Search

G proteins and phospholipids are two major classes of signalling molecule. ey are each-independently and together-involved in diverse 'signalling pathways' - bio- chemical networks through which cells maintain healthy responses to stimuli. A unique 'cross-talk motif' is formed by regulation of the phospholipid-modifying enzymes phospholipase D (PLD) and phosphatidylinositol 4-phosphate 5-kinase (PI4P5K) by the Arf family of small G proteins and-curiously-each other's product. Here, understanding of this inherently complex motif has been strengthened by the development and analysis of mathematical models, specifically systems of ordinary differential equations (ODEs). Construction of simple empirical models suggests asymmetry in the mechanisms of regulation of the enzymes is responsible for production of two distinct outgoing signals from a single input signal, one displaying threshold activation behaviour. Additionally, well-defined quasi-steady-state (QSS) mechanistic models (à la Michaelis- Menten) have been developed for each of: PLD; PI4P5K; and G protein/Arf regula- tion. During this process-due to insufficient pre-existing descriptions-biochemically- plausible assumptions were required for certain regulatory and catalytic interactions. Analysis of the G protein regulation models establishes that-contrary to previous representations-this regulation is best described by a balance/unbalance mechanism, where observed activation absolutely requires the presence of the inactivator. Together, the QSS models can be combined to form a complete model of the Arf/PLD/ PI4P5K motif suitable for computational simulation - preliminary parameters show that this model is capable of displaying physiologically-plausible behaviours ese results give a be er understanding of the signalling role of the Arf/PLD/PI4P5K motif; lead to novel biological hypotheses amenable to later experimental validation; highlight where our current biological understanding of the system is insufficient; and suggest novel methods for the therapeutic control of G proteins.

Educating high needs/low performing students in the public education setting has proved challenging. Student success can sometimes be traced to a specific teacher or approach. Some teachers have demonstrated greater success in fostering learning with this population than others. The purpose of this phenomenological study was to better understand the perceptions and the strategies employed by teachers identified as being successful in fostering learning with high needs/low performing students. Stated another way, this study looks at what certain teachers are doing in how they approach and structure the learning experiences for these groups of students. The process of this study involved individual, confidential interviews with four teachers who were identified by their principal as being successful in fostering learning with high needs/low performing students. These teachers were from the same high school which has an enrollment of approximately 910 students, 30% of which are classified as economically disadvantaged and 10% as minorities. The Aid Ratio (AR) of this school district was 0.5528 indicating average relative wealth in comparison to other school districts within this state. Throughout the course of this study the themes of student self-perceptions, reframing learning, including/engaging, caring/respect and growth orientation emerged. The data gained through these teacher interviews may provide educators and school districts with insights into the thinking and planning needed to experience success with high needs/low performing students. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]

This thesis considers the current state of technology in three areas of novel protein production, namely: single cell protein, leaf protein and novel oilseed crops, with particular reference to oilseed rape. These three topics are chosen for study because of the potential contribution which they could make to UK food supply, and it is the quality and quantity of that contribution which is explored in this work. The assessment of the technologies is aci1ieved by a broadly based and thorough literature review to enable likely future developments to be made clear. A forecasting study is used to assess future prospects for oilseed crops such as· oilseed rape, lupin, sunflower and linseed in the United Kingdom. Energy and economic analyses are used to develop a comparative picture of the three novel processes. Finally, a model predicting the protein and energy supply of UK agriculture based on a vegan system is considered and the novel technologies are applied to it. Similarly, vegetarian and conventional systems are reviewed and the contribution of oilseeds, single cell protein and leaf protein are included in those systems. Little advantage is revealed by the use of the novel proteins in a vegan system of agriculture. When animal production is included in the model a contribution from novel proteins is seen to be of value. However, taken in turn, single cell protein is seen to have a limited future owing to its high energy and capital requirements, and the success of leaf protein is still limited by necessary further technical and process innovation. Agriculturally produced proteins are the cheapest and most acceptable in the UK, with home-grown oilseed rape providing an increasing proportion of our requirements.

The processes involved in the high temperature-creep deformation and fracture of low alloy steels have been extensively reviewed. The fracture behaviour of two series of alloy steels, 2 ¼ Cr 1Mo and ½ Cr ½ Mo ¼ V, has been investigated over a range of temperature extending from the ambient to that experienced under typical power plant operating conditions. The effect of prior heat treatment, stress state and presence of tramp elements on the accumulation of creep damage has also been studied. In a heavily tempered condition, the 2 ¼ Cr 1Mo alloy steels exhibited a high ductility and similar rupture mode over a wide temperature range. The sliding of adjacent prior austenite and bainite plate boundaries contributed to the overall creep strain. The presence of wide precipitate free zones suppressed the nucleation of grain boundary cavities and the dominant mechanism of damage accumulation involved decohesion, after large plastic strains, at the interface of coarse M23C6 particles and the matrix. Growth of such damage occurred by -a viscous process that was inhibited by the introduction of a hydrostatic compressive component of stress. Additions of Sn had no effect on creep life or ductility over the range explored. The simulated heat affected zone structure of the ½ Cr ½ Mo ¼ V alloy steel possessed extremely limited ductility at typical power plant operating temperatures. Failure occurred by the nucleation, growth and interlinkage of cavities at the prior austenite grain boundaries. A nucleation mechanism has been invoked, involving the interaction of matrix dislocations and grain boundary precipitates. Growth of cavities probably occurred by vacancy transport. Detailed quantitative fractography has yielded empirical laws governing the nucleation and growth of such cavities which show some similarities to those suggested for the phenomenon in single phase materials. It was demonstrated that remaining creep life was a function of the previous stress history of the material.

In the last several years, there has been an interest in graphical user interfaces as compared with character user interfaces. The "mouse" is the device most closely associated with graphical user interfaces. Key strokes are more closely associated with character user interfaces. Given these associations, is there a preference for the keyboard or for the mouse as an input device? The determination of user preference was reduced to the determination of preference of key strokes or mouse clicks for selection of main menu items. The subjects, university students working with Microsoft Works by Microsoft Corporation, copyright 1987-1989, were learning how to use application software. While Microsoft Works was running, tracking software recorded every user key stroke and mouse click, together with data about these key strokes and mouse clicks. From the analysis of these data, common preference for the means of menu item selection was determined.

During the early 1960's, an increasing number of U.S. industrial corporations moved into the world of public affairs, The trend had been evident for some time, but ·observers of the movement did not realize exactly how much it was growing. Examination of recent public affairs surveys conducted by the National Industrial Conference Board and Effective Citizens Organization, Inc., has provided some surprising answers to the extent of public affairs participation by business, Of I,033 U.S. corporations surveyed by the NICB, 815 were found to have a public affairs function. The grouping of the elements of public affairs permits the development of two public affairs "models." A "significant" public affairs program requires a written statement of policy on public affairs. The history of public affairs participation by business is short, and can be thought of as an introduction to the future. Public affairs is appearing as a newly created function of management that is commanding the attention of our top business leaders. As the problems of government and business become more complex, business can no longer sit back in-satisfied complacency. Public Affairs can be a productive industrial investment.

U.M.

New York, 1944. 33p.