MM Algorithms for Minimizing Nonsmoothly Penalized Objective Functions

In this paper, we propose a general class of algorithms for optimizing an extensive variety of nonsmoothly penalized objective functions that satisfy certain regularity conditions. The proposed framework utilizes the majorization-minimization (MM) algorithm as its core optimization engine. The resulting algorithms rely on iterated soft-thresholding, implemented componentwise, allowing for fast, stable updating that avoids the need for any high-dimensional matrix inversion. We establish a local convergence theory for this class of algorithms under weaker assumptions than previously considered in the statistical literature. We also demonstrate the exceptional effectiveness of new acceleration methods, originally proposed for the EM algorithm, in this class of problems. Simulation results and a microarray data example are provided to demonstrate the algorithm's capabilities and versatility.Comment: A revised version of this paper has been published in the Electronic Journal of Statistic

Colugos: obscure mammals glide into the evolutionary limelight

Substantial molecular evidence indicates that tree-shrews, colugos and primates cluster together on the mammalian phylogenetic tree. Previously, a sister-group relationship between colugos and primates seemed likely. A new study of colugo chromosomes indicates instead an affinity between colugos and tree-shrews

Updates of PDFs for the 2nd LHC run

I present results on continuing updates in PDFs within the framework now called MMHT14 due to both theory improvements and the inclusion of new data sets, including most of the up-to-date LHC data. A new set of PDFs is essentially finalised, with no changes expected to the PDFs presented here.Comment: 6 pages, 5 figures. Proceedings of the 37th International Conference of High-Energy Physics (ICHEP2014), 2-9 July 2014, Valencia, Spai

Imaging starspot evolution on Kepler target KIC 5110407 using light curve inversion

The Kepler target KIC 5110407, a K-type star, shows strong quasi-periodic light curve fluctuations likely arising from the formation and decay of spots on the stellar surface rotating with a period of 3.4693 days. Using an established light-curve inversion algorithm, we study the evolution of the surface features based on Kepler space telescope light curves over a period of two years (with a gap of .25 years). At virtually all epochs, we detect at least one large spot group on the surface causing a 1-10% flux modulation in the Kepler passband. By identifying and tracking spot groups over a range of inferred latitudes, we measured the surface differential rotation to be much smaller than that found for the Sun. We also searched for a correlation between the seventeen stellar flares that occurred during our observations and the orientation of the dominant surface spot at the time of each flare. No statistically-significant correlation was found except perhaps for the very brightest flares, suggesting most flares are associated with regions devoid of spots or spots too small to be clearly discerned using our reconstruction technique. While we may see hints of long-term changes in the spot characteristics and flare statistics within our current dataset, a longer baseline of observation will be needed to detect the existence of a magnetic cycle in KIC 5110407.Comment: 32 pages, 15 figures, accepted to Ap

Dirac Fields in Loop Quantum Gravity and Big Bang Nucleosynthesis

Big Bang nucleosynthesis requires a fine balance between equations of state for photons and relativistic fermions. Several corrections to equation of state parameters arise from classical and quantum physics, which are derived here from a canonical perspective. In particular, loop quantum gravity allows one to compute quantum gravity corrections for Maxwell and Dirac fields. Although the classical actions are very different, quantum corrections to the equation of state are remarkably similar. To lowest order, these corrections take the form of an overall expansion-dependent multiplicative factor in the total density. We use these results, along with the predictions of Big Bang nucleosynthesis, to place bounds on these corrections.Comment: 15 pages, 2 figures; v2: new discussion of relevance of quantum gravity corrections (Sec. II) and new estimates (Sec. V

Colojejunal Fistula Resulting from a D-PEJ Feeding Tube

Numerous procedures have been developed to provide adequate enteral nutrition to patients with gastrointestinal disorders. Previously, operative placement of a feeding gastrostomy or jejunostomy tube was the accepted means of gaining chronic enteral access. However, improved technology and experience with endoscopic techniques have quickly replaced primary operative placement of enteral access. Direct percutaneous endoscopic jejunostomy (D-PEJ) is a procedure that was designed to deliver enteral feeding solutions for patients with proximal disease after unsatisfactory results from percutaneous endoscopic gastrostomy tubes with jejunal extensions (PEG-J). As with any procedure, it is associated with complications. We present the first reported case of a colojejunal fistula resulting from a D-PEJ placement. While D-PEJ has been shown to be relatively safe, complications related to the inherent limitations of the procedure need to be considered when the patient experiences unusual post-procedure symptoms and worked up appropriately

Myocyte Swelling and Plasmalemmal Integrity During Early Experimental Myocardial Ischemia in vivo

Using scanning and transmission electron microscopy, the structure of myocytes early in the phase of irreversible injury induced by 40 minutes of severe regional ischemia has been investigated, paying particular attention to the effects of cell swelling on the SEM appearance of the myocytes. Swollen myocytes showed an increased space beneath the plasmalemma and between organelles. True subsarcolemmal blebs were not seen and the attachment complexes between the Z-band and the underlying myofibrils remained intact. The proportion of the PS face of the plasmalemma which appeared en face (0.70%, SD:1.22 vs 5.0196, SD:3.72) in freeze-fracture faces of ischemic tissue was increased significantly. The increase may be due to swelling of the cell in the subplasmalemmal space or may be mediated through structurally unapparent alterations in the cytoskeleton. The PS face showed frequent longitudinal shifts in the alignment of Z band-plasmalemmal attachment between adjacent myofibers. T-tubule ostia, caveolae and junctional SR were demonstrable on the PS face. With standard preparative methods and instrumentation, no discrete fibrillar network associated with Z band attachment or subjacent to the plasmalemma was detected and there was no direct structural evidence of cytoskeletal alteration as a result of ischemic injury. Osmium-ligand preparation of tissue samples resulted in less damage induced by the electron beam, but did not allow significantly better resolution