Cut-rose production in response to planting density in two contrasting cultivars

Growing in lower planting density, rose plants produce more assimilates, which can be used to produce more and/or heavier flowering shoots. The effect of planting density was investigated during a period including the first five flowering flushes of a young crop. In a heated greenhouse two cut-rose cultivars were grown under bent canopy management. ‘Akito’ on own-roots and ‘Ilios’ on ‘Natal Briar’ rootstock were planted with densities of 8 and 4 plants per m2. Starting at the end of June 2007, flowering shoots were harvested over a time span of eight months. Based on ‘flowering flushes’, times of high harvest rate, the harvesting time span could be divided into five consecutive periods, each including one flush. The cultivars showed contrasting responses to planting density. In the first three periods the response in ‘Ilios’ was extraordinary, because at low density plants did not produce more flowering shoots, as would be expected. However, the response in shoot fresh weight was larger for ‘Ilios’ than for ‘Akito’, 35% compared to 21% over the entire study period. The results imply that there was a genetic difference in the effect of assimilate availability and/or local light environment. During the first three periods, these factors can not have influenced shoot number in ‘Ilios’, while they did in ‘Akito’. It is suggested that decreases of assimilate availability in winter caused the shoot number response to emerge for ‘Ilios’ later on

Noncoherent Space-Time Coding: An Algebraic Perspective

Cataloged from PDF version of article.The design of space–time signals for noncoherent block-fading channels where the channel state information is not known a priori at the transmitter and the receiver is considered. In particular, a new algebraic formulation for the diversity advantage design criterion is developed. The new criterion encompasses, as a special case, the well-known diversity advantage for unitary space–time signals and, more importantly, applies to arbitrary signaling schemes and arbitrary channel distributions. This criterion is used to establish the optimal diversity-versus-rate tradeoff for training based schemes in block-fading channels. Our results are then specialized to the class of affine space–time signals which allows for a low complexity decoder. Within this class, space–time constellations based on the threaded algebraic space–time (TAST) architecture are considered. These constellations achieve the optimal diversity-versus-rate tradeoff over noncoherent block-fading channels and outperform previously proposed codes in the considered scenarios as demonstrated by the numerical results. Using the analytical and numerical results developed in this paper, nonunitary space–time codes are argued to offer certain advantages in block-fading channels where the appropriate use of coherent space–time codes is shown to offer a very efficient solution to the noncoherent space–time communication paradigm

Expression of collier in the premandibular segment of myriapods: support for the traditional Atelocerata concept or a case of convergence?

<p>Abstract</p> <p>Background</p> <p>A recent study on expression and function of the ortholog of the <it>Drosophila collier </it>(<it>col</it>) gene in various arthropods including insects, crustaceans and chelicerates suggested a <it>de novo </it>function of <it>col </it>in the development of the appendage-less intercalary segment of insects. However, this assumption was made on the background of the now widely-accepted Pancrustacea hypothesis that hexapods represent an in-group of the crustaceans. It was therefore assumed that the expression of <it>col </it>in myriapods would reflect the ancestral state like in crustaceans and chelicerates, i.e. absence from the premandibular/intercalary segment and hence no function in its formation.</p> <p>Results</p> <p>We find that <it>col </it>in myriapods is expressed at early developmental stages in the same anterior domain in the head, the parasegment 0, as in insects. Comparable early expression of <it>col </it>is not present in the anterior head of an onychophoran that serves as an out-group species closely related to the arthropods.</p> <p>Conclusions</p> <p>Our findings suggest either that i) the function of <it>col </it>in head development has been conserved between insects and myriapods, and that these two classes of arthropods may be closely related supporting the traditional Atelocerata (or Tracheata) hypothesis; or ii) alternatively <it>col </it>function could have been lost in early head development in crustaceans, or may indeed have evolved convergently in insects and myriapods.</p

Duplicated Hox genes in the spider Cupiennius salei

BACKGROUND: Hox genes are expressed in specific domains along the anterior posterior body axis and define the regional identity. In most animals these genes are organized in a single cluster in the genome and the order of the genes in the cluster is correlated with the anterior to posterior expression of the genes in the embryo. The conserved order of the various Hox gene orthologs in the cluster among most bilaterians implies that such a Hox cluster was present in their last common ancestor. Vertebrates are the only metazoans so far that have been shown to contain duplicated Hox clusters, while all other bilaterians seem to possess only a single cluster. RESULTS: We here show that at least three Hox genes of the spider Cupiennius salei are present as two copies in this spider. In addition to the previously described duplicated Ultrabithorax gene, we here present sequence and expression data of a second Deformed gene, and of two Sex comb reduced genes. In addition, we describe the sequence and expression of the Cupiennius proboscipedia gene. The spider Cupiennius salei is the first chelicerate for which orthologs of all ten classes of arthropod Hox genes have been described. The posterior expression boundary of all anterior Hox genes is at the tagma border of the prosoma and opisthosoma, while the posterior boundary of the posterior Hox genes is at the posterior end of the embryo. CONCLUSION: The presence of at least three duplicated Hox genes points to a major duplication event in the lineage to this spider, perhaps even of the complete Hox cluster as has taken place in the lineage to the vertebrates. The combined data of all Cupiennius Hox genes reveal the existence of two distinct posterior expression boundaries that correspond to morphological tagmata boundaries

Expression of myriapod pair rule gene orthologs

Background Segmentation is a hallmark of the arthropods; most knowledge about the molecular basis of arthropod segmentation comes from work on the fly Drosophila melanogaster. In this species a hierarchic cascade of segmentation genes subdivides the blastoderm stepwise into single segment wide regions. However, segmentation in the fly is a derived feature since all segments form virtually simultaneously. Conversely, in the vast majority of arthropods the posterior segments form one at a time from a posterior pre-segmental zone. The pair rule genes (PRGs) comprise an important level of the Drosophila segmentation gene cascade and are indeed the first genes that are expressed in typical transverse stripes in the early embryo. Information on expression and function of PRGs outside the insects, however, is scarce. Results Here we present the expression of the pair rule gene orthologs in the pill millipede Glomeris marginata (Myriapoda: Diplopoda). We find evidence that these genes are involved in segmentation and that components of the hierarchic interaction of the gene network as found in insects may be conserved. We further provide evidence that segments are formed in a single-segment periodicity rather than in pairs of two like in another myriapod, the centipede Strigamia maritima. Finally we show that decoupling of dorsal and ventral segmentation in Glomeris appears already at the level of the PRGs. Conclusions Although the pair rule gene network is partially conserved among insects and myriapods, some aspects of PRG interaction are, as suggested by expression pattern analysis, convergent, even within the Myriapoda. Conserved expression patterns of PRGs in insects and myriapods, however, may represent ancestral features involved in segmenting the arthropod ancestor

Patterning of ultrathin YBCO nanowires using a new focused-ion-beam process

Manufacturing superconducting circuits out of ultrathin films is a challenging task when it comes to patterning complex compounds, which are likely to be deteriorated by the patterning process. With the purpose of developing high-T$_c$ superconducting photon detectors, we designed a novel route to pattern ultrathin YBCO films down to the nanometric scale. We believe that our method, based on a specific use of a focused-ion beam, consists in locally implanting Ga^{3+} ions and/or defects instead of etching the film. This protocol could be of interest to engineer high-T$_c$ superconducting devices (SQUIDS, SIS/SIN junctions and Josephson junctions), as well as to treat other sensitive compounds.Comment: 13 pages, 7 figure

Electric-Field Tuning of Spin-Dependent Exciton-Exciton Interactions in Coupled Quantum Wells

We have shown experimentally that an electric field decreases the energy separation between the two components of a dense spin-polarized exciton gas in a coupled double quantum well, from a maximum splitting of $\sim 4$ meV to zero, at a field of $\sim$35 kV/cm. This decrease, due to the field-induced deformation of the exciton wavefunction, is explained by an existing calculation of the change in the spin-dependent exciton-exciton interaction with the electron-hole separation. However, a new theory that considers the modification of screening with that separation is needed to account for the observed dependence on excitation power of the individual energies of the two exciton components.Comment: 5 pages, 4 eps figures, RevTeX, Physical Review Letters (in press

Eddington-limited X-ray Bursts as Distance Indicators. I. Systematic Trends and Spherical Symmetry in Bursts from 4U 1728-34

We investigate the limitations of thermonuclear X-ray bursts as a distance indicator for the weakly-magnetized accreting neutron star 4U 1728-34. We measured the unabsorbed peak flux of 81 bursts in public data from the Rossi X-Ray Timing Explorer (RXTE). The distribution of peak fluxes was bimodal: 66 bursts exhibited photospheric radius expansion and were distributed about a mean bolometric flux of 9.2e-8 erg/cm^2/s, while the remaining (non-radius expansion) bursts reached 4.5e-8 erg/cm^2/s, on average. The peak fluxes of the radius-expansion bursts were not constant, exhibiting a standard deviation of 9.4% and a total variation of 46%. These bursts showed significant correlations between their peak flux and the X-ray colors of the persistent emission immediately prior to the burst. We also found evidence for quasi-periodic variation of the peak fluxes of radius-expansion bursts, with a time scale of approximately 40 d. The persistent flux observed with RXTE/ASM over 5.8 yr exhibited quasi-periodic variability on a similar time scale. We suggest that these variations may have a common origin in reflection from a warped accretion disk. Once the systematic variation of the peak burst fluxes is subtracted, the residual scatter is only approximately 3%, roughly consistent with the measurement uncertainties. The narrowness of this distribution strongly suggests that i) the radiation from the neutron star atmosphere during radius-expansion episodes is nearly spherically symmetric, and ii) the radius-expansion bursts reach a common peak flux which may be interpreted as a standard candle intensity.Adopting the minimum peak flux for the radius-expansion bursts as the Eddington flux limit, we derive a distance for the source of 4.4-4.8 kpc.Comment: 9 pages, 7 figures, accepted by ApJ. Minor referee's revisions, also includes 9 newly public X-ray burst