1,208 research outputs found
Matrix eQTL: Ultra fast eQTL analysis via large matrix operations
Expression quantitative trait loci (eQTL) mapping aims to determine genomic
regions that regulate gene transcription. Expression QTL is used to study the
regulatory structure of normal tissues and to search for genetic factors in
complex diseases such as cancer, diabetes, and cystic fibrosis. A modern eQTL
dataset contains millions of SNPs and thousands of transcripts measured for
hundreds of samples. This makes the analysis computationally complex as it
involves independent testing for association for every transcript-SNP pair. The
heavy computational burden makes eQTL analysis less popular, often forces
analysts to restrict their attention to just a subset of transcripts and SNPs.
As larger genotype and gene expression datasets become available, the demand
for fast tools for eQTL analysis increases. We present a new method for fast
eQTL analysis via linear models, called Matrix eQTL. Matrix eQTL can model and
test for association using both linear regression and ANOVA models. The models
can include covariates to account for such factors as population structure,
gender, and clinical variables. It also supports testing of heteroscedastic
models and models with correlated errors. In our experiment on large datasets
Matrix eQTL was thousands of times faster than the existing popular software
for QTL/eQTL analysis. Matrix eQTL is implemented as both Matlab and R packages
and thus can easily be run on Windows, Mac OS, and Linux systems. The software
is freely available at the following address:
http://www.bios.unc.edu/research/genomic_software/Matrix_eQTLComment: 9 pages, 1 figur
Final state interaction in decay
Contrary to wide-spread opinion that the final state interaction (FSI)
enhances the amplitude , we argue that FSI does not increase
the absolute value of this amplitude.Comment: 9 page
Existence of \sigma(600)/\kappa(900)-Particle and New Chiral Scalar Nonet ``Chiralons''
The \sigma(600) and \kappa(900), observed in the phase shift analyses,
satisfy rather well the mass and width relation predicted by the SU(3)LsM and
the SU(3)LsM with the vector and axial-vector meson nonets, and deserve to be
the members of scalar \sigma-nonet, together with the observed resonances
a_0(980) and f_0(980), as a chiral partner of pseudoscalar \pi-nonet. In the
phase shift analyses an introduction of repulsive background phase \delta_{BG}
is essential, whose origin has a close connection to the \lambda\phi^4
interaction in LsM. It is argued that the members of this \sigma-nonet,
"Chiralons", have different properties and should be discriminated from the
conventional ^3P_0-qqbar-scalar nonet.Comment: Talk at HADRON'97, the 7th int. conf. on hadron spectroscopy, BNL,
August 1997. 4 pages with 1 eps figur
Loop-Less Electric Dipole Moment of the Nucleon in the Standard Model
We point out that the electric dipole moment of the neutron in the Standard
Model is generated already at tree level to the second order in the weak
interactions due to bound-state effects, without short-distance Penguin loops.
The related contribution has a regular nonvanishing chiral limit and does not
depend on the mass splitting between s and d quarks. We estimate it to be
roughly 10^(-31)e*cm and expect a more accurate evaluation in the future. We
comment on the connection between d_n and the direct CP-violation in D decays.Comment: 10 pages, 2 figure
Discrete Symmetries on the Light Front and a General Relation Connecting Nucleon Electric Dipole and Anomalous Magnetic Moments
We consider the electric dipole form factor, F_3(q^2), as well as the Dirac
and Pauli form factors, F_1(q^2) and F_2(q^2), of the nucleon in the
light-front formalism. We derive an exact formula for F_3(q^2) to complement
those known for F_1(q^2) and F_2(q^2). We derive the light-front representation
of the discrete symmetry transformations and show that time-reversal- and
parity-odd effects are captured by phases in the light-front wave functions. We
thus determine that the contributions to F_2(q^2) and F_3(q^2), Fock state by
Fock state, are related, independent of the fundamental mechanism through which
CP violation is generated. Our relation is not specific to the nucleon, but,
rather, is true of spin-1/2 systems in general, be they lepton or baryon. The
empirical values of the anomalous magnetic moments, in concert with empirical
bounds on the associated electric dipole moments, can better constrain theories
of CP violation. In particular, we find that the neutron and proton electric
dipole moments echo the isospin structure of the anomalous magnetic moments,
kappa^n ~ - kappa^p.Comment: 25 pages, 1 figure. Published version. Ref. adde
CP violation in decay
CP violation leads to a difference between the parameters and
describing the energy distributions of the charged pions produced in the and decays. We study the
difference as a function of the relative contributions from the
QCD-penguin and the electroweak-penguin diagrams. We find that the combination
of these contributions in is very similar to the corresponding
one defining the parameter in the decays. This
observation allows a determination of the value of , using data on
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