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The androgenic and anabolic effects of pine pollen on Nile tilapia (Oreochromis niloticus)

- Abaho, Ivan

Authors: Abaho, Ivan
Date: 2023-10-13
Subjects: Uncatalogued
Language: English
Type: Academic theses , Doctoral theses , text
Identifier: http://hdl.handle.net/10962/431615 , vital:72790 , DOI 10.21504/10962/431615
Description: All-male tilapia aquaculture is desirable to control unwanted breeding. Besides, male tilapia individuals grow faster and bigger than females. Presently, most farmers use 17α- methyltestosterone (MT) to produce an all-male stock, although the hormone is associated with human health and environmental risks. Recently, plant-based products have been reported to induce masculinisation in fish and are considered safe nature-based alternatives to MT. The present study utilised pine pollen (PP) to induce female-to-male sex change in Nile tilapia (Oreochromis niloticus). Prior to the start of the research, there was insufficient information on the use of PP for sex inversion, with no published data on the sex change mechanism, hence limiting the progress in the application of the product from experimental to hatchery levels. In this study, the optimal dietary inclusion of PP for maximum masculinisation of Nile tilapia was investigated by feeding three-day-old fish graded PP levels (80, 160, 320, 640, 1,280, 1,920, 2,560 and 3,200 mg kg-1 basal diet) from 3 to 30 days post-hatch (dph). This was compared with fish of the same batch fed the same basal diet with no PP (CT; negative control) or the same basal diet supplemented with 60 mg MT kg-1 (MT; positive control). To confirm whether the sex change was complete, fish in all treatments were fed only a basal diet for an additional 84 days. The associated differences in the growth of the fish were also determined. Pine pollen and MT significantly skewed the expected 50:50 (male: female) ratio towards more male individuals (Chi-square: X2 = 54.396, df = 9, P < 0.001). The 1,280 mg PP kg-1 of diet equally induced masculinisation (80.0 ± 2.9 % males) as MT (89.2 ± 2.2 %), and both were significantly higher than 50.8 ± 2.2 % in the CT treatment. In addition to masculinization, dietary inclusion of 1,280 mg PP kg-1 improved fish growth, with the specific growth rate significantly higher than fish from the MT and CT treatments (One-way ANOVA: F(9, 20) =14.196, P < 0.001). An increment in the dietary levels of PP from 1,280 to 3,200 mg kg-1 further promoted the growth of the fish but did not affect masculinisation. The mechanism underlying PP-induced sex masculinisation was investigated using all-female Nile tilapia fed a basal diet supplemented with 1,280 mg PP kg-1 for 28 days from 3 dph, in comparison with fish fed a basal diet incorporated with 60 mg MT kg-1 (MT treatment) or only a basal diet (CT treatment). The expression of sex-related genes (dmrt1, amh, cyp19a1a, and foxl2), changes in sex steroid profiles (T: testosterone, 11-KT: 11-ketotestosterone, and E2: 17β-estradiol), and gonadal histology were analysed. Gene expression and sex steroid concentrations were significantly influenced by the interaction between dietary treatment and time, with the expression changing differently over time among the treatments (RM-ANOVA: P < 0.001). Pine pollen significantly up-regulated the expression of dmrt1 and amh, while cyp19a1a and foxl2 were down-regulated. Corresponding to male sex gene up-regulation, male-based steroids (11-KT and T) levels were also significantly amplified in both PP and MTtreated fish. The gene expression pattern and changes in sex steroids corresponded to a higher proportion of male individuals obtained in the MT and PP treatments (MT: 97.8 ± 1.1 % and PP: 77.8 ± 2.9 % males), implying female-to-male sex change induction. Subsequently, spermatogonia and spermatocytes were the dominant germ cells in the histological sections of the gonads obtained from the PP-treated fish. At the same time, the individuals from the MT treatment exhibited mainly spermatids and spermatozoa. In contrast, all the fish from the CT treatment remained females, having only ovarian tissues. This thesis confirmed that PP induces female-to-male sex change in Nile tilapia and enhances fish growth. The research contributed novel information on the mechanism underlying PP induced sex change, which included disrupting the expression of sex genes and the androgento- estrogen balance, ultimately determining the sexual fate of the fish. The findings provide a foundation for understanding the role of PP in masculinisation, with broad potential application in the aquaculture industry. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2023
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Date Issued: 2023-10-13

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Design of Immunobiosensors for Detection of Tumor-Associated Anti-P53 Autoantibodies: Method Development

- Adeniyi, Omotayo Kayode

Authors: Adeniyi, Omotayo Kayode
Date: 2020
Subjects: Uncatalogued
Language: English
Type: thesis , text , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/162988 , vital:41002 , 10.21504/10962/162988
Description: Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020. , Detection and profiling of circulating tumor-associated autoantibodies (TAAbs) are useful for screening and early-stage diagnosis of asymptomatic lung cancer. Immunobiosensor technologies aimed to accomplish the highly sensitive, rapid and low-cost detection of TAAbs can improve the early-stage detection of lung cancer. Immunobiosensors for the detection of anti-P53-tumour associated autoantibodies have been developed in this work. The design of sensing interfaces with immobilized P53 protein (P53ag) as a sensing element layer on a solid interface was investigated. Several methods of detecting anti-P53-antibodies (anti-P53ab) were investigated. These methods are label-free detection using electrochemical impedance spectroscopy (EIS) and two label techniques. The label-free electrochemical techniques utilize gold electrode pre-modified with a conducting layer of electrochemically grafted phenylethylamine for covalent immobilization of P53ag. The limit of anti-P53ab detection with the label-free EIS was 103.0 pg.ml-1. The labeled technique developed utilizes fluorescent, and peroxidase-like nanomaterial labeled antibody as a detection probe. For the fluorescence detection, fluorescent silica nanoparticles were synthesized by overloading FITC into the silica matrix and conjugated to detection antibody (anti-IgG). The detection of the anti-P53ab was based on the dissolution of the silica nanoparticles to release the loaded dye as a signal amplification strategy. The fluorescence detection was carried out on a microplate, and magnetic bead modified P53-antigen platforms and limit of detection (LoD) were 42.0 fg.ml-1 and 3.3 fg.ml-1 for anti-P53ab; respectively. Fe3O4@SiNP-APTES-Au@Pd hybrid nanoparticles were synthesized, and their peroxidase-like activity and colorimetric detection were evaluated. The Fe3O4@SiNP-APTES-Au@Pd exhibited comparable activity to HRP. The Fe3O4@SiNP-APTES-Au@Pd was conjugated to protein-G-anti-IgG for the detection of anti-P53ab on a microplate and cellulose paper platforms. The LoD was 20.0 fg.ml-1 and 63.0 fg.ml-1 for the microplate and cellulose paper platform; respectively. The potential application of the designed immunobiosensor was evaluated in simulated serum samples. The developed sensors showed higher detection sensitivity, stability and had a lower detection limit for anti-P53ab when compared with the ELISA based detection. The results have provided alternative and effective quantification approaches to ELISA and a promising future for multiplexed detection of tumor-associated autoantibodies. The developed methodologies in this thesis could be applied for the detection of other autoantibodies in other cancer types and auto-immune diseases.
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Date Issued: 2020

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Design of immunosensor for the detection of C-reactive protein using oriented antibody immobilization

- Adesina, Abiola Olanike

Authors: Adesina, Abiola Olanike
Date: 2020
Subjects: Uncatalogued
Language: English
Type: thesis , text , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/163080 , vital:41010 , https://dx.doi.org/10.21504/10962/163080
Description: Early diagnosis of cardiovascular diseases (CVDs) has been a major challenge since CVDs are clinically silent. The current methods available for the diagnosis are not sensitive enough at the onset of the disease. Also, the use of sophisticated equipments and experts in the result interpretation has created a lot of barriers to the early diagnosis of CVDs. Biomarkers detection using electrochemical immunoassay offers great advantages in terms of sensitivity, miniaturization and low cost. This can be integrated into portable devices which can be made available in the remote areas for easy assessment of health care services. The fabrication of piezoelectric and electrochemical immunosensors for the detection of C-reactive protein (a cardiac biomarker) are presented in this thesis. The electrochemical immunosensor investigates the effect of linkers chain length on the analytical performance of the immunosensor. The fabricated immunosensors were based on two simple and sensitive label-free impedimetric assay. Oriented immobilization of anti-CRP monoclonal antibody (mAb) unto gold surface was achieved using carbohydrate specific boronic ester reaction for enhanced capture and specific detection of CRP protein. Quartz crystal microbalance with dissipation (QCM-D) was employed to establish the immunocomplex formation between the mAb and CRP antigen. This was achieved by forming a self-assembled monolayer (SAM) of 4-mercaptophenylboronic acid (MPBA) onto the quartz crystal surface. The limit of detection (LoD) for the direct and sandwich immunoassay was 5.45 and 3.65 ng mL-1, respectively. The Au-MPBA-mAb/glucose immunosensor with the shortest chain length of boronic acid was fabricated. The use of SAM of 4-mercaptophenylboronic acid (MPBA) afforded a thio phenylboronic acid functionalized gold surface (Au-MPBA SAM). The anti-CRP-mAb capture antibody was immobilized in an oriented manner onto gold thiophenylboronic acid to yield an Au-MPBA-mAb surface. The non-specific boronic surface was blocked using glucose to yield an Au-MPBA-mAb/glucose. The modified gold surface could detect CRP antigen. The limit of detection (LoD) was found to be 9.82 and 6.23 ng mL-1 for the direct and sandwich immunoassay; respectively. The Au-MBA-APBA-mAb/glucose immunosensor was designed by forming a SAM of 4-mercaptobenzoic acid (MBA) onto gold electrode surface. The terminal -COOH group of the MBA SAM reacted with an amino (NH2) group the 4-aminophenylboronic acid (APBA) using EDC/NHS coupling. This was followed by the immobilization of the capture antibody and the blocking of non-specific binding sites using glucose. Improved analytical parameters were obtained with LoD for the direct and sandwich immunoassays found to be 2.90 and 1.20 ng mL-1; respectively. A more stable immunosensor utilizing electrochemical grafting was investigated for the fabrication of Au-PEA-SA-APBA-mAb/glucose. The enhanced stability of the immunosensor was through the electrochemical reduction of 4-aminoethyl benzene diazonium (AEBD) salt. The surface was further derivatized with succinic anhydride to have a carboxylic derivatized surface. Carbodiimide chemistry was used to form a covalent linkage between the APBA amine group and the surface -COOH terminal group to yield an Au-PEA-SA-APBA surface. The immobilization of mAb and glucose resulted in Au-PEA-SA-APBA-mAb/glucose immunosensor. For the detection and signal enhancement, the magnetic nanoparticles conjugated with anti-CRP polyclonal antibody (pAb) was prepared. The sandwich immunoassay was used to detect CRP by the first capture at Au-PEA-SA-APBA-mAb/glucose. This was followed by signal amplification using magnetic nanoparticles coated with a silica shell and conjugated to pAb (MNP-SiO-APTES-PBA-pAb/glucose). The limit of detection was found to be 560 pg mL-1 and much lower than sandwich immunosensor fabricated using SAMS. The signal enhancement, lower detection limits and high sensitivity were obtained due to the nanoparticles for the sandwich immunoassay. The linear range for all the fabricated immunosensor ranges from 10 – 100 ng mL-1. The sensitivity obtained for Au-MPBA-mAb/glucose, Au-MBA-APBA-mAb/glucose, and Au-PEA-SA-APBA-mAb/glucose were 0.691, 0.885, and 11.08 kΩ.ng-1.ml.cm-2 for the sandwich immunoassay. The piezoelectric immunosensor was regenerated using 0.1 M HCl without affecting the immobilized capture antibody. The real sample analysis was carried out in 10 % serum in a recovery study for all the fabricated immunosensor. The percentage of recovery was very close to 100 %. , Thesis (PhD)--Rhodes University, Science Faculty, Department of Chemistry, 2020.
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Date Issued: 2020

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The design, synthesis and antiplasmodial activity of a series of halogenated fosmidomycin analogues and hybrid drugs

- Afolayan, Anthonia Folake

Authors: Afolayan, Anthonia Folake
Date: 2012
Subjects: Uncatalogued
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/64370 , vital:28538
Description: Malaria continues to be a devastating disease and a major cause of death in sub-Saharan Africa. With resistance against most of the available antimalarial drugs, there is a need for ongoing research and development of antimalarial agents. Fosmidomycin and its acetyl analogue FR900098 have been identified as potent inhibitors of Plasmodium falciparum, the causative agent of the most deadly form of malaria. Clinical trials of these agents have revealed poor absorption due to their high hydrophilicity. In the present studies the effect of halogenation of the acyl chain as well as the biological effect of extending the acyl sidechain was explored. This provided the basis on which fosmidomycin hybrids were designed to investigate the feasibility of hybrid extending into NADPH binding pocket. Synthesis of a series of halogenated FR900098 analogues was carried out in three stages. This included i) The introduction of the phosphonate group by reaction with 1,3dibromopropane in an Arbuzov reaction, ii) The introduction of a hydroxamate group by reaction of the propyl phosphonate by means of a nucleophilic substitution reaction with BocNHOBn and iii) The introduction of a halogenated acyl side chain on a protected fosmidomycin backbone. The synthesis of fosmidomycin-hybrids for which chloroquinefosmidomycin hybrids were used as the prototype, involved convergence of the two separately constructed moieties i.e. fosmidomycin and the quinoline moieties in a covalent linkage. The quinoline moiety was easily synthesized from the reaction of 4,7dichloroquinoline with 1,2-diamino ethane. The aminoquinoline so formed resulted in chloroquine-fosmidomycin hybrids 3.8 and 3.9 when reacted with halogenated FR900098 analogues. Antiplasmodial assays were conducted on the chloroquine-fosmidomycin hybrids and the halogenated fosmidomycin derivatives against the chloroquine resistant Gambian FCR-3 strain of P. falciparum. The most potent iodoacetyl fosmidomycin analogues 2.21 gave an IC50 value of 5.54 µM which is eight times more potent than the known antiplasmodial FR900098 which gave an IC50 value of 41.67 µM. All the halogenated FR900098 analogues showed better antiplasmodial activity than their non-halogenated derivatives. This indicated that the presence of halogens in the FR900098 analogues contributes to their biological Chapter 1 Literature review activity. The acetyl and propyl linked hybrids 3.8 and 3.9 showed potent antiplasmodial activity with IC50 values of 0.18 and 0.82 µM respectively. These were by far the most potent hybrids synthesized and provided leads for a new class of promising antimalarial agents. Preliminary E. coli DXR enzyme inhibition assays were carried out on the halogenated fosmidomycin analogues. The results showed good inhibition of the enzyme by the phosphonic acids of the chloroacetyl and chloropropyl analogues 2.1 and 2.2 respectively. Molecular modelling of the compounds on E. coli (PDB code: 2EGH) and P. falciparum (PDB code: 3AUA) DXR showed strong binding of the halogenated fosmidomycin analogues while the hybrids in the absence of docked NADPH showed minimum binding to the enzymes.
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Date Issued: 2012

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The impact of Ghana's entrepreneurial ecosystem on women's entrepreneurial performance: the moderating role of entrepreneurial identity

- Akuamoah Boateng, Irene

Authors: Akuamoah Boateng, Irene
Date: 2025-04-02
Subjects: Uncatalogued
Language: English
Type: Academic theses , Doctoral theses , text
Identifier: http://hdl.handle.net/10962/479559 , vital:78324 , DOI 10.21504/10962/479559
Description: Women business leaders are generating a tremendous impact in their markets, industries and communities through innovation, job creation and economic growth. However, their contributions are often lost in the prevailing narrative that women are over-represented among the poorest and most vulnerable entrepreneurs globally. A review of the extant literature has postulated challenges that women entrepreneurs faced several challenges in the ecosystem in which it operates. Women entrepreneurs have access to limited capital as compared to its men counterparts, fewer opportunities to network and build relationships with other entrepreneurs, investors, and mentors, which affects their access to resources and knowledge. Due to the issue of gender-based stereotypes and biases that women entrepreneurs constantly face, they are unable to meet mentors who can provide them with guidance and support to grow their business. These women-specific challenges have become barriers limiting the growth of women entrepreneurs, however insufficient reports highlight how these hindering factors can create opportunities for the growth of women entrepreneurs. Dwelling on the Process theory, the study explored the impact of Ghana’s entrepreneurial ecosystem on women’s entrepreneurial performance with the moderating role of entrepreneurial identity. The study was a cross-sectional quantitative research design with data collected from 413 women entrepreneurs in the Greater Accra Region using structured questionnaire collected using the survey monkey online tool. The data was analyzed using IBM SPSS v.25 and the PLS-SEM v.4.0. The first objective was examined through 12 hypotheses, while the second was analyzed using 2.The study finds that access to finance has positive and insignificant effect on the entrepreneurial performance of women in Ghana. Likewise, education and training have a negative and insignificant effect on the market and operational performance of women entrepreneurs in Ghana. The results of the study postulated that the availability of infrastructure and resources has a negative but significant effect on both the market and operational performance of Ghanaian women entrepreneurs. The results of the study further reported a positive but insignificant impact of network and social capital on the market performance and operational performance of women entrepreneurs in Ghana. The results of the study in relations to the regulatory environment and women entrepreneurial performance indicates an insignificant relationship between regulatory environment and market performance and regulatory performance whilst cultural and social factors within the Ghanaian ecosystem negatively but significantly influence the entrepreneurial performance of women in Ghana but innovation and knowledge spillover have a positive and significant impact on both the market performance and operational performance. Furthermore, the findings of the study suggest that Ghana's entrepreneurial ecosystem may not have a substantial direct impact on women's entrepreneurial performance in Ghana. Further practical and theoretical implications of the study are discussed in the thesis. , Thesis (PhD) -- Faculty of Commerce, Rhodes Business School, 2025
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Date Issued: 2025-04-02

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A phenomenological investigation of the beginning therapist's experience of the first session of psychotherapy with the first patient

- Allen, Jennifer Ann

Authors: Allen, Jennifer Ann
Date: 1987
Subjects: Uncatalogued
Language: English
Type: Master's theses , text
Identifier: http://hdl.handle.net/10962/193129 , vital:45301
Description: The aim of this project is to come to an understanding of how the situation of the first session of psychotherapy with the first patient is lived by the beginning therapist and what meaning this situation holds for him. The writer's interest in this phenomenon grew out of her own experience of this situation as a clinical Masters coursework student, an experience which was of important to the writer and meaningful still as a therapist in training. In dialogue with experienced therapists the importance of this situation was again made apparant. It was the opinion of these therapists that although for some the details of this experience had become dulled by time, what remained meaningful to them was that this experience was seen as the beginning of a project which remains important to them - they identified this situation as an important moment in the history of their development as psychotherapists. In the hope that the literature pertaining to psychotherapy would throw some light on this situation, the writer turned to a number of sources in this area to discover that no literature available to her elucidated this situation in a holistic manner. This led the writer to go back to the beginning therapists themselves so that they may speak for themselves of their experience of this situation. A phenomenological method of enquiry is implemented in this study as it renders the subject matter accessible to investigation, and allows it to reveal itself as it essentially is. This project is then an attempt to come to a general description of the beginning therapist's experience of the first session of psychotherapy with the first patient and thus to articulate the structure of the beginning therapist's lived situation (world) in this context. , Thesis (MA) -- Faculty of Humanities, Psychology, 1987
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Date Issued: 1987

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Self-reports on the effectiveness of psychotherapy with therapists-in-training: an 18-month follow-up study at a psychology training clinic

- Angus, Catherine Clare

Authors: Angus, Catherine Clare
Date: 1993
Subjects: Uncatalogued
Language: English
Type: Master's theses , text
Identifier: http://hdl.handle.net/10962/193069 , vital:45295
Description: The purpose of this study is to ascertain whether the clients who make use of the services of the Psychology Clinic at Rhodes University perceive the masters students being trained at the Clinic as providing adequate psychotherapy. Using a sample of 18 clients, who underwent psychotherapy at the Rhodes Psychology Clinic during 1990, a follow-up study was conducted to ascertain the perceived success of that psychotherapy. Those variables most pertinent to the outcome of psychotherapy are examined. The study uses both qualitative and quantitative methodology and shows that, overall, 89% of the clients who participated in this study perceived the psychotherapy at the Rhodes Psychology Clinic to be satisfactory. The study also highlights those factors which were perceived to be negative in the psychotherapeutic equation and it is hoped that the findings can be beneficial in planning more efficient services for the Clinic in the future. , Thesis (MA) -- Faculty of Humanities, Psychology, 1993
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Date Issued: 1993

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The construction of a swept-frequency polarimeter for observing decametric radiation from Jupiter

- Baker, Dirk E.

Authors: Baker, Dirk E.
Date: 1970-01
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/447507 , vital:74652
Description: This thesis describes the design and construction of a swept-frequency polarimeter for observing Jupiter’s decametric radiation in the frequency range from 15 to 45 MHz. The frequency band is tuned in two parts using two receivers for observing the left- and right-circular components of the radiation in the 15 to 26 MHz range and two receivers for observing the circular components in the 30 to 45 MHz range. The receivers are tuned electronically by means of varactor diodes and are of novel design in that they do not have any intermediate-frequency stages. The frequency band can be swept 10 times per second or 100 times per second. The antennas used for the polarimeter are helical beam antennas, two for each of the circular components in the 15 to 26 MHz range and two for the 30 to 45 MHz range. Model studies of the antennas were conducted to establish whether they have suitable characteristics for observing the polarisation of Jupiter’s decametric radiation over a wide frequency range. Many spectral records of Jupiter’s decametric radiation were obtained using a preliminary version of the swept-frequency receiver and a log-periodic dipole antenna. Some of the records are presented and one record which shows an interesting case of Faraday rotation is analysed. , Thesis (MSc) -- Faculty of Science, Physics, 1970
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Date Issued: 1970-01

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Left-invariant optimal control problems on the Heisenberg group and the associated Hamilton-Poisson systems: classification, stability and integration

- Bartlett, Catherine Eve

Authors: Bartlett, Catherine Eve
Date: 2015-04-10
Subjects: Uncatalogued
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/480312 , vital:78428
Description: This thesis examines the left-invariant control affine systems of full rank, evolving on the three-dimensional Heisenberg group H3. Such systems are classified under state space equivalence, detached feedback equivalence and strongly detached feedback equivalence; a complete list of equivalence representatives is obtained. The equivalence of cost-extended control systems corresponding to left-invariant optimal control problems on H3 with fixed terminal time, affine dynamics, and affine quadratic cost is also considered. To left-invariant optimal control problems on H3 with quadratic cost, one may, via the Pontryagin Maximum Principle, associate a quadratic Hamilton-Poisson system on the (minus) Lie-Poisson space h3􀀀. Homogeneous and inhomogeneous quadratic Hamilton-Poisson systems are investigated. These systems are classified up to an affine isomorphism. Furthermore, the stability nature of the equilibria of the systems are analysed and explicit expressions for all integral curves are determined. , Thesis (MSc) -- Faculty of Science, Mathematics (Pure and Applied), 2015
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Date Issued: 2015-04-10

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