Search results for "Algorithm"
showing 10 items of 4887 documents
Alternative reproductive tactics and the propensity of hybridization
2009
One explanation for hybridization between species is the fitness benefits it occasionally confers to the hybridizing individuals. This explanation is possible in species that have evolved alternative male reproductive tactics: individuals with inferior tactics might be more prone to hybridization provided it increases their reproductive success and fitness. Here we experimentally tested whether the propensity of hybridization in the wild depends on male reproductive tactic in Calopteryx splendens damselflies. Counter to our expectation, it was males adopting the superior reproductive tactic (territoriality) that had greatest propensity to hybridize than males adopting the inferior tactics (…
Evaluating a Two-Level vs. Three-Level Fall Risk Screening Algorithm for Predicting Falls Among Older Adults
2020
Background and Objectives: Falls account for the highest proportion of preventable injury among older adults. Thus, the United States' Centers for Disease Control and Prevention (CDC) developed the Stopping Elderly Accidents, Deaths, and Injuries (STEADI) algorithm to screen for fall risk. We referred to our STEADI algorithm adaptation as “Quick-STEADI” and compared the predictive abilities of the three-level (low, moderate, and high risk) and two-level (at-risk and not at-risk) Quick-STEADI algorithms. We additionally assessed the qualitative implementation of the Quick-STEADI algorithm in clinical settings. Research Design and Methods: We followed a prospective cohort (N = 200) of adults …
Antibiotics and Resistance: A Fatal Attraction
2013
When penicillin and other classes of antibiotics were discovered and used to treat infectious diseases human morbidity and mortality due to infective microorganisms were successfully contrasted. However, almost as soon as antibacterial drugs were introduced in clinics, bacterial resistance spread. From a biological and microbiological viewpoint, antibacterial drug resistance is a fascinating aspect of molecular evolution, and resistome concept has been introduced to shed light on driving forces that control the spreading and maintenance of resistance genes within microbial populations. Despite the wide range of chemical complexity of antibiotics, there is a restricted number of modes of act…
A genetic algorithm to calibrate dynamical systems: Confidence intervals for parameters and residuals
2018
This paper presents a genetic algorithm to calibrate dynamical systems that is able to calculate confidence intervals for the parameters of the system. As an application case is used to calibrate the system that reproduces the dynamical response of the General Factor of Personality (GFP) to a given stimulus, particularly to a stimulant drug dose. The model is called in Literature as the response model and includes an integro-differential equation. The presented application case is a single case ABC experimental design where the stimulus is methylphenidate.
An implicitly parallel EDA based on restricted boltzmann machines
2014
We present a parallel version of RBM-EDA. RBM-EDA is an Estimation of Distribution Algorithm (EDA) that models dependencies between decision variables using a Restricted Boltzmann Machine (RBM). In contrast to other EDAs, RBM-EDA mainly uses matrix-matrix multiplications for model estimation and sampling. Hence, for implementation, standard libraries for linear algebra can be used. This allows an easy parallelization and leads to a high utilization of parallel architectures. The probabilistic model of the parallel version and the version on a single core are identical. We explore the speedups gained from running RBM-EDA on a Graphics Processing Unit. For problems of bounded difficulty like …
The Brain’s Camera. Optimal Algorithms for Wiring the Eye to the Brain Shape How We See
2016
The problem of sending information at long distances, without significant attenuation and at a low cost, is common to both artificial and natural environments. In the brain, a widespread strategy to solve the cost-efficiency trade off in long distance communication is the presence of convergent pathways, or bottlenecks. In the visual system, for example, to preserve resolution, information is acquired by a first layer with a large number of neurons (the photoreceptors in the retina) and then compressed into a much smaller number of units in the output layer (the retinal ganglion cells), to send that information to the brain at the lowest possible metabolic cost. Recently, we found experimen…
Microaneurysm detection with radon transform-based classification on retina images.
2012
The creation of an automatic diabetic retinopathy screening system using retina cameras is currently receiving considerable interest in the medical imaging community. The detection of microaneurysms is a key element in this effort. In this work, we propose a new microaneurysms segmentation technique based on a novel application of the radon transform, which is able to identify these lesions without any previous knowledge of the retina morphological features and with minimal image preprocessing. The algorithm has been evaluated on the Retinopathy Online Challenge public dataset, and its performance compares with the best current techniques. The performance is particularly good at low false p…
Images perceived after chromatic or achromatic contrast sensitivity losses.
2010
Purpose. We simulate how subjects with losses in chromatic and achromatic contrast sensitivity perceive colored images by using the spatiochromatic corresponding pair algorithm. Methods. This is a generalized version of the algorithm by Capilla et al. (J Opt Soc Am (A) 2004;21:176 –186) for simulating color perception of color deviant subjects, which incorporates a simple spatial vision model, consisting of a linear filtering stage, with a band-pass achromatic filter and two low-pass chromatic ones, for the red-green and blue-yellow mechanisms. These filters, except for the global scaling, are the subject’s contrast sensitivity functions measured along the cardinal directions of the color s…
A novel automated segmentation method for retinal layers in OCT images proves retinal degeneration after optic neuritis.
2015
Aim The evaluation of inner retinal layer thickness can serve as a direct biomarker for monitoring the course of inflammatory diseases of the central nervous system such as multiple sclerosis (MS). Using optical coherence tomography (OCT), thinning of the retinal nerve fibre layer and changes in deeper retinal layers have been observed in patients with MS. Here, we first compare a novel method for automated segmentation of OCT images with manual segmentation using two cohorts of patients with MS. Using this method, we also aimed to reproduce previous findings showing retinal degeneration following optic neuritis (ON) in MS. Methods Based on a 5×5 expansion of the Prewitt operator to efficie…
Frequency-Sliding Generalized Cross-Correlation: A Sub-Band Time Delay Estimation Approach
2020
The generalized cross correlation (GCC) is regarded as the most popular approach for estimating the time difference of arrival (TDOA) between the signals received at two sensors. Time delay estimates are obtained by maximizing the GCC output, where the direct-path delay is usually observed as a prominent peak. Moreover, GCCs play also an important role in steered response power (SRP) localization algorithms, where the SRP functional can be written as an accumulation of the GCCs computed from multiple sensor pairs. Unfortunately, the accuracy of TDOA estimates is affected by multiple factors, including noise, reverberation and signal bandwidth. In this paper, a sub-band approach for time del…