INVOLVEMENT OF WALL COMPONENTS IN ADSORPTION OF SILICONE ANTIFOAM TO SACCHAROMYCES CEREVISIAE

The ability of Saccharomyces cerevisiae NCYC 366 to adsorb polydimethylsiloxane (PDS), dispersed in an aqueous emulsion containing stearate emulsifiers and cellulose-based thickeners, is diminished after treatment with trypsin, KOH and HF; treatment with β-glucanase initially caused an increase in binding which diminished on prolonged incubation. Trypsin and KOH removed most of the mannan, protein and phosphorus from isolated walls, while exposure to β-glucanase removed about half of the glucan, protein and phosphorus. HF treatment removed most of the phosphorus but had little effect on the contents of other wall components. Cells treated with trypsin or β-glucanase had pH-mobility curves similar to those of untreated cells. Those treated with KOH or HF had lower mobilities at all pH values. Treatment of cells with each of the reagents except β-glucanase lowered their capacity to bind fluorescein-labelled antibody. The ability of cells to bind fluorescein-labelled concanavalin A was decreased only after trypsin and KOH treatment. Treatment of PDS-containing cells with trypsin, β-glucanase or KOH caused release of bound silicone, the effect being smallest with β-glucanase treatment. It is concluded that binding of PDS-containing antifoam to yeast mainly involves ionogenic groups in the wall phosphomannan-protein.     

节理产状对岩石单轴抗压强度的影响研究

运用岩石破坏过程分析RFPA^2D系统,采用控制变量法,分别研究了节理不同位置、方向和迹长对于岩石试件单轴抗压强度的影响。结果表明:试件节理位置对应值(裂纹尖端到受压面的距离)与抗压强度值有近似的线性关系;岩石试件中所含节理倾角不同时,试件的破坏模式不同,随着倾角的增大,试件的强度先降低随后增大;随着节理迹长与试件直径比值的增大,试件强度随之减小。数值模拟结果同物理试验结果相吻合,研究结果对于深入揭示断续节理岩石在单轴压缩下损伤破坏机制具有重要参考价值。     

Constitutive models describing the influence of the geometry of partially-spanning joints on jointed rock mass strength: Regression and fuzzy logic analysis of experimental data

Using existing experimental data from Uniaxial Compressive Strength (UCS) testing, constitutive models were produced to describe the influence of joint geometry (joint location, trace length and orientation) on the UCS of rock containing partially-spanning joints. Separate approaches were used to develop two models: a multivariable regression model, and a fuzzy inference system model. Comparison of model predictions to the experimental data demonstrates that both models are capable of accurately describing the UCS of jointed rock with partially-spanning joints using information relating to joint geometry. However, according to the statistical evaluation methods used for performance evaluation, the multivariable regression model was significantly more accurate. Analysis of predictions made by the fuzzy inference system model showed that it was capable of resolving certain peculiarities in the influence of partially-spanning joint orientation on the compressive strength of rock that, from rock mechanics and fracture mechanics theory, should be expected. The multivariable regression model, whilst more accurate, did not recognise these peculiarities. Due to the additional insight that can be gleaned from the fuzzy inference system modelling, we recommend the use of the fuzzy inference system constitutive model in combination with the multivariable regression model.     

Assessment of nutritional status of children under five years of age, pregnant women, and lactating women living in relief camps after the tsunami in Sri Lanka

BACKGROUND: A strong earthquake that hit Aceh on December 26, 2004, triggered a powerful tsunami, resulting in an unprecedented catastrophe in Sri Lanka. The initial phase of the disaster was marked by limited access to food coupled with an inadequate supply of safe water and poor environmental hygiene and sanitation, all of which placed children at increased risk for undernutrition. OBJECTIVE: To assess the nutritional status of children under five years of age, pregnant women, and lactating women residing in 40 relief camps after the tsunami. METHODS: A cross-sectional, 30-cluster study was performed. Thirty children under five from each cluster (camp) and all pregnant and lactating women in selected camps were studied. Data were collected by interviews with the primary caregivers of the children, interviews with key informants in the camps, direct observation, and focus group discussions with mothers. Weight, height, or length was measured on children and pregnant women. Mid-upper-arm circumference of lactating women was measured. RESULTS: A total of 878 children were assessed, of whom 16.1%, 20.2%, and 34.7% were wasted, stunted, and underweight, respectively. The prevalence of each indicator was higher in boys than in girls. During the 2 weeks before the survey, 69.5% of the children had acute respiratory tract infections and 17.9% had diarrhea. Although the general food distribution was well in place, the food supply lacked diversity, and 70.9% of the children did not get appropriate supplementary food. The prevalence of undernutrition among pregnant women (n = 168) was 37%. Thirty-one percent of lactating women (n = 97) were underweight, and 20% were overweight. CONCLUSIONS: The prevalence of both acute and chronic undernutrition among children in the camps is significantly higher than the national Sri Lankan average. There is a need to establish nutritional surveillance systems to monitor the nutritional status of displaced and nondisplaced children and mothers.     

Prevalence of challenging nutritional problems among adolescents in Sri Lanka

BACKGROUND: Although 21% of the population of Sri Lanka consists of adolescents, studies of nutritional status among this group are limited. OBJECTIVE: To assess nutritional problems and dietary and activity patterns among adolescents in Sri Lanka. METHODS: A nationally representative cross-sectional study was conducted on 6,264 adolescents 10 to 15 years of age. All subjects were clinically examined for Bitot's spots, and their weights and heights were measured. The subjects were interviewed during regular class time. Hemoglobin concentration and dietary and activity patterns were assessed among a subsample (n = 787) of 1,521 adolescents. The World Health Organization age- and sex-specific references for body-mass index and height-for-age were used to estimate the prevalence of underweight and stunting, respectively. The International Obesity Task Force age- and sex-specific reference for body-mass index was used to estimate the prevalence of overweight. Age-specific WHO-defined cut off points were used to estimate the prevalence of anemia. RESULTS: The prevalence rates of underweight, stunting, and overweight were 47.2%, 28.5%, and 2.2%, respectively. The prevalence rates of anemia and vitamin A deficiency were 11.1% and 0.4%, respectively. During the previous 6 months, 10.4% of the subjects had usually not eaten breakfast before going to school. During the week before the interview, 24.4% of the children had not consumed green leafy vegetables, 26.6% had not consumed fruit, 19.0% had not participated in physical activities, and 27.5% had watched television for more than 2 hours per day. CONCLUSIONS: The nutritional problems of adolescents aged 10 to 15 years should be addressed through the schools. Specific policies should be developed in collaboration with the Ministry of Health and Education to control nutritional problems among adolescents.     

Case Study: Model to Simulate Regional Flow in South Florida

South Florida has a complex regional hydrologic system that consists of thousands of miles of networked canals, sloughs, highly pervious aquifers, open areas subjected to overland flow and sheet flow, agricultural areas and rapidly growing urban areas. This region faces equally complex problems related to water supply, flood control, and water quality management. Advanced computational methods and super fast computers alone have limited success in solving modern day problems such as these because the challenge is to model the complexity of the hydrologic system, while maintaining computational efficiency and acceptable levels of numerical errors. A new, physically based hydrologic model for South Florida called the regional simulation model (RSM) is presented here. The RSM is based on object oriented design methods, advanced computational techniques, extensible markup language, and geographic information system. The RSM uses a finite volume method to simulate two-dimensional (2D) surface and groundwater flow. It is capable of working with unstructured triangular and rectangular mesh discretizations. The discretized control volumes for 2D flow, canal flow and lake flow are treated as abstract “water bodies” that are connected by abstract “water movers.” The numerical procedure is designed to work with these and many other abstractions. An object oriented code design is used to provide robust and highly extensible software architecture. A weighted implicit numerical method is used to keep the model fully integrated and stable. A limited error analysis was carried out and the results were compared with analytical error estimates. The paper describes an application of the model to the L-8 basin in South Florida and the strength of this approach in developing models over complex areas.     

Miscibility,melting, and crystallization behavior of poly(hydroxybutyrate) and poly(D,L‐lactic acid) blends

Melting behavior and crystal morphology of poly(3‐hydroxybutyrate)‐poly(D ,L ‐lactic acid) (PHB‐RPLA) blends with various compositions have been investigated by modulated temperature differential scanning calorimetry (mt‐DSC), polarized optical thermomicroscopy (POTM), modulated force thermomechanometry (mf‐TM), and small angle X‐ray scattering (SAXS). Thermal properties were investigated after fast cooling crystallization treatment. Multiple melting peak behavior was observed for all polymers. mt‐DSC data revealed that PHB‐RPLA blends undergo melting‐recrystallization‐remelting during heating, as evidenced by exothermic peaks in the nonreversing heat capacity. A decrease in degree of crystallinity due to significant melt‐recrystallization was observed for blends. PHB‐RPLA showed different crystal morphologies for various compositions. POTM results showed that the crystallization rates and sizes of spherulites were significantly reduced as RPLA content increased. mf‐TM results confirmed miscibility of these two polymers. SAXS data provided evidence of lamella thickness of blends, which increased with increasing RPLA content. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Modification of Canal Flow due to Stream-Aquifer Interaction

Unsteady canal flow in an integrated canal-flow–groundwater-flow system is analyzed by solving the coupled equations governing canal flow, groundwater flow and the seepage between them. Analytical solutions are obtained for the coupled system for small water-level disturbances using Fourier analysis methods and complex variables. Dimensionless parameter groups characterizing the aquifer, the canal, and the sediment layer are identified using the governing equations and the solution. The influence in the aquifer and the semipermeable bottom sediment layer due to disturbances in canal flow is studied. The analytical solutions are compared to numerical solutions obtained using the MODFLOW model and the Hydrologic Simulation Engine of the South Florida Regional Simulation Model. Results of the analysis are useful in determining the range of aquifer, sediment, and canal characteristics for which stream-aquifer interaction is important. The results can be used to determine the conditions for which the canal is hydraulically disconnected from the aquifer because of the sediment layer. The analytical solution is useful to understand the propagation characteristics of small-amplitude water-level disturbances in the canal and the aquifer. The characteristics studied include the amplitude decay constant and the speed. The solution can be used to design benchmark problems that can be used to evaluate integrated canal-flow–groundwater-flow models. The results of the study can be used to estimate the space and time steps needed in the canal and the aquifer when simulating stream-aquifer interaction.