Interaction of the nonionic surfactant C12E8 with high molar mass poly(ethylene oxide) studied by dynamic light scattering and fluorescence quenching methods

Dynamic light scattering has been used to investigate ternary aqueous solutions of n-dodecyl octaoxyethylene glycol monoetber (C12E8) with high molar mass poly(ethylene oxide) (PEO). The measurements were made at 20 °C, always below the cloud point temperature (Tc) of the mixed solutions. The relaxation time distributions are bimodal at higher PEO and surfactant concentrations, owing to the preacute of free surfactant micelles, which coexist with the slower component, representing the polymer coil/micellar cluster comptex. As the surfactant concentration is increased, the apparent hydrodynamic radius (RH) of the coil becomes progressively larger. It is suggested that the complex structure consists of clusters of micelles sited within the polymer coil, as previously concluded for the PEO-C12E8-water system. However. C12E8 interacts less strongly than C12E8 with PEO; at low concentrations of surfactant the complex does not contribute significantly to the total scattered intensity. The perturbation of the PEO coil radius with C12E8 is also smaller than that in the C12E8 system. The addition of PEO strongly decreases the clouding temperature of the system, as previously observed for C12E8/PEO mixtures in solution Addition of PEO up to 0.2% to C12E8 (10 wt %) solutions doss not alter the aggregation number (Nagg) of the micelles probably because the surfactant monomers are equally partitioned as bound and unbound micelles. The critical micelle concentration (cmc), obtained from the I1/I3 ratio (a measure of the dependence of the vibronic band intensities on the pyrene probe environment), does not change when PEO is added, suggesting that for neutral polymer/surfactant systems the trends in Nagg and the cmc do not unambiguously reflect the strength of interaction.

Initial-condition problem for a chiral Gross-Neveu system

A time-dependent projection technique is used to treat the initial-value problem for self-interacting fermionic fields. On the basis of the general dynamics of the fields, we derive formal equations of kinetic-type for the set of one-body dynamical variables. A nonperturbative mean-field expansion can be written for these equations. We treat this expansion in lowest order, which corresponds to the Gaussian mean-field approximation, for a uniform system described by the chiral Gross-Neveu Hamiltonian. Standard stationary features of the model, such as dynamical mass generation due to chiral symmetry breaking and a phenomenon analogous to dimensional transmutation, are reobtained in this context. The mean-field time evolution of nonequilibrium initial states is discussed.

Sintering and mass transport features of (Sn,Ti)O2 polycrystalline ceramics

Different (Sn,Ti)O2 compositions were sintered at 1450 °C for 2 h with the purpose of investigating their sintering and mass transport properties. Highly dense ceramics were obtained and their structural properties studied by X-ray diffraction and scanning electron microscopy. The changes in lattice parameters were analyzed by the Rietveld method and two mass transport mechanisms were observed during sintering in different temperature ranges, evidenced by the linear shrinkage rate as a function of temperature. The effect of the concentration of TiO2 on mass transport and densiffication during sintering was analyzed by considering the intrinsic defects. System densiffication was attributed to a mass transport mechanism in the SnO2 matrix, caused by the presence of TiO2, which formed a solid solution phase. The change in the mass transport mechanism was attributed to chemical bonding between SnO2 and TiO2, which improves ionic difusion as the concentration of TiO2 increased in (Sn,Ti)O2 compositions. © 2002 Elsevier Science Ltd. All rights reserved.

Schwinger-dyson equations and dynamical gluon mass generation

We discuss the solutions obtained for the gluon propagador in Landau gauge within two distinct approximations for the Schwinger-Dyson equations (SDE). The first, named Mandelstam's approximation, consist in neglecting all contributions that come from fermions and ghosts fields while in the second, the ghosts fields are taken into account leading to a coupled system of integral equations. In both cases we show that a dynamical mass for the gluon propagator can arise as a solution. © 2005 American Institute of Physics.

An evaporative and desiccant cooling system for air conditioning in humid climates

Evaporative cooling operates using water and air as working fluids. It consists in water evaporation, through the passage of an airflow, thus decreasing the air temperature. This system has a great potential to provide thermal comfort in places where air humidity is low, being, however, less efficient where air humidity is high. A way to solve this problem is to use dehumidifiers to pre-conditioning the process air. This paper presents a system that can be used in humid climates coupling desiccant dehumidification equipment to evaporative coolers. The paper shows, initially, the main characteristics of the evaporative cooling and of the adsorption dehumidification systems. Later on the coupled systems, in which occurs a dehumidification by adsorption in a counter flow rotary heat exchanger following the evaporate cooling of the air in evaporative coolers, are analyzed. The thermodynamic equations of state are also presented. Following, this paper analyzes some operation parameters such as: reactivation temperature, R/P relationship (reactivation air flow/ process air flow) and the thermodynamic conditions of the entering air flow. The paper shows the conditions for the best operation point, with regard to thermal comfort conditions and to the energy used in the process. In addition this paper presents an application of the system in different climate characteristics of several tropical and equatorial cities. Copyright © 2005 by ABCM.

Experimental damage detection using system norms

Nowadays there is great interest in structural damage detection in systems using nondestructive tests. Once the failure is detected, as for instance a crack, it is possible to take providences. There are several different approaches that can be used to obtain information about the existence, location and extension of the fault in the system by non-destructive tests. Among these methodologies, one can mention different optimization techniques, as for instance classical methods, genetic algorithms, neural networks, etc. Most of these techniques, which are based on element-byelement adjustments of a finite element (FE) model, take advantage of the dynamic behavior of the model. However, in practical situations, usually, is almost impossible to obtain an accuracy model. In this paper, it is proposed an experimental technique for damage location. This technique is based on H: norm to obtain the damage location. The dynamic properties of the structure were identified using experimental data by eigensystem realization algorithm (ERA). The experimental test was carried out in a beam structure through varying the mass of an element. For the output signal was used a piezoelectric sensor. The signal of input of sine form was generated through SignalCalc® software.

Swarm control designs applied to a micro-electro-mechanical gyroscope system (MEMS)

This paper analyzes the non-linear dynamics of a MEMS Gyroscope system, modeled with a proof mass constrained to move in a plane with two resonant modes, which are nominally orthogonal. The two modes are ideally coupled only by the rotation of the gyro about the plane's normal vector. We demonstrated that this model has an unstable behavior. Control problems consist of attempts to stabilize a system to an equilibrium point, a periodic orbit, or more general, about a given reference trajectory. We also developed a particle swarm optimization technique for reducing the oscillatory movement of the nonlinear system to a periodic orbit. © 2010 Springer-Verlag.

The aster mission: Exploring for the first time a triple system asteroid

2001 SN263 is a triple system asteroid. Although it was discovery in 2001, in 2008 astronomical observation carried out by Arecibo observatory revealed that it is actually a system with three bodies orbiting each other. The main central body is an irregular object with a diameter about 2.8 km, while the other two are small objects with less than 1 km across. This system presents an orbital eccentricity of 0.47, with perihelion of 1.04 and aphelion of 1.99, which means that it can be considered as a Near Earth Object. This interesting system was chosen as the target for the Aster mission - first Brazilian space exploration undertaking. A small spacecraft with 150 kg of total mass, 30 kg of payload with 110 W available for the instruments, is scheduled to be launched in 2015, and in 2018 it will approach and will be put in orbit of the triple system. This spacecraft will use electric propulsion and in its payload it will carry image camera, laser rangefinder, infrared spectrometer, mass spectrometer, and experiments to be performed in its way to the asteroid. This mission represents a great challenge for the Brazilian space program. It is being structured to allow the full engagement of the Brazilian universities and technological companies in all the necessary developments to be carried out. In this paper, we present some aspects of this mission, including the transfer trajectories to be used, and details of buss and payload subsystems that are being developed and will be used. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

On the dynamic behaviour of a nonlinear system weakly connected to a linear single degree-of-freedom system

This paper discusses the dynamic behaviour of a nonlinear two degree-of-freedom system consisting of a harmonically excited linear oscillator weakly connected to a nonlinear attachment that behaves as a hardening Duffing oscillator. A system which behaves in this way could be a shaker (linear system) driving a nonlinear isolator. The mass of the nonlinear system is taken to be much less than that in the linear system and thus the nonlinear system has little effect on the dynamics of the linear system. Of particular interest is the situation when the linear natural frequency of the nonlinear system is less than the natural frequency of the linear system such that the frequency response curve of the nonlinear system bends to higher frequencies and thus interacts with the resonance frequency of the linear system. It is shown that for some values of the system parameters a complicated frequency response curve for the nonlinear system can occur; closed detached curves can appear as a part of the overall amplitude-frequency response. The reason why these detached curves appear is presented and approximate analytical expressions for the jump-up and jump-down frequencies of the system under investigation are given.

Effects of liver S9 enzymes on somalargine and solasodine cytotoxicity and mass spectrometric fragmentation

The steroidal glycoalkaloid solamargine and its parent aglycone solasodine, isolated from Solanum palinacanthum, were studied in vitro for cytotoxicity and biotransformation by the hepatic S9 fraction as the metabolic activating system. The MTT uptake assay was used to determine viability after 24 h in RAW 264.7 mouse macrophage-like and SiHa cells exposed to various concentrations of the alkaloids in the presence and absence of the hepatic S9 microsomal fraction. The dose-response curves were established for solamargine and solasodine in the presence and absence of external metabolizing system. From these data, the cytotoxic index (CI50) was calculated with mean values of 7.2 and 13.6 μg/mL for Raw cells and 8.6 and 26.0 μg/mL for SiHa cells, respectively. Mass spectrometry was performed to compare the fragmentation patterns of the alkaloids to predict metabolism by the S9 fraction. The mass spectra demonstrated a distinct fragmentation patterns for solamargine and solasodine after the addition of the S9 fraction. In the present study, we demonstrate that the cytotoxic effect of solamargine and solasodine and their metabolites prepared in vitro by biotransformation with the S9 fraction are comparable. These findings suggest that the metabolic activation system S9 fraction may fail to suppress the cytotoxicity of these alkaloids. © 2013 Springer-Verlag Berlin Heidelberg.

Measurement of masses in the tt̄ system by kinematic endpoints in pp collisions at √s = 7 TeV

A simultaneous measurement of the top-quark, W-boson, and neutrino masses is reported for tt̄ events selected in the dilepton final state from a data sample corresponding to an integrated luminosity of 5.0 fb-1 collected by the CMS experiment in pp collisions at √s = 7 TeV. The analysis is based on endpoint determinations in kinematic distributions. When the neutrino and W-boson masses are constrained to their world-average values, a top-quark mass value of Mt = 173.9 ± 0.9 (stat)+1.7 -2.1(syst.) GeV is obtained. When such constraints are not used, the three particle masses are obtained in a simultaneous fit. In this unconstrained mode the study serves as a test of mass determination methods that may be used in beyond standard model physics scenarios where several masses in a decay chain may be unknown and undetected particles lead to underconstrained kinematics. © 2013 CERN for the benefit of the CMS collaboration.

Production of a bioherbicide agent in liquid and solid medium and in a biphasic cultivation system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Continuous vs. segmented second-dimension system gradients for comprehensive two-dimensional liquid chromatography of sugarcane (Saccharum spp.)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Root system and root and stem base organic reserves of pasture Tanzania grass fertilizer with nitrogen under grazing

The goal of this study was to evaluate the concentrations of non-structural carbohydrate (NSC) and of total nitrogen (N), as well as, to evaluate the root system in Tanzania-grass pastures fertilized with doses of urea in fall, spring and summer. The experiment was conducted at the Experimental Farm of Iguatemi, Maringa, Parana, Brazil, from March 2007 to March 2008. The experimental design was complete random blocks with subplots and four repetitions. The plots showed doses of N (50, 100 e 150 kg ha(-1) of N) plus the control (no N fertilization), and the subplots the season of the year. Root samples were taken at depths of 0-10, 10-20 and 20-40 cm. Root biomass showed a trend for mass accumulation up to a dosage of 100 kg ha(-1) for all seasons evaluated. Also, about 80% of the root system of Tanzaniagrass plants was found on the 0-10 cm layer for all dosages of N. Nitrogen fertilizer above 100 kg ha(-1) may foster fast forage plant growth reducing its NSC root storage capacity although favoring NSC and total N storage at stem base. NSC and total N concentrations were highest in fall, demonstrating that its usage is greater in spring due to the weather conditions being favorable to plant growth. In the regrowth, the largest reserve of total N was at the 0-10 cm root layer and the largest NSC reserve is at stem base.

Assessing melatonin and its oxidative metabolites amounts in biological fluid and culture medium by liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)