bluuebunny/crossref_metadata_2025 huggingface dataset:
The Theatre of Pina Bausch
Authors: Hoghe Raimund
Published: April 2006

Two jokes; a dream. “A man came to the circus manager and asked him if he needed a bird imitator. ‘No,’ answered the circus manager. Then the man flew away through the window.” This and a second joke are told twice—in the first and in the last part—in Pina Bausch's Arien (Aries). “Berlin. A man asks a cabdriver: ‘Can you tell me how I can get to the Philharmonic?’ The cabdriver answers. ‘Sure, man, that's very easy: practice, practice, practice.’” “They practiced and could fly for two hours,” someone noted after an Arien performance. In Pina Bausch's Macbeth paraphrase there is the same dream. “How will you live?” Lady Macduff asks her son. “As the birds do.” It is cited twice.
The Haifa Theatre Project Group
Authors: Belkin Ahuva
Published: April 2006

A Bike for a Year and Bars, both recent productions by the young actors of the Haifa Theatre Project Group, raised a two fold debate with both the public and theatre critics. One issue involved the artistic qualities of the shows as they reached the stage; the other concerned the social settings against which they were produced—for both productions were the results of special experiments in theatrical activity.

The initiator of the Haifa Theatre Project Group was Nola Chilton, a newcomer to Israel from the United States. A former Lee Strasberg student and now a member of a kibbutz, she is a resident director with the Haifa Municipal Theatre. Her most successful work there was based on a collectively compiled social research which evolved, over a prolonged period of study and experiment, into a stage-documentary.
The New Mime Festival at Dance Theatre Workshop
Authors: Cunningham Kitty
Published: April 2006

Mime in America today is a many-faceted art form without a single clear definition or a place to call its own. Mime is sometimes joined with theatre, sometimes placed with dance. To some people it is street mime or clowns but since 1955, when Marcel Marceau took the country by storm, most people associate mime with white-face illusionary pantomime vignettes, if they think of mime at all.

When David White produced four American mime artists in September 1980 under the heading “New Mime: New Investigations in a Theatre of Movement” at the Dance Theatre Workshop, it was no accident that the word “new” was used twice in the title. By presenting some of the most imaginative concert artists working in mime today, White took an innovative step toward reaching a fresh audience for what has been consistently a neglected stepchild of the arts.
Structure and Energetics of Three Minnesota Forests
Authors: Reiners W. A.
Published: April 2006

Three contiguous ecosystems, an upland oak forest, marginal fen, and cedar swamp, were analyzed along a gentle topographic gradient on the Anoka Sand Plain in east—central Minnesota. The organic structure and aboveground primary productivities of these forests were compared with similar data for other natural ecosystems of the sand plain. Living, aboveground biomass totals of the oak, fen, and swamp forests were 124.6, 98.8, and 159.6 mt/ha, respectively. Aboveground, net annual productivities were 8.9, 7.1, and 10.3 mt/ha, respectively, which compared well with other forest data for the region and with a predicted value based on actual evapotranspiration. Several measures of structure were compared in the analysis. Species richness and equitability were greatest in the marginal fen where biomass and productivity were the least. Richness and equitability were lowest in the oak forest. The highest biomass—to—production ratio was found for the Thuja swamp, although it had the highest annual production. Apparently the high production in the swamp was achieved with a large mass of relatively inefficient foliage concentrated in Thuja occidentalis. The percentages of primary production entering detritus pathways were 52, 62, and 48 for oak, fen, and swamp, respectively. Total detritus, including dead boles, branches, and forest floors, was large in relation to living biomass in all three forests, but was especially important in the fen and swamp systems where deep forest floors had accumulated. Total detritus was 61%, 331%, and 577% of aboveground biomass in the oak, fen, and swamp, respectively. All data were produced in caloric as well as weight units.
Why Do Bumblebees Major? A Mathematical Model
Authors: Oster G. , Heinrich B.
Published: April 2006

We have developed a model which indicates that the pure strategy of "majoring"is always better than random foraging if the reward structure remains approximately constant through time. "Minoring" is a necessary compromise required to track resources changing through time.
Landscape Evolution, Peatland Types, and the Environment in the Lake Agassiz Peatlands Natural Area, Minnesota
Authors: Heinselman M. L.
Published: April 2006

The vegetation and peatland types of the Lake Agassiz Peatlands Natural Area are related to topography, waterflow patterns, water chemistry, and the evolution of the landscape as recorded by peat stratigraphy. Eight peatland types are distinguished: (1) minerotrophic swamp, (2) weakly minerotrophic swamp, (3) string bog and patterned fen, (4) forest island and fen complex, (5) transitional forested bog, (6) semi—ombrotrophic bog, (7) ombrotrophic bog (raised bog), and (8) raised bog drain. Consistent differences in pH, Ca, and Mg were found between waters of contrasting peatland types. These differences agree with the division of peatland types by degree of mineral soil water influence (minerotrophy). A general topographic alignment of vegetation and peatland types agrees with the hypothesis of chemical controls. Vegetation types often have sharp boundaries related to changes in water properties, peat surface configuration, and paths of waterflow. Landscape evolution included five phases: (1) Recession of Lake Agassiz about 11,700 years ago. (2) Organic sedimentation of local basins beginning 11,100 years ago. Aquatic peats eventually covered 6% of the substratum. (3) Development of fens, marshes, and carr during the postglacial warm—dry interval, beginning about 8,000 years ago. These peatlands built the sedge peats that now cover 46% of the substratum. Paludification caused water tables to rise, and most water basins were overgrown. (4) Invasion of minerotrophic swamp forests around the perimeter of the peatland and along substratum ridges, beginning about 5,000 years ago as the climate cooled and precipitation increased. These forests built the basal forest peats that now cover 48% of the substratum. (5) Capture of part of the watershed by Northeast Brook about 3,100 years ago, which caused a water—table divide and mineral depletion, initiated sphagnum invasion, and led to development of the present ombrotrophic raised bogs. As convexity grew, a sharp vegetation and chemical gradient developed along the limit of mineral soil water. Myrtle Lake rose steadily with paludification and now stands 11.8 ft (3.6 m) above the ridge 1 mile (1.6 km) north of the lake. Water tables rose 10—20 ft (3.0—6.1 m) over much of a 70—square—mile (181—km2) area. This history does not agree with early concepts of succession, which postulate a trend toward mesophytism with peat accumulation. The only "direction" here is a possible trend toward landscape diversity.
The Structure of a Colorado Tick Fever Ecosystem
Authors: Carey A. B. , McLean R. G. , Maupin G. O.
Published: April 2006

The habitat hyperspace of a south—facing slope ecosystem in Rocky Mountain National Park, Colorado, USA was characterized by two major gradients, soil depth and soil moisture. Richardson's ground squirrels (Spermophilus richardsonii) were limited in their distribution by areas of shallow soil, and excluded golden—mantled ground squirrels (S. lateralis) from areas of deep soil. The habitat hypervolume of the golden—mantled ground squirrel included that of the least chipmunk (Eutamias minimus); the golden—mantled ground squirrels suppressed the population of least chipmunks. Deer mice (Peromyscus maniculatus), least chipmunks, and golden—mantled ground squirrels were the principal hosts of larval wood ticks (Dermacentor andersoni). The golden—mantled ground squirrels and least chipmunks were the principal hosts of nymphal wood ticks. The circulation of Colorado tick fever virus was maintained through the interactions of the wood ticks, least chipmunks, and golden—mantled ground squirrels. Areas of wood tick abundance were accurately described by a discriminant function of five easily measured habitat hyperspace variables, areas of virus activity with seven variables.
Within‐ and Between‐Habitat Avian Diversity in African and Neotropical Lowland Habitats
Authors: Karr James R.
Published: April 2006

The general pattern of changes in avian communities along latitudinal, successional, or moisture gradients have been clarified in recent years. However, few studies have compared avifaunas of similar vegetation types and climates in two tropical regions. In this study I asked two questions. How similar ecologically are the avian communities in two tropical areas (Panama and Liberia) with similar climate? To what extent might differences be due to historical factors? In general, there is convergence in the structural and functional characteristics of species and communities in the two tropical regions. However, because historical factors have been different in detail, avifaunas of varying faunal complexity have developed. The forest fauna of Panama is richer than that of Africa but the situation is reversed in grassland and savanna. This seems to be due to the geographic extent of these habitats and their degree of fragmentation during the Pleistocene. Food and habitat specializations are more striking in the neotropics than in Africa. In addition, several feeding guilds, especially bark—gleaners, hover—gleaners, and salliers, are less well represented in Africa. A lower number of bird species feeding on fruit and flower resources in Africa parallels a similar trend in bat communities. The reasons for these differences are complex and outweigh the trends toward convergent evolution in areas of similar climate. Differences of historical geography in the two regions are correlated with the differences in the two avifaunas. These include long— and short—term effects of weather and climate, differences in distribution and abundance of dispersal barriers, trophic role replacements, variation in coevolutionary interactions among groups, and varying histories of human influence. In brief, it appears that the avifaunas of Central America and Africa would be more similar if (1) there were fewer isolating barriers (especially mountains and rivers) in South America, (2) Central America were more isolated from the barriers and consequent high speciation rates of South America, (3) man's influence had been of longer duration in Central America, and (4) the Central American dry season was longer and/or less predictable. These factors and their interactions have produced faunas that are clearly tropical but which are different in a number of respects.
Pollination and Wind Dispersal of Pollen in Arceuthobium
Authors: Player Glade
Published: April 2006

The mode of pollination was studied in 2 dwarf mistletoes, Arceuthobium douglasii and A. strictum, from Utah and northern Mexico. Insect visitations to the staminate flowers of A. strictum were common. Visits were found to be rare, however, to the pistillate flowers and to either sex of A. douglasii. Pollen was found to be consistently liberated by the wind from the well—exposed anthers. Air—borne pollen concentration decreased rapidly with distance from the source. No inferences, however, could be made from the data as to dispersal distance. The paucity of insect visitations, the abundance of air—borne pollen, and the moderate to high seed set combined with the absence of apomixis (in A. douglasii) were considered evidence for an anemophilous pollination syndrome. The genus as a whole appears to be anemophilous based on the uniformity of the reproductive morphology. The floral characteristics of Arceuthobium were reevaluated with respect to their suggested role in wind pollination.
Alpine and High Subalpine Plant Communities of the North Cascades Range, Washington and British Columbia
Authors: Douglas George W. , Bliss L. C.
Published: April 2006

Community types were described from 209 stands in the alpine zone of the North Cascades Range. The maritime to continental climatic change from west to east has a profound effect on regional vegetation patterns. Most of the community types in the eastern North Cascades are closely related to those in the Rocky Mountains, southern Alaska and the southern Yukon whereas communities in the western North Cascades are more similar to communities in other west coast ranges. Soils in the region include Entisols, Inceptisols, and Spodosols. Physical properties are quite similar in most soils. Organic matter, total cation exchange capacity, and pH generally decrease from west to east while exchangeable cations and nutrient levels are low throughout the region. A fellfield—dry graminoid—mesic environmental gradient was examined on Grouse Ridge, Mt. Baker. High soil temperature and low soil moisture regimes were typical of the ridgetop fellfield. During drought periods, on the vegetated portion of the slope, soil temperatures decreased and soil moisture stress increased with distance downslope; a reflection of increased plant cover and greater evapotranspiration towards the base of the slope. Species at the base of the slope had reduced vigor and much lower leaf water potential than those upslope. Phenological patterns were closely related to date of snowmelt and early—season temperature regimes along the gradient.
Seasonal, Annual, and Among‐site Variation in the Ground Ant Community of a Deciduous Tropical Forest: Some Causes of Patchy Species Distributions
Authors: Levings Sally C.
Published: April 2006

I examined patterns of species distributions in ground ants on Barro Colorado Island (BCI), Republic of Panama, using baited transect samples and Berlese extraction of litter arthropods. I sampled during wet and dry seasons in 1976 and 1977. All sites sampled were under closed—canopy rain forest at least 75 yr old. More species and more individuals were collected in wet than dry season using either method. Evenness of species abundance at baits also increased during the wet season. Ant activity was higher in 1977 than 1976 at all periods; this was correlated with increased rainfall during the dry season. Measures of species abundance and activity were positively correlated with protection from physical stresses. Over all seasons, fewer species and fewer individuals were collected at drier, sunnier sites. Patterns of seasonal and annual change were similar at bait transects and in Berlese samples. Species that were both active at baits and collected in Berlese samples varied in abundance the same way in both sampling methods. Several lines of evidence suggest that moisture availability is an important contributor to these patterns of among—site and among—season variation. First, ant activity, measured in several different ways, increased rapidly when moisture availability was increased, either through rainfall or through experimental watering during the dry season. Second, moisture availability may affect the distribution of suitable nest sites. This hypothesis was supported by differences in the number of colonies collected in Berlese samples from sites which differ in moisture availability. Third, the availability of food among sites may be correlated positively with soil moisture content, but there was not enough evidence to test this possibility. Fourth, there is some evidence that reduction of army ant raids in drier parts of the island during the dry season may concentrate the effects of these ant predators in moist, sheltered areas of BCI. Establishment and persistence of a given species in an area is a complex function of the availability of suitable food and nest sites and the strength of competitors and predators. Patchy species distributions were more the result of changes in the frequency of a species' occurrence among areas, than due to the existence of unique groups of species at separate sites, at least during the periods I sampled. Thus physical conditions were probably at least marginally acceptable to a large fraction of the fauna at all sites. However, differences in abundance and activity of ant species were correlated with changes in moisture availability. I have considered four hypotheses to account for these patterns, but they are by no means exhaustive. Moisture availability, acting through many intermediate steps, has major effects on the small—scale composition of ant faunas, even in a relatively sheltered environment like a tropical forest floor.
Nonlinear Demographic Dynamics: Mathematical Models, Statistical Methods, and Biological Experiments
Authors: Dennis Brian , Desharnais Robert A. , Cushing J. M. , Costantino R. F.
Published: April 2006

Our approach to testing nonlinear population theory is to connect rigorously mathematical models with data by means of statistical methods for nonlinear time series. We begin by deriving a biologically based demographic model. The mathematical analysis identifies boundaries in parameter space where stable equilibria bifurcate to periodic 2—cycles and aperiodic motion on invariant loops. The statistical analysis, based on a stochastic version of the demographic model, provides procedures for parameter estimation, hypothesis testing, and model evaluation. Experiments using the flour beetle Tribolium yield the time series data. A three—dimensional map of larval, pupal, and adult numbers forecasts four possible population behaviors: extinction, equilibria, periodicities, and aperiodic motion including chaos. This study documents the nonlinear prediction of periodic 2—cycles in laboratory cultures of Tribolium and represents a new interdisciplinary approach to understanding nonlinear ecological dynamics.
Microhabitat Resource Use, Activity Patterns, and Episodic Catastrophe: Conus on Tropical Intertidal Reef Rock Benches
Authors: Leviten Paul J. , Kohn Alan J.
Published: April 2006

Low species richness (five to nine species) and high population density (means of 0.2—8.6 individuals per square metre) characterize Conus assemblages on intertidal benches throughout the tropical Indo—West Pacific region. Data from 16 such habitats in Hawaii, Marshall Islands, Australia, Maldives, and Seychelles indicate that similarity of microhabitats between species is equal to or greater than random expectation. Significant between—species differences in zonation pattern occur across benches at a given time and place. The peak of C. ebraeus abundance typically occurs closest to shore; C. chaldaeus and C. sponsalis are usually most distant from shore. However, we found about as man significant within—species differences between censuses made at different times on the same bench as between—species differences within censuses. Co—occurring species thus tend not to use microhabitat resources differentially. Physical environmental variables including tide level, strength of water flow and time of day determine refuging and foraging activity patterns, and all species appear to respond similarly to these factors. The data thus do not support the hypothesis of temporal resource partitioning. We found evidence neither for homing, as mark—recapture results suggested that individuals occupy any convenient refuge after foraging, nor for interference competition for protected sites among Conus. species diversity is significantly correlated with (1) substrate topographic diversity measured either independently or as the diversity of microhabitats utilized by all species together, and (2) the proportion of individuals occupying protected sites. Where refuges (potholes and crevices) comprise only 2—9% of bench surface area, an average of 63% of Conus individuals occupy them, indicating strong selection for protected microhabitats. The presence and quality of these physical refuges are less important on benches with thick mats of algal turf binding sand. The gastropods burrow in these mats during periods of stress. A catastrophic rainstorm coinciding with low tide caused high mortality in an inner bench population at Enewetak, but more C. ebraeus survived (30%) than other species (8%). Tolerance to such unpredictable physical stress may explain the observed patterns of zonation of Conus of different species and sizes across benches.
Prunus mahaleb and Birds: The High‐Efficiency Seed Dispersal System of a Temperate Fruiting Tree
Authors: Herrera Carlos M. , Jordano Pedro
Published: April 2006

Seed dispersal of Prunus mahaleb (Rosaceae), a tree producing large fruit crops, was studied in southeastern Spain to establish the degree of reciprocal dependence between the plant and the birds which disperse it. P. mahaleb drupes contain a relatively large seed (pulp: stone ratio 0.62). The water content of pulp is 82.9% and dry flesh contains 3.2% crude fat and 2.8% crude protein, being largely made up of carbohydrates. Four bird species were the main seed dispersers. Visitation rates, feeding efficiency, and degree of dependence on P. mahaleb fruits for food varied substantially among species. Turdus merula and Sylvia atricapilla showed the highest visitation rates, were behaviorally the most efficient, removed the bulk of seeds and, after feeding, tended to fly preferentially towards the apparently safest sites for growth and survival of saplings. They were also most heavily dependent on P. mahaleb fruits for food, whereas the other disperser species relied largely on insects. Individual plant location and dispersers' habitat preferences produced a differential seeding pattern over the patchy habitat surrounding study trees. The "key" dispersers T. merula and S. atricapilla are specialized frugivores, efficiently dispersing seeds of a plant producing large numbers of extremely low—reward fruits. These results conflict with theoretical expectations and suggest that both the nature of the correlation between bird— and plant—related coevolutionary gradients and their amplitudes, as well as the nature of bird—plant coevolutionary interactions, may differ between tropical and temperate habitats.
The Phenology, Growth and Ecosystem Dynamics of Erythronium americanum in the Northern Hardwood Forest
Authors: Muller Robert N.
Published: April 2006

In the northern hardwood forest, growth of vernal photosynthetic herbs is temporally restricted to the period between spring snowmelt and summer canopy development. This characteristic suggests that several unique adaptations exist which allow the species to complete their life cycles, and that temporal separation of production in the herbaceous layer may add to structural and functional complexity of the ecosystem. Erythronium americanum Ker. (Liliaceae) was examined in central New Hampshire with respect to its natural history, growth characteristics and influence on energy flow and mineral cycling in the deciduous forest ecosystem. Growth leading to the early spring development of photosynthetic tissue begins with fall root growth and continues through a long winter phase during which the shoot elongates from the perennating organ, through the soil and into the snowpack. Following snowmelt, the shoots begin rapid unfurling and maturation of the photosynthetic tissue. The length of the mature leaf phase is controlled by the timing of snowmelt and canopy development, and may be quite variable between successive years. During the short period of production, total biomass increased by 190% in 1972 and 338% in 1973; however, plant weight at the end of the winter period in 1973 had decreased to 28% of the spring 1972 maximum. In the annual energy cycle, biomass losses during the nonphotosynthetic period may amount to more than production during the preceding spring. In comparison with summer green herbs, Erythronium shoot tissue contained significantly higher concentrations of N but lower levels of K, Mg and Ca, suggesting that the spring adaptation may be oriented toward higher N levels of the soil during the spring period as well as higher light levels at the forest floor. Significant correlations of biomass of vernal photosynthetic herbs with summer green species imply that temporally separated species may utilize the same physical site and resources. This adds to the structural complexity and production of the herbaceous layer; however, the vernal photosynthetics account for only 0.5% of total aboveground primary production of the ecosystem. The temporal character of Erythronium's growth and its capacity for rapid biomass accumulation combine to make it a significant factor in nutrient dynamics in the deciduous forest. Uptake of N and K during spring flushing of nutrients from the ecosystem and later release through senescence of shoot tissue appear to reduce gross ecosystem losses of these elements.
Thermoregulation of Monitor Lizards in Australia: An Evaluation of Methods in Thermal Biology
Authors: Christian Keith A. , Weavers Brian W.
Published: April 2006

The aims of this paper are to compare the thermal ecology of four species of varanid lizards that occupy a range of habitats and climatic regions, and to assess the efficacy of methods for evaluating the extent to which ectothermic animals exploit their thermal environments. Hertz et al. (1993) have proposed several indices of thermoregulation, and these are evaluated with respect to our data from varanid lizards. The thermoregulatory characteristics of three tropical monitor lizards (Varanus panoptes, V. gouldii, and the semiaquatic V. mertensi), and the temperate—zone V. rosenbergi were studied throughout the year. Radiotelemetry was used to measure the body temperatures (Tbs) of free—ranging animals, and microclimatic data were collected to determine the range of possible Tbs that an animal could achieve. Operative temperatures (Tb's) were estimated by biophysical models for each set of animal characteristics and microclimatic conditions. The Tb's selected by animals in a laboratory thermal gradient were used to determine the set—point range of Tb's that the animals voluntarily select. Plots that superimpose Tb's, Tb's, and the set—point range across the day are extremely useful for describing the thermoregulatory characteristics of ectotherms. These plots can be used to determine the extent to which the animals exploit their thermal environment: we define an index of thermal exploitation (Ex) as the time in which Tb's are within the set—point range, divided by the time available for the animal to have its Tb's within the set—point range. Only V. mertensi was active throughout the year. In general, during seasons of inactivity, the Tb's of inactive species fell outside the set—point range, but during periods of activity all species selected Tb's within their set—point range. The temperate—zone species (V. rosenbergi) thermoregulates very carefully during periods when environmental conditions allow the animals to attain the set—point range, and V. gouldii also thermoregulates carefully in the wet season. V. mertensi selects Tb's that are significantly lower than the other species both in the field and in the laboratory, and thermoregulatory indices of this species were intermediate relative to the other species. The amount of time spent in locomotion each day was not correlated with the indices of thermoregulation: the most active species, V. panoptes, was, with respect to several indices, the least careful thermoregulator. The type of question that is being addressed, with respect to the interactions between an animal's thermal environment and its thermoregulatory behavior, determines the appropriateness of the various indices of thermoregulation. The Ex index describes the thermoregulatory characteristics of ecotherms in a heterogeneous thermal environment, and in such an environment a large amount of information can easily be interpreted graphically. This index is less useful in a thermally homogeneous environment.
Performance Workshops: Three Types
Authors: Argelander Ron
Published: April 2006

One of the most frequently encountered words in the avant-garde theatre community has become the term “workshop.” Everywhere one turns, there is talk of a new workshop being offered, or of so-and-so's workshop of last summer, or desperate inquiries of young actors concerning whether so-and-so is giving another workshop soon, and if so how does one get in? Clearly, the experimental theatre workshop is now a popular phenomenon rather than the exclusive domain of a select few. Publications such as Viola Spolin's Improvisation for the Theatre (1963), Jerzy Grotowski's Towards a Poor Theatre (1968) and Robert Pasolli's A Book on the Open Theatre (1970) have been responsible for disseminating workshop ideas to mass audiences, while many groups' early touring efforts helped to reach audiences and actors who might never have found out that an alternative form of theatre existed.
The Rituals of Walking and Flying: Public Participatory Events at Actor's Lab
Authors: Grimes Ron
Published: April 2006

I am in a state of culture shock. When this way of naming my state occurred to me, I thought it metaphoric. Now I do not. I have decided that the Public Participatory Event (PPE) was a nascent community, a subculture appearing as an event. An event is more ephemeral than the network of structures we call a “culture,” but the event I concluded a few days ago leaves me more a stranger at home and work than I felt the first day I stepped foot in either. I have no choice but to reconceive the assumption which I have carried to much of my scholarly work in religious studies and anthropology, namely, that culture is a configuration largely of language, thought, and art. I am certain now that culture also resides quite literally in the bones; that is, in our patterns of moving, breathing, walking and so on.
Flow‐through drying of porous media
Authors: Mahadevan Jagannathan , Sharma Mukul M. , Yortsos Yannis C.
Published: April 2006

The flow of a gas (saturated or dry) through a porous medium, which is partially occupied by a liquid phase, causes evaporation. The latter occurs, even if the inlet gas is fully saturated, as a result of volume expansion. This process, referred to as flow‐through drying, is important in a variety of natural and industrial applications, such as convective drying, fuel cells, and natural gas production, which is the context of this work. In this article, a mathematical model is developed to understand the process and to predict drying rates and the evolution of liquid saturation profiles. The model includes the effects of gas compressibility and capillarity. Compressibility effects account for the evaporation into the saturated gas phase, whereas the capillary pressure gradients cause the liquid flow that leads to spreading of the saturation profile. Two important parameters, a normalized viscous pressure drop across the medium and capillary “wicking” number, control the two respective regimes. Capillary‐driven flow from regions of high saturation to regions of low saturation leads to more uniform saturation profiles or spreading drying fronts. The results are compared against experimental data obtained by X‐ray imaging. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Enantioselective addition of diethylzinc to aldehydes catalyzed by titanium(IV) complexes of n‐sulfonylated β‐amino alcohols with four stereogenic centers
Authors: Hsieh Sheng‐Hsiang , Gau Han‐Mou
Published: April 2006

An N‐sulfonylated β‐amino alcohol (R,S,S,R)‐9 with four stereogenic centers is prepared. The titanium complex of 9 is an effective catalyst to induce excellent enantioselectivities for diethylzinc addition to aromatic aldehydes with ee values up to 99%. The feature of doubling the quantity of Ti(O‐i‐Pr)4 required relative to the catalytic system of the Ti complex of bidentate N‐sulfonylated β‐amino alcohols suggests that the two N‐sulfonylated β‐amino alcohol moieties in 9 behave as two independent bidentate ligands in the catalytic system. The results obtained using ligand 15 having one N‐sulfonylated β‐amino alcohol blocked support the argument of two independent active bidentate moieties in 9. Chirality, 2006. © 2006 Wiley‐Liss, Inc.
Enantiomer separation of 1,4‐sulfanylalcohols by conventional and low‐temperature gas chromatography
Authors: Filippi Jean‐Jacques , Fernandez Xavier , Loiseau André‐Michel , Lizzani‐Cuvelier Louisette , Meierhenrich Uwe J.
Published: April 2006

Since 1990, the family of organosulfur molecules has assumed increasing importance in pheromone, flavour, and fragrance chemistry. Depending on the constitution of the functional groups, various volatile sulfur‐containing compounds are chiral. However, hitherto it has been impossible to study the chirality of 1,4‐sulfanylalcohols, since no adequate enantioselective analytical technique has been available. Here we report on the enantiomer separation of ten volatile 1,4‐sulfanylalcohol homologues by applying an heptakis(6‐O‐tert‐butyldimethylsilyl‐2,3‐di‐O‐methyl)‐β‐cyclodextrin phase, involving in some cases the use of a low‐temperature gas chromatographic (ltGC) technique. The results are expected to open research potential on the asymmetry of volatile organosulfur molecules, particularly in the fields of pheromone, flavour, and fragrance research. Chirality 18:559–561, 2006. © 2006 Wiley‐Liss, Inc.
Cover Picture: Synthesis and Characterization of PY2‐ and TPA‐Appended Diphenylglycoluril Receptors and Their Bis‐CuI Complexes (Eur. J. Org. Chem. 10/2006)
Authors: Sprakel Vera S. I. , Elemans Johannes A. A. W. , Feiters Martin C. , Lucchese Baldo , Karlin Kenneth D. , Nolte Roeland J. M.
Published: April 2006

The cover picture shows the superposition of a synthetic model of the dinuclear copper enzyme catechol oxidase over the surface and active site of this enzyme. The model is the bis‐CuI complex of a ligand‐appended diphenylglycoluril basket. This combines a reactive dinuclear copper site (the CuI ions held by the ligands) for the binding and activation of molecular oxygen with a binding site (the diphenylglycoluril clip) for aromatic substrates to be oxidized. Details on this are discussed in the article by M. C. Feiters et al. on p. 2281 ff.
Attitudinal and structural factors contributing to challenges in the work of the scholarship of teaching and learning
Authors: McKinney Kathleen
Published: April 2006

Much progress has been made in efforts to conduct, support, value, and use the scholarship of teaching and learning in higher education. Nevertheless, to further enhance student learning, many challenges remain.
Visitors or immigrants? International students in the United States
Authors: Hazen Helen D. , Alberts Heike C.
Published: April 2006

Even though international students are officially temporary migrants, many eventually become immigrants to the United States. Despite the large number of students who adjust their status, little is known about their migration intentions and decisions. We used a questionnaire sent to international students at the University of Minnesota to investigate these migration intentions. Here we report the factors that students consider in deciding whether to stay in the US or return to their home country on completion of their studies, and how these factors vary by nationality or other characteristics, such as gender or field of study. We also investigate whether international students see their stay in the US as temporary or as a springboard towards permanent immigration. Our findings suggest that few students arrive in the US with the intention of immigrating permanently. Instead, a wide variety of professional, societal and personal factors influence students in an ongoing decision‐making process. Broadly speaking, economic and professional factors typically act as strong incentives to stay in the US, while personal and societal factors tend to draw students back to their home countries. In the long run, a natural progression of professional and personal decisions leads many to become permanent immigrants. Copyright © 2006 John Wiley & Sons, Ltd.
Second-order recombination in a parallel shear flow
Authors: Smith Ronald
Published: April 2006

For a reactive solute, with weak second-order recombination, an investigation is made of the near-source behaviour (where concentrations are high), and of the far field (where the recombination has an accumulative effect). Despite the loss of material and increased spread due to recombination, the far-field concentration distribution is shown to be nearly Gaussian. This permits a simplified (Gaussian) treatment of the chemical nonlinearity. Explicit solutions are given for the total amount of solute, variance and kurtosis for solutes with no first-order reactions.
Condensation phenomena in a turbine blade passage
Authors: Skillings S. A.
Published: April 2006

The mechanisms associated with the formation and growth of water droplets in the large low-pressure turbines used for electrical power generation are poorly understood and recent measurements have indicated that an unusually high loss is associated with the initial nucleation of these droplets. In order to gain an insight into the phenomena which arise in the turbine situation, some experiments were performed to investigate the behaviour of condensing steam flows in a blade passage. This study has revealed the fundamental significance of droplet nucleation in modifying the single-phase flow structure and results are presented which show the change in shock wave pattern when inlet superheat and outlet Mach number are varied. The trailing-edge shock wave structure appears considerably more robust towards variations of inlet superheat than purely one-dimensional considerations may suggest and the inadequacies of adopting a one-dimensional theory to analyse multi-dimensional condensing flows are demonstrated. Over a certain range of outlet Mach numbers an oscillating shock wave will establish in the throat region of the blade passage and this has been shown to interact strongly with droplet nucleation, resulting in a considerably increased mean droplet size. The possible implications of these results for turbine performance are also discussed.
Characteristic-eddy decomposition of turbulence in a channel
Authors: Moin Parviz , Moser Robert D.
Published: April 2006

The proper orthogonal decomposition technique (Lumley's decomposition) is applied to the turbulent flow in a channel, to extract coherent structures by decomposing the velocity field into characteristic eddies with random coefficients. In the homogeneous spatial directions a generalization of the shot-noise expansion is used to determine the characteristic eddies. In this expansion the Fourier coefficients of the characteristic eddy cannot be obtained from second-order statistics. Three different techniques are used to determine the phases of these coefficients: (i) a technique based on the bispectrum, (ii) a spatial compactness requirement, and (iii) a functional continuity argument. Results from these three techniques are found to be very similar. The implications of these techniques and the shot-noise expansion are discussed in the Appendix. The dominant eddy is found to contribute as much as 76% to the turbulent kinetic energy. In two and three dimensions, the characteristic eddies consist of an ejection region straddled by streamwise vortices which leave the wall in a very short streamwise distance of approximately 100 wall units.
The growth and collapse of cavitation bubbles near composite surfaces
Authors: Shima A. , Tomita Y. , Gibson D. C. , Blake J. R.
Published: April 2006

An experimental study has been made of the growth and collapse of a bubble near a composite surface consisting of two viscoelastic materials. The migratory characteristics of the bubble are examined by means of streak photography. The bubble migration depends not only on the properties of the composite surface but also on bubble size and distance from the surface. Both the surface stiffness and surface inertia are considered to be effective parameters contributing to the bubble migration: the former seeming to be a particularly important factor. The state of neutral bubble collapse, with no migration towards or away from a surface, can be made to occur with an appropriate combination of the surface stiffness and inertia.
Further experiments on the evolution of turbulent stresses and scales in uniformly sheared turbulence
Authors: Tavoularis S. , Karnik U.
Published: April 2006

Measurements of the Reynolds stresses, integral lengthscales and Taylor microscales are reported for several cases of uniformly sheared turbulent flows with shear values in a range substantially wider than those of previous measurements. It is shown that such flows demonstrate a self-preserving structure, in which the dimensionless Reynolds stress ratios and the dissipation over production ratio, ε/P, remain essentially constant. Flows with sufficiently large $k_{\rm s} = (1/\overline{U_{\rm c}}){\rm d}\overline{U_1}dx_2$ have exponentially growing stresses and ε/P ≈ 0.68; a linear relationship between the coefficient in the exponentiallaw and ks is shown to be compatible with measurements having ks > 3. The possibility of a self-preserving structure with asymptotically constant stresses and ε/P ≈ 1.0 is also compatible with measurements, corresponding to flows with small values of ks. The integral lengthscales appear to grow according to a power law with an exponent of about 0.8, independent of the mean shear, while the Taylor microscales, in general, approach constant values. Various attempts to scale the stresses and to predict their evolution are discussed and the applicability of Hasen's theory is scrutinized. Finally, an ‘exact’ expression for the pressure-strain rate covariance is derived and compared to some popular models.
Open channel flows with submerged obstructions
Authors: Dias Frrédéric , Vanden-Broeck Jean-Marc
Published: April 2006

Free-surface flows past a submerged triangular obstacle at the bottom of a channel are considered. The flow is assumed to be steady, two-dimensional and irrotational; the fluid is treated as inviseid and incompressible and gravity is taken into account. The problem is solved numerically by series truncation. It is shown that there are solutions for which the flow is suberitical upstream and supercritical downstream and other flows for which the flow is supercritical both upstream and downstream. The latter flows have limiting configurations with a stagnation point on the free surface with a 120° angle at it. It is found that solutions exist for triangular obstacles of arbitrary size. Local solutions are constructed to describe the flow near the apex when the height of the triangular obstacle is infinite.
A numerical and experimental investigation of a new solution in the Taylor vortex problem
Authors: Anson D. K. , Mullin T. , Cliffe K. A.
Published: April 2006

We present the results of a numerical and experimental study of the five-cell flow in the Taylor vortex problem. There is evidence for a new five-cell solution which is different in nature to the previously recorded solution. We find that there is an exchange in stability between the two solutions which we explain in terms of bifurcation theory. Streamline plots of the numerical results are compared with photographs of the observed flow. The agreement between the calculations and experiments is good. We use the Schaeffer homotopy to study the new solution in the periodic model. The results show that the new solution is not connected in any continuous manner to the trivial Couette flow solution.
The role of the surface density field in subtropical gyre circulation
Authors: Janowitz G. S.
Published: April 2006

The effects of the surface density field on wind-driven subtropical gyre circulation are examined within the content of a continuously stratified, potential vorticity conserving model. It is found that the ventilated fluid downwelled from the mixed layer is confined to a relatively thin layer in subtropical regions; the maximum depths of the ventilated region occur in the eastern and southern regions of the gyre. As a consequence of the relative thinness of the ventilated region in the wind-driven gyre, the transport associated with the surface density field is a small part of the total transport in subtropical regions. Thus the surface density field and the potential vorticity associated with ventilated fluid play a minor role in subtropical gyre dynamics and the potential vorticity of unventilated recirculating fluid is found to play the major role in subtropical gyre dynamics. A method of calculating the flow in the relatively large recirculating region is developed and the results of a specific example are discussed.
The instability of a dispersion of sedimenting spheroids
Authors: Koch Donald L. , Shaqfeh Eric S. G.
Published: April 2006

It is shown that hydrodynamic interactions between non-Brownian, non-spherical, sedimenting particles give rise to an increase in the number of neighbouring particles in the vicinity of any given particle. This result suggests that the suspension is unstable to particle density fluctuations even in the absence of inertia; a linear stability analysis confirms this inference. It is argued that the instability will lead to convection on a lengthscale (nl)−½, where l is a characteristic particle length and n is the particle number density. Sedimenting suspensions of spherical particles are shown to be stable in the absence of inertial effects.
Flow in curved ducts. Part 2. Rotating ducts
Authors: Daskopoulos P. , Lenhoff A. M.
Published: April 2006

When a coiled tube is rotated about the coil axis, the effects of rotation interact with centrifugal and viscous effects to complicate the flow characteristics beyond those seen in stationary curved ducts. The phenomena encountered are examined for steady, fully developed Newtonian flow in circular tubes of small curvature. The governing equations are solved using orthogonal collocation, and the results presented cover both the nature of the flow and the bifurcation structure. When rotation is in the same direction as the axial flow imposed by a pressure gradient, the flow structure remains similar to that seen in stationary ducts, i.e. with two- or four-vortex secondary flows in addition to the axial flow. There are, however, quantitative changes, which are due to the Coriolis forces resulting from rotation. The bifurcation structure also shows only quantitative changes from that for stationary ducts at all values of Taylor number examined. More complex behaviour is possible when rotation opposes the flow due to the pressure gradient. In particular, the direction of the secondary flow may be reversed at higher rotational strengths, and the mechanism of the flow reversal is explored. The flow reversal occurs smoothly at low Taylor numbers, but at higher rotational strengths a cusp appears in the primary solution branch in the vicinity of the flow reversal.
Energy stability of thermocapillary convection in a model of the float-zone crystal-growth process
Authors: Shen Y. , Neitzel G. P. , Jankowski D. F. , Mittelmann H. D.
Published: April 2006

Energy stability theory has been applied to a basic state of thermocapillary convection occurring in a cylindrical half-zone of finite length to determine conditions under which the flow will be stable. Because of the finite length of the zone, the basic state must be determined numerically. Instead of obtaining stability criteria by solving the related Euler–Lagrange equations, the variational problem is attacked directly by discretization of the integrals in the energy identity using finite differences. Results of the analysis are values of the Marangoni number, MaE, below which axisymmetric disturbances to the basic state will decay, for various values of the other parameters governing the problem.