341 research outputs found

    Normal subgroups of diffeomorphism and homeomorphism groups of R^n and other open manifolds

    Full text link
    We determine all the normal subgroups of the group of C^r diffeomorphisms of R^n, r = 1,2,...,infinity, except when r=n+1 or n=4, and also of the group of homeomorphisms of R^n (r=0). We also study the group A_0 of diffeomorphisms of an open manifold M that are isotopic to the identity. If M is the interior of a compact manifold with nonempty boundary, then the quotient of A_0 by the normal subgroup of diffeomorphisms that coincide with the identity near to a given end e of M is simple.Comment: This version corrects an error regarding the diffeomorphism groups of R^1, since the line has two ends, in contrast to higher dimension

    Asymptotic linking of volume-preserving actions of Rk{\mathbb R}^k

    Full text link
    We extend V. Arnold's theory of asymptotic linking for two volume preserving flows on a domain in R3{\mathbb R}^3 and S3S^3 to volume preserving actions of Rk{\mathbb R}^k and Râ„“{\mathbb R}^\ell on certain domains in Rn{\mathbb R}^n and also to linking of a volume preserving action of Rk{\mathbb R}^k with a closed oriented singular â„“\ell-dimensional submanifold in Rn{\mathbb R}^n, where n=k+â„“+1n=k+\ell+1. We also extend the Biot-Savart formula to higher dimensions.Comment: 32 pages. We extend Arnol'd's asymptotic linking to actions of {\mathbb^R}^k and {\mathbb^R}^\ell. The only change in this version is that several latex errors and internal references were corrected. The MSC 2020 classification was correcte

    How do distracted and normal driving differ: an analysis of the ACAS naturalistic driving data

    Full text link
    SAfety VEhicles using adaptive Interface Technology (SAVE-IT Project)To determine how distracted and normal driving differ, this report re-examines driving performance data from the advanced collision avoidance system (ACAS) field operational test (FOT), a naturalistic driving study (96 drivers, 136,792 miles). In terms of overall driving performance statistics, distraction (defined as 4 successive video frames where the driver’s head was not oriented to the forward scene) had almost no effect, except for decreasing mean throttle opening by 36% and mean speed by 6%. No consistent normal/distracted differences were found in the parameters that fit the distributions of steering wheel angle, heading, and speed (all double exponential) and throttle opening (gamma) for each road type by driver age combination. In contrast, logistic regression identified other statistics and factors that discriminated between normal and distracted driving. They included (a) turn signal use and age group for expressways, (b) gender and if the lead vehicle range exceeded 60 m for major roads, and (c) lane width, lane offset, and lead vehicle velocity for minor roads. Finally, in a supplemental analysis, throttle holds (1 - 4 s periods of essentially no throttle change suggesting the driver may not be attending to driving) were actually more common for normal driving when a single time window (1 s) by threshold change combination (4 %) was selected. However, when settings (time windows of 1 – 4 s, thresholds of 1 – 4 %) were tailored for each age group by road class combination, throttle holds could identify when the driver was distracted.Delphi Delco Electronic Systemshttp://deepblue.lib.umich.edu/bitstream/2027.42/64458/1/102430.pd

    Analysis of a Proper-Motion Selected Sample of Stars in the Ursa Minor Dwarf Spheroidal Galaxy

    Get PDF
    We have studied the stellar population and internal structure of the core of the Ursa Minor dwarf spheroidal galaxy, using a sample of stars selected to be members based on their proper motions. In agreement with previous studies, we find Ursa Minor to be dominated by an old, metal-poor stellar population. A small number of stars with high membership probabilities lie redward of the red giant branch. The brightest (V <= 18) such stars are known to be Carbon stars, rather than metal-rich first-ascent giants. A number of stars with high membership probabilities lie blueward of the red giant branch, and are more luminous than the horizontal branch. We speculate that these are post-horizontal branch stars. There may also be one or two stars in the post-AGB phase. Spectroscopy of the candidate post-HB and post-AGB stars is required to determine their nature. We recover the internal substructure in Ursa Minor that has been noted by several authors in the last 15 years. Using a variety of two- and three-dimensional statistical tests, we conclude that this substructure is statistically significant at the 0.005 level. There is no evidence that the regions of density excess have stellar populations that differ from the main body of Ursa Minor. The crossing time for a typical density excess is only ~5 million years. They are therefore clearly not due to intermediate age star-forming bursts. We conclude that they are instead due to tidal interactions between the Galaxy and Ursa Minor.Comment: LaTeX with AASTeX style file, 22 pages with 7 figures. Accepted for publication in The Astronomical Journal (Dec. 2001

    Alternative splicing and differential gene expression in colon cancer detected by a whole genome exon array

    Get PDF
    BACKGROUND: Alternative splicing is a mechanism for increasing protein diversity by excluding or including exons during post-transcriptional processing. Alternatively spliced proteins are particularly relevant in oncology since they may contribute to the etiology of cancer, provide selective drug targets, or serve as a marker set for cancer diagnosis. While conventional identification of splice variants generally targets individual genes, we present here a new exon-centric array (GeneChip Human Exon 1.0 ST) that allows genome-wide identification of differential splice variation, and concurrently provides a flexible and inclusive analysis of gene expression. RESULTS: We analyzed 20 paired tumor-normal colon cancer samples using a microarray designed to detect over one million putative exons that can be virtually assembled into potential gene-level transcripts according to various levels of prior supporting evidence. Analysis of high confidence (empirically supported) transcripts identified 160 differentially expressed genes, with 42 genes occupying a network impacting cell proliferation and another twenty nine genes with unknown functions. A more speculative analysis, including transcripts based solely on computational prediction, produced another 160 differentially expressed genes, three-fourths of which have no previous annotation. We also present a comparison of gene signal estimations from the Exon 1.0 ST and the U133 Plus 2.0 arrays. Novel splicing events were predicted by experimental algorithms that compare the relative contribution of each exon to the cognate transcript intensity in each tissue. The resulting candidate splice variants were validated with RT-PCR. We found nine genes that were differentially spliced between colon tumors and normal colon tissues, several of which have not been previously implicated in cancer. Top scoring candidates from our analysis were also found to substantially overlap with EST-based bioinformatic predictions of alternative splicing in cancer. CONCLUSION: Differential expression of high confidence transcripts correlated extremely well with known cancer genes and pathways, suggesting that the more speculative transcripts, largely based solely on computational prediction and mostly with no previous annotation, might be novel targets in colon cancer. Five of the identified splicing events affect mediators of cytoskeletal organization (ACTN1, VCL, CALD1, CTTN, TPM1), two affect extracellular matrix proteins (FN1, COL6A3) and another participates in integrin signaling (SLC3A2). Altogether they form a pattern of colon-cancer specific alterations that may particularly impact cell motility

    GPs views on transfer of information about terminally ill patients to the out-of-hours co-operative

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>In the Netherlands, the increase in of out-of-hours care that is provided by GP co-operatives is challenging the continuity of care for the terminally ill in general practice. Aim of this study is to investigate the views of general practitioners (GPs) on the transfer of information about terminally ill patients to the GP co-operatives. GPs were asked to give their view from two different perspectives: as a GP in their daily practice and as a locum in the GP co-operative.</p> <p>Methods</p> <p>Retrospective web based questionnaire sent to all 424 GPs in the Amsterdam region.</p> <p>Results</p> <p>With a response rate of 42%, 177 physicians completed the questionnaire. Transfer of information to the GP co-operative about most of their terminally ill patients was reported by 82% of the GPs and 5% did not do so for any of their patients. A faster than foreseen deterioration of the patient's situation was the most frequently reported reason for not transferring information.</p> <p>Of those who transferred information to the GP co-operative, more than 95% reported that they provided information about the diagnosis and terminally ill status of the patient. Information about medication, patient wishes regarding treatment, and prognosis was reported by respectively 90%, 87%, and 74% of the GPs. Less than 50% of the GPs reported that they transferred information about the patient's awareness of both the diagnosis and the prognosis, about the psychosocial context, and intolerances.</p> <p>In their role as locum, over 90% of the GPs wanted to receive information about the diagnosis, the terminally ill status of the patient, the medication and the patient's wishes regarding treatment.</p> <p>Conclusions</p> <p>Although most GPs reported that they transferred information about their terminally ill patients to the GP co-operative, the content of this information varies considerably. Only 21% of the GPs, working out of hours as a locum, were satisfied with the quality of the information transferred.</p

    Molecular tests support the viability of rare earth elements as proxies for fossil biomolecule preservation

    Get PDF
    The rare earth element (REE) composition of a fossil bone reflects its chemical alteration during diagenesis. Consequently, fossils presenting low REE concentrations and/or REE profiles indicative of simple diffusion, signifying minimal alteration, have been proposed as ideal candidates for paleomolecular investigation. We directly tested this prediction by conducting multiple biomolecular assays on a well-preserved fibula of the dinosaur Edmontosaurus from the Cretaceous Hell Creek Formation previously found to exhibit low REE concentrations and steeply-declining REE profiles. Gel electrophoresis identified the presence of organic material in this specimen, and subsequent immunofluorescence and enzyme-linked immunosorbant assays identified preservation of epitopes of the structural protein collagen I. Our results thereby support the utility of REE profiles as proxies for soft tissue and biomolecular preservation in fossil bones. Based on considerations of trace element taphonomy, we also draw predictions as to the biomolecular recovery potential of additional REE profile types exhibited by fossil bones
    • …
    corecore