Rapeseed meal and egg taint: The role of sinapine

Neither the administration of sinapine bisulphate in the diet, nor the repeated intramuscular or intravenous injection of large doses of this substance, reduced the ability of chicks or laying hens to oxidise trimethylamine (TMA), as measured by the activity of TMA oxidase in hepatic microsomes or the amounts of ¹⁴C-TMA oxide that appeared in the plasma after the infusion of a standard dose of ¹⁴C-TMA. Thus, in contrast to its behaviour in vitro, sinapine did not produce significant inhibition of TMA oxidase under these conditions. Since the amount included in the diet was similar to that which would be provided by a diet containing 10% rapeseed meal, it was concluded that sinapine is not involved in the depression of TMA oxidation that occurs when the meal is fed and acts solely as a source of TMA in the consequent production of egg taint.     

Improving Escherichia coli alkaline phosphatase efficacy by additional mutations inside and outside the catalytic pocket

We describe a strategy that allowed us to confer on a bacterial (E. coli) alkaline phosphatase (AP) the high catalytic activity of the mammalian enzyme while maintaining its high thermostability. First, we identified mutations, at positions other than those occupied by essential catalytic residues, which inactivate the bacterial enzyme without destroying its overall conformation. We transferred concomitantly into the bacterial enzyme four residues of the mammalian enzyme, two being in the catalytic pocket and two being outside. Second, the gene encoding the inactive mutant was submitted to random mutagenesis. Enzyme activity was restored upon the single mutation D330N, at a position that is 12 A away from the center of the catalytic pocket. Third, this mutation was combined with other mutations previously reported to increase AP activity slightly in the presence of magnesium. As a result, at pH 10.0 the phosphatase activity of both mutants D330N/D153H and D330N/D153G was 17-fold higher than that of the wild-type AP. Strikingly, although the two individual mutations D153H and D153G destabilize the enzyme, the double mutant D330N/D153G remained highly stable (T(m)=87 degrees C). Moreover, when combining the phosphatase and transferase activities, the catalytic activity of the mutant D330N/D153G increased 40-fold (k(cat)=3200 s-1) relative to that of the wild-type enzyme (k(cat)=80 s-1). Due to the simultaneous increase in K(m), the resulting k(cat)/K(m) value was only increased by a factor of two. Therefore, a single mutation occurring outside a catalytic pocket can dramatically control not only the activity of an enzyme, but also its thermostability. Preliminary crystallographic data of a covalent D330N/D153G enzyme-phosphate complex show that the phosphate group has significantly moved away from the catalytic pocket, relative to its position in the structure of another mutant previously reported.     

The attraction of contributors in free and open source software projects

As firms increasingly sanction an open sourcing strategy, the question of which open source project to undertake remains tentative. The lack of established metrics makes it difficult to formulate such strategy. While many projects have been formed and created, only a few managed to remain active. With the majority of these projects failing, firms need a reliable set of criteria to assess what makes a project appealing not only to developers but also to visitors, users and commercial sponsors. In this paper, we develop a theoretical model to explore the contextual and causal factors of project attractiveness in inducing activities such as source code contribution, software maintenance, and usage. We test our model with data derived from more than 4000 projects spanning 4 years. Our main findings include that projects’ set of conditions such as license restrictiveness and their available resources provide the context that directly influence the amount of work activities observed in the projects. It was also found that indirect and unintended contributions such as recommending software, despite of being non-technical, cannot be ignored for project activeness, diffusion and sustainability. Finally, our analysis provide evidence that higher attractiveness leads to more code-related activities with the downside of slowing down responsiveness to address projects’ tasks, such as the implementation of new features and bug fixes. Our model underscores the significance of the reinforcing effects of attractiveness and work activities in open source projects, giving us the opportunity to discuss strategies to manage common traps such as the liability of newness. We conclude by discussing the applicability of the research model to other user-led initiatives.     

The use of lay-flat polythene tubing in the fumigation of stacks of bagged maize

The small-bore distribution systems normally employed in methyl bromide fumigations of bagged grain have certain disadvantages, especially where large stacks are concerned, and an alternative method, based on lay-flat polythene tubing, is described.

The results of a comparative trial, in which the two methods were applied under almost identical conditions, show that improved distribution of fumigant within the stack can be achieved with the ‘lay-flat system’.     

The Future of the Phone Box

It is difficult to go almost anywhere in the world these days without finding a payphone somewhere. They have become commonplace and in many countries an essential tool for cheap speech communications. But this is only a fraction of what a payphone or phonebox booth could provide. The same pair of wires that carry the speech could at the same time carry many millions of bits of data to facilitate all sorts of additional features both in and around the booth.This paper aims to look into the future of the payphone, look at what additional features could be added and speculate on how the concept of the payphone might change in its battle with the upcoming generation of personal portable cell-phones.     

An observer for time lag systems

A full state vector observer is derived for a class of linear differential state delayed control systems. The approach dualizes a feedback stabilization theory based on the reducing transformation technique. A major feature of the approach is that the observer, or the combined controller/observer, can be designed by well-known finite-dimensional state vector methods once the set of unstable and poorly damped modes of the system has been determined     

Proposal for naming complex boron-type structures

A proposal is made for naming structure types of elemental boron and boron-rich phases that contain specific icosahedral and/or fused icosahedral boron arrangements, yet have various distributions of interpolyhedral atoms.     

Closed-Loop Control of an Anesthesia Delivery System: Development and Animal Testing

An anesthesia system which integrates closed-loop control of ventilation, oxygen, nitrous oxide, and anesthetic agent delivery into a closed breathing circuit is described. Breathing circuit volume is regulated by controlling the sum of oxygen and nitrous oxide flow, and oxygen concentration in the breathing circuit is regulated by controlling the ratio of oxygen flow to the sum of oxygen and nitrous oxide flow. End-tidal anesthetic agent concentration is regulated by controlling the agent delivery, and end-tidal carbon dioxide concentration is regulated by controlling the ventilation. After tuning the ventilation and anesthetic delivery controllers in preliminary trials in ten dogs, the system was tested and evaluated in five dogs. All control loops were stable and exhibited time responses to step changes in setpoint or external disturbances which were clinically acceptable. The system makes available the advantages of closed-system anesthesia without encumbering the anesthesiologist with the control tasks associated with the technique.     

Packet video

The 1990s will see a large increase in the use of video for many purposes, made possible through the use of new optical storage and transmission methods, as well as radio and satellite communication. HDTV, new broadcast services and 64 kbit/s ISDN video are all at an advanced stage of development. Digital methods of transmission and storage feature prominently in future scenarios of video usage. To avoid long delays in transmission, packet video techniques for storage of high-quality material on optical discs are being considered. Coded video signals can be transmitted in packet form at variable bit rate. The author discusses the principles of packet video. Packet loss, queueing delay and layered coding are discussed. The future developments are also discussed     

Nuclear Power Plant Control beyond the 1980s

Designers of nuclear power plant control and instrumentation systems are being pushed by an electronics technology that currently passes through several generations of development during the time taken to design and bring a plant into production. Despite the success of existing designs and the pressure to stick to them, the rapidity with which new components become available and others drop from the suppliers' shelves, require that we give attention to system architectures that are more tolerant of this situation. A distributed data base, containing both on-line and archival information, made available to all systems of a nuclear power plant by means of a highly reliable communications medium, could form the basis for such an architecture. It could not only solve this problem of rapid component development but also provide for complete and comprehensive plant control and surveillance. The possibility of implementing such schemes in an operating plant is probably ten years away but development must begin now if the new electronics technology is to have a planned place in the architectures of the future. At the Chalk River Nuclear Laboratories a long range program is underway. It is exploiting extensive additions that were needed in the data acquisition and processing capability associated with engineering experiments in the large research reactors NRU and NRX.