340 research outputs found
An Algorithm for Obtaining Reliable Priors for Constrained-Curve Fits
We introduce the ``Sequential Empirical Bayes Method'', an adaptive
constrained-curve fitting procedure for extracting reliable priors. These are
then used in standard augmented-chi-square fits on separate data. This better
stabilizes fits to lattice QCD overlap-fermion data at very low quark mass
where a priori values are not otherwise known. We illustrate the efficacy of
the method with data from overlap fermions, on a quenched
lattice with spatial size La=3.2 fm and pion mass as low as 180 MeV.Comment: Lattice2003(machine), 3 pages, 3 figure
Internal anatomy of a fossilized embryonic stage of the Cambrian-Ordovician scalidophoran Markuelia
The Wangcun fossil Lagerstätte in Hunan, South China, has yielded hundreds of fossilized embryos of Markuelia hunanensis representing different developmental stages. Internal tissues have only rarely been observed, impeding further understanding of the soft tissue anatomy, phylogenetic affinity and evolutionary significance of Markuelia. In this study, we used synchrotron radiation X-ray tomographic microscopy (SRXTM) to study a new collection of fossil embryos from the Wangcun fossil Lagerstätte. We describe specimens exhibiting a spectrum of preservation states, the best of which preserves palisade structures underneath the cuticle of the head and tail, distinct from patterns of centripetal mineralization of the cuticle and centrifugal mineralization of hypha-like structures, seen elsewhere in this specimen and other fossils within the same assemblage. Our computed tomographic reconstruction of these mineralization phases preserves the gross morphology of (i) longitudinal structures associated with the tail spines, which we interpret as the proximal ends of longitudinal muscles, and (ii) a ring-shaped structure internal to the introvert, which we interpret as a ring-shaped brain, as anticipated of the cycloneuralian affinity of Markuelia. This is the first record of a fossilized nervous system in a scalidophoran, and the first instance in Orsten-style preservation, opening the potential for further such records within this widespread mode of high-fidelity three-dimensional preservation
Quenched Chiral Log and Light Quark Mass from Overlap Fermions
We study the quenched chiral behavior of the pion with mass as low as
MeV. The calculation is done on a quenched lattice of size
and fm with 80 configurations using overlap fermions
and an improved gauge action. Using an improved constrained curve fitting
technique, we find that the ground state pseudoscalar mass versus bare quark
mass behavior is well controlled with small statistical errors; this permits a
reliable fit of the quenched chiral log effects, a determination of the chiral
log parameter (), and an estimate of the renormalized mass of
the light quark ().Comment: Lattice2002(spectrum), 3 pages, 3 figure
Venice: Exploring Server Architectures for Effective Resource Sharing
Consolidated server racks are quickly becoming the backbone of IT infrastructure for science, engineering, and business, alike. These servers are still largely built and organized as when they were distributed, individual entities. Given that many fields increasingly rely on analytics of huge datasets, it makes sense to support flexible resource utilization across servers to improve cost-effectiveness and performance. We introduce Venice, a family of data-center server architectures that builds a strong communication substrate as a first-class resource for server chips. Venice provides a diverse set of resource-joining mechanisms that enables user programs to efficiently leverage non-local resources.
To better understand the implications of design decisions
about system support for resource sharing we have constructed a hardware prototype that allows us to more accurately measure end-to-end performance of at-scale applications and to explore tradeoffs among performance, power, and resource-sharing transparency. We present results from our initial studies analyzing these tradeoffs when sharing memory, accelerators, or NICs. We find that it is particularly important to reduce or hide latency, that data-sharing access patterns should match the features of the communication channels employed, and that inter-channel collaboration can be exploited for better performance
Bis{4,4′-[oxalylbis(azanediyl)]dipyridinium} octamolybdate
In the crystal structure of the title compound, (C12H12N4O2)2[Mo8O26], the amino and pyridinium groups of the N
1,N
2-di(pyridinium-4-yl)oxalamide cations are hydrogen bonded to the O atoms of the centrosymmetric isopolyoxometalate β-[Mo8O26]4− anions, forming a three-dimensional supramolecular architecture
A Weighted Two-Level Bregman Method with Dictionary Updating for Nonconvex MR Image Reconstruction
Nonconvex optimization has shown that it needs substantially fewer measurements than l1 minimization for exact recovery under fixed transform/overcomplete dictionary. In this work, two efficient numerical algorithms which are unified by the method named weighted two-level Bregman method with dictionary updating (WTBMDU) are proposed for solving lp optimization under the dictionary learning model and subjecting the fidelity to the partial measurements. By incorporating the iteratively reweighted norm into the two-level Bregman iteration method with dictionary updating scheme (TBMDU), the modified alternating direction method (ADM) solves the model of pursuing the approximated lp-norm penalty efficiently. Specifically, the algorithms converge after a relatively small number of iterations, under the formulation of iteratively reweighted l1 and l2 minimization. Experimental results on MR image simulations and real MR data, under a variety of sampling trajectories and acceleration factors, consistently demonstrate that the proposed method can efficiently reconstruct MR images from highly undersampled k-space data and presents advantages over the current state-of-the-art reconstruction approaches, in terms of higher PSNR and lower HFEN values
Improved Measure of Local Chirality
It is popular to probe the structure of the QCD vacuum indirectly by studying
individual fermion eigenmodes, because this provides a natural way to filter
out UV fluctuations. The double-peaking in the distribution of the local chiral
orientation parameter (X) has been offered as evidence, by some, in support of
a particular model of the vacuum. Here we caution that the X-distribution
peaking varies significantly with various versions of the definition of X.
Furthermore, each distribution varies little from that resulting from a random
reshuffling of the left-handed (and independently the right-handed) fields,
which destroys any QCD-induced left-right correlation; that is, the
double-peaking is mostly a phase-space effect. We propose a new universal
definition of the X parameter whose distribution is uniform for randomly
reshuffled fields. Any deviations from uniformity for actual data can then be
directly attributable to QCD-induced dynamics. We find that the familiar double
peak disappears.Comment: Lattice 2004(topology), Fermilab, June 21-26, 2004; 3 pages, 4
figure
A Single Tri-Epitopic Antibody Virtually Recapitulates the Potency of a Combination of Three Monoclonal Antibodies in Neutralization of Botulinum Neurotoxin Serotype A.
The standard of treatment for botulism, equine antitoxin, is a foreign protein with associated safety issues and a short serum half-life which excludes its use as a prophylactic antitoxin and makes it a less-than-optimal therapeutic. Due to these limitations, a recombinant monoclonal antibody (mAb) product is preferable. It has been shown that combining three mAbs that bind non-overlapping epitopes leads to highly potent botulinum neurotoxin (BoNT) neutralization. Recently, a triple human antibody combination for BoNT/A has demonstrated potent toxin neutralization in mouse models with no serious adverse events when tested in a Phase I clinical trial. However, a triple antibody therapeutic poses unique development and manufacturing challenges. Thus, potentially to streamline development of BoNT antitoxins, we sought to achieve the potency of multiple mAb combinations in a single IgG-based molecule that has a long serum half-life. The design, production, and testing of a single tri-epitopic IgG1-based mAb (TeAb) containing the binding sites of each of the three parental BoNT/A mAbs yielded an antibody of nearly equal potency to the combination. The approach taken here could be applied to the design and creation of other multivalent antibodies that could be used for a variety of applications, including toxin elimination
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