This paper describes a measurement principle for calculating component values from measurements conducted under less than
optimal conditions, as is the case in the IEEE Std 1149.4 environment. Also presented are equations that take into account
switch resistances on the signal paths, the output resistance of the signal generator, and the loading effect caused by the
input impedance of the voltmeter together with the pin capacitances in parallel to the voltmeter. In addition, the paper presents
characterization methods to determine values for these impedances. The inaccuracies achieved in the impedance range from kΩ
to MΩ are of the order of few percent.
A simple method for absolute-frequency measurements of molecular transitions in the mid-IR region is reported. The method is based on a cw singly resonant optical parametric oscillator (SRO), which is tunable from 3.2 to 3.45?μm. The mid-IR frequency of the SRO is referenced to an optical frequency comb through its pump and signal beams. Sub-Doppler spectroscopy and absolute-frequency measurement of the P(7) transition of the ν3 band of CH4 are demonstrated. 相似文献
Noble-gas hydride molecules with the general formula HNgY (Ng denotes noble-gas atom and Y denotes electronegative fragment) are usually prepared in solid noble gases. In many cases, the matrix-isolated HNgY molecules show a characteristic structure of the H-Ng stretching absorption: A close doublet as the main spectral feature and a weaker satellite at higher energy. This characteristic band structure is studied here for matrix-isolated HXeBr and HKrCl molecules. Based on the experimental and theoretical results, we suggest a model explaining the common features of the band structure of the HNgY molecules in noble-gas matrices. In this model, the main doublet bands are attributed to matrix sites where the splitting is caused by specific interactions of the embedded molecule with noble-gas matrix atoms in certain local morphology. The weaker blueshifted band is probably a fingerprint of hindered rotation (libration) of the embedded molecule in the lattice. This librational band has a mirror counterpart at lower energies appearing at higher matrix temperatures. Our present ab initio calculations for the one-to-one Xe...HXeBr complexes and the simulation of hindered rotation in a matrix support this image. 相似文献
Microspheres were prepared using a hydrocarbon-perfluorocarbon solvent extraction process. The effect of the physical properties and the emulsification conditions on the mean microsphere size was investigated. The viscosity of the dispersed and the continuous phase greatly affected the microsphere size. Smaller microspheres were produced at the same mixing intensity when the viscosity of the dispersed phase decreased. Increased continuous phase viscosity reduced the coalescenceof the droplets and hence smaller microspheres were produced. The mean microsphere size first decreased as the volume ratio of the dispersed phase to the continuous phase increased but upon further increase the mean microsphere size increased. The effect of the volume ratio on the microsphere size was linked to the surfactant concentration. The stability of the studied hydrocarbon-in-fluorocarbon emulsion is poor. One reason for the poor stability is the high density difference between the phases. The emulsion droplets were solidified by siphoning part of the emulsion in the fresh continuous phase, which extracted the solvent from the dispersed phase. The effect of emulsion transfer time between the emulsification and solidification steps on the particle size was studied but no significant effect was observedduring the controlled time interval. 相似文献
Polyimides are well established as gas separation membranes due to their intrinsically low free volume and correspondingly high H2 selectivity relative to other gases such as CO2. Prior studies have established that H2/CO2 selectivity can be improved by crosslinking polyimides with diamines differing in spacer length. In this work, we follow the evolution of macroscopic and microscopic properties of a commercial polyimide over long crosslinking times (tx) with 1,3‐diaminopropane. According to spectroscopic analysis, the crosslinking reaction saturates after ≈24 h, whereas tensile, nanoindentation and stress relaxation tests reveal that the material stiffens, and possesses a long relaxation time that increases with increasing tx. Although differential scanning calorimetry shows that the glass transition temperature decreases systematically with increasing tx, permeation studies indicate that the permeabilities of H2 and CO2 decrease, while the H2/CO2 selectivity increases markedly, with increasing tx. At long tx, the polyimide becomes impermeable to CO2, suggesting that it could be used as a barrier material.
The reaction of (1R,2R)‐(–)‐1,2‐diaminocyclohexane ( 1 ) [DACH] with the aldehyde (1R)‐(–)‐myrtenal ( 2 ) in MeOH afforded the bidentate diimine ligand, (1R,2R)‐(–)‐N1,N2‐bis{(1R)‐(–)myrtenylidene}‐1,2‐diaminocyclohexane ( 3 ) in a high yield. Reduction of 3 using LiAlH4 led to the formation of the desired ligand ( 4 ) (1R,2R)‐(–)‐N1,N2‐bis{(1R)‐(–)myrtenyl}‐1,2‐diaminocyclohexane. Treatment of compound 4 with K2PtCl4 or K2PdCl4 yielded the corresponding platinum(II) and palladium(II) complexes, Pt‐5 and Pd‐6 , respectively. The reaction of compound 3 with K2PtCl4 gave the diimine complex Pt‐7 . The cytotoxic activity of the complexes Pt‐5 , Pd‐6 and Pt‐7 was tested and compared to the approved drugs, cisplatin ( Cis ‐Pt ) and oxaliplatin ( Ox‐Pt ). The complexes ( Pt‐5 , Pd‐6 and Pt‐7 ) inhibit L1210 cell line proliferation with an IC50 of 0.6, 4.2, and 0.7 μL, respectively as evidenced by measuring thymidine incorporation. 相似文献
Three pyridylimine based complexes of NiII and CoII were reacted with methylaluminoxane (MAO) and tested as catalysts in ethylene polymerization. The two nickel catalysts produced mainly methyl branched polymers with good to moderate activity, while the cobalt compound showed only marginal activity. Reaction conditions strongly affect the polymer properties, such as molecular weight, melting temperature, degree of branching, and chain end unsaturation type. 相似文献
