Analysis of Passive Charge Balancing for Safe Current-Mode Neural Stimulation

Charge balancing has been often considered as one of the most critical requirement for neural stimulation circuits. Over the years several solutions have been proposed to precisely balance the charge transferred to the tissue during anodic and cathodic phases. Elaborate dynamic current sources/sinks with improved matching, and feedback loops have been proposed with a penalty on circuit complexity, area or power consumption. Here we review the dominant assumptions in safe stimulation protocols, and derive mathematical models to determine the effectiveness of passive charge balancing in a typical application scenario

A formal analysis of why heuristic functions work

AbstractMany optimization problems in computer science have been proven to be NP-hard, and it is unlikely that polynomial-time algorithms that solve these problems exist unless P=NP. Alternatively, they are solved using heuristics algorithms, which provide a sub-optimal solution that, hopefully, is arbitrarily close to the optimal. Such problems are found in a wide range of applications, including artificial intelligence, game theory, graph partitioning, database query optimization, etc. Consider a heuristic algorithm, A. Suppose that A could invoke one of two possible heuristic functions. The question of determining which heuristic function is superior, has typically demanded a yes/no answer—one which is often substantiated by empirical evidence. In this paper, by using Pattern Classification Techniques (PCT), we propose a formal, rigorous theoretical model that provides a stochastic answer to this problem. We prove that given a heuristic algorithm, A, that could utilize either of two heuristic functions H1 or H2 used to find the solution to a particular problem, if the accuracy of evaluating the cost of the optimal solution by using H1 is greater than the accuracy of evaluating the cost using H2, then H1 has a higher probability than H2 of leading to the optimal solution. This unproven conjecture has been the basis for designing numerous algorithms such as the A* algorithm, and its variants. Apart from formally proving the result, we also address the corresponding database query optimization problem that has been open for at least two decades. To validate our proofs, we report empirical results on database query optimization techniques involving a few well-known histogram estimation methods

Lucilia sericata strain from Colombia: Experimental Colonization, Life Tables and Evaluation of Two Artifcial Diets of the Blowfy Lucilia sericata (Meigen) (Diptera: Calliphoridae), Bogotá, Colombia Strain

The objective of this work was to establish, under experimental laboratory conditions, a colony of Lucilia sericata, Bogotá-Colombia strain, to build life tables and evaluate two artifcial diets. This blowfy is frequently used in postmortem interval studies and in injury treatment. The parental adult insects collected in Bogotá were maintained in cages at 22°C±1 average temperature, 60%±5 relative humidity and 12 h photoperiodicity. The blowfies were fed on two artifcial diets that were evaluated over seven continuous generations. Reproductive and population parameters were assessed. The life cycle of the species was expressed in the number of days of the different stages: egg = 0.8±0.1, larvae I = 1.1±0.02, larvae II = 1.94±0.16, larvae III = 3.5±0.54, pupae = 6.55±0.47, male adult = 28.7±0.83 and female adult = 33.5±1.0. Total survival from egg stage to adult stage was 91.2% for diet 1, while for diet 2 this parameter was 40.5%. The lifetime reproductive output was 184.51±11.2 eggs per female. The population parameters, as well as the reproductive output of the blowfies that were assessed, showed relatively high values, giving evidence of the continuous increase of the strain over the different generations and making possible its maintenance as a stable colony that has lasted for more than two years

Object oriented modeling of resource assignment problems formulated as CSPs

Discrete combinatorial problems can be solved with Constraint Programming (CP) as long as they are formulated as Constraint Satisfaction Problems (CSP). In this paper we propose an object oriented model to solve combinatorial problems of resource assignment including applications in industry, commerce, and general organizations. Problems of these environments are those having entities that have to be assigned to places. A particular case of these problems is proposed and modeled here. This problem, named the Classroom Problem, is in a school with teachers; each teacher is to be assigned to any of the rooms of the school in different schedules and days. Besides there is a set of constraints limiting such assignment. The advantages with respect to other approaches which deal with a particular case of the problem considered in this work are identified and discussed.Eje: Ingeniería de software. Bases de datosRed de Universidades con Carreras en Informática (RedUNCI

An instance of the clp(x) scheme which allows to deal with temporal reasoning problems

In many applications oftemporal reasoning is necessary to express metric and symbolic temporal constraints among temporal objects whether they are points or intervals. In order to cope with these requirements different formalisms have been issued., those that allow to express symbolic temporal constraints by one hand, and others involvingmetric temporal constraints. AJthough this formalism are suitable to represent just sorne kind of problems, in many cases, it is necessary to handle and represent in the same framework both metric and symbolic constraints among temporal objects, whether they are point or interval. . Starting from the previous schemes, different formalisms to integrate metric and symbolic temporal constraints have been issued. A common limitation of these proposals is that none of them allows to represent disjunctive constraints involving a metric component and a symbolic one. This type of eonstraints arises for example in scheduling problems, where an activity must be performed beforé or after another activity, but considering the setting time of the used resources [lbáñez,92b]. Besides in.many planning applications, the formulation ofthe problem itself, must be expressed as logic formulas with a periQd of time associated. Therefore, a temporal reasoning system oriented to planning should be able to express both the logic and the temporal part in a same frame. Unfortunately, none of the approaches to integrate symbolic and tnetric temporal constraints allows to express the logic part of the problem. The main aim of this paper is to de.fine a temporal tool which allows to express and unify metric and symbolic temporal constraints among temporal objects (intervals and points). The temporal model proposed in this paper is based on intervals. However, as opposed to other formalisms, the duration of the intervals may be zero, and therefore temporal points are incIuded. In other words, the concept of temporal interval used in the literature (where the duration is strictly greater than zero), is generalized. Starting from the temporal model, a new operational framework oriented to the resolution oí the problems rather than focused to the representation oftemporal reasoning problems is defined. TIte proposed . operational frarn.ework was designed as a new instance oí the CLP(X) scheme [lbáñez,93] in which the computational domain is formed from temporal objects. Conceptually, the variables of the CLP(Temp) language have associated a finite set of pairs of value5 representing temporal intervals.Eje: 3er Workshop sobre Aspectos teóricos de la inteligencia artificialRed de Universidades con Carreras en Informática (RedUNCI

Gene Expression in Trypanosomatid Parasites

The parasites Leishmania spp., Trypanosoma brucei, and Trypanosoma cruzi are the trypanosomatid protozoa that cause the deadly human diseases leishmaniasis, African sleeping sickness, and Chagas disease, respectively. These organisms possess unique mechanisms for gene expression such as constitutive polycistronic transcription of protein-coding genes and trans-splicing. Little is known about either the DNA sequences or the proteins that are involved in the initiation and termination of transcription in trypanosomatids. In silico analyses of the genome databases of these parasites led to the identification of a small number of proteins involved in gene expression. However, functional studies have revealed that trypanosomatids have more general transcription factors than originally estimated. Many posttranslational histone modifications, histone variants, and chromatin modifying enzymes have been identified in trypanosomatids, and recent genome-wide studies showed that epigenetic regulation might play a very important role in gene expression in this group of parasites. Here, we review and comment on the most recent findings related to transcription initiation and termination in trypanosomatid protozoa

The Blackholic energy and the canonical Gamma-Ray Burst IV: the "long", "genuine short" and "fake - disguised short" GRBs

(Shortened) [...] After recalling the basic features of the "fireshell model", we emphasize the following novel results: 1) the interpretation of the X-ray flares in GRB afterglows as due to the interaction of the optically thin fireshell with isolated clouds in the CircumBurst Medium (CBM); 2) an interpretation as "fake - disguised" short GRBs of the GRBs belonging to the class identified by Norris & Bonnell [...] consistent with an origin from the final coalescence of a binary system in the halo of their host galaxies with particularly low CBM density [...]; 3) the first attempt to study a genuine short GRB with the analysis of GRB 050509B, that reveals indeed still an open question; 4) the interpretation of the GRB-SN association in the case of GRB 060218 via the "induced gravitational collapse" process; 5) a first attempt to understand the nature of the "Amati relation", a phenomenological correlation between the isotropic-equivalent radiated energy of the prompt emission E_{iso} with the cosmological rest-frame \nu F_{\nu} spectrum peak energy E_{p,i}. In addition, recent progress on the thermalization of the electron-positron plasma close to their formation phase, as well as the structure of the electrodynamics of Kerr-Newman Black Holes are presented. An outlook for possible explanation of high-energy phenomena in GRBs to be expected from the AGILE and the Fermi satellites are discussed. As an example of high energy process, the work by Enrico Fermi dealing with ultrarelativistic collisions is examined. It is clear that all the GRB physics points to the existence of overcritical electrodynamical fields. In this sense we present some progresses on a unified approach to heavy nuclei and neutron stars cores, which leads to the existence of overcritical fields under the neutron star crust.Comment: 68 pages, 50 figures, in the Proceedings of the XIII Brazilian School on Cosmology and Gravitation, M. Novello, S.E. Perez-Bergliaffa, editor

Object oriented modeling of resource assignment problems formulated as CSPs

Discrete combinatorial problems can be solved with Constraint Programming (CP) as long as they are formulated as Constraint Satisfaction Problems (CSP). In this paper we propose an object oriented model to solve combinatorial problems of resource assignment including applications in industry, commerce, and general organizations. Problems of these environments are those having entities that have to be assigned to places. A particular case of these problems is proposed and modeled here. This problem, named the Classroom Problem, is in a school with teachers; each teacher is to be assigned to any of the rooms of the school in different schedules and days. Besides there is a set of constraints limiting such assignment. The advantages with respect to other approaches which deal with a particular case of the problem considered in this work are identified and discussed.Eje: Ingeniería de software. Bases de datosRed de Universidades con Carreras en Informática (RedUNCI

A fully automatic gridding method for cDNA microarray images

<p>Abstract</p> <p>Background</p> <p>Processing cDNA microarray images is a crucial step in gene expression analysis, since any errors in early stages affect subsequent steps, leading to possibly erroneous biological conclusions. When processing the underlying images, accurately separating the sub-grids and spots is extremely important for subsequent steps that include segmentation, quantification, normalization and clustering.</p> <p>Results</p> <p>We propose a parameterless and fully automatic approach that first detects the sub-grids given the entire microarray image, and then detects the locations of the spots in each sub-grid. The approach, first, detects and corrects rotations in the images by applying an affine transformation, followed by a polynomial-time optimal multi-level thresholding algorithm used to find the positions of the sub-grids in the image and the positions of the spots in each sub-grid. Additionally, a new validity index is proposed in order to find the correct number of sub-grids in the image, and the correct number of spots in each sub-grid. Moreover, a refinement procedure is used to correct possible misalignments and increase the accuracy of the method.</p> <p>Conclusions</p> <p>Extensive experiments on real-life microarray images and a comparison to other methods show that the proposed method performs these tasks fully automatically and with a very high degree of accuracy. Moreover, unlike previous methods, the proposed approach can be used in various type of microarray images with different resolutions and spot sizes and does not need any parameter to be adjusted.</p