Novel method for simultaneous measurement of film thickness and mass fraction of urea–water solution

Quantitative knowledge of the film thickness and mass fraction of the urea-water solution is very crucial in many practical applications. Film thickness or mass fraction can only be determined individually by conventional measurement techniques. We develop a novel measurement method to measure the film thickness and mass fraction of ure~water solution simultaneously. The absorption coefficients of urea-water solution （5 50 wt%） are measured, a pair of optimized wavelengths is then chosen to achieve high measurement sensitivity. Cross validation is also performed and uncertainties of the technique are smaller than 0.68% for thickness measurements and 1.86% for mass fractions.     

Synthesis of Enantioenriched Vicinal Tertiary and Quaternary Carbon Stereogenic Centers within an Acyclic Chain

Overcoming the inherent difficulty to prepare quaternary carbon stereogenic centers, the diastereo‐ and enantioselective preparation of acyclic carbon backbones possessing vicinal quaternary and tertiary stereogenic centers (i.e. in a 1,2‐relationship) causes distorted geometries and represents a very acute problem in organic synthesis. Several approaches are discussed in this minireview underlining the challenges illustrated by the rather limited number of approaches available to practitioners.     

Fourier transform spectroscopy of N2O weak overtone transitions in the 1-2 μm region

The absorption spectrum of the natural sample of nitrous oxide has been recorded at Doppler limited resolution with a Fourier-transform spectrometer in the spectral range 5000-10 000 cm⁻¹. Ten cold bands (8Σ − Σ and 2Σ − Π), thirteen hot bands (11Π − Π, Σ − Σ, and Δ − Δ) of ¹⁴N₂¹⁶O and the 3ν₃ band of ¹⁴N¹⁵N¹⁶O have been newly detected. The uncertainty of the line position determination is estimated to be about 0.005 cm⁻¹ for unblended lines. The assignment of the spectrum has been done with the help of the prediction performed within the framework of the polyad model of effective Hamiltonian. The spectroscopic parameters G_v, B_v, D_v, H_v, and q_v have been determined for all newly detected bands. The line intensities of 13 weak bands have been measured. The uncertainty of the obtained line intensity values varies from 7 to 13%.     

Preliminary analysis of CH3D from 3250 to 3700 cm

The infrared spectrum of CH₃D from 3250 to 3700 cm⁻¹ was studied for the first time to assign transitions involving the ν₂ + ν₃, ν₂ + ν₅, ν₂ + ν₆, ν₃ + 2ν₆ and 3ν₆ vibrational states. Line positions and intensities were measured at 0.011 cm⁻¹ resolution using Fourier transform spectra recorded at Kitt Peak with isotopically enriched samples. Some 2852 line positions (involving over 900 upper state levels) and 874 line intensities were reproduced with RMS values of 0.0009 cm⁻¹ and 4.6%, respectively. The strongest bands were found to be ν₂ + ν₃ at 3499.7 cm⁻¹ and ν₂ + ν₆ at 3342.5 cm⁻¹ with integrated strengths, respectively, of 8.17 × 10⁻²⁰ and 2.44 × 10⁻²⁰ (cm⁻¹/molecule · cm⁻²) at 296 K (for 100% CH₃D). The effective Hamiltonian was expressed in terms of irreducible tensor operators and adapted to symmetric top molecules. Its present configuration in the MIRS package permitted simultaneous consideration of the four lowest polyads of CH₃D: the Ground State (G.S.), the Triad from 6.3 to 9.5 μm, the Nonad from 3.1 to 4.8 μm and now the Enneadecad (19 bands) from 2.2 to 3.1 μm. The CH₃D line parameters for this interval were calculated to create a new database for the 3 μm region.     

小波分形分析重叠峰信号

用连续小波变换与分形理论相结合的小波分形峰位法对含噪重叠信号峰位置的提取进行了研究, 同时考察了信噪比和分离度对该法提取峰位置的影响; 结果表明 该法是一种提取含噪重叠信号中各单独峰峰位置的有效工具, 即使对于重叠程度和噪声干扰严重的信号也能得到较好的结果; 将其用于 Cd(Ⅱ )和 In(Ⅲ )重叠伏安信号的处理, 峰位置提取的相对误差小于± 1%; 该法具有准确、快捷、简便易行等特点, 发展前景广阔.     

Study of excited nucleon states at EBAC: status and plans

We present an overview of a research program for the excited nucleon states in Excited Baryon Analysis Center (EBAC) at Jefferson Lab. Current status of our analysis of the meson production reactions based on the unitary dynamical coupled-channels model is summarized, and the N~* pole positions extracted from the constructed scattering amplitudes are presented. Our plans for future developments are also discussed.     

Wide dynamic detection range of methane gas based on enhanced cavity absorption spectroscopy

Integrated cavity output spectroscopy (ICOS) is an effective technique in trace gase detection. The strong absorption due to the long optical path of this method makes it challenging in the application scenes that have large gas concentration fluctuation, especially when the gas concentration is high. In this paper, we demonstrate an extension of the dynamic range of ICOS by using a detuned laser combined with an off-axis integrating cavity. With this, we improve the upper limit of the dynamic detection range from 0.1% (1000 ppm) to 20% of the gas concentration. This method provides a way of using ICOS in the applications with unpredictable gas concentrations such as gas leak detection, ocean acidification, carbon sequestration, etc.     

Gas chromatographic retention of 180 polybrominated diphenyl ethers and prediction of relative retention under various operational conditions

The gas chromatographic (GC) retention times of 180 polybrominated diphenyl ethers (PBDEs) were obtained under different operational conditions on two types of commonly used capillary columns, Restek Rtx-1614 and J&W DB-5MS, of different dimensions. The relative retention times (RRTs) for PBDEs were calculated by normalizing the retention times of individual congeners to the sum of those of BDEs 47 and 183. In clear contrast to polychlorinated biphenyls (PCBs), the elution of PBDEs has few cross-homolog overlaps, and this observation is discussed in terms of molecular conformation with regard to co-planarity. Within a homolog, ortho substitution in PBDEs tends to decrease GC retention, and such an effect is stronger for higher homologs. With the RRT database established in this work, a simple approach is evaluated for the identification of all mono to hepta PBDEs from the RRTs of 39 congeners under various GC conditions to facilitate the identification of unknown PBDE peaks for which chemical standards are not available.     

Zur Kenntnis von Strontiumhydroxidchlorid und Strontiumhydroxidbromid – Darstellung,Kristallstrukturen, IR- und Raman-Spektren

Strontium Hydroxide Chloride and Strontium Hydroxide Bromide – Preparation, Crystal Structure, and IR and Raman Spectra The partly hitherto unknown compounds Sr(OH)Cl, Sr(OH)Br mC16 and Sr(OH)Br cP16 have been established by both dehydration of the hydrates (Sr(OH)Cl, Sr(OH)Br mC16) and melting together stoichiometric mixtures of Sr(OH)₂ and SrCl₂ or SrBr₂ (Sr(OH)Cl, Sr(OH)Br cP16). The monoclinic polymorph of the bromide is monotropically changed above 650 K (high-temperature X-ray and high-temperature Raman studies) into the cubic modification. Sr(OH)Cl crystallizes in the Cd(OH)Cl structure type (space group P6₃mc, Z = 2, a = 414.41(2), c = 995.16(10) pm), Sr(OH)Br mC16 and cP16 crystallizing in own structures (C2/m, Z = 4, a = 1100.66(7), b = 429.55(3), c = 726.25(5) pm, β = 106.285(4)°, P2₁3, Z = 4, a = 675.79(2) pm). The structures were refined from X-ray powder diffractograms (Sr(OH)Cl: R_I = 11.4%, 4668 observations, Sr(OH)Br mon.: R_I = 13%, 1082 observations), neutron powder diffractograms (Sr(OD)Br cub.: R_I = 3,8%, 793 observations), and X-ray single-crystal studies, respectively (Sr(OH)Br cub.: R1 = 5.02%, 585 independent reflections). The positions of the hydrogen atoms of Sr(OH)Cl and Sr(OH)Br mon. were determined by the method of minimum cohesive energy. Sr(OH)Cl and Sr(OH)Br mon. crystallize in layered structures with monocapped distorted octahedrally (3 OH^– and 4 X^–) coordinated strontium ions. Sr(OH)Br cub. crystallizes in a structure built up of three-dimensional nets, the coordination of Sr, however, corresponds to that of Sr(OH)Cl and Sr(OH)Br mon. IR and Raman spectra are presented and discussed together with the structure data with respect to the strength of the O–H…X hydrogen bonds (stretching modes of matrix isolated OD^– ions: 2641 cm^–1 (Sr(OH)Cl), 2662 cm^–1 (Sr(OH)Br mon.), and 2614 cm^–1 and 2572 cm^–1 (Sr(OH)Br cub.) (295 K)) and the dependence of the librations of the OH^– ions on the strength of the hydrogen bonds and the packing of the structure. The OH^– ions of Sr(OH)Br cub. display a temperature dependent disorder between a thermodynamically more stable position with trifurcated hydrogen bonds and one with stronger, almost linear bonds.