32,682 research outputs found
Motor drivers for dc brushless motors
Nondestructive tests of motor drivers for delta wound dc brushless motor
Enhanced and directional single photon emission in hyperbolic metamaterials
We propose an approach to enhance and direct the spontaneous emission from
isolated emitters embedded inside hyperbolic metamaterials into single photon
beams. The approach rests on collective plasmonic Bloch modes of hyperbolic
metamaterials which propagate in highly directional beams called quantum
resonance cones. We propose a pumping scheme using the transparency window of
the hyperbolic metamaterial that occurs near the topological transition.
Finally, we address the challenge of outcoupling these broadband resonance
cones into vacuum using a dielectric bullseye grating. We give a detailed
analysis of quenching and design the metamaterial to have a huge Purcell factor
in a broad bandwidth inspite of the losses in the metal. Our work should help
motivate experiments in the development of single photon sources for broadband
emitters such as nitrogen vacancy centers in diamond.Comment: 29 pages, 9 figure
Quantum Corrections to Newton's Law
We present a new approach to quantum gravity starting from Feynman's
formulation for the simplest example, that of a scalar field as the
representative matter. We show that we extend his treatment to a calculable
framework using resummation techniques already well-tested in other problems.
Phenomenological consequences for Newton's law are described.Comment: 7 pages, 1 figure; improved fig., refs;improved discussion;more
discussion; proo
Estimation of linkage disequilibrium in a sample of the United Kingdom dairy cattle population using unphased genotypes
The association between genetic marker alleles was estimated for two regions of the bovine genome from a random sample of 50 young dairy bulls born in the United Kingdom between 1988 and 1995. Microsatellite marker genotypes were obtained for six markers on chromosome 2 and seven markers on chromosome 6, spanning 38 and 20 cM, respectively. Two different methods, which do not require family information, were used to estimate population haplotype frequencies. Haplotype frequencies were estimated for pairs of loci using the expectation-maximization algorithm and for all linked loci using a Bayesian approach via a Markov chain-Monte Carlo algorithm. Significant (P = 0.0007) linkage disequilibrium was detected between pairs of loci in syntenic groups (that is, loci in the same linkage group), extending to about 10 cM. No significant linkage disequilibrium was detected between markers in nonsyntenic regions. Given the observed level of linkage disequilibrium, mapping methods based on population-wide association might provide a better resolution than traditional quantitative trait loci mapping methods in the U.K. dairy cattle population and may reduce the required sample sizes of the experiments
Chemotaxis of Arbacia punctulata spermatozoa to resact, a peptide from the egg jelly layer
Resact, a peptide of known sequence isolated from the jelly layer of Arbacia punctulata eggs, is a potent chemoattractant for A. punctulata spermatozoa. The chemotactic response is concentration dependent, is abolished by pretreatment of the spermatozoa with resact, and shows an absolute requirement for millimolar external calcium. A. punctulata spermatozoa do not respond to speract, a peptide isolated from the jelly layer of Strongylocentrotus purpuratus eggs. This is the first report of animal sperm chemotaxis in response to a defined egg-derived molecule
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