bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rates and patterns of estuarine sediment accumulation
Authors: Brush Grace S. 
Published: April 2010

Estuarine sedimentation rates are estimated for vertical increments of sediment cores by adjusting average rates between dated horizons with the ratio of pollen concentration to concentration of sediment. The method assumes independent influxes of pollen and sediment into the estuary, similar patterns of transport and deposition for both pollen and fine sediment, a uniform influx of pollen over the time interval between dated horizons, and preservation of the majority of pollen entering the estuary.Comparisons of detailed, pollen‐derived sedimentation rates with historical records of climatic and anthropogenic events in upper Chesapeake Bay show that highest rates of sediment accumulation occur in upper and middle stretches of tidal tributaries and coincide with major storms and periods of intensive land clearance when > 20% of total land area in a given watershed is deforested and under cultivation.
The upwelling light stream in natural waters
Authors: Kirk J. T. O. 
Published: April 2010

The upwelling light field in natural waters is of great importance for the appearance of the water bodies, for visibility of objects seen through the water, and for remote sensing of water properties. As a contribution to the understanding of this radiant flux, a study has been carried out by the Monte Carlo simulation technique of the behavior of photons scattered upward from the downwelling light stream within water bodies. Immediately after scattering the angular distribution of these photons is biased very much toward small angles to the horizontal. As a consequence, the rate of attenuation of this photon population as it travels upward is initially very high. With increasing distance upward the rate of attenuation progressively diminishes as the more horizontally traveling photons are selectively extinguished.The upwelling flux at any depth originates in upward scattering events at lower depths, mostly within quite small optical distances below the reference depth. A new parameter, κ(z), is defined which is the average upward vertical attenuation coefficient exhibited by all the upwelling photons received at depth z meters as they travel upward from their point of origin by upward scattering to depth z : κ is always Kd (vertical attenuation coefficient for downward irradiance in that water) and, to a reasonable approximation, κ ∼ 2.5Kd in the middle of the euphotic zone.The diffuse backscattering coefficient for the downwelling light stream is shown to be approximately equal to the irradiance reflectance for the downwelling light stream multiplied by (Kd + κ). This relationship is used to describe a new method for estimating the scattering coefficients of water bodies from irradiance data.
Effects of algae on the Secchi transparency of the southeastern Mediterranean Sea
Authors: Megard Robert O. , Berman Tom 
Published: April 2010

The mean transparency (37.5 m) measured by Secchi disk at “blue‐water” pelagic sampling stations in the southeastern Mediterranean Sea during 3 yr was greater than in most other seawater. Our measurements in the Mediterranean and those by others in the English Channel, Atlantic Ocean, and Pacific Ocean obey the Lambert‐Bouguer law if it is specified that transparency depends on the vertical attenuation coefficient for downward irradiance in the waveband of underwater sunlight that has lowest attenuance. Mean downward irradiance (±95% C.L.) at the depth where a Secchi disk disappears, calculated from 187 paired estimates of transparency and attenuation coefficients from these oceanic regions, is 22±1% of surface irradiance in this waveband. This value is significantly larger than the value (18%) that has been used widely since an early study by Poole and Atkins, who calculated attenuation coefficients incorrectly.As predicted by the Lambert‐Bouguer law, reciprocal transparency was proportional to the attenuation coefficient for the most‐penetrating waveband. Attenuance of this waveband and reciprocal transparency both increase linearly with increasing concentration of phytoplankton chlorophyll in pelagic water. Chlorophyll concentrations in pelagic Mediterranean water were very low (0.02–0.14 mg m−3), but attenuance by units of phytoplankton chlorophyll was about 10 times larger than in more productive seawater, probably because blue light was predominant and many of the phytoplankton were very small coccolithophorids (cell diameters <10 µm) with optically dispersive cell surfaces.Measurements of transparency by Secchi disk are as accurate and precise as estimates of attenuation coefficients calculated from irradiances measured at sea with photoelectric sensors. The Poole‐Atkins equation for transparency in terms of the waveband with lowest attenuance describes the variation of transparency as well as the Duntley‐Preisendorfer equation does. Much of the information needed for interpreting satellite ocean‐color imagery could be obtained very efficiently with closely spaced measurements of transparency from surface vessels during synoptic cruises.
Spectral reflectance and water quality of Adirondack mountain region lakes
Authors: Vertucci Frank A. , Likens Gene E. 
Published: April 2010

The reflectance properties of lakes in the Adirondack mountain region are described. Five distinct types of reflectance spectra are identified and related to differences in water quality. No relationship was found between reflectance and acidification status.A reflectance model based on literature absorbance and scattering cross‐sections of water, plant pigments, dissolved organic carbon (DOC), and suspended inorganic matter is used to generate reflectance spectra of each reflectance type. Use of a variable Q factor during the conversion of remotely sensed reflectance to irradiance reflectance improves the correspondence between measured and modeled irradiance reflectance spectra. Comparison of measured reflectance with model reflectance also demonstrates the importance of small concentration changes as well as the interactive influence of plant pigments, DOC, and suspended material on lake color.Correlograms depict the wavelength‐dependent relationships between reflectance and water quality. Plant pigments, DOC, and suspended material are negatively correlated with reflectance from 400 to 600 nm and positively correlated from 600 to 750 nm; parameters associated with lake acidification, pH, alkalinity, and aluminum concentrations are poorly correlated with reflectance. Adirondack lakes exhibit a high degree of covariance between pigment, DOC, and suspended matter concentrations.Regression models predicting total pigments and DOC are developed which suggest that these parameters can be estimated remotely in these lakes, but remote estimation of pH, alkalinity, and aluminum is not possible with reflectance measures. A regression model estimating total pigments from the reflectance ratio of 525 : 554 nm is similar in slope and accuracy to one derived for the Coastal Zone Color Scanner (CZCS) for coastal marine waters. However, neither of the “recommended” CZCS pigment algorithms perform best with the Adirondack lake reflectance and pigment data.
A bridge between ocean optics and microbial ecology
Authors: Yentsch Charles S. , Phinney David A. 
Published: April 2010

Phytoplankton cell size is believed to be closely regulated by the nutrient regime of water masses in the western North Atlantic Ocean. Since particle size affects attenuation of light in ocean water, we argue that a bridge between classical ocean optics and microbial ecology has formed whereby the physics of ocean color must include consideration of ecological factors important to the diversity of phytoplankton species.Observations of the specific absorption coefficient, a*, have been made during 10 oceanographic cruises in the western North Atlantic. The range in Chl a concentration for ocean samples from the various water masses in this region was 0.1–8.0 µg liter−1. Diffuse attenuation spectra of particles measured by a glass‐fiber filter technique show strong correlations between extracted chlorophyll and blue (440 nm) or red (670 nm) absorption. Of the two, a*440 is the most variable. Average specific absorption coefficients are calculated to be 0.049 m2 mg−1 at 440 nm and 0.028 at 670 nm, but both relationships are seen to be nonlinear. The nonlinearity observed is attributed to differences in cell size “packaging” within natural phytoplankton populations. Variation in cell size and a* are primarily related to the availability of nitrate‐N. In addition, other factors contribute to the variability in a*440, such as detritus and short wavelength UV‐absorbing pigments.
Determination of the cross‐section absorption coeffcient of individual phytoplankton cells by analytical flow cytometry
Authors: Perry Mary Jane , Porter Steven M. 
Published: April 2010

An empirical relationship between the cellular cross‐section absorption coefficient (σ) and the Chl a fluorescence of individual plankton cells was established. Chl a fluorescence of single cells was measured in a flow cytometer with 488‐nm argon‐ion laser excitation. Absorption by dilute suspensions of cells was measured spectrophotometrically and normalized to cell number for computation of σ(488) (m2 cell−1). At the high excitation irradiances characteristic of lasers, a constant proportion of photons absorbed by photosynthetic pigments was re‐emitted as Chl a fluorescence; a strong correlation was observed between absorption at 488 nm and Chl a fluorescence (r2 = 0.93; P ≪ 0.001). The regression predicted the total phytoplankton absorption coefficient [aphyt(488) (m−1)] at 488 nm for mixtures of five monospecific cultures with <9% error. For field samples, discrepancies between the flow cytometric method and the filter pad spectrophotometric method for estimating aphyt(488) were greater.Relatively large, rare phytoplankton cells accounted for a disproportionate percentage of total aphyt(488). The coherence between absorption at 488 nm and at other wavelengths was high and provides a basis for extrapolating from σ(488) to single‐cell absorption coefficients at all visible wavelengths. The single‐cell spectral absorption coefficients can be used to compute total in situ photon absorption for modeling light‐limited photosynthetic rates of individual phytoplankton cells in the ocean.
Greigite and the magnetic properties of sediments
Authors: Hilton J. 
Published: April 2010

X‐ray diffraction spectra of freeze‐dried sediments from a lake in the English Lake District positively identified the presence of greigite, a magnetic iron sulfide (Fe3S4) mineral. The sediments also show considerable loss of magnetic intensity when wet samples are allowed to oxidize. Several hypotheses have been proposed elsewhere to explain the intensity loss, but an assessment of the evidence suggests that oxidation of greigite is responsible in these sediments.Data from several lakes and from laboratory experiments are used to deduce the environmental requirements for greigite formation. These conditions of high labile C concentrations, good sources of labile Fe and S, and an oscillating oxycline depth in the sediments are likely to be found only in mono‐ or dimictic eutrophic lakes, estuaries, and salt marshes and are unlikely to be found in meromictic lakes, unstratified lakes, oligotrophic lakes, or deep‐sea sediments.
A comparison of the acidification efficiencies of nitric and sulfuric acids by two whole‐lake addition experiments
Authors: Rudd John W. M. , Kelly C. A. , Schindler D. W. , Turner M. A. 
Published: April 2010

The acidification efficiencies of nitric and sulfuric acids were compared for 5 yr by separate experimental additions of the acids to the partitioned north and south basins of Lake 302. In the epilimnion, nitric acid was 70% as efficient as sulfuric acid in reducing alkalinity. On a whole‐lake basis, acidification by nitric acid was about half as efficient as by sulfuric acid. In‐lake processes removed 70 and 57% of the added nitric and sulfuric acids.Before acidification, algal uptake and sediment SO42− uptake were of about equal importance in terms of in‐lake SO42− removal. NO3− was primarily removed by algal uptake and sedimentation. After acidification, algal uptake of NO3− and SO42− did not change, but rates of uptake in the sediments by bacterial processes increased and dominated in‐lake removal.Nitric acid acidified the north basin because the acid additions exceeded the capacity of all biological removal processes. Algal uptake and sedimentation of N could not increase in proportion to increases in NO3− because of P limitation. Sediment‐denitrification rates increased tremendously (∼40‐fold) but only removed a portion of the incoming NO3− because denitrification was limited by the rate of transport to the sediment‐water interface.
An investigation ofhydrogen peroxide chemistry in surface waters of Vineyard Sound with H218O2 and 18O2
Authors: Moffett James W. , Zajiriou Oliver C. 
Published: April 2010

18O‐labeled H2O2 and O2 have been used to determine absolute rates and pathways of peroxide formation and decay processes in surface waters of a coastal marine site. Reactions were followed by incubating seawater samples with 18O2 or H218O2 and following the chemical transformation of the isotope label.Decomposition of H218O2 was dominated by biological processes and led to the formation of 18O2 and H218O; the product distribution indicates that 65–80% of the decay was due to catalase with 20–35% due to peroxidase activity. Photochemical oxidation of H218O2 to 18O2 was also observed.Particle‐dependent, light‐independent peroxide production was also observed in freshly collected samples, with rates ranging from 0.8 to 2.4 nM h−1 . These rates are low relative to photochemical production rates in surface waters, but may be important under conditions of low light intensity. Experiments with a metabolic inhibitor suggest that at least some of this production was biologically mediated. However, there was no evidence for light‐dependent biological production.
Alkalinities of Maine lakes: Are they really changing?
Authors: Staufferl Robert E. 
Published: April 2010

Alkalinity changes between 1938–1944 and 1985 were evaluated for Maine lakes (zmax ≳ 15 m) in granitic watersheds. Modern (late summer 1985) Gran alkalinities for the hypolimnion were compared with historical alkalinities computed using:

urn:x-wiley:00243590:media:lno19903561238:lno19903561238-math-0001

where pH(T) is the historic reported colorimetric pH at each hypolimnetic sampling depth and temperature, pK'1(T) the temperature‐dependent negative logarithm of the first dissociation constant for carbonic acid, and H2CO3* represents initial CO2 at last spring overturn, plus the change in CO2 associated with the hypolimnetic oxygen deficit developed over summer (estimated from the historic oxygen data). With modern data for representative Maine lakes and historical (1932) data on dissolved gases reported for northern Wisconsin lakes, the apparent respiratory quotient relating ΔCO2 to ΔO2 = 0.92. The above model yields alkalinity estimates with a relative root‐mean‐square (RMS) error of ∼15%.The alkalinities of the Maine lakes have increased by 15–50 µeq liter−1 (>30%) since the original surveys. Lake alkalization is not the result of differences in antecedent weather, since abnormally dry weather predating 1942 would have acted to elevate alkalinities.
Seasonal spillover and varve formation in the Santa Barbara Basin, California
Authors: Reimers Clare E. , Lange Carina B. , Tabak Marialana , Bernhard Joan M. 
Published: April 2010

A temporal record of oxygen and NO3− concentrations in the bottom water of the Santa Barbara Basin indicates that outside waters spill over into the basin seasonally. It is proposed that an annual bottom‐water cycle leads ultimately to varve production.As evidence in support of a benthic mechanism for varve formation, we present results of surface sediment and pore‐water analyses, from box‐core collections during three seasons in 1988. The greater degree of bottom‐water oxygen depletion that occurs regularly in late summer and fall was coincident with a smaller pool of pore‐water Fe, penetration of ∑H2S up to the sediment‐water interface, maximal numbers of benthic Foraminifera, and bacterial mat growth. The latter was indicated by increases in concentrations of extractable ATP, organic C, and total N in sediments from the depth intervals 0–0.25 and 0.25–0.5 cm. The greatest numbers of siliceous phytoplankton skeletons were found on the sea floor soon after the late spring, surface‐water, Chl a maximum. This event coincides with additions of new and more‐oxygenated seawater to the deep basin.
Adaptive Internal Model Control with fractional order parameter
Authors: Ladaci S. , Loiseau J. J. , Charef A. 
Published: April 2010

AbstractIn this paper we have introduced as a model in the adaptive Internal Model Control (IMC) structure a fractional order system to obtain a fractional adaptive IMC scheme. We have shown that this adaptive control scheme always provides theoretical guarantees of stability when a stable fractional order transfer function is used as an IMC parameter and that the use of this fractional IMC parameter can improve the performances of the control system along with its robustness against noises. A comparative simulation example is given to illustrate the efficiency of the proposed fractional order adaptive control scheme. Copyright © 2010 John Wiley & Sons, Ltd.
Mechanisms, Kinetics, and Dynamics of Oxidation and Reactions on Oxide Surfaces Investigated by Scanning Probe Microscopy
Authors: Altman Eric I. , Schwarz Udo D. 
Published: April 2010

AbstractAdvances in scanning probe microscopies (SPM) have allowed the mechanisms and rates of adsorption, diffusion and reactions on surfaces to be characterized by directly observing the motions of the individual atoms and molecules involved. The importance of oxides as thermal and photocatalysts, chemical sensors, and substrates for epitaxial growth has motivated dynamical SPM studies of oxide surfaces and their formation. Work on the TiO2 (110) surface is reviewed as an example of how dynamic SPM studies have revealed unexpected interactions between adsorbates and defects that influence macroscopic reaction rates. Studies following diffusion, adsorption and phase transitions on bulk and surface oxides are also discussed. A perspective is provided on advanced SPM techniques that hold great promise for yielding new insights into the mechanisms and rates of elemental processes that take place either during oxidation or on oxide surfaces, with particular emphasis on methods that extend the time and chemical resolution of dynamical SPM measurements.
Nanoelectronic Biosensing of Dynamic Cellular Activities Based on Nanostructured Materials
Authors: Huang Yinxi , Chen Peng 
Published: April 2010

AbstractDetecting subtle cellular activities that occur dynamically as regulated temporally and spatially by molecular machinery is of obvious importance in fundamental biology as well as in drug discovery. Additionally, it demands fast and sensitive detection modality. The emerging nanoelectronic biosensors based on nanostructured materials have shown promising potential to resolve the dynamic biological processes of living cells with high sensitivity and high temporal and spatial resolution. Here, the recent advances in the nanoelectronic biosensing of regulated secretion of biomolecules and bioelectrical activities of ion channels using carbon nanotubes and silicon nanowires are briefly reviewed. The perspectives and key issues of future development are also discussed.
Hydrothermal Synthesis of Ionic Liquid [Bmim]OH‐Modified TiO2 Nanoparticles with Enhanced Photocatalytic Activity under Visible Light
Authors: Hu Shaozheng , Wang Anjie , Li Xiang , Wang Yao , Löwe Holger 
Published: April 2010

AbstractTiO2 nanocomposites modified with the ionic liquid [Bmim]OH are synthesized by a hydrothermal procedure. X‐ray diffraction, Zeta‐potential measurement, TEM, thermogravimetric analysis, photoluminescence, UV/Vis, FTIR, and X‐ray photoelectron spectroscopy are used to characterize the TiO2 nanocomposites. The TiO2 nanocomposites consist of pure anatase particles of about 10 nm. The modification of [Bmim]OH on the surface of the TiO2 particles extends the TiO2 absorption edge to the visible‐light region. The electrochemical redox potentials indicated that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of [Bmim]OH match well with the valence band (VB) and conduction band (CB) of the TiO2 semiconductor. [Bmim]OH‐modified TiO2 is much more active than pristine TiO2 under visible‐light irradiation in the photocatalytic degradation of methylene blue in aqueous solution. [Bmim]OH is chemically bonded to the surface TiOH of TiO2 particles rather than adsorbed on the surface. A possible mechanism for the photocatalysis is proposed.
Water Accessibility to the Binding Cleft as a Major Switching Factor from Entropy‐Driven to Enthalpy‐Driven Binding of an Alkyl Group by Synthetic Receptors
Authors: Matsumoto Sayaka , Iwamoto Hiroya , Mizutani Tadashi 
Published: April 2010

AbstractFree energy, enthalpy, and entropy changes in the binding of alkyl pyridines to water‐soluble zinc porphyrin receptors with varying accessibility of water to the binding cleft were determined to explain why the driving force of hydrophobic effects is enthalpic in some occasions and entropic in others. Zinc porphyrins bearing four alkyl pillars with terminal solubilizing poly(oxyethylene) (POE) chains of molecular weight of 750 (1), with eight alkyl pillars with terminal solubilizing POE chains of molecular weight of 350 (3), and with eight alkyl pillars with POE of molecular weight of 750 (4) had a binding cleft with decreasing water accessibility in this order as revealed by binding selectivity of imidazole/pyridine. Although all these porphyrins showed that the free energy of binding (−ΔGo) increases linearly as the alkyl group of the guest is lengthened (−ΔGo per CH2 was 2.6, 2.8, and 2.6 kJ mol−1 for 1, 3, and 4, respectively), the origin of the free energy gain was much different. Receptor 1 with the most hydrophilic binding site bound the alkyl group by an enthalpic driving force (4‐pentylpyridine favored over 4‐methylpyridine by ΔΔHo=−16.4 kJ mol−1), while receptor 4 with the most hydrophobic binding site by an entropic driving force (4‐pentylpyridine favored over 4‐methylpyridine by ΔΔSo=39.6 J K−1 mol−1). Receptor 3 showed intermediate behavior: both enthalpic and entropic terms drove the binding of the alkyl group with the enthalpic driving force being dominant. The binding site of the four‐pillared receptor (1) is open and accessible to water molecules, and is more hydrophilic than that of the eight‐pillared receptor (4). We propose that the alkyl chains of 1 are exposed to water to produce a room to accommodate the guest to result in enthalpy‐driven hydrophobic binding, whereas 4 can accommodate the guest without such structural changes to lead to entropy‐driven hydrophobic binding. Therefore, accessibility of water or exposure of the binding site to the water phase switches the driving force of hydrophobic effects from an entropic force to an enthalpic force.