Equatorial Ones Research Articles

Precipitation inequality exacerbates streamflow inequality, but dams moderate it

Access to clean water is a fundamental human right, yet millions worldwide face the dire consequences of water scarcity and inadequate sanitation. Water inequality, characterized by disparities in access and availability of water resources, has emerged as a critical global challenge with far-reaching social, economic, and environmental implications. Using a globally representative observational streamflow dataset and Gini coefficients, this study investigates how streamflow inequality, which has a large impact on inequality of water availability, varies spatially and temporally, and its relationship with different underlying catchment characteristics. This study finds that watersheds in arid climates exhibit a higher degree of streamflow inequality than polar and equatorial ones. Africa experiences the highest streamflow inequality, followed by Australia, while South America experiences relatively lower streamflow inequality. Around 19.6 % of the catchments in Australia display an increasing trend in streamflow inequality, pointing to worsening conditions. Conversely, South America experiences a decreasing trend in streamflow inequality in 18.3 % of its catchments during the same period. It is also found that a more evenly distributed precipitation within the catchment and higher dam storage capacity corresponds to more evenly distributed streamflow availability throughout the year. This study enhances our understanding of streamflow inequality worldwide, which will aid policy formulation to foster sustainable development.

Topological changes in the magnetic field of LQ Hya during an activity minimum

Aims. Previous studies have related surface temperature maps, obtained with the Doppler imaging (DI) technique, of LQ Hya with long-term photometry. Here, we compare surface magnetic field maps, obtained with the Zeeman Doppler imaging (ZDI) technique, with contemporaneous photometry, with the aim of quantifying the star’s magnetic cycle characteristics. Methods. We inverted Stokes IV spectropolarimetry, obtained with the HARPSpol and ESPaDOnS instruments, into magnetic field and surface brightness maps using a tomographic inversion code that models high signal-to-noise ratio mean line profiles produced by the least squares deconvolution (LSD) technique. The maps were compared against long-term ground-based photometry acquired with the T3 0.40 m Automatic Photoelectric Telescope (APT) at Fairborn Observatory, which offers a proxy for the spot cycle of the star, as well as with chromospheric Ca II H&K activity derived from the observed spectra. Results. The magnetic field and surface brightness maps reveal similar patterns relative to previous DI and ZDI studies: non-axisymmetric polar magnetic field structure, void of fields at mid-latitudes, and a complex structure in the equatorial regions. There is a weak but clear tendency of the polar structures to be linked with a strong radial field and the equatorial ones with the azimuthal field. We find a polarity reversal in the radial field between 2016 and 2017 that is coincident with a spot minimum seen in the long-term photometry, although the precise relation of chromospheric activity to the spot activity remains complex and unclear. The inverted field strengths cannot be easily related with the observed spottedness, but we find that they are partially connected to the retrieved field complexity. Conclusions. This field topology and the dominance of the poloidal field component, when compared to global magnetoconvection models for rapidly rotating young suns, could be explained by a turbulent dynamo, where differential rotation does not play a major role (so-called 2 or 2 dynamos) and axi- and non-axisymmetric modes are excited simultaneously. The complex equatorial magnetic field structure could arise from the twisted (helical) wreaths often seen in these simulations, while the polar feature would be connected to the mostly poloidal non-axisymmetric component that has a smooth spatial structure.

To the Question of the Influence of the Polar Region Seismicity on the Ground Transportation Infrastructure

A harmonic analysis is carried out for a simplified finite element model of the Earth with characteristic important elements of transportation infrastructure in the equatorial and polar regions. The results are presented for the calculation of the Earth model with the sections of the main pipelines attached in the specified areas, as well as the results of a similar calculation for the assembled rails and sleepers with the embankment and basements with different properties under harmonic displacements of the basements. The calculations show significantly greater load on the considered elements of the transportation infrastructure in the polar region as compared to the equatorial one because the displacements of the Earth’s surface in the polar zones of the model are much greater in magnitude than in the equatorial ones. Consequently, it is necessary to consider these phenomena in the calculations and experimental measurements of seismic impacts when designing transportation infrastructure in the Arctic region.

On the making of Ptolemy’s star catalog

The assumption that Ptolemy adopted star coordinates from a star catalog by Hipparchus is investigated based on Hipparchus’ equatorial star coordinates in his Commentary on the phenomena of Aratus and Eudoxus. Since Hipparchus’ catalog was presumably based on an equatorial coordinate system, his star positions must have been converted into the ecliptical system of Ptolemy’s catalog in his Almagest. By means of a statistical analysis method, data groups consistent with this conversion of coordinates are identified. The found groups show a high degree of agreement between Hipparchus’ and Ptolemy’s data. The value of the obliquity of the ecliptic underlying the conversion is estimated by adjustment and statistically agrees with Ptolemy’s value of this parameter. The results allow the assumption that Ptolemy’s coordinates were determined from Hipparchus’ coordinates by an accurate star globe or even by calculation. For a calculative derivation of ecliptical coordinates from equatorial ones, possible calculation methods are discussed considering the mathematics of the Almagest.

Synthesis, Characterization and Structural Aspects of Three New Nonsymmetrical Bimetallic Dibutyltin (IV) Derivatives

Three new nonsymmetric bimetallic diorganotin com- pounds derived from hexadentate Schiff bases were obtained by reac- tion of 2,6-dihydroxybenzene-1,3-dicarbaldehyde with R-(-)-phenyl- glycinol, glycine and 2-amino-5-nitrophenol, in the presence of dibutyltin oxide. The full multinuclear NMR analysis, IR and elemen- tal analyses allowed to establish the structures of all new compounds. In the three cases, the 119 Sn chemical shifts are indicative of two dif- ferent pentacoordinated tin atoms in solution. The molecular structure of compound 4 in the solid state shows two distinct tin atoms with different geometries, one is a distorted trigonal bipyramid with the oxygen atoms in the axial positions and the organic moieties and imine nitrogen in equatorial ones; while the other tin shows distorted octahedral geometry due to Sn(2)-O(4) intermolecular coordination, leading to a dimeric specie, with a Sn-O-Sn-O four-membered ring. The most interesting issue in the solid state is that only one of the tin atoms exhibits intermolecular coordination, in spite of the fact that the atoms are nearly equivalents.

Macrocyclic copper(II) complexes containing diazacyclam-based ligand: spectral, structural and docking studies

The macrocyclic copper complex, [Cu(ACE)(NO3)2] (ACE = 1,3,6,10,12,15-hexaazatricyclo[13.3.1.16,10]eicosane), was synthesized by template condensation from a mixture of N1-(2-aminoethyl)-1,3-diaminopropane, formaldehyde and copper(II) nitrate. Replacement of the nitrate with thiocyanato and azido ligands gives [Cu(ACE)NSC]NSC (2) and the 1D-coordination polymer, [Cu(ACE)(μ-N3)]n[N3]n (3), respectively. Complex 1, [Cu(ACE)(NO3)]NO3, is an intermediate product in which one of the nitrate ions is separated from its parent molecule. The formation of 1 allowed us to conclude that the mechanism of ion exchange in the parent molecule is similar to SN1. These complexes have been characterized by FT-IR spectroscopy and X-ray crystallography. In the crystal structures of 1 and 2, the copper(II) ion has a distorted square pyramidal geometry in which the N4-donor ACE ligand lies on the equatorial plane and other ligand occupies the axial position. The copper(II) ion in 3 has an octahedral geometry, coordinating to one ACE ligand in the equatorial plane and two N-donor bridging azido groups in the axial positions. In all structures, owing to the Jahn-Teller effect, the coordinated bond length of the axial position is longer than the equatorial ones. The ability of the ACE ligand and its complexes 1 and 2, along with their analogues, to interact with 10 selected biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS, Top II and B-DNA) was investigated by docking calculations and compared with that of doxorubicin.

Earth crust vertical movements according to ITRF2000, ITRF2005, ITRF2008 and ITRF2014 coordinate systems and their comparing analysis

The analysis of Earth’s crust movement vertical velocities was made both for separate regions, and averaged on regions. As input data coordinates and velocities of earth crust points, obtained in International Coordinate Systems ITRF2000, ITRF2005, ITRF2008 on the base of processing radio interferometric (VLBI), laser (SLR), Doppler (DORIS) and GPS observations was used. For the purpose of global analysis all input velocity values were averaged in the х trapezoids. For filling trapezoids the spherical function expansion to N=36 was made. Expansion harmonic coefficients allowed determine the global characteristics of earth crust movements both for all Earth, and for separate hemispheres, polar and equatorial regions, continents and oceans. It appears, that polar regions were risen, and equatorial ones were lowered, that can indicate the modern Earth oblateness reduction. The constructed maps of vertical velocities were compared with obtained by us map of earth crust strain distribution. It is appeared, that regions of modern earth surface rising (Fennoscandia, Canada, Antarctica) coincide with regions of vertical extension strain, and the lowering regions – with compression regions. Simultaneously with the determination of harmonious coefficients the mean-square error of approximation for expansion of power n=1 N and power dispersion were determined. Whereas the results converge badly and dispersion increased with the n grows, hence we can concludes, that vertical movements do not characterized global earth crust movement and denotes the unrelated character of these movement. Seemingly, the main cause of such movement origin is the local seismic events (earthquake, volcanic eruption and so on). It confirms by our conclusions about correspondence of vertical strain maximal gradient (and therefore vertical velocities) map of the earthquake distribution. In work the detailed analysis of obtained results for separate Earth’s regions was made.

Core surface sub-centennial magnetic flux patches: characteristics and evolution

Short-term constituents of the secular variation, at inter-decadal (20–30 years) and sub-centennial (60–90 years) time scales, present in observatory data and main field models, are also found in the radial field evolution at core surface. The paper is focused on the sub-centennial constituent in the gufm1 model. Time–Longitude (t–λ) plots, covering the 400 years time span of the model, at various latitudes between 70°N and 70°S, show a clear westward movement of the sub-centennial constituent field features in the 20°N–20°S latitude band. The sub-centennial constituent at latitudes larger than 50°N/S stands in fact for the fine structure of high-latitude flux lobes. Since 1900 this fine structure shows a westward displacement. Time–Latitude (t–φ) plots indicate also northward and southward components of the movement. The traveling speeds of the sub-centennial constituent field are derived, on one hand, empirically based on Time–Longitude and Time–Latitude plots, and on the other, mathematically by means of the Radon transform method. Important results of this paper are related to characterization of the evolution of the radial field at core surface at sub-centennial time scales, namely (1) evidencing two types of azimuthal flow, equatorial and high latitude ones, responsible for the observed westward drift of the surface field, and (2) quantitative information on meridional displacements of the core surface magnetic flux patches.

Accurate gas-phase structure ofpara-dioxane by fs Raman rotational coherence spectroscopy andab initiocalculations

p-Dioxane is non-polar, hence its rotational constants cannot be determined by microwave rotational coherence spectroscopy (RCS). We perform high-resolution gas-phase rotational spectroscopy of para-dioxane-h8 and -d8 using femtosecond time-resolved Raman RCS in a gas cell at T = 293 K and in a pulsed supersonic jet at T∼130 K. The inertial tensor of p-dioxane-h8 is strongly asymmetric, leading to a large number of asymmetry transients in its RCS spectrum. In contrast, the d8-isotopomer is a near-oblate symmetric top that exhibits a much more regular RCS spectrum with few asymmetry transients. Fitting the fs Raman RCS transients of p-dioxane-h8 to an asymmetric-top model yields the ground-state rotational constants A0 = 5084.4(5) MHz, B0 = 4684(1) MHz, C0 = 2744.7(8) MHz, and (A0 + B0)/2 = 4884.5(7) MHz (±1σ). The analogous values for p-dioxane-d8 are A0 = 4083(2) MHz, B0 = 3925(4) MHz, C0 = 2347.1(6) MHz, and (A0 + B0)/2 = 4002.4(6) MHz. We determine the molecular structure with a semi-experimental approach involving the highly correlated coupled-cluster singles, doubles and iterated triples method and the cc-pCVXZ basis set series from double- to quadruple-zeta (X = D, T, Q). Combining the calculated vibrationally averaged rotational constants A0calc(X),B0calc(X),C0calc(X) for increasing basis-set size X with non-linear extrapolation to the experimental constants A0exp,B0exp,C0exp allows to determine the equilibrium ground state structure of p-dioxane. For instance, the equilibrium C-C and C-O bond lengths are re(CC) = 1.5135(3) Å and re(CO) = 1.4168(4) Å, and the four axial C-H bond lengths are 0.008 Å longer than the four equatorial ones. The latter is ascribed to the trans-effect (anomeric effect), i.e., the partial delocalization of the electron lone-pairs on the O atoms that are oriented trans, relative to the axial CH bonds.

Behavior of causal geodesics on a Kerr–de Sitter spacetime

We analyze the behavior of causal geodesics on a Kerr-de Sitter spacetime with particular emphasis on their completeness property. We set up an initial value problem of which the solutions lead to a global understanding of causal geodesics on these spacetimes. Causal geodesics that avoid the rotation axis are complete except the ones that hit the ringlike curvature singularity and those that encounter the ring singularity are necessary equatorial ones. We also show the existence of geodesics that cross or lie on the rotation axis. The equations governing the latter family show the repulsive nature of the ring singularity. The results of this work show that, as far as properties of causal geodesics are concerned, Kerr-de Sitter spacetimes behave in a similar manner as the family of Kerr spacetimes.

Global monsoon precipitation responses to large volcanic eruptions.

Climate variation of global monsoon (GM) precipitation involves both internal feedback and external forcing. Here, we focus on strong volcanic forcing since large eruptions are known to be a dominant mechanism in natural climate change. It is not known whether large volcanoes erupted at different latitudes have distinctive effects on the monsoon in the Northern Hemisphere (NH) and the Southern Hemisphere (SH). We address this issue using a 1500-year volcanic sensitivity simulation by the Community Earth System Model version 1.0 (CESM1). Volcanoes are classified into three types based on their meridional aerosol distributions: NH volcanoes, SH volcanoes and equatorial volcanoes. Using the model simulation, we discover that the GM precipitation in one hemisphere is enhanced significantly by the remote volcanic forcing occurring in the other hemisphere. This remote volcanic forcing-induced intensification is mainly through circulation change rather than moisture content change. In addition, the NH volcanic eruptions are more efficient in reducing the NH monsoon precipitation than the equatorial ones, and so do the SH eruptions in weakening the SH monsoon, because the equatorial eruptions, despite reducing moisture content, have weaker effects in weakening the off-equatorial monsoon circulation than the subtropical-extratropical volcanoes do.

Tuning the high-temperature properties of Pr2NiO4+δby simultaneous Pr- and Ni-cation replacement

Novel Pr2−xSrxNi1−xCoxO4±δ (x = 0.25; 0.5; 0.75) oxides with the tetragonal K2NiF4-type structure have been prepared. Room-temperature neutron powder diffraction (NPD) study of x = 0.25 and 0.75 phases together with iodometric titration results have shown the formation of hyperstoichiometric oxide for x = 0.25 (δ = 0.09(2)) and a stoichiometric one for x = 0.75. High-temperature X-ray powder diffraction (HT XRPD) showed substantial anisotropy of the thermal expansion coefficient (TEC) along the a- and c-axis of the crystal structure, which increases with increasing the Co content from TEC(c)/TEC(a) = 2.4 (x = 0.25) to 4.3 (x = 0.75). High-temperature NPD (HT NPD) study of the x = 0.75 sample reveals that a very high expansion of the axial (Ni/Co)–O bonds (75.7 ppm K−1 in comparison with 9.1 ppm K−1 for equatorial ones) is responsible for such behaviour, and is caused by a temperature-induced transition between low- and high-spin states of Co3+. This scenario has been confirmed by high-temperature magnetization measurements on a series of Pr2−xSrxNi1−xCoxO4±δ samples. For compositions with high Ni content (x = 0.25 and 0.5) we synthesised K2NiF4-type oxides Pr2−x−ySrx+y(Ni1−xCox)O4±δ, y = 0.0–0.75 (x = 0.25); y = 0.0–0.5 (x = 0.5). The studies of the TEC, high-temperature electrical conductivity in air, chemical stability of the prepared compounds in oxygen and toward interaction with Ce2−xGdxO2−x/2 (GDC) at high temperatures reveal optimal behaviour of Pr1.35Sr0.65Ni0.75Co0.25O4+δ. This compound shows stability in oxygen at 900 °C and does not react with GDC at least up to 1200 °C. It features low TEC of 13 ppm K−1 and high-temperature electrical conductivity in air of 280 S cm−1 at 900 °C, thus representing a promising composition for use as a cathode material in intermediate temperature solid oxide fuel cells (IT-SOFC).

Discriminating solar and antisolar differential rotation in high-precision light curves

Surface differential rotation (DR) is one major ingredient of the magnetic field generation process in the Sun and likely in other stars. The term solar-like differential rotation describes the observation that solar equatorial regions rotate faster than polar ones. The opposite effect of polar regions rotating faster than equatorial ones (termed as antisolar DR) has only been observed in a few stars, although there is evidence from theoretical dynamo models. We present a new method to detect the sign of DR (i.e. solar-like or antisolar DR) by analyzing long-term high-precision light curves with the Lomb-Scargle periodogram.We compute the Lomb-Scargle periodogram and identify a set of significant periods $P_k$, which we associate with active regions located at different latitudes on the the stellar surface. If detectable, the first harmonics ($P_k'$) of these periods were identified to compute their peak-height-ratios $r_k:=h(P_k')/h(P_k)$. Spots rotating at lower latitudes generate less sine-shaped light curves, which requires additional power in the harmonics, and results in larger ratios $r_k$. Comparing different ratios $r_k$ and the associated periods $P_k$ yields information about the spot latitudes, and reveals the sign of DR. We tested our method on different sets of synthetic light curves all exhibiting solar-like DR. The number of cases where our method detects antisolar DR is the false-positive rate of our method. Depending on the set of light curves, the noise level, the required minimum peak separation, and the presence or absence of spot evolution, our method fails to detect the correct sign in at most 20%. We applied our method to 50 Kepler G stars and found 21-34 stars with solar-like DR and 5-10 stars with antisolar DR, depending on the minimum peak separation.

A purely vibrational insight on the tetragonal distortion of [Cu(DMF)6]2+

Raman spectra of N,N-dimethylformamide (DMF) solutions containing copper perchlorate at different compositions have been recorded. The spectral changes exhibited at the rmethyl region of DMF, in the presence of the Cu(II) salt, were reported for the first time. A correlation with the δOCN region is made. The quantitative Raman analysis performed at the rmethyl region allowed the determination of an average number of 6 DMF molecules per Cu(II) in the first solvation shell. This value as combined to the spectral variations observed in both regions of DMF allow us to propose the existence of axial bond lengths longer than equatorial ones in the octahedron. The spectra also reveal that the counter-ion is not capable of affecting the stability of the [Cu(DMF)6]2+ complex for the whole investigated concentration range.

First-principles study of low-compressibility of B<sub>13</sub>C<sub>2 </sub>and B<sub>7</sub>C<sub>8</sub>

The property changes from B13C2 to its derivative substituted by six C atoms for all of the B atoms sitting at the polar sites in B12 icosahedra are studied using the projector augmented wave (PAW) method based on the density function theory. The analysis of comparative calculation shows that the charge density both between the polar atoms and between the equatorial ones declines, and the Muliken population changes from positive to negative, which is to express that the chemical bond transfer to anti bonding from bonding, and that the interaction between them becomes decreased in each B6C6 icosahedra. However, the charge density not only between the polar atom and the equatorial one in the same icosahedra but also between the polar atoms in neighboring icosahedra increases relatively, and the length of the bond between them becomes short and sp hybridization goes remarkable, which indicates the interaction between them increased. It is resulted that the body modulus goes up and the shear modulus goes down. The electronic property becomes metallic from semiconductive. The population of charge turns to localized heavily on the polar from well-proportioned on the surface of icosahedra. For the computational hardness of the weakest bond breaks a fall, the theoretical hardness of the material decreases correspondingly.

Wave energy resources: Wave climate and exploitation

In identifying the most convenient zones for harvesting wave energy, it is natural to be attracted by the areas where we find the highest mean energy values. The obvious examples are the storm belts. A more careful analysis reveals that for practical use other factors need to be taken into account. Some of the main ones are the energy spread in frequency and direction, and its seasonality, without discussing the cost of the structure basically related to the conditions to be withstood. This reveals that other areas, in particular the equatorial ones, can be conveniently used, and be possibly advantageous from various points of view. Based on the results of the ECMWF ERA-Interim reanalysis and of altimeter data, we have carried out a comparative analysis between two locations with opposite characteristics, in the North Atlantic and in the Equatorial Pacific respectively. The quantified results confirm that less energetic, but more regular and less extreme, areas have a potential comparable to that of the classically considered storm belts.

Electronic structure analysis and properties of Sr2CeO4 grown by sol–gel method

Sr2CeO4 is a very promising material due to its various industrial applications, e.g. for the construction of field emission displays and light emitting diodes. In this work, the phosphor was synthesized by the sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) methods. They proved to be very good structural properties of the material and identified negligible impurities from the technological process. The decomposition of the surface of the nanocrystals was found but this did not decrease the spectral features of the compound. The analysis of the XPS O2p lines revealed contributions of two kinds of bonds: terminal and equatorial ones, in the ratio of 2/4. They are separated by 1.2eV what is in agreement with the observed absorption spectra. A presence of the decomposed layers may produce asymmetric widening of the emission spectra towards a lower energy.

Synthesis and structural characterization of a novel tellurane with four sulfur ligands

AbstractThe molecular structure of a novel hypervalent tellurium(IV) compound, 2,2′‐spirobi[4,7‐diisopropyl‐1,3,2‐benzodithiatellurole] (1), has been determined by a single crystal X‐ray diffraction study. The results represent the first crystal structural characterization of a hypervalent tellurium(IV), tellurane, with only four sulfur ligands. The tellurane has a distorted pseudo‐trigonal‐bipyramidal geometry with the axial sulfur atoms bending toward the equatorial ones. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:586–589, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20697

Molecular Structure of 1-Germatrahol and its Complex With Chloroform

The crystal structures of anhydrous 1-germatranol and its complex with HCCl3 are centrosymmetrical dimers because of their intermolecular hydrogen bonds. In the germatranol crystal, the axial and equatorial oxygen atoms of its two molecules are hydrogen bonded into an eight-membered coordination cycle. In the complex with HCCl3, the two molecules of germatranol are likewise linked in dimers, and both axial oxygen atoms are H bonded with HCCl3. In the investigated structures, the axial Ge—O bond is shorter than the equatorial ones. Depending on the number and strength of the hydrogen bonds, the interatomic Ge—O and Ge ← N distances change markedly. The quantitative estimates of the H bond energy are obtained from quantum chemical calculations of the model systems containing 1-germatranol and HCCl3 molecules.

Quantum-chemical study of chlorophosphoranes: II. Structure of molecules of (Cl2) a P(Cl n X3−n ) e series, and mutual influence of axial and equatorial substituents

The quantum-chemical calculations by the methods RHF/6-31G(d) and MP2/6-31G(d) of chlorophosphoranes of a series (Cl2)aP(ClnX3−n)e with complete and partial optimization of their geometry were performed. The results of calculations were used for evaluation of the frequencies of 35Cl NQR and the asymmetry parameters of the electric field gradient on the 35Cl nuclei of these molecules. According to the results of calculations with the partial geometry optimization and the experimental data on 35Cl NQR the bond lengths of central atom P in the solid state of the corresponding compounds were used. A substantial change in the NQR frequencies of the axial chlorine atoms and a weak change in the frequencies of the equatorial ones at a change in the number of the latter was explained.