Bis{2-[(pyridin-4-yl-κN)sulfan­yl]pyrazine}­silver(I) tetra­fluoridoborate

In the title mononuclear complex, [Ag(C9H7N3S)2]BF4, the AgI ion adopts a virtually linear coordination geometry [N—Ag—N = 178.06 (11)°] with the two ligands bound to the metal atom via the pyridine N atoms. The metal-coordinated pyridine rings are almost coplanar, making a dihedral angle of 1.5 (2)°, while the two pendent pyrazine rings are arranged on the same side of the N—Ag—N line. Along the a axis, the mononuclear coordination units are stacked with π–π inter­actions between the pyridine rings [centroid–centroid distance = 3.569 (4) Å], leading to infinite chains. The chains are inter­connected through inter­molecular N(pyrazine)⋯π(pyrazine) inter­actions forming layers parallel to the ab plane [N⋯centroid = 3.268 (5) Å]. These layers are further stacked along the c-axis direction, furnishing a three-dimensional supra­molecular framework with the tetra­fluoridoborate anions embedded within the inter­stices

Heterogeneity in structurally arrested hard spheres

When cooled or compressed sufficiently rapidly, a liquid vitrifies into a glassy amorphous state. Vitrification in a dense liquid is associated with jamming of the particles. For hard spheres, the density and degree of order in the final structure depend on the compression rate: simple intuition suggests, and previous computer simulation demonstrates, that slower compression results in states that are both denser and more ordered. In this work, we use the Lubachevsky-Stillinger algorithm to generate a sequence of structurally arrested hard-sphere states by varying the compression rate. We find that while the degree of order, as measured by both bond-orientation and translation order parameters, increases monotonically with decreasing compression rate, the density of the arrested state first increases, then decreases, then increases again, as the compression rate decreases, showing a minimum at an intermediate compression rate. Examination of the distribution of the local order parameters and the distribution of the root-mean-square fluctuation of the particle positions, as well as direct visual inspection of the arrested structures, reveal that they are structurally heterogeneous, consisting of disordered, amorphous regions and locally ordered crystal-like domains. In particular, the low-density arrested states correspond with many interconnected small crystal clusters that form a polycrystalline network interspersed in an amorphous background, suggesting that jamming by the domains may be an important mechanism for these states

Research on forming quality of poly-wedge pulley spinning

As an important power transmission part, pulleys are widely used in automobile industry, agricultural machinery, pumps and machines. A near-net forming process for six-wedge belt pulleys manufacturing was put forward. For this purpose, the required tooth shape and size can be formed directly by spinning without machining. The whole manufacturing procedures include blanking, drawing and spinning. The spinning procedure includes five processes, performing, drumming, thickening, toothing and finishing. The forming defects occurred during each forming processes of poly-wedge pulley spinning, such as the drumming failure, flanged opening-end, folded side-wall, insufficient bottom size, flashed opening-end, cutting-off bottom, are introduced, and the factors influencing the defects are analyzed. The corresponding preventive measures are put forward

Jet Structure and Burst Environment of GRB 221009A

We conducted a comprehensive investigation of the brightest-of-all-time GRB 221009A using new insights from very high energy (VHE) observations from LHAASO and a complete multiwavelength afterglow dataset. Through data fitting, we imposed constraints on the jet structure, radiation mechanisms, and burst environment of GRB 221009A. Our findings reveal a structured jet morphology characterized by a core+wing configuration. A smooth transition of energy within the jet takes place between the core and wing, but with a discontinuity in the bulk Lorentz factor. The jet structure differs from both the case of short GRB 170817A and the results of numerical simulations for long-duration bursts. The VHE emission can be explained by the forward-shock synchrotron self-Compton radiation of the core component, but requiring a distinctive transition of the burst environment from uniform to wind-like, suggesting the presence of complex pre-burst mass ejection processes. The low-energy multiwavelength afterglow is mainly governed by the synchrotron radiation from the forward and reverse shocks of the wing component. Our analysis indicates a magnetization factor of 5 for the wing component. Additionally, by comparing the forward shock parameters of the core and wing components, we find a potential correlation between the electron acceleration efficiency and both the Lorentz factor of the shock and the magnetic field equipartition factor. We discuss the significance of our findings, potential interpretations, and remaining issues.Comment: Minor Revision, ApJ accepte

Bis[5-(pyridin-2-yl)pyrazine-2-carbo­nitrile-κ2 N 4,N 5]silver hexa­fluorido­phosphate

In the mononuclear title complex, [Ag(C10H6N4)2]PF6, two κ2 N,N′-chelating 5-(pyridin-2-yl)pyrazine-2-carbonitrile ligands surround the AgI atom, forming a distorted N4 tetra­hedral coordination geometry. The mononuclear units are inter­connected through π–π inter­actions [centroid–centroid distances = 3.801 (2) and 3.979 (3) Å] and the hexa­fluoridophosphate anions are embedded within the inter­stices. C N⋯π inter­actions [N⋯centroid = 3.519 (2) Å] and C—H.⋯N hydrogen-bonding inter­actions also occur