UNAM Gā-aisib Repository (University of Namibia)
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Immunomodulatory effects of some Namibian plants traditionally used for treating inflammatory diseases
No full textEthnopharmacological relevance: Acanthosicyos naudininus, Gomphocarpus fruticosus, and Cryptolepis decidua are, according to the knowledge of traditional healers, used in Namibia to treat inflammatory disorders such as pain, fever and skin rashes.
Aim of the study: The present study was conducted to evaluate the immunomodulatory effects and the possible underlying mechanisms of action of the plant extracts on peripheral blood mononuclear cells (PBMCs) such as T-lymphocytes.
Materials and methods: Methanolic and EtOAc extracts of A. naudinianus, G. fruticosus and C. decidua were analysed for their immunomodulatory potential. PBMCs were isolated from the blood of healthy donors and incubated with the plant extracts at concentrations 100, 30, 10, 3, 1 and 0.3 μg/mL. Effects on proliferation and viability of activated human lymphocytes were assessed in comparison to ciclosporin A by flow cytometry using carboxyfluorescein succinimidyl ester (CFSE) and WST-1 assay. Flow cytometry by annexin V/propidium iodide (PI) staining was performed to investigate the necrotic/apoptotic effect of the plant extracts on mitogen-activated human lymphocytes. In addition, analysis of the influence of plant extracts on the regulatory mechanisms of T-lymphocytes was performed using activation marker and cytokine production assays. An HPLC-PDA-ELSDESIMS profile was recorded for each of the extracts.
Results: T-lymphocyte proliferation was inhibited in a dose-dependent manner by the extracts of A. naudinianus, G. fruticosus, and C. decidua in concentrations not causing apoptosis or necrosis. This effect was mediated by inhibition of lymphocyte activation, specifically the suppression of CD25 and CD69 surface receptor expression. Moreover, the extracts suppressed effector functions, as indicated by reduced production of IFN-γ and IL-2. Based on the HPLC profile, possible responsible compound classes could be identified for the extracts of A. naudinianus (cucurbitacins) and C. decidua (indole alkaloids), but not for G. fruticosus.
Conclusions: The data show that the extracts of A. naudinianus, G. fruticosus and C. decidua have in vitro immunomodulatory activity and they interfere with the function of immunocompetent cells, suggesting an antiinflammatory mode-of-action. The present chemical determination and pattern recognition results explain the therapeutic potency. However, further studies to investigate the therapeutic potential of the plants in inflammatory disorders should be done
Deconstruction off gender stereotypes in the media: An analysis of media framing of women in leadership positions in parliament and State-Owned Enterprises (SOE'S) in Namibia
No full textA thesis submitted in fulfilment of the requirements for the Degree of Master of Arts (Media Studies)The study examines the power the media play in driving public perceptions and makes a cogent case to challenge the traditional gender stereotypical frameworks assigned to women in media reportage in politics and corporate business. The study analysed gender stereotypical frameworks in the Namibian print media on women in leadership positions in Parliament and State Owned Enterprises (SOEs) by employing the triangulation method of using both the quantitative and qualitative tools of analysis of data collected from news articles in four newspapers, namely: The Namibian, Namibian Sun, New Era and Windhoek Observer, for a period of seven years (2013-2019).The study established that, among others, women in leadership positions in both Parliament and SOEs are targets of gendered stereotypes and the Namibian print media are more prone to discuss women in leadership’s behavioural and character traits, name-calling is recurrent, their position of power is challenged, their competency is questioned and masculine frames are reinforced. The study recommends that media houses endorse policies that can heighten and deconstruct the language used in media reportage on women in leadership positions in Parliament and SOEs. The public sector and civil society need to reinforce policy direction on gender through on-going training courses for journalists to periodically resuscitate gender-awareness in their writing. Government needs to introduce a national drive to popularise the National Gender Policy and address patriarchal attitudes, while universities and colleges need to incorporate gendered media studies into their curriculums
Comparison of growth rings of Dichrostachys Cinerea and Senegalia Mellifera along a rainfall gradient: Implications for bush encroachment in a changing climate
No full textA thesis submitted in fulfilment of the requirements for the Degree of Master of ScienceTree ring studies, known as dendrochronology, have been an important tool for studying climate variations since the beginning of 1900s. This is because the information preserved in tree rings of most tree species for many years serves as environmental archives for both abiotic and biotic factors, tools that can be used to monitor climate changes. This study was the first to compare the growth rings of Dichrostachys cinerea and Senegalia mellifera along a rainfall gradient to infer implications for bush encroachment in a changing climate. Rainfall gradient in this study was defined by three study sites namely; 1) John Alphons Pandeni Research Station (600 mm); 2) Farm Onyoka (450 mm) and 3) Farm Ebenhaezer (250 mm). Stem discs of different sizes of the two species were sampled from each site and polished for dendrochronological study. The growth rings of D. cinerea trees were substantially influenced by the amounts of site rainfall, but the growth rings of S. mellifera trees were not influenced by site rainfall. Therefore, D. cinerea is a better sensor and indicator of rainfall variability and climate shifts than S. mellifera, which tolerates dry climates as much as the wet seasons. However, the growth patterns of D. cinerea trees did not differ significantly along a rainfall gradient (H = 4.256, df= 2, p= 0.119 > 0. 05). On the contrary, S. mellifera tree growth patterns differed significantly (H = 42.366, df= 2, p= 0.000 < 0. 05). Senegalia mellifera trees from John Pandeni grew faster compared to the ones from Ebenhaezer and Onyoka. The study concluded that species response to climate change vary by geographical location, through the influence of complex interactions of various factors including rainfall. For further dendroclimatology studies in Namibia, site and species should be carefully selected to include species that are more sensitive to soil moisture (rainfall) and/or other climatic factors. Steeper rainfall gradient should be investigated in order to fully understand site climate variability of the recent past and to enable future projection of the results using climate models
Assessment of provisional taxpayers compliance with tax laws: A case for Oshakati Office
No full textA thesis submitted in partial fulfilment of the requirements for the Degree of Master of Business Administration FinanceThe purpose of the study was to make an assessment of the provisiona l taxpayers· compliance
with tax laws at the Oshakati Inland Revenue Offi ce. The study seek answer to the fo llowing
resea rch questions; (I ) What is the level of compliance to tax laws among the provisional tax
payers registered with the IRD Oshakati Office? (2) What are the fac tors that influence
provisiona l taxpayers' compliance with tax laws among the provisional taxpayers registered
with the fRD Oshakati Office? (3) What strategies can be used to mitiga te on the compliance
with tax laws among the provisiona l tax payers registered with Oshakati Office? The study
utili zed a mi xed method to co llect data from employees fo r lRD Oshakati Offi ce and the
taxpayers for IRD Oshakati Offi ce. The quantitati ve dimension of the study used a stratified
random sampling strategy to select 3 76 taxpayers who completed a closed ended que tionnaire
and a purposeful sampling strategy through the use of an in-depth face to face interview was
used to select data from 14 empl oyees fo r Oshakati Inland Revenue. The findings of the study
show that the level of compliance to tax payment by tax payers at the Oshakati Inland Revenue
office is 36.9% which is less than 50%. In addition, the study also found out that the attitudes
of the taxpayers have effect on their compliance to tax payment at the IRD Oshakati Office.
The study a lso fo und out that the level o f compliance of the taxpayers relate to their income.
Those who earn more, are more compliant than those who earn less. The study also fo und out
that the level of governmental accountability and transparency detem1ines their level of
compliance to the payment. More so, the study a lso unveiled that the level of educa tion,
understanding public responsibility towards the benefits of paying taxes influence an
individua l's decision to be compliant with tax laws.
Based on the findings above, the study recommended the need to educa te the genera l
publi c on the importaJJCe of complying with tax laws, and that the taxpayers need to be given
a total ownership and autonomy understand that they are the ones who keep the government
revenue run and economically functional. The study also recommended that there should be a
li ve broadcast and campaigns to a lert the general public of their legitimate role in being
compliant to paying their taxe
Social media integration in educational administration as information and smart systems: Digital literacy for economic, social, and political engagement in Namibia
No full textThe proliferation and access to social media platforms that allow easy access to information systems and services, content creation, and sharing, in a convenient form, has taken education administration and management by storm. Facebook is one of the many online media that can let education administrators and managers interact with each other or their subordinates by sharing information about themselves or any topical community issue via personal profiles or institutional profiles. Furthermore, it is noted that social media applications by their nature have the capabilities of educating, informing, entertaining (leisure), and socializing the audience. The research revealed that there are various groups on Facebook where youthful education administrators can use to post educational information and discuss pertinent issues concerning their institutions. Indeed, social media are being used as channels to foster economic, social, and political development education among Namibian educational administrator
No safety net in the face of climate change: The case of pastoralists in Kunene region, Namibia
No full textOver the past decade, pastoralists in Kunene Region, Namibia, have endured recurrent drought and flood events that have culminated in the loss of their primary form of livelihood– pastoralism. Most pastoralists are finding it difficult to sustain their livelihoods, and their communities have fallen into extreme poverty. Ecosystem-based Adaptation (EbA) approaches are increasingly acknowledged as having the potential to enhance the adaptive capacity of vulnerable communities. The first step is to develop an understanding of how affected communities live, their perceptions of and how they respond to climate change and the biophysical impacts of climate change in their communities. This study aims to collect this information in order to explore the use of EbA to help pastoralists adapt to climate change. We examined an isolated pastoral Himba community, to understand their perceptions, experiences and understanding of climate change and its related impacts on their livelihoods. A nested mixed-methods approach using structured interviews was employed to address the study objectives. Interview results revealed that pastoralists lack scientific knowledge of climate change, and they have no access to climate change information. Though pastoralists have coping and adaptation approaches at the community level (such as making gardens, fishing, etc.), these have become ineffective as climatic uncertainty and change persist. Furthermore, pastoralists no longer get benefits from the environment, such as food and fodder. Despite this, there are currently no biodiversity interventions at the community level to address the impacts of climate change. Pastoralists have indicated their adaptation needs, particularly the provision of water supply to grow food. This is an open avenue to explore EbA approaches, specifically ecological restoration, while still addressing the need of the pastoralists. There is an urgent need to develop new practical adaptation strategies, including restoration options that will strengthen their adaptive capacity
Examining price setting behaviour in Namibia: Evidence from the manufacturing sector
No full textA thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science in EconomicsPrice-setting behavior is a key variable to any central bank, as it determines the nature of price stickiness and the effect of monetary policy on inflation and real variables. As a result, this study examines the price setting behaviours (behavioural mechanisms) of companies in the manufacturing sector in Namibia by establishing the decision process companies followed in their price setting practices. The study used an in-depth price setting behaviour questionnaire survey on 20 manufacturing companies based in Windhoek. It used quantitative analytical approach using confirmatory factor analysis (CFA) to tests propositions and hypothesis related to the linkages between the price setting practices and the manufacturing firms’ pricing decisions.
The study found significant positive relationships between Price Review Strategies and Product Sales Pricing (beta = 0.282). The findings also revealed a direct positive relationship between Price Decisions and Price Review Strategies (beta = 0.539) while Market Structure was found to have a direct positive relationship with Price Decisions (beta = 0.607). This concludes that price decisions were linked to price setting behaviours by way of price review strategies that forces companies to make fixed price increases influenced by the market structure. The study recommends that managers should not only stick to one particular pricing approach. They should use a mix of cost based and value-based approaches that ensure that their price decisions process incorporates the distribution channels, cost effects, price hindrances, price setting methods, price review strategies, price elasticity and market structure
Namibia’s 1999 Caprivi conflict and the consequences of a peacebuilding deficit – A first consideration
No full textIn August 1999, armed men belonging to the Caprivi Liberation Movement (CLM) launched an attack on government installations in Katima Mulilo, in an attempt to bring about the secession of the then Caprivi region (now Zambezi region) from Namibia. The Namibian Defence Force (NDF) and Namibian Police responded swiftly and contained the insurgency, leading to the arrest of more than 140 people while at least 14 individuals were killed. A state of emergency was declared during this first major internal conflict in independent Namibia. Namibia’s independence came as a result of an internationally supported and mediated conflict resolution that provided for peacemaking, peacekeeping and peacebuilding. Given the country’s experience with conflict resolution, one is fully justified in assuming that the post-independent state would be inclined to pursue conflict resolution and peacebuilding in relation to the 1999 event and its aftermath. Two decades after the conflict, the major intervention has been of a military nature. The Namibian State failed to engage in any form of meaningful peacebuilding. The secession sentiments remain and have since been acknowledged by key actors in the security system. This state of affairs can only mean that there is a possibility, that given the right context, the conflict may erupt sometime in the future, unless the State engages differently with local actors
Characterisation, bioactivity and qsar studies of natural products from selected Namibian red marine algae
No full textA dissertation submitted in fulfilment of the requirements for the reward of the Degree of Doctor of Philosophy in Pharmaceutical ChemistryThe objective of this research was to discover new drug leads from Namibian marine algae. Plocamium extracts were screened and their phytochemical contents were quantified. Both the antioxidant activity and the antimicrobial activity of the crude extracts were determined, as well as the dose-response relationship for Plocamium extracts in BALB/c mice. This was done by using acute and sub-acute toxicity parameters. In addition, the structural elucidation of the major metabolite found in the crude extract was determined and the Quantitative Structure Activity Relationships (QSARs) of the compound were determined. Methods: Frozen Plocamium leaves were soaked in dichloromethane (DCM) and methanol (MeOH) in a ratio 1:1 (v/v) for 48 hours. Concentrated Plocamium extracts were screened for phytochemical constituents. Total phenolic and flavonoid contents as well as antioxidant activity were quantified. Dried algal extracts were also reconstituted with different solvents and tested in vitro for antimicrobial activity against 12 pathogens using the Kirby Bauer disc diffusion method. Mice of known weights were infected with Escherichia coli and Pseudomonas aeruginosa by intravenous injection and sub-cutaneous methods respectively. The mice were later treated with gentamycin and ampicillin injections. Other groups of mice were treated with different concentrations of Plocamium extract over a period of five days. E. coli and P. aeruginosa loads in the faeces of the test mice were quantified daily. Plocamium extracts were purified using HPLC to fractionate the extracts. Major fractions were collected and identified by means of one and two dimensional NMR spectroscopy data and MS analysis. In terms of QSAR, the structures of the metabolites were theoretically optimized using the Merck Molecular Force Field. In addition, several physicochemical properties were computed by using the B3LYP variant of Density Functional Theory in conjunction with the 6-31G (d) basis set. Results: Plocamium cornutum and Plocamium rigidum extracted using DCM had total phenolic content of 132.85 ± 0.82 mg and 188.65 ± 0.45 mg Gallic acid equivalents per gram respectively. The IC50 values for Plocamium rigidum and Plocamium cornutum were 28.87 ± 0.82 μM and 40.11 ± 0.38 μM respectively. Ethanolic extracts of Plocamium rigidum showed a zone of inhibition of 6.35 ± 0.25 mm against Listeria monocytogenes while the standard ampicillin had no activity. From the probit plot, the LD50 was calculated to be 3556 mg/kg. A therapeutic dosage of P. rigidum of 355 mg/kg in BALB/c mice reduced E. coli load to pre-evaluation levels on the fifth day. The chemical structure of Plocamium sample I and II (Plocamium rigidum and Plocamium cornutum respectively) yielded two known compounds namely, 3,4-erythro-7-dichloromethyl-3-methyl-3,4,8-trichloro-1,5E,7E-octatriene (from sample I) and 1E,3R,4S,5E,7Z-1-bromo-3,4,8-trichloro-7-(dichloromethyl)-3-methylocta-1,5,7-triene (from sample II) respectively. CPKOvality and HLgap are physicochemical properties that best describe the variation in biological activity of the metabolites. The equation of the best fit was determined as: pIC50 = 9.91CPKovality + 0.270HL-gap-17.149 (R2 = 0.71, Adj. R2 = 0.56, R = 0.84, Std error = 0.31, and q2 = 0.55)
Conclusion: DCM is a better solvent than methanol for the extraction of natural products from Plocamium species. P. rigidum showed inhibition against E. coli and L. monocytogenes in vitro. Although P. rigid inhibited the growth of E. coli, the possible development of liver lesions (in vivo) after chronic exposure is an indication of liver injury which is a sign of the chronic toxicity of P. rigidum, even at low concentrations.
The probable compound responsible for this action is sample (II) above. The variables in the equation above are the parameters that best describe the variation in biological activity of the halogenated monoterpenes extracted and identified. The equation also shows that CPKovality (moderate size and shape of ligands) and a small H-L gap with high reactivity are the parameters that best optimised structure to predict improved biological activity of Plocamium metabolites
Photo-electrical conversion efficiency of dye sensitized solar cells prepared from Mopane leaf chlorophyll extract
No full textA mini thesis submitted in partial fulfillment of the requirements for the Degree of master of Science (Chemistry)In times of fossil fuel shortage, increasing crude oil prices, as well as rejection of conventional energy sources (e.g. coal or nuclear power plants), sustainable energy forms become more and more the focus of attention. One of several offered solutions is to develop a photovoltaic device (solar cells), since solar energy is abundant. Especially, Namibia receives solar radiation of 5.8 to 6.4 KWh per square meter per day – one of the highest in the world. With 8 to 11 average hours of sunshine per day throughout the year, this offers fantastic potential for solar energy, both photovoltaics and solar thermal. Dye Sensitized Solar Cell (DSSC) which is presented here is a thin film cell. Manufacturing of DSSCs is simple, mostly low cost, and incorporate environmentally friendly materials. They have a good efficiency (about 10-14 %) even under low flux of sunlight. However, a major drawback is the temperature sensitivity of the liquid electrolyte. Hence, this study presents the ongoing research to improve the electrolyte’s performance by using natural dye. A transparent conductive oxide (TCO) film of Fluorine - doped Tin Oxide (FTO) was used as an anode. In this research, chlorophyll extracted from Colophospermum Mopane leaves using methanol was employed as the dye for TiO2-based DSSC. TiO2 precursor solution prepared by Molecular precursor method (MPM) was spin-coated on top of Fluorine- Doped Tin Oxide (FTO) conductive glass and calcined at 420 ̊ C for 20 min to act as an anode electrode. The cathode electrode was a supportive glass substrate coated with a layer TiO2 paste (Degussa P25) followed by graphene layer obtained from charcoals sold in Namibian markets. The anode electrode was then immersed in the dye for 20 min, to make the TiO2-chlorophyll thin film. An iodide/triiodide solution was used as the electrolyte. Both electrodes were then pressed together and sealed so that the cell does not leak to make TiO2-Graphene-Chlorophyll-TiO2 sandwich structure based DSSC. An external load was supplied when sunlight shine on the anode of the cell. The photovoltaic performance of this assembled DSSC was then measured using a multi-meter employing eDAG Potentiostat R466 and Echem software under direct sunlight illumination. Furthermore, the assembled cell efficiency was determined by plotting an IV-curve. The current and voltage values for the cell were 157.4 μA and 510 mV respectively. The resistance of the assembled DSSC was 0.931 Ω. Open circuit voltage 287.1 mV, short circuit current 170.8 μA, fill factor 33.5 %, with an efficiency of 0.37 % was obtained. The cell was tested under direct sunlight illumination having a power input of 4.5 mW, on the solar cell area of 7.8 cm2. These results were supported by the UV/Vis analysis showing that both chlorophyll and TiO2 do absorb photons in the wide range of 300 nm to 1000nm. A wide absorption range means that the cell can absorb in the visible and IR light which make up about 90% of the solar spectrum. Large active surface area exposure for the TiO2, enabled more dye and electrolyte to be stored inside the material so that photon adsorptions from solar energy became more effective, resulting in higher efficiency. Despite the small efficiency, this work demonstrated the opportunities of Chlorophyll and TiO2 to be applied as a DSSC