bluuebunny/crossref_metadata_2025_split huggingface dataset:
Frequency Dependence of Dislocation Damping in Single-Crystal Copper
Authors: Heiple Clinton R. , Birnbaum H. K. 
Published: January 2005

The frequency dependence of the amplitude-independent and amplitude-dependent dislocation damping was measured on the same high-purity copper single crystal in both the kilocycle and megacycle frequency ranges. The dislocation contribution to the elastic modulus was also measured in the kilocycle range. The results are discussed in terms of a theoretical calculation which treats the dislocation as a pinned elastic string which experiences a viscous drag proportional to its velocity. The kilocycle dislocation damping exhibited an approximately linear frequency dependence; however, a somewhat better fit to the data can be made with a relation of the form Δ=αω−1+βω. It is proposed that the term αω−1 is a contribution from the high-frequency side of a low-frequency dislocation damping maximum. The dislocation damping in the megacycle range was proportional to ω−1. The kilocycle and megacycle data are consistent with a curve of the form Δ=K[ωτ/(1+ω2τ2)] (except at the lower kilocycle frequencies measured), as predicted by the string model. The maximum is at 1.7 Mc/sec. Based on the agreement of the data with the theoretical model, the dislocation density is calculated to be 1.1×106 cm−2 and the average loop length to be 5.7×10−4 cm, assuming an exponential loop-length distribution. The modulus defect was found to be independent of frequency, except for a possible small rise with decreasing frequency below 30 kc/sec.
The amplitude-dependent internal friction of the specimen in the kilocycle range was found to be frequency dependent in the annealed state and to be frequency independent in the irradiated state. The strain amplitude above which the specimen exhibited amplitude dependence was observed to increase with frequency in the kilocycle range.
Interactions between a Solute Atom and an Array of Edge Dislocations
Authors: Cosgrove G. J. , Liu H. W. 
Published: January 2005

Elastic and electrostatic interactions between an impurity atom and an edge-dislocation array have been investigated. The elastic interaction is calculated from the volume difference of the solute atom and the stress field of an edge-dislocation array piled up at a barrier. The range of the elastic interaction of an array of dislocations with an impurity extends much further than that with an isolated dislocation.
Classical electrostatic theory has been employed to study the interaction between a charged impurity atom and an array of edge dislocations. In the calculation, a linear electric dipole is assumed to be associated with each edge dislocation. The electrostatic-interaction potential of a dislocation array with an impurity atom is taken as the sum of the potentials of all the dislocations in the array. An expression for the electrostatic-interaction potential has been derived and numerical results are calculated and compared with the interaction between a charged impurity atom and an isolated dislocation as given by Cottrell, Hunter, and Nabarro. The electrostatic-interaction potential of an array is found to be higher than the interaction with an individual dislocation only when the leading dislocations are very close together. This is expected since the range of the electrostatic field of a dipole is very short. Both electrostatic and elastic interactions are dependent upon the net applied stress on the slip plane.
Transformation Theory of Guided Waves in Moving Media
Authors: Jiang Ching Lin 
Published: January 2005

The problem of wave propagation in a waveguide filled with a moving medium is investigated theoretically. There is no limitation on the velocity of the medium. Without solving the Maxwell's equations in moving media as viewed by a stationary observer, the normal-mode wave solutions in the guide are constructed by a transformation of the field tensors. The orthogonality conditions and the mode completeness are shown to be still valid, and the power flow is also discussed.
Two cases of the media are considered in detail: (a) the nondispersive dielectric and (b) the cold plasma. Several interesting features concerning the cutoff phenomena, phase velocity, and group velocity are discussed and compared for both cases.
Determination of Average Plasma Conductivity by rf Probes
Authors: Ciampi M. , Talini N. 
Published: January 2005

Study of determination of the spatial average plasma conductivity by a radio-frequency probe is tackled for a cylindrical plasma assumed radially inhomogeneous.
The real and imaginary part of the probe impedance vs the probing frequency are found numerically for inhomogeneous plasmas with conductivity profiles of the type σ(ρ) = σmax(1−mρn).
With such an analysis only two independent average conductivities are found, both at low frequency.
The analytical form of the average conductivities is obtained, comparing, in a low-frequency approximation, the tested inhomogeneous medium with a fictitious homogeneous one for which the real or imaginary part of the probe impedance varies in the same way.
As a result of a measurement of the rf energy dissipation in the medium (effected by evaluating the probe Q-factor), the average conductivity is σ*=(4/R4) ∫ 0Rσ(r)r3dr;the average conductivity becomes σ**2=34[(4/R4) ∫ 0Rσ(r)r3dr]2+(3/2R6) ∫ 0Rr5dr[(4/r4) ∫ 0rσ(r)r3dr]2in case of a measurement of the inductance variation.
An application of the method is carried out in a flow facility plasma jet; with Q-factor measurements from 0.5 to 1.5 MHz, average conductivity values from 75 to 100 mho/m are obtained.
The probe is calibrated with electrolytic solutions (H2SO4) of standard conductivity.
Elastic Aftereffects and Dielectric Absorption in Glass
Authors: Taylor Nelson W. 
Published: January 2005

Taylor and Doran have found that in stabilized glasses the total elastic adjustment under a given load may be represented as the sum of several terms of the type l=l0e−kt, and have drawn the conclusion that there are several sizes of complex silicate ions in glass which respond independently and with different rates to applied stress.
Hopkinson proposed that there are several independent ``elements'' responding to the application of an electric field to a glass condenser, and von Schweidler showed that the anomalous charging current accompanying dielectric polarization is the sum of several terms of the type i=Ae−t/T. This expression is identical in form with that for elastic polarization if the rate constant k is replaced by a characteristic relaxation time constant 1/T. The dielectric phenomena thus appear to support the concept of independently acting ions in glass. This idea is in harmony with the x-ray evidence of a random ionic network, and with other physico-chemical evidence.
An interpretation of memory phenomena such as reversal effects in glass and rubber has been offered. Such reversals appear to be due to the superposition of two or more independent operations with different rate constants and directions.
Quantitative tests of interaction between pollinating and non‐pollinating fig wasps on dioeciousFicus hispida
Authors: Peng Yan Q. , Yang Da R. , Wang Qiu Y. 
Published: January 2005

Abstract. 1. The interaction betweenFicusspecies and their pollinating wasps (Agaonidae) represents a striking example of a mutualism. Figs also shelter numerous non‐pollinating chalcids that exploit the fig–pollinator mutualism.2. Previous studies showed a weak negative correlation between numbers of pollinating and non‐pollinating adults emerging from the same fruit. Little is known about the patterns and intensities of interactions between fig wasps. In the Xishuangbanna tropical rainforests of China, the dioeciousFicus hispidaL. is pollinated byCeratosolen solmsi marchaliMayr and is also exploited by the non‐pollinatorsPhilotrypesis pilosaMayr,Philotrypesissp., andApocrypta bakeriJoseph. Here, the interaction of pollinator and non‐pollinators onF. hispidais studied quantitatively.3. The exact time of oviposition was determined for each species of fig wasp. Based on observational and experimental work it is suggested that (i) the relationship between pollinator and non‐pollinators is a positive one, and that the genusPhilotrypesisappears to have no significant impact on the pollinator population, whereasApocryptahas a significant effect on bothPhilotrypesisandCeratosolen; (ii) gall numbers do not always increase with increasing number of foundresses, but developmental mortality of larvae correlates positively with the number of foundresses; and (iii) there is a positive correlation between non‐pollinator numbers and their rates of parasitism, but the three species of non‐pollinators differed in their rates of parasitism and show different effects on pollinator production.4. The rates of parasitism when combined with the coexistent percentage and developmental mortality, underpin the way non‐pollinating fig wasps successfully exploit and coexist stably in a fig–pollinator mutualism.
Dispersal ability and host‐plant characteristics influence spatial population structure of monophagous beetles
Authors: St Pierre Matthew J. , Hendrix Stephen D. , Lewis Cassandra K. 
Published: January 2005

Abstract. 1. Dispersal plays an integral role in determining spatial population structure and, consequently, the long‐term survival of many species. Theoretical studies indicate that dispersal increases with population density and decreasing habitat stability. In the case of monophagous insect herbivores, the stability of host‐plant populations may influence their spatial population structure.2. The tallgrass prairie in Iowa, U.S.A. is highly fragmented and most prairie insects face a landscape with fewer habitat patches and smaller host‐plant populations than 150 years ago, potentially making dispersal between patches difficult. Some herbivores, however, use native plant species with weedy characteristics that have increased in abundance because of disturbances.3. Mark–recapture data and presence–absence surveys were used to examine dispersal and spatial population structure of two monophagous beetles with host plants that exhibit different population stability and have responded differently to fragmentation of tallgrass prairie.4.Chrysochus auratusFabricius exhibits a patchy population structure and has relatively large dispersal distances and frequencies. Its host plant is variable locally in time and space, but is more abundant than 150 years ago. The other species,Anomoea laticlaviaForster, exhibits a metapopulation or non‐equilibrium population structure and has relatively small dispersal distances and frequencies. Its host‐plant populations are stable in time and space.5. The results indicate that dispersal ability of monophagous beetles reflects the life‐history dynamics of their host plants, but the spatial population structure exhibited today is strongly influenced by how the host plants have responded to the fragmentation process over both time and space.
Role of nesting resources in organising diverse bee communities in a Mediterranean landscape
Authors: Potts Simon G. , Vulliamy Betsy , Roberts Stuart , O'Toole Chris , Dafni Amots , Ne'eman Gidi , Willmer Pat 
Published: January 2005

Abstract.  1. The habitat components determining the structure of bee communities are well known when considering foraging resources; however, there is little data with respect to the role of nesting resources.2. As a model system this study uses 21 diverse bee communities in a Mediterranean landscape comprising a variety of habitats regenerating after fire. The findings clearly demonstrate that a variety of nesting substrates and nest building materials have key roles in organising the composition of bee communities.3. The availability of bare ground and potential nesting cavities were the two primary factors influencing the structure of the entire bee community, the composition of guilds, and also the relative abundance of the dominant species. Other nesting resources shown to be important include availability of steep and sloping ground, abundance of plant species providing pithy stems, and the occurrence of pre‐existing burrows.4. Nesting resource availability and guild structure varied markedly across habitats in different stages of post‐fire regeneration; however, in all cases, nest sites and nesting resources were important determinants of bee community structure.
Density, dispersal, and feeding impact of western flower thrips (Thysanoptera: Thripidae) on flowering chrysanthemum at different spatial scales
Authors: Rhainds Marc , Shipp Les , Woodrow Lorna , Anderson Dale 
Published: January 2005

Abstract.  1. This study evaluated the effect of dispersal on the density and feeding impact of a phytophagous insect in relation to the spatial distribution of its host plants.2. The interaction between density, dispersal, and feeding impact of western flower thrips on flowering chrysanthemum was quantified at three spatial scales, with infested and uninfested plants either isolated in 0.25 m2 individual cages, or enclosed together in 2.25 m2 communal cages or 75 m2 greenhouses.3. In individual cages, the rate of dispersal from chrysanthemum plants to blue sticky traps increased with the density of thrips for females but not males. Uninfested plants consistently had fewer thrips when they were individually caged rather than enclosed with plants infested with adults, indicating that dispersal mediates inter‐plant distribution of thrips.4. The feeding impact of thrips on inflorescences was evaluated using the absorbance of ethanol extracts at wavelengths characteristic of yellow carotenoid pigments associated with chrysanthemum inflorescences (415, 445, and 472 nm). Increasing absorbance of extracts with increasing density of thrips per inflorescence suggests that feeding by thrips results in ruptured cells leaching carotenoid pigments.5. In communal cages, the distribution of thrips was uniform for infested and uninfested plants, whereas the density and feeding impact of thrips in greenhouses were higher for infested than uninfested plants. These results suggest that short‐range dispersal by adults homogenises the density and feeding impact of thrips among host plants only on a small spatial scale.
Flower‐heads, herbivores, and their parasitoids: food web structure along a fertility gradient
Authors: Fonseca Carlos Roberto , Prado Paulo I. , Almeida‐Neto Mário , Kubota Umberto , Lewinsohn Thomas M. 
Published: January 2005

Abstract.  1. The ways in which a soil fertility gradient affects three trophic level food webs defined by plants of the family Asteraceae, flower‐head herbivores, and their parasitoids was investigated. It was tested how the fertility gradient alters: (i) the abundance and richness of plants, herbivores, and their parasitoids, (ii) the herbivore–plant ratio, and (iii) the connectance of the plant–herbivore community matrix.2. From April to May 2000, plants and insects were sampled in 16 Brazilian Cerrado (sensu stricto) sites along a physiognomic gradient varying from open shrublands (cerrado) to closed woodlands (cerradão). Sites were objectively positioned along the physiognomic gradient by a single index, tree density. Sixty‐seven per cent of the variation in tree density among sites was correlated to two principal components of a PCA, representing gradients of soil fertility.3. Asteraceae abundance, richness, and flower‐head availability were negatively related to tree density due to their preference for sunny environments, despite the surplus of soil nutrients. The abundance and richness of Diptera and Lepidoptera, the most important flower‐head herbivores, were also negatively related to tree density. Parasitoid abundance decreased with tree density; however, the number of parasitoids per hosts was lower in cerrado, suggesting that top‐down forces are not getting stronger in more productive sites, as could be expected.4. Community allometry analyses showed that the herbivore to plant ratio was independent of community richness and did not respond to tree density.5. Connectance of the plant–herbivore matrix was dependent on the community matrix size. Proportionally, species‐rich cerrado sites had fewer interactions than their species‐poor counterparts. Nevertheless, after removing the effect of the matrix size, connectance was not related to tree density.6. Soil fertility, as the primary cause of the cerrado–cerradão physiognomic gradient, strongly affected the abundance and richness of plants, herbivores and their parasitoids; however, it had little effect on important community attributes, such as the herbivore–plant ratio and the connectance of the plant–herbivore matrix.
Pollution by conspecifics as a component of intraspecific competition among Aedes aegypti larvae
Authors: Bédhomme Stéphanie , Agnew Philip , Sidobre Christine , Michalakis Yannis 
Published: January 2005

Abstract.  1. The role of pollution by conspecifics in the costs associated with larval intraspecific competition was investigated for Aedes aegypti (Diptera: Culicidae).2. The growth of larval A. aegypti mosquitoes reared in clean water and water in which another larva had previously grown was compared; this procedure eliminates interactions through food consumption between competitors and allows the effects of other processes to be expressed.3. A cost of growing in polluted water was found: this cost was expressed as an increase in developmental time and a reduction of adult longevity when starved, starved adult dry weight, and wing length.4. Contrary to previously reported results of an experiment allowing for competition for food, these costs were not expressed in a sex‐specific manner and were independent of the sex of the polluter.5. It was thus demonstrated that competition arises from both resource depletion and other effects that result in deterioration of the environment, with chemical pollution of the environment being the most likely cause.
Direct and indirect interactions involving ants, insect herbivores, parasitoids, and the host plantBaccharis dracunculifolia(Asteraceae)
Authors: Fagundes Marcílio , Neves Frederico S. , Fernandes G. Wilson 
Published: January 2005

Abstract. 1. The relative importance of direct and indirect interactions in controlling organism abundance is still an unresolved question. This study investigated the role of the direct and indirect interactions involving ants, aphids, parasitoids, and the host plantBaccharis dracunculifolia(Asteraceae) on a galling herbivoreBaccharopelma dracunculifoliae(Homoptera: Psyllidae).2. The effects of these interactions on the galling herbivore's performance were evaluated by an exclusion experiment during two consecutive generations of the galling insect.3. Ants had a direct negative effect on the performance of the galling herbivore by reducing the number of nymphs per gall. In contrast, ants had no indirect effects on gall mortality through the associated parasitoids.4. Aphids negatively affected gall development, suggesting that galls and aphids might be partitioning photoassimilates and nutrients moving throughout host‐plant tissues.5. In addition, galls that developed during the rainy season were heavier, indicating that variation in the host plant, due to weather changes, can affect the development ofB. dracunculifoliaegalls. However, variation in the development ofB. dracunculifoliaegalls due to presence of aphids or the weather changes did not affect parasitoid attack.6. These results suggest that direct interactions between ants and galls influenced galling insect abundance, whereas numerical indirect effects involving galling insects, ants, aphids, and host plants were less conspicuous.
Interactions between granivorous and omnivorous ants in a desert grassland: results from a long‐term experiment
Authors: Valone Thomas J. , Kaspari Michael 
Published: January 2005

Abstract.  1. There is growing evidence that granivorous ants compete for seeds in desert ecosystems. But ants that diverge in diet may still interact strongly if existing colonies deter foundress queens. Granivores (seed eaters) and omnivores (ants that scavenge and feed on plant exudates) are common components of desert ecosystems.2. The results of a 15‐year granivore reduction experiment to explore the responses of two common omnivorous ants, Forelius cf pruinosus and Dorymyrmex insana, in a desert grassland were analysed. The food competition hypothesis predicts that granivore removal will have no net effect on omnivores. The spatial competition hypothesis predicts compensatory increases in omnivores on granivore removal plots.3. A grain‐based gut poison significantly reduced the densities of three of the four common granivorous ants. Densities of the large‐colony (105‐worker) omnivore Forelius did not increase with granivore removal. In contrast, and consistent with the hypothesis of competition for space, densities of the small‐colony omnivore (102−103 worker) Dorymyrmex increased on granivore removal plots; however, this effect was only observed in years of high Dorymyrmex abundance.
Does differential predation permit invasive and native mosquito larvae to coexist in Florida?
Authors: Griswold Marcus W. , Lounibos L. Philip 
Published: January 2005

Abstract. 1. The hypothesis that selective predation on larvae of the invasiveAedes albopictus(Skuse) could account for its stable coexistence with the native mosquito species and inferior competitorOchlerotatus triseriatus(Say) in Florida treeholes and container systems was tested experimentally.2. Functional responses of the two dipteran predatorsToxorhynchites rutilus(Coquillett) andCorethrella appendiculata(Grabham) were evaluated separately forA. albopictusandO. triseriatusprey. Both predators exhibited type II functional responses and consistently consumed more of the invasive species. Handling time ofT. rutilusfeeding uponO. triseriatuswas significantly longer than when preying upon the invasive species.3. When either predator species was offered varying ratios of the two prey species,A. albopictuswas consumed preferentially. The absence of a prey ratio effect on preference indicated that switching probably does not occur.4. The higher maximum feeding rate upon, and preference for,A. albopictussuggests that differential predation may foster coexistence of the invasive and native mosquito prey species in Florida.