待定系数法在无理函数积分中的应用

在教学过程中通过对练习题: 的求解、分析、综合和归纳得: (1) 式中P_n(X)_9 Q_n(x)均为n次多项式,其中Q_n(x)的各项系数待定。 (2) 式中P_n(x)为n次多项式,f_(n-1)(x)为各项系数待定的(n-1)次多项式,μ_n为待定常数。     

利用V型三能级原子与相干态光场Raman相互作用传送未知原子态

描述了简并V型三能级原子与单模相干态光场的Raman相互作用,获得了处于激发态单态的原子与相干态光场相互作用的结果.利用探测原子与光场的相互作用将原子和光场制备成最大缠结态,并注入待测原子,通过原子与腔模构成的Bell基矢演化,对腔场进行选择性探测,获得探测原子相互作用后可能的量子状态,然后对待测原子与腔场进行联合探测,接着对探测原子的量子状态实施幺正变换,就将探测原子制备到待测原子的初始量子态上,从而实现未知原子态的隐形传送.     

生存教育:素质教育的重要内容

“生存教育”是以培养和训练学生生存能力为主要目的的教育。形势发展的需要和现实的差距，要求我们必须把生存教育当作素质教育的重要任务和内容来抓。生存教育要使学生学会在“独自”情况下生存，学会在压力下生存，学会在紧急状况下生存，学会在集体中生存，学会在逆境中生存。应从多个方面、多种途径实施生存教育。     

Inner-sphere oxidation of iron(II) by tris(malonato)cobaltate(III)

The kinetics of oxidation of Fe²⁺ by [Co(C₃H₂O₄)₃]^3? in acidic solutions at 605 nm showed a simple first-order dependence in each reactant concentration. The second-order rate constant dependence on [H⁺] is in accordance with eqn (i) k₂ = k′₂ + k₃[H⁺] (i) where k′₂ and k₃ have values of 73.4 ± 14.0 M ^?1 s^?1 and 353 ± 41 M^?2 s^?1, respectively, at 1.0 M ionic strength (NaClO₄) and 25°C. At 310 nm the formation and decomposition of an intermediate, believed to be [FeC₃H₂O₄]⁺, was observed. The increase in the rate of oxidation with increasing [H⁺] was interpreted in terms of a “one-ended” dissociation mechanism which facilitates chelation of Fe₂₊ by the carbonyl oxygens of malonate in the transition state.     

Synthesis and properties of alkyldicyclopentadienyl-vanadium(III) compounds

The compounds Cp₂VR (R = CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁, CH₂C(CH₃)₃ or CH₂Si(CH₃)₃) have been prepared from Cp₂ VCl and RMgX in n-pentane. The air-sensitive compounds are stable at room temperature, but decompose between 65 and 138°C. The thermal stability decreases in the order R = CH₃ CH₂Si(CH₃)₃ > C₂H₅ > CH₂C(CH₃)₃ > n-C₅H₁₁ > n-C₄H₉ > n-C₃H₇. Compounds with R = i-C₃H₇ or t-C₄H₉ could not be obtained.     

Chelatometric titration of tin in non-ferrous alloys with hedta

A new titrimetric method for determination of tin (4%) in aluminium alloys, tin- and lead-base alloys, solders, white bearing alloys, special bronzes and silver brazing alloys is proposed. HEDTA, Semi-Xylenol Orange and bismuth perchlorate are used as titrant, indicator and back-titrant respectively. Measures are taken to overcome the hydrolysis of Sn(IV). Monochloroacetic acid and ethylene glycol are added as auxiliary agents. The standard deviation of this method was found to be 0.2 mg and its coefficient of variation to vary from 0.25 to 2%, according to amount of tin. A novel method of sample decomposition and a modified method for separating Sn(IV) are also suggested.     

Dehydrochlorination of monodisperse poly(vinylidene chloride) latex

The objective of the work described in this paper was to produce dispersions of small spherical carbon particles, having particle diameters in the region of 0.1 μm. To this end, the dehydrochlorination of poly(vinylidene chloride) (PVDC) latex particles was attempted. The PVDC latex was prepared by a dispersion polymerization route. Both chemical and thermal dehydrochlorination routes were attempted. Chemical dehydrochlorination, using a variety of base/solvent systems, led to nonporous, spherical black particles of the required size, but which contained only 60% carbon; most of the remainder was oxygen, introduced by nucleophilic substitution reactions. Thermal dehydrochlorination, at 700°C under a nitrogen atmosphere, using a fluidized bed arrangement, on the other hand, led to black particles, having 90% carbon and which retained their sphericity, but which were highly porous. Initial chemical dehydrochlorination, prior to thermal treatment, did not seem to reduce the porosity of the final carbons. Dispersions of the carbon particles in a variety of solvents were readily achieved.     

Excess enthalpies of (methyl propanoate or methyl pentanoate + 1-alkanol) at 298.15 K

The excess molar enthalpies H_m^E of methyl propanoate or methyl pentanoate + 1-butanol, + 1-hexanol, + 1-octanol, and + 1-decanol have been determined experimentally at 298.15 K using a Calvet microcalorimeter. For all these mixtures H_m^E > 0; the values increase with the chain length of the alkanol but decrease as the ester chain lengthens.     

Electrode kinetics of the metal complexes with aminopolycarboxylic acids: Part II. Cadmium-ethylenediamine-N,N,N′,N′-tetraacetate (EDTA) complexes

The d.c. polarographic current-potential curves of Cd(II)-EDTA complexes were examined in the pH range 0.5–10.0, to elucidate the mechanism of their electrode processes and to determine the relevant electrochemical kinetic parameters. It was shown that the first wave observed below pH 3 at ?0.58 to ?0.65 V vs. SCE is the reversible reduction wave of Cd(II) aquo-ion with kinetically-controlled limiting current, and the second wave observed above pH 1.5 at ?0.75 to ?1.21 V vs. SCE corresponds to the simultaneous irreversible reduction of four complex species, CdH₃L⁺, CdH₂L, CdHL^? and CdL^2?, where CdH_pL^(p?2)+ and L^4? denote the protonated complex species with p protons and the unprotonated EDTA ion, respectively. Analysis of the dependence of limiting current on the hydrogen ion concentration led to the conclusion that the preceding reaction determining the behaviour of limiting current is CdH₃L⁺?Cd²⁺+H₃L^? with k₃^d=6.3×10² s^?1 and k₃^f=3.3×10⁶ s^?1M^?1, where k₃^d and k₃^f are the dissociation and formation rate constants, respectively. On the other hand, from analysis of the dependence of half-wave potentials of the second wave on the hydrogen ion concentration, the kinetic parameters of the four complex species were evaluated, and are given in Table 1. Further, it was shown that the cathodic rate constants of these four charge transfer processes at some reference potential together with those of Cd(II)-HEDTA complexes fulfil the linear free energy relationship.     

The chemistry and the sterechemistry of Poly(N-Alkyliminoalanes: XIII. The crystal and molecular structure of the hexamers (ClAlN-i-Pr)6 and (Me0.83H0.17AlN-i-Pr)6MeAlN-i-Pr)6

The crystall and molecular structures of (ClAlN-i-Pr)₆ (I), and of (Me_0.83H_0.17AlN-i-Pr)₆(MeAlN-i-Pr)₆ have been determined by single crystal three-dimensional X-ray analysis. Block-matrix least-squares refinements led to conventional R factor of 0.039 for I and 0.037 for II. The compounds are isostructural, as the cage molecules consist of a prismatic hexagonal framework, (AlN)₆, similar to that observed for the parent hydrogenated analogue (HAlN-i-Pr)₆.Some differences in bond distances and angles are discussed, in connection with the different Al-bonded substituents. Crystal data: I, trigonal space group R$\text{3}$; a = 17.083(2), c = 9.652(1); Z = 3; D_c 1.46 g cm^?3; II, trigonal space group R$\text{3}$, a = 17.378(3), c = 9.706(3) »; Z = 3; D_c 1.15 g cm^?3.