bluuebunny/crossref_metadata_2025 huggingface dataset:
Long tipping times of a quantum rod
Authors: Lundeberg Mark B , Shegelski Mark RA
Published: June 2006

We calculate the tipping time of a quantum rod that has a height several times that of the edge length of its square base. We use an expression for the tipping time that has heuristic value, and gives the average time at which, upon measurement, the initially balanced rod is found to tip. We use two methods to calculate the tipping time. One method is to examine the "late time" behaviour of the quantum state of the center of mass of the rod by using an equation that has the form of the time-independent Schrödinger equation except that it involves a "complex energy." The other method uses energy resonances in the eigenstates of the Hamiltonian to determine the tipping time. We use the well-known WentzelKramersBrillouin approximation to calculate the energy eigenstates. With these methods, we obtain expressions for the tipping time that are valid for very long tipping times. PACS Nos.: 03.65.w, 03.65.Xp
Electronic structure of cubic BaTbO3 from first-principles pseudopotential calculations
Authors: Gao G Y , Yao K L , Liu Z L
Published: June 2006

First-principles calculations of the electronic structure are performed for cubic BaTbO3 using the plane-wave pseudopotential method within the framework of density functional theory and using the generalized gradient approximation for the exchange-correlation potential. Our calculations show that cubic BaTbO3 is metallic, and that this metallic character is mainly governed by the Tb 4f electrons and the hybridization between the Tb 5d and O 2p states. From the analysis of the density of states, band structure, and charge density contour, we find that the chemical bonding between Tb and O is covalent while that between Ba and TbO3 is ionic. PACS Nos.: 71.15.Mb, 71.20.-b
The renormalization group with exact β-functions
Authors: Elias V , McKeon D.G.C.
Published: June 2006

The perturbative β-function is known exactly in a number of supersymmetric theories and in the ‘t Hooft renormalization scheme in the [Formula: see text] model. It is shown how this allows one to compute the effective action exactly for certain background field configurations and to relate bare and renormalized couplings. The relationship between the minimal subtraction scheme and the supersymmetry subtraction scheme in N = 1 super YangMills theory is discussed.PACS No.: 11.10Z
An improved landslide mobility model
Authors: Kwan Julian SH , Sun H W
Published: June 2006

A relatively simple and versatile numerical model known as DAN, developed by Oldrich Hungr for the assessment of landslide mobility, has been enhanced to incorporate the consideration of a trapezoidal-shaped flow channel for more realistic modelling purposes. This enhanced debris mobility model (DMM) has been programmed to run on a spreadsheet and has been calibrated against detailed landslide data in Hong Kong. In contrast to previous work, the enhanced DMM eliminates the limitations inherited from the assumption of a rectangular flow channel with frictionless side boundaries. When using DMM, no predefined width of landslide is needed. The DMM simulates landslide mobility with the flow resistance on the whole wetted perimeter of the channel, calculates the surface width of the landslide based on the cross-sectional geometry of the channel, and is capable of predicting a lobe-shaped debris deposition area. This technical note presents details of the enhancement to the DAN formulation.Key words: landslides, debris flows, runout analysis, landslide mobility, dynamic modelling, numerical methods.
Physical modelling of consolidation of Hong Kong marine clay with prefabricated vertical drains
Authors: Fang Zhen , Yin Jian-Hua
Published: June 2006

In this study, a small-scale physical model with full instrumentation was set up and used to measure the full consolidation process of a cylinder of clay with one prefabricated vertical drain (PVD) in its middle. The model test produced several interesting phenomena: (i) a delayed pore-water pressure increase under a constant pressure during loading stages, (ii) a delayed pore-water pressure decrease under a constant pressure during unloading stages, and (iii) residual excess pore-water pressures at the end of loading. Two analytical solutions accounting for the well resistance and a smear zone with reduced permeability are used to calculate the variation of average excess pore-water pressure with time, and these are compared with the measured variation. The well resistance of the PVD has a larger influence on the consolidation process than the permeability of the smear zone, especially during the latter stages of consolidation. The analytical solutions are able to show the influence of the well resistance of the PVD strip, but they cannot satisfactorily simulate the pattern of the residual excess pore-water pressure with time.Key words: consolidation, vertical drain, marine clay, physical modelling.
Determination of synthetic hydrate content in sand specimens using dielectrics
Authors: Kliner J R , Grozic J LH
Published: June 2006

Gas hydrates are solid crystalline compounds (clathrates) that encage gas molecules inside the lattices of hydrogen bonded water molecules within a specific temperaturepressure stability zone. It is imperative that reliable detection and quantification modi operandi are developed, as proposed in this research, to identify hydrate-laden strata and determine economic viability of this potential energy yield. This paper presents the experimental analysis of synthetic refrigerant (R-11) hydrates in 20/30 Ottawa sand using dielectric principles to determine specific hydrate content. Hydrate specimens were constructed via moist tamped Ottawa sand, purged with carbon dioxide (CO2), saturated with de-aired water, and mixed with a known amount of R-11 to produce precise hydrate contents. The specimen's bulk dielectric constant was measured using a ThetaProbe by applying the principles of time domain reflectometry (TDR). A distinct relationship between hydrate content and the bulk dielectric constant of sand specimens is determined, as well; volumetric expansion associated with hydrate formation is also portrayed.Key words: gas hydrates, synthetic hydrates, dielectrics, Ottawa sand, laboratory testing.
The role of epiphytes in rainfall interception by forests in the Pacific Northwest. II. Field measurements at the branch and canopy scale
Authors: Pypker Thomas G , Unsworth Michael H , Bond Barbara J
Published: June 2006

To determine how epiphytes affect the canopy hydrology of old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests, we measured rainfall interception by individual branches and an entire stand from March 2003 to May 2004. Epiphyte-laden branches at heights of 3.1, 24.8 and 46.5 m remained partially saturated for most of the wet season and required more than 30 mm of rainfall to become saturated. We used the mean, minimum, and individual storm methods to estimate canopy water storage capacity. Canopy water storage capacity averaged 3.15.0 mm, but these are probably underestimates of the maximum canopy water storage capacity, because the canopy was partially saturated prior to most storm events and the saturation of the canopy was delayed by preferential flow through the epiphyte-laden branches. Contrary to expectation, the water stored on epiphyte-laden branches after exposure to natural rainfall increased with rainfall intensity because the rough three-dimensional structure of the lichen and bryophyte mats limits water loss from raindrop splash and impedes the drainage of water from the branch. We conclude that epiphytic lichens and bryophytes increase canopy water storage capacity, prolong the time required for the canopy to saturate and dry, and alter the transfer of water through the canopy.
Life cycle of Arceuthobium americanum on Pinus banksiana based on inoculations in Edmonton, Alberta
Authors: Brandt J P
Published: June 2006

While lodgepole pine dwarf mistletoe, Arceuthobium americanum Nutt. ex Engelm., is one of the most damaging pests of jack pine (Pinus banksiana Lamb.) in western Canada, no studies have examined the life cycle of this parasite in this pathosystem. Twenty-five jack pine trees in a plantation in Edmonton, Alberta, were inoculated with seeds of A. americanum in the fall of 1998 and 1999; these inoculants were monitored until the dwarf mistletoe plants that arose completed their life cycle. Ninety-two percent of inoculated seeds overwintered on their host. Seventy percent of these seeds germinated, mostly in May. Of these germinants, 69% developed holdfasts. Sixty-eight percent of germinants that developed holdfasts infected their host and produced shoots, primarily between July and August in the second season after inoculation. Of the 56 plants that developed from the 175 inoculations, 34 were pistillate plants and 19 were staminate plants, and 3 immature plants died because the host branch died. Pistillate plants flowered significantly earlier than staminate plants (4.1 vs. 4.7 years). Most pistillate plants produced seed in the fifth year, although one plant produced seed in 4 years. Thus, A. americanum probably has a 5-year life cycle on jack pine.
Modeling seed-origin oak regeneration in the central Appalachians
Authors: Gould P J , Steiner K C , McDill M E , Finley J C
Published: June 2006

We describe the development of a model to quantify seed-origin oak regeneration potential in advance of complete overstory removal in central Appalachian oak stands. The model was developed using a "top-down" modeling approach that differs significantly from the approaches used to develop similar models for other regions. The modeling approach was designed to take advantage of the best data available for the region. A stand-level model was first fit using a long-term data set from Pennsylvania that was developed, in part, from operational data collected through the course of timber sales. The stand-level model describes the relationship between oak advanced regeneration distribution (the percentage of 4 m2sample plots that contained at least one oak seedling before harvest) and third-decade seed-origin oak stocking (the percentage of growing space occupied by seed-origin oaks in the third decade after harvest). Inverse modeling was used to fit a plot-level model using a highly detailed short-term data set collected as part of an ongoing study of regeneration development in Pennsylvania. A negative exponential function (1  eαx) was used for the plot-level model to simplify the calculation of multiple seedling success probabilities. The plot-level model predicts the probability that a 4 m2plot will be occupied by an oak during the third decade after harvest based on the sum of the heights of oak advanced regeneration (aggregate height). The top-down inverse modeling approach used here proved to be a feasible alternative to the more common individual seedling modeling approach, which requires more specialized data that are often difficult to obtain.
Synergistic stem volume response to combinations of vegetation control and seedling size in conifer plantations in Oregon
Authors: Rosner Lee S , Rose Robin
Published: June 2006

There are few published studies examining the effects of the interaction of seedling size and vegetation control on the growth of Pacific Northwest conifer species. Data from two vegetation management studies encompassing five planting sites, four conifer species, and two stock types were analyzed to determine the relative effects of seedling size at planting and intensity of vegetation control on subsequent seedling growth. Study 1 tested eight combinations of annual broadcast weed control or no weed control applied over the course of 5 years. Study 2 tested spot herbicide applications of differing area, as well as herbaceous-only and woody-only control treatments. The effect of seedling size was determined by analysis of covariance, with basal diameter as the covariate. Both seedling size and weed control increased growth of all conifer species through 4, 5, or 12 years, but responses varied by species and site. Diameter and height responses to weed control and seedling size were additive, whereas volume differences between treatments increased with increasing seedling size. The implication for management is that the volume return from increased weed control is maximized by planting the largest possible seedlings; conversely, the volume from increased seedling size is maximized at the highest weed control intensities.
Economic analysis of health effects from forest fires
Authors: Rittmaster R , Adamowicz W L , Amiro B , Pelletier R T
Published: June 2006

Epidemiological studies have shown that high levels of fine particulate matter (PM) are correlated with adverse human health effects. Approximately one-third of PM emissions in Canada originate from forest fires. However, air quality concerns are not typically included in resource allocation decisions in fire management. In this paper we examine the economic magnitude of these health concerns and compare them to other costs of forest fires using the 2001 fire in Chisholm, Alberta, as a case study. We construct an empirical air dispersion model to estimate the concentration of PM arising from the fire. Benefit transfer methods were used to determine the health impacts associated with elevated PM from the fire and to value these impacts. The economic impacts appear to be substantial, second only to timber losses. The approaches used in this case study can be extended to construct a map that identifies the values at risk from health effects. The use of monetary values of these impacts helps in comparison and aggregation of the values at risk.
A multivariate, nonparametric stem-curve prediction method
Authors: Lappi Juha
Published: June 2006

The paper presents a general method for predicting the stem curve, volume, and merchantable height of a tree if breast height diameter (DBH) is measured, or if DBH and total height (H) as well as diameters at any heights are measured. Estimates for prediction variances are obtained both for diameters and volumes. The approach is multivariate and nonparametric. At the estimation stage, a multivariate model is developed for the total height and a fixed set of diameters: four diameters at absolute heights below breast height and eight diameters at relative distances between the breast height and the top of the tree. The expected values and variances of the dimensions and the correlations between dimensions are expressed as functions of DBH. These functions were estimated using smoothing splines. The model is applied by predicting unobserved dimensions from the observed dimensions using a linear predictor. If total height is not measured, then prediction is done using an approach based on two-point distributions. Correlation of total heights of different trees in the same stand is also modeled, and with this model, measured total heights in a stand can be used to predict unmeasured total heights. The approach provides both a detailed analysis of variation and covariation of stem curves and a practical prediction method.
Boreal mixedwood tree growth on contrasting soils and disturbance types
Authors: Martin Jennifer L , Gower Stith T
Published: June 2006

Mixedwood forests are an ecologically and economically important ecosystem in the boreal forest of northern Canada. The objectives of this study were to (i) compare the ageheight relationships for dominant tree species growing on two contrasting soil types and originating from different disturbances (logging versus wildfire), and (ii) determine the influence of competition on tree growth. Eight stands were selected that encompassed two age-classes replicated on two soil types (clay loam and sand) in a split-plot design. Four of the eight stands originated from logging (2126 years old), and the four others originated from wildfires (80 years old). Nonlinear ageheight analyses were used to compare annual height and radial increment growth of black spruce (Picea mariana (Mill.) BSP), jack pine (Pinus banksiana Lamb.), and trembling aspen (Populus tremuloides Michx.). Species, soil type, and size class explained significant amounts of the measured variation in the ageheight models. Aspen, black spruce, and jack pine were 16%, 27%, and 19% taller, respectively, on clay soils than on sandy soils at the burned stand. Tree heights did not differ significantly among species or between soil types in logged stands. Diameter growth decreased as competition increased for black spruce and jack pine in the burned stands. The results for these three important boreal tree species are discussed in the context of sustainable forestry for boreal mixedwood forests.
Genetic variation in basal area increment phenology and its correlation with growth rate in loblolly and slash pine families and clones
Authors: Emhart Veronica I , Martin Timothy A , White Timothy L , Huber Dudley A
Published: June 2006

We quantified basal area increment phenology over a 2-year period in one loblolly pine (Pinus taeda L.) and four slash pine (Pinus elliottii Engelm. var. elliottii) full-sib families propagated as rooting cuttings. In 2002, basal area growth started in March and stopped in October for both species, while in 2003, initiation and cessation occurred 2 weeks earlier for all families. In both years, peaks in basal area increment occurred in short (23 week) periods in the early spring for all families, followed by linear basal area growth until cessation. While there were significant size differences among taxa (species and families) at age 6 and 7 years, genetic differences in basal area growth rate were only expressed during short, discrete time periods primarily in the spring and fall. Basal area growth rate increased during periods when water soil availability increased (up to 300 mm), but an excess in water availability in the soil had a negative impact on growth. Within-family individual-tree broad-sense heritabilities ranged from 0.01 to 0.37 for all traits. In general, heritabilities were higher for growth traits than for phenological traits for all families. Both the strength and direction of correlation estimates of phenological traits with growth rate varied across families and years.
Light and nutrient effects on growth and allocation of Inga vera (Leguminosae), a successional tree of Puerto Rico
Authors: Myster Randall W
Published: June 2006

With the aim of acquiring a better understanding of ecological growth and biomass allocation of Neo tropical trees, I inoculated Inga vera Willd. (Leguminosae) plants from cuttings with Rhizobium spp. and arbuscular mycorrhizal fungi and grew them in a greenhouse for 8 months under varying light (L), phosphorus (P), and nitrogen (N) treatments. I obtained the following results: (1) L, P × N, and L × P × N treatments affected every response variable, but most increases occurred under full light; that is, light levels influenced growth of Inga vera to a greater extent than did P and N additions by themselves; (2) response variables showed a high degree of similarity in regard to which combination of treatment levels had the greatest positive response (full light  low N  high P) and which combination led to other significant increases (full light  low N  no P, full light  high N  no P); and (3) percent AM colonization was affected mainly by light, not P levels. I conclude that growth responses of Inga vera are primarily controlled by light availability, which can interact with nutrient addition to affect biomass allocation to both above- and below-ground structures.
Estimation of biophysical characteristics for highly variable mixed-conifer stands using small-footprint lidar
Authors: Jensen Jennifer L. Rooker , Humes Karen S , Conner Tamara , Williams Christopher J , DeGroot John
Published: June 2006

Although lidar data are widely available from commercial contractors, operational use in North America is still limited by both cost and the uncertainty of large-scale application and associated model accuracy issues. We analyzed whether small-footprint lidar data obtained from five noncontiguous geographic areas with varying species and structural composition, silvicultural practices, and topography could be used in a single regression model to produce accurate estimates of commonly obtained forest inventory attributes on the Nez Perce Reservation in northern Idaho, USA. Lidar-derived height metrics were used as predictor variables in a best-subset multiple linear regression procedure to determine whether a suite of stand inventory variables could be accurately estimated. Empirical relationships between lidar-derived height metrics and field-measured dependent variables were developed with training data and acceptable models validated with an independent subset. Models were then fit with all data, resulting in coefficients of determination and root mean square errors (respectively) for seven biophysical characteristics, including maximum canopy height (0.91, 3.03 m), mean canopy height (0.79, 2.64 m), quadratic mean DBH (0.61, 6.31 cm), total basal area (0.91, 2.99 m2/ha), ellipsoidal crown closure (0.80, 0.08%), total wood volume (0.93, 24.65 m3/ha), and large saw-wood volume (0.75, 28.76 m3/ha). Although these regression models cannot be generalized to other sites without additional testing, the results obtained in this study suggest that for these types of mixed-conifer forests, some biophysical characteristics can be adequately estimated using a single regression model over stands with highly variable structural characteristics and topography.
Songbird diversity and movement in upland and riparian habitats in the boreal mixedwood forest of northeastern Ontario
Authors: Mosley Erin , Holmes Stephen B , Nol Erica
Published: June 2006

Little is known about the importance of riparian areas in supporting avifaunal diversity in the boreal mixedwood forest, especially outside of the breeding season. Bird populations were sampled by mist netting 18 upland and 18 riparian sites along six streams in a forested region of northeastern Ontario. Riparian sites generally had more variable vegetation than upland sites. Some riparian sites formed distinctive habitats, while others were structurally and compositionally similar to upland sites. During spring and fall migration, there was no significant difference in bird abundance or species richness between riparian and upland habitats. During the breeding period, riparian areas had greater avian species richness and abundance and more insects than upland forests, suggesting that birds were selecting these habitats because they contain more food. More birds were captured in nets placed perpendicular to the stream than parallel during the breeding and fall migration periods, suggesting that riparian areas may function as movement corridors. A greater understanding of the importance of riparian habitats to songbird communities is needed if we are to maximize the effectiveness of these regions for conserving avian biodiversity in the boreal mixedwood forest.
Effects of imaging conditions on crown diameter measurements from high-resolution aerial images
Authors: Mäkinen Antti , Korpela Ilkka , Tokola Timo , Kangas Annika
Published: June 2006

Imaging geometry, the structure of the forest, and certain tree properties can cause inaccuracy in image measurements of the crown dimensions of individual trees. Measurement error of the crown diameter was studied in relation to various factors to explain this error. A secondary aim was to generate calibration models for improving the accuracy of crown diameter image measurements. The crown diameters of a total of 715 sample trees in southern Finland were measured in the field and from aerial photographs at scales 1:6000, 1 : 12 000, and 1 : 16 000. The photo grammetric image measurement seemed to systematically underestimate the true crown diameter, and the major factor affecting the bias was tree species. The mean underestimation varied from 0.30 to 0.80 m, with root mean square errors of 0.951.10 m depending on the tree species. Linear regression analysis was employed to define the factors that had an effect on the image measurements, and calibration models in the form of linear regression models were generated. The calibration models worked reasonably well, and the root mean square error for the calibrated observations decreased by 22% for Scots pine (Pinus sylvestris L.), 53% for Norway spruce (Picea abies (L.) Karst), and 47% for silver birch (Betula pendula Roth).
Exotic earthworm invasion increases soil carbon and nitrogen in an old-growth forest in southern Quebec
Authors: Wironen M , Moore T R
Published: June 2006

To test whether invasion of exotic earthworms affects soil carbon (C) and nitrogen (N), we sampled the litter and upper mineral soil (to 30 cm) at a series of sites varying in their earthworm populations in an old-growth beechmaple forest at Mont St. Hilaire, southern Quebec. We measured earthworm abundance and biomass using hand-sorting and chemical extraction (allyl isothiocyanate) methods. They gave similar results, though there was evidence of size and species-specific biases. Abundance and biomass of the earthworms ranged from <10 to >100 earthworms·m2 and from <10 to 125 g·m2, respectively, and were correlated with distance from a nearby lake (negatively) and soil pH (positively). The presence of earthworms was associated with a decrease in the mass and thickness and an increase in the C/N quotient of the litter layer. There were no significant changes in C and N mass of the mineral soil between 0 and 10 cm, but the underlying layers (1020 and 2030 cm) in sites with >10 earthworms·m2 showed significantly (p < 0.05) greater concentrations and masses of both C and N than did sites with <10 earthworms·m2. The overall profile (litter plus soil to 30 cm) average C was 13.7 and 10.1 kg·m2 with and without earthworms, respectively, and the equivalent figures for N were 1.01 and 0.68 kg·m2. These results demonstrate that invasion of earthworms into deciduous forests affects both the litter and mineral soil, and sampling to a depth of 30 cm suggests that earthworm invasion (from <10 to >10 earthworms·m2) may increase overall C and N.
The effect of initial tree-planting density on timber and wood-fuel properties of red alder and sycamore
Authors: Mmolotsi Ronnie M , Teklehaimanot Zewge
Published: June 2006

Studies on red alder (Alnus rubra Bong.) and sycamore (Acer pseudoplatanus L.) were carried out to assess their timber and wood-fuel properties when grown at wide spacing as in a silvopastoral system. Initial tree-planting density had significant effects on the modulus of elasticity (MOE) in red alder and compression strength in sycamore. Wood samples taken from red alder in high-density plots of 2500 stems·ha1 had a significantly higher MOE than those from trees in low-density plots of 400 stems·ha1 (silvopastoral system). Sycamore wood from the high-density plots had significantly higher compression strength than that from the low-density plots. However, there was no significant effect of planting density on the modulus of rupture in either species. On average, red alder had lower wood density, modulus of rupture, and compression strength than sycamore, but there was no significant difference in MOE between the two species. Planting density did not have any effect on the wood-fuel higher heating value of either red alder or sycamore, nor was there a significant difference in wood-fuel higher heating value between the two species. However, red alder wood had a significantly higher fuel-value index than sycamore, owing to its lower ash content.
Effectiveness of solitary retention trees for conserving epiphytes: differential short-term responses of bryophytes and lichens
Authors: Lõhmus Piret , Rosenvald Raul , Lõhmus Asko
Published: June 2006

Green-tree retention (GTR) on clearcuts is an attempt to mimic natural disturbances and provide habitat for species that are generally absent in clear-cut stands, but its efficacy for sustaining biodiversity is poorly known. We studied (i) the total cover and vitality of lichens and bryophytes on four common tree species in three locations (centre and edge of GTR cuts and adjacent forest) and (ii) the composition of and damage to various epiphytic species on European aspen (Populus tremula L.) and birches (Betula spp.) in Estonia during 2 postharvesting years. Bryophytes on all tree species throughout the GTR cuts were severely unhealthy (60% of shoots desiccated, on average); lichens were much more robust (2% of thalli bleached or broken), particularly at the edges of harvested areas and on aspen and European ash (Fraxinus excelsior L.; hereinafter referred to as ash). Most lichen damage appeared to be unrelated to logging (the damaged species were also affected in forests). Aspen hosted many more species, including those of conservation concern, than birch. If tree species, size, and bark texture are carefully considered, GTR could be a successful tool for conserving lichens, particularly many microlichens on aspen and ash. However, bryophytes on solitary trees were generally unhealthy, at least in the short term.
Influence of repeated fertilization on forest ecosystems: relative habitat use by mule deer and moose
Authors: Sullivan Thomas P , Sullivan Druscilla S , Lindgren Pontus M.F , Ransome Douglas B
Published: June 2006

This study was designed to test the hypothesis that large-scale precommercial thinning (PCT) and repeated fertilization of young lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) stands would enhance relative habitat use by mule deer (Odocoileus hemionus Rafinesque) and moose (Alces alces L.) in summer and winter periods, compared to that in mature and old-growth stands. Replicate study areas were located near Summerland, Kelowna, and Williams Lake in south central British Columbia, Canada. Each study area had a range of PCT densities, with and without fertilization, and mature and old-growth stands. Habitat use in summer and winter was measured by pellet-group counts of deer and moose from 1999 to 2003, 610 years after the onset of treatments. During summer months, habitat use by deer was enhanced by PCT with fertilization, and the 1000 stems/ha fertilized stands experienced greater use than the unthinned or mature stands. Winter habitat use by deer was similar in the 1000 stems/ha fertilized stands and old-growth stands. In both summer and winter, moose preferred fertilized to unfertilized stands and low-density to high-density stands. Intensive management of young lodgepole pine forests has considerable potential to develop summer and winter ranges for these ungulates.
Influence of long-term nutrient optimization on biomass, carbon, and nitrogen acquisition and allocation in Norway spruce
Authors: Iivonen Sari , Kaakinen Seija , Jolkkonen Annika , Vapaavuori Elina , Linder Sune
Published: June 2006

We examined the effects of a long-term nutrient-optimization treatment on the acquisition and allocation of biomass, carbon (C), and nitrogen (N) in young Norway spruce (Picea abies (L.) Karst.) growing in northern Sweden. After 12 years of fertilization the absolute biomass of stem, needles, living branches, and stump and coarse roots was more than doubled by nutrient optimization (irrigation  liquid fertilization treatment, IL), but the standing biomass of fine and small roots was unaffected compared with that of control trees. Biomass allocation among aboveground organs was not plastic to nutrient optimization and only the relative proportion of dead branches was reduced by nutrient optimization. Within the crown, biomass allocation to living branches was shifted towards the apex in IL trees. The N content in IL trees was substantially higher than in control trees. Most of the total N was allocated to needles and most of the needle N was found in the middle stratum of the living crown in both treatments, although the N concentration of current-year and older needles increased towards the apex in IL trees but not in control trees. The C concentration in the biomass components was not affected by the optimized fertilization. The results clearly show that there is a large potential to increase biomass production of Norway spruce (C sequestration) in the Nordic countries. This would secure the supply of raw material for the forest industry at the same time as the demand for biofuel from forest biomass is increasing.
Design-unbiased estimation for point-to-tree distance sampling
Authors: Kleinn Christoph , Vilčko Frantiek
Published: June 2006

Point-to-tree distance sampling designs, sometimes also referred to as k-tree sampling or fixed-count sampling, are practical response design options for field sampling in forest inventories and ecological surveys. While practitioners accept and use several approaches to estimate stem density and other stand attributes, a major concern from a statistical point of view is the lack of a general unbiased estimator for this class of sampling strategies. In this paper we analyse point-to-tree distance sampling in the framework of design-based probabilistic sampling and present an unbiased estimator valid for estimation of any stand attribute. This estimator draws upon the idea of defining an inclusion zone around each tree. A tree is taken as a sample tree if a selected sample point falls into its inclusion zone. The size of the inclusion zone is therefore a measure of the individual tree's inclusion probability when sampling is done with random sample points. Once the inclusion probabilities are known for all sampled trees, the Horwitz-Thompson estimator can be used as an unbiased estimator for any stand variable. In point-to-tree distance sampling, the inclusion zone of a particular tree depends exclusively on the spatial arrangement of the neighbouring trees. Such inclusion zones are determined by k-order Voronoi polygons, where k is the number of trees being sampled per sample point. The approach, however, requires the positions of the k sample trees and a number of surrounding trees to be mapped. Field application is therefore difficult, but a comparison of plot designs by simulation studies in fully mapped stands can now also be done with an unbiased estimator for k-tree sampling.
Predicting past and future diameter growth for trees in the northeastern United States
Authors: Westfall James A
Published: June 2006

Tree diameter growth models are widely used in forestry applications, often to predict tree size at a future point in time. Also, there are instances where projections of past diameters are needed. A relative diameter growth model was developed to allow prediction of both future and past growth rates. Coefficients were estimated for 15 species groups that cover most tree species in the northeastern United States. Application of the model to independent data generally showed slight underprediction of growth, although the bias was negligible. Correlated observations were accounted for via a mixed-effects modeling approach, and an error function was specified to address heterogeneous variance. The models use a minimum amount of field-collected data, thus keeping data acquisition costs low and facilitating use in many forest growth applications.
Spatial and temporal dynamics in canopy dominance of an old-growth central Appalachian forest
Authors: McEwan Ryan W , Muller Robert N
Published: June 2006

Many old-growth deciduous forests in eastern North America exhibit dynamics that suggest succession from dominance by oaks (Quercus spp.) to dominance by maples (Acer spp.). We examined this phenomenon using 20 years of vegetation data from an old-growth central Appalachian forest. Considering the site as a whole, the importance of Quercus spp. declined and that of Acer spp. increased. In particular, Acer rubrum L. exhibited increasing importance in the overstory canopy on upper slopes, and Quercus spp. exhibited a contraction in spatial distribution, particularly in the midstory (P < 0.05). This narrowing of distribution in Quercus spp. was associated with regeneration being restricted to dry, acidic sites. We also considered successional dynamics within three previously identified ecological communities in the study area: oak, mixed mesophytic, and beech. This analysis indicated that increased A. rubrum importance was limited to the upper-slope oak community. A successional dynamic was not apparent in the mixed mesophytic community, and the beech community was characterized by increasing importance of Tsuga canadensis (L.) Carr. Our results suggest that ecological communities have distinct successional trajectories and that predictions of future dynamics must consider topographic and ecological gradients.
COLLAPSING WORDS: A PROGRESS REPORT
Authors: ANANICHEV D. S. , PETROV I. V. , VOLKOV M. V.
Published: June 2006

A word w over a finite alphabet Σ is n-collapsing if for an arbitrary DFA [Formula: see text], the inequality |δ(Q, w)| ≤ |Q| - n holds provided that |δ(Q, u)| ≤ |Q| - n for some word u ∈ Σ+(depending on [Formula: see text]). We overview some recent results related to this notion. One of these results implies that the property of being n-collapsing is algorithmically recognizable for any given positive integer n.
PROPERTIES OF THE CONTOUR PATH OF DISCRETE SETS
Authors: BRLEK S. , LABELLE G. , LACASSE A.
Published: June 2006

We consider paths in the square lattice and use a valuation called the winding number in order to exhibit some combinatorial properties on these paths. As a corollary, we obtain a characteristic property of non-crossing closed paths, generalizing in this way a result of Daurat and Nivat (2003) on the boundary properties of polyominoes concerning salient and reentrant points. Moreover we obtain a similar result for hexagonal lattices and show that there is no other regular lattice having that property.
Chronic ethanol-mediated decrease in cAMP primes macrophages to enhanced LPS-inducible NF-κB activity and TNF expression: relevance to alcoholic liver disease
Authors: Gobejishvili Leila , Barve Shirish , Joshi-Barve Swati , Uriarte Silvia , Song Zhenyuan , McClain Craig
Published: June 2006

Increased plasma and hepatic TNF-α activity has been implicated in the pathogenesis of alcoholic liver disease (ALD). We previously reported that monocytes from alcoholic patients show enhanced constitutive as well as LPS-inducible NF-κB activation and TNF-α production. Studies in monocytes have shown that cAMP plays an important role in regulating TNF-α expression, and elevation of cellular cAMP suppresses TNF-α production. The effects of chronic ethanol exposure on the cellular levels of cAMP as well as TNF expression in monocytes were examined in vitro and in rat primary hepatic Kupffer cells obtained from a clinically relevant enteral alcohol feeding model of ALD. Chronic ethanol exposure significantly decreased cellular cAMP levels in both LPS-stimulated and unstimulated monocytes. Consistent with the decrease in cAMP levels, ethanol led to an increase in LPS-inducible TNF-α production by affecting NF-κB activation and induction of TNF mRNA expression, without any change in TNF mRNA stability. Enhancement of cellular cAMP with dibutyryl cAMP abrogated LPS-mediated TNF-α expression in ethanol-treated cells. Importantly, cAMP did not affect LPS-inducible NF-κB activation but significantly decreased its transcriptional activity. Together, these data strongly suggest that ethanol can synergize with LPS to upregulate the induction of TNF gene expression and consequent TNF overproduction by decreasing the cellular cAMP levels in monocytes/macrophages. Furthermore, these data also support the notion that cAMP-elevating agents could constitute an effective therapeutic approach in attenuating or preventing the progression of liver disease in alcoholic patients.
Hibernation confers resistance to intestinal ischemia-reperfusion injury
Authors: Kurtz Courtney C. , Lindell Susanne L. , Mangino Martin J. , Carey Hannah V.
Published: June 2006

The damaging effects of intestinal ischemia-reperfusion (I/R) on the gut and remote organs can be attenuated by subjecting the intestine to a prior, less severe I/R insult, a process known as preconditioning. Because intestines of hibernating ground squirrels experience repeated cycles of hypoperfusion and reperfusion, we examined whether hibernation serves as a model for natural preconditioning against I/R-induced injury. We induced intestinal I/R in either the entire gut or in isolated intestinal loops using rats, summer ground squirrels, and hibernating squirrels during natural interbout arousals (IBA; body temperature 37–39°C). In both models, I/R induced less mucosal damage in IBA squirrels than in summer squirrels or rats. Superior mesenteric artery I/R increased MPO activity in the gut mucosa and lung of rats and summer squirrels and the liver of rats but had no effect in IBA squirrels. I/R in isolated loops increased luminal albumin levels, suggesting increased gut permeability in rats and summer squirrels but not IBA squirrels. The results suggest that the hibernation phenotype is associated with natural protection against intestinal I/R injury.
Induction of intestinal peptide transporter 1 expression during fasting is mediated via peroxisome proliferator-activated receptor α
Authors: Shimakura Jin , Terada Tomohiro , Saito Hirofumi , Katsura Toshiya , Inui Ken-ichi
Published: June 2006

We previously demonstrated that starvation markedly increased the amount of mRNA and protein levels of the intestinal H+/peptide cotransporter (PEPT1) in rats, leading to altered pharmacokinetics of the PEPT1 substrates. In the present study, the mechanism underlying this augmentation was investigated. We focused on peroxisome proliferator-activated receptor α (PPARα), which plays a pivotal role in the adaptive response to fasting in the liver and other tissues. In 48-h fasted rats, the expression level of PPARα mRNA in the small intestine markedly increased, accompanied by the elevation of serum free fatty acids, which are endogenous PPARα ligands. Oral administration of the synthetic PPARα ligand WY-14643 to fed rats increased the mRNA level of intestinal PEPT1. Furthermore, treatment of the human intestinal model, Caco-2 cells, with WY-14643 resulted in enhanced PEPT1 mRNA expression and uptake activity of glycylsarcosine. In the small intestine of PPARα-null mice, augmentation of PEPT1 mRNA during fasting was completely abolished. In the kidney, fasting did not induce PEPT1 expression in either PPARα-null or wild-type mice. Together, these results indicate that PPARα plays critical roles in fasting-induced intestinal PEPT1 expression. In addition to the well-established roles of PPARα, we propose a novel function of PPARα in the small intestine, that is, the regulation of nitrogen absorption through PEPT1 during fasting.
Role of changes in cardiac metabolism in development of diabetic cardiomyopathy
Authors: An Ding , Rodrigues Brian
Published: June 2006

In patients with diabetes, an increased risk of symptomatic heart failure usually develops in the presence of hypertension or ischemic heart disease. However, a predisposition to heart failure might also reflect the effects of underlying abnormalities in diastolic function that can occur in asymptomatic patients with diabetes alone (termed diabetic cardiomyopathy). Evidence of cardiomyopathy has also been demonstrated in animal models of both Type 1 (streptozotocin-induced diabetes) and Type 2 diabetes (Zucker diabetic fatty rats and ob/ob or db/db mice). During insulin resistance or diabetes, the heart rapidly modifies its energy metabolism, resulting in augmented fatty acid and decreased glucose consumption. Accumulating evidence suggests that this alteration of cardiac metabolism plays an important role in the development of cardiomyopathy. Hence, a better understanding of this dysregulation in cardiac substrate utilization during insulin resistance and diabetes could provide information as to potential targets for the treatment of cardiomyopathy. This review is focused on evaluating the acute and chronic regulation and dysregulation of cardiac metabolism in normal and insulin-resistant/diabetic hearts and how these changes could contribute toward the development of cardiomyopathy.
E22K mutation of RLC that causes familial hypertrophic cardiomyopathy in heterozygous mouse myocardium: effect on cross-bridge kinetics
Authors: Dumka D. , Talent J. , Akopova I. , Guzman G. , Szczesna-Cordary D. , Borejdo J.
Published: June 2006

Familial hypertrophic cardiomyopathy is a disease characterized by left ventricular and/or septal hypertrophy and myofibrillar disarray. It is caused by mutations in sarcomeric proteins, including the ventricular isoform of myosin regulatory light chain (RLC). The E22K mutation is located in the RLC Ca2+-binding site. We have studied transgenic (Tg) mouse cardiac myofibrils during single-turnover contraction to examine the influence of E22K mutation on 1) dissociation time (τ1) of myosin heads from thin filaments, 2) rebinding time (τ2) of the cross bridges to actin, and 3) dissociation time (τ3) of ADP from the active site of myosin. τ1was determined from the increase in the rate of rotation of actin monomer to which a cross bridge was bound. τ2was determined from the rate of anisotropy change of the recombinant essential light chain of myosin labeled with rhodamine exchanged for native light chain (LC1) in the cardiac myofibrils. τ3was determined from anisotropy of muscle preloaded with a stoichiometric amount of fluorescent ADP. Cross bridges were induced to undergo a single detachment-attachment cycle by a precise delivery of stoichiometric ATP from a caged precursor. The times were measured in Tg-mutated (Tg-m) heart myofibrils overexpressing the E22K mutation of human cardiac RLC. Tg wild-type (Tg-wt) and non-Tg muscles acted as controls. τ1was statistically greater in Tg-m than in controls. τ2was shorter in Tg-m than in non-Tg, but the same as in Tg-wt. τ3was the same in Tg-m and controls. To determine whether the difference in τ1was due to intrinsic difference in myosin, we estimated binding of Tg-m and Tg-wt myosin to fluorescently labeled actin by measuring fluorescent lifetime and time-resolved anisotropy. No difference in binding was observed. These results suggest that the E22K mutation has no effect on mechanical properties of cross bridges. The slight increase in τ1was probably caused by myofibrillar disarray. The decrease in τ2of Tg hearts was probably caused by replacement of the mouse RLC for the human isoform in the Tg mice.