bluuebunny/crossref_metadata_2025 huggingface dataset:
Trusset: Parallel Development of Software and Construction Systems for Space-Truss Structures
Authors: Clarke Cory , Anzalone Phillip
Published: May 2006

This paper documents our current progress on the parallel development of a building system and corresponding agent-based software design tools; together the two produce a seamless pipeline from design to fabrication and assembly. The building system is a clad differential space-truss designed for fabrication entirely with computer numerically controlled (CNC) linear cutting devices such as CNC laser cutters or two-axis mills. The software component is a set of agent-based design tools for developing surfaces and envelopes formally suitable to be built using our space-truss system.
A Parametric Approach to the Design of Vaulted Tensegrity Networks
Authors: Liapi Katherine A. , Kim Jinman
Published: May 2006

Significant new research in tensegrity theory and technology encourages tensegrity's implementation in architecture. A recently developed technology makes possible the rapid modular assembly of deployable tensegrity units, and the construction of alternate curved configurations by re-using the same modules [1]. Although a form exploration method for tensegrity structures already exists [2], estimating the structure's new geometry remains a challenge due to difficulties designers encounter in understanding and following the method's geometric construction process. Besides, the method doesn't address the geometry of vaulted configurations. This paper presents algorithms that link together the geometric parameters that determine the shape of tensegrity vaults by addressing different design-construction scenarios, and a software code that generates parametric models of tensegrity vaulted structures. The application of the algorithms to the morphological study of a tensegrity vaulted dome, which constituted the main feature of an entry to a recent international architectural competition, is also presented.
Architectural Representation Software: A Design Tool
Authors: Manes Sergio
Published: May 2006

In the last decades, design processes have been approached with absolutely new representation techniques: digital media. This new tool was naturally incorporated to the architectural task not only in universities but also in Architectural offices. However, their evolution and utilization have been so sudden that their impact on the design object could not be properly assessed. Simply they stated to be used by translating analogical representation techniques into the digital media. In the Latin American context, in which the media interaction paradigm has not yet been completely established within universities and teachers, this work presents an exploration of the underlying ideas contained in the architectural representation software, as well as a series of exercises intended to teach how to use digital media as a design tool, instead of teaching how to use them as a mere representation tool.
Crisis? What Crisis? Approaching Information Space: New Dimensions in the Field of Architecture
Authors: Elger Dietrich , Russell Peter , Elger Dietrich , Russell Peter
Published: May 2006

The paper describes the current situation concerning career opportunities in the field of architecture in developed western countries. Several aspects that are almost universal mark this situation. Firstly, there are too many architects chasing traditional work in competition with other engineers. Secondly, the needs of the building industry have changed over the past years so that the skills that architects are able to offer are not necessarily those that are sought. Lastly, the constant specialisation of work has continued unabated. Architects, as generalists, have seen their areas of expertise be usurped from neighbouring fields. The situation is not lost, so long as architects are able to recognise what is desired from the point of view of the client and what is desired from the point of view of the architect. For educators, it must be clear that the real potential architects possess is their encompassing knowledge of the building information. Architectural Information Management is a necessary skill to be taught alongside the more traditional architectural skills. A brief outlook as to how this might come about is detailed in the paper. The authors propose didactic steps to achieve this. Primarily, the education of computer supported planning should not simply end with a series of lectures or seminars, but culminate in integrated Design Studios (which include Design-Build scenarios).
30S ribosomal subunits can be assembled in vivo without primary binding ribosomal protein S15
Authors: Bubunenko Mikhail , Korepanov Alexey , Court Donald L. , Jagannathan Indu , Dickinson Daniel , Chaudhuri Biswajoy Roy , Garber Maria B. , Culver Gloria M.
Published: May 2006

Assembly of 30S ribosomal subunits from Escherichia coli has been dissected in detail using an in vitro system. Such studies have allowed characterization of the role for ribosomal protein S15 in the hierarchical assembly of 30S subunits; S15 is a primary binding protein that orchestrates the assembly of ribosomal proteins S6, S11, S18, and S21 with the central domain of 16S ribosomal RNA to form the platform of the 30S subunit. In vitro S15 is the sole primary binding protein in this cascade, performing a critical role during assembly of these four proteins. To investigate the role of S15 in vivo, the essential nature of rpsO, the gene encoding S15, was examined. Surprisingly, E. coli with an in-frame deletion of rpsO are viable, although at 37°C this ΔrpsO strain has an exaggerated doubling time compared to its parental strain. In the absence of S15, the remaining four platform proteins are assembled into ribosomes in vivo, and the overall architecture of the 30S subunits formed in the ΔrpsO strain at 37°C is not altered. Nonetheless, 30S subunits lacking S15 appear to be somewhat defective in subunit association in vivo and in vitro. In addition, this strain is cold sensitive, displaying a marked ribosome biogenesis defect at low temperature, suggesting that under nonideal conditions S15 is critical for assembly. The viability of this strain indicates that in vivo functional populations of 70S ribosomes must form in the absence of S15 and that 30S subunit assembly has a plasicity that has not previously been revealed or characterized.
Widespread siRNA “off-target” transcript silencing mediated by seed region sequence complementarity
Authors: Jackson Aimee L. , Burchard Julja , Schelter Janell , Chau B. Nelson , Cleary Michele , Lim Lee , Linsley Peter S.
Published: May 2006

Transfected siRNAs and miRNAs regulate numerous transcripts that have only limited complementarity to the active strand of the RNA duplex. This process reflects natural target regulation by miRNAs, but is an unintended (“off-target”) consequence of siRNA-mediated silencing. Here we demonstrate that this unintended off-target silencing is widespread, and occurs in a manner reminiscent of target silencing by miRNAs. A high proportion of unintended transcripts silenced by siRNAs showed 3' UTR sequence complementarity to the seed region of the siRNA. Base mismatches within the siRNA seed region reduced the set of original off-target transcripts but generated new sets of silenced transcripts with sequence complementarity to the mismatched seed sequence. An inducible shRNA silenced a subset of transcripts that were silenced by an siRNA of the same sequence, demonstrating that unintended silencing is sequence mediated and is independent of delivery method. In all cases, off-target transcript silencing was accompanied by loss of the corresponding protein and occurred with dependence on siRNA concentration similar to that of silencing of the target transcript. Thus, short stretches of sequence complementarity to the siRNA or shRNA seed region are key to the silencing of unintended transcripts.
Position-specific chemical modification of siRNAs reduces “off-target” transcript silencing
Authors: Jackson Aimee L. , Burchard Julja , Leake Devin , Reynolds Angela , Schelter Janell , Guo Jie , Johnson Jason M. , Lim Lee , Karpilow Jon , Nichols Kim , Marshall William , Khvorova Anastasia , Linsley Peter S.
Published: May 2006

Transfected siRNAs regulate numerous transcripts sharing limited complementarity to the RNA duplex. This unintended (“off-target”) silencing can hinder the use of RNAi to define gene function. Here we describe position-specific, sequence-independent chemical modifications that reduced silencing of partially complementary transcripts by all siRNAs tested. Silencing of perfectly matched targets was unaffected by these modifications. The chemical modification also reduced off-target phenotypes in growth inhibition studies. Key to the modification was 2′-O-methyl ribosyl substitution at position 2 in the guide strand, which reduced silencing of most off-target transcripts with complementarity to the seed region of the siRNA guide strand. The sharp position dependence of 2′-O-methyl ribosyl modification contrasts with the broader position dependence of base-pair substitutions within the seed region, suggesting a role for position 2 of the guide strand distinct from its effects on pairing to target transcripts.
Delay Analysis for the Fixed-Cycle Traffic-Light Queue
Authors: van Leeuwaarden J. S. H.
Published: May 2006

We consider the fixed-cycle traffic-light (FCTL) queue, where vehicles arrive at an intersection controlled by a traffic light and form a queue. The traffic-light signal alternates between green and red periods, and delayed vehicles are assumed to depart during the green period at equal time intervals.

Most of the research done on the FCTL queue assumes that the vehicles arrive at the intersection according to a Poisson process and focuses on deriving formulas for the mean queue length at the end of green periods and the mean delay. For a class of discrete arrival processes, including the Poisson process, we derive the probability generating function of both the queue length and delay, from which the whole queue length and delay distribution can be obtained. This allows for the evaluation of performance characteristics other than the mean, such as the variance and percentiles of the distribution.

We discuss the numerical procedures that are required to obtain the performance characteristics, and give several numerical examples.
The nation’s data? The UK census – guaranteed confidentiality but only limited information
Authors: Purdam K.
Published: May 2006

English

In the UK, the census is one of the key resources for policy makers, determining planning and resource allocation at both the national and local level. Recent disputes between the Office for National Statistics (ONS) and a number of local authorities concerning the accuracy of the 2001 Census population counts have highlighted the importance of the census in funding allocation terms. Drawing on research into the 1991 and 2001 Census programmes and discussions with census users and commercial data providers, this article explores the complex relationship between the needs of policy makers and researchers and the issues of data access and confidentiality. The analysis is placed within the wider context of ongoing developments in both the public and commercial sectors with respect to data collection, storage and data release in and outside the UK. While consultation on the 2011 Census is ongoing, we argue that, in the context of the increasing demands for accurate data to inform evidence-based policy making and service provision, there is a pressing need for a more radical review of the current approaches to census content and census data access in the UK.
Digital media in architectural design education: reflections on the e-studio pedagogy
Authors: Al-Qawasmi Jamal
Published: May 2006

This article examines the impact of digital media on architectural design education based on teaching experience in the e-studio. The primary goal of the estudio is to teach students how to think and design using digital media as the only design medium. The article reports on e-studio practices, discusses the pedagogical implications of the studio and contributes to understanding the relationship between digital media, design practices and education. It reveals that digital media as used in the e-studio can bring important changes to the architectural design process, the design studio praxis, the design outcome and the way in which students envision and describe architecture. The article highlights the ambivalent nature of digital media as design tools and shows the need to reconsider our traditional understanding of the design studio culture.
Immunochemical quantification of free immunoglobulin light chains from an analytical perspective
Authors: Nakano Takanari , Miyazaki Shuichi , Takahashi Hidenori , Matsumori Akira , Maruyama Taro , Komoda Tsugikazu , Nagata Atsuo
Published: May 2006

Immunoglobulin light chains are components of antibodies, but some exist in a free form in serum and urine as a result of their excess production over heavy chains. Free light chain (FLC) levels are of the order of milligram per liter in normal serum and urine, but marked increases have been observed in various disease conditions. It has now been established that the measurement of FLC levels contributes to diagnosis and clinical management in monoclonal gammopathies. Recent developments in FLC assays have been adapted to several automated platforms and they have now become available in laboratories. There have, however, been some concerns regarding the analytical aspects. The current assay specificity appears to be insufficient to prevent the influence of intact light chains of several orders of magnitude greater than FLCs in serum. Moreover, the heterogeneous nature of light chains makes accurate quantification unreliable. FLC assays have never been standardized because of the lack of an international reference calibrator. In this review, we summarize the reports on FLC measurements and examine the specificity of anti-FLC antibodies and the reliability of FLC assays. We also discuss difficulties in the standardization and setting of normal reference intervals for FLC assays.
Digitale Holografie an reflektierenden Mikrosystemen (Digital Holography Applied to Reflective Microsystems)
Authors: Falldorf Claas , Kopylow Christoph von , Jüptner Werner
Published: May 2006

In diesem Beitrag wird ein Interferometer auf Basis der digitalen Holografie vorgestellt, welches die Erfassung der Form und der Deformation reflektierender Mikrosysteme ermöglicht. Ein Schwerpunkt liegt hierbei auf dem Modell zur Rückführung der Geometriedaten aus den gemessenen Phasenverteilungen. Die Ergebnisse lassen sich so in metrische Einheiten überführen und dienen damit als Grundlage zum Vergleich mit numerischen Modellrechnungen.

Die Formerfassung und die Ermittlung der unter thermischer Belastung auftretenden Verschiebungen werden beispielhaft an einer Testkomponente aus dem Bereich der Mikrosystemtechnik demonstriert. Im Bereich der Verschiebungsmessung können die vorteilhaften Eigenschaften der digitalen Holografie genutzt werden, um zwischen den Messungen auftretende Ganzkörperverschiebungen der Belastungseinheit in Richtung der optischen Achse zu kompensieren.
Incidence and Clinical Presentation of Invasive Neonatal Group B Streptococcal Infections in Germany
Authors: Fluegge Kirsten , Siedler Anette , Heinrich Beate , Schulte-Moenting Juergen , Moennig Maria-Jantje , Bartels Dorothee B. , Dammann Olaf , von Kries Ruediger , Berner Reinhard ,   for the German Pediatric Surveillance Unit Study Group
Published: May 2006

OBJECTIVE. Streptococcus agalactiae (group B Streptococcus) is an important cause of morbidity and mortality in newborn infants. So far, there have been no published data on the incidence, morbidity, and mortality of invasive neonatal group B Streptococcus infections in Germany.

METHODS. A prospective active surveillance study involving all of the pediatric hospitals, which reported their cases to the German Pediatric Surveillance Unit, and all of the microbiological laboratories serving pediatric hospitals, which reported their cases to the Laboratory Sentinel Group at Robert Koch Institute Berlin, was conducted between 2001 and 2003. Capture-recapture analysis was used to evaluate the completeness of reported neonatal invasive group B Streptococcus infections.

RESULTS. We collected and analyzed data from 347 and 360 infants with invasive group B Streptococcus infection during the first 3 months of life, as reported by pediatricians to the German Pediatric Surveillance Unit and microbiologists to the Robert Koch Institute Berlin, respectively. Using capture-recapture analysis, we calculated an incidence of 0.47 per 1000 live births. Nearly 60% of the infants suffered from early-onset disease, and 16% of these presented with meningitis. In contrast, 61.8% of infants with late-onset disease presented with meningitis. Prematurity was present in 22.4% of early-onset disease and 39.7% of late-onset disease cases, respectively. A high proportion of infants suffered from sequelae because of group B Streptococcus infection at the time of discharge from the hospital. Most common sequelae were hydrocephalus and cerebral seizure. Case fatality rate was 4.3%.

CONCLUSIONS. This study, which is the first to provide information on the current national incidence and morbidity of invasive group B Streptococcus infection in Germany, demonstrates remarkable country-specific variation in comparison with other European countries, which gather data in a similar fashion. Therefore, the importance of country-specific prevention guidelines has to be stressed.
Influence of tree cover on the diversity of herbaceous communities in subalpine wooded pastures
Authors: Gillet François , Murisier Béatrice , Buttler Alexandre , Gallandat Jean‐Daniel , Gobat Jean‐Michel
Published: May 2006

Abstract. The relationships between several diversity indices and tree cover in subalpine wooded pastures with Larix de‐cidua were analysed at two spatial scales: phytocoenoses (2500‐m2 plots) and herbaceous synusia (1‐m2 quadrats). Diversity indices have a non‐linear relationship to Larix cover; the best fit was obtained with Gaussian regressions. Species richness was influenced by Larix cover more than evenness. At the phytocoenosis level, the optimum for species and synusial richness in the herb layer was near 25 % tree cover. At the synusia level, species richness of the herb layer showed an optimum when mean distance to the four nearest Larix trees was ca. 30 m, or when the potential number of sunshine hours between April and September was close to 1250 h. Canonical Correspondence Analysis confirmed the influence of Larix cover on the composition of phytocoenoses and herbaceous synusiae, but included also the role of altitude, slope and aspect.
The influence of coniferous canopies on understorey vegetation and soils in mountain forests of the northern Calcareous Alps
Authors: Ewald Jörg
Published: May 2006

Abstract. Compositional and edaphic gradients were studied in montane forests of the Bavarian Alps (Germany), in which natural mixed deciduous‐coniferous tree layers have been altered by past management in favour of Picea abies. Data on species composition and ecological factors were collected in a stratified random sample of 84 quadrats comprising a gradient from pure Picea to pure Fagus sylvatica stands. Data about the understorey composition were subjected to indirect (DCA) and direct gradient analysis (RDA) with the proportion of Picea in the canopy as a constraining variable. Three principal components of a matrix containing seven descriptors of mineral soil, relief and tree layer cover were included as covariables describing the variability of primary ecological factors. Gradients of organic topsoil morphology and chemistry were extracted correspondingly. Responses of individual species, species group and topsoil attributes were studied by simple and partial correlation analysis.

Mosses were significantly more abundant and diverse under Picea stands. Few graminoid and herb species were partially associated with Picea, and total understorey richness and cover did not differ systematically by stand type. No relationship between tree layer and understorey diversity was detected at the studied scale. Juvenile Fagus sylvatica was the only woody species significantly less abundant under Picea. In the topsoil lower base saturation, lower pH and larger C/N‐ratios in the litter layer were partially attributable to the proportion of Picea, only for base saturation a relationship was detected in greater soil depth also. The frequency of broad humus form types did not differ by tree species, nor was overall depth of organic forest floor attributable to canopy composition.
Vegetation survey in the former brown coal mining area of eastern Germany by integrating remote sensing and ground‐based methods
Authors: Felinks Birgit , Pilarski Monika , Wiegleb Gerhard
Published: May 2006

Abstract. In the former brown coal mining area of eastern Germany, now scheduled as a nature conservation area, an analysis of the spatial distribution of vegetation was considered as an important tool in landscape planning. Therefore a comprehensive vegetation survey by means of satellite imagery (Landsat‐TM), airborne imagery (CASI), and ground‐based methods, notably habitat mapping and vegetation sampling was carried out. With respect to the scales of resolution the classification results of the four methods are, to a certain degree, comparable. Differences in the outcome can be ascribed to the fact that methods of low resolution result in a discrete array of polygons whereas methods of high resolution depict a mosaic structure with an underlying, continuously changing gradient. Provided that the biological meaning of the remote sensing classification is known, a shift from single vegetation patterns to the landscape scale will be possible. Neither satellite nor airborne imagery is restricted to the purpose of mapping but may also serve for vegetation classification itself.
Indigenous and Ammophila arenaria‐dominated dune vegetation on the South African Cape coast
Authors: Hertling Ursula M. , Lubke Roy A.
Published: May 2006

Abstract. Communities formed by the potentially invasive European Ammophila arenaria (marram grass) are compared with those dominated by indigenous dune plant species in coastal dune systems. Sampling of communities was carried out along the Cape coast for species richness, species diversity, importance values and species associations. The influence of soil and other environmental factors on vegetation were also compared. While species richness values in A. arenaria communities appear similar to those of indigenous dune plant communities, diversity indices are significantly lower. However, on the basis of importance values of individual species, A. arenaria does not show extreme dominance to the exclusion of other species, as it does on the North American Pacific coast, where it has also been introduced. Because of its growth in dense tufts, A. arenaria is accompanied mostly by small chamaephytes and therophytes, while indigenous stands support more phanerophytes. Moreover, A. arenaria forms weaker species associations than dominant indigenous dune plant species. The alien status of A. arenaria in South Africa is confirmed by applying classification and ordination analyses which failed to differentiate A. arenaria communities according to their geographical origin as achieved with indigenous communities. This may be attributed to the lack of vigorous indigenous plants in A. arenaria communities, which accounts for the low variety in species composition of A. arenaria communities along the coastline. With regard to environmental factors, A. arenaria communities were observed to be less sensitive to extrinsic factors, such as climate, than indigenous dune plant communities. Results confirm that A. arenaria is an alien plant species in South Africa, but do not imply its invasiveness in the present or near future.
Ecohydrological characterization of a groundwater‐fed alluvial floodplain mire
Authors: De Becker P. , Hermy M. , Butaye J.
Published: May 2006

Abstract.In a small alluvial floodplain depression (21 ha) of the river Dijle, a selection of 56 characteristic, mainly groundwater‐depending plant species was mapped using a regular 20 by 20 m square cell mapping grid. In order to understand the spatial distribution of the plant species and their vegetation types, several environmental variables, including groundwater regime, groundwater chemistry, soil texture, soil chemical composition and management type were measured in detail.

Using Detrended Correspondence Analysis and Canonical Detrended Correspondence Analysis, the relation between these environmental variables and the plant species and vegetation types, respectively, is described in detail. Management type and groundwater fluctuations are recognized as the two main sets of environmental variables causing the specific spatial distribution of plant species and vegetation types for the mire‐ecosystem of the silty alluvial floodplain.
Ecosystem classification and mapping: a proposal for Italian landscapes
Authors: Blasi Carlo , Carranza Maria Laura , Frondoni Raffaella , Rosati Leonardo
Published: May 2006

Abstract. This paper deals with the development of a hierarchical land classification for describing and mapping landscapes at different scales. After a brief overview of the theoretical background, an integrative framework is proposed which incorporates different hierarchical levels from plant sociology as diagnostic attributes. The feasibility of this proposal has been tested in different sample landscapes in central Italy. This system has a potential for applications to Italian landscapes from national to local scales, because it is based on solid theory and on information which is generally available in Italy.
Identification and Quantitative Measurement of Plant Pigments in Soil Humus Layers
Authors: Sanger Jon E.
Published: May 2006

Pigments in soil organic matter layers of an oak forest, a spruce—cedar woodland, and a prairie have been identified and measured quantitatively. In all cases lutein was the dominant carotenoid accompanied by smaller amounts of Beta—carotene. Phenophytin a and chlorophyllide a commonly present in the L and F organic layers. Pigment ratios were examined and compared in all three humus types.
Escape of Cassia Grandis L. Beans From Predators in Time and Space
Authors: Janzen Daniel H.
Published: May 2006

In Central American deciduous forests, most of the seeds of the caesalpinaceous legume tree Cassia grandis are killed by the larvae of two bruchid beetles, Pygiopachymerus lineola and Zabrotes interstitialis. Pygiopachymerus lineola oviposits on the large pods, the first—instar larvae bore into the seeds, and the emerging adults cut large exit holes in the pod wall. Moth larvae gain access through these holes and eat clean much of the sticky pulp around the seeds. Simultaneously, the adults of Z. interstitialis enter through the P. lineola exit holes and oviposit directly on all clean seeds. In heavily disturbed communities where vertebrate dispersal agents are absent, these host—specific bruchids achieve almost 100% predation on the C. grandis seed crop; however, the more rapidly the dispersal agents remove the seed pods, the less seed predation there will be by Z. interstitialis. Since C. grandis bears mature fruit every other year, the size of each seed crop is large enough to surpass the predation abilities of the bruchids that survive the distance in time and space between seed crops. The system may be viewed as an example of predator satiation. The potential for further co—evolution of the bruchid—Cassia interaction is high, but numerous opposing forces in the selective process can be identified.
Differential Niche Utilization in a Grassland Sparrow
Authors: Robins Jerome D.
Published: May 2006

Henslow's Sparrow (Ammospiza henslowii) is a secondary sexually monomorphic breeding bird in meadows, hayfields, prairies, grasslands, and some croplands in eastern North America. Foraging behavior during the nestling period involved no intersexual differences in prey selection, and both sexes were opportunistic in food choice. Sexual spatial partitioning of the feeding niche was accomplished by adults foraging in different directions and at different distances from the nests. Males, which defend the territories alone, forage at greater distances from the nest than females. Females forage closer to the nest and in different areas than males, which enhances survival of young because females do most of the feeding and all brooding of young.
Changes in Thirty‐One Years in a Sierra Nevada Ecotone
Authors: Heath James P.
Published: May 2006

Resurveys of a plot established in a Sierra Nevada ecotone in 1937 show significant decreases in four major species, similar changes in six lesser species, and increases in only four species.
Carboxydismutase and Phosphoenolpyruvate Carboxylase Activities From Leaves of Some Plant Species from the Northern Mojave and Southern Great Basin Deserts
Authors: Wallace A. , Hale V. Q. , Kleinkopf G. E. , Huffaker R. C.
Published: May 2006

Of 14 xerophytic plant species studied, only two (members of the Chenopodiaceae) exhibited high phosphoenolpyruvate (PEP) carboxylase and low carboxydismutase activities. Three other members of the Chenopodiaceae exhibited carobyxlase activities characteristic of both the C_4—dicarboxylic acid pathway and the Calvin cycle in the same species. Activities range from high PEP carboxylase and moderately high carboxydismutase to, conversely, high carboxydismutase and moderately high PEP carboxylase activity, including moderately high levels of nearly equal activities of each enzyme. Hence, gradations between extremes of the two photosynthetic systems can occur in the same species. Members of three other families (Ephedraceae, Zygophyllaceae, and Liliaceae) had carboxylase activities characteristic of both photosynthetic systems in the same species. The enzymatic activity of plants which continue to grow during hot summers was characteristic of either the C_4—dicarboxylic acid pathway or of both photosynthetic pathways.
Observations of Paramecium Occupying Arboreal Standing Water in Costa Rica
Authors: Vandermeer John , Addicott John , Andersen Ayesha , Kitasko John , Pearson David , Schnell Charles , Wilbur Henry
Published: May 2006

Some observations on the natural history of the Paramecium—Heliconia system are presented. The pattern of distribution in the wet season seams to be either a random colonization or a colonizing bias toward younger bracts, but ultimately the mosquito larvae in the older bract build up, resulting in the death of the local Paramecium population. The dry season pattern appears to be different at least in that there are very few mosquito larvae. The observation of Maguire and Belk (1967) that Paramecium do get to bromeliads was repeated. Experiments were performed demonstrating that if Paramecium do get to bromeliads, the biological interactions between the Paramecium and the regular microfauna of the bromeliad are such that the Paramecium are driven to extinction.
Comparative Photosynthesis of Quebec and California Ecotypes of Typha Latifolia
Authors: McNaughton S. J.
Published: May 2006

Photosynthesis and transpiration were examined in detached leaves of broad—leaved cattail (Typha latifolia L.) ecotypes from a long growing season continental climate in California's central valley and a short growing season continental in northwestern Quebec when grown under identical conditions. The principal difference between the ecotypes were (a) greater temperature dependence of net photosynthesis in the Quebec ecotype, particularly when young leaves were compared, (b) a decline in temperature dependence of Quebec leaves as they aged, but not of California leaves, (c) a downward shift in the photosynthetic temperature curve when California plants were transferred to cooler growing conditions, while the curve was stable in Quebec plants, (d) an increase in photosynthetic rate at the optimum temperature when Quebec plants were transferred to cooler conditions, but a decline in California plants, (e) a more phenotypically plastic acclimation response in the California ecotype, and(f) greater sensitivity to photosynthesis inhibition by high oxygen in Quebec leaves. Differences in net assimilation rates were less than would be expected from previous studies of other species.
Adaptive Variation in Size of Cricket Frogs
Authors: Nevo Eviatar
Published: May 2006

Geographic variation in body size (BL) and relative foot size (F/B) was studied across the ranges of two sibling species of cricket frogs, genus Acris (Hylidae)in North America. Acris crepitans has a large range in eastern and central states extending from mesic woodlands to xeric grasslands, whereas A. gryllus has a limited range in southeastern states in mesic woodlands. Measurements of BL and F/B of 5,286 frogs from 108 localities were divided into 11 biogeographical regions and subjected to discriminant and multiple regression analyses. BL varies primarily in A. crepitans, negatively correlated with annual rainfall, which is its best single predictor, accounting for about .50 of size variance. A combination of three humidity variables explains .60 of BL variance.Desiccation experiments indicate that loss of body weight and vital time limit regress linearly on size and are highly correlated with it. Larger frogs lose less water and reach their limit of tolerance in twice as long a time as do small ones. F/B in both species is positively correlated and best predicted by a combination of temperature, precipitation, and longitude or sympatric anuran species. It is suggested that BL is casually related to humidity, large size being an adaptation to arid climates, and that F/B is casually related to predation pressure and/or competition for food, large F/B being an adaptation for increased jumping efficiency.
The Impact of the Leaf Cutter Ant Atta Colombica on the Energy Flow of a Tropical West Forest
Authors: Lugo Ariel E. , Farnworth Edward G. , Pool Douglas , Jerez Patricio , Kaufman Glen
Published: May 2006

The patterns, quantity, and activities associated with the leaf—cutting of Atta colombica were studied August 20—27, 1971, in a lowland tropical wet forest at Osa Peninsula, Costa Rica (Lat. 08 42'N Long. 83 29'W). The study nest had an area of 44.8 m2 and covered 1.4 ha of forest floor. Daily, on a m2 of forest floor, the study nest had inputs of 10.17 leaf fragments with an area of 0.0108 m2, a weight of 0.0813 g, an ash content of 0.0039 g, and a potential energy of 0.3455 Kcalories. The ants return to the forest floor 0.0525 g of refuse with a potential energy of 0.0764 Kcalories and an ash content of 0.0212 g/m2 day. It was calculated that the leaf—cutting activity of ants reduced the gross production of the forest by 1.76 Kcal/m2 day but accelerated net production by at least 1.80 Kcal/m2 day through the return of ash rich in phosphorus to the forest floor. The size of the Atta nest may be determined by the balance of the energy input to the nest and the cost of obtaining, carrying (concentrating), and distributing the potential energy into the nest. Of a work force of 12,000 ants/m2 of trail, 75% were not carrying leaves and were assumed to be doing trail maintenance work. Rainfall and litter fall were the main obstacles of leaf transport, which was about 70% efficient. The ant's energy allocation for maintenance, which limits growth, and the establishment of reward feedbacks to their energy producers have implications for man's urban system development.
Ecological Separation of Three Genera of Pocket Gophers (Geomyidae)
Authors: Best Troy L.
Published: May 2006

A study of the ecology and distribution of Geomys bursarius jugossicularis Hooper, Thomomys bottae cultellus Kelson, and Pappogeomys castanops Baird was conducted in northeastern New Mexico. Comparisons of body size, soils utilized, burrow characteristics, distinguishing surface features, and winter activity revealed each species to be ecologically separate. Altitude and soils are discussed as factors influencing the geographical separation of the species, although soil appears to be the primary limiting factor. Based on the observed distribution and range of soils inhabited, the most limited distribution and the broadest range of soil types is found for the largest species P. castonops, followed by T. bottae and then G. bursarius.
Territorial Behavior of the Striped Parrotfish Scarus Croicensis Bloch (Scaridae)
Authors: Buckman Nancy S. , Ogden John C.
Published: May 2006

A detailed study of a territorial form of the striped parrotfish (Scarus croicensis) was done on the reefs surrounding Isla Pico Feo on the Caribbean coast of Panama. Territories were located in shallow water (less than 3 m), averaged 12 m2 in size, and appeared to serve as feeding and occasionally spawning grounds. The dominant territorial fish was female. A terminal—phase male, which may be paired with the female, usually defended the same area. Uncommonly a striped—phased male defended the territory in place of or in addition to the terminal—phase male. The territorial female tolerated the presence of one to three subordinate non—territorial females. These associations of territorial fish remained constant for varying periods of time, and if a fish was removed, either naturally or experimentally, it would be rapidly replaced. The characteristic territorial display by the female involved the extension of yellow pelvic fins. Highly aggressive displays between neighboring territorial females involved mouth—to—mouth interactions. All territorial behavior was directed intraspecifically, but extensive interspecific interactions were also observed. Interaction between the territorial female and the territorial male varied with spawning condition. Territorial behavior in striped parrotfish may be related to proterogynous sex reversal in the scarids.
Corrections for Bias in Regression Estimates After Logarithmic Transformation
Authors: Beauchamp John J. , Olson Jerry S.
Published: May 2006

Experience with biological data, such as dimensions of organisms, often confirms that logarithmic transformations should precede the testing of hypotheses about regression relations. However, estimates also may be needed in terms of untransformed variables. Just taking antilogarithms of values from a log—log regression line or function leads to biased estimates. This note compares corrections for this bias, and includes an example relating mass of tree parts (bole, branches, and leaves) to tree diameter of tulip poplar (Liriodendron tulipifera L.) in Oak Ridge, Tennessee, forests. An Appendix summarizes derivation of exact and approximate unbiased estimators of expected values from log—antilog regression, and of variance around the unbiased regression line.
Stand Structure, Succession, and Use of Southern Alberta's Rocky Mountain Forest
Authors: Day Robert J.
Published: May 2006

Structural analysis of the subalpine forest in southern Alberta shows that the old—growth Picea—Abies forest has succeeded even—aged stands of Pinus contorta var. latifolia Engelm. that became established after fire 150—200 or more years ago. Because P. Contorta regeneration fails beneath its own canopy, an irregular— to uneven—aged understory of Picea engelmannii Parry x P. glaca (Moench) Voss. and Abies lasiocarpa (Hook) Nutt. becomes established. As the even—aged P. contorta overstory ages, sporadic death of overmature trees permits an irregular— to all—aged Picea—Abies forest to emerge and dominate, unless fire reinitiates the succession to even—aged P. contorta. Extensive and frequent fires in the past, mainly initiated by "dry" electrical storms, have prevented long—term successional development and have maintained most of the forest in the early P. contorta—dominated phase of the succession. Introduction of effective fire protection is now permitting progress toward the late successional phases. Widespread development of the Picea—Abies phase and the decadent Abies—Picea phase that follows are forecast. The ecological effects of such fire—protection policies are questioned. A silvicultural program of fire prescription is suggested for the maintenance of the fauna and wilderness value of the mountain national parks. Silvicultural alternatives in harmony with the ecology of the forest are suggested for the implementation of multiple—use policies in the Rocky Mountain Reserve.
Patterns of Water Movement in Trees and Shrubs
Authors: Waisel Y. , Liphschitz Nili , Kuller Z.
Published: May 2006

Paths of water flow in trees and shrubs of different sizes and chorotypes were investigated with injected dyes. Aged shrubs possessed a sectorial ascent. Young specimens of these species showed a sectorial turning into a ring ascent. Differences in pattern of water flow were observed among various tree species. Species with large and tall crowns showed either a spiral pattern or a sectorial straight pattern turning into a ring pattern of ascent. Other species exhibited a sectorial straight pattern. Since independence of branches or trunk segments is characteristic of shrubs, it is suggested that woody species exhibiting a sectorial pattern of water movement should be considered as chamaephytes.
Nutrient Content of Litter Fall on the Hubbard Brook Experimental Forest, New Hampshire
Authors: Gosz James R. , Likens Gene E. , Bormann F. Herbert
Published: May 2006

Litter fall was collected throughout the year beneath a mature northern hardwood forest in New Hampshire. The material, separated by species and plant part, was analyzed for dry weight and for 11 elements. Total aboveground litter fall average 5,702 kg/ha per year; leaves, branches, stems, and bark contributed 49.1%, 22.2%, 14.1%, and 1.7%, respectively. Other deciduous structures (i.e., bud scales, flowers, fruit), as well as insect frass and miscellaneous tissues, contributed 10.9%. The overstory contributed 98.0% of the total, and shrub and herbaceous layers contributed only 1.2% and 0.8%, respectively. The nutrient content of the litter totaled 140.4 kg/ha per year. The relative abundance for these 11 elements was N > Ca > K > Mn > Mg > S > P > Zn > Fe > Na > Cu. Nitrogen, Ca, and K accounted for 80.6% of the total, and Zn, Fe, Na, and Cu contributed only 0.8%. The overstory, shrub, and herbaceous layers suppled 96.6%, 1.7%, and 1.6% of the nutrients, respectively. Litter fall occurred throughout the year, but there were seasonal peaks for many types of tissues. Autumn was most important, accounting for 49.7% of the litter and 56.0% of the nutrients. Summer and winter seasons supplied similar quantities of the litter, 21.2% and 22.4%; however, 22.6% of the total nutrient fall occurred during summer compared with only 17.2% during the winter. Spring months supplied 6.7% and 4.1% of litter and nutrients, respectively. Storms were very important in the timing of litter and nutrient fall. The extreme variability of litter fall is the result of differences between species, tissues, vertical structure of the vegetation, elevation, site, and time of year. In spite of this variation, nutrient—budget studies reveal relatively small losses from the ecosystem. Larger fluctuations in rates of nutrient flow, via litter fall, are readily absorbed within the ecosystem, thus preventing nutrient loss and maintaining efficient nutrient cycling.
Grass and Grass Utilization in Iceland
Authors: Fridriksson Sturla
Published: May 2006

The total area of Iceland is approximately 103,500 sq.km. of which 40,000 sq.km. presumably was covered with vegetation at the time of settlement in 874 A.D. During the 1,100 years of occupancy serious erosion has taken place, resulting in the deterioration of the grassland. At present, the total area of vegetation is only 20,000 sq.km. giving an average annual erosion rate of 20 sq.km. As the human population, which reached 80,000 individuals during the Age of Settlement, relied to a great extent on animal products it was indirectly dependent on the output of the natural grassland that dwindled with time and thus the human population decreased up to the last century. With modern cultivation techniques erosion is gradually being checked and it has been possible to provide fodder for the nation's increased livestock. Today the natural grassland, which to some extent is overstocked, provides summer pasture for 800,000 sheep and 30,000 ponies while the lowland pastures around the homesteads supply grazing for 60,000 dairy cattle. Sheep and cattle are housed and fed indoors on hay and artificial feeds during the winter months. Half the fodder is now obtained from cultivated land. Thus the Icelandic winter months. Half the fodder is now obtained from cultivated land. Thus the Icelandic agriculture is, at present, capable of supporting a nation of 200,000 individuals.
Predation by Damselfly Naiads on Cladoceran Populations: Fluctuating Intensity
Authors: Johnson Dan M.
Published: May 2006

Ishnura verticalis naiads (Odonata: Zygoptera) were reared among simulated aquatic plants in eight large pools. Simocephalus serrulatus (Crustacea: Cladocera) was the principle prey. The intensity of damselfly predation on Simocephalus was estimated using two independent procedures: (1) a mathematical model predicating the potential density of prey at the end of successive 4—day intervals, and (2) exclosure nets which permit random samples of the prey population to grow, free from predation, during each 4—day interval. Potential densities minus observed density yield estimates of Simocephalus mortality during each interval. These estimates fluctuate dramatically, suggesting an intermittent influence of the predators. Peaks in prey mortality tend to follow periods during which large number of naiads molted. It is hypothesized that changes in feeding behavior associated with developmental phenomena are responsible for fluctuations in the intensity of predation by damselfly naiads.
Comparative Demography of Two Viviparous Iguanid Lizards (Sceloporus Jarrovi and Sceloporus Poinsetti)
Authors: Ballinger Royce E.
Published: May 2006

Population studies of Sceloporus jarrovi using mark—recapture procedures were conducted on two study plots near Portal, Chiricahua Mountains, Cochise Co., Arizona during the summer months of 1969 and 1970. Similar studies of Sceloporus poinsetti were conducted on a study plot near Mertzon, Irion Co., Texas during the summer months of 1968, 1969, and 1970. Series of these lizards were taken from areas near the study plots and autopsied to determine their reproductive condition. The reproductive cycle of both species involved mating in the fall, with parturition occurring the following June. A single litter was produced each year. S. poinsetti attained maturity during the second mating season after birth, at about 16—17 months, although approximately 60% of the S. jarrovi females matured in their first mating season at about 5 months. Female S. jarrovi which matured as yearlings produced an average of four young in their 1st year, whereas older females produced an average of 10.5 young (7—15). The increase in litter size with snout—vent length was one embryo per 3 mm of body length. S. poinsetti females produced an average of 10.4 young (6—23) with an increase of one embryo per 3 mm of body length. Body sizes of young at birth were 29—35 mm in S. poinsetti and 25—32 mm in S. jarrovi. Newborn of both species were larger than hatchlings of similar sized oviparous species of Sceloporus. Newborn of S. poinsetti from large litters were significantly smaller than newborn from small litters. Populations of both S. jarrovi and S. poinsetti had 50:50 sex ratios. In June, the ratio of yearlings to older animals was approximately 50:50 in S. poinsetti and 60:40 in S. jarrovi. Of the eggs ovulated, 4.5% died before parturition in both species. Percent annual mortalities of S. poinsetti and S. jarrovi were respectively 86% and 81% (newborn), 54% and 56% (yearlings), and 57% and 63% (adults). The life history strategy of S. poinsetti appears to be relatively K—selected. S. jarrovi is more r—selected than S. poinsetti but more K—selected than most oviparous species.