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1.
E. Golomer P. Dupui H. Monod 《European journal of applied physiology and occupational physiology》1997,76(2):140-144
We investigated the effects of maturation on the dynamic body sways of healthy girls. Prepubertal and postpubertal girls
practising professional physical activities requiring a good ability to maintain equilibrium (acrobats and dancers) were asked
to stand on a free seesaw platform and the results compared to those for untrained age-matched girls. This platform (stabilometer)
allows self-induced body sways. Stabilograms were obtained by a double integration of the angular acceleration from the recordings
of the platform sways made with an accelerometer. Fast Fourier transform processing of stabilograms allowed spectral frequency
analysis. The total spectrum energy and the energies of three frequency bands (0–0.5 Hz, 0.5–2 Hz, 2–20 Hz) were determined.
ANOVA showed that, for all groups of different equilibrium activity and independent of visual input, prepubertal girls had
higher energy values than postpubertal girls in the 0- to 0.5-Hz band whereas the opposite was true for 0.5- to 2-Hz band.
Ballet dancers were more dependent than acrobats on visual inputs for the regulation of their postural control but were less
dependent than untrained girls at both ages. Maturation seemed to shift body sways towards higher frequencies and the utilization
of the cues of postural control was different according to the type of equilibrium activity practised by the subjects.
Accepted: 7 February 1997 相似文献
2.
Akihisa Hattori 《Journal of Ethology》2006,24(1):51-57
The distribution patterns of the leathery sea anemone, Heteractis crispa, which contains an algal endosymbiont (zooxanthellae) and anemonefish, were investigated in relation to size distribution on a shallow fringing reef (3.2 ha, 0–4 m depth) in Okinawa, Japan. Individual growth and movements were also examined. Large individuals (>1,000 cm2) inhabited reef edges up to a depth of 4 m, while small anemone (<500 cm2) inhabited shallow reefs including inner reef flats. Individuals rarely moved, and their sizes were significantly correlated with their water depths. Growth of small anemones was negatively correlated with their distance from the reef edge, suggesting that reef edges provide more prey and lower levels of physiological stress. This study suggested that deep reef edges are suitable habitats for H. crispa. Large anemones were inhabited by large Amphiprion perideraion or large Amphiprion clarkii, both of which are effective defenders against anemone predators. Anemones that settle in deep reef edges may enjoy a higher survival rate and attain a large size because of their symbiotic relationship with anemonefish. However, early settlers do not harbor anemonefish. Their mortality rate would be higher in the deep edges than in shallow edges, the complicated topography of which provides refuge. 相似文献
3.
H V Meredith 《American journal of physical anthropology》1979,51(1):63-66
This article examines a recently reported generalization. Materials from more than a score of invetigations are drawn upon. These materials show there is not a substantial research base for the claim that interbreeding in the United States between black people of African ancestry and white people of European ancestry has resulted in increased lower limb height relative to sitting height. 相似文献
4.
The cost of mutualism in a fly-fungus interaction 总被引:2,自引:0,他引:2
The movement ability of individuals has become increasingly important to a variety of ecological questions. In this study,
I investigate how plant structure and changes in body size through development affect the movement ability of a predaceous
stinkbug, Podisus maculiventris, on three species of goldenrod (Solidago spp.) representing a wide range of surface complexities. I adapt existing techniques for quantifying movement in two dimensions
to the study of movement on natural plant structures in three dimensions. These experiments indicate that plant structure
and insect size are significant factors affecting the movement ability of P. maculiventris. Changes in movement ability due to factors of ontogeny and different habitat structures suggest that the scale of an individual’s
ambit or ecological sphere of influence may vary within its lifespan. Considering the influence of ontogeny and habitat structure
on movement ability may be useful to investigations of population dynamics, foraging behavior, and pest management.
Received: 14 July 1999 / Accepted: 23 March 2000 相似文献
5.
6.
Identification of hydrogen selenide and other volatile selenols by derivatization with 1-fluoro-2,4-dinitrobenzene 总被引:2,自引:0,他引:2
A procedure is described for the trapping and identification of hydrogen selenide and methyl selenol ( CH3SeH ). The volatile selenols were generated by reducing selenious acid or dimethyldiselenide with Zn dust and hydrochloric acid under a stream of nitrogen and passing into a trapping solution composed of 50 mM 1-fluoro-2,4-dinitrobenzene plus 83 mM sodium bicarbonate in 67% dimethylformamide:33% water. The selenols react rapidly to form stable dinitrophenyl (DNP) selenoethers that can be extracted into benzene; these are easily identified by TLC, HPLC, or mass spectrometry. Hydrogen selenide is trapped in 90-99% yield, primarily as the di-DNP- monoselenide with a trace of di-DNP- diselenide . 相似文献
7.
8.
The relationship between ecological segregation and sexual body size dimorphism in large herbivores 总被引:4,自引:0,他引:4
A. Mysterud 《Oecologia》2000,124(1):40-54
Ecological segregation (sexual differences in diet or habitat use) in large herbivores has been intimately linked to sexual
body size dimorphism, and may affect both performance and survival of the sexes. However, no one has tested comparatively
whether segregation occurs at a higher frequency among more dimorphic species. To test this comparatively, data on sex-specific
diet, habitat use and body size of 40 species of large herbivores were extracted from the literature. The frequency of ecological
segregation was higher among more dimorphic herbivores; however, this was only significant for browsers. This provides the
first evidence that segregation is more common among more dimorphic species. The comparative evidence supported the nutritional-needs
hypothesis over the incisor breadth hypothesis, as there was no difference in frequency of segregation between seasons with
high and low resource levels, and since segregation was also evident among browsers. Whether the absence of a correlation
between ecological segregation and level of sexual body size dimorphism for intermediate feeders and grazers is due to biological
differences relative to browsers or to the fact that the monomorphic species included in the analysis were all browsers is
discussed.
Received: 18 August 1999 / Accepted: 31 January 2000 相似文献
9.
B. L. Bennett R. D. Hagan K. A. Huey C. Minson D. Cain 《European journal of applied physiology and occupational physiology》1995,70(4):322-328
This study evaluated the effectiveness of a six-pack versus a four-pack cool vest in reducing heat strain in men dressed in firefighting ensemble, while resting and exercising in a warm/humid environment [34.4°C (day bulb), 28.9°C (wet bulb)]. Male volunteers (n = 12) were monitored for rectal temperature (T
re), mean skin temperature (T
sk), heart rate, and energy expenditure during three test trials: control (no cool vest), four-pack vest, and six-pack vest. The cool vests were worn under the firefighting ensemble and over Navy dungarees. The protocol consisted of two cycles of 30 min seated rest and 30 min walking on a motorized treadmill (1.12 m · s–1, 0% grade). Tolerance time for the control trial (93 min) was significantly less than both vest trials (120 min). Throughout heat exposure, energy expenditure varied during rest and exercise, but no differences existed among all trials (P > 0.05). During the first 60 min of heat exposure, physiological responses were similar for the four-pack and six-pack vests. However, during the second 60 min of heat exposure the six-pack vest had a greater impact on reducing heat strain than the four-pack vest. PeakT
e andT
sk at the end of heat exposure for 6-pack vest [mean (SD) 38.0(0.3)°C and 36.8(0.7)°C] were significantly lower compared to four-pack [38.6 (0.4)°C and 38.1(0.5)°C] and controls [38.9(0.5)°C and 38.4(0.5)°C]. Our findings suggest that the six-pack vest is more effective than the four-pack vest at reducing heat strain and improves performance of personnel wearing a firefighting ensemble. 相似文献
10.
Retardation of bone development was observed in the Koshima troop of free ranging Japanese macaques. In the control group,
epiphyseal unions of appendicular long bones generally started to close at about 4 yrs of age and were completed at about
8 or 9 yrs of age. Limb bone unions of the Koshima troop, however, started to close at about 9 yrs of age and completely closed
at about 15 yrs of age. In the epiphyseal unions of trunk and girdle bones, the Koshima troop again showed a retardation of
closure compared with the control group. Until long bones reached their full length, that is, until about 15 yrs of age, their
size was small in the Koshima troop compared with the control group, though the sample size of the Koshima troop was small.
After 15 yrs of age, however, many osteometrical measurements of the Koshima troop were nearly the same as controls. A prolonged
growing duration compensated for the slow growth and allowed them to become as large as controls. This prolongation may be
an adaptation in response to small size during the developmental period.
In some parts of the body, however, Koshima macaques failed to reach the adult size of controls. Males were less likely than
females to reach full size. Causes of the retardation and small size in the Koshima troop are discussed, but they remain open
to further studies. 相似文献