The frequency, v, for O-D stretching in D2O films between the superimposed layers of different micas and montmorillonites was measured at several film thicknesses and temperatures of 2° and 25°C by infrared spectroscopy. The molar absorptivity, ε, for O-D stretching in HDO films between the montmorillonite layers was also measured at different film thicknesses and 25°C. It was found that v is related to mw/mm, the mass ratio of D2O to mica or montmorillonite, by the equation v = v0 exp β/(mwmm where v0 is the O-D stretching frequency in pure D2O and ß is a constant. Since mw/mm is proportional to a, the area under the absorption peak, mw/mm can be replaced by a in this equation. It was also found that ε decreased dramatically as the thickness of the water film between the montmorillonite layers decreased. These results were interpreted to mean that the structure of the interlayer water is perturbed by the interlayer cations and/or silicate surfaces.

Background: Efgartigimod, a human immunoglobulin G (IgG)1 antibody Fc fragment, blocks the neonatal Fc receptor, decreasing IgG recycling and reducing pathogenic IgG autoantibody levels. ADHERE assessed the efficacy and safety of efgartigimod PH20 subcutaneous (SC; co-formulated with recombinant human hyaluronidase PH20) in chronic inflammatory demyelinating polyneuropathy (CIDP). Methods: ADHERE enrolled participants with CIDP (treatment naive or on standard treatments withdrawn during run-in period) and consisted of open-label Stage A (efgartigimod PH20 SC once weekly [QW]), and randomized (1:1) Stage B (efgartigimod or placebo QW). Primary outcomes were clinical improvement (assessed with aINCAT, I-RODS, or mean grip strength; Stage A) and time to first aINCAT score deterioration (relapse; Stage B). Secondary outcomes included treatment-emergent adverse events (TEAEs) incidence. Results: 322 participants entered Stage A. 214 (66.5%) were considered responders, randomized, and treated in Stage B. Efgartigimod significantly reduced the risk of relapse (HR: 0.394; 95% CI: 0.25–0.61) versus placebo (p=0.000039). Reduced risk of relapse occurred in participants receiving corticosteroids, intravenous or SC immunoglobulin, or no treatment before study entry. Most TEAEs were mild to moderate; 3 deaths occurred, none related to efgartigimod. Conclusions: Participants treated with efgartigimod PH20 SC maintained a clinical response and remained relapse-free longer than those treated with placebo.

The prevailing concept that positive-edge to negative-face attraction accounts for the rheological behavior of montmorillonite suspensions at low electrolyte concentration was investigated. In one experiment, Mg2+ released from Na-montmorillonite was measured at several NaCl concentrations; in a second experiment, the viscosity, η, and the extrapolated shear stress, θ, were measured at several clay concentrations, pHs, and NaCl concentrations; and in a third experiment, the absorbance, A, was measured at two wavelengths (450 and 760 nm) at different clay and electrolyte concentrations. The released Mg2+ decreased with increasing NaCl concentration until it became zero at a NaCl concentration between 0.01 and 0.02 M, depending on pH. Thereafter, it increased with increasing NaCl concentration. Both θ and η were highly correlated with the amount of released Mg2+. Also, A remained constant until the NaCl concentration corresponded to that at the minimum of θ. Thereafter, it increased and became linearly related to θ. These results suggest: (1) positive-edge to negative-face interaction cannot solely account for the rheological properties of montmorillonite at low electrolyte concentration, and (2) the release of octahedral Mg2+ from montmorillonite affects θ, because it reduces the negative charge on the particles and, thereby, the repulsive force between them.

The specific surface area, S, of a clay is commonly measured by the adsorption of ethylene glycol monoethyl ether (EGME); however, this method can be tedious and time consuming, especially if the clay is saturated with a monovalent, highly hydrated cation. An alternative method for measuring S was developed involving infrared internal reflectance spectroscopy. This method is based on the discovery that the ratio of R1, the reflectance of a clay-HOD mixture at the frequency of O-D stretching, to R2, the reflectance of the mixture at the frequency of H-O-D bending, is linearly related to S. The correlation coefficient between R1/R2 and S, as measured by the adsorption of EGME, was 0.995. Consequently, a calibration curve of R1/R2 versus S was constructed, and the measured values of R1/R2 for any clay-HOD mixture were referred to it for the determination of S. Results were obtained in triplicate in about an hour; hence, this method of determining S is more rapid and convenient than that involving the adsorption of EGME. Moreover, it applies to clays in a natural condition, i.e., swollen in water.