Dilution of non-reactive tracers in variably saturated sandy structures

Based on a dye tracer experiment in a sand tank we addressed the problem of local dispersion of conservative tracers in the unsaturated zone. The sand bedding was designed to have a defined spatial heterogeneity with a strong anisotropy. We estimated the parameters that characterize the local dispersion and dilution from concentration maps of a high spatial and temporal resolution obtained by image analysis. The plume spreading and mixing behavior was quantified on the basis of the coefficient of variation of the concentration and of the dilution index. The heterogeneous structure modified the flow pattern depending on water saturation. The shape of the tracer plumes revealed the structural signature of the sand bedding at low saturation only. In this case pronounced preferential flow was observed. At higher flow rates the structure remained hidden by a spatially almost homogeneous behavior of the plumes. In this context, we mainly discuss the mechanism of re-distributing a finite mass of inert solutes over a large volume, due to macro- and micro-heterogeneities of the structure. (C) 2001 Elsevier Science Ltd. AU rights reserved.

Upscaling of anisotropy in unsaturated Miller-similar porous media

Geological and pedological processes rarely form isotropic media as is usually assumed in transport studies. Anisotropy at the Darcy or field scale may be detected directly by measuring flow parameters or may become indirectly evident from movement and shape of solute plumes. Anisotropic behavior of a soil at one scale may, in many cases, be related to the presence of lower-scale directional structures. Miller similitude with different pore-scale geometries of the basic element is used to model macroscopic flow and transport behavior. Analytical expressions for the anisotropic conductivity tensor are derived based on the dynamic law that governs the flow problem at the pore scale. The effects of anisotropy on transport parameters are estimated by numerical modeling.

Health control beliefs in old age - relationship with subjective and objective health and health behavior

The main purpose of this paper is to explore health control beliefs (internality, powerful others, chance) in different age cohorts of elderly people and to examine the relationship between health control beliefs and objective and subjective health, and health behaviour. This contribution shows data from an interdisciplinary longitudinal ageing study: (a) a descriptive analysis of age- and time-correlated changes in health control beliefs of different cohorts of elderly people by taking into account gender as a differential aspect; (b) group comparisons between objectively and subjectively healthy or sick people and their health control beliefs and health relevant behaviour. Participants are 442 community elderly, 309 men, 133 women, aged 65± 94 years (mean age: 74.95 years). Our data demonstrate the dominance of chance control beliefs over internality and powerful others in all age cohorts. It can be concluded that internal control remains stable well into old age, whereas a signi® cant age-correlated increase of externality can be observed. Our results show the signi® cant relationship of subjective health self-evaluations with health control beliefs and health behaviour which is not the case for objective health parameters. Strong gender effects are found for internality and social externality: women have signi® cantly lower internality and powerful others scores than men.

Apolipoprotein E genotypes and cognitive functions in healthy elderly persons

Objectives- We investigated whether apoE genotypes correlate with cognitive functions in clinically healthy persons. Methods - In 1993 and 1995, we measured information processing speed, delayed free recall and semantic aspects of long-term memory in 227 men and 105 women aged 65 and over, a randomly selected subsample of the prospective Basel Study. Cardiovascular risk factors and education were assessed. Results -E2 were more prevalent in old-old (>75 years, 23.5% vs 15%) compared to E4 than in young-old (<75 years, 19.3% vs 23.5%). Taking into account age and education, subjects with ɛ3/ɛ4 or ɛ4/ɛ4 alleles (E4) performed lowest in all 3 tests compared to those homozygous for ɛ3 (E3) or carriers of one or two ɛ2 alleles (E2) (reaction time P=0.009, free recall P=0.05, WAIS-R vocabulary P<0.05). In old-old there was a significant difference between E2 and E4 for reaction time (P=0.02) and free recall (P<0.02) but not for vocabulary (P=0.086). In all 3 groups there were no significant changes after 2 years. The subgroup with the genotype ɛ2/ɛ4 performed consistently best in the cognitive tests. Cholesterol was significantly increased in the E4 and E3 group compared to the E2 group. Conclusion - ApoE genotype correlates with cognitive performance. The increased prevalence of E2 in the old-old and the significantly lower plasma cholesterol levels suggest differential morbidity and mortality as important factors influencing the prevalence of cognitive disorders in late life.

Differential aspects of memory self-evaluation in old and very old people

The aim of this paper was to examine age-related changes and gender differences in memory self-evaluation in old people and to examine the predictive power of objective memory performance and of personality variables (neuroticism and extraversion) on memory self-evaluation. In a cross-sectional study, 301 not institutionalized people aged 65± 94, 207 male and 94 female, were tested on three parameters. Subjective memory evaluation was operationalized with three one-item ratings: temporal comparison, social comparison, situation-speci® c memory self-evaluation just after performing a memory test. Objective memory assessment (free recall) used a computerized test. Personality assessment included the two main sub-scales `extraversion’ and `neuroticism’ from the Freiburger PersoÈ nlichkeits-Inventar.The results shaved that persons of all age groups have a realistic appraisal of their age-related memory decline.No gender effects were found for any of the three forms of memory self-evaluation. The relationship between objective memory performance, personality variables and memory self-evaluation however depends on age and gender. Our results show that objective memory performance is predictive for memory self-evaluation in men aged >75 years, whereas in men <75 neuroticism is the only signi® cant predictor.Men of the older cohort seem to have adapted to the age-related memory decline whereas the young old are still coping with the ongoing changes. In women of both age groups the objective memory performance is the only and strong predictor of memory self-evaluation. Our results suggest that gender-speci® c educational socialization might be the reason for these differences.

Wohlbefinden, Gesundheit und kognitive Kompetenz im Alter : Ergebnisse der Basler Interdisziplinären Altersstudie IDA

Hier wird ein Überblick über den aktuellen Forschungsstand zu Wohlbefinden, Gesundheit und Gedächtnis im Alter gegeben, der ergänzt wird mit Ergebnissen einer grossen interdisziplinären Studie, die u.a. auf folgende Themenkomplexe eingeht -> Stellenwert des Gesundheitsverhaltens Ernährung, Vitaminstatus, Sport, Rauchen) und sozialer Netzwerke in Bezug auf Wohlbefinden, Gesundheit und Gedächtnis. -> Effiziez vn Interventionsmöglichkeiten (Gedächtnistraining, Schauspieltraining, Krafttraining) für die Erhaltung von Wohlbefinden, Gesundheit udn geistiger Leistungsfähigkeit. -> Welche Rolle spielen diesbezüglich Persönlichkeit und Selbstverantwortlichkeit? Angesichts der grossen sozialpolitischen Bedeutung, die den Fragen nach den Determinanten gesunden und autonomen Alterns zukommt, gibt dieses Buch neue Impulse für prophylaktische und diagnostische Interventionsmassnahmen.

Domains of expansin gene expression define growth regions in the shoot apex of tomato

Expansins are members of a multigene family of extracellular proteins, which increase cell wall extensibility in vitro and thus are thought to be involved in cell expansion. The major significance of the presence of this large gene family may be that distinctly expressed genes can independently regulate cell expansion in place and time. Here we report on LeExp9, a new expansin gene from tomato, and compare its expression in the shoot tip with that of LeExp2 and LeExp18. LeExp18 gene is expressed in very young tissues of the tomato shoot apex and the transcript levels are upregulated in the incipient primordium. LeExp2 mRNA accumulated in more mature tissues and transcript levels correlated with cell elongation in the elongation zone. In situ hybridization experiments showed a uniform distribution of LeExp9 mRNA in submeristematic tissues. When gibberellin-deficient mutant tomatoes that lacked elongation of the internodes were treated with gibberellin, the phenotypic rescue was correlated with an increase in LeExp9 and LeExp2, but not LeExp18 levels. We propose that the three expansins define three distinct growing zones in the shoot tip. In the meristem proper, gibberellin-independent LeExp18 mediates the cell expansion that accompanies cell division. In the submeristematic zone, LeExp9 mediates cell expansion at a time that cell division comes to a halt. LeExp9 expression requires gibberellin but the hormone is not normally limiting. Finally, LeExp2 mediates cell elongation in young stem tissue. LeExp2 expression is limited by the available gibberellin. These data suggest that regulation of cell wall extensibility is controlled, at least in part, by differential regulation of expansin genes.

Simple hormones but complex signalling

It has not been easy to make sense of the pleiotropic effects of plant hormones, especially of auxins; but now, it has become possible to study these effects within the framework of what we know about signal transduction in general. Changes in local auxin concentrations, perhaps even actively maintained auxin gradients, signal to networks of transcription factors, which in turn signal to downstream effectors. Transcription factors can also signal back to hormone biosynthetic pathways.