Search

In this paper, we describe an algorithm for fitting an analytic and bandlimited closed or open curve to interpolate an arbitrary collection of points in R 2 . The main idea is to smooth the parametrization of the curve by iteratively filtering the Fourier or Chebyshev coefficients of both the derivative of the arc-length function and the tangential angle of the curve and applying smooth perturbations, after each filtering step, until the curve is represented by a reasonably small number of coefficients. The algorithm produces a curve passing through the set of points to an accuracy of machine precision, after a limited number of iterations. It costs O(N log N) operations at each iteration, provided that the number of discretization nodes is N. The resulting curves are smooth, affine invariant, and visually appealing and do not exhibit any ringing artifacts. The bandwidths of the constructed curves are much smaller than those of curves constructed by previous methods. We demonstrate the performance of our algorithm with several numerical experiments. [ABSTRACT FROM AUTHOR]

When an impact load is sufficiently small, its influence on the pavement structure is mainly from the surface layer material. To explore the influence depth of an impact load and back‐calculation of the pavement surface modulus, both numerical calculation and experimental testing were conducted, and the results are presented in this paper. The numerical calculation was performed through a DEM‐FDM‐coupled model. After a new modulus back‐calculation algorithm is formed by analyzing the numerical modeling results, experimental tests were also conducted for verification, and the results were analyzed. The max value of the falling weight impact force was closely related to the elastic modulus of the material, and the influence depth was controllable. Finally, it is proved that the method can be used to calculate the surface layer modulus and estimate the surface layer thickness. [ABSTRACT FROM AUTHOR]

Disadvantages of semi-rigid materials bring a significant challenge to the maintenance of the semi-rigid base pavement. The micro-cracking treatment employs the falling weight to break the semi-rigid base into interlocking blocks to create a new base material to regenerate the old base. To study the micro-cracking mechanism, the cracking patterns and mechanical responses of the semi-rigid base under different types of falling weights and drop heights were obtained in field tests. The DEM-FDM coupling model was established to investigate the cracking distribution further. The results showed that as the impact contact area of the falling weight decreases, the depth of the groove progressively deepens, and the resilient modulus of the semi-rigid base decreases. Besides, the flat-bottomed falling weight produced the highest compressive stress, while the big convex points falling weight caused the most vertical displacement. Combined with simulation analysis, the flat-bottomed falling weight almost exclusively caused shear cracking on the contact edge. The small convex points falling weight mainly generated the shear cracking on the surface, and the big convex points falling weight induced more extensive tensile cracking within the semi-rigid base. Therefore, the big convex points falling weight is more recommended for micro-cracking treatment, which creates a greater cracking degree in semi-rigid base and is conducive to breaking the semi-rigid base into interlocking small blocks. • We studied impact cracking patterns & responses of semi-rigid base. • Falling weight types have significant influence on cracking patterns. • Linked internal displacement, stress, and cracking law in semi-rigid base. • Impact contact areas determines semi-rigid base residual resilient modulus. • DEM-FDM simulation helped to understand the impact cracking mechanism. [ABSTRACT FROM AUTHOR]

RsmI and RsmH are conserved S-Adenosylmethionine (AdoMet)-dependent methyltransferases (MTases) that are responsible for the 2′-O-methylation and N4-methylation of C1402 in bacterial 16S rRNA, respectively. Methylation of m4Cm1402 plays a role in fine-tuning the shape and functions of the P-site to increase the decoding fidelity, and was recently found to contribute to the virulence of Staphylococcus aureus in host animals. Here we report the 2.20-Å crystal structure of homodimeric RsmI from Escherichia coli in complex with the cofactor AdoMet. RsmI consists of an N-terminal putative RNA-binding domain (NTD) and a C-terminal catalytic domain (CTD) with a Rossmann-like fold, and belongs to the class III MTase family. AdoMet is specifically bound into a negatively charged deep pocket formed by both domains by making extensive contacts. Structure-based mutagenesis and isothermal titration calorimetry (ITC) assays revealed Asp100 and Ala124 are vital for AdoMet-binding. Although the overall fold of RsmI shows remarkable similarities to the characterized MTases involved in vitamin B12 biosynthesis, it exhibits a distinct charge distribution especially around the AdoMet-binding pocket because of different substrate specificity. The docking model of RsmI-AdoMet-RNA ternary complex suggested a possible base-flipping mechanism of the substrate RNA that has been observed in several known RNA MTases. Our structural and biochemical studies provide novel insights into the catalytic mechanism of C1402 methylation in 16S rRNA. [ABSTRACT FROM AUTHOR]

RsmI and RsmH are AdoMet-dependent methyltransferases that are responsible for the 2′- O-methylation and N4-methylation of C1402 of Escherichia coli 16S rRNA, respectively. Modification of this site has been found to play a role in fine-tuning the shape and function of the P-site to increase the decoding fidelity. It is interesting to study the mechanism by which C1402 can be methylated by both RsmI and RsmH. The crystal structure of RsmH in complex with AdoMet and cytidine has recently been determined and provided some implications for N4-methylation of this site. Here, the purification and crystallization of RsmI as well as its preliminary crystallographic analysis are reported. Co-crystallization of RsmI with AdoMet was carried out by the sitting-drop vapour-diffusion method and X-ray diffraction data were collected to 2.60 Å resolution on beamline 1W2B at BSRF. The crystal contained three molecules per asymmetric unit and belonged to space group C2, with unit-cell parameters a = 121.9, b = 152.5, c = 54.2 Å, β = 93.4°. [ABSTRACT FROM AUTHOR]

Summary: Archaea have evolved various strategies in chromosomal organization. While histone homologues exist in most archaeal phyla, Cren7 is a chromatin protein conserved in the Crenarchaeota. Here, we show that Cren7 preferentially binds DNA with AT‐rich sequences over that with GC‐rich sequences with a binding size of 6~7 bp. Structural studies of Cren7 in complex with either an 18‐bp or a 20‐bp double‐stranded DNA fragment reveal that Cren7 binds to the minor groove of DNA as monomers in a head‐to‐tail manner. The neighboring Cren7 monomers are located on the opposite sides of the DNA duplex, with each introducing a single‐step sharp kink by intercalation of the hydrophobic side chain of Leu28, bending the DNA into an S‐shape conformation. A structural model for the chromatin fiber folded by Cren7 was established and verified by the analysis of cross‐linked Cren7‐DNA complexes by atomic force microscopy. Our results suggest that Cren7 differs significantly from Sul7, another chromatin protein conserved among Sulfolobus species, in both DNA binding and deformation. These data shed significant light on the strategy of chromosomal DNA organization in crenarchaea. Cren7 serves critical roles in chromosomal DNA organization in Crenarchaea. Structural studies reveal that Cren7 binds to the minor groove of DNA as monomers in a head‐to‐tail manner with a binding size of ~6 bp. The neighboring Cren7 monomers are located on the opposite sides of the DNA duplex, with each introducing a single‐step sharp kink by intercalation of the hydrophobic side chain of Leu28, bending the DNA into an S‐shape conformation. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Chronic lymphocytic leukaemia (CLL) is a rare blood cancer that always relapses as refractory disease and eventually leads to death. To date, therapeutic options for CLL patients are scarce and there is an urgent need to develop novel chemotherapeutics that are both effective and safe. Gold-containing compounds induce a lethal oxidative and endoplasmic reticulum stress response in cultured and primary CLL cells via inhibition of thioredoxin reductase (TrxR). However, traditional gold-containing medicines have revealed side effects during clinical applications. Therefore, safer gold-containing drugs are needed to overcome this challenge. In this study, a novel peptide templated gold cluster Au 25 Sv 9 was synthesized and its therapeutic effect on CLL cells was evaluated. This nanocluster could induce cell apoptosis in MEC-1 cells in a dose-dependent manner which correlated with the uptake amount of clusters in cells. As expected, increasing intracellular reactive oxidative species (ROS) in MEC-1 cells was exhibited with the increase of cluster dosage. Further analyses demonstrated the underlying mechanism that the nanoclusters suppress the activity of TrxR1, increase the level of intracellular ROS, destroy the mitochondrial membrane potential and finally trigger the mitochondrial apoptotic pathway in MEC-1 cells. Furthermore, the direct interaction between Au 25 Sv 9 clusters and TrxR1 was confirmed for the first time by isothermal titration calorimetry. These findings explored the preclinical efficacy and potential mechanism of gold clusters in CLL therapy and provided a fundamental reference for the development of other novel gold-containing chemotherapeutics to treat CLL. [ABSTRACT FROM AUTHOR]

Naturalized plants play pivotal roles in local plant biodiversity and ecological functions; however, the drivers of naturalization remain poorly understood at a fine scale. Thus, understanding the processes of the development and dominance of alien plants in local natural habitats is of paramount importance. In the present study, we report for the first time the naturalization of Cydonia oblonga in China based on community structure and population dynamics at a fine scale. We conducted a comprehensive survey of the species through field community investigations, interviews, and a literature review. Cydonia oblonga is an ancient fruit tree with a long introduction history of over 4500 years worldwide and a cultivation history of over 2500 years in China. We analyzed C. oblonga community structure using the spatiotemporal substitution method and quantitatively analyzed population dynamics using a static life table, survivorship curve, and time series model to explore the naturalization processes. The following results were obtained. (i) The community comprised 31 coexisting vascular plant species (16 woody and 15 herbaceous species) belonging to 28 genera in 20 families. Rosaceae and Asteraceae were the two most dominant families. (ii) All individuals in the shrub layer as well as the C. oblonga population exhibited a roughly inverted J‐shaped basal diameter distribution. A complete age structure was noted, and the survival curve was classified as Deevey type II. According to time series analysis, the population is estimated to increase in the future, specifically of medium and large individuals. (iii) Religious exchange, potent resource competitiveness, and similarity with the native habitat may be the major drivers of the introduction and successful naturalization of C. oblonga. These results suggest that alien species closely related to native ones are more likely to invade, naturalize, and dominate communities in local habitats. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reversible and non-volatile modulation of the resistivity of SmNiO 3 was realized by electrochemical (de)intercalation of Zn2+. • Phase transition of SmNiO 3 modulated by Al3+ was reversible and volatile. • The electronic phase transition of SmNiO 3 was characterized with various techniques. • The structural distortion of SmNiO 3 was identified to be the decisive factor for the resistivity change. Perovskite rare earth nickelates possess the electronic phase transition property that can be harnessed for a multitude of exciting applications. Herein, we report the use of high-valence cations (Zn2+ and Al3+) to reconstruct the electronic band structure of samarium nickelate (SmNiO 3) and realize reversible resistivity modulation. Under positive gate voltage, the resistivity of SmNiO 3 exhibits a colossal increase upon the Zn2+ intercalation and the concurrent electron doping. Under negative gate voltage, the Zn2+ ions are extracted and the resistivity decreases significantly. The resistivity modulation using Zn2+ is non-volatile. Electrochromic behavior is also observed during the Zn2+ insertion and extraction. The electronic phase transition is characterized using various techniques. Moreover, the trivalent Al3+ ions are also investigated as charge carriers to modulate the resistivity of SmNiO 3 in a volatile manner. First-principles density functional theory calculations reveal the effect of electron doping on the electronic band structure. The resistivity change of SmNiO 3 is mainly attributed to the structural distortion induced by electron doping, rather than the Mott-like insulation. This work demonstrates the feasibility of reversible resistivity modulation of SmNiO 3 with the use of high-valence cations under applied voltage, underscoring the potential for applications in novel emerging electronic devices. [ABSTRACT FROM AUTHOR]

T:G base pair arising from spontaneous deamination of 5mC or polymerase errors is a great challenge for DNA repair of hyperthermophilic archaea, especially Crenarchaea. Most strains in this phylum lack the protein homologues responsible for the recognition of the mismatch in the DNA repair pathways. To investigate whether Cren7, a highly conserved chromatin protein in Crenarchaea, serves a role in the repair of T:G mispairs, the crystal structures of Cren7-GTAATTGC and Cren7-GTGATCGC complexes were solved at 2.0 Å and 2.1 Å. In our structures, binding of Cren7 to the AT-rich DNA duplex (GTAATTGC) induces opening of T2:G15 but not T10:G7 base pair. By contrast, both T:G mispairs in the GC-rich DNA duplex (GTGATCGC) retain the classic wobble type. Structural analysis also showed DNA helical changes of GTAATTGC, especially in the steps around the open T:G base pair, as compared to GTGATCGC or the matched DNAs. Surface plasmon resonance assays revealed a 4-fold lower binding affinity of Cren7 for GTAATTGC than that for GTGATCGC, which was dominantly contributed by the decrease of association rate. These results suggested that binding of Cren7 to DNA leads to T:G mispair opening in a sequence dependent manner, and therefore propose the potential roles of Cren7 in DNA repair. [ABSTRACT FROM AUTHOR]