The Hydrogen Atom in Combined Electric and Magnetic Fields with Arbitrary Mutual Orientations

For the hydrogen atom in combined magnetic and electric fields we investigate the dependence of the quantum spectra, classical dynamics, and statistical distributions of energy levels on the mutual orientation of the two external fields. Resonance energies and oscillator strengths are obtained by exact diagonalization of the Hamiltonian in a complete basis set, even far above the ionization threshold. At high excitation energies around the Stark saddle point the eigenenergies exhibit strong level repulsions when the angle between the fields is varied. The large avoided crossings occur between states with the same approximately conserved principal quantum number, n, and this intramanifold mixing of states cannot be explained, not even qualitatively, by conventional perturbation theory. However, it is well reproduced by an extended perturbation theory which takes into account all couplings between the angular momentum and Runge-Lenz vector. The large avoided crossings are interpreted as a quantum manifestation of classical intramanifold chaos. This interpretation is supported by both classical Poincar\'e surfaces of section, which reveal a mixed regular-chaotic intramanifold dynamics, and the statistical analysis of nearest-neighbor-spacingComment: two-column version, 10 pages, REVTeX, 10 figures, uuencoded, submitted to Rhys. Rev.

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

TAKE CoVer: EXPLOITING VERSION SUPPORT IN COOPERATIVE SYSTEMS

Current CSCW applications support one or more modes of cooperative work. The selection of and transition between these modes is usually placed on the users. At IPSI we built the SEPIA cooperative hypermedia authoring environment supporting a complete set of situations arising during collaborative work and the smooth transitions between them. While early use of the system shows the benefits of supporting smooth transitions between different collaborative modes, it also reveals some deficits regarding parallel work, management of alternative documents, or reuse of document parts. We propose to integrate version support to overcome these limitations. This leads to a versioned data management and an extended user-interface enabling concurrent users to select a certain state of their work, to be aware of related changes, and to cooperate with others either asynchronously or synchronously

TAKE CoVer: Exploiting Version Support in Cooperative Systems

Current CSCW applications support one or more modes of cooperative work. The selection of and transition between these modes is usually placed on the users. We built the SEPIA cooperative hypermedia authoring environment supporting a complete set of situations arising during collaborative work and the smooth transitions between them. While early use of the system shows the benefits of supporting smooth transitions between different collaborative modes, it also reveals some deficits regarding parallel work, management of alternative documents, or reuse of document parts. We propose to integrate version support to overcome these limitations. This leads to a versioned data management and an extended user-interface enabling concurrent users to select a certain state of their work, to be aware of related changes, and to cooperate with others either asynchronously or synchronously

Tailoring Groupware: The Cooperative Hypermedia Approach

Tailoring groupware has to deal with adapting properties of a shared information space as well as with adapting properties of the cooperation support to the group&apos;s needs. In this paper, an approach for tailoring both aspects of groupware in an integrated fashion is proposed. This approach uses cooperative hypermedia as a unifying representation of shared information structures, functionality, and the coordination medium of a shared application. It enables cooperative definition of shared information structures, shared process models and their access models not only before collaboration starts, but also on the fly, when emergent processes evolve. The proposed approach addresses tailoring at all stages of the development and use of a groupware application. A prototype system called CHIPS is presented and different possibilities of tailoring in CHIPS are discussed. Examples of CHIPS demonstrate that the cooperative hypermedia approach to tailoring groupware can support the adaptation to different evolving tasks and processes performed by changing teams

Supporting Collaborative Writing of Hyperdocuments in SEPIA

Today, most cooperative systems support primarily either asynchronous or synchronous (real time) cooperative work. We feel that both synchronous and asynchronous cooperation are extremely important aspects of working in groups, and to ignore one or the other is to supply only half a solution to users. In this paper, we describe the extension of the hypertext authoring system SEPIA developed at GMD-IPSI to support cooperative work among hypertext authors. Cooperative SEPIA is unique not only in its ability to support cooperative work in both of these categories, but also in how smoothly and naturally it supports the transition between these two categories

Supporting Problem Based Learning by a Collaborative Virtual Environment: A Cooperative Hypermedia Approach

Problem based learning promotes engagement in meaningful learning and cooperation among students. When applying PBL in distributed groups distance has to be bridged by means of technology. Collaborative virtual environments (CVE) can help to overcome two crucial problems of PBL, if used in a distributed learning situation: Firstly, learners have problems to understand, interact with, and tailor shared learning environments, so that they match their needs. Secondly, groups of learners have problems to construct shared knowledge in a shared learning environment. Our approach is to provide a CVE designed to support PBL. We use the metaphor of a virtual institute to organize the learning environment and to facilitate orientation in and tailoring of the CVE. In addition, we provide a graphical cooperative knowledge representation tool to help groups to construct shared knowledge in a PBL process. We use cooperative hypermedia technology to represent both shared learning spaces and shared information spaces as shared hyperdocuments