Treatment of the complex [U(Tren(TMS))(Cl)(THF)] [1, Tren(TMS) = N(CH(2)CH(2)NSiMe(3))(3)] with Me(3)SiI at room temperature afforded known crystalline [U(Tren(TMS))(I)(THF)] (2), which is reported as a new polymorph. Sublimation of 2 at 160 °C and 10(-6) mmHg afforded the solvent-free dimer complex [{U(Tren(TMS))(μ-I)}(2)] (3), which crystallizes in two polymorphic forms. During routine preparations of 1, an additional complex identified as [U(Cl)(5)(THF)][Li(THF)(4)] (4) was isolated in very low yield due to the presence of a slight excess of [U(Cl)(4)(THF)(3)] in one batch. Reaction of 1 with one equivalent of lithium dicyclohexylamide or bis(trimethylsilyl)amide gave the corresponding amide complexes [U(Tren(TMS))(NR(2))] (5, R = cyclohexyl; 6, R = trimethylsilyl), which both afforded the cationic, separated ion pair complex [U(Tren(TMS))(THF)(2)][BPh(4)] (7) following treatment of the respective amides with Et(3)NH·BPh(4). The analogous reaction of 5 with Et(3)NH·BAr(f)(4) [Ar(f) = C(6)H(3)-3,5-(CF(3))(2)] afforded, following addition of 1 to give a crystallizable compound, the cationic, separated ion pair complex [{U(Tren(TMS))(THF)}(2)(μ-Cl)][BAr(f)(4)] (8). Reaction of 7 with K[Mn(CO)(5)] or 5 or 6 with [HMn(CO)(5)] in THF afforded [U(Tren(TMS))(THF)(μ-OC)Mn(CO)(4)] (9); when these reactions were repeated in the presence of 1,2-dimethoxyethane (DME), the separated ion pair [U(Tren(TMS))(DME)][Mn(CO)(5)] (10) was isolated instead. Reaction of 5 with [HMn(CO)(5)] in toluene afforded [{U(Tren(TMS))(μ-OC)(2)Mn(CO)(3)}(2)] (11). Similarly, reaction of the cyclometalated complex [U{N(CH(2)CH(2)NSiMe(2)Bu(t))(2)(CH(2)CH(2)NSiMeBu(t)CH(2))}] with [HMn(CO)(5)] gave [{U(Tren(DMSB))(μ-OC)(2)Mn(CO)(3)}(2)] [12, Tren(DMSB) = N(CH(2)CH(2)NSiMe(2)Bu(t))(3)]. Attempts to prepare the manganocene derivative [U(Tren(TMS))MnCp(2)] from 7 and K[MnCp(2)] were unsuccessful and resulted in formation of [{U(Tren(TMS))}(2)(μ-O)] (13) and [MnCp(2)]. Complexes 3-13 have been characterized by X-ray crystallography, (1)H NMR spectroscopy, FTIR spectroscopy, Evans method magnetic moment, and CHN microanalyses. 相似文献
This paper presents a study of neural networks for prediction of acoustical properties of polyurethane foams. The proposed neural network model of the foam uses easily measured parameters such as frequency, airflow resistivity and density to predict multiple acoustical properties including the sound absorption coefficient and the surface impedance. Such a model is quite robust in the sense that it can be used to develop models for many different classes of materials with different sets of input and output parameters. The current neural network model of the foam is empirical and provides a useful complement to the existing analytical and numerical approaches. 相似文献
Several factors in temperature measurement that can affect the precision of melting points and phase-change phenomena are discussed. In many cases, critical errors may arise in the measurement and control of temperatures due to incorrect placement and/or interpretation of the output of temperature sensors in the various system types that are in current use. Advantages can be obtained by using one temperature sensor only for temperature measurement and temperature control in a low mass infrared gold image fumace for the analytical studies in both the constant rate and stepwise isothermal thermoanalytical heating and cooling modes. Illustrations of the use of this instrumentation for measurements in both modes are given. 相似文献
This study was designed to evaluate a disease-specific outcome measure for patients with selected voice disorders and to relate this instrument to a standardized quality of life measurement. In addition, the study attempts to document the degree of handicap for dysphonia patients globally, between different vocal pathologies, and in comparison to other chronic diseases. In this prospective, observational study, 260 adult patients evaluated for alterations of voice completed a general quality of life measure (the Medical Outcomes Trust Short Form 36-Item[SF-36]) and a voice-specific instrument (Voice Handicap Index [VHI]) pretreatment.
The highest correlation was between the social functioning score of the SF-36and the total score of the VHI and the physical, emotional, and functional subscales (p < 0.001) of the VHI. Significant correlation was also obtained for the SF-36 domains mental health (p < 0.01), general health (p < 0.01), and role functioning emotional (p < 0.017) with the three VHI domains and the total VHI score. Patients had significantly lower scores than the general U.S. population in five of the eight domains of SF-36. Patients with vocal fold paralysis had the highest level of pretreatment disability as measured on both the VHI and SF-36 among voice patients. The patients with dysphonia had a lower level of physical functioning than the patients with chronic sinusitis (p < 0.01), reflecting a greater handicap. In addition, the dysphonia group had lower levels of social functioning than the angina (p < 0.01) and sciatica (p < 0.01) groups and a lower score for mental health than the angina group (p < 0.01).
The SF-36 correlates with the VHI in the domains of social functioning,mental health, and role functioning emotional. The baseline handicap for voice disorders represents a significant disability even in comparison to conditions such as angina pectoris, sciatica, and chronic sinusitis. 相似文献
Systems are studied whose state vector x is governed by the usual set of first-order differential equations. When the extremals x(t) that originate at a fixed point inn-dimensional state-variable space are stopped at a fixed final time, the locus of their endpoints defines a hypersurface called the wavefront. The well-known adjoint vector is normal to the wavefront. The principal point of this paper is that a second wavefront normal can be constructed from the x(t) vectors that are available if the test for Jacobi conjugate points is performed. Verifying that the two normals are almost collinear shows that the errors due to computer truncation and numerical integration are negligible. This check is particularly useful when using the finite-difference approximation x(t) xi(t) – xj(t), where xi(t) and xj(t) are close but nonneighboring extremals. This approximation can simplify considerably the analysis and computation required for a conjugate-point test, particularly if the extremals have corners. 相似文献
Analogues of the cannabinoid-like anti-emetic nonabine (BRL 4664), in which the 4-pyridinyl and 1,2-dimethylheptyl groups have been replaced by other aryl and alky groups respectively, have been synthesised from the appropriate resorcinol by a novel procedure. The route has been shown to be of general applicability, although in the case of nonabine itself the procedure does not represent a viable alternative to that previously published. 相似文献
The development of an analytical technique is described which may be used to determine chromium, chromium(III) and chromium(VI) in estuarine and coastal waters. The method is based on selective micro-solvent extraction with subsequent GFAAS. The technique has been applied in a major North Sea estuary. The results obtained confirm that thermodynamic factors alone cannot be relied upon to describe the form of chromium in estuaries. Kinetic factors appear to have a strong influence over speciation and lead to the persistence of Cr(III) species in environments where Cr(VI) would be expected to be present. 相似文献
The results of recent powder neutron diffraction investigations of the high pressure and high temperature phases within the
binary Cu and Ag halides are summarised, with emphasis on the relationship between the observed structural disorder and evidence
for fast-ion behaviour provided by other techniques such as ionic conductivity measurements, differential thermal analysis
and molecular dynamics simulations.
Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997 相似文献
Errors in the analysis of liquid samples are often large enough to be important. For solid materials, additional potential complications arise in separating the determinand from the sample matrix and in controlling possible interferences from co-extracted species. These considerations have led to the development of a stepwise, co-ordinated approach by which a group of laboratories have achieved predefined standards of accuracy. Sample digestion has been examined. The analysis of digests has then been addressed; the control of analytical precision has been emphasised. Finally, a demonstration of overall comparability has been undertaken. The results are presented. 相似文献