Water diffusion in rough carbon nanotubes

We use molecular dynamics simulations to study the diffusion of water inside deformed carbon nanotubes with different degrees of deformation at 300 K. We found that the number of hydrogen bonds that water forms depends on nanotube topology, leading to enhancement or suppression of water diffusion. The simulation results reveal that more realistic nanotubes should be considered to understand the confined water diffusion behavior, at least for the narrowest nanotubes, when the interaction between water molecules and carbon atoms is relevant.Comment: 17 pages, 8 figure

Diffusion behavior of water confined in deformed carbon nanotubes

We use molecular dynamics simulations to study the diffusion of water inside deformed carbon nanotubes, with different degrees of eccentricity at 300K. We found a water structural transition between tubular-like to single-file for the (7,7) nanotubes associated with a change from a high to low mobility regimes. The water which in the undeformed (9,9) nanotubes is frozen, becomes liquid for the distortion above a certain threshold. These water diffusion enhancement (suppresion) is related to a reduction (increase) in the number of hydrogen bonds. This suggests that the shape of the nanotube is a particularly important ingredient when considering the dynamical and structural properties of confined water.Comment: 16 pages, 9 figure

Enzimatic polycondensation of 1,4-butanediol and diethyl succinate

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Exact Foldy-Wouthuysen transformation for gravitational waves and magnetic field background

We consider an exact Foldy-Wouthuysen transformation for the Dirac spinor field on the combined background of a gravitational wave and constant uniform magnetic field. By taking the classical limit of the spinor field Hamiltonian we arrive at the equations of motion for the non-relativistic spinning particle. Two different kinds of the gravitational fields are considered and in both cases the effect of the gravitational wave on the spinor field and on the corresponding spinning particle may be enforced by the sufficiently strong magnetic field. This result can be relevant for the astrophysical applications and, in principle, useful for creating the gravitational wave detectors based on atomic physics and precise interferometry

Water diffusion in carbon nanotubes for rigid and flexible models

We compared the diffusion of water confined in armchair and zigzag carbon nanotubes for rigid and flexible water models. Using one rigid model, TIP4P/2005, and two flexible models, SPC/Fw and SPC/FH, we found that the number of the number of hydrogen bonds that water forms depends on the structure of the nanotube, directly affecting the diffusion of water. The simulation results reveal that due to the hydrophobic nature of carbon nanotubes and the degrees of freedom imposed by the water force fields, water molecules tend to avoid the surface of the carbon nanotube. This junction of variables plays a central role in the diffusion of water, mainly in narrow and/or deformed nanotubes, governing the mobility of confined water in a non-trivial way, where the greater the degree of freedom of the water force field, the smaller it will be mobility in confinement, as we limit the competition between area/volume, and it no longer plays the unique role in changing water diffusivity.Comment: 28 pages, 6 figure

Biocontrol potential of Trichoderma and Bacillus species on Fusarium oxysporum f. sp vasinfectum.

Fusarium wilt, caused by Fusarium oxysporum f. sp. vasinfectum, is one of the major diseases of cotton. Preventive methods to manage this disease should be adopted what includes the seed treatment with biocontrol agents as a good alternative. This work aimed to evaluate the efficiency of biological products based on Trichoderma spp. and Bacillus subtilis in the control of Fusarium oxysporum f. sp. vasinfectum (Fov) applied in seeds and seedlings of cotton. The experiment was carried out at the Laboratório de Fitopatologia of the Centro de Ciências Agrárias, of the Universidade Federal de Paraíba (CCA-UFPB), located in the city of Areia, Paraíba - Brazil. The disease transmission of the seeds to the seedlings was evaluated. After the transmission test, cotton seeds of the variety Mocó (Gossypium hirsutum var. Marie-gallante (Watt) Hutch.), BRS 286 and Topázio cultivar (Gossypium hirsutum L.) were submitted to the treatments T1 - Control, T2 - Trichodel® (0,5 mL); T3-Trichodel® (1.0 mL); T4-Trichodel® (1.5 mL); T5-Trichodel® (2.0 mL); T6- Bactel® (2.0 mL); T7-Bactel® (2.5 mL); T8-Bactel® (3.0 mL); T9-Bactel® (3.5 mL) diluted in 100 mL SDW; T10 - Fungicide Captana (240 g / 100 kg of seeds) and inoculated with Fov. The pathogen incidence of the seeds was evaluated seven days after the inoculation (DAI). To evaluate the biological control of Fov in the seedlings, the treated seeds were submitted to the following inoculation methods: 1 - inoculation of the substrate with a pathogen conidia suspension; 2 - immersion of the seeds in the conidia suspension and 3 - direct contact of the seeds with the pathogen mycelium. Twenty-one DAI the disease severity and percentage of seedlings with vascular darkening were evaluated. It was observed a transmission rate of 64.0 to 89.0% of the seeds to the seedlings. Trichodel® reduced the incidence and severity of Fov in the cotton seedlings and was the most efficient product

Edge wetting of an Ising three-dimensional system

The effect of edge on wetting and layering transitions of a three-dimensional spin-1/2 Ising model is investigated, in the presence of longitudinal and surface magnetic fields, using mean field (MF) theory and Monte Carlo (MC) simulations. For T=0, the ground state phase diagram shows that there exist only three allowed transitions, namely: surface and bulk transition, surface transition and bulk transition. However, there exist a surface intra-layering temperature $T_{L}^{s}$, above which the surface and the intra-layering surface transitions occur. While the bulk layering and intra-layering transitions appear above an other finite temperature $T_{L}^{b} (\ge T_{L}^{s})$. These surface and bulk intra-layering transitions are not seen in the perfect surfaces case. Numerical values of $T_{L}^{s}$ and $T_{L}^{b}$, computed by Monte Carlo method are found to be smaller than those obtained using mean field theory. However, the results predicted by the two methods become similar, and are exactly those given by the ground state phase diagram, for very low temperatures. On the other hand, the behavior of the local magnetizations as a function of the external magnetic field, shows that the transitions are of the first order type. $T_{L}^{s}$ and $T_{L}^{b}$ decrease when increasing the system size and/or the surface magnetic field. In particular, $T_{L}^{b}$ reaches the wetting temperature $T_{w}$ for sufficiently large system sizes.Comment: 11 Pages latex, 12 Figures P

Dengue Infection Increases the Locomotor Activity of Aedes aegypti Females

BACKGROUND: Aedes aegypti is the main vector of the virus causing Dengue fever, a disease that has increased dramatically in importance in recent decades, affecting many tropical and sub-tropical areas of the globe. It is known that viruses and other parasites can potentially alter vector behavior. We investigated whether infection with Dengue virus modifies the behavior of Aedes aegypti females with respect to their activity level. METHODS/PRINCIPAL FINDINGS: We carried out intrathoracic Dengue 2 virus (DENV-2) infections in Aedes aegypti females and recorded their locomotor activity behavior. We observed an increase of up to ∼50% in the activity of infected mosquitoes compared to the uninfected controls. CONCLUSIONS: Dengue infection alters mosquito locomotor activity behavior. We speculate that the higher levels of activity observed in infected Aedes aegypti females might involve the circadian clock. Further studies are needed to assess whether this behavioral change could have implications for the dynamics of Dengue virus transmission