Primary fields and screening currents of gl(2|2) non-unitary conformal field theory

The non-semisimple $gl(2|2)_k$ current superalgebra in the standard basis and the corresponding non-unitary conformal field theory are investigated. Infinite families of primary fields corresponding to all finite-dimensional irreducible typical and atypical representations of $gl(2|2)$ and three (two even and one odd) screening currents of the first kind are constructed explicitly in terms of ten free fields.Comment: LaTex 16 pages, to appear in Nucl. Phys.

Drinfeld Basis And a Nonclassical Free Boson Representation of Twisted Quantum Affine Superalgebra Uq[osp(2∣2)(2)]U_q[osp(2|2)^{(2)}]}

We derive from the super RS algebra the Drinfeld basis of the twisted quantum affine superalgebra $U_q[osp(2|2)^{(2)}]$ by means of the Gauss decomposition technique. We explicitly construct a nonclassical level-one representation of $U_q[osp(2|2)^{(2)}]$ in terms of two $q$-deformed free boson fields.Comment: Change of title, and one added section on a nonclassical free boson realization; LaTex file 10 page

Determination and Validation of Parameters for Riedel-Hiermaier-Thoma Concrete Model

Numerical modelling of the complex physical processes such as concrete structures subjected to high-impulsive loads relies on suitable material models appropriate for impact and explosion problems. One of theextensive used concrete material models, the RHT model, contains all essential features of concrete materialssubjected to high dynamic loading. However, the application of the RHT model requires a set of material propertiesand model parameters without which reliable results cannot be expected. The present paper provides adetailed valuation of the RHT model and proposes a method of determining the model parameters for C40 concrete.Furthermore, the dynamic compressive and tensile strength function of the model formulation are modified toenhance the performance of the model as implemented in the hydrocode AUTODYN. The performance of thedetermined parameters of the modified RHT model is demonstrated by comparing to available experimentaldata, and further verified via simulations of physical experiments of concrete penetration by steel projectiles.The results of numerical analyses are found closely match the penetration depth and the crater size in the frontsurface of the concrete targets.Defence Science Journal, 2013, 63(5), pp.524-530, DOI:http://dx.doi.org/10.14429/dsj.63.386

Friedel oscillations in graphene gapped by breaking \u3ci\u3eƤ\u3c/i\u3e and \u3ci\u3eT\u3c/i\u3e symmetries: Topological and geometrical signatures of electronic structure

The measurement of Friedel oscillations (FOs) is conventionally used to recover the energy dispersion of electronic structure. Besides the energy dispersion, the modern electronic structure also embodies other key ingredients such as the geometrical and topological properties; it is one promising direction to explore the potential of FOs for the relevant measurement. Here, we present a comprehensive study of FOs in substrate-supported graphene under off-resonant circularly polarized light, in which a valley-contrasting feature and topological phase transition occur due to the combined breaking of inversion (Ƥ) and time reversal (T) symmetries. Depending on the position of the Fermi level, FOs may be contributed by electronic backscattering in one single valley or two valleys. In the single-valley regime, the oscillation periods of FOs can be used to determine the topological phase boundary of electronic structure, while the amplitudes of FOs distinguish trivial insulators and topological insulators in a quantitative way. In the two-valley regime, the unequal Fermi surfaces lead to a beating pattern (robust two-wave-front dislocations) of FOs contributed by intravalley (intervalley) scattering. This study implies the great potential of FOs in characterizing topological and geometrical properties of the electronic structure of two-dimensional materials

Characterization of photosystem II in transgenic tobacco plants with decreased iron superoxide dismutase

AbstractIron superoxide dismutases (FeSODs) play an important role in preventing the oxidative damage associated with photosynthesis. To investigate the mechanisms of FeSOD in protection against photooxidative stress, we obtained transgenic tobacco (Nicotiana tabacum) plants with severely decreased FeSOD by using a gene encoding tobacco chloroplastic FeSOD for the RNAi construct. Transgenic plants were highly sensitive to photooxidative stress and accumulated increased levels of O2•− under normal light conditions. Spectroscopic analysis and electron transport measurements showed that PSII activity was significantly reduced in transgenic plants. Flash-induced fluorescence relaxation and thermoluminescence measurements revealed that there was a slow electron transfer between QA and QB and decreased redox potential of QB in transgenic plants, whereas the donor side function of PSII was not affected. Immunoblot and blue native gel analyses showed that PSII protein accumulation was also decreased in transgenic plants. PSII photodamage and D1 protein degradation under high light treatment was increased in transgenic plants, whereas the PSII repair was not affected, indicating that the stability of the PSII complex was decreased in transgenic plants. The results in this study suggest that FeSOD plays an important role in maintaining PSII function by stabilizing PSII complexes in tobacco plants

Greater chemical signaling in root exudates enhances soil mutualistic associations in invasive plants compared to natives

Invasive plants can change soil properties resulting in improved growth. Although invaders are known to alter soil chemistry, it remains unclear if chemicals secreted by roots facilitate invasive plant–soil mutualisms. With up to 19 confamilial pairs of invasive and native plants, and most of which were congeners, we explored the root exudate-induced changes in plant–arbuscular mycorrhizal (AM) fungal mutualisms. We found that, relative to natives, invaders had greater AM colonization, greater biomass and their root exudates contained higher concentrations of two common chemical signals – quercetin and strigolactones – which are known to stimulate AM fungal growth and root colonization. An exudate exchange experiment showed that root exudates from invaders increased AM colonization more than exudates from natives. However, application of activated carbon led to greater reduction in AM colonization and plant biomass for invaders than natives, suggesting stronger effects of chemical signals in root exudates from invaders. We show that nonnative plants promote interactions with soil mutualists via enhancing root exudate chemicals, which could have important implications for invasion success