A comparison of general-purpose optimization algorithms forfinding optimal approximate experimental designs

Several common general purpose optimization algorithms are compared for findingA- and D-optimal designs for different types of statistical models of varying complexity,including high dimensional models with five and more factors. The algorithms of interestinclude exact methods, such as the interior point method, the Nelder–Mead method, theactive set method, the sequential quadratic programming, and metaheuristic algorithms,such as particle swarm optimization, simulated annealing and genetic algorithms.Several simulations are performed, which provide general recommendations on theutility and performance of each method, including hybridized versions of metaheuristicalgorithms for finding optimal experimental designs. A key result is that general-purposeoptimization algorithms, both exact methods and metaheuristic algorithms, perform wellfor finding optimal approximate experimental designs

Quantization of Weyl invariant unimodular gravity with antisymmetric ghost fields

The enforcement of the unimodularity condition in a gravity theory by means of a Lagrange multiplier leads, in general, to inconsistencies upon quantization. This is so, in particular, when the classic linear splitting of the metric between the background and quantum fields is used. To avoid the need of introducing such a Lagrange multiplier while using the classic linear splitting, we carry out the quantization of unimodular gravity with extra Weyl symmetry by using Becchi-Rouet-Stora-Tyutin (BRST) techniques. Here, two gauge symmetries are to be gauge-fixed: transverse diffeomorphisms and Weyl transformations. We perform the gauge-fixing of the transverse diffeomorphism invariance by using BRST transformations that involve antisymmetric ghost fields. We show that these BRST transformations are compatible with the BRST transformations needed to gauge-fix the Weyl symmetry, so that they can be combined in a set of transformations generated by a single BRST operator. Newton's law of gravitation is derived within the BRST formalism we put forward as well as the Slavnov-Taylor equation.Comment: 24 pages, 1 table, 1 figur

Wiping DNA Methylation: Wip1 Regulates Genomic Fluidity on Cancer

Wip1 phosphatase plays an important role in cancer by inactivating p53 and INK4a/ARF pathways. In this issue of Cancer Cell, Filipponi and colleagues further connect the oncogenic role of Wip1 with heterochromatin dynamics, transposable element expression, and a mutation-prone environment that may enhance heterogeneity and ultimately contribute to tumor evolution

Outflow of hot and cold molecular gas from the obscured secondary nucleus of NGC3256: closing in on feedback physics

The nuclei of merging galaxies are often deeply buried in dense layers of gas and dust. In these regions, gas outflows driven by starburst and AGN activity are believed to play a crucial role in the evolution of these galaxies. However, to fully understand this process it is essential to resolve the morphology and kinematics of such outflows. Using near-IR integral-field spectroscopy obtained with VLT/SINFONI, we detect a kpc-scale structure of high-velocity molecular hydrogen (H2) gas associated with the deeply buried secondary nucleus of the IR-luminous merger NGC3256. We show that this structure is likely the hot component of a molecular outflow, which is detected also in the cold molecular gas by Sakamoto et al. This outflow, with a molecular gas mass of M(H2)~2x10^7 Msun, is among the first to be spatially resolved in both the hot H2 gas with VLT/SINFONI and the cold CO-emitting gas with ALMA. The hot and cold components share a similar morphology and kinematics, with a hot-to-cold molecular gas mass ratio of ~6x10^-5. The high (~100 pc) resolution at which we map the geometry and velocity structure of the hot outflow reveals a biconical morphology with opening angle ~40 deg and gas spread across a FWZI~1200 km/s. Because this collimated outflow is oriented close to the plane of the sky, the molecular gas may reach maximum intrinsic outflow velocities of ~1800 km/s, with an average mass outflow rate of at least ~20 Msun/yr. By modeling the line-ratios of various near-IR H2 transitions, we show that the H2 gas in the outflow is heated through shocks or X-rays to a temperature of ~1900K. The energy needed to drive the outflow is likely provided by a hidden Compton-thick AGN or by the nuclear starburst. We show that the global kinematics of the molecular outflow in NGC3256 mimic those of CO-outflows that have been observed at low spatial resolution in starburst- and active galaxies.Comment: Accepted in Astronomy and Astrophysics (accepted 29 Aug 2014 v.3, initial submission v.1 14 March 2014), 13 pages, 8 figure

A Model for the Strings of Eta Carinae

We propose a model based on ionization shadows to explain the formation of the long and narrow strings of Eta Carinae. Five strings are known, all located along the symmetry axis outside the Homunculus. The model assumes that each string is formed in a shadow behind a dense clump near the symmetry axis. The surrounding gas is ionized first, becomes much hotter, and compresses the gas in the shadow. This leads to the formation of a radial, dense, long, and narrow region, i.e., a string. Later the neutral material in the strings is ionized, and becomes brighter. Still later it re-expands, and we predict that in about 200 years the strings will fade. The condition for the model to work is that the ionization front, due to the diffuse ionizing recombination radiation of the surrounding gas, proceeds into the shadow at a velocity slower than the compression speed. From that we get a condition on the mass loss rate of the mass loss episode that formed the strings, which should be less than 10^{-4} Mo/year. The model can also explain the strings in the planetary nebula NGC 6543.Comment: 8 pages; Submitted to A&

Direct wide-angle measurement of photonic band-structure in a three-dimensional photonic crystal using infrared fourier imaging spectroscopy

We propose a method to directly visualize the photonic band-structure of micrometer-sized photonic crystals using wide-angle spectroscopy. By extending Fourier imaging spectroscopy sensitivity into the infrared range, we have obtained accurate measurements of the band structures along the high-symmetry directions (X-W-K-L-U) of polymeric three-dimensional, rod-connected diamond photonic crystals. Our implementation also allows us to record single wavelength reflectance far-field patterns showing very good agreement with simulations of the same designs. This technique is suitable for the characterization of photonic structures working in the infrared and, in particular, to obtain band-structure information of complete photonic band gap materials