Lie properties of symmetric elements in group rings

Let * be an involution of a group G extended linearly to the group algebra KG. We prove that if G contains no 2-elements and K is a field of characteristic p, 0 2, then the *-symmetric elements of KG are Lie nilpotent (Lie n-Engel) if and only if KG is Lie nilpotent (Lie n-Engel). (C) 2008 Elsevier Inc. All rights reserved.

Star-group identities and groups of units

Analogous to *-identities in rings with involution we define *-identities in groups. Suppose that G is a torsion group with involution * and that F is an infinite field with char F not equal 2. Extend * linearly to FG. We prove that the unit group U of FG satisfies a *-identity if and only if the symmetric elements U(+) satisfy a group identity.

A BROADER CONTEXT FOR MONOTONICALLY MONOLITHIC SPACES

This is a sequel of the work done on (strongly) monotonically monolithic spaces and their generalizations. We introduce the notion of monotonically kappa-monolithic space for any infinite cardinal kappa and present the relevant results. We show, among other things, that any sigma-product of monotonically kappa-monolithic spaces is monotonically kappa-monolithic for any infinite cardinal kappa; besides, it is consistent that any strongly monotonically omega-monolithic space with caliber omega(1) is second countable. We also study (strong) monotone kappa-monolithicity in linearly ordered spaces and subspaces of ordinals.

Myoglobin-H(2)O(2) catalyzes the oxidation of beta-ketoacids to alpha-dicarbonyls: Mechanism and implications in ketosis

Acetoacetate (AA) and 2-methylacetoacetate (MAA) are accumulated in metabolic disorders such as diabetes and isoleucinemia. Here we examine the mechanism of AA and MAA aerobic oxidation initiated by myoglobin (Mb)/H(2)O(2). We propose a chemiluminescent route involving a dioxetanone intermediate whose thermolysis yields triplet alpha-dicarbonyl species (methylglyoxal and diacetyl). The observed ultraweak chemiluminescence increased linearly on raising the concentration of either Mb (10-500 mu M) or AA (10-100 mM). Oxygen uptake studies revealed that MAA is almost a 100-fold more reactive than AA. EPR spin-trapping studies with MNP/MAA revealed the intermediacy of an alpha-carbon-centered radical and acetyl radical. The latter radical, probably derived from triplet diacetyl, is totally suppressed by sorbate, a well-known quencher of triplet carbonyls. Furthermore, an EPR signal assignable to MNP-AA(center dot) adduct was observed and confirmed by isotope effects. Oxygen consumption and a-dicarbonyl yield were shown to be dependent on AA or MAA concentrations (1-50 mM) and on H(2)O(2) or tert-butOOH added to the Mb-containing reaction mixtures. That ferrylMb is involved in a peroxidase cycle acting on the substrates is suggested by the reaction pH profiles and immunospin-trapping experiments. The generation of radicals and triplet dicarbonyl products by Mb/H(2)O(2)/beta-ketoacids may contribute to the adverse health effects of ketogenic unbalance. (C) 2011 Elsevier Inc. All rights reserved.

Optical and electrical characterization of samaria-doped ceria

Ce(0.8)SM(0.2)O(1.9) and CeO(2) nanomaterials were prepared by a solution technique to produce an ultrafine particulate material with high sinterability. In this work, the structural characteristics, the photoluminescent behavior and the ionic conductivity of the synthesized materials are focused. The thermally decomposed material consists of less than 10 nm in diameter nanoparticles. The Raman spectrum of pure CeO(2) consists of a single triple degenerate F(2g) model characteristic of the fluorite-like structure. The full width at half maximum of this band decreases linearly with increasing calcination temperature. The photoluminescence spectra show a broadened emission band assigned to the ligand-to-metal charge-transfer states O -> Ce(4+). The emission spectra of the Ce(0.8)Sm(0.2)O(1.9) specimens present narrow bands arising from the 4G(5/2) -> (6)H(J) transitions (J = 5/2, 7/2, 9/2 and 11/2) of Sm(3+) ion due to the efficient energy transfer from the O -> Ce(4+) transitions to the emitter 4G(5/2) level. The ionic conductivity of sintered specimens shows a significant dependence on density. (C) 2009 Elsevier B.V. All rights reserved.

Solvation in Pure Liquids: What Can Be Learned from the Use of Pairs of Indicators?

The solvation of six solvatochromic probes in a large number of solvents (33-68) was examined at 25 degrees C. The probes employed were the following: 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1-yl) phenolate (RB); 4-[(E)2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePM; 1-methylquinolinium-8-olate, QB; 2-bromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePMBr, 2,6-dichloro-4-(2,4,6-triphenyl pyridinium-1-yl) phenolate (WB); and 2,6-dibromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl] phenolate, MePMBr(2), respectively. Of these, MePMBr is a novel compound. They can be grouped in three pairs, each with similar pK(a) in water but with different molecular properties, for example, lipophilicity and dipole moment. These pairs are formed by RB and MePM; QB and MePMBr; WB and MePMBr(2), respectively. Theoretical calculations were carried out in order to calculate their physicochemical properties including bond lengths, dihedral angles, dipole moments, and wavelength of absorption of the intramolecular charge-transfer band in four solvents, water, methanol, acetone, and DMSO, respectively. The data calculated were in excellent agreement with available experimental data, for example, bond length and dihedral angles. This gives credence to the use of the calculated properties in explaining the solvatochromic behaviors observed. The dependence of an empirical solvent polarity scale E(T)(probe) in kcal/mol on the physicochemical properties of the solvent (acidity, basicity, and dipolarity/polarizability) and those of the probes (pK(a), and dipole moment) was analyzed by using known multiparameter solvation equations. For each pair of probes, values of E(T)(probe) (for example, E(T)(MePM) versus E(T)(RB)) were found to be linearly correlated with correlation coefficients, r, between 0.9548 and 0.9860. For the mercyanine series, the values of E(T)(probe) also correlated linearly, with (r) of 0.9772 (MePMBr versus MePM) and 0.9919 (MePMBr(2) versus MePM). The response of each pair of probes (of similar pK(a)) to solvent acidity is the same, provided that solute-solvent hydrogen-bonding is not seriously affected by steric crowding (as in case of RB). We show, for the first time, that the response to solvent dipolarity/polarizability is linearly correlated to the dipole moment of the probes. The successive introduction of bromine atoms in MePM (to give MePMBr, then MePMBr(2)) leads to the following linear decrease: pK(a) in water, length of the phenolate oxygen-carbon bond, length of the central ethylenic bond, susceptibility to solvent acidity, and susceptibility to solvent dipolarity/polarizability. Thus studying the solvation of probes whose molecular structures are varied systematically produces a wealth of information on the effect of solute structure on its solvation. The results of solvation of the present probes were employed in order to test the goodness of fit of two independent sets of solvent solvatochromic parameters.

Thermo-solvatochromism of merocyanine polarity probes - What are the consequences of increasing probe lipophilicity through annelation?

The question raised in the title has been answered by comparing the solvatochromism of two series of polarity probes, the lipophilicities of which were increased either by increasing the length of an alkyl group (R) attached to a fixed pyridine-based structure or through annelation (i.e., by fusing benzene rings onto a central pyridine-based structure). The following novel solvatochromic probes were synthesized: 2,6-dibromo-4-[(E)-2-(1-methylquinolinium-4-yl)ethenyl]-phenolate (MeQMBr(2)) and 2,6-dibromo-4-[(E)-2-(1-methyl-acridinium-4- yl) ethenyl)]phenolate (MeAMBr(2) The solvatochromic behavior of these probes, along with that of 2,6dibromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl]phenol-ate(MePMBr(2)) was analyzed in terms of increasing probe lipophilicity, through annelation. Values of the empirical solvent polarity scale [E(T)(MePMBr(2))] in kcalmol(-1) correlated linearly with ET(30), the corresponding values for the extensively employed probe 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1-yl)phenolate (RB). On the other hand, the nonlinear correlations of ET(MeQMBr(2)) or ET(MeAMBr(2)) with E(T)(30) are described by second-order polynomials. Possible reasons for this behavior include: i) self-aggregation of the probe, ii) photoinduced cis/trans isomerization of the dye, and iii) probe structure- and solvent-dependent contributions of the quinonoid and zwitterionic limiting formulas to the ground and excited states of the probe. We show that mechanisms (i) and (ii) are not operative under the experimental conditions employed; experimental evidence (NMR) and theoretical calculations are presented to support the conjecture that the length of the central ethenylic bond in the dye increases in the order MeAMBr(2) > MeQMBr(2) > MePMBr(2), That is, the contribution of the zwitterionic limiting formula predominates for the latter probe, as is also the case for RB, this being the reason for the observed linear correlation between the ET(MePMBr2) and the ET(30) scales. The effect of increasing probe lipophilicity on solvatochromic behavior therefore depends on the strategy employed. Increasing the length of R affects solvatochromism much less than annelation, because the former structural change hardly perturbs the energy of the intramolecular charge-transfer transition responsible for solvatochromism. The thermo-solvatochromic behavior (effect of temperature on solvatochromism) of the three probes was studied in mixtures of water with propanol and/or with DMSO. The solvation model used explicitly considers the presence of three ""species"" in the system: bulk solution and probe solvation shell [namely, water (W), organic solvent (Solv)], and solvent-water hydrogen-bonded aggregate (Solv-W). For aqueous propanol, the probe is efficiently solvated by Solv-W; the strong interaction of DMSO with W drastically decreases the efficiency of Solv-W in solvating the probe, relative to its precursor solvents. Temperature increases resulted in desolvation of the probes, due to the concomitant reduction in the structured characters of the components of the binary mixtures.

Acetylation of cellulose in LiCl-N,N-dimethylacetamide: first report on the correlation between the reaction efficiency and the aggregation number of dissolved cellulose

The acylation of three cellulose samples by acetic anhydride, Ac(2)O, in the solvent system LiCl/N,N-dimethylacetamide, DMAc (4 h, 110 A degrees C), has been revisited in order to investigate the dependence of the reaction efficiency on the structural characteristics of cellulose, and its aggregation in solution. The cellulose samples employed included microcrystalline, MCC; mercerized cotton linters, M-cotton, and mercerized sisal, M-sisal. The reaction efficiency expresses the relationship between the degree of substitution, DS, of the ester obtained, and the molar ratio Ac(2)O/AGU (anhydroglucose unit of the biopolymer); 100% efficiency means obtaining DS = 3 at Ac(2)O/AGU = 3. For all celluloses, the dependence of DS on Ac(2)O/AGU is described by an exponential decay equation: DS = DS(o) - Ae(-[(Ac2O/AGU)/B]); (A) and (B) are regression coefficients, and DS(o) is the calculated maximum degree of substitution, achieved under the conditions of each experiment. Values of (B) are clearly dependent on the cellulose employed: B((M-cotton)) > B((M-sisal)) > B((MCC)); they correlate qualitatively with the degree of polymerization of cellulose, and linearly with the aggregation number, N(agg), of the dissolved biopolymer, as calculated from static light scattering measurements: (B) = 1.709 + 0.034 N(agg). To our knowledge, this is the first report on the latter correlation; it shows the importance of the physical state of dissolved cellulose, and serves to explain, in part, the need to use distinct reaction conditions for MCC and fibrous celluloses, in particular Ac(2)O/AGU, time, temperature.

Surface Properties of Calcinated Titanium Dioxide Probed by Solvatochromic Indicators: Relevance to Catalytic Applications

Titanium dioxide was obtained by hydrolysis of the corresponding ethoxide, followed by washing, drying, and calcination at 80, 160, 240, 320, 400, and 700 C, respectively. The following surface properties of the solids obtained were determined as a function of the calcinations temperature: T(Calcn); area by the BET method; BrOnsted acidity by titration with sodium hydroxide; empirical polarity, ET(30); Lewis acidity, alpha(Surf); Lewis basicity, beta(Surf); and dipolarity/polarizability pi*(Sturf), by use of solvatochromic indicators. Except for le surf whose value increased slightly, heating the samples resulted in a decrease of all of the above-mentioned surface properties, due to the decrease of surface hydroxyl groups. This conclusion has been corroborated by FTIR. Values of E(T)(30), alpha(Surf), and pi*(Surf) are higher than those of water and alcohols; the BrOnsted and Lewis acidities of the samples correlate linearly. The advantages of using solvatochromic indicators to probe the surface properties and relevance of the results to the applications of TiO(2) are discussed.

Behaviour of TiO(2)-SiMgO(x) hybrid composites on the solar photocatalytic degradation of polluted air

The photocatalytic performance of TiO(2)-SiMgO(x) ceramic plates for trichloroethylene abatement in gas phase has been evaluated under sun irradiance conditions. A continuous flow Pyrex glass reactor fixed on the focus of a compound parabolic collector has been used. The performance of the hybrid photocatalyst has been evaluated as the variation of TCE conversion and reaction products formation with the solar irradiance at different total gas flow, TCE concentration, and water vapour content. SiMgO(x) not only provides adsorbent properties to the photocatalyst, but it also allows the effective use of the material during low solar irradiance conditions. The adsorption-desorption phenomena play a pivotal role in the behaviour of the system. Thus, TCE conversion curves present two different branches when the sun irradiance increases (sunrise) or decreases (sunset). CO(2), COCl(2) and DCAC were the most relevant products detected. Meanwhile CO(2) concentration was insensitive to the branch analysed, COCl(2) or DCAC were not indicating the ability of these compounds to be adsorbed on the composite. An increase of the UV irradiation at total TCE conversion promotes the CO(2) selectivity. The excess of energy arriving to the reactor favours the direct reaction pathway to produce CO(2). The photonic efficiency, calculated as a function of the rate of CO(2) formation, decreases linearly with the solar irradiance up to around 2 mW cm(-2), where it becomes constant. For decontamination systems high TCE conversion is pursuit and then high solar irradiance values are required, in spite of lower photonic efficiency values. The present photocatalyst configuration, with only 17% of the reactor volume filled with the photoactive material, allows total TCE conversion for 150 ppm and 1 L min(-1) in a wide sun irradiance window from 2 to 4 mW cm(-2). The incorporation of water vapour leads to an increase of the CO(2) selectivity keeping the TCE conversion around 90%, although significant amounts of COCl(2) were observed. (c) 2010 Elsevier B.V. All rights reserved.

Anodic stripping voltammetric determination of copper(II) using a functionalized carbon nanotubes paste electrode modified with crosslinked chitosan

The development and application of a functionalized carbon nanotubes paste electrode (CNPE) modified with crosslinked chitosan for determination of Cu(II) in industrial wastewater, natural water and human urine samples by linear scan anodic stripping voltammetry (LSASV) are described. Different electrodes were constructed using chitosan and chitosan crosslinked with glutaraldehyde (CTS-GA) and epichlorohydrin (CTS-ECH). The best voltammetric response for Cu(II) was obtained with a paste composition of 65% (m/m) of functionalized carbon nanotubes, 15% (m/m) of CTS-ECH, and 20% (m/m) of mineral oil using a solution of 0.05 mol L(-1) KNO(3) with pH adjusted to 2.25 with HNO(3), an accumulation potential of 0.3V vs. Ag/AgCl (3.0 mol L(-1) KCl) for 300 s and a scan rate of 100 mV s(-1). Under these optimal experimental conditions, the voltammetric response was linearly dependent on the Cu(II) concentration in the range from 7.90 x 10(-8) to 1.60 x 10(-5) mol L(-1) with a detection limit of 1.00 x 10(-8) mol L(-1). The samples analyses were evaluated using the proposed sensor and a good recovery of Cu(II) was obtained with results in the range from 98.0% to 104%. The analysis of industrial wastewater, natural water and human urine samples obtained using the proposed CNPE modified with CTS-ECH electrode and those obtained using a comparative method are in agreement at the 95% confidence level. (C) 2009 Elsevier B. V. All rights reserved.

A surface-enhanced infrared absorption spectroscopic (SEIRAS) study of the oscillatory electro-oxidation of methanol on platinum

The oscillatory electro-oxidation of methanol was studied by means of in situ infrared (IR) spectroscopy in the attenuated total reflection (ATR) configuration using a platinum film on a Si prism as working electrode. The surface-enhanced infrared absorption (SEIRA) effect considerably improves the spectroscopic resolution, allowing at following the coverage of some adsorbing species during the galvanostatic oscillations. Carbon monoxide was the main adsorbed specie observed in the induction period and within the oscillatory regime. The system was investigated at two distinct time-scales and its dynamics characterized accordingly. During the induction period the main transformation observed as the system move through the phase space towards the oscillatory region was the decrease of the coverage of adsorbed carbon, coupled to the increase of the electrode potential. Similar transition characterizes the evolution within the oscillatory region, but at a considerably slower rate. Experiments with higher time resolution revealed that the electrode potential oscillates in-phase with the frequency of the linearly adsorbed CO vibration and that the amount of adsorbed CO oscillates with small amplitude. Adsorbed formate was found to play, if any, a very small role. Results are discussed and compared with other systems. (C) 2010 Elsevier B.V. All rights reserved.

Accelerated aging of thick glass second surface silvered reflectors under sandstorm conditions

Concentrated solar power systems are expected to be sited in desert locations where the direct normal irradiation is above 1800 kWh/m2.year. These systems include large solar collector assemblies, which account for a significant share of the investment cost. Solarreflectors are the main components of these solar collector assemblies and dust/sand storms may affect their reflectance properties, either by soiling or by surface abrasion. While soiling can be reverted by cleaning, surface abrasion is a non reversible degradation.The aim of this project was to study the accelerated aging of second surface silvered thickglass solar reflectors under simulated sandstorm conditions and develop a multi-parametric model which relates the specular reflectance loss to dust/sand storm parameters: wind velocity, dust concentration and time of exposure. This project focused on the degradation caused by surface abrasion.Sandstorm conditions were simulated in a prototype environmental test chamber. Material samples (6cm x 6cm) were exposed to Arizona coarse test dust. The dust stream impactedthese material samples at a perpendicular angle. Both wind velocity and dust concentrationwere maintained at a stable level for each accelerated aging test. The total exposure time in the test chamber was limited to 1 hour. Each accelerated aging test was interrupted every 4 minutes to measure the specular reflectance of the material sample after cleaning.The accelerated aging test campaign had to be aborted prematurely due to a contamination of the dust concentration sensor. A robust multi-parametric degradation model could thus not be derived. The experimental data showed that the specular reflectance loss decreasedeither linearly or exponentially with exposure time, so that a degradation rate could be defined as a single modeling parameter. A correlation should be derived to relate this degradation rate to control parameters such as wind velocity and dust/sand concentration.The sandstorm chamber design would have to be updated before performing further accelerated aging test campaigns. The design upgrade should improve both the reliability of the test equipment and the repeatability of accelerated aging tests. An outdoor exposure test campaign should be launched in deserts to learn more about the intensity, frequencyand duration of dust/sand storms. This campaign would also serve to correlate the results of outdoor exposure tests with accelerated exposure tests in order to develop a robust service lifetime prediction model for different types of solar reflector materials.

Testing linear cointegration against smooth-transition cointegration

This paper studies a smooth-transition (ST) type cointegration. The proposed ST cointegration allows for regime switching structure in a cointegrated system. It nests the linear cointegration developed by Engle and Granger (1987) and the threshold cointegration studied by Balke and Fomby (1997). We develop F-type tests to examine linear cointegration against ST cointegration in ST-type cointegrating regression models with or without time trends. The null asymptotic distributions of the tests are derived with stationary transition variables in ST cointegrating regression models. And it is shown that our tests have nonstandard limiting distributions expressed in terms of standard Brownian motion when regressors are pure random walks, while have standard asymptotic distributions when regressors contain random walks with nonzero drift. Finite-sample distributions of those tests are studied by Monto Carlo simulations. The small-sample performance of the tests states that our F-type tests have a better power when the system contains ST cointegration than when the system is linearly cointegrated. An empirical example for the purchasing power parity (PPP) data (monthly US dollar, Italy lira and dollar-lira exchange rate from 1973:01 to 1989:10) is illustrated by applying the testing procedures in this paper. It is found that there is no linear cointegration in the system, but there exits the ST-type cointegration in the PPP data.

Sobre o sistema de amortização linear crescente

Aiming to reach a compromise solution to the issues of default risk and the payment capacity of takers of housing loans, Jorge Oscar de Mello Flôres submited to the Banco Nacional de Habitação, which was then in charge of the Brazilian System of Housing Financing, what he named as the Linearly Increasing System of Amortization. (LISA). Following a critical analysis of the LISA, it is proposed the alternative named as the Generalyzed System of Mixed Amortization (GSMA).