9,084 research outputs found
High-resolution mapping of cancer cell networks using co-functional interactions.
Powerful new technologies for perturbing genetic elements have recently expanded the study of genetic interactions in model systems ranging from yeast to human cell lines. However, technical artifacts can confound signal across genetic screens and limit the immense potential of parallel screening approaches. To address this problem, we devised a novel PCA-based method for correcting genome-wide screening data, bolstering the sensitivity and specificity of detection for genetic interactions. Applying this strategy to a set of 436 whole genome CRISPR screens, we report more than 1.5 million pairs of correlated "co-functional" genes that provide finer-scale information about cell compartments, biological pathways, and protein complexes than traditional gene sets. Lastly, we employed a gene community detection approach to implicate core genes for cancer growth and compress signal from functionally related genes in the same community into a single score. This work establishes new algorithms for probing cancer cell networks and motivates the acquisition of further CRISPR screen data across diverse genotypes and cell types to further resolve complex cellular processes
Impact of ETO propellants on the aerothermodynamic analyses of propulsion components
The operating conditions and the propellant transport properties used in Earth-to-Orbit (ETO) applications affect the aerothermodynamic design of ETO turbomachinery in a number of ways. Some aerodynamic and heat transfer implications of the low molecular weight fluids and high Reynolds number operating conditions on future ETO turbomachinery are discussed. Using the current SSME high pressure fuel turbine as a baseline, the aerothermodynamic comparisons are made for two alternate fuel turbine geometries. The first is a revised first stage rotor blade designed to reduce peak heat transfer. This alternate design resulted in a 23 percent reduction in peak heat transfer. The second design concept was a single stage rotor to yield the same power output as the baseline two stage rotor. Since the rotor tip speed was held constant, the turbine work factor doubled. In this alternate design, the peak heat transfer remained the same as the baseline. While the efficiency of the single stage design was 3.1 points less than the baseline two stage turbine, the design was aerothermodynamically feasible, and may be structurally desirable
Hadronic contribution to the muon g-2: a theoretical determination
The leading order hadronic contribution to the muon g-2, , is
determined entirely from theory using an approach based on Cauchy's theorem in
the complex squared energy s-plane. This is possible after fitting the
integration kernel in with a simpler function of . The
integral determining in the light-quark region is then split
into a low energy and a high energy part, the latter given by perturbative QCD
(PQCD). The low energy integral involving the fit function to the integration
kernel is determined by derivatives of the vector correlator at the origin,
plus a contour integral around a circle calculable in PQCD. These derivatives
are calculated using hadronic models in the light-quark sector. A similar
procedure is used in the heavy-quark sector, except that now everything is
calculable in PQCD, thus becoming the first entirely theoretical calculation of
this contribution. Using the dual resonance model realization of Large
QCD to compute the derivatives of the correlator leads to agreement with the
experimental value of . Accuracy, though, is currently limited by the
model dependent calculation of derivatives of the vector correlator at the
origin. Future improvements should come from more accurate chiral perturbation
theory and/or lattice QCD information on these derivatives, allowing for this
method to be used to determine accurately entirely from theory,
independently of any hadronic model.Comment: Several additional clarifying paragraphs have been added. 1/N_c
corrections have been estimated. No change in result
Gravitational Lens Statistics and The Density Profile of Dark Halos
We investigate the influence of the inner profile of lens objects on
gravitational lens statistics taking into account of the effect of
magnification bias and both the evolution and the scatter of halo profiles. We
take the dark halos as the lens objects and consider the following three models
for the density profile of dark halos; SIS (singular isothermal sphere), the
NFW (Navarro Frenk White) profile, and the generalized NFW profile which has a
different slope at smaller radii. The mass function of dark halos is assumed to
be given by the Press-Schechter function. We find that magnification bias for
the NFW profile is order of magnitude larger than that for SIS. We estimate the
sensitivity of the lensing probability of distant sources to the inner profile
of lenses and to the cosmological parameters. It turns out that the lensing
probability is strongly dependent on the inner density profile as well as on
the cosmological constant. We compare the predictions with the largest
observational sample, the Cosmic Lens All-Sky Survey. The absence or presence
of large splitting events in larger surveys currently underway such as the 2dF
and SDSS could set constraints on the inner density profile of dark halos.Comment: 22 pages, minor changes and references added, accepted for
publication in Ap
Some continuum physics results from the lattice V-A correlator
We present preliminary results on extractions of the chiral LECs L_10 and
C_87 and constraints on the excited pseudoscalar state pi(1300) and pi(1800)
decay constants obtained from an analysis of lattice data for the flavor ud
light quark V-A correlator. A comparison of the results for the correlator to
the corresponding mildly-model-dependent continuum results (based primarily on
experimental hadronic tau decay data) is also givenComment: 7 pages, 3 figures. Prepared for the Proceedings of the 30th
International Symposium on Lattice Field Theory, Cairns, Australia, June
24-29, 2012; expanded version of Reference 1
New results from the lattice on the theoretical inputs to the hadronic tau determination of V_us
Recent sum rule determinations of |V_us|, employing flavor-breaking
combinations of hadronic tau decay data, are significantly lower than either
expectations based on 3-family unitarity or determinations from K_ell3 and
Gamma[K_mu2]/Gamma[pi_mu2]. We use lattice data to investigate the
accuracy/reliability of the OPE representation of the flavor-breaking
correlator combination entering the tau decay analyses. The behavior of an
alternate correlator combination, constructed to reduce problems associated
with the slow convergence of the D = 2 OPE series, and entering an alternate
sum rule requiring both electroproduction cross-section and hadronic tau decay
data, is also investigated. Preliminary updates of both analyses, with the
lessons learned from the lattice data in mind, are also presented.Comment: 8 pages, 5 figures. Prepared for the proceedings of the 12th
International Workshop on Tau Lepton Physics, Sep. 17-21, 2012, Nagoya, Japan
and the 10th International Conference on Confinement and the Hadron Spectrum,
Oct. 6-13, 2012, Garching/Munich, German
Electron heating mechanisms in dual frequency capacitive discharges
We discuss electron heating mechanisms in the sheath regions of dual-frequency capacitive discharges, with the twin aims of identifying the dominant mechanisms and supplying closed-form expressions from which the heating power can be estimated. We show that the heating effect produced by either Ohmic or collisionless heating is much larger when the discharge is excited by a superposition of currents at two frequencies than if either current had acted alone. This coupling effect occurs because the lower frequency current, while not directly heating the electrons to any great extent, strongly affects the spatial structure of the discharge in the sheath regions
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