Biooxidación de tiosulfato como mecanismo indirecto para la lixiviación de minerales mediante cepas nativas acidófilas

The mechanisms of conversion to elemental sulfur, sulphites, sulfates and others; they are diverse, leading to the formation of sulfuric acid and therefore, to the acidification of the medium. Based on these characteristics, acidophilic bacteria are considered as sulfur chemolytotrophs, since they obtain their energy from the conversion of sulfur compounds and, in most cases, the final product is sulfate. The acid formed by these bacteria that oxidize sulfides is sulfuric acid. Similarly, bacteria isolated from acid drains, during their metabolic action, generate a decrease in pH. The Thiobacillus genus is relevant among the others for its ability to oxidize sulfur compounds, producing elemental sulfur extracellularly. The energy required to carry out its functions is derived from the oxidation of one or more reduced sulfur compounds including sulfide and thiosulfate. In the study of the oxidation of thiosulfate, the increase in the bacterial population was observed up to 8.6x108Cel / ml and oxide reduction potentials (ORP) of up to 615mV. At pH values ​​between 1.8 and 2.2 and at thiosulfate concentrations of 2.2 gr / L . The greatest population increase of the bacteria was obtained in periods of 10 and 15 days of evolution. The monitoring of the potential made it possible to identify the state of operation of the sulfoxidant system. A direct relationship was found between the ORP and the bacterial population.Los mecanismos de conversión a azufre elemental, sulfitos, sulfatos y otros; son diversos, conllevando a la formación de ácido sulfúrico y por ende, a la acidificación del medio. En base a estas características, las bacterias acidófilas son consideradas como quimiolitótrofas de azufre, ya que obtienen su energía a partir de la conversión de compuestos de azufre y, en la mayoría de los casos, el producto final es el sulfato. El ácido formado por estas bacterias que oxidan los sulfuros es el ácido sulfúrico. Del mismo modo, las bacterias aisladas de drenajes ácidos, durante su acción metabólica, generan la disminución del pH. El género Thiobacillus es relevante entre los demás por su capacidad de oxidar compuestos azufrados, produciendo azufre elemental de manera extracelular. La energía necesaria para llevar a cabo sus funciones se deriva de la oxidación de uno o más compuestos reducidos de azufre incluyendo sulfuro y tiosulfato. En el estudio de la oxidación del tiosulfato se observó el incremento de la población bacteriana hasta 8.6x108Cel/ml y potenciales de óxido reducción (ORP) de hasta 615mV.a valores de pH entre 1.8 y 2.2 y a concentraciones de tiosulfato de 2.2 gr/L. El mayor incremento poblacional de la bacteria se obtuvo en periodos de 10 y 15 días de evolución. El monitoreo del potencial permitió identificar el estado de funcionamiento que tiene el sistema sulfoxidante. Se encontró una relación directa entre el ORP y la población bacteriana

Biolixiviación de cobre a partir de minerales sulfurados con altos tenores de pirita y arsenopirita

The study was carried out with isolated strains of acid drainage and consisted of processing of highly mineralized copper sulphides that mainly contained 45.30% pyrite and 13.12% arsenopyrite. Bioleaching was carried out in 500 ml flasks, where 300 ml of 9k medium, 30 ml of bacterial inoculum (10% V / V) of 7.05x107 Cell / ml and various amounts of FeSO4.7H2O were added. The pH was regulated to 1.8 and they were subjected to platform agitation with 150 RPM at ambient temperature of 20 ° C on average. The tests were carried out in three successive stages at different concentrations of ferrous salt. In the first stage, 72.64% copper was obtained with 6 g / l of FeSO4.7H2O in 22 days. In the second stage, 85.6% of copper was achieved in the absence of the ferrous salt. Greater bacterial growth was also achieved with 15 g / l FeSO4.7H2O and 25.62% copper recovery in 24 days of leaching; In addition, the existence of a direct relationship between the increase in bacterial density and the recovery of copper from the sulphided mineral is determined. In the third stage, 89.38% of copper is recovered in the absence of the ferrous salt and in just 20 days of bioleaching.El estudio fue realizado con cepas aisladas de drenaje ácido y consistió en procesamiento de sulfuros de cobre de alta mineralización que contenían principalmente 45.30 % de pirita y 13.12 % de arsenopirita. La biolixiviación fue realizada en matraces de 500 ml, donde se agregaron 300 ml de medio 9k, 30 ml de inóculo bacteriano (10% V/V) de 7.05x107 Cell/ml y diversas cantidades de FeSO4.7H2O. Se reguló el pH a 1.8 y se sometieron a agitación en plataforma con 150 RPM a temperatura ambiental de 20°C en promedio. Los ensayos se realizaron en tres etapas sucesivas a diferentes concentraciones de sal ferrosa. En la primera etapa se obtuvo 72.64 % de cobre con 6 g/l de FeSO4.7H2O en 22 días. En la segunda etapa se logró 85.6 % de cobre en ausencia de la sal ferrosa, también se logra mayor crecimiento bacteriano con 15 g/l FeSO4.7H2O y 25.62 % de recuperación de cobre en 24 días de lixiviación; además, se determina la existencia de una relación directa entre el incremento de la densidad bacteriana y la recuperación de cobre a partir del mineral sulfurado. En la tercera etapa se logra recuperar 89.38% de cobre en ausencia de la sal ferrosa y en tan solo 20 días de biolixiviación

The global abundance of tree palms

Aim Palms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change. Location Tropical and subtropical moist forests. Time period Current. Major taxa studied Palms (Arecaceae). Methods We assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure. Results On average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work. Conclusions Tree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests

Les droits disciplinaires des fonctions publiques : « unification », « harmonisation » ou « distanciation ». A propos de la loi du 26 avril 2016 relative à la déontologie et aux droits et obligations des fonctionnaires

The production of tt‾ , W+bb‾ and W+cc‾ is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98±0.02 fb−1 . The W bosons are reconstructed in the decays W→ℓν , where ℓ denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.The production of $t\overline{t}$, $W+b\overline{b}$ and $W+c\overline{c}$ is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 $\pm$ 0.02 \mbox{fb}^{-1}. The $W$ bosons are reconstructed in the decays $W\rightarrow\ell\nu$, where $\ell$ denotes muon or electron, while the $b$ and $c$ quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions

Measurement of the J/ψ pair production cross-section in pp collisions at s=13 \sqrt{s}=13 TeV

The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=13$ TeV, corresponding to an integrated luminosity of 279 ±11 pb$^{−1}$. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y < 4.5. The production cross-section is measured to be 15.2 ± 1.0 ± 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions.The production cross-section of $J/\psi$ pairs is measured using a data sample of $pp$ collisions collected by the LHCb experiment at a centre-of-mass energy of $\sqrt{s} = 13 \,{\mathrm{TeV}}$, corresponding to an integrated luminosity of $279 \pm 11 \,{\mathrm{pb^{-1}}}$. The measurement is performed for $J/\psi$ mesons with a transverse momentum of less than $10 \,{\mathrm{GeV}}/c$ in the rapidity range $2.0<y<4.5$. The production cross-section is measured to be $15.2 \pm 1.0 \pm 0.9 \,{\mathrm{nb}}$. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the $J/\psi$ pair are measured and compared to theoretical predictions

Measurement of forward W→eνW\to e\nu production in pppp collisions at s=8 \sqrt{s}=8\,TeV

A measurement of the cross-section for $W \to e\nu$ production in $pp$ collisions is presented using data corresponding to an integrated luminosity of $2\,$fb$^{-1}$ collected by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=8\,$TeV. The electrons are required to have more than $20\,$GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive $W$ production cross-sections, where the $W$ decays to $e\nu$, are measured to be \begin{align*} \begin{split} \sigma_{W^{+} \to e^{+}\nu_{e}}&=1124.4\pm 2.1\pm 21.5\pm 11.2\pm 13.0\,\mathrm{pb},\\ \sigma_{W^{-} \to e^{-}\bar{\nu}_{e}}&=\,\,\,809.0\pm 1.9\pm 18.1\pm\,\,\,7.0\pm \phantom{0}9.4\,\mathrm{pb}, \end{split} \end{align*} where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The $W^{+}/W^{-}$ cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of $W$ boson branching fractions is determined to be \begin{align*} \begin{split} \mathcal{B}(W \to e\nu)/\mathcal{B}(W \to \mu\nu)=1.020\pm 0.002\pm 0.019, \end{split} \end{align*} where the first uncertainty is statistical and the second is systematic.A measurement of the cross-section for $W \to e\nu$ production in $pp$ collisions is presented using data corresponding to an integrated luminosity of $2\,$fb$^{-1}$ collected by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=8\,$TeV. The electrons are required to have more than $20\,$GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive $W$ production cross-sections, where the $W$ decays to $e\nu$, are measured to be \begin{equation*} \sigma_{W^{+} \to e^{+}\nu_{e}}=1124.4\pm 2.1\pm 21.5\pm 11.2\pm 13.0\,\mathrm{pb}, \end{equation*} \begin{equation*} \sigma_{W^{-} \to e^{-}\bar{\nu}_{e}}=\,\,\,809.0\pm 1.9\pm 18.1\pm\,\,\,7.0\pm \phantom{0}9.4\,\mathrm{pb}, \end{equation*} where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The $W^{+}/W^{-}$ cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of $W$ boson branching fractions is determined to be \begin{equation*} \mathcal{B}(W \to e\nu)/\mathcal{B}(W \to \mu\nu)=1.020\pm 0.002\pm 0.019, \end{equation*} where the first uncertainty is statistical and the second is systematic.A measurement of the cross-section for W → eν production in pp collisions is presented using data corresponding to an integrated luminosity of 2 fb$^{−1}$ collected by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=8$ TeV. The electrons are required to have more than 20 GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive W production cross-sections, where the W decays to eν, are measured to be ${\sigma}_{W^{+}\to {e}^{+}{\nu}_e}=1124.4\pm 2.1\pm 21.5\pm 11.2\pm 13.0\kern0.5em \mathrm{p}\mathrm{b},$ ${\sigma}_{W^{-}\to {e}^{-}{\overline{\nu}}_e}=809.0\pm 1.9\pm 18.1\pm \kern0.5em 7.0\pm \kern0.5em 9.4\,\mathrm{p}\mathrm{b},$ where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination

Measurement of the B0s→μ+μ− Branching Fraction and Effective Lifetime and Search for B0→μ+μ− Decays

A search for the rare decays Bs0→μ+μ- and B0→μ+μ- is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4  fb-1. An excess of Bs0→μ+μ- decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(Bs0→μ+μ-)=(3.0±0.6-0.2+0.3)×10-9, where the first uncertainty is statistical and the second systematic. The first measurement of the Bs0→μ+μ- effective lifetime, τ(Bs0→μ+μ-)=2.04±0.44±0.05  ps, is reported. No significant excess of B0→μ+μ- decays is found, and a 95% confidence level upper limit, B(B0→μ+μ-)<3.4×10-10, is determined. All results are in agreement with the standard model expectations.A search for the rare decays $B^0_s\to\mu^+\mu^-$ and $B^0\to\mu^+\mu^-$ is performed at the LHCb experiment using data collected in $pp$ collisions corresponding to a total integrated luminosity of 4.4 fb$^{-1}$. An excess of $B^0_s\to\mu^+\mu^-$ decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be ${\cal B}(B^0_s\to\mu^+\mu^-)=\left(3.0\pm 0.6^{+0.3}_{-0.2}\right)\times 10^{-9}$, where the first uncertainty is statistical and the second systematic. The first measurement of the $B^0_s\to\mu^+\mu^-$ effective lifetime, $\tau(B^0_s\to\mu^+\mu^-)=2.04\pm 0.44\pm 0.05$ ps, is reported. No significant excess of $B^0\to\mu^+\mu^-$ decays is found and a 95 % confidence level upper limit, ${\cal B}(B^0\to\mu^+\mu^-)<3.4\times 10^{-10}$, is determined. All results are in agreement with the Standard Model expectations

Measurements of prompt charm production cross-sections in pp collisions at s=5 \sqrt{s}=5 TeV

Production cross-sections of prompt charm mesons are measured using data from $pp$ collisions at the LHC at a centre-of-mass energy of $5\,$TeV. The data sample corresponds to an integrated luminosity of $8.60\pm0.33\,$pb$^{-1}$ collected by the LHCb experiment. The production cross-sections of $D^0$, $D^+$, $D_s^+$, and $D^{*+}$ mesons are measured in bins of charm meson transverse momentum, $p_{\text{T}}$, and rapidity, $y$. They cover the rapidity range $2.0 < y < 4.5$ and transverse momentum ranges $0 < p_{\text{T}} < 10\, \text{GeV}/c$ for $D^0$ and $D^+$ and $1 < p_{\text{T}} < 10\, \text{GeV}/c$ for $D_s^+$ and $D^{*+}$ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of $1 < p_{\text{T}} < 8\, \text{GeV}/c$ are determined to be \begin{equation*} \sigma(pp\rightarrow D^0 X) = 1190 \pm 3 \pm 64\,\mu\text{b} \end{equation*} \begin{equation*} \sigma(pp\rightarrow D^+ X) = 456 \pm 3 \pm 34\,\mu\text{b} \end{equation*} \begin{equation*} \sigma(pp\rightarrow D_s^+ X) = 195 \pm 4 \pm 19\,\mu\text{b} \end{equation*} \begin{equation*} \sigma(pp\rightarrow D^{*+} X)= 467 \pm 6 \pm 40\,\mu\text{b} \end{equation*} where the uncertainties are statistical and systematic, respectively.Production cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5 TeV. The data sample corresponds to an integrated luminosity of 8.60 ± 0.33 pb$^{−1}$ collected by the LHCb experiment. The production cross-sections of D$^{0}$, D$^{+}$, D$_{s}^{+}$ , and D$^{∗+}$ mesons are measured in bins of charm meson transverse momentum, p$_{T}$, and rapidity, y. They cover the rapidity range 2.0 < y < 4.5 and transverse momentum ranges 0 < p$_{T}$ < 10 GeV/c for D$^{0}$ and D$^{+}$ and 1 < p$_{T}$ < 10 GeV/c for D$_{s}^{+}$ and D$^{∗+}$ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of 1 < p$_{T}$ < 8 GeV/c are determined to be $\begin{array}{l}\sigma \left( pp\to {D}^0X\right)=1004\pm 3\pm 54\mu \mathrm{b},\\ {}\sigma \left( pp\to {D}^{+}X\right)=402\pm 2\pm 30\mu \mathrm{b},\\ {}\sigma \left( pp\to {D}_s^{+}X\right)=170\pm 4\pm 16\mu \mathrm{b},\\ {}\sigma \left( pp\to {D}^{\ast +}X\right)=421\pm 5\pm 36\mu \mathrm{b},\end{array}$ where the uncertainties are statistical and systematic, respectively.Production cross-sections of prompt charm mesons are measured using data from $pp$ collisions at the LHC at a centre-of-mass energy of $5\,$TeV. The data sample corresponds to an integrated luminosity of $8.60\pm0.33\,$pb$^{-1}$ collected by the LHCb experiment. The production cross-sections of $D^0$, $D^+$, $D_s^+$, and $D^{*+}$ mesons are measured in bins of charm meson transverse momentum, $p_{\text{T}}$, and rapidity, $y$. They cover the rapidity range $2.0<y<4.5$ and transverse momentum ranges $0 < p_{\text{T}} < 10\, \text{GeV}/c$ for $D^0$ and $D^+$ and $1 < p_{\text{T}} < 10\, \text{GeV}/c$ for $D_s^+$ and $D^{*+}$ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of $1 < p_{\text{T}} < 8\, \text{GeV}/c$ are determined to be \sigma(pp\rightarrow D^0 X) = 1004 \pm 3 \pm 54\,\mu\text{b} \sigma(pp\rightarrow D^+ X) = 402 \pm 2 \pm 30\,\mu\text{b} \sigma(pp\rightarrow D_s^+ X) = 170 \pm 4 \pm 16\,\mu\text{b} \sigma(pp\rightarrow D^{*+} X)= 421 \pm 5 \pm 36\,\mu\text{b} where the uncertainties are statistical and systematic, respectively

Liber secundus De mundi historia

Datos de publicación tomados del colofónSign.: A-Z8, a-r8, s

Using Facebook as a Pedagogical Tool to Enhance the English Learning Process

Tesis (Pedagogía en Inglés)In the following Thesis Project, the impact that a social network with academic purposes might have was explored. In arder to choose the best tool, questionnaires with the purpose of identifying the students' interests were made and implemented. The result was Facebook. This investigation is divided into three main parts: Theoretical Framework, Methodological Framework, and Conclusions and Proposals. The main purpose of this investigation is to explore the changes that Facebook may have in terms of level of motivation in the learning of the English subject as well as in terms of academic performance results in teenagers. In arder to achieve this objective, an investigation related to the usage of technology and the impact it has had in our society was started. To do this, what renowned authors have said regarding the tapie was researched. Through this research it was possible to preve the benefits that an intervention using a social network with academic purposes has. Due to this exploration and implementation, the teaching of the English language, which is of great importance nowadays, could be complemented effectively. This has great educational implication since one of the characteristics of our country is that there is availability of technological resources at educational institutions, but it has not been given an appropriate and stimulating use to promete the learning in students yet. The context in which this implementation was conducted, was two schools in Santiago of Chile; a private school (School A), and a public school (School B), Tenth and Eleventh grades respectively. Once the intervention had already been conducted in these institutions, measurement instruments were employed in order to collect information regarding the impact that the process of using Facebook had on students.En el siguiente Seminario de Grado se exploró el impacto que puede tener una red social con fines académicos. Para poder elegir la mejor herramienta se realizaron cuestionarios para identificar las preferencias de los estudiantes. El resultado fue: Facebook. Esta investigación se divide en tres partes principales: Marco Teórico, Marco Metodológico y Conclusiones y Propuestas. El propósito principal de esta investigación es explorar los cambios que puede producir Facebook tanto en la motivación hacia el aprendizaje del idioma Inglés en adolescentes como en los resultados en términos de desempeño académico. Para lograr este objetivo, se comenzó con una investigación relacionada al uso de la tecnología y el impacto que ha tenido en nuestra sociedad, para lo cual se llevó a cabo una investigación sobre qué han dicho autores renombrados con respecto al tema. A través de esta investigación pudimos comprobar los beneficios que tiene una intervención utilizando como medio académico una red social. Gracias a esta exploración e implementación se pudo complementar efectivamente la enseñanza del idioma inglés, idioma de gran importancia en nuestros tiempos. Esto tiene gran implicancia educacional puesto que una de las características de nuestro país es que existe disponibilidad de elementos tecnológicos en los establecimientos educacionales, pero aún no se les da un uso apropiado y estimulante para promover el aprendizaje. El contexto en el cual se realizó esta implementación fueron dos colegios de la comuna de Santiago, un colegio privado (School A) y un colegio público (School B), segundo y tercero medio respectivamente. Una vez hecha la intervención en estos establecimientos, se emplearon instrumentos de medición para recolectar información con respecto al impacto que tuvo el trabajo realizado con Facebook en los estudiantes