Spatio-temporal patterns of birch regrowth in a Western Norwegian treeline ecotone

The study investigates spatio-temporal patterns of birch regrowth in a mountain valley in which intensive livestock grazing was formerly practised. Vegetation changes were identified through analysis of three sets of aerial photographs. The results of GIS analyses, one-way ANOVA and PCA showed that regrowth patterns are complex. In the early phase of succession, grazing history has a strong impact on where new forest establishes, both at a distance from the seasonal farmsteads where grazing intensity prior to abandonment was highest, and close to previously existing forest. Sprouting is most likely to be the dominating regeneration strategy in this early phase. In a later phase of succession, the impact of grazing history on forest distribution patterns decreases, as exemplified by the increasing distance from existing forest. The largest amounts of birch forest then establish in warm locations with moderate moisture. Protection against wind appears to be important for birch establishment.     

THERMALLY INDUCED VIBRATIONS OF COMPOSITE BEAMS WITH INTERLAYER SLIP

Thermally excited vibrations of composite viscoelastic two-layer beams with interfacial slip are analyzed. Geometrically linearized conditions are considered, and the Bernoulli-Euler hypothesis is applied to each layer. At the interface a linear viscoelastic slip law is assigned. The resulting sixth-order initial boundary value problem of the deflection is solved in the time domain by separating the dynamic response in a quasistatic and a complementary dynamic portions. The quasistatic solution is determined in closed form, and the remaining complementary dynamic part is approximated by a truncated modal series that exhibits accelerated convergence. Numerical results are obtained for single-span composite beams with interlayer slip by means of a time-stepping procedure based on the linear interpolation of the driving terms within the time intervals.     

A rigorous small area modelling-study for the helicobacter pylori epidemiology

This paper presents an investigation into spatial risk differences over small distances for the Helicobacter pylori infection in the city of Leipzig, Germany and two rural districts. A model, using Bayesian inference, was developed that adjusts the risk for individual-specific factors, and for spatial or individual over-dispersion, respectively. Additionally, the model takes into account conditional spatial autocorrelation. We found a significant positive association to the H. pylori infection risk for: “more than three children live in the household” (OR = 2.4, p = 0.001), “more persons live per sq.m than average” (OR = 1.4, p = 0.03), “home situated at main road” (OR = 1.4, p = 0.04) and “using well water” (OR = 2.3, p = 0.05). A protective effect was identified for “travelled to low prevalence region” (OR = 0.4, p < 0.0001) and “born in Germany” (OR = 0.2, p < 0.0001). Three administrative areas with significantly increased spatial risk were identified: one in the rural district and two in the city of Leipzig. The model explained 24.9% of the total deviance. Contrary to expectations, the largest part of deviance of the data was not explained by the identified significant risk factors, but by individual-specific heterogeneities. We conclude that further - so far not discussed - factors influence the risk and the spatial variation of the H.pylori infection. Furthermore, from the results we speculate about a possible impact of long-time air pollution and surface water.     

Stochastic modeling of grain wear in geometric physically-based grinding simulations

Grinding processes can be optimized by simulating the influence of individual grains on process forces and surface topographies. However, the process results are significantly influenced by tool wear. Simulating this effect allows, e.g., the prediction of necessary tool changes when manufacturing large forming tools. Therefore, a new point-based approach for modeling arbitrarily shaped grains in different states of tool wear was developed. Based on a small amount of representative wear investigations, a flexible tool model was defined, which can be used for various tool shapes without further experiments. This model can be applied for grinding processes with varying engagement situations.     

Feeding stimulatory and inhibitory chemicals from an acceptable nonhost plant forManduca sexta: Improved detection by larvae deprived of selected chemosensory organs

The chemical basis of feeding responses to the acceptable nonhost plantVigna sinensis (cowpea) by larvae ofManduca sexta was investigated using chemical isolation techniques directed by a novel chemosensory-based bioassay. The presence of feeding stimulatory and inhibitory compounds in leaves or leaf extracts was determined in a two-choice preference test using leaf disks or glass fiber filter paper disks laced with leaf extract as test substrate and filter paper disks laced with water as control. Larvae strongly prefer the control disks over leaf disks, indicating the presence of feeding inhibitory compounds in the leaf. An ethanol extract of both fresh and dried leaves neither stimulated nor inhibited feeding. The cause of this inactivity was examined by using larvae that respond strongly to either feeding stimulatory or inhibitory compounds due to selective chemosensory deprivation. Larvae having chemosensory organs remaining only on the maxillary palps are stimulated to feed by whole leaf disks and by the ethanol extracts. In contrast, larvae having only the medial and lateral maxillary sensilla styloconica and the epipharyngeal sensilla remaining are strongly inhibited by whole leaf disks and the ethanol extract of fresh leaves. Thus, the ethanol extract contains both feeding stimulatory and inhibitory compounds, which elicit opposite behavioral effects in unoperated larvae, therefore nullifying any stimulatory and inhibitory activity. These compounds can only be demonstrated by using discrimination-enhanced larvae in the choice tests. Further isolation of the feeding stimulatory principle inV. sinensis yielded two separate fractions of neutral compounds, suggesting at least two different chemicals belonging to two different classes: nonpolar and polar lipids. Feeding inhibitory chemicals have apparently polar properties because strong activity was found in the ethyl acetate and methanol extracts of dried leaves. The role of feeding stimulatory and inhibitory compounds in food selection ofM. sexta larvae is discussed.     

pH- and salt-dependent molecular combing of DNA: experiments and phenomenological model

λ-DNA as well as plasmids can be successfully deposited by molecular combing on hydrophobic surfaces, for pH values ranging from 4 to 10. On polydimethylsiloxane (PDMS) substrates, the deposited DNA molecules are overstretched by about 60-100%. There is a significant influence of sodium ions (NaCl) on the surface density of the deposited DNA, with a maximum near to 100 mM NaCl for a DNA solution (28 ng μl(-1)) at pH 8. The combing process can be described by a micromechanical model including: (i) the adsorption of free moving coiled DNA at the substrate; (ii) the stretching of the coiled DNA by the preceding meniscus; (iii) the relaxation of the deposited DNA to the final length. The sticky ends of λ-DNA cause an adhesion force in the range of about 400 pN which allows a stable overstretching of the DNA by the preceding meniscus. The exposing of hidden hydrophobic bonds of the overstretched DNA leads to a stable deposition on the hydrophobic substrate. The pH-dependent density of deposited DNA as well as the observed influence of sodium ions can be explained by their screening of the negatively charged DNA backbone and sticky ends, respectively. The final DNA length can be derived from a balance of the stored elastic energy of the overstretched molecules and the energy of adhesion.     

Sensorische Beurteilung des Bittergeschmacks von Amarogentin und Austauschm?glichkeiten gegen Chinin in Erfrischungsgetr?nken

Zusammenfassung In der vorliegenden Arbeit wurde mit Hilfe sensorischer Beurteilung der Einfluß von Saccharose, Anhydrocitronensäure und Limettearoma auf die Bitternote von Amarogentin, einem natürlichen Bitterstoff der Enzianwurzel, im Hinblick auf Austauschmöglichkeiten gegen Chinin in Erfrischungsgetränken, untersucht. Um die Austauschmöglichkeiten von Chinin durch Amarogentin beurteilen zu können, wurden die unterschiedlichen Bitterverläufe von Amarogentin und Chinin sensorisch beurteilt. Die Versuche ergaben, daß identische Bitternoten für Amarogentin und Chinin nicht zu erreichen waren. Darüber hinaus erwies sich Amarogentin gegenüber Konzentrationsänderungen von Citronensäure und Saccharose im Vergleich zu Chinin als wesentlich empfindlicher. Änderungen der Amarogentin-Konzentration hingegen hatten kaum Auswirkungen auf die Bitternote. Für Chinin ergaben sich ausschließlich Änderungen in der Intensität, nicht in der Bitternote. Amarogentin zeichnete sich durch eine abgerundete und reine Bitternote ohne störenden Nachgeschmack aus.

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Sensory evaluation of the bitter taste of amarogentin and the feasibility of its exchange for quinine in soft drinks1. Influence of sucrose and anhydrous citric acid

Summary The influence of sucrose, anhydrous citric acid and lemon flavour on the bitter taste of amarogentin, a natural bitter-tasting component of gentian root, has been investigated. The investigation, based on sensory evaluation, is aimed at evaluating the possibility of exchanging amarogentin for quinine in soft drinks. To do this the different states of bitter taste of quinine and amarogentin had to be noted in a particular way. The tests showed the possibility of obtaining identical bitter tastes from quinine and amarogentin. Additionally, amarogentin proved to be much more sensitive to changes in concentration of anhydrous citric acid and sucrose than quinine. In contrast, different amarogentin concentrations did not produce remarkable effects on the bitter taste. With quinine, the sensory tests showed a change in intensity of the bitter taste with concentration. Amarogentin produced a well-rounded and pure bitter taste without any after-taste which could impair the quality.

     

Estrogen receptor accessory proteins augment receptor-DNA interaction and DNA bending

The human Cu/Zn superoxide dismutase (hSOD-1) gene, catalyses the dismutation of O2 to H2O2 and O2. It is located on chromosome 21 in q22.1 and is overexpressed in Down's syndrome (DS) patients. These patients present various abnormalities including mental retardation, congenital heart disease, immunological deficits and premature aging. In order to explore the potential role of SOD-1 overexpression in DS, we have generated two lineages of transgenic mice for the hSOD-1 gene and studied, at the ultrastructural level, the effect of hSOD-1 overexpression on the thymic microenvironment. Modification of the cellular architecture and morphology associated with a lipidic invasion, signs of a premature involution of the thymus, were observed in both lineages. A rupture of the filamentous network in the extracellular and probably also in the intracellular matrix was first observed. These results correlate the thymic alterations visualized in light microscopy, on the thymus from DS patients, and raise the question of the relationship between the SOD-1 overexpression and the different morphological alterations associated with the premature thymic involution observed in SOD-1 transgenic mice. They suggest that thymic and immunological impairments present in DS patients may be related to the SOD-1 gene dosage effect.     

A relation between Newton and Gauss-Newton steps for singular nonlinear equations

The Gauss-Newton step belonging to an appropriately chosen bordered nonlinear system is analyzed. It is proved that the Gauss-Newton step calculated after a sequence of Newton steps is equal to the doubled Newton step within the accuracy ofO(‖x?x ^*‖²). The theoretical insight given by the proof can be exploited to derive a Gauss-Newton-like algorithm for the solution of singular equations.