Extraction of Uranium(VI) by N-Octanoylpiperidine in Toluene

The extraction of uranium(VI) from nitric acid by N-octanoylpiperidine (OPPD) in toluene has been investigated at varying concentrations of nitric acid, extractant, salting-out agent LiNO₃ and at different temperatures. The mechanism of extraction is discussed in the light of the results obtained. The extracted species have also been investigated using FT-IR spectrometry. The related thermodynamic functions were calculated.     

X-射线荧光光谱测定氧化铍中杂质元素

拟定了ＢｅＯ中１２种痕量杂质元素的Ｘ－射线荧光光谱测定方法,采用光谱纯试剂人工合成校准标样,粉末压块法制备分析样片。考虑到ＢｅＯ对Ｘ射线的透明性,在样片与样品盒支架之间垫置钼片消除试样盒发射线的干扰并产生附加激发以提高灵敏度。本文分析结果与等离子民发射和原子吸收光谱对照相吻合。     

One Novel Three-dimensional Network Constructed from [Mn(4,4′-bip)<Subscript>2</Subscript>(OH<Subscript>2</Subscript>)<Subscript>4</Subscript>]<Superscript>2+</Superscript> Cations and DBA<Superscript>2−</Superscript> Anions via Hydrogen-bonding and π–π Interactions

Abstract One new mononuclear manganese complex of [Mn(4,4′-bip)₂(OH₂)₄](DBA) · 4H₂O (1) (4,4′-bipyridine, 4,4′-bip; H₂DBA, benzene-1,3-dicarboxylic acid) has been obtained from the hydrothermal reaction of MnCl₂ · 4H₂O, 4,4′-bipyridine and H₂DBA in the solvent of H₂O at 140 °C for 3 days, characterized by X-ray analysis, spectroscopic methods, and thermal analysis. Packing diagram shows that the three-dimensional network was formed via hydrogen bonds and strong π–π interactions. Graphical abstract One Novel Three-dimensional Network Constructed from [Mn(4,4′-bip) ₂ (OH ₂ ) ₄ ] ²⁺ Cations and DBA ²⁻ Anions via Hydrogen-bonding and π–π Interactions Ying Liu, Bao Zhang, Jian-min Dou, Da-qi Wang, Da-cheng Li, Lei Zhou One new mononuclear manganese complex of [Mn(4,4’-bip)₂(OH₂)₄](DBA) · 4H₂O (1) (4,4’-bipyridine, 4,4’-bip; H₂DBA, benzene-1, 3-dicarboxylic acid) has been obtained and haracterized by X-ray analysis, spectroscopic methods, and thermal analysis. Packing diagram shows that the three-dimensional network was formed via hydrogen bonds and strong π-π interactions.      

Study on Stiffness of the Symmetry Energy at High Densities by π－/π+ Ratio

using the isospin–and momentum–dependent transport model, for three different symmetry energies, we have calculated the π^–/π⁺ ratio as a function of time and tranverse–momentum in central 132sn+124 sn collision at e_beam/A=400mev. the results show that the π^–/π⁺ ratios is very sensitive to the stiffness of the symmetry energy. thus we can probe the stiffness of the symmetry energy at high densities by using the π–/π+ ratio at different time or transverse momentum more accurately than before. comparing experimental data with the calculations will reveal crucial information about the stiffness of the symmetry energy more accurately.hadronic transport model, symmetry energy, π–/π+ ratio     

原位漫反射红外光谱中采用新的实验手段研究煤岩显微组分中的氢键

首次提出采用小瓷片反应器,结合增大载气流量的方法进行产生挥发组分固体的原位漫反射红外光谱实验,研究了两种煤的镜质组和丝质组中的氢键分布及热稳定性.两种显微组分间氢键分布的规律相似;镜质组中SH-N、羧酸二聚体和自缔合羟基等的热稳定性比丝质组中的高.但对OH-N、羟基四聚体和OH-OR₂的热稳定性随煤岩组分的变化无明显规律;随着温度的升高,OH-π含量先升高后降低,于350～380℃达最大值,其中镜质组OH-π的含量增加较快.显微组分中氢键的变化规律反映了其结构上的差异.     

Electronic structure of Yb/H－Si (111) interface

Photoemission spectra are measured for Yb covered surface of wet-chemically-etched H－Si (111). The results reveal that the lattice structure of the H－Si (111) surface is stable against the deposition of Yb atoms. X-ray photoemission spectra indicate the formation of a polarized (dipole) surface layer, with the silicon negatively charged. Ultraviolet photoemission spectra exhibit the semiconducting property of the interface below one monolayer coverage. Work function variation during the formation of the Yb/H－Si (111) interface is measured by the secondary-electron cutoff in the ultraviolet photoemission spectral line. The largest decrease of work function is ～1.65eV. The contributions of the dipole surface layer and the band bending to the work function change are determined to be ～1.15eV and ～0.5eV, respectively. The work function of metal Yb is determined to be ～2.80±0.05eV.     

A design of novel type superconducting magnet for super—high field functional magnetic resonance imaging by using the harmonic analysis method of magnetic vector potentials

The approach of expanding the magnetic scalar potential in a series of Legendre polynomials is suitable for designing a conventional superconducting magnetic resonance imaging magnet of distributed solenoidal configuration. Whereas the approach of expanding the magnetic vector potential in associated Legendre harmonics is suitable for designing a single-solenoid magnet that has multiple tiers, in which each tier may have multiple layers with different winding lengths. A set of three equations to suppress some of the lowest higher-order harmonics is found. As an example, a 4T single-solenoid magnetic resonance imaging magnet with 4×6 layers of superconducting wires is designed. The degree of homogeneity in the 0.5m diameter sphere volume is better than 5.8 ppm. The same degree of homogeneity is retained after optimal integralization of turns in each correction layer. The ratio B_m/B₀ in the single-solenoid magnet is 30% lower than that in the conventional six-solenoid magnet. This tolerates higher rated superconducting current in the coil. The Lorentz force of the coil in the single-solenoid system is also much lower than in the six-solenoid system. This novel type of magnet possesses significant advantage over conventional magnets, especially when used as a super-high field functional magnetic resonance imaging magnet.     

A polynomial approximation for the scattering wavefunction of an arbitrary spherically symmetric potential

A new variational approach is proposed to calculate scattering phase shifts.In this approach,the variational parameter is contained not explicitly in the trial function but in the boundary conditions that the scattering wavefunction should satisfy.It was found that a high accuracy could be reached.Furthermore,the scattering wavefunction appears as a polynomial of finite orders in the interior region.This expression is convenient for applications.     

Positive Solutions of Fully Nonlinear Elliptic Equations on General Bounded Domains

We prove the refined ABP maximum principle, comparison principle, and related existence and uniqueness theorem for the positive solutions of the Dirichlet problems of second order fully nonlinear elliptic equations on arbitrary bounded domains.     

Interpolation in the unit ball ofC n

A necessary and sufficient condition is given for a discrete multiplicity variety in the unit ballB _n ofC ⁿ to be an interpolating variety for weighted spaces of holomorphic functions inB _n . Partially supported by NSF Grant DMS-9706376.