bluuebunny/crossref_metadata_2025 huggingface dataset:
A model of growth and development in copepods
Authors: van den Bosch Frank , Gabriel Wilfried
Published: May 2010

We present a model for the growth and development of copepods based on the simple assumption that a constant fraction of assimilated carbon is invested in the formation of a new carapace. The individual molts into the next stage when the weight of the accumulated carapace building bricks is a fixed fraction of the body mass at the beginning of the stage. This simple stage‐transition coordinating system is built into an individual growth model.

The model predicts decreasing stage duration and increasing body weight with increasing food concentrations. These trends closely agree with published data. Anisochronality, as found in many copepod species, agrees with model predictions. Acartia species usually show isochronal development. The model predicts isochronal development for one particular value of a parameter of the feeding process. Literature data show that this parameter value is realistic for Acartia spp. “Equiproportionality” is predicted by the model. The model thus shows close agreement with observed growth and development patterns.
Settlement of oyster (Crassostrea virginica) larvae: Effects of water flow and a water‐soluble chemical cue
Authors: Turner E. J. , Zimmer‐Faust R. K. , Palmer M. A. , Luckenbach M. , Pentchef N. D.
Published: May 2010

Although previous evidence indicates that larvae of benthic marine invertebrates can respond to waterborne cues in still water, the importance of waterborne cues in mediating natural settlement out of flowing water has been questioned. Here, we summarize the results of flume experiments demonstrating enhanced settlement of oyster larvae in small target wells (circles of 7‐cm diam) with the release of a waterborne settlement cue compared to identical substrates without the cue. In concurrent still‐water experiments, more oyster larvae settled in solutions of waterborne cue than in seawater controls. Velocity and electrochemical measurements of a conservative tracer verified that at low flow velocities (2 and 6 cm s−1) with U* values <0.25 cm s−1, the waterborne cue was present above the targeted substrate to a height of ≤4 mm. Rapid vertical swimming or sinking in response to the waterborne cue can concentrate larvae in near‐bottom waters and enhance larval settlement. Our investigation provides the first experiimental evidence to demonstrate that dissolved chemical cues can mediate settlement by larvae under hydrodynamic conditions approaching those of natural benthic habitats.
Midwater zooplankton communities on pelagic detritus (giant larvacean houses) in Monterey Bay, California
Authors: Steinberg Deborah K. , Silver Mary W. , Pilskaln Cynthia H. , Coale Susan L. , Paduan Jennifer B.
Published: May 2010

The mucus feeding structures or “houses” of the giant larvacean Bathochordaeus provide abundant material for the study of deep sea detrital communities, particularly their poorly known zooplankton associates. We sampled houses between 100 and 500 m in Monterey Bay with a submersible ROV (remotely operated vehicle) and surveyed houses for metazoans by database search of video footage taken from the ROV. Up to an order of magnitude more metazoans were found on houses than in surrounding waters. On average, copepods constituted as much as 96% of the assemblage on houses, and many of the species possess benthiclike morphology and feeding strategies. Poecilostomatoid copepods (genus Oncaea) averaged as many as 64.6 house−1, and scarcely known calanoid copepods (genus Scopalatum) occurred in 56% of the samples. Higher numbers of metazoans occurred on shallower houses (100–300 m), likely due to a difference in the species of larvacean present and (or) to reduce oxygen levels at greater depths. At least one copepod species, Scopalatum vorax, occurred on houses more frequently during the non‐upwelling season, possibly due to the lack of other food. Our results suggest that midwater detritus contains a unique invertebrate community that has been largely undetected, mostly due to sampling difficulties. The houses also provide benthiclike habitats for midwater zooplankton and serve as feeding centers. These particle‐associated zooplankton may therefore contribute to remineralization of particulate organic carbon at depth.
Interspecific differences in the diel vertical migration of marine copepods: The implications of size, color, and morphology
Authors: Hays G. C. , Proctor C. A. , John A. W. G. , Warner A. J.
Published: May 2010

Samples collected by continuous plankton recorders (CPRs) between 1948 and 1992 were used to describe the diel vertical migration (DVM) behavior of 41 copepod taxa in the northeast Atlantic between 45 and 55°N and 11 and 31°W. A total of 13,622 samples, each representing ∼18.5 km (10 nm) of tow, were analyzed. Since CPRs are towed in near‐surface waters, taxa that exhibit DVM occur predominantly in samples taken at night. Larger taxa showed significantly stronger DVM, with body size explaining 47% of the intertaxa variation in DVM. For small taxa (<1 mm wide) the residual variation in DVM was correlated with carotenoid pigment levels but not with body morphology, with more heavily pigmented taxa exhibiting DVM. For larger taxa (>1 mm wide) the residual variation in DVM was correlated with body morphology but not with carotenoid pigment levels, with more elongate copepods not exhibiting DVM.
Retention of elements absorbed by juvenile fish (Menidia menidia, Menidia beryllina) from zooplankton prey
Authors: Reinfelder John R. , Fisher Nicholas S.
Published: May 2010

Radiolabeled copepods (Acartia spp.) were fed to juvenile silversides (Menidia menidia and Menidia beryllina) to study clement absorption in the fish. Copepods were reared from nauplii in the presence of different radiotracers (14C,109Cd, 57Co, 32P,35S,75Se, or 65Zn) and were analyzed for relative concentrations of these elements in their tissue fractions. Copepod exoskeletons contained nearly all of the trace metals (>97%), 60% of the Se, and less than half of the C, P, and S accumulated by the copepods. Within the nonexoskeleton tissues of the copepods, nonpolar (CHCl3 extractable) material contained 34 and 24% of the total C and P, but only 8 and 2% of the total S and Se

Absorption efficiencies of trace metals in juvenile silversides (2.7% for Cd, 2.1% for Co, 6.2% for Zn) were an order of magnitude lower than those for nonmetals (29% for Se, 50% for S and C, 60% for P). The absorption efficiencies in the juvenile silversides of all seven elements studied were directly related to the percent of each element in the nonexoskeleton fraction of the copepod prey, indicating that the fish absorbed the soft tissues of the copepods and egested the chitinous exoskeleton and its associated elements.
Evidence for a dome‐shaped relationship between turbulence and larval fish ingestion rates
Authors: MacKenzie Brian R. , Miller Thomas J. , Cyr Stéphane , Leggett William C.
Published: May 2010

Recent theoretical work suggests that small‐scale turbulence enhances encounter rates between larval fish and their prey. This finding has been extended to suggest that feeding rates will increase in turbulent environments. However, this extrapolation assumes that turbulence has no detrimental effects on post‐encounter behaviors (e.g. pursuit success). We develop an analytical model to estimate the probability that larval fish feeding in turbulent environments successfully pursue encountered prey. We show that the overall probability of feeding is a dome‐shaped function of turbulent velocity and that the height and location of the maxima depend on turbulence level and the behavioral characteristics of predator and prey. Highly turbulent conditions (e.g. storms) will reduce feeding rates below those which occur during calmer conditions and will affect the type of prey captured and ingested.
Temporal and spatial distribution of benthic microfauna in sediments of a gravel streambed
Authors: Schmid-Araya J. M.
Published: May 2010

Densities of microfauna (large heterotrophic flagellates and three ciliate size classes) inhabiting surface sediments and the hyporheic zone of a gravel‐bed brook were investigated at 14‐d sampling intervals between October 1991 and October 1992. Abundances of both flagellates and ciliates were higher in the hyporheic zone than in surface sediments. Flagellates were distributed at all depths over the sampling period, but densities were highest at 30–40‐cm depth before a spate in April 1992. Ciliate depth distribution also showed high densities from 10 to 40 cm in April 1992, and patches of high abundance occurred at 30–40 cm in summer 1992. Preliminary estimates of resilience suggested that flagellates were more resilient than ciliates and that large flagellate individuals and ciliates <50 µm in the hyporheic zone had higher resilience values than those in the streambed surface sediments. The combined effect of hydrophysical variables on flagellate and ciliate densities differed between microfauna inhabiting the surface of the streambed and the hyporheic zone.
Enhanced settlement on microtopographical high points by the intertidal red alga Halosaccion glandiforme
Authors: Johnson Ladd E.
Published: May 2010

The early colonization patterns of the red alga Halosaccion glandiforme (Gmel.) were examined on artificial substrata cast from molds of both real (e.g. barnacles) and model surfaces with and without surface “roughness” at the scale of 100–1,200 µm. Settlement over a 3‐d period was always at least 35 times higher on rough substrata than on smooth substrata. This difference was due to the high (84–98%) settlement of spores on the tips of individual small‐scale surface projections (i.e. the roughness elements). An outplanting experiment suggested that the greater abundance of sporelings on the tips of surface projections resulted from settlement processes rather than differential postsettlement mortality. When sporeling densities were compared at larger spatial scales (e.g. areas near the base of the substrata vs. areas near the top), they varied greatly on smooth substrata, with highest densities found near surface transitions (e.g. corners and edges). On rough surfaces, the sporelings were more evenly distributed among the various areas. Thus, smaller scale features (i.e. 100–1,200 µm) of the surface appear to be more important than larger scale features (1–2 cm) in determining the settlement of H. glandiforme.
Freshwater flow into a coastal embayment: Groundwater and surface water inputs
Authors: Millham Newton P. , Howes Brian L.
Published: May 2010

Freshwater discharge to a shallow coastal embayment was measured with two upland hydrologic and three embayment physical methods for 2 yr. Parallel measurements from the five methods ranged from 3,900 (±630) to 9,400 (±3,400) m3 d−1, and four of the methods showed close agreement and averaged 4,800 (± 670) m3 d−1. The most precise estimate of discharge was from a chloride balance, while the best understanding of the rate and pattern of groundwater flow was from a Darcian streamtube approach.

Groundwater dominated the freshwater budget, accounting for >95% of the total annual input, and was partitioned almost equally between direct seepage to embayment waters and seepage to a stream with final discharge via surface flow. Freshwater inputs decreased rapidly toward the mouth of the estuary and >80% entered into the upper half. The lack of fixed watershed boundaries resulted in large errors in both the location and area of the topographically defined watershed when compared to a watershed defined by water‐table mapping. Seasonal variations were found in both the boundaries of the watershed (8%) and in groundwater discharge (6‐fold) in response to changing water‐table gradients due to recharge. Hydrologic alterations of the upland through the import of water and the increased recharge from impermeable surfaces led to an apparent increase in the total freshwater discharge to the embayment of nearly 50% over “natural” levels.
Aquatic fulvic acids in algal‐rich antarctic ponds
Authors: McKnight Diane M. , Andrews Edmund D. , Spaulding Sarah A. , Aiken George R.
Published: May 2010

We isolated fulvic acids from two antarctic coastal ponds by means of preparative scale column chromatography with XAD‐8 resin. Both ponds are on Ross Island. Pony Lake at Cape Royds has abundant phytoplankton populations, and Feather Pond at Cape Bird has a luxuriant benthic algal mat. Neither site has higher plants in the watershed. The dissolved organic carbon (DOC) concentration in Pony Lake was very high, but the percentage of DOC accounted for by fulvic acid was low, as has been observed for other lakes with algal‐derived DOC sources. Fulvic acid from Pony Lake was more enriched in nitrogen than fulvic acid from Feather Pond, with a C: N atomic ratio of 13 in Pony Lake and a C: N ratio of 24 in Feather Pond. The [13C]NMR spectra for the coastal pond samples showed that the content of sp2‐hybridized carbon atoms (aromatic or olefinic) was only 16.5% of the total spectral area for Pony Lake and only 20.1% for Feather Pond.
Fluorometric analysis of chlorophyll a in the presence of chlorophyll b and pheopigments
Authors: Welschmeyer Nicholas A.
Published: May 2010

A fluorometric method is described which provides sensitive measurements of extracted chlorophyll a free from the errors associated with conventional acidification techniques. Fluorometric optical configurations were optimized to produce maximum sensitivity to Chl a while maintaining desensitized responses from both Chl b and pheopigments. Under the most extreme Chl b:Chl a ratio likely to occur in nature (1 : 1 molar), the new method results in only a 10% overestimate of the true Chl a value, while estimates from older acidification methods are 2.5‐fold low. Under conditions of high pheopigment concentrations (pheo a: Chl a = 1 : 1 molar), the new method provides Chl a estimates that are equivalent to those determined from the acidification technique. The new simple method requires a single fluorescence determination and provides adequate sensitivity for small sample sizes (<200 ml) even in the most oligotrophic marine and freshwater environments.
A simple device to transfer large and delicate planktonic organisms
Authors: Acuňa José Luis , Deibel Don , Sooley Steve
Published: May 2010

A device to transfer large, delicate gelatinous zooplankton is described. Instead of using suction as conventional pipettes do, the macroplankton transfer device (MTD) encloses parcels of water, thus eliminating the turbulence that may damage gelatinous organisms. The MTD is of simple construction, is easy to use, and has proven effective with large (up to 10 cm) appendicularian tunicates, jellyfish, pteropods, and ctenophores. Without the MTD it has been difficult, in some cases impossible, to transfer these organisms without damage. We have used MTDs to perform shipboard feeding experiments on large appendicularians collected with plankton nets.
A model for the size‐fractionated biomass and production of marine phytoplankton
Authors: Tremblay Jean-Eric , Legendre Louis
Published: May 2010

Mathematical relationships are developed to derive potential export (i.e. sedimentation, grazing, or advection) from the proportions of production and biomass in two size fractions of phytoplankton. Size‐fractionated data (540 points) from 40 published studies are plotted on a production‐ biomass diagram, from which potential export is predicted. The predictions are supported by published information. Six ecological domains are defined from the positions of data points on the production‐biomass diagram: equatorial/tropical oceanic, tropical neritic, and subtropical oceanic waters, oceanic North Atlantic, Southern Ocean, and upwelling areas together with coastal northwest Atlantic blooms. The resulting picture is coherent, especially when the heterogeneity of data sources is considered.
Characteristics of Beginning Agriculture Teachers and Their Commitment to Teaching
Authors: Warnick Brian K. , Thompson Gregory W. , Tarpley Rudy S.
Published: May 2010

The purpose of this study was to describe the characteristics of beginning agriculture teachers and their perceived likelihood of teaching secondary agriculture in the future. Information was gathered from secondary agriculture teachers across the U.S. who were in their second year of teaching agricultural education during the 2003–2004 academic year. A survey instrument was created specifically for this study through which information about the experience of beginning teachers, the demographic characteristics of the beginning teacher, and the perceived likelihood of teaching secondary agriculture in the future was gathered. Data were analyzed using descriptive statistics and a multiple regression analysis. While nearly three–fourths of the respondents reported they were highly likely to teach secondary agriculture one–year from the time of the survey, less than one–third reported they were highly likely to do so at five years, and only 15% reported they were highly likely to do so twenty years from the time of the survey. No statistically significant relationship was found between the characteristics of beginning teachers and their perceived likelihood of remaining in the profession.
Perceptions of Agriculture Teachers toward Including Students with Disabilities
Authors: Giffing Monica D. , Warnick Brian K. , Tarpley Rudy S. , Williams Natalie Allen
Published: May 2010

The inclusion of students with special needs in regular education classrooms has been required by federal law for more than three decades. However, much of the responsibility for successful accommodation of students with disabilities rests upon the shoulders of teachers. Previous research has indicated that successful inclusion of students with special needs is strongly influenced by the attitude of teachers involved. In this study, secondary agriculture teachers in one western state were surveyed to determine their attitudes and perceptions related to their willingness and ability to include students with special needs in their classrooms and laboratories. Selected personal and professional characteristics were correlated with these attitudes and perceptions. A large majority of teachers responded that they understand the concept of inclusion, are in favor of including students with disabilities, and have had a positive experience teaching students with special needs. However, fewer respondents indicated that they had the skill level to successfully include students with disabilities. Overall, while teachers indicated willingness to include students with specific disability types, they were less positive in their perceived abilities to successfully accommodate these same students.
What is Scholarship? Faculty Knowledge and Perceptions of the Scholarship of Teaching and Learning.
Authors: Maxwell Lucas D. , Ball Anna L.
Published: May 2010

The purpose of this study was to determine faculty members’ knowledge and perceptions of the Scholarship of Teaching and Learning (SoTL) at the University of Florida. Faculty with appointments in the College of Agricultural and Life Sciences, Emerging Pathogens, Genetics, and Water multidisciplinary institutes served as the population for this study. The objectives of the study were to describe characteristics of faculty in regard to teaching, determine knowledge of the definition of the SoTL, describe faculty involvement in the SoTL, and determine faculty members’ perceptions about the value of and attitudes toward the SoTL. Nearly one–third of respondents were not familiar with the SoTL. More than 80% indicated that they had never, on their own or through collaboration, completed research about the SoTL. Almost 60% of respondents strongly agreed or agreed that SoTL is a valid form of scholarship, yet less than one–third of respondents felt that conducting research in the SoTL would be useful to their tenure and promotion dossier. In general, most faculty were neutral or positive in regards to the SoTL with almost two–thirds indicating they would like to learn more about the topic.
Measurements and comparison of primary biological aerosol above and below a tropical forest canopy using a dual channel fluorescence spectrometer
Authors: Gabey A. M. , Gallagher M. W. , Whitehead J. , Dorsey J. R. , Kaye P. H. , Stanley W. R.
Published: May 2010

Abstract. Aerosol particle size distributions were measured below and above a tropical rainforest canopy in Borneo, Malaysia, in June/July 2008 using the WIBS-3: a single particle dual channel fluorescence spectrometer. Material in the size range 0.8–20 μm was characterized according to optical equivalent diameter (DP), morphology and fluorescence at 310–400 nm and 400–600 nm following excitation at 280 nm and 370 nm respectively. Particles fluorescent after both excitations are likely to be fluorescent primary biological aerosol particles (FBAP). Measured FBAP number concentration (NFBAP) at both sites exhibited clear diurnal cycles. The largest variability was observed in the understorey, where NFBAP reached a minimum of 50–100 L−1 in late morning. In mid afternoon it exhibited strong transient fluctuations as large as 4000 L−1 that were followed by sustained concentrations of 1000–2500 L−1 that reduced steadily between midnight and sunrise. Above the canopy FBAP number ranged from 50–100 L−1 during the daytime to 200–400 L−1 at night but did not exhibit the transient enhancements seen in the understorey. The strong FBAP fluctuations were attributed to the release of fungal spores below the canopy and appeared to be linked to elevated relative humidity. The mean FBAP number fraction in the size range 0.8 μm
Observed 20th century desert dust variability: impact on climate and biogeochemistry
Authors: Mahowald N. M. , Kloster S. , Engelstaedter S. , Moore J. K. , Mukhopadhyay S. , McConnell J. R. , Albani S. , Doney S. C. , Bhattacharya A. , Curran M. A. J. , Flanner M. G. , Hoffman F. M. , Lawrence D. M. , Lindsay K. , Mayewski P. A. , Neff J. , Rothenberg D. , Thomas E. , Thornton P. E. , Zender C. S.
Published: May 2010

Abstract. Desert dust perturbs climate by interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were in the net increasing or decreasing desert dust. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere) over the 20th century to be −0.14±0.11 W/m2 (1990–1999 vs. 1905–1914). The estimated radiative change due to aerosols is especially strong between the dusty 1980–1989 and the less dusty 1955–1964 time periods (−0.57±0.46 W/m2), which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 °C. Model simulations also indicate strong regional shifts in precipitation and temperature from the desert dust changes, causing 6 ppm (12 Pg C) reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 Pg C) of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and biogeochemistry, and our understanding of these changes and their impacts should continue to be refined.
A closer looking at dimming and brightening in China during 1961–2005
Authors: Xia X.
Published: May 2010

Abstract. This study investigates dimming and brightening of surface solar radiation (SSR) during 1961–2005 in China as well as its relationships to total cloud cover (TCC). This is inferred from daily ground-based observational records at 45 pyranometer stations. A statistical method is introduced to study contributions of changes in the frequency of TCC categories and their atmospheric transparency to the secular SSR trend. The surface records suggest a renewed dimming beyond 2000 in North China after the stabilization in the 1990s; however, a slight brightening appears beyond 2000 in South China. Inter-annual variability of SSR is negatively correlated with that of TCC, but there is a positive correlation between decadal variability of SSR and TCC in most cases. The dimming during 1961–1990 is exclusively attributable to decreased atmospheric transparency, a portion of which is offset by TCC frequency changes in Northeast and Southwest China. The dimming during 1961–1990 in Northwest and Southeast China primarily results from decreased atmospheric transparency under all sky conditions and the percentage of dimming stemming from TCC frequency changes is 11% in Northwest and 2% in Southeast China. Decreased atmospheric transparencies during 1991–2005 in North China in most cases lead to the dimming. TCC frequency changes also contribute to the dimming during this period in North China. This feature is more pronounced in summer and winter when TCC frequency changes can account for more than 80% of dimming. In South China, increased atmospheric transparencies lead to the brightening during 1991–2005. A substantial contribution by TCC frequency changes to the brightening is also evident in spring and autumn.
Variations in chemical and physical properties of Amazon forest soils in relation to their genesis
Authors: Quesada C. A. , Lloyd J. , Schwarz M. , Patiño S. , Baker T. R. , Czimczik C. , Fyllas N. M. , Martinelli L. , Nardoto G. B. , Schmerler J. , Santos A. J. B. , Hodnett M. G. , Herrera R. , Luizão F. J. , Arneth A. , Lloyd G. , Dezzeo N. , Hilke I. , Kuhlmann I. , Raessler M. , Brand W. A. , Geilmann H. , Moraes Filho J. O. , Carvalho F. P. , Araujo Filho R. N. , Chaves J. E. , Cruz Junior O. F. , Pimentel T. P. , Paiva R.
Published: May 2010

Abstract. Soil samples were collected in six South American countries in a total of 71 different 1 ha forest plots across the Amazon Basin as part of the RAINFOR project. They were analysed for total and exchangeable cations, C, N, pH with various P fractions also determined. Physical properties were also examined and an index of soil physical quality proposed. A diverse range of soils was found. For the western areas near the Andean cordillera and the southern and northern fringes, soils tend to be distributed among the lower pedogenetic levels, while the central and eastern areas of Amazonia have more intensely weathered soils. This gives rise to a large variation of soil chemical and physical properties across the Basin, with soil properties varying predictably along a gradient of pedogenic development. Nutrient pools generally increased slightly in concentration from the youngest to the intermediate aged soils after which a gradual decline was observed with the lowest values found in the most weathered soils. Soil physical properties were strongly correlated with soil fertility, with favourable physical properties occurring in highly weathered and nutrient depleted soils and with the least weathered, more fertile soils having higher incidence of limiting physical properties. Soil phosphorus concentrations varied markedly in accordance with weathering extent and appear to exert an important influence on the nitrogen cycle of Amazon forest soils.
A comprehensive, multi-process box-model approach to glacial-interglacial carbon cycling
Authors: de Boer A. M. , Watson A. J. , Edwards N. R. , Oliver K. I. C.
Published: May 2010

Abstract. The canonical question of which physical, chemical or biological mechanisms were responsible for oceanic uptake of atmospheric CO2 during the last glacial is yet unanswered. Insight from paleo proxies has led to a multitude of hypotheses but none so far have been convincingly supported in three dimensional numerical modelling experiments. The processes that influence the CO2 uptake and export production are inter-related and too complex to solve conceptually while complex numerical models are time consuming and expensive to run which severely limits the combinations of mechanisms that can be explored. Instead, an intermediate inverse box model approach is used here in which the whole parameter space is explored. The glacial circulation and biological production states are derived from these using proxies of glacial export production and the need to draw down CO2 into the ocean. We find that circulation patterns which explain glacial observations include reduced Antarctic Bottom Water formation and high latitude mixing and to a lesser extent reduced equatorial upwelling. The proposed mechanism of CO2 uptake by an increase of eddies in the Southern Ocean, leading to a reduced residual circulation, is not supported. Regarding biological mechanisms, an increase in the nutrient utilization in either the equatorial regions or the northern polar latitudes can reduce atmospheric CO2 and satisfy proxies of glacial export production. Consistent with previous studies, CO2 is drawn down more easily through increased productivity in the Antarctic region than the sub-Antarctic, but that violates observations of lower export production there.
Numerical study of the evaporation process and parameter estimation analysis of an evaporation experiment
Authors: Schneider-Zapp K. , Ippisch O. , Roth K.
Published: May 2010

Abstract. Evaporation is an important process in soil-atmosphere interaction. The determination of hydraulic properties is one of the crucial parts in the simulation of water transport in porous media. Schneider et al. (2006) developed a new evaporation method to improve the estimation of hydraulic properties in the dry range. In this study we used numerical simulations of the experiment to study the physical dynamics in more detail, to optimise the boundary conditions and to choose the optimal combination of measurements. The physical analysis exposed, in accordance to experimental findings in the literature, two different evaporation regimes: (i) a soil-atmosphere boundary layer dominated regime (regime I) close to saturation and (ii) a hydraulically dominated regime (regime II). During this second regime a drying front (interface between unsaturated and dry zone with very steep gradients) forms which penetrates deeper into the soil as time passes. The sensitivity analysis showed that the result is especially sensitive at the transition between the two regimes. By changing the boundary conditions it is possible to force the system to switch between the two regimes, e.g. from II back to I. Based on this findings a multistep experiment was developed. The response surfaces for all parameter combinations are flat and have a unique, localised minimum. Best parameter estimates are obtained if the evaporation flux and a potential measurement in 2 cm depth are used as target variables. Parameter estimation from simulated experiments with realistic measurement errors with a two-stage Monte-Carlo Levenberg-Marquardt procedure and manual rejection of obvious misfits lead to acceptable results for three different soil textures.
Modelling the hydrological behaviour of a coffee agroforestry basin in Costa Rica
Authors: Gómez-Delgado F. , Roupsard O. , Moussa R. , le Maire G. , Taugourdeau S. , Bonnefond J. M. , Pérez A. , van Oijen M. , Vaast P. , Rapidel B. , Voltz M. , Imbach P. , Harmand J. M.
Published: May 2010

Abstract. The profitability of hydropower in Costa Rica is affected by soil erosion and sedimentation in dam reservoirs, which are in turn influenced by land use, infiltration and aquifer interactions with surface water. In order to foster the provision and payment of Hydrological Environmental Services (HES), a quantitative assessment of the impact of specific land uses on the functioning of drainage-basins is required. The present paper aims to study the water balance partitioning in a volcanic coffee agroforestry micro-basin (1 km2, steep slopes) in Costa Rica, as a first step towards evaluating sediment or contaminant loads. The main hydrological processes were monitored during one year, using flume, eddy-covariance flux tower, soil water profiles and piezometers. A new Hydro-SVAT lumped model is proposed, that balances SVAT (Soil Vegetation Atmosphere Transfer) and basin-reservoir routines. The purpose of such a coupling was to achieve a trade-off between the expected performance of ecophysiological and hydrological models, which are often employed separately and at different spatial scales, either the plot or the basin. The calibration of the model to perform streamflow yielded a NS coefficient equal to 0.80, while the validation of the water balance partitioning was consistent with the independent measurements of actual evapotranspiration (R2=0.79, energy balance closed independently), soil water content (R2=0.49) and water table level (R2=0.90). An uncertainty analysis showed that the streamflow modelling was precise for nearly every time step, while a sensitivity analysis revealed which parameters mostly affected model precision, depending on the season. It was observed that 64% of the incident rainfall R flowed out of the basin as streamflow, 25% as evapotranspiration and the remaining 11% was attributed to deep percolation. The model indicated an interception loss equal to 4% of R, a surface runoff of 5% and an infiltration component of 91%. The modelled streamflow was constituted by 63% of baseflow originating from the aquifer, 29% of subsurface non-saturated runoff and 8% of surface runoff. Given the low surface runoff observed under the current physical conditions (andisol) and management practices (no tillage, planted trees, bare soil kept by weeding), this agroforestry system on a volcanic soil demonstrated potential to provide valuable HES, such as a reduced superficial displacement-capacity for fertilizers, pesticides and sediments, as well as a streamflow regulation function provided by the highly efficient mechanisms of aquifer recharge and discharge. The proposed combination of experimentation and modelling across ecophysiological and hydrological approaches proved to be useful to account for the behaviour of a given basin, so that it can be applied to compare HES provision for different regions or management alternatives.
Investigating household food interpurchase behavior through market segmentation
Authors: Dong Diansheng , Kaiser Harry M.
Published: May 2010

In this study, a market segmentation approach is developed and applied to analyze U.S. households' cheese purchases. The segmentation is based on household interpurchase time, or the hazard rate of purchases. In this study, four segments have been discovered in the U.S. market for household cheese purchases. Two of the segments jointly represent about 40% of all cheese‐purchasing households and are characterized as frequent buyers with an average interpurchase time of 2 weeks. These frequent‐purchase households are larger in size, have greater incomes, have a smaller proportion of African Americans, and are insensitive to coupons. They are often described in the marketing literature as loyal customers. In contrast, the other two segments, which jointly represent about 60% of the households, are characterized by infrequent buyers with an average interpurchase time of 6 weeks. These infrequent‐purchase households are smaller in size, have less income, have a higher proportion of African Americans, and are sensitive to coupons. Marketing promotions typically target the infrequent‐purchase households. [EconLit citations: D12, C51, C41]. © 2010 Wiley Periodicals, Inc.
Failure to confirm genetic association of the FXYD6 gene with schizophrenia: The Japanese population and meta‐analysis
Authors: Iwata Yasuhide , Yamada Kazuo , Iwayama Yoshimi , Anitha Ayyappan , Thanseem Ismail , Toyota Tomoko , Hattori Eiji , Ohnishi Tetsuo , Maekawa Motoko , Nakamura Kazuhiko , Suzuki Katsuaki , Matsuzaki Hideo , Tsuchiya Kenji J. , Suda Shiro , Sugihara Genichi , Takebayashi Kiyokazu , Yamamoto Shigeyuki , Iwata Keiko , Mori Norio , Yoshikawa Takeo
Published: May 2010

The FXYD domain‐containing ion transport regulator 6 (FXYD6) gene encodes phosphohippolin that regulates cellular ion transport by altering the kinetic properties of Na,K‐ATPase. Phosphohippolin is highly expressed in brain regions that are relevant to schizophrenia. The FXYD6 gene is located at chromosome 11q22–24, one of the most established linkage regions for schizophrenia. Therefore, it may be possible that genetic variants in FXYD6, including the regulatory genomic elements could cause abnormal function or expression of phosphohippolin and increase the genetic risk for schizophrenia. A previous study suggested that polymorphisms in FXYD6 are associated with schizophrenia in UK samples. However, conflicting results have been reported in the Japanese population. In this study, we aimed to test the prior genetic association findings using different samples from the ethnically homogeneous Japanese population (1,060 schizophrenic patients and 1,060 age‐ and sex‐matched controls). From the FXYD6 gene, we examined six single nucleotide polymorphisms (rs11216573, rs555577, rs1815774, rs4938445, rs4938446, and rs497768), all of which were previously analyzed for association. We did not detect any significant allelic, genotypic or haplotypic association in our Japanese samples. Meta‐analysis incorporating previous and the present studies also showed that the FXYD6 gene is not associated with schizophrenia. We conclude that the FXYD6 gene does not have a major influence on susceptibility to schizophrenia across populations. © 2010 Wiley‐Liss, Inc.
Flame retardance and mechanical properties of a polyamide 6/polyethylene/surface‐modified metal hydroxide ternary composite via a master‐batch method
Authors: Liu Shu‐Mei , Huang Jun‐Yi , Jiang Zhi‐Jie , Zhang Chen , Zhao Jian‐Qing , Chen Jun
Published: May 2010

Surface‐modified aluminum hydroxide and magnesium hydroxide mixtures (SAMHs) were filled with linear low‐density polyethylene (LLDPE) with a maleic anhydride grafted polyethylene (PE) compatibilizer to produce a SAMH master batch, which was then dispersed in polyamide 6 (PA6) to yield a PA6/PE/SAMH (50/20/30 by weight ratio) ternary composite. Through such a master‐batch method, an effective flame retardance UL94 V‐0 rating at a 3.2 mm thickness with a 33% limiting oxygen index was achieved. The flame‐retardance mechanism of the ternary composite was investigated by thermogravimetric analysis and scanning electron microscopy/energy dispersive X‐ray spectroscopy analysis. A cocontinuous PA6/PE polymer host and a preferential dispersion of SAMH particles in the matrix induced the formation of a compact flame‐resistant char layer and a high residue rate during burning; this resulted in the desired flame retardance of the ternary composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Systematic study of interfacial interactions between clays and an ionomer
Authors: Gao Yan , Choudhury Namita Roy , Dutta Naba K.
Published: May 2010

To study the interfacial interactions between an ionomer [poly(ethylene‐co‐acrylic acid) neutralized by zinc salts (PI)] and clays, PI–clay nanocomposites were prepared using a solution method. Two types of commercially available montmorillonite clays respectively K10 and KSF were used, and were modified with organic modifiers with chain lengths of 12–18 carbons. The interactions between the PI, clays, and modifiers were evaluated through study of the structure, morphology, and properties of the PI–clay nanocomposites. We found that the modifiers were successfully intercalated into the clay layers (Fourier transform infrared spectroscopy). The clay modified with a long‐chain agent showed an exfoliated nature in the nanocomposite. The thermal stability and storage modulus of PI were improved greatly by the addition of the clays, especially when the long‐chain modifier was used (thermogravimetric analysis and dynamic mechanical analysis). The differential scanning calorimetry results show that clay layers are inserted into the clusters because of solvent‐directed morphological evolution, so the transition of the ionic domains and the crystallinity of PI are changed. The interaction between PI, the modifier, and the silicate layer played an important role in the determination of the properties of the nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Evolutionary computing approach for evaluating flory distribution curves in gel permeation chromatography: Study of the poly(1‐octene) system
Authors: Singh Gurmeet , Kaur Sukhdeep , Naik Dhananjay G. , Gupta Virendra K.
Published: May 2010

We carried out deconvolution of the molecular weight distribution curves from gel permeation chromatography for polyolefins into individual active sites considering Flory distribution by an evolutionary‐computing‐based real‐coded genetic algorithm, a nonlinear multivariate optimization algorithm. We applied the deconvolution to homopolymers of 1‐octene synthesized using heterogeneous Ziegler–Natta catalysts with different amounts of hydrogen. The molecular weight distribution was deconvoluted in to five Flory distributions, which showed a sensitivity to hydrogen amounts. With no hydrogen presence, the peaks corresponding to high‐molecular‐weight fractions were intense. As the amount of hydrogen was increased, not only did the intensities of the high‐molecular‐weight peaks decrease, but also peaks corresponding to low‐molecular‐weight fractions were observed. The method allowed us to determine the active site distribution of the polymer molecular weight distribution obtained from gel permeation chromatography. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Relationship between the material properties and fatigue crack‐growth characteristics of natural rubber filled with different carbon blacks
Authors: Nie Yijing , Wang Bingyin , Huang Guangsu , Qu Liangliang , Zhang Peng , Weng Gengsheng , Wu Jinrong
Published: May 2010

An investigation of the influence of different types of carbon black on fatigue crack‐growth behavior was undertaken. Fatigue tests were carried out on edge‐notched specimens under cyclic tension loading. A power‐law dependency between the crack‐growth rate and tearing energy was obtained. Natural rubber (NR) filled with N330 (the mean diameter is 30 nm) carbon black possessed the lowest values of exponent b and constant B (the two crack growth parameters determined from cyclic crack growth testing), which denoted the strongest resistance to crack growth at a given tearing energy. Strain‐induced crystallization was investigated by the modified Mooney–Rivlin equation and showed the earliest appearance and strongest ability of the crystallization of the NR/N330 composite at the largest amount of bound rubber. The study on the viscoelastic properties by dynamic mechanical analysis confirmed that the NR/N330 composite had the largest viscoelastic contribution, which was attributed to the viscoelastic dissipation in the viscoelastic region in front of the crack tip. All of these results confirm the best crack‐propagation resistance of NR filled with N330. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Characterization of acrylic acid grafted poly(ethylene terephthalate) fabric
Authors: Grover Navdeep , Singh Harpal , Gupta Bhuvanesh
Published: May 2010

The preirradiation grafting of acrylic acid (AA) onto poly(ethylene terephthalate) (PET) had been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with various graft levels were characterized by thermal gravimetric analysis (TGA), ATR‐FTIR spectroscopy, contact angle, differential scanning calorimetry (DSC), X‐ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The initial decomposition temperature and T50 were increased with the increase in degree of grafting. The percentage crystallinity was decreased as the degree of grafting increases. The detailed elemental analysis was done by X‐ray photoelectron spectroscopy (XPS). The atomic ratio (O1s/C1s) was found to increase significantly with increasing the degree of grafting and reached 0.64 at 14.5% grafting from 0.38 for virgin PET. The surface topography and morphology was strongly influenced as the degree of grafting was increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Ionic conductivity of solid polymer electrolytes for dye‐sensitized solar cells
Authors: Kim Joo Wan , Bae Young Chan
Published: May 2010

We developed an ionic conductivity model of solid polymer electrolytes for dye‐sensitized solar cells (DSSCs) based on the Nernst–Einstein equation in which the diffusion coefficient is derived from the molecular thermodynamic model. We introduced concentration‐dependence of the diffusion coefficient into the model, and the diffusion coefficient was expressed by differentiating the chemical potential by concentration. The ionic conductivities of polymer electrolytes (PEO/LiI/I2 system) were investigated at various temperatures and compositions. We prepared a set of PEO in which an EO : LiI mole ratio of 10 : 1 was kept constant for PEO·LiI·(I2)n compositions with n = 0.02, 0.05, 0.1, 0.15, 0.2, and 0.3 (mole ratio of LiI : I2). The ionic conductivities of the electrolytes were measured using a stainless steel/polymer‐electrolyte/stainless steel sandwich‐type electrode structure using alternating current impedance analysis. The values calculated using the proposed model agree well with experimental data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Effect of sodium hexametaphosphate concentration on the swelling and controlled drug release properties of chitosan hydrogels
Authors: Sánchez‐Díaz Juan C. , Becerra‐Bracamontes Fausto , González‐Álvarez Alejandro , Cruz‐Barba L. Emilio , Martínez‐Ruvalcaba Agustín
Published: May 2010

An ionically crosslinked polymer network composed of chitosan and sodium hexametaphosphate (SHMP) was synthesized to determine their swelling and ascorbic acid release kinetics at various SHMP concentrations. The chitosan/SHMP hydrogels were synthesized using an acetic acid aqueous solution (1% v/v). Ionization constants (pKb) of the SHMP were obtained by potentiometric titration. The results show that the SHMP was hydrolyzed in acidic medium forming orthophosphate and trimetaphosphate. The swelling percentages were measured at different swelling media pH's; the higher swelling capacities were for the systems that were swollen in neutral solution. Also, it was studied the ionic crosslinking degree by turbidimetric titration, comparing the electrostatic interactions between the chitosan and the SHMP; the results shows that electrostatic interactions between the amine groups of the chitosan and the anionic groups of the SHMP are dependent of the swelling medium pH. The ascorbic acid diffusion inside the hydrogel follows the second law of Fick, and the diffusion coefficients were obtained for different SHMP concentrations. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010