The sessile-drop method is used to measure the surface tension and density of liquid indium and uranium under high vacuum. Measurements are made over the temperature range 156–500°C for In and at the melting point for U. Surface oxides are efficiently removed with a glow discharge system. Drop profiles are captured by photograph and processed using nonlinear regression to yield the surface tension and density. In this regression procedure, normal distances from calculated profiles to data points are minimized. For indium, the density and surface tension measurements yield mp = 7.05 × 103kg/m3, d/dT = −0.776 kg/m3·°C, and γmp = 0.568 N/m, dγ/dT = −9.45 × 10−5 N/m·°C. The results for uranium at the melting point are mp = 17.47 × 103 kg/m3 and γmp = 1.653 N/m. 相似文献
13C- and 195Pt-NMR. spectra for the complexes trans-PtCl2(amine)(CH2?CH2) have been measured. For amine = (S)-N-methyl-α-methylbenzylamine the two diastereomers present may be distinguished from the values 3J(Pt,C). The 195Pt-chemical shift is shown to be sensitive to subtle differences stemming from intramolecular non-bonded interactions. 相似文献
A system involving two polymer-supported reagents for the selective and organocatalytic oxidation of alcohols to aldehydes or ketones has been developed in which both polymeric reagents can be recovered and reused. 相似文献
Solutions are presented herein of some contact problems connected with the torsion of a composite half-space. In the general case the problem of the torsion of a composite elastic half-space is examined by means of the rotation of a stiff finite cylinder welded into a vertical recess of this half-space. Moreover, the following particular problems on the torsion of such a half-space are considered.
1. 1) A composite half-space with a vertical elastic infinite core, twisted by means of the rotation of a stiff stamp affixed to the upper endplate of the elastic core.
2. 2) A half-space with a vertical cylindrical infinite hole, twisted by means of the rotation of a stiff finite cylinder welded into the upper part of this hole.
In the general case the solution of the problem reduces to the solution of an integral equation of the second kind on a half-line. The question of the solvability of this fundamental integral equation is investigated, and it is shown that its solution may be constructed by successive approximations.
Let us note that the problem of the torsion of a homogeneous half space and of an elastic layer by means of rotation of a stiff stamp has been considered by Rostovtsev [1], Reissner and Sagoci [2], Ufliand [3], Florence [4], Grilitskii [5] and others.
The problem of the torsion of a circular cylindrical rod and the half-space welded to it which are subject to a torque applied to the free endface of the rod has been considered by Grilitskii and Kizyma[6].
The torsion of an elastic half-space with a vertical cylindrical inclusion of some other material by the rotation of a stiff stamp on the surface of this half-space has been considered in [7], wherein it has been assumed that the stamp is symmetrically disposed relative to the axis of the inclusion and lies simultaneously on both materials. 相似文献
The crystal structures of hydrate (1) and anhydrate (2) forms of 2,3-pentamethylene-3,4-dihydroquinazolin-4-one hydrochloride have been determined by X-ray structure analysis. Crystal data of 1 are 2(C13H14N2O)*3(HCl)*4.5 (H2O), triclinic P?1, Z=2, a=8.004(5), b=13.129(7), c=15.725(7) Å, α=106.45(4), β=92.61(4), γ=97.98(5), R=0.0652 and 2 are C13H14N2O*HCl, monoclinic C2/c, Z=8, a=21.360(4), b=5.954(1), c=21.263(4), β=117.89(3), R=0.0556. The crystal of the hydrate form 1is unstable. This form collapses easily with evaporation of H2O and part of HCl molecules from crystals. By recrystallizing destroyed form has been obtained stable crystal form 2. 相似文献
Inner- and valence-shell electron energy loss spectra of gaseous SF6, SeF6 and TeF6 have been measured at high impact energy (2.0–3.7 keV) and zero degree scattering angle. The resulting inner-shell excitation spectra include F 1s, S 2s and 2p in SF6: F 1s, Se 3s, 3p and 3d in SeF6 and F 1s, Te 4s, 4p, 4d and 3d in TeF6. The results for each of these hexafluorides are interpreted, in the framework of the potential barrier model, as excitations to resonances involving a common manifold of virtual valence (inner-well) orbitals and also to Rydberg (outer-well) orbitals. The below-edge shape resonances in corresponding inner-shell excitation spectra of these hexafluorides show very similar variations in intensities in accord with expectations based on electric-dipole selection rules. This is an indication that these below-edge resonances in SeF6 and TeF6 are of the same symmetry as those in SF6 (i.e. a1g and t1u). The continuum (above-edge) shape resonances in SeF6 also show similar spectral behavior to those of SF6 and can be understood by including Se 4d and S 3d orbitals in the basis for the respective MO schemes. However, in TeF6 completely different spectral behavior is observed for the continuum resonances. In particular, there is a dramatic series of intense resonances observed above the Te 3d and 4d edges. The TeF6 spectrum can only be understood by extending the MO basis set to include the Te 4f orbitals which are even lower lying than the Te 5d orbitals. Therefore, these continuum resonances which are also seen in the F 1 s and Te 3p spectra of TeF6 are assigned to l=3 (f-type) continuum shape resonances due to involvement of the 4f orbitals rather than the l=2 (d-type) continuum resonances observed in SF6 and SeF6. This is the first reported observation of such f-type continuum shape resonances and such considerations will likely prove to be important in the understanding of near-edge spectra of heavy atom containing species. The VSEELS spectra which are very similar for the three hexafluorides also show significant continuum shape resonances. A consideration of both the ISEELS and the VSEELS spectra indicates that there is a weakening of the potential barrier in going through the series from SF6, SeF6 to TeF6. 相似文献
A one-step sequential method for preparing AgCl@polypyrrole-chitosan core-shell nanoparticles and subsequently the formation of polypyrrole-chitosan hollow nanospheres is reported. The formation of the core and the shell is performed in one reaction medium almost simultaneously. Transmission electron microscopy (TEM) images show the presence of core-shell nanoparticles and hollow nanospheres. Ultraviolet-visible (UV-vis) studies reveal that AgCl was formed first followed by polypyrrole. X-ray diffration (XRD) and UV-vis studies show that AgCl was present in the core-shell nanoparticles and could be removed completely from the core. 相似文献
The Mitsunobu reaction is a widely used and versatile method for the dehydrative oxidation–reduction condensation of an acid/pronucleophile usually with a primary or secondary alcohol that requires the combination of a reducing phosphine reagent together with an oxidizing azo reagent. The utility of this reaction stems from the fact that it is generally highly stereoselective and occurs with inversion of the stereochemical configuration of the alcohol starting material. Furthermore, as carboxylic acids, phenols, imides, sulfonamides, and other compounds can be used as the acid/pronucleophile, this reaction is useful for the preparation of a wide variety of functional groups. This Focus Review of the Mitsunobu reaction summarizes its origins, the current understanding of its mechanism, and recent improvements and applications. 相似文献