Butane extraction of model organic pollutants from water

In this study, n-butane (n-C(4)H(10)), a by-product of the oil refining process, was used as the extractant to remove various model organic pollutants including halogenated hydrocarbons, phenols and aromatic compounds from aqueous matrices. The presence of salt, inorganic acid and dissolved organic materials in the aqueous matrix were found to have little influence on the removal efficiency. High removal efficiencies are readily achievable for a great number of organic pollutants. The removal efficiencies for hydrophobic pollutants were greater than 90% for a single stripping stage for pollutants with a distribution constants (K(D)) greater than 45 and for a n-butane to aqueous phase ratio of 1-5. Results were also reported for the removal of residual butane in treated effluent by combinations of depressurization, air stripping and elevating operating temperature.     

Design and simulation of MEMS optical switch using photonic bandgap crystal

This paper details the novel design of a non-blocking in-plane microelectromechanical systems (MEMS) optical cross connect (OXC) designed and simulated with a new class of material known as the photonic bandgap (PBG) crystal for integration of device technology in optical switching and telecommunication applications. Particularly, silicon is the material of choice being investigated for the PBG MEMS device designed to address the objectives of achieving high optical performance with strategic exploitation for potential applications. Based on the physical and mathematical theories, the PBG and MEMS structures are studied and modelled. Simulations were carried out based on the plane wave method (PWM) and the finite difference time domain (FDTD) method to explore the benefits of integrating photonic crystals with MEMS technology to improve the performance of OXC devices.     

Continuous-time envelope-constrained filter design via Laguerrefilters and ℋ∞ optimization methods

The envelope-constrained filtering problem is concerned with the design of a time-invariant filter to process a given input signal such that the noiseless output of the filter is guaranteed to lie within a specified output mask while minimizing the noise gain of the filter. An algorithm is developed to solve the continuous-time envelope-constrained filter design problem with the ℋ_∞ norm of the filter as the cost and an orthonormal set of basis filters. It is shown that the problem can be reformulated and solved as a constrained ℋ _∞ model-matching problem. To illustrate the effectiveness of the design method, two numerical examples are presented that deal with the design of equalization filters for digital transmission channels     

Directing Orbits of Chaotic Systems in the Presence of Noise: Feedback Correction

In thispaper, we consider the directing of orbits of chaotic dynamicalsystems towards desired targets in the presence of random dynamicalnoise. Our aim is to significantly reduce the time needed toreach a target region by applying only small, bounded perturbations.We outline a technique for deriving open-loop controllers basedon optimal control theory, and then propose methods for improvingthe performance of these controllers to counter the effects ofnoise. The improvements are illustrated by examples.     

Splenic lymphoma with villus lymphocytes--an uncommon cause for lymphocytosis

We describe the clinical and laboratory features of four patients who presented with mild to moderate lymphocytosis but with no peripheral lymphadenopathy. These patients in the past, would have been classified as chronic lymphocytic leukaemia (CLL). However, it is now realised that chronic lymphoproliferative disorders are very heterogeneous and the clinical and laboratory features of our patients would support a diagnosis of splenic lymphoma with villus lymphocytes (SLVL) with characteristic morphological features. SLVL usually runs a benign clinical course but symptoms related a benign clinical course but symptoms related to splenomegaly or hypersplenism may be a problem. Splenectomy is considered the treatment of choice in these patients. Two of our patients had splenectomy and the other two patients are on regular follow-up without any specific treatment. It is therefore important to recognise this uncommon condition and also to differentiate it from CLL.     

Control of a 2-DOF manipulator with a flexible forearm

In this paper we present experimental results on the position and vibration control of the end-effector of a 2-DOF parallelogram manipulator with a flexible forearm. A dynamic model of the manipulator is first obtained. Control strategies are implemented to control the manipulator. The first control strategy uses the computed torque method based on a reduced-order dynamic model of the manipulator which is obtained by assuming that all the links are rigid. This method is referred to as the reduced-order computed torque (ROCT) method. Experimental results demonstrate that such a strategy is not good for vibration control of the end-effector of the manipulator. The second control strategy is a state feedback control law designed based on a local linearization of the nonlinear dynamic model. Experimental results show that this control strategy achieves good vibration control of the end-effector of the manipulator. However, since the strategy is based on local linearization, it is valid only in a neighbourhood of the operating point. A hybrid controller that uses the ROCT method for the initial large movement of the manipulator is then implemented. Based on a switching rule, the controller is switched to the state feedback controller based on the linearized model when the manipulator is sufficiently close to the equilibrium state. Experimental results are reported and the successful performance of the controller in dampening out end-point vibrations is demonstrated.     

Antiarrhythmic therapies for the prevention of sudden cardiac death

Despite remarkable advances in cardiovascular therapeutics, sudden cardiac death remains a significant problem. In this review, data from clinical trials and other studies on antiarrhythmic therapies have been evaluated in order to determine effective strategies for the prevention of sudden cardiac death in high risk patients. Overall, routine prophylactic use of class I antiarrhythmic agents in high risk patients, mostly survivors of acute myocardial infarction, is associated with increased risk of death [61 trials, 23,486 patients: odds ratio (OR) 1.13; 95% confidence interval (CI) 1.01 to 1.27, p < 0.05]. Conversely, beta-blockers are associated with highly significant reductions in risk of death in postinfarction patients (56 trials, 53,521 patients: OR 0.81; 95% CI 0.75 to 0.87, p < 0.00001). Overall data from the amiodarone trials on high risk patients, including postinfarction patients, patients with congestive heart failure or survivors of cardiac arrest, suggest that this agent is effective in reducing the risk of death (14 trials, 5713 patients: OR 0.83; 95% CI 0.72 to 0.95, p = 0.01) although further studies are needed to better define which types of patients will potentially benefit most from this agent. No benefits were seen with calcium channel blockers (26 trials, 21,644 patients: OR 1.03; 95% CI 0.94 to 1.13, p = NS). The implantable cardioverter-defibrillator is a promising option for high risk patients, but definition of its role awaits the completion of ongoing clinical trials. Since causes of sudden death are heterogeneous, the clinician should pursue a multifactorial approach to its prevention. Primary and secondary prevention of cardiac ischaemia, through the treatment of cardiovascular risk factors and maximising the use of aspirin, beta-blockers, lipid-lowering drugs, and angiotensin converting enzyme inhibitors after acute myocardial infarction, should lead to a future decrease in the incidence of sudden cardiac death.     

A survey of management practices for isolated systolic hypertension

OBJECTIVE: To determine the management practices of clinicians for patients with isolated systolic hypertension, with particular attention to treatment thresholds, medication choices, and target blood pressures. DESIGN: Self-administered questionnaire. SETTING: Edmonton, Alberta, a large Canadian city. PARTICIPANTS: A random sample of 348 family physicians and 125 internists. MEASUREMENTS: Demographics of the respondents, first and second choice of antihypertensives, treatment thresholds, and target blood pressures for patients with isolated systolic hypertension. RESULTS: Excluding 54 nondeliverable questionnaires, a response rate of 67% (281 surveys) was obtained. The responding clinicians reported treatment thresholds and target blood pressures consistent with the evidence from randomized clinical trials and the recommendations of the Canadian Hypertension Society and the Fifth Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure. Thiazide diuretics were recommended as first line therapy by 74% of internists and 58% of family physicians. Angiotensin converting enzyme inhibitors were the most frequently chosen second line drug (27% of internists and 45% of family physicians). CONCLUSIONS: The reported management practices of this group of clinicians are consistent with the evidence from randomized clinical trials and the recommendations of national consensus guidelines.     

Dynamic properties of optically switched bistable semiconductorlasers

The dynamic properties of optically switched semiconductor lasers biased from below-to-above threshold are presented theoretically. An analytic expression for the carrier density in the active region of a laser with respect to time is given to discuss the switching-off time. The numerical results show that the switching-on time and the switching-off time are governed by different mechanisms. They are related to the laser parameters for the free-running laser. They also depend on the optical power and the time duration of the input optical pulse and the frequency detuning between the frequency of the free-running laser and that of the input optical pulse. A small frequency detuning is desired to reduce both the switching-on and switching-off times. However, there is an optimal detuning to maximize the energy of the output optical pulse. On the other hand, for fixed detuning and injection power, a larger bias current results in a shorter switching-off time, but a lower bias current results in a shorter switching-on time