15,550 research outputs found
Profound effect of profiling platform and normalization strategy on detection of differentially expressed microRNAs
Adequate normalization minimizes the effects of systematic technical variations and is a prerequisite for getting meaningful biological changes. However, there is inconsistency about miRNA normalization performances and recommendations. Thus, we investigated the impact of seven different normalization methods (reference gene index, global geometric mean, quantile, invariant selection, loess, loessM, and generalized procrustes analysis) on intra- and inter-platform performance of two distinct and commonly used miRNA profiling platforms. We included data from miRNA profiling analyses derived from a hybridization-based platform (Agilent Technologies) and an RT-qPCR platform (Applied Biosystems). Furthermore, we validated a subset of miRNAs by individual RT-qPCR assays. Our analyses incorporated data from the effect of differentiation and tumor necrosis factor alpha treatment on primary human skeletal muscle cells and a murine skeletal muscle cell line. Distinct normalization methods differed in their impact on (i) standard deviations, (ii) the area under the receiver operating characteristic (ROC) curve, (iii) the similarity of differential expression. Loess, loessM, and quantile analysis were most effective in minimizing standard deviations on the Agilent and TLDA platform. Moreover, loess, loessM, invariant selection and generalized procrustes analysis increased the area under the ROC curve, a measure for the statistical performance of a test. The Jaccard index revealed that inter-platform concordance of differential expression tended to be increased by loess, loessM, quantile, and GPA normalization of AGL and TLDA data as well as RGI normalization of TLDA data. We recommend the application of loess, or loessM, and GPA normalization for miRNA Agilent arrays and qPCR cards as these normalization approaches showed to (i) effectively reduce standard deviations, (ii) increase sensitivity and accuracy of differential miRNA expression detection as well as (iii) increase inter-platform concordance. Results showed the successful adoption of loessM and generalized procrustes analysis to one-color miRNA profiling experiments
Embedding, compression and fiberwise homotopy theory
Given Poincare spaces M and X, we study the possibility of compressing
embeddings of M x I in X x I down to embeddings of M in X. This results in a
new approach to embedding in the metastable range both in the smooth and
Poincare duality categories.Comment: Published by Algebraic and Geometric Topology at
http://www.maths.warwick.ac.uk/agt/AGTVol2/agt-2-15.abs.htm
The power spectrum of galaxies in the 2dF 100k redshift survey
We compute the real-space power spectrum and the redshift-space distortions
of galaxies in the 2dF 100k galaxy redshift survey using pseudo-Karhunen-Loeve
eigenmodes and the stochastic bias formalism. Our results agree well with those
published by the 2dFGRS team, and have the added advantage of producing
easy-to-interpret uncorrelated minimum-variance measurements of the
galaxy-galaxy, galaxy-velocity and velocity-velocity power spectra in 27
k-bands, with narrow and well-behaved window functions in the range 0.01h/Mpc <
k < 0.8h/Mpc. We find no significant detection of baryonic wiggles, although
our results are consistent with a standard flat Omega_Lambda=0.7
``concordance'' model and previous tantalizing hints of baryonic oscillations.
We measure the galaxy-matter correlation coefficient r > 0.4 and the
redshift-distortion parameter beta=0.49+/-0.16 for r=1 (beta=0.47+/- 0.16
without finger-of-god compression). Since this is an apparent-magnitude limited
sample, luminosity-dependent bias may cause a slight red-tilt in the power
spectum. A battery of systematic error tests indicate that the survey is not
only impressive in size, but also unusually clean, free of systematic errors at
the level to which our tests are sensitive. Our measurements and window
functions are available at http://www.hep.upenn.edu/~max/2df.html together with
the survey mask, radial selection function and uniform subsample of the survey
that we have constructed.Comment: Replaced to match accepted MNRAS version, with new radial/angular
systematics plot and sigma8 typo corrected. High-res figures, power spectra,
windows and our uniform galaxy subsample with mask at
http://www.hep.upenn.edu/~max/2df.html or from [email protected]. 26
journal pages, 28 fig
Numerical and Theoretical Study of a Monodisperse Hard-Sphere Glass Former
There exists a variety of theories of the glass transition and many more
numerical models. But because the models need built-in complexity to prevent
crystallization, comparisons with theory can be difficult. We study the
dynamics of a deeply supersaturated \emph{monodisperse} four-dimensional (4D)
hard-sphere fluid, which has no such complexity, but whose strong intrinsic
geometrical frustration inhibits crystallization, even when deeply
supersaturated. As an application, we compare its behavior to the mode-coupling
theory (MCT) of glass formation. We find MCT to describe this system better
than any other structural glass formers in lower dimensions. The reduction in
dynamical heterogeneity in 4D suggested by a milder violation of the
Stokes-Einstein relation could explain the agreement. These results are
consistent with a mean-field scenario of the glass transition.Comment: 5 pages, 3 figure
Analytical Models for the Energetics of Cosmic Accretion Shocks, their Cosmological Evolution, and the Effect of Environment
We present an analytical description of the energetics of the population of
cosmic accretion shocks, for a concordance cosmology. We calculate how the
shock-processed accretion power and mass current are distributed among
different shock Mach numbers, and how they evolve with cosmic time. We
calculate the cumulative energy input of cosmic accretion shocks of any Mach
number to the intergalactic medium as a function of redshift, and we compare it
with the energy output of supernova explosions as well as with the energy input
required to reionize the universe. In addition, we investigate and quantify the
effect of environmental factors, such as local clustering properties and
filament preheating on the statistical properties of these shocks. We find that
the energy processed by accretion shocks is higher than the supernova energy
output for z<3 and that it becomes more than an order of magnitude higher in
the local universe. The energy processed by accretion shocks alone becomes
comparable to the energy required to reionize the universe by z~3.5. Finally,
we establish both qualitative and quantitatively that both local clustering as
well as filament compression and preheating are important factors in
determining the statistical properties of the cosmic accretion shock
population.Comment: 13 pages, 5 figures, emulateap
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