Hopping motion of lattice gases through nonsymmetric potentials under strong bias conditions

The hopping motion of lattice gases through potentials without mirror-reflection symmetry is investigated under various bias conditions. The model of 2 particles on a ring with 4 sites is solved explicitly; the resulting current in a sawtooth potential is discussed. The current of lattice gases in extended systems consisting of periodic repetitions of segments with sawtooth potentials is studied for different concentrations and values of the bias. Rectification effects are observed, similar to the single-particle case. A mean-field approximation for the current in the case of strong bias acting against the highest barriers in the system is made and compared with numerical simulations. The particle-vacancy symmetry of the model is discussed.Comment: 8 pages (incl. 6 eps figures); RevTeX 3.

Die Pathogenese des Pezicula-Krebses der Amerikanischen Roteiche (Quercus rubra L.), verursacht durch Pezicula cinnamomea (DC.) Sacc., im Vergleich mit anderen Rindenerkrankungen der Eiche

SIGLEAvailable from: Hannover Univ. (Germany, F.R.). Universitaetsbibliothek / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Controlled inoculation of Norway spruce (<em>Picea abies</em>) with <em>Sirococcus conigenus</em>: PCR-based quantification of the pathogen in host tissue and infection-related increase of phenolic metabolites.

Controlled inoculation of spruce seedling needle crowns and of shoots of 4-year-old spruce trees by Sirococcus conigenus led to disease symptoms (discoloration and necrosis) and to the induction of phenolic metabolites. Even upon complete infection, as proved by reisolation of the pathogen from inoculated seedlings, only 40% of the plants developed visible disease symptoms after 38 days. A Sirococcus-specific polymerase chain reaction (PCR) primer pair, SIRO1 and SIRO6, was designed based on sequences of a RAPD fragment. The primer pair permitted the detection of 1 pg fungal DNA (10-40 genomes) in 1 mg fresh weight spruce tissues (needles, bark, wood), regardless of visible disease symptoms. The amounts of the major phenolic compound of spruce needles, catechin, increased significantly in all of the five spruce provenances as a response to inoculation with Sirococcus. The second major phenolic compound, picein, increased in three of the provenances, whereas the remaining two had high concentrations to begin with and showed no reaction. Minor phenolic compounds increased in response to infection regardless of provenance. In a preliminary field study, Sirococcus infection of spruce was detectable by PCR even in the presence of massive infection by other fungi, such as Rhizospaera spp. and Lophodermium spp

Beech leaf colonization by the endophyte <em>Apiognomonia errabunda</em> dramatically depends on light exposure and climatic conditions.

Ozone and light effects on endophytic colonization by Apiognomonia errabunda of adult beech trees (Fagus sylvatica) and their putative mediation by internal defence compounds were studied at the Kranzberg Forest free-air ozone fumigation site. A. errabunda colonization was quantified by &quot;real-time PCR&quot; (QPCR). A. errabunda-specific primers allowed detection without interference by DNA from European beech and several species of common genera of plant pathogenic fungi, such as Mycosphaerella, Alternaria, Botrytis, and Fusarium. Colonization levels of sun and shade leaves of European beech trees exposed either to ambient or twice ambient ozone regimes were determined. Colonization was significantly higher in shade compared to sun leaves. Ozone exhibited a marginally inhibitory effect on fungal colonization only in young leaves in 2002. The hot and dry summer of 2003 reduced fungal colonization dramatically, being more pronounced than ozone treatment or sun exposure. Levels of soluble and cell wall-bound phenolic compounds were approximately twice as high in sun than in shade leaves. Acylated flavonol 3- O-glycosides with putatively high UV-B shielding effect were very low in shade canopy leaves. Ozone had only a minor influence on secondary metabolites in sun leaves. It slightly increased kaempferol 3- O-glucoside levels exclusively in shade leaves. The frequently prominent hydroxycinnamic acid derivative, chlorogenic acid, was tested for its growth inhibiting activity against Apiognomonia and showed an IC50 of approximately 8 mM. Appearance of Apiognomonia-related necroses strongly correlated with the occurrence of the stress metabolite, 3,3&#39;,4,4&#39;-tetramethoxybiphenyl. Infection success of Apiognomonia was highly dependent on light exposure, presumably affected by the endogenous levels of constitutive phenolic compounds. Ozone exerted only minor modulating effects, whereas climatic factors, such as pronounced heat periods and drought, were dramatically overriding