Análisis de los parámetros y selección de hornos para la combustión de biomasa

El presente estudio fue realizar una estimación analítica de los parámetros necesarios para poder operar un horno de combustión en condiciones óptimas para cuando utilizamos residuos agrícolas tales como: bagazo de caña, cascarilla de arroz y cascarilla de café como un combustible alterno. Para estimar estos parámetros utilicé ecuaciones basadas en la termodinámica de la combustión y ecuaciones empíricas. Al final de este estudio obtuve valores estimados de los parámetros tales como: temperatura adiabática de llama, relación aire/combustible y tiempo de residencia. Adicionalmente a lo anterior también seleccione el tipo de horno para cada biomasa. Para poder saber que tan exactos fueron los parámetros teóricos obtenidos, realicé una comparación con otro método analítico que me permitió determinar el porcentaje de error. Adicionalmente elaboré unas gráficas que me permitieron saber el comportamiento de las biomasas en el proceso de combustión al variar los parámetros

The Metal-dependent Function of C2α: A Conditional Membrane Domain from Protein Kinase Cα

Protein Kinase C (PKC) isoforms function in signaling pathways responsible for controlling cell proliferation, survival and apoptosis. Up or down-regulation of PKCs has been implicated in cancer progression, cardiovascular dysfunction, and neurological disorders. Moreover, the conventional Protein Kinase Calpha (PKCalpha) has also been identified as an important molecular target in Pb2+ poisoning. Two out of three Pb^(2+) sites in full-length PKCalpha were mapped onto its C2 domain (C2alpha), which associates with anionic membranes in response to binding Ca^(2+) ions in the first step of activation. The objective of this work was to determine the specific role of divalent metal ions on the modulation of C2alpha structure, function, and interactions with other PKCalpha domains. Nuclear magnetic resonance (NMR) and Förster resonance energy transfer were used to characterize the specific role of divalent metal ions in C2alpha membrane-interactions. Pb^(2+) and Cd^(2+) ions bind C2alpha with high affinity. Pb^(2+) drives C2alpha association with lipid-membranes, whereas Cd^(2+) does not support membrane-binding. This work provides direct evidence for the specific role of divalent metal ions in mediating protein-membrane interactions and illustrates the opposite responses produced by toxic metal ions in a single molecular target. The structures of metal-free (1.9 Å) and Pb2+-bound (1.5 Å) C2alpha were determined using X-ray crystallography. These revealed a remarkable coexistence of hemi- and holo-directed coordinated geometries for the two Pb^(2+) ions that are bound to the Ca^(2+) binding loops (CBLs). The overall backbone conformation does not change upon metal-binding. However, elevated B-factors were observed in the CBLs of metal-free C2alpha, suggesting that this region is dynamic. NMR techniques were used to identify the dynamic regions and to quantify the timescales of C2alpha motions in different states of metal ligation. Metal-binding quenches the microsecond-timescale motions of the CBLs but results in elevated millisecond-timescale dynamics of the N- and C-terminal regions. These regions are implicated in the interactions of C2 with other regulatory domains of PKC. Our data suggest that the changes in protein dynamics is a mechanism by which the information about the metal-binding event propagates to other regions of the protein. We then extended our structural and dynamical studies to the two-domain construct of PKCalpha comprising two regulatory domains, C1B-C2. NMR chemical shift perturbation and dynamic studies showed that these domains do not behave as independent modules in solution. The linker region connecting the functional modules shows significant chemical shifts and conformational dynamic changes induced by Ca^(2+)-binding. These results support our hypothesis that Ca^(2+)-binding triggers the rearrangement of the C1B and C2 domains. The strategy of using paramagnetic relaxation enhancement experiments to refine the C1B-C2 structure is presented. A prevailing view in the PKC field is that the function of metal ion is to alter the electrostatic potential of the C2 domain and thereby facilitate the protein insertion into the negatively charged membranes. The results of our work support the multi-faceted role of metal ions, which includes the formation of specific coordination bonds with lipid head groups, as well as the modulation of protein dynamics and inter-domain orientation

CHOICE OF MACROPHYTE SUBSTRATE IN THE USE OF DIATOMS AS INDICATORS OF POND WATER QUALITY ASSESSMENT: PRELIMINARY DATA ON THE CASE OF ALALAY POND (COCHABAMBA, BOLIVIA)

Alalay Pond is a 230-hectare, shallow aquatic ecosystem within Cochabamba, the third largest city in Bolivia. With the aim to determine the suitability of epiphytic diatoms for water quality assessment in the pond and to choose a substrate that would hold a representative bioindicator epiphytic community, the macrophytes Schoenoplectus californicus subsp. tatora (Kunth) T. Koyama, Typha dominguensis Pers., Myriophyllum verticillatum L. and Azolla filiculoides Lam. were selected and differences in diatom community composition and structure were tested. Diatoms were collected during four sampling campaigns in the March-September, 2011 period, from three stations contiguous to the pelagic zone and prepared for analysis using standard, internationally used protocols. In all, 27 samples were collected from which 28 taxa characteristic of eutrophic environments were identified and 17 others could not be assigned names from the literature. Although many of the species are shared among sampling sites, the epiphytic communities developing at each station were different in structure and composition. Although, there are marked temporal variations in community features on each of the macrophytes, Shannon-Wiener and Pielou indexes, as well as canonical correspondence analysis, showed no marked differences within a single campaign and station among the 4 macrophytes. Shifts in structure and composition are denoted less commonly by species replacement and more often by changes in percent relative abundance of dominant and rare species. Very few species are restricted to a station or seem to show strong preference for a particular substrate. Taking into account growth, structural and ecological characteristics, as well as some phenological features of the macrophytes, S. californicus subsp. tatora and T. dominguensis are the most suitable substrates for water quality assessments in the pond. As demonstrated by multivariate analyses, among-site and time-scale differences in community composition and structure were attributable to alkalinity, chemical oxygen demand (COD), ammonium-nitrogen, conductivity and dissolved oxygen (DO). More frequent sampling, diversification of substrates and extending the study for a longer period are recommended to establish a monitoring program during any future restoration of the pon

HIV-1 integrase modulates the interaction of the HIV-1 cellular cofactor LEDGF/p75 with chromatin

<p>Abstract</p> <p>Background</p> <p>Chromatin binding plays a central role in the molecular mechanism of LEDGF/p75 in HIV-1 DNA integration. Conflicting results have been reported in regards to the relevance of the LEDGF/p75 chromatin binding element PWWP domain in its HIV-1 cofactor activity.</p> <p>Results</p> <p>Here we present evidence that re-expression of a LEDGF/p75 mutant lacking the PWWP domain (ΔPWWP) rescued HIV-1 infection in cells verified to express background levels of endogenous LEDGF/p75 that do not support efficient HIV-1 infection. The HIV-1 cofactor activity of LEDGF/p75 ΔPWWP was similar to that of LEDGF/p75 wild type (WT). A possible molecular explanation for the nonessential role of PWWP domain in the HIV-1 cofactor activity of LEDGF/p75 comes from the fact that coexpression of HIV-1 integrase significantly restored the impaired chromatin binding activity of LEDGF/p75 ΔPWWP. However, integrase failed to promote chromatin binding of a non-chromatin bound LEDGF/p75 mutant that lacks both the PWWP domain and the AT hook motifs (ΔPWWP/AT) and that exhibits negligible HIV-1 cofactor activity. The effect of integrase on the chromatin binding of LEDGF/p75 requires the direct interaction of these two proteins. An HIV-1 integrase mutant, unable to interact with LEDGF/p75, failed to enhance chromatin binding, whereas integrase wild type did not increase the chromatin binding strength of a LEDGF/p75 mutant lacking the integrase binding domain (ΔIBD).</p> <p>Conclusions</p> <p>Our data reveal that the PWWP domain of LEDGF/p75 is not essential for its HIV-1 cofactor activity, possibly due to an integrase-mediated increase of the chromatin binding strength of this LEDGF/p75 mutant.</p

Escala de Calgary para el diagnóstico del síncope vasovagal. Estudio de pruebas diagnósticas

ResumenObjetivoEvaluar la utilidad de la escala de Calgary en el diagnóstico de síncope vasovagal comparada con los resultados de la prueba de mesa inclinada (Tilt test) bajo protocolo sensibilizado con medicamentos.MetodologíaEstudio prospectivo de pruebas diagnósticas en pacientes con sospecha de síncope vasovagal sometidos a prueba de mesa inclinada (Tilt test) con vasodilatación inducida con nitroglicerina por vía sublingual. Se incluyeron pacientes mayores de 18 años de edad y se excluyeron pacientes con cardiopatía estructural documentada.ResultadosSe analizaron 100 pacientes, promedio de 48,7 años (DE 19,7), 69% de género femenino y 4% residentes en área rural. La mediana de síncopes al momento del Tilt test fue de 5 (RIQ 2-15) con presentación del primer episodio a los 41 años (RIQ 21-57), en el 52% de los pacientes no se identificaron desencadenantes y las manifestaciones clínicas referidas en los episodios previos al Tilt test fueron diaforesis (58%), palidez (55%), mareo (70%), palpitaciones (50%) y náuseas (42%); durante el Tilt test se reportaron mareo (65%), diaforesis (19%), náuseas (18%) y visión borrosa (18%). Se obtuvo una sensibilidad del 77,7% (IC95%: 66,7-88,8) y una especificidad del 40,5% (IC95%: 23,3-57,7) para la escala de Calgary.ConclusionesDebido a su buena sensibilidad y fácil aplicación, la escala de Calgary es un instrumento útil para el abordaje diagnóstico de pacientes con sospecha de síncope vasovagal y corazón estructuralmente sano, especialmente en menores de 50 años de edad.AbstractObjectiveEvaluate the utility of Calgary score for the diagnosis of vasovagal syncope compared with the results of the Tilt table test using sensibilized protocol with medicines.MethodologyProspective study of diagnostic tests in patients with suspected diagnostic of vasovagal syncope who underwent tilt table test with induced vasodilation with sublingual nitroglycerin. Patients over 18 years were included and patients with documented structural heart disease were excluded.Results100 patients were analyzed, averaging 48.7 years of age (SD 19.7), 69% of feminine genre and 4% residents in rural area. Medium of syncope at the moment of tilt table test was 5 (IQR 2-15), with presentation of first episode at 41 years (IQR 21-57), in 52% of the patients triggers were not identified and the clinical manifestations referred in episodes previous to Tilt test were diaphoresis (58%), pallor (55%), dizziness (70%), palpitations (50%) and nausea (42%); during the test dizziness (65%), diaphoresis (19%), nausea (18%) and blurred vision (18%) were reported. A sensitivity of 77.7% was obtained (95% CI 88.8 66.7) and specificity of 40.5% (95% CI 23.3 - 57.7) for the Calgary score.ConclusionsDue to its high sensitivity and easy application, the Calgary score is a useful diagnostic approach instrument for patients with suspected vasovagal syncope and who have a structurally healthy heart, especially in those younger than 50 years

Revising the diversity within the Dwarf Dog-faced Bat, Molossops temminckii (Chiroptera, Molossidae), with the revalidation of the endangered Molossops griseiventer

The genus Molossops includes two monotypic species of insectivore bats distributed in South America: Molossops neglectus and Molossops temminckii. Both can be differentiated, based on sizes, M. temminckii being smaller (forearm less than 33 mm). Despite being monotypic, at least two additional subspecies have been described for M. temminckii, of which M. temminckii griseiventer from the inter-Andean Valley of the Magdalena River in Colombia might represent a valid taxon. To test the taxonomic status of M. t. griseiventer, we reviewed specimens of M. temminckii from cis- and trans-Andean localities in Colombia. We used Cytochrome-b and Cytochrome Oxidase I comparisons to test the phylogenetic position of cis- and trans-Andean samples and compared qualitative morphology, morphometric and bioacoustics. Our results show that M. t. griseiventer is differentiated from cis-Andean specimens, providing further evidence of its validity at the species level. Furthermore, M. temminckii (sensu stricto) is also distributed in Colombia, but both M. griseiventer and M. temminckii are allopatric, with the Andes acting as a barrier. The specific identity of the specimens from the Caribbean Region of Colombia needs a new evaluation, but our results clearly show that the diversity of Molossops is underestimated

Estacionalidad en la efectividad de la metodología de aula invertida en un curso de ciencia de materiales

Actualmente existen en México más de 900 programas educativos de ingeniería acreditados nacionalmente y un número creciente de instituciones están evolucionando hacia estándares globales y buscando el reconocimiento internacional, al tiempo que se evoluciona de modelos basados en contenidos a los basados en competencias. Estos avances van aparejado por esfuerzos por incorporar metodologías vanguardistas en la enseñanza de la ingeniería, que sin embargo parece ser todavía esencialmente tradicionalista

Strings in bubbling geometries and dual Wilson loop correlators

We consider a fundamental string in a bubbling geometry of arbitrary genus dual to a half-supersymmetric Wilson loop in a general large representation R of the SU(N) gauge group in N= 4 Supersymmetric Yang-Mills. We demonstrate, under some mild conditions, that the minimum value of the string classical action for a bubbling geometry of arbitrary genus precisely matches the correlator of a Wilson loop in the fundamental representation and one in a general large representation. We work out the case in which the large representation is given by a rectangular Young tableau, corresponding to a genus one bubbling geometry, explicitly. We also present explicit results in the field theory for a correlator of two Wilson loops: a large one in an arbitrary representation and a “small” one in the fundamental, totally symmetric or totally antisymmetric representation.Instituto de Física La Plat

Efectividad de la metodología de aula invertida en un curso de álgebra para ingenieros

En el presente trabajo se discute un análisis comparativo en la implementación de la metodología tradicional y de aula invertida para la enseñanza de un curso de Algebra para Ingeniería a estudiantes de primer año de la Facultad de Ingeniería Mecánica y Eléctrica de la Universidad Autónoma de Nuevo León (FIME- UANL). Se consideraron dos grupos de la misma asignatura durante el semestre Enero- Junio 2015. El grupo 1(G1) con 29 estudiantes fue elegido para la metodología de aula inversa, la cual fue bien aceptada. Se identificaron y determinaron algunos factores como la dependencia al profesor, disciplina de trabajo en casa, bajo nivel de conocimientos previos, la carga de cursos de ciencias exactas en primer año y el proceso de adaptación, entre otros. En el grupo 2(G2) con 43 estudiantes, el mismo curso se impartió de manera tradicional, tomando en cuenta que un sondeo inicial, reveló una actitud de escasa aceptación de nuevas metodologías correlacionada con el horario del curso (14h30). El desempeño académico en ambos grupos fue notablemente distinto, el G1 obtuvo un aprovechamiento mayor en trece puntos porcentuales con respecto al grupo G2, que resultó estadísticamente significativo. Nuestros resultados coinciden cualitativamente con estudios internacionales previos y corroboran además que la metodología de aula invertida promueve un mayor interés y participación que la metodología tradicional, aunque no parece aconsejable en todas las circunstancias. El estudio nos permitió reflexionar sobre la importancia de explorar e implementar nuevas metodologías que permitan desarrollar en el estudiante de ingeniería el perfil analítico necesario para el desempeño de su profesión