The propagation and dispersal of misinformation in ecology: Is there a relationship between citation accuracy and journal impact factor?

The biological and physico-chemical structure of near bottom habitats located under densely growing submerged vegetation, and their significance in the functioning of whole aquatic ecosystems, are very little known due to difficulties in sampling. Corer-type samplers, believed to be the best in littoral studies, do not work properly in such places, because their tube opening is easily clogged by plant shoots, acting as a stopper. In order to overcome this problem, an alteration to the shape of the tube ending is proposed. This can be done by its trimming at an accurate angle, or by fitting (permanently or interchangeably) a metal collar made of stainless steel to its end, so that the ending would resemble the shape of a needle. The modification can be applied to virtually all corer samplers. It was found to be efficient while sampling sediment cores for the purposes of both hydrobiological and paleolimnological studies on heavily overgrown macrophyte-dominated water ecosystems.     

Effect of arm-shoulder fatigue on carpenters at work

The purpose of the study was to analyse the effect of arm-shoulder fatigue on manual performance. Ten experienced carpenters performed three standardized tasks (nailing, sawing and screwing). Electromyographic activity was recorded from six arm-shoulder muscles and the performances were video-filmed. After 45 min of standardized arm-cranking (arm-shoulder-fatiguing exercise of approximately 70%-80% maximal oxygen consumption), the tasks were repeated. The number of work movements and the time taken for each task were recorded and the quality of the work performed was compared. After the fatiguing exercise, only nailing was perceived as being harder and more mistakes were made during nailing and sawing. Movement performance was not influenced during nailing but was slightly slower during sawing and faster during screwing. However, there were increased mean EMG amplitudes in the upper trapezius and biceps muscles during nailing, in the upper trapezius, anterior deltoid and infraspinatus muscles during sawing and in the anterior deltoid muscle during screwing. Of the muscles studied the upper trapezius and anterior deltoid muscles increased their activity most after the arm-shoulder-fatiguing exercise.     

A multisensory integration model of human stance control

A model is presented to study and quantify the contribution of all available sensory information to human standing based on optimal estimation theory. In the model, delayed sensory information is integrated in such a way that a best estimate of body orientation is obtained. The model approach agrees with the present theory of the goal of human balance control. The model is not based on purely inverted pendulum body dynamics, but rather on a three-link segment model of a standing human on a movable support base. In addition, the model is non-linear and explicitly addresses the problem of multisensory integration and neural time delays. A predictive element is included in the controller to compensate for time delays, necessary to maintain erect body orientation. Model results of sensory perturbations on total body sway closely resemble experimental results. Despite internal and external perturbations, the controller is able to stabilise the model of an inherently unstable standing human with neural time delays of 100 ms. It is concluded, that the model is capable of studying and quantifying multisensory integration in human stance control. We aim to apply the model in (1) the design and development of prostheses and orthoses and (2) the diagnosis of neurological balance disorders. Received: 25 August 1997 / Accepted in revised form: 8 December 1998     

Effects of monoclonal anti-H-2Ld and anti-H-2Dd alloantibodies in the immunological enhancement of skin grafts and neonatal heart grafts in the mouse

Three anti-H-2Ld and two anti-H-2Dd monoclonal alloantibodies were analyzed for their capacity to enhance skin graft and neonatal heart graft survival. Of two anti-H-2Ld antibodies with the same specificity but with different isotypes, IgG2a antibody 30-5-7S prolonged graft survival in a skin graft combination with an Ld difference, whereas IgM antibodies did not. A second IgG2a antibody, but with a specificity different from 30-5-7S, was ineffective on its own. However, when mixed with 30-5-7S, skin graft survival was augmented as compared with the prolongation by 30-5-7S alone. Enhancement by anti-H-2Ld antibodies was dependent on the extent of the H-2 graft barrier. It was abrogated on extension of the graft barrier to a D-end H-2 difference by using the B10.A----B10.BR combination. Also, anti-Dd antibodies, either alone or in combination with anti-Ld, were ineffective in this skin graft combination. By using the same graft combination but the less immunogenic neonatal heart graft model, anti-Ld antibodies were still ineffective, but both anti-Dd antibodies were able to enhance graft survival from 15 to 22 days. When mixed with anti-Ld antibody 30-5-7S, graft survival was augmented further to 30 days. These results indicate that two kinds of enhancing alloantibodies may be distinguished. One category interacts with immunodominant epitopes on H-2 molecules, but their effectiveness may be limited to a particular H-2 difference, because immunodominance may vary from one graft barrier to another. In the second category, antibodies are ineffective on their own but they are able to potentiate the effects of antibodies of the first kind. These allocations are relative, however, because they are dependent on the type of graft examined.