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Spiral wave reentry as a mechanism of lethal ventricular arrhythmias has been widely demonstrated in animal experiments and recordings from human hearts. It has been shown that in structurally normal hearts spiral waves are unstable, breaking up into multiple wavelets via dynamical instabilities. However, many of the second-generation action potential models give rise only to stable spiral waves, raising issues regarding the underlying mechanisms of spiral wave breakup. In this study, we carried out computer simulations of two-dimensional homogeneous tissues using five ventricular action potential models. We show that the transient outward potassium current (Ito), although it is not required, plays a key role in promoting spiral wave breakup in all five models. As the maximum conductance of Ito increases, it first promotes spiral wave breakup and then stabilizes the spiral waves. In the absence of Ito, speeding up the L-type calcium kinetics can prevent spiral wave breakup, however, with the same speedup kinetics, spiral wave breakup can be promoted by increasing Ito. Increasing Ito promotes single-cell dynamical instabilities, including action potential duration alternans and chaos, and increasing Ito further suppresses these action potential dynamics. These cellular properties agree with the observation that increasing Ito first promotes spiral wave breakup and then stabilizes spiral waves in tissue. Implications of our observations to spiral wave dynamics in the real hearts and action potential model improvements are discussed. NEW & NOTEWORTHY Spiral wave breakup manifesting as multiple wavelets is a mechanism of ventricular fibrillation. It has been known that spiral wave breakup in cardiac tissue can be caused by a steeply sloped action potential duration restitution curve, a property mainly determined by the recovery of L-type calcium current. Here, we show that the transient outward potassium current (Ito) is another current that plays a key role in spiral wave breakup, that is, spiral waves can be stable for low and high maximum Ito conductance but breakup occurs for intermediate maximum Ito conductance. Since Ito is present in normal hearts of many species and required for Brugada syndrome, it may play an important role in the spiral wave stability and arrhythmogenesis under both normal condition and Brugada syndrome. [ABSTRACT FROM AUTHOR]

Spiral wave reentry as a mechanism of lethal ventricular arrhythmias has been widely demonstrated in animal experiments and recordings from human hearts. It has been shown that in structurally normal hearts spiral waves are unstable, breaking up into multiple wavelets via dynamical instabilities. However, many of the second-generation action potential models give rise only to stable spiral waves, raising issues regarding the underlying mechanisms of spiral wave breakup. In this study, we carried out computer simulations of two-dimensional homogeneous tissues using five ventricular action potential models. We show that the transient outward potassium current (Ito), although it is not required, plays a key role in promoting spiral wave breakup in all five models. As the maximum conductance of Ito increases, it first promotes spiral wave breakup and then stabilizes the spiral waves. In the absence of Ito, speeding up the L-type calcium kinetics can prevent spiral wave breakup, however, with the same speedup kinetics, spiral wave breakup can be promoted by increasing Ito. Increasing Ito promotes single-cell dynamical instabilities, including action potential duration alternans and chaos, and increasing Ito further suppresses these action potential dynamics. These cellular properties agree with the observation that increasing Ito first promotes spiral wave breakup and then stabilizes spiral waves in tissue. Implications of our observations to spiral wave dynamics in the real hearts and action potential model improvements are discussed. [ABSTRACT FROM AUTHOR]

Spiral wave reentry as a mechanism of lethal ventricular arrhythmias has been widely demonstrated in animal experiments and recordings from human hearts. It has been shown that in structurally normal hearts spiral waves are unstable, breaking up into multiple wavelets via dynamical instabilities. However, many of the second-generation action potential models give rise only to stable spiral waves, raising issues regarding the underlying mechanisms of spiral wave breakup. In this study, we carried out computer simulations of two-dimensional homogeneous tissues using five ventricular action potential models. We show that the transient outward potassium current (Ito), although it is not required, plays a key role in promoting spiral wave breakup in all five models. As the maximum conductance of Ito increases, it first promotes spiral wave breakup and then stabilizes the spiral waves. In the absence of Ito, speeding up the L-type calcium kinetics can prevent spiral wave breakup, however, with the same speedup kinetics, spiral wave breakup can be promoted by increasing Ito. Increasing Ito promotes single-cell dynamical instabilities, including action potential duration alternans and chaos, and increasing Ito further suppresses these action potential dynamics. These cellular properties agree with the observation that increasing Ito first promotes spiral wave breakup and then stabilizes spiral waves in tissue. Implications of our observations to spiral wave dynamics in the real hearts and action potential model improvements are discussed. [ABSTRACT FROM AUTHOR]

Spiral wave reentry as a mechanism of lethal ventricular arrhythmias has been widely demonstrated in animal experiments and recordings from human hearts. It has been shown that in structurally normal hearts spiral waves are unstable, breaking up into multiple wavelets via dynamical instabilities. However, many of the second-generation action potential models give rise only to stable spiral waves, raising issues regarding the underlying mechanisms of spiral wave breakup. In this study, we carried out computer simulations of two-dimensional homogeneous tissues using five ventricular action potential models. We show that the transient outward potassium current (Ito), although it is not required, plays a key role in promoting spiral wave breakup in all five models. As the maximum conductance of Ito increases, it first promotes spiral wave breakup and then stabilizes the spiral waves. In the absence of Ito, speeding up the L-type calcium kinetics can prevent spiral wave breakup, however, with the same speedup kinetics, spiral wave breakup can be promoted by increasing Ito. Increasing Ito promotes single-cell dynamical instabilities, including action potential duration alternans and chaos, and increasing Ito further suppresses these action potential dynamics. These cellular properties agree with the observation that increasing Ito first promotes spiral wave breakup and then stabilizes spiral waves in tissue. Implications of our observations to spiral wave dynamics in the real hearts and action potential model improvements are discussed. [ABSTRACT FROM AUTHOR]

Background: Rice (Oryza sativa L.) is the staple food of more than half of the world's population. The identification of genetic diversity in local varieties of rice compared with that of improved or introduced varieties is important in breeding elite varieties for sustainable agriculture. Array-based single nucleotide polymorphism (SNP) detection is a useful technique for such studies and breeding applications. Results: We developed a 5291-SNP genome-wide array and used it to genotype 471 indica rice accessions in China using Illumina's Infinium technology. Local, introduced, and improved rice varieties were clustered into three sub-groups, with some overlapping shown in principal component analysis and neighbor-joining tree, also confirmed by model-based structure. A minor allele frequency ≥0.2 was observed in 72% of polymorphic SNPs in local rice varieties, which was higher than that in other sub-groups. Local rice varieties also had the highest mean polymorphism information content (PIC) and genetic diversity. Analysis of molecular variance showed that 90.61% of genetic variation was a result of differences within sub-groups. Conclusions: Our results revealed that SNP analysis clustered local varieties, introduced varieties, and improved varieties into three clear sub-groups. The distribution of parameter PIC values on sub-group genomes revealed that genetic differentiation among them might not be on a genome-wide scale, but rather on selected loci or chromosomal intervals. The result of Gene Ontology enrichment analysis showed that genes nearby those selected SNPs associated different molecular functions or various traits among sub-groups. [ABSTRACT FROM AUTHOR]

Avila and Jitomirskaya prove that the spectral measure μƒλ,v,α,x of quasi-periodic Schrödinger operator is 1/2-Hölder continuous with appropriate initial vector ƒ, if α satisfies Diophantine condition and λ is small. In the present paper, the conclusion is extended to that for all α with β(α) < λv,α,x, the spectral measure μμƒλ,v,α,x is 1/2-Hölder continuous with small λ, if v is real analytic in a neighbor of {|Jx|≤Cβ}, where C is a large absolute constant. In particular, the spectral measure μƒλ,α,x of almost Mathieu operator is 1/2-Hölder continuous if |λ|

For almost Mathieu operator (Hλ, α, θu) n = un + 1 + un−1+2λ cos 2π (θ + nα) un, the dry version of the Ten Martini Problem predicts that the spectrum Σλ,α of Hλ,α,θ has all gaps open for all λ ≠ 0 and α∈ℝ\Q. Avila and Jitomirskaya prove that Σλ,α has all gaps open for Diophantine αα and 0 < |λ| < 1. In the present paper, we show that Σλ,α has all gaps open for all α∈ℝ\Q with small λλ. [ABSTRACT FROM AUTHOR]

An abstract Birkhoff normal form theorem is constructed for infinite dimensional Hamiltonian systems with unbounded perturbations. It is shown, for a class of derivative nonlinear Schrödinger equations, that any solution with small initial value remains small in high index Sobolev norm over a long time. [ABSTRACT FROM AUTHOR]

The existence of lower dimensional KAM tori is shown for a class of nearly integrable Hamiltonian systems of infinite dimensions where the second Melnikov’s conditions are completely eliminated and the algebraic structure of the normal frequencies are not needed. As a consequence, it is proved that there exist many invariant tori and thus quasi-periodic solutions for nonlinear wave equations, Schrödinger equations and other equations of any spatial dimensions. [ABSTRACT FROM AUTHOR]

Understanding the onset and episodes of magmatism is essential for comprehending tectonic history, crustal extension, and geodynamic processes. However, due to physical constraints, many places have remained unexplored, which makes it difficult to understand their geological evolution. Following thorough sedimentary provenance analysis, the chronology and periods of magmatism within a drainage area can be revealed through the detrital zircon U-Pb dating method. Here, we present detrital zircon U-Pb ages (n = 1429) obtained from sediments in modern rivers of the Gongga batholith in the eastern Tibetan Plateau. Our results reveal five major magmatic episodes since the early Mesozoic. Three episodes of magmatism occurred in the early to middle Mesozoic (ca. 230–200 Ma, ca. 200–180 Ma, and ca. 180–160 Ma), followed by a protracted period of magmatic quiescence. During the Cenozoic, there were two main periods of magmatism at ca. 50–25 Ma and ca. 25–5 Ma. This is consistent with bedrock geochronological data acquired previously. We propose that the Mesozoic magmatism was most likely caused by postcollisional extension after the closure of the Paleo-Tethys Ocean. The two Cenozoic magmatic episodes are coeval with the progressive intensification of Xianshuihe fault activity. Consequently, these episodes highlight two significant phases of plateau growth in the eastern Tibetan Plateau: the northward push of the Indian plate and “lateral extrusion,” which is consistent with the ongoing subduction of the Indian plate beneath the Eurasian plate. [ABSTRACT FROM AUTHOR]

Drainage basins delineate the Earth's land surface into individual water collection units. Basin shape and river sinuosity determine water and sediment dynamics, affecting landscape evolution and connectivity between ecosystems and freshwater species. However, a high-resolution global dataset for the boundaries and geometry of basins is still missing. Using a 90-meter resolution digital elevation model, we measured the areas, lengths, widths, aspect ratios, slopes, and elevations for basins greater than 50 km2 globally. Additionally, we calculated the lengths and sinuosities of the longest river channels within these 0.67 million basins. We built a new global dataset, Basin90m, to present the basins and rivers, as well as their morphological metrics. To highlight the use cases of Basin90m, we explored differences between the nine stream orders, spatial distribution of drainage systems, and correlations between morphological metrics, such as Hack's law. By comparing with HydroSHEDS, Goole Earth images, and a few other datasets, we have demonstrated the high accuracy of Basin90m. Basin90m, available in Shapefile format, can be used in various GIS platforms, including QGIS, ArcGIS, and GeoPandas. Basin90m has substantial application prospects in geomorphology, hydrology, and ecology. [ABSTRACT FROM AUTHOR]

The averaging principle with a small initial value is constructed for a Hamiltonian perturbed Korteweg-de Vries (KdV) equation under periodic boundary condition where the positive integer n0 is not divisible by three and K1 and K2 are real analytic functions. More precisely, any action I with the small initial value evolves slowly over a long time interval: where s is the index of some space. [ABSTRACT FROM AUTHOR]

Because plant mechanical strength influences plant growth and development, the regulatory mechanisms underlying cell-wall synthesis deserve investigation. Rice mutants are useful for such research. We have identified a novel brittle culm 25 (bc25) mutant with reduced growth and partial sterility. BC25 encodes an UDP-glucuronic acid decarboxylase involved in cellulose synthesis and belongs to the UXS family. A single-nucleotide mutation in BC25 accounts for its altered cell morphology and cellwall composition. Transmission electron microscopy analysis showed that the thickness of the secondary cell wall was reduced in bc25. Monosaccharide analysis revealed significant increases in content of rhamnose and arabinose but not of other monosaccharides, indicating that BC25 was involved in xylose synthesis with some level of functional redundancy. Enzymatic assays suggested that BC25 functions with high activity to interconvert UDP-glucuronic acid (UDP-GlcA) and UDP-xylose. GUS staining showed that BC25 was ubiquitously expressed with higher expression in culm, root and sheath, in agreement with that shown by quantitative real-time (qRT)-PCR. RNA-seq further suggested that BC25 is involved in sugar metabolism. We conclude that BC25 strongly influences rice cell wall formation. [ABSTRACT FROM AUTHOR]

Background: Rice blast disease is one of the most serious and recurrent problems in rice-growing regions worldwide. Most resistance genes were identified by linkage mapping using genetic populations. We extensively examined 16 rice blast strains and a further genome-wide association study based on genotyping 0.8 million single nucleotide polymorphism variants across 366 diverse indica accessions. Results: Totally, thirty associated loci were identified. The strongest signal (Chr11_6526998, P =1.17 × 10−17) was located within the gene Os11g0225100, one of the rice Pia-blast resistance gene. Another association signal (Chr11_30606558) was detected around the QTL Pif. Our study identified the gene Os11g0704100, a disease resistance protein containing nucleotide binding site-leucine rich repeat domain, as the main candidate gene of Pif. In order to explore the potential mechanism underlying the blast resistance, we further examined a locus in chromosome 12, which was associated with CH149 (P =7.53 × 10−15). The genes, Os12g0424700 and Os12g0427000, both described as kinase-like domain containing protein, were presumed to be required for the full function of this locus. Furthermore, we found some association on chromosome 3, in which it has not been reported any loci associated with rice blast resistance. In addition, we identified novel functional candidate genes, which might participate in the resistance regulation. Conclusions: This work provides the basis of further study of the potential function of these candidate genes. A subset of true associations would be weakly associated with outcome in any given GWAS; therefore, large-scale replication is necessary to confirm our results. Future research will focus on validating the effects of these candidate genes and their functional variants using genetic transformation and transferred DNA insertion mutant screens, to verify that these genes engender resistance to blast disease in rice. [ABSTRACT FROM AUTHOR]

Strike-slip faults are classically associated with pull-apart basins where continental crust is thinned between two laterally offset fault segments. We propose a subsidence mechanism to explain the formation of a new type of basin where no substantial segment offset or synstrike-slip thinning is observed. Such "flexural strike-slip basins" form due to a sediment load creating accommodation space by bending the lithosphere. We use a two-way coupling between the geodynamic code ASPECT and surface-processes code FastScape to show that flexural strike-slip basins emerge if sediment is deposited on thin lithosphere close to a strikeslip fault. These conditions were met at the Andaman Basin Central fault (Andaman Sea, Indian Ocean), where seismic reflection data provide evidence of a laterally extensive flexural basin with a depocenter located parallel to the strike-slip fault trace. [ABSTRACT FROM AUTHOR]

The existence of two-dimensional Kolmogorov–Arnold–Moser invariant tori is proved for cubic complex Ginzburg–Landau equation of higher spatial dimension. As a consequence, the equation possesses a Cantorian branch of nontraveling-wave quasiperiodic solutions of two-dimensional frequency vector. [ABSTRACT FROM AUTHOR]

Background: Increasing rice (Oryza sativa L.) yield is a crucial challenge for modern agriculture. The ideal plant architecture is considered to be critical to enhance rice yield. Elite plant morphological traits should include compact plant type, short stature, few unproductive tillers, thick and sturdy stems and erect leaves. To reveal the genetic variations of important morphological traits, 523 germplasm accessions were genotyped using the Illumina custom-designed array containing 5,291 single nucleotide polymorphisms (SNPs) and phenotyped in two independent environments. Genome-wide association studies were performed to uncover the genotypic and phenotypic variations using a mixed linear model. Results: In total, 126 and 172 significant loci were identified and these loci explained an average of 34.45 % and 39.09 % of the phenotypic variance in two environments, respectively, and 16 of 298 (~5.37 %) loci were detected across the two environments. For the 16 loci, 423 candidate genes were predicted in a 200-kb region (±100 kb of the peak SNP). Expression-level analyses identified four candidate genes as the most promising regulators of tiller angle. Known (NAL1 and Rc) and new significant loci showed pleiotropy and gene linkage. In addition, a long genome region covering ~1.6 Mb on chromosome 11 was identified, which may be critical for rice leaf architecture because of a high association with flag leaf length and the ratio of flag leaf length and width. The pyramid effect of the elite alleles indicated that these significant loci could be beneficial for rice plant architecture improvements in the future. Finally, 37 elite varieties were chosen as breeding donors for further rice plant architectural modifications. Conclusions: This study detected multiple novel loci and candidate genes related to rice morphological traits, and the work demonstrated that genome-wide association studies are powerful strategies for uncovering the genetic variations of complex traits and identifying candidate genes in rice, even though the linkage disequilibrium decayed slowly in self-pollinating species. Future research will focus on the biological validation of the candidate genes, and elite varieties will also be of interest in genome selection and breeding by design. [ABSTRACT FROM AUTHOR]

One major and under-appreciated aspect of stratigraphic modeling based on diffusion is the wide range of diffusion coefficients used in the literature to simulate natural examples without considering their meaning in term of transport and deposition processes. Most of the time, stratigraphic simulation tools are indeed used as a semi-inversion tool based on a "best-fit" approach to reproduce well-constrained sedimentary architectures. The aim of this work is to consolidate inputs of stratigraphic numerical modeling such as slopes of sedimentary systems, grain-size distributions and diffusion coefficients calibrated on natural examples of passive margin deltas: the Plio-Pleistocene Ogooué Delta in Gabon and the Mio- to Pleistocene Zambezi Delta in Mozambique.We calculated diffusion coefficients from high resolution seismic stratigraphy and well log analyses in three-steps: (1) calibration of sand/shale ratio variations (from wells) along the depositional profile; (2) restoration of the slope of sedimentary systems at time of deposition (including differential compaction corrections); (3) calculation of accumulation rates using a high resolution age model and quantification of uncompacted volumes for each time step in various stratigraphic context.Most of diffusion coefficients calculated on the two natural examples range over two orders of magnitude (x0,01 to 10 km2/ka), in agreement with most of the published diffusion process-based stratigraphic modeling (x0,0001 to x10 km2/ka). Our results suggest that: (1) neither the stratigraphic context nor the sand/clay ratio impact the diffusion coefficients but, (2) they strongly depend on the slopes along the depositional profiles. We also observe (3) a high variability of coefficients on the shelf and the basin floor that could reflect the occurrence of sedimentary processes that cannot be simplified to a simple diffusion (e.g. waves or flood on the shelf; oceanic currents, turbiditic channels or hemipelagites in the most distal domain). Finally, investigations of the influence of the temporal and spatial resolution on coefficient values show that diffusion process is optimal at a scale of several kilometers and million years for which the lesser coefficient variability suggests that the diffusion approach allows averaging numerous sedimentary processes.We use the diffusion coefficient values and geometrical parameters of observed stratigraphic architectures to calibrate the marine deposition of a new coupled erosion-deposition numerical model developed by Yuan et al. (COLORS project, funded by Total) that accounts for both erosion onshore and sediment deposition in the marine domain. Highly efficient, this model allows for inverse simulations to be run and to address a large variety of questions in various setups. [ABSTRACT FROM AUTHOR]