bluuebunny/crossref_metadata_2025 huggingface dataset:
Revisit to the Samek Rule. A Comparative Study on Lactone Configurations by Synthesis, NMR, and MM2
Authors: Tori Motoo , Yoshimura Shin , Kuroda Chiaki , Asakawa Yoshinori
Published: May 2006

Steric energy and the conformation of nepalensolide A and frullanolide, having the cis lactones, and four types of possible model lactones as well as some synthetic compounds are calculated by MM2 and the allylic coupling constant of the exomethylenes are estimated to discuss the Samek rule.
Magnetic Circular Dichroism and Linear Dichroism for Elucidation of Electronic Transitions and Their Orientations in a Reaction Center Isolated from a Thermophilic Purple Sulfur Photosynthetic Bacterium Chromatium tepidum
Authors: Nozawa Tsunenori , Mimuro Mamoru , Kobayashi Masayuki , Tanaka Hideki
Published: May 2006

Electronic transitions and orientations of pigments in reaction center complex isolated from a purple sulfur bacterium Chromatium tepidum were determined by magnetic circular dichroism and linear dichroism. They are very similar to those of non-sulfur purple bacteria, indicating a convergent nature of this complex in the photosynthetic organisms.
Baker’s Yeast Mediated Bioreduction of Prochiral Ketones Having 6-(4-Oxo-1,3-dioxinyl) Group
Authors: Sakaki Jun-ichi , Suzuki Miwako , Kobayashi Satoshi , Sato Masayuki , Kaneko Chikara
Published: May 2006

Prochiral ketones having 6-(4-oxo-1,3-dioxinyl) group as one terminal unit by fermenting baker’s yeast gave chiral alcohols, which could be convertible to optically active hydroxyesters, β-ketoesters, and lactones.
Tris(1-phenylethylcarbamate)s of Cellulose and Amylose as Useful Chiral Stationary Phases for Chromatographic Optical Resolution
Authors: Okamoto Yoshio , Kaida Yuriko , Hayashida Hiromi , Hatada Koichi
Published: May 2006

(R)-, (S)-, and (RS)-1-phenylethylcarbamates of cellulose and amylose were synthesized and used as chiral stationary phases for high-performance liquid chromatography. The chiral recognition abilities of the 1-phenylethyl derivatives depended greatly on the chirality of 1-phenylethyl groups. Among six derivatives, amylose tris((S)-1-phenylethylcarbamate) showed high optical resolving ability for many compounds.
Monoclonal Antibodies as Tailor-Made Hosts for Porphyrins
Authors: Harada Akira , Okamoto Kazutake , Kamachi Mikiharu , Honda Takeshi , Miwatani Toshio
Published: May 2006

Monoclonal antibodies against tetracarboxyphenylporphyrin(TCPP) were prepared by immunizing Balb/c mice with TCPP bound keyhole limpet hemocyanin covalently and fusing the spleen cells with myeloma cells by using poly(ethylene glycol). The antibodies bind TCPP strongly with the dissociation constants of 10−6 − 2.5 × 10−7 M.
Synthesis and Characterization of a Novel Linear Tetranuclear Manganese Complex with Three Different Oxidation States (II,III,IV,II)
Authors: Suzuki Masatatsu , Senda Hitoshi , Suenaga Machiko , Sugisawa Toshiharu , Uehara Akira
Published: May 2006

A novel linear tetranuclear manganese(II,III,IV,II) complex, was prepared, [Mn4(tpdp)2(O)2(H2O)4](ClO4)5·4H2O, where Htpdp is 1,3-bis[bis(2-pyridylmethyl)amino]-2-propanol, and its crystal structure was determined by X-ray structure analysis. The complex cation consists of di(μ-oxo)dimanganese(III,IV) mixed valent unit to which two manganese(II) ions are linked by the alkoxo bridges of tpdp, forming a linear tetranuclear structure Mn(II,III,IV,II).
Efficient and Stable Photocatalytic Systems for Reductive Dechlorination of p-Chlorobiphenyl by Sodium Borohydride
Authors: Ishikawa Masashi , Fukuzumi Shunichi
Published: May 2006

Acridine Derivatives (9,10-dihydro-10-methylacridine and acriflavine) act as efficient and stable photocatalysts for reductive dechlorination of p-chlorobiphenyl as well as dehalogention of bromochlorobenzenes with sodium borohydride in acetonitrile/H2O (9:1 v/v) at 298 K. In the case of acriflavine, the limiting quantum yield at irradiation wavelength λ = 350 nm has reached 0.63.
Synthesis and Electrooptical Properties of Terminal–Terminal Type of Ferroelectric Liquid Crystal
Authors: Shiraisffi Kohei , Kato Koichi , Sugiyama Kazuo
Published: May 2006

A novel terminal-terminal type of ferroelectric liquid crystal, (S)-bis(2-methylbutyl) 3,3′-[1,20-eicosanediylbis[oxy-4,1-phenylenemethylidynenitrilo-4,1-phenylene]]bis[2-propenoate] (BMBEPMNP), was prepared, which composed of two chiral mesogenic groups interconnected by a very long flexible spacer chain. From the electrooptical effect originating in deformation of helical structure at a Sc* state, the electrooptical response time (τsr) was found to be 843 μs at 130 °C in 32 kV·cm−1.
Functional conformations of the L11–ribosomal RNA complex revealed by correlative analysis of cryo-EM and molecular dynamics simulations
Authors: Li Wen , Sengupta Jayati , Rath Bimal K. , Frank Joachim
Published: May 2006

The interaction between the GTPase-associated center (GAC) and the aminoacyl-tRNA·EF-Tu·GTP ternary complex is of crucial importance in the dynamic process of decoding and tRNA accommodation. The GAC includes protein L11 and helices 43–44 of 23S rRNA (referred to as L11–rRNA complex). In this study, a method of fitting based on a systematic comparison between cryo-electron microscopy (cryo-EM) density maps and structures obtained by molecular dynamics simulations has been developed. This method has led to the finding of atomic models of the GAC that fit the EM maps with much improved cross-correlation coefficients compared with the fitting of the X-ray structure. Two types of conformations of the L11–rRNA complex, produced by the simulations, match the cryo-EM maps representing the states either bound or unbound to the aa-tRNA·EF-Tu·GTP ternary complex. In the bound state, the N-terminal domain of L11 is extended from its position in the crystal structure, and the base of nucleotide A1067 in the 23S ribosomal RNA is flipped out. This position of the base allows the RNA to reach the elbow region of the aminoacyl-tRNA when the latter is bound in the A/T site. In the unbound state, the N-terminal domain of L11 is rotated only slightly, and A1067 of the RNA is flipped back into the less-solvent-exposed position, as in the crystal structure. By matching our experimental cryo-EM maps with much improved cross-correlation coefficients compared to the crystal structure, these two conformations prove to be strong candidates of the two functional states.
Worst-Case Analysis for Split Delivery Vehicle Routing Problems
Authors: Archetti Claudia , Savelsbergh Martin W. P. , Speranza M. Grazia
Published: May 2006

In the vehicle routing problem (VRP) the objective is to construct a minimum cost set of routes serving all customers where the demand of each customer is less than or equal to the vehicle capacity and where each customer is visited once. In the split delivery vehicle routing problem (SDVRP) the restriction that each customer is visited once is removed. We show that the cost savings that can be realized by allowing split deliveries is at most 50%. We also study the variant of the VRP in which the demand of a customer may be larger than the vehicle capacity, but where each customer has to be visited a minimum number of times. We show that the cost savings that can be realized by allowing more than the minimum number of required visits is again at most 50%. Furthermore, we analyze the performance of simple heuristics that handle customers with demands larger than the vehicle capacity by employing full load out-and-back trips to these customers until the demands become less than or equal to the vehicle capacity. Finally, we investigate situations in which demands are discrete and vehicle capacities are small.
Evaluation of serum levels of p53 in hepatocellular carcinoma in Egypt
Authors: El Far Mohamed A. , Atwa Mohamed A. , Yahya Raida S. , El Basuni Mohamed A.
Published: May 2006

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-induced death. Somatic mutation of the
Utilizing ultrafiltration to remove alkaline phosphatase from clinical analyzer water
Authors: Bôle Julien , Mabic Stéphane
Published: May 2006

Alkaline phosphatase (ALP) conjugated to antibodies is often used in enzyme immunoassays (EIAs). These assays are notably sensitive to experimental conditions. A possible source of interference is bacterial ALP, which is released when bacterial contamination occurs in clinical analyzers. Preliminary experiments led to the selection of a detection kit, ALP source, and specific types of tubes for collecting water samples and performing assays. The release of ALP from various strains of bacteria identified in pure water was demonstrated (10–30×10
Elektronische Speckle-Pattern-Interferometrie zur Charakterisierung von Mikrosystemverbunden (Electronic Speckle Pattern Interferometry for the Characterization of Microsystem Packages)
Authors: Schubach Hans Reinhard
Published: May 2006

Zur Charakterisierung von Mikrosystemverbunden ist eine hochgenaue und rückwirkungsfreie Messtechnik von herausragender Bedeutung. Die optische Messtechnik kann hierzu einen wertvollen Beitrag leisten. Im Besonderen ist die elektronische Speckle-Interferometrie aufgrund ihrer hohen Auflösung geeignet, die mechanische und thermische Charakterisierung hochgenau und flächenhaft durchzuführen.
Risk-Stratified Seroprevalence of Severe Acute Respiratory Syndrome Coronavirus Among Children in Hong Kong
Authors: Lee Pamela P.W. , Wong Wilfred H.S. , Leung Gabriel M. , Chiu Susan S. , Chan Kwok-Hung , Peiris Joseph S.M. , Lam Tai-Hing , Lau Yu-Lung
Published: May 2006

BACKGROUND. Severe acute respiratory syndrome was relatively mild in children, and the incidence was significantly lower when compared with adults. Although previous seroepidemiological studies demonstrated that asymptomatic infection was uncommon among health care workers and adult contacts of patients with severe acute respiratory syndrome, it is unclear whether this would extend to the pediatric population.

OBJECTIVE. The purpose of this study was to determine the seroprevalence of severe acute respiratory syndrome coronavirus among asymptomatic children living near Amoy Gardens (site of largest community outbreak of severe acute respiratory syndrome in Hong Kong) compared with a low-risk region where no community transmission occurred.

METHODS. The study was conducted from September to October 2003. Target subjects living in the defined high-risk and low-risk areas were approached through the schools within the respective localities. We recruited 353 and 361 children, respectively, from the high-risk and low-risk areas and collected 3 to 5 mL of blood for severe acute respiratory syndrome coronavirus IgG antibody testing by immunofluorescence antibody assay and confirmation by neutralization test. Parents of all of the subjects who joined the study were contacted by telephone, and a standardized questionnaire was administered by a research nurse to collect information including sociodemographic data, history of severe acute respiratory syndrome coronavirus infection in the subjects and members of the household, history of contact with known cases of severe acute respiratory syndrome, presence of severe acute respiratory syndrome-like symptoms since onset of the severe acute respiratory syndrome epidemic, travel history of the child and his/her relatives within the 15 days before any such symptom onset, use of health service as a result of such symptoms, and whether there were deaths of relatives as a result of severe acute respiratory syndrome.

RESULTS. Two (0.57%) of 353 asymptomatic children from the high-risk area were tested positive for severe acute respiratory syndrome coronavirus antibody compared with 0 of 361 in the low-risk region. None of the 14 children who lived in the high-risk area and had known contacts with severe acute respiratory syndrome patients were seropositive.

Conclusions. As in adults, subclinical severe acute respiratory syndrome coronavirus infection was rare in children in the 2003 epidemic. The very low seroprevalence implies little or no population herd immunity to protect against future resurgence of severe acute respiratory syndrome.
Agricultural sustainability does not imply biocenotic sustainability
Authors: Gigon Andreas
Published: May 2006

Abstract. Sustainability is an important quality of the types of agriculture nowadays promoted in central Europe, notably ‘biological agriculture’ and ‘integrated production’. Agronomists, decision‐makers and the public generally assume that this agricultural sustainability implies the maintenance of species diversity. However, this assumption often does not hold true. This is shown in a case study of moderately ferti‐lized Arrhenatheretum meadows in northern Switzerland. Earlier and more frequent mowing, simultaneous harvesting of all the grasslands in a region, and ecological changes in surrounding arable fields, hedges and other ecosystems often cause a decline in plant and animal species richness, while agricultural yield does not noticeably change. To emphasize the distinction the concept of biocenotic sustainability is proposed for describing the capability of a community to maintain its species composition and structure. For maintaining or attaining biocenotic sustainability. results of modern ecology have to be taken into account, e.g. the theories of island biogeography, minimum viable populations, dispersal, and metapopulations. There is evidence that biocenotic sustainability always implies sustainability of agricultural yield.
Some critical questions concerning the restorability of damaged raised bogs
Authors: Money R.P. , Wheeler B.D.
Published: May 2006

Abstract.In principle, the restoration of damaged raised bogs has rather few requirements: (1) a sufficient supply, and retention, of precipitation water of appropriate quality; and (2) the availability of a suitable range of recolonist species. However, to meet these requirements it may be necessary to engineer the topography of the peatland and drainage systems and to adopt a policy of species introduction. This paper provides a critical summary review of: (1) existing knowledge about the environmental conditions necessary for the effective regeneration of damaged ombrogenous peatlands; (2) approaches adopted for generating conditions appropriate for the re‐establishment of plant species typical of raised bogs; (3) possible external constraints (especially atmospheric contaminants) upon the feasibility of restoration; and (4) the prospects and possibilities for effective species recolonization. Particular attention is given to the identification of uncertainties and critical gaps in existing knowledge about raised bog restoration and of some of the natural processes that help regulate the development of raised bogs.
Restoration of a species‐rich fen‐meadow after abandonment: response of 64 plant species to management
Authors: Hald A.B. , Vinther E.
Published: May 2006

Abstract. Eleven years of abandonment of a species‐rich fen‐meadow under undisturbed environmental conditions resulted in transformation into areas with tall herb‐, sedge‐ and rush‐dominated communities and areas with Alnus thicket. Species cover was measured in permanent plots in both community types and succession was monitored during 14 yr of restoration following reintroduction of management. The annual increase in accumulated species number followed a log‐log‐time linear regression during 10 yr of grazing management. The expected number of years taken before this annual rate was equal to annual extinction, i.e. a stable situation according to species density, was up to six. The response of 64 species to management was evaluated through paired statistical tests of changes in cover and frequency over time. In total, 55 species could each be allocated to one unique response model (monotone or non‐monotone, concave models) independently of the importance value used (cover or frequency) and type of management (grazing following felling or mowing and mowing without grazing). Species which increased in response to grazing had the most persistent seed banks and CR‐strategies, while species decreasing in response to grazing had less persistent seed banks and CS‐strategies. Some of the species which increased due to grazing followed a model with a local maximum in cover and frequency. The results are discussed in relation to management of species with high cover value during restoration succession.
Digitized photographs in vegetation analysis ‐ a comparison of cover estimates
Authors: Vanha‐Majamaa I. , Salemaa M. , Tuominen S. , Mikkola K.
Published: May 2006

Abstract. The use of digital images in measuring plant species cover and species number in boreal forest vegetation was studied. Plant cover was estimated by manual delineation on photographs and subsequent digitized measurement of the areas. This value was regarded as the reference and compared with cover obtained by visual estimate, point frequency and automatic image analysis methods. The automatic image analysis was based on scanned photographs. Supervised image classification with ERDAS software was then used to distinguish between the covers of different plant species. When comparing the ability of the methods to detect species, the visual estimate method gave values similar to the reference. The study material was collected from three sites along a heavy‐metal pollution transect in western Finland. All four methods detected, in a similar manner, differences between the plant species abundances along the transect. Compared with the reference, the digital images underestimated the cover of the lichens Cladina spp. and Cetraria islandica, but gave similar estimates for the dwarf shrubs Empetrum nigrum and Vaccinium vitis‐idaea. The point frequency method overestimated the cover of all the species studied. The visual estimates of lichens were close to the reference, while the dwarf shrub covers were overestimated. The number of species detected using supervised image analysis and the point frequency method was lower than that with visual estimation. Visual estimation was faster, and the estimate closer to the reference cover values than the others. Digital images may be useful in detecting changes in some selected species in vegetation with a simple vertical structure but with taller, multilayered vegetation and a higher species number, the reliability of the cover estimates is lower.
Past and present forest vegetation in NE Slovenia derived from old maps
Authors: Čarni Andraž , Jarnjak Marjan , Oštir‐Sedej Krištof
Published: May 2006

Abstract. Using old military and cadastral maps and modern vegetation maps, the changes in land use over the past 230 yr were followed. The following maps were used: the military map from the second half of the 18th century, the cadastral map of the ‘Economic cadastral survey for regulation of land taxes’ from the first half of the 19th century, and a field map made in the 1980s. A vegetation map of the area was made on the basis of satellite images. We used basic classification techniques combined with extensive field inspections and aerial photographs. The output of this procedure was verified in the field. Additionally, a comparison of statistical data about land use categories is presented. It was established that the last remaining areas of inundated riverine forest disappeared 200 yr ago, and since then only minor changes in land use have occurred.
Telescopic Observation of the Moon as a Means for Observing Migration of the Army Cutworm, Chorizagrotis Auxiliaris (Lepidoptera: Noctuidae)
Authors: Pruess K. P. , Pruess Neva C.
Published: May 2006

Nocturnal insect activity was observed through telescopes focused on the moon. Flight direction was computed and methods were developed for estimating height and determining vertical distribution. Total density was correlated with light—trap catches; effective range of a light—trap was about 7 meters. Species identification was impossible but the method was selective for larger and higher—flying insects. Characteristics of insect activity observed during periods of army cutworm abundance indicate that it orients to the west during spring migration. Activity and altitude of flight were modified by wind direction and velocity but flight direction during migration was independent of wind.
A Dynamic Analysis of Age in Sugar Maple Seedlings
Authors: Hett Joan M.
Published: May 2006

Age data from populations of sugar maple (Acer saccharum Marsh.) seedlings in southern Wisconsin were used to investigate two plant—population models: a negative exponential model and a power function model. A weighted death probability was calculated and compared to densities of potential germinants, and the influence of seed—crop numbers on stem density was analyzed. The power function model, implying a decreasing mortality rate as the seedling ages, is a good model for describing population dynamics of sugar maple seedlings. Seed crops and potentially viable seeds appear to have no effect on the numbers of stems remaining in the population after several years. However, the density of the initial input into the population system does affect the probability of a seedling surviving during its germination year.
Population Regulation in Quill Mites (Acarina: Syringophilidae)
Authors: Kethley John
Published: May 2006

The wing quills of the House Sparrow (Passer domesticus L.) may host as many as three species of quill mites, suggesting ecological differences in the quill mite habitat. Detailed investigation of a single species of quill mite, Syringophiloidus minor (Berl.) reveals adaptations that maximize mite success within the confines of the feather calmus and suggests a mechanism that allows partitioning of the wing by two or more different—sized quill mite species. Quill mites live inside the feather calmus and feed on host tissue fluids by piercing the quill wall with long styletlike chelicerae. Mite reproduction and development take place within the calmus. Only adult female mites disperse. Females can move into newly developing quills during host moult in the fall, or into the developing feathers of nestlings in the spring. The quills in which the mites live represent a closed system, with calmus volume limiting the number of mites that may mature and calmus wall thickness limiting the ability of the mites to feed. Female mites cease egg production before the quill contains enough mites to fill it. As a result, the quill does not become filled with immature forms that would be incapable of mating and dispersing. Males of S. minor are smaller than the females and have a frequency of exactly 1:11. Thus over 95% of the limiting resource, calmus volume, is occupied by females, the potential dispersants. The size of a female is evidently limited by two opposing selective pressures: the smaller they are, the more can disperse from a given quill, but if they become too small the mouthparts will not be able to reach through the quill wall to feed. Thus each quill size has an optimum mite size, and the mite species occur in a corresponding diversity of sizes.
Species Diversity of Net Zooplankton and Physiochemical Conditions in Keystone Reservoir, Oklahoma
Authors: Kochsiek Kenneth A. , Wilhm Jerry L. , Morrison Robert
Published: May 2006

Net zooplankton collections and physiochemical measurements were made monthly in four stations each in the Cimarron River and Arkansas River arms and one station at the dam of Keystone Reservoir, Oklahoma, from June 21, 1967, to June 24, 1968. Conductivity was considerably greater in the Cimarron Arm than in the Arkansas arm or the dam, while turbidity, alkalinity, and zooplankton density were generally higher in the Arkansas arm. Variation among stations in temperature and dissolved oxygen was slight. A total of 44 taxa of zooplankton were collected. Shannon's formula was used to evaluate species diversity (d) of zooplankton. Variance values of d indicated only a slight gain in precision by increasing the sample size to above 400 individuals. Mean annual species diversity was slightly lower in the Cimarron Arm than in the Arkansas Arm. Diversity values decreased slightly through early winter and decreased abruptly and reached minimum values in late winter and early spring. Coefficients of correlation between physiochemical parameters and species diversity unadjusted for month and station effect were compared with adjusted coefficients.
Weather and the “Regulation” of Subalpine Populations
Authors: Ehrlich Paul R. , Breedlove Dennis E. , Brussard Peter F. , Sharp Margaret A.
Published: May 2006

Unusual spring weather climaxed by a late June snowstorm in the subalpine area around Gothic, Gunnison County, Colorado, had a profound effect on the biota. Damage to herbaceous prennial plans was extensive and the size of insect and small mammal populations was depressed. The storm caused the extinction of at least one butterfly population. The significance of these events to arguments concerning the regulation of animal population is discussed.
Homeostasis and Polymorphism in Vernal Development of Chaoborus Americanus
Authors: Bradshaw William E.
Published: May 2006

Last instar larvae of Chaoborus americanus overwinter in a state of developmental arrest (diapause) but remain otherwise active and capable of feeding. The diapausing larvae are developmentally responsive to long—day photoperiod and food. A portion of a wild—caught population responds rapidly to these conditions; the remainder of the population is more conservative. For either morph, the closer an individual approaches adult emergence, the more its rate of development is retarded by a small drop in water temperature. This response to temperature both promotes synchronous adult emergence and insures favorable climatic conditions at that time. Even this individual thermal homeostasis does not ensure survivorship throughout the total range of vernal climates encountered in a single shallow pond. The fast—responding morph predominates following warm, continuous springs; the more conservative morph predominates following a spring where the initial thaw is succeeded by a refreezing of the pond. Response time polymorphism is thus envisioned as an adaptive extension of the individual thermal homeostasis and serves as a model for persistent polymorphism.
Establishment of Early Successional Plant Populations on Forest and Prairie Soil
Authors: Raynal D. J. , Bazzaz F. A.
Published: May 2006

Seed germination and plant community development on adjacent forest and prairie soils (Typic Hapludalf and Typic Halplaquoll) were studied to elucidate the causes of variation in plant community composition during the first growing season after crop harvest. The number of plant individuals in July on the forest soil was three times larger than on the prairie soil. Abutilon theophrasti, Chenopodium album, Polygonum pensylvanicum, and Setaria faberii occurred in large numbers on the forest soil but were considerably less important on the prairie soil. Ipomoea hederacea predominated on the prairie soil. The seed load after abandonment on the forest soil was larger than on the prairie soil both before and after overwintering. Total numbers of plants that reached maturity were significantly higher (at the 5% level) on the forest soil than on the prairie soil. Population levels were generally constant throughout the growing season. Diversity peaked in June and was higher on the prairie soil than on the forest soil throughout the growing season. Germination of Ambrosia artemisiifolia, Lactuca scariola, and Polygonum was enhanced by moist soil conditions, whereas germination of Amaranthus hybridus was higher under dry soil conditions. Lactuca and Polygonum were the most sensitive to water stress and Abutilon and Setaria the most tolerant. It appears that the kinds and numbers of plants that become established in an abandoned field are a function of the number of germinable seeds present in the soil and the seed—soil water relationships. Of the soil parameters that may control seed germination, there is strong evidence to suggest that soil moisture the extreme upper portion of the profile is the major factor.
Survival of Brook Trout in a Bog‐Derived Acidity Gradient
Authors: Dunson William A. , Martin Ronald R.
Published: May 2006

The acidity in Bear Meadows Bog water (pH 3.7 — 4.7) is not due to carbonic acid or to any other volatile acid. The approximate pK of the unknown bog water acid(s) is 6.0 — 6.5. Fish do not occur in Bear Meadows Bog or in Sinking Creek over a 4.8—km section below the bog where water pH is too low for their survival. The lowest pH in which brook trout and white suckers were caught in Sinking Creek was 4.25 at area 5 (5.25 km below the bog) after a period of unusually heavy rainfall. At a different time brook trout alone were caught at area 4, 5.2 km below the bog, when the pH was 4.75. The lowest recorded pH at this site was 4.0. Survival times of hatchery brook trout placed in boxes in Sinking Creek was directly related to pH. Individual differences in tolerance to low pH were quite marked.
Adaptation of Rotifers to Seasonal Variation
Authors: King Charles E.
Published: May 2006

Most lakes display extensive seasonal variation in both their biotic and abiotic components. The question posed in this paper is how do rotifers adapt to this temporal heterogeneity?. Three alternate models of population structure for temporal adaptation are advanced and considered. If the physiological state of population varies continuously with its environment, the relative fitness of a population will be constant. To test this hypothesis, rotifers (Euchlanis dilatata) were periodically collected from a nature, cloned, allowed to adapt to the laboratory environment for 10 generations, and then used in experiments to determine the intrinsic rate of population growth, r. The r values of clones collected at different times indicated that physiological adaptation alone is not the major factor involved in adaptation to seasonal variation. Moreover, the pattern of variation in r revealed genetic differences among clones collected at different times. An alternate explanation, genetic discontinuity through time, is presented in two forms. Both models assume that different genotypes are maximally adapted to different parts of the environmental spectrum. The first model further assumes that adults of all genotypes are present throughout the spring and summer, but that the frequencies of the genotypes vary directly with the environmental variation. This model is the most likely statement of rotifer population structure if there is considerable gene flow throughout the population and if interclonal competition is not important. If either of these conditions does not hold,the population is expected to be subdivided into a number of genetically discrete units, each unit occupying a different temporal part of the environmental mosaic. An insufficient number of clones was tested to distinguish between the two models of temporal genetic polymorphism. However, the data that were obtained demonstrate that the large genetic component is necessary to explain the adaptation of E. dilatata to seasonal variation.
Seedling Response to Salinity in Four Dune Grasses from the Outer Banks of North Carolina
Authors: Seneca Ernest D.
Published: May 2006

Tolerance to salt in the substratum was determined in seedlings of four perennial dune grasses: Ammophila breviligulata Fern., Panicum amarulum Hitch. & Chase., Spartina patens (Ait.) Muhl., and Uniola paniculata L. An inverse linear relationship existed between growth and increased salinity in A. breviligulata, S. patens, and U. paniculata. Panicum amarulum seedlings demonstrated a curvilinear response to salinity. Seedlings of A. breviligulata and U. paniculata grew moderately well in salinities up to 1.0% NaCl, those of P. amarulum achieved even better growth in this salinity range, and some seedlings of S. patens survived the entire 28—day experimental period at 4.0% NaCl. Seedlings of S. patens collected from the field were more salt tolerant than those grown from seed collected from the field and germinated in the laboratory. In the other species the performance of field— and laboratory—grown seedlings did not differ. Based on seedling growth response, the order of decreasing salt tolerance for the four species is S. patens, P. amarulum, U. paniculata, and A. breviligulata. This pattern correlates well with performance in nature.
Differential Seasonal Migration of the Crayfish, Orconectes Virilis (Hagen) in Marl Lakes
Authors: Momot Walter T. , Gowing Howard
Published: May 2006

In an earlier study during 1962 and 1963, movement of female Orconectes virilis from shallow to deeper water in summer was noted in West Lost Lake, Otsego County, Michigan. The present additional observations on O. virilis, during three summers and in three lakes, confirm this migration. Evidence from other areas suggest that this movement is a general phenomenon of the species throughout most of its range. Migration of females appears to be associated essentially with muturation of the gonads.
Seed Germination and Salt Tolerance of Crops in Coastal Alluvial Soils of New Brunswick, Canada
Authors: Saini G. R.
Published: May 2006

The relative salt tolerance of crops grown on coastal alluvial soils was determined by adding NaCl to the soil to give electrical conductivity of saturated extract (ECe) ranging up to 20 mmhos/cm. Crop germination varied with oats > barley > timothy > clover. Yields equivalent to 70% of those obtained on soil without NaCl added indicated that oats was the most tolerant crop, followed by barley, clover, and timothy. Approximate ECe values at this yield level were 5, 4, 4, and 3 mmhos/cm, respectively. Barley is reported in the literature to be more salt tolerant than oats, but ECe as an indication of salt tolerance of barley was lower than that reported for saline soils of arid zones. The study shows that salt tolerance in coastal alluvial soils is comparable to that of other saline soils.
Effects of Fire on a Derbyshire Grassland Community
Authors: Lloyd P. S.
Published: May 2006

An experiment is reported in which the effects of fire (heat, litter removal, nutrient redistribution) were separated by a combination of burning and clipping treatments in a limestone grassland community dominated by the tussock grasses Festuca ovina L. and Helictorichon pratense (L.) Pilger and with a light covering of litter. Burning, but not clipping, stimulated the production of inflorescenses of H. pratense and killed many plants of F. ovina. Denudation, whether caused by burning or clipping (with or without the return of plant ash), resulted in hig her soil temperatures and increased frequency of annual and biennial species. Soil moisture tensions were not affected by the treatments. No effects of fire could be attributed to the deposition of ash. The result of the experiment are compared with studies of fire in prairie and other grassland communities.
Germinable Alkali Sacation Seed Content of Soils in the Rio Puerco Basin, West Central New Mexico
Authors: Knipe O. D. , Springfield H. W.
Published: May 2006

Barren sites are interspersed through native stands of alkali sacaton (Sporbolus airoides Torr.) in west central New Mexico. To determine if these sites remain bare because of lack of viable seeds, soil samples were collected three times each year for three years, and emerging sacaton seedlings were counted. Fewer germinable seeds were found in soil from barren sits than in soil from within stands. Moreover, the number of germinable seeds varied with time of collection. Seed movement from stands to barren sites were determined through collection made weekly during the period of seed dissemination. It was found that a substantial number of alkali sacaton seeds cross the barren sites, mainly through wind action. As many as 40—50 seeds/sq. ft. (400—500 m2) were collected 25 to 50 feet (7.6 to 15.2 m) from established stands. The results suggest most seeds are blown across the barren sites. The few seeds trapped in microsites in the soil soon after dissemination apparently are either removed by wind water animals, or insects, or are killed due to unfavorable moisture—temperature conditions.
Root Distribution Under Some Forest Types Native to West Virginia
Authors: Kochenderfer James N.
Published: May 2006

Strip—mine high walls and road cuts less than 2 years old were used to observe root distribution in several soil and forest types common to north—central West Virginia. Seventy—seven to 89% of all the observed root endings were found in the upper 0.6 m of soil; the highest percentages occurred in the northern hardwood type. The number of roots was greatest in coarse soil and decreased as the soil texture became finer.
Daily Activity of Namib Desert Arthropods in Relation to Climate
Authors: Holm Erik , Edney E. B.
Published: May 2006

Timed traps and visual observations were used to measure the distribution of activity of desert insects, principally tenbrionid beetles, in southwest Africa. Differences between species as regards seasonal and daily cycles were observed. Summer and winter faunas were almost entirely different. Measurements showed how hot and cold extremes may be avoided and how activity may be correlated with microclimatic variables. Daily activity of the tenebrionid Onymacris rugatipennis was bimodal in the summer, unimodal in the winter, and the difference could be correlated with the temperature regime.
Sizes of Populations of a Marine Snail
Authors: Spight Tom M.
Published: May 2006

Many animal and plant species form small populations which vary greatly from year to year and are likely to become extinct. Survival of such a species is dependent upon asynchrony of numerical changes in adjacent populations, and recolonization, rather than long—continued occupancy of particular sites by well—regulated individual populations. The marine snail, Thais lamellosa, is an example of such a species. Once each year, the adult Thais lamellosa aggregate in small breeding groups. Numbers in these aggregations varied from a few dozen to several hundred adults, 1968 to 1972, with an overall mean size of 145 snails. Aggregation size varied clinally over a kilometer of beach, and from site to site on and around San Juan Island, Washington. Sizes of aggregations formed were independent of the density of adults on the shore. Individual snails are likely to breed with the same group in successive years, and a juvenile is likely to return to the vicinity of its hatching site when it breeds for the first time (at age four). These breeding units are natural and persistent units of the continuous distribution of snails on the shore, and are here viewed as "populations." The size of each population varied over the period. Food density increased greatly, 1968 to 1972, and accelerated growth and spawning by individuals. Despite the increased food abundance, the population of the whole shore decreased gradually. Adjacent units were out of synchrony with each other, and few paralleled the slow decline of the whole shore population. The asynchronies canceled each other to yield a regional population stability. Fluctuations were extreme; populations are likely to become extinct at a rate somewhat greater than one per 200 population—years. Individuals countered this by moving among the asynchronous populations; on average, 41% of one's offspring bred at least once in another population, and 12% of the snails that bred once bred in two different populations.
Effects of Salinity on Growth of Several Aquatic Macrophytes
Authors: Haller William T. , Sutton D. L. , Barlowe W. C.
Published: May 2006

Growth rates of 10 aquatic macrophytes in various salinities under greenhouse conditions varied widely. Salt concentrations of 1.66% and 2.5% were toxic to Pistia stratiotes L. and Eichornia crassipes (Mart.) Solms, respectively. Salinities of 16.65% or higher were toxic to Lemna minor L., but growth of Lemna was increased by salt concentrations of 0.83%, 1.66%, 2.50%, and 3.33% as compared to other Lemna plants grown in fertilized pondwater. Other species studied, Hydrilla verticillata Royle, Myriophyllum spicatum L., Najas quadalupensis (Spreng.) Magnus, Vallisneria americana Michx., Azolla caroliniana Willd., and Salvinia rotundifolia Willd., gradually declined in growth as salinity increased. Transpiration of the emersed growth form of Myriophyllum brasiliense Camb. decreased with increasing levels of salinity, but root growth was stimulated by salt concentrations of 0.83%—3.33%, presumably a response of the plant to overcome an internal water deficit resulting from the saline solutions.
Coloniality, Activity Patterns and Feeding in a Tropical Orb‐Weaving Spider
Authors: Buskirk Ruth E.
Published: May 2006

Orb—weaving spiders Metabus gravidus (Cambridge) (Araneae: Araneidae) spin, maintain, and defend individual webs. Colonies of 5—70 species form multilayered meshes of orbs connected by common support lines over mountain streams at the study site, Monteverde, Costa Rica. Habitat selection, preference for spinning with a group, and maintenance of year—round population levels result in relatively permanent aggregations. Grouped spiders can build orbs in areas of high prey density more efficiently than single spiders, but they do not cooperate in web construction or food capture. Activity patterns relate closely to prey abundance and also depend upon individual energy demands. Cost—benefit analysis for different positions within the colony suggests no single optimal position on the basis of prey capture and the construction, maintenance, and defense of orbs. Colonies are maintained by the composite movements of unspecialized individuals, which benefit in the exploitation of resources not available to solitary spiders.
Ecotypic Adaptation in Sitanion hystrix
Authors: Clary Warren P.
Published: May 2006

Ecotypic differentiation as a response to climatic conditions was studied in an adaptable grass species Sitanion hystrix (Nutt.) J. G. Smith. Twelve collection were obtained from seven states: Arizona, Colorado, Nebraska, Nevada, New Mexico, South Dakota, and Utah. The collection sites varied in elevation from 1,380 to 2,980 m and in annual precipitation from 310 to 739 mm. Plant materials were grown under uniform conditions in a transplant garden and a growth chamber. The effective growing seasons at the original collection sites were apparently as limited by moisture stress as by cold temperatures. Relative phenological development could be predicted by a climatic scale representing temperature and moisture conditions at the original collection sites. Plant size and dry matter production could not be predicted as reliably, suggesting that the primary factors which influence morphological and production characteristics may be more numerous or complex than those which influence penology. The populations represented in this study have adapted to different climatic conditions primarily through variations in timing of phenological development and in rate of growth. No differences in water use efficiency were found. Under uniform conditions: (1) plants from warm, dry habitats flowered early and had low dry matter production; (2) plants from habitats with moderate temperature and moisture conditions flowered latest and had relatively high dry matter production; and (3) plants from cool, wet habitats flowered early and had relatively high dry matter production. Flowering dates of the different collections varied as much as 2 mo.
Shrub Age Structures on a Mule Deer Winter Range in Colorado
Authors: Roughton Robert D.
Published: May 2006

Age—determination techniques for selected shrub species utilized by deer were tested on known—age specimens and refined. Intact plants and descriptive data were collected on circular milacre plots in random locations in selected stands. Prepared specimens of Purshia tridentata and Artemisia tridentata were readily aged by crossdating xylem growth layers. Cercocarpus montanus proved difficult and supplemental ring counts were used, reducing accuracy of the age determinations. Ribes cereum samples were unsuitable for the techniques employed. Ages in years were estimated for 3,231 plants, and age structures were graphed by 5—year classes. The "die—away" curve is used as a hypothetical norm for self—replacing populations in the interpretation of age structures. Shrub age structures may reflect current and past reproductive success and, hence, successional status. Irregularities may be related to fires, climate, rodent seed—caching, reproductive cycling, and use by animals.
Intraspecific Shore‐Level Size Gradients in Intertidal Molluscs
Authors: Vermeij Geerat J.
Published: May 2006

A synthesis of new data and literature observations indicates that, when rocky intertidal gastropod species (1) shell size tends to increase in an upshore direction in species characteristic of the littoral fringe and in high intertidal limpets, and (2) shell size often decreases in an upshore direction in species typical of lower intertidal levels. These size gradients are considered to be a response to gradients in the intensity and nature of postlarval prereproductive mortality on the shore. In gastropods whose size gradients are of type 1, mortality generally resulting from physical extremes operates from above and is most effective against small individuals. Among snails with size gradients of type 2, mortality often in the form of predation or other biotic intraction is most intense at low levels. Sedentary species can become graded according to size with shore level only through differential mortality of one size group relative to another over the entire vertical range of the species, while mobile forms may become size segregated by active migration of one size group relative to another.
Estimating Snow‐Water Equivalent from Point Density Measurements of Forest Stands
Authors: Golding D. L. , Harlan R. L.
Published: May 2006

To define the cumulative influence of adjacent trees on snow accumulation, the Bitterlich point—sampling technique was used with four angle size in the area of relatively homogeneous spruce—fir with similar slope—aspect conditions. Snow—water equivalent at 50 points for 10 measurement dates was correlated with point density. Correlations were higher for that point density determined with angle 147.34 min than for the angles 73.66, 104.18, and 208.38 min. A linear regression model combining weight point—density measurements using three angle sizes gave the highest correlations. There was a trend of increasing correlation from January to April.
Water Relations of Plants in Raised Sphagnum Peat Bogs
Authors: Small Ernest
Published: May 2006

The water relations of woody plants of a raised sphagnum peat bog were examined by evaluation of water potential employing the pressure bomb and by measuring transpiration resistance with a leaf—resistance porometer. The plants studied proved to be similar to those of a number of mesophytes growing adjacent to the bog and exhibited no evidence of drought stress. The concept of physiological drought is an inadequate explanation of the extremely xeromorphic characteristics of bog vegetation, which are more plausibly accounted for by other factors.