Instar and outstar learning with memristive nanodevices

The instar and outstar synaptic models are among the oldest and most useful in the field of neural networks. In this paper we show how to approximate the behavior of instar and outstar synapses in neuromorphic electronic systems using memristive nanodevices and spiking neurons. Memristive nanodevices are especially attractive for this application since such devices are tiny, can be densely packed in crossbar-like structures and possess the long time constants, or memory, needed by the synaptic models.     

Application of synthetic fluid inclusions to simultaneous temperature–pressure logging in high-temperature (sub- to supercritical) geothermal systems

Batch-autoclave experiments have been conducted to evaluate the potential use of synthetic fluid inclusions as a simultaneous temperature–pressure (and fluid sampling) logging tool in deep-seated, high-temperature (>350 °C) geothermal systems. The application of synthetic fluid inclusions allows us to obtain information about thermal-pressure conditions in deep-seated geothermal systems, where conventional tools cannot be used because of the extreme temperature conditions. Fluid inclusions, up to 50 μm long, have been readily synthesized during 5-day autoclave experiments (conducted at 375–475 °C and 39–62 MPa) in pre-fractured, inclusion- and impurity-free artificial quartz. Inferred fluid inclusion (temperature–pressure) trapping conditions are calculated by deducing the intersection of isochores derived from microthermometric data for three sets of simultaneously trapped synthetic fluid inclusions in healed microfractures. Synthetic fluid inclusion logging offers a precise borehole temperature measurement technique without need of any pressure correction. Pressure estimates are less precise, although the method may be improved by using a combination of H₂O–NaCl and H₂O–KCl solutions/salinities, and fluid/quartz/amorphous silica systems that facilitate crack healing but trap fluids that do not homogenize at near-critical conditions.     

Epitope mapping of a 95 kDa antigen in complex with antibody by solution-phase amide backbone hydrogen/deuterium exchange monitored by Fourier transform ion cyclotron resonance mass spectrometry

The epitopes of a homohexameric food allergen protein, cashew Ana o 2, identified by two monoclonal antibodies, 2B5 and 1F5, were mapped by solution-phase amide backbone H/D exchange (HDX) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) and the results were compared to previous mapping by immunological and mutational analyses. Antibody 2B5 defines a conformational epitope, and 1F5 defines a linear epitope. Intact murine IgG antibodies were incubated with recombinant Ana o 2 (rAna o 2) to form antigen-monoclonal antibody (Ag-mAb) complexes. mAb-complexed and uncomplexed (free) rAna o 2 were then subjected to HDX. HDX instrumentation and automation were optimized to achieve high sequence coverage by protease XIII digestion. The regions protected from H/D exchange upon antibody binding overlap and thus confirm the previously identified epitope-bearing segments: the first extension of HDX monitored by mass spectrometry to a full-length antigen-antibody complex in solution.     

Valence parity to distinguish c' and z• ions from electron capture dissociation/electron transfer dissociation of peptides: effects of isomers, isobars, and proteolysis specificity

Valence parity provides a way to distinguish between N-terminal and C-terminal electron capture dissociation/electron transfer dissociation (ECD/ETD) product ions based on their number of hydrogen plus nitrogen atoms determined by accurate mass measurement and forms a basis for de novo peptide sequencing. The effect of mass accuracy (0.1-1 ppm error) on c'/z(?) overlap and unique elemental composition overlap is evaluated for a database of c'/z(?) product ions each based on all possible amino acid combinations and four subset databases containing the same c' ions but with z(?) ions determined by in silico digestion with trypsin, Glu-C, Lys-C, or chymotrypsin. High mass accuracy reduces both c'/z(?) overlap and unique elemental composition overlap. Of the four proteases, trypsin offers slightly better discrimination between N- and C-terminal ECD/ETD peptides. Interestingly, unique elemental composition overlap curves for c'/c' and z(?)/z(?) peptide ions exhibit discontinuities at certain nominal masses for 0.1-1.0 ppm mass error. Also, as noted in the companion article (Polfer et al. Anal. Chem.2011, DOI: 10.1021/ac201624t), the number of ECD/ETD product ion amino acid compositions as a function of nominal mass increases exponentially with mass but with a superimposed modulation due to higher prevalence of certain elemental compositions.     

Technique based on LED multispectral imaging and multivariate analysis for monitoring the conservation state of the Dead Sea Scrolls

The aim of this project is the development of a noninvasive technique based on LED multispectral imaging (MSI) for monitoring the conservation state of the Dead Sea Scrolls (DSS) collection. It is well-known that changes in the parchment reflectance drive the transition of the scrolls from legible to illegible. Capitalizing on this fact, we will use spectral imaging to detect changes in the reflectance before they become visible to the human eye. The technique uses multivariate analysis and statistical process control theory. The present study was carried out on a "sample" parchment of calfskin. The monitoring of the surface of a commercial modern parchment aged consecutively for 2 h and 6 h at 80 °C and 50% relative humidity (ASTM) was performed at the Imaging Lab of the Library of Congress (Washington, DC, U.S.A.). MSI is here carried out in the vis-NIR range limited to 1 μm, with a number of bands of 13 and bandwidths that range from about 10 nm in UV to 40 nm in IR. Results showed that we could detect and locate changing pixels, on the basis of reflectance changes, after only a few "hours" of aging.     

Natural versus wastewater derived dissolved organic carbon: implications for the environmental fate of organic micropollutants

The interaction of organic micropollutants with dissolved organic carbon (DOC) can influence their transport, degradation and bioavailability. While this has been well established for natural organic carbon, very little is known regarding the influence of DOC on the fate of micropollutants during wastewater treatment and water recycling. Dissolved organic carbon-water partition coefficients (K_DOC) for wastewater derived and reference DOC were measured for a range of micropollutants using a depletion method with polydimethylsiloxane disks. For micropollutants with an octanol-water partition coefficient (log K_OW) greater than 4 there was a significant difference in K_DOC between reference and wastewater derived DOC, with partitioning to wastewater derived DOC over 1000 times lower for the most hydrophobic micropollutants. The interaction of nonylphenol with wastewater derived DOC from different stages of a wastewater and advanced water treatment train was studied, but little difference in K_DOC was observed. Organic carbon characterisation revealed that reference and wastewater derived DOC had very different properties due to their different origins. Consequently, the reduced sorption capacity of wastewater derived DOC may be related to their microbial origin which led to reduced aromaticity and lower molecular weight. This study suggests that for hydrophobic micropollutants (log K_OW > 4) a higher concentration of freely dissolved and thus bioavailable micropollutants is expected in the presence of wastewater derived DOC than predicted using K_DOC values quantified using reference DOC. The implication is that naturally derived DOC may not be an appropriate surrogate for wastewater derived DOC as a matrix for assessing the fate of micropollutants in engineered systems.     

Demonstration of the conditions conducive to agglomeration of zinc calcine in fluidized bed roasters

Agglomeration in the fluidized bed roasting of zinc sulphide concentrate was investigated in a continuous pilot-scale fluidized bed roaster. Alone or together, low stoichiometric excess oxygen (<10%) and high temperature (>940 °C) contributed most significantly to agglomeration of zinc calcine particles. Only one test – with 0% excess oxygen at 940 °C – led to severe agglomeration and subsequent defluidisation. Neither large initial particle size nor low gas superficial velocity promoted agglomeration as much as the combination of low stoichiometric excess oxygen and high temperature.Lead sulphide, a common impurity in zinc sulphide concentrate, also appeared to have played a key role in agglomeration. Both low excess oxygen and high temperature favoured a high partial pressure of sublimated lead sulphide. Upon contact with oxygen, lead sulphide oxidised to lead oxide, which then precipitated as a liquid onto the rather inert bed particles. As a liquid, lead oxide formed coatings that caused small particles to adhere to larger ones, as well as liquid bridges that bound particles together.     

Deconstructing the Effects of Matrix Elasticity and Geometry in Mesenchymal Stem Cell Lineage Commitment

A wide variety of environmental factors including physical and biochemical signals are responsible for stem cell behavior and function. In particular, matrix elasticity and cell shape have been shown to determine stem cell function, yet little is known about the interplay between how these physical cues control cell differentiation. For the first time, by using ultraviolet (UV) lithography to pattern poly(ethylene) glycol (PEG) hydrogels, it is possible to manufacture microenvironments capable of parsing the effects of matrix elasticity, cell shape, and cell size in order to explore the relationship between matrix elasticity and cell shape in mesenchymal stem cell (MSC) lineage commitment. These data show that cells cultured on 1000 μm² circles, squares, and rectangles are primarily adipogenic lineage regardless of matrix elasticity, while cells cultured on 2500 and 5000 μm² shapes more heavily depend on shape and elasticity for lineage specification. It is further characterized how modifying the cell cytoskeleton through pharmacological inhibitors can modify cell behavior. By showing MSC lineage commitment relationships due to physical signals, this study highlights the importance of cell shape and matrix elasticity in further understanding stem cell behavior for future tissue engineering strategies.     

Parallel implementation of synthetic aperture radar algorithms

Two sequences of operations necessary for implementation of high resolution image formation in strip and spotlight modes of the synthetic aperture radar (SAR) are presented. The sequences are mapped onto a mesh-connected SIMD architecture. The mapping includes not only parallel implementation of all the basic computation steps, but also all the necessary data transformation and communication operations. Detailed estimates of the processing times are provided for Hughes Research Laboratories Systolic/Cellular architecture.This work was partially supported by NSF grant No MIP-8714689     

Copper Oxide Precipitates in NBS Standard Reference Material 482

Copper oxide has been detected in the copper containing alloys of NBS Standard Reference Material (SRM) 482. This occurrence is significant because it represents heterogeneity within a standard reference material that was certified to be homogeneous on a micrometer scale. Oxide occurs as elliptically to spherically shaped precipitates whose size differs with alloy composition. The largest precipitates occur in the Au20-Cu80 alloy and range in size from submicrometer up to 2 μm in diameter. Precipitates are observed using light microscopy, electron microscopy, and secondary ion mass spectrometry (SIMS). SIMS has demonstrated that the precipitates are present within all the SRM 482 wires that contain copper. Only the pure gold wire is precipitate free. Initial results from the analysis of the Au20-Cu80 alloy indicate that the percentage of precipitates is less than 1 % by area. Electron probe microanalysis (EPMA) of large (2 μm) precipitates in this same alloy indicates that precipitates are detectable by EPMA and that their composition differs significantly from the certified alloy composition. The small size and low percentage of these oxide precipitates minimizes the impact that they have upon the intended use of this standard for electron probe microanalysis. Heterogeneity caused by these oxide precipitates may however preclude the use of this standard for automated EPMA analyses and other microanalysis techniques.