Formation of topological defects in nematic shells with a dumbbell-like shape.

The present study investigates dumbbell-shaped nematic liquid crystal shells. Using molecular dynamics (MD) simulations, we consider the effects of an external electric field on nematic ordering by computing the average molecular alignment's time evolution and equilibrium configuration. We show that the number and location of topological defects are strongly affected by the external field, with the orientational ordering's equilibrium configuration depending on field direction about the shell's long axis. For a transverse external field, it is verified that the defect rearrangement presents a non-linear dynamics, with a field independent characteristic time scale delimiting the short and long time regimes. Effects associated with varying the shell's Gaussian curvature are also analyzed.

Surface and finite-size effects on N-Sm-A-Sm-C phase transitions in free-standing films.

The present study is devoted to the investigation of surface anchoring and finite-size effects on nematic-smectic-A-smectic-C (N-Sm-A-Sm-C) phase transitions in free-standing films. Using an extended version of the molecular theory for smectic-C liquid crystals, we analyze how surface anchoring and film thickness affect the thermal behavior of the order parameters in free-standing smectic films. In particular, we determine how the transition temperature depends on the surface ordering and film thickness. We show that the additional orientational order imposed by the surface anchoring may lead to a stabilization of order parameters in central layers, thus modifying the nature of the phase transitions. We compare our results with experimental findings for typical thermotropic compounds presenting a N-Sm-A-Sm-C phase sequence.

Tunable topological valence in nematic shells on spherocylindrical colloidal particles.

We perform molecular dynamics simulations of the orientational ordering on nematic shells delimited by spherocylindrical nanoscopic colloidal particles. We show that under conditions of degenerate planar anchoring, the equilibrium director field structure in these shells exhibits pairs of +1/2 topological defects at the poles of spherical cups in the absence of an external electric field. In addition, a certain number of pairs of ±1/2 defects occurs on the spherical cups far from the poles, thus resulting in a total of eight valence spots. A strong field applied along the main spherocylindrical axis removes the ±1/2 defect pairs while it coalesces the polar ones into a single +1 topological defect. A strong transverse field destroys all defects on the spherical cups but generates four +1/2 defects in the cylindrical part. Therefore, an external field can be used to control the number of valence centers in spherocylindrical nematic shells, thus unveiling their capability of acting as multivalent building blocks for nanophotonic devices.

Use of morpho-agronomic traits and DNA profiling for classification of genetic diversity in papaya.

We examined the genetic diversity of papaya (Carica papaya) based on morpho-agronomic and molecular data. Twenty-seven genotypes grown in Brazil were analyzed with 11 AFLP primer combinations, 23 ISSR markers, 22 qualitative, and 30 quantitative descriptors. For the joint analyses, we used the Gower algorithm (Joint Gower) and the average value of the individual dissimilarity matrix for each type of data (Average-Joint Gower); 359 AFLP and 52 ISSR polymorphic bands were found. Approximately 29.2 and 7.7% of the AFLP and ISSR bands, respectively, were genotype-specific and may therefore be used for papaya variety protection. Although there was a significant correlation between the qualitative and quantitative descriptor dissimilarity matrices (r = 0.43), the morpho-agronomic data were not highly correlated with the molecular data. Moreover, correlation between AFLP and ISSR dissimilarity matrices was nearly null (r = -0.01). Joint Gower analysis of all data showed high correlations, especially for AFLP markers, most likely due to the larger number of bands, generating a strong bias in the diversity estimates. The Average-Joint Gower analysis allowed a better balance between the correlations for the continuous and the discrete variables. The results generated by clustering analysis distinguished 5 genetically distinct groups. While we found that papaya genotypes are significantly variable for many traits, we observed that Average-Joint Gower analysis allowed for genotype clustering based on the most widely used criterion for classifying papaya genotypes, which is fruit type ('Formosa' or 'Solo'). This information helps provide an accurate estimate of the genetic diversity and structure of papaya germplasm, which will be used for further breeding strategies.

Thermal effects on photon-induced quantum transport in a single quantum dot.

We theoretically investigate laser induced quantum transport in a single quantum dot attached to electrical contacts. Our approach, based on a nonequilibrium Green function technique, allows us to include thermal effects on the photon-induced quantum transport and excitonic dynamics, enabling the study of non-Markovian effects. By solving a set of coupled integrodifferential equations, involving correlation and propagator functions, we obtain the photocurrent and the dot occupation as a function of time. Two distinct sources of decoherence, namely, incoherent tunneling and thermal fluctuations, are observed in the Rabi oscillations. As temperature increases, a thermally activated Pauli blockade results in a suppression of these oscillations. Additionally, the interplay between photon and thermally induced electron populations results in a switch of the current sign as time evolves and its stationary value can be maximized by tuning the laser intensity.

Genetic structure of Blastocerus dichotomus populations in the Parana River basin (Brazil) based on protein variability.

The population structure of 147 marsh deer (Blastocerus dichotomus) from three areas in the Paraná River basin, Brazil, was studied by observing protein polymorphism at 17 loci. Six loci were polymorphic and 11 monomorphic. The proportion of polymorphic loci (P) was 35.29% and the average heterozygosity (H) was 6.31%. Wright's FST indicated that only 4.9% of the total variation in allelic frequencies was due to genetic differences between the three groups. The high value of F(IS) (0.246) indicated inbreeding in the marsh deer. Genetic distance values (D = 0.014-0.051) showed little divergence between the three areas. We suggest that probable mechanisms accounting for the genetic structure are female phylopatry and polygyny and also that inbreeding has resulted from decreasing areas of wetland leading to isolation, overhunting, and diseases transmitted by cattle.

Does dietary tryptophan play a role in the control of convulsive activity?

The convulsive response to pentylenetetrazol was investigated in rats receiving different dietary tryptophan inputs. In the first experiment the animals were fed either a corn or a corn-supplemented diet. In the second one they received either a control diet supplemented with tryptophan, a low-protein/high-carbohydrate diet, or a low-protein/high-carbohydrate tryptophan-supplemented diet. The control groups for both experiments were fed a diet containing 22% milk protein. The corn diet facilitated seizures; the low-protein/high-carbohydrate/tryptophan diet prevented seizures. These results suggest that the brain serotonin levels determined by dietary tryptophan, or tryptophan by itself, could play a role in the convulsive response.