Calculation of activities and solubilities of alkali metal perchlorates at high ionic strengths in multicomponent aqueous systems

The equations of Nývlt, of Bromley, and of Pitzer for the representation of activity coefficients of electrolytes in multicomponent ionic systems have been used to fit solubility data for some alkali metal perchlorates and ammonium perchlorate in mixture with other electrolytes at ionic strengths varying from 0.08 mol-kg^–1 to as high as 24 mol-kg^–1. Only the Pitzer equations can be used rellably to fit the solubility data over the whole range of ionic strengths encountered for ternary systems but there are certain limitations and certain assumptions which have to be made concerning the Pitzer ionic interaction parameters. A method is also proposed for the calculation of the Pitzer single electrolyte parameters, ⁰,¹ andC , for the less soluble perchlorates from fitting their solubility data over a wide range of high ionic strengths.     

A numerical study of the effect of free surface and water depth on the stability of wakes: use of GDQ formulation

The instability character of a wake in the presence of a free surface is examined by a recently developed GDQ (generalized differential quadrature) numerical method. It is shown that at low Froude number the wake near a free surface is convectively unstable, but when the Froude number is increased further it becomes absolutely unstable. The effect of water depth on the stability property of the wake flow is also investigated. It is found that the influence of water depth on the critical point of instability is limited to at most 20% variation in the complex frequency, while the change in temporal growth rate is also limited to about 20%. © 1997 John Wiley & Sons, Ltd.     

Regioselective Lactonization of α‐(2→8)‐Trisialic Acid

A simple and selective method has been developed to obtain both monolactones of the title compound, a model compound for biologically important polyneuraminic acid derivatives: acidic lactonization and alkaline hydrolysis of dilactone 1 . The two monolactonized trimers can be separated by capillary electrophoresis, and then distinguished by enzymatic hydrolysis with neuraminidase; only the 2‐monolactone undergoes reaction.     

A study of the antitumor activity of four dibutyltin(IV)-N-arylidene-α-amino acid complexes

This paper reports the activity of four dibutyltin(IV)–N-arylidene-α-amino acid complexes against the National Cancer Institute (NCI) panel of 60 cell lines. The results indicated that three of the organotin complexes (C₁₇H₂₅NO₃Sn, C₁₈H₂₇NO₃Sn and C₂₀H₃₁NO₃Sn) exhibit their highest cytotoxic effect on the NCI-522 (non-small cell lung cancer) cell line. The fourth complex, C₂₁H₂₇NO₃Sn, exhibits its highest cytotoxic activity on the cell line RXF-631L (renal cancer). In general, a low to moderate cellular response was observed for all the organotin complexes, with at least one cell line in each subpanel of cells exhibiting a very low growth inhibition response to all the organotin complexes. The low-responding cell lines included HOP-62 (non-small lung cancer), DLD-1 (colon cancer), SF-539 (CNS cancer), SK-MEL-5 (melanoma), IGROV-1 (ovarian cancer) and RPMI-8226 (leukemia). The results also indicated that the compounds did not exhibit any significant subpanel activity and suggested that the compounds were not active in all the cell lines contained in any subpanel. The low to moderate activity of these compounds across the cell lines was attributed to the presence of nitrogen-bearing ligands which prevented the dissociation of the compound and the subsequent binding to DNA. © 1998 John Wiley & Sons, Ltd.     

On near-wall hot-wire measurements

A specially constructed hot-wire probe was used to obtain very near-wall velocity measurements in both a fully developed turbulent channel flow and flat plate boundary layer flow. The near-wall hot-wire probe, having been calibrated in a specially constructed laminar flow calibration rig, was used to measure the mean streamwise velocity profile, distributions of streamwise and spanwise intensities of turbulence and turbulence kinetic energy k in the viscous sublayer and beyond; these distributions compare very favorably with available DNS results obtained for channel flow. While low Reynolds number effects were clearly evident for the channel flow, these effects are much less distinct for the boundary layer flow. By assuming the dissipating range of eddy sizes to be statistically isotropic and the validity of Taylor's hypothesis, the dissipation rate ɛ _iso in the very near-wall viscous sublayer region and beyond was determined for both the channel and boundary layer flows. It was found that if the convective velocity U _c in Taylor's hypothesis was assumed to be equal to the mean velocity Uˉ at the point of measurement, the value of (ɛ⁺ _iso)₁ thus obtained agrees well with that of (ɛ ⁺)_DNS for y ⁺ ≥ 80 for channel flow; this suggests the validity of assuming U _c=Uˉ and local isotropy for large values of y ⁺. However, if U _c was assumed to be 10.6u _τ , the value of (ɛ⁺ _iso)₂ thus obtained was found to compare reasonably well with the distribution of (ɛ⁺ _iso)_DNS for y ⁺≤ 15. Received: 31 May 1999/Accepted: 20 December 1999     

Doorway states in the gamma decay-out of the yrast superdeformed band in 59Cu

The decay-out process of the yrast superdeformed band in 59Cu has been investigated. The firm determination of spin, parity, excitation energy, and configuration of the states involved in this process constitutes a unique situation for a detailed understanding of the decay-out mechanism. A theoretical model is introduced that includes a residual interaction and tunneling matrix element between bands, calculated in the configuration-dependent cranked Nilsson-Strutinsky model. This interaction causes the decay to occur via a small number of observed doorway states.     

Time-delayed laser scattering in a multi-level atom with Raman resonance

A general theory of time-delayed coherent scattering in an atomic medium is presented. Two short laser pulses are incident on the atom initially, followed by a third laser at a later time. Detailed time dependent expressions for the atomic coherence and the third order dipole matrix elements are obtained. We have included the effects of excited level population, phase matching, single and two-photon resonances, and atomic relaxation and dephasing. Detailed discussions are given for the case where the first two lasers are in a Raman resonance withthe atomic system. Some useful features of this type of scattering, for example, background elimination, are also pointed out.     

Evidence for triaxial shapes in Pt nuclei

Positive parity levels in ¹⁹¹Pt obtained from (α, xnγ) reactions and β-decay are presented as a first example of a rather complete $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ level family. The spectrum confirms triaxial shapes found before from $\text{h}{}_{\mathrm{<mtext>11</mtext><mtext>2</mtext>}}$ and $\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ proton structures in this mass region. In addition to the usual decoupled yrast band, a second ΔI = 2 band within the $\text{i}{}_{\mathrm{<mtext>13</mtext><mtext>2</mtext>}}$ family, built on a low-lying $\text{j?1 =}\text{11}\text{2}$ state, is observed in agreement with theory.