1,808 research outputs found
Size-Dependent Tile Self-Assembly: Constant-Height Rectangles and Stability
We introduce a new model of algorithmic tile self-assembly called
size-dependent assembly. In previous models, supertiles are stable when the
total strength of the bonds between any two halves exceeds some constant
temperature. In this model, this constant temperature requirement is replaced
by an nondecreasing temperature function that depends on the size of the smaller of the two halves. This
generalization allows supertiles to become unstable and break apart, and
captures the increased forces that large structures may place on the bonds
holding them together.
We demonstrate the power of this model in two ways. First, we give fixed tile
sets that assemble constant-height rectangles and squares of arbitrary input
size given an appropriate temperature function. Second, we prove that deciding
whether a supertile is stable is coNP-complete. Both results contrast with
known results for fixed temperature.Comment: In proceedings of ISAAC 201
Branching rules for the subgroups of the unitary group
Expressions are given in terms of simple matrices d for the reduction of the Kronecker (outer) product of two or more irreducible representations which can be characterized by Young patterns. These are then used to obtain practical formulas for branching rules. The needed matrices d can be constructed by a very efficient recursive process.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69691/2/JMAPAQ-19-3-720-1.pd
Large-Area Scintillator Hodoscope with 50 ps Timing Resolution Onboard BESS
We describe the design and performance of a large-area scintillator hodoscope
onboard the BESS rigidity spectrometer; an instrument with an acceptance of 0.3
m^{2}sr.
The hodoscope is configured such that 10 and 12 counters are respectively
situated in upper and lower layers.
Each counter is viewed from its ends by 2.5 inch fine-mesh photomultiplier
tubes placed in a stray magnetic field of 0.2 Tesla.
Various beam-test data are presented.
Use of cosmic-ray muons at ground-level confirmed 50 ps timing resolution for
each layer, giving an overall time-of-flight resolution of 70 ps rms using a
pure Gaussian resolution function.
Comparison with previous measurements on a similar scintillator hodoscope
indicates good agreement with the scaling law that timing resolution is
proportional to 1/, where is the effective
number of photoelectrons.Comment: 16 pages, 14 figure
Microscopic analysis of core deformation for nuclei in the proton-rich Xe---Nd region
A shell model study in terms of a severely truncated pseudo-SU3 basis has been made of typical rotational-limit nuclei in the proton-rich Xe---Nd region. The competition between prolate and oblate shapes and E2 properties have been studied.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22571/1/0000116.pd
MTSS1 is a critical epigenetically regulated tumor suppressor in CML
Chronic myeloid leukemia (CML) is driven by malignant stem cells that can persist despite therapy. We have identified Metastasis suppressor 1 (Mtss1/MIM) to be downregulated in hematopoietic stem and progenitor cells from leukemic transgenic SCLtTA/Bcr-Abl mice and in patients with CML at diagnosis, and Mtss1 was restored when patients achieved complete remission. Forced expression of Mtss1 decreased clonogenic capacity and motility of murine myeloid progenitor cells and reduced tumor growth. Viral transduction of Mtss1 into lineage depleted SCLtTA/Bcr-Abl bone marrow cells decreased leukemic cell burden in recipients, and leukemogenesis was reduced upon injection of Mtss1 overexpressing murine myeloid 32D cells. Tyrosine kinase inhibitor (TKI) therapy and reversion of Bcr-Abl expression increased Mtss1 expression but failed to restore it to control levels. CML patient samples revealed higher DNA methylation of specific Mtss1 promoter CpG sites that contain binding sites for Kaiso and Rest transcription factors. In summary, we identified a novel tumor suppressor in CML stem cells that is downregulated by both Bcr-Abl kinase-dependent and -independent mechanisms. Restored Mtss1 expression markedly inhibits primitive leukemic cell biology in vivo, providing a therapeutic rationale for the Bcr-Abl-Mtss1 axis to target TKI resistant CML stem cells in patients
An SU(3) model for octet baryon and meson fragmentation
The production of the octet of baryons and mesons in e^+ e^- collisions is
analysed, based on considerations of SU(3) symmetry and a simple model for
SU(3) symmetry breaking in fragmentation functions. All fragmentation
functions, D_q^h(x, Q^2), describing the fragmentation of quarks into a member
of the baryon octet (and similarly for fragmentation into members of the meson
octet) are expressed in terms of three SU(3) symmetric functions, \alpha(x,
Q^2), \beta(x, Q^2), and \gamma(x, Q^2). With the introduction of an SU(3)
breaking parameter, \lambda, the model is successful in describing
hadroproduction data at the Z pole. The fragmentation functions are then
evolved using leading order evolution equations and good fits to currently
available data at 34 GeV and at 161 GeV are obtained.Comment: 24 pages LaTeX file including 11 postscript figure file
Critical Exponents and Particle Multiplicity Distributions in High Energy Collisions
Data from the L3, Tasso, Opal and Delphi collaborations are analyzed in terms
of a statistical model of high energy collisions. The model contains a power
law critical exponent tau and Levy index alpha. These data are used to study
values of tau and alpha. The very high multiplicity events in L3, Opal and
Delphi are consistent with a model based on a Feynman-Wilson gas which has a
tail exponent tau=3/2 and alpha=1/2.Comment: 10 pages, new table adde
Systematic event generator tuning for the LHC
In this article we describe Professor, a new program for tuning model
parameters of Monte Carlo event generators to experimental data by
parameterising the per-bin generator response to parameter variations and
numerically optimising the parameterised behaviour. Simulated experimental
analysis data is obtained using the Rivet analysis toolkit. This paper presents
the Professor procedure and implementation, illustrated with the application of
the method to tunes of the Pythia 6 event generator to data from the LEP/SLD
and Tevatron experiments. These tunes are substantial improvements on existing
standard choices, and are recommended as base tunes for LHC experiments, to be
themselves systematically improved upon when early LHC data is available.Comment: 28 pages. Submitted to European Physical Journal C. Program sources
and extra information are available from
http://projects.hepforge.org/professor
Superconformal constraints for QCD conformal anomalies
Anomalous superconformal Ward identities and commutator algebra in N = 1
super-Yang-Mills theory give rise to constraints between the QCD special
conformal anomalies of conformal composite operators. We evaluate the
superconformal anomalies that appear in the product of renormalized conformal
operators and the trace anomaly in the supersymmetric spinor current and check
the constraints at one-loop order. In this way we prove the universality of QCD
conformal anomalies, which define the non-diagonal part of the anomalous
dimension matrix responsible for scaling violations of exclusive QCD amplitudes
at the next-to-leading order.Comment: 30 pages, 2 figures, LaTe
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