Detailed simulations of cell biology with Smoldyn 2.1.

Most cellular processes depend on intracellular locations and random collisions of individual protein molecules. To model these processes, we developed algorithms to simulate the diffusion, membrane interactions, and reactions of individual molecules, and implemented these in the Smoldyn program. Compared to the popular MCell and ChemCell simulators, we found that Smoldyn was in many cases more accurate, more computationally efficient, and easier to use. Using Smoldyn, we modeled pheromone response system signaling among yeast cells of opposite mating type. This model showed that secreted Bar1 protease might help a cell identify the fittest mating partner by sharpening the pheromone concentration gradient. This model involved about 200,000 protein molecules, about 7000 cubic microns of volume, and about 75 minutes of simulated time; it took about 10 hours to run. Over the next several years, as faster computers become available, Smoldyn will allow researchers to model and explore systems the size of entire bacterial and smaller eukaryotic cells

IMPACT OF SOCIOECONOMIC CHARACTERISTICS ON ATTITUDES TOWARD FOOD IRRADIATION

Irradiation of food products is one of several techniques that reduce the risk of food-borne illness. Despite its advantages, the technique has been used sparingly because consumers are wary about this technology. A logit model is used to evaluate the impacts of demographic factors on attitudes toward purchasing foods that have been irradiated and toward paying more for irradiated foods. An important finding of this study is that consumers who are familiar with irradiation are significantly more likely to buy and pay more for irradiated products than those who have never heard of irradiation. This implies that educational programs aimed at informing consumers about the benefits of irradiation can work.Consumer/Household Economics, Food Consumption/Nutrition/Food Safety,

University of Colorado: 1971 Summer Field Season in East Baffin Island

Research was continued by University of Colorado faculty and graduate students in the area of Cumberland Peninsula. Baffin Island, Northwest Territories. The work was divided into four main phases: 1) studies on the glacial chronology of the Penny Ice Cap and local mountain ice caps; 2) the mass balance of the Boas Glacier; 3) air-sea interactions using ground stations, instrumented aircraft and satellite data; and 4) evaluation of climatic trends. ..

Governance Indicators Can Make Sense: Under-five Mortality Rates are an Example

Governance indicators have come under fire in recent years, especially the World Governance Indicators (WGIs). Critics present these indicators as a-theoretical and biased. Critics of the critics counter that no better alternatives exist. We suggest otherwise, arguing that more appropriate ‘governance’ indicators will (i) have theoretical grounding, (ii) focus on specific fields of engagement, (iii) emphasize outcomes, and (iv) control for key contextual differences in comparing countries. Such measures can help indicate where countries seem to have governance problems, allowing second stage analyses of what these problems are. We present under national five mortality rates adjusted for country income groups as an example of such measure, presenting data for contextually controlled outcomes in this specific field to show where governance seems better and worse. The United States is shown up as relatively weak, whereas a country like Pakistan seems to have better governance in this sector than other low income countries. The indicator allows questions about why governance of this sector might be problematic in certain contexts and easier in others

5th Annual Symposium of the United Kingdom & Ireland Engineering Education Research Network: Time for change

The proceedings of the 5th symposium of the UK & IE Engineering Education Network set about challenging the status quo in all areas of engineering education. Over two days colleagues discussed and debated a number of issues ranging from engineering in schools and attracting young people into engineering, to innovative engineering pedagogies. The highly contentious question of whether ‘maths’ is, or is not, a vital prerequisite to studying engineering at university was debated whilst an expert panel asked the question “Are engineering educators fit for purpose?”.Needless to say the Symposium proved to be a lively event. In an attempt to provide the engineering education community with a taste of the debates the short Symposium Papers presented here represent ‘the tip of the iceberg’ with regards to the wide range of problems and solutions discussed and proposed. Divided into three main sections this publication shows that the Symposium did indeed achieve its objective of ‘challenging the status quo’. The papers presented in the first section argue the case for change in engineering education. Whilst the second section turns to look at engineering education practice and pedagogy, with an additional section included to assure non-expert researchers are given a voice. The final section brings the document to a close with a number of papers that look at how colleagues across the UK are beginning to innovate change in the engineering classroom and beyond

Immiscible phase incorporation during directional solidification of hypermonotectics

Solidification processes in immiscible samples were investigated by directly observing the events taking place at the solid-liquid interface during directional solidification. Visualization of these events was made possible through the use of a transparent metal analog system and a temperature gradient stage assembly fitted to an optical microscope. The immiscible transparent analog system utilized was the succinonitrile-glycerol system. This system has been shown to exhibit the same morphological transitions as observed in metallic alloys of monotectic composition. Both monotectic and hypermonotectic composition samples were directionally solidified in order to gain an improved understanding of the manner in which the excess hypermonotectic liquid is incorporated into the solidifying structure. The processing conditions utilized prevented sedimentation of the excess hypermonotectic liquid by directionally solidifying the samples in very thin (13 microns), horizontally oriented cells. High thermal gradient to growth rate ratios (G/R) were used in an effort to prevent constitutional supercooling and the subsequent formation of L(sub 2) droplets in advance of the solidification front during the growth of fibrous composite structures. Results demonstrated that hypermonotectic composites could be produced in samples up to two weight percent off of the monotectic composition by using a G/R ratio greater than or equal to 4.6 x 10(exp 4) C(s)/mm(sup 2) to avoid constitutional supercooling. For hypermonotectic samples processed with G/R ratios below 4.6 x 10(exp 4) C(s)/mm(sup 2), constitutional supercooling occurred and resulted in slight interfacial instability. For these samples, two methods of incorporation of the hypermonotectic liquid were observed and are reported. The correlation between the phase spacing, lambda, and the growth rate, R, was examined and was found to obey a relationship generally associated with a diffusion controlled coupled growth process. For samples with compositions ranging from the monotectic composition up to 2 percent off of the monotectic composition, data indicated that the square of the phase spacing (lambda) varied linearly with the inverse of the growth rate (R)

Evaluating a Computer Program with a Structured Expert Review Process

A structured expert review process was implemented to evaluate the technical content and usability of a program on aeration system design for grain storages. Technical evaluation was used to determine if the computer program generated solutions similar to expert solutions. Other aspects of the evaluation focused on measures of ease of use, effectiveness of information conveyance and usefulness of solution. The evaluation procedure and questionnaires are described and results from the evaluation of an aeration system design program are summarized. The evaluation process served to validate the aeration system design program, generate suggestions for improving the program, identify areas for further research and advance aeration system design technology by bringing together experts representing the range of practice. The review process was beneficial and could be adapted for use with other decision support programs

Quantitative Dark-Field Mass Analysis of Ultrathin Cryosections in the Field-Emission Scanning Transmission Electron Microscope

The availability of a cryotransfer stage, highly efficient electron energy loss spectrometers, and ultrathin-window energy-dispersive x-ray spectrometers for the VG Microscopes HB501 field-emission scanning transmission electron microscope (STEM) provides this instrument with the potential for high resolution biological microanalysis. Recent technical advances offer cryosections that are thin enough to take advantage of the analytical capabilities of this microscope. This paper first discusses the quantitative characterization of freeze-dried, ultrathin cryosections of directly frozen liver and brain by low-dose dark-field STEM imaging. Such images reveal high-quality sections with good structural detail, mainly due to reduced preparation artifacts and electron beam damage. These sections are thin enough for dark-field mass analysis, so that the mass of individual organelles can be measured in situ, and their water content deduced. This permits the measurement of mass loss-corrected subcellular elemental concentrations. The results suggest several new applications for cryosections as illustrated by data on synaptic activity-dependent calcium regulation in Purkinje cells of mouse cerebellum. Low-dose mass analysis of cryosections in combination with x-ray and electron spectroscopy is a promising approach to quantitating physiological changes in mass distribution and elemental composition