Asymptotic analysis of state-to-state tetraatomic reactions using row-orthonormal hyperspherical coordinates

The state-to-state asymptotic analysis of tetraatomic reactions is presented. It is assumed that the four-atom time-independent partial wave Schrödinger equation has been solved subject to the condition that in the limit of very compact geometries the wave function vanishes. These solutions are initially obtained in body-fixed row-orthonormal hyperspherical coordinates and transformed in the asymptotic arrangement channel regions of nuclear configuration space to Jacobi body-fixed coordinates. From the latter, compact explicit expressions for the reactance (R) and scattering (S) matrices, useful for accurate numerical calculations, are obtained. The different systems of coordinates used and their interrelations are given. The approach described is particularly well suited for implementation on massively parallel architectures and is appropriate for the calculation of benchmark-quality state-to-state integral and differential cross sections on currently available computers

TetSplat: Real-time Rendering and Volume Clipping of Large Unstructured Tetrahedral Meshes

We present a novel approach to interactive visualization and exploration of large unstructured tetrahedral meshes. These massive 3D meshes are used in mission-critical CFD and structural mechanics simulations, and typically sample multiple field values on several millions of unstructured grid points. Our method relies on the pre-processing of the tetrahedral mesh to partition it into non-convex boundaries and internal fragments that are subsequently encoded into compressed multi-resolution data representations. These compact hierarchical data structures are then adaptively rendered and probed in real-time on a commodity PC. Our point-based rendering algorithm, which is inspired by QSplat, employs a simple but highly efficient splatting technique that guarantees interactive frame-rates regardless of the size of the input mesh and the available rendering hardware. It furthermore allows for real-time probing of the volumetric data-set through constructive solid geometry operations as well as interactive editing of color transfer functions for an arbitrary number of field values. Thus, the presented visualization technique allows end-users for the first time to interactively render and explore very large unstructured tetrahedral meshes on relatively inexpensive hardware

Semi-immersive space mission design and visualization: case study of the "terrestrial planet finder" mission

The paper addresses visualization issues of the Terrestrial Planet Finder Mission (C.A. Beichman et al., 1999). The goal of this mission is to search for chemical signatures of life in distant solar systems using five satellites flying in formation to simulate a large telescope. To design and visually verify such a delicate mission, one has to analyze and interact with many different 3D spacecraft trajectories, which is often difficult in 2D. We employ a novel trajectory design approach using invariant manifold theory, which is best understood and utilized in an immersive setting. The visualization also addresses multi-scale issues related to the vast differences in distance, velocity, and time at different phases of the mission. Additionally, the parameterization and coordinate frames used for numerical simulations may not be suitable for direct visualization. Relative motion presents a more serious problem where the patterns of the trajectories can only be viewed in particular rotating frames. Some of these problems are greatly relieved by using interactive, animated stereo 3D visualization in a semi-immersive environment such as a Responsive Workbench. Others were solved using standard techniques such as a stratify approach with multiple windows to address the multiscale issues, re-parameterizations of trajectories and associated 2D manifolds and relative motion of the camera to "evoke" the desired patterns

Physically-Based Droplet Interaction

In this paper we present a physically-based model for simulating realistic interactions between liquid droplets in an efficient manner. Our particle-based system recreates the coalescence, separation and fragmentation interactions that occur between colliding liquid droplets and allows systems of droplets to be meaningfully repre- sented by an equivalent number of simulated particles. By consid- ering the interactions specific to liquid droplet phenomena directly, we display novel levels of detail that cannot be captured using other interaction models at a similar scale. Our work combines experi- mentally validated components, originating in engineering, with a collection of novel modifications to create a particle-based interac- tion model for use in the development of mid-to-large scale droplet- based liquid spray effects. We demonstrate this model, alongside a size-dependent drag force, as an extension to a commonly-used ballistic particle system and show how the introduction of these interactions improves the quality and variety of results possible in recreating liquid droplets and sprays, even using these otherwise simple systems

Merkingsforsøk i fisketrappa ved Løpet i Renavassdraget i perioden 1985-2000

I perioden 1985-2000 ble 3159 harr og 1110 ørret registrert og merket i fisketrappa ved Løpet. Oppgangen av begge arter varierte mye fra år til år. Det var en negativ utvikling i oppgangen av ørret i løpet av undersøkelsesperioden, mens det var ingen tilsvarende trend i den årlige oppgangen av harr. Det vil si at det relative innslaget av harr i forhold til ørret i trappa har økt i perioden. Med ett unntak, en sik på 39 cm, var det kun harr og ørret som ble registrert i trappa. Gjennomsnittslengden til harr og ørret som ble merket i trappa var på henholdsvis 29.7 og 28 cm, og det var hovedsakelig individer > 20 cm av begge arter som ble registrert. Lengdefordelingen til harr eller ørret som gikk i trappa så ikke ut til å ha endret seg i løpet av undersøkelsesperioden. Innrapporterte gjenfangster av harr og ørret fra fiskerne viste at henholdsvis 88 % og 90 % av gjenfangstene ble foretatt innenfor en avstand på 20 km fra merkestedet. En stor andel av gjenfangstene av harr (87 %) og ørret (61 %) ble gjenfanget oppstrøms merkestedet, og områdene ved Rødsbrua (9 km fra Løpet) og Deset (17 km fra Løpet) peker seg ut med spesielt mange gjenfangster. Merkingene viser at både harr og ørret kan tilbakelegge store avstander i vassdraget. Ørret merket ved Løpet ble gjenfanget oppstrøms så langt opp som ved Flena’s utløp i Storsjøen (60 km fra Løpet) og nedstrøms så langt ned som til Strandfossen i Glomma (32 km fra Løpet). Gjenfangstene av harr ble innrapportert så langt opp som ved Andrå i Storsjøen (50 km fra Løpet) og nedstrøms så langt ned som til Strandfossen. Selv om enkelte gjenfangster av både harr og ørret viser at de kan forflytte seg over store avstander, er trolig omfanget av fiskevandringer i vassdraget mindre nå enn tidligere. Merkings-forsøk av harr i Løpet på slutten av 1960-tallet viste blant annet en større spredning av gjenfangstene enn det som ble registrert i denne undersøkelsen. Det ble ikke registrert massiv tilbakevandring av harr på høsten til overvintringsområder i Storsjøen slik som beskrevet tidligere (bl.a. Sømme’s beskrivelse av ”gangharren”). Gjennomsnittlig gjenfangstprosent (av fiskere) av harr og ørret i løpet av undersøkelsesperioden var på henholdsvis 13.6 og 12.3 %, men det var en tydelig nedgang i gjenfangstprosenten i løpet av undersøkelsesperioden for begge arter. Dette kan nok delvis skyldes lavere beskatning, men skyldes sannsynligvis også at andelen fiskere som sendte inn merke sank i løpet av perioden.English: A total of 3159 grayling Thymallus thymallus and 1110 brown trout Salmo trutta were tagged with Floy anchor tags in the fish ladder at Løpet in the regulated river Rena during the period 1985-2000. The annual number of observations of brown trout declined during the study period, whereas no significant trend in the annual number of observations of grayling was found. The mean lengths of tagged grayling and brown trout were 29.7 and 28 cm, respectively, and few individuals < 20 cm were recorded in the fish ladder. Most recaptures of both grayling (87 %) and brown trout (61 %) by anglers were reported from the upstream face of the dam. The mean frequencies of recaptures of grayling and brown trout reported by anglers were 13.6 % and 12.3 %, but there was a decreasing trend in the frequency of individuals recaptured during the study period. This might partly be explained by a lower rate of fishing mortality. The frequency of anglers actually reporting recaptures, however, was probably declining towards the end of the study period

Level set modeling and segmentation of diffusion tensor magnetic resonance imaging brain data

Segmentation of anatomical regions of the brain is one of the fundamental problems in medical image analysis. It is traditionally solved by iso-surfacing or through the use of active contours/deformable models on a gray-scale magnetic resonance imaging (MRI) data. We develop a technique that uses anisotropic diffusion properties of brain tissue available from diffusion tensor (DT)-MRI to segment brain structures. We develop a computational pipeline starting from raw diffusion tensor data through computation of invariant anisotropy measures to construction of geometric models of the brain structures. This provides an environment for user-controlled 3-D segmentation of DT-MRI datasets. We use a level set approach to remove noise from the data and to produce smooth, geometric models. We apply our technique to DT-MRI data of a human subject and build models of the isotropic and strongly anisotropic regions of the brain. Once geometric models have been constructed they can be combined to study spatial relationships and quantitatively analyzed to produce the volume and surface area of the segmented regions

Modulating the Folding Landscape of Superoxide Dismutase 1 with Targeted Molecular Binders

Amyotrophic lateral sclerosis, or Lou Gehrig's disease, is characterized by motor neuron death with average survival times of 2 ‐ 5 years. One cause of this disease is the misfolding of superoxide dismutase 1 (SOD1), a protein whose stability and aggregation propensity are affected by point mutations spanning the protein. Here, we use an epitope‐specific, high‐throughput screen to identify peptides that both stabilize the native conformation of SOD1 as well as accelerate its folding by 2.5‐fold. Ligands targeted to the electrostatic loop on the periphery of the protein tightened the non‐metalated structure and accelerated its folding. This strategy may be useful for fundamental studies of protein energy landscapes as well as designing new classes of therapeutics

Wave curves: Simulating Lagrangian water waves on dynamically deforming surfaces

We propose a method to enhance the visual detail of a water surface simulation. Our method works as a post-processing step which takes a simulation as input and increases its apparent resolution by simulating many detailed Lagrangian water waves on top of it. We extend linear water wave theory to work in non-planar domains which deform over time, and we discretize the theory using Lagrangian wave packets attached to spline curves. The method is numerically stable and trivially parallelizable, and it produces high frequency ripples with dispersive wave-like behaviors customized to the underlying fluid simulation