Location of stable and unstable equilibrium configurations using a model trust region quasi-Newton method and tunnelling

A hybrid method for locating multipole equilibrium configurations has been proposed recently. The hybrid method combined the efficiency of a quasi-Newton method capable of locating stable and unstable equilibrium solutions with a robust homotopy method capable of tracking equilibrium paths with turning points and exploiting sparsity of the Jacobian matrix at the same time. A quasi-Newton method in conjunction with a deflation technique is proposed here as an alternative to the hybrid method. The proposed method not only exploits sparsity and symmetry, but also represents an improvement in efficiency.     

The structure of sea urchin spines, large biogenic single crystals of calcite

Sea urchin spines are porous, single crystal Mg-rich calcite [(Mg, Ca)(CO₃)] with a three dimensional meshwork architecture. The crystallographic orientation of large (10 cm in length) spines from Heterocentrotus trigonarius was determined using the X-ray back-reflection Laue technique; the long axis of all spines is parallel to the 00·1 direction of calcite. The internal structure was studied using SEM and TEM. The macropore structure dominated the SEM images, whereas many small (80 nm) protein occlusions can be observed within the single crystal spines using TEM. The spines appeared crystallographically perfect in the TEM. The bend strengths of a group of spines were also determined and varied between 13 and 41 MPa.     

Interactive collision detection in three-dimensional visualizations of simulated construction operations

This paper presents research that led to the design and implementation of fast and interactive collision detection methods that can be used to identify and report undesirable conflicts that occur among static (e.g., structure in-place, idle equipment), dynamic (e.g., active machines and workers), and abstract (e.g., hazard spaces) construction resources in 3D animations of construction operations modeled using discrete-event simulation. Computational efficiency and interactive speed in the designed interference detection methods were the primary challenges that the research addressed. In addition, the efficiency and speed were achieved with minimal trade-off against accuracy. In order to achieve this, the authors capitalized on advanced documented algorithms for proximity queries between arbitrarily moving 3D geometric objects to design mechanisms for interference detection, control, and response in construction process visualizations. The designed methods are implemented in a software tool called C-Collide that integrates as an add-on with the VITASCOPE visualization system.     

Georeferenced Registration of Construction Graphics in Mobile Outdoor Augmented Reality

This paper describes research that investigated the application of the global positioning system and 3 degree-of-freedom (3-DOF) angular tracking to address the registration problem during interactive visualization of construction graphics in outdoor augmented reality (AR) environments. The global position and the three-dimensional (3D) orientation of a user’s viewpoint are tracked, and this information is reconciled with the known global position and orientation of superimposed computer-aided design (CAD) objects. Based on this computation, the relative translation and axial rotations between the user’s viewpoint and the CAD objects are continually calculated. The relative geometric transformations are then applied to the CAD objects inside a virtual viewing frustum that is coincided with the real world space that is in the user’s view. The result is an augmented outdoor environment where superimposed graphical objects stay fixed to their real world locations as the user navigates. The algorithms are implemented in a software tool called UM-AR-GPS-ROVER that is capable of interactively placing static and dynamic 3D models at any location in outdoor augmented space. The concept and prototype are demonstrated with an example in which scheduled construction activities for the erection of a structural steel frame are graphically simulated in outdoor AR.     

Evaluation of Augmented Reality for Rapid Assessment of Earthquake-Induced Building Damage

This paper discusses the feasibility of using augmented reality (AR) to evaluate earthquake-induced building damage. In the proposed approach, previously stored building information is superimposed onto a real structure in AR. Structural damage can then be quantified by measuring and interpreting key differences between the real and augmented views of the facility. Proof-of-concept experiments were performed in conjunction with large-scale cyclic shear wall tests. In these, CAD images of the walls were superimposed onto the wall specimens. Then, as the wall specimens were deformed under applied loading, the horizontal drifts between the walls and the augmented images were computed using two different techniques and compared with actual wall drifts. The obtained results highlight the potential of using AR for rapid damage detection and indicate that the accuracy of structural displacements measured using AR is a direct function of the accuracy with which augmented images can be registered with the real world. The limitations of the technology, considerations for field implementation, and the potential for other related applications of AR are also discussed.     

Three distinct D-amino acid substitutions confer potent antiangiogenic activity on an inactive peptide derived from a thrombospondin-1 type 1 repeat

Mal II, a 19-residue peptide derived from the second type 1 properdin-like repeat of the antiangiogenic protein thrombospondin-1 (TSP-1), was inactive in angiogenesis assays. Yet the substitution of any one of three L-amino acids by their D-enantiomers conferred on this peptide a potent antiangiogenic activity approaching that of the intact 450-kDa TSP-1. Substituted peptides inhibited the migration of capillary endothelial cells with an ED50 of 8.5 nM for the D-Ile-15 substitution, 10 nM for the D-Ser-4 substitution, and 0.75 nM for the D-Ser-5 substitution. A peptide with D-Ile at position 15 could be shortened to its last seven amino acids with little loss in activity. Like whole TSP-1, the Mal II D-Ile derivative inhibited a broad range of angiogenic inducers, was selective for endothelial cells, and required CD36 receptor binding for activity. A variety of end modifications further improved peptide potency. An ethylamide-capped heptapeptide was also active systemically in that when injected i.p. it rendered mice unable to mount a corneal angiogenic response, suggesting the potential usefulness of such peptides as antiangiogenic therapeutics.     

A combined approach of conventional and molecular cytogenetics for detailed karyotypic analysis of the small cell lung carcinoma cell line U2020

Until recently the ability to analyze complex karyotypic rearrangements was totally dependent upon light microscopy of G-banded chromosomes. Developments in the area of molecular cytogenetics have revolutionized such analysis, making it possible to determine the nature of complex rearrangements. An extensive analysis has been made of the small cell lung carcinoma (SCLC) cell line U2020, using a combined approach of conventional and molecular cytogenetics, enabling a highly detailed karyotype to be constructed revealing rearrangements previously undetected by G-banding alone. This approach offers the opportunity to reassess other tumor karyotypes, particularly those of high complexity found in solid tumors, for tumor-specific consistent rearrangements indecipherable by conventional karyotyping.     

The effect of grain size and composition on the fracture toughness of Ti–Al–Nb alloys undergoing stress-induced martensitic transformation

The effect of grain size and composition on the fracture toughness of Ti–Al–Nb alloys in β solution-treated condition was investigated. The fracture toughness of the alloys was found to increase with an increase in grain size initially, reach a maximum and subsequently decrease with further increase in grain size. This trend was attributed primarily to the effect of grain size on the enhancement of fracture toughness due to stress-induced martensitic transformation (SIMT) at the crack tip, which in turn can be related to the effect of grain size on trigger stress for SIMT. Alloys containing higher Al and Nb showed a higher toughness for the same grain size, which was also explained in terms of effect of composition on the trigger stress.     

Algorithm for Accurate Three-Dimensional Scene Graph Updates in High-Speed Animations of Previously Simulated Construction Operations

Abstract:   Visualization of construction operations is an important technique to communicate the logic of simulation models in detail. Early efforts resulted in a scene graph and frame update algorithm that was capable of converting discrete information from simulation models into smooth and continuous 3D animations. That algorithm did not account for high speed or concurrent animation because the need to do so was not anticipated. Recent advances in computing power and an interest in using the technology for next generation applications now demand accurate high speed and concurrent animations. This article presents the design of the original algorithm at a previously undocumented level of detail and specificity, and that allows for the analysis of its shortcomings when used at high speeds or concurrently with simulation. Two subsequent but still inadequate designs of the algorithm are also presented and analyzed in detail so that they can serve as an illustration of the path toward the final design and place it in proper context. The article concludes with the final design and evaluation of the algorithm, which is accurate at very high animation speeds and supports concurrent animation of simulation models.     

A Generalized System for Photo-Responsive Membrane Rupture in Polymersomes

Polymersomes are vesicles whose membranes are comprised of self-assembled block co-polymers. We recently showed that co-encapsulating conjugated multi-porphyrin dyes in a polymersome membrane with ferritin protein in the aqueous lumen confers photo-lability to the polymersome. In the present study, we illustrate that the photo-lability can be extended to vesicles containing dextran, an inert and inexpensive polysaccharide, as the luminal solute. Here we explore how structural features of the polymersome/porphyrin/dextran composite affect its photo-response. Increasing dextran molecular weight, decreasing block copolymer molecular weight, and altering fluorophore-membrane interactions results in increasing the photo-responsiveness of the polymersomes. Amphiphilic interactions of the luminal encapsulant with the membrane coupled with localized heat production in the hydrophobic bilayer likely cause differential thermal expansion in the membrane and the subsequent membrane rupture. This study suggests a general approach to impart photo-responsiveness to any biomimetic vesicle system without chemical modification, as well as a simple, bio-inert method for constructing photo-sensitive carriers for controlled release of encapsulants.