bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the thermodynamic and transport properties of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with LiClO4 and Bu4NBr in water at 25 °C
Authors: Perron Gérald , Brouillette Dany , Desnoyers Jacques E.
Published: May 2006

Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) is a promising electrolyte for lithium batteries. While it presents many interesting features in aprotic solvents (high solubility and conductivity, electrochemical stability, etc.), little is known about its properties in water. The solid–liquid phase diagram, surface tension, volume, heat capacity, and conductivity were therefore measured at 25 °C and compared with the same properties of typical hydrophilic (LiClO4) and hydrophobic (Bu4NBr) electrolytes. To help in the comparison, some of the literature data for LiClO4 and Bu4NBr were extended. The standard Λ0, [Formula: see text] and [Formula: see text] are respectively 71.12 S cm2 mol−1, 139.7 cm3 mol−1 and 543 J K−1 mol−1at 25 °C. LiTFSI s quite soluble, and shows surface activity and a small tendency for self-association in water. The aggregation number estimated from a mass-action model is of the order of 4. Keywords: lithium bis(trifluoromethylsulfonyl)imide, lithium perchlorate, tetrabutylammonium bromide, volume, heat capacity, phase diagram, thermal analysis, surface tension, conductance.
Preparation and characterization of oxide film electrodes
Authors: Battisti A. De , Lodi G. , Nanni L. , Battaglin G. , Benedetti A.
Published: May 2006

In this paper are presented data on the preparation and characterization of different oxide electrodes. RuO2–TiO2, IrO2–TiO2, and SnO2–Sb2O5 mixed-oxide films have been taken as model systems. For the first, the traditional preparation method based on the pyrolysis of precursor salt deposits was adopted. For the SnO2-based films, the spray pyrolysis preparation has been used. The characterization of RuO2–TiO2 films confirms the existence of a solid solution between the two component oxides over a wide composition range. Rutherford backscattering spectrometry confirms the occurrence of segregation of titanium oxide species in the outermost part of the films. Nuclear reaction analysis indicates that large amounts of carbon and hydrogen impurities are trapped in the oxide films. SnO2-based films were found to be less porous and chemically more simple. The differences between the two systems have been discussed in terms of the preparation method and the differences in chemical properties of the precursors. Keywords: oxide film electrodes, mixed-oxide films, Rutherford backscattering spectrometry, nuclear reaction analysis.
Capacitive and kinetic characteristics of Ru–Ti oxide electrodes: influence of variation in the Ru content
Authors: Tilak B.V. , Chen C.-P. , Birss V.I. , Wang J.
Published: May 2006

A systematic investigation has been carried out of thermally formed Ru–Ti oxide electrodes of varying Ru content, correlating their voltammetric and impedance characteristics in NaCl solutions with the kinetics of the chlorine evolution reaction. The Tafel slope increases markedly with lower Ru content (< ca. 25 at.%), indicative either of the contribution of increasing oxide resistance or of a change in mechanism. The exchange current density is linearly proportional to the Ru content down to <10 at.% Ru, below which the film appears to respond more like a highly resistive film material. The film resistance and capacitance, determined by equivalent circuit fitting in the absence of dissolved chlorine, were used to calculate the expected impedance response of the oxide film, based on a model of an activation-controlled surface redox reaction occurring in a porous matrix. The calculated results show the dominant signature of the matrix resistance at low Ru loadings, in both the phase angle impedance data and in the Tafel plots, in agreement with the experimental observations. Keywords: Ru oxide, Ru–Ti oxide, chlorine evolution, kinetics, capacitance, equivalent circuit, impedance, Tafel data.
MATRIX TECHNIQUES FOR TWO-DIMENSIONAL O(N) MODELS
Authors: AGUADO MIGUEL
Published: May 2006

Recently developed matrix techniques, useful in the study of O (N) models on a two-dimensional lattice with different boundary conditions, are reviewed. Their application to perturbative problems is considered for illustration.
VACUUM STABILITY IN SPLIT SUSY AND LITTLE HIGGS MODELS
Authors: DATTA ALAKABHA , ZHANG XINMIN
Published: May 2006

We study the stability of the effective Higgs potential in the split supersymmetry and Little Higgs models. In particular, we study the effects of higher dimensional operators in the effective potential on the Higgs mass predictions. We find that the size and sign of the higher dimensional operators can significantly change the Higgs mass required to maintain vacuum stability in Split SUSY models. In the Little Higgs models the effects of higher dimensional operators can be large because of a relatively lower cutoff scale. Working with a specific model we find that a contribution from the higher dimensional operator with coefficient of O(1) can destabilize the vacuum.
THE PHENOMENOLOGY OF UNIVERSAL EXTRA DIMENSIONS AT HADRON COLLIDERS
Authors: MACESANU COSMIN
Published: May 2006

Theories with extra dimensions of inverse TeV size (or larger) predict a multitude of signals which can be searched for at present and future colliders. In this paper, we review the different phenomenological signatures of a particular class of models, universal extra dimensions, where all matter fields propagate in the bulk. Such models have interesting features, in particular Kaluza–Klein (KK) number conservation, which makes their phenomenology similar to that of supersymmetric theories. Thus, KK excitations of matter are produced in pairs, and decay to a lightest KK particle (LKP), which is stable and weakly interacting, and therefore will appear as missing energy in the detector (similar to a neutralino LSP). Adding gravitational interactions which can break KK number conservation greatly expands the class of possible signatures. Thus, if gravity is the primary cause for the decay of KK excitations of matter, the experimental signals at hadron colliders will be jets + missing energy, which is typical of supergravity models. If the KK quarks and gluons decay first to the LKP, which then decays gravitationally, the experimental signal will be photons and/or leptons (with some jets), which resembles the phenomenology of gauge mediated supersymmetry breaking models.
The Homeric Narrator and His Own kleos
Authors: de Jong Irene
Published: May 2006

The Homeric narrator's celebrated reticence about his own person, work, and aspirations has led scholars to call him modest. In this paper I argue that there are enough implicit or indirect signs which point at a Homeric narrator himself aspiring to kleos, just like the heroes he celebrates.
Using the Bootstrap Method for a Statistical Significance Test of Differences between Summary Histograms
Authors: Xu Kuan-Man
Published: May 2006

A new method is proposed to compare statistical differences between summary histograms, which are the histograms summed over a large ensemble of individual histograms. It consists of choosing a distance statistic for measuring the difference between summary histograms and using a bootstrap procedure to calculate the statistical significance level. Bootstrapping is an approach to statistical inference that makes few assumptions about the underlying probability distribution that describes the data. Three distance statistics are compared in this study. They are the Euclidean distance, the Jeffries–Matusita distance, and the Kuiper distance.

The data used in testing the bootstrap method are satellite measurements of cloud systems called “cloud objects.” Each cloud object is defined as a contiguous region/patch composed of individual footprints or fields of view. A histogram of measured values over footprints is generated for each parameter of each cloud object, and then summary histograms are accumulated over all individual histograms in a given cloud-object size category. The results of statistical hypothesis tests using all three distances as test statistics are generally similar, indicating the validity of the proposed method. The Euclidean distance is determined to be most suitable after comparing the statistical tests of several parameters with distinct probability distributions among three cloud-object size categories. Impacts on the statistical significance levels resulting from differences in the total lengths of satellite footprint data between two size categories are also discussed.
Relationship between SAR-Derived Wind Vectors and Wind at 10-m Height Represented by a Mesoscale Model
Authors: Koch Wolfgang , Feser Frauke
Published: May 2006

Wind vectors over the ocean were extracted from a large number of synthetic aperture radar (SAR) images from the European Remote Sensing Satellites (ERS-1 and ERS-2). The wind directions are inferred from the orientation of wind streaks that are imaged by the SAR, while the wind speeds are retrieved by inversion of the C-band model CMOD4. The derived wind directions and speeds were compared to wind vectors from the numerical Regional Model (REMO) that are available hourly on a 55-km grid. The large number of comparisons and independent weather situations allowed for an analysis of subsets that are classified by SAR-derived wind speed. A strong decrease of the standard deviation of directional differences with increasing wind speed was found. Biases of directional differences depend on SAR wind speed as well. Furthermore, the influence of the temporal difference between SAR overflight and model and an automatic image filtering on the directional error is demonstrated. Overall, reasonable fields of wind vectors were extracted from SAR imagery in 70 of 80 cases. These fields provide valuable information for validation of numerical models of the atmosphere and case studies of coastal wind fields.
The Role of Anomalously Warm Sea Surface Temperatures on the Intensity of Hurricane Juan (2003) during Its Approach to Nova Scotia
Authors: Fogarty Christopher T. , Greatbatch Richard J. , Ritchie Harold
Published: May 2006

When Hurricane Juan tracked toward Nova Scotia, Canada, in September 2003, forecasters were faced with the challenge of predicting the intensity and timing of the hurricane’s landfall. There were two competing factors dictating the storm’s intensity: 1) the decreasing sea surface temperatures (SSTs) over which the hurricane tracked that were conducive to weakening; and 2) the increased forward motion of the storm that enhanced the surface winds on the right (storm relative) side of the storm. Since Hurricane Juan was moving very quickly (forward speed approximately 15 m s−1) it spent less time over the cooler continental shelf waters between Nova Scotia and the >26°C water of the Gulf Stream than would have been the case for a slower-moving storm. However, those waters were warmer than normal during this event, by ∼4°C. It is argued that these warmer SSTs made a significant contribution (among other factors) to this rare category-2 hurricane at landfall in Nova Scotia. To assess the role of SSTs on the decay rate of Hurricane Juan, the Mesoscale Compressible Community model of the atmosphere is used. The model consists of a fixed, nested 3-km grid driven by a coarser 12-km grid, and is initiated using a synthetic hurricane vortex constructed from observational information such as storm size and intensity, thus giving a decent representation of the real storm. The model is initiated at 0000 UTC 28 September, when the hurricane was close to maximum intensity. An ensemble of experiments are conducted for each of two SST configurations: 1) analyzed SST of 28 September 2003 and 2) climatological SST representative of late September. Results from the 3-km simulations indicate that the intensity of Hurricane Juan’s maximum surface wind just prior to landfall was ∼5 m s−1 (±∼1.5 m s−1) weaker in the normal SST case, a result that is statistically significant at the 99% level. The destructiveness of the maximum landfall winds in the normal SST case is generally about 70% of that in the observed (warmer than normal) SST case. Model performance is measured using surface weather data, as well as data collected from a research aircraft that flew into the storm just prior to landfall.
Phospholipase A₂-Generated Lipid Mediators in the Brain: The Good, the Bad, and the Ugly
Authors: Farooqui Akhlaq A. , Horrocks Lloyd A.
Published: May 2006

Phospholipase A2 (PLA2) generates arachidonic acid, docosahexaenoic acid, and lysophospholipids from neural membrane phospholipids. These metabolites have a variety of physiological effects by themselves and also are substrates for the synthesis of more potent lipid mediators such as eicosanoids, platelet activating factor, and 4-hydroxynonenal (4-HNE). At low concentrations, these mediators act as second messengers. They affect and modulate several cell functions, including signal transduction, gene expression, and cell proliferation, but at high concentrations, these lipid mediators cause neurotoxicity. Among the metabolites generated by PLA2, 4-HNE is the most cytotoxic metabolite and is associated with the apoptotic type of neural cell death. Levels of 4-HNE are markedly increased in neurological disorders such as Alzheimer disease, Parkinson disease, ischemia, spinal cord trauma, and head injury. The purpose of this review is to summarize and integrate the vast literature on metabolites generated by PLA2 for a wider audience. The authors hope that this discussion will jump-start more studies not only on the involvement of PLA2 in neurological disorders but also on the importance of PLA2-generated lipid mediators in physiological and pathological processes.
Identifying systematic reviews of the adverse effects of health care interventions
Authors: Golder Su , McIntosh Heather M , Loke Yoon
Published: May 2006

Background

In order to carry out a methodological research survey of systematic reviews of adverse effects we needed to retrieve a sample of systematic reviews in which the primary outcome is an adverse effect or effects.

Methods

We carried out searches of the Database of Abstracts of Reviews of Effects (DARE) and the Cochrane Database of Systematic Reviews (CDSR) for systematic reviews of adverse effects published between 1994 to 2005. The search strategies used a combination of text words in the title and abstract, Medical Subject Headings (MeSH) and subheadings/qualifiers. In addition, DARE records in progress were hand searched. No language restrictions were placed on any of the searches. The performance, in terms of sensitivity and precision, of the search strategies and their combinations were tested in DARE and CDSR.

Results

In total 3635 records were screened of which 257 met our inclusion criteria. The precision of the searches in CDSR was low (0% to 3%), and no one search strategy could retrieve all the relevant records in either DARE or CDSR. Hand searching the records from DARE and CDSR not retrieved by our searches indicated that we had missed relevant systematic reviews in both DARE and CDSR. The sensitivities of many of the search combinations were comparable to those found when searching for primary studies in which adverse effects are secondary outcomes.

Conclusion

Searching major databases of systematic reviews, for systematic reviews of adverse effects, proved more difficult than anticipated due to a lack of standard terminology used by the authors, inadequate indexing and the variations in the search interfaces of the databases. At present hand searching all records in DARE and CDSR seems to be the only way to ensure retrieval of all systematic reviews of adverse effects in these databases.
Cyano Group Transfer of Acetone Cyanohydrin to Aldehyde Mediated by Titanium Alkoxide and Aluminum Alkyls
Authors: Mori Atsunori , Kinoshita Koichi , Osaka Masahiko , Inoue Shohei
Published: May 2006

Cyano group transfer reaction of acetone cyanohydrin to various aldehydes in the presence of titanium alkoxide and aluminum alkyls to give the corresponding aldehyde cyanohydrins in high yield is described.
Enantio-and Stereo-controlled Construction of Tertiary and Quaternary Carbon Centers Using Chiral O-Benzylglycidol as Template
Authors: Takano Seiichi , Shimazaki Youichi , Moriya Minoru , Ogasawara Kunio
Published: May 2006

An efficient method for the enantio- and stereo-controlled construction of tertiary and quaternary carbon centers in a highly functionalized system has been developed using chiral O-benzylglycidol as template.
Self-Organization of Surface Transportation Networks
Authors: Levinson David , Yerra Bhanu
Published: May 2006

This research investigates the self-organization of surface transportation networks. Using a travel demand model coupled with revenue, cost, and investment models, experiments are run under a variety of parameters on a grid network. It is found that roads, contiguous sections of multiple links operating with similar characteristics, and hierarchies of roads emerge under a broad range of assumptions from networks with neither defined roads nor clearly organized hierarchies. The factors that drive this are the (dis)economies of scale, the presence of boundaries, and any initial asymmetry in the network. This research thus finds that roads and hierarchies, which are often thought to be the product of conscious design, can also arise without such intention.
An Airspace-Planning and Collaborative Decision-Making Model: Part II—Cost Model, Data Considerations, and Computations
Authors: Sherali Hanif D. , Staats Raymond W. , Trani Antonio A.
Published: May 2006

In Part I of this paper, we presented a large-scale airspace-planning and collaborative decision-making (APCDM) model that is part of a Federal Aviation Administration (FAA)-sponsored effort to enhance the management of the National Airspace System (NAS). Given a set of flights that must be scheduled during some planning horizon, along with alternative surrogate trajectories for each flight, we developed a mixed-integer programming model to select a set of flight plans from among these alternatives, subject to flight safety, air-traffic control workload, and airline equity considerations. The present paper offers insights related to, and a detailed description of, implementing this APCDM model, including the development of a comprehensive cost model, a study for prescribing a set of appropriate parameter values for the overall model, and an investigation on incorporating a suitable set of valid inequalities in the model formulation. Computational results are presented based on several test cases derived from the Enhanced Traffic Management System (ETMS) data provided by the FAA. The results indicate that under plausible probabilistic trajectory error assumptions and with the incorporation of star subgraph convex hull-based valid inequalities, the model offers a viable tool that can be used by the FAA for both tactical and strategic applications.
Using and generating evidence: policy makers’ reflections on commissioning and learning from the Scottish Health Demonstration Projects
Authors: Mackenzie Mhairi , Blamey Avril , Hanlon Phil
Published: May 2006

English

This article discusses the gap between rhetoric and reality in evidence-based policy making using data derived from external evaluations of two of Scotland’s national Health Demonstration Projects. More specifically, it reports on the extent to which policy makers used evidence to commission the projects, and on the type of evidence that they expected to flow from them to feed into future government strategy. Using primary data, this article confirms that policy decisions are made on the basis of factors that go beyond research evidence and suggests that both policy makers and evaluators would gain from more explicit acknowledgement of what lies beneath the veneer of evidence-based policy making.
RTD evaluation and policy in the European Research Area
Authors: Schmidt Evanthia Kalpazidou
Published: May 2006

English

Evaluation of Research and Technological Development (RTD) processes and outcomes is gaining importance in European policy as funds are reallocated to research and demands for accountability are growing. However, a common evaluation ground is not seen yet in Europe. The theme for this article is the landscape of RTD evaluations in Europe and their use in research and technology policy. Based on a comparative study of 22 European countries, concepts of public evaluations and their impacts on policy at meso- and macro-level are outlined and discussed. The article points to future needs and challenges with regard to the construction of public RTD evaluations and their use in policy, in particular with a view to creating the European Research Area (ERA). It concludes that some rethinking of evaluation concepts and practices is called for.
Shading by Phragmites australis: a threat for species‐rich fen meadows?
Authors: Güsewell Sabine , Edwards Peter
Published: May 2006

Abstract. Common reed (Phragmites australis Trin.) has spread in fen meadows on the Swiss Plateau during the last decades. An increased dominance of this tall grass may reduce the plant species richness and displace rare or endangered species because of the additional shade. To investigate whether this has actually happened and whether shading by Phragmites was likely to be responsible for the reduction, the plant species composition was surveyed in 241 plots (4 m2) with differing above‐ground biomass of Phragmites (ABP). Species richness and the occurrence of characteristic fen species were negatively related to site productivity (total above‐ground biomass), but correlations with ABP were generally weaker. The main change associated with increasing ABP within species‐rich fens (alliances Molinion and Caricion davallianae) was an increase of species characteristic of the more species‐poor alliance Filipendulion. Thus, Phragmites did apparently not play a disproportionate role in the reduction of species richness in the plant communities studied. Selective clipping experiments and light measurements also indicated that shading by Phragmites does not have a strong effect upon the performance of other species in the community, at least in the short term. The reason appeared to lie in the later seasonal growth of Phragmites compared with the other species. These results suggest that the direct impact of shading by Phragmites on the species richness of fen meadows is probably lower than has been assumed. However, possible long‐term or indirect effects still need to be investigated.
Establishment of helophytes in the course of fen restoration
Authors: Roth S. , Seeger T. , Poschlod P. , Pfadenhauer J. , Succow M.
Published: May 2006

Abstract. In two fen areas of northeastern Germany, different techniques of re‐introduction to establish reed‐bed species in formerly intensively used, species‐poor, grasslands, after rewetting, were studied under three hydrological regimes (permanent inundation, temporary inundation, border irrigation) with the aims (1) to establish peat‐forming vegetation and (2) to enhance species richness.

Establishment was successful for nearly all species investigated under all hydrological variants. There were differences between individuals sown and those which had been planted. Wet, but not inundated soil linked with vegetation gaps create ‘safe sites’ which enable successful germination and seedling establishment. The survival rate for both planted and sown individuals was generally high, with the exception of Cladium mariscus, Eupatorium cannabinum and Phragmites australis Recommendations for restoration management include the establishment of the following successful species: Carex acutiformis, C elata and C paniculata to establish peat‐forming vegetation; Iris pseudacorus, Lysimachia vulgaris, Lythrum salicaria to enhance species richness.
Grid map analysis and its application for detecting vegetation changes in Japan
Authors: Nakagoshi Nobukazu , Hikasa Mutsumi , Koarai Mamoru , Goda Toshiyuki , Sakai Isao
Published: May 2006

Abstract. Grid maps are used as a basic vegetation data base in Japan; they are simplified from vector‐based vegetation maps. We estimated the frequency error or lack of information corresponding to reduced resolution and examined the reliable limits of this data base. We produced 10 grid maps on five different scales from 50 m to 1000 m using two different methods using both the whole cell (W‐method) and only the central circle (C‐method) from a vegetation map at scale 1: 25 000. We found that patches larger than the area of a cell on a vector‐based map could be kept almost certainly on any map, but many patches of less than the cell size were lost. The number of missing patches with the C‐method is fewer at every scale than those with the W‐method. Though the value of Morisita's Cλ (p) index showed that the similarity with the original map was high ‐ from the 50‐m to the 200‐m resolution ‐ it was increasingly lower on the 400‐m and 1000‐m grid maps. The values of the Shannon index on the original map, 50‐m and 100‐m grid maps were not different, but they decreased from the 200‐m to 1000‐m grid maps. Because the vegetation data base of the Japanese Environment Agency used a 1000‐m C‐method grid map, we found that much information on patches less than 100 ha had disappeared. Information about dominant vegetation or large patches is almost accurate in this data base.
Seasonal Progression of Flowering in Clarkia
Authors: Vasek Frank C. , Sauer Ronald H.
Published: May 2006

Clarkia tembloriensis and "Caliente" (an undescribed Clarkia species) in a low elevation grassland habitat flower about 2 weeks earlier than sympatric or adjacent populations of C. unguiculata. At higher elevations in a woodland habitat C. exilis blooms later than the lowland populations, but about 2 and 4 weeks earlier than adjacent populations of C. unguiculata and C. xantiana, respectively. Time of flowering is differentially correlated with, and interpreted in terms of adaptation to, the onset of summer heat and drought.
Effects of Fire on Alpine Plant Communities in the North Cascades, Washington
Authors: Douglas George W. , Ballard T. M.
Published: May 2006

Alpine heath and krummholz communities were studied on Sourdough Ridge at 1,900 m, 29 years after fire. Fire effects are observable in structure and compositional details (species presence, frequency, and coverage) of these communities and in acidity and humus forms of the soils. Unburned krummholz stands are dominated by Abies lasiocarpa and Tsuga mertensiana, with Phyllodoce empetriformis and Vaccinium deliciosum as major understory species. Unburned heath communities are dominated by V. deliciosum, P. empetriformis, and Cassiopemertensiana. Of these species, only V. deliciosum persists as a frequent element on burned sites. Fire effects substantial and persistent increases in diversity of both krummholz and heath communities.
Natural Mortality of Eggs and Larvae of Ambystoma T. Tigrinum
Authors: Anderson James D. , Hassinger Dawn D. , Dalrymple George H.
Published: May 2006

All the eggs deposited by an isolated breeding population of Ambystoma t. tigrinum were located. Egg deposition was not synchronous. Mortality was determined in the field by counting living and dead eggs until hatching. After hatching the larval population size was estimated at intervals until metamorphosis. Gastrulation, hatching, and metamorphosis were critical stages in the field. Between these stages survivorship curves are hyperbolic. Small egg masses incurred heavier mortality than larger masses. Heavy mortality within an egg mass did not influence survival of remaining eggs as it does in the laboratory. The environment acts on individual eggs rather than on the mass as aunit. Low temperature was probably the major source of embryonic mortality although freezing, predation, and low pH may be important. Predation was probably the most important source of hatchling mortality. Free—swimming larvae suffered negligible mortality, but this may vary from year to year depending upon embryonic and hatchling mortality. Survival from egg deposition to metamorphosis averaged 3.3%, varying in three ponds from 0% to 8.7%. This high mortality may be characteristic of pond—dwelling amphibians of the temperate region.
Bird Species Diversity: The Effect of Species Richness and Equitability on the Diversity Index
Authors: Kricher John C.
Published: May 2006

A study of bird species diversity (BSD) on three seral stages characteristic of secondary succession on the New Jersey Piedmont was done during the winter of 1968—69, the spring of 1969, and the summer of 1969. The seral studies were a 2— to 33—year—old field (the herbaceous field), a 30—year—old field (the cedar field), and a climax oak—hickory forest (the oak forest). Two study plots, each with an area of 2 hectares, were chosen within each seral stage. Diversity indices were calculated using the Shannon—Weaver information formula, H'=—‐Σpilogepi. The species count (species richness) was found to account for many of the differences in BSD between the seral stages. The evenness with which species were numerically distributed (equitability) was found to be lowest and to be lowest and to have its greatest influence on the diversity index in the herbaceous field, due to the presence of large flocks of non—nesting species. Equitability was higher and more constant in the cedar field and oak forest. Territoriality was thought to account for the higher equitabilities observed in summer. In winter, the more rigorous environment was thought to be a factor in lowering the equitability at least in the cedar field.Equitability was not lowered as much in the oak forest, possibly due to aggregations of birds into mixed species flocks. The cedar field and oak forest were qui te different in the seasonal patterns of equitability. Both species richness and equitability were concluded to be important parameters in ecological study.
Comparative Feeding Ecology of a Tropical Grassland Finch (Tiaris Olivacea)
Authors: Pulliam H. Ronald
Published: May 2006

The feeding ecology of the yellow—faced grassquit (Tiaris olivacea) was studied on a large island (Jamaica) and on the mainland (Costa Rica). Despite an apparent reduction in competition on Jamaica, yellow—faced grassquits are less abundant in Jamaica than in Costa Rica and are found in approximately the same number of habitats on the island and on the mainland. There seem to be no changes in the magnitude, variance, and sexual dimorphism of hill size of island grassquits which would lead to their eating more kinds of food than the mainland grassquits. However, in a series of experiments on seed—size preference, it was noted that the grassquits from Jamaica were significantly less stereotyped in their choice of seed size than were the Costa Rican grassquits. It is suggested that an increase in the variance of bill size of island grassquits occurs only in large populations and concomitant with an increase in the number of habitats occupied by the population.
Effect of Arrival Time on Recruitment, Mortality, and Reproduction in Successional Plant Populations
Authors: Holt Buford R.
Published: May 2006

Delay in immigration significantly reduced emergence, delayed reproduction, and reduced seed production per unit area, but had little effect on juvenile mortality of Daucus carota L. (Umbelliferae) in southern Michigan old fields. Establishment of reproductive populations was most sensitive to events prior to seedling emergence. Reductions in seedling emergence and delays of reproduction were strongly responsive to the present of perennial grasses.
Variables Affecting the Density and Territory Size of Breeding Spruce‐Woods Warblers
Authors: Morse Douglass H.
Published: May 2006

Between 1969 and 1972 and during 1974 I obtained data on population density, territory size, habitat, food taken, and food available to four species of Dendroica warblers (Parulidae). Densities usually were: Black—throated Green (D. virens) > Blackburnian (D. fusca) > Yellow—rumped (D. coronata) > Magnolia (D. magnolia). Black—throated Green Warblers were commoner in red spruces than in white spruces; they showed a preference for red spruce foilage. Populations of all four species were stable between 1969 and 1972, but following two poor breeding seasons populations declined in several areas. Species with dense populations had small territories and vice versa. Territory sizes of Black—throated Green Warblers in red spruces were smaller than in white spruces. Territory size usually fluctuated even less than population density, although some territories eventually increased markedly after strong declines in abundance. The food supply usually peaked in early July. Food was more abundant in white spruces than red spruces early in June but did not consistently differ subsequently. Warblers took lepidopteran larvae in preference to other prey. The number of Dendroica species in an area was closely related to the physical characteristics of the forest, but interactions among these species mediated many of the differences in density or species composition. Mature undistributed forests in this geographic area support four of these species on a long—term basis.
Fungal Feeding or Oribatid Mites (Acari: Cryptostigmata) in an Aspen Woodland Soil
Authors: Mitchell Myron J. , Parkinson Dennis
Published: May 2006

The feeding ecology of five oribatid mite taxa from an aspen woodland soil was examined. Ceratozetes kananaskis, Ceratozetes gracilis, and Scheloribates spp. were predominant in the fermentation (F) and humus (H) horizons while Eremaeus spp. and Eupterotegaeus rostratus were restricted to the litter (L) horizon. In laboratory studies the five mite taxa were fed and reared upon the seven most common fungal species which had been isolated from the aspen soil. The mite inhabitants of the F and H—horizons showed variation in amount of feeding and reproductive success among the fungi tested. There was no direct relationship between the amount of mite feeding and reproductive success on any given fungus. The L inhabitants fed very little on fungus in culture and showed no reproduction. Gut content analyses from field specimens showed that all taxa fed on fungi and demonstrated that laboratory feeding studies were a poor indication of feeding type. All taxa fed predominately on the pigmented fungi with the F and H inhabitants showing a higher proportion of hyaline fungi than the L inhabitants; this difference was probably related to the fungal distribution in the soil. Seasonal variation in amount of gut contents was directly related to a postulated level of microbial activity in the soil. Only 2% of the fungal standing crop would be consumed in 1 yr by the total oribatid mite community emphasizing the importance of assessing the effect of the oribatid mites in conjunction with the other mycophagous members of the soil fauna. Possible interactions between oribatid mites and the fungal community were given and the consequences of the interactions related to organic matter decomposition.
Trophic Structure Determination and Equilibrium in an Arthropod Community
Authors: Simberloff Daniel
Published: May 2006

Heatwole and Levins (1972) contend that the island recolonization experiment of Simberloff and Wilson (1969) demonstrates a community trophic structure equilibrium determined by species interactions. Data do not support this contention. Heatwole and Levins may have overstated the determinateness and importance of trophic structure for two reasons: (1) they pooled data from separate islands, (2) the statistic with which they characterize trophic structure is strongly dependent on species number. That trophic interactions are important in this system remains unproven; on the other hand, such species characteristics as dispersal ability and microhabitat requirements may be critical to some dominant species.
Natural Selection for Resistance to Epidemics
Authors: Gillespie John H.
Published: May 2006

A model of selection for resistance to epidemics in haploid and diploid organisms is described. Using results from the mathematical theory of epidemics, I show that such selection is both frequency— and density—dependent, and that it can lead to genetic polymorphism if certain conditions are met. This form of selection may account for some of the observed genetic variation in natural populations.
The Meaning and Measurement of Frequency‐Dependent Competition
Authors: DeBenedictis Paul A.
Published: May 2006

This paper criticises use of the concept of frequency—dependent competition. The usual definition of frequency—dependent competition, based on deWit's Replacement Series Analysis is trivial in the sense that it admits no interesting alternative hypotheses. A more general definition is proposed: competition is frequency—dependent whenever per individual competitive effects vary with species frequency. Frequency—dependent competition may be distinguished from density—dependent competition. Replacement Series Analysis, although a useful indicator of possible competitive interactions, is incapable of discriminating between frequency—dependent and frequency—independent competition as defined herein. Data reported by previous investigators are reanalyzed and found generally to support the claim that Drosophila competition is frequency—dependent. However, these data do not eliminate the possibility that changes in competitive abilities are simply density—dependent. Little other evidence of the phenomenon exists.
Yearly Variation in Larval Survival of Ambystoma Maculatum
Authors: Shoop C. Robert
Published: May 2006

Survivorship of larval Ambystoma maculatum from a single pond varied each year although the variability was not dependent on the number of eggs deposited each year. The survival depends greatly on developmental rates of the larvae, pond duration, and suitable climatic conditions at the time of dispersal. The variations in length of the larval period appear adaptive and cannot be explained by variation in dates of egg deposition. Developmental rates may be altered slightly by environmental factors.
Distribution and Abundance of an Isolated Population of Terebra Gouldi (Gastropoda: Terebridae) on a Hawaiian Subtidal Sand Flat
Authors: Miller Bruce A. , Croker Robert A.
Published: May 2006

Species of the carnivorous gastropod genus Terebra are common members of tropical subtidal sand associations. Despite superficially uniform sand habitats, these species occupy well—defined population centers. The distributional pattern of Terebra gouldi Deshayes, an endemic Hawaiian species, and the physical and biological factors influencing this pattern, were studied on a subtidal sand flat surrounding Ahu O Laka Island in Kaneohe Bay, Hawaii. The species was not widely distributed around this sand flat, but rather was concentrated in two sub—populations located on the windward and leeward sides of the island, where densities were as high as 15 animals per m2. Of more than 40 associated infaunal species, only the prey, Ptychodera flava, appeared to have an important effect on T. gouldi distribution. There was no preference by T. gouldi for a specific sand particle size, or for a specific degree of sediment sorting. Substratum factors determining subtidal distribution through an influence on crawling, burrowing, and prey capture included the presence of attached vegetation, hard compacted sand, and limestone platform. Factors preventing dispersal of the species into intertidal areas are also discussed. Two hypotheses are advanced to explain observed intra—population density gradients. These are chemoreceptive locomotory activity in response to prey, and life history factors including recruitment of young in high density adult population centers, followed by gradual dispersal of maturing animals.
Difference in Pollination Niche Relationships in Early and Late Successional Plant Communities
Authors: Parrish J. A. D. , Bazzaz F. A.
Published: May 2006

Alpha—niche parameters involving pollination resources were examined for plants in communities of 3 different successional ages. Niche breadths and overlaps were compared in early successional annual, early perennial, and prairie communities. Niche axes examined were seasonal time of flowering, species of flower visitor, daily time of visit, and 2—dimensional parameter, species of visitor x daily time. Seasonal flowering was clumped in all communities. It occurred fairly synchronously in midsummer in the annual community and in the fall in the perennial community. Flowering in the winter annual and prairie communities occurred at 3 distinct seasonal times; spring, summer and fall. In this annual community, the different flowering times reflected varied life history strategies demonstrating adaptations mainly to the physical environment. In the prairie, the same 3 seasonal flowering aggregations were most likely formed through adaptation to the biotic environment. The prairie species had smaller seasonal flowering niche breadths, but showed no reduction in seasonal niche overlap. In fact, there was some evidence for convergence in flowering time of species attracting similar vector species. There was little difference in daily time of flowering for most species pairs in all communities. Only in early and midsummer was there evidence for niche separation in daily time of visitation. In early spring and fall, mean overlaps between species were > in comparable random data sets, suggesting convergence in daily time of insect visitation. The relative proportions of general types of visitor differed among the communities. There were tendencies for annuals to be visited more by halictid bees and syrphid flies and there were strong tendencies for prairie species to be visited more by apid and megachilid bees and by lepidopterans. Because of the latter groups are considered to be more effective pollinators, significantly more of the visits could have effected cross—pollination in the prairie than in annual communities. Niche overlaps of species of visitor were significantly lower than random for all communities, indicating some niche differentiation on that axis. The mean similarities of species of visitor and the 2—dimensional visitor species x daily time for the prairie plants were significantly lower than the means for the annuals, and showed a tendency to be lower than the means of the early perennials. Niche breadths on the same 2 parameters were also lower in the prairie. Therefore, species of the late successful community, the tallgrass prairie, showed more niche specialization and separation than did species of early successional communities. We conclude that α—scale differentiation on these pollination parameters does occur between plant species, and the degree to which it occurs increases with the successional age of the community. These results support the hypothesis that selection to reduce competition has resulted in greater niche differentiation in late successional communities.
Natural Selection and Clutch Size in the European Starling
Authors: Crossner Kenneth Alan
Published: May 2006

In a field experiment, broods of 1—10 chicks of equal age were artificially established. The natural food supply was supplemented with an ad libitum supply in some of the nests of 6—10 chicks per nest. Among broods that did not receive extra food, weights gradually increased with brood size up to size 3 chicks per nest, gradually decrerased when brood size increased to 6 chicks per nest, and dropped precipitously with additional increase in brood size beyond 6 chicks per nest. Nests of 10 without extra food wer always completely unsuccessful. Broods of sizes 5 and 6 were probably optimal because their chicks were almost as heavy as those of smaller broods. Brood size 6 is probably the upper limit at which parents can increase their foraging efforts with increasing brood size. The observed mean clutch size of 4.68 @+ 0.16 (1.96 SE) is close to, but less than, the optimal clutch size. This evidence is consistent with predictions assuming that the population is reproducing maximally and supports Lack's theory of maximized reproductive rates. Among broods that did have an ad libitum food supplement, chicks in broods of 10 and below achieved weights as large as those of chicks in much smaller broods that did not receive extra food. This indicates that the ability to rear young is a function of both brood size and the current food supply, supporting Lack's theory that the breeding season's food supply is a determinant of the selection for clutch size in nidicolous species. The intrinsic growth rate (ro of the logistic model) seems to be unaffected by either food supply or brood size, but the duration of growth appears to be shortened by an abrupt peak energy demand in excess of the available food. Thermoregulatory stress may cause poor growth in broods of 1 and 2 chicks and the observed larger—than—normal weight recession of the bigger broods. A new method of estimating the value of the parameters ro and K of the logistic equation from empirical data, without a priori knowledge of the asymptote, is briefly presented.
Dimorphic Foraging Strategies of a Salticid Spider (Phidippus Audax)
Authors: Givens Robert P.
Published: May 2006

Adult ♂ and ♀ Phidippus audax (Salticidae) have different feeding strategies reflecting major differences in their time budgets and food requirements. Males are 89% as large as ♀ ♀ (measured by cephalothorax width), but size dimorphism is insufficient to account for differences between their rate and pattern of feeding on flies provided experimentally. The ♂ ♂ feed at a uniformly low rate throughout adult life. They become sated rapidly and extract less from individual prey as they approach satiation. Individual prey sufficiently large to sate a ♂ spider are discarded before being fully utilized. Both ♂ ♂ and ♀ ♀ remove °76% of the prey biomass from fully utilized dipteran prey. Adult ♀ ♀ feed at a high rate until they have developed a large egg mass. They then nearly cease feeding and deposit their eggs. During their period of high feeding, ♀ ♀ are insatiable and utilize all dipteran prey fully, regardless of prey size or the number of prey previously eaten. Difficult prey, those that require longer handling time than do similarly—size dipteran prey such as highly sclerotized beetles (Dermestes sp.), are consumed less fully by ♂ ♂ than ♀ ♀. Females utilize difficult and easy prey (Diptera) to a similar degree. Because ♂ ♂ spend the same amount of time handling and feeding on items of similar size regardless of their handling difficulty, they extract less food from difficult prey than from other prey. Both ♂ ♂ and ♀ ♀ reject the large milkweed bug (Oncopeltus fasciatus) and are unable to penetrate the cuticle of the lightning beetle (Photuris pennsylvanicus). Males prefer small prey (6 and 19 mg) when offered a choice of 4 (6, 19, 38, and 94 mg) sizes of dipterans. Females prefer intermediate (38 mg) sized prey. Size preferences are more distinct in ♂ ♂ than ♀ ♀, and ♀ ♀ capture a more even distribution of different prey sizes than ♂ ♂. For both sexes the largest portion of prey biomass per spider is contributed by the largest prey selected preferentially. This is true for ♂ ♂ even though they show a stronger preference for smaller prey.