Leaching of zinc sulfide concentrate from the ganesh-himal deposit of nepal

The leaching of zinc concentrate obtained from the zinc ore located in the Ganesh-Himal region of Nepal has been carried out in the presence of ammonium persulfate (APS) as an oxidant. Leaching variables such as time, temperature, acid, and oxidant concentration, E _h , and particle size of sphalerite concentrate were studied to optimize the condition and to understand the mechanism of the reaction. The zinc extraction increased up to a temperature of 333 K and a further rise in the temperature to 343 K resulted in lowering of metal extraction. A decrease in particle size and increase in oxidant concentration enhanced the dissolution rate of zinc. The leaching data best fitted to the mixed controlled kinetic model. An activation energy of 43 kJ/mol was obtained for the dissolution of zinc in the temperature range 303 to 333 K with APS. The leaching mechanism was further established by characterizing the original concentrate and the leach residue by X-ray diffraction (XRD) phase identification and scanning electron microscopy (SEM) studies.     

Stormwater reuse: designing biofiltration systems for reliable treatment.

Stormwater reuse is increasing in popularity as a technique for overcoming water shortages in urban Australia. However, technology for the reliable treatment of stormwater for reuse is still not fully developed. This paper presents the first steps in refining biofilters for stormwater reuse. Six different filter media were selected, to target specific stormwater pollutants, as well as support plant growth. They were tested in the laboratory, where the filters were dosed three times per week with semi-synthetic stormwater for five weeks. Pollutant removal performance was monitored, and revealed that all soil-based filters performed similarly (while sand filters behaved somewhat differently). All filters removed more than 80% of solids and greater than 90% of lead, copper, and zinc. Three filter types were able to remove some phosphorus (particularly in the top 30 cm of the media). Apart from sand, all filter media were net producers of nitrogen, leading to an important conclusion that non-vegetated, soil-based filters are not suitable for targeting nutrients. However, since heavy metals are the primary pollutant of concern with respect to stormwater reuse for irrigation (the most popular end-use), it was concluded that biofilters may be promising technologies for treatment of stormwater for reuse.     

Off flavours in large waterbodies: physics, chemistry and biology in synchrony.

The Laurentian Great Lakes of North America are a drinking water source for millions of Canadian and US consumers. These waterbodies have undergone extensive change over the past century as a result of widespread degradation and remediation. Many of the Lakes are prone to taste and odour (T&O), and although these outbreaks have been poorly monitored, evidence suggests that they are increasing in frequency. Tracing and controlling T&O in such large systems presents a challenging task, due to their physical size and complexity. This paper presents an overview of recent investigative and management approaches to T&O in Lake Ontario and its outflow, the St. Lawrence River. We have identified three distinct patterns of T&O in these source-waters, caused by geosmin and 2-methylisoborneol and differing in their planktonic and benthic sources, and temporal and spatial dynamics. Each pattern has required a different approach by scientists and management, in partnership with the water industry. We have shown these T&O outbreaks are caused and moderated by physical, chemical and biological mechanisms over a spectrum of spatial and temporal scales. Canadian municipalities affected by these outbreaks have been key to the investigation of the links between T&O and ecosystem processes with the aim to develop more proactive water treatment and long-term management.     

Computer-aided design: a case of strategy in implementing a newtechnology

In this case study the introduction of computer-aided design (CAD) in an engineering company was analyzed. The process of change as well as repercussions of the new technology on work organization and communication patterns within the company were studied. The designers has received the new technology favorably and were even impatient about the pace of change. As the development of the system was limited to a small group close to the design management, the introduction had less than desirable effects on the work situation of the designers and on the cooperation with other functions that was envisaged in the planned CAD/CAM step. The study confirms that CAD, as such, will have little effect on a bureaucratic organization unless such a change is included as an explicit objective. For a full utilization of any new technology a joint forum for outlining a strategy is needed     

Physiological and pathological factors influencing bovine alpha-lactalbumin and beta-lactoglobulin concentrations in milk

Bovine alpha-lactalbumin and beta-lactoglobulin concentrations were determined by radial immunodiffusion in 354 milk samples from uninfected and 98 samples from infected quarters from 42 Holstein-Friesian cows taken at 30, 150, and 270 days of lactation. alpha-Lactalbumin and beta-lactoglobulin concentrations were not affected by quarter location. The alpha-lactalbumin decreased at the end of lactation and in samples collected beyond second lactation. The beta-lactoglobulin concentration increased with stage of lactation. There was a positive correlation between alpha-lactalbumin and beta lactoglobulin (r = .12). Milk from uninfected quarters had mean alpha-lactalbumin and beta-lactoglobulin concentrations of 1.47 and 4.6 mg/ml, respectively. Milk from quarters infected by major pathogens or Corynebacterium bovis had less alpha-lactalbumin. Milk from quarters infected by minor pathogens had less beta-lactoglobulin. There was a negative correlation between alpha-lactalbumin concentration and somatic cell count (r = .31), which was amplified by infection status of quarters. No correlation was noted between somatic cell count and beta-lactoglobulin concentration when considered over the whole sampling period, but the correlation became negative in quarters infected by major pathogens.     

StoryGrid [educational computing]

The StoryGrid project undertook studying the role new interface technologies might play in education, particularly at the high school level. Unfortunately, technology often seizes center stage in high school classrooms; i.e., it becomes the topic of instruction. We believe that learning about technology would be most successful when technology is not the topic, but simply a tool used during instruction. StoryGrid, therefore, was designed to support and to enhance existing narrative activity in classrooms by adhering to the following goals: trigger reflection and interpretation, accommodate individual expression and encourage student discourse.     

Modeling phosphorus in the upper Etowah River basin: identifying sources under uncertainty.

The Uniform Covering by Probabilistic Rejection (UCPR) algorithm was used, in conjunction with the Soil and Water Assessment Tool (SWAT) model, to identify P loads from point source and nonpoint source polluters in the upper Etowah River basin (UERB) in Georgia. The key findings of the research are as follows. The mean absolute error was preferred over the root mean square error as a search criterion for the UCPR algorithm when water quality observations are scarce. The undocumented P load from point sources in the UERB was consistently estimated as about 43 kg/d by the proposed method; but the method was not able to identify the broiler litter application rate to the poultry/beef operation pastures. Point sources (both documented and undocumented), poultry/beef operation pastures, and forests are the three major contributors of P. During 1992-1996, on average they accounted for 36.4, 31.7, and 17.2% of P load from the UERB, respectively.     

Acid-base interaction of the components in sodium-borosilicate glasses

The effect of the coordination groups of boron, aluminum, and silicon on the acid-base properties of the glass mass and the change in the redox state of copper in boron-containing melts are studied. Indicators are proposed for evaluating the redox potential of the glass mass. The acid-base properties of commercial alkali-alumoborosilicate glasses are compared using these indicators. __________ Translated from Steklo i Keramika, No. 7, pp. 3–7, July, 2007.     

Nonlinear self-guiding and switching in an all-fiber device

We study the nonlinear propagation of light in optical fibers in the strong nonlinearity limit. In this limit, the transverse guiding properties are altered and cannot be decoupled from the longitudinal part of the wave equation. We consider a refractive index profile with no bound modes at low intensities and show that stable self-guiding occurs at a critical intensity. This critical intensity is a property of the guide and can be made much lower than the threshold for unstable self-focusing. We consider a particular design for which self-guiding occurs at three orders of magnitude lower than the self-focusing threshold.