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Multivariate statistical process control of platinum: a case of mining company in Shabani, Zimbabwe
No full textApplication of statistical methods in monitoring and control of industrial processes are generally
known as statistical process control (SPC). Since most of the modern day industrial processes
are multivariate in nature, multivariate statistical process control (MSPC), supplanted
univariate SPC techniques. MSPC techniques are not only significant for scholastic pursuit; it
has been addressing industrial problems in recent past. Monitoring and controlling a chemical
process is a challenging task because of their multivariate, highly correlated and non-linear
nature. In this paper, a series of techniques were applied. Time series plot was implemented to
determine the stationarity of the data. The Box-Jenkins methodology of model identification,
estimation and validation; was used to generate ARIMA models based on multiple non
sequential data. As a result, the residuals from ARIMA models have shown four attributes:
normally distributed, uncorrelated, independent and no autocorrelation between successive time
points. Two MSPC techniques; Multivariate Cumulative Sum (MCUSUM) and Multivariate
Exponentially Weighted Moving Average (MEWMA) were implemented as control charts for
monitoring residuals. All the charts indicate the out of control signals in the process, which were
believed to be from one or more variables combined together. The problem of which variable is
causing the out-of-control process and when is that out-of-control happening was alleviated
through the construction of individual Cumulative Sum (CUSUM) control charts. Elimination of
out-of-control signals resulted in a successful in control process shown in both MCUSUM and
MEWMA charts. Comparison between these two multivariate charts shows that MCUSUM is
more powerful in detecting smaller shifts than the MEWMA chart. Therefore, monitoring of
residuals provided a valuable proof-of-concept that validated the use of time series analysis in
conjunction with MSPC tools in modeling and monitoring the behaviour of industrial processes
Pesticide Induced Alterations On Cellular Parameters In On-Target Species And Their Potential Effects On Ecosystems: A Review.
No full textPresented at the "International Conference on Pesticide Use in Developing Countries" in October 2006.Pesticide use has been associated with threats to human and ecosystem health. Inhibition of nerve function is usually the target for insect and pest control. In non-target species, there may be a: variety of additional effects of the pesticides besides nerve inhibition. Several studies have shown that pesticide exposure can cause a number of effects at the cellular level causing physiological and other disturbances in organisms. Amongst others, these include the following; endocrine disruption, oxidative stress, altered enzyme function or gene regulation. These cellular and physiological effects in individual species/organisms can manifest at higher levels within an ecosystem. Thus, reproductive and behavioural effects in organisms at a single trophic level can affect profoundly the entire ecosystem health and balance. This paper will provide an overview of these possible effects as well as show examples where they have been shown or known to operate.ANCA
International Open Access Week Report 2011: National University of Science and Technology
No full textPresented after the International Open Access week at NUST from the 25th to the 27th of October 2011The International open access week at the National University of Science and Technology was marked by a series of activities at the main Library which is temporarily located in the Central Business District (CBD) and also at the main Campus of the University which is located 7 km from the CBD. This paper serves to give a detailed report of the proceedings of the Open Access week. The focus was on educating students on the open access movement and practically demonstrating the various open access resources available for respective faculties. Seminars focusing on the benefits of the NUST institutional repository were also organized for academic staff on the 25th and the 27th of October at the main Campus. Some of the activities were captured on picture in this report paper.National University of Science and Technology Library
Model Reference Adaptive Control System for Moisture Regulation in Cotton Ginning.
No full textPresented as part of the SAIIE25 Proceedings, 9th ? 11th of July 2013, Stellenbosch, South Africa ? 2013 SAIIE.Moisture content (mc) within the cotton fibre is an important aspect for all stages of
the ginning process. However due to the process dynamics, mc is currently being
controlled by regulating the water and air temperatures from the Humidifiers.
Human intervention and lack of consistence on set-points determination has resulted
in inconsistent mc during humidification. This procedure requires a control system
which will be able to adjust the process set-points automatically by eliminating the
need for human intervention. In this paper a robust Model Reference Adaptive
Control (MRAC) system for a Samuel Jackson Humidifier is presented. This system
improves upon the existing system by creating a closed loop controller with
parameters that can be updated to change the response from reference model. The
control parameters are then updated based on this error thus the parameters
converge to ideal values that cause the plant response to match the response of the
reference model
Species and Sex Related Differences in Antioxidant Enzymes in Fish Collected From Umguza and Auchmacoy Wright Dams, Bulawayo, Zimbabwe.
No full textPresented in October 2002.Agricultural and industrial activity results in the pollution of our environment by pesticides and metals usually causing deleterious effects on both humans and other animals in the environment. We are interested in the effects of pesticides and metals on non-human targets, such as fish, in the environment. Literature reports suggest that there are species and sex differences amongst fish in the metabolism of foreign compounds (xenobiotics) on the detoxifying enzymes of aquatic organisms. The aim of this study was to assess whether there are any species and sex differences in antioxidant enzyme activities of local fish. Catfish (Clarius gariepinus) and bream (Oreochromis mossambicus) collected from two dams, one polluted (Umguza) and one pristine (Auchmacoy Wright) in the Bulawayo area. Gills, liver and kidneys from captured (gill netted) fish were excised, homogenized and centrifuged to obtain S-9 fractions. The S-9 fraction was used to assay for activities of the antioxidant enzymes, catalase, glutathione peroxidase and DT- diaphorase. Significant sex-related differences in the activity of catalase in liver and gill but not in kidney of catfish collected from Umguza Dam were noted (Student t test, P< 0.05). No sex-related differences in catalase activity were observed in bream tissues collected from Umguza Dam. Catalase activity in female bream collected from Umguza Dam was/significantly higher when compared to female catfish catalase from the same dam. Glutathione peroxidase activity in catfish collected from Umguza Dam were Seen to be sex dependent in gill and liver but not in kidney (Student t test, P < 0.05) whilst species differences were noted only in liver, with higher activities in catfish. Umguza bream showed significant sex differences in glutathione peroxidase activity onfy in the gills. DT- diaphorase activity in catfish collected from Umguza Dam was shown to be sex dependent in gill and kidney but not in liver. In Umguza bream, DT-diaphorase activity was seen to be sex dependent only in gills. Species differences in DT-diaphorase activity were only seen when male catfish and male bream were compared. DT-diaphorase activity was shown to be significantly higher in male catfish compared to male bream but there were no differences in activity when female catfish were compared to female bream in all the tissues. For fish collected from Auchmacoy Wright Dam, significant differences in bream catalase activity was seen in all the three tissues studied. Species difference in catalase activity were noted in liver and gill but not in kidney. Significant sex differences in the activity of glutathione peroxidase were noted only in the kidneys of the bream. Species differences in glutathione peroxidase activity were noted only in the gills of female fish. No significant diffe.rences in DT-diaphorase activity either by sex or species were noted in all the tissues of fish collected from Auchmacoy Wright
Dam. Our data indicates that enzyme activity is species, sex and tissue dependent in fish and that enzyme activity is also affected by the presence of pollutants.Biochemistry and Molecular Biology Society of Zimbabw
Metal Levels and Antioxidant Enzyme Activities in Freshwater Snails Exposed to Sediments From Polluted and Pristine Dams in Zimbabwe
No full textPresented at the Fourth International Conference of the Society for Free Radical Research - Africa in October 2003.The aim of this study was to determine the metal and antioxidant enzyme activities (AGE's) in the freshwater snail Lymnaea natalensis, exposed to sediments form a polluted (Umguza) and pristine (Wright) dams around Bulawayo City, Zimbabwe with a view to developing a biomarker of freshwater pollution. Adult lab reared snails (10-15 mm) were exposed for 4 weeks to water and sediment cofiected from 4 different sites of Umguza Dam (a sink of domestic and industrial effluent) and Wright Dam (privately owned -and considered to be relatively pristine). Antioxidant.
enzymes, heavy metals and malondia1dehyde (MDA) analyses were performed using the S-9 fraction of whole snail soft tissue. Catalase and glutathione peroxidase activities were significantly elevated in snails exposed to Umguza Dam water and sediment (Student t-test, p < 0.01 and p < 0.001) when compared to snails exposed to Wright Dam. DT- diaphorase activity was significantly reduced in snails exposed to Umguza Dam water and sediment (p < 0.001) when compared to snails exposed to Wright Dam water and sediment. Snails exposed to Umguza Dam water and
sediment bad a higher total metal load compared to those exposed to Wright Dam elements and the MDA levels were correspondingly elevated in snails exposed to polluted water and sediment (p < 0.01). The higher MDA levels and altered AGE activities suggest that the snails exposed to Umguza Dam elements are under higher oxidative stress.SFR
Thionphosphate Inhibition Of Esterase Activity In Freshwater Snail Hellsoma Duryi
No full textA paper covering Thionphosphate inhibition of esterase activity in freshwater snails.Organophosphorus insecticides (OP's) are among the most commonly used pesticides in most African countries. These compounds are esters, amides or thiol derivatives of either phosphoric acid or thiophosphoric acids. The majority now in use such as azinphos methyl, chlorpyrifos, pirimiphos methyl and malathion contain the thiono moiety (=8) for (=0) on the phosphorus atom which increases the toxicity of the insecticide. There are six different chemical classes of OPls namely orthophosphates, thionphosphates, thiolphosphates, dithiophosphates, phosphonates and pyrophosphoramides (Hassall, 1990). When used in the vicinity of aquatic ecosystems the insecticides may enter in water bodies as a result of erosion and leaching in concentrations that I may affect non-target species such as fish and snails. Also the diversity in chemical structure of OP's that exist, results in variability in their toxicity. There is a need therefore to constantly monitor effects of these organic compounds on non-target organisms: The effects'of pirimiphos methyl, a thionphosphate on esterase activity in a freshwater snail Helisoma duryi was investigated with the aim of assessing its potential as a bioindicator of presence of OP's in water. Juvenile snails reared outdoors were exposed to pirimiphos methyl in either Matopos (pristi':le) dam water or Umguza (highly contaminated with industrial waste) dam water for 1, 7, or 14 days: Esterase activity determined in post mitochondrial supernatants was significantly depressed in',a dose dependent manner. Carboxylesterase activity measured using a-naphthyl acetate and'lpnitrophenyl acetate was reduced in the range (6-90 %) and (18-79 %) respectively while cholinesterase measured using acetylthiocholine iodide was inhibited in the range (19-85 %) depending on the water source. A decrease with time in degree of inhibition of esterase activity was also observed, suggesting a recovery with time of the snails from pesticide poisoning. This recovery of the snails was probably due to both natural and microbial decomposition of the pesticides with time. It's also possible that newly synthesized esterases replaced the inhibited ones. On comparing data from the two dams, higher inhibitions were observed in snails exposed
to Matopos dam water than those exposed to Umguza dam water. Probably the higher microbial load in the contaminated Umguza dam resulted in increased pesticide decomposition and hence reduced inhibition of the snails in those waters whel} compared to those snails in Matopos, a pristine dam. Our results have shown that esterase activity altered by up to 90% is sensitive, to presence of pesticide pollutants and hence has a potential as a bio-indicator for detecting organophosphate pollution in water samples
Esterases And Antioxidant Enzymes Of The Cotton Pests Helicovepa Armigera And Diparopsis Castanea
No full textPresented at the 10th International Congress on the Chemistry of Crop Protection in 2002.Helicoverpa armigera and Diparopsis castanea are pests of economic importance in a number of crops, such as cotton, in Zimbabwe. The excessive use of insecticides such as organophosphates
and pyrethroids, in the control of H. armigera has subjected it to high selection pressure. Many detoxifying enzymes of insects are thought to be responsible for insecticide resistance. The
enzymes include the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), OTdiaphorase (OTO) as well as the glutathione S-transferases (GST) and esterases (EST). This study was aimed at measuring these enzyme activities in H. armigera collected from two geographical sites in Zimbabwe. The effect of diet (natural vs artificial) and age (instar) on the activities was also determined. A comparison was also made between the enzyme activities in H. armigera and O. castanea in samples collected from the same geographical area. Whole insects were homogenised in buffer and the homogenate was centrifuged at 15,000 x g and the supernatant was used to measure enzyme activity. Esterase activity was measured using three different substrates to differentiate aryl (phenyl acetate) and carboxylesterase (alphanaphthyl acetate and 4-nitrophenyl acetate) activity.
Neither H. armigera diet nor geographical location produced any significant change in SOD,
CAT, OTO or GST activities. Diet and geographical location did, however, produce a difference
in the esterase activities depending on the substrate used. Age did not affect SOD, CAT, OTD and GST activities. Esterase activity varied with age and the 3rd and 5th instars showed generally lower activity than the 4th instar. When 3rd and 4th instars of red bollworm Oiparopsis castanea and H. annigera were compared,the SOD, CAT and OTO activities again showed little differences while the GST activity washigher in H. arnligera than O. castanea. The esterase activity using all three substrates was also found to be higher in H. annigera. Thus, in general, antioxidant enzyme activity did not vary significantly while esterase activity varied with diet and age and was species dependent.Our data suggests that there is likely to be an age and species dependent susceptibility to organophosphate pesticides for H.annigera and D.castanea.IUPA
Genetic parameters estimation and animal model ranking for cold carcass mass using Sp statistic in goat.
No full textFull Length Research Paper. It is also available at : http://www.peakjournals.org/sub-journals-PJAS.htmlGenetic parameters for simple carcass traits in developing countries where goats are numerous are scarce. Variance components for additive direct, additive maternal, permanent environmental maternal effects, the covariance between additive direct and maternal effects were estimated by restricted maximum likelihood, fitting six animal models from 2341 cold carcass mass pedigree records of indigenous Matebele goat of Zimbabwe. All investigated models included a random direct genetic effect, but different combinations of random maternal genetic and permanent environmental effects as well as direct-maternal genetic covariance. The direct heritability (h2a) ranged from 0.05 to 0.25 when the maternal genetic effects were included in the model, whereas h2a estimates were 0.06 and 0.26 when maternal effects were excluded. The maternal heritability (h2m) was 0.00 when only maternal genetic effects were included in the model and were 0.05 and 0.10 when the permanent environmental effect of the dam was added. The permanent environmental effect of the dam was negligible and, both positive and negative co variances between direct and maternal genetic effects (?2am) were observed. Using Sp statistic Model 5 which had all the random effects, and a covariance fitted proved to be the ?best? among the six models