Multi-ring Basins Research Articles

Using multi-ring structure for suppression of mode competition in stable single-longitudinal-mode erbium fiber laser

In this demonstration, a stable and tunable single-longitudinal-mode (SLM) erbium-doped fiber (EDF) laser with multiple-ring configuration is proposed and investigated. The proposed compound-ring structure can create different free spectrum ranges (FSRs) to result in the mode-filter effect based on the Vernier effect for suppressing the other modes. Additionally, the output stabilization of power and wavelength in the proposed EDF multiple-ring laser are also discussed.

Structural design and performance analysis of a new type of axial magnetic bearings with multi-ring redundant structure in circular direction

Structural design and performance analysis of a new type of axial magnetic bearings with multi-ring redundant structure in circular direction

Depth of Origin of the Peak (Inner) Ring in Lunar Impact Basins

AbstractNumerical modeling of the peak‐ring basin formation showed that the peak‐ring forms from the material that is part of the central uplift outwardly thrust over the inwardly collapsing transient crater rim. Simulations of the lunar basin formation showed that the peak or inner ring in peak ring or multiring basins, respectively, is composed of the overturned crust and deep‐seated material, possibly from the upper mantle. Numerical impact simulations were used to trace the depth of origin of material exposed within the peak (or inner) ring. We estimate the scaling trends between basin size and the depth of origin of material exposed within the ring. We also report on the likely crust, mantle, and projectile abundances exposed within the ring. Quantifying the excavation depths during the formation of the peak or inner ring provides a step toward understanding the lunar crust and mantle stratigraphy.

New morphological mapping and interpretation of ejecta deposits from Orientale Basin on the Moon

Orientale Basin is one of the youngest and best-preserved multi-ring impact basins in the Solar System. The structure is ∼950 km across and is located on the western edge of the nearside of the Moon. The interior of the basin, which possesses three distinct rings and a post-impact mare fill, has been studied extensively using modern high-resolution datasets. Exterior to these rings, Orientale has an extensive ejecta blanket that extends out radially for at least 800 km from the basin rim in all directions and covers portions of both the nearside and farside of the Moon. These deposits, known as the Hevelius Formation, were first mapped using photographic data from the Lunar Orbiter IV probe. In this study, we map in detail the morphology of each distinct facies observed within the Orientale ejecta blanket using high resolution Lunar Reconnaissance Orbiter (LRO) Wide Angle Camera (WAC) and Narrow Angle Camera (NAC) images and Lunar Orbiter Laser Altimeter (LOLA) elevation data. We identified 5 unique facies within the ejecta blanket. Facies A is identified as a region of hummocky plains located in a low-lying topographic region between the Outer Rook and Cordillera rings. This facies is interpreted to be a mix of crater-derived impact melt and km-scale blocks of ballistic ejecta and host rock broken up during the modification stage and formation of the Cordillera ring. Facies B is an inner facies marked by radial grooves extending outward from the direction of the basin center. This facies is interpreted as the continuous ballistic ejecta blanket. Facies C consists of inner and outer groupings of flat smooth-surfaced deposits isolated in local topographic lows. Facies D displays characteristic sinuous ridges and lobate extensions. Facies C and D are interpreted to be impact melt-rich materials, which manifest as flows and ponds. Our observations suggest that these facies were emplaced subsequent to the ballistic ejecta blanket – most likely during the modification stage of crater formation – and flowed and ponded in topographically low-lying regions. Facies E consists of distinct crater chains emanating radially from the basin center and extending from ∼700 to ∼1000 km from the center of Orientale. This facies is considered to be chains of secondary craters formed from large blocks of ballistic ejecta. Our mapping effort shows that the individual ejecta facies were influenced and controlled to varying degrees by pre-existing slopes and topography. At the basin scale, the overall downslope direction toward the lunar lowlands to the east and southeast of the basin center resulted in large impact melt flows 100's of kilometers in length, while the regional upslope trends in the west and northwest inhibited the development of extensive impact melt flows. On a smaller scale it can be observed that ground-hugging ejecta collected behind and flowed around high topographic obstacles while diverting into topographic low regions (e.g., around uplifted pre-existing crater rims, but down into pre-existing crater floors).The dispersion of the various ejecta facies mapped here also indicates both a direction and an angle for the impact event that formed Orientale Basin. The bilateral distribution of both ballistic and impact melt-rich ejecta deposits across a line running northeast – southwest suggests the impact occurred from the northeast toward the southwest. Careful mapping of the secondary impact crater chains (Facies E) shows the development of a “forbidden zone” lacking these impacts to the northeast as well as a concentration of the longest secondary crater chains to the northwest and southeast, perpendicular to the aforementioned line of bilateral ejecta distribution. This distribution of secondary impact craters contrasts with the circularity of the basin and suggests that Orientale Basin was formed by ∼ 25–45° impact from the northeast.

Polycyclic Aromatic Hydrocarbon Growth by Diradical Cycloaddition/Fragmentation.

The recent theoretical and experimental investigations on the growth of polycyclic aromatic hydrocarbons in pyrolytic environments highlight the possible role of the 1,4-cycloaddition/fragmentation (1,4-CAF) steps in the formation of PAH intermediates and consequently soot. The present theoretical study explores the possibility to generalize such mechanism to reactions involving various diradical compounds and stable multiring structures. The calculations were performed using the uB3LYP/6-311G(d,p) method and different composite methods, when possible, for more accurate energy estimates. First, the complex potential energy surface for the reactions between o-benzyne and naphthalene was investigated, including the 1,4-CAF mechanism to form anthracene and acetylene through the dibenzobicyclo[2.2.2]octatriene intermediate. Moreover, the products of the addition reactions to the α- and β-carbons and to the ring-junction atoms were determined. The energies for the optimized CAF structures, which constitute the most-favorable pathway from an energetic point of view, were calculated using CBS-QB3, G3(MP2)B3, and G3B3 methods and compared to the corresponding values for the o-benzyne + benzene reactions. Additional calculations were focused on the possible CAF reactions between o-benzyne and larger multiring structures, such as anthracene, phenanthrene, pyrene, and the four-ring PAHs. The results indicate how the energetics of such reactions is influenced by both the size of the PAH compound and the position of the carbon atoms involved. In the second part of the study, the energy barriers necessary to form multiring diradicals from the corresponding radical molecules were analyzed at a G3(MP2)B3 level of theory. Such calculations are preliminary for the subsequent study on the CAF reactions between the different diradical intermediates and benzene. While the size of the diradical does not affect significantly the energy barriers, the position of the diradical site is critical. The concerted Diels-Alder reactions between the naphthynes and naphthalene were also studied in order to further clarify the analogies between the reactions involving different diradicals. Based on these results, kinetic considerations were provided based on the comparison with the simpler o-benzyne + benzene system, although further higher-level calculations and master equation kinetic analyses will be required to derive the general kinetic rules.

Probing the Influence of SSZ‐13 Zeolite Pore Hierarchy in Methanol‐to‐Olefins Catalysis by Using Nanometer Accuracy by Stochastic Chemical Reactions Fluorescence Microscopy and Positron Emission Profiling

AbstractAn understanding of the role of the hierarchical pore architecture of SSZ‐13 zeolites on the catalytic performance in the methanol‐to‐olefins (MTO) reaction is crucial to guide the design of better catalysts. We investigated the influence of the space velocity on the performance of a microporous SSZ‐13 zeolite and several hierarchically structured SSZ‐13 zeolites. Single catalytic turnovers, as recorded by nanometer accuracy by using stochastic chemical reactions (NASCA) fluorescence microscopy verified that the hierarchical zeolites contain pores larger than the 0.38 nm apertures native to SSZ‐13 zeolite. The amount of fluorescent events correlated well with the additional pore volume available because of the hierarchical structuring of the zeolite. Positron emission tomography (PET) using 11C‐labeled methanol was used to map the 2 D spatial distribution of the deposits formed during the MTO reaction in the catalyst bed. We used PET imaging to demonstrate that hierarchical structuring not only improves the utilization of the available microporous cages of SSZ‐13 but also that the aromatic hydrocarbon pool species are involved in more turnovers before they condense into larger multiring structures that deactivate the catalyst.

Temperature and Size Dependence of Characteristic Hydrogen-Bonded Network Structures with Ion Core Switching in Protonated (Methanol)6-10-(Water)1 Mixed Clusters: A Revisit.

Hydrogen-bonded network structures and preferential ion core in the protonated methanol-water mixed clusters, H+(methanol)n-(water)1 (n = 6-10), were explored by a combination of infrared spectroscopy and theoretical calculations. Infrared spectra of the OH stretch region of the clusters were measured at the two different temperature ranges by using Ar-tagging. Stable isomer structures of the clusters were searched by the multiscale modeling approach and temperature dependent infrared spectra were simulated based on the statistical populations of the isomers. The combined experimental and theoretical studies revealed that the characteristic multiring structures begin to form at n = 7 under the low temperature condition and they are preferential at the wide temperature range in n ≥ 8. It was also demonstrated that the preferential ion core type changes from methanol (MeOH2+) to water (H3O+) with increasing cluster size. In n ≤ 8, the observed infrared spectral features partly depend on the monitoring vibrational predissociation channel, and weak correlations between the hydrogen-bonded network structure and preferential dissociation channels were suggested. However, the ion core type does not necessarily correlate to the preferential dissociation channel. This implies that large rearrangement of the hydrogen-bonded network structure occurs prior to the dissociation.

Adaptive Zonal Protection for Ring Microgrids

In a fault situation on a microgrid with multiple sources, a ring distribution architecture permits healthy parts of the power distribution network to remain operational while isolating a fault. However, fault localization in a multi-ring power distribution system can be considerably more complex than for a radially distributed network. This paper presents a nonintrusive approach for making microgrid protection systems aware of load operating condition in order to improve fault detection, e.g., for detecting destructive high-impedance and arcing faults.

Bridging the Gap III: Impact cratering in nature, experiment, and modeling

Bridging the Gap III: Impact cratering in nature, experiment, and modeling

Microwave Thermal Emission Features of Mare Orientale Revealed by CELMS Data

Mare Orientale is the youngest and best-preserved multiring impact basin, whose microwave thermal emission (MTE) research has great significance for studying the internal thermal features and thermal structures of the lunar surface. In this paper, the microwave sounder (Chang'E Lunar Microwave Sounder, CELMS) data from Chang'E-2 satellite were used to study the MTE features of the Mare Orientale. The results indicate that the MTE features of the lunar regolith are much different between those in the superficial layer and in the substrate layer. Also, substrate temperature in the Orientale Basin is likely much higher than what we know. In addition, a new perspective is given to the Hevelius Formation, which is divided into the northeastern, northwestern, and southern parts, and has several potential linear structures. The results are of substantial geologic importance to study the thermal evolution of the Moon.

Formation of the Orientale lunar multiring basin

Multiring basins, large impact craters characterized by multiple concentric topographic rings, dominate the stratigraphy, tectonics, and crustal structure of the Moon. Using a hydrocode, we simulated the formation of the Orientale multiring basin, producing a subsurface structure consistent with high-resolution gravity data from the Gravity Recovery and Interior Laboratory (GRAIL) spacecraft. The simulated impact produced a transient crater, ~390 kilometers in diameter, that was not maintained because of subsequent gravitational collapse. Our simulations indicate that the flow of warm weak material at depth was crucial to the formation of the basin's outer rings, which are large normal faults that formed at different times during the collapse stage. The key parameters controlling ring location and spacing are impactor diameter and lunar thermal gradients.

Synthesis of Tetracyclic Molecules Containing Medium-Sized Heterocycles: Scope Expansion of Cascade Nicholas and Pauson–Khand Methodology

Unique tetracyclic molecules containing heteroatom-embedded, medium-sized rings were synthesized by employing cascade Nicholas and Pauson–Khand cyclization reactions. We successfully established a divergent synthetic route for quick access to unprecedented multi-ring systems via an alkyne cobalt complex, and an expanded substrate scope for this methodology was realized.

Synthesis of aromatic liquid crystals with asymmetric diester based on rod-like multi-ring system by two-step esterification method

ABSTRACTA novel method of two-step esterifications was developed to synthesize compounds with asymmetric double ester groups. By using this method, six rod-like double ester compounds were prepared with p-hydroxy benzaldehyde, p-hydroxy benzoic acid bicyclohexyl carboxylic acid, cyclohexyl benzoic acid and biphenyl carboxylic acid substituted by n-propyl and n-pentyl as main reactants. The structures and properties of target compounds were confirmed by IR, MS, 1H NMR, elemental analysis, differential scanning calorimetry (DSC) and hot stage polarizing optical microscope (HS-POM). Typical yields of the target molecules were more than 70%. All the molecules have mesophases with the textures of nematic type, indicating a rod-like molecule with a longer rigid skeleton can keep its mesophases. There was no clearing point observed for any of the derivatives before they decomposed so that the temperature ranges of the mesophases could not be determined. The energy differences between frontier molecular orbitals (HOMO-LUMO) (Eg) of the compounds were calculated by cyclic voltammetry (CV). The terminal ring system has an obvious influence on the energy levels and the energy gaps (Eg).

Estimates of primary ejecta and local material for the Orientale basin: Implications for the formation and ballistic sedimentation of multi-ring basins

A clear understanding of thickness distributions of primary ejecta and local material is critical to interpreting the process of ballistic sedimentation, provenances of lunar samples, the evolution of the lunar surface, and the origin of multi-ring basins. The youngest lunar multi-ring basin, Orientale, provides the best preserved structure for determining the thicknesses of primary ejecta and local material. In general, the primary ejecta thickness was often estimated using crater morphometry. However, previous methods ignored either crater erosion, the crater interior geometry, or both. In addition, ejecta deposits were taken as mostly primary ejecta. And, as far as we know, the local material thickness had not been determined for the Orientale. In this work, we proposed a model based on matching measurements of partially filled pre-Orientale craters (PFPOCs) with the simulations of crater erosion to determine their thicknesses. We provided estimates of primary ejecta thickness distribution with the thickness of 0.85 km at Cordillera ring and a decay power law exponent of b=2.8, the transient crater radius of 200 km, excavation volume of 2.3×106 km3, primary ejecta volume of 2.8×106 km3. These results suggest that previous works (e.g., Fassett et al., 2011; Moore et al., 1974) might overestimate the primary ejecta thicknesses of Orientale, and the primary ejecta thickness model of Pike (1974a) for multi-ring basins may give better estimates than the widely cited model of McGetchin et al. (1973) and the scaling law for impacts into Ottawa Sand (Housen et al., 1983). Structural uplift decays slower than previously thought, and rim relief is mostly rim uplift for Orientale. The main reason for rim uplift may be the fracturing and squeezing upward of the surrounding rocks. The proportion of local material to ejecta deposits increases with increasing radial distance from basin center, and the thickness of local material is larger than that of primary ejecta at distance larger than certain distance (∼1.5 basin radius for Orientale). These results suggest ballistic sedimentation is important for multi-ring basins, and ejecta deposits can't be considered as mostly primary ejecta everywhere.

Experimental investigation of thermal processes in the multi-ring Couette system with counter rotation of cylinders

The effect of parameters of the multi-ring Couette system with counter rotating coaxial cylinders on the process of thermal energy release in a viscous liquid filling this system is considered with regard to the problem of determining the possibility of creating the high-performance wind heat generator. The multi-cylinder rotor design allows directly conversion of the mechanical power of a device consisting of two “rotor” wind turbines with a common axis normal to the air flow into the thermal energy in a wide range of rotational speed of the cylinders. Experimental results on the measurement of thermal power released in the pilot heat generator at different relative angular speeds of cylinder rotation are presented.

Meteorite Impact Origin of Yellowstone Hotspot

Origin of the Yellowstone hotspot & Columbia River Basalts has remained uncertain until now. Here, we present evidence of meteorite impact origin. The hotspot is shallow, only 200 km deep, invalidating a theory of mantle plume origin. The hotspot track runs from the Yellowstone National Park in NW Wyoming to the volcanic Modoc Plateau in NE California. We present evidence of apparent remnants of an impact crater existing in the Modoc, a large multi-ring structure at least 160 km diameter. Much of the complex crater has become obliterated by later Cascadia and Sierra orogenies. The crater has a tall 4,100 foot central uplift cone, locally known as Chalk Mountain, consisting of diatomaceous earth, presumably the rebound cone of a meteorite impact. This falsifies a theoretical prohibition of cosmic impact volcanism. Based on recent insights into explosive volcanism a plausible mechanism is proposed for how meteorite impacts can lead to resurgent calderas of the Yellowstone type, & of apparent LIP origin from thin crust ET impacts, invalidating theoretical constructs of mantle plumes. We mention chaotic terrains, including plutons, arising antipodal to impacts.

Caloris basin, Mercury: History of deformation from an analysis of tectonic landforms

The 1640km diameter Caloris basin is the largest impact basin on Mercury and hosts three distinct suites of tectonic structures in its substantially deformed smooth plains, indicative of the basin’s complex history. These structures, i.e. radial graben comprising Pantheon Fossae, concentric graben/troughs arranged in an irregular pattern, and wrinkle ridges, are found at various regions throughout the basin and occasionally interact. We document the locations, orientations, and cross-cutting relationships of these structures using high-resolution MESSENGER images. We suggest that Caloris shows a history of continuous deformation, resulting from the contemporaneous formation of sets of strain compatible tectonic structures, rather than discrete stages of deformation producing each suite independently in temporal sequence. We propose that radial graben formed continuously in the basin’s early deformational history, following initial wrinkle ridge formation possibly representative of a multi-ring basin structure, overlapping with continued wrinkle ridge formation, and persisting with the formation of concentric graben after contraction ceased.

The formation of peak-ring basins: Working hypotheses and path forward in using observations to constrain models of impact-basin formation

Impact basins provide windows into the crustal structure and stratigraphy of planetary bodies; however, interpreting the stratigraphic origin of basin materials requires an understanding of the processes controlling basin formation and morphology. Peak-ring basins (exhibiting a rim crest and single interior ring of peaks) provide important insight into the basin-formation process, as they are transitional between complex craters with central peaks and larger multi-ring basins. New image and altimetry data from the Lunar Reconnaissance Orbiter as well as a suite of remote sensing datasets have permitted a reassessment of the origin of lunar peak-ring basins. We synthesize morphometric, spectroscopic, and gravity observations of lunar peak-ring basins and describe two working hypotheses for the formation of peak rings that involve interactions between inward collapsing walls of the transient cavity and large central uplifts of the crust and mantle. Major facets of our observations are then compared and discussed in the context of numerical simulations of peak-ring basin formation in order to plot a course for future model refinement and development.

Investigating the onset of multi-ring impact basin formation

Multi-ring basins represent some of the largest, oldest, rarest and, therefore, least understood impact crater structures. Various theories have been put forward to explain their formation; there is currently, however, no consensus. Here, numerical modeling is used to investigate the onset of multi-ring basin formation on the Moon using two thermal profiles suitable for the lunar basin-forming epoch. Various multi-ring basin formation hypotheses are discussed, compared, and evaluated against target deformation and strain distribution in the models, as well as geological and geophysical observations. The mechanism that most closely resembles the numerical models in terms of basin formation and structure, as well as observations, appears to be the ring tectonic theory, whereby ring formation is dependent on transient cavities penetrating entirely through the Moon’s lithosphere into the asthenosphere below. The numerical models suggest that all lunar basins larger than Schrödinger (320km diameter) should be capable of forming multiple rings, as their transient cavities penetrate into the asthenosphere for both thermal profiles. Additionally, the models demonstrate that the target’s thermal profile starts to influence basin formation and structure when impact energy exceeds that of the Schrödinger event.

Effects of Molecular Structure and Aggregated Structure on Photoluminescence Properties of Liquid-crystalline Gold(I) Complexes with Various Aromatic Rings

Rod-like gold(I) complexes with phenyl, biphenyl, or naphthyl rings in a mesogenic core were synthesized by complexation of ethynyl-substituted aromatic derivatives with (tetrahydrothiophene)AuCl, followed by ligand exchange with alkyl isocyanide, to investigate the effects of molecular and molecular-aggregated structures on their liquid-crystalline (LC) behavior and photoluminescence properties. The gold complexes exhibited enantiotropic liquid crystallinity. Introduction of multi-ring systems into the mesogenic core effectively expanded the LC temperature range. A comparison of the photoluminescence properties in the crystalline phase showed that the molecular-aggregated structure plays a crucial role in the luminescence of these gold complexes.