Indoor Optical Wireless Receiver – Theory And Design

This paper presents a systematic approach to the design of receiver for indoor optical wireless communication. In particular, it is concerned with how one can properly chooses the front-end preamplifier and biasing circuitry for the photodetector. A comparison between differences types of amplifier, and bandwidth enhancement technique is also discussed. For most photodetector applications, large values of RL and CD would severely restrict bandwidth. It is shown that a proper front-end design incorporates a transimpedance preamplifier which tends to integrate the detector output. Such a design provides significant reduction in photodiode capacitance and increase bandwidth when compared to a design which does not integrate initially. Two novel techniques, using bandwidth adjustment for better service quality with a bootstrapped transimpedance amplifier and bootstrapped composite transimpedance amplifier is presented. A controllable capacitance is introduced at the output of the second stage of the amplifier. These technique permits a bandwidth adjustment from 52Hz to 233MHz for a capacitance range of 10uF to 1pF, while the composite amplifier bandwidth adjustment of the circuit can be controlled in the frequency range of 6MHz to 60MHz for a capacitance range of 50pF to 1nF

Tooling materials compatible with carbon fibre composites in a microwave environment

Although metals are the most commonly used tooling materials to cure composites, they do not provide optimal results in a microwave environment. Following a selection process based on the properties of the materials, an alternative tooling material in carbon fibre reinforced plastic (CFRP) was successfully utilised to cure CFRP panels in laboratory and industrial microwaves. The conductive carbon fibres in the tool facilitated the fast heat transfer across the part. Other tooling materials including a glass fibre cyanate ester prepreg and tooling board were trialled, although the latter exhibited damage during cure. These advantages demonstrate that the CFRP tool is a compatible material that can be used when microwave curing composites

JAK2V617F promotes replication fork stalling with disease-restricted impairment of the intra-S checkpoint response

Cancers result from the accumulation of genetic lesions, but the cellular consequences of driver mutations remain unclear, especially during the earliest stages of malignancy. The V617F mutation in the JAK2 non-receptor tyrosine kinase (JAK2V617F) is present as an early somatic event in most patients with myeloproliferative neoplasms (MPNs), and the study of these chronic myeloid malignancies provides an experimentally tractable approach to understanding early tumorigenesis. Introduction of exogenous JAK2V617F impairs replication fork progression and is associated with activation of the intra-S checkpoint, with both effects mediated by phosphatidylinositide 3-kinase (PI3K) signaling. Analysis of clonally derived JAK2V617F-positive erythroblasts from MPN patients also demonstrated impaired replication fork progression accompanied by increased levels of replication protein A (RPA)-containing foci. However, the associated intra-S checkpoint response was impaired in erythroblasts from polycythemia vera (PV) patients, but not in those from essential thrombocythemia (ET) patients. Moreover, inhibition of p53 in PV erythroblasts resulted in more gamma-H2Ax (γ-H2Ax)–marked double-stranded breaks compared with in like-treated ET erythroblasts, suggesting the defective intra-S checkpoint function seen in PV increases DNA damage in the context of attenuated p53 signaling. These results demonstrate oncogene-induced impairment of replication fork progression in primary cells from MPN patients, reveal unexpected disease-restricted differences in activation of the intra-S checkpoint, and have potential implications for the clonal evolution of malignancies

Cell and gene therapies at the forefront of innovative medical care: Implications for South Africa

The fields of cell and gene therapy are moving rapidly towards providing  innovative cures for incurable diseases. A current and highly topical  example is immunotherapies involving T-cells that express chimeric antigen receptors (CAR T-cells), which have shown promise in the treatment of leukaemia and lymphoma. These new medicines are indicative of the changes we can anticipate in the practice of medicine in the near future. Despite their promise, they pose challenges for introduction into the healthcare sector in South Africa (SA), including: (i) that they are  technologically demanding and their manufacture is resource intensive; (ii) that the regulatory system is underdeveloped and likely to be challenged by ethical, legal and social requirements that accompany these new therapies; and (iii) that costs are likely to be prohibitive, at least initially, and before economies of scale take effect. Investment should be made into finding novel and innovative ways to introduce these therapies into SA sooner rather than later to ensure that SA patients are not excluded from these exciting new opportunitie

Bayesian Parameter Estimation and Model Selection of a Nonlinear Dynamical System using Reversible Jump Markov Chain Monte Carlo

The aim of this paper is to demonstrate the potential of the Reversible Jump Markov Chain Monte Carlo (RJMCMC) algorithm when applied to system identification problems which involve both parameter estima- tion and model selection. Within the context of Bayesian Inference, Markov Chain Monte Carlo (MCMC) methods have been used for a long period of time to address the parameter estimation of linear and nonlinear systems, which are described approximately by a model. It is often the case that there are a set of competing model structures that could potentially produce good approximations of the real system - this raises the issue of model selection. Even though they address parameter estimation, many MCMC samplers cannot address model selection. As an extension to one of the most well known MCMC samplers, the Metropolis-Hastings algorithm, the RJMCMC algorithm is a MCMC method that covers model selection as well as parameter estimation simultaneously. RJMCMC can be applied when models contain different numbers of parameters. The algorithm is capable of moving between parameter spaces of different dimension in order to find the most appropriate model that describes the system and the most probable parameters within that model. In this contribution the RJMCMC algorithm is introduced in the context of nonlinear dynamical systems and is demonstrated on simulated data