钢包加入、残留痕量稀土对U71Mn钢重轨组织和性能的影响

采用金相、图像分析和测量HRC等方法,对较洁净的U71Mn钢及其在钢包加入0．02％和0．04％RE、残留稀土为0．0022％～0．0025％的U71MnRE钢重轨的组织与性能进行了“profile”实验研究,同时测量了试验钢热轧态及变形态样品的内耗。结果表明：在VD精炼的钢包加入稀土不仅能有效净化钢质,而且残留的痕量稀土能改变钢的夹杂物、细化珠光体、有效减轻和抑制钢组织与性能的不均匀性。U71MnRE钢里高出的0.06％C增加了钢轨的硬度及嵌镶内应力、应变量,因而增大了SKK阻尼和高温过程组尼。     

Separation of variables and search algorithm for internal rotation coordinates and kinematic coefficients in the theory of nuclear motions in polyatomic molecules

The construction algorithm is proposed for the internal rotation coordinates in polyatomic molecules. It is based on the properties of the matrix of kinematic coefficients when an excessive system of natural coordinates is introduced. The approximations providing the separation of variables are considered. The exact form of the kinetic energy operator is given.     

Rheological and electron microscopic characterization of aqueous carboxymethyl cellulose gels Part II: Visualization of the gel structure by freeze-fracturing

The spatial structure of gels of sodium carboxymethyl cellulose (NaCMC-gel) and carboxymethyl cellulose in the free acid form can be imaged in the transmission electron microscope (TEM). The freeze-fracturing technique is suitable for this. Experiments with test preparations (10 % aqueous glycerol solution) show that cooling rates during freeze-fixing are decisive for visualization, and that cooling rates can be improved substantially by using a cryojet. The increase of the cooling rate to more than 15 000 K/s makes it possible to obtain extremely fine network structures with a mesh width of 5–25 nm and with a filament thickness of 2–3 nm. The results obtained after jet-freezing show differences in the structure of the two gels: quasi-crystalline microaggregates in the HCMC-gel can be seen, and they cause an increased elasticity and opalescence of the aged HCMC-gels.     

Liquid chromatography/tandem mass spectrometric method for the simultaneous determination of tobacco-specific nitrosamine NNK and its five metabolites

A sensitive and robust high-performance liquid chromatography-electrospray ionization tandem mass spectrometry method to analyze 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and its five metabolites in one passage was developed and validated. The method achieved excellent reproducibility and accuracy. Linearity was observed for all six compounds (R² = 0.999) with detection limits (S/N ≥ 3) ranging from 0.2 to 2.4 pg on column and 0.01-0.12 ng ml⁻¹ in samples injected. Average intra-day and inter-day variations (% R.S.D.) were 1.2 and 3.5%, respectively. A sample preparation method involving C8 and C18 solid phase extraction provided satisfactory recovery of the analytes in mouse urine. Each NNK metabolite was identified by its chromatographic retention time and specific fragmentation pattern. Since the carcinogenicity of NNK is related to its metabolism, the method described in this report should facilitate toxicological investigations into the carcinogenesis due to NNK exposure in the environment.     

Restricted rotation in unbridged sandwich complexes: rotational behavior of closo-[Co(eta 5-NC4H4)(C2B9H11)] derivatives

Rotation about the centroid/metal/centroid axis in ferrocene is facile; the activation energy is 1-5 kcal mol(-1). The structurally similar sandwich complexes derived from closo-[3-Co(eta5-NC4H4)-1,2-C2B9H11] (1) have a different rotational habit. In 1, the cis rotamer in which the pyrrolyl nitrogen atom bisects the carboranyl cluster atoms is 3.5 kcal mol(-1) more stable in energy than the rotamer that is second lowest in energy. This cis rotamer is wide, spanning 216 degrees , and may be split into three rotamers of almost equal energy by substituting the N and the carboranyl carbon atoms adequately. To support this statement, closo-[3-Co(eta5-NC4H4)-1,2-(CH3)2-1,2-C2B9H9] (2), closo-[3-Co(eta5-NC4H4)-1,2-(mu-CH2)3-1,2-C2B9H9] 3, 2-->BF3, and 3-->BF3 have been prepared. Two rotamers are found at low temperature for 2-->BF(3) and 3-->BF3. Compounds 2, 3, and 1-->BF3 behave similarly to 1. Rotational energy barriers and the relative populations of the different energy states are calculated from 1H DNMR spectroscopy (DNMR, dynamic NMR). These results agree with those of semiempirical calculations. Without exception, the cis rotamer is energetically the more stable. The fixed conformation of 1 assists in elucidating the rotational preferences of the [3,3'-Co(1,2-C2B9H11)2]- ion in the absence of steric hindrance; the [3,3'-Co(1,2-C2B9H11)2]- ion is commonly accepted to present a cisoid orientation. Complex 1 is electronically similar to the [3,3'-Co(1,2-C2B9H11)2]- ion. Both have heteroatoms in the pi ligands, and they have the same electronegativity difference between the constituent atoms. This leads to a view of the [NC4H4]- as [7,8-C2B9H11]2- ion, with no steric implications. Therefore the [3,3'-Co(1,2-C2B9H11)2]- ion should be considered to have a cisoid structure, and the different rotamers observed to be the result of steric factors and of the interaction of the counterion with either B-H groups and/or ancillary ligands. The rotamer adopted is the one with the atoms holding the negative charges furthest apart.     

Block spin approach to φ 3 4 field theory

A block spin approach to the Euclidean ⁴ field theory in three dimensions is proposed by using the three-dimensional version of Gawedzki and Kupiainen's block spin transformation method. The lattice ₃ ⁴ model recovers the rotation invariance in the continuum limit, when the coupling constant is small.     

Creatinine and creatininium cation in DMSO-d6 solution. Structure and restricted internal rotation of NH2 group

Investigation of 15N NMR spectra of isotopically enriched creatinine has unequivocally shown that in DMSO-d6 solution it exists as amino tautomer (2-amino-1-methylimidazoline-4-one), which in the presence of acid is protonated at N-3. Free energies of activation of the amino group rotation in creatinine and its cation have been determined to be 56 kJ/mol and 60 kJ/mol, respectively, at 298 K, by performing the simultaneous analysis of the lineshapes of -NH2 proton signals in the whole set of 1H NMR spectra recorded at various temperatures and magnetic fields. These results have been theoretically reproduced by the calculations of molecular structures and energies of creatinine and creatininium cation in their ground states and transition states of the amino group rotation, using DFT (B3LYP) method, involving the influence of the solvent.     

掺杂Nd对GdFeCo薄膜的磁光性能的影响

制备了三元GdFeCo合金薄膜和四元NdGdFeCo合金薄膜,测量了其磁饱和磁化强度对温度的依赖关系、磁滞回线以及可见光范围内的克尔谱.研究了轻稀土Nd掺杂对GdFeCo磁光薄膜的克尔旋转角的影响,发现在一定掺杂范围内能够有效提高薄膜在短波长下的克尔旋转角.掺入适量的轻稀土Nd可以使GdFeCo薄膜在短波长下的磁光性能提高,更好的适用于作为中心孔探测磁超分辨的短波长磁光读出层材料.     

Die inneren Schwingungen der Tetrahetero-Tetrahedran-Anionen Ge44, Sn44- und Pb44

The Internal Vibration of the Tetrahetero-Tetrahedrane Anions Ge₄^4?, Sn₄⁴-, and Pb₄⁴ The Frequencies of the internal vibrations ν₁ (A₁), ν₂(E), ν₃(T₂) of the tetrahetero-tetrahedrane an ions Ge₄⁴- and Sn₄⁴- are determined from the infrared and Raman spectra of K₇LiGe₈ and KSn, respectively. A comparison of the characteristic vibration of tetrahedrane anions X₄⁴- (X = Si, Ge, Sn)and the isoelectronic neutral tetrahedranes Y₄ of the neighbouring elements (Y = P, As, Sb) shows a rather constant ratio of the corresponding frequencies k = v^?(X₄⁴-) = 0,77. This allows for an estimate of v^?(Pb₄⁴-) from the known Bi₄data. In the inflated spectrum of KPb bands are observed in the predicted frequency range.