The evolution of inflorescence diversity in the nightshades and heterochrony during meristem maturation

One of the most remarkable manifestations of plant evolution is the diversity for floral branching systems. These "inflorescences" arise from stem cell populations in shoot meristems that mature gradually to reproductive states in response to environmental and endogenous signals. The morphology of the shoot meristem maturation process is conserved across distantly related plants, raising the question of how diverse inflorescence architectures arise from seemingly common maturation programs. In tomato and related nightshades (Solanaceae), inflorescences range from solitary flowers to highly branched structures bearing hundreds of flowers. Since reproductive barriers between even closely related Solanaceae have precluded a genetic dissection, we captured and compared meristem maturation transcriptomes from five domesticated and wild species reflecting the evolutionary continuum of inflorescence complexity. We find these divergent species share hundreds of dynamically expressed genes, enriched for transcription factors. Meristem stages are defined by distinct molecular states and point to modified maturation schedules underlying architectural variation. These modified schedules are marked by a peak of transcriptome expression divergence during the reproductive transition, driven by heterochronic shifts of dynamic genes, including transcriptional regulators with known roles in flowering. Thus, evolutionary diversity in Solanaceae inflorescence complexity is determined by subtle modifications of transcriptional programs during a critical transitional window of meristem maturation, which we propose underlies similar cases of plant architectural variation. More broadly, our findings parallel the recently described transcriptome "inverse hourglass" model for animal embryogenesis, suggesting both plant and animal morphological variation is guided by a mid-development period of transcriptome divergence

Dynamical modelling of the elliptical galaxy NGC 2974

In this paper we analyse the relations between a previously described oblate Jaffe model for an ellipsoidal galaxy and the observed quantities for NGC 2974, and obtain the length and velocity scales for a relevant elliptical galaxy model. We then derive the finite total mass of the model from these scales, and finally find a good fit of an isotropic oblate Jaffe model by using the Gauss-Hermite fit parameters and the observed ellipticity of the galaxy NGC 2974. The model is also used to predict the total luminous mass of NGC 2974, assuming that the influence of dark matter in this galaxy on the image, ellipticity and Gauss-Hermite fit parameters of this galaxy is negligible within the central region, of radius $0.5R_{\rm e}.$Comment: 7 figure

Soil microbial beta-diversity is linked with compositional variation in aboveground plant biomass in a semi-arid grassland

Background and aims: Exploring biodiversity linkages between aboveground and belowground biota is a core topic in ecology, and can have implications on our understanding of ecosystem process stability. Yet, this topic still remains underexplored. Here, we explored diversity linkages, in terms of both alpha- and beta- diversity, between plant and top soil microbial communities in a semi-arid grassland ecosystem. Methods: Soil microbial community structure was assessed based on both 16S rRNA and functional genes, and plant community composition was evaluated by traditional “species composition” and a newly-defined “biomass composition”, which includes the information on the biomass of each species. Results: The bacterial alpha-diversity, expressed as the richness and Shannon diversity of 16S rRNA genes, was significantly correlated with plant species richness and Shannon diversity, whereas the alpha-diversity of microbial functional genes showed marginal association with total plant biomass. Microbial beta-diversity, evaluated by 16S rRNA genes, showed close relationship with plant beta-diversity estimated by both “species composition” and “biomass composition”, while the microbial beta-diversity based on functional genes was only associated with the compositional variation in aboveground plant biomass. Conclusions: These results showed that the differences in metabolic potential of soil microbial communities, which is closely related with ecosystem functions, can be better predicted by the variation of plant-derived resources returned to soil, than merely by the species composition of the macro-organism communities

Aharonov-Bohm Effect for Parallel and T-shaped Double Quantum Dots

We investigate the Aharonov-Bohm (AB) effect for the double quantum dots in the Kondo regime using the slave-boson mean-field approximation. In contrast to the non-interacting case, where the AB oscillation generally has the period of 4$\pi$ when the two-subring structure is formed via the interdot tunneling $t_c$, we find that the AB oscillation has the period of 2$\pi$ in the Kondo regime. Such effects appear for the double quantum dots close to the T-shaped geometry even in the charge-fluctuation regime. These results follow from the fact that the Kondo resonance is always fixed to the Fermi level irrespective of the detailed structure of the bare dot-levels.Comment: 3 pages, 4 figures; minor change

Interacting Dipoles from Matrix Formulation of Noncommutative Gauge Theories

We study the IR behavior of noncommutative gauge theory in the matrix formulation. We find that in this approach, the nature of the UV/IR mixing is easily understood, which allows us to perform a reliable calculation of the quantum effective action for the long wavelength modes of the noncommutative gauge field. At one loop, we find that our description is weakly coupled only in the supersymmetric theory. At two loops, we find non-trivial interaction terms suggestive of dipole degrees of freedom. These dipoles exhibit a channel duality reminiscent of string theory.Comment: LaTeX 11 pages, 4 figures; v.2 minor changes and some references added; v.3 many more technical details added and significantly different presentation, use REVTeX 4, to appear in PR

Whole genome resequencing reveals signatures of selection and timing of duck domestication

Background The genetic basis of animal domestication remains poorly understood, and systems with substantial phenotypic differences between wild and domestic populations are useful for elucidating the genetic basis of adaptation to new environments as well as the genetic basis of rapid phenotypic change. Here, we sequenced the whole genome of 78 individual ducks, from two wild and seven domesticated populations, with an average sequencing depth of 6.42X per individual. Results Our population and demographic analyses indicate a complex history of domestication, with early selection for separate meat and egg lineages. Genomic comparison of wild to domesticated populations suggest that genes affecting brain and neuronal development have undergone strong positive selection during domestication. Our FST analysis also indicates that the duck white plumage is the result of selection at the melanogenesis associated transcription factor locus. Conclusions Our results advance the understanding of animal domestication and selection for complex phenotypic traits

The PLATO Dome A Site-Testing Observatory : instrumentation and first results

The PLATeau Observatory (PLATO) is an automated self-powered astrophysical observatory that was deployed to Dome A, the highest point on the Antarctic plateau, in 2008 January. PLATO consists of a suite of site-testing instruments designed to quantify the benefits of the Dome A site for astronomy, and science instruments designed to take advantage of the unique observing conditions. Instruments include CSTAR, an array of optical telescopes for transient astronomy; Gattini, an instrument to measure the optical sky brightness and cloud cover statistics; DASLE, an experiment to measure the statistics of the meteorological conditions within the near-surface layer; Pre-HEAT, a submillimeter tipping radiometer measuring the atmospheric transmission and water vapor content and performing spectral line imaging of the Galactic plane; and Snodar, an acoustic radar designed to measure turbulence within the near-surface layer. PLATO has run completely unattended and collected data throughout the winter 2008 season. Here we present a detailed description of the PLATO instrument suite and preliminary results obtained from the first season of operation

Path Selection for Quantum Repeater Networks

Quantum networks will support long-distance quantum key distribution (QKD) and distributed quantum computation, and are an active area of both experimental and theoretical research. Here, we present an analysis of topologically complex networks of quantum repeaters composed of heterogeneous links. Quantum networks have fundamental behavioral differences from classical networks; the delicacy of quantum states makes a practical path selection algorithm imperative, but classical notions of resource utilization are not directly applicable, rendering known path selection mechanisms inadequate. To adapt Dijkstra's algorithm for quantum repeater networks that generate entangled Bell pairs, we quantify the key differences and define a link cost metric, seconds per Bell pair of a particular fidelity, where a single Bell pair is the resource consumed to perform one quantum teleportation. Simulations that include both the physical interactions and the extensive classical messaging confirm that Dijkstra's algorithm works well in a quantum context. Simulating about three hundred heterogeneous paths, comparing our path cost and the total work along the path gives a coefficient of determination of 0.88 or better.Comment: 12 pages, 8 figure

Canonical Quantization of Noncommutative Field Theory

A simple method to canonically quantize noncommutative field theories is proposed. As a result, the elementary excitations of a (2n+1)-dimensional scalar field theory are shown to be bilocal objects living in an (n+1)-dimensional space-time. Feynman rules for their scattering are derived canonically. They agree, upon suitable redefinitions, with the rules obtained via star-product methods. The IR/UV connection is interpreted within this framework.Comment: 8 pages, 1 figur