Construcción de una teoría de "lo grande" : inteligencia acumulativa en la definición de una realidad aumentada

La tesis analiza los antecedentes y el contexto arquitectónico de aquellas obras que se pueden enmarcar dentro del concepto de lo Grande. Arrancando en los movimientos utópicos, megaestructuralistas o radicales de los años sesenta, nos conduce hasta conceptos, proyectos y teorías contemporáneos. Para ello es preciso, definir lo Grande no solo a través de cuestiones dimensionales, sino también de cambio de dimensión espacial y conceptual. Se estudian arquitecturas, que, una vez superado un cierto volumen, magnitud o grado de complejidad, se convierten en un ‘edificio grande’, adquiriendo propiedades de otra naturaleza, generando un cambio o salto entre escalas, o un desplazamiento entre campos, rompiendo los límites habituales de la escala, el tamaño u otras codificaciones con las que se categorizan los proyectos entre la ‘arquitectura’ y la ‘ciudad’. El cuerpo de tesis principal se estructura en dos secciones, ‘Genealogías y asociaciones’ y ‘Desplazamiento de conceptos’, y una Conclusión, que trata de compilar las consideraciones o conclusiones extraídas de lo anterior, construyendo así la propia teoría de lo Grande. Genealogías y asociaciones revisa las formas de conocimiento que contextualizan lo Grande, haciendo un barrido de las estructuras sociales, económicas y políticas, desde una perspectiva y un marco con influencia directa en la arquitectura. Recorre teorías, tesis y proyectos que reflexionan o trabajan en lo Grande y en los límites entre las escalas desde la década de los sesenta hasta hoy día. En ese barrido examina conceptos y condiciones capaces de abrir nuevos paradigmas y escenarios arquitectónicos. El contexto sociocultural que lo enmarca resulta crucial para definir posteriormente conceptos, en un barrido desde la cultura de masas a la sociedad de la información, repasando la influencia y repercusión que ha tenido la tecnología y la globalización en el desarrollo de la arquitectura. Por último, se estudian conceptos entre el espacio y a la política, mediante una análisis que enmarque las posiciones de apoyo, refuerzo o rechazo en la relación de la obra de arquitectura y la naturaleza política que esta adquiere por la mera condición de ser Grande. Desplazamiento de conceptos, ofrece condiciones y ejemplos que permiten definir las ‘propiedades’ de lo Grande, a través de una investigación teórica y analítica de las herramientas y estrategias que operan en estas escalas, para confirmar cómo, desarrollos aparentemente cuantitativos, pueden dar lugar a avances cualitativos o a mutaciones que permitan superar los paradigmas anteriores. El objetivo es la definición del conjunto de instrumentos, estrategias y operaciones que sintetizan los valores de cada concepto, con las que construir una ‘cosmogonía’ sobre el tema, apoyándose para ello en textos de referencia, proyectos paradigmáticos y conceptos derivados de los análisis. Los conceptos a estudio devienen directamente de ciertos atributos y características detectadas en las genealogías de lo Grande. Así, consideramos Grande a aquella arquitectura cuya escala y tamaño ha experimentado lo que definiremos como ‘cambio de dimensiones’, no solo a nivel dimensional, sino también perceptivo, técnico y contextual; su tamaño no solo depende de sus magnitudes sino también de la cantidad de materia que contiene el sistema o que circula por él; que tiene trazas, dotes y propiedades de infraestructura; que está instalada, y por tanto, es reactiva con el medio; por ello, es al mismo tiempo autónoma respecto al todo, aunque relacionada con él; un espacio capaz de aceptar la indeterminación de ciertas partes frente a la especificidad de otras, como forma de admitir la pérdida del control total y el detalle; por tanto, que ha desplazado la planificación y el diseño por la investigación programática y la estrategia operativa. En definitiva una arquitectura que desplaza o muta conceptos, atributos y estrategias de otras disciplinas, de los saltos entre escalas y de los nuevos programas. ABSTRACT The thesis will analyze the architectural background and context of those works which can be framed within the concept of Bigness. From the utopian, megastructuralism and radical movements of the sixties, it will lead to contemporary concepts, projects and theories, and ultimately define a theory of Bigness. It will be necessary to define Bigness or the Large, not only in terms of size, but also considering change in spatial and conceptual dimensions. Its case studies are architectures which, surpassing a certain volume, magnitude or degree of complexity, become a ‘large building’ and acquire characteristics of another nature. This generates a change or ‘leap’ in scale, or a displacement in fields, breaking the conventional limits of scale, size and other codes used to categorise projects within ‘architecture’ or the ‘city’. The main body of the thesis is structured into two sections, Genealogies and Associations and Displacement of Concepts, and the Conclusion, which will compile the considerations and conclusions extracted from the previous parts, building the actual theory of Bigness. The first section, Genealogies and Associations, will review the forms of knowledge which contextualize the Large, covering a spectrum of social, economic and political structures from the framework and perspective of their direct influence on architecture. It will account theories, thesis and projects which reflect or work on Bigness and on the limits between scales from the sixties to today, examining those concepts and conditions which may be useful to unfold new settings and paradigms. As the sociocultural context will also prove crucial in order to later define concepts, a broad sweep will cover from the mass society to the information society, revising the influence and repercussions of technology and globalization on the development of architecture. Lastly, it will study concepts in-between space and politics, by means of a study framing positions of support, assistance or rejection towards the work of architecture, and the political nature the work is given only due to its condition of being Big. The following section, Displacement of Concepts, provides conditions and examples which allow the definition of the ‘characteristics’ of Bigness by means of a theoretical and analytical investigation of the tools and strategies which operate on these scales. This is in order to confirm how apparently quantitative developments can lead to qualitative advances or to mutations that enable the overcoming of previous paradigms. The objective is to define the set of strategies, operations and tools, which synthesize the values of each concept; the grounding for a “cosmogony” of the subject, underpinned by relevant reference texts, paradigmatic projects and concepts stemming from the analyses. The concepts of study arise directly from certain attributes and characteristics detected in Bigness. For this purpose, it is that architecture whose dimensions and size have experienced what we will define as a ‘change of dimensions’, not only of size, but also perceptual, technical and contextual;its size depends not only on its magnitude but also the amount of material that contains or flows through system; which possesses traits, faculties and features of an infrastructure; which is installed, and is therefore reactive with its surroundings; due to this, it will be autonomous with respect to the whole and yet related to it; a space which can accept the undetermined nature of some of its parts as well as the specificity of other parts, acknowledging the loss of total control and detail; and thus, which has displaced planning and design with operational strategies. In conclusion, an architecture that displaces or mutates concepts, attributes and strategies stemming from other disciplines, from the jumps between scales, and from the new programs.

En un intervalo del límite : una nueva lectura del movimiento moderno desde la realidad virtual de lo ambiguo

Esta tesis doctoral busca estudiar el espacio desde la premisa de que el espacio es, fundamentalmente, lo intermedio. El entre, lo que hay entre las cosas mismas y que les da, precisamente, su definición como cosas en un constante proceso de delimitación. Este entre, lo que hay entre las cosas, no es sin embargo un resto que queda, sino bien al contrario el principio activo que hace que las cosas, desde lo que hay alrededor, se configuren en su ser sensible y puedan percibirse. El entre, lo intermedio, no es así una línea, un corte puro, sino un intervalo, un espacio en sí mismo, un ámbito en que se desarrolla un proceso. Es por tanto un espacio de formación, en el que las cosas aún no son y ya están siendo, un intervalo ambiguo pleno de virtualidades, unas desplegadas otras que permanecen en espera, siempre en movimiento. Es la hipótesis principal de esta tesis que en el llamado Movimiento Moderno en la arquitectura del siglo veinte esta condición ambigua del límite se pone de manifiesto como la raíz articuladora de los cambios espaciales y formales que definen su ser y su estética. Para desarrollar esta hipótesis, se parte de una doble premisa: por una parte, como un entre que es en sí misma, la arquitectura se encuentra delimitada por las disciplinas artísticas contemporáneas, especialmente pintura y escultura y a la vez las delimita. Por tanto, se explorarán una serie de momentos claves en las vanguardias de comienzos del siglo veinte en paralelo a una serie de arquitecturas contemporáneas para estudiar esta doble dialéctica entre límites. Por otra parte, y entendiendo que lo propio de la arquitectura es el espacio, se estudiarán en profundidad las concepciones espaciales que en la física y la estética del finales del siglo diecinueve y principios del veinte se desarrollan, para comprender cómo estas nuevas concepciones, centradas en las ideas de relatividad y de espacio-tiempo como magnitudes interlimitadas, determinan a su vez las concepciones espaciales que se desarrollan simultáneamente en las artes plásticas y en la arquitectura. La tríada espacio/tiempo/luz regirá este recorrido, en un doble camino: a través de la física y la teoría del arte, y a través de la arquitectura y las artes plásticas. Se trata por tanto de incardinar la arquitectura en su contexto artístico y científico, y comprobar cómo la comprensión del espacio como un entre, como un intervalo del límite y no como un absoluto trascendente, se generaliza en dichos ámbitos en una exploración paralela que condiciona los resultados en todos ellos y que define, por tanto, la arquitectura de la modernidad como una arquitectura del entre. El encuadre enmarca como motivo principal el Movimiento Moderno a través de la figura de Le Corbusier. Se muestra el modo en que los recursos y mecanismos empleados provocan el encuentro del espacio indecible a través de la polifonía de las artes. Desde el espaciamiento del límite, su borradura, su ambigüedad, producidos mediante el entrelazamiento de los recursos artísticos, la continuidad de lo lineal, el encabalgamiento, el maridaje, la ambivalencia, la relatividad del color y la luz, el intersticio. Ello se analiza a través de la obra de le Corbusier, destacando la dialéctica entre Le Cheminée y Nature morte aux nombreux objets; Ma maison y el pabellón del Zurichhorn; Unité y L’espace indicible. Aclaradas las premisas fundamentales y las consecuencias inmediatas para la arquitectura del Movimiento Moderno, la cuarta parte y final de la tesis, mucho más breve que las anteriores, expone una primera aproximación a las consecuencias que todo esto ha tenido en un momento liminal también: el comienzo de la postmodernidad. En realidad se trata de una apertura a lo que ha de venir, pues establecida la operatividad de la hipóteisi inicial, se trata aquí solamente de abrir el camino a una interpretación que en realidad escapa del alcance de esta tesis. Así se deja apuntado cómo, a través de la obra de tres arquitectos, teóricos y artistas trabajando en los años setenta y comienzos de los ochenta del pasado siglo, una comprensión más clara de la revolución moderna precipitada por esta nueva comprensión del espacio como límite-entre queda patente. Chamberworks de Daniel Libeskind, Wexner Center for the Visual Arts de Peter Eisenman y Manhattan Transcripts de Bernard Tschumi servirían de privilegiados ejemplo. Como queda patente que las consecuencias de todo ello aún las estamos sintiendo en nuestra contemporaneidad. ABSTRACT This thesis aims to study the space from the premise that space is mainly the in-between. The in-between, what is in-between the things themselves and gives them precisely its definition as things in a constant process of delimitation. This in-between, what is in between things, is not a remnant that remains, but on the contrary it is the active ingredient that produces things from what is around, that configures them in a sensitive to be perceived. The in-between, the intermediate, is not a line, a pure cut, but an interval, a space in itself, an area in which a process is developed. It is therefore a space in development, where things are still not and already been, delimiting an ambiguous range full of potentialities, some present and others that remain only as virtualities. It is the main hypothesis of this thesis that in the so-called Modern Movement in the architecture of the twentieth century this ambiguous boundary condition is revealed as the result of the articulatation of spatial and formal changes. To develop this hypothesis, I posit this double premise: On the one hand, as an in-between which is in itself, architecture is defined by contemporary artistic disciplines, especially painting and sculpture and simultaneously defines them. Therefore, a number of key moments in the avantgarde of the early twentieth century in parallel with a number of contemporary architecture to study this double dialectic between boundaries will be explored. On the other hand, and considering that the “essence” of the architecture is space, I will study in depth the spatial concepts in physics and aesthetics of late-nineteenth century and early twentieth century to understand how these new concepts centered on the ideas of relativity and space-time as interlimited magnitudes in turn determine the spatial conceptions that take place simultaneously in the visual arts and architecture. The space / time / light triad governs this journey in a double way: through physics and theory of art, and through architecture and the arts. The aim is to anchor architecture in its artistic and scientific context, and to see how the understanding of space as an in-between interval and not as an absolute transcendent determines the results in all of them, defining, therefore, the architecture of modernity as an architecture of the in-between. The frame of the study is centered in the modern movement through the figure of Le Corbusier and how rthe different resources and mechanisms employed provoke an unspeakable space of encounter through the polyphony of the arts. From the spacing of the limit, its erasure, its ambiguity, produced by the intertwining of artistic resources to continuity of the linear, the marriage, the ambivalence, the relativity of color and light, the gap. All this is analyzed through the work of Le Corbusier, highlighting the dialectic between Le Cheminée and Nature morte aux nombreux objets, Ma maison and Zürichhorn pavilion, Unité and L’espace indicible. Once the basic premises and immediate consequences for the architecture of the Modern Movement are set, the fourth and final part of the thesis aims to explore the impact that all this has had in another liminal time: the beginning of postmodernism. Of course, this part is shorter, in fact it is more a prospective survey and an opening of possibilities than a truly articulated body of theory, since the conceptual core of this thesis has been developed in the central part. Hence, through the work of three architects, theorists and artists working in the seventies and early eighties of last century, a clearer understanding of the modern revolution precipitated by this new understanding of space as a boundary- between is proposed. Chamberworks by Daniel Libeskind, Wexner Center for the Visual Arts by Peter Eisenman and Manhattan Transcripts by Bernard Tschumi will exemplify this approach. The consequences of all this are still haunting our contemporaneity.

Two terrestrial records of rapid climatic change during the glacial–Holocene transition (14,000– 9,000 calendar years B.P.) from Europe

Two independent multidisciplinary studies of climatic change during the glacial–Holocene transition (ca. 14,000–9,000 calendar yr B.P.) from Norway and Switzerland have assessed organism responses to the rapid climatic changes and made quantitative temperature reconstructions with modern calibration data sets (transfer functions). Chronology at Kråkenes, western Norway, was derived from calibration of a high-resolution series of 14C dates. Chronologies at Gerzensee and Leysin, Switzerland, were derived by comparison of δ18O in lake carbonates with the δ18O record from the Greenland Ice Core Project. Both studies demonstrate the sensitivity of terrestrial and aquatic organisms to rapid temperature changes and their value for quantitative reconstruction of the magnitudes and rates of the climatic changes. The rates in these two terrestrial records are comparable to those in Greenland ice cores, but the actual temperatures inferred apply to the terrestrial environments of the two regions.

A quantitative method for evaluating the stabilities of nucleic acids

We report a general method for screening, in solution, the impact of deviations from canonical Watson-Crick composition on the thermodynamic stability of nucleic acid duplexes. We demonstrate how fluorescence resonance energy transfer (FRET) can be used to detect directly free energy differences between an initially formed “reference” duplex (usually a Watson-Crick duplex) and a related “test” duplex containing a lesion/alteration of interest (e.g., a mismatch, a modified, a deleted, or a bulged base, etc.). In one application, one titrates into a solution containing a fluorescently labeled, FRET-active, reference duplex, an unlabeled, single-stranded nucleic acid (test strand), which may or may not compete successfully to form a new duplex. When a new duplex forms by strand displacement, it will not exhibit FRET. The resultant titration curve (normalized fluorescence intensity vs. logarithm of test strand concentration) yields a value for the difference in stability (free energy) between the newly formed, test strand-containing duplex and the initial reference duplex. The use of competitive equilibria in this assay allows the measurement of equilibrium association constants that far exceed the magnitudes accessible by conventional titrimetric techniques. Additionally, because of the sensitivity of fluorescence, the method requires several orders of magnitude less material than most other solution methods. We discuss the advantages of this method for detecting and characterizing any modification that alters duplex stability, including, but not limited to, mutagenic lesions. We underscore the wide range of accessible free energy values that can be defined by this method, the applicability of the method in probing for a myriad of nucleic acid variations, such as single nucleotide polymorphisms, and the potential of the method for high throughput screening.

Assessment and discrimination of odor stimuli in rat olfactory bulb by dynamic functional MRI

Dynamic blood oxygenation level-dependent functional MRI was applied at 7 T in the rat olfactory bulb (OB) with pulsed delivery of iso-amyl acetate (IAA) and limonene. Acquisition times for single-slice and whole OB data were 8 and 32 s, respectively, with spatial resolution of 220 × 220 × 250 μm. On an intrasubject basis, short IAA exposures of 0.6 min separated by 3.5-min intervals induced reproducible spatial activity patterns (SAPs) in the olfactory nerve layer, glomerular layer, and external plexiform layer. During long exposures (≈10 min), the initially dominant dorsal SAPs declined in intensity and area, whereas in some OB regions, the initially weak ventral/lateral SAPs increased first and then decreased. The SAPs of different concentrations were topologically similar, which implies that whereas an odor at various concentrations activates the same subsets of receptor cells, different concentrations are assessed and discriminated by variable magnitudes of laminarspecific activations. IAA and limonene reproducibly activated different subsets of receptor cells with some overlaps. Whereas qualitative topographical agreement was observed with results from other methods, the current dynamic blood oxygenation level-dependent functional MRI results can provide quantitative SAPs of the entire OB.

ACTIVITY: a database on DNA/RNA sites activity adapted to apply sequence-activity relationships from one system to another

ACTIVITY is a database on DNA/RNA site sequences with known activity magnitudes, measurement systems, sequence-activity relationships under fixed experimental conditions and procedures to adapt these relationships from one measurement system to another. This database deposits information on DNA/RNA affinities to proteins and cell nuclear extracts, cutting efficiencies, gene transcription activity, mRNA translation efficiencies, mutability and other biological activities of natural sites occurring within promoters, mRNA leaders, and other regulatory regions in pro- and eukaryotic genomes, their mutant forms and synthetic analogues. Since activity magnitudes are heavily system-dependent, the current version of ACTIVITY is supplemented by three novel sub-databases: (i) SYSTEM, measurement systems; (ii) KNOWLEDGE, sequence-activity relationships under fixed experimental conditions; and (iii) CROSS_TEST, procedures adapting a relationship from one measurement system to another. These databases are useful in molecular biology, pharmacogenetics, metabolic engineering, drug design and biotechnology. The databases can be queried using SRS and are available through the Web, http://wwwmgs.bionet.nsc.ru/systems/Activity/.

Importance of anchor genomes for any plant genome project

Progress in agricultural and environmental technologies is hampered by a slower rate of gene discovery in plants than animals. The vast pool of genes in plants, however, will be an important resource for insertion of genes, via biotechnological procedures, into an array of plants, generating unique germ plasms not achievable by conventional breeding. It just became clear that genomes of grasses have evolved in a manner analogous to Lego blocks. Large chromosome segments have been reshuffled and stuffer pieces added between genes. Although some genomes have become very large, the genome with the fewest stuffer pieces, the rice genome, is the Rosetta Stone of all the bigger grass genomes. This means that sequencing the rice genome as anchor genome of the grasses will provide instantaneous access to the same genes in the same relative physical position in other grasses (e.g., corn and wheat), without the need to sequence each of these genomes independently. (i) The sequencing of the entire genome of rice as anchor genome for the grasses will accelerate plant gene discovery in many important crops (e.g., corn, wheat, and rice) by several orders of magnitudes and reduce research and development costs for government and industry at a faster pace. (ii) Costs for sequencing entire genomes have come down significantly. Because of its size, rice is only 12% of the human or the corn genome, and technology improvements by the human genome project are completely transferable, translating in another 50% reduction of the costs. (iii) The physical mapping of the rice genome by a group of Japanese researchers provides a jump start for sequencing the genome and forming an international consortium. Otherwise, other countries would do it alone and own proprietary positions.

Mechanical bases of frequency tuning and neural excitation at the base of the cochlea: Comparison of basilar-membrane vibrations and auditory-nerve-fiber responses in chinchilla

We review the mechanical origin of auditory-nerve excitation, focusing on comparisons of the magnitudes and phases of basilar-membrane (BM) vibrations and auditory-nerve fiber responses to tones at a basal site of the chinchilla cochlea with characteristic frequency ≈ 9 kHz located 3.5 mm from the oval window. At this location, characteristic frequency thresholds of fibers with high spontaneous activity correspond to magnitudes of BM displacement or velocity in the order of 1 nm or 50 μm/s. Over a wide range of stimulus frequencies, neural thresholds are not determined solely by BM displacement but rather by a function of both displacement and velocity. Near-threshold, auditory-nerve responses to low-frequency tones are synchronous with peak BM velocity toward scala tympani but at 80–90 dB sound pressure level (in decibels relative to 20 microPascals) and at 100–110 dB sound pressure level responses undergo two large phase shifts approaching 180°. These drastic phase changes have no counterparts in BM vibrations. Thus, although at threshold levels the encoding of BM vibrations into spike trains appears to involve only relatively minor signal transformations, the polarity of auditory-nerve responses does not conform with traditional views of how BM vibrations are transmitted to the inner hair cells. The response polarity at threshold levels, as well as the intensity-dependent phase changes, apparently reflect micromechanical interactions between the organ of Corti, the tectorial membrane and the subtectorial fluid, and/or electrical and synaptic processes at the inner hair cells.

Intermediate-term earthquake prediction.

An earthquake of magnitude M and linear source dimension L(M) is preceded within a few years by certain patterns of seismicity in the magnitude range down to about (M - 3) in an area of linear dimension about 5L-10L. Prediction algorithms based on such patterns may allow one to predict approximately 80% of strong earthquakes with alarms occupying altogether 20-30% of the time-space considered. An area of alarm can be narrowed down to 2L-3L when observations include lower magnitudes, down to about (M - 4). In spite of their limited accuracy, such predictions open a possibility to prevent considerable damage. The following findings may provide for further development of prediction methods: (i) long-range correlations in fault system dynamics and accordingly large size of the areas over which different observed fields could be averaged and analyzed jointly, (ii) specific symptoms of an approaching strong earthquake, (iii) the partial similarity of these symptoms worldwide, (iv) the fact that some of them are not Earth specific: we probably encountered in seismicity the symptoms of instability common for a wide class of nonlinear systems.

Implications of fault constitutive properties for earthquake prediction.

The rate- and state-dependent constitutive formulation for fault slip characterizes an exceptional variety of materials over a wide range of sliding conditions. This formulation provides a unified representation of diverse sliding phenomena including slip weakening over a characteristic sliding distance Dc, apparent fracture energy at a rupture front, time-dependent healing after rapid slip, and various other transient and slip rate effects. Laboratory observations and theoretical models both indicate that earthquake nucleation is accompanied by long intervals of accelerating slip. Strains from the nucleation process on buried faults generally could not be detected if laboratory values of Dc apply to faults in nature. However, scaling of Dc is presently an open question and the possibility exists that measurable premonitory creep may precede some earthquakes. Earthquake activity is modeled as a sequence of earthquake nucleation events. In this model, earthquake clustering arises from sensitivity of nucleation times to the stress changes induced by prior earthquakes. The model gives the characteristic Omori aftershock decay law and assigns physical interpretation to aftershock parameters. The seismicity formulation predicts large changes of earthquake probabilities result from stress changes. Two mechanisms for foreshocks are proposed that describe observed frequency of occurrence of foreshock-mainshock pairs by time and magnitude. With the first mechanism, foreshocks represent a manifestation of earthquake clustering in which the stress change at the time of the foreshock increases the probability of earthquakes at all magnitudes including the eventual mainshock. With the second model, accelerating fault slip on the mainshock nucleation zone triggers foreshocks.

Detection of sub-8-nm movements of kinesin by high-resolution optical-trap microscopy.

Kinesin is a molecular motor that transports organelles along microtubules. This enzyme has two identical 7-nm-long motor domains, which it uses to move between consecutive tubulin binding sites spaced 8 nm apart along a microtubular protofilament. The molecular mechanism of this movement, which remains to be elucidated, may be common to all families of motor proteins. In this study, a high-resolution optical-trap microscope was used to measure directly the magnitude of abrupt displacements produced by a single kinesin molecule transporting a microscopic bead. The distribution of magnitudes reveals that kinesin not only undergoes discrete 8-nm movements, in agreement with previous work [Svoboda, K., Schmidt, C. F., Schnapp, B. J. & Block, S.M. (1993) Nature (London) 365, 721-727], but also frequently exhibits smaller movements of about 5 nm. A possible explanation for these unexpected smaller movements is that kinesin's movement from one dimer to the next along a protofilament involves at least two distinct events in the mechanical cycle.

Supercondutividade em ligas de Ta1-xZrx

No presente estudo, amostras policristalinas ricas em Ta e com estequiometrias Ta1-xZrx; x < 0.15; foram preparadas através da mistura apropriada dos elementos metálicos, os quais foram fundidos em forno a arco elétrico sobre uma placa de cobre refrigerada a água e sob atmosfera de argônio de alta pureza. Os padrões de difração de raios-X das ligas, como fundidas (as cast) e tratadas termicamente a 850 °C por 24 h, revelaram a ocorrência de uma estrutura cristalina cúbica de corpo centrada bcc, tipo W, e parâmetros de rede que aumentam suavemente com o aumento do teor de Zr nas ligas. Medidas de susceptibilidade magnética dc, conduzidas nas condições de resfriamento da amostra em campo zero (ZFC) e do resfriamento com o campo magnético aplicado (FC), indicaram que supercondutividade volumétrica é observada abaixo de ~ 5.8, 6.9, 7.0 K em amostras com x = 0.05, 0.08, e 0.10, respectivamente. Essas temperaturas críticas supercondutoras são bastante superiores àquela observada no Ta elementar ~ 4.45 K. Medidas de resistividade elétrica na presença de campos magnéticos aplicados de até 9 T confirmaram a temperatura crítica supercondutora das amostras estudadas. O campo crítico superior Hc2 e o comprimento de coerência E foram estimados a partir dos dados de magnetorresistência. Os valores estimados de Hc2 foram de ~ 0.46, 1.78, 3.85 e 3.97 T, resultando em valores de E ~ 26.0, 13.6, 9.2 e 9.1 nm para as ligas as cast com x = 0.00, 0.05, 0.08 e 0.10, respectivamente. A partir dos dados experimentais do calor específico Cp das ligas, magnitudes estimadas do salto em Cp nas vizinhanças das transições supercondutoras indicaram valores maiores que o previsto pela teoria BCS. Utilizando as equações analíticas derivadas da teoria do acoplamento forte da supercondutividade foi então proposto que o aumento da temperatura de transição supercondutora nas ligas devido a substituição parcial do Ta por Zr está intimamente relacionado ao aumento do acoplamento elétron-fônon, visto que a densidade de estados eletrônicos no nível de Fermi foi estimada ser essencialmente constante através da série Ta1-xZrx com x < 0.10.

Detectivity comparison of bolometric optical antennas

The practical application of optical antennas in detection devices strongly depends on its ability to produce an acceptable signal-to-noise ratio for the given task. It is known that, due to the intrinsic problems arising from its sub-wavelength dimensions, optical antennas produce very small signals. The quality of these signals depends on the involved transduction mechanism. The contribution of different types of noise should be adapted to the transducer and to the signal extraction regime. Once noise is evaluated and measured, the specific detectivity, D*, becomes the parameter of interest when comparing the performance of antenna coupled devices with other detectors. However, this parameter involves some magnitudes that can be defined in several ways for optical antennas. In this contribution we are interested in the evaluation and comparison of D_ values for several bolometric optical antennas working in the infrared and involving two materials. At the same time, some material and geometrical parameters involved in the definition of noise and detectivity will be discussed to analyze the suitability of D_ to properly account for the performance of optical antennas.

Finite size effects in the specific heat of glass-formers

We report clear finite size effects in the specific heat and in the relaxation times of a model glass former at temperatures considerably smaller than the Mode Coupling transition. A crucial ingredient to reach this result is a new Monte Carlo algorithm which allows us to reduce the relaxation time by two order of magnitudes. These effects signal the existence of a large correlation length in static quantities.

The imprint of the crustal magnetic field on the thermal spectra and pulse profiles of isolated neutron stars

Isolated neutron stars (NSs) show a bewildering variety of astrophysical manifestations, presumably shaped by the magnetic field strength and topology at birth. Here, using state-of-the-art calculations of the coupled magnetic and thermal evolution of NSs, we compute the thermal spectra and pulse profiles expected for a variety of initial magnetic field configurations. In particular, we contrast models with purely poloidal magnetic fields to models dominated by a strong internal toroidal component. We find that, while the former displays double-peaked profiles and very low pulsed fractions, in the latter, the anisotropy in the surface temperature produced by the toroidal field often results in a single pulse profile, with pulsed fractions that can exceed the 50–60 per cent level even for perfectly isotropic local emission. We further use our theoretical results to generate simulated ‘observed’ spectra, and show that blackbody (BB) fits result in inferred radii that can be significantly smaller than the actual NS radius, even as low as ∼1–2 km for old NSs with strong internal toroidal fields and a high absorption column density along their line of sight. We compute the size of the inferred BB radius for a few representative magnetic field configurations, NS ages and magnitudes of the column density. Our theoretical results are of direct relevance to the interpretation of X-ray observations of isolated NSs, as well as to the constraints on the equation of state of dense matter through radius measurements.