bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of copepod foraging behavior on predation risk: An experimental study of the predatory copepod Pareuchaeta norvegica feeding on Acartia clausi and A. tonsa (Copepoda)
Authors: Tiselius Peter , Jonsson Per R. , Kuurtvedt Stein , Olsen Esben Moland , Jørstud Tom
Published: May 2010

The effect of foraging behavior on predation risk was studied by exposing the two small calanoid copepods Acartia clausi and Acartia tonsa to 0 or 1 ppm (~1,500 cells ml−1) of the diatom Thalassiosira weissflogii and to presence of the predator Pareuchaeta norvegica. In filtered water, predation rate was the same on the two species. In algal suspension, predation rate on A. clausi was half that in filtered water and half that on A. tonsa. Video observations revealed distinct differences in motility of Acartia depending on algal concentration. Both species performed frequent short feeding bouts in algal suspension; nonfeeding copepods in filtered water alternately sank or adjusted their vertical distribution by stronger jumps. Jump frequency nearly doubled for A. clausi in filtered water, but no significant difference was observed for A. tonsa. To explain the predation, assuming that P. norvegica is a rheotactic predator, we developed a model of potential hydrodynamic disturbance associated with each foraging behavior. Increased encounter rate with P. norvegica caused by frequent strong jumps by A. clausi in the absence of algae could explain >40% of the observed increase in predation rate. For A. tonsa, jump frequencies and predation rates were similar in both food treatments, which is in accordance with the model.
Some aspects of the analysis of size spectra in aquatic ecology
Authors: Vidondo Beatriz , Prairie Yves T. , Blanco Jose M. , Duarte Carlos M.
Published: May 2010

The established approach to model seston size distributions involves the grouping of particles within logarithmic size classes and the examination of the relationship between density, or normalized biomass, and the characteristic sizes of the classes. Here we examine the distributional basis of the established approach and draw a connection between the biomass size spectrum and the Pareto distribution, a model widely used in other disciplines dealing with size‐structured systems. We provide efficient estimators of the parameters and also suggest that datasets exhibiting significant departures from a smooth power function decline can be adequately modeled using a Pareto type II distribution.
Effects of nitrogen supply and continuous darkness on growth and photosynthesis of the arctic kelp Laminaria solidungula
Authors: Henley William J. , Dunton Kenneth H.
Published: May 2010

Sporophytes of the arctic kelp Laminaria solidungula were collected from the Beaufort Sea and kept for 7 months at 0±1.5°C in a factorial experiment under two light (continuous darkness or 25 µmol photons m−2 s−1 on a 12: 12 L/D cycle) and two nutrient regimes (with or without added nitrate). We monitored growth rate and at the end of the experiment measured the following on both new and old blades: carbon and nitrogen content, chlorophyll and carotenoids, photosynthetic light‐response (P vs. I) curves, and photosynthetic unit size (Chl/P700). New blade initiation was independent of light and external nitrate, but blades grew minimally in darkness. Both new (B1) and old (B2) blades of plants held in darkness (with or without added nitrate) had the same quantum yield (ϕm) and area‐normalized photosynthetic capacity (Pm), but a slightly lower respiration (Rd) and compensation irradiance ≤ 1.5 µmol photons m−2 s−1) as B2 of plants grown in the light with added nitrate. Nitrogen starvation in the light, but not in darkness, caused reduced pigments, Pm, and ϕm, and increased Ic. Tissue C and N were primarily affected by light, whereas pigments were more strongly affected by N and lightXN interaction. Based on these results, previous results for field‐collected plants, and continuous in situ light data, we conclude that total annual growth in this population is severely light‐limited, with N having an important but secondary role.
Nutrient‐limited growth of Microcystis aeruginosa and Phormidium tenue and competition under various N:P supply ratios and temperatures
Authors: Fujimoto Naoshi , Sudo Ryuichi , Sugiura Norio , Inamori Yuhei
Published: May 2010

The blue‐green algae Microcystis aeruginosa and Phormidium tenue were grown in nutrient‐limited continuous cultures and together in mixed continuous cultures under various N:P supply ratios and temperatures. The Droop model accurately described the growth of these two algae. Competitive abilities for P and N distinctively differed among these two algae. In competition experiments, M. aeruginosa was the superior competitor under conditions of low N: P supply ratio and high temperature, whereas P. tenue was superior under conditions of high N : P supply ratio and low temperature, which corresponded to field observations of the algal community in Lake Kasumigaura. Both laboratory and field observations suggest that the N: P supply ratio and temperature are significant environmental factors affecting the relative abundances of M. aeruginosa and P. tenue.
An anoxic event and other biogeochemical effects of the Pantanal wetland on the Paraguay River
Authors: Hamilton Stephen K. , Sippel Suzanne J. , Calheiros DÓbora F. , Melack John M.
Published: May 2010

The Paraguay River was sampled throughout the annual cycle at two sites located downriver from most of the Pantanal, and major tributaries were occasionally sampled close to their entry into the Pantanal. The floodplains strongly modulate the discharge regime and substantially reduce runoff by enhancing evapotranspirative losses. Contact of the river water with the floodplain results in depletion of dissolved O2, oversaturation of CO2 and CH4 loss of suspended sediments, and reduced export of N and P. Oxygen depletion and associated chemical changes are most marked when river water first contacts the floodplain; in 1995, the water remained anoxic throughout the river channel for 6 weeks, causing massive fish mortality. Bottle incubations showed that the rate of O2 consumption by the river water during the anoxic event was high at first (7.2 µM h−1) but declined exponentially over several hours and was not stimulated by organic carbon and nutrient additions. The O2 demand may be due largely to bacterial CH4 oxidation; the concentration of CH4 in the river was particularly high (∼31 µM) at the time of the incubations. The O2 depletion corresponded with higher concentrations of most major ions, Si, and dissolved organic carbon but was not accompanied by elevated concentrations of inorganic N and P, H2S, or most of the 46 dissolved trace elements that were measured. In contrast to O2 depletion and associated chemical changes, sediment retention by the floodplains was greatest at maximum river stages. Most chemical weathering of minerals seems to take place in the upland drainage basins rather than on the floodplains, and most major solutes display conservative mixing in the river‐floodplain system.
Observations of a deep‐mixing event in Crater Lake, Oregon
Authors: Crawford G. B. , Collier R. W.
Published: May 2010

We present observations of the evolution of a deep‐mixing event in a deep, temperate lake. The observations were obtained from thermistors mounted on a long‐term mooring in the lake. The event seems to have originated near 150‐m depth and resulted in a plume or layer of cold water from the upper half of the lake that descended to the lake bottom (590 m) over a 3‐d period. Net mixing associated with this event resulted in an overall vertical heat exchange of nearly 1015 J and a volume exchange of 0.7–3.2 km3 (4–18% of the lake volume) between the upper and lower portions of the lake. The deep water displaced during the event is estimated to have carried 0.3–2.5 × 106 mol of nitrate to the upper lake, which accounts for a significant portion of the average annual nitrate flux (∼2–4 × 106 mol yr−1) thought to be upwelled in this highly oligotrophic system.
Observations of tidal flux between a submersed aquatic plant stand and the adjacent channel in the Potomac River near Washington, D.C
Authors: Rybicki Nancy B. , Jenter Harry L. , Carter Virginia , Baltzer Robert A. , Turtora Michael
Published: May 2010

Dye injection studies and direct velocity and water‐level measurements were made in macrophyte stands and adjacent channels in order to observe the effects of the macrophyte stand on flow and mass exchange in the tidal Potomac River. During the summer, dense stands of submersed aquatic plants cover most shoals <2 m deep. Continuous summertime water‐level records within a submersed aquatic plant stand and in the adjacent channel revealed time‐varying gradients in water‐surface elevation between the two areas. Water‐level gradients are created by differing rates of tidal water‐level change in vegetated and unvegetated areas. Results were consistent with the idea that on a rising tide the water was slower to enter a macrophyte stand, and on a falling tide it was slower to leave it. Differences in water elevation between the stand and the open channel generated components of velocity in the stand that were at right angles to the line of flow in the channel. Seasonal differences in flow speed and direction over the shoals indicate substantial differences in resistance to flow as a result of the vegetation.
The influence of pore‐water chemistry and physiology on the distribution of vesicomyid clams at cold seeps in Monterey Bay: Implications for patterns of chemosynthetic community organization
Authors: Barry J. P. , Kochevar R. E. , Baxter C. H.
Published: May 2010

Analyses of sulfide, methane, oxygen, and CO2 in pore‐water samples from three cold seep sites in Monterey Bay indicate that fluid chemistry is a strong determinant of the distribution of chemolithoautotrophic vesicomyid clams. The distribution of Calyptogena pacifica and Calyptogena kilmeri were aligned closely with sulfide concentrations at all cold seeps and reflected species‐specific capabilities for sulfide binding. Live clams occurred only in sediment where sulfide was detectable. Sulfide was not detected in the absence of vesicomyid clams. The relative abundances of five vesicomyid species varied greatly among seeps. C. kilmeri accounted for 85–99% of all vesicomyids at seeps with high sulfide content, and C. pacifica dominated (73%) seeps with low sulfide levels. These species were also partially segregated along sulfide gradients from the center to the margin of seeps, analogous to zonation of rocky intertidal communities. We hypothesize that the absence of thiotrophic or methanotrophic mytilid mussels from Monterey Bay cold seeps is related to the lack of physiological specializations for concentrating reduced sulfur compounds or methane and the absence of hypersaline brines that could extend the persistence of methane or sulfide‐rich fluids very near the sea floor.
Increase of PCO2 during blooms of Emiliania huxleyi: Theoretical considerations on the asymmetry between acquisition of HCO3‐ and respiration of free CO2
Authors: Crawford David W. , Purdie Duncan A.
Published: May 2010

The principal source of dissolved inorganic carbon (CT) of most marine phytoplankton is thought to be free CO2, but Emiliania huxleyi can utilize HCO3− ion both for calcification (C) and photosynthesis (P) . We present a simple model that simulates continuous diurnal removal of CT as either free CO2 or HCO3− across the range of CT typically encountered in seawater (2,100–1,800 µmol kgsw−1). Removal as free CO2 forces a drawdown in partial pressure of dissolved carbon dioxide (Pco2), at given CT, of up to 170 µatm greater than that forced by removal as HCO3− by E. huxleyi (assuming Cnet : Pnet = 1.0). Diurnal Cnet : Pnet must exceed 1.5 for Pco2 to increase during removal of HCO3−. When nocturnal respiration of free CO2 (R) is incorporated into the model, the respective drawdowns in Pco2 forced by diurnal removal of free CO2 and HCO3 are balanced by diel ratios R : Pnet = 1.0 and R : (P + C)net ≈ 0.15. Therefore, with diel R : (P + C)net > 0.15 but diurnal Cnet : Pnet = 1.0, E. huxleyi can theoretically grow with net diel increase in Pco2; however, diel Cnet : Pnet > 1.0 is forced by nocturnal loss of particulate organic carbon but not particulate inorganic carbon. Published values for C : P do not necessarily represent diel Cnet : Pnet and caution is required when extrapolating these ratios to predict changes in CT and Pco2 during natural blooms of E. huxleyi.
Processing of ingested matter in Strombidium sulcatum, a marine ciliate (Oligotrichida)
Authors: Dolan John R. , Šimek Karel
Published: May 2010

We examined the hypothesis that different types of ingested matter may be processed at different rates by a marine microzooplankter. Ciliates were exposed to a prey item and then diluted at 1:100. Disappearance or digestion of inert (fluorescent microspheres) and digestible prey items (heat‐killed and fluorescently labeled Synechococcus, natural Synechococcus, and Isochrysis galbana) were determined from changes in cell contents using epifluorescence microscopy. Ingested prey declined exponentially, and prey analogues were processed like natural prey. There were no significant differences in rates of disappearance or decay constants for the different prey items or in feeding vs. nonfeeding ciliates or between ciliates cultured on (or naive to) natural Synechococcus. The overall average t½ of cell contents at 22°C was 75 min. The exponential declines in cell contents indicated that some ingested chlorophyll a, whether in Synechococcus or Isochrysis, can be long‐lived. The relatively invariant decay constant for ingested matter opens the possibility of using a gut passage approach to estimate instantaneous rates of grazing for natural populations of oligotrich ciliates.
Spatially explicit simulations of a microbial food web
Authors: Blackburn Nicholas , Azam Farooq , Hagström Åke
Published: May 2010

A mechanistic model of a simplified microbial food web was implemented based on spatially explicit transport of nutrients and energy sources by molecular diffusion. Individual organisms were simulated to interact in a two‐dimensional arena consisting of 70 × 70 interconnected hexagonal compartments each of 2 nl in volume. Release of dissolved organic matter in conjunction with predation events resulted in patches of increased concentration lasting long enough to be consumed completely by bacteria before being dispersed. Individual bacteria encountered concentrations of dissolved organic matter varying up to 100‐fold within time scales significant for growth. The simulations also predicted that given a chemotactic response to nutrient gradients, bacteria could grow 50% faster on average when gathered in loose clusters within patches. Extending the scenario to the three‐dimensional case and looking at a 1‐ml volume, patch‐generating events were estimated to occur several times per hour and spread to within a few millimeters in radius before being eroded by bacteria. The erosion time scale is probably longer than the time between patch appearances resulting in patches overlapping and creating a markedly inhomogeneous microenvironment. In such a scenario, foraging strategies enabling bacteria and predators to respond to elevated concentrations of food could represent a significant adaptive advantage.
Ecological stoichiometry of N and P in pelagic ecosystems: Comparison of lakes and oceans with emphasis on the zooplankton‐phytoplankton interaction
Authors: Hassett R. P. , Cardinale B. , Stabler L. B. , Elser J. J.
Published: May 2010

By using an elemental‐stoichiometry approach to zooplankton‐phytoplankton interactions, we compare elemental composition and aspects of nutrient deficiency across a variety of marine and freshwater ecosystems. During 1992 and 1993 we sampled a total of 31 lakes (in northern Wisconsin and Michigan and the Experimental Lakes Area of northern Ontario) and 21 marine stations (at seven estuarine, coastal, and open‐ocean sites in the Atlantic and Pacific) for elemental composition of zooplankton, seston, and dissolved components. Relative degree of nutrient deficiency was assessed by phytoplankton dark uptake of ammonia and phosphate, as well as growth response of phytoplankton to N and P addition. Marine and freshwater systems differed greatly in N and P concentrations, N:P stoichiometry, and the distribution of N and P within dissolved, seston, and zooplankton pools. Particularly notable was the high proportion of N and, especially, P that was incorporated in the particulate fraction (seston + zooplankton) of lakes compared to marine sites. In freshwater systems, Daphnia spp., which have low body N: P, dominated zooplankton communities when seston C:P and N:P were also low, and calanoids that tend to have high body N:P dominated when seston C: P and N: P was high. This relationship between zooplankton community composition and seston elemental stoichiometry supports arguments for the importance of food quality constraints on zooplankton growth in freshwater systems. Such patterns were not seen in marine systems.
Seasonal effects of variable recruitment of a dominant piscivore on pelagic food web structure
Authors: Post David M. , Carpenter Stephen R. , Christensen David L. , Cottingham Kathryn L. , Kitchell James F. , Schindler Daniel E. , Hodgson James R.
Published: May 2010

Piscivorous fish play an important role in regulating lake food web structure. However, most ultimately piscivorous fish pass through a period of planktivory before becoming piscivorous. In 1993 and 1994, two large cohorts of young‐of‐the‐year largemouth bass (Micropterus salmoides) were recorded in Paul Lake, Michigan. The 1993 and 1994 cohorts were the largest recorded in data extending back to 1984 and occurred during a period in which adult and juvenile bass biomass was low. In 1993, consumption of large‐bodied zooplankton by the young‐of‐the‐year cohort eliminated large‐bodied cladocerans by the middle of August. As large cladocerans declined, small cladocerans, especially Bosmina longirostris, increased. By early September the biomass of B. longirostris was similar to that of the entire cladoceran community in previous years. Coincident with the shifts in the cladoceran community were increases in epilimnetic Chl a concentrations <35 µm. However, total epilimnetic Chl a did not increase. In contrast, the 1994 cohort had no discernible effect on pelagic food web structure because production of large‐bodied zooplankton rapidly exceeded predation. Our results show the potential for large cohorts of piscivorous fish to affect food web structure, at a seasonal scale, through intense planktivory.
Inorganic nutrient limitation of oceanic bacterioplankton
Authors: Rivkin Richard B. , Anderson M. Robin
Published: May 2010

Although it is commonly accepted that dissolved organic carbon (DOC) of algal origin limits bacterial growth in pelagic systems, there are relatively few empirical studies documenting this effect. Depending on site and season, both organic and inorganic nutrients can limit the growth of freshwater bacteria. By contrast, inorganic nutrients have only recently been implicated as potentially growth‐limiting for marine bacteria. At stations in the Gulf Stream, Sargasso, and Caribbean seas, we used a factorial experimental design to examine effects of inorganic (NH4 and PO4) and organic (glucose) nutrients on the uptake of thymidine and leucine and changes in bacterial abundance. Bacterial growth in seawater dilution cultures varied with station and treatment. Growth rates for the unamended controls (mean ± SD = 0.11 ± 0.02 d−1) were not significantly different among the stations or from the in situ rates. In the Caribbean Sea, additions of NH4 and PO4 resulted in a modest increase in growth rate(µ = 0.20–0.35 d−1), whereas glucose, either alone or in combination with PO4 and NH4, resulted in the largest increase(µ = 0.50–0.55 d−1). By contrast, in the Gulf Stream and Sargasso Sea, the addition of glucose, either alone or in combination with NH4, resulted in the smallest increase in growth rate (µ = 0.2–0.4 d−1), whereas the addition of PO4, either alone or in combination with glucose and NH4 resulted in the largest increase(µ = 0.55–0.60 d−1). Growth rates in the PO4‐amended seawater culture were 5–6‐fold greater than the controls, suggesting that ambient concentrations of labile DOC were sufficient to sustain vigorous growth. We propose that PO4 limitation of bacterial growth may directly influence the accumulation of DOC in the surface layer and thus have a significant impact on carbon cycling in the sea. If bacterial growth were not constrained by inorganic nutrients, more DOC could be assimilated into bacterial biomass and subsequently transferred to protistan and metazoan grazers. At the third trophic step beyond bacteria, >90% of the DOC initially assimilated would be released as CO2 and <5% would be transferred to mesozooplankton and hence converted into exportable biomass. Thus, when bacterial growth is P limited, the quantity of biogenic carbon (POC + DOC) exported to depth may be greater than would occur if DOC were first incorporated into bacterial biomass.
Fish predation on a Daphnia hybrid species complex: A factor explaining species coexistence?
Authors: Spaak Piet , Hoekstra J. Rob
Published: May 2010

Recent studies on the life histories of Daphnia hybrids and their parental species have revealed that hybrids can combine an intermediate size with a relatively high reproductive rate, which might explain their success in many European lakes. Based on this information, we formulated the temporal hybrid superiority hypothesis to explain the coexistence of parental species and their hybrids. Our hypothesis states that in temporally changing environments, such as lakes, hybrids can coexist with their parental species because hybrid individuals have a higher fitness compared to the parental individuals during specific periods of the year. This is in contrast to the hypothesis that hybrids have a lower fitness than the parentals, which should be compensated by recurrent hybrid production. To test this hypothesis we studied population dynamics and seasonal changes in body size of two Daphnia species (D. galeata and D. cucullata) and their interspecific hybrid D. cucullata × D. galeata in Tjeukemeer, a shallow eutrophic lake in the Netherlands. In 1989, the year with the highest fish predation pressure, the larger D. galeata was first replaced by the smaller hybrid that was soon succeeded by the even smaller D. cucullata. In 1990 the Daphnia community was dominated by the hybrid and in 1991 by D. galeata. Deviations of the instantaneous rate of increase, averaged over the three species, showed a positive relationship with fish predation risk for D. cucullata, a negative relationship for D. galeata, and no relationship for the hybrid. This suggests a higher influence of fish predation on D. galeata. We conclude that the selective advantage of the hybrid over D. galeata under fish predation, expected from life‐history experiments, is in agreement with our field data.
Microbiological turnover of amino acids immobilized from groundwater discharged through hyporheic sediments
Authors: Fiebig Douglas M.
Published: May 2010

A pulse of 14C‐labeled dissolved free amino acids (DFAA) was immobilized rapidly from groundwater discharged through cores of hyporheic sediment from an upland stream. Mean turnover distance within the cores was <1.5 cm but, once immobilized, DFAA carbon was retained for longer than would be expected if bacterial cycling was the only retention mechanism. It took 28 weeks for 88% of the original 1.2 µg of DFAA carbon that had been immobilized to be respired and exported from the cores, whereas bacterial respiration alone should have mineralized >99% of this carbon within 7.4–11.4 weeks, depending on the bacterial growth efficiency assumed. Abiotic retention processes associated with organic and mineral surfaces appear to enhance the initial immobilization of DFAA and contribute to a delayed recycling of DFAA carbon within the sediment, increasing the effective availability of this labile organic carbon in the hyporheic zone. Abiotic retention of dissolved organic carbon might help sustain the high levels of bacterial production found in hyporheic sediments while reducing the demand for organic carbon imported into the hyporheic zone.
Riverine contribution of biogenic silica to the oceanic silica budget
Authors: Conley Daniel J.
Published: May 2010

Biological uptake of dissolved silicate (DSi) and formation of biogenic silica (BSi) during diatom growth modifies the form of Si carried from the continents to the world ocean. Significant concentrations of BSi, averaging 28.0 µmol L−1, are found in all sizes of rivers. The global contribution of BSi carried by rivers was estimated as 1.05 ± 0.20 Tmol Si year−1. Combined with the global mean riverine DSi concentration of 150 µmol liter−1, 16% of the gross riverine Si load is delivered to the world ocean as BSi. Most of this BSi would be remobilized by dissolution in marine environments. These results demonstrate that the contribution of biogenic silica carried in suspension by rivers is an important component in the world ocean Si budget that has not been recognized previously.
Short‐term sediment trap fluxes from Chatham Rise, southwest Pacific Ocean
Authors: Nodder S. D.
Published: May 2010

Sediment trap, nephelometer, and particulate matter (PM) data were collected in the vicinity of the Subtropical Convergence, north of Chatham Rise (42–43°S), southwest Pacific Ocean, in austral autumn 1992. Free‐floating cylindrical sediment traps were deployed below the euphotic zone at 200‐, 300‐, and 500‐m water depths. Increases in total mass flux and concomitant proportional decreases in other particulate fluxes (total carbon, nitrogen, and phosphorus) with depth reflected the collection of relatively refractory material, enriched in particulate carbon, as evinced by increases in C: N and C: P ratios below 300 m. Nephelometer and PM concentration profiles indicate that resuspension of sea‐floor sediments from the nearby submarine high (Chatham Rise) probably contributed to the observed increase in total mass flux with depth. Published pCO2 estimates, biological productivity data, and moderate particulate fluxes, as indicated by the present study suggest that oceanic water types east of New Zealand may be a biologically mediated regional sink for atmospheric CO2.
Seasonal cycle and temperature dependence of pinene oxidation products, dicarboxylic acids and nitrophenols in fine and coarse air particulate matter
Authors: Zhang Y. , Müller L. , Winterhalter R. , Moortgat G. K. , Hoffmann T. , Pöschl U.
Published: May 2010

Abstract. Filter samples of fine and coarse air particulate matter (PM) collected over a period of one year in central Europe (Mainz, Germany) were analyzed for water-soluble organic compounds (WSOCs), including the α- and β-pinene oxidation products pinic acid, pinonic acid and 3-methyl-1,2,3-butanetricarboxylic acid (3-MBTCA), as well as a variety of dicarboxylic acids and nitrophenols. Seasonal variations and other characteristic features in fine, coarse, and total PM (TSP) are discussed with regard to aerosol sources and sinks in comparison to data from other studies and regions. The ratios of adipic acid and phthalic acid to azelaic acid indicate that the investigated samples were mainly influenced by biogenic sources. A strong Arrhenius-type correlation was found between the 3-MBTCA concentration and inverse temperature (R2=0.79, n=52, Ea=126±10 kJ mol−1, temperature range 275–300 K). Model calculations suggest that the temperature dependence observed for 3-MBTCA can be explained by enhanced photochemical production due to an increase of hydroxyl radical (OH) concentration with increasing temperature, whereas the influence of gas-particle partitioning appears to play a minor role. The results indicate that the OH-initiated oxidation of pinonic acid is the rate-limiting step in the formation of 3-MBTCA, and that 3-MBTCA may be a suitable tracer for the chemical aging of biogenic secondary organic aerosol (SOA) by OH radicals. An Arrhenius-type temperature dependence was also observed for the concentration of pinic acid (R2=0.60, n=56, Ea=84±9 kJ mol−1); it can be tentatively explained by the temperature dependence of biogenic pinene emission as the rate-limiting step of pinic acid formation.
A combined observational and modeling approach to study modern dust transport from the Patagonia desert to East Antarctica
Authors: Gassó S. , Stein A. , Marino F. , Castellano E. , Udisti R. , Ceratto J.
Published: May 2010

Abstract. The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS, POLDER, OMI), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (~54° S) and from the shores of the Colihue Huapi lake in Central Patagonia (~46° S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6–7 and 9–10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant deposition over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and $\\sim $800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the presence of dust at ~1500 km SW of South Africa five days after, the limited capabilities of existing satellite platforms to differentiate between aerosol types do not permit a definitive conclusion. In addition, the model simulations show dust lifting to the free troposphere as it travels south but it could not be confirmed by the satellite observations due to cloudiness. This work demonstrates that complementary information from existing transport models, satellite and surface data can yield a consistent picture of the dust transport from the Patagonia desert to Antarctica. It also illustrates the limitation of using any of these approaches individually to characterize the transport of dust in a heavily cloudy area.
Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event
Authors: Pihlatie M. K. , Kiese R. , Brüggemann N. , Butterbach-Bahl K. , Kieloaho A.-J. , Laurila T. , Lohila A. , Mammarella I. , Minkkinen K. , Penttilä T. , Schönborn J. , Vesala T.
Published: May 2010

Abstract. Fluxes of greenhouse gases (GHG) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC) technique (CO2 and N2O), and automatic and manual chambers (CO2, CH4 and N2O). In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content) in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes during freezing and thawing of the top-soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 and a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat, which were unfrozen throughout the measurement period. During the frost-thaw events of the litter layer distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with a delay after the thawing of the litter layer. CH4 fluxes did not respond to the thawing of the peat soil. The CO2 and N2O emission peaks were not captured by the manual chambers and hence we conclude that high time-resolution measurements with automatic chambers or EC are necessary to quantify fluxes during peak emission periods. Sub-canopy EC measurements and chamber-based fluxes of CO2 and N2O were comparable, although the fluxes of N2O measured by EC were close to the detection limit of the system. We conclude that if fluxes are high enough, i.e. greater than 5–10 μg N m−2 h−1, the EC method is a good alternative to measure N2O and CO2 fluxes at ecosystem scale, thereby minimizing problems with chamber enclosures and spatial representativeness of the measurements.
Water resources change in response to climate change in Changjiang River basin
Authors: Huang Y. , Yang W. F. , Chen L.
Published: May 2010

Abstract. Doubtlessly, global climate change and its impacts have caught increasing attention from all sectors of the society world-widely. Among all those affected aspects, hydrological circle has been found rather sensitive to climate change. Climate change, either as the result or as the driving-force, has intensified the uneven distribution of water resources in the Changjiang (Yangtze) River basin, China. In turn, drought and flooding problems have been aggravated which has brought new challenges to current hydraulic works such as dike or reservoirs which were designed and constructed based on the historical hydrological characteristics, yet has been significantly changed due to climate change impact. Thus, it is necessary to consider the climate change impacts in basin planning and water resources management, currently and in the future. To serve such purpose, research has been carried out on climate change impact on water resources (and hydrological circle) in Changjiang River. The paper presents the main findings of the research, including main findings from analysis of historical hydro-meteorological data in Changjiang River, and runoff change trends in the future using temperature and precipitation predictions calculated based on different emission scenarios of the 24 Global Climate Modes (GCMs) which has been used in the 4th IPCC assessment report. In this research, two types of macro-scope statistical and hydrological models were developed to simulate runoff prediction. Concerning the change trends obtained from the historical data and the projection from GCMs results, the trend of changes in water resources impacted by climate change was analyzed for Changjiang River. Uncertainty of using the models and data were as well analyzed.
Monitoring working conditions and health of older workers in Dutch construction industry
Authors: Hoonakker Peter , van Duivenbooden Cor
Published: May 2010

Background

Accurate reporting of work‐related conditions is necessary to monitor workplace health and safety and to identify the interventions that are most needed. In the Netherlands, working conditions and health are monitored on an aggregated level in the construction industry. One of the purposes of monitoring is to identify specific risk factors and risk groups. The objectives of this study was to examine (1) whether older workers (≥55 years) in the construction industry are a special group at risk and (2) whether there are specific risk factors for older workers in the construction industry.

Methods

Every 2 years, more than 70,000 construction workers in the Netherlands fill out a questionnaire as part of their periodic health checkup. In a repeated cross‐sectional (trend) design, we compared working conditions (physical and psychological demands), musculoskeletal disorders (symptoms and conditions), and injuries of older workers with other age categories.

Results

Older construction workers have fewer complaints about physically demanding work and psychosocial workload, but have more complaints about working in awkward postures. Older workers have more complaints about their health than workers in other age categories. Older construction workers have fewer injuries than younger workers.

Conclusions

Older construction workers are a risk group for musculoskeletal disorders. Working in awkward postures can be considered a risk factor for older workers in construction industry. Am. J. Ind. Med. 53: 641–653, 2010. © 2010 Wiley‐Liss, Inc.
Evaluating the improvement in diagnostic utility from adding new predictors
Authors: Li Caixia , Lu Ying
Published: May 2010

Multiple diagnostic tests and risk factors are commonly available for many diseases. This information can be either redundant or complimentary. Combining them may improve the diagnostic/predictive accuracy, but also unnecessarily increase complexity, risks, and/or costs. The improved accuracy gained by including additional variables can be evaluated by the increment of the area under (AUC) the receiver‐operating characteristic curves with and without the new variable(s). In this study, we derive a new test statistic to accurately and efficiently determine the statistical significance of this incremental AUC under a multivariate normality assumption. Our test links AUC difference to a quadratic form of a standardized mean shift in a unit of the inverse covariance matrix through a properly linear transformation of all diagnostic variables. The distribution of the quadratic estimator is related to the multivariate Behrens–Fisher problem. We provide explicit mathematical solutions of the estimator and its approximate non‐central F‐distribution, type I error rate, and sample size formula. We use simulation studies to prove that our new test maintains prespecified type I error rates as well as reasonable statistical power under practical sample sizes. We use data from the Study of Osteoporotic Fractures as an application example to illustrate our method.
Gelation‐Induced Enhanced Fluorescence Emission from Organogels of Salicylanilide‐Containing Compounds Exhibiting Excited‐State Intramolecular Proton Transfer: Synthesis and Self‐Assembly
Authors: Nayak Manoj Kumar , Kim Byung‐Hwa , Kwon Ji Eon , Park Sanghyuk , Seo Jangwon , Chung Jong Won , Park Soo Young
Published: May 2010

Self‐assembly structure, stability, hydrogen‐bonding interaction, and optical properties of a new class of low molecular weight organogelators (LMOGs) formed by salicylanilides 3 and 4 have been investigated by field‐emission scanning electron microscopy (FESEM), X‐ray diffraction (XRD), UV/Vis absorption and photoluminescence, as well as theoretical studies by DFT and semiempirical calculations with CI (AM1/PECI=8) methods. It was found that salicylanilides form gels in nonpolar solvents due to π‐stacking interaction complemented by the presence of both inter‐ and intramolecular hydrogen bonding. The supramolecular arrangement in these organogels predicted by XRD shows lamellar and hexagonal columnar structures for gelators 3 and 4, respectively. Of particular interest is the observation of significant fluorescence enhancement accompanying gelation, which was ascribed to the formation of J‐aggregates and inhibition of intramolecular rotation in the gel state.
Guest⊂Guest⊂Host Multicomponent Molecular Crystals: Entrapment of Guest⊂Guest in Honeycomb Networks Formed by Self‐Assembly of 1,3,5‐Tri(4‐hydroxyaryl)benzenes
Authors: Moorthy Jarugu Narasimha , Natarajan Palani
Published: May 2010

Sterically‐engineered rigid trigonal molecular modules based on 1,3,5‐tri(4‐hydroxyphenyl)benzenes H1 and H2 undergo O‐H⋅⋅⋅O hydrogen‐bonded self‐assembly into eight‐fold catenated hexagonal (6,3) and two‐fold interpenetrated undulated square (4,4) networks, respectively. In the presence of [18]crown‐6 as a guest, the triphenol H1 is found to self‐assemble into a honeycomb network with hexagonal voids created between three triphenol building blocks. The guest [18]crown‐6 molecules are found to be nicely nested in hexagonal enclosures. The empty spaces within the crowns can be further filled with neutral (MeOH/water, MeOH/MeNO2) or ionic guest species such as KI/KAcAc to furnish novel multicomponent assemblies, that is, guest⊂guest⊂host, that typify Russian dolls. In contrast, triphenol H2 is found to yield analogous multicomponent molecular crystals in which the guest crown–K+ acts as a spacers in the hydrogen‐bonded self‐assembly that leads to distorted chicken wire networks.
Chirality‐Sensing Binaphthocrown Ether–Polythiophene Conjugate
Authors: Fukuhara Gaku , Inoue Yoshihisa
Published: May 2010

An enantiomeric binaphthyl unit was tethered to adjacent thiophenes with oxyethylene linkers to give a chiral polythiophene with binaphthocrown ether cavities. Upon inclusion of a chiral cationic guest in the cavity of the chiral crown ether–polythiophene conjugate, the bithiophene unit was twisted to shorten the effective conjugation length of polythiophene backbone, enabling us to sense the guest binding by reading out the amplified optical signal gains arising from the backbone structure change. This strategy allowed us to discriminate the guest chirality without using chiroptical signals or a circular dichroism spectrometer to achieve the highest enantioselectivity of 7.3 for valine methyl ester with a 40‐fold enhanced sensitivity compared with the corresponding monomeric sensor.
Synthesis and Properties of Chiral Pyrazolidines Derived from (+)‐Pulegone
Authors: Jakob Florian , Herdtweck Eberhardt , Bach Thorsten
Published: May 2010

Several enantiomerically pure N(2)‐substituted octahydroindazoles were prepared as bicyclic pyrazolidine derivatives of (+)‐pulegone. Condensation of pulegone with hydrazine delivered a hexahydroindazole intermediate, which underwent N(2)‐substitution with various electrophiles (alkyl halides, acyl chlorides, phenyl isocyanate). The resulting N(2)‐substituted hexahydroindazoles could be reduced with LiBEt3H in THF to the target compounds. In addition, a N(2)‐thiobenzoyl and some N(2)‐carbamoyl derivatives as well as a N(1)‐substituted octahydroindazole were synthesized. The compounds showed medium activity as iminium ion catalysts promoting quantitatively the Michael addition of nitroethane to cinnamaldehyde in up to 82 % ee for the resulting syn‐diastereoisomer and 78 % ee for the anti‐diastereoisomer. Unexpectedly, the N(2)‐acyloctahydroindazoles were readily oxidized under aerobic conditions. Moreover, it was shown that an oxidation of methyl phenyl sulfide to the corresponding sulfoxide is promoted by an N(2)‐acyloctahydroindazole in deuterochloroform as solvent. It is proposed that the oxidation of N(2)‐acyloctahydroindazoles proceeds by in situ generation of hydrogen peroxide, which in turn can act as an oxidant.
Sterically Crowded peri‐Substituted Naphthalene Phosphines and their PV Derivatives
Authors: Knight Fergus R. , Fuller Amy L. , Bühl Michael , Slawin Alexandra M. Z. , Woollins J. Derek
Published: May 2010

Three sterically crowded peri‐substituted naphthalene phosphines, Nap[PPh2][ER] (Nap=naphthalene‐1,8‐diyl; ER=SEt, SPh, SePh) 1–3, which contain phosphorus and chalcogen functional groups at the peri positions have been prepared. Each phosphine reacts to form a complete series of PV chalcogenides Nap[P(E′)(Ph2)(ER)] (E′=O, S, Se). The novel compounds were fully characterised by using X‐ray crystallography and multinuclear NMR spectroscopy, IR spectroscopy and MS. X‐ray data for 1, 2, n O, n S, n Se (n=1–3) are compared. Eleven molecular structures have been analysed by naphthalene ring torsions, peri‐atom displacement, splay angle magnitude, X⋅⋅⋅E interactions, aromatic ring orientations and quasi‐linear arrangements. An increase in the congestion of the peri region following the introduction of heavy chalcogen atoms is accompanied by a general increase in naphthalene distortion. P⋅⋅⋅E distances increase for molecules that contain bulkier atoms at the peri positions and also when larger chalcogen atoms are bound to phosphorus. The chalcogenides adopt similar conformations that contain a quasi‐linear E⋅⋅⋅PC fragment, except for 3 O, which displays a twist‐axial‐twist conformation resulting in the formation of a linear O⋅⋅⋅SeC alignment. Ab initio MO calculations performed on 2 O, 3 O, 3 S and 3 Se reveal Wiberg bond index values of 0.02 to 0.04, which indicates only minor non‐bonded interactions; however, calculations on radical cations of 3 O, 3 S and 3 Se reveal increased values (0.14–0.19).
ChemInform Abstract: Shape and Phase Control of ZnS Nanocrystals: Template Fabrication of Wurtzite ZnS Single‐Crystal Nanosheets and ZnO Flake‐Like Dendrites from a Lamellar Molecular Precursor ZnS× (NH2CH2CH2NH2)0.5.
Authors: Yu Shu‐Hong , Yoshimura Masahiro
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: A Neutron Diffraction Study of HfFe6Ge6‐Type ErMn6Ge6‐xGax Compounds (x = 0.2, 0.4 and 1.0).
Authors: Lefevre C. , Venturini G. , Malaman B.
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Magnetic Structure of Tb2Mn3Si5.
Authors: Nirmala R. , Morozkin A. V. , Hofmann M. , Sankaranarayanan V. , Sethupathi K. , Yamamoto Y. , Hori H.
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Enantioselective Conjugate Additions of Aldoximes to 3‐Crotonoyl‐2‐oxazolidinone and 1‐Crotonoyl‐3‐phenyl‐2‐imidazolidinone Catalyzed by the Aqua Complex Between R,R‐DBFOX/Ph and Zinc(II) Perchlorate.
Authors: Nakama Kimitaka , Seki Sumito , Kanemasa Shuji
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Heck Arylations of N‐Acyl‐3‐pyrroline and N‐Acyl‐1,2,5,6‐tetrahydropyridine with Aryldiazonium Salts. Short Syntheses of Aryl γ‐ and δ‐Lactams, Baclofen, Homobaclofen and Analogues.
Authors: Carpes Marcos Jose S. , Correia Carlos Roque D.
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.