Organometallic neptunium(III) complexes

Studies of transuranic organometallic complexes provide a particularly valuable insight into covalent contributions to the metal–ligand bonding, in which the subtle differences between the transuranium actinide ions and their lighter lanthanide counterparts are of fundamental importance for the effective remediation of nuclear waste. Unlike the organometallic chemistry of uranium, which has focused strongly on UIII and has seen some spectacular advances, that of the transuranics is significantly technically more challenging and has remained dormant. In the case of neptunium, it is limited mainly to NpIV. Here we report the synthesis of three new NpIII organometallic compounds and the characterization of their molecular and electronic structures. These studies suggest that NpIII complexes could act as single-molecule magnets, and that the lower oxidation state of NpII is chemically accessible. In comparison with lanthanide analogues, significant d- and f-electron contributions to key NpIII orbitals are observed, which shows that fundamental neptunium organometallic chemistry can provide new insights into the behaviour of f-elements

Brief Optogenetic Inhibition of Dopamine Neurons Mimics Endogenous Negative Reward Prediction Errors

Correlative studies have strongly linked phasic changes in dopamine activity with reward prediction error signaling. But causal evidence that these brief changes in firing actually serve as error signals to drive associative learning is more tenuous. While there is direct evidence that brief increases can substitute for positive prediction errors, there is no comparable evidence that similarly brief pauses can substitute for negative prediction errors. Lacking such evidence, the effect of increases in firing could reflect novelty or salience, variables also correlated with dopamine activity. Here we provide such evidence, showing in a modified Pavlovian over-expectation task that brief pauses in the firing of dopamine neurons in rat ventral tegmental area at the time of reward are sufficient to mimic the effects of endogenous negative prediction errors. These results support the proposal that brief changes in the firing of dopamine neurons serve as full-fledged bidirectional prediction error signals

Power Quality Enhancement Using VSI Based STATCOM for SEIG Feeding Non Linear Loads

This paper deals with the performance analysis of static compensator (STATCOM) based voltage regulator for self- excited induction generators (SEIGs) feeding non-linear single phase loads. The presence of non-linear loads in some applications injects harmonics into the generating system. Because an SEIG is a weak isolated system, these harmonics have a great effect on its performance. Additionally, SEIGrsquos offer poor voltage regulation and require an adjustable reactive power source to maintain a constant terminal voltage under a varying load. A three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC-VSI) known as STATCOM is used for harmonic elimination. It also provides the required reactive power an SEIG needs to maintain a constant terminal voltage under varying loads. A dynamic model of an SEIG-STATCOM system with the ability to compensate the unbalanced current caused by single-phase loads that are connected across the two terminals of the three-phase SEIGnbsp undernbsp varying loadsnbsp has been analyzed by using D-Q frame theory algorithm. This enables us to predict the behavior of the system under transient conditions. The simulated results shows that by using a STATCOM based voltage regulator the SEIG can balance the current in addition to that the STATCOM is able to regulate the terminal voltage of the generator and suppresses the harmonic currents injected by non- linear loads