Electrooptic effect in cholesteric blue phases with small positive dielectric anisotropy

An electrooptic effect in the blue phase of the cholesteric mixture S811-and the nematic mixture N5 is reported. To demonstrate this effect ac voltages (ƒ = 1000 Hz) between 0 and 150 νwere applied. Wavelength shifts of 70 nm were obtained.

A general stability criterion for switched linear systems having stable and unstable subsystems

We report conditions on a switching signal that guarantee that solutions of a switched linear systems converge asymptotically to zero. These conditions are apply to continuous, discrete-time and hybrid switched linear systems, both those having stable subsystems and mixtures of stable and unstable subsystems.

Optical behaviour of cholesteric blue phases in electric fields

The optical behaviour of cholesteric mixtures of negative dielectric anisotrony under electric fields is reported. A mixture of S 311~ (31.35 %) + N 5 was employed. AC voltages (f = 1000 Hz) betweeen 0 and 150 volts were applied. Cells 23 micron thick, with internal SnO2 electrodes, were used.

Preliminary mineralogy and ore petrology of the intermediate-sulfidation pallancata deposit, Ayacucho, Peru

Se investiga la compleja mineralogía del Yacimiento de Pallancata (6º productor de plata del mundo) y se establecen las condiciones de formación (P.T) basadas en la petrología de las menas comparada con los datos de mineralogía experimental y en la petrografía y microtermometría de inclusiones fluídas en la ganga silicatada, resultando un depósito típicamente caracterizado como epitermal de sulfuración intermedia.ABSTRACT:Pallancata is a world-class intermediate-sulfidation epithermal deposit, hosted by upper Miocene volcanics of the south-central Peruvian Andes in a sinuous N70ºW, ∼75º SW strike-slip structure, with wide (up to 35 m) pull-apart dilation zones related to bends of the vein strike. The structural evolution of the vein from earlier brecciation to later open space infill resembles the Shila Paula district (Chauvet et al. 2006). Fluid inclusion petrography and microthermometry show that ore deposition is related to protracted boiling of very diluted, mainly meteoric fluids, starting at 250–260 ºC, under ∼300 m hydrostatic head. The mineralogical-petrological study reveals a complex sequence of mineralization (eight stages) and mineral reactions consistent with Ag2S enrichment or Sb2S3 depletion, or both, during cooling over the temperature range 250–200 ºC: pyrite, sphalerite, galena, miargyrite, pyrargyrite-proustite, chalcopyrite, polybasite-pearceite, argentite (now acanthite), and Au–Ag alloy (“electrum”). This Ag2S enrichment and Sb2S3depletion during cooling may be explained by decay of a Ag-rich galena precursor at deeper levels (Pb2S2–AgSbS2 solid solution), which rapidly becomes unstable with decreasing temperature, producing residual (stoichiometric) PbS and more mobile Ag and Sb sulfide phases, which migrated upward and laterally away from the thermal core of the system. The core is still undisclosed by mining works, but the available geochemical evidence (logAg/log Pb ratios decreasing at depth) is consistent with this interpretation, implying a deeper potential resource. Data from sulfide geothermometry, based on mineral equilibria, document the thermal evolution of the system below 200 ºC (stephanite, uytenbogaardtite, jalpaite, stromeyerite, mckinstryite, among others). The end of the most productive stages (3, 4, and 5) is marked by the precipitation of stephanite at temperatures below 197 ± 5 ºC, but precipitation of residual silver continues through the waning stages of the hydrothermal system down to <93.3 ºC (stromeyerite) or in a supergene redistribution (stage 8, acanthite II).

Effects of forage type on diversity in bacterial pellets isolated from liquid and solid phases of the rumen content in sheep and goats.

Two sheep and two goats, fitted with a ruminal cannula, received two diets composed of 30% concentrate and 70% of either alfalfa hay (AL) or grass hay (GR) as forage in a two-period crossover design. Solid and liquid phases of the rumen were sampled from each animal immediately before feeding and 4 h post-feeding. Pellets containing solid associated bacteria (SAB) and liquid associated bacteria (LAB) were isolated from the corresponding ruminal phase and composited by time to obtain 2 pellets per animal (one SAB and one LAB) before DNA extraction. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S ribosomal DNA was used to analyze bacterial diversity. A total of 78 and 77 bands were detected in the DGGE gel from sheep and goats samples, respectively. There were 18 bands only found in the pellets from sheep fed AL-fed sheep and 7 found exclusively in samples from sheep fed the GR diet. In goats, 21 bands were found only in animals fed the AL diet and 17 were found exclusively in GR-fed ones. In all animals, feeding AL diet tended (P < 0.10) to promote greater NB and SI in LAB and SAB pellets compared with the GR diet. The dendrogram generated by the cluster analysis showed that in both animal species all samples can be included in two major clusters. The four SAB pellets within each animal species clustered together and the four LAB pellets grouped in a different cluster. Moreover, SAB and LAB clusters contained two clear subclusters according to forage type. Results show that in all animals bacterial diversity was more markedly affected by the ruminal phase (solid vs. liquid) than by the type of forage in the diet.

Feo, inútil, inestable: pensamiento crítico contemporáneo y procesos proyectivos en arquitectura = Ugly, useless, unstable: contemporary critical thought and projective processes in architecture

La presente tesis doctoral persigue dos objetivos simultáneos: Determinar el alcance de los criterios clásicos para la evaluación de arquitectura y poner en crisis la prevalencia de esos mismos criterios dentro del marco crítico y productivo actual. En concreto, esta tesis se interroga sobre la posible contribución de determinadas corrientes del pensamiento post-estructuralista y neo-materialista a las tareas de expansión y transformación de los criterios clásicos antes mencionados. Asimismo, se plantea la oportunidad de formalizar estas incorporaciones conceptuales como metodologías para el proyectar arquitectónico. La tesis emplea un análisis pormenorizado de las cualidades implícitas en la triada Firmitas, Utilitas, Venustas elaborada por Vitruvio como vehículo para calibrar la influencia de los paradigmas de pensamiento clásico en nuestras posiciones críticas contemporáneas. Como reacción al carácter dominante de dichos paradigmas, y con la ayuda de una compilación selectiva de ejemplos procedentes de los campos artístico y arquitectónico, la presente tesis procede a examinar y clasificar diversas estrategias arquitectónicas basadas en la no conformidad con los criterios clásicos de evaluación de la disciplina. A la hora de realizar esta tarea, y con el objetivo de superar el dualismo trascendental que caracteriza la gran mayoría de dichos criterios clásicos, se propone un modelo analítico y multidimensional que formula las instancias arquitectónicas como posibles posiciones dentro de un extenso continuo combinatorio de cualidades formales, estructurales y organizativas. Este modelo conceptual permite replantear el aparente antagonismo entre los principios de Vitruvio y sus opuestos, estableciendo en su lugar un dominio operativo continuo de producción arquitectónica. Esta operación abre una ventana de oportunidad para expandir los límites del marco crítico actual más allá de las fronteras establecidas por nuestra herencia clásica. En consecuencia con esta voluntad, la presente tesis pretende habilitar un ámbito para el análisis crítico de las estrategias que caracterizan ciertas corrientes del proyectar contemporáneo, pero también contribuir a informar nuevas aproximaciones metodológicas al proceso de proyecto, desplazando progresivamente su foco desde lo descriptivo hacia lo proyectivo. ABSTRACT This doctoral thesis attempts to simultaneously determine the scope of the classical criteria for the evaluation of architecture and challenge their prevalence within the current framework of architectural production and criticism. It examines how specific strands of post-structuralism and neo-materialism may contribute to both the expansion and the transformation of these criteria and, in doing so, sets itself the goal of mobilising these conceptual incorporations as explicit design methodologies. A detailed analysis of the formal, structural and organisational qualities implicit in Vitruvius’ triad Firmitas, Utilitas, Venustas is used as a starting point to determine the influence of classical paradigms in our current critical positions. As a reaction to this critical pervasiveness, and supported by a curated collection of artistic and architectural works, diverse approaches to non-compliance with the classical criteria of assessment are examined and classified. In order to facilitate this endeavour -and to overcome the transcendental dualism of most classical critical approaches in architecture- this thesis puts forward an analytical, multidimensional model that formulates architectural instances as possible positions within a larger combinatory continuum of formal, structural and organisational qualities. Using this conceptual model, the apparent antagonism between Vitruvius’ principles and its non-compliant opposites is reframed as a continuous operative domain of architectural production, which in turn opens up a window of opportunity to expand the limits of our critical framework beyond the boundaries of classical paradigms. In doing so, this thesis attempts not only to foster a better understanding of some of the strategic approaches that characterise contemporary systems of architectural production, but also to inform future methodological approaches to architectural design, hence situating itself beyond the domain of the descriptive and moving towards the projective.

Analysis of single and binary phases in cerium doped sodium bismuth titanate -Na0.5Bi0.5TiO3 materials

The pure and cerium doped sodium bismuth titanate inorganic powders were synthesized by solid state reaction method. The presence of rhombohedral phase was observed in cerium doped NBT compounds. At 1200 ºC, the 5% of cerium doped NBT compound forms single perovskite phase. The samples of x = 0.10 and 0.15 were heat treated to 1350 ºC, the binary phases with cerium and bismuth oxides were observed. The X-ray diffraction, fourier transform infrared spectroscopy, reflectance spectra, differential thermal analysis and thermo gravimetric analysis were used to analyze the various properties of samples. Moreover, the effects of cerium doping and calcining temperature on NBT samples were investigated. In this work we present our recent results on the synthesis and characterization of Ce doped sodium bismuth titanate materials.

Epigenetic phenotypes distinguish microsatellite-stable and -unstable colorectal cancers

Aberrant DNA methylation is a common phenomenon in human cancer, but its patterns, causes, and consequences are poorly defined. Promoter methylation of the DNA mismatch repair gene MutL homologue (MLH1) has been implicated in the subset of colorectal cancers that shows microsatellite instability (MSI). The present analysis of four MspI/HpaII sites at the MLH1 promoter region in a series of 89 sporadic colorectal cancers revealed two main methylation patterns that closely correlated with the MSI status of the tumors. These sites were hypermethylated in tumor tissue relative to normal mucosa in most MSI(+) cases (31/51, 61%). By contrast, in the majority of MSI(−) cases (20/38, 53%) the same sites showed methylation in normal mucosa and hypomethylation in tumor tissue. Hypermethylation displayed a direct correlation with increasing age and proximal location in the bowel and was accompanied by immunohistochemically documented loss of MLH1 protein both in tumors and in normal tissue. Similar patterns of methylation were observed in the promoter region of the calcitonin gene that does not have a known functional role in tumorigenesis. We propose a model of carcinogenesis where different epigenetic phenotypes distinguish the colonic mucosa in individuals who develop MSI(+) and MSI(−) tumors. These phenotypes may underlie the different developmental pathways that are known to occur in these tumors.

Characteristics of virus-specific CD8+ T cells in the liver during the control and resolution phases of influenza pneumonia

Dissection of the primary and secondary response to an influenza A virus established that the liver contains a substantial population of CD8+ T cells specific for the immunodominant epitope formed by H-2Db and the influenza virus nucleoprotein peptide fragment NP366–374 (DbNP366). The numbers of CD8+ DbNP366+ cells in the liver reflected the magnitude of the inflammatory process in the pneumonic lung, though replication of this influenza virus is limited to the respiratory tract. Analysis of surface phenotypes indicated that the liver CD8+ DbNP366+ cells tended to be more “activated” than the set recovered from lymphoid tissue but generally less so than those from the lung. The distinguishing characteristic of the lymphocytes from the liver was that the prevalence of the CD8+ DbNP366+ set was always much higher than the percentage of CD8+ T cells that could be induced to synthesize interferon γ after short-term, in vitro stimulation with the NP366–374 peptide, whereas these values were generally comparable for virus-specific CD8+ T cells recovered from other tissue sites. Also, the numbers of apoptotic CD8+ T cells were higher in the liver. The results overall are consistent with the idea that antigen-specific CD8+ T cells are destroyed in the liver during the control and resolution phases of this viral infection, though this destruction is not necessarily an immediate process.

Lipidic cubic phases: A novel concept for the crystallization of membrane proteins

Understanding the mechanisms of action of membrane proteins requires the elucidation of their structures to high resolution. The critical step in accomplishing this by x-ray crystallography is the routine availability of well-ordered three-dimensional crystals. We have devised a novel, rational approach to meet this goal using quasisolid lipidic cubic phases. This membrane system, consisting of lipid, water, and protein in appropriate proportions, forms a structured, transparent, and complex three-dimensional lipidic array, which is pervaded by an intercommunicating aqueous channel system. Such matrices provide nucleation sites (“seeding”) and support growth by lateral diffusion of protein molecules in the membrane (“feeding”). Bacteriorhodopsin crystals were obtained from bicontinuous cubic phases, but not from micellar systems, implying a critical role of the continuity of the diffusion space (the bilayer) on crystal growth. Hexagonal bacteriorhodopsin crystals diffracted to 3.7 Å resolution, with a space group P63, and unit cell dimensions of a = b = 62 Å, c = 108 Å; α = β = 90° and γ = 120°.

Stripe phases in high-temperature superconductors

Stripe phases are predicted and observed to occur in a class of strongly correlated materials describable as doped antiferromagnets, of which the copper-oxide superconductors are the most prominent representatives. The existence of stripe correlations necessitates the development of new principles for describing charge transport and especially superconductivity in these materials.

Two Genetically Separable Phases of Growth Inhibition Induced by Blue Light in Arabidopsis Seedlings1

High fluence-rate blue light (BL) rapidly inhibits hypocotyl growth in Arabidopsis, as in other species, after a lag time of 30 s. This growth inhibition is always preceded by the activation of anion channels. The membrane depolarization that results from the activation of anion channels by BL was only 30% of the wild-type magnitude in hy4, a mutant lacking the HY4 BL receptor. High-resolution measurements of growth made with a computer-linked displacement transducer or digitized images revealed that BL caused a rapid inhibition of growth in wild-type and hy4 seedlings. This inhibition persisted in wild-type seedlings during more than 40 h of continuous BL. By contrast, hy4 escaped from the initial inhibition after approximately 1 h of BL and grew faster than wild type for approximately 30 h. Wild-type seedlings treated with 5-nitro-2-(3-phenylpropylamino)-benzoic acid, a potent blocker of the BL-activated anion channel, displayed rapid growth inhibition, but, similar to hy4, these seedlings escaped from inhibition after approximately 1 h of BL and phenocopied the mutant for at least 2.5 h. The effects of 5-nitro-2-(3-phenylpropylamino)-benzoic acid and the HY4 mutation were not additive. Taken together, the results indicate that BL acts through HY4 to activate anion channels at the plasma membrane, causing growth inhibition that begins after approximately 1 h. Neither HY4 nor anion channels appear to participate greatly in the initial phase of inhibition.

Nonuniformity of the constitutive law parameters for shear rupture and quasistatic nucleation to dynamic rupture: a physical model of earthquake generation processes.

Based on the recent high-resolution laboratory experiments on propagating shear rupture, the constitutive law that governs shear rupture processes is discussed in view of the physical principles and constraints, and a specific constitutive law is proposed for shear rupture. It is demonstrated that nonuniform distributions of the constitutive law parameters on the fault are necessary for creating the nucleation process, which consists of two phases: (i) a stable, quasistatic phase, and (ii) the subsequent accelerating phase. Physical models of the breakdown zone and the nucleation zone are presented for shear rupture in the brittle regime. The constitutive law for shear rupture explicitly includes a scaling parameter Dc that enables one to give a common interpretation to both small scale rupture in the laboratory and large scale rupture as earthquake source in the Earth. Both the breakdown zone size Xc and the nucleation zone size L are prescribed and scaled by Dc, which in turn is prescribed by a characteristic length lambda c representing geometrical irregularities of the fault. The models presented here make it possible to understand the earthquake generation process from nucleation to unstable, dynamic rupture propagation in terms of physics. Since the nucleation process itself is an immediate earthquake precursor, deep understanding of the nucleation process in terms of physics is crucial for the short-term (or immediate) earthquake prediction.

Direct structure analysis in protein electron crystallography: crystallographic phases for halorhodopsin to 6-A resolution.

The crystal structure of halorhodopsin was determined in (centrosymmetric) projection to 6-A resolution by direct methods that use only the amplitudes of the electron diffraction pattern. A multisolution technique was used to generate initial 15-A-resolution basis sets, and after selection of the best phase set (by the closest match of magnitude of Eobs and magnitude of Ecalc), annealing of individual reflections was used to improve its accuracy. The Sayre equation was then used to expand the phase terms to 10 A, followed again by phase annealing. A final expansion with the Sayre equation enlarged this corrected phase set to 6 A. When the condition of density flatness was used to locate the best phase solution after each extension, a final structure could be observed that was quite similar to the one found earlier by analysis of electron micrographs.

O nado de atletas de águas abertas: características do desempenho e da organização temporal das braçadas

A natação de águas abertas tem registrado aumento no número de competições e participantes em todo mundo. Acompanhando esta tendência têm sido desenvolvidos estudos para identificar as características físicas e as respostas fisiológicas dos atletas neste tipo de prova. Entretanto, são escassos estudos ao nível de análise comportamental, principalmente, em condições reais de distância e meio ambiente (mar). Foi objetivo deste estudo investigar as características de desempenho e da organização temporal das braçadas de nadadores de águas abertas. Mais especificamente, conhecer quais recursos os atletas de águas abertas lançam mão para atingir sua meta de vencer um percurso no mar no menor tempo possível. A amostra foi constituída por 23 atletas, com média de idade de 26,4(±3,2) anos. A tarefa foi nadar um trajeto de 1500 metros em forma de um circuito em mar aberto. Para a captação das variáveis relacionadas ao desempenho utilizou-se um GPS (Garmin modelo Fênix 3) e um cronômetro (FINIS modelo Accusplit Eagle AX602). O registro das imagens para captação dos dados relacionados à descrição da organização temporal das braçadas ocorreu em três pontos do trajeto: início (I) - 20 a 40 metros, meio (M) - 800 a 820 metros e final (F) - 1450 a 1470 metros. Foi utilizada uma filmadora (Nikon Coolpix S5300) afixada à embarcação. O software Kinovea 8.20 permitiu a análise quadro a quadro das braçadas. Foram consideradas variáveis dependentes relacionadas ao desempenho (tempo, velocidade e distância total percorrida, bem como, a frequência de braçadas em cada um dos três pontos do trajeto); aos aspectos variantes das braçadas (tempo total do ciclo, das braçadas, das fases aérea e aquática) e aos aspectos invariantes das braçadas (timing relativo das fases aérea e aquática e sua variabilidade). A análise de variância de medidas repetidas foi usada para comparar os três momentos da tarefa (I, M e F) para todas as variáveis, e a correlação de Pearson para analisar a magnitude das relações entre as variáveis de desempenho, enquanto o teste t de Student para medidas pareadas foi utilizado para comparar as possíveis diferenças entre os braços direito e esquerdo para cada um dos momentos e determinou-se como significância estatística α≤=0,05. Em relação ao desempenho, os resultados indicaram que os nadadores fizeram uso de frequência de braçada (Fb) diferente para os três momentos, sendo maior no I quando comparada ao M e F, e no M, menor que em F; estas mudanças foram acompanhadas por ajustes nos aspectos variantes como o tempo total do ciclo, das braçadas e das fases aérea e aquática. Ainda, nos três momentos os nadadores apresentaram simetria temporal entre as braçadas dos dois braços, apesar de as diferenças serem evidenciadas entre as fases das braçadas quando comparados os braços. Com relação aos aspectos invariantes detectou-se mudança do padrão de I para M e F da tarefa, sendo que em M e F os atletas utilizaram a mesma estrutura temporal. Quanto à variabilidade dos aspectos variantes e invariantes para as braçadas e as fases das braçadas, observou-se diminuição da magnitude ao longo da tarefa sendo que o braço esquerdo apresentou nos três momentos maior variabilidade que o direito. Assim, diante dos resultados, concluiu-se que os recursos utilizados por nadadores habilidosos para nadar em ambiente pouco estável, em condições reais de distância e meio ambiente (mar) compreendem a alteração do desempenho (Fb) associado a ajustes nos aspectos variantes, concomitantemente à alteração dos aspectos invariantes das braçadas, em função do momento da tarefa