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Lower Positions (lower + position)

Distribution by Scientific Domains

Life Sciences	57%

Selected Abstracts

Variation in fruit- and seed set among and within inflorescences of Melampyrum roseum var. japonicum (Scrophulariaceae)

PLANT SPECIES BIOLOGY, Issue 1 2002
Kayako Hiei
Abstract Variations in fruit set and seed set among and within inflorescences of the annual herb, Melampyrum roseum var. japonicum, were studied. Under natural conditions, although the mean fruit set was slightly different among inflorescences, the mean seedset was not significantly different among inflorescences within the plants. In constrast, within the inflorescences, the flowers located at a lower position of the inflorescence and which opened earlier showed higher fruit set than those at a higher position and which opened later. However, the seed set of matured capsules were not significantly different from each other, regardless of the position of flowers within the inflorescences. Patterns of the fruit- and seed set under open pollination indicated that variation in seed reproduction of M. roseum is due to variation in fruit production. The results of clipping experiments of flowers revealed that there was no functional limitation in seed production among flowers located at various positions within the inflorescence. It seemed that the variation in the fruit set within the inflorescences of M. roseum was not attributable to ,architectural effects'. Reduction of the number of flowers within the inflorescences resulted in an increase of fruit set and seed weight, indicating that the flowers in an inflorescence compete for resources. This phenomenon supports the ,resource competition hypothesis', and variation in fruit set within the inflorescence is attributable to competition among flowers within the inflorescence for limited resources. Consequently, it was concluded that, under natural conditions, the early blooming flowers located at lower positions of the inflorescences obtain more resources and produce more fruits than the late blooming flowers located at higher positions in M. roseum. [source]

Emergency Medicine Residency Applicant Perceptions of Unethical Recruiting Practices and Illegal Questioning in the Match

ACADEMIC EMERGENCY MEDICINE, Issue 6 2009
R. Jason Thurman MD
Abstract Objectives:, The authors hypothesized that unethical recruiting practices and illegal questioning occur during emergency medicine (EM) resident recruitment. The objectives were to estimate the prevalence of specific unethical recruiting practices and illegal questioning by EM programs based on the perceptions of residency applicants and to measure the effect of these perceptions on applicant appraisal of programs. Methods:, This was a cross-sectional survey of all applicants who matched to U.S. EM programs in 2005 and 2006. The survey questionnaire was developed by the study authors and was validated by pretesting on a small group representative of the study population. The survey addressed specific questions regarding program recruiting behaviors and interview questioning. The hyperlink to the secure anonymous online survey questionnaire was distributed to all EM program directors, asking them in turn to forward the hyperlink to their newly matched incoming residency class. All data were calculated with Score method with continuity correction and reported in proportions with 95% confidence intervals (CIs). Results:, The authors received 671 survey responses. Among respondents, 56 (8.3%, 95% CI = 6.4% to 10.7%) stated that they were specifically asked to disclose at least one program's position on their rank list by a program representative, and 44 (6.6%, 95% CI = 4.9% to 8.9%) reported that they matched at a program residing lower on their rank list than at least one other program that had informed the applicant they were ranked to match. Furthermore, 201 respondents (30.0%, 95% CI = 26.5% to 33.7%) believed that they were asked at least one illegal question during their interviews, the most common of which was inquiry into their marital status (189 respondents: 28.2%, 95% CI = 24.8% to 31.9%). Respondents were 11 times more likely to move a program to a lower position of preference on their rank order list (12.2%, 95% CI = 9.8% to 15.0%) rather than a higher position (1.1%, 95% CI = 0.5% to 2.3%) as a result of perceiving unethical recruiting behaviors or illegal questioning. Conclusions:, These results demonstrate that among survey respondents, some perceived unethical recruiting behaviors and illegal questioning in the 2005 and 2006 Match. Perceptions of such behaviors appeared to have a negative impact on applicant appraisal of EM residency programs. [source]

Raised thermoregulatory costs at exposed song posts increase the energetic cost of singing for willow warblers Phylloscopus trochilus

JOURNAL OF AVIAN BIOLOGY, Issue 4 2005
Sally Ward
Sexually selected displays, such as bird song, are expected to be costly. We examined a novel potential cost to bird song: whether a less favourable microclimate at exposed song posts would be predicted to raise metabolic rate. We measured the microclimate and height at which willow warblers Phylloscopus trochilus sang and foraged. Song posts were higher than foraging sites. The wind speed was 0.6±0.3 ms,1 greater at song posts (mean±SD, N=12 birds). Song rate and song post selection were not influenced consistently by temperature or wind speed, but the birds sang from lower positions on one particularly windy day. This may have resulted from difficulty in holding on to exposed branches in windy conditions rather than a thermoregulatory constraint. The results suggest that the extra thermoregulatory costs at song posts would increase metabolic rate by an average of 10±4% and a maximum of 25±8% (N=12 birds) relative to birds singing at foraging sites. We estimated that metabolic rate would be 3,8% greater during singing than during quiet respiration because of heat and evaporative water loss in exhaled gases. The combined energy requirements for sound production, thermoregulation at exposed song posts and additional heat loss in exhaled air could increase the metabolic rate of willow warblers by an average of 14,23%, and a maximum of 42,63%, during singing. The energetic cost of singing may thus be much greater for birds in a cold, windy environment than for birds singing in laboratory conditions. [source]

Evolutionary and comparative anatomical investigations of the autonomic cardiac nervous system in the African cercopithecidae

JOURNAL OF MORPHOLOGY, Issue 9 2007
Tomokazu Kawashima
Abstract The purpose of this study was to clarify the general architecture and morphological variations of the autonomic cardiac nervous system (ACNS) in the African Cercopithecidae (Old World monkeys), and to discuss the evolutionary changes between this system in African/Asian Cercopithecidae and humans. A detailed macroscopic comparative morphological investigation of the ACNS was performed by examining the left and right sides of 11 African cercopithecid specimens, including some previously unreported species (Abyssinian colobus, Angola pied colobus, Savanna monkey, and lesser white-nosed guenon). The common characteristics of the ACNS in the African Cercopithecidae are described in detail. Consequently, homologies of the ACNS between Asian (macaques) and African Cercopithecidae, and differences between the Asian/African Cercopithecidae and humans, were found. In particular, differences in the sympathetic (cardiac) systems of the Cercopithecidae and humans were recognized, despite the similar morphology of the parasympathetic vagal (cardiac) system. These differences include the composition of the cervicothoracic ganglion, the lower positions of the middle cervical and cervicothoracic ganglia, and the narrow range for the origin of the cardiac nerves in the Cercopithecidae, compared with that in humans. In conclusion, these findings are considered with regard to the morphology of the last common ancestors of the Cercopithecidae. J. Morphol., 2007 © 2007 Wiley-Liss, Inc. [source]

Positional effects on citation and readership in arXiv

JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 11 2009
Asif-ul Haque
arXiv.org mediates contact with the literature for entire scholarly communities, providing both archival access and daily email and web announcements of new materials. We confirm and extend a surprising correlation between article position in these initial announcements and later citation impact, due primarily to intentional "self-promotion" by authors. There is, however, also a pure "visibility" effect: the subset of articles accidentally in early positions fared measurably better in the long-term citation record. Articles in astrophysics (astro-ph) and two large subcommunities of theoretical high energy physics (hep-th and hep-ph) announced in position 1, for example, respectively received median numbers of citations 83%, 50%, and 100% higher than those lower down, while the subsets there accidentally had 44%, 38%, and 71% visibility boosts. We also consider the positional effects on early readership. The median numbers of early full text downloads for astro-ph, hep-th, and hep-ph articles announced in position 1 were 82%, 61%, and 58% higher than for lower positions, respectively, and those there accidentally had medians visibility-boosted by 53%, 44%, and 46%. Finally, we correlate a variety of readership features with long-term citations, using machine learning methods, and conclude with some observations on impact metrics and the dangers of recommender mechanisms. [source]

Recruitment limitation along disturbance gradients in river flood plains

JOURNAL OF VEGETATION SCIENCE, Issue 1 2005
W.H.J.M. van Eck
Abstract. Question: Along river floodplains lower distribution limits of plant species seem largely determined by their tolerance to rarely occurring floods in the growing season. Such distribution patterns remain fixed for many years suggesting additional effects of winter floods at lower positions. Our objective was to investigate the direct and indirect effects of winter floods on colonization of floodplains in a series of field experiments. Location: River Rhine, The Netherlands. Methods: We measured the direct effects of winter floods on seedling survival and seed removal and survival at low and high floodplain elevation. Indirect effects of winter flooding through changes in the soil were investigated by measuring seedling emergence on soil transplants that were exchanged between high and low floodplain elevation. To investigate indirect effects of floods on the germination environment through changes in the vegetation structure, we measured the effects of vegetation removal on recruitment of sown species. Results: Recruitment was seed limited at both floodplain elevations. An additional effect of vegetation removal on seedling emergence was also observed. Soil types from both zones did not differently affect seedling emergence. Seeds were not removed from the soil surface by a single winter flood. Moreover, seeds remained viable in the soil for at least two years, while the experimental plots were flooded several times during the experimental period. During one of those floods a thick sand layer was deposited at the low zone and subsequently no seedlings were observed anymore. Conclusions: Colonization of low floodplain zones in years between subsequent summer floods is prevented by seed limitation while the direct effects of winter floods are limited except for irregularly occurring sand depositions. [source]