bluuebunny/crossref_metadata_2025 huggingface dataset:
Microscopical characterization of the salivary glands of the carnivorous cephalaspidean Philinopsis depicta (Mollusca, Opisthobranchia)
Authors: Lobo-da-Cunha A. , Ferreira I. , Calado G.
Published: August 2009

Cephalaspideans are a group of opisthobranch gastropods comprising carnivorous and herbivorous species, allowing an investigation of the relationship between these diets and the morphofunctional features of the salivary glands.In this study, the salivary glands of the carnivorous cephalaspidean Philinopsis depicta were observed by light microscopy using semithin sections and by transmission electron microscopy. A central duct runs along the length of these thin ribbon-shaped glands dividing them in two halves, each formed by a single row of tubules perpendicularly attached to the central duct. The simple epithelium of the central duct and lateral tubes contains ciliated cells and two types of secretory cells, named granular cells and cells with apical vacuole (Fig. 1). A very thin outer layer of connective tissue covers the epithelium (Fig. 1). The ciliated cells are numerous but very thin, forming small clusters between secretory cells. The nucleus, several mitochondria and a few lysosomes are located in the apical region were the cells are wider. A very thin cytoplasmic stalk reaches the base of the epithelium and contains bundles of filaments in addition to some mitochondria.
Gender and aging in the liver: preliminary data using design-based stereological methods
Authors: Marcos Ricardo , Malhão Fernanda , Monteiro Rogério , Rocha Eduardo
Published: August 2009

Different epidemiological studies demonstrated that male gender and age are risk factors for the progression of liver disease. Regarding age, it has been associated with liver mass and blood flow reduction, whereas in gender, the estradiol has revealed protective roles in models of liver fibrosis and of trauma-hemorrhage in rats. So far, most of the studies on aging focused their attention in hepatocyte (HEP) structure and function and few data exists pertaining to other liver cell subpopulations, including hepatic stellate cells (HSC) and Kupffer cells (KC). To the best of our knowledge, an integrative analysis (with modern stereology) of the liver cell populations, throughout aging and gender, has never been performed.
Electrical and mechanical probing of nanostructures with transmission electron microscopy
Authors: Costa P. M. F. J. , Bando Y. , Golberg D.
Published: August 2009

Recent developments in the design of holders for transmission electron microscopes (TEM) have enabled widespread property analysis of nanostructures with unprecedented spatial resolution. It is now possible to routinely and reliably test the mechanical and electrical characteristics of a single carbon nanotube (CNT), for instance. Furthermore, due to the multitasking capability of TEMs, the study can even integrate simultaneous imaging and spectroscopical analysis. The combination of real-time gathering of structural, chemical, electrical and mechanical information provides an outstanding view of the materials' reactions when subjected to external stimulus such as current or heat.
Electron scanning microscopy analysis of fracture surfaces in laser welded samples of hardmetals
Authors: Miranda R. M. , Silva R. J. C.
Published: August 2009

Hardmetals of tungsten carbides in a cobalt matrix have been attempted to weld in similar joints by Nd/YAG laser in continuous wave mode. The combination of mechanical and thermo-physical properties of these materials poses a significant difficulty in welding these materials, especially for grades with low Co content, as 6 to 12% in volume. However, grades with higher Co content also showed a poor weldability. In fact, when welding hardmetals with a Co content of 25% in volume, a large amount of pores was observed on the fracture surface. Analysis under scanning electron microscopy showed these pores were coated with a thin film.Observations with energy dispersive spectroscopy (SEM-EDS) revealed this film is rich in cobalt and is highly unstable. Figure 1 shows the characteristics of the film around a pore evidencing its corrugated aspect originated during rapid cooling conditions verified during laser welding.
CVD diamond/substrate interface FIB preparation of cutting tools
Authors: Peripolli S. B. , Almeida F. A. , Gomes L. S. , Oliveira F. J. , Silva R. F. , Achete C. A.
Published: August 2009

CVD diamond coated cutting tools are used for machining of abrasive and hard materials such as Al-Si alloys and tungsten carbide. The knowledge of the mechanisms governing the diamond/substrate interfacial strength is crucial in cutting tools design. The most adequate substrate material for maximizing the adhesion of diamond films is the silicon nitride (Si3N4) ceramic that possesses a thermal expansion coefficient similar to that of diamond. Buchkremer-Hermanns and co-workers consider the formation of a SiC interlayer between diamond and Si3N4, which may favour chemical bonding to diamond, although they could not detect it by glazing incidence X-Ray diffraction. They believed that insufficient detection sensitivity for very thin films, texture effects or presence of amorphous layers are possible reasons. In the case of TiN substrates, a graded interlayer of amorphous TiCN of only 8 Å was suggested by Contreras, as observed by HRTEM images and EDS measurements. Due to the difficulty in the detection of such layers, which can be in the order of a few angstrons, a definite evidence of their nature is yet to be demonstrated.
Biodegradation assessment of a 16th century fresco from Southern Portugal
Authors: Martins R. , Fialho S. , Lima M. , Tavares D. , Mirão J. , Valadas S. , Candeias A. E.
Published: August 2009

This work reports the study of the frescoes from the Casa de Fresco dos Sanches Baena in Vila Viçosa (Southeast Portugal) to allow their material characterisation, to identify the different microorganism populations and to assess their role in the deterioration of these paintings. The Casa de Fresco dos Sanches Baena is a small semi-underground building constructed in a Palace garden over a well and used as a cool refreshing place by the owners. The frescoes that cover the ceilings (composed of 4 panels) present rich mythological scenes and have other decorative elements, which make them an unusual example of this art form. Unfortunately, due to partial abandonment the paintings are in an advanced state of degradation exhibiting partial detachment of paint layers and mortars, salt efflorescences and abundant biological colonisations (Fig.1).
Microstructure and reaction mechanisms at γ-TiAl brazed interfaces
Authors: Guedes A. , Pinto A. M. P. , Sequeiros E. W. , Vieira M. F. , Viana F.
Published: August 2009

Titanium aluminide alloys based on the γ-TiAl intermetallic compound are emerging as potential materials for high performance applications on aircraft engines components, aerospace vehicles and automotive engines, owing to their low density, high specific stiffness, excellent strength retention at high temperature and good creep and oxidation resistance. The development of adequate techniques to join γ-TiAl alloys, either to themselves or to other materials, is a key issue regarding the effective use of these alloys. Understanding of the reaction mechanisms that promote bonding is mandatory when optimization of the joining procedure is envisaged.
Joining of TiAl alloys using Ni/Al multilayers
Authors: Simões S. , Viana F. , Ventzke V. , Koçak M. , Ramos A. S. , Vieira M. T. , Vieira M. F.
Published: August 2009

The development of joining processes for TiAl alloys is fundamental to integrate them into functional structures and to widen their application field. Diffusion bonding has become the most reported technique for joining TiAl alloys but have the disadvantage of requiring high temperature stages. Diffusion bonding of TiAl at the 950-1200°C temperature range has been reported to produce defect-free bonds. Çam et al., successfully joined TiAl at 950 °C/30 MPa/3 h and 1000 °C/30 MPa/1 h, however, the bond interfaces were clearly visible.
Defect formation and microstructural changes in friction stir welds between pure copper and a brass alloy
Authors: Leal Rui M. , Leitão Carlos , Loureiro Altino , Rodrigues Dulce M.
Published: August 2009

Several attempts have been made in the last few years for joining similar pure copper and brass alloys using the solid state friction stir welding (FSW) process. For both material types, all the works performed reported that the production of defect free welds is largely dependent on the correct choice of process parameters. It was also observed that, despite grain refinement occurred in the centre of all the welds, the welds in copper showed a slight reduction in strength, when compared to that of the base material, as opposed to welds in brass alloys, for which an increase in strength was observed. Regardless of the encouraging results obtained in similar FWS of these materials, in the knowledge of the authors, few reports exist concerning dissimilar joints between them. In his work, dissimilar welds between Cu DHP cooper plates and Cu-Zn 37 brass plates, both of 1 mm thickness, with the brass plate positioned in the advancing side of the tool, were analysed. Welds were carried out with a solid tool made of high speed steel. Tool geometry was characterized by a tool shoulder of 10 mm in diameter, containing a conical cavity of 6 degrees, and a threaded probe of 3 mm in diameter. Welds were done in a milling machine, in position control, using the working parameters indicated in table 1.
Imaging characterization of friction stir welds in the AA 5182-H111 aluminium alloy
Authors: Leal Rui M. , Leitão Carlos , Loureiro Altino , Rodrigues Dulce M.
Published: August 2009

The environmentally friendly friction stir welding (FSW) process is being increasingly used in joining similar and dissimilar aluminium and copper alloys and other soft materials. In this process a rotating tool promotes significant shear strain and frictional heating of the base materials, in order to stir them into a highly plasticized weld region, at the trailing side of the tool. Due to the intense plastic deformation, complex material flow patterns, such as vortices, swirls and whorls occur during welding. In dissimilar welds, these patterns are readily revealed by differential etching and the respective microstructures characterized. However, in similar welds, such as the welds between plates of AA 5182-H111 aluminium alloy, it is hard to distinguish the different features in the welds and characterize their microstructures. Fig. 1 illustrates optical and TEM micrographs of a weld in this alloy. In the optical image of the weld, at the top of the image, it is possible to distinguish three main areas signalized by numbers: the weld nugget (1), with a very fine grain structure with 2.8 um mean grain size, and a transition region (2) between the nugget and the base material (3), which is usually called the Thermomechanical Affected Zone (TMAZ).
Surface Analysis by MeV Ion Beams and Microscopy
Authors: de Carvalho José A. R. Pacheco , Pacheco Cláudia F. F. P. R. , Reis António D.
Published: August 2009

Material analysis, specially surface analysis of materials, has been increasingly important. A wide range of surface analysis techniques is available. The techniques are, generally, complementary. There are nuclear and non-nuclear techniques, e.g. microscopy. Nuclear techniques, which are nondestructive, permit analysis for a few microns near the surface. They have been applied to areas such as scientific, technologic, industry, arts and medicine, using MeV ion beams. Nuclear reactions permit to achieve high sensitivities for detection of light elements in heavy substrates and also discrimination of isotopes. We use ion-ion nuclear reactions, elastic scattering and the energy analysis method, where an energy spectrum is obtained of ions from the target for a chosen energy of the incident ion beam. The target composition and concentration profile information contained in the spectrum is computationally obtained through a computer program that has been developed for predicting such energy spectra. Predicted spectra obtained for variations of target parameters are compared with experimental data, giving that information. SEM and TEM are also used.
Dispersion mechanisms of nanoclays in a polymer matrix by electron microscopy
Authors: Almeida M. F. , Machado A. V. , Covas J. A. , Larocca N. M. , Pessan L. A.
Published: August 2009

This work investigates the dispersion of nanoclays in polymer/montmorillonite (MMT) nanocomposites. Nanocomposites were prepared in a twin screw extruder and the collected samples were analyzed by SEM and TEM. It was possible to study the dispersion of the nanoclays and moreover understand its effect as compatibilizer.
Phase inversion phenomena of EPDM/PP - based TPVs by Electronic Microscopy
Authors: Antunes C. F. , Machado A. V. , van Duin M.
Published: August 2009

Morphology development during phase inversion is a very complex and not well understood process. EPDM/PP -based TPVs were prepared and characterize by different electronic microscopy techniques. Using a low Mw-EPDM, morphology development during phase inversion was successfully followed by scanning electron microscopy with a back scattered electron detector.
Integrating peatlands and permafrost into a dynamic global vegetation model: 2. Evaluation and sensitivity of vegetation and carbon cycle processes
Authors: Wania R. , Ross I. , Prentice I. C.
Published: August 2009

Peatlands and permafrost are important components of the carbon cycle in the northern high latitudes. The inclusion of these components into a dynamic global vegetation model required changes to physical land surface routines, the addition of two new peatland‐specific plant functional types, incorporation of an inundation stress mechanism, and deceleration of decomposition under inundation. The new model, LPJ‐WHy v1.2, was used to simulate net ecosystem production (NEP), net primary production (NPP), heterotrophic respiration (HR), and soil carbon content. Annual peatland NEP matches observations even though the seasonal amplitude is overestimated. This overestimation is caused by excessive NPP values, probably due to the lack of nitrogen or phosphorus limitation in LPJ‐WHy. Introduction of permafrost reduces circumpolar (45–90°N) NEP from 1.65 to 0.96 Pg C a−1 and leads to an increase in soil carbon content of almost 40 Pg C; adding peatlands doubles this soil carbon increase. Peatland soil carbon content and hence HR depend on model spin‐up duration and are crucial for simulating NEP. These results highlight the need for a regional peatland age map to help determine spin‐up times. A sensitivity experiment revealed that under future climate conditions, NPP may rise more rapidly than HR resulting in increases in NEP.
Solar activity dependence of the topside ionosphere at low latitudes
Authors: Chen Yiding , Liu Libo , Wan Weixing , Yue Xinan , Su Shin‐Yi
Published: August 2009

We investigated the solar activity dependence of the topside ionosphere with ROCSAT‐1 observations. The distribution of the plasma density at 600 km altitude shows features with considerable local time, season, and solar activity differences. In the daytime, plasma density peaks around the dip equator. This peak is more distinct in equinoxes and weaker in May–July, and it enhances with solar activity in all seasons. The seasonal behavior of this peak is primarily controlled by the seasonal variations of neutral density and E × B vertical drift. The enhancement of the peak with solar activity is related to the effect of E × B vertical drift. Around sunset, double peaks are found in the latitudinal distribution of plasma density in solar maximum equinoxes and December solstice, which are mainly attributed to the effects of strong prereversal enhancement (PRE) vertical drift. Moreover, the plasma density at 600 km altitude strongly depends on the solar proxy P = (F107 + F107A)/2. At higher altitudes, e.g., 800 km, the amplification trend prevails in the solar activity variations of plasma density. In contrast, the plasma density at 600 km altitude presents three kinds of patterns (linear, amplification, and saturation), which has not been reported. Saturation effect is found at equinox sunset around the dip equator. This saturation effect is attributed to the increase in the PRE vertical drift with solar activity. Solar activity effects of ROCSAT‐1 plasma density are argued to be the combined effects induced by the changes in the peak height, the scale height, and the peak electron density, respectively. Among these factors, the rise of the F2 peak is more important for the equatorial plasma density at 600 km altitude.
Observations of bed form evolution with field‐scale oscillatory hydrodynamic forcing
Authors: Nichols C. S. , Foster D. L.
Published: August 2009

The evolution of rippled beds in response to irregular waves was examined over short temporal scales. Observations of natural irregularly rippled beds and the oscillatory, two‐dimensional, time‐varying velocity field were collected using a submersible particle image velocimetry (PIV) system. Bed form evolution regimes characterized by the ripple radius of curvature were examined relative to measures of the nondimensional bed stress (the grain roughness Shields parameter), the nondimensional pressure gradient (the Sleath parameter), and the water column coherent structure formation from the ripples (the swirling strength). Bed forms were found to respond to individual waves by modulating amplitude as wave groups passed. The bed form approached its initial geometry following the passage of a group even when the critical value of the Shields parameter for sheet flow was exceeded. However, when the Sleath parameter exceeded the critical value for plug flow, the bed form profile flattened, requiring significant time after the wave group passed to rebuild the ripples. These observations suggest that the ability to predict bed form geometry with respect to wave forcing is possible but requires knowledge of the initial bed form geometry, as well as the flow field evolution.
Age characteristics in a multidecadal Arctic sea ice simulation
Authors: Hunke Elizabeth C. , Bitz Cecilia M.
Published: August 2009

Results from adding a tracer for age of sea ice to a sophisticated sea ice model that is widely used for climate studies are presented. The consistent simulation of ice age, dynamics, and thermodynamics in the model shows explicitly that the loss of Arctic perennial ice has accelerated in the past three decades, as has been seen in satellite‐derived observations. Our model shows that the September ice age average across the Northern Hemisphere varies from about 5 to 8 years, and the ice is much younger (about 2–3 years) in late winter because of the expansion of first‐year ice. We find seasonal ice on average comprises about 5% of the total ice area in September, but as much as 1.34 × 106 km2 survives in some years. Our simulated ice age in the late 1980s and early 1990s declined markedly in agreement with other studies. After this period of decline, the ice age began to recover, but in the final years of the simulation very little young ice remains after the melt season, a strong indication that the age of the pack will again decline in the future as older ice classes fail to be replenished. The Arctic ice pack has fluctuated between older and younger ice types over the past 30 years, while ice area, thickness, and volume all declined over the same period, with an apparent acceleration in the last decade.
Radar reflectivity as a proxy for convective mass transport
Authors: Mullendore G. L. , Homann A. J. , Bevers K. , Schumacher C.
Published: August 2009

More observations of vertical mass transport in deep convection are needed to improve dynamical understanding of detrainment processes and for verification of transport models. A methodology for using radar reflectivity as a direct observation of vertical transport of mass from the boundary layer to the upper troposphere and lower stratosphere is investigated, and the “level of maximum detrainment” (LMD) is proposed. The case investigated is the 26 January 1999 squall line from the Tropical Rainfall Measuring Mission Large‐Scale Biosphere‐Atmosphere field campaign. Echo top heights and dual‐Doppler derived divergence profiles are used to define the mass detrainment range. Over 10% of anvil echo tops occurred above the sounding‐derived level of neutral buoyancy of 15.4 km during the mature stage of the storm, and convective tops reached above 18 km. Anvil ice water content, with a simple correction for ice fall speed, is found to be a good proxy for both the LMD, which for the storm analyzed is 11.25 km, and for the detrainment range of 6 to 17 km. More cases need to be analyzed to confirm the strength of this methodology, but the case study presented shows a strong correlation between anvil properties determined from radar reflectivity and the mass detrainment profile. Thus, radar reflectivity can be used as an indicator of the LMD to test model convective and transport parameterizations.
Response of bedrock channel width to tectonic forcing: Insights from a numerical model, theoretical considerations, and comparison with field data
Authors: Turowski Jens M. , Lague Dimitri , Hovius Niels
Published: August 2009

The morphology of bedrock river channels is controlled by climatic and tectonic conditions and substrate properties. Knowledge of tectonic controls remains scarce. This is partly due to slow tectonic rates and long response times of natural channels and partly due to the difficulty in isolating and constraining tectonic forcing conditions in the field. To study the effect of tectonic forcing on channel geometry, we have developed a numerical model of the cross‐sectional evolution of a detachment‐limited channel. Its predictions are matched by an analytical model based on the assumption of the minimization of potential energy expenditure. Using these models, we illustrate how local tectonics can alter the observed width‐discharge scaling and discuss published field data in light of our findings. Except for one case, the models fail to correctly describe field observations of well‐constrained cases. This implies that the shear stress/stream‐power family of models is too simple to describe the behavior of natural channels. Additional complexities such as sediment effects and discharge variability exert a strong control on channel morphology and need to be taken into account in the modeling of channel dynamics and steady state.
Imprint of foreland structure on the deformation of a thrust sheet: The Plio‐Pleistocene Gela Nappe (southern Sicily, Italy)
Authors: Ghisetti Francesca C. , Gorman Andrew R. , Grasso Mario , Vezzani Livio
Published: August 2009

In Sicily, the progressive imbrication of the Apenninic thrust belt above the Pelagian‐African Foreland is traced by the southward migration of marine basins that were progressively shortened during the late Miocene‐Pleistocene. The outermost and youngest thrust sheet (Gela Nappe) displays a peculiar shortening, with Messinian to early Pliocene E‐W folds refolded in the late Pliocene–early Pleistocene by approximately N‐S folds (subparallel to the transport direction of the thrust sheets). This structural interference is documented in south Sicily within localized belts of refolding spaced ∼5–8 km apart. The significance of this fold interference pattern is highlighted by our analysis of the offshore seismic reflection line M23A (CROP Mare Project) that intersects the Gela Nappe along a trace suborthogonal to the thrust transport direction. Migration and depth conversion of the line reveal multiple imbrications and draping of the allochthonous units above structural highs of the foreland, delimited by inherited N‐S faults. The largest faults bound mid‐late Miocene extensional basins but were reactivated in compression during the late Pliocene–early Pleistocene, causing (1) superposed folding along discordant N‐S structural trends, (2) compressional extrusion of the whole wedge of the Gela Nappe, and (3) offset of its sole thrust. The reactivation of faults subparallel to the transport direction accommodates differential flexure of the rigid foreland beneath the Apenninic wedge, and these late stage deformations in the foreland are responsible for the superposition of E‐W finite shortening onto N‐S shortening.
Reactive iodine species in a semi‐polluted environment
Authors: Mahajan Anoop S. , Oetjen Hilke , Saiz‐Lopez Alfonso , Lee James D. , McFiggans Gordon B. , Plane John M. C.
Published: August 2009

Iodine chemistry in the marine boundary layer has attracted increasing attention over the last few years because iodine oxides cause ozone destruction, change the atmospheric oxidising capacity, and can form ultrafine particles. However, the chemistry of iodine in polluted environments is not well understood: its effects are assumed to be inhibited by reactions involving NOx (NO2 & NO). This paper describes Differential Optical Absorption Spectroscopy (DOAS) observations of iodine species (I2, OIO and IO) and the nitrate radical (NO3) at a semi‐polluted coastal site in Roscoff, France. Significant concentrations of IO and I2 were measured during daytime, indicating efficient recycling of iodine from iodine nitrate (IONO2). I2, IO, OIO and NO3 were observed at night. These observations are interpreted using a one dimensional model to demonstrate that iodine plays an important role even in polluted environments due to recycling mechanisms not considered previously.
Taking the pulse of the Sun during the Holocene by joint analysis of 14C and 10Be
Authors: Knudsen Mads Faurschou , Riisager Peter , Jacobsen Bo Holm , Muscheler Raimund , Snowball Ian , Seidenkrantz Marit‐Solveig
Published: August 2009

We have studied solar variations during the Holocene (i.e., last ∼11,700 yr) by combining a new model of the Earth's dipole moment with 14C data from the IntCal04 record and 10Be data from the GRIP ice core. Joint spectral analysis of the two nuclide records suggests that the periodic behavior of the Sun was particularly pronounced between 6000–4500 yr BP and 3000–2000 yr BP, with dominating periodicities of ∼88, ∼150, ∼220, and ∼400 years, while this rhythmic behavior faded during other time intervals. The fact that the two reconstructions, based on radionuclides with distinct geochemical properties, agree with respect to both the frequency and timing of the periodic behavior, strongly suggests that they reflect the actual behavior of the Sun. Subtle but systematic differences between the amplitude spectra may point to an interplay between the climate system and the ∼220‐ and ∼400‐year solar cycles during intervals when these were particularly prominent.
Invasive Plant (Microstegium vimineum) Reduces Abundance and Richness of Insect Communities
Authors: Simao Maria Carolina , Rudgers Jennifer , Flory S. Luke
Published: August 2009

Plant invasions are known to have negative impacts on native plant communities, yet their effects on higher trophic levels have not been well documented. Past studies investigating the effects of invasive plants on herbivores and carnivores have been largely observational in nature and thus lack the ability to tease apart whether differences are a cause or consequence of the invasion. In addition, understanding how plant traits and plant species compositions change in invaded habitats may increase our ability to predict when and where invasive plants will have effects that cascade to animals. We experimentally introduced a non-native plant (Microstegium vimineum, Japanese stiltgrass) to evaluate impacts on arthropods. We also investigated possible mechanisms through which the invader could affect associated arthropods, including changes in native plant species richness, aboveground plant biomass, light availability, and vegetation height. In experimentally invaded plots, arthropod abundance was reduced by 39%, and species richness declined by 19%. Carnivores experienced greater reductions in abundance than herbivores (61% versus 31% reduction). Arthropod composition significantly diverged between experimentally invaded and control plots, and particular species belonging to the families Aphididae (aphids), Formicidae (ants) and Phalacridae (shining flower beetles) contributed the most to compositional differences. Among the mechanisms we investigated, only the reduction in native plant species richness caused by invasion was strongly correlated with total arthropod abundance and richness. In sum, our results demonstrate negative impacts of M. vimineum invasion on higher trophic levels and suggest that these effects occur, in part, indirectly through invader-mediated reductions in the richness of the native plant community. The particularly strong response of carnivores suggests that plant invasion could reduce top-down control of herbivorous species for native plants. The cascading effects of plant invasion on arthropods reported here reinforce motivation to control M. vimineum spread.
Changes in Simpson’s Diversity Index in Microcosms Impacted with Monosodium Methane Arsenate
Authors: Kish Peter , Daniel Nelson
Published: August 2009

The objective of our studies is to analyze environmental impacts of Monosodium Methane Arsenate, MSMA, on aquatic habitats using the Aqua-Terra microcosm system. MSMA was applied at environmentally relevant(recommended) doses to microcosms to determine the change in biodiversity and the bio-concentration of arsenic in the aquatic plants (Elodea Sp.) used in the microcosms as an oxygen source. The microcosms are filled with unfiltered pond water and the diversity of each microcosm was determined before application of the herbicide. After population stabilization, the herbicide is applied to the terrestrial portion of the microcosm. The herbicide is watered into the microcosm by allowing the herbicide to be filtered by soil into the aquatic portion of the microcosm. Diversity of the microcosm was determined by physical counts of invertebrate organisms and quantified using Simpson’s Index of Diversity. Calculating Simpson’s Index of Diversity indicate there is an overall decline in the diversity of the microcosms from 0.327 to 0.763 for recommended manufacturer’s formulation and 0.512 to 0.546 for twice the recommended manufacturer’s formulation. Plants take up arsenic using the same metabolic pathways that they use to take up phosphorus. This makes arsenic available for trophic transfer to the primary consumers as any primary producer is consumed. In Elodea sp., total arsenic concentrations (ashed from fresh samples) range from 15 ppb to 214 ppb before and after application of the herbicide. Water samples show the same increase, from 5 ppb to 70 ppb before and after application. These data indicate that the arsenic in the MSMA compound is either being liberated by bacterial decomposing or it is passing through the soil unmodified.
Five years of winter climate change-related research in the Canadian low Arctic: What have we learned?
Authors: Grogan Paul , Buckeridge Kate
Published: August 2009

The importance of the fall, winter and spring periods to ecosystem functioning and biogeochemical cycling in tundra has only become apparent in the past two decades. Our research group has been conducting winter climate change-related studies at a low arctic tundra site near Daring Lake, north of Yellowknife in northern Canada for the past five years. Most of these studies have focused on the biogeochemical interactions between plants, soils, and soil microbes during fall, winter and spring, and on their responses to experimentally deepened snow. In addition, we have measured trace gas production and isotopic nitrogen tracer distributions among plant and soil components in several vegetation-types. The central goal has been to understand the potential importance of cold season soil N transformation processes to ecosystem-level biogeochemistry during the subsequent plant growing season, and then to develop predictions of how changes in winter climate may impact these seasonal processes. In this talk, I will present a synthesis of those studies, emphasizing temperature-moisture interactions, and highlighting future research priorities.
Local winter deer density: Effects of forest structure and snow in a managed forest landscape
Authors: Millington James , Walters Michael , Matonis Megan , Liu Jianguo
Published: August 2009

Background/Questions/Methods

White-tailed deer (Odocoileus virginianus) are a ‘keystone herbivore’ with the potential to cause tree regeneration failure and greatly affect vegetation dynamics, stand structure and ecological function of forests across eastern North America. In northern mixed conifer-hardwood forests, local winter-time deer populations are dependent on habitat characterized by patterns of forest cover that provide shelter from snow and cold temperatures (lowland conifer stands) in close proximity to winter food (deciduous hardwood stands). Stand structure may also influence winter spatial deer distribution. Consequently, modification of forest cover patterns and stand structure by timber harvesting will affect local spatial deer distributions, with potential ecological and economic consequences. Here, we ask if forest cover pattern and stand structure, and their interactions with snow depth, can explain winter deer density in the managed forests of the central Upper Peninsula of Michigan, USA. For each local winter deer density estimate (from fecal pellet counts) we calculate stand-level characteristics for surrounding ‘landscapes of influence’ of radius 200 m. For these data, and modeled snow depth estimates, we use multivariate techniques to produce predictive models and to identify the most important factors driving local deer densities across our 400,000 ha study area.

Results/Conclusions

Distance to the nearest conifer stand consistently explains the most variance in univariate regression models. Deer densities are highest near lowland conifer stands in areas where mean hardwood tree diameter-at-breast-height is low. Multiple regression models including these factors explain 22% of variance in deer density and have up to a 65% chance of correctly ranking a site’s deer density (relative to other sites within our study area). We use model ensembles to produce maps of estimated deer density (and associated uncertainty) for a subset of our study area and show how managers might use these maps to aid co-management of deer and forest regeneration. Our results highlight the importance of local and regional factors (forest cover-type pattern, stand structure, climate) on winter white-tailed deer density in managed hardwood-conifer forests. Use of these results, and the simulation model being developed, will help identify management practices that can decrease deer impacts and ensure the ecological and economic sustainability of forests in which deer browse is proving problematic for tree regeneration.
The human HIF (hypoxia-inducible factor)-3α gene is a HIF-1 target gene and may modulate hypoxic gene induction
Authors: Tanaka Tetsuhiro , Wiesener Michael , Bernhardt Wanja , Eckardt Kai-Uwe , Warnecke Christina
Published: August 2009

HIF (hypoxia-inducible factor)-3α is the third member of the HIF transcription factor family. Whereas HIF-1α and -2α play critical roles in the cellular and systemic adaptation to hypoxia, little is known about the regulation and function of HIF-3α. At least five different splice variants may be expressed from the human HIF-3α locus that are suggested to exert primarily negative regulatory effects on hypoxic gene induction. In the present paper, we report that hypoxia induces the human HIF-3α gene at the transcriptional level in a HIF-1-dependent manner. HIF-3α2 and HIF-3α4 transcripts, the HIF-3α splice variants expressed in Caki-1 renal carcinoma cells, rapidly increased after exposure to hypoxia or chemical hypoxia mimetics. siRNA (small interfering RNA)-mediated HIF-α knockdown demonstrated that HIF-3α is a specific target gene of HIF-1α, but is not affected by HIF-2α knockdown. In contrast with HIF-1α and HIF-2α, HIF-3α is not regulated at the level of protein stability. HIF-3α protein could be detected under normoxia in the cytoplasm and nuclei, but increased under hypoxic conditions. Promoter analyses and chromatin immunoprecipitation experiments localized a functional hypoxia-responsive element 5′ to the transcriptional start of HIF-3α2. siRNA-mediated knockdown of HIF-3α increased transactivation of a HIF-driven reporter construct and mRNA expression of lysyl oxidase. Immunohistochemistry revealed an overlap of HIF-1α-positive and HIF-3α-positive areas in human renal cell carcinomas. These findings shed light on a novel aspect of HIF-3α as a HIF-1 target gene and point to a possible role as a modulator of hypoxic gene induction.
The crystal structure of caspase-6, a selective effector of axonal degeneration
Authors: Baumgartner Renato , Meder Gabriele , Briand Christophe , Decock Arnaud , D'arcy Allan , Hassiepen Ulrich , Morse Richard , Renatus Martin
Published: August 2009

Neurodegenerative diseases pose one of the most pressing unmet medical needs today. It has long been recognized that caspase-6 may play a role in several neurodegenerative diseases for which there are currently no disease-modifying therapies. Thus it is a potential target for neurodegenerative drug development. In the present study we report on the biochemistry and structure of caspase-6. As an effector caspase, caspase-6 is a constitutive dimer independent of the maturation state of the enzyme. The ligand-free structure shows caspase-6 in a partially mature but latent conformation. The cleaved inter-domain linker remains partially inserted in the central groove of the dimer, as observed in other caspases. However, in contrast with the structures of other caspases, not only is the catalytic machinery misaligned, but several structural elements required for substrate recognition are missing. Most importantly, residues forming a short anti-parallel β-sheet abutting the substrate in other caspase structures are part of an elongation of the central α-helix. Despite the dramatic structural changes that are required to adopt a canonical catalytically competent conformation, the pre-steady-state kinetics exhibit no lag phase in substrate turnover. This suggests that the observed conformation does not play a regulatory role in caspase-6 activity. However, targeting the latent conformation in search for specific and bio-available caspase-6 inhibitors might offer an alternative to active-site-directed approaches.
Eukaryotic GCP1 is a conserved mitochondrial protein required for progression of embryo development beyond the globular stage in Arabidopsis thaliana
Authors: Haussuehl Kirsten , Huesgen Pitter F. , Meier Marc , Dessi Patrick , Glaser Elżbieta , Adamski Jerzy , Adamska Iwona
Published: August 2009

GCPs (glycoproteases) are members of the HSP70 (heat-shock protein 70)/actin ATPase superfamily that are highly conserved in taxonomically diverse species from bacteria to man, suggesting an essential physiological role. Although originally identified and annotated as putative endopeptidases, a proteolytic activity could not be confirmed for these proteins. Our survey of genome databases revealed that all eukaryotic organisms contain two GCP genes [called GCP1 and GCP2/Kae1 (kinase-associated endopeptidase 1)], whereas prokaryotes have only one, either of the GCP1- (Bacteria) or the GCP2/Kae1- (Archaea) type. GCP2/Kae1 is essential for telomere elongation and transcription of essential genes, although little is known about the localization, expression and physiological role of GCP1. In the present study on GCP1-type proteins from eukaryotic organisms we demonstrated that GCP1 is a mitochondrial protein in Homo sapiens [called here GCP1/OSGEPL1 (O-sialoglycoprotein endopeptidase)] and Arabidopsis thaliana, which is located/anchored to the mitochondrial inner membrane. Analysis of mRNA and protein levels revealed that the expression of GCP1/OSGEPL1 in A. thaliana and H. sapiens is tissue- and organ-specific and depends on the developmental stage, suggesting a more specialized function for this protein. We showed that homozygous A. thaliana GCP1 T-DNA (transferred DNA) insertion lines were embryonic lethal. Embryos in homozygous seeds were arrested at the globular stage and failed to undergo the transition into the heart stage. On the basis of these data we propose that the mitochondrial GCP1 is essential for embryonic development in plants.
Producing American English Vowels During Vocal Tract Growth: A Perceptual Categorization Study of Synthesized Vowels
Authors: Ménard Lucie , Davis Barbara L. , Boë Louis-Jean , Roy Johanna-Pascale
Published: August 2009

Purpose

To consider interactions of vocal tract change with growth and perceived output patterns across development, the influence of nonuniform vocal tract growth on the ability to reach acoustic–perceptual targets for English vowels was studied.

Method

Thirty-seven American English speakers participated in a perceptual categorization experiment. For the experiment, an articulatory-to-acoustic model was used to synthesize 342 five-formant vowels, covering maximal vowel spaces for speakers at 5 growth stages (from 6 months old to adult).

Results

Results indicate that the 3 vowels /i u æ/ can be correctly perceived by adult listeners when produced by speakers with a 6-month-old vocal tract. Articulatory-to-acoustic relationships for these 3 vowels differ across growth stages. For a given perceived vowel category, the infant’s tongue position is more fronted than the adult’s. Furthermore, nonuniform vocal tract growth influences degree of interarticulator coupling for a given perceived vowel, leading to a reduced correlation between jaw height and tongue body position in infantlike compared with adult vocal tracts.

Conclusion

Findings suggest that nonuniform vocal tract growth does not prevent the speaker from producing acoustic–auditory targets related to American English vowels. However, the relationships between articulatory configurations and perceptual targets change from birth to adulthood.
Individual Differences in Ambiguous-Figure Perception: Degree of Handedness and Interhemispheric Interaction
Authors: Christman Stephen D , Sontam Varalakshmi , Jasper John D
Published: August 2009

Research has shown that persons with strong right-hand preference (ie who report using their dominant hand for all manual activities) display a decreased tendency to update bodily and conceptual representations, possibly arising from decreased interaction between the left and right cerebral hemispheres. Current experiments extend these findings to the domain of perceptual representations. In experiments 1 and 2, strong right-handedness was associated with a decreased ability to update perceptual representations in response to gradually changing perceptual input. In experiment 3, strong right-handedness was associated with lower spontaneous reversal rates during the extended viewing of ambiguous figures, and experiment 4 ruled out an explanation in terms of response bias.
Photoelectrochemical synthesis of DNA microarrays
Authors: Chow Brian Y. , Emig Christopher J. , Jacobson Joseph M.
Published: August 2009

Optical addressing of semiconductor electrodes represents a powerful technology that enables the independent and parallel control of a very large number of electrical phenomena at the solid-electrolyte interface. To date, it has been used in a wide range of applications including electrophoretic manipulation, biomolecule sensing, and stimulating networks of neurons. Here, we have adapted this approach for the parallel addressing of redox reactions, and report the construction of a DNA microarray synthesis platform based on semiconductor photoelectrochemistry (PEC). An amorphous silicon photoconductor is activated by an optical projection system to create virtual electrodes capable of electrochemically generating protons; these PEC-generated protons then cleave the acid-labile dimethoxytrityl protecting groups of DNA phosphoramidite synthesis reagents with the requisite spatial selectivity to generate DNA microarrays. Furthermore, a thin-film porous glass dramatically increases the amount of DNA synthesized per chip by over an order of magnitude versus uncoated glass. This platform demonstrates that PEC can be used toward combinatorial bio-polymer and small molecule synthesis.
A network of interactions among seminal proteins underlies the long-term postmating response in Drosophila
Authors: Ram K. Ravi , Wolfner Mariana F.
Published: August 2009

Despite the importance of seminal proteins in fertility and their capacity to alter mated females' physiology, the molecular pathways and networks through which they act have not been well characterized.
Drosophila
seminal fluid includes proteins that fall into biochemical classes conserved from insects to mammals, making it an excellent model with which to address this question.
Drosophila
seminal fluid also contains a “sex peptide” (SP, Acp70A) that plays a major role in regulating egg production and mating behavior in females for several days after mating. This long-term postmating response (LTR) initially requires the association of SP with sperm. The LTR also requires members of the conserved seminal protein classes (two lectins, a protease, and a cysteine-rich secretory protein). Here, we show that these seminal proteins function interdependently, regulating a three-step cascade (first, at the level of seminal protein transfer to the female; second, at the level of stability; and third, at the level of localization within females), leading to the normal localization of SP to sperm-storage organs. This localization is, in turn, necessary for successful induction of the LTR. The requirements for manifestation of the LTR in
Drosophila
establish the paradigm that multiple seminal proteins can exert their actions through a multistep, multicomponent network of interactions.
Nucleosome disassembly intermediates characterized by single-molecule FRET
Authors: Gansen Alexander , Valeri Alessandro , Hauger Florian , Felekyan Suren , Kalinin Stanislav , Tóth Katalin , Langowski Jörg , Seidel Claus A. M.
Published: August 2009

The nucleosome has a central role in the compaction of genomic DNA and the control of DNA accessibility for transcription and replication. To help understanding the mechanism of nucleosome opening and closing in these processes, we studied the disassembly of mononucleosomes by quantitative single-molecule FRET with high spatial resolution, using the SELEX-generated “Widom 601” positioning sequence labeled with donor and acceptor fluorophores. Reversible dissociation was induced by increasing NaCl concentration. At least 3 species with different FRET were identified and assigned to structures: (
i
) the most stable high-FRET species corresponding to the intact nucleosome, (
ii
) a less stable mid-FRET species that we attribute to a first intermediate with a partially unwrapped DNA and less histones, and (
iii
) a low-FRET species characterized by a very broad FRET distribution, representing highly unwrapped structures and free DNA formed at the expense of the other 2 species. Selective FCS analysis indicates that even in the low-FRET state, some histones are still bound to the DNA. The interdye distance of 54.0 Å measured for the high-FRET species corresponds to a compact conformation close to the known crystallographic structure. The coexistence and interconversion of these species is first demonstrated under non-invasive conditions. A geometric model of the DNA unwinding predicts the presence of the observed FRET species. The different structures of these species in the disassembly pathway map the energy landscape indicating major barriers for 10-bp and minor ones for 5-bp DNA unwinding steps.