Crack initiation characteristics of ring chain of heavy-duty scraper conveyor under time-varying loads

Crack initiation characteristics of ring chain of heavy-duty scraper conveyor under time-varying loads were investigated in this study. The dynamic tension of ring chain of the heavy-duty scraper conveyor was obtained using the time-varying dynamic analysis. Finite element analyses of three-dimensional contacts between adjacent chain rings at straight and bending segments were carried out to explore three-dimensional stress distributions of chain rings. The crack initiation life of chain ring was predicted employing the multiaxial fatigue theory. The results show that the ring chain is subjected to time-varying dynamic tensions during operation. During tension-tension contact fatigue, as compared to the straight segment of ring chain, the bending segment engaging in the sprocket presents an overall lower (or higher) equivalent stress distribution in the case of flat (or vertical) chain ring, respectively. Maximum equivalent stresses at the contact regions of adjacent chain rings both present time-varying dynamic characteristics similar to evolutions of dynamic tension. During tension-torsion contact fatigue, an increase in torsion angle level causes unobvious difference between equivalent stress distributions at contact regions of adjacent rings. Predicted crack initiation lives of chain rings during tension-tension contact fatigue indicates more severe fatigue damages of the vertical chain ring at the straight segment and of the flat chain ring at the right bending segment.

Redetermination of (D-penicillaminato)lead(II)

In the title coordination polymer, [Pb(C5H9NO2S)]n{systematic name:catena-poly[(μ-2-amino-3-methyl-3-sulfidobutanoato)lead(II)]}, the D-penicillaminate ligand coordinates to the metal ion in anN,S,O-tridentate mode. The S atom acts as a bridge to two neighbouring PbIIions, thereby forming a double thiolate chain. Moreover, the coordinating carboxylate O atom forms bridges to the PbIIions in the adjacent chain. The overall coordination sphere of the PbIIion can be described as a highly distorted pentagonal bipyramid with a void in the equatorial plane between the long Pb—S bonds probably occupied by the stereochemically active inert electron pair. The amino H atoms form N—H...S and N—H...O hydrogen bonds, resulting in a cluster of four complex units, giving rise to anR44(16) ring lying in theabplane. The crystal structure of the title compound has been reported previously [Freemanet al.(1974).Chem. Soc. Chem. Commun.pp. 366–367] but the atomic coordinates have not been deposited in the Cambridge Structural Database (refcode DPENPB). Additional details of the hydrogen bonding are presented here.

Anilinium dihydrogen phosphate

The triclinic structure of the title compound, C6H8N+·H2PO4−, with three symmetry-independent structural units (Z′ = 3), is formed of separate organic and inorganic layers alternating along thebaxis. The building blocks of the inorganic layer are deformed H2PO4tetrahedra assembled into infinite ladders by short and hence strong hydrogen bonds. The anilinium cations forming the organic layer are not hydrogen bonded to one another, but they are anchored by four N—H...O crosslinks between the dihydrogen phosphate chains of adjacent ladders. Two H atoms of each –NH3group then form one normal and one bifurcated N—H...O hydrogen bond to the P=O oxygens of two tetrahedra of one chain, while the third H atom is hydrogen bonded to the nearest O atom of an adjacent chain belonging to another dihydrogen phosphate ladder.

Pseudorevertants of a Semliki Forest Virus Fusion-Blocking Mutation Reveal a Critical Interchain Interaction in the Core Trimer

ABSTRACT Semliki Forest virus (SFV) is an enveloped alphavirus that infects cells by a low-pH-triggered membrane fusion reaction mediated by the viral E1 protein. E1 inserts into target membranes and refolds to a hairpin-like homotrimer containing a central core trimer and an outer layer composed of domain III and the juxtamembrane stem region. The key residues involved in mediating E1 trimerization are not well understood. We recently showed that aspartate 188 in the interface of the core trimer plays a critical role. Substitution with lysine (D188K) blocks formation of the core trimer and E1 trimerization and strongly inhibits virus fusion and infection. Here, we have isolated and characterized revertants that rescued the fusion and growth defects of D188K. These revertants included pseudorevertants containing acidic or polar neutral residues at E1 position 188 and a second-site revertant containing an E1 K176T mutation. Computational analysis using multiconformation continuum electrostatics revealed an important interaction bridging D188 of one chain with K176 of the adjacent chain in the core trimer. E1 K176 is completely conserved among the alphaviruses, and mutations of K176 to threonine (K176T) or isoleucine (K176I) produced similar fusion phenotypes as D188 mutants. Together, our data support a model in which a ring of three salt bridges formed by D188 and K176 stabilize the core trimer, a key intermediate of the alphavirus fusion protein.

Identification of Isomorphism of Kinematic Chains Through Link’s Adjacent-Chain Table

A completely new concept about the kinematic chain, called the link’s adjacent-chain table (shortened as ACT), is originated in this paper. It is an invariant which can be used to describe the topological relationships between links in the kinematic chain (shortened as KC). In comparison with the traditional representation of the KC, i.e. with the adjacent matrix, link’s ACT is much more audio-visual and simpler. Using the link’s ACT, the isomorphism of the KC can be easily determined. Among the existing methods for the identification of the isomorphic graphs, link’s ACT takes the least time in calculation. So it’s introduction of the link’s ACT leads to a effectual solution to identify the isomorphism of the KC.

Structural Studies of RSHgII Complexes Containing (-Hg-SR-)n Rings and Chains

Crystals of acetato(methanethiolato)-γ-picolinemercury(11), MeSHgO2CMe,C6H7N (I), are monoclinic, P21/a, a 16.617(9), b 7.271(3), c 20.476(2) � β 113.31(5)�, Z 8. The structure resembles that of its pyridine analogue, being based on a polymeric (-Hg-SMe-)n chain with acetate and picoline groups coordinated at each mercury; a similar structure is found for EtSHgO2CMe,C5H5N (2), monoclinic, P21/c, a 9.344(2), b 17.917(9), c 7.179(2) �,β 106.24(3)�, Z 4. The structure of tetrachlorotetra(2-methylpropane-2-thiolato)di(γ-picoline) tetramercury(11), (BUtS)4Cl4Hg4(C6H7N)2 (3), also resembles that of its pyridine analogue being based on an unusual tetranuclear grouping of mercury atoms linked by chloride and thiolate bridges. Crystals of (3) are monoclinic, P21/c a 12.334(7), b 17.468(9), c 9.999(5) �, β 91.18(4)�, Z 2. Crystals of MeSHgBr (4) are monoclinic, P21/c, a 7.770(9), b 7.500(5), c 7.945(10) �, β 91.71(3)�, Z 4, and contain parallel chains (-Hg-SMe-)n with neighbouring chains linked by bridging bromine atoms into parallel sheets. Each bromine is triply bridging, being coordinated to two mercury atoms in one chain, and one mercury atom in an adjacent chain. The structure of MeSHgCl appears to be isomorphous.

X-RAY DIFFRACTION STUDIES ON AMYLOID FILAMENTS

The filamentous protein component of amyloid-laden tissue was studied by x-ray diffraction procedures. The principal features of the x-ray pattern from nonoriented amyloid material consist of a sharp, intense ring at 4.75 Å overlaying a diffuse halo at 4.3 Å, and a broad and less intense ring at 9.8 Å. When oriented, the material gives a "cross-β" x-ray pattern. The x-ray findings are interpreted in terms of a "pleated sheet" structure formed by the amyloid polypeptide chain folding in a regular manner on itself such that adjacent chain segments are laterally arranged in an antiparallel manner. The x-ray patterns from oriented amyloid suggest further that the axes of the chain segments run transverse to the filament axis.

Chemorheology of Polysulfide Rubbers

Experimental results indicate that the socalled “cold flow” of polysulfide rubbers is almost certainly chemical rather than physical in nature. The term chemorheology has been adopted to describe this chemical type of plasticity. The experimental method employed in this investigation was the measurement of relaxation of stress in stretched rubber samples held at a constant elongation. The changes in relaxation rate produced by changing the molecular structure of the rubber (by cross-linking), by incorporating carbon black, by illuminating with ultraviolet light, and by treating the rubber with various chemical agents, such as sulfur, a thiol, and agents that destroy thiol groups, were studied by this method. From the results of the above experiments and from additional considerations, it is concluded that the chemical reaction responsible for cold flow is an intermolecular exchange reaction, and that this exchange reaction is probably an exchange between a terminal thiol group of one chain and a disulfide linkage of an adjacent chain.