Comments on Correlation Functions of Large Spin Operators and Null Polygonal Wilson Loops

We discuss the relation between correlation functions of twist-two large spin operators and expectation values of Wilson loops along light-like trajectories. After presenting some heuristic field theoretical arguments suggesting this relation, we compute the divergent part of the correlator in the limit of large 't Hooft coupling and large spins, using a semi-classical worldsheet which asymptotically looks like a GKP rotating string. We show this diverges as expected from the expectation value of a null Wilson loop, namely, as $(\ln{\mu^{-2}})^ 2$, $\mu$ being a cut-off of the theory.Comment: 16+3 pages, 3 figures. Computation in section 4.1 has been clarified. Some comments on the vertex contributions has been added in section 4.2. Some other minor corrections. Version to appear in Nucl. Phys.

Worldsheet four-point functions in AdS(3)/CFT(2)

We calculate some extremal and non-extremal four-point functions on the sphere of certain chiral primary operators for strings on AdS_3 x S^3 x T^4. The computation is done for small values of the spacetime cross-ratio where global SL(2) and SU(2) descendants may be neglected in the intermediate channel. Ignoring also current algebra descendants, we find that in the non-extremal case the integrated worldsheet correlators factorize into spacetime three-point functions, which is non-trivial due to the integration over the moduli space. We then restrict to the extremal case and compare our results with the four-point correlators recently computed in the dual boundary theory. We also discuss a particular non-extremal correlator involving two chiral and two anti-chiral operators.Comment: 34 pages, subsection on crossing symmetry adde

The logistic map and the birth of period-3 cycle

The goal of this paper is to present a proof that for the logistic map the period-3 begins at . The third-iterate map is the key for understanding the birth of the period-3 cycle. Any point in a period-3 cycle repeats every three iterates by definition. Such points satisfy the condition ,and they are therefore fixed points of the third-iterate map. This fact and the so called tangent bifurcation for the logistic map, as well as the fixed points definition, are used for finding the value. The algebraic treatment utilizes some properties of symmetric polynomials in three variables. For the purposes of this paper, the bifurcation diagram for the logistic map is also presented, as well as a program in Mathematica for its construction

Sustainable Biorefineries: What was Learned from the Design, Analysis and Implementation

Bioeconomies need sustainable technologies and strategies for biomass processing. One of the best ways to do that is to consider biorefineries as a practical way to achieve real developments in the industry for integral production of energy, food, feed and chemicals under an ideal dream of replacing today’s crude-oil and basically using the accessible biomass in the world as much as possible. Additionally, the existent biofuel facilities are constantly adding new processing lines without integral design strategies, and possibly repeating the past design and implementation errors in refineries based on crude-oil. In recent years, more as a fashion or tendency, these processing lines from biofuels industry have been integrated in a system called “biorefinery” and many sectors have supported this idea through policies to incentivize the development of the bio-based economies adopting this concept. The design of biorefineries is presented as a relevant topic due to the multiple processing paths that could be available to obtain a set of desirable products. However, after many scientific efforts in design through well validated methodologies the biorefineries currently are not working properly or are more close to a conventional standalone biomass processing. Some big facilities already implemented today as biorefineries are closed or working just as standalone process (biofuels plant), but not through a promising multiproduct biorefinery configuration for which the resulting design was developed. In this work, 13 biorefineries were analysed including 4 industrial cases that were implemented after specific design and different industrial plants that use different raw materials of renewable origin. To achieve this, different strategic cases were considered: raw materials with inherent logistics restrictions, technical, economic, environmental assessments together with social considerations and finally market restrictions. As a result, and based on different case studies (where these process engineering strategies where applied through conceptual design using Aspen Plus and Potential Environmental Impacts) the positive and negative lessons are discussed in detail. The main result is an overall learning from different cases of study for future design, analysis and implementation of new biorefineries with a real sustainability and avoiding a repetition of the same evolution that risky and controversial crude-oil refineries had

¿Contribuyen los talleres en el Museo de Ciencias a fomentar actitudes hacia la conservación del ambiente?

Esta investigación se centró en evaluar el impacto de seis talleres sobre la adopción de actitudes deseables respecto a la conservación del ambiente y la sostenibilidad, por parte de distintos públicos visitantes de un Museo Interactivo. La metodología incluyó: a) el diseño de escalas con cuatro opciones de respuesta que se aplicaron antes y después del taller b) entrevistas telefónicas o visita a instituciones educativas, dos meses después de la visita al Museo. El análisis cuantitativo mostró que las actitudes de los participantes mejoraron en todos los talleres aunque no siempre fue estadísticamente significativo. El análisis cualitativo reveló que los participantes mostraron actitudes de compromiso y cuidado hacia el ambiente. Algunas estuvieron asociadas a los talleres y otras a actitudes desarrolladas con anterioridad al taller.This research focused on assessing the impact of six workshops on the adoption of desirable attitudes about environmental conservation and sustainability, of different group visitors of an interactive museum. The methodology included: a) the design of four-option scales that were applied before and after the workshop b) either telephone interviews or visits to schools, two months after the visit to the museum. The quantitative analysis showed that the attitudes of the participants improved in all the workshops but not all of them were statistically significant. The qualitative analysis revealed that participants demonstrated attitudes of commitment and care towards the environment. Some of these attitudes were associated with the workshops and other associated with attitudes developed prior to the workshop

A meta‐analysis of published studies of endothelial dysfunction does not support its routine clinical use

Summary Background Endothelial dysfunction is a marker of future cardiovascular disease (CVD) risk, yet epidemiological studies have yielded inconsistent results. We therefore studied the association between endothelial dysfunction and CVD under diverse circumstances. Methods and results Literature-based meta-analysis of prospective observational studies with ≥ 12 months of follow-up published in Medline and having information on endothelial function and CVD outcomes. Tabular data on participant characteristics, endothelial function assessments and incident CVD outcomes were abstracted from individual studies. Random-effects meta-analysis was used to quantify pooled associations, and I2 statistic to evaluate between-study heterogeneity. Potential sources of heterogeneity were explored by subgroup analyses and meta-regression. Thirty five studies involving 17,206 participants met the inclusion criteria. During more than 80,000 person-years of observation, up to 2755 CVD events were accrued, yielding a pooled relative risk (RR) of 1.25 (95% confidence interval 1.15–1.35) for CVD comparing top (i.e. more severe) vs. bottom (less severe) third of endothelial dysfunction. There was significant between-study heterogeneity and evidence of publication bias. RRs varied importantly according to the method used to ascertain endothelial function, and were higher among older individuals and among participants with risk factors for CVD or established CVD at baseline. Conclusions Although endothelial dysfunction is an important determinant of cardiovascular outcomes in people with pre-existing CVD, current evidence base does not support its use as a potentially useful measurement for risk stratification in people at lower risk of CVD

Costos derivados del uso de la maquinaria agrícola en la zona algodonera del Valle Del Rio Ariguaní

El objeto del presente estudio se encuentra localizada en la zona conformada por los municipios de Bellavista, si Dios Quiere, Riomar, Algarrobo, en el Departamento del Magdalena y Caracolicito en el Departamento del Cesar; situado al noroeste de Colombia, zona algodonera ocupa el valle geográfico del río Ariguaní con un total de 100.072 hectáreas, de las cuales 24.287 están dedicadas al algodonero, que es el único cultivo agrícola en el área de estudio, equivalente al 85% de las tierras agrícolas. Las siguientes son algunas de las características del área: la altura sobre el nivel del mar varía entre 30 y 80 mts. aproximadamente, con precipitaci6n anual promedio que oscila entre 1.000 y 1. 400 milímetros, con temperatura promedia anual de 28' C. Se tomaron un total de 24 fincas algodoneras (7.217 hectáreas) de las 232 existentes. Se estratificaron luego, para obtener una mejor información, la cual fue recopilada por medio de encuestas debidamente probadas y corregidas en la región. Los objetivos básicos de la investigación fueron los costos derivados del uso de la maquinaria agrícola, con un análisis pormenorizado de ellos, y haciendo referencia a los factores de más incidencia. 72 Se logró determinar que el costo promedio general para el área estudiada fue de $73.862 pesos por finca y de$1.575,8 pesos como promedio general por hectárea. En la mayor parte de las fincas, los costos variables fueron superiores a los costos fijos. En la composición de los primeros, las reparaciones y el mantenimiento constituyeron las mayores erogaciones. Esta particularidad reflejó la obsolencia del equipo agrícola, debido más que todo, a las dificultades de su reposición, consecución de repuestos y reparaciones oportunas entre otras causas. La zona presente un promedio bajo de unidades de tracción mecanizada, ya que el caballaje promedio por tractor fue de 69 H. P. La región objeto de este estudio presenta limitaciones en el manejo de las explotaciones y un deficiente criterio técnico en la escogencia, operación y mantenimiento de la maquinaria agrícola

9-[(E)-2-phenylethenyl]anthracene and 9-[(E)-2-(naphthalen-2-yl)ethenyl]anthracene as traps for singlet oxygen: photosensitized oxidation and photodynamic effect on Leishmania tarentolae parasites

Introducción: El oxígeno singulete es una especie reactiva que se obtiene mediante t r a n s f e r e n c i a e n e r g é t i c a u s a n d o u n fotosensibilizador. Su cuantificación directa requiere de instrumentación costosa, por lo cual es necesario recurrir a métodos indirectos que tengan suficiente selectividad y bajo costo. Estos procedimientos se basan en la interceptación química del oxígeno singulete produciendo una especie que se pueda detectar por métodos analíticos convencionales. En este artículo se describe la utilización del 9-[(E)-2-feniletenil] antraceno 1 (PEA) y del 9-[(E)-2-(naftalen-2-il) etenil]antraceno 2 (NEA), como alternativas viables y económicas para la cuantificación indirecta del oxígeno singulete, en medios acuosos. Su ventaja radica en la fácil detección de la desactivación de su fluorescencia una vez son oxidados por el oxígeno singulete. Materiales y Métodos: Los compuestos se sintetizaron y caracterizaron siguiendo procedimientos previamente reportados. Su capacidad para atrapar oxígeno singulete se determinó siguiendo su oxidación fotosensibilizada en solución de H2O/THF y en parásitos de Leishmania tarentolae, empleando azul de metileno o rosa bengala como fotosensibilizadores. Las muestras experimentales se iluminaron con una lámpara de emisión de luz visible, y se utilizaron métodos espectroscópicos (absorción UV-Vis, fluorescencia, RMN-1H) y espectrometría de masas para monitorear el atrapamiento y fotooxidación. Resultados y Discusión: Las pruebas espectroscópicas demostraron la capacidad que tienen los compuestos PEA 1 y NEA 2 para atrapar oxígeno singulete en solución acuosa y dentro de parásitos de L. tarentolae. Estudios de viabilidad parasitaria demuestran que PEA 1 es citotóxico en la oscuridad y cuando los cultivos son expuestos a la luz, mientras que NEA 2 no es citotóxico en la oscuridad, pero sí lo es cuando el cultivo es expuesto a la luz. En conclusión, los compuestos estudiados pueden servir como sondas para detectar y medir la producción de oxígeno singulete en medio acuoso y potencialmente en cultivos celulares, aunque es recomendable evaluar su actividad citotóxica en la oscuridad y bajo iluminación en estos casos.Introduction: Singlet oxygen is a reactive species obtained via energy transfer using a photosensitizer. Its direct quantification requires expensive instrumentation, so it is necessary to use indirect methods having sufficient selectivity and low cost. These procedures are based on the chemical interception of singlet oxygen producing a species that can be detected using conventional analytical methods. This article describes the utilization of 9-[(E)-2- phenylethenyl]anthracene 1 (PEA) and 9-[(E)-2- (naphtalen-2-yl)ethenyl]anthracene 2 (NEA) as suitable and economic alternatives for the indirect quantification of singlet oxygen in aqueous media. Their advantage is the easy detection of their fluorescence once they are oxidized by singlet oxygen. Materials and Methods: Compounds were synthesized and characterized following procedures previously reported. Their capacity to trap singlet oxygen was determined by monitoring their photosensitized oxidation in either a H2 O/THF solution or within Leishmania tarentolae parasites, utilizing methylene blue or rose bengal as photosensitizers. Experimental samples were illuminated with a lamp emitting visible light, while spectroscopical techniques (absorption, fluorescence, 1 H-NMR) and mass spectrometry were used to monitor trapping and photooxidation. Results and Discussion: Spectroscopical evidence demonstrates that both PEA 1 and NEA 2 are capable of trapping singlet oxygen in both aqueous media and within L. tarentolae parasites. Viability studies demonstrate that PEA 1 is cytotoxic in the dark and when parasite cultures were exposed to light, while NEA 2 does not show dark cytotoxicity, but is toxic when cultures were exposed to light. It can be concluded that both compounds under study may be utilized as probes to detect and quantify the production of singlet oxygen in aqueous media and potentially in cell cultures, although it is recommended to evaluate their cytotoxic activity both in the dark and upon light exposure in these cases

El enclavamiento encerrojado de Grosse-Kempf en el tratamiento de las fracturas diafisarias del fémur

Se presentan 50 fracturas diafisarias de fémur tratadas mediante enclavamiento endomedular encerrojado de Grosse-Kempf. Realizamos un estudio retrospectivo utilizando para la valoración del resultado la escala de Thorensen, que considera la existencia de callos viciosos radiológicos, la flexión de rodilla, la dismetría y la presencia de dolor e inflamación. El resultado a los 20 meses del tratamiento (12-27) es excelente en 32 casos, bueno en 13, regular en 4 y malo en 1. Creemos que este método de enclavamiento constituye un buen procedimiento para el tratamiento de este tipo de fracturas, especialmente de las fracturas conminutas de las zonas 2, 3, 4 y 5 de Wiss. La mayoría de los resultados regulares y malos son debidos a fallos en la técnica quirúrgica.We present 50 femoral shaft fractures treated by Grosse-Kempf intramedullary nailing. A retrospective study was performed by using the Thorensen scale for the evaluation of results. This scale takes into account different parameters such as radiological malposition, range of motion of the knee, shortening of the femur, pain, and swelling. Twenty months after treatment (range: 12-27), the results were excellent in 32 cases, good in 13, fair in 4 and poor in one. Grosse-Kempf nailing seems to be a good method for treating this type of fractures, particularly in conminuted fractures localized in the 2, 3, 4 and 5 Wiss's zones. The majority of fair and poor results are caused by errors in the surgical technique