Lack of correlation between constitutive and induced resistance to a herbivore in crucifer plants: real or flawed by experimental methods?

The correlation between constitutive and induced resistance to herbivores in plants has long been of interest to evolutionary biologists, and various approaches to determining levels of resistance have been used in this field of research. In this study, we examined the relationship between constitutive and induced resistance to the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), in 11 closely related species of wild crucifers. We assessed the survival, development, and reproduction of the test insects and calculated their intrinsic rate of increase as an indicator of constitutive and induced resistance for the plants. We used larvae of P. xylostella and jasmonic acid as elicitors of the induced response. We failed to find a correlation between constitutive and induced resistance in these crucifer plants when the induction of resistance was initiated by either herbivory or jasmonic acid application. Analysis of the results suggests that the failure to detect a relationship between the two types of resistance could be caused by flaws in measuring constitutive resistance, which was apparently confounded with induced resistance. We discuss the difficulties and pitfalls in measuring constitutive resistance and ways to improve the methodology in investigating the relationships between constitutive and induced resistance in plant

Vector Meson Propagator and Baryon Current Conservation

If baryons couple only with $\omega$-mesons, one found the baryon spectral function may be negative. We show this unacceptable result is caused by the $k_\mu k_\nu$-terms in the $\omega$-meson propagator. Their contribution may not vanish in approximate calculations which violate the baryon current conserves. A rule is suggested, by which the calculated baryon spectral function is well behaved.Comment: 9 pages (LaTeX file), 3 figures (PostScript file

Coupled Dyson-Schwinger Equations and Effects of Self-Consistency

Using the $\sigma -\omega$ model as an effective tool, the effects of self-consistency are studied in some detail. A coupled set of Dyson-Schwinger equations for the renormalized baryon and meson propagators in the $\sigma -\omega$ model is solved self-consistently according to the dressed Hartree-Fock scheme, where the hadron propagators in both the baryon and meson self-energies are required to also satisfy this coupled set of equations. It is found that the self-consistency affects the baryon spectral function noticeably, if only the interaction with $\sigma$ mesons is considered. However, there is a cancellation between the effects due to the $\sigma$ and $\omega$ mesons and the additional contribution of $\omega$ mesons makes the above effect insignificant. In both the $\sigma$ and $\sigma -\omega$ cases the effects of self-consistency on meson spectral function are perceptible, but they can nevertheless be taken account of without a self-consistent calculation. Our study indicates that to include the meson propagators in the self-consistency requirement is unnecessary and one can stop at an early step of an iteration procedure to obtain a good approximation to the fully self-consistent results of all the hadron propagators in the model, if an appropriate initial input is chosen. Vertex corrections and their effects on ghost poles are also studied.Comment: 20 pages (include 5 tables), 17 figures (PostScript file

A Comparative Study of fBf_B within QCD Sum Rules with Two Typical Correlators up to Next-to-Leading Order

The B-decay constant $f_B$ is an important component for studying $B$-meson decays, which can be studied through QCD sum rules. We make a detailed discussion on $f_B$ from two sum rules, i.e. sum rules I and II, which are derived from the conventional correlator and the correlator with chiral currents respectively. It is found that these two sum rules are consistent with each other. However, the sum rules II has less uncertainty sources than that of sum rules I, and then it can be more accurate if we know the dimension-four gluon condensate well. It is found that $f_B$ decreases with the increment of $m_b$, and to compare with the Belle experimental data on $f_B$, both sum rules prefer smaller pole $b$-quark mass, $m_b=4.68\pm0.07$ GeV. By varying all the input parameters in their reasonable region and adding all the uncertainties together in quadrature, we obtain $f_B=172^{+23}_{-25}$ MeV for sum rules I and $f_B=214_{-34}^{+26}$ MeV for sum rules II.Comment: 11 pages, 4 figures, 2 tables. To match the printed version. To be published in Communications in Theoretical Physic

Effect of cultivation, tillage practice, and fertilization on total organic carbon, light fraction, and microbial biomass carbon in soils from the Loess Plateau of China and the Canadian prairies

Non-Peer ReviewedThree soils: Huangmian, Huihe, Heilu soil, from the Loess Plateau and one soil: Orthic Brown Chernozem, from the Canadian Prairies, were used to evaluate the effect of cultivation time, tillage system and fertilization, on total soil organic carbon (SOC), light fraction (LF), and microbial biomass carbon (MB-C). Upon cultivation, Huangmian soil lost 77% of total organic carbon within 5 years (0-20 cm), at a decrease rate of 2.15 tonnes C ha-1 yr-1. The Huihe soil lost 70% of total organic carbon at rate of 0.96-1.06 tonnes C ha-1 yr—1 over 42 years (0-20 cm). Comparably, the Orthic Brown Chernozem lost 11% and 44% of the total soil organic carbon mass (0-20 cm), after 40 and 80 years of cultivation respectively, at a corresponding rate of 0.17 tonnes C ha-1 yr-1 and 0.45 tonnes C ha-1 yr-1. Water erosion for the Huangmian and Huihe soil, and wind erosion for the Brown Chernozem during 1930’s, are the main reasons for organic carbon decline. The light fraction of organic carbon (LFOC) decreased more rapidly than total organic carbon: LFOC decreased by 73% and 90% for the Huangmian and Huihe soil for the corresponding period, and decreased by 70% and 74% for Brown Chernozem brought under cultivated 40 and 80 years ago respectively. The change of microbial biomass carbon (MB-C) showed same trend as total organic carbon and LFOC. On the Heilu soil, a 29% decrease of SOC, which was comparable to average 22% decline of SOC during about hundred years of cultivation on the Prairie, was observed after thousands of years of cultivation relative to native sod. Some management practices had a positive effect on restoring and maintaining soil organic carbon. On the Orthic Brown Chernozem, dry matter of light fraction in 0-5 cm was increased after no-tillage was practiced for 7 years. As well, LFOC in 0-5 cm was increased significantly after switching from cereal-fallow to continuous cropping for 10 years. Growing alfalfa for 10 years after 60 years cereal-fallow increased total organic carbon by 80% and 27% in 0-5 cm and 5-10 cm depths respectively, while dry matter of LF and LFOC were increased by 54% and 194%, and 245% and 286% in 0-5 cm and 5-10 cm respectively. Application of manure alone and manure plus chemical fertilizer was found to restore total organic carbon, LFOC, and MB-C in the Heilu soil

Lopsidedness of cluster galaxies in modified gravity

We point out an interesting theoretical prediction for elliptical galaxies residing inside galaxy clusters in the framework of modified Newtonian dynamics (MOND), that could be used to test this paradigm. Apart from the central brightest cluster galaxy, other galaxies close enough to the centre experience a strong gravitational influence from the other galaxies of the cluster. This influence manifests itself only as tides in standard Newtonian gravity, meaning that the systematic acceleration of the centre of mass of the galaxy has no consequence. However, in the context of MOND, a consequence of the breaking of the strong equivalence principle is that the systematic acceleration changes the own self-gravity of the galaxy. We show here that, in this framework, initially axisymmetric elliptical galaxies become lopsided along the external field's direction, and that the centroid of the galaxy, defined by the outer density contours, is shifted by a few hundreds parsecs with respect to the densest point.Comment: accepted for publication in JCA

Relaxation- and Decoherence-free subspaces in networks of weakly and strongly coupled resonators

We consider a network of interacting resonators and analyze the physical ingredients that enable the emergence of relaxation-free and decoherence-free subspaces. We investigate two different situations: i) when the whole network interacts with a common reservoir and ii) when each resonator, strongly coupled to each other, interacts with its own reservoir. Our main result is that both subspaces are generated when all the resonators couple with the same group of reservoir modes, thus building up a correlation (among these modes), which has the potential to shield particular network states against relaxation and/or decoherence.Comment: 5 page

Crystallization of diamond-like carbon to graphene under low energy ion beam modification

Low-energy ion beam modification was proposed to create graphene on the top of the insulated diamond-like carbon films. In such low-temperature fabrication process the surface of the amorphous carbon could crystallize to graphene as a result of point defect creation and enhanced diffusion caused by the ion bombardment. In the experiment 130 eV argon ion irradiation was used. After the modification the resistivity of the sample surface drops. Raman spectra of the samples measured at 633 nm showed partial crystallization and were similar to the spectra of defected graphene. This result is very encouraging and we hope that by improving this technology it will be possible to fabricate defect-free graphene, which can be used in electronics without transfer to other substrate

Local minimal energy landscapes in river networks

The existence and stability of the universality class associated to local minimal energy landscapes is investigated. Using extensive numerical simulations, we first study the dependence on a parameter $\gamma$ of a partial differential equation which was proposed to describe the evolution of a rugged landscape toward a local minimum of the dissipated energy. We then compare the results with those obtained by an evolution scheme based on a variational principle (the optimal channel networks). It is found that both models yield qualitatively similar river patterns and similar dependence on $\gamma$. The aggregation mechanism is however strongly dependent on the value of $\gamma$. A careful analysis suggests that scaling behaviors may weakly depend both on $\gamma$ and on initial condition, but in all cases it is within observational data predictions. Consequences of our resultsComment: 12 pages, 13 figures, revtex+epsfig style, to appear in Phys. Rev. E (Nov. 2000

Partially spin polarized quantum Hall effect in the filling factor range 1/3 < nu < 2/5

The residual interaction between composite fermions (CFs) can express itself through higher order fractional Hall effect. With the help of diagonalization in a truncated composite fermion basis of low-energy many-body states, we predict that quantum Hall effect with partial spin polarization is possible at several fractions between $\nu=1/3$ and $\nu=2/5$. The estimated excitation gaps are approximately two orders of magnitude smaller than the gap at $\nu=1/3$, confirming that the inter-CF interaction is extremely weak in higher CF levels.Comment: 4 pages, 3 figure