Ocular trauma

Ocular trauma is an important cause of unilateral blindness and visual impairment across the world. Most injuries are accidental, work-related injuries in developed countries, while assaults predominate as a cause in developing countries. Trauma may result in various forms of ocular injuries, ranging from minor insult to major functional impairment. Any ocular structure may be involved, and a careful, systematic approach to the examination of a patient is essential to avoid missing occult injury and resultant visual impairment. This paper highlights key points regarding the clinical evaluation of patients with ocular trauma and covers the presentation and primary care management of the more common ocular injuries

Predictors of HIV self-testing among health workers at Nyeri Provincial Hospital in Kenya

Background: HIV self-testing is recognised as a possible option of expanding access to HIV testing and counselling (HTC). There is high demand for self testing among health workers. However, in many health facilities in Kenya, the rate of unregulated self-testing and factors influencing the practice remain unknown.Objectives: To determine the prevalence and factors influencing HIV self-testing among health workersDesign: A descriptive cross-sectional study.Setting: Nyeri Provincial Hospital, the largest public hospital in Central Kenya.Subjects: Four hundred and fourteen Health workers at Nyeri Provincial Hospital who included the following cadres: Nurses, Doctors, Clinical officers, Laboratory Technicians, Community Health Workers and HTC counsellors.Results: The proportion of self-testers were 65.8% (N=348). The significant predictors of HIV self-testing were identified as age, difficulty of conducting HIV self-test, reliability of HIV self-test results and confidence in HIV positive self-test results. Self-testers (n=229) identified factors that influenced them to self-test as: easy access to test kits, obligation to test themselves, saves time and fear of stigma. Non self-testers (n=119) identified inability to handle HIV positive results; idea of self-test scares me, fear of stigma and lack of access to test kits as factors inhibiting self-testing.Conclusions: Self-testing is highly practiced by health workers at Nyeri provincial hospital. HIV related stigma needs to be addressed. Increasing access to test kits may increase self-testing

Ocular trauma

Ocular trauma is an important cause of unilateral blindness and visual  impairment across the world. Most injuries are accidental, work-related injuries in developed countries, while assaults predominate as a cause in developing countries. Trauma may result in various forms of ocular injuries, ranging from minor insult to major functional impairment. Any ocular structure may be involved, and a careful, systematic approach to the examination of a patient is essential to avoid missing occult injury and resultant visual impairment.  This paper highlights key points regarding the clinical evaluation of patients with ocular trauma and covers the presentation and primary care management of the more common ocular injuries

One-dimensional spectral analysis techniques for multilevel PWM strategies

This paper presents a novel spectral analysis technique for multilevel modulation. Conventionally, such analyses use a double Fourier series technique, but this approach can become intractable when complex reference waveforms (e.g., multilevel space vector offsets) and regular sampling processes are considered. In contrast, the strategy proposed in this paper separates the multilevel pulse width modulation (PWM) waveform into a spectral image of the reference, and sideband basis functions which are then expanded using a one-dimensional Fourier series. The coefficients of this Fourier series are defined by a one-dimensional Fourier integral that is simpler in form compared to the corresponding double integral associated with the double Fourier series. This analysis technique naturally incorporates regular sampling, and a discrete formulation is developed that enables complex PWM reference waveforms, including centered space vector offsets, to be solved. Results of this analysis are validated against previously published multilevel inverter double Fourier series results and matching switched simulations

Ripple compensation for a class-D amplifier

This paper presents the first detailed mathematical analysis of the ripple compensation technique for reducing audio distortion in a class-D amplifier with negative feedback. The amplifier converts a relatively low-frequency audio signal to a high-frequency train of rectangular pulses whose widths are slowly modulated according to the audio signal (pulse-width modulation, PWM). Distortion manifests itself through unwanted audio-frequency harmonics that arise in the output due to nonlinearities inherent in the design. In this paper, we first develop a small-signal model, which describes the fate of small-amplitude perturbations to a constant input, and demonstrate how this traditional engineering tool may be extended to allow one to infer the most significant contributions to the full output in response to a general audio input. We then compute the audio output of the amplifier through a perturbation expansion based on the ratio between audio and switching frequencies. Our results explicitly demonstrate how the ripple compensation technique significantly linearizes the output, thereby reducing the distortion

Integration of inverter constraints in geometrical quantification of the optimal solution to an MPC controller

Published Conference ProceedingsThis paper considers a model predictive controller with reference tracking that manipulates the integer switch positions of a power converter. It can be shown that the optimal switch position can be computed without solving an optimization problem. Specifically, in a new coordinate system, the optimization problem can be solved offline, leading to a polyhedral partition of the solution space. The optimal switch position can then be found using a binary search tree. This concept is exemplified for a three-level single-phase converter with an RL load

Continuous Synthesis of Gold Nanoparticles in Micro- and Milli-fluidic Systems

Gold nanomaterials have diverse applications ranging from healthcare and nanomedicine to analytical sciences and catalysis. Microfluidic and millifluidic reactors offer multiple advantages for their synthesis and manufacturing, including controlled or fast mixing, accurate reaction time control and excellent heat transfer. These advantages are demonstrated by reviewing gold nanoparticle synthesis strategies in flow devices. However, there are still challenges to be resolved, such as reactor fouling, particularly if robust manufacturing processes are to be developed to achieve the desired targets in terms of nanoparticle size, size distribution, surface properties, process throughput and robustness. Solutions to these challenges aremore effective through a coordinated approach from chemists, engineers and physicists, which has at its core a qualitative and quantitative understanding of the synthesis processes and reactor operation. This is important as nanoparticle synthesis is complex, encompassing multiple phenomena interacting with each other, often taking place at short timescales. The proposed methodology for the development of reactors and processes is generic and contains various interconnected considerations. It aims to be a starting point towards rigorous design procedures for the robust and reproducible continuous flow synthesis of gold nanoparticles

Comprehensive Survey of the Distribution of Colour and Phenolics of Different Red Grape Wine Vineyard Blocks from the Robertson Area in South Africa

Colour and phenolic content of red grapes are two of the most important constituents required to producea quality red wine. In the Robertson grape growing area, difficulty is sometimes experienced with colourdevelopment of grapes. This is especially linked to location and most probably greatly influenced byseason. Forty four vineyard blocks of the cultivars Pinotage, Merlot, Cabernet Sauvignon and Shiraz,were studied over 3 seasons primarily to focus on colour and phenolic content, but secondly on totalsoluble solids, titratable acidity and pH of the grapes. High performance liquid chromatography andspectrophotometric methods were used to determine various colour and phenolic parameters present atharvest. This data was used to indicate how colour and phenolic constitution of a part of the Robertsongrape growing area was distributed in relation to various factors, such as cultivar and season. GPS pointswere used to map data for the blocks visually. Results showed variable colour and phenolic content forthese grapes based on blocks and phenolic compounds investigated. Shiraz displayed a wider distributionof certain phenolic compounds over the three seasons than the other 3 cultivars. Seasonality had a greatinfluence on these results, with outlying blocks being identified