Experimental Results of a Cost-Effective Ozone Generator for Water Treatment in Colombia

Obtaining high-quality cost-effective water, minimizing the public health risk generated by pathogenic elements or disinfection sub-products such as trihalomethane and/or chlorophenol, has made necessary the use of technologies different to chlorination. In this paper, we present the implementation of a high-voltage, high-frequency flyback inverter to generate ozone, and outline the main characteristics and uses of a prototype of water ozonation from a well for a hospital in Colombia. With the prototype, the ozone dose can be adjusted through the duty cycle modulation; switching was done with a Mosfet and the voltage signal was increased with a ferrite technology transformer. The source is characterized by its simplicity, good performance and low cost.     

NaOH Regeneration of Pb and Phenol-Laden Activated Carbon. I. Batch Study Results

Abstract

Granular activated carbon (GAC) has been used to remove organics and metals simultaneously from wastewaters (4). For a regeneration procedure to be effective on GAC containing both metals and organics, it must remove both the metals and organic compounds. In this study, GAC saturated with Pb and phenol was regenerated using an NaOH rinse in batch mode. Four variables were investigated: 1) regenerant concentration (0, 0.1, and 1.0 N), 2) regenerant to carbon mass ratio (5:1 and 10:1), 3) regenerant temperature (22 and 80°C), and 4) regeneration time (0.33, 1, 3, 7, and 21 days). Maximum regenerations of 47% for Pb and 48% for phenol were observed. The 1.0 N NaOH regenerated a higher percentage of both Pb and phenol when compared to the other regenerants. The 10:1 regenerant to carbon ratio resulted in increased regeneration over the 5:1 regenerations. Pb regeneration was slightly higher at 80°C than at 22°C whereas phenol regeneration was slightly lower at 80°C than at 22°C. Maximum regenerations for both Pb and phenol were observed within the first day of regeneration, in most cases within the first 8 hours.     

Modeling of Shallow Fluidized Bed Reactors: I. analytic solution of a simplified model

A fairly general dynamic model for shallow fluidized bed reactors is developed, and analytic solutions for the governing equations of the model are obtained after some simplification. The bubble size, the lateral dispersion coefficient of solids, the level of the excess fluid reactant and the structure of the bed are examined to determine their effects on the conversion of solids. It has been shown that the conversion of solids is influenced profoundly by the bubble size and that it is advantageous to employ a shallow fluidized bed reactor if a high conversion of solids is required.     

赤峰地区黄金开采及采矿方法研究

介绍了峰地区黄金矿山开采情况及采矿方法研究成果。     

Influence of breakfast on cognitive functions of children from an urban area in Valencia, Venezuela

It's well known that physical growth and intellectual activity is influenced by nutritional status. With the purpose of evaluate the fasting effects on the cognitive functions, anthropometric state and cognitive functions (logic and school work performance), under fasting and post-breakfast condition were assessed in a group of 68 school children age 9 and 10 years, who studied in a private school (1998-1999). Logic reasoning was measured with Raven test and attention, precision, velocity and fatigue with the Lepez test. The main of the children (80%) were well-nourished and 20% had showed overweight. At breakfast condition all subjects were over 50 percentil for Raven test. Consumption of breakfast influence on logic reasoning (p < 0.001) and school work performance (p < 0.01). It is concluded that in these well nourished children, breakfast consumption improved cognitive performance.     

快速分析南方某城市污水处理厂污水BOD_5试验研究

研究了南方某城市污水处理厂不同处理节点污水在不同过滤情况下的三维荧光特性,评估该污水处理厂运用荧光光谱法分析污水BOD5的可行性。结果表明,该城市污水处理厂进水中有机污染物主要是蛋白质类有机物等,对于未预处理及不同过滤情况下的污水样本,类色氨酸类有机物的特征峰荧光强度与BOD5的相关性更好(R2>0.8),说明可通过分析污水的类色氨酸特征峰荧光强度来获得该污水的BOD5情况。在开发BOD5现场荧光测试技术时,可采用类色氨酸特征峰T1(λ_(Ex/Em)=275/340 nm)作为测试通道的荧光信号。     

Surprising Results of a Study on the Plasticity in Strontium Titanate

Oxides such as SrTiO₃ are expected to fail via brittle fracture at low temperatures. Surprisingly, in the present study, SrTiO₃ single crystals could be plastically deformed in compression in two temperature ranges: from 78 K to ∼1050 K and from 1500 K to 1800 K. SrTiO₃ was brittle at temperatures between these two ranges (∼1050–1500 K). This phenomenon of a ductile–brittle–ductile transition, together with microstructural investigations, suggests that the role of dislocations in the plasticity of ceramics must be reconsidered.     

Measurement of interfacial area in a packed column by the sulfite oxidation method. Comparison with the wetted area

Interfacial area of a column packed with Raschig rings, 10 mm in diameter, is measured by the classical sulfite oxidation method. It is shown that the column behaves as a recycle differential reactor. Values of the interfacial area are compared, on the one hand with those obtained by Vidwans and Sharma under similar conditions, on the other hand with the results previously obtained by ourselves on the same packing by wetted area measurements. Good agreement is observed in either case.     

Prevalence of nutritional anemia in women of reproductive age. Costa Rica. National nutrition survey, 1996

In 1996, The Ministry of Health and Inciensa conducted the latest National Nutrition Survey, to provide support and guidance to the national policies, plans and programs in the field of food and nutrition. The present paper reports the results for the prevalence of anemia estimated in a total of 884 women of reproductive age, in three areas: metropolitan area, other urban areas and rural areas. Anemia was determined through measurements of hemoglobin, plasma ferritin and plasma folates. In addition, hemoglobin patterns were determined by electrophoresis. The cutt-off points used were those recommended by the WHO. Anemia was present in 18.6% of the women. Severe to moderate deficiency of iron (< 12 ng/dl) and of folates (< 6 ng/dl) were found in 43.2 and 24.7% of women respectively, with statistically significant differences by area of residence. The magnitude of the problem for anemia can be classified as mild, for iron deficiency as severe, and for folate deficiency as moderate. In conclusion, Anemia represents a public health problem for Costa Rica that has remained constant throughout the last decade. In women of reproductive age, iron deficiency is the main cause of Anemia, followed by folates deficiency, and in a small percentage hemoglobinopathies. Intestinal parasites are not longer a mayor cause of Anemia. Prevalence of Anemia is influenced by place of residence, but not by age. In summary, despite the favorable health conditions present in Costa Rica, the prevalence of Anemia and of iron deficiency are similar to those of the Latin-American region. To improve this situation, public health interventions are necessary.     

Mineral nutrition of slash pine in subtropical australia. I. stand growth response to fertilization

Fertilization at plantation establishment and later age is often required to maximize stand growth of slash pine (Pinus elliottii) in subtropical Australia. A field experiment was conducted to examine stand growth response of slash pine in the first 11.5 years of plantation following (1) initial fertilization at plantation establishment with phosphorus (P) at 11, 22, 45 and 90 kg P ha^–1 which were either banded or broadcast in the presence or absence of basal fertilizers containing 50 kg nitrogen (N) ha^–1, 50 kg potassium (K) ha^–1 and 5 kg copper (Cu) ha^–1 and (2) additional application of 40 kg P ha^–1 at age 10 years.The initial P fertilization significantly increased the stand growth in the first 9.6 years. The P banded application was more effective in improving the stand growth than the P broadcast application. Application of the N, K and Cu basal fertilizers did not affect the stand growth. Overall, 53–73% of the variation in basal area and volume growth in the first 9.6 years was explained by the initial P fertilization, indicating that P deficiency was the major factor limiting the stand growth under the experimental conditions. Optimum plantation age, at which the maximum periodical annual increment (PAI) of basal area was obtained, increased from age 10.9 to 12 years when the initial P rate increased from 11 to 90 kg P ha^–1. Application of additional 40 kg P ha^–1 at age 10 years resulted in a further improvement in the stand growth at age 11.5 years. With 66% of the variation in basal area PAI between ages 9.6 and 11.5 years, 50% was explained by the initial P fertilization and 16% by the additional P applied at age 10 years. Similarly, 51% and 12% of the variation in volume PAI were attributed to the initial P fertilization and the additional P application, respectively. This highlights the need of refertilization with P on some established stands of slash pine at later ages.     

Experimental Results of Low Thermal Inertia Molding. I. Length of Filling

In injection molding, complete mold cavity filling is a design goal that has to be met 100% every time. Mold cavity filling is a complicated process which depends on many variables such as mold cavity surface temperature, injection pressure, injection speed, melt temperature, flow index of material being molded, etc. The aim of experimental investigation of the low thermal inertia molding (LTIM) [1] process is to demonstrate the feasibility of molding completely filled, thin parts at low injection pressure and injection speed without sacrificing part quality. The evaluation of the new molding concept consists of comparison of a conventionally molded thin rectangular part with an identical part molded by the LTIM process. The length of filling in the conventional cavity and in the LTIM cavity are compared at different injection pressures and injection speeds. The mold design, experimental procedure, and results of the molding are discussed in the following sections.     

Study of mixing in an axisymmetric coflowing liquid jet by coupling L.D.A. to an electrochemical method

Local and simultaneous velocity and concentration fluctuations were analysed in an axisymmetric jet of an aqueous electrolyte solution moving in a codirectional water stream. The determination of the convection velocity of the turbulent eddies as well as correlation between axial velocity and concentration fluctuations was made possible by coupling L.D.A. to an electrochemical technique. The influence of the ratio of the coflowing stream velocity to the jet exit velocity was investigated. The mean velocity and concentration profiles, the turbulence intensity, the integral length scales relative to axial velocity and concentration were also determined.     

Coalescence of an emulsion in a fibrous bed: Part I. Theory

A model of a fibrous bed coalescer is presented which relates the collision frequency between particles and fibers to the overall coalescence frequency. The model will predict the ratio of outlet to inlet particle number densities (Y) and takes into account the mean inlet particle size, mean fiber size, void fraction of the bed, superficial velocity through the bed, degree of bed saturation, and bed length. The ratio of outlet to inlet particle number density, in terms of these parameters, is given by \documentclass{article}\pagestyle{empty}\begin{document} \[Y = \exp \left\{{- \frac{{3(1 - \in)S(1 + d_{10} /d_f)}} {{4d_f (1 - S)}}\eta _e L} \right\} \] \end{document} where η is defined as the coalescence efficiency and varies between 0 and 1 with the fiber Reynolds number.     

Study on skin roughness caused by surfactants: I. A new method in vivo for evaluation of skin roughness

A simple and accurate method for evaluating skin roughness caused by surfactants has been developed. The intensities of the roughness have been correlated with the chemical structures of surfactants by using this method. Results indicated in general, that the surfactants having 12 carbons in their alkyl chain gave the skin more roughness than did those which had more or less than 12. The results obtained by this method were in good agreement with those from the immersion method usually used.     

大肠杆菌氨基酰化酶工程菌的固定化研究

分别以聚乙烯醇(PVA)、海藻酸钠(SA)及PVA-SA为固定化载体对大肠杆菌氨基酰化酶工程菌进行固定。结果表明,PVA-SA固定化凝胶颗粒具有较好的机械强度和稳定性。确定PVA-SA的最佳包埋条件如下:PVA质量分数为8%、SA质量分数为1%、固定剂为pH值6.7的3%硼酸-1%氯化钙,此条件下制备的固定化细胞的酶回收率为91.46%。固定化细胞于4℃保存7 d、再室温保存14 d后,其酶活力为初始对照的90.76%,而游离细胞只有初始对照的29.69%。     

结晶紫合成工艺研究

阐述了碱性染料结晶紫,即Ｃ．Ｉ．ＢａｓｉｃＶｉｏｌｅｔ３的合成工艺,选用了催化氧化工艺路线,成功地完成了工业规模的制备。