665 research outputs found

    Some considerations on coastal processes relevant to sea level rise

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    The effects of potential sea level rise on the shoreline and shore environment have been briefly examined by considering the interactions between sea level rise and relevant coastal processes. These interactions have been reviewed beginning with a discussion of the need to reanalyze previous estimates of eustatic sea level rise and compaction effects in water level measurement. This is followed by considerations on sea level effects on coastal and estuarine tidal ranges, storm surge and water level response, and interaction with natural and constructed shoreline features. The desirability to reevaluate the well known Bruun Rule for estimating shoreline recession has been noted. The mechanics of ground and surface water intrusion with reference to sea level rise are then reviewed. This is followed by sedimentary processes in the estuaries including wetland response. Finally comments are included on some probable effects of sea level rise on coastal ecosystems. These interactions are complex and lead to shoreline evolution (under a sea level rise) which is highly site-specific. Models which determine shoreline change on the basis of inundation of terrestrial topography without considering relevant coastal processes are likely to lead to erroneous shoreline scenarios, particularly where the shoreline is composed of erodible sedimentary material. With some exceptions, present day knowledge of shoreline response to hydrodynamic forcing is inadequate for long-term quantitative predictions. A series of interrelated basic and applied research issues must be addressed in the coming decades to determine shoreline response to sea level change with an acceptable degree of confidence. (PDF contains 189 pages.

    Deadlock Free Message Routing in Multiprocessor Interconnection Networks

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    A deadlock-free routing algorithm can be generated for arbitrary interconnection networks using the concept of virtual channels. A necessary and sufficient condition for deadlockfree routing is the absence of cycles in the channel dependency graph. Given an arbitrary network and a routing function, the cycles of the channel dependency graph can be removed by splitting physical channels into groups of virtual channels. This method is used to develop deadlock-free routing algorithms for k-ary n-cubes, for cube connected cycles, and for shuffleexchange networks

    High order magnon bound states in the quasi-one-dimensional antiferromagnet α\alpha-NaMnO2_2

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    Here we report on the formation of two and three magnon bound states in the quasi-one-dimensional antiferromagnet α\alpha-NaMnO2_2, where the single-ion, uniaxial anisotropy inherent to the Mn3+^{3+} ions in this material provides a binding mechanism capable of stabilizing higher order magnon bound states. While such states have long remained elusive in studies of antiferromagnetic chains, neutron scattering data presented here demonstrate that higher order n>2n>2 composite magnons exist, and, specifically, that a weak three-magnon bound state is detected below the antiferromagnetic ordering transition of NaMnO2_2. We corroborate our findings with exact numerical simulations of a one-dimensional Heisenberg chain with easy-axis anisotropy using matrix-product state techniques, finding a good quantitative agreement with the experiment. These results establish α\alpha-NaMnO2_2 as a unique platform for exploring the dynamics of composite magnon states inherent to a classical antiferromagnetic spin chain with Ising-like single ion anisotropy.Comment: 5 pages, 4 figure

    Modeling Tube-Forming of an Austenitic Stainless Steel with Exploitation of Martensite Evolution

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    Within the last years the industrial manufacturing of tubes has developed to an increasingly complex process. In particular, during the forming procedure of sheets made of austenitic stainless steel, the increase and the content of strain-induced martensite needs to be controlled in order to achieve the optimal structural properties of the manufactured tube with respect to very-high-cycle fatigue (VHCF). On the basis of experimental investigations this contribution deals with the numerical simulation of the forming process with special consideration of the martensite ratio as a function of temperature and deformation field. A convenient approach of modeling the martensite evolution as well as the extension of this model to polyaxial states of stress and a comparison with experimental results is presented

    Nonequilibrium brittle fracture propagation: Steady state, oscillations and intermittency

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    A minimal model is constructed for two-dimensional fracture propagation. The heterogeneous process zone is presumed to suppress stress relaxation rate, leading to non-quasistatic behavior. Using the Yoffe solution, I construct and solve a dynamical equation for the tip stress. I discuss a generic tip velocity response to local stress and find that noise-free propagation is either at steady state or oscillatory, depending only on one material parameter. Noise gives rise to intermittency and quasi-periodicity. The theory explains the velocity oscillations and the complicated behavior seen in polymeric and amorphous brittle materials. I suggest experimental verifications and new connections between velocity measurements and material properties.Comment: To appear in Phys. Rev. Lett., 6 pages, self-contained TeX file, 3 postscript figures upon request from author at [email protected] or [email protected], http://cnls-www.lanl.gov/homepages/rafi/rafindex.htm

    Phytoplasmas associated with grapevine yellows in Virginia belong to group 16SrI, subgroup A (tomato big bud phytoplasma subgroup), and group 16SrIII, new subgroup I

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    Grapevine yellows disease in Virginia closely resembles flavescence doree and other grapevine yellows diseases, but the phytoplasmas infecting grapevines in Virginia are distinct from other grapevine yellows pathogens. RFLP analysis of PCR-amplified 16S rDNA indicated that a Virginia grapevine yellows phytoplasma, designated VGYIII was distinct from all other phytoplasmas studied, but was most closely related to spirea stunt (SP1), walnut witches' broom (WWB), and poinsettia branch-inducing (PoiB 1) phytoplasmas in subgroups E, G, and H, respectively, of 16S I RNA group 16SrIII. RFLP analysis also indicated the existence of sequence heterogeneity between the two rRNA operons in the genomes of SP 1 and WWB. Based on the results from RFLP and sequence comparisons with other group 16SrIII phytoplasmas, the VGYIII phytoplasma was classified in a new subgroup, designated 16SrIII-I. A second phytoplasma (VGYI) was detected in cultivated grapevines(Vitis vinifera L.) and in wild grapevines(V. riparia Michx.) and identified as a member of subgroup 16SrI-A. There was no evidence of flavescence doree, bois noir, or Australian grapevine yellows phytoplasmas in Virginia

    The Effectiveness of Text Message Reminder- Recalls on Human Papilloma Virus Vaccination Coverage in Georgia

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    Background: Routine vaccination against Human Papilloma Virus (HPV), the main cause of cervical cancer, is recommended by the Advisory Committee on Immunization Practices for adolescents ages 11 to 12 years, yet vaccine coverage remains low. The Georgia Comprehensive Cancer Control Program and Georgia Immunization Program implemented and evaluated a textmessaging campaign aimed at improving HPV vaccination coverage, using the Georgia Immunization Registry (GRITS). Methods: The text message reminder-recall campaign, aimed at the parents of adolescents 9 – 18 years, was launched in July 2015. A total of 208,792 adolescents in the GRITS database met the inclusion criterion, receipt of at least one dose of the threedose series HPV vaccine. We determined the rate of HPV vaccine series completion for adolescents with a valid parent/guardian mobile phone number and for those without. Results: A total of 9,711 text messages were successfully sent to parents of adolescents 9 – 18 years. HPV vaccine series completion was 16% among adolescents whose parent/guardian received a text message as compared to 7% among those who did not. Conclusions: Text message reminder-recalls have a positive effect on HPV vaccine series coverage for adolescents in Georgia. Text messaging reminder-recalls may be an effective strategy to improve HPV vaccination coverage statewide
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