部分相干平顶光束在非Kolmogorov湍流中的湍流距离

给出了部分相干平顶光束通过非Kolmogorov湍流传输的湍流距离解析表达式,并研究了非Kolmogorov湍流的湍流广义指数、内尺度、外尺度和光束参数对部分相干平顶光束湍流距离的影响。研究表明:湍流距离随相干参数、束腰、外尺度(当湍流广义指数的取值为3.6~4.0时)的增大而减小;随光束阶数、内尺度的增大而增大;随湍流广义指数先减小后增大,且在湍流广义指数取3.11时存在极小值,即光束扩展的极大值。同时利用湍流广义指数及光束参数,具体比较了湍流距离与瑞利区间的大小,并指出光束参数及湍流广义指数决定了湍流是否在瑞利区间内就能对光束扩展构成明显的影响。     

Enantioseparation of Phenylsuccinic Acid Enantiomers Using Aqueous Two-Phase Flotation and Their Determination by HPLC and UV Detection

Aqueous two-phase flotation (ATPF) is especially applicable to bioseparation. However, there is no previous work reporting on its application in enantioseparation. Using phenylsuccinic acid (H₂A) as the model enantiomers, ATPF was first introduced into the field of chiral separation. The contributions of a series of ATPF systems to the enantioseparation were investigated. The results indicated that an appropriate increase in the amount of phase-forming components and a decrease in pH values (from 5.5 to 2) are both beneficial for the enantioseparation. Enantioselective flotation and partitioning behavior are mainly dependent on pH values of the solutions, types, and concentrations of chiral selectors. Furthermore, salt, PEG, flow rates of air, and flotation time also have some effects on the enantioseparation. Under the optimal conditions, the enantioselectivity was calculated in terms of the separation factor (α) and enantiomer excess (e.e. %) as 1.99 and 23.49 %, respectively. Finally, the most reasonable mechanisms for H₂A enantioseparation in ATPF system have been proposed. An ATPF system composed of PEG2000/(NH₄)₂SO₄ was proved to have the best ability for the separation of H₂A enantiomers. The explorations in our study will further enrich the enantioseparation methods and pave the way for the application of ATPF in the enantioseparation field.     

Determination of phenolic compounds in water samples by HPLC following ionic liquid dispersive liquid-liquid microextraction and cold-induced aggregation

We report on the determination of bisphenol A and 2-naphthol in water samples using ionic liquid cold-induced aggregation dispersive liquid-liquid microextraction combined with HPLC. Parameters governing the extraction efficiency (disperser solvent, volume of extraction and disperser solvent, pH, temperature, extraction time) were optimized and resulted in enrichment factors of 112 for bisphenol A and of 186 for 2-naphthol. The calibration curve was linear with correlation coefficients of 0.9995 and 0.9998, respectively, in the concentration range from 1.5 to 200?ng?mL^?1. The relative standard deviations are 2.3% and 4.1% (for n?=?5), the limits of detection are 0.58 and 0.86?ng?mL^?1, and relative recoveries in tap, lake and river water samples range between 100.1 and 108.1%, 99.4 and 106.2%, and 97.1 and 103.8%, respectively.

Amine-assisted synthesis of concave polyhedral platinum nanocrystals having {411} high-index facets

High-index surfaces of a face-centered cubic metal (e.g., Pd, Pt) have a high density of low-coordinated surface atoms and therefore possess enhanced catalysis activity in comparison with low-index faces. However, because of their high surface energy, the challenge of chemically preparing metal nanocrystals having high-index facets remains. We demonstrate in this work that introducing amines as the surface controller allows concave Pt nanocrystals having {411} high-index facets to be prepared through a facile wet-chemical route. The as-prepared Pt nanocrystals display a unique octapod morphology with {411} facets. The presence of high-index {411} exposed facets endows the concave Pt nanocrystals with excellent electrocatalytic activity in the oxidation of both formic acid and ethanol.     

Elusive O═P≡N, a rare example of phosphorus σ2λ5-coordination

Two linear isomers, OPN and ONP, were formed in an Ar matrix at 16 K by ArF laser (λ = 193 nm) photolysis of phosphoryl triazide, OP(N(3))(3), and comprehensively characterized by their mid- and far-IR spectra as well as (14/15)N isotopic data. Two intermediates, (N(3))(2)P(O)N and N(3)P(O)N(4), have been isolated in an Ar matrix and spectroscopically characterized. Photolysis of these intermediates using near-UV/vis light (λ > 320 nm) was shown to yield exclusively ONP, which under ArF laser irradiation selectively photo-isomerized to OPN. The photochemical and molecular properties of OPN and ONP are discussed on the basis of experimental and ab initio calculated results.     

Synthesis and Structure Investigation of a Novel 3-Dimensional Potassium Supermolecular Compound Based on 2,4-Dinitro Resorcinol

A novel 3‐dimensional potassium supermolecular compound [K(HDNR)(H₂DNR)(H₂O)]_n (H₂DNR?2,4‐dinitro resorcinol) was synthesized and characterized by elemental analysis and FT‐IR spectroscopy. The crystal structure investigated by X‐ray single crystal diffraction shows that [K(HDNR)(H₂DNR)(H₂O)]_n crystallizes with a monoclinic unit cell in the space group P2(1)/c with unit cell dimensions of a=17.648(5) Å, b=12.527(3) Å, c=7.735(2) Å, β=94.33(2)°, V=1705.00(73) ų, Z=4. The structure was refined to the final R=0.0670 and wR=0.0722 for 2022 observed reflections with I>2σ(I). In the compound, potassium cation is assembled into one‐dimensional chains along c‐axis through oxygen atoms from water molecules, and the chains were connected by the bridged HDNR^? anions to form a two‐dimensional net structure. The two‐dimensional nets constructed a three‐dimensional supramolecular architecture via intermolecular hydrogen bonds and N–O···π interaction. Density functional theory (DFT) B3LYP was employed to optimize the structure and calculate energies for three tautomers of HDNR^? univalent anion. Three stable tautomers were located. It was found that the structure (I) with O(1) losing hydrogen atom is more stable than the structure (II) also with O(1) losing hydrogen atom and the structure (III) with O(4) losing hydrogen atom.     

Synthesis of biphenyl-2-carbonitrile derivatives via a palladium-catalyzed sp2 C-H bond activation using cyano as a directing group

Pd(II)-catalyzed aromatic C-H bond activation using cyano as a directing group was carried out in TFA medium. Biphenyl-2-carbonitrile derivatives were therefore synthesized from aryl nitriles and aryl halides in moderate to good yields.     

A fourth-order derivative-free algorithm for nonlinear equations

A two-step derivative-free iterative algorithm is presented for solving nonlinear equations. Error analysis shows that the algorithm is fourth-order with efficiency index equal to 1.5874. A lot of numerical results show that the algorithm is effective and is preferable to some existing derivative-free methods in terms of computation cost.     

Synthesis and characterization of sulfuryl diazide, O2S(N3)2

Sulfuryl diazide, O(2)S(N(3))(2), previously described as an "exceedingly explosive" compound, has been isolated and characterized by IR (Ar matrix, gas) and Raman (solid) spectroscopy, and its structure has been determined by X-ray crystallography. It has a melting point of -15 °C and can be handled in small quantities in gas, liquid, and solid states. Vibrational spectroscopic studies suggest the presence of only one conformer in both gas and solid states, and the X-ray crystallography revealed an anti conformation of the two azido groups with respect to the NSN plane. Calculations predict the anti (C(2)) conformer to be 6.6 kJ mol(-1) lower in energy than the syn (C(s)) one at the CBS-QB3 level of theory. The related chlorosulfuryl azide, ClSO(2)N(3), has also been prepared and characterized by IR and Raman spectroscopy.