal branch, branch of left colic artery, branch of sigmoid artery, branch of the superior rectal artery, and branch of the middle rectal artery. Technical success with effective control of active bleeding was achieved in all patients (100%). Clinical success attributed to TAE was documented in 18 of the 20 patients (90%). Major complications included death due to pulmonary embolism, heart infarction, and multiorgan failure in the 3rd week after TAE; a procedure-related colonic infarction occurred in one patient. A minor complication occurred in one patient who developed a groin hematoma. CONCLUSIONS: Superselective embolization may be used for effective, minimally invasive control of acute LGI bleeding.

Work in Progress: Social Work, the State and Europe

Social work has had varying relationships with the nation state both over time and between different countries. From its early stages the occupation had both state sanctioned and voluntary streams. Its international dimension has been enhanced in the European context through policy and funding measures over the past few decades. During this period we have also seen the rise of globalising trends leading to questions about the ongoing powers of nation states. This paper examines some aspects of the relationship between social work and the state, taking into account the emergence of European and also international policies and frameworks. The paper focuses initially on migration as an example of a common trend; an area of policy with both national and European dimensions; and a field in which social professionals are engaged to varying degrees. Secondly, it considers the progress of the ‘professional project’ in Europe, using developments in five countries to illustrate some of the issues associated with ‘professionalization’. European and international frameworks may lead to some convergence in national understandings of the key roles of social workers and an enhanced sense of professional identity across nation states, despite very different starting points and current forms of organisation.

Stud.IP and ILIAS in an EU-Funded Project for the Middle East

In autumn 2005 InWEnt (Internationale Weiterbildung und Entwicklung/Capacity Building International gGmbH) on behalf of the EU invited to tender for three web based trainings (WBT). The precondition: either the open-source-platform Stud.IP or ILIAS should be used. The company data-quest decided not to offer the use of either Stud.IP or ILIAS, but both in combination - and won the contract. Several month later, the new learning environment with the combined powers of Stud.IP and ILIAS was ready to serve WBT-participants from all over the world. The following text describes the EU-Project "Efficient Management of Wastewater, its Treatment and Reuse in the Mediterranean Countries" (EMWater), the WBT concept and the experiences with the new Stud.IP-ILIAS-interface.

La división de las ciencias y el tema del hombre-microcosmos según algunos maestros de artes de París hacia 1250

En las divisiones de la ciencia provenientes de la Facultad de Artes de París, algunos maestros (Pseudo-Peckham, Iohannes Pagus) establecen conexiones entre las facultades del alma y los objetos del mundo propios a la actividad de cada una de tales facultades, determinando así las diversas ciencias que surgen a partir de estas relaciones. El enlace de estos elementos se hace posible dentro del marco del hombre como microcosmos que los maestros desarrollan a partir de adagios aristotélicos tomados del De anima y de la Física con la utilización de algunas fuentes neoplatónicas. Según los maestros de artes, el conocimiento de todas las cosas es asequible al hombre precisamente porque en él se encuentran, de alguna manera, el resumen y la presencia de todas las cosas.

Imágenes de entresiglos

El trabajo analiza una serie de crónicas y fotografías del entresiglos puertorriqueño (XIX-XX), llevadas a la escena pública internacional cuando, en virtud del Tratado de París que puso fin a la Guerra Hispanoamericana, la isla deja de ser colonia española y se convierte en posesión de los Estados Unidos. Construidas por viajeros norteamericanos que llegan a Puerto Rico para registrar el cambio de dominación y el rostro isleño, las imágenes verbales e iconográficas seleccionadas exhiben los poderes de una mirada imperial que justifica el programa expansionista y colonizador, subrayando los relieves de una tierra dominable, dispuesta a entregarse al nuevo amo.