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Bimodal Pattern (bimodal + pattern)
Selected AbstractsSeasonal prevalence of blowflies and flesh flies in Osaka CityENTOMOLOGICAL SCIENCE, Issue 4 2006Shin-Ichiro TACHIBANA Abstract Blowflies (Diptera: Calliphoridae) and flesh flies (Sarcophagidae) were collected using a bait trap in Osaka City between April 1998 and June 1999. Seven species from four Calliphoridae genera and three species from one Sarcophagidae genus were captured. Seasonal fluctuations of captured adults for most blowflies showed a bimodal pattern, having peaks in spring and autumn, whereas all flesh flies were captured between spring and autumn. The sex ratios of captured flies were mostly biased toward females. [source] Cohort splitting in bluefish, Pomatomus saltatrix, in the US mid-Atlantic BightFISHERIES OCEANOGRAPHY, Issue 3 2008JODY L. CALLIHAN Abstract Atlantic bluefish exhibit cohort splitting, whereby two modes of juvenile recruits originate from spatially distinct spring- and summer-spawning regions in US Atlantic shelf waters. We evaluate the pattern of cohort splitting in a transition area (US Maryland coastal region and Chesapeake Bay) between the two major spawning regions. Spring and summer cohorts were differentially represented in Maryland estuarine (Chesapeake Bay) and coastal waters. The spring cohort was dominant in Chesapeake Bay, but was not well represented in the ocean environment, and the converse true for the summer cohort. We hypothesized that ocean temperatures control the bimodal spawning behavior and extent of cohort splitting. As evidence, we observed an intervening early summer cohort produced in years when shelf temperatures during early summer were suitably warm for spawning. In most years however, two dominant cohorts were evident. We propose that vernal warming dynamics in the mid-Atlantic Bight influence spawning behavior and the resultant bimodal pattern of seasonal juvenile cohort production commonly observed along the US east coast. [source] The spatial pattern of summertime subtropical anticyclones over Asia and Africa: A climatological reviewINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2010Azar Zarrin Abstract The National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) monthly mean reanalysis dataset has been used to analyze spatial variations of summertime subtropical anticyclones over the Asia,Africa region. The geopotential height and zonal wind components of 1000, 500, 200, and 100 hPa in a 30-year period (1971,2000) have been used to determine the spatial and temporal variations of the anticyclone centres, their monthly frequency and latitudinal axis variations during April,October. The results revealed that there is a clear difference in the location of the summer anticyclone centres in lower, middle and upper levels of the troposphere. In the lower levels, the Azores subtropical anticyclone is located at the east of North Atlantic. In the middle levels, the frequencies of anticyclone centre are concentrated over the northwest of Africa, Arabian Peninsula and Iranian Plateau. In the upper troposphere, the geographical location of the anticyclone centres and their frequencies in the summer season exhibit a scattered pattern from south of China up to western Iran at 200 hPa, and a bimodal pattern over the Tibetan and the Iranian Plateaus at 100 hPa. In fact, in the entire study domain, the Iranian Plateau is a preferable location of the middle and upper troposphere anticyclones. The highest observed latitude of the subtropical anticyclone at 100, 200 and 500 hPa levels have been seen over north of Tibetan plateau, a large area from east to west of Asia and Iran during August, July,August and July, respectively. The maximum monthly variation in the latitude of the ridgeline is seen at 500, 200, and 100 hPa from June to July which goes even up to 10 degrees at some longitudes. Copyright © 2009 Royal Meteorological Society [source] Stable water isotope simulation in different reservoirs of Manaus, Brazil, by Community Land Model incorporating stable isotopic effectINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2009Xin-Ping Zhang Abstract The daily and monthly variations of stable water isotopes in different reservoirs at Manaus, Brazil, are simulated and inter-compared in an equilibrium year, using the Community Land Model (CLM) involving the stable isotopic effects as a diagnostic tool for an in-depth understanding of the hydrometeorological processes. On the daily scale, the ,18O in precipitation, vapour and surface runoff have clear seasonality, with marked negative correlations with the corresponding water amount. However, the ,18O in surface dew displays marked positive correlation with dew amount. On the diurnal time scale, the ,18O in precipitation displays an unclear diurnal variation and an unmarked correlation with the precipitation amount. However, the ,18O in vapour keeps consistency with specific humidity. On the monthly time scale, the ,18O in precipitation and surface runoff displays distinct bimodal seasonality, with two maxima in January and in July, and two minima in April and in October; Vapor displays a similar bimodal pattern, two maxima appear in January and August, and two minima in April and November. The amount effect simulated on the monthly time scale has consistency with the actual survey result at the Manaus station, from 1965 to 1990, set up by International Atomic Energy Agency (IAEA)/World Meteorological Organization (WMO). In addition, the slope (7.49) and the intercept (6.25) of the simulated meteoric water line (MWL) are all smaller than those of the actual mean MWL. However, compared with the annual MWL, the simulated MWL lies within the variation range of actual MWLs. Copyright © 2008 Royal Meteorological Society [source] Body mass change strategies in blackbirds Turdus merula: the starvation,predation risk trade-offJOURNAL OF ANIMAL ECOLOGY, Issue 2 2005R. MACLEOD Summary 1It is theoretically well established that body mass in birds is the consequence of a trade-off between starvation risk and predation risk. There are, however, no studies of mass variation from sufficiently large wild populations to model in detail the range of diurnal and seasonal mass change patterns in natural populations and how these are linked to the complex environmental and biological variables that may affect the trade-off. 2This study used data on 17 000 individual blackbirds Turdus merula to model how mass changes diurnally and seasonally over the whole year and over a wide geographical area. Mass change was modelled in respect of temperature, rainfall, day length, geographical location, time of day and time of year and the results show how these mass changes vary with individual size, age and sex. 3The hypothesis that seasonal mass is optimized over the year and changes in line with predictors of foraging uncertainty was tested. As theory predicts, reduced day length and reduced temperature result in increased mass and the expected seasonal peak of mass in midwinter. 4The hypothesis that diurnal mass gain is optimized in terms of starvation,predation risk trade-off theory was also tested. The results provide the first empirical evidence for intraspecies seasonal changes in diurnal mass gain patterns. These changes are consistent with shifts in the relative importance of starvation risk and predation risk and with the theory of mass-dependent predation risk. 5In winter most mass was gained in the morning, consistent with reducing starvation risk. In contrast, during the August,November non-breeding period a bimodal pattern of mass gain, with increases just after dawn and before dusk, was adopted and the majority of mass gain occurred at the end of the day consistent with reducing mass-dependent predation risk. The bimodal diurnal mass gain pattern described here is the first evidence that bird species in the wild gain mass in this theoretically predicted pattern. [source] Reproductive seasonality in the Tete veld rat (Aethomys ineptus) (Rodentia: Muridae) from southern AfricaJOURNAL OF ZOOLOGY, Issue 2 2006S. P. Muteka Abstract Very little is known about the reproductive biology of the recently recognized Tete veld rat Aethomys ineptus. In the present study, we investigated the seasonality of reproduction in this newly recognized rodent using a number of histological and endocrinological parameters. Body mass, reproductive tract morphometrics, gonadal histology, and plasma testosterone concentrations in males and plasma oestradiol-17, and progesterone concentrations in females were assessed from a population in the north-central part of South Africa over a 12-month period in order to ascertain the pattern of reproduction in the species. Seminiferous tubule diameters in 59 males were significantly larger between September and February relative to between March and August. Although spermatogenesis was prevalent in the southern hemisphere winter (June,August), the number of spermatozoa in the epididymides decreased in the southern hemisphere spring (September,November), summer (December,February) and autumn (March,May). Testicular mass relative to body mass and testicular volume regressed between May and September but exhibited recrudescence between September and April, whereas plasma testosterone concentrations increased significantly between September and February relative to between March and August. Ovarian histology of 67 females showed corpora lutea to be present throughout the year, but decreased in number during winter, whereas mean plasma progesterone concentration increased significantly between August and November and again between February and April. This bimodal pattern of progesterone concentration suggests that up to two litters per breeding season may be raised by the Tete veld rat. Gravid females were found between October and April, whereas gravid or lactating females were conspicuously absent between May and September. Collation of all these data suggests that the Tete veld rat is a seasonal breeder with reproduction confined predominantly to summer and autumn months of the southern hemisphere. However, the presence of follicular development in females and the presence of corpora lutea outside the breeding season imply that the Tete veld rat may undergo spontaneous ovulation. [source] Double stimulation of the inner ear organs of an anuran species (Alytes cisternasii) with simple tonal advertisement callsJOURNAL OF ZOOLOGY, Issue 4 2003J. Bosch Midwife toads present one of the simplest calls in anurans, with the whole energy concentrated in a single band without frequency modulation. The tuning curves of the Iberian midwife toads Alytes cisternasii show the typical bimodal pattern in anurans, with two best excitatory frequencies at 0.412 kHz (corresponding to the amphibian papilla) and at 1.358 kHz (corresponding to the basilar papilla and matching the male call frequency). In this study, the hypothesis that complex calls arose in anurans because they were inherently more attractive to females, since they provided greater acoustic stimulation, was tested. However, our results indicate that splitting the call energy to stimulate both inner ear organs simultaneously, the male call is not more attractive to female midwife toads, but sometimes renders it unattractive. The biological role of the amphibian papilla is discussed in ecological and evolutionary terms. [source] Growth rates of small abdominal aortic aneurysms correlate with clinical eventsBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 1 2010A. R. Thompson Background: This retrospective analysis of prospectively collected abdominal aortic aneurysm (AAA) screening data aimed to identify predictors of AAA-related events (surgery or death) with a view to better targeting of screening. Methods: For the interval 1984,2007, data for 1649 subjects with an AAA were collected prospectively as part of the Chichester AAA screening programme. This included serial aortic size measurements, blood pressure, risk factors for arterial disease and concurrent medications. AAA growth rates were adjusted for risk factor confounders using flexible hierarchical modelling. AAA growth distribution was analysed using Silverman's test of multimodality. Results: Some 1231 subjects met the inclusion criteria of having more than one scan and a surveillance interval of over 3 months. AAA growth showed a bimodal pattern with nearly 50 per cent of all aneurysms never progressing to surgery or rupture. Adjusted annual AAA growth rates of at least 2 mm significantly predicted AAA-related events. Conclusion: This analysis identified a bimodal growth pattern for AAA, with a significant association between annual AAA growth rate of at least 2 mm and AAA-related events. Copyright © 2010 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] Evaluating different soil and plant hydraulic constraints on tree function using a model and sap flow data from ponderosa pinePLANT CELL & ENVIRONMENT, Issue 7 2001M. Williams Relationships between tree size and physiological processes such as transpiration may have important implications for plant and ecosystem function, but as yet are poorly understood. We used a process-based model of the soil,plant,atmosphere continuum to investigate patterns of whole-tree sap flow in ponderosa pine trees of different size and age (36 m and ,250 years versus 13 m and 10,50 years) over a developing summer drought. We examined three different hypothetical controls on hydraulic resistance, and found that size-related differences in sap flow could be best explained by absolute differences in plant resistance related to path length (hypothesis 1) rather than through different dynamic relationships between plant resistance and leaf water potential (hypothesis 2), or alterations in rates of cumulative inducement and repair of cavitation (hypothesis 3). Reductions in sap flow over time could be best explained by rising soil,root resistance (hypothesis 1), rather than by a combination of rising plant and soil,root resistance (hypothesis 2), or by rising plant resistance alone (hypothesis 3). Comparing hourly predictions with observed sap flow, we found that a direct relationship between plant resistance and leaf water potential (hypothesis 2) led to unrealistic bimodal patterns of sap flow within a day. Explaining seasonal reduction in sap flow purely through rising plant resistance (hypothesis 3) was effective but failed to explain the observed decline in pre-dawn leaf water potential for small trees. Thus, hypothesis 1 was best corroborated. A sensitivity analysis revealed a significant difference in the response to drought-relieving rains; precipitation induced a strong recovery in sap flow in the hypothetical case of limiting soil,root resistance (hypothesis 1), and an insignificant response in the case of limiting plant resistance (hypothesis 3). Longer term monitoring and manipulation experiments are thus likely to resolve the uncertainties in hydraulic constraints on plant function. [source] | |||||||||||||