A heuristic technique for CTIS image reconstruction

An iterative method is presented for computed tomography imaging spectrometer (CTIS) image reconstruction in the presence of both photon noise in the image and postdetection Gaussian system noise. The new algorithm, which assumes the transfer matrix of the system has a particular structure, is evaluated experimentally with the result that it is significantly better, for larger problems, than both the multiplicative algebraic reconstruction technique (MART) and the mixed-expectation image-reconstruction technique (MERT) with respect to accuracy and computation time.     

Reductions in the social anxiety of women associated with group membership: Distraction, anonymity, security, or diffusion of evaluation?

This study examined whether social anxiety is diminished among women in the company of a group and, if so, whether it is associated with perceptions of anonymity, being distracted, feelings of security, or an expectation that any evaluation will be diffused across the members of the group. Two social scenarios were presented to 61 female undergraduate students: a physique-salient and a general social situation. For the former situation, self-presentational anxiety was less pronounced in a group of female friends and a mixed group of male and female friends than when alone or in a group of male friends. For the general social situation, in comparison with being alone, being in a group of female friends, being in a group of male friends, and being in a mixed group of male and female friends were associated with less social anxiety. Diffusion of evaluation and perceptions of security were most strongly associated with the reduction in social anxiety. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Closure to discussion of “Performance evaluation ofsteel-conduit-enclosed power systems”

The authors of “Performance evaluation of steel-conduit-enclosed power systems” (see ibid., vol. 35, no. 3, p. 515-23, 1999) respond to the comments on the original paper. They argue that the intention of their paper is that the users should use the proper value of overcurrent device rating as it will be dictated by the application     

Bioreactor and probe system for magnetic resonance microimaging and spectroscopy of chondrocytes and neocartilage

We have developed a nuclear magnetic resonance (NMR)-compatible hollow fiber chondrocyte bioreactor (HFBR), permitting the noninvasive study of neocartilage under conditions optimized for cell growth and matrix expression. The system was used to investigate the properties of neocartilage which developed from embryonic chick chondrocytes. Histologic studies performed 30 days after inoculation of the HFBR with chondrocytes showed cartilage growth units demarcated by stromal layers surrounding each fiber; the tissue itself was highly cellular with abundant proteoglycan content. Spin-density, spin-lattice, and spin-spin relaxation and magnetization transfer contrast images revealed heterogeneous tissue with NMR properties that correlated well with histologic data. It was found that the apparent free water content of the neocartilage was greater than that seen in mature cartilage, even in regions of relatively low cell density. The bioenergetic profile of the cells in culture was monitored with ³¹P-NMR spectroscopy, and the presence of phosphocreatine was clearly demonstrated. Overall metabolic stability was confirmed between days 10 and 17 after inoculation. A significant decrease in intracellular pH with time was observed during early development of the chondrocyte system. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 285–292, 1997     

Engineering the atomic interface of porous ceria nanorod with single palladium atoms for hydrodehalogenation reaction

Tuning the electronic properties of single atom catalysts(SACs)between the central metal and the neighboring surface atoms has emerged as an efficient strategy to boost catalytic efficiency and metal utilization.Here we describe a simple and efficient approach to create atomically dispersed palladium atoms supported over defect-containing porous ceria nanorod containing palladium up to 0.26 wt.%.The existence of singly dispersed palladium atoms is confirmed by spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurements.This catalyst shows excellent efficiency in hydrodehalogenation reactions at low H2 pressure under mild conditions,along with satisfactory recyclability and scalability.Density functional theory(DFT)calculations reveal that the high activity stems from the spatial isolation of palladium atoms and the modified electronic structure of palladium confined in defect-containing ceria nanorod.This work may lay the foundation for the facile creation of single atom catalysts within the synthetic community and shed light on the possibility for scale-up production.     

Optically trapping confocal Raman microscopy of individual lipid vesicles: kinetics of phospholipase A(2)-catalyzed hydrolysis of phospholipids in the membrane bilayer

Phospholipase A2 (PLA2)-catalyzed hydrolysis at the sn-2 position of 1,2-dimyristoyl-sn-glycero-3-phosphocholine in optically trapped liposomes is monitored in situ using confocal Raman microscopy. Individual optically trapped liposomes (0.6 microm in diameter) are exposed to PLA2 isolated from cobra (Naja naja naja) venom at varying enzyme concentrations. The relative Raman scattering intensities of C-C stretching vibrations from the trans and gauche conformers of the acyl chains are correlated directly with the extent of hydrolysis, allowing the progress of the reaction to be monitored in situ on a single vesicle. In dilute vesicle dispersions, the technique allows the much higher local concentration of lipid molecules in a single vesicle to be detected free of interferences from the surrounding solution. Observing the local composition of an optically trapped vesicle also allows one to determine whether the products of enzyme-catalyzed hydrolysis remain associated with the vesicle or dissolve into solution. The observed reaction kinetics exhibited a time lag prior to the rapid hydrolysis. The lag time varied inversely with the enzyme concentration, which is consistent with the products of enzyme-catalyzed lipid hydrolysis reaching a critical concentration that allows the enzyme to react at a much faster rate. The turnover rate of membrane-bound enzyme determined by Raman microscopy during the rapid, burst-phase kinetics was 1200 s(-1). Based on previous measurements of the equilibrium for PLA2 binding to lipid membranes, the average number of enzyme molecules responsible for catalyzing the hydrolysis of lipid on a single optically trapped vesicle is quite small, only two PLA2 molecules at the lowest enzyme concentration studied.     

Hybrid imaging using linear retroreflectors

It has been observed that retroreflective materials can be used in combination with beam splitters to produce real images. This is practical on a large size scale but has a maximum optical efficiency of 25%. Conversely, curved reflectors efficiently produce real images, but their cost increases very rapidly with size. We introduce a new imaging method, which combines the advantages of both systems, through the use of a linear retroreflective film. This material is retroreflective in one plane and conventionally reflective in the perpendicular plane. The net result is an efficient real image system that can have unlimited extent in one transverse direction, and which can be inexpensively manufactured on a large scale.     

Developing detailed records of relative sea-level change using a foraminiferal transfer function: an example from North Norfolk, UK

This paper provides a brief overview of the transfer function approach to sea-level reconstruction. Using the example of two overlapping sediment cores from the North Norfolk coast, UK, the advantages and limitations of the transfer function methodology are examined. While the selected cores are taken from different sites, and display contrasting patterns of sedimentation, the foraminiferal transfer function distils comparable records of relative sea-level change from both sequences. These reconstructions are consistent with existing sea-level index points from the region but produce a more detailed record of relative sea-level change. Transfer functions can extract sea-level information from a wider range of sedimentary sub-environments. This increases the amount of data that can be collected from coastal deposits and improves record resolution. The replicability of the transfer function methodology, coupled with the sequential nature of the data it produces, assists in the compilation and analysis of sea-level records from different sites. This technique has the potential to bridge the gap between short-term (instrumental) and long-term (geological or geophysical) records of sea-level change.     

Skeletal tissues as nanomaterials

Collagen is the most abundant protein in the body and, though the fibre-forming collagens have a ‘common’ structure, it is adapted to perform a large range of functions—from the differing mechanical needs of tendon versus bone to forming a transparent support structure in the cornea. This perfidy also suggests that collagen could form a generic basis for a range of scaffold needs for tissue engineering or medical device coating applications. We at the London Centre for Nanotechnology—a joint venture between University College London and Imperial College—are taking a bottom-up approach having decided that many of the ‘accepted dogmas’ of collagen biology may not be quite as soundly based as currently held. We are using several of the tools of ‘hard’ nanotechnology—such as atomic force microscopy—to re-examine collagen structure with the longer term aim of using such information to design materials with appropriate physical attributes. Examples of our current research on mineralised and soft tissue collagens are presented.     

Examining natural rock varnish and weathering rinds with laser-induced breakdown spectroscopy for application to ChemCam on Mars

A laser-induced breakdown spectroscopy (LIBS) instrument is traveling to Mars as part of ChemCam on the Mars Science Laboratory rover. Martian rocks have weathered exteriors that obscure their bulk compositions. We examine weathered rocks with LIBS in a martian atmosphere to improve interpretations of ChemCam rock analyses on Mars. Profile data are analyzed using principal component analysis, and coatings and rinds are examined using scanning electron microscopy and electron probe microanalysis. Our results show that LIBS is sensitive to minor compositional changes with depth and correctly identifies rock type even if the series of laser pulses does not penetrate to unweathered material.