Assessment of linear anionic polyacrylamide application to irrigation canals for seepage control

South- central area of Chile area has a Mediterranean climate and high crop water requirements. Irrigation water is distributed through long channels which have low water conveyance efficiency (Ec), difficult to improve by conventional techniques. The objective of this study was to quantify Ec and to evaluate the use of Linear Anionic Polyacrylamide (LA-PAM) to reduce seepage losses. The study was carried out in south-central area of Chile, (UTM Coordinate N 5745000; E 725000 m, datum is WGS-84, zone 18S) in 250 km of channels whose flow varied between 0.12 and 24.6 m3 s–1. Water users indicated channel reaches with potential low Ec, which were selected for LA-PAM application. In 11 reaches between 0.51 and 3 km in length, 1 to 3 LAPAM applications were performed at rates of 10 kg ha–1, considering the wet perimeter area as basis of calculation. Thirty-one LA-PAM applications were performed over a 30.5 km length. Most of the channels were large enough to allow motorboat moving against the current to carry-out LA-PAM application. Water flow was measured (StreamPro ADCP) at both ends of selected reaches before and after granular LAPAM application. Weekly measurements were made to quantify treatment effect duration. Water turbidity and temperature were measured. Channels showed variable Ec from 87% to 94%. Two reaches showed 6% water gains. In more than 80% cases LA-PAM effect was positive, achieving loss reductions of 15 to 760 L s–1. In other cases LA-PAM had a negative effect since it mainly affected water entry into the channel. It was determined that field conditions referred by users as indicators of Ec are not always correct and vary in time according to climatic conditions. Ec was estimated and it was possible to reduce seepage through LA-PAM applications. This allow increasing irrigation security in critical periods, especially under drought conditions

Effect of Uropathogenic <i>Escherichia coli</i> on Human Sperm Function and Male Fertility

Infections of the reproductive tract represent nearly 15% of male infertility cases. The most frequently isolated bacterium in the ejaculate of infertile men is Escherichia coli (E. coli), which causes between 60 and 85% of cases of chronic bacterial prostatitis leading to sperm damage. The aim of this chapter is to discuss the negative effects of E. coli on sperm quality and male fertility. The E. coli isolated from semen is uropathogenic (UPEC) and can damage sperm in different ways. UPEC induces activation of polymorphonuclear leukocytes with the release of cytokines and reactive oxygen species, the latter being harmful due to their ability to induce lipid peroxidation and early sperm capacitation. Also, UPEC decreases sperm motility, vitality and mitochondrial membrane potential through direct contact or mediated by its soluble metabolites. The negative effects are higher with strains with specific characteristics such as hemolytic capacity. In vivo studies with mice models have shown that UPEC inoculated into the epididymis induces inflammatory damage with testicular mass decrease and low sperm concentration. Future studies are needed to clarify the molecular mechanisms by which E. coli damages sperm. This knowledge will make it possible to take measures to avoid deleterious consequences on the fertilizing potential of men

CLÁUSULAS ABUSIVAS EN LA CONTRATACIÓN AGRÍCOLA. ALTERNATIVAS DE CONTROL EN EL DERECHO CHILENO

El trabajo analiza la problemática de las cláusulas abusivas presentes en la contratación agrícola, en particular, aquellas que son impuestas al productor agrícola por sus compradores. Luego de examinar los factores que influyen en la posición de desventaja que afecta, generalmente, al productor agrícola en la cadena agroalimentaria, se exponen las inicitivas que a nivel europeo han tratado el problema, para posteriormente analizar si el derecho positivo chileno ofrece alternativas para el control de estas cláusulas

Empresa de servicios transitorios y suministro de trabajadores. Analisis comparado entre el sistema chileno y el espanol

76 p.El día 16 de octubre de 2006, se publicó la Ley Nº 20.123 que regula el trabajo en régimen de subcontratación y suministro de trabajadores. Esta Ley altera las reglas generales del Derecho del Trabajo al considerar empleador a la empresa de servicios transitorios. Asimismo, identifica los sujetos intervinientes, las relaciones jurídicas que nacen entre ellos, y por último, establece un régimen de responsabilidad tanto de la empresa de servicios transitorios como de la empresa usuaria Es por ello, que fue necesario realizar un análisis comparativo de los principales aspectos de la reciente regulación del suministro de trabajadores, a la luz de la misma regulación en el Derecho Español contenida en la Ley 14/1994. La investigación realizada permite constatar la gran similitud que posee nuestra regulación respecto de su par española, en cuanto a defectos y virtudes. Asimismo, permite realizar un análisis crítico a nuestra primitiva, pero positiva ley

Reconstrucción tridimensional de rostros a partir de imágenes de rango por medio de funciones de base radial de soporte compacto tri-dimensional

En este trabajo se muestra la utilización de funciones de base radial de soporte compacto para la reconstrucción tridimensional de rostros. En trabajos anteriores se habían explorado diferentes técnicas y diferentes funciones de base radial para reconstrucción de superficies; ahora presentamos los algoritmos y los resultados de la utilización de funciones de base radial de soporte compacto las cuales presentan ventajas comparativas en términos del tiempo de construcción de un interpolante para la reconstrucción. Se presentan comparaciones con técnicas ampliamente utilizadas en este campo y se detalla el proceso global de reconstrucción de superficies

Rewording theoretical predictions at colliders with vacuum amplitudes

We propose multiloop vacuum amplitudes as the optimal building blocks for efficiently assembling theoretical predictions at high-energy colliders. This hypothesis is strongly supported by the manifestly causal properties of the loop-tree duality (LTD) representation of a vacuum amplitude. The vacuum amplitude, acting as a kernel, encodes all the final states contributing to a given scattering or decay process through residues in the on-shell energies of the internal propagators. It also naturally implements gauge invariance and the wave function renormalisation of the external legs. This methodological approach, dubbed LTD causal unitary, leads to a novel representation of differential cross sections and decay rates that is locally free of ultraviolet and infrared singularities at all orders in perturbation theory. Unitary threshold singularities also match between different phase-space residues. Most notably, it allows us to conjecture for the first time the local functional form of initial-state collinear singularities. The fulfillment of all these properties provides a theoretical description of differential observables at colliders that is well defined in the four physical dimensions of the space-time.Comment: 8 pages, 3 figure

Contractual formalities in modern contracting. No oral modification clauses and the doctrine of venire contra factum proprium as a limit to its enforceability

Although the principle of consensualism is still the general rule in modern contracting, it is common, especially in complex and long-term commercial contracts, to include clauses limiting the parties’ freedom to modify or terminate them, unless certain formalities are observed. In this context, this paper analyses the so-called “no oral modification” clauses, putting forward the arguments for accepting their enforceability, as well as their limits, by means of the application of the doctrine of venire contra factum proprium.Si bien el principio del consensualismo sigue rigiendo como regla general en la contratación moderna, es habitual que se incluyan, especialmente en contratos comerciales complejos y de larga duración, cláusulas que limiten la libertad de las partes para modificarlos o terminarlos, a menos que se observen ciertas formalidades. En este contexto, el presente trabajo analiza las denominadas “cláusulas de no modificación oral”, planteando los argumentos para aceptar su exigibilidad, como asimismo sus límites, por medio de la aplicación de la doctrina de los actos propios

From five-loop scattering amplitudes to open trees with the Loop-Tree Duality

Characterizing multiloop topologies is an important step towards developing novel methods at high perturbative orders in quantum field theory. In this article, we exploit the Loop-Tree Duality (LTD) formalism to analyse multiloop topologies that appear for the first time at five loops. Explicitly, we open the loops into connected trees and group them according to their topological properties. Then, we identify a kernel generator, the so-called N$^7$MLT universal topology, that allow us to describe any scattering amplitude of up to five loops. Furthermore, we provide factorization and recursion relations that enable us to write these multiloop topologies in terms of simpler subtopologies, including several subsets of Feynman diagrams with an arbitrary number of loops. Our approach takes advantage of many symmetries present in the graphical description of the original fundamental five-loop topologies. The results obtained in this article might shed light into a more efficient determination of higher-order corrections to the running couplings, which are crucial in the current and future precision physics program.Comment: 14 pages, 6 figures, 2 table