bluuebunny/crossref_metadata_2025 huggingface dataset:
The biofilm polysaccharide matrix: A buffer against changing organic substrate supply?
Authors: Freeman Christopher , Lock Maurice A.
Published: May 2010

In contrast to the widely held view that microorganisms respond rapidly to changes in environmental conditions, the microbes in biofilms appear remarkably resilient to substantial changes in the abundance of dissolved organic substrates. Removal of high‐molecular‐weight dissolved materials from waters supplied to river biofilms generally did not affect bacterial densities or the synthesis of phospholipids and DNA. Even the complete elimination of exogenous materials from the overlying waters allowed heterotrophic activity to continue unaffected. Moreover, that continued activity was not supported by the catabolism of endogenous reserves of C (poly‐β‐hydroxy alkanoate—PHA). The addition of inorganic nutrients to substrate‐free waters allowed heterotrophic activity to increase within the biofilm. Since neither exogenous sources of river DOC or endogenous reserves (PHA) served as the source of C, we propose that an alternative, namely the polysaccharide matrix (and any absorbed or incorporated organic matter), served as the primary carbon reserve for biofilm microorganisms during the imposed organic substrate deprivation.
Methane transfer across the water‐air interface in stagnant wooded swamps of Florida: Evaluation of mass‐transfer coefficients and isotropic fractionation
Authors: Happell James D. , Chanton Jeffrey P. , Showers William J.
Published: May 2010

Emission rates from the standing water of swamps to the atmosphere calculated from literature‐derived exchange coefficients were greater than measured diffusive fluxes of CH4. In north Florida mixed hardwood swamp experiments performed in the absence of ebullition, the calculated flux of CH4 was 3.6±2.6 (n = 22) times larger than the measured flux. In an Everglades cypress dome, calculated CH4 fluxes were 3.1±2.5 (n = 3) times greater than measured fluxes. New mass‐transfer coefficients at zero windspeed were calculated for CH4 emission from the stagnant swamp water in the mixed hardwood swamps (0.75±0.54 cm h−1, n = 22) and in the cypress dome (0.83±0.51 cm h− 1, n = 3). These values were significantly less than the calculated mass‐transfer coefficient for CH4 (1.7 cm h−1) determined in another study. We hypothesize that insoluble organic surface films physically, chemically, or biologically inhibited CH4 transfer from the floodwater to the atmosphere. Consistent with these findings we also observed greater retardation of 13CH4 efflux relative to 12CH4 efflux in swamp experiments relative to those conducted in the laboratory. Methane emitted from standing water was depleted in 13C by 0.8±0.3‰ (n = 16), 3.6±3.2‰ (n = 12), and 2.6±0.8‰ (n = 3) relative to the isotopic composition of dissolved CH4 in the laboratory, mixed hardwood swamps, and cypress dome.
The effect of bivalve excurrent jet dynamics on mass transfer in a benthic boundary layer
Authors: O'Riordan C. A. , Monismith S. G. , Koseff J. R.
Published: May 2010

Predictions of phytoplankton depletion by benthic bivalves in shallow, tidally driven estuaries must account for the formation of concentration boundary layers resulting from the dynamic interaction of bivalve siphonal currents with the overlying turbulent boundary layer. To study the near‐bed hydrodynamics of the benthic boundary layer, we conducted experiments in a laboratory flume using multiple jets and sinks to represent feeding by the siphonate species Tapes japonica and Potamocorbula amurensis. Refiltration fractions were determined by monitoring the concentration of dye ingested by incurrent siphons, and PLIF (planar laser‐induced fluorescence) was used to characterize the concentration fields.

Results show that refiltration fractions can be as high as 48% and are a function of several dimensionless parameters: animal spacing (S/do), velocity ratio (uj: u*), siphon height (hs/do), and crossflow Reynolds number (Rex). (S is the mean distance between animals, do the excurrent siphon diameter, h the animal siphon height, uj the excurrent jet velocity, and u* the mean shear velocity.) We found that a good estimate of maximum refiltration (nmax) based on animal spacing is (nmaxS/do) ≈ 2−3 and have incorporated this result into a conceptual mass‐transfer model. Differences in concentration profiles calculated from PLIF images are likely due to the relative influence of four sources of turbulence in the flow: boundary‐layer shear, boundary roughness, jet in a crossflow, and multiple jet interactions.
Effect of total organic content of eggs on hatching success and naupliar survival in the copepod Calanus helgolandicus
Authors: Guisande Castor , Harris Roger
Published: May 2010

We collected female Calanus helgolandicus weekly from 12 July to 16 August 1993 at a station southwest of Plymouth, England. We estimated the amount of food available by analyzing surface‐water samples for total particulate protein, carbohydrate, and lipid in three size fractions: 0.6–100, 5–100, and 10–100 µm. Size and the protein, carbohydrate, and lipid content of the eggs laid by these females varied with time and were positively correlated with the amount of food available. An experiment with adult female C. helgolandicus kept at six different food concentrations confirmed the field results. Hatching success and naupliar survival under starvation increased with egg size. Thus, variation in egg size is important to the population dynamics of this species.
Direct positive effect of invertebrate predators on birth rate in Daphnia studied with a new method of birth rate analysis
Authors: Polishchuk Leonard V.
Published: May 2010

Three natural Daphnia populations in which the previously established impact of invertebrate predators on the death rate (but not on the birth rate) were investigated. Two other cladoceran populations primarily affected by food were used for comparison. The effect of predators on the per capita birth rate of Daphnia was detected by decomposing changes in birth rate into components dependent on changes in egg development rate, mean clutch size, and proportion of adults and then comparing them. This method revealed short‐term changes in the proportion of adults, which dominated changes in birth rate. The effect can be attributed to size‐selective feeding of the invertebrate planktivores that normally prey on young daphnids, and it did not occur in food‐dependent cladocerans. Invertebrate predation pressure tends to increase the per capita birth rate of Daphnia, which may provide a mechanism that stabilizes prey.
Functional structure and production of the benthic community in a Piedmont river: 1956‐1957 and 1991‐1992
Authors: Grubaugh Jack W. , Wallace J. Bruce
Published: May 2010

Taxonomic composition and functional group abundance, biomass, and annual production were measured in 1991–1992 for the macroinvertebrate community in a Piedmont river. Abundances and biomass values were influenced by standing crops of Podostemum ceratophyllum, a hydrophyte which covered bedrock substratum. Collector‐filterers, collector‐gatherers, and scrapers dominated functional‐group abundance; scrapers and collector‐filterers dominated biomass. Benthic production was 181.9 g ash‐free dry mass m−2 yr−1; 57% was attributable to collector‐filterer hydropsychid caddisflies and 13% to a scraper snail. Results were compared to a previous study conducted at the same site in 1956–1957. Physical parameters of temperature and discharge regimes, P. ceratophyllum standing crops, and riparian vegetation were similar between studies, but marked changes in land use had occurred within the catchment. Benthic community structure was dominated by small, multivoltine collector‐gatherers and microfilterers in 1956–1957; in 1991–1992 dominant taxa consisted of larger, longer lived macrofilterers and scrapers. Changes in community structure and indices of biotic integrity indicate stream condition improved in 1991–1992 relative to 1956–1957; changing land‐use practices are implicated as the key factor for improvement.
Role of colloids in upper ocean biogeochemistry in the northeast Pacific Ocean elucidated from 238U‐234Th disequilibria
Authors: -An Huh Chih , Prahl Fredrick G.
Published: May 2010

Detailed upper ocean profiles of 234Th in dissolved (<10,000 Daltons), colloidal (10,000 Da–0.45 µm), and particulate (>0.45 µm) forms were measured at a station (46°45′N, 126°W) in the northeast Pacific Ocean. On average, dissolved, colloidal, and particulate 234Th accounted for ∼78, 12, and 10% of the total 234Th in the euphotic zone (0–100 m). A highly positive correlation exists between colloidal 234Th and chlorophyll a; both are characterized by higher concentrations in surface waters, a subsurface maximum at 55 m in the seasonal thermocline, and undetectable levels below the euphotic zone. POC: Chl a ratios in the water column suggest phytoplankton as primary producers of the colloidal material. Scavenging residence times of dissolved, colloidal, and particulate 234Th with respect to their removal processes in the euphotic zone are ∼50, 6, and 8 d. The scavenging rate constant of Th apparently increases with the concentration of colloids.
Carbon and nitrogen stable isotopes of primary producers in coral reef ecosystems
Authors: Yamamuro Masumi , Kayanne Hajime , Minagawao Masao
Published: May 2010

To examine the importance of new primary production and nitrogen fixation in coral reef ecosystems, we compared δ13C and δ15N values of various organic materials (coral tissues, macrophytes, particulate organic materials, and zooplankton) from Palau (7°N) and Ishigaki (24°30′N) coral reefs in the western Pacific Ocean. The δ15N (4–6‰) abundance of coral tissues suggests that zooplankton was not the main source of N for these corals. Low δ15N values of other benthic primary producers (2–6‰) indicate that their nitrogen originates from nitrogen fixation. These values and the high δ13C (−6 to −9‰) of macrophytes sampled at the landward part of both coral reefs lead us to conclude that coral reef ecosystems are sinks of CO2 because of primary production accompanied by uptake of new nitrogen.
Cadmium: A nutrient for the marine diatom Thalassiosira weissflogii
Authors: Lee Jennlfer G. , Roberts Samantha B. , Morel Franqois M. M.
Published: May 2010

Although cadmium is known to be very toxic, it exhibits nutrientlike vertical concentration profiles in the open ocean. Recent work has shown that under conditions of zinc limitation, cadmium enhances the growth of the marine diatom Thalassiosira weissflogii. Here, we conclusively demonstrate that Cd is a nutrient for T. weissflogii at inorganic Zn and Cd concentrations typical of surface seawater, although Cd cannot completely replace Zn. Over a wide range of external Cd and Zn concentrations, Cd uptake kinetics are regulated and the intracellular Cd quotas are maintained at relatively constant levels. The same low level of inorganic Cd that enhances the growth rate of Zn‐limited cells restores the activity of carbonic anhydrase (CA), thought to be the key enzyme limiting growth of T. weissflogii at low Zn. Cd also coelutes with some of the isoforms of CA, indicating that Cd substitution in CA is likely partly responsible for the nutritional role of Cd. The substitution of Cd for Zn in CA links the geochemical cycle of Cd to those of Zn and C.
Ultraphytoplankton succession is triggered by deep winter mixing in the Gulf of Aqaba (Eilat), Red Sea
Authors: Lindell Debbie , Post Anton F.
Published: May 2010

The seasonal dynamics of ultraphytoplankton for the northern Gulf of Aqaba (29°28′N, 34°55′E) were investigated in detail. Monthly analysis of pigments by HPLC and cell abundances by epifluorescence microscopy showed large fluctuations in ultraphytoplankton community structure concurrent with strong seasonal changes in water‐column conditions. Following extensive winter mixing, ultraphytoplankton seasonal succession progressed rapidly as water‐column stratification strengthened. Eucaryotic algae dominated in nutrient‐replete winter mixing conditions, Synechococcus was the major component of the ultraphytoplankton during a spring bloom of massive proportions, and Prochlorococcus was dominant in nutrient‐depleted summer‐stratified waters. Over the fall–winter period, as water‐column mixing progressed, succession was in the reverse order but at a much slower rate. Prochlorococcus was the major component of the community during summer stratification, yet was not detected at the height of the mixing event in late winter. The reestablishment of the population occurred only 3 months after the onset of stratification. This is the first report on seasonal succession involving all three ultraphytoplankton groups. We suggest that water‐column stability is an important factor influencing seasonal variations in ultraphytoplankton community structure.
Evidence of iron deficiency in seagrasses growing above carbonate sediments
Authors: Duarte Carlos M. , Martín Merino , Margarita Gallegos
Published: May 2010

A comparison of available data on iron concentration in seagrass tissues shows iron concentrations in seagrass leaves growing on carbonate sediments to be below critical levels for angiosperms [< 100 µg Fe (g DW)− 1]. Iron concentrations of leaves in Caribbean seagrasses declined by 5–10‐fold from terrigenous to carbonate sediments (inner Gulf of Mexico to the Caribbean coast off the Yucatan Peninsula). This observation provided evidence of possible iron deficiency in seagrasses, which was confirmed by an experimental demonstration that adding iron to the sediments stimulates growth of the Caribbean seagrass Thalassia testudinum and increases the chlorophyll a concentration of both T. testudinum and Syringodium filiforme growing above coralline carbonate sediments. We conclude that seagrasses growing above carbonate sediments are likely to experience iron deficiency.
Viruses and protists cause similar bacterial mortality in coastal seawater
Authors: Fuhrman Jed A. , Noble Rachel T.
Published: May 2010

Mesocosms filled with 80 liters of coastal seawater from Santa Monica, California, were used twice (June and November) to budget bacterial production and loss, as well as to assess the relative significance of viral lysis and protist grazing in bacterial mortality. Bacterial abundance was ~6 × 109 cells liter‒1 in June and 2 × 109 in November, with viral abundances ~2 × 1010 particles liter‒1 in June and 1.5 × 1010 in November. Incorporation of [3H]thymidine and leucine yielded essentially identical production estimates and allowed calculation of total bacterial mortality in these closed systems. Bacterial growth rates were 1–2 d‒1 in June and 1–3 d‒1 in November. Three independent lines of evidence indicated that bacterial mortality attributed to grazing by protists was about equal to that attributed to viruses: size fractionation of disappearance of labeled DNA, with a 50% reduction after protists were removed; comparison of protist grazing rates estimated with fluorescently labeled bacteria and virus production‐based bacterial lysis rates, with 40–50% of the total ascribed to viruses; and model‐based interpretation of the 3.3–4.6% of bacteria visibly infected with assembled intracellular viruses, suggesting that 24–66% of loss is due to infection. Redundant production and loss measurements as well as the independent loss process estimates agreed within ~30%, yielding a reasonably balanced budget. We believe the loss of bacteria to viruses reflects a significant dissipation of energy in this ecosystem and that viruses and protists contribute similarly to bacterial mortality.
An empirical model of the phytoplankton chlorophyll : carbon ratio‐the conversion factor between productivity and growth rate
Authors: Cloern James E. , Grenz Christian , Vidergar‐Lucas Lisa
Published: May 2010

We present an empirical model that describes the ratio of phytoplankton chlorophyll a to carbon, Chl: C, as a function of temperature, daily irradiance, and nutrient‐limited growth rate. Our model is based on 219 published measurements of algal cultures exposed to light‐limited or nutrient‐limited growth conditions. We illustrate an approach for using this estimator of Chl: C to calculate phytoplankton population growth rate from measured primary productivity. This adaptive Chl: C model gives rise to interactive light‐nutrient effects in which growth efficiency increases with nutrient availability under low‐light conditions. One implication of this interaction is the enhancement of phytoplankton growth efficiency, in addition to enhancement of biomass yield, as a response to eutrophication.
An alternative approach to absorption measurements of aquatic particles retained on filters
Authors: Tassan Stelvio , Ferrari Giovanni M.
Published: May 2010

We made modifications to the procedure used for absorption measurements of aquatic particles retained on glass‐fiber filters that extend the procedure's application range to “case 2” waters with high suspended sediment content and allow the determination of phytoplankton pigment absorption in situations where the standard solvent extraction method is not effective.

The first result was achieved by combining light‐transmission and light‐reflection measurements (the latter made possible by the use of a commercially available integrating‐sphere attachment for the dual‐beam spectrophotometer) so as to remove the spurious contribution to the measured absorption caused by sample backscattering. The second result was obtained by bleaching the sample with a NaClO solution‐a method that proved satisfactory even with water‐soluble pigments (e.g. the important class of the phycobilins) and solvent‐resistant Chlorophyceae. This process also allows for depigmentation of the particle suspension, and thus it was used to evaluate the empirical expression for converting the filter‐retained sample absorbance to the equivalent particle suspension value.

Both features of the modified procedure have been positively tested through measurements carried out on solvent‐resistant phytoplankton species and on samples of inorganic suspended sediment.
Dynamics of dissolved organic carbon (DOC) in oceanic environments
Authors: Guo Laodong , Santschi Peter H. , Warnken Kent W.
Published: May 2010

Cross‐flow ultrafiltration techniques and a high‐temperature combustion (HTC) method were used to investigate the distributions and fluxes of dissolved (DOC) and colloidal organic carbon (COC) in the Gulf of Mexico and in the Middle Atlantic Bight. Concentrations of DOC in both regions decreased from ≤80 uM in surface waters to ∼45 µM in deep waters and showed large vertical gradients in the subsurface layer. The vertical distributions of DOC were oceanographically consistent. A conservative mixing behavior of DOC was observed in slope waters, and water mixing processes were important factors in controlling the distribution of DOC in the ocean. Calculated downward fluxes of DOC are comparable to those measured for particulate organic C. Size fractionation results revealed that COC (1 kDa‒0.2 µm) comprised ∼40–50% of the total DOC in seawater off Cape Hatteras, while it comprised ∼30–40% in the Gulf of Mexico. High‐molecular‐weight COC10 (10 kDa‒0.2 µm) represented 4–10% of the total DOC in both study areas. Concentrations of COC1, COC3, and COC10 and their percentages in the total DOC decreased from nearshore to offshore and from surface to deep waters. The COC fractions seem to partition in a predictable way in seawater, with DOC concentration as a master variable. On average, 4–7% of the total DOC was in the COC10 fraction, 7–14% was in the 3–10‐kDa fraction, and ~24% was in the 1–3‐kDa fraction, leaving 55– 65% in the <1‐kDa fraction.
Ontogenetic and seasonal variation in the diel vertical migration of the copepods Metridia lucens and Metridia longa
Authors: Hays Graeme C.
Published: May 2010

Plankton samples collected and analyzed by the Continuous Plankton Recorder survey were used to examine the length of time spent near the surface in the North Atlantic and the North Sea by three closely related groups of zooplankton (copepodite stages 1–4 Metridia spp., copepodite stages 5–6 Metridia lucens, and copepodite stages 5–6 Metridia longa). For all three groups, the mean daily length of time spent near the surface in each month of the year covaried seasonally with day length. In addition, the amount of time spent near the surface varied significantly between the three groups, being longest for the copepods of smallest body size (C 1–C4 Metridia spp.) and shortest for the copepods of largest body size (C5–C6 M. longa). These results support the suggestion that diel vertical migration serves to reduce the risk of mortality from visually orienting predators.
Flow hydrodynamics in tidal marsh canopies
Authors: Leonard Lynn A. , Luther Mark E.
Published: May 2010

The transport of particulate and dissolved matter on the surface of coastal marshes is controlled by the hydrodynamic characteristics of over‐marsh flows. High‐frequency (5 Hz) in situ measurements of flow speed were collected in Spartina alterniflora, Juncus roemerianus, and Distichlis spicata canopies using hot‐film anemometry sensor arrays. These data indicate that mean flow speed, turbulence intensity, and the shape of the vertical speed profile are influenced by variations in plant morphology and stem density.

Mean flow speed and turbulence intensity are inversely related to stern density and to distance from the creek edge. Flow energies decrease by about one order of magnitude when flows encounter the vegetated marsh surface and continue to decrease as vegetation density increases. Turbulent flow energy also decays exponentially with increasing distance from the creek edge. Reductions in flow speed coupled with energy decay provide a hydrologic mechanism for sediment deposition patterns commonly observed in marsh systems.

Suspended matter transport is also affected by plant‐flow interactions. Vertical flow structure is strongly influenced by canopy morphology (plant type and plant shape). Plant‐flow interactions result in vertical speed profiles whose shapes deviate from the logarithmic profile typical in free‐stream conditions and in the development of transitional flow regimes (i.e. neither laminar nor fully turbulent).
DNA distributions in planktonic bacteria stained with TOTO or TO‐PRO
Authors: Li W. K. W. , Jellett J. F. , Dickie P. M.
Published: May 2010

The blue‐excitable nucleic acid‐binding fluorochromes, TOTO and TO‐PRO, were used to stain bacteria in marine plankton communities. Flow cytometric counts of cells stained with these dyes agreed well with counts made by epifluorescence microscopy of DAPI‐stained cells. We have used these new dyes in a study of bacteria from various waters in the North Atlantic and the eastern Mediterranean. The results indicate a distinction among bacterial groups of different fluorescence intensities (apparent DNA content). At large spatial and temporal scales, about half of the variation in the percentage of bacteria with high apparent DNA content (termed group II bacteria) could be explained by the variation in chlorophyll. Further, the apparent mean DNA content of group II bacteria was also correlated with chlorophyll.
Chemical composition of PM10 and PM1 at the high-altitude Himalayan station Nepal Climate Observatory-Pyramid (NCO-P) (5079 m a.s.l.)
Authors: Decesari S. , Facchini M. C. , Carbone C. , Giulianelli L. , Rinaldi M. , Finessi E. , Fuzzi S. , Marinoni A. , Cristofanelli P. , Duchi R. , Bonasoni P. , Vuillermoz E. , Cozic J. , Jaffrezo J. L. , Laj P.
Published: May 2010

Abstract. We report chemical composition data for PM10 and PM1 from the Nepal Climate Observatory-Pyramid (NCO-P), the world's highest aerosol observatory, located at 5079 m a.s.l. at the foothills of Mt. Everest. Despite its high altitude, the average PM10 mass apportioned by the chemical analyses is of the order of 6 μg m−3 (i.e., 10 μg/scm), with almost a half of this mass accounted for by organic matter, elemental carbon (EC) and inorganic ions, the rest being mineral dust. Organic matter, in particular, accounted for by 2.0 μg m−3 (i.e., 3.6 μg/scm) on a yearly basis, and it is by far the major PM10 component beside mineral oxides. Non-negligible concentrations of EC were also observed (0.36 μg/scm), confirming that light-absorbing aerosol produced from combustion sources can be efficiently transported up the altitudes of Himalayan glaciers. The concentrations of carbonaceous and ionic aerosols follow a common time trend with a maximum in the premonsoon season, a minimum during the monsoon and a slow recovery during the postmonsoon and dry seasons, which is the same phenomenology observed for other Nepalese Himalayan sites in previous studies. Such seasonal cycle can be explained by the seasonal variations of dry and moist convection and of wet scavenging processes characterizing the climate of north Indian subcontinent. We document the effect of orographic transport of carbonaceous and sulphate particles upslope the Himalayas, showing that the valley breeze circulation, which is almost permanently active during the out-of-monsoon season, greatly impacts the chemical composition of PM10 and PM1 in the high Himalayas and provides an efficient mechanism for bringing anthropogenic aerosols into the Asian upper troposphere (>5000 m a.s.l.). The concentrations of mineral dust are impacted to a smaller extent by valley breezes and follow a unique seasonal cycle which suggest multiple source areas in central and south-west Asia. Our findings, based on two years of observations of the aerosol chemical composition, provide clear evidence that the southern side of the high Himalayas is impacted by transport of anthropogenic aerosols which constitute the Asian brown cloud.
Organic aerosol components observed in Northern Hemispheric datasets from Aerosol Mass Spectrometry
Authors: Ng N. L. , Canagaratna M. R. , Zhang Q. , Jimenez J. L. , Tian J. , Ulbrich I. M. , Kroll J. H. , Docherty K. S. , Chhabra P. S. , Bahreini R. , Murphy S. M. , Seinfeld J. H. , Hildebrandt L. , Donahue N. M. , DeCarlo P. F. , Lanz V. A. , Prévôt A. S. H. , Dinar E. , Rudich Y. , Worsnop D. R.
Published: May 2010

Abstract. In this study we compile and present results from the factor analysis of 43 Aerosol Mass Spectrometer (AMS) datasets (27 of the datasets are reanalyzed in this work). The components from all sites, when taken together, provide a holistic overview of Northern Hemisphere organic aerosol (OA) and its evolution in the atmosphere. At most sites, the OA can be separated into oxygenated OA (OOA), hydrocarbon-like OA (HOA), and sometimes other components such as biomass burning OA (BBOA). We focus on the OOA components in this work. In many analyses, the OOA can be further deconvolved into low-volatility OOA (LV-OOA) and semi-volatile OOA (SV-OOA). Differences in the mass spectra of these components are characterized in terms of the two main ions m/z 44 (CO2+) and m/z 43 (mostly C2H3O+), which are used to develop a new mass spectral diagnostic for following the aging of OA components in the atmosphere. The LV-OOA component spectra have higher f44 (ratio of m/z 44 to total signal in the component mass spectrum) and lower f43 (ratio of m/z 43 to total signal in the component mass spectrum) than SV-OOA. A wide range of f44 and O:C ratios are observed for both LV-OOA (0.17±0.04, 0.73±0.14) and SV-OOA (0.07±0.04, 0.35±0.14) components, reflecting the fact that there is a continuum of OOA properties in ambient aerosol. The OOA components (OOA, LV-OOA, and SV-OOA) from all sites cluster within a well-defined triangular region in the f44 vs. f43 space, which can be used as a standardized means for comparing and characterizing any OOA components (laboratory or ambient) observed with the AMS. Examination of the OOA components in this triangular space indicates that OOA component spectra become increasingly similar to each other and to fulvic acid and HULIS sample spectra as f44 (a surrogate for O:C and an indicator of photochemical aging) increases. This indicates that ambient OA converges towards highly aged LV-OOA with atmospheric oxidation. The common features of the transformation between SV-OOA and LV-OOA at multiple sites potentially enable a simplified description of the oxidation of OA in the atmosphere. Comparison of laboratory SOA data with ambient OOA indicates that laboratory SOA are more similar to SV-OOA and rarely become as oxidized as ambient LV-OOA, likely due to the higher loadings employed in the experiments and/or limited oxidant exposure in most chamber experiments.
Can we trust empirical marine DMS parameterisations within projections of future climate?
Authors: Halloran P. R. , Bell T. G. , Totterdell I. J.
Published: May 2010

Abstract. Dimethylsulphide (DMS) is a globally important aerosol precurser. In 1987 Charlson and others proposed that an increase in DMS production by certain phytoplankton species in response to a warming climate could stimulate increased aerosol formation, increasing the lower-atmosphere's albedo, and promoting cooling. Despite two decades of research, the global significance of this negative climate feedback remains contentious. It is therefore imperative that schemes are developed and tested, which allow for the realistic incorporation of phytoplankton DMS production into Earth System models. Using these models we can investigate the DMS-climate feedback and reduce uncertainty surrounding projections of future climate. Here we examine two empirical DMS parameterisations within the context of an Earth System model and find them to perform marginally better than the standard DMS climatology at predicting observations from an independent global dataset. We then question whether parameterisations based on our present understanding of DMS production by phytoplankton, and simple enough to incorporate into global climate models, can be shown to enhance the future predictive capacity of those models. This is an important question to ask now, as results from increasingly complex Earth System models lead us into the 5th assessment of climate science by the Intergovernmental Panel on Climate Change. Comparing observed and predicted inter-annual variability, we suggest that future climate projections may underestimate the magnitude of surface ocean DMS change. Unfortunately this conclusion relies on a relatively small dataset, in which observed inter-annual variability may be exaggerated by biases in sample collection. We therefore encourage the observational community to make repeat measurements of sea-surface DMS concentrations an important focus, and highlight areas of apparent high inter-annual variability where sampling might be carried out. Finally, we assess future projections from two similarly valid empirical DMS schemes, and demonstrate contrasting results. We therefore conclude that the use of empirical DMS parameterisations within simulations of future climate should be undertaken only with careful appreciation of the caveats discussed.
Thermodynamic origin of life
Authors: Michaelian K.
Published: May 2010

Abstract. Understanding the thermodynamic function of life may shed light on its origin. Life, as are all irreversible processes, is contingent on entropy production. Entropy production is a measure of the rate of the tendency of Nature to explore available microstates. The most important irreversible process generating entropy in the biosphere and, thus, facilitating this exploration, is the absorption and transformation of sunlight into heat. Here we hypothesize that life began, and persists today, as a catalyst for the absorption and dissipation of sunlight on the surface of shallow seas. The resulting heat could then be efficiently harvested by other irreversible processes such as the water cycle, hurricanes, and ocean and wind currents. RNA and DNA are the most efficient of all known molecules for absorbing the intense ultraviolet light that penetrated the dense early atmosphere and are remarkably rapid in transforming this light into heat in the presence of liquid water. From this perspective, the origin and evolution of life, inseparable from water and the water cycle, can be understood as resulting from the natural thermodynamic imperative of increasing the entropy production of the Earth in its interaction with its solar environment. A mechanism is proposed for the reproduction of RNA and DNA without the need for enzymes, promoted instead through UV light dissipation and the ambient temperature conditions of prebiotic Earth.
Modelling the hydrologic response of a mesoscale Andean watershed to changes in land use patterns for environmental planning
Authors: Stehr A. , Aguayo M. , Link O. , Parra O. , Romero F. , Alcayaga H.
Published: May 2010

Abstract. A multidisciplinary approach is followed for analysis of the effect of changes in land use patterns on the hydrologic response of the Vergara watershed (4340 km2) located in central Chile. Probable future land use scenarios were generated using heuristic rules and logistic regression models, in order to identify and represent the main pressure on the watershed, namely forestation of extensive areas used for agriculture with rapid growing exotic species. The hydrologic response of the watershed was computed with a physically based distributed precipitation-runoff model, which was calibrated and validated for the current observed scenario. Results show that mean annual discharge increase with agricultural land use and diminish with forest coverage. Thus, implementation of protection laws for native species conservation and regulated land use change are strongly recommended
Biofouling protection for marine environmental sensors
Authors: Delauney L. , Compère C. , Lehaitre M.
Published: May 2010

Abstract. These days, many marine autonomous environment monitoring networks are set up in the world. These systems take advantage of existing superstructures such as offshore platforms, lightships, piers, breakwaters or are placed on specially designed buoys or underwater oceanographic structures. These systems commonly use various sensors to measure parameters such as dissolved oxygen, turbidity, conductivity, pH or fluorescence. Emphasis has to be put on the long term quality of measurements, yet sensors may face very short-term biofouling effects. Biofouling can disrupt the quality of the measurements, sometimes in less than a week. Many techniques to prevent biofouling on instrumentation are listed and studied by researchers and manufacturers. Very few of them are implemented on instruments and of those very few have been tested in situ on oceanographic sensors for deployment of at least one or two months. This paper presents a review of techniques used to protect against biofouling of in situ sensors and gives a short list and description of promising techniques.
The Northeast Asia mountain glaciers in the near future by AOGCM scenarios
Authors: Ananicheva M. D. , Krenke A. N. , Barry R. G.
Published: May 2010

Abstract. We studied contrasting glacier systems in continental (Orulgan, Suntar-Khayata and Chersky ranges located in the Pole of Cold of Eurasia area at the contact of Atlantic and Pacific influences and maritime (Kamchatka Peninsula) – under Pacific influence. Our purpose is to present a simple projection method to asses the main parameters of these glacier regions under climate change. To achieve this, constructed vertical profiles of mass balance (accumulation and ablation) based both on meteorological data for 1950–90s and ECHAM4 for 2040–2069 are used, the latter – as a climatic scenario. Also for selected key glacier systems other models were applied for comparison. The observations and scenarios were used to define the recent and future equilibrium line altitude (ELA) and glacier termini elevation for each glacier system. The altitudinal distributions of ice areas were determined for present and future, they were used for prediction of the elevation spreading of glaciers in the system taking into account the correlation between the ELA and glacier-termini level change. We tested two hypotheses of ice distribution versus altitude in mountain (valley) glaciers – linear and non-linear. The results are estimates of the possible changes of the areas and morphological structure of Northeastern Asia glacier systems and their mass balance characteristics for 2049–60. Finally, we compare characteristics of the stability of continental and maritime glacier systems under global warming.
Preparation of polyaniline/phosphorylated poly(vinyl alcohol) nanoparticles and their aqueous redispersion stability
Authors: Chen Fei , Liu Peng
Published: May 2010

A novel approach for the preparation of the colloidal conducting polyaniline (PANI) nanoparticles was developed. The polyaniline/partially phosphorylated poly(vinyl alcohol)(PANI/P‐PVA) nanoparticles were prepared by the chemical oxidative dispersion polymerization of aniline monomer in 1.0 M HCl aqueous media with the partially phosphorylated poly(vinyl alcohol) (P‐PVA) as the stabilizer and codopant. The PANI/P‐PVA nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), electrical conductivity measurement, and redispersion stability testing. All the results were compared with the properties of the conventional polyaniline in the emeraldine salt form (PANI ES). It was found that the P‐PVA/aniline feeding ratio obviously affected the morphology, redispersion stability and electrical conductivity of the PANI/P‐PVA nanoparticles. When the P‐PVA/aniline feeding ratio ranged from 50 to 60 wt %, the PANI/P‐PVA nanoparticles showed spherical shape with good uniformity, significant redispersion stability in aqueous media, and good electrical conductivity up to 7 S/cm. © 2010 American Institute of Chemical Engineers AIChE J, 2011
Molecular diversity of PBAN family peptides from fire ants
Authors: Choi Man‐Yeon , Vander Meer Robert K. , Valles Steven M.
Published: May 2010

The PBAN/Pyrokinin peptide family is a major neuropeptide family characterized with a common FXPRLamide in the C‐termini. These peptides are ubiquitously distributed in the Insecta and are involved in many essential endocrinal functions, e.g., pheromone production. Previous work demonstrated the localization of PBAN in the fire ant central nervous system, and identified a new family of PBAN from the red imported fire ant, Solenopsis invicta. In this study, we identified five more PBAN/Pyrokinin genes from S. geminata, S. richteri, S. pergandii, S. carolinensis, and a hybrid of S. invicta and S. richteri. The gene sequences were used to determine the phylogenetic relationships of these species and hybrid, which compared well to the morphologically defined fire ant subgroup complexes. The putative PBAN and other peptides were determined from the amino acid sequences of the PBAN/pyrokinin genes. We summarized all known insect PBAN family neuropeptides, and for the first time constructed a phylogenetic tree based on the full amino acid sequences translated from representative PBAN cDNAs. The PBAN/pyrokinin gene is well conserved in Insecta and probably extends into the Arthropod phylum; however, translated pre‐propeptides may vary and functional diversity may be retained, lost, or modified during the evolutionary process. Published 2010 Wiley Periodicals, Inc.
Robust face tracking control of a mobile robot using self‐tuning Kalman filter and echo state network
Authors: Tsai Chi‐Yi , Dutoit Xavier , Song Kai‐Tai , Van Brussel Hendrik , Nuttin Marnix
Published: May 2010

This paper presents a novel design of face tracking algorithm and visual state estimation for a mobile robot face tracking interaction control system. The advantage of this design is that it can track a user's face under several external uncertainties and estimate the system state without the knowledge about target's 3D motion‐model information. This feature is helpful for the development of a real‐time visual tracking control system. In order to overcome the change in skin color due to light variation, a real‐time face tracking algorithm is proposed based on an adaptive skin color search method. Moreover, in order to increase the robustness against colored observation noise, a new visual state estimator is designed by combining a Kalman filter with an echo state network‐based self‐tuning algorithm. The performance of this estimator design has been evaluated using computer simulation. Several experiments on a mobile robot validate the proposed control system.

Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Vector control for induction motor drives based on adaptive variable structure control algorithm
Authors: Barambones O. , Alkorta P.
Published: May 2010

This paper presents a new adaptive robust control for induction motor drives. The proposed control scheme is based on the so‐called field oriented control theory that allows to control the induction motor like a separately excited direct current motor drive, where the field flux (produced by the field current) and the armature flux (produced by the armature current) are decoupled. The robust control law is based on the sliding mode control theory, but unlike the traditional sliding mode control schemes, the proposed design incorporates an adaptive switching gain that avoids the need of calculating an upper limit of the system uncertainties. Moreover the proposed control law is smoothed out in order to avoid the high control activity inherent to the switching control laws. The resulting closed loop system is proven to be stable using the Lyapunov stability theory.

Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Of mites and millipedes: Recent progress in resolving the base of the arthropod tree
Authors: Caravas Jason , Friedrich Markus
Published: May 2010

Deep‐level arthropod phylogeny has been in a state of upheaval ever since the emergence of molecular tree reconstruction approaches. While a consensus has settled in that hexapods are more closely related to crustaceans than to myriapods, the phylogenetic position of the latter has remained a matter of debate. Mitochondrial, nuclear, and genome‐scale studies have proposed rejecting the long‐standing superclade Mandibulata, which unites myriapods with insects and crustaceans, in favor of a clade that unites myriapods with chelicerates and has become known as Paradoxapoda or Myriochelata. Here we discuss the progress, problems, and prospects of arriving at the final arthropod tree.
Understanding on the residue contact network using the log‐normal cluster model and the multilevel wheel diagram
Authors: Sun Weitao , He Jing
Published: May 2010

Residue clusters play essential role in stabilizing protein structures in the form of complex networks. We show that the cluster sizes in a native protein follow the log‐normal distribution for a dataset consisting of 424 proteins. To our knowledge, this is the first time of such fitting for the native structures. Based on log‐normal model, the asymptotically increasing mean cluster sizes produce a critical protein chain length of about 200 amino acids, beyond which length most globular proteins have nearly the same mean cluster sizes. This suggests that the larger proteins use a different packing mechanism than the smaller proteins. We confirmed the scale‐free property of the residue contact network for most of the protein structures in the dataset, although the violations were observed for the tightly packed proteins. Residue cluster network wheel (RCNW) is proposed to visualize the relationship between the multiple properties of the residue network such as the cluster size, the residue types and contacts, and the flexibility of the residue. We noticed that the residues with large cluster size have smaller Cα displacement measured using the normal mode analysis. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 904–916, 2010.
Control of microbial attachment by inhibition of ATP and ATP‐mediated autoinducer‐2
Authors: Xu Huijuan , Liu Yu
Published: May 2010

In this study, 2,4‐dinitrophenol (DNP), a typical chemical uncoupler, was employed to investigate the possible roles of ATP and autoinducer‐2 (AI‐2) of suspended microorganisms in attachment onto nylon membrane and glass slide surfaces. Results showed that DNP could disrupt ATP synthesis, subsequently led to a reduced production of AI‐2 which is a common signaling molecule for cellular communication. Attachment of suspended microorganisms exposed to DNP was significantly suppressed as compared to microorganisms without contact with DNP. These suggest that an energized state of suspended microorganisms would favor microbial attachment to both nylon membrane and glass slide surfaces. The extent of microbial attachment was found to be positively related to the AI‐2 content of microorganisms. This study offers insights into the control of biofouling by preventing initial microbial attachment through inhibition of energy metabolism. Biotechnol. Bioeng. 2010;107: 31–36. © 2010 Wiley Periodicals, Inc.
Effects of glucose and insulin on HepG2‐C3A cell metabolism
Authors: Iyer Vidya V. , Yang Hong , Ierapetritou Marianthi G. , Roth Charles M.
Published: May 2010

HepG2, hepatocellular carcinoma cells, are used in drug toxicity studies and have also been explored for bioartificial livers. For these applications, the cells are under variable levels of nutrients and hormones, the effects of which on metabolism are poorly understood. In this study, HepG2‐C3A cells were cultured under varying levels of glucose (high, low, and glucose‐free) and insulin (without and with physiological levels of insulin) for 5 days. Cell growth was found to be comparable between high and low glucose media and lowest for glucose‐free medium. Several features of central metabolism were affected profoundly by the medium glucose levels. Glucose consumption was greater for low glucose medium compared to high glucose medium, consistent with known glucose feedback regulation mechanisms. Urea productivity was highest in glucose‐free medium. Further, it was seen that lactate acted as an alternative carbon source in the absence of glucose, whereas it acted as a sink for the high and low glucose media. Using a metabolic network flexibility analysis (MNFA) framework with stoichiometric and thermodynamic constraints, intracellular fluxes under varying levels of glucose and insulin were evaluated. The analysis indicates that urea production in HepG2‐C3A cells arises via the arginase II pathway rather than from ammonia detoxification. Further, involvement of the putrescine metabolism with glutamine metabolism caused higher urea production in glucose‐free medium consistent with higher glutamine uptake. MNFA indicated that in high and low glucose media, glycolysis, glutaminolysis, and oxidative phosphorylation were the main sources of energy (NADH, NADPH, and ATP). In the glucose‐free medium, due to very low glycolytic flux, higher malate to pyruvate glutaminolytic flux and TCA cycle contributed more significantly to energy metabolism. The presence of insulin lowered glycerol uptake and corresponding fluxes involved in lipid metabolism for all glucose levels but otherwise exerted negligible effect on metabolism. HepG2‐C3A cells thus show distinct differences from primary hepatocytes in terms of energy metabolism and urea production. This knowledge can be used to design media supplements and metabolically engineer cells to restore necessary hepatic functions to HepG2‐C3A cells for a range of applications. Biotechnol. Bioeng. 2010;107: 347–356. © 2010 Wiley Periodicals, Inc.