Two gimbal bearing case studies: Some lessons learned

Two troublesome, torque related problems associated with gimbal actuators are discussed. Large, thin section angular contact bearings can have a surprisingly high torque sensitivity to radial thermal gradients. A predictive thermal-mechanical bearing analysis, as described, was helpful in establishing a safe temperature operating envelope. In the second example, end-of-travel torque limits of an oscillatory gimbal bearing appoached motor stall during limit cycling life tests. Bearing modifications required to restore acceptable torque performance are described. The lessons learned from these case studies should benefit designers of precision gimbals where singular bearing torque related problems are not uncommon

An engineering approach to automatic programming

An exploratory study of the automatic generation and optimization of symbolic programs using DECOM - a prototypical requirement specification model implemented in pure LISP was undertaken. It was concluded, on the basis of this study, that symbolic processing languages such as LISP can support a style of programming based upon formal transformation and dependent upon the expression of constraints in an object-oriented environment. Such languages can represent all aspects of the software generation process (including heuristic algorithms for effecting parallel search) as dynamic processes since data and program are represented in a uniform format

Will the United States continue to allocate a growing proportion of its GDP to health care?

What policy options would improve the access, efficiency, and quality shortcomings found in the current U.S. health care system? This session will address the efficacy of the available policy alternatives and their likely interactions. What, for instance, are the cost implications of providing better insurance coverage and encouraging ongoing scientific progress? How should these desirable objectives be financed? Can better measures of quality and outcomes and more effective management systems help to balance our health care goals?Health care reform

Civil Service and Military Service Pensions In China

As quoted by Palacios and Whitehouse, there are separate pension schemes for civil servants in about half the world’s countries. This includes the People’s Republic of China. In some countries pension costs for public sector employees form a disproportionately large part of the total pension expenditure, and this applies to China. Whereas a considerable volume of material is available on the Chinese national pension systems, there has been far less study of the pension arrangements in place for the civil service, public service employees and military personnel in China. Indeed it has proven particularly difficult to obtain reliable and accurate information as to the pension arrangements for the People’s Liberation Army. Of course pension provision worldwide is attracting a great deal of attention because of its importance at a micro level, i.e. as replacement income for individuals after retirement, and at a macro level, viz. the impact on the overall economy of both funded and unfunded arrangements. The major pressures affecting the different pension systems in China, and indeed worldwide, include: - rapidly improving life expectancy; - changing work patterns, including greater labour mobility; - the effect of the global financial crisis on pension assets and on government budgets. This paper will describe the main elements of pension provision in China, i.e.: - state pension system for urban workers;- supplementary benefits for urban workers;- the National Social Security Fund;- the proposed rural pension system;- civil service and public servants pensions;- the military pension system. A description of certain reforms affecting public servants is given, together with comment on the desirability of further harmonising the various pension arrangements in China

Issues in the development of advance directives in mental health care

<i>Background</i>: Interest in advance directives in mental health care is growing internationally. There is no clear universal agreement as to what such an advance directive is or how it should function. <i>Aim</i>: To describe the range of issues embodied in the development of advance directives in mental health care. <i>Method</i>: The literature on advance directives is examined to highlight the pros and cons of different versions of advance directive. <i>Results</i>: Themes emerged around issues of terminology, competency and consent, the legal status of advance directives independent or collaborative directives and their content. Opinions vary between a unilateral legally enforceable instrument to a care plan agreed between patient and clinician. <i>Conclusion</i>: There is immediate appeal in a liberal democracy that values individual freedom and autonomy in giving weight to advance directives in mental health care. They do not, however, solve all the problems of enforced treatment and early access to treatment. They also raise new issues and highlight persistent problems. <i>Declaration</i> <i>of</i> <i>interest</i>: The research was funded by the Nuffield Foundation grant number MNH/00015G

Central pattern generator for swimming in Melibe

The nudibranch mollusc Melibe leonina swims by bending from side to side. We have identified a network of neurons that appears to constitute the central pattern generator (CPG) for this locomotor behavior, one of only a few such networks to be described in cellular detail. The network consists of two pairs of interneurons, termed `swim interneuron 1\u27 (sint1) and `swim interneuron 2\u27 (sint2), arranged around a plane of bilateral symmetry. Interneurons on one side of the brain, which includes the paired cerebral, pleural and pedal ganglia, coordinate bending movements toward the same side and communicate via non-rectifying electrical synapses. Interneurons on opposite sides of the brain coordinate antagonistic movements and communicate over mutually inhibitory synaptic pathways. Several criteria were used to identify members of the swim CPG, the most important being the ability to shift the phase of swimming behavior in a quantitative fashion by briefly altering the firing pattern of an individual neuron. Strong depolarization of any of the interneurons produces an ipsilateral swimming movement during which the several components of the motor act occur in sequence. Strong hyperpolarization causes swimming to stop and leaves the animal contracted to the opposite side for the duration of the hyperpolarization. The four swim interneurons make appropriate synaptic connections with motoneurons, exciting synergists and inhibiting antagonists. Finally, these are the only neurons that were found to have this set of properties in spite of concerted efforts to sample widely in the Melibe CNS. This led us to conclude that these four cells constitute the CPG for swimming. While sint1 and sint2 work together during swimming, they play different roles in the generation of other behaviors. Sint1 is normally silent when the animal is crawling on a surface but it depolarizes and begins to fire in strong bursts once the foot is dislodged and the animal begins to swim. Sint2 also fires in bursts during swimming, but it is not silent in non-swimming animals. Instead activity in sint2 is correlated with turning movements as the animal crawls on a surface. This suggests that the Melibe motor system is organized in a hierarchy and that the alternating movements characteristic of swimming emerge when activity in sint1 and sint2 is bound together

High-resolution UKIRT observations of circumnuclear star formation in M100

We present high-resolution, near-infrared imaging of the circumnuclear region of the barred spiral galaxy M100 (=NGC 4321), accompanied by near-infrared spectroscopy. We identify a total of 43 distinct regions in the K-band image, and determine magnitudes and colours for 41 of them. By comparison with other near-infrared maps we also derive colour excesses and K-band extinctions for the knots. Combining the imaging and spectroscopic results, we conclude that the knots are the result of bursts of star formation within the last 15-25 Myr. We discuss the implications of these new results for our dynamical and evolutionary understanding of this galaxy.Comment: 10 pages, 4 figures, uses mn-1.4.sty. Accepted for publication in Monthly Notices of the Royal Astronomical Societ

On the Speed of Gravity and the v/cv/c Corrections to the Shapiro Time Delay

Using a relatively simple method, I compute the v/c correction to the gravitational time delay for light passing by a massive object moving with speed v. It turns out that the v/c effects are too small to have been measured in the recent experiment involving Jupiter and quasar J0842+1845 that was used to measure the speed of gravity.Comment: 8 pages, LaTeX (or Latex, etc), one figure, which is also available at http://www-theory.lbl.gov/~samuel/sog_figure.pdf; Revised version is the one to appear in Phys. Rev. Lett

Trachemys gaigeae

Number of Pages: 6Integrative BiologyGeological Science