Stem injection of triazoles for the protection of Vitis vinifera L. (‘Riesling’) against powdery mildew (Uncinula necator)

The aim of this study was to find suitable substances to control powdery mildew by means of stem injection. The triazoles myclobutanil, penconazol and tebuconazol were used as test substances. In the first experiment, single xylem injections of these triazoles were carried out to test their effect against powdery mildew. The injections were carried out on field-grown grapevines using the ChemJet® tree injector. Applications invariably yielded efficiency factors of over 60 %. A practiceoriented effect on leaves and grapes was most notably gained using tebuconazol. In the second experiment, the repeated xylem injection of myclobutanil, penconazol and tebuconazol was carried out on field-grown grapevines with a prototypal stationary injection system to evaluate the longer-term effects. Grapevines sprayed with formulated myclobutanil (Systhane 20 EW®), penconazol (Topas®) and tebuconazol (Folicur 250 EW®) enable the methods to be compared. Applications using the prototypal stationary injection system only yielded moderate efficiency factors. A practice-oriented effect was gained using the sprayed application. Future options for stem injection, such as combating wood-destroying fungi and phytoplasmosis, were discussed.

Stem application of metalaxyl for the protection of Vitis vinifera L. (‘Riesling’) leaves and grapes against downy mildew (Plasmopara viticola)

The direct application of plant protective agents into tree xylem is an ecologically sound method of plant protection, which has already been used for trees in urban environements. In order to make this system viable for grapevines (Vitis), the effectiveness of the protective system must be ensured. In the first experiment, the effect of the fungicide agents dimethomorph, fosetyl-al, iprovalicarb and metalaxyl applied to the stem of field-grown grapevines was investigated. As a result, injection experiments using non-formulated metalaxyl showed the desired protective effects against downy mildew (Plasmopora viticola). In the second experiment, non-formulated metalaxyl was applied several times in succession over a period of several weeks to the xylem of test grapevines using an injection system, affixed long-term to the vine stems. Grapevines sprayed with formulated metalaxyl (Fonganil Gold®) enabled the methods to be compared. The efficiency factors with regard to the control of downy mildew in leaves and grapes were very similar in both approaches, with values of practical relevance of over 70 %.

Elemental boron doping behavior in silicon molecular beam epitaxy

Boron-doped Si epilayers were grown by molecular beam epitaxy (MBE) using an elemental boron source, at levels up to 2×1020 cm−3, to elucidate profile control and electrical activation over the growth temperature range 450–900 °C. Precipitation and surface segregation effects were observed at doping levels of 2×1020 cm−3 for growth temperatures above 600 °C. At growth temperatures below 600 °C, excellent profile control was achieved with complete electrical activation at concentrations of 2×1020 cm−3, corresponding to the optimal MBE growth conditions for a range of Si/SixGe1−x heterostructures

Negative Differential Resistance in the Scanning Tunneling Spectroscopy of Organic molecules

The conductance-voltage spectrum of molecular nanostructures measured by scanning tunneling spectroscopy (STS) is generally assumed to reflect the local density of states of the molecule. This excludes the possibility of observing negative differential resistance (NDR). We report here the observation of NDR in the scanning tunneling microscope (STM) current-voltage (I-V) characteristics of self-assembled monolayer (SAM) of 4-p-Terphenylthiol molecules on gold substrate measured using a platinum probe. We argue that the NDR arises from narrow structures in the local density of states at the tip apex atom and show that depending on the electrostatic potential profile across the system, NDR could be observed in one or both bias directions.Comment: 13 Pages, 4 figures, submitted to Phys. Rev. B Rapid Communicatio

The Optical Gravitational Lensing Experiment. Monitoring of QSO 2237+0305

We present results from 2 years of monitoring of Huchra's lens (QSO 2237+0305) with the 1.3 m Warsaw telescope on Las Campanas, Chile. Photometry in the V band was done using a newly developed method for image subtraction. Reliable subtraction without Fourier division removes all complexities associated with the presence of a bright lensing galaxy. With positions of lensed images adopted from HST measurements it is relatively easy to fit the variable part of the flux in this system, as opposed to modeling of the underlying galaxy. For the first time we observed smooth light variation over a period of a few months, which can be naturally attributed to microlensing. We also describe automated software capable of real time analysis of the images of QSO 2237+0305. It is expected that starting from the next observing season in 1999 an alert system will be implemented for high amplification events (HAE) in this object. Time sampling and photometric accuracy achieved should be sufficient for early detection of caustic crossings.Comment: 8 pages (including 4 figures and table), latex, emulateapj, submitted to ApJ, revised version - minor change

Concentration of atomic hydrogen diffused into silicon in the temperature range 900–1300 °C

Boron-doped Czochralski silicon samples with [B]~1017 cm−3 have been heated at various temperatures in the range 800–1300 °C in an atmosphere of hydrogen and then quenched. The concentration of [H-B] pairs was measured by infrared localized vibrational mode spectroscopy. It was concluded that the solubility of atomic hydrogen is greater than [Hs] = 5.6 × 1018 exp( − 0.95 eV/kT)cm−3 at the temperatures investigated