Mate Finding in the Parasitic Wasp Cephalonomia tarsalis (Ashmead): More than one way to a Female’s Heart

The parasitic wasp, Cephalonomia tarsalis (Hymenoptera: Bethylidae), parasitizes larvae of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), and is used for biological control of this worldwide pest of stored grain. To study the hypothesis that C. tarsalis not only mates at its natal patch but also uses olfactory cues to find mating partners elsewhere, we investigated semiochemical use by male C. tarsalis. Olfactometer experiments revealed that male C. tarsalis are arrested by odors emanating from the cocoons of conspecifics, from young unmated females, and from feces of the host. Dodecanal, which was identified from extracts of filter paper contaminated by young females, had an arresting effect on males but not on females and was, therefore, considered as a sex pheromone. These findings indicate that C. tarsalis is a species with partial local mate competition. Males mate with females: 1) at the emergence site following location of females by sex pheromones from their cocoons, and 2) after dispersal from the natal patch following location of females directly by dodecanal and indirectly by unidentified sexual kairomones from host feces.     

Initial stages of the ion-beam assisted epitaxial GaN film growth on 6H-SiC(0001)

Ultra-thin gallium nitride (GaN) films were deposited using the ion-beam assisted molecular-beam epitaxy technique. The influence of the nitrogen ion to gallium atom flux ratio (I/A ratio) during the early stages of GaN nucleation and thin film growth directly, without a buffer layer on super-polished 6H-SiC(0001) substrates was studied. The deposition process was performed at a constant substrate temperature of 700 °C by evaporation of Ga and irradiation with hyperthermal nitrogen ions from a constricted glow-discharge ion source. The hyperthermal nitrogen ion flux was kept constant and the kinetic energy of the ions did not exceed 25 eV. The selection of different I/A ratios in the range from 0.8 to 3.2 was done by varying the Ga deposition rate between 5 × 10¹³ and 2 × 10¹⁴ at. cm^− 2 s^− 1. The crystalline surface structure during the GaN growth was monitored in situ by reflection high-energy electron diffraction. The surface topography of the films as well as the morphology of separated GaN islands on the substrate surface was examined after film growth using a scanning tunneling microscope without interruption of ultra-high vacuum. The results show, that the I/A ratio has a major impact on the properties of the resulting ultra-thin GaN films. The growth mode, the surface roughness, the degree of GaN coverage of the substrate and the polytype mixture depend notably on the I/A ratio.     

VEGFR-1 Overexpression Identifies a Small Subgroup of Aggressive Prostate Cancers in Patients Treated by Prostatectomy

The VEGFR-1 is suggested to promote tumor progression. In the current study we analyzed prevalence and prognostic impact of the VEGFR-1 by immunohistochemistry on a tissue microarray containing more than 3000 prostate cancer specimens. Results were compared to tumor phenotype, ETS-related gene (ERG) status, and biochemical recurrence. Membranous VEGFR-1 expression was detectable in 32.6% of 2669 interpretable cancers and considered strong in 1.7%, moderate in 6.7% and weak in 24.2% of cases. Strong VEGFR-1 expression was associated with TMPRSS2:ERG fusion status as determined by fluorescence in situ hybridization (FISH) and immunohistochemistry (p < 0.0001 each). Elevated VEGFR-1 expression was linked to high Gleason grade and advanced pT stage in TMPRSS2:ERG negative cancers (p = 0.0008 and p = 0.001), while these associations were absent in TMPRSS2:ERG positive cancers. VEGFR-1 expression was also linked to phosphatase and tensin homolog (PTEN) deletions. A comparison with prostate specific antigen (PSA) recurrence revealed that the 1.7% of prostate cancers with the highest VEGFR-1 levels had a strikingly unfavorable prognosis. This could be seen in all cancers, in the subsets of TMPRSS2:ERG positive or negative, PTEN deleted or undeleted carcinomas (p < 0.0001 each). High level VEGFR-1 expression is infrequent in prostate cancer, but identifies a subgroup of aggressive cancers, which may be candidates for anti-VEGFR-1 targeted therapy.     

Direct Evidence for Membrane Transport of Host-Plant-Derived Pyrrolizidine Alkaloid N-Oxides in Two Leaf Beetle Genera

The chrysomelid leaf beetles Longitarsus jacobaeae, Oreina cacaliae, and O. speciosissima sequester pyrrolizidine alkaloids from their asteracean host plants and store them as nontoxic N-oxides. Previous analyses showed that Longitarsus is able to N-oxidize protoxic tertiary PAs, but did not resolve in which form N-oxides are taken up. For Oreina, beetles seem able to directly transmit the polar PA N-oxides from the gut into the hemolymph and prevent any reduction of them in the gut yielding protoxic free bases. Here, we confirm the predicted direct uptake of PAs as N-oxides by Oreina, and elucidate the situation for Longitarsus by applying double-labeled [14C]senecionine [18O]N-oxide as tracer. The beetles were fed with the tracer and subsequently senecionine N-oxide was recovered from the defensive secretions (Oreina) and beetle extracts (Longitarsus), purified by HPLC, and submitted to ESI-MS, GC-MS, and analysis of the specific radioactivity. The 18O-label is retained without any loss in the labeled senecionine N-oxide recovered from the two Oreina species. Analysis of the Longitarsus experiment was complicated by a contamination of the HPLC-purified senecionine N-oxide with a second compound, identified as a dihydrosenecionine N-oxide by high-resolution CID analysis. The dihydrosenecionine N-oxide, probably the 15,20-dihydro derivative, constitutes a major idiosyncratic senecionine metabolite present in the beetle. The recovered senecionine N-oxide retained 74% 18O-label. The remaining 25% is mostly due to loss of 18O by reduction and subsequent re-N-oxidation. The experiments confirm for both beetle genera a direct uptake of the polar nontoxic PA N-oxides, which requires specific membrane carriers. Accumulation of detrimental free base PA is prevented by glucosylation (Oreina) or N-oxidation (Longitarsus).     

Comparison of nonnested asymmetric heteroskedastic models

The GJR-GARCH model is a popular choice among nonlinear models of the well-known asymmetric volatility phenomenon in financial market data. However, recent work employs double threshold nonlinear models to capture both mean and volatility asymmetry. A Bayesian model comparison procedure is proposed to compare the GJR-GARCH with various double threshold GARCH specifications, by designing a reversible jump Markov chain Monte Carlo algorithm. A simulation experiment illustrates good performance in estimation and model selection over reasonable sample sizes. In a study of seven markets strong evidence is found that the DTGARCH, with US market news as threshold variable, outperforms the GJR-GARCH and traditional self-exciting DTGARCH models. This result was consistent across six markets, excluding Canada.     

High-resolution capillary tube NMR. A miniaturized 5-microL high-sensitivity TXI probe for mass-limited samples,off-line LC NMR,and HT NMR

A new triple-resonance (TXI) (1H, 13C, 15N) high-resolution nuclear magnetic resonance (NMR) capillary probe with 2.5-microL NMR-active sample volume (V(obs)) was built and tested for applications with mass- and volume-limited samples and for coupling of microbore liquid chromatography to NMR. This is the first microliter probe with optimized coil geometry for use with individual capillary tubes with an outer diameter of 1 mm. The 90 degree pulse lengths of the 1-mm microliter probe were below 2 micros for proton, below 8 micros for carbon, and below 20 micros for nitrogen, and a spectral line width at signal half-height below 1 Hz was obtained. Compared to a conventional 5-mm probe, the new 600-MHz 1-mm TXI microliter probe with z-gradient shows an increase in mass sensitivity by a factor of 5, corresponding to a 25-fold reduction in measuring time. The consumption of costly deuterated solvent is reduced by at least 2 orders of magnitude. The 1-mm TXI microliter probe with z-gradient allows the measurement of one-dimensional 1H NMR and two-dimensional heteronuclear NMR spectra with a few nanomoles (micrograms) of compound with high sensitivity, speed, and quality. This is a breakthrough for discrete sample NMR spectroscopy with paramount importance for structure elucidation in natural compound chemistry and metabolic research. It offers also advantages for linking chromatographic methods to NMR in a nindustrial environment. Capillary tube NMR may find new applications in areas where high sample throughput is essential, e.g., in the quality control of large sample arrays from parallel chemistry, screening, and compound depositories. It has the potential to increase the sample throughput by 1 order of magnitude or more if new hardware for fast sample handling and exchange becomes available.     

EURAXLES – A global approach for design,production and maintenance of railway axles: WP4 – “Tools,technologies and surface protection systems minimizing the negative influence of corrosion or surface damage on the free axle surface“

Work Package 4 “Tools, technologies and surface protection systems minimizing the negative influence of corrosion or surface damage on the axle surface” of the EURAXLES project aimed on development of practical solutions for wheelset protection systems to avoid corrosion and damages at the axles and thus minimizing the risk of axle failures. The work included investigations for improving the paint adhesion by grit‐blasting of the axle surface, alternative and innovative coating systems, recommendations for quality tests of painting and coatings and also investigation of unpainted axles.     

Piezotronic Tuning of Potential Barriers in ZnO Bicrystals

Coupling of magnetic, ferroelectric, or piezoelectric properties with charge transport at oxide interfaces provides the option to revolutionize classical electronics. Here, the modulation of electrostatic potential barriers at tailored ZnO bicrystal interfaces by stress‐induced piezoelectric polarization is reported. Specimen design by epitaxial solid‐state transformation allows for both optimal polarization vector alignment and tailoring of defect states at a semiconductor–semiconductor interface. Both quantities are probed by transmission electron microscopy. Consequently, uniaxial compressive stress affords a complete reduction of the potential barrier height at interfaces with head‐to‐head orientation of the piezoelectric polarization vectors and an increase in potential barrier height at interfaces with tail‐to‐tail orientation. The magnitude of this coupling between mechanical input and electrical transport opens pathways to the design of multifunctional electronic devices like strain triggered transistors, diodes, and stress sensors with feasible applications for human–computer interfacing.     

Influence of gold thin-film interlayers on anodic bonding of copper microstructures produced by LIGA

 Neither pure copper nor solid gold can be anodically bonded to glass. It is only the gold coating on the copper which allows a joint to be built up as a result of the copper ions diffusing into the gold layer, but not many of them being able to migrate into the glass. To encapsulate microstructures produced by the LIGA technique, anodic bonding of gold-coated copper to Corning 0211-type glass was studied. For demonstration purposes, a glass platelet made of Corning 0211 was anodically bonded to a LIGA linear actuator consisting of electroplated copper coated with 1 μm of gold. A better understanding about the decisive parameters in anodic bonding was obtained by varying the bonding temperature and the thickness of the gold layer. Glass can be bonded on to the entire surface of gold layers 0.5–1 μm thick at temperatures as low as 300 °C; however, when the systems cool to room temperature, stress-induced cracks arise in the glass. On the other hand, thicker gold layers of 2.5 to 10 μm thickness require higher bonding temperatures for the same period of heating, but prevent the occurrence of such cracks because of their higher ductility. Received: 11 December 1997/Accepted: 11 March 1998