Genotypic variation of cut chrysanthemum response to high CO2 concentration: Growth, time to flowering and visual quality

In this study sixteen cut chrysanthemum cultivars were used to evaluate the effects of high CO2 concentration (1500 µmol mol-1) on growth, time to flowering and visual quality as compared to the concentration used in commercial greenhouses (600 µmol mol-1). CO2 enrichment increased light use efficiency (11-41%) and total plant dry mass (TDM) (5-40%) in a cultivar dependent manner. This TDM increase was a result of: (i) higher relative growth rate during the long day period (i.e., 0 to 2 weeks; LD); and (ii) higher absolute growth rate both during the period between 2 to 6 weeks (SD1), and 6 weeks to final harvest (SD2). Cultivar differences in TDM at flowering between the two CO2 concentrations could be explained by differences in growth rate during the LD and SD2 periods. Furthermore, growing at high CO2 regime enhanced the number of flowers and flower buds per plant (NoF, 4-48%). Interestingly, the cultivars that showed the highest percentage of TDM increase, with CO2 enrichment, were not the ones that had the highest increase in the percentage of NoF. In contrast, high CO2 concentration had only a minor or no effect on the number of internodes on the main stem and on the reaction time in all the cultivars examined. From this research it is concluded that there is a large variation in the response of cut chrysanthemum cultivars to CO2 enrichment, in terms of TDM and NoF, which gives possibilities for breeding

Dual pairing of symmetry groups and dynamical groups in physics

This article reviews many manifestations and applications of dual representations of pairs of groups, primarily in atomic and nuclear physics. Examples are given to show how such paired representations are powerful aids in understanding the dynamics associated with shell-model coupling schemes and in identifying the physical situations for which a given scheme is most appropriate. In particular, they suggest model Hamiltonians that are diagonal in the various coupling schemes. The dual pairing of group representations has been applied profitably in mathematics to the study of invariant theory. We show that parallel applications to the theory of symmetry and dynamical groups in physics are equally valuable. In particular, the pairing of the representations of a discrete group with those of a continuous Lie group or those of a compact Lie with those of a non-compact Lie group makes it possible to infer many properties of difficult groups from those of simpler groups. This review starts with the representations of the symmetric and unitary groups, which are used extensively in the many-particle quantum mechanics of bosonic and fermionic systems. It gives a summary of the many solutions and computational techniques for solving problems that arise in applications of symmetry methods in physics and which result from the famous Schur-Weyl duality theorem for the pairing of these representations. It continues to examine many chains of symmetry groups and dual chains of dynamical groups associated with the several coupling schemes in atomic and nuclear shell models and the valuable insights and applications that result from this examination.Comment: 51 pages, 5 figures and 5 table

Effect of Relative Air Himidity on the Stomatal Functionality in Fully Developed Leaves

Several studies have shown that stomata developed under long-term high relative air humidity (RH =85%) are malfunctional, resulting in a poor control of water loss. Yet, little is known about the dynamics of stomatal adaptation to moderate RH, and the possibilities to improve or reverse the destabilized stomatal responsiveness. In this study, a reciprocal transfer experiment was conducted in climate chambers using Rosa hybrida ‘Prophyta’, grown at moderate RH (60%) or at high RH (90%). The adaptation of fully developed leaves to the new RH environment was assessed at day 0, 4, 8 and 12 after plant transfer by measuring the transpiration rate in detached leaves. Stomata fully developed at high RH had a lower closing capacity in response to a decrease in leaf Relative Water Content (RWC) (i.e. water loss was considerably high at RWC below 20%, whereas in moderate RH stomata the water loss almost ceased at 57% RWC). Furthermore, stomata developed at high RH did not become functional after 12 days of cultivation at moderate RH. Similarly, stomata developed at moderate RH and transferred to high RH for a 12 day period did not loose their ability to close in response to desiccation. This indicates that stomatal functionality is determined during leaf development, while after this period stomata have a limited capacity to adapt to new RH environment. It is concluded that stomata from fully developed rose leaves conserve their behaviour independently of the post-development humidity leve

In vivo selection of resistant E. coli after ingestion of milk with added drug residues.

Antimicrobial resistance represents a major global threat to modern medicine. In vitro studies have shown that very low concentrations of drugs, as frequently identified in the environment, and in foods and water for human and animal consumption, can select for resistant bacteria. However, limited information is currently available on the in vivo impact of ingested drug residues. The objective of our study was to evaluate the effect of feeding preweaned calves milk containing antimicrobial drug residues (below the minimum inhibitory concentration), similar to concentrations detected in milk commonly fed to dairy calves, on selection of resistant fecal E. coli in calves from birth to weaning. At birth, thirty calves were randomly assigned to a controlled feeding trial where: 15 calves were fed raw milk with no drug residues (NR), and 15 calves were fed raw milk with drug residues (DR) by adding ceftiofur, penicillin, ampicillin, and oxytetracycline at final concentrations in the milk of 0.1, 0.005, 0.01, and 0.3 µg/ml, respectively. Fecal samples were rectally collected from each calf once a week starting at birth prior to the first feeding in the trial (pre-treatment) until 6 weeks of age. A significantly greater proportion of E. coli resistant to ampicillin, cefoxitin, ceftiofur, streptomycin and tetracycline was observed in DR calves when compared to NR calves. Additionally, isolates from DR calves had a significant decrease in susceptibility to ceftriaxone and ceftiofur when compared to isolates from NR calves. A greater proportion of E. coli isolates from calves in the DR group were resistant to 3 or more antimicrobial drugs when compared to calves in the ND group. These findings highlight the role that low concentrations of antimicrobial drugs have on the evolution and selection of resistance to multiple antimicrobial drugs in vivo

Fast gates for ion traps by splitting laser pulses

We present a fast phase gate scheme that is experimentally achievable and has an operation time more than two orders of magnitude faster than current experimental schemes for low numbers of pulses. The gate time improves with the number of pulses following an inverse power law. Unlike implemented schemes which excite precise motional sidebands, thus limiting the gate timescale, our scheme excites multiple motional states using discrete ultra-fast pulses. We use beam-splitters to divide pulses into smaller components to overcome limitations due to the finite laser pulse repetition rate. This provides gate times faster than proposed theoretical schemes when we optimise a practical setup.Comment: 20 pages, 8 figure

Double vector meson production in the International Linear Collider

In this paper we study double vector meson production in $\gamma \gamma$ interactions at high energies and, using the color dipole picture, estimate the main observables which can be probed at the International Linear Collider (ILC). The total $\gamma (Q_1^2) + \gamma (Q_2^2) \rightarrow V_1 + V_2$ cross-sections for $V_i = \rho$, $\phi$, $J/\psi$ and $\Upsilon$ are computed and the energy and virtuality dependencies are studied in detail. Our results demonstrate that the experimental analysis of this process is feasible at the ILC and it can be useful to constrain the QCD dynamics at high energies.Comment: 11 pages, 8 figure