Handgrip and Box Tilting Strategies in Handling: Effect on Stability and Trunk and Knee Efforts

The purpose of this study was to evaluate the effect of four handgrip/box tilting strategies (right, left, backward, and no tilt of the box) on trunk and knee efforts, body posture, and the stability of 14 participants with limited experience in handling. The tasks consisted of transferring a low-lying box placed in front of the participant to a shelf of the same height at the participant’s left. It was hypothesized that tilting the box could reduce trunk and knee efforts as well as body asymmetry and improve stability. A tridimensional dynamic rigid body model was used to estimate the triaxial net muscular moment magnitudes at the trunk (L5/SI) and at the knees. An approach to quantify the participants’ dynamic stability was also included. Finally, five angles were computed to characterize body asymmetries. The results showed that tilting the box affected specific trunk efforts, but did not succeed in reducing trunk asymmetric efforts. However, the tilts were executed in a single direction, and it may be possible that combined tilts of the box could help reduce trunk asymmetric efforts. Tilting the box had little effect on knee loadings, and the left tilt strategy reduced participants’ stability. This study showed the importance of considering the position of the box when assessing the risks encountered in asymmetrical handling.     

On comparing monopoly and competition in exhaustible resource exploitation

It is widely believed that exhaustible resource monopolies do not enjoy as much market power as standard non-resource monopolies, and may even produce in a socially optimal way. We argue that this paradoxical result arises from an inappropriate comparison methodology. When similar assumptions are applied to the resource, and the conventional cases, we show that the resource monopoly behaves as expected, i.e., restricts supply.     

Morphology, chemistry and distribution of neoformed spherulites in agricultural land affected by metallurgical point-source pollution

Metal distribution patterns in superficial soil horizons of agricultural land affected by metallurgical point-source pollution were studied using optical and electron microscopy, synchrotron radiation and spectroscopy analyses. The site is located in northern France, at the center of a former entry lane to a bunker of World War II, temporarily paved with coarse industrial waste fragments and removed at the end of the war. Thin sections made from undisturbed soil samples from A and B horizons were studied. Optical microscopy revealed the occurrence of yellow micrometer-sized (Ap horizon) and red decamicrometer-sized spherulites (AB, B(1)g horizons) as well as distinct distribution patterns. The chemical composition of the spherulites was dominated by Fe, Mn, Zn, Pb, Ca, and P. Comparison of calculated Zn stocks, both in the groundmass and in spherulites, showed a quasi-exclusive Zn accumulation in these neoformed features. Their formation was related to several factors: (i) liberation of metal elements due to weathering of waste products, (ii) Ca and P supply from fertilizing practices, (iii) co-precipitation of metal elements and Ca and P in a porous soil environment, after slow exudation of a supersaturated soil solution in more confined mineral media.     

Evaluation of the variegated scallop Chlamys varia as a biomonitor of temporal trends of Cd, Cu, and Zn in the field

This study assesses the potential of the scallop Chlamys varia as a biomonitor of metal contamination in the field. Cd, Cu, and Zn concentrations were determined in the soft tissues and organs of individuals from the French Atlantic coast sampled over a 1 year period and covering a wide range of size. All metals were selectively distributed among the different body compartments considered, and their concentrations were influenced by the size of the specimens or the sampling-season. The present work shows the importance of considering the body compartment, the sampling period and the size in studies aiming at using this scallop as a biomonitor species. Among tissues, the digestive gland and kidneys exhibited the highest metal concentrations whatever the season or the size. The digestive gland contained 65 and 48% of the whole Cd and Cu body burdens, respectively, and kidneys accounted for 85% of the Zn load. Those tissues are therefore particularly recommended for use in biomonitoring programs.     

Cytogenetic analysis of human oocytes after subzonal insemination

Subzonal insemination has been proposed to achieve fertilization in cases where standard in vitro fertilization has failed. We present the results of chromosome analysis of oocytes after subzonal insemination. Our data suggest that the main cause (76 per cent) of the absence of cleavage after subzonal insemination is the total absence of sperm nucleus evolution of the injected spermatozoa. Our results also suggest that spermatozoa chromatin development is normal after subzonal insemination. Aneuploidy does not seem to be increased in zygotes after subzonal insemination. However, polyploidy was often more important than predicted by the observation of pronuclei (PN). Pronucleus development might be asynchronous and can appear earlier or later than after standard IVF. The cytogenetic risk after subzonal insemination might therefore be triploidy (if a triploid egg is transferred, because only 2 PN were seen) rather than aneuploidy or structural abnormalities.     

Trophic specialisations in alternative heterochronic morphs

Polymorphisms are suspected of reducing competition among conspecifics in heterogeneous environments by allowing differential resource use. However the adaptive significance of alternative morphs has been poorly documented. The aim of this study is to determine food partitioning of two heterochronic morphs of the Alpine newt, Triturus alpestris, in mountain lakes. The morphs differ in the functional morphology of their feeding apparatus. Only paedomorphs are able to expel water during prey suction behind the mouth through gill slits. We observed a substantial trophic differentiation between morphs in all lakes. Paedomorphs preyed mainly on plankton, whereas metamorphs foraged on terrestrial invertebrates that fell upon the water surface. This resource partitioning may facilitate the coexistence of the alternative morphs in lakes devoid of vertebrate competitors. Food diversity may thus favour the evolutionary maintenance of facultative polymorphism in natural populations.