Laser Ablation and Fluid Flows Show a Single Force Mechanism Governs Spindle Positioning

Few techniques are available for elucidating the nature of forces that drive subcellular behaviors. Here we develop two complementary ones: 1) femtosecond stereotactic laser ablation (FESLA), which rapidly creates complex cuts of subcellular structures, thereby allowing precise dissection of when, where, and in what direction forces are generated; and 2) assessment of subcellular fluid flows, by comparing direct flow measurements, using microinjected fluorescent nanodiamonds, to large-scale fluid-structure simulations of different models of force transduction. We apply these to study centrosomes in Caenorhabditis elegans early embryos, and use the data to construct a biophysically-based model of centrosome dynamics. Taken together, we demonstrate that cortical pulling forces provide a general explanation for many behaviors mediated by centrosomes, including pronuclear migration/centration and rotation, metaphase spindle positioning, asymmetric spindle elongation and spindle oscillations. In sum, this work establishes new methodologies for disentangling the forces responsible for cell biological phenomena.

Algorithms for Finding Diameter Cycles of Biconnected Graphs

In this paper, we first coin a new graph theoretic problem called the diameter cycle problem with numerous applications. A longest cycle in a graph G = (V, E) is referred to as a diameter cycle of G iff the distance in G of every vertex on the cycle to the rest of the on-cycle vertices is maximal. We then present two algorithms for finding a diameter cycle of a biconnected graph. The first algorithm is an abstract intuitive algorithm that utilizes a brute-force mechanism for expanding an initial cycle by repeatedly replacing paths on the cycle with longer paths. The second algorithm is a concrete algorithm that uses fundamental cycles in the expansion process and has the time and space complexity of O(n^6) and O(n^2), respectively. To the best of our knowledge, this problem was neither defined nor addressed in the literature. The diameter cycle problem distinguishes itself from other cycle finding problems by identifying cycles that are maximally long while maximizing the distances between vertices in the cycle. Existing cycle finding algorithms such as fundamental and longest cycle algorithms do not discover cycles where the distances between vertices are maximized while also maximizing the length of the cycle.

Comparative Analysis of Three Typical Cantilever Scaffold Supporting Systems

In order to effectively guide the selection of scaffold in designing the cantilever scaffold, comprehensive analyses of three typical scaffold supporting systems (including fully cantilever, bottom-supporting cantilever and pull-up cantilever) are carried out. The calculation formulas of the internal force for the three scaffold supporting systems are proposed based on the theoretical analysis, which are effectively verified by the finite element method (FEM). In addition, the force mechanism and benefits of the three scaffold supporting systems are compared and analyzed combined with actual engineering. The results indicate that there is high calculating accuracy for the proposed internal force and deflection calculation formulas about the scaffold supporting systems. According to the distribution uniformity of the internal force and controlling of the deformation of the main girder, the bottom-supporting cantilever system is undoubtedly the best choice. While the pull-up cantilever supporting system is the best choice when considering the aspects of cost, construction period and social benefits, which ought to be popularized in engineering practice.

Parametric study on mechanical properties of basalt leno textile applied as concrete reinforcement

In this study, the mechanical properties of the basalt leno textile applied as concrete reinforcement were experimentally investigated considering different parameters including the impregnation materials, geometrical characteristics (the number of yarns, yarn structure, and yarn spacing), and loading rate. The tensile strength, elastic modulus, and failure mode were examined. Furthermore, the force mechanism of impregnated leno textile under tensile load was analyzed. The experimental results showed that the textile with a stiff impregnation material exhibited a higher strength and modulus than that with a flexible material. The leno textile with the straight yarn had a better performance than those with the twisted yarns. Besides, the constraint of the weft yarns is obvious to the textile in the warp direction, while the warp yarn makes no contributions to the bearing capacity of textile in the weft direction. The weft yarn spacing had a significant impact on mechanical properties of the textile in the warp direction. Furthermore, the loading rate of approximately 1.2 mm/min was suggested to determine the maximum force of the impregnated basalt leno textile. A tensile strength model was proposed considering the effects of the impregnation material, consistent deformation, torsion damage, and twisted angle.

STUDY ON FORCE MECHANISM OF CABLE-TRUSS FRAME AND JUMPED LAYOUT OF ANNULAR CROSSED CABLE-TRUSS STRUCTURE

A new type of cable-strut tension structure named Annular Crossed Cable-truss Structure(ACCTS) comprises a series of planar cable-truss frames crossed each other. To investigate the force mechanism of ACCTS, a cable-truss frame model with 2-bar and 6-cable has been developed, and its initial stiffness formula has been derived as well. The model is further simplified to make it is upper and lower vector heights equal, and then the initial stiffness formula and the critical slack load formula are further deduced. Based on ANSYS software and cable-truss frame with a span of 60m, the influences of the number of struts and position of jumped layout on the cable-truss frame are studied. According to the former 60m span cable-truss frame's research results, the jumped layout of ACCTS with a span of 100m is studied. The static and dynamic performances of two schemes, the optimal jumped layout scheme and the original scheme, are systematically studied. It is shown that the number of struts would be about 6~8 for the planar cable-truss frame and the optimal order of jumped layout is strut 6-7→strut 4-5→strut 2-3. The optimal order of jumped layout of ACCTS agrees with that of the cable-truss frame, verifying the feasibility of conclusions. In the condition of no variation in the original structure's static and dynamic performance, the optimal scheme of the jumped layout will lower the steel consumption and enhance the buckling loads. Moreover, it also simplifies structure for easy construction.

Design, Analysis and Experimental Eerification of a Epatial Constant Force End-Effector for Polishing/Deburring Operations

Controlling the contact force on workpieces is a challenging task for industrial deburring operations. To solve this issue, a novel constant force mechanism(CFM) based on the combination of positive and negative sti ness mechanism is proposed by using folding beam and bi-stable beam. Without using any additional sensors and control algorithms, the proposed mechanism can produce a travel range in constant force manner. In this paper, the design concepts, analytical modeling, finite element analysis (FEA) simulation and experimental studies are presented and discussed. Firstly, a novel spatial CFM is proposed and using the pseudo rigid body(PRB) to established the mathematical model of the whole mechanism. Then, the FEA simulation is performed to validate the correctness of theoretical analysis. In addition, to eliminate the force variation, particle swarm optimization (PSO) method is utilized to find optimal architectural parameters solutions of the CFM. Finally, the experimental tests are performed to verify the performance of the designed CFM. The confguration design and parameter optimization can be further applied to the design of other CFM mechanisms for polishing operations.

Quantum Fundamentals of Coal Bed Methane Hazards

The paper focuses on the challenges concerned with prevention of methane and coal outbursts. It provides data on outbursts in 2017-2020. It is shown that there are no effective ways to prevent such phenomena, as no methods are available for predicting the outburstprone areas in the coal seams. The research objectives and methods are presented. The problem needs to be solved through identification of the outburstprone areas in the coal seams with the account for objective patterns in peat deposition and development of cyclic energy processes of formation and increase in the methane dynamic pressure based on the quantum theory. Five objective criteria are shown that are justified with documented and instrumental data based on analysis of 267 outbursts within the same field. The main features are the interbed layers at the seam junctions and similar contour lines within the neighboring mines. It is noted that the known hypotheses consider physical and chemical processes inside the coal seam without taking into account the energy sources. The authors describe the quantum theory of energy sources inside the coal seam. The objective application conditions of this theory are justified. For the first time ever it was proved that electromagnetic irradiation of atoms in the molecular structure of the coal matter with electrons is the reason for methane formation and the metamorphic processes. It has been demonstrated that separation of atoms is triggered by electromagnetic radiation and by force. The force mechanism is manifested through the compression of atoms, and it is the main process accompanying the seam subsidence in areas of geological faults and in the impact zone of mining excavations. It is recommended to investigate the ways to prevent the forced processes of increasing the temperature and methane dynamic pressure in hazardous coal seam layers using the quantum theory.