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  • Publication
    Automatic pneumonia detection based on ultrasound video analysis
    Pneumonia is a disease which causes high mortality in children under five years old, particularly in developing countries. This paper proposes a novel application of ultrasound video analysis for the detection of pneumonia. This application is based on the processing of small video chunks, in which an image processing algorithm analyzes each frame to get some overall video statistics. Then, based on these quantities, the likeness of presence of pneumonia in the video is determined. The algorithm exploits different geometrical properties of typical anatomical and pathological features that commonly appear in lung sonography and which are already clinically typified in the literature. Our technique has been tested on different transverse thoracic scanning protocols and probe's maneuvers, thus, under a variety of clinical and usage protocols. Then, it can be targeted towards screening applications. We present encouraging results (AUC measure between 0.7851 and 0.9177) based on the analysis of 346 videos with an average duration of eight seconds. The analyzed videos were taken from children who were between three and five years old. Finally, our algorithm can be used directly as a classifier, but we detail how its performance may be enhanced if used as a first stage of a larger pipeline of other complementary pneumonia detection processes.
  • Publication
    Multiple norovirus infections in a birth cohort in a peruvian periurban community
    ( 2014-02-15) ;
    Goel-Apaza S.
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    Velasquez D.
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    Crabtree J.E.
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    Black R.E.
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    Checkley W.
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    Bern C.
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    Cama V.
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    Background. Human noroviruses are among the most common enteropathogens globally, and are a leading cause of infant diarrhea in developing countries. However, data measuring the impact of norovirus at the community level are sparse.Methods. We followed a birth cohort of children to estimate norovirus infection and diarrhea incidence in a Peruvian community. Stool samples from diarrheal episodes and randomly selected nondiarrheal samples were tested by polymerase chain reaction for norovirus genogroup and genotype. Excretion duration and rotavirus coinfection were evaluated in a subset of episodes.Results. Two hundred twenty and 189 children were followed to 1 and 2 years of age, respectively. By 1 year, 80% (95% confidence interval [CI], 75%-85%) experienced at least 1 norovirus infection and by 2 years, 71% (95% CI, 65%-77%) had at least 1 episode of norovirus-associated diarrhea. Genogroup II (GII) infections were 3 times more frequent than genogroup 1 (GI) infections. Eighteen genotypes were found; GII genotype 4 accounted for 41%. Median excretion duration was 34.5 days for GII vs 8.5 days for GI infection (P =. 0006). Repeat infections by the same genogroup were common, but repeat infections by the same genotype were rare. Mean length-for-age z score at 12 months was lower among children with prior norovirus infection compared to uninfected children (coefficient: -0.33 [95% CI, -.65 to -.01]; P =. 04); the effect persisted at 24 months.Conclusions. Norovirus infection occurs early in life and children experience serial infections with multiple genotypes, suggesting genotype-specific immunity. An effective vaccine would have a substantial impact on morbidity, but may need to target multiple genotypes. © 2013 The Author 2013. Published by Oxford University Press on behalf of the Infectious Diseases Society of America.
  • Publication
    Disinfection of natural water by solar photocatalysis using immobilized TiO 2 devices: Efficiency in eliminating indicator bacteria and operating life of the system
    Natural water has been disinfected using TiO 2 as the fixed catalyst incorporated in a homemade photoreactor, in which the dimensions and the design parameters are representative of devices that are currently employed at larger scale. The catalyst was immobilized on the external surface of a cylinder of frosted glass situated in the longitudinal axis of a tubular glass reactor. Two alternative methods of immobilizing the catalyst on glass were studied: in the first, a commercial titanium oxide powder (Aeroxide® TiO 2 P25) was mounted on a polymeric support; and in the second, it was applied by sol-gel deposition. Illumination was effected by installing the glass reactor in the irradiation chamber of a solar simulator. Under laboratory conditions, groundwater contaminated with cultured and wild bacteria was treated photocatalytically, and the influence of the photolysis, the pumping, and the catalysts was studied. The results obtained have demonstrated that the catalyst immobilized in the interior of the photoreactor presents similar results, in the disinfection of E. coli, as 0.5 g/l of TiO 2 P25; and that, in 1.5 h approximately of simulated solar illumination (167 kW UVA s/m 2) on the sol-gel deposit of TiO 2, it is possible to eliminate 100% of the bacteria covered by international regulations in respect of water for human consumption. With regard to the aging assay of the system, it was observed at 250 h of operation a reduction in the effectiveness of the disinfection process. At 0 and 250 h of operation, the percentages of elimination of E. coli after 50 min of illumination were 100% and 99.5%, respectively. This reduction in the effectiveness of the process was due to the formation of a film of calcium carbonate adhering to the internal glass wall of the photoreactor, which is in contact with the liquid being treated, and to the presence of calcium carbonate precipitates on catalyst surface. © 2012 American Society of Mechanical Engineers.
  • Publication
    Solar photocatalytic water disinfection of Escherichia coli, Enterococcus spp. and Clostridium Perfringens using different low-cost devices
    (John Wiley and Sons Ltd., 2016-07-01)
    Gutiérrez-Alfaro S.
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    Acevedo A.
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    Manzano M.
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    BACKGROUND: The purpose of this work was to evaluate the disinfection capacity of two handmade low-cost devices based on solar photocatalytic disinfection (SPC-DIS): a plastic bottle (2 L) with a cylinder inside coated with TiO2 doped with zinc and a glass reactor (9 L) with an inner cylinder coated with pure TiO2. Disinfection experiments of wastewater-derived Escherichia coli, Enterococcus spp. and Clostridium perfringens (104-105 CFU per 100 mL) were carried out under natural sunlight during winter. RESULTS: Clostridium perfringens was the most resistant microorganism and E. coli the least in all cases. The SPC-DIS bottle achieved 100% disinfection for E. coli, but only 98.97% for Enterococcus spp. and 96.28% for C. perfringens. The SPC-DIS reactor achieved, under optimum operating conditions, 100% disinfection for E. coli, 100% for Enterococcus spp. and 99.44% for C. perfringens. Maximum sustainable flow rate (22 L min-1) and maximum illumination ratio (1:2) were the best operating conditions. Operating with recirculation (interrupted illumination) favored C. perfringens spore formation. Best kinetic models were biphasic for E. coli and log-linear for Enterococcus spp. and C. perfringens. CONCLUSION: The two new devices showed higher disinfection capacity than common PET bottles (increase in disinfection rates up to 1.5 and 4.6 times), proving to be promising alternatives to the traditional method SODIS.
  • Publication
    Thermodecomposition synthesis of porous β-Bi2O3/Bi2O2CO3 heterostructured photocatalysts with improved visible light photocatalytic activity
    (Royal Society of Chemistry, 2015-09-29)
    Zhu G.
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    Liu Y.
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    Hojamberdiev M.
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    Han J.
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    Bilmes S.A.
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    Liu P.
    Novel porous β-Bi2O3/Bi2O2CO3 p-n heterostructures were synthesized by partially decomposing porous Bi2O2CO3 at 300-375 °C. The structures, morphologies, optical properties, and specific surface areas of the as-synthesized samples were characterized by means of thermogravimetry and differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, UV-Vis spectroscopy, and N2 gas adsorption. Two types of dyes, methyl orange (MO) and methylene blue (MB), were chosen as model organic pollutants to evaluate the photocatalytic activity of the as-synthesized samples. The porous β-Bi2O3/Bi2O2CO3 p-n heterostructures exhibited much higher photocatalytic activity than β-Bi2O3 and Bi2O2CO3 and MO and MB could be completely degraded within 24 and 50 min, respectively. In addition, phenol as a colorless organic pollutant was also chosen to further study the photocatalytic activity of Bi2O2CO3, β-Bi2O3 and β-Bi2O3/Bi2O2CO3. The β-Bi2O3/Bi2O2CO3 heterostructures also showed much higher photocatalytic activity for the photodegradation of phenol than β-Bi2O3 and Bi2O2CO3. The obtained results indicated that the formed p-n heterojunction in the porous β-Bi2O3/Bi2O2CO3 composite significantly contributed to the improvement of electron-hole separation and the enhancement of photocatalytic activity. The mechanisms for the enhanced photodegradation of selected organic pollutants over the β-Bi2O3/Bi2O2CO3 composite are discussed in this study.