Effects of Palladium Dispersions on Gas-Sensitive Conductivity of Semiconducting Ga2O3 Thin-Film Ceramics

The gas sensitivity of Ga₂O₃ thin-film n -type conductors was investigated at temperatures of 500–1000°C. Palladium dispersions whose particle sizes are dependent on the preceding annealing processes were deposited by a wet-chemical technique onto Ga₂O₃ thin-film ceramics. The palladium clusters and their temperature-dependent growth were detected using scanning electron microscopy micrographs and X-ray photoemission spectroscopy measurements. The effect of the palladium dispersions on the gas-sensitive behavior of the Ga₂O₃ ceramics was investigated in various O₂/H₂ mixtures in the N₂ carrier gas at 700°C. The conductivity of the ceramics treated in this way was dependent on the O₂ partial pressure, as well as on the H₂ partial pressure of the surrounding gas atmosphere. The ceramic conductivity can be described as a function of the O₂:H₂ ratio, in accordance with the relation σ( p O₂/ p H₂/)^−1/3.     

Chemoenzymatic Synthesis of Glycopeptides to Explore the Role of Mucin 1 Glycosylation in Cell Adhesion

Post-translational modifications affect protein biology under physiological and pathological conditions. Efficient methods for the preparation of peptides and proteins carrying defined, homogeneous modifications are fundamental tools for investigating these functions. In the case of mucin 1 (MUC1), an altered glycosylation pattern is observed in carcinogenesis. To better understand the role of MUC1 glycosylation in the interactions and adhesion of cancer cells, we prepared a panel of homogeneously O-glycosylated MUC1 peptides by using a quantitative chemoenzymatic approach. Cell-adhesion experiments with MCF-7 cancer cells on surfaces carrying up to six differently glycosylated MUC1 peptides demonstrated that different glycans have a significant impact on adhesion. This finding suggests a distinct role for MUC1 glycosylation patterns in cancer cell migration and/or invasion. To decipher the molecular mechanism for the observed adhesion, we investigated the conformation of the glycosylated MUC1 peptides by NMR spectroscopy. These experiments revealed only minor differences in peptide structure, therefore clearly relating the adhesion behaviour to the type and number of glycans linked to MUC1.     

Evidence for a Phase Transition of β-Gallium Oxide at Very Low Oxygen Pressures

Depending on the operating temperature, gas sensors that are based on n-type-semiconductor, polycrystalline gallium oxide (Ga₂O₃) thin films are used to detect oxygen (at temperatures, T, of 850°C) or reducing gases (T 900°C). At high temperatures (T 900°C), beta-Ga₂O₃has an oxygen deficiency in the crystal lattice that is in dynamic equilibrium with the oxygen in the surrounding atmosphere. Variations in the conductivity of the sensor are caused by variations of the concentration of ionized oxygen vacancies. Therefore, a reduction in the proportion of oxygen or an increase in the concentration of reducing gases in the atmosphere in which the sensor is located leads to an increasing number of conducting electrons and, hence, an increasing conductivity. During a research project to investigate the long-term stability of thin beta-Ga₂O₃ films in a variety of strongly reducing atmospheres at T > 600°C, a previously unknown phenomenon has been observed when measurements on low oxygen partial pressures (pO₂10_-10 Pa (10^-15bar)) have been made. A sharp decrease in sensor conductivity, by several orders of magnitude, is observed each time when pO₂ is reduced to a value of <10^-15bar at temperatures in the range of ˜750°-1000°C. The reason for this may be a phase transition in the β-Ga₂O₃ layer. However, attempts to freeze the new state with subsequent identification by X-ray diffractometry have not succeeded in identifying the new phase.     

Predicting acidification recovery at the Hubbard Brook Experimental Forest, New Hampshire: evaluation of four models

The performance and prediction uncertainty (owing to parameter and structural uncertainties) of four dynamic watershed acidification models (MAGIC, PnET-BGC, SAFE, and VSD) were assessed by systematically applying them to data from the Hubbard Brook Experimental Forest (HBEF), New Hampshire, where long-term records of precipitation and stream chemistry were available. In order to facilitate systematic evaluation, Monte Carlo simulation was used to randomly generate common model input data sets (n = 10,000) from parameter distributions; input data were subsequently translated among models to retain consistency. The model simulations were objectively calibrated against observed data (streamwater: 1963-2004, soil: 1983). The ensemble of calibrated models was used to assess future response of soil and stream chemistry to reduced sulfur deposition at the HBEF. Although both hindcast (1850-1962) and forecast (2005-2100) predictions were qualitatively similar across the four models, the temporal pattern of key indicators of acidification recovery (stream acid neutralizing capacity and soil base saturation) differed substantially. The range in predictions resulted from differences in model structure and their associated posterior parameter distributions. These differences can be accommodated by employing multiple models (ensemble analysis) but have implications for individual model applications.     

高性能精梳机的质量

描述了立达E65/E75新型精梳机的特征,包括工艺过程和所加工的精梳条的特点.E65/E75已在工艺和技术上实现了高性能棉精梳的新概念.目前在纺纱厂生产高质量纱线时可以达到450钳次/min.