Sesquiterpene Lactones with Anti-Hepatitis C Virus Activity Using Molecular Descriptors

Hepatitis C is a worldwide public health problem. The available therapies are limited by their partial effectiveness and with meaningful side-effects. Sesquiterpene lactones (SLs) are a group of natural products with a wide variety of chemical structures and biological activities associated. There are few studies about the influence of the molecular structure of SLs for the anti-hepatitis C virus activity. In the present work, SLs are investigated in a subgenomic RNA replicon assay system and were analyzed using multiple linear regression along with self-organizing maps with DRAGON descriptors in order to identify the structural requirements for their biological activity and to predict the inhibitory potency of SLs. Characteristics such as stereochemistry and electronic effects demonstrated to be important for their anti-HCV activity, and the SOM produced a clear separation betwenn active and inactive compounds. Therefore, it is possible to use this map as a filter for virtual screening to predict the anti-HCV activity of SLs.

COMPARISON MEASURES OF MAPS GENERATED BY GEOSTATISTICAL METHODS

This study uses several measures derived from the error matrix for comparing two thematic maps generated with the same sample set. The reference map was generated with all the sample elements and the map set as the model was generated without the two points detected as influential by the analysis of local influence diagnostics. The data analyzed refer to the wheat productivity in an agricultural area of 13.55 ha considering a sampling grid of 50 x 50 m comprising 50 georeferenced sample elements. The comparison measures derived from the error matrix indicated that despite some similarity on the maps, they are different. The difference between the estimated production by the reference map and the actual production was of 350 kilograms. The same difference calculated with the mode map was of 50 kilograms, indicating that the study of influential points is of fundamental importance to obtain a more reliable estimative and use of measures obtained from the error matrix is a good option to make comparisons between thematic maps.

Morphological, molecular and cross-breeding analysis of geographic populations of coconut-mite associated predatory mites identified as Neoseiulus baraki: evidence for cryptic species?

Surveys were conducted in Brazil, Benin and Tanzania to collect predatory mites as candidates for control of the coconut mite Aceria guerreronis Keifer, a serious pest of coconut fruits. At all locations surveyed, one of the most dominant predators on infested coconut fruits was identified as Neoseiulus baraki Athias-Henriot, based on morphological similarity with regard to taxonomically relevant characters. However, scrutiny of our own and published descriptions suggests that consistent morphological differences may exist between the Benin population and those from the other geographic origins. In this study, we combined three methods to assess whether these populations belong to one species or a few distinct, yet closely related species. First, multivariate analysis of 32 morphological characters showed that the Benin population differed from the other three populations. Second, DNA sequence analysis based on the mitochondrial cytochrome oxidase subunit I (COI) showed the same difference between these populations. Third, cross-breeding between populations was unsuccessful in all combinations. These data provide evidence for the existence of cryptic species. Subsequent morphological research showed that the Benin population can be distinguished from the others by a new character (not included in the multivariate analysis), viz. the number of teeth on the fixed digit of the female chelicera.

Acceptance Threshold Hypothesis is Supported by Chemical Similarity of Cuticular Hydrocarbons in a Stingless Bee, Melipona asilvai

The ability to discriminate nestmates from non-nestmates in insect societies is essential to protect colonies from conspecific invaders. The acceptance threshold hypothesis predicts that organisms whose recognition systems classify recipients without errors should optimize the balance between acceptance and rejection. In this process, cuticular hydrocarbons play an important role as cues of recognition in social insects. The aims of this study were to determine whether guards exhibit a restrictive level of rejection towards chemically distinct individuals, becoming more permissive during the encounters with either nestmate or non-nestmate individuals bearing chemically similar profiles. The study demonstrates that Melipona asilvai (Hymenoptera: Apidae: Meliponini) guards exhibit a flexible system of nestmate recognition according to the degree of chemical similarity between the incoming forager and its own cuticular hydrocarbons profile. Guards became less restrictive in their acceptance rates when they encounter non-nestmates with highly similar chemical profiles, which they probably mistake for nestmates, hence broadening their acceptance level.

The Role of Molecular Conformation and Polarizable Embedding for One- and Two-Photon Absorption of Disperse Orange 3 in Solution

Solvent effects on the one- and two-photon absorption (IPA and 2PA) of disperse orange 3 (DO3) in dimethyl sulfoxide (DMSO) are studied using a discrete polarizable embedding (PE) response theory. The scheme comprises a quantum region containing the chromophore and an atomically granulated classical region for the solvent accounting for full interactions within and between the two regions. Either classical molecular dynamics (MD) or hybrid Car-Parrinello (CP) quantum/classical (QM/MM) molecular dynamics simulations are employed to describe the solvation of DO3 in DMSO, allowing for an analysis of the effect of the intermolecular short-range repulsion, long-range attraction, and electrostatic interactions on the conformational changes of the chromophore and also the effect of the solute-solvent polarization. PE linear response calculations are performed to verify the character, solvatochromic shift, and overlap of the two lowest energy transitions responsible for the linear absorption spectrum of DO3 in DMSO in the visible spectral region. Results of the PE linear and quadratic response calculations, performed using uncorrelated solute-solvent configurations sampled from either the classical or hybrid CP QM/MM MD simulations, are used to estimate the width of the line shape function of the two electronic lowest energy excited states, which allow a prediction of the 2PA cross-sections without the use of empirical parameters. Appropriate exchange-correlation functionals have been employed in order to describe the charge-transfer process following the electronic transitions of the chromophore in solution.

The influence of different indium-composition profiles on the electronic structure of lens-shaped InxGa1-xAs quantum dots

We present effective-mass calculations of the bound-state energy levels of electrons confined inside lens-shaped InxGa1-xAs quantum dots (QDs) embedded in a GaAs matrix, taking into account the strain as well as the In gradient inside the QDs due to the strong In segregation and In-Ga intermixing present in the InxGa1-xAs/GaAs system. In order to perform the calculations, we used a continuum model for the strain, and the QDs and wetting layer were divided into their constituting monolayers, each one with a different In concentration, to be able to produce a specific composition profile. Our results clearly show that the introduction of such effects is very important if one desires to correctly reproduce or predict the optoelectronic properties of these nanostructures.

Genetic diversity of Stryphnodendron adstringens (Mart.) Coville determined by AFLP molecular markers

Bark extracts of Stryphnodendron adstringens (Mart) Coville a Leguminosae species, well known in Brazil as barbatimao, are popularly used as healing agent. The objective of this work was to determine the genetic diversity of S. adstringens populations and to correlate genetic distances to the production of tannins. S. adstringens accessions from populations found in Cerrado regions in the states of Goias, Minas Gerais and Sao Paulo were analyzed using the AFLP (Amplified Fragment Length Polymorphism) technique. A total of 236 polymorphic bands were scored and higher proportion of genetic diversity was found inter populations (70.9%), rather than intra populations (29.1%). F-ST value was found to be significantly greater than zero (0.2906), demonstrating the complex genetic structure of S. adstringens populations. Accessions collected in Cristalina, GO, showed higher percentage of polymorphic loci (87.3%) and the highest genetic diversity. The lowest genetic variability was detected among accessions from the population growing in Caldas Novas, GO. The genetic distance among populations was estimated using the Unweighted Pair Group Method with Arithmetic Mean (UPGMA), which grouped populations into 3 clusters. Moreover, chemotypes with tannin concentration above 40% showed higher genetic similarity. AFLP analysis proved to be an efficient gene mapping technique to determine the genetic diversity among remaining populations of S. adstringens. Obtained results may be employed to implement further strategies for the conservation of this medicinal plant. (C) 2011 Elsevier Ltd. All rights reserved.

Decoherence of quantum kinematical correlations: Elastic scattering of identical particles

We include the dynamics of the angular straggling process in the angular distributions of Mott scattering of heavy ions. We model the passage of an incoming nucleus through a target as a diffusion process. It is then possible to derive a simple and physically transparent expression for the angular dispersion due to the straggling. The angular dispersion should be folded with the theoretical Mott cross section to see its effect on the amplitude of the Mott oscillations. Our results agree very well with data of Pb-208 + Pb-208 scattering. We define the "classical" limit as the limit when the angular dispersion due to straggling becomes comparable with the Mott oscillation period and get the disappearance of quantum interference occurring at the limit 0.050 root xi Z(4)/E-3/2 >= 1, where xi stands for the target thickness, Z is the system's charge, and E is the center-of-mass energy. The experiments on lead are very close to this limit. We show that the kinematical correlations due to the identity of the particles is maintained, as it should be, and the action of the environment is to reduce the fringe visibility.

Phylogenetic and Similarity Analysis of HTLV-1 Isolates from HIV-Coinfected Patients from the South and Southeast Regions of Brazil

HTLV-1 is endemic in Brazil and HIV/ HTLV-1 coinfection has been detected, mostly in the northeast region. Cosmopolitan HTLV-1a is the main subtype that circulates in Brazil. This study characterized 17 HTLV-1 isolates from HIV coinfected patients of southern (n = 7) and southeastern (n = 10) Brazil. HTLV-1 provirus DNA was amplified by nested PCR (env and LTR) and sequenced. Env sequences (705 bp) from 15 isolates and LTR sequences (731 bp) from 17 isolates showed 99.5% and 98.8% similarity among sequences, respectively. Comparing these sequences with ATK (HTLV-1a) and Mel5 (HTLV-1c) prototypes, similarities of 99% and 97.4%, respectively, for env and LTR with ATK, and 91.6% and 90.3% with Mel5, were detected. Phylogenetic analysis showed that all sequences belonged to the transcontinental subgroup A of the Cosmopolitan subtype, clustering in two Latin American clusters.

Magnetophotoluminescence study of GaAs/AlGaAs coupled double quantum wells with bimodal heterointerface roughness

This work reports on the results of magnetophotoluminescence (MPL) measurements carried out in a sample containing two Al0.35Ga0.65As/GaAs, coupled double quantum wells (CDQWs), with inter-well barriers of different thicknesses, which have the heterointerfaces characterized by a distribution of bimodal roughness. The MPL measurements were performed at 4 K, with magnetic fields applied parallel to the growth direction, and varying from 0 to 12 T. The diamagnetic shift of the photoluminescence (PL) peaks is more sensitive to changes in the confinement potential, due to monolayer variations in the mini-well thickness, rather than to the exciton localization at the local potential fluctuations. As the magnetic field increases, the relative intensities of the two peaks in each PL band inverts, what is attributed to the reduction in the radiative lifetime of the delocalized excitons, which results in the radiative recombination, before the excitonic migration between the higher and lower energy regions in each CDQW occurs. The dependence of the full width at half maximum (FWHM) on magnetic field shows different behaviors for each PL peak, which are attributed to the different levels and correlation lengths of the potential fluctuations present in the regions associated with each recombination channel. (C) 2011 Elsevier B.V. All rights reserved.

Exact dynamics of single-qubit-gate fidelities under the measurement-based quantum computation scheme

Measurement-based quantum computation is an efficient model to perform universal computation. Nevertheless, theoretical questions have been raised, mainly with respect to realistic noise conditions. In order to shed some light on this issue, we evaluate the exact dynamics of some single-qubit-gate fidelities using the measurement-based quantum computation scheme when the qubits which are used as a resource interact with a common dephasing environment. We report a necessary condition for the fidelity dynamics of a general pure N-qubit state, interacting with this type of error channel, to present an oscillatory behavior, and we show that for the initial canonical cluster state, the fidelity oscillates as a function of time. This state fidelity oscillatory behavior brings significant variations to the values of the computational results of a generic gate acting on that state depending on the instants we choose to apply our set of projective measurements. As we shall see, considering some specific gates that are frequently found in the literature, the fast application of the set of projective measurements does not necessarily imply high gate fidelity, and likewise the slow application thereof does not necessarily imply low gate fidelity. Our condition for the occurrence of the fidelity oscillatory behavior shows that the oscillation presented by the cluster state is due exclusively to its initial geometry. Other states that can be used as resources for measurement-based quantum computation can present the same initial geometrical condition. Therefore, it is very important for the present scheme to know when the fidelity of a particular resource state will oscillate in time and, if this is the case, what are the best times to perform the measurements.

Self-Assembly of Poly(4-vynil-N-alkylpyridinium) Bromide onto Silica: Effect of Side-Chain Length on Structural Aspects at a Molecular Level

Self-assembly of poly(4-vynil-N-alkyl)pyridinium bromide with alkyl side chains of 2, 5, 7, 10, or 16 carbons from ethanolic solutions onto flat silica surfaces was studied by means of ellipsometry, atomic force microscopy (AFM), contact angle measurements, and sum-frequency generation (SFG) vibrational spectroscopy in the CH3 and CH2 stretch region. Ab initio quantum-chemical calculations on the N-alkylpyridinium side-group with restricted Hartree-Fock (RHF) method and 6-311G (d,p) basis set were C one to estimate the charge distribution along the pyridinium ring and the alkyl side-chain. SFG results showed that longer side chains promote the disorientation of the alkyl groups at the surface, corroborating with the contact angle values. AFM images revealed film homogeneity, regardless the alkyl side group. However, after 24 h contact with water, ringlike structures appeared on the film surfaces, when the polycation alkyl side chain had 7 or less carbons, and as the alkyl chain increased to 10 or 16 carbons, the films dewetted because the hydrophobic interactions prevailed over the electrostatic interactions between the pyridinium charged groups and the negatively charged SiO2 surface. Under acid conditions (HCl 0.1 mol.L-1), the film mean thickness values decreased up to 50% of original values when the alkyl side chains were ethyl or pentyl groups due to ion-pair disruption, but for longer groups they remained unchanged. Quantum-chemical optimization and Mulliken electron population showed that (i) from C2 to C15 the positive charge at the headgroup (HG) decreased 0.025, while the charge at combined HG + alpha-CH2 increased 0.037; and (ii) for C6 or longer, the alkyl side group presents a tilt in the geometry, moving away from the plane. Such effects summed up over the whole polymer chain give support to suggest that when the side chains are longer than 7 carbons, the hydrophobic interaction decreases film stability and increases acid resistance.

Two-photon absorption in oxazole derivatives: An experimental and quantum chemical study

Experimental and theoretical studies on the two-photon absorption properties of two oxazole derivatives: 2,5-diphenyloxazole (PPO) and 2-(4-biphenylyI)-5-phenyl-1,3,4-oxadiazole (PBD) are presented. The two-photon absorption cross-section spectra were determined by means of the Z-scan technique, from 460 up to 650 nm, and reached peak values of 84 GM for PBD and 27 GM for PPO. Density Functional Theory and response function formalism are used to determine the molecular structures and the one- and two-photon absorption properties and to assist in the interpretation of the experimental results. The Polarizable Continuum Model in one-photon absorption calculations is used to estimate solvent effects. (C) 2011 Elsevier B.V. All rights reserved.

Atomically resolved study of the morphology change of InAs/GaAs quantum dot layers induced by rapid thermal annealing

The optoelectronic properties of InAs/GaAs quantum dots can be tuned by rapid thermal annealing. In this study, the morphology change of InAs/GaAs quantum dots layers induced by rapid thermal annealing was investigated at the atomic-scale by cross-sectional scanning tunneling microscopy. Finite elements calculations that model the outward relaxation of the cleaved surface were used to determine the indium composition profile of the wetting layer and the quantum dots prior and post rapid thermal annealing. The results show that the wetting layer is broadened upon annealing. This broadening could be modeled by assuming a random walk of indium atoms. Furthermore, we show that the stronger strain gradient at the location of the quantum dots enhances the intermixing. Photoluminescence measurements show a blueshift and narrowing of the photoluminescence peak. Temperature dependent photoluminescence measurements show a lower activation energy for the annealed sample. These results are in agreement with the observed change in morphology. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4770371]

Hepatitis B virus infection in Haemodialysis Centres from Santa Catarina State, Southern Brazil. Predictive risk factors for infection and molecular epidemiology

Abstract Background Patients under haemodialysis are considered at high risk to acquire hepatitis B virus (HBV) infection. Since few data are reported from Brazil, our aim was to assess the frequency and risk factors for HBV infection in haemodialysis patients from 22 Dialysis Centres from Santa Catarina State, south of Brazil. Methods This study includes 813 patients, 149 haemodialysis workers and 772 healthy controls matched by sex and age. Serum samples were assayed for HBV markers and viraemia was detected by nested PCR. HBV was genotyped by partial S gene sequencing. Univariate and multivariate statistical analyses with stepwise logistic regression analysis were carried out to analyse the relationship between HBV infection and the characteristics of patients and their Dialysis Units. Results Frequency of HBV infection was 10.0%, 2.7% and 2.7% among patients, haemodialysis workers and controls, respectively. Amidst patients, the most frequent HBV genotypes were A (30.6%), D (57.1%) and F (12.2%). Univariate analysis showed association between HBV infection and total time in haemodialysis, type of dialysis equipment, hygiene and sterilization of equipment, number of times reusing the dialysis lines and filters, number of patients per care-worker and current HCV infection. The logistic regression model showed that total time in haemodialysis, number of times of reusing the dialysis lines and filters, and number of patients per worker were significantly related to HBV infection. Conclusions Frequency of HBV infection among haemodialysis patients at Santa Catarina state is very high. The most frequent HBV genotypes were A, D and F. The risk for a patient to become HBV positive increase 1.47 times each month of haemodialysis; 1.96 times if the dialysis unit reuses the lines and filters ≥ 10 times compared with haemodialysis units which reuse < 10 times; 3.42 times if the number of patients per worker is more than five. Sequence similarity among the HBV S gene from isolates of different patients pointed out to nosocomial transmission.