The application of the locally implicit method to upwind TVD schemes

The local implicit scheme of Reddyet al. is extended to the minmod and third-order upwind TVD schemes. Numerical tests show that the proposed scheme is stable. In addition, it is found that if the flow field has a dominant direction, setting the iteration sweep to align with this direction can significantly improve the converging speed.     

Will the numbers add up for sub-7-nm magnetic spacings? Future metrology issues for disk drive lubricants, overcoats, and topographies

To achieve disk drive recording densities greater than one terabit per square inch, future head-media spacings (HMSs) will need to be less than 7 nm. This will place severe demands on the metrology tools used to measure the thickness and topographies of the contributors to the head-media spacing. Here, we first review some of the metrologies used for characterizing overcoats, lubricants, and topographies and discuss some of the limits that will make it difficult to achieve a sub-7-nm HMS. We next show new results for measuring lubricant redistribution on disk surfaces after contact with a small pad on the slider and present a new method for determining wear rates of these slider contact pads.     

Noise characteristics of erbium-doped fiber amplifier pumped at 980nm

A noise figure of 2.9±0.4 dB, measured in a high-gain erbium-doped fiber amplifier for input signals in the range -35 to -15 dBm and for pump powers of >5.8 mW, is discussed. The spontaneous emission factor n_sp was 0.99±0.09 for input signals less than -15 dBm. These low figures are attributable to the optimized fiber design and the use of a pump wavelength of 980 nm, at which erbium operates as a true three-level system. These two factors contribute to the very low (~500 μW) pump threshold seen in fiber, which permits nearly complete inversion to be achieved for the low pump powers employed     

The effect of scene elevation on the coherence of wide-angle crossing-node SAR pairs

The interference between two radar images, acquired from approximately the same location, has a number of uses. In particular, the literature abounds with examples of coherent change detection (CCD) and interferometric synthetic aperture radar (InSAR) uses that, respectively, enable the detection of small changes and the extraction of terrain elevation. In almost all of these examples, collections have been deliberately constrained so that they have almost identical collection geometries. Details of the variation in geometry have been analyzed extensively but generally only with respect to variation in the mean grazing angle. Much of this variation is due to the angular variation in the scene reflectivity; however, when collection geometries differ in other respects, the reduction in performance cannot be entirely explained by angular variations alone. This paper identifies a source of performance degradation when the collection geometries are different for scenes containing local relief. The error is due to approximations during image formation that both the collection geometry and the terrain are flat. The effect of these errors is derived as a blurring kernel to the true scene. The impact of the blurring is then assessed in the interferometric case and broken into common and differential blurring terms to facilitate the impact of some special cases and to explain why the parallel-pass geometry works as well as it does even though the true three-dimensional nature of the collection and the ground are ignored.     

Pervasive information — the key to ‘true’ mobility

Since Weiser’s vision in 1991 for ubiquitous (also called pervasive) computing there has been little tangible progress towards it. However, over time the communications industry has begun to erode many of the hardware barriers to this vision. Even so, the utopia of pervasive computing remains out of reach, primarily as a result of the continued fixation with devices and connectivity as a way to realise mobility. However, it could be argued that users ultimately require access to information or content irrespective of the devices and connectivity around them. Consequently, pervasive information is seen as the key to true user mobility. This paper will introduce a potential secure pervasive information architecture that fits Weiser’s vision, and position it with respect to a sub-set of current contenders for future systems from both academia and the telecommunications industry, and highlight their strengths and weaknesses.     

Biospecific Self‐Assembly of a Nanoparticle Coating for Targeted and Stimuli‐Responsive Drug Delivery

Biology provides a range of materials, mechanisms, and insights to meet the diverse requirements of nanomedicine. Here, a biologically based nanoparticle coating system that offers three characteristic features is reported. First, the coating can be self‐assembled through a noncovalent biospecific interaction mechanism between a lectin protein (Concanavalin A) and the polysaccharide glycogen. This biospecific self‐assembly enables the coating to be applied simply without the generation of covalent bonds. Second, glycoprotein‐based biofunctionality can be incorporated into the coating through the same noncovalent biospecific interaction mechanism. Here, the glycoprotein transferrin is incorporated into the coating since this moiety is commonly used to target cancer cells through a receptor‐mediated endocytosis mechanism. Third, the coating can be triggered to disassemble in response to a reduction in pH that is characteristic of endosomal uptake. In a proof‐of‐concept study, comparing coated and uncoated nanoparticles, model drug‐loaded nanoparticles (doxorubicin‐loaded mesoporous silica nanoparticles) are prepared and it is observed that the coated nanoparticle has enhanced cytotoxicity for cancer cell lines but attenuated cytotoxicity for noncancerous cell lines. These studies demonstrate that biology provides unique materials and mechanism appropriate to meet the needs for emerging applications in the medical and life sciences.     

Uranium sorption on various forms of titanium dioxide--influence of surface area, surface charge, and impurities

Titanium dioxide (TiO(2)) has often served as a model substrate for experimental sorption studies of environmental contaminants. However, various forms of Ti-oxide have been used, and the different sorption properties of these materials have not been thoroughly studied. We investigated uranium sorption on some thoroughly characterized TiO(2) surfaces with particular attention to the influence of surface area, surface charge, and impurities. The sorption of U(VI) differed significantly between samples. Aggressive pretreatment of one material to remove impurities significantly altered the isoelectric point, determined by an electroacoustic method, but did not significantly impact U sorption. Differences in sorption properties between the various TiO(2) materials were related to the crystallographic form, morphology, surface area, and grain size, rather than to surface impurities or surface charge. In-situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopic studies showed that the spectra of the surface species of the TiO(2) samples are not significantly different, suggesting the formation of similar surface complexes. The data provide insights into the effect of different source materials and surface properties on radionuclide sorption.