Inherent Negative Refraction on Acoustic Branch of Two Dimensional Phononic Crystals

Guided by theoretical predictions, we have demonstrated experimentally the existence of negative refraction on the lowest two (acoustic) passbands (shear and longitudinal modes) of a simple two dimensional phononic crystal consisting of an isotropic stiff (aluminum) matrix and square- patterned isotropic compliant (PMMA) circular inclusions. At frequencies and wave vectors where the refraction is negative, the effective mass density and the effective stiffness tensors of the crystal can be positive-defnite, and that, this is an inherent property of phononic crystals with an isotropic stiff matrix containing periodically distributed isotropic compliant inclusions. The equi-frequency contours and energy ux vectors as fuctions of the phase-vector components, reveal a rich body of refractive properties that can be exploited to realize, for example, beam splitting, focusing, and frequency filtration on the lowest passbands of the crystal where the dissipation is the least. By proper selection of material and geometric parameters these phenomena can be realized at remarkably low frequencies (large wave lengths) using rather small simple two-phase unit cells. Keywords: Doubly periodic phononic crystals, acoustic branch negative refraction, beam splitting, focusing, imaging, frequency filtration at large wave length

Diversity and Distribution of Marine Synechococcus: Multiple Gene Phylogenies for Consensus Classification and Development of qPCR Assays for Sensitive Measurement of Clades in the Ocean

Marine Synechococcus is a globally significant genus of cyanobacteria that is comprised of multiple genetic lineages or clades. These clades are thought to represent ecologically distinct units, or ecotypes. Because multiple clades often co-occur together in the oceans, Synechococcus are ideal microbes to explore how closely related bacterial taxa within the same functional guild of organisms co-exist and partition marine habitats. Here we sequenced multiple gene loci from cultured strains to confirm the congruency of clade classifications between the 16S–23S rDNA internally transcribed spacer (ITS), 16S rDNA, narB, ntcA, and rpoC1 loci commonly used in Synechococcus diversity studies. We designed quantitative PCR (qPCR) assays that target the ITS for 10 Synechococcus clades, including four clades, XV, XVI, CRD1, and CRD2, not covered by previous assays employing other loci. Our new qPCR assays are very sensitive and specific, detecting down to tens of cells per ml. Application of these qPCR assays to field samples from the northwest Atlantic showed clear shifts in Synechococcus community composition across a coastal to open-ocean transect. Consistent with previous studies, clades I and IV dominated cold, coastal Synechococcus communities. Clades II and X were abundant at the two warmer, off-shore stations, and at all stations multiple Synechococcus clades co-occurred. qPCR assays developed here provide valuable tools to further explore the dynamics of microbial community structure and the mechanisms of co-existence

Adaptive predictors based on probabilistic SVM for real time disruption mitigation on JET

Peer reviewe

Extremely narrow spectrum of GRB110920A: further evidence for localised, subphotospheric dissipation

Much evidence points towards that the photosphere in the relativistic outflow in GRBs plays an important role in shaping the observed MeV spectrum. However, it is unclear whether the spectrum is fully produced by the photosphere or whether a substantial part of the spectrum is added by processes far above the photosphere. Here we make a detailed study of the $\gamma-$ray emission from single pulse GRB110920A which has a spectrum that becomes extremely narrow towards the end of the burst. We show that the emission can be interpreted as Comptonisation of thermal photons by cold electrons in an unmagnetised outflow at an optical depth of $\tau \sim 20$. The electrons receive their energy by a local dissipation occurring close to the saturation radius. The main spectral component of GRB110920A and its evolution is thus, in this interpretation, fully explained by the emission from the photosphere including localised dissipation at high optical depths.Comment: 14 pages, 11 figures, accepted to MNRA

Assessment of the baseline scenario at q(95) similar to 3 for ITER

Peer reviewe

Genome Sequence of the Estuarine Synechococcus sp. Strain NB0720_010

Synechococcus spp. are unicellular cyanobacteria widely distributed in the world\u27s oceans. We report the complete genome sequence of Synechococcus sp. strain NB0720_010, isolated from Narragansett Bay, Rhode Island. NB0702_10 has several large (.3,000-amino acid) protein-coding genes that may be important in its interactions with other cells, including grazers in estuarine habitats

Creep in oak material from the Vasa ship: verification of linear viscoelasticity and identification of stress thresholds

Creep deformation is a general problem for large wooden structures, and in particular for shipwrecks in museums. In this study, experimental creep data on the wooden cubic samples from the Vasa ship have been analysed to confirm the linearity of the viscoelastic response in the directions where creep was detectable (T and R directions). Isochronous stress-strain curves were derived for relevant uniaxial compressive stresses within reasonable time spans. These curves and the associated creep compliance values justify that it is reasonable to assume a linear viscoelastic behaviour within the tested ranges, given the high degree of general variability. Furthermore, the creep curves were fitted with a one-dimensional standard linear solid model, and although the rheological parameters show a fair amount of scatter, they are candidates as input parameters in a numerical model to predict creep deformations. The isochronous stress-strain relationships were used to define a creep threshold stress below which only negligible creep is expected. These thresholds ranges were 0.3-0.5 MPa in the R direction and 0.05-0.2 MPa in the T direction