Kinetics and thermodynamics of adsorption of red dye 40 from acidic aqueous solutions onto a novel chitosan sulfate

The kinetic and thermodynamics of adsorption of Red Dye 40 from acidic aqueous solutions onto a partially sulfated chitosan (ChS) was studied. The partially sulfated ChS was water insoluble in the pH range of 2-12. Experiments were carried out batch wise to determine the effect of pH, dye concentration, and temperature on the adsorption capacity of ChStowards Red Dye 40. It was found that the equilibrium dye-binding capacity of ChS (qe) increased with increasing initial dye concentration; however, the percentage of dye removal decreased. Dye adsorption capacity of ChS increased when the solution pH was reduced. The Langmuir model was better fitted the experimental adsorption equilibrium data, and therate of dye adsorption onto ChS follows the pseudosecond order kinetic model. The adsorption capacity of ChS was enhanced by increasing the temperature.The thermodynamic adsorption parameters, enthalpy(ΔH°), entropy (ΔS°), and Gibbs energy (ΔG°) were evaluated. The adsorption process was endothermic, and the Gibbs energy negative indicating that it occurred spontaneously

Chitosan selectivity for removing cadmium (II), copper (II), and lead (II) from aqueous phase: pH and organic matter effect

"The aim of this study was to investigate the selectivity of chitosan for cadmium, copper and lead in the presence and absence of natural organic matter (NOM) in different pH solutions. Adsorption isotherms of one and three adsorbates at initial concentration of 5–100 mg/L were carried out in batch reactors at pH 4, 5, or 7 and 25 °C in reactive and clarified water. The chitosan employed had a MW of 107.8 × 103 g/mol and degree of acetylation (DA) of 33.7%. The chitosan adsorption capacity at pH 4 in reactive water was 0.036, 0.016, 0.010 mmol/g for Pb2+, Cd2+, and Cu2+, respectively, and it decreased for Pb2+ and Cd2+ in clarified water. Conversely, experiments carried out in clarified water showed that the cadmium adsorption capacity of chitosan was enhanced about three times by the presence of NOM at pH 7: an adsorption mechanism was proposed. Furthermore, it was found that the biosorbent selectivity, in both reactive and clarified water at pH 4, was as follows Cu2+ > Cd2+ > Pb2+. Finally, the preliminary desorption experiments of Cd2+ conducted at pH 2 and 3 reported 68 and 44.8% of metal desorbed, which indicated that the adsorption mechanism occurred by electrostatic interactions and covalent bonds.

First record of eucalyptus gall wasp Leptocybe invasa (Hymenoptera: Eulophidae) in Mexico

The presence of the invader eucalyptus gall wasp Leptocybe invasa Fischer & La Salle (Hymenoptera: Eulophidae) is recorded for the first time in Mexico. This forest pest has been detected in northern México City, at an elevation of ≈2,240m, with an average temperature of 17.9°C. It has also been detected in the areas of Nezahualcóyotl and Texcoco, State of México; Cuautla, Morelos; Guadalajara, Jalisco and Ciudad Victoria, Tamaulipas. In these states, L. invasa attacked Eucalyptus camaldulensis Dehnh. About 2.6% of the E. camaldulensis trees reported in México City had infestations in about 27% of the twigs. In addition, 25% of the leaves had galls, with an average of 23.5±4.8 galls per branches of 20cm in length

Enemigos naturales de Dactylopius Opuntiae (Cockerell) en opuntia ficus-indica (l.) Miller en el centro de México

. Prickly pear, Opuntia ficus-indica (L.) Miller, is cultivated for many purposes around the world. In Mexico, people consume young pads as vegetables and call them nopalitos. The production of nopalitos occurs mainly around Mexico City where cochineal insects (Dactylopius spp.) are one of the most important pests. Farmers partly control Dactylopius using insecticides, but biological control could offer a tool for the Integrated Pest Management. In this paper the cochineal insects and their natural enemies were studied in Tlalnepantla, Morelos, one of the most important regions for nopalitos production in Mexico. In order to determine Dactylopius species, 30 samples sites were selected in this region. Additionally natural enemies were collected every other week during one year period in five different zones. Dactylopius opuntiae (Cockerell) was the only cochineal species found in Tlalnepantla. The natural enemies, in order of abundance, were Leucopis bellula, Sympherobius barberi, Laetilia coccidivora, Hyperaspis trifurcata, Salpingogaster cochenillivorus, Sympherobius angustus, and Chilocorus cacti. We also included some lab and field biology descriptions of these predators. Diverse factors of crop management appeared to affect D. opuntiae population and their natural enemies.El nopal Opuntia ficus-indica se cultiva con diversos propósitos en el mundo, mientras que en México, principal productor y consumidor mundial, particularmente se consume como verdura (nopalitos). La producción de nopalitos se ubica, principalmente, en los alrededores de la Ciudad de México donde las cochinillas silvestres Dactylopius spp. son de los insectos más nocivos para el cultivo. El control químico es el método de más uso por los productores, aunque el control biológico podría ser útil para un manejo integrado de plagas. No obstante, los estudios taxonómicos sobre las especies de cochinilla y sus enemigos naturales en México no son abundantes. En esta investigación se planteó conocer las especies presentes de Dactylopius y sus enemigos naturales en Tlalnepantla, Morelos, una de las áreas de mayor producción de nopalitos en México. Se seleccionaron 30 sitios distribuidos en esta región y se establecieron cinco sitios para monitoreo de enemigos naturales cada dos semanas durante un año. La única especie de cochinilla silvestre del nopal que se encontró correspondió a Dactylopius opuntiae (Cockerell), los enemigos naturales en orden de abundancia fueron Leucopis bellula, Sympherobius barberi, Laetilia coccidivora, Hyperaspis trifurcata, Salpingogaster cochenillivorus, Sympherobius angustus y Chilocorus cacti. Se proporcionan descripciones de biología de los enemigos naturales en campo y laboratorio. Diversos factores relacionados con el manejo del cultivo tuvieron un efecto sobre las poblaciones de D. opuntiae y sus enemigos naturales

Measuring access to medicines: a review of quantitative methods used in household surveys

<p>Abstract</p> <p>Background</p> <p>Medicine access is an important goal of medicine policy; however the evaluation of medicine access is a subject under conceptual and methodological development. The aim of this study was to describe quantitative methodologies to measure medicine access on household level, access expressed as paid or unpaid medicine acquisition.</p> <p>Methods</p> <p>Searches were carried out in electronic databases and health institutional sites; within references from retrieved papers and by contacting authors.</p> <p>Results</p> <p>Nine papers were located. The methodologies of the studies presented differences in the recall period, recruitment of subjects and medicine access characterization.</p> <p>Conclusions</p> <p>The standardization of medicine access indicators and the definition of appropriate recall periods are required to evaluate different medicines and access dimensions, improving studies comparison. Besides, specific keywords must be established to allow future literature reviews about this topic.</p

Beam energy dependent two-pion interferometry and the freeze-out eccentricity of pions in heavy ion collisions at STAR

We present results of analyses of two-pion interferometry in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV measured in the STAR detector as part of the RHIC Beam Energy Scan program. The extracted correlation lengths (HBT radii) are studied as a function of beam energy, azimuthal angle relative to the reaction plane, centrality, and transverse mass ($m_{T}$) of the particles. The azimuthal analysis allows extraction of the eccentricity of the entire fireball at kinetic freeze-out. The energy dependence of this observable is expected to be sensitive to changes in the equation of state. A new global fit method is studied as an alternate method to directly measure the parameters in the azimuthal analysis. The eccentricity shows a monotonic decrease with beam energy that is qualitatively consistent with the trend from all model predictions and quantitatively consistent with a hadronic transport model.Comment: 27 pages; 27 figure