Sequential memory-guided saccades and target selection: a neural model of the frontal eye fields

AbstractWe present a neural model of the frontal eye fields. It consists of several retinotopic arrays of neuron-like units that are recurrently connected. The network is trained to make memory-guided saccades to sequentially flashed targets that appear at arbitrary locations. This task is interesting because the large number of possible sequences does not permit a pre-learned response. Instead locations and their priority must be maintained in active working memory. The network learns to perform the task. Surprisingly, after training it can also select targets in visual search tasks. When targets are shown in parallel it chooses them according to their salience. Its search behavior is comparable to that of humans. It exhibits saccadic averaging, increased reaction times with more distractors, latency vs accuracy trade-offs, and inhibition of return. Analysis of the network shows that it operates like a queue, storing the potential targets in sequence for later execution. A small number of unit types are sufficient to encode this information, but the manner of coding is non-obvious. Units respond to multiple targets similar to quasi-visual cells recently studied [Exp. Brain Res. 130 (2000) 433]. Predictions are made that can be experimentally tested

Structure/activity relationships applied to the hydrogenation of α,β-unsaturated carbonyls: The hydrogenation of 3-butyne-2-one over alumina-supported palladium catalysts

The gas phase hydrogenation of 3-butyne-2-one, an alkynic ketone, over two alumina-supported palladium catalysts is investigated using infrared spectroscopy in a batch reactor at 373 K. The mean particle size of the palladium crystallites of the two catalysts are comparable (2.4 ± 0.1 nm). One catalyst (Pd(NO3)2/Al2O3) is prepared from a palladium(II) nitrate precursor, whereas the other catalyst (PdCl2/Al2O3) is prepared using palladium(II) chloride as the Pd precursor compound. A three-stage sequential process is observed with the Pd(NO3)2/Al2O3 catalyst facilitating complete reduction all the way through to 2-butanol. However, hydrogenation stops at 2-butanone with the PdCl2/Al2O3 catalyst. The inability of the PdCl2/Al2O3 catalyst to reduce 2-butanone is attributed to the inaccessibility of edge sites on this catalyst, which are blocked by chlorine retention originating from the catalyst’s preparative process. The reaction profiles observed for the hydrogenation of this alkynic ketone are consistent with the site-selective chemistry recently reported for the hydrogenation of crotonaldehyde, an alkenic aldehyde, over the same two catalysts. Thus, it is suggested that a previously postulated structure/activity relationship may be generic for the hydrogenation of α,β-unsaturated carbonyl compounds over supported Pd catalysts

NGO Presence and Activity in Afghanistan, 2000–2014: A Provincial-Level Dataset

This article introduces a new provincial-level dataset on non-governmental organizations (NGOs) in Afghanistan. The data—which are freely available for download—provide information on the locations and sectors of activity of 891 international and local (Afghan) NGOs that operated in the country between 2000 and 2014. A summary and visualization of the data is presented in the article following a brief historical overview of NGOs in Afghanistan. Links to download the full dataset are provided in the conclusion

Is it Possible to Care for the "Difficult" Male? A Study Exploring the Interface Between Gender Issues, Nursing Practice, and Men's Health

This thesis is about caring for males, especially those males who could be considered "difficult" to care for through their use of behaviours such as silence, anger or defensive humour. This thesis is positioned in the view that these behaviours are often expressions of distress, which typically distance males from those who attempt to care for them. Hence the word "distress" more accurately reflects the theme of the thesis and is used throughout the work. This thesis explores the interface between gender issues, nursing practice and caring for males. It is informed by a review of relevant literature and data gathered from a focus group of nine registered nurses. The analysis is framed by questions that are developed from a series of reflections on my personal and professional life. Critical social theory, with its emphases on dominant dialogue, power and emancipation is used to inform and guide this analysis. What is most obvious is the contrast between themes arising from the literature and those arising from the focus group. It appears that the literature, in the main, is critical of males in regard to concepts of masculinity, issues related to gender, and men's health. Males are portrayed as arbitrators of their own misfortune, as deliberately choosing a lifestyle that reflects poorly on their health, their self-expression, and communication with others. Concepts such as power and control over others, both at a societal and individual level, often feature. Conversely, the literature is noticeably lacking in regard to information about the health related experiences of males and about caring for males. In contrast, the participants of the focus group frame their discussion in the positive. For example, they suggest that males are interested in their health but require an environment that supports this expression of interest. They support this by identifying a range of behaviors they believe are effective in caring for males. The participants also suggest that it is the registered nurse rather than the male who manages issues to do with power and control. The thesis concludes that creating and sustaining an environment supportive of, and sensitive to the needs of males, is an activity that requires considerable thought, skill and experience. These areas are not adequately addressed in academic dialogue, research activity, or in the education of registered nurses. The thesis suggests that this situation is inconsistent with an ethic of care and that nursing should make a priority of broadening its research and knowledge base to better understand and care for males

Plant interactions are unimportant in a subarctic-alpine plant community

We investigated whether plant interaction intensity in a subarctic-alpine meadow is important for determining community structure and species abundance. Using two common species as phytometers, we measured interaction intensity using a neighbor removal approach. Eight biotic and abiotic variables known to influence species abundance and community structure were measured, with regression trees used to examine how plant interactions and the biotic and abiotic variables were related to species evenness, richness, and phytometer spatial cover. A range of interactions was present, with both strong competition and facilitation present over small-scale abiotic and biotic gradients. Despite the variation in interaction intensity, it was generally unrelated to either community structure or phytometer cover. In other words, plant interactions were intense in many cases but were not important to community structure. This may be due to the prevalence of clonal species in this system and the influence of previous year's interactions on plant survival and patterns of community structure. These results also suggest how conflicting theories of the role of competition in unproductive environments may be resolved. Our findings suggest that plant interactions may be intense in reducing individual growth, while simultaneously not important in the context of community structure. Plant interactions need to be viewed and tested relative to other factors and stresses to accurately evaluate their importance in plant communities, with continued differentiation between the intensity of plant interactions and their relative importance in communities

An Overview of NASA Project Management, Maven Magic, and Lessons Learned

No abstract availabl

From Creation to Launch...Following MAVEN's Successful Magical, Mystery Tour

No abstract availabl

How good was the profitability of British Railways, 1870-1912?

This paper provides new estimates of the return on capital employed (ROCE) for major British railway companies. It shows that ROCE was generally below the cost of capital after the mid-1870s and fell till the turn of the century. Addressing issues of cost inefficiency could have restored ROCE to an adequate level in the late 1890s but not in 1910. Declines in ROCE hit share prices and returns to shareholders were negative after 1897. Optimal portfolio analysis shows that, whilst railway securities would have had a substantial weight prior to this date, investors would have been justified in rushing to the exits thereafter