Identical Textures Research Articles

Enhancing touch sensibility by sensory retraining in a sensory discrimination task via haptic rendering.

Stroke survivors are commonly affected by somatosensory impairment, hampering their ability to interpret somatosensory information. Somatosensory information has been shown to critically support movement execution in healthy individuals and stroke survivors. Despite the detrimental effect of somatosensory impairments on performing activities of daily living, somatosensory training—in stark contrast to motor training—does not represent standard care in neurorehabilitation. Reasons for the neglected somatosensory treatment are the lack of high-quality research demonstrating the benefits of somatosensory interventions on stroke recovery, the unavailability of reliable quantitative assessments of sensorimotor deficits, and the labor-intensive nature of somatosensory training that relies on therapists guiding the hands of patients with motor impairments. To address this clinical need, we developed a virtual reality-based robotic texture discrimination task to assess and train touch sensibility. Our system incorporates the possibility to robotically guide the participants' hands during texture exploration (i.e., passive touch) and no-guided free texture exploration (i.e., active touch). We ran a 3-day experiment with thirty-six healthy participants who were asked to discriminate the odd texture among three visually identical textures –haptically rendered with the robotic device– following the method of constant stimuli. All participants trained with the passive and active conditions in randomized order on different days. We investigated the reliability of our system using the Intraclass Correlation Coefficient (ICC). We also evaluated the enhancement of participants' touch sensibility via somatosensory retraining and compared whether this enhancement differed between training with active vs. passive conditions. Our results showed that participants significantly improved their task performance after training. Moreover, we found that training effects were not significantly different between active and passive conditions, yet, passive exploration seemed to increase participants' perceived competence. The reliability of our system ranged from poor (in active condition) to moderate and good (in passive condition), probably due to the dependence of the ICC on the between-subject variability, which in a healthy population is usually small. Together, our virtual reality-based robotic haptic system may be a key asset for evaluating and retraining sensory loss with minimal supervision, especially for brain-injured patients who require guidance to move their hands.

Reversibility of the β ↔ α Phase Transformations as the Key Factor Determining Whether the Pd–Cu Membrane Foil Texture Depends on the Foil Preparation Process

We have studied the phase composition and texture of a Pd–Cu solid solution with a nearly equiatomic composition in different steps of the preparation of membrane foil by rolling to 300, 175, 100, and 20 μm and 7-μm-thick foil produced by magnetron sputtering of a target having the same composition as the foil. We have identified orientation relationships between the β- and α-phases in the as-prepared two-phase structures and demonstrated that, after heating to 600°C and subsequent cooling, the ordered solid solutions (β-phase) prepared by the two processes, have identical textures, which can be understood in terms of the transformation mechanism.

Correlation between 3D Texture of Steel Substrate and TiN-Coated Surface with Various Coating Masses

When producing thick Class II hot-dip tin coating, surface texture becomes smoother and more uniform. Amplitude characteristics of surface texture Sa, Sq and the core void volume (Vvc) decrease, number of surface peaks (characteristic Sds) decrease dramatically. These result from Sn particles filling in the surface irregularities. When producing thinner Class I hot-dip tin coating, characteristics of surface texture Sa, Sq increase, characteristic Sds slightly decreases, and characteristic Vvc slightly increases. These changes can be explained by the fact that Sn particles settle more efficiently onto peaks of irregularities. When producing very thin electrolytic coatings, the steel substrate and coating have identical surface textures for coating mass up to 3.42 g/m2.

Microstructure and mechanical property characterisation of aluminium–steel joints fabricated using ultrasonic additive manufacturing

ABSTRACTDriven by the interest to weld steel and aluminium in the solid state to prevent intermetallic formation, 9 kW ultrasonic additive manufacturing (UAM) has been used to fabricate Al 6061-4130 steel dissimilar metal builds. In addition, Al 6061-Al-6061 builds were fabricated using similar techniques to provide a baseline for mechanical property measurement. Mechanical testing performed using pushpin testing shows that steel–aluminium dissimilar metal welds fail across multiple layers while Al–Al welds delaminate from the substrate. Multi-scale characterisation indicates that the change in failure morphology is due to the formation of metallurgical bonds in the Al–steel builds. Texture analysis shows identical textures at the interface of Al–steel, Al–Al and Al–Ti joints; showing that the bond formation in all cases relies extensively on plastic deformation across multiple materials. In addition, no changes to the bonding mechanism occurred when the materials used as foils and substrate were swapped.

3D textural evidence for the formation of ultra-high tenor precious metal bearing sulphide microdroplets in offset reefs: An extreme example from the Platinova Reef, Skaergaard Intrusion, Greenland

The Platinova Reef in the Skaergaard Intrusion, east Greenland, is an example of a type of layered-intrusion-hosted, precious metal-enriched, stratiform, disseminated sulphide deposit referred to as “offset reefs”. These typically show platinum-group element (PGE) enrichment immediately below a major increase in the abundance of Cu-rich sulphides, with a prominent peak in Au enrichment exactly at that transition between the PGE-rich and the Cu-sulphide-rich zones. The reasons for the relative sequence of offsets in metal peaks, and the occasionally very high metal tenors have been subject to great debate. Here we use an integrated approach of high-resolution X-ray computed tomography (HRXCT), SEM, synchrotron and desktop microbeam XRF mapping, and thin section petrography to comprehensively classify the textural relations of the precious metal-bearing sulphides of the Platinova Reef as an extreme end member example of an exceedingly high tenor offset deposit. Our results show that in the zones of PGE enrichment, precious metal minerals (PMMs) are intimately associated with Cu sulphide globules, mostly located at, or close to, silicate and oxide boundaries. The textures are identical in zones enriched in Pd and Au, and thus we do not see any evidence for different processes forming the different zones. The PMM:Cu sulphide ratio in each globule varies significantly but overall the size of the globules increases from the Pd-rich, through the Au-rich, and into the Cu zone, with a significant corresponding decrease in PM tenor. As such, this records a progression of exceedingly high tenor, microdroplets of sulphide, which progressively get larger up through the section, and decrease in tenor proportionally to their size. Cumulus droplets of Cu sulphide became enriched in metals, and were trapped in situ without significant transport from their point of nucleation. The transition to larger sulphides represents a change from sulphides nucleated and trapped in situ, to larger ones that liquated from magma devoid of crystals, and that were able to grow and sink. This feature is common in all offset reef deposits, and is marked by the major enrichment in Au. Although the metal ratios of PGE to Au in the Pd- and Au-rich offset zones differ, the identical textures and comparable mineralogy show the physical mechanisms of concentration are the same, indicating a similar physical method of concentration. The relative position of the Pd, Au and Cu peaks in the Platinova Reef is essentially the same as that in numerous other offset reefs, suggesting that common overarching processes are responsible for the enrichment in metals, and relative offsets in peak metal concentrations in all such deposits. The most important of these processes are their relative Dsul/sil values and the diffusivities of the metals, which determine the order of offsets and the high tenors of the smallest sulphide droplets. The Platinova Reef therefore records the extreme enrichment via equilibrium and diffusive partitioning into sulphide liquid microdroplets very close to their point of nucleation.

Effect of texture and grain size on magnetic flux density and core loss in non-oriented electrical steel containing 3.15% Si

In an attempt to differentiate the impact of grain size and crystallographic texture on magnetic properties of non-oriented (NO) electrical steel sheets, samples with different grain sizes and textures were produced and analyzed regarding magnetic flux density B and core loss W. The textures of the NO electrical steel samples could be precisely quantified with the help of elliptical Gaussian distributions. In samples with identical textures, small grain sizes resulted in about 15% higher core loss W than larger grains, whereas grain size only moderately affected the magnetic flux density B. In samples having nearly the same grain size, a correlation of the magneto-crystalline anisotropic properties of B and W with texture was obtained via the anisotropy parameter A(h→). With increasing A(h→) a linear decrease of B and a linear increase of W were observed.

Petrology and trace element geochemistry of Robert Massif 04261 and 04262 meteorites, the first examples of geochemically enriched lherzolitic shergottites

Shergottites sampled two distinct geochemical reservoirs on Mars. Basaltic and olivine-phyric shergottites individually sampled both geochemically enriched and depleted reservoirs, whereas lherzolitic shergottites are previously known only to exhibit a relatively limited intermediate geochemical signature that may have resulted from the mixing of the two geochemical end-member reservoirs. Here we show that recently discovered shergottites Robert Massif (RBT) 04261 and RBT 04262 are the first examples of lherzolitic shergottites originating from the enriched reservoir. RBT 04261 and RBT 04262, initially identified as olivine-phyric shergottites, are actually lherzolitic shergottites. Both meteorites exhibit nearly identical textures and mineral compositions, suggesting that they should be paired. Each consists of two distinct textures: poikilitic and non-poikilitic. The poikilitic areas are composed of pyroxene oikocrysts enclosing olivine grains; all pyroxene oikocrysts have pigeonite cores mantled by augite. The non-poikilitic areas are composed of olivine, pyroxene, maskelynite and minor amounts of merrillite, chromite and ilmenite. Olivine and pyroxene show the lowest Mg-number, and maskelynite has the lowest anorthite component among the lherzolitic shergottites. Moreover, the modal abundances of maskelynite in these two meteorites are distinctly higher than the other lherzolitic shergottites. The rare earth element (REE) budgets of RBT 04261 and RBT 04262 are dominated by merrillite. The slightly light rare earth element (LREE)-enriched pattern of this mineral is similar to that of merrillite in the geochemically enriched basaltic shergottites Shergotty and Zagami, and unlike the LREE-depleted pattern of merrillite in the other lherzolitic shergottites. The REE patterns of both high- and low-Ca pyroxenes are also similar to those in Shergotty and Zagami. The REE pattern of a melt calculated to be in equilibrium with the core of a pyroxene oikocryst is parallel to that of the RBT 04262 whole-rock as well as whole-rock compositions of other geochemically enriched basaltic shergottites. These observations imply that RBT 04262 sampled an enriched and oxidized reservoir similar to that sampled by some of the basaltic shergottites and are consistent with an oxidizing condition for the formation of RBT 04262 (log fO 2 = QFM-1.6). The petrographic and geochemical observations presented here suggest that RBT 04261 and RBT 04262 represent the most evolved magma among the lherzolitic shergottites and that this magma originated from a geochemically enriched reservoir on Mars. Based on an evaluation of the relationship between petrographic, geochemical and chronological signatures for shergottites including RBT 04261 and RBT 04262, we propose that both geochemically enriched and depleted shergottites were ejected from the same launch site on Mars.

Surface analysis of the elastomer in lip seals run against shafts manufactured with micro-cavity patterns

Radial lip seals are used to retain lubricants and to prevent external contamination. When running against a plain stainless steel shaft, it is generally accepted that the micro-asperities that are developed on the lip seal elastomer by the shaft surface characteristics are responsible for the sealing mechanism in the form of reverse pumping. In this study, lip seals are tested against conventional stainless steel shafts and shafts manufactured with deterministic triangular micro-cavities of different orientations. Comprehensive surface characterization and wear ana-lysis are done using a scanning electron microscope and an optical profilometer to investigate the elastomer micro-asperities and shaft micro-cavities. Surface parameters are computed from the lip seal wear track of both the initial (before testing) and final (after testing) shaft surface. The lip seal elastomer surface wears away depending on the surface characteristics of the shaft. Previous work has concluded that incorporating surface textures on the shaft surface allows for control of the pumping direction through the seal but that the magnitude of that pumping rate has a large variability even for identical shaft surface textures. This study finds that this large variability may be due to the large variability in the elastomer sealing zone surface characteristics that develop due to wear over time. This study also confirms the previous results showing that the deterministic surface textures manufactured on the shaft surface dominate the lip seal pumping direction in spite of the large variation in the elastomer surface. Finally and most interestingly, this study finds a correlation between the axial location of the smoothest portion of the lip seal elastomer and the pumping rate of the lip seals.

Erodibility of soil and organic matter: independence of organic matter resistance to interrill erosion

AbstractThe enrichment of organic matter in interrill sediment is well documented; however, the respective roles of soil organic matter (SOM) and interrill erosion processes for the enrichment are unclear. In this study, organic matter content of sediment generated on two silts with almost identical textures, but different organic matter contents and aggregations, was tested. Artificial rainfall was applied to the soils in wet, dry and crusted initial conditions to determine the effects of soil moisture and rainfall and drying history on organic matter enrichment in interrill sediment. While erosional response of the soils varied significantly, organic matter enrichment of sediment was not sensitive to initial soil conditions. However, enrichment was higher on the silt with a lower organic matter content and lower interrill erodibility. The results show that enrichment of organic matter in interrill sediment is not directly related to either SOM content or soil interrill erodibility, but is dominated by interrill erosion processes. As a consequence of the complex interaction between soil, organic matter and interrill erosion processes, erodibility of organic matter should be treated as a separate variable in erosion models. Further research on aggregate breakdown, in particular the content and fate of the organic matter in the soil fragments, is required. Copyright © 2007 John Wiley & Sons, Ltd.

Simulation of recrystallization microstructures and textures: Effects of preferential growth

Three-dimensional (3-D) simulations of recrystallization were carried out using an approach where grains of different orientations are characterized by different nucleation and growth parameters. The aim was, by simulation, to study the effects of preferential growth on recrystallization under various nucleation assumptions. The simulations were based on the assumptions that (1) a material can be represented by two types of grains, one that grows 1.5 to 2.5 times faster than the other type; (2) the nucleation takes place either instantaneously when annealing is started or continuously during the annealing period; and (3) the nucleation sites are distributed either randomly or in clusters (around points, along lines, or on planes). These assumptions relate to common experimental observations. It was found that the nucleation and growth assumptions have very significant influences on the recrystallization characteristics. The preferential growth of one type of grain in particular affects the width of the recrystallized grain size distribution and the texture development. Furthermore, it was found that many different nucleation and growth assumptions can result in identical recrystallization microstructures and textures. The results of the simulations are discussed with reference to typical experimental findings.

In situ formation of welded tuff-like textures in the carapace of a voluminous silicic lava flow, Owyhee County, SW Idaho

The Badlands rhyolite, on the Owyhee Plateau of southwestern Idaho, can be demonstrated to be a large lava flow on the basis of its geometry of large and small flow lobes, its well-exposed near-vent features, and its response to pre-existing topography. However, samples of the dense upper vitrophyre of the unit reveal a range of annealed fragmental textures, including material which closely resembles the compressed, welded glass shards which are characteristic of ignimbrites. Formation of these tuff-like textures involved processes probably common to emplacement of most silicic lava flow units. Decompression upon extrusion causes inflation of pumice at the surface of the lava flow; some of this pumice is subsequently comminuted, producing loose bubble-wall shards, bits of pumice, chips of dense glass, and fragments of phenocrysts. This debris sifts down around loose blocks and into open fractures deeper in the flow, where it can be reheated, compressed, and annealed to varying degrees. The end result is a dense vitrophyre layer (beneath the true upper, non-welded carapace breccia) which can be extremely texturally heterogeneous, with areas of flow-foliated lava occurring very near lava which in many aspects looks like welded ignimbrite, complete with flattened pumices. Identical textures in other silicic units have been cited by previous workers as evidence that those units erupted as pyroclastic flows which then underwent sufficient rheomorphism to create a flow-foliated rock which otherwise appears to be lava. The textures described herein indicate that lava flows can come to mimic rheomorphic ignimbrites, at least at scales ranging from thin sections to outcrops. Voluminous silicic units with scattered fragmental textures, but with otherwise lava-like features, are probably true effusive lava flows.

Physical volcanology of a voluminous rhyolite lava flow: The Badlands lava, Owyhee Plateau, southwestern Idaho

This paper describes an extraordinarily well preserved example of a large, high-SiO 2 rhyolite unit that by its exposed physical features can be demonstrated to be an effusive lava flow, not a rheomorphic ignimbrite. The Badlands lava flow of southwestern Idaho shows a multi-lobate form, with flow lobes that advanced along several azimuths from a long fissure vent. The lava flowed around one of its tephra ridges and a bedrock topographic high, creating a kipuka in the middle of the flow; the other tephra ridge was shoved aside by the lava. The lava itself is everywhere flow foliated, with foliation horizontal at the base, steepening toward the top, and convex in the direction of flow advance. The foliation parallels the margins of the flow lobes and reveals the position and orientation of the vent. Many samples of the lava flow's dense upper vitrophyre show one or more fragmental textures that formed by the settling of pumiceous and glassy debris into open fractures and the debris' subsequent welding into a rock that in many respects resembles welded tuff. By this process, the lava flow mimics an ignimbrite at the scale of an outcrop or thin section. Identical textures in other units have been cited as indicative of ash-flow emplacement mechanisms. The Badlands eruption tapped a stratified magma chamber, in which a large volume of phenocryst-rich (30 vol.%) magma underlay a small volume of magma more evolved and nearly aphyric. The lava flow shows mingling relations between the two magmas, with minor volumes of the aphyric magma occurring as early, small lava lobes and as individual layers in the dominant phenocryst-rich lava. Effusion of the 15 km 3 of rhyolite lava may have continued for as short as 6 or as long as 16 years, with effusion rates comparable to those observed at the Mount St. Helens dome. The Badlands lava had a pre-eruptive volatile content of about 2.75 wt.% H 2O or less, and erupted at approximately 830 °C, much lower than the temperatures of many similar voluminous lavas. A low viscosity due to a high magmatic temperature is not a prerequisite for formation of an extensive lava flow; the low magmatic water content (which likely prevented a large explosive eruption) and large available magma volume were probably the most important factors allowing the Badlands to erupt as a lava flow.

Langmuir−Blodgett Deposition of Octadecyl Methacrylate Monolayers on Glass and Their E-Beam Polymerization

π−A isotherms of octadecyl methacrylate (ODMA) were recorded in the range 10−42 °C to investigate the experimental parameters for LB deposition of ODMA monolayers onto hydrophilic glass substrates. In the range 10−20 °C two monolayer phase transitions were detected in the π−A isotherm. Monolayer stability and the onset of monolayer collapse were investigated using relaxation phenomena. Isotherm recording was supported by Brewster angle microscopy (BAM), by which different tilt-oriented textures were detected. For monolayers of ODMA deposited onto glass at 10 °C and 16 mN/m, identical textures were found by BAM at the subphase and at the substrate. E-beam polymerization (10 MeV) of the deposited monolayer in a nitrogen atmosphere was indirectly proved by the change in the resistance of the layer with respect to evaporation in vacuum, where the Brewster angle reflectivity of the layers and their edges were used as an indication. It is suggested that the loss of tilt orientation detected by BAM in the deposited monolayer and at the layer edge results from polymerization.

Comparative Study of the Low Pressure Chemical Vapor Deposition Processes of W and Mo

We present a comparative study of low pressure chemical vapor deposition (LPCVD) of the refractory metals W and Mo on silicon substrates by the silicon reduction of their fluorides and . Our results contribute a new insight into the LPCVD process, explaining both the microstructure of the films and the kinetics of their deposition. The processes of W and Mo deposition follow a very similar course as indicated by the similarity of the deposits; both films are porous, and their interfaces with silicon have identical textures. Moreover, from experiments with excess , even the intermediate reactions contributing into the deposition process follow similar course. Despite the similarity of W and Mo deposition the two processes exhibit a puzzling difference. Mo films grow linearly with time, whereas tungsten deposition is inhibited at an early stage by a self‐limiting effect. We propose a mechanism in which the nonvolatile lower fluorides of W interrupt further deposition of metal tungsten. Our model is supported by SIMS studies. In terms of our model, it becomes clear why the self‐limiting effect never occurs during Mo deposition: since all Mo subfluorides are volatile, they cannot act as a blocking agent and interrupt the process. The difference in volatility between Mo‐F and W‐F compounds may also explain why the process of Mo deposition via hydrogen reduction never loses its absolute selectivity, whereas the analogous tungsten process is plagued by the selectivity loss.

Soil morphology and preferential flow along macropores

Preferential flow of water along macropores can only be characterized in quantitative terms when the flow system is functionally characterized by using tracers. Standard descriptions of soil structure do not provide adequate information. Expensive micromorphometric techniques allow specific measurements of macropores in terms of size, type, shape and continuity. In expensive macromorphometric techniques are attractive for field use. Preferential flow in saturated soil involves rapid displacement of water from macropores (hydrodynamic dispersion). In unsaturated soil, flow into air-filled macropores (short-circuiting) occurs, which is followed by lateral absorption. Examples are discussed which illustrate the use of soil morphology to characterize preferential flow along macropores: (i) empirical extrapolation of measured data on the basis of macrostructure descriptions. So far, this procedure could only be applied to breakthrough curves of soils with identical textures but very different macrostructures; (ii) using staining techniques which provide essential boundary conditions for newly developed physical flow models. The latter describe macropores in terms of size, type and shape, rather than in terms of relative volumes; and (iii) developing physical interpretations of pedological features, such as mottling patterns. The examples are based on four case studies which deal with practical problems of soil water management. In these studies, morphological methods provided essential data, which could not have been obtained by physical methods.

Origin of Carbonate Pseudopellets

Several lines of evidence are presented including lack of fossils and bioturbation, highly irregular contacts between lamina and micrite, identical textures of aggregates and micrite, presence of lamina and association of aggregates with sorted ferrugenous grains, and hydraulic equivalence of pellets and detritals. These suggest that certain micro-sized, ellipsoidal to spherical, rounded aggregates of micrite, here termed pseudopellets, are formed by hydraulic forces.

Emplacement of the Twin Sisters dunite, Washington

The large, elliptical, 36-sq-mi Twin Sisters dunite and 2 smaller dunite bodies are located along a NW.-trending, nearly vertical fault and are intrusive into several thrust plates and locally into the unconformably overlying Swauk Formation \[Cretaceous-Paleocene\]. The time of emplacement was post-Paleocene, and definitely later than the main Cretaceous orogeny. The Twin Sisters mass is composed of a virtually unaltered, coarse-grained enstatite-bearing dunite with accessory amounts of chromite and chromium diopside. Every section displays abundant evidence of cataclasis, including granulation and bending of mineral grains, and translation bands in olivine. Completely identical textures have recrystallized. These recrystallized cataclastic features now consist of fine-grained, unstrained olivine mosaic zones rounding and embaying large, strained porphyroclasts. Locally thin mosaic zones cut single, large crystals. The translation bands have recrystallized into bandlike forms with irregular, sutured boundaries. This recrystallization is thought to have taken place at moderate temperatures. Serpentinites are marginal to and gradational with the large Twin Sisters mass and 1 exposed smaller body. The width of this narrow marginal zone is essentially the same for both the large and the small, and is thus independent of the size of the mass. In detail, there is an outward transition from unaltered dunite to partially serpentinized dunite to massive serpentinite and finally to schistose serpentinite at the actual contact. Serpentine is very rare in the core area. It is concluded that the Twin Sisters dunite mass moved and deformed while still hot enough to recrystallize (possibly during the intrusive rise), later by cataclasis alone. Near the last stages of emplacement serpentinizing fluids were added from the country rock to the marginal portions. This reduced friction at the contact, and further intrusion was accomplished by marginal faulting.