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Using distributed OLTP technology in a high performance storage system
The design of scaleable mass storage systems requires various system components to be distributed across multiple processors. Most of these processes maintain persistent database-type information (i.e., metadata) on the resources they are responsible for managing (e.g., bitfiles, bitfile segments, physical volumes, virtual volumes, cartridges, etc.). These processes all participate in fulfilling end-user requests and updating metadata information. A number of challenges arise when distributed processes attempt to maintain separate metadata resources with production-level integrity and consistency. For example, when requests fail, metadata changes made by the various processes must be aborted or rolled back. When requests are successful, all metadata changes must be committed together. If all metadata changes cannot be committed together for some reason, then all metadata changes must be rolled back to the previous consistent state. Lack of metadata consistency jeopardizes storage system integrity. Distributed on-line transaction processing (OLTP) technology can be applied to distributed mass storage systems as the mechanism for managing the consistency of distributed metadata. OLTP concepts are familiar to manN, industries such as banking and financial services but are less well known and understood in scientific and technical computing. As mass storage systems and other products are designed using distributed processing and data-management strategies for performance, scalability, and/or availability reasons, distributed OLTP technology can be applied to solve the inherent challenges raised by such environments. This paper discusses the benefits in using distributed transaction processing products. Design and implementation experiences using the Encina OLTP product from Transarc in the High Performance Storage System are presented in more detail as a case study for how this technology can be applied to mass storage systems designed for distributed environments
Analytic Solution of Emden-Fowler Equation and Critical Adsorption in Spherical Geometry
In the framework of mean-field theory the equation for the order-parameter
profile in a spherically-symmetric geometry at the bulk critical point reduces
to an Emden-Fowler problem. We obtain analytic solutions for the surface
universality class of extraordinary transitions in for a spherical shell,
which may serve as a starting point for a pertubative calculation. It is
demonstrated that the solution correctly reproduces the Fisher-de Gennes effect
in the limit of the parallel-plate geometry.Comment: (to be published in Z. Phys. B), 7 pages, 1 figure, uuencoded
postscript file, 8-9
New Criticality of 1D Fermions
One-dimensional massive quantum particles (or 1+1-dimensional random walks)
with short-ranged multi-particle interactions are studied by exact
renormalization group methods. With repulsive pair forces, such particles are
known to scale as free fermions. With finite -body forces (m = 3,4,...), a
critical instability is found, indicating the transition to a fermionic bound
state. These unbinding transitions represent new universality classes of
interacting fermions relevant to polymer and membrane systems. Implications for
massless fermions, e.g. in the Hubbard model, are also noted. (to appear in
Phys. Rev. Lett.)Comment: 10 pages (latex), with 2 figures (not included
Perturbations in choline metabolism cause neural tube defects in mouse embryos in vitro.
A role for choline during early stages of mammalian embryogenesis has not been established, although recent studies show that inhibitors of choline uptake and metabolism, 2-dimethylaminoethanol (DMAE), and 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3), produce neural tube defects in mouse embryos grown in vitro. To determine potential mechanisms responsible for these abnormalities, choline metabolism in the presence or absence of these inhibitors was evaluated in cultured, neurulating mouse embryos by using chromatographic techniques. Results showed that 90%-95% of 14C-choline was incorporated into phosphocholine and phosphatidylcholine (PtdCho), which was metabolized to sphingomyelin. Choline was oxidized to betaine, and betaine homocysteine methyltransferase was expressed. Acetylcholine was synthesized in yolk sacs, but 70 kDa choline acetyltransferase was undetectable by immunoblot. DMAE reduced embryonic choline uptake and inhibited phosphocholine, PtdCho, phosphatidylethanolamine (PtdEtn), and sphingomyelin synthesis. ET-18-OCH3 also inhibited PtdCho synthesis. In embryos and yolk sacs incubated with 3H-ethanolamine, 95% of recovered label was PtdEtn, but PtdEtn was not converted to PtdCho, which suggested that phosphatidylethanolamine methyltransferase (PeMT) activity was absent. In ET-18-OCH3 treated yolk sacs, PtdEtn was increased, but PtdCho was still not generated through PeMT. Results suggest that endogenous PtdCho synthesis is important during neurulation and that perturbed choline metabolism contributes to neural tube defects produced by DMAE and ET-18-OCH3
Cumulant ratios and their scaling functions for Ising systems in strip geometries
We calculate the fourth-order cumulant ratio (proposed by Binder) for the
two-dimensional Ising model in a strip geometry L x oo. The Density Matrix
Renormalization Group method enables us to consider typical open boundary
conditions up to L=200. Universal scaling functions of the cumulant ratio are
determined for strips with parallel as well as opposing surface fields.Comment: 4 pages, RevTex, one .eps figure; references added, format change
Casimir Dispersion Forces and Orientational Pairwise Additivity
A path integral formulation is used to study the fluctuation-induced
interactions between manifolds of arbitrary shape at large separations. It is
shown that the form of the interactions crucially depends on the choice of the
boundary condition. In particular, whether or not the Casimir interaction is
pairwise additive is shown to depend on whether the ``metallic'' boundary
condition corresponds to a ``grounded'' or an ``isolated'' manifold.Comment: 6 pages, RevTe
Boundary critical behavior at m-axial Lifshitz points for a boundary plane parallel to the modulation axes
The critical behavior of semi-infinite -dimensional systems with
-component order parameter and short-range interactions is
investigated at an -axial bulk Lifshitz point whose wave-vector instability
is isotropic in an -dimensional subspace of . The associated
modulation axes are presumed to be parallel to the surface, where . An appropriate semi-infinite model representing the
corresponding universality classes of surface critical behavior is introduced.
It is shown that the usual O(n) symmetric boundary term
of the Hamiltonian must be supplemented by one of the form involving a
dimensionless (renormalized) coupling constant . The implied boundary
conditions are given, and the general form of the field-theoretic
renormalization of the model below the upper critical dimension
is clarified. Fixed points describing the ordinary, special,
and extraordinary transitions are identified and shown to be located at a
nontrivial value if . The surface
critical exponents of the ordinary transition are determined to second order in
. Extrapolations of these expansions yield values of these
exponents for in good agreement with recent Monte Carlo results for the
case of a uniaxial () Lifshitz point. The scaling dimension of the surface
energy density is shown to be given exactly by , where
is the anisotropy exponent.Comment: revtex4, 31 pages with eps-files for figures, uses texdraw to
generate some graphs; to appear in PRB; v2: some references and additional
remarks added, labeling in figure 1 and some typos correcte
Apparent phase transitions in finite one-dimensional sine-Gordon lattices
We study the one-dimensional sine-Gordon model as a prototype of roughening
phenomena. In spite of the fact that it has been recently proven that this
model can not have any phase transition [J. A. Cuesta and A. Sanchez, J. Phys.
A 35, 2373 (2002)], Langevin as well as Monte Carlo simulations strongly
suggest the existence of a finite temperature separating a flat from a rough
phase. We explain this result by means of the transfer operator formalism and
show as a consequence that sine-Gordon lattices of any practically achievable
size will exhibit this apparent phase transition at unexpectedly large
temperatures.Comment: 7 pages, 4 figure
Persistence in a Stationary Time-series
We study the persistence in a class of continuous stochastic processes that
are stationary only under integer shifts of time. We show that under certain
conditions, the persistence of such a continuous process reduces to the
persistence of a corresponding discrete sequence obtained from the measurement
of the process only at integer times. We then construct a specific sequence for
which the persistence can be computed even though the sequence is
non-Markovian. We show that this may be considered as a limiting case of
persistence in the diffusion process on a hierarchical lattice.Comment: 8 pages revte
Persistence of a Continuous Stochastic Process with Discrete-Time Sampling: Non-Markov Processes
We consider the problem of `discrete-time persistence', which deals with the
zero-crossings of a continuous stochastic process, X(T), measured at discrete
times, T = n(\Delta T). For a Gaussian Stationary Process the persistence (no
crossing) probability decays as exp(-\theta_D T) = [\rho(a)]^n for large n,
where a = \exp[-(\Delta T)/2], and the discrete persistence exponent, \theta_D,
is given by \theta_D = \ln(\rho)/2\ln(a). Using the `Independent Interval
Approximation', we show how \theta_D varies with (\Delta T) for small (\Delta
T) and conclude that experimental measurements of persistence for smooth
processes, such as diffusion, are less sensitive to the effects of discrete
sampling than measurements of a randomly accelerated particle or random walker.
We extend the matrix method developed by us previously [Phys. Rev. E 64,
015151(R) (2001)] to determine \rho(a) for a two-dimensional random walk and
the one-dimensional random acceleration problem. We also consider `alternating
persistence', which corresponds to a < 0, and calculate \rho(a) for this case.Comment: 14 pages plus 8 figure
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