The organic geochemistry of crude oil in the Saltpond Basin(Ghana):Organic source input,depositional environment,and thermal maturity

The Saltpond Basin,situated within the South Atlantic margin of Ghana,is a significant area for petro-leum exploration but has received relatively limited research attention.Previous studies have examined source rock com-position,but data on crude oil organic chemistry are lack-ing,hindering understanding of the basin’s petroleum system and evolution.To address this gap,we analyzed biomarkers and stable carbon-isotope ratios in Saltpond Basin crude oil using gas chromatography–mass spectrometry and gas chromatography–isotope ratio mass spectrometry to eluci-date organic matter source,depositional environment,and thermal maturity.Findings were compared with oils from the West African segment of the South Atlantic margin,namely the Tano Basin and the Niger Delta Basin,to iden-tify potential correlations and gain insights into regional variations.Molecular and isotopic results unveiled a sig-nificant prevalence of organic matter derived from lower marine organisms.Patterns of organic matter deposition and preservation in Saltpond oil samples suggested a suboxic marine transitional environment,contradicting conventional understanding of terrestrial dominance in such settings.Moreover,the potential for degradation processes to obscure differentiation between terrestrial and marine organic mat-ter origins underscores the complex nature of organic mat-ter dynamics in transitional marine environments.Analysis of molecular thermal maturity indices suggested Saltpond oils were expelled from source rocks exhibiting thermal maturity at the early maturity stage.Correlation analysis unveiled genetic disparities among crude oils sourced from the Saltpond Basin and those from the Tano and Niger Delta Basin,primarily due to variations in source input and depo-sitional environment conditions.Saltpond oil exhibits lower terrestrial organic input than Tano Basin’s crude oils,which also have less terrestrial input than Niger Delta Basin crude oils.Additionally,its paleodepositional environment nota-bly differs from oils in the Tano Basin(anoxic transitional marine-lacustrine settings)and the Niger Delta Basin(sub-oxic–oxic terrigenous deltaic or marine or lacustrine envi-ronments).Thermal maturity range of Saltpond oil is com-parable to oils in the Tano Basin but lower than oils in the Niger Delta Basin.Thesefindings provide valuable insights into petroleum generation history and unique organic geo-chemical characteristics within the Saltpond Basin,essen-tial for exploration,production,and environmental manage-ment efforts in the region.Furthermore,correlation studies provide evidence that distinct biological,geological,and paleoenvironmental conditions shaped various oil types in the West African segment of the South Atlantic margin.

CAUCHY TYPE INTEGRALS AND A BOUNDARY VALUE PROBLEM IN A COMPLEX CLIFFORD ANALYSIS

Clifford analysis is an important branch of modern analysis;it has a very important theoretical significance and application value,and its conclusions can be applied to the Maxwell equation,Yang-Mill field theory,quantum mechanics and value problems.In this paper,we first give the definition of a quasi-Cauchy type integral in complex Clifford analysis,and get the Plemelj formula for it.Second,we discuss the H?lder continuity for the Cauchy-type integral operators with values in a complex Clifford algebra.Finally,we prove the existence of solutions for a class of linear boundary value problems and give the integral representation for the solution.

Detecting the core of a network by the centralities of the nodes

Many networks exhibit the core/periphery structure.Core/periphery structure is a type of meso-scale structure that consists of densely connected core nodes and sparsely connected peripheral nodes.Core nodes tend to be well-connected,both among themselves and to peripheral nodes,which tend not to be well-connected to other nodes.In this brief report,we propose a new method to detect the core of a network by the centrality of each node.It is discovered that such nodes with non-negative centralities often consist in the core of the networks.The simulation is carried out on different real networks.The results are checked by the objective function.The checked results may show the effectiveness of the simulation results by the centralities of the nodes on the real networks.Furthermore,we discuss the characters of networks with the single core/periphery structure and point out the scope of the application of our method at the end of this paper.

Study on the effective elastic performance of composites containing decagonal symmetric two-dimensional quasicrystal coatings

On account of the Mori-Tanaka approach,the effective elastic performance of composites containing decagonal symmetric two-dimensional(2D)quasicrystal(QC)coatings is studied.Explicit expressions for the effective elastic constants of rare-earth QC reinforced magnesium-based composites are provided.Detailed discussion is presented on the effects of the volume fraction of the inclusions,the aspect ratio of the inclusions,the coating thickness,and the coating material parameters on the effective elastic constants of the composites.The results indicate that considering the coating increases the effective elastic constants of the composites to some extent.

Analysis of optical axis deviation caused by structural stiffness in equatorial telescopes

The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of a telescope on advanced control technologies,thereby improving its economic feasibility.Although full-system finite element analyses are reliable,they are encumbered by significant time requirements and limitations in covering all possible telescope orientations.Therefore,we propose an efficient and comprehensive analytical method to evaluate the optical axis deviation of equatorial telescopes across a full range of angles.To address the challenge of ensuring that the analysis covers all possible positions of an equatorial telescope,based on a model from SiTian project,we analyze the optical axis deviations caused by the fork arm at 25 different angles and then use fitting methods to obtain results for all angles.Based on the analysis results of the optical axis deviation caused by the stiffness of the optical tube in the horizontal position,we derive the results for the tube at any position using geometric relationships.Finally,we calculate the coupling factors and combine these impacts.Furthermore,we identify six discrete feature points to reflect possible telescope orientations and conduct comprehensive finite element analyses.The results are in alignment with those acquired through a comprehensive computational approach.

Study on the X-Ray Re-brightening Signature of GRB 220117A

The Swift/XRT detected the X-ray afterglow of long burst GRB 220117A,which began to rebrighten 300 s after triggering and followed a single power-law decay segment after thousands of seconds of the orbital observation gap.This segment is different from the shallow decay segment(plateau)and flare,and may belong to a giant X-ray bump.We investigated this segment by the fall-back accretion model and found that the model can interpret this segment with reasonable parameter values.Within this physical model scenario,the fall-back accretion rate reaches a peak value~1.70×10~(-5)M_⊙s~(-1)around 300 s in the central engine frame,which is compatible with the late mass supply rate of some low-metallicity massive progenitor stars.The initial black hole(BH)spin is a_0=0.64_(-0.26)~(+0.24)and implies that this re-brightening signature requires a larger BH spin.The total accretion mass during the fall-back process is M_(acc)=(3.09±0.02)×10~(-2)M_⊙.The jet energy from the fall-back accretion is(9.77±0.65)×10~(52)erg,with a ratio of 0.066 to the isotropic-equivalent radiation energies of the GRB prompt phase in the 1-10~4 keV band.The fall-back radius r_p corresponding to the peak time of fall-back t_p is(3.16±0.05)×10~(10)cm,which is consistent with the typical radius of Wolf-Rayet stars.In summary,our results provide additional support for the origin of the long burst from the core collapse of Wolf-Rayet stars,and its late central engine activity is likely due to the fall-back accretion process.

Bifurcations for counterintuitive post-inhibitory rebound spike related to absence epilepsy and Parkinson disease

Seizures are caused by increased neuronal firing activity resulting from reduced inhibitory effect and enhancement of inhibitory modulation to suppress this activity is used as a therapeutic tool.However,recent experiments have shown a counterintuitive phenomenon that inhibitory modulation does not suppress but elicit post-inhibitory rebound(PIR)spike along with seizure to challenge the therapeutic tool.The nonlinear mechanism to avoid the PIR spike can present theoretical guidance to seizure treatment.This paper focuses on identifying credible bifurcations that underlie PIR spike by modulating multiple parameters in multiple theoretical models.The study identifies a codimension-2 bifurcation called saddle-node homoclinic orbit(SNHOB),which is an intersection between saddle node bifurcation on invariant cycle(SNIC)and other two bifurcations.PIR spike cannot be evoked for the SNIC far from the SNHOBbut induced for the SNIC close to the SNHOB,which extends the bifurcation condition for PIR spike from the well-known Hopf to SNIC.Especially,in a thalamic neuron model,increases of conductance of T-type Ca^(2+)(TC a)channel induce SNIC bifurcation approaching to the SNHOB to elicit PIR spikes,closely matching experimental results of the absence seizure or Parkinson diseases.Such results imply that,when inhibition is employed to relieve absence seizure and Parkinson diseases related to PIR spike,modulating SNIC to get far from the SNHOBto avoid PIR spike is the principle.The study also addresses the complex roles of TCacurrent and comprehensive relationships between PIR spike and nonlinear conceptions such as bifurcation types and shapes of threshold curve.

Metamaterial terahertz device with temperature regulation function that can achieve perfect absorption and complete reflection conversion of ultrawideband

The field of terahertz devices is important in terahertz technology.However,most of the current devices have limited functionality and poor performance.To improve device performance and achieve multifunctionality,we designed a terahertz device based on a combination of VO_(2)and metamaterials.This device can be tuned using the phase-transition characteristics of VO_(2),which is included in the triple-layer structure of the device,along with SiO_(2)and Au.The terahertz device exhibits various advantageous features,including broadband coverage,high absorption capability,dynamic tunability,simple structural design,polarization insensitivity,and incidentangle insensitivity.The simulation results showed that by controlling the temperature,the terahertz device achieved a thermal modulation range of spectral absorption from 0 to 0.99.At 313 K,the device exhibited complete reflection of terahertz waves.As the temperature increased,the absorption rate also increased.When the temperature reached 353 K,the device absorption rate exceeded 97.7%in the range of 5-8.55 THz.This study used the effective medium theory to elucidate the correlation between conductivity and temperature during the phase transition of VO_(2).Simultaneously,the variation in device performance was further elucidated by analyzing and depicting the intensity distribution of the electric field on the device surface at different temperatures.Furthermore,the impact of various structural parameters on device performance was examined,offering valuable insights and suggestions for selecting suitable parameter values in real-world applications.These characteristics render the device highly promising for applications in stealth technology,energy harvesting,modulation,and other related fields,thus showcasing its significant potential.

Simulation study of multi-layer titanium nitride nanodisk broadband solar absorber and thermal emitter

Solar energy has always been a kind of energy with large reserves and wide application.It is well utilized through solar absorbers.In our study,the finite difference time domain method(FDTD)is used to simulate the absorber composed of refractory metal materials,and its absorption performance and thermal emission performance are obtained.The ultra-wide band of 200 nm-3000 nm reaches 95.93%absorption efficiency,of which the bandwidth absorption efficiency of2533 nm(200 nm-2733 nm)is greater than 90%.The absorption efficiency in the whole spectrum range(200 nm-2733 nm)is 97.17%on average.The multilayer nanodisk structure of the absorber allows it to undergo strong surface plasmon resonance and near-field coupling when irradiated by incident light.The thermal emission performance of the absorber enables it to also be applied to the thermal emitter.The thermal emission efficiency of 95.37%can be achieved at a high temperature of up to 1500 K.Moreover,the changes of polarization and incident angle do not cause significant changes in absorption.Under the gradual change of polarization angle(0°-90°),the absorption spectrum maintains a high degree of consistency.As the incident angle increases from 0°to 60°,there is still 85%absorption efficiency.The high absorption efficiency and excellent thermal radiation intensity of ultra-wideband enable it to be deeply used in energy absorption and conversion applications.

Probing the structure of multi-center molecules with odd–even high harmonics

We study high-order harmonic generation(HHG)from multi-center asymmetric linear molecules numerically and analytically.Our simulations show that odd and even HHG spectra of the asymmetric multi-center system respond differently to the change of the molecular structure.Specifically,when the internuclear distances between these nuclei of the molecule have a small change,the odd spectra usually do not change basically,but the even spectra differ remarkably.Based on this phenomenon,a simple procedure is proposed to probe the positions of these nuclei with odd–even HHG.Our results shed light on attosecond probing of the structure of multi-center molecules using HHG.

SIR Model of Spread of Zika Virus Infections: ZIKV Linked to Microcephaly Simulations

An SIR model of Zika virus (ZIKV) spread is formulated that includes ZIKV infections to newborns. Analytically, the model has one disease free and one endemic equilibrium point. The free one is stable for some conditions when R0 and unstable when R0>1. In Brazil, when R0≈2>1 ZIKV infections expand and for R0 = 0.875R0) of the model. There are parameters for human-mosquito transmission and some for sexual-transmission factor. It appears that controlling spread of ZIKV infections by human-mosquito transmission may greatly reduce the value of R0.

The{P,k+1}-reflexive Solution to System of Matrix Equations AX=C,XB=D

Let P∈C^(n×n)be a Hermitian and{k+1}-potent matrix,i.e.,P^(k+1)=P=P^(*),where(·)^(*)stands for the conjugate transpose of a matrix.A matrix X∈C^(n×n)is called{P,k+1}-reflexive(anti-reflexive)if PXP=X(P XP=-X).The system of matrix equations AX=C,XB=D subject to{P,k+1}-reflexive and anti-reflexive constraints are studied by converting into two simpler cases:k=1 and k=2,the least squares solution and the associated optimal approximation problem are also considered.

The Global and Pullback Attractors for a Strongly Damped Wave Equation with Delays

In this paper, we study the global and pullback attractors for a strongly damped wave equation with delays when the force term belongs to different space. The results following from the solution generate a compact set.

Weak Type Weighted Inequalities for the Commutators of the Multilinear Calderón-Zygmund Operators

For the commutators of multilinear Calder ′on-Zygmund singular integral operators with B MO functions, the weak type weighted norm inequalities with respect to A^P weights are obtained.

Detection of the quantum states containing at most k−1 unentangled particles

There are many different classifications of entanglement for multipartite quantum systems,one of which is based on the number of the unentangled particles.In this paper,we mainly study the quantum states containing at most k−1 unentangled particles and provide several entanglement criteria based on the different forms of inequalities,which can both identify quantum states containing at most k−1 unentangled particles.We show that these criteria are more effective for some states by concrete examples.

Reanalysis of the Isotopic Mixture of Neutron-Capture Elements in the Metal-Poor Star HD 175305

The neutron-capture process is traditionally postulated to be responsible for the nucleosynthesis of heavy elements beyond Fe.Based on theleast squares method and solar isotopic abundances from the classical model,we estimate the relative contributions of the s- and r-processes to the abundance of neutron-capture elements in the metalpoor star HD 175305 from the component coefficients.Applying the calculated component coefficients C_(r) and C_(s),the model predicts the isotopic fractions of elements Nd,Sm and Eu to be f_(142+144) =0.482,f_(152+154) =0.525 and f_(l51) =0.450,respectively.As well as the observed abundances,the isotropic fractions are also consistent with the calculations.Finally,for the first time,we estimated the contribution percentage of the two neutron processes (the r- and s-processes) from the observed isotopic fractions of different elements in HD 175305,e.g.an r-process contribution of 67%^(+21%)_(-32%) from the 4604 (A) line of Sm.

The Group of Automorphisms of Transitive 2-(v, 23, 1) Designs

This paper is a contribution to the study of the automorphism groups of 2 - （v, k, 1） designs. Let D be a 2 - （v, 23, 1） design and G a block-transitive and point-primitive group of automorphism of D. Then the socle of G is not Sz（q） and 2G2（q）.

EPr Solution to a System of Matrix Equations

A square complex matrix is called if it can be written in the form with being fixed unitary and being arbitrary matrix in . We give necessary and sufficient conditions for the existence of the solution to the system of complex matrix equation and present an expression of the solution to the system when the solvability conditions are satisfied. In addition, the solution to an optimal approximation problem is obtained. Furthermore, the least square solution with least norm to this system mentioned above is considered. The representation of such solution is also derived.

On Least Squares Solutions of Matrix Equation MZN=S

Let be a given Hermitian matrix satisfying . Using the eigenvalue decomposition of , we consider the least squares solutions to the matrix equation , with the constraint .

Turing pattern selection for a plant-wrack model with cross-diffusion

We investigate the Turing instability and pattern formation mechanism of a plant-wrack model with both self-diffusion and cross-diffusion terms.We first study the effect of self-diffusion on the stability of equilibrium.We then derive the conditions for the occurrence of the Turing patterns induced by cross-diffusion based on self-diffusion stability.Next,we analyze the pattern selection by using the amplitude equation and obtain the exact parameter ranges of different types of patterns,including stripe patterns,hexagonal patterns and mixed states.Finally,numerical simulations confirm the theoretical results.