A Feynman integral in Lifshitz-point and Lorentz-violating theories in R^D ⨁ R<i>^m</i>

We evaluate a 1-loop, 2-point, massless Feynman integral ID,m(p,q) relevant for perturbative field theoretic calculations in strongly anisotropic d=D+m dimensional spaces given by the direct sum RD ⨁ Rm . Our results are valid in the whole convergence region of the integral for generic (noninteger) codimensions D and m. We obtain series expansions of ID,m(p,q) in terms of powers of the variable X:=4p2/q4, where p=|p|, q=|q|, p Є RD, q Є Rm, and in terms of generalised hypergeometric functions 3F2(−X), when X&lt;1. These are subsequently analytically continued to the complementary region X≥1. The asymptotic expansion in inverse powers of X1/2 is derived. The correctness of the results is supported by agreement with previously known special cases and extensive numerical calculations

Phenomenology of a light scalar: the dilaton

We make use of the language of non-linear realizations to analyze electro-weak symmetry breaking scenarios in which a light dilaton emerges from the breaking of a nearly conformal strong dynamics, and compare the phenomenology of the dilaton to that of the well motivated light composite Higgs scenario. We argue that -- in addition to departures in the decay/production rates into massless gauge bosons mediated by the conformal anomaly -- characterizing features of the light dilaton scenario (as well as other scenarios admitting a light CP-even scalar not directly related to the breaking of the electro-weak symmetry) are off-shell events at high invariant mass involving two longitudinally polarized vector bosons and a dilaton, and tree-level flavor violating processes. Accommodating both electro-weak precision measurements and flavor constraints appears especially challenging in the ambiguous scenario in which the Higgs and the dilaton fields strongly mix. We show that warped higgsless models of electro-weak symmetry breaking are explicit and tractable realizations of this limiting case. The relation between the naive radion profile often adopted in the study of holographic realizations of the light dilaton scenario and the actual dynamical dilaton field is clarified in the Appendix.Comment: 21 page

Single-mode whispering gallery lasing from metal-clad GaN nanopillars

An ordered hexagonal closed-packed nanopillar array is fabricated on GaN. A metal coating is then applied to encapsulate the pillars for promoting optical confinement within the cylindrical cavity. Room-temperature lasing at 373 nm is observed under pulsed excitation, at a lasing threshold of 0.42 MW/cm 2. With pillar diameters of around 980 nm, the number of modes overlapping the emission spectrum is reduced, giving rise to single-mode whispering gallery stimulated emission. Finite-difference time-domain simulations are carried out for the prediction of resonant frequencies and electric field patterns corresponding to the resonant modes. © 2012 Optical Society of America.published_or_final_versio

Tunable clover-shaped GaN photonic bandgap structures patterned by dual-step nanosphere lithography

The fabrication of close-packed clover-shaped photonic crystal structure on GaN by dual-step nanosphere lithography is demonstrated. By shrinkage of spheres prior to pattern transfer, a non-closed-packed clover-shaped photonic bandgap (PBG) structure, as designed by modified 3D finite-difference time-domain simulation, is also realized. The PBG of the close-packed and non-close-packed clover-shaped structures is verified through optical transmission spectroscopy, found to agree well with simulated results. A threefold enhancement in photoluminescence (PL) intensity is observed from the optimized structure, when the PBG is tuned to overlap with the emission band of the InGaN/GaN multi-quantum wells. From time-resolved PL measurements, shortened decay lifetimes are observed. © 2012 American Institute of Physics.published_or_final_versio

High-Q whispering-gallery mode lasing from nanosphere-patterned GaN nanoring arrays

A hexagonal-close-packed ordered array of nanorings was fabricated on GaN with a modified nanosphere lithography process. The spheres initially served as etch masks for the formation of closed-packed nanopillars. The spheres were then shrunk and, with a layer of oxide deposited, the roles of the spheres became masks for liftoff. The final etch produced nanorings with wall widths of 140 nm. Photopumped lasing with splitting modes was observed at room temperature, with a low lase threshold of ∼10 mJ/cm 2 and high quality factor of ∼5000, via whispering-gallery modes. The resonant frequencies were verified through finite-difference time-domain simulations. © 2011 American Institute of Physics.published_or_final_versio

Vertically mounted InGaN-on-Sapphire light-emitting diodes

An InGaN/GaN light-emitting diode (LED) chip mounted in a vertical configuration (vmLED) is demonstrated, exhibiting significant enhancement to light extraction, compared with a LED mounted in a conventional planar geometry. By flipping the chip orthogonally, two large illumination surfaces of the device are exposed for direct light extraction. Comparisons, through ray-trace modeling and experiment data with conventional surface-mounted LEDs, indicate that the vmLEDs achieve superior light extraction efficiency. A sapphire-prism-mounted vmLED is further proposed to improve heat sinking, which is well suited for higher current operations. © 2006 IEEE.published_or_final_versio

Optically pumped whispering-gallery mode lasing from 2-micron GaN micro-disks pivoted on Si

published_or_final_versio

Cluster Randomized Trail of the uptake of a take-home Infant dose of Nevirapine in Kenya

Objective: To test whether a single take home dose of infant nevirapine increased infant uptake without decreasing institutional deliveries. Design: Cluster randomized post-test only study with control group. Setting: Ten hospitals in urban areas of Coast, Rift Valley, and Western provinces, Kenya. Participants: Pregnant women with HIV, 18 years and older, and at least 32 weeks gestation recruited during antenatal care and followed up at home approximately one week after delivery. Intervention: In the intervention group, women were given a single infant&rsquo;s dose of nevirapine to take home prior to delivery. In the control group, no changes were made to the standard of care. Main outcome measures: Mothers&rsquo; reports of infant uptake of nevirapine and place of delivery. Results: Uptake of the infant&rsquo;s nevirapine dose was high, 94% in the intervention group and 88% in the control group (p=0.096). Among women who delivered at home, uptake was higher significantly among infants whose mothers got the take home dose compared to women who did not get the dose (93% vs. 53%, p&lt;0.01). The intervention did not influence place of delivery. Providers were positive about the take home dose concept; difficulties were attributed to HIV-related stigma. Conclusions: Making take home infant nevirapine available either as a single dose administered within 72 hours of birth or as part of a more complex six week postnatal regimen, will increase infant uptake especially among women who deliver at home without affecting place of delivery.East African Medical Journal Vol. 87 No. 7 July 201

Melting glaciers: A probable source of DDT to the Antarctic marine ecosystem

Persistent organic pollutants reach polar regions by long-range atmospheric transport and biomagnify through the food web accumulating in higher trophic level predators. We analyzed Adelie penguin (Pygoscelis adeliae) samples collected from 2004 to 2006 to evaluate current levels of Sigma DDT (p,p\u27-DDT + p,p\u27-DDE) in these birds, which are confined to Antarctica. Ratios of p,p\u27-DDT to p,p\u27-DDE in Adelie penguins have declined significantly since 1964 indicating current exposure to old rather than new sources of Sigma DDT. However, Sigma DDT has not declined in Adelie penguins from the Western Antarctic Peninsula for more than 30 years and the presence of p,p\u27-DDT in these birds indicates that there is a current source of DDT to the Antarctic marine food web. DDT has been banned or severely restricted since peak use in the 1970s, implicating glacier meltwater as a likely source for DDT contamination in coastal Antarctic seas. Our estimates indicate that 1-4 kg.y(-1) Sigma DDT are currently being released into coastal waters along the Western Antarctic Ice Sheet due to glacier ablation