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A novel modulation technique is presented for an Isolated DC/AC multistage Converter, based on Pulsating DC Link principle. In this converter, the absence of a filter at the output of the first stage provides high reliability features, fast dynamic response and Zero Voltage Transitions (ZVT) of the secondary stage switches thanks to the zero voltage time intervals of the pulsating DC link. The proposed modulation techniques allows the use of two different switching frequencies for the two converter stages in such a way that each stage can be modulated with the best switching frequency to improve the efficiency, dynamic performances and converter size. Moreover, the modulation technique permits the optimization of the ratio between the switching frequencies of the two power stages which is fundamental to avoid that the pulsating DC link can compromise the Total Harmonic Distortion THD of the output voltage. An exhaustive description of the presented modulation logic is provided, highlighting the benefits due to the increase of the switching frequency of the first stage. The synchronization between the power stages is also used to guarantee the ZV commutations of the second stage, during the freewheeling phases of the first stage with consequent reduction of losses. Furthermore the effects of the predistortion of modulating signals on the distortion of output voltages are discussed and the simulations results are presented. The experimental results, obtained by the characterization of 20kW prototype, are presented and discussed to validate the features of the proposed modulation logic.

The serine/threonine kinase, GSK-3, is a promising drug discovery target for treating multiple pathological disorders. Most GSK-3 inhibitors that were developed function as ATP competitive inhibitors, with typical limitations in specificity, safety and drug-induced resistance. In contrast, substrate competitive inhibitors (SCIs), are considered highly selective, and more suitable for clinical practice. The development of SCIs has been largely neglected in the past because the ambiguous, undefined nature of the substrate-binding site makes them difficult to design. In this study, we used our previously described structural models of GSK-3 bound to SCI peptides, to design a pharmacophore model and to virtually screen the &ldquo, drug-like&rdquo, Zinc database (~6.3 million compounds). We identified leading hits that interact with critical binding elements in the GSK-3 substrate binding site and are chemically distinct from known GSK-3 inhibitors. Accordingly, novel GSK-3 SCI compounds were designed and synthesized with IC50 values of~1&ndash, 4 &mu, M. Biological activity of the SCI compound was confirmed in cells and in primary neurons that showed increased &beta, catenin levels and reduced tau phosphorylation in response to compound treatment. We have generated a new type of small molecule GSK-3 inhibitors and propose to use this strategy to further develop SCIs for other protein kinases.

In this paper we present the operation principle of a Metal Oxide Vacuum Field Effect Transistor (MOVFET). The idea is to exploit a technology proposed in the literature to realize nano devices with low threshold voltage for power applications. The principle of operation of the MOVFET is based on the emission of electrons from a cold cathode in a vacuum in such a way to obtain a pentode-like characteristics with a very low on resistance. This last feature is particularly interesting for the application as switches in power electronics applications. Moreover, the absence of a gate oxide which is always present in traditional MOSFETs suggests that this device can have better reliability features even in rad hard applications. A numerical simulator is used to evaluate the impact of the technological parameters on the static characteristics of the device and the perspective performances in power electronics applications.

An exhaustive analysis of the evolution of current in the input power stage of insulated multistage DC/AC power converter based on the Pulsating DC link principle, characterized by Zero Voltage Transition (ZVT) of the output stage, is provided in this work. This topology is featured by an input power stage which provides on the second stage a pulsed voltage characterized by zero phases (pulsating DC link) which are used to achieve the ZVT conditions for the commutations of this stage. The specific and innovative topology of this converter influences the evolution of the main electrical characteristics and requires more attention on the design. The parameters that affects the behavior of the current in this particular topology, especially in the crucial working phases, are identified and their influence are analyzed to define the constraints of this system. A complete study of the current has been accomplished by LTSPICE simulator for different combination of leakage parameters of the architecture and switching frequency of the two power stages. The obtained results are presented and discussed to provide the limits of the design of the main components that compose this particular power converter. For the experimental validation of the results of the simulation, a 3.5kW prototype of the power converter was assembled and tested at different load conditions.