bluuebunny/crossref_metadata_2025 huggingface dataset:
Physiological limitation of phytoplankton photosynthesis in the eastern equatorial Pacific determined from variability in the quantum yield of fluorescence
Authors: Greene Richard M. , Kolber Zbigniew S. , Swift Dorothy G. , Tindale Neil W. , Falkowski Paul G.
Published: May 2010

On a transect study in the eastern equatorial Pacific, from the high‐nutrient, low‐chlorophyll tropical waters to the oligotrophic subtropical waters, we determined the variability in the maximum change in the quantum yield of chlorophyll fluorescence (Δϕm) by means of a fast repetition rate fluorometer. Δϕm is a quantitative measure of photochemical energy conversion efficiency in photosystem 2, the variability of which is determined by the functional organization of the photosynthetic apparatus. The results revealed that Δϕm was relatively low throughout the nutrient‐rich equatorial waters, providing unequivocal evidence for physiological limitation of photochemical energy conversion efficiency in the natural phytoplankton populations. Shipboard enrichment studies showed that Δϕm increased following addition of nanomolar concentrations of inorganic iron as well as aerosol dust added at similar iron concentrations. This response reflects an iron‐induced repair of photosystem 2 function in the enclosed bottle community. Low Δϕm at the top of the Equatorial Undercurrent indicated that the amount of iron upwelled to the surface was insufficient to repair photosystem 2 function. Our results strongly suggest that iron availability limits photochemical energy conversion efficiency and is the principal mechanism controlling rates of photosynthesis and growth in the nutrient‐rich equatorial Pacific.
N‐acetylglucosamine dynamics in freshwater environments: Concentration of amino sugars, extracellular enzyme activities, and microbial uptake
Authors: Nedoma Jiří , Vrba Jaroslav , Hejzlar Josef , Šimek Karel , Straškrabová Věra
Published: May 2010

As a first approach to the study of the dynamics of amino sugars in freshwater environments, we measured microbial uptake of N‐acetylglucosamine and hydrolysis of 4‐MUF‐N‐acetyl‐β‐glucosaminide by extracellular enzymes in fishponds, reservoirs, backwaters, and lakes. Amino sugars were present in all localities and comprised up to several percent of both dissolved and particulate organic matter. Processes involving N‐acetylglucosamine (extracellular enzymes, microbial uptake) were also detected in all localities; their potential rates accounted for ∼10–100% of the rates of analogical processes involving glucose and were correlated with dissolved organic C and with general microbial activity. Two types of 4‐MUF‐β‐N‐acetylglucosaminidases (high and low affinity) were distinguished kinetically. The activity of the high‐affinity enzyme was tightly correlated with variables coupled to bacterial activity. In fishponds, uptake of N‐acetylglucosamine by diatoms and cyanobacteria was detected via autoradiography.
Size‐fractionated iron concentrations in the water column of the western North Atlantic Ocean
Authors: Wu Jingfeng , Luther George W.
Published: May 2010

We used an improved adsorptive cathodic stripping square‐wave voltametry method to determine vertical profiles of three operationally defined fractions of iron in the western North Atlantic Ocean. “Dissolved Fe” (<0.2‐µm fraction) exhibited a nutrient‐type distribution during our October 1991 cruise, with concentrations increasing from 0.2 nM in the surface water to 0.9 nM at 1,000 m. However, during our July 1992 cruise, the concentration of dissolved Fe was higher in the surface water (0.6 nM), decreased to a subsurface minimum of 0.2 nM at a depth of 50 m, then increased to 0.7–0.8 nM below 1,000 m. During the July cruise, the concentration of “colloidal Fe” (0.2–0.4‐µm fraction) was relatively constant at 0.15–0.25 nM from 10‐ to 500‐m depth, then decreased to below the detection limit at depths ≥ 750 m. “Particulate Fe” (>0.4‐µm fraction) increased from 0.1 nM in the surface water to 1.3 nM at depths below 1,000 m. Our results suggest the need to consider the temporal variation of iron and its size fractions in seawater if we are to understand the influence of iron on phytoplankton production in the ocean.
Sediment pore‐water dynamics of Little Rock Lake, Wisconsin: Geochemical processes and seasonal and spatial variability
Authors: Sherman Leslie A. , Baker Lawrence A. , Weir Edward P. , Brezonik Patrick L.
Published: May 2010

The nature of sediment alkalinity generation processes and the temporal and spatial variability of the pore‐water chemistry of an experimentally acidified seepage lake (Little Rock Lake, Wisconsin) were determined. Analysis of vertical gradients of solutes near the sediment‐water interface indicates that sulfate reduction and base cation production were the major mechanisms of alkalinity generation. A comparison of surficial accumulation rates and burial rates indicates that the major source of cations to the pore water occurred by release of organically bound and exchangeable cations through decomposition. Pore‐water measurements also reveal significant seasonal changes in solute fluxes, including a sudden change in sediment metabolism following a springtime algal bloom. Spatial differences in particle deposition caused pore‐water fluxes of ammonium and alkalinity to be almost an order of magnitude higher at a hypolimnetic site than at epilimnetic sites. After 2 yr of acidification, pore‐water gradients of sulfate, calcium, and alkalinity showed only minor changes, and the pore‐water pH in the acidified basin remained within 0.5 pH units of preacidification pH.
Sulfur during early diagenesis in Sphagnum peat: Insights from δ34S ratio profiles in 21Pb‐dated peat cores
Authors: Novák Martin , Wieder R. Kelman , Schell William R.
Published: May 2010

210Pb chronologies and depth profiles of stable S isotope ratios (δ34S) and concentrations of organic and inorganic S fractions were determined in peat cores from nine sites in the U.S. and the Czech Republic. Results indicate that depth profiles in S concentrations, S accumulation, and δ34S ratios in peat deposits are affected not only by historical patterns in atmospheric S deposition but also by ongoing depth‐dependent changes in S reduction‐oxidation and S immobilization‐mineralization processes within a peat deposit. These processes impart a certain degree of mobility to S in peat, bringing into question the validity of reconstructing historical records of S accumulation using dated peat profiles. Over long‐term diagenesis, isotopically light S may be continually released from deep peat. This release may result in redistribution of S and S isotopes in peat and suggests that short‐term patterns in S accumulation may not persist over much longer time scales.
The trophic status of various oceanic provinces as revealed by phytoplankton pigment signatures
Authors: Claustre Hervé
Published: May 2010

For various oceanic regimes, a pigment biomarker approach is used to investigate the relationship between the biomass and taxonomic composition of autotrophic communities. It is demonstrated that chlorophyll standing stocks are linearly related to the diatom (fucoxanthin) and dinoflagellate (peridinin) contents; other phytoplankton diagnostic pigments do not present any significant correlation with chlorophyll standing stocks. A pigment ratio, Fp, is proposed as an estimator of the proportion of new producers’ biomass in a phytoplankton community. The variation of the Fp‐ratio with chlorophyll a biomass and (modeled) primary production rates suggests strong similarities between Fp and the f‐ratio (new production: total production).
Disequilibrium between 226Ra and supported 210Pb in a sediment core from a shallow Florida lake
Authors: Brenner Mark , Peplow Arthur J. , Schelske Claire L.
Published: May 2010

210Pb dating can be used to assign ages in lake sediment cores, calculate rates of sediment accumulation, and determine the timing of recent changes in lake‐watershed ecosystems. We used low‐background gamma counting to measure 226Ra and total 210Pb activities in a core from Lake Rowell, Florida. 226Ra activity was high and strongly variable throughout the core, even exceeding total 210Pb activity in recently deposited sediments. We traced one source of Ra‐rich sediments to the only inflow, Alligator Creek, where stream‐bottom deposits display disequilibrium between 226Ra and supported 210Pb. High and variable 226Ra activity in the Lake Rowell profile argues for direct estimates of in situ Ra in lake sediment cores from disturbed watersheds that have Ra‐bearing bedrock. Isotopic disequilibrium between 226Ra and supported 210Pb makes it difficult to distinguish between supported and unsupported 210Pb activity throughout the Lake Rowell core and would require special assumptions and nonconventional dating models to establish age‐depth relationships.
Influence of long‐term climatic changes on the stratification of a subtropical, warm monomictic lake
Authors: Hambright K. David , Gophen Moshe , Serruya Salvador
Published: May 2010

Analysis of long‐term records of temperature profiles in subtropical Lake Kinneret revealed changes in thermal stratification during the period 1969–1991. Thermocline depth and rate of seasonal thermocline deepening have decreased and the period of stable stratification has increased. These changes appear related to a long‐term decline in mean winter air temperatures, which has produced cooler hypolimnetic waters and increased density gradients across the metalimnion. These changes in thermal structure have been accompanied by increases in hypolimnetic phosphorus concentrations and increased phytoplankton abundances in subsequent years. Although mean thermocline depth in the lake is intermediate relative to predictions based on surface area or fetch from published data on temperate and tropical lakes, winter air temperatures in the region have a salient impact on Lake Kinneret thermal dynamics in any given year.
Chemical induction of colony formation in a green alga (Scenedesmus acutus) by grazers (Daphnia)
Authors: Lampert Winfried , Rothhaupt Karl Otto , von Elert Eric
Published: May 2010

The green alga, Scenedesmus acutus, grows in culture in unicellular form, but it forms colonies (coenobia) when exposed for 48 h to a chemical released by the grazer Daphnia magna. The colony‐forming response can be evoked only in growing cells. The Daphnia factor affects colony size but not algal growth rate. The minimum concentration of Daphnia factor that induces colony formation is equivalent to a Daphnia biomass of 0.5 mg dry wt liter−1 in the culture medium. Actively feeding daphniids induce a stronger response than starved ones. Homogenized Scenedesmus, homogenized Daphnia, ammonium, and urea are not effective. The Daphnia factor is a nonvolatile, organic substance of small molecular mass (<500 Da). It is moderately lipophilic, heat stable, pH‐resistant in a range from 1 to 12, and not affected by treatment with Pronase E. The chemical activity is not lost when the substance is dried but disappears during incineration. Colony formation can be interpreted as a grazing defense mechanism. The phenotypic response may have evolved because of the tradeoff between higher sinking rates and grazing resistance of colonial forms.
Processes controlling recruitment of the marine Calanoid copepod Temora longicornis in Long Island Sound: Egg production, egg mortality, and cohort survival rates
Authors: Peterson William T. , Kimmerer William J.
Published: May 2010

Three phytoplankton blooms were observed during our 6‐month study period and each resulted in increased rates of egg production (EPR) by female Temora longicornis. An EPR of 50 eggs female−1 d−1 was observed during the first bloom (spring bloom, March). The maximum EPR observed during the other blooms (May and July) was 20 and 30 eggs female−1 d−1. At all other times the EPR was nearly zero. Each pulse in egg production initiated a distinct cohort. Survivorship from egg to adult was low: 3% for the first cohort and 0.8% for the second. The third cohort did not reach maturity. Mortality was highest in the egg stage—only 10% of the eggs produced survived to first nauplius. Rates of egg mortality were positively correlated with clearance rates of T. longicornis, suggesting cannibalism as a cause of high mortality. However, the clearance rates required would be ∼34‐fold too high, suggesting a different density‐dependent factor, such as disease, viruses, ecto‐parasitism or consumption by dinoflagellates. Advection and resting egg production do not appear to explain high rates of egg loss.
Nitrogen cycling in the Barents Sea–Seasonal dynamics of new and regenerated production in the marginal ice zone
Authors: Kristiansen Svein , Farbrot Tove , Wheeler Patricia A,
Published: May 2010

The uptake rates of nitrate, ammonium, and urea were measured with a 15N technique during seven cruises in the marginal ice zone (MIZ) in the Barents Sea in 1984–1988. The results from all the cruises were pooled to obtain means for the prebloom, bloom, transition, and postbloom periods. New production—nitrate uptake as percent of total uptake—was high (92–96%) during the prebloom and bloom periods and decreased thereafter. Regenerated production—summed ammonium + urea uptake as percent of total uptake—increased through the bloom cycle and was at its maximum (75–93%) during the postbloom period. New production (as percent of the total) was higher in the ice‐filled parts than in the icefree parts, especially during the postbloom period. Nitrate uptake rates, however, were highest (9–25 nM h−1) in open and ice‐free parts during the bloom and transition period. Mean growth rate of phytoplankton‐nitrogen was 0.5 doubling d−1 during the bloom and ranged from 0.3 to 0.4 doubling d−1 after the bloom. We hypothesize that primary production in the MIZ is not nutrient limited but is proportional to phytoplankton standing stocks.
Empirical models of phosphorus and nitrogen excretion rates by zooplankton
Authors: Wen Yuan Hua , Peters Robert Henry
Published: May 2010

Although rates of P and N excretion by zooplankton have important implications for nutrient cycling in aquatic ecosystems, the literature offers few quantitative general models of these processes. We used data collected from published studies to construct potentially predictive models of P and N excretion rates by zooplankton from freshwater and marine habitats. Excretion rates of P and N are strongly correlated (r2 = 0.88) and consequently each predicts the other best. Respiration rate is also highly significantly correlated with P and N excretion rates and is the second best predictor. Although body size explained relatively less overall variability, the inclusion of temperature, container volume, and experimental duration as independent variables in multiple regressions substantially improved the predictive power of models based on body size. The models can be corrected for taxonomic biases in zooplankton, but these biases were usually small. These models could provide both a basis for further empirical analysis of the determinants of zooplankton nutrient excretion and a means of predicting the fate of nutrients in aquatic ecosystems.
The impact of light intensity and daylength on silicate and nitrate competition among marine phytoplankton
Authors: Sommer Ulrich
Published: May 2010

I tested the extent to which differences in light supply could influence the outcome of nutrient (Si and N) competition between marine phytoplankton. Competition experiments were performed with 11 species of marine phytoplankton at Si: N ratios from 16 to 124 : 1, light intensities from 28 to 225 µmol quanta m−2 s−1, and three different daylengths. Thus, light supply was the composite result of two components: photoperiod and intensity. Diatoms were dominant competitors at higher Si: N ratios, nonsiliceous flagellates at lower ones. Light had no impact on the transition from flagellate to diatom dominance along the Si: N gradient. However, species within those groups were separated along the light gradient. Contrary to theoretical expectations, changes in light intensity and changes in daylength led to similar shifts in species dominance. Therefore, it was possible to describe the light climate by the integral parameter “daily light dose.”
Diffuse reflectance of oceanic shallow waters: Influence of water depth and bottom albedo
Authors: Maritorena Stéphane , Morel André , Gentili Bernard
Published: May 2010

We used simplifying assumptions to derive analytical formulae expressing the reflectance of shallow waters as a function of observation depth and of bottom depth and albedo. These formulae also involve two apparent optical properties of the water body: a mean diffuse attenuation coefficient and a hypothetical reflectance which would be observed if the bottom was infinitely deep. The validity of these approximate formulae was tested by comparing their outputs with accurate solutions of the radiative transfer obtained under the same boundary conditions by Monte Carlo simulations. These approximations were also checked by comparing the reflectance spectra for varying bottom depths and compositions determined in coastal lagoons with those predicted by the formulae. These predictions were based on separate determinations of the spectral albedos of typical materials covering the floor, such as coral sand and various green or brown algae. The simple analytical expressions are accurate enough for most practical applications and also allow quantitative discussion of the limitations of remote‐sensing techniques for bottom recognition and bathymetry.
A model for internal self‐shading in planktonic organisms and its implications for the usefulness of ultraviolet sunscreens
Authors: Garcia‐Pichel Ferran
Published: May 2010

I present a bio‐optical model that estimates the internal self‐shading caused by absorbing matter in planktonic organisms as well as the specific benefit afforded by the accumulation of sunscreen compounds. The model is applied to the examination of case studies of sunscreen‐bearing microorganisms and to the prediction of the effects of organismal size on both the inherent sensitivity to ultraviolet radiation and the possible amelioration of this condition by means of sunscreen accumulation. The model predicts that sunscreens cannot be used as a photoprotective mechanism of any relevance by picoplankters (cell radii, < 1 µm), which are also the most inherently sensitive size‐class. Conversely, the microplankters (cell radii, 10−> 100 µm) can use sunscreens with efficiencies comparable to well‐studied damage‐repair mechanisms. Among nanoplankters (cell radii, 1−< 10 µm), sunscreens can afford considerable benefits but only at the expense of relatively heavy investments and with restricted efficiencies.
Cell‐surface oxidation of amino acids in seawater
Authors: Pantoja Silvio , Lee Cindy
Published: May 2010

Recently, it was shown that certain phytoplankton species in laboratory culture can use cell‐surface enzymes to oxidize amino acids and amines and take up ammonium produced during the oxidation. Previously, we developed a fluorescent analog of the amino acid lysine (LYA‐lysine) to act as a tracer of cell‐surface oxidation processes. In the present study, a kinetic approach demonstrated that these fluorescent probes effectively compete with natural amino acids and are thus similar to the natural compounds. Field studies showed that naturally occurring phytoplankton and bacteria‐size organisms oxidized the fluorescent analog, extending the discovery of this oxidation process to natural waters. Parallel experiments measuring uptake of 14C‐labeled amino acids and oxidation of LYA‐lysine showed that oxidation rates could be as much as 40% of the total removal rate. This finding suggests that removal of amino acids from seawater might be significantly underestimated if uptake across the cell membrane were the only process considered. However, cell‐surface oxidative deamination was detected only in summer, when temperatures exceeded 22°C.
The effect of pH, dissolved humic substances, and ionic composition on the transfer of iron and phosphate to particulate size fractions in epilimnetic lake water
Authors: Shaw Peter J.
Published: May 2010

Transformations of dissolved iron and phosphate to particulate material (>0.2 µm) were investigated by adding 55FeCl3 and 32PO43 to pH adjusted epilimnetic lake water samples of contrasting ionic strengths and dissolved humic substances (DHS) concentrations. The distributions of these tracers between particulate size fractions in samples without appreciable DHS after 24 h of dark incubation varied markedly over the pH range 4–8. The effect of pH on the movement of 55Fe and 32P to particulate size fractions in clear‐water samples depended on the ionic strength. Over the same pH range, the presence of DHS suppressed the movement of 55Fe and 32P to particulate size fractions. There was little difference between low and high ionic strength DHS‐rich samples. The capability of DHS to maintain added 55Fe and 32P in solution (<0.2 µm) was confirmed by simultaneous measurements of precipitation losses.
Flume experiments on food supply to the blue mussel Mytilus edulis L. as a function of boundary‐layerflow
Authors: Butman Cheryl Ann , Fréchette Marcel , Geyer W. Rockwell , Starczak Victoria R.
Published: May 2010

A two‐dimensional, advection‐difusion model of phytoplankton depletion above an assemblage of suspension feeders was tested in a laboratory flume containing a 6.1‐m‐long bed of the blue mussel Mytilus edulis L. Flows with near‐surface velocities of ∼5 and 15 cm s−1 were tested in three experiments. Phytoplankton concentrations (as estimated by fluorescence) were measured just upstream of and near the end of the mussel bed. Vertical profiles of velocity indicated that turbulent stress, and thus turbulent mixing, were three (slow flow) to ten (fast flow) times higher over the mussel bed compared to the smooth flume bottom. In two experiments that used natural seawater, initial fluorescence was low and there was little temporal depletion at either flow speed. In the one experiment in which cultured phytoplankton were added to filtered seawater so that initial fluorescence was much higher, significant vertical and substantial horizontal gradients in fluorescence developed. In this experiment, depletion was enhanced in slow flow compared to fast flow in both the downstream and vertical directions, as qualitatively predicted by the model. Furthermore, with a flow‐speed‐dependent mussel filtration velocity, modeled vertical profiles of fluorescence were consistent with the observations.
Optical absorption and fluorescence properties of chromophoric dissolved organic matter in natural waters
Authors: Green Sarah A. , Blough Neil V.
Published: May 2010

Complete optical absorption and fluorescence spectra were collected for a diverse suite of 0.2‐µm‐filtered marine, riverine, and estuarine waters, as well as for colored dissolved organic matter (CDOM) isolated from several of these waters by solid‐phase C18 extraction. Absorption and fluorescence parameters for these samples arc reported. For surface waters, variations in the fluorescence quantum yields obtained with 355‐ and 337‐nm excitation fell within a narrow window (<2.5‐fold variation about the mean values), demonstrating that fluorescence measurements can be used to determine absorption coefficients of CDOM in the ultraviolet region with reasonably good accuracy. Methods for predicting absorption coefficients and line shapes from the fluorescence data are introduced and tested. The absorption and fluorescence spectra of CDOM extracted from some seawaters differed significantly from those of the original waters, demonstrating that material isolated by hydrophobic adsorption is not necessarily representative of the suite of colored organic matter present in aquatic systems. These results clearly illustrate that great care must be taken when extracted material is used to infer the optical properties of natural waters.
Stable isotopes of oxygen and hydrogen in the Truckee River‐Pyramid Lake surface‐water system. 3. Source of water vapor overlying Pyramid Lake
Authors: Benson L. V. , White J. W. C.
Published: May 2010

During 1988 and 1989, a series of water‐vapor extractions were conducted in the Pyramid Lake basin to determine the source of moisture that overlies the lake. Calculations of the isotopic and water‐vapor balances were made from isotopic and meteorological data from the Pyramid Lake and Reno, Nevada, areas. The results indicate that in the warm season, most of the moisture that overlies the lake is derived from evaporation as opposed to advected moisture. Isotopic fluxes at the lake surface can be approximated by climatic data from the lake site, which simplifies the calculation of this input in numerical simulations of the isotopic evolution of the lake.
Iron‐limited growth of cyanobacteria: Multiple siderophore production is a common response
Authors: Wilhelm Steven W. , Trick Charles G.
Published: May 2010

During periods when levels of biologically available iron are low, cyanobacteria produce low‐molecular‐weight ferric‐specific chelators (siderophores). We investigated the frequency of siderophore production in iron‐deficient culture of freshwater and marine cyanobacteria and examined the effects of extracellular iron chelators on iron uptake in a coccoid marine species. The results confirm that iron chelate production is prevalent among freshwater and marine species and that some of these iron chelators function as siderophores. The frequent identification of catechol‐type siderophores further indicates that these iron chelators may be as important in high‐affinity iron transport as are the hydroxamic acid‐type siderophores.
An Examination of Life Skill Development by Louisiana 4-H Club Officers
Authors: Tassin Mark G. , Higgins Chadwick C. , Kotrlik Joe W.
Published: May 2010

During a recent legislative impact audit of the Louisiana 4-H program, it was noted that there was very little data to document the impact 4-H programming has on the state’s youth. Because of the nature of 4- H, informal or authentic assessments have been the cornerstones of evaluation, but innovative strategies were needed to strengthen the program’s evaluation efforts. One area of concern was the life skill development of youth participants. Therefore, this study focused on the life skill development of 4-H Club/Group officers. The results show that 4-H Club/Groups Officers' life skills improved as a result of the training. This improvement was noted in most of the officers’ life skills examined in the study. Previous service as a 4-H officer resulted in increased life skills for presidents, vice– presidents, and secretaries, but no change for other officers. Years of officer training had low to moderate positive relationships with most officers’ life skills levels. Years of holding other 4-H offices had low or moderate positive relationships with most of the presidents’ and vice–presidents’ life skills levels but negligible relationships existed for the other officers.
Influences on Agricultural Agents’ Decisions to Remain in an Extension Career
Authors: Arnold Shannon , Place Nick
Published: May 2010

This qualitative study sought to explore and describe why Florida agricultural agents remained in an extension career. A purposive sample was used to select twelve agents who were classified into one of the three stages of the career stages model (Kutilek, Gunderson, & Conklin, 2002). In–depth interviews were used to investigate positive and negative influences that affected agents’ decisions. Grounded theory was used as the primary data analysis method (Strauss & Corbin, 1998). Seven selective codes emerged as the most influential factors on agents’ employment decisions. These codes were internal satisfaction, community leadership, external motivators, career benefits, change agents, network of support, and extension work environment. A grounded theory was created to delineate the relationships between the codes and explain the findings.
Developing an Instrument to Measure the Utilization of Principles of Teaching and Learning During Class Sessions*
Authors: Foster Daniel D. , Whittington M. Susie
Published: May 2010

The purpose of this study was to develop an instrument, the Principles of Teaching and Learning Assessment (PTLA) to measure the frequency of use of principles of teaching and learning (Newcomb, McCracken, Warmbrod, & Whittington, 2004) during class sessions. The following research objectives guided the study: operationalize the principles of teaching and learning by developing concrete classroom observation criteria for each principle; establish face and content validity of the PTLA as measured using qualitative data from a panel of experts; establish reliability of the PTLA as measured through analysis of test–retest data; and write foundational premises for developing the PTLA. Grounded in Piaget’s Theory of Cognitive Development (1961), the study was further guided by a conceptual framework for studying cognitive levels of teaching and learning (Ewing and Whittington, 2007). An instrument for measuring the use of principles of teaching and learning during class sessions is needed for documenting teaching effectiveness. The PTLA will be used to facilitate data collection regarding professor behaviors and their relationship to student variables in teaching environments.
The Conceptualization and Investment of Leadership Development by Department Heads in Colleges of Agriculture at Land Grant Universities
Authors: Williams Jennifer , Blackwell Cindy , Bailey Lucy
Published: May 2010

The complexity of leading, specifically leading an academic department, is daunting. Nationally, there has been an increase in open department head positions, but also a lack of faculty interest in making the move from faculty member to administrator. Skill level of chosen department heads in leadership varies, but the majority of academic administrators are not chosen because of their leadership knowledge, skills, or abilities. This generative study looked at the conceptualization of the phenomenon of “leadership development” by department heads in Colleges of Agriculture at Land–Grant Universities in order to gain an understanding of the experience of department heads in leadership development. Inductive and deductive analytic procedures led to four categorical themes: prior experience with leadership development, leadership training, leadership education, and leadership development. Sub–themes indicated the complexity of the main themes and offered a more focused view from the department heads.
Identifying Confidence Levels and Instructional Strategies of High School Agricultural Education Teachers When Working with Students with Special Needs
Authors: Stair Kristin S. , Moore Gary E. , Wilson Beth , Croom Barry , Jayaratne K.S.U.
Published: May 2010

The purpose of this study was to identify confidence levels of high school agriculture teachers when working with students with special needs and to determine what strategies teachers are using within their classrooms. One state was randomly selected from each of the six National Association for Agricultural Education regions and a stratified random sampling method was used. A random sample of 333 was selected with a response rate of 62%. Participants completed a questionnaire that measured teacher confidence, identified the teaching strategies that were being used, ascertained the perceived effectiveness of the strategies, and collected demographic information. Data analysis indicated that teachers are using recognized practices in their classes, though they are more likely to use practices that are easy to implement and that benefit more students than specific individualized strategies. Overall, teachers are confident in their abilities; however, they disagree that their teacher training programs and in–service opportunities have prepared them to work with students with special needs. Multiple regression analysis was used to determine predictors of confidence, and the model for total teacher confidence accounted for 11.7% of the variance. The total regression model involved in–service participation, age, and having a friend or family member with a disability.
Patterns of mercury dispersion from local and regional emission sources, rural Central Wisconsin, USA
Authors: Kolker A. , Olson M. L. , Krabbenhoft D. P. , Tate M. T. , Engle M. A.
Published: May 2010

Abstract. Simultaneous real-time changes in mercury (Hg) speciation- reactive gaseous Hg (RGM), elemental Hg (Hg°), and fine particulate Hg (Hg-PM2.5), were determined from June to November, 2007, in ambient air at three locations in rural Central Wisconsin. Known Hg emission sources within the airshed of the monitoring sites include: 1) a 1114 megawatt (MW) coal-fired electric utility generating station; 2) a Hg-bed chlor-alkali plant; and 3) a smaller (465 MW) coal-burning electric utility. Monitoring sites, showing sporadic elevation of Hg°, Hg-PM2.5, and RGM were positioned at distances of 25, 50 and 100 km northward of the larger electric utility. Median concentrations of Hg°, Hg-PM2.5, and RGM were 1.3–1.4 ng m−3, 2.6–5.0 pg m−3, and 0.6–0.8 pg m−3, respectively. A series of RGM events were recorded at each site. The largest, on 23 September, occurred under prevailing southerly winds, with a maximum RGM value (56.8 pg m-3) measured at the 100 km site, and corresponding elevated SO2 (10.4 ppbv; measured at 50 km site). The finding that RGM, Hg°, and Hg-PM2.5 are not always highest at the 25 km site, closest to the large generating station, contradicts the idea that RGM decreases with distance from a large point source. This may be explained if: 1) the 100 km site was influenced by emissions from the chlor-alkali facility or by RGM from regional urban sources; 2) the emission stack height of the larger power plant promoted plume transport at an elevation where the Hg is carried over the closest site; or 3) RGM was being generated in the plume through oxidation of Hg°. Operational changes at each emitter since 2007 should reduce their Hg output, potentially allowing quantification of the environmental benefit in future studies.
Release of mercury halides from KCl denuders in the presence of ozone
Authors: Lyman S. N. , Jaffe D. A. , Gustin M. S.
Published: May 2010

Abstract. KCl-coated denuders have become a standard method for measurement of gaseous oxidized mercury, but their performance has not been exhaustively evaluated, especially in field conditions. In this study, KCl-coated and uncoated quartz denuders loaded with HgCl2 and HgBr2 lost 29–55% of these compounds, apparently as elemental mercury, when exposed to ozone (range of 6–100 ppb tested). This effect was also observed for denuders loaded with gaseous oxidized mercury at a field site in Nevada (3–37% of oxidized mercury lost). In addition, collection efficiency decreased by 12–30% for denuders exposed to 50 ppb ozone during collection of HgCl2. While data presented were obtained from laboratory tests and as such do not exactly simulate field sampling conditions, these results indicate that the KCl denuder GOM collection method may not be as robust as previously thought. This work highlights needs for further testing of this method, clear identification of gaseous oxidized mercury compounds in the atmosphere, and development of field calibration methods for these compounds.
Assessment of the calibration performance of satellite visible channels using cloud targets: application to Meteosat-8/9 and MTSAT-1R
Authors: Ham S.-H. , Sohn B. J.
Published: May 2010

Abstract. To examine the calibration performance of the Meteosat-8/9 Spinning Enhanced Visible Infra-Red Imager (SEVIRI) 0.640-μm and the Multi-functional Transport Satellite (MTSAT)-1R 0.724-μm channels, three calibration methods were employed. First, a ray-matching technique was used to compare Meteosat-8/9 and MTSAT-1R visible channel reflectances with the well-calibrated Moderate Resolution Imaging Spectroradiometer (MODIS) 0.646-μm channel reflectances. Spectral differences of the response function between the two channels of interest were taken into account for the comparison. Second, collocated MODIS cloud products were used as inputs to a radiative transfer model to calculate Meteosat-8/9 and MTSAT-1R visible channel reflectances. In the simulation, the three-dimensional radiative effect of clouds was taken into account and was subtracted from the simulated reflectance to remove the simulation bias caused by the plane-parallel assumption. Third, an independent method used the typical optical properties of deep convective clouds (DCCs) to simulate reflectances of selected DCC targets. Although the three methods were not in perfect agreement, the results suggest that calibration accuracies were within 5–10% for the Meteosat-8 0.640-μm channel, 4–9% for the Meteosat-9 0.640-μm channel, and up to 20% for the MTSAT-1R 0.724-μm channel. The results further suggest that the solar channel calibration scheme combining the three methods in this paper can be used as a tool to monitor the calibration performance of visible sensors that are particularly not equipped with an onboard calibration system.
CO2 and its correlation with CO at a rural site near Beijing: implications for combustion efficiency in China
Authors: Wang Y. , Munger J. W. , Xu S. , McElroy M. B. , Hao J. , Nielsen C. P. , Ma H.
Published: May 2010

Abstract. Although China has surpassed the United States as the world's largest carbon dioxide emitter, in situ measurements of atmospheric CO2 have been sparse in China. This paper analyzes hourly CO2 and its correlation with CO at Miyun, a rural site near Beijing, over a period of 51 months (December 2004 through February 2009). The CO2-CO correlation analysis binned by local time is shown to provide useful information with statistical significance even in the growing seasons. We found that the intercept, representing initial condition imposed by global distribution of CO2 with influence of photosynthesis and respiration, exhibits diurnal cycles differing by season. The background CO2 (CO2,b) derived from Miyun observations is comparable to CO2 observed at an upwind baseline station. Annual growth of overall mean CO2 at Miyun is estimated at 2.7 ppm yr−1 while that of CO2,b
Comparing high-resolution gridded precipitation data with satellite rainfall estimates of TRMM_3B42 over Iran
Authors: Javanmard S. , Yatagai A. , Nodzu M. I. , BodaghJamali J. , Kawamoto H.
Published: May 2010

Abstract. To evaluate satellite rainfall estimates of Tropical Rain Measurement Mission (TRMM) level 3 output (3B42) (TRMM_3B42) over Iran (20°–45° N, 40°–65° E), we compared these data with high-resolution gridded precipitation datasets (0.25°×0.25° latitude/longitude) based on rain gauges (Iran Synoptic gauges Version 0902 (IS0902)). Spatial distribution of mean annual and mean seasonal rainfall in both IS0902 and TRMM_3B42 from 1998 to 2006 shows two main rainfall patterns along the Caspian Sea and over the Zagros Mountains. Scatter plots of annual average rainfall from IS0902 versus TRMM_3B42 for each 0.25°×0.25° grid cell over the entire country (25°–40° N, 45°–60° E), along the Caspian Sea (35°–40° N, 48°–56° E), and over the Zagros Mountains (28°–37° N, 46°–55° E) were derived. For the entire country, the Caspian Sea region, and the Zagros Mountains, TRMM_3B42 underestimates mean annual precipitation by 0.17, 0.39, and 0.15 mm day−1, respectively, and the mean annual rainfall spatial correlation coefficients are 0.77, 0.57, and 0.75, respectively. The mean annual precipitation temporal correlation coefficient for IS0902 and TRMM_3B42 is ~0.8 in the area along the Zagros Mountains, and ~0.6 in the Caspian Sea and desert regions.
On the role of the planetary boundary layer depth in the climate system
Authors: Esau I. , Zilitinkevich S.
Published: May 2010

Abstract. The planetary boundary layer (PBL) is a part of the Earth's atmosphere where turbulent fluxes dominate vertical mixing and constitute an important part of the energy balance. The PBL depth, h, is recognized as an important parameter, which controls some features of the Earth's climate and the atmospheric chemical composition. It is also known that h varies by two orders of magnitude on diurnal and seasonal time scales. This brief note highlights effects of this variability on the atmospheric near-surface climate and chemical composition. We interpret heat capacity parameter of a Budyko-type energy balance model in terms of quasi-equilibrium h. The analysis shows that it is the shallowest, stably-stratified PBL with the smallest h that should be of particular concern for climate modelling. The reciprocal dependence between the PBL depth and temperature (concentrations) is discussed. In particular, the analysis suggests that the climate characteristics during stably stratified PBL episodes should be significantly more sensitive to perturbations of the Earth's energy balance as well as emission rates. On this platform, h from ERA-40 reanalysis data, the CHAMP satellite product and the DATABASE64 data were compared. DATABASE64 was used to assess the Troen-Mahrt method to determine h through available meteorological profile observations. As it has been found before, the shallow PBL requires better parameterization and better retrieval algorithms. The study demonstrated that ERA-40 and CHAMP data are biased toward deeper h in the shallow polar PBL. This, coupled with the scarcity of in-situ observations might mislead the attribution of the origins of the Arctic climate change mechanisms.
Calcareous nannofossil assemblages from the Central Mediterranean Sea over the last four centuries: the impact of the little ice age
Authors: Incarbona A. , Ziveri P. , Di Stefano E. , Lirer F. , Mortyn G. , Patti B. , Pelosi N. , Sprovieri M. , Tranchida G. , Vallefuoco M. , Albertazzi S. , Bellucci L. G. , Bonanno A. , Bonomo S. , Censi P. , Ferraro L. , Giuliani S. , Mazzola S. , Sprovieri R.
Published: May 2010

Abstract. We present decadal-scale calcareous nannofossil data from four short cores (Station 272, 37° 17' N, 12° 48' E, 226 m depth; St 342, 36° 42' N, 13° 55' E, 858.2 m depth; St 407, 36° 23' N, 14° 27' E, 345.4 m depth; C90-1M, 40° 36' N, 14° 42' E, 103.4 m depth) recovered in the central Mediterranean Sea (northern Sicily Channel and Tyrrhenian Sea), which, on the basis of 210Pb activity span the last 200–350 years. Assemblages are dominated by placoliths, mostly Emiliania huxleyi, while, at least in the Sicily Channel sediments, Florisphaera profunda was an important part of the coccolithophore community. The paleoenvironmental reconstruction, based on ecological preference of species and groups, suggests that the Tyrrhenian core C90-1M maintained higher productivity levels over recent centuries, with respect to the Sicily Channel sites, possibly because of more pronounced winter phytoplankton blooms, in agreement with modern primary productivity variations over the last ten years. The lowermost part of the record of one of the cores from the Sicily Channel, Station 407, which extends down to 1650 AD, is characterized by drastic changes in productivity. Specifically, below 1850 AD, the decrease in abundance of F. profunda and the increase of placoliths, suggest increased productivity. The chronology of this change is related to the main phase of the Little Ice Age, which might have impacted the hydrography of the southern coast of Sicily and promoted vertical mixing in the water column. The comparison with climatic forcings points out the importance of stronger and prolonged northerlies, together with decreased solar irradiance. The identification of the LIA in the northern Sicily Channel cover the Bond cycle BO that was missing in a previous study of Holocene climatic anomalies in the Sicily Channel. Finally, we suggest that major abundance changes in reworked nannofossil specimens, recorded in the Tyrrhenian core C90-1M, might be linked to variations in terrigenous supply from land. Paradoxically, higher amounts of reworking correspond to dry periods. We argue that soil and rock vulnerability is enhanced during times of prolonged drought and vegetation cover loss.
Quantifying Mental Foramen Position in Extant Hominoids and Australopithecus: Implications for its Use in Studies of Human Evolution
Authors: Robinson Chris A. , Williams Frank L.
Published: May 2010

The location of the mental foramen on the mandibular corpus has figured prominently in debates concerning the taxonomy of fossil hominins and Gorilla gorilla. In this study we quantify the antero/posterior (A/P) position of the mental foramen across great apes, modern humans and Australopithecus. Contrary to most qualitative assessments, we find significant differences between some extant hominoid species in mental foramen A/P position supporting its potential usefulness as a character for taxonomic and phylogenetic analyses of fossil hominoids. Gorilla gorilla, particularly the eastern subspecies, with a comparatively longer dental arcade and fossil and extant hominins with reduced canines and incisors tend to exhibit more anteriorly positioned mental foramina. Conversely, Pan troglodytes exhibits more posteriorly positioned mental foramina. Variation in this character among Gorilla gorilla subspecies supports recent taxonomic assessments that separate eastern and western populations. In all taxa other than Pan troglodytes the A/P position of the mental foramen is positively allometric with respect to dental arcade length. Thus, within each of these species, specimens with longer dental arcades tend to have more posteriorly positioned mental foramina. Those species with greater sexual dimorphism in canine size and dental arcade length (i.e., Gorilla gorilla and Pongo pygmaeus) exhibit more extreme differences between smaller and larger individuals. Moreover, among great apes those individuals with greater anterior convergence of the dental arcade tend to exhibit more posteriorly positioned mental foramina. Dental arcade length, canine crown area and anterior convergence are all significantly associated with mental foramen A/P position, suggesting that these traits may influence taxonomic variation in the A/P position of the mental foramen. Anat Rec 293:1337–1349, 2010. © 2010 Wiley‐Liss, Inc.
Nuclear Localization of Annexin A1 Correlates With Advanced Disease and Peritoneal Dissemination in Patients with Gastric Carcinoma
Authors: Zhu Fengjia , Xu Chaoyang , Jiang Zhinong , Jin Mei , Wang Linbo , Zeng Su , Teng Lisong , Cao Jiang
Published: May 2010

Annexin A1 (ANXA1) is a multifunctional molecule, which mediates various important physiologic processes depending on its subcelluar localization. The purpose of this study was to investigate the expression of ANXA1 level and its subcellular localization in paired clinical samples of gastric adenocarcinoma and adjacent normal counterpart. The study also assesses the clinical significance of ANXA1 subcelluar localization in gastric adenocarcinoma. A total of 104 paired resected gastric adenocarcinoma and corresponding normal specimens were collected in this study. Expression of ANXA1 was examined by immunohistochemical staining. Both cytoplasmic and nuclear ANXA1 expression levels and their correlation with clinicopathological parameters were assessed. ANXA1 protein expression was positive in 72 of 104 (69.2%) normal tissues and 47 of 104 (45.2%) gastric adenocarcinoma tissues. ANXA1 staining was predominantly localized in the cytoplasm in all 72 ANXA1‐positive normal specimens, whereas 12 ANXA1‐positive gastric adenocarcinoma specimens showed positive nuclear staining. The positive nuclear staining correlated well with serosal invasion, peritoneal dissemination and TNM stage. Cases with positive nuclear staining presented more peritoneal dissemination (41.7%, 5/12) than those with negative nuclear staining (8.7%, 8/92; P = 0.007). A logistic regression model revealed that positive ANXA1 nuclear staining had an independent association with peritoneal dissemination (P = 0.039; hazards ratio, 9.499; 95% confidence interval, 1.159–77.815). These results indicated that ANXA1 is expressed in both gastric adenocarcinoma and normal tissues. In gastric adenocarcinoma tissues ANXA1 is expressed both in cytoplasm and nucleus and its nuclear localization correlates with advanced disease stage and peritoneal dissemination. Anat Rec 293:1310–1314, 2010. © 2010 Wiley‐Liss, Inc.