Optimum blade configurations for the cutting of soft solids

For the same amount of work in separating surfaces of soft solids, the forces normal and tangential to an element of a cutting blade are determined by the local velocities of the material past the cutting edge, in particular by the ratio ξ of ‘slice’ to ‘push’ velocities. The greater the ξ, the lower the forces and hence reduced damage to the cut surfaces (i.e., better surface finish). Different examples are considered of flat blades of variable curvature (such spiral-profiled blades in food cutting machinery, scythes, sickles, sabres, etc.) where the local forces vary along the edge of the blade as the curvature changes. How to maximise ξ is discussed along with questions of whether the material to be cut is restrained or not. The mechanics of cutting by a cylinder lawn mower is also investigated. Here the blades are arranged on helices around the cylinder and ξ is determined by the helix angle and by N = (rω/f) which is the ‘gearing’ of the cylinder with respect to the forward speed of the machine. There is a compromise between low cutting forces and flatness of cut surface that has to be adopted in design of practical machines.     

Aberrations of spherocylindrical spectacle lenses

A procedure has been developed for tracing a bundle of rays through and ophthalmic lens and a schematic eye with its primary line of sight pointed through various parts of the lens. A bundle of eight rays can provide data for assessing the quality of the image formed by such a system. To test the procedure and to generate data which can help in selecting a method for evaluating image quality, we selected a single lens as an example. The lens selected has a spherical back surface (-5.00 diopters) and a toric front surface (+15.00 diopters in the vertical and /10.00 diopters in the horizontal). It has a center thickness of 5 mm and glass of index 1.523. Spot diagrams were generated with the eye pointed in various directions through the ophthalmic lens. The data generated showed that peripheral bundles which fall between the principal meridians emerge as astigmatic bundles. This leads to the proposal that blur circle theory can be used for evaluating the quality of the optical image and that it suffices in the case of a spherocylindrical ophthalmic lens to base the tolerances for refractive power on measurements made in the principal meridians.     

A memetic algorithm for multiple-drug cancer chemotherapy schedule optimization.

This correspondence introduces a multidrug cancer chemotherapy model to simulate the possible response of the tumor cells under drug administration. We formulate the model as an optimal control problem. The algorithm in this correspondence optimizes the multidrug cancer chemotherapy schedule. The objective is to minimize the tumor size under a set of constraints. We combine the adaptive elitist genetic algorithm with a local search algorithm called iterative dynamic programming (IDP) to form a new memetic algorithm (MA-IDP) for solving the problem. MA-IDP has been shown to be very efficient in solving the multidrug scheduling optimization problem.     

Quantum Information Storage in the Localized State of a Spin Chain

We describe a chain of qubits with always on exchange interaction in the presence of a spatial inhomogeneity in the qubit level spacing. Similarly to the phenomenon of Anderson localization, this system has a localized eigenstate which can be used to store or trap quantum information. We discuss both the fidelity of storage and the leakage of information from this localized state and show that even a very small defect can be useful. Presented at the 38th Symposium on Mathematical Physics “Quantum Entanglement & Geometry”, Toruń, June 4–7, 2006.     

Using multimedia and Web3D to enhance anatomy teaching

Anatomy teaching is undergoing significant changes due to time constraints, limited availability of cadavers and technological developments in the areas of three-dimensional modelling and computer-assisted learning. This paper gives an overview of methods used to teach anatomy to undergraduate medical students and discusses the educational advantages and disadvantages of using three-dimensional computer models. A ‘work in progress’ account is then given of a project to develop two Web3D resources to enhance undergraduate tuition of the nervous system. Our approach is to support existing curricula using advanced modelling tools and a variety of delivery mechanisms.     

Overlap of clusters of psychiatric symptoms among clients of a comprehensive addiction treatment service.

This article describes the prevalence and overlap of psychiatric symptoms among 2,784 clients of the outpatient programs at a comprehensive addictions treatment facility. The psychiatric symptoms were assessed by a computer-based questionnaire, and the analysis focused on the overlap of symptom clusters (multimorbidity) and their relation to selected intake variables known to be predictors of treatment outcome. Of all clients, 27.4% scored positive for 1, 18.9% for 2, and 22.3% for 3 or more clusters, the most frequent being depression, anxiety, and history of conduct disorder. Multimorbidity was significantly correlated with female gender, unemployment, less social support, cannabis problems, fewer legal problems, and increased treatment engagement. Clients with more substance use disorders presented more psychiatric symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigations of the attenuation coefficient of a narrow-bandwidth pulsed laser beam in water

The attenuation coefficient of a pulsed laser beam in water is investigated experimentally. It is found that the attenuation coefficient is dependent on the pulse energy and the linewidth of the laser, rather than a constant. The attenuation coefficient for a narrow linewidth laser can exceed that of a broad linewidth laser due to stimulated Brillouin scattering when the laser intensity is larger than a certain value. A theoretical analysis is provided.