4,702 research outputs found
Reconstruction of protein structures from a vectorial representation
We show that the contact map of the native structure of globular proteins can
be reconstructed starting from the sole knowledge of the contact map's
principal eigenvector, and present an exact algorithm for this purpose. Our
algorithm yields a unique contact map for all 221 globular structures of
PDBselect25 of length . We also show that the reconstructed contact
maps allow in turn for the accurate reconstruction of the three-dimensional
structure. These results indicate that the reduced vectorial representation
provided by the principal eigenvector of the contact map is equivalent to the
protein structure itself. This representation is expected to provide a useful
tool in bioinformatics algorithms for protein structure comparison and
alignment, as well as a promising intermediate step towards protein structure
prediction.Comment: 4 pages, 1 figur
Three-dimensional N=4 supersymmetry in harmonic N=3 superspace
We consider the map of three-dimensional N=4 superfields to N=3 harmonic
superspace. The left and right representations of the N=4 superconformal group
are constructed on N=3 analytic superfields. These representations are
convenient for the description of N=4 superconformal couplings of the Abelian
gauge superfields with hypermultiplets. We analyze the N=4 invariance in the
non-Abelian N=3 Yang-Mills theory.Comment: Latex file, 22 pages; v2 two references adde
Cosmological perturbations in a healthy extension of Horava gravity
In Horava's theory of gravity, Lorentz symmetry is broken in exchange for
renormalizability, but the original theory has been argued to be plagued with
problems associated with a new scalar mode stemming from the very breaking of
Lorentz symmetry. Recently, Blas, Pujolas, and Sibiryakov have proposed a
healthy extension of Horava gravity, in which the behavior of the scalar mode
is improved. In this paper, we study scalar modes of cosmological perturbations
in extended Horava gravity. The evolution of metric and density perturbations
is addressed analytically and numerically. It is shown that for vanishing
non-adiabatic pressure of matter the large scale evolution of cosmological
perturbations converges to that described by a single constant, , which
is an analog of a curvature perturbation on the uniform-density slicing
commonly used in usual gravitational theories. The subsequent evolution is thus
determined completely by the value of .Comment: 10 pages, 4 figures; v2: published versio
Intelligent Financial Fraud Detection Practices: An Investigation
Financial fraud is an issue with far reaching consequences in the finance
industry, government, corporate sectors, and for ordinary consumers. Increasing
dependence on new technologies such as cloud and mobile computing in recent
years has compounded the problem. Traditional methods of detection involve
extensive use of auditing, where a trained individual manually observes reports
or transactions in an attempt to discover fraudulent behaviour. This method is
not only time consuming, expensive and inaccurate, but in the age of big data
it is also impractical. Not surprisingly, financial institutions have turned to
automated processes using statistical and computational methods. This paper
presents a comprehensive investigation on financial fraud detection practices
using such data mining methods, with a particular focus on computational
intelligence-based techniques. Classification of the practices based on key
aspects such as detection algorithm used, fraud type investigated, and success
rate have been covered. Issues and challenges associated with the current
practices and potential future direction of research have also been identified.Comment: Proceedings of the 10th International Conference on Security and
Privacy in Communication Networks (SecureComm 2014
Constraining the Detailed Balance Condition in Horava Gravity with Cosmic Accelerating Expansion
In 2009 Ho\v{r}ava proposed a power-counting renormalizable quantum gravity
theory. Afterwards a term in the action that softly violates the detailed
balance condition has been considered with the attempt of obtaining a more
realistic theory in its IR-limit. This term is proportional to , where is a constant parameter and is the spatial
Ricci scalar. In this paper we derive constraints on this IR-modified
Ho\v{r}ava theory using the late-time cosmic accelerating expansion
observations. We obtain a lower bound of that is nontrivial and
depends on , the cosmological constant of the three dimensional
spatial action in the Ho\v{r}ava gravity. We find that to preserve the detailed
balance condition, one needs to fine-tune such that - 2.29\times
10^{-4}< (c^2 \Lambda_W)/(H^2_0 \currentDE) - 2 < 0 , where and
\currentDE are the Hubble parameter and dark energy density fraction in the
present epoch, respectively. On the other hand, if we do not insist on the
detailed balance condition, then the valid region for is much
relaxed to -0.39< (c^2 \Lambda_W)/(H^2_0 \currentDE) - 2 < 0.12. We find that
although the detailed balance condition cannot be ruled out, it is strongly
disfavored.Comment: 22 pages with 7 figures, references adde
Trends in Tissue Engineering for Blood Vessels
Over the years, cardiovascular diseases continue to increase and affect not only human health but also the economic stability worldwide. The advancement in tissue engineering is contributing a lot in dealing with this immediate need of alleviating human health. Blood vessel diseases are considered as major cardiovascular health problems. Although blood vessel transplantation is the most convenient treatment, it has been delimited due to scarcity of donors and the patient's conditions. However, tissue-engineered blood vessels are promising alternatives as mode of treatment for blood vessel defects. The purpose of this paper is to show the importance of the advancement on biofabrication technology for treatment of soft tissue defects particularly for vascular tissues. This will also provide an overview and update on the current status of tissue reconstruction especially from autologous stem cells, scaffolds, and scaffold-free cellular transplantable constructs. The discussion of this paper will be focused on the historical view of cardiovascular tissue engineering and stem cell biology. The representative studies featured in this paper are limited within the last decade in order to trace the trend and evolution of techniques for blood vessel tissue engineering
Background field formalism and construction of effective action for N=2, d=3 supersymmetric gauge theories
We review the background field method for three-dimensional Yang-Mills and
Chern-Simons models in N=2 superspace. Superfield proper time (heat kernel)
techniques are developed and exact expressions of heat kernels for constant
backgrounds are presented. The background field method and heat kernel
techniques are applied for evaluating the low-energy effective actions in N=2
supersymmetric Yang-Mills and Chern-Simons models as well as in N=4 and N=8 SYM
theories.Comment: 1+30 pages, dedicated to the 60 year Jubilee of Professor D.I.
Kazakov; references added. arXiv admin note: substantial text overlap with
arXiv:1010.496
Ultrafast supercontinuum spectroscopy of carrier multiplication and biexcitonic effects in excited states of PbS quantum dots
We examine the multiple exciton population dynamics in PbS quantum dots by
ultrafast spectrally-resolved supercontinuum transient absorption (SC-TA). We
simultaneously probe the first three excitonic transitions over a broad
spectral range. Transient spectra show the presence of first order bleach of
absorption for the 1S_h-1S_e transition and second order bleach along with
photoinduced absorption band for 1P_h-1P_e transition. We also report evidence
of the one-photon forbidden 1S_{h,e}-1P_{h,e} transition. We examine signatures
of carrier multiplication (multiexcitons for the single absorbed photon) from
analysis of the first and second order bleaches, in the limit of low absorbed
photon numbers (~ 10^-2), at pump energies from two to four times the
semiconductor band gap. The multiexciton generation efficiency is discussed
both in terms of a broadband global fit and the ratio between early- to
long-time transient absorption signals.. Analysis of population dynamics shows
that the bleach peak due to the biexciton population is red-shifted respect the
single exciton one, indicating a positive binding energy.Comment: 16 pages, 5 figure
Kaluza-Klein Higher Derivative Induced Gravity
The existence and stability analysis of an inflationary solution in a
-dimensional anisotropic induced gravity is presented in this paper.
Nontrivial conditions in the field equations are shown to be compatible with a
cosmological model in which the 4-dimension external space evolves
inflationary, while, the D-dimension internal one is static. In particular,
only two additional constraints on the coupling constants are derived from the
abundant field equations and perturbation equations. In addition, a compact
formula for the non-redundant 4+D dimensional Friedmann equation is also
derived for convenience. Possible implications are also discussed in this
paper.Comment: 13 pages, typos/errors corrected, three additional appendices adde
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