bluuebunny/crossref_metadata_2025 huggingface dataset:
2004 Bader Award LectureMetal-ion-catalyzed acyl and phosphoryl transfer reactions to alcohols: La3+-promoted alcoholysis of activated amides, carboxylate esters, and neutral organophosphorus esters
Authors: Brown R Stan , Neverov Alexei A , Tsang Josephine SW , Gibson Graham TT , Montoya-Pelaez Pedro J
Published: February 2005

Unlike metal-ion-catalyzed hydrolysis processes, metal-ion-catalyzed methanolysis processes have received scant attention in the literature particularly from the standpoint of mechanistic studies. La3+, introduced into methanol solution as its triflate or perchlorate salt, is particularly effective in promoting methanolysis reactions of unactivated and activated esters, phosphate triesters, and activated amides such as acetyl imidazoles and lactams. Studies of the kinetics of methanolysis of these substrates as a function of solution pH and [La3+] indicate that the solution comprises lanthanum dimers with one to five associated methoxides (La23+(OCH3)15), the most catalytically active form being La23+(OCH3)2, which is produced at near neutral pH in methanol (8.4). Mechanisms for all the acyl and phosphoryl transfer reactions are proposed where the metal ion serves a dual role of acting as a Lewis acid to activate the C=O or P=O system to nucleophilic attack by a metal-coordinated methoxide nucleophile. In cases where direct comparisons can be made, the La23+ catalyst system is more active for the methanolysis of nonactivated substrates than for activated substrates. Another general characteristic of this system is that the catalytic rate constant for the metal complex exceeds the second-order rate constant for free methoxide, in some cases by as much as 4600-fold. Overall the catalytic effects exhibited by the La23+ system is spectacular for such substrates as paraoxon, where as little as 2 mmol L1 La(OTf)3 in the presence of equimolar NaOCH3 accelerates the methanolysis by 109-fold relative to the background reaction at neutral pH and ambient temperature.Key words: kinetics of methanolysis, metal ion catalysis, lanthanides, methanolysis of carboxylate esters and phosphate esters.
New cycloaddition of diarylazines with 1,2-dehydrobenzene, 1,1,2,2-tetracyanoethylene, and dibenzoylacetylene  Facile synthesis of acridinones, pyrazolidine, and pyridazine derivatives
Authors: Aly Ashraf A , Gomaa Mohsen A.-M
Published: February 2005

Diarylazines were reacted with 1,2-dehydrobenzene (o-benzyne) to give 10-amino-3-substituted-9(10H)-acridinones. On the other hand, 1,1,2,2-tetracyanoethylene was reacted with diarylazines through Michael addition to yield 5-arylpyrazolidine-3,3,4,4-tetracarbonitriles. On reacting the same azines with dibenzoylacetylene, pyridazine derivatives were obtained via a DielsAlder reaction.Key words: diarylazines, 1,2-dehydrobenzene, tetracyanoethylene, dibenzoylacetylene.
2003 Alfred Bader Award LecturePredicting the rates of chemical reactions
Authors: Guthrie J Peter
Published: February 2005

The dream of being able to predict the rate of a chemical reaction corresponding to a detailed mechanism is now almost within our grasp. No barrier theory (NBT), which makes the calculations relatively facile, is described, as are various applications of the approach to date. Illustrations are given of the use of NBT not just as a quantitative tool for predicting rates, but as a qualitative tool for thinking about which of a pair of reactions will have the higher intrinsic barrier, and thus be slower for similar thermodynamic driving force.Key words: rate, equilibrium, thermodynamics, kinetics, no barrier theory, computational chemistry, chemical reactivity.
An approach to optimizing field data collection in an inventory by compartments
Authors: Mehtätalo Lauri , Kangas Annika
Published: February 2005

This study presents models for the expected error of the total volume and saw timber volume due to sampling errors of stand measurements. The measurements considered are horizontal point sample plots, stem numbers from circular plots, sample tree heights, sample order statistics (i.e., quantile trees), and sample tree heights from the previous inventory. Different measurement strategies were constructed by systematically varying the numbers of these measurements. A model system developed for this study was used in a data set of 170 stands to predict the total volume and saw timber volume of each stand with each measurement strategy. The errors of these volumes were modeled using stand characteristics and the numbers of measurements as predictors. The most important factors affecting the error in the total volume were the number of horizontal point sample plots and height sample trees. In addition, the number of quantile trees had a strong effect on the error of saw timber volume. The errors were slightly reduced when an old height measurement was used. There were significant interactions between stand characteristics and measurement strategies. Thus, the optimal measurement strategy varies between stands. A demonstration is provided of how constrained optimization can be used to find the optimal strategy for any one stand.
Forest dependence and community well-being in rural Canada: variation by forest sector and region
Authors: Stedman Richard C , Parkins John R , Beckley Thomas M
Published: February 2005

The forest products sector is a major employer in much of rural Canada, and it is often assumed by policy makers that increased timber harvest is a viable means of rural economic development. Despite burgeoning research in the United States, relatively little attention has focused on the relationship between forest dependence and well-being in rural Canada. Especially lacking are macrocomparisons of regions and of forest sectors. This note presents an overview of the relationship between forest dependence and well-being in Canada. Analysis of 1996 Statistics Canada data revealed a great deal of variation in the effect of forest dependence on indicators of well-being (e.g., human capital, unemployment, income): some sectors had fairly positive outcomes (e.g., pulp and paper); others had more negative outcomes (e.g., logging). These relationships, however, vary a great deal by region, suggesting the need for more mid-range explanatory models that incorporate the particulars of place and sector.
Spatially explicit modeling of PAR transmission and growth of Picea glauca and Abies balsamea in the boreal forests of Alberta and Quebec
Authors: Stadt Kenneth J , Lieffers Victor J , Hall Ronald J , Messier Christian
Published: February 2005

To investigate the feasibility of a spatially explicit, radiation-based regeneration model for the boreal forest, we tested the predictions of a three-dimensional simulator of photosynthetically active radiation transmission (%PAR), MIXLIGHT, and the growth response of understory Abies balsamea (L.) Mill. (balsam fir) and Picea glauca (Moench) Voss (white spruce) to %PAR in two large (>1 ha) mixed-species forest sites, one in eastern Canada at Lac Duparquet, Quebec, and one in western Canada at Calling Lake, Alberta. Overstory tree locations and dimensions were obtained from aerial photographs or ground measurements and allometric relationships. Seasonal %PAR calculated by MIXLIGHT for the Calling Lake site was very similar to seasonal %PAR measured by quantum sensors (n = 5, %PAR range = 15%33%, r = 0.93). Daily measurements of %PAR were also predicted well by simulations at both sites (n = 3436, %PAR range = 1%45%, r ≥ 0.76). Functional relationships, designed to saturate at the maximum height growth potential of these sites, were developed to predict sapling height growth from simulated seasonal %PAR and initial height (R2 ≥ 0.74). These results demonstrate the potential of the MIXLIGHT simulator for estimating PAR at microsites within heterogeneous forests and for modeling understory tree growth.
Tree growth prediction using size and exposed crown area
Authors: Wyckoff Peter H , Clark James S
Published: February 2005

We address the relationships between tree growth rate and growing environment for 21 co-occurring species. Tree growth rates are obtained from mapped plots at the Coweeta Long-Term Ecological Research site in the southern Appalachian Mountains. We employ high-resolution aerial photography to assess the light environment for trees growing in these plots, using exposed crown area (ECA) as a surrogate for light interception. The relationship between growth and ECA is compared with two other growth predictors: tree size and shade-tolerance classification. We find that ECA is an excellent predictor of tree growth (average R2 = 0.69 for nine species). When ECA is combined with tree size, growth rate prediction is improved (average R2 = 0.76). Tree size alone is also a strong predictor of tree growth (average R2 = 0.68). Shade-tolerance classification, by contrast, is a poor predictor of tree growth.
Sensitivity of tree growth to the atmospheric vertical profile in the Boreal Plains of Manitoba, Canada
Authors: Girardin Martin-Philippe , Tardif Jacques
Published: February 2005

This paper investigates the influence of surface climate and atmospheric circulation on radial growth of eight boreal tree species growing in the Duck Mountain Provincial Forest, Manitoba, Canada. Tree-ring residual chronologies were built, transformed into principal components (PCs), and analysed through correlation and response functions to reveal their associations to climate (temperature, precipitation, and drought data for the period 19121999, as well as local geopotential height data for the period 19481999). Geopotential height correlation and composite charts for the Northern Hemisphere were also constructed. Correlation and response function coefficients indicated that radial growth of all species was negatively affected by temperature-induced drought stresses from the summers previous and current to ring formation. The summer drought stress alone explained nearly 28% of the variance in PC1. Warm spring temperature was also a positive factor for Pinus banksiana Lamb. and Picea glauca (Moench) Voss, but a negative one for all hardwoods. Analyses performed on geopotential height highlighted the importance of the Northern Hemispheric atmospheric circulation in the species' response to climate. The variability within the 500-hPa level over southern Manitoba explained 39% and 58% of the variability in PC1 and PC2, respectively. The relationships were highly significant with the middle and high troposphere during spring and late summer (determinant factor for growing season length) and with the troposphere and stratosphere during summer. The sensitivity of tree growth to atmospheric circulation exceeded the synoptic scale, with a response associated with yearly variations in the amplitude of the mid-tropospheric longwaves.
Eleven-year growth response of young conifers to biosolids or nitrogen and phosphorus fertilizer on northern Vancouver Island
Authors: Prescott Cindy E , Blevins Leandra L
Published: February 2005

To test the hypothesis that fertilization with municipal biosolids causes a larger long-term tree growth response than fertilization with conventional chemical fertilizers, we measured the height and diameter of planted western redcedar (Thuja plicata Donn ex D. Don), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and amabilis fir (Abies amabilis (Dougl.) Forbes) 11 years after fertilization with biosolids or nitrogen and phosphorus fertilizer. There were four replicate plots of each tree species and treatment combination. The stand volume in cedar plots doubled in response to both treatments; in treated hemlock and fir plots, the stand volume was about triple that in control plots. There was little difference in tree response between biosolids-amended and fertilized plots. A type 3 response (growth rates remain elevated relative to those in the control) was evident for hemlock and fir. Biosolids appear to be as effective as chemical fertilizers in promoting conifer growth on these nutrient-poor sites, but their effect is neither greater nor more prolonged.
Genotypic variation and recovery of Populus tremuloides from biomass removal and compaction in northern Wisconsin, USA
Authors: Bockheim J G , Park H , Gallagher J
Published: February 2005

This study was initiated in 1990 to determine the effects of simulated logging practices on long-term productivity of trembling aspen (Populus tremuloides Michx.). Treatments included three levels of biomass removal (entire aboveground woody biomass, control; control + coarse woody detritus, LS; and LS + forest floor, FF) and two levels of compaction (light compaction on winter skid roads, TRA; heavy simulated compaction with FF, COM). The study was conducted on a Typic Haplorthod and a Haplic Glossudalf of medium site quality (site index50 years = 21 and 23 m, respectively) on the Brule State Forest. Twelve years after treatment, the following results were noted: (1) there were no significant differences in aspen height growth among treatments at either site except for lower stocking, height, diameter, and basal area on heavily compacted plots (COM, forest floor removed before compaction) at the clay site; (2) there was considerable genotypic variation in aspen height growth; and (3) recovery of physical properties, as reflected by bulk density, occurred within 12 years of treatment but was not manifested by improved aspen growth. These results suggest that concern over long-term effects of intensified biomass removal and soil compaction should be matched by a concern over protection of the aspen gene pool in the upper Great Lakes region.
Silviculture alters the genetic structure of an eastern hemlock forest in Maine, USA
Authors: Hawley Gary J , Schaberg Paul G , DeHayes Donald H , Brissette John C
Published: February 2005

We evaluated the influence of long-term silvicultural selection on the genetic structure of an eastern hemlock (Tsuga canadensis (L.) Carr.) forest at the Penobscot Experimental Forest, in Maine, USA. Plots in this forest received one of the following three treatments: (1) selection cuts in which small and poorly formed trees were preferentially removed in 1957 and 1977; (2) diameter-limit cuts in which trees at least 24 cm in diameter were removed in 1952, 1973, and 1994; or (3) no harvesting (an unmanaged control). Because of an association between the occurrence of rare alleles and tree phenotypes, phenotypically based tree removals were associated with a shift in allelic frequency. Where smaller trees with inferior phenotypes were preferentially removed (selection cut), the number of rare alleles and estimates of future genetic potential were lower than in the control group. Because of the theoretical long-term evolutionary benefit of unique gene forms, the loss of rare alleles could diminish the potential of populations to adapt to and survive ongoing environmental change. In contrast, alleles that were rare in the control group existed at a higher frequency in the diameter-limit cut. However, productivity was low in this stand, where the frequency of characteristically rare alleles was artificially amplified.
Patterns of decomposition and carbon, nitrogen, and phosphorus dynamics of litter in upland forest and peatland sites in central Canada
Authors: Moore T R , Trofymow J A , Siltanen M , Prescott C , Group CIDET Working
Published: February 2005

We tested whether upland or peatland location affected rates of litter decomposition and nutrient dynamics. We examined the patterns of mass loss and carbon (C), nitrogen (N), and phosphorus (P) gain, retention, or loss in 11 forest tissues over 6 years at three upland and three peatland sites in the Low Boreal, High Boreal, and Low Subarctic zones of central Canada. After 6 years of decomposition, the average litter mass remaining ranged from 35% for fescue grass to 75% for western redcedar needles and 94% for wood blocks placed on the soil surface, with exponential decay coefficients (k) of 0.16, 0.05, and 0.01, respectively. At one pair of sites, the mass remaining and the k values indicated that faster decomposition occurred in the upland site than in the nearby peatland site. The reverse was the case in a second pair. No overall pattern was apparent in the third. In general, Douglas-fir needles decomposed significantly faster in peatland than upland sites, and the reverse pattern occurred for bracken fern. Most foliar litters retained their original N mass and lost P as they decomposed. There were few major differences between N and P dynamics in litters decomposing at upland and peatland sites, though N and P retention in some cases was greater at the peatland sites. These results suggest that longer term (>6 years) differences in decomposition rate and differences in litter quality account for larger C accumulation in peatland than in upland soils.
Modeling infection and spread of Heterobasidion annosum in even-aged Fennoscandian conifer stands
Authors: Pukkala Timo , Möykkynen Timo , Thor Magnus , Rönnberg Jonas , Stenlid Jan
Published: February 2005

Heterobasidion annosum (Fr.) Bref. s. lato causes severe damage to forests. This study describes a model for simulating the infection and spread of Heterobasidion spp. in stands of Picea abies (L.) Karst. and Pinus sylvestris L. The model includes submodels for stand dynamics (plot simulation, growth and yield, and cross-cutting of trees) and disease dynamics: (i) spore infection, (ii) stump colonization, (iii) colonization of stump roots, (iv) vegetative transfer to tree roots, (v) spread of disease in tree roots, (vi) spread of decay in stems, and (vii) disease effect on tree growth and survival. To illustrate the model, a simulation was carried out on a Swedish Norway spruce stand where logging occurred during the high-risk season for spore infection. The model provides a means of incorporating the impact of root disease into forest planning. A change of parameters indicated that model predictions were sensitive to the spread rate and presence of initial disease centers. Further research is called for in areas related to the development of coarse root systems of various tree species and the probability and rate of transfer of disease from various sources of inoculum to healthy trees.
Response of beaver, moose, and snowshoe hare to clear-cutting in a Quebec boreal forest: a reassessment 10 years after cut
Authors: Potvin François , Breton Laurier , Courtois Réhaume
Published: February 2005

We studied the response of beaver (Castor canadensis Kuhl), moose (Alces alces L.), and snowshoe hare (Lepus americanus Erxl.) to clear-cutting in three blocks that had been logged 10 years ago. In a previous study, these species had been surveyed in the same blocks 2 years before and 2 years after logging. We also surveyed an uncut block of the initial experimental design that was logged more recently. Over the 10-year period, the shrub layer and available browse have improved markedly in clear-cut areas. As compared with logged coniferous stands, logged mixed stands had higher lateral cover (62% vs. ≈55%) and taller regeneration (>4 m vs. <3 m). Beaver density did not change over the period because its feeding habitat remained unchanged in the riparian forest strips. Moose densities increased 54%87% in two harvested blocks as a result of both logging and stricter hunting regulations (selective hunting). Based on the rate of increase observed in a control block, we estimate that a 25% density increase in the mixed forest block can be related to logging, while selective hunting can solely be responsible for the change in the coniferous forest block. Snowshoe hare have started to reoccupy logged coniferous stands, but their relative density still remained less than half that of uncut stands. We conclude that, after 10 years, logged mixed stands already offer good habitat conditions for moose and snowshoe hare. Conversely, in logged black spruce (Picea mariana (Mill.) BSP) stands, habitat conditions still remain poor for snowshoe hare because of a lack of cover.
Stand structure and dynamics in a mixed and multilayered forest in the Upper Susa Valley, Piedmont, Italy
Authors: Motta R , Edouard J L
Published: February 2005

Size, age, and spatial structures were studied in a mixed, multilayered forest located in the Upper Susa Valley in Piedmont, Italy, using complete stem mapping, dendrochronology, and spatial analysis on a 1-ha permanent plot. All trees with a diameter >4 cm at 50 cm height (991) and stumps (322) were mapped, measured, and cored. The 639 cross-dated samples were used to reconstruct the disturbance history, and dendroecological results were then compared with information on forest and land use from documentary archives. The stand has undergone substantial shifts in forest structure and species composition over the last 200 years, from an open structure with larch (Larix decidua Mill.), Swiss mountain pine (Pinus uncinata L.), Norway spruce (Picea abies (L.) Karst.), and scattered regeneration to a dense multilayered structure with silver fir (Abies alba Mill.) and Norway spruce with dense regeneration. Shifts in dominance and structure were found to be consistent with land-use changes rather than with disturbance history. These results confirm the importance of multiple sources of independent data to characterize the disturbances that have affected the origin and development of stands heavily impacted by humans. Knowledge of stand history and understanding of potential ecological transformations are essential for the correct application of close-to-nature silvicultural practices.
A site model for Pyrenean oak (Quercus pyrenaica) stands using a dynamic algebraic difference equation
Authors: Carvalho João P , Parresol Bernard R
Published: February 2005

This paper presents a growth model for dominant-height and site-quality estimations for Pyrenean oak (Quercus pyrenaica Willd.) stands. The BertalanffyRichards function is used with the generalized algebraic difference approach to derive a dynamic site equation. This allows dominant-height and site-index estimations in a compatible way, using any desirable base age and allowing estimations to be time independent, which are important properties for site models. The database contains all possible height-growth intervals. The model is fitted considering residual autocorrelation, giving more efficient parameter estimates. Finally, the model behavior is analyzed by calculating error statistics from dominant-height and site-index estimations at different ages.
Factors influencing early vegetation establishment following soil scarification in a mixed forest in northern Japan
Authors: Yoshida Toshiya , Iga Yoko , Ozawa Megumi , Noguchi Mahoko , Shibata Hideaki
Published: February 2005

Scarification is widely conducted in northern Japan to remove understory dwarf bamboo species in degraded forests for replacement with tree species. To explore ways to enhance species diversity and restoration of mixed forest at the treated site, we clarified the mechanisms that lead to compositional heterogeneity of plant species. We evaluated the relative importance of environmental factors (scarification properties, soil properties, light conditions, litter cover, and presence of canopy trees) for the demography of tall tree species (emergence, mortality, and growth) and whole vegetation structure (species diversity and composition) over the two growing seasons immediately following scarification. Of tall tree species, Betula spp. were dominant (60% in total density), followed by Abies sachalinensis (Fr. Schm.) Masters, Acer mono Maxim., and Phellodendron amurense Rupr. Light intensity was an important factor, having mostly negative effects on the demography of these species. Soil factors (e.g., nitrogen content, moisture) affected the demography mainly of shade-intolerant or hygrophilous species. In general, extreme environmental conditions led to the dominance of grasses, forbs, and lianas rather than tall trees. Maintenance of canopy cover, which limits light and supplies seeds as well as litter, proved to be most important in promoting plant species diversification on the scarification site.
Postfire environmental conditions influence the spatial pattern of regeneration for Pinus ponderosa
Authors: Bonnet V H , Schoettle A W , Shepperd W D
Published: February 2005

Regeneration of ponderosa pine after fire depends on the patterns of seed availability and the environmental conditions that define safe sites for seedling establishment. A transect approach was applied in 2002 to determine the spatial distribution of regeneration from unburned to burned areas within the landscape impacted by the Jasper Fire of 2000 in the Black Hills of South Dakota (USA). Canopy conditions alone, reflecting seed availability, at the stand level were not correlated with regeneration success. However, canopy conditions in combination with ground conditions explained patterns of regeneration success at the plot level (2 m × 6 m scale), and ground conditions explained these patterns at the quadrat level (0.2 m × 0.2 m scale). Only at the finer level of the quadrat could environmental factors explain seedling survival. Safe sites were characterized, in part, by the presence of scorched needle litter on blackened mineral soil. Areas with high understory cover restricted regeneration in the undisturbed forest and reduced seedling survival in the burned areas. The description of environmental conditions that favor and discourage ponderosa pine regeneration success will improve our understanding of how environmental heterogeneity within burned areas will contribute to the future forested landscape.
Soil and root respiration in mature Alaskan black spruce forests that vary in soil organic matter decomposition rates
Authors: Vogel Jason G , Valentine David W , Ruess Roger W
Published: February 2005

Climate warming at high latitudes is expected to increase root and microbial respiration and thus cause an increase in soil respiration. We measured the root and microbial components of soil respiration near Fairbanks, Alaska, in 2000 and 2001, in three black spruce (Picea mariana (Mill) B.S.P.) forests. We hypothesized faster decomposition correlates with greater amounts of both root and microbial contributions to soil respiration. Contrary to our prediction, the site with the coolest summer soil temperatures and slowest decomposition (site identification "high-np") had significantly (p < 0.05) greater growing season soil respiration (485 g C·m2·year1) than the two other sites (372 and 332 g C·m2·year1). Spruce C allocation to root respiration was significantly greater, and fine-root N concentration was 10% and 12% greater (p < 0.05) at high-np than at the other two sites. High-np spruce foliage was also more enriched in 13C and depleted in 15N, suggesting either lower available moisture or slower N turnover. Either factor could drive greater C allocation to roots; however, a literature review suggests moisture deficit corresponds to greater C allocation to roots in black spruce forests across the boreal ecosystem. Controls on spruce C allocation need to be resolved before making the generalization that soil respiration will increase with warming in this forest type.
Nondestructive estimation of Pinus taeda L. wood properties for samples from a wide range of sites in Georgia
Authors: Jones P D , Schimleck L R , Peter G F , Daniels R F , Clark III A
Published: February 2005

Preliminary studies based on small sample sets show that near infrared (NIR) spectroscopy has the potential for rapidly estimating many important wood properties. However, if NIR is to be used operationally, then calibrations using several hundred samples from a wide variety of growing conditions need to be developed and their performance tested on samples from new populations. In this study, 120 Pinus taeda L. (loblolly pine) radial strips (cut from increment cores) representing 15 different sites from three physiographic regions in Georgia (USA) were characterized in terms of air-dry density, microfibril angle (MFA), and stiffness. NIR spectra were collected in 10-mm increments from the radial longitudinal surface of each strip and split into calibration (nine sites, 729 spectra) and prediction sets (six sites, 225 spectra). Calibrations were developed using untreated and mathematically treated (first and second derivative and multiplicative scatter correction) spectra. Strong correlations were obtained for all properties, the strongest R2 values being 0.83 (density), 0.90 (MFA), and 0.93 (stiffness). When applied to the test set, good relationships were obtained (Rp2 ranged from 0.80 to 0.90), but the accuracy of predictions varied depending on math treatment. The addition of a small number of cores from the prediction set (one core per new site) to the calibration set improved the accuracy of predictions and importantly minimized the differences obtained with the various math treatments. These results suggest that density, MFA, and stiffness can be estimated by NIR with sufficient accuracy to be used in operational settings.
Modelling survival probability of individual trees in Norway spruce stands under different thinning regimes
Authors: Karlsson Kjell , Norell Lennart
Published: February 2005

The probability that an individual tree will remain in even-aged Norway spruce (Picea abies (L.) Karst.) stands subjected to different thinning programmes was modelled, using data from a thinning experiment established in 25 localities in southern Sweden. A logistic regression approach was used to predict the probability and the HosmerLemeshow goodness-of-fit test to evaluate the fit. Diameter at breast height (DBH), quadratic mean DBH, thinning intensity, thinning quotient, basal area, number of stems per hectare, stand age, number of thinnings, and site index were used as explanatory variables. Separate analyses for stands thinned from below, stands thinned from above, and unthinned stands were performed. The modelled probability graphs for trees not being removed, plotted against their diameter at breast height, had clear S-shapes for both unthinned stands and stands thinned from below. The graph for stands thinned from above was bell-shaped.
Modeling response curves and testing treatment effects in repeated measures experiments: a multilevel nonlinear mixed-effects model approach
Authors: Zhao Dehai , Wilson Machelle , Borders Bruce E
Published: February 2005

A multilevel nonlinear mixed-effects modeling approach is used to model loblolly pine (Pinus taeda L.) stand volume growth in conjunction with four silvicultural treatments. Comparisons of treatment effects over time are integrated with the model-building process. Three-level random effects are introduced into a modified Richards growth model. Within-plot heterogeneity and correlation still occur, which are described by the exponential variance function and a first-order autoregressive model. The combination of complete vegetation control with fertilization results in the largest growth response; annual fertilization has the next largest growth response, with the exception that at very early stages the response is lower than that of vegetation control only; the control has the lowest growth response. The advantages of the multilevel nonlinear mixed effects model include its ability to handle unbalanced and incomplete repeated measures data, its flexibility to model multiple sources of heterogeneity and complex patterns of correlation, and its higher power to make treatment comparisons. We address in detail a general strategy of multilevel nonlinear mixed effects model building.
Variable responses of folivorous sawflies to leaf quality of mountain birch
Authors: Riipi Marianna , Kause Antti , Haukioja Erkki , Ossipov Vladimir , Ossipova Svetlana , Pihlaja Kalevi
Published: February 2005

We studied whether the larval performance of four sawfly species feeding on mountain birch (Betula pubescens subsp. czerepanovii (Orlova) Hämet-Ahti) leaves at different times of the growing season was related to the same chemical and physical leaf traits. In the three phenologically earliest species, larval growth was related to the same set of leaf traits. In contrast, consumption of leaf material was related to different leaf traits in all of the four species. Leaf suitability for herbivore growth and tree resistance to herbivore consumption were thus not always determined by the same leaf traits. Leaf water content and toughness had the strongest associations with larval performance. Phenolics, which are often considered the main resistance compounds in deciduous trees, explained only a small part of the variance in leaf consumption, but some groups of phenolics were negatively related to larval growth. In conclusion, the same mountain birch trees were not resistant to all of the studied sawflies in terms of leaf consumption, but low leaf suitability, which was related to the same set of leaf traits in the case of three sawfly species, may serve birch resistance, e.g., by exposing larvae to natural enemies for a longer period.
Are the old-growth forests of the Clay Belt part of a fire-regulated mosaic?
Authors: Cyr Dominic , Bergeron Yves , Gauthier Sylvie , Larouche Alayn C
Published: February 2005

Old-growth forests make up a substantial proportion of the forest mosaic in the Clay Belt region of Ontario and Quebec, Canada, despite fire cycles that are presumed to be relatively short. Two hypotheses have been suggested as explanations for this phenomenon: (1) the old-growth forests in question are located on sites that are protected from fire or (2) the fire hazard is just as great there as elsewhere, and that part of the mosaic is simply the tail of the distribution, having been spared from fire merely by chance. The tree-ring method has proven inadequate as a means of determining the date of the most recent fire in these old-growth forests, as the time that has elapsed since that date probably exceeds the age of the oldest trees. Accordingly, a paleoecological study was conducted with a view to determining the date of the last fire in these forests. Charcoal horizons were located and radiocarbon dated in six old-growth forests. The possibility that these forests have never burned at all is ruled out by the fact that macroscopic charcoal fragments were found at all sites. The proximity of potential firebreaks has a significant influence in the survival model, suggesting fire-cycle heterogeneity throughout the landscape. However, the proportion of old-growth forests observed is in agreement with what would be expected assuming that fire hazard is independent of stand age. Old-growth stands could thus be incorporated into natural disturbance based management, although the great variability of the intervals between catastrophic disturbances should be carefully considered.
LOSSILY COMPRESSED MEDICAL MODALITIES: OBJECTIVE AND SUBJECTIVE QUALITY MEASURES IN RELEVANT TO THE STATISTICAL AND FREQUENCY EVALUATIONS
Authors: HUI OH TICK
Published: February 2005

Compressed image will always reduce the image fidelity. This is especially so if the image is compressed at lower bit rates, which most of the time cannot be tolerated. In medical field, this is even more significant. But compression is necessary due to the limited transmission bandwidth and storage capacity. In this paper, the lossy compression performance of the new JPEG2000 and the more conventional JPEG is being studied. The common objective measure, peak signal-to-noise ratio (PSNR) is definitely not adequate as a perceptual quality measurement. Therefore, subjective measures such as picture quality scale (PQS) and mean opinion score (MOS) are included, plus the statistical and frequency measures for the image characteristics evaluation. Four types of medical modalities are used — X-Ray, Magnetic Resonance Imaging (MRI), Ultrasound, and Computed Tomography (CT). From these various measurements, the general acceptance compression bit rate for each of the medical modality is determined.
NUMERICAL STUDY OF A TRANSIENT GAS AND PARTICLE FLOW IN A HIGH-SPEED NEEDLE-FREE BALLISTIC PARTICULATE VACCINE DELIVERY SYSTEM
Authors: LIU Y. , KENDALL M. A. F.
Published: February 2005

A unique biolistic method of vaccination is operated by accelerating particulate vaccines with a high-speed gas jet generated by a convergent-divergent conical nozzle to sufficient momentum to penetrate the outer layer of human skin. The targeted cells elicit an immunological response. In this paper, Computational Fluid Dynamics (CFD) is utilized to simulate the operation of a prototype biolistics delivery system. The key features of transient gas dynamics and gas-particle interaction are discussed.
STEADY VORTICES IN ARTERIAL FLOWS
Authors: SLAWOMIRSKI MARIUSZ R. , PALLOTTI GIOVANNI , PETTAZZONI PAOLO
Published: February 2005

Many authors describe the movement in veins and arteries applying the Poisseuille flow pattern, according to which all streamlines are parallel to the walls of vessels, and the blood flow rate is proportional to the pressure drop.

The presence of vortices may imply two-dimensional stress state in the wall of the vessel. It may be suggest that the additional stress may increase the probability to injure the cells of endothelium. The progressive development of atheroma sedimentation in the vicinity of bifurcations of arteries confirms the hypothesis mentioned above.
PHYSIOLOGICAL SYSTEMS' NUMBERS IN MEDICAL DIAGNOSIS AND HOSPITAL COST-EFFECTIVE OPERATION
Authors: GHISTA DHANJOO N.
Published: February 2005

In paper, we are providing a novel concept of analyzing physiological systems in terms of non-dimensional physiological indices (NDPIs), for quantifying patient health and disease status as well as patient improvement. We have developed NDPI's for several physiological phenomena and systems, and indicated as to how they can be employed diagnostically. NDPIs have been formulated and evaluated for (i) left-ventricular pumping performance, (ii) cardiac fitness and conditioning, (iii) lung ventilatory function, (iv) Oral glucose tolerance test, (v) arteriosclerosis, (vi) atherosclerosis and peripheral resistance, (vii) mitral valve property, and (viii) osteoporosis. We have then also applied these NDPI's for (i) formulating and assessing the performance indices of hispital units and (ii) determining the resource index for cost-effective operation, contributory to hospital management-science.
NONLINEAR PULSATILE FLOWS IN RIGID AND DISTENSIBLE ARTERIES
Authors: HUNG TIN-KAN , TSAI TOMMY M.-C.
Published: February 2005

Blood flow in distensible arteries is nonlinear and time-dependent. The radial motion of the wall alters the dimension and geometry of the flow field. The nonlinear pulsating flow processes are successfully computed by mapping the wavy flow field to a fixed domain and by casting the geometric, kinematic and dynamic parameters of the flow into a dimensionless form of the Navier–Stokes equations. The complexity of the equations is compensated by a significant advantage in finite difference solutions. It is accomplished by using a fixed regular mesh network to model time-dependent irregular meshes in the physical domain for boundary layer development and vortices in pulsatile flows.
TISSUE ENGINEERING APPROACH TO OSTEOCHONDRAL REPAIR AND REGENERATION
Authors: GOH J. C. H. , SHAO X. X. , HUTMACHER D. W. , LEE E. H.
Published: February 2005

Repair of osteochondral lesions remains difficult in current clinical medicine. This is due to the lack of self-reparatory capacity in adult cartilage to respond to injuries. Furthermore, current surgical based treatment is unable to achieve long-term satisfactory results. Cell therapies combined with scaffolds has become a promising tissue engineering approach for osteochondral regeneration. This article briefly outlines the approaches and limitations in osteochondral tissue engineering from three key aspects, namely: (1) Cells and Cell Source; (2) Biomaterials and Scaffold design and fabrication; and (3) Mechanical and Biochemical Stimulus. Current optimal candidate cells for tissue engineering include bone marrow and adipose tissue derived mesenchymal stem cells. As for scaffolds, the structural design and biomaterials used should support cell growth and the organization of new functional tissue formation. Using Fused Deposition Modeling (FDM) technique, the authors developed a novel polycaprolactone osteochondral scaffold which was shown to have the ability to recruit mesenchymal stem cells and the potential for repairing defects in vivo. The article also discussed mechanical and biological stimulus for enhancing in vitro growth of tissue-engineered constructs. The final challenge is the integration of the tissue-engineered tissues into a living system as a functional device.
DEVELOPMENT OF AN ANTHROPOMORPHIC NUMERICAL SURROGATE FOR INJURY REDUCTION (ANSIR)
Authors: YANG KING H. , KING ALBERT I.
Published: February 2005

The current paradigm of designing a safer vehicle is to conduct biomechanical studies in order to obtain human response data for the design of more human-like anthropomorphic crash dummies. These are in turn used to develop and evaluate new concepts for vehicular safety systems. Unfortunately, significant differences exist between the dummy and the human. For instance, dummies are designed to emulate human responses in a handful of impact directions and are unable to fully simulate bony fractures. Nonetheless, dummies have become part of the governmental regulatory Proceedings, and as a result, while modern day cars are much safer than their predecessors, the fact remains that today's cars are designed to be safe for dummies. With the rapid advancement in computing technology, computer models of the human occupant have become an alternate surrogate and the purpose of this study was to establish guidelines for the development of a family of numerical surrogates to investigate human injury mechanisms and tolerance. The project is code-named ANSIR (Anthropomorphic Numerical Surrogate for Injury Reduction).
THERMAL-WAVE PROPAGATION PHENOMENON IN THIN FILMS HEATED WITH LASER HEAT SOURCE
Authors: TORII SHUICHI , YANG WEN-JEI
Published: February 2005

A numerical study is performed on the effect of laser radiation on the propagation phenomenon of a thermal wave in a very thin film subjected to a symmetrical heating on both sides. Laser heating is modelled as an internal heat source. The non-Fourier, hyperbolic heat conduction equation is solved by a numerical technique based on MacCormack's predictor-corrector scheme. Consideration is given to the time history of heat transfer behaviour before and after symmetrical collision of wave fronts from two sides of a film. It is disclosed that (i) if the absorption coefficient of the laser increases, temperature overshoot causes in a very thin film within a very short period of time, and (ii) the overshoot and oscillation of thermal wave depend on the frequency of the heat source time characteristics. This trend becomes minor in a thick film.
STABILIZER ORBIT OF VIRASORO ACTION AND INTEGRABLE SYSTEMS
Authors: GUHA PARTHA
Published: February 2005

We study the stabilizer orbit of the coadjoint action of the Virasoro algebra on its dual. The vector field associated to the stabilizer orbit is called projective vector field. It was shown by Kirillov that the pair formed by the projective vector field and its square root comprises superalgebra. The Euler–Poincaré flow on the "Fermionic" part of the superalgebra yields a pseudospherical type equation. In this paper we express the solutions of the Ermakov–Pinney, Normalized Ermakov–Pinney, Painlevé II and C. Neumann system type (0+1) dimensional integrable systems in terms of the global and local projective vector field, a vector field leaves fixed a given projective connection.
THE BACH TENSOR AND OTHER DIVERGENCE-FREE TENSORS
Authors: BERGMAN JONAS , BRIAN EDGAR S. , HERBERTHSON MAGNUS
Published: February 2005

In four dimensions, we prove that the Bach tensor is the only symmetric divergence-free 2-tensor which is also quadratic in Riemann and has good conformal behavior. In n > 4 dimensions, we prove that there are no symmetric divergence-free 2-tensors which are also quadratic in Riemann and have good conformal behavior, nor are there any symmetric divergence-free 2-tensors which are concomitants of the metric tensor gab together with its first two derivatives, and have good conformal behavior.
REDUCTION AND UNFOLDING: THE KEPLER PROBLEM
Authors: D'AVANZO ANTONELLA , MARMO GIUSEPPE
Published: February 2005

In this paper, we show, in a systematic way, how to relate the Kepler problem to the isotropic harmonic oscillator. Unlike previous approaches, our constructions are carried over in the Lagrangian formalism dealing, with second order vector fields. We therefore provide a tangent bundle version of the Kustaanheimo-Stiefel map.
PERTURBATIVE SOLUTIONS OF DIFFERENTIAL EQUATIONS IN LIE GROUPS
Authors: ANIELLO PAOLO
Published: February 2005

We show that, given a matrix Lie group [Formula: see text] and its Lie algebra [Formula: see text], a 1-parameter subgroup of [Formula: see text] whose generator is the sum of an unperturbed matrix Â0 and an analytic perturbation Â♢(λ) can be mapped — under suitable conditions — by a similarity transformation depending analytically on the perturbative parameter λ, onto a 1-parameter subgroup of [Formula: see text] generated by a matrix [Formula: see text] belonging to the centralizer of Â0 in [Formula: see text]. Both the similarity transformation and the matrix [Formula: see text] can be determined perturbatively, hence allowing a very convenient perturbative expansion of the original 1-parameter subgroup.
Residual heterogeneity of intra- and interregional pulmonary perfusion in short-term microgravity
Authors: Montmerle Stéphanie , Sundblad Patrik , Linnarsson Dag
Published: February 2005

We hypothesized that the perfusion heterogeneity in the human, upright lung is determined by nongravitational more than gravitational factors. Twelve and six subjects were studied during two series of parabolic flights. We used cardiogenic oscillations of O2/SF6 as an indirect estimate of intraregional perfusion heterogeneity ( series 1) and phase IV amplitude (P4) as a indirect estimate of interregional perfusion heterogeneity ( series 2). A rebreathing-breath holding-expiration maneuver was performed. In flight, breath holding and expiration were performed either in microgravity (0 G) or in hypergravity. Controls were performed at normal gravity (1 G). In series 1, expiration was performed at 0 G. Cardiogenic oscillations of O2/SF6 were 19% lower when breath holding was performed at 0 G than when breath holding was performed at 1 G [means (SD): 1.7 (0.3) and 2.3 (0.6)% units] ( P = 0.044). When breath holding was performed at 1.8 G, values did not differ from 1-G control [2.6 (0.8)% units, P = 0.15], but they were 17% larger at 1.8 G than at 1 G. In series 2, expiration was performed at 1.7 G. P4 changed with gravity ( P < 0.001). When breath holding was performed at 0 G, P4 values were 45 (46)% of control. When breath holding was performed at 1.7 G, P4 values were 183 (101)% of control. We conclude that more than one-half of indexes of perfusion heterogeneity at 1 G are caused by nongravitational mechanisms.
Old Persian in Athens Revisited (Ar. Ach. 100)
Authors: Willi Andreas
Published: February 2005

The Old Persian line in Aristophanes' Acharnians (100) is commonly believed to contain nothing but comic gibberish. Against this view, it is argued here that a responsible reconstruction of an Old Persian original is possible if one takes into account what we nowadays know about late fifth-century Old Persian. Moreover, the result, whose central element is the Persian verb for 'writing',fits in with both general considerations on linguistic realism in drama and the historical reality of diplomatic interaction between Greece and Persia during the Peloponnesian War.