Dynamic Detection of Topological Information from Grid-Based Generalized Voronoi Diagrams

In the context of robotics, the grid-based Generalized Voronoi Diagrams (GVDs) are widely used by mobile robots to represent their surrounding area. Current approaches for incrementally constructing GVDs mainly focus on providing metric skeletons of underlying grids, while the connectivity among GVD vertices and edges remains implicit, which makes high-level spatial reasoning tasks impractical. In this paper, we present an algorithm named Dynamic Topology Detector (DTD) for extracting a GVD with topological information from a grid map. Beyond the construction and reconstruction of a GVD on grids, DTD further extracts connectivity among the GVD edges and vertices. DTD also provides efficient repair mechanism to treat with local changes, making it work well in dynamic environments. Simulation tests in representative scenarios demonstrate that (1) compared with the static algorithms, DTD generally makes an order of magnitude improvement regarding computation times when working in dynamic environments; (2) with negligible extra computation, DTD detects topologies not computed by existing incremental algorithms. We also demonstrate the usefulness of the resulting topological information for high-level path planning tasks

Formation Control of Robotic Swarm Using Bounded Artificial Forces

Formation control of multirobot systems has drawn significant attention in the recent years. This paper presents a potential field control algorithm, navigating a swarm of robots into a predefined 2D shape while avoiding intermember collisions. The algorithm applies in both stationary and moving targets formation. We define the bounded artificial forces in the form of exponential functions, so that the behavior of the swarm drove by the forces can be adjusted via selecting proper control parameters. The theoretical analysis of the swarm behavior proves the stability and convergence properties of the algorithm. We further make certain modifications upon the forces to improve the robustness of the swarm behavior in the presence of realistic implementation considerations. The considerations include obstacle avoidance, local minima, and deformation of the shape. Finally, detailed simulation results validate the efficiency of the proposed algorithm, and the direction of possible futrue work is discussed in the conclusions

A Scalable GVT Estimation Algorithm for PDES: Using Lower Bound of Event-Bulk-Time

Global Virtual Time computation of Parallel Discrete Event Simulation is crucial for conducting fossil collection and detecting the termination of simulation. The triggering condition of GVT computation in typical approaches is generally based on the wall-clock time or logical time intervals. However, the GVT value depends on the timestamps of events rather than the wall-clock time or logical time intervals. Therefore, it is difficult for the existing approaches to select appropriate time intervals to compute the GVT value. In this study, we propose a scalable GVT estimation algorithm based on Lower Bound of Event-Bulk-Time, which triggers the computation of the GVT value according to the number of processed events. In order to calculate the number of transient messages, our algorithm employs Event-Bulk to record the messages sent and received by Logical Processes. To eliminate the performance bottleneck, we adopt an overlapping computation approach to distribute the workload of GVT computation to all worker-threads. We compare our algorithm with the fast asynchronous GVT algorithm using PHOLD benchmark on the shared memory machine. Experimental results indicate that our algorithm has a light overhead and shows higher speedup and accuracy of GVT computation than the fast asynchronous GVT algorithm

Assessment of Genetic Diversity of an Endangered Species Fraxinus hupehensis Based on ISSR Markers

Investigation on the level and pattern of genetic diversity of 10 natural populations of the endangered species Fraxinus hupehensis using inter-simple sequence repeat (ISSR) markers was crucial for understanding the structure of the population and assessing the best genetic protection strategies. A total of 180 polymorphic bands with the polymorphic rate of 100.00% were amplified by 14 primers. The genetic diversity at population level (Percentage of polymorphic loci, PPL=64.06; Nei’s gene diversity index, h=0.1519; Shannon’s information index, I=0.2434) was lower than that at species level (PPL= 100.00%, h=0.1833, I=0.3041). Analysis of molecular variance (AMOVA) demonstrated the low level of the genetic variation occurred between the populations (16.05%). This also can be corroborated by the gene flow (Nm 2.424) and the coefficient of gene differentiation (Gst=0.1710) among populations. Cluster analysis based on the unweighted pair group method with arithmetic averages (UPGMA) revealed four groups for 10 populations according to Nei’s genetic identity and seven categories for the 196 individuals according to SM values. Furthermore, the endangered mechanism and genetic structure of F. hupehensis were discussed, and appropriate targeted protection measures were proposed based on these findings

catena-Poly[[pyridinecopper(II)]-μ-N-[(2-oxido-1-naphth­yl)methyl­ene]glycinato]

In the title compound, [Cu(C13H9NO3)(C5H5N)], the CuII atom is coordinated in a distorted square-pyramidal geometry, with two N and two O atoms in the basal positions and one O atom in the apical position. The apical Cu—O bond [2.3520 (16) Å] is much longer than the basal Cu—O and Cu—N bonds [1.9139 (14)–2.0136 (17) Å]. The carboxyl­ate group bridges CuII atoms, forming a zigzag chain along the a axis

Efficient inhibition of hepatitis B virus replication by hepatitis delta virus ribozymes delivered by targeting retrovirus

<p>Abstract</p> <p>Background</p> <p>Hepatitis delta virus (HDV) ribozyme is an attractive molecular tool that can specifically recognize and catalyze the self-cleavage of the viral RNA phosphodiester backbone. However, a major obstacle in the medical application of the HDV ribozyme is the lack of specificity in the delivery of the ribozyme to defined target cells.</p> <p>Results</p> <p>The objective of this study was to determine whether retroviral vectors can deliver the HDV ribozyme into the target cells and to elucidate whether HDV ribozyme plays a role in hepatitis B virus (HBV) replication. In our study, the transduction of helper-free pseudotyped retrovirus, which showed a broad host range, in human hepatoma cells was performed under 2 conditions, that is, in the presence of polymerized human serum albumin (pHSA) and in the absence of pHSA. The transduction ability in the presence of pHSA was higher than in the absence of pHSA. Moreover, HBsAg and HBeAg levels after transductions with pHSA were significantly lower than those in the absence of pHSA, thus indicating that the recombinant retrovirus had HBV-specific cleavage activity and targeted HepG2215 cells.</p> <p>Conclusions</p> <p>These data suggest that this system provides a new approach for targeting hepatocytes and has a great potential in gene therapy for HBV infection.</p

(2-Acetyl­phenolato)(2,2′-bipyridine)nitratocopper(II)

In the title compound, [Cu(C8H7O2)(NO3)(C10H8N2)], the CuII ion is five-coordinate in a distorted square-pyramidal geometry. The basal positions are occupied by two N atoms from a 2,2′-bipyridine ligand and two O atoms from the 2-acetyl­phenolate anion. The axial position is occupied by one O atom of a nitrate anion. In the bipyridine ligand, the two pyridine rings are slightly twisted by an angle of 3.5 (1)°. The crystal structure is stabilized by C—H⋯O hydrogen bond

{N,N-Dimethyl-N′-[1-(2-pyrid­yl)ethyl­idene]propane-1,3-diamine}bis(thio­cyanato-κN)­copper(II)

In the title complex, [Cu(NCS)2(C12H19N3)], the CuII atom is five-coordinated in a square-pyramidal geometry defined by one pyridine N, one imine N, and one amine N atom of the tridentate Schiff base ligand and two N-bonded thio­cyanate ions (one of the latter occupying the apical site). The three bridging C atoms and the two terminal C atoms of the Schiff base are disordered over two sets of sites, with occupancies of 0.465 (2) and 0.535 (2)

Aqua­{N-[1-(2-oxidophen­yl)ethyl­idene]-l-serinato}copper(II) monohydrate

In the title compound, [Cu(C11H11NO4)(H2O)]·H2O, each CuII ion is four-coordinated by one N and two O atoms from the tridentate Schiff base ligand, and by one O atom from the coordinated water mol­ecule in a distorted square-planar geometry. Inter­molecular O—H⋯O hydrogen bonds link complex mol­ecules and solvent water mol­ecules into flattened columns propagated in [100]