Effects of urea analogs on egg hatching and movement of unhatched larvae of monogenean parasiteAcanthocotyle lobianchi from skin ofRaja montagui

Rapid hatching in the monogenean parasiteAcanthocotyle lobianchi from the skin ofRaja montagui is stimulated by urea. Structurally similar to the urea molecule, the following analogs of urea provide amino groups, carboxyl groups, or combinations of these, but fail to stimulate hatching at concentrations of 1 mM in seawater: methylurea (MU); 1, 3-dimethylurea (DU); 1, 1, 3, 3-tetramethylurea (TMU); thiourea (TU); 1, 1, 3, 3-tetramethyl-2-thiourea (TMTU); and 1-phenyl-2-thiourea (PTU). All of these analogs except PTU elicit movements of unhatched larvae, and posttreatment of the eggs with urea showed that the ability to hatch is not impaired by initial treatment with any of the urea analogs. Thus the larval chemoreceptor that initiates hatching appears to be highly specific for the urea molecule.     

Relation between velocity and curvature in movement: Equivalence and divergence between a power law and a minimum-jerk model.

Unconstrained hand movements typically display a decrease in hand speed around highly curved sections of a trajectory. It has been suggested that this relation between tangential velocity and radius of curvature conforms to a one-third power law. We demonstrate that a one-third power law can be explained by models taking account of trajectory costs such as a minimum-jerk model. Data were analyzed from 6 subjects performing elliptical drawing movements of varying eccentricities. Conformity to the one-third power law in the average was obtained but is shown to be artifactual. It is demonstrated that asymmetric velocity profiles may result in consistent departures from a one-third power law but that such differences may be masked by inappropriate analysis procedures. We introduce a modification to the original minimum-jerk model by replacing the assumption of a Newtonian point-mass with a visco-elastic body. Simulations with the modified model identify a basis for asymmetry of velocity profiles and thereby predict departures from a one-third law commensurate with the empirical findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Euroroute

Since early in the 18th century, a variety of schemes for a fixed crossing of the 21-mile channel between England and France have been proposed. None has yet been built. The volume of traffic crossing the channel has created a resurgence of interest in the idea: 20 million people and 16 million tons of unitized freight are now carried by the ferries each year. In this paper, the author outlines proposals initiated by him at the British Steel Corporation for a combined road and rail link. The concept draws its inspiration from the crossing at Chesapeake Bay. Bridges would carry the roadways out to manmade islands at the edges of the main shipping lanes. Here the roadways would descend to a submerged tube tunnel laid in a trench, which they would share with the railway that previously crossed the inshore zone by tunnel. Bridge and tunnel sections would be fabricated at coastal sites and floated to the crossing. The offshore islands, embodying North Sea oil platform construction techniques, would also be partly prefabricated. One hundred thousand jobs for five years would be created by this scheme, which is now under consideration by the British and French governments.     

Energy management in educational premises and staff morale

Local education authorities in Britain currently find themselves being expected to act on two specific fronts by central government. They are being urged to curb their expenditure by explicitly ‘managing’ the consumption of fuel in the buildings they own. They are also being asked to prepare the teachers they employ for a new task, teaching children to be pro-energy conservation. This paper contains an exploration of these two areas of proposed activity in the context of one specific English education authority. Connexions are sought between technical and non-technical measures taken by the Authority to cut its energy costs and its employees' perceptions of their primary duty, teaching. To this end, attention is focused on the intermediary role which buildings can play between employees and those for whom they work. It is concluded that local government officers, who are charged with responsibility for managing energy, cannot assume that it is a consensus issue—either as an abstract idea or as a set of practices. Hence the social acceptability of energy management cannot be taken for granted. Instead its approval and consent are problematic. They have to be earned. The criteria by which and the context in which employees judge the conservation and management of energy may make acceptance and co-operation difficult to achieve. But failure to do so may also influence their reactions to introducing energy studies into the curriculum.     

Neural control of a batch distillation

The purpose of the work reported here was to investigate the application of neural control to a common industrial process. The chosen problem was the control of a batch distillation. In the first phase towards deployment, a complex software simulation of the process was controlled. Initially, the plant was modelled with a neural emulator. The neural emulator was used to train a neural controller using the back propagation through time algorithm. A high accuracy was achieved with the emulator after a large number of training epochs. The controller converged more rapidly, but its performance varied more widely over its operating range. However, the controlled system was relatively robust to changes in ambient conditions.     

Expression of HIV-1 nef in yeast: The 27 kDa nef protein is myristylated and fractionates with the nucleus

The nef gene of human immunodeficiency virus type 1 (HIV-1) has been expressed in the yeast Saccharomyces cerevisiae to produce native Nef proteins. The proteins of M_r 27 kDa and 25 kDa, produced by translation from the first and second start codons of the nef gene react with human HIV-1 antisera. Under low-level steady-state expression conditions, Nef27 undergoes myristylation and is targeted to the nuclear fraction while Nef25 is not myristylated and not nuclear localized. When produced rapidly and to high levels, Nef27 is initially present in the cytoplasm as a soluble myristylated protein that later fractionates with the nucleus.     

The distribution of some fluorescent anionic surfactants applied to wool

The distribution of surfactants in the different regions of the wool fibre has been studied by applying several novel fluorescent surfactants to wool under various conditions and studying sections of the treated fibres under the fluorescence microscope. The intercellular and cell remnant regions appear to be the preferred locations for these surfactants in the wool fibre, but various distributions can be obtained, depending on the length of the hydrocarbon chain of the surfactant and the conditions under which it is applied. The similarities in surface activity, sorption and extraction behaviour of the more typical surfactant sodium dodecyl sulphate and some of the fluorescent surfactants suggest that the former surfactant may have a similar distribution between the different regions of wool.     

The rearrangement of fatty cyclopropenoids in the presence of boron trifluoride

The destruction of the cyclopropenoid ring system of methyl 9,10 methyleneoctadec-9-enoate (methyl sterculate) with boron trifluoride etherate has been shown to give a complex mixture of products, including methyl esters of C₁₉ allenes (12%), a C₁₈ alkyne (11%) and a variety of C₁₉ and C₂₀ conjugated dienes containing either a methyl or methylene branch. The methylene group lost from the methyl sterculate reactant in the formation of methyl octadec-9-ynoate is incorporated into a second molecule of reactant to yield a mixture of methyl 9-methylene-trans-nonadec-10-enoate and the 11-methylene-trans-9-isomer.