Sphingophospholipids of species ofAedes andCulex mosquito cells cultivated in suspension culture from logarithmic and stationary phases of growth

Two sphingophospholipids, sphingomyelin (ceramide phosphorylcholine), and ceramide phosphorylethanolamine, were isolated and purified from cells of four mosquito species obtained from the logarithmic and stationary phases of growth. Quantitation of the two lipids in both phases of growth from cells of each species was made. The fatty acid composition of the two lipids was compared between the cell types and the two phases of growth. There was a tendency for an increase of ceramide phosphorylcholine and a decrease of ceramide phosphorylethanolamine in the stationary phase. Longer chain fatty acids of ceramide phosphorylcholine were observed in the stationary phase than in the logarithmic phase of growth of the mosquito cells. The four species had distinctly different fatty acid patterns in the two complex lipids which might be useful for taxonomic purposes and cell identification.     

Mitigating the risk of high power damage to the BT network

Optical powers used in optical telecommunications networks have increased over time with the advent of technologies such as erbium doped fibre amplifiers, dense WDM, and fibre Raman amplifiers. Erbium fibre and Raman amplifiers with output powers up to 1 W and 2 W respectively are now available for deployment giving optical power densities of ≈14 000 MW/m² per Watt launched into a single mode fibre. This compares with 74 MW/m² for the surface of the sun. It is thus essential to ensure that the risk of optical damage to the fibre is understood and steps are taken to mitigate it where necessary. Research carried out by BT over the last few years has shown that fibres carrying relatively modest optical powers, as low as 200 mW for the most sensitive fibres, can be catastrophically damaged at tight fibre bends. Damage is caused by some of the optical power lost at the bend being absorbed by the fibre coating that may over time lead to a sudden increase in temperature to over 700 °C causing either the silica to kink mimicking a fibre break, or the coating to burn off at the bend leading to fibre failure on subsequent handling. This paper describes factors that increase the risk of short-term catastrophic damage at fibre bends, presents experimental results to show the variation in sensitivity between different fibres, and discusses new important theoretical results modelling the temperature rise in the fibre.     

泥浆录井技术新进展(一)

正数十年来,地面采集的样品和计量结果为录井人员提供了洞察钻头端面条件的重要信息。通过录井采集的信息使作业者提前了解油藏潜力,甚至提前预防地层压力问题。而新型采样和分析技术,以及地面传感器设计和监测系统的进步,使录井科学正以新的面貌迈进21世纪。长期以来,泥浆录井仪一直是井场的常用设备。1939年,泥浆录井仪首次投入商用。当时这种移动实验室中仅包括咖啡壶、用于检查地层岩屑的     

Lubricious zinc oxide films: synthesis, characterization and tribological behaviour

Solid lubricants that are effective over an extreme range of operating temperatures are necessary for the development of new generation high-performance gas turbine engines with increased propulsion capability. While oxides have the potential to perform as high-temperature lubricants, they typically have high friction and create abrasive wear debris at low temperature. The objective of this work was to create oxides that have good tribological properties at room temperature through control of microstructure and stoichiometry. Zinc oxide films were grown by pulsed-laser deposition. The stoichiometry and microstructure of the films were controlled by adjusting substrate temperature and oxygen partial pressure during pulsed-laser deposition. Chemistry and microstructure were probed using SEM, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. Friction coefficients and wear life were measured using a ball-on-flat tribometer. The degree of similarity of the coatings to bulk ZnO was RT, vac<RT, O2<300°C, vac<300°C, O2. Coatings with oxygen deficiency and nanoscale structure have low friction (i.e. μ<0.2) and long wear lives (i.e., greater than 106 cycles) at room temperature. As the chemistry and crystal structure of a coating approaches that of bulk ZnO, its tribological properties degrade and can become load/speed sensitive. An important result of this study is that oxides can be made to provide good tribological properties at room temperature. Thus, there is significant potential to produce low-friction, low-wear oxide coatings for wide-temperature range applications by controlling nanostructure and oxygen vacancies. This revised version was published online in November 2006 with corrections to the Cover Date.     

Development of Integrated Thermionic Circuits for High-Temperature Applications

This paper describes a class of microminiature, thin-film devices known as integrated thermionic circuits (ITC) capable of extended operation in ambient temperatures up to 500°C. The evolution of the ITC concept is discussed. A set of practical design and performance equations is demonstrated. Recent experimental results are discussed in which both devices and simple circuits have successfully operated in 500°C environments for extended periods of time (greater than 11000 h).     

Force spectroscopy of an elastic peptide: effect of D₂O and temperature on persistence length

This study explores the mechanical unfolding of elastic protein analogues as a function of temperature, in both H₂O and D₂O, using atomic force microscopy (AFM) force spectroscopy in a specially constructed AFM liquid cell. This represents the first time that the effect of D₂O on protein flexibility has been investigated at the single molecule level by this technique. Model elastic peptides, R6, were encoded from synthetic genes expressed in Escherichia coli. The peptides possess short N‐ and C‐terminal domains with central repetitive domains containing 13 repeats of the motif PGQGQQ‐plus‐GYYPTSLQQ. These sequences mimic those in native high molecular weight subunit glutenin proteins which confer elasticity to bread dough. Fitting single molecule stretching events to the worm‐like chain model, allows determination of the molecular persistence length under various experimental conditions. The effect of increasing the temperature is to increase the persistence length of the peptide in both H₂O and D₂O, consistent with the expected “thermal softening” effect. However, the effect is significantly enhanced in D₂O, in which the persistence length at 45°C is ～25% greater than the value measured in H₂O at the same temperature. Stronger intrapeptide H‐bonding due to isotopic substitution of hydrogen for deuterium is the most likely cause of the enhanced backbone rigidity. Microsc. Res. Tech. 74:170–176, 2011. © 2010 Wiley‐Liss, Inc.     

New risk assessment methodology for coal mine excavated slopes

This paper presents a new risk assessment methodology for coal mine excavated slopes. This new empirical-statistical slope stability assessment methodology(SSAM) is intended for use by geotechnical engineers at both the design review and operational stages of a mine's life to categorise the risk of an excavated coal mine slope. A likelihood of failure is determined using a new slope stability classification system for excavated coal mine slopes developed using a database of 119 intact and failed case studies sourced from open cut coal mines in Australia. Consequence of failure is based on slope height and stand-off distance at the toe of the excavated slope. Results are presented in a new risk matrix, with slope risk being divided into low, medium and high categories. The SSAM is put forward as a new risk assessment methodology to assess the potential for, and consequence of, excavated coal mine slope failure.Unlike existing classification systems, assumptions about the likely failure mode or mechanism are not required. Instead, the SSAM applies an approach which compares the conditions present within the excavated slope face, with the known past performance of slopes with similar geotechnical and geometrical conditions, to estimate the slope's propensity for failure. The SSAM is novel in that it considers the depositional history of strata in an excavated slope and how this sequence affects slope stability. It is further novel in that it does not require explicit measurements of intact rock, rock mass and/or defect strength to rapidly calculate a slope's likelihood of failure and overall risk. Ratings can be determined entirely from visual observations of the excavated slope face. The new SSAM is designed to be used in conjunction with existing slope stability assessment tools.     

Towards a closed-loop cochlear implant system: application of embedded monitoring of peripheral and central neural activity

Although the cochlear implant (CI) is widely considered the most successful neural prosthesis, it is essentially an open-loop system that requires extensive initial fitting and frequent tuning to maintain a high, but not necessarily optimal, level of performance. Two developments in neuroscience and neuroengineering now make it feasible to design a closed-loop CI. One development is the recording and interpretation of evoked potentials (EPs) from the peripheral to the central nervous system. The other is the embedded hardware and software of a modern CI that allows recording of EPs. We review EPs that are pertinent to behavioral functions from simple signal detection and loudness growth to speech discrimination and recognition. We also describe signal processing algorithms used for electric artifact reduction and cancellation, critical to the recording of electric EPs. We then present a conceptual design for a closed-loop CI that utilizes in an innovative way the embedded implant receiver and stimulators to record short latency compound action potentials ( ~1 ms), auditory brainstem responses (1-10 ms) and mid-to-late cortical potentials (20-300 ms). We compare EPs recorded using the CI to EPs obtained using standard scalp electrodes recording techniques. Future applications and capabilities are discussed in terms of the development of a new generation of closed-loop CIs and other neural prostheses.