EFFECT OF SWIM PADDLES ON THE INTRA-CYCLIC VELOCITY VARIATIONS AND ON THE ARM COORDINATION OF FRONT CRAWL STROKE

This study analysed the effect of swimming with hand paddles on arm coordination and velocity pattern. Eight competitive swimmers performed two maximal aerobic tests. The maximal aerobic velocity was significantly higher when swimming with paddles but stroke rate, maximal heart rate and blood lactate values did not differ. The index of coordination (IdC) determined according to Chollet et al. (2000) and the intra-cyclic velocity variations were measured in two 25 m tests, one with and one without swim paddles, at a fixed stroke rate. When swimming with paddles, IdC and the duration of the propulsive phase increased significantly (~~0.0a5n)d the velocity signal frequency spectrum showed fewer harmon~cs (

Reconstructing the impact of human activities in a NW Iberian Roman mining landscape for the last 2500 years

This article was made available through the Brunel Open Access Publishing Fund.Little is known about the impact of human activities during Roman times on NW Iberian mining landscapes beyond the geomorphological transformations brought about by the use of hydraulic power for gold extraction. We present the high-resolution pollen record of La Molina mire, located in an area intensely used for gold mining (Asturias, NW Spain), combined with other proxy data from the same peat core to identify different human activities, evaluate the strategies followed for the management of the resources and describe the landscape response to human disturbances. We reconstructed the timing and synchronicity of landscape changes of varying intensity and form occurred before, during and after Roman times. An open landscape was prevalent during the local Late Iron Age, a period of relatively environmental stability. During the Early Roman Empire more significant vegetation shifts took place, reflected by changes in both forest (Corylus and Quercus) and heathland cover, as mining/metallurgy peaked and grazing and cultivation increased. In the Late Roman Empire, the influence of mining/metallurgy on landscape change started to disappear. This decoupling was further consolidated in the Germanic period (i.e., Visigothic and Sueve domination of the region), with a sharp decrease in mining/metallurgy but continued grazing. Although human impact was intense in some periods, mostly during the Early Roman Empire, forest regeneration occurred afterwards: clearances were local and short-lived. However, the Roman mining landscape turned into an agrarian one at the onset of the Middle Ages, characterized by a profound deforestation at a regional level due to a myriad of human activities that resulted in an irreversible openness of the landscape. © 2014 The Authors

Courtship Initiation Is Stimulated by Acoustic Signals in Drosophila melanogaster

Finding a mating partner is a critical task for many organisms. It is in the interest of males to employ multiple sensory modalities to search for females. In Drosophila melanogaster, vision is thought to be the most important courtship stimulating cue at long distance, while chemosensory cues are used at relatively short distance. In this report, we show that when visual cues are not available, sounds produced by the female allow the male to detect her presence in a large arena. When the target female was artificially immobilized, the male spent a prolonged time searching before starting courtship. This delay in courtship initiation was completely rescued by playing either white noise or recorded fly movement sounds to the male, indicating that the acoustic and/or seismic stimulus produced by movement stimulates courtship initiation, most likely by increasing the general arousal state of the male. Mutant males expressing tetanus toxin (TNT) under the control of Gr68a-GAL4 had a defect in finding active females and a delay in courtship initiation in a large arena, but not in a small arena. Gr68a-GAL4 was found to be expressed pleiotropically not only in putative gustatory pheromone receptor neurons but also in mechanosensory neurons, suggesting that Gr68a-positive mechanosensory neurons, not gustatory neurons, provide motion detection necessary for courtship initiation. TNT/Gr68a males were capable of discriminating the copulation status and age of target females in courtship conditioning, indicating that female discrimination and formation of olfactory courtship memory are independent of the Gr68a-expressing neurons that subserve gustation and mechanosensation. This study suggests for the first time that mechanical signals generated by a female fly have a prominent effect on males' courtship in the dark and leads the way to studying how multimodal sensory information and arousal are integrated in behavioral decision making

Effet Kerr et électrostriction dans des verres aux silicates de plomb

The low (7 kHz) and the high frequency Kerr (5 MHz) constants have been measured in a number of lead silicate optical glasses and fused silica at 6 328 Å and room temperature. Apart from two glasses, the difference between these experimental constants agrees with the computed electrostrictive contribution. Two glasses give evidence for a correlation between the electro-optic and the photoelastic effects. The application of a low frequency a.c. electric field to one glass (WG 1) shows up the electrostriction. These results suggest a new experimental method for the measurement of ionic conduction and homogeneity in glasses.Les constantes de Kerr en basse (7 kHz) et haute fréquence (5MHz) d'une série de verres aux silicates de plomb et de la silice vitreuse ont été mesurées à 6 328 Å et à température ambiante. Hormis deux verres, l'écart entre ces valeurs expérimentales est en bon accord avec la contribution calculée de l'électrostriction. Deux verres témoignent d'une corrélation entre les effets électrooptiques et photoélastiques. L'action d'un champ électrique basse fréquence sur un verre WG 1 met en évidence l'électrostriction. Ces observations suggèrent une nouvelle approche expérimentale de la conduction ionique et du contrôle de l'homogénéité dans les verres

Reproductive isolation through homogamy in two sympatric « habitat reaces » of Drosophila melanogaster

Il est mis en évidence une situation d'homogamie dans deux races-d'habitat quasi-sympatriques dans la région de Brazzaville au Congo chez Drosophila melanogaster. Cette homogamie (indice d'isolement 0,2) contribue a maintenir distinctes ces deux races. L'une (Loua = L) d'origine campagnarde, vit sur des résidus de manioc, l'autre citadine se trouve dans les bars et utilise les résidus de bière dans les bouteilles vides. Elles sont morphologiquement indiscernables, mais se distinguent par leurs génotypes enzymatiques pour l'allèle de l'alcooldéshydrogénase. Cette enzyme est liée à la tolérance à l'alcool et se retrouve dans 85 % des individus K, et seulement 5 % des L dans la nature (100 % et 0 % respectivement par sélection au laboratoir