Molar enamel thickness in European Miocene and extant hominoidea

Based on a roentgenographic analysis, the molar enamel of certain European Miocene dryopithecines is absolutely thick (r=1.03–1.30 mm in thickness); the molar enamel of certain European pliopithecines is thin (r=0.32–0.82 mm thick). The rank order for enamel thickness in extant hominoids (from thickest to thinnest) is confirmed to beHomo, Pongo, Gorilla, Pan, andHylobates. There is a great deal of enamel thickness variability within the great ape sample. Extant analogues suggest that dryopithecines were probably adapted to a frugivorous/gramnivorous dietary regimen, while pliopithecines were probably better suited to folivory.     

Mass transfer limitation of sulfate in methanogenic aggregates

The role of mass transfer limitation of sulfate as a factor governing the competition between sulfate reducing and methane producing bacteria in methanogenic aggregates was theoretically evaluated by the calculation of steady-state sulfate microprofiles using a reference set of parameters obtained from the literature. The shooting method was used as a numerical technique for solving the mathematical model. The effect of the parameters on mass transport limitation was tested by varying each reference value of the parameters with a factor of 3. Sulfate limitation within granules prevailed at moderate (0.1 kg m(-3)) and low sulfate concentrations in the bulk liquid, at high maximum sulfate utilization rates (3.73 x 10(-5) kg SO(4) (2-) kg(-1) VSS S(-1) or biomass concentrations (40 KG VSS m(-3)), and in large aggregates (radius of 7.5 10(-4) m). The effective diffusion coefficient of sulfate and the affinity constant were less determinative for the penetration depth of sulfate within a granule. (c) 1994 John Wiley & Sons, Inc.     

Early response of herbaceous vegetation to Rhododendron ponticum subsp. baeticum invasion in European Atlantic forests

Questions

Rhododendron ponticum subsp. baeticum is an invasive shrub of growing concern in continental Europe, but little is known about its impact on native plant communities. Here we ask: do environmental conditions differ between forest stands invaded by it and uninvaded stands? Do these differences correlate with R. ponticum's cover? Are these differences associated with differences in taxonomic and functional diversity of vascular plant species of the herb layer? Can these vegetation changes be explained by the sorting of certain life-history traits by R. ponticum-induced environmental changes?

Location

Several forests invaded by R. ponticum in the French Atlantic domain.

Methods

We recorded vegetation composition and a number of environmental variables in 400-m² plots that were established in 64 paired forest stands (32 invaded vs 32 uninvaded). We compiled traits from existing databases. We computed several metrics of taxonomic and functional diversity. We compared environmental variables and diversity metrics between invaded and uninvaded stands. We used correlation and regression analyses to relate them with R. ponticum's cover. We ran RLQ and fourth-corner analyses to explore the relationships between R. ponticum invasion, environmental variables, species traits, and vegetation composition.

Results

Independent of its abundance, R. ponticum invasion was associated with lower light arrival at the forest floor and increased litter thickness. Concomitantly, species richness and diversity and trait diversity were reduced. The major driver of species assemblages was soil pH, which strongly interacted with the invasion gradient. R. ponticum did not sort species according to traits associated with shade tolerance and thick-litter tolerance. However, tree and shrub saplings were more abundant in invaded than uninvaded stands, at the expense of graminoid and fern species.

Conclusions

As R. ponticum becomes the dominant shrub, it exerts new selection forces on life-history traits of extant species, mostly via reduced light availability, increased litter thickness, and physical competition, thereby reducing taxonomic and functional diversity of the herb layer, without impeding tree and shrub self-regeneration, at least in the short term.     

武夷山常绿阔叶林乔木与灌木小枝树皮主要功能性状的趋同

树皮是维管形成层以外的所有组织,其功能性状是反映植物生态适应策略的重要研究对象。为了揭示亚热带山地乔、灌木小枝树皮功能性状特征及其关联性,采用独立样本T检验和标准主轴回归方法对武夷山19种常见木本植物小枝树皮的主要功能性状的基本特征及其相关性进行了分析。结果发现：(1)树皮厚度、树皮密度与树皮含水量在乔、灌木之间无显著差异,其均值分别为(0.78±0.06)mm、(0.58±0.03)mg/cm³和(155.07±14.16)%。树皮碳(C)、氮(N)、磷(P)生态化学计量特征在乔、灌木之间差异也不显著,C、N、P平均值分别为(492.43±4.25)mg/g、(8.90±0.74)mg/g和(0.61±0.06)mg/g,树皮C∶N、C∶P与N∶P平均值分别为60.76±4.17、905.53±67.36与15.19±0.84。(2)树皮性状之间存在关联,其中树皮厚度与密度、密度与含水量均呈异速生长关系,而树皮厚度与含水量、氮含量与磷含量均呈等速生长关系。乔木树皮碳含量和磷含量间、灌木树皮密度和氮含量间均呈异速生长关系,乔木与灌木各性状间关系差异不显著。结果表明...     

Quantitative analysis of biofilm thickness variability

The thickness variability of biofilms of Pseudomonas aeruginosa, Klebsiella pneumoniae, and the binary population combination of these two species was quantified. The experimental method involved cryoembedding biofilms with a commercial tissue embedding agent, sectioning, and applying image analysis to construct thickness profiles along linear transects (up to 1 cm in length) across the substratum. Biofilms embedded and sectioned by this method were locally as thin as a single cell attached to the surface (<5 mum) and as thick as 1000 mum. Week-old biofilms of three different species compositions displayed distinct structural features as indicated by their mean thicknesses and by a roughness coefficient. Monopopulation biofilms of P. aeruginosa (29 mum mean thickness) or K. pneumoniae (100 mum mean thickness) were thinner than the binary population biofilm (400 mum mean thickness). A roughness coefficient developed in this investigation corroborated the qualitative visual characterization of P. aeruginosa biofilms as relatively uniformly thick (mean roughness coefficient 0.15), K. pneumoniae biofilms as patchy (mean roughness coefficient 1.14), and the binary population biofilm as intermediate (mean roughness coefficient 0.26). Whereas P. aeruginosa and binary population biofilms covered the substratum completely, significant areas of essentially bare substratum were apparent in K. pneumoniae biofilms. The patchiness of K. pneumoniae biofilms may be due to the fact that this organism is nonmotile. A spatial correlation analysis of the thickness data indicated that thickness measurements were still correlated even when separated by distances that exceeded the mean biofilm thickness. Cell aggregates, some of them hundreds of microns in size, were observed in the effluent of K. pneumoniae and binary population biofilm reactors. Measurements of thickness variability and other observations reported in this article provide a quantitative basis for analysis of microscale structural heterogeneity of biofilms. (c) 1995 John Wiley & Sons, Inc.     

Leishmania mexicana: Immunology and histopathology in C3H mice

C3H mice were infected subcutaneously with 10⁵ promastigotes of Leishmania mexicana and subsequent lesions were examined at 3, 5, and 8 months. All animals developed persistent nonulcerating nodules of variable size which did not metastasize. The nodules contained amastigotes with a mononuclear infiltrate of histiocytes, lymphocytes, and plasma cells, but without formation of tuberculoid-type granulomas. Neutrophils and eosinophils were also encountered in some cases. Specific antileishmanial antibodies and delayed-type hypersensitivity to leishmanial antigen were present at 3, 5, and 8 months postinfection. L. mexicana infection in C3H mice differs from classic self-healing cutaneous leishmaniasis by the pesistence of nonhealing, nonulcerating, nonmetastasizing lesions, despite evidence of cellular and humoral immunity.     

Growth of rural and urban children in the Valley of Oaxaca,Mexico

Weight, stature, arm circumference, and the triceps skinfold were measured in 1,410 school children, 6 through 14 years of age, from two urban colonias in the city of Oaxaca de Juarez (n = 479), and from two rural Ladino (n = 467) and two rural Zapotec (n = 464) communities in the Valley of Oaxaca in southern Mexico. Children from rural Ladino communities and urban colonias are significantly taller, heavier, and more muscular than children in rural Zapotec communities. The differences between rural Ladino and urban colonia children favor the former, particularly for weight and stature. These observations thus suggest (1) that children in the rural, indigenous communities in the Valley of Oaxaca are relatively undernourished compared to children in Ladinoized and urban communities, and (2) that rural-to-urban migration does not necessarily result in improved growth status.     

Growth of rural and urban children in the valley of Oaxaca,Mexico

Weight, stature, arm circumference, and the triceps skinfold were measured in 1,410 school children, 6 through 14 years of age, from two urban colonias in the city of Oaxaca de Juarez (n = 479), and from two rural Ladino (n = 467) and two rural Zapotec (n = 464) communities in the Valley of Oaxaca in southern Mexico. Children from rural Ladino communities and urban colonias are significantly taller, heavier, and more muscular than children in rural Zapotec communities. The differences between rural Ladino and urban colonia children favor the former, particularly for weight and stature. These observations thus suggest (1) that children in the rural, indigenous communities in the Valley of Oaxaca are relatively undernourished compared to children in Ladinoized and urban communities, and (2) that rural-to-urban migration does not necessarily result in improved growth status.     

The influence of basic plan parameters on calculated small field output factors – A multicenter study

PurposeThe influence of basic plan parameters such as slice thickness, grid resolution, algorithm type and field size on calculated small field output factors (OFs) was evaluated in a multicentric study.Methods and materialsThree computational homogeneous water phantoms with slice thicknesses (ST) 1, 2 and 3 mm were shared among twenty-one centers to calculate OFs for 1x1, 2x2 and 3x3 cm² field sizes (FSs) (normalized to 10x10 cm² FS), with their own treatment planning system (TPS) and the energy clinically used for stereotactic body radiation therapy delivery. OFs were calculated for each combination of grid resolution (GR) (1, 2 and 3 mm) and ST and finally compared with the OFs measured for the TPS commissioning. A multivariate analysis was performed to test the effect of basic plan parameters on calculated OFs.ResultsA total of 509 data points were collected. Calculated OFs are slightly higher than measured ones. The multivariate analysis showed that Center, GR, algorithm type, and FS are predictive variables of the difference between calculated and measured OFs (p < 0.001). As FS decreases, the spread in the difference between calculated and measured OFs became larger when increasing the GR. Monte Carlo and Analytical Anisotropic Algorithms, presented a dependence on GR (p < 0.01), while Collapsed Cone Convolution and Acuros did not. The effect of the ST was found to be negligible.ConclusionsModern TPSs slightly overestimate the calculated small field OFs compared with measured ones. Grid resolution, algorithm, center number and field size influence the calculation of small field OFs.