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Opposite Trend (opposite + trend)
Selected AbstractsSize-Related Advantages for Reproduction in a Slightly Dimorphic Raptor: Opposite Trends between the SexesETHOLOGY, Issue 12 2007Fabrizio Sergio Despite many comparative analyses and more than 20 proposed hypotheses, there is still little consensus over the factors promoting the evolution of reversed sexual dimorphism (RSD) in raptorial species. Furthermore, intrapopulation studies, which may elucidate how RSD is maintained once evolved, have been surprisingly scarce and only focused on a handful of species with medium to high dimorphism. We examined the reproductive advantages associated with body size and condition, measured in the pre-laying period, in a diurnal raptor with low sexual dimorphism, the black kite (Milvus migrans). The study population was essentially monomorphic in size. For females, there was an evidence of reproductive benefits associated with larger size and/or with better body condition. Larger females had also access to higher quality partners and territories, consistent with the ,intrasexual selection' hypothesis, by which members of the larger sex enjoy size-related advantages in intrasexual competition over a scarce resource, the smaller sex. Opposite trends emerged for males: smaller, leaner males had higher breeding output, consistent with the ,small efficient male' hypothesis. Overall, the fact that we observed in an essentially monomorphic population the same selection pressures previously found in species with marked dimorphism suggests that such reproductive advantages may be counterbalanced in our study model by opposite selection pressures during other stages of the life cycle. This casts some doubts on the evolutionary significance of studies focusing exclusively on reproduction and calls for the need of more comprehensive analyses incorporating trait-mediated differentials in survival and recruitment. [source] Recent accumulation variability and change on the Antarctic Peninsula from the ERA40 reanalysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 11 2008Georgina M. Miles Abstract The Antarctic Peninsula has displayed significant climate change over recent decades. Understanding contemporaneous changes in accumulation is made difficult because the region's complex orography means that ice-core data are not necessarily representative of a wider area. In this paper, the patterns of regional spatial accumulation variability across the Antarctic Peninsula region are presented, based on an Empirical Orthogonal Function (EOF) analysis of European Centre for Medium Range Forecasts Reanalysis (ERA40) data over the 23-year period from 1979 through 2001. Annual and seasonal trends in the sign and strength of these patterns are identified, as is their relationship with mean sea level pressure, temperature and indices of large-scale circulation variability. The results reveal that the first pattern of accumulation variability on the Peninsula is primarily related to pressure in the circumpolar trough and the second pattern to temperature: together the two EOFs explain ,45,65% of the annual/seasonal accumulation. The strongest positive trend in an EOF occurs with EOF2 in the austral autumn March-April-May (MAM). This is highly correlated with the Southern Annular Mode (SAM) in this season, suggesting stronger westerly winds have caused an increase in orographic precipitation along the west Antarctic Peninsula. A significant correlation with ENSO occurs only in the winter EOF1, associated with blocking in the Bellingshausen Sea. Inter-annual ERA40 accumulation is shown to compare favourably with an ice core in the south of the Peninsula, but, for a variety of reasons, correlates poorly with accumulation as measured in an ice core from the northern tip. Opposite trends in accumulation at these two sites can be explained by the spatial pattern and trend of EOF2 in MAM and thus by recent changes in the SAM. The results of this study will aid in the understanding of temporal accumulation changes observed in the regional ice-core record. Copyright © 2007 Royal Meteorological Society [source] Race and religion: differential prediction of anxiety symptoms by religious coping in African American and European American young adults,DEPRESSION AND ANXIETY, Issue 3 2010L. Kevin Chapman Ph.D. Abstract Background: Psychosocial factors, including religious coping, consistently have been implicated in the expression of anxiety disorders. This study sought to investigate the relationship between religious coping on anxiety symptoms among a nonclinical sample of African American and European American young adults. Methods: One hundred twenty-one European American and 100 African American young adults completed measures of anxiety and religious coping. Results: As predicted, results differed according to race. African Americans reported significantly more positive religious coping, less negative religious coping, and experienced fewer anxiety symptoms than European Americans. European Americans demonstrated a significant, positive relationship between negative religious coping and anxiety symptoms, and an opposite trend related to anxiety and positive religious coping. However, no such relationships emerged among the African American sample. Conclusions: Implications and suggestions for future research are discussed. Depression and Anxiety, 2010. © 2008 Wiley-Liss, Inc. [source] Threshold electrical stimulation (TES) in ambulant children with CP: a randomized double-blind placebo-controlled clinical trialDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 6 2002Christineí Dali MD A randomized double-blind placebo-controlled clinical trial was carried out to determine whether a group of stable children with cerebral palsy (36 males, 21 females; mean age 10 years 11 months, range 5 to 18 years) would improve their motor skills after 12 months of threshold electrical stimulation (TES). Two thirds received active and one third received inactive stimulators. For the primary outcome we constructed a set of plausible motor function tests and studied the change in summary indices of the performance measurements. Tests were videotaped and assessed blindly to record qualitative changes that might not be reflected in performance measurements. We also judged range of motion, degree of spasticity, and muscle growth measured by CT. Fifty seven of 82 outpatients who were able to walk at least with a walker, completed all 12 months of treatment (hemiplegia n=25, diplegia n=32). There was no significant difference between active and placebo treatment in any of the tested groups, nor combined. Visual and subjective assessments favoured TES (ns), whereas objective indices showed the opposite trend. We conclude that TES in these patients did not have any significant clinical effect during the test period. [source] Flexural deformation capacity of rectangular RC columns determined by the CAE methodEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2006Iztok Peru Abstract A non-parametric empirical approach, called the conditional average estimator (CAE) method, has been implemented for the estimation of the flexural deformation capacity of reinforced concrete rectangular columns expressed in terms of the ultimate (,near collapse') drift. Two databases (PEER and Fardis), which represent subsets of the original databases, were used. Four input parameters were employed in the basic model: axial load index, index related to confinement, shear span index, and concrete compressive strength. The results of analyses suggest that, in general, ultimate drift decreases with increasing axial load index, and increases with better confinement. An increase in the shear span-to-depth ratio has a beneficial effect until a turning point is reached. After that the opposite trend can be observed, i.e. a decrease in the ultimate drift with further increasing of the shear span-to-depth ratio. No clear trend is observed in the case of concrete compressive strength. The predictions, obtained by using the Fardis database are in general somewhat larger than the predictions from the PEER database, due to the difference in the definition of ultimate drift. The scatter of results is large. The local coefficient of variation, which is a measure for dispersion, amounts to about 0.2,0.5. The ultimate drifts obtained by using the two databases, were compared with the values predicted by the Eurocode 8 empirical formula. Copyright © 2006 John Wiley & Sons, Ltd. [source] Variation in the abundance of fungal endophytes in fescue grasses along altitudinal and grazing gradientsECOGRAPHY, Issue 3 2007Gustaf Granath Epichloë festucae, a common fungal symbiont of the genus Festuca (family Poaceae), can provide its host plant with protection against herbivores. However, infection might also be associated with a cost to its host plant. We examined the distribution of Epichloë festucae infection in natural populations of three fescue grasses, Festuca rubra, F. ovina and F. vivipara, on mountains in northern Sweden to determine whether infection frequency varied with reindeer Rangifertarandus grazing pressure and altitude. Two differently-scaled approaches were used: 1) infection frequency was measured at a local scale along ten elevational transects within a ca 400 km2 area and 2) infection frequency was measured on a regional scale along elevational transects on 17 mountains classified as having a history of high or low reindeer grazing pressure. Mean infection frequencies in F. rubra were 10% (vegetative tillers at a local scale), and 23% (flowering culms at a regional scale), and in F. ovina they were 13% (local scale) and 15% (regional scale). Endophyte infection frequency in F. vivipara, was, on average, 12% (local scale) and 37% (regional scale). In F. rubra, infection decreased significantly with increasing altitude at both the local and regional scale, and was positively correlated with grazing pressure. In F. ovina, an opposite trend was found at the regional scale: infection frequency increased significantly with increasing altitude, while no discernible distribution pattern was observed at the local scale. No elevational trends were observed in infection of F. vivipara. These patterns in the distribution of endophyte-infected grasses in non-agricultural ecosystems may be explained by both biotic (grazing) and abiotic factors (altitude). Differences in ecology and life history of the studied grass species may also be of importance for the different results observed among species. [source] Variation in the relationship between numbers of breeding pairs and woodland area for passerines in fragmented habitatECOGRAPHY, Issue 1 2000P. E. Bellamy Species may differ in the relationship between the numbers of breeding pairs present and woodland area, because the proportion of a wood that forms suitable habitat will vary with woodland size. In this paper, we examine the pattern of variation in abundance with woodland area for eight breeding bird species, and also show how this pattern varied between years. During 1990-1997, we made annual censuses of 53,160 woods, of up to 10 ha in size, and fitted a power function to describe the relationships between numbers of breeding pairs and woodland area. Seven of the eight species, blackbird Turdus merula, dunnock Prunella modularis, wren Troglodytes troglodytes, great tit Parus major, chaffinch Fringilla coelebs, robin Erithacus rubecula and blue tit Parus caeruleus showed a pattern of proportionally higher numbers in smaller woods. Only long-tailed tit Aegithalos caudatus occurred in proportionally higher numbers in larger woods. Blackbird and dunnock showed a trend towards lower numbers in large woods during years with low regional population levels; for these species large woods may provide sub-optimal habitat. Great tit, blue tit, chaffinch and robin showed the opposite trend, towards lower numbers in small woods during years with low regional population levels; for these species small woods may provide sub-optimal habitat. Wren and long-tailed tit, which also showed large annual population fluctuations, showed no change in distribution with regional population level. In great tit and chaffinch, the distribution of pairs in any one year may have been influenced by site fidelity producing a lag in the response associated with regional population levels. [source] Sorption of humic acids and ,-endosulfan by clay mineralsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2006Sarunya Hengpraprom Abstract Sorption of ,-endosulfan by kaolinite and montmorillonite alone and in the presence of sorbed and dissolved humic acid (HA) was investigated (pH 8 and 25°C). Three types of HA, Elliot soil HA (EHA), Peat HA (PHA), and Summit Hill HA (SHHA), were used to represent typical humic substances found in soils. For sorption of HA by either mineral, Freundlich sorption coefficient (Kf) values appeared to decrease in the order of EHA > PHA > SHHA, which followed increasing polarity (expressed as the O/C atomic ratio) and decreasing percent-carbon content. For both clays, sorption of ,-endosulfan by the HA mineral complex was greater than for sorption by the clay alone. Sorption of ,-endosulfan by the HA mineral complexes followed the same order as the Kf of the HAs (EHA > PHA > SHHA). Based on the amount of HA adsorbed by each mineral, organic carbon partition coefficients (KOC) were determined for sorption of ,-endosulfan by two of the HA mineral complexes. The value of KOC for ,-endosulfan sorption was greater for kaolinite EHA than kaolinite SHHA. However, the opposite trend was found with the montmorillonite HA complexes. Montmorillonite appeared to sorb ,-endosulfan and/or HA with higher affinity than kaolinite, which likely is due to its 2:1 layer structure and higher surface area. Sorption of endosulfan diol, a hydrolysis product, by the minerals was much less than the parent pesticide. [source] Divergent trends of euroscepticism in countries and regions of the European UnionEUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 6 2010MARCEL LUBBERS Changes in different aspects of euroscepticism developed at different paces and in varying directions in the regions and countries of the European Union (EU) from 1994 to 2004. Using Eurobarometer data, along with data on country and region characteristics, information on the positions of the political parties and media attention paid to the EU, it is tested in detail whether opposite developments in euroscepticism were associated with opposite developments in influencing contextual characteristics. The authors found that the Netherlands became systematically more sceptical towards the EU, whereas the opposite trend was found in Spain. The introduction of the Euro partially explains these divergent trends, but the direction of this effect varies with countries' GDP. Changes in media attention on the EU further explain the changes in the public's attitude. However, this effect is contingent upon specific circumstances. Growing media attention increases political euroscepticism in countries with a negative EU budget balance, whereas it decreases such scepticism in countries with a positive balance. The effect of left-right ideological placement is contingent upon the EU budget balance as well. Finally, the effect of education on euroscepticism is found to be smaller in countries with a higher GDP. [source] Temperature-dependent stock-recruitment model for walleye pollock (Theragra chalcogramma) around northern JapanFISHERIES OCEANOGRAPHY, Issue 6 2007TETSUICHIRO FUNAMOTO Abstract Changes in fish year-class strength have been attributed to year-to-year variability in environmental conditions and spawning stock biomass (SSB). In particular, sea temperature has been shown to be linked to fish recruitment. In the present study, I examined the relationship between sea surface temperature (SST), SSB and recruitment for two stocks of walleye pollock (Theragra chalcogramma) around northern Japan [Japanese Pacific stock (JPS) and northern Japan Sea stock (JSS)] using a temperature-dependent stock-recruitment model (TDSRM). The recruitment fluctuation of JPS was successfully reproduced by the TDSRM with February and April SSTs, and February SST was a better environmental predictor than April SST. In addition, the JPS recruitment was positively related to February SST and negatively to April SST. The JSS recruitment modeled by the TDSRM incorporating February SST was also consistent with the observation, whereas the relationship between recruitment and February SST was negative, that is the opposite trend to JPS. These findings suggest that SST in February is important as a predictor of recruitment for both stocks, and that higher and lower SSTs in February act favorably on the recruitment of JPS and JSS respectively. Furthermore, Ricker-type TDSRM was not selected for either of the stocks, suggesting that the strong density-dependent effect as in the Ricker model does not exist for JPS and JSS. I formulate hypotheses to explain the links between SST and recruitment, and note that these relationships should be considered in any future attempts to understand the recruitment dynamics of JPS and JSS. [source] Climate change-driven forest fires marginalize the impact of ice cap wasting on KilimanjaroGLOBAL CHANGE BIOLOGY, Issue 7 2005Andreas Hemp Abstract The disappearing glaciers of Kilimanjaro are attracting broad interest. Less conspicuous but ecologically far more significant is the associated increase of frequency and intensity of fires on the slopes of Kilimanjaro, which leads to a downward shift of the upper forest line by several hundred meters as a result of a drier (warmer) climate since the last century. In contrast to common belief, global warming does not necessarily cause upward migration of plants and animals. Here, it is shown that on Kilimanjaro the opposite trend is under way, with consequences more harmful than those due to the loss of the showy ice cap of Africa's highest mountain. [source] How does grazing intensity influence the diversity of plants and insects in a species-rich upland grassland on basalt soils?GRASS & FORAGE SCIENCE, Issue 1 2009B. Dumont Abstract The effect of stocking rate on the species richness, abundance and functional diversity of vascular plants, butterflies and grasshoppers was examined in a semi-natural upland pasture in central France. Over a 5-year period, 3·6-ha plots were continuously grazed by Charolais heifers at 1·4 (High stocking rate), 1·0 (Intermediate) and 0·6 (Low) livestock units (LU) ha,1. To evaluate botanical diversity, percentage cover of all plant species was estimated in late July in ten fixed 1 m × 1 m quadrats per plot. Butterflies were counted on three occasions between late June and early August along three fixed 50-m-long transects per plot using the ,Pollard walk', with grasshoppers being recorded on two occasions along the same transects. Diversity patterns of the three taxa were affected by stocking rate. For plants, species abundance changed more than species number. Abundance of forbs became higher under the Low compared with the High stocking rate. Stress-tolerant grasses were also more abundant in plots grazed at the Low stocking rate, while an opposite trend was observed for competitive grasses. Butterflies consistently responded to alterations in vegetation composition, especially to the dynamics of nectar plants. The species richness of grasshoppers also increased in plots at the Low stocking rate. The Low and Intermediate stocking rates were suitable for providing a high diversity of the three taxonomic groups. The results suggested that at least butterfly diversity would peak in vegetation taller than that of vascular plants. [source] Highly Cooperative Behavior of Peptide Nucleic Acid-Linked DNA-Modified Gold-Nanoparticle and Comb-Polymer AggregatesADVANCED MATERIALS, Issue 6 2009Abigail K. R. Lytton-Jean PNA is used to assemble gold nanoparticles,DNA and polymer,DNA hybrids into highly cooperative aggregates with sharp melting transitions. The melting temperatures of these aggregates are found to increase with increasing salt concentrations, while the opposite trend is observed for unmodified PNA:DNA duplexes. This cooperative behavior is attributed to the presence of closely spaced duplexes inside the aggregate. [source] Differential effect of hyperthyroidism on rat epididymal glycosidasesINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 4 2001R. R. M. Maran The impact of hyperthyroidism on epididymal glycosidases was studied in albino rats. Hyperthyroidism was induced in Wistar rats aged 30 days by daily injection of T4 (25 ,g/100 g body weight/day intramuscularly) for 30 or 60 days; control rats were injected with vehicle (alkaline saline, pH 7.8). One set of hyperthyroid rats was reverted to euthyroid status by withdrawing T4 treatment after 30 days of hyperthyroidism. To asses the direct effect of thyroid hormone on epididymal hexosaminidases, caput, corpus and cauda tissues were stimulated with 25, 50 or 100 ng/mL T3 for 24 h, after an initial culture of 24 h. The activity of ,-glucosidase decreased in caput, corpus and cauda epididymis of hyperthyroid rats. ,-Galactosidase activity increased in the caput epididymis irrespective of the duration of hyperthyroidism. While a similar decrease occurred in the corpus and cauda epididymis in the 30 day hyperthyroid group, an opposite trend was observed in 60 day hyperthyroid rats. Caput ,- N -acetylglucosaminidase activities increased at both time points, whereas activity decreased in the corpus and cauda in 30 day, but increased in 60 day hyperthyroid rats. Hyperthyroidism consistently increased caput and corpus ,- N -acetylgalactosaminidase activity irrespective of the duration. Cauda epididymal ,- N -acetylgalactosaminidase activity was decreased in 30 day and increased in 60 day hyperthyroid rats. Hyperthyroidism induced changes in caput ,-galactosidase, ,- N -acetylgalactosaminidases, corpus ,-N-acetylglucosaminidase and cauda ,- N -acetylgalactosaminidase which were irreversible while the remaining actvities were brought back to normal when T4 treatment was withdrawn. In vitro studies showed that T3 stimulates epididymal hexosaminidases (,- N -acetylglucosaminidase and ,- N -acetylgalactosaminidase) irrespective of the dose. These data suggest that thyroid hormones have a specific and direct influence on glycosidases in specific regions of the epididymis. [source] Trends in daily precipitation and temperature extremes across western Germany in the second half of the 20th centuryINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2005Yeshewatesfa Hundecha Abstract The evolution of daily extreme precipitation and temperature from 1958 to 2001 was investigated within the German side of the Rhine basin. Trends of a set of extreme precipitation and temperature indices defined on daily time series of precipitation and temperature were calculated at 611 precipitation and 232 temperature stations located within the study area and their corresponding significances were tested using the non-parametric Kendall- tau test. The results obtained indicated that both the daily minimum and maximum extreme temperatures have increased over the investigation period, with the degree of change showing seasonal variability. On an annual basis, the change in the daily minimum extreme temperature was found to be greater than that of the daily maximum extreme temperature. The daily extreme heavy precipitation has shown increasing trends both in magnitude and frequency of occurrence in all seasons except summer, where it showed the opposite trend. The station values of the daily precipitation were also interpolated on a regular grid of 5 km × 5 km so that the changes in the indices could be investigated on areal precipitation by aggregating the interpolated precipitation to any desired scale. This enables assessment of the hydrological consequences of the changes in the extreme precipitation. Although the spatial pattern remained more or less similar with that of the point-scale trends for all indices, the average trend magnitude showed an increase with the scale of the area on which precipitation was aggregated. Copyright © 2005 Royal Meteorological Society [source] Impacts of land use change on South-east Asian forest butterflies: a reviewJOURNAL OF APPLIED ECOLOGY, Issue 4 2007LIAN PIN KOH Summary 1South-east Asia has the highest relative rate of habitat loss and degradation in the humid tropics. The responses of less ,charismatic' groups, including butterflies, to habitat disturbance remain relatively poorly understood. Many South-east Asian butterflies are endemic to the region and face global extinction if current levels of deforestation were to continue. 2Here, I highlight South-east Asia as a region urgently in need of butterfly conservation research and review empirical studies of the responses of South-east Asian butterflies to land use change. Additionally, I discuss some methodological pitfalls for such studies. Furthermore, I argue for the importance of identifying the ecological correlates of sensitivity of butterfly species to forest modification and the potential biological mechanisms underlying their responses to land use change. 3There has been no consensus among previous studies on the effects of land use change on butterfly communities in South-east Asia. Of the 20 studies I reviewed, seven reported higher species richness/diversity in undisturbed (or the least disturbed) forest than in disturbed habitats, nine reported the opposite trend, three reported no difference and one reported a strong influence of seasonality on the impacts of logging. 4Some of these studies may contain inherent methodological biases resulting from the failure to control for sampling effects, the lack of consideration for the spatial scale of analysis and incomplete sampling of the vertical strata in tropical rainforests. 5Synthesis and applications. Empirical studies of the effects of land use change on tropical forest insects are sorely lacking from South-east Asia. Butterflies are an ideal taxonomic group for such investigations. Future studies should be designed carefully to avoid the methodological pitfalls highlighted here. Determining the ecological correlates of sensitivity of butterflies to forest modification is important for the pre-emptive identification of species of conservation concern and for generating testable hypotheses on the differential responses of species to forest modification. Experimental studies are needed to determine the mechanisms underlying the responses of species to land use change in order to develop effective strategies for the conservation of butterflies in human disturbed landscapes. [source] Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007H. A. Khonakdar Abstract Uncrosslinked and chemically crosslinked binary blends of low- and high-density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt-mixing process using 0,3 wt % tert -butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation-at-break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co-continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261,3270, 2007 [source] Climate change and its impact on the forests of KilimanjaroAFRICAN JOURNAL OF ECOLOGY, Issue 2009Andreas Hemp Abstract Cloud forests are of great importance in the hydrological functioning of watersheds in subhumid East Africa. However, the montane forests of Mt. Kilimanjaro are heavily threatened by global change impacts. Based on an evaluation of over 1500 vegetation plots and interpretation of satellite imagery from 1976 and 2000, land-cover changes on Kilimanjaro were evaluated and their impact on the water balance estimated. While the vanishing glaciers of Kilimanjaro attract broad interest, the associated increase of frequency and intensity of fires on the slopes of Kilimanjaro is less conspicuous but ecologically far more significant. These climate change-induced fires have lead to changes in species composition and structure of the forests and to a downward shift of the upper forest line by several hundred metres. During the last 70 years, Kilimanjaro has lost nearly one-third of its forest cover, in the upper areas caused by fire, on the lower forest border mainly caused by clearing. The loss of 150 km2 of cloud forest , the most effective source in the upper montane and subalpine fog interception zone , caused by fire during the last three decades means a considerable reduction in water yield. In contrast to common belief, global warming does not necessarily cause upward migration of plants and animals. On Kilimanjaro the opposite trend is under way, with consequences more harmful than those due to the loss of the showy ice cap of Africa's highest mountain. [source] META-ANALYSIS OF GRAZER CONTROL OF PERIPHYTON BIOMASS ACROSS AQUATIC ECOSYSTEMS,JOURNAL OF PHYCOLOGY, Issue 4 2009Helmut Hillebrand Grazer control of periphyton biomass has been addressed in numerous experimental studies in all kinds of aquatic habitats. In this meta-analysis, the results of 865 experiments are quantitatively synthesized in order to address the following questions: (i) Do lotic, lentic, and marine ecosystems differ in their degree of grazer control of periphyton biomass? (ii) Which environmental variables affect the degree of grazer control? (iii) How much does the result of these experiments depend on facets of experimental design? Across all ecosystems, the grazers removed on average 59% of the periphyton biomass, with grazing being significantly stronger for laboratory (65%) than for field (56%) experiments. Neither field nor lab experiments showed a significant difference among lotic, lentic, and coastal habitats. Among different taxonomic consumer groups, crustaceans (amphipods and isopods) and trichopteran larvae removed the highest proportion of periphyton biomass. Grazer effects increased with increasing algal biomass, with decreasing resource availability and with increasing temperature, especially in field experiments. Grazer effects also increased with increasing total grazer biomass in field experiments but showed the opposite trend in lab experiments, indicating a tendency toward overcrowded lab experiments. Other aspects of experimental design, such as cage type, size, and duration of the study, strongly affected the outcome of the experiments, suggesting that much care has to be placed on the choice of experimental design. [source] PHOTOSYNTHETIC PERFORMANCE, LIGHT ABSORPTION, AND PIGMENT COMPOSITION OF MACROCYSTIS PYRIFERA (LAMINARIALES, PHAEOPHYCEAE) BLADES FROM DIFFERENT DEPTHS,JOURNAL OF PHYCOLOGY, Issue 6 2006María Florencia Colombo-Pallotta Macrocystis pyrifera (L.) C. Agardh is a canopy-forming species that occupies the entire water column. The photosynthetic tissue of this alga is exposed to a broad range of environmental factors, particularly related to light quantity and quality. In the present work, photosynthetic performance, light absorption, pigment composition, and thermal dissipation were measured in blades collected from different depths to characterize the photoacclimation and photoprotection responses of M. pyrifera according to the position of its photosynthetic tissue in the water column. The most important response of M. pyrifera was the enhancement of photoprotection in surface and near-surface blades. The size of the xanthophyll cycle pigment pool (XC) was correlated to the nonphotochemical quenching (NPQ) of chl a fluorescence capacity of the blades. In surface blades, we detected the highest accumulation of UV-absorbing compounds, photoprotective carotenoids, ,XC, and NPQ. These characteristics were important responses that allowed surface blades to present the highest maximum photosynthetic rate and the highest PSII electron transport rate. Therefore, surface blades made the highest contribution to algae production. In contrast, basal blades presented the opposite trend. These blades do not to contribute significantly to photosynthetate production of the whole organism, but they might be important for other functions, like nutrient uptake. [source] DFT study and NBO analysis of the mutual interconversion of cumulene compoundsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2007Davood Nori-Shargh Abstract The B3LYP/6-31G* method was used to investigate the configurational properties of allene (1,2-propadiene) (1), 1,2,3-butatriene (2), 1,2,3,4-pentateriene (3), 1,2,3,4,5-hexapentaene (4), 1,2,3,4,5,6-heptahexaene (5), 1,2,3,4,5,6,7-octaheptaene (6), 1,2,3,4,5,6,7,8-nonaoctaene (7), and 1,2,3,4,5,6,7,8,9-decanonaene (9). The calculations at the B3LYP/6-31G* level of theory showed that the mutual interconversion energy barrier in compounds 1,8 are: 209.73, 131.77, 120.34, 85.00, 80.91, 62.19, 55.56, and 46.83,kJ,mol,1, respectively. The results showed that the difference between the average CC double bond lengths () values in cumulene compounds 1 and 2, is larger than those between 7 and 8, which suggest that with large n (number of carbon atoms in cumulene chain), the values approach a limiting value. Accordingly, based on the plotted data, the extrapolation to n,=,,, gives nearly the same limiting (i. e., ). Also, NBO results revealed that the sum of , -bond occupancies, , decrease from 1 to 8, and inversely, the sum of , -antibonding orbital occupancies, , increase from compound 1 to compound 8. The decrease of values for compounds 1,8, is found to follow the same trend as the barrier heights of mutual interconversion in compounds 1,8, while the decrease of the barrier height of mutual interconversion in compounds 1,8 is found to follow the opposite trend as the increase in the number of carbon atom. Accordingly, besides the previously reported allylic resonant stabilization effect in the transition state structures, the results reveal that the values, , ,(EHOMO,,,ELUMO), and the C atom number could be considered as significant criteria for the mutual interconversion in cumulene compounds 1,8. This work reports also useful predictive linear relationships between mutual interconversion energy barriers () in cumulene compounds and the following four parameters: , , ,(EHOMO,,,ELUMO), and CNumber. Copyright © 2007 John Wiley & Sons, Ltd. [source] Molecular polarizability of fullerenes and endohedral metallofullerenesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2002Francisco Torrens Abstract The interacting induced dipoles polarization model implemented in our program POLAR is used for the calculation of the molecular dipole µ and tensor quadrupole moments and also the dipole,dipole polarizability . The method is tested with Scn, Cn (fullerene and graphite) and endohedral Scn@Cm clusters. The polarizability is an important quantity for the identification of clusters with different numbers of atoms and even for the separation of isomers. The results for the polarizability are of the same order of magnitude as from reference calculations performed with our version of the program PAPID. The bulk limit for the polarizability is estimated from the Clausius,Mossotti relationship. The polarizability trend for these clusters as a function of size is different from what one might have expected. The clusters are more polarizable than what one might have inferred from the bulk polarizability. Previous theoretical work yielded the same trend for Sin, Gen and GanAsm small clusters. However, previous experimental work yielded the opposite trend for Sin, GanAsm and GenTem larger clusters. At present, the origin of this difference is problematic. One might argue that smaller clusters need not behave like those of intermediate size. The high polarizability of small clusters is attributed to dangling bonds at the surface of the cluster. In this respect, semiconductor clusters resemble metallic clusters. Copyright © 2002 John Wiley & Sons, Ltd. [source] Properties of Compositionally Graded BiScO3,PbTiO3 Thin Films Fabricated by a Sol,Gel ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2007Hai Wen The compositionally graded BiScO3,PbTiO3 (BSPT) thin films were fabricated on Pt/Ti/SiO2/Si by a sol,gel method. For the up-graded thin film, the PbTiO3 content increased from the film,substrate interface to the surface of the film, while the down-grade thin film showed the opposite trend. The graded thin films exhibited single-phase structures and dense microstructures. The dielectric and ferroelectric properties of the thin films were investigated. The results showed that the compositionally graded BSPT thin films had similar remanent polarization value but a higher dielectric constant, dielectric tunability, and piezoelectric coefficient d33 compared with the homogeneous thin film with a composition of 0.36BiScO3,0.64PbTiO3 at the morphotropic phase boundary. [source] Nutritional quality of red shrimp, Aristeus antennatus (Risso), pink shrimp, Parapenaeus longirostris (Lucas), and Norway lobster, Nephrops norvegicus (Linnaeus),JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2004Rui Rosa Abstract The proximate composition, amino acid and fatty acid profiles, lipid classes and cholesterol and glycogen contents were determined in the edible part of red shrimp, Aristeus antennatus (Risso), pink shrimp, Parapenaeus longirostris (Lucas), and Norway lobster, Nephrops norvegicus (Linnaeus), in two distinct periods of the year. The proximate composition did not vary significantly between species or between periods of sampling. Significant differences in glycogen content were obtained between winter and summer; the lowest values were attained in winter (1.2, 1.1 and 1.0% wet weight for red shrimp, pink shrimp and Norway lobster respectively). With the exception of Norway lobster, an opposite trend was obtained for cholesterol content, ie lower values in summer (60.8 and 57.8 mg per 100 g wet weight for red shrimp and pink shrimp respectively). The major essential amino acids (EAA) were arginine, lysine and leucine and the limiting amino acid was methionine in all three crustacean species. The most important non-essential amino acids (NEAA) were glutamic acid, aspartic acid, proline and glycine. In respect to lipid classes, phospholipids and free cholesterol predominated. The major fatty acids were 16:0, 18:1n-9, 20:5n-3 and 22:6n-3. The polyunsaturated fraction was dominant (42.1,48.4%), followed by the monounsaturated (26.3,34.6%) and saturated (22.9,27.4%) fatty acids. In conclusion, the nutritional quality of these shellfish species is similar, they are valuable protein and lipid sources for the human diet and are adequate elements of the traditional Portuguese diet. Copyright © 2003 Society of Chemical Industry [source] The effects of perceived predation risk on pre- and post-metamorphic phenotypes in the common frogJOURNAL OF ZOOLOGY, Issue 3 2009C. E. Stamper Abstract Where organisms undergo radical changes in habitat during ontogeny, dramatic phenotypic reshaping may be required. However, physiological and functional interrelationships may constrain the extent to which an individual's phenotype can be equally well adapted to their habitat throughout the life cycle. The phenotypic response of tadpoles to the presence of a predator has been reported for several species of anuran but the potential post-metamorphic consequences have rarely been considered. We reared common frog Rana temporaria tadpoles in the presence or absence of a larval odonate predator, Aeshna juncea, and examined the consequences of the resulting phenotypic adjustment in the aquatic larval stage of the life cycle for the terrestrial juvenile phenotype. In early development tadpoles developed deeper tail fins and muscles in response to the predator and, in experimental trials, swam further than those reared in the absence of a predator. While the difference in swimming ability remained significant throughout the larval period, by the onset of metamorphosis we could no longer detect any differences in the morphological parameters measured. The corresponding post-metamorphic phenotypes also did not initially differ in terms of morphology. At 12 weeks post-metamorphosis, however, froglets that developed from predator-exposed tadpoles swam more slowly and less far than those that developed from tadpoles reared in the absence of predators, the opposite trend to that observed in the larval stage of the life cycle, and had narrower femurs. These results suggest that there may be long-term costs for subsequent life-history stages of tailoring the larval phenotype to prevailing environmental conditions. [source] Freezing resistance varies within the growing season and with elevation in high-Andean species of central ChileNEW PHYTOLOGIST, Issue 2 2009Angela Sierra-Almeida Summary ,,Predicted increases in the length of the growing season as a result of climate change may more frequently expose high-elevation plants to severe frosts. Understanding the ability of these species to resist frosts during the growing season is essential for predicting how species may respond to changes in temperature regimes. ,,Here, we assessed the freezing resistance of 24 species from the central Chilean Andes by determining their low temperature damage (LT50), ice nucleation temperature (NT), freezing point (FP) and freezing resistance mechanism (i.e. avoidance or tolerance). ,,The Andean species were found to resist frosts from ,8.2 to ,19.5°C during the growing season, and freezing tolerance was the most common resistance mechanism. Freezing resistance (LT50) varied within the growing season, decreasing towards the end of this period in most of the studied species. However, the FP showed the opposite trend. LT50 increased with elevation, whilst FP was lower in plants from lower elevations, especially late in the growing season. ,,Andean species have the potential to withstand severe freezing conditions during the growing season, and the aridity of this high-elevation environment seems to play an important role in determining this high freezing resistance. [source] Above and below ground impacts of terrestrial mammals and birds in a tropical forestOIKOS, Issue 4 2008Amy E. Dunham Understanding the impact of losing trophic diversity has global significance for managing ecosystems as well as important theoretical implications for community and ecosystem ecology. In several tropical forest ecosystems, habitat fragmentation has resulted in declines and local extinctions of mammalian and avian terrestrial insectivores. To assess the ability of a tropical rainforest community in Ivory Coast to resist perturbation from such loss of trophic diversity, I traced feedbacks in above and below ground communities and measured changes in nutrient levels and herbivory rates in response to an experimental exclosure of avian and mammalian terrestrial insectivores. I present evidence that loss of this functional group may result in increased tree seedling herbivory and altered nutrient regimes through changes in the abundance and guild structure of invertebrates. Exclusion of top predators of the forest floor resulted in increased seedling herbivory rates and macro-invertebrate (>5 mm) densities with strongest effects on herbivorous taxa, spiders and earthworms. Densities of microbivores including Collembola, Acarina and Sciaridae showed the opposite trend as did levels of inorganic phosphorus in the soil. Results were evaluated using path analysis which supported the presence of a top down trophic cascade in the detrital web which ultimately affected turnover of phosphorus, a limiting nutrient in tropical soils. Results illustrate the potential importance of vertebrate predators in both above and belowground food webs despite the biotic diversity and structural heterogeneity of the rainforest floor. [source] Ultraviolet-B Radiation Effects on the Structure and Function of Lower Trophic Levels of the Marine Planktonic Food WebPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2006Gustavo A. Ferreyra ABSTRACT The impact of UV-B radiation (UVBR; 280,320 nm) on lower levels of a natural plankton assemblage (bacteria, phytoplankton and microzooplankton) from the St. Lawrence Estuary was studied during 9 days using several immersed outdoor mesocosms. Two exposure treatments were used in triplicate mesocosms: natural UVBR (N treatment, considered as the control treatment) and lamp-enhanced UVBR (H treatment, simulating 60% depletion of the ozone layer). A phytoplankton bloom developed after day 3, but no significant differences were found between treatments during the entire experiment for phytoplankton biomass (chlorophyll a and cell carbon) nor for phytoplankton cell abundances from flow cytometry and optical microscopy of three phytoplankton size classes (picoplankton, nanoplankton and microplankton). In contrast, bacterial abundances showed significantly higher values in the H treatment, attributed to a decrease in predation pressure due to a dramatic reduction in ciliate biomass (, 70,80%) in the H treatment relative to the N treatment. The most abundant ciliate species were Strombidinium sp., Prorodon ovum and Tintinnopsis sp.; all showed significantly lower abundances under the H treatment. P. ovum was the less-affected species (50% reduction in the H treatment compared with that of the N control), contrasting with ,90% for the other ones. Total specific phytoplanktonic and bacterial production were not affected by enhanced UVBR. However, both the ratio of primary to bacterial biomass and production decreased markedly under the H treatment. In contrast, the ratio of phytoplankton to bacterial plus ciliate carbon biomass showed an opposite trend than the previous results, with higher values in the H treatment at the end of the experiment. These results are explained by the changes in the ciliate biomass and suggest that UVBR can alter the structure of the lower levels of the planktonic community by selectively affecting key species. On the other hand, linearity between particulate organic carbon (POC) and estimated planktonic carbon was lost during the postbloom period in both treatments. On the basis of previous studies, our results can be attributed to the aggregation of carbon released by cells to the water column in the form of transparent exopolymer particles (TEPs) under nutrient limiting conditions. Unexpectedly, POC during such a period was higher in the H treatment than in controls. We hypothesize a decrease in the ingestion of TEPs by ciliates, in coincidence with increased DOC release by phytoplankton cells under enhanced UVBR. The consequences of such results for the carbon cycle in the ocean are discussed. [source] Oxygen isotope enrichment (,18O) reflects yield potential and drought resistance in maizePLANT CELL & ENVIRONMENT, Issue 11 2009LLORENÇ CABRERA-BOSQUET ABSTRACT Measurement of stable isotopes in plant dry matter is a useful phenotypic tool for speeding up breeding advance in C3 crops exposed to different water regimes. However, the situation in C4 crops is far from resolved, since their photosynthetic metabolism precludes (at least in maize) the use of carbon isotope discrimination. This paper investigates the use of oxygen isotope enrichment (,18O) as a new secondary trait for yield potential and drought resistance in maize (Zea mays L). A set of tropical maize hybrids developed by the International Maize and Wheat Improvement Center was grown under three contrasting water regimes in field conditions. Water regimes clearly affected plant growth and yield. In accordance with the current theory, a decrease in water input was translated into large decreases in stomatal conductance and increases in leaf temperature together with concomitant 18O enrichment of plant matter (leaves and kernels). In addition, kernel ,18O correlated negatively with grain yield under well-watered and intermediate water stress conditions, while it correlated positively under severe water stress conditions. Therefore, genotypes showing lower kernel ,18O under well-watered and intermediate water stress had higher yields in these environments, while the opposite trend was found under severe water stress conditions. This illustrates the usefulness of ,18O for selecting the genotypes best suited to differing water conditions. [source] Formation of microporous poly(hydroxybutyric acid) membranes for culture of osteoblast and fibroblastPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2009Han-Shiang Huag Abstract Microporous membranes of a biodegradable polymer, poly(hydroxybutyric acid) (PHB), were prepared by a phase-inversion process and their cell compatibility was evaluated in vitro. A ternary system, ethanol/chloroform/PHB, was employed to prepare the membranes, wherein ethanol and chloroform were served as the nonsolvent and solvent for PHB, respectively. In the phase-inversion process, the polymer dissolution temperature was varied from 80 to 120°C to yield membranes with specific morphologies, such as globular particles, porous channels, etc. Moreover, cell viability was examined on the formed membranes. Two cell lines, osteoblast hFOB1.19 and fibroblast L929, were cultured in vitro. It was found that these two types of cells exhibited different responses on different membranes: the hFOB1.19 cells showed significant increase in cell proliferation with increase in surface roughness, whereas the L929 cells demonstrated an opposite trend, preferring to attach and grow on a flat surface. PHB membranes with different morphologies exhibit different cell compatibilities, which may be useful means for the architectural design of materials for tissue engineering. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||