Polyhedral Configuration Research Articles

All-in-one probe for exploring self-organized two-fluid equilibria in toroidal plasmas.

This paper presents the development of an all-in-one probe to simultaneously measure all components of the generalized Ohm's law in reversed-field pinch plasmas and tokamaks. The polyhedral configuration of the Mach probe is achieved through the specific arrangement, angle, and depth of the collimator channel apertures drilled into the surface of a hollow boron nitride cylinder encasing it. This probe includes a central Mach probe to assess the ion velocity field in three dimensions. Initial tests at the RELAX and Madison Symmetric Torus machines have confirmed the probe's effectiveness, revealing an octahedron form similar to a tetrahedron. The probe seems to function correctly and is expected to facilitate the empirical validation of two-fluid equilibria at the periphery of toroidal plasmas.

Hierarchical porous cobalt nanoparticles encapsulated in heteroatom-doped hollow carbon as an enhancing multifunctional catalyst for hydrolysis of sodium borohydride and hydrogenation of bromate in water

Multifunctional heterogeneous catalysts have been consistently explored in recent years because of their distinctive catalytic activity in different catalysis areas at once. Here, a cobalt (Co) nanoparticles encapsulated in nitrogen-doped hollow carbon (denoted as Co@NHC) is prepared by two-step modifications of acid etching and high temperature carbonization in the inert atmosphere using a peculiar polyhedral configuration Co-ZIF as an initial template. Benefiting from an intriguing polyhedral configuration hollow structure with high specific surface area and pore volume supplying plentiful active sites, Co@NHC shows exceptional catalytic activity in catalyzing hydrolysis of NaBH4 and hydrogenation of toxic bromate in water. From experimental results, Co@NHC could efficiently enhance the generation of H2 with a H2 generation rate of 1515.4 mL min−1 gcat−1 meanwhile the activation energy (Ea) calculated from Co@NHC/NaBH4 system was only 12.6 kJ mol−1. Besides, the combination of Co@NHC and NaBH4 could further reduce toxic bromate ions into bromide via catalytic hydrogenation with a maximum bromate removal capacity of 390.6 μmol g−1. More importantly, due to its strong magnetization, Co@NHC could be simply recovered after reactions, making it well-preserve the unique structure as well as catalytic activity for multiple continuous recycles in both catalytic applications. Additionally, the plausible reaction mechanisms in catalyzing hydrolysis of NaBH4 and hydrogenation of bromate were also proposed. This work has pioneered a promising approach on preparing an engrossing magnetic heterogeneous Co-based catalyst that is practically applicable in various areas of catalysis.

Comparative study on devolatilization behavior, microstructural evolution and resultant properties during calcination of petroleum coke with distinct mesophase texture

Petroleum coke as an affordable and abundant material represents significant opportunities for using in both traditional and emerging fields, whereas a lack of understanding transformation chemistry during essential calcination hampers its development. Herein, relevance among devolatilization behavior, microstructural evolution and resultant properties during calcination of green coke were investigated. Calcination is found to be roughly distinguished into three regimes according to average stacking height (Lc) and average interlayer spacing (d002) obtained by analysis of WAXS as well as appearance of D2 peak in Raman spectra. The first regime below 800ºC shows starting transformation from semi-coke to coke, mainly induced by volatilization of low-molecular-weight components, dealkylation and intramolecular dehydro-condensation. Simultaneously, progressive healing of in-plane defects, gradual increase of mesogen-layer size and decrease of interlayer spacing was accompanied, causing significant growth of real density. Thereafter, intermolecular dehydro-polymerization and heteroatoms elimination become dominant in 800–1400 °C, leading to removal of interstitial defects. Consequently, larger stacking height and more homogeneous stacking of well-developed hexagonal carbon layers are formed, further promoting microstrength and electric-conductivity of resultant coke. Next, graphite-like microcrystallites would be rearranged into polyhedral configuration in 1400–1600ºC, indicating a transition from coke to semi-graphite. Notably, the mode of arrangement of mesophase units in the green coke would largely predetermine the coke microstructure. This work could give a guidance for regulating structural evolution via selection of green coke and calcination condition according to application.

Establishment of iterative modeling method for spherical tensegrity structure using rotational symmetry and regular polyhedron configuration

Tensegrity structures are attractive light-weight structures. In particular, spherical tensegrity structures are expected to be applied in various fields. This article proposes a simple method for modeling spherical tensegrities. Firstly, the nodal coordinates of the spherical tensegrity are systematically determined based on rotational symmetry and regular polyhedral configuration. This approach enables the systematic acquisition of the nodal coordinates of spherical tensegrities of all sizes by introducing a three-dimensional rotation matrix and the dihedral angle of the regular polyhedron. Secondly, the prestress ratio is determined iteratively. For the stability analysis of the spherical tensegrity, nonlinear analysis with prestress is required. For the analysis considering the prestress, a tangent stiffness matrix is applied in this study. The simple determination method enables the modeling of spherical tensegrities. The natural frequencies and mode shapes of the spherical tensegrity are identified by frequency analysis. A vibration experiment is conducted as a verification experiment. The natural frequencies from the analysis are compared to the resonance frequencies from the experiment. This comparison confirms the validity of the frequency analysis results, based on the two proposed methods.

Symmetry‐Driven Assembly of a Penta‐Shell Keplerate Cuprofullerene for Metallofullerene Frameworks

AbstractTwo metallofullerene frameworks (MFFs) constructed from a penta‐shell Keplerate cuprofullerene chloride, C60@Cu24@Cl44@Cu12@Cl12, have been successfully prepared via a C60‐templated symmetry‐driven strategy. The icosahedral cuprofullerene chloride is assembled on a C60 molecule through [η2‐(C=C)]−CuI and CuI−Cl coordination bonds, resulting in the penta‐shell Keplerate with the C60 core canopied by 24 Cu, 44 Cl, 12 Cu and 12 Cl atoms that fulfill the tic@rco@oae@ico@ico penta‐shell polyhedral configuration. By sharing the outmost‐shell Cl atoms, the cuprofullerene chlorides are connected into 2D or 3D (snf net) frameworks. TD‐DFT calculations reveal that the charge transfer from the outmost CuI and Cl to C60 core is responsible for their light absorption expansion to near‐infrared region, implying anionic halogenation may be an effective strategy to tune the light absorption properties of metallofullerene materials.

Symmetry-Driven Assembly of a Penta-Shell Keplerate Cuprofullerene for Metallofullerene Frameworks.

Two metallofullerene frameworks (MFFs) constructed from a penta-shell Keplerate cuprofullerene chloride, C60 @Cu24 @Cl44 @Cu12 @Cl12 , have been successfully prepared via a C60 -templated symmetry-driven strategy. The icosahedral cuprofullerene chloride is assembled on a C60 molecule through [η2 -(C=C)]-CuI and CuI -Cl coordination bonds, resulting in the penta-shell Keplerate with the C60 core canopied by 24 Cu, 44 Cl, 12 Cu and 12 Cl atoms that fulfill the tic@rco@oae@ico@ico penta-shell polyhedral configuration. By sharing the outmost-shell Cl atoms, the cuprofullerene chlorides are connected into 2D or 3D (snf net) frameworks. TD-DFT calculations reveal that the charge transfer from the outmost CuI and Cl to C60 core is responsible for their light absorption expansion to near-infrared region, implying anionic halogenation may be an effective strategy to tune the light absorption properties of metallofullerene materials.

Stability of submarine bi-material pipeline-liner system with novel polyhedral composites subjected to thermal and mechanical loading fields

This study is concerned with the thermal and mechanical instability behaviors of composite novel liners encased in deteriorated pipelines. A liner may contain many connected segments, and two adjacent segments may become disconnected after long years of service. In such a case, the single disconnected segment may reduce to a ring. An innovative polyhedral configuration is introduced to improve the bending stiffness of the composite ring that is confined by the pipeline. The radius and bending rigidity of the ring are simplified analytically to facilitate the derivation of the critical buckling load. By employing the classical shell criteria, and defining an admissible displacement function, the expression of the potential energy function is obtained with only two unknown parameters. Taking the first derivative of the energy function to the two unknowns respectively generates two equilibrium equations. By solving the two equations, the analytical buckling load is obtained for a composite polyhedral ring in a thermal variational field. Then, two comparisons are taken between the present analytical predictions and results from elsewhere, and good agreements are obtained. An amplification coefficient is defined as the ratio between the buckling load of the polyhedral and circular rings. Finally, parametric evaluations indicate the amplification coefficient reduces with the increase of thickness-to-radius ratio, the increase of the number of sides, and the increase of the temperature variation, respectively. Therefore, a polyhedral ring with a low thickness-to-radius ratio is recommended in engineering applications.

Regulating the coordination geometry of polyhedra in zero-dimensional metal halides for tunable emission.

Although self-trapped exciton (STE) emissions in zero-dimensional metal halides have been intensively investigated, the understanding of the relationship between the coordination geometries of the metal halides and their photophysical properties is still lacking. In this work, we successfully synthesized single crystals, with strong STE emissions, of the bimetallic materials (Bmpip)9[Pb3Br11](ZnBr4)2 (PbZn-Br) and (Bmpip)9[Pb3Br11](MnBr4)2 (PbMn-Br), where Bmpip+ is 1-butyl-1-methyl-piperidinium (C10H22N+), via a facile anti-solvent crystallization strategy. With respect to the monometallic material, (Bmpip)2[PbBr4] (Pb-Br), the introduction of Zn2+ and Mn2+ effectively alters the coordination geometry of the lead bromide polyhedral configuration from a PbBr42- tetrahedron to a Pb3Br115- trimer. As a result, the maximum emission peak of PbZn-Br exhibits an obvious red shift and the full width at half maximum is almost two-fold wider than that of Pb-Br due to stronger electron-phonon coupling. Moreover, due to the intrinsic emission of the Mn2+ ions, an intriguing tunable emission was achieved in PbMn-Br with an impressively high photoluminescence quantum yield of up to 67%. The ultra-stable PbMn-Br single crystals show potential as an ideal down-conversion phosphor for use in UV-pumped white light-emitting diode devices.

Structural configuration-radiation stability relationship in the degradation of dumbbelled POSSs

The stability of the inorganic filler, polyhedral oligomeric sisesquioxane (POSS) powders modified as dumbbelled structures is analyzed. This study was conducted by γ-irradiation at four γ-doses, when the degradation of compounds was accomplished. The radiochemical stability was investigated by nonisothermal chemiluminescence. This procedure allowed to establish the sequence of radiation resistance as a characteristic feature in their applications as hybrid filler. The activation energies required for the delaying oxidation in the minor component were calculated. The consequences of defined molecular structure are discussed in the relation of the initiation of the material ageing in the formulation they would be included. The shown stabilization property is closely related to the activation energies that is required for the oxidation. The radiochemical modification occurred in dumbbell POSSs is characterized by the resistance of internal bridges rather than the degradation strength of spatial polyhedral configuration. The degradation profiles resulting from nonisothermal CL measurements are conditioned by the structural reasons and the diffusion of fed oxygen which maintains the spontaneous ageing of polymers, where these fillers would be added. The present results are appropriate proofs for the utilization of dumbbelled POSSs as suitable stabilizers for polymer materials subjected to radiation sterilization.

Asymmetrical Polyhedral Configuration of Giant Vesicles Induced by Orderly Array of Encapsulated Colloidal Particles.

Giant vesicles (GVs) encapsulating colloidal particles by a specific volume fraction show a characteristic configuration under a hypertonic condition. Several flat faces were formed in GV membrane with orderly array of inner particles. GV shape changed from the spherical to the asymmetrical polyhedral configuration. This shape deformation was derived by entropic interaction between inner particles and GV membrane. Because a part of inner particles became to form an ordered phase in the region neighboring the GV membrane, free volume for the other part of particles increased. Giant vesicles encapsulating colloidal particles were useful for the model of “crowding effect” which is the entropic interaction in the cell.

Novel Analysis of Cation Solvation Using a Graph Theoretic Approach

A new method for analyzing molecular dynamics simulation data is employed to study the solvent shell structure and exchange processes of mono-, di-, and trivalent metal cations in water. The instantaneous coordination environment is characterized in terms of the coordinating waters' H-bonding network, orientations, mean residence times, and the polyhedral configuration. The graph-theory-based algorithm provides a rapid frame-by-frame identification of polyhedra and reveals fluctuations in the solvation shell shape--previously unexplored dynamic behavior that in many cases can be associated with the exchange reactions of water between the first and second solvation shells. Extended solvation structure is also analyzed graphically, revealing details of the hydrogen bonding network that have practical implications for connecting molecular dynamics data to ab initio cluster calculations. Although the individual analyses of water orientation, residence time, etc., are commonplace in the literature, their combination with graphical algorithms is new and provides added chemical insight.

Synthesis of Single Crystalline Hematite Polyhedral Nanorods Via a Facile Hydrothermal Process

Single‐crystalline α‐Fe2O3 nanorods with a polyhedral configuration have been successfully synthesized via a facile hydrothermal process at 180°C. X‐ray powder diffraction, transmission electron microscopy observations, field emission scanning electron microscopy, and selected area electron diffraction patterns were used to characterize the as‐synthesized samples. The result reveals that goethite nanorods were first generated and then transformed into hematite via dehydration in the successive hydrothermal treatment, in which the α‐Fe2O3 inherited the rod‐like morphology of the goethite precursor. The effect of surfactant and treatment time on the phase and morphology of the final products has been studied, and a possible growth mechanism is proposed.

Polymorphism in the short-range order of Zr 70Pd 30 metallic glasses

We investigated the origin of the short-range order (SRO) of Zr–Pd based metallic glasses by different processing routes: melt spinning (MS) and mechanical milling (MM). The atomic pair distribution function (PDF) was observed using high energy synchrotron X-rays. Reverse Monte Carlo (RMC) simulations of the experimentally measured atomic pair distributions were performed to identify contrasting aspects of the partial pair distributions and differences in local chemical order between isochemical amorphous alloys prepared by these two very different synthesis techniques. The MS alloy is shown to have a SRO dominated by a random polyhedral configuration close to icosahedral symmetry. The MM samples have SRO to medium-range order (MRO) which is topologically similar to the MoSi 2-type structure ( I4/ mmm), but chemically closer to the Al 2Cu-type structure ( I4/ mcm).

Order-disorder approach to calcioaravaipaite, [PbCa2Al(F,OH)9]: The crystal structure of the triclinic MDO polytype

The crystal structure of calcioaravaipaite, PbCa 2 Al(F,OH) 9 , was initially solved by direct methods in the monoclinic space group A 2/ m ( R = 12.4%). Further study demonstrated the OD nature of the structure, and showed that the crystal was twinned. The structure was solved in the triclinic space group C 1, a = 7.722(3), b = 7.516(3), c = 12.206(4) A, α = 98.86(1), β = 96.91(1), γ = 90.00(1)°, V = 694.8(3) A 3 , Z = 4, yielding R = 5.1% for 1420 reflections with F o > 4σ( F o ). Calcioaravaipaite belongs to a family of order-disorder (OD) structures formed by equivalent layers of symmetry C 2/ m . Two maximum-degree-of-order (MDO) polytypes are possible. MDO1 results from a regular alternation of stacking operators 2 1/2 and 2 −1/2 and yields a monoclinic structure with C 2/ c , a = 7.72, b = 7.52, c = 24.12 A, β = 96.99°. MDO2 results from the sequence 2 1/2 / 2 1/2 / 2 1/2 /… and yields a triclinic structure with a = 7.72, b = 7.52, c = 12.21 A, α = 98.86, β = 96.91, γ = 90.00°. The structure of calcioaravaipaite is comprised of two kinds of alternating polyhedral slabs parallel to (001). Slab 1 consists of a fluorite-like double layer of edge-sharing (CaF 8 ) distorted cubes and slab 2 is a composite of face- and edge-sharing (PbF 12 ) polyhedra and outlying (AlF 6 ) octahedra, the latter sharing faces and edges with the (PbF 12 ) polyhedra, but no elements with one another. Aravaipaite and calcioaravaipaite share a common fluorite-type layer; however, in aravaipaite the presence of Pb 2+ rather than Ca 2+ in this layer results in slabs of strikingly different polyhedral configuration.

Ba3AlO4H: Synthesis and Structure of a New Hydrogen-Stabilized Phase

The title compound and its deuteride were synthesized in high yield by sintering appropriate mixtures of BaH2(BaD2), BaO and Al2O3in welded Ta containers at 1100°C under a hydrogen (deuterium) pressure of 600–700 torr. The structure was determined by a combination of single crystal X-ray and time-of-flight powder neutron diffraction means (orthorhombicPnma,Z=4,a=10.4911(9),b=8.1518(7),c=7.2399(6) Å for the deuteride). The compound contains nominal Ba2+cations, AlO5−4complex anions and H−(D−) anions. The hydride is bound in a strongly distorted barium octahedron while the tetrahedral AlO5−4anion is surrounded by eleven barium atoms in a peculiar polyhedral configuration. The HBa6octahedra are linked together by corner-sharing to form a three dimension framework with large voids defined by eight of the HBa6octahedra that are occupied by the tetrahedral AlO5−4anions. The structure is closely related in a hierarchical way to that of orthorhombic inverse perovskitic Ba3GeO.

Shape and size changes induced by taurine depletion in neonatal cardiomyocytes.

Taurine is a very important organic osmolyte in most adult cells. Because of this property it has been proposed that large changes in the intracellular content of taurine can osmotically stress the cell, causing changes in its size and shape. This hypothesis was examined by measuring cell dimensions of taurine deficient cardiomyocytes using confocal microscopy. Incubation of isolated neonatal rat myocytes with medium containing 5 mM beta-alanine led to a 55% decrease in intracellular taurine content. Associated with the loss of taurine was a reduction in cell size. Two factors contributed to the change in cell size. First, there was a shift in cell shape, favoring the smaller of the two cellular configurations commonly found in the myocyte cell culture. Second, the size of the polyhedral configuration was reduced after beta-alanine treatment. These same two events also contributed to size reduction in cardiomyocytes incubated with medium containing 30 mM mannitol. Nonetheless, some qualitative differences exist between cells osmotically stressed by increasing the osmolality of the incubation medium and decreasing intracellular osmolality. The results support a role for taurine in the regulation of osmotic balance in the neonatal cardiomyocyte.

Bare phosphorus and binary phosphide cluster ions generated by laser ablation

Both positive and negative phosphorus cluster ions were generated from the laser ablation of a red phosphorus sample. The mass distribution of phosphorus cluster ions was found to be very sensitive to the power density of the ablation laser. The P 7 + species exhibits the highest signal intensity in the recorded mass spectra of bare phosphorus cluster cations, as does P 5 - among the anions. Their special structural stability can be attributed to their planar configuration and their aromatic character. As the phosphorus cluster size increases, the odd/even alternation of the signal intensity becomes more pronounced. For the P n + species with n > 24, the relative abundance varies in the order of 8 and P n + with n = 8k + 1 (k = 3–11) are more intense than their neighbors. For comparison, some binary phosphide cluster ions, including CnP m - , SinP m - , BnP m + and AlnP m + , were produced as well. The mass distribution of binary phosphide cluster ions changes with different components. From analysis of the recorded mass spectra of the phosphide cluster ions, the larger clusters may be in a polyhedral configuration and tend to have all valence electrons paired.

Surface morphology of mouse and rat thymic lymphocytes: An in situ scanning electron microscopic study

The present paper deals with a scanning electron microscopic investigation which was undertaken in order to make a direct study of geometrical conformations of thymocytes, to determine the effect of external mechanical forces and finally to analyse the relation of the cell surface morphology to the differentiation and release of thymocytes into circulation. Thymocytes in situ revealed a striking polyhedral configuration with distinct edges and angles that permit a close orientation of cells in a minimum space. This conformation is probably acquired under the influence of forces in the microenvironment of the cells. The immature thymocytes in the cortex were smooth surfaced and constituted a homogenous population with regards to surface morphology except for slight variations in the size and angles of varoius facets of the polyhedra. A minority of the cell population occupying the medulla, however, exhibited a departure in possessing surface undulations and stubby protuberances. Thymocytes isolated in suspension and those in postcapillary venules of thymus did not show the polyhedral shape characteristic of the cells in thymic tissue. They were always rounded, with their surfaces often exhibiting undulations or microvilli. The variations observed in situ are discussed in light of external mechanical forces, cell surface characteristics and the inherent properties of differentiating thymocytes.

Lateral Deflections of Circular Cylinder Walls during Buckling

The lateral deflections of circular cylinders with thin walls were recorded during buckling. Ten pick-up points were chosen along a transverse section of the cylinder, and their deflections recorded simultaneously. The results suggest, within the precision of the measurements made, that buckling starts simultaneously or with a delay not larger than 0·02 sec, in a large region of the transverse section. Sometimes a local buckling wave appears before general collapse, but this wave does not seem to propagate continuously towards the final shape of the buckled surface. It can also be concluded that, at buckling and after 0·01 or 0·02 sec, the wall tends directly to a stable polyhedral configuration, with a well-determined number of sides. No intermediate stage could be detected. These results are interpreted according to previous studies of one of the authors, in such a way that an explanation of the ‘jump’ phenomenon is attempted, without the necessity to pass over Tsien's ‘energy jump’.