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51.
In recent years the presence of haloforms has been observed by some researchers in waters of various origins.The aim of this study is to determine the conditions in which chloroform is formed by chlorination of aqueous solutions of some organic compounds.The first part of this work was carried out by chlorination of synthetic basic solutions of acetone and thus enabled us to determine the reagent concentrations needed to obtain the maximum quantity of chloroform.We studied next the effect of chlorination on organic material solutions (humic acids and phenols), in the course of an oxidation treatment; the results obtained by chlorination of aqueous solutions of humic substances show that the quantity of chloroform produced passes through a maximum value which depends on the time of ozonisation. Similar results were obtained for the chlorination of phenol solutions during oxidation by the u.v. + H2O2 system. These results may be explained by the partial degradation of the molecules which leads in the formation of reactional intermediate precursors of the haloform reaction. We undertook at the same time the study of a rapid test allowing us to detect the presence of haloform reaction precursors in a certain sample of water.  相似文献   
52.
In this paper experiments are described in a bio-disc pilot plant. A new method has been developed for a reproducible measurement of the thickness of the waterfilm on the rotating discs. The results were used to calculate the oxygen transfer coefficient into water (KL). The values of KL, calculated in this way, appeared to be considerably higher than experimental KL-values, which is mainly due to the fact that the water layer on the rotating disc is outdistanced by the disc. This effect has not been taken into account in the literature so far.  相似文献   
53.
Conclusions 1. In engineering-geologic explorations, it is necessary to investigate the engineering-geologic morphology to a depth of 15–18 m: lenses and interlayers of weak soils - unevenly compacted silty-sand fills, peat, slime, etc.2. Open unwatering of pits in the vicinity (10–15 m) of existing structures is impermissible, since it leads to removal of fine soil fractions because of piping, and to large and impermissible deformations of the load-bearing elements of the structures. In such cases, deep groundwater lowering by means of wellpoints should be used.In the case described in this article, the industrial structure underwent a mean settlement of about 20 cm, a tilt of 0.015, and a wall deflection of 0.002. By using deep groundwater lowering, such deformations could have been prevented.3. The development of settlements with time was due to the presence of weak soils - peat lenses and thin slime interlayers - in the foundation bed of the shop.4. An effective means for stopping the settlement of the industrial structure was the construction, under the walls, of two rows of cast-in-place piles with cantilever beams to which the wall loads were transmitted.Scientific-Research Institute of Foundations. GIPROLESKhIM. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 5–7, January–February, 1975.  相似文献   
54.
A short-term study of a commercially-available physical—chemical waste treatment plant is reported. Results indicate that an excellent quality of effluent can be consistently obtained despite wide fluctuations of influent wastewater characteristics. Physical, chemical, and biological parameters were monitored. The short-term data obtained offer some evidence of superior treatment efficiency in terms of COD, color, turbidity, and phosphorus removals when compared to more conventional treatment methods.  相似文献   
55.
Bacterial epiphytes on the surface of the fresh-water plant Alisma plantago-aquatica collected from a polluted river were found to be a major factor in contributing to the total metal concentrations of the plant. The removal of epiphytes from the leaf surface resulted in significant reductions in the concentrations of Cr (reduced by 15–50%), Cu (30–35%), Fe, Pb, and Zn (10–50%). While numbers of epiphytes and concentrations of heavy metals increased in samples collected from polluted water compared with from unpolluted water, the fraction of metals held by the epiphytes appeared to remain similar for all samples.  相似文献   
56.
Book reviews     
The Annals of Regional Science -  相似文献   
57.
The introduction of ionic additives, such as KCN, or acidic comonomer units, such as methacrylic acid, which change the nature of the mechanism of nitrile oligomerization reaction from radical to ionic and cause its initiation at lower temperature, allows the level of obscurity and the total amount of smoke production, both in smouldering and flaming conditions to be decreased. An opposite result is obtained if diphenylpicrylhydrayl (DPPH) radicals in polyacrylonitrile is introduced; DPPH retards the initiation of the radical nitrile oligomerization reaction. The acrylonitrile-methacrylic acid copolymers have a limiting oxygen index, which increases with the methacrylic acid content. Owing to the increased amount of NH3 produced during pyrolysis, the copolymers have a swelling behavior during the combustion test.  相似文献   
58.
Lin JL  Huang C  Chin CJ  Pan JR 《Water research》2008,42(17):4457-4466
The size and structure of flocs during floc formation were monitored for various coagulation mechanisms. Two distinctive mechanisms, namely, enmeshment and electrostatic patch, govern the dynamics of kaolin particles coagulation by polyaluminum chloride (PACl). They were investigated by small angle static light scattering (SASLS) and solid-state 27Al NMR. In addition, a novel wet SEM (WSEM) was used in-situ to image the morphology of the aggregate in aqueous solution. Synthetic suspended particles were coagulated by two PACl products, a commercial product (PACl) and one laboratory product (PACl-E). The PACl-E contained more than 60% Al13 while the PACl contained only 7% Al13, with large percentage of colloidal Al. For coagulation by PACl at neutral pH and high dosage where the strong repulsion between particles occurs, the enmeshment ruled by reaction-limited aggregation (RLA) results in larger sweep flocs as well as higher fractal dimensional structure. For coagulation by PACl-E at alkaline pH and low dosage, the flocs were coagulated predominately by electrostatic patch with Al13 aggregates. At such condition, it is likely that diffusion-limited aggregation (DLA) predominately rule PACl-E coagulation. The fractal dimension (Ds) values of PACl and PACl-E flocs formed at enmeshment and electrostatic patch increased with dosage, respectively. When breakage of flocs occurs, the breakage rate of PACl-E flocs is slower than that of sweep flocs. By WSEM imaging, the adsorption of spherical Al precipitates onto the particles was observed to form sweep flocs with a rough and ragged contour, while the PACl-E flocs were formed with a smooth and glossy structure.  相似文献   
59.
The intensive use of antimicrobial agents, mainly oxytetracycline, to prevent and control bacterial pathologies in Chilean salmon culture is a frequent practice. A total of 103 gram-negative oxytetracycline-resistant bacteria recovered from various sources of 4 Chilean freshwater salmon farms were identified and investigated for their susceptibility patterns to various antibacterial agents, by using an agar disk diffusion method. Antibacterial resistance patterns of isolates were not correlated with bacterial species or strain source. A high number of bacteria resistant to amoxicillin, ampicillin. erythromycin, and furazolidone, as well as an important frequency of bacterial resistance to florfenicol, chloramphenicol, cefotaxime and trimethoprim-sulfamethoxazole was found. On the contrary, the proportion of bacteria resistant to gentamicin, kanamycin, flumequine and enrofloxacin was rather low. Resistant microflora showed a high taxonomic variability and mainly consisted of non-fermenting bacteria (77.7%). These strains mainly belonged to the species Pseudomonas fluorescens (29), Aeromonas hydrophila (10), Stenotrophomonas maltophilia (6), isolated from salmon fingerlings, and Acinetobacter lwoffii (5) isolated from pelletized feed. The occurrence of simultaneous resistance to various antibacterials was frequent. We observe a high frequency of bacteria resistant to 6-10 antibacterials (74 strains), and antibiotic resistance index (ARI) values ranging from 0.38 to 0.48 for the four salmon farms studied. These results suggest that Chilean salmon farms might play a role as reservoirs of antibacterial multiresistant bacteria, thus prompting the necessity for a more restrictive attitude towards the intensive use of antibacterials in salmon farming.  相似文献   
60.
M. Chiba  N. Yamaki  J. Tani 《Thin》1984,2(3):265-284
Theoretical analyses are presented for the linear free vibration of a clamped-free cylindrical shell partially filled with an incompressible, inviscid liquid. For the vibration of the shell itself, the dynamic version of the Donnell equations was used and the problem was solved with the modified Galerkin procedure, taking the effect of the axisymmetric deformation due to the static liquid pressure into consideration. Concerning the vibration relevant to the liquid motion, the solution for the velocity potential was assumed as a sum of two sets of linear combinations of the suitable harmonic function, the unknown parameters of which were imposed to satisfy both boundary conditions along the wetted shell wall and the free liquid surface in a sense of appropriate series expansions. The procedure stated in the foregoing leads to a determinantal equation for the determination of the natural frequencies of the present shell-liquid system. To compare with the experimental results which will be stated in a companion paper,14 detailed numerical results will be presented in another companion paper13 on the free vibration characteristics of the two test cylinders partially filled with water.  相似文献   
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