Additive Manufactured Antennas and Novel Frequency Selective Sensors

The research work carried out and reported in this thesis focuses on the application of additive manufacturing (AM) for the development antennas and novel frequency selective surfaces structures. Various AM techniques such as direct writing (DW), material extrusion, nanoparticle conductive inks are investigated for the fabrication of antennas and FSS based sensors. This research has two parts. The first involves the development of antennas at the microwave and millimetre wave bands using AM techniques. Inkjet printing of nanoparticle silver inks on paper substrate is employed in the fabrication of antennas for an origami robotic bird. This provides an exploration on the practicability of developing foldable antennas which can be integrated on expendable robots using low-cost household inkjet printers. This is followed using Aerosol jet printing in the fabrication of fingernail wearable antennas. The antennas are developed to operate at microwave and millimetre wave bands for potential use in 5G Internet of Things (IoT) or body-centric networks. The second part of the research work involves the development of frequency selective sensors. Trenches have been incorporated on an FSS structure to produce a new concept of liquid sensor. The sensor is fabricated using standard etching techniques and then using FDM method in conjunction with nanoparticle conductive ink. Finally, a new concept displacement sensor using an FSS coupled with a retracting substrate complement is introduced. The displacement sensor is a 3D structure which is conveniently fabricated using AM techniques

Anti-inflammatory activity of selected plants used by the Ilkisonko Maasai, Kenya

Background: The Ilkisonko Maasai are a Kenyan pastoralist community that uses indigenous plants for the management of pain and inflammatory conditions such as arthritis. Objectives: The purpose of this study was to validate the use of plants for medicinal purposes by the Ilkisonko Maasai through testing for anti-inflammatory activity using the carrageenan-induced rat paw oedema assay. Methodology: The methanol extracts (400 mg/kg body weight) of Rhus natalensis (bark), Acacia drepanolobium (bark), Acacia nilotica (bark), Acacia reficiens (bark), Acacia robusta (bark), Grewia villosa (bark), Ximenia americana (bark and leaves) and Rhus vulgaris (leaves) were evaluated for in vivo anti-inflammatory efficacy using the carrageenan-induced rat paw oedema assay. Diclofenac (20 mg/kg body weight) was used as the positive control and paw volume was measured by a plethysmometer. Results: The maximum percentage inhibition (PI) of the extracts was observed as Grewia villosa (58.6% at 24 h), Rhus vulgaris (57.8% at 24 h), Acacia nilotica (55.5% at 1 h), Ximenia americana (54.5% at 1 h), Acacia drepanolobium (50.9% at 24 h), Acacia reficiens (47.6% at 1 h), Rhus natalensis (43.8% at 24 h) and Acacia robusta (37.4% at 24 h) (p < 0.05 for all PI). Diclofenac (20 mg/kg) showed a steady increase in PI from 1 h to 4 h with a maximum PI of 66.2% (p < 0.05) at 4 h and the lowest PI of 14.3% at 24 h. Conclusion: All extracts of the plants assessed exhibited anti-inflammatory activity at early phase of inflammation. Additionally, extracts of five plants, namely Rhus natalensis, Acacia drepanolobium, Acacia robusta, Grewia villosa and Rhus vulgaris showed anti-inflammatory activity at both early and late phases of inflammation. There is need for further studies to identify phytochemicals with active anti-inflammatory activity. Key words- Ilkisonko Maasai, carrageenan, inflammation, Rhus, Acacia, Grewia and Ximeni

Solid-Phase Peptide Synthesis of Arginine-vasopressin with Amide Side-chain of Asparagine Protected with 1-Tetralinyl Group

Arginine-vasopressin, a nonapeptide amide, was synthesized on a benzhydryl-resin using the Boc-strategy. Benzyl group was used in the protection of sulfhydryl group of cysteine and tyrosine side-chain. Benzhydryl, tetralinyl and tosyl groups were used in the protection of glutamine, asparagine and arginine side-chains respectively. TFMSA-TFA-thioanisole-1,2-ethanedithiol (2:20:2:1 v/v) was used to cleave the peptide from  the resin under different conditions to obtain arginine-vasopressin in a one-pot reaction. The cleavage at 40°C for two hours gave arginine-vasopressin quantitatively (77% yield) Keywords: Solid-Phase Peptide Synthesis, resin, protecting group, cleavage, nonapeptide

1-Tetralinyl as Carboxamide-Protecting Group for Asparagine and Application to N-alpa- t-Butyloxycarbonyl (Boc) Solid-phase Peptide Synthesis of Oxytocin

Oxytocin, a nonapeptide amide, was synthesized on a benzhydryl-resin using the Boc strategy. Benzyl group was used in the protection of sulfhydryl group of cysteine and tyrosine side-chain. Benzhydryl and tetralinyl groups were used in the protection of glutamine and asparagine side-chains respectively. TFMSA-TFA-thioanisole-1,2-ethanedithiol (2:20:2:1 v/v) was used on the peptide-resin under different cleavage conditions to obtain oxytocin in a one-pot reaction. The cleavage at 40°C for two hours gave oxytocin quantitatively. Oxytocin could be isolated in 56% yield. Keywords: Boc-strategy, Solid-phase peptide Synthesis, nonapeptide, resin, protecting grou

Strategies Used For Persuasion in Kimuthambi

Persuasion is inherent in everyday communication and is very important in relationships, leadership, peace building and success in virtually every area of livelihood. This study’s main goal is to provide an analysis of persuasion in Kimuthambi. The objective of the study is to identify and discuss strategies used for persuasion in Kimuthambi. The study is guided by the relevance theory by Sperber and Wilson. It utilizes both qualitative and quantitative research designs and is carried out in Muthambi Division, Tharaka Nithi County, Kenya. The population includes all the Kimuthambi communicative events. The researcher purposively sampled ten real life communicative events conducted in Kimuthambi which involved forteen speakers. Data was collected using a digital audio recorder and an observation schedule. The recorder captured conversations in Kimuthambi in the selected communicative events and the observation schedule was used to record the contextual information. The researcher transcribed utterances from the data collected that utilizes stragetegies used for persuasion. The transcribed utterances are one hundred and thirty six. Then guided by the communicative principle of relevance, the researcher identifies and discusses eighty four utterances used for persuasion in Kimuthambi. The study establishes that persuasion in Kimuthambi is mainly through the use of logical appeals, emotional appeals and sensationalism. This study enhances the analysis of Kimuthambi as a language variety and adds to the existing knowledge on strategies of persuasion in various languages of the world. In addition it enriches knowledge on the tenets of the relevance theory.Thus it contributes to crosslinguistic studies from the perspective of a unique cultural orientation. Key words: Persuasion, Kimuthambi, Strategies, Relevanc

In vitro inhibition of tomato Fusarium wilt causative agent by zearalenone from a soil inhabiting fungus

To find naturally occurring compounds for the control of Fusarium wilt disease of tomato in the farming fields, 200 fungal strains were cultured in liquid media and screened for antifungal activity against Fusarium oxysporium f. sp. Lycosperci. The screening was carried out using in vitro antifungal assays and coincidentally a strain of Fusarium species was found to produce secondary metabolites, which were prepared as crude extracts that showed strong antifungal activity. The responsible compound was purified using column chromatography and the chemical structure of the purified compound was determined using nuclear magnetic resonance (NMR) spectroscopic techniques. A known compound, zearalenone, was found to be responsible for the antifungal activity, with a minimum inhibitory concentration (MIC) of 550 ± 10.5 ppm. This is a sufficient inhibition for F. oxysporium f. sp. Lycosperci, which is the causative agent for Fusarium wilt disease to tomato. Given the global abundance of zearalenone and its implication to human health, the results from this study suggest a sustainable manner of disposing of the mycotoxin and simultaneous benefit in control of the Fusarium wilt disease. It is recommended from this finding that it can be used to suppress fungal attack onto the roots of tomato plant to manage the Fusarium wilt disease.Keywords: Fusarium oxysporium f. sp. Lycosperci, tomato, submerged cultures, column chromatography, zearalenon

3D Frequency Selective Surface Displacement Sensor using Complementary Dielectrics

A novel displacement sensor using a frequency selective surface (FSS) with a removable substrate complement is proposed. The new concept sensor is based on modifying the effective permittivity of the FSS when the substrate complement is gradually withdrawn. The change in the effective permittivity produces a change in capacitance, and thus in the resonant frequency. The FSS consists of an array of square loops elements in a square lattice. A 3D convoluted version of the FSS sensor improves the angle of incident behavior and increases the displacement range. The dielectric layers of the 3D FSS sensor were 3D printed while the metal layers were painted using silver conductive paint. The transmission response, S 21 , has been employed as the validation parameter. The proposed sensor operates in a frequency range between 2.0 GHz and 2.8 GHz and has achieved a 0.052 GHz/mm sensitivity and 12 mm dynamic range and has a dimension of 207mm by 207mm. The sensor is passive, compact, inexpensive, and easy to operate. The envisaged application is the wireless detection of structural movement, which can be critical in civil structures such as bridges or buildings or earthquake monitoring

A Liquid Sensor based on Frequency Selective Surfaces

A novel, simple and easy-to-fabricate liquid sensor using frequency selective surfaces (FSS) is proposed. The new sensor concept is based on modifying the capacitance between adjacent FSS elements when materials of different electrical characteristics are inserted. The change in capacitance produces a change in resonant frequency. The FSS design consists of a 9 x 9 array of square loops on 0.31λ x 0.31λ square unit cells with trenches between the loops. The trenches are filled with liquids under test (LTU). The structure operates at 4.6 GHz without any liquid. When liquids are inserted in the trenches, the resonance frequency varies in relation to the dielectric constant of the liquid. This is observed by measuring the transmission coefficient (S 21 ). Butan-1-ol, ethanol, methanol, propan-2-ol, and Xylene are used to demonstrate the sensing function. A maximum sensitivity of 8.65 % for Xylene was achieved. Further, very low differences were observed between the measured and expected dielectric constant and loss tangent, thus validating the design. The device is inexpensive, compact, and easy to make and scalable for large area operations in liquid detection for microwave sensing applications. This technique has potential applications in reconfigurable FSS

Quality Control Report of Drugs Analyzed in the Drug Analysis and Research Unit during the Period 2011-2015

During the period 2011-2015, the Drug Analysis and Research Unit (DARU) analyzed 1972 drug samples. The samples consisted of 21.5% locally manufactured and 78.2% imported products while the origin of 0.3% of products was indeterminate. Samples were subjected to compendial and/or in-house analytical specifications. The overall non-compliance rate was 4.5% comprising 2.5% local products and 2.0% imports. High failure rates were recorded for uterotonics (37.5%), hemostatics (33%), anthelmintics (17%) and anticancers (10.5%) while ophthalmic, immunomodulatory, musculoskeletal and endocrine drugs all complied with the quality acceptance criteria. Erectile dysfunction drugs, received by the laboratory for the first time, all complied with specifications. The results obtained demonstrate an improvement in the quality of samples submitted to DARU when compared to previous performance

3D Printed Fingernail Antennas for 5G Applications

3D printing of antennas on removable fingernail for on-body communications at microwave and millimetre waves is proposed. Aerosol Jet technology, a fine-feature material deposition solution, has been used to directly print microstrip patch antennas on an acrylonitrile butadiene styrene (ABS) removable finger nail substrate. Two antennas have been printed and assessed, one operating at 15 GHz and the other at 28 GHz. Nanoparticle conductive silver ink has been employed to create the microstrip patch antennas and corresponding transmission line using an Optomec machine. The inks are then cured using a PulseForge machine. A further copper layer is added to the millimeter wave antenna via an electroplating process. The antennas have been simulated and measured off-the-finger and on-the-finger. Simulated and measured reflection coefficients (S 11 ) and radiation patterns are found to be in good agreement. The proposed on-body antennas can find application in the Internet of Things (IoT) where large amount of sensing data can be shared at the microwave and millimetre wave spectrum of future 5G communications. The removable finger nails could include other electronic devices such as on-body sensors, computational, storage and communication systems