The influence of structure and composition of a reverse SDS microemulsion on enzymatic activities and electrical conductivities

The activity of the enzyme horse radish peroxidase (HRP) is studied in a series of reverse microemulsions composed of dodecane, aqueous buffer, sodium dodecylsufate (SDS) and alcohols of the homologous series 1-butanol to 1-octanol. The HRP catalyzed reaction is the oxidation of a classical water soluble substrate, the 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) by hydrogen peroxide. In parallel electrical conductivity measurements are performed on the same solutions. The structural changes in the microemulsions, as inferred by the conductivity measurements, correlate remarkably well with the changes in the enzymatic activities. In particular it is found that (a) the maximum activity of the enzyme is always related to its optimum hydration and that this hydration can be related to the microemulsion structures, (b) the enzyme inhibition caused by the alcohols in microemulsions is a consequence of both the solubility of the alcohols in the buffer and the rigidity of the interfacial film. Consequently, it can be concluded that enzymatic activity measurements are a valuable tool to study confined systems such as microemulsions and, in particular, the amount of available hydration water. Enzymatic activities can be finely tuned by small changes in microemulsion structures, probably in a predictive way.     

Magnetic birefringence of minerals

The earliest reports of magnetically induced optical birefringence included data for liquids, magnetic fluids and colloidal suspensions. Recent work has shown that with relatively straightforward apparatus, when carefully designed and aligned, measurable effects can be recorded even for suspensions of relatively weak diamagnetic materials, including mineral particles. By recording the magnitude of the birefringence induced in magnetic fields of up to two Tesla, a method for the analysis of the magnetic and optical characteristics of these diamagnetic colloids is evidenced. The principles, apparatus and methodology involved are described and novel data reported for the minerals attapulgite, bentonite, hectorite, kaolinite, montmorillonite and vermiculite. Preliminary experiments using pulsed fields on vermiculite sols show that, in favourable circumstances, estimates of particle size can be made by analysing signal response rates.     

Brownian motion,Lp properties of Schrödinger operators and the localization of binding

We use Brownian motion ideas to study Schrödinger operators $\text{H =}\text{built?1}\text{2}\text{Δ + V}\text{on}\text{L}{}^{\mathrm{p}}\text{(R}{}^{\mathrm{v}}\text{)}$. In particular: (a) We prove that lim_t→∞t^?1In ∥ e^?tH ∥_p,p is p-independent for a very large class of V's where ∥ A ∥_p,p = norm of A as an operator from L^pto L^p. (b) For v ? 3 and $\text{V ? L}{}^{\mathrm{<mtext>v</mtext><mtext>2\; ?\; ?</mtext>}}\text{∩ L}{}^{\mathrm{<mtext>v</mtext><mtext>2\; +\; ?</mtext>}}$, we show that sup ∥ e^?tH ∥_∞,∞ < ∞ if and only if H has no negative eigenvalues or zero energy resonances. (c) We relate the “localization of binding” recently noted by Sigal to Brownian hitting probabilities.     

Synthesis of 1,2,4,6-thiatriazine 1,1-dioxides. Part III

Novel 1,2,4,6-thiatriazine 1, 1-dioxides substituted at either the 2 or 4 ring nitrogen atom have been prepared by cyclizing sulfamido-iso(thio)urea derivatives.     

Mean field upper bound on the transition temperature in multicomponent ferromagnets

Using local Ward identities and a new correlation inequality, we prove that the mean field transition temperature is an upper bound on the true transition temperature in multicomponent Heisenberg-type classical ferromagnets.Research partially supported by the NSF under Grant MCS-78-01885.     

Some Numerical Data for Single-Server Queues Involving Deterministic Input Arrangements

The steady-state parameters of the bulk input queue D _c /M/1 and the Erlang service queue D/E _c /1 have been tabulated for C = 1(1)6(2)12(4)20 and 25, 50 and 100 and for ρ = 0·1(0·1)0·9. The tabulation includes the mean waiting time, idle time and queue size. In addition the queue D/E _c /1 has been compared with the queue M/E _c /1 to indicate the gains to be achieved by regularizing the arrival mechanism for a given E _c service facility.     

Coupling constant thresholds in nonrelativistic quantum mechanics. I. Short-range two-body case

Consider ?Δ + λV with V short range at a value λ₀ where some eigenvalue e(λ) → 0 as λ ↓ λ₀. We analyze two questions: (i) What is the leading order of e(λ), i.e., for what α does e(λ) ～ c(λ ? λ₀)^α? (ii) Is e(λ) analytic at λ = λ₀ and, if not, what is the natural expansion parameter? The results are highly dimension dependent.