Scanning-helium-ion-beam lithography with hydrogen silsesquioxane resist

A scanning-helium-ion-beam microscope is now commercially available. This microscope can be used to perform lithography similar to, but of potentially higher resolution than, scanning electron-beam lithography. This article describes the control of this microscope for lithography via beam steering/blanking electronics and evaluates the high-resolution performance of scanning helium-ion-beam lithography. The authors found that sub-10 nm-half-pitch patterning is feasible. They also measured a point-spread function that indicates a reduction in the micrometer-range proximity effect typical in electron-beam lithography.National Science Foundation (U.S.). Graduate Research Fellowship Progra

Arginine–glycine–aspartic acid functional branched semi-interpenetrating hydrogels

For the first time a series of functional hydrogels based on semi-interpenetrating networks with both branched and crosslinked polymer components have been prepared and we show the successful use of these materials as substrates for cell culture. The materials consist of highly branched poly(N-isopropyl acrylamide)s with peptide functionalised end groups in a continuous phase of crosslinked poly(vinyl pyrrolidone). Functionalisation of the end groups of the branched polymer component with the GRGDS peptide produces a hydrogel that supports cell adhesion and proliferation. The materials provide a new synthetic functional biomaterial that has many of the features of extracellular matrix, and as such can be used to support tissue regeneration and cell culture. This class of high water content hydrogel material has important advantages over other functional hydrogels in its synthesis and does not require postprocessing modifications nor are functional-monomers, which change the polymerisation process, required. Thus, the systems are amenable to large scale and bespoke manufacturing using conventional moulding or additive manufacturing techniques. Processing using additive manufacturing is exemplified by producing tubes using microstereolithography

Optimization of observation plan based on the stochastic characteristics of the geodetic network

Optimal design of geodetic network is a basic subject of many engineering projects. An observation plan is a concluding part of the process. Any particular observation within the network has through adjustment a different contribution and impact on values and accuracy characteristics of unknowns. The problem of optimal design can be solved by means of computer simulation. This paper presents a new method of simulation based on sequential estimation of individual observations in a step-by-step manner, by means of the so-called filtering equations. The algorithm aims at satisfying different criteria of accuracy according to various interpretations of the covariance matrix. Apart of them, the optimization criterion is also amount of effort, defined as the minimum number of observations required. A numerical example of a 2-D network is illustrated to view the effectiveness of presented method. The results show decrease of the number of observations by 66% with respect to the not optimized observation plan, which still satisfy the assumed accuracy

Behaviour and Modelling of Semi-rigid Structural Frame Systems

A computational finite element model is developed to predict the load-deflection characteristic of portal frames with semi-rigid welded and bolted joints. Plate components of frame members and joints are modelled by thin shell finite elements while bolt connectors by springs with the force-deformation characteristic evaluated from test results. The computer software ABAQUS is used. Experimental investigations were designed in order to evaluate frame load-deflection characteristics, joint local rotations, failure modes, and the contribution of end-plates and bolt connectors to the joint rotations. Theoretical results of frame load-deflection characteristics predicted with use of ABAQUS program are compared with the experimental results. The modelling of friction effect between the contact surfaces of bolted joints is verified to be the most important factor. The comparative analysis leads to the conclusion that the proposed advanced shell model can be very useful in the verification of simplified models being developed for practical applications. (Botswana Journal of Technology: 2003 12(2): 51-61

Production and Applications of Cellulose Nanomaterials

This publication features more than 100 short technical summaries on preparation, characterization and applications of cellulose nanomaterialso Represents completed and ongoing work from 45 institutions in 10 countrieso Preparation and characterization of cellulose nanocrystals and cellulose nanofibrilso Applications covered include: coating, films, medical, composites, liquid gels, aereogels and morehttps://digitalcommons.library.umaine.edu/fac_monographs/1326/thumbnail.jp

Automated Transmission-Mode Scanning Electron Microscopy (tSEM) for Large Volume Analysis at Nanoscale Resolution

Transmission-mode scanning electron microscopy (tSEM) on a field emission SEM platform was developed for efficient and cost-effective imaging of circuit-scale volumes from brain at nanoscale resolution. Image area was maximized while optimizing the resolution and dynamic range necessary for discriminating key subcellular structures, such as small axonal, dendritic and glial processes, synapses, smooth endoplasmic reticulum, vesicles, microtubules, polyribosomes, and endosomes which are critical for neuronal function. Individual image fields from the tSEM system were up to 4,295 µm2 (65.54 µm per side) at 2 nm pixel size, contrasting with image fields from a modern transmission electron microscope (TEM) system, which were only 66.59 µm2 (8.160 µm per side) at the same pixel size. The tSEM produced outstanding images and had reduced distortion and drift relative to TEM. Automated stage and scan control in tSEM easily provided unattended serial section imaging and montaging. Lens and scan properties on both TEM and SEM platforms revealed no significant nonlinear distortions within a central field of ~100 µm2 and produced near-perfect image registration across serial sections using the computational elastic alignment tool in Fiji/TrakEM2 software, and reliable geometric measurements from RECONSTRUCT™ or Fiji/TrakEM2 software. Axial resolution limits the analysis of small structures contained within a section (~45 nm). Since this new tSEM is non-destructive, objects within a section can be explored at finer axial resolution in TEM tomography with current methods. Future development of tSEM tomography promises thinner axial resolution producing nearly isotropic voxels and should provide within-section analyses of structures without changing platforms. Brain was the test system given our interest in synaptic connectivity and plasticity; however, the new tSEM system is readily applicable to other biological systems.This study was funded by United States National Institutes of Health (http://www.nih.gov; grant numbers NS021184, NS074644, and MH095980 to KMH) and Texas Emerging Technologies Fund (http://governor.state.tx.us/ecodev/etf/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Biological Sciences, School o