Remoción de quistes de giardia duodenalis por filtración rápida

Con el objetivo de evaluar la remoción de quistes de Giardia duodenalis en agua, se construyó un filtro rápido por gravedad, a escala laboratorio, con arena (Tamaño efectivo: 0,95±0,03 mm) como material filtrante. El agua para la prueba de remoción (160 L) se preparó diluyendo una suspensión de quistes con H2Od hasta una turbiedad de 4 UNT. Para recuperar los quistes no removidos, el agua filtrada se pasó a través de membranas de nitrato de celulosa de 0,45 μm. El conteo de quistes se realizó en cámara de Neubauer. Mediante pruebas hidráulicas se estableció el espesor del lecho (0,75 m) y el tiempo de retención (5 min). La concentración de parásitos en el agua de entrada fue de 2,2 104 quistes/L, obteniéndose una remoción de 1,5 log (96,9 %). La turbiedad durante el periodo de filtración fue ≤ 1,22 UNT. Este trabajo confirma que aún en condiciones de filtración apropiadas, los quistes de Giardia pueden aparecer en el agua tratada cuando ocurre una elevada contaminación de la fuente.In order to evaluate the removal of cysts of Giardia duodenalis in water, a rapid gravity filter was constructed on laboratory scale with sand (effective size: 0.95 ± 0.03 mm) as a filter material. Water for the test (160 L) was prepared by diluting a suspension of cysts with H2Od until a turbidity of 4 UNT. To recover the unremoved cysts, the filtered water was passed through 0.45 μm cellulose nitrate membranes. The cysts count was performed in Neubauer chamber. The filter bed thickness (0.75 m) and the retention time (5 min) were established by hydraulic tests. The concentration of parasites in the incoming water was 2.2 104 cysts / L obtaining a removal of 1.5 log (96.9 %). The turbidity during the filtration period was ≤ 1.22 UNT. This investigation confirms that even under appropriate filtration conditions, cysts of Giardia can appear in the treated water when high source contamination occurs.Fil: Pizarro, A.. Universidad Nacional del LitoralFil: Zerbatto, M.. Universidad Nacional del LitoralFil: Pizarro, M.. Universidad Nacional del LitoralFil: Modini, L.. Universidad Nacional del Litora

Inclusion of [H3PW12O40] and [H4SiW12O40] into a silica gel matrix via "sol-gel" methodology

Indexación: Web of Science; Scopus.Here we report the inclusion of two Keggin Polyoxometalates (POMs), [H3PW12O40] and [H4SiW12O40], into silica gels by integrating them during the preparation of the SiO2 matrix via "sol-gel" methods. Aerogels were produced by supercritical drying of the wet gels impregnated with the POMs, and lyogels were obtained by means of a lyophilization process. These materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR) spectroscopy and thermoanalytical techniques (TGA-DSC). We found that a large fraction of POMs are lost during the aging time, and solvent exchange for lyophilization. However the thermal stability of the bare matrix is modified by the inclusion of POMs. Some aggregates with a high content of POMs were found via SEM-EDX.http://ref.scielo.org/3fg9t

Closing the gap between business undergraduate education and the organisational environment: A Chilean case study applying experiential learning theory

In response to the continuous changes in Latin American higher education and the increasing demands for better prepared professionals, the Learning Connected to the Organisational Environment method was introduced in the course of Marketing at one public University in Chile. This was aimed as an integrated approach to education, providing pedagogical and social value by connecting organisations and real challenges with the learning objectives. This paper describes its design, implementation and initial impact on students’ learning process. Results on the impact of the LCOE method show that students valued learning with this new initiative (n = 158) and showed higher performance and improved quality of their written reports, along with higher evaluations of the teaching staff compared to students in the same course learning with traditional methods (n = 158). Discussion is centred on the value of this initiative and on suggestions for transference and future research

Valve-sparing neo-aortic root replacement after Fontan completion for hypoplastic left heart syndrome

Digitalitzat per Artypla

Effect of addition of an ammonium source in UASB and EGSB reactors when treating low concentrated wastewater: granules morphology

In this work the effect on granules morphology by adding a supplementary nitrogen-ammonium source to UASB and EGSB reactors, treating a low concentrated wastewater is studied. Previously, a complex-synthetic-medium-concentratedwastewater (C/N ratio, 100:4) was fed for granule development and maturation, achieving similar removal performances (higher than 95 % in terms of COD) in both reactors. A subsequent period of 88 days treating low concentrated wastewater (C/N ratio, 100:0.5) led to the destabilisation of granules properties and operational performance in general in both reactors (COD removal efficiencies of approximately 50 %). Ammonium was subsequently supplemented to the low concentrated wastewater, in order to balance the nutrient content (C/N ratio, 100:10) and to study its effect on destabilised granules. After 28 days operating under these conditions, COD removal efficiencies recovered values of 82 and 90 % in UASB and EGSB, respectively. It was also observed, an improvement in granule appearance as given by microscopic observation.CONICYT (Chile); GRICES (Portugal)

GPCA vs. PCA in Recognition and 3-D Localization of Ultrasound Reflectors

In this paper, a new method of classification and localization of reflectors, using the time-of-flight (TOF) data obtained from ultrasonic transducers, is presented. The method of classification and localization is based on Generalized Principal Component Analysis (GPCA) applied to the TOF values obtained from a sensor that contains four ultrasound emitters and 16 receivers. Since PCA works with vectorized representations of TOF, it does not take into account the spatial locality of receivers. The GPCA works with two-dimensional representations of TOF, taking into account information on the spatial position of the receivers. This report includes a detailed description of the method of classification and localization and the results of achieved tests with three types of reflectors in 3-D environments: planes, edges, and corners. The results in terms of processing time, classification and localization were very satisfactory for the reflectors located in the range of 50–350 cm