933 resultados para Existence and structure of the pullback attractor
Resumo:
In isolation and characterization studies, expression level U1 and U2 snRNA isoforms were obtained from the 5th instar larval stage silk gland (SG). The DNA content of the SG cells is approximately 200,000-fold higher compared to the usual (2N) somatic cells of B. mori due to endoreduplication. In this study, the existence of U1 and U2 snRNA isoforms in the SG of the organism is investigated. Bombyx mori U1 and U2-specific RT-PCR libraries from the silk gland were generated. Five U1 and eight U2 isoforms were isolated and characterized. Nucleotide differences, structural alterations, as well as protein and RNA interaction sites were analyzed in these variants. For the U1 snRNA variants, they were compared to the previously reported BmN isoforms. In all these U-snRNA variants, polymorphic sites do not predominate at the core of known functional sequences, which were interspecifically conserved. Variant sites and inter-species differences are located in moderately conserved regions. Free energy (ΔG) values for the entire U1 and U2 snRNA secondary structures and for the individual stem/loops domains of the isoforms were generated and compared to determine their structural stability. This will be the first time that U1 and U2 variants are shown specific for a development stage (larval) other than embryonic or adult. ^ Using phylogenetic analysis, evolutionary trees were generated for the U1 and U2 snRNAs using animal, plant, protista and fungal species. The resulting trees were boostrapped for robustness and rooted with the self-splicing RNA group II intron sequence from the cyanobacterium Calothrix. Using phylogenetic analyses, possible structural and functional evolutionary interdependence between the U1 and U2 snRNAs was investigated. ^
Resumo:
Par Pond is a man-made 1120 ha cooling reservoir located on the Savannah River Site near Aiken, South Carolina. From 1972-1978 a detailed study on the status of the alligator in Par Pond was conducted by Tom Murphy (unpub. MS thesis Univ. of GA, 1977). Murphy estimated that approximately 110 alligators inhabited Par Pond with an adult (> 1.8 m) to juvenile (< 1.8 m) ratio of (1.8:1), an overall sex ratio of 3.2:1, and an average of only 2.3 nests/yr. The purpose of this study (1986-1989) was to determine the current population size and structure, determine how the population has changed in the last 15 years and to examine growth and survival of juvenile alligators. Data were collected by monthly night-time eyeshine counts aerial surveys, capturing animals, and locating and following the fate of nests. There was a strong positive correlation between water temperature and the number of alligators observed during eyeshine counts. Both eyeshine counts and aerial surveys were highest in spring and varied seasonally. A total of 184 different non-hatchling and 157 hatchling alligators were captured between May 1986 and November 1988. Population estimates and size distributions based on capture data indicate that over the last 15 years the population has increased from approximately 110 to 200 alligators, and the size distribution has shifted from one dominated by large adults to one that has a higher proportion of juveniles. The current sex ratio (2.6:1) is not significantly different from that reported by Murphy (1977, 3.2:1). However, the average number of nests/yr has increased from 2.3 to 4.0. Data on juvenile growth and survival show that the growth rate of hatchlings (32.9 cm/yr total length) is greater than that of animals age 1-3 (21.6 cm/yr total length) and survival of all ages is variable between years and between clutches. Results from this study indicate that from 1972-988 the population has increased ac an average exponential rate of 6 % per year. If conditions in Par Pond do not change, the population size should continue to increase.
An investigation by AFM and TEM of the mechanism of anodic formation of nanoporosity in n-InP in KOH
Resumo:
The early stages of nanoporous layer formation, under anodic conditions in the absence of light, were investigated for n-type InP with a carrier concentration of ∼3× 1018 cm-3 in 5 mol dm-3 KOH and a mechanism for the process is proposed. At potentials less than ∼0.35 V, spectroscopic ellipsometry and transmission electron microscopy (TEM) showed a thin oxide film on the surface. Atomic force microscopy (AFM) of electrode surfaces showed no pitting below ∼0.35 V but clearly showed etch pit formation in the range 0.4-0.53 V. The density of surface pits increased with time in both linear potential sweep and constant potential reaching a constant value at a time corresponding approximately to the current peak in linear sweep voltammograms and current-time curves at constant potential. TEM clearly showed individual nanoporous domains separated from the surface by a dense ∼40 nm InP layer. It is concluded that each domain develops as a result of directionally preferential pore propagation from an individual surface pit which forms a channel through this near-surface layer. As they grow larger, domains meet, and the merging of multiple domains eventually leads to a continuous nanoporous sub-surface region.
Resumo:
The Bifibobacterium longum subsp. longum 35624™ strain (formerly named Bifidobacterium longum subsp. infantis) is a well described probiotic with clinical efficacy in Irritable Bowel Syndrome clinical trials and induces immunoregulatory effects in mice and in humans. This paper presents (a) the genome sequence of the organism allowing the assignment to its correct subspeciation longum; (b) a comparative genome assessment with other B. longum strains and (c) the molecular structure of the 35624 exopolysaccharide (EPS624). Comparative genome analysis of the 35624 strain with other B. longum strains determined that the sub-speciation of the strain is longum and revealed the presence of a 35624-specific gene cluster, predicted to encode the biosynthetic machinery for EPS624. Following isolation and acid treatment of the EPS, its chemical structure was determined using gas and liquid chromatography for sugar constituent and linkage analysis, electrospray and matrix assisted laser desorption ionization mass spectrometry for sequencing and NMR. The EPS consists of a branched hexasaccharide repeating unit containing two galactose and two glucose moieties, galacturonic acid and the unusual sugar 6-deoxy-L-talose. These data demonstrate that the B. longum 35624 strain has specific genetic features, one of which leads to the generation of a characteristic exopolysaccharide.
Resumo:
The sill and pillow complex cored on Deep Sea Drilling Project Leg 61 (Site 462) is divided into two groups, A and B types, on the basis of chemical composition and volcanostratigraphy. The A-type basalt is characterized by a higher FeO*/MgO ratio and abundant TiO2, whereas the B-type basalt is characterized by a lower FeO*/MgO ratio and scarcity of TiO2. The A type is composed of sills interbedded with hyaloclastic sediments, and the B type consists of basalt sills and pillow basalt with minor amounts of sediment. However, the structure of pillow basalts in the B type is atypical; they might be eruptive. From paleontological study of the interbedded sediments and radiometric age determination of the basalt, the volcanic event of A type is assumed to be Cenomanian to Aptian, and that of B type somewhat older. The oceanic crust in the Nauru Basin was assumed to be Oxfordian, based on the Mesozoic magnetic anomaly. Consequently, two events of intraplate volcanism are recognized. It is thus assumed that the sill-pillow complex did not come from a normal oceanic ridge, and that normal oceanic basement could therefore underlie the complex. The Site 462 basalts are quartz-normative, and strongly hypersthene-normative, and have a higher FeO*/MgO ratio and lower TiO2 content. Olivine from the Nauru Basin basalts has a lower Mg/(Mg + Fe**2+) ratio (0.83-0.84) and coexists with spinel of lower Mg/(Mg + Fe**2+) ratio when compared to olivine-spinel pairs from mid-ocean ridge (MAR) basalt. The glass of spinel-bearing basalts has a higher FeO*/(FeO* + MgO) ratio (0.58-0.60) than that of MAR (<0.575). Therefore, the Nauru Basin basalts are chemically and mineralogically distinct from ocean-ridge tholeiite. That the Nauru Basin basalts are quartz-normative and strongly hypersthene-normative and have a lower TiO2 content suggests that the basaltic liquids of Site 462 were generated at shallower depths (<5 kbar) than ocean-ridge tholeiite: Site 462 basalts are similar to basalts from the Manihiki Plateau and the Ontong-Java Plateau, but different from Hawaiian tholeiite of hot-spot type, with lower K2O and TiO2 content. We propose a new type of basalt, ocean-plateau tholeiite, a product of intraplate volcanism.
Resumo:
Focusing on the UK, this article addresses key issues facing the international distribution industry arising from over-the-top digital distribution and the fragmentation of audiences and revenues. Building on the identification of these issues, it investigates the extent to which UK distribution has altered over a ten-year period, pinpointing continuities in the destination and type of sales alongside changes in the role and structure of the industry as UK-based distributors adapt to a changing UK broadcasting landscape and global production environment. At one level increasing US ownership of UK-based distributors and the arrival of OTT players like Netflix, highlight the tensions between the national orientations of UK broadcasters and the global aspirations of independent producers and distributors. At another level VOD has boosted international sales of UK drama. Although the full impact of SVOD on content and rights has yet to materialise, significant changes in the industry predate the arrival of SVOD.
Resumo:
Over the last years, operations in Pharmaceutical Companies have become more complex, trying to adapt to new demands of the market environment. Overall, the observed change of paradigm requires adapting, mainly by the setting of new priorities, diversification of investments, cost containment strategies, exploring new markets and developping new sets of skills. In this context, new functions have been created, the relevance of some has diminished, and the importance of others has arisen. Amongst these, the medical structure within a Pharmaceutical Company, increased to meet demands, with companies adopting different models to respond to these needs, and becoming a pillar to the business. Assuming the leading role within a medical department, the medical director function often lies in the shadow. It is a key function within Pharma Industry, either on a country or on a Global basis. It has evolved and changed in the past years to meet the constant demands of a changing environment. The Medical Director is a highly skilled and differeniated professional who provides medical and scientific governance within a Pharmaceutical company, since early stages of drug development and up to loss of exclusivity, not only but also by leading a team of other physicians, pharmacists or life scientists whose functions comprise specificities that the medical director needs to understand, provide input to, oversee and lead. As the organization of Pharmaceutical Companies tends to be different, in accordance to values, culture, markets and strategies, the scope of activities of a Medical Director can be broader or may be limited, depending on size of the organization and governance model, but they must fulfil a large set of requirements in order to leverage impact on internal and internal customers. Key technical competencies for medical directors such as an MD degree, a strong clinical foundation, knowledge of drug development, project and team management experience and written and verbal skills are relatively easy to define, but underlying behavioural competencies are more difficult to ascertain, and these are more often the true predictors of success in the role. Beyond seamless proficiency in technical skills, at this level interpersonal skills become far more important, as they are the driver and the distinctive factor between a good and an excelent medical director. And this has impact in the business and in the people doing it.
Resumo:
Fluxes of nutrients (NH sub(4) super(+), NO sub(3) super(-), PO sub(4) super(3-) and Si(OH) sub(4)) were studied on an intertidal mudflat in Marennes-Oleron Bay, France, at two different seasons and at different times of the emersion period. Fluxes through the sediment-water interface were both calculated from vertical profiles of nutrient concentration in pore-water (diffusive fluxes, JD) and measured in light and dark benthic mini-chambers (measured fluxes, J sub(0)). Results indicate that ammonia was mainly released in summer while nitrate was mainly taken up in late winter. This uptake from the overlying water was probably due to the coupling of nitrification-denitrification within the sediment. The J sub(0) /J sub(D) ratio further indicates that bioturbation likely enhanced ammonia release in summer. Concerning phosphate, the comparison of diffusive and measured fluxes suggests that PO sub(4) super(3-) could be assimilated by the biofilm in winter while it was released in summer at a high rate due to both bioturbation and desorption because of the relative summer anoxic conditions. Silica was always released by the sediment, but at a higher rate in summer. Statistically significant differences in measured fluxes were detected in dark chambers at different times of low tide, thus suggesting a short-term variability of fluxes. Microphytobenthos preferred ammonia to nitrate, but assimilated nitrate when ammonia was not available. It also turned out that benthic cells could be limited in nitrogen during low tide in late winter. In summer, ammonia was not limiting and microphytobenthic activity significantly decreased the measured flux of NH sub(4) super(+) in the middle of low tide when its photosynthetic capacity was highest.
Resumo:
The main objectives of this dissertation were: (i) to develop experimental and analytical procedures to quantify different physico-chemical properties of the ultra-thin (~ 100 nm) active layers of reverse osmosis (RO) and nanofiltration (NF) membranes and their interactions with contaminants; (ii) to use such procedures to evaluate the similarities and differences between the active layers of different RO/NF membranes; and (iii) to relate characterization results to membrane performance. Such objectives were motivated by the current limited understanding of the physico-chemical properties of active layers as a result of traditional characterization techniques having limitations associated with the nanometer-scale spatial resolution required to study these ultra-thin films. Functional groups were chosen as the main active layer property of interest. Specific accomplishments of this study include the development of procedures to quantify in active layers as a function of pH: (1) the concentration of both negatively and positively ionized functional groups; (2) the stoichiometry of association between ions (i.e., barium) and ionized functional groups (i.e., carboxylate and sulfonate); and (3) the steric effects experienced by ions (i.e., barium). Conceptual and mathematical models were developed to describe experimental results. The depth heterogeneity of the active layer physico-chemical properties and interactions with contaminants studied in this dissertation was also characterized. Additionally, measured concentrations of ionized functional groups in the polyamide active layers of several commercial RO/NF membranes were used as input in a simplified RO/NF transport model to predict the rejection of a strong electrolyte (i.e., potassium iodide) and a weak acid (i.e., arsenious acid) at different pH values based on rejection results at one pH condition. The good agreement between predicted and experimental results showed that the characterization procedures developed in this study serve as useful tools in the advancement of the understanding of the properties and structure of the active layers of RO/NF membranes, and the mechanisms of contaminant transport through them.
Resumo:
We show that the multiscale entanglement renormalization ansatz (MERA) can be reformulated in terms of a causality constraint on discrete quantum dynamics. This causal structure is that of de Sitter space with a flat space-like boundary, where the volume of a spacetime region corresponds to the number of variational parameters it contains. This result clarifies the nature of the ansatz, and suggests a generalization to quantum field theory. It also constitutes an independent justification of the connection between MERA and hyperbolic geometry which was proposed as a concrete implementation of the AdS-CFT correspondence.
Resumo:
We study spatially localized states of a spiking neuronal network populated by a pulse coupled phase oscillator known as the lighthouse model. We show that in the limit of slow synaptic interactions in the continuum limit the dynamics reduce to those of the standard Amari model. For non-slow synaptic connections we are able to go beyond the standard firing rate analysis of localized solutions allowing us to explicitly construct a family of co-existing one-bump solutions, and then track bump width and firing pattern as a function of system parameters. We also present an analysis of the model on a discrete lattice. We show that multiple width bump states can co-exist and uncover a mechanism for bump wandering linked to the speed of synaptic processing. Moreover, beyond a wandering transition point we show that the bump undergoes an effective random walk with a diffusion coefficient that scales exponentially with the rate of synaptic processing and linearly with the lattice spacing.
Resumo:
The production of reactive oxygen species (ROS) within endothelial cells may have several effects, including alterations in the activity of paracrine factors, gene expression, apoptosis, and cellular injury. Recent studies indicate that a phagocyte-type NAD(P)H oxidase is a major source of endothelial ROS. In contrast to the high-output phagocytic oxidase, the endothelial enzyme has much lower biochemical activity and a different substrate specificity (NADH.NADPH). In the present study, we (1) cloned and characterized the cDNA and predicted amino acid structures of the 2 major subunits of rat coronary microvascular endothelial cell NAD(P)H oxidase, gp91-phox and p22-phox; (2) undertook a detailed comparison with phagocytic NADPH oxidase sequences; and (3) studied the subcellular location of these subunits in endothelial cells. Although these studies revealed an overall high degree of homology (.90%) between the endothelial and phagocytic oxidase subunits, the endothelial gp91-phox sequence has potentially important differences in a putative NADPH-binding domain and in putative glycosylation sites. In addition, the subcellular location of the endothelial gp91-phox and p22-phox subunits is significantly different from that reported for the neutrophil oxidase, in that they are predominantly intracellular and collocated in the vicinity of the endoplasmic reticulum. This first detailed characterization of gp91-phox and p22-phox structure and location in endothelial cells provides new data that may account, in part, for the differences in function between the phagocytic and endothelial NAD(P)H oxidases.
Resumo:
Non-finite clauses are sentential constituents with a verbal head that lacks a morphological specification for tense and agreement. In this paper I contend that these clauses are defective not only morphologically but also syntactically, in the sense that they all lack some of the functional categories that make up a full sentence. In particular I argue that to-infinitive clauses, gerund(ive) clauses and participial clauses differ among themselves, and with respect to other subordinate clauses, in the degree of structural defectiveness they display, which goes from the almost complete functional structure of the infinitive to the maximal degree of syntactic truncation of participial clauses (analyzed here as verbal small clauses). I also show the significant parallelism that exists in this respect between English and Spanish non-finite clauses, pointing to the implication this may have for a cross-linguistic approach to the cartography of syntactic structures.