bluuebunny/crossref_metadata_2025 huggingface dataset:
GROWTH ESTIMATES FOR WARPING FUNCTIONS AND THEIR GEOMETRIC APPLICATIONS
Authors: CHEN BANG-YEN , WEI SHIHSHU WALTER
Published: August 2009

By applying Wei, Li and Wu's notion (given in ‘Generalizations of the uniformization theorem and Bochner's method in p-harmonic geometry’, Comm. Math. Anal. Conf., vol. 01, 2008, pp. 46–68) and method (given in ‘Sharp estimates on -harmonic functions with applications in biharmonic maps, preprint) and by modifying the proof of a general inequality given by Chen in ‘On isometric minimal immersion from warped products into space forms’ (Proc. Edinb. Math. Soc., vol. 45, 2002, pp. 579–587), we establish some simple relations between geometric estimates (the mean curvature of an isometric immersion of a warped product and sectional curvatures of an ambient m-manifold $\tilde M^m_c$ bounded from above by a non-positive number c) and analytic estimates (the growth of the warping function). We find a dichotomy between constancy and ‘infinity’ of the warping functions on complete non-compact Riemannian manifolds for an appropriate isometric immersion. Several applications of our growth estimates are also presented. In particular, we prove that if f is an Lq function on a complete non-compact Riemannian manifold N1 for some q > 1, then for any Riemannian manifold N2 the warped product N1 ×fN2 does not admit a minimal immersion into any non-positively curved Riemannian manifold. We also show that both the geometric curvature estimates and the analytic function growth estimates in this paper are sharp.
Burrow development, nutrient fluxes, carnivory and caching behaviour by Calocaris macandreae (Crustacea: Decapoda: Thalassinidea)
Authors: Pinn Eunice H. , Atkinson R. James A.
Published: August 2009

Using aquaria containing natural sediment, medium-term burrow development was investigated. After initial construction, and over the first month, relatively little burrow development was observed in terms of the number of openings and tunnels created. After an additional six months, however, there was a significant increase in the number of openings and tunnels constructed. In contrast to what might be expected from the number of openings and tunnels created during this period, a significant proportion of the sediment movement was sub-surface and relatively little sediment expulsion occurred. The concentration of nitrite, ammonia and phosphate in the burrow water was generally greater than that of the surface water, whilst the nitrate and sulphate measurements showed no particular pattern. Only the differences in phosphate concentrations were found to be significantly different. These results were indicative of Calocaris macandreae influencing rates of denitrification. This study also provided further evidence of carnivory and caching behaviour in this species.
Relationships between shallow-water cumacean assemblages and sediment characteristics facing the Iranian coast of the Persian Gulf
Authors: Martin Daniel , Fernadez-Arcaya Ulla , Tirado Paula , Dutrieux Éric , Corbera Jordi
Published: August 2009

During two sampling campaigns carried out in August 1998 and November 2002, 232 cumaeans from eight species belonging to the families Bodotriidae and Nannastacidae were collected. This paper presents the first ecological data on a shallow water tropical cumacean assemblage from the Persian Gulf, where 50% of the existing species were recently described as new for the science. Neither the environmental conditions (except for the sediment organic content) nor the cumacean assemblage descriptors differed between the two sampling periods. However, two different species dominated in each period (i.e. Eocuma travancoricum and Heterocuma inerme in 1998 and 2002, respectively) and the MDS analysis revealed differences in the assemblage composition between periods, particularly for the deepest sampling stations. An increasing density together with the increase in gravel content, and a decreasing density together with the increasing silt content characterized the distribution pattern of both the whole cumacean assemblages and the two dominant species, the latter being also positively correlated with the mean grain size and negatively correlated with depth and organic matter (E. travancoricum) and with depth (H. inerme).
Karyotypic analysis of the hermaphroditic viviparous polychaete, Hediste limnicola (Polychaeta: Nereididae): possibility of sex chromosome degeneration
Authors: Tosuji Hiroaki , Togami Kotaro , Miyamoto Junko
Published: August 2009

Karyotypes of the hermaphroditic polychaete Hediste limnicola were examined using an air-drying method and genetic material prepared from regenerating tail and newborn juveniles. Materials were obtained from a lineage of cultured worms originating from Watsonville Slough (California, USA) and maintained for six years in the laboratory. Giemsa-stained preparations were analysed by a computer-assisted image-analysing system for the identification of each chromosome pair. A diploid chromosome number of 26 was obtained from well-spread metaphase chromosomes of mitotic cells, consisting of metacentric (N = 11), submetacentric (N = 1) and telocentric (N = 1) chromosomes. It is possible that hermaphroditism in this species evolved through loss of a pair of sex chromosomes, which are present in closely related congeneric species.
Bilateral comparison ofin situneurolipofuscin accumulation inCallinectes sapiduscaught in the wild
Authors: Pereira Cátia R. , D'Incao Fernando , Fonseca Duane B.
Published: August 2009

Age determination using quantification ofin situneurolipofuscin has been an useful and reliable tool to understand population dynamics of crustaceans. In the present investigation,in situneurolipofuscin was quantified in the medulla terminalis of eyestalks (cluster A cell mass, MT-A), and in the olfactory lobe cell mass 10 (OLCM-10) of the supra-oesophageal ganglion of unknown age blue crabs(Callinectes sapidus)caught in the wild. No significant difference in neurolipofuscin quantity was found between right and left MT-A and between right and left OLCM-10. Comparison between MT-A and OLCM-10 resulted in a weaker correlation. Average neurolipofuscin was 0.353±0.038% vol. and 0.896±0.105% vol. in MT-A and OLCM-10, respectively. Size explained 23% of the variation of neurolipofuscin loading in OLCM-10. No significant relationship was found between size and MT-A neurolipofuscin content. It can be concluded that both structures are suitable for the quantification of neurolipofuscin, and they have the potential for age determination forC. sapidus.
Spatial variability of planktonic invertebrate larvae in the Canary Islands area
Authors: Landeira J.M. , Lozano-Soldevilla F. , Hernández-León S. , Barton E.D.
Published: August 2009

In October 1991, invertebrate larvae abundances were analysed to study the influence of the disturbance of the Canary Current flow by the Canary Islands archipelago on the variability of larval distribution. Two transects and two time-series stations located to the north (non-perturbed zone) and the south (perturbed zone) of the Canary Islands were sampled. Oceanographical data showed a highly stratified water column and zonally uniform salinity and temperature seaward of the African upwelling in the non-perturbed zone, while the perturbed zone presented strong turbulence in the form of mesoscale eddies. Invertebrate larval abundances were lower for most taxa studied in the non-perturbed zone and northern time-series station. Significant differences (P < 0.001) of invertebrate larval abundance between the two zones sampled were found. Decapod larvae were the most abundant larval group in both zones. Stations located in eddy structures presented the highest values of larval densities. Specifically, the larvae collected at Station 18, located in the core of an anticyclonic eddy, represented 60±18% of total larvae collected in the south transect. Finally, our results suggest that eddies, mainly anticyclonic eddies, act as a strong larval retention zone south of the islands, and that there is a local northward transport from the Canary Islands.
The role of birds in dissemination ofFrancisella tularensis: first direct molecular evidence for bird-to-human transmission
Authors: PADESHKI P. I. , IVANOV I. N. , POPOV B. , KANTARDJIEV T. V.
Published: August 2009

During a recent large tularemia outbreak in Bulgaria we found several cases that were remote from the main focus. One case had an unusual mode of transmission. A hunter acquired tularemia through a nail scratch from a buzzard (Buteo buteo) and consequently developed a typical ulceroglandular form of the disease. The diagnosis was confirmed by serological methods and successful cultivation. Comparative strain typing was performed by high-resolution multi-locus variable-number tandem repeat analysis (MLVA). The isolated strain was identical to one of the outbreak genotypes. We consider that this case represents a bird-to-human transmission ofF. tularensis.
Flock management and histomoniasis in free-range turkeys in France: description and search for potential risk factors
Authors: CALLAIT-CARDINAL M. P. , GILOT-FROMONT E. , CHOSSAT L. , GONTHIER A. , CHAUVE C. , ZENNER L.
Published: August 2009

The relationship between flock management and histomoniasis, a re-emergent infection in poultry, was investigated by statistical techniques used in veterinary epidemiology to deal with various problems including: multicollinearity, confounding, interaction or sample size. Associations between the variables describing flock management were examined by multivariate descriptive analysis to reduce the number of independent variables, prior to investigating associations with the disease. No homogenous groups of farms were found in the 44 free-range turkey flocks sampled in France. Histomonas meleagridis was identified in 26/38 flocks and histomoniasis was confirmed in 19 flocks. Cleanliness of the building, wet litter and diarrhoea were linked with H. meleagridis and severity of histomoniasis. Sharing outdoor fields simultaneously with chickens was related to serious macroscopic lesions determined by post-mortem examinations. Contrary to general belief, acidification of drinking water with organic acid had consistent association with the presence of H. meleagridis in turkey caeca. These results confirm previous findings and provide several new hypotheses on the effects of hygiene and water management on H. meleagridis and histomoniasis.
Duality of Ends
Authors: BRUHN HENNING , STEIN MAYA
Published: August 2009

We investigate the end spaces of infinite dual graphs. We show that there exists a natural homeomorphism * between the end spaces of a graph and its dual, and that * preserves the ‘end degree’. In particular, * maps thick ends to thick ends. Along the way, we prove that Tutte-connectivity is invariant under taking (infinite) duals.
Broadband seismic wave radiation process of the 2000 western Tottori, Japan, earthquake revealed from wavelet domain inversion
Authors: Suzuki Wataru , Iwata Tomotaka
Published: August 2009

We develop a new inversion method to obtain the low‐ and high‐frequency wave radiation processes whose border is 1 Hz. In this method, we adopt a consecutive approach to evaluate the fitness between the observed and synthetic strong motions and to synthesize the waveforms. A new feature of our inversion is an evaluation of the fitness of broadband strong motions, including the high‐frequency range, using the wavelet coefficient of velocity waveforms based on the frequency‐dependent characteristics of seismic waves. Another new feature is the introduction into the source inversion of a hybrid Green's function, which is constructed from theoretical and empirical Green's functions for the low‐ and high‐frequency ranges, respectively. In order to reach the global minimum by nonlinear inversion, we introduce a multiscale approach for the low‐frequency inversion. After a synthetic test, the inversion method was applied to the 2000 western Tottori earthquake for three frequency bands. The low‐frequency inversion (0.0625–1 Hz) reveals that the asperity extends from the southeast of the hypocenter to the shallow part of the fault above the hypocenter. The waves of 1–2 Hz are radiated most intensely from the rupture starting area of the southeast asperity. On the other hand, the higher‐frequency waves of 2–4 Hz are radiated most strongly from the edge of the southeast asperity. The inversion result suggests a possibility that broadband strong motions are generated from the asperities, and the high‐frequency wave radiations are particularly related to the initiation and termination of the asperity rupture.
Variation in wind speed and surface shear stress from open floor to porous parallel windbreaks: A wind tunnel study
Authors: Guan De‐Xin , Zhong Ye , Jin Chang‐Jie , Wang An‐Zhi , Wu Jia‐Bing , Shi Ting‐Ting , Zhu Ting‐Yao
Published: August 2009

As vegetative windbreaks become established on a large scale in agricultural ecosystems, understanding the influence of windbreak networks on the momentum budget of the atmospheric boundary layer becomes important. The authors conducted a wind tunnel experiment to study the variation of wind speed profile and surface shear stress of wind flow passing from an open surface to another with parallel windbreaks. Five spacing (L = 5, 10, 15, 20, 30 h, wherein h is the windbreak height) windbreak arrays with moderate porosity (aerodynamic porosity α = 0.501) were used in the experiments. Both near‐floor and over‐array wind speed measurements showed that airflow will approach equilibrium state behind a special windbreak of the array, varying from 4th to 9th windbreak when the spacing change from 30 to 5 h. Within the range of L/h values investigated, arrays with narrower spacing cause higher friction velocity and roughness length, which were up to 2.26 and nearly 100 times those observed over open floor, respectively. A semiempirical momentum budget model is developed on the arrayed surface to estimate windbreak drag and shear stress on the protected floor. Windbreak drag accounts for more than 80% of shear stress on the arrayed surface, and the shear stress on protected floor is less than 20% when L/h < 40 based on the model estimation. The sum of the two estimated components agrees well with the estimates obtained from over‐array wind profiles.
Automated classification of visible and infrared spectra using cluster analysis
Authors: Marzo G. A. , Roush T. L. , Hogan R. C.
Published: August 2009

Planetary space experiments collect large volumes of data whose scientific content requires understanding. Marzo et al. (2006) presented an unsupervised cluster analysis scheme that is able to reduce a spectral data set to a few clusters, allowing for more focused and rapid evaluation of their scientific meaning. Here, we extend the original approach to account for the measurement uncertainty and build a classification scheme. We apply the clustering technique to the ASTER and RELAB libraries of visible and infrared spectral reflectance. These spectral libraries are documented, allowing assignment of a label to each spectrum reflecting its physical and chemical properties. We assess the ability of the original and extended approaches to identify natural clusters of the library spectra and estimate associated uncertainties of the results. We evaluate the scientific meaning of the derived clusters based on the labels contained within each cluster. Once the cluster meanings are defined, we test our classification scheme using a training‐testing approach and evaluate the accuracy of assigning the unknown spectra to the correct cluster.
Seasonality in spatial variability and influence of land use/land cover and watershed characteristics on stream water nitrate concentrations in a developing watershed in the Rocky Mountain West
Authors: Gardner Kristin K. , McGlynn Brian L.
Published: August 2009

In recent decades, the Rocky Mountain West has been one of the fastest growing regions in the United States. Headwater streams in mountain environments may be particularly susceptible to nitrogen enrichment from residential and resort development. We utilized stream water chemistry from six synoptic sampling campaigns combined with land use/land cover (LULC) and terrain analysis in geostatistical modeling to examine the spatial and seasonal variability of LULC impacts on stream water nitrate. Stream water nitrate was spatially correlated for longer distances during the dormant season than during the growing season, suggesting the importance of biological retention. Spatial linear models indicated that anthropogenic sources best predicted stream water nitrate in the dormant season, while variables describing biological processing were the best predictors in the growing season. This work demonstrates the importance of (1) incorporating spatial relationships into water quality modeling and (2) investigating stream water chemistry across seasons to gain a more complete understanding of development impacts on stream water quality.
Characterization of unsaturated porous media by high‐field and low‐field NMR relaxometry
Authors: Stingaciu L. R. , Pohlmeier A. , Blümler P. , Weihermüller L. , van Dusschoten D. , Stapf S. , Vereecken H.
Published: August 2009

A comparison study of nuclear magnetic resonance relaxometry at high and low magnetic field (7 and 0.1 T) has been initiated for investigating the influence of the magnetic field strength, variable clay content, and different degrees of saturation on the relaxometric properties of four ideal porous media. The samples consisted of medium sand with increasing fractions of kaolin clay ranging from 0 to 15%. Six different volumetric water contents between saturation and θ = 0.05 were used. Changes in water content of the samples were achieved by slow evaporation.T2relaxation curves were monitored by the Carr‐Purcell‐Meiboom‐Gill sequence and were further analyzed by inverse Laplace transformation, yieldingT2distribution functions. Sand shows a slight continuous shift with decreasing water content of a bimodal distribution function ofT2to faster relaxation at high and low magnetic field. Sand‐clay mixtures show broad, bimodal distribution functions for both magnetic field intensities which shift slightly with decreasing water content. Signal amplitude behavior with variation of saturation degree was also monitored. An expected proportionality of the total signal amplitude with water content was observed for all samples at 0.1 T, whereas at 7 T deviations occurred for samples with a clay content higher than 5%, which are assigned to loss of signal in the first echo periods. The relaxivity in unsaturated clay‐based porous media is mostly surface dominated, as the weak and comparable dependence of 1/T2onTEat both field strengths shows. Nevertheless, for a reliable determination of water content in mixed systems with varying texture and saturation the employment of multiecho sequences at low magnetic field strength are preferable.
Chemical and isotopic signature of old groundwater and magmatic solutes in a Costa Rican rain forest: Evidence from carbon, helium, and chlorine
Authors: Genereux David P. , Webb Mathew , Solomon D. Kip
Published: August 2009

C, He, and Cl concentrations and isotopes in groundwater and surface water in a lowland Costa Rican rain forest are consistent with the mixing of two distinct groundwaters: (1) high‐solute bedrock groundwater representing interbasin groundwater flow (IGF) into the rain forest and (2) low‐solute local groundwater recharged in the lowlands. In bedrock groundwater, high δ13C (−4.89‰), low 14C (7.98 pM), high R/RA for He (6.88), and low 36Cl/Cl (17 × 10−15) suggest that elevated tracer concentrations are derived from magmatic outgassing and/or weathering of volcanic rock beneath nearby Volcan Barva. In local groundwater, the magmatic signature is absent, and data suggest atmospheric sources for He and Cl and a biogenic soil gas CO2 source for dissolved inorganic carbon. Dating of 14C suggests that the age of bedrock groundwater is 2400–4000 years (most likely at the lower end of the range). Local groundwater has 14C > 100 pM, indicating the presence of “bomb carbon” and thus ages less than ∼55 years. Overall, data are consistent with a conceptual hydrologic model originally proposed on the basis of water budget and major ion data: (1) large variation in solute concentrations can be explained by mixing of the two distinct groundwaters, (2) bedrock groundwater is much older than local groundwater, (3) elevated solute concentrations in bedrock groundwater are derived from volcanic fluids and/or rock, and (4) local groundwater has not interacted with volcanic rock. Tracers with different capabilities converge on the same hydrologic interpretation. Also, transport of magmatic CO2 into the lowland rain forest via IGF seems to be significant relative to other large ecosystem‐level carbon fluxes.
Laboratory‐measured H2SO4‐H2O‐NH3 ternary homogeneous nucleation rates: Initial observations
Authors: Benson David R. , Erupe Mark E. , Lee Shan‐Hu
Published: August 2009

We have measured nucleation rates of sulfuric acid‐water‐ammonia (H2SO4‐H2O‐NH3) ternary homogeneous nucleation (THN), with a fast flow nucleation reactor attached to two chemical ionization mass spectrometers (CIMSs) to measure H2SO4 and NH3 concentrations simultaneously. Under our experimental conditions with a temperature of 288 K and RH from 4–42% and initial [H2SO4] in the 108–109 cm−3 range and [NH3] from 10–50 ppbv (∼2 × 1011–1 × 1012 cm−3), the enhancement factor (EF) compared to the binary system ranges up to ∼1,000 depending on [H2SO4], [NH3] and RH; EF also exponentially increases with decreasing RH and decreasing initial [H2SO4]. The numbers of H2SO4 (9–10) and H2O molecules (6–15) in the critical clusters are reduced in the presence of NH3 [(6–8) and (4–10), respectively]; the number of NH3 molecules in the critical clusters is smaller than 2, under our experimental conditions.
Aircraft measurement of HONO vertical profiles over a forested region
Authors: Zhang Ning , Zhou Xianliang , Shepson Paul B. , Gao Honglian , Alaghmand Marjan , Stirm Brian
Published: August 2009

Here we present the first HONO vertical profiles in the atmospheric boundary layer (BL) and the lower free troposphere (FT) over a forested region in northern Michigan and the neighboring Great Lakes, measured from a small aircraft in summer of 2007. The HONO mixing ratios ranged from 4 to 17 pptv in the FT and from 8 to 74 pptv in the BL. The HONO distribution pattern was strongly influenced by the air column stability, i.e., strong negative HONO gradients existed in stable BL in the morning hours, whereas the HONO distribution was relatively uniform in the unstable and well‐mixed BL in the afternoons. The ground surface was a major source of HONO in the lower BL. The presence of substantial daytime HONO in the FT (∼8 pptv) and in the upper BL (25 pptv) suggests that a significant in situ source of HONO exists in the air column.
Boundary layer plasma flows from high‐latitude reconnection in the summer hemisphere for northward IMF: THEMIS multi‐point observations
Authors: Hasegawa H. , McFadden J. P. , Constantinescu O. D. , Bogdanova Y. V. , Wang J. , Dunlop M. W. , Angelopoulos V. , Frey H. U. , Takada T. , Lavraud B. , Zhang Q.‐H. , Pu Z. Y. , Fazakerley A. N. , Panov E. V. , Volwerk M. , Shen C. , Shi J. K.
Published: August 2009

On 2008‐07‐11, the THEMIS spacecraft, separated both longitudinally and radially, traversed the dayside low‐latitude boundary layer (LLBL) under extended northward IMF. They detected southward flows of magnetosheath plasma from magnetopause reconnection poleward of the northern cusp, which were cold‐dense, and had southward velocity ∼100 km/s and longitudinal extent >3 RE. These features all agree with a global MHD simulation of the magnetosphere for similar conditions, in which under large geomagnetic dipole tilt, an LLBL forms via poleward‐of‐the‐cusp reconnection first in the summer hemisphere and later in the other. Contrary to the simulation, however, the observed LLBL was mostly magnetically closed, characterized by balanced field‐aligned and anti‐field‐aligned electron fluxes, and was less thick (≤0.5 RE). The former suggests comparable reconnection rate in both hemispheres, while the latter suggests the actual reconnection rate being lower, and/or the plasma transport toward the magnetotail being faster, than in the simulation.
A global sensitivity analysis and Bayesian inference framework for improving the parameter estimation and prediction of a process‐based Terrestrial Ecosystem Model
Authors: Tang Jinyun , Zhuang Qianlai
Published: August 2009

A global sensitivity analysis and Bayesian inference framework was developed for improving the parameterization and predictability of a monthly time step process‐based biogeochemistry model. Using a Latin Hypercube sampler and an existing Terrestrial Ecosystem Model (TEM), a set of 500,000 Monte Carlo ensemble simulations was conducted for a black spruce forest ecosystem. A global sensitivity analysis was then conducted to identify the key model parameters and examine the interaction structures among TEM parameters. Bayesian inference analysis was also performed using these ensemble simulations and eddy flux data of carbon, latent heat flux, and MODIS gross primary production (GPP) to reduce the uncertainty of parameter estimation and prediction of TEM. We found that (1) the simulated carbon fluxes are mostly affected by parameters of the maximum rate of photosynthesis (CMAX), the half‐saturation constant for CO2 uptake by plants (kc), the half‐saturation constant for Photosynthetically Active Radiation used by plants (ki), and the change in autotrophic respiration due to 10°C temperature increase (RHQ10); (2) the effect of parameters on seasonal carbon dynamics varies from one parameter to another during a year; (3) to well constrain the uncertainties of TEM predictions and parameters using the Bayesian inference technique, at least two different fluxes of NEP, GPP, and ecosystem respiration (RESP) are required; and (4) different assumptions of the error structures of the flux data used in the Bayesian inference analysis result in different uncertainty bounds of the posterior parameters and model predictions. We further found that, using the Bayesian framework and eddy flux and satellite data, the uncertainty of simulated carbon fluxes has been remarkably reduced. The developed global sensitivity analysis and Bayesian framework could further be used to analyze and improve the predictability and parameterization of relatively coarse time step biogeochemistry models when the eddy flux and satellite data are available for other terrestrial ecosystems.
Structural Integrity of the Golgi is Temperature Sensitive in Conditional‐Lethal Mutants with No Detectable GM130
Authors: Vasile Eliza , Perez Tomas , Nakamura Nobuhiro , Krieger Monty
Published: August 2009

At 39.5 °C in the temperature‐sensitive, conditional‐lethal mutant ldlG, glycoprotein processing is disrupted and secretion is blocked. The ultrastructure of the Golgi apparatus in ldlG cells was examined using immunofluorescence and immunoelectron microscopy. At 34 °C the structure of the Golgi apparatus was normal, whereas after incubation at 39.5 °C for 12 h it disassembled into dispersed vesicles. These reassembled into stacks when cells were returned to 34 °C for 6 h. At both 34 and 39.5 °C, all Golgi markers examined were present at wild‐type levels except GM130, which was undetectable (<5% of control). Transfection with GM130 corrected the mutant phenotypes. Although the endogenous gene encoding NSF is apparently normal in ldlG cells, all mutant phenotypes were corrected by transfection with NSF, suggesting that NSF functioned as an extragenic suppressor. These findings provide additional support for a role of GM130 in determining the properties of the Golgi apparatus and for NSF in influencing GM130 stability and function. They also suggest that, at 34 °C, detectable levels of GM130 are not required for normal Golgi morphology and function, but that GM130 – or a GM130‐dependent protein(s) – does play a role in protecting the Golgi, and thus the cells, from stress at higher temperatures.
MIREOT: the Minimum Information to Reference an External Ontology Term
Authors: Courtot Mélanie , Gibson Frank , Lister Allyson , Malone James , Schober Daniel , Brinkman Ryan , Ruttenberg Alan
Published: August 2009

While the Web Ontology Language (OWL) provides a mechanism to import ontologies, this mechanism is not always suitable. First, given the current state of editing tools and the issues they have working with large ontologies, direct OWL imports have sometimes proven impractical for day-to-day development. Second, ontologies chosen for integration may be under active development and not aligned with the chosen design principles. Importing heterogeneous ontologies in their entirety may lead to inconsistencies or unintended inferences. In this paper we propose a set of guidelines for importing required terms from an external resource into a target ontology. We describe the guidelines, their implementation, present some examples of application, and outline future work and extensions.
The Effects of Climate Change on the Phenological Interactions of Plants and Pollinators
Authors: Inouye David
Published: August 2009

Symposium title: Interdisciplinary Canary: Linkages between Ecology and Sustainable Decision Making in a Dynamic Environment*1)

Background/Question/Methods*

The responses of pollinators to climate change could include changes in phenology of migratory pollinators and in the routes or destinations for their migration, changes in the phenology and distribution of non-migratory species, and changes in the host plants they visit for nectar and pollen. Plants face similar challenges with regard to changes in their distributions, their reproductive phenology, and interactions with both co-flowering species and pollinators (competition, facilitation, etc.). Unless pollinators and their host plants are responding similarly to changing environmental cues that affect their phenology, their historical patterns of interaction, both mutualistic and competitive, are likely to change. Long-term data are essential to investigating which if any of these potential outcomes are occurring. A 36-year record of abundance and phenology of flowering of 90+ wildflower species, surveys of the altitudinal distribution of bumble bees in the 1970s and the past few years, and data from a long-term Malaise trap sampling program, all near the Rocky Mountain Biological Laboratory (West Elk mountains, Colorado) are used for this investigation.

Results/Conclusions*

Although the flowering phenology of all species examined to date is affected by a single environmental event, disappearance of the winter snowpack (range 22 April -19 June since 1975), either their responses to that single cue are not uniform, or different species respond to additional cues in addition to snowmelt (e.g., growing degree days). Thus the community of co-flowering species varies temporally and quantitatively among years; differential sensitivity to frost damage is an example of an environmental variable that generates the quantitative variation among years, and is in turn affected by date of snowmelt. Arrival dates of migratory Broad-tailed Hummingbirds are significantly correlated with the amount of snow remaining on 30 April, and with the day of first flowering of Erythronium grandiflorum (glacier lily), the first flower that they visit at this site in the spring. Altitudinal distributions of at least some bumble bee species, and of the flowers they feed on, are also changing, with one bee species occurring about 600m higher than it did 30 years ago and one wildflower (Mertensia cilata) disappearing from lower altitudes where it was historically common. As these communities of plants and pollinators respond to environmental changes with changes in phenology and distribution, new interactions will be created and old ones will be lost.
Kolmogorov's Hypotheses and Eulerian Turbulence Theory
Authors: Kraichnan Robert H.
Published: August 2009

It is argued that Eulerian formulations are intrinsically unsuited for deriving the Kolmogorov theory because low-order Eulerian moments do not express sufficiently well a statistical dependence of nonsimultaneous amplitudes that accompanies the convection of small spatial scales by large spatial scales. Illustration is made by applying the direct-interaction approximation and a related, higher Eulerian approximation to an idealized convection problem and to a modified Navier-Stokes equation. Convection effects of low wavenumbers on high wavenumbers are removed in the modified equation, and as a consequence the direct-interaction approximation for it yields the Kolmogorov spectrum. Low-order Lagrangian moments provide a promisingly more complete description of the convection of small spatial scales by large, and a search for satisfactory Lagrangian closure approxi-mations seems highly desirable.
Nonstationary Diffusion
Authors: Sandler Stanley I. , Dahler John S.
Published: August 2009

A simple proof is given that the telegrapher's equation provides a more rigorous description of diffusion than does the familiar diffusion equation. Solutions of these two equations are compared and it is shown that they are numerically indistinguishable for most cases of interest. The signal velocity of a concentration pulse is found to be (p/ρ)12 with p the pressure and ρ the fluid density. It is found that in special circumstances the reflection and/or dispersion of concentration waves can occur.
Analysis of Nonsteady Two-Phase Flow
Authors: Rudinger George , Chang Angela
Published: August 2009

The techniques for solving problems of nonsteady, quasi-one-dimensional flows by the method of characteristics have been extended to flows of suspensions of small solid or liquid particles in a gas. The particles cannot follow the rapid velocity and temperature changes that are produced by pressure waves, and complicated relaxation processes result. Such flows are described by six simultaneous differential equations, and their characteristics and associated compatibility equations have been obtained. Terms are included to allow for variable duct area, for external forces that may act on the particles or on the gas, and for heat addition to the particles or the gas. To illustrate the application of the results, two flows in a pipe, filled with a suspension of small particles, are analyzed with the help of a small digital computer. In the first example, one end of the pipe is suddenly opened to a low-pressure reservoir, and the resulting expansion wave is computed. In the second example, a piston in the pipe is impulsively accelerated, and the flow between the resulting shock wave and the piston is obtained. A striking feature of this flow is the slow adjustment of the shock strength from its initial to its equilibrium value.
Stability of Helium II Flow Down an Inclined Plane
Authors: Hsieh Din-Yu
Published: August 2009

The stability of a layer of helium II flowing down an inclined plane is investigated on the basis of the two fluid theory. The expression of mutual friction as suggested by Gorter and Mellink is used in the analysis. In the limit that essentially only the normal fluid is present, the Yih-Benjamin result is recovered. A similar stability criterion holds for the limit that essentially only the superfluid is present. In general, the flow system is stable only when the fluid layer is fairly thin. Then the system may be stable for certain intermediate compositions even when the fluid is flowing down the under-side of the plane. The results may have some bearing on the problem of film flow in superfluid helium.
Exact Evaluation of Tricomi's Transonic Approximation
Authors: Laitone E. V.
Published: August 2009

The exact solution given by Ringleb for the isentropic potential flow about a semi-infinite wall is used to provide a numerical comparison for the corresponding transonic flow solutions obtained from various transformations of the hodograph plane. It is found that the transonic solution given by the Chaplygin transformation is in much better agreement with the exact solution than is the transonic solution obtained from the canonical transformation. It is also found that an appropriate combination of Bessel functions of the ±1/3 order allows the analytic continuation of the transonic potential flow through the sonic line in exact agreement with the Ringleb solution. This solution not only has a smooth expansion from subsonic to supersonic flow but also has an isentropic compression from super-sonic to subsonic flow.
Hydromagnetic Stability of a Vortex Sheet in Compressible Fluids
Authors: Wang K. C. , Maslen S. H.
Published: August 2009

The stability of a vortex sheet between two compressible, perfectly conducting fluids in the presence of uniform, parallel magnetic fields is examined. The ratio between the Alfvén speed and the sound speed is shown to play an important role. In particular, when this ratio is equal to unity in both media, a vortex sheet can be completely stable.
Excitation of Hydromagnetic Waves in a Highly Conducting Liquid
Authors: Gothard Nicholas
Published: August 2009

A study is made of the propagation of hydromagnetic waves along a circular stainless steel wave-guide filled with a fluid (Nak 78) and subject to a steady magnetic field parallel to the guide. The dependence of wavelength and input impedance on frequency was calculated theoretically and confirmed experimentally. The excitation and detection arrangements used are described.
Finite Amplitude Compression Waves in a Collision-Free Plasma
Authors: Morton K. W.
Published: August 2009

One-dimensional compression waves in a collision-free plasma are studied using the adiabatic two-fluid model. It is supposed that an initial magnetic field makes an arbitrary angle θ with the direction of wave propagation and ε2 denotes the electron-ion mass ratio. An extensive study of the steady flows is carried out which is particularly full in the limiting cases ε = 0 or 1; the effect of introducing a friction term in the equations is also considered. Then an asymptotic treatment is found to provide a simple but qualitatively correct picture of the dependence of small amplitude waves on ε and θ between these extremes. Finally the picture is filled in by solving the piston problem numerically. It is found that two types of wave occur: roughly when tan θ > ε−1 − ε, the usual flow consists of a main wavefront followed by an oscillatory wave train; while, in the contrary case, the wave front is preceded by an oscillatory precursor. This precursor is on the scale of the ion gyromagnetic radius while the wave train scales like the geometric mean of this and the electron gyro-radius.
Collision Damping of Two-Stream Instabilities in a Plasma
Authors: May Robert M.
Published: August 2009

Doubt exists as to whether the Gross-Krook collision model is adequate to describe the collisional damping of two-stream instabilities. It is shown here that the model is indeed adequate—the instability ceases to grow after a time of the order of one collision time.
Nonlinear Ambipolar Diffusion of an Isothermal Plasma across a Magnetic Field
Authors: Mosburg E. R. , Persson K.-B.
Published: August 2009

Solutions are presented of the first two moment equations, including nonlinear terms, for the ambipolar diffusion of an isothermal plasma across a magnetic field. The two geometries considered are the plane parallel case and the infinite cylinder with axial symmetry. The Bohm criterion is automatically satisfied by the solutions. It is shown that the singularity in the space derivative of the ambipolar drift velocity at the plasma boundary cannot be removed by an axial magnetic field of any strength. Thus the plasma drift velocity and the plasma density remain monotonic functions of the position coordinate. It is also shown, under the assumptions of this theory, that the ambipolar space charge field is always directed outward and does not reverse direction in this isothermal approximation even for extremely high magnetic fields. One is forced to conclude that a realistic theory of ambipolar diffusion requires the consideration of thermal gradients within the plasma.
Cylindrical Plasma Column in a Transverse Magnetic Field
Authors: Ecker G. , Kanne H.
Published: August 2009

The effect of a transverse homogeneous magnetic field B on a stationary cylindrical plasma column is considered. The problem is solved for the collision-dominated and the collision-free case using first-order perturbation theory in B. The potential and density distributions, the temperature and the Hall reduction factor α = UHall/2Rvd-B are calculated. The limitations of the theory are considered in detail.
Perturbation of a Plasma by a Probe
Authors: Waymouth John F.
Published: August 2009

The theory of the electrostatic probe immersed in a plasma is discussed under the assumptions that particle mean free paths are comparable with or smaller than probe radius. The range of validity of the results is for λc/rp < 10, rp/100λD > 1, λc/λD > 10, where rp is probe radius, λc is particle mean free path, and λD is the Debye length. In the limit of λc/rp approaching infinity, the results converge toward the Langmuir result for the same probe. The probe-current vs voltage characteristic obtained when mean free paths are short is distorted because the degree of perturbation of plasma density and potential vary with probe voltage. An unexpected result is that the shape of the probe characteristic in the vicinity of the "knee" is sensitive to ion temperature, and may possibly be used to determine the ion temperature.
A Percus–Yevick description of the microstructure of short-range interacting metastable colloidal suspensions
Authors: Muratov A. , Moussaïd A. , Narayanan T. , Kats E. I.
Published: August 2009

We present a revised form of the Percus–Yevick approach applicable to dispersions of interacting colloidal particles such as colloid-polymer mixtures and square-well attractive colloids. Our approach is suitable for treating short-range interparticle potentials including excluded volume hard-sphere repulsion, short-range depletion attraction, and square-well attraction. In all these cases, the Ornstein–Zernike equation for the pair correlation function can be satisfied by a trial function, which generalizes the Wertheim [Phys. Rev. Lett. 10, 321 (1963)] and Baxter [J. Chem. Phys. 49, 2770 (1968)] ansatz. Structure factors (or x-ray scattering intensities) calculated by this method are in good agreement with experimental data for colloid-polymer mixtures over a range of parameters pertaining to the stable fluid phase and the metastable state with moderate attraction. On the same footing, we have determined the stability limits and analyzed contributions to the scattered intensity from particle aggregates appearing prior to the phase separation for sufficiently strong short-range attraction. Similar features are observed in the case of square-well attractive colloids when the attraction is turned on.
Three-dimensional “Mercedes-Benz” model for water
Authors: Dias Cristiano L. , Ala-Nissila Tapio , Grant Martin , Karttunen Mikko
Published: August 2009

In this paper we introduce a three-dimensional version of the Mercedes-Benz model to describe water molecules. In this model van der Waals interactions and hydrogen bonds are given explicitly through a Lennard-Jones potential and a Gaussian orientation-dependent terms, respectively. At low temperature the model freezes forming Ice-I and it reproduces the main peaks of the experimental radial distribution function of water. In addition to these structural properties, the model also captures the thermodynamical anomalies of water: The anomalous density profile, the negative thermal expansivity, the large heat capacity, and the minimum in the isothermal compressibility.
Origin and suppression of V-shaped defects in the capping of self-assembled InAs quantum dots on graded Si1−xGex/Si substrate
Authors: Tanoto H. , Yoon S. F. , Ng T. K. , Ngo C. Y. , Dohrman C. , Fitzgerald E. A. , Tan L. H. , Tung C. H.
Published: August 2009

Self-assembled InAs quantum dots (QDs) on graded Si1−xGex/Si substrate were observed to adopt a truncated pyramidal shape when capped with GaAs. Our results suggest that atomic migration from the QD apex to the GaAs cap layer contributes to the formation of the symmetrical V-shaped defects near the top edges of the truncated pyramidal QDs. By employing an In0.1Ga0.9As cap, material migration and strain around the QDs were reduced, hence suppressing the occurrence of the V-shaped defects. Furthermore, photoluminescence thermal quenching rate of the QDs is significantly slower compared to the QDs with GaAs cap. Finally, 1.3 μm room-temperature photoluminescence was observed.
Spontaneous formation of a polariton condensate in a planar GaAs microcavity
Authors: Wertz Esther , Ferrier Lydie , Solnyshkov Dmitry D. , Senellart Pascale , Bajoni Daniele , Miard Audrey , Lemaître Aristide , Malpuech Guillaume , Bloch Jacqueline
Published: August 2009

We report on polariton condensation in a planar GaAs microcavity under nonresonant optical excitation. Angularly resolved photoluminescence measurements demonstrate polariton condensation for temperature up to 40 K. Numerical simulations using Boltzmann equations give an overall description of the observed condensation for various detunings and temperatures. This model highlights the importance of the polariton relaxation rate as compared to the polariton decay for condensation to occur on the lowest energy polariton states.
Effect of defect saturation on terahertz emission and detection properties of low temperature GaAs photoconductive switches
Authors: Rihani Samir , Faulks Richard , Beere Harvey , Page Hideaki , Gregory Ian , Evans Michael , Ritchie David A. , Pepper Michael
Published: August 2009

We present a study into the properties of terahertz (THz) emission and detection using low temperature grown GaAs photoconductive switches over a range of ex situ anneal temperatures. Our analysis focuses on the effect of defect saturation, which has been confirmed in many experiments. However its effect on the THz emission and detection has so far not been fully investigated. In this letter, we examine the dependence of the radiated THz pulse width (full width at half maximum) upon optical power, and show that the differences in the characteristics with annealing can be theoretically accounted for when defect saturation is taken into account. Defect saturation was found to substantially increase the trapping time of photoexcited electrons, which in turn can cause THz pulse broadening at high optical powers. This effect was found to increase with anneal temperature due to the decrease in defect density. The radiated peak THz amplitude from emitters increases monotonically with increasing optical power across the range of anneal temperatures investigated. In the detector configuration, however, the detected peak THz amplitude reaches a maximum before starting to decrease with increasing optical power. The latter trend was observed for devices annealed at temperatures higher than 300 °C and is attributed to the onset of defect saturation.