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Characterization of Effluent from Textile Wet Finishing Operations
No full textProceedings of the World Congress on Engineering and Computer Science October 20-22, 2009, San Francisco, USAThe physico-chemical characteristics of effluent
from textile wet finishing operations processing denim and
other textile fabrics were evaluated. The effluent was
characterized in terms of its organic and inorganic pollutant
loading and amenability to biodegradation. The major pollution
indicator parameters were the chemical oxygen demand (COD),
biochemical oxygen demand (BOD), total dissolved solids
(TDS), suspended solids (SS), colour and heavy metals levels.
The effluent was highly turbid and coloured with average
organic and inorganic loadings of 1766 kg COD.day-1 and
964 kg TDS.day-1 respectively. Overall mean COD, TDS and SS
levels of the effluent were 5849 mgl-1, 3193 mgl-1 and 521 mgl-1
respectively. Cu, Fe and Cr (VI) levels were less than 4 mgL-1.
Analysis of the BOD curves revealed an initial lag in microbial
activity of between 1-2 days indicating the presence of
non-persistent toxic substances that affect microbial activity.
After the initial lag an average BOD rate constant (KL) value of
0.55 day-1 was obtained, which was above the acceptable sewer
discharge limit of 0.17 day-1. BOD5:COD ratios ranged from
0.2-0.5 indicating that the effluent contained a large proportion
of non-biodegradable organic matter. The COD and TDS levels
were above the generally accepted levels for discharge into
municipality sewers. Even though the concentrations of these
pollutants were not far above accepted limits, high pollutant
mass loadings were obtained due to high discharge volumes.
Based on its overall characteristics, the effluent was considered
not to be suitable for discharge into municipality sewers without
pretreatment. Thus, a pre-treatment step involving coagulation
and flocculation coupled with carbon adsorption was
recommended
On the Origins of the Stellar Initial Mass Function: Azimuthally Symmetric Theory of Gravitation (III)
No full textThis is an articleIn this reading, a new theoreticalmodel of star and cluster formation is posited. Thismodel seeks
to set a mathematical framework to understand the origins of the stellar Initial Mass Function
and within this framework, explain star and cluster formation from a unified perspective by tieing
together into a single garment three important observational facts: (1) that the most massive
stars of most observed clusters of stars are preferentially found in their centers; (2) Larson?s
1982 empirical observation that the maximum stellar mass is related to the total mass of the
parent cloud; (3) that clump masses in giant molecular clouds exhibit a power mass spectrum
law akin to that found in star clusters and this behavior is also true for molecular clouds as well.
Key to this model is the way the cloud fragments to form cores from which the new stars are
born. We show that the recently proposed azimuthally symmetric theory of gravitation has two
scale of fragmentation where one is the scale that leads to cloud collapse and the other is the
scale on which the cloud fragments. The collapse and fragmentation takes place simultaneously.
If the proposed model is anything to go by, then, one can safely posit that the slope of the IMF
can be explained from two things: the star formation rate of the cores from which these stars
form and the density index describing the density profile. Additionally and more importantly,
if the present is anything to by, then, fragmentation of molecular clouds is posited as being a
result of them possessing some spin angular momentum
Theoretical analysis of mixed Plasmodium malariae and Plasmodium falciparum infections with partial cross-immunity.
No full textA deterministic model for assessing the dynamics of mixed species malaria infections in a human population is presented to investigate the effects of dual infection with Plasmodium malariae and Plasmodium falciparum.Qualitative analysis of the model including positivity and boundedness is
performed.In addition to the disease free equilibrium, we show that there exists a boundary equilibrium corresponding to each species. The isolation reproductive number of each species is computed as well as the reproductive number of the full model. Conditions for global stability of the
disease free equilibrium as well as local stability of the boundary equilibria are derived. The model has an interior equilibrium which exists if at least one of the isolation reproductive numbers is greater than unity. Among the interesting dynamical behaviours of the model, the phenomenon of backward bifurcation where as table boundary equilibrium coexists with a stable interior equilibrium,for a certain range of the associated invasion reproductive number less than unity is observed.Results from analysis of the model show that,when cross-immunity between the two species is weak, there is a high probability of coexistence of the two species and when cross-immunity is strong, competitive exclusion is high. Further,an increase in the reproductive number of species i increases the stability of its boundary equilibrium and its ability to invade an equilibrium of species j. Numerical simulations support our analytical conclusions and illustrate possible behaviour scenarios of the mode
Studies of the Effects on Ostrich Growth, of Silage, Altering Feed Levels and Some Nutritional Supplements in Feed.
No full textInternational Journal of Poultry Science 8 (12): 1132-1136, 2009In this study we tested the effect of altering ostrich feed, by adding silage to feed in the ratio 2:1,
by reducing feed levels to 90% and 75%, by adding antimicrobial growth promoter Zinc bacitricin and
flavoumycin and presenting probiotics as liquid and powder. For each trial a control was set up with only
normal prescribed feed supplied. All the birds used were health kept under high hygiene and vaccinated and
dewormed to remove interference from pathogens. The results indicated that silage improved palatability
and food intake. Reducing feed levels did not significantly alter the FCR or the performance of the birds.
Growth promoters increased FCR but mortality was high. Probiotics were more effective when presented in
liquid form than powder. The results show that data on effectiveness of feed supplements should be
extrapolated to ostriches with caution
Azimuthally SymmetricTheory of Gravitation (I) On the Perihelion Precession of Planetary Orbits
No full textFrom a purely none-general relativistic standpoint,we solve the empty space Poisson equation(?2?=0) for an azimuthally symmetric setting, i.e., for a spinning gravitational system like the Sun. We seek the general solution of the form? = ?(r,?). This general solution is constrained such
that in the zeroth order approximation it reduces to Newton?swell known inverse
square law of gravitation. For this general solution, it is seen that it has implications on the orbits of test bodies in the gravitational ?eld of this spinning body. We show that to second order approximation,this azimuthally symmetric gravitational ?eld is capable of explaining at least two things (1) the observed perihelion shift of solar planets (2) that the mean Earth-Sun distance must be increasing?this resonates with the observations of two independent groups of
astronomers(Krasinsky&Brumberg 2004; Standish 2005) who have measured that the mean Earth-Sun distance must be increasing at a rate of about7.0?0.2m/cy (Standish 2005) to 15.0?0.3m/cy (Krasinsky&Brumberg 2004).In-principle,we are able to explain this result as a consequence of loss of orbit alangular momentum?this loss of orbit alangular momentum is a direct prediction of the theory.Further,we show that the theory is able to explain at a satisfactory level
the observed secular increase Earth Year (1.70?0.05ms/yr; Miuraet al. 2009).
Furthermore, we show that the theory makes a signi?cant and testable prediction to the effect that the period of the solar spin must be decreasing at a rate of at least8.00?2.00s/cy
Mathematical analysis of a model for HIV-malaria co-infection
No full textA deterministic model for the co-interaction of HIV and malaria
in a community is presented and rigorously analyzed. Two sub-models, namely
the HIV-only and malaria-only sub-models, are considered first of all. Unlike
the HIV-only sub-model, which has a globally-asymptotically stable disease-
free equilibrium whenever the associated reproduction number is less than
unity, the malaria-only sub-model undergoes the phenomenon of backward
bifurcation, where a stable disease-free equilibrium co-exists with a stable en-
demic equilibrium, for a certain range of the associated reproduction number
less than unity. Thus, for malaria, the classical requirement of having the as-
sociated reproduction number to be less than unity, although necessary, is not
sufficient for its elimination. It is also shown, using centre manifold theory,
that the full HIV-malaria co-infection model undergoes backward bifurcation.
Simulations of the full HIV-malaria model show that the two diseases co-exist
whenever their reproduction numbers exceed unity (with no competitive ex-
clusion occurring). Further, the reduction in sexual activity of individuals
with malaria symptoms decreases the number of new cases of HIV and the
mixed HIV-malaria infection while increasing the number of malaria cases. Fi-
nally, these simulations show that the HIV-induced increase in susceptibility
to malaria infection has marginal effect on the new cases of HIV and malaria
but increases the number of new cases of the dual HIV-malaria infection
Role of value addition to mineral resources in enhancing economic growth - A case for Zimbabwe
No full textProceedings of the 4th TWAS ROSSA Young Scientists Conference, Nairobi, Kenya, 2009.Economic growth is a result of value addition that creates wealth for nations. Nations utilise the gifts of nature which are the raw materials to manufacturing. Africa has abundancy of these natural resources but lacks appropriate economic development due to lack of Science and Technology. In the worst case, raw materials are extracted from Africa and exported in their raw state at very low prices. Value addition or processing is done outside the countries of origin and the finished goods or processed materials imported as finished products that attract more money. The importation at high prices opens the gap between poverty and wealthy nations. This paper highlights the plight of Zimbabwe due to lack of appropriate technologies to engage in complete value addition to the raw materials that are abundant in their nations. This unavailability of such
technologies is quickly capitalized by rich nations who already have the technology but
do not have adequate raw materials in their nations. Such a scenario creates exploitation
of natural resources from African nations. This then makes it difficult to meet the
Millennium Development Goals (MDGs) that were agreed upon by the United Nations
member states. The paper highlights the case for Zimbabwe which prides the mineral rich
Great Dyke which has various precious minerals but extraction is limited by appropriate technologies to go the full length on the value addition. Lack of science and technology leaves Zimbabwe among other developing nations at the mercy of developed countries.
Efforts are being made at national level to promote Science and Technology but the
associated political policies are affecting the same. Developing countries need to foster a
"win-win" partnership with developing nations so as to promote science and technology
enterprises targeted at capacity building in value addition
The dynamics of an HIV/AIDS model with screened disease carriers
No full textThe presence of carriers usually complicates the dynamics and prevention of a disease. They are not recognized as disease cases themselves unless they are screened and they usually spread the infection without them being aware.We argue that this has been one of the major causes of the spread of human immunodeficiency virus (HIV). We propose, in this paper, a model for the heterogeneous transmission of HIV/acquired immunodeficiency syndrome in the presence of
disease carriers. The model allows us to assess the role of screening, as an intervention program that can slow the epidemic. A threshold value c*, for the screening rate is obtained. It is shown
numerically that if 80% or more of the carrier population is screened, the epidemic can be contained. The qualitative analysis is done in terms of the model reproduction number R. The model has two equilibria, the disease free equilibrium and a unique endemic equilibrium. The disease free equilibrium is globally stable of R<1 and the endemic equilibrium is is locally
stable for R>1. A detailed discussion of the model reproduction number is given and numerical simulations are done to show the role of some of the important model parameters
Metal Accumulation and Antioxidant Enzyme Activity in C. gariepinus, Catfish, and 0. mossambicus, Tilapia, Collected from Lower Mguza and Wright Dams, Zimbabwe
No full textBull Environ Contam Toxicol ArticleThe aim of this study was to measure antioxidant
enzyme activities as biological indicators of pollution in
tissues of two species of fish. Five Clarius gariepinus and
three Oreochromis mossambicus were collected from Umguza
Dam (polluted dam) whilst seven C. gariepinus and
eight 0. mossambicus were collected from Wright Dam
(relatively pristine dam). Diphosphotriphoshodiaphorase
and catalase activities were consistently lower (42 f 2%
and 78 f 20%, respectively) in liver whilst malondialdehyde
levels were two times higher in muscles of both species
of fish collected from Umguza Dam. However, seleniumdependent
glutathione peroxidase (Se-GPX) activity was
elevated four-fold in liver and gills of 0. mossambicus collected
from Umguza Dam. Metal levels were two to five
times higher in muscles of both species of fish collected from
Umguza Dam. Fish from Umguza Dam seem to have
responded to pollution by increasing Se-GPX specific
activity in an effort to detoxify peroxides produced as a result
of metal induced oxidative stress.
Keywords Antioxidant enzymes . Heavy metals .
0. mossambicus . C. gariepinus
High levels of trace metals in freshwater may occur as a
result of natural weathering of minerals in the sediments
and bed rocks or as a result of anthropogenic activities such
as mining, industrial, municipal and agricultural discharges
(Winston 1991). Most trace metals are essential in small
concentrations for normal metabolic processes in mammals
including fish and humans. At abnormally high concentrations,
metals can cause death in fish. Metals such as lead
(Pb), cadmium (Cd), copper (Cu) mercury (Hg), silver (Hg)
and cobalt (Co) have been shown to be extremely toxic
when they bind to fish gills (Tao et al. 2000). Fish are
exposed to metals through contaminated food and the water
column in chronically contaminated aquatic ecosystems,
the main routes of accumulation being through gills (Tao
et al. 2000). Sublethal and chronic concentration of metals
exerts their toxicity on fish by generating free radicals such
as the hydroxyl radical ('OH), peroxyl-radical (Roo2) and
superoxide (Oo2-) and some non-radical ROS such as
hydrogen peroxide (H202). These ROS can trigger oxidative
damage to proteins, nucleic acids and lipids (Winston
1991). However, defensive antioxidant enzymes, which
detoxify reactive oxygen species, are present in the liver,
kidneys, gills and intestine (Buhler and Williams 1988).
Antioxidant enzymes have been used as biomarkers of
pollution by metals and organic compounds that generate
oxidative stress in molluscs (Cossu et al. 2000) whilst MDA
levels have also been shown to be affected by oxidative stress
(Rodrigues-Ariza et al. 1993). As antioxidant enzyme
activities and MDA levels can be used as biomarkers of
pollution, this study was undertaken to determine the relat~
onship between concentration of metals, antioxidant
enzyme activities and MDA levels in two species of fish
collected from Mguza Dam (which receives domestic and
industrial effluent from Bulawayo City sewage works) and
from Wright Dam with no history of pollution.This work was supported by grants from
International Program of Chemical Sciences, Sweden and Research
Board, National University of Science and Technology, Zimbabwe
Optimal Control of a Sex-Structured HIV/AIDS Model with Condom Use.
No full textOptimal control theory is applied to a sex-structured HIV/AIDS model with condom use as an intervention strategy. An objective functional to maximise condom use in a population and minimise cases of infectious HIV is adopted. The optimal control is characterised and solved numerically. Simulation results suggest that high percentage of condom usage is associated with reduced HIV incidence,while high costs of condom usage campaigns reduces the percentage condom usage.Targeting issuance of condoms to infectious individuals enables reduction of condom usage campaign costs, hence ensures high percentage of condom usage