Cenozoic plate driving forces

Past studies of plate driving forces have concluded that the forces due to subducted slabs in the upper mantle and those due to the thickening of the oceanic lithosphere are the principal driving forces. We reexamine the balance of driving forces for the present-day and extend our analysis through the Cenozoic, using an analytical torque balance method which accounts for interactions between plates via viscous coupling to the induced mantle flow, We use an evolving mantle density heterogeneity field based on the last 200 Myr. of subduction to drive plate motions, an approach which has proven successful in predicting the present-day mantle heterogeneity field. We find that for plausible upper mantle viscosities the forces due to subducted slabs in the Cenozoic and Mesozoic account for in excess of 90% of plate driving forces and those due to lithospheric thickening for less than 10%

Optically induced free carrier light modulator

Signal carrier laser beam is optically modulated by a second laser beam of different frequency acting on a free carrier source to which the signal carrier laser is directed. The second laser beam affects the transmission characteristics of the free carrier source to light from the signal carrier laser, thus modulating it

Thermal-structural panel buckling tests

The buckling characteristics of a titanium matrix composite hat-stiffened panel were experimentally examined for various combinations of thermal and mechanical loads. Panel failure was prevented by maintaining the applied loads below real-time critical buckling predictions. The test techniques used to apply the loads, minimize boundary were shown to compare well with a finite-element buckling analysis for previous panels. Comparisons between test predictions and analysis for this panel are ongoing

Unlocking the potential of contract farming: lessons from Ghana

This paper analyses sorghum contract farming in north-east Ghana in order to explore ways of making such arrangements viable for small farmers. The analysis draws on the convergence of sciences approach, which sees both science and social relations (interactions among the relevant stakeholders) as important for developing small farmer-relevant agricultural innovations (technology, procedures, new forms of organisation). The study reveals that the failure and problems encountered in this particular contracting scheme were both technical and institutional. The technical issues were a combination of pest problems, the environment and the sorghum variety chosen. The institutional issues involved the contractual arrangements and relations between the contracting parties. The authors argue that if contracts are to be fair, they must allow for compensation, contingencies and production risks. But scientific knowledge is required in order to adequately incorporate these elements

Laserlight visual cueing device for freezing of gait in Parkinson's disease: a case study of the biomechanics involved

AbstractBackground: Freezing of gait (FOG) is a serious gait disorder affecting up to two-thirds of people with Parkinson's disease (PD). Cueing has been explored as a method of generating motor execution using visual transverse lines on the floor. However, the impact of a laser light visual cue remains unclear. Objective: To determine the biomechanical effect of a laser cane on FOG in a participant with PD compared to a healthy age- and gender-matched control. Methods: The participant with PD and healthy control were given a task of initiating gait from standing. Electromyography (EMG) data were collected from the tibialis anterior (TA) and the medial gastrocnemius (GS) muscles using an 8-channel system. A 10-camera system (Qualisys) recorded movement in 6 degrees of freedom and a calibrated anatomical system technique was used to construct a full body model. Center of mass (COM) and center of pressure (COP) were the main outcome measures. Results: The uncued condition showed that separation of COM and COP took longer and was of smaller magnitude than the cued condition. EMG activity revealed prolonged activation of GS, with little to no TA activity. The cued condition showed earlier COM and COP separation. There was reduced fluctuation in GS, with abnormal, early bursts of TA activity. Step length improved in the cued condition compared to the uncued condition. Conclusion: Laserlight visual cueing improved step length beyond a non-cued condition for this patient indicating improved posture and muscle control

Communicative Needs in Foreign Language Learning

The theme of language and the learner's communicative needs is a familiar one in language teaching. In recent years applied linguistics has been revitalized by attempts to describe how language reflects its communicative uses, and by demonstrations of how syllabus design and methodology can respond to the need for communicative uses of language in classrooms and teaching materials. This paper attempts to contribute to our general understanding of how language use reflects underlying communicative needs by considering some central aspects of communication. Five assumptions about the nature of verbal communication will be discussed, namely, that communication is meaning based, conventional, appropriate, interactional and structured. These will be discussed in relation to the communicative needs of second or foreign language learners

Method and apparatus for optical modulating a light signal Patent

Method and apparatus for optically modulating light or microwave bea