Field Representations of Vector Supersymmetry

We study some field representations of vector supersymmetry with superspin Y=0 and Y=1/2 and nonvanishing central charges. For Y=0, we present two multiplets composed of four spinor fields, two even and two odd, and we provide a free action for them. The main differences between these two multiplets are the way the central charge operators act and the compatibility with the Majorana reality condition on the spinors. One of the two is related to a previously studied spinning particle model. For Y=1/2, we present a multiplet composed of one even scalar, one odd vector and one even selfdual two-form, which is a truncation of a known representation of the tensor supersymmetry algebra in Euclidean spacetime. We discuss its rotation to Minkowski spacetime and provide a set of dynamical equations for it, which are however not derived from a Lagrangian. We develop a superspace formalism for vector supersymmetry with central charges and we derive our multiplets by superspace techniques. Finally, we discuss some representations with vanishing central charges.Comment: 37 page

Functional Approach to Quantum Decoherence and the Classical Final Limit

For a wide set of quantum systems it is demonstrated that the quantum regime can be considered as the transient phase while the final classical statistical regime is a permanent state. A basis where exact matrix decoherence appears for these final states is found. The relation with the decoherence of histories formalism is studied. A set of final intrinsically consistent histories is found.Comment: 20 pages. Phys. Rev A in press 200

Cuantificacion de la significacion agregada en procesos de auditorias de estados financieros

El trabajo presenta una propuesta metodológica en relación a la determinación del nivel de significación global o agregado a ser calculado en la etapa de planificación de una auditoría de estados financieros.La referida propuesta se sustenta en la posibilidad que tiene el auditor, una vez identificados los usuarios críticos de la información contenida en los estados financieros y as decisiones que toman los mismos en base a tal información, de construir un conjunto de elementos que actúen como facilitadores de decisiones determinando, a su vez, los valores que provocarían cambios en las decisiones de los usuarios y, a partir de los mismos, reproducir las cifras de los estados financieros que provocarían tales medidas, determinando de este modo el nivel de significación.La propuesta metodológica se ajusta plenamente al concepto de significación previsto en los principales ordenamientos contables a nivel nacional e internacional.Palabras claves: Significación, Materialidad, Auditoría de Estados Financieros, Riesgo de Auditoría, Planificación de la Auditoría

Emergent Properties of Tumor Microenvironment in a Real-life Model of Multicell Tumor Spheroids

Multicellular tumor spheroids are an important {\it in vitro} model of the pre-vascular phase of solid tumors, for sizes well below the diagnostic limit: therefore a biophysical model of spheroids has the ability to shed light on the internal workings and organization of tumors at a critical phase of their development. To this end, we have developed a computer program that integrates the behavior of individual cells and their interactions with other cells and the surrounding environment. It is based on a quantitative description of metabolism, growth, proliferation and death of single tumor cells, and on equations that model biochemical and mechanical cell-cell and cell-environment interactions. The program reproduces existing experimental data on spheroids, and yields unique views of their microenvironment. Simulations show complex internal flows and motions of nutrients, metabolites and cells, that are otherwise unobservable with current experimental techniques, and give novel clues on tumor development and strong hints for future therapies.Comment: 20 pages, 10 figures. Accepted for publication in PLOS One. The published version contains links to a supplementary text and three video file

Experimental realisation of Shor's quantum factoring algorithm using qubit recycling

Quantum computational algorithms exploit quantum mechanics to solve problems exponentially faster than the best classical algorithms. Shor's quantum algorithm for fast number factoring is a key example and the prime motivator in the international effort to realise a quantum computer. However, due to the substantial resource requirement, to date, there have been only four small-scale demonstrations. Here we address this resource demand and demonstrate a scalable version of Shor's algorithm in which the n qubit control register is replaced by a single qubit that is recycled n times: the total number of qubits is one third of that required in the standard protocol. Encoding the work register in higher-dimensional states, we implement a two-photon compiled algorithm to factor N=21. The algorithmic output is distinguishable from noise, in contrast to previous demonstrations. These results point to larger-scale implementations of Shor's algorithm by harnessing scalable resource reductions applicable to all physical architectures.Comment: 7 pages, 3 figure

Sojización y productividad de los suelos

Fil: Alvarez, Roberto. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Fil: Berhongaray, Gonzalo. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Fil: Paepe, Josefina Luisa de. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Fil: Mendoza, María R. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Fil: Steinbach, Haydée Sara. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Fil: Caride, Constanza. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Fil: Cantet, Rodolfo Juan Carlos. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.Fil: Alvarez, Carina Rosa. Universidad de Buenos Aires. Facultad de Agronomía. Buenos Aires, Argentina.La producción agropecuaria argentina ha sido escenario de grandes y continuas transformaciones en las últimas décadas. La tradicional ‘rotación agrícola-ganadera’ que se utilizaba hasta la década del 60, que alternaba un período agrícola con cultivos de granos y otro de pasturas para alimentación del ganado, se reemplazó progresivamente por planteos de agricultura continua. Durante el período de pastura se buscaba recuperar la fertilidad del suelo perdida en la fase agrícola, logrando pequeños aumentos de los contenidos de materia orgánica y nutrientes. Paralelamente al avance de la agricultura, a mediados de la década del 70 irrumpe en escena el cultivo de soja, que se difundió exponencialmente a partir de entonces y generó el fenómeno conocido como sojización (figura 2A).\nEl avance de la soja se debió a numerosos factores como bajos costos de producción, precios favorables, gran adaptabilidad del cultivo a distintas condiciones ambientales, baja necesidad de fertilizantes, adopción de la siembra directa de los cultivos sin necesidad de labrar el suelo previamente y posibilidad de hacer dos cultivos por año en lugar de solo uno cultivando la secuencia trigo-soja, en la cual el trigo se cultiva en invierno y la soja inmediatamente a continuación de la cosecha del trigo, en verano. Otro elemento clave que contribuyó al avance del cultivo de soja fue la introducción de cultivares transgénicos con resistencia a herbicidas de acción total (glifosato).\nA nivel de toda la región pampeana el proceso de sojización no produjo una reducción importante de la superficie destinada a los cultivos tradicionales como trigo, maíz y girasol, sino que generó el reemplazo en las rotaciones de las pasturas por agricultura con soja y la expansión de la frontera agrícola hacia regiones anteriormente no cultivadas.il., tbls., grafs., fot., mapasEste artículo había sido publicado anteriormente en Ciencia Hoy volumen 24 número 142 (febrero-marzo 2015

Reverse Engineering Gene Networks with ANN: Variability in Network Inference Algorithms

Motivation :Reconstructing the topology of a gene regulatory network is one of the key tasks in systems biology. Despite of the wide variety of proposed methods, very little work has been dedicated to the assessment of their stability properties. Here we present a methodical comparison of the performance of a novel method (RegnANN) for gene network inference based on multilayer perceptrons with three reference algorithms (ARACNE, CLR, KELLER), focussing our analysis on the prediction variability induced by both the network intrinsic structure and the available data. Results: The extensive evaluation on both synthetic data and a selection of gene modules of "Escherichia coli" indicates that all the algorithms suffer of instability and variability issues with regards to the reconstruction of the topology of the network. This instability makes objectively very hard the task of establishing which method performs best. Nevertheless, RegnANN shows MCC scores that compare very favorably with all the other inference methods tested. Availability: The software for the RegnANN inference algorithm is distributed under GPL3 and it is available at the corresponding author home page (http://mpba.fbk.eu/grimaldi/regnann-supmat

Bacterial Killing Via A Type Iv Secretion System.

Type IV secretion systems (T4SSs) are multiprotein complexes that transport effector proteins and protein-DNA complexes through bacterial membranes to the extracellular milieu or directly into the cytoplasm of other cells. Many bacteria of the family Xanthomonadaceae, which occupy diverse environmental niches, carry a T4SS with unknown function but with several characteristics that distinguishes it from other T4SSs. Here we show that the Xanthomonas citri T4SS provides these cells the capacity to kill other Gram-negative bacterial species in a contact-dependent manner. The secretion of one type IV bacterial effector protein is shown to require a conserved C-terminal domain and its bacteriolytic activity is neutralized by a cognate immunity protein whose 3D structure is similar to peptidoglycan hydrolase inhibitors. This is the first demonstration of the involvement of a T4SS in bacterial killing and points to this special class of T4SS as a mediator of both antagonistic and cooperative interbacterial interactions.6645

Innovation, R&D Investment and Productivity in Chile

This paper uses two sources of information and different methodologies to analyze the causal effect of product and process innovation on productivity in the Chilean manufacturing industry during the past decade. In general, the evidence suggests there is not a contemporaneous effect of product innovation on productivity, but there is a positive effect of process innovation. This notsignificant effect of product innovation contrasts with evidence of studies for other countries. However, the results show the presence of lagged effects product innovation on productivity two years after innovation. Compared with the case of developed countries, this evidence might be consistent with a very slow process of learning by doing on the part of Chilean firms with regard to mastering new technologies. These slow and frequently uncertain gains in productivity could help to explain the low levels of investment in research and development (R&D) activities by Chilean firms