Pharmacological interactions of essential oil constituents on the viability of micro-organisms

Complex interactions between numerous components of essential oils often contribute to the pharmacological effect and therapeutic outcome. To further elucidate these interactions, several essential oil constituents (EOCs) were combined in different ratios and their inhibitory effects on the growth of bacteria and yeast determined using the minimum inhibitory concentration (MIC) microplate assay. When combined and tested against Candida albicans, (+)-beta-pinene interacted antagonistically with (-)-menthone (sigmaFIC(T) = 9.80), but synergistically with 1,8-cineole (sigmaFIC(T) = 0.35). Against Escherichia coli, the combination of E- and Z-(+/-)-nerolidol and geranyl acetate displayed an additive interaction (sigmaFIC(T) = 1.04); while a variable interaction was observed between E- and Z-(+/-)-nerolidol and eugenol with antagonism and synergy being observed at different ratios of each EOC. The combination of either carvacrol or eugenol with an antimicrobial agent (ciprofloxacin or amphotericin B) resulted in synergistic interactions against all microorganisms tested. These favourable results further support the use of essential oil constituents as adjuvants in the development of a new generation of phytopharmaceuticals that can be used in combination with synthetic drugs against drug-resistant microorganisms.     

Microbial transformation of marine halogenated sesquiterpenes

The sesquiterpene pacifenol is one of the main constituents of the red alga Laurencia claviformis. Earlier work on the semisynthetic derivatives of pacifenol afforded a series of halogenated sesquiterpenes. The aim of the present work was to obtain new hydroxylated derivatives of halogenated sesquiterpenes by means of microbial transformation using Aspergillus niger, Gibberella fujikuroi and Mucor plumbeus. The best results were obtained with M. plumbeus. The microbiological transformation by M. plumbeus of pacifenol, and two semisynthetic derivatives, is described. The structures of the new compounds obtained were determined by spectroscopic means.     

Shrimp-shape domains in a dissipative kicked rotator

Some dynamical properties for a dissipative kicked rotator are studied. Our results show that when dissipation is taken into account a drastic change happens in the structure of the phase space in the sense that the mixed structure is modified and attracting fixed points and chaotic attractors are observed. A detailed numerical investigation in a two-dimensional parameter space based on the behavior of the Lyapunov exponent is considered. Our results show the existence of infinite self-similar shrimp-shaped structures corresponding to periodic attractors, embedded in a large region corresponding to the chaotic regime.     

Local Well-Posedness for Membranes in the Light Cone Gauge

In this paper we consider the classical initial value problem for the bosonic membrane in light cone gauge. A Hamiltonian reduction gives a system with one constraint, the area preserving constraint. The Hamiltonian evolution equations corresponding to this system, however, fail to be hyperbolic. Making use of the area preserving constraint, an equivalent system of evolution equations is found, which is hyperbolic and has a well-posed initial value problem. We are thus able to solve the initial value problem for the Hamiltonian evolution equations by means of this equivalent system. We furthermore obtain a blowup criterion for the membrane evolution equations, and show, making use of the constraint, that one may achieve improved regularity estimates.     

Hydrogen‐bonded nucleophile effects in ANS: the reactions of 1‐chloro and 1‐fluoro‐2,4‐dinitrobenzene with 2‐guanidinobenzimidazole, 1‐(2‐aminoethyl)piperidine and N‐(3‐aminopropyl)morpholine in aprotic solvents

The kinetics of the reactions of 2,4‐dinitrofluorobenzene (DNFB) and 2,4‐dinitrochlorobenzene (DNClB) with 2‐guanidinobenzimidazole (2‐GB) at 40 ± 0.2 °C in dimethylsulphoxide (DMSO), toluene, and in toluene–DMSO mixtures, and with 1‐(2‐aminoethyl)piperidine (2‐AEPip) and N‐(3‐aminopropyl)morpholine (3‐APMo) in toluene at 25 ± 0.2 °C were studied under pseudo first‐order conditions. For the reactions of 2‐GB carried out in pure DMSO, the second‐order rate coefficients were independent of the amine concentration. In contrast, the reactions of 2‐GB with DNFB in toluene, showed a kinetic behaviour consistent with a base‐catalysed decomposition of the zwitterionic intermediate. These results suggest an intramolecular H‐bonding of 2‐GB in toluene, which is not present in DMSO. To confirm this interpretation the reactions were studied in DMSO–toluene mixtures. Small amounts of DMSO produce significant increase in rate that is not expected on the basis of the classical effect of a dipolar aprotic medium; the effect is consistent with the formation of a nucleophile/co‐solvent mixed aggregate. For the reactions of 3‐APMo with both substrates in toluene, the second‐order rate coefficients, k_A, show a linear dependence on the [amine]. 3‐APMo is able to form a six‐membered ring by an intramolecular H‐bond which prevents the formation of self‐aggregates. In contrast, a third order was observed in the reactions with 2‐AEPip: these results can be interpreted as a H‐bonded homo‐aggregate of the amine acting as a better nucleophile than the monomer. Most of these results can be well explained within the frame of the ‘dimer nucleophile’ mechanism. Copyright © 2010 John Wiley & Sons, Ltd.     

Modeling of the functionalization of single-wall carbon nanotubes towards its solubilization in an aqueous medium

A theoretical study of the functionalization of some single-walled carbon nanotubes (SWCNT) is presented using density functional theory. The pristine SWCNT consists of a finite, open (5, 5) nanotube with all the dangling bonds at the tips saturated with hydrogen. The structural and electronic properties of the pristine tube, with formula C₈₀H₂₀, are compared to those of a SWCNT with a vacancy defect at the sidewall, providing insight into the reactivity induced by the presence of those defects. The nanotubes were functionalized with some organic molecules: (a) formic acid, as a model carboxylic acid, (b) aminotriethylene glycol, as a model amide, and (c) ethylenglycol, as a model of the corresponding polymer. We study the effects of functionalization on both the pristine SWCNT and the SWCNT with a vacancy at the wall. Structures and electronic properties (dipole moments, ionization potentials, electron affinities, electronegativities, chemical hardnesses and HOMO-LUMO gaps) of both pristine and functionalized nanotubes are calculated, as well as the charge transfer and the binding energies of the organic radicals to the nanotubes. Binding to defects is thermodynamically favorable. The electrical dipole moments increase with the functionalization, and this enhances the solubility of the nanotubes in water, as shown by the favorable changes in the free energies of solvation. This should improve the biocompatibility of the nanotubes and lower their toxicity.     

Hydrogen‐bonding controls the solid‐state and enantiomeric comformations of the amino alcohol ligand 2‐[(2‐hydroxyethyl)amino]cyclohexanol

The crystal structure of the title compound, C₈H₁₇NO₂, consists of (R,R) and (S,S) enantiomeric pairs packed in adjacent double layers which are characterized by centrosymmetric hydrogen‐bonded dimers, generated via N—H...O and O—H...O interactions, respectively. Intermolecular interactions, related to acceptor and donor molecule chirality, link the achiral double layers into tubular columns, which consist of a staggered hydrophilic inner core surrounded by a hydrophobic cycloalkyl outer surface and extend in the [011] direction.     

Thermal analysis of hair treated with oxidative hair dye under influence of conditioners agents

This research aimed the effect on Caucasian hair tresses treated with oxidative hair dye, either incorporated or not with conditioners agents, analyzed by Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TG). The formulations of hair dyes were emulsions oil-in-water with light blond color containing or not the conditioners agents: silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose. Each dye (1.5 g) was applied in the hair tress (2.0 g/20.0 cm of length of Caucasian light-brown), previously treated, more 1.5 g of hydrogen peroxide 20 vol during 40 min. Evaluation of mass loss of the different hair sample demonstrates that these chemical hair treatments impair the hair fibers, reduced their moisture content with respect to the untreated hair. The incorporation of conditioners agents (silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose) in oxidative hair dyes types did not decrease the damage caused on the tresses by the coloring process quantified by TG/DTG. However, the DSC curves demonstrated those conditioners agents (silanetriol and panthenol; PEG-12 dimethicone) dislocated the beginning of the third event in 20 °C and they inhibited the presence of the fourth event, having characterized thermal protection to the hair.     

Determination of the Mechanical Properties of Powdered Agricultural Products and Sugar

Grain, forage cereals and different types of flour are commonly stored in silos. Their behavior within these structures is mainly governed by their mechanical properties. Since their advent, numerical methods have increasingly been used in silo design. However, the results obtained using these methods strongly depend on the variables employed to define the materials stored. Since the literature provides little information on the variables required for modeling the behavior of agricultural powdered materials, the goals of the present work were to: i) provide values for the different variables that are needed when designing silos using numerical methods (e.g., the Poisson ratio, the dilatancy angle and the modulus of elasticity, etc.), and ii) investigate the suitability of tests used in soil mechanics for powdered materials (e.g., the direct shear and the oedometric and triaxial test). Recommended values for these variables are proposed.