An assessment of the performance of high density polyethylene copolymers for natural gas distribution pipes

The total thermoplastics pipe market in west Europe is estimated at 900,000 metric tonnes for 1977 and is projected to grow to some 1.3 million tonnes of predominantly PVC and polyolefins pipe by 1985. By that time, polyethylene for gas distribution pipe and fittings will represent some 30% of the total polyethylene pipe market. The performance characteristics of a high density polyethylene are significantly influenced by both molecular weight and type of comonomer; the major influences being in the long-term hoop stress resistance and the environmental stress cracking resistance. Minor amounts of hexene-1 are more effective than comonomers lower in the homologous series, although there is some sacrifice of density related properties. A synergistic improvement is obtained by combining molecular weight increase with copolymerisation. The Long-term design strength of polyethylene copolymers can be determined from hoop stress measurement at elevated temperatures and by means of a separation factor of approximate value 22, extrapolation can be made to room temperature performance for a water environment. A polyethylene of black composition has a sufficiently improved performance over yellow pigmented pipe to cast doubts on the validity of internationally specifying yellow coded pipe for gas distribution service. The chemical environment (condensate formation) that can exist in natural gas distribution networks has a deleterious effect on the pipe performance the reduction amounting to at least two decades in log time. Desorption of such condensate is very slow and the influence of the more aggressive aromatic components is to lead to premature stress cracking. For natural gas distribution purposes, the design stress rating should be 39 Kg/cm2 for polyethylenes in the molecular weight range of 150 - 200,000 and 55 Kg/cm2 for higher molecular weight materials.

Avaliação da interação entre aflatoxina M1 e B1 com a fração proteica do leite

Dissertação composta por 02 artigos.

Physico-chemical properties of sol-gel synthesized titanosilicates for the uptake of radionuclides from aqueous solutions

Harnessing the power of nuclear reactions has brought huge benefits in terms of nuclear energy, medicine and defence as well as risks including the management of nuclear wastes. One of the main issues for radioactive waste management is liquid radioactive waste (LRW). Different methods have been applied to remediate LRW, thereunder ion exchange and adsorption. Comparative studies have demonstrated that Na2Ti2O3SiO4·2H2O titanosilicate sorption materials are the most promising in terms of Cs+ and Sr2+ retention from LRW. Therefore these TiSi materials became the object of this study. The recently developed in Ukraine sol-gel method of synthesizing these materials was chosen among the other reported approaches since it allows obtaining the TiSi materials in the form of particles with size ≥ 4mm. utilizing inexpensive and bulk stable inorganic precursors and yielded the materials with desirable properties by alteration of the comparatively mild synthesis conditions. The main aim of this study was to investigate the physico-chemical properties of sol-gel synthesized titanosilicates for radionuclide uptake from aqueous solutions. The effect of synthesis conditions on the structural and sorption parameters of TiSi xerogels was planned to determine in order to obtain a highly efficient sorption material. The ability of the obtained TiSis to retain Cs+, Sr2+ and other potentially toxic metal cations from the synthetic and real aqueous solutions was intended to assess. To our expectations, abovementioned studies will illustrate the efficiency and profitability of the chosen synthesis approach, synthesis conditions and the obtained materials. X-ray diffraction, low temperature adsorption/desorption surface area analysis, X-ray photoelectron spectroscopy, infrared spectroscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy was used for xerogels characterization. The sorption capability of the synthesized TiSi gels was studied as a function of pH, adsorbent mass, initial concentration of target ion, contact time, temperature, composition and concentration of the background solution. It was found that the applied sol-gel approach yielded materials with a poorly crystalline sodium titanosilicate structure under relatively mild synthesis conditions. The temperature of HTT has the strongest influence on the structure of the materials and consequently was concluded to be the control factor for the preparation of gels with the desired properties. The obtained materials proved to be effective and selective for both Sr2+ and Cs+ decontamination from synthetic and real aqueous solutions like drinking, ground, sea and mine waters, blood plasma and liquid radioactive wastes.

Measurement of the elastic electron-proton cross section and separation of the electric and magnetic form factor in the Q 2 range from 0.004 to 1 (GeV/c) 2

The electromagnetic form factors of the proton are fundamental quantities sensitive to the distribution of charge and magnetization inside the proton. Precise knowledge of the form factors, in particular of the charge and magnetization radii provide strong tests for theory in the non-perturbative regime of QCD. However, the existing data at Q^2 below 1 (GeV/c)^2 are not precise enough for a hard test of theoretical predictions.rnrnFor a more precise determination of the form factors, within this work more than 1400 cross sections of the reaction H(e,e′)p were measured at the Mainz Microtron MAMI using the 3-spectrometer-facility of the A1-collaboration. The data were taken in three periods in the years 2006 and 2007 using beam energies of 180, 315, 450, 585, 720 and 855 MeV. They cover the Q^2 region from 0.004 to 1 (GeV/c)^2 with counting rate uncertainties below 0.2% for most of the data points. The relative luminosity of the measurements was determined using one of the spectrometers as a luminosity monitor. The overlapping acceptances of the measurements maximize the internal redundancy of the data and allow, together with several additions to the standard experimental setup, for tight control of systematic uncertainties.rnTo account for the radiative processes, an event generator was developed and implemented in the simulation package of the analysis software which works without peaking approximation by explicitly calculating the Bethe-Heitler and Born Feynman diagrams for each event.rnTo separate the form factors and to determine the radii, the data were analyzed by fitting a wide selection of form factor models directly to the measured cross sections. These fits also determined the absolute normalization of the different data subsets. The validity of this method was tested with extensive simulations. The results were compared to an extraction via the standard Rosenbluth technique.rnrnThe dip structure in G_E that was seen in the analysis of the previous world data shows up in a modified form. When compared to the standard-dipole form factor as a smooth curve, the extracted G_E exhibits a strong change of the slope around 0.1 (GeV/c)^2, and in the magnetic form factor a dip around 0.2 (GeV/c)^2 is found. This may be taken as indications for a pion cloud. For higher Q^2, the fits yield larger values for G_M than previous measurements, in agreement with form factor ratios from recent precise polarized measurements in the Q2 region up to 0.6 (GeV/c)^2.rnrnThe charge and magnetic rms radii are determined as rn⟨r_e⟩=0.879 ± 0.005(stat.) ± 0.004(syst.) ± 0.002(model) ± 0.004(group) fm,rn⟨r_m⟩=0.777 ± 0.013(stat.) ± 0.009(syst.) ± 0.005(model) ± 0.002(group) fm.rnThis charge radius is significantly larger than theoretical predictions and than the radius of the standard dipole. However, it is in agreement with earlier results measured at the Mainz linear accelerator and with determinations from Hydrogen Lamb shift measurements. The extracted magnetic radius is smaller than previous determinations and than the standard-dipole value.

Separation of the transcriptional coactivator and antirepression functions of transcription factor IIA.

Human transcription factor IIA (TFIIA) is composed of three subunits (alpha, beta, and gamma). TFIIA interacts with the TATA-box binding protein and can overcome repression of transcription. TFIIA was found to be necessary for VP16-mediated transcriptional activation through a coactivator function. We have separated the coactivator and antirepression activities of TFIIA. A TFIIA lacking the alpha subunit was isolated from HeLa cells. This "mini-TFIIA" interacts with the TATA-box binding protein and can overcome repression of transcription, but it is defective in transcriptional coactivator function.

The Portuguese version of the Psychological Adjustment to Separation Test-Part A (PAST-A): a study with recently and non-recently divorced adults

Past research has demonstrated that divorced adults show more health problems and psychological distress than married adults. Considering the high prevalence rates of divorce among Western countries, new and robust measures should be developed to measure psychological distress after this specific transition in adulthood. The aim of this study was to adapt and validate a Portuguese version of the Psychological Adjustment to Separation Test-Part A (PAST-A; Sweeper and Halford in J Family Psychol 20(4):632–640, 2006). PAST-A is a self-report measure that assesses two key dimensions of separation adjustment problems: lonely-negativity and former partner attachment. Psychometric properties of the Portuguese version of PAST-A were assessed in terms of factor structure, internal consistency, and convergent and divergent validity, in an online convenience sample with divorced adults (N = 460). The PAST-A two-factor structure was confirmed by exploratory and confirmatory factor analyses, with each factor demonstrating very satisfactory internal consistency and good convergence. In terms of discriminant validity, the Portuguese PAST-A reveals a distinct factor from psychological growth after divorce. The results provided support for the use of the Portuguese PAST-A with divorced adults and also suggested that the explicative factors of the psychological adjustment to divorce may be cross-cultural stable. The non-existence of validated divorce-related well-being measures and its implications for divorce research are also discussed.

Regulation of membrane trafficking and organ separation by the NEVERSHED ARF-GAP protein.

Cell separation, or abscission, is a highly specialized process in plants that facilitates remodeling of their architecture and reproductive success. Because few genes are known to be essential for organ abscission, we conducted a screen for mutations that alter floral organ shedding in Arabidopsis. Nine recessive mutations that block shedding were found to disrupt the function of an ADP-ribosylation factor-GTPase-activating protein (ARF-GAP) we have named NEVERSHED (NEV). As predicted by its homology to the yeast Age2 ARF-GAP and transcriptional profile, NEV influences other aspects of plant development, including fruit growth. Co-localization experiments carried out with NEV-specific antiserum and a set of plant endomembrane markers revealed that NEV localizes to the trans-Golgi network and endosomes in Arabidopsis root epidermal cells. Interestingly, transmission electron micrographs of abscission zone regions from wild-type and nev flowers reveal defects in the structure of the Golgi apparatus and extensive accumulation of vesicles adjacent to the cell walls. Our results suggest that NEV ARF-GAP activity at the trans-Golgi network and distinct endosomal compartments is required for the proper trafficking of cargo molecules required for cell separation.

A new factor stimulating peptidoglycan hydrolysis to separate daughter cells in Caulobacter crescentus.

Cell division in Gram-negative bacteria involves the co-ordinated invagination of the three cell envelope layers to form two new daughter cell poles. This complex process starts with the polymerization of the tubulin-like protein FtsZ into a Z-ring at mid-cell, which drives cytokinesis and recruits numerous other proteins to the division site. These proteins are involved in Z-ring constriction, inner- and outer-membrane invagination, peptidoglycan remodelling and daughter cell separation. Three papers in this issue of Molecular Microbiology, from the teams of Lucy Shapiro, Martin Thanbichler and Christine Jacobs-Wagner, describe a novel protein, called DipM for Division Involved Protein with LysM domains, that is required for cell division in Caulobacter crescentus. DipM localizes to the mid-cell during cell division, where it is necessary for the hydrolysis of the septal peptidoglycan to remodel the cell wall. Loss of DipM results in severe defects in cell envelope constriction, which is deleterious under fast-growth conditions. State-of-the-art microscopy experiments reveal that the peptidoglycan is thicker and that the cell wall is incorrectly organized in DipM-depleted cells compared with wild-type cells, demonstrating that DipM is essential for reorganizing the cell wall at the division site, for envelope invagination and cell separation in Caulobacter.

Evolutionary and Functional Analyses of the Interaction between the Myeloid Restriction Factor SAMHD1 and the Lentiviral Vpx Protein.

SAMHD1 has recently been identified as an HIV-1 restriction factor operating in myeloid cells. As a countermeasure, the Vpx accessory protein from HIV-2 and certain lineages of SIV have evolved to antagonize SAMHD1 by inducing its ubiquitin-proteasome-dependent degradation. Here, we show that SAMHD1 experienced strong positive selection episodes during primate evolution that occurred in the Catarrhini ancestral branch prior to the separation between hominoids (gibbons and great apes) and Old World monkeys. The identification of SAMHD1 residues under positive selection led to mapping the Vpx-interaction domain of SAMHD1 to its C-terminal region. Importantly, we found that while SAMHD1 restriction activity toward HIV-1 is evolutionarily maintained, antagonism of SAMHD1 by Vpx is species-specific. The distinct evolutionary signature of SAMHD1 sheds light on the development of its antiviral specificity.

Targeting of DNA polymerase to the adenovirus origin of DNA replication by interaction with nuclear factor I.

Efficient initiation by the DNA polymerase of adenovirus type 2 requires nuclear factor I (NFI), a cellular sequence-specific transcription factor. Three functions of NFI--dimerization, DNA binding, and activation of DNA replication--are colocalized within the N-terminal portion of the protein. To define more precisely the role of NFI in viral DNA replication, a series of site-directed mutations within the N-terminal domain have been generated, thus allowing the separation of all three functions contained within this region. Impairment of the dimerization function prevents sequence-specific DNA binding and in turn abolishes the NFI-mediated activation of DNA replication. NFI DNA-binding activity, although necessary, is not sufficient to activate the initiation of adenovirus replication. A distinct class of NFI mutations that abolish the recruitment of the viral DNA polymerase to the origin also prevent the activation of replication. Thus, a direct interaction of NFI with the viral DNA polymerase complex is required to form a stable and active preinitiation complex on the origin and is responsible for the activation of replication by NFI.

Ultra-trace monitoring of copper in environmental and biological samples by inductively coupled plasma atomic emission spectrometry after separation and preconcentration by using octadecyl silica membrane disks modified by a new schiff's base

Ultra-trace amounts of Cu(II) were separated and preconcentrated by solid phase extraction on octadecyl-bonded silica membrane disks modified with a new Schiff,s base (Bis- (2-Hydroxyacetophenone) -2,2-dimethyl-1,3-propanediimine) (SBTD) followed by elution and inductively coupled plasma atomic emission spectrometric detection. The method was applied as a separation and detection method for copper(II) in environmental and biological samples. Extraction efficiency and the influence of sample matrix, flow rate, pH, and type and minimum amount of stripping acid were investigated. The concentration factor and detection limit of the proposed method are 500 and 12.5 pg mL-1, respectively.

Development of a flotation method for preconcentration-separation of trace amounts of some metal ions in plant tissues prior to their FAAS determinations

An efficient flotation method based on the combination of flame atomic absorption spectrometry (FAAS) and separation and preconcentration step for determination of Cr3+, Cu 2+, Co2+, Ni2+, Zn2+, Cd 2+, Fe3+ and Pb2+ ions in various real samples by the possibility of applying bis(2-hydroxyacetophenone)-1,4-butanediimine (BHABDI) as a new collector was studied. The influence of pH, amount of BHABDI as collector, sample matrix, type and amount of eluting agent, type and amount of surfactant as floating agent, ionic strength and air flow rates i.e. variables affecting the efficiency of the extraction system was evaluated. It is ascertained that metal ions such as iron can be separated simultaneously from matrix in the presence of 0.012 mM ligand, 0.025% (w/v) of CTAB to a test sample of 750 mL at pH 6.5. These ions can be eluted quantitatively with 6 mL of 1.0 mol L-1 HNO3 in methanol which lead to the enrichment factor of 125. The detection limits for analyte ions were in the range of 1.3-2.4 ng mL-1. The method has been successfully applied for determination of trace amounts of ions in various real samples.

Intraoperative hemodynamic instability during and after separation from cardiopulmonary bypass : importance, mechanism and prevention

Chaque année, environ 1 à 1,25 million d’individus subiront une chirurgie cardiaque. [1] Environ 36 000 chirurgies cardiaques sont effectuées au Canada et 8000 procédures au Québec (http://www.ccs.ca). Le vieillissement de la population aura pour conséquence que la chirurgie cardiaque sera offerte à des patients de plus en plus à risque de complications, principalement en raison d’une co-morbidité plus importante, d’un risque de maladie coronarienne plus élevée, [2] d’une réserve physiologique réduite et par conséquent un risque plus élevé de mortalité à la suite d’une chirurgie cardiaque. L’une des complications significatives à la suite d’une chirurgie cardiaque est le sevrage difficile de la circulation extracorporelle. Ce dernier inclut la période au début du sevrage de la circulation extracorporelle et s’étend jusqu’au départ du patient de la salle d’opération. Lorsque le sevrage de la circulation extracorporelle est associé à une défaillance ventriculaire droite, la mortalité sera de 44 % à 86 %. [3-7] Par conséquent le diagnostic, l’identification des facteurs de risque, la compréhension du mécanisme, la prévention et le traitement du sevrage difficile de la circulation extracorporelle seront d’une importance majeure dans la sélection et la prise en charge des patients devant subir une chirurgie cardiaque. Les hypothèses de cette thèse sont les suivantes : 1) le sevrage difficile de la circulation extracorporelle est un facteur indépendant de mortalité et de morbidité, 2) le mécanisme du sevrage difficile de la circulation extracorporelle peut être approché d’une façon systématique, 3) la milrinone administrée par inhalation représente une alternative préventive et thérapeutique chez le patient à risque d’un sevrage difficile de la circulation extracorporelle après la chirurgie cardiaque.

Genesis and expansion of metazoan transcription factor gene classes

We know little about the genomic events that led to the advent of a multicellular grade of organization in animals, one of the most dramatic transitions in evolution. Metazoan multicellularity is correlated with the evolution of embryogenesis, which presumably was underpinned by a gene regulatory network reliant on the differential activation of signaling pathways and transcription factors. Many transcription factor genes that play critical roles in bilaterian development largely appear to have evolved before the divergence of cnidarian and bilaterian lineages. In contrast, sponges seem to have a more limited suite of transcription factors, suggesting that the developmental regulatory gene repertoire changed markedly during early metazoan evolution. Using whole- genome information from the sponge Amphimedon queenslandica, a range of eumetazoans, and the choanoflagellate Monosiga brevicollis, we investigate the genesis and expansion of homeobox, Sox, T- box, and Fox transcription factor genes. Comparative analyses reveal that novel transcription factor domains ( such as Paired, POU, and T- box) arose very early in metazoan evolution, prior to the separation of extant metazoan phyla but after the divergence of choanoflagellate and metazoan lineages. Phylogenetic analyses indicate that transcription factor classes then gradually expanded at the base of Metazoa before the bilaterian radiation, with each class following a different evolutionary trajectory. Based on the limited number of transcription factors in the Amphimedon genome, we infer that the genome of the metazoan last common ancestor included fewer gene members in each class than are present in extant eumetazoans. Transcription factor orthologues present in sponge, cnidarian, and bilaterian genomes may represent part of the core metazoan regulatory network underlying the origin of animal development and multicellularity.

Separation of performance-approach and performance-avoidance achievement goals: A broader analysis

In the literature on achievement goals, performance-approach goals (striving to do better than others) and performance-avoidance goals (striving to avoid doing worse than others) tend to exhibit a moderate to high correlation, raising questions about whether the 2 goals represent distinct constructs. In the current article, we sought to examine the separability of these 2 goals using a broad factor-analytic approach that attended to issues that have been overlooked or underexamined in prior research. Five studies provided strong evidence for the separation of these 2 goal constructs: Separation was observed not only with exploratory factor analysis across different age groups and countries (Studies 1a and 1b) but also with change analysis (Study 2), ipsative factor analysis (Study 3), within-person analysis (Study 4), and behavioral genetics analysis (Study 5). We conclude by discussing the implications of the present research for the achievement goal literature, as well as the psychological literature in general.