Arturo Ortega

Gas identification with tin oxide sensor array and self organizing maps: adaptive correction of sensor drifts

Low cost tin oxide gas sensors are inherently nonspecific. In addition they feature several non-desirable behaviors such as slow time response, nonlinearities and long term drifts. This paper shows that the combination of a gas sensor array together with self organizing maps can solve the gas classification problems. That is, the system is able to determine the gas present in the test chamber with error rates lower than 3%. The correction of the sensor drift with an adaptative SOM has also been investigated.

The effects of uranium on reproduction, gestation, and postnatal survival in mice

Uranyl acetate dihydrate was tested for its effects on reproduction, gestation, and postnatal survival in Swiss mice. Four groups of animals, each of which consisted of 25 males and 25 females, were administered 0, 5, 10, and 25 mg/kg/day of uranyl acetate dihydrate. Mature male mice were treated orally for 60 days prior to mating with mature virgin female mice treated orally for 14 days prior to mating. Treatment of the females continued throughout mating, gestation, parturition, and nursing of the litters. One-half of the dams in each group were sacrificed on Day 13 of gestation and the remaining dams were allowed to deliver and wean their offspring. Postnatal development was monitored after 0, 4, and 21 days of lactation. No adverse effects on fertility were evident at the doses employed in this study. Nevertheless, embryolethality could be observed in the 25 mg/kg/day group. Significant increases in the number of dead young per litter were seen at birth and at Day 4 of lactation in the 25 mg/kg/day group. The growth of the offspring was always significantly lower for the uranium-treated animals. However, the present results suggest that uranium does not cause any adverse effects on fertility, general reproductive parameters, or offspring survival at the concentrations usually ingested by man.

An intelligent detector based on temperature modulation of a gas sensor with a digital signal processor

Abstract An intelligent detector based on a hot-plate gas sensor and a digital signal processor (DSP) is presented. The work comprises sensor measurements and gas identification with a pattern recognition (PARC) system along with a systematic verification of both stages, thanks to clustering validity methods and performance tests. Commercial silicon micromachined tin-oxide sensors have been used to capture dynamic measurements modulating the sensor heater at different temperatures, waveforms and frequencies. Feature extraction is based on the spectral and transient analysis of the sensor output signals. The PARC systems are based on self-organizing maps (SOM) and recent variations of these well-known neural networks. The proposed hardware is in charge of the whole system: the sensor temperature modulation and signal processing.

Evaluation of the oral toxicity of uranium in a 4-week drinking-water study in rats

Uranium is an ubiquitous constituent of mans natural environment. Most exposure to uranium bas occurred during the mininz, processin~, and transformation of the metal into fuel elements for nuclear reactors (Cothern and Lappenbusch 1983; Tasat and De Rey 1987), The enormous expansion in the operations involving uranium that bas occurred over the last forty years bas led to the dispersion of concentrated uranium at many sites over almost the entire world, While the dangers due to nuclear reactions are ~iven wide play in the public press, the toxicolo~ical hazards of increased levels of uranium are less widely appreciated.

Developmental Toxicity Evaluation of Orthovanadate in the Mouse

Sodium orthovanadate in deionized water was administered once daily by gavage on gestational days 6–15 to mice at doses of 0, 7.5, 15, 30, and 60 mg/kg. Dams were killed on day 18 of pregnancy, and fetuses were examined for external, visceral, and skeletal defects. Maternal toxicity was observed at the highest doses of sodium orthovanadate, as evidenced by a significant number of deaths (60 and 30 mg/kg/d) and reduced weight gain and food consumption (30 and 15 mg/kg/d). Embryolethality and teratogenicity were not observed at maternally toxic doses and below, but fetal toxicity was evidenced by a significant delay in the ossification process of some skeletal districts at 30 mg/kg/d. The no-observed-adverse-effect level (NOAEL) for maternal toxicity was 7.5 mg/kg/d, and 15 mg/kg/d. represented a NOAEL for developmental toxicity in mice under the conditions of this study.

New pattern recognition systems designed for electronic noses

Abstract Electronic noses represent a big challenge for the pattern recognition (PARC) systems due to several particular problems they involve. The work presented in this paper is targeted to develop specific methods for these kinds of problems. One of the main issues to deal with, is the concentration variation, as a main cause of pattern dispersion in aroma/gas recognition. Such dispersion hinders easy cluster separation, specially for small aroma intensities. Specific algorithms for gas identification are introduced. They cope with the usual elongated cluster structure found in electronic noses. The PARC systems combine self-organising maps (SOM) and minimum spanning tree (MST) to build curvilinear prototypes. The method is exemplified with a minimal tin dioxide sensor array chosen for CO and CH 4 detection in domestic premises.

Oral meso‐2, 3‐dimercaptosuccinic acid in pregnant sprague‐dawley rats: Teratogenicity and alterations in mineral metabolism. I. Teratological evaluation

meso-2,3-Dimercaptosuccinic acid (DMSA), an effective antagonist for the treatment of lead, arsenic, mercury, and cadmium poisoning, was evaluated for developmental toxicity in pregnant Sprague-Dawley rats. DMSA was administered by gavage on d 6-15 of gestation at doses of 0, 100, 300, or 1000 mg DMSA/kg/d. At termination on d 20 of gestation, fetuses were examined for external, visceral, and skeletal malformations and variations. Maternal toxicity was observed at all doses, as evidenced by a significant decrease in body weight gain. There were no effects with respect to hematology or clinical chemistry. Increased early resorptions, increased percentage postimplantation loss, and reduced fetal body weight per litter were observed at 100, 300, and 1000 mg/kg/d. Examination of fetuses for gross external abnormalities, visceral and skeletal malformations, or ossification variations revealed that DMSA did not produce teratogenicity at any dosage level. However, significant fetotoxicity was observed at 100, 300, and 1000 mg/kg/d. The no-observable-effect level (NOEL) for maternal and developmental toxicity was less than 100 mg DMSA/kg/d.

The removal of strontium from the mouse by chelating agents

The effects of the chelating agents monosodium glutamate, Tiron, tartaric acid, ascorbic acid, 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6), 2,3-dimercaptosuccinic acid (DMSA), succinic acid, malic acid, ethylendiaminetetraacetic acid (EDTA), ethylenglycol-bis-(β-amino-ethylether)-N,N′ tetraacetic acid (EGTA), cyclohexanediaminetetraacetic acid (CDTA) and diethylentriaminepentaacetic acid (DTPA) on the distribution and excretion of intraperitoneally injected strontium were investigated in male Swiss mice. Strontium nitrate was given at a dose equal to 3.78 mmol/kg and ten minutes after, chelators were administered intraperitoneally at doses approximately equal to one-fourth of their respective LD50 values. DTPA, followed by CDTA, EDTA and tartaric acid, was consistently the most effective in increasing the urinary excretion of strontium. Only ascorbic acid increased significantly the fecal excretion of strontium. CDTA, DTPA and ascorbic acid were also the most effective chelators in reducing the concentration of strontium found in various tissues. CDTA, DTPA and tartaric acid are the most effective agents of those tested in the removal of strontium after a single administration.

Oral meso‐2,3‐dimercaptosuccinic acid in pregnant sprague‐dawley rats: Teratogenicity and alterations in mineral metabolism. II. Effect on mineral metabolism

The effect of meso-2,3-dimercaptosuccinic acid (DMSA) on mineral metabolism was investigated in pregnant Sprague-Dawley rats. Animals were given by gavage doses of 0, 100, 300, or 1000 mg DMSA/kg/d on gestational d 6-15. On d 20 of gestation dams were killed and fetuses were removed from the uterus. The levels of calcium, magnesium, zinc, copper, and iron were measured in maternal liver, kidney, and intestine, as well as in whole fetus and in fetal liver. Mineral analysis of maternal and fetal tissues revealed pronounced effects of DMSA on mineral metabolism. The results of this investigation indicate a strong possibility that the negative effects of the drug on pregnancy are due in part to the changes in mineral metabolism.

Quantitative signal processing algorithms for low cost methane and carbon monoxide detectors

Natural gas and carbon monoxide domestic detectors available in the market present serious deficiencies in terms of selectivity. Their problems result in a high percentage of false alarms. A possible solution of this problem is to improve the performance by means of signal processing. The authors present the work carried out towards the improvement of signal processing in quantitative analysis. in this paper we present the results obtain by some quantitative algorithms together with their application examples focused in the selective detection of methane and carbon.