5,720 research outputs found
The influence of particle type on the mechanics of sand-rubber mixtures
Triaxial and oedometer tests were used to demonstrate that a critical state framework can be applied to sand–rubber mixtures of similar soil grain and rubber sizes. It described well the behavior of a crushable sand and a quartz sand with either rubber fibers or granules of a variety of quantities, from small to large strains. Together with additional oedometer tests on soils of a wider variety of gradings, the work enabled the influences of sand particle type, grading, and rubber shape to be established. The sand particle type, specifically whether the grains were weak or strong, was found to be a key factor. It affected the yield in compression, even when large quantities of rubber were added. It controlled the critical state stress ratio, except for those mixtures with the highest content of rubber fibers, as well as the stress strain behavior. Sand particle type also determined the critical state line (CSL) location in the volumetric plane for lower rubber contents, but at higher rubber contents the behavior tended to converge for the two sand types. The grading and rubber type were not found to affect the compression or swelling indices significantly, which were mainly controlled by rubber content. Gradings that had nonconvergent compression paths without added rubber tended to retain this feature with rubber. The addition of both types of rubber led to higher volumetric compression in isotropic or one-dimensional compression but reduced volumetric strain during shear, altering the shapes of the state boundary surfaces
Bone marrow mesenchymal stem cells do not enhance intra-synovial tendon healing despite engraftment and homing to niches within the synovium
Intra-synovial tendon injuries display poor healing, which often results in reduced functionality and pain. A lack of effective therapeutic options has led to experimental approaches to augment natural tendon repair with autologous mesenchymal stem cells (MSCs) although the effects of the intra-synovial environment on the distribution, engraftment and functionality of implanted MSCs is not known. This study utilised a novel sheep model which, although in an anatomically different location, more accurately mimics the mechanical and synovial environment of the human rotator cuff, to determine the effects of intra-synovial implantation of MSCs
Low-Cost Virtual Reality System - PC Driven System
The concept of Virtual Reality has been around since early 1960s, but the availability and development of Virtual Reality systems were largely limited due to its nature of high cost and difficulty in maintenance. Until recently, thanks to the fast development of the modern technology, the idea of building Virtual Reality system using commodity-off-the-shelf hardware became feasible. By using Personal Computers, we have in this project developed a Low-Cost Distributed Virtual Reality system that is much cheaper, easier to maintain and mobile. In this project, the design of stereo vision, corner projection and distributed architecture had been discussed and applied in the implementation of the Virtual Reality system. User experiment had been conducted. The aim of the user experiment is to test the system for presence level, Slater, Usoh and Steed (SUS) questionnaire was used as an indication to the level of presence. Furthermore, network performance related to scene complexities were also evaluated. From these experiment, we have found that the Virtual Reality system developed creates a good level of presence to the participants and scene complexity would influence the roundtrip time of the network. Lastly, this paper concludes by discussing why the Low-Cost Virtual Reality system developed to be an effective Virtual Reality system
Low-Cost Virtual Reality System (PS2-driven)
A low cost virtual reality system that generates corner projection using three PlayStation2 is presented. Two display stations each connected to one projector is used to provide panoramic view of the VR scene. A control station receives user input and broadcasts the instruction to the two display stations in order to update their respective camera positions and orientations. A demo application which immerses the user inside a glider flying through a night city has also been implemented. We report the performance of our system using random primitives. The benchmark revealed a gradual decline in frame rate in response to polygon counts in the scene. Polygon rate in our system remained near constant and does not vary with the polygon count on the screen. The results indicated for our system, a polygon count of 3540 on the screen with a refresh rate of 24fps is optimum in an interactive environment. Investigation on the relationship between roundtrip time and scene complexity revealed a significant positive correlation of (0.966). This suggests system response to user command can be delayed in a complex virtual environment
More unlabelled data or label more data? A study on semi-supervised laparoscopic image segmentation
Improving a semi-supervised image segmentation task has the option of adding more unlabelled images, labelling the unlabelled images or combining both, as neither image acquisition nor expert labelling can be considered trivial in most clinical applications. With a laparoscopic liver image segmentation application, we investigate the performance impact by altering the quantities of labelled and unlabelled training data, using a semi-supervised segmentation algorithm based on the mean teacher learning paradigm. We first report a significantly higher segmentation accuracy, compared with supervised learning. Interestingly, this comparison reveals that the training strategy adopted in the semi-supervised algorithm is also responsible for this observed improvement, in addition to the added unlabelled data. We then compare different combinations of labelled and unlabelled data set sizes for training semi-supervised segmentation networks, to provide a quantitative example of the practically useful trade-off between the two data planning strategies in this surgical guidance application
Compactification on negatively curved manifolds
We show that string/M theory compactifications to maximally symmetric
space-times using manifolds whose scalar curvature is everywhere negative, must
have significant warping, large stringy corrections, or both.Comment: 18 pages, JHEP3.cl
Ripple modulated electronic structure of a 3D topological insulator
3D topological insulators, similar to the Dirac material graphene, host
linearly dispersing states with unique properties and a strong potential for
applications. A key, missing element in realizing some of the more exotic
states in topological insulators is the ability to manipulate local electronic
properties. Analogy with graphene suggests a possible avenue via a topographic
route by the formation of superlattice structures such as a moir\'e patterns or
ripples, which can induce controlled potential variations. However, while the
charge and lattice degrees of freedom are intimately coupled in graphene, it is
not clear a priori how a physical buckling or ripples might influence the
electronic structure of topological insulators. Here we use Fourier transform
scanning tunneling spectroscopy to determine the effects of a one-dimensional
periodic buckling on the electronic properties of Bi2Te3. By tracking the
spatial variations of the scattering vector of the interference patterns as
well as features associated with bulk density of states, we show that the
buckling creates a periodic potential modulation, which in turn modulates the
surface and the bulk states. The strong correlation between the topographic
ripples and electronic structure indicates that while doping alone is
insufficient to create predetermined potential landscapes, creating ripples
provides a path to controlling the potential seen by the Dirac electrons on a
local scale. Such rippled features may be engineered by strain in thin films
and may find use in future applications of topological insulators.Comment: Nature Communications (accepted
Deciphering interplay between Salmonella invasion effectors
Bacterial pathogens have evolved a specialized type III secretion system (T3SS) to translocate virulence effector proteins directly into eukaryotic target cells. Salmonellae deploy effectors that trigger localized actin reorganization to force their own entry into non-phagocytic host cells. Six effectors (SipC, SipA, SopE/2, SopB, SptP) can individually manipulate actin dynamics at the plasma membrane, which acts as a ‘signaling hub’ during Salmonella invasion. The extent of crosstalk between these spatially coincident effectors remains unknown. Here we describe trans and cis binary entry effector interplay (BENEFIT) screens that systematically examine functional associations between effectors following their delivery into the host cell. The results reveal extensive ordered synergistic and antagonistic relationships and their relative potency, and illuminate an unexpectedly sophisticated signaling network evolved through longstanding pathogen–host interaction
Strategically Equivalent Contests
Using a two-player Tullock-type contest, we show that intuitively and structurally different contests can be strategically equivalent. Strategically equivalent contests generate the same best response functions and, as a result, the same equilibrium efforts. However, strategically equivalent contests may yield different equilibrium payoffs. We propose a simple two-step procedure to identify strategically equivalent contests. Using this procedure, we identify contests that are strategically equivalent to the original Tullock contest, and provide new examples of strategically equivalent contests. Finally, we discuss possible contest design applications and avenues for future theoretical and empirical research
Does the lateral intercondylar ridge disappear in ACL deficient patients?
The aim of this study was to determine whether there is a difference in the presence of the lateral intercondylar ridge and the lateral bifurcate ridge between patients with sub-acute and chronic ACL injuries. We hypothesized that the ridges would be present less often with chronic ACL deficiency. Twenty-five patients with a chronic ACL injury were matched for age and gender to 25 patients with a sub-acute ACL injury. The lateral intercondylar ridge and lateral bifurcate ridge were scored as either present, absent, or indeterminate due to insufficient visualization by three blinded observers. The kappa for the three observers was .61 for the lateral intercondylar ridge and .58 for the lateral bifurcate ridge. The lateral intercondylar ridge was present in 88% of the sub-acute patients and 88% of the chronic patients. The lateral bifurcate ridge was present in 48% of the sub-acute and 48% of the chronic patients. This matched-pairs case–control study was unable to show a difference in the presence of the femoral bony ridges between patients with acute and chronic ACL injuries. The authors would suggest looking for the ridges as a landmark of the native ACL insertion site during ACL reconstruction in both acute and chronic ACL injuries
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