Comparación de tres frecuencias de remoción de frutos enfermos en el control de Monilia roreri Cif. y Par.

Se estudió el efecto de varias frecuencias de remoción de frutos enfermos en la incidencia de Monilia y en los rendimientos de cadao en grano. El ensayo se realizó en una plantación de cacao de híbrido ICS 6 x SCA 6 de 4 años de edad, localizada en la Estación Experimental Tulenapa, en Chigorodó (Antioquia). Los tratamientos comparados fueron 3, a saber: recolección de frutos enfermos una vez por semana, recolección de frutos enfermos dos veces por semana y recolección de frutos enfermos una vez al mes. Los resultados indican que las frecuencias de remoción de material enfermo una y dos veces por semana ejercen un control satisfactorio de la enfermedad. La remoción de frutos una vez por semana, determina un incremento de la producción de cacao en grano de orden de 398 k sobre el tratamientos de remoción de frutos enfermos una vez al mes. En los 4 meses posteriores al período seco se registraron las más bajas incidencias de Monilia y no hubo diferecia entre los tratamientos. Este resultado se atribuye al efecto represivo del verano sobre la enfermedad

Characterization of oral yeasts isolated from healthy individuals attended in different Colombian dental clinics

The aim of this study was to identify the most frequent yeasts in the oral cavity of adult individuals without immune disorders and to associate the presence of these oral yeasts with different characteristics of each individual. Oral rinse samples were obtained from 96 healthy adults and cultured in Sabouraud dextrose agar media and CHROMagar. Yeasts were identified by sequencing the D1/D2 region of the 28S rRNA gene. Probable association among the socio-demographic characteristics, body mass index, family and personal medical history, oral hygiene, tobacco and/or alcohol consumption habits and presence of oral fungi was analyzed. Contingency tables and logistic regression were employed to evaluate possible relationships between the presence of oral fungi and mixed colonization with these variables. 57.3% of the healthy individuals had oral yeasts and 21.8% had mixed colonization. The most prevalent yeasts were Candida albicans (52%), C. parapsilosis (17.9%), and C. dubliniensis (7.57%). Yeasts with most frequently mixed colonization were C. albicans and C. parapsilosis. No relationships were found among the variables analyzed. However, the presence of mixed colonization was related to the presence of dental prostheses (P less than 0.006), dental apparatuses (P=0.016) and O'Leary index (P=0.012). This is the first study that characterized oral yeasts in Colombian healthy individuals, determined the most prevalent oral yeasts C. albicans, C. parapsilosis and C. dublinensis and an association of mixed colonization with the use of dental prostheses and aparatology and poor hygiene. © 2019 by the Journal of Biomedical Research

Computing arbitrage upper bounds on basket options in the presence of bid–ask spreads

We study the problem of computing the sharpest static-arbitrage upper bound on the price of a European basket option, given the bid–ask prices of vanilla call options in the underlying securities. We show that this semi-infinite problem can be recast as a linear program whose size is linear in the input data size. These developments advance previous related results, and enhance the practical value of static-arbitrage bounds as a pricing technique by taking into account the presence of bid–ask spreads. We illustrate our results by computing upper bounds on the price of a DJX basket option. The MATLAB code used to compute these bounds is available online at www.andrew.cmu.edu/user/jfp/arbitragebounds.html

Completely positive reformulations for polynomial optimization

Polynomial optimization encompasses a very rich class of problems in which both the objective and constraints can be written in terms of polynomials on the decision variables. There is a well established body of research on quadratic polynomial optimization problems based on reformulations of the original problem as a conic program over the cone of completely positive matrices, or its conic dual, the cone of copositive matrices. As a result of this reformulation approach, novel solution schemes for quadratic polynomial optimization problems have been designed by drawing on conic programming tools, and the extensively studied cones of completely positive and of copositive matrices. In particular, this approach has been applied to solve key combinatorial optimization problems. Along this line of research, we consider polynomial optimization problems that are not necessarily quadratic. For this purpose, we use a natural extension of the cone of completely positive matrices; namely, the cone of completely positive tensors. We provide a general characterization of the class of polynomial optimization problems that can be formulated as a conic program over the cone of completely positive tensors. As a consequence of this characterization, it follows that recent related results for quadratic problems can be further strengthened and generalized to higher order polynomial optimization problems. Also, we show that the conditions underlying the characterization are conceptually the same, regardless of the degree of the polynomials defining the problem. To illustrate our results, we discuss in further detail special and relevant instances of polynomial optimization problems

Computing general static-arbitrage bounds for European basket options via Dantzig-Wolfe decomposition

We study the problem of computing general static-arbitrage bounds for European basket options; that is, computing bounds on the price of a basket option, given the only assumption of absence of arbitrage, and information about prices of other European basket options on the same underlying assets and with the same maturity. In particular, we provide a simple efficient way to compute this type of bounds by solving a large finite non-linear programming formulation of the problem. This is done via a suitable Dantzig-Wolfe decomposition that takes advantage of an integer programming formulation of the corresponding subproblems. Our computation method equally applies to both upper and lower arbitrage bounds, and provides a solution method for general instances of the problem. This constitutes a substantial contribution to the related literature, in which upper and lower bound problems need to be treated differently, and which provides efficient ways to solve particular static-arbitrage bounds for European basket options; namely, when the option prices information used to compute the bounds is limited to vanilla and/or forward options, or when the number of underlying assets is limited to two assets. Also, our computation method allows the inclusion of real-world characteristics of option prices into the arbitrage bounds problem, such as the presence of bid-ask spreads. We illustrate our results by computing upper and lower arbitrage bounds on gasoline/heating oil crack spread options

Glossary of fault and other fracture networks

Increased interest in the two- and three-dimensional geometries and development of faults and other types of fractures in rock has led to an increasingly bewildering terminology. Here we give definitions for the geometric, topological, kinematic and mechanical relationships between geological faults and other types of fractures, focussing on how they relate to form networks

Interacting faults

The way that faults interact with each other controls fault geometries, displacements and strains. Faults rarely occur individually but as sets or networks, with the arrangement of these faults producing a variety of different fault interactions. Fault interactions are characterised in terms of the following: 1) Geometry – the spatial arrangement of the faults. Interacting faults may or may not be geometrically linked (i.e. physically connected), when fault planes share an intersection line. 2) Kinematics – the displacement distributions of the interacting faults and whether the displacement directions are parallel, perpendicular or oblique to the intersection line. Interacting faults may or may not be kinematically linked, where the displacements, stresses and strains of one fault influences those of the other. 3) Displacement and strain in the interaction zone – whether the faults have the same or opposite displacement directions, and if extension or contraction dominates in the acute bisector between the faults. 4) Chronology – the relative ages of the faults. This characterisation scheme is used to suggest a classification for interacting faults. Different types of interaction are illustrated using metre-scale faults from the Mesozoic rocks of Somerset and examples from the literature