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Search Results: 1 - 10 of 462495 matches for " Perry A. Chodash "
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Observations of Fallout from the Fukushima Reactor Accident in San Francisco Bay Area Rainwater
Eric B. Norman, Christopher T. Angell, Perry A. Chodash
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0024330
Abstract: We have observed fallout from the recent Fukushima Dai-ichi reactor accident in samples of rainwater collected in the San Francisco Bay area. Gamma ray spectra measured from these samples show clear evidence of fission products – 131,132I, 132Te, and 134,137Cs. The activity levels we have measured for these isotopes are very low and pose no health risk to the public.
Global Well-Posedness and Long-time Asymptotics for the Defocussing Davey-Stewartson II Equation in $H^{1,1}(R^2)$
Peter A. Perry
Mathematics , 2011,
Abstract: We show that the inverse scattering map for the linear system associated with the defocussing Davey-Stewartson II equation is locally Lipschitz continuous with locally Lipschitz continuous inverse on $H^{1,1}(R^2)$. From the inverse scattering method we then obtain global well-posedness for the defocussing Davey-Stewartson II equation. We show that these global solutions are dispersive by computing their leading asymptotic behavior as $t \rightarrow \infty$ in terms of an associated linear problem.
Miura Maps and Inverse Scattering for the Novikov-Veselov Equation
Peter A. Perry
Mathematics , 2012,
Abstract: We use the inverse scattering method to construct classical solutions for the Novikov-Veselov (NV) equation, solving a problem posed by Lassas, Mueller, Siltanen, and Stahel. We exploit Bogadanov's Miura-type map which transforms solutions of the modified Novikov-Veselov (mNV) equation into solutions of the NV equation. We show that the Cauchy data of conductivity type considered by Lassas, Mueller, Siltanen, and Stahel correspond precisely to the range of the Miura map, so that it suffices to study the mNV equation. We solve the mNV equation using the scattering transform associated to the defocussing Davey-Stewartson II equation.
Distinguishing fissions of 232Th, 237Np and 238U with beta-delayed gamma rays
A. Iyengar,E. B. Norman,C. Howard,C. Angell,A. Kaplan,J. J. Ressler,P. Chodash,E. Swanberg,A. Czeszumska,B. Wang,R. Yee,H. A. Shugart
Physics , 2012, DOI: 10.1016/j.nimb.2013.03.054
Abstract: Measurements of beta-delayed gamma-ray spectra following 14-MeV neutron-induced fissions of 232Th, 237Np, and 238U were conducted at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. Spectra were collected for times ranging from 1 minute to 14 hours after irradiation. Intensity ratios of gamma-ray lines were extracted from the data that allow identification of the fissioning isotope.
Assessing Injection Techniques in the Treatment of Trigger Finger  [PDF]
John R Fowler, Lauren Ogrich, Perry Evangelista, Alyssa A Schaffer
Modern Plastic Surgery (MPS) , 2012, DOI: 10.4236/mps.2012.24020
Abstract: Background: Trigger finger is characterized by the inability to smoothly flex and extend the digit. Corticosteroids are an accepted non-surgical treatment option and can be delivered via two techniques. While the palmar approach is more commonly used, some have suggested that the mid-axial approach may be less painful for patients and yield higher intrasheath injection rates. The purpose of this study is to compare the accuracy of the palmar and midaxial approaches for delivery of corticosteroids into the flexor tendon sheath using radio-opaque dye in a cadaver model. Methods: A total of 50 injections were performed, 25 via midaxial technique and 25 via palmar technique. A one inch, 25-gauge needle was used to inject 1 mL of Isovue contrast dye into the flexor tendon sheath under live fluoroscopy. The fluoroscopic images were examined after injection to determine intrasheath versus extrasheath delivery of the dye, with visualization of contrast filling the sheath defining a successful injection. Results: The midaxial approach had a success rate of 52% compared to the conventional palmar approach success rate of 36%, p=0.5. The ring finger is the most common location of trigger finger and the rates of success were equal between groups for this digit (80%). Conclusions: Based on our findings, there is no statistical difference in the accuracy of intrasheath injection between the midaxial technique and palmar technique. The midaxial technique can be considered as an alternative to the palmar technique for trigger finger injection.
Global Solar Variations and Effects of Relativistic 2D-Hydrogen  [PDF]
G. Dreschhoff, H. Jungner, K. W. Wong, C. A. Perry
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.68114
Abstract: Characteristics of the temporal evolution of the global solar magnetic field were found to display a 2-step cycling mode consistent with a pattern of a fundamental harmonic progression underlying all solar cycles at all times and having its seat in the fusion region of the core via nuclear magnetic resonance as part of the hydrogen and helium fusion chain. In addition to the three principal zones in the interior of the sun, core, radiative zone, and convection zone, a sub-surface layer is being suggested to take part in the processes of varying solar activity, which would be an extension of relativistic 2D hydrogen being formed throughout the plasma body under the influence of pressure waves originating in the core. The major participants confined to such a 2D layer is for the most part 2D hydrogen particularly in its form of relativistic 2D hydrogen, where the Bohratom binding energies are replaced by binding energies in the range of Eo = 0.5 MeV. For this reason it is conjectured that this condition lends itself to providing contributions to (a) the energy release including 0.5 MeV and lower energy γ-photons as well as (b) superimposing a radial component to the global dipole field.
Cdc25 and Wee1: analogous opposites?
Jennifer A Perry, Sally Kornbluth
Cell Division , 2007, DOI: 10.1186/1747-1028-2-12
Abstract: Entry into mitosis is driven by the activity of the cell cycle regulatory kinase, Cdc2/Cyclin B, which oscillates throughout the cell cycle, peaking in mitosis and dropping during interphase. This precise temporal regulation is ensured by the coordinate action of positive and negative regulators of Cdc2 catalytic activity and localization. During interphase, once Cyclin B synthesis has begun, the newly formed Cdc2/Cyclin B complexes are kept inactive by phosphorylation on Cdc2 at two residues, Thr14 and Tyr15. These phosphorylations are catalyzed by the Myt1 and Wee1 kinases, which are located at cytoplasmic membranes and within the nucleus, respectively. At the G2/M transition, Myt1 and Wee1 are inactivated while the dual specificity phosphatase, Cdc25, is activated. Cdc25 dephosphorylates Thr14 and Tyr15, allowing for activation of the Cdc2/Cyclin B complex and entry into mitosis [1,2].Just as Cdc2/Cyclin B activation is highly regulated, both Wee1 and Cdc25 activity are tightly controlled through the cell cycle. Interestingly, in considering what we know currently about the regulation of Wee1 and Cdc25, it appears that these two molecules are similarly regulated, though their activities oscillate in opposition to one another, consistent with their respective roles in inhibiting or activating mitotic entry. Both are phosphorylated and bind to 14-3-3 during interphase; both are controlled directly by other mitotic kinases, including Polo-like kinases and Cdc2/Cyclin B itself. Integrating data from yeast, Xenopus, and mammalian cells over the last decade, we can now take a comprehensive look at how cells coordinate the opposing actions of Wee1 and Cdc25 via post-translational modifications in order to regulate Cdc2/Cyclin B and entry into mitosis.The Cdc25 family of phosphatases is responsible for dephosphorylating inhibitory Tyr and Thr residues on cyclin-dependent kinases in order to promote their activation. Three isoforms (A, B and C) have been identified in mam
Dynamic D8-branes in IIA string theory
A. Chamblin,M. J. Perry
Physics , 1997,
Abstract: In this paper we perform a detailed investigation of the Dirichlet eight-brane of the Type IIA string theory, when the effects of gravity are included. In particular, consider what happens when one allows the ten-form field strength $F_{10}$ to vary discontinuously across the worldvolume of the brane. Since the ten-form is constant on each side of the brane ($d*F_{10} = 0$), a variation in the bulk term $\int F_{10}*F_{10}$ gives rise to a net pressure acting on the surface of the brane. This means that the infinite `planar' eight-brane is no longer a static configuration with these boundary conditions. Instead, a static configuration is found only when the brane `compactifies' to the topology of an eight-sphere, $S^8$. These spherical eight-branes are thus bubbles which form boundaries between different phases of the massive Type IIA supergravity theory. While these bubbles are generically unstable and will want to expand (or contract), we show that in certain cases there is a critical radius, $r_c$, at which the (inward) tension of the brane is exactly counterbalanced by the (outward) force exerted by the pressure terms. Intuitively, these `compactified' branes are just spherical bubbles where the effective cosmological constant jumps by a discrete amount as you cross a brane worldsheet. We argue that these branes will be unstable to various semi-classical decay processes. We discuss the implications of such processes for the open strings which have endpoints on the eight-brane.
Inverse scattering results for manifolds hyperbolic near infinity
D. Borthwick,P. A. Perry
Mathematics , 2009,
Abstract: We study the inverse resonance problem for conformally compact manifolds which are hyperbolic outside a compact set. Our results include compactness of isoresonant metrics in dimension two and of isophasal negatively curved metrics in dimension three. In dimensions four or higher we prove topological finiteness theorems under the negative curvature assumption.
Global solutions for the zero-energy Novikov-Veselov equation by inverse scattering
Michael Music,Peter A. Perry
Mathematics , 2015,
Abstract: Using the inverse scattering method, we construct global solutions to the Novikov-Veselov equation for real-valued decaying initial data q with the property that the associated Schrodinger operator with potential q is nonnegative. Such initial data are either critical (an arbitrarily small perturbation of the potential makes the operator nonpositive) or subcritical (sufficiently small perturbations of the potential preserve non-negativity of the operator). Previously, Lassas, Mueller, Siltanen and Stahel proved global existence for critical potentials, also called potentials of "conductivity type." We extend their results to include the much larger class of subcritical potentials. We show that the subcritical potentials form an open set and that the critical potentials form the nowhere dense boundary of this open set. Our analysis draws on previous work of the first author and on ideas of P. G. Grinevich and S. V. Manakov.
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