bluuebunny/crossref_metadata_2025 huggingface dataset:
N : P stoichiometry and ontogeny of crustacean zooplankton: A test of the growth rate hypothesis
Authors: Main T. M. , Dobberfuhl D. R. , Elser J. J.
Published: May 2010

Recent studies have hypothesized that differences in elemental composition of zooplankton (N : P ratio) are related to differences in specific growth rate, as increased growth rate requires greater ribosomal RNA, which should result in increased %P and decreased N : P. This hypothesis was tested interspecifically using zooplankton taxa with different specific growth rates and intraspecifically using different ontogenetic stages within single species. Among all five species, growth rate was positively correlated with %N and %P and negatively correlated with N : P. However, %N increased only from ∼8% to ∼9% while %P varied fourfold across the observed range of growth rates, indicating that changes in %P drive the negative relationship between growth rate and N : P. Intraspecific comparisons showed that growth rate was positively related to %P and negatively related to N : P for Daphnia lumholtzi, but growth rate was unrelated to %P and N : P for D. magna and D. obtusa. Mean %P, %N, and N : P differed significantly among Daphnia spp. and among populations of Scapholebris mucronata and Bosmina longirostris. These data strongly support the growth rate hypothesis as an explanation for differences in body N : P in zooplankton and indicate that the biological stoichiometry of a rapid growth rate life‐history is phosphorus intensive.
Release and bioavailability of C, N, P Se, and Fe following viral lysis of a marine chrysophyte
Authors: Gobler Christopher J. , Hutchins David A. , Fisher Nicholas S. , Cosper Elizabeth M. , Saňudo‐Wilhelmy Sergio A.
Published: May 2010

The potential importance of the viral lysis of phytoplankton for nutrient and carbon cycling has been acknowledged, but no quantitative assessments of this phenomenon exist. Radiotracer experiments examined the release and bioavailability of C, N, P, Fe, and Se following viral lysis of the “brown tide” chrysophyte Aureococcus anophagefferens. Photochemical effects on the dissolved‐particulate partitioning and biological uptake of virally released elements were also investigated. Viral lysis of A. anophagefferens released 50% more C and Se than uninfected control cells to the dissolved phase, while N, P, and Fe remained in the particulate phase. There was a significant inverse correlation between A. anophagefferens and bacterial densities, as well as an increase in particulate organic nitrogen levels in cultures during viral lysis. These observations indicate that released dissolved organic matter supported bacterial growth and may be a pathway by which various elements are diverted in microbial food webs. Dissolved nutrients released by viral lysis were accumulated to varying degrees by natural assemblages of marine bacteria and cultured diatoms, and virally regenerated N and P relieved diatom nutrient limitation. During a 4‐wk incubation, 80% of C and P within cell lysis debris was released to the dissolved phase, likely due to bacterial activity. Photochemical degradation of cell lysis debris enhanced dissolved levels of Se (100%) and Fe (50%) and reduced total dissolved C by 15%. Photochemistry doubled the bioavailabiliity of virally released Se to diatoms, while decreasing the bioavailability of C to bacteria threefold. The viral lysis of an A. anophagefferens bloom in the field could release 40 µM dissolved organic carbon and rapidly transfer other released elements to bacteria. Such occurrences may significantly affect water column chemistry, species composition, and succession within marine plankton communities.
A validated model for daily variations in the flux, origin, and distribution of settling particles within lakes
Authors: Weyhenmeyer Gesa A. , Håkanson Lars , Meili Markus
Published: May 2010

We performed intensive sediment trap studies at different water depths and locations in nine Swedish lakes to determine the flux, distribution, and origin of settling particulate matter in the pelagic zone. From these data, we developed a dynamic model that includes important mechanisms controlling fluxes of autochthonous, allochthonous, and resuspended particles in lakes during both stratification and turnover. The data suggest that during the period of turnover, sediment resuspension is a function of direct wind/wave activities. During these periods, resuspended particles are quite evenly distributed in the water column. During stratification, however, particles in deeper lakes are enriched in the hypolimnion. We suggest that these particles are resuspended due mainly to internal water motions. The model describes how much and at which water depths material is resuspended, and how this material is distributed in the water column. This includes the process of sediment focusing. The model allows determination of sediment accumulation at different water depths and of the boundary between erosion, transportation, and accumulation of sediment. Furthermore, the model shows the time dependence of the flux and distribution of settling particles in relation to changes in wind speed. The model is driven by wind, stratification, and lake morphometric data that can be determined with good accuracy. Some coefficients describing particle dynamics are also needed, e.g. particle settling velocity, vertical water mixing velocity, and sediment resuspension rate. The most uncertain coefficients were subjected to sensitivity analyses. The model can explain differences over time in the flux, origin, and distribution of settling particles in different lakes. Because it has earlier been recognized that the flux and distribution of settling particles can be of great importance for the dispersal, burial, biouptake, and ecological effects of nutrients and contaminants, the model may provide valuable information for lake management.
Bacteria and digestive enzymes in the alimentary tract of Radix peregra (Gastropoda, Lymnaeidae)
Authors: Brendelberger Heinz
Published: May 2010

The extracellular digestive enzymes cellobiase and chitobiase were quantitatively determined in the esophagus, stomach, and intestine of Radix peregra. Although both enzymes had comparable Michaelis constants between 16 and 32 µM liter−1, the enzyme activities were significantly higher for cellobiase (2 nanoKatals [nKat] from the whole gut tract) than for chitobiase (0.3 nKat). As became evident after a treatment with antibiotics, chitobiase was provided by bacteria and cellobiase was synthesized in the digestive glands of the animals. A lysozyme assay indicated that R. peregra was able to digest bacterial food.
Impact of cell shape and chain formation on nutrient acquisition by marine diatoms
Authors: Pahlow Markus , Riebesell Ulf , Wolf‐Gladrow Dieter A.
Published: May 2010

Diatoms have evolved a multitude of morphologies, including highly elongated cells and cell chains. Elongation and chain formation have many possible functions, such as grazing protection or effects on sinking. Here, a model of diffusive and advective nutrient transport is used to predict impacts of cell shape and chain length on potential nutrient supply and uptake in a turbulent environment. Rigid, contiguous, prolate spheroids thereby represent the shapes of simple chains and solitary cells. At scales larger than a few centimeters, turbulent water motions produce a more or less homogeneous nutrient distribution. At the much smaller scale of diatom cells, however, turbulence creates a roughly linear shear and nutrients can locally become strongly depleted because of nutrient uptake by phytoplankton cells. The potential diffusive nutrient supply is greater for elongated than for spherically shaped cells of similar volume but lower for chains than for solitary cells. Although the relative increase in nutrient transport due to turbulence is greater for chains, single cells still enjoy a greater total nutrient supply in turbulent environments. Only chains with specialized structures, such as spaces between the cells, can overcome this disadvantage and even obtain a higher nutrient supply than do solitary cells. The model results are compared to laboratory measurements of nutrient uptake under turbulent conditions and to effects of sinking.
Different roles of pedogenic fulvic acids and aquagenic biopolymers on colloid aggregation and stability in freshwaters
Authors: Wilkinson Kevin J. , Joz‐Roland Anthony , Buffle Jacques
Published: May 2010

Carbohydrates have been shown to attain 25% of the organic matter pool during periods of high productivity in a small eutrophic lake. The chemical nature of the organic matter in the water column, as determined by its source, had an important influence on its role in the coagulation and aggregation of inorganic colloids. During periods of high productivity, inorganic colloids were observed to be depleted at depths of maximum polysaccharide concentrations. Furthermore, in field experiments, depletion rates of colloidal particles were correlated to the presence of aquagenic biopolymers. In controlled laboratory experiments, the coagulation rate of colloidal montmorillonite was increased in the presence of 2.0 or 4.0 mg C liter−1 of aquagenic biopolymers. Sedimentation also increased with increasing biopolymer concentrations (0–2.3 mg C liter−1). On the other hand, 0.1–6.3 mg C liter−1 of pedogenically derived fulvic acids were shown to stabilize colloidal solutions, in agreement with previous studies.
Phosphorus limitation and not light controls the extracellular release of allelopathic compounds by Trichormus doliolum (Cyanobacteria)
Authors: von Elert Eric , Jüttner Friedrich
Published: May 2010

The planktonic freshwater cyanobacterium Trichormus doliolum (Bharadw.) Komárek and Anagnostidis released secondary metabolites that strongly inhibited the growth of other cyanobacteria. The major allelopathic compound inhibited PS II‐mediated photosynthetic electron transport. The allelopathic compounds were released under P‐limited and replete exponential growth; the release of the major allelopathic compound, however, increased 30‐fold under P‐limited growth. Increased irradiance under P‐limited growth led tc elevated release of dissolved organic carbon, but there was no increase in release of the major allelopathic compound. This suggests that there are different control mechanisms for extracellular release of gross carbon and allelopathic secondary metabolices in T. doliolum. Allelopathic compounds released by T. doliolum grown under phosphorus limitation significantly reduced the growth of Anabaena variabilis even when the biomass of the latter was 20‐fold greater than that of T. doliolum. This suggests that under P limitation less abundant species can exert allelopathic effects on more abundant taxa.
Growth rates of three symbiotic corals in the Red Sea
Authors: Vago R. , Dubinsky Z. , Genin A. , Ben‐Zion M. , Kizner Z.
Published: May 2010

Growth rates of the hydrocoral Millepora dichotoma and the corals Acropora variabilis and Stylophora pistillata were studied by applying the buoyant weighing technique and statistical analysis. We found that M. dichotoma exhibited the slowest relative growth, whereas S. pistillata and A. variabilis were faster growers, with weight‐based doubling times of about 3, 1.2, and 1.3 yr, respectively. In the case of A. variabilis, as well as in bladed colonies of M. dichotoma, growth rate per unit weight was size independent, whereas in S. pistillata a clear positive correlation was found between the relative growth rates and the initial colony buoyant weights. M. dichotoma and A. variabilis demonstrated distinct seasonal growth oscillations (2‐month time lag with respect to the seasonal trend of the ambient water temperature). We conclude that the oscillations in the absolute growth rate of corals resulted from the seasonal changes in water temperature.
Intercomparison methods for satellite measurements of atmospheric composition: application to tropospheric ozone from TES and OMI
Authors: Zhang L. , Jacob D. J. , Liu X. , Logan J. A. , Chance K. , Eldering A. , Bojkov B. R.
Published: May 2010

Abstract. We analyze the theoretical basis of three different methods to validate and intercompare satellite measurements of atmospheric composition, and apply them to tropospheric ozone retrievals from the Tropospheric Emission Spectrometer (TES) and the Ozone Monitoring Instrument (OMI). The first method (in situ method) uses in situ vertical profiles for absolute instrument validation; it is limited by the sparseness of in situ data. The second method (CTM method) uses a chemical transport model (CTM) as an intercomparison platform; it provides a globally complete intercomparison with relatively small noise from model error. The third method (averaging kernel smoothing method) involves smoothing the retrieved profile from one instrument with the averaging kernel matrix of the other; it also provides a global intercomparison but dampens the actual difference between instruments and adds noise from the a priori. We apply the three methods to a full year (2006) of TES and OMI data. Comparison with in situ data from ozonesondes shows mean positive biases of 5.3 parts per billion volume (ppbv) (10%) for TES and 2.8 ppbv (5%) for OMI at 500 hPa. We show that the CTM method (using the GEOS-Chem CTM) closely approximates results from the in situ method while providing global coverage. It reveals that differences between TES and OMI are generally less than 10 ppbv (18%), except at northern mid-latitudes in summer and over tropical continents. The CTM method further allows for CTM evaluation using both satellite observations. We thus find that GEOS-Chem underestimates tropospheric ozone in the tropics due to possible underestimates of biomass burning, soil, and lightning emissions. It overestimates ozone in the northern subtropics and southern mid-latitudes, likely because of excessive stratospheric influx of ozone.
Explaining global surface aerosol number concentrations in terms of primary emissions and particle formation
Authors: Spracklen D. V. , Carslaw K. S. , Merikanto J. , Mann G. W. , Reddington C. L. , Pickering S. , Ogren J. A. , Andrews E. , Baltensperger U. , Weingartner E. , Boy M. , Kulmala M. , Laakso L. , Lihavainen H. , Kivekäs N. , Komppula M. , Mihalopoulos N. , Kouvarakis G. , Jennings S. G. , O'Dowd C. , Birmili W. , Wiedensohler A. , Weller R. , Gras J. , Laj P. , Sellegri K. , Bonn B. , Krejci R. , Laaksonen A. , Hamed A. , Minikin A. , Harrison R. M. , Talbot R. , Sun J.
Published: May 2010

Abstract. We synthesised observations of total particle number (CN) concentration from 36 sites around the world. We found that annual mean CN concentrations are typically 300–2000 cm−3 in the marine boundary layer and free troposphere (FT) and 1000–10 000 cm−3 in the continental boundary layer (BL). Many sites exhibit pronounced seasonality with summer time concentrations a factor of 2–10 greater than wintertime concentrations. We used these CN observations to evaluate primary and secondary sources of particle number in a global aerosol microphysics model. We found that emissions of primary particles can reasonably reproduce the spatial pattern of observed CN concentration (R2=0.46) but fail to explain the observed seasonal cycle (R2=0.1). The modeled CN concentration in the FT was biased low (normalised mean bias, NMB=−88%) unless a secondary source of particles was included, for example from binary homogeneous nucleation of sulfuric acid and water (NMB=−25%). Simulated CN concentrations in the continental BL were also biased low (NMB=−74%) unless the number emission of anthropogenic primary particles was increased or a mechanism that results in particle formation in the BL was included. We ran a number of simulations where we included an empirical BL nucleation mechanism either using the activation-type mechanism (nucleation rate, J, proportional to gas-phase sulfuric acid concentration to the power one) or kinetic-type mechanism (J proportional to sulfuric acid to the power two) with a range of nucleation coefficients. We found that the seasonal CN cycle observed at continental BL sites was better simulated by BL particle formation (R2=0.3) than by increasing the number emission from primary anthropogenic sources (R2=0.18). The nucleation constants that resulted in best overall match between model and observed CN concentrations were consistent with values derived in previous studies from detailed case studies at individual sites. In our model, kinetic and activation-type nucleation parameterizations gave similar agreement with observed monthly mean CN concentrations.
Insights into secondary organic aerosol formed via aqueous-phase reactions of phenolic compounds based on high resolution mass spectrometry
Authors: Sun Y. L. , Zhang Q. , Anastasio C. , Sun J.
Published: May 2010

Abstract. Recent work has shown that aqueous-phase reactions of phenolic compounds – phenol (C6H6O), guaiacol (C7H8O2), and syringol (C8H10O3) – can form secondary organic aerosol (SOA) at high yields. Here we examine the chemical characteristics of this SOA and its formation mechanisms using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-AMS), an Ion Chromatography system (IC), and a Total Organic Carbon (TOC) analyzer. The phenolic SOA are highly oxygenated with oxygen-to-carbon (O/C) ratios in the range of 0.80–1.06 and carbon oxidation states (=2×O/C-H/C) between −0.14 and +0.47. The organic mass-to-carbon (OM/OC) ratios determined by the HR-AMS (=2.21–2.55) agree well with values determined based on the SOA mass measured gravimetrically and the OC mass from the TOC analyzer. Both the O/C and OM/OC ratios of the phenolic SOA are similar to the values observed for ambient low-volatility oxygenated/secondary OA (LV-OOA). Oxalate is a minor, but ubiquitous, component of the SOA formed from all three phenolic precursors, accounting for 1.4−5.2% of the SOA mass, with generally higher yields in experiments with H2O2 added as an OH source compared to without. The AMS spectra show evidence for the formation of syringol and guaiacol dimers and higher oligomers via C-C and C-O coupling of phenoxyl radicals, which are formed through oxidation pathways such as abstraction of the phenolic hydrogen atom or OH addition to the aromatic ring. This latter pathway leads to hydroxylation of the aromatic ring, which is one mechanism that increases the degree of oxidation of the SOA products. Compared to direct photochemical reactions of the phenols, OH-initiated reactions favor the formation of smaller oxidation products but less dimers or higher oligomers. Two unique and prominent ions in the syringol and guaiacol SOA spectra, m/z 306 (C16H18O6+) and m/z 246 (C14H14O4+), respectively, are observed in ambient aerosols significantly influenced by wood combustion and fog processing. Our results indicate that cloud and fog processing of phenolic compounds, especially in areas with active biomass burning, might represent an important pathway for the formation of low-volatility and highly oxygenated organic species, which would remain in the particle phase after fog/cloud evaporation and affect the chemical and optical properties of atmospheric particles.
In situ measurements of molecular iodine in the marine boundary layer: the link to macroalgae and the implications for O3, IO, OIO and NOx
Authors: Huang R.-J. , Seitz K. , Buxmann J. , Pöhler D. , Hornsby K. E. , Carpenter L. J. , Platt U. , Hoffmann T.
Published: May 2010

Abstract. Discrete in situ atmospheric measurements of molecular iodine (I2) were carried out at Mace Head and Mweenish Bay on the west coast of Ireland using diffusion denuders in combination with a gas chromatography-mass spectrometry (GC-MS) method. I2, IO and OIO were also measured by long-path differential optical absorption spectroscopy (LP-DOAS). The simultaneous denuder and LP-DOAS I2 measurements were well correlated (R2=0.80) but the denuder method recorded much higher concentrations. This can be attributed to the fact that the in situ measurements were made near to macroalgal sources of I2 in the intertidal zone, whereas the LP-DOAS technique provides distance-averaged mixing ratios of an inhomogeneous distribution along the light-path. The observed mixing ratios of I2 at Mweenish Bay were significantly higher than that at Mace Head, which is consistent with differences in local algal biomass density and algal species composition. Above algal beds, levels of I2 were found to correlate inversely with tidal height and positively with the concentrations of O3 in the surrounding air, indicating a role for O3 in the production of I2 from macroalgae, as has been previously suggested from laboratory studies. However, measurements made ~150 m away from the algal beds showed a negative correlation between O3 and I2 during both day and night. We interpret these results to indicate that the released I2 can also lead to O3 destruction via the reaction of O3 with I atoms that are formed by the photolysis of I2 during the day and via the reaction of I2 with NO3 radicals at night. The results show that the concentrations of daytime IO are correlated with the mixing ratios of I2, and suggest that the local algae sources dominate the inorganic iodine chemistry at Mace Head and Mweenish Bay.
Parametric representation of the cloud droplet spectra for LES warm bulk microphysical schemes
Authors: Geoffroy O. , Brenguier J.-L. , Burnet F.
Published: May 2010

Abstract. Parametric functions are currently used to represent droplet spectra in clouds and to develop bulk parameterizations of the microphysical processes and of their interactions with radiation. The most frequently used parametric functions are the Lognormal and the Generalized Gamma which have three and four independent parameters, respectively. In a bulk parameterization, two parameters are constrained by the total droplet number concentration and the liquid water content. In the Generalized Gamma function, one parameter is specified a priori, and the fourth one, like the third parameter of the Lognormal function, shall be tuned, for the parametric function to statistically best fit observed droplet spectra. These parametric functions are evaluated here using droplet spectra collected in non-or slightly precipitating stratocumulus and shallow cumulus. Optimum values of the tuning parameters are derived by minimizing either the absolute or the relative error for successively the first, second, fifth, and sixth moments of the droplet size distribution. A trade-off value is also proposed that minimizes both absolute and relative errors for the four moments concomitantly. Finally, a parameterization is proposed in which the tuning parameter depends on the liquid water content. This approach significantly improves the fit for the smallest and largest values of the moments.
Atmospheric wet deposition of mercury and other trace elements in Pensacola, Florida
Authors: Landing W. M. , Caffrey J. M. , Nolek S. D. , Gosnell K. J. , Parker W. C.
Published: May 2010

Abstract. In an effort to understand and quantify the impact of local, regional, and far-distant atmospheric mercury sources to rainfall mercury deposition in the Pensacola, Florida watershed, a program of event-based rainfall sampling was started in late 2004. Modified Aerochem-Metrics wet/dry rainfall samplers were deployed at three sites in the region around the Crist coal-fired power plant and event-based samples were collected continuously for three years. Samples were analyzed for total Hg and a suite of trace elements including Al, As, Ba, Bi, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, La, Li, Mg, Mn, Na, Nb, Ni, P, Pb, Sb, Se, Si, Sn, Sr, Th, U, V, and Zn. Nutrients (ammonia and nitrate) and major anions (chloride and sulfate) were also measured on each sample. Multivariate statistical methods were used to sort these tracers into factors that represent potential source categories contributing to the rainfall chemistry. As, Hg, Sb, Se, Sn, and non sea-salt sulfate were all significantly correlated (R>0.6) with one factor which we interpret as an anthropogenic source term reflecting input from coal combustion throughout the southeastern US. Using ratios of total Hg to volatile elements, we estimate that 22–33% of the rainfall Hg results from coal combustion in the southeastern US with the majority coming from the global background.
Heterogeneity in pre-monsoon aerosol types over the Arabian Sea deduced from ship-borne measurements of spectral AODs
Authors: Kaskaoutis D. G. , Kalapureddy M. C. R. , Krishna Moorthy K. , Devara P. C. S. , Nastos P. T. , Kosmopoulos P. G. , Kambezidis H. D.
Published: May 2010

Abstract. Ship-borne sunphotometer measurements obtained in the Arabian Sea (AS) in the pre-monsoon season (18 April–10 May 2006) during a cruise campaign (ICARB) have been used to retrieve the Aerosol Optical Depth (AOD; τ) and the Ångström wavelength exponent (α). The continents surrounding the AS produce natural and anthropogenic aerosols that have distinctive influences on α and its spectral distribution. The α values were estimated by means of the least-squares method over the spectral bands 340–1020 nm and 340–870 nm. The spectral distribution of AOD in logarithmic co-ordinates could be fit using a 2nd order polynomial with higher accuracy in the wavelength band 340–1020 nm than in the 340–870 nm band. A polynomial fit analytically parameterizes the observed wavelength dependencies of AOD with least errors in spectral variation of α and yields accurate estimates of the coefficients (a1 and a2). The coarse-mode (positive curvature in the lnτλ vs. lnλ) aerosols are mainly depicted in the Northern part of the AS closely associated with the nearby arid areas while fine-mode aerosols are mainly observed over the far and coastal AS regions. In the study period the mean AOD at 500 nm is 0.25±0.11 and the α340-1020 is 0.90±0.19. The α340-870 exhibits similar values (0.92±0.18), while significant differences revealed for the constant terms of the polynomial fit (a1 and a2) proportionally to the wavelength band used for their determination. Observed day-to-day variability in the aerosol load and optical properties are direct consequence of the local winds and air-mass trajectories along with the position of the ship.
The effects of clouds and aerosols on net ecosystem CO2 exchange over semi-arid Loess Plateau of Northwest China
Authors: Jing X. , Huang J. , Wang G. , Higuchi K. , Bi J. , Sun Y. , Yu H. , Wang T.
Published: May 2010

Abstract. The impacts of clouds and atmospheric aerosols on the terrestrial carbon cycle at semi-arid Loess Plateau in Northwest China are investigated, by using the observation data obtained at the SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) site. Daytime (solar elevation angles of larger than 50°) NEE of CO2 obtained during the midgrowing season (July–August) are analyzed with respect to variations in the diffuse radiation, cloud cover and aerosol optical depth (AOD). Results show a significant impact by clouds and aerosols on the CO2 uptake by the grassland (with smaller LAI values) located in a semi-arid region, quite different from areas covered by forests and crops. The light saturation levels in canopy are lower, with a value of about 434.8 W m−2. Thus, under overcast conditions of optically thick clouds, the CO2 uptake increases with increasing clearness index, and a maximum CO2 uptake and light use efficiency of vegetation occur with the clearness index of about 0.37 and lower air temperature. Under other sky conditions the CO2 uptake decreases with the cloudiness but the light use efficiency is enhanced, due to increase in the fraction of diffuse PAR. Additionally, under cloudy conditions, changes in the NEE of CO2 also result from the interactions of many environmental factors, especially the air temperature. In contrast to its response to changes in solar radiation, the carbon uptake shows a negative response to increased AOD. The reason for the difference in the response of the semi-arid grassland from that of the forest and crop lands may be due to the difference in the canopy's architectural structure.
Characterizing aerosol transport into the Canadian High Arctic using aerosol mass spectrometry and Lagrangian modelling
Authors: Kuhn T. , Damoah R. , Bacak A. , Sloan J. J.
Published: May 2010

Abstract. We report the analysis of measurements made using an aerosol mass spectrometer (AMS; Aerodyne Research Inc.) that was installed in the Polar Environment Atmospheric Research Laboratory (PEARL) in summer 2006. PEARL is located in the Canadian high Arctic at 610 m above sea level on Ellesmere Island (80° N 86° W). PEARL is unique for its remote location in the Arctic and because most of the time it is situated within the free troposphere. It is therefore well suited as a receptor site to study the long range tropospheric transport of pollutants into the Arctic. Some information about the successful year-round operation of an AMS at a high Arctic site such as PEARL will be reported here, together with design considerations for reliable sampling under harsh low-temperature conditions. Computational fluid dynamics calculations were made to ensure that sample integrity was maintained while sampling air at temperatures that average −40 °C in the winter and can be as low as −55 °C. Selected AMS measurements of aerosol mass concentration, size, and chemical composition recorded during the months of August, September and October 2006 will be reported. During this period, sulfate was at most times the predominant aerosol component with on average 0.115 μg m−3 (detection limit 0.003 μg m−3). The second most abundant component was undifferentiated organic aerosol, with on average 0.11 μg m−3 detection limit (0.04 μg m−3). The nitrate component, which averaged 0.007 μg m−3, was above its detection limit (0.002 μg m−3), whereas the ammonium ion had an apparent average concentration of 0.02 μg m−3, which was approximately equal to its detection limit. A few episodes having increased mass concentrations and lasting from several hours to several days are apparent in the data. These were investigated further using a statistical analysis to determine their common characteristics. High correlations among some of the components arriving during the short term episodes provide evidence for common sources. Lagrangian methods were also used to identify the source regions for some of the episodes. These showed that the source regions for the two selected episodes were located in north-eastern North America and western Siberia. We believe the former is associated with sulfate emissions from motor vehicles, power plants and heavy industry. The latter coincides with the locations of the largest Russian oil and gas fields. These conclusions show that the Arctic is the destination for significant amounts of pollution from high- and mid-latitude industrial and resource activity.
Observations of Saharan dust microphysical and optical properties from the Eastern Atlantic during NAMMA airborne field campaign
Authors: Chen G. , Ziemba L. D. , Chu D. A. , Thornhill K. L. , Schuster G. L. , Winstead E. L. , Diskin G. S. , Ferrare R. A. , Burton S. P. , Ismail S. , Kooi S. A. , Omar A. H. , Slusher D. L. , Kleb M. M. , Reid J. S. , Twohy C. H. , Zhang H. , Anderson B. E.
Published: May 2010

Abstract. As part of the international project entitled "African Monsoon Multidisciplinary Analysis (AMMA)", NAMMA (NASA AMMA) aimed to gain a better understanding of the relationship between the African Easterly Waves (AEWs), the Sahara Air Layer (SAL), and tropical cyclogenesis. The NAMMA airborne field campaign was based out of the Cape Verde Islands during the peak of the hurricane season, i.e., August and September 2006. Multiple Sahara dust layers were sampled during 62 encounters in the eastern portion of the hurricane main development region, covering both the eastern North Atlantic Ocean and the western Saharan desert (i.e., 5–22° N and 10–35° W). The centers of these layers were located at altitudes between 1.5 and 3.3 km and the layer thickness ranged from 0.5 to 3 km. Detailed dust microphysical and optical properties were characterized using a suite of in situ instruments aboard the NASA DC-8 that included a particle counter, an Ultra-High Sensitivity Aerosol Spectrometer, an Aerodynamic Particle Sizer, nephelometer, and Particle Soot Absorption Photometer. The NAMMA dust observations showed relatively low particle number densities, ranging from 268 to 461 cm−3, but highly elevated volume density with an average at 45 μm3 cm−3. NAMMA dust particle size distributions were well represented by tri-modal lognormal regressions. The estimated volume median diameter (VMD) is averaged at 2.1 μm with a small range of variation regardless of the vertical and geographical sampling locations. The absorption coefficient measurements exhibited a strong wavelength dependence for absorption but a weak one for scattering. The single scattering albedo was estimated at 0.97±0.02. Closure analyses showed that observed scattering and absorption coefficients are highly correlated with those calculated from spherical Mie-Theory and observed dust particle size distributions. The imaginary part of the refractive index for Sahara dust was estimated at 0.0022, with a range from 0.0015 to 0.0044. These values are generally consistent with literature values.
Flow tilt angles near forest edges – Part 2: Lidar anemometry
Authors: Dellwik E. , Mann J. , Bingöl F.
Published: May 2010

Abstract. A novel way of estimating near-surface mean flow tilt angles from ground based Doppler lidar measurements is presented. The results are compared with traditional mast based in-situ sonic anemometry. The tilt angle assessed with the lidar is based on 10 or 30 min mean values of the velocity field from a conically scanning lidar. In this mode of measurement, the lidar beam is rotated in a circle by a prism with a fixed angle to the vertical at varying focus distances. By fitting a trigonometric function to the scans, the mean vertical velocity can be estimated. Lidar measurements from (1) a fetch-limited beech forest site taken at 48–175 m a.g.l. (above ground level), (2) a reference site in flat agricultural terrain and (3) a second reference site in complex terrain are presented. The method to derive flow tilt angles and mean vertical velocities from lidar has several advantages compared to sonic anemometry; there is no flow distortion caused by the instrument itself, there are no temperature effects and the instrument misalignment can be corrected for by assuming zero tilt angle at high altitudes. Contrary to mast-based instruments, the lidar measures the wind field with the exact same alignment error at a multitude of heights. Disadvantages with estimating vertical velocities from a lidar compared to mast-based measurements are potentially slightly increased levels of statistical errors due to limited sampling time, because the sampling is disjunct, and a requirement for homogeneous flow. The estimated mean vertical velocity is biased if the flow over the scanned circle is not homogeneous. It is demonstrated that the error on the mean vertical velocity due to flow inhomogeneity can be approximated by a function of the angle of the lidar beam to the vertical and the vertical gradient of the mean vertical velocity, whereas the error due to flow inhomogeneity on the horizontal mean wind speed is independent of the lidar beam angle. For the presented measurements over forest, it is evaluated that the systematic error due to the inhomogeneity of the flow is less than 0.2°. The results of the vertical conical scans were promising, and yielded positive flow angles for a sector where the forest is fetch-limited. However, more data and analysis are needed for a complete evaluation of the lidar technique.
Femorotibial subchondral bone area and regional cartilage thickness: A cross‐sectional description in healthy reference cases and various radiographic stages of osteoarthritis in 1,003 knees from the Osteoarthritis Initiative
Authors: Frobell Richard B. , Nevitt Michael C. , Hudelmaier Martin , Wirth Wolfgang , Wyman Bradley T. , Benichou Olivier , Dreher Donatus , Davies Richard , Lee Jennifer H. , Baribaud Frédéric , Gimona Alberto , Eckstein Felix
Published: May 2010

Objective

To identify structural differences in total subchondral bone area (tAB) and cartilage thickness between healthy reference knees and knees with radiographic osteoarthritis (OA).

Methods

Baseline magnetic resonance images from 1 knee of 1,003 Osteoarthritis Initiative participants were studied: 112 healthy reference knees without radiographic OA, symptoms, or risk factors; 70 preradiographic OA knees (calculated Kellgren/Lawrence [K/L] grade 0/1); and 821 radiographic OA knees (calculated K/L grade ≥2). Means and standard (Z) scores (SD unit differences compared with normal subjects) of the tAB and regional cartilage thickness were assessed in the weight‐bearing femorotibial joint and compared between groups.

Results

In men, tAB was 8.2% larger in preradiographic OA knees and 6.6%, 8.1%, and 8.5% larger in calculated K/L grade 2, 3, and 4 radiographic OA knees, respectively, than in reference knees. In women, the differences were +6.8%, +7.3%, +9.9%, and +8.1%, respectively. The external medial tibia showed the greatest reduction in cartilage thickness (Z scores −5.1/−5.6 in men/women) with Osteoarthritis Research Society International medial joint space narrowing (JSN) grade 3, and the external lateral tibia (Z scores −6.0 for both sexes) showed the greatest reduction with lateral JSN grade 3. In all subregions of end‐stage radiographic OA knees, ≥25% of the average normal cartilage thickness was maintained. An overall trend toward thicker cartilage was found in preradiographic OA and calculated K/L grade 2 knees, especially in the external central medial femur.

Conclusion

tABs were larger in preradiographic OA and radiographic OA knees than in healthy reference knees, and the difference did not become larger with higher calculated K/L grades. Specific subregions with substantial cartilage thickening or thinning were identified in pre‐, early, and late radiographic OA.
Quill Embroidery: A Case Study in the Mechanics of Biological Materials
Authors: Weiss Ingrid M. , Kirchner Helmut O. K.
Published: May 2010

In quill embroidery, leather goods are beautified with patterns stitched with stripes of the cortex of peacock feathers. Our new structural, geometric and mechanical data for the tail cover feathers of the peacock allow an understanding of the mechanisms of embroidery. This study serves as an example of how biological materials can be analyzed like engineering materials, giving insight into the optimization processes during evolution.
Sol–Gel Derived Nanocomposites for Optical Applications
Authors: de Oliveira Peter W. , Becker‐Willinger Carsten , Jilavi Mohammad H.
Published: May 2010

This paper provides a selective description of the development of nanostructured materials and the fabrication of the devices for optical applications. Examples are interference coatings, refractive and diffractive lenses, and macro‐ and micro‐GRIN (graded refractive index) optical elements. Hybrid materials containing nanoparticles are of particular interest for the production of optical elements because, by exploiting the intrinsic solid state properties of the nanoparticles, nanocomposites can be tailored to exhibit the desired properties. A particular advantage of wet chemical processing lies in its great flexibility for depositing functional coatings.
Two novel diorganotin phosphonic diamides: syntheses, crystal structures, spectral properties and in vitro antibacterial studies
Authors: Gholivand Khodayar , Farshadian Sedigheh , Hosseini Zahra , Khajeh Khosro , Akbari Neda
Published: May 2010

Two diorganotin complexes with general formulae SnCl2(CH3)2[C6H5P(O)(NHCH(CH3)2)2]2 (1) and SnCl2(CH3)2[C6H5P(O) (NHC(CH3)3)2] (2) were prepared by the addition of one equivalent SnCl2Me2 to two equivalents of PhP(O)(NHiPr)2 and PhP(O)(NHtBu)2, respectively. The compounds were characterized by elemental analysis, IR and multinuclear NMR (1H, 13C, 31P and 119Sn) spectroscopy. The crystal structures of the complexes were determined by X‐ray single crystal analysis, which revealed that complex 1 has a distorted octahedral geometry and complex 2 has a distorted trigonal bipyramidal structure with non‐equivalent chlorine atoms. Preliminary antibacterial tests of the compounds against Gram‐positive and ‐negative bacteria were carried out using the filter paper disk method and chloroamphenicol was used as standard for comparison. Copyright © 2010 John Wiley & Sons, Ltd.
Molybdenum hexacarbonyl supported on amine modified multi‐wall carbon nanotubes: an efficient and highly reusable catalyst for epoxidation of alkenes withtert‐butylhydroperoxide
Authors: Moghadam Majid , Tangestaninejad Shahram , Mirkhani Valiollah , Mohammadpoor‐Baltork Iraj , Mirbagheri Naghmeh Sadat
Published: May 2010

In the present work, highly efficient epoxidation of alkenes catalyzed by Mo(CO)6supported on multi‐wall carbon nanotubes modified by 2‐aminopyrazine, APyz‐MWCNTs, is reported. The prepared catalyst was characterized by elemental analysis, scanning electron microscopy, FT IR and diffuses reflectance UV–vis spectroscopic methods. This new heterogenized catalysts, [Mo(CO)6@APyz‐MWCNT], was used as a highly efficient catalyst for epoxidation of alkenes withtert‐BuOOH. This robust catalyst was reused several times without loss of its catalytic activity. Copyright © 2010 John Wiley & Sons, Ltd.
Virtual humans elicit socially anxious interactants' verbal self‐disclosure
Authors: Kang Sin‐Hwa , Gratch Jonathan
Published: May 2010

We explored the relationship between interactants' social anxiety and the interactional fidelity of virtual humans. We specifically addressed whether the contingent non‐verbal feedback of virtual humans affects the association between interactants' social anxiety and their verbal self‐disclosure. This subject was investigated across three experimental conditions where participants interacted with real human videos and virtual humans in computer‐mediated interview interactions. The results demonstrated that socially anxious people revealed more information and greater intimate information about themselves when interacting with a virtual human when compared with real human video interaction, whereas less socially anxious people did not show this difference. We discuss the implication of this association between the interactional fidelity of virtual humans and social anxiety in a human interactant on the design of an embodied virtual agent for social skills' training and psychotherapy. Copyright © 2010 John Wiley & Sons, Ltd.
Transductive graph based cartoon synthesis
Authors: Yu Jun , Liu Dongquan , Seah Hock Soon
Published: May 2010

To reduce tedious works in cartoon animation, some computer‐assisted systems including automatic inbetweening and cartoon reusing systems have been proposed. In existing automatic inbetweening systems, accurate correspondence construction, which is a prerequisite for inbetweening, cannot be achieved. For cartoon reusing systems, the lack of efficient similarity estimation method and reusing mechanism makes it impractical for the users. The Transductive Graph based Cartoon Synthesis (TGCS) approach proposed in this paper aims at synthesizing smooth cartoons from the existing data. In this approach, the similarity between cartoon frames can be accurately evaluated by calculating the distance based on local shape context, which is rotation, and scaling invariant. According to the similarity, the label propagation based graph transduction method is adopted to generate cartoon clips, which is smoother than the clips generated by the shortest path method used in previous cartoon reusing approaches. Besides, the synthesized cartoon clips can be applied in accurate correspondence building, based on which the inbetweening method can be used to refine the results. Experimental results on our cartoon dataset suggest the effectiveness of the proposed approach for cartoon synthesis. Additional experiments on correspondence show our approach's performance on accurate correspondence building. Copyright © 2010 John Wiley & Sons, Ltd.
ChemInform Abstract: Theoretical Study on Clusters of Magnesium
Authors: Koehn Andreas , Weigend Florian , Ahlrichs Reinhart
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Structure of the SO2F‐ Anion, a Problem Case.
Authors: Lork Enno , Mews Ruediger , Viets Detlef , Watson Paul G. , Borrmann Tobias , Vij Ashwani , Boatz Jerry A. , Christe Karl O.
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: New Dion—Jacobson‐Type Layered Perovskite Oxyfluorides, ASrNb2O6F (A: Li, Na, and Rb).
Authors: Choy Jin‐Ho , Kim Jong‐Young , Kim Seung‐Joo , Sohn Joon‐Sung , Han Oc Hee
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Synthesis and Characterization of NaGaTe2O6×2.4H2O: A New Open‐Framework Tellurite Related to Zemannite.
Authors: Bhuvanesh N. S. P. , Halasyamani P. Shiv
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: The Quest for Beryllium Peroxides.
Authors: Berger Raphael J. F. , Hartmann Michael , Pyykkoe Pekka , Sundholm Dage , Schmidbaur Hubert
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: A Bose—Einstein Condensate of Metastable Atoms.
Authors: Robert A. , Sirjean O. , Browaeys A. , Poupard J. , Nowak S. , Boiron D. , Westbrook C. I. , Aspect A.
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Anhydrous Tin and Lead Hexacyanoferrates(II). Part 2. Electronic Structure and Chemical Bonding
Authors: Zhukov Vladlen P. , Zainullina Veronika M. , Zubkov Vladimir G. , Tyutyunnik Alexander P. , Denisova Tatiana A.
Published: May 2010

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Rubidium and Cesium Compounds with the Isopolyanion [Ta6O19]8‐ — Synthesis, Crystal Structures, Thermogravimetric and Vibrational Spectroscopic Analysis of the Oxotantalates A8[Ta6O19]×nH2O (A: Rb, Cs; n = 0, 4, 14).
Authors: Hartl Hans , Pickhard Frank , Emmerling Franziska , Roehr Caroline
Published: May 2010

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