Status of the scalar singlet dark matter model

One of the simplest viable models for dark matter is an additional neutral scalar, stabilised by a \(\mathbb {Z}_2\) symmetry. Using the GAMBIT package and combining results from four independent samplers, we present Bayesian and frequentist global fits of this model. We vary the singlet mass and coupling along with 13 nuisance parameters, including nuclear uncertainties relevant for direct detection, the local dark matter density, and selected quark masses and couplings. We include the dark matter relic density measured by Planck, direct searches with LUX, PandaX, SuperCDMS and XENON100, limits on invisible Higgs decays from the Large Hadron Collider, searches for high-energy neutrinos from dark matter annihilation in the Sun with IceCube, and searches for gamma rays from annihilation in dwarf galaxies with the Fermi-LAT. Viable solutions remain at couplings of order unity, for singlet masses between the Higgs mass and about 300 GeV, and at masses above \(\sim \)1 TeV. Only in the latter case can the scalar singlet constitute all of dark matter. Frequentist analysis shows that the low-mass resonance region, where the singlet is about half the mass of the Higgs, can also account for all of dark matter, and remains viable. However, Bayesian considerations show this region to be rather fine-tuned.     

Chaotic attractors of an infinite-dimensional dynamical system

We study the chaotic attractors of a delay differential equation. The dimension of several attractors computed directly from the definition agrees to experimental resolution with the dimension computed from the spectrum of Lyapunov exponents according to a conjecture of Kaplan and Yorke. Assuming this conjecture to be valid, as the delay parameter is varied, from computations of the spectrum of Lyapunov exponents, we observe a roughly linear increase from two to twenty in the dimension, while the metric entropy remains roughly constant. These results are compared to a linear analysis, and the asymptotic behavior of the Lyapunov exponents is derived.     

Design and initial operation of a high-solids,pilot-scale reactor for dilute-acid pretreatment of lignocellulosic biomass

Applied Biochemistry and Biotechnology - A recently installed 100-L horizontal shaft custom-fabricated mixer/reactor, made of Carpenter 20 Cb-3 stainless steel and designed for high-solids,...     

Assessment of murine neuroblastoma (N1E-115) resting membrane potential by confocal microscopy

Digital imaging (confocal microscopy) and a slow potentiometric dye (tetramethylrhodamine methyl ester) were used to assess the resting membrane potential (V _m) of murine neuroblastoma cells (N1E-115). The averageV _m was found to be –64.0±2.0 mV. The difference between this and the previously reported higher values was attributed to the use of glass microelectrode techniques that probably caused mechanical injury to the cell membranes: Digital imaging of N1E-115V _m was found to be sensitive, reproducible, fast, and simple.     

On determining the dimension of chaotic flows

We describe a method for determining the approximate fractal dimension of an attractor. Our technique fits linear subspaces of appropriate dimension to sets of points on the attractor. The deviation between points on the attractor and this local linear subspace is analyzed through standard multilinear regression techniques. We show how the local dimension of attractors underlying physical phenomena can be measured even when only a single time-varying quantity is available for analysis. These methods are applied to several dissipative dynamical systems.