Time-resolved diffuse optical spectroscopy up to 1700 nm by means of a time-gated InGaAs/InP single-photon avalanche diode

We present a new compact system for time-domain diffuse optical spectroscopy of highly scattering media operating in the wavelength range from 1100 nm to 1700 nm. So far, this technique has been exploited mostly up to 1100 nm: we extended the spectral range by means of a pulsed supercontinuum light source at a high repetition rate, a prism to spectrally disperse the radiation, and a time-gated InGaAs/InP single-photon avalanche diode working up to 1700 nm. A time-correlated single-photon counting board was used as processing electronics. The system is characterized by linear behavior up to absorption values of about 3.4 cm(-1) where the relative error is 17%. A first measurement performed on lipids is presented: the absorption spectrum shows three major peaks at 1200 nm, 1400 nm, and 1700 nm.     

Study of green Sicilian table olive fermentations through microbiological,chemical and sensory analyses

The production of five different green table olive cultivars was studied by a combined strategy consisting of chemical, microbiological and sensory analyses. Cultivable microflora of samples collected during processing was monitored by plate counts on seven synthetic culture media. In all samples Enterobacteriaceae, Pseudomonaceae, staphylococci, lactic acid bacteria and spore-forming bacteria were undetectable. Yeasts and moulds were countable from the day 42 (2 log CFU/ml) till the end of fermentation (6 log CFU/ml). The use of three different approaches for microorganism detection, including a culture-independent methodology, revealed the presence of barely three yeast species during the entire fermentation period: Candida parapsilosis, Pichia guilliermondii and Pichia kluyveri. Biochemical features of technological interest were evaluated for 94 strains in order to investigate their potential role in fermentation of green Sicilian table olives.     

Estimation of motor unit conduction velocity from surface EMG recordings by signal-based selection of the spatial filters

Muscle fiber conduction velocity (CV) can be estimated by the application of a pair of spatial filters to surface electromagnetic (EMG) signals and compensation of the spatial filter transfer function with equivalent temporal filters. This method integrates the selection of the spatial filters for signal detection to the estimation of CV. Using this approach, in this paper, we propose a novel technique for signal-based selection of the spatial filter pair that minimizes the effect of nonpropagating signal components (end-of-fiber effects) on CV estimates (optimal filters). The technique is applicable to signals with one propagating and one nonpropagating component, such as single motor unit action potentials. It is shown that the determination of the optimal filters also allows the identification of the propagating and nonpropagating signal components. The new method was applied to simulated and experimental EMG signals. Simulated signals were generated by a cylindrical, layered volume conductor model. Experimental signals were recorded from the abductor pollicis brevis with a linear array of 16 electrodes. In the simulations, the proposed approach provided CV estimates with lower bias due to nonpropagating signal components than previously proposed methods based on the entire signal waveform. In the experimental signals, the technique separated propagating and nonpropagating signal components with an average reconstruction error of 2.9 +/- 0.9% of the signal energy. The technique may find application in single motor unit studies for decreasing the variability and bias of CV estimates due to the presence and different weights of the nonpropagating components.     

Electrochemical and corrosion behaviour of iron in acetonitrile solutions

The behaviour of the iron-acetonitrile system has been examined and data important from a practical point of view have been obtained. The simultaneous presence of oxygen and acidity is completely unacceptable even at level of 10^?3M in H⁺. The influence of stirring is also potentially dangerous in the presence of dissolved oxygen and free acidity. The conditions for the onset of localized corrosion (e.g. crevice corrosion) are outlined.     

Tube-based robust sampled-data MPC for linear continuous-time systems

This note extends to the continuous-time case the “tube-based” approach for the design of discrete-time robust model predictive control (MPC) algorithms developed in Mayne, Seron, and Rakovi? (2005). This extension is of interest in view of the simplicity and popularity of the method as well as of the industrial relevance of continuous-time implementations of MPC. The proposed robust control law is composed of two terms: (1) a sampled-data MPC control law and (2) a continuous-time state feedback term.     

On the extension of commercial planar circuit CAD packages to the analysis of two‐port waveguide components

We introduce a simple algorithm that enables several commercial codes, based on the method of moments (MoM) and developed for the analysis of planar structures, to address the analysis of a class of two‐port waveguide components. Its key step is a numerical calibration that can be easily automated. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 113–117, 2003.     

Hydroxyapatite-alginate biocomposite promotes bone mineralization in different length scales in vivo

Tissue engineering is a multidisciplinary research area that aims to develop new techniques and/or biomaterials for medical applications. The objective of the present study was to evaluate the osteogenic potential of a composite of hydroxyapatite and alginate in bone defects with critical sizes, surgically made in the calvaria region of rats. The rats (48 adult males), Rattus norvegicus Wistar, were divided into two groups: control (without composite implantation) and experimental (with composite implantation) and analyzed by optical microscopy at the biological time points 15, 45, 90 and 120 d, and transmission electron microscopy 120 d after the implantation of the biomaterial. It was observed that the biomaterial presented a high degree of fragmentation since the first experimental points studied, and that the fragments were surrounded by new bone after the duration of the project. These areas were studied by analytical transmission electron microscopy using an energy dispersive X-ray spectrometer. Three regions could be distinguished: (1) the biomaterial rich in hydroxyapatite; (2) a thin contiguous region containing phosphorus but without calcium; (3) a region of initial ossification containing mineralizing collagen fibrils with a calcium/phosphorus ratio smaller than the particles of the composite. The intermediate region (without calcium or containing very low amounts of calcium), which just surrounded the composite had not been described in the literature yet, and is probably associated specifically to the biocomposite used. The high performance of the biomaterial observed may be related to the fact that alginate molecules form highly anionic complexes and are capable of adsorbing important factors recognized by integrins from osteoblasts. Regions of fibrotic tissue were also observed mainly in the initial experimental points analyzed. However, it did not significantly influence the final result. In conclusion, the biomaterial presents a great potential for application as bone grafts in the clinical area.     

A note on discrete-time positive realizations

A discrete-time positive linear system has the property that any nonnegative initial state and any nonnegative input produces a nonnegative trajectory in the state space and output for all time. Such systems are Rⁿ⁺-reachable if every state of the nonnegative orthant Rⁿ⁺ is reachable from origin with a nonnegative input function, in a finite-time interval. A simple necessary and sufficient condition for Rⁿ⁺-realizability, i.e. for the existence of a nonnegative realization that is also Rⁿ⁺-reachable, is stated. The realization procedure is straightforward.