The effect of hydrodynamic coupling on the thinning of a film between a drop and its homophase

The rate of thinning of a film trapped between a drop approaching its homophase according to a model incorporating hydrodynamic coupling is dramatically different from earlier, uncoupled models. Implications for film thinning of microflows analyzed in the preceding paper are here investigated using similar analytical methods to derive a nonautonomous, nonlinear evolution equation for the film thickness which has been solved numerically under a variety of conditions after asymptotic analytical behavior has been extracted. The applied force squeezing the film, together with the initial motion in the three phases, determines the rate of film thinning in a complicated manner through the coupling parameter R = (ρ_Aμ_A/ρ_Bμ_B)^{$\text{1}\text{2}$}. Experimental observations that normal drop circulation enhances thinning, whereas reversed drop circulation can cause thickening, are predicted theoretically for the first time. Films much more viscous than their surroundings are found to thin faster than the converse case, a conclusion at odds with offhand intuition but substantiated experimentally; both classes of systems behave differently, often qualitatively so, from predictions of hydrodynamically decoupled systems, and in particular film thinning rates are generally faster because of less resistance to drainage, although the limit of vanishing R does recover the special case of Reynolds' model. For short times, films are shown analytically to thin more rapidly if there is initially outward film motion and normal drop circulation, but with decreasing effectiveness as R increases, in contrast to the effect of R for intermediate and longer times; if there is initially inward film motion, thickening tendencies are enhanced by reverse drop circulation but with decreasing effectiveness as R increases. These and other detailed conclusions, most predicted theoretically for the first time, are not only in qualitative agreement with experimental observations, they are in quantitative agreement with available data.     

Spectrophotometric investigation of the reaction of CU(II) and Cu(I) with 1-isonitroso-(1,2,3,4)-tetrahydrophenazine

The reactions of Cu(II) and Cu(I) with 1-isonitroso-(1,2,3,4)-tetrahydrophenazine (HITF) have been studied spectrophotometrically. Both ions form complexes with metal/ligand ratio 1:2. The complex of Cu(I) and ITF can be used for copper determination in the range 2-50 x 10(-6)M, and has been separated as the perchlorate in crystalline form. The spectrophotometric characteristics and the equilibrium constants for the ligand and for the complexes are reported.     

Isotope ratio monitoring gas chromatography/Mass spectrometry of D/H by high temperature conversion isotope ratio mass spectrometry

Of all the elements, hydrogen has the largest naturally occurring variations in the ratio of its stable isotopes (D/H). It is for this reason that there has been a strong desire to add hydrogen to the list of elements amenable to isotope ratio monitoring gas chromatography/mass spectrometry (irm-GC/MS). In irm-GC/MS the sample is entrained in helium as the carrier gas, which is also ionized and separated in the isotope ratio mass spectrometer (IRMS). Because of the low abundance of deuterium in nature, precise and accurate on-line monitoring of D/H ratios with an IRMS requires that low energy helium ions be kept out of the m/z 3 collector, which requires the use of an energy filter. A clean mass 3 (HD(+.)) signal which is independent of a large helium load in the electron impact ion source is essential in order to reach the sensitivity required for D/H analysis of capillary GC peaks. A new IRMS system, the DELTA(plus)XL(trade mark), has been designed for high precision, high accuracy measurements of transient signals of hydrogen gas. It incorporates a retardation lens integrated into the m/z 3 Faraday cup collector. Following GC separation, the hydrogen bound in organic compounds must be quantitatively converted into H(2) gas prior to analysis in the IRMS. Quantitative conversion is achieved by high temperature conversion (TC) at temperatures >1400 degrees C. Measurements of D/H ratios of individual organic compounds in complicated natural mixtures can now be made to a precision of 2 per thousand (delta notation) or, better, with typical sample amounts of approximately 200 ng per compound. Initial applications have focused on compounds of interest to petroleum research (biomarkers and natural gas components), food and flavor control (vanillin and ethanol), and metabolic studies (fatty acids and steroids). Copyright 1999 John Wiley & Sons, Ltd.     

The Effect of Organizational Communication Media on Organizational Culture and Performance: An Agent-Based Simulation Model

This paper examines the mutual relationship between the communication richness of media used for conducting organizational communication and organizational culture. The richness of the media influences how well the organization might maintain its culture. On the other hand, a strong organizational culture allows a more effective use of the media by providing members with some of the necessary common ground to better understand the information exchanged. These relationships are investigated using an agent-based simulation model (ABM). Our ABM incorporates many partial theories into a coherent and fully defined model, which helps formalize and integrate those theories. Our model allows us to analyze non-linearities and interaction effects, which are difficult to investigate using other techniques. Additionally, the ABM allows us to investigate the dynamics of the phenomenon and generate hypotheses that could then be tested using empirical studies. Given the substantial resources necessary to conduct empirical studies, we think that the present ABM is valuable in helping guide data collection efforts. In this paper, we present results that show that organizational culture can influence the effectiveness of the media used for organizational communication and that a high media richness can help maintain and stabilize a culture. The effect of media richness on organizational culture depends on the initial strength of the culture. In general, for a given richness of the media, an initially strong culture stabilizes faster and becomes stronger through time than an initially weak culture. Additionally, the model suggests that a stable network of contacts among agents fosters a high achievement of organizational tasks. Conversely, when agents are forced to establish contacts with agents outside the usual network for doing their work, the accomplishment of tasks decreases.     

Novel rearranged ring C monoaromatic steroid hydrocarbons in sediments and petroleums

Two series of novel rearranged ring C monoaromatic steroid hydrocarbons (C₂₁,C₂₂, C₂₇–C₂₉) occurring in sediments and petroleums have been characterised by synthesis of C₂₁ and C₂₇ homologues $\text{1}$ and $\text{2}$.     

The effect of hydrodynamic coupling on the axisymmetric drainage of thin films

The effect of hydrodynamic coupling of adjacent phases on the axisymmetric drainage of thin films is examined using a prototype model of coalescence. For long times, pressure forces in the film dominate flow in all three regions, and finally all move effectively as one, whereas for short times, profiles are sharp and initial flow differences in the three regions can dominate pressure effects. For intermediate times, temporal evolution of velocity profiles depends in a complicated way on the kinematic viscosity ratio and the parameter $\text{R = (?}{}_{\mathrm{A}}\text{μ}{}_{\mathrm{A}}\text{/?}{}_{\mathrm{B}}\text{/μ}{}_{\mathrm{B}}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, as well as on initial conditions and pressure gradient. Generally speaking, the initial flows have less of an effect on overall drainage time than the presence of induced circulation in adjacent phases. Analytical solutions are plotted for a range of systems and representative initial conditions and pressure gradients. In a subsequent article, film-thinning equations are solved using this information.