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[en] The performance of different polymers used to flocculate red mud particulate materials in the Bayer process can be evaluated on the basis of their efficiency to achieve adequate settling velocities and turbidity levels. In this study, three commercially available flocculants are evaluated under typical conditions found in the last washer of a Bayer plant. The different shear levels are produced by using a modified Couette flow system. Great differences are noticed in the performance of the polymers when they are compared at different dosages and at different shear rate levels. The data collected also suggests that conventional cylinder settling tests may not be adequate to measure the performance of certain types of polymers. (author)
[en] This paper is devoted to studies of the accuracy of approximate equations for the reflection function of semi-infinite turbid media. It is assumed that the probability of photon absorption β by a particle is low. We derive quadratic and cubic terms of the expansion of the reflection function with respect to (β)1/2. Our results show that the cubic term makes a great improvement in the accuracy in the region of values of the similarity parameter that are not small. (author)
[en] Laboratory dose-response experiments with organophosphate and pyrethroid pesticides, and dose-response experiments with increasing particle loads were used to determine which of these stressors were likely responsible for the toxicity and macroinvertebrate impacts previously observed in the Salinas River. Experiments were conducted with the amphipod Hyalella azteca, the baetid mayfly Procloeon sp., and the midge Chironomus dilutus (Shobanov, formerly Chironomus tentans). The results indicate the primary stressor impacting H. azteca was pesticides, including chlorpyrifos and permethrin. The mayfly Procloeon sp. was sensitive to chlorpyrifos and permethrin within the range of concentrations of these pesticides measured in the river. Chironomus dilutus were sensitive to chlorpyrifos within the ranges of concentrations measured in the river. None of the species tested were affected by turbidity as high as 1000 NTUs. The current study shows that pesticides are more important acute stressors of macroinvertebrates than suspended sediments in the Salinas River. - Pesticides are the primary stressor impacting macroinvertebrates in sections of the lower Salinas River
[en] This is a field-based work that describes the stratigraphy and sedimentology of the Andatza Conglomerate Formation. Based on facies analysis three facies associations of a coarse-grained turbidite system and the related slope have been identified: (1) an inner fan of a turbidite system (or canyon) and (2) a low- and (3) a high-gradient muddy slope respectively. The spatial distribution of the facies associations and the palaeocurrent analysis allow to interpret a depositional model for the Andatza Conglomerates consisting of an L-shaped, coarse-grained turbidite system, whose morphology was structurally controlled by synsedimentary basement-involved normal faults. The coarse-grained character of the turbidite system indicates the proximity of the source area, with the presence of a narrow shelf that fed the turbidite canyon from the north.
[es]En este trabajo se describe la estratigrafía y sedimentología de la Formación Conglomerados de Andatza. Mediante el análisis de facies se han interpretado tres asociaciones de facies principales correspondientes a un sistema turbidítico (de grano grueso) y al talud: un sistema turbidítico interno (o cañón), un talud fangoso de alto gradiente y otro de bajo gradiente. La distribución cartográfica de las asociaciones de facies junto con el análisis de paleocorrientes describen un modelo sedimentario de sistema turbidítico de grano grueso en forma de “L” para los Conglomerados de Andatza, cuya morfología fue controlada por fallas normales sinsedimentarias de basamento. El carácter grosero del tamaño de grano de este sistema turbidítico indica la proximidad del área fuente de los conglomerados, que alimentaría el cañón turbidítico desde el norte a través de una estrecha plataforma marina.
[en] Hydroxypropyl starch derivatives were prepared from pigeon pea starch (NPPS) which is an unconventional starch source. Functional parameters and characterization of both native and modified starches were carried out. The starch granules appeared oval or elliptical in shape with sizes ranging from 7 - 40 μm in width and 10 . 30 μm in length. Hydroxypropylation did not alter the shape of the starch granules in a pronounced way. Generally, the x-ray diffractograms of both native and hydroxypropyl derivatives showed the 'C' pattern. However, slight reductions were observed in the intensity of starches after modification. At all temperatures studied (30 - 90 deg. C), swelling and solubility of hydroxypropylated starches were higher than the NPPS. Progressive increases in swelling capacity and solubility were observed as the MS increased among the hydroxypropylated starches. Hydroxypropylation reduced starch paste turbidity on storage. Also, studies showed that syneresis reduced after hydroxypropylation. In addition, syneresis reduced as the MS of the hydroxypropyl starches increased. The results indicate that pasting temperature and peak temperature reduced after modification but peak viscosity increased in hydroxypropylated starch derivatives compared with the native starch. Setback reduced in hydroxypropylated starches compared with the native starch. Enthalpy of gelatinization and percentage retrogradation reduced after hydroxypropylation and progressive reductions were observed as the MS increased among the starch derivatives. Hydroxypropylation increased enzymatic digestibility. (author)
[en] Measurements of direct solar radiation intensity, using an Angstrom compensation pyrheliometer carried out over three harmattan seasons (1985-1987) at Ile-Ife (7.29N, 4.34E) Nigeria, have been used to determine atmospheric turbidity based on five different models of turbidity, viz: Schuepp (B), Angstrom (β), Kastrov (C), Unsworth (τa) and Linke (T). The five parameters indicate high aerosol loading of the atmosphere during the period and high correlation is established between them: (0.919 ≤ τ ≤ 0.999). An inverse relationship has been noticed between horizontal visibility and atmospheric turbidity: (-0.80 ≤ τ ≤ -0.76). (author). 35 refs, 15 figs, 4 tabs
[en] The pool (3mx6mx10m) in Irradiated Materials Examination Facility is generally used for the purpose of taking the specimen out of cask loaded into the pool, and carrying in/out the specimen to/from the hot cell. Always, it must be cared for the water into the pool to be fine condition because all operation are worked with the naked eye during taking an irradiated materials out of the cask and plunging - 2 - them in the bucket-elevator. In the aspects of the radioactive contamination control, remained substances in the water must be controlled so that the amount of substances are to be lower than the standard amount prescribed by RCA Korea Activity in a part of radioactive contamination control. This paper describes a behavior of the quality of water and the radioactive contamination of pool water for working of pool water purging system and contamination diffusion distribution behavior of each specimens carried in/out
[en] In this work, the fundamental study of on-line monitoring of SiO_2 particles in the size range of 40 nm to 725 nm was carried out using turbidimetry. The size of particle was measured using a field emission scanning electron microscope (FE-SEM). The factors affecting on the turbidity were discussed, for example, wavelength, size, and concentration. In order to observe the dependence of turbidity on the wavelength, a turbidimetric system equipped with charged coupled detector (CCD) was built. The shape of the transmitted peak was changed and the peak maximum was shifted to the red when the concentration of particle was increased. This result indicates that the turbidity is related to the wavelength, which corresponds to the characteristic of the Mie extinction coefficient, Q, that is a function of not only particle diameter and refractive index but also wavelength. It is clear that a linear calibration curve for each particle in different size can be obtained at an optimized wavelength