Cm Diameter (cm + diameter)

Distribution by Scientific Domains
Distribution within Life Sciences

Selected Abstracts

Current density mapping approach for design of clinical magnetic resonance imaging magnets

Stuart Crozier
Abstract Novel current density mapping (CDM) schemes are developed for the design of new actively shielded, clinical magnetic resonance imaging (MRI) magnets. This is an extended inverse method in which the entire potential solution space for the superconductors has been considered, rather than single current density layers. The solution provides an insight into the required superconducting coil pattern for a desired magnet configuration. This information is then used as an initial set of parameters for the magnet structure, and a previously developed hybrid numerical optimization technique is used to obtain the final geometry of the magnet. The CDM scheme is applied to the design of compact symmetric, asymmetric, and open architecture 1.0,1.5 T MRI magnet systems of novel geometry and utility. A new symmetric 1.0-T system that is just 1 m in length with a full 50-cm diameter of the active, or sensitive, volume (DSV) is detailed, as well as an asymmetric system in which a 50-cm DSV begins just 14 cm from the end of the coil structure. Finally a 1.0-T open magnet system with a full 50-cm DSV is presented. These new designs provide clinically useful homogeneous regions and have appropriately restricted stray fields but, in some of the designs, the DSV is much closer to the end of the magnet system than in conventional designs. These new designs have the potential to reduce patient claustrophobia and improve physician access to patients undergoing scans. © 2002 Wiley Periodicals, Inc. Concepts in Magnetic Resonance (Magn Reson Engineering) 15: 208,215, 2002 [source]

The Aquatic Conservation Strategy of the Northwest Forest Plan

gestión de ecosistemas; gestión ribereña; modelos de soporte de decisiones; terrenos públicos Abstract:,Implemented in 1994, the Aquatic Conservation Strategy of the Northwest Forest Plan was designed to restore and maintain ecological processes for aquatic and riparian area conservation on federal lands in the western portion of the Pacific Northwest. We used decision support models to quantitatively evaluate changes in the condition of selected watersheds. In the approximately 10 years since strategy implementation, watershed condition scores changed modestly, but conditions improved in 64% of 250 sampled watersheds, declined in 28%, and remained relatively the same in 7%. Watersheds that had the largest declines included some where wildfires burned 30,60% of their area. The overall statistical distribution of the condition scores did not change significantly, however. Much of the increase in watershed condition was related to improved riparian conditions. The number of large trees (>51 cm diameter at breast height) increased 2,4%, and there were substantial reductions in tree harvest and other disturbances along streams. Whether such changes will translate into longer-term improvements in aquatic ecosystems across broader landscapes remains to be seen. Resumen:,Implementada en 1994, la Estrategia de Conservación Acuática del Plan Forestal del Noroeste fue diseñada para restaurar y mantener procesos ecológicos para la conservación de áreas acuáticas y ribereñas en terrenos federales en la porción occidental del Pacífico Noroeste (E.U.A.). Utilizamos modelos de soporte de decisiones para evaluar cuantitativamente los cambios en la condición de cuencas seleccionadas. En los casi 10 años desde la implementación de la estrategia, los valores de la condición de las cuencas cambiaron someramente, pero las condiciones mejoraron en 64% de las 250 cuencas muestreadas, declinaron en 28% y permanecieron relativamente iguales en 7%. Las cuencas con las mayores declinaciones incluyeron algunas en las que 30-60% de su superficie fue quemada por fuegos sin control. Sin embargo, la distribución espacial total de los valores no cambió significativamente. Buena parte del incremento en las condiciones de la cuenca se relacionó con el mejoramiento de las condiciones ribereñas. El número de árboles grandes (>51 cm diámetro a la altura del pecho) aumentó 2-4%, y hubo reducciones sustanciales en la cosecha de árboles y otras perturbaciones a lo largo de arroyos. Aun habrá que ver si tales cambios se traducirán en mejoramientos a largo plazo en los ecosistemas acuáticos en paisajes más extensos. [source]

Separating host-tree and environmental determinants of honeydew production by Ultracoelostoma scale insects in a Nothofagus forest

Abstract 1.,Sugar-rich honeydew excreted (,produced') by insects feeding on phloem sap is a key energy flow in a range of temperate and tropical ecosystems. The present study measured honeydew produced by Ultracoelostoma sp. (Homoptera: Coelostomidiidae) scale insects feeding on Nothofagus solandri var. solandri (Hook f.) Oerst. trees in a temperate evergreen forest in New Zealand. Simultaneous measurements of environmental variables and canopy photosynthesis were conducted to allow separation of host-tree and environmental determinants of honeydew production. These relationships were further examined in experiments where canopy photosynthesis was manipulated by shading or plant nitrogen levels increased by foliar spray. 2.,Rates of honeydew production varied nine-fold from a maximum (± 1 SE) of 64.4 ± 15.2 mg dry mass m,2 bark h,1 in early summer (December) to a minimum of 7.4 ± 4.2 mg m,2 h,1 in winter (August). Rates of production measured 1.4 m from the base of the trees' stems varied significantly with stem diameter, and were higher on medium-sized (18 cm diameter) than small or large stems. 3.,Rates of production were significantly related to environmental conditions over the hours preceding measurement (air temperature and air saturation deficit averaged over the preceding 24 and 12 h respectively). There was no evidence that rates of production were directly related to short-term changes in the supply of carbohydrates from the canopy (either when compared with measurements of unmanipulated photosynthetic rate, or after sugar levels were manipulated by shading 80% of host-trees' leaf area), or to changes in phloem nitrogen content. 4.,The results show that there is no clear effect of host-tree carbon supply on honeydew production; if production is related to photosynthesis, the effect of this is much less important that the large and significant direct effect of environmental conditions on honeydew production. [source]

Preferential phosphorus leaching from an irrigated grassland soil

G. S. Toor
Summary Intact lysimeters (50 cm diameter, 70 cm deep) of silt loam soil under permanent grassland were used to investigate preferential transport of phosphorus (P) by leaching immediately after application of dairy effluent. Four treatments that received mineral P fertilizer alone (superphosphate at 45 kg P ha,1 year,1) or in combination with effluent (at , 40,80 kg P ha,1 year,1) over 2 years were monitored. Losses of total P from the combined P fertilizer and effluent treatments were 1.6,2.3 kg ha,1 (60% of overall loss) during eight drainage events following effluent application. The rest of the P lost (40% of overall loss) occurred during 43 drainage events following a significant rainfall or irrigation compared with 0.30 kg ha,1 from mineral P fertilizer alone. Reactive forms of P (mainly dissolved reactive P: 38,76%) were the dominant fractions in effluent compared with unreactive P forms (mainly particulate unreactive P: 15,56%). In contrast, in leachate following effluent application, particulate unreactive P was the major fraction (71,79%) compared with dissolved reactive P (1,7%). The results were corroborated by 31P nuclear magnetic resonance analysis, which showed that inorganic orthophosphate was the predominant P fraction present in the effluent (86%), while orthophosphate monoesters and diesters together comprised up to 88% of P in leachate. This shows that unreactive P forms were selectively transported through soil because of their greater mobility as monoesters (labile monoester P and inositol hexakisphosphate) and diesters. The short-term strategies for reducing loss of P after application of dairy effluent application should involve increasing the residence time of applied effluent in the soil profile. This can be achieved by applying effluent frequently in small amounts. [source]

Mitigation of the produced voltages in AC overhead power-lines/pipelines parallelism during power frequency and lightning conditions

I. A. Metwally
Abstract This paper presents a theoretical simulation for a pipeline running in parallel to AC overhead power lines using the ,CONCEPT II' package. This package is based on the method of moment combined with a transmission-line model. A 1,km long, 132,kV, three-phase, double-circuit transmission line, and a 2,km long, 40,cm diameter, 1,m high above-ground pipeline are modelled. Extra shielding wires (ESW) under the phase conductors are investigated. Produced voltages in the pipeline are computed under steady-state power frequency (50,Hz) as well as under direct and indirect lightning strikes to the power line. Different current waveforms are simulated to cover the whole range of those of the anticipated lightning. Under lightning strikes, the voltages across line insulators are computed, too. The results reveal that the ESW give many advantages; namely, (1) reducing the power-frequency electric and magnetic fields at the ground level to meet the regularity limits, (2) improving the shielding effectiveness during lightning strikes by reducing the insulator voltages, (3) mitigating the induced voltages in any metallic structure near the power lines, e.g., pipelines, and (4) using them as optical ground wires for telecommunication purposes, where the probability of lightning strikes to such ESW is much lower than that for the normally used grounding wire(s) at the tower top. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Structural biomass partitioning in regrowth and undisturbed mesquite (Prosopis glandulosa): implications for bioenergy uses

GCB BIOENERGY, Issue 1 2010
Abstract Honey mesquite (Prosopis glandulosa Torr.) which grows on grasslands and rangelands in southwestern USA may have potential as a bioenergy feedstock because of existing standing biomass and regrowth potential. However, regrowth mesquite physiognomy is highly different from undisturbed mesquite physiognomy and little is known regarding growth rates and structural biomass allocation in regrowth mesquite. We compared canopy architecture, aboveground biomass and relative allocation of biomass components in regrowth (RG) trees of different known ages with undisturbed (UD) trees of similar canopy height to each RG age class. RG trees in most age classes (2,12 years old) had greater canopy area, leaf area, basal stem number, twig (<0.5 cm diameter) mass and small stem (0.5,3 cm diameter) mass than UD trees of the same height. Large stem (>3 cm diameter) mass was similar between RG and UD trees in all height classes. Ages of UD trees were determined after harvest and further comparisons were made between age, canopy structure and biomass in RG and UD trees. Relationships between age and total mass, age and height, and age and canopy area indicated a faster growth rate in RG than in UD trees. Large stem mass as a percentage of total tree mass accumulated more rapidly with age in RG than UD trees. Leaf area index and leaf : twig mass ratio were maintained near 1 in all RG and UD trees. Regrowth potential may be one of the most important features of mesquite in consideration as a bioenergy feedstock. [source]

Synthesis and Processing of Monodisperse Oligo(fluorene- co -bithiophene)s into Oriented Films by Thermal and Solvent Annealing

Lichang Zeng
Abstract A series of oligo(fluorene- co -bithiophene)s, OF2Ts, have been synthesized and characterized to investigate the effects of oligomer length and pendant aliphatic structure on glassy-nematic mesomorphism. The OF2Ts comprising more than one repeat unit and their polymer analogue, PF2T, carrying 52 number-average repeat units, possess the highest occupied molecular orbital energy level at ,5.3,±,0.2,eV, but the anisotropic field-effect mobilities increase with the oligomer length. Spin coating from high-boiling chlorobenzene with and without subsequent exposure to saturated chlorobenzene vapor constitute solvent-vapor annealing and quasi-solvent annealing, respectively. Solvent-vapor annealing yields monodomain glassy-nematic films in which OF2Ts are aligned as well as with thermal annealing across a 2,cm diameter. Quasi-solvent annealing, however, amounts to kinetically trapping a lower orientational order than solvent-vapor or thermal annealing. While amenable to thermal annealing at elevated temperatures, PF2T shows no alignment at all following either strategy of solvent annealing. [source]

Variation in wood density determines spatial patterns inAmazonian forest biomass

Timothy R. Baker
Abstract Uncertainty in biomass estimates is one of the greatest limitations to models of carbon flux in tropical forests. Previous comparisons of field-based estimates of the aboveground biomass (AGB) of trees greater than 10 cm diameter within Amazonia have been limited by the paucity of data for western Amazon forests, and the use of site-specific methods to estimate biomass from inventory data. In addition, the role of regional variation in stand-level wood specific gravity has not previously been considered. Using data from 56 mature forest plots across Amazonia, we consider the relative roles of species composition (wood specific gravity) and forest structure (basal area) in determining variation in AGB. Mean stand-level wood specific gravity, on a per stem basis, is 15.8% higher in forests in central and eastern, compared with northwestern Amazonia. This pattern is due to the higher diversity and abundance of taxa with high specific gravity values in central and eastern Amazonia, and the greater diversity and abundance of taxa with low specific gravity values in western Amazonia. For two estimates of AGB derived using different allometric equations, basal area explains 51.7% and 63.4%, and stand-level specific gravity 45.4% and 29.7%, of the total variation in AGB. The variation in specific gravity is important because it determines the regional scale, spatial pattern of AGB. When weighting by specific gravity is included, central and eastern Amazon forests have significantly higher AGB than stands in northwest or southwest Amazonia. The regional-scale pattern of species composition therefore defines a broad gradient of AGB across Amazonia. [source]

Quantification of termite attack on lying dead wood by a line intersection method in the Kabili-Sepilok Forest Reserve, Sabah, Malaysia

Abstract., 1A line intersection method was used to estimate abundance (technically linear abundance: m1 m,2), biovolume (m3 ha,1) and size class distribution (defined by diameter) of lying dead wood in tropical forest. Additional semi-quantitative protocols assessed decay state (4 classes), termite attack (5 classes) and live termite occupancy (3 classes). 2Three forest types (kerangas, alluvial and sandstone) were sampled in the Kabili-Sepilok Forest Reserve of Eastern Sabah, using plots of 30 × 30 m. Approximately 50 man-hours were required per site, at a replication of three plots per site and three well-separated sites per forest type. 3Mean biovolume of lying dead wood exceeded 8 × 103 m3 ha,1 in kerangas (= heath) forest, with lower values in other types. Large items (> 19 cm diameter) were less than 10% of total abundance, but represented the largest biovolume, exceeding (alluvial) or equalling (kerangas) the total biovolumes of smaller categories combined. Most items (not less than 75%) were present as small wood (< 10 cm diameter). Items in the highest decay class had the highest biovolume. 4Termite attack was greater in the kerangas, where nearly 90% of items showed evidence of consumption, compared with 58% in the alluvial and 40% in the sandstone forests. Over 40% of items in the kerangas contained live termites compared with 25% in the alluvial and 15% in the sandstone. Items in the highest attack class (= almost total internal destruction) represented about one-half of the total biovolume available in the alluvial and kerangas forest types, and about one-third in the sandstone. [source]

Indications for laparoscopic adrenalectomy for non-functional adrenal tumor with hypertension: Usefulness of adrenocortical scintigraphy

Aim:, Laparoscopic adrenalectomy is currently indicated for biochemically and clinically functional adrenal tumors and potentially malignant tumors of the adrenal glands. Non-functional adenomas greater than 5 cm in diameter of the adrenal gland are generally considered to represent potentially malignant tumors. The present study shows indications of laparoscopic adrenalectomy for non-functional adrenal tumors with hypertension in a retrospective fashion. Methods:, Between 1994 and 2004, 110 laparoscopic adrenalectomies were performed at Tokushima University Hospital. All 110 patients underwent detailed endocrinological examination before surgery. Medical and operative records of these 110 patients (57 men, 53 women), including operative parameters, histopathological findings and pre- and postoperative hypertension, were reviewed. Forty-five patients underwent laparoscopic adrenalectomy for non-functional adrenal tumors, and [131I]6,-iodomethyl-19-norcholest-5(10)-en-3,-ol (NP-59) scintigraphy was performed for patients with preoperative hypertension. Results:, Mean patient age was 55.0 years (range, 22,77 years). Mean maximum tumor diameter was 42 mm (range, 20,105 mm). All adrenal tumors were removed successfully by laparoscopic surgery. Hypertension was postoperatively improved in seven of the 11 patients with preoperative hypertension, without subclinical Cushing syndrome. Importantly, all patients who improved hypertension after adrenalectomy displayed strong accumulation in adrenal tumors with visualization of the contralateral gland on NP-59 scintigraphy. Conversely, blood pressure did not improve in four patients for whom scintigraphy yielded negative results. Conclusions:, The indication of laparoscopic adrenalectomy for non-functional adrenal tumors is generally considered for lesions more than 5 cm diameter. However, the present study suggests that laparoscopic surgery should be considered even in patients with tumors less than 5 cm in diameter, if both hypertension and accumulation in tumors on NP-59 scintigraphy are present. [source]

The lognormal distribution is not an appropriate null hypothesis for the species,abundance distribution

Summary 1Of the many models for species,abundance distributions (SADs), the lognormal has been the most popular and has been put forward as an appropriate null model for testing against theoretical SADs. In this paper we explore a number of reasons why the lognormal is not an appropriate null model, or indeed an appropriate model of any sort, for a SAD. 2We use three empirical examples, based on published data sets, to illustrate features of SADs in general and of the lognormal in particular: the abundance of British breeding birds, the number of trees > 1 cm diameter at breast height (d.b.h.) on a 50 ha Panamanian plot, and the abundance of certain butterflies trapped at Jatun Sacha, Ecuador. The first two are complete enumerations and show left skew under logarithmic transformation, the third is an incomplete enumeration and shows right skew. 3Fitting SADs by ,2 test is less efficient and less informative than fitting probability plots. The left skewness of complete enumerations seems to arise from a lack of extremely abundant species rather than from a surplus of rare ones. One consequence is that the logit-normal, which stretches the right-hand end of the distribution, consistently gives a slightly better fit. 4The central limit theorem predicts lognormality of abundances within species but not between them, and so is not a basis for the lognormal SAD. Niche breakage and population dynamical models can predict a lognormal SAD but equally can predict many other SADs. 5The lognormal sits uncomfortably between distributions with infinite variance and the log-binomial. The latter removes the absurdity of the invisible highly abundant half of the individuals abundance curve predicted by the lognormal SAD. The veil line is a misunderstanding of the sampling properties of the SAD and fitting the Poisson lognormal is not satisfactory. A satisfactory SAD should have a thinner right-hand tail than the lognormal, as is observed empirically. 6The SAD for logarithmic abundance cannot be Gaussian. [source]

Diversity and composition of trees and shrubs in Kasagala forest: a semiarid savannah woodland in central Uganda

Samson Gwali
Abstract The diversity and composition of trees and shrubs of ,5 cm diameter at breast height (DBH) were investigated in Kasagala woodland in central Uganda using 1 ha permanent sample plots. A total of 2745 trees and shrubs with a mean stem density of 686 ha,1 were recorded. These included 69 tree species belonging to 28 families and 47 genera. There was a larger number of small stems compared with that of larger stems. There was significant variation in stem size class distribution between the plots (F = 3.14, P = 0.027). The variation in stem densities (counts) across different size classes was significant (F = 8.31, P < 0.001). Species diversity was higher in the low lands compared with that in the elevated sites in the woodland. The species encountered were unevenly distributed across the plots. Species abundance was not significantly different across the sample plots (F = 2.63, P = 0.053). We suggest that the structure of the forest is typical of any regenerating forest, but other human influences may have played a part in the dominance of size classes <10 cm DBH. The causes of the present status and composition of the woodland require further investigation. Résumé La diversité et la composition des arbres et arbustes de plus de 5 cm dbh ont étéétudiées dans la forêt de Kasagala, au centre de l'Ouganda, en utilisant des parcelles échantillons permanentes d'un hectare. On a relevé la présence de 2745 arbres et arbustes, avec une densité moyenne de 686 troncs ha,1. Ceux-ci comprenaient 69 espèces d'arbres appartenant à 28 familles et à 47 genres. Il y avait un plus grand nombre de petits troncs que de gros. Il y avait une variation significative de la distribution des classes de taille entre les parcelles (F = 3.14, P = 0.027). La variation de la densité des troncs (comptages) entre les différentes classes de taille était significative (F = 8.31, P < 0.001). La diversité des espèces était plus grande dans les terres basses que dans les sites plus élevés dans la forêt. Les espèces rencontrées étaient distribuées de façon inégale entre les parcelles. L'abondance des espèces n'était pas significativement différente selon les parcelles échantillons (F = 2.63, P = 0.053). Nous suggérons que la structure de la forêt est typique de toute forêt en voie de régénération, mais que d'autres influences humaines peuvent avoir joué un rôle dans la dominance des classes de taille <10 cm dbh. Les raisons du statut et de la composition actuels de la forêt requièrent de nouvelles investigations. [source]

Natural regeneration and population dynamics of the tree Afzelia quanzensis in woodlands in Southern Africa

Karin Gerhardt
Abstract The logging of tree species of high commercial value is increasing throughout the African continent, yet the ecology of these species is generally poorly known. We studied the regeneration pattern and size class distribution of Afzelia quanzensis populations in northern South Africa over a 5-year period. Recruitment was low as the annual seedling mortality was >65%. Seedlings were located under the canopy and were affected by drought and browsing. The adults were scattered or were in a clump-dispersed pattern, which would result in higher recruitment of offspring near parents. Individuals of 0,10 cm diameter at breast height (DBH) were few, while there were 32 trees ha,1 at >10 cm DBH with an annual mortality of 0.8%. Annual diameter increments varied between 0.06 and 0.28 cm. It appears that the transition from the sapling into the juvenile stage could be a bottleneck in the regeneration of the species. A longer study, including more rainfall cycles, may reveal other patterns as dry and wet years have different impacts on dynamics. Résumé La coupe d'espèces d'arbres de grande valeur commerciale augmente dans tout le continent africain, pourtant l'écologie de ces espèces est généralement mal connue. Nous avons étudié le schéma de régénération et la distribution des classes d'âge des populations d'Afzelia quanzensis dans le nord de l'Afrique du Sud pendant cinq ans. Le recrutement était faible car la mortalité annuelle des jeunes plants était de plus de 65%. Les jeunes plans se trouvaient sous la canopée et étaient affectés par la sécheresse et par le broutage des animaux. Les adultes étaient dispersés ou se trouvaient en un schéma en bosquet, qui résulte en un plus fort recrutement de la progéniture près des parents. Les individus de 0,10 cm DBH étaient rares, alors qu'il y avait32 arbres ha,1à >10 cm DBH, avec une mortalité annuelle de 0,8%. L'incrément annuel du diamètre variait entre 0,06 et 0,28 cm. Il semble que la transition entre le stade de jeune arbre et celui de juvénile pourrait bien constituer un étranglement dans la régénération de l'espèce. Une étude plus longue, comprenant plus de cycles de pluies, pourrait révéler un autre schéma étant donné que les années sèches et humides ont des impacts différents sur cette dynamique. [source]

Changes in the structure and composition of miombo woodlands mediated by elephants (Loxodonta africana) and fire over a 26-year period in north-western Zimbabwe

Isaac Mapaure
Abstract Changes in structure and composition of miombo woodlands mediated by elephants and fire were studied in 26-year-old permanent transects established in 1972 in north-western Zimbabwe. Elephants caused 48% decline in proportions of large trees (>11 cm diameter), significant reductions (30.9,90.9%) in tree heights, reductions in stem areas (43.5%) and densities (2.5%) of all trees. There were increases in proportions of small trees (64.8%), shrub canopy volumes (271%) and shrub densities (172%). These increases are attributed to natural recruitment because of longer fire-free periods and reduction of tree suppression effects on lower strata as a result of elephant-induced tree declines. Frequencies of occurrence of most species dropped by 28,89.6%. Brachystegia boehmii was replaced by Pseudolachnostylis maprouneifolia as the most dominant tree, largely because of high elephant preference for Brachystegia boehmii. A new suite of species, dominated by Combretaceae, increased in dominance resulting in local floristic changes. Reductions in old elephant (33.4%), old unknown (89.9%) and new elephant (13.7%) damage suggest that elephant occupancy of miombo woodlands has declined, possibly because of limited availability of preferred browse species. This study clearly shows that elephants and fire have contributed significantly to the changes in miombo woodlands in the area. Résumé Les changements de la structure et de la composition des forêts de miombo dus aux éléphants et aux feux ont étéétudiés sur des transects permanents établis en 1972 dans le nord-ouest du Zimbabwe. Les éléphants ont causé un déclin de 48% de la proportion de grands arbres (>11 cm de diamètre), des réductions significatives (30,9,90,9%) de la hauteur des arbres, des réductions de la surface des tiges (43,5%) et de la densité (2,5%) de tous les arbres. Il y avait des augmentations de la proportion de petits arbres (64,8%), du volume des buissons (271%) et de leur densité (172%). Ces augmentations sont attribuées au recrutement naturel dûà de plus longues périodes sans feux, et à la réduction des effets suppressifs des arbres sur les couches inférieures due au déclin des arbres induit par les éléphants. La fréquence de la plupart des espèces a chuté de 28%à 89,6%. Brachystegia boehmi a été remplacé par Pseudolachnostylis maprouneifolia comme arbre dominant, en grande partie à cause de la forte préférence marquée par les éléphants pour Brachystegia boehmi. Une nouvelle série d'espèces, dominée par des Combrétacées, a accru sa dominance et entraîné des changements floristiques locaux. La réduction des dommages « anciens dus aux éléphants » (33,4%), « anciens d'origine inconnue » (,9,9%) et « nouveaux dus aux éléphants » (13,7%) suggère que l'occupation des forêts de miombo par les éléphants a diminué, peut-être à cause de la disponibilité limitée des espèces fourragères qu'ils préfèrent. Cette étude montre clairement que les éléphants et les feux ont contribué significativement aux changements survenus dans les forêts de miombo de la région. [source]

Cutaneous localized annular chromoblastomycosis

Claudio G. Salgado
Chromoblastomycosis (CBM) is a difficult-to-treat dermal mycosis characterized by the presence of round, pigmented, sclerotic bodies formed by black fungi found in polymorphic lesions. According to the morphology of a lesion, different clinical types of the disease have been described. We present three patients who each developed a single, 10-cm diameter, 8 to 15-year-old, well-circumscribed, slow-growing, annular, papulosquamous or papulosquamous-verrucous lesion, with no regression despite the use of topical antifungals. Skin scrapings and biopsies confirmed CBM and microculture defined the agent as Fonsecaea pedrosoi. The patients were treated with 200 mg/day of itraconazole for 6,9 months and were discharged after complete regression of the lesions. All were examined after the first and second year of the end of treatment and there were no signs of recurrence. A new clinical type of CBM is described, and itraconazole appears to be effective and safe in curing these patients after no more than 9 months of therapy. [source]

Above- versus below-ground competitive effects and responses of a guild of temperate tree species

K. David Coates
Summary 1The neutral theory debate has highlighted the scarcity of robust empirical estimates of the magnitude of competitive effects and responses within guilds of co-occurring tree species. Our analysis quantifies the relative magnitude of all possible pairwise competitive interactions within a guild of nine co-occurring tree species in temperate forests of northern, interior British Columbia, and explicitly partitions the competitive effects of neighbours into the effects of shading versus the residual effects of ,crowding', assumed to reflect below-ground competition. 2Models that treated neighbours as equivalent in their competitive effects were the most parsimonious for the five species with the smallest sample sizes. For the remaining species (samples sizes of > 150 individuals), the best models estimated separate competition coefficients for all nine species of neighbours. We take this as evidence that species do indeed differ in their competitive effects, but that there can be a minimum sample size required to discriminate between them. 3There was a strong size-dependency in potential growth. Six species showed an optimal growth at a size between 5 and 20 cm diameter. Potential growth declined moderately to strongly as diameter increased. Sensitivity to crowding varied as a function of tree size for five of the nine species; however, this response was not consistent by tree species. 4The magnitude of reduction in growth due to crowding was greater on average than the reduction in growth due to shading, except for the two least shade tolerant conifers. Sensitivity to shading among the conifer species was correlated with their shade tolerance. 5The per capita effects of crowding by different species of neighbours varied widely. A large number of the estimated pairwise per capita competition coefficients were very low. The relative magnitude of the strength of intra- versus interspecific competition also varied widely among the tree species. 6Synthesis. Model selection techniques effectively separated above- and below-ground competition in complex forests, and allowed us to assess differences among species in competitive effects and responses. While below-ground effects were strong, they were due to proximity of neighbours from a very specific (and small) subset of strong competitors within the guild. Response to crowding varied with tree size but the nature of the relationship varied widely among the species. [source]

Forest canopy and community dynamics in a temperate old-growth evergreen broad-leaved forest, south-western Japan: a 7-year study of a 4-ha plot

Masahiro Miura
Summary 1Forest canopy gap and community dynamics were studied in a 4-ha permanent plot of an old-growth evergreen broad-leaved forest dominated by Castanopsis cuspidata var. sieboldii and Distylium racemosum in the Tatera Forest Reserve, Tsushima Islands, south-western Japan. The forest was affected by a powerful typhoon in 1987 and was monitored from 1990 to 1997. 2In 1990, all woody stems , 5 cm diameter at breast height (d.b.h.) in the plot were identified, mapped and marked, and the state of 1600 5 m × 5 m contiguous quadrats used to locate canopy gaps. Gaps occupied 17.1% of the plot, which contained 4494 tree and shrub stems (total basal area 63.48 m2 ha,1). Gaps were re-censused in 1997 and both marked and newly recruited (, 5 cm d.b.h.) stems were recorded in 1992 and 1997. 3Over 7 years the rates of canopy gap formation and closure were 0.72% year,1 and 1.61% year,1, respectively, mortality and recruitment rates were 0.97% year,1 and 0.99% year,1, and the rates of loss and gain in basal area were 0.95% year,1 and 0.83% year,1. 4The mortality of stems was size-dependent, with those in middle size classes having the lowest rates. Mortality of stems was lower in canopy and higher in the understorey, while the proportion of stems killed by disturbances increased with height. 5Stems that died during the 7 years were predominantly located in newly created gaps, whereas stems were recruited into both established and new gaps. Deciduous broad-leaved species were largely restricted to gaps that remained open throughout the study. 6Both composition and structure of the forest changed in response to disturbance-related effects on canopy dynamics. [source]


ABSTRACT Precooked biscuits (7 cm diameter × 2 cm thickness), preserved by freezing, were evaluated in a regional bakery. Heat and mass transfer during these processes and through the final baking were studied. Precooking was conducted at 180C for 18 min; convection and conduction were the predominant phenomena for heat transfer, with an ,, = 1.71 × 10,7 m2/s. Diffusion mechanism adequately modeled (r2 = 0.94, PEM < 2.5%) the moisture loss during cooking stage, with a D = 1.04 × 10,6 m2/s. The freezing point obtained inside a tunnel freezer (forced air at ,,40C), was , 6.73C, consistent with the predicted value. Volume changes were minimal during frozen storage because of high fat content and few variations in the freezer temperature. Final baking in conventional gas and microwave ovens were compared. Higher moisture loss and minimal color change occurred in the microwave baking. Instrumental texture of both final treatments were significantly different, in contrary to sensory evaluation (, = 0.05). The methods produced a good choice for product commercialization after baking. [source]


ABSTRACT Sensory characteristics of broiled and grilled patties from grain-fed bison were evaluated by a 13-member trained sensory panel. Ground patties (approximately 113 g, 12.2 cm diameter, 0.9 cm thick) from 6 grinding dates were broiled (260C) or grilled (163C) to 71C internal temperature. Cooking time was significantly shorter (p < 0.0001) for grilled than broiled patties, while cooking yields were similar. Broiled patties were judged to have a more gray than brown surface color, a more red than gray interior color, to be more juicy, and to be more tender than grilled, while their aromatic and flavor intensities were similar. [source]

Continuous process for production of hydrogenated nitrile butadiene rubber using a Kenics® KMX static mixer reactor

AICHE JOURNAL, Issue 11 2009
Chandra Mouli R. Madhuranthakam
Abstract A continuous process for hydrogenating nitrile butadiene rubber (NBR) was developed and its performance was experimentally investigated. A Kenics® KMX static mixer (SM) is used in the process as a gas,liquid reactor in which gaseous hydrogen reacts with NBR in an organic solution catalyzed by an organometallic complex such as an osmium complex catalyst. The Kenics® KMX SM was designed with 24 mixing elements with 3.81 cm diameter and arranged such that the angle between two neighboring elements is 90°. The internal structure of each element is open blade with the blades being convexly curved. The dimensions of the SM reactor are: 3.81 cm ID 80 S and 123 cm length and was operated cocurrently with vertical upflow. The NBR solutions of different concentrations (0.418 and 0.837 mol/L with respect to [CC]) were hydrogenated by using different concentrations of the osmium catalyst solution at various residence times. The reactions were conducted at a constant temperature of 138°C and at a constant pressure of 3.5 MPa. From the experimental results, it is observed that a conversion and/or degree of hydrogenation above 95% was achieved in a single pass from the designed continuous process. This is the first continuous process for HNBR production that gives conversions above 95% till date. Optimum catalyst concentration for a given mean residence time to achieve conversions above 95% were obtained. Finally, a mechanistic model for the SM reactor performance with respect to hydrogenation of NBR was proposed and validated with the obtained experimental results. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Oscillatory zoning in garnet from the Willsboro Wollastonite Skarn, Adirondack Mts, New York: a record of shallow hydrothermal processes preserved in a granulite facies terrane

C. C. Clechenko
Abstract Oscillatory zoning in low ,18O skarn garnet from the Willsboro wollastonite deposit, NE Adirondack Mts, NY, USA, preserves a record of the temporal evolution of mixing hydrothermal fluids from different sources. Garnet with oscillatory zoning are large (1,3 cm diameter) euhedral crystals that grew in formerly fluid filled cavities. They contain millimetre-scale oscillatory zoning of varying grossular,andradite composition (XAdr = 0.13,0.36). The ,18O values of the garnet zones vary from 0.80 to 6.26, VSMOW and correlate with XAdr. The shape, pattern and number of garnet zones varies from crystal to crystal, as does the magnitude of the correlated chemistry changes, suggesting fluid system variability, temporal and/or spatial, over the time of garnet growth. The zones of correlated Fe content and ,18O indicate that a high Fe3+/Al, high ,18O fluid mixed with a lower Fe3+/Al and ,18O fluid. The high ,18O, Fe enriched fluids were likely magmatic fluids expelled from crystallizing anorthosite. The low ,18O fluids were meteoric in origin. These are the first skarn garnet with oscillatory zoning reported from granulite facies rocks. Geochronologic, stable isotope, petrologic and field evidence indicates that the Adirondacks are a polymetamorphic terrane, where localized contact metamorphism around shallowly intruded anorthosite was followed by a regional granulite facies overprint. The growth of these garnet in equilibrium with meteoric and magmatic fluids indicates an origin in the shallow contact aureole of the anorthosite prior to regional metamorphism. The zoning was preserved due to the slow diffusion of oxygen and cations in the large garnet and protection from deformation and recrystallization in zones of low strain in thick, rigid, garnetite layers. The garnet provide new information about the hydrothermal system adjacent to the shallowly intruded massif anorthosite that predates regional metamorphism in this geologically complex, polymetamorphic terrane. [source]

97 Sensitivity of cyanobacteria to a potential biological control agent, bacterium SG-3

K. Wilkinson
Cyanobacteria cause many problems in freshwater ecosystems. For example, the production of off-flavor compounds by cyanobacteria causes serious problems in catfish aquaculture. Control of cyanobacteria is generally limited to treatment with copper compounds, which are non-selective and sometimes ineffective at controlling certain species of cyanobacteria. Biological control could provide selective management by removing unwanted species while leaving desirable algae species. A bacterium (SG-3) (NRRL B-30043) lyses a number of planktonic species of cyanobacteria including bloom-forming species of Anabaena and Oscillatoria. We tested SG-3 for activity against 10 isolates, representing seven species, of mat-forming cyanobacteria within the genera Oscillatoria, Lyngbya, and Phormidium. Plugs (0.5 cm diameter) were cut from mats of the cyanobacterium, inoculated with liquid cultures of SG-3, and incubated as static cultures. The reduction in dry weights ranged from ,0.5% to 90% compared to the untreated controls and appeared to be species specific. For example, dry weight reductions of Oscillatoria deflexoides and O. amoena ranged from 80 to 90% whereas the reduction of O. limosa tended to be lower at 36 to 72%. Although results varied among and within species, they indicate that this bacterium could have potential for use as a biological control for mat-forming cyanobacteria. Light microscopic observations indicate the bacteria do not penetrate the cyanobacteria cells. Currently, we are studying the possible causes of the observed cell lysis. [source]

Bone differentiation of marrow-derived mesenchymal stem cells using ,-tricalcium phosphate,alginate,gelatin hybrid scaffolds

Mohamadreza Baghaban Eslaminejad
Abstract The aim of the present study was to establish a 3D culture system for bone differentiation of mesenchymal stem cells (MSCs), using a new hybrid sponge. To manufacture the scaffold, a composite of ,-tricalcium phosphate,alginate,gelatin was prepared and cast as pellets of 1 cm diameter. The sponge was then fabricated by drying in freeze-dryer for 12 h. The porosity, mean pore size, compressive modulus and strength of the composite sponge fabricated in this study were 89.7%, 325.3 µm, 1.82 and 0.196 MPa, respectively. To establish a 3D culture system, the rat bone marrow-derived MSCs were suspended in 500 µl diluted collagen gel, loaded into the porous sponge and provided with medium with or without osteogenic supplements for 3 weeks. The day after loading, the cells appeared in the scaffold's internal spaces, where later some of them from either culture survived by anchoring on the surfaces. At the end of cultivation period, individually adhered cells from both cultures were observed to be replaced by cell aggregates, in which mineralized matrix was detected by alizarin red staining. Furthermore, RT-PCR analysis indicated that the bone-specific gene osteocalcin was expressed in cultures in both the presence and absence of the osteogenic supplements. Taken together, it seems that the studied scaffolds are cell-compatible and, more importantly, possess some osteo-inductive properties. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Spatial pattern of downed logs and wood-decaying fungi in an old-growth Picea abies forest

Mattias Edman
See section on Field methods Abstract. Since many wood-living forest species are influenced by the dynamics of coarse woody debris (CWD), information about the spatial pattern of CWD under natural conditions is essential to understand species distributions. In this study we examined the spatial pattern of downed logs and wood-decaying fungi in an old-growth boreal Picea abies forest in northwestern Sweden that is governed by gap-phase dynamics. The spatial pattern of wood-decaying fungi was studied to draw conclusions about species dispersal abilities. A total of 684 logs with a diameter > 10 cm were mapped and analysed with Ripley's K -function. The distribution of all logs taken together displayed a significant aggregated pattern up to 45 m. The different decay stages also deviated from random expectations. Fairly fresh logs and logs in the middle decay stage were clumped up to about 25 and 35 m respectively, and late decayed logs aggregated up to 95 m. Logs with diameters from 10,29 cm were aggregated up to 25 m, whereas logs ,30 cm diameter were randomly distributed. The result suggests that gap-dynamics do have an impact on the spatial pattern of the CWD, creating fine-scale clumping. The random distribution of large logs may result from the slightly regular spacing of large living trees. The spatial patterns of 16 species (n > 20) of wood-decaying fungi were analysed with Ripley's K -function. Three patterns were aggregated, for Gloeophyllum sepiarium, Coniophora olivacea and Vesiculomyces citrinus. These results indicate that the distribution of most species at the stand level is generally not influenced by dispersal limitations. [source]

Experimentally testing the role of foundation species in forests: the Harvard Forest Hemlock Removal Experiment

Aaron M. Ellison
Summary 1.,Problem statement, Foundation species define and structure ecological systems. In forests around the world, foundation tree species are declining due to overexploitation, pests and pathogens. Eastern hemlock (Tsuga canadensis), a foundation tree species in eastern North America, is threatened by an exotic insect, the hemlock woolly adelgid (Adelges tsugae). The loss of hemlock is hypothesized to result in dramatic changes in assemblages of associated species with cascading impacts on food webs and fluxes of energy and nutrients. We describe the setting, design and analytical framework of the Harvard Forest Hemlock Removal Experiment (HF-HeRE), a multi-hectare, long-term experiment that overcomes many of the major logistical and analytical challenges of studying system-wide consequences of foundation species loss. 2.,Study design, HF-HeRE is a replicated and blocked Before-After-Control-Impact experiment that includes two hemlock removal treatments: girdling all hemlocks to simulate death by adelgid and logging all hemlocks >20 cm diameter and other merchantable trees to simulate pre-emptive salvage operations. These treatments are paired with two control treatments: hemlock controls that are beginning to be infested in 2010 by the adelgid and hardwood controls that represent future conditions of most hemlock stands in eastern North America. 3.,Ongoing measurements and monitoring, Ongoing long-term measurements to quantify the magnitude and direction of forest ecosystem change as hemlock declines include: air and soil temperature, light availability, leaf area and canopy closure; changes in species composition and abundance of the soil seed-bank, understorey vegetation, and soil-dwelling invertebrates; dynamics of coarse woody debris; soil nitrogen availability and net nitrogen mineralization; and soil carbon flux. Short-term or one-time-only measurements include initial tree ages, hemlock-decomposing fungi, wood-boring beetles and throughfall chemistry. Additional within-plot, replicated experiments include effects of ants and litter-dwelling microarthoropods on ecosystem functioning, and responses of salamanders to canopy change. 4.,Future directions and collaborations, HF-HeRE is part of an evolving network of retrospective studies, natural experiments, large manipulations and modelling efforts focused on identifying and understanding the role of single foundation species on ecological processes and dynamics. We invite colleagues from around the world who are interested in exploring complementary questions to take advantage of the HF-HeRE research infrastructure. [source]

Modelling approaches to compare sorption and degradation of metsulfuron-methyl in laboratory micro-lysimeter and batch experiments

Maik Heistermann
Abstract Results of laboratory batch studies often differ from those of outdoor lysimeter or field plot experiments,with respect to degradation as well as sorption. Laboratory micro-lysimeters are a useful device for closing the gap between laboratory and field by both including relevant transport processes in undisturbed soil columns and allowing controlled boundary conditions. In this study, sorption and degradation of the herbicide metsulfuron-methyl in a loamy silt soil were investigated by applying inverse modelling techniques to data sets from different experimental approaches under laboratory conditions at a temperature of 10 °C: first, batch-degradation studies and, second, column experiments with undisturbed soil cores (28 cm length × 21 cm diameter). The column experiments included leachate and soil profile analysis at two different run times. A sequential extraction method was applied in both study parts in order to determine different binding states of the test item within the soil. Data were modelled using ModelMaker and Hydrus-1D/2D. Metsulfuron-methyl half-life in the batch-experiments (t1/2 = 66 days) was shown to be about four times higher than in the micro-lysimeter studies (t1/2 about 17 days). Kinetic sorption was found to be a significant process both in batch and column experiments. Applying the one-rate-two-site kinetic sorption model to the sequential extraction data, it was possible to associate the stronger bonded fraction of metsulfuron-methyl with its kinetically sorbed fraction in the model. Although the columns exhibited strong significance of multi-domain flow (soil heterogeneity), the comparison between bromide and metsulfuron-methyl leaching and profile data showed clear evidence for kinetic sorption effects. The use of soil profile data had significant impact on parameter estimates concerning sorption and degradation. The simulated leaching of metsulfuron-methyl as it resulted from parameter estimation was shown to decrease when soil profile data were considered in the parameter estimation procedure. Moreover, it was shown that the significance of kinetic sorption can only be demonstrated by the additional use of soil profile data in parameter estimation. Thus, the exclusive use of efflux data from leaching experiments at any scale can lead to fundamental misunderstandings of the underlying processes. Copyright © 2003 Society of Chemical Industry [source]

Vertical Migration and Motility Responses in Three Marine Phytoplankton Species Exposed to Solar Radiation,

Peter R. Richter
ABSTRACT Diurnal vertical migration in the water column and the impact of solar radiation on motility were investigated in three marine phytoplankton species: Tetraselmis suecica, Dunaliella salina and Gymnodinium chlorophorum. Cells were exposed to solar radiation either in ultraviolet radiation (UVR, 280,400 nm) transparent Plexiglas tubes (45 cm length, 10 cm diameter) or in quartz tubes under three radiation treatments: PAB (280,700 nm), PA (320,700 nm) and P (400,700 nm). The three species displayed different behavior after exposure to solar radiation. Tetraselmis suecica was insensitive to UVR and under high solar radiation levels, cells accumulated preferentially near the surface. Exposure experiments did not indicate any significant changes in swimming speed nor in the percentage of motile cells after 5 h of exposure. On the other hand, D. salina was sensitive to UV-B displaying a significant decrease in swimming speed and percentage of motile cells after 2,3 h of exposure. Moreover, D. salina cells migrated deep in the water column when irradiance was high. The response of G. chlorophorum was in between that of the other two species tested, with a slight (but significant) decrease in swimming speed and percentage of motile cells in all radiation treatments after 5 h of exposure. While G. chlorophorum cells were more or less homogenously distributed in the water column, a slight (but significant) avoidance response to high radiation was observed at local noon, with cells migrating deep in the water column. Our data clearly indicate that these sub-lethal effects of solar radiation are species-specific and they might have important implications for the aquatic ecosystem. [source]

Restoration of a Forest Understory After the Removal of an Invasive Shrub, Amur Honeysuckle (Lonicera maackii)

Kurt M. Hartman
Abstract The recruitment of native seedlings is often reduced in areas where the invasive Amur honeysuckle (Lonicera maackii) is abundant. To address this recruitment problem, we evaluated the effectiveness of L. maackii eradication methods and restoration efforts using seedlings of six native tree species planted within eradication and unmanipulated (control) plots. Two eradication methods using glyphosate herbicide were evaluated: cut and paint and stem injection with an EZ-Ject lance. Lonicera maackii density and biomass as well as microenvironmental characteristics were measured to study their effects on seedling growth and survivorship. Mean biomass of Amur honeysuckle was 361 ± 69 kg/ha, and density was 21,380 ± 3,171 plants/ha. Both eradication treatments were effective in killing L. maackii (, 94%). The injection treatment was most effective on large L. maackii individuals (>1.5 cm diameter), was 43% faster to apply than cutting and painting and less fatiguing for the operator, decreased operator exposure to herbicide, and minimized impact to nontarget vegetation. Deer browse tree protectors were used on half of the seedlings, but did not affect survivorship or growth. After 3 years, survival of native seedlings was significantly less where L. maackii was left intact (32 ± 3%) compared with the eradication plots (p < 0.002). Seedling survival was significantly different between cut (51 ± 3%) and injected (45 ± 3%) plots. Species had different final percent survival and rates of mortality. Species survival differed greatly by species (in descending order): Fraxinus pennsylvanica > Quercus muehlenbergii , Prunus serotina, Juglans nigra > Cercis canadensis > Cornus florida. Survivorship and growth of native seedlings was affected by a severe first-year drought and by site location. One site exhibited greater spring soil moisture, pH, percent open canopy, and had greater survivorship relative to the other site (55 ± 2 vs. 30 ± 2%). Overall, both L. maackii eradication methods were successful, but restorationists should be aware of the potential for differential survivorship of native seedlings depending on species identity and microenvironmental conditions. [source]

Simulations of Bubble Column Reactors Using a Volume of Fluid Approach: Effect of Air Distributor

M. Abid Akhtar
Abstract Two- and three-dimensional numerical simulations have been performed on a laboratory scale bubble column reactor using a volume-of-fluid approach. The effect of hole-size and superficial gas velocity on the bubble size distribution and their trajectories has been investigated on a 20 cm diameter and 1 m high cylindrical reactor. All simulations were performed in a transient manner using a FLUENT solver. Surface tension between two phases has been modelled as a body force with a constant value. Turbulence was modelled using the k-, turbulence approach. A comparison between simulation predictions and the reported experimental studies has shown a good agreement. On a effectué des simulations numériques bi et tridimensionnelles dans un réacteur à colonne à bulles à l'échelle de laboratoire à l'aide d'une approche volume-de-fluide. L'effet de la taille du trou et de la vitesse de gaz superficielle sur la distribution de tailles des bulles et leurs trajectoires a été étudié dans un réacteur cylindrique de 20 cm de diamètre et de 1 m de hauteur. Toutes les simulations ont été réalisées selon un mode transitoire à l'aide du logiciel FLUENT. La tension de surface entre deux phases a été modélisée comme une force volumique avec une valeur constante. La turbulence a été modélisée par la méthode de turbulence k-,. Une comparaison entre les prédictions des simulations et les études expérimentales mentionnées montre un bon accord. [source]

Selection of sleeping trees in pileated gibbons (Hylobates pileatus)

Rungnapa Phoonjampa
Abstract Selection and use patterns of sleeping sites in nonhuman primates are suggested to have multiple functions, such as predation avoidance, but they might be further affected by range defense as well as foraging constraints or other factors. Here, we investigate sleeping tree selection by the male and female members of one group of pileated gibbons (Hylobates pileatus) at Khao Ang Rue Nai Wildlife Sanctuary, Thailand. Data were collected on 113 nights, between September 2006 and January 2009, yielding data on 201 sleeping tree choices (107 by the female and 94 by the male) and on the characteristics of 71 individual sleeping trees. Each sleeping tree and all trees ,40,cm diameter at breast height (DBH) in the home range were assessed (height, DBH, canopy structure, liana load) and mapped using a GPS. The gibbons preferentially selected tall (mean=38.5,m), emergent trees without lianas. The majority of the sleeping trees (53.5%) were used only once and consecutive reuse was rare (9.5%). Sleeping trees were closer to the last feeding tree of the evening than to the first feeding tree in the morning, and sleeping trees were located in the overlap areas with neighbors less often than expected based on time spent in these areas. These results suggest avoidance of predators as the main factor influencing sleeping tree selection in pileated gibbons. However, other non-mutually exclusive factors may be involved as well. Am. J. Primatol. 72:617,625, 2010. © 2010 Wiley-Liss, Inc. [source]