Motion patterns of Nabesna Glacier (Alaska) revealed by interferometric SAR techniques

Nabesna Glacier is one of the longest land-terminus mountain glaciers in North America. However, its flow has never been studied. We derived detailed motion patterns of Nabesna Glacier in winter and spring 1994–1996 from the synthetic aperture radar (SAR) images acquired by the European Remote Sensing satellites (ERS-1 and ERS-2) using interferometric SAR (InSAR) techniques. Special effort was made to assess the accuracy of the motion estimates, and remove data points with high uncertainty from the motion profiles, enabling us to obtain reliable glacier flow patterns along the highly curved main course of Nabesna Glacier. The results, covering 80 km of the 87 km main course of the glacier, were used to delineate four distinctive sections in terms of spatial and temporal variability of the glacier speed: (1) the upper section where glacier flow was apparently random both temporally and spatially presumably due to development of crevasses; (2) the upper-middle section with relatively steady flow around 0.27 to 0.4 m/day; (3) the middle section with a stable pattern of acceleration from 0.27–0.3 m/day to the maximum about 0.67–0.73 m/day, followed by a general deceleration to 0.17–0.33 m/day before reaching (4) the lower section where the glacier motion was generally slow yet highly variable although uncertainty in the estimation is high. Occurrence of the flow maximum, as well as many local maxima and minima at consistent locations over different periods suggests that the valley geometry affect the overall flow pattern. On top of this general trend, many small-scale temporal/spatial variations in the glacier flow patterns were observed along the glacier, especially in the lower sections. On average, the flow speeds were in the range of 0.3 to 0.7 m/day; however this lacks any measurements of summer flow speeds which are expected to be significantly higher.     

Implementation of multipoint connections in an ATM switching network

This paper presents the problems in the implementation of multipoint connections at switching level using the example of an ATM switching network. By choosing the proper routeing mechanism and the appropriate architecture of the switching element, a switching network can gradually be adapted to an increasing share of multipoint traffic. The first section describes the problems with the handling of multipoint connections within a multiple stage connection oriented switching network. In particular this refers to the routeing of the cells through the switching network. Several alternatives on this issue are discussed. Both, the selected approach based on a differentiated self-routeing mechanism and the corresponding cell format are introduced. In the second part of this article several switch architectures are compared in respect of their multipoint capability. It is demonstrated that at present the most promising solution are switching elements based on the principle of central buffering. A single chip solution using this concept is employed in the presented switching network.     

节理边坡渗流离散元模拟及边坡可靠性分析

采用定性研究和定量分析相结合的方法,对地下水对节理边坡稳定性的影响进行了较为全面的研究.首先采用离散元方法进行了节理边坡地下水流动的数值模拟:其次用不确定性方法——模糊点估计方法对有水和无水作用两种情况下的边坡稳定性进行了模糊随机可靠性对比分析.研究表明,地下水的存在使边坡的破坏面积增大,破坏概率剧增,边坡可靠性指标极大地降低,因此地下水对节理边坡稳定性具有不可忽视的作用.     

11C‐ and 18F‐Labeled Radioligands for P‐Glycoprotein Imaging by Positron Emission Tomography

P‐Glycoprotein (P‐gp) is an efflux transporter widely expressed at the human blood–brain barrier. It is involved in xenobiotics efflux and in onset and progression of neurodegenerative disorders. For these reasons, there is great interest in the assessment of P‐gp expression and function by noninvasive techniques such as positron emission tomography (PET). Three radiolabeled aryloxazole derivatives: 2‐[2‐(2‐methyl‐(¹¹C)‐5‐methoxyphenyl)oxazol‐4‐ylmethyl]‐6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinoline ([¹¹C]‐ 5 ); 2‐[2‐(2‐fluoromethyl‐(¹⁸F)‐5‐methoxyphenyl)oxazol‐4‐ylmethyl]‐6,7‐dimethoxy‐1,2,3,4‐tetra‐hydroisoquinoline ([¹⁸F]‐ 6 ); and 2‐[2‐(2‐fluoroethyl‐(¹⁸F)‐5‐methoxyphenyl)oxazol‐4‐ylmethyl]‐6,7‐dimethoxy‐1,2,3,4‐tetrahydroisoquinoline ([¹⁸F]‐ 7 ), were tested in several in vitro biological assays to assess the effect of the aryl substituent in terms of potency and mechanism of action toward P‐gp. Methyl derivative [¹¹C]‐ 5 is a potent P‐gp substrate, whereas the corresponding fluoroethyl derivative [¹⁸F]‐ 7 is a P‐gp inhibitor. Fluoromethyl compound [¹⁸F]‐ 6 is classified as a non‐transported P‐gp substrate, because its efflux increases after cyclosporine A modulation. These studies revealed a promising substrate and inhibitor, [¹¹C]‐ 5 and [¹⁸F]‐ 7 , respectively, for in vivo imaging of P‐gp by using PET.     

Identification and characterization of a glucan-producing enzyme from Lactobacillus hilgardii TMW 1.828 involved in granule formation of water kefir

Water kefir is a home made fermented beverage based on a sucrose solution with fruit extracts. The inoculum of such fermentations consists of macroscopic granula containing lactic and acetic acid bacteria, and yeasts, which are embedded in an exopolysaccharide (EPS) matrix. In this work, a strain of Lactobacillus hilgardii producing large amounts of the granule-forming dextran could be isolated. The glycosyltransferans (Gtf) commonly called glucansucrase responsible for the production of this dextran was purified from L. hilgardii. Characteristic enzyme kinetic data were obtained. Optimum activity was observed between pH 4.3 and 4.6 and temperatures between 40 °C and 45 °C. A Michaelis–Menten kinetic could be fit to the experimental data and a K_M of 0.0385 M was calculated. The corresponding gtf gene was identified and characterized. It encodes a 1448 amino acid protein with higher homologies to Gtfs of Lactobacillus parabuchneri, Lactobacillus sakei and Lactobacillus fermentum followed by lower homologies to Lactobacillus reuteri Gtfs. By knockout experiments the role of this gene in granule dextran production was demonstrated.     

Basic investigations on debris cooling

An experimental investigation of boiling phenomena in inductively heated particle beds has been performed. The major aim of these experiments is to provide data for validating numerical codes used in reactor safety. The experiments can be divided in three parts: boiling experiments, dryout experiments and quenching experiments. In boiling experiments, the pressure gradients have been measured along the bed height for different flow modes, different heat inputs and different system pressures. In dryout experiments, the minimum heat input has been determined for which the particle bed starts to superheat significantly above the saturation temperature. The final test series deals with the cool down behaviour of strongly superheated particles by flooding them with cold water. The initial temperatures ranged from 200 up to 900 °C in top-quenching experiments and from 230 up to 450 °C in bottom-quenching experiments. All experiments were performed with pre-oxidised stainless steel balls of 6 and 3 mm diameter in a cylindrical crucible. The bed height was 640 mm and the bed diameter was 125 mm for boiling and dryout experiments, respectively 150 mm for quenching experiments. The experimental results are compared with various available dryout models.     

Prognose der Sorptionskinetik organischer Schadstoffe in heterogenem Aquifermaterial

A model for the simulation of kinetic sorption processes in heterogeneous aquifer material is presented. Sorption kinetics is responsible for the long persistence of many organic contaminants in the subsurface. Therefore, reliable model predictions of these processes are of major importance concerning, for instance, the design of efficient remediation strategies. The modeling approach presented here recognizes sorption kinetics as retarded diffusion within the intra-particle pore space and, in particular, takes into account the sedimentological and petrographical composition of the aquifer material. This is in accordance with results from laboratory experiments quantifying sorption/desorption processes. For solving the model equations a finite-difference scheme is applied which incorporates several features proven to be relevant in practical model applications (mass balance, flexible choice of boundary conditions, easy handling). The simulation results shown here focus on the impact of aquifer heterogeneity (lithological composition, grain size distribution) on sorption and desorption kinetics of organic contaminants. Furthermore, this approach can be straightforwardly coupled to existing software for simulating multi-dimensional solute transport.