Channel modelling for visible light communication systems

Visible Light Communications (VLCs) have been identified as a potential solution for mitigating the looming Radio Frequency (RF) spectrum crisis. Having the ability to provide illumination and communication at the same time, this technology has been considered as one of the most promising communication technologies for future wireless networks. VLCs are a viable candidate for short-range indoor applications with very high data rates. In terms of outdoor applications, Vehicular VLCs (VVLCs) play an important role in vehicular ad hoc networks and Intelligent Transportation Systems (ITS). Adopting visible light in vehicular networks offers a great potential to enhance road safety and traffic efficiency towards accident-free driving. For the sake of VLC system design and performance evaluation, it is indispensable to develop accurate, efficient, and flexible channel models, which can fully reflect the characteristics of VLC channels. In this thesis, we first give a comprehensive and up-to-date literature review of the most important indoor Optical Wireless Communications (OWCs) measurement campaigns and channel models, primarily for Wireless Infrared Communications (WIRCs) and VLCs. Consequently, we can identify that an appropriate channel model for VLC systems is currently missing in the literature. This Ph.D. project is therefore devoted to the modelling of VLC channels for both indoor and outdoor communication systems. Second, a new Two-Dimensional (2D) stationary Field of View (FoV) one-ring Regular-Shape Geometry Based Stochastic Model (RS-GBSM) for VLC Single-Input Single-Output (SISO) channels is proposed. The proposed model considers the Line-of-Sight (LoS) and Single-Bounce (SB) components. VLC channel characteristics are analysed based on different positions of the Photodetector (PD) and FoV constraint. Third, we propose a new 2D stationary multiple-bounce RS-GBSM for VLC SISO channels. The proposed model employs a combined two-ring and confocal ellipse model. This model is sufficiently generic and adaptable to a variety of indoor scenarios since the received signal is constructed as the summation of the LoS, SB, Double-Bounce (DB), and Triple-Bounce (TB) rays with different powers. Fourth, a new 2D mobile RS-GBSM for vehicular VLC SISO channels is proposed. The proposed model combines a two-ring model and a confocal ellipse model, and considers SB and DB components in addition to LoS component. Unlike conventional models, the proposed model considers the light that is reflected off moving vehicles around the Transmitter (Tx) and Receiver (Rx), as well as the light that is reflected off the stationary roadside environments. Vehicular VLC channel characteristics are analysed along different distance ranges between 0 and 70 m and different PD heights. Fifth, we propose a novel Three-Dimensional (3D) mobile RS-GBSM for vehicular VLC Multiple-Input Single-Output (MISO) channels. The proposed model combines two-sphere and elliptic-cylinder models. Both the LoS component and SB components, which are reflected off moving vehicles and stationary roadside environments, are considered. The proposed 3D RS-GBSM has the ability to study the impact of the vehicular traffic density on the received power and jointly considers the azimuth and elevation angles by using the von Mises-Fisher (VMF) distribution. In summary, this work proposes new realistic VLC channel models which are useful for the design, test, and performance evaluation of advanced indoor and outdoor VLC systems. Furthermore, it identifies important directions that can be considered in future research, and helps propose new applications that require the development of more realistic channel models before the actual implementation

Assessment Of The Global Fallout Of Plutonium Isotopes In The Topsoil Of Qatar: Establishing A Baseline Concentrations Of 238pu, 239pu, And 240pu

A radio-analytical technique for determination of plutonium (Pu) isotopes in soil samples is tested against NIST and IAEA standard reference materials to determine its accuracy and precision for reliable results. The technique is then used in the investigation of 132 topsoil samples, collected from the natural environment of Qatar, to assess the effect of global fallout accumulation of these radionuclides in the region. Plutonium was sequentially leached form 1000 g of each soil sample using nitric and hydrochloric acids. The residual fine particles were separated by filtration and centrifuge. The solution was reduced to 1 ml by evaporation in dry oven and measured directly by CRC-ICP-MS/MS without prior chemical separation of Pu. The concentrations of 238Pu in the collected soil samples vary from < 0.026 - 0.058 fg/g (< 0.0160 - 0.0266 Bq/kg) with a mean value of 0.034 fg/g (0.0195 Bq/kg) and a median value of 0.032 fg/g (0.0195 Bq/kg). The concentrations of 239Pu fall in the range 5.67 - 166.09 fg/g (0.014 - 0.381 Bq/kg) with a mean value of 67.33 fg/g (0.154 Bq/kg) and a median value of 63.21 fg/g (0.145 Bq/kg). The concentrations of 240Pu fall in the range 1.48 - 28.21 fg/g (0.013 - 0.240 Bq/kg) with a mean value of 11.46 fg/g (0.098 Bq/kg) and a median value of 10.835 fg/g (0.093 Bq/kg). The isotopic and activity concentrations ratios of 238Pu/239Pu, 240Pu/239Pu, and 238Pu/239+240Pu can be used to identify the source. The main isotope ratios of 238Pu/239Pu in Qatari soils is (3.33 ± 1.02) x 10-4. A reported global and Chernobyl fallouts isotope ratio of 238Pu/239Pu are 1.77 x 10-4 and 4.3 x 10-3, respectively. The main isotope ratio of 240Pu/239Pu in Qatari soils is 0.1749 ± 0.0211. A reported global and Chernobyl fallouts isotope ratios of 240Pu/239Pu are 0.18-0.19 and 0.34-0.57, respectively. The average isotopic and activity ratios of 238Pu/239,240Pu in Qatari soils are (2.856 ± 0.881) x 10-4 and 0.0505 ± 0.0032, respectively. The activity ratio 238Pu/239+240Pu in releases from nuclear fuel reprocessing plants, nuclear tests, weapons grade, and Chernobyl fallout are about 0.25, 0.026, 0.014 and 0.47, respectively. Accordingly, it is difficult to identify the source, but it may be due to the contribution of more than one source. The most probable sources are both Chernobyl fallout of Pu isotopes and several decades of fallout Pu accumulation due to nuclear weapons testing. Novel Aspect New data base was established for the concentration and isotope ratios of Pu isotopes (238Pu, 239Pu, and 240Pu) in Qatar topsoil.qscienc

Retinal cell regeneration using tissue engineered polymeric scaffolds

Degenerative retinal diseases, such as age-related macular degeneration (AMD), can lead to permanent sight loss. Although intravitreal anti-vascular endothelial growth factor (VEGF) and steroid injections are effective for the management of early stages of wet and/or neovascular AMD (nAMD), no proven treatments currently exist for dry AMD or for the advanced geographic atrophy of the retina that follows. Tissue engineering (TE) has recently emerged as a promising alternative to repair retinal damaged and restore its functions. Here, we review recent advances in TE, with a particular emphasis on retinal regeneration. We provide an overview of retinal diseases, followed by a comprehensive review of TE techniques, cells, and polymers used in the fabrication of scaffolds for retinal cell regenerations, in particular the retinal pigment epithelium (RPE). - 2019Scopu

Assembling surfactants-mucoadhesive polymer nanomicelles (ASMP-nano) for ocular delivery of cyclosporine-A

The physiological protective mechanisms of the eye reduce the bioavailability of topically administered drugs above all for those with high molecular weight and /or lipophilic characteristics, such as Cyclosporine A (CyA). The combined strategy based on the association of nanomicelles and mucoadhesive polymer seems promising since a limited number of commercial products containing CyA have been recently approved. The scope of this investigation was the design of Assembling Surfactants-Mucoadhesive Polymer Nanomicelles (ASMP-Nano), based on a binary system of two surfactants in combination with hyaluronic acid, and their biopharmaceutical evaluation. The optimisation of the ASMP-Nano in term of the amount of surfactants, CyA-loading and size determined the selection of the clear and stable Nano1HAB-CyA formulation containing 0.105% w/w CyA loaded-nanomicelles with a size of 14.41 nm. The nanostructured system had a protective effect towards epithelial corneal cells with a cell viability of more than 80%. It interacted with cellular barriers favouring the uptake and the accumulation of CyA into the cells as evidenced by fluorescent probe distribution, by hindering CyA permeation through reconstituted corneal epithelial tissue. In pharmacokinetics study on rabbits, the nanomicellar carrier prolonged the CyA retention time in the precorneal area mainly in presence of hyaluronic acid (HA), a mucoadhesive polymer

Synthesis and Biological Activity of Three Novel Azo Dyes

The azo dyes that named, (E)-4-((2-nitrophenyl) diazenyl) benzene-1,3-diol (1), (E)-4- ((3-nitrophenyl) diazenyl) benzene-1,3-diol (2) and (E)-4-((4-nitrophenyl) diazenyl) benzene-1,3-diol (3) were synthesized and then characterized using IR, UV-visible spectrum. These results were compared with that obtained by ChemBio 3D Ultra - [Chem3D XML] Gaussian Interface and were seems to be identical. Then, the antimicrobial activity of each azo dye was carried out against two bacterial strains: Staphylococcus aureus NCTC 6571, and Escherichia coli ATCC 25922, and fungal strains of Candida albicans using Agar-well diffusion method. The results were showed that the three azo dyes were biologically active and the best reactivity was observed in (2). Though, the biological activity of (1) with NO2 group in ortho- position remained reasonable against Candida albicans. But, the effect of (1) was resisted by Staphylococcus aureus and Escherichia coli. However, the (2) and (3) with substituted NO2 group in meta- and para- positions respectively were showed better reactivity’s than (1) towered Candida albicans and Staphylococcus aureus. Further, the Gaussian interface properties and the conformational analysis of (1), (2) and (3) were intended. The results were indicated that the variations in the properties of each azo dye and their conformational energies of generated conformers can affect their biological activity afterward. Keywords: key words, Azo dyes, Staphylococcus aureus, Escherichia coli, Candida albicans, Agar-well diffusion method, Antimicrobial activit

Monocaprin eye drop formulation to combat antibiotic resistant gonococcal blindness

Abstract: Neisseria gonorrhoeae bacteria are acknowledged as an urgent threat to human health because this species has developed resistances to all of the antibiotics used clinically to treat its infections. N. gonorrhoeae causes the sexually transmitted disease gonorrhoea, but also causes blindness when the bacteria infect the eyes. Infants are particularly susceptible, acquiring the infection from their mothers at birth. We have shown that the monoglyceride monocaprin rapidly kills N. gonorrhoeae and other bacterial species and is non-irritating in ocular assays. Here we show that the physical and chemical properties of monocaprin make it ideal for use in a thickened eye drop formulation to combat eye infections. Monocaprin-containing formulations were assessed using analytical techniques and for antimicrobial activity in vitro and in ex vivo infections. Monocaprin-containing formulations retained activity after three years and are non-irritating, unlike preparations of povidone iodine in our assays. A recommended formulation for further development and investigation is 0.25% monocaprin in 1% HPMC with 1% polysorbate 20

Electrically atomised formulations of timolol maleate for direct and on-demand ocular lens coatings

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link

Studies on surfactants, cosurfactants, and oils for prospective use in formulation of ketorolac tromethamine ophthalmic nanoemulsions

Nanoemulsions (NE) are isotropic, dispersions of oil, water, surfactant(s) and cosurfactant(s). A range of components (11 surfactants, nine cosurfactants, and five oils) were investigated as potential excipients for preparation of ketorolac tromethamine (KT) ocular nanoemulsion. Diol cosurfactants were investigated for the effect of their carbon chain length and dielectric constant (DEC), Log P, and HLB on saturation solubility of KT. Hen’s Egg Test—ChorioAllantoic Membrane (HET-CAM) assay was used to evaluate conjunctival irritation of selected excipients. Of the investigated surfactants, Tween 60 achieved the highest KT solubility (9.89 ± 0.17 mg/mL), followed by Cremophor RH 40 (9.00 ± 0.21 mg/mL); amongst cosurfactants of interest ethylene glycol yielded the highest KT solubility (36.84 ± 0.40 mg/mL), followed by propylene glycol (26.23 ± 0.82 mg/mL). The solubility of KT in cosurfactants was affected by four molecular descriptors: carbon chain length, DEC, log P and HLB. KT solubility was directly proportional to DEC and the HLB yet, inversely proportional to carbon chain length and log P. All surfactants, except Labrasol ALF, were non-irritant. The majority of cosurfactants were slightly irritant, butylene glycol was a moderate irritant, pentylene and hexylene glycols were strong irritants. These findings will inform experiments aimed at developing NE formulations for ocular administration of KT

Incorporating morpholine and oxetane into benzimidazolequinone anti-tumor agents : the discovery of 1,4,6,9-tetramethoxyphenazine from hydrogen peroxide and hydroiodic acid-mediated oxidative cyclizations

The reactivity of hydrogen peroxide and catalytic hydroiodic acid towards 3,6-dimethoxy-2-(cycloamino)anilines is tunable to give ring-fused benzimidazoles or 1,4,6,9-tetramethoxyphenazine in high yield. Mechanisms via a detected nitroso-intermediate are proposed for oxidative cyclization and the unexpected intermolecular displacement of the oxazine. An aqueous solution of molecular iodine is capable of the same transformations. Oxidative demethylation gave targeted benzimidazolequinones, including without cleavage of the incorporated oxetane