bluuebunny/crossref_metadata_2025 huggingface dataset:
Tensile and fracture properties of NiAl/Ni micro-laminated composites prepared by reaction synthesis
Authors: Kim Hee Y. , Chung Dong S. , Enoki M. , Hong Soon H.
Published: May 2006

The mechanical properties of NiAl/Ni micro-laminated composites with highly gradient microstructure have been investigated. Two types of composites with different gradient microstructures were prepared by reaction synthesis. Intermetallics of type I and type II composites mainly consisted of Al-rich Ni0.45Al0.55 with variable thickness and Ni-rich Ni0.58Al0.42 with similar thickness, respectively. As intermetallic volume fraction increased, yield strength of type II followed the rule-of-mixture well, while that of type I deviated due to the composition variation of intermetallic phases. Fracture toughness of type II was higher than that of type I, and all showed KR curves with upward curvature by large-scale bridging. Even though the relative strength of constituent phases in intermetallic/metal laminates was not constant due to the gradient microstructure, the fracture mode transition showed similar behavior to that of metal/ceramic laminates.
Growth of carbon nanotube on micro-sized Al2O3 particle and its application to adsorption of metal ions
Authors: Hsieh Shu-Huei , Horng Jao-Jia , Tsai Cheng-Kuo
Published: May 2006

Carbon nanotubes (CNTs) were grown on micron-sized Al2O3 particles in an atmosphere of methane and hydrogen at 700 °C under the catalysis of Fe–Ni nanoparticles that had been deposited on the surface of Al2O3 particles by an electroless plating technique. The individual and competitive adsorption capacities of Pb2+, Cu2+, and Cd2+ from aqueous solution by CNTs on Al2O3 particles were studied. The results showed that the adsorption behavior of these metal ions by as-grown CNTs on Al2O3 particles is in good agreement with the Langmuir adsorption model. The maximum individual adsorption capacities of Pb2+, Cu2+, and Cd2+ from water by as-grown CNTs on Al2O3 particles are 62.50, 27.03, and 9.30 mg/g, respectively. The CNTs on Al2O3 particles have promising potential applications in removing soluble heavy metals from aqueous solutions.
Lead-free solders: Enthalpies of mixing of liquid alloys in the Ag–Ni and Ag–Ni–Sn systems
Authors: Saeed Usman , Flandorfer Hans , Ipser Herbert
Published: May 2006

Partial and integral enthalpies of mixing of liquid Ag–Ni and Ag–Ni–Sn alloys were determined at different temperatures, i.e., at 1500 °C for binary Ag–Ni alloys and at 1000, 1220, and 1400 °C for ternary Ag–Ni–Sn alloys. Two different Calvet-type micro-calorimeters were used for the measurements employing drop calorimetry techniques. The binary data were evaluated by means of a standard Redlich–Kister polynomial fit whereas ternary data were fitted on the basis of an extended Redlich–Kister–Muggianu model for substitutional solutions. No significant temperature dependence could be detected for the ternary enthalpies of mixing. From the experimental ternary data, it was possible to deduce the liquidus isotherm at 1000 °C as well as the extension of the liquid miscibility gap at 1220 and 1400 °C.
Donor passivation in pseudomorphic-high electron mobility transistors due to plasma-incorporated fluorine impurities observed using x-ray photoemission spectroscopy
Authors: Uchiyama Hiroyuki , Kikawa Takeshi , Taniguchi Takafumi , Shiota Takashi
Published: May 2006

To investigate the effect of plasma-incorporated fluorine on Si donors in pseudomorphic-high electron mobility transistors (P-HEMTs), we used x-ray photoemission spectroscopy to analyze three layers near the Si δ-doped layer and the Si δ-doped layer itself, in which we previously found fluorine accumulation after post-thermal annealing following fluorocarbon-based plasma exposure. For this evaluation, we developed controllable and low-speed AlGaAs wet-chemical etching using citric-acid-based wet etchant. We used it to expose one of the layers to be analyzed: one 7.5 nm above the Si δ-doped layer, one 1.5 nm above it, the δ-doped layer itself, and one 1.5 nm below it. We found that the accumulated fluorine localized in the δ-doped layer and reacted with Si donors. This is apparently the main reason for the carrier passivation in the fluorocarbon-based plasma-exposed P-HEMTs.
Mechanical properties of helically perforated thin films
Authors: Fernando S.P. , Elias A.L. , Brett M.J.
Published: May 2006

The mechanical behavior of a helically perforated thin film structure was simulated by finite element analysis. The validity of the results was confirmed by comparison to a nanoindentation measurement performed on a nickel helically perforated thin film sample. It was found that variation of the helical pitch angle from 35° to 70° resulted in a change of 1.5 times in the elastic modulus. Since the fabrication process used to create the actual samples allows for variation of the pitch angle, this result may enable the tailoring of materials for use in micro- and nanoscale devices.
Preparation and characterization of polyamide 66 nanotubes and nanowires on an anodic aluminum oxide template by a physical wetting method
Authors: She Xilin , Song Guojun , Li Jianjiang , Han Ping , Yang Shujing , Peng Zhi
Published: May 2006

Polyamide 66 (PA66) nanotubes with an array structure were prepared by infiltrating a solution of normal molecular weight PA66 into anodic aluminum oxide (AAO) templates with a pore diameter of 200 nm. The results of field-emission scanning electron microscopy (FESEM) demonstrate that PA66 nanotubes with a wall thickness of about 60 nm can be fabricated by a solution-wetting method and PA66 nanotubes and nanowires can be obtained by a melt-wetting method at different temperature. We also find that PA66 nanotubes have the “super plasticity” for the crystalline belts in their wall may arrange by spiraling and rounding style. Thermogravimetric analysis (TGA) indicates the nanotubes have a better thermal stability than bulk polymer PA66. The mechanism of forming polymer nanotubes by polymer melt-wetting method has been proposed.
Lessons for Management of Sexually Transmitted Infection Treatment Programs as Part of HIV/AIDS Prevention Strategies
Authors: McKay Julienne , Campbell David , Gorter Anna Cornelia
Published: May 2006

We analyzed the treatment schedule of a long-running HIV/AIDS prevention program in Managua, Nicaragua, that targets sex workers through mass and specific clinic-based treatment of sexually transmitted infections and confirmed the role of frequency of treatment in generating a sustained reduction in measured prevalence of sexually transmitted infections.

Unplanned variations in the time between treatments, a situation common to public health programs, provided the basis for attributing changes in measured levels of sexually transmitted infections to the program and for testing the statistical significance of the relationship. This information is critical to program design and funding and to resource allocation.
Reborn a Virgin: Adolescents’ Retracting of Virginity Pledges and Sexual Histories
Authors: Rosenbaum Janet E.
Published: May 2006

Objectives. We examined retractions of virginity pledges and of sexual histories among adolescents taking part in waves 1 and 2 of the National Longitudinal Study of Adolescent Health.

Methods. Logistic regression analyses were used to compare respondents’ reports of virginity pledges and sexual histories at waves 1 and 2.

Results. Among wave 1 virginity pledgers, 53% denied having made a pledge at wave 2; after control for confounders, pledgers who subsequently initiated sexual activity were 3 times as likely to deny having made a pledge as those who did not initiate sexual activity (odds ratio [OR] = 3.21; 95% confidence interval [CI] = 2.04, 5.04). Among wave 1 nonvirgins who subsequently took virginity pledges, 28% retracted their sexual histories at wave 2; respondents who took virginity pledges were almost 4 times as likely as those who did not to retract reports of sexual experience (OR=3.88; 95% CI=1.87, 8.07).

Conclusions. Adolescents who initiate sexual activity are likely to recant virginity pledges, whereas those who take pledges are likely to recant their sexual histories. Thus, evaluations of sexual abstinence programs are vulnerable to unreliable data. In addition, virginity pledgers may incorrectly assess the sexually transmitted disease risks associated with their prepledge sexual behavior.
Patterns and Correlates of Deliberate Abstinence Among Men and Women With HIV/AIDS
Authors: Bogart Laura M. , Collins Rebecca L. , Kanouse David E. , Cunningham William , Beckman Robin , Golinelli Daniela , Bird Chloe E.
Published: May 2006

Objectives. We examined correlates of deliberate sexual abstinence among gay/bisexual men, heterosexual men, and women in a national probability sample of adults with HIV.

Methods. Participants in the HIV Cost and Services Utilization Study (HCSUS; n=1339) answered questions about oral, anal, or vaginal sexual intercourse in the past 6 months; those who reported none of these behaviors (n=415) were asked about their reasons for abstinence. Of these, 201 participants (11% of gay/bisexual men, 18% of women, 18% of heterosexual men) indicated that their abstinence was deliberate. Multivariate models were used to predict deliberate abstinence.

Results. In multivariate analyses, not having a primary relationship partner/spouse was a significant correlate of deliberate abstinence for all 3 groups. Higher perceived responsibility for limiting disease transmission and nondrinking status were related to deliberate abstinence only among gay/bisexual men. Worse health was associated with deliberate abstinence only among heterosexual men.

Conclusions. Perhaps because HIV is more common in gay communities, abstinence choices may be more closely linked to a higher sense of responsibility for reducing transmission among gay/bisexual men, and their illness may be less of an impediment to sexual activity.
On Lizard Species Diversity: North American Flatland Deserts
Authors: Pianka Eric R.
Published: May 2006

Eight potential mechanisms for the determination of species diversity are described and discussed, and data relevant to each are presented for a particular diversity gradient: namely that of the flat land desert lizards of western North America. It is concluded that ecological time, spatial heterogeneity, length of growing season, and amount of warm season productivity are all factors which determine the total number of lizard species occurring on an area, but that the most important single factor is the spatial heterogeneity (mainly vegetative) of the environment. It is suggested that climatic variability allows the coexistence of many different plant life forms, the variety of which in turn controls the number of lizard species.
The Upland Forest Continuum in Northern New Jersey
Authors: Buell Murray F. , Langford Arthur N. , Davidson Donald W. , Ohmann Lewis F.
Published: May 2006

Quantitative data on trees, saplings and tree seedlings were taken from 60 acceptably homogeneous upland stands on a wide variety of geological substrata and topographic positions throughout northern New Jersey, partly to test the applicability of a unidimensional continuum in a heterogeneous environment. The strong negative correlation between stand altitude and continuum index could not be ascribed to altitude alone because rich calcareous soils were found at low altitides while poor, shallow soils from more resistant rocks were found at higher elevations. Species diversity was greatest in forests on limestone substrata. Although Quercus species were found as leading species in 54 of the 60 stands, sapling data showed that in these forests as a whole succession is leading from dominance by oaks to dominance by Tsuga canadensis or by Acer saccharum, the association between these two species being weak. Though useful as a tool for the study of vegetation, a linear continuum was not applicable to the forests of northern New Jersey; they appear to conform to a pluridimensional continuum. It is concluded that the Clementsian concept of climax, as a process, is in no way degraded by the concept of the continuum, either linear or pluridimensional.
The Clonal Growth Habit of American Aspens
Authors: Barnes Burton V.
Published: May 2006

Bigtooth and trembling aspens (Populus grandidentata and P. tremuloides) typically occur in Michigan and throughout much of their native range in natural clones of several to many genetically identical individuals. A clone is initiated by the establishment of a seedling (the ortet); suckers (ramets) arise from the root system of the ortet. Death of ramets and decay of root connections may result in formation of several independent root systems within the same clone. Average size of individual clones of both species on the research sites in Michigan was approximately 0.007 acre. Male and female clones did not differ in size. Clones are established, expand, intergrow, and coalesce depending upon the ease of seedling establishment, rapidity of root expansion, inherent suckering ability, and amount of disturbance. Although the aspens are typically recognized as pioneer species, they may be more permanently part of the habitat than most of their non—clonal associates. Recognition of the clonal structure of most aspen stands is important in many aspects of research.
Habitat Selection by the Queens of to Field‐Dwelling Species of Ants
Authors: Wilson Edwards O. , Hunt George L.
Published: May 2006

The movements of queens of Lasius neoniger and Solenopsis molesta were followed visually during nuptial flights and with the aid of radioactive tracers after the flights. The queens of both species controlled their own direction during the flights, keeping to the preferred major habitat (moved field) with nearly perfect efficiency. When dealated queens of L. neoniger were experimentally displaced after the flights to woodland they exhibited a higher frequency of negative geotaxis but were very inefficient at moving out of this unfavorable environment. Displaced S. molesta queens showed no behavior different from that in the favorable habitat and hence were completely inefficient at further macrohabitat selection. On the other hand, queens of both species choose the microhabitats (the points at which the first nests are excavated) after the flights.
Late‐Quaternary Cladocera of Lake Zeribar Western Iran
Authors: Megard Robert O.
Published: May 2006

Between about 22,500 and 12,000 years ago cosmopolitan and northern Chydoridae were dominant in Lake Zeribar. Species with southern affinities replaced the northern species between 12,000 and 5,000 years ago. During the last 5,000 years the chydorid fauna has been composed of southern and cosmopolitan species, and the planktonic cladoceran, Bosmina longirostris, has been more abundant than it was earlier in the lake's history. The fauna prior to 12,000 years ago was similar in several ways to the fauna in Allerod lake sediments in Germany and England, thus implying a cool temperate climate in the vicinity of Lake Zeribar during the latest Pleistocene. The replacement of northern species by southern species between 12,000 and 5,000 years ago suggests gradual warming, but temperatures probably never have been warmer than they are now. Th chydorid assemblage has been relatively stable during the last 5,000 years. The abundance of planktonic Cladocera during this interval suggests that the lake probably has been deeper than at any time during its earlier history, and that rainfall was probably greater than before.
Postfire Chaparral Succession in Southern California
Authors: Hanes Ted L. , Jones Harold W.
Published: May 2006

The vegetation of two chaparral stands of different age in the San Gabriel Mountains of Southern California was analyzed in 1959, was completely destroyed by wildfire in 1960, and was reanalyzed by 1/100—acre quadrats in 1965, 4½ year after the wildfire. The 1965 vegetation of north—facing slopes in both stands contained more plants and more species and generally taller individual plants than south—facing slopes. Postfire vegetation was composed mainly of rootcrown sprouts and seedlings of prefire species. Direct comparisons of prefire (1959) and postfire vegetation (1965) showed that, although overall shrub composition of chaparral in Southern California is relatively stable, vegetation after fire was altered in plant number within species and in species composition. Seedlings of invading species are influential in stand succession.
Preliminary Life Tables for Pine Sawflies in the Neodiprion Fulviceps Complex (Hymenoptera: Diprionidae)
Authors: Dahlsten Donald L.
Published: May 2006

Three populations of one or possibly two species of sawflies in the Neodiprion fuliceps complex were followed in detail from the egg stage to adult emergence in a brush—field pine plantation near Mt. Shasta, California. All observed mortality factors were quantitively assessed and preliminary life tables and survivorship curves were formulated for the 1960—61 generation. Total mortality was of such a magnitude that the populations were shown to be declining. High egg loss could not be explained but mortality from cold temperatures was suspected. Cold temepratures were also felt to be a major factor in high early first instar larval mortality in two other areas. Mortality of feeding larvae exceeded the early first instar larval mortality only in one area due to evening grosbeak predation. Generally, mortality of the feeding larvae was low, Prespinning larval mortality was considerable but the causes were not determinable. The heaviest losses occurred during the cocoon stage which is the most vulnerable stage in the life cycle. However, the full impact of cocoon predation was not realized in this study due to the time of sampling. Other mortality factors are discussed and biological information is given on several of the parasites.
Phytograph: Useful Tool or Decorative Doodle?
Authors: McCormick Jack , Harcombe Paul A.
Published: May 2006

The phytograph is a quadriaxial polygonal graph used to present data on species performance in vegetation. The area of the quadrilateral formed by connecting plotted points on adjacent axes is considered to portray the mass effect of the four axial values. This mass effect is an expression of the relative importance of the species. Since Lutz (1930) introduced the phytograph, it has been used in at least 34 original studies of North American forest vegetation. Lutz's original phytograph employed relative, semi—relative, and non—relative bases on different axes. Subsequent users have introduced many modifications in parameters and form, but every published phytograph has included at least one non—relative parameter. A major defect in the phytograph previously has been undetected. The area of the quadrilateral negatively distorts the graphic representation of relative importance. The value of the phytograph depends on the legitimacy of expressing parameter values in relative terms and of combining three or more terms to describe the relative importance of a species. If phytographs are used, their accuracy and information content can be increase by adopting several modifications, such as rescaling the axes by a square—root percentage method and using relative values on all axes.
Bombus (Hymenoptera, Apidae) Queen Foraging in Relation to Vernal Pollination in Wisconsin
Authors: Macior Lazarus W.
Published: May 2006

Eleven hundred bumblebee (Bombus) queens and cuckoo bee (Psithyrus) females were gathered as they hunted nesting sites and foraged on native and introduced plants in farmland of southeastern Wisconsin in the spring of 1965. Insect behavior was related to the phenology of plant blooming periods for 9 Bombus, 1 Psithyrus, and 19 plant species. Of 933 foragers 23.8% carried corbicular pollen loads. Of 222 loads 55.4/% were pure, 30.6/% contained two kinds of pollen, 11.3/% contained three kinds, and 2.7/% had four kinds. In all but four mixed loads, one pollen type formed more than 50% of the total grain number of each load. The pollen in 28.5% of the pure loads was from a species other than that of the plant being visited by the pollen carrier.
A Critical Evaluation of the Trophic Level Concept. I. Ecological Efficiencies
Authors: Kozlovsky Daniel G.
Published: May 2006

A scheme of ecological efficiencies is presented in the interest of equating the terminology of various authors. Some efficiency ratios are calculated from the data of natural communities, and it is shown that a rigorous analysis indicates that several widely held assumptions about trophic dynamics, such as the existence of progressive efficiencies of energy utilization at higher tropic levels, cannot be substantiated. The ideas of community efficiency and community productivity are discussed, and several new ways of calculating these, based upon a consideration of the net productivities of all trophic levels or populations, are suggested.
Evidence for Reproductive Periodicity in the Deep Sea
Authors: Schoener Amy
Published: May 2006

Deep sea bottom samples taken at depths between 1,100 m and 3,800 m in the western North Atlantic during the summer months of 1964, 1965 and 1966 yielded large numbers of young of the brittlestars Ophiura ljungmani and Ophiomusium lymani, whereas proportionately fewer young were present in samples taken at approximately the same depths during winter and spring. In two winter samples of one species, well—developed gonads and eggs were found, whereas in a sample obtained in May this was not the case. This evidence suggest that a period of increased reproductive activity occurs, even though the deep sea has been considered to provide a relatively constant physical environment. These findings are discussed in light of present ecological information, and several possible explanations are offered.
Seasonal Changes in Biomass and Annual Production of an Old‐Field Pinus Virginiana Stand
Authors: Madgwick H. A. I.
Published: May 2006

Biomass of the aboveground portion of a 16—year—old Pinus virginiana stand was estimated for nine dates throughout the growing season using 45 sample trees. Total production for the season was estimated to be 14.3 metric tons per hectare of which 41%, 30%, 17%, 8%, and 4% were boles, fascicles, old branches, new twigs, and flowers, respectively. Attempts to estimate the pattern of within—season production were unsuccessful because of the difficulties involved in estimating within—season growth of boles and, more particularly, older branches.
A Recording Photometer for Biological Studies
Authors: Berry R. E. , Raney L. W.
Published: May 2006

The construction and use of an automatic range—selecting, continuously—recording photometer is described. Its range is from nocturnal light to bright sunlight.
Territorial Behavior of the Owl Limpet, Lottia Gigantea
Authors: Stimson John
Published: May 2006

Lottia gigantea, a large (up to 8 cm in length) limpet of the California and northern Mexican coast, lives in association with an approximately 1,000 cm2 area of algal film in which its grazing marks can be seen, whereas the remainder of the rock surface is usually free of any visible film. These areas of algal film represent the territories of the Lottia; within them the animals do all their grazing. They keep their territories free of other organisms by shoving off any intruders: other Lottia, grazing limpets of the genus Acmaea, predatory snails, and sessile organisms such as anemones and barnacles. Within 2—3 weeks after Lottia were removed from their territories, the density of Acmaea in these territories increases to that found outside them, and the algal film disappeared. Apparently the defense of the territories against intrusions by other grazers permits the growth of a thick algal film on which the Lottia can effectively graze. Their reaction to sessile organisms prevents these animals from encroaching on and covering the territory. Their response to predatory snails may be a defense mechanisms.
Thermal Response of a Plant Canopy to Drifting Cloud Shadows
Authors: Lambert John L.
Published: May 2006

With appropriate modifications, Lettau's climatonomical theory (quantitative climatic description) may be applied to the characterization of vegetative influences on microclimate. The theory was tested on a sumac canopy which was alternately shaded and unshaded by the drift of cumulus cloud shadows. Results showed that the canopy layer had a relatively low thermal admittance, but the geometry of the canopy elements had a profound influence on the thermal properties of the layer. The observed thermal responses for the given meteorological conditions represent a single spectral distribution, characteristic of this particular canopy.
Wildland Fires and Ecosystems‐‐A Hypothesis
Authors: Mutch Robert W.
Published: May 2006

Plant species which have survived fires for tens of thousands of years may not only have selected survival mechanisms, but also inherent flammable properties that contribute to the perpetuation of fire—dependent plant communities. This concept goes by beyond the commonly accepted fire climate—fuel moisture basis of wildland fire occurrence. Plant communities may be ignited accidentally or randomly, but the character of burning is not random. The following hypothesis treats this interaction between fire and the ecosystem: Fire—dependent plant communities burn more readily than non—fire—dependent communities because natural selection has favored development of characteristics that make them more flammable. The hypothesis was experimentally derived following laboratory combustion tests with litter of eucalyptus (Eucalyptus obliqua L'Herit), ponderosa pine (Pinus ponderosa Laws.), and tropical hardwood leaves.
Seasonal Course of Xylem Sap Tension
Authors: Hickman James C.
Published: May 2006

More than 1,000 xylem tension measurements were made with a pressure chamber on plants of various life forms, including delicate herbs. Five patterns of seasonal change in tension were discerned. The commonest pattern consists of marked diurnal fluctuations which steadily increase in magnitude. Actively growing annuals and perennials exhibiting this pattern were found to withstand tensions greater than 70 atm. Other perennials showed seasonally constant maxima, with minima increasing until there was little diurnal fluctuation. One species evidenced no seasonal change in either maximum or minimum tension. Of the ephemeral annuals exemplifying the remaining two patterns, one species showed increasingly prominent diurnal fluctuations with a critical point beyond which plants desiccated rapidly, whereas another species exhibited little diurnal fluctuation and had an earlier and lower critical point. Annuals have the ability to maintain low tensions under high radiation loads, and the ability to withstand extremely high internal tensions. These responses appear to be alternative adaptations to a seasonally decreasing moisture supply.
Forest Productivity Estimated from Carbon Dioxide Uptake
Authors: Botkin Daniel B. , Woodwell G. M. , Tempel Neal
Published: May 2006

Net photosynthesis of the three dominant tree species of the oak—pine forest of central Long Island was monitored intensively throughout one growing season to test the practicality of field measurements of net photosynthesis for estimating gross production of a forest. White Oak (Quercus alba) leaves absorbed 16.9 g CO2/g of leaf during the growing season; scarlet oak (Q. coccinea) absorbed 9.9 g/g; pitch pine (Pinus rigida), 7.5 g/g. Previously published data integrated with the CO2 exchange rates over the growing season gave a new estimate of gross production for the forest of 2,950 g dry matter/m2 per year. This value is approximately 10—22% higher than previous estimates which were based principally on harvest techniques. The discrepancy between estimates emphasizes the difficulty of the measurements and the scale of the errors one must expect even with elaborate techniques.
Measurement of Transpiration in Tropical Trees with Tritiated Water
Authors: Kline J. R. , Martin J. R. , Jordan C. F. , Koranda J. J.
Published: May 2006

The measurement of transpiration of water by trees in the field with tritiated water as a tracer depends upon a new application of established theory of radionuclide dynamics in steady—state systems. The techniques required are non—destructive to the trees and probably have negligible disturbing effects on transpiration. Average transpiration rates ranging from 1.75 to 372 liters per day per tree were measured by the proposed method on tropical forest trees which ranged from the understory to the canopy in size. Statistical errors range from 12.1% on the largest tree to 6.2% on the smallest for one standard deviation. Non—random sources of error in the method may include (1) loss of tritium from leaves due to rainfall; and (2) possible enrichment of tritiated water in leaves due to differences in vapor pressure and molecular diffusion coefficients between tritiated water and ordinary water. These require further experimental evaluation. The method may be generally applicable to field measurements of transpiration in trees.
Thermal Ecology of the Lizard, Anolis Limifrons with Comparative Notes on Three Additional Panamanian Anoles
Authors: Ballinger Royce E. , Marion Ken R. , Sexton Owen J.
Published: May 2006

Data on the thermoregulation of Anolis limifrons in Panama suggest that at least some tropical species are less warm adapted than previously thought. Anolis limifrons has a lower minimum voluntary temperature, eccritic temperature, and critical thermal maximum than a majority of the temperate zone lizards thus far studied. Thermoregulatory adjustment is by behavioral mechanisms as indicated by observations on basking and orientation. A seasonality in the preferred temperature is indicated by field data from the wet and dry seasons. It is suggested that the lower preferred temperature in the dry season is an adaptation to conserve water or minimize water loss. Anoles (A. limifrons and A. frenatus) in colsed canopy forests are less warm adapted than the grassland A. auratus, whereas an ecotone species (A. tropidogaster) is intermediate in its thermoregulatory characteristics. Differences in dermal morphology in three species of Panamanian anoles are suggested to be an adaptation to varied capacities of heat gain.
A Method for Comparing Individual Growth Rates of Aquatic Insects with Special Reference to the Odonata
Authors: Benke A. C.
Published: May 2006

A method for representing individual growth rates of aquatic insects from field sampling is presented using the mean instar number as the age criterion. Various examples are used to show how the method is useful in making both intra— and interspecific comparisons. Significantly different growth rates are shown between populations of the same species in different habitats. Also, an example is presented which shows the possible role of temporal separation in niche differentiation between two similar species.
Dominance Relations of Red and Grey Squirrels
Authors: Ackerman Ralph , Weigl Peter D.
Published: May 2006

The relationship between captive red squirrels (Tamiasciurus hudsonicus) and grey squirrels (Sciurus carolinensis) was studied by comparing the behavior or mixed pairs and conspecific pairs in a large outdoor cage containing one primary nest box above ground and another exposed on the ground surface. While red squirrels always shared the nest box with conspecifics, grey squirrels never did so. When both species were present, the grey squirrels occupied the nest box, but shared it 37% of the time with the red squirrels. No fighting or wounds were observed. The much publicized aggressiveness of the red squirrel toward the grey may be a function of territorial behavior in certain parts of its range (conifer forest) rather than an inherent characteristic of the species.
Colonization of Secondary Habitats by Peruvian Birds
Authors: Terborgh John , Weske John S.
Published: May 2006

Complete surveys of the bird faunas of 4— to 10—acre study plots in six habitats were undertaken at a locality in the Apurimac Valley of Peru. Two of the habitats, forest and matorral, represent the primary vegetation of the region. Four secondary habitats incorporated varying degrees of departure from the structure and species composition of natural vegetation. Of the 211 species of land birds found in the 6 habitats, all but 10 were recorded in at least of the 2 primary habitats. With the exception of these 10 species the fauna of the secondary habitats was drawn from 3 species pools: forest, martorral and species common to both. The proportions of forest and matorral species in the secondary habitats varied greatly in relation of the vegetation of the habitats and their proximity to the source faunas. Mist nets were used in all the study plots to sample the using the airspace between 6 in. and 6 ft above the ground. The species diversity in samples of 100, calculated according to the Shannon—Wiener formula, showed rather little variation from one habitat to another. Of greater interest was the fact that in most nests caught fewer than half of the species known to be present. In temperature habitats virtually all species are eventually captured. This contrast is considered to reflect a fundamental difference in the spatial relationships of bird niches in temperate and tropical forests. The above and other evidence indicate that many tropical bird species confine their foraging activities to narrow vertical zones in the vegetational column. The number of bird species in the four secondary habitats was much lower than in primary habitats having similar foliage height profiles. The discrepancies are accounted for by an hypothesis that evokes two complementary parameters: the isolation of tracts of secondary habitat from primary vegetation and certain qualitative aspects of habitat that are not adequately expressed by the foilage height diversity index.
Foliage Profile by Vertical Measurements
Authors: MacArthur Robert H. , Horn Henry S.
Published: May 2006

A technique is described for estimating a foilage profile in a forest by a combination of measurements over random lines of points: (1) counts of leaf contacts on a plumb line below a tripod, (2) sightings on the heights of lowest leaves over grids of points, and (3) the proportions of sky unobscured by leaves.
The Incidence and Intensity of Predation on Lake‐Dwelling Triclads in the Laboratory
Authors: Davies Ronald W. , Reynoldson T. B.
Published: May 2006

Predation on the four common species of lake—dwelling triclads Polycelis nigra, P. tenuis, Dugesia lugurbis and Dendrocoelum lacteum was investigated by exposing them to potential predators in the laboratory and using a serological technique to test cases of suspected predation. The highest intensities of predation were found for fish Scardinius erythrophthalmus, Rutilus rutilus, Gasterosteus aculeatus and Salmo trutta together with Odonata larvae, all species characteristics of weeded habitats. The leech, Erpobdella octoculata, the caddisfly larvae Plectrocnemia geniculata Polycentropus flavomaculatus and the snail Lymnae stagnalis fed only on the three planariid species of triclad and not on Dendroceleum lacteum. Shrunken adults and young triclads of the same size were preyed upon the equal intensity. Selection for size of triclad, irrespective of species was shown to occur in several of the predators. Despite differences in adult size of three of the triclad species, the potential effect of selection for size in the field compared to specific predation was difficult to ascertain. Dugesia lugubris was the only species which practiced cannibalism and preyed on other triclad species (Polycelis sp.)
Prediction of Net Photosynthesis of Trees From Light Intensity and Temperature
Authors: Botkin D. B.
Published: May 2006

Daily rates of net photosynthesis of tree leaves were predicted from sunlight and temperature conditions near leaf surfaces for oaks in a coastal plain forest on Long Island, New York. Predictions were based on the observed relationships between CO2 uptake, sunlight, and temperature for a single sun—exposed white oak leaf during a single day in midsummer. Of 18 such predictions, including those for white oak leaves in a variety of weather conditions at shaded, exposed, apical, and basal locations, eight were within a factor of 0.1 of observed values, 15 within 0.7 to 1.3, and all within a factor of two of the observations. The same relationship predicted net photosynthesis for scarlet oak leaves in the same forest with similar success. The uniformity of the response of these leaves to sunlight and temperature reflects the simple of the coastal plain forest, which is low and open and lacks deep shade.
An Index to Measure Weather‐Induced Stress of Trees Associated With Outbreaks of Psyllids in Australia
Authors: White T. C. R.
Published: May 2006

A measure of the changes in soil water which induce water deficits–and thus physiological stress–in the tissues of plants is described, and named the stress index. Known outbreaks of psyllids throughout Australia were strongly correlated with suddenly increasing high levels of this stress index. It is postulated that physiological stress of plants at these times increased the amount of nitrogeneous food available to the psyllids, thus greatly increasing the chances of young surviving and reproducing. A similar correlation of outbreaks of other sorts of phytophagous insects with the appropriate stress index has been found, and it is suggested that herein may lie an ecological generalization of some significance.
Penetration of Coniferous Trees by DDT
Authors: McDaniel Ivan N.
Published: May 2006

Cages of wooden framing have in some cases caused mortality of mosquitoes in our laboratory. Analytical tests have indicated the presence of DDT in the wood. It is suggested that DDT may penetrate conifers and become stored in the woody tissues. Even very low concentrations of DDT in wood could cause problems when used in cages to hold insects that are highly sensitive to this compound.
Effect of Shade of Photosynthesis and Dry Weight Distribution in Yellow Birch (Betula Alleghaniensis Britton) Seedlings
Authors: Gordon John C.
Published: May 2006

Yellow birch seedlings were grown under heavy (86%) shade, moderate (72%) shade, and full sun. Shaded seedlings grew more in height and leaf area, but those in full sun accumulated more dry weight. Shaded seedlings were also more efficient photosynthetically near the end of the growing season than unshaded seedlings. Percentage dry weight was greater in leaves and stems of shaded seedlings and greater in roots of unshaded seedlings.
Bird Species Diversity: Components of Shannon's Formula
Authors: Tramer Elliot J.
Published: May 2006

Shannon's diversity index H' = Σpi log2 pi was calculated for 267 breeding bird censuses. The index was resolved into its components, species richness and relative abundance, to determine which components played a larger role in the determination of diversity patterns. Changes in diversity were correlated closely with species richness (r = 0.972), while the relative abundance component remained stable. Among the nine community types represented, diversity and species richness increased with foliage height diversity. The relatively abundance component was strikingly low in the marshes due to the presence of gregarious birds which nest in colonies and feed outside the community. Photoplankton differ from birds in that the relative abundance component is not stable from one collection to the next. This is attributed to differences in the environmental uncertainty encountered by the two groups, plankton inhabiting relatively uncertain environments and being "opportunistic," while birds occupy predictable environments and therefore "equilibrium" species. The distribution of relative abundances in birds is more even than in trees, herbaceous—shrub communities, or phytoplankton. Since this is in part the result of intraspecific territoriality, it is predicted that nonbreeding bird populations, species' relative abundances will be less even than they are during the breeding season. It is suggested that the regulation of diversity by either the species richness or relative abundance components represent alternative strategies which are suited to predictable/nonrigorous and unpredictable/rigorous environments, respectively. Therefore, differences similar to those observed between birds and phytoplankton might be expected in other groups of organisms.
Systems Analysis of 134Cesium Kinetics in Terrestrial Microcosms
Authors: Patten Bernard C. , Witkamp Martin
Published: May 2006

Laboratory experiments were conducted to determine patterns and rates of 134Cs exchange in microecosystems composed of different combinations of radioactive leaf litter, soil, microflora, millipedes, and aqueous leachate. Rate constants were determined by fitting models to data with an analog computer. Simulations with the models permitted comparisons of different microcosms in terms of time to radiocesium equilibrium, steady state concentrations, concentration factors, input and output fluxes, turnover rates, and stability. Rate constants varied with different compartment combinations, indicating both qualitative and quantitative differences in the cesium exchange patterns within different systems. This result is generalized: transfers of energy and matter in ecosystems are functions of networks which define intercompartmental interactions; internal coupling should be considered a significant variable in investigation of ecosystems processes. Points of particular interest derived from the computer simulations are (i) organism concentration factors for a material may vary in different systems, depending upon how the organism is coupled to other compartments; (ii) total flux of a material in a steady state system may vary considerably from that in another system which receives identical input; (iii) material turnover within compartments and in the system as a whole tends to increase as more compartments are added; and (iv) stability of material concentration does not appear to increase with system complexity.
The Chemistry of Artemia Habitats
Authors: Cole Gerald A. , Brown Robert J.
Published: May 2006

Some populations of Artemia salina (L.) occur in high carbonate waters and potassium—rich media where Na/K ratios are low. These habitats previously have been thought to exclude this crustacean.
Populations of Hexagenia Mayfly Naiads in Pool 19, Mississippi River, 1959‐1963
Authors: Carlander Kenneth D. , Carlson Clarence A. , Gooch Vijaya , Wenke Thomas L.
Published: May 2006

June populations of Hexagenia naiads in Pool 19 of the Mississippi River were estimated at 3.6, 18.7, 6.7, 23.6 and 11.9 billion in 1959 to 1963, suggesting an alternate year cycle of abundance. Although population density varied in different sections of the river, little pattern was evident. Water depths from 0.5 to 6 m and bottom deposits from soft mud to soft muds with shells or plant debris had little consistent relation to population density. Sand and gravel areas had few or no Hexagenia. Naiads increased in average size in June. In late July after major emergences, there were few naiads collected, but small naiads increased in August. Flood may have shifted part of the population in 1960. Tendipes plumosus larvae were more abundant in 1961, when Hexagenia populations were lower, than in 1960. Usually H. limbata was the more abundant species (among naiads over 16 mm) in early June and in August and H. bilineata, in late June and July. Sex ratios were usually near 50:50.
Determination of Absolute Pollen Frequency
Authors: Davis Margaret B.
Published: May 2006

Changes in technique have simplified and made more reliable a method for determining the absolute numbers of pollen grains in sediment samples. The prepared sample is suspended in its entirety in the volume of fluid from which measured portions are taken for counting; tertiary butyl alcohol, instead of benzene with dissolved silicone fluid, is used as the suspending fluid.
The Competitive Structure of Communities: An Experimental Approach with Protozoa
Authors: Vandermeer John H.
Published: May 2006

An empirical test of the existence of higher order interactions was carried out using four ciliate protozoans, Paramecium caudatum, P. bursaria, P. aurelia, and Blepharisma sp. All four ciliates were cultured individually, and their population histories were described quite well by the simple logistic equation. Attempts to explain minor deviations of the data from the logistic by use of the one or two time lag logistic failed. A more complicated time lag phenomenon must be operative. Every possible pair of the four ciliates was cultured and a trial and error procedure was used to estimate @a and @b of the Gause equations. In all cases the simple Gause equations seemed adequately to describe the data. All four ciliates were cultured together and compared to predictions made by use of the competition coefficients estimated from pair—wise competition and population parameters estimated from single species population growth. The correspondence between prediction and data suggests that the higher order interactions have slight or no effect on the dynamics of this artificial community.
An Ecologial Significance of Seasonal Leaf Variability in a Desert Shrub
Authors: Cunningham G. L. , Strain B. R.
Published: May 2006

Encelia farinosa is one of a number of species of desert perennial shrubs in which individuals exhibit considerable seasonal variation in the amount and structure of leaf tissue. The function of seasonal leaf variability in adapting this species to the desert environment was investigated. Field observations demonstrated that leaf quantity and structure are controlled by the moisture status of the environment. The field observations also established the influence which leaf quantity and structure have on the CO2 exchange capacity and water status of the shrub. These observations were corroborated by laboratory experiments. The laboratory investigations also indicated that the influences of leaf structure are brought about by alterations in the resistances to CO2 and water vapor diffusion.
Species Diversity of a Stratified Oak‐Hickory Community
Authors: Monk Carl D. , Child George I. , Nicholson Stuart A.
Published: May 2006

The herb, shrub, understory, and canopy strata (each arbitrarily delineated by size classes) were sampled separately. The latter two were sampled by a series of two different plot sizes and by a plotless sampling technique. Diversity (= —Σpi ln pi) of each stratum was estimated for each set of census data. Species diversity within a stratum was independent of sample plot size above a minimum cumulative area. Estimates of diversity based on plotless and plot samples gave similar values. It was suggested that diversity of a stratified community could be determined by pooling the data needed to estimated diversity of each stratum.
Home Range, Movements, and Activity of the Eastern Worm Snake, Carphophis Amoenus Amoenus
Authors: Barbour Roger W. , Harvey Michael J. , Hardin James W.
Published: May 2006

Movements of 10 eastern worm snakes (Carphophis amoenus amoenus) were studied using radioisotope tagging and tracing techniques. The study was conducted at Robinson Forest, Breathitt County, Kentucky, from early May to late October 1966. Snakes were tagged subcutaneously, using a hypodermic needle and plunger apparatus, with 50—80 μc Cp60 alloy wire tags. Detection apparatus consisted of a Victoreen model 489 Thyac II survey meter equipped with earphones, shoulder strap, and scintillation probe mounted at one end of a 3—m tubular aluminum pole. Each snake was located 46 to 89 times. Home ranges were calculated using the minimum area method and averaged 253 m2 (range, 23—486 m2). The longest known movement during a 24 hr period was 45 m (in 14 hr 30 min). Most movements were initiated in late afternoon and early evening. Most periods of activity were of less than 12 hr duration. Periods of inactivity ranged from a few minutes to over 14 days. Snakes displaced distances of 150, 400, and 800 m from where captured exhibited no homing ability.