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## Copolimerização em emulsão de estireno e acrilato de butila com alto teor de sólidos: estudo experimental e modelagem matemática do processo em reator semicontínuo.; Emulsion copolymerization of styrene and butyl acrylate with gigh solids contents: experimental study and mathematical modeling of the process in a semi-batch reactor.

Marinangelo, Giovane
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Relevância na Pesquisa
16.25%
Neste trabalho estudou-se a copolimerização em emulsão de estireno e acrilato de butila em processo semicontínuo onde o produto final é um látex com alto teor de sólidos. Foi dado enfoque à distribuição de tamanhos de partículas do látex e seus efeitos no produto. Foi realizada uma série de experimentos de copolimerização em emulsão em um reator de vidro, empregando receitas com teores de sólidos de até 64% em massa. Durante os experimentos, amostras eram retiradas periodicamente do reator visando analisar o teor de polímeros (conversão dos monômeros) por gravimetria, a concentração de monômero residual por cromatografia gasosa headspace, o diâmetro médio das partículas por espectroscopia de espalhamento dinâmico de luz e a distribuição de tamanhos de partículas por microscopia eletrônica de transmissão. A viscosidade do látex final era obtida em viscosímetro Brookfield. Aplicando estratégias para renucleação de novas partículas no decorrer do processo, foram obtidos látices com distribuição bimodal de tamanhos de partículas e com viscosidades reduzidas. Aplicou-se um modelo matemático para descrever o processo, incluindo a evolução no tempo da distribuição de tamanhos de partículas...

## Inferência por redes neurais da distribuição de tamanho de partícula em reações contínuas de polimerização em emulsão

Ferrari, Jarbas Cleber
Tipo: Tese de Doutorado Formato: 161 p.| il., grafs., tabs.
POR
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## Assessing the accuracy of routine photon correlation spectroscopy analysis of heterogeneous size distributions

Frantzen, Christer B.; Ingebrigtsen, Lars; Skar, Merete; Brandl, Martin
Tipo: Artigo de Revista Científica
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The aim of the current study was to investigate the ability of a fixed-angle routine photon correlation spectrometer (PCS) to resolve bimodal size distributions. The focus was on dispersions consisting of a majority of smaller and a minority of bigger particles. Monodisperse latex beads of sizes from 21 to 269 nm were measured first as single-size dispersions and then with various binary blends. For single-size dispersions, the mean diameters obtained were as indicated by the manufacturer, except for 21- and 34-nm particles, which were somewhat smaller. PCS analysis of blends of 21+102-nm and 34+102-nm particles resulted in bimodal distributions with particle diameters of the 2 peaks in the expected magnitude down to critical blending ratios of 0.002% and 0.08% of bigger particles, respectively. At these ratios, PCS results became inconsistent, and an increased number of monomodal results and/or high residuals were seen. For 21+102-nm blends, at even smaller ratios (0.001%), more consistent results were obtained again with predominantly monomodal distributions in the size range of the smaller particles (ie, the bigger particles were neglected). PCS analysis of blends of 21+269-nm particles yielded bimodal distributions with diameters within the expected magnitude as long as the content of bigger particles did not exceed 0.005%. Above this ratio...

## Estudo da influencia das condições de síntese no tamanho de partícula de látices de poliestireno e poli(metilmetacrilato) e incorporação de complexos de latanídeos

Bezerra Costa Silva, Sidicleia; Galembeck, André (Orientador)
Tipo: Outros
PT_BR
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26.09%

## PUSHING THE BOUNDARIES OF CONCENTRATED DISPERSIONS, High Solids Content Bimodal Latex for Paper Coating Applications

Pacheco de Moraes, Raul
Fonte: Quens University Publicador: Quens University
EN; EN
Relevância na Pesquisa
56.36%
New processes for the production of polymeric dispersions with high solids content and low viscosity were developed, investigated and characterized. The specifications required for the desired application of paper coating, which constitutes one of the major innovative aspects of this thesis, requires in average particle sizes smaller than 200 nm. This particle size is significantly smaller than obtained in previous work in this area. The main objective of this project was to increase the solids content of existing products from ~50 to ~60 wt% while keeping the viscosity at low levels (< 1200 mPa•s at 20 s-1). In order to produce high solids content latexes with low viscosity, bimodal particle size distributions were resorted to. To obtain highest packing fraction, the small particle size population should be about 7 times smaller than the large particles, bringing the size of the small particles to less than 30 nm. Modified (micro)emulsion processes were developed in order to produce small particle size latex with reduced surfactant concentration and increased solids content. The large particle population was developed using a semi-batch emulsion polymerization process, simulating a product that is commercially available (~52 wt% solids content and viscosity of ~500 mPa•s at 20 s-1). To increase the solids content of this product up to 60 wt%...

## Wolf-Rayet stars and GRB connection

Cherepashchuk, A. M.; Postnov, K. A.
Tipo: Artigo de Revista Científica
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Observed properties of GRBs, WR stars and their CO-cores in the end of evolution are analyzed. A possible bimodality of the observed GRB energy distribution ($10^{48}$ erg for GRB9809425; $3\times 10^{51}\div 2\times 10^{54}$ erg for others) is in accord with the bimodal mass distribution of relativistic objects ($M_{NS}=(1.35\pm 0.15) M_\odot$; $M_{BH}=(4\div 15) M_\odot$). The peculiarity of SN1998bw can be related to the rotation of the collapsing CO-core. The expected galactic collapse rate of CO-cores of most compact WR stars of type WO is $\sim 10^{-5}$ per year, only by one and a half order of magnitude higher than the GRB rate. The allowance for a gamma-ray beaming or random outcome of the CO-core collapse due to some instabilities brings this rate in accordance GRB rate. We argue that WR stars (most probably, of type WO) can be considered as progenitors of cosmic gamma-ray bursts. Two types of GRBs are predicted in correspondence with the bimodal mass distribution of the relativistic objects. Three types of optical afterglows should appear depending on which CO-core is collapsing: of a single WR star, of a WR star in a WR+O or a hypothetic WR+(A-M) binary system. We briefly discuss a model of GRB as a transient phenomenon occurring at early stages of galactic evolution ($z>1$)...

## The star cluster system of the 3 Gyr old merger remnant NGC 1316: Clues from optical and near-infrared photometry

Goudfrooij, Paul; Alonso, M. Victoria; Maraston, Claudia; Minniti, Dante
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
16.07%
The giant merger remnant galaxy NGC 1316 (Fornax A) is an ideal probe for studying the long-term effects of a past major merger on star cluster systems, given its spectroscopically derived merger age of ~3 Gyr which we reported in a recent paper. Here we present new ground-based, large-area optical and near-IR imaging of star clusters in NGC 1316, complemented with deep HST/WFPC2 imaging. We find that the optical-near-IR colours and luminosities of the brightest ~10 clusters in NGC 1316 are consistent with those of intermediate-age (2-3 Gyr) populations. Unlike normal' giant ellipticals, the B-I colour distribution of clusters in NGC 1316 is not clearly bimodal. However, the luminosity functions (LFs) of the blue and red parts of the cluster colour distribution are different: The red cluster LF is well represented by a power law with index -1.2 +/- 0.3, extending to about 1.5 mag brighter (in B) than those of typical giant ellipticals. In contrast, the shape of the blue cluster LF is consistent with that of normal' spiral and elliptical galaxies. We conclude that the star cluster system of NGC 1316 is a combination of a population of age ~3 Gyr having roughly solar metallicity and a population of old, metal-poor clusters which probably belonged to the pre-merger galaxies. After the 3 Gyr old...

## Bimodal Coherence in Dense Self-Interacting Neutrino Gases

Samuel, Stuart
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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Analytical solutions are obtained to the nonlinear equations describing neutrino oscillations when explicit neutrino-antineutrino asymmetries are present. Such a system occurs in the early Universe if neutrinos have a non-zero chemical potential. Solutions to the equations lead to a new type of coherent behavior governed by two modes. These bimodal solutions provide new insights into dense neutrino gases and into neutrino oscillations in the early Universe, thereby allowing one to surmise the flavor behavior of neutrinos with a non-zero chemical potential.; Comment: 21 pages in Latex, 11 figures packaged in one Postscript file. Figures also obtainable as 20 gif files at http://www.sci.ccny.cuny.edu/~ssamuel/bimodalfigs.html Revision on 4/19/96 was to pack the figures more sensibly. This paper is to appear in a May issue of Phys. Rev. D

## Evidence of Substructure in the Cluster of Galaxies A3558

Dantas, Christine C.; de Carvalho, Reinaldo R.; Capelato, Hugo V.; Mazure, Alain
Tipo: Artigo de Revista Científica
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We investigate the dynamical properties of the cluster of galaxies A3558 (Shapley 8). Studying a region of one square degree ($\sim$ 3 Mpc$^2$) centered on the cluster cD galaxy, we have obtained a statistically complete photometric catalog with positions and magnitudes of 1421 galaxies (down to a limiting magnitude of $B \sim 21$). This catalog has been matched to the recent velocity data obtained by Mazure et al. (1997) and from the literature, yielding a radial velocity catalog containing 322 galaxies. Our analysis shows that the position/velocity space distribution of galaxies shows significant substructure. A central bimodal core detected previously in preliminary studies is confirmed by using the Adaptive Kernel Technique and Wavelet Analysis. We show that this central bimodal subtructure is nevertheless composed of a projected feature, kinematically unrelated to the cluster, plus a group of galaxies probably in its initial merging phase into a relaxed core. The cD velocity offset with respect to the average cluster redshift, reported earlier by several authors, is completely eliminated as a result of our dynamical analysis. The untangling of the relaxed core component also allows a better, more reliable determination of the central velocity dispersion...

## Sub-Poissonian Shot Noise In A Diffusive Conductor

de Jong, M. J. M.; Beenakker, C. W. J.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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A review is given of the shot-noise properties of metallic, diffusive conductors. The shot noise is one third of the Poisson noise, due to the bimodal distribution of transmission eigenvalues. The same result can be obtained from a semiclassical calculation. Starting from Oseledec's theorem it is shown that the bimodal distribution is required by Ohm's law.; Comment: 9 pages, LaTeX, including 2 figures

## The bimodal spiral galaxy surface brightness distribution

Bell, E. F.; de Blok, W. J. G.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.24%
We have assessed the significance of Tully and Verheijen's (1997) bimodal Ursa Major Cluster spiral galaxy near-infrared surface brightness distribution, focussing on whether this bimodality is simply an artifact of small number statistics. A Kolmogorov-Smirnov style of significance test shows that the total distribution is fairly represented by a single-peaked distribution, but that their isolated galaxy subsample (with no significant neighbours within a projected distance of around 80 kpc) is bimodal at the 96 per cent level. We have also investigated the assumptions underlying the isolated galaxy surface brightness distribution, finding that the (often large) inclination corrections used in the construction of this distribution reduce the significance of the bimodality. We conclude that the Ursa Major Cluster dataset is insufficient to establish the presence of a bimodal near-infrared surface brightness distribution: an independent sample of around 100 isolated, low inclination galaxies is required to establish bimodality at the 99 per cent level.; Comment: 5 pages LaTeX; 2 embedded figures; re-submitted to MNRAS after replying to referee's comments

## Stellar Photometry of the Globular Cluster NGC 6229. I. Data Reduction and Morphology of the Brighter Part of the CMD

Borissova, J.; Catelan, M.; Spassova, N.; Sweigart, A. V.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
16.17%
BV CCD photometry of the central (1.5 arcmin x 2.0 arcmin) part of the mildly concentrated outer-halo globular cluster NGC 6229 is presented. The data reduction in such a crowded field was based on a wavelet transform analysis. Our larger dataset extends the previous results by Carney et al. (1991, AJ, 101, 1699) for the outer and less crowded fields of the cluster, and confirms that NGC 6229 has a peculiar color-magnitude diagram for its position in the Galaxy. In particular, NGC 6229's horizontal branch (HB) presents several interesting features, among which stand out: a well populated and very extended blue tail; a rather blue overall morphology, with (B-R)/(B+V+R) = 0.24+/-0.02; a bimodal color distribution, resembling those found for NGC 1851 and NGC 2808; and gaps on the blue HB. NGC 6229 is the first bimodal-HB cluster to be identified in the Galactic outer halo. A low value of the R parameter is confirmed, suggestive of a low helium abundance or of the presence of a quite substantial population of extreme HB stars fainter than our photometric limit (~ 2.5 mag below the RR Lyrae level in V). Twelve new possible variable stars were found in the central part of the cluster. The morphology of the red giant branch (RGB) also seems to be peculiar. In particular...

## Hubble Space Telescope Imaging of the Globular Cluster System around NGC 5846

Forbes, Duncan A.; Brodie, Jean P.; Huchra, John
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
16.07%
Bimodal globular cluster metallicity distributions have now been seen in a handful of large ellipticals. Here we report the discovery of a bimodal distribution in the dominant group elliptical NGC 5846, using the Hubble Space Telescope's Wide Field and Planetary Camera 2 (WFPC2). The two peaks are located at V-I = 0.96 and 1.17, which roughly correspond to metallicities of [Fe/H] = -1.2 and -0.2 respectively. The luminosity functions of the blue and red subpopulations appear to be the same, indicating that luminosity does not correlate with metallicity within an individual galaxy's globular cluster system. Our WFPC2 data cover three pointings allowing us to examine the spatial distribution of globular clusters out to 30 kpc (or 2.5 galaxy effective radii). We find a power law surface density with a very flat slope, and a tendency for globular clusters to align close to the galaxy minor axis. An extrapolation of the surface density profile, out to 50 kpc, gives a specific frequency S_N = 4.3 +/- 1.1. Thus NGC 5846 has a much lower specific frequency than other dominant ellipticals in clusters but is similar to those in groups. The central galaxy regions reveal some filamentary dust features, presumably from a past merger or accretion of a gas-rich galaxy. This dust reaches to the very nucleus and so provides an obvious source of fuel for the radio core. We have searched for proto-globular clusters that may have resulted from the merger/accretion and find none. Finally...

## Color-Magnitude Diagrams of Merged Globular Clusters: Metallicity Effects

Catelan, M.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
16.24%
Mergers of globular clusters (GCs) once associated with dwarf spheroidal (dSph) galaxies have recently been suggested as an explanation for the bimodal horizontal branches (HBs) of some Galactic GCs, most notably NGC 1851, NGC 2808, and NGC 6229. Through analysis of the available color-magnitude diagrams for the GCs in the Fornax and Sagittarius dSph satellites of the Milky Way, as well as their metallicity distributions, we argue that the merger of two GCs would most likely produce a bimodal distribution in red giant branch (RGB) colors, or at least a significant broadening of the RGB, due to the expected difference in metallicity between the two merging globulars. No GC with a bimodal RGB is currently known, and the tightness of the RGB sequences in the above bimodal-HB GCs implies that a merger origin for their HB bimodality is unlikely.; Comment: 9 pages, LaTeX, uses AASTeX v4.0, two embedded postscript figures. To appear in The Astrophysical Journal, Letters to the Editor

## A domain wall between single-mode and bimodal states and its transition to dynamical behavior in inhomogeneous systems

van Hecke, M.; Malomed, B. A.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.07%
We consider domain walls (DW's) between single-mode and bimodal states that occur in coupled nonlinear diffusion (NLD), real Ginzburg-Landau (RGL), and complex Ginzburg-Landau (CGL) equations with a spatially dependent coupling coefficient. Group-velocity terms are added to the NLD and RGL equations, which breaks the variational structure of these models. In the simplest case of two coupled NLD equations, we reduce the description of stationary configurations to a single second-order ordinary differential equation. We demonstrate analytically that a necessary condition for existence of a stationary DW is that the group-velocity must be below a certain threshold value. Above this threshold, dynamical behavior sets in, which we consider in detail. In the CGL equations, the DW may generate spatio-temporal chaos, depending on the nonlinear dispersion.; Comment: 16 pages (latex) including 11 figures; accepted for publication in Physica D

## Fragmentation versus Stability in Bimodal Coalitions

Galam, Serge
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.07%
Competing bimodal coalitions among a group of actors are discussed. First, a model from political sciences is revisited. Most of the model statements are found not to be contained in the model. Second, a new coalition model is built. It accounts for local versus global alignment with respect to the joining of a coalition. The existence of two competing world coaltions is found to yield one unique stable distribution of actors. On the opposite a unique world leadership allows the emergence of unstable relationships. In parallel to regular actors which have a clear coalition choice, neutral" frustrated" and risky" actors are produced. The cold war organisation after world war II is shown to be rather stable. The emergence of a fragmentation process from eastern group disappearance is explained as well as continuing western group stability. Some hints are obtained about possible policies to stabilize world nation relationships. European construction is analyzed with respect to european stability. Chinese stability is also discussed.; Comment: 14 pages, latex, no figures, to appear in Physica A

## Why NS and BH mass distribition is bimodal?

Prokhorov, M. E.; Postnov, K. A.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
25.86%
The observed mass distribution for the compact remnants of massive stars (neutron stars and black holes) and its relationship to possible mechanisms for the ejection of the envelopes of type II and Ib/c supernovae is analyzed. The conclusion is drawn that this distribution can be obtained only by a magneto-rotational mechanism for the supernovae with sufficiently long time of the field amplification, and a soft equation of state for neutron stars with limiting masses \sim1.5-1.6M_\odot. Some consequences of this hypothesis are discussed.; Comment: latex, 4 pages, 5 figures, Talk given at 5th Int. Tsessevich Conf. "Variable Stars", Odessa, Ukraine, August 2001

## On the Bimodal Distribution of Gamma-Ray Bursts

Mao, Shude; Narayan, Ramesh; Piran, Tsvi
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
26.07%
Kouveliotou et al. (1993) recently confirmed that gamma-ray bursts are bimodal in duration. In this paper we compute the statistical properties of the short ($\le 2$~s) and long ($>2$~s) bursts using a method of analysis that makes no assumption regarding the location of the bursts, whether in the Galaxy or at a cosmological distance. We find the 64 ms channel on BATSE to be more sensitive to short bursts and the 1024 ms channel is more sensitive to long bursts. We show that all the currently available data are consistent with the simple hypothesis that both short and long bursts have the same spatial distribution and that within each population the sources are standard candles. The rate of short bursts is $\sim 0.4$ of the rate of long bursts. Although the durations of short and long gamma-ray bursts span several orders of magnitude and the total energy of a typical short burst is smaller than that of a typical long burst by a factor of $\sim 20$, surprisingly the peak luminosities of the two kinds of bursts are equal to within a factor of $\sim 2$.; Comment: 14 pages, LaTeX, figures not included. For figures please contact smao@cfa.harvard.edu

## Some New Aspects of Bimodal Fission in 258Fm Isotope

Staszczak, A.; Lojewski, Z.
Tipo: Artigo de Revista Científica
Using the multidimensional dynamic--programming method (MDPM) in the four--dimensional deformation space $\{\beta_{\lambda}\}$ with $\lambda$=2, 4, 35 and 6 we were able to study evolution of the action integral for the fissioning nucleus $^{258}$Fm. We found the second minimum on the cross--section of the action integral for $\beta_2 \approx 1$ , what we interpret as the dynamical evidence of the bimodal fission in this heavy Fm isotope.; Comment: 7 pages, LaTeX, 4 figures attached as PostScript files