Galois Theory of Parameterized Differential Equations and Linear Differential Algebraic Groups

We present a Galois theory of parameterized linear differential equations where the Galois groups are linear differential algebraic groups, that is, groups of matrices whose entries are functions of the parameters and satisfy a set of differential equations with respect to these parameters. We present the basic constructions and results, give examples, discuss how isomonodromic families fit into this theory and show how results from the theory of linear differential algebraic groups may be used to classify systems of second order linear differential equations

Magnetic susceptibility variations in Loess sequences and their relationship to astronomical forcing

The long, well-exposed and often continuous sequences of loess found throughout the world are generally thought to provide an excellent opportunity for studying long-term, large-scale environmental change during the last few million years. In recent years, the most fruitful loess studies have been those involving the deposits of the loess in China. One of the most intriguing results of that work has been the discovery of an apparent correlation between variations in the magnetic susceptibility of the loess sequence and the oxygen isotope record of the deep sea. This correlation implies that magnetic susceptibility variations are being driven by astronomical parameters. However, the basic data have been interpreted in various ways by different authors, most of whom assumed that the magnetic minerals in the loess have not been affected by post-depositional processes. Using a chemical extraction procedure that allows us to separate the contribution of secondary pedogenic magnetic minerals from primary inherited magnetic minerals, we have found that the magnetic susceptibility of the Chinese paleosols is largely due to a pedogenic component which is present to a lesser degree in the loess. We have also found that the smaller inherited component of the magnetic susceptibility is about the same in the paleosols and the loess. These results demonstrate the need for additional study of the processes that create magnetic susceptibility variations in order to interpret properly the role of astronomical forcing in producing these variations

On the interactions of lipids and proteins in the red blood cell membrane

The effects of temperature and of the action of a purified phospholipase C enzyme preparation on human red blood cell membranes has been investigated by chemical analyses, circular dichroism, and proton magnetic resonance measurements. The results indicate that a substantial fraction of the phospholipids and the proteins of the membranes can change structure independently of one another, suggesting a mosaic pattern for the organization of the lipids and proteins in membranes

Investigating periphyton biofilm response to changing phosphorus concentrations in UK rivers using within-river flumes

The excessive growth of benthic algal biofilms in UK rivers is a widespread problem, resulting in loss of plant communities and wider ecological damage. Elevated nutrient concentrations (particularly phosphorus) are often implicated, as P is usually considered the limiting nutrient in most rivers. Phosphorus loadings to rivers in the UK have rapidly decreased in the last decade,due to improvements in sewage treatment and changes to agricultural practises. However, in many cases, these improvements in water quality have not resulted in a reduction in nuisance algal growth. It is therefore vital that catchment managers know what phosphorus concentrations need to be achieved, in order to meet the UK’s obligations to attain good ecological status, under the EU’s Water Framework Directive. This study has developed a novel methodology, using within river mesocosms, which allows P concentrations of river water to be either increased or decreased, and the effect on biofilm accrual rate is quantified. These experiments identify the phosphorus concentrations at which algae becomes P-limited, which can be used to determine knowledge-based P targets for rivers. The ability to reduce P concentrations in river water enables algae–nutrient limitation to be studied in nutrient-enriched rivers for the first time

Operational Failures and Problem Solving: An Empirical Study of Incident Reporting

Operational failures occur in all industries with consequences that range from minor inconveniences to major catastrophes. Many organizations have implemented incident reporting systems to highlight actual and potential operational failures in order to encourage problem solving and prevent subsequent failures. Our study is among the first to develop and empirically test theory regarding which reported operational failures are likely to spur problem solving. We hypothesize that problem solving activities are especially likely to follow reported operational failures that provoke financial and legal liability risks. We also hypothesize that management commitment to problem solving, enacted through managers' communication and engagement practices, can encourage frontline workers to conduct problem solving. We test our hypotheses in the health care context, in which the use of incident reporting systems to highlight operational failures is widespread. Using data on nearly 7,500 reported incidents from a single hospital, we find support for our hypotheses. Our findings suggest that frontline workers' participation in problem solving is motivated by some inherent characteristics of the problems as well as by particular management practices.

Managerial practices that promote voice and taking charge among frontline workers

Process-improvement ideas often come from frontline workers who speak up by voicing concerns about problems and by taking charge to resolve them. We hypothesize that organization-wide process-improvement campaigns encourage both forms of speaking up, especially voicing concern. We also hypothesize that the effectiveness of such campaigns depends on the prior responsiveness of line managers. We test our hypotheses in the healthcare setting, in which problems are frequent. We use data on nearly 7,500 reported incidents extracted from an incident-reporting system that is similar to those used by many organizations to encourage employees to communicate about operational problems. We find that process-improvement campaigns prompt employees to speak up and that campaigns increase the frequency of voicing concern to a greater extent than they increase taking charge. We also find that campaigns are particularly effective in eliciting taking charge among employees whose managers have been relatively unresponsive to previous instances of speaking up. Our results therefore indicate that organization-wide campaigns can encourage voicing concerns and taking charge, two important forms of speaking up. These results can enable managers to solicit ideas from frontline workers that lead to performance improvement.