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Full-Text Articles in Physical Sciences and Mathematics

Field Line Distribution Of Density At L=4.8 Inferred From Observations By Cluster, R E. Denton, P Décréau, M J. Engebretson, F Darrouzet Feb 2009

Field Line Distribution Of Density At L=4.8 Inferred From Observations By Cluster, R E. Denton, P Décréau, M J. Engebretson, F Darrouzet

Dartmouth Scholarship

For two events observed by the CLUSTER space- craft, the field line distribution of mass density ρ was inferred from Alfve ́n wave harmonic frequencies and compared to the electron density ne from plasma wave data and the oxy- gen density nO+ from the ion composition experiment. In one case, the average ion mass M≡ρ/ne was about 5amu (28 October 2002), while in the other it was about 3 amu (10 September 2002). Both events occurred when the CLUSTER 1 (C1) spacecraft was in the plasmatrough. Nevertheless, the electron density ne was significantly lower for the first event (ne =8 …


Short Telomeres In Hatchling Snakes: Erythrocyte Telomere Dynamics And Longevity In Tropical Pythons, Beata Ujvari, Thomas Madsen Jan 2009

Short Telomeres In Hatchling Snakes: Erythrocyte Telomere Dynamics And Longevity In Tropical Pythons, Beata Ujvari, Thomas Madsen

Faculty of Science - Papers (Archive)

Background: Telomere length (TL) has been found to be associated with life span in birds and humans. However, other studies have demonstrated that TL does not affect survival among old humans. Furthermore, replicative senescence has been shown to be induced by changes in the protected status of the telomeres rather than the loss of TL. In the present study we explore whether age- and sex-specific telomere dynamics affect life span in a long-lived snake, the water python (Liasis fuscus). Methodology/Principal Findings: Erythrocyte TL was measured using the Telo TAGGG TL Assay Kit (Roche). In contrast to other vertebrates, TL of …


Cross-Basin Comparison Of Phosphorus Stress And Nitrogen Fixation In Trichodesmium, Annette M. Hynes, P. Dreux Chappell, Sonya T. Dyhrman, Scott C. Doney, Eric A. Webb Jan 2009

Cross-Basin Comparison Of Phosphorus Stress And Nitrogen Fixation In Trichodesmium, Annette M. Hynes, P. Dreux Chappell, Sonya T. Dyhrman, Scott C. Doney, Eric A. Webb

OES Faculty Publications

We investigated the phosphorus (P) status and N2 fixation rates of Trichodesmium populations from the North Pacific, western South Pacific, and western North Atlantic. Colonies of Trichodesmium were collected and analyzed for endogenous alkaline phosphatase (AP) activity using enzyme-labeled fluorescence ( ELF) and for nitrogenase activity using acetylene reduction. AP hydrolyzes dissolved inorganic phosphate (DIP) from dissolved organic phosphorus and is active in Trichodesmium colonies experiencing P stress. Across multiple stations in the subtropical North and South Pacific, there was low to moderate ELF labeling in Trichodesmium, although labeling was present in other taxa. In contrast, Trichodesmium ELF …


A Single Particle Impact Model For Motion In Avalanches, J. J. P. Veerman, Dacian Daescu, M. J. Romero-Vallés, P. J. Torres Jan 2009

A Single Particle Impact Model For Motion In Avalanches, J. J. P. Veerman, Dacian Daescu, M. J. Romero-Vallés, P. J. Torres

Mathematics and Statistics Faculty Publications and Presentations

We describe the global behavior of the dynamics of a particle bouncing down an inclined staircase. For small inclinations all orbits eventually stop (independent of the initial condition). For large enough inclinations all orbits end up accelerating indefinitely (also independent of the initial conditions). There is an interval of inclinations of positive length between these two. In that interval the behavior of an orbit depends on its initial condition. In addition to stopping and accelerating orbits, there are also orbits with speeds bounded away from both zero and infinity. A second hallmark of the dynamics is that the orbits going …


Dynamics And Rheology Of Biaxial Liquid Crystal Polymers, Sarthok K. Sircar Jan 2009

Dynamics And Rheology Of Biaxial Liquid Crystal Polymers, Sarthok K. Sircar

Theses and Dissertations

In this thesis we derive a hydrodynamical kinetic theory to study the orientational response of a mesoscopic system of nematic liquid crystals in the presence of an external flow field. Various problems have been attempted in this direction. First, we understand the steady-state behavior of uniaxial LCPs under an imposed elongational flow, electric and magnetic field respectively. We show that (1) the Smoluchowski equation can be cast into a generic form, (2) the external field is parallel to one of the eigenvectors of the second moment tensor, and (3) the steady state probability density function is of the Boltzmann type. …