WorldWideScience

Sample records for stand age structure

  1. Age structure of a southern pine stand following 72 years of uneven-aged silviculture

    Science.gov (United States)

    Don C. Bragg

    2012-01-01

    Work on uneven-aged silviculture in southern pine stands on the Crossett Experimental Forest (CEF) began in the 1930s, when a number of 16.2-ha compartments were placed into a series of demonstration projects and studies (Reynolds 1980). Two of these compartments, the Good and Poor Farm Forestry Forties, have been maintained continuously in this silvicultural regime...

  2. Forest stand structure, productivity, and age mediate climatic effects on aspen decline

    Science.gov (United States)

    Bell, David M.; Bradford, John B.; Lauenroth, William K.

    2014-01-01

    Because forest stand structure, age, and productivity can mediate the impacts of climate on quaking aspen (Populus tremuloides) mortality, ignoring stand-scale factors limits inference on the drivers of recent sudden aspen decline. Using the proportion of aspen trees that were dead as an index of recent mortality at 841 forest inventory plots, we examined the relationship of this mortality index to forest structure and climate in the Rocky Mountains and Intermountain Western United States. We found that forest structure explained most of the patterns in mortality indices, but that variation in growing-season vapor pressure deficit and winter precipitation over the last 20 years was important. Mortality index sensitivity to precipitation was highest in forests where aspen exhibited high densities, relative basal areas, quadratic mean diameters, and productivities, whereas sensitivity to vapor pressure deficit was highest in young forest stands. These results indicate that the effects of drought on mortality may be mediated by forest stand development, competition with encroaching conifers, and physiological vulnerabilities of large trees to drought. By examining mortality index responses to both forest structure and climate, we show that forest succession cannot be ignored in studies attempting to understand the causes and consequences of sudden aspen decline.

  3. Rotated sigmoid structures in managed uneven-aged northern hardwood stands: a look at the Burr Type III distribution

    Science.gov (United States)

    Jeffrey H. Gove; Mark J. Ducey; William B. Leak; Lianjun Zhang

    2008-01-01

    Stand structures from a combined density manipulation and even- to uneven-aged conversion experiment on the Bartlett Experimental Forest (New Hampshire, USA) were examined 25 years after initial treatment for rotated sigmoidal diameter distributions. A comparison was made on these stands between two probability density functions for fitting these residual structures:...

  4. Generalized biomass and leaf area allometric equations for European tree species incorporating stand structure, tree age and climate

    OpenAIRE

    FORRESTER DAVID; TACHAUER ELOISE; ANNIGHOEFER PETER; BARBEITO IGNACIO; PRETZSCH HANS; RUIZ-PEINADO RICARDO; STARK HENDRIK; VACCHIANO GIORGIO; ZLATANOV TZVETAN; CHAKRABORTY TAMALIKA; SAHA SOMID; SILESHI GUDETA W.

    2017-01-01

    Biomass and leaf area equations are often required to assess or model forest productivity, carbon stocks and other ecosystem services. These factors are influenced by climate, age and stand structural attributes including stand density and tree species diversity or species composition. However, such covariates are rarely included in biomass and leaf area equations. We reviewed the literature and built a database of biomass and leaf area equations for 24 European tree species and 3 introduced ...

  5. Leaf area and structural changes after thinning in even-aged Picea rubens and Abies balsamea stands in Maine, USA

    Science.gov (United States)

    R. Justin DeRose; Robert S. Seymour

    2012-01-01

    We tested the hypothesis that changes in leaf area index (LAIm2 m-2) and mean stand diameter following thinning are due to thinning type and residual density. The ratios of pre- to postthinning diameter and LAI were used to assess structural changes between replicated crown, dominant, and low thinning treatments to 33% and 50% residual density in even-aged Picea rubens...

  6. Early-seral stand age and forest structural changes in public and private forestlands in Western Oregon and Washington

    Science.gov (United States)

    Robert L Deal; Sharon Stanton; Matthew Betts; Zhiqiang. Yang

    2015-01-01

    Federal forests in the Pacific Northwest region have undergone exceptional changes in management over the past 20 years, and these changes have led to a reduction in regional timber production and significant changes in the management and current age structure of forests. Public lands include large areas of older forests with relatively little younger early-seral...

  7. Uneven-aged management of old-growth spruce-fir forests: Cutting methods and stand structure goals for the initial entry

    Science.gov (United States)

    Robert R. Alexander; Carleton B. Edminster

    1977-01-01

    Topics discussed include: (1) cutting methods, (2) stand structure goals, which involve choosing a residual stocking level, selecting a maximum tree size, and establishing a diameter distribution using the "q" technique, and (3) harvesting and removal of trees. Examples illustrate how to determine realistic stand structures for the initial entry for...

  8. Stand structure and stocking control in Appalachian mixed hardwoods

    Science.gov (United States)

    George R., Jr. Trimble; H. Clay Smith

    1976-01-01

    Uneven-aged management using a "q" technique for structure control is discussed for Appalachian mixed hardwoods. The success in attaining stand structure goals with periodic selection cuts was evaluated. Where these goals had not been reached, the authors speculated, on the basis of current stand conditions, whether they would be reached, and if so, when. For...

  9. Crown structure and growth efficiency of red spruce in uneven-aged, mixed-species stands in Maine

    Science.gov (United States)

    Douglas A. Maguire; John C. Brissette; Lianhong. Gu

    1998-01-01

    Several hypotheses about the relationships among individual tree growth, tree leaf area, and relative tree size or position were tested with red spruce (Picea rubens Sarg.) growing in uneven-aged, mixed-species forests of south-central Maine, U.S.A. Based on data from 65 sample trees, predictive models were developed to (i)...

  10. The role of forest stand structure as biodiversity indicator

    DEFF Research Database (Denmark)

    Gao, Tian; Hedblom, Marcus; Emilsson, Tobias

    2014-01-01

    be achieved if indicators are derived from existing data. In this study, a model for classifying forest stand structures was developed and tested as an indicator of overall plant species diversity at stand level. The model combines four stand structure parameters: canopy coverage, age of canopy trees, tree...... species composition and canopy stratification. Using data from the National Inventory of Landscapes in Sweden and General Linear Mixed Model, plant species diversity (Shannon diversity index, SHDI) and composition (Sørensen-Dice index, SDI) were tested between 26 different stand structure types and nine...... soil classes. The results showed that mature stands with a stratified canopy had the highest plant species diversity across the soil classes, particularly if they comprised mixed coniferous and broadleaved species with a semi-open canopy. In contrast, young (...

  11. Relationship of stand age to streamwater nitrate in New Hampshire

    Science.gov (United States)

    William B. Leak; C. Wayne Martin

    1975-01-01

    Streamwater nitrate content of six watersheds during spring and summer was apparently related to stand age or age since disturbance. Nitrate concentration averaged 10.3 ppm right after cutting, dropped to a trace in medium-aged stands, and then rose again to a maximum of 4.8 ppm as stands became overmature.

  12. Unravelling the importance of forest age stand and forest structure driving microbiological soil properties, enzymatic activities and soil nutrients content in Mediterranean Spanish black pine(Pinus nigra Ar. ssp. salzmannii) Forest.

    Science.gov (United States)

    Lucas-Borja, M E; Hedo, J; Cerdá, A; Candel-Pérez, D; Viñegla, B

    2016-08-15

    This study aimed to investigate the effects that stand age and forest structure have on microbiological soil properties, enzymatic activities and nutrient content. Thirty forest compartments were randomly selected at the Palancares y Agregados managed forest area (Spain), supporting forest stands of five ages; from 100 to 80years old to compartments with trees that were 19-1years old. Forest area ranging from 80 to 120years old and without forest intervention was selected as the control. We measured different soil enzymatic activities, soil respiration and nutrient content (P, K, Na, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb and Ca) in the top cm of 10 mineral soils in each compartment. Results showed that the lowest forest stand age and the forest structure created by management presented lower values of organic matter, soil moisture, water holding capacity and litterfall and higher values of C/N ratio in comparison with the highest forest stand age and the related forest structure, which generated differences in soil respiration and soil enzyme activities. The forest structure created by no forest management (control plot) presented the highest enzymatic activities, soil respiration, NH4(+) and NO3(-). Results did not show a clear trend in nutrient content comparing all the experimental areas. Finally, the multivariate PCA analysis clearly clustered three differentiated groups: Control plot; from 100 to 40years old and from 39 to 1year old. Our results suggest that the control plot has better soil quality and that extreme forest stand ages (100-80 and 19-1years old) and the associated forest structure generates differences in soil parameters but not in soil nutrient content. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Aboveground net primary production decline with stand age: potential causes.

    Science.gov (United States)

    Gower, S T; McMurtrie, R E; Murty, D

    1996-09-01

    Aboveground net primary production (ANPP) commonly reaches a maximum in young forest stands and decreases by 0-76% as stands mature. However, the mechanism(s) responsible for the decline are not well understood. Current hypotheses for declining ANPP with stand age include: (1) an altered balance between photosynthetic and respiring tissues, (2) decreasing soil nutrient availability, and (3) increasing stomatal limitation leading to reduced photosynthetic rates. Recent empirical and modeling studies reveal that mechanisms (2) and (3) are largely responsible for age-related decline in ANPP for forests in cold environments. Increasing respiratory costs appear to be relatively unimportant in explaining declining productivity in ageing stands.

  14. Growth of site trees and stand structure in mixed stands of Pacific silver fir and western hemlock.

    Science.gov (United States)

    Marshall D. Murray; Peggy C. Leonard

    1990-01-01

    Height and diameter growth of Pacific silver fir (Abies amabilis Dougl. ex Forbes) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) site trees, as well as overall stand structure on 0.15-acre plots, were analyzed in mixed stands 43 to 57 years old in breast height age at six locations in western Washington. These mixed...

  15. Stand Structure and Composition 32 Years after Precommercial Thinning Treatments in a Mixed Northern Conifer Stand in Central Maine

    Science.gov (United States)

    Aaron R. Weiskittel; Laura S. Kenefic; Rongxia Li; John Brissette

    2011-01-01

    The effects of four precommercial thinning (PCT) treatments on an even-aged northern conifer stand in Maine were investigated by examining stand structure and composition 32 years after treatment. Replicated treatments applied in 1976 included: (1) control (no PCT), (2) row thinning (rowthin; 5-ft-wide row removal with 3-ft-wide residual strips), (3) row thinning with...

  16. Stand structure and regeneration of harvested Araucaria araucana ...

    African Journals Online (AJOL)

    Stand structure and regeneration of harvested Araucaria araucana–Nothofagus stands in central Chile. Rafael M Navarro-Cerrillo, Fernando Olave, Francisco Moreno, Sergio de Miguel, Margarita Clemente ...

  17. Relative size and stand age determine Pinus banksiana mortality

    Science.gov (United States)

    Han Y. H. Chen; Songling Fu; Robert A. Monserud; Ian C. Gillies

    2008-01-01

    Tree mortality is a poorly understood process in the boreal forest. Whereas large disturbances reset succession by killing all or most trees, background tree mortality was hypothesized to be affected by competition, ageing, and stand composition. We tested these hypotheses on jack pine (Pinus banksiana Lamb.) mortality using data from long-term...

  18. Height prediction equations for even-aged upland oak stands

    Science.gov (United States)

    Donald E. Hilt; Martin E. Dale

    1982-01-01

    Forest growth models that use predicted tree diameters or diameter distributions require a reliable height-prediction model to obtain volume estimates because future height-diameter relationships will not necessarily be the same as the present height-diameter relationship. A total tree height prediction equation for even-aged upland oak stands is presented. Predicted...

  19. Stand age and climate drive forest carbon balance recovery

    Science.gov (United States)

    Besnard, Simon; Carvalhais, Nuno; Clevers, Jan; Herold, Martin; Jung, Martin; Reichstein, Markus

    2016-04-01

    Forests play an essential role in the terrestrial carbon (C) cycle, especially in the C exchanges between the terrestrial biosphere and the atmosphere. Ecological disturbances and forest management are drivers of forest dynamics and strongly impact the forest C budget. However, there is a lack of knowledge on the exogenous and endogenous factors driving forest C recovery. Our analysis includes 68 forest sites in different climate zones to determine the relative influence of stand age and climate conditions on the forest carbon balance recovery. In this study, we only included forest regrowth after clear-cut stand replacement (e.g. harvest, fire), and afforestation/reforestation processes. We synthesized net ecosystem production (NEP), gross primary production (GPP), ecosystem respiration (Re), the photosynthetic respiratory ratio (GPP to Re ratio), the ecosystem carbon use efficiency (CUE), that is NEP to GPP ratio, and CUEclimax, where GPP is derived from the climate conditions. We implemented a non-linear regression analysis in order to identify the best model representing the C flux patterns with stand age. Furthermore, we showed that each C flux have a non-linear relationship with stand age, annual precipitation (P) and mean annual temperature (MAT), therefore, we proposed to use non-linear transformations of the covariates for C fluxes'estimates. Non-linear stand age and climate models were, therefore, used to establish multiple linear regressions for C flux predictions and for determining the contribution of stand age and climate in forest carbon recovery. Our findings depicted that a coupled stand age-climate model explained 33% (44%, average site), 62% (76%, average site), 56% (71%, average site), 41% (59%, average site), 50% (65%, average site) and 36% (50%, average site) of the variance of annual NEP, GPP, Re, photosynthetic respiratory ratio, CUE and CUEclimax across sites, respectively. In addition, we showed that gross fluxes (e.g. GPP and Re) are

  20. Stocking and structure for maximum growth in sugar maple selection stands.

    Science.gov (United States)

    Thomas R. Crow; Carl H. Tubbs; Rodney D. Jacobs; Robert R. Oberg

    1981-01-01

    The impacts of stocking, structure, and cutting cycle on basal area, cubic foot volume, board foot volume, and diameter growth are considered. Recommendations are provided for maximum growth in uneven-aged sugar maple stands.

  1. Application of Lidar remote sensing to the estimation of forest canopy and stand structure

    Science.gov (United States)

    Lefsky, Michael Andrew

    A new remote sensing instrument, SLICER (Scanning Lidar Imager of Canopies by Echo Recovery), has been applied to the problem of remote sensing the canopy and stand structure of two groups of deciduous forests, Tulip Poplar-Oak stands in the vicinity of Annapolis, MD. and bottomland hardwood stands near Williamston, NC. The ability of the SLICER instrument to remotely sense the vertical distribution of canopy structure (Canopy Height Profile), bulk canopy transmittance, and several indices of canopy height has been successfully validated using twelve stands with coincident field and SLICER estimates of canopy structure. Principal components analysis has been applied to canopy height profiles from both field sites, and three significant factors were identified, each closely related to the amount of foliage in a recognizable layer of the forest, either understory, midstory, or overstory. The distribution of canopy structure to these layers is significantly correlated with the size and number of stems supporting them. The same layered structure was shown to apply to both field and SLICER remotely sensed canopy height profiles, and to apply to SLICER remotely sensed canopy profiles from both the bottomland hardwood stands in the coastal plain of North Carolina, and to mesic Tulip-Poplars stands in the upland coastal plain of Maryland. Linear regressions have demonstrated that canopy and stand structure are correlated to both a statistically significant and useful degree. Stand age and stem density is more highly correlated to stand height, while stand basal area and aboveground biomass are more closely related to a new measure of canopy structure, the quadratic mean canopy height. A geometric model of canopy structure has been shown to explain the differing relationships between canopy structure and stand basal area for stands of Eastern Deciduous Forest and Douglas Fir Forest.

  2. Analysis of tree stand horizontal structure using random point field methods

    Directory of Open Access Journals (Sweden)

    O. P. Sekretenko

    2015-06-01

    Full Text Available This paper uses the model approach to analyze the horizontal structure of forest stands. The main types of models of random point fields and statistical procedures that can be used to analyze spatial patterns of trees of uneven and even-aged stands are described. We show how modern methods of spatial statistics can be used to address one of the objectives of forestry – to clarify the laws of natural thinning of forest stand and the corresponding changes in its spatial structure over time. Studying natural forest thinning, we describe the consecutive stages of modeling: selection of the appropriate parametric model, parameter estimation and generation of point patterns in accordance with the selected model, the selection of statistical functions to describe the horizontal structure of forest stands and testing of statistical hypotheses. We show the possibilities of a specialized software package, spatstat, which is designed to meet the challenges of spatial statistics and provides software support for modern methods of analysis of spatial data. We show that a model of stand thinning that does not consider inter-tree interaction can project the size distribution of the trees properly, but the spatial pattern of the modeled stand is not quite consistent with observed data. Using data of three even-aged pine forest stands of 25, 55, and 90-years old, we demonstrate that the spatial point process models are useful for combining measurements in the forest stands of different ages to study the forest stand natural thinning.

  3. Age-Related Differences in Quality of Standing Balance Using a Composite Score

    NARCIS (Netherlands)

    Pasma, J.H.; Bijlsma, A.Y.; van der Bij, M.D.W.; Arendzen, J.H.; Meskers, C.G.M.; Maier, A.B.

    2014-01-01

    Background: Age-related differences in standing balance are not detected by testing the ability to maintain balance. Quality of standing balance might be more sensitive to detect age-related differences. Objective: To study age-related differences in quality of standing balance, center of pressure

  4. Calculation of Economic Rotation Period for Even-Aged Stand in Croatia

    Directory of Open Access Journals (Sweden)

    Karlo Beljan

    2011-12-01

    Full Text Available Background and Purpose: Even-aged forests prevail in Croatia’s forestry. Rotation period is based mostly on natural parameters. In practice, rotation period is given by Croatian Rulebook of forest management. Cutting age is determined based on inventory data and many other stand characteristics. Rotation period is a planned time and it always has to be unique for particular tree species, and cutting age is the age of a stand at the moment of the final cut. The aim of the paper is to compare rotation period based on economic parameters and rotation period determined by using forest inventory data. Material and Methods: Owing to absence of long term stand calculation data, research object was taken from Forest Management Handbook (1995. Mean annual increment (MAI and current annual increment (CAI provided fundamental data for calculations. The research was conducted at one hectare Common Beech (Fagus sylvatica L. stand. Assortment structure and value of timber was estimated by the present cutting value method calculated by using Croatian forests Ltd. Price list for the year 2008. Labor costs in forest exploitation were also taken into account. Results and Conclusion: In order to achieve cost-effective management of common beech stands, it is necessary to adjust current optimal rotation period. Optimal rotation period should be based on management goals as the main factors. So far the most common criterion adopted in Croatian forestry has been the rotation of maximum sustained yield or maximum Mean annual increment. The presented results indicate that common forest management practice should be changed in order to achieve cost-effective management of beech stands in the future.

  5. Consequences of stand age and species’ functional trait changes on ecosystem water use of forests

    Energy Technology Data Exchange (ETDEWEB)

    Ewers, Brent; Bond-Lamberty, Benjamin; Mackay, D. Scott

    2011-07-22

    We tested whether using stomatal conductance could capture the dynamic in transpiration with forest age. To do this we by answered the question “If we chose a reference stomatal conductance from one stand age of the entire chronosequence to put into a model, would modeled transpiration be biased from the other ages?” with a resounding yes. We found that obtaining the right stomatal conductance was crucial for accurate models in two different chronosequences. This strongly suggests that stomatal conductance is the appropriate integrator of inter- and intra-species change in tree transpiration with forest age. If we had tried to use a single reference canopy stomatal conductance, it would not have been able to capture the variability in transpiration with stand age despite the suggestion that hydraulic limitation was consistently acting on the trees; the situation is even more complex in many boreal systems, where a transition to nonstomatal bryophytes may occur over the course of succession. Because we used a biophysical approach, even if our and other researchers’ chronosequences do not fit the assumptions, the results are still useful. Further, our synthesis of sap flux based estimates of tree transpiration showing a large dynamic suggest that our approach to modeling is crucial in the face of anthropogenic changes to forest age structure. We have now provided the framework for a mechanistically rigorous yet simple approach based on simple tree hydraulics to measuring and modeling stand transpiration with changing forest age and/or species composition.

  6. Reconstructed old-growth forest stand structure and composition of two stands on the Olympic Peninsula, Washington state

    Science.gov (United States)

    David H. Peter; Constance A. Harrington

    2010-01-01

    We reconstructed the stand structure and composition for two western Washington old-growth forest stands harvested around 1930 (named Fresca and Rail) from field and historical data. Both old-growth stands had a codominant or dominant 250-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) overstory with a few scattered older Douglas-fir....

  7. Structural attributes of stand overstory and light under the canopy

    Directory of Open Access Journals (Sweden)

    Alice Angelini

    2015-02-01

    Full Text Available  This paper reviews the literature relating to the relationship between light availability in the understory and the main qualitative and quantitative attributes of stand overstory usually considered in forest management and planning (species composition, density, tree sizes, etc. as well as their changes as consequences of harvesting. The paper is divided in two sections: the first one reviews studies which investigated the influence of species composition on understory light conditions; the second part examines research on the relationships among stand parameters determined from dendrometric field data and the radiation on understory layer. The objective was to highlight which are the most significant stand traits and management features to build more practical models for predicting light regimes in any forest stand and, in more general terms, to support forest managers in planning and designing silvicultural treatments that retain structure in different way in order to meet different objectives.

  8. Rapid Assessment of Age-Related Differences in Standing Balance

    Directory of Open Access Journals (Sweden)

    Tobias Kalisch

    2011-01-01

    Full Text Available As life expectancy continues to rise, in the future there will be an increasing number of older people prone to falling. Accordingly, there is an urgent need for comprehensive testing of older individuals to collect data and to identify possible risk factors for falling. Here we use a low-cost force platform to rapidly assess deficits in balance under various conditions. We tested 21 healthy older adults and 24 young adults during static stance, unidirectional and rotational displacement of their centre of pressure (COP. We found an age-related increase in postural sway during quiet standing and a reduction of maximal COP displacement in unidirectional and rotational displacement tests. Our data show that even low-cost computerized assessment tools allow for the comprehensive testing of balance performance in older subjects.

  9. Spatial Patterns of Canopy Disturbance, Structure, and Species Composition in a Multi-Cohort Hardwood Stand

    Directory of Open Access Journals (Sweden)

    Scott Ford

    2017-03-01

    Full Text Available Multi-cohort stands are increasingly recognized and valued because of their biological functioning, biological diversity, and resistance and resiliency to perturbations. These forest ecosystems are epitomized by multiple age classes, and often contain multiple canopy layers, a range of tree size classes, and large amounts of woody debris. Disturbance history reconstructions in multi-cohort stands provide an understanding of the processes that create these systems. In this study, we documented structure and composition, and used dendroecological techniques to reconstruct disturbance history on a 1 ha plot in a multi-cohort hardwood stand in the Fall Line Hills of Alabama. The stand was dominated by Quercus alba L. and Liriodendron tulipifera L. Mingling index and stem maps indicated that most species were well dispersed throughout the stand, with the exception of L. tulipifera and Carya tomentosa (Poiret Nuttal, which were relatively clustered. The oldest trees in the stand established in the 1770s, however, the largest recruitment event occurred ca. 1945 in conjunction with a stand-wide canopy disturbance. We posit that spatial heterogeneity of canopy removal during this event was largely responsible for the observed compositional and spatial complexity documented in the stand. In addition to the 1945 event, we recorded another stand-wide canopy disturbance in 1906 and 84 gap-scale disturbance events from 1802 to 2003. The conditions documented in the stand can be used as a benchmark to guide the creation and maintenance of complex multi-cohort stand characteristics, an increasingly popular management goal.

  10. Evaluating the Ecological Integrity of Structural Stand Density Management Models Developed for Boreal Conifers

    Directory of Open Access Journals (Sweden)

    Peter F. Newton

    2015-04-01

    Full Text Available Density management decision-support systems (e.g., modular-based structural stand density management models (SSDMMs, which are built upon the modeling platform used to develop stand density management diagrams, incorporate a number of functional relationships derived from forest production theory and quantitative ecology. Empirically, however, the ecological integrity of these systems has not been verified and hence the degree of their compliance with expected ecological axioms is unknown. Consequently, the objective of this study was to evaluate the ecological integrity of six SSDMMs developed for black spruce (Picea mariana and jack pine (Pinus banksiana stand-types (natural-origin and planted upland black spruce and jack pine stands, upland natural-origin black spruce and jack pine mixtures, and natural-origin lowland black spruce stands. The assessment included the determination of the biological reasonableness of model predictions by determining the degree of consistency between predicted developmental patterns and those expected from known ecological axioms derived from even-aged stand dynamics theoretical constructs, employing Bakuzis graphical matrices. Although the results indicated the SSDMMs performed well, a notable departure from expectation was a possible systematic site quality effect on the asymptotic yield-density relationships. Combining these results with confirmatory evidence derived from the literature suggest that the site-invariant self-thinning axiom may be untenable for certain stand-types.

  11. Mixing Effects in Norway Spruce—European Beech Stands Are Modulated by Site Quality, Stand Age and Moisture Availability

    Directory of Open Access Journals (Sweden)

    Léa Houpert

    2018-02-01

    Full Text Available Although mixing tree species is considered an efficient risk-reduction strategy in the face of climate change, the conditions where mixtures are more productive than monocultures are under ongoing debate. Generalizations have been difficult because of the variety of methods used and due to contradictory findings regarding the effects of the species investigated, mixing proportions, and many site and stand conditions. Using data from 960 plots of the Swiss National Forest Inventory data, we assessed whether Picea abies (L. Karst–Fagus sylvatica L. mixed stands are more productive than pure stands, and whether the mixing effect depends on site- or stand-characteristics. The species proportions were estimated using species proportion by area, which depends on the maximum stand basal area of an unmanaged stand (BAmax. Four different alternatives were used to estimate BAmax and to investigate the effect of these differing alternatives on the estimated mixture effect. On average, the mixture had a negative effect on the growth of Picea abies. However, this effect decreased as moisture availability increased. Fagus sylvatica grew better in mixtures and this effect increased with site quality. A significant interaction between species proportions and quadratic mean diameter, a proxy for stand age, was found for both species: the older the stand, the better the growth of Fagus sylvatica and the lower the growth of Picea abies. Overyielding was predicted for 80% of the investigated sites. The alternative to estimate BAmax weakly modulated the estimated mixture effect, but it did not affect the way mixing effects changed with site characteristics.

  12. Mapping post-disturbance stand age distribution in Siberian larch forest based on a novel method

    Science.gov (United States)

    Chen, D.; Loboda, T. V.; Krylov, A.; Potapov, P.

    2014-12-01

    The Siberian larch forest, which accounts for nearly 20% of the global boreal forest biome, is unique, important, yet significantly understudied. These deciduous needleleaf forests with a single species dominance over a large continuous area are not found anywhere except the extreme continental zones of Siberia and the Russian Far East. Most of these forests are located in remote and sparsely populated areas and, therefore, little is known about spatial variability of their structure and dynamics. Wall-to-wall repeated observations of this area are available only since the 2000s. Previously, we developed methods for reconstruction of stand-age distribution from a sample of 1980-2000 disturbances in Landsat TM and ETM+ imagery. However, availability of those images in Siberian larch forests is particularly limited. Built upon the hypothesis that the spectral characteristics of the disturbed forest in the region change with time consistently, this paper proposes a novel method utilizing the newly released Global Forest Change (GFC) 2000-2012 dataset. We exploit the data-rich era of annual forest disturbance samples identified between 2000 and 2012 in the Siberian larch forest by the GFC dataset to build a robust training set of spectral signatures from regrowing larch forests as they appear in Landsat imagery in 2012. The extracted statistics are ingested into a random forest, which predicts the approximate stand age for every forested pixel in the circa 2000 composite. After merging the estimated stand age distribution for 1989-2000 with the observed disturbance records for 2001-2012, a gap-free 30 m resolution 24-year long record of stand age distribution is obtained. A preliminary accuracy assessment against the Advanced Very High Resolution Radiometer (AVHRR) burned area product suggested satisfactory performance of the proposed method.

  13. Silvicultural interpretation of natural vegetation dynamics in ageing Scots pine stands for their conversion into mixed broadleaved stands

    NARCIS (Netherlands)

    Kint, V.; Geudens, G.; Mohren, G.M.J.; Lust, N.

    2006-01-01

    In many West-European regions there is principal consensus on the conversion of homogeneous even-aged Scots pine plantations into mixed broadleaved stands. In recent years, interest is growing for conversion management in which managers try to maximise the use of natural processes by steering or

  14. Assesment of standing long jump at children of primery - school age in athletic prep school

    OpenAIRE

    Klapetková, Kristýna

    2017-01-01

    Title: Assesment of standing long jump at children of primery - school age in athletic prep school Aim: Aim of this thesis was to evaluate and compare differences of movement level in standing long jump between children of primary - school age who attend athletic prep school and those who don't. Another aim was the getting to know and the application of Haywood's and Getchell's methodology for qualitative assessment of standing long jump of children. Methodology: The movement level of standin...

  15. Spatial Structure Indices of Mature Pedunculate Oak Stands in NW Croatia

    Directory of Open Access Journals (Sweden)

    Krunoslav Indir

    2013-06-01

    Full Text Available Background and Purpose: In order to potentiate a valid comparison of forest stands, numerous indices were developed to express forest structure numerically. Each of those indices described a specific measured or calculated value. In the present study, three of the stand structure indicators, dependent on tree distance, were used: the aggregation index of Clark and Evans, the species mingling index and the diameter differentiation index. The objectives of this study were: to obtain further information about forest structure using the selected indices and to discover any limitations that the implemented indices might display. Materials and Methods: Mature pedunculate oak stands were selected as objects of the study, all located within the “Repaš – Gabajeva Greda” forest management unit, the Forest Administration of Koprivnica. The stands were aged 75 to 132 years. A systematic 500 m grid of 45 circle sample plots was established. The sample plot radius was 15, 25 or 30 meters, depending on the stand’s age. In 2001, the DBH (diameter at breast height and tree positions in regard to the centre of a plot were measured on each sample plot. The mutual distances between trees were calculated, as well as the values of the three selected stand structure indices. The two procedures of the aggregation index of Clark and Evans were calculated for all 45 sample plots. In the first case only the pedunculate oak trees were observed, and in the other all trees on the plot. The species mingling index and the diameter differentiation index were calculated for each tree in two procedures: in relatio to three and four nearest neighbouring trees. The plot/stand totals were managed as the average index of individual trees. Results: Values of the aggregation index of Clark and Evans after all trees have been observed were from 0.89 to 1.28, which indicated a random distribution of trees. In case of considering only pedunculate oak trees, the index of the plots

  16. Measuring light in uneven-aged hardwood stands

    Science.gov (United States)

    Leon S. Minckler

    1961-01-01

    Light, essential in the development of a forest, can be controlled within a stand by silvicultural practices. Measuring it, however, has always been a problem for silvicultural researchers. And accurate measurements are necessary, especially in studying the relation between light and reproduction. The desired objective is to measure the total visible light in specific...

  17. Distribution of Estimated Stand Age Across Siberian Larch Forests, 1989-2012

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides mapped estimates of the stand age of young (less than 25 years old) larch forests across Siberia from 1989-2012 at 30-m resolution. The age...

  18. Distribution of Young Forests and Estimated Stand Age across Russia, 2012

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides the distribution of young forests (forests less than 27 years of age) and their estimated stand ages across the full extent of Russia at 500-m...

  19. The magnitude of interannual variability of ecosystem photosynthetic capacity is controled by stand age and biodiversity

    Science.gov (United States)

    Musavi, Talie; Migliavacca, Mirco; Mahecha, Miguel D.; Reichstein, Markus; Kattge, Jens; Wirth, Christian; Black, T. Andrew; Janssens, Ivan; Knohl, Alexander; Loustau, Denis; Roupsard, Olivier; Varlagin, Andrej; Rambal, Serge; Cescatti, Alessandro; Gianelle, Damiano; Kondo, Hiroaki; Tamrakar, Rijan

    2017-04-01

    Gross primary productivity, GPP, the total uptake of carbon dioxide (CO2) by ecosystems via photosynthesis, is the largest flux in the global carbon cycle. The photosynthetic capacity at light saturation (GPPsat) is a fundamental ecosystem functional property and its interannual variability (IAV) is propagated to the net ecosystem exchange of CO2. In this contribution we made use of a variety of data streams consisting of ecosystem-atmosphere CO2 fluxes measured at eddy covariance flux sites with more than 4 years of data, the GPPsat derived at the different sites, information about climate (temperature, precipitation, and water availability index - WAI), biodiversity information and species richness, stand age, and plant traits, nutrient availability indexes derived from field campaigns, ancillary databases, and the literature. We also used data about forest structure derived from satellite products. Sites were selected according to the availability of eddy covariance flux measurements for at least 4 years, information about stand age, canopy cover, canopy height, and species abundance. The resulting global database consisted of 50 sites with different vegetation types across different climatic regions. Considering the importance of the understanding of IAV in CO2 fluxes to improve the predictive capacity of the global carbon cycle we analyzed a range of alternative hypotheses and potential drivers of the magnitude of IAV in GPPsat in forest ecosystems. The results show that the IAV in GPPsat within sites is driven by climate (i.e. fluctuations in air temperature and soil water availability), but the magnitude of IAV in GPPsat is related to ecosystem structure, and more in details to stand age and biodiversity (R2=0.55, p<0.0001). We conclude that irrespective of forest type the IAV of GPPsat in older and more diverse forests is dampened, and is higher in younger forests with few dominant species.

  20. Bark Beetles as Significant Forest Disturbances: Estimating Susceptibility Based On Stand Structure

    Science.gov (United States)

    Hicke, J. A.; Jenkins, J. C.

    2007-12-01

    In the western United States, bark beetle outbreaks affect millions of hectares of forests. These disturbances have multiple effects on ecosystems, including modifications to biogeochemical cycles, interactions with fire, and changes in land cover type and species composition. In recent years, extensive outbreaks have occurred in multiple forest ecosystems in the West, thought to be caused by climate variability and stand structure. In this study, we focus on epidemics of mountain pine beetle. We used USDA Forest Service inventories and a model to estimate lodgepole pine susceptibility to mountain pine beetle attack in the West. The model considers stand age, stem density, and percentage of large lodgepole pine to estimate stand susceptibility. Over 150,000 trees in 4454 plots across the western United States were used to compute susceptibility at the plot scale as well as map susceptibility at the county scale. We found that regional susceptibility was high (estimated potential of losses of 34% of stand basal area) for 2.8 Mha, or 46%, of lodgepole pine forests. The highest susceptibility occurred in the Rocky Mountains, with lower susceptibility in coastal states. This study reveals that a substantial fraction of lodgepole pine forest could be subjected to bark beetle outbreaks under current climate conditions. Because climate and weather affect beetle populations, projected future warming will influence outbreak regimes. Thus, forest ecosystems in the West may experience more frequent, extensive, and/or severe disturbances than in recent decades due to current stand structure, and these disturbances may be intensified under climate change.

  1. Determinants of tree quality and lumber value in natural uneven-aged southern pine stands

    Science.gov (United States)

    Jeffrey P. Prestemon; Joseph Buongiorno

    2000-01-01

    An ordered-probit model was developed to predict tree grade from tree- and stand-level variables, some of which could be changed by management. Applied to uneven-aged mixed loblolly (Pinus taeda L.) - shortleaf pine (Pinus echinata Mill.) stands, the model showed that the grade of pine trees was highly correlated with tree diameter...

  2. Regenerating uneven-aged stands of loblolly and shortleaf pines: the current state of knowledge

    Science.gov (United States)

    Michael G. Shelton; Michael D. Cain

    2000-01-01

    Periodic regeneration is crucial to creating or sustaining uneven-aged (UEA) stands of loblolly (Pinus taeda L.) and shortleaf (P. echinata Mill.) pines. Although both species are shade intolerant, they have silvical characteristics that are conducive to natural regeneration in UEA stands. Their seed production is fairly consistent...

  3. Age-related differences in quality of standing balance using a composite score.

    Science.gov (United States)

    Pasma, Jantsje H; Bijlsma, Astrid Y; van der Bij, Mark D W; Arendzen, J Hans; Meskers, Carel G M; Maier, Andrea B

    2014-01-01

    Age-related differences in standing balance are not detected by testing the ability to maintain balance. Quality of standing balance might be more sensitive to detect age-related differences. To study age-related differences in quality of standing balance, center of pressure (CoP) movement was evaluated using a wide range of CoP parameters in several standing conditions in healthy young and old participants. In 35 healthy young (18-30 years) and 75 healthy old (70-80 years) participants, CoP movement was assessed in eight standing conditions on a force plate, including side-by-side, one-leg, semi-tandem and tandem stance, both with eyes open and eyes closed. Direction-specific CoP composite scores were calculated from standardized single CoP parameters (mean amplitude, amplitude variability, mean velocity, velocity variability and range) in anterior-posterior (AP) and medial-lateral (ML) direction. Linear regression analysis was used to detect age-related differences in single CoP parameters and composite scores - adjusted for gender, height and weight. Overall, single CoP parameters were higher in old compared to young participants, but no single CoP parameter consistently demonstrated the largest effect size for all standing conditions. Age-related differences were demonstrated for CoP composite scores in AP direction (tandem eyes open; semi-tandem eyes closed; p CoP composite scores in ML direction were consistently higher for all standing conditions in old compared to young participants (p CoP composite scores in ML direction were the most consistent parameters to detect age-related differences in quality of standing balance in healthy participants and might be of clinical value to detect subtle changes in quality of standing balance. © 2014 S. Karger AG, Basel

  4. Stand structure and dynamics of sand pine differ between the Florida panhandle and peninsula

    Science.gov (United States)

    Drewa, P.B.; Platt, W.J.; Kwit, C.; Doyle, T.W.

    2008-01-01

    Size and age structures of stand populations of numerous tree species exhibit uneven or reverse J-distributions that can persist after non-catastrophic disturbance, especially windstorms. Among disjunct populations of conspecific trees, alternative distributions are also possible and may be attributed to more localized variation in disturbance. Regional differences in structure and demography among disjunct populations of sand pine (Pinus clausa (Chapm. ex Engelm.) Vasey ex Sarg.) in the Florida panhandle and peninsula may result from variation in hurricane regimes associated with each of these populations. We measured size, age, and growth rates of trees from panhandle and peninsula populations and then compiled size and age class distributions. We also characterized hurricanes in both regions over the past century. Size and age structures of panhandle populations were unevenly distributed and exhibited continuous recruitment; peninsula populations were evenly sized and aged and exhibited only periodic recruitment. Since hurricane regimes were similar between regions, historical fire regimes may have been responsible for regional differences in structure of sand pine populations. We hypothesize that fires were locally nonexistent in coastal panhandle populations, while periodic high intensity fires occurred in peninsula populations over the past century. Such differences in local fire regimes could have resulted in the absence of hurricane effects in the peninsula. Increased intensity of hurricanes in the panhandle and current fire suppression patterns in the peninsula may shift characteristics of sand pine stands in both regions. ?? 2007 Springer Science+Business Media B.V.

  5. Functional and structural causes of forests productivity decay with age: experimental analysis of a chrono-sequence of maritime pine stands; Causes fonctionnelles et structurales du declin de productivite des forets avec l'age: analyse experimentale d'une chronosequence de peuplements de pin maritime

    Energy Technology Data Exchange (ETDEWEB)

    Delzon, S.

    2004-06-15

    The aim of this work was to understand the causes of forest growth decline with increasing age. We investigated changes in several eco-physiological parameters in a chrono-sequence of four even-aged maritime pine stands. Above-ground productivity declined by a factor of 2.5 from the youngest to the oldest stands. This decline was explained by a decrease of gross primary production, due to a decline in both stand leaf area and foliar productivity. Our measurements clearly showed a decrease in leaf-specific hydraulic conductance with increasing tree height (50% lower in 30 m trees than in 10 m trees). We also found that needle water potential was maintained above a minimum threshold value of -2.0 MPa independently of tree age and height. This hydraulic homeostasis occurred through a decline in leaf / sapwood area ratio (hydraulic compensation) and a decline in stomatal conductance (physiological compensation). Both the increased investment in non-productive versus productive tissues and stomatal closure may have contributed to the observed decrease in foliar productivity with increasing tree height. Consequently, over-storey transpiration was reduced by a factor of three between the 10-yr and the 91-yr old stands. Nevertheless, our findings suggest that the total ecosystem evaporation remains constant in ageing forests due to an increase in under-storey transpiration, which may counterbalance the decrease in tree transpiration. Photosynthetic capacity also decreased in older stands, mainly through a decline in phosphorus concentration. Our results support the hypothesis that the age-related decline in forest growth is associated with decreased availability of the most limiting resource, this being phosphorus for the maritime Pine chrono-sequence investigated. (author)

  6. Wildlife response to stand structure of deciduous woodlands

    Science.gov (United States)

    Robert A. Hodorff; Carolyn Hull Sieg; Raymond L. Linder

    1988-01-01

    Deciduous woodlands provide important habitat for wildlife but comprise Fraxinus pennsylvanica) woodlands in northwestern South Dakota. Closed-canopy stands were multilayered communities with dense...

  7. [Biomass- and energy allocation in Eucalyptus urophylla x Eucalyptus tereticornis plantations at different stand ages].

    Science.gov (United States)

    Zhou, Qun-Ying; Chen, Shao-Xiong; Han, Fei-Yang; Chen, Wen-Ping; Wu, Zhi-Hua

    2010-01-01

    An investigation was made on the biomass- and energy allocation in 1-4-year-old Eucalyptus urophylla x Eucalyptus tereticornis plantations at Beipo Forest Farm of Suixi County in Guangdong Province. Stand age had significant effects on the retained biomass of the plantations (P branch > bark > root > leaf, and that in 3- and 4 -year-old plantations was in order of stem > root > branch > bark > leaf. The mean ash content (AC) of the five components at different stand ages ranged from 0.47% to 5.91%, being the highest in bark and the lowest in stem. The mean gross caloric value (GCV) and ash free caloric value (AFCV) of different components ranged from 17.33 to 20. 60 kJ x g(-1) and from 18.42 to 21.59 kJ x g(-1) respectively. Of all the components, leaf had the highest GVC and AFCV, while bark had the lowest ones. Stand age had significant effects on the GVC of branch, stem, and bark, and on the AFCV of leaf, stem, and bark (P 0.05). The retained energy of 1-4-year-old plantations ranged from 199.98 to 2837.20 GJ x hm(-2), with significant differences among the stand ages (P < 0.01). The retained energy of various components and plantations increased with stand age, and the energy allocation of various components had the same trend as biomass allocation.

  8. Red Alder-Conifer Stands in Alaska: An Example of Mixed Species Management to Enhance Structural and Biological Complexity

    Directory of Open Access Journals (Sweden)

    Robert L. Deal

    2017-04-01

    Full Text Available There is worldwide interest in managing forests to improve biodiversity, enhance ecosystem services and assure long-term sustainability of forest resources. An increasingly important goal of forest management is to increase stand diversity and improve wildlife and aquatic habitat. Well-planned silvicultural systems containing a mixture of broadleaf-conifer species have potential to enhance stand diversity and provide other ecosystem services earlier than typical even-aged conifer plantations. Here, we use the example of mixed Sitka spruce/western hemlock and red alder in young, managed stands in southeast Alaska to achieve these goals. We briefly describe the silvics of Sitka spruce, western hemlock and red alder plantations as pure conifer stands or pure broadleaf stands. Then, we synthesize studies of mixed red alder-Sitka spruce/western hemlock stands in southeast Alaska and present their potential for improving stand structural complexity, biodiversity and other ecosystem services over pure conifer forests. Finally, we discuss some of the opportunities and potential tradeoffs for managing mixed broadleaf-conifer stands for providing a number of natural resources and the influence of these broadleaf-conifer forests on ecosystem linkages and processes.

  9. An experimental test of the causes of forest growth decline with stand age.

    Science.gov (United States)

    Michael G. Ryan; Dan Binkley; James H. Fownes; Christian Giardina; Randy S. Senock

    2004-01-01

    The decline in aboveground wood production after canopy closure in even-aged forest stands is a common pattern in forests, but clear evidence for the mechanism causing the decline is lacking. The problem is fundamental to forest biology, commercial forestry (the decline sets the rotation age), and to carbon storage in forests. We tested three hypotheses...

  10. Changes in sensory reweighting of proprioceptive information during standing balance with age and disease

    OpenAIRE

    Pasma, J. H.; Engelhart, D.; Maier, A. B.; Schouten, A. C.; van der Kooij, H.; Meskers, C. G. M.

    2015-01-01

    With sensory reweighting, reliable sensory information is selected over unreliable information during balance by dynamically combining this information. We used system identification techniques to show the weight and the adaptive process of weight change of proprioceptive information during standing balance with age and specific diseases. Ten healthy young subjects (aged between 20 and 30 yr) and 44 elderly subjects (aged above 65 yr) encompassing 10 healthy elderly, 10 with cataract, 10 with...

  11. Examining conifer canopy structural complexity across forest ages and elevations with LiDAR data

    Science.gov (United States)

    Van R. Kane; Jonathan D. Bakker; Robert J. McGaughey; James A. Lutz; Rolf F. Gersonde; Jerry F. Franklin

    2010-01-01

    LiDAR measurements of canopy structure can be used to classify forest stands into structural stages to study spatial patterns of canopy structure, identify habitat, or plan management actions. A key assumption in this process is that differences in canopy structure based on forest age and elevation are consistent with predictions from models of stand development. Three...

  12. Simulating historical disturbance regimes and stand structures in old-forest ponderosa pine/Douglas-fir forests

    Science.gov (United States)

    Mike Hillis; Vick Applegate; Steve Slaughter; Michael G. Harrington; Helen Smith

    2001-01-01

    Forest Service land managers, with the collaborative assistance from research, applied a disturbance based restoration strategy to rehabilitate a greatly-altered, high risk Northern Rocky Mountain old-forest ponderosa pine-Douglas-fir stand. Age-class structure and fire history for the site have been documented in two research papers (Arno and others 1995, 1997)....

  13. Eucalyptus urophylla stands wood utilization at two different ages for production of particleboard panels

    Directory of Open Access Journals (Sweden)

    Lourival Marin Mendes

    2009-09-01

    Full Text Available This work aimed to assess the quality of wood particle panels manufactured with wood from Eucalyptus urophylla stands at age 7 and at age 12 years. To that end, particleboard, oriented strand board (OSB and cement-bonded panels were produced in a laboratory and then analyzed for the following physical and mechanical properties: water absorption and thickness swell 2 and 24 hours after immersion, internal bond, compression parallel, as well as MOE and MOR from static bending. The obtained results demonstrate that tree age had little influence on the physical and mechanical properties of particleboard, OSB and cement-bonded panels. After evaluating the physical and mechanical properties of these three panel types, all manufactured with wood from Eucalyptus urophylla stands at age 7 and at age 12, we can argue that our results are satisfactory in comparison to existing literature results.

  14. Bryophyte species associations with coarse woody debris and stand ages in Oregon

    Science.gov (United States)

    Rambo, T.; Muir, Patricia S.

    1998-01-01

    We quantified the relationships of 93 forest floor bryophyte species, including epiphytes from incorporated litterfall, to substrate and stand age in Pseudotsuga menziesii-Tsuga heterophylla stands at two sites in western Oregon. We used the method of Dufrêne and Legendre that combines a species' relative abundance and relative frequency, to calculate that species' importance in relation to environmental variables. The resulting "indicator value" describes a species' reliability for indicating the given environmental parameter. Thirty-nine species were indicative of either humus, a decay class of coarse woody debris, or stand age. Bryophyte community composition changed along the continuum of coarse woody debris decomposition from recently fallen trees with intact bark to forest floor humus. Richness of forest floor bryophytes will be enhanced when a full range of coarse woody debris decay classes is present. A suite of bryophytes indicated old-growth forest. These were mainly either epiphytes associated with older conifers or liverworts associated with coarse woody debris. Hardwood-associated epiphytes mainly indicated young stands. Mature conifers, hardwoods, and coarse woody debris are biological legacies that can be protected when thinning managed stands to foster habitat complexity and biodiversity, consistent with an ecosystem approach to forest management.

  15. Mapping Deciduous Rubber Plantation Areas and Stand Ages with PALSAR and Landsat Images

    Directory of Open Access Journals (Sweden)

    Weili Kou

    2015-01-01

    Full Text Available Accurate and updated finer resolution maps of rubber plantations and stand ages are needed to understand and assess the impacts of rubber plantations on regional ecosystem processes. This study presented a simple method for mapping rubber plantation areas and their stand ages by integration of PALSAR 50-m mosaic images and multi-temporal Landsat TM/ETM+ images. The L-band PALSAR 50-m mosaic images were used to map forests (including both natural forests and rubber trees and non-forests. For those PALSAR-based forest pixels, we analyzed the multi-temporal Landsat TM/ETM+ images from 2000 to 2009. We first studied phenological signatures of deciduous rubber plantations (defoliation and foliation and natural forests through analysis of surface reflectance, Normal Difference Vegetation Index (NDVI, Enhanced Vegetation Index (EVI, and Land Surface Water Index (LSWI and generated a map of rubber plantations in 2009. We then analyzed phenological signatures of rubber plantations with different stand ages and generated a map, in 2009, of rubber plantation stand ages (≤5, 6–10, >10 years-old based on multi-temporal Landsat images. The resultant maps clearly illustrated how rubber plantations have expanded into the mountains in the study area over the years. The results in this study demonstrate the potential of integrating microwave (e.g., PALSAR and optical remote sensing in the characterization of rubber plantations and their expansion over time.

  16. Biological and Economic Productivity of Mixed-Aged Loblolly Pine Stands in the South

    Science.gov (United States)

    Ronald Raunikar; Joseph Buongiorno; Jeffrey P. Prestemon; Karen Lee-Abt

    1999-01-01

    The financial performance of the 991 sample plots of uneven-aged loblolly-hardwood stands in the Central South FIA database examined in this report depend crucially on real price trends. Equivalent annual income (EAI) is the measure of economic performance. The regional market stumpage price data are from the Timber Mart-South database. For this set of prices, a...

  17. Does Prescribed Burning Have a Place in Regenerating Uneven-Aged Loblolly-Shortleaf Pine Stands?

    Science.gov (United States)

    Michael D. Cain; Michael G. Shelton

    2002-01-01

    Before the 1981 growing season, a study was installed in southeastern Arkansas to examine the effects of three dormant-season burn intervals (low, moderate, and high frequency) and an unburned treatment on natural regeneration in uneven-aged stands of loblolly and shortleaf pines (Pinus taeda and P. echinata, respectively)....

  18. Stand structure, recruitment and growth dynamics in mixed subalpine spruce and Swiss stone pine forests in the Eastern Carpathians.

    Science.gov (United States)

    Popa, Ionel; Nechita, Constantin; Hofgaard, Annika

    2017-11-15

    Natural subalpine forests are considered to be sensitive to climate change, and forest characteristics are assumed to reflect the prevalent disturbance regime. We hypothesize that stand history determines different stand structures. Based on large full inventory datasets (including tree biometric data, spatial coordinates, tree age, and basal area increment) we assessed the size structure, tree recruitment dynamics and radial growth patterns in three permanent plots along an altitudinal gradient in a mixed coniferous forest (Picea abies and Pinus cembra) in the Eastern Carpathians. Both discrete disturbances (large scale or small scale) and chronic disturbances (climate change) were identified as drivers of stand structure development in the studied plots. A stand replacing wind disturbance generated a unimodal bell-shaped size and age distribution for both species characterized by a sharp increase in post-disturbance recruitment. By contrast, small-scale wind-caused gaps led to a negative exponential diameter distribution for spruce and a left-asymmetric unimodal for pine. Climate-driven infilling processes in the upper subalpine forest were reflected as J-shaped size and age distributions for both species, but with pine predating spruce. The growth patterns for both species demonstrated an increased basal area increment since the early 1900s, with an emphasis in the last few decades, irrespective of stand history. Pine demonstrated a competitive advantage compared to spruce due to the higher growth rate and size at the same age. Recognition of combined discrete and chronic disturbances as drivers of the tree layer characteristics in a subalpine coniferous forest is essential in both stand history analyses and growth predictions. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. How to formulate and solve "optimal stand density over time" problems for even-aged stands using dynamic programming.

    Science.gov (United States)

    Chung M. Chen; Dietmar W. Rose; Rolfe A. Leary

    1980-01-01

    Describes how dynamic programming can be used to solve optimal stand density problems when yields are given by prior simulation or by a new stand growth equation that is a function of the decision variable. Formulations of the latter type allow use of a calculus-based search procedure; they determine exact optimal residual density at each stage.

  20. Optimal uneven-aged stocking guides: an application to spruce-fir stands in New England

    Science.gov (United States)

    Jeffrey H. Gove; Mark J. Ducey

    2014-01-01

    Management guides for uneven-aged forest stands periodically need to be revisited and updated based on new information and methods. The current silvicultural guide for uneven-aged spruce-fir management in Maine and the northeast (Frank, R.M. and Bjorkbom, J.C. 1973 A silvicultural guide for spruce-fir in the northeast. General Technical Report NE-6, Forest Service. U.S...

  1. The Multivariate Largest Lyapunov Exponent as an Age-Related Metric of Quiet Standing Balance

    Directory of Open Access Journals (Sweden)

    Kun Liu

    2015-01-01

    Full Text Available The largest Lyapunov exponent has been researched as a metric of the balance ability during human quiet standing. However, the sensitivity and accuracy of this measurement method are not good enough for clinical use. The present research proposes a metric of the human body’s standing balance ability based on the multivariate largest Lyapunov exponent which can quantify the human standing balance. The dynamic multivariate time series of ankle, knee, and hip were measured by multiple electrical goniometers. Thirty-six normal people of different ages participated in the test. With acquired data, the multivariate largest Lyapunov exponent was calculated. Finally, the results of the proposed approach were analysed and compared with the traditional method, for which the largest Lyapunov exponent and power spectral density from the centre of pressure were also calculated. The following conclusions can be obtained. The multivariate largest Lyapunov exponent has a higher degree of differentiation in differentiating balance in eyes-closed conditions. The MLLE value reflects the overall coordination between multisegment movements. Individuals of different ages can be distinguished by their MLLE values. The standing stability of human is reduced with the increment of age.

  2. Object-oriented classification of forest structure from light detection and ranging data for stand mapping

    Science.gov (United States)

    Alicia A. Sullivan; Robert J. McGaughey; Hans-Erik Andersen; Peter. Schiess

    2009-01-01

    Stand delineation is an important step in the process of establishing a forest inventory and provides the spatial framework for many forest management decisions. Many methods for extracting forest structure characteristics for stand delineation and other purposes have been researched in the past, primarily focusing on high-resolution imagery and satellite data. High-...

  3. Proximity effects in free-standing EBID structures

    International Nuclear Information System (INIS)

    Burbridge, Daniel J; Gordeev, Sergey N

    2009-01-01

    Proximity effects causing thickening and bending of closely spaced, free-standing pillars grown by electron-beam-induced deposition are investigated. It is shown that growth of a new pillar induces deposition of a layer of additional material on the side of already grown pillars facing the new pillar. We present experimental results which suggest that the bending of pillars is caused by shrinkage of the newly formed layer on exposure to the primary electron beam.

  4. Are the Economically Optimal Harvesting Strategies of Uneven-Aged Pinus nigra Stands Always Sustainable and Stabilizing?

    Directory of Open Access Journals (Sweden)

    Carmen Fullana-Belda

    2013-10-01

    Full Text Available Traditional uneven-aged forest management seeks a balance between equilibrium stand structure and economic profitability, which often leads to harvesting strategies concentrated in the larger diameter classes. The sustainability (i.e., population persistence over time and influence of such economically optimal strategies on the equilibrium position of a stand (given by the stable diameter distribution have not been sufficiently investigated in prior forest literature. This article therefore proposes a discrete optimal control model to analyze the sustainability and stability of the economically optimal harvesting strategies of uneven-aged Pinus nigra stands. For this model, we rely on an objective function that integrates financial data of harvesting operations with a projection matrix model that can describe the population dynamics. The model solution reveals the optimal management schedules for a wide variety of scenarios. To measure the distance between the stable diameter distribution and the economically optimal harvesting strategy distribution, the model uses Keyfitz’s delta, which returns high values for all the scenarios and, thus, suggests that those economically optimal harvesting strategies have an unstabilizing influence on the equilibrium positions. Moreover, the economically optimal harvesting strategies were unsustainable for all the scenarios.

  5. Aging in a Structural Glass

    OpenAIRE

    Kob, Walter; Barrat, Jean-Louis

    1998-01-01

    We discuss the relaxation dynamics of a simple structural glass which has been quenched below its glass transition temperature. We demonstrate that time correlation functions show strong aging effects and investigate in what way the fluctuation dissipation theorem is violated.

  6. Forest structure and plant diversity in maritime pine (Pinus pinaster Ait.) stands in central Spain

    Energy Technology Data Exchange (ETDEWEB)

    Osorio, L. F.; Bravo, F.; Zaldivar, P.; Pando, V.

    2009-07-01

    The relationship between forest structure and plant diversity in Mediterranean Maritime pine stands (Pinus pinaster Ait.) in the Iberian Range (Spain) was studied. Forty eight stands were sampled. In each, a circular plot (15 m radius) and a transect (25*1 m{sup 2}) were established to estimate stand variables and record presence and abundance of vascular species respectively. Canonical correlation analysis (CCA), simple correlations and multiple stepwise linear regressions were used to explore the relationship between plant diversity and forest structure. Correlation between diversity measurements and stand variables is very weak, but significant correlations were found when evaluating each set of variables separately. Presence and cover of some species (for instance, Veronica arvensis L. or Micropyrum tenellum (L.) Link) is correlated with stand variables; however, determination coefficients found in step-by-step regression are not significant. (Author) 34 refs.

  7. Declining forest productivity in aging forest stands: a modeling analysis of alternative hypotheses.

    Science.gov (United States)

    Murty, Danuse; McMurtrie, Ross E.; Ryan, Michael G.

    1996-01-01

    Several explanations have been advanced to account for the decline in forest net primary productivity (NPP) with age in closed-canopy stands including the hypotheses that: (1) sapwood maintenance respiration rate increases, reducing the availability of carbon to support new growth; (2) stomatal conductance and hence photosynthetic efficiency decline; and (3) soil nutrient availability declines. To evaluate these hypotheses we applied the ecosystem model G'DAY to a 40- and a 245-year-old stand of lodgepole pine (Pinus contorta Dougl. ex Loud.), growing on infertile soils. Net primary productivity estimated from biomass data was 0.47 and 0.25 kg C m(-2) year(-1) and foliar nitrogen/carbon ratio (N/C) was 0.0175 and 0.017 for the 40- and 245-year-old stands, respectively. Productivities of the young and old stands were derived from a graphical analysis of the G'DAY model. The graphical analysis also indicated that the observed age-related decline in NPP can be explained in terms of interacting processes associated with Hypotheses 2 and 3. However, the relative importance of these two hypotheses differed depending on key model assumptions, in particular those relating to variation in soil N/C ratio. Thus, if we assumed that soil N/C ratio can vary significantly during stand development, then Hypotheses 2 and 3 jointly explain the decline in NPP, whereas if we assumed that soil N/C ratios are constant, then Hypothesis 3 alone explains the decline in NPP. The analysis revealed that only a small fraction of the decline of NPP can be explained in terms of increasing sapwood respiration.

  8. Jumping Stand Apparatus Reveals Rapidly Specific Age-Related Cognitive Impairments in Mouse Lemur Primates.

    Directory of Open Access Journals (Sweden)

    Jean-Luc Picq

    Full Text Available The mouse lemur (Microcebus murinus is a promising primate model for investigating normal and pathological cerebral aging. The locomotor behavior of this arboreal primate is characterized by jumps to and from trunks and branches. Many reports indicate insufficient adaptation of the mouse lemur to experimental devices used to evaluate its cognition, which is an impediment to the efficient use of this animal in research. In order to develop cognitive testing methods appropriate to the behavioral and biological traits of this species, we adapted the Lashley jumping stand apparatus, initially designed for rats, to the mouse lemur. We used this jumping stand apparatus to compare performances of young (n = 12 and aged (n = 8 adults in acquisition and long-term retention of visual discriminations. All mouse lemurs completed the tasks and only 25 trials, on average, were needed to master the first discrimination problem with no age-related differences. A month later, all mouse lemurs made progress for acquiring the second discrimination problem but only the young group reached immediately the criterion in the retention test of the first discrimination problem. This study shows that the jumping stand apparatus allows rapid and efficient evaluation of cognition in mouse lemurs and demonstrates that about half of the old mouse lemurs display a specific deficit in long-term retention but not in acquisition of visual discrimination.

  9. Structural aging program status report

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.; Graves, H.L. III

    1994-01-01

    Research is being conducted at the Oak Ridge National Laboratory under Nuclear Regulatory Commission (USNRC) sponsorship to address aging management of safety-related concrete structures. Documentation is being prepared to provide the USNRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Program accomplishments have included development of the Structural Materials Information Center containing data and information on the time variation of 144 material properties under the influence of pertinent environmental stressors or aging factors, performance assessments of reinforced concrete structures in several United Kingdom nuclear power facilities, evaluation of European and North American repair practices for concrete, an evaluation of factors affecting the corrosion of metals embedded in concrete, and application of the time-dependent reliability methodology to reinforced concrete flexure and shear structural elements to investigate the role of in-service inspection and repair on their probability of failure

  10. Diversity of Soil Macrofauna at Different Stages of the Age of Sengon’s Stand in Jatirejo, Kediri

    Directory of Open Access Journals (Sweden)

    SUGIYARTO

    2000-07-01

    Full Text Available Soil fauna have important roles on increasing and maintaining soil productivity through it’s function on organic decomposition processes, and optimizing physics, chemist and biology of soil characters. The research was conducted to investigate structure of the community of soil macrofauna from different stages of the age of sengon’s (Paraserianthes falcataria stand in wet season of year 2000. Pit fall trap and hand-shorting methods were used to catch soil macrofauna. Sampling was done on 8 different age stages (year of sengon plant each with triplicate repetition. Twenty-seven macrofauna species in the soil and 26 macrofauna species in soil surface were found in this study. Those species belong to the phylum of Mollusc, Annelid and Arthropod. Pontoscolex sp and Lobopelta ocellifera were species that having high important value. Similarities analysis resulting in an index of 65% indicating low level of diversity differences among soil macrofauna from different ages of the sengon stand. Simple correlation analysis indicates that macrofauna diversity in the soil was closely related with soil organic content, domination of ground vegetation and soil humidity; while macrofauna diversity of soil surface was closely related with the level of light penetration.

  11. An evaluation of uneven-aged cutting methods in even-aged oak-hickory stands in the Boston mountains of Arkansas

    Science.gov (United States)

    David L. Graney; Paul A. Murphy

    1997-01-01

    A test of group-selection and single-tree selection cutting methods was installed in 80-year-old even-aged oak-hickory stands in the Boston Mountains of northern Arkansas. Twenty-four 11-ac study plots were installed in well stocked stands representing north or east and south or west aspects. Stands between group openings were cut to residual basal areas of 65 and 85...

  12. Modelling Variable Fire Severity in Boreal Forests: Effects of Fire Intensity and Stand Structure.

    Science.gov (United States)

    Miquelajauregui, Yosune; Cumming, Steven G; Gauthier, Sylvie

    2016-01-01

    It is becoming clear that fires in boreal forests are not uniformly stand-replacing. On the contrary, marked variation in fire severity, measured as tree mortality, has been found both within and among individual fires. It is important to understand the conditions under which this variation can arise. We integrated forest sample plot data, tree allometries and historical forest fire records within a diameter class-structured model of 1.0 ha patches of mono-specific black spruce and jack pine stands in northern Québec, Canada. The model accounts for crown fire initiation and vertical spread into the canopy. It uses empirical relations between fire intensity, scorch height, the percent of crown scorched and tree mortality to simulate fire severity, specifically the percent reduction in patch basal area due to fire-caused mortality. A random forest and a regression tree analysis of a large random sample of simulated fires were used to test for an effect of fireline intensity, stand structure, species composition and pyrogeographic regions on resultant severity. Severity increased with intensity and was lower for jack pine stands. The proportion of simulated fires that burned at high severity (e.g. >75% reduction in patch basal area) was 0.80 for black spruce and 0.11 for jack pine. We identified thresholds in intensity below which there was a marked sensitivity of simulated fire severity to stand structure, and to interactions between intensity and structure. We found no evidence for a residual effect of pyrogeographic region on simulated severity, after the effects of stand structure and species composition were accounted for. The model presented here was able to produce variation in fire severity under a range of fire intensity conditions. This suggests that variation in stand structure is one of the factors causing the observed variation in boreal fire severity.

  13. Age-gender differences in the postural sway during squat and stand-up movement.

    Science.gov (United States)

    Kim, Ji-Won; Kwon, Yuri; Ho, Yeji; Jeon, Hyeong-Min; Bang, Min-Jung; Jun, Jae-Hoon; Eom, Gwang-Moon; Park, Byung Kyu; Cho, Yeong Bin

    2014-01-01

    Incidence of falling among elderly female has been reported to be much higher than that of elderly male. Although the gender differences in the elderly were reported for the static postural sway, there has been no investigation of the gender difference for the dynamic postural sway. This study investigates how age and gender affect the postural sway during dynamic squat and stand-up movement. 124 subjects (62 subjects for each of young and elderly) performed consecutive squat and stand-up movement, 2 times in one session, and 2 sessions per subject. Center of pressure (COP) was measured using force platform during the test. Outcome measures included peak-to-peak sways of the COP (COP sway) in the sagittal plane (anteroposterior) and frontal plane (mediolateral) and also those normalized by body height. Two-way ANOVA and post-hoc comparisons were performed for the outcome measures with the independent factors of age and gender. All outcome measures, excluding mediolateral COP sway, showed significant interaction of age and gender (pelderly female than elderly male. This may be related to the greater fall rate of elderly female than that of elderly men while performing dynamic activities.

  14. Declining forest productivity in aging forest stands: a modeling analysis of alternative hypotheses

    Energy Technology Data Exchange (ETDEWEB)

    Murty, D.; McMurtrie, R. E. [New South Wales Univ., Sydney, NSW (Australia); Ryan, M. G. [Forest Service, Fort Collins, CO (United States). Rocky Mountain Forest and Range Experiment Station

    1996-01-01

    Various hypotheses regarding the decline in forest net primary productivity (NPP) with age in closed-canopy stands were evaluated by graphical analysis using the G`DAY model. Results indicated that the interaction between decline in stomatal conductance, hence photosynthetic efficiency and decline in soil nutrient availability, provided the most plausible answer to reduced productivity, although the relative importance of these two explanations varied according to certain key model assumptions. Increased sapwood respiration, one of the hypotheses tested, was found to have only a minor effect on the decline of forest productivity. 60 refs., 6 figs.

  15. A stand-alone demography and landscape structure module for Earth system models

    Science.gov (United States)

    Nieradzik, L. P.; Haverd, V.; Smith, B.; Cook, G. D.; Briggs, P.; Roxburgh, S.; Liedloff, A.; Meyer, C.; Canadell, J.

    2013-12-01

    We propose and demonstrate a new approach for the simulation of woody ecosystem stand dynamics, demography and disturbance-mediated heterogeneity suitable for continental to global applications and designed for coupling to the terrestrial ecosystem component of any earth system model (Haverd et al., 2013). The approach is encoded in a model called Populations-Order-Physiology (POP). We demonstrate the behaviour and performance of POP coupled to the Community Atmosphere Biosphere Land Exchange model (CABLE) for two contrasting applications: (i) to the Northern Australian Tropical Transect, featuring gradients in savanna vegetation cover, rainfall and fire disturbance and (ii) to a set of globally distributed forest locations coinciding with observations of forest biomass allometry. Along the Northern Australian Tropical Transect, CABLE-POP is able to simultaneously reproduce observation-based estimates of key functional and structural variables, namely gross primary production, tree foliage projective cover, basal area and maximum tree height. This application particularly demonstrates the ability of POP to quantify the contributions of drought and fire to tree mortality. Drought is manifested as an increase in mortality due to a decline in growth efficiency, while fires are treated as partial disturbance events, with tree mortality depending on tree size and fire intensity. In the application to global forests, POP is integrated with global forest data by calibrating it against paired observations of stem biomass and number density. The calibrated POP model is then coupled with CABLE and the coupled model is evaluated against leaf-stem allometry observations from forest stands ranging in age from 20 to 400 years. Results indicate that, in contrast to simulations from many global land surface models (Wolf et al., 2011), simulated biomass pools conform well with observed allometry. We conclude that POP, which can readily be coupled to the terrestrial carbon cycle

  16. Stand structure and dead wood characterization in cork forest of Calabria region (southern Italy

    Directory of Open Access Journals (Sweden)

    Barreca L

    2010-07-01

    Full Text Available The cork forests are one the most interesting forest ecosystems in the Mediterranean area. Their distribution and ecological characteristics have undergone a significant transformation after the significant changes following the development and establishment of agricultural crops. Currently, only a few stands, which survive in hard to reach places, prove the wide spread distribution of this species was also in the recent past. This study describes the stand structure of some cork forests in Calabria region (southern Italy. In order, to characterize the vertical structure Latham index has been applied, while for the description of the horizontal distribution NBSI group indices has been used. Detailed surveys on dead wood were also conducted determining the occurring volume and its decay stage according to the decay classes system proposed by Hunter. The aim of this study is to provide guidelines for sustainable management of cork forests, improving and promoting the structural complexity and functional efficiency of these forest stands.

  17. STATUS OF X-BAND STANDING WAVE STRUCTURE STUDIES AT SLAC

    International Nuclear Information System (INIS)

    Dolgashev, Valery A.

    2003-01-01

    The linacs proposed for the Next Linear Collider (NLC) and Japanese Linear Collider (JLC) would contain several thousand X-Band accelerator structures that would operate at a loaded gradient of 50 MV/m. An extensive experimental and theoretical program is underway at SLAC, FNAL and KEK to develop structures that reliably operate at this gradient. The development of standing wave structures is a part of this program. The properties of standing wave structures allow them to operate at the loaded gradient in contrast to traveling wave structures that need conditioning to the unloaded gradient (65 MV/m for NLC/JLC). The gradients in the standing structures tested thus far have been limited by input coupler breakdowns. The behavior of these breakdowns is consistent with a model of pulsed heating due to high magnetic fields. New input couplers have been designed to reduce maximum magnetic fields. This paper discusses design considerations related to high power performance, wakefield suppression and results of high power tests of prototype standing wave structures

  18. Tree Age Effects on Fine Root Biomass and Morphology over Chronosequences of Fagus sylvatica, Quercus robur and Alnus glutinosa Stands.

    Science.gov (United States)

    Jagodzinski, Andrzej M; Ziółkowski, Jędrzej; Warnkowska, Aleksandra; Prais, Hubert

    2016-01-01

    There are few data on fine root biomass and morphology change in relation to stand age. Based on chronosequences for beech (9-140 years old), oak (11-140 years) and alder (4-76 years old) we aimed to examine how stand age affects fine root biomass and morphology. Soil cores from depths of 0-15 cm and 16-30 cm were used for the study. In contrast to previously published studies that suggested that maximum fine root biomass is reached at the canopy closure stage of stand development, we found almost linear increases of fine root biomass over stand age within the chronosequences. We did not observe any fine root biomass peak in the canopy closure stage. However, we found statistically significant increases of mean fine root biomass for the average individual tree in each chronosequence. Mean fine root biomass (0-30 cm) differed significantly among tree species chronosequences studied and was 4.32 Mg ha(-1), 3.71 Mg ha(-1) and 1.53 Mg ha(-1), for beech, oak and alder stands, respectively. The highest fine root length, surface area, volume and number of fine root tips (0-30 cm soil depth), expressed on a stand area basis, occurred in beech stands, with medium values for oak stands and the lowest for alder stands. In the alder chronosequence all these values increased with stand age, in the beech chronosequence they decreased and in the oak chronosequence they increased until ca. 50 year old stands and then reached steady-state. Our study has proved statistically significant negative relationships between stand age and specific root length (SRL) in 0-30 cm soil depth for beech and oak chronosequences. Mean SRLs for each chronosequence were not significantly different among species for either soil depth studied. The results of this study indicate high fine root plasticity. Although only limited datasets are currently available, these data have provided valuable insight into fine root biomass and morphology of beech, oak and alder stands.

  19. Thermophysical, mechanical and microstructural characterization of aged free-standing plasma-sprayed zirconia coatings

    Energy Technology Data Exchange (ETDEWEB)

    Cernuschi, F. [CESI RICERCA, Via Rubattino 54, 20134 Milano (Italy)], E-mail: federico.cernuschi@cesiricerca.it; Bison, P.G.; Marinetti, S. [CNR ITC, Corso Stati Uniti 4, 35100 Padova (Italy); Scardi, P. [Department of Materials Engineering and Industrial Technologies, University of Trento, 38100 via Mesiano 77, Trento (Italy)

    2008-10-15

    The effect of porosity on the thermal diffusivity and elastic modulus has been studied on artificially aged, free-standing thermal barrier coatings (TBCs) produced by air plasma spray (APS). The activation energy of the sintering phenomenon was estimated from the variation in diffusivity with time and temperature. X-ray diffraction was used to evaluate the phase stability of 7 wt.% yttria partially stabilized zirconia (YPSZ) coatings. The thermal diffusivity and elastic modulus as measured by photothermal techniques and three-point bending, respectively, are reported as a function of the ageing time. Correlations between the thermal and mechanical parameters are investigated by suitable models based on the microstructural features revealed by electron microscopy. The reliability of porosity information provided by image analysis and used as input for the modelling is critically discussed.

  20. Thermophysical, mechanical and microstructural characterization of aged free-standing plasma-sprayed zirconia coatings

    International Nuclear Information System (INIS)

    Cernuschi, F.; Bison, P.G.; Marinetti, S.; Scardi, P.

    2008-01-01

    The effect of porosity on the thermal diffusivity and elastic modulus has been studied on artificially aged, free-standing thermal barrier coatings (TBCs) produced by air plasma spray (APS). The activation energy of the sintering phenomenon was estimated from the variation in diffusivity with time and temperature. X-ray diffraction was used to evaluate the phase stability of 7 wt.% yttria partially stabilized zirconia (YPSZ) coatings. The thermal diffusivity and elastic modulus as measured by photothermal techniques and three-point bending, respectively, are reported as a function of the ageing time. Correlations between the thermal and mechanical parameters are investigated by suitable models based on the microstructural features revealed by electron microscopy. The reliability of porosity information provided by image analysis and used as input for the modelling is critically discussed

  1. Age structure and growth of California black oak (Quercus kelloggii) in the central Sierra Nevada, California

    Science.gov (United States)

    Barrett A. Garrison; Christopher D. otahal; Matthew L. Triggs

    2002-01-01

    Age structure and growth of California black oak (Quercus kelloggii) was determined from tagged trees at four 26.1-acre study stands in Placer County, California. Stands were dominated by large diameter (>20 inch dbh) California black oak and ponderosa pine (Pinus ponderosa). Randomly selected trees were tagged in June-August...

  2. Predicting temperate forest stand types using only structural profiles from discrete return airborne lidar

    Science.gov (United States)

    Fedrigo, Melissa; Newnham, Glenn J.; Coops, Nicholas C.; Culvenor, Darius S.; Bolton, Douglas K.; Nitschke, Craig R.

    2018-02-01

    Light detection and ranging (lidar) data have been increasingly used for forest classification due to its ability to penetrate the forest canopy and provide detail about the structure of the lower strata. In this study we demonstrate forest classification approaches using airborne lidar data as inputs to random forest and linear unmixing classification algorithms. Our results demonstrated that both random forest and linear unmixing models identified a distribution of rainforest and eucalypt stands that was comparable to existing ecological vegetation class (EVC) maps based primarily on manual interpretation of high resolution aerial imagery. Rainforest stands were also identified in the region that have not previously been identified in the EVC maps. The transition between stand types was better characterised by the random forest modelling approach. In contrast, the linear unmixing model placed greater emphasis on field plots selected as endmembers which may not have captured the variability in stand structure within a single stand type. The random forest model had the highest overall accuracy (84%) and Cohen's kappa coefficient (0.62). However, the classification accuracy was only marginally better than linear unmixing. The random forest model was applied to a region in the Central Highlands of south-eastern Australia to produce maps of stand type probability, including areas of transition (the 'ecotone') between rainforest and eucalypt forest. The resulting map provided a detailed delineation of forest classes, which specifically recognised the coalescing of stand types at the landscape scale. This represents a key step towards mapping the structural and spatial complexity of these ecosystems, which is important for both their management and conservation.

  3. Stand structure and recent climate change constrain stand basal area change in European forests: a comparison across boreal, temperate and Mediterranean biomes

    OpenAIRE

    Ruiz-Benito, Paloma; Madrigal-Gonzalez, Jaime; Ratcliffe, S.; Coomes, D.C.; Kändler, G.; Lehtonen, A.; Wirth, C.; Zavala, M.A.

    2014-01-01

    European forests have a prominent role in the global carbon cycle and an increase in carbon storage has been consistently reported during the 20th century. Any further increase in forest carbon storage, however, could be hampered by increases in aridity and extreme climatic events. Here we use forest inventory data to identify the relative importance of stand structure (stand basal area and mean d.b.h.), mean climate (water availability) and recent climate change (temperature a...

  4. Proceedings of standing conference on health and safety in the nuclear age

    International Nuclear Information System (INIS)

    1990-01-01

    From 5 to 6 December 1989 the second meeting of the Standing Conference on Health and Safety in the Nuclear Age was held in Brussels. The subject of the meeting was informing the public on improvements in emergency preparedness and nuclear accident management. The Standing Conference was created by the Commission of the European Communities in 1986 and its goal is to convey to the European public, via the mass media, factual information on nuclear subjects of current interest. About 100 experts and representatives of the mass media, competent authorities and socio-economic organizations followed the meeting, the specific objective of which was to discuss, from the point of view of radiation protection of the public and the environment, the improvements that nuclear accident management and intervention plans have undergone in recent years. Invited contributions underlined the presently improved levels of international and Community cooperation in radiation and nuclear safety, particularly in the fields of emergency preparedness and planning, where recent years have witnessed significant developments. The conference requested the Commission to pursue its public information efforts aimed at improving the understanding that the citizens of the Community have on the potential risks and the protective measures which were implemented in the nuclear sphere

  5. A conversion method of young hornbeam coppices and its possible impact on future stand structural attributes

    Directory of Open Access Journals (Sweden)

    Cezar Tulbure

    2012-12-01

    Full Text Available The paper analyse the substitution of hornbeam coppice stands and conversion into high forest stands, formed by species that better valorise the site conditions. An improved alternative for the method of substitution in corridors is presented. The main goal of this new substitution-conversion alternative is to gradually conduct the actual structure of the coppice stands towards the target structure imposed by the forest management objectives, without a total elimination of the species that will be substituted. Two plot areas were selected in order to put into practice the proposed method. Bands were created for reducing the effective costs of the substitution process. 450 respectively 468, small seedlings (of beech, pedunculate oak and sessile oak per hectare were planted in the created bands. The planting scheme took into account the shadow tolerance of the species from the target composition. Based on the field data and using the yield tables, the evolution of the stands in the two selected plots was simulated. In this respect, the forest treatments were parameterized according to the Romanian forest rules regarding the application of thinning and regeneration cuttings. The substitution-conversion process started from an almost pure hornbeam coppice and, simulating the application of the proposed method for 120 years, it was predicted that the method allows directing the actual stand structure to the target structure. The dynamics of species and structural diversity were assessed and the results of 120 years simulation indicate an important increase of both the species (the Shannon species index increases from 0.203 to 1.073 and structural diversity (the Gini structural index increases from 0.032 to 0.200. 

  6. Floristic diversity, stand structure, and composition 11 years after herbicide site preparation

    Science.gov (United States)

    James H. Miller; Robert S. Boyd; M. Boyd. Edwards

    1999-01-01

    This study tested for effects of site preparation herbicides applied at high labeled rates 11 years earlier on plant species richness, diversity, and stand structure and composition. Four study sites in three physiographic provinces were established in central Georgia in 1984. Six herbicide treatments were included on each site: hexazinone liquid, hexazinone pellets,...

  7. A data structure for describing sampling designs to aid in compilation of stand attributes

    Science.gov (United States)

    John C. Byrne; Albert R. Stage

    1988-01-01

    Maintaining permanent plot data with different sampling designs over long periods within an organization, and sharing such information between organizations, requires that common standards be used. A data structure for the description of the sampling design within a stand is proposed. It is composed of just those variables and their relationships needed to compile...

  8. Species richness, abundance, and composition of hypogeous and epigeous ectomycorrhizal fungal sporocarps in young, rotation-age, and old-growth stands of Douglas-fir (Pseudotsuga menziesii) in the Cascade Range of Oregon, U.S.A.

    Science.gov (United States)

    J.E. Smith; R. Molina; M.M.P. Huso; D.L. Luoma; D. McKay; M.A. Castellano; T. Lebel; Y. Valachovic

    2002-01-01

    Knowledge of the community structure of ectomycorrhizal fungi among successional forest age-classes is critical for conserving fungal species diversity. Hypogeous and epigeous sporocarps were collected from three replicate stands in each of three forest age-classes (young, rotation-age, and old-growth) of Douglas-fir (Pseudotsuga menziesii (Mirb.)...

  9. Effects of Age and Stand Density of Mother Trees on Early Pinus thunbergii Seedling Establishment in the Coastal Zone, China

    Directory of Open Access Journals (Sweden)

    Peili Mao

    2014-01-01

    Full Text Available Effects of age and stand density of mother tree on seed germination, seedling biomass allocation, and seedling growth of Pinus thunbergii were studied. The results showed that age of mother tree did not have significant influences on seed germination, but it was significant on seedling biomass allocation and growth. Seedlings from the minimum and maximum age of mother tree had higher leaf mass ratio and lower root mass ratio than from the middle age of mother tree. Moreover, they also had higher relative height growth rate and slenderness, which were related to their biomass allocation. Stand density of mother tree mainly demonstrated significant effects on seed germination and seedling growth. Seed from higher stand density of mother tree did not decrease germination rate, but had higher mean germination time, indicating that it delayed germination process. Seedlings of higher stand density of mother tree showed higher relative height growth rate and slenderness. These traits of offspring from higher stand density of mother tree were similar to its mother, indicating significant environmental maternal effects. So, mother tree identity of maternal age and environments had important effects on natural regeneration of the coastal P. thunbergii forest.

  10. Effects of age and stand density of mother trees on early Pinus thunbergii seedling establishment in the coastal zone, China.

    Science.gov (United States)

    Mao, Peili; Han, Guangxuan; Wang, Guangmei; Yu, Junbao; Shao, Hongbo

    2014-01-01

    Effects of age and stand density of mother tree on seed germination, seedling biomass allocation, and seedling growth of Pinus thunbergii were studied. The results showed that age of mother tree did not have significant influences on seed germination, but it was significant on seedling biomass allocation and growth. Seedlings from the minimum and maximum age of mother tree had higher leaf mass ratio and lower root mass ratio than from the middle age of mother tree. Moreover, they also had higher relative height growth rate and slenderness, which were related to their biomass allocation. Stand density of mother tree mainly demonstrated significant effects on seed germination and seedling growth. Seed from higher stand density of mother tree did not decrease germination rate, but had higher mean germination time, indicating that it delayed germination process. Seedlings of higher stand density of mother tree showed higher relative height growth rate and slenderness. These traits of offspring from higher stand density of mother tree were similar to its mother, indicating significant environmental maternal effects. So, mother tree identity of maternal age and environments had important effects on natural regeneration of the coastal P. thunbergii forest.

  11. Assortment structure in beech coppice stands in the Crni vrh region

    Directory of Open Access Journals (Sweden)

    Danilović Milorad

    2003-01-01

    Full Text Available Assortment structure in beech coppice stands was studied for the region of Crni vrh. Assortment structure was determined according to the standard (JUS in two ecological units. The study results show that the assortment value structure significantly increases with the increase of tree diameter and that there are no statistically significant differences in assortment structure between the selected ecological units. The dependence of the assortment value structure on tree diameter can be represented by an exponential function. The value percentage of assortments made of stem wood in theoretical crosscutting depending on tree diameter has an increasing tendency, except for the wood for excelsior.

  12. Damage Detection on Thin-walled Structures Utilizing Laser Scanning and Standing Waves

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Se Hyeok; Jeon, Jun Young; Kim, Du Hwan; Park, Gyuhae [Chonnam Nat’l Univ., Gwangju (Korea, Republic of); Kang, To; Han, Soon Woo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2017-05-15

    This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.

  13. Ageing management of concrete structure

    International Nuclear Information System (INIS)

    Parthipan, P.; Ramaprasad, G.S.; Senthil, R.

    2006-01-01

    It is a generally accepted fact that while designing a concrete structure the durability parameters of construction materials should be evaluated as carefully as possible like other properties such as mechanical, physical and chemical properties. No material is inherently durable as result of environmental interaction with microstructure and consequently, the properties of the materials change with time due to weathering action, chemical attack, abrasion or any mode of degradation. The main cause of ageing on structure, water, which is primary for both creation and destruction on many natural materials. In porous materials, water creates different types of physical and chemical process of degradation. The water movement through porous materials are controlled by the permeability of the respective materials. The rate of deterioration is affected by type of concentration of ions present in the water and chemical deposition of materials. Controlling weathering action, chemical attack, abrasion and selecting good quality construction material and methods of construction can increase the service life of the structure. (author)

  14. Changes in sensory reweighting of proprioceptive information during standing balance with age and disease.

    Science.gov (United States)

    Pasma, J H; Engelhart, D; Maier, A B; Schouten, A C; van der Kooij, H; Meskers, C G M

    2015-12-01

    With sensory reweighting, reliable sensory information is selected over unreliable information during balance by dynamically combining this information. We used system identification techniques to show the weight and the adaptive process of weight change of proprioceptive information during standing balance with age and specific diseases. Ten healthy young subjects (aged between 20 and 30 yr) and 44 elderly subjects (aged above 65 yr) encompassing 10 healthy elderly, 10 with cataract, 10 with polyneuropathy, and 14 with impaired balance, participated in the study. During stance, proprioceptive information of the ankles was disturbed by rotation of the support surface with specific frequency content where disturbance amplitude increased over trials. Body sway and reactive ankle torque were measured to determine sensitivity functions of these responses to the disturbance amplitude. Model fits resulted in a proprioceptive weight (changing over trials), time delay, force feedback, reflexive stiffness, and damping. The proprioceptive weight was higher in healthy elderly compared with young subjects and higher in elderly subjects with cataract and with impaired balance compared with healthy elderly subjects. Proprioceptive weight decreased with increasing disturbance amplitude; decrease was similar in all groups. In all groups, the time delay was higher and the reflexive stiffness was lower compared with young or healthy elderly subjects. In conclusion, proprioceptive information is weighted more with age and in patients with cataract and impaired balance. With age and specific diseases the time delay was higher and reflexive stiffness was lower. These results illustrate the opportunity to detect the underlying cause of impaired balance in the elderly with system identification. Copyright © 2015 the American Physiological Society.

  15. Changes in sensory reweighting of proprioceptive information during standing balance with age and disease

    Science.gov (United States)

    Engelhart, D.; Maier, A. B.; Schouten, A. C.; van der Kooij, H.; Meskers, C. G. M.

    2015-01-01

    With sensory reweighting, reliable sensory information is selected over unreliable information during balance by dynamically combining this information. We used system identification techniques to show the weight and the adaptive process of weight change of proprioceptive information during standing balance with age and specific diseases. Ten healthy young subjects (aged between 20 and 30 yr) and 44 elderly subjects (aged above 65 yr) encompassing 10 healthy elderly, 10 with cataract, 10 with polyneuropathy, and 14 with impaired balance, participated in the study. During stance, proprioceptive information of the ankles was disturbed by rotation of the support surface with specific frequency content where disturbance amplitude increased over trials. Body sway and reactive ankle torque were measured to determine sensitivity functions of these responses to the disturbance amplitude. Model fits resulted in a proprioceptive weight (changing over trials), time delay, force feedback, reflexive stiffness, and damping. The proprioceptive weight was higher in healthy elderly compared with young subjects and higher in elderly subjects with cataract and with impaired balance compared with healthy elderly subjects. Proprioceptive weight decreased with increasing disturbance amplitude; decrease was similar in all groups. In all groups, the time delay was higher and the reflexive stiffness was lower compared with young or healthy elderly subjects. In conclusion, proprioceptive information is weighted more with age and in patients with cataract and impaired balance. With age and specific diseases the time delay was higher and reflexive stiffness was lower. These results illustrate the opportunity to detect the underlying cause of impaired balance in the elderly with system identification. PMID:26424578

  16. A stand-alone tree demography and landscape structure module for Earth system models: integration with global forest data

    Science.gov (United States)

    Haverd, V.; Smith, B.; Nieradzik, L. P.; Briggs, P. R.

    2014-02-01

    Poorly constrained rates of biomass turnover are a key limitation of Earth system models (ESM). In light of this, we recently proposed a new approach encoded in a model called Populations-Order-Physiology (POP), for the simulation of woody ecosystem stand dynamics, demography and disturbance-mediated heterogeneity. POP is suitable for continental to global applications and designed for coupling to the terrestrial ecosystem component of any ESM. POP bridges the gap between first generation Dynamic Vegetation Models (DVMs) with simple large-area parameterisations of woody biomass (typically used in current ESMs) and complex second generation DVMs, that explicitly simulate demographic processes and landscape heterogeneity of forests. The key simplification in the POP approach, compared with second-generation DVMs, is to compute physiological processes such as assimilation at grid-scale (with CABLE or a similar land surface model), but to partition the grid-scale biomass increment among age classes defined at sub grid-scale, each subject to its own dynamics. POP was successfully demonstrated along a savanna transect in northern Australia, replicating the effects of strong rainfall and fire disturbance gradients on observed stand productivity and structure. Here, we extend the application of POP to a range of forest types around the globe, employing paired observations of stem biomass and density from forest inventory data to calibrate model parameters governing stand demography and biomass evolution. The calibrated POP model is then coupled to the CABLE land surface model and the combined model (CABLE-POP) is evaluated against leaf-stem allometry observations from forest stands ranging in age from 3 to 200 yr. Results indicate that simulated biomass pools conform well with observed allometry. We conclude that POP represents a preferable alternative to large-area parameterisations of woody biomass turnover, typically used in current ESMs.

  17. TCP Final Report: Measuring the Effects of Stand Age and Soil Drainage on Boreal Forest

    Energy Technology Data Exchange (ETDEWEB)

    Michael L. Goulden

    2007-05-02

    This was a 6-year research project in the Canadian boreal forest that focused on using field observations to understand how boreal forest carbon balance changes during recovery from catastrophic forest fire. The project began with two overarching goals: (1) to develop techniques that would all the year round operation of 7 eddy covariance sites in a harsh environment at a much lower cost than had previously been possible, and (2) to use these measurements to determine how carbon balance changes during secondary succession. The project ended in 2006, having accomplished its primary objectives. Key contributions to DOE during the study were: (1) Design, test, and demonstrate a lightweight, fully portable eddy flux system that exploits several economies of scale to allow AmeriFlux-quality measurements of CO{sub 2} exchange at many sites for a large reduction in cost (Goulden et al. 2006). (2) Added seven year-round sites to AmeriFlux, at a relatively low per site cost using the Eddy Covariance Mesonet approach (Goulden et al. 2006). These data are freely available on the AmeriFlux web site. (3) Tested and rejected the conventional wisdom that forests lose large amounts of carbon during the first decade after disturbance, then accumulate large amounts of carbon for {approx}several decades, and then return to steady state in old age. Rather, we found that boreal forests recovers quickly from fire and begins to accumulate carbon within {approx}5 years after disturbance. Additionally, we found no evidence that carbon accumulation declines in old stands (Goulden et al. 2006, Goulden et al. in prep). (4) Tested and rejected claims based on remote sensing observations (for example, Myneni et al 1996 using AVHRR) that regions of boreal forest have changed markedly in the last 20 years. Rather, we assembled a much richer data set than had been used in the past (eddy covariance observations, tree rings, biomass, NPP, AVHRR, and LandSat), which we used to establish that the

  18. Composition, structure, and intra-stand spatial patterns along a disturbance severity gradient in a Quercus stand

    Science.gov (United States)

    Lauren E. Cox; Justin L. Hart; Daniel C. Dey; Callie J. Schweitzer

    2016-01-01

    Natural forest disturbances, which drive succession and development, differ in extent, severity, and return interval and range from frequent, gap-scale disturbances, to infrequent stand-replacing events. Most studies have focused on natural disturbances near the ends of the disturbance severity gradient and relatively little quantitative information is available on...

  19. Productivity of aboveground coarse wood biomass and stand age related to soil hydrology of Amazonian forests in the Purus-Madeira interfluvial area

    Science.gov (United States)

    Cintra, B. B. L.; Schietti, J.; Emillio, T.; Martins, D.; Moulatlet, G.; Souza, P.; Levis, C.; Quesada, C. A.; Schöngart, J.

    2013-04-01

    The ongoing demand for information on forest productivity has increased the number of permanent monitoring plots across the Amazon. Those plots, however, do not comprise the whole diversity of forest types in the Amazon. The complex effects of soil, climate and hydrology on the productivity of seasonally waterlogged interfluvial wetland forests are still poorly understood. The presented study is the first field-based estimate for tree ages and wood biomass productivity in the vast interfluvial region between the Purus and Madeira rivers. We estimate stand age and wood biomass productivity by a combination of tree-ring data and allometric equations for biomass stocks of eight plots distributed along 600 km in the Purus-Madeira interfluvial area that is crossed by the BR-319 highway. We relate stand age and wood biomass productivity to hydrological and edaphic conditions. Mean productivity and stand age were 5.6 ± 1.1 Mg ha-1 yr-1 and 102 ± 18 yr, respectively. There is a strong relationship between tree age and diameter, as well as between mean diameter increment and mean wood density within a plot. Regarding the soil hydromorphic properties we find a positive correlation with wood biomass productivity and a negative relationship with stand age. Productivity also shows a positive correlation with the superficial phosphorus concentration. In addition, superficial phosphorus concentration increases with enhanced soil hydromorphic condition. We raise three hypotheses to explain these results: (1) the reduction of iron molecules on the saturated soils with plinthite layers close to the surface releases available phosphorous for the plants; (2) the poor structure of the saturated soils creates an environmental filter selecting tree species of faster growth rates and shorter life spans and (3) plant growth on saturated soil is favored during the dry season, since there should be low restrictions for soil water availability.

  20. Growth patterns of Tsuga canadensis in managed uneven-aged northern conifer stands

    Science.gov (United States)

    Laura S. Kenefic; Robert S. Seymour

    2000-01-01

    This study reports patterns of regeneration and growth for 100 eastern hemlock (Tsuga canadensis (L.) Carr.) up to 20 inches (50 cm) dbh in two mixed-species selection stands on the Penobscot Experimental Forest in east-central Maine. The study stands are part of a U.S.D.A. Forest Service experiment in which eastern hemlock has remained stable over a...

  1. Elevated Air Humidity Changes Soil Bacterial Community Structure in the Silver Birch Stand

    OpenAIRE

    Truu, Marika; Ostonen, Ivika; Preem, Jens-Konrad; L?hmus, Krista; N?lvak, Hiie; Ligi, Teele; Rosenvald, Katrin; Parts, Kaarin; Kupper, Priit; Truu, Jaak

    2017-01-01

    Soil microbes play a fundamental role in forest ecosystems and respond rapidly to changes in the environment. Simultaneously with the temperature increase the climate change scenarios also predict an intensified hydrological cycle for the Baltic Sea runoff region. The aim of this study was to assess the effect of elevated air humidity on the top soil microbial community structure of a silver birch (Betula pendula Roth.) stand by using a free air humidity manipulation facility (FAHM). The bact...

  2. Comparison of Different Height–Diameter Modelling Techniques for Prediction of Site Productivity in Natural Uneven-Aged Pure Stands

    Directory of Open Access Journals (Sweden)

    Guangshuang Duan

    2018-01-01

    Full Text Available Reliable estimates of forest site productivity are a central element of forest management. The model of height-diameter relationship of dominant trees using algebraic difference approach (ADA is a commonly used method to measure site productivity of natural uneven-aged stands. However, the existing models of this method do not recognize site type or sample plot specific variability in height curves; thus, it cannot be effectively used to estimate site type or sample plot-related site productivity for natural uneven-aged stands. Two primary subject-specific approaches, ADA with dummy variable (DV (ADA + DV and ADA with combination of dummy variable and nonlinear mixed-effects modelling (CM (ADA + CM, were proposed for height–diameter modelling. Height–diameter models developed with ADA, ADA + DV and ADA + CM were compared using data from 4161 observations on 349 permanent sample plots of four major natural uneven-aged pure stands (Spruce, Korean Larch, Mongolian Oak, and White Birch in northeastern China. It was found that models developed with ADA + CM provided the best performance, followed by the models with ADA + DV, and the models developed with ADA performed the worst. Random effects at the plot level were substantial, and their inclusion greatly improved the model’s accuracy. More importantly, the models developed with ADA + CM provide an effective method for quantifying site type- and sample plot-specific forest site productivity for uneven-aged pure stands.

  3. Effects of Market Prices and Silvicultural Practices on Lumber Value of Standing Trees In Uneven-Ages Plots

    Science.gov (United States)

    David W. Patterson

    1998-01-01

    Uneven-aged management plots were established using three variables (site index, basal area, and maximum diameter). This study looked at the significance of the variables on the lumber volume per acre, lumber value per thousand board feet (Mbf), and stand value per acre as well as the influence on these analysis by market prices (May 1997, May 1998, and October 1998)....

  4. Understory Vegetation 3 Years after Implementing Uneven-Aged Silviculture in a Shortleaf Pine-Oak Stand

    Science.gov (United States)

    Michael G. Shelton; Paul A. Murphy

    1997-01-01

    The effects of retaining overstory hardwoods on understory vegetation were determined after implementing uneven-aged silviculture usingsingle-tree selection in a shortleaf pine-oak stand (Pinus echinata Mill. and Quercus spp.) in the Ouachita Mountains. Treatments were the following hardwood basal areas (square feet per acre) and...

  5. Growth expectations from alternative thinning regimes and prescribed burning in naturally regenerated loblolly-shortleaf pine stands through age 20

    Science.gov (United States)

    Michael D. Cain

    1996-01-01

    Pine growth was monitored for 14 years after mechanically strip-thinning a dense, naturally regenerated, even-aged stand of 6-year-old loblolly pines (Pinus taeda L.) and shortleaf pines (Pinus echinata Mill.) that averaged 41 000 trees per hectare in southeastern Arkansas, USA. Prescribed winter bums were conducted...

  6. Study of age-related changes in postural control during quiet standing through Linear Discriminant Analysis

    Directory of Open Access Journals (Sweden)

    Andrade Adriano O

    2009-11-01

    Full Text Available Abstract Background The human body adopts a number of strategies to maintain an upright position. The analysis of the human balance allows for the understanding and identification of such strategies. The displacement of the centre of pressure (COP is a measure that has been successfully employed in studies regarding the postural control. Most of these investigations are related to the analysis of individuals suffering from neuromuscular disorders. Recent studies have shown that the elderly population is growing very fast in many countries all over the world, and therefore, researches that try to understand changes in this group are required. In this context, this study proposes the analysis of the postural control, measured by the displacement of the COP, in groups of young and elderly adults. Methods In total 59 subjects participated of this study. They were divided into seven groups according to their age. The displacement of the COP was collected for each subject standing on a force plate. Two experimental conditions, of 30 seconds each, were investigated: opened eyes and closed eyes. Traditional and recent digital signal processing tools were employed for feature computation from the displacement of the COP. Statistical analyses were carried out in order to identify significant differences between the features computed from the distinct groups that could allow for their discrimination. Results Our results showed that Linear Discrimination Analysis (LDA, which is one of the most popular feature extraction and classifier design techniques, could be successfully employed as a linear transformation, based on the linear combination of standard features for COP analysis, capable of estimating a unique feature, so-called LDA-value, from which it was possible to discriminate the investigated groups and show a high correlation between this feature and age. Conclusion These results show that the analysis of features computed from the displacement of

  7. Stand dynamics and tree coexistence in an analytical structured model: the role of recruitment.

    Science.gov (United States)

    Angulo, Óscar; Bravo de la Parra, Rafael; López-Marcos, Juan C; Zavala, Miguel A

    2013-09-21

    Understanding the mechanisms of coexistence and niche partitioning in plant communities is a central question in ecology. Current theories of forest dynamics range between the so-called neutral theories which assume functional equivalence among coexisting species to forest simulators that explain species assemblages as the result of tradeoffs in species individual strategies at several ontogenetic stages. Progress in these questions has been hindered by the inherent difficulties of developing analytical size-structured models of stand dynamics. This precludes examination of the relative importance of each mechanism on tree coexistence. In previous simulation and analytical studies emphasis has been given to interspecific differences at the sapling stage, and less so to interspecific variation in seedling recruitment. In this study we develop a partial differential equation model of stand dynamics in which competition takes place at the recruitment stage. Species differ in their size-dependent growth rates and constant mortality rates. Recruitment is described as proportional to the basal area of conspecifics, to account for fecundity and seed supply per unit of basal area, and is corrected with a decreasing function of species specific basal area to account for competition. We first analyze conditions for population persistence in monospecific stands and second we investigate conditions of coexistence for two species. In the monospecific case we found a stationary stand structure based on an inequality between mortality rate and seed supply. In turn, intra-specific competition does not play any role on the asymptotic extinction or population persistence. In the two-species case we found that coexistence can be attained when the reciprocal negative effect on recruitment follows a given relation with respect to intraspecific competition. Specifically a tradeoff between recruitment potential (i.e. shade tolerance or predation avoidance) and fecundity or growth rate

  8. Lightning Protection and Structural Bonding for the B2 Test Stand

    Science.gov (United States)

    Kinard, Brandon

    2015-01-01

    With the privatization of the space industry, NASA has entered a new era. To explore deeper parts of the solar system, NASA is developing a new spacecraft, the Space Launch System (SLS), capable of reaching these destinations, such as an asteroid or Mars. However, the test stand that is capable of testing the stage has been unused for many years. In addition to the updating/repair of the stand, more steel is being added to fully support the SLS. With all these modifications, the lightning protection system must be brought up to code to assure the protection of all personnel and assets. Structural bonding is a part of the lightning protection system. The focus of this project was to assure proper structural bonding. To begin, all relevant technical standards and the construction specifications were reviewed. This included both the specifications for the lightning protection and for general construction. The drawings were reviewed as well. From the drawings, bolted structural joints were reviewed to determine whether bonding was necessary. Several bolted joints were determined to need bonding according to the notes in the drawings. This exceeds the industry standards. The bolted joints are an electrically continuous joint. During tests, the stand experiences heavy vibration that may weaken the continuity of the bolted joint. Therefore, the secondary bonding is implemented to ensure that the structural joint has low resistance. If the structural joint has a high resistance because of corrosion, a potential gradient can occur that can cause a side flash. Damage, injury, or death can occur from a side flash so they are to be prevented. A list of the identified structural joints was compiled and sent to the contractor to be bonded. That covers the scope of this project.

  9. Design of hybrid electron linac with standing wave buncher and traveling wave structure

    International Nuclear Information System (INIS)

    Kutsaev, S.V.; Sobenin, N.P.; Smirnov, A.Yu.; Kamenschikov, D.S.; Gusarova, M.A.; Nikolskiy, K.I.; Zavadtsev, A.A.; Lalayan, M.V.

    2011-01-01

    A disk-loaded waveguide (DLW) is the most common structure for compact linear accelerators working in a traveling wave (TW) regime. Among its advantages are high shunt impedance and manufacturing simplicity. The other popular structure is an on-axis coupled bi-periodical accelerating structure (BAS) that works in standing wave (SW) regime. Both the standing and the traveling wave regimes have their own advantages and disadvantages. The design of the hybrid accelerator with SW buncher and TW accelerating section presented in this paper unites the advantages of both regimes. For example, the buncher in the hybrid accelerator is shorter than in a pure TW accelerator, and it requires no solenoid; this structure is more technologically convenient as it does not require a circulator. The other way to combine the advantages of DLW and BAS is to design a magnetic coupled disk-loaded waveguide (DLW-M). This paper also presents the results of a survey study that analyzed the electrodynamical parameters of such a structure and compared them with those of DLW. The experimental data is also presented. Higher order modes, multipacting discharge and thermal simulations show that DLW-M structure is more preferable to classical DLW.

  10. Reproductive ecology and stand structure of Joshua tree forests across climate gradients of the Mojave Desert

    Science.gov (United States)

    Hoines, Joshua

    2018-01-01

    Climate change is restructuring plant populations and can result in range shifts depending on responses at various life stages of plants. In 2013, a widespread and episodic flowering event provided an opportunity to characterize how Joshua tree’s reproductive success and population structure vary in response to the climate variability across its range. We examined the reproductive success and stand structure of 10 Joshua tree populations distributed across the Mojave Desert. Joshua tree density varied by more than an order of magnitude across sites. At 8 of the 10 sites, nearly 80% of the Joshua trees were in bloom, and at the other two 40% were in bloom. The range of seed production and fruit set across the study populations varied by more than an order of magnitude. Fruit production occurred at all of our study sites suggesting that yucca moth pollinators were present at our sites. Increasing temperature had strong positive correlations with the number of trees in bloom (R2 = 0.42), inflorescences per tree (R2 = 0.37), and fruit mass (R2 = 0.77) and seed size (R2 = 0.89. In contrast, temperature was negatively correlated with Joshua tree stand density (R2 = -0.80). Positive correlations between temperature and greater flower and seed production suggest that warming may positively affect Joshua Tree reproduction while negative relationships between temperature and stand density are suggestive of potential constraints of warmer temperatures on establishment success. PMID:29474414

  11. Changes in sensory reweighting of proprioceptive information during standing balance with age and disease

    NARCIS (Netherlands)

    Pasma, J.H.; Engelhart, D.; Maier, A.B.; Schouten, A.C.; van der Kooij, H.; Meskers, C.G.M.

    2015-01-01

    With sensory reweighting, reliable sensory information is selected over unreliable information during balance by dynamically combining this information. We used system identification techniques to show the weight and the adaptive process of weight change of proprioceptive information during standing

  12. Development of small C-band standing-wave accelerator structure

    International Nuclear Information System (INIS)

    Miura, S.; Takahashi, A.; Hisanaga, N.; Sekido, H.; Yoshizumi, A.

    2000-01-01

    We have newly developed a compact C-band (5712 MHz) standing-wave accelerator for the medical product/waste sterilization applications. The accelerator consists of an electron gun operating at 25 kV DC followed by a single-cell pre-buncher and 3-cell buncher section, and 11-cell of the side-coupled standing-wave accelerating structure. The total length including the electron gun is about 600 mm. The first high-power test was performed in March 2000, where the accelerator successively generated the electron beam of 9 MeV energy and 160 mA peak-current at 3.8 MW RF input power. Mitsubishi Heavy Industry starts to serve the sterilization systems using C-band accelerator reported here, and also supplies the accelerator components for the medical oncology applications. (author)

  13. Age determination and age structure of a striped fieldmouse ...

    African Journals Online (AJOL)

    Thereafter, the only reliable technique of age determination Involves a visual evaluation of the degree of molar tooth wear. Five wear classes are described and used to assess the age of 780 R. pumilio collected during a five-year period. The annual cycles of population age structure and size were dependent on seasonal ...

  14. Effect of stand structure on models for volume and aboveground biomass assessment (Castelfusano pinewood, Roma

    Directory of Open Access Journals (Sweden)

    2009-03-01

    Full Text Available The main purpose of this research was to analyse the effects of stand structure on biomass allocation and on the accurancy of estimation models for volume and aboveground biomass of Italian stone pine (Pinus pinea L.. Although the species is widely distributed on Mediterranean coasts, few studies on forest biomass estimation have focused on pinewoods. The research was carried out in the Castelfusano’s pinewood (Rome and concerned the two most common structural types: (a 50 years-old pinewood originated by broadcast seeding; and (b 62 years-old pinewood originated by partial seeding alternating worked strips to firm strips. Some 83 sample trees were selected for stem volume estimation and a subset of 32 trees used to quantify the total epigeous biomass, the wooden biomass compartment, including stem and big branches (diameter > 3 cm and the photosynthetic biomass, including thin branches (diameter < 3 cm and needles. Collected data were used to elaborate allometric relations for stem volume, total biomass and specific relations for both compartments, based on one (d2 or two (d2h indipendent variables, for both structural types. Furthermore, pinewood specific biomass expansion factors (BEF - indexes used to estimate carbon stocks starting from stem biomass data - were obtained. The achieved estimation models were subjected to both parallelism and coincidence tests, showing significant effects of stand structure on the accurancy of the allometric relations. The effects of stand structure and reliability of tree height curves on the accurancy of estimation models for volume and aboveground biomass and on biomass allocation in different compartments are analysed and discussed.

  15. Quality of standing balance in community-dwelling elderly: Age-related differences in single and dual task conditions.

    Science.gov (United States)

    Coelho, Tiago; Fernandes, Ângela; Santos, Rubim; Paúl, Constança; Fernandes, Lia

    2016-01-01

    To examine the relationship between age and quality of standing balance in single and dual task conditions. A cross-sectional study was conducted using a sample of 243 community-dwellers aged ≥65 years. Quality of standing balance was assessed by measuring the center of pressure (COP) sway with a pressure platform. Measurements were performed under single task (orthostatic position) and dual task (orthostatic position while performing a verbal fluency task) conditions. The mean age of the participants was 79.1(±7.3)years and 76.1% were women. Older age was associated with an increased COP sway, mainly in the medial/lateral (ML) direction. Most COP sway parameters were higher under dual task conditions than under single task. After controlling for the effect of the number of words enunciated in dual task conditions, only the differences in COP sway parameters in the ML direction remained significant. There was no significant interaction between age group (65-79; ≥80 years) and condition, which indicates that differences in COP sway caused by performing a secondary task were similar for younger and for older participants. Age did not seem to influence significantly the decline in the quality of standing balance triggered by performing a concurrent cognitive task. However, older age was consistently associated with poorer standing balance, both in single and in dual task conditions. Therefore, performing a secondary task may lead older individuals to reach their postural stability limits and, consequently, to fall. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  16. Average Stand Age from Forest Inventory Plots Does Not Describe Historical Fire Regimes in Ponderosa Pine and Mixed-Conifer Forests of Western North America.

    Science.gov (United States)

    Stevens, Jens T; Safford, Hugh D; North, Malcolm P; Fried, Jeremy S; Gray, Andrew N; Brown, Peter M; Dolanc, Christopher R; Dobrowski, Solomon Z; Falk, Donald A; Farris, Calvin A; Franklin, Jerry F; Fulé, Peter Z; Hagmann, R Keala; Knapp, Eric E; Miller, Jay D; Smith, Douglas F; Swetnam, Thomas W; Taylor, Alan H

    Quantifying historical fire regimes provides important information for managing contemporary forests. Historical fire frequency and severity can be estimated using several methods; each method has strengths and weaknesses and presents challenges for interpretation and verification. Recent efforts to quantify the timing of historical high-severity fire events in forests of western North America have assumed that the "stand age" variable from the US Forest Service Forest Inventory and Analysis (FIA) program reflects the timing of historical high-severity (i.e. stand-replacing) fire in ponderosa pine and mixed-conifer forests. To test this assumption, we re-analyze the dataset used in a previous analysis, and compare information from fire history records with information from co-located FIA plots. We demonstrate that 1) the FIA stand age variable does not reflect the large range of individual tree ages in the FIA plots: older trees comprised more than 10% of pre-stand age basal area in 58% of plots analyzed and more than 30% of pre-stand age basal area in 32% of plots, and 2) recruitment events are not necessarily related to high-severity fire occurrence. Because the FIA stand age variable is estimated from a sample of tree ages within the tree size class containing a plurality of canopy trees in the plot, it does not necessarily include the oldest trees, especially in uneven-aged stands. Thus, the FIA stand age variable does not indicate whether the trees in the predominant size class established in response to severe fire, or established during the absence of fire. FIA stand age was not designed to measure the time since a stand-replacing disturbance. Quantification of historical "mixed-severity" fire regimes must be explicit about the spatial scale of high-severity fire effects, which is not possible using FIA stand age data.

  17. Average Stand Age from Forest Inventory Plots Does Not Describe Historical Fire Regimes in Ponderosa Pine and Mixed-Conifer Forests of Western North America

    Science.gov (United States)

    Stevens, Jens T.; Safford, Hugh D.; North, Malcolm P.; Fried, Jeremy S.; Gray, Andrew N.; Brown, Peter M.; Dolanc, Christopher R.; Dobrowski, Solomon Z.; Falk, Donald A.; Farris, Calvin A.; Franklin, Jerry F.; Fulé, Peter Z.; Hagmann, R. Keala; Knapp, Eric E.; Miller, Jay D.; Smith, Douglas F.; Swetnam, Thomas W.; Taylor, Alan H.

    2016-01-01

    Quantifying historical fire regimes provides important information for managing contemporary forests. Historical fire frequency and severity can be estimated using several methods; each method has strengths and weaknesses and presents challenges for interpretation and verification. Recent efforts to quantify the timing of historical high-severity fire events in forests of western North America have assumed that the “stand age” variable from the US Forest Service Forest Inventory and Analysis (FIA) program reflects the timing of historical high-severity (i.e. stand-replacing) fire in ponderosa pine and mixed-conifer forests. To test this assumption, we re-analyze the dataset used in a previous analysis, and compare information from fire history records with information from co-located FIA plots. We demonstrate that 1) the FIA stand age variable does not reflect the large range of individual tree ages in the FIA plots: older trees comprised more than 10% of pre-stand age basal area in 58% of plots analyzed and more than 30% of pre-stand age basal area in 32% of plots, and 2) recruitment events are not necessarily related to high-severity fire occurrence. Because the FIA stand age variable is estimated from a sample of tree ages within the tree size class containing a plurality of canopy trees in the plot, it does not necessarily include the oldest trees, especially in uneven-aged stands. Thus, the FIA stand age variable does not indicate whether the trees in the predominant size class established in response to severe fire, or established during the absence of fire. FIA stand age was not designed to measure the time since a stand-replacing disturbance. Quantification of historical “mixed-severity” fire regimes must be explicit about the spatial scale of high-severity fire effects, which is not possible using FIA stand age data. PMID:27196621

  18. Effects of climate, CO2 concentration, nitrogen deposition, and stand age changes on the carbon budget of China's forests

    Science.gov (United States)

    Zhang, C.; Ju, W.; Zhang, F.; Mao, D.; Wang, X.

    2017-12-01

    Forests play an irreplaceable role in the Earth's terrestrial carbon budget which retard the atmospheric CO2 buildup. Understanding the factors controlling forest carbon budget is critical for reducing uncertainties in projections of future climate. The relative importance of climate, atmospheric CO2 concentration, nitrogen deposition, and stand age changes on carbon budget, however, remains unclear for China's forests. In this study, we quantify individual contribution of these drivers to the trends of forest carbon budget in China from 1901 to 2012 by integrating national datasets, the updated Integrated Terrestrial Ecosystem Carbon Cycle (InTEC) model and factorial simulations. Results showed that the average carbon sink in China's forests from 1982 to 2012 was 186.9 Tg C yr-1 with 68% (127.6 Tg C yr-1) of the sink in living biomass because of the integrated effects of climate, atmospheric CO2 concentration, nitrogen deposition, and stand age factors. Compared with the simulation of all factors combined, the estimated carbon sink during 1901-2012 would be reduced by 41.8 Tg C yr-1 if climate change, atmospheric CO2 concentration and nitrogen deposition factors were omitted, and reduced by 25.0 Tg C yr-1 if stand age factor was omitted. In most decades, these factors increased forest carbon sinks with the largest of 101.3, 62.9, and 44.0 Tg C yr-1 from 2000 to 2012 contributed by stand age, CO2 concentration and nitrogen deposition, respectively. During 1901-2012, climate change, CO2 concentration, nitrogen deposition and stand age contributed -13.3, 21.4, 15.4 and 25.0 Tg C yr-1 to the averaged carbon sink of China's forests, respectively. Our study also showed diverse regional patterns of forest carbon budget related to the importance of driving factors. Stand age effect was the largest in most regions, but the effects of CO2 concentration and nitrogen deposition were dominant in southern China.

  19. Effects of stand age and soil properties on soil bacterial and fungal community composition in Chinese pine plantations on the Loess Plateau.

    Directory of Open Access Journals (Sweden)

    Peng Dang

    Full Text Available The effects of Chinese pine (Pinus tabuliformis on soil variables after afforestation have been established, but microbial community changes still need to be explored. Using high-throughput sequencing technology, we analyzed bacterial and fungal community composition and diversity in soils from three stands of different-aged, designated 12-year-old (PF1, 29-year-old (PF2, and 53-year-old (PF3, on a Chinese pine plantation and from a natural secondary forest (NSF stand that was almost 80 years old. Abandoned farmland (BL was also analyzed. Shannon index values of both bacterial and fungal community in PF1 were greater than those in PF2, PF3 and NSF. Proteobacteria had the lowest abundance in BL, and the abundance increased with stand age. The abundance of Actinobacteria was greater in BL and PF1 soils than those in other sites. Among fungal communities, the dominant taxa were Ascomycota in BL and PF1 and Basidiomycota in PF2, PF3 and NSF, which reflected the successional patterns of fungal communities during the development of Chinese pine plantations. Therefore, the diversity and dominant taxa of soil microbial community in stands 12 and 29 years of age appear to have undergone significant changes; afterward, the soil microbial community achieved a relatively stable state. Furthermore, the abundances of the most dominant bacterial and fungal communities correlated significantly with organic C, total N, C:N, available N, and available P, indicating the dependence of these microbes on soil nutrients. Overall, our findings suggest that the large changes in the soil microbial community structure of Chinese pine plantation forests may be attributed to the phyla present (e.g., Proteobacteria, Actinobacteria, Ascomycota and Basidiomycota which were affected by soil carbon and nutrients in the Loess Plateau.

  20. Effects of stand age and soil properties on soil bacterial and fungal community composition in Chinese pine plantations on the Loess Plateau.

    Science.gov (United States)

    Dang, Peng; Yu, Xuan; Le, Hien; Liu, Jinliang; Shen, Zhen; Zhao, Zhong

    2017-01-01

    The effects of Chinese pine (Pinus tabuliformis) on soil variables after afforestation have been established, but microbial community changes still need to be explored. Using high-throughput sequencing technology, we analyzed bacterial and fungal community composition and diversity in soils from three stands of different-aged, designated 12-year-old (PF1), 29-year-old (PF2), and 53-year-old (PF3), on a Chinese pine plantation and from a natural secondary forest (NSF) stand that was almost 80 years old. Abandoned farmland (BL) was also analyzed. Shannon index values of both bacterial and fungal community in PF1 were greater than those in PF2, PF3 and NSF. Proteobacteria had the lowest abundance in BL, and the abundance increased with stand age. The abundance of Actinobacteria was greater in BL and PF1 soils than those in other sites. Among fungal communities, the dominant taxa were Ascomycota in BL and PF1 and Basidiomycota in PF2, PF3 and NSF, which reflected the successional patterns of fungal communities during the development of Chinese pine plantations. Therefore, the diversity and dominant taxa of soil microbial community in stands 12 and 29 years of age appear to have undergone significant changes; afterward, the soil microbial community achieved a relatively stable state. Furthermore, the abundances of the most dominant bacterial and fungal communities correlated significantly with organic C, total N, C:N, available N, and available P, indicating the dependence of these microbes on soil nutrients. Overall, our findings suggest that the large changes in the soil microbial community structure of Chinese pine plantation forests may be attributed to the phyla present (e.g., Proteobacteria, Actinobacteria, Ascomycota and Basidiomycota) which were affected by soil carbon and nutrients in the Loess Plateau.

  1. Relationships between net primary productivity and stand age for several forest types and their influence on China's carbon balance.

    Science.gov (United States)

    Wang, Shaoqiang; Zhou, Lei; Chen, Jingming; Ju, Weimin; Feng, Xianfeng; Wu, Weixing

    2011-06-01

    Affected by natural and anthropogenic disturbances such as forest fires, insect-induced mortality and harvesting, forest stand age plays an important role in determining the distribution of carbon pools and fluxes in a variety of forest ecosystems. An improved understanding of the relationship between net primary productivity (NPP) and stand age (i.e., age-related increase and decline in forest productivity) is essential for the simulation and prediction of the global carbon cycle at annual, decadal, centurial, or even longer temporal scales. In this paper, we developed functions describing the relationship between national mean NPP and stand age using stand age information derived from forest inventory data and NPP simulated by the BEPS (Boreal Ecosystem Productivity Simulator) model in 2001. Due to differences in ecobiophysical characteristics of different forest types, NPP-age equations were developed for five typical forest ecosystems in China (deciduous needleleaf forest (DNF), evergreen needleleaf forest in tropic and subtropical zones (ENF-S), deciduous broadleaf forest (DBF), evergreen broadleaf forest (EBF), and mixed broadleaf forest (MBF)). For DNF, ENF-S, EBF, and MBF, changes in NPP with age were well fitted with a common non-linear function, with R(2) values equal to 0.90, 0.75, 0.66, and 0.67, respectively. In contrast, a second order polynomial was best suitable for simulating the change of NPP for DBF, with an R(2) value of 0.79. The timing and magnitude of the maximum NPP varied with forest types. DNF, EBF, and MBF reached the peak NPP at the age of 54, 40, and 32 years, respectively, while the NPP of ENF-S maximizes at the age of 13 years. The highest NPP of DBF appeared at 122 years. NPP was generally lower in older stands with the exception of DBF, and this particular finding runs counter to the paradigm of age-related decline in forest growth. Evaluation based on measurements of NPP and stand age at the plot-level demonstrates the reliability

  2. Elevated Air Humidity Changes Soil Bacterial Community Structure in the Silver Birch Stand.

    Science.gov (United States)

    Truu, Marika; Ostonen, Ivika; Preem, Jens-Konrad; Lõhmus, Krista; Nõlvak, Hiie; Ligi, Teele; Rosenvald, Katrin; Parts, Kaarin; Kupper, Priit; Truu, Jaak

    2017-01-01

    Soil microbes play a fundamental role in forest ecosystems and respond rapidly to changes in the environment. Simultaneously with the temperature increase the climate change scenarios also predict an intensified hydrological cycle for the Baltic Sea runoff region. The aim of this study was to assess the effect of elevated air humidity on the top soil microbial community structure of a silver birch ( Betula pendula Roth.) stand by using a free air humidity manipulation facility (FAHM). The bacterial community structures of bulk soil and birch rhizosphere were analyzed using high-throughput sequencing of bacteria-specific16S rRNA gene fragments and quantification of denitrification related genes. The increased air humidity altered both bulk soil and rhizosphere bacterial community structures, and changes in the bacterial communities initiated by elevated air humidity were related to modified soil abiotic and biotic variables. Network analysis revealed that variation in soil bacterial community structural units is explained by altered abiotic conditions such as increased pH value in bulk soil, while in rhizosphere the change in absorptive root morphology had a higher effect. Among root morphological traits, the absorptive root diameter was strongest related to the bacterial community structure. The changes in bacterial community structures under elevated air humidity are associated with shifts in C, N, and P turnover as well as mineral weathering processes in soil. Increased air humidity decreased the nir and nosZ gene abundance in the rhizosphere bacterial community. The potential contribution of the denitrification to the N 2 O emission was not affected by the elevated air humidity in birch stand soil. In addition, the study revealed a strong link between the bacterial community structure, abundance of denitrification related genes, and birch absorptive root morphology in the ecosystem system adaptation to elevated air humidity.

  3. Sustaining recruitment of oak reproduction in uneven-aged stands in the Ozark Highlands.

    Science.gov (United States)

    David R. Larsen; Edward F. Loewenstein; Paul S. Johnson

    1999-01-01

    Successful application of the single-tree selection system in Ozark oak forests depends on sustaining adequate recruitment of reproduction into the overstory. In turn, this requires maintaining stand density at ecologically appropriate levels. The ecological requirements for oak recruitment are discussed and guiding curves are presented that meet those requirements...

  4. Estimating long-term carbon sequestration patterns in even- and uneven-aged southern pine stands

    Science.gov (United States)

    Don C. Bragg; James M. Guldin

    2010-01-01

    Carbon (C) sequestration has become an increasingly important consideration for forest management in North America, and has particular potential in pine-dominated forests of the southern United States. Using existing literature on plantations and long-term studies of naturally regenerated loblolly (Pinus taeda) and shortleaf (Pinus echinata) pine-dominated stands on...

  5. Spatially explicit modeling of 1992-2100 land cover and forest stand age for the conterminous United States

    Science.gov (United States)

    Sohl, Terry L.; Sayler, Kristi L.; Bouchard, Michelle; Reker, Ryan R.; Friesz, Aaron M.; Bennett, Stacie L.; Sleeter, Benjamin M.; Sleeter, Rachel R.; Wilson, Tamara; Soulard, Christopher E.; Knuppe, Michelle; Van Hofwegen, Travis

    2014-01-01

    Information on future land-use and land-cover (LULC) change is needed to analyze the impact of LULC change on ecological processes. The U.S. Geological Survey has produced spatially explicit, thematically detailed LULC projections for the conterminous United States. Four qualitative and quantitative scenarios of LULC change were developed, with characteristics consistent with the Intergovernmental Panel on Climate Change (IPCC) Special Report on 5 Emission Scenarios (SRES). The four quantified scenarios (A1B, A2, B1, and B2) served as input to the Forecasting Scenarios of Land-use Change (FORE-SCE) model. Four spatially explicit datasets consistent with scenario storylines were produced for the conterminous United States, with annual LULC maps from 1992 through 2100. The future projections are characterized by a loss of natural land covers in most scenarios, with corresponding expansion of 10 anthropogenic land uses. Along with the loss of natural land covers, remaining natural land covers experience increased fragmentation under most scenarios, with only the B2 scenario remaining relatively stable in both proportion of remaining natural land covers and basic fragmentation measures. Forest stand age was also modeled. By 2100, scenarios and ecoregions with heavy forest cutting have relatively lower mean stand ages compared to those with less 15 forest cutting. Stand ages differ substantially between unprotected and protected forest lands, as well as between different forest classes. The modeled data were compared to the National Land Cover Database (NLCD) and other data sources to assess model characteristics. The consistent, spatially explicit, and thematically detailed LULC projections and the associated forest stand age data layers have been used to analyze LULC impacts on carbon and greenhouse gas fluxes, 20 biodiversity, climate and weather variability, hydrologic change, and other ecological processes.

  6. [Population structure of soil arthropod in different age Pinus massoniana plantations].

    Science.gov (United States)

    Tan, Bo; Wu, Fu-zhong; Yang, Wan-qin; Zhang, Jian; Xu, Zhen-feng; Liu, Yang; Gou, Xiao-lin

    2013-04-01

    An investigation was conducted on the population structure of soil arthropod community in the 3-, 8-, 14-, 31-, and 40-years old Pinus massoniana plantations in the upper reaches of the Yangtze River in spring (May) and autumn (October), 2011, aimed to search for the scientific management of the plantation. A total of 4045 soil arthropods were collected, belonging to 57 families. Both the individual density and the taxonomic group number of the soil arthropod community decreased obviously with increasing soil depth, and this trend increased with increasing stand age. The dominant groups and ordinary groups of the soil arthropod community varied greatly with the stand age of P. massoniana plantation, and a significant difference (P<0.05) was observed in the individual density and taxonomic group number among different age P. massoniana plantations. In comparison with other stand age P. massoniana plantations, 3years old P. massoniana plantation had a significant difference in the structure and diversity of soil arthropod community, and the similarity index of the soil arthropod community was lower. The individual density, taxonomic group number, and diversity of soil arthropod community were the highest in 8-years old P. massoniana plantation, and then, decreased obviously with increasing stand age. It was suggested that the land fertility of the P. massoniana plantations could be degraded with increasing stand age, and it would be appropriate to make artificial regulation and restoration in 8-years old P. massoniana plantation.

  7. Modelling canopy fuel and forest stand variables and characterizing the influence of thinning in the stand structure using airborne LiDAR

    Directory of Open Access Journals (Sweden)

    A. Hevia

    2016-02-01

    Full Text Available Forest fires are a major threat in NW Spain. The importance and frequency of these events in the area suggests the need for fuel management programs to reduce the spread and severity of forest fires. Thinning treatments can contribute for fire risk reduction, because they cut off the horizontal continuity of forest fuels. Besides, it is necessary to conduct a fire risk management based on the knowledge of fuel allocation, since fire behaviour and fire spread study is dependent on the spatial factor. Therefore, mapping fuel for different silvicultural scenarios is essential. Modelling forest variables and forest structure parameters from LiDAR technology is the starting point for developing spatially explicit maps. This is essential in the generation of fuel maps since field measurements of canopy fuel variables is not feasible. In the present study, we evaluated the potential of LiDAR technology to estimate canopy fuel variables and other stand variables, as well as to identify structural differences between silvicultural managed and unmanaged P. pinaster Ait. stands. Independent variables (LiDAR metrics of greater explanatory significance were identified and regression analyses indicated strong relationships between those and field-derived variables (R2 varied between 0.86 and 0.97. Significant differences were found in some LiDAR metrics when compared thinned and unthinned stands. Results showed that LiDAR technology allows to model canopy fuel and stand variables with high precision in this species, and provides useful information for identifying areas with and without silvicultural management.

  8. Physical Aging of Thin and Ultrathin Free-Standing Polymer Films: Effect of Stress and Reduced Glass Transitions

    Science.gov (United States)

    Pye, Justin; Roth, Connie

    2014-03-01

    While great effort has been made in elucidating the effect of confinement on the glass transition (Tg) in polymers, considerably less work has been done on physical aging. Starting with supported films, we have previously shown that the reduced physical aging rates in ultrathin polystyrene (PS) films can be linked to the reduced Tg near the free surface [Macromolecules 2010, 43, 8296]. We then showed that high molecular weight (MW) free-standing PS films have two reduced Tgs suggesting that two separate mechanisms are acting simultaneously to propagate enhanced mobility at the free surface deeper into the film [PRL 2011, 107, 235701]. To help determine the mechanisms of these two reduced Tgs, we performed physical aging measurements on these high MW free-standing PS films. For thick films (220-1800 nm) in which there are no Tg reductions, we find that the physical aging rate depends strongly on stress caused by thermal expansion mismatch between film and support. This stress, applied to the films as they are quenched into the glassy state, can nearly double the physical aging rate when changing the frame material from polycarbonate to silicon [Macromolecules 2013, DOI:10.1021/ma401872u]. Finally, ultrathin high MW PS films held at a temperature between the two Tgs do exhibit physical aging, indicating that at least some of the film is glassy between these two transitions.

  9. Structure and dendroecology of Thuja occidentalis in disjunct stands south of its contiguous range in the central Appalachian Mountains, USA

    Directory of Open Access Journals (Sweden)

    Joshua A. Kincaid

    2016-11-01

    Full Text Available Background Information on forest structure, growth, and disturbance history is essential for effective forest management in a dynamic landscape. Because most of our research concerning the ecology and growth of Thuja occidentalis comes from sites in northern portions of its range, highly contextual biotic and abiotic factors that affect the species in more southern locales may not be fully accounted for. This research characterized the structural attributes and growth dynamics of Thuja occidentalis in disjunct forest stands south of its contiguous range margin. Methods The Thuja occidentalis forests examined in this research were located in the central Appalachian Mountains, USA, approximately 440 km south of the contiguous range margin of the species. Forest structural attributes were characterized in two Thuja occidentalis forest stands, which are rare in the region. Tree-ring chronologies were used to examine the influences of disturbance and climate on the growth of Thuja occidentalis. Results The forests contained a total of 13 tree species with Thuja occidentalis contributing substantially to the basal area of the sites. Thuja occidentalis stems were absent in the smallest size class, while hardwood species were abundant in the smallest classes. Thuja occidentalis stems also were absent from the < 70 years age class. By contrast, Thuja occidentalis snags were abundant within stands. Growth-release events were distributed across the disturbance chronology and generally affected a small number of trees. The Thuja occidentalis tree-ring chronology possessed an interseries correlation of 0.62 and mean sensitivity of 0.25. The correlation between mean temperature and Thuja occidentalis growth was weak and variable. Growth and moisture variables were more strongly correlated, and this relationship was predominantly positive. Conclusions Structural attributes indicate the forests are in the understory reinitiation stage of forest development

  10. Effect of Forest Structural Change on Carbon Storage in a Coastal Metasequoia glyptostroboides Stand

    Science.gov (United States)

    Cheng, Xiangrong; Yu, Mukui; Wu, Tonggui

    2013-01-01

    Forest structural change affects the forest's growth and the carbon storage. Two treatments, thinning (30% thinning intensity) and underplanting plus thinning, are being implemented in a coastal Metasequoia glyptostroboides forest shelterbelt in Eastern China. The vegetation carbon storage significantly increased in the underplanted and thinned treatments compared with that in the unthinned treatment (P carbon storage in the underplanted treatment were significantly higher than those in the unthinned treatment (P carbon storage in the underplanted and thinned treatments increased by 35.3% and 26.3%, respectively, compared with that in the unthinned treatment, an increase that mainly came from the growth of vegetation aboveground. Total ecosystem carbon storage showed no significant difference between the underplanted and thinned treatments (P > 0.05). The soil light fraction organic carbon (LFOC) was significantly higher at the 0–15 cm soil layer in the thinned and underplanted stands compared with that in the unthinned stand (P carbon sequestration for M. glyptostroboides plantations in the coastal areas of Eastern China. PMID:24187525

  11. Effects of intermediate-severity disturbance on composition and structure in mixed Pinus-hardwood stands

    Science.gov (United States)

    Benjamin Trammell; Justin Hart; Callie Schweitzer; Daniel C. Dey; Michael Steinberg

    2017-01-01

    Increasingly, forest managers intend to create or maintain mixed Pinus-hardwood stands. This stand assemblage may be driven by a variety of objectives but is often motivated by the desire to enhance native forest diversity and promote resilience to perturbations. Documenting the effects of natural disturbances on species composition and stand...

  12. WestPro: a computer program for simulating uneven-aged Douglas-fir stand growth and yield in the Pacific Northwest.

    Science.gov (United States)

    Rebecca Ralston; Joseph Buongiorno; Benedict Schulte; Jeremy. Fried

    2003-01-01

    WestPro is an add-in program designed to work with Microsoft Excel to simulate the growth of uneven-aged Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands in the Pacific Northwest region of the United States. Given the initial stand state, defined as the number of softwood and hardwood trees per acre by diameter class, WestPro predicts the...

  13. A Pine Is a Pine and a Spruce Is a Spruce – The Effect of Tree Species and Stand Age on Epiphytic Lichen Communities

    Science.gov (United States)

    Bäcklund, Sofia; Jönsson, Mari; Strengbom, Joachim; Frisch, Andreas; Thor, Göran

    2016-01-01

    With an increasing demand for forest-based products, there is a growing interest in introducing fast-growing non-native tree species in forest management. Such introductions often have unknown consequences for native forest biodiversity. In this study, we examine epiphytic lichen species richness and species composition on the trunks of non-native Pinus contorta and compare these to the native Pinus sylvestris and Picea abies in managed boreal forests in northern Sweden across a chronosequence of age classes. Overall, we recorded a total of 66,209 lichen occurrences belonging to 57 species in the 96 studied forest stands. We found no difference in species richness of lichens between stands of P. contorta and P. sylvestris, but stands of P. abies had higher total species richness. However, species richness of lichens in stands of P. abies decreased with increasing stand age, while no such age effect was detected for P. contorta and P. sylvestris. Lichen species composition progressively diverged with increasing stand age, and in 30-year-old stands all three tree species showed species-specific assemblages. Epiphytic lichen assemblages in stands of 30-year-old P. contorta were influenced by greater basal area, canopy closure, and average diameter at breast height, P. abies stands by higher branch density and canopy closure, and stands of P. sylvestris by greater bark crevice depth. Differences in lichen species richness and composition were mainly explained by canopy closure and habitat availability, and the greater canopy closure in mature P. abies stands promoted the colonization and growth of calicioid lichen species. Our results indicate that the non-native P. contorta have similar species richness as the native P. sylvestris. The main difference in lichen species richness and composition is between P. abies and Pinus spp. in managed forests of boreal Sweden. PMID:26799558

  14. A Pine Is a Pine and a Spruce Is a Spruce--The Effect of Tree Species and Stand Age on Epiphytic Lichen Communities.

    Science.gov (United States)

    Bäcklund, Sofia; Jönsson, Mari; Strengbom, Joachim; Frisch, Andreas; Thor, Göran

    2016-01-01

    With an increasing demand for forest-based products, there is a growing interest in introducing fast-growing non-native tree species in forest management. Such introductions often have unknown consequences for native forest biodiversity. In this study, we examine epiphytic lichen species richness and species composition on the trunks of non-native Pinus contorta and compare these to the native Pinus sylvestris and Picea abies in managed boreal forests in northern Sweden across a chronosequence of age classes. Overall, we recorded a total of 66,209 lichen occurrences belonging to 57 species in the 96 studied forest stands. We found no difference in species richness of lichens between stands of P. contorta and P. sylvestris, but stands of P. abies had higher total species richness. However, species richness of lichens in stands of P. abies decreased with increasing stand age, while no such age effect was detected for P. contorta and P. sylvestris. Lichen species composition progressively diverged with increasing stand age, and in 30-year-old stands all three tree species showed species-specific assemblages. Epiphytic lichen assemblages in stands of 30-year-old P. contorta were influenced by greater basal area, canopy closure, and average diameter at breast height, P. abies stands by higher branch density and canopy closure, and stands of P. sylvestris by greater bark crevice depth. Differences in lichen species richness and composition were mainly explained by canopy closure and habitat availability, and the greater canopy closure in mature P. abies stands promoted the colonization and growth of calicioid lichen species. Our results indicate that the non-native P. contorta have similar species richness as the native P. sylvestris. The main difference in lichen species richness and composition is between P. abies and Pinus spp. in managed forests of boreal Sweden.

  15. Microbeam high-resolution diffraction and x-ray standing wave methods applied to semiconductor structures

    International Nuclear Information System (INIS)

    Kazimirov, A; Bilderback, D H; Huang, R; Sirenko, A; Ougazzaden, A

    2004-01-01

    A new approach to conditioning x-ray microbeams for high angular resolution x-ray diffraction and scattering techniques is introduced. We combined focusing optics (one-bounce imaging capillary) and post-focusing collimating optics (miniature Si(004) channel-cut crystal) to generate an x-ray microbeam with a size of 10 μm and ultimate angular resolution of 14 μrad. The microbeam was used to analyse the strain in sub-micron thick InGaAsP epitaxial layers grown on an InP(100) substrate by the selective area growth technique in narrow openings between the oxide stripes. For the structures for which the diffraction peaks from the substrate and the film overlap, the x-ray standing wave technique was applied for precise measurements of the strain with a Δd/d resolution of better than 10 -4 . (rapid communication)

  16. Twenty-four years after theYellowstone Fires: Are postfire lodgepole pine stands converging in structure and function?

    Science.gov (United States)

    Turner, Monica G; Whitby, Timothy G; Tinker, Daniel B; Romme, William H

    2016-05-01

    Disturbance and succession have long been of interest in ecology, but how landscape patterns of ecosystem structure and function evolve following large disturbances is poorly understood. After nearly 25 years, lodgepole pine (Pinus contorta var. latifolia) forests that regenerated after the 1988 Yellowstone Fires (Wyoming, USA) offer a prime opportunity to track the fate of disturbance-created heterogeneity in stand structure and function in a wilderness setting. In 2012, we resampled 72 permanent plots to ask (1) How have postfire stand structure and function changed between 11 and 24 yr postfire, and what variables explain these patterns and changes? (2) How has landscape-level (among-stand) variability in postfire stand structure and function changed between 11 and 24 yr postfire? We expected to see evidence of convergence beginning to emerge, but also that initial postfire stem density would still determine trajectories of biomass accumulation. After 24 yr, postfire lodgepole pine density remained very high (mean = 21,738 stems/ha, range = 0-344,067 stems/ha). Stem density increased in most plots between 11 and 24 yr postfire, but declined sharply where 11-yr-postfire stem density was > 72,000 stems/ha. Stems were small in high-density stands, but stand-level lodgepole pine leaf area, foliage biomass, and live aboveground biomass increased over time and with increasing stem density. After 24 yr, mean annual lodgepole pine aboveground net primary production (ANPP) was high (mean = 5 Mg · ha⁻¹ · yr⁻¹, range = 0-16.5 Mg · ha⁻¹ · yr⁻¹). Among stands, lodgepole pine ANPP increased with stem density, which explained 69% of the variation; another 8% of the variation was explained by environmental covariates. Early patterns of postfire lodgepole pine regeneration, which were contingent on prefire serotiny and fire severity, remained the dominant driver of stand structure and function. We observed mechanisms that would lead to convergence in stem density

  17. Restraint Effects in Early Age Concrete Structures

    OpenAIRE

    Al-Gburi, Majid

    2015-01-01

    One of the widespread issues in concrete structures is cracks occurring at early age. Cracks that appear in the young concrete may cause early start of corrosion of rebars or early penetration of harmful liquids or gases into the concrete body. These situations could result in reduced service life and in significantly increased maintenance cost of structures. Therefore it is important for construction companies to avoid these cracks.Volumetric deformations in early age concrete are caused by ...

  18. Occupations Classified by Their Age Structure

    Science.gov (United States)

    Smith, John M.

    1975-01-01

    An analysis of occupational age structures for males has pragmatic implications for vocational advice and decisions (particularly for older workers), personnel and manpower planning, and experimental research. (A 5-page appendix lists occupational age ratios for 2( categories of occupations based on 1961 census data.) (Author/AG)

  19. Influence of Anthropogenic Disturbances on Stand Structural Complexity in Andean Temperate Forests: Implications for Managing Key Habitat for Biodiversity

    Science.gov (United States)

    2017-01-01

    Forest attributes and their abundances define the stand structural complexity available as habitat for faunal biodiversity; however, intensive anthropogenic disturbances have the potential to degrade and simplify forest stands. In this paper we develop an index of stand structural complexity and show how anthropogenic disturbances, namely fire, logging, livestock, and their combined presence, affect stand structural complexity in a southern Global Biodiversity Hotspot. From 2011 to 2013, we measured forest structural attributes as well as the presence of anthropogenic disturbances in 505 plots in the Andean zone of the La Araucanía Region, Chile. In each plot, understory density, coarse woody debris, number of snags, tree diameter at breast height, and litter depth were measured, along with signs of the presence of anthropogenic disturbances. Ninety-five percent of the plots showed signs of anthropogenic disturbance (N = 475), with the combined presence of fire, logging, and livestock being the most common disturbance (N = 222; 44% of plots). The lowest values for the index were measured in plots combining fire, logging, and livestock. Undisturbed plots and plots with the presence of relatively old fires (> 70 years) showed the highest values for the index of stand structural complexity. Our results suggest that secondary forests forests should be managed to retain structural attributes, including understory density (7.2 ± 2.5 # contacts), volume of CWD (22.4 ± 25.8 m3/ha), snag density (94.4 ± 71.0 stems/ha), stand basal area (61.2 ± 31.4 m2/ha), and litter depth (7.5 ± 2.7 cm). Achieving these values will increase forest structural complexity, likely benefiting a range of faunal species in South American temperate forests. PMID:28068349

  20. Age structure and expansion of pinon-juniper woodlands: a regional perspective in the Intermountain West

    Science.gov (United States)

    Richard F. Miller; Robin J. Tausch; E. Durant McArthur; Dustin D. Johnson; Stewart C. Sanderson

    2008-01-01

    Numerous studies have documented the expansion of woodlands in the Intermountain West; however, few have compared the chronology of expansion for woodlands across different geographic regions or determined the mix and extent of presettlement stands. We evaluated tree age structure and establishment for six woodlands in four ecological provinces in the central and...

  1. An update on the Structural Aging Program

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.; Mori, Y.; Arndt, E.G.

    1992-01-01

    The Structural Aging (SAG) Program is being conducted at the Oak Ridge National Laboratory (ORNL) for the Nuclear Regulatory Commission (NRC). The SAG Program is addressing the aging management of safety-related concrete structures in nuclear power plants for the purpose of providing improved technical bases for their continued service. The program is organized into four tasks: Program Management, Materials Property Data Base, Structural Component Assessment/Repair Technologies, and Quantitative Methodology for Continued Service Determinations. Objectives and a summary of accomplishments under each of these tasks are presented

  2. An Evaluation of the Use of Simulated Annealing to Optimize Thinning Rates for Single Even-Aged Stands

    Directory of Open Access Journals (Sweden)

    Kai Moriguchi

    2015-01-01

    Full Text Available We evaluated the potential of simulated annealing as a reliable method for optimizing thinning rates for single even-aged stands. Four types of yield models were used as benchmark models to examine the algorithm’s versatility. Thinning rate, which was constrained to 0–50% every 5 years at stand ages of 10–45 years, was optimized to maximize the net present value for one fixed rotation term (50 years. The best parameters for the simulated annealing were chosen from 113 patterns, using the mean of the net present value from 39 runs to ensure the best performance. We compared the solutions with those from coarse full enumeration to evaluate the method’s reliability and with 39 runs of random search to evaluate its efficiency. In contrast to random search, the best run of simulated annealing for each of the four yield models resulted in a better solution than coarse full enumeration. However, variations in the objective function for two yield models obtained with simulated annealing were significantly larger than those of random search. In conclusion, simulated annealing with optimized parameters is more efficient for optimizing thinning rates than random search. However, it is necessary to execute multiple runs to obtain reliable solutions.

  3. Age-related decrease in motor cortical inhibition during standing under different sensory conditions

    NARCIS (Netherlands)

    Papegaaij, Selma; Taube, Wolfgang; Hogenhout, Margot; Baudry, Stephane; Hortobagyi, Tibor

    2014-01-01

    Background: Although recent studies point to the involvement of the primary motor cortex in postural control, it is unknown if age-related deterioration of postural control is associated with changes in motor cortical circuits. We examined the interaction between age and sensory condition in the

  4. Aging management of nuclear fuel pool structures

    International Nuclear Information System (INIS)

    Hookham, C.J.

    1991-01-01

    The long-term operations of a nuclear power plant (NPP) are currently impacted by the utility's capabilities with respect to spent fuel storage. Available options for the safe, long-term storage of spent fuel are quite limited; as such, maximized usage of existing on-site storage capacity (NPP) is quite important. The service life of existing fuel pool structures may be determined by a number of operations or age-related events. Management of these events is often critical to the structure's integrity and durability. From an operations vantage point, aging management relates to such characteristics as storage capacity, performance of pool water treatment systems, and physical liner damage. Primary issues related to structural integrity include materials degradation and environmental enclosure factors. The development of an effective aging management program should address both operational and structural issues. The goal of this paper is to provide recommendations for pool structure aging management, with benefits to both short and long-term, or extended life, operations. Because of their critical nature, the report will focus on spent fuel pools. Many of the concepts generated in this report may also be applied to other NPP pool structures (i.e., new fuel pools, reactor internals pits and transfer canals) because of similar physical/environmental effects

  5. Structural imaging measures of brain aging.

    Science.gov (United States)

    Lockhart, Samuel N; DeCarli, Charles

    2014-09-01

    During the course of normal aging, biological changes occur in the brain that are associated with changes in cognitive ability. This review presents data from neuroimaging studies of primarily "normal" or healthy brain aging. As such, we focus on research in unimpaired or nondemented older adults, but also include findings from lifespan studies that include younger and middle aged individuals as well as from populations with prodromal or clinically symptomatic disease such as cerebrovascular or Alzheimer's disease. This review predominantly addresses structural MRI biomarkers, such as volumetric or thickness measures from anatomical images, and measures of white matter injury and integrity respectively from FLAIR or DTI, and includes complementary data from PET and cognitive or clinical testing as appropriate. The findings reveal highly consistent age-related differences in brain structure, particularly frontal lobe and medial temporal regions that are also accompanied by age-related differences in frontal and medial temporal lobe mediated cognitive abilities. Newer findings also suggest that degeneration of specific white matter tracts such as those passing through the genu and splenium of the corpus callosum may also be related to age-related differences in cognitive performance. Interpretation of these findings, however, must be tempered by the fact that comorbid diseases such as cerebrovascular and Alzheimer's disease also increase in prevalence with advancing age. As such, this review discusses challenges related to interpretation of current theories of cognitive aging in light of the common occurrence of these later-life diseases. Understanding the differences between "Normal" and "Healthy" brain aging and identifying potential modifiable risk factors for brain aging is critical to inform potential treatments to stall or reverse the effects of brain aging and possibly extend cognitive health for our aging society.

  6. Formation of Fine Structures in Uniform Suspension under Standing Waves Action

    Science.gov (United States)

    Kalinichenko, V. F.; Chashechkin, Yu. D.

    2012-04-01

    Structurization of initially uniform suspension in fields of standing gravity waves was studied in a rectangular tank oscillating in vertical direction. The tank with aspect ratio of 50:4 was placed at shaker table with a low level of horizontal components of acceleration during the motion. Diluted aluminum powder suspension in water filled in tank with was undergone wave action in frequency range corresponding to first and second modes of intrinsic oscillations. For visualizations and tracers velocity measurements a digital high-speed video camera was used. The formation of large and small scale structures in initially uniform suspension was registered. Experiments were performed in tanks with flat smooth and rough bottom as well as with water above stationary ripples and deformable sand riffles. Large and small scales irregularities of initially smooth field of concentration were observed in the whole volume of the fluid. Large voids with shapes reminding the bottom topography features were formed first. Later the fine extended filaments were observed. Their horizontal scales were determined by bed forms extension, and the vertical scale grows in time. Depending on the wave mode the filament structures arose from the bottom or sank from the free surface. The evolution of the structure geometrical parameters were measured both in vertical and horizontal directions. The difference of dynamical behaviour of suspension concentration in vicinity and far from free surface, flat bottom or bed topography was determined and discussed. In theoretical description of the flow compete fundamental set of governing equations. Complete solution of the set contains family of thin singular perturbed components which are characterized by singular perturbed functions. These flow components can accumulate of admixtures and maintain non-uniform pattern of admixture concentration. The presented experiments were performed on set-up USU "HPC IPMec RAS" under support of Ministry of

  7. Quantifying Standing Dead Tree Volume and Structural Loss with Voxelized Terrestrial Lidar Data

    Science.gov (United States)

    Popescu, S. C.; Putman, E.

    2017-12-01

    Standing dead trees (SDTs) are an important forest component and impact a variety of ecosystem processes, yet the carbon pool dynamics of SDTs are poorly constrained in terrestrial carbon cycling models. The ability to model wood decay and carbon cycling in relation to detectable changes in tree structure and volume over time would greatly improve such models. The overall objective of this study was to provide automated aboveground volume estimates of SDTs and automated procedures to detect, quantify, and characterize structural losses over time with terrestrial lidar data. The specific objectives of this study were: 1) develop an automated SDT volume estimation algorithm providing accurate volume estimates for trees scanned in dense forests; 2) develop an automated change detection methodology to accurately detect and quantify SDT structural loss between subsequent terrestrial lidar observations; and 3) characterize the structural loss rates of pine and oak SDTs in southeastern Texas. A voxel-based volume estimation algorithm, "TreeVolX", was developed and incorporates several methods designed to robustly process point clouds of varying quality levels. The algorithm operates on horizontal voxel slices by segmenting the slice into distinct branch or stem sections then applying an adaptive contour interpolation and interior filling process to create solid reconstructed tree models (RTMs). TreeVolX estimated large and small branch volume with an RMSE of 7.3% and 13.8%, respectively. A voxel-based change detection methodology was developed to accurately detect and quantify structural losses and incorporated several methods to mitigate the challenges presented by shifting tree and branch positions as SDT decay progresses. The volume and structural loss of 29 SDTs, composed of Pinus taeda and Quercus stellata, were successfully estimated using multitemporal terrestrial lidar observations over elapsed times ranging from 71 - 753 days. Pine and oak structural loss rates

  8. Growth and yield of all-aged Douglas-fir -- western hemlock forest stands: a matrix model with stand diversity effects.

    Science.gov (United States)

    Jingjing Liang; Joseph Buonglorno; Robert A. Monserud

    2005-01-01

    A density-dependent matrix model was developed for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) -- western hemlock (Tsuga heterophylla (Raf.) Sarg.) forest stands in the Pacific Northwest of the United States. The model predicted the number and volume of trees for 4 species groups and 19 diameter classes. The parameters...

  9. The use of hyperspectral remote sensing for mapping the age composition of forest stands

    Czech Academy of Sciences Publication Activity Database

    Skoupý, O.; Zejdová, L.; Hanuš, Jan

    2012-01-01

    Roč. 58, č. 6 (2012), s. 287-297 ISSN 1212-4834 Institutional support: RVO:67179843 Keywords : age classification * forestry * hyperspectral * object oriented * segmentation * spruce Subject RIV: EH - Ecology, Behaviour

  10. Effects of Dwarf Mistletoe on Stand Structure of Lodgepole Pine Forests 21-28 Years Post-Mountain Pine Beetle Epidemic in Central Oregon

    Science.gov (United States)

    Agne, Michelle C.; Shaw, David C.; Woolley, Travis J.; Queijeiro-Bolaños, Mónica E.

    2014-01-01

    Lodgepole pine (Pinus contorta) forests are widely distributed throughout North America and are subject to mountain pine beetle (Dendroctonus ponderosae) epidemics, which have caused mortality over millions of hectares of mature trees in recent decades. Mountain pine beetle is known to influence stand structure, and has the ability to impact many forest processes. Dwarf mistletoe (Arceuthobium americanum) also influences stand structure and occurs frequently in post-mountain pine beetle epidemic lodgepole pine forests. Few studies have incorporated both disturbances simultaneously although they co-occur frequently on the landscape. The aim of this study is to investigate the stand structure of lodgepole pine forests 21–28 years after a mountain pine beetle epidemic with varying levels of dwarf mistletoe infection in the Deschutes National Forest in central Oregon. We compared stand density, stand basal area, canopy volume, proportion of the stand in dominant/codominant, intermediate, and suppressed cohorts, average height and average diameter of each cohort, across the range of dwarf mistletoe ratings to address differences in stand structure. We found strong evidence of a decrease in canopy volume, suppressed cohort height, and dominant/codominant cohort diameter with increasing stand-level dwarf mistletoe rating. There was strong evidence that as dwarf mistletoe rating increases, proportion of the stand in the dominant/codominant cohort decreases while proportion of the stand in the suppressed cohort increases. Structural differences associated with variable dwarf mistletoe severity create heterogeneity in this forest type and may have a significant influence on stand productivity and the resistance and resilience of these stands to future biotic and abiotic disturbances. Our findings show that it is imperative to incorporate dwarf mistletoe when studying stand productivity and ecosystem recovery processes in lodgepole pine forests because of its potential to

  11. Effects of dwarf mistletoe on stand structure of lodgepole pine forests 21-28 years post-mountain pine beetle epidemic in central Oregon.

    Directory of Open Access Journals (Sweden)

    Michelle C Agne

    Full Text Available Lodgepole pine (Pinus contorta forests are widely distributed throughout North America and are subject to mountain pine beetle (Dendroctonus ponderosae epidemics, which have caused mortality over millions of hectares of mature trees in recent decades. Mountain pine beetle is known to influence stand structure, and has the ability to impact many forest processes. Dwarf mistletoe (Arceuthobium americanum also influences stand structure and occurs frequently in post-mountain pine beetle epidemic lodgepole pine forests. Few studies have incorporated both disturbances simultaneously although they co-occur frequently on the landscape. The aim of this study is to investigate the stand structure of lodgepole pine forests 21-28 years after a mountain pine beetle epidemic with varying levels of dwarf mistletoe infection in the Deschutes National Forest in central Oregon. We compared stand density, stand basal area, canopy volume, proportion of the stand in dominant/codominant, intermediate, and suppressed cohorts, average height and average diameter of each cohort, across the range of dwarf mistletoe ratings to address differences in stand structure. We found strong evidence of a decrease in canopy volume, suppressed cohort height, and dominant/codominant cohort diameter with increasing stand-level dwarf mistletoe rating. There was strong evidence that as dwarf mistletoe rating increases, proportion of the stand in the dominant/codominant cohort decreases while proportion of the stand in the suppressed cohort increases. Structural differences associated with variable dwarf mistletoe severity create heterogeneity in this forest type and may have a significant influence on stand productivity and the resistance and resilience of these stands to future biotic and abiotic disturbances. Our findings show that it is imperative to incorporate dwarf mistletoe when studying stand productivity and ecosystem recovery processes in lodgepole pine forests because of its

  12. Effects of dwarf mistletoe on stand structure of lodgepole pine forests 21-28 years post-mountain pine beetle epidemic in central Oregon.

    Science.gov (United States)

    Agne, Michelle C; Shaw, David C; Woolley, Travis J; Queijeiro-Bolaños, Mónica E

    2014-01-01

    Lodgepole pine (Pinus contorta) forests are widely distributed throughout North America and are subject to mountain pine beetle (Dendroctonus ponderosae) epidemics, which have caused mortality over millions of hectares of mature trees in recent decades. Mountain pine beetle is known to influence stand structure, and has the ability to impact many forest processes. Dwarf mistletoe (Arceuthobium americanum) also influences stand structure and occurs frequently in post-mountain pine beetle epidemic lodgepole pine forests. Few studies have incorporated both disturbances simultaneously although they co-occur frequently on the landscape. The aim of this study is to investigate the stand structure of lodgepole pine forests 21-28 years after a mountain pine beetle epidemic with varying levels of dwarf mistletoe infection in the Deschutes National Forest in central Oregon. We compared stand density, stand basal area, canopy volume, proportion of the stand in dominant/codominant, intermediate, and suppressed cohorts, average height and average diameter of each cohort, across the range of dwarf mistletoe ratings to address differences in stand structure. We found strong evidence of a decrease in canopy volume, suppressed cohort height, and dominant/codominant cohort diameter with increasing stand-level dwarf mistletoe rating. There was strong evidence that as dwarf mistletoe rating increases, proportion of the stand in the dominant/codominant cohort decreases while proportion of the stand in the suppressed cohort increases. Structural differences associated with variable dwarf mistletoe severity create heterogeneity in this forest type and may have a significant influence on stand productivity and the resistance and resilience of these stands to future biotic and abiotic disturbances. Our findings show that it is imperative to incorporate dwarf mistletoe when studying stand productivity and ecosystem recovery processes in lodgepole pine forests because of its potential to

  13. AGING EFFECTS ON SHIP STRUCTURAL INTEGRITY

    Directory of Open Access Journals (Sweden)

    Joško Parunov

    2017-01-01

    Full Text Available The most important degradation effects of ship structures are corrosion and fatigue cracks. Both of these aging effects have clear consequences of increasing the level of stresses and degrading the strength of ship structures for almost all relevant failure modes. This study presents an overview of some recent developments on the aging effects on the ship structural integrity. The analysis of the thickness measurements has been undertaken to improve understanding of the corrosion degradation phenomena and to develop prediction models of aging effects suitable for practical applications in the ship structural design and analysis. The study also deals with the application of the non-linear finite element analysis as a suitable tool for a collapse assessment of uniaxially loaded plates and stiffened panels of ship structures weakened by non-uniform corrosion degradation and fatigue cracks. Experimental studies have also been reviewed to better understand the recently found degradation of mechanical properties of corroded steel, while theoretical calculations have been performed to evaluate consequences of such degradation on the ship structural integrity.

  14. Forest stand structure and pattern of old-growth western hemlock/Douglas-fir and mixed-conifer forests

    Science.gov (United States)

    Malcolm North; Jiquan Chen; Brian Oakley; Bo Song; Mark Rudnicki; Andrew Gray; Jim Innes

    2004-01-01

    With fire suppression, many western forests are expected to have fewer gaps and higher stem density of shade-tolerant species as light competition becomes a more significant influence on stand pattern and composition. We compared species composition, structure, spatial pattern, and environmental factors such as light and soil moisture between two old-growth forests:...

  15. Composition, structure, and dynamics of a mature, unmanaged, pine-dominated old-field stand in southeastern Arkansas

    Science.gov (United States)

    Don C. Bragg; Eric Heitzman

    2009-01-01

    This study describes the composition and structure of a mature, second-growthPinus taeda (Loblolly Pine) and Pinus echinata (Shortleaf Pine)-dominatedold-field stand. Now owned by the University of Arkansas, this 22.5-ha parcel justoutside of the city of Monticello, AR, has been protected as a de facto natural area

  16. Free-standing nanomechanical and nanophotonic structures in single-crystal diamond

    Science.gov (United States)

    Burek, Michael John

    Realizing complex three-dimensional structures in a range of material systems is critical to a variety of emerging nanotechnologies. This is particularly true of nanomechanical and nanophotonic systems, both relying on free-standing small-scale components. In the case of nanomechanics, necessary mechanical degrees of freedom require physically isolated structures, such as suspended beams, cantilevers, and membranes. For nanophotonics, elements like waveguides and photonic crystal cavities rely on light confinement provided by total internal reflection or distributed Bragg reflection, both of which require refractive index contrast between the device and surrounding medium (often air). Such suspended nanostructures are typically fabricated in a heterolayer structure, comprising of device (top) and sacrificial (middle) layers supported by a substrate (bottom), using standard surface nanomachining techniques. A selective, isotropic etch is then used to remove the sacrificial layer, resulting in free-standing devices. While high-quality, crystalline, thin film heterolayer structures are readily available for silicon (as silicon-on-insulator (SOI)) or III-V semiconductors (i.e. GaAs/AlGaAs), there remains an extensive list of materials with attractive electro-optic, piezoelectric, quantum optical, and other properties for which high quality single-crystal thin film heterolayer structures are not available. These include complex metal oxides like lithium niobate (LiNbO3), silicon-based compounds such as silicon carbide (SiC), III-V nitrides including gallium nitride (GaN), and inert single-crystals such as diamond. Diamond is especially attractive for a variety of nanoscale technologies due to its exceptional physical and chemical properties, including high mechanical hardness, stiffness, and thermal conductivity. Optically, it is transparent over a wide wavelength range (from 220 nm to the far infrared), has a high refractive index (n ~ 2.4), and is host to a vast

  17. Variation in Carbon Storage and Its Distribution by Stand Age and Forest Type in Boreal and Temperate Forests in Northeastern China

    Science.gov (United States)

    Wei, Yawei; Li, Maihe; Chen, Hua; Lewis, Bernard J.; Yu, Dapao; Zhou, Li; Zhou, Wangming; Fang, Xiangmin; Zhao, Wei; Dai, Limin

    2013-01-01

    The northeastern forest region of China is an important component of total temperate and boreal forests in the northern hemisphere. But how carbon (C) pool size and distribution varies among tree, understory, forest floor and soil components, and across stand ages remains unclear. To address this knowledge gap, we selected three major temperate and two major boreal forest types in northeastern (NE) China. Within both forest zones, we focused on four stand age classes (young, mid-aged, mature and over-mature). Results showed that total C storage was greater in temperate than in boreal forests, and greater in older than in younger stands. Tree biomass C was the main C component, and its contribution to the total forest C storage increased with increasing stand age. It ranged from 27.7% in young to 62.8% in over-mature stands in boreal forests and from 26.5% in young to 72.8% in over-mature stands in temperate forests. Results from both forest zones thus confirm the large biomass C storage capacity of old-growth forests. Tree biomass C was influenced by forest zone, stand age, and forest type. Soil C contribution to total forest C storage ranged from 62.5% in young to 30.1% in over-mature stands in boreal and from 70.1% in young to 26.0% in over-mature in temperate forests. Thus soil C storage is a major C pool in forests of NE China. On the other hand, understory and forest floor C jointly contained less than 13% and forests respectively, and thus play a minor role in total forest C storage in NE China. PMID:23977252

  18. Changes to oak woodland stand structure and ground flora composition caused by thinning and burning

    Science.gov (United States)

    Kinkead, Carter O.; Kabrick, John M.; Stambaugh, Michael C.; Grabner, Keith W.

    2013-01-01

    Our objective was to quantify the cumulative effects of prescribed burning and thinning on forest stocking and species composition at a woodland restoration experiment site in the Ozark Highlands of Missouri. Our study used four treatments (burn, harvest, harvest and burn, control) on three slope position and aspect combinations (south, north, ridge) replicated in three complete blocks. Harvested stands were thinned from below to 40 percent residual stocking. Two prescribed fires were applied to both burn and harvest-burn treatment units in a 5-year period. Results reflect changes that have taken place over a 6-year period, from pretreatment conditions to 1 year after the last fire. In this period, there was a 10-percent reduction in the stocking in burned stands compared to control and a 6-percent reduction in harvested and burned stands compared to harvested stands. Compared to the control, percentage ground cover of woodland indicators was seven times greater in burned stands, six times greater in harvested stands, and 22 percent greater in harvested and burned stands. Th ere was no significant (P > 0.05) interaction between aspect and treatment on stocking or ground flora cover. Th is study indicated that silvicultural treatments do achieve various goals that are common to managers who aim to restore woodland communities.

  19. Probing the electrical double-layer structure at the rutile-water interface with x-ray standing waves.

    Energy Technology Data Exchange (ETDEWEB)

    Fenter, P.; Cheng, L.; Rihs, S.; Machesky, M.; Bedzyk, M. J.; Sturchio, N. C.

    2000-11-28

    We demonstrate that the X-ray standing wave (XSW) technique is a powerful probe of the electrical double-layer (EDL) structure. Measurements were made of Sr adsorption at the rutile (110)-water interface from aqueous solutions. Our results show that Bragg XSW, using small-period standing waves generated by Bragg diffraction from the substrate, precisely probes the location of ions within the condensed layer, and the in situ partitioning of ions between the condensed and diffuse layers. Such measurements can provide important constraints for the development and verification of theoretical models that describe ion adsorption at the solid-water interface.

  20. Foraging loads of red wood ants: Formica aquilonia (Hymenoptera: Formicidae in relation to tree characteristics and stand age

    Directory of Open Access Journals (Sweden)

    Heloise Gibb

    2016-05-01

    Full Text Available Background. Foraging efficiency is critical in determining the success of organisms and may be affected by a range of factors, including resource distance and quality. For social insects such as ants, outcomes must be considered at the level of both the individual and the colony. It is important to understand whether anthropogenic disturbances, such as forestry, affect foraging loads, independent of effects on the quality and distribution of resources. We asked if ants harvest greater loads from more distant and higher quality resources, how individual efforts scale to the colony level, and whether worker loads are affected by stand age. Methods. First, we performed a fine-scale study examining the effect of distance and resource quality (tree diameter and species on harvesting of honeydew by red wood ants, Formica aquilonia, in terms of crop load per worker ant and numbers of workers walking up and down each tree (ant activity (study 1. Second, we modelled what the combination of load and worker number responses meant for colony-level foraging loads. Third, at a larger scale, we asked whether the relationship between worker load and resource quality and distance depended on stand age (study 2. Results. Study 1 revealed that seventy percent of ants descending trees carried honeydew, and the percentage of workers that were honeydew harvesters was not related to tree species or diameter, but increased weakly with distance. Distance positively affected load mass in both studies 1 and 2, while diameter had weak negative effects on load. Relationships between load and distance and diameter did not differ among stands of different ages. Our model showed that colony-level loads declined much more rapidly with distance for small diameter than large diameter trees. Discussion. We suggest that a negative relationship between diameter and honeydew load detected in study 1 might be a result of crowding on large diameter trees close to nests, while the

  1. Foraging loads of red wood ants: Formica aquilonia (Hymenoptera: Formicidae) in relation to tree characteristics and stand age.

    Science.gov (United States)

    Gibb, Heloise; Andersson, Jon; Johansson, Therese

    2016-01-01

    Background. Foraging efficiency is critical in determining the success of organisms and may be affected by a range of factors, including resource distance and quality. For social insects such as ants, outcomes must be considered at the level of both the individual and the colony. It is important to understand whether anthropogenic disturbances, such as forestry, affect foraging loads, independent of effects on the quality and distribution of resources. We asked if ants harvest greater loads from more distant and higher quality resources, how individual efforts scale to the colony level, and whether worker loads are affected by stand age. Methods. First, we performed a fine-scale study examining the effect of distance and resource quality (tree diameter and species) on harvesting of honeydew by red wood ants, Formica aquilonia, in terms of crop load per worker ant and numbers of workers walking up and down each tree (ant activity) (study 1). Second, we modelled what the combination of load and worker number responses meant for colony-level foraging loads. Third, at a larger scale, we asked whether the relationship between worker load and resource quality and distance depended on stand age (study 2). Results. Study 1 revealed that seventy percent of ants descending trees carried honeydew, and the percentage of workers that were honeydew harvesters was not related to tree species or diameter, but increased weakly with distance. Distance positively affected load mass in both studies 1 and 2, while diameter had weak negative effects on load. Relationships between load and distance and diameter did not differ among stands of different ages. Our model showed that colony-level loads declined much more rapidly with distance for small diameter than large diameter trees. Discussion. We suggest that a negative relationship between diameter and honeydew load detected in study 1 might be a result of crowding on large diameter trees close to nests, while the increase in honeydew

  2. AGE STRUCTURE OR FUNCTIONAL RESPONSE? RECONCILING ...

    African Journals Online (AJOL)

    However, if the ECOSIM Arena is seen as a proxy for age structure rather than as a function of predator/prey behaviour, the original derivation of von Bertalanffy growth equations, applied as a modification of ECOSIM, may allow the predictions made by biomass dynamics ecosystem models to incorporate critical life-history ...

  3. Nutrition initiatives in the context of population aging: where does the United States stand?

    Science.gov (United States)

    Chalé, Angela; Unanski, Amanda G; Liang, Raymond Y

    2012-01-01

    In 2011, the earliest segment of the baby boom generation turned 65 years of age. This event marks the beginning of a new phase of growth of the older adult population in the United States and is in line with what is referred to worldwide as "population aging." By 2030, older adults will comprise 20% of the U.S. population. With the impending increase in the older adult population, the United States is unprepared to handle the accompanying social and economic impact of growing rates of age-related diseases such as diabetes, hypertension, and cardiovascular disease. These diseases have nutritional determinants and, as such, they signify the need for effective preventive nutrition initiatives to address population aging in the United States. Comparatively, the European Union (EU) is projected to reach an older adult population of 24% by 2030. In this special article we evaluate nutrition initiatives for older adults in the United States and also examine nutrition initiatives in the European Union in search of an ideal model. However, we found that available data for EU initiatives targeted at population aging were limited. We conclude by offering the proposal of a physician-based model that establishes the primary care physician as the initiator of nutrition screening, education, referrals, and follow-up for the older adult population in the United States as a long-term goal. Apropos of the immediate future, we consider barriers that underscore the establishment of a physician-based model and suggest objectives that are attainable. Although the data are limited for the European Union, this model may serve to guide management of chronic diseases with a nutritional component in economies similar to the United States worldwide.

  4. Data base on structural materials aging properties

    International Nuclear Information System (INIS)

    Oland, C.B.

    1992-01-01

    The US Nuclear Regulatory Commission has initiated a Structural Aging Program at the Oak Ridge National Laboratory to identify potential structural safety issues related to continued service of nuclear power plants and to establish criteria for evaluating and resolving these issues. One of the tasks in this program focuses on the establishment of a Structural Materials Information Center where long-term and environment-dependent properties of concretes and other structural materials are being collected and assembled into a data base. These properties will be used to evaluate the current condition of critical structural components in nuclear power plants and to estimate the future performance of these materials during the continued service period

  5. A top-down approach for fabricating free-standing bio-carbon supercapacitor electrodes with a hierarchical structure

    OpenAIRE

    Yingzhi Li; Qinghua Zhang; Junxian Zhang; Lei Jin; Xin Zhao; Ting Xu

    2015-01-01

    Biomass has delicate hierarchical structures, which inspired us to develop a cost-effective route to prepare electrode materials with rational nanostructures for use in high-performance storage devices. Here, we demonstrate a novel top-down approach for fabricating bio-carbon materials with stable structures and excellent diffusion pathways; this approach is based on carbonization with controlled chemical activation. The developed free-standing bio-carbon electrode exhibits a high specific ca...

  6. Aging of nuclear safety related concrete structures

    International Nuclear Information System (INIS)

    Cerny, R.; Vydra, V.; Toman, J.; Vodak, F.

    1994-01-01

    An analysis of aging processes in nuclear-safety-related concrete structures (NSRCS) is presented. The major environmental stressor and aging factors affecting the performance of NSRCS are summarized, as are drying and plastic shrinkage, expansion of water during the freeze-thaw cycle, water passing through cracks dissolving or leaching the soluble calcium hydroxide, attack of acid rain and ground water, chemical reactions between particular aggregates and the alkaline solution within cement paste, reaction of calcium hydroxide in cement paste hydration products with atmospheric carbon dioxide, and physical radiation effects of neutrons and gamma radiation. The current methods for aging management in NSRCS are analyzed and evaluated. A new treatment is presented for the monitoring, evaluation and prediction of aging processes, consisting in a combination of theoretical methods, laboratory experiments, in-situ measurements and numerical simulations. 24 refs

  7. Ectomycorrhizal diversity and community structure in stands of Quercus oleoides in the seasonally dry tropical forests of Costa Rica

    Science.gov (United States)

    Desai, Nikhilesh S.; Wilson, Andrew W.; Powers, Jennifer S.; Mueller, Gregory M.; Egerton-Warburton, Louise M.

    2016-12-01

    Most conservation efforts in seasonally dry tropical forests have overlooked less obvious targets for conservation, such as mycorrhizal fungi, that are critical to plant growth and ecosystem structure. We documented the diversity of ectomycorrhizal (EMF) and arbuscular mycorrhizal (AMF) fungal communities in Quercus oleoides (Fagaceae) in Guanacaste province, Costa Rica. Soil cores and sporocarps were collected from regenerating Q. oleoides plots differing in stand age (early vs late regeneration) during the wet season. Sequencing of the nuclear ribosomal ITS region in EMF root tips and sporocarps identified 37 taxa in the Basidiomycota; EMF Ascomycota were uncommon. The EMF community was dominated by one species (Thelephora sp. 1; 70% of soil cores), more than half of all EMF species were found only once in an individual soil core, and there were few conspecific taxa. Most EMF taxa were also restricted to either Early or Late plots. Levels of EMF species richness and diversity, and AMF root colonization were similar between plots. Our results highlight the need for comprehensive spatiotemporal samplings of EMF communities in Q. oleoides to identify and prioritize rare EMF for conservation, and document their genetic and functional diversity.

  8. The Period Ratio for Standing Kink and Sausage Modes in Solar Structures with Siphon Flow. I. Magnetized Slabs

    Science.gov (United States)

    Li, Bo; Habbal, Shadia Rifai; Chen, Yanjun

    2013-04-01

    In the applications of solar magneto-seismology, the ratio of the period of the fundamental mode to twice the period of its first overtone, P 1/2P 2, plays an important role. We examine how field-aligned flows affect the dispersion properties, and hence the period ratios, of standing modes supported by magnetic slabs in the solar atmosphere. We numerically solve the dispersion relations and devise a graphic means to construct standing modes. For coronal slabs, we find that the flow effects are significant for the fast kink and sausage modes alike. For the kink ones, they may reduce P 1/2P 2 by up to 23% compared with the static case, and the minimum allowed P 1/2P 2 can fall below the lower limit analytically derived for static slabs. For the sausage modes, while introducing the flow reduces P 1/2P 2 by typically case, it significantly increases the threshold aspect ratio only above which standing sausage modes can be supported, meaning that their detectability is restricted to even wider slabs. In the case of photospheric slabs, the flow effect is not as strong. However, standing modes are distinct from the coronal case in that standing kink modes show a P 1/2P 2 that deviates from unity even for a zero-width slab, while standing sausage modes no longer suffer from a threshold aspect ratio. We conclude that transverse structuring in plasma density and flow speed should be considered in seismological applications of multiple periodicities to solar atmospheric structures.

  9. Post-fire stand structure impacts carbon storage within Siberian larch forests

    Science.gov (United States)

    Alexander, H. D.; Natali, S.; Loranty, M. M.; Mack, M. C.; Davydov, S. P.; Zimov, N.

    2015-12-01

    Increased fire severity within boreal forests of the Siberian Arctic has the potential to alter forest stand development thereby altering carbon (C) accumulation rates and storage during the post-fire successional interval. One potential change is increased stand density, which may result from fire consumption of the soil organic layer and changes to the seedbed that favor germination and establishment of larch trees during early succession. In this study, we evaluated above- and belowground C pools across 12 stands of varying tree density within a single 75-year old fire scar located near Cherskii, Sakha Republic, Russia. In each stand, we inventoried the size and density of larch trees and large shrubs (Salix and Betula spp.), and in combination with with allometric equations, estimated aboveground contribution to C pools. We quantified woody debris C pools using the line intercept method. We sampled belowground C pools in the soil organic layer + upper (0-10 cm) mineral soil and coarse roots (> 2 mm diameter) using sediment cores and 0.25 x 0.25-m trenches, respectively. We found that high density stands store ~ 20% more C (~7,500 g C m-2) than low density stands (~5,800 g C m-2). In high density stands, about 35% more C is stored aboveground within live larch trees (1650 g C m-2) compared to low density stands (940 g C m-2), and about 15% more C is stored in the soil organic layer and upper mineral soil. Coarse root C was 20% higher in high density stands (~475 g C m-2) compared to those with low density (~350 g C m-2). Less C was stored in large shrubs in high density stands, both in aboveground portions and coarse roots, but these amounts were relatively small (< 10% of total C pools). A fire-driven shift to denser larch stands could increase C storage, leading to a negative feedback to climate, but the combined effects of density on C dynamics, summer and winter albedo, and future fire regimes will interact to determine the magnitude of any vegetation

  10. Quantification of the sit-to-stand movement for monitoring age-related motor deterioration using the Nintendo Wii Balance Board.

    Science.gov (United States)

    Yamako, Go; Chosa, Etsuo; Totoribe, Koji; Fukao, Yuu; Deng, Gang

    2017-01-01

    Simple methods for quantitative evaluations of individual motor performance are crucial for the early detection of motor deterioration. Sit-to-stand movement from a chair is a mechanically demanding component of activities of daily living. Here, we developed a novel method using the ground reaction force and center of pressure measured from the Nintendo Wii Balance Board to quantify sit-to-stand movement (sit-to-stand score) and investigated the age-related change in the sit-to-stand score as a method to evaluate reduction in motor performance. The study enrolled 503 participants (mean age ± standard deviation, 51.0 ± 19.7 years; range, 20-88 years; male/female ratio, 226/277) without any known musculoskeletal conditions that limit sit-to-stand movement, which were divided into seven 10-year age groups. The participants were instructed to stand up as quickly as possible, and the sit-to-stand score was calculated as the combination of the speed and balance indices, which have a tradeoff relationship. We also performed the timed up and go test, a well-known clinical test used to evaluate an individual's mobility. There were significant differences in the sit-to-stand score and timed up and go time among age groups. The mean sit-to-stand score for 60s, 70s, and 80s were 77%, 68%, and 53% of that for the 20s, respectively. The timed up and go test confirmed the age-related decrease in mobility of the participants. In addition, the sit-to-stand score measured using the Wii Balance Board was compared with that from a laboratory-graded force plate using the Bland-Altman plot (bias = -3.1 [ms]-1, 95% limit of agreement: -11.0 to 3.9 [ms]-1). The sit-to-stand score has good inter-device reliability (intraclass correlation coefficient = 0.87). Furthermore, the test-retest reliability is substantial (intraclass correlation coefficient = 0.64). Thus, the proposed STS score will be useful to detect the early deterioration of motor performance.

  11. Quantification of the sit-to-stand movement for monitoring age-related motor deterioration using the Nintendo Wii Balance Board.

    Directory of Open Access Journals (Sweden)

    Go Yamako

    Full Text Available Simple methods for quantitative evaluations of individual motor performance are crucial for the early detection of motor deterioration. Sit-to-stand movement from a chair is a mechanically demanding component of activities of daily living. Here, we developed a novel method using the ground reaction force and center of pressure measured from the Nintendo Wii Balance Board to quantify sit-to-stand movement (sit-to-stand score and investigated the age-related change in the sit-to-stand score as a method to evaluate reduction in motor performance. The study enrolled 503 participants (mean age ± standard deviation, 51.0 ± 19.7 years; range, 20-88 years; male/female ratio, 226/277 without any known musculoskeletal conditions that limit sit-to-stand movement, which were divided into seven 10-year age groups. The participants were instructed to stand up as quickly as possible, and the sit-to-stand score was calculated as the combination of the speed and balance indices, which have a tradeoff relationship. We also performed the timed up and go test, a well-known clinical test used to evaluate an individual's mobility. There were significant differences in the sit-to-stand score and timed up and go time among age groups. The mean sit-to-stand score for 60s, 70s, and 80s were 77%, 68%, and 53% of that for the 20s, respectively. The timed up and go test confirmed the age-related decrease in mobility of the participants. In addition, the sit-to-stand score measured using the Wii Balance Board was compared with that from a laboratory-graded force plate using the Bland-Altman plot (bias = -3.1 [ms]-1, 95% limit of agreement: -11.0 to 3.9 [ms]-1. The sit-to-stand score has good inter-device reliability (intraclass correlation coefficient = 0.87. Furthermore, the test-retest reliability is substantial (intraclass correlation coefficient = 0.64. Thus, the proposed STS score will be useful to detect the early deterioration of motor performance.

  12. Ageing in civil engineering materials and structures

    Energy Technology Data Exchange (ETDEWEB)

    Jaeger, Jean-Marc [SETEC TPI, Tour Gamma D 58, quai de la Rapee, 75583 Paris (France)

    2005-07-01

    SETEC TPI will address the 'Aging' topic of the Dijon Symposium by talking about: aging in civil engineering materials and structures, prevention of aging phenomena, in-operation monitoring of degradations related to aging and compensatory measures required to maintain a good safety level. Works as the Millau viaduct, the EdF skyscraper at La Defense - Paris, the renovation of the Grand Palais of Paris and special structures with Monaco's floating dam as well as the 'number 10' shaped gateway boat at Marseilles are illustrations for the issues discussed. The durability of civil engineering structures has become a major concern for designers. The Millau viaduct is designed for a service life of 120 years, and the Monaco dam for 100 years. Calculation rules have been evolving toward the incorporation of the concept of life cycle, for example, the Eurocodes 2 rules (reinforced concrete). The talk will expose the factors which are being taken into account to delay aging versus structure types. This part will be focused towards materials and corresponding regulations: - Reinforced concrete (coating of reinforcements, opening of cracks, choice of reinforcement types), BAEL and Eurocodes 2 rules; - Frame steel (protection, sacrificial anode), CM66 and Eurocodes 3 rules. New materials will also be mentioned: - Ultra high-performance fiber/concrete, with the example of CERACEM applied at Millau for the covering of the toll area barrier; - Titanium, which is starting to appear in the building trades, as for instance for the Beijing China Opera House shell. The second part of the talk will be devoted to a specific case namely, the 'number 10' shaped gateway bridge, a prestressed concrete structure immersed in the Port of Marseilles, which will be used to illustrate the aging phenomenon in a corrosive environment. We will focus on the types of inspection series performed by the Autonomous Port Authority of Marseilles to check the behavior of

  13. Progress in research on aging of structures

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.; Mori, Y.; Arndt, E.G.

    1991-01-01

    The Structural Aging (SAG) Program is conducted for the Nuclear Regulatory Commission. The program has the overall objective of preparing an expandable handbook or report which will provide the NRC with potential structural safety issues and acceptance criteria for use in nuclear power plant evaluations for continued service. Initial focus of the program is on concrete and concrete-related materials which comprise the safety-related (Category I) structures in light-water reactor facilities. The program consists of a management task and three technical tasks: materials property data base, structural component assessment/repair technology, and quantitative methodology for continued service determinations. Objectives, background information, and accomplishments under each of these tasks are presented

  14. Progress in research on aging of structures

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.; Mori, Y.; Arndt, E.G.

    1992-01-01

    The Structural Aging (SAG) Program is conducted for the Nuclear Regulatory Commission. The program has the overall objective of preparing an expandable handbook or report which will provide the NRC with potential structural safety issues and acceptance criteria for use in nuclear power plant evaluations for continued service. Initial focus of the program is on concrete and concrete-related materials which comprise the safety-related (Category 1) structures in light-water reactor facilities. The program consists of a management task and three technical tasks: materials property data base, structural component assessment/repair technology, and quantitative methodology for continued service determinations. Objectives, background information, and accomplishments under each of these tasks are presented

  15. An overview of the Structural Aging Program

    International Nuclear Information System (INIS)

    Naus, D.J.; Arndt, E.G.

    1992-01-01

    The structural Aging Program is conducted at the Oak Ridge National Laboratory (ORNL) for the Nuclear Regulatory Commission (NRC). The program has the overall objective of preparing an expandable handbook or report which will provide NRC with potential structural safety issues and acceptance criteria for use in nuclear power plant evaluations for continued service. Initial focus of the program is on concrete and concrete-related materials which comprise safety-related (Category I) structures in light-water reactor facilities. The program is organized into four tasks: Task S.1 -- Program Management, Task S.2 -- Materials Property Data Base, Task S.3 -- Structural Component Assessment/Repair Technology, and Task S.4 -- Quantitative Methodology for Continued Service Determinations. Objectives, background information, and accomplishments under each of these tasks are presented

  16. Optimizing management regimes for carbon storage and other benefits in uneven-aged stands dominated by Norway spruce, with a derivation of the economic supply of carbon storage

    Science.gov (United States)

    Joseph Buongiorno; Espen Andreas Halvorsen; Ole Martin Bollandsas; Terje Gobakken; Ole Hofstad

    2012-01-01

    This study sought optimal sustainable management regimes of uneven-aged Norway spruce-dominated stands with multiple objectives. The criteria were financial returns, CO2 sequestration and diversity of tree size and species. At prevailing timber prices, harvest and transport costs, and interest rates, uneven-aged management for timber alone was...

  17. A stand-alone tree demography and landscape structure module for Earth system models: integration with inventory data from temperate and boreal forests

    Science.gov (United States)

    Haverd, V.; Smith, B.; Nieradzik, L. P.; Briggs, P. R.

    2014-08-01

    Poorly constrained rates of biomass turnover are a key limitation of Earth system models (ESMs). In light of this, we recently proposed a new approach encoded in a model called Populations-Order-Physiology (POP), for the simulation of woody ecosystem stand dynamics, demography and disturbance-mediated heterogeneity. POP is suitable for continental to global applications and designed for coupling to the terrestrial ecosystem component of any ESM. POP bridges the gap between first-generation dynamic vegetation models (DVMs) with simple large-area parameterisations of woody biomass (typically used in current ESMs) and complex second-generation DVMs that explicitly simulate demographic processes and landscape heterogeneity of forests. The key simplification in the POP approach, compared with second-generation DVMs, is to compute physiological processes such as assimilation at grid-scale (with CABLE (Community Atmosphere Biosphere Land Exchange) or a similar land surface model), but to partition the grid-scale biomass increment among age classes defined at sub-grid-scale, each subject to its own dynamics. POP was successfully demonstrated along a savanna transect in northern Australia, replicating the effects of strong rainfall and fire disturbance gradients on observed stand productivity and structure. Here, we extend the application of POP to wide-ranging temporal and boreal forests, employing paired observations of stem biomass and density from forest inventory data to calibrate model parameters governing stand demography and biomass evolution. The calibrated POP model is then coupled to the CABLE land surface model, and the combined model (CABLE-POP) is evaluated against leaf-stem allometry observations from forest stands ranging in age from 3 to 200 year. Results indicate that simulated biomass pools conform well with observed allometry. We conclude that POP represents an ecologically plausible and efficient alternative to large-area parameterisations of woody

  18. Structural brain variation, age, and response time.

    Science.gov (United States)

    Haier, Richard J; Jung, Rex E; Yeo, Ronald A; Head, Kevin; Alkire, Michael T

    2005-06-01

    Response time (RT) generally slows with aging, but the contribution of structural brain changes to this slowing is unknown. We used voxel-based morphometry (VBM) to determine gray matter (GM) and white matter (WM) brain volumes in 9 middle-aged adults (38-58 years old) and 9 seniors (66-82 years old). We correlated brain volumes with RT assessed in both a simple visual stimulus-response task and a visual continuous recognition memory task. No GM correlations with simple RT were significant; there was one WM correlation in the right fusiform gyrus. In the memory task, faster RT was correlated (p BAs 19, 37, 46, 9, 8, 6, 13, 10, 41, and 7). The results suggest that individual differences in specific brain structure volumes should be considered as potential moderating factors in cognitive brain imaging studies.

  19. Cooperation and age structure in spatial games.

    Science.gov (United States)

    Wang, Zhen; Wang, Zhen; Zhu, Xiaodan; Arenzon, Jeferson J

    2012-01-01

    We study the evolution of cooperation in evolutionary spatial games when the payoff correlates with the increasing age of players (the level of correlation is set through a single parameter, α). The demographic heterogeneous age distribution, directly affecting the outcome of the game, is thus shown to be responsible for enhancing the cooperative behavior in the population. In particular, moderate values of α allow cooperators not only to survive but to outcompete defectors, even when the temptation to defect is large and the ageless, standard α=0 model does not sustain cooperation. The interplay between age structure and noise is also considered, and we obtain the conditions for optimal levels of cooperation. © 2012 American Physical Society

  20. Republic of Macedonia and Citizens Participation in the Digital Age: Where Do We Stand?"

    Directory of Open Access Journals (Sweden)

    Cvetanova, Ganka

    2016-10-01

    Full Text Available The paper evaluates citizens’ participation in e-democracy processes in the Republic of Macedonia i.e. e-participation. It reflects upon the availability of digital tools and availability of online platforms set up by the institutions on their official webpages in order to enable active citizens’ participation. Methodological approach used in this research relies on analysis of the obtained answers from an online questionnaire that explores citizens’ awareness of the possibility to use digital tools in the democratic process, their participation via usage of digital tools and their attitudes towards e-democracy process. The questionnaire was distributed via social networks Facebook and LinkedIn in the period from November 2015 to February 2016. The empirical findings in this study research enhance our understanding of citizens’ awareness of the possibility to use digital tools in the democratic process, their participation via usage of digital tools and their attitudes towards e-democracy process in the Republic of Macedonia. As findings suggest, there is stillroom for improvement of the factors that determine citizens’ participation in digital age.

  1. Daily operation optimisation of hybrid stand-alone system by model predictive control considering ageing model

    International Nuclear Information System (INIS)

    Dufo-López, Rodolfo; Fernández-Jiménez, L. Alfredo; Ramírez-Rosado, Ignacio J.; Artal-Sevil, J. Sergio; Domínguez-Navarro, José A.; Bernal-Agustín, José L.

    2017-01-01

    Highlights: • Method for optimising the daily operation of photovoltaic-wind-diesel-battery systems. • Weather forecasts of hourly wind speed, irradiation, temperature and load are used. • Each day five control variables are optimised for the control of the system. • Operating cost includes real ageing of the batteries and the diesel generator. • Results show that the optimal control strategy used for each day led to cost savings. - Abstract: This article presents a method for optimising the daily operation (minimising the total operating cost) of a hybrid photovoltaic-wind-diesel-battery system using model predictive control. The model uses actual weather forecasts of hourly values of wind speed, irradiation, temperature and load. Five control variables are optimised, and thus their optimal set points values determine the optimal control strategy for each day. This involves the use of an accurate model for estimating the degradation of the batteries by considering the capacity loss due to corrosion and degradation. The model considers the extra costs of maintaining and replacing the diesel generator due to running out of its optimal conditions. The optimisation is carried out by means of genetic algorithms. An example of application compares the total operating cost obtained using the optimal control strategy for each day with the cost of using the optimal control strategy found for the whole year, obtaining savings of up to 7.8%. Also the comparison with the cost of using the “load following” control strategy is analysed, obtaining savings of up to 37.7%.

  2. Local-scale patterns of genetic variability, outcrossing, and spatial structure in natural stands of Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Kirsten Bomblies

    2010-03-01

    Full Text Available As Arabidopsis thaliana is increasingly employed in evolutionary and ecological studies, it is essential to understand patterns of natural genetic variation and the forces that shape them. Previous work focusing mostly on global and regional scales has demonstrated the importance of historical events such as long-distance migration and colonization. Far less is known about the role of contemporary factors or environmental heterogeneity in generating diversity patterns at local scales. We sampled 1,005 individuals from 77 closely spaced stands in diverse settings around Tübingen, Germany. A set of 436 SNP markers was used to characterize genome-wide patterns of relatedness and recombination. Neighboring genotypes often shared mosaic blocks of alternating marker identity and divergence. We detected recent outcrossing as well as stretches of residual heterozygosity in largely homozygous recombinants. As has been observed for several other selfing species, there was considerable heterogeneity among sites in diversity and outcrossing, with rural stands exhibiting greater diversity and heterozygosity than urban stands. Fine-scale spatial structure was evident as well. Within stands, spatial structure correlated negatively with observed heterozygosity, suggesting that the high homozygosity of natural A. thaliana may be partially attributable to nearest-neighbor mating of related individuals. The large number of markers and extensive local sampling employed here afforded unusual power to characterize local genetic patterns. Contemporary processes such as ongoing outcrossing play an important role in determining distribution of genetic diversity at this scale. Local "outcrossing hotspots" appear to reshuffle genetic information at surprising rates, while other stands contribute comparatively little. Our findings have important implications for sampling and interpreting diversity among A. thaliana accessions.

  3. Accounting for density reduction and structural loss in standing dead trees: Implications for forest biomass and carbon stock estimates in the United States.

    Science.gov (United States)

    Domke, Grant M; Woodall, Christopher W; Smith, James E

    2011-11-24

    Standing dead trees are one component of forest ecosystem dead wood carbon (C) pools, whose national stock is estimated by the U.S. as required by the United Nations Framework Convention on Climate Change. Historically, standing dead tree C has been estimated as a function of live tree growing stock volume in the U.S.'s National Greenhouse Gas Inventory. Initiated in 1998, the USDA Forest Service's Forest Inventory and Analysis program (responsible for compiling the Nation's forest C estimates) began consistent nationwide sampling of standing dead trees, which may now supplant previous purely model-based approaches to standing dead biomass and C stock estimation. A substantial hurdle to estimating standing dead tree biomass and C attributes is that traditional estimation procedures are based on merchantability paradigms that may not reflect density reductions or structural loss due to decomposition common in standing dead trees. The goal of this study was to incorporate standing dead tree adjustments into the current estimation procedures and assess how biomass and C stocks change at multiple spatial scales. Accounting for decay and structural loss in standing dead trees significantly decreased tree- and plot-level C stock estimates (and subsequent C stocks) by decay class and tree component. At a regional scale, incorporating adjustment factors decreased standing dead quaking aspen biomass estimates by almost 50 percent in the Lake States and Douglas-fir estimates by more than 36 percent in the Pacific Northwest. Substantial overestimates of standing dead tree biomass and C stocks occur when one does not account for density reductions or structural loss. Forest inventory estimation procedures that are descended from merchantability standards may need to be revised toward a more holistic approach to determining standing dead tree biomass and C attributes (i.e., attributes of tree biomass outside of sawlog portions). Incorporating density reductions and structural

  4. Soil microbial biomass under pine forests in the north-western Spain: influence of stand age, site index and parent material

    Energy Technology Data Exchange (ETDEWEB)

    Mahia, J.; Perez-Ventura, L.; Cabaneiro, A.; Diaz-Ravina, M.

    2006-07-01

    The effects of stand age, site index and parent material on soil biochemical properties related to biomass (extractable C, microbial C and metabolic quotient) were examined in the 0-15 cm mineral soil layers of Pinus pinaster and Pinus sylvestris stand from NW Spain. Two productivity levels (low and high site index), two ages (young and old) and two parent soil materials (granite and acid schists) were considered. The data indicated that there were differences in microbial parameters in soils under different species. In general in P. pinaster forest higher values of biochemical parameters expressed on organic C basis, were observed in the stands of high site index as compared with the low ones; in contrast, in P. sylvestris no differences among stand site index were detected. In both species different results were also observed depending on parent material and a significant effect of stand age was detected for extractable C and microbial C in P. pinaster forest developed over granite. The data seem to indicate that measured parameters may have the potential to be used as indicators of the effect of forest management on soil organic matter quality. (Author) 25 refs.

  5. Linguistic and Structural Analyses of Stand-Alone Literature Reviews: Seventy-Five Years of Change

    Science.gov (United States)

    Wright, Heidi Rachel

    2016-01-01

    The purpose of this dissertation is to offer a multifaceted overview of stand-alone literature reviews. These texts, literature reviews published unattached to research articles, have existed for centuries but remained largely unstudied by linguists. Thus, the goal of this project is to present these reviews' situational, grammatical, and…

  6. Growth, yield, and structure of extended rotation Pinus resinosa stands in Minnesota, USA

    Science.gov (United States)

    Anthony W. D' Amato; Brian J. Palik; Christel C. Kern

    2010-01-01

    Extended rotations are increasingly used to meet ecological objectives on forestland; however, information about long-term growth and yield of these systems is lacking for most forests in North America. Additionally, long-term growth responses to repeated thinnings in older stands have received little attention. We addressed these needs by examining the growth and...

  7. The carbon consequences of thinning techniques: stand structure makes a difference

    Science.gov (United States)

    Coeli Hoover; Susan Stout

    2007-01-01

    Using results from a 25-year study of thinning in a northwestern Pennsylvania Allegheny hardwood stand, we assess whether and how thinning method affected carbon sequestration and merchantable volume production. Plots were thinned to similar residual relative density by removing trees from different portions of the diameter distribution. Plots that were thinned from...

  8. Cone Characteristics and Seed Quality 10 Years After An Uneven-Aged Regeneration Cut In Shortleaf Pine Stands

    Science.gov (United States)

    Kenneth J. Grayson; Robert F. Wittwer; Michael G. Shelton

    2002-01-01

    Cone characteristics and seed quality for 16 released (stand density 14 square meters per hectare) and 16 unreleased (stand density 28 square meters per hectare) shortleaf pine (Pinus echinata Mill.) trees were described by d.b.h. class (28, 33, 38, 43 centimeters) and crown position (upper south, upper north, lower south, and lower north). The 38-...

  9. THE PERIOD RATIO FOR STANDING KINK AND SAUSAGE MODES IN SOLAR STRUCTURES WITH SIPHON FLOW. I. MAGNETIZED SLABS

    International Nuclear Information System (INIS)

    Li Bo; Habbal, Shadia Rifai; Chen Yanjun

    2013-01-01

    In the applications of solar magneto-seismology, the ratio of the period of the fundamental mode to twice the period of its first overtone, P 1 /2P 2 , plays an important role. We examine how field-aligned flows affect the dispersion properties, and hence the period ratios, of standing modes supported by magnetic slabs in the solar atmosphere. We numerically solve the dispersion relations and devise a graphic means to construct standing modes. For coronal slabs, we find that the flow effects are significant for the fast kink and sausage modes alike. For the kink ones, they may reduce P 1 /2P 2 by up to 23% compared with the static case, and the minimum allowed P 1 /2P 2 can fall below the lower limit analytically derived for static slabs. For the sausage modes, while introducing the flow reduces P 1 /2P 2 by typically ∼ 1 /2P 2 that deviates from unity even for a zero-width slab, while standing sausage modes no longer suffer from a threshold aspect ratio. We conclude that transverse structuring in plasma density and flow speed should be considered in seismological applications of multiple periodicities to solar atmospheric structures.

  10. Individual tree height increment model for managed even-aged stands of ponderosa pine throughout the western United States using linear mixed effects models

    Science.gov (United States)

    Fabian Uzoh; William W. Oliver

    2006-01-01

    A height increment model is developed and evaluated for individual trees of ponderosa pine throughout the species range in western United States. The data set used in this study came from long-term permanent research plots in even-aged, pure stands both planted and of natural origin. The data base consists of six levels-of-growing stock studies supplemented by initial...

  11. Hardwood Control Treatments to Enhance Natural Regeneration and Growth of Loblolly-Shortleaf Pines in an Uneven-Aged Stand: 12-Year Results

    Science.gov (United States)

    Michael D. Cain

    1999-01-01

    To facilitate natural regeneration of loblolly (Pinus taeda L.) and shortleaf pines (P. echinata Mill.) in an overstocked, uneven-aged pine stand in southeastern Arkansas, hardwoods were controlled by either basal injection of Tordon® 101 R, soil application of Velpar® L, or rotary mowing followed by a broadcast spray of Tordon®...

  12. A 9-year comparison of hardwood control treatments for enhancing natural regeneration and growth of loblolly-shortleaf pines in an uneven-aged stand

    Science.gov (United States)

    Michael D. Cain

    1998-01-01

    Preharvest control of hardwoods facilitated natural regeneration of loblolly and shortleaf pines (Pinus taeda L. and P. enchinata Mill.) in an overstocked, uneven-aged stand in southern Arkansas. During spring 1983, hardwoods were controlled by either basal injection of Tordon® 101R, soil application of Velpar® L, or rotary mowing...

  13. A 10-Year Evaluation of Prescribed Winter Burns in Uneven-Aged Stands of Pinus taeda L. and P. echinata Mill.: Woody Understorey Vegetation Response

    Science.gov (United States)

    Michael D. Cain

    1993-01-01

    Abstract.The effects of burning cycles and pine basal area levels were assessed on natural pine regeneration and hardwood development in uneven-aged stands of loblolly andshortleafpines (Pinw taeda L. and P. echinata Mill.). The treatments included an unburned control and prescribed winter burrs at 3-, 6-, and 9-yr intervals. Basal area treatments were 9, 14, 18, and...

  14. Investigation and comparison of natural regeneration structure of forest stands in protected and non-protected areas in Arasbaran.

    Science.gov (United States)

    Alijanpour, Ahmad; Mahmoudzadeh, Ahmad

    2007-05-15

    In this study, a part of Arasbaran forest stands in two protected and non-protected areas have been compared for quantitative and qualitative factors of regeneration. Thus, using aerial photographs of 1967 in the scale of 1:20000, the similarity of these stands was examined and the comparable stands were chosen. Afterward, 77 circle plots of 0.01 ha in protected area and in the same way 77 circle plots of 0.01 ha in non-protected area with a grid size of 250x250 m were established. In each plot, all species with diameter at breast height (dbh) from zero to 7.5 cm were measured. According to the results the number of regeneration average in protected area was significantly higher than that in non-protected area. Oak and Hornbeam regeneration percentages showed highest significant difference in the selected areas. Additionally, these two species have the highest mixture percentage. The regeneration structure in both areas includes high and coppice systems, but coppice is prevalent. In both regions cutting, branching and grazing are the most important destructive factors, and the effects of these factors are higher in non-protected area.

  15. Edaphic, salinity, and stand structural trends in chronosequences of native and non-native dominated riparian forests along the Colorado River, USA

    Science.gov (United States)

    Merritt, David M.; Shafroth, Patrick B.

    2012-01-01

    Tamarix spp. are introduced shrubs that have become among the most abundant woody plants growing along western North American rivers. We sought to empirically test the long-held belief that Tamarix actively displaces native species through elevating soil salinity via salt exudation. We measured chemical and physical attributes of soils (e.g., salinity, major cations and anions, texture), litter cover and depth, and stand structure along chronosequences dominated by Tamarix and those dominated by native riparian species (Populus or Salix) along the upper and lower Colorado River in Colorado and Arizona/California, USA. We tested four hypotheses: (1) the rate of salt accumulation in soils is faster in Tamarix-dominated stands than stands dominated by native species, (2) the concentration of salts in the soil is higher in mature stands dominated by Tamarix compared to native stands, (3) soil salinity is a function of Tamarix abundance, and (4) available nutrients are more concentrated in native-dominated stands compared to Tamarix-dominated stands. We found that salt concentration increases at a faster rate in Tamarix-dominated stands along the relatively free-flowing upper Colorado but not along the heavily-regulated lower Colorado. Concentrations of ions that are known to be preferentially exuded by Tamarix (e.g., B, Na, and Cl) were higher in Tamarix stands than in native stands. Soil salt concentrations in older Tamarix stands along the upper Colorado were sufficiently high to inhibit germination, establishment, or growth of some native species. On the lower Colorado, salinity was very high in all stands and is likely due to factors associated with floodplain development and the hydrologic effects of river regulation, such as reduced overbank flooding, evaporation of shallow ground water, higher salt concentrations in surface and ground water due to agricultural practices, and higher salt concentrations in fine-textured sediments derived from naturally saline

  16. Stand Structure and Substrate Diversity as Two Major Drivers for Bryophyte Distribution in a Temperate Montane Ecosystem

    Directory of Open Access Journals (Sweden)

    Yun Chen

    2017-05-01

    Full Text Available Elucidating the major drivers of bryophyte distribution is the first step to protecting bryophyte diversity. Topography, forest, substrates (ground, tree trunks, roots, rocks, and rotten wood, and spatial factor, which factors are the major drivers of bryophyte distribution? In this study, 53 plots were set in 400 m2 along the elevation gradient in Xiaoqinling, China. All bryophytes in the plots were collected and identified. Regression analysis was used to examine the relationship between bryophyte and substrate diversity. We compared the patterns of overall bryophyte diversity and diversity of bryophytes found on the ground, tree, and rock along elevational gradients. Canonical correspondence analysis was applied to relate species composition to selected environmental variables. The importance of topography, forest, substrates, and spatial factors was determined by variance partitioning. A total of 1378 bryophyte specimens were collected, and 240 species were identified. Bryophyte diversity was closely related to substrate diversity. The overall bryophyte diversity significantly increased with elevation; however, the response varied among ground, tree, and rock bryophytes. Tree diversity and herb layer were considered important environmental factors in determining bryophyte distribution. Species abundance was best explained by stand structure (17%, and species diversity was best explained by stand structure (35% and substrate (40%. Results directly indicated that substrate diversity can improve bryophyte species diversity. The effects of micro-habitat formed by stand structure and substrate diversity were higher than those of spatial processes and topography factors on bryophyte distribution. This study proved that the determinant factors influencing bryophyte diversity reflect the trends in recent forest management, providing a real opportunity to improve forest biodiversity conservation.

  17. Neighborhood age structure and its implications for health.

    Science.gov (United States)

    Cagney, Kathleen A

    2006-09-01

    Age structure at the neighborhood level is rarely considered in contextual studies of health. However, age structure can play a critical role in shaping community life, the availability of resources, and the opportunities for social engagement-all factors that, research suggests, have direct and indirect effects on health. Age structure can be theorized as a compositional effect and as a contextual effect. In addition, the dynamic nature of age structure and the utility of a life course perspective as applied to neighborhood effects research merits attention. Four Chicago neighborhoods are summarized to illustrate how age structure varies across small space, suggesting that neighborhood age structure should be considered a key structural covariate in contextual research on health. Considering age structure implies incorporating not only meaningful cut points for important age groups (e.g., proportion 65 years and over) but attention to the shape of the distribution as well.

  18. A new approach to defining rotation ages on the basis of productive and technological aspects. Application to natural Pinus sylvestris L. stands in Central Spain

    Energy Technology Data Exchange (ETDEWEB)

    Rojo-Alboreca, A.; García-Villabrille, J.D.; Corral-Rivas, J.J.; Alía, R.; Montero, G.

    2017-11-01

    Aim of study: To propose a new approach to defining rotation ages on the basis of productive and technological aspects and to present an example of application of the methodology to natural Pinus sylvestris stands in relation to silvicultural treatment (light or heavy thinning) and site index. Area of study: Central Spain. Material and methods: We assumed that the price per m3 of logwood suitable for veneer is four times higher than logwood not apt for veneer. Considering the yield distribution for different technological and commercial classes, a model of diameter distributions and yield tables, the variation in an average price index for different age classes, site indexes and silvicultural treatments was calculated. The age at which the price index rises by less than 3%, the proportion of trees with d.b.h. higher than 40 cm, and other aspects such as the possible presence of fungal decay in old-growth stands were also taken into account to establish three criteria for defining rotation ages. Main results: The proposed methodology generates a wide range of rotation ages between 100 and 140 years for lightly thinned stands, and between 90 and 140 years for heavily thinned stands, depending on the site index. Research highlights: The proposed approach is based on technological and productive criteria, with the limitations imposed by sanitary risks. The methodology can be applied to generate rotation ages in relation to different site indexes and silvicultural treatments, provided that the timber market prices and the yield distribution for different technological and commercial classes are known, and that a model of diameter distributions and yield tables are available.

  19. A new approach to defining rotation ages on the basis of productive and technological aspects. Application to natural Pinus sylvestris L. stands in Central Spain

    Directory of Open Access Journals (Sweden)

    Alberto Rojo-Alboreca

    2017-10-01

    Full Text Available Aim of study: To propose a new approach to defining rotation ages on the basis of productive and technological aspects and to present an example of application of the methodology to natural Pinus sylvestris stands in relation to silvicultural treatment (light or heavy thinning and site index. Area of study: Central Spain. Material and methods: We assumed that the price per m3 of logwood suitable for veneer is four times higher than logwood not apt for veneer. Considering the yield distribution for different technological and commercial classes, a model of diameter distributions and yield tables, the variation in an average price index for different age classes, site indexes and silvicultural treatments was calculated. The age at which the price index rises by less than 3%, the proportion of trees with d.b.h. higher than 40 cm, and other aspects such as the possible presence of fungal decay in old-growth stands were also taken into account to establish three criteria for defining rotation ages. Main results: The proposed methodology generates a wide range of rotation ages between 100 and 140 years for lightly thinned stands, and between 90 and 140 years for heavily thinned stands, depending on the site index. Research highlights: The proposed approach is based on technological and productive criteria, with the limitations imposed by sanitary risks. The methodology can be applied to generate rotation ages in relation to different site indexes and silvicultural treatments, provided that the timber market prices and the yield distribution for different technological and commercial classes are known, and that a model of diameter distributions and yield tables are available.

  20. A new approach to defining rotation ages on the basis of productive and technological aspects. Application to natural Pinus sylvestris L. stands in Central Spain

    International Nuclear Information System (INIS)

    Rojo-Alboreca, A.; García-Villabrille, J.D.; Corral-Rivas, J.J.; Alía, R.; Montero, G.

    2017-01-01

    Aim of study: To propose a new approach to defining rotation ages on the basis of productive and technological aspects and to present an example of application of the methodology to natural Pinus sylvestris stands in relation to silvicultural treatment (light or heavy thinning) and site index. Area of study: Central Spain. Material and methods: We assumed that the price per m3 of logwood suitable for veneer is four times higher than logwood not apt for veneer. Considering the yield distribution for different technological and commercial classes, a model of diameter distributions and yield tables, the variation in an average price index for different age classes, site indexes and silvicultural treatments was calculated. The age at which the price index rises by less than 3%, the proportion of trees with d.b.h. higher than 40 cm, and other aspects such as the possible presence of fungal decay in old-growth stands were also taken into account to establish three criteria for defining rotation ages. Main results: The proposed methodology generates a wide range of rotation ages between 100 and 140 years for lightly thinned stands, and between 90 and 140 years for heavily thinned stands, depending on the site index. Research highlights: The proposed approach is based on technological and productive criteria, with the limitations imposed by sanitary risks. The methodology can be applied to generate rotation ages in relation to different site indexes and silvicultural treatments, provided that the timber market prices and the yield distribution for different technological and commercial classes are known, and that a model of diameter distributions and yield tables are available.

  1. Drive Stands

    Data.gov (United States)

    Federal Laboratory Consortium — The Electrical Systems Laboratory (ESL)houses numerous electrically driven drive stands. A drive stand consists of an electric motor driving a gearbox and a mounting...

  2. Age structure at diagnosis affects aggression in a psychiatric inpatient population: age structure affecting inpatient aggression.

    Science.gov (United States)

    Cho, Un Jung; Lee, JooYoung; Kim, Hyo-Won; Lee, Jung Sun; Joo, Yeon-Ho; Kim, Seong-Yoon; Kim, Chang Yoon; Shin, Yong-Wook

    2014-12-30

    Study of inpatient aggression in psychiatric inpatient units (PIUs), where vulnerable patients interact intensely in small groups, is hampered by a lack of systematic monitoring of aggressive events in the context of group dynamics. Our current study examines the relationship between aggression and group structure in the PIU of a general tertiary-care hospital over a 9-month period. The severity of aggression was monitored daily using the Overt Aggression Scale (OAS). Clinical data including the daily number and mean age of subpopulations with different diagnoses were acquired. Cross-correlation function and autoregressive integrated moving average modeling were used to assess the effects of various group structure parameters on the incidence of aggressive events in the PIU. The daily total OAS score correlated positively with the daily mean age of patients with schizophrenia and bipolar disorder. By contrast, the OAS total score demonstrated a negative correlation with the daily mean age of patients with major depression. The age of the patients at diagnosis is an important group structure that affects the incidence of aggression in a PIU.

  3. Heavy thinning of ponderosa pine stands: An Arizona case study

    Science.gov (United States)

    Peter F. Ffolliott; Jr. Baker; Gerald J. Gottfried

    2000-01-01

    Growth and structural changes in a mosaic of even-aged ponderosa pine (Pinus ponderosa) stands were studied for 25 years to determine the long-term impacts of a heavy thinning treatment to a basal-area level of 25 ft2/acre. Basal area and volume growth of these stands has increased since thinning and likely will continue to...

  4. A Comparison of pi/2-mode standing wave structures for Linac4

    CERN Document Server

    Wegner, R; CERN. Geneva. AB Department

    2006-01-01

    Cell coupled structures at twice the basic frequency provide a higher shunt impedance for proton energies above 90 MeV for Linac4 when compared to drift tube based geometries. For this reason the nominal accelerating structure for the energy range of 90-160 MeV in Linac4 was chosen to be a Side Coupled Structure at 704.4 MHz. High power klystrons will feed this structure, with the consequence that a large number of cells are coupled together in one module. To provide field stability in a long chain of resonators, a pi/2-mode structure will be used. In this report, the three best known and most widely used ones - the Annular Ring Coupled Structure (ACS), the On Axis Coupled Structure (OCS) and the Side Coupled Structure (SCS) - are compared in terms of the electrical parameters Q-value and shunt impedance as well as structure dimensions.

  5. Spatial Scales of Genetic Structure in Free-Standing and Strangler Figs (Ficus, Moraceae) Inhabiting Neotropical Forests.

    Science.gov (United States)

    Heer, Katrin; Kalko, Elisabeth K V; Albrecht, Larissa; García-Villacorta, Roosevelt; Staeps, Felix C; Herre, Edward Allen; Dick, Christopher W

    2015-01-01

    Wind-borne pollinating wasps (Agaonidae) can transport fig (Ficus sp., Moraceae) pollen over enormous distances (> 100 km). Because of their extensive breeding areas, Neotropical figs are expected to exhibit weak patterns of genetic structure at local and regional scales. We evaluated genetic structure at the regional to continental scale (Panama, Costa Rica, and Peru) for the free-standing fig species Ficus insipida. Genetic differentiation was detected only at distances > 300 km (Jost´s Dest = 0.68 ± 0.07 & FST = 0.30 ± 0.03 between Mesoamerican and Amazonian sites) and evidence for phylogeographic structure (RST>permuted RST) was only significant in comparisons between Central and South America. Further, we assessed local scale spatial genetic structure (SGS, d ≤ 8 km) in Panama and developed an agent-based model parameterized with data from F. insipida to estimate minimum pollination distances, which determine the contribution of pollen dispersal on SGS. The local scale data for F. insipida was compared to SGS data collected for an additional free-standing fig, F. yoponensis (subgenus Pharmacosycea), and two species of strangler figs, F. citrifolia and F. obtusifolia (subgenus Urostigma) sampled in Panama. All four species displayed significant SGS (mean Sp = 0.014 ± 0.012). Model simulations indicated that most pollination events likely occur at distances > > 1 km, largely ruling out spatially limited pollen dispersal as the determinant of SGS in F. insipida and, by extension, the other fig species. Our results are consistent with the view that Ficus develops fine-scale SGS primarily as a result of localized seed dispersal and/or clumped seedling establishment despite extensive long-distance pollen dispersal. We discuss several ecological and life history factors that could have species- or subgenus-specific impacts on the genetic structure of Neotropical figs.

  6. Spatial Scales of Genetic Structure in Free-Standing and Strangler Figs (Ficus, Moraceae Inhabiting Neotropical Forests.

    Directory of Open Access Journals (Sweden)

    Katrin Heer

    Full Text Available Wind-borne pollinating wasps (Agaonidae can transport fig (Ficus sp., Moraceae pollen over enormous distances (> 100 km. Because of their extensive breeding areas, Neotropical figs are expected to exhibit weak patterns of genetic structure at local and regional scales. We evaluated genetic structure at the regional to continental scale (Panama, Costa Rica, and Peru for the free-standing fig species Ficus insipida. Genetic differentiation was detected only at distances > 300 km (Jost´s Dest = 0.68 ± 0.07 & FST = 0.30 ± 0.03 between Mesoamerican and Amazonian sites and evidence for phylogeographic structure (RST>>permuted RST was only significant in comparisons between Central and South America. Further, we assessed local scale spatial genetic structure (SGS, d ≤ 8 km in Panama and developed an agent-based model parameterized with data from F. insipida to estimate minimum pollination distances, which determine the contribution of pollen dispersal on SGS. The local scale data for F. insipida was compared to SGS data collected for an additional free-standing fig, F. yoponensis (subgenus Pharmacosycea, and two species of strangler figs, F. citrifolia and F. obtusifolia (subgenus Urostigma sampled in Panama. All four species displayed significant SGS (mean Sp = 0.014 ± 0.012. Model simulations indicated that most pollination events likely occur at distances > > 1 km, largely ruling out spatially limited pollen dispersal as the determinant of SGS in F. insipida and, by extension, the other fig species. Our results are consistent with the view that Ficus develops fine-scale SGS primarily as a result of localized seed dispersal and/or clumped seedling establishment despite extensive long-distance pollen dispersal. We discuss several ecological and life history factors that could have species- or subgenus-specific impacts on the genetic structure of Neotropical figs.

  7. Yield Tables and Stand Structure for Unthinned Longleaf Pine Plantations in Louisiana and Texas

    Science.gov (United States)

    Richard E. Longrey; Robert L. Bailey

    1977-01-01

    A system of equations is developed to forecast number of trees per acre, basal area, and cubic foot yields in eight volume categories by l-inch diameter classes for several combinations of site index, age from planting, and either number of trees planted, number of trees surviving, or basal area at a given age.

  8. Accounting for density reduction and structural loss in standing dead trees: Implications for forest biomass and carbon stock estimates in the United States

    Directory of Open Access Journals (Sweden)

    Domke Grant M

    2011-11-01

    Full Text Available Abstract Background Standing dead trees are one component of forest ecosystem dead wood carbon (C pools, whose national stock is estimated by the U.S. as required by the United Nations Framework Convention on Climate Change. Historically, standing dead tree C has been estimated as a function of live tree growing stock volume in the U.S.'s National Greenhouse Gas Inventory. Initiated in 1998, the USDA Forest Service's Forest Inventory and Analysis program (responsible for compiling the Nation's forest C estimates began consistent nationwide sampling of standing dead trees, which may now supplant previous purely model-based approaches to standing dead biomass and C stock estimation. A substantial hurdle to estimating standing dead tree biomass and C attributes is that traditional estimation procedures are based on merchantability paradigms that may not reflect density reductions or structural loss due to decomposition common in standing dead trees. The goal of this study was to incorporate standing dead tree adjustments into the current estimation procedures and assess how biomass and C stocks change at multiple spatial scales. Results Accounting for decay and structural loss in standing dead trees significantly decreased tree- and plot-level C stock estimates (and subsequent C stocks by decay class and tree component. At a regional scale, incorporating adjustment factors decreased standing dead quaking aspen biomass estimates by almost 50 percent in the Lake States and Douglas-fir estimates by more than 36 percent in the Pacific Northwest. Conclusions Substantial overestimates of standing dead tree biomass and C stocks occur when one does not account for density reductions or structural loss. Forest inventory estimation procedures that are descended from merchantability standards may need to be revised toward a more holistic approach to determining standing dead tree biomass and C attributes (i.e., attributes of tree biomass outside of sawlog

  9. [Effects of stand structure regulation on soil labile organic carbon in Pinus elliottii plantation].

    Science.gov (United States)

    Tan, Gui-Xia; Liu, Yuan-Qiu; Li, Lian-Lian; Liu, Wu; Zan, Yu-Ting; Huo, Bing-Nan; He, Mu-Jiao

    2014-05-01

    Taking 21-year-old Pinus elliottii pure plantation as the control, effects of enrichment planting with broadleaf trees (Liquidambar fornosana) after thinning the conifer trees (P. elliottii) on soil labile organic carbon of different plantations, including 3-year-old, 6-year-old, 9-year-old P. elliottii and 21-year-old P. elliottii-L. fornosana mixed plantations, were investigated. The results showed that the contents of soil dissolved organic carbon (DOC), readily oxidizable organic carbon (ROC), and microbial biomass carbon (MBC) significantly increased in the 6-year-old and 9-year-old plantations compared with those in the 21-year-old P. elliottii pure plantation. Soil labile organic carbon contents in the 21-year-old P. elliottii-L. fornosana mixed plantation increased significantly than those in 3-year-old, 6-year-old, 9-year-old stands, and the DOC, ROC and MBC contents increased by 113.1%, 53.3% and 54.6%, respectively, compared with those in the 21-year-old P. elliottii pure plantation. The results suggested that replanting with broadleaf trees are an effective measure to improve the soil ecological function in pure P. elliottii plantation.

  10. Clearance of buildings for demolition: ways to clearance on the standing structure for covered surfaces and inaccessible areas

    International Nuclear Information System (INIS)

    Thraenert, S.; Riemann, T.

    2014-01-01

    In general terms, the TUV NORD Nuclear services encompass safety assessments, design reviews, documentation re-views and inspections. They reflect the full scope of a technical service provider in the nuclear field. In the domestic market, these services are provided for the regulator, whereas in the international market any party involved in a nuclear project is a potential customer of TUV NORD Nuclear. This implies that TUV NORD Nuclear is offering consultancy, engineering and inspection services. Regarding the clearance of buildings for demolition, there are two different possible ways for the radiological characterization. The first option is a characterization on the standing structure before demolition and the second option is the characterization of the building rubble after demolition. According to the German Radiation Protection Ordinance, buildings of decommissioned nuclear sites have to be preferentially cleared on the standing structure. If compliance with the surface specific clearance levels is achieved on the standing structure, usually the cleared buildings can be demolished and the resulting rubble may be used without any further radiological considerations. In the case of the former nuclear power plant Wuergassen the majority of the building rubble is scheduled to stay on site to serve as backfill for the building pit. As such a scenario was not considered in the radiological considerations of, e.g., the German Radiation Protection Ordinance, an additional dose calculation was carried out for Wuergassen NPP basing on its radiological characteristics to directly prove compliance with the de-minimis-concept. The radiation controlled area (RCA) of Wuergassen NPP comprises an area of about 140.000 m 2 . This area is more or less easily accessible to characterization and decontamination using, if necessary, scaffoldings or lifting platforms. Up to the beginning of 2013, compliance with the surface specific clearance levels was verified on the standing

  11. Estimating population age structure using otolith morphometrics

    DEFF Research Database (Denmark)

    Doering-Arjes, P.; Cardinale, M.; Mosegaard, Henrik

    2008-01-01

    Traditional age reading is a rather subjective method that lacks true reproducibility, producing ageing error that propagates up to stock assessment. One alternative is represented by the use of otolith morphometrics as a predictor of age. An important issue with such a method is that it requires...... known-age fish individuals. Here we used known-age Atlantic cod (Gadus morhua) from the Faroe Bank and Faroe Plateau stocks. Cod populations usually show quite large variation in growth rates and otolith shape. We showed that including otolith morphometrics into ageing processes has the potential...... populations. The intercalibration method was successful but generalization from one stock to another remains problematic. The development of an otolith growth model is needed for generalization if an operational method for different populations is required in the future....

  12. Malcolm Grow USAF Medical Center Standing Committee Structure: Accreditation and Governing Board Compliance

    Science.gov (United States)

    1993-08-01

    teach the FOCUS- PDCA (Find, Organize, Clarify, Understand, Select-Plan, Do, Check, Act) methodology. Regardless of the method , in the constant search...requirements regarding committee structure including the presence of specific committees, and the application of Total Quality Management (TQM) and...Continuous Quality Improvement (CQI) in committee structure operations. It also considers environmental adaptation in the recommendations. A recent committee

  13. Evoluţia diversităţii structurale şi compoziţionale a arboretelor cu ajutorul indicelui UMF: un studiu de caz la nivel de unitate de producţie[The evolution of stand structural and compositional diversity assessed with the UMF index: A case study at production unit level

    Directory of Open Access Journals (Sweden)

    Mihai Catalin Burlui

    2014-08-01

    Full Text Available In this article we present the UMF index (Uneven-aged, Mixed, Forest an index because the forest management, whose values are determined easily, data from management planning are the main support. The study was conducted in the Suha Mare area from Mălini, Suceava county. Wet analyzed stand descriptions for all stands for two periods (1956, 1995, using structural and site characteristics required by index. Data were obtained from management plans of the studied forest area. The index values were calculated for each stand, and its value for the total forest area was determined by summing the values calculated for stand, weighted by stand area. Index values vary between the two periods analyzed (1956, 1995, there are differences from a subplot to another, which is explained by the different treatments applied, the number of tree species and the structural heterogeneity, but also - for 1995 - by functional zoning that changed the forest management. UMF index is a good tool to determine structural and compositional diversity of a given area, using data from forest management plans. The results can be analyzed for longer periods of time and may indicate the direction of evolution of an area in relation with anthropogenic changes: from even-aged structure to uneven-aged, from monocultures to mixed stands.

  14. FEA modeling of CMUT with membrane stand-off structures to enable selectable frequency-mode operation.

    Science.gov (United States)

    Eames, Matthew D C; Reck, Theodore J; Kilroy, Joseph P; Hossack, John A

    2011-12-01

    A selectable, dual-frequency, capacitive micro- machined ultrasonic transducer (CMUT) designed for both high-frequency imaging and low-frequency therapeutic effect is presented. A validated finite element analysis (FEA) CMUT model was used to examine the performance of the proposed dual-frequency transducer. CMUT device simulations were used to design a hybrid device incorporating stand-off structures that divide a large, low-frequency membrane into smaller, high-frequency sub-membranes when the membrane is partially collapsed so that the stand-offs contact the substrate. In low-frequency operation, simulations indicated that the peak negative pressure achieved by the hybrid device, when biased by 30.0 VDC and excited by a 2-MHz signal with 30.0 V amplitude, exceeded 190 kPa, which is sufficient for microbubble rupture. Low-frequency mode bandwidth was 93% at a center frequency of 2.1 MHz. In the high-frequency mode of operation, the device was excited by 175 Vdc and 87.5 Vac, which generated a peak negative pressure of 247 kPa. Device center frequency was 44.1 MHz with a - 6-dB fractional bandwidth of 42%.

  15. Flexible free-standing luminescent two-component fiber films with tunable hierarchical structures based on hydrogen-bonding architecture.

    Science.gov (United States)

    Yan, Dongpeng; Williams, Gareth R; Zhao, Min; Li, Changming; Fan, Guoling; Yang, Hejia

    2013-12-17

    Although the fabrication of hierarchical architectures with highly ordered functional units is of great importance for both fundamental science and practical application, the development of one-dimensional (1D) organic hierarchical micro/nanostructures based on low-molecular-weight (LMW) building blocks remains at an early stage. Herein, we report two types of micro/nanoscaled multicomponent fluorescent fiber systems with tunable hierarchical morphologies through a one-step coassembly process. With the aid of hydrogen-bonding motifs, LMW precursors (1,4-bis(5-phenyloxazol-2-yl)benzene (A) and two coassembled building blocks: 4-bromotetrafluorobenzene carboxylic acid (B) and 2,3,4,5,6-pentafluorophenol (C)) have been self-organized into fibers and flexible free-standing films, which show hierarchical micro/nanostructures as well as tunable one-/two-photon luminescence. The disassembly of the multicomponent A.B and A.C fibers occurs at high temperature, which further alters the luminescence properties of the multicomponent materials. Therefore, this work provides a facile wet chemical route for fabricating multicomponent LMW self-assembled fibers and free-standing film systems with tunable hierarchical structures and photoemission behaviors, and such self-organized systems may have potential applications in fields of two-photon luminescence and thermal sensors.

  16. Period ratios for standing kink and sausage modes in magnetized structures with siphon flow on the Sun

    Science.gov (United States)

    Yu, Hui; Chen, Shao-Xia; Li, Bo; Xia, Li-Dong

    2016-06-01

    Standing oscillations with multiple periods have been found in a number of atmospheric structures on the Sun. The ratio of the period of the fundamental to twice the one of its first overtone, P 1/2P 2, is important in applications of solar magneto-seismology. We examine how field-aligned flows impact P 1/2P 2 of standing modes in solar magnetic cylinders. For coronal loops, the flow effects are significant for both fast kink and sausage modes. For kink modes, they reduce P 1/2P 2 by up to 17% relative to the static case even when the density contrast between the loop and its surroundings approaches infinity. For sausage modes, the reduction in P 1/2P 2 due to flow is typically ≲ 5.5% compared with the static case. However, the threshold aspect ratio, only above which can trapped sausage modes be supported, may increase dramatically with the flow magnitude. For photospheric tubes, the flow effect on P 1/2P 2 is not as strong. However, when applied to sausage modes, introducing field-aligned flows offers more possibilities in interpreting the multiple periods that have recently been measured. We conclude that field-aligned flows should be taken into account to help better understand what causes the departure of P 1/2P 2 from unity.

  17. Modeling aging of cementitious pore structure

    NARCIS (Netherlands)

    Ukrainczyk, N.; Koenders, E.A.B.

    2014-01-01

    Coupled reactive-transport processes in cementitious materials play a crucial role in the aging process pf building materials. Up to now, the effect of aging on microstructure and evolution of it’s properties, in three dimensions, was studied only by dissolution of certain phases at random

  18. Forest structure, stand composition, and climate-growth response in montane forests of Jiuzhaigou National Nature Reserve, China.

    Science.gov (United States)

    Schwartz, Mark W; Dolanc, Christopher R; Gao, Hui; Strauss, Sharon Y; Schwartz, Ari C; Williams, John N; Tang, Ya

    2013-01-01

    Montane forests of western China provide an opportunity to establish baseline studies for climate change. The region is being impacted by climate change, air pollution, and significant human impacts from tourism. We analyzed forest stand structure and climate-growth relationships from Jiuzhaigou National Nature Reserve in northwestern Sichuan province, along the eastern edge of the Tibetan plateau. We conducted a survey to characterize forest stand diversity and structure in plots occurring between 2050 and 3350 m in elevation. We also evaluated seedling and sapling recruitment and tree-ring data from four conifer species to assess: 1) whether the forest appears in transition toward increased hardwood composition; 2) if conifers appear stressed by recent climate change relative to hardwoods; and 3) how growth of four dominant species responds to recent climate. Our study is complicated by clear evidence of 20(th) century timber extraction. Focusing on regions lacking evidence of logging, we found a diverse suite of conifers (Pinus, Abies, Juniperus, Picea, and Larix) strongly dominate the forest overstory. We found population size structures for most conifer tree species to be consistent with self-replacement and not providing evidence of shifting composition toward hardwoods. Climate-growth analyses indicate increased growth with cool temperatures in summer and fall. Warmer temperatures during the growing season could negatively impact conifer growth, indicating possible seasonal climate water deficit as a constraint on growth. In contrast, however, we found little relationship to seasonal precipitation. Projected warming does not yet have a discernible signal on trends in tree growth rates, but slower growth with warmer growing season climates suggests reduced potential future forest growth.

  19. STAND STRUCTURE OF Pinus hartwegii AFFECTED BY FIRE USING NEIGHBOURHOOD PARAMETERS IN THE SIERRA MADRE ORIENTAL, MEXICO.

    Directory of Open Access Journals (Sweden)

    Diana Yemilet Avila Flores

    2012-08-01

    Full Text Available The objective of this research was to characterize the pattern of spatial structure of a Pinus hartwegii forest in the Sierra Madre Oriental, affected by a fire in 1998. Sampling was stratified by fire severity. Three fire severity classes were defined based on the degree of crown consumption (low, medium and high. Three sample plots of 40m x 40m were established for each severity. The variables obtained for all trees with a diameter at breast height (DBH ≥ 5 cm in each plot were: DBH to 1.30 m (cm, height (m, spatial location by recording the azimuth (° and distance (m from center of the plot to each tree. To describe the stand structure three groups of indices were employed: “contagion” and “distances” (Wi and Di, “dominance” (Ui, and “size differentiation” (TDi and THi for DBH and height respectively. An analysis of variance was performed to detect differences between dasometrics parameters by fire severity. Statistical analysis shows significant differences (p>0.001 in the parameters such as basal area, diameter, and height, along the low, medium, and high fire severities. The characterization of the Pinus hartwegii spatial structure suggests that, with increasing degree of fire severity, the stands showed an increase on the aggregation index, however, the dimensional differentiation and dominance indices decreases as the fire severity increases.

  20. Forest structure, stand composition, and climate-growth response in montane forests of Jiuzhaigou National Nature Reserve, China.

    Directory of Open Access Journals (Sweden)

    Mark W Schwartz

    Full Text Available Montane forests of western China provide an opportunity to establish baseline studies for climate change. The region is being impacted by climate change, air pollution, and significant human impacts from tourism. We analyzed forest stand structure and climate-growth relationships from Jiuzhaigou National Nature Reserve in northwestern Sichuan province, along the eastern edge of the Tibetan plateau. We conducted a survey to characterize forest stand diversity and structure in plots occurring between 2050 and 3350 m in elevation. We also evaluated seedling and sapling recruitment and tree-ring data from four conifer species to assess: 1 whether the forest appears in transition toward increased hardwood composition; 2 if conifers appear stressed by recent climate change relative to hardwoods; and 3 how growth of four dominant species responds to recent climate. Our study is complicated by clear evidence of 20(th century timber extraction. Focusing on regions lacking evidence of logging, we found a diverse suite of conifers (Pinus, Abies, Juniperus, Picea, and Larix strongly dominate the forest overstory. We found population size structures for most conifer tree species to be consistent with self-replacement and not providing evidence of shifting composition toward hardwoods. Climate-growth analyses indicate increased growth with cool temperatures in summer and fall. Warmer temperatures during the growing season could negatively impact conifer growth, indicating possible seasonal climate water deficit as a constraint on growth. In contrast, however, we found little relationship to seasonal precipitation. Projected warming does not yet have a discernible signal on trends in tree growth rates, but slower growth with warmer growing season climates suggests reduced potential future forest growth.

  1. A biologically inspired modular structure to control the sit-to-stand transfer of a biped robot.

    Science.gov (United States)

    Andani, M Emadi; Bahrami, F; Maralani, P Jabedar

    2007-01-01

    In this study, a biologically inspired control structure to control the sit-to-stand (STS) transfer from a chair is developed and simulated. STS movement is consisted of two main phases. First phase of the movement is before leaving the seat (seat-off moment). In this phase seat reactions forces act on the body parts which are in contact with the seat. The second phase is after seat-off, where the only external forces acting on the body are ground reaction forces. A proper control algorithm of the STS transfer needs to consider switching between these two phases, which correspond to two different dynamical structures. The control structure developed and discussed in this work is based on the MOSAIC structure, proposed first by Wolpert and Kawato [1]. Original MOSAIC structure has a modular architecture which is based on multiple pairs of forward and inverse models of the dynamical system to be controlled, and each module is trained separately to learn one part of a given task. The number of effective modules is predetermined. We have developed a new method to train all modules simultaneously. This method is based on reinforcement and cooperative competitive learning, and the number of effective modules is determined automatically. In this study, the simulation was begun with four modules. Our results showed that only two modules out of four were selected to control the STS task. Responsibility of controlling the task was switched between the two modules around the seat-off moment.

  2. Status of High Power Tests of Normal Conducting Single-Cell Standing Wave Structures

    Energy Technology Data Exchange (ETDEWEB)

    Dolgashev, Valery; /SLAC; Tantawi, Sami; /SLAC; Yeremian, Anahid; /SLAC; Higashi, Yasuo; /KEK, Tsukuba; Spataro, Bruno; /INFN, Rome

    2012-06-25

    Our experiments are directed toward the understanding of the physics of rf breakdown in systems that can be used to accelerate electron beams at {approx}11.4 GHz. The structure geometries have apertures, stored energy per cell, and rf pulse duration close to that of the NLC or CLIC. The breakdown rate is the main parameter that we use to compare rf breakdown behavior for different structures at a given set of rf pulse parameters (pulse shape and peak power) at 60 Hz repetition rate. In our experiments, the typical range of the breakdown rate is from one per few hours to {approx}100 per hour. To date we have tested 29 structures. We consistently found that after the initial conditioning, the behavior of the breakdown rate is reproducible for structures of the same geometry and material, and the breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for structures of different geometries. Below we report the main results from tests of seven structures made from hard copper, soft copper alloys and hard-copper alloys. Additional details on these and other structures will be discussed in future publications.

  3. Cultural intensity and planting density effects on individual tree stem growth, stand and crown attributes, and stand dynamics in thinned loblolly pine plantations during the age 12- to age 15- year period in the Upper Coastal Plain and Piedmont of the Southeastern United States

    Science.gov (United States)

    Evan Johnson; Michael Kane; Dehai Zhao; Robert Teskey

    2015-01-01

    Three existing loblolly pine (Pinus taeda L.) installations in the Plantation Management Research Cooperative's Upper Coastal Plain/Piedmont Culture Density Study were used to examine the effects of two cultural intensities, four initial planting densities, and their interactions on stem growth at the individual tree level from age 12 to 15 years and at the stand...

  4. Age-related and stand-wise estimates of carbon stocks and sequestration in the aboveground coarse wood biomass of wetland forests in the northern Pantanal, Brazil

    Science.gov (United States)

    Schöngart, J.; Arieira, J.; Felfili Fortes, C.; Cezarine de Arruda, E.; Nunes da Cunha, C.

    2011-11-01

    In this study we use allometric models combined with tree ring analysis to estimate carbon stocks and sequestration in the aboveground coarse wood biomass (AGWB) of wetland forests in the Pantanal, located in central South America. In four 1-ha plots in stands characterized by the pioneer tree species Vochysia divergens Pohl (Vochysiaceae) forest inventories (trees ≥10 cm diameter at breast height, D) have been performed and converted to estimates of AGWB by two allometric models using three independent parameters (D, tree height H and wood density ρ). We perform a propagation of measurement errors to estimate uncertainties in the estimates of AGWB. Carbon stocks of AGWB vary from 7.8 ± 1.5 to 97.2 ± 14.4 Mg C ha-1 between the four stands. From models relating tree ages determined by dendrochronological techniques to C-stocks in AGWB we derived estimates for C-sequestration which differs from 0.50 ± 0.03 to 3.34 ± 0.31 Mg C ha-1 yr-1. Maps based on geostatistic techniques indicate the heterogeneous spatial distribution of tree ages and C-stocks of the four studied stands. This distribution is the result of forest dynamics due to the colonizing and retreating of V. divergens and other species associated with pluriannual wet and dry episodes in the Pantanal, respectively. Such information is essential for the management of the cultural landscape of the Pantanal wetlands.

  5. The effect of aging on network structure

    OpenAIRE

    Zhu, Han; Wang, Xin-Ran; Zhu, Jian-Yang

    2003-01-01

    In network evolution, the effect of aging is universal: in scientific collaboration network, scientists have a finite time span of being active; in movie actors network, once popular stars are retiring from stage; devices on the Internet may become outmoded with techniques developing so rapidly. Here we find in citation networks that this effect can be represented by an exponential decay factor, $e^{-\\beta \\tau}$, where $\\tau $ is the node age, while other evolving networks (the Internet for ...

  6. Yield Tables and Stand Structure For Loblolly Pine Plantations In Tennessee, Alabama, and Georgia Highlands

    Science.gov (United States)

    Glendon W. Smalley; Robert L. Bailey

    1974-01-01

    Detailed schedules of trees per acre, basal area, mean tree height, and cubic-foot yields in eight volume categories by l-inch diameter classes are presented for all combinations of four site indexes, seven ages from seed, and nine planting densities.

  7. Yield Tables and Stand Structure For Shortleaf Pine Plantations In Tennessee, Alabama, and Georgia Highlands

    Science.gov (United States)

    Glendon W. Smalley; Robert L. Bailey

    1974-01-01

    Detailed schedules of trees per acre, basal area, mean tree height, and cubic-foot yields in eight volume categories by l-inch diameter classes are presented for all combinations of four site indexes, seven ages from seed, and six planting densities.

  8. Reverberant Acoustic Testing and Direct Field Acoustic Testing Acoustic Standing Waves and their Impact on Structural Responses

    Science.gov (United States)

    Kolaini, Ali R.; Doty, Benjamin; Chang, Zensheu

    2012-01-01

    The aerospace industry has been using two methods of acoustic testing to qualify flight hardware: (1) Reverberant Acoustic Test (RAT), (2) Direct Field Acoustic Test (DFAT). The acoustic field obtained by RAT is generally understood and assumed to be diffuse, expect below Schroeder cut-of frequencies. DFAT method of testing has some distinct advantages over RAT, however the acoustic field characteristics can be strongly affected by test setup such as the speaker layouts, number and location of control microphones and control schemes. In this paper the following are discussed based on DEMO tests performed at APL and JPL: (1) Acoustic wave interference patterns and acoustic standing waves, (2) The structural responses in RAT and DFAT.

  9. Impact of Acoustic Standing Waves on Structural Responses: Reverberant Acoustic Testing (RAT) vs. Direct Field Acoustic Testing (DFAT)

    Science.gov (United States)

    Kolaini, Ali R.; Doty, Benjamin; Chang, Zensheu

    2012-01-01

    Loudspeakers have been used for acoustic qualification of spacecraft, reflectors, solar panels, and other acoustically responsive structures for more than a decade. Limited measurements from some of the recent speaker tests used to qualify flight hardware have indicated significant spatial variation of the acoustic field within the test volume. Also structural responses have been reported to differ when similar tests were performed using reverberant chambers. To address the impact of non-uniform acoustic field on structural responses, a series of acoustic tests were performed using a flat panel and a 3-ft cylinder exposed to the field controlled by speakers and repeated in a reverberant chamber. The speaker testing was performed using multi-input-single-output (MISO) and multi-input-multi-output (MIMO) control schemes with and without the test articles. In this paper the spatial variation of the acoustic field due to acoustic standing waves and their impacts on the structural responses in RAT and DFAT (both using MISO and MIMO controls for DFAT) are discussed in some detail.

  10. Stand structure and climate influence on the growth trends of a marginal forest population of Pinus nigra spp. nigra

    Directory of Open Access Journals (Sweden)

    Maurizio Marchi

    2015-12-01

    Full Text Available The Black pine of Villetta Barrea (Pinus nigra ssp. nigra var italica is a variety of the nigra subspecies. It is naturally distributed only in the Abruzzo Region, near the village of Villetta Barrea, with a rear-edge marginal population.  A dendrochronological sampling of the population was implemented with the aim of studying its stand structure and the most probable interactions between growth trends and climate. Mensurational data were used to characterize the stand and, furthermore, the general correlation function (CF and the moving correlation function (MCF, with a 30 years window, were used to assess the interrelation between the growth of the tree rings and the climate.The results indicated that the past forest management, mainly carried out with thinnings from below and selective cuttings, influenced the current structure of the forest (mean diameter but no differences in growth trends were detected within the population.The survey on Villetta Barrea Black pine showed a positive and statistically significant correlation between the ring-width and the average temperatures of the months of December (before the ring formation - t-1, February and March; but it also showed a negative correlation with the temperatures of July, September and October of the current year (t.Moreover, the analysis with moving correlation functions suggested that, in the last decades, the population has negatively reacted to very few climate factors and, in particular, to the changes in temperatures (both minimum and maximum temperatures. This is especially true for the shifts occurred in September, the year of the ring formation.

  11. Influence of stocking, site quality, stand age, low-severity canopy disturbance, and forest composition on sub-boreal aspen mixedwood carbon stocks

    Science.gov (United States)

    Reinikainen, Michael; D’Amato, Anthony W.; Bradford, John B.; Fraver, Shawn

    2014-01-01

    Low-severity canopy disturbance presumably influences forest carbon dynamics during the course of stand development, yet the topic has received relatively little attention. This is surprising because of the frequent occurrence of such events and the potential for both the severity and frequency of disturbances to increase as a result of climate change. We investigated the impacts of low-severity canopy disturbance and average insect defoliation on forest carbon stocks and rates of carbon sequestration in mature aspen mixedwood forests of varying stand age (ranging from 61 to 85 years), overstory composition, stocking level, and site quality. Stocking level and site quality positively affected the average annual aboveground tree carbon increment (CAAI), while stocking level, site quality, and stand age positively affected tree carbon stocks (CTREE) and total ecosystem carbon stocks (CTOTAL). Cumulative canopy disturbance (DIST) was reconstructed using dendroecological methods over a 29-year period. DIST was negatively and significantly related to soil carbon (CSOIL), and it was negatively, albeit marginally, related to CTOTAL. Minima in the annual aboveground carbon increment of trees (CAI) occurred at sites during defoliation of aspen (Populus tremuloides Michx.) by forest tent caterpillar (Malacosoma disstria Hubner), and minima were more extreme at sites dominated by trembling aspen than sites mixed with conifers. At sites defoliated by forest tent caterpillar in the early 2000s, increased sequestration by the softwood component (Abies balsamea (L.) Mill. and Picea glauca (Moench) Voss) compensated for overall decreases in CAI by 17% on average. These results underscore the importance of accounting for low-severity canopy disturbance events when developing regional forest carbon models and argue for the restoration and maintenance of historically important conifer species within aspen mixedwoods to enhance stand-level resilience to disturbance agents and maintain

  12. Effect of environmental variables and stand structure on ecosystem respiration components in a Mediterranean beech forest

    Czech Academy of Sciences Publication Activity Database

    Guidolotti, G.; Rey, A.; D'Andrea, E.; Matteucci, G.; De Angelis, Paolo

    2013-01-01

    Roč. 33, č. 9 (2013), s. 960-972 ISSN 0829-318X Institutional support: RVO:67179843 Keywords : ecosystem respiration * Fagus sylvatica * leaf respiration * soil CO2 efflux * stem CO2 efflux * total non-structural carbohydrates Subject RIV: EH - Ecology, Behaviour Impact factor: 3.405, year: 2013

  13. Stand structure influences nekton community composition and provides protection from natural disturbance in Micronesian mangroves

    Science.gov (United States)

    Richard A. MacKenzie; Nicole. Cormier

    2012-01-01

    Structurally complex mangrove roots are thought to provide foraging habitat, predation refugia, and typhoon protection for resident fish, shrimp, and crabs. The spatially compact nature of Micronesian mangroves results in model ecosystems to test these ideas. Tidal creek nekton assemblages were compared among mangrove forests impacted by Typhoon Sudal and differing in...

  14. Capturing suboptical dynamic structures in lipid bilayer patches formed from free-standing giant unilamellar vesicles

    DEFF Research Database (Denmark)

    Bhartia, Tripta; Cornelius, Flemming; Ipsen, John H

    2017-01-01

    treatment with magnesium chloride, they collapse to form planar lipid bilayer (PLB) patches. Rapid GUV collapse onto the mica preserves the lateral organization of freestanding membranes and thus makes it possible to image 'snapshots' of GUVs up to nanometer resolution by high-resolution microscopy...... up a new avenue for quantitative biophysical studies of suboptical dynamic structures in biomembranes, which are local and short-lived. Preparation of GUVs, PLB patches and their imaging takes

  15. Free-standing carbon nanotube composite sensing skin for distributed strain sensing in structures

    Science.gov (United States)

    Burton, Andrew R.; Minegishi, Kaede; Kurata, Masahiro; Lynch, Jerome P.

    2014-04-01

    The technical challenges of managing the health of critical infrastructure systems necessitate greater structural sensing capabilities. Among these needs is the ability for quantitative, spatial damage detection on critical structural components. Advances in material science have now opened the door for novel and cost-effective spatial sensing solutions specially tailored for damage detection in structures. However, challenges remain before spatial damage detection can be realized. Some of the technical challenges include sensor installations and extensive signal processing requirements. This work addresses these challenges by developing a patterned carbon nanotube composite thin film sensor whose pattern has been optimized for measuring the spatial distribution of strain. The carbon nanotube-polymer nanocomposite sensing material is fabricated on a flexible polyimide substrate using a layer-by-layer deposition process. The thin film sensors are then patterned into sensing elements using optical lithography processes common to microelectromechanical systems (MEMS) technologies. The sensor array is designed as a series of sensing elements with varying width to provide insight on the limitations of such patterning and implications of pattern geometry on sensing signals. Once fabrication is complete, the substrate and attached sensor are epoxy bonded to a poly vinyl composite (PVC) bar that is then tested with a uniaxial, cyclic load pattern and mechanical response is characterized. The fabrication processes are then utilized on a larger-scale to develop and instrument a component-specific sensing skin in order to observe the strain distribution on the web of a steel beam. The instrumented beam is part of a larger steel beam-column connection with a concrete slab in composite action. The beam-column subassembly is laterally loaded and strain trends in the web are observed using the carbon nanotube composite sensing skin. The results are discussed in the context of

  16. Contenido de nutrientes en las raices finas y el mantillo de rodales de Eucalyptus grandis de diferente edad en la Mesopotomia Argentina [Fine roots and litter nutrient content of Eucalyptus grandis stands presenting different ages in Mesopotomia Argentina

    Science.gov (United States)

    C. Perez; J. Frangi; J.F. Goya; A. Luy; M. Arturi; NO-VALUE

    2013-01-01

    Entre Ríos province is an important center of Eucalyptus spp. plantations in Argentina. It was hypothesized that fine root biomass and litter mass increased with age increasing in plantations. Five, seven and seventeen year old stands of Eucalyptus grandis were sampled. All of them were first rotation stands. We estimated the mass of litter and fine roots (

  17. Susceptibility of ponderosa pine, Pinus ponderosa (Dougl. Ex Laws.), to mountain pine beetle, Dendroctonus ponderosae Hopkins, attack in uneven-aged stands in the Black Hills of South Dakota and Wyoming USA

    Science.gov (United States)

    Jose F. Negron; Kurt Allen; Blaine Cook; John R. Withrow

    2008-01-01

    Mountain pine beetle, Dendroctonus ponderosae Hopkins can cause extensive tree mortality in ponderosa pine, Pinus ponderosa Dougl. ex Laws., forests in the Black Hills of South Dakota and Wyoming. Most studies that have examined stand susceptibility to mountain pine beetle have been conducted in even-aged stands. Land managers...

  18. Nuclear Structure Data for the Present Age

    International Nuclear Information System (INIS)

    Baglin, Coral M.

    2005-01-01

    The US Nuclear Data Program maintains and provides easy and free access to several comprehensive databases that assist scientists to sift through and assess the vast quantity of published nuclear structure and decay data. These databases are an invaluable asset for nuclear-science experimentalists and theorists alike, and the recommended values provided for nuclear properties such as decay modes, level energies and lifetimes, and radiation properties can also be of great importance to specialists in other fields such as medicine, geophysics, and reactor design. The Evaluated Nuclear Structure Data File (ENSDF) contains experimental nuclear structure data for all known nuclides, evaluated by the US nuclear data program evaluators in collaboration with a number of international data groups; the Nuclear Science Reference (NSR) database provides complementary bibliographic information; the Experimental Unevaluated Nuclear Data Listing (XUNDL) exists to enable rapid access to experimental nuclear-structure data compiled from the most recent publications (primarily in high-spin physics). This paper presents an overview of the nuclear structure and decay data available through these databases, with emphasis on recent and forthcoming additions to and presentations of the available material

  19. Development of a Laser-Powered Dielectric Structure-Based Accelerator as a Stand-Alone Particle Source

    International Nuclear Information System (INIS)

    Yoder, R. B.; Travish, G.; Arab, E. R.; Fong, D.; Hoyer, Z.; Lacroix, U. H.; Vartanian, N.; Rosenzweig, J. B.

    2010-01-01

    An experimental program to develop and build a dielectric-based slab-symmetric structure (the micro-accelerator platform, or MAP) for generating and accelerating low-energy electrons is underway at UCLA and Manhattanville College. This optical acceleration structure is effectively a resonant cavity powered by a side-coupled laser, and has applications as a radiation source for medicine or industry. We present recent experimental and computational results on the accelerator, and progress toward its incorporation into a self-contained particle source. Such a particle source would incorporate a micron-scale electron emitter and a non-relativistic capture region to enable self-injection into the synchronous field within the accelerator. A prototype of the accelerator itself has been constructed from candidate dielectric materials using micromanufacturing techniques; the current status of the testing program is described. A novel electron emitter incorporating pyroelectric crystals with field-enhancing tips has been demonstrated to produce steady currents; the results are dependent on tip geometry, and appear suitable for injection into a microstructure. Extension of the MAP concept to non-relativistic velocities, as in the stand-alone source, requires a tapered structure that gives rise to numerous complications including beam defocusing and manufacturing challenges; approaches for addressing these complications are mentioned.

  20. A top-down approach for fabricating free-standing bio-carbon supercapacitor electrodes with a hierarchical structure.

    Science.gov (United States)

    Li, Yingzhi; Zhang, Qinghua; Zhang, Junxian; Jin, Lei; Zhao, Xin; Xu, Ting

    2015-09-23

    Biomass has delicate hierarchical structures, which inspired us to develop a cost-effective route to prepare electrode materials with rational nanostructures for use in high-performance storage devices. Here, we demonstrate a novel top-down approach for fabricating bio-carbon materials with stable structures and excellent diffusion pathways; this approach is based on carbonization with controlled chemical activation. The developed free-standing bio-carbon electrode exhibits a high specific capacitance of 204 F g(-1) at 1 A g(-1); good rate capability, as indicated by the residual initial capacitance of 85.5% at 10 A g(-1); and a long cycle life. These performance characteristics are attributed to the outstanding hierarchical structures of the electrode material. Appropriate carbonization conditions enable the bio-carbon materials to inherit the inherent hierarchical texture of the original biomass, thereby facilitating effective channels for fast ion transfer. The macropores and mesopores that result from chemical activation significantly increase the specific surface area and also play the role of temporary ion-buffering reservoirs, further shortening the ionic diffusion distance.

  1. Assessing the Impact of Canopy Structure Simplification in Common Multilayer Models on Irradiance Absorption Estimates of Measured and Virtually Created Fagus sylvatica (L. Stands

    Directory of Open Access Journals (Sweden)

    Pol Coppin

    2009-11-01

    Full Text Available Multilayer canopy representations are the most common structural stand representations due to their simplicity. Implementation of recent advances in technology has allowed scientists to simulate geometrically explicit forest canopies. The effect of simplified representations of tree architecture (i.e., multilayer representations of four Fagus sylvatica (L. stands, each with different LAI, on the light absorption estimates was assessed in comparison with explicit 3D geometrical stands. The absorbed photosynthetic radiation at stand level was calculated. Subsequently, each geometrically explicit 3D stand was compared with three multilayer models representing horizontal, uniform, and planophile leaf angle distributions. The 3D stands were created either by in situ measured trees or by modelled trees generated with the AMAP plant growth software. The Physically Based Ray Tracer (PBRT algorithm was used to simulate the irradiance absorbance of the detailed 3D architecture stands, while for the three multilayer representations, the probability of light interception was simulated by applying the Beer-Lambert’s law. The irradiance inside the canopies was characterized as direct, diffuse and scattered irradiance. The irradiance absorbance of the stands was computed during eight angular sun configurations ranging from 10° (near nadir up to 80° sun zenith angles. Furthermore, a leaf stratification (the number and angular distribution of leaves per LAI layer inside a canopy analysis between the 3D stands and the multilayer representations was performed, indicating the amount of irradiance each leaf is absorbing along with the percentage of sunny and shadow leaves inside the canopy. The results reveal that a multilayer representation of a stand, using a multilayer modelling approach, greatly overestimated the absorbed irradiance in an open canopy, while it provided a better approximation in the case of a closed canopy. Moreover, the actual stratification

  2. A last stand in the Po valley: genetic structure and gene flow patterns in Ulmus minor and U. pumila.

    Science.gov (United States)

    Bertolasi, B; Leonarduzzi, C; Piotti, A; Leonardi, S; Zago, L; Gui, L; Gorian, F; Vanetti, I; Binelli, G

    2015-03-01

    Ulmus minor has been severely affected by Dutch elm disease (DED). The introduction into Europe of the exotic Ulmus pumila, highly tolerant to DED, has resulted in it widely replacing native U. minor populations. Morphological and genetic evidence of hybridization has been reported, and thus there is a need for assessment of interspecific gene flow patterns in natural populations. This work therefore aimed at studying pollen gene flow in a remnant U. minor stand surrounded by trees of both species scattered across an agricultural landscape. All trees from a small natural stand (350 in number) and the surrounding agricultural area within a 5-km radius (89) were genotyped at six microsatellite loci. Trees were morphologically characterized as U. minor, U. pumila or intermediate phenotypes, and morphological identification was compared with Bayesian clustering of genotypes. For paternity analysis, seeds were collected in two consecutive years from 20 and 28 mother trees. Maximum likelihood paternity assignment was used to elucidate intra- and interspecific gene flow patterns. Genetic structure analyses indicated the presence of two genetic clusters only partially matching the morphological identification. The paternity analysis results were consistent between the two consecutive years of sampling and showed high pollen immigration rates (∼0·80) and mean pollination distances (∼3 km), and a skewed distribution of reproductive success. Few intercluster pollinations and putative hybrid individuals were found. Pollen gene flow is not impeded in the fragmented agricultural landscape investigated. High pollen immigration and extensive pollen dispersal distances are probably counteracting the potential loss of genetic variation caused by isolation. Some evidence was also found that U. minor and U. pumila can hybridize when in sympatry. Although hybridization might have beneficial effects on both species, remnant U. minor populations represent a valuable source of

  3. Sit-to-stand movement changes in preschool-aged children with spastic diplegia following one neurodevelopmental treatment session--a pilot study.

    Science.gov (United States)

    Yonetsu, Ryo; Iwata, Akira; Surya, John; Unase, Kazunori; Shimizu, Junichi

    2015-01-01

    This study was designed to provide a better understanding of how a single neurodevelopmental treatment (NDT) session affects sit-to-stand (STS) movements in children with cerebral palsy (CP). Eight children with spastic diplegia and five typically developing children, aged 4-6 years, participated in this study. The CP participants performed STS movements immediately before and after a 40-min NDT session. Using a three-dimensional, four-camera analysis system, angular movements involving the hip, knee and ankle joints of the participants were obtained. During forward tilt of the trunk, the maximum and final angles after the NDT session significantly decreased compared with those before the session (p spastic diplegia, with limited ability to independently transfer from a sitting position, and dependent on a wheelchair for mobility experience obstacles to enhanced activities of daily life and social participation. A single neurodevelopmental treatment session would enable children with spastic diplegia to perform sit-to-stand movements more efficiently, with selective muscle control. Understanding how a single neurodevelopmental treatment session affects sit-to-stand movements in children with spastic diplegia is invaluable for therapists planning more efficient therapeutic programs and may enable children with spastic diplegia to develop improved mobility.

  4. Structural aging program -- a summary of activities, results, and conclusions

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

    1997-01-01

    Research has been conducted by the Oak Ridge National Laboratory to address aging management of nuclear power plant concrete structures. The purpose was to identify potential structural safety issues and acceptance criteria for use in continued service assessments. Primary program accomplishments have included formulation of a Structural Materials Information Center that contains data and information on the time variation of material properties under the influence of pertinent environmental stressors and aging factors for 144 materials, an aging assessment methodology to identify critical structures and degradation factors that can potentially impact their performance, guidelines and evaluation criteria for use in condition assessments of reinforced concrete structures, and a reliability-based methodology for current condition assessments and estimations of future performance of reinforced concrete nuclear power plant structures. In addition, the Structural Aging Program conducted in-depth evaluations of several nondestructive evaluation and repair-related technologies to develop guidance on their applicability

  5. An unsupervised two-stage clustering approach for forest structure classification based on X-band InSAR data - A case study in complex temperate forest stands

    Science.gov (United States)

    Abdullahi, Sahra; Schardt, Mathias; Pretzsch, Hans

    2017-05-01

    Forest structure at stand level plays a key role for sustainable forest management, since the biodiversity, productivity, growth and stability of the forest can be positively influenced by managing its structural diversity. In contrast to field-based measurements, remote sensing techniques offer a cost-efficient opportunity to collect area-wide information about forest stand structure with high spatial and temporal resolution. Especially Interferometric Synthetic Aperture Radar (InSAR), which facilitates worldwide acquisition of 3d information independent from weather conditions and illumination, is convenient to capture forest stand structure. This study purposes an unsupervised two-stage clustering approach for forest structure classification based on height information derived from interferometric X-band SAR data which was performed in complex temperate forest stands of Traunstein forest (South Germany). In particular, a four dimensional input data set composed of first-order height statistics was non-linearly projected on a two-dimensional Self-Organizing Map, spatially ordered according to similarity (based on the Euclidean distance) in the first stage and classified using the k-means algorithm in the second stage. The study demonstrated that X-band InSAR data exhibits considerable capabilities for forest structure classification. Moreover, the unsupervised classification approach achieved meaningful and reasonable results by means of comparison to aerial imagery and LiDAR data.

  6. Sagittal standing posture and its association with spinal pain: a school-based epidemiological study of 1196 Flemish adolescents before age at peak height velocity.

    Science.gov (United States)

    Dolphens, Mieke; Cagnie, Barbara; Coorevits, Pascal; Vanderstraeten, Guy; Cardon, Greet; Dʼhooge, Roseline; Danneels, Lieven

    2012-09-01

    Cross-sectional baseline data set on the sagittal standing posture of 1196 adolescents. To describe and quantify common variations in the sagittal standing alignment in boys and girls who are in the same phase of growth and to explore the association between habitual standing posture and measures for spinal pain. Data on postural characteristics and spinal pain measures in adolescence are sparse, especially when somatic and biological maturity status is to be considered. Our understanding of the relationship between standing posture in the sagittal plane and spinal pain is also deficient. A total of 639 boys (age [mean ± SD], 12.6 ± 0.54 yr) and 557 girls (10.6 ± 0.47 yr), with predicted years from peak height velocity (PHV) being 1.2 ± 0.71 and 1.2 ± 0.59 pre-PHV, respectively, were studied. Postural examination included the assessment of global alignment and local spinopelvic characteristics, using post hoc analyses of digital images and direct body measurements (palpation, digital inclinometry, and wheeled accelerometry). Spinal pain experience was assessed by questionnaire. A wide interindividual variation in sagittal posture characteristics was observed. Logistic regression analyses yielded global alignment parameters to be associated with low back pain (lifetime prevalence), neck pain (lifetime prevalence, 1-mo prevalence, and doctor visit), and thoracic spine pain (doctor visit) outcome measures. None of the included local spinopelvic parameters could be identified as an associated factor with measures of spinal pain. The orientation of gross body segments with respect to the gravity line seems superior to local spinopelvic features in terms of clinical importance, at least in the current pre-PHV cohort. Opportunities may exist for postural subgrouping strategies to begin with global alignment parameters in order to gain further insight into the relationship between sagittal alignment and the relative risk of developing spinal pain/seeking medical

  7. Aging of concrete structures in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Pland, C.B.; Arndt, E.G.

    1991-01-01

    The Structural Aging (SAG) Program, sponsored by the US Nuclear Regulatory Commission (USNRC) and conducted by the Oak Ridge National Laboratory (ORNL), had the overall objective of providing the USNRC with an improved basis for evaluating nuclear power plant structures for continued service. The program consists of three technical tasks: materials property data base, structural component assessment/repair technology, and quantitative methodology for continued service determinations. Major accomplishments under the SAG Program during the first two years of its planned five-year duration have included: development of a Structural Materials Information Center and formulation of a Structural Aging Assessment Methodology for Concrete Structures in Nuclear Power Plants. 9 refs

  8. Adaptation of brain functional and structural networks in aging.

    Directory of Open Access Journals (Sweden)

    Annie Lee

    Full Text Available The human brain, especially the prefrontal cortex (PFC, is functionally and anatomically reorganized in order to adapt to neuronal challenges in aging. This study employed structural MRI, resting-state fMRI (rs-fMRI, and high angular resolution diffusion imaging (HARDI, and examined the functional and structural reorganization of the PFC in aging using a Chinese sample of 173 subjects aged from 21 years and above. We found age-related increases in the structural connectivity between the PFC and posterior brain regions. Such findings were partially mediated by age-related increases in the structural connectivity of the occipital lobe within the posterior brain. Based on our findings, it is thought that the PFC reorganization in aging could be partly due to the adaptation to age-related changes in the structural reorganization of the posterior brain. This thus supports the idea derived from task-based fMRI that the PFC reorganization in aging may be adapted to the need of compensation for resolving less distinctive stimulus information from the posterior brain regions. In addition, we found that the structural connectivity of the PFC with the temporal lobe was fully mediated by the temporal cortical thickness, suggesting that the brain morphology plays an important role in the functional and structural reorganization with aging.

  9. Adaptation of brain functional and structural networks in aging.

    Science.gov (United States)

    Lee, Annie; Ratnarajah, Nagulan; Tuan, Ta Anh; Chen, Shen-Hsing Annabel; Qiu, Anqi

    2015-01-01

    The human brain, especially the prefrontal cortex (PFC), is functionally and anatomically reorganized in order to adapt to neuronal challenges in aging. This study employed structural MRI, resting-state fMRI (rs-fMRI), and high angular resolution diffusion imaging (HARDI), and examined the functional and structural reorganization of the PFC in aging using a Chinese sample of 173 subjects aged from 21 years and above. We found age-related increases in the structural connectivity between the PFC and posterior brain regions. Such findings were partially mediated by age-related increases in the structural connectivity of the occipital lobe within the posterior brain. Based on our findings, it is thought that the PFC reorganization in aging could be partly due to the adaptation to age-related changes in the structural reorganization of the posterior brain. This thus supports the idea derived from task-based fMRI that the PFC reorganization in aging may be adapted to the need of compensation for resolving less distinctive stimulus information from the posterior brain regions. In addition, we found that the structural connectivity of the PFC with the temporal lobe was fully mediated by the temporal cortical thickness, suggesting that the brain morphology plays an important role in the functional and structural reorganization with aging.

  10. Stand development and population dynamics of curlleaf mountain mahogany (Cercocarpus ledifolius Nutt.) woodlands in Utah's Bear River Mountains

    Science.gov (United States)

    Seth A. Ex; Robert DeRose; James N. Long

    2011-01-01

    Curlleaf mountain mahogany (Cercocarpus ledifolius Nutt.) is a little-studied woodland tree that occurs in pure stands throughout the Intermountain West. Stand development and population dynamics of this species are poorly understood, despite their relevance to management. We describe here the development of stand age structures and population dynamics of mahogany...

  11. Size, longevity and cancer: age structure.

    Science.gov (United States)

    Wensink, Maarten J

    2016-09-14

    There is significant recent interest in Peto's paradox and the related problem of the evolution of large, long-lived organisms in terms of cancer robustness. Peto's paradox refers to the expectation that large, long-lived organisms have a higher lifetime cancer risk, which is not the case: a paradox. This paradox, however, is circular: large, long-lived organisms are large and long-lived because they are cancer robust. Lifetime risk, meanwhile, depends on the age distributions of both cancer and competing risks: if cancer strikes before competing risks, then lifetime risk is high; if not, not. Because no set of competing risks is generally prevalent, it is instructive to temporarily dispose of competing risks and investigate the pure age dynamics of cancer under the multistage model of carcinogenesis. In addition to augmenting earlier results, I show that in terms of cancer-free lifespan large organisms reap greater benefits from an increase in cellular cancer robustness than smaller organisms. Conversely, a higher cellular cancer robustness renders cancer-free lifespan more resilient to an increase in size. This interaction may be an important driver of the evolution of large, cancer-robust organisms. © 2016 The Authors.

  12. Evaluation of the load carrying capacity of large cross section coniferous timber in standing structures

    Directory of Open Access Journals (Sweden)

    Arriaga, F.

    2005-12-01

    Full Text Available A total of 85 large section timber pieces (Pinus sylvestris L. and Pinus pinaster Alt. found in a number of old buildings were visually analyzed and graded pursuant to Spanish standard UNE 56544 and German standard 4074. The object was to formulate a non-destructive method to reliably and effectively determine the mechanical properties of existing timber structures with large cross sections. A new system is proposed based on the chief visual grading parameters and consisting in a single grade; the percentage of rejections with this system is low. In this regard, a specific strength class is established for large cross section members in existing coniferous wood structures, namely F14/E9/D380 (MOR of 14 N/mm2, MOE of 9 kN/mm2 and characteristic density of 380 kg/m3. The use of ultrasonic velocity is proposed to define the next higher strength class - F16/E10/D380, to which timber with velocities of 4,900 m/s or over would be assigned.

    Se han clasificado visualmente 85 piezas de madera de gruesa sección (Pino silvestre y Pino pinaster procedentes de varios edificios antiguos de acuerdo con las normas UNE 56544 y DIN 4074. El objetivo es establecer una metodología no destructiva para asignar propiedades mecánicas a las piezas de estructuras existentes de madera con gruesas escuadrías con un nivel de seguridad y de rendimiento aceptables. Se propone un único grado de calidad con un porcentaje bajo de rechazos, aplicando los principales parámetros de la clasificación visual. De esta forma, se establece una clase resistente específica para las piezas de gruesa escuadría de estructuras de madera de conifera existentes definida como FI4/E9/D380 (resistencia característica a flexión igual a 14 N/mm2, módulo de elasticidad de 9 kN/mn2 y densidad característica de 380 kg/m3. Para alcanzar una clase resistente superior se propone utilizar el parámetro añadido de la

  13. Investigation of stand-off distance effect on structure, adhesion and hardness of copper coatings obtained by the APS technique

    Science.gov (United States)

    Masoumeh, Goudarzi; Shahrooz, Saviz; Mahmood, Ghoranneviss; Ahmad, Salar Elahi

    2018-03-01

    The outbreak of the disease and infection in the hospital environment and medical equipment is one of the concerns of modern life. One of the effective ways for preventing and reducing the complications of infections is modification of the surface. Here, the handmade atmospheric plasma spray system is used for accumulating copper as an antibacterial agent on the 316L stainless steel substrate, which applies to hospital environment and medical equipment. As a durable coating with proper adhesion is needed on the substrate, the effect of stand-off distance (SOD) which is an important parameter of the spray on the microstructure, the hardness and adhesion of the copper coating on the 316L stainless steel were investigated. The structure and phase composition of copper depositions were investigated using scanning electron microscopy and X-ray diffraction. The adhesion and hardness of depositions are evidenced using the cross cut tester and Vickers hardness tester, respectively. The findings confirm that the voids in the coatings increase with increasing SOD, which leads to decreasing the hardness of coatings and also the adhesion strength between depositions and substrate. In addition, by increasing the SOD, the oxygen content and the size of grains in the lamellae (fine structure) of coatings also increase.

  14. Uranium-series ages of fossil corals from Mallorca, Spain: The "Neotyrrhenian" high stand of the Mediterranean Sea revisited

    Science.gov (United States)

    Muhs, Daniel R.; Simmons, Kathleen R.; Porat, Naomi

    2015-01-01

    The emergent marine deposits of the Mediterranean basin have been recognized as an important record of Quaternary sea level history for more than a century. Previous workers identified what have been interpreted to be two separate high stands of sea in the late Quaternary, namely the “Eutyrrhenian” (thought to be ~ 120 ka) and the “Neotyrrhenian” (thought to be either ~ 100 ka or ~ 80 ka). On Mallorca, Spain, both of these named deposits lie close to present sea level, implying paleo-sea levels slightly above present during both marine isotope stages (MIS) 5.5/5e and either 5.3/5c or 5.1/5a. If these interpretations are correct, they conflict, at least in part, with sea level records from far-field localities.

  15. The standing pool of genomic structural variation in a natural population of Mimulus guttatus.

    Science.gov (United States)

    Flagel, Lex E; Willis, John H; Vision, Todd J

    2014-01-01

    Major unresolved questions in evolutionary genetics include determining the contributions of different mutational sources to the total pool of genetic variation in a species, and understanding how these different forms of genetic variation interact with natural selection. Recent work has shown that structural variants (SVs) (insertions, deletions, inversions, and transpositions) are a major source of genetic variation, often outnumbering single nucleotide variants in terms of total bases affected. Despite the near ubiquity of SVs, major questions about their interaction with natural selection remain. For example, how does the allele frequency spectrum of SVs differ when compared with single nucleotide variants? How often do SVs affect genes, and what are the consequences? To begin to address these questions, we have systematically identified and characterized a large set of submicroscopic insertion and deletion (indel) variants (between 1 and 200 kb in length) among ten inbred lines from a single natural population of the plant species Mimulus guttatus. After extensive computational filtering, we focused on a set of 4,142 high-confidence indels that showed an experimental validation rate of 73%. All but one of these indels were less than 200 kb. Although the largest were generally at lower frequencies in the population, a surprising number of large indels are at intermediate frequencies. Although indels overlapping with genes were much rarer than expected by chance, approximately 600 genes were affected by an indel. Nucleotide-binding site leucine-rich repeat (NBS-LRR) defense response genes were the most enriched among the gene families affected. Most indels associated with genes were rare and appeared to be under purifying selection, though we do find four high-frequency derived insertion alleles that show signatures of recent positive selection.

  16. Ectomycorrhizal Community Structure and Soil Characteristics of Mature Lodgepole Pine (Pinus Contorta) and Adjacent Stands of Old Growth Mixed Conifer in Yellowstone National Park, Wyoming USA

    Science.gov (United States)

    Douglas, Robert B.; Parker, V. Thomas; Cullings, Kenneth W.; Sun, Sidney (Technical Monitor)

    2003-01-01

    Forest development patterns following disturbance are known to influence the physical and chemical attributes of soils at different points in time. Changes in soil resources are thought to have a corresponding effect on ectomycorrhizal (ECM) community structure. We used molecular methods to compare below-ground ECM species richness, composition, and abundance between adjacent stands of homogenous lodgepole pine and old growth mixed conifer in Yellowstone National Park (YNP). In each stand-type we collected soil cores to both identify mycorrhizae and assess soil chemistry. Although no statistical difference was observed in the mean number of ECM root tips per core between stand types, the total number of species identified (85 versus 35) and the mean number of species per core (8.8 +/- 0.6 versus 2.5 +/- 0.3) were significantly higher in lodgepole pine. Differences between the actual and estimated species richness levels indicated that these forest types support a high number of ECM species and that undersampling was severe. Species compositions were widely disparate between stands where only four species were shared out of a total of 116. Soil analysis also revealed that mixed conifer was significantly lower in pH, but higher in organic matter, potassium, phosphorus, and ammonium when compared to lodgepole pine stands. Species richness per core was correlated with these chemical data, however, analysis of covariance indicated that stand type was the only statistically significant factor in the observed difference in species richness. Our data suggest that ECM fungal richness increases as homogenous lodgepole pine stands grow and mature, but declines after Engelmann spruce and subalpine fir colonize. Despite difficulties linking species composition with soil chemistry, there are a variety of physical and chemical factors that could be influencing ECM community structure. Future field experiments are necessary to test some of the mechanisms potentially operating

  17. Response of forest soil Acari to prescribed fire following stand structure manipulation in the southern Cascade Range.Can

    Science.gov (United States)

    Michael A. Camann; Nancy E. Gillette; Karen L. Lamoncha; Sylvia R. Mori

    2008-01-01

    We studied responses of Acari, especially oribatid mites, to prescribed low-intensity fire in an east side pine site in the southern Cascade Range in California. We compared oribatid population and assemblage responses to prescribed fire in stands that had been selectively logged to enhance old growth characteristics, in logged stands to minimize old growth...

  18. Analysis of the Genetic Diversity and Population Structure of Latvian Ash (Fraxinus excelsior L. Stands using Nuclear and Chloroplast SSR Markers

    Directory of Open Access Journals (Sweden)

    Ruņģis Dainis

    2016-06-01

    Full Text Available Common ash (Fraxinus excelsior L. has a widespread distribution throughout Europe, and Latvia is almost at the north eastern edge of the distribution range. In Europe, ash is threatened by ash dieback, a disease caused by the introduced ascomycete Hymenoscyphus fraxineus. Chloroplast and nuclear DNA markers have been used to study the genetic diversity and population structure of ash both in a broader pan-European context as well as in more restricted regions. Some of the markers analysed in these previously published reports were also utilised in this study, enabling comparisons of the genetic parameters calculated from the nuclear SSR marker data and of the haplotypes identified with the chloroplast markers. Analysis of chloroplast markers revealed one dominant haplotype in Latvian stands, which corresponds to the haplotype previously found in Eastern Europe and Scandinavia. A second haplotype, corresponding to a previously reported central European haplotype was found in all individuals from the Ķemeri stand, indicating that this stand was naturally established from introduced germplasm, which was planted in a neighbouring park. The nuclear SSR markers revealed low levels of differentiation of Latvian F. excelsior stands, probably due efficient pollen flow between stands. The analysis of both chloroplast and nuclear DNA markers has revealed different aspects of the structure and provenance of Latvian F. excelsior populations.

  19. Age-related and stand-wise estimates of carbon stocks and sequestration in the aboveground coarse wood biomass of wetland forests in the northern Pantanal, Brazil

    Directory of Open Access Journals (Sweden)

    J. Schöngart

    2011-11-01

    Full Text Available In this study we use allometric models combined with tree ring analysis to estimate carbon stocks and sequestration in the aboveground coarse wood biomass (AGWB of wetland forests in the Pantanal, located in central South America. In four 1-ha plots in stands characterized by the pioneer tree species Vochysia divergens Pohl (Vochysiaceae forest inventories (trees ≥10 cm diameter at breast height, D have been performed and converted to estimates of AGWB by two allometric models using three independent parameters (D, tree height H and wood density ρ. We perform a propagation of measurement errors to estimate uncertainties in the estimates of AGWB. Carbon stocks of AGWB vary from 7.8 ± 1.5 to 97.2 ± 14.4 Mg C ha−1 between the four stands. From models relating tree ages determined by dendrochronological techniques to C-stocks in AGWB we derived estimates for C-sequestration which differs from 0.50 ± 0.03 to 3.34 ± 0.31 Mg C ha−1 yr−1. Maps based on geostatistic techniques indicate the heterogeneous spatial distribution of tree ages and C-stocks of the four studied stands. This distribution is the result of forest dynamics due to the colonizing and retreating of V. divergens and other species associated with pluriannual wet and dry episodes in the Pantanal, respectively. Such information is essential for the management of the cultural landscape of the Pantanal wetlands.

  20. Modeling and analysis of horizontal structure of a mixed tree stands (on example of sample plots in the «Bastak» nature reserve in the Middle Amur river area

    Directory of Open Access Journals (Sweden)

    A. N. Kolobov

    2015-06-01

    Full Text Available The results of the research model and real data spatial distribution of trees in single-species, ages and mixed stands are studied. Modeling of the horizontal structure of the stand was based on a computer simulation model. Investigation of the horizontal structure of the stand allows drawing of conclusions about the processes of intraspecific and interspecific competition. It is shown that the model used to generate spatial data model reflects the basic mechanisms of stacked-mosaic structure of the stand, which is observed in natural communities. It allows future use of this model to study the characteristics of the formation of the spatial structure of mixed forest communities, developing under the influence of internal (competition and external (logging, windfalls, herbivores, etc. factors. Statistical analysis of the tree spatial distribution for shade-tolerant and light-loving species relative to each other showed that, on average, around an arbitrarily chosen shade-tolerant tree species, there is an area within which the opportunity to meet the tree light-loving species is less than it would be under their random placement. Around an arbitrarily chosen «large» tree of shade-tolerant species there is an area within which the opportunity to meet the «small» or «medium» light-loving tree species is less than would have been at their random placement. It is shown that the mutual arrangement of «large» light-loving trees and «small», «medium» shade-tolerant trees is no different from a random allocation. As a result of competitive processes of spatial arrangement for light-loving tree species is determined by the placement of shade-tolerant trees. Location of light-loving trees does not affect the location of shade-tolerant trees. The relative placement of different types of shade-tolerant trees, especially spruce, fir and pine, are independent of each other.

  1. Bark beetles and dwarf mistletoe interact to alter downed woody material, canopy structure, and stand characteristics in northern Colorado ponderosa pine

    Science.gov (United States)

    Jennifer G. Klutsch; Russell D. Beam; William R. Jacobi; Jose F. Negron

    2014-01-01

    Due to the recent outbreaks of bark beetles in western U.S.A., research has focused on the effects of tree mortality on forest conditions, such as fuel complexes and stand structure. However, most studies have addressed outbreak populations of bark beetles only and there is a lack of information on the effect of multiple endemic, low level populations of biotic...

  2. Effects of dwarf mistletoe on stand structure of lodgepole pine forests 21-28 years post-mountain pine beetle epidemic in central Oregon

    Science.gov (United States)

    Michelle C. Agne; David C. Shaw; Travis J. Woolley; Mónica E. Queijeiro-Bolaños; Mai-He. Li

    2014-01-01

    Lodgepole pine (Pinus contorta) forests are widely distributed throughout North America and are subject to mountain pine beetle (Dendroctonus ponderosae) epidemics, which have caused mortality over millions of hectares of mature trees in recent decades. Mountain pine beetle is known to influence stand structure, and has the ability to impact many forest processes....

  3. Momentum-resolved electronic structure at a buried interface from soft X-ray standing-wave angle-resolved photoemission

    NARCIS (Netherlands)

    Gray, A.X.; Minar, J.; Plucinski, L.; Huijben, Mark; Bostwick, A.; Rotenberg, E.; Yang, S.-H.; Braun, J.; Winkelmann, A.; Conti, G.; Eiteneer, D.; Rattanachata, A.; Greer, A.A.; Ciston, J.; Ophus, C.; Rijnders, Augustinus J.H.M.; Blank, David H.A.; Doennig, D.; Pentcheva, R.; Kortright, J.B.; Schneider, C.M.; Ebert, H.; Fadley, C.S.

    2013-01-01

    Angle-resolved photoemission spectroscopy (ARPES) is a powerful technique for the study of electronic structure, but it lacks a direct ability to study buried interfaces between two materials. We address this limitation by combining ARPES with soft X-ray standing-wave (SW) excitation (SWARPES), in

  4. [Age estimation and age structure of Cycas fairylakea population in Shenzhen City].

    Science.gov (United States)

    Wang, Dian-Pei; Ji, Shu-Yi; Chen, Fei-Peng; Peng, Shao-Lin

    2007-03-01

    Based on the structural characteristics of Cycas trunk, including vegetative leaf base scars, sporophyll concave rings, and average occurrence probabilities of vegetative leaf and sporophyll, a method for the age estimation of Cycas fairylakea population was developed, and the age of each individual was calculated. Three approaches, i.e., age structure diagram, age distribution curve and curve estimation were used to study the age structure of C. fairylakea population at genet and clone population levels. The age structure diagram showed that the clone population of C. fairylakea was stable, but the genet population was in declining. However, both of the clone and genet populations were in declining when using the other two approaches. It was considered that the C. fairylakea population was in declining, and needed an urgent protection.

  5. Visualising the demographic factors which shape population age structure

    Directory of Open Access Journals (Sweden)

    Tom Wilson

    2016-09-01

    Full Text Available Background: The population pyramid is one of the most popular tools for visualising population age structure. However, it is difficult to discern from the diagram the relative effects of different demographic components on the size of age-specific populations, making it hard to understand exactly how a population's age structure is formed. Objective: The aim of this paper is to introduce a type of population pyramid which shows how births, deaths, and migration have shaped a population's age structure. Methods: Births, deaths, and population data were obtained from the Human Mortality Database and the Australian Bureau of Statistics. A variation on the conventional population pyramid, termed here a components-of-change pyramid, was created. Based on cohort population accounts, it illustrates how births, deaths, and net migration have created the population of each age group. A simple measure which summarises the impact of net migration on age structure is also suggested. Results: Example components-of-change pyramids for several countries and subnational regions are presented, which illustrate how births, deaths, and net migration have fashioned current population age structures. The influence of migration is shown to vary greatly between populations. Conclusions: The new type of pyramid aids interpretation of a population's age structure and helps to understand its demographic history over the last century.

  6. Financial Performance of Mixed-Age Naturally Regenerated Loblolly-Hardwood Stands in the South Central United States

    Science.gov (United States)

    Ronald Raunikar; Joseph Buongiorno; Jeffrey P. Prestemon; Karen Lee Abt

    2000-01-01

    To estimate the financial performance of a natural mixed species and mixed-age management in the loblolly-pine forest type, we examined 991 FIA plots in the south central states. The plots were of the loblolly pine forest type, mixed-age, and had been regenerated naturally. We gauged the financial performance of each plot from the equivalent annual income (EAI)...

  7. Age structure and age-related performance of sulfur cinquefoil (Potentilla recta).

    Science.gov (United States)

    Dana L. Perkins; Catherine G. Parks; Kathleen A. Dwire; Bryan A. Endress; Kelsi L. Johnson

    2006-01-01

    Age distributions of sulfur cinquefoil populations were determined on sites that were historically grazed, cultivated, and mechanically disturbed. From 12 sites, a total of 279 reproductively active plants were collected and aged by using herbchronology (counting rings in the secondary root xylem of the root crown) to (1) estimate the age structure of the populations...

  8. Age-gender Structure of Croats in Vojvodina Province

    Directory of Open Access Journals (Sweden)

    Tamara Kovačević

    2010-11-01

    Full Text Available The paper elaborates the age – gender structure of Croats in Vojvodina and gives insight how old is the Croatian population and does it in general older than population of Vojvodina. Particular attention was given to the period after the Second World War, e.g. on the second half of 20th and at the beginning of 21st century. The main task of the paper was the identification of tendencies in age structure of Croats. Statistical methods and mathematics proceeding are used to compare different parameters of age structure (e.g. middle age, index of ageing etc. The paper proves that Croats are one of the oldest ethnic groups among the population of Vojvodina province. The results of the study will enhance the knowledge about demographic characteristics of Croats in Vojvodina and therefore might be useful for further research in the field.

  9. The Age Structure of Canadian University Teachers and Its Implications.

    Science.gov (United States)

    von Zur-Muehlen, Max

    1979-01-01

    The enrollment pattern, age structure, rank distribution, and salary levels of full time faculty at Canadian universities are examined and their consequences for the present and future are explored. (JMF)

  10. Tuberculosis in Cape Town: An age-structured transmission model

    Directory of Open Access Journals (Sweden)

    Nello Blaser

    2016-03-01

    Conclusion: The protective effect of a first latent infection on subsequent infections and the faster progression in previously treated patients are the key determinants of the age-structure of TB notification rates in Cape Town.

  11. Aging management of containment structures in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.; Graves, H.L. III; Norris, W.E.

    1994-01-01

    Research is being conducted by ORNL under US Nuclear Regulatory Commission (USNRC) sponsorship to address aging management of nuclear power plant containment and other safety-related structures. Documentation is being prepared to provide the USNRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Accomplishments include development of a Structural Materials Information Center containing data and information on the time variation of 144 material properties under the influence of pertinent environmental stressors or aging factors, evaluation of models for potential concrete containment degradation factors, development of a procedure to identify critical structures and degradation factors important to aging management, evaluations of nondestructive evaluation techniques. assessments of European and North American repair practices for concrete, review of parameters affecting corrosion of metals embedded in concrete, and development of methodologies for making current condition assessments and service life predictions of new or existing reinforced concrete structures in nuclear power plants

  12. China's marriage squeeze: A decomposition into age and sex structure.

    Science.gov (United States)

    Jiang, Quanbao; Li, Xiaomin; Li, Shuzhuo; Feldman, Marcus W

    2016-06-01

    Most recent studies of marriage patterns in China have emphasized the male-biased sex ratio but have largely neglected age structure as a factor in China's male marriage squeeze. In this paper we develop an index we call "spousal sex ratio" (SSR) to measure the marriage squeeze, and a method of decomposing the proportion of male surplus into age and sex structure effects within a small spousal age difference interval. We project that China's marriage market will be confronted with a relatively severe male squeeze. For the decomposition of the cohort aged 30, from 2010 to 2020 age structure will be dominant, while from 2020 through 2034 the contribution of age structure will gradually decrease and that of sex structure will increase. From then on, sex structure will be dominant. The index and decomposition, concentrated on a specific female birth cohort, can distinguish spousal competition for single cohorts which may be covered by a summary index for the whole marriage market; these can also be used for consecutive cohorts to reflect the situation of the whole marriage market.

  13. Age structure changes and extraordinary lifespan in wild medfly populations.

    Science.gov (United States)

    Carey, James R; Papadopoulos, Nikos T; Müller, Hans-Georg; Katsoyannos, Byron I; Kouloussis, Nikos A; Wang, Jane-Ling; Wachter, Kenneth; Yu, Wei; Liedo, Pablo

    2008-06-01

    The main purpose of this study was to test the hypotheses that major changes in age structure occur in wild populations of the Mediterranean fruit fly (medfly) and that a substantial fraction of individuals survive to middle age and beyond (> 3-4 weeks). We thus brought reference life tables and deconvolution models to bear on medfly mortality data gathered from a 3-year study of field-captured individuals that were monitored in the laboratory. The average time-to-death of captured females differed between sampling dates by 23.9, 22.7, and 37.0 days in the 2003, 2004, and 2005 field seasons, respectively. These shifts in average times-to-death provided evidence of changes in population age structure. Estimates indicated that middle-aged medflies (> 30 days) were common in the population. A surprise in the study was the extraordinary longevity observed in field-captured medflies. For example, 19 captured females but no reference females survived in the laboratory for 140 days or more, and 6 captured but no reference males survived in the laboratory for 170 days or more. This paper advances the study of aging in the wild by introducing a new method for estimating age structure in insect populations, demonstrating that major changes in age structure occur in field populations of insects, showing that middle-aged individuals are common in the wild, and revealing the extraordinary lifespans of wild-caught individuals due to their early life experience in the field.

  14. [Influence of mulching management on the relationships between foliar non-structural carbohydrates and N, P concentrations in Phyllostachys violascens stand].

    Science.gov (United States)

    Guo, Zi-wu; Hu, Jun-jing; Yang, Qing-ping; Li, Ying-chun; Chen, Shuang-lin; Chen, Wei-jun

    2015-04-01

    To understand the physiological adaptive mechanism of Phyllostachys violascens to intensive mulching management, the effect of mulching management (CK, 1, 3 and 6 years) on the concentrations and ratios of non-structural carbohydrates (NSC), nitrogen (N) and phosphorus (P) in bamboo foliage, and their stoichiometry was investigated. The results showed the concentrations of NSC and soluble sugar increased, while the starch content and N/P decreased markedly in bamboo stand with 1-year mulching, compared to CK stand, which suggested the N limitation to bamboo growth was strengthened. Foliar soluble sugar content decreased significantly, while the starch content increased dramatically, and the NSC content by per unit mass of N and P reached the maximum in the bamboo stand with 3-year mulching, compared to all other treatments. Foliar NSC and soluble sugar contents decreased significantly, while foliar starch content and N/P increased dramatically in the stand with 6-year mulching, which suggested the P limitation to bamboo growth was strengthened. Foliar NSC content was positively correlated with N and P concentrations in a short-term mulching management stand (≤ 3 years), while showed negative relationship with N/P. The foliar starch content in the stand with 6-year mulching was negatively correlated with N and P contents, while was positively correlated with N/P. The results indicated that short-term mulching management accelerated the accumulation of soluble sugar and decomposition of starch in foliage, thus the growth and activity of Ph. violascens was enhanced greatly. Long-term mulching management promoted the starch accumulation, which led to the transition from N limitation to P limitation for bamboo growth. In summary, long-term (6 years) mulching management caused the decrease of growth and activity of Ph. violascens dramatically, thus enhancing the bamboo stand degradation. The utilization efficiency of N and P reached the highest in the stand with 3-year

  15. ECOLOGICAL STRUCTURE OF ORIBATID MITE COMMUNITIES IN ACER PLATANOIDES L. STAND ON THE REMEDIATED SITE OF PAVLOGRADSKAYA MINE (PAVLOGRAD, THE DNIPROPETROVSK REGION

    Directory of Open Access Journals (Sweden)

    Y. L. Kulbachko

    2014-04-01

    Full Text Available Species composition and features of ecological structure of oribatid mite communities were studied on various options of bulk artificial-mixed soil in Acer platanoides L. stand growing on the remediated site of Pavlogradskaya mine (Pavlograd, Dnipropetrovsk Region. The ecological structure of oribatid population generally was damaged and this is typical for the man-modified ecosystems. Oribatid mite density in maple litter was higher than in the top layer of bulk soil (loess loam and chernozem by 4.1–7.4 times. Species abundance of oribatid mite was almost equal in maple litter and bulk soil. Punctoribates liber Pavlitshenko, 1991 prevailed generally as eudominant species in oribatid mite structure in Acer platanoides stand. The representatives of unspecialized life-forms were dominated among the oribatid life-forms in the remediated site with chernozem bulk. Key words: oribatid mites, forest remediation, mine dumps.

  16. Intra-stand variation of cone structure and seed production in Siberian stone pine: pattern and use for breeding

    Directory of Open Access Journals (Sweden)

    V.S. Akimov

    2013-12-01

    Full Text Available Siberian stone pine (Pinus sibirica Du Tour in Russia is primarily valued as a nut-bearing species. Therefore, intra-standvariation in its cone structure and seed production have been actively studied during the last 50 years. However, these studies arepoorly related to practical breeding. We used a novel system of traits to characterize yearly seed crops at the different levels of itsstructural organization. The purpose is to analyze the results of long-term observations of the intra-stand variation of the reproductivefeatures complex, and to reveal the pattern and character of its diversity. This information would be useful to develop the method ofsearching the initial material for breeding. The research plot is established in the Nizhne-Sechenovo forest located 25 km fromTomsk in the south part of the boreal zone (170 years old, mean height 22 m, mean d.b.h. 60 cm. The number of sampled trees variedbetween 40-120 among years. The registration of seed crop and analysis of its structure was conducted every year from 1990 to 2005. Theintra-stand variation of the traits' level was determined as a standard deviation in percent from the simple average. The level ofvariability rose sharply and the correlations between them decreased in the years of the low crops. The results concerning variation in seedand cone traits are listed in the next table. The number of full seeds depended rather on losses in the processes of development (r =0.80*-0.85* than on their starting number (r =0.55*-0.60*. The mass of one seed with sound endosperm rose with an increase in the ratio ofthe ovules, which were lost at the earlier stagesof development (r = 0.20-0.25* and the flat seed ratio (r = 0.35*-0.40*. In year-to-year dynamics, the number of cones per tree ispositively connected with the number of filled seeds per cone (r = 0.78* and with other indices characterizing 'the crop quality'.The breeding rank of trees by all important

  17. On the Effect of Thinning on Tree Growth and Stand Structure of White Birch (Betula platyphylla Sukaczev and Siberian Larch (Larix sibirica Ledeb. in Mongolia

    Directory of Open Access Journals (Sweden)

    Alexander Gradel

    2017-03-01

    Full Text Available The forests of North Mongolia are largely dominated either by larch (Larix sibirica Ledeb. or birch (Betula platyphylla Sukaczev. The increasing demand for timber and firewood is currently met by removal of wood from these forest stands. Therefore, silvicultural approaches that account for both utilization and protection are needed. Thinning trials were established in the research area Altansumber, in the mountain forest steppe west of the town of Darkhan. We analyzed the response of non-spatial and spatial structure and growth of birch and larch stands on thinning. Before thinning, spatial tree distribution was largely clumped. Thinning promoted regular tree distribution. Ingrowth of new stems after thinning tended to redirect stand structure towards clumping. Both relative and absolute tree growth and competition were evaluated before, directly after, and three years after the thinning. Competition played a significant role in tree growth before thinning. A reduction in competition after thinning triggered significantly increased growth of both birch and larch. The observed positive growth response was valid in absolute and relative terms. A methodically based forest management strategy, including thinning operations and selective cuttings, could be established, even under the harsh Mongolian conditions. Our findings could initiate the development of broader forest management guidelines for the light-taiga dominated stands.

  18. Implementation of New Materials on Aging Aircraft Structure

    Science.gov (United States)

    2000-04-01

    Structure f Aging Aircraft [les Nouveaux Materiaux metalliques pour les structures des aeronefs d’ancienne generation] To order the complete...verified the empirical analysis and showed a 50% decrease in in-flight deflections (Figure 11). 2-10 Spares Rework Costs at Depot Current New Design

  19. Tuneable micro- and nano-periodic structures in a free-standing flexible urethane/urea elastomer film.

    Science.gov (United States)

    Godinho, M H; Trindade, A C; Figueirinhas, J L; Melo, L V; Brogueira, P; Deus, A M; Teixeira, P I C

    2006-12-01

    We have studied the control and manipulation of tuneable equilibrium structures in a free-standing urethane/urea elastomer film by means of atomic force microscopy, small-angle light scattering and polarising optical microscopy. The urethane/urea elastomer was prepared by reacting a poly(propyleneoxide)-based triisocyanate-terminated prepolymer (PU) with poly(butadienediol) (PBDO), with a weight ratio of 60% PU/40% PBDO. An elastomer film was shear-cast onto a glass plate and allowed to cure, first in an oven, then in air. Latent micro- and nano-periodic patterns are induced by ultra-violet (UV) irradiation of the film and can be "developed" by applying a plane uniaxial stress or by immersing the elastomer in an appropriate solvent and then drying it. For this elastomer we describe six pattern states, how they are related and how they can be manipulated. The morphological features of the UV-exposed film surface can be tuned, reproducibly and reversibly, by switching the direction of the applied mechanical field. Elastomers extracted in toluene exhibit different surface patterns depending upon the state in which they were developed. Stress-strain data collected for the films before and after UV irradiation reveal anisotropy induced by the shear-casting conditions and enhanced by the mechanical field. We have interpreted our results by assuming the film to consist of a thin, stiff surface layer ("skin") lying atop a thicker, softer substrate ("bulk"). The skin's higher stiffness is hypothesised to be due to the more extensive cross-linking of chains located near the surface by the UV radiation. Patterns would thus arise as a competition between the effects of bending the skin and stretching/compressing the bulk, as in the work of Cerda and Mahadevan (Phys. Rev. Lett. 90, 074302 (2003)). We present some preliminary results of a simulation of this model using the Finite Element package ABAQUS.

  20. Travelling Wave Solutions in Multigroup Age-Structured Epidemic Models

    Science.gov (United States)

    Ducrot, Arnaut; Magal, Pierre; Ruan, Shigui

    2010-01-01

    Age-structured epidemic models have been used to describe either the age of individuals or the age of infection of certain diseases and to determine how these characteristics affect the outcomes and consequences of epidemiological processes. Most results on age-structured epidemic models focus on the existence, uniqueness, and convergence to disease equilibria of solutions. In this paper we investigate the existence of travelling wave solutions in a deterministic age-structured model describing the circulation of a disease within a population of multigroups. Individuals of each group are able to move with a random walk which is modelled by the classical Fickian diffusion and are classified into two subclasses, susceptible and infective. A susceptible individual in a given group can be crisscross infected by direct contact with infective individuals of possibly any group. This process of transmission can depend upon the age of the disease of infected individuals. The goal of this paper is to provide sufficient conditions that ensure the existence of travelling wave solutions for the age-structured epidemic model. The case of two population groups is numerically investigated which applies to the crisscross transmission of feline immunodeficiency virus (FIV) and some sexual transmission diseases.

  1. Report on aging of nuclear power plant reinforced concrete structures

    Energy Technology Data Exchange (ETDEWEB)

    Naus, D.J.; Oland, C.B. [Oak Ridge National Lab., TN (United States); Ellingwood, B.R. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Civil Engineering

    1996-03-01

    The Structural Aging Program provides the US Nuclear Regulatory Commission with potential structural safety issues and acceptance criteria for use in continued service assessments of nuclear power plant safety-related concrete structures. The program was organized under four task areas: Program Management, Materials Property Data Base, Structural Component Assessment/Repair Technology, and Quantitative Methodology for Continued Service Determinations. Under these tasks, over 90 papers and reports were prepared addressing pertinent aspects associated with aging management of nuclear power plant reinforced concrete structures. Contained in this report is a summary of program results in the form of information related to longevity of nuclear power plant reinforced concrete structures, a Structural Materials Information Center presenting data and information on the time variation of concrete materials under the influence of environmental stressors and aging factors, in-service inspection and condition assessments techniques, repair materials and methods, evaluation of nuclear power plant reinforced concrete structures, and a reliability-based methodology for current and future condition assessments. Recommendations for future activities are also provided. 308 refs., 61 figs., 50 tabs.

  2. Report on aging of nuclear power plant reinforced concrete structures

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

    1996-03-01

    The Structural Aging Program provides the US Nuclear Regulatory Commission with potential structural safety issues and acceptance criteria for use in continued service assessments of nuclear power plant safety-related concrete structures. The program was organized under four task areas: Program Management, Materials Property Data Base, Structural Component Assessment/Repair Technology, and Quantitative Methodology for Continued Service Determinations. Under these tasks, over 90 papers and reports were prepared addressing pertinent aspects associated with aging management of nuclear power plant reinforced concrete structures. Contained in this report is a summary of program results in the form of information related to longevity of nuclear power plant reinforced concrete structures, a Structural Materials Information Center presenting data and information on the time variation of concrete materials under the influence of environmental stressors and aging factors, in-service inspection and condition assessments techniques, repair materials and methods, evaluation of nuclear power plant reinforced concrete structures, and a reliability-based methodology for current and future condition assessments. Recommendations for future activities are also provided. 308 refs., 61 figs., 50 tabs

  3. [Analysis and design structure of an aging society].

    Science.gov (United States)

    Fujimasa, Iwao

    2012-01-01

    On observing present Japanese society, we can find deep gaps between the present system and its probable future. One of the gaps may be due to the misconception that future societal make up is not definite. The aim of the current study was to investigate a future societal structure and to develop methods of adding a timed dimension policy to the societal structure. This is named "A theory of structuralism economics". We developed 3 societal structure projection engines and applied a system of dynamics language to estimate the future total population of Japan. The Japan total population reached a maximum in 2005, and thereafter depopulation begun. The populations in the younger working age group (from 25 to 54 years old) and those in the elderly working age group (from 55 to 84 years old) became almost equal in 2010. As economic growth rate depends upon an increase in the working population, the increase in national income rate of Japan approached over 10% per year between 1950 to 1970. The increased working age population of the same period exceeded 2.5% annually. However, after 2005 depopulation began in Japan. In future, national income will decrease proportional to the working age population, but personal national income will hold almost unchanged. We propose a new strategy for future society structure. The working age should be extended by 10 years. Labor power will come to exceed 60% of the population and will thereafter become stable.

  4. Structural Aging Program approach to providing an improved basis for aging management of safety-related concrete structures

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.

    1993-01-01

    The Structural Aging (SAG) Program is being conducted at the Oak Ridge National Laboratory (ORNL) for the United States Nuclear Regulatory Commission (USNRC). The SAG Program is addressing the aging management of safety-related concrete structures in nuclear power plants for the purpose of providing improved technical bases for their continued service. The program is organized into four tasks: Program Management, Materials Property Data Base, Structural Component Assessment/Repair Technologies, and Quantitative Methodology for Continued Service Determinations. Objectives and a summary of recent accomplishments under each of these tasks are presented

  5. Age structure of the workforce and firm performance

    DEFF Research Database (Denmark)

    Westergård-Nielsen, Niels Chr.; Grund, Christian

    2008-01-01

    Purpose - Given the ongoing demographic change in European countries, this paper aims to exploreempirically the link between age structures of employees in firms and firm performance. Design/methodology/approach - Based on theoretical considerations, the paper examines the linkbetween both...... the average age and the standard deviation of employees' age and firms' value added per employee. Linked employer employee data of all private-sector firms in Denmark with at least 20 employees is used. Findings - A pyramidal or inverse U-shaped interrelation is found between mean age and standarddeviation...... of age and value added per employee, respectively. Research limitations/implications - It would be interesting to determine whether the results hold for different countries with other institutional environments.Originality/value - This is the first paper to examine the link between corporate age...

  6. Grazing Incidence X-Ray Fluorescence of periodic structures – a comparison between X-ray Standing Waves and Geometrical Optics calculations.

    OpenAIRE

    Reinhardt Falk; Nowak Stanislaw H.; Beckhoff Burkhard; Dousse Jean-Claude; Schoengen Max

    2014-01-01

    Grazing incidence X-ray fluorescence spectra of nano-scaled periodic line structures were recorded at the four crystal monochromator beamline in the laboratory of the Physikalisch-Technische Bundesanstalt at the synchrotron radiation facility BESSY II. For different tilt angles between the lines and the plane of incidence of the monochromatic synchrotron radiation, spectral features are observed which can be understood and explained with calculations of the emerging X-ray standing wave (XSW) ...

  7. [Judging method of individual age and age structure of Stellera chamaejasme population in degraded steppe].

    Science.gov (United States)

    Xing, Fu; Gou, Jixun; Wei, Chunyan

    2004-11-01

    Based on the minute observation of branches morphology of root-crown of Stellera chamaejasme in Cleistogenes squarosa community and its growth characteristics, this paper studied the age structure of S. chamaejasme population, and an individual age judging method "the times of quasi-dichotomous branching plus two" was put forward for the first time. Remnant stubbles, branch trace, and annular trace on the root crown were regarded as important morphological features, and used to confirm the times of quasi-dichotomous branching. The results showed that the oldest individuals at three grazing succession stages (i.e., heavy grazing, over grazing and extreme grazing) were 15, 16 and 19 years old, respectively. Among all age classes, the numbers of eight years old individuals were the largest, and the age ratio was 18.71%, 24.20% and 19.06%, respectively, at the different succession stages. There were no one- and two-year old individuals at heavy grazing stage, and no one-year old individuals at the other two grazing stages. The age structures of the populations were "early declining types", and the survival curves were similar to protuberant type or Deevey I type. The numbers of old age individuals (thirteen years old and more) at the three succession stages accounted for 4.83%, 2.84% and 14.02%, respectively. The age structure of the population tended to aging with the increase of grazing intensity.

  8. Aging effects on regional brain structural changes in schizophrenia.

    Science.gov (United States)

    Nenadić, Igor; Sauer, Heinrich; Smesny, Stefan; Gaser, Christian

    2012-06-01

    Although mostly conceptualized as a neurodevelopmental disorder, there is an increasing interest in progressive changes of cognitive deficits and brain structure and function in schizophrenia across the life span. In this study, we investigated age-related changes in regional gray matter using voxel-based morphometry in a sample of 99 patients (age range 18-65 years) with Diagnostic and Statistical Manual of Mental Disorders-IV schizophrenia and 113 healthy controls (age range 19-59 years) using a cross-sectional design. We found steeper age-related decline in gray matter in patients in a cluster comprising the left superior temporal cortex and adjacent inferior parietal lobule. We then divided the schizophrenia sample in 3 subgroups based on a 3-factor model of psychopathology ratings. Age-related changes were markedly different in each of the 3 subgroups (compared with healthy controls). While patients with predominantly paranoid symptoms showed stronger age-related progression in the left superior temporal cortex and right inferior frontal gyrus, those of the disorganized subgroup had stronger gray matter loss in the left lateral cerebellum, while the predominantly negative subgroup showed minor effects in the left superior temporal gyrus. Our findings show that differences in brain structural changes associated with aging diverge between schizophrenia patients and healthy subjects and that different subgroups within a patient sample might be at higher risk of age-related regional gray matter loss.

  9. Consistent definition and application of Reineke's Stand Density Index in silviculture and stand projection

    Science.gov (United States)

    John D. Shaw; James N. Long

    2010-01-01

    Reineke’s Stand Density Index (SDI) has been available to silviculturists for over 75 years, but application of this stand metric has been inconsistent. Originally described as a measurement of relative density in single-species, even-aged stands, it has since been generalized for use in uneven-aged stands and mixed-species stands. However, methods used to establish...

  10. Diffusion Tensor Tractography Reveals Disrupted Structural Connectivity during Brain Aging

    Science.gov (United States)

    Lin, Lan; Tian, Miao; Wang, Qi; Wu, Shuicai

    2017-10-01

    Brain aging is one of the most crucial biological processes that entail many physical, biological, chemical, and psychological changes, and also a major risk factor for most common neurodegenerative diseases. To improve the quality of life for the elderly, it is important to understand how the brain is changed during the normal aging process. We compared diffusion tensor imaging (DTI)-based brain networks in a cohort of 75 healthy old subjects by using graph theory metrics to describe the anatomical networks and connectivity patterns, and network-based statistic (NBS) analysis was used to identify pairs of regions with altered structural connectivity. The NBS analysis revealed a significant network comprising nine distinct fiber bundles linking 10 different brain regions showed altered white matter structures in young-old group compare with middle-aged group (p < .05, family-wise error-corrected). Our results might guide future studies and help to gain a better understanding of brain aging.

  11. Scope and selection of structures subject to aging management review

    International Nuclear Information System (INIS)

    Mendoza, G.; Diaz, A.; Viais, J.; Carmona, M.; Santander, L.

    2014-10-01

    The purpose of this work is to determine the structures included within the scope of license renewal based on the performance of the functions and select those intended for aging management review; one purpose is to show the methodology used to establish the structure and structural components that are subject to a review of aging management, within the framework of license renewal rule. This is through the application of different types of structures and structural components related and unrelated to safety located in the rooms of the reactor building where there are components of the reactor core isolation cooling system (Rcic), these structures are poured concrete, concrete block, structural steel, shielding walls, attached metal, pile foundations, etc.; other non- security related , such as: 1) inherent characteristics not related to security that protect the equipment related to the safety of the missiles, that is, walls, low walls, dikes, doors, etc., which also provide flood barriers to structures, systems and components related to safety, 2 ) whipping restrictions on non- security, shields mitigation jet, vent panels , etc. that are designed and installed to protect equipment related with the safety of the effects of a broken line of high energy. Only rooms where there are components of the Rcic 68 structures within the scope were identified. (Author)

  12. Red alder-conifer stands in Alaska: An example of mixed species management to enhance structural and biological complexity

    Science.gov (United States)

    Robert Deal; Ewa Orlikowska; David D’Amore; Paul Hennon

    2017-01-01

    There is worldwide interest in managing forests to improve biodiversity, enhance ecosystem services and assure long-term sustainability of forest resources. An increasingly important goal of forest management is to increase stand diversity and improve wildlife and aquatic habitat. Well-planned silvicultural systems containing a mixture of broadleaf-conifer species have...

  13. Spatial structure of standing wave electromagnetic fields at the lower harmonics of the ionospheric Alfvén resonator

    Czech Academy of Sciences Publication Activity Database

    Prikner, Karel; Feygin, F. Z.; Raita, T.

    2014-01-01

    Roč. 58, č. 2 (2014), s. 326-337 ISSN 0039-3169 Grant - others:European Commission(XE) HPRI 200100132 Institutional research plan: CEZ:AV0Z30120515 Keywords : ionospheric Alfvén resonator * full-wave numerical simulation * EISCAT measurements * standing wave oscillations Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.806, year: 2014

  14. Ageing evaluation model of nuclear reactors structural elements

    International Nuclear Information System (INIS)

    Ziliukas, A.; Jutas, A.; Leisis, V.

    2002-01-01

    In this article the estimation of non-failure probability by random faults on the structural elements of nuclear reactors is presented. Ageing is certainly a significant factor in determining the limits of nuclear plant lifetime or life extensions. Usually the non failure probability rates failure intensity, which is characteristic for structural elements ageing in nuclear reactors. In practice the reliability is increased incorrectly because not all failures are fixed and cumulated. Therefore, the methodology with using the fine parameter of the failures flow is described. The comparison of non failure probability and failures flow is carried out. The calculation of these parameters in the practical example is shown too. (author)

  15. The structure of spruce-fir tree stands mortality under impact of the Middle Ural copper smelter emissions

    Directory of Open Access Journals (Sweden)

    I. E. Bergman

    2015-04-01

    Full Text Available The influence of industrial pollution on mortality values (dead fallen wood and dead standing trees and its distribution by degrees of decomposition were investigated in spruce-fir forest stands in the vicinity of the Middle Ural copper smelter (the city of Revda, Sverdlovsk region. The total mortality and mortality in each size category did not depend on the distance to the source of pollution. At the same time, the amount of dead fallen wood was significantly greater (1.9 times in the polluted area (2 and 4 km from the smelter as compared with the background territory (30 km from the smelter. Mortality proportion out of the total number of the trees (both live and dead did not differ significantly between the sites, although this parameter tended to increase nearer the smelter. The distribution of mortality by size categories revealed significant differences between background territory and site with average level of contamination, as well as background territory and highly contaminated site. Observed differences are associated with an increased proportion of lesser mortality near the smelter (by 15 % and 12 % as compared with areas of background and middle levels of contamination, respectively, as well as because of double-declining of medium- and large-sized mortality near the smelter. The distribution of the living tree stands by size categories also has a connection with level of contamination. The average diameters of the living tree stand and the elements of coarse woody debris (dead fallen wood and dead standing trees do not differ significantly between sites with different levels of contamination. For the small-sized dead fallen wood, the proportion of weakly decomposed stems increased with the level of pollution, while proportion of strongly decomposed stems decreased. The distribution of medium- and large-sized dead fallen wood on the stages of decomposition does not vary between sites with different levels of pollution.

  16. Mind-Reading Ability and Structural Connectivity Changes in Aging.

    Science.gov (United States)

    Cabinio, Monia; Rossetto, Federica; Blasi, Valeria; Savazzi, Federica; Castelli, Ilaria; Massaro, Davide; Valle, Annalisa; Nemni, Raffaello; Clerici, Mario; Marchetti, Antonella; Baglio, Francesca

    2015-01-01

    The Mind-Reading ability through the eyes is an important component of the affective Theory of Mind (ToM), which allows people to infer the other's mental state from the eye gaze. The aim of the present study was to investigate to which extent age-associated structural brain changes impact this ability and to determine if this association is related to executive functions in elderly subjects. For this purpose, Magnetic Resonance Imaging was used to determine both gray matter and white matter (WM) areas associated with aging. The resulting areas have been included in a subsequent correlation analysis to detect the brain regions whose structure was associated with the Mind-Reading ability through the eyes, assessed with the Italian version of the "Reading the Mind in the Eyes" (RME) test, in a sample of 36 healthy subjects ranging from 24 to 79 years of age. The analysis resulted in three important findings: (1) the performance to the RME test is relatively stable across the decades 20-70 (despite a slight decrease of this ability with aging) and independent from executive functions; (2) structural brain imaging demonstrated the involvement of a great number of cortical ToM areas for the execution of the RME test: the bilateral precentral gyrus, the bilateral posterior insula, the left superior temporal gyrus and the left inferior frontal gyrus, which also showed a significant volume decrease with age; (3) an age and task-related decline in WM connectivity on left fronto-temporal portion of the brain. Our results confirm the age-related structural modifications of the brain and show that these changes have an influence on the Mind-Reading ability through the eyes.

  17. Mind-Reading ability and structural connectivity changes in aging

    Directory of Open Access Journals (Sweden)

    Monia eCabinio

    2015-11-01

    Full Text Available The Mind-Reading ability through the eyes is an important component of the affective Theory of Mind (ToM, which allows people to infer the other’s mental state from the eye gaze. The aim of the present study was to investigate to which extent age-associated structural brain changes impact this ability and to determine if this association is related to executive functions in elderly subjects. For this purpose, Magnetic Resonance Imaging was used to determine both gray matter and white matter areas associated with aging. The resulting areas have been included in a subsequent correlation analysis to detect the brain regions whose structure was associated with the Mind-Reading ability through the eyes, assessed with the Italian version of the Reading the Mind in the Eyes (RME test, in a sample of 36 healthy subjects ranging from 24 to 79 years of age. The analysis resulted in three important findings: 1 the performance to the RME test is relatively stable across the decades 20-70 (despite a slight decrease of this ability with aging and independent from executive functions; 2 structural brain imaging demonstrated the involvement of a great number of cortical ToM areas for the execution of the RME test: the bilateral precentral gyrus, the bilateral posterior insula, the left superior temporal gyrus and the left inferior frontal gyrus, which also showed a significant volume decrease with age; 3 an age and task-related decline in white matter connectivity on left fronto-temporal portion of the brain. Our results confirm the age-related structural modifications of the brain and show that these changes have an influence on the Mind-Reading ability through the eyes.

  18. Visitor preferences of thinning practice in young even-aged stands of pedunculate oak (Quercus robur L.)

    DEFF Research Database (Denmark)

    Petucco, Claudio; Jensen, Frank Søndergaard; Meilby, Henrik

    2018-01-01

    This study compared visitor preferences of forestry professionals across six European countries (Sweden, Denmark, Great Britain, Austria, Romania and Portugal) using a questionnaire survey. The 598 interviewees were asked to rank photographs depicting recently thinned experimental plots in a 13......, Austrian and Romanian respondents generally favoured thinned, but dense stands, whereas Danish and British respondents preferred very heavily thinned stands. Swedish respondents preferred open stands resulting from extremely heavy thinning. Photographs taken along rows were favoured to photographs across...

  19. MRI assessment of whole-brain structural changes in aging.

    Science.gov (United States)

    Guo, Hui; Siu, William; D'Arcy, Ryan Cn; Black, Sandra E; Grajauskas, Lukas A; Singh, Sonia; Zhang, Yunting; Rockwood, Kenneth; Song, Xiaowei

    2017-01-01

    One of the central features of brain aging is the accumulation of multiple age-related structural changes, which occur heterogeneously in individuals and can have immediate or potential clinical consequences. Each of these deficits can coexist and interact, producing both independent and additive impacts on brain health. Many of the changes can be visualized using MRI. To collectively assess whole-brain structural changes, the MRI-based Brain Atrophy and Lesion Index (BALI) has been developed. In this study, we validate this whole-brain health assessment approach using several clinical MRI examinations. Data came from three independent studies: the Alzheimer's Disease Neuroimaging Initiative Phase II (n=950; women =47.9%; age =72.7±7.4 years); the National Alzheimer's Coordinating Center (n=722; women =55.1%; age =72.7±9.9 years); and the Tianjin Medical University General Hospital Research database on older adults (n=170; women =60.0%; age =62.9±9.3 years). The 3.0-Tesla MRI scans were evaluated using the BALI rating scheme on the basis of T1-weighted (T1WI), T2-weighted (T2WI), T2-weighted fluid-attenuated inversion recovery (T2-FLAIR), and T2*-weighted gradient-recalled echo (T2*GRE) images. Atrophy and lesion changes were commonly seen in each MRI test. The BALI scores based on different sequences were highly correlated (Spearman r 2 >0.69; P age ( r 2 >0.29; P 26.48, P aging and dementia-related decline of structural brain health. Inclusion of additional MRI tests increased lesion differentiation. Further research is to integrate MRI tests for a clinical tool to aid the diagnosis and intervention of brain aging.

  20. Structural approach to the aging of phosphylated cholinesterases.

    Science.gov (United States)

    Masson, Patrick; Nachon, Florian; Lockridge, Oksana

    2010-09-06

    Phosphylated cholinesterases (ChE) can undergo a side reaction that progressively decreases their reactivatability. This process, termed "aging", results from dealkylation of the adduct and depends on the structure of the organophosphyl moiety. Aged ChEs are resistant to reactivation by oximes. Owing to the toxicological importance of OPs, the molecular mechanism of aging has been the subject of research for decades. It was not clear whether aging involves the same bond breakage regardless the type of OP or is a scission of P-O-C bonds (P-O or O-C) in phosphates/phosphonates, P-N-C bonds in phosphoramidates, and P-S-C bonds in phosphonothionates. It was assumed that the resulting negatively charged atom on phosphorus of the aged adduct prevented nucleophilic attack by oximates, but studies on negatively charged model molecules do not support this hypothesis. Decrease in conformational flexibility of aged enzymes may contribute to their non-reactivatability by preventing proper adjustment of reactivators in the active site gorge. MALDI-TOF mass spectrometry of phosphylated human butyrylcholinesterase (hBChE) in water and in (18)O-water provided evidence that aging results from O-C breakage, i.e. O-dealkylation. In contrast, the isomalathion-BChE conjugate ages mostly through P-S bond cleavage, but a minor product results from O-C and/or S-C breakage. The crystal structures of hBChE and hAChE inhibited by tabun showed that aging of tabun-ChE conjugates results from O-dealkylation. However, depending on the nature of O-alkyl and N-alkyl chains, aging of BChE inhibited by other phosphoramidates results either from O-C breakage or deamination, i.e. P-N breakage. It was found that dealkylation of branched alkoxy involves a transient carbocation. Dealkylation of OP-ChE conjugates is accompanied by enzyme conformational changes. Urea, organic solvent, heat and pressure denaturation of human BChE showed that the conformational stability of aged OP-BChE conjugates is

  1. Thalamic structures and associated cognitive functions: Relations with age and aging

    Science.gov (United States)

    Fama, Rosemary; Sullivan, Edith V.

    2015-01-01

    The thalamus, with its cortical, subcortical, and cerebellar connections, is a critical node in networks supporting cognitive functions known to decline in normal aging, including component processes of memory and executive functions of attention and information processing. The macrostructure, microstructure, and neural connectivity of the thalamus changes across the adult lifespan. Structural and functional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) have demonstrated, regional thalamic volume shrinkage and microstructural degradation, with anterior regions generally more compromised than posterior regions. The integrity of selective thalamic nuclei and projections decline with advancing age, particularly those in thalamofrontal, thalamoparietal, and thalamolimbic networks. This review presents studies that assess the relations between age and aging and the structure, function, and connectivity of the thalamus and associated neural networks and focuses on their relations with processes of attention, speed of information processing, and working and episodic memory. PMID:25862940

  2. Structural brain changes in aging: courses, causes and cognitive consequences.

    Science.gov (United States)

    Fjell, Anders M; Walhovd, Kristine B

    2010-01-01

    The structure of the brain is constantly changing from birth throughout the lifetime, meaning that normal aging, free from dementia, is associated with structural brain changes. This paper reviews recent evidence from magnetic resonance imaging (MRI) studies about age-related changes in the brain. The main conclusions are that (1) the brain shrinks in volume and the ventricular system expands in healthy aging. However, the pattern of changes is highly heterogeneous, with the largest changes seen in the frontal and temporal cortex, and in the putamen, thalamus, and accumbens. With modern approaches to analysis of MRI data, changes in cortical thickness and subcortical volume can be tracked over periods as short as one year, with annual reductions of between 0.5% and 1.0% in most brain areas. (2) The volumetric brain reductions in healthy aging are likely only to a minor extent related to neuronal loss. Rather, shrinkage of neurons, reductions of synaptic spines, and lower numbers of synapses probably account for the reductions in grey matter. In addition, the length of myelinated axons is greatly reduced, up to almost 50%. (3) Reductions in specific cognitive abilities--for instance processing speed, executive functions, and episodic memory--are seen in healthy aging. Such reductions are to a substantial degree mediated by neuroanatomical changes, meaning that between 25% and 100% of the differences between young and old participants in selected cognitive functions can be explained by group differences in structural brain characteristics.

  3. Structural Model of Motor Readiness of Young Gymnasts Aged 6-8

    Directory of Open Access Journals (Sweden)

    О. Худолій

    2015-12-01

    Full Text Available The purpose of the research is to determine the factor structure of the motor readiness of young gymnasts aged 6—8. Research methods. To achieve the tasks set, the research relies on theoretical and empirical methods used: analysis and collation of scientific and methodological literature; modeling, pedagogical observations and experiment, factor analysis. The research recorded the following indicators: the number of repetitions required to teach the exercises; score for the unit-directional movement coordination exercise (test 3; score for the differently directed movement coordination exercise (test 4; error in spatial precision of hand movements (test 9; error in spatial accuracy of leg movements (test 14; error in time accuracy of executing the sitting-to-lying event (test 17; error in time accuracy of five jumps on marks in 5 seconds (test 18; error in evaluation of muscular efforts with visual control (test 24; error in evaluation of muscular efforts without visual control (test 25; vestibular stability, error (test 28; wrist strength; back strength; standing long jump. The participants in the study were 40 gymnasts aged 6-7 and 32 gymnasts aged 7-8. Research results. The young gymnasts aged 6-8 have quite distinct elements that determine the development of their sports skills, namely: learning ability, motor experience, coordination complexity of exercises; relationship between the strength development and the ability to differentiate muscular efforts; movement coordination, movement control and vestibular apparatus stability.

  4. Economic effects of full corrosion surveys for aging concrete structures

    NARCIS (Netherlands)

    Polder, R.B.; Peelen, W.H.A.; Raupach, M.; Reichling, K.

    2013-01-01

    This paper investigates the economic effects of full corrosion surveys of concrete structures. The background is that the existing concrete infrastructure is aging, while being exposed to aggressive influences, which increases the occurrence of corrosion and related concrete damage over time. The

  5. Capturing the age and spatial structures of migration

    NARCIS (Netherlands)

    Rogers, A; Raymer, J; Willekens, F

    In this paper we model the structures found in the level (generation) and allocation (distribution) components of age-specific and origin-destination-specific migration flows. For the examples, we examine the regional migration patterns in the USA for four periods: 1955-60, 1965-70, 1975-80, and

  6. Reconstructed forest age structure in Europe 1950-2010

    NARCIS (Netherlands)

    Vilén, T.; Gunia, K.; Verkerk, P.J.; Seidl, R.; Schelhaas, M.J.; Lindner, M.; Bellassen, V.

    2012-01-01

    Forest age structure is an important factor for understanding the history of forests, their current functioning and their future development. It is, for instance, crucial information to be able to assess sustainable harvesting potentials. Furthermore, since the development of growing stock and

  7. Changes in Age Structure and Rural Community Growth.

    Science.gov (United States)

    McGranahan, David A.

    1985-01-01

    Whatever migration patterns evolve, changes in the age structure mean that rural communities in general can expect fairly stable elementary school population, reduced high school population, slower growth in new business and employment, and continued increase in the elderly population. (JHZ)

  8. Structura unor arborete exploatabile din regiunea de munte [Structure of some exploitable forest stands from the mountainous area

    Directory of Open Access Journals (Sweden)

    Prodan M

    2005-07-01

    Full Text Available The paper presents one of the first scientific works of the prof. dr. dr. h. c. Michail Prodan, published in the Romanian forestry journal “Viaţa forestieră” (“The forestry life”, in 1940, before starting his prodigious career in Germany. The used data - as in some of his next papers - are from the forest inventories performed in the forest districts of the Romanian Orthodox Religion Found from Bucovina (Eastern Carpathians with the occasion of the forest management plans renewal. Some details: (natural, almost primeval forest stands between 100-200 years, pure or mixed from species Norway spruce, Silver fir, Beech, in total 200,000 records. The analyzed stands were grouped based on Feistmantel class fertility and the basic analysis were the distribution of tree diameters, for these tree species and fertility classes. were computed the theoretical distribution for the diameter classes, using the Charlier approach

  9. Estimating density dependence from time series of population age structure.

    Science.gov (United States)

    Lande, Russell; Engen, Steinar; Saether, Bernt-Erik; Coulson, Tim

    2006-07-01

    Population fluctuations are caused by demographic and environmental stochasticity, time lags due to life history, and density dependence. We model a general life history allowing density dependence within and among age or stage classes in a population undergoing small or moderate fluctuations around a stable equilibrium. We develop a method for estimating the overall strength of density dependence measured by the rate of return toward equilibrium, and we also consider a simplified population description and forecasting using the density-dependent reproductive value. This generality comes at the cost of requiring a time series of the population age or stage structure instead of a univariate time series of adult or total population size. The method is illustrated by analyzing the dynamics of a fully censused population of red deer (Cervus elaphus) based on annual fluctuations of age structure through 21 years.

  10. An age-structured extension to the vectorial capacity model.

    Directory of Open Access Journals (Sweden)

    Vasiliy N Novoseltsev

    Full Text Available Vectorial capacity and the basic reproductive number (R(0 have been instrumental in structuring thinking about vector-borne pathogen transmission and how best to prevent the diseases they cause. One of the more important simplifying assumptions of these models is age-independent vector mortality. A growing body of evidence indicates that insect vectors exhibit age-dependent mortality, which can have strong and varied affects on pathogen transmission dynamics and strategies for disease prevention.Based on survival analysis we derived new equations for vectorial capacity and R(0 that are valid for any pattern of age-dependent (or age-independent vector mortality and explore the behavior of the models across various mortality patterns. The framework we present (1 lays the groundwork for an extension and refinement of the vectorial capacity paradigm by introducing an age-structured extension to the model, (2 encourages further research on the actuarial dynamics of vectors in particular and the relationship of vector mortality to pathogen transmission in general, and (3 provides a detailed quantitative basis for understanding the relative impact of reductions in vector longevity compared to other vector-borne disease prevention strategies.Accounting for age-dependent vector mortality in estimates of vectorial capacity and R(0 was most important when (1 vector densities are relatively low and the pattern of mortality can determine whether pathogen transmission will persist; i.e., determines whether R(0 is above or below 1, (2 vector population growth rate is relatively low and there are complex interactions between birth and death that differ fundamentally from birth-death relationships with age-independent mortality, and (3 the vector exhibits complex patterns of age-dependent mortality and R(0 ∼ 1. A limiting factor in the construction and evaluation of new age-dependent mortality models is the paucity of data characterizing vector mortality

  11. Structural and Functional Changes in Human Kidneys with Healthy Aging.

    Science.gov (United States)

    Hommos, Musab S; Glassock, Richard J; Rule, Andrew D

    2017-10-01

    Aging is associated with significant changes in structure and function of the kidney, even in the absence of age-related comorbidities. On the macrostructural level, kidney cortical volume decreases, surface roughness increases, and the number and size of simple renal cysts increase with age. On the microstructural level, the histologic signs of nephrosclerosis (arteriosclerosis/arteriolosclerosis, global glomerulosclerosis, interstitial fibrosis, and tubular atrophy) all increase with age. The decline of nephron number is accompanied by a comparable reduction in measured whole-kidney GFR. However, single-nephron GFR remains relatively constant with healthy aging as does glomerular volume. Only when glomerulosclerosis and arteriosclerosis exceed that expected for age is there an increase in single-nephron GFR. In the absence of albuminuria, age-related reduction in GFR with the corresponding increase in CKD (defined by an eGFRage-standardized mortality risk or ESRD. These findings raise the question of whether disease labeling of an age-related decline in GFR is appropriate. These findings also emphasize the need for a different management approach for many elderly individuals considered to have CKD by current criteria. Copyright © 2017 by the American Society of Nephrology.

  12. Selfing and sibship structure in a two-cohort stand of maritime pine (Pinus pinaster Ait.) using nuclear SSR markers

    OpenAIRE

    González-Martínez, Santiago; Gerber, Sophie; Cervera, María-Teresa; Martínez-Zapater, José-Miguel; Alía, Ricardo; Gil, Luis

    2003-01-01

    International audience; The genetic relatedness between pairs of trees was analyzed in an adult stand of maritime pine with abundant advanced natural regeneration using three highly polymorphic microsatellites ($EP$ $>$ 90%). Only five possible self-pollinated offspring were found, thus meaning a maximum selfing rate based on dispersed progeny of 3.8%. Likelihood ratios were used to detect sib relationships in both mature trees and natural regeneration. The percentage of half-sib and full-sib...

  13. Structural and Functional Changes With the Aging Kidney.

    Science.gov (United States)

    Denic, Aleksandar; Glassock, Richard J; Rule, Andrew D

    2016-01-01

    Senescence or normal physiologic aging portrays the expected age-related changes in the kidney as compared to a disease that occurs in some but not all individuals. The microanatomical structural changes of the kidney with older age include a decreased number of functional glomeruli from an increased prevalence of nephrosclerosis (arteriosclerosis, glomerulosclerosis, and tubular atrophy with interstitial fibrosis), and to some extent, compensatory hypertrophy of remaining nephrons. Among the macroanatomical structural changes, older age associates with smaller cortical volume, larger medullary volume until middle age, and larger and more numerous kidney cysts. Among carefully screened healthy kidney donors, glomerular filtration rate (GFR) declines at a rate of 6.3 mL/min/1.73 m(2) per decade. There is reason to be concerned that the elderly are being misdiagnosed with CKD. Besides this expected kidney function decline, the lowest risk of mortality is at a GFR of ≥75 mL/min/1.73 m(2) for age kidney functional reserve when they do actually develop CKD, and they are at higher risk for acute kidney injury. Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

  14. Aging management of containment structures in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

    1994-01-01

    Research is being conducted by Oak Ridge National Laboratory under U.S. Nuclear Regulatory Commission sponsorship to address aging management of nuclear power plant containment and other safety-related structures. Documentation is being prepared to provide the US-NRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Accomplishments include development of a Structural Materials Information Center containing data and information on the time variation of 144 material properties under the influence of pertinent environmental stressors or aging factors, evaluation of models for potential concrete containment degradation factors, development of a procedure to identify critical structures and degradation factors important to aging management, evaluations of nondestructive evaluation techniques, assessments of European and North American repair practices for concrete, review of parameters affecting corrosion of metals embedded in concrete, and development of methodologies for making current condition assessments and service life predictions of new or existing reinforced concrete structures in nuclear power plants. (author). 29 refs., 2 figs

  15. Aging management of containment structures in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.; Graves, H.L. III; Norris, W.E.

    1996-01-01

    Research is being conducted by Oak Ridge National Laboratory under US nuclear regulatory commission (USNRC) sponsorship to address aging management of nuclear power plant containment and other safety-related structures. Documentation is being prepared to provide the USNRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Accomplishments include development of a structural materials information center containing data and information on the time variation of 144 material properties under the influence of pertinent environmental stressors or aging factors, evaluation of models for potential concrete containment degradation factors, development of a procedure to identify critical structures and degradation factors important to aging management, evaluations of non-destructive evaluation techniques, assessments of European and North American repair practices for concrete, review of parameters affecting corrosion of metals embedded in concrete, and development of methodologies for making current condition assessments and service life predictions of new or existing reinforced concrete structures in nuclear power plants. (orig.)

  16. Solution and crystal structure of BA42, a protein from the Antarctic bacterium Bizionia argentinensis comprised of a stand-alone TPM domain.

    Science.gov (United States)

    Aran, Martin; Smal, Clara; Pellizza, Leonardo; Gallo, Mariana; Otero, Lisandro H; Klinke, Sebastián; Goldbaum, Fernando A; Ithurralde, Esteban R; Bercovich, Andrés; Mac Cormack, Walter P; Turjanski, Adrián G; Cicero, Daniel O

    2014-11-01

    The structure of the BA42 protein belonging to the Antarctic flavobacterium Bizionia argentinensis was determined by nuclear magnetic resonance and X-ray crystallography. This is the first structure of a member of the PF04536 family comprised of a stand-alone TPM domain. The structure reveals a new topological variant of the four β-strands constituting the central β-sheet of the αβα architecture and a double metal binding site stabilizing a pair of crossing loops, not observed in previous structures of proteins belonging to this family. BA42 shows differences in structure and dynamics in the presence or absence of bound metals. The affinity for divalent metal ions is close to that observed in proteins that modulate their activity as a function of metal concentration, anticipating a possible role for BA42. © 2014 Wiley Periodicals, Inc.

  17. Super-resolution x-ray imaging using interaction between periodic structure of object and standing wave generated with total-reflection-mirror interferometer

    Science.gov (United States)

    Suzuki, Yoshio

    2017-06-01

    A super-resolution method in projection-type x-ray imaging is proposed. In this method, interference fringes generated with a two-beam interferometer are used for detecting the fine periodic structure of the object. When the sample has a fine periodic structure, the structure can be detected as interaction between the periodic structure of object and the standing wave formed by the two-beam interferometer. Feasibility studies have been carried out using wavefront-division interferometer with total-reflection-mirror optics and a resolution test chart as a model sample. The fine structures with a period up to 100 nm were detected as modulation of transmitting x-ray intensity at 11.5 keV.

  18. Early-age monitoring of cement structures using FBG sensors

    Science.gov (United States)

    Wang, Chuan; Zhou, Zhi; Zhang, Zhichun; Ou, Jinping

    2006-03-01

    With more and more broad applications of the cement-based structures such as neat cement paste, cement mortar and concrete in civil engineering, people hope to find out what their performances should like. The in-service performances of cement-based structures are highly affected by their hardening process during the early-age. But it is still a big problem for traditional sensors to be used to monitor the early curing of cement-based structures due to such disadvantages as difficulties to install sensors inside the concrete, limited measuring points, poor durability and interference of electromagnetic wave and so on. In this paper, according to the sensing properties of the Fiber Bragg Grating sensors and self-characters of the cement-based structures, we have successfully finished measuring and monitoring the early-age inner-strain and temperature changes of the neat cement paste, concrete with and without restrictions, mass concrete structures and negative concrete, respectively. Three types of FBG-based sensors have been developed to monitor the cement-based structures. Besides, the installation techniques and the embedding requirements of FBG sensors in cement-based structures are also discussed. Moreover, such kind of technique has been used in practical structure, 3rd Nanjing Yangtze Bridge, and the results show that FBG sensors are well proper for measuring and monitoring the temperature and strain changes including self-shrinkage, dry shrinkage, plastic shrinkage, temperature expansion, frost heaving and so on inside different cement-based structures. This technique provides us a new useful measuring method on early curing monitoring of cement-based structures and greater understanding of details of their hardening process.

  19. Soil Respiration at Different Stand Ages (5, 10, and 20/30 Years) in Coniferous (Pinus tabulaeformis Carrière) and Deciduous (Populus davidiana Dode) Plantations in a Sandstorm Source Area

    DEFF Research Database (Denmark)

    Zhao, Xin; Li, Fadong; Zhang, Wanjun

    2016-01-01

    Understanding the effects of stand age and forest type on soil respiration is crucial for predicting the potential of soil carbon sequestration. Thus far, however, there is no consensus regarding the variations in soil respiration caused by stand age and forest type. This study investigated soil...... that mean soil respiration in the 5-, 10-, and 20/30-year-old plantations was 3.37, 3.17, and 2.99 μmol·m−2·s−1 for P. tabulaeformis and 2.92, 2.85, and 2.57 μmol·m−2·s−1 for P. davidiana, respectively. Soil respiration decreased with stand age for both species. There was no significant difference in soil...... respiration between the two plantation species at ages 5 and 10 years (p > 0.05). Temperature sensitivity of soil respiration, which ranged from 1.85–1.99 in P. tabulaeformis and 2.20–2.46 in P. davidiana plantations, was found to increase with stand age. Temperature sensitivity was also significantly higher...

  20. Aging of concrete containment structures in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.; Mori, Yasuhiro; Arndt, E.G.

    1992-01-01

    Concrete structures play a vital role in the safe operation of all light-water reactor plants in the US Pertinent concrete structures are described in terms of their importance design, considerations, and materials of construction. Degradation factors which can potentially impact the ability of these structures to meet their functional and performance requirements are identified. Current inservice inspection requirements for concrete containments are summarized. A review of the performance history of the concrete components in nuclear power plants is provided. A summary is presented. A summary is presented of the Structural Aging (SAG) Program being conducted at the Oak Ridge National Laboratory for the US Nuclear Regulatory Commission. The SAG Program is addressing the aging management of safety-related concrete structures in nuclear power plants for the purpose of providing improved bases for their continued service. The program consists of a management task and three technical tasks: materials property data base, structural component assessment/repair technologies, and quantitiative methodology for continued service conditions. Objectives and a summary of accomplishments under each of these tasks are presented

  1. Canadian Provincial Population Growth: Fertility, Migration, and Age Structure Effects

    Directory of Open Access Journals (Sweden)

    Edmonston, Barry

    2009-01-01

    Full Text Available AbstractThe effect of changes in rates of mortality, fertility, and migration depend not only on the age specific patterns and levels of these rates, but on the age structure of the population. In orderto remove the influences of the age structure and concentrate on the impact of the demographic rates themselves, a common practice is to analyze the influences of the rates for a standard age structure. This paper adapts the general approach of using a standard age structure to a stationary population equivalent (SPE model, and analyzes current population change, using the SPE model, for provinces of Canada. Below-replacement fertility levels are only partially offset by net immigration. The SPE model evidences the decrease in the eventual provincial populations brought about by the below replacement fertility. Out-migration for some provincesto other areas of Canada accentuates their eventual population decreases.RésuméLes effets des changements des taux de mortalité, fécondité, et de migration dépendent non seulement des modèles par âge et des niveaux de ces taux, mais aussi de la structure par âge de la population. Pour éliminer les influences de la structure par âge et se concentrer sur les effets des taux démographiques mêmes, une pratique courante est d’analyser les influences des taux par une structure par âge de norme. Cet article adapte l’approche générale de la structure parâge à un modèle de population stationnaire équivalente (PSE. Cet article analyse les changements de population, en utilisant le modèle de PSE, dans les provinces canadiennes. Le taux de fécondité inférieur au seuil de reproduction de la population n’est que légèrement compensé par l’immigration nette. Le modèle de PSE démontre le déclin des populations provinciales éventuelles causé par le taux de fécondité inférieur au seuil de reproduction de la population. Le taux d’émigration entre certaines provinces et reste du

  2. Implications of alternative field-sampling designs on Landsat-based mapping of stand age and carbon stocks in Oregon forests

    Science.gov (United States)

    Maureen V. Duane; Warren B. Cohen; John L. Campbell; Tara Hudiburg; David P. Turner; Dale. Weyermann

    2010-01-01

    Empirical models relating forest attributes to remotely sensed metrics are widespread in the literature and underpin many of our efforts to map forest structure across complex landscapes. In this study we compared empirical models relating Landsat reflectance to forest age across Oregon using two alternate sets of ground data: one from a large (n ~ 1500) systematic...

  3. Nonlinear dynamical structure of sway path during standing in patients with multiple sclerosis and in healthy controls is affected by changes in sensory input and cognitive load.

    Science.gov (United States)

    Negahban, Hossein; Sanjari, Mohammad Ali; Mofateh, Razieh; Parnianpour, Mohamad

    2013-10-11

    Although several studies have applied traditional linear measures to evaluate postural control of patients with multiple sclerosis (MS), little is known about the nonlinear dynamics of this patient group. In this study, recurrence quantification analysis (RQA), a well documented nonlinear method, was used to compare the nonlinear dynamical structure of postural sway in two groups consisting of MS patients (n=23) and healthy matched controls (n=23). The study focuses on three levels of postural difficulty consisting of (1) standing on a rigid surface (force platform) with eyes open, (2) standing on a rigid surface with eyes closed, and (3) standing on a foam surface with eyes closed. The two levels of cognitive difficulty measured, consisted of a single postural task and a dual postural-cognitive task. It was observed that as the postural conditions became more difficult, the center of pressure (COP) time series of both groups became less regular as recorded in lower recurrence rate, less complex in deterministic structure as reflected in lower RQA entropy, and less nonstationary as reflected in the recording of lower Trend. Moreover, as cognitive conditions became more difficult, COP time series became less regular (lower %Rec in the anteroposterior direction and lower %Det in both directions), less complex in deterministic structure (lower RQA Ent in the anteroposterior direction), and less nonstationary (lower trend in the anteroposterior direction). The analytical results of the research show that there is a similar dynamical structure for both the MS patients and the control group; however, the nonlinear behavior of both groups was different under various experimental conditions. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  4. A-1 Test Stand work

    Science.gov (United States)

    2010-01-01

    Employees at NASA's John C. Stennis Space Center work to maneuver a structural steam beam into place on the A-1 Test Stand on Jan. 13. The beam was one of several needed to form the thrust takeout structure that will support a new thrust measurement system being installed on the stand for future rocket engine testing. Once lifted onto the stand, the beams had to be hoisted into place through the center of the test stand, with only two inches of clearance on each side. The new thrust measurement system represents a state-of-the-art upgrade from the equipment installed more than 40 years ago when the test stand was first constructed.

  5. Dynamics of dense direct-seeded stands of southern pines

    Science.gov (United States)

    J.C.G. Goelz

    2006-01-01

    Direct seeding of southern pines is an effective method of artificial regeneration, producing extremely dense stands when survival exceeds expectations. Long-term studies of dense direct-seeded stands provide ideal data for exploring development of stands as they approach the limit of maximum stand density. I present data from seven studies with ages of stands ranging...

  6. Reoccupation of floodplains by rivers and its relation to the age structure of floodplain vegetation

    Science.gov (United States)

    Konrad, Christopher P.

    2012-01-01

    River channel dynamics over many decades provide a physical control on the age structure of floodplain vegetation as a river occupies and abandons locations. Floodplain reoccupation by a river, in particular, determines the interval of time during which vegetation can establish and mature. A general framework for analyzing floodplain reoccupation and a time series model are developed and applied to five alluvial rivers in the United States. Channel dynamics in these rivers demonstrate time-scale dependence with short-term oscillation in active channel area in response to floods and subsequent vegetation growth and progressive lateral movement that accounts for much of the cumulative area occupied by the rivers over decades. Rivers preferentially reoccupy locations recently abandoned causing a decreasing probability of reoccupation with time since abandonment. For a typical case, a river is 10 times more likely to reoccupy an area it abandoned in the past decade than it is to reoccupy an area it abandoned 30 yrs ago. The decreasing probability of reoccupation over time is consistent with observations of persistent stands of late seral stage floodplain forest. A power function provides a robust approach for estimating the cumulative area occupied by a river and the age structure of riparian forests resulting from a specific historical sequence of streamflow in comparison to either linear or exponential alternatives.

  7. Stand-alone XLIF

    DEFF Research Database (Denmark)

    Hansen, E. J.; Simony, A.; Hummel, Stefan

    2015-01-01

    and clinical/radiological results in 22 patients treated with XLIF procedure for DS or degenerative disc disease (DDD). Material and methods: 22 consecutive patients with DS underwent surgery with the XLIF stand-alone procedure, with follow-up of 24 months. Clinical outcome scores were collected. Complications......Introduction: Adult thoracolumbar degeneration is an increasing challenge in the aging population. With age the progressive degeneration of the discs leads to an asymmetric collapse and a thoracolumbar coronal plane deformity, a degenerative scoliosis (DS). Aim: To evaluate the complication rate......-year follow-up, with a 31.8% revision rate. Due to the high revision rate we recommend supplementary posterior instrumentation, to achieve a higher fusion rate. When considering XLIF-stand-alone procedure for DS or DDD without supplemental posterior instrumentation, only single-level disease should...

  8. Soil Respiration at Different Stand Ages (5, 10, and 20/30 Years in Coniferous (Pinus tabulaeformis Carrière and Deciduous (Populus davidiana Dode Plantations in a Sandstorm Source Area

    Directory of Open Access Journals (Sweden)

    Xin Zhao

    2016-07-01

    Full Text Available Understanding the effects of stand age and forest type on soil respiration is crucial for predicting the potential of soil carbon sequestration. Thus far, however, there is no consensus regarding the variations in soil respiration caused by stand age and forest type. This study investigated soil respiration and its temperature sensitivity at three stand ages (5, 10, and 20 or 30 years in two plantations of coniferous (Pinus tabulaeformis Carrière and deciduous (Populus davidiana Dode species using an automated chamber system in 2013 in the Beijing-Tianjin sandstorm source area. Results showed that mean soil respiration in the 5-, 10-, and 20/30-year-old plantations was 3.37, 3.17, and 2.99 μmol·m−2·s−1 for P. tabulaeformis and 2.92, 2.85, and 2.57 μmol·m−2·s−1 for P. davidiana, respectively. Soil respiration decreased with stand age for both species. There was no significant difference in soil respiration between the two plantation species at ages 5 and 10 years (p > 0.05. Temperature sensitivity of soil respiration, which ranged from 1.85–1.99 in P. tabulaeformis and 2.20–2.46 in P. davidiana plantations, was found to increase with stand age. Temperature sensitivity was also significantly higher in P. davidiana plantations and when the soil water content was below 12.8%. Temperature sensitivity incorporated a combined response of soil respiration to soil temperature, soil water content, soil organic carbon, and fine root biomass and, thus, provided an ecological metric for comparing forest carbon dynamics of these species.

  9. A singularly perturbed SIS model with age structure.

    Science.gov (United States)

    Banasiak, Jacek; Phongi, Eddy Kimba; Lachowicz, Mirosław

    2013-06-01

    We present a preliminary study of an SIS model with a basic age structure and we focus on a disease with quick turnover, such as influenza or common cold. In such a case the difference between the characteristic demographic and epidemiological times naturally introduces two time scales in the model which makes it singularly perturbed. Using the Tikhonov theorem we prove that for certain classes of initial conditions the nonlinear structured SIS model can be approximated with very good accuracy by lower dimensional linear models.

  10. Effects of a stand-alone web-based electronic screening and brief intervention targeting alcohol use in university students of legal drinking age: A randomized controlled trial.

    Science.gov (United States)

    Ganz, Thomas; Braun, Michael; Laging, Marion; Schermelleh-Engel, Karin; Michalak, Johannes; Heidenreich, Thomas

    2018-02-01

    Many intervention efforts targeting student drinking were developed to address US college students, which usually involves underage drinking. It remains unclear, if research evidence from these interventions is generalizable to university and college students of legal drinking age, e.g., in Europe. To evaluate the effectiveness of a translated and adapted version of the eCHECKUP TO GO, applied as stand-alone web-based electronic screening and brief intervention (e-SBI), in German university students at risk for hazardous drinking. A fully automated web-based two-arm parallel-group randomized controlled trial was conducted. Participants were randomized to an e-SBI or assessment-only (AO) condition. The current paper analyzed students with baseline AUDIT-C scores ≥3 for women and ≥4 for men (sample at baseline: e-SBI [n=514], AO [n=467]; 3-month follow-up: e-SBI [n=194], AO [n=231]; 6-month follow-up: e-SBI [n=146], AO [n=200]). The primary outcome was prior four weeks' alcohol consumption. Secondary outcomes were frequency of heavy drinking occasions, peak blood alcohol concentration, and number of alcohol-related problems. Mixed linear model analyses revealed significant interaction effects between groups and time points on the primary outcome after 3 and 6months. Compared to students in the AO condition, students in the e-SBI condition reported consuming 4.11 fewer standard drinks during the previous four weeks after 3months, and 4.78 fewer standard drinks after 6months. Mixed results were found on secondary outcomes. The results indicate that evidence on and knowledge of web-based e-SBIs based on US college student samples is transferable to German university students of legal drinking age. However, knowledge of what motivates students to complete programs under voluntary conditions, although rare, is needed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Structural developmental psychology and health promotion in the third age.

    Science.gov (United States)

    Bauger, Lars; Bongaardt, Rob

    2017-01-12

    In response to the ever-increasing longevity in Western societies, old age has been divided into two different periods, labelled the third and fourth age. Where the third age, with its onset at retirement, mostly involves positive aspects of growing old, the fourth age involves functional decline and increased morbidity. This article focuses on the entry to the third age and its potential for health promotion initiatives. Well-being is an important factor to emphasize in such health promotion, and this article views the lifestyle of third agers as essential for their well-being. The structural developmental theory of Robert Kegan delineates how a person's way of knowing develops throughout the life course. This theory is an untapped and salient perspective for health promotion initiatives in the third age. This article outlines Kegan's approach as a tool for developing psychologically spacious health promotion, and suggests future directions for research on the topic. © The Author 2017. Published by Oxford University Press.

  12. A data base for aging of structural materials

    International Nuclear Information System (INIS)

    Oland, C.B.; Naus, D.J.; Jerath, S.

    1993-01-01

    The U.S. Nuclear Regulatory Commission (USNRC) initiated a Structural Aging (SAG) Program at the Oak Ridge National Laboratory (ORNL). The objective of the program is to provide assistance in identifying potential structural safety issues and to establish acceptance criteria for use in nuclear power plant evaluations for continued service. One of the main parts of the program focuses on the development of a Structural Materials Information Center where long-term and environment-dependent material properties are being collected and assembled into a data base. This data base is presented in two complementary formats. The Structural Materials Handbook is an expandable, hard-copy reference document that contains the complete data base for each material. The Structural Materials Electronic Data Base is accessible using an IBM-compatible personal computer. This paper presents an overview of the Structural Materials Information Center and briefly describes the features of the handbook and the electronic data base. In addition, a proposed method for using the data base to establish current property values for materials in existing concrete structures and to estimate the future performance of these materials is also presented. (author)

  13. A data base for aging of structural materials

    International Nuclear Information System (INIS)

    Oland, C.B.; Naus, D.J.; Jerath, S.

    1993-01-01

    USNRC initiated a Structural Aging (SAG) Program ORNL. The objective of the program is to provide assistance in identifying potential structural safety issues and to establish acceptance criteria for use in nuclear power plant evaluations for continued service. One main part focuses on the development of a Structural Materials Information Center where long-term and environment-dependent material properties are being collected and assembled into a data base. This data base is presented in two complementary formats. The Structural Materials Handbook is an expandable, hard-copy reference document that contains the complete data base for each material. The Structural Materials Electronic Data Base is accessible using an IBM-compatible personal computer. This paper presents an overview of the Structural Materials Information Center and briefly describes the features of the handbook and the electronic data base. In addition, a proposed method for using the data base to establish current property values for materials in existing concrete structures and to estimate the future performance of these materials is also presented

  14. Computer Simulation of Sexual Selection on Age-Structured Populations

    Science.gov (United States)

    Martins, S. G. F.; Penna, T. J. P.

    Using computer simulations of a bit-string model for age-structured populations, we found that sexual selection of older males is advantageous, from an evolutionary point of view. These results are in opposition to a recent proposal of females choosing younger males. Our simulations are based on findings from recent studies of polygynous bird species. Since secondary sex characters are found mostly in males, we could make use of asexual populations that can be implemented in a fast and efficient way.

  15. Minority group status and healthful aging: social structure still matters.

    Science.gov (United States)

    Angel, Jacqueline L; Angel, Ronald J

    2006-07-01

    During the last 4 decades, a rapid increase has occurred in the number of survey-based and epidemiological studies of the health profiles of adults in general and of the causes of disparities between majority and minority Americans in particular. According to these studies, healthful aging consists of the absence of disease, or at least of the most serious preventable diseases and their consequences, and findings consistently reveal serious African American and Hispanic disadvantages in terms of healthful aging. We (1) briefly review conceptual and operational definitions of race and Hispanic ethnicity, (2) summarize how ethnicity-based differentials in health are related to social structures, and (3) emphasize the importance of attention to the economic, political, and institutional factors that perpetuate poverty and undermine healthful aging among certain groups.

  16. Ageing management of french NPP civil work structures

    Science.gov (United States)

    Gallitre, E.; Dauffer, D.

    2011-04-01

    This paper presents EDF practice about concrete structure ageing management, from the mechanisms analysis to the formal procedure which allows the French company to increase 900 MWe NPP lifetime until 40 years; it will also introduce its action plan for 60 years lifetime extension. This practice is based on a methodology which identifies every ageing mechanism; both plants feedback and state of the art are screened and conclusions are drawn up into an "ageing analysis data sheet". That leads at first to a collection of 57 data sheets which give the mechanism identification, the components that are concerned and an analysis grid which is designed to assess the safety risk. This analysis screens the reference documents describing the mechanism, the design lifetime hypotheses, the associated regulation or codification, the feedback experiences, the accessibility, the maintenance actions, the repair possibility and so one. This analysis has to lead to a conclusion about the risk taking into account monitoring and maintenance. If the data sheet conclusion is not clear enough, then a more detailed report is launched. The technical document which is needed, is a formal detailed report which summarizes every theoretical knowledge and monitoring data: its objective is to propose a solution for ageing management: this solution can include more inspections or specific research development, or additional maintenance. After a first stage on the 900 MWe units, only two generic ageing management detailed reports have been needed for the civil engineering part: one about reactor building containment, and one about other structures which focuses on concrete inflating reactions. The second stage consists on deriving this generic analysis (ageing mechanism and detailed reports) to every plant where a complete ageing report is required (one report for all equipments and structures of the plant, but specific for each reactor). This ageing management is a continuous process because the

  17. [Age structure and growth characteristic of Castanopsis fargesii population].

    Science.gov (United States)

    Song, Kun; Da, Liang-jun; Yang, Tong-hui; Yang, Xu-feng

    2007-02-01

    In this paper, the age structure and growth characteristics of Castanopsis fargesii population in a shade-tolerant broadleaved evergreen forest were studied, aimed to understand more about the regeneration patterns and dynamics of this population. The results showed that the age structure of C. fargesii population was of sporadic type, with two death peaks of a 30-year gap. This population had a good plasticity in growth to light condition. Because there were no significant differences in light condition under the canopy in vertical, the saplings came into their first suppression period when they were 5-8 years old, with a height growth rate less than 0. 1 m x a(-1) lasting for 10 years. The beginning time of the first growth suppression period was by the end of the first death peak of the population, and the ending time of the first growth suppression period was at the beginning of the second death peak of the population, demonstrating that growth characteristic was the key factor affecting the age structure of C. fargesii.

  18. [Esophageal wall structure in people of elderly and senile age].

    Science.gov (United States)

    aminova, G G; Grigorenko, D E; Sapin, M R; Mkhitarov, V A

    2014-01-01

    Using histological methods, the esophageal wall structure and the cytoarchitectonics of mucous membrane were studied in the individuals of elderly (n = 5) and senile (n = 10) age. The control group included the individuals of I (n = 3) and II (n = 3) periods of mature age. It was demonstrated that with advancing age in most cases the destructive processes took place in the epithelium (delamination of the layer, separation of large fragments, formation of microerosions etc.) in most of the studied cases. Lymphocytes, neutrophils and eosinophils were found between the epithelial cells; the numbers of infiltrating cells was increased 2-3 times during aging. Mucosal lamina propria and the submucosa, in particular, were characterized by the thickening of the bundles of collagen fibers. A two-fold increase in the number of the cells of the fibroblast lineage was found. The number of leukocytes in the lamina propria was increased by the eldery age in the upper and lower parts of the esophagus (3.5 and 1.75 times respectively). The changes in lamina muscularis were manifested by its thinning, delamination and myocyte dissociation. Remodeling of the muscular tunic was less pronounced. The degree of changes increased distally and varied widely depending on the individual peculiarities.

  19. Active sensors for health monitoring of aging aerospace structures

    Science.gov (United States)

    Giurgiutiu, Victor; Redmond, James M.; Roach, Dennis P.; Rackow, Kirk

    2000-06-01

    A project to develop non-intrusive active sensors that can be applied on existing aging aerospace structures for monitoring the onset and progress of structural damage (fatigue cracks and corrosion) is presented. The state of the art in active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) electro-mechanical (E/M) impedance technique are cited and briefly discussed. The instrumentation of these specimens with piezoelectric active sensors is illustrated. The main detection strategies (E/M impedance for local area detection and wave propagation for wide area interrogation) are discussed. The signal processing and damage interpretation algorithms are tuned to the specific structural interrogation method used. In the high frequency E/M impedance approach, pattern recognition methods are used to compare impedance signatures taken at various time intervals and to identify damage presence and progression from the change in these signatures. In the wave propagation approach, the acousto- ultrasonic methods identifying additional reflection generated from the damage site and changes in transmission velocity and phase are used. Both approaches benefit from the use of artificial intelligence neural networks algorithms that can extract damage features based on a learning process. Design and fabrication of a set of structural specimens representative of aging aerospace structures is presented. Three built-up specimens, (pristine, with cracks, and with corrosion damage) are used. The specimen instrumentation with active sensors fabricated at the University of South Carolina is illustrated. Preliminary results obtained with the E/M impedance method on pristine and cracked specimens are presented.

  20. Active sensors for health monitoring of aging aerospace structures

    Energy Technology Data Exchange (ETDEWEB)

    GIURGIUTIU,VICTOR; REDMOND,JAMES M.; ROACH,DENNIS P.; RACKOW,KIRK A.

    2000-02-29

    A project to develop non-intrusive active sensors that can be applied on existing aging aerospace structures for monitoring the onset and progress of structural damage (fatigue cracks and corrosion) is presented. The state of the art in active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) electro-mechanical (E/M) impedance technique are cited and briefly discussed. The instrumentation of these specimens with piezoelectric active sensors is illustrated. The main detection strategies (E/M impedance for local area detection and wave propagation for wide area interrogation) are discussed. The signal processing and damage interpretation algorithms are tuned to the specific structural interrogation method used. In the high-frequency E/M impedance approach, pattern recognition methods are used to compare impedance signatures taken at various time intervals and to identify damage presence and progression from the change in these signatures. In the wave propagation approach, the acousto-ultrasonic methods identifying additional reflection generated from the damage site and changes in transmission velocity and phase are used. Both approaches benefit from the use of artificial intelligence neural networks algorithms that can extract damage features based on a learning process. Design and fabrication of a set of structural specimens representative of aging aerospace structures is presented. Three built-up specimens (pristine, with cracks, and with corrosion damage) are used. The specimen instrumentation with active sensors fabricated at the University of South Carolina is illustrated. Preliminary results obtained with the E/M impedance method on pristine and cracked specimens are presented.

  1. Active sensors for health monitoring of aging aerospace structures

    Energy Technology Data Exchange (ETDEWEB)

    GIURGIUTIU,VICTOR; REDMOND,JAMES M.; ROACH,DENNIS P.; RACKOW,KIRK A.

    2000-03-08

    A project to develop non-intrusive active sensors that can be applied on existing aging aerospace structures for monitoring the onset and progress of structural damage (fatigue cracks and corrosion) is presented. The state of the art in active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) electro-mechanical (NM) impedance technique are sighted and briefly discussed. The instrumentation of these specimens with piezoelectric active sensors is illustrated. The main detection strategies (E/M impedance for local area detection and wave propagation for wide area interrogation) are discussed. The signal processing and damage interpretation algorithms are tuned to the specific structural interrogation method used. In the high-frequency EIM impedance approach, pattern recognition methods are used to compare impedance signatures taken at various time intervals and to identify damage presence and progression from the change in these signatures. In the wave propagation approach, the acoustic-ultrasonic methods identifying additional reflection generated from the damage site and changes in transmission velocity and phase are used. Both approaches benefit from the use of artificial intelligence neural networks algorithms that can extract damage features based on a learning process. Design and fabrication of a set of structural specimens representative of aging aerospace structures is presented. Three built-up specimens, (pristine, with cracks, and with corrosion damage) are used. The specimen instrumentation with active sensors fabricated at the University of South Carolina is illustrated. Preliminary results obtained with the E/M impedance method on pristine and cracked specimens are presented.

  2. Ultrasonographic assessment of skin structure according to age

    Directory of Open Access Journals (Sweden)

    Diana Crisan

    2012-01-01

    Full Text Available Background: High-frequency ultrasound is a noninvasive tool that offers characteristic markers, quantifying the cutaneous changes of the physiological senescence process. Aims: The aim was to assess the changes in skin thickness, dermal density and echogenicity, as part of the ageing process, with different age intervals. Methods : The study was performed on 160 patients, aged 40.4 ± 21.2, divided into four age categories: <20, 21-40, 41-60, 61-80. Ultrasonographic images (Dermascan device were taken from three sites: dorsal forearm (DF, medial arm (MA, zygomatic area (ZA. We assessed the thickness of epidermis and dermis (mm, number of low, medium, high echogenicity pixels, the ratio between the echogenicity of the upper and lower dermis (LEPs/LEPi, and SLEB (subepidermal low echogenicity band. The statistical analysis was performed using SPSS 15.00. A P value <0.05 was considered significant. Results: On all examined sites, it was found that the dermal thickness increases in the 21 to 40 year interval (P<0.0001. After the 21 to 40 year interval, the number of low echogenic pixels increases significantly, especially on photoexposed sites. High-echogenic pixels follow the same pattern on all examined sites: they increase in the 21 to 40 year interval and decrease in the 3rd and 4th age category. The LEPs/LEPi ratio increases significantly with age, at all sites (P<0.05, due to an increase of hypoechogenic pixels in the upper dermis. Conclusions: High-frequency ultrasound is a noninvasive "histological" tool that can assess the cutaneous structure and age-related changes. It offers imagistic markers, comparable to the histological parameters and also characteristic ultrasonographic markers. Histology remains the gold standard for the investigation of the integumentary system.

  3. Age structure and disturbance legacy of North American forests

    Directory of Open Access Journals (Sweden)

    Y. Pan

    2011-03-01

    Full Text Available Most forests of the world are recovering from a past disturbance. It is well known that forest disturbances profoundly affect carbon stocks and fluxes in forest ecosystems, yet it has been a great challenge to assess disturbance impacts in estimates of forest carbon budgets. Net sequestration or loss of CO2 by forests after disturbance follows a predictable pattern with forest recovery. Forest age, which is related to time since disturbance, is a useful surrogate variable for analyses of the impact of disturbance on forest carbon. In this study, we compiled the first continental forest age map of North America by combining forest inventory data, historical fire data, optical satellite data and the dataset from NASA's Landsat Ecosystem Disturbance Adaptive Processing System (LEDAPS project. A companion map of the standard deviations for age estimates was developed for quantifying uncertainty. We discuss the significance of the disturbance legacy from the past, as represented by current forest age structure in different regions of the US and Canada, by analyzing the causes of disturbances from land management and nature over centuries and at various scales. We also show how such information can be used with inventory data for analyzing carbon management opportunities. By combining geographic information about forest age with estimated C dynamics by forest type, it is possible to conduct a simple but powerful analysis of the net CO2 uptake by forests, and the potential for increasing (or decreasing this rate as a result of direct human intervention in the disturbance/age status. Finally, we describe how the forest age data can be used in large-scale carbon modeling, both for land-based biogeochemistry models and atmosphere-based inversion models, in order to improve the spatial accuracy of carbon cycle simulations.

  4. The effects of temperature and diet on age grading and population age structure determination in Drosophila.

    Science.gov (United States)

    Aw, Wen C; Ballard, J William O

    2013-10-01

    The age structure of natural population is of interest in physiological, life history and ecological studies but it is often difficult to determine. One methodological problem is that samples may need to be invasively sampled preventing subsequent taxonomic curation. A second problem is that it can be very expensive to accurately determine the age structure of given population because large sample sizes are often necessary. In this study, we test the effects of temperature (17 °C, 23 °C and 26 °C) and diet (standard cornmeal and low calorie diet) on the accuracy of the non-invasive, inexpensive and high throughput near-infrared spectroscopy (NIRS) technique to determine the age of Drosophila flies. Composite and simplified calibration models were developed for each sex. Independent sets for each temperature and diet treatments with flies not involved in calibration model were then used to validate the accuracy of the calibration models. The composite NIRS calibration model was generated by including flies reared under all temperatures and diets. This approach permits rapid age measurement and age structure determination in large population of flies as less than or equal to 9 days, or more than 9 days old with 85-97% and 64-99% accuracy, respectively. The simplified calibration models were generated by including flies reared at 23 °C on standard diet. Low accuracy rates were observed when simplified calibration models were used to identify (a) Drosophila reared at 17 °C and 26 °C and (b) 23 °C with low calorie diet. These results strongly suggest that appropriate calibration models need to be developed in the laboratory before this technique can be reliably used in field. These calibration models should include the major environmental variables that change across space and time in the particular natural population to be studied. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. Effects of micro-topographies on stand structure and tree species diversity in an old-growth evergreen broad-leaved forest, southwestern Japan

    Directory of Open Access Journals (Sweden)

    Tran Van Do

    2015-07-01

    Full Text Available Stand structure and species diversity were studied in correspondence with micro-topographies in an old-growth forest in southwestern Japan. The study was conducted in a 200×200m2 permanent plot, which were divided into 400 subplots using grids of 10m×10m. Subplots were categorized to four micro-topographies as crest slope (CS, head hollow (HH, upper slope (US and lower slope (LS, basing on slope of forest floor and plot position, and to two elevational zones as below 450 m and above 450 m. Tree censuses for all individuals with diameter at breast height (DBH ⩾ 5 cm were conducted in 2009 and 2013. The results indicated that CS had subplot means of living stems, dead stems, DBH, basal area (G, and basal area increment (▵G significantly higher than that in LS. While, means of recruited stems and Shannon diversity index were significantly lower. Comparing between below and above 450 m elevational zones indicated the significantly higher parameters of stand structure and species diversity in above 450 m elevational zone. The differences of edaphic conditions led to difference of density of living stems, species density, DBH, G, and ▵G among micro-topographies. Therefore, crest slope, upper slope, and higher elevational zones should be encouraged for the purposes of carbon accumulation and storage. While, the lower elevational zones should be used for the purposes of species diversity conservation.

  6. Strengthening, modification and repair techniques’ prioritization for structural integrity control of ageing offshore structures

    International Nuclear Information System (INIS)

    Samarakoon, Samindi M.K.; Ratnayake, R.M. Chandima

    2015-01-01

    Structural integrity control is vital for existing ageing as well as newly built offshore and onshore structures. Structural integrity control becomes highly sensitive to interventions under a potential loss of structural integrity when it comes to offshore oil and gas production and process facilities. This is mainly due to the inherent constraints present in carrying out engineering work in the offshore atmosphere. It has been further exacerbated by the ageing offshore structures and the necessity of carrying out life extension toward the end of their design service lives. Local and international regulations demand the implementation of appropriate strengthening, modification and repair plans when significant changes in the structural integrity are revealed. In this context, strengthening, modification and repair techniques such as welding, member removal/reduction of loading, mechanical clamping and grouted repairs play a vital role. This manuscript presents an approach for prioritizing the strengthening, modification and repair techniques using a multi-criteria analysis approach. An analytic hierarchy process has been selected for the analysis via an illustrative case. It also provides a comprehensive overview of currently existing; strengthening, modification and repair techniques and their comparative pros and cons. - Highlights: • Structural integrity control (SIC) of ageing and intact offshore structures. • Strengthening, modification and/or repair (SMR) techniques have been explained. • Application of multi-criteria analysis conserving SI has been illustrated. • SMR techniques prioritization and sensitivity analysis has been performed

  7. Impact of structural aging on seismic risk assessment of reinforced concrete structures in nuclear power plants

    International Nuclear Information System (INIS)

    Ellingwood, B.; Song, J.

    1996-03-01

    The Structural Aging Program is addressing the potential for degradation of concrete structural components and systems in nuclear power plants over time due to aging and aggressive environmental stressors. Structures are passive under normal operating conditions but play a key role in mitigating design-basis events, particularly those arising from external challenges such as earthquakes, extreme winds, fires and floods. Structures are plant-specific and unique, often are difficult to inspect, and are virtually impossible to replace. The importance of structural failures in accident mitigation is amplified because such failures may lead to common-cause failures of other components. Structural condition assessment and service life prediction must focus on a few critical components and systems within the plant. Components and systems that are dominant contributors to risk and that require particular attention can be identified through the mathematical formalism of a probabilistic risk assessment, or PRA. To illustrate, the role of structural degradation due to aging on plant risk is examined through the framework of a Level 1 seismic PRA of a nuclear power plant. Plausible mechanisms of structural degradation are found to increase the core damage probability by approximately a factor of two

  8. An age-structured model with delay mortality.

    Science.gov (United States)

    Tchuenche, J M

    2005-09-01

    Many species experience aperiodic mortality. Yet, there is little or no understanding of how this event affects population dynamics. We have considered one of the most simple class of age-structured models, namely, the MacKendrick Von Foerster type equations with suitable modifications to suit the purpose of this study. The main result shows the effect of delay in the estimate of the population. If the delay parameter is taken as a period, then the model equations describe the dynamics of seasonal insects such as locusts whose large population decreases very fast.

  9. Mind-Reading Ability and Structural Connectivity Changes in Aging

    OpenAIRE

    Cabinio, Monia; Rossetto, Federica; Blasi, Valeria; Savazzi, Federica; Castelli, Ilaria; Massaro, Davide; Valle, Annalisa; Nemni, Raffaello; Clerici, Mario; Marchetti, Antonella; Baglio, Francesca

    2015-01-01

    The Mind-Reading ability through the eyes is an important component of the affective Theory of Mind (ToM), which allows people to infer the other’s mental state from the eye gaze. The aim of the present study was to investigate to which extent age-associated structural brain changes impact this ability and to determine if this association is related to executive functions in elderly subjects. For this purpose, Magnetic Resonance Imaging was used to determine both gray matter and white matter ...

  10. Mind-Reading ability and structural connectivity changes in aging

    OpenAIRE

    Monia eCabinio; Federica eRossetto; Federica eRossetto; Valeria eBlasi; Federica eSavazzi; Ilaria eCastelli; Davide eMassaro; Annalisa eValle; Raffaello eNemni; Raffaello eNemni; Mario eClerici; Mario eClerici; Antonella eMarchetti; Francesca eBaglio

    2015-01-01

    The Mind-Reading ability through the eyes is an important component of the affective Theory of Mind (ToM), which allows people to infer the other’s mental state from the eye gaze. The aim of the present study was to investigate to which extent age-associated structural brain changes impact this ability and to determine if this association is related to executive functions in elderly subjects. For this purpose, Magnetic Resonance Imaging was used to determine both gray matter and white matter ...

  11. Structural MRI markers of brain aging early after ischemic stroke.

    Science.gov (United States)

    Werden, Emilio; Cumming, Toby; Li, Qi; Bird, Laura; Veldsman, Michele; Pardoe, Heath R; Jackson, Graeme; Donnan, Geoffrey A; Brodtmann, Amy

    2017-07-11

    To examine associations between ischemic stroke, vascular risk factors, and MRI markers of brain aging. Eighty-one patients (mean age 67.5 ± 13.1 years, 31 left-sided, 61 men) with confirmed first-ever (n = 66) or recurrent (n = 15) ischemic stroke underwent 3T MRI scanning within 6 weeks of symptom onset (mean 26 ± 9 days). Age-matched controls (n = 40) completed identical testing. Multivariate regression analyses examined associations between group membership and MRI markers of brain aging (cortical thickness, total brain volume, white matter hyperintensity [WMH] volume, hippocampal volume), normalized against intracranial volume, and the effects of vascular risk factors on these relationships. First-ever stroke was associated with smaller hippocampal volume ( p = 0.025) and greater WMH volume ( p = 0.004) relative to controls. Recurrent stroke was in turn associated with smaller hippocampal volume relative to both first-ever stroke ( p = 0.017) and controls ( p = 0.001). These associations remained significant after adjustment for age, sex, education, and, in stroke patients, infarct volume. Total brain volume was not significantly smaller in first-ever stroke patients than in controls ( p = 0.056), but the association became significant after further adjustment for atrial fibrillation ( p = 0.036). Cortical thickness and brain volumes did not differ as a function of stroke type, infarct volume, or etiology. Brain structure is likely to be compromised before ischemic stroke by vascular risk factors. Smaller hippocampal and total brain volumes and increased WMH load represent proxies for underlying vascular brain injury. Copyright © 2017 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.

  12. Impact of a Mountain Pine Beetle Outbreak on Young Lodgepole Pine Stands in Central British Columbia

    Directory of Open Access Journals (Sweden)

    Amalesh Dhar

    2015-09-01

    Full Text Available The current mountain pine beetle (MPB (Dendroctonous ponderosae Hopkins epidemic has severely affected pine forests of Western Canada and killed millions of hectares of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm. forest. Generally, MPB attack larger and older (diameter > 20 cm or >60 years of age trees, but the current epidemic extends this limit with attacks on even younger and smaller trees. The study’s aim was to investigate the extent of MPB attack in young pine stands and its possible impact on stand dynamics. Although MPB attacks were observed in trees as small as 7.5 cm diameter at breast height (DBH and as young as 13 years old, the degree of MPB attack (percent stems ha−1 increased with increasing tree diameter and age class (13–20, 21–40, 41–60, and 61–80 years old (6.4%, 49.4%, 62.6%, and 69.5% attack, respectively, by age class which is greater than that reported from previous epidemics for stands of this age. The mean density of surviving residual structure varied widely among age classes and ecological subzones. Depending on age class, 65% to 77% of the attacked stands could contribute to mid-term timber supply. The surviving residual structure of young stands offers an opportunity to mitigate the effects of MPB-attack on future timber supply, increase age class diversity, and enhance ecological resilience in younger stands.

  13. Accounting for age Structure in Ponderosa Pine Ecosystem Analyses: Integrating Management, Disturbance Histories and Observations with the BIOME-BGC Model

    Science.gov (United States)

    Hibbard, K. A.; Law, B.; Thornton, P.

    2003-12-01

    Disturbance and management regimes in forested ecosystems have been recently highlighted as important factors contributing to quantification of carbon stocks and fluxes. Disturbance events, such as stand-replacing fires and current management regimes that emphasize understory and tree thinning are primary suspects influencing ecosystem processes, including net ecosystem productivity (NEP) in forests of the Pacific Northwest. Several recent analyses have compared simulated to measured component stocks and fluxes of carbon in Ponderosa Pine (Pinus ponderosa var. Laws) at 12 sites ranging from 9 to 300 years in central Oregon (Law et al. 2001, Law et al. 2003) using the BIOME-BGC model. Major emphases on ecosystem model developments include improving allocation logic, integrating ecosystem processes with disturbance such as fire and including nitrogen in biogeochemical cycling. In Law et al. (2001, 2003), field observations prompted BIOME-BGC improvements including dynamic allocation of carbon to fine root mass through the life of a stand. A sequence of simulations was also designed to represent both management and disturbance histories for each site, however, current age structure of each sites wasn't addressed. Age structure, or cohort management has largely been ignored by ecosystem models, however, some studies have sought to incorporate stand age with disturbance and management (e.g. Hibbard et al. 2003). In this analyses, we regressed tree ages against height (R2 = 0.67) to develop a proportional distribution of age structure for each site. To preserve the integrity of the comparison between Law et al. (2003) and this study, we maintained the same timing of harvest, however, based on the distribution of age structures, we manipulated the amount of removal. Harvest by Law et al. (2003) was set at stand-replacement (99%) levels to simulate clear-cutting and reflecting the average top 10% of the age in each plot. For the young sites, we set removal at 73%, 51% and

  14. [Analysis on age structure and dynamics of Kindonia uniflora populations].

    Science.gov (United States)

    Zhang, Wenhui; Li, Jingxia; Li, Hong; Liu, Xiangjun

    2004-04-01

    Kindonia uniflora is a perennial clone herbaceous plant, and also, a native endangered plant in China. This paper studied its age structure, life table and survivorship curve in different habitats in Taibai mountain area. The results indicated that the age structure and dynamics of K. uniflora populations in the Betula utilis forest at altitude 2500-2700 m, in the Abies fargesii forest at altitude 2700-2900 m, and in the Larix chinensis forest at altitude 2900-3100 m had the similar pattern and developing tendency. The number of younger ramets at 1-2 years old or older than 5 years was less, and the number of ramets at 3-5 years old was the highest in the age structures. The negative values of dx (dead number), qx (mortality rate) and Kx (Killing rate) in the life table showed the increasing rate of the population sizes during the age stage. The survivorship curve of K. uniflora populations in different habitats belonged to Deevey C after 3-5 years old. The mortality rate of populations during 5-10 years stage was higher, and was stable after 10 years old. As for the characters of asexual propagation and clone growth, the rhizomes of the populations were in humus of soil, and developed and expanded as guerilla line style. During growth season, only one leaf grew above ground at every inter-node, and the population growth and development were rarely influenced by external factors. The forest communities, such as Betula utilis, Abies fargesii and Larix chinensis forest, in which K. uniflora populations lived, were at middle or higher mountain, where there were rarely disturbance from human being. Therefore, the habitats for K. uniflora populations to live were relatively stable. As the altitude increased, the disturbances from human being became less, the density of K. uniflora populations increased, the life cycle expanded, the peak of population death delayed, and the population living strategy changed to adapt to the habitats. K. uniflora populations preferred to

  15. A non-contact technique for evaluation of elastic structures at large stand-off distances: applications to classification of fluids in steel vessels.

    Science.gov (United States)

    Kaduchak, G; Sinha, D N; Lizon, D C; Kelecher, M J

    2000-01-01

    A novel technique for non-contact evaluation of structures in air at large stand-off distances (on the order of several meters) has been developed. It utilizes a recently constructed air-coupled, parametric acoustic array to excite the resonance vibrations of elastic, fluid-filled vessels. The parametric array is advantageous for NDE applications in that it is capable of producing a much narrower beamwidth and broader bandwidth than typical devices that operate under linear acoustic principles. In the present experiments, the array operates at a carrier frequency of 217 kHz, and the sound field several meters from the source is described spectrally by the envelope of the drive voltage. An operating bandwidth of more than 25 kHz at a center frequency of 15 kHz is demonstrated. For the present application, the array is used to excite vibrations of fluid-filled, steel containers at stand-off distances of greater than 3 m. The vibratory response of a container is detected with a laser vibrometer in a monostatic configuration with the acoustic source. By analyzing the change in the response of the lowest order, antisymmetric Lamb wave as the interior fluid loading conditions of the container are changed, the fluid contained within the steel vessel is classified.

  16. Individual tree diameter increment model for managed even-aged stands of ponderosa pine throughout the western United States using a multilevel linear mixed effects model

    Science.gov (United States)

    Fabian C.C. Uzoh; William W. Oliver

    2008-01-01

    A diameter increment model is developed and evaluated for individual trees of ponderosa pine throughout the species range in the United States using a multilevel linear mixed model. Stochastic variability is broken down among period, locale, plot, tree and within-tree components. Covariates acting at tree and stand level, as breast height diameter, density, site index...

  17. Second-year growth and bole quality response of residual poletimber trees following thinning in an even-aged bottomland hardwood sawtimber stand

    Science.gov (United States)

    Daniel A., Jr. Skojac; James S. Meadows; Andrew W. Ezell

    2010-01-01

    Poletimber trees were classified as either superior or inferior poletimber stock, and then retained on separate plots receiving identical thinning treatments. Differences in post-treatment response were used to evaluate the potential of the two poletimber classes to produce grade sawtimber in the thinned sawtimber stand. Treatments included: an unthinned control, two...

  18. Influence of age on growth efficiency of Tsuga canadensis and Picea rubens trees in mixed-species, multiaged northern conifer stands

    Science.gov (United States)

    Robert S. Seymour; Laura S. Kenefic

    2002-01-01

    Well-known patterns in the fundamental relationship between tree-level stemwood volume increment (VINC) and projected leaf area (PLA) are examined and quantified for Tsuga Canadensis (L.) Carriere (eastern hemlock) and Picea rubens Sarg. (red spruce) growing in managed, mixed-species, multiaged stands in east-central Maine, U.S.A....

  19. The neutron structure of urate oxidase resolves a long-standing mechanistic conundrum and reveals unexpected changes in protonation.

    Directory of Open Access Journals (Sweden)

    Esko Oksanen

    Full Text Available Urate oxidase transforms uric acid to 5-hydroxyisourate without the help of cofactors, but the catalytic mechanism has remained enigmatic, as the protonation state of the substrate could not be reliably deduced. We have determined the neutron structure of urate oxidase, providing unique information on the proton positions. A neutron crystal structure inhibited by a chloride anion at 2.3 Å resolution shows that the substrate is in fact 8-hydroxyxanthine, the enol tautomer of urate. We have also determined the neutron structure of the complex with the inhibitor 8-azaxanthine at 1.9 Å resolution, showing the protonation states of the K10-T57-H256 catalytic triad. Together with X-ray data and quantum chemical calculations, these structures allow us to identify the site of the initial substrate protonation and elucidate why the enzyme is inhibited by a chloride anion.

  20. Reference stand condition - Effects of Thinning on Forest Structure important to the recovery of ESA-listed species

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This study evaluates the effects of thinning regimes designed to accelerate the development of late-successional forest structure for the benefit of salmon and other...

  1. Determining maximum stand density index in mixed species stands for strategic-scale stocking assessments

    Science.gov (United States)

    Chris W. Woodall; Patrick D. Miles; John S. Vissage

    2005-01-01

    Stand density index (SDI), although developed for use in even-aged monocultures, has been used for assessing stand density in large-scale forest inventories containing diverse tree species and size distributions. To improve application of SDI in unevenaged, mixed species stands present in large-scale forest inventories, trends in maximum SDI across diameter classes...

  2. Overstory species composition, structure, and conservation challenges of a mature, natural-origin pine stand after decades of management

    Science.gov (United States)

    Don C. Bragg

    2016-01-01

    This study provides a preliminary assessment of 4 compartments on the Crossett Experimental Forest (CEF) being restored to old-growth-like conditions. After being partially cleared for agriculture or lumbered in the late 1910s, Compartments 1, 2, 11, and 12 were included in a combination of pulpwood-thinning and uneven-aged cutting-cycle studies for the next 50 y....

  3. Structure of ultrathin films of Co on Cu(111) from normal-incidence x-ray standing wave and medium-energy ion scattering measurements

    International Nuclear Information System (INIS)

    Butterfield, M.T.; Crapper, M.D.; Noakes, T.C.Q.; Bailey, P.; Jackson, G.J.; Woodruff, D.P.

    2000-01-01

    Applications of the techniques of normal-incidence x-ray standing wave (NIXSW) and medium-energy ion scattering (MEIS) to the elucidation of the structure of an ultrathin metallic film, Co on Cu(111), are reported. NIXSW and MEIS are shown to yield valuable and complementary information on the structure of such systems, yielding both the local stacking sequence and the global site distribution. For the thinnest films of nominally two layers, the first layer is of entirely fcc registry with respect to the substrate, but in the outermost layer there is significant occupation of hcp local sites. For films up to 8 monolayers (ML) thick, the interlayer spacing of the Co layers is 0.058±0.006 Aa smaller than the Cu substrate (111) layer spacing. With increasing coverage, the coherent fraction of the (1(bar sign)11) NIXSW decreases rapidly, indicating that the film does not grow in a fcc continuation beyond two layers. For films in this thickness range, hcp-type stacking dominates fcc twinning by a ratio of 2:1. The variation of the (1(bar sign)11) NIXSW coherent fraction with thickness shows that the twinning occurs close to the Co/Cu interface. For thicker films of around 20 ML deposited at room temperature, medium-energy ion scattering measurements reveal a largely disordered structure. Upon annealing to 300 deg. C the 20-ML films order into a hcp structure

  4. [Aging and spirituality: Factorial structure and reliability of 2 scales].

    Science.gov (United States)

    Galiana, Laura; Sancho, Patricia; Oliver, Amparo; Tomás, José Manuel; Calatayud, Pablo

    2016-01-01

    In the field of gerontology, the study of the improvement of health and quality of life, and «successfully aging», spirituality plays a key role and, is one of the current research approaches. However, its incorporation into scientific literature is arduous and slow, a fact that is in part due to the absence of developed and validated measurement tools, particularly, in the Spanish speaking area. This work aims to present evidence of the psychometric properties of two tools for the measurement of spirituality: the Functional Assessment of Chronic Illness Therapy Spiritual Well-Being (FACIT-Sp) and the GES Questionnaire. A sample of 224 elderly persons from Valencia (Spain) was recruited, on which two confirmatory factor analyses were estimated, with the proposed a priori structures for each tool, together with several reliability coefficients. Both models presented an good fit to the data: χ(2)51=104.97 (P.05); CFI=.996; RMSEA=.050 for the GES Questionnaire. Reliability indices also supported the use of the scales in elderly population, with alphas of .85 and .86, respectively. These results may be useful as a starting point to include spirituality in works that aim to discover the mechanisms involved in successful aging. Copyright © 2016 SEGG. Publicado por Elsevier España, S.L.U. All rights reserved.

  5. Aging Evaluation Programs for Jet Transport Aircraft Structural Integrity

    Directory of Open Access Journals (Sweden)

    Borivoj Galović

    2012-10-01

    Full Text Available The paper deals with criteria and procedures in evaluationof timely preventive maintenance recommendations that willsupport continued safe operation of aging jet transports untiltheir retirement from service. The active service life of commercialaircraft has increased in recent years as a result of low fuelcost, and increasing costs and delivery times for fleet replacements.Air transport industry consensus is that older jet transportswill continue in service despite anticipated substantial increasesin required maintenance. Design concepts, supportedby testing, have worked well due to the system that is used to ensureflying safety. Continuing structural integrity by inspectionand overhaul recommendation above the level contained inmaintenance and service bulletins is additional requirement, insuch cases. Airplane structural safety depends on the performanceof all participants in the system and the responsibility forsafety cannot be delegated to a single participant. This systemhas three major participants: the manufacturers who design,build and support airplanes in service, the airlines who operate,inspect and mantain airplanes and the airworthiness authoritieswho establish rules and regulations, approve the design andpromote airline maintenance performance.

  6. Standing equine dental surgery.

    Science.gov (United States)

    Menzies, Robert A; Easley, Jack

    2014-04-01

    Dental surgeries refer to procedures that affect the dental tissues or their supporting structures. With the development of specific, efficacious, and conservative treatments, morbidity risks have been lowered and chances of benefiting the health of equids improved. Advances in quality of sedation, analgesia, and locoregional anesthesia allow a majority of dental surgeries to be performed in the standing patient. This update focuses on an orthograde endodontic technique, a minimally invasive buccotomy technique, with the potential to combine it with a transbuccal screw extraction technique, and revisits the AO pinless external fixator for fractures of the body of the mandible. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Avaliação da continuidade espacial de características dendrométricas em diferentes idades de povoamentos clonais de Eucalyptus sp. Evaluation of spatial continuity of dendrometric characteristics of clonal stands of Eucalyptus sp. at different ages

    Directory of Open Access Journals (Sweden)

    Honório Kanegae Junior

    2007-10-01

    variation in the variables to be estimated in successive inventories. This control can be achieved by using of stratifiers based on maps from statistical kriging. However, kriging lacks information on the spatial continuity of descriptor variables for Eucalyptus sp. stands, as well as the behavior of this characteristic over time. This study evaluated the structure of spatial continuity for three dendrometric characteristics of 23 clonal stands of Eucalyptus sp. in 3 successive measurements, located in different areas of SP state. For each stand, variable and measurement, experimental semivariograms were adjusted by the weighted least squares method. Through the degree of spatial dependence obtained by the experimental semivariograms, the behavior of the spatial continuity of variables was evaluated. More than 70% of the analyzed stands showed average to strong spatial dependence for volume and 80% for the variables basal area and dominant height. The range of the variables showed variations from 300 to 3.000 m, depending on the stand and age of measurement. The percentage of stands with strong spatial dependence decreases with age, tending to a sill of average spatial dependence, for all the analyzed variables. The degree of spatial dependence along successive measurements varies from stand to stand and from measurement to measurement, being likely to decrease or increase with time, suggesting a specific analysis of spatial dependence for the variable of interest for each stand and measurement.

  8. Bark beetles responses to stand structure and prescribed fire at Black Mountain Experimental Forest, California, USA: 5-year data

    Science.gov (United States)

    C.J. Fettig; S.R. McKelvey

    2010-01-01

    Highly effective fire suppression and selective harvesting of large-diameter, fire-tolerant tree species, such as ponderosa pine (Pinus ponderosa C. Lawson) and Jeffrey pine (P. jeffreyi Balf.), have resulted in substantial changes to the structure and composition of interior ponderosa pine forests. Mechanical thinning and the...

  9. Horizontal, but not vertical canopy structure is related to stand functional diversity in a subtropical slope forest

    NARCIS (Netherlands)

    Lang, A.C.; Härdtle, W.; Bruelheide, H.; Kröber, W.; Schröter, M.; Wehrden, von H.; Oheimb, von G.

    2012-01-01

    The aim of this study was to analyse the relation of horizontal and vertical canopy structure to tree functional diversity of a highly diverse subtropical broad-leaved slope forest, stratified for different successional stages. This is of particular interest because many key ecosystem processes and

  10. Probing buried solid-solid interfaces in magnetic multilayer structures and other nanostructures using spectroscopy excited by soft x-ray standing waves

    International Nuclear Information System (INIS)

    Yang, S.-H.; Mun, B.S.; Mannella, N.; Sell, B.; Ritchey, S.B.; Fadley, C.S.; Pham, L.; Nambu, A.; Watanabe, M.

    2004-01-01

    Full text: Buried solid-solid interfaces are becoming increasingly more important in all aspects of nanoscience, and we here dis- cuss the st applications of a new method for selectively studying them with the vuv/soft x-ray spectroscopies. As specific examples, magnetic multilayer structures represent key elements of current developments in spintronics, including giant magnetoresistance, exchange bias, and magnetic tunnel resistance. The buried interfaces in such structures are of key importance to their performance, but have up to now been difficult to study selectively with these spectroscopies. This novel method involves excitation of photoelectrons or fluorescent x-rays with soft x-ray standing waves created by Bragg reflection from a multilayer mirror substrate on which the sample is grown. We will discuss core and valence photoemission, as well soft x-ray emission, results from applying this method to multilayer structures relevant to both giant magnetoresistance (Fe/Cr-[2]) and magnetic tunnel junctions (Al 2 O 3 /FeCo) , including magnetic dichroism measurements. Work supported by the Director, Of e of Science, Of e of Basic Energy Sciences, Materials Science and Engineering Division, U.S. Department of Energy, Contract No. DE-AC03-76SF000

  11. Study on the structural, optical, and electrical properties of the yellow light-emitting diode grown on free-standing (0001) GaN substrate

    Science.gov (United States)

    Deng, Gaoqiang; Zhang, Yuantao; Yu, Ye; Yan, Long; Li, Pengchong; Han, Xu; Chen, Liang; Zhao, Degang; Du, Guotong

    2018-04-01

    In this paper, GaN-based yellow light-emitting diodes (LEDs) were homoepitaxially grown on free-standing (0001) GaN substrates by metal-organic chemical vapor deposition. X-ray diffraction (XRD), photoluminescence (PL), and electroluminescence (EL) measurements were conducted to investigate the structural, optical, and electrical properties of the yellow LED. The XRD measurement results showed that the InGaN/GaN multiple quantum wells (MQWs) in the LED structure have good periodicity because the distinct MQWs related higher order satellite peaks can be clearly observed from the profile of 2θ-ω XRD scan. The low temperature (10 K) and room temperature PL measurement results yield an internal quantum efficiency of 16% for the yellow LED. The EL spectra of the yellow LED present well Gaussian distribution with relatively low linewidth (47-55 nm), indicating the homogeneous In-content in the InGaN quantum well layers in the yellow LED structure. It is believed that this work will aid in the future development of GaN on GaN LEDs with long emission wavelength.

  12. Deep-water stands of Cystoseira zosteroides C. Agardh (Fucales, Ochrophyta) in the Northwestern Mediterranean: Insights into assemblage structure and population dynamics

    Science.gov (United States)

    Ballesteros, Enric; Garrabou, Joaquim; Hereu, Bernat; Zabala, Mikel; Cebrian, Emma; Sala, Enric

    2009-04-01

    Populations dominated by Cystoseira zosteroides, an endemic and threatened Mediterranean seaweed, colonize deep-water rocky habitats down to more than 50 m depth. Assemblages dominated by this species display high algal and invertebrate species richness. Algal biomass averages 1134 g dw m -2. Erect and turf algae account for only 25% of total algal dry weight, while encrusting corallines are responsible for the remaining 75%. Sponges, bryozoans and ascidians constitute the dominant sessile macrofauna. Cystoseira zosteroides is the dominant erect algae, with a mean biomass of 60.6 g dw m -2, and densities ranging from 4 to 7 plants m -2. The alien turf alga Womersleyella setacea has a biomass of 104.2 g dw m -2 and covers most of the understory substrate. The size-frequency distribution of C. zosteroides populations shows differences over time. Mean annual growth of the main axis is around 0.5 cm and mean annual mortality rate is lower than 2%. Recruitment was almost nil during the studied period of time (10 years). Processes structuring these deep-water Cystoseira stands must be driven by episodic disturbances, after-disturbance recruitment pulses, and long periods of steady growth that last at least 10 years. However, it is also possible that recruitment is irreversibly inhibited by the alien alga W. setacea in which case these old-growth stands are faced with extinction. The highly diversified assemblages and the low growth and low mortality rates of C. zosteroides indicate high vulnerability to natural and anthropogenic disturbances, and call for effective measures to ensure their conservation.

  13. Stand structure, composition and illegal logging in selectively logged production forests of Myanmar: Comparison of two compartments subject to different cutting frequency

    Directory of Open Access Journals (Sweden)

    Tual Cin Khai

    2016-07-01

    Full Text Available Appropriate cutting cycles and annual allowable cuts are crucial to ensure sustainability of tropical selective logging, but there have been limited field data to verify long-term effects of different cutting cycles. This study reveals some evidence of forest degradation in selectively logged production forests of Myanmar, which are subject to inappropriate cutting frequency. We compared stand structure, commercial species composition, and incidence of illegal logging between two compartments with low (LCF; 1 time and high (HCF; 5 times cutting frequency over a recent 18 years. Prior to the latest cutting, LCF had 176 trees ha−1 with an inverted-J shape distribution of diameter at breast height (DBH, including a substantial amount of teak (Tectona grandis and other commercially important species in each DBH class. HCF prior to the latest cut had only 41 trees ha−1 without many commercially important species. At HCF, nearly half the standing trees of various species and size were illegally cut following legal operations; this was for charcoal making in nearby kilns. At LCF, two species, teak and Xylia xylocarpa, were cut illegally and sawn for timber on the spot. More extensive and systematic surveys are needed to generalize the findings of forest degradation and illegal logging. However, our study calls for urgent reconsideration of logging practices with high cutting frequency, which can greatly degrade forests with accompanying illegal logging, and for rehabilitating strongly degraded, bamboo-dominated forests. To reduce illegal logging, it would be important to pay more attention on a MSS regulation stating that logging roads should be destroyed after logging operations.

  14. Changes in carbon pool and stand structure of a native subtropical mangrove forest after inter-planting with exotic species Sonneratia apetala.

    Science.gov (United States)

    Lu, Weizhi; Yang, Shengchang; Chen, Luzhen; Wang, Wenqing; Du, Xiaona; Wang, Canmou; Ma, Yan; Lin, Guangxuan; Lin, Guanghui

    2014-01-01

    In this study, we compared stand structure, biomass and soil carbon pools, and litterfall production between a mixed mangrove forest consisting of Aegiceras corniculatum inter-planted with the exotic Sonneratia apetala and a native monospecific forest dominated by A. corniculatum in the intertidal area of Zhanjiang, Guangdong Province, southeast China. The goal of this study was to test the hypothesis that inter-planting fast growing exotic mangrove S. apetala into subtropical native mangrove forests will significantly increase C sequestration. Although the tree heights and basal diameters of S. apetala were significantly higher than those of A. corniculatum, the density of the 12-year-old S. apetala trees in the mixed forest was much smaller than that of A. corniculatum in the monospecific forest. In contrast to several previous studies on S. apetala forests planted directly on mangrove-free mudflats, the mixed mangrove forest showed no significant difference in either standing biomass or soil carbon pools from the native monospecific mangrove forest (p = 0.294 and 0.073, respectively) twelve years after inter-planting with S. apetala. Moreover, carbon cycling was likely speeded up after inter-planting S. apetala due to higher litterfall input and lower C/N ratio. Thus, inter-planting fast-growing S. apetala into native mangrove forest is not an effective way to increase carbon sequestration in this subtropical mangrove forest. Given that exotic plant species may exert negative impact on native mangrove species and related epifauna, this fast-growing mangrove species is not suitable for mangrove plantation projects aiming mainly at enhancing carbon sequestration.

  15. Growth of GaN free-standing nanowires by plasma-assisted molecular beam epitaxy: structural and optical characterization

    International Nuclear Information System (INIS)

    Tchernycheva, M; Sartel, C; Cirlin, G; Travers, L; Patriarche, G; Harmand, J-C; Dang, Le Si; Renard, J; Gayral, B; Nevou, L; Julien, F

    2007-01-01

    This paper reports on the growth, structural and optical properties of GaN free-stranding nanowires synthesized in catalyst-free mode on Si(111) substrate by plasma-assisted molecular beam epitaxy. Cylindrical nanowires with a hexagonal cross-section defined by {1 0 1-bar 0} planes and diameters down to 20 nm were observed. The nanowire length increases as a function of their diameter, following the Gibbs-Thomson expression. The growth rate in the lateral direction was studied using thin AlN marker layers showing that the lateral over axial growth rate ratio can be tuned from ∼1% to ∼10% by changing the III/V flux ratio, with the lateral growth remaining homogeneous along the NW axis. Nanowire ensembles showed a strong near band edge photoluminescence up to room temperature. Low-temperature micro-photoluminescence from a single wire is peaked at 3.478 eV with broadening of 6-10 meV. This emission is similar to the luminescence of nanowire ensembles, which demonstrates strain homogeneity from wire to wire. The optical properties along the wire axis probed by micro-cathodoluminescence were found to be uniform, with no evidence of a higher defect density in the bottom part of the nanowires next to the Si substrate

  16. Structural and electronic properties of free standing one-sided and two-sided hydrogenated silicene: A first principle study

    Energy Technology Data Exchange (ETDEWEB)

    Mohan, Brij, E-mail: brijmohanhpu@yahoo.com; Kumar, Ashok, E-mail: brijmohanhpu@yahoo.com; Ahluwalia, P. K., E-mail: brijmohanhpu@yahoo.com [Department of Physics, Himachal Pradesh University, Shimla-171005 (India)

    2014-04-24

    We performed first-principle study of the structural and electronic properties of two-dimensional hydrogenated silicene for two configurations; one is hydrogenation along one side of silicene sheet and second is hydrogenation in both sides of silicene sheet. The one-side hydrogenated silicene is found stable at planar geometry while increased buckling of 0.725 Å is found for both-side hydrogenated silicene. The result shows that the hydrogenation occupy the extended π-bonding network of silicene, and thus it exhibits semi-conducting behaviour with a band gap of 1.77 eV and 2.19 eV for one-side hydrogenated silicene and both-side hydrogenated silicene respectively. However, both-side hydrogenated silicene of binding energy 4.56 eV is more stable than one-side hydrogenated silicene of binding energy 4.30 eV, but experimentally silicene is synthesized on substrates which interacts one side of silicene layer and only other side is available for H-atoms. Therefore, practically one-side hydrogenation is also important.

  17. Structural and electronic properties of free standing one-sided and two-sided hydrogenated silicene: A first principle study

    International Nuclear Information System (INIS)

    Mohan, Brij; Kumar, Ashok; Ahluwalia, P. K.

    2014-01-01

    We performed first-principle study of the structural and electronic properties of two-dimensional hydrogenated silicene for two configurations; one is hydrogenation along one side of silicene sheet and second is hydrogenation in both sides of silicene sheet. The one-side hydrogenated silicene is found stable at planar geometry while increased buckling of 0.725 Å is found for both-side hydrogenated silicene. The result shows that the hydrogenation occupy the extended π-bonding network of silicene, and thus it exhibits semi-conducting behaviour with a band gap of 1.77 eV and 2.19 eV for one-side hydrogenated silicene and both-side hydrogenated silicene respectively. However, both-side hydrogenated silicene of binding energy 4.56 eV is more stable than one-side hydrogenated silicene of binding energy 4.30 eV, but experimentally silicene is synthesized on substrates which interacts one side of silicene layer and only other side is available for H-atoms. Therefore, practically one-side hydrogenation is also important

  18. Tuberculosis in Cape Town: An age-structured transmission model

    NARCIS (Netherlands)

    Blaser, Nello; Zahnd, Cindy; Hermans, Sabine; Salazar-Vizcaya, Luisa; Estill, Janne; Morrow, Carl; Egger, Matthias; Keiser, Olivia; Wood, Robin

    2016-01-01

    Tuberculosis (TB) is the leading cause of death in South Africa. The burden of disease varies by age, with peaks in TB notification rates in the HIV-negative population at ages 0-5, 20-24, and 45-49 years. There is little variation between age groups in the rates in the HIV-positive population. The

  19. Accounting for density reduction and structural loss in standing dead trees: Implications for forest biomass and carbon stock estimates in the United States

    Science.gov (United States)

    Grant M. Domke; Christopher W. Woodall; James E. Smith

    2011-01-01

    Standing dead trees are one component of forest ecosystem dead wood carbon (C) pools, whose national stock is estimated by the U.S. as required by the United Nations Framework Convention on Climate Change. Historically, standing dead tree C has been estimated as a function of live tree growing stock volume in the U.S.'s National Greenhouse Gas Inventory. Initiated...

  20. Long-term (13-year) effects of repeated prescribed fires on stand structure and tree regeneration in mixed-oak forests

    Science.gov (United States)

    Todd F. Hutchinson; Daniel A. Yaussy; Robert P. Long; Joanne Rebbeck; Elaine Kennedy. Sutherland

    2012-01-01

    The survival and growth of oak advance regeneration is often limited by shade-tolerant species that are abundant in the understory of oak stands. Evidence of historic burning has prompted the use of prescribed fire as a tool to improve the competitive status of oak regeneration in mature stands. A primary shortfall of fire effects research in oak forests has been a...

  1. The Siberian Stone Pine Stands Near Settlements in Tomsk Region. Problems of Sustainable Forest Use

    Directory of Open Access Journals (Sweden)

    N. M. Debkov

    2014-06-01

    Full Text Available A review of the Siberian stone pine stands' formation near settlements in Tomsk region is given in historical aspect. Their current status is described in detail. Age, tree species, and typological structure, as well as productivity and dynamics of forest inventory indices have been identified. Forest management practices in leased and non-leased Siberian stone pine stands have been analyzed. The ways and procedures for an expansion of the existing Siberian stone pine stands and creation of new Siberian stone pine forests near settlements is proposed.

  2. Practice-Oriented Yield Table for White Poplar Stands Growing under Sandy Soil Conditions in Hungary

    Directory of Open Access Journals (Sweden)

    Károly Rédei

    2012-06-01

    Full Text Available Background and Purpose: White poplar (Populus alba L. and its most important natural hybrid, the grey poplar (Populus x canescens SM. are native tree species in Hungary, covering 3.2% of the forested area. Thanks to their favourite silvicultural and growth characteristics as well as the wood utilization possibilities, their present area is increasing continuously. The most important task ahead of Hungarian poplar growers is to improve the quality and to increase the quantity of poplar stands for wood production. To determine their growth rate and yield as exactly as possible, a yield table has been. Material and Methods: Chapman – Richards function with three parameters was successfully used as a growth function for constructing the height growth model. The white poplar yield table was constructed from data gathered on 50 permanent and 40 temporary plots (cca. 500-1000 m2. The age of the stands varied between 5 and 45 years. In the course of the stand surveys the key stand characteristics were measured, and then, on the basis of data collected, were calculated such major stand structure features as the average height, diameter (DBH, volume, basal area and stem number given separately for the main (remaining, secondary (removal and total stands per hectare. Results and Conclusion: The numerical (tabulated yield table of normative nature presents data given to six yield classes (base age: 25 years including the most important stand structural and yield features expressing in terms of main stand, removing stand (which can be removed in tending operations and the total stand. It is based on the Hungarian applied tending operations’ practice. The published yield table has already been utilized in the field of the relevant forest inventory as well.

  3. [Supplementary health care regulation and age structure of beneficiaries].

    Science.gov (United States)

    Stivali, Matheus

    2011-09-01

    The paper exposes the changes in rules of price readjustment of health plans by age thresholds and demographic changes observed between 1998 and 2008. By calculating aging indicators and building population pyramids, it assesses whether the demographic changes coupled with the regulation caused any alteration in young people subscribing to supplementary healthcare plans. The indicators reveal the aging trend of beneficiaries of health plans, especially among those contracted individually, and also that this has not resulted in young people quitting supplementary healthcare plans.

  4. Mollified birth in natural-age-grid Galerkin methods for age-structured biological systems

    International Nuclear Information System (INIS)

    Ayati, Bruce P; Dupont, Todd F

    2009-01-01

    We present natural-age-grid Galerkin methods for a model of a biological population undergoing aging. We use a mollified birth term in the method and analysis. The error due to mollification is of arbitrary order, depending on the choice of mollifier. The methods in this paper generalize the methods presented in [1], where the approximation space in age was taken to be a discontinuous piecewise polynomial subspace of L 2 . We refer to these methods as 'natural-age-grid' Galerkin methods since transport in the age variable is computed through the smooth movement of the age grid at the natural dimensionless velocity of one. The time variable has been left continuous to emphasize this smooth motion, as well as the independence of the time and age discretizations. The methods are shown to be superconvergent in the age variable

  5. Effect of crystal structure peculiarities of ageing alloys on dislocation structure during active deformation

    International Nuclear Information System (INIS)

    Travina, N.T.; Nikitin, A.A.; Zimina, L.N.

    1980-01-01

    On coarse-grain polycrystal samples of commercial KhN67MVTYu (EhP202), Kh60MVTYu (EhP487) and KhN60MKVYu (EhI661) alloys, aged under various conditions, studied are mechnanical properties after active deformation by extension at room temperature and dislocation structure corresponding to these structural states. Crystal and dislocation structures have been studied using electron microscope. In the alloys with mode--rate (13-14 v.%) quantity of γ' phase (KhN67MVTYu and KhN60MVTYu) at the stage of coherent-conjugated bond of particles with matrix deformation runs mainly according to the mechanism of cutting particles by separate dislocations; at the break of coherent bond - by bending of particles according to the Orovan mechanism or by their cutting with clusters of dislocations. At high volume part of particles of γ'-phase (40 v%, KhN60MKVYu alloy) the Orovan mechanism does not manifest itself in any of studied states. In this alloy at this stage of the break of the γ'-phase coherent bond with matrix in the result of ordered position of particles along the directions in matrix formed are interlayers free from particles on which strain is being mainly developed. Dislocation structure is compared with mechanical properties of the alloys

  6. Breakdown mechanism in AlGaN/GaN high-electron mobility transistor structure on free-standing n-type GaN substrate

    Science.gov (United States)

    Tanabe, Shinichi; Watanabe, Noriyuki; Matsuzaki, Hideaki

    2016-05-01

    The breakdown mechanism in a high-electron mobility transistor structure on free-standing n-type GaN substrates consisting of a C-doped GaN layer as a high-resistivity buffer was investigated with a two-terminal vertical device that has a C-doped GaN buffer between electrodes. Initially, current density increases with the square of bias voltage. This is then followed by an abrupt increase by several orders of magnitude within ten volts, which results in breakdown. These behaviors are consistent with the theory of the space-charge limited current. In this theory, current density increases steeply when trap sites at a certain energy level are completely filled with injected carriers. These results indicate that the existence of trap levels in the C-doped GaN layer is one of the possible factors that determine the breakdown. The trap density and trap level of the C-doped GaN layer were also evaluated.

  7. Accelerated aging of preservative-treated structural plywood

    Science.gov (United States)

    C. Adam Senalik; Robert J. Ross; Samuel L. Zelinka; Stan T. Lebow; Zhiyong Cai

    2017-01-01

    In this study, the changes in physical properties and preservative retention of high-grade plywood when subjected to artificial aging processes were examined. The plywood was 15/32-in.-thick panels manufactured from southern yellow pine A and C grades of veneer. The artificial aging processes consisted of three primary mechanisms of degradation: thermal degradation,...

  8. Estimation of age structure of fish populations from length-frequency data

    International Nuclear Information System (INIS)

    Kumar, K.D.; Adams, S.M.

    1977-01-01

    A probability model is presented to determine the age structure of a fish population from length-frequency data. It is shown that when the age-length key is available, maximum-likelihood estimates of the age structure can be obtained. When the key is not available, approximate estimates of the age structure can be obtained. The model is used for determination of the age structure of populations of channel catfish and white crappie. Practical applications of the model to impact assessment are discussed

  9. The Vintage Effect in TPF-Growth : An Analysis of the Age Structure of Capital

    NARCIS (Netherlands)

    Gittleman, M.; Ten Raa, T.; Wolff, E.N.

    2003-01-01

    The age structure of capital plays an important role in the measurement of productivity.It has been argued that the slowdown in the 1970 s can be ascribed to the aging of the stock of capital.In this paper we incorporate the age structure in productivity measurement.One proposition proves that

  10. Monitoring post-fire changes in species composition and stand structure in boreal forests using high-resolution, 3-D aerial drone data and Landsat

    Science.gov (United States)

    Alonzo, M.; Morton, D. C.; Cook, B.; Andersen, H. E.; Mack, M. C.

    2017-12-01

    The growing frequency and severity of boreal forest fires has important consequences for fire carbon emissions and ecosystem composition. Severe fires are typically associated with high degrees of both canopy and soil organic layer (SOL) consumption, particularly in black spruce stands. Complete canopy consumption can decrease the likelihood of spruce regeneration due to reduced viability of the aerial seedbank. Deeper burning of the SOL increases fire emissions and can expose mineral soil that promotes colonization by broadleaf species. There is mounting evidence that a disturbance-driven shift from spruce to broadleaf forests may indicate an ecological state change with feedbacks to regional and global climate. If post-fire successional dynamics can be characterized at an ecosystem scale using remote sensing data, we will be better equipped to constrain carbon and energy fluxes from SOL losses and albedo changes. In this study, we used Landsat time series, very high-resolution structure-from-motion (SFM) drone imagery, and field measurements to investigate post-fire regrowth 13 years after the 2004 Taylor Complex (TC) fires in interior Alaska. Twenty-seven TC plots span a gradient of moisture conditions and burn severity as estimated by loss of SOL. A range of variables potentially governing seedling species dominance (e.g., moisture status, distance to seed sources) have been collected systematically over the years following fire. In July 2017, we additionally collected 700 pts/m2) RGB-colored point clouds using SFM techniques. With these point clouds and high resolution orthomosaics, we estimated: 1) snag heights and biomass, 2) remnant snag fine branching, and 3) species and structure of shrubs and groundcover that have regrown since fire. We additionally assembled a dense Landsat time series arranged by day-of-year to monitor pre-fire and post-fire phenology. Our preliminary results illustrate how ultra-fine and moderate-scale remote sensing can be used to

  11. Population structure, density and food sources of Terebralia palustris (Potamididae: Gastropoda) in a low intertidal Avicennia marina mangrove stand (Inhaca Island, Mozambique)

    Science.gov (United States)

    Penha-Lopes, Gil; Bouillon, Steven; Mangion, Perrine; Macia, Adriano; Paula, José

    2009-09-01

    Population structure and distribution of Terebralia palustris were compared with the environmental parameters within microhabitats in a monospecific stand of Avicennia marina in southern Mozambique. Stable carbon and nitrogen isotope analyses of T. palustris and potential food sources (leaves, pneumatophore epiphytes, and surface sediments) were examined to establish the feeding preferences of T. palustris. Stable isotope signatures of individuals of different size classes and from different microhabitats were compared with local food sources. Samples of surface sediments 2.5-10 m apart showed some variation (-21.2‰ to -23.0‰) in δ13C, probably due to different contributions from seagrasses, microalgae and mangrove leaves, while δ15N values varied between 8.7‰ and 15.8‰, indicating that there is a very high variability within a small-scale microcosm. Stable isotope signatures differed significantly between the T. palustris size classes and between individuals of the same size class, collected in different microhabitats. Results also suggested that smaller individuals feed on sediment, selecting mainly benthic microalgae, while larger individuals feed on sediment, epiphytes and mangrove leaves. Correlations were found between environmental parameters and gastropod population structure and distribution vs. the feeding preferences of individuals of different size classes and in different microhabitats. While organic content and the abundance of leaves were parameters that correlated best with the total density of gastropods (>85%), the abundance of pneumatophores and leaves, as well as grain size, correlated better with the gastropod size distribution (>65%). Young individuals (height < 3 cm) occur predominantly in microhabitats characterized by a low density of leaf litter and pneumatophores, reduced organic matter and larger grain size, these being characteristic of lower intertidal open areas that favour benthic microalgal growth. With increasing shell

  12. Motor Control and Aging: Links to Age-Related Brain Structural, Functional, and Biochemical Effects

    OpenAIRE

    Seidler, Rachael D.; Bernard, Jessica A.; Burutolu, Taritonye B.; Fling, Brett W.; Gordon, Mark T.; Gwin, Joseph T.; Kwak, Youngbin; Lipps, David B.

    2009-01-01

    Although connections between cognitive deficits and age-associated brain differences have been elucidated, relationships with motor performance are less well understood. Here, we broadly review age-related brain differences and motor deficits in older adults in addition to cognition-action theories. Age-related atrophy of the motor cortical regions and corpus callosum may precipitate or coincide with motor declines such as balance and gait deficits, coordination deficits, and movement slowing...

  13. Forest evaporation models: Relationships between stand growth and evaporation

    CSIR Research Space (South Africa)

    Le Maitre, David C

    1997-06-01

    Full Text Available The relationships between forest stand structure, growth and evaporation were analysed to determine whether forest evaporation can be estimated from stand growth data. This approach permits rapid assessment of the potential impacts of afforestation...

  14. The age structure of the Milky Way's halo

    Science.gov (United States)

    Carollo, D.; Beers, T. C.; Placco, V. M.; Santucci, R. M.; Denissenkov, P.; Tissera, P. B.; Lentner, G.; Rossi, S.; Lee, Y. S.; Tumlinson, J.

    2016-12-01

    We present a new, high-resolution chronographic (age) map of the Milky Way's halo, based on the inferred ages of ~130,000 field blue horizontal-branch (BHB) stars with photometry from the Sloan Digital Sky Survey. Our map exhibits a strong central concentration of BHB stars with ages greater than 12 Gyr, extending up to ~15 kpc from the Galactic Centre (reaching close to the solar vicinity), and a decrease in the mean ages of field stars with distance by 1-1.5 Gyr out to ~45-50 kpc, along with an apparent increase of the dispersion of stellar ages, and numerous known (and previously unknown) resolved over-densities and debris streams, including the Sagittarius Stream. These results agree with expectations from modern lambda cold dark matter cosmological simulations, and support the existence of a dual (inner/outer) halo system, punctuated by the presence of over-densities and debris streams that have not yet completely phase-space mixed.

  15. Stand structure and regeneration of a mixed forest (Abies alba-Fagus sylvatica in the Central Pyrenees, Ordesa National Park, Spain

    Directory of Open Access Journals (Sweden)

    Doležal, J.

    2004-12-01

    Full Text Available The locations and biometrical characteristics of 2391 living and dead trees > 1.3 m tall of Abies alba and Fagus sylvatica, and the 378 understory shrubs o/Buxus sempervirens, were mapped in a 1.4 ha plot on the northern slope of Ordesa Valley to evaluate several hypotheses about stand structural development, tree species regeneration and coexistence. The plot is located in relatively undisturbed old-growth forest, but contains areas at low elevation which were formerly pasture. Abies is typically represented by many young trees and gradually declining numbers of trees in successively older size classes, whereas Fagus has greater numbers of trees in larger size and older age classes. This would imply a shift in dominance from beech to fir if the two species have similar mortality rates. We tested two hypotheses about the coexistence of ecologically similar species: (1 based on differentiation of regeneration niches, and (2 by means of different life history strategies (preference for survivorship or fecundity. Redundancy analysis (RDA was used to determine if the two species prefer different habitats. The analysis of spatial patterns and interspecific associations by Ripley's K-function was used to estimate the role of competition among trees in forest dynamics. The data provide empirical support for both tested hypotheses, although it has been shown that their importance varies depending on the degree of environmental heterogeneity along the slope across the plot. Different life history strategies appear critical to the success of coexistence in moderate environment at lower elevations, where co-dominant species have overlapping regeneration niches.

    [fr] Dans une parcelle de 1, 4 Ha au versant nord de la vallée d'Ordesa nous avons cartographie à petite échelle et pris des données biométriques sur 2391 hêtres (Fagus sylvatica et sapins (Abies alba vivants ou morts mais tous s'élevant à plus de 1,3 m, ainsi

  16. Analysis of Fish Age Structure and Growth in the Illinois River

    Science.gov (United States)

    2007-06-01

    ULong Term Resource Monitoring Program Technical Report 2007-TO02 Analysis of Fish Age Structure and Growth in the Illinois River DISTRIBUTION...qWycsp Analysis of Fish Age Structure and Growth in the Illinois River by Michael A. Smith, Mark A. Pegg, and Kevin S. Irons Report submitted to U.S. Army...Analysis of fish age structure and growth in the Illinois River. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse

  17. On the dynamics of the age structure, dependency, and consumption

    Science.gov (United States)

    Hock, Heinrich

    2013-01-01

    We examine the effects of population aging due to declining fertility and rising elderly life expectancy on consumption possibilities in the presence of intergenerational transfers. Our analysis is based on a highly tractable continuous-time overlapping generations model in which the population is divided into three groups (youth dependents, workers, and elderly dependents) and lifecourse transitions take place in a probabilistic fashion. We show that the consumption-maximizing response to greater longevity in highly developed countries is an increase in fertility. However, with larger transfer payments, the actual fertility response will likely be the opposite, leading to further population aging. PMID:24353374

  18. FY 2017 – Thermal Aging Effects on Advanced Structural Materials

    Energy Technology Data Exchange (ETDEWEB)

    Li, Meimei [Argonne National Lab. (ANL), Argonne, IL (United States); Natesan, K [Argonne National Lab. (ANL), Argonne, IL (United States); Chen, Wei-Ying [Argonne National Lab. (ANL), Argonne, IL (United States)

    2017-08-01

    This report provides an update on the evaluation of the effect of thermal aging on tensile properties of existing laboratory-sized heats of Alloy 709 austenitic stainless steel and the completion of effort on the thermal aging effect on the tensile properties of optimized G92 ferritic-martensitic steel. The report is a Level 3 deliverable in FY17 (M3AT-17AN1602081), under the Work Package AT-17AN160208, “Advanced Alloy Testing - ANL” performed by the Argonne National Laboratory (ANL), as part of the Advanced Reactor Technologies Program.

  19. On the dynamics of the age structure, dependency, and consumption.

    Science.gov (United States)

    Hock, Heinrich; Weil, David N

    2012-07-01

    We examine the effects of population aging due to declining fertility and rising elderly life expectancy on consumption possibilities in the presence of intergenerational transfers. Our analysis is based on a highly tractable continuous-time overlapping generations model in which the population is divided into three groups (youth dependents, workers, and elderly dependents) and lifecourse transitions take place in a probabilistic fashion. We show that the consumption-maximizing response to greater longevity in highly developed countries is an increase in fertility. However, with larger transfer payments, the actual fertility response will likely be the opposite, leading to further population aging.

  20. Structure and Correlates of Cognitive Aging in a Narrow Age Cohort

    Science.gov (United States)

    2014-01-01

    Aging-related changes occur for multiple domains of cognitive functioning. An accumulating body of research indicates that, rather than representing statistically independent phenomena, aging-related cognitive changes are moderately to strongly correlated across domains. However, previous studies have typically been conducted in age-heterogeneous samples over longitudinal time lags of 6 or more years, and have failed to consider whether results are robust to a comprehensive set of controls. Capitalizing on 3-year longitudinal data from the Lothian Birth Cohort of 1936, we took a longitudinal narrow age cohort approach to examine cross-domain cognitive change interrelations from ages 70 to 73 years. We fit multivariate latent difference score models to factors representing visuospatial ability, processing speed, memory, and crystallized ability. Changes were moderately interrelated, with a general factor of change accounting for 47% of the variance in changes across domains. Change interrelations persisted at close to full strength after controlling for a comprehensive set of demographic, physical, and medical factors including educational attainment, childhood intelligence, physical function, APOE genotype, smoking status, diagnosis of hypertension, diagnosis of cardiovascular disease, and diagnosis of diabetes. Thus, the positive manifold of aging-related cognitive changes is highly robust in that it can be detected in a narrow age cohort followed over a relatively brief longitudinal period, and persists even after controlling for many potential confounders. PMID:24955992

  1. Introducing sit-stand desks increases classroom standing time among university students

    Directory of Open Access Journals (Sweden)

    Matthew Jerome

    2017-12-01

    Full Text Available Excessive sedentary behavior has been associated with many negative health outcomes. While an understudied health topic, there is evidence that university students are excessively sedentary. Sit-stand desks have been shown to reduce sedentary time among pre-university students (ages 5–18years and sedentary workers but have not been tested in university classrooms. This study tested the effects of introducing sit-stand desks into a university classroom on student's classroom sitting and standing behaviors. Using a cross-over design, students received access to both traditional seated desks and sit-stand desks for six weeks. Data were collected between September and December, 2016. We recruited 304 healthy undergraduate university students enrolled in one of two small (25 seats classrooms at a large Midwestern university during the fall of 2016. Average minutes of standing/hour/student, average percent class time spent standing, and the number of sit-stand transitions/student/hour were directly observed with video camera surveillance. Participants stood significantly more (p<0.001 when provided access to sit-stand desks (7.2min/h/student; 9.3% of class time spent standing compared to when they had access to seated desks (0.7min/h/student; 1.6% of class time spent standing but no differences were observed for the number of sit-stand transitions (p=0.47. Students reported high favorability for the sit-stand desks and improvements in several student engagement and affective outcomes while using the sit-stand desks. These findings support introducing sit-stand desks in university classrooms as an approach to reduce sedentary behaviors of university students. Keywords: Sedentary, University students, Sit-stand desk

  2. [Age structure and dynamics of Keteleeria davidiana var. chien-peii population in Guizhou Province].

    Science.gov (United States)

    Liang, Shich; Li, Jiulin; Cheng, Shize

    2002-01-01

    Type and dynamics of age structure of Keteleeria davidiana var. chien-peii population and its relationship to community succession and environment were analyzed. The results showed that the age structures were classified into four types:growing, stable, initial and middle sensecent types. The survival curves had concave, convex, disconnected and dotted shapes. Along with development and succession of community, the age structure changes from growing, stabilized, senescent to residual type. The important factors causing change to the age structure were biological features of Keteleeria davidiana var. chien-peii, development of broad-leaved tree species, geographic isolation, and human disturbance.

  3. Reading in Healthy Aging: Selective Use of Information Structuring Cues

    Science.gov (United States)

    Price, Jessica M.; Sanford, Anthony J.

    2018-01-01

    Previous research has shown that information referring to a named character or to information in the main clause of a sentence is more accessible and facilitates the processing of anaphoric references. We investigated whether the use of such cues are maintained in healthy aging. We present two experiments investigating whether information…

  4. Can anchovy age structure be estimated from length distribution ...

    African Journals Online (AJOL)

    The analysis provides a new time-series of proportions-at-age 1, together with associated standard errors, for input into assessments of the resource. The results also caution against the danger of scientists reading more information into data than is really there. Keywords: anchovy, effective sample size, length distribution, ...

  5. Sex difference in age-related changes in knee extensor strength and power production during a 10-times-repeated sit-to-stand task in Japanese elderly.

    Science.gov (United States)

    Yanagawa, Naoko; Shimomitsu, Teruichi; Kawanishi, Masashi; Fukunaga, Tetsuo; Kanehisa, Hiroaki

    2015-11-14

    For middle-aged and elderly women, age-related decline in an index representing power production during STS task (STS-PI), calculated by using an equation reported previously, has been shown to be greater than that in the force generation capability of lower extremity. Whether this is specific to women remains unclear. This study examined how the age-related changes in knee extensor strength and power production during STS differ between Japanese men and women aged 65 years or older. The time taken for a 10-times-repeated STS test (STS time) and force developed during maximal voluntary isometric knee extension (KE-F) were determined in Japanese younger-old (262 men and 285 women) aged 65-74 years and older-old (96 men and 89 women) aged 75-90 years. STS-PI was calculated using the following equation: STS-PI = (body height - 0.4) × body mass × 10/STS time. KE-F and STS-PI were significantly greater in the younger-old than in the older-old group (p movement such as STS in older women than in older men.

  6. Low-temperature atomic layer deposition of SiO2/Al2O3 multilayer structures constructed on self-standing films of cellulose nanofibrils

    Science.gov (United States)

    Putkonen, Matti; Sippola, Perttu; Svärd, Laura; Sajavaara, Timo; Vartiainen, Jari; Buchanan, Iain; Forsström, Ulla; Simell, Pekka; Tammelin, Tekla

    2017-12-01

    In this paper, we have optimized a low-temperature atomic layer deposition (ALD) of SiO2 using AP-LTO® 330 and ozone (O3) as precursors, and demonstrated its suitability to surface-modify temperature-sensitive bio-based films of cellulose nanofibrils (CNFs). The lowest temperature for the thermal ALD process was 80°C when the silicon precursor residence time was increased by the stop-flow mode. The SiO2 film deposition rate was dependent on the temperature varying within 1.5-2.2 Å cycle-1 in the temperature range of 80-350°C, respectively. The low-temperature SiO2 process that resulted was combined with the conventional trimethyl aluminium + H2O process in order to prepare thin multilayer nanolaminates on self-standing CNF films. One to six stacks of SiO2/Al2O3 were deposited on the CNF films, with individual layer thicknesses of 3.7 nm and 2.6 nm, respectively, combined with a 5 nm protective SiO2 layer as the top layer. The performance of the multilayer hybrid nanolaminate structures was evaluated with respect to the oxygen and water vapour transmission rates. Six stacks of SiO2/Al2O with a total thickness of approximately 35 nm efficiently prevented oxygen and water molecules from interacting with the CNF film. The oxygen transmission rates analysed at 80% RH decreased from the value for plain CNF film of 130 ml m-2 d-1 to 0.15 ml m-2 d-1, whereas the water transmission rates lowered from 630 ± 50 g m-2 d-1 down to 90 ± 40 g m-2 d-1. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

  7. Ames and other European networks in integrity of ageing structures

    International Nuclear Information System (INIS)

    Davies, L.M.; Von Estorff, U.; Crutzen, S.

    1996-01-01

    Several European institutions and organisations and the Joint Research Centre have developed co-operative programmes now organised into Networks for mutual benefit. They include utilities, engineering companies, Research and Development laboratories and regulatory bodies. Networks are organised and managed like the successful Programme for the Inspection of Steel Components (PISC). The JRC's Institute for Advanced Materials of the European Commission plays the role of Operating Agent and manager of these Networks: ENIQ. AMES, NESC, each of them dealing with specific aspect of fitness for purpose of materials in structural components. This paper describes the structure and the objectives of these networks. Particular emphasis is given to the network AMES

  8. Factor structure of functional state of primary school age children

    Directory of Open Access Journals (Sweden)

    Davidenko O.V.

    2011-02-01

    Full Text Available The examination of primary school children to determine the ranking of significant factors that determine the structure of their functional state depending on the level of physical health. It is shown that the main factor in the structure of the functional state of younger schoolchildren in low-and lower-middle level of physical fitness is selected morpho-functional status, which characterizes the functions of the body at rest. For children with average or above average level of physical fitness is a leading factor in physical fitness of schoolchildren.

  9. Age structure of refractory interstellar dust and isotopic consequences

    Science.gov (United States)

    Clayton, Donald D.; Scowen, Paul; Liffman, Kurt

    1989-01-01

    A sputtering and recycling Monte Carlo model, developed by Liffman and Clayton (1988) is used to calculate the distribution of existence times of the matter in interstellar dust composed of refractory metals. The mean age of each dust particle is defined not as the time it has existed but rather as the mass-weighted existence times of its parts at t = 6 Gyr of the modeled solar system formation. It is shown that Galactic evolution generates a mean correlation, applying to large numbers of particles binned according to size rather than according to individual particles, whose mean ages fluctuate statistically. The cosmochemical consequence is that if interstellar particles can be dynamically sorted into separate size populations during the aggregation history of solar system bodies, the collections of larger grains will constitute matter that is chemically older than collections of smaller grains. The macroscopic age difference generates isotopic anomalies by virtue of the time dependence of the secondary/primary nucleosynthesis yields. Results are compared with three different prescriptions for the sputtering of interstellar dust.

  10. Motor control and aging: links to age-related brain structural, functional, and biochemical effects.

    Science.gov (United States)

    Seidler, Rachael D; Bernard, Jessica A; Burutolu, Taritonye B; Fling, Brett W; Gordon, Mark T; Gwin, Joseph T; Kwak, Youngbin; Lipps, David B

    2010-04-01

    Although connections between cognitive deficits and age-associated brain differences have been elucidated, relationships with motor performance are less well understood. Here, we broadly review age-related brain differences and motor deficits in older adults in addition to cognition-action theories. Age-related atrophy of the motor cortical regions and corpus callosum may precipitate or coincide with motor declines such as balance and gait deficits, coordination deficits, and movement slowing. Correspondingly, degeneration of neurotransmitter systems-primarily the dopaminergic system-may contribute to age-related gross and fine motor declines, as well as to higher cognitive deficits. In general, older adults exhibit involvement of more widespread brain regions for motor control than young adults, particularly the prefrontal cortex and basal ganglia networks. Unfortunately these same regions are the most vulnerable to age-related effects, resulting in an imbalance of "supply and demand". Existing exercise, pharmaceutical, and motor training interventions may ameliorate motor deficits in older adults. Copyright 2009 Elsevier Ltd. All rights reserved.

  11. Avaliação de um modelo de passo invariante na predição da estrutura de um povoamento de Eucalyptus sp. Evaluation of a step invariant model for the prediction of eucalyptus stand structure

    Directory of Open Access Journals (Sweden)

    Thelma Shirlen Soares

    2007-04-01

    Full Text Available O objetivo deste estudo foi avaliar o modelo de distribuição diamétrica de passo invariante proposto por Guimarães (1994 na projeção da produção de um povoamento de Eucalyptus sp., simulando as alterações nas estruturas horizontal e vertical ao longo do tempo. Utilizaram-se dados da primeira rotação de povoamentos de eucalipto híbrido estaca (Eucalyptus grandis x Eucalyptus urophylla, plantados no espaçamento 3,0 x 2,0 m, localizados na região noroeste do Estado da Bahia, provenientes de medições anuais com idade de medição variando entre 25 e 89 meses. Para realizar as prognoses, foram empregados percentis tomados a 50 e 75% da distribuição diamétrica e as alturas correspondentes aos diâmetros nessas posições. Verificou-se que o modelo de projeção é factível e pode ser utilizado com eficiência, já que ocorreram tendências semelhantes entre os volumes prognosticados e os observados nas parcelas. Além disso, devido à sua simplicidade e à compatibilidade dos resultados, recomenda-se a sua utilização na projeção do crescimento e produção de Eucalyptus sp.This study was carried out to evaluate the step-invariant diametric distribution model, proposed by Guimarães (1994, for the prediction of a Eucalyptus stand production, simulating the alterations in the horizontal and vertical structures with time. Data were taken from annual measurements, with measurement age between 25 and 89 months, of the first rotation of hybrid eucalyptus stands (Eucalyptus grandis x Eucalyptus urophylla, plant spacing of 3.0 x 2.0 m, located in the northeast region of State of Bahia. To perform prognoses percentiles were taken at 50 and 75% of the diametric distribution, and the heights corresponding to the diameters in these positions. The prediction model was proved to be feasible for efficient use, since there were similar tendencies between the forecasted and the observed volumes in the plots. Besides, its use in growth and

  12. Structure and Composition of Vegetation on Longleaf Plantation Sites Compared to Natural Stands Occurring Along an Environmental Gradient at the Savannah River Site

    Energy Technology Data Exchange (ETDEWEB)

    Smith, G.P.

    2000-10-01

    The diversity and abundance of native grasses and herbaceous species characteristic of the longleaf savanna were compared between remnant stands that were not previously under agriculture and recent old-fields.The objective of the study was to establish a baseline for future restoration objectives and to compare the degree of degradation associated with agriculture. In most cases even the natural stands have suffered degradation as a result of fire exclusion and as such are not representative of pristine conditions. Community classification and ordination procedures were implemented to array the communities. Three distinct sub-units were identified and associated with xeric, sub-xeric, and medic types associated with texture and soil moisture. Between plantations and natural stands, the xeric group demonstrated the most similarity. The presence of a B horizon was the most important discriminate variable in both groups.

  13. Conversion of cropland to forest increases soil CH4 oxidation and abundance of CH4 oxidizing bacteria with stand age

    DEFF Research Database (Denmark)

    Bárcena, Teresa G; D'Imperio, Ludovica; Gundersen, Per

    2014-01-01

    We investigated CH4 oxidation in afforested soils over a 200-year chronosequence in Denmark including different tree species (Norway spruce, oak and larch) and ages. Samples of the top mineral soil (0–5 cm and 5–15 cm depth) were incubated and analyzed for the abundance of the soil methane...

  14. Radiostratigraphy and age structure of the Greenland Ice Sheet.

    Science.gov (United States)

    MacGregor, Joseph A; Fahnestock, Mark A; Catania, Ginny A; Paden, John D; Prasad Gogineni, S; Young, S Keith; Rybarski, Susan C; Mabrey, Alexandria N; Wagman, Benjamin M; Morlighem, Mathieu

    2015-02-01

    Several decades of ice-penetrating radar surveys of the Greenland and Antarctic ice sheets have observed numerous widespread internal reflections. Analysis of this radiostratigraphy has produced valuable insights into ice sheet dynamics and motivates additional mapping of these reflections. Here we present a comprehensive deep radiostratigraphy of the Greenland Ice Sheet from airborne deep ice-penetrating radar data collected over Greenland by The University of Kansas between 1993 and 2013. To map this radiostratigraphy efficiently, we developed new techniques for predicting reflection slope from the phase recorded by coherent radars. When integrated along track, these slope fields predict the radiostratigraphy and simplify semiautomatic reflection tracing. Core-intersecting reflections were dated using synchronized depth-age relationships for six deep ice cores. Additional reflections were dated by matching reflections between transects and by extending reflection-inferred depth-age relationships using the local effective vertical strain rate. The oldest reflections, dating to the Eemian period, are found mostly in the northern part of the ice sheet. Within the onset regions of several fast-flowing outlet glaciers and ice streams, reflections typically do not conform to the bed topography. Disrupted radiostratigraphy is also observed in a region north of the Northeast Greenland Ice Stream that is not presently flowing rapidly. Dated reflections are used to generate a gridded age volume for most of the ice sheet and also to determine the depths of key climate transitions that were not observed directly. This radiostratigraphy provides a new constraint on the dynamics and history of the Greenland Ice Sheet. Phase information predicts reflection slope and simplifies reflection tracingReflections can be dated away from ice cores using a simple ice flow modelRadiostratigraphy is often disrupted near the onset of fast ice flow.

  15. Toward a Demographic Understanding of Incarceration Disparities: Race, Ethnicity, and Age Structure.

    Science.gov (United States)

    Vogel, Matt; Porter, Lauren C

    2016-01-01

    Non-Hispanic blacks and Hispanics in the United States are more likely to be incarcerated than non-Hispanic whites. The risk of incarceration also varies with age, and there are striking differences in age distributions across racial/ethnic groups. Guided by these trends, the present study examines the extent to which differences in age structure account for incarceration disparities across racial and ethnic groups. We apply two techniques commonly employed in the field of demography, age-standardization and decomposition, to data provided by the Bureau of Justice Statistics and the 2010 decennial census to assess the contribution of age structure to racial and ethnic disparities in incarceration. The non-Hispanic black and Hispanic incarceration rates in 2010 would have been 13-20 % lower if these groups had age structures identical to that of the non-Hispanic white population. Moreover, age structure accounts for 20 % of the Hispanic/white disparity and 8 % of the black/white disparity. The comparison of crude incarceration rates across racial/ethnic groups may not be ideal because these groups boast strikingly different age structures. Since the risk of imprisonment is tied to age, criminologists should consider adjusting for age structure when comparing rates of incarceration across groups.

  16. 15 CFR 50.5 - Fee structure for age search and citizenship information.

    Science.gov (United States)

    2010-01-01

    ... THE CENSUS § 50.5 Fee structure for age search and citizenship information. Type of service Fee... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Fee structure for age search and citizenship information. 50.5 Section 50.5 Commerce and Foreign Trade Regulations Relating to Commerce and...

  17. Age-structure-dependent recruitment: a meta-analysis applied to Northeast Atlantic fish stocks

    NARCIS (Netherlands)

    Brunel, T.P.A.

    2010-01-01

    Exploitation alters the age structure of fish stocks. Several stock-specific studies have suggested that changes in the age structure might have consequences for subsequent recruitment, but the evidence is not universal. To investigate how common such effects are among 39 Northeast Atlantic fish

  18. Is age structure a relevant criterion for the health of fish stocks?

    NARCIS (Netherlands)

    Brunel, T.P.A.; Piet, G.J.

    2013-01-01

    The age and size structure of exploited fish stocks is one of the criteria for Good Environmental Status of commercial fish. However, two underlying assumptions to this criterion remain to be tested: first, that a well-balanced age structure is indeed indicative of a “healthier” stock, and second,

  19. Planter unit test stand

    Science.gov (United States)

    A planter test stand was developed to evaluate individual row-crop metering units in early 2013. This test stand provided the ability to quantify actual seed metering in terms of population, seed spacing, skips, and multiples over a range of meter RPMs and vacuum pressures. Preliminary data has been...

  20. Experimental research on the structural characteristics of high organic soft soil in different deposition ages

    Science.gov (United States)

    Liu, Fei; Lin, Guo-he

    2018-03-01

    High organic soft soil, which is distributed at Ji Lin province in China, has been studied by a lot of scholars. In the paper, structural characteristics with different deposition ages have been researched by experimental tests. Firstly, the characteristics of deposition age, degree of decompositon, high-pressure consolidation and microstructure have been measured by a series of tests. Secondly, structural strengths which were deposited in different ages, have been carried out to test the significant differences of stress-strain relations between remoulded and undisturbed high organic soft soil samples. Results showed that high organic soft soil which is deposited at different ages will influence its structural characteristics.

  1. Predictive Modeling of Black Spruce (Picea mariana (Mill. B.S.P. Wood Density Using Stand Structure Variables Derived from Airborne LiDAR Data in Boreal Forests of Ontario

    Directory of Open Access Journals (Sweden)

    Bharat Pokharel

    2016-12-01

    Full Text Available Our objective was to model the average wood density in black spruce trees in representative stands across a boreal forest landscape based on relationships with predictor variables extracted from airborne light detection and ranging (LiDAR point cloud data. Increment core samples were collected from dominant or co-dominant black spruce trees in a network of 400 m2 plots distributed among forest stands representing the full range of species composition and stand development across a 1,231,707 ha forest management unit in northeastern Ontario, Canada. Wood quality data were generated from optical microscopy, image analysis, X-ray densitometry and diffractometry as employed in SilviScan™. Each increment core was associated with a set of field measurements at the plot level as well as a suite of LiDAR-derived variables calculated on a 20 × 20 m raster from a wall-to-wall coverage at a resolution of ~1 point m−2. We used a multiple linear regression approach to identify important predictor variables and describe relationships between stand structure and wood density for average black spruce trees in the stands we observed. A hierarchical classification model was then fitted using random forests to make spatial predictions of mean wood density for average trees in black spruce stands. The model explained 39 percent of the variance in the response variable, with an estimated root mean square error of 38.8 (kg·m−3. Among the predictor variables, P20 (second decile LiDAR height in m and quadratic mean diameter were most important. Other predictors describing canopy depth and cover were of secondary importance and differed according to the modeling approach. LiDAR-derived variables appear to capture differences in stand structure that reflect different constraints on growth rates, determining the proportion of thin-walled earlywood cells in black spruce stems, and ultimately influencing the pattern of variation in important wood quality attributes

  2. Age-related changes in grey and white matter structure throughout adulthood

    OpenAIRE

    Giorgio, Antonio; Santelli, Luca; Tomassini, Valentina; Bosnell, Rose; Smith, Steve; De Stefano, Nicola; Johansen-Berg, Heidi

    2010-01-01

    Normal ageing is associated with gradual brain atrophy. Determining spatial and temporal patterns of change can help shed light on underlying mechanisms. Neuroimaging provides various measures of brain structure that can be used to assess such age-related change but studies to date have typically considered single imaging measures. Although there is consensus on the notion that brain structure deteriorates with age, evidence on the precise time course and spatial distribution of changes is mi...

  3. Derivation of stochastic partial differential equations for size- and age-structured populations.

    Science.gov (United States)

    Allen, Edward J

    2009-01-01

    Stochastic partial differential equations (SPDEs) for size-structured and age- and size-structured populations are derived from basic principles, i.e. from the changes that occur in a small time interval. Discrete stochastic models of size-structured and age-structured populations are constructed, carefully taking into account the inherent randomness in births, deaths, and size changes. As the time interval decreases, the discrete stochastic models lead to systems of Itô stochastic differential equations. As the size and age intervals decrease, SPDEs are derived for size-structured and age- and size-structured populations. Comparisons between numerical solutions of the SPDEs and independently formulated Monte Carlo calculations support the accuracy of the derivations.

  4. Forest growth along a rainfall gradient in Hawaii: Acacia koa stand structure, productivity, foliar nutrients, and water- and nutrient-use efficiencies

    Science.gov (United States)

    Robin A. Harrington; James H. Fownes; Frederick C. Meinzer; Paul G. Scowcroft

    1995-01-01

    We tested whether variation in growth of native koa (Acacia koa) forest along a rainfall gradient was attributable to differences in leaf area index (LAI) or to differences in physiological performance per unit of leaf area. Koa stands were studied on western Kauai prior to Hurricane Iniki, and ranged from 500 to 1130 m elevation and from 850 to...

  5. Developments to the Sylvan stand structure model to describe wood quality changes in southern bottomland hardwood forests because of forest management

    Science.gov (United States)

    Ian R. Scott

    2009-01-01

    Growth models can produce a wealth of detailed information that is often very difficult to perceive because it is frequently presented either as summary tables, stand view or landscape view visualizations. We have developed new tools for use with the Sylvan model (Larsen 1994) that allow the analysis of wood-quality changes as a consequence of forest management....

  6. Stand Dynamics, Humus Type and Water Balance Explain Aspen Long Term Productivity across Canada

    Directory of Open Access Journals (Sweden)

    Kenneth A. Anyomi

    2015-02-01

    Full Text Available This study examined the relative importance of soil, stand development and climate hypotheses in driving productivity for a species that is widely distributed in North America. Inventory plots, 3548 of such, either dominated by aspen or made up of species mixture of which aspen occurs in dominant canopy position were sampled along a longitudinal gradient from Quebec to British Columbia. Site index (SI, was used as a measure of productivity, and soil, climate and stand attributes were correlated with site index in order to determine their effects on productivity. Results show a decline in productivity with high moisture deficit. Soil humus correlates significantly with SI but does not sufficiently capture differential rates of litter deposition and decomposition effects over the long-term. Consequently, aspen composition, stand ageing, and stand structural changes dominate variability in productivity. Within the context where deciduous cover has being increasing, there are implications for forest productivity.

  7. Evidences from long-term monitoring of Italian forests. Tree radial growth as response index to disturbances and its relations with the stand structure

    Directory of Open Access Journals (Sweden)

    Bertini G

    2013-09-01

    Full Text Available The paper deals with the work undertaken since 1995 within the national level II network framed into the ICP-Forests ICP-IM programme. A synthesis of results from tree growth monitoring and relationships with stand structure and related parameters, are reported. Current changes in the growth medium, i.e. physics and chemistry of atmosphere and soil, (increase of average air temperature, rainfall shortage and drought, CO2 enrichment, ozone level, nitrogen fertilization, sulphate deposition drive today the soil-tree-atmosphere relationships. The overall result of these concurrent and counteracting factors is recorded along each growing seasons by radial stem growth, it providing a sensitive response. A few occurrences of disturbances to growth at regional and at case-study level, likely due to climate deviations, are discussed. Seasonal fluctuations and anomalous or extreme events are, as a matter of fact, the major evidences over the last decade. The heat wave 2003 is the main case occurred over a large part of Europe. Growth rate 2000-04 compared with 1997-2000, showed reductions up to 50% on plots located within the Southern continental border of the heat wave. These occurred more specifically at low elevations and for pre-determined early growth species (beech and oaks. Over the following time-window 2005-09, a significant growth decrease was vice versa detected within the coniferous spruce forests located at medium-high elevation in the Alps, where repeated seasonal anomalies both in air temperature and rainfall were recorded over the same time-span. The heavy effect of climate disturbance at a local scale is finally examined where two oak species with different auto-ecology grow together at the same site. Reasons why and awaited goals from protocols’ updating and the more intensive surveys applied to core-areas in 2009-10 under LIFE+FutMon, are reported. Perspectives at short to medium term of monitoring programme at national and European

  8. Long-standing poliomyelitis and psychological health.

    Science.gov (United States)

    Shiri, Shimon; Gartsman, Irina; Meiner, Zeev; Schwartz, Isabella

    2015-01-01

    To compare the psychological health of the individuals with long-standing poliomyelitis, with or without post-polio syndrome (PPS), to the general population and to identify the role of work as well as other variables with regard to their psychological health. A cross-sectional study. One hundred and ninety-five polio patients attending postpolio clinic in Jerusalem. Emotional distress (ED) was measured using the general health questionnaire (GHQ-12). Demographic, medical, social and functional data were recorded using a specific structured questionnaire. Each polio patient was compared to four age- and sex-matched controls. ED was higher in the polio population as compared to the general population. Within the polio population ED was inversely correlated with work status. No correlation was found between ED and the functional level of polio participants and no difference was found in GHQ score between polio participants with or without post-polio. In addition, ED was less affected by subjective perception of physical health among polio patients as compared to the general population. Long-standing poliomyelitis is associated with decreased psychological health as compared to the general population. Yet, the resilience of polio survivors is manifested by their ability to block further decline of their psychological health in spite of deterioration in their physical health. Work appears as a significant source of resilience in the polio population. Implications for Rehabilitation Individuals with long-standing poliomyelitis often suffer from high emotional distress and may benefit from psychotherapy aimed at reducing distress. As active employment status is associated with increased mental health among polio survivors, encouraging participation at work needs to be a significant component of psychotherapeutic programs. Polio survivors, although physically disabled, may be relatively resilient, as their mental health is less affected by their negative health perception

  9. Forest age structure as indicator of boreal forest sustainability under alternative management and fire regimes: a landscape level sensitivity analysis

    NARCIS (Netherlands)

    Didion, M.P.; Fortin, M.J.; Fall, A.

    2007-01-01

    Effective forest ecosystem-based management requires a thorough understanding of the interactions between anthropogenic and natural disturbance processes over larger spatial and temporal scales than stands and rotation ages. Because harvesting does not preclude fire, it is important to evaluate the

  10. Investigating the Theoretical Structure of the DAS-II Core Battery at School Age Using Bayesian Structural Equation Modeling

    Science.gov (United States)

    Dombrowski, Stefan C.; Golay, Philippe; McGill, Ryan J.; Canivez, Gary L.

    2018-01-01

    Bayesian structural equation modeling (BSEM) was used to investigate the latent structure of the Differential Ability Scales-Second Edition core battery using the standardization sample normative data for ages 7-17. Results revealed plausibility of a three-factor model, consistent with publisher theory, expressed as either a higher-order (HO) or a…

  11. Age

    Science.gov (United States)

    ... Resources About Policymakers Media ASA Member Toolkit Risks Age Explore this page: Age Do anesthesia risks increase ... can you reduce anesthesia risks in older patients? Age Age may bring wisdom but it also brings ...

  12. Local-area age structure and population composition: implications for elderly health in Japan.

    Science.gov (United States)

    Vogelsang, Eric M; Raymo, James M

    2014-03-01

    This study examines relationships between local-area age structure and health at older ages. We estimate random intercept models for two disability measures using four waves of data from a national panel study of 3,580 Japanese older adults. Elderly living in relatively older areas reported more difficulties with activities of daily living compared with those living in an "average" age structure. Controlling for individual characteristics and time did little to change this relationship; while a similar relationship between older age structure and functional limitations emerged. Residents of relatively older areas tended to have lower socioeconomic status, but this "disadvantage" was offset by their higher rates of employment and marriage. These compositional differences highlight the role of local-area age structure in identifying and understanding elderly health variation between places.

  13. Structural Aging Program to evaluate continued performance of safety-related concrete structures in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

    1994-01-01

    This report discusses the Structural Aging (SAG) Program which is being conducted at the Oak Ridge National Laboratory (ORNL) for the United States Nuclear Regulatory commission (USNRC). The SAG Program is addressing the aging management of safety-related concrete structures in nuclear power plants for the purpose of providing improved technical bases for their continued service. The program is organized into three technical tasks: Materials Property Data Base, Structural Component Assessment/Repair Technologies, and Quantitative Methodology for continued Service Determinations. Objectives and a summary of recent accomplishments under each of these tasks are presented

  14. Structural aging program to evaluate continued performance of safety-related concrete structures in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

    1994-01-01

    The Structural Aging (SAG) Program is being conducted at the Oak Ridge National Laboratory (ORNL) for the United States Nuclear Regulatory Commission (USNRC). The SAG Program is addressing the aging management of safety-related concrete structures in nuclear power plants for the purpose of providing improved technical bases for their continued service. The program is organized into three technical tasks: Materials Property Data Base, Structural Component Assessment/Repair Technologies, and Quantitative Methodology for Continued Service Determinations. Objectives and a summary of recent accomplishments under each of these tasks are presented. (Author)

  15. Influence of Scarification on the Germination Capacity of Acorns Harvested from Uneven-Aged Stands of Pedunculate Oak (Quercus robur L.

    Directory of Open Access Journals (Sweden)

    Zdzisław Kaliniewicz

    2018-02-01

    Full Text Available Scarification involves the partial removal of the seed coat on the side of the hilum, opposite the radicle, to speed up germination in acorns. The aim of this study was to determine the influence of scarification on the germination capacity of pedunculate oak acorns, selected and prepared for sowing. The diameter, length and mass of acorns were measured before and after scarification in four batches of acorns harvested from uneven-aged trees (76, 91, 131 and 161 years. The measured parameters were used to determine the correlations between acorn dimensions and mass, and to calculate the dimensional scarification index and the mass scarification index in acorns. Individual complete and scarified acorns from every batch were germinated on sand and peat substrate for 28 days. The analyzed acorns were characterized by average size and mass. Scarification decreased acorn mass by around 22% and acorn length by around 31% on average. Scarification and the elimination of infected acorns increased germination capacity from around 64% to around 81% on average. Acorns can be divided into size groups before scarification to obtain seed material with varied germination capacity. Larger acorns with higher germination capacity can be used for sowing in container nurseries, whereas smaller acorns with lower germination capacity can be sown in open-field nurseries.

  16. Variable Attitude Test Stand

    Data.gov (United States)

    Federal Laboratory Consortium — The Variable Attitude Test Stand designed and built for testing of the V-22 tilt rotor aircraft propulsion system, is used to evaluate the effect of aircraft flight...

  17. Influence of competition and age on tree growth in structurally complex old-growth forests in northern Minnesota, USA

    Science.gov (United States)

    Tuomas Aakala; Shawn Fraver; Anthony W. D' Amato; Brian J. Palik

    2013-01-01

    Factors influencing tree growth in structurally complex forests remain poorly understood. Here we assessed the influence of competition on Pinus resinosa (n = 224) and Pinus strobus (n = 90) growth in four old-growth stands in Minnesota, using mixed effects models. A subset of trees, with...

  18. Population structure age of Paraná state between 1970 and 2010

    Directory of Open Access Journals (Sweden)

    Eduardo de Pintor

    2014-06-01

    Full Text Available The theory of demographic transition began with an effort of Frank Notestein (1945 to understand the demographic changes that were occurring in Western Europe since the late nineteenth century. The demographic transition is the transition between two scenarios of population growth, which changes the age structure of the population. The aim of the article is to discuss the evolution of population structure age of Paraná state between 1970 and 2010. The changes in the age structure of the Paraná indicate a reduction in the share of young population and increasing aging population, an increase in the relative weight of the elderly population. Public policies on education, health, social security and labor market should consider the current change in the age structure. Thus, the aim of this study was to analyze the change in the age structure of the population of the state of Paraná. For this we used data Censuses of the Brazilian Institute of Geography and Statistics (IBGE on the age distribution of urban and rural Paraná and its Mesoregions. It was concluded that the change in structure occurs group widespread in all Mesoregions state. However, it occurs unevenly between urban and rural population.

  19. Aging management of safety-related concrete structures in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Arndt, E.G.

    1990-01-01

    The Structural Aging Program has the overall objective of providing the US Nuclear Regulatory Commission with an improved basis for evaluating nuclear power plants for continued service. In meeting this objective, a materials property data base is being developed as well as an aging assessment methodology for concrete structures in nuclear power plants. Furthermore, studies are well under way to review and assess inservice inspection techniques for concrete structures and to develop a methodology which can be used for performing current as well as reliability-based future conditions assessments of these structures. 16 refs., 2 tabs

  20. Structural Validity of the Movement ABC-2 Test: Factor Structure Comparisons across Three Age Groups

    Science.gov (United States)

    Schulz, Joerg; Henderson, Sheila E.; Sugden, David A.; Barnett, Anna L.

    2011-01-01

    Background: The Movement ABC test is one of the most widely used assessments in the field of Developmental Coordination Disorder (DCD). Improvements to the 2nd edition of the test (M-ABC-2) include an extension of the age range and reduction in the number of age bands as well as revision of tasks. The total test score provides a measure of motor…

  1. Methods for evaluating crown area profiles of forest stands

    Science.gov (United States)

    Dubrasich, Michael E.; Hann, D.W.; Tappeiner, J. C.

    1997-01-01

    Canopy architectures of five structurally complex forest stands and three structurally simple forest stands in southwest Oregon and the Willamette Valley, Oregon, were evaluated and quantified through crown area profiles. Mixed conifer and mixed conifer hardwood stands across a range of sites were sampled for crown widths and heights. Crown width and shape equations were derived and used to quantify the stand crown area at incremental heights above the forest floor. Crown area profiles describe the spatial arrangement of aboveground forest vegetation and the total pore spaces between crowns. Plot by plot profiles were combined to produce vertical and horizontal displays of the stand crown area distribution. In complex stands, the forest space was moderately occupied by crowns from the forest floor up to heights over 30 m, producing uniform distributions of between-crown porosity. The structurally complex stands had between-crown porosity values of 70% to 90% for more than 23 vertical metres of canopy, and they had total between-crown porosities of 86% to 91%. The structurally simple stands had between-crown porosity values of 70% to 90% for less than 8 vertical metres of canopy, and they had total between-crown porosities of 69% to 85%. Variances in crown area indicate that variation in horizontal crown area (within heights) was larger in complex stands than in simple stands, but vertical crown areas (between heights) varied less in complex stands. The study provides a basis for discriminating between canopy architectures and for quantifying the porosity of forest canopies.

  2. Generation time, net reproductive rate, and growth in stage-age-structured populations

    DEFF Research Database (Denmark)

    Steiner, Uli; Tuljapurkar, Shripad; Coulson, Tim

    2014-01-01

    to age-structured populations. Here we generalize this result to populations structured by stage and age by providing a new, unique measure of reproductive timing (Tc) that, along with net reproductive rate (R0), has a direct mathematical relationship to and approximates growth rate (r). We use simple...... examples to show how reproductive timing Tc and level R0 are shaped by stage dynamics (individual trait changes), selection on the trait, and parent-offspring phenotypic correlation. We also show how population structure can affect dispersion in reproduction among ages and stages. These macroscopic...... features of the life history determine population growth rate r and reveal a complex interplay of trait dynamics, timing, and level of reproduction. Our results contribute to a new framework of population and evolutionary dynamics in stage-and-age-structured populations....

  3. A spatial- and age-structured assessment model to estimate the ...

    African Journals Online (AJOL)

    , thereby indirectly negatively impacting juvenile abalone which rely on the urchins for shelter. A model is developed for abalone that is an extension of more standard age-structured assessment models because it explicitly takes spatial effects ...

  4. Cardiovascular evaluation of middle-aged/ senior individuals engaged in leisure-time sport activities: position stand from the sections of exercise physiology and sports cardiology of the European Association of Cardiovascular Prevention and Rehabilitation.

    Science.gov (United States)

    Borjesson, Mats; Urhausen, Alex; Kouidi, Evangelia; Dugmore, Dorian; Sharma, Sanjay; Halle, Martin; Heidbüchel, Hein; Björnstad, Hans Halvor; Gielen, Stephan; Mezzani, Alessandro; Corrado, Domenico; Pelliccia, Antonio; Vanhees, Luc

    2011-06-01

    Regular aerobic exercise at moderate intensities and an increased physical fitness are associated with a reduced risk of fatal and nonfatal coronary events in middle-aged individuals. In contrast, moderate and vigorous physical exertion is associated with an increased risk for cardiac events, including sudden cardiac death in individuals harbouring cardiovascular disease. The risk-benefit ratio may differ in relation to the individual’s age, fitness level, and presence of cardiovascular disease; sedentary individuals with underlying coronary artery disease are at greatest risk. The intention of the present position stand of the European Association of Cardiovascular Prevention and Rehabilitation is to encourage individuals to participate in regular physical activity and derive the benefits of physical exercise while minimizing the risk of cardiovascular adverse events. Therefore, the aim is to establish the most practical method of cardiovascular evaluation in middle-age/senior individuals, who are contemplating exercise or who are already engaged in nonprofessional competitive or recreational leisure sporting activity. These recommendations rely on existing scientific evidence, and in the absence of such, on expert consensus. The methodology of how middle-aged and older individuals should be evaluated appropriately before engaging in regular physical activity is both complex and controversial. On practical grounds the consensus panel recommend that such evaluation should vary according to the individual’s cardiac risk profile and the intended level of physical activity. Self assessment of the habitual physical activity level and of the risk factors, are recommended for screening of large populations. Individuals deemed to be at risk require further evaluation by a qualified physician. In senior/adult individuals with an increased risk for coronary events, maximal exercise testing (and possibly further evaluations) is advocated. Hopefully, the recommendations

  5. Association of structural global brain network properties with intelligence in normal aging.

    Directory of Open Access Journals (Sweden)

    Florian U Fischer

    Full Text Available Higher general intelligence attenuates age-associated cognitive decline and the risk of dementia. Thus, intelligence has been associated with cognitive reserve or resilience in normal aging. Neurophysiologically, intelligence is considered as a complex capacity that is dependent on a global cognitive network rather than isolated brain areas. An association of structural as well as functional brain network characteristics with intelligence has already been reported in young adults. We investigated the relationship between global structural brain network properties, general intelligence and age in a group of 43 cognitively healthy elderly, age 60-85 years. Individuals were assessed cross-sectionally using Wechsler Adult Intelligence Scale-Revised (WAIS-R and diffusion-tensor imaging. Structural brain networks were reconstructed individually using deterministic tractography, global network properties (global efficiency, mean shortest path length, and clustering coefficient were determined by graph theory and correlated to intelligence scores within both age groups. Network properties were significantly correlated to age, whereas no significant correlation to WAIS-R was observed. However, in a subgroup of 15 individuals aged 75 and above, the network properties were significantly correlated to WAIS-R. Our findings suggest that general intelligence and global properties of structural brain networks may not be generally associated in cognitively healthy elderly. However, we provide first evidence of an association between global structural brain network properties and general intelligence in advanced elderly. Intelligence might be affected by age-associated network deterioration only if a certain threshold of structural degeneration is exceeded. Thus, age-associated brain structural changes seem to be partially compensated by the network and the range of this compensation might be a surrogate of cognitive reserve or brain resilience.

  6. Association of Structural Global Brain Network Properties with Intelligence in Normal Aging

    Science.gov (United States)

    Fischer, Florian U.; Wolf, Dominik; Scheurich, Armin; Fellgiebel, Andreas

    2014-01-01

    Higher general intelligence attenuates age-associated cognitive decline and the risk of dementia. Thus, intelligence has been associated with cognitive reserve or resilience in normal aging. Neurophysiologically, intelligence is considered as a complex capacity that is dependent on a global cognitive network rather than isolated brain areas. An association of structural as well as functional brain network characteristics with intelligence has already been reported in young adults. We investigated the relationship between global structural brain network properties, general intelligence and age in a group of 43 cognitively healthy elderly, age 60–85 years. Individuals were assessed cross-sectionally using Wechsler Adult Intelligence Scale-Revised (WAIS-R) and diffusion-tensor imaging. Structural brain networks were reconstructed individually using deterministic tractography, global network properties (global efficiency, mean shortest path length, and clustering coefficient) were determined by graph theory and correlated to intelligence scores within both age groups. Network properties were significantly correlated to age, whereas no significant correlation to WAIS-R was observed. However, in a subgroup of 15 individuals aged 75 and above, the network properties were significantly correlated to WAIS-R. Our findings suggest that general intelligence and global properties of structural brain networks may not be generally associated in cognitively healthy elderly. However, we provide first evidence of an association between global structural brain network properties and general intelligence in advanced elderly. Intelligence might be affected by age-associated network deterioration only if a certain threshold of structural degeneration is exceeded. Thus, age-associated brain structural changes seem to be partially compensated by the network and the range of this compensation might be a surrogate of cognitive reserve or brain resilience. PMID:24465994

  7. Structural integrity and management of aging in internal components of BWR reactors

    International Nuclear Information System (INIS)

    Arganis J, C.R.

    2004-01-01

    Presently work the bases to apply structural integrity and the handling of the aging of internal components of the pressure vessel of boiling water reactors of water are revised and is carried out an example of structural integrity in the horizontal welding H4 of the encircling one of the core of a reactor, taking data reported in the literature. It is also revised what is required to carry out the handling program or conduct of the aging (AMP). (Author)

  8. Compact attractors for time-periodic age-structured population models

    Directory of Open Access Journals (Sweden)

    Pierre Magal

    2001-10-01

    Full Text Available In this paper we investigate the existence of compact attractors for time-periodic age-structured models. So doing we investigate the eventual compactness of a class of abstract non-autonomous semiflow (non necessarily periodic. We apply this result to non-autonomous age-structured models. In the time periodic case, we obtain the existence of a periodic family of compact subsets that is invariant by the semiflow, and attract the solutions of the system.

  9. Assessment and management of aging of nuclear power plant safety-related structures

    International Nuclear Information System (INIS)

    Naus, D.J.; Graves, H.L. III; Ellingwood, B.R.

    2003-01-01

    Background information and data have been developed for improving existing and developing new methods to assist in quantifying the effects of age-related degradation on the performance of nuclear power plant (NPP) safety-related structures. Factors that can lead to age-related degradation of safety-related structures are identified and their manifestations described. Current regulatory testing and inspection requirements are reviewed and a summary of degradation experience presented. Techniques commonly used to inspect NPP concrete structures to assess and quantify age-related degradation are summarized. An approach for conduct of condition assessments of structures in NPPs is presented. Criteria, based primarily on visual indications, are provided for use in classification and assessment of concrete degradation. Materials and techniques for repair of degraded structures are noted and guidance provided on repair options available for various forms of degradation. A probabilistic methodology for condition assessment and reliability-based life prediction has been developed and applied to structures subject to combinations of structural load processes and to structural systems. The methodology has also been used to investigate optimization of in-service inspection and maintenance strategies to maintain failure probability below a specified target value as well as to minimize costs. Fragility assessments involving analytical solutions and finite-element methods have been utilized to predict the effect of aging degradation on structural component performance. (author)

  10. Geroprotectors.org: a new, structured and curated database of current therapeutic interventions in aging and age-related disease.

    Science.gov (United States)

    Moskalev, Alexey; Chernyagina, Elizaveta; de Magalhães, João Pedro; Barardo, Diogo; Thoppil, Harikrishnan; Shaposhnikov, Mikhail; Budovsky, Arie; Fraifeld, Vadim E; Garazha, Andrew; Tsvetkov, Vasily; Bronovitsky, Evgeny; Bogomolov, Vladislav; Scerbacov, Alexei; Kuryan, Oleg; Gurinovich, Roman; Jellen, Leslie C; Kennedy, Brian; Mamoshina, Polina; Dobrovolskaya, Evgeniya; Aliper, Alex; Kaminsky, Dmitry; Zhavoronkov, Alex

    2015-09-01

    As the level of interest in aging research increases, there is a growing number of geroprotectors, or therapeutic interventions that aim to extend the healthy lifespan and repair or reduce aging-related damage in model organisms and, eventually, in humans. There is a clear need for a manually-curated database of geroprotectors to compile and index their effects on aging and age-related diseases and link these effects to relevant studies and multiple biochemical and drug databases. Here, we introduce the first such resource, Geroprotectors (http://geroprotectors.org). Geroprotectors is a public, rapidly explorable database that catalogs over 250 experiments involving over 200 known or candidate geroprotectors that extend lifespan in model organisms. Each compound has a comprehensive profile complete with biochemistry, mechanisms, and lifespan effects in various model organisms, along with information ranging from chemical structure, side effects, and toxicity to FDA drug status. These are presented in a visually intuitive, efficient framework fit for casual browsing or in-depth research alike. Data are linked to the source studies or databases, providing quick and convenient access to original data. The Geroprotectors database facilitates cross-study, cross-organism, and cross-discipline analysis and saves countless hours of inefficient literature and web searching. Geroprotectors is a one-stop, knowledge-sharing, time-saving resource for researchers seeking healthy aging solutions.

  11. The effects of maternal immunity and age structure on population immunity to measles.

    Science.gov (United States)

    McKee, A; Ferrari, M J; Shea, K

    2015-05-01

    Measles was successfully eradicated in the Pan-American Health Region in 2002. However, maintenance of elimination in parts of Africa, Europe, the USA, and other regions is proving difficult, despite apparently high vaccine coverage. This may be due to the different age structure in developed and developing populations, as well as to differences in the duration of maternal immunity. We explore the interaction between maternal immunity and age structure and quantify the resulting immunity gap between vaccine coverage and population immunity; we use this immunity gap as a novel metric of vaccine program success as it highlights the difference between actual and estimated immunity. We find that, for some combinations of maternal immunity and age structure, the accepted herd immunity threshold is not maintainable with a single-dose vaccine strategy for any combination of target age and coverage. In all cases, the herd immunity threshold is more difficult to maintain in a population with developing age structure. True population immunity is always improved if the target age at vaccination is chosen for the specific combination of maternal immunity and age structure.

  12. China’s marriage squeeze: A decomposition into age and sex structure

    Science.gov (United States)

    LI, Xiaomin; LI, Shuzhuo; FELDMAN, Marcus W.

    2016-01-01

    Most recent studies of marriage patterns in China have emphasized the male-biased sex ratio but have largely neglected age structure as a factor in China’s male marriage squeeze. In this paper we develop an index we call “spousal sex ratio” (SSR) to measure the marriage squeeze, and a method of decomposing the proportion of male surplus into age and sex structure effects within a small spousal age difference interval. We project that China’s marriage market will be confronted with a relatively severe male squeeze. For the decomposition of the cohort aged 30, from 2010 to 2020 age structure will be dominant, while from 2020 through 2034 the contribution of age structure will gradually decrease and that of sex structure will increase. From then on, sex structure will be dominant. The index and decomposition, concentrated on a specific female birth cohort, can distinguish spousal competition for single cohorts which may be covered by a summary index for the whole marriage market; these can also be used for consecutive cohorts to reflect the situation of the whole marriage market. PMID:27242390

  13. Factor Structure of Attention Deficit Hyperactivity Disorder Symptoms for Children Age 3 to 5 Years

    Science.gov (United States)

    McGoey, Kara E.; Schreiber, James; Venesky, Lindsey; Westwood, Wendy; McGuirk, Lindsay; Schaffner, Kristen

    2015-01-01

    The diagnosis of attention deficit hyperactivity disorder (ADHD) distinguishes two dimensions of symptoms, inattention and hyperactivity-impulsivity for ages 3 to adulthood. Currently, no separate classification for preschool-age children exists, whereas preliminary research suggests that the two-factor structure of ADHD may not match the…

  14. 76 FR 74831 - Aging Management of Stainless Steel Structures and Components in Treated Borated Water

    Science.gov (United States)

    2011-12-01

    ... inhibitor in place of other aging management activities. As a result, aging effects such as loss of material... of the Water Chemistry Program to manage loss of material and cracking of stainless steel structures... this extension will allow stakeholders a chance to better prepare their responses to LR-ISG-2011-01...

  15. The influence of age-group structure on genetic gain and ...

    African Journals Online (AJOL)

    that the age structure has a significant influence on genetic gain in Merino flocks. This is due to the inverse relationship be- tween the intensity of selection and the generation interval which becomes apparent when the number of male and female age-groups is changed. An important conclusion from their results was that ...

  16. Microscopic structural study of collagen aging in isolated fibrils using polarized second harmonic generation

    Science.gov (United States)

    Aït-Belkacem, Dora; Guilbert, Marie; Roche, Muriel; Duboisset, Julien; Ferrand, Patrick; Sockalingum, Ganesh; Jeannesson, Pierre; Brasselet, Sophie

    2012-08-01

    Polarization resolved second harmonic generation (PSHG) is developed to study, at the microscopic scale, the impact of aging on the structure of type I collagen fibrils in two-dimensional coatings. A ribose-glycated collagen is also used to mimic tissue glycation usually described as an indicator of aging. PSHG images are analyzed using a generic approach of the molecular disorder information in collagen fibrils, revealing significant changes upon aging, with a direct correlation between molecular disorder and fibril diameters.

  17. Continuing the service of aging concrete structures in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Oland, C.B.; Arndt, E.G.

    1993-01-01

    The (SAG) Structural Aging Program has the objective of preparing documentation to help provide criteria for use by the USNRC in evaluating requests for continuing the service of NPPs. The program consists of three tasks: Materials property data base, structural component assessment/repair technologies, and quantitative methodology for continued service determinations. These tasks are detailed in this report

  18. Structural aging program to assess the adequacy of critical concrete components in nuclear power plants

    International Nuclear Information System (INIS)

    Naus, D.J.; Marchbanks, M.F.; Oland, C.B.; Arndt, E.G.

    1989-01-01

    The Structural Aging (SAG) Program is carried out by the Oak Ridge National Laboratory (ORNL) under sponsorship of the United States Nuclear Regulatory Commission (USNRC). The Program has evolved from preliminary studies conducted to evaluate the long-term environmental challenges to light-water reactor safety-related concrete civil structures. An important conclusion of these studies was that a damage methodology, which can provide a quantitative measure of a concrete structure's durability with respect to potential future requirements, needs to be developed. Under the SAG Program, this issue is being addressed through: establishment of a structural materials information center, evaluation of structural component assessment and repair technologies, and development of a quantitative methodology for structural aging determinations. Progress to date of each of these activities is presented as well as future plans. 7 refs., 5 figs

  19. A structural factor analysis of vocabulary knowledge and relations to age.

    Science.gov (United States)

    Bowles, Ryan P; Grimm, Kevin J; McArdle, John J

    2005-09-01

    Vocabulary knowledge may not be a unidimensional construct, and the relations between vocabulary knowledge and age may depend on the aspect of vocabulary knowledge being assessed. In this study, we examined the factor structure of a vocabulary test given to a large nationally representative sample of individuals (N approximately 20,500). Results indicated that the vocabulary test is not unidimensional but bidimensional, with Basic Vocabulary and Advanced Vocabulary factors. An analysis of age differences indicates that basic vocabulary is highest around the age of 30, with a negative relation to age in late adulthood; in contrast, advanced vocabulary is unrelated to age between ages 35 and 70. Cohort effects may explain some of the differential age trend.

  20. Mathematical Model of Three Age-Structured Transmission Dynamics of Chikungunya Virus

    Science.gov (United States)

    Agusto, Folashade B.; Easley, Shamise; Freeman, Kenneth; Thomas, Madison

    2016-01-01

    We developed a new age-structured deterministic model for the transmission dynamics of chikungunya virus. The model is analyzed to gain insights into the qualitative features of its associated equilibria. Some of the theoretical and epidemiological findings indicate that the stable disease-free equilibrium is globally asymptotically stable when the associated reproduction number is less than unity. Furthermore, the model undergoes, in the presence of disease induced mortality, the phenomenon of backward bifurcation, where the stable disease-free equilibrium of the model coexists with a stable endemic equilibrium when the associated reproduction number is less than unity. Further analysis of the model indicates that the qualitative dynamics of the model are not altered by the inclusion of age structure. This is further emphasized by the sensitivity analysis results, which shows that the dominant parameters of the model are not altered by the inclusion of age structure. However, the numerical simulations show the flaw of the exclusion of age in the transmission dynamics of chikungunya with regard to control implementations. The exclusion of age structure fails to show the age distribution needed for an effective age based control strategy, leading to a one size fits all blanket control for the entire population. PMID:27190548

  1. Aging influence on grey matter structural associations within the default mode network utilizing Bayesian network modeling

    Directory of Open Access Journals (Sweden)

    Yan eWang

    2014-05-01

    Full Text Available Recent neuroimaging studies have revealed normal aging-related alterations in functional and structural brain networks such as the default mode network (DMN. However, less is understood about specific brain structural dependencies or interactions between brain regions within the DMN in the normal aging process. In this study, using Bayesian network (BN modeling, we analyzed grey matter volume data from 109 young and 82 old subjects to characterize the influence of aging on associations between core brain regions within the DMN. Furthermore, we investigated the discriminability of the aging-associated BN models for the young and old groups. Compared to their young counterparts, the old subjects showed significant reductions in connections from right inferior temporal cortex (ITC to medial prefrontal cortex (mPFC, right hippocampus (HP to right ITC, and mPFC to posterior cingulate cortex (PCC and increases in connections from left HP to mPFC and right inferior parietal cortex (IPC to right ITC. Moreover, the classification results showed that the aging-related BN models could predict group membership with 88.48% accuracy, 88.07% sensitivity and 89.02% specificity. Our findings suggest that structural associations within the DMN may be affected by normal aging and provide crucial information about aging effects on brain structural networks.

  2. Weak temperature dependence of ageing of structural properties in atomistic model glassformers

    Science.gov (United States)

    Jenkinson, Thomas; Crowther, Peter; Turci, Francesco; Royall, C. Patrick

    2017-08-01

    Ageing phenomena are investigated from a structural perspective in two binary Lennard-Jones glassformers, the Kob-Andersen and Wahnström mixtures. In both, the geometric motif assumed by the glassformer upon supercooling, the locally favoured structure (LFS), has been established. The Kob-Andersen mixture forms bicapped square antiprisms; the Wahnström model forms icosahedra. Upon ageing, we find that the structural relaxation time has a time-dependence consistent with a power law. However, the LFS population and potential energy increase and decrease, respectively, in a logarithmic fashion. Remarkably, over the time scales investigated, which correspond to a factor of 104 change in relaxation times, the rate at which these quantities age appears almost independent of temperature. Only at temperatures far below the Vogel-Fulcher-Tamman temperature do the ageing dynamics slow.

  3. An evaluation of FIA's stand age variable

    Science.gov (United States)

    John D. Shaw

    2015-01-01

    The Forest Inventory and Analysis Database (FIADB) includes a large number of measured and computed variables. The definitions of measured variables are usually well-documented in FIA field and database manuals. Some computed variables, such as live basal area of the condition, are equally straightforward. Other computed variables, such as individual tree volume,...

  4. Extended Aging Theories for Predictions of Safe Operational Life of Critical Airborne Structural Components

    Science.gov (United States)

    Ko, William L.; Chen, Tony

    2006-01-01

    The previously developed Ko closed-form aging theory has been reformulated into a more compact mathematical form for easier application. A new equivalent loading theory and empirical loading theories have also been developed and incorporated into the revised Ko aging theory for the prediction of a safe operational life of airborne failure-critical structural components. The new set of aging and loading theories were applied to predict the safe number of flights for the B-52B aircraft to carry a launch vehicle, the structural life of critical components consumed by load excursion to proof load value, and the ground-sitting life of B-52B pylon failure-critical structural components. A special life prediction method was developed for the preflight predictions of operational life of failure-critical structural components of the B-52H pylon system, for which no flight data are available.

  5. Beyond Technology, there Stands Magic

    Directory of Open Access Journals (Sweden)

    Lúcia Fernandes Lobato

    2013-07-01

    Full Text Available This article shows evidence that despite the prominent influences of the technological revolution and the spectacular panoramas on the contemporary world, magic seems to stand beyond technology. To support this hypothesis, the author investigates the images on the cinema, pointing out that to discover magic in a film, for instance, it is necessary to recognize its subjective structures disguised in the objectivity of the screen. Finally, the author indicates that in the field of image production, dance films that are created out of a cross-disciplinary effort are another by product of the fusion between art and video, born out of technological advancements.

  6. Benefits of gregarious feeding by aposematic caterpillars depend on group age structure.

    Science.gov (United States)

    Campbell, Stuart A; Stastny, Michael

    2015-03-01

    Gregarious feeding is a common feature of herbivorous insects and can range from beneficial (e.g. dilution of predation risk) to costly (e.g. competition). Group age structure should influence these costs and benefits, particularly when old and young larvae differ in their feeding mode or apparency to predators. We investigated the relative value of gregarious feeding by aposematic larvae of Uresiphita reversalis that we observed feeding in groups of mixed ages and variable densities on wild Lupinus diffusus. In a manipulative field experiment, the survivorship and growth of young larvae were enhanced in the presence of older conspecifics, but not in large groups of similarly aged larvae. Estimates of insect damage and induced plant responses suggest that mixed-age groups enhance plant quality for young larvae while avoiding competition. We conclude that benefits of gregariousness in this species are contingent on group age structure, a finding of significance for the ecology and evolution of gregariousness and other social behaviours.

  7. Armillaria species in coniferous stands

    Directory of Open Access Journals (Sweden)

    Anna Żółciak

    2013-12-01

    Full Text Available Identification of the Armillaria species in selected coniferous stands (Scots pine stands, Norway spruce stands and fir stands was the aim of the work carried out on the basis of mating tests and consideration of macroscopic traits of fruit-bodies. One species of Armillaria [A. ostoyae (Romagnesi Herink] was found in Scots pine stands, three species [A. ostoyae, A. cepistipes Velenovský and A. borealis Marxmüller et Korhonen] were found in Norway spruce stands and two species [A. ostoyae and A. cepistipes] were found in fir stands.

  8. Components of Appearance in the Structure of Perception of Visual Representations of Age

    OpenAIRE

    Shkurko T.A.; Nikolaeva E.G.

    2015-01-01

    The article discusses the problem of perception of age (one’s own and that of other people), which is regarded as a special case of social perception. The aim of this study was to analyze the components of another person’s appearance in the structure of perception of visual representations of age. For these purposes the authors created a special technique, “Identifying Age through Photo Visualization” (Shkurko T.A., Nikolaeva E. G.). The study enrolled 20 individuals (10 men, 10 women aged 18...

  9. Effects of aging on sleep structure throughout adulthood: a population-based study.

    Science.gov (United States)

    Moraes, Walter; Piovezan, Ronaldo; Poyares, Dalva; Bittencourt, Lia Rita; Santos-Silva, Rogerio; Tufik, Sergio

    2014-04-01

    Although many studies have shown the evolution of sleep parameters across the lifespan, not many have included a representative sample of the general population. The objective of this study was to describe age-related changes in sleep structure, sleep respiratory parameters and periodic limb movements of the adult population of São Paulo. We selected a representative sample of the city of São Paulo, Brazil that included both genders and an age range of 20-80 years. Pregnant and lactating women, people with physical or mental impairments that prevent self-care and people who work every night were not included. This sample included 1024 individuals who were submitted to polysomnography and structured interviews. We subdivided our sample into five-year age groups. One-way analysis of variance was used to compare age groups. Pearson product-moment was used to evaluate correlation between age and sleep parameters. Total sleep time, sleep efficiency, percentage of rapid eye movement (REM) sleep and slow wave sleep showed a significant age-related decrease (Page. The reduction in the percentage of REM sleep significantly correlated with age in women, whereas the reduction in the percentage of slow wave sleep correlated with age in men. The periodic limb movement (PLM) index increased with age in men and women. Sleep structure and duration underwent significant alterations throughout the aging process in the general population. There was an important correlation between age, sleep respiratory parameters and PLM index. In addition, men and women showed similar trends but with different effect sizes. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Brain Events Underlying Episodic Memory Changes in Aging: A Longitudinal Investigation of Structural and Functional Connectivity.

    Science.gov (United States)

    Fjell, Anders M; Sneve, Markus H; Storsve, Andreas B; Grydeland, Håkon; Yendiki, Anastasia; Walhovd, Kristine B

    2016-03-01

    Episodic memories are established and maintained by close interplay between hippocampus and other cortical regions, but degradation of a fronto-striatal network has been suggested to be a driving force of memory decline in aging. We wanted to directly address how changes in hippocampal-cortical versus striatal-cortical networks over time impact episodic memory with age. We followed 119 healthy participants (20-83 years) for 3.5 years with repeated tests of episodic verbal memory and magnetic resonance imaging for quantification of functional and structural connectivity and regional brain atrophy. While hippocampal-cortical functional connectivity predicted memory change in young, changes in cortico-striatal functional connectivity were related to change in recall in older adults. Within each age group, effects of functional and structural connectivity were anatomically closely aligned. Interestingly, the relationship between functional connectivity and memory was strongest in the age ranges where the rate of reduction of the relevant brain structure was lowest, implying selective impacts of the different brain events on memory. Together, these findings suggest a partly sequential and partly simultaneous model of brain events underlying cognitive changes in aging, where different functional and structural events are more or less important in various time windows, dismissing a simple uni-factorial view on neurocognitive aging. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  11. A longitudinal study of structural brain network changes with normal aging

    Directory of Open Access Journals (Sweden)

    Kai eWu

    2013-04-01

    Full Text Available The aim of this study was to investigate age-related changes in the topological organization of structural brain networks by applying a longitudinal design over 6 years. Structural brain networks were derived from measurements of regional gray matter volume and were constructed in age-specific groups from baseline and follow-up scans. The structural brain networks showed economical small-world properties, providing high global and local efficiency for parallel information processing at low connection costs. In the analysis of the global network properties, the local and global efficiency of the baseline scan were significantly lower compared to the follow-up scan. Moreover, the annual rate of changes in local and global efficiency showed a positive and negative quadratic correlation with the baseline age, respectively; both curvilinear correlations peaked at approximately the age of 50. In the analysis of the regional nodal properties, significant negative correlations between the annual rate of changes in nodal strength and the baseline age were found in the brain regions primarily involved in the visual and motor/ control systems, whereas significant positive quadratic correlations were found in the brain regions predominately associated with the default-mode, attention, and memory systems. The results of the longitudinal study are consistent with the findings of our previous cross-sectional study: the structural brain networks develop into a fast distribution from young to middle age (approximately 50 years old and eventually became a fast localization in the old age. Our findings elucidate the network topology of structural brain networks and its longitudinal changes, thus enhancing the understanding of the underlying physiology of normal aging in the human brain.

  12. Golden rule (standing theology)

    OpenAIRE

    Ellis, Randolph

    2017-01-01

    This study offers an example of ‘standing theology’ as distinguished from sitting theology or kneeling theology. The occasion was the Fourth Sunday of Easter in Bangor Cathedral, 2015. The Epistle reading was 1 John 3: 16–24.\\ud \\ud

  13. Economics of stand management

    Science.gov (United States)

    David K. Lewis

    1986-01-01

    This paper sets out to demonstrate the importance of considering the wealth represented by the growing stock in economic analyses of stand management alternatives, and to demonstrate the role of thinning in the manipulation of the efficiency of growing stock in the management of shortleaf pine (Pinus echinata Mill.). These goals are achieved through a demonstration of...

  14. Principles of managing stands

    Science.gov (United States)

    David A. Marquis; Rodney Jacobs

    1989-01-01

    Forest stands are managed to achieve some combination of desired products or values. These products or values may include income and tangible benefits from timber production or fees for hunting rights and other recreational activities. The values may be intangible, such as the enjoyment of seeing wildlife or flowering plants, or the simple satisfaction of knowing that...

  15. Does white matter structure or hippocampal volume mediate associations between cortisol and cognitive ageing?

    Science.gov (United States)

    Cox, Simon R.; MacPherson, Sarah E.; Ferguson, Karen J.; Royle, Natalie A.; Maniega, Susana Muñoz; Hernández, Maria del C. Valdés; Bastin, Mark E.; MacLullich, Alasdair M.J.; Wardlaw, Joanna M.; Deary, Ian J.

    2015-01-01

    Elevated glucocorticoid (GC) levels putatively damage specific brain regions, which in turn may accelerate cognitive ageing. However, many studies are cross-sectional or have relatively short follow-up periods, making it difficult to relate GCs directly to changes in cognitive ability with increasing age. Moreover, studies combining endocrine, MRI and cognitive variables are scarce, measurement methods vary considerably, and formal tests of the underlying causal hypothesis (cortisol → brain → cognition) are absent. In this study, 90 men, aged 73 years, provided measures of fluid intelligence, processing speed and memory, diurnal and reactive salivary cortisol and two measures of white matter (WM) structure (WM hyperintensity volume from structural MRI and mean diffusivity averaged across 12 major tracts from diffusion tensor MRI), hippocampal volume, and also cognitive ability at age 11. We tested whether negative relationships between cognitive ageing differences (over more than 60 years) and salivary cortisol were significantly mediated by WM and hippocampal volume. Significant associations between reactive cortisol at 73 and cognitive ageing differences between 11 and 73 (r = −.28 to −.36, p cognition associations (cognitive ageing differences from childhood to the early 70s, partly via brain WM structure. PMID:26298692

  16. Sleep Duration and Age-Related Changes in Brain Structure and Cognitive Performance

    Science.gov (United States)

    Lo, June C.; Loh, Kep Kee; Zheng, Hui; Sim, Sam K.Y.; Chee, Michael W.L.

    2014-01-01

    Study Objectives: To investigate the contribution of sleep duration and quality to age-related changes in brain structure and cognitive performance in relatively healthy older adults. Design: Community-based longitudinal brain and cognitive aging study using a convenience sample. Setting: Participants were studied in a research laboratory. Participants: Relatively healthy adults aged 55 y and older at study commencement. Interventions: N/A. Measurements and Results: Participants underwent magnetic resonance imaging and neuropsychological assessment every 2 y. Subjective assessments of sleep duration and quality and blood samples were obtained. Each hour of reduced sleep duration at baseline augmented the annual expansion rate of the ventricles by 0.59% (P = 0.007) and the annual decline rate in global cognitive performance by 0.67% (P = 0.050) in the subsequent 2 y after controlling for the effects of age, sex, education, and body mass index. In contrast, global sleep quality at baseline did not modulate either brain or cognitive aging. High-sensitivity C-reactive protein, a marker of systemic inflammation, showed no correlation with baseline sleep duration, brain structure, or cognitive performance. Conclusions: In healthy older adults, short sleep duration is associated with greater age-related brain atrophy and cognitive decline. These associations are not associated with elevated inflammatory responses among short sleepers. Citation: Lo JC, Loh KK, Zheng H, Sim SK, Chee MW. Sleep duration and age-related changes in brain structure and cognitive performance. SLEEP 2014;37(7):1171-1178. PMID:25061245

  17. Overview of the age-related degradation of nuclear power plant structures

    International Nuclear Information System (INIS)

    Deng, Daniel

    2004-01-01

    License renewal of nuclear power plants is an issue of increasing interest to the U.S. nuclear industry and the U.S. NRC. This paper presents and evaluates the plausible age-related degradation mechanisms that may affect the concrete and steel containment structures and other Class I structures to continue to perform their safety functions. Preventive and/or mitigative options are outlined for managing degradation mechanisms that could significantly affect plant performance during the license renewal period. The provided technical information and the degradation management options may be used as references for comparison with plant specific conditions to ensure that age-related degradation is controlled during the license renewal term. Plausible degradation mechanisms described and analyzed as they may affect the concrete, reinforcing steel, containment steel shell, prestressed-tendon, steel liner and other structural components typically used in Class I structures. The significance of these age-related degradation mechanisms to the structural components are evaluated, giving consideration to the design basis and quality of construction; typical service conditions; operating and maintenance history; and current test, inspection and refurbishment practices for containment and Class I structures. Degradation mechanisms which cannot be generically dispositioned on the basis of the two-step approach: (1) they will not cause significant degradation, or (2) any potential degradation will be bounded by current test, inspection, analytical evaluation, and/or refurbishment programs are identified. Aging degradation management measures are recommended to address the remaining age-related degradation mechanisms. A three-phase approach for the management of the containment and Class I structures is introduced. Various techniques, testing tools and the acceptable criteria for each step of the evaluation of the structures status are provided. The preventive and mitigative

  18. Age, growth and population structure of invasive lionfish (Pterois volitans/miles in northeast Florida using a length-based, age-structured population model

    Directory of Open Access Journals (Sweden)

    Eric G. Johnson

    2016-12-01

    Full Text Available The effective management of invasive species requires detailed understanding of the invader’s life history. This information is essential for modeling population growth and predicting rates of expansion, quantifying ecological impacts and assessing the efficacy of removal and control strategies. Indo-Pacific lionfish (Pterois volitans/miles have rapidly invaded the western Atlantic, Gulf of Mexico and Caribbean Sea with documented negative impacts on native ecosystems. To better understand the life history of this species, we developed and validated a length-based, age-structured model to investigate age, growth and population structure in northeast Florida. The main findings of this study were: (1 lionfish exhibited rapid growth with seasonal variation in growth rates; (2 distinct cohorts were clearly identifiable in the length-frequency data, suggesting that lionfish are recruiting during a relatively short period in summer; and (3 the majority of lionfish were less than two years old with no lionfish older than three years of age, which may be the result of culling efforts as well as ontogenetic habitat shifts to deeper water.

  19. Geographic variation in age structure and longevity in the nine-spined stickleback (Pungitius pungitius).

    Science.gov (United States)

    DeFaveri, Jacquelin; Shikano, Takahito; Merilä, Juha

    2014-01-01

    Variation in age and size of mature nine-spined sticklebacks (Pungitius pungitius) within and among 16 Fennoscandian populations were assessed using skeletochronology. The average age of individuals in a given population varied from 1.7 to 4.7 years. Fish from pond populations were on average older than those from lake and marine populations, and females tended to be older than males. Reproduction in marine and lake populations commenced typically at an age of two years, whereas that in ponds at an age of three years. The maximum life span of the fish varied from 3 to 7 years. Mean body size within and among populations increased with increasing age, but the habitat and population differences in body size persisted even after accounting for variation in population age (and sex) structure. Hence, the population differences in mean body size are not explainable by age differences alone. As such, much of the pronounced intraspecific variation in population age structure can be attributed to delayed maturation and extended longevity of the pond fish. The results are contrasted and discussed in the context of similar data from the three-spined stickleback (Gasterosteus aculeatus) occupying the same geographic area.

  20. The basic approach to age-structured population dynamics models, methods and numerics

    CERN Document Server

    Iannelli, Mimmo

    2017-01-01

    This book provides an introduction to age-structured population modeling which emphasises the connection between mathematical theory and underlying biological assumptions. Through the rigorous development of the linear theory and the nonlinear theory alongside numerics, the authors explore classical equations that describe the dynamics of certain ecological systems. Modeling aspects are discussed to show how relevant problems in the fields of demography, ecology, and epidemiology can be formulated and treated within the theory. In particular, the book presents extensions of age-structured modelling to the spread of diseases and epidemics while also addressing the issue of regularity of solutions, the asymptotic behaviour of solutions, and numerical approximation. With sections on transmission models, non-autonomous models and global dynamics, this book fills a gap in the literature on theoretical population dynamics. The Basic Approach to Age-Structured Population Dynamics will appeal to graduate students an...

  1. Structural and Functional Recovery of Sensory Cilia in C. elegans IFT Mutants upon Aging.

    Directory of Open Access Journals (Sweden)

    Astrid Cornils

    2016-12-01

    Full Text Available The majority of cilia are formed and maintained by the highly conserved process of intraflagellar transport (IFT. Mutations in IFT genes lead to ciliary structural defects and systemic disorders termed ciliopathies. Here we show that the severely truncated sensory cilia of hypomorphic IFT mutants in C. elegans transiently elongate during a discrete period of adult aging leading to markedly improved sensory behaviors. Age-dependent restoration of cilia morphology occurs in structurally diverse cilia types and requires IFT. We demonstrate that while DAF-16/FOXO is dispensable, the age-dependent suppression of cilia phenotypes in IFT mutants requires cell-autonomous functions of the HSF1 heat shock factor and the Hsp90 chaperone. Our results describe an unexpected role of early aging and protein quality control mechanisms in suppressing ciliary phenotypes of IFT mutants, and suggest possible strategies for targeting subsets of ciliopathies.

  2. Changes of population by age and gender structure of Regions in the Republic of Macedonia

    Directory of Open Access Journals (Sweden)

    Resul Hamiti

    2015-07-01

    Full Text Available This paper analyzes the changes of population by age and the gender structure in the regions of the Republic of Macedonia. Age and gender is very important not only for the development of demographic process but also for the development of regions. They play an important role in planning the health care needs and other services with the socio-economic and cultural character. In this sense they affect the performance of demographic processes (births, deaths, marriages, etc. and are a result of bilateral relations fertility, mortality, migration movements and other social processes. The main objective of this paper is to identify the aging phenomenon of population in state level and regions. This paper also dedicates special importance to the changes of age and sex structure, during the period between1981-2014 in the regions of the republic of Macedonia.

  3. Reliability assessment of aging structures subjected to gradual and shock deteriorations

    International Nuclear Information System (INIS)

    Wang, Cao; Zhang, Hao; Li, Quanwang

    2017-01-01

    Civil structures and infrastructure facilities are susceptible to deterioration posed by the effects of natural hazards and aggressive environmental conditions. These factors may increase the risk of service interruption of infrastructures, and should be taken into account when assessing the structural reliability during an infrastructure's service life. Modeling the resistance deterioration process reasonably is the basis for structural reliability analysis. In this paper, a novel model is developed for describing the deterioration of aging structures. The deterioration is a combination of two stochastic processes: the gradual deterioration posed by environmental effects and the shock deterioration caused by severe load attacks. The dependency of the deterioration magnitude on the load intensity is considered. The Gaussian copula function is employed to help construct the joint distribution of correlated random variables. Semi-analytical methods are developed to assess the structural failure time and the number of significant load events (shocks) to failure. Illustrative examples are presented to demonstrate the applicability of the proposed model in structural reliability analysis. Parametric studies are performed to investigate the role of deterioration-load correlation in structural reliability. - Highlights: • A new resistance deterioration model for aging structures is proposed. • Time-dependent reliability analysis methods incorporating the proposed deterioration model are developed. • Parametric studies are performed to investigate the role of deterioration-load correlation in structural reliability.

  4. Scaling from Stand to Landscape of Climate Change Mitigation by Afforestation and Forest Management: a Modeling Approach

    NARCIS (Netherlands)

    Garcia-Quijano, J.F.; Deckmyn, G.; Ceulemans, R.; van Orsthoven, J.; Muys, B.

    2008-01-01

    There is a gap between the increased scientific understanding of carbon pools and fluxes at individual trees/stand and that of forested landscape with complex structures (i.e. variety of species, age classes, site characteristic and management practices). The question about how results generated

  5. Developing a Computerized Aging Management System for Concrete Structures in Finnish Nuclear Power Plants

    Science.gov (United States)

    Al-Neshawy, F.; Piironen, J.; Sistonen, E.; Vesikari, E.; Tuomisto, M.; Hradil, P.; Ferreira, M.

    2013-07-01

    Finland has four nuclear reactors units in two power plants. The first unit started operation in 1977 and in the early 1980's all four units were in use. During the last few years the aging management of the Nuclear Power Plant's (NPP) concrete structures has grown an important issue because the existing structures are reaching the end of their licensed operating lifetime (about 40 years). Therefore the nuclear power companies are developing aging management systems to avoid premature degradation of NPP facilities and to be able to extend their operating lifetime. This paper is about the development of a computerized ageing management system for the nuclear power plants concrete structures. The computerized ageing management system is built upon central database and implementation applications. It will assist the personnel of power companies to implement the aging management activities at different phases of the lifetime of a power plant. It will provide systematic methods for planning, surveillance, inspection, monitoring, condition assessment, maintenance and repair of structures.

  6. [Age structure and genetic diversity of Homatula pycnolepis in the Nujiang River basin].

    Science.gov (United States)

    Yue, Xing-Jian; Liu, Shao-Ping; Liu, Ming-Dian; Duan, Xin-Bin; Wang, Deng-Qiang; Chen, Da-Qing

    2013-08-01

    This study examined the age structure of the Loach, Homatula pycnolepis through the otolith growth rings in 204 individual specimens collected from the Xiaomengtong River of the Nujiang River (Salween River) basin in April, 2008. There were only two different age classes, 1 and 2 years of age-no 3 year olds were detected. The age structure of H. pycnolepis was simple. The complete mitochondrial DNA cytochrome b gene sequences (1140) of 80 individuals from 4 populations collected in the Nujiang River drainage were sequenced and a total of 44 variable sites were found among 4 different haplotypes. The global haplotype diversity (Hd) and nucleotide diversity (Pi) were calculated at 0.7595, 0.0151 respectively, and 0, 0 in each population, indicating a consistent lack of genetic diversity in each small population. There was obvious geographic structure in both the Nujiang River basin (NJB) group, and the Nanding River (NDR) group. The genetic distance between NJB and NDR was calculated at 0.0356, suggesting that genetic divergence resulted from long-term isolation of individual population. Such a simple age structure and a lack of genetic diversity in H. pycnolepis may potentially be due to small populations and locale fishing pressures. Accordingly, the results of this study prompt us to recommend that the NJB, NDR and Lancang River populations should be protected as three different evolutionary significant units or separated management units.

  7. Age-related differences in implicit learning of subtle third-order sequential structure.

    Science.gov (United States)

    Bennett, Ilana J; Howard, James H; Howard, Darlene V

    2007-03-01

    Age-related implicit learning deficits increase with sequence complexity, suggesting there might be limits to the level of structure that older adults can learn implicitly. To test for such limits, we had 12 younger and 12 older adults complete an alternating serial reaction time task containing subtle structure in which every third trial follows a repeating sequence and intervening trials are determined randomly. Results revealed significant age deficits in learning. However, both groups did learn the subtle regularity without explicit awareness, indicating that older adults remain sensitive to highly complex sequential regularities in their environment, albeit to a lesser degree than younger adults.

  8. Age-related changes in grey and white matter structure throughout adulthood.

    Science.gov (United States)

    Giorgio, Antonio; Santelli, Luca; Tomassini, Valentina; Bosnell, Rose; Smith, Steve; De Stefano, Nicola; Johansen-Berg, Heidi

    2010-07-01

    Normal ageing is associated with gradual brain atrophy. Determining spatial and temporal patterns of change can help shed light on underlying mechanisms. Neuroimaging provides various measures of brain structure that can be used to assess such age-related change but studies to date have typically considered single imaging measures. Although there is consensus on the notion that brain structure deteriorates with age, evidence on the precise time course and spatial distribution of changes is mixed. We assessed grey matter (GM) and white matter (WM) structure in a group of 66 adults aged between 23 and 81. Multimodal imaging measures included voxel-based morphometry (VBM)-style analysis of GM and WM volume and diffusion tensor imaging (DTI) metrics of WM microstructure. We found widespread reductions in GM volume from middle age onwards but earlier reductions in GM were detected in frontal cortex. Widespread age-related deterioration in WM microstructure was detected from young adulthood onwards. WM decline was detected earlier and more sensitively using DTI-based measures of microstructure than using markers of WM volume derived from conventional T1-weighted imaging. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  9. Age Differences in Interhemispheric Interactions: Callosal Structure, Physiological Function, and Behavior

    Directory of Open Access Journals (Sweden)

    Brett W Fling

    2011-03-01

    Full Text Available There is a fundamental gap in understanding how brain structural and functional network connectivity are interrelated, how they change with age, and how such changes contribute to older adults’ sensorimotor deficits. Recent neuroimaging approaches including resting state functional connectivity MRI (fcMRI and diffusion tensor imaging (DTI have been used to assess brain functional (fcMRI and structural (DTI network connectivity, allowing for more integrative assessments of distributed neural systems than in the past. Declines in corpus callosum size and microstructure with advancing age have been well documented, but their contributions to age deficits in unimanual and bimanual function are not well defined. Our recent work implicates age-related declines in callosal size and integrity as a key contributor to unimanual and bimanual control deficits. Moreover, our data provide evidence for a fundamental shift in the balance of excitatory and inhibitory interhemispheric processes that occurs with age, resulting in age differences in the relationship between functional and structural network connectivity. Training studies suggest that the balance of interhemispheric interactions can be shifted with experience, making this a viable target for future interventions.

  10. The leverage of demographic dynamics on carbon dioxide emissions: does age structure matter?

    Science.gov (United States)

    Zagheni, Emilio

    2011-02-01

    This article provides a methodological contribution to the study of the effect of changes in population age structure on carbon dioxide (CO(2)) emissions. First, I propose a generalization of the IPAT equation to a multisector economy with an age-structured population and discuss the insights that can be obtained in the context of stable population theory. Second, I suggest a statistical model of household consumption as a function of household size and age structure to quantitatively evaluate the extent of economies of scale in consumption of energy-intensive goods, and to estimate age-specific profiles of consumption of energy-intensive goods and of CO(2) emissions. Third, I offer an illustration of the methodologies using data for the United States. The analysis shows that per-capita CO(2) emissions increase with age until the individual is in his or her 60s, and then emissions tend to decrease. Holding everything else constant, the expected change in U.S. population age distribution during the next four decades is likely to have a small, but noticeable, positive impact on CO(2) emissions.

  11. India's Proposed Universal Health Coverage Policy: Evidence for Age Structure Transition Effect and Fiscal Sustainability.

    Science.gov (United States)

    Narayana, Muttur Ranganathan

    2016-12-01

    India's High Level Expert Group on Universal Health Coverage in 2011 recommended a universal, public-funded and national health coverage policy. As a plausible forward-looking macroeconomic reform in the health sector, this policy proposal on universal health coverage (UHC) needs to be evaluated for age structure transition effect and fiscal sustainability to strengthen its current design and future implementation. Macroeconomic analyses of the long-term implications of age structure transition and fiscal sustainability on India's proposed UHC policy. A new measure of age-specific UHC is developed by combining the age profile of public and private health consumption expenditure by using the National Transfer Accounts methodology. Different projections of age-specific public health expenditure are calculated over the period 2005-2100 to account for the age structure transition effect. The projections include changes in: (1) levels of the expenditure as gross domestic product grows, (2) levels and shape of the expenditure as gross domestic product grows and expenditure converges to that of developed countries (or convergence scenario) based on the Lee-Carter model of forecasting mortality rates, and (3) levels of the expenditure as India moves toward a UHC policy. Fiscal sustainability under each health expenditure projection is determined by using the measures of generational imbalance and sustainability gap in the Generational Accounting methodology. Public health expenditure is marked by age specificities and the elderly population is costlier to support for their healthcare needs in the future. Given the discount and productivity growth rates, the proposed UHC is not fiscally sustainable under India's current fiscal policies except for the convergence scenario. However, if the income elasticity of public expenditure on social welfare and health expenditure is less than one, fiscal sustainability of the UHC policy is attainable in all scenarios of projected public

  12. Computational explorations of the influence of structured knowledge on age-related cognitive decline.

    Science.gov (United States)

    Mireles, David E; Charness, Neil

    2002-06-01

    Experience in a domain can sometimes offset cognitive declines that occur with aging. Using a series of neural network simulations of learning chess opening positions, the authors investigated how structured knowledge in a distributed representation may influence age-related declines. Aging manipulations implemented as modulations of neural noise showed increased knowledge as being protective of performance on a chess memory span task, whereas changes in neural plasticity and neural loss lead to main effects without interactions and steeper declines for the initially more able. The models could also simulate the increase in variability in older groups.

  13. Factorial Structure and Age-Related Psychometrics of the MIDUS Personality Adjective Items across the Lifespan

    Science.gov (United States)

    Zimprich, Daniel; Allemand, Mathias; Lachman, Margie E.

    2014-01-01

    The present study addresses issues of measurement invariance and comparability of factor parameters of Big Five personality adjective items across age. Data from the Midlife in the United States (MIDUS) survey were used to investigate age-related developmental psychometrics of the MIDUS personality adjective items in two large cross-sectional samples (exploratory sample: N = 862; analysis sample: N = 3,000). After having established and replicated a comprehensive five-factor structure of the measure, increasing levels of measurement invariance were tested across ten age groups. Results indicate that the measure demonstrates strict measurement invariance in terms of number of factors and factor loadings. Also, we found that factor variances and covariances were equal across age groups. By contrast, a number of age-related factor mean differences emerged. The practical implications of these results are discussed and future research is suggested. PMID:21910548

  14. High temperature aging structures of Ni-20Cr-20W alloys

    International Nuclear Information System (INIS)

    Ohmura, Taizo; Sahira, Kensho; Sakonooka, Akihiko; Yonezawa, Noboru

    1977-01-01

    High temperature aging structures and age hardening of Ni-20Cr-20W alloys developed as the superalloys for the nuclear energy steelmaking, and effects of C and Zr additions to the alloys and the effect of preheat treatment on these properties were studied. M 6 C, α-W and two kinds of M 23 C 6 having different lattice parameters were found as precipitates in the alloys. M 23 C 6 whose lattice parameter was around 10.7A precipitated in the early stage of aging at 700 0 C-1,150 0 C, and the carbide changed to M 6 C at higher temperature than 1,000 0 C, but it remained as a stable carbide at lower temperature than 900 0 C. α-W precipitated at 800 0 C-1,100 0 C after precipitation of M 23 C 6 and it disappeared with increase of M 6 C. M 23 C 6 having the larger lattice parameter (10.9A) precipitated transitionally in aging stage of 26 x 10 3 in Larson Miller parameter at 900 0 C and 1,000 0 C. Age hardening corresponded to the precipitation of M 23 C 6 and it was reduced by the double pre-heat-treatment. Zr addition and amount of C influenced on the aging structure and age hardening. Zr seemed to be a favorable element to stabilize the carbide. (auth.)

  15. Structural architecture supports functional organization in the human aging brain at a regionwise and network level.

    Science.gov (United States)

    Zimmermann, Joelle; Ritter, Petra; Shen, Kelly; Rothmeier, Simon; Schirner, Michael; McIntosh, Anthony R

    2016-07-01

    Functional interactions in the brain are constrained by the underlying anatomical architecture, and structural and functional networks share network features such as modularity. Accordingly, age-related changes of structural connectivity (SC) may be paralleled by changes in functional connectivity (FC). We provide a detailed qualitative and quantitative characterization of the SC-FC coupling in human aging as inferred from resting-state blood oxygen-level dependent functional magnetic resonance imaging and diffusion-weighted imaging in a sample of 47 adults with an age range of 18-82. We revealed that SC and FC decrease with age across most parts of the brain and there is a distinct age-dependency of regionwise SC-FC coupling and network-level SC-FC relations. A specific pattern of SC-FC coupling predicts age more reliably than does regionwise SC or FC alone (r = 0.73, 95% CI = [0.7093, 0.8522]). Hence, our data propose that regionwise SC-FC coupling can be used to characterize brain changes in aging. Hum Brain Mapp 37:2645-2661, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  16. Do brain image databanks support understanding of normal ageing brain structure? A systematic review

    International Nuclear Information System (INIS)

    Dickie, David Alexander; Job, Dominic E.; Wardlaw, Joanna M.; Poole, Ian; Ahearn, Trevor S.; Staff, Roger T.; Murray, Alison D.

    2012-01-01

    To document accessible magnetic resonance (MR) brain images, metadata and statistical results from normal older subjects that may be used to improve diagnoses of dementia. We systematically reviewed published brain image databanks (print literature and Internet) concerned with normal ageing brain structure. From nine eligible databanks, there appeared to be 944 normal subjects aged ≥60 years. However, many subjects were in more than one databank and not all were fully representative of normal ageing clinical characteristics. Therefore, there were approximately 343 subjects aged ≥60 years with metadata representative of normal ageing, but only 98 subjects were openly accessible. No databank had the range of MR image sequences, e.g. T2*, fluid-attenuated inversion recovery (FLAIR), required to effectively characterise the features of brain ageing. No databank supported random subject retrieval; therefore, manual selection bias and errors may occur in studies that use these subjects as controls. Finally, no databank stored results from statistical analyses of its brain image and metadata that may be validated with analyses of further data. Brain image databanks require open access, more subjects, metadata, MR image sequences, searchability and statistical results to improve understanding of normal ageing brain structure and diagnoses of dementia. (orig.)

  17. Take a Stand!

    DEFF Research Database (Denmark)

    Danquah, I. H.; Kloster, S.; Holtermann, A.

    2017-01-01

    Background: Prolonged sitting time has been associated with adverse health outcomes. Interventions at work may contribute to reduced sitting. The objective was to test if a multicomponent work-based intervention can reduce sitting time and the number of prolonged sitting periods (> 30 min......), increase the number of sit-to-stand transitions and decrease waist circumference and body fat percentage among office workers. Primary outcomes were: change in sitting time, prolonged sitting periods and sit-to-stand transitions at followup 1 month later. Methods: At four workplaces, 19 offices (317...... workers in total) were cluster randomized for intervention or control. The intervention included the appointment of local ambassadors, management support, environmental changes, a lecture and a workshop. Sitting time was measured using an ActiGraph GT3X+ fixed on the thigh. Data were processed using Acti4...

  18. Spatio-temporal variation in age structure and abundance of the endangered snail kite: Pooling across regions masks a declining and aging population

    Science.gov (United States)

    Reichert, Brian E.; Kendall, William L.; Fletcher, Robert J.; Kitchens, Wiley M.

    2016-01-01

    While variation in age structure over time and space has long been considered important for population dynamics and conservation, reliable estimates of such spatio-temporal variation in age structure have been elusive for wild vertebrate populations. This limitation has arisen because of problems of imperfect detection, the potential for temporary emigration impacting assessments of age structure, and limited information on age. However, identifying patterns in age structure is important for making reliable predictions of both short- and long-term dynamics of populations of conservation concern. Using a multistate superpopulation estimator, we estimated region-specific abundance and age structure (the proportion of individuals within each age class) of a highly endangered population of snail kites for two separate regions in Florida over 17 years (1997–2013). We find that in the southern region of the snail kite—a region known to be critical for the long-term persistence of the species—the population has declined significantly since 1997, and during this time, it has increasingly become dominated by older snail kites (> 12 years old). In contrast, in the northern region—a region historically thought to serve primarily as drought refugia—the population has increased significantly since 2007 and age structure is more evenly distributed among age classes. Given that snail kites show senescence at approximately 13 years of age, where individuals suffer higher mortality rates and lower breeding rates, these results reveal an alarming trend for the southern region. Our work illustrates the importance of accounting for spatial structure when assessing changes in abundance and age distribution and the need for monitoring of age structure in imperiled species.

  19. Spatio-Temporal Variation in Age Structure and Abundance of the Endangered Snail Kite: Pooling across Regions Masks a Declining and Aging Population.

    Science.gov (United States)

    Reichert, Brian E; Kendall, William L; Fletcher, Robert J; Kitchens, Wiley M

    While variation in age structure over time and space has long been considered important for population dynamics and conservation, reliable estimates of such spatio-temporal variation in age structure have been elusive for wild vertebrate populations. This limitation has arisen because of problems of imperfect detection, the potential for temporary emigration impacting assessments of age structure, and limited information on age. However, identifying patterns in age structure is important for making reliable predictions of both short- and long-term dynamics of populations of conservation concern. Using a multistate superpopulation estimator, we estimated region-specific abundance and age structure (the proportion of individuals within each age class) of a highly endangered population of snail kites for two separate regions in Florida over 17 years (1997-2013). We find that in the southern region of the snail kite-a region known to be critical for the long-term persistence of the species-the population has declined significantly since 1997, and during this time, it has increasingly become dominated by older snail kites (> 12 years old). In contrast, in the northern region-a region historically thought to serve primarily as drought refugia-the population has increased significantly since 2007 and age structure is more evenly distributed among age classes. Given that snail kites show senescence at approximately 13 years of age, where individuals suffer higher mortality rates and lower breeding rates, these results reveal an alarming trend for the southern region. Our work illustrates the importance of accounting for spatial structure when assessing changes in abundance and age distribution and the need for monitoring of age structure in imperiled species.

  20. INVESTIGETING THE EFFECTS OF STANDING TRAINING ON BODY FUNCTIONS AND ACTIVITY FOR NONAMBULATORY CHILDREN WITH MYELOMENINGOCELE

    Directory of Open Access Journals (Sweden)

    Ozge Cankaya

    2017-09-01

    Full Text Available Background: It was indicated in many studies that verticalization have positive effects such as preventing fractures,regulating cardiopulmonary functions, increasing the head control, and the facilitation of postural muscles in pediatric patients, however, no study showing the effect of supported standing in patients with myelomeningocele on body functions and activity was encountered. The aim of this study is to examine the effects of structured supported standing training in children with myelomeningocele on body functions and activity according to ICF-CY. Methods: Twenty-five children with MMC aged between 3 and 17, who were divided into two groups-SST and control. The supported standing training was given to supported standing group 2 hours a day for 8 weeks in addition to the routine physical therapy program. Body functions were assessed with the Trunk Impairment Scale, and activity levels were assessed with the Gross Motor Function Measurement-88 and Pediatric Functional Independence Measurement at the beginning of the study, at the end of 8 weeks and at the end of 12 weeks from beginning. Results: The results of the structured supported standing training program during 8 weeks showed that children’s body functions and activity increased statistically significantly in SST group (p0.05. Conclusion: The results show that supported standing training effects the body functions and activity positively. It is recommended to educate the families for the supported standing training to be added to the routine physiotherapy and rehabilitation program for children with MMC and continue the training at home.