Bayesian outlier analysis in binary regression

We propose alternative approaches to analyze residuals in binary regression models based on random effect components. Our preferred model does not depend upon any tuning parameter, being completely automatic. Although the focus is mainly on accommodation of outliers, the proposed methodology is also able to detect them. Our approach consists of evaluating the posterior distribution of random effects included in the linear predictor. The evaluation of the posterior distributions of interest involves cumbersome integration, which is easily dealt with through stochastic simulation methods. We also discuss different specifications of prior distributions for the random effects. The potential of these strategies is compared in a real data set. The main finding is that the inclusion of extra variability accommodates the outliers, improving the adjustment of the model substantially, besides correctly indicating the possible outliers.

2006 GEP-ISFG collaborative exercise on mtDNA: reflections about interpretation, artefacts, and DNA mixtures

We report the results of the seventh edition of the GEP-ISFG mitochondrial DNA (mtDNA) collaborative exercise. The samples submitted to the participant laboratories were blood stains from a maternity case and Simulated forensic samples, including a case of mixture. The success rate for the blood stains was moderate (similar to 77%); even though four inexperienced laboratories concentrated about one-third of the total errors. A similar success was obtained for the analysis of mixed samples (78.8% for a hair-saliva mixture and 69.2% for a saliva-saliva Mixture). Two laboratories also dissected the haplotypes contributing to the saliva-saliva mixture. Most of the errors were due to reading problems and misinterpretation of electropherograms, demonstrating once more that the lack of a solid devised experimental approach is the main cause of error in mtDNA testing. (C) 2007 Elsevier B.V. All rights reserved.

Thermodynamic properties of liquid mixtures. II. Dimethylformamide-water

The excess enthalpy of mixing of DMF-water was measured at 25° C in the 0-1 molar fraction range. The maximum of heat is developed for a 0.33 DMF molar fraction. The excess partial molar and other excess quantities were also calculated for the DMF-water system at 25° C. The results suggest a strong interaction between DMF and water. © 1983.

Spectrophotometric study of binary and ternary systems involving metal ions and benzylidenepyruvates: Equilibria in aqueous solutions

The protonation of 4-dimethylaminobenzylidenepyruvate (DMBP) and 2-chloro-4-dimethylaminobenzylidenepyruvate (2-CI-DMBP) and their complex formation with Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cd(II) and Al(III) have been studied by potentiometric and spectrophotometric methods at 25 °C and ionic strength 0.500 M, held with sodium perchlorate. The stability order found for 1 :1 complexes of both ligands is Al(III) > Cu(II) > Pb(II) > Ni(II) > Zn(II) > Co(II) > Cd(II) > Mn(II). The stability changes move in the same direction as the pKa of the ligands. The results are compared with literature values reported for metal ion pyruvate systems. Thermodynamic stabilities of ternary complexes formed in Cu(II)-B-L- systems, where B = 2,2′-bipyridyl (bipy), ethylenediamine or glycinate and L = DMBP or 2-CI-DMBP, were also determined. The Cu(bipy)L+ species are more stable than would be expected on purely statistical grounds. The importance of the :t system associated with bipy on the enhanced stability of its mixed ligand complexes is stressed. Analytical applications of the investigated ligands are outlined.

Counterion effects on the structure and solubilization properties of anionic detergents. Role of hydrophobic cations in stabilizing micelles and attenuating their solvent properties

A series of alkyl sulfate detergents has been investigated in the presence of the cations Na +, methylviologen(2+) (MV 2+), 4-(cyanomethyl)pyridinium(1+) (CMP +), and tetramethylammonium (TMA +). The binding of these ions to the aqueous micellar assemblies has been measured through studies of luminescence quenching with the extramicellar probe, RuL 34-, where L = 4,4′-dicarboxy-2,2′-bipyridine. A general comparison of the alkyl sulfate aggregates with the nonquenching cations Na + and TMA + shows that the latter ion reduces the critical micelle concentration but at the same time depresses the ability of the detergent assemblies to bind or solubilize the hydrophobic quencher cations MV 2+ or CMP +. The reduced binding ability of the TMA + aggregates compared to that of the corresponding Na + soaps shows up largely in the form of a reduced favorable ΔS° for the solubilization in the case of the former. The results are in accord with a picture of the TMA + micelle as being more stable and more disordered than the corresponding assembly with Na + as the counterion. © 1989 American Chemical Society.

Thermodynamic properties of liquid mixtures. III. Acetone-water

The excess enthalpy of mixing of acetone-water was measured at 25°C in the 0-1 molar fraction range. The minimum and the maximum in the H E (X 2) curve occurred at X 2 = 0.18 and X 2 = 0.85, respectively. The excess partial molar and other excess quantities were also calculated for the acetone-water system at 25°C. The results are interpreted in view of the influence of acetone on the structure of water. © 1983.

Phonons in binary BCC lithium-sodium alloys

The dispersion relations along the principal symmetry directions in BCC lithium-sodium alloys are calculated using second-order perturbation theory. The local modified Hoshino-Youngmodel potential was used for the lithium and the local Harrison model potential for sodium. The phonon density of states, the root mean square displacements and (Θ-T) curves are also calculated. In the absence of experimental data, just the theoretical predictions are presented here.

EXAFS and Raman spectroscopy study of binary indium fluoride glasses

Extended X-ray absorption fine spectroscopy (EXAFS) and Raman scattering studies of InF3-BaF2 and InF3-SrF2 binary glasses are reported. For all compositions, the local structure of the glasses is built with InF6 units. For all glasses studied, the indium neighbour's number and the In-F mean bond length are equal to the values of the InF3 crystalline phase (6 and 0.205 nm, respectively). © 1996 Chapman & Hall.

Ethanol tolerance of thermotolerant yeasts cultivated on mixtures of sucrose and ethanol

The final levels of ethanol (levels of ethanol produced plus that added initially to the media) reached by the thermotolerant yeasts were highest (16.5-20.3%, v/v) at 8% initial ethanol. The thermotolerant yeasts were found to have the following characteristics: constant levels of ethanol formation (10.5-12.3%, v/v), fog additions of external ethanol within the range 2-8% (v/v) of initial ethanol; constant values of product coefficients when initial ethanol was in the range of 2-6%, which increased or decreased, depending on the strain, when initial ethanol exceeded 6%; growth activity was inhibited at different levels of addition of external ethanol when final biomass and specific rate of growth were compared; significant differences among the yeast strains in the amount of external ethanol capable of reducing biomass formation by one half. In addition, the viability of the strains (early stationary phase) varied with the amount of external ethanol, the lowest viabilities occurring at concentrations of initial ethanol ranging from 4 to 7% and the highest in the range of 7 to 8% (v/v). The relative levels of trehalose (with/without 7% ethanol added initially) in the yeast strains (the stationary phase) ranged from 1.03 to 1.75, suggesting that the effect of produced ethanol on trehalose accumulation was stronger than that of external ethanol. The levels of final ethanol shown by the yeast strains were also correlated with the cellular levels of glycerol-3-phosphate dehydrogenase (increase in enzyme levels with decrease in final ethanol) for cells harvested at the stationary phase.

Study of water and dimethylformamide interaction by computer simulation

Monte Carlo simulations of water-dimethylformamide (DMF) mixtures were performed in the isothermal and isobaric ensemble at 298.15 K and 1 atm. The intermolecular interaction energy was calculated using the classical 6-12 Lennard-Jones pairwise potential plus a Coulomb term. The TIP4P model was used for simulating water molecules, and a six-site model previously optimised by us was used to represent DMF. The potential energy for the water-DMF interaction was obtained via standard geometric combining rules using the original potential parameters for the pure liquids. The radial distribution functions calculated for water-DMF mixtures show well characterised hydrogen bonds between the oxygen site of DMF and hydrogen of water. A structureless correlation curve was observed for the interaction between the hydrogen site of the carbonyl group and the oxygen site of water. Hydration effects on the stabilisation of the DMF molecule in aqueous solution have been investigated using statistical perturbation theory. The results show that energetic changes involved in the hydration process are not strong enough to stabilise another configuration of DMF than the planar one.

Smooth landscape solvent dynamics in electron transfer reactions

Solvent effects play a major role in controlling electron-transfer reactions. The solvent dynamics happens on a very high-dimensional surface, and this complex landscape is populated by a large number of minima. A critical problem is to understand the conditions under which the solvent dynamics can be represented by a single collective reaction coordinate. When this unidimensional representation is valid, one recovers the successful Marcus theory. In this study the approach used in a previous work [V. B. P. Leite and J. N. Onuchic; J. Phys. Chem. 100, 7680 (1996)] is extended to treat a more realistic solvent model, which includes energy correlation. The dynamics takes place in a smooth and well behaved landscape. The single shell of solvent molecules around a cavity is described by a two-dimensional system with periodic boundary conditions with nearest neighbor interaction. It is shown how the polarization-dependent effects can be inferred. The existence of phase transitions depends on a factor y proportional to the contribution from the two parameters of the model. For the present model, γ suggests the existence of weak kinetic phase transitions, which are used in the analysis of solvent effects in charge-transfer reactions. © 1999 American Institute of Physics.

Variational studies and replica symmetry breaking in the generalization problem of the binary perceptron

We analyze the average performance of a general class of learning algorithms for the nondeterministic polynomial time complete problem of rule extraction by a binary perceptron. The examples are generated by a rule implemented by a teacher network of similar architecture. A variational approach is used in trying to identify the potential energy that leads to the largest generalization in the thermodynamic limit. We restrict our search to algorithms that always satisfy the binary constraints. A replica symmetric ansatz leads to a learning algorithm which presents a phase transition in violation of an information theoretical bound. Stability analysis shows that this is due to a failure of the replica symmetric ansatz and the first step of replica symmetry breaking (RSB) is studied. The variational method does not determine a unique potential but it allows construction of a class with a unique minimum within each first order valley. Members of this class improve on the performance of Gibbs algorithm but fail to reach the Bayesian limit in the low generalization phase. They even fail to reach the performance of the best binary, an optimal clipping of the barycenter of version space. We find a trade-off between a good low performance and early onset of perfect generalization. Although the RSB may be locally stable we discuss the possibility that it fails to be the correct saddle point globally. ©2000 The American Physical Society.

Interfacial concentrations of chloride and bromide and selectivity for ion exchange in vesicles prepared with dioctadecyldimethylammonium halides, lipids, and their mixtures

The local concentrations of chloride, Cl b, and bromide, Br b, in the interface of vesicles prepared with dioctadecyldimethylammonium chloride, DODAC, or bromide, DODAB, dipalmitoylphosphatidylcholine, DPPC, dimyristoylphosphatidylcholine, DMPC, and mixtures of DMPC, DPPC, and DODAC were determined by chemical trapping by analyzing product yields from spontaneous dediazoniation of vesicle-bound 2,6-dimethyl-4-hexadecylbenzenediazonium ion. The values of Cl b and Br b in DODAC and DODAB vesicles increase with vesicle size, in agreement with previous data showing that counterion dissociation decreases with vesicle size. Addition of tetramethylammonium chloride displaces bromide from the DODAB vesicular interface. The value for the selectivity constant for Br/Cl exchange at the DODAB vesicular interface obtained by chemical trapping was ∼2.0, well within values obtained for comparable amphiphiles. In vesicles of DPPC the values of Cl b were very sensitive to the nature of the cation and decreased in the order Ca 2+ > Mg 2+ > Li + > Na + > K + = Cs + = Rb + ≥ +. The effect of the cation becomes more important as temperature increases above the phase transition temperature, T m, of the lipid. The values of Cl b increased sigmoidally with the mol % of DODAC in vesicles prepared with DODAC/lipid mixtures. In sonicated vesicles prepared with DODAC and DMPC (or DPPC), the values of Cl b reach local concentrations measured for the pure amphiphile at 80 mol % DODAC. These results represent the first extensive study of local concentration of ions determined directly by chemical trapping in vesicles prepared with lipids, synthetic ampliiphiles, and their mixtures.

Evaluation of the mixtures ammonium phosphate/magnesium nitrate and palladium nitrate/magnesium nitrate as modifiers for simultaneous determination of Cd, Cr, Ni and Pb in mineral water by GFAAS

A method is described for the simultaneous determination of Cd, Cr, Ni and Pb in mineral water samples by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer (THGA) and a longitudinal Zeeman-effect background correction system. The electrothermal behavior of analytes during pyrolysis and atomization steps was studied without modifier, in presence of 5 μg Pd and 3 μg Mg(NO3)2 and in presence of 50 μg NH4H2PO4 and 3 μg Mg(NO3)2. A volume of 20 μL of a 0.028 mol L -1 HNO3 solution containing 50 μg L-1 Ni and Pb, 10 μg L-1 Cr and 5 μg L-1 Cd was dispensed into the graphite tube at 20°C. The mixture palladium/magnesium was selected as the optimum modifier. The pyrolysis and atomization temperatures were fixed at 1000°C and 2300°C, respectively. The characteristic masses were calculated as 2.2 pg Cd, 10 pg Cr, 42 pg Ni and 66 pg Pb and the lifetime of the graphite tube was around 600 firings. Limits of detection based on integrated absorbance were 0.02 μg L-1Cd, 0.94 μg L-1 Cr, 0.45 μg L-1 Ni and 0.75 μg L-1 Pb, which exceeded the requirements of Brazilian Food Regulation that establish the maximum permissible level for Cd, Cr, Ni and Pb at 3 μg L-1, 50 μg L-1, 20 μg L-1 and 10 μg L-1, respectively. The recoveries of Cd, Cr, Ni and Pb added to mineral water samples varied within the 93-108%, 96-104%, 87-101% and 98-108% ranges, respectively. Results of analysis of standard reference materials (National Institute of Standards and Technology: 1640-Trace Elements in Natural Water; 1643d-Trace Elements in Water) were in agreement with certified values at the 95% confidence level.

Atividade anti Staphylococcus aureus de extratos de própolis (EP) de Apis mellifera preparados com diferentes concentrações de etanol

Propolis has been used in folk medicine and possesses a broad spectrum of biological activities, specially antibacterial activity. Studies have demonstrated that the composition of propolis extract may have influence in such activity. The goal of this study was to investigate the antibacterial activity of eleven propolis extracts (PE) against sixty one Staphylococcus aureus strains, isolated from newborn clinical specimens. The PE from Apis mellifera were prepared by using pure water and mixtures of water with ethanol at different concentrations (from 0 to 100%), 25g of propolis in 100 mL of solvent, and three days of maceration followed by filtration. Determination of Minimal Inhibitory Concentration (MIC) by agar dilution method was performed and serial concentrations from each PE were achieved (%v/v) in plates containing Mueller Hinton agar. It was possible to verify that the anti S. aureus activity was directly proportional to ethanol concentration and no significant differences were observed among PE with ethanol concentration from 70 to 100%. The MIC 90% values ranged from 0.4 to 0.6% (v/v) and the 70% ethanolic extract were the most efficient to inhibit bacterial growth (MIC 90%=0.42%, v/v). In conclusion, our results suggest that the EP composition and, consequently, the concentration of ethanol used as solvent may influence the antibacterial activity of propolis from A. mellifera.