Evidence for Mn clustering in dilute CuMn alloys from high-field (40 T) magnetization curves at 4.2 K

Magnetization curves of CuMn alloys with Mn concentration between 1.5 and 10 at.% have been measured at 4.2 K in fields up to 40 T, using a pulsed-field method.The results found for different concentrations can be scaled upon one another, which is a clear indication for the occurance of magnetic clusters. Analysis of this universal curve in terms of Brillouin functions yields the values $\text{z}{}_{\mathrm{I}}\text{J}{}_{\mathrm{I}}\text{/k??44K}$, $\text{z}{}_{\mathrm{II}}\text{J}{}_{\mathrm{II}}\text{/k??10K}$ and $\text{z}{}_{\mathrm{III}}\text{J}{}_{\mathrm{III}}\text{/k??0.5K}$, for the largest three interactions within each cluster.     

Stereochemistry of protonation and mercuration of trisubstituted double bond during cyclization of isoprenoids

Conclusions Initiation of the reaction for the cyclization of isoprenoids by acids proceeds as a nonstereospecific process at the 2,3 bond, while when this reaction is initiated by mercury salts it proceeds as a stereospecific reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1151–1153, May, 1973.     

Stereospecific addition of sulfur-containing electrophiles to a trisubstituted double bond

Conclusions On the example of the reaction for the cylization of the D₃-analog of geranic ester under the influence of sulfur-containing reagents it was shown that the addition of these reagents to a trisubstituted double bond is stereospecific.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1349–1351, June, 1973.     

Kalman filter applied to setpoint control in continuous titrations

A state-space model is described for continuous titrations based on first-order dynamics. The Kalman filter allows on-line monitoring of an empirically established setpoint in the titration curve. The algorithm advocated is examined for potentiometric titrations of ca. 10^?3 M solutins of acids, silver(I) and copper(II). Only gross indications of the essential parameters such as the time constant and noise covariances are required. The computer-controlled titration system is compared with a conventional setpoint titrator. Especially in cases of slow response times and steep inflections, there are advantages in both accuracy and speed when the Kalman filter is applied.     

A coarse-graining approach for the proton complex in protonated aluminosilicates

We have developed a computational framework for the adsorption of linear alkanes in protonated aluminosilicates. These zeolites contain trace amounts of water that form hydrated proton complexes. The presence of hydrated protons makes the simulations at the fully atomistic level difficult. Instead of constructing an elaborate and complex model, we show that an approach based on a coarse-graining of the proton-complex accurately describes the available experimental isotherms, Henry coefficients, heats of adsorption, and oxygen-proton distances. Our approach is supported by MP2 quantum mechanical simulations. The model gives remarkably good agreement with experimental data beyond the initial calibration set.     

Influence of a TiCl4 post-treatment on nanocrystalline TiO2 films in dye-sensitized solar cells

In this study, the influence of the TiCl(4) post-treatment on nanocrystalline TiO(2) films as electrodes in dye-sensitized solar cells is investigated and compared to nontreated films. As a result of this post-treatment cell efficiencies are improved, due to higher photocurrents. On a microscopic scale TiO(2) particle growth on the order of 1 nm is observed. Despite a corresponding decrease of BET surface area, more dye is adsorbed onto the oxide surface. Although it seems trivial to match this finding with the improved photocurrent, this performance improvement cannot be attributed to higher dye adsorption only. This follows from comparison between incident photon to current conversion efficiency (IPCE) and light absorption characteristics. Since the charge transport properties of the TiO(2) films are already more than sufficient without treatment, the increase in short circuit current density J(SC) cannot be related to improvements in charge transport either. Transient photocurrent measurements indicate a shift in the conduction band edge of the TiO(2) upon TiCl(4) treatment. It is concluded that the main contribution to enhanced current originates from this shift in conduction band edge, resulting in improved charge injection into the TiO(2).