Model-based 3-D segmentation of multiple sclerosis lesions in magnetic resonance brain images

Human investigators instinctively segment medical images into their anatomical components, drawing upon prior knowledge of anatomy to overcome image artifacts, noise, and lack of tissue contrast. The authors describe: 1) the development and use of a brain tissue probability model for the segmentation of multiple sclerosis (MS) lesions in magnetic resonance (MR) brain images, and 2) an empirical comparison of the performance of statistical and decision tree classifiers, applied to MS lesion segmentation. Based on MR image data obtained from healthy volunteers, the model provides prior probabilities of brain tissue distribution per unit voxel in a standardized 3-D "brain space". In comparison to purely data-driven segmentation, the use of the model to guide the segmentation of MS lesions reduced the volume of false positive lesions by 50-80%     

Design and implementation of optical wireless communications with optically powered smart dust motes

Complete electronic and micro-mechanical systems can now be fabricated on the scale of hundreds of microns. Implementing radio frequency wireless communications with such 'smart dust' is challenging, due to the power required and the small size of any antennas that can be implemented. Optical wireless communications, using a modulated retro-reflector at the smart dust has the advantages of low-power consumption and highly directive channels that allow long communications ranges. In this paper we report the design and implementation of a communications system that uses a base station to communicate with, and power, smart dust motes, over ranges of 10s of metres. A base station that uses holographic beamsteering is described, and dust motes that use silicon ICs to provide communications, power and modulation control. Results indicate the dust mote will operate at a range of over 30m from the base station.     

Enhancing Ion Migration in Grain Boundaries of Hybrid Organic–Inorganic Perovskites by Chlorine

Ionicity plays an important role in determining material properties, as well as optoelectronic performance of organometallic trihalide perovskites (OTPs). Ion migration in OTP films has recently been under intensive investigation by various scanning probe microscopy (SPM) techniques. However, controversial findings regarding the role of grain boundaries (GBs) associated with ion migration are often encountered, likely as a result of feedback errors and topographic effects common in to SPM. In this work, electron microscopy and spectroscopy (scanning transmission electron microscopy/electron energy loss spectroscopy) are combined with a novel, open‐loop, band‐excitation, (contact) Kelvin probe force microscopy (BE‐KPFM and BE‐cKPFM), in conjunction with ab initio molecular dynamics simulations to examine the ion behavior in the GBs of CH₃NH₃PbI₃ perovskite films. This combination of diverse techniques provides a deeper understanding of the differences between ion migration within GBs and interior grains in OTP films. This work demonstrates that ion migration can be significantly enhanced by introducing additional mobile Cl^? ions into GBs. The enhancement of ion migration may serve as the first step toward the development of high‐performance electrically and optically tunable memristors and synaptic devices.     

The capacity of binary channels that use linear codes and decoders

This paper analyzes the performance of concatenated coding systems operating over the binary-symmetric channel (BSC) by examining the loss of capacity resulting from each of the processing steps. The techniques described in this paper allow the separate evaluation of codes and decoders and thus the identification of where loss of capacity occurs. They are, moreover, very useful for the overall design of a communications system, e.g., for evaluating the benefits of inner decoders that produce side information. The first two sections of this paper provide a general technique (based on the coset weight distribution of a binary linear code) for calculating the composite capacity of the code and a BSC in isolation. The later sections examine the composite capacities of binary linear codes, the BSC, and various decoders. The composite capacities of the (8,4) extended Hamming, (24, 12) extended Golay, and (48, 24) quadratic residue codes appear as examples throughout the paper. The calculations in these examples show that, in a concatenated coding system, having an inner decoder provide more information than the maximum-likelihood (ML) estimate to an outer decoder is not a computationally efficient technique, unless generalized minimum-distance decoding of an outer code is extremely easy. Specifically, for the (8,4) extended Hamming and (24, 12) extended Golay inner codes, the gains from using any inner decoder providing side information, instead of a strictly ML inner decoder, are shown to be no greater than 0.77 and 0.34 dB, respectively, for a BSC crossover probability of 0.1 or less, However, if computationally efficient generalized minimum distance decoders for powerful outer codes, e.g., Reed-Solomon codes, become available, they will allow the use of simple inner codes, since both simple and complex inner codes have very similar capacity losses     

Spectral mixture analysis of simulated thermal infraredspectrometry data: An initial temperature estimate bounded TESSMA searchapproach

At sensor thermal infrared (TIR) radiation varies depending on the temperature and emissivity of surface materials and the modifying impact of atmospheric absorption and emission. TIR imaging spectrometry often involves extracting temperature, emissivity, and/or surface composition, which are useful in diverse studies ranging from climatology to land use analyses. A two-stage application of temperature emissivity separation (TES) using spectral mixture analysis (SMA) or TESSMA, was employed to characterize isothermal mixtures on a subpixel basis. This two-stage approach first uses the relationship between a virtual cold endmember fraction and surface temperature to extract initial image temperature estimates. Second, an isothermal SMA application searches the region within the maximum temperature error range of the initial estimate, selecting the best subpixel spectral mixture fit. Work presented includes characterizations of synthetically generated temperature and constituent mixture gradient test images, and a discussion of errors associated with selecting temperature search ranges 25% and 75% smaller than the initial temperature calculation error range. Results using this two-stage approach indicate improved overall temperature estimates, constituent estimates, and constituent fraction estimates using simulated TIR data     

Multifunctional hydrogels that promote osteogenic hMSC differentiation through stimulation and sequestering of BMP2

The extracellular environment controls many cellular activities thereby linking external material cues to internal cell function. By better understanding these processes, synthetic extracellular material niches can be tailored to present cells with highly regulated physical and/or chemical cues that promote or suppress selected cell functions. Here, poly(ethylene glycol) (PEG) hydrogels were functionalized with fluvastatin-releasing grafts and growth factor binding heparin domains to enable the dynamic exchange of information between the material and cells from the outside-in and inside-out (i.e., bidirectional signaling). By incorporating a fluvastatin-releasing graft and carefully controlling the dose and temporal release, materials were designed to promote bone morphogenic protein (BMP2) and alkaline phosphatase (ALP) production by human mesenchymal stem cells (hMSCs). When the release of fluvastatin was controlled to occur over 2 weeks, BMP2 and ALP production was increased 2.2-fold and 1.7-fold, respectively, at day 28 compared to hMSCs cultured in the absence of fluvastatin. By introducing a heparin functionality into the gel to sequester and localize the hMSC-produced BMP2, the osteogenic differentiation of hMSCs was further augmented over fluvastatin delivery alone. Osteopontin and core binding factor α1 gene expression was 6-fold and 4-fold greater for hMSCs exposed to fluvastatin in the presence of the heparin functionalities, respectively. These results demonstrate how multifunctional gels that interact with cells in a bidirectional manner can efficiently promote selected cell functions, such as the osteogenic differentiation of hMSCs.     

An EPR study of defects induced in 6H-SiC by ion implantation

Crystalline (0001) plane wafers of n-type 6H-SiC have been implanted at room temperature with 200 keV Ge⁺ ions in the dose range 10¹² to 10¹⁵ cm⁻². Electron paramagnetic resonance (EPR) measurements have been made on these samples both before and after annealing them at temperatures in the range room temperature to 1500°C. The as-implanted samples have a single isotropic and asymmetric line EPR spectrum whose width, ΔB_pp, increases with ion dose before falling when a buried continuous amorphous layer is produced. This increase is interpreted in terms of the change in the relative intensity of a line with g = 2.0028 ± 0.0002, ΔB_pp = 0.4 mT associated primarily with carbon dangling bonds in a-SiC and a line with g in the range 2.0033 to 2.0039 of uncertain origin. The variation with anneal temperature of the populations of these defects is reported.     

Electrochemically Tuned Properties for Electrolyte‐Free Carbon Nanotube Sheets

Injecting high electronic charge densities can profoundly change the optical, electrical, and magnetic properties of materials. Such charge injection in bulk materials has traditionally involved either dopant intercalation or the maintained use of a contacting electrolyte. Tunable electrochemical charge injection and charge retention, in which neither volumetric intercalation of ions nor maintained electrolyte contact is needed, are demonstrated for carbon nanotube sheets in the absence of an applied field. The tunability of electrical conductivity and electron field emission in the subsequent material is presented. Application of this material to supercapacitors may extend their charge‐storage times because they can retain charge after the removal of the electrolyte.     

Histochemical localization and possible antibacterial role of xanthine oxidase in the bovine mammary gland

Xanthine oxidase (XO) was demonstrated to be present in the teat canal and secretory tissue of the bovine mammary gland by histochemical techniques. Homogenates of these tissues were able to replace XO in an antibacterial assay with Streptococcus uberis. The action of XO on its substrate hypoxanthine was shown to provide an essential component for anti-streptococcal activity mediated by lactoperoxidase. A mechanism is proposed whereby the interaction of XO, lactoperoxidase and thiocyanate may provide antibacterial activity in the teat canal.     

Wood adhesives based on tannin extracts from barks of some pine and spruce species

Barks available in commercial quantities in Australia and overseas have been examined for their efficacy as raw materials for conversion to high quality adhesives for reconstituted wood products. Previously bark from maturePinus radiata was found to be suitable. This paper examines the suitability of barks from four mature pine species (Pinus caribaea, Pinus elliottii, Pinus pinaster andPinus sylvestris), one young pine species (Pinus radiata) and one spruce species (Picea abies). Only the bark extracts ofPinus caribaea andPinus pinaster gave high quality (Type A bond, WBP) wood adhesives. The gluing properties of the adhesives derived from the extracts appeared to be dependent on their contents of formaldehyde-reactive polyflavanoids as indicated by their Stiasny values, with a value of 65% being the minimum for producing a high quality adhesive by the methods used.