The Atlas power-flow system-a status report

Atlas is a high-energy, pulsed-power facility under development to study materials properties and hydrodynamics under extreme conditions. Atlas will implode heavy liner loads (m ~ 45 gm) with a peak current of 27-32 MA delivered in 4 μs, and it is energized by 96, 240-kV Marx generators storing a total of 23 MJ. The power-flow system transports current from the Marx generators to the load. It includes a load protection switch to protect the load in case of a prefire; 24 oil-insulated, vertically oriented, radially converging, triplate transmission lines; a transition region that couples the transmission lines to the power-flow channel; and a radially converging, dielectric-insulated, horizontal and conical, power-flow channel. Proposed experiments, the design of the power-flow system, test results, and status are presented     

Functional rearrangement of 3-Cl or 3,3-diCl-γ-lactams bearing a secondary 1-chloroalkyl substituent at C-4

The study of the reaction with MeONa/MeOH of chlorinated γ-lactams, prepared from the atom transfer radical cyclization of N-allyl-α-perchloroamides, has been extended to the case of substrates carrying an exo halogen atom on a branched carbon. Only with secondary exo C-Cl groups, that are not located on a fused ring, does the functional rearrangement follow the typical transformation route, which with trichloro-lactams can proceed further to give 4-alkylidene derivatives. From a practical point of view, the outcome of the reaction with di- or trichloro N-cinnamylamides is synthetically valuable, affording the 5-methoxy-1H-pyrrol-2(5H)-one or 3-benzylidenepyrrolidine-2,5-dione, respectively, in good to excellent yield.     

Cyclisation of dienes using phosphorus-centred radicals to form organophosphorus adducts

Reaction of various dienes with phosphites or related phosphorus hydrides, under free radical cyclisation conditions, affords cyclic organophosphorus adducts. This quick, mild and technically clean approach affords 5- and 6-ring carbocycles and heterocycles in good to excellent yield.     

Characterizing Pressure‐Induced Uranium CH Agostic Bonds

The diuranium(III) compound [UN′′₂]₂(μ‐η⁶:η⁶‐C₆H₆) (N′′=N(SiMe₃)₂) has been studied using variable, high‐pressure single‐crystal X‐ray crystallography, and density functional theory . In this compound, the low‐coordinate metal cations are coupled through π‐ and δ‐symmetric arene overlap and show close metal? CH contacts with the flexible methyl CH groups of the sterically encumbered amido ligands. The metal–metal separation decreases with increasing pressure, but the most significant structural changes are to the close contacts between ligand CH bonds and the U centers. Although the interatomic distances are suggestive of agostic‐type interactions between the U and ligand peripheral CH groups, QTAIM (quantum theory of atoms‐in‐molecules) computational analysis suggests that there is no such interaction at ambient pressure. However, QTAIM and NBO analyses indicate that the interaction becomes agostic at 3.2 GPa.     

Measurements and theoretical interpretation of points of zero charge/potential of BSA protein

The points of zero charge/potential of proteins depend not only on pH but also on how they are measured. They depend also on background salt solution type and concentration. The protein isoelectric point (IEP) is determined by electrokinetical measurements, whereas the isoionic point (IIP) is determined by potentiometric titrations. Here we use potentiometric titration and zeta potential (ζ) measurements at different NaCl concentrations to study systematically the effect of ionic strength on the IEP and IIP of bovine serum albumin (BSA) aqueous solutions. It is found that high ionic strengths produce a shift of both points toward lower (IEP) and higher (IIP) pH values. This result was already reported more than 60 years ago. At that time, the only available theory was the purely electrostatic Debye-Hu?ckel theory. It was not able to predict the opposite trends of IIP and IEP with ionic strength increase. Here, we extend that theory to admit both electrostatic and nonelectrostatic (NES) dispersion interactions. The use of a modified Poisson-Boltzmann equation for a simple model system (a charge regulated spherical colloidal particle in NaCl salt solutions), that includes these ion specific interactions, allows us to explain the opposite trends observed for isoelectric point (zero zeta potential) and isoionic point (zero protein charge) of BSA. At higher concentrations, an excess of the anion (with stronger NES interactions than the cation) is adsorbed at the surface due to an attractive ionic NES potential. This makes the potential relatively more negative. Consequently, the IEP is pushed toward lower pH. But the charge regulation condition means that the surface charge becomes relatively more positive as the surface potential becomes more negative. Consequently, the IIP (measuring charge) shifts toward higher pH as concentration increases, in the opposite direction from the IEP (measuring potential).     

Papieruntersuchung

Analytical and Bioanalytical Chemistry -     

Das Vorkommen von Aconits?ure im Zuckerrohrsaft und Colonialzucker

Ohne Zusammenfassung     

Eine Methode der Pflanzenanalyse

Ohne Zusammenfassung