Maximum-likelihood estimation of circle parameters via convolution.

The accurate fitting of a circle to noisy measurements of circumferential points is a much studied problem in the literature. In this paper, we present an interpretation of the maximum-likelihood estimator (MLE) and the Delogne-K?sa estimator (DKE) for circle-center and radius estimation in terms of convolution on an image which is ideal in a certain sense. We use our convolution-based MLE approach to find good estimates for the parameters of a circle in digital images. In digital images, it is then possible to treat these estimates as preliminary estimates into various other numerical techniques which further refine them to achieve subpixel accuracy. We also investigate the relationship between the convolution of an ideal image with a "phase-coded kernel" (PCK) and the MLE. This is related to the "phase-coded annulus" which was introduced by Atherton and Kerbyson who proposed it as one of a number of new convolution kernels for estimating circle center and radius. We show that the PCK is an approximate MLE (AMLE). We compare our AMLE method to the MLE and the DKE as well as the Cramér-Rao Lower Bound in ideal images and in both real and synthetic digital images.     

Slurry Chemistry Control to Produce Easily Redispersible Ceramic Powder Compacts

The slurry-based Three Dimensional Printing (3DP^TM) process requires the production of an easily redispersible powder bed from a well-dispersed slurry. Understanding and control of the interparticle potential in the dispersed state, as well as in the dry consolidated state, are important. The strength of the particle–particle interactions in the dry state determines the redispersion efficiency. One factor that controls the interparticle strength is the chemical stability of the ceramic powders in the dispersed state. For unstable powders, a partial dissolution and/or hydration of the powders can occur and eventually impede the redispersion by forming insoluble salt bridges at the necks of the particles. Redispersion of the powder bed can be improved substantially by weakening the strength of the particle–particle bonds. The formation of strong chemical bonds between particles should be avoided by adjusting the slurry pH to an appropriate range where the powders are chemically stable in the slurry. Replacement of the chemical bonds by soluble physical bonds, using a low-molecular-weight hydrophilic polymer, also reduces the interparticle strength and enhances redispersion.     

Prevalence of tobacco use in Eritrea: results from a noncommunicable disease risk factor survey.

The prevalence of noncommunicable diseases in Eritrea is increasing. Tobacco use is a recognized risk factor for most of these diseases, especially cardiovascular disease. No data have been published on tobacco use in Eritrea. The present study sought to establish the prevalence of tobacco smoking in Eritrea. The World Health Organization STEPwise approach was used for the survey, conducted in 2004 on a random national sample size of 2,460 subjects (response rate = 93.7%). The prevalence of tobacco smoking in the general population was 8.1%; the prevalence was 15% among men, compared with 0.6% among women. Prevalence rates were higher in those older than 45 years of age. The prevalence of tobacco smoking was higher among Muslims (11.4%) than Orthodox Christians (5.8%), and among alcohol drinkers (10.2%) than nondrinkers (6.6%). The majority of tobacco users (89.3%) used commercially available cigarettes. A study on knowledge, attitudes, and practices regarding tobacco use is needed to determine the behavioral factors leading to tobacco smoking among the vulnerable groups.     

The geography of science in 12 European countries: a NUTS2-level analysis

Scientometrics - Europe has a long history as a global center of scientific research, but not all European regions are alike. Regions such as Île de France and the corridor that stretches from...     

Time multiplexing superresolution based on interference grating projection

In a previous work done by the authors, it was shown that the superresolution concept based on two moving gratings could be effected by a physical grating attached to the object and a virtual grating. This concept was shown to be very efficient and exhibited features that are helpful in removing some artifacts caused when coherent illumination is used. Furthermore, it simplifies the optical and mechanical modules of the super-resolving system by removing the need for mechanical movement of one grating. However, the system still required the need for moving the first (encoding) grating attached to the input. In this study the encoding grating is replaced by use of a projected grating. This approach simplifies the need for attaching the grating to the input object and thus new applications, such as remote sensing can be considered. The theoretical concept is demonstrated and experimental results are shown.     

Network location of a reliable center using the most reliable route policy

This paper considers a single location on an undirected network with unreliable edges that maximizes the lowest performance level of the network service with respect to all nodes. The problem is termed the reliable 1-center problem and finds applications in telecommunication and computer networks. The users are concerned with the network capability of establishing a route to some service provider. The objective function is formally stated as either minimizing the maximum expected number of unsuccessful responses to demand requests over all nodes, named the reli-minmax problem, or maximizing the minimum expected number of successful responses to demand requests over all nodes, named the reli-maxmin problem, as sub-problems of the most general reliable 1-center problem. Solutions are presented that solve the problem in polynomial time or reduce it to the 1-center problem when it is applied on general networks using a pre-designated route policy, e.g. the most reliable route policy.     

Human-centered control scheme for delayed bilateral teleoperation of mobile robots

Teleoperation task performance strongly depends on how well the human operator’s commands are executed. In this paper, we propose a control scheme for delayed bilateral teleoperation of mobile robots that considers user’s commands execution in order to achieve a high-performance teleoperation system in some important aspects like time to complete the task, safety, and operator dependence. We describe some evaluation metrics that allow us to address these aspects and a quantitative metric is proposed and incorporated in the control scheme to compensate wrong commands. A force feedback is applied to the master at the local site as a haptic cue. In addition, the system stability is analyzed taking into consideration the master and remote robot dynamic models and the asymmetric time-varying delays of the communication channel. Multiple human-in-the-loop simulations were carried out and the results of the evaluation metrics were discussed. Additionally, we present experiments where a user teleoperates a mobile robot via the Internet connection between Argentina and Italy.     

The Quorum Sensing Auto-Inducer 2 (AI-2) Stimulates Nitrogen Fixation and Favors Ethanol Production over Biomass Accumulation in Zymomonas mobilis

Autoinducer 2 (or AI-2) is one of the molecules used by bacteria to trigger the Quorum Sensing (QS) response, which activates expression of genes involved in a series of alternative mechanisms, when cells reach high population densities (including bioluminescence, motility, biofilm formation, stress resistance, and production of public goods, or pathogenicity factors, among others). Contrary to most autoinducers, AI-2 can induce QS responses in both Gram-negative and Gram-positive bacteria, and has been suggested to constitute a trans-specific system of bacterial communication, capable of affecting even bacteria that cannot produce this autoinducer. In this work, we demonstrate that the ethanologenic Gram-negative bacterium Zymomonas mobilis (a non-AI-2 producer) responds to exogenous AI-2 by modulating expression of genes involved in mechanisms typically associated with QS in other bacteria, such as motility, DNA repair, and nitrogen fixation. Interestingly, the metabolism of AI-2-induced Z. mobilis cells seems to favor ethanol production over biomass accumulation, probably as an adaptation to the high-energy demand of N₂ fixation. This opens the possibility of employing AI-2 during the industrial production of second-generation ethanol, as a way to boost N₂ fixation by these bacteria, which could reduce costs associated with the use of nitrogen-based fertilizers, without compromising ethanol production in industrial plants.     

Diphtheria toxin fused to granulocyte-macrophage colony-stimulating factor is toxic to blasts from patients with juvenile myelomonocytic leukemia and chronic myelomonocytic leukemia

We have previously demonstrated that human granulocyte-macrophage colony-stimulating factor fused to a truncated diphtheria toxin (DT388-GM-CSF) is toxic to patient acute myeloid leukemia progenitors bearing the GM-CSF receptor, but not normal marrow progenitors. We now report that exposure of mononuclear cells from five of seven (71%) juvenile myelomonocytic leukemia (JMML) patients and from 12 of 20 (60%) adult chronic myelomonocytic leukemia (CMML) patients to 10(-9) mol/L DT388-GM-CSF for 48 hours in culture reduces the number of cells capable of forming colonies in semisolid medium (colony-forming units-leukemia) 10-fold to 300-fold (1 to 2.5 log decrease). In contrast, normal myeloid progenitors (colony-forming unit-granulocyte-macrophage) from six different donors treated and assayed under identical conditions were consistently insensitive to the same fusion toxin even when treated as highly purified CD34(+) cells. The leukemic progenitors from the two other JMML patients showed intermediate sensitivity to DT388-GM-CSF and the leukemic progenitors from eight of the 20 (40%) CMML patients were not different from normal progenitors. Parallel measurements of the number and affinity of GM-CSF receptors on cells from the same samples showed no consistent differences between JMML, CMML, and normal light density or CD34(+) bone marrow cells. The increased sensitivity of leukemic progenitors from all JMML progenitors and some CMML patients to the fusion toxin is therefore not likely to be explained by an increased density of GM-CSF receptors on these cells. We also examined the DT388-GM-CSF sensitivity of two murine cell lines transfected with cDNAs encoding varying portions of the human GM-CSF receptor and/or beta chains. These studies showed that high-affinity ligand binding was sufficient for DT388-GM-CSF-induced toxicity, as this could occur even in the absence of functional signal transduction and that the background of the host cell had a major influence on the degree to which this decreased the toxicity of DT388-GM-CSF. The selective sensitivity to DT388-GM-CSF of leukemic progenitors from a majority of JMML and CMML patients suggests that this agent could have therapeutic potential for some patients with these diseases.     

A small theorem on the nonlinearity of switched systems

A criterion for actual examination the nonlinearity of some systems composed of switched linear elements is given.