离子选择电极阵列土壤中硝态氮测定

土壤硝态氮反映土壤短期氮素供应水平,实时了解土壤硝态氮的含量为精准农业和农业面源污染防控提供支撑,因此,在线实时检测土壤硝态氮方法突破就显得十分迫切。土壤硝态氮中的硝酸根离子在土壤中的高水溶性和流动性为全固态硝酸根离子选择电极高敏感检测土壤中硝态氮提供了条件,固态硝态氮离子选择电极的离子选择膜反应硝酸根离子在被测溶液中的浓度。采用全固态硝酸根离子选择电极,且与温度电极和pH电极融合组成电极阵列对土壤饱和溶液中的硝态根离子进行检测。设计了高输入阻抗运算放大电路对电极信号进行采集,并通过微处理控制蠕动泵完成土壤硝态氮待测溶液连续流动测量及实时传输结果。实验结果表明,电极响应时间≤15 s,斜率-51.63 mV/decade,线性范围10-5-10-2.2 mol/L,最低检测限10-5.23 mol/L。相对标准差在0.78%-4.47%范围内,加标回收率均在90%-110%以内。与国家标准紫外可见分光光度法测试结果相比,相关系数（R2）为0.9952,为土壤硝态氮在现场检测奠定技术基础。     

Studies on the thermal properties of silicone polymer based thermal protection systems for space applications

Journal of Thermal Analysis and Calorimetry - Thermal decomposition, thermal conductivity, specific heat and flammability of polydimethyl siloxane (PDMS) resin and three PDMS-based systems with...     

Hilbert functions of points on Schubert varieties in orthogonal Grassmannians

Given a point on a Schubert variety in an orthogonal Grassmannian, we compute the multiplicity, more generally the Hilbert function. We first translate the problem from geometry to combinatorics by applying standard monomial theory. The solution of the resulting combinatorial problem forms the bulk of the paper. This approach has been followed earlier to solve the same problem for Grassmannians and symplectic Grassmannians.     

Measurements ofg-factor in94Mo

Then _th,α)-reaction spectroscopical data are reported on⁹⁵Mo,¹²³Te and¹⁴⁵Nd (target nuclei). The⁹⁵Mo(n, α)⁹²Zr and¹²³Te(n, α)¹²⁰Sn reactions showed up two lines each corresponding to the ground state and the 1st excited state with a total cross section of 32 ub and 52 μb respectively. In the case of¹⁴⁵Nd(n, α)¹⁴²Ce, a transition only to the 1st excited state of¹⁴²Ce is present. It is shown that in the case of⁹⁵Mo,¹⁴⁵Nd and probably¹²³Te, most of the cross-section comes respectively from the 2⁺ possibly 4^?, and 0 bound levels whose widths are determined to beΓ ^α=0.5 × 10^?6 eV,Γ ^α=1.6×10^?8 eV andΓ ^α=1.6 × 10^?6 eV. The present results on these three nuclei, when combined with the existing data, are consistent with the calculated statistical model values.     

The polarography of oximes: I. 9,10-Phenanthraquinone monoxime

Polarography of 9,10-phenanthraquinone monoxime has been carried out in buffers (pH 3.50 to 13.40) of constant ionic strength 0.5 M in 40% alcoholic solutions at 35 ± 0.5 °C. The oxime group underwent diffusion-controlled reduction (4e) over the whole pH range studied. The number of electrons involved in the reduction was found coulometrically as well as by incorporating the value of the diffusion coefficient, obtained by using a McBain-Dawson cell, into the Ilkovic equation. Controlled potential electrolyses and uv spectroscopic methods were used to identify the products. Koutecky's method was used to compute the kinetic parameters (αn_aand ?log k_f,h^o) for the reduction of the oxime group and reduction mechanisms are proposed.     

Observations on the nuclear interactions of cosmic ray pions and nucleons at energies ≳ 20 GeV

Detailed features of extremely collimated nuclear interactions induced by cosmic ray particles in carbon and brass (belonging to group I as classified in Part I of this series of papers) are presented. These extremely collimated nuclear interactions seem to be preferentially induced by pions rather than by nucleons; also the relative frequency of these seems to be less when brass is used as target compared to the case with carbon as target. The distribution of multiplicities of secondary particles emitted in the forward direction show certain regularities in the case of interactions induced by charged primaries. Observations on the γ-rays associated with these events give support to the interpretation that in these inelastic collisions pions are produced in pairs in the forward direction with low transverse momentum. It is suggested that such a low energy di-pion system could be the same as found in the so-called ABC effect.     

Measurement of gamow-teller strength for 176Yb --> 176Lu and the efficiency of a solar neutrino detector

We report a 0 degrees 176Yb(p,n)176Lu measurement at IUCF where we used 120 and 160 MeV protons and the energy dependence method to determine Gamow-Teller (GT) matrix elements relative to the model independent Fermi matrix element. The data show that there is an isolated concentration of GT strength in the low-lying 1(+) states making the proposed Low Energy Neutrino Spectroscopy detector (based on neutrino captures on 176Yb) sensitive to pp and 7Be neutrinos and a promising detector to resolve the solar neutrino problem.     

Gamow-teller strengths of the inverse beta transition 176Yb-->176Lu for spectroscopy of proton-proton and other sub-MeV solar neutrinos

Discrete Gamow-Teller (GT) transitions 176Yb-->176Lu at low excitation energies have been measured via the ( 3He,t) reaction at 450 MeV and at 0 degrees. For 176Yb, two low-lying states are observed, setting low thresholds Q(nu) = 301 and 445 keV for neutrino ( nu) capture. Capture rates estimated from the measured GT strengths, the simple two-state excitation structure, and the low Q(nu) in Yb-Lu indicate that Yb-based nu detectors are well suited for a direct measurement of the sub-MeV solar electron-neutrino ( nu(e)) spectrum including pp neutrinos.     

Characterization of chemical heterogeneity in polymer systems using hydrolysis and tapping‐mode atomic force microscopy

Characterization of polymer coatings microstructure is critical to the fundamental understanding of the corrosion of coated metals. An approach for mapping the chemical heterogeneity of a polymer system using chemical modification and tapping‐mode atomic force microscopy (TMAFM) is demonstrated. This approach is based on the selective degradation of one of the phases in a multiphase polymer blend system and the ability of TMAFM to provide nanoscale lateral information about the different phases in the polymer system. Films made of a 70:30 polyethyl acrylate/polystyrene (PEA/PS) blend were exposed to a hydrolytic acidic environment and analyzed using TMAFM. Pits were observed to form in the PEA/PS blend films, and this degradation behavior was similar to that of the PEA material. Using these results, the domains in the 70:30 blend were identified as the PS‐rich regions and the matrix as the PEA‐rich region. This conclusion was confirmed by Fourier transform infrared‐attenuated total reflection analyses that revealed the hydrolysis of the PEA material. TMAFM phase imaging was also used to follow pit growth of the blend as a function of exposure time. The usefulness of the chemical modification/AFM imaging approach in understanding the degradation process of a coating film is discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1460–1470, 2001