Spatio-Temporal Dynamics of Human Intention Understanding in Temporo-Parietal Cortex: A Combined EEG/fMRI Repetition Suppression Paradigm

Inferring the intentions of other people from their actions recruits an inferior fronto-parietal action observation network as well as a putative social network that includes the posterior superior temporal sulcus (STS). However, the functional dynamics within and among these networks remains unclear. Here we used functional magnetic resonance imaging (fMRI) and high-density electroencephalogram (EEG), with a repetition suppression design, to assess the spatio-temporal dynamics of decoding intentions. Suppression of fMRI activity to the repetition of the same intention was observed in inferior frontal lobe, anterior intraparietal sulcus (aIPS), and right STS. EEG global field power was reduced with repeated intentions at an early (starting at 60 ms) and a later (∼330 ms) period after the onset of a hand-on-object encounter. Source localization during these two intervals involved right STS and aIPS regions highly consistent with RS effects observed with fMRI. These results reveal the dynamic involvement of temporal and parietal networks at multiple stages during the intention decoding and without a strict segregation of intention decoding between these networks

Movement distributions of stroke survivors exhibit distinct patterns that evolve with training

BACKGROUND: While clinical assessments provide tools for characterizing abilities in motor-impaired individuals, concerns remain over their repeatability and reliability. Typical robot-assisted training studies focus on repetition of prescribed actions, yet such movement data provides an incomplete account of abnormal patterns of coordination. Recent studies have shown positive effects from self-directed movement, yet such a training paradigm leads to challenges in how to quantify and interpret performance. METHODS: With data from chronic stroke survivors (n = 10, practicing for 3 days), we tabulated histograms of the displacement, velocity, and acceleration for planar motion, and examined whether modeling of distributions could reveal changes in available movement patterns. We contrasted these results with scalar measures of the range of motion. We performed linear discriminant analysis (LDA) classification with selected histogram features to compare predictions versus actual subject identifiers. As a basis of comparison, we also present an age-matched control group of healthy individuals (n = 10, practicing for 1 day). RESULTS: Analysis of range of motion did not show improvement from self-directed movement training for the stroke survivors in this study. However, examination of distributions indicated that increased multivariate normal components were needed to accurately model the patterns of movement after training. Stroke survivors generally exhibited more complex distributions of motor exploration compared to the age-matched control group. Classification using linear discriminant analysis revealed that movement patterns were identifiable by individual. Individuals in the control group were more difficult to identify using classification methods, consistent with the idea that motor deficits contribute significantly to unique movement signatures. CONCLUSIONS: Distribution analysis revealed individual patterns of abnormal coordination in stroke survivors and changes in these patterns with training. These findings were not apparent from scalar metrics that simply summarized properties of motor exploration. Our results suggest new methods for characterizing motor capabilities, and could provide the basis for powerful tools for designing customized therapy

Phase formation and phase separation in multiphase thin film hard coatings

Recent studies on thin films and coatings containing multiple phases have demonstrated their potential for improving hardness and tribological performance. Coatings for these applications are typically used in the as-deposited condition, so it therefore becomes important to understand the phase formation and separation processes that occur during deposition. In this work, we demonstrate that thermodynamic considerations, particularly free energy-composition diagrams, can help predict the phase separation process for a given film composition. The results of numerous experimental studies of phase formation in co-deposited thin films are reviewed with the goal of rationalizing the observed phases in terms of thermodynamic principles. Additional kinetic considerations are also discussed and a model is devised where phase separation takes place in a thin surface layer followed by crystallization of one or both phases. The fact that phase separation must precede crystallization has important implications for the microstructure that develops and the crystallinity of the phases formed. (C) 2004 Elsevier B.V. All rights reserved

Fabrication and tribological properties of composite coatings produced by lithographic and microbeading methods

The deposition of composite coatings for tribological applications is reviewed in this article. The focus of recent research has been to fabricate hard coatings that incorporate noble metals with the goal of reducing friction in dry contact. In the present case, we consider coating systems intended for applications in temperature regimes where oxidation and thermal structural evolution is limited. Deposition of coatings with immiscible components (such as TiC/Ag) results in a composite-structured coating that under certain conditions (such as vacuum or high temperatures) has demonstrated reduced friction. Another approach is to pattern coatings by artificial methods such as masking, laser drilling, or photolithography. Our recent work has focused on photolithographic methods. as well as a new masking approach which we refer to as microbeading. Evaluation of microreservoir-containing coatings fabricated by the microbeading method was carried out by depositing a TiN film and using graphite as the solid lubricant. Pin-on-disk tests using an alumina counterface showed that substantial reductions in friction coefficients were obtained for the larger bead sizes (5-10 mu m). The microbeading coating method was also implemented on cutting tools for machining where indium was used as the solid lubricant. Turning tests were conducted by high-speed machining of hardened 4340 steel, and the TiN-In coated inserts showed flank wear (in liquid lubricated machining conditions) of up to 4 times longer wear life than a TiN coating without indium. However, the role of the microreservoirs was not clear as the In coated TiN sample without microreservoirs also showed a significant performance improvement over TiN alone. Additional studies were made on samples using photolithography (TiN coatings incorporating either 4 or 9 mu m reservoirs) and tested with various solid lubricants using a pin-on-disk test. We observed lubricant entrapment (within the reservoirs) of graphite, but also found examples of debris collection, both from the counterface (a steel ball) and hard coating (TiO2 transformed from TiN). (C) 2009 Elsevier B.V. All rights reserved

Welcome to Lubricants, a New Open Access Journal for Interdisciplinary Research in the Field of Tribology

Welcome to Lubricants, a new open access journal for researchers and practitioners working in the field of tribology. The journal will publish peer-reviewed research papers, reviews, letters and communications, as well as papers on research ideas and proposals. The concept of open access is exciting because it allows free access of all publications to anyone, resulting in the widest dissemination possible for the authors publishing in the journal. In addition, publication is rapid, and full use can be made of color figures which are published at no additional cost to the authors. The contents of the journal will nonetheless be archival and articles can therefore have a long-term impact. [...

Microstructure and mechanical properties of Mo-Si-C and Zr-Si-C thin films: compositional routes for film densification and hardness enhancement

Transition metal carbides exhibit high hardness, thermal stability and excellent wear resistance making them attractive for applications such as tool and die coatings. However, when deposited in thin film form using physical vapor deposition methods the mechanical properties can degrade due to poor film density. In this study we examine the addition of SiC to two transition metal carbides, Mo2C and ZrC, as a possible route for film densification and hardness enhancement. Mo-Si-C and Zr-Si-C films were deposited with a range of Si concentrations using rf magnetron co-sputtering. Films were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, electron microscopy and nano-indentation and micro-indentation hardness testing. For Mo-Si-C the Si additions caused significant alterations to the microstructure, affecting the grain size, the amount of amorphous phases, and crystal structure. The hardness of the Mo2C films containing Si first increased slightly with Si content, and declined at higher Si concentrations, but was never above that expected for bulk Mo2C. For Zr Si-C, two sets of experiments were conducted: one with a large substrate-to-source distance and low rate of deposition, giving compositionally uniform films, and the second with a very short distance giving a compositionally graded film. For the first set, ZrC films without Si exhibited high porosity and low hardness, but with 31.5% SiC, the films were at the bulk levels for ZrC and the porosity was significantly reduced. This hardness improvement was explained in terms of a continuous re-nucleation process and resultant nanocrystalline grain structure. For the second set of films a hardness enhancement above rule of mixtures was observed, with a maximum of 4500 HK10 for films containing 9.3% SiC. This was explained in terms of an implantation of Si atoms. (c) 2006 Elsevier B.V. All rights reserved

The effects of substrate bias on phase stability and properties of sputter-deposited tungsten carbide

The effects of substrate bias on phase formation and physical properties of rf magnetron sputter-deposited tungsten carbide films have been investigated in this work. Films were deposited at 275 degreesC using bias levels ranging from 0 to -150 V and at room temperature and -160 V At low bias levels, the films were primarily composed of the WC1-x/W-2(C,O) phases, both of which have the B1 structure, and the fraction of the hexagonal W2C phase increased with bias level. The increased substrate bias levels also correlated with a reduction in oxygen content, suggesting that reducing oxygen content promotes formation of the W2C phase. However, the film deposited at room temperature and -160 V bias had an oxygen content of only 3%, yet did not form the W2C phase, indicating a minimum level of thermal activation is also required to form W2C. Increasing the bias voltage also resulting in increases in film hardness, modulus and compressive residual stress, while reducing resistivity. (C) 2004 Elsevier B.V. All rights reserved

Mechanisms of self-lubrication in patterned TiN coatings containing solid lubricant microreservoirs

The tribological mechanisms of friction and lubrication have been investigated in TIN coatings patterned to contain microscopic reservoirs for solid lubricant entrapment. Photo-lithography was used to fabricate three sets of samples on silicon wafers, varying the reservoir size (4 and 9 mu m) and spacing (11 and 25 mu m), which resulted in samples with a nominal reservoir area of either 2 or 10%. Pin-on-disk tests were run using lubricants of graphite and indium and counterfaces of alumina and steel (440C). In most cases, the samples with the 9 mu m holes spaced 25 mu m apart gave the lowest friction coefficients and longest wear life. Analysis of the wear tracks by SEM/EDS methods showed carbon to be present in the holes of the graphite/steel counterface samples, but TiO(2) was found in the holes of the graphite/alumina counterface samples. For the indium/steel counterface samples indium was detected within the microreservoirs, but iron was also found, transferred from the ball. These experiments highlight a variety of tribological mechanisms that can operate in microreservoir-patterned coatings. (C) 2010 Elsevier B.V. All rights reserved

Nanostructure and mechanical properties of WC-SiC thin films

The mechanical properties of WC-SiC thin films deposited by dual radio frequency magnetron sputtering were investigated. The films were characterized by x-ray photoelectron spectroscopy, x-ray diffraction (XRD), and transmission electron microscopy (TEM) to evaluate the details of the microstructure and degree of amorphization. The results indicate that small additions of SiC (\u3c25%) can significantly increase hardness compared to a pure WC film, but higher,SiC contents do not strongly affect hardness. XRD studies show the SiC had a disordering effect. TEM results showed that WC films had coarse porous structure, but films with a low silicon carbide content (approximately 10 to 25 at%) had a denser nanocrystalline structure. Samples with greater than 25% SiC were amorphous. The initial hardness increase at lower SiC contents correlated well with the observed densification, but the transition to an amorphous structure did not strongly affect hardness

The Effects of Ti Additions and Deposition Parameters on the Structural and Mechanical Properties of Stainless Steel-Nitride Thin Films

This study examines the structure and properties of stainless steel coatings deposited to incorporate large concentrations of nitrogen along with varying amounts of titanium. Deposition was carried out using magnetron co-sputtering of stainless steel and titanium from separate targets in a mixed Ar/N2 gas atmosphere. Composition analysis by X-ray photoelectron spectroscopy showed that while films with up to 4 at.% Ti exhibited little change in nitrogen content (compared to films deposited without Ti) and remained sub-stoichiometric with respect to N content. Films with 7−8 at.% Ti had a higher N level and further increasing the Ti level to 11−12 at.% resulted in stoichiometric N levels. X-ray diffraction showed that the films all had a nominally FCC structure with no additional phases. However, the peak locations for the (111) and (200) reflections indicated a distorted lattice characteristic of the S-phase, with calculated c/a values ranging from 1.007 to 1.033. The Ti additions, along with the corresponding increase in N content, helped reduce the extent of lattice distortion. The film microstructure of the higher (11−12 at.%) Ti films also showed higher density, lower surface roughness, and a finer grain structure. As a result, these films had a higher hardness compared to the sub-stoichiometric films, with hardness levels in the range of 18−23 GPa, typical of transition metal nitrides coatings