Control of a model of DNA division via parametric resonance

We study the internal resonance, energy transfer, activation mechanism, and control of a model of DNA division via parametric resonance. While the system is robust to noise, this study shows that it is sensitive to specific fine scale modes and frequencies that could be targeted by low intensity electro-magnetic fields for triggering and controlling the division. The DNA model is a chain of pendula in a Morse potential. While the (possibly parametrically excited) system has a large number of degrees of freedom and a large number of intrinsic time scales, global and slow variables can be identified by (1) first reducing its dynamic to two modes exchanging energy between each other and (2) averaging the dynamic of the reduced system with respect to the phase of the fastest mode. Surprisingly, the global and slow dynamic of the system remains Hamiltonian (despite the parametric excitation) and the study of its associated effective potential shows how parametric excitation can turn the unstable open state into a stable one. Numerical experiments support the accuracy of the time-averaged reduced Hamiltonian in capturing the global and slow dynamic of the full system

Electromagnetic and hadronic decay of fully heavy tetraquark

In this study, we compute the electromagnetic and hadronic decay widths of the S-wave fully heavy tetraquark $T_{4Q}$ ($Q=c$ or $b$) at lowest order in $\alpha_s$ and $v$, in the framework of nonrelativistic QCD. The short-distance coefficients are determined through the standard procedure of matching. The nonperturbative long-distance matrix elements are related to the phenomenological four-body Schr\"odinger wave functions at the origin, whose values are taken from literature. The branching fractions are predicted to be around $10^{-3}$ and $10^{-6}$ for the $T_{4c}$ hadronic decay and electromagnetic decay, respectively. Combing our results with the $T_{4c}$ production cross sections at the LHC, we also predict the event numbers for various decay channels. With integrated luminosity $\mathcal{L}=100 \,{\rm fb}^{-1}$, it is expected that the event numbers can reach $10^3- 10^4$ for $T_{4c}\to \gamma\gamma$, and $10^5- 10^6$ for $T_{4c}\to {\rm LH}$, at the LHC. The detecting prospect is promising.Comment: 12 pages, 1 figures, 3 tables, errors in Eqs. (11c) and (12c) are corrected, numerical values in Tabs.(II) and (III) (for 0^++ channel) are slightly changed, all the conclusions do not chang

Understanding rice domestication and implications for cultivar improvement

Considerable insights were recently gained into the history and process of rice domestication. It becomes increasingly clear that artificial and natural selections coupled with extensive introgression have shaped the genomes of cultivated rice. The interplay of these evolutionary forces gave rise to the cultivated species, Oryza sativa, with divergent genomic backgrounds from two wild species, O. rufipogon and O. nivara, governed by a set of domestication alleles which had originated primarily at one location of initial cultivation. The mechanistic understanding of domestication suggests that the combination of quantitative trait locus mapping, genome-wide association study, and genome scan will be effective means for discovering potentially valuable alleles from the cultivated and wild species. The accumulation and appropriate sampling of germplasm collections for these analyses should effectively grow the useful allele pool, which combined with molecular breeding may get to a point literally triggering the re-domestication of rice varieties for sustainable food production Introduction Food crops have gone through many stages of development. The domestication of major cereal crops began approximately 10 000 years ago in different continents, which initiated a long-term evolutionary experiment giving rise to a number of new species adapted to the agricultural system However, this success did not come without costs. While continuing conversion of natural ecosystem into cropland and increasing uses of synthetic fertilizer and pesticide push up the crop yield, we apparently are running out of options for meeting the growing needs for food. Meanwhile, the over uses of cropland with heavy fertilization have severely reduced the quality and productivity of the cropland. With the high-quality cropland and other natural resources for food crop production getting in the trend of decrease, finding ways to ensure sustainable food production has become an increasingly important and challenging problem for research The origin and evolution of cultivated rice was subjected to considerable debate over the past several years. The debate centered on whether the two major rice cultivars, O. sativa ssp. indica and ssp. japonica, were derived from a single ancestor or domesticated independently at different locations The origin of indica and japonica cultivars It has long been recognized that there are two distinct groups of rice cultivars, namely indica and japonica subspecies of O. sativa, which differ in a series of morphological and physiological traits. The difference at the genomic level was also revealed, with multiple lines of evidence suggesting that the genomic cores of the two subspecies have diverged for 200 000 years or longe

Development of energy plants from hybrids between Miscanthus sacchariflorus and M. lutarioriparius grown on reclaimed mine land in the Loess Plateau of China

Miscanthus, a promising bioenergy plant, has a high biomass yield with high cellulose content suitable for biofuel production. However, harsh climatic and poor soil conditions, such as barren lands or abandoned mines, pose a challenge to the survival and yield of Miscanthus feedstock on the marginal land. The selection from the interspecific hybrids of Miscanthus might combine high survival rates and high yield, which benefits energy crop development in multi-stressful environments. A total of 113 F1 hybrids between Miscanthus sacchariflorus and M. lutarioriparius together with the parents were planted and evaluated for multiple morphological and physiological traits on the mine land of the Loess Plateau of China. The majority of hybrids had higher establishment rates than M. sacchariflorus while M. lutarioriparius failed to survive for the first winter. Nearly all hybrid genotypes outperformed M. lutarioriparius for yield-related traits including plant height, tiller number, tiller diameter, and leaf area. The average biomass of the hybrids was 20 times higher than that of surviving parent, M. sacchariflorus. Furthermore, the photosynthetic rates and water use efficiency of the hybrids were both significantly higher than those of the parents, which might be partly responsible for their higher yield. A total of 29 hybrids with outstanding traits related to yield and stress tolerance were identified as candidates. The study investigated for the first time the hybrids between local individuals of M. sacchariflorus and high-biomass M. lutarioriparius, suggesting that this could be an effective approach for high-yield energy crop development on vast of marginal lands

An efficient constrained weighted least squares method with bias reduction for TDOA-based localization

This paper addresses the source location problem by using time-difference-of-arrival (TDOA) measurements. The two-stage weighted least squares (TWLS) algorithm has been widely used in the TDOA location. However, the estimation accuracy of the source location is poor and the bias is significant when the measurement noise is large. Owing to the nonlinear nature of the system model, we reformulate the localization problem as a constrained weighted least squares problem and derive the theoretical bias of the source location estimate from the maximum-likelihood (ML) estimation. To reduce the location bias and improve location accuracy, a novel bias-reduced method is developed based on an iterative constrained weighted least squares algorithm. The new method imposes a set of linear equality constraints instead of the quadratic constraints to suppress the bias. Numerical simulations demonstrate the significant performance improvement of the proposed method over the traditional methods. The bias is reduced significantly and the Cramér–Rao lower bound accuracy can also be achieve

Mapping 49 quantitative trait loci at high resolution through sequencing-based genotyping of rice recombinant inbred lines

Mapping chromosome regions responsible for quantitative phenotypic variation in recombinant populations provides an effective means to characterize the genetic basis of complex traits. We conducted a quantitative trait loci (QTL) analysis of 150 rice recombinant inbred lines (RILs) derived from a cross between two cultivars, Oryza sativa ssp. indica cv. 93-11 and Oryza sativa ssp. japonica cv. Nipponbare. The RILs were genotyped through next-generation sequencing, which accurately determined the recombination breakpoints and provided a new type of genetic markers, recombination bins, for QTL analysis. We detected 49 QTL with phenotypic effect ranging from 3.2 to 46.0% for 14 agronomics traits. Five QTL of relatively large effect (14.6–46.0%) were located on small genomic regions, where strong candidate genes were found. The analysis using sequencing-based genotyping thus offers a powerful solution to map QTL with high resolution. Moreover, the RILs developed in this study serve as an excellent system for mapping and studying genetic basis of agricultural and biological traits of rice. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00122-010-1449-8) contains supplementary material, which is available to authorized users