bluuebunny/crossref_metadata_2025 huggingface dataset:
Taxonomic richness of stream benthic algae: Effects of flood disturbance and nutrients
Authors: Biggs Barry J. F. , Smith Robert A.
Published: June 2010

We sampled benthic algae monthly for 15 months in 12 New Zealand gravel‐bed streams to investigate amongstream differences in algal taxonomic richness and how this might relate to among‐stream differences in flood disturbance and nutrient resource regimes. The mean number of benthic algal taxa per month ranged from 9.4 to 21.3 among streams. There were moderate month‐to‐month fluctuations in richness, partly in response to flood disturbances. Flow perturbations generally reduced richness in streams with unarmored bed sediments but had little or no effect on richness in streams with armored sediments. Richness was moderate within days of floods in most streams but then did not vary significantly for periods of up to 50 d. However, in streams with prolonged periods without bed‐moving floods, richness slowly increased after ~100 d, and, in two of these streams, it peaked at 200–300 d before declining. Unexpectedly, there was not a significant pattern in mean monthly richness among the streams as a function of annual flood frequency. Mean richness was strongly negatively related to soluble nutrient concentrations (particularly with soluble inorganic nitrogen [SIN]; R2 = 0.511, P = 0.018). However, this was not a direct relationship, because nitrogen‐fixing taxa were common in the streams with low SIN, resulting in intermediate to high mat‐scale nitrogen concentrations. This possibly shifted these communities to P‐limited growth. A combination of disturbance frequency and mat P gave the most parsimonious model of among‐stream variations in benthic algal richness (R2 = 0.635, P = 0.037). The highest richness occurred in streams with low to intermediate frequencies of flood disturbance (up to 10 bed‐moving events yr-1) and intermediate to high concentrations of mat P (>0.6% P). We could not define an upper nutrient concentration that negatively affected benthic algal richness (perhaps because none of our streams were highly enriched). We discuss our results in relation to three contemporary models of biodiversity.
Sources of inorganic carbon for photosynthesis in a strain of Phaeodactylum tricornutum
Authors: Cassar Nicolas , Laws Edward A. , Popp Brian N. , Bidigare Robert R.
Published: June 2010

Diatoms are an important functional group of marine phytoplankton because of their role in the fixation of atmospheric carbon dioxide (CO2) and transfer of organic carbon to deep waters. Carbon‐concentrating‐mechanisms, such as active CO2 and bicarbonate (HCO3−) uptake and carbonic anhydrase activity, are believed to be essential to marine photosynthesis, because the main carbon‐fixing enzyme, ribulose‐1,5‐bisphosphate carboxylase‐oxygenase, is less than half saturated at normal seawater CO22 concentrations. On the basis of short‐term inorganic 14C uptake experiments, Tortell et al. (1997; Nature 390: 243–244) recently argued that marine diatoms are capable of HCO3− uptake. However, as discussed herein, the extent of HCO3− uptake cannot be assessed on the basis of these experiments. Using short‐term 14CO2‐disequilibrium experiments, we show that a clone of the marine diatom Phaeodactylum tricornutum takes up little or no HCO3− even under conditions of severe CO22 limitation. Predicting the response of the oceans to increased CO2 concentrations will require, among other things, a careful assessment of the extent to which marine algae take up HCO3− or CO2. Because the plasmalemma of microalgae is gas permeable, all phytoplankton exchange CO2 with the growth medium. Experimental results that are merely consistent with HCO3− uptake are insufficient to prove that HCO3− uptake is occurring. Our results are in accord with predictions based on stable carbon isotopic fractionation data. Combining isotopic disequilibrium experiments with continuous growth cultures and stable isotope fractionation experiments is a powerful tool for understanding the response of oceanic primary producers to anthropogenic CO2 emissions as well as for interpreting paleoceanographic carbon isotope data.
Iron‐sulfur‐phosphorus cycling in the sediments of a shallow coastal bay: Implications for sediment nutrient release and benthic macroalgal blooms
Authors: Rozan Tim F. , Taillefert Martial , Trouwborst Robert E. , Glazer Brian T. , Ma Shufen , Herszage Julian , Valdes Lexia M. , Price Kent S. , Luther III George W.
Published: June 2010

We conducted a study to determine the seasonal relationship between iron, sulfur, and phosphorus in the upper sediments and pore waters of a shallow intercoastal bay. From April 1999 to September 2000, sediment cores were collected from Rehoboth Bay, Delaware. Analyses of the sediments in the upper 4 cm revealed that redox conditions controlled Fe‐S‐P concentrations in the sediments, pore waters, and overlying water. Monthly sampling showed a marked decrease in the reactive solid phase P pool (ascorbate leachable fraction, ASC‐P) and sharp increases in soluble P (measured as PO43‐) in pore waters and overlying waters, as the conditions became more reducing throughout the summer months. These changes were paralleled by decreases in the amorphous Fe(III) (ascorbate leachable fraction, ASC‐Fe) and total Fe(III)oxyhydroxide pools [dithionite extracted fraction, Fe(III)2] and increases in solid FeS/FeS2. The release of soluble P from sulfidic sediments to oxygenated overlying waters only occurred during periods of solid FeS/FeS2 production, which indicates that Fe(III) oxides act as a barrier to diffusive P flux. During these anoxic conditions, the regenerative P appears to induce secondary benthic algal blooms and promotes eutrophication in these inland bays through late summer. By the late fall and into early spring, sulfide production diminished and oxic conditions were reestablished as indicated by increases in solid amorphous and crystalline Fe(III) oxides and decreases in FeS/FeS2 concentrations. During this period, increasing ASC‐Fe concentrations correlated with increases in ASC‐P concentrations and decreases in pore‐water PO43‐. The seasonal correlations between Fe‐S‐P indicate that Fe redox chemistry controls sediment P flux to the overlying water column.
Nutritional quality of food resources for zooplankton (Daphnia) in a tidal freshwater system (Sacramento‐San Joaquin River Delta)
Authors: Müller‐Solger Anke B. , Jassby Alan D. , Müller‐Navarra Dörthe C.
Published: June 2010

We examined the relative nutritional values of natural phytoplankton and particulate detritus for zooplankton growth in a detritus‐rich environment. Seston was collected seasonally from four different habitat types in a tidal freshwater system and fed to juvenile Daphnia magna under controlled culture conditions by use of a flow‐through design. Seston particulate organic carbon (POC) and chlorophyll a contents ranged from ~330 to 3,800 µg L-1 POC and 1.4 to 45 µg L-1 Chl a. A partial residual analysis revealed that detrital carbon concentrations were only weakly related to Daphnia growth, whereas Chl a proved to be highly predictive of Daphnia growth rates across all investigated habitat types. Overall, habitat type had a strong effect on growth rates, whereas season of seston collection did not, but differences among habitats could be attributed to differing Chl a concentrations. The results from this study imply that, even in systems with overwhelming amounts of detrital carbon from a variety of sources, nutritional factors associated with phytoplankton can be dominant in regulating zooplankton growth.
Eastߞwest gradients in the photosynthetic potential of phytoplankton and iron concentration in the subarctic Pacific Ocean during early summer
Authors: Suzuki Koji , Liu Hongbin , Saino Toshiro , Obata Hajime , Takano Michiaki , Okamura Kei , Sohrin Yoshiki , Fujishima Yukiyo
Published: June 2010

In the subarctic Pacific and its adjacent waters, the photochemical quantum yield (Fv/Fm) and the functional absorption cross section (ΣPSII) of photosystem II for surface phytoplankton were continuously measured during the early summer of 1999 using a fast repetition rate fluorometer. Concentrations of total dissolvable iron (TD‐Fe) were also determined at each sampling station. The maximum value (0.61) of Fv/Fm was observed off the Aleutian Peninsula, where TD‐Fe concentrations were relatively high. The Western Subarctic Gyre (WSG) and the Alaskan Gyre (AG), located in the northwest and northeast subarctic Pacific, respectively, were in high‐nutrient, low‐chlorophyll (HNLC) conditions. Surface TD‐Fe generally remained in the WSG but was depleted (<0.01 nmol L−1) in the AG. Nighttime Fv/Fm and ΣPSII in the WSG were significantly higher (p < 0.01) and lower (p < 0.01), respectively, than in the AG. Iron or nitrogen limitations generally lead to a decrease in Fv/Fm and an increase in ΣPSII. These results suggested that there was an east‐west gradient (WSG . AG) in the photosynthetic competence of phytoplankton in the subarctic Pacific and that the difference was probably caused by iron levels in seawater. Indeed, our iron enrichment experiment in the AG revealed that Fv/Fm increased from 0.27 to 0.49 and ΣPSII decreased from 496 x 10−20 to 365 x 10−20 m2 photon−1 after a 0.8 nmol L−1 iron addition. At the same time, a dramatic floristic shift from phytoflagellates to diatoms was found by pigment signatures. Iron could principally control the photosynthetic physiology of phytoplankton in the whole subarctic Pacific.
Molecular isotopic tracing of carbon flow and trophic relationships in a methane‐supported benthic microbial community
Authors: Werne Josef P. , Baas M. , Sinninghe Damsté J. S.
Published: June 2010

A molecular isotopic study in cold‐seep sediments from Kazan mud volcano in the eastern Mediterranean Sea indicates that a significant proportion of methane released in this environment is incorporated into biomass in methane‐supported chemosynthetic microbial communities. Furthermore, extremely 13C depleted biomarkers (as much as –111‰ Vienna Pee Dee Belemnite (VPDB)) have revealed pathways of methane‐derived carbon flow through the microbial community and into eukaryotic biomass. Specifically, we are able to trace the flow of methane derived carbon through anaerobic methane‐oxidizing archaea into sulfate‐reducing bacteria, as well as into aerobic methane‐oxidizing bacteria. The methane‐derived carbon is then incorporated into eukaryotic biomass through heterotrophy by bacterivorous ciliates.
Differential retention and utilization of dissolved organic carbon by bacteria in river sediments
Authors: Fischer Helmut , Sachse Anke , Steinberg Christian E. W. , Pusch Martin
Published: June 2010

The differential ability of natural sediment biofilms to store and metabolize specific dissolved organic carbon (DOC) fractions was studied with a set of perfusion experiments that combined a chromatographic method for the analysis of several DOC fractions with the measurement of bacterial abundance and activity. High proportions of low‐molecular‐weight substances and polysaccharides and low but significant proportions of humic substances were retained in sediment cores after perfusion. Bacterial abundance and production in these cores were high (1.7—3.0 × 109 cells cm−3 and 0.7—12.0 µg C cm−3 h−1, respectively). Bacterial abundance, production, and turnover times were correlated with the retention of various DOC fractions, especially polysaccharides, indicating a differential microbial utilization of DOC. Temperature as well as the quantity and quality of retained organic matter were the major factors that influenced bacterial production. However, particulate organic carbon represented the main energy source for sediment bacteria. It is concluded that certain fractions of DOC may be readily utilized for bacterial growth, irrespective of molecular size. Instead, the presence and abundance of specific chemical groups might be decisive. Hence, the processing of organic substrates by the microbial biofilm may largely influence the biogeochemistry of DOC in river waters.
Impact of sea grass density on carbonate dissolution in Bahamian sediments
Authors: Burdige David J. , Zimmerman Richard C.
Published: June 2010

Carbonate dissolution has been widely observed in shallow water tropical sediments. However, sediment budgets have generally not been closed with respect to the amount of acid required to produce the observed carbonate dissolution. Recently it has been suggested that enhanced oxygen transport into sediments through the roots and rhizomes of sea grasses might play a role in resolving this mass balance problem. We conducted studies of sea grass‐carbonate sediment interactions around Lee Stocking Island, Exuma Islands, Bahamas to further examine this problem. Our studies showed that alkalinity, total dissolved inorganic carbon (σCO2) and Ca2+ increased with depth in the pore waters, while pH and calculated carbonate ion concentration decreased with depth. These observations are consistent with the occurrence of carbonate dissolution in these sediments. The magnitude of pore water alkalinity, σCO2, and Ca21 changes was also related to sea grass density, with the largest gradients seen in the sediments of dense sea grass beds. Calculations suggested that less than ~50% of the O2 needed to drive aerobic respiration (and ultimately carbonate dissolution via CO2 production) could be supplied by transport processes such as diffusion, bioturbation, and physical pore water advection. Furthermore, the O2 needed to balance the carbonate dissolution budget could be provided by the transport of <15% of the photosynthetically derived O2 to the sediments through sea grass roots and rhizomes without enhancing the removal of carbonate dissolution end products. Thus sea grasses play an important role in controlling the rates of carbonate dissolution in shallow water tropical marine sediments.
Stable isotope systematics of two cenotes from the northern Yucatan Peninsula, Mexico
Authors: Socki Richard A. , Perry Eugene Jr. C. , Romanek Christopher S.
Published: June 2010

Deep water‐filled sinkholes, cenotes, are common in the northern Yucatan Peninsula. At least five of these cenotes are deep enough to extend through a freshwater lens of meteoric origin in which δ18O and δD follow the trend δD = 8.11 × δ18O + 10.4. Below this freshwater lies saline water that originated as seawater and has retained its seawater isotopic identity. Deep cenotes, characterized by input of variable amounts of organic debris from tropical vegetation and by poor circulation below the fresh‐/saltwater interface, provide excellent water columns in which to study sulfur redox phenomena. Measurements include O, H, and S isotope composition, conductivity, sulfur speciation, and pH from two cenotes (Ucil, 98 m deep, and Xcolac, 125 m deep). Strong 34S enrichment of sulfate and 34S depletion of sulfide indicate anaerobic bacterial reduction of sulfate. A shift in the isotopic composition of sulfur in Xcolac from a seawater value of +21.0‰ (CDT) to +41.8‰ indicates conversion of sulfate to isotopically light sulfide. Mass balance calculations indicate that escape of isotopically light sulfur from the system is a slow process. At 80 m in Xcolac, a difference in sulfur isotope composition between sulfate and sulfide (△34S) of 63.2‰ is observed and could be the result of multiple sulfate reduction reactions. Higher in the water column, sulfide oxidation occurs, probably the result of bacterially mediated sulfide oxidation processes. A deep observation well (lacking organic matter input) shows only a slight deviation in sulfur isotope composition of sulfate from seawater values.
Water column interleaving: A new physical mechanism determining protist communities and bacterial states
Authors: Lovejoy Connie , Carmack Eddy C. , Legendre Louis , Price Neil M.
Published: June 2010

During a spring‐summer bloom in a large Arctic polynya, vertically distinct protist communities (phytoplankton and protozoa) occurred within layers caused by interleaving and entrainment of different water masses. We developed a ternary community distance index to quantify the variability in protist community structure in these heterogeneous surface layers. This index was highly correlated (r = 0.984, n = 6) with the extent of physical interleaving (quantified as the root mean square deviations in temperature between measured and smoothed profiles) indicating a high degree of physical‐biotic coupling within water columns of the polynya. Water mass layering created favorable conditions for ciliate blooms. These blooms were associated with distinct temperature‐salinity layers. These layers might act as processing traps for particulate organic matter, with highest concentrations of viruses and bacteria (specifically cells with open or leaky membranes, suggesting microbial grazing pressure) occurring in highly interleaved water columns. In contrast, viral and bacterial concentrations were lowest at a noninterleaved station where protist biomass was dominated by flagellates and small dinoflagellates that were evenly distributed down the water column. Water mass interleaving is likely to contribute to microbial biodiversity, community structure and vertical segmentation of biogeochemical processes in the upper ocean.
Bacterioplankton distribution and production in the bathypelagic ocean: Directly coupled to particulate organic carbon export?,
Authors: Hansell D. A. , Ducklow H. W.
Published: June 2010

A recently published evaluation of bacterioplankton abundance and productivity in the bathypelagic North Pacific suggests that these properties are generally coupled with particulate organic carbon (POC) fluxes. In that analysis, bacterial biomass and productivity were several–fold greater in subarctic than subtropical waters, consistent with the basin–scale distribution of POC flux and suggestive of a sinking POC > DOC > bacteria transformation of the carbon. To test this hypothesis, we sought to determine whether the very strong spatial and temporal gradients in POC flux in the Arabian Sea would force similar deep–ocean gradients in bacterial variables. On both a within and between–cruise basis, there was variability in bacterial abundance and thymidine incorporation in the deep Arabian Sea, but correspondence was equivocal between these variables and several correlates to export: flux of biogenic carbon from the euphotic zone, state of the monsoon, and proximity to productive coastal upwelling zones. However, when annual mean bacterial abundance at 2,000 m was compared with annual POC flux at that depth, a strong correspondence emerged: high annual flux supported high bacterial abundance (such a correspondence was not found for bacterial productivity). This finding suggests that bathypelagic bacterial abundance responds to the long–term mean input of organic matter and less to episodic inputs. A comparative evaluation of the North Pacific revealed that although the bathypelagic bacteria there showed correspondence to deep POC flux, that variable alone would not account for the wide meridional variations in bacterial abundance that have been reported.
Meristematic oxygen variability in eelgrass (Zostera marina)
Authors: Greve Tina Maria , Borum Jens , Pedersen Ole
Published: June 2010

We examined the variability in oxygen content of meristematic tissues in eelgrass in order to evaluate its potential role in events of sudden mass mortality within eelgrass beds. Oxygen content within intact eelgrass plants could be described by use of microelectrode techniques at high temporal and spatial resolution in the laboratory and in the field. Under both situations, the meristematic oxygen content was highly variable, ranging from 0 to 200% of air saturation depending on environmental conditions. Changes from steady‐state maximum oxygen content to steady‐state minimum content occurred within 30 min following experimental manipulation. The internal oxygen content exceeded water column oxygen concentration in the light and was intimately coupled to changes in irradiance because of the photosynthetic oxygen release within the leaves. The photosynthetically produced pool of oxygen could, however, not function as an efficient storage to support nighttime respiration. In the dark, oxygen was primarily supplied from the water column via diffusion into leaves, and the meristem quickly turned anoxic if the water column was anoxic. Experimental reduction of oxygen conditions immediately around the basal plant meristem had no major effect on internal oxygen content. High temperatures had a dramatic effect on the internal oxygen balance of eelgrass. Increasing temperature stimulated plant respiration more than photosynthesis, and the meristem went anoxic, even in the light, at water temperatures above 30°C. We hypothesize that low meristematic oxygen content is a key factor in events of seagrass die‐off.
Contribution of fluorescence to the spectral signature and perceived color of corals
Authors: Mazel Charles H. , Fuchs Eran
Published: June 2010

Solar‐induced fluorescence from pigments in the host tissues of reef corals can make a significant contribution to their spectral signature and can affect their apparent color as perceived by a human observer. The relative magnitudes of the reflectance and fluorescence contributions to the spectrum can vary as a function of illumination conditions. We have combined measured coral reflectance and fluorescence spectra with modeled downwelling spectral irradiances to investigate the contribution of fluorescence to coral spectra and color. Variations in depth, fluorescence efficiency, and solar zenith angle were modeled. Fluorescence enhancement is greatest when the coral absorbs light at wavelengths that are transmitted well by seawater and emits light efficiently at wavelengths that are moderately attenuated. The methodology provides a means of predicting the combined reflectance and fluorescence spectral signatures and perceived colors of fluorescent corals under arbitrary illumination conditions.
Green‐fluorescent proteins in Caribbean corals
Authors: Mazel Charles H. , Lesser Michael P. , Gorbunov Maxim Y. , Barry Thomas M. , Farrell Julianne H. , Wyman Kevin D. , Falkowski Paul G.
Published: June 2010

Fluorescent pigments in several Indo‐Pacific and Caribbean anthozoans have recently been identified as proteins related to the Green‐fluorescent protein (GFP) of the hydromedusa Aequorea victoria. Here we show that GFP is widely distributed in many Caribbean species. The fluorescence excitation and emission spectra for the pigment are similar to those reported elsewhere for coral and noncoral GFP and the fluorescence quantum yield is estimated to be 35%. Spectral and molecular characterization of the isolated protein clearly show it to be GFP, and laboratory and in situ fluorescence measurements and Western blot analysis show that it is widespread. Bathymetric studies of GFP content using Western blots for the ecologically important congeneric corals Montastraea faveolata and Montastraea cavernosa show that there is no significant correlation between depth and GFP concentration. Nucleotide sequence data of GFP from M. faveolata and M. cavernosa show 88.2% sequence homology with each other and 46.4% homology with A. victoria GFP, whereas the percent homology with A. victoria at the amino acid level was 31.1 and 28.4% for M. cavernosa and M. faveolata, respectively, and 82.7% with each other. Measurements of reflectance and of the excitation spectrum for chlorophyll fluorescence in GFP‐containing corals indicate that GFP absorption, emission, and reflection have negligible impact on the level of solar radiation reaching the zooxanthellae and therefore play no role in coral photosynthesis by either addition or removal of photons.
Effects of epiphyte load on optical properties and photosynthetic potential of the seagrasses Thalassia testudinum Banks ex König and Zostera marina L.
Authors: Drake1 Lisa A. , Dobbs Fred C. , Zimmerman Richard C.
Published: June 2010

The biomass and optical properties of seagrass leaf epiphytes were measured to evaluate their potential impact on the photosynthetic performance of the seagrasses Thalassia testudinum Banks ex König (turtlegrass) and Zostera marina L. (eelgrass). Turtlegrass was obtained from oligotrophic waters near Lee Stocking Island, Bahamas; eelgrass was collected from a eutrophic environment in Monterey Bay, California. Leaf‐epiphyte loads were characterized visually and quantified using measurements of their phospholipid biomass. Light absorption and reflectance of the intact epiphyte layer were determined spectrophotometrically. Turtlegrass epiphytes from the oligotrophic site absorbed a maximum of 36% of incident light in peak chlorophyll absorption bands, whereas higher epiphyte loads on eelgrass from the more eutrophic Monterey Bay absorbed 60% of incident light in peak chlorophyll absorption bands. The combination of intact epiphyte‐leaf complexes and spectral measurements enabled us to construct a quantitative relationship between epiphyte biomass and light attenuation, and, by extension, between epiphyte biomass and seagrass photosynthesis. The model yielded a robust, positive relationship between epiphyte biomass and the absorption of photons in photosynthetically important wavelengths, and it generated a strong negative relationship between epiphyte biomass and spectral photosynthesis of their seagrass hosts. Furthermore, the calculations of photosynthesis highlighted the significant differences between PAR and spectral models of photosynthesis, illustrating that the spectral quality of the incident flux must be considered when evaluating the effects of epiphyte load on seagrass leaf photosynthesis. Verification of the model—using direct measurements of photosynthesis and a variety of epiphyte and macrophyte combinations from different locations—is warranted.
High‐resolution determination of coral reef bottom cover from multispectral fluorescence laser line scan imagery
Authors: Mazel Charles H. , Strand Michael P. , Lesser Michael P. , Crosby Michael P. , Coles Bryan , Nevis Andrew J.
Published: June 2010

A prototype in‐water laser line‐scanning multispectral fluorescence imaging system was evaluated for its ability to provide data that could be used to determine the quantitative distribution and abundance of various functional groups on coral reefs. The system collected fluorescence imagery in three spectral bands with 1 cm2 resolution at sites in Florida and the Bahamas. Fluorescence excitation was at 488 nm, and imagery was collected in emission bands centered at 520, 580, and 685 nm. Ground truth data on bottom cover was collected by divers using conventional line transect and photographic quadrat methods. A set of classification rules based on the relative signal levels in the three fluorescence channels was developed to assign the image pixels to functional groups. Once the image was classified, percent cover data for the groups were computed for the full image and for subsets of the image chosen to simulate line transect, grid survey, and photographic quadrat surveys. The statistics of percent cover of various bottom types derived from the fluorescence image compared favorably with those determined by diver survey techniques. The results demonstrate that fluorescence imaging has the long‐term potential to provide coverage of large spatial areas of coral reefs at high resolution, with automated classification and quantification of functional groups in the image.
Determination of water depth with high‐resolution satellite imagery over variable bottom types
Authors: Stumpf Richard P. , Holderied Kristine , Sinclair Mark
Published: June 2010

A standard algorithm for determining depth in clear water from passive sensors exists; but it requires tuning of five parameters and does not retrieve depths where the bottom has an extremely low albedo. To address these issues, we developed an empirical solution using a ratio of reflectances that has only two tunable parameters and can be applied to low‐albedo features. The two algorithms—the standard linear transform and the new ratio transform— were compared through analysis of IKONOS satellite imagery against lidar bathymetry. The coefficients for the ratio algorithm were tuned manually to a few depths from a nautical chart, yet performed as well as the linear algorithm tuned using multiple linear regression against the lidar. Both algorithms compensate for variable bottom type and albedo (sand, pavement, algae, coral) and retrieve bathymetry in water depths of less than 10–15 m. However, the linear transform does not distinguish depths .15 m and is more subject to variability across the studied atolls. The ratio transform can, in clear water, retrieve depths in >25 m of water and shows greater stability between different areas. It also performs slightly better in scattering turbidity than the linear transform. The ratio algorithm is somewhat noisier and cannot always adequately resolve fine morphology (structures smaller than 4–5 pixels) in water depths >15–20 m. In general, the ratio transform is more robust than the linear transform.
The Health Information Technology Workforce
Authors: Hersh W.
Published: June 2010

Background: There is increasing recognition that a competent and well-trained workforce is required for successful implementation of health information technology.

Methods: New and previous research was gathered through literature and Web searching as well as domain experts. Overall themes were extracted and specific data collated within each.

Results: There is still a paucity of research concerning the health information technology workforce. What research has been done can be classified into five categories: quantities and staffing ratios, job roles, gaps and growth, leadership qualifications, and education and competencies. From several countries it can be seen that substantial numbers of individuals are needed with diverse backgrounds and competencies.

Conclusions: Additional research is necessary to determine the optimal organization and education of the health information technology workforce.

Citation: Hersh W. : The health information technology workforce: Estimations of demands and a framework for requirements. Appl Clin Inf 2010; 1: 197–212 http://dx.doi.org/10.4338/ACI-2009-11-R-0011
Impact of aftertreatment devices on primary emissions and secondary organic aerosol formation potential from in-use diesel vehicles: results from smog chamber experiments
Authors: Chirico R. , DeCarlo P. F. , Heringa M. F. , Tritscher T. , Richter R. , Prevot A. S. H. , Dommen J. , Weingartner E. , Wehrle G. , Gysel M. , Laborde M. , Baltensperger U.
Published: June 2010

Abstract. Diesel particulate matter (DPM) is a significant source of aerosol in urban areas and has been linked to adverse health effects. Although newer European directives have introduced increasingly stringent standards for primary PM emissions, gaseous organics emitted from diesel cars can still lead to large amounts of secondary organic aerosol (SOA) in the atmosphere. Here we present results from smog chamber investigations characterizing the primary organic aerosol (POA) and the corresponding SOA formation at atmospherically relevant concentrations for three in-use diesel vehicles with different exhaust aftertreatment systems. One vehicle lacked exhaust aftertreatment devices, one vehicle was equipped with a diesel oxidation catalyst (DOC) and the final vehicle used both a DOC and diesel particulate filter (DPF). The experiments presented here were obtained from the vehicles at conditions representative of idle mode, and for one car in addition at a speed of 60 km/h. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was used to measure the organic aerosol (OA) concentration and to obtain information on the chemical composition. For the conditions explored in this paper, primary aerosols from vehicles without a particulate filter consisted mainly of black carbon (BC) with a low fraction of organic matter (OM, OM/BC<0.5), while the subsequent aging by photooxidation resulted in a consistent production of SOA only for the vehicles without a DOC and with a deactivated DOC. After 5 h of aging ~80% of the total organic aerosol was on average secondary and the estimated "emission factor" for SOA was 0.23–0.56 g/kg fuel burned. In presence of both a DOC and a DPF, primary particles with a mobility diameter above 5 nm were 300±19 cm−3, and only 0.01 g SOA per kg fuel burned was produced within 5 h after lights on. The mass spectra indicate that POA was mostly a non-oxidized OA with an oxygen to carbon atomic ratio (O/C) ranging from 0.097 to 0.190. Five hours of oxidation led to a more oxidized OA with an O/C range of 0.208 to 0.369.
The utility of daily large-scale climate data in the assessment of climate change impacts on daily streamflow in California
Authors: Maurer E. P. , Hidalgo H. G. , Das T. , Dettinger M. D. , Cayan D. R.
Published: June 2010

Abstract. Three statistical downscaling methods were applied to NCEP/NCAR reanalysis (used as a surrogate for the best possible general circulation model), and the downscaled meteorology was used to drive a hydrologic model over California. The historic record was divided into an "observed" period of 1950–1976 to provide the basis for downscaling, and a "projected" period of 1977–1999 for assessing skill. The downscaling methods included a bias-correction/spatial downscaling method (BCSD), which relies solely on monthly large scale meteorology and resamples the historical record to obtain daily sequences, a constructed analogues approach (CA), which uses daily large-scale anomalies, and a hybrid method (BCCA) using a quantile-mapping bias correction on the large-scale data prior to the CA approach. At 11 sites we compared three simulated daily flow statistics: streamflow timing, 3-day peak flow, and 7-day low flow. While all downscaling methods produced reasonable streamflow statistics at most locations, the BCCA method consistently outperformed the other methods, capturing the daily large-scale skill and translating it to simulated streamflows that more skillfully reproduced observationally-driven streamflows.
An LMI approach to design observer for unknown inputs Takagi‐Sugeno fuzzy models
Authors: Chadli M.
Published: June 2010

This paper considers the design of an observer for a Takagi‐Sugeno (T‐S) fuzzy model subject to unknown inputs affecting states and outputs of the system simultaneously. Uncertainties affecting state matrices are also considered. Based on the Lyapunov method, sufficient conditions in Linear Matrix Inequalities (LMI) terms are proposed to design the given unknown input T‐S observer. In order to improve the performances of the proposed T‐S observer, the pole placement in an LMI region is also considered. An numerical example is given to illustrate the validity of the derived results.

Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
The JNK pathway modulates expression and phosphorylation of 4E‐BP1 in MIN6 pancreatic β‐cells under oxidative stress conditions
Authors: Tominaga Ryu , Yamaguchi Suguru , Satake Chihiro , Usui Masahiro , Tanji Yasuhiro , Kondo Keiichi , Katagiri Hideki , Oka Yoshitomo , Ishihara Hisamitsu
Published: June 2010

Stress‐mediated apoptosis may play a crucial role in loss of pancreatic β‐cell mass, contributing to the development of diabetes. We have recently identified that translational control involving the translational suppressor eIF4E binding protein‐1 (4E‐BP1) which is important for β‐cell survival under endoplasmic reticulum (ER) stress. The Eif4ebp1 gene, encoding 4E‐BP1, is a direct target of a transcription factor activating transcription factor‐4 (ATF4), a master regulator of gene expression in stress responses. In the current study, we investigated 4E‐BP1 expression in mouse insulinoma line 6 (MIN6) cells treated with arsenite, an inducer of oxidative stress which is another contributor of β‐cell loss. We found that arsenite‐induced 4E‐BP1 expression level was lower than that induced by thapsigargin, an ER stress inducer, although ATF4 was similarly induced by these agents. The ratio of the dephosphorylated form of 4E‐BP1, which has the highest activity, to phosphorylated forms was, however, greater in MIN6 cells treated with arsenite as compared to that in thapsigargin‐treated cells. Arsenite‐induced 4E‐BP1 mRNA and protein expressions were augmented by simultaneous treatment with a c‐Jun N‐terminal kinase (JNK) specific inhibitor, SP600125. The agent also suppressed the level of the dephosphrylated form of 4E‐BP1 in arsenite‐treated MIN6 cells. Thus, JNK activated by oxidative stress is involved in the modulation of 4E‐BP1 expression and phosphorylation in MIN6 cells, which may contribute to fine tuning of translational control under stress conditions. Copyright © 2010 John Wiley & Sons, Ltd.
Melatonin attenuates methotrexate‐induced oxidative stress and renal damage in rats
Authors: Abraham Premila , Kolli Viswa Kalyan , Rabi Suganthy
Published: June 2010

Nephrotoxicity is an adverse side effect of methotrexate (MTX) chemotherapy. The present study verifies whether melatonin, an endogenous antioxidant prevents MTX‐induced renal damage. Adult rats were administered 7 mg/kg body weight MTX intraperitoneally for 3 days. In the melatonin pretreated rats, 40 mg/ kg body weight melatonin was administered daily intraperitoneally 1 h before the administration of MTX. The rats were killed 12 h after the final dose of MTX/vehicle. The kidneys were used for light microscopic and biochemical studies. The markers of oxidative stress were measured along with the activities of the antioxidant enzymes and myeloperoxidase activity in the kidney homogenates. Pretreatment with melatonin reduced MTX induced renal damage both histologically and biochemically as revealed by normal plasma creatinine levels. Melatonin pretreatment reduced MTX induced oxidative stress, alteration in the activity of antioxidant enzymes as well as elevation in myeloperoxidase activity. The results suggest that melatonin has the potential to reduce MTX induced oxidative stress, neutrophil infiltration as well as renal damage. As melatonin is an endogenous antioxidant and is non‐toxic even in high doses it is suggested that melatonin may be beneficial in minimizing MTX induced renal damage in humans. Copyright © 2010 John Wiley & Sons, Ltd.
Speciation analysis of arsenic and selenium compounds by CE‐dynamic reaction cell‐ICP‐MS
Authors: Hsieh Meng‐Wei , Liu Chen‐Ling , Chen Jing‐Huan , Jiang Shiuh‐Jen
Published: June 2010

A dynamic reaction cell ICP‐MS was used as a CE detector for the speciation analysis of arsenic and selenium. Samples containing arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine, selenite, selenate, selenocysteine, selenomethione, and Se‐methylselenocysteine were subjected to electrophoretic separation before being introduced into the microconcentric nebulizer (CEI‐100) for their determination by ICP‐MS. The separation has been achieved in a 60 cm length×75 μm id fused‐silica capillary. The electrophoretic buffer used was 25 mmol/L CAPS, and 0.5 mmol/L SDS at pH 9.5, whereas the applied voltage was set at 25 kV. The potentially interfering 38Ar40Ar+ and 40Ar40Ar+ at the selenium masses m/z 78 and 80 were reduced in intensity by approximately three orders of magnitude by using 1.4 mL/min CH4 as reactive cell gas in the dynamic reaction cell. Arsenic was determined as the adduct ion 75As12CH at m/z 89. The LOD for arsenic and selenium was in the range of 0.6–1.8 ng/mL, and 0.5–1.4 ng/mL, respectively, based on peak height. This method has been applied to determine various arsenic and selenium compounds in NIST SRM 1633a Coal Fly Ash and NRCC DOLT‐3 Dogfish Liver reference materials and a selenium dietary supplement. The arsenic and selenium compounds were extracted from fish liver and dietary supplement by using Protease XIV and Lipase, and from coal fly ash with HF solution. The spike recoveries were in the range 91–103% for all the species studied.
Differentiation of organic goat's milk based on its hippuric acid content as determined by capillary electrophoresis
Authors: Carpio Azahara , Rodríguez‐Estévez Vicente , Sánchez‐Rodríguez Manuel , Arce Lourdes , Valcárcel Miguel
Published: June 2010

Organic foods have lately aroused interest by virtue of their quality and their essential, exclusive characteristics. In this study, we assessed the potential of CE to detect a marker that is able to identify the particular food given to the goats and develop an effective method to determine directly the most abundant organic acid in goat's milk (viz. hippuric acid). In addition, we examined the use of the hippuric acid content of goat's milk as a general marker for authenticating organic goat's milk. The feeding of these goats can be influenced by the time of the year. For this reason, we have collected samples from 20 conventionally fed goats and 20 organically fed goats over a period of 2 months. A threshold value dependent on the hippuric acid content was thus established for the first time with a view to discriminating between conventional and organic goat's milk. Organic acids in goat's milk were separated in a running buffer consisting of 120 mM sodium tetraborate decahydrate and 0.5 mM CTAB set to pH 8. The precision of the ensuing method is acceptable for hippuric acid; thus, the RSD for peak area and migration time was less than 10 and 4%, respectively. Also, calibration curves were linear throughout the studied concentration range.
Simultaneous determination of six non‐polar heterocyclic amines in meat samples by supercritical fluid extraction–capillary electrophoresis under fluorimetric detection
Authors: De Andrés Fernando , Zougagh Mohammed , Castañeda Gregorio , Ríos Angel
Published: June 2010

A novel, sensitive and selective method for the separation and quantification of a group of non‐polar heterocyclic amines (9H‐pyrido‐[3,4‐b] indole, norharmane; 1‐methyl‐9H‐pyrido‐[3,4‐b] indole, harmane; 2‐amino‐9H‐pyrido‐[2,3‐b] indole, AαC; 2‐amino‐3‐methyl‐9H‐pyrido‐[2,3‐b] indole, MeAαC; 3‐amino‐1,4‐dimethyl‐5H‐pyrido‐[4,3‐b] indole, Trp‐P‐1 and 3‐amino‐1‐methyl‐5H‐pyrido‐[4,3‐b] indole, Trp‐P‐2) in commercial meat samples has been developed. This methodology is faster than others previously described. The method is based on the combination of a supercritical fluid extraction procedure, followed by the analysis of the extracted plug by CE with fluorescence detection. The supercritical fluid extraction procedure was optimized for the clean‐up of the samples and the extraction of the analytes. For the electrophoretic separation, the effect of composition, pH and concentration of buffer, organic modifier content, pressure and time of injection, capillary temperature and voltage applied were studied. A 10 mmol/L formic acid–ammonium formate–ACN (10%, v/v) solution at pH 1.5 was selected as the running electrolyte. With 5‐s hydrodynamic injection, linear responses in the range from 100 to 1000 ng/mL and detection limits ranging from 15.9 to 28.1 ng/mL were obtained for different amines in less than 13 min. ACN–water (1:1 in volume) was used as a sample solvent. Fluorescence detection enhances the sensitivity and avoids interferences coming from non‐fluorescent compounds present in the matrices of the sample extracts.
Normal biventricular function, volumes, and mass in children aged 8 to 17 years
Authors: Robbers‐Visser Daniëlle , Boersma Eric , Helbing Willem A.
Published: June 2010

Purpose

To assess normal values for biventricular function, volumes, and mass with current cardiovascular magnetic resonance (CMR) imaging sequences in children.

Materials and Methods

Included in the study were 60 healthy children aged 8–17 years. A short axis set of contiguous slices was acquired with CMR imaging employing steady‐state free precession. Biventricular end‐diastolic volume (EDV), end‐systolic volume (ESV), ejection fraction (EF), and mass were determined. Uni‐ and multivariate linear regression analyses were performed to study the interrelation of age, gender, and body surface area (BSA) on biventricular volumes and mass. The coefficient of variation was calculated for intra‐ and interobserver variability.

Results

EF did not differ between boys and girls (mean LV‐EF 69 ± (SD) 5%, mean RV‐EF 65 ± 5%). BSA had good (EDV, mass) and modest (ESV) correlation with biventricular measurements. Gender appeared a significant modifier of these relations, whereas age had no independent contribution. The intra‐ and interobserver coefficient of variation was in the range 2.1%–13.9% for biventricular EDV, ESV, and mass.

Conclusion

This study reveals gender‐specific normative data for biventricular function, volumes, and mass in children age 8–17 years that can be used as reference data in the follow‐up of pediatric cardiac patients. J. Magn. Reson. Imaging 2009;29:552–559. © 2009 Wiley‐Liss, Inc.
Dynamic birefringence of polyolefins
Authors: Sasaguri K. , Stein R. S.
Published: June 2010

The use of the dynamic birefringence method was extended to the study of the relationship between structural changes and mechanical properties for polyethylene, atactic and isotactic polypropylene, and polybutene‐1. The phase angle between birefringence and strain was measured which permitted the resolution of the strain‐optical coefficient into real and imaginary parts. The real and imaginary parts of the dynamic relaxation modulus were also measured and compared with the optical data. Results for the crystalline polymers were interpreted in terms of the two‐stage mechanism of deformation, involving spherulite deformation followed by internal crystalline reorientation. For the atactic polymer, the viscoelastic flow of amorphous regions contributes to the birefringence. The temperature dependence of birefringence and stress is similar for this mechanism but not for the crystalline contribution.
Differential thermal analysis of synthetic fibers
Authors: Schwenker Robert F. , Zuccarello Robert K.
Published: June 2010

The application of differential thermal analysis (DTA) for the characterization and the investigation of the thermal degradation of synthetic textile fibers, to include polyester, nylon 6, propropylene, and polytetrafluoroethylene fibers, has been studied. The temperature range was from 50 to 650°C. using laboratory‐built DTA apparatus. Experimental considerations and techniques are discussed and such variables as sample preparation, size, cell packing, atmosphere control, and heating rate have been investigated. The conventional technique of grinding or milling DTA samples is shown to cause significant changes in certain samples, particularly in undrawn fibers. The control of sample atmosphere by dynamic gas flow through the sample cell gave peaks that were generally sharper and larger than those found when control was by gas diffusion. Data are given on the various low temperature transitions found in such fibers. Significant differences in low temperature transitions were observed between polypropylene fiber and the bulk polymer as well as between drawn and undrawn nylon 6 fibers. The interpretation of the DTA curves for the decomposition and other reactions at elevated temperatures is discussed. Nylon 6 and polypropylene showed only endothermic reactions indicative of depolymerization processes whereas other fibers showed both endothermic and exothermic reactions in the decomposition range.
Crystallization of polypropylene measured by differential thermal analysis
Authors: Donald H. J. , Humes E. S. , White L. W.
Published: June 2010

The crystallization of polypropylene has been studied by DTA in a linear thermal gradient type furnace. The crystallization rate was found to be linear with temperature, and the rate data were correlated on an Arrhenius type plot. The rate of crystallization of the low molecular weight fraction was lower at the same temperature than the rate for a higher molecular weight fraction.