TLA+ Proofs

TLA+ is a specification language based on standard set theory and temporal logic that has constructs for hierarchical proofs. We describe how to write TLA+ proofs and check them with TLAPS, the TLA+ Proof System. We use Peterson's mutual exclusion algorithm as a simple example to describe the features of TLAPS and show how it and the Toolbox (an IDE for TLA+) help users to manage large, complex proofs.Comment: A shorter version of this article appeared in the proceedings of the conference Formal Methods 2012 (FM 2012, Paris, France, Springer LNCS 7436, pp. 147-154

Molecular Basis For H3.3/h4 Deposition By The Hira Histone Chaperone Complex

The HIRA histone chaperone complex is composed of the proteins HIRA, UBN1, and CABIN1 that cooperate with ASF1a to specifically mediate deposition of H3.3/H4 into chromatin. While many of the protein/protein contacts that allow for assembly of this multi-protein histone chaperone complex have been elucidated, how these proteins are able to cooperate to specifically bind and deposit H3.3/H4 over H3.1/H4, which differ by only 5 amino acids, has remained unclear. Here we demonstrate the HIRA complex subunit UBN1 specifically binds to H3.3/H4 over H3.1/H4 using a combination of biochemical and structural studies. We show H3.3-specific binding is mediated by highly conserved residues in the UBN1 Hpc2-related domain (HRD) and residue G90 in H3.3. Interestingly the UBN1 HRD and another H3.3-specific histone chaperone, Daxx, bind to H3.3/H4 in the region of G90 with striking similarity. Using sequence conservation and secondary structure prediction we have identified the UBN1 middle domain. We show the middle domain is able to form monomer and dimer populations as well as bind to H3/H4 through interaction with the N-terminal histone tails. We have additionally discovered that a loop region linking the UBN1 HRD and middle domains binds non-specifically to DNA with nanomolar affinity, although UBN1 fragments containing the HRD, DNA binding loop, and middle domain are unable to bind assembled nucleosomes. Finally we demonstrate with analytical ultracentrifugation that the HIRA C-terminal domain forms a stable trimer and interacts with CABIN1 in a HIRA(3)/CABIN1(2) stoichiometry. We show that the HIRA C-terminal domain is organized into separate strand and helical regions that must be linked for trimer formation. Further we show that a replisome protein called Ctf4 is structurally related to HIRA, as it also arranges into a trimer composed of separate strand and helical regions and interacts in a 3:2 stoichiometry with binding partners. From these observations we propose a model for H3.3/H4 deposition by the HIRA complex involving DNA binding and dimer formation by UBN1 to mediate (H3.3/H4)2 tetramer formation organized on a HIRA(3)/UBN1(3)/CABIN1(2) complex where the third UBN1 molecule may harbor ASF1a/H3.3/H4 in reserve

Análisis de la demanda y oferta de carne de pollo utilizando ecuaciones simultaneas mediante mínimos cuadrados en dos etapas

Abstract Chicken meat production is one of the fastest growing industries in Colombia with an average per person consumption of 35.6 kg. Due to the increase in demand and to the growing importance of the chicken meat production to the Colombian economy the objective of the study was to estimate the demand and supply response and the short run elasticities for chicken meat using a two-stage least squares technique for simultaneous equations. Results indicated that chicken meat demand was responsive to changes in own and beef prices as well as income. The direction of the independent variables were as expected, with the exception of pork prices. The response of chicken meat supply to own-price changes was found to be inelastic in the short run. Chicken feed and the exchange rate elasticities did not present a great impact on the percentage changes of the quantity offered of chicken meat. The proposed model can be useful for producers, chicken meat companies managers and policymakers as understanding the factors that affect the chicken market can lead to optimal managerial and financial decisionsLa producción de carne de pollo es una de las industrias de más rápido crecimiento en Colombia con un consumo promedio por persona de 35.6 kg. Debido al aumento de la demanda y la creciente importancia de la producción de carne de pollo para la economía colombiana, el objetivo del estudio fue estimar la respuesta de la demanda y la oferta y las elasticidades a corto plazo utilizando el modelo de ecuaciones simultaneas mediante mínimos cuadrados en dos etapas. Los resultados indicaron que la demanda de carne de pollo respondía a los cambios en los precios propios y de la carne, así como a los ingresos. La dirección de las variables independientes fue la esperada, con la excepción de los precios del cerdo. Se encontró que la respuesta de la oferta de carne de pollo a los cambios en su precio era inelástica a corto plazo. Alimentos para pollo y las elasticidades del tipo de cambio no presentaron un gran impacto en los cambios porcentuales de la cantidad ofrecida de carne de pollo. El modelo propuesto puede ser útil para productores, gerentes de empresas de carne de pollo y formuladores de políticas, ya que comprender los factores que afectan el mercado del pollo puede conducir a decisiones administrativas y financieras óptimas

Análisis de regresión de los factores que afectan la rentabilidad económica de la producción de curuba

Banana passion fruit production in Colombia contributes to the development of the country’s economy as it generates income and provides raw material for the agro-based industries. Profitability is a key aspect of economic efficiency and plays an important role in farmer´s decision-making therefore; the purpose of the study was to determine the different factors affecting the economic profitability of banana passion fruit production. A descriptive, quantitative, correlational and non-experimental design was selected and a regression analysis was performed. Results showed that the stationarity, normality, homoscedasticity and non-autocorrelation assumptions were not violated; all estimated coefficients were statistically significant and consistent with hypothesized sign. As such, the independent variables contributed to explain individually banana passion fruit economic profitability.La producción de curuba en Colombia contribuye al desarrollo de la economía del país una vez que genera ingresos y proporciona materia prima para las industrias agrícolas. La rentabilidad es un aspecto clave de la eficiencia económica y juega un papel importante en la toma de decisiones de los agricultores, por lo tanto, el propósito del estudio fue determinar los factores que afectan la rentabilidad económica de la producción de curuba. Se seleccionó un diseño descriptivo, cuantitativo, correlacional no experimental para describir las relaciones entre las variables y se realizó un análisis de regresión. Los resultados mostraron que no se violaron los supuestos de linealidad, normalidad, homocedasticidad y no autocorrelación; todos los coeficientes estimados fueron estadísticamente significativos y consistentes con el signo esperado. En este sentido, las variables seleccionadas contribuyeron a explicar individualmente la rentabilidad económica de curuba

Spatial analysis of ecosystem service relationships to improve targeting of payments for hydrological services

Payment for hydrological services (PHS) are popular tools for conserving ecosystems and their water-related services. However, improving the spatial targeting and impacts of PHS, as well as their ability to foster synergies with other ecosystem services (ES), remain challenging. We aimed at using spatial analyses to evaluate the targeting performance of Mexico\u27s National PHS program in central Veracruz. We quantified the effectiveness of areas targeted for PHS in actually covering areas of high HS provision and social priority during 2003-2013. First, we quantified provisioning and spatial distributions of two target (water yield and soil retention), and one non-target ES (carbon storage) using InVEST. Subsequently, pairwise relationships among ES were quantified by using spatial correlation and overlap analyses. Finally, we evaluated targeting by: (i) prioritizing areas of individual and overlapping ES; (ii) quantifying spatial co-occurrences of these priority areas with those targeted by PHS; (iii) evaluating the extent to which PHS directly contribute to HS delivery; and (iv), testing if PHS targeted areas disproportionately covered areas with high ecological and social priority. We found that modelled priority areas exhibited non-random distributions and distinct spatial patterns. Our results show significant pairwise correlations between all ES suggesting synergistic relationships. However, our analysis showed a significantly lower overlap than expected and thus significant mismatches between PHS targeted areas and all types of priority areas. These findings suggest that the targeting of areas with high HS provisioning and social priority by Mexico\u27s PHS program could be improved significantly. This study underscores: (1) the importance of using maps of HS provisioning as main targeting criteria in PHS design to channel payments towards areas that require future conservation, and (2) the need for future research that helps balance ecological and socioeconomic targeting criteria

Un modelo Box Jenkins ARIMA para modelar y pronosticar la producción de mora de castilla en Colombia

Blackberry production in Colombia contributes to the nation´s gross domestic profit, employment and farmers’ social well-being. It is considered of great economic importance as blackberry fruits are used as raw material for the agroindustry. In this manner, production instability affects farmers’ economic profitability; therefore, forecasting plays an important role in monitoring production as well as in farmers´ planting decision and resource allocation. Hence, the purpose of the study was to model and forecast blackberry production in Colombia using a Box Jenkins ARIMA approach for the period 1992-2023. A quantitative, non-experimental, correlational and descriptive research design was selected. The appropriateness of the model and its predictive capacity was assessed by verifying the different goodness-of-fit criteria. Results showed that the ARIMA (1,1,0) was the most suitable model as it captured the behavior of the actual time series. Based on the forecasted values it is expected a 5.47% increase in blackberry production for the period 2021-2023 which will consequently improve farmers´ income and thus contribute to the reduction in poverty.La producción de mora de castilla en Colombia contribuye al producto interno bruto, al empleo y al bienestar social de los agricultores del país. Es considerado de gran importancia económica una vez que los frutos de la mora son utilizados como materia prima para la agroindustria. De esta manera, la inestabilidad de la producción afecta la rentabilidad económica de los agricultores; por lo tanto, el pronóstico de la producción de mora posee un importante papel en la asignación de recursos y la toma de decisiones de los agricultores. Por lo tanto, el propósito del estudio fue modelar y pronosticar la producción de mora en Colombia utilizando un enfoque ARIMA de Box Jenkins para el período 1992-2023. Se seleccionó una investigación tipo cuantitativa, no experimental, correlacional y descriptiva. Se evaluó la adecuación del modelo y su capacidad predictiva mediante la verificación de los diferentes criterios de bondad de ajuste. Los resultados mostraron que ARIMA (1,1,0) fue el modelo más adecuado una vez que capturó el comportamiento de la serie temporal actual. Con base en los valores pronosticados se espera un aumento de 5,47% en la producción de mora para el período 2021-2023 lo que mejorará los ingresos de los agricultores y contribuirá, así a la reducción de la pobreza en el campo