Spot addressing for microarray images structured in hexagonal grids

In this work, an efficient method for spot addressing in images, which are generated by the scanning of hexagonal structured microarrays, is proposed. Initially, the blocks of the image are separated using the projections of the image. Next, all the blocks of the image are processed separately for the detection of each spot. The spot addressing procedure begins with the detection of the high intensity objects, which are probably the spots of the image. Next, the Growing Concentric Hexagon algorithm, which uses the properties of the hexagonal grid, is introduced for the detection of the non-hybridized spots. Finally, the Voronoi diagram is applied to the centers of the detected spots for the gridding of the image. The method is evaluated using spots generated from the scanning of the Beadchip of Illumina, which is used for the detection of Single Nucleotide Polymorphisms in the human genome, and uses hexagonal structure for the location of the spots. For the evaluation, the detected centers for each of the spot in the image are compared to the centers of the annotation, obtaining up to 98% accuracy for the spot addressing procedure.     

A Broadband Monitoring System for Electromagnetic-Radiation Assessment

A broadband monitoring system for measuring the total electric field radiated from broadcasting (radio, TV) and communications (mobile telephony, TETRA, WLAN) systems is presented. The system has been implemented for recording the field on a 24-hour basis. It has an omnidirectional sensor antenna and the appropriate electronic circuits. The heart of the system is a low-power, eight-bit RISC Microchip microcontroller, running at 10 MHz. Various digital and analog peripherals are connected to the microcontroller. The system can send the data to a personal computer through a USB interface, and can communicate through a GSM modem. Low cost and high reliability render the system inexpensive for the deployment of electromagnetic radiation-monitoring networks, and make it trustworthy for the public. Several tests of the sensor's pattern, the linearity of the response, and the frequency response have shown that the system can be successfully compared with commercially available systems.     

Ferritin Assembly in Enterocytes of Drosophila melanogaster

Ferritins are protein nanocages that accumulate inside their cavity thousands of oxidized iron atoms bound to oxygen and phosphates. Both characteristic types of eukaryotic ferritin subunits are present in secreted ferritins from insects, but here dimers between Ferritin 1 Heavy Chain Homolog (Fer1HCH) and Ferritin 2 Light Chain Homolog (Fer2LCH) are further stabilized by disulfide-bridge in the 24-subunit complex. We addressed ferritin assembly and iron loading in vivo using novel transgenic strains of Drosophila melanogaster. We concentrated on the intestine, where the ferritin induction process can be controlled experimentally by dietary iron manipulation. We showed that the expression pattern of Fer2LCH-Gal4 lines recapitulated iron-dependent endogenous expression of the ferritin subunits and used these lines to drive expression from UAS-mCherry-Fer2LCH transgenes. We found that the Gal4-mediated induction of mCherry-Fer2LCH subunits was too slow to effectively introduce them into newly formed ferritin complexes. Endogenous Fer2LCH and Fer1HCH assembled and stored excess dietary iron, instead. In contrast, when flies were genetically manipulated to co-express Fer2LCH and mCherry-Fer2LCH simultaneously, both subunits were incorporated with Fer1HCH in iron-loaded ferritin complexes. Our study provides fresh evidence that, in insects, ferritin assembly and iron loading in vivo are tightly regulated.     

Measurement of the dynamic displacements and of the modal frequencies of a short-span pedestrian bridge using GPS and an accelerometer

Signal analysis techniques (supervised-type learning filter in combination with a Chebyshev filter) constrained and tested by independent accelerometer data were used to process noisy GPS measurements of oscillations of 40 m long steel footbridge excited by coordinated jumps of a group of people. This approach permitted to de-noise the geodetic displacement record and reconstruct a minimum bias waveform for the dynamic displacement of this stiff bridge (4.3 Hz modal frequency, ∼6 mm oscillation amplitude). This result indicates that properly processed high-frequency satellite geodetic data may be used to measure dynamic displacements not only of high-rise buildings, cable-stayed bridges and other flexible structures, but of stiff civil engineering structures as well and may be useful for the Structural Health Monitoring, analysis and design of a large range of engineering structures. It was also found that although currently used 10 Hz sampling rate GPS receivers may underestimate certain high-frequency peak displacements, this will not be a problem for the recently introduced 50-100 Hz receivers.     

A generalized methodology for the gridding of microarray images with rectangular or hexagonal grid

Microarrays provide a simple way to measure the level of hybridization of known probes of interest with one or more samples under different conditions. The rapid development of microarray technology requires the implementation of smart and flexible algorithms to deal either with the great amount of data or with the variations of the used hardware. In this paper, a generalized methodology for spot addressing and gridding of microarray images is presented. The methodology can cope with both rectangular and hexagonal grids, which are used for the probes placement onto the substrate. Initially, the methodology identifies the structure of the image, and an efficient spot-by-spot approach has been developed for the detection of all spots in the image. The evaluation of the methodology was performed using both rectangular and hexagonal structured images, merged in a single dataset. The methodology results in high accuracy in the spots detection, ranging from 92.8 to 99.8 % depending on the dataset used.     

Noise characteristics of high-frequency,short-duration GPS records from analysis of identical,collocated instruments

High-rate (>1 Hz) GPS, currently used for measurement of dynamic processes and as a universal time and frequency standard, is usually assumed to be affected by site-specific errors and only limited studies of the error properties of high-frequency (10 Hz), short-duration (<100 s) GPS records exist. Preliminary studies, provided evidence of instrument-specific errors, which were investigated on the basis of systematic experiments with various types of stationary, collocated, identical GPS units. This analysis revealed differences between couples of receiver/antenna units, while spectral analyses revealed low-frequency colored noise, statistically significant below 0.2 Hz and, gradually decaying with increasing duration of observations, so that above 2.5 Hz measurements are contaminated only by white noise.