bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrothermal‐vent alvinellid polychaete dispersal in the eastern Pacific. 1. Influence of vent site distribution, bottom currents, and biological patterns
Authors: Chevaldonne Pierre , Jollivet Didier , Vangriesheim Annick , Desbruyères Daniel
Published: May 2010

Deep‐sea hydrothermal‐vent habitats are typically linear, discontinuous, and short‐lived. Some of the vent fauna such as the endemic polychaete family Alvinellidae are thought to lack a planktotrophic larval stage and therefore not to broadcast‐release their offspring. The genetic evidence points to exchanges on a scale that seems to contradict this type of reproductive pattern. However, the rift valley may topographically rectify the bottom currents, thereby facilitating the dispersal of propagules between active vent sites separated in some cases by 10s of kilometers or more along the ridge axis. A propagule flux model based on a matrix of intersite distances, long‐term current‐meter data, and information on the biology and ecology of Alvinellidae was developed to test this hypothesis. Calculations of the number of migrants exchanged between two populations per generation (Nm) allowed comparisons with estimates obtained from genetic studies. Nm displays a logarithmic decrease with increasing dispersal duration and reaches the critical value of 1 after 8 d when the propagule flux model was run in standard conditions. At most, propagule traveling time cannot reasonably exceed 15–30 d, according to the model, whereas reported distances between sites would require longer lasting dispersal abilities. Two nonexclusive explanations are proposed. First, some aspects of the biology of Alvinellidae have been overlooked and long‐distance dispersal does occur. Second, such dispersal never occurs in Alvinellidae, but the spatial‐temporal dynamics of vent sites over geological timescales allows short‐range dispersal processes to maintain gene flow.
Methyl iodide production from marine phytoplankton cultures
Authors: Manley Steven L. , de la Cuesta John L.
Published: May 2010

Unialgal cultures of 15 species of marine phytoplankton were examined for the production of methyliodide (CH3I). CH3I production was quantified during log and stationary phases of phytoplankton growth in f/2 medium and compared to CH3I levels in control vessels. Significant increases in CH3I production were seen in five cultures. Phytoplankton CH3I production varied from a low of 10−4 amol CH3I cell−1 d−1 to a high of 8 × 10 3 amol CH3I cell−1 d−1. In three diatom cultures, the increase in total CH3I and cell‐based CH3I production rates were much higher during the log phase than during the stationary phase, even though the bacterial numbers continued to increase, supporting the premise of phytoplankton CH3I production. In two cultures, it was more difficult to distinguish between phytoplankton and bacterial production. Additional biotic and abiotic sources and sinks of CH3I were considered in the analysis, including bacterial consumption, chemical removal, and photochemical production. The only significant CH3I sink during the course of the experiment was its nucleophilic substitution with Cl−.
Charcoal analysis in marine sediments
Authors: Verardo David J.
Published: May 2010

A technique is described for measuring charcoal in small samples (5 mg) of marine sediments to quantify the contribution of charcoal to the total organic carbon loading of marine sediments. Charcoal is measured as elemental carbon by gas chromatography after acidification with hot concentrated nitric acid in situ within aluminum sample cups to remove calcium carbonate and refractory carbon such as coal, pollen, and humic acids. The in situ acidification eliminates sample loss during sequential decarboxylation and oxidation and provides a precise (±2.2% of the measured value) and rapid (~50 analyses per week per analyst) means to measure charcoal in marine sediments. The absolute detection limit of the charcoal determinations is 0.70 µg C (3 times mean blank value) and the relative detection limit is 0.01%.
Stable isotope studies on Mono Lake (California). 1. d18 in lake sediments as proxy for climatic change during the last 150 years
Authors: Li Hong‐Chun , Ku Teh‐Lung , Stott Lowell D. , Anderson Robert F.
Published: May 2010

Mono Lake is a hypersaline, alkaline lake in the Mono Basin located at the eastern base of the Californian Sierra Nevada. Its lake‐level history since 1912 has been recorded instrumentally, showing the decline of lake‐surface elevations initiated by the 1941 artificial diversion of stream inflow. We have made high‐resolution oxygen isotopic measurements on the total carbonate fraction of lake sediments and shown that the δ18O record parallels the lake‐level fluctuations rather well. The measurements were carried out on sediments that had been leached with deionized water to isolate the isotopic signals of the calcium carbonate from those of pore water and water‐soluble carbonate salts in the sediment. Extending the δ18O record back in time, we found that lake level changed markedly during the past 150 yr, reflecting climatic variations and resultant runoff fluctuations. Lake levels were high around 1845, 1880, and 1915 and low around 1860, 1900, and 1933. This study demonstrates that closed‐basin lake sediment δ18O provides an effective means of probing past precipitation variations in arid to semiarid regions such as the Great Basin in the western United States.
The role of photochemical degradation of dissolved organic carbon in regulating the UV transparency of three lakes on the Pocono Plateau
Authors: Morris Donald P. , Hargreaves Bruce R.
Published: May 2010

The role of photochemical degradation of dissolved organic carbon (DOC) on UV transparency (280–400 nm) was investigated in three Pocono Plateau lakes. Diffuse attenuation coefficients (KdUV) in the epilimnia of these lakes varied seasonally (39–81% decline from maximum Kd320nm), with minimum KdUV values occurring near summer solstice. Declines in KdUV corresponded to reductions in UV absorbance by dissolved material (adUV), caused by declines in both DOC concentration and UV (ad : [DOC]). The seasonal decline in KdUV was also accompanied by substantial increases in an absorption coefficient ratio (ad250nm : ad365nm) and decreases in spectral slopes (S).

Experimental studies of photochemical degradation were also performed using filtered lake water and natural sunlight. Exposure to solar radiation produced a number of changes in optical parameters and DOC that resembled those observed in the water column: adUV (−35 to −52%), UV absorptivity (−31 to −48%), ad250nm : ad365nm (0 to +39%), spectral slope, S (0 to −27%), and DOC concentration (0 to −20%).

Changes in adUV were correlated with absorbed UV dose. The derived rate constants were used in a model to estimate the contribution of photochemical degradation of DOC to water column declines in KdUV. Results suggest that rates of photochemical degradation were sufficient to account for the summer reductions in KdUV observed in the three lakes.
Effects of natural light on nitrogen cycling rates in the Mississippi River plume
Authors: Gardner Wayne S. , Cavaletto Joann F. , Cotner James B. , Johnson Jefsrey R.
Published: May 2010

Isotope‐dilution experiments with 15NH4+ were conducted on near‐surface water samples in the Mississippi River plume during May 1992 and July 1993 to quantify community cycling rates for ammnonium and determine whether regeneration rates are enhanced by light. Experiments done under natural light in May showed ranges of potential uptake and regeneration rates of 0–0.4 µM h−1 and 0–0.18 µM h−1. Samples collected offshore from the Atchafalaya River and the Southwest Pass of the Mississippi River in July yielded potential uptake rates of 0.4–1.8 µM h−1 under natural light vs. 0–0.45 µM h−1 in the dark. Ammonium regeneration rates ranged from 0.08 to 0.75 µM h−1 in the light and from 0.02 to 0.3 µM h−1 in the dark. The observed light/dark regeneration‐rate differences imply a close coupling between phytoplankton production and ammonium regeneration. The ratio of bacterial cell‐specific regeneration to uptake rates increased in the outer regions of the plume, indicating a changing contribution of bacterial‐sized organisms to nitrogen cycling processes in different regions of the plume.
Minor and trace element chemistry of Lake Baikal, its tributaries, and surrounding hot springs
Authors: Falkner K. Kenison , Church M. , Measures C. I. , Lebaron G. , Thouron D. , Jeandel C. , Stordal M. C. , Gill G. A. , Mortlock R. , Froelich P. , Chan L.‐H.
Published: May 2010

A Russian‐American fieldwork effort on Lake Baikal, its tributaries, and surrounding hot springs was undertaken in June–July 1991. Here we report on aspects of major ion (Ca2+, Mg2+, Alk, Cl−, SO42−) and several minor and trace element (Li isotopes, Sr isotopes, Ba, Al, V, Cr, Ni, Cu, Ge, Cd, Hg, U) cycles. Our riverine data for major ions generally concur with the more extensive, time‐averaged Russian database; for the most part the homogeneously distributed major ions appear to be at steady state and dominated by riverine throughputs in the lake. Exceptions include Mg2+, which may be removed to a small extent (≤ 15% of its riverine flux) by hydrothermal activity, and Na+ and Cl−, which seem to be impacted by pollution. Of the minor and trace elements, V also seems subject to anthropogenic disturbance. Other elements for which reliable data are available show conservative steady‐state distributions (Li, Cr, Sr) or are subject to redistribution and removal within the lake (Ge, Al, Cu, Ni, Ba, U) as a result of involvement in a variety of particle cycling processes that tend to obscure non‐natural influences. Chemical geothermometers for the four hot springs sampled (Smeyney, Khakuci, Kotelnikovski, Davsha) indicate subsurface reaction temperatures ranging from 70 to 150°C and converging to smaller ranges (±15°C) for a given spring. Both depletions (Mg, Ba, Cu, Ni, Sr, U) and enrichments (Na, K, Cl, Li, Al, Ge, Sr, U) with respect to lake water were observed. Ge levels in spring waters are sufficiently enriched over lake waters that Ge could serve as a useful tracer of subaquatic hydrothermal waters.
The cellular basis of divergent head morphologies in Daphnia
Authors: Beaton Margaret J. , Hebert Paul D. N.
Published: May 2010

Morphological defenses against predation in zooplankton result from targeted cell division and growth and provide unique opportunities for the integrated study of ecology and cell biology. This study examined the cellular basis of the various predator‐induced head shapes (neckteeth, spines, and helmets) in the cladoceran genus Daphnia. Several lines of evidence suggest that polyploid cells serve as developmental control centers to govern head shape. First, polyploid cells are present in the cephalic epidermis of Daphnia and their distribution seems to be linked to changes in head shape. For example, a strong correspondence exists between the position of polyploid cells and the presence of neckteeth. Second, variation in the number of polyploid cells seemsc linked to helmet size across members of the subgenus Ctenodaphnia and perhaps within Hyalodaphnia mendotae. Third, only among those species capable of producing spines or helmets were the DNA contents of epidermal polyploid cells routinely higher in the cephalic than in thoracic regions. Finally, mitotic activity in the cephalic epidermis of H. mendotae was concentrated in regions surrounding polyploid cells, suggesting that these cells serve as active developmental fields. This effect may be produced through the release of a mitogen, whose subsequent diffusion results in a chemical concentration gradient, with division rates of diploid cells varying in relationship to their position in this gradient.
Internal seiche climatology in a small lake where transversal and second vertical modes are usually observed
Authors: Roget E. , Salvadé G. , Zamboni F.
Published: May 2010

From the analysis of thermistor chain data recorded in a small elongated lake, compared with the results of numerical simulations, second vertical modes of the internal seiches are shown to be active during more than two‐thirds of the whole stratified period, although no resonance with the wind is observed. On the other hand, due to the wind pattern, transversal sciches (mainly the first vertical mode) are also usually excited and they sometimes dominate. At the end of the stratified period. however, when the thermocline is very sharp, first vertical modes—longitudinal and transversal—are the only ones that are excited. Finally, due to the wind, a forced oscillation of the whole lake is excited.
Zooplankton grazing and growth: Scaling within the 2‐2,‐μm body size range
Authors: Hansen Per Juel , Bjørnsen Peter Koefoed , Hansen Benni Winding
Published: May 2010

In order to study the size dependency of grazing and growth rates in zooplankton, data were collected from laboratory studies in the literature, covering both limnic and marine organisms. Data were obtained from about 60 species of nano‐, micro‐, and mesozooplankton, representing flagellates, ciliates, rotifers, meroplankton larvae, copepods, and cladocerans. Estimates of maximum ingestion and clearance were extracted from functional responses (ingestion rates as a function of food density) established from laboratory experiments. Maximum specific rates were expressed as a function of predator body volume. Maximum specific clearance and ingestion rates decreased with predator volume within each group of zooplankton, with a common exponent (scaling factor) of −0.23 (SE = ±0.12) in accordance with previous findings. However, significant differences were found between groups. In particular, among the protists, ciliates display maximum ingestion, growth, and clearance rates that exceed those of dinoflagellates by a factor of 2–4. Among the metazooplankton, calanoid copepods have maximum clearance rates that exceed those of filter‐feeding cladocerans and meroplankton larvae by a factor of 10. Because of these differences between the groups, the entire set of observations could not be fitted by an overall regression.
High-frequency urban measurements of molecular hydrogen and carbon monoxide in the United Kingdom
Authors: Grant A. , Stanley K. F. , Henshaw S. J. , Shallcross D. E. , O'Doherty S.
Published: May 2010

Abstract. High-frequency measurements of atmospheric molecular hydrogen (H2) and carbon monoxide (CO) were made at an urban site in the United Kingdom (UK) from mid-December, 2008 until early March, 2009. Very few measurements of H2 exist in the urban environment, particularly within the UK, but are an essential component in the assessment of anthropogenic emissions of H2 and to a certain extent CO. These data provide detailed information on urban time-series, diurnal cycles as well as sources and sinks of both H2 and CO at urban locations. High-frequency data were found to be strongly influenced by local meteorological conditions of wind speed and temperature. Diurnal cycles were found to follow transport frequency very closely due to the sites proximity to major carriageways, consequently a strong correlation was found between H2 and CO mole fractions. Background subtracted mean and rush hour molar H2/CO emission ratios of 0.53±0.08 and 0.57±0.06 respectively, were calculated from linear fitting of data. The scatter plot of all H2 and CO data displayed an unusual two population pattern, thought to be associated with a large industrial area 85 km to the west of the site. However, the definitive source of this two branch pattern could not be fully elucidated. H2 emissions from transport in the UK were estimated to be 188±39 Gg H2/yr, with 8.1±2.3 Tg/yr of H2 produced from vehicle emissions globally. H2 and CO deposition velocities were calculated during stable night-time inversion events when a clear decay of both species was observed. CO was found to have a much higher deposition velocity than H2, 1.3±0.8×10−3 and 2.2±1.5×10−4 m s−1 (1σ) respectively, going against the law of molecular diffusivity. The source of this unusual result was investigated, however no conclusive explanation was found for increased loss of CO over H2 during stable night time inversion events.
Multi-year (2004–2008) record of nonmethane hydrocarbons and halocarbons in New England: seasonal variations and regional sources
Authors: Russo R. S. , Zhou Y. , White M. L. , Mao H. , Talbot R. , Sive B. C.
Published: May 2010

Abstract. Multi-year time series records of C2-C6 alkanes, C2-C4 alkenes, ethyne, isoprene, C6-C8 aromatics, trichloroethene (C2HCl3), and tetrachloroethene (C2Cl4) from canister samples collected during January 2004–February 2008 at the University of New Hampshire (UNH) AIRMAP Observatory at Thompson Farm (TF) in Durham, NH are presented. The objectives of this work are to identify the sources of nonmethane hydrocarbons (NMHCs) and halocarbons observed at TF, characterize the seasonal and interannual variability in ambient mixing ratios and sources, and estimate regional emission rates of NMHCs. Analysis of correlations and comparisons with emission ratios indicated that a ubiquitous and persistent mix of emissions from several anthropogenic sources is observed throughout the entire year. The highest C2-C8 anthropogenic NMHC mixing ratios were observed in mid to late winter. Following the springtime minimums, the C3-C6 alkanes, C7-C8 aromatics, and C2HCl3 increased in early to mid summer, presumably reflecting enhanced evaporative emissions. Mixing ratios of C2Cl4 and C2HCl3 decreased by 0.7±0.2 and 0.3±0.05 pptv/year, respectively, which is indicative of reduced usage and emissions of these halogenated solvents. Emission rates of C3-C8 NMHCs were estimated to be 109 to 1010 molecules cm−2 s−1 in winter 2006. The emission rates extrapolated to the state of New Hampshire and New England were ~2–60 Mg/day and ~12–430 Mg/day, respectively. Emission rates of benzene, toluene, ethylbenzene, xylenes, and ethyne in the 2002 and 2005 EPA National Emissions Inventories were within ±50% of the TF emission rates.
Response of heterotrophic and autotrophic microbial plankton to inorganic and organic inputs along a latitudinal transect in the Atlantic Ocean
Authors: Martínez-García S. , Fernández E. , Calvo-Díaz A. , Marañón E. , Morán X. A. G. , Teira E.
Published: May 2010

Abstract. The effects of inorganic and/or organic nutrient inputs on phytoplankton and heterotrophic bacteria have never been concurrently assessed in open ocean oligotrophic communities over a wide spatial gradient. We studied the effects of potentially limiting inorganic (nitrate, ammonium, phosphate, silica) and organic nutrient (glucose, aminoacids) inputs added separately as well as jointly, on microbial plankton biomass, community structure and metabolism in five microcosm experiments conducted along a latitudinal transect in the Atlantic Ocean (from 26° N to 29° S). Primary production rates increased up to 1.8-fold. Bacterial respiration and microbial community respiration increased up to 14.3 and 12.7-fold respectively. Bacterial production and bacterial growth efficiency increased up to 58.8-fold and 2.5-fold respectively. The largest increases were measured after mixed inorganic-organic nutrients additions. Changes in microbial plankton biomass were small as compared with those in metabolic rates. A north to south increase in the response of heterotrophic bacteria was observed, which could be related to a latitudinal gradient in phosphorus availability. Our results suggest that organic matter inputs will result in a predominantly heterotrophic versus autotrophic response and in increases in bacterial growth efficiency, particularly in the southern hemisphere. Subtle differences in the initial environmental and biological conditions are likely to result in differential microbial responses to inorganic and organic matter inputs.
Exchange of reactive nitrogen compounds: concentrations and fluxes of total ammonium and total nitrate above a spruce canopy
Authors: Wolff V. , Trebs I. , Foken T. , Meixner F. X.
Published: May 2010

Abstract. Total ammonium (tot-NH4+) and total nitrate (tot-NO3−) provide chemically conservative quantities in the measurement of surface exchange of reactive nitrogen compounds ammonia (NH3), particulate ammonium (NH4+), nitric acid (HNO3), and particulate nitrate (NO3−), using the aerodynamic gradient method. Total fluxes were derived from concentration differences of total ammonium (NH3 and NH4+) and total nitrate (HNO3 and NO3−) measured at two levels. Gaseous species and related particulate compounds were measured selectively, simultaneously and continuously above a spruce forest canopy in south-eastern Germany in summer 2007. Measurements were performed using a wet-chemical two-point gradient instrument, the GRAEGOR. Median concentrations of NH3, HNO3, NH4+, and NO3− were 0.57, 0.12, 0.76, and 0.48 μg m−3, respectively. Total ammonium and total nitrate fluxes showed large variations depending on meteorological conditions, with concentrations close to zero under humid and cool conditions and higher concentrations under dry conditions. Mean fluxes of total ammonium and total nitrate in September 2007 were directed towards the forest canopy and were −65.77 ng m−2 s−1 and −41.02 ng m−2 s−1 (in terms of nitrogen), respectively. Their deposition was controlled by aerodynamic resistances only, with very little influence of surface resistances. Including measurements of wet deposition and findings of former studies on occult deposition (fog water interception) at the study site, the total N deposition in September 2007 was estimated to 5.86 kg ha−1.
Simulation of snow distribution and melt under cloudy conditions in an alpine watershed
Authors: Li H.-Y. , Wang J.
Published: May 2010

Abstract. An energy balance method and remote sensing data were used to simulate snow distribution and melt in an alpine watershed in Northwestern China within a complete snow accumulation-melt period. Spatial energy budgets were simulated using the meteorological observations and digital elevation model of the watershed. A linear interpolation method was used to discriminate daily snow cover area under cloudy conditions, using Moderate Resolution Imaging Spectroradiometer data. Hourly snow distribution and melt, snow cover extent, and daily discharge were included in the simulated results. The bias error between field snow water equivalent samplings and simulated results is −2.1 cm, and Root Mean Square Error is 33.9 cm. The Nash and Sutcliffe efficiency statistic (R2) between measured and simulated discharges is 0.673, and the volume difference (Dv) is 3.9%. Using the method introduced in this article, modeling spatial snow distribution and melt runoff will become relatively convenient.
The effects of clay dispersion on the mechanical, physical, and flame‐retarding properties of wood fiber/polyethylene/clay nanocomposites
Authors: Lee Yoon H. , Kuboki Takashi , Park Chul B. , Sain Mohini , Kontopoulou Marianna
Published: May 2010

In this study, nanosized clay particles were introduced into wood fiber/plastic composites (WPCs) to improve their mechanical properties and flame retardancy, which are especially important in various automotive and construction applications. A high degree of exfoliation for nanoclay in the wood fiber/high density polyethylene (HDPE) composites was successfully achieved with the aid of maleated HDPE (PE‐g‐MAn), through a melt blending masterbatch process. The structures and morphologies of the composites were determined using X‐ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. This article presents the effects of clay content and degree of clay dispersion on the mechanical and physical properties and flame retardancy of wood fiber/HDPE composites that contained a small amount of clay, in the range of 3–5 wt %. We concluded that achieving a higher degree of dispersion for the nanosized clay particles is critical to enhance the mechanical properties and the flame retardancy of WPCs when small amounts of clay are used. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Mass DSC/TG and IR ascertained structure and color change of polyacrylonitrile fibers in air/nitrogen during thermal stabilization
Authors: Sun Tongqing , Hou Yongping , Wang Haojing
Published: May 2010

The structure evolution was studied by mass spectrum (MS), differential scanning calorimetry (DSC) and thermogravimetry (TG), Fourier transform infrared (FTIR) spectroscopy. The results indicated that the CN and CC groups appeared gradually with the increase of the temperature in air and nitrogen. The CO groups appeared because of oxidative reaction in air. The CN, CC and CO groups were all chromophores. The effect of conjugated CN and CC on the absorption of the visible light was shifted to longer wavelengths and indicated π‐π* transition. There was a strong bathochromic effect as the number of CC bonds were increased. The effect of CO and –NH2 on the absorption of the visible light was shifted to longer wavelengths and indicated n‐π* transition. Oxygen could facilitate chemical reactions in air. Hence, the color of PAN in air was deeper than in nitrogen at the same temperature. The structural change of PAN in air was faster and more complex than in nitrogen. PAN fibers treated in air turned black after 230°C. However, PAN fibers turned black at 350°C in nitrogen. The MS and FTIR indicated that cyclization occurred before dehydrogenation during stabilization in air and nitrogen. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Flocculated decolorization of vinylsulfone reactive dye solutions with a β‐cyclodextrin‐based copolymer
Authors: Tian Xiuzhi , Wu Dan , Zhang Jing , Wang Shugen , Jiang Xue
Published: May 2010

A β‐cyclodextrin (β‐CD)‐based copolymer (β‐CD–maleic anhydride–N‐trimethylaminoethylmethacrylate chloride) with good thermal stability was designed and synthesized for flocculated decolorization of Reactive Brilliant Blue KN‐R solutions. Jar tests indicated that with the optimal stirring mode as 120 rpm for 5 min and then 40 rpm for 5 min with a flocculant‐to‐dye ratio of 2 : 5 (w/w), a pH of 8–10, and a temperature of 20°C, the maximum color removal reached. It is reported first in this article that, in addition to the polymer bridge and charge neutralization, the covalent bond of the reactive dye to the target flocculant molecules, which had a similar chemical structure to that of cellulose, contributed to the mechanism of flocculated decolorization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Mechanical properties and morphology of polylactide, linear low‐density polyethylene, and their blends
Authors: Singh Gursewak , Bhunia H. , Rajor Anita , Jana R. N. , Choudhary Veena
Published: May 2010

Melt blending of linear low density polyethylene (LLDPE) and polylactide (PLA) was performed in an extrusion mixer with post extrusion blown film attachment with and without compatibilizer‐grafted low density polyethylene maleic anhydride. The blend compositions were optimized for tensile properties as per ASTM D 882‐91. On the basis of this, LLDPE 80 [80 wt % LLDPE and 20 wt % poly(L‐lactic acid) (PLLA)] and MA‐g‐low‐density polyethylene 80/4 (80 wt % LLDPE, 20 wt % PLLA, and 4 phr compatibilizer) were found to be an optimum composition. The blends were characterized according to their mechanical, thermal, and morphological behavior. Fourier transform infrared spectroscopy revealed that the presence of compatibilizer enhanced the blend compatibility to some extent. The morphological characteristics of the blends with and without compatibilizer were examined by scanning electron microscopy. The dispersion of PLLA in the LLDPE matrix increased with the addition of compatibilizer. This blend may be used for packaging applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Starch esters with improved mechanical properties through melt compounding with nanoclays
Authors: Hassan Nejad Mehdi , Ganster Johannes , Volkert Bert
Published: May 2010

Biobased nanocomposites were manufactured through the melt intercalation of nanoclays and starch esters synthesized at the Fraunhofer Institute for Applied Polymer Research (IAP) from high amylose starch. Starch acetates (SAs) and starch propionates (SPs) were tested in combination with glycerol triacetate (triacetin) as a plasticizer for concentrations up to 30 and 20 wt %, respectively, with different types of organomodified and unmodified montmorillonites (MMTs). The mechanical properties of injection‐molded test bars were determined by a tensile experiment giving the strength, modulus, and elongation of the composites. X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) were used to study clay dispersion and intercalation/exfoliation. Dynamic mechanical analysis was used to track the temperature dependence of the storage modulus and tan δ behavior of the starch/clay hybrid. Because they were the best performing compositions, SP with 5 wt % plasticizer and SA with 20 wt % plasticizer were filled with 5 wt % nanoclay. For SP, a certain increase in modulus was observed for all clays. However, the strength was practically unchanged, and the elongation decreased in most cases. One exception was found for the 2.5 wt % organomodified clay composition, where the elongation increased. For SA, the addition of 5 wt % nanoclay always increased the strength and modulus, in one case up to 60 and 75%, respectively. In the particular case with 5 wt % unmodified clay, the strength, modulus, and elongation increased by 30, 40, and 1000%, respectively. This was a dramatic improvement in the ductility of the material without losses in the strength and stiffness. XRD and TEM revealed the existence of exfoliated modified clay throughout the starch matrix, whereas for the unmodified case (with the exceptional increase in the elongation), no intercalation was observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Solid‐state mechanical properties of polypropylene/nylon 6/clay nanocomposites
Authors: Somwangthanaroj A. , Ubankhlong W. , Tanthapanichakoon W.
Published: May 2010

The mechanical and thermomechanical properties as well as microstructures of polypropylene/nylon 6/clay nanocomposites prepared by varying the loading of PP‐MA compatibilizer and organoclay (OMMT) were investigated. The compatibilizer PP‐MA was used to improve the adhesion between the phases of polymers and the dispersion of OMMT in polymer matrix. Improvement of interfacial adhesion between the PP and PA6 phases occurred after the addition of PP‐MA as confirmed by SEM micrographs. Moreover, as shown by the DSC thermograms and XRD results, the degree of crystallinity of PA6 decreased in the presence of PP‐MA. The presence of OMMT increased the tensile modulus as a function of OMMT loading due to the good dispersion of OMMT in the matrix. The insertion of polymer chains between clay platelets was verified by both XRD and TEM techniques. The viscosity of the nanocomposites decreased as PP‐MA loading increased due to the change in sizes of PA6 dispersed phase, and the viscosity increased as OMMT loading increased due to the interaction between the clay platelets and polymer chains. The clay platelets were located at the interface between PP and PA6 as confirmed by both SEM and TEM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Thermal decomposition kinetics of azomethine oligomer and its some metal complexes
Authors: Doğan Fatih , Kaya İsmet , Bilici Ali , Saçak Mehmet
Published: May 2010

In our previous study, we presented the synthesis, characterization, and some physical properties of a new azomethine oligomer and its some metal complexes. This study focuses on the thermal decomposition kinetics of these reported materials. The studied compounds were 1,4‐bis[(2‐hydroxyphenyl)methylene]phenylenediamine, oligo‐1,4‐bis[(2‐hydroxyphenyl)methylene] phenylenediamine, and oligo‐1,4‐bis[(2‐hydroxyphenyl)methylene]phenylenediamine–metal complexes. Several kinetic methods based on a single heating rate such as Coats‐Redfern, MacCallum‐Tanner, van Krevelen, Horowitz‐Metzger, Wanjun‐Yuwen‐Hen‐Cunxin, and Madhusudanan‐Krishnan‐Ninan were used to elucidate the kinetic parameters of the decomposition processes. The parameters such as activation energy E, frequency factor A, reaction order n, entropy change ΔS*, enthalpy change ΔH*, and Gibbs free energy change ΔG* were calculated by means of the above methods. The activation energy values obtained by each method were in good agreement with each other. An appropriate mechanism for the thermal decomposition process of each material was also determined by means of the thermogravimetric analysis. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Aliphatic polyamidoamine hyperbranched polymers/layered silicate nanocomposites
Authors: Amin A. , Taha A. S. , Abd El‐Ghaffar M. A.
Published: May 2010

Polyamidoamine hyperbranched polymer (Hyp)/clay nanocomposites were synthesized by using both of montmorillonite and laponite clays. Poly amidoamine hyperbranched polymer (Hyp) was prepared by one‐pot polymerization via couple monomer methodology. Afterward, the amino ends of Hyp were modified with methyl methacrylate (MMA), styrene (St) and butyl methacrylate (n‐BuMA) polymers which were previously prepared via ATRP (atom transfer radical polymerization) to form the corresponding new hyperbranched polymers Hyp1, Hyp2 and Hyp3. Those formed polymers were inserted into the modified clay, such as montmorillonite and laponite to form their nanocomposites. The formed polymer/clay nanocomposites were characterized via XRD, TEM, and thermal analyses. The formed hyperbranched polymers generally showed intercalation behavior more than the exfoliation one mostly because of the bulkiness of the hyperbranched skeleton. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Controlling the architecture of nanofiber‐coated microfibers using electrospinning
Authors: Thorvaldsson Anna , Engström Jonas , Gatenholm Paul , Walkenström Pernilla
Published: May 2010

This study shows that electrospinning nanofibers onto single microfibers allows for careful tailoring of material properties that may suit a wide variety of applications. The nanofiber‐coated microfibers are created by electrospinning nanofibers alongside a microfiber toward a collector that rotates around the microfiber. This force the nanofibers to be collected around the microfiber, creating a hierarchical structure that can be modified at nano scale. In this study, control of nanofiber diameters, nanofiber alignment, and nanofiber loading was evaluated. It was seen that varying polymer concentration affected the nanofiber diameters, collecting the nanofiber‐coated microfibers at different speeds changed the degree of alignment of the nanofibers and that changing the polymer feeding rate affected the loading density of the nanofibers collected. The carefully designed nanofiber‐coated microfibers have great potential in creation of highly porous materials with tailored properties down to nano scale. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Simple method to determine flow characteristics of injectable hydrogels
Authors: Nadarajan Sundar Babu , Nguyen An , Kolb James Thomas , Stepanskiy Leonard , Papazoglou Elisabeth S.
Published: May 2010

This article presents a simple inexpensive method to measure flow and viscoelastic properties of calcium alginate hydrogels or gel solutions and is particularly suitable for quality control in small laboratory settings. This method can be considered an extension of the Melt Flow Index (MFI) method, which is routinely used in the polymer industry to indirectly determine the molecular weight of polymers. Results of alginate gels at various crosslinking densities obtained with this new test are compared to complex viscosity data obtained from a standard cone and plate rheometer, and demonstrate very good correlation. A mathematical model describing the apparent viscosity of the alginate gels in this test has also been developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Retracted: Isolation and chemical structure characterization of enzymatic lignin from Populus deltoides wood
Authors: Abdulkhani Ali , Karimi Alinaghi , Mirshokraie Ahmad , Hamzeh Yahya , Marlin Nathalie , Mortha Gerard
Published: May 2010

The following article from the Journal of Applied Polymer Science, “Isolation and chemical structure characterization of enzymatic lignin from Populus deltoides wood,” by Ali Abdulkhani, Alinaghi Karimi, Ahmad Mirshokraie, Yahya Hamzeh, Nathalie Marlin, and Gerard Mortha, published online on 21 May 2010 in Wiley Online Library (wileyonlinelibrary.com), and in Volume 118, pp. 469‐479, has been retracted by agreement between the authors, the journal's editors, and Wiley Periodicals, Inc. The retraction has been agreed due to unacknowledged overlap between Figure 5 in the above paper and Figure 1 in Industrial Crops and Products, Volume 30 (2009), p. 137, as well as inappropriate data manipulation associated with this figure. The publisher acknowledges that co‐authors Nathalie Marlin and Gerard Mortha are not responsible for the issues associated with this article.
Effect of organoclay reinforcement on the curing characteristics and technological properties of SBR sulphur vulcanizates
Authors: Diez J. , Bellas R. , Ramírez C. , Rodríguez A.
Published: May 2010

Styrene‐butadiene rubber (SBR) nanocomposites with different organoclay contents (up to 15 phr) were prepared by a melt compounding procedure, followed by a compression‐molding step in which the SBR matrix was sulfur crosslinked. The vulcanizates were characterized in respect to their curing, mechanical and viscoelastic properties, and thermal stability. The optimum cure time decreased with increasing organoclay content. This effect was attributed to the ammonium modifier present in the organoclay, which takes part in the curing reaction acting like an accelerator. The results of mechanical test on the vulcanizates showed that the nanocomposites presented better mechanical properties than unfilled SBR vulcanizate, indicating the nanoreinforcement effect of clay on the mechanical properties of SBR/organoclay nanocomposites. The addition of organoclay did not significantly change the glass transition temperature. However, the heights of tan δ value at the glass transition temperature for the nanocomposites are lower than that of the unfilled SBR. This suggests a strong interaction between the organoclay and the SBR matrix as the molecular relaxation of the latter is hampered. The temperature at which 50% degradation occurs (T50) and the temperature when the degradation rate is maximum (DTGmax) showed an improvement in thermal stability, probably related to the uniform dispersion of organoclay. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Impact behavior of hybrid composite plates
Authors: Sayer Metin , Bektaş Numan Behlül , Çallioğlu Hasan
Published: May 2010

This experimental study deals with the impact response of hybrid composite laminates. Two different hybrid composite laminates, aramid/glass and aramid/carbon, and two different stacking sequences, such as [0/0/90/90]A+ [90/90/0/0]G for AG1 and [0/90/±45]A+ [±45/90/0]G for AG2 and so on (see Table I), were chosen for impact testing. The impact energy was gradually increased until complete perforation took place, and an energy profiling method (EPM) was used to identify the perforation thresholds of composites. The damaged samples were visually inspected. The images of the several samples subjected to various impact energies were registered and used for comparison and identifying damage mechanisms. The perforation thresholds for [0/90/±45]s aramid/glass and aramid/carbon laminates were found to be approximately 5% higher than those for their counterparts with the [0/0/90/90]s stacking sequence. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Hypoxia‐inducible factor regulation of ANK expression in nucleus pulposus cells: Possible implications in controlling dystrophic mineralization in the intervertebral disc
Authors: Skubutyte Renata , Markova Dessislava , Freeman Theresa A. , Anderson D. Greg , Dion Arnold S. , Williams Charlene J. , Shapiro Irving M. , Risbud Makarand V.
Published: May 2010

Objective

Since nucleus pulposus cells reside under conditions of hypoxia, we determined if the expression of ANK, a pyrophosphate transporter, is regulated by the hypoxia‐inducible factor (HIF) proteins.

Methods

Quantitative reverse transcription–polymerase chain reaction and Western blot analyses were used to measure ANK expression in nucleus pulposus cells from rats and humans. Transfections were performed to determine the effect of HIF‐1/2 on ANK promoter activity.

Results

ANK was expressed in embryonic and mature rat discs. Oxygen‐dependent changes in ANK expression in nucleus pulposus cells were minimal. However, silencing of HIF‐1α and HIF‐2α resulted in increased ANK expression and up‐regulation of promoter activity. HIF‐mediated suppression of ANK was validated by measuring promoter activity in HIF‐1β–null embryonic fibroblasts. Under conditions of hypoxia, there was induction of promoter activity in the null cells as compared with the wild‐type cells. Overexpression of HIF‐1α and HIF‐2α in nucleus pulposus cells resulted in a significant suppression of ANK promoter activity. Since the ANK promoter contains 2 hypoxia‐responsive elements (HREs), we performed site‐directed mutagenesis and measured promoter activity. We found that HIF‐1 can bind to either of the HREs and can suppress promoter activity; in contrast, HIF‐2 was required to bind to both HREs in order to suppress activity. Finally, analysis of human nucleus pulposus tissue showed that while ANK was expressed in normal tissue, there was increased expression of ANK along with alkaline phosphatase in the degenerated state.

Conclusion

Both HIF‐1 and HIF‐2 serve as negative regulators of ANK expression in the disc. We propose that baseline expression of ANK in the disc serves to prevent mineral formation under physiologic conditions.
Phase‐Controlled Synthesis of Transition‐Metal Phosphide Nanowires by Ullmann‐Type Reactions
Authors: Wang Junli , Yang Qing , Zhang Zude , Sun Shouheng
Published: May 2010

Transition‐metal phosphide nanowires were facilely synthesized by Ullmann‐type reactions between transition metals and triphenylphosphine in vacuum‐sealed tubes at 350–400 °C. The phase (stoichiometry) of the phosphide products is controllable by tuning the metal/PPh3 molar ratio and concentration, reaction temperature and time, and heating rate. Six classes of iron, cobalt, and nickel phosphide (Fe2P, FeP, Co2P, CoP, Ni2P, and NiP2) nanostructures were prepared to demonstrate the general applicability of this new method. The resulting phosphide nanostructures exhibit interesting phase‐ and composition‐dependent magnetic properties, and magnetic measurements suggested that the Co2P nanowires with anti‐PbCl2 structure show a ferromagnetic–paramagnetic transition at 6 K, while the MnP‐structured CoP nanowires are paramagnetic with Curie–Weiss behavior. Moreover, GC‐MS analyses of organic byproducts of the reaction revealed that thermally generated phenyl radicals promoted the formation of transition‐metal phosphides under synthetic conditions. Our work offers a general method for preparing one‐dimensional nanoscale transition‐metal phosphides that are promising for magnetic and electronic applications.
How Post‐Translational Modifications Influence Amyloid Formation: A Systematic Study of Phosphorylation and Glycosylation in Model Peptides
Authors: Broncel Malgorzata , Falenski Jessica A. , Wagner Sara C. , Hackenberger Christian P. R. , Koksch Beate
Published: May 2010

A reciprocal relationship between phosphorylation and O‐glycosylation has been reported for many cellular processes and human diseases. The accumulated evidence points to the significant role these post‐translational modifications play in aggregation and fibril formation. Simplified peptide model systems provide a means for investigating the molecular changes associated with protein aggregation. In this study, by using an amyloid‐forming model peptide, we show that phosphorylation and glycosylation can affect folding and aggregation kinetics differently. Incorporation of phosphoserines, regardless of their quantity and position, turned out to be most efficient in preventing amyloid formation, whereas O‐glycosylation has a more subtle effect. The introduction of a single β‐galactose does not change the folding behavior of the model peptide, but does alter the aggregation kinetics in a site‐specific manner. The presence of multiple galactose residues has an effect similar to that of phosphorylation.
Electrophilicity versus Electrofugality of Tritylium Ions in Aqueous Acetonitrile
Authors: Horn Markus , Mayr Herbert
Published: May 2010

First‐order rate constants kw for the reactions of a series of donor‐substituted triphenylmethylium (tritylium) ions with water in aqueous acetonitrile have been determined photometrically at 20 °C using stopped‐flow and laser‐flash techniques. The rate constants follow the linear free energy relationship log k(20 °C)=s(N+E). The reactivities kw of the methyl‐ and methoxy‐substituted tritylium ions towards water correlate linearly with the corresponding pK values with a Leffler–Hammond coefficient α=δΔG≠/δΔG0 of 0.62. The amino‐substituted compounds react more slowly than expected from the correlation of the less stabilized systems. Quantum chemical calculations of tritylium ions and the corresponding triarylmethanols and 1,1,1‐triarylethanes have been performed at the MP2(FC)/6‐31+G(2d,p)//B3LYP/6‐31G(d,p) level. The calculated gas‐phase hydroxide and methyl anion affinities of the tritylium ions correlate linearly with a slope of unity, indicating that the relative anion affinities do not depend on the nature of the anion. The pK values of the methyl‐ and methoxy‐substituted tritylium ions correlate linearly with the calculated gas‐phase hydroxide affinities, and the slope of this correlation shows that the differences in carbocation stabilities in the gas phase are attenuated to 66 % in solution. Mono‐ and bis(dimethylamino)‐substituted derivatives deviate from this correlation; their pK values are higher than expected from their calculated gas‐phase hydroxide affinities, which is explained by the extraordinary solvation of unsymmetrically amino‐substituted tritylium ions. Complete free‐energy profiles for the solvolyses of substituted trityl benzoates in 90:10 (v/v) acetonitrile/water have been constructed.