Long-Range Plasmon Assisted Energy Transfer Between Fluorescent Emitters

We demonstrate plasmon assisted energy transfer between fluorophores located at distances up to $7 \, \mu$m on the top of a thin silver film. Thanks to the strong confinement and large propagation length of surface plasmon polaritons, the range of the energy transfer is almost two orders of magnitude larger than the values reported in the literature so far. The parameters driving the energy transfer range are thoroughly characterized and are in very good agreement with theoretically expected values.Comment: 5 pages, 4 figures, accepted for publication in Physical Review Letter

Fluctuations of the local density of states probe localized surface plasmons on disordered metal films

We measure the statistical distribution of the local density of optical states (LDOS) on disordered semi-continuous metal films. We show that LDOS fluctuations exhibit a maximum in a regime where fractal clusters dominate the film surface. These large fluctuations are a signature of surface-plasmon localization on the nanometer scale

The actual performance of aspiring low energy social houses in the United Kingdom

This paper compares the actual energy performance of six flats and two houses built to low energy standards (Code for Sustainable Homes Levels 4 and 5) with a near identical flat and house built to minimum compliance only (Building Regulations). As low energy homes are only recently emerging in the United Kingdom housing stock, and even fewer are subject to Post Occupancy Evaluation, little is known about their actual energy use in operation. The results show that low energy dwellings may consume more energy than expected and the behaviour of the occupants residing in low energy homes plays an important role in determining their actual energy consumption

A new section of Begonia (Begoniaceae) from West Central Africa

Previous analyses of macromorphological and molecular data on the continental African species Begonia iucunda (Begoniaceae) suggest that it occupies an isolated phylogenetic position within a clade consisting otherwise of species in sections Cristasemen, Filicibegonia, Loasibegonia and Scutobegonia. Accordingly, the new monotypic section Chasmophila is here described. Its taxonomic position and relationship to other African sections are discussed and data on its distribution and ecology are presented

The embryonic genes Dkk3, Hoxd8, Hoxd9 and Tbx1 identify muscle types in a diet-independent and fiber-type unrelated way

<p>Abstract</p> <p>Background</p> <p>The mouse skeletal muscle is composed of four distinct fiber types that differ in contractile function, number of mitochondria and metabolism. Every muscle type has a specific composition and distribution of the four fiber types. To find novel genes involved in specifying muscle types, we used microarray analysis to compare the gastrocnemius with the quadriceps from mice fed a low fat diet (LFD) or high fat diet (HFD) for 8 weeks. Additional qPCR analysis were performed in the gastrocnemius, quadriceps and soleus muscle from mice fed an LFD or HFD for 20 weeks.</p> <p>Results</p> <p>In mice fed the 8-week LFD 162 genes were differentially expressed in the gastrocnemius <it>vs</it>. the quadriceps. Genes with the strongest differences in expression were markers for oxidative fiber types (e.g. <it>Tnni1</it>) and genes which are known to be involved in embryogenesis (<it>Dkk3</it>, <it>Hoxd8</it>,<it>Hoxd9 </it>and <it>Tbx1</it>). Also <it>Dkk2, Hoxa5, Hoxa10, Hoxc9, Hoxc10, Hoxc6 </it>and <it>Tbx15 </it>were detectably, but not differentially expressed in adult muscle tissue. Expression of differentially expressed genes was not influenced by an 8-week or 20-week HFD. Comparing gastrocnemius, quadriceps and soleus, expression of <it>Hoxd8 </it>and <it>Hoxd9 </it>was not related with expression of markers for the four different fiber types. We found that the expression of both <it>Hoxd8 </it>and <it>Hoxd9 </it>was much higher in the gastrocnemius than in the quadriceps or soleus, whereas the expression of <it>Dkk3 </it>was high in quadriceps, but low in both gastrocnemius and soleus. Finally, expression of <it>Tbx1 </it>was high in quadriceps, intermediate in soleus and low in gastrocnemius.</p> <p>Conclusions</p> <p>We found that genes from the Dkk family, Hox family and Tbx family are detectably expressed in adult mouse muscle. Interestingly, expression of <it>Dkk3</it>, <it>Hoxd8, Hoxd9 </it>and <it>Tbx1 </it>was highly different between gastrocnemius, quadriceps and soleus. In fact, every muscle type showed a unique combination of expression of these four genes which was not influenced by diet. Altogether, we conclude that genes important for embryogenesis identify mouse muscle types in a diet-independent and fiber type-unrelated manner.</p

Four-fold basal plane anisotropy of the nonlocal magnetization of YNi2B2C

Studies of single crystal YNi2B2C have revealed a four-fold anisotropy of the equilibrium magnetization in the square crystallographic basal plane. This pi/2 periodicity occurs deep in the superconductive mixed state. In this crystal symmetry, an ordinary superconductive mass anisotropy (as in usual London theory) allows only a constant, isotropic response. In contrast, the experimental results are well described by generalized London theory incorporating non-local electrodynamics, as needed for this clean, intermediate-k superconductor.Comment: 4 pages, 4 figure

Nature of 45 degree vortex lattice reorientation in tetragonal superconductors

The transformation of the vortex lattice in a tetragonal superconductor which consists of its 45 degree reorientation relative to the crystal axes is studied using the nonlocal London model. It is shown that the reorientation occurs as two successive second order (continuous) phase transitions. The transition magnetic fields are calculated for a range of parameters relevant for borocarbide superconductors in which the reorientation has been observed

The Phase Transition to a Square Vortex Lattice in Type-II Superconductors with Fourfold Anisotropy

We investigate the stability of the square vortex lattice which has been recently observed in experiments on the borocarbide family of superconductors. Taking into account the tetragonal symmetry of these systems, we add fourfold symmetric fourth-derivative terms to the Ginzburg-Landau(GL) free energy. At $H_{c2}$ these terms may be treated perturbatively to lowest order to locate the transition from a distorted hexagonal to a square vortex lattice. We also solve for this phase boundary numerically in the strongly type-II limit, finding large corrections to the lowest-order perturbative results. We calculate the relative fourfold $H_{c2}$ anisotropy for field in the $xy$ plane to be 4.5% at the temperature, $T_c^{\Box}$, where the transition occurs at $H_{c2}$ for field along the $z$ axis. This is to be compared to the 3.6% obtained in the perturbative calculation. Furthermore, we find that the phase boundary in the $H-T$ phase diagram has positive slope near $H_{c2}$.Comment: 15 pages including 2 figures, LaTe