In this study acetic and lactic acid Minimal Inhibitory Concentration (MIC) were determined for different Aspergillus flavus strains in solid medium: toxigenic strains A. flavus AFUNL1, AFUNL2 and ...AFUNL3; and a non-toxigenic strain A. flavus AFUNQ6. A. flavus AFUNQ6 was the most resistant strain to acetic acid, with a MIC value of 41.6mM (pH 4,62) while acetic acid MIC was the same for the three toxigenic strains (38.1mM, pH 4.69), the lactic acid MIC was different for all the strains: 357.7mM (pH 2.74), 405.4mM (pH 2.69), 274.2mM (pH 2.95) and 393.4mM (pH 2.59) for A. flavus AFUNQ6, AFUNL1, AFUNL2 and AFUNL3 respectively. MIC values for non dissociated lactic acid were almost tenfold higher than MIC vales for non dissociated acetic acid for the A. flavus strains.
Growth kinetic parameters: growth rate (KD) and lag phase were determined to evaluate fungal inhibition. An increase of undissociated acid concentration produced a decrease in KD values and an increase in lag phase duration. Lactic and acetic acid mixtures showed a synergistic effect, reducing the concentration necessary of every acid in the mixture for fungal inhibition compared with the individual MIC values. The minimal acids mixture that obtained the fungal inhibition for all the strains was lactic acid 78mM acetic Acid 31.2mM at a pH 3.4.
► We studied lactic and acetic acid effect on Aspergillus flavus growth. ► Acetic and lactic acid MIC were determined for different Aspergillus flavus strains. ► MIC values for lactic acid were tenfold higher than MIC for acetic acid. ► Synergistic effect on fungal inhibition was observed with lactic and acetic mixtures.
X-ray powder diffraction and differential thermal analysis (DTA) measurements were made on polycrystalline samples of the Cu2Zn1-zFezGeSe4 alloy system. The diffraction patterns were used to show the ...equilibrium conditions and to estimate crystalline parameter values. It was found that, at room temperature, a single phase solid solution with the tetragonal stannite structure occurs across the whole composition range. The DTA thermograms were used to construct the phase diagram of the Cu2Zn1-zFezGeSe4 alloy system. It was confirmed that the Cu2ZnGeSe4 compound melts incongruently. It was observed that undercooling effects occur for samples with z > 0.9.
X-ray powder diffraction measurements and differential thermal analysis (DTA) were made on polycrystalline samples of the Cu2Cd1-zMnzGeSe4 and Cu2Cd1-zFezGeSe4 alloy systems. The diffraction patterns ...were used to show the equilibrium conditions and to derive lattice parameter values. The effect of the annealing temperature and cooling rate to room temperature are discussed. For the Cu2Cd1-zFezGeSe4 system, only two single solid phase fields, the tetragonal stannite alpha and the wurtz-stannite delta structures were found to occur in the diagram. For the Cu2Cd1-zMnzGeSe4 system, in addition to the tetragonal stannite alpha and the wurtz-stannite delta phases, MnSe was found to exist in the diagram. The DTA experiments showed that the cooling curves for both systems exhibited effects of undercooling.
► Cerebellar astrocytoma impaired the spatial orientation attentional network in children. ► The orientation network scores impairment is not due to motor or sensory processes. ► The ...cortico–pontine–cerebellar–thalamic–cortical loop would be the basis for this impairment.
Cerebellum astrocytomas are the most typical nervous system tumors in children. Several cognitive deficits have been previously described. These deficits are probably produced by cerebellar connection and gray matter damage. The present study examines attentional deficits in children operated on for cerebellum astrocytomas, using an attentional paradigm with theoretical and clinical bases: the Attentional Network Test (ANT). This test was designed considering the attentional network theory proposed by Posner, and its usefulness has been demonstrated in clinical settings. Children operated on for cerebellar astrocytoma showed a mild attentional deficit in the orientation network.
Dead wood can be an important component of the carbon pool in many forests, but few measurements have been made of this pool in tropical forests. To fill this gap, we determined the quantity of dead ...wood (downed and standing dead) in 25 long-term (up to 30 yr) permanent forest plots located in six different life zones of Venezuela. Downed wood was separated into fine (< 10 cm in diameter) and coars (≥ 10 cm in diameter) classes, and three decomposition states (sound, intermediate, or rotten). The total quantity of dead wood, averaged by life zone, was lowest in the dry (2.43 Mg/ha), reached a peak in the moist (42.33 Mg/ha) and decreased slightly in the wet (34.50 Mg/ha) life zone. Most of the dead wood was in the standing dead category (about 42-76% of the total). The decomposition state of dead wood in all plots was mostly rotten (45%) or intermediate (44%); there was little sound wood (11%). Turnover rates of dead wood generally ranged between 0.03/yr to 0.52/yr with no clear trend with life zone. The large amount of dead wood in some plots was equivalent to about 20 percent or less of aboveground biomass, indicating that dead wood can represent a significant amount of carbon in these forests.
Conducting polymers (CPs), thanks to their unique properties, structures made on-demand, new composite mixtures, and possibility of deposit on a surface by chemical, physical, or electrochemical ...methodologies, have shown in the last years a renaissance and have been widely used in important fields of chemistry and materials science. Due to the extent of the literature on CPs, this review, after a concise introduction about the interrelationship between electrochemistry and conducting polymers, is focused exclusively on the following applications: energy (energy storage devices and solar cells), use in environmental remediation (anion and cation trapping, electrocatalytic reduction/oxidation of pollutants on CP based electrodes, and adsorption of pollutants) and finally electroanalysis as chemical sensors in solution, gas phase, and chiral molecules. This review is expected to be comprehensive, authoritative, and useful to the chemical community interested in CPs and their applications.
Derivatives of pyridinones were found to inhibit human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) activity and prevent the spread of HIV-1 infection in cell culture without an ...appreciable effect on other retroviral or cellular polymerases. 3-{(4,7-Dimethyl-1,3-benzoxazol-2-yl)methylamino}-5-ethyl-6- methylpyridin-2(1H)-one (L-697,639) and 3-{(4,7-dichloro-1,3-benzoxazol-2- yl)methylamino}-5-ethyl-6-methylpyridin-2(1H)-one (L-697,661), two compounds within this series, had HIV-1 RT IC50values in the range of 20-800 nM, depending upon the template-primer used. The most potent inhibition was obtained with rC· dG and dA· dT as template-primers. With rC· dG, reversible slow-binding non-competitive inhibition was observed. 3HL-697,639 bound preferentially to enzyme-template-primer complexes. This binding was magnesium-dependent and saturable with a stoichiometry of 1 mol of 3HL-697,639 per mol of RT heterodimer. Displacement of 3HL-697,639 was seen with phosphonoformate. In human T-lymphoid-cell culture, L-697,639 and L-697,661 inhibited the spread of HIV-1 infection by at least 95% at concentrations of 12-200 nM. Synergism between 3'-azido-3'- deoxythymidine or dideoxyinosine and either of these compounds was also demonstrated in cell culture. Based upon their specificity for HIV-1 RT activity, template-primer dependence on potency and ability to displace 3HL-697,639; a tetrahydroimidazo4,5,1-jk1,4-benzodiazepin-2(1H)- thione derivative R82150 and the dipyridodiazepinone BI-RG-587 appear to inhibit RT activity by the same mechanism as the pyridinones.
Chemical reduction has become an accessible and useful alternative to obtain silver nanoparticles (AgNPs). However, its toxicity capacity depends on multiple variables that generate differences in ...the ability to inhibit the growth of microorganisms. Thus, optimazing parameters for the synthesis of AgNPs can increase its antimicrobial capacity by improving its physical-chemical properties.
In this study a Face Centered Central Composite Design (FCCCD) was carried out with four parameters:
concentration, sodium citrate (TSC) concentration,
concentration and the pH of the reaction with the objective of inhibit the growth of microorganisms. The response variables were the average size of AgNPs, the peak with the greatest intensity in the size distribution, the polydispersity of the nanoparticle size and the yield of the process. AgNPs obtained from the optimization were characterized physically and chemically. The antimicrobial activity of optimized AgNPs was evaluated against
,
,
AmpC resistant, and
and compared with AgNPs before optimization. In addition, the cytotoxicity of the optimized AgNPs was evaluated by the colorimetric assay MTT (3- (4,5- Dimethylthiazol- 2- yl)- 2, 5 - Diphenyltetrazolium Bromide).
It was found that the four factors studied were significant for the response variables, and a significant model (p < 0.05) was obtained for each variable. The optimal conditions were 8 for pH and 0.01 M, 0.0 6M, 0.01 M for the concentration of TSC,
, and
, respectively. Optimized AgNPs spherical and hemispherical were obtained, and 67.66% of it had a diameter less than 10.30 nm. A minimum bactericidal concentration (MBC) and minimum fungicidal Concentration (MFC) of optimized AgNPs was found against
,
,
AmpC resistant, and
at 19.89, 9.94, 9.94, 2.08
g/mL, respectively. Furthermore, the lethal concentration 50 (
) of optimized AgNPs was found on 19.11
g/mL and 19.60
g/mL to Vero and NiH3T3 cells, respectively.
It was found that the factors studied were significant for the variable responses and the optimization process used was effective to improve the antimicrobial activity of the AgNPs.
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