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Search Results: 1 - 10 of 224662 matches for " Peterson R.; "
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Radiation-induced errors in memory chips
Peterson, R. J.;
Brazilian Journal of Physics , 2003, DOI: 10.1590/S0103-97332003000200013
Abstract: we have measured probabilities for proton, neutron and pion beams from accelerators to induce temporary or soft errors in a wide range of modern 16 mb and 64 mb dram memory chips, typical of those used in aircraft electronics. relations among the cross sections for these particles are deduced. measurement of alpha particle yields from pions on aluminum, as a surrogate for silicon, indicate that these reaction products are the proximate cause of the charge deposition resulting in errors.
Darwin ¢ € s Legacy: What Evolution Means Today
Peterson, Gregory R.
Ars Disputandi : the Online Journal for Philosophy of Religion , 2004,
Abstract:
Radiation-induced errors in memory chips
Peterson R. J.
Brazilian Journal of Physics , 2003,
Abstract: We have measured probabilities for proton, neutron and pion beams from accelerators to induce temporary or soft errors in a wide range of modern 16 Mb and 64 Mb DRAM memory chips, typical of those used in aircraft electronics. Relations among the cross sections for these particles are deduced. Measurement of alpha particle yields from pions on aluminum, as a surrogate for silicon, indicate that these reaction products are the proximate cause of the charge deposition resulting in errors.
Phase statistics and the Hamiltonian
I. R. Peterson
Physics , 2002,
Abstract: Modern statistical thermodynamics retains the concepts employed by Landau of the order parameter and a functional depending on it, now called the Hamiltonian. The present paper investigates the limits of validity for the use of the functional to describe the statistical correlations of a thermodynamic phase, particularly in connection with the experimentally accessible scattering of X-rays, electrons and neutrons. Guggenheim's definition for the functional is applied to a generalized system and the associated paradoxes are analyzed. In agreement with Landau's original hypothesis, it is demonstrated that the minimum is equal to the thermodynamic free energy, requiring no fluctuation correction term. Although the fluctuation amplitude becomes large in the vicinity of a second-order phase transition in low dimensionalities, it does not diverge and the equilibrium order parameter remains well defined.
The Gibbs Representation of 3D Rotations
Ian R. Peterson
Computer Science , 2001,
Abstract: This paper revisits the little-known Gibbs-Rodrigues representation of rotations in a three-dimensional space and demonstrates a set of algorithms for handling it. In this representation the rotation is itself represented as a three-dimensional vector. The vector is parallel to the axis of rotation and its three components transform covariantly on change of coordinates. The mapping from rotations to vectors is 1:1 apart from computation error. The discontinuities of the representation require special handling but are not problematic. The rotation matrix can be generated efficiently from the vector without the use of transcendental functions, and vice-versa. The representation is more efficient than Euler angles, has affinities with Hassenpflug's Argyris angles and is very closely related to the quaternion representation. While the quaternion representation avoids the discontinuities inherent in any 3-component representation, this problem is readily overcome. The present paper gives efficient algorithms for computing the set of rotations which map a given vector to another of the same length and the rotation which maps a given pair of vectors to another pair of the same length and subtended angle.
Impact of Non-Clinical Years on Surgery Residents’ Technical Skills: Evaluation of a Technical Skills Refresher Curriculum  [PDF]
Ross E. Willis, Kent R. Van Sickle, Richard M. Peterson
Surgical Science (SS) , 2013, DOI: 10.4236/ss.2013.42025
Abstract:

We ascertained the opinions of residents and faculty regarding technical skills decay during non-clinical training years and evaluated the effectiveness of a technical skills refresher curriculum (TSRC) offered to residents in the month prior to rejoining clinical training years. 32 faculty and 14 residents completed surveys which gleaned opinions regarding technical skills decay during non-clinical years. Six residents completed a TSRC during the month prior to rejoining clinical training. We compared clinical evaluations of the residents who completed the TSRC to residents who rejoined clinical training prior to the implementation of the curriculum. Surveys indicated that residents and faculty believe that non-clinical years have a slightly negative impact on technical skills and residents who completed dedicated research years would require up to 4 months for technical skills to return to the level of their non-research peers. Residents who completed the TSRC reported having significantly higher comfort levels with their technical skills after the curriculum (p < 0.048). Clinical evaluations of these residents were significantly higher than the cohort that completed research years prior to curriculum implementation (p < 0.041). The TSRC is a viable method of preparing residents for rejoining clinical training.

Gastrointestinal Neoplasia Associated with Bowel Parasitosis: Real or Imaginary?
Michael R. Peterson,Noel Weidner
Journal of Tropical Medicine , 2011, DOI: 10.1155/2011/234254
Abstract: Several parasitic species are well known to have carcinogenic properties, namely; Schistosoma hematobium (squamous cell carcinoma of the bladder) and the liver flukes Opisthorchis and Chlonorchis (cholangiocarcinoma). A large number of parasites are known to colonize the gastrointestinal tract. We sought to review the evidence that implicates these parasites in gastrointestinal neoplasia. Schistosoma japonicum, which is endemic primarily in east Asia, has been shown in multiple studies to convey a mildly increased risk of colorectal adenocarcinoma. The data supporting a causative role for Schistosoma mansoni in colorectal or other neoplastic processes are less convincing, limited primarily to small case-control studies and case series. Reports of possible associations between other gastrointestinal parasites (e.g., E. histolytica and A. lumbricoides) and neoplasia may be found in the literature but are limited to individual cases. We conclude that, other than S. japonicum and to a lesser extent S. mansoni, there is little evidence of an association between gastrointestinal parasites and neoplasia. 1. Introduction A wide variety of parasites are known to cause disease in the human gastrointestinal tract, including some species that are very prevalent over a large geographical area. Human parasites are traditionally divided into two broad groups, protozoa and helminths. The phylum protozoa includes a number of gastrointestinal parasites, with some notable members such as Entamoeba histolytica, Giardia lamblia, Cryptosporidia, and Trypansoma cruzi. The multi cellular helminths are further divided into three groups, cestodes/tapeworms (e.g., Taenia solium and Diphyllobothrium latum), nematodes/round worms (e.g., Ascaris lumbricoides, Strongyloides stercoralis, and Enterobius vermicularis), and trematodes/flukes (e.g., Schistosoma japonicum and Schistosoma mansoni). There has long been scientific interest in exploring the possibility of infectious causes of cancer, including bacterial, viral, and parasitic causes. Mathematical modeling has estimated that approximately 16% of cancers throughout the world may be attributable to infection [1]. The fraction of this that is attributable to parasitic infection is currently unknown. Historically, one of the first proposed links between parasitosis and cancer garnered Dr. J. A. G. Fibiger the Nobel Prize in 1926 for his work demonstrating that mice infected with the nematode Spiroptera later developed stomach cancer. This work was later debunked on at least two levels. It was shown that the risk of “cancer” was only
The Effects of Landau level mixing on the fractional quantum Hall effect in monolayer Graphene
Michael R. Peterson,Chetan Nayak
Physics , 2014, DOI: 10.1103/PhysRevLett.113.086401
Abstract: We report results of exact diagonalization studies of the spin- and valley-polarized fractional quantum Hall effect in the $N=0$ and 1 Landau levels in graphene. We use an effective model that incorporates Landau level mixing to lowest-order in the parameter $\kappa = \frac{e^2/\epsilon\ell}{\hbar v_F/\ell}=\frac{e^2}{\epsilon v_F\hbar}$ which is magnetic field independent and can only be varied through the choice of substrate. We find Landau level mixing effects are negligible in the $N=0$ Landau level for $\kappa\lesssim 2$. In fact, the lowest Landau level projected Coulomb Hamiltonian is a better approximation to the real Hamiltonian for graphene than it is for semiconductor based quantum wells. Consequently, the principal fractional quantum Hall states are expected in the $N=0$ Landau level over this range of $\kappa$. In the $N=1$ Landau level, fractional quantum Hall states are expected for a smaller range of $\kappa$ and Landau level mixing strongly breaks particle-hole symmetry producing qualitatively different results compared to the $N=0$ Landau level. At half-filling of the $N=1$ Landau level, we predict the anti-Pfaffian state will occur for $\kappa \sim 0.25$-$0.75$.
More Realistic Hamiltonians for the Fractional Quantum Hall Regime in GaAs and Graphene
Michael R. Peterson,Chetan Nayak
Physics , 2013, DOI: 10.1103/PhysRevB.87.245129
Abstract: We construct an effective Hamiltonian for electrons in the fractional quantum Hall regime for GaAs and graphene that takes into account Landau level mixing (for both GaAs and graphene) and subband mixing (for GaAs, due to the nonzero width of the quantum well). This mixing has the important qualitative effect of breaking particle-hole symmetry as well as renormalizing the strength of the interparticle interactions. Both effects could have important consequences for the prospect that the fractional quantum Hall effect at $\nu=5/2$ is described by states that support non-Abelian excitations such as the Moore-Read Pfaffian or anti-Pfaffian states. For GaAs, Landau level and subband mixing break particle-hole symmetry in all Landau levels and subband mixing, due to finite thickness, causes additional short-distance softening of the Coulomb interaction, further renormalizing the Hamiltonian; additionally, the Landau level and subband energy spacings are comparable so it is crucial to consider both effects simultaneously. We find that in graphene, Landau level mixing only breaks particle-hole symmetry outside of the lowest Landau level ($N\neq0$). Landau level mixing is likely to be especially important in graphene since the Landau level mixing parameter is independent of the external magnetic field and is of order one. Our realistic Hamiltonians will serve as starting points for future numerical studies.
Distance between two random k-out digraphs, with and without preferential attachment
Nicholas R. Peterson,Boris Pittel
Mathematics , 2013,
Abstract: A random k-out mapping (digraph) on [n] is generated by choosing k random images of each vertex one at a time, subject to a "preferential attachment" rule: the current vertex selects an image i with probability proportional to a given parameter \alpha = \alpha(n) plus the number of times i has already been selected. Intuitively, the larger \alpha gets, the closer the resulting k-out mapping is to the uniformly random k-out mapping. We prove that \alpha = \Theta(n^{1/2}) is the threshold for \alpha growing "fast enough" to make the random digraph approach the uniformly random digraph in terms of the total variation distance. We also determine an exact limit for this distance for \alpha = \beta n^{1/2}.
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