Inversion Axis Research Articles

Utilizing 3D seismic velocities within the Triassic Bacton Group to estimate the exhumation of the Rotliegend Group, Blocks 48/8 and 48/9, UK Southern North Sea

In the UK Southern North Sea, the exploration of pre-Zechstein structures depends upon accurate depth conversion of reflection seismic data. In Quadrant 48, depth conversion by conventional methods, such as linear velocity v. depth methods ( V = kZ + V 0 , or ‘ V 0 K ’), is challenging due to the influence of the Sole Pit Inversion. This leads to velocities being higher over the inversion axis than present-day burial would suggest and strong lateral velocity gradients within consistent intervals. To overcome this, velocity modelling was undertaken utilizing advanced seismic velocity extraction techniques to improve spatial resolution over that of well-based point data alone. The seismic velocities have been used to calculate the post-burial uplift of the Bacton Group, using seismic velocities of the unit. The results, which have been calibrated for local halokinesis, approximate Rotliegend Group uplift and aim to further de-risk the depth conversion uncertainty at target level, offering new insight into the inversion of the pre-salt section, with implications for future hydrocarbon exploration.

2-(Pyridin-4-yl)-2,3-di-hydro-1H-naphtho-[1,8-de][1,3,2]di-aza-borinine.

The title compound, C15H12BN3, is a type of di-aza-borinane featuring substitution at 1, 2, and 3 positions in the nitro-gen-boron six-membered heterocycle. It is comprised of two almost planar units, the pyridyl ring and the Bdan (dan = 1,8-di-aminona-phtho) group, which subtend a dihedral angle of 24.57 (5)°. In the crystal, the mol-ecules are linked into R 4 4(28) hydrogen-bonding networks around the fourfold inversion axis, giving cyclic tetra-mers. The mol-ecules form columnar stacks along the c axis.

Chiral and Polar Duality Design of Heteroanionic Compounds: Sr18 Ge9 O5 S31 Based on [Sr3 OGeS3 ]2+ and [Sr3 SGeS3 ]2+ Groups.

Chirality and polarity are the two most important and representative symmetry-dependent properties. For polar structures, all the twofold axes perpendicular to the principal axis of symmetry should be removed. For chiral structures, all the mirror-related symmetries and inversion axes should be removed. Especially for duality (polarity and chirality), all of the above symmetries should be broken and that also represents the highest-level challenge. Herein, a new symmetry-breaking strategy that employsheteroanionic groups to construct hourglass-like [Sr3 OGeS3 ]2+ and [Sr3 SGeS3 ]2+ groups to design and synthesize a new oxychalcogenide Sr18 Ge9 O5 S31 with chiral-polar duality is proposed. The presence of two enantiomers of Sr18 Ge9 O5 S31 is confirmed by the single-crystal X-ray diffraction. Its optical activity and ferroelectricity are also studied by solid-state circular dichroism spectroscopy and piezoresponse force microscopy, respectively. Further property measurements show that Sr18 Ge9 O5 S31 possesses excellent nonlinear optical properties, including the strong second harmonic generation efficiency (≈2.5 × AGS), large bandgap (3.61eV), and wide mid-infrared transparent region (≈15.3µm). These indicate that the unique microstructure groups of heteroanionic materials are conducive to realizing symmetry-breaking and are able to provide some inspiration for exploring the chiral-polar duality materials.

Accurate X-ray diffraction data required for proper evaluation of bond valence sums and global instability indexes: redetermination of the crystal structures of diamond-like Cu2CdSiS4 and Cu2HgSnS4 as a case study.

Our calculations of the global instability index (G) values for some diamond-like materials with the general formula I2-II-IV-VI4 have indicated that the structures may be unstable or incorrectly determined. To compute the G value of a given compound, the bond valence sums (BVSs) must first be calculated using a crystal structure. Two examples of compounds with high G values, based on data from the literature, are the wurtz-stannite-type dicopper cadmium silicon tetrasulfide (Cu2CdSiS4) and the stannite-type dicopper mercury tin tetrasulfide (Cu2HgSnS4), which were first reported in 1967 and 1965, respectively. In the present study, Cu2CdSiS4 and Cu2HgSnS4 were prepared by solid-state synthesis at 1000 and 900 °C, respectively. The phase purity was assessed by powder X-ray diffraction. Optical diffuse reflectance UV/Vis/NIR spectroscopy was used to estimate the optical bandgaps of 2.52 and 0.83 eV for Cu2CdSiS4 and Cu2HgSnS4, respectively. The structures were solved and refined using single-crystal X-ray diffraction data. The structure type of Cu2CdSiS4 was confirmed, where Cd2+, Si4+ and two of the three crystallographically unique S2- ions lie on a mirror plane. The structure type of Cu2HgSnS4 was also verified, where all ions lie on special positions. The S2- ion resides on a mirror plane, the Cu+ ion is situated on a fourfold rotary inversion axis and both the Hg2+ and the Sn4+ ions are located on the intersection of a fourfold rotary inversion axis, a mirror plane and a twofold rotation axis. Using the crystal structures solved and refined here, the G values were reassessed and found to be in the range that indicates reasonable strain for a stable crystal structure. This work, together with some examples gathered from the literature, shows that accurate data collected on modern instrumentation should be used to reliably calculate BVSs and G values.

Reconstructing the Volume Density Profile of Prestellar Cores with the Anisotropic Inverse Abel Transform Method

Most studies of the 3D density structure of prestellar cores have used isotropic evolution models, which are projected into 2D for direct comparison with observation data. In this study, we introduced the anisotropic inverse Abel transform method for reconstructing the 3D volume density profile of prestellar cores. We demonstrated that this approach could accurately preserve information about the realistic 3D structure with numerical simulation. This method has great advantages compared to the shape-assumption methods, particularly in high-density regions. We applied this method to the Herschel 2D column density maps of three prestellar cores, and the results showed good agreement with theoretical models. By changing the direction of the inversion axis of symmetry, we confirmed that the density profiles of prestellar cores exhibit nearly cylindrical symmetry.

Direct dating of overprinting fluid systems in the Martabe epithermal gold deposit using highly retentive alunite

Abstract. The Martabe gold deposits in Sumatra formed in a shallow crustal epithermal environment associated with intermediate mafic intrusions adjacent to an active right-lateral wrench system. Gas/fluid temperatures reached 200–350 ∘C. The structural geology suggests episodic switches in stress orientations during a Plio-Pleistocene seismotectonic evolution. Different mineralisation events may have been associated with oscillations in this earthquake cycle, so samples containing alunite were collected for 40Ar / 39Ar geochronology to constrain the timing. 39Ar diffusion experiments were performed to constrain variation in argon retentivity. The age spectra were produced by incremental step-heating with heating times chosen so similar percentages of 39Ar gas release occurred during as many steps as possible. This ensured the detail necessary for analysis of the complex morphology of these spectra by applying the method of asymptotes and limits, which enabled recognition of different growth events of alunite in overprinting fluid systems. It was possible to provide estimates as to the frequency of individual events and their duration. The heating schedule also ensured that Arrhenius data populated the inverse temperature axis with sufficient detail to allow modelling. Activation energies were between 370–660 kJ mol−1. Application of Dodson's recursion determined closure temperatures that range from 400–560 ∘C for a cooling rate of 100 ∘C Ma−1. Such estimates are higher than any temperature to be expected in the natural system, giving confidence that the ages represent the timing of growth during periods of active fluid movement and alteration: a hypothesis confirmed by modelling age spectra using the MacArgon program. We conclude that gold in the Purnama pit resulted from overprinting fluid rock interactions during very short mineralisation episodes at ∼2.25 and ∼2.00 Ma.

Inversion tectonics in the Sorgenfrei–Tornquist Zone: insight from new marine seismic data at the Bornholm Gat, SW Baltic Sea

ABSTRACT New seismic profiles located within the Bornholm Gat in the SW Baltic Sea area image Late Cretaceous-Paleogene inversion and exhumation of a previously poorly characterized narrow crustal zone in the southern end of the Sorgenfrei–Tornquist Zone (STZ), a long pre-Alpine tectonic lineament in Europe. Thrusts and pop-up structures developed along the inversion axis accompanied by subsidence troughs on its sides. Stratigraphic analysis of chalk deposits indicates that structural shortening and inversion resulted from compressional deformation. Marginal troughs formed synchronously to inversion and adjacent to the tectonically active slope, where sediment redeposition was focused. Deposition of chalk units, composed predominantly of contourites and gravity-driven sedimentation were largely controlled by inversion tectonics and influenced by intensification of bottom currents. We find that allochthonous chalk has been buried in horizontally deposited autochthonous (pelagic) chalk. An erosional unconformity represents the base of the Maastrichtian and marks the onset of along slope deposition due to a more hydrodynamic environment. The revealed asymmetric inversion across the STZ with fold tightening and superposition of NE-NW folds attest to more than one pulse during the Late Cretaceous-Cenozoic inversion. The STZ may belong to the end-member mode of intraplate foreland basins resulting from a far-field NE-SW compression transmitted from the Africa-Iberia-Europe convergence. The intraplate stress associated with the following Maastrichtian enhanced collisional coupling between the Alpine-Carpathian orogen and its foreland, which is widely recognized (e.g., the Mid-Polish Trough, the Bohemian Massif and the Central Graben), may also have had its maximum extent to the northeast in southern Sweden.

Tetra-kis(di-cyclo-hexyl-amido)-zirconium(IV).

The reaction of ZrCl4 with three equivalents of LiNCy2 (Cy is cyclo-hex-yl) resulted in the formation of tris-(di-cyclo-hexyl-amido)-zirconium chloride and the title compound, [Zr(C12H22N)4]. The latter is isotypic with its cerium(IV) analogue and crystallizes with three independent mol-ecules in the asymmetric unit. One mol-ecule is located about a twofold rotation axis, and the other two on fourfold inversion axes. In each mol-ecule, the ZrIV atom has a distorted tetra-hedral coordination environment. The crystal under investigation was twinned by inversion in a 1:1 ratio.

One-dimensional topological insulators with noncentered inversion symmetry axis

In this Rapid Communication, we discuss the characteristic features of one-dimensional topological insulators with inversion symmetry but noncentered inversion axis in the unit cell, for any choice of the unit cell. In these systems, the global inversion operation generates a $k$-dependent inversion operator within the unit cell and this implies a nonquantized Zak's phase both for the trivial and nontrivial topological phases. By relating the Zak's phase with the eigenvalues of modified parity operators at the inversion invariant momenta, a corrected quantized form of the Zak's phase is derived. We show that finite energy topological edge states of this family of chains are symmetry protected not by usual chiral symmetry but by a hidden sublattice chiral-like symmetry. A simple justification is presented for shifts in the polarization quantization relation for any choice of endings of these chains.

Shear Surface Acoustic Waves in Twinned Piezoelectric Crystals of the $$\bar {6}$$m2 Symmetry Class

Shear surface acoustic waves, whose existence is due to the difference in the signs of piezoelectric modulus tensors of adjoining halves of crystal, are studied on flat interfaces of twinned hexagonal piezoelectric crystals of the $$\bar {6}$$m2 symmetry class. In this case, the inversion axis $$\bar {6}$$ is perpendicular to the interface between the halves. It is shown that, at a weak piezoelectric effect, the characteristic penetration depth of these waves is inversely proportional to the square of component e222 and may significantly exceed the length of the surface wave.

Orientational phase transition in methane-intercalated fullerite C60

The known first-order orientational phase transition in pure ${\mathrm{C}}_{60}$ occurs at 260 K and is accompanied by the change from face-centered cubic $(Fm3m)$ to simple cubic unit cell $(Pa\overline{3})$. While ${\mathrm{C}}_{60}$ molecules rotate freely above 260 K, they are fixed in inversion centers below 260 K. The phase transition in methane-intercalated ${\mathrm{C}}_{60}$, ${(\mathrm{C}{\mathrm{H}}_{4})}_{x}({\mathrm{C}}_{60})$, occurs at $236\ifmmode\pm\else\textpm\fi{}2\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. It was studied by DSC and single crystal x-ray diffraction. Above 236 K, the intercalate adopts the face-centered cubic structure which is characterized by freely rotating ${\mathrm{C}}_{60}$ and disordered ${\mathrm{CH}}_{4}$ molecules. The ordered low-temperature crystal structure possesses simple cubic unit cell in the space group $Pa\overline{3}$ in which both ${\mathrm{C}}_{60}$ and ${\mathrm{CH}}_{4}$ molecules are fixed on threefold inversion axes. In the structure of ${(\mathrm{C}{\mathrm{H}}_{4})}_{0.72}{\mathrm{C}}_{60}$ at 100 K, a ${\mathrm{C}}_{60}$ molecule is fixed by its 12 ${\mathrm{C}}_{60}$ neighbors due to donor-acceptor van der Waals interactions between electron-rich 6:6 C-C bonds and electron-deficient cage pentagons. At 200 K, the second orientation of a ${\mathrm{C}}_{60}$ molecule is present (with 7.5% occupancy) in which 6:6 C-C bonds are directed to cage hexagons. The methane molecules are situated in octahedral holes and statistically disordered over two orientations around inversion centers. The phase transition temperature of $(\mathrm{C}{\mathrm{H}}_{4})\phantom{\rule{0.16em}{0ex}}{\mathrm{C}}_{60}$ intercalate is lower than in ${\mathrm{C}}_{60}$ by $\ensuremath{\sim}24\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ due to the increased ${\mathrm{C}}_{60}\ensuremath{\cdots}{\mathrm{C}}_{60}$ separation. This study provides a reliable structural information about the low-temperature structure of the ${(\mathrm{C}{\mathrm{H}}_{4})}_{0.7}({\mathrm{C}}_{60})$ intercalate thus demonstrating significant differences between orientational phase transitions in pure fullerite ${\mathrm{C}}_{60}$ and ${\mathrm{C}}_{60}$ intercalated with methane. In addition, the molecular structure of ${\mathrm{C}}_{60}$ fullerene in the ${(\mathrm{C}{\mathrm{H}}_{4})}_{0.7}{\mathrm{C}}_{60}$ intercalate is distinguished by a high precision which is superior to the former experimental data for ${\mathrm{C}}_{60}$ and its adducts reported in the literature.

Study of ECG changes in patients with acute stroke: a hospital based cross sectional study

Background: Physicians are confronted on having ECG in patients with acute stroke as it can mimic that of myocardial infarction/ischemia. They should be aware of these changes taking place in patients with acute stroke and not due to myocardial infarction/ischemia. The objective of the present study was to study ECG changes in patients with acute stroke.Methods: A hospital based cross sectional study was carried out for a period of six months at Malla Reddy Hospital. A total of 100 patients were included who were eligible for the presents study as per the inclusion and exclusion criteria. Detailed clinical examination, history, lipid profile, blood pressure, BMI, addictions, RBS and ECG were done for all selected patients. Data was analysed using means, proportions. Statistical tests like chi square test and t test were used.Results: Majority of patients with acute stroke were above 60 years of age, males, urban residents, professional and skilled persons, and alcoholics. Based on the study of ECG among patients with acute stroke it was found that T wave inversion was the most common ECG change found in 33% and this was more in females (36.1%) compared to 31.3% in males. LVH was next common condition found on ECG of acute stroke patients but this time its incidence was more in males (25%) compared to females with only 13.9%. Factors like age, BMI, SBP, DBP, TC, TG, LDL, VLDL, HDL, addictions, residence, sex, family history were not found to be associated with ECG changes.Conclusions: T wave inversion and left axis deviation along with left ventricular hypertrophy were common ECG changes in patients with acute stroke. No studied factor was found to be associated with ECG changes in patients with acute stroke.

(Invited) Dielectric Response and Quantum Motion of Lithium Cations Trapped inside Carbon Cages

Endohedral fullerenes trapping atoms and molecules with magnetic and electric moments have a potential to be used for quantum computing. A C60 fullerene trapping a Li+ cation has an electric monopole moment, and forms a rock-salt-type cubic crystal, [Li@C60](PF6). The dielectric response and quantum motion of the Li+ cations in the crystal at low temperature were revealed by the dielectric and X-ray diffraction measurements [1]. The Li+ cations are moving inside the C60 cages by the hopping and tunneling motion between the potential wells under 20 hexagons above 100 K. The Li+ motion is suppressed to be localized at two equivalent positions on the threefold inversion axis with decreasing temperature below 100 K. The simultaneous occupation of the Li+ cation at the two positions is mainly achieved by the tunneling motion. The hopping motion is slowing down and hindered by the energy barriers between the wells. The tunneling motion is also hindered below T C = 24 K by the antiferroelectric interactions among local electric dipole moments formed between the Li+ cations inside and the PF6 − anions outside the C60 cages. The tunneling motion and intermolecular interaction of the Li+ cation found in [Li@C60](PF6) show that Li+@C60 has a potential to be used as a qubit in a quantum computer using electric dipole moments. [1] S. Aoyagi, A. Tokumitu, K. Sugimoto, H. Okada, N. Hoshino, and T. Akutagawa, J. Phys. Soc. Jpn. 85, 094605 (2016)

Three-point-support method based on position determination of supports and wafers to eliminate gravity-induced deflection of wafers

The flatness measurement of large and thin wafers is affected greatly by gravity. Inverting method is often used to cancel the effect. However, it is required that the positions of the supports and wafers are perfectly symmetric about the inversion axis. In this study a three-point-support method based on position determination of supports and wafers was proposed. The supporting balls and the wafer were placed in arbitrary positions and their positions were obtained by measurement and fed into the FEM model which was developed to calculate the gravity-induced deflection (GID). The methods to acquire the positions of the supports and the wafer were proposed. The position measurement accuracy of the supports was improved greatly by circle fitting to the profile of the supporting ball. Wafer edge point was obtained accurately as the intersection point between the wafer surface line and the edge profile. The method to measure the wafer thickness using only one displacement sensor on the same equipment was presented. The simulation results were verified by experimental results. The centering device for the wafer and the positioning accuracy requirements of the supports are not needed any more. The effect of the positions of the supports and the wafer was reduced to be less than 1μm for a 300mm diameter and 397μm thickness wafer with GID over 140μm. This method could also be used for accurate flatness measurement of other large and thin panels.

Crystal structures of cristobalite-type and coesite-type PON redetermined on the basis of single-crystal X-ray diffraction data.

Hitherto, phospho-rus oxonitride (PON) could not be obtained in the form of single crystals and only powder diffraction experiments were feasible for structure studies. In the present work we have synthesized two polymorphs of phospho-rus oxonitride, cristobalite-type (cri-PON) and coesite-type (coe-PON), in the form of single crystals and reinvestigated their crystal structures by means of in house and synchrotron single-crystal X-ray diffraction. The crystal structures of cri-PON and coe-PON are built from PO2N2 tetra-hedral units, each with a statistical distribution of oxygen and nitro-gen atoms. The crystal structure of the coe-PON phase has the space group C2/c with seven atomic sites in the asymmetric unit [two P and three (N,O) sites on general positions, one (N,O) site on an inversion centre and one (N,O) site on a twofold rotation axis], while the cri-PON phase possesses tetra-gonal I-42d symmetry with two independent atoms in the asymmetric unit [the P atom on a fourfold inversion axis and the (N,O) site on a twofold rotation axis]. In comparison with previous structure determinations from powder data, all atoms were refined with anisotropic displacement parameters, leading to higher precision in terms of bond lengths and angles.

Bis[bis(pentamethylcyclopentadienyl)cobalt(III)] tetrachloridocobaltate(II) dichloromethane disolvate

The title compound, [Co(C10H15)2]2[CoCl4]·2CH2Cl2, was isolated as a dichloromethane solvate and was formed in the reaction between lithium penta­methyl­cyclo­penta­dienide and anyhydrous cobalt(II) chloride in tetra­hydro­furan. There are two deca­methyl­cobaltocenium cations, one tetrachloridocobaltate(II) anion and two di­chloro­methane solvent mol­ecules in the formula unit. There is a slight disorder of the di­chloro­methane solvent which was treated with a two-site model [occupancy rates = 0.765 (4) and 0.235 (4)]. The di­chloro­methane mol­ecules display significant C—H⋯Cl inter­actions with the tetrachloridocobaltate(II) dianion. The cobalt atom of the deca­methyl­cobaltocenium cation sits on a twofold rotation axis, with only one penta­methyl­cyclo­penta­diene ligand being unique and the second generated by symmetry. The cobalt atom of the [CoCl4]−2 ion sits on a special site with -4 symmetry, with one unique chloride ligand and the others generated by the fourfold inversion axis.

Zinc mercury(II) tetrakis(selenocyanate)

The title crystal, [HgZn(NCSe)4]n, a coordination polymer, has a diamond-like network. In the crystal, the metal ions, Zn2+ and Hg2+, are both located on fourfold inversion axes and mimic the role of C atoms in the structure of diamond, and the linear seleno­cyanate bridges replace the C—C bonds. The C—N—Zn unit is almost linear and the C—Se—Hg unit is nearly a right angle. Thus, the HgZn4 (or ZnHg4) arrangement is midway between a tetra­hedron and a square plane, with two types of Hg—Zn—Hg (or Zn—Hg—Zn) angles of 92.38 (6) and 156.45 (6)°.

Reversible high-temperature phase transition of a manganese(II) formate framework with imidazolium cations

A new metal-formate framework, poly[1H-imidazol-3-ium [tri-μ2-formato-manganese(II)]], {(C3H5N2)[Mn(HCOO)3]}n, was synthesized and its structural phase transition was studied by thermal analysis and variable-temperature X-ray diffraction analysis. The transition temperature is around 435 K. The high-temperature phase is tetragonal and the low-temperature phase is monoclinic, with a β angle close to 90°. The relationship of the unit cells between the two phases can be described as: a(HT) = 0.5a(LT) + 0.5b(LT); b(HT) = -0.5a(LT) + 0.5b(LT); c(HT) = 0.5c(LT). In the high-temperature phase, both the framework and the guest 1H-imidazol-3-ium (HIm) cations are disordered; the HIm cations are located about 2mm sites and were modelled as fourfold disordered. The Mn and a formate C atom are located on fourfold rotary inversion axes, while another formate C atom is on a mirror plane. The low-temperature structure is ordered and consists of two crystallographically independent HIm cations and two crystallographically independent Mn(2+) ions. The phase transition is attributable to the order-disorder transition of the HIm cations.

Bis(chlorido)(dimethylsulfoxide-κO)barium(II)

The title compound, [BaCl2(C2H6SO)], forms a Ba6Cl9 cluster in which the BaCl2 units are connected via dimethyl­sulfoxide (DMSO) and chloride bridges. The central Cl atom of the Ba6Cl9 cluster is located on a threefold inversion axis and is coordinated octa­hedrally to six barium cations. In the crystal, the clusters are arranged in rows, which are inter­connected by the DMSO mol­ecules, forming a three-dimensional network.

Electron spins in an array of tunnel-coupled quantum dots

Mechanisms of electron spin relaxation in semiconductor arrays with tunnel-coupled quantum dots are reviewed. The contribution for anisotropic exchange interaction is shown for asymmetrical quantum dots having no inversion axis relative to their plane. The configuration of vertically coupled double Ge/Si quantum dots is found where anisotropic exchange coupling does not contribute to spin decoherence. It could be a basic configuration of spin-based quantum computation schemes.