STM Simulation of Molecules on Ultrathin Insulating Overlayers Using Tight-Binding: Au-Pentacene on NaCl bilayer on Cu

We present a fast and efficient tight-binding (TB) method for simulating scanning tunneling microscopy (STM) imaging of adsorbate molecules on ultrathin insulating films. Due to the electronic decoupling of the molecule from the metal surface caused by the presence of the insulating overlayer, the STM images of the frontier molecular orbitals can be simulated using a very efficient scheme, which also enables the analysis of phase shifts in the STM current. Au-pentacene complex adsorbed on a NaCl bilayer on Cu substrate provides an intricate model system, which has been previously studied both experimentally and theoretically. Our calculations indicate that the complicated shape of the molecular orbitals may cause multivalued constant current surfaces -- leading to ambiguity of the STM image. The results obtained using the TB method are found to be consistent with both DFT calculations and experimental data.Comment: 19 pages, 5 figure

Changes in bacterial populations along roots of wheat (Tricticum aestivum L.) seedlings

In this study the bacterial populations on root tips (1–2 days old) of wheat (Triticum aestivum L.) were compared with the populations on root segments about 1 week older (root base). The isolates were characterized with a set of physiological tests and the test results were used to group the bacteria by means of cluster analysis. Some clusters contained bacteria that occurred mainly on the root tips and were characterized by the ability to produce acid from different sugars and by the presence of the enzymes nitrate reductase, lipase, and oxidase; they were sensitive to high salt concentrations in the media. Another cluster included significantly more isolates from the root-base segments; these bacteria were characterized by a negative reaction to most of the physiological tests; the colonies formed by these bacteria had yellow pigmentation. Possiblemechanisms for the changes in the bacterial populations are discussed

Influence of different application rates of nitrogen to soil on rhizosphere bacteria

Onderzoek naar de bacterieele populaties in de rhizosfeer van tarwe bij verschillende stikstofregimes. De stikstofgift (250 mg N en 50 mg ␛ per plant) werd gegeven in een eenmalige of gesplitste gift, waarbij steeds kleinere hoeveelheden werden gegeven. De verschillende giften maken het mogelijk om de bacterieele populaties te bestuderen in relatie tot de stikstofconcentraties in de wortels en in de bodem bij overeenkomstige biomassaprodukti

Changes in bacterial populations along roots of wheat (Tricticum aestivum L.) seedlings

In this study the bacterial populations on root tips (1–2 days old) of wheat (Triticum aestivum L.) were compared with the populations on root segments about 1 week older (root base). The isolates were characterized with a set of physiological tests and the test results were used to group the bacteria by means of cluster analysis. Some clusters contained bacteria that occurred mainly on the root tips and were characterized by the ability to produce acid from different sugars and by the presence of the enzymes nitrate reductase, lipase, and oxidase; they were sensitive to high salt concentrations in the media. Another cluster included significantly more isolates from the root-base segments; these bacteria were characterized by a negative reaction to most of the physiological tests; the colonies formed by these bacteria had yellow pigmentation. Possiblemechanisms for the changes in the bacterial populations are discussed