Aproveitamento da casca de banana na elaboração de barras de cereais: avaliação dos compostos bioativos, características físicas e sensoriais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Impact of Solvent Quality on the Density Profiles of Looped Triblock Copolymer Brushes by Neutron Reflectivity Measurements

Preferential adsorption of poly(2-vinylpyridine)-deuterated polystyrene-poly(2-vinylpyridine) (PVP-dPS-PVP) triblock copolymers from toluene onto silicon leads to the formation of dPS loops tethered by the PVP end blocks. Using neutron reflectometry, we have determined the segment density profiles of these looped polymer brushes in toluene, a good solvent for the dPS block, and in cyclohexane at 20 °C (poor solvent), 32 °C, (near-Θ solvent), and 50 °C (marginal solvent). While the swelling behavior qualitatively agrees with that observed for singly grafted brushes, there are interesting differences in the local structural details: In a good solvent, the segment density profiles are composed of an inner parabolic region and a long, extended tail. In cyclohexane, the profiles are described by exponential decays. We ascribe these features to a novel polydispersity effect that arises due to tethering the PS loops by both ends. The results also show that the less dense layers undergo more significant changes in swollen height as solvent quality is changed and that the looped brushes of different molecular weight, asymmetry, and tethering density adhere to scaling relationships derived for lightly cross-linked polymer gels.

Stability of Order in Solvent-Annealed Block Copolymer Thin Films

ABSTRACT: One way to produce high order in a block copolymer thin film is by solution casting a thin film and slowly evaporating the solvent in a sealed vessel. Such a solvent-annealing process is a versatile method to produce a highly ordered thin film of a block copolymer. However, the ordered structure of the film degrades over time when stored under ambient conditions. Remarkably, this aging process occurs in mesoscale thin films of polystyrene-polyisoprene triblock copolymer where the monolayer of vitrified 15 nm diameter polystyrene cylinders sink in a 20 nm thick film at 22 °C. The transformation is studied by atomic force microscopy (AFM). We describe the phenomena, characterize the aging process, and propose a semiquantitative model to explain the observations. The residual solvent effects are important but not the primary driving force for the aging process. The study may lead to effective avenue to improve order and make the morphology robust and possibly the solvent-annealing process more effective.

Effective Thermal Conductivity Estimates Of Particulate Mixtures

Several theories have been advanced to estimate effective thermal conductivities of particulate mixtures, but most theories have focused on the dilute case. A method is proposed to estimate the effective thermal conductivity coefficient of mixtures of arbitrary concentration. Earlier the authors developed a theory to determine the expected contact area between different species. This theory is employed to determine the Kapitza resistance of the heterogeneous mixture and forms part of an overall theory to estimate the effective thermal conductivity. Results are compared with other theoretical estimates and with experiments.

Dissolution Enhancement and Characterization of Nimodipine Solid Dispersions with Poloxamer 407 or PEG 6000

The solid dispersion approach is an alternative to increase drug solubility. Many carriers have been studied, but there is few information about poloxamer 407 (P407). Consequently, the objective of this study was to evaluate P407 as a carrier for nimodipine solid dispersions and to compare its solubility and dissolution rates with those from polyethylene glycol (PEG 6000). The solid dispersions were prepared by the hot melting and solvent methods and they were characterized by FTIR, DSC, solubility, and dissolution tests. The results indicated a three-fold increase in solid dispersions solubility in the presence with P407 than those prepared with PEG.

A cyclic bipolar wind in the interacting binary V 393 Scorpii

V393 Scorpii is a double periodic variable characterized by a relatively stable non-orbital photometric cycle of 253 d. Mennickent et al. argue for the presence of a massive optically thick disc around the more massive B-type component and describe the evolutionary stage of the system. In this paper, we analyse the behaviour of the main spectroscopic optical lines during the long non-orbital photometric cycle. We study the radial velocity of the donor determining its orbital elements and find a small but significant orbital eccentricity (e = 0.04). The donor spectral features are modelled and removed from the spectrum at every observing epoch using the light-curve model given by Mennickent et al. We find that the line emission is larger during eclipses and mostly comes from a bipolar wind. We also find that the long cycle is explained in terms of a modulation of the wind strength; the wind has a larger line and continuum emissivity at the high state. We report the discovery of highly variable chromospheric emission in the donor, as revealed by the Doppler maps of the emission lines Mg II 4481 and C I 6588. We discuss notable and some novel spectroscopic features like discrete absorption components, especially visible at blue depressed O I 7773 absorption wings during the second half-cycle, Balmer double emission with V/R curves showing 'Z-type' and 'S-type' excursions around secondary and main eclipses, respectively, and H beta emission wings extending up to +/- 2000 km s(-1). We also discuss possible causes for these phenomena and for their modulations with the long cycle.

MHD numerical simulations of colliding winds in massive binary systems - I. Thermal versus non-thermal radio emission

In the past few decades detailed observations of radio and X-ray emission from massive binary systems revealed a whole new physics present in such systems. Both thermal and non-thermal components of this emission indicate that most of the radiation at these bands originates in shocks. O and B-type stars and WolfRayet (WR) stars present supersonic and massive winds that, when colliding, emit largely due to the freefree radiation. The non-thermal radio and X-ray emissions are due to synchrotron and inverse Compton processes, respectively. In this case, magnetic fields are expected to play an important role in the emission distribution. In the past few years the modelling of the freefree and synchrotron emissions from massive binary systems have been based on purely hydrodynamical simulations, and ad hoc assumptions regarding the distribution of magnetic energy and the field geometry. In this work we provide the first full magnetohydrodynamic numerical simulations of windwind collision in massive binary systems. We study the freefree emission characterizing its dependence on the stellar and orbital parameters. We also study self-consistently the evolution of the magnetic field at the shock region, obtaining also the synchrotron energy distribution integrated along different lines of sight. We show that the magnetic field in the shocks is larger than that obtained when the proportionality between B and the plasma density is assumed. Also, we show that the role of the synchrotron emission relative to the total radio emission has been underestimated.

Hydration and anomalous solubility of the Bell-Lavis model as solvent

We address the investigation of the solvation properties of the minimal orientational model for water originally proposed by [Bell and Lavis, J. Phys. A 3, 568 (1970)]. The model presents two liquid phases separated by a critical line. The difference between the two phases is the presence of structure in the liquid of lower density, described through the orientational order of particles. We have considered the effect of a small concentration of inert solute on the solvent thermodynamic phases. Solute stabilizes the structure of solvent by the organization of solvent particles around solute particles at low temperatures. Thus, even at very high densities, the solution presents clusters of structured water particles surrounding solute inert particles, in a region in which pure solvent would be free of structure. Solute intercalates with solvent, a feature which has been suggested by experimental and atomistic simulation data. Examination of solute solubility has yielded a minimum in that property, which may be associated with the minimum found for noble gases. We have obtained a line of minimum solubility (TmS) across the phase diagram, accompanying the line of maximum density. This coincidence is easily explained for noninteracting solute and it is in agreement with earlier results in the literature. We give a simple argument which suggests that interacting solute would dislocate TmS to higher temperatures.

Effect of humidity and solvent vapor phase on cellulose esters films

In the present study the effect of relative humidity (RH) during spin-coating process on the structural characteristics of cellulose acetate (CA), cellulose acetate phthalate (C-A-P), cellulose acetate butyrate (CAB) and carboxymethyl cellulose acetate butyrate (CMCAB) films was investigated by means of atomic force microscopy (AFM), ellipsometry and contact angle measurements. All polymer solutions were prepared in tetrahydrofuran (THF), which is a good solvent for all cellulose esters, and used for spin-coating at RH of (35 +/- A 5)%, (55 +/- A 5)% or (75 +/- A 5)%. The structural features were correlated with the molecular characteristics of each cellulose ester and with the balance between surface energies of water and THF and interface energy between water and THF. CA, CAB, CMCAB and C-A-P films spin-coated at RH of (55 +/- A 5)% were exposed to THF vapor during 3, 6, 9, 60 and 720 min. The structural changes on the cellulose esters films due to THF vapor exposition were monitored by means of AFM and ellipsometry. THF vapor enabled the mobility of cellulose esters chains, causing considerable changes in the film morphology. In the case of CA films, which are thermodynamically unstable, dewetting was observed after 6 min exposure to THF vapor. On the other hand, porous structures observed for C-A-P, CAB and CMCAB turned smooth and homogeneous after only 3 min exposure to THF vapor.

Estimation and diagnostics for heteroscedastic nonlinear regression models based on scale mixtures of skew-normal distributions

An extension of some standard likelihood based procedures to heteroscedastic nonlinear regression models under scale mixtures of skew-normal (SMSN) distributions is developed. This novel class of models provides a useful generalization of the heteroscedastic symmetrical nonlinear regression models (Cysneiros et al., 2010), since the random term distributions cover both symmetric as well as asymmetric and heavy-tailed distributions such as skew-t, skew-slash, skew-contaminated normal, among others. A simple EM-type algorithm for iteratively computing maximum likelihood estimates of the parameters is presented and the observed information matrix is derived analytically. In order to examine the performance of the proposed methods, some simulation studies are presented to show the robust aspect of this flexible class against outlying and influential observations and that the maximum likelihood estimates based on the EM-type algorithm do provide good asymptotic properties. Furthermore, local influence measures and the one-step approximations of the estimates in the case-deletion model are obtained. Finally, an illustration of the methodology is given considering a data set previously analyzed under the homoscedastic skew-t nonlinear regression model. (C) 2012 Elsevier B.V. All rights reserved.

Epiphany root canal sealer prepared with resinous solvent is irritating to rat subcutaneous tissues

Objective: This study assessed the biocompatibility of the Epiphany endodontic sealer prepared with resinous solvent of Epiphany system (Thinning resin) in rat subcutaneous tissues. Study Design: Polyethylene tubes were filled with the sealer and 4 groups were established: GI, Epiphany prepared with 1 drop of resinous solvent (RS); GII, Epiphany prepared with 1 drop of RS and photoactivated; GIII, Epiphany associated with self-etch primer and prepared with 1 drop of RS; GIV, Epiphany associated with self-etch primer, prepared with 1 drop of RS and photoactivated. The filled tubes were implanted into 4 different regions of the dorsum of 20 adult male rats. Results: After 7, 14 and 21 days, all groups presented a moderate to severe chronic inflammation, necrosis and foreign-body giant cells. At 42 days, although the intensity of chronic inflammatory reaction decreased, the other features still were observed. Conclusion: The Epiphany sealer prepared with the RS was irritating to rat subcutaneous tissues.

Transesterification of Palm Oil Catalyzed by Pseudomonas fluorescens Lipase in a Packed-Bed Reactor

Transesterification of palm oil with ethanol catalyzed by Pseudomonas fluorescens lipase immobilized on epoxy-polysiloxane-polyvinyl alcohol composite (epoxy-SiO2-PVA) was performed in a continuous packed-bed reactor (PBR). Two strategies were used for improving the miscibility of the substrates: the addition of the organic solvent tert-butanol and the surfactant Triton X-100. Results were compared to those obtained in a solventless reactor, which displayed a biphasic system that passed through the reactor. Using this system, the ethyl ester yield of 61.6 +/- 1.2% was obtained at steady state. Both Triton X-100 and tert-butanol systems were found to be suitable to promote the miscibility of the starting materials; however, the use of Triton X-100 reduced the yield to levels lower than 20%, because of the enzyme desorption from the support surface, as confirmed by scanning electron microscopy analysis. The best performance was found for the reactor running in the presence of tert-butanol which resulted in a stable operating system and an average yield of 87.6 +/- 2.5%. This strategy also gave high biocatalyst operational stability, revealing a half-life of 48 days and an inactivation constant of 0.6 X 10(-3) h(-1).

Polarimetry of the binary PDS 144

Aims. Our goal is to study the circumstellar environment associated with each component of the wide intermediate-mass pre-main sequence binary system PDS 144 using broadband polarimetry. Methods. We present near-infrared (NIR) linear polarimetric observations of PDS 144 gathered with the IAGPOL imaging polarimeter along with the CamIV infrared camera at the Observatorio do Pico dos Dias (OPD). In addition, we re-analyzed OPD archive optical polarization to separate the binary and estimate the interstellar polarization using foreground stars. Results. After discounting the interstellar component, we found that both stars of the binary system are intrinsically polarized. The polarization vectors at optical and NIR bands of both components are aligned with the local magnetic field and the jet axis. These findings indicate an interplay between the interstellar magnetic field and the formation of the binary system. We also found that the PDS 144N is less polarized than its southern companion in the optical. However, in the NIR PDS 144N is more polarized. Our polarization data can only be explained by high inclinations (i greater than or similar to 80 degrees) for the disks of both members. In particular, comparisons of our NIR data with young stellar objects disk models suggest predominantly small grains in the circumstellar environment of PDS 144N. In spite of the different grain types in each component, the infrared spectral indexes indicate a coeval system. We also found evidence of coplanarity between the disks.

Latent residual analysis in binary regression with skewed link

Model diagnostics is an integral part of model determination and an important part of the model diagnostics is residual analysis. We adapt and implement residuals considered in the literature for the probit, logistic and skew-probit links under binary regression. New latent residuals for the skew-probit link are proposed here. We have detected the presence of outliers using the residuals proposed here for different models in a simulated dataset and a real medical dataset.

Accelerated Solvent Extraction for Gas Chromatographic Analysis of Nicotine and Cotinine in Meconium Samples

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)