Precision full-wave rectifier

Simplified circuit uses one operational amplifier and two precision resistors. The amplifier is operated open loop for switching and closed loop for linear gain, both simultaneously

Applying causality principles to the axiomatization of probabilistic cellular automata

Cellular automata (CA) consist of an array of identical cells, each of which may take one of a finite number of possible states. The entire array evolves in discrete time steps by iterating a global evolution G. Further, this global evolution G is required to be shift-invariant (it acts the same everywhere) and causal (information cannot be transmitted faster than some fixed number of cells per time step). At least in the classical, reversible and quantum cases, these two top-down axiomatic conditions are sufficient to entail more bottom-up, operational descriptions of G. We investigate whether the same is true in the probabilistic case. Keywords: Characterization, noise, Markov process, stochastic Einstein locality, screening-off, common cause principle, non-signalling, Multi-party non-local box.Comment: 13 pages, 6 figures, LaTeX, v2: refs adde

The organisational and human resource challenges facing primary care trusts : protocol of a multiple case study

BACKGROUND: The study is designed to assess the organisational and human resource challenges faced by Primary Care Trusts (PCTs). Its objectives are to: specify the organisational and human resources challenges faced by PCTs in fulfilling the roles envisaged in government and local policy; examine how PCTs are addressing these challenges, in particular, to describe the organisational forms they have adopted, and the OD/HR strategies and initiatives they have planned or in place; assess how effective these structures, strategies and initiatives have been in enabling the PCTs to meet the organisational and human resources challenges they face; identify the factors, both internal to the PCT and in the wider health community, which have contributed to the success or failure of different structures, strategies and initiatives. METHODS: The study will be undertaken in three stages. In Stage 1 the key literature on public sector and NHS organisational development and human resources management will be reviewed, and discussions will be held with key researchers and policy makers working in this area. Stage 2 will focus on detailed case studies in six PCTs designed to examine the organisational and human resources challenges they face. Data will be collected using semi-structured interviews, group discussion, site visits, observation of key meetings and examination of local documentation. The findings from the case study PCTs will be cross checked with a Reference Group of up to 20 other PCG/Ts, and key officers working in organisational development or primary care at local, regional and national level. In Stage 3 analysis of findings from the preparatory work, the case studies and the feedback from the Reference Group will be used to identify practical lessons for PCTs, key messages for policy makers, and contributions to further theoretical development

A high-speed microscopy approach to single-molecule studies of eukaryote signal transduction

Metabolic processes underlie all forms of life. An organism’s ability to utilise chemical energy to stay alive and eventually reproduce is a central feature of life, regardless of organism length scale. To achieve this, an organism must be adaptable. That is, it must be able to adjust to varying surrounding environmental conditions. Cells must be able to sense this environment, ‘transduce’ the signal and bring about some cell level response. Cells respond to external stimuli by releasing chemical cascades along often intricate signalling pathways which regulate cellular function. In this thesis, I have developed a novel optical microscopy system coupled to microfluidics and image analysis tools to help address challenging biological questions relating to metabolic sensing in eukaryotic life, using Saccharomyces cerevisiæ, as a model system. A set of biophysical tools was developed to monitor signal transduction events in live yeast cells. A bespoke optical microscope was developed that can monitor single living cells and determine their response to controlled variations in environmental nutrient concentration at high sampling speeds comparable to the molecular diffusion time scale in a cells internal environment. High-speed imaging at up to 200 frames per second and exposure times of 4.7 ms can be achieved. An electronic gain of 300x makes the camera system sensitive enough to track diffusion of single or small clusters of fluorescent protein molecules under physiological conditions. A high intensity laser excitation system was developed to deliver the light required to follow single fluorescent proteins in the living cells. A bespoke microfluidics system was built wherein cells can be exposed to rapidly changing extracellular environments and make it possible to follow individual cell responses to changing glucose conditions. Image analysis tools were adapted and developed to facilitate the automated measurement of protein mobility, stoichiometry and copy number, one cell at a time

A high-speed microscopy approach to single-molecule studies of eukaryote signal transduction

Metabolic processes underlie all forms of life. An organism’s ability to utilise chemical energy to stay alive and eventually reproduce is a central feature of life, regardless of organism length scale. To achieve this, an organism must be adaptable. That is, it must be able to adjust to varying surrounding environmental conditions. Cells must be able to sense this environment, ‘transduce’ the signal and bring about some cell level response. Cells respond to external stimuli by releasing chemical cascades along often intricate signalling pathways which regulate cellular function. In this thesis, I have developed a novel optical microscopy system coupled to microfluidics and image analysis tools to help address challenging biological questions relating to metabolic sensing in eukaryotic life, using Saccharomyces cerevisiæ, as a model system. A set of biophysical tools was developed to monitor signal transduction events in live yeast cells. A bespoke optical microscope was developed that can monitor single living cells and determine their response to controlled variations in environmental nutrient concentration at high sampling speeds comparable to the molecular diffusion time scale in a cells internal environment. High-speed imaging at up to 200 frames per second and exposure times of 4.7 ms can be achieved. An electronic gain of 300x makes the camera system sensitive enough to track diffusion of single or small clusters of fluorescent protein molecules under physiological conditions. A high intensity laser excitation system was developed to deliver the light required to follow single fluorescent proteins in the living cells. A bespoke microfluidics system was built wherein cells can be exposed to rapidly changing extracellular environments and make it possible to follow individual cell responses to changing glucose conditions. Image analysis tools were adapted and developed to facilitate the automated measurement of protein mobility, stoichiometry and copy number, one cell at a time