One-Quadrant Switched-Mode Power Converters

This article presents the main topics related to one-quadrant power converters. The basic topologies are analysed and a simple methodology to obtain the steady-state output-input voltage ratio is set out. A short discussion of different methods to control one-quadrant power converters is presented. Some of the reported derived topologies of one-quadrant power converters are also considered. Some topics related to one-quadrant power converters such as synchronous rectification, hard and soft commutation, and interleaved converters are discussed. Finally, a brief introduction to resonant converters is given.Comment: 25 pages, contribution to the 2014 CAS - CERN Accelerator School: Power Converters, Baden, Switzerland, 7-14 May 201

The synthesis and utilization of low molecular weight ozonides for air revitalization purposes

Synthesis and utilization of low molecular weight ozonides for air revitalizatio

The synthesis and utilization of low molecular weight ozonides for air revitalization purposes Interim report, 14 Aug. 1964 - 14 Oct. 1965

Synthesis and characterization of alkali and alkaline earth superoxides and ozonide

“The Earth Calculus”: Babbage, tables, and the calculating machine in the study of geology

Charles Babbage is best known as a pioneer of computer science, but his contributions to the study of the Earth are not as well known. A curious and tireless traveler, on one of his trips to Italy, he dwelt on the remains of the Temple of Serapis, located about one-hundred feet from the coast of the small bay near Pozzuoli, south-west of Naples. On his return to England, also using his Difference Engine, he developed a theory to explain the phenomena related to the area of Serapeo, accompanied by illustrations and mathematical calculations, aimed at explaining the geological phenomena that had helped to make the site so interesting. With the same precision used for his calculation engine, Babbage proposed innovative techniques for the printing of diagrams and tables to be used in earth sciences. Just as his calculation engine had to be reliable by helping to eliminate human error, so the innovative techniques proposed had to allow a representation of geology as a reliable scientific experience

ROLE OF EZH2 METHYLTRANSFERASE ACTIVITY IN THE MAINTENANCE OF MYC-DRIVEN B CELL LYMPHOMAS

The Polycomb group protein Ezh2 catalyzes the Histone H3 lysine-27 trimethylation (H3K27me3) within the Polycomb Repressive Complex 2 (PRC2). PRC2 exerts a critical control over the expression of a large set of target genes controlling important biological functions, including cell proliferation, differentiation and stem cell self-renewal. Aberrant Ezh2 function is commonly observed in several cancer types and is due to deregulated enzymatic activity and/or expression of the Polycomb protein. Studies in preclinical models have started to reveal the importance of Ezh2 in B cell lymphomagenesis. In contrast, little is known about the effects of Ezh2 deregulated function/constitutive expression in B cell tumor maintenance and progression. The present study addresses this issue taking advantage of a MYC-driven mouse lymphoma model, featuring high Ezh2 expression as a result of malignant B cell transformation. Conditional, genetic inactivation of Ezh2 methyltransferase activity in aggressive primary Burkitt-like mouse B cell lymphomas led to the identification of two classes of tumors, differentially responding to the loss of Polycomb function. In type-1 lymphomas, Ezh2 inactivation impaired clonal tumor growth starting from single lymphoma cells. Instead, type-2 lymphomas were largely resistant to the loss of Ezh2 catalytic function, giving rise to a substantial number of Ezh2 mutant clones. Transcriptome analyses allowed the identification of a molecular signature discriminating type-1 from type-2 lymphomas, including genes controlling cell cycle progression, DNA replication and cell survival, which were more expressed in type-2 tumors. These results correlated with a more aggressive behavior of type-2 lymphomas when transplantated into immunoproficient hosts. The growth of rare Ezh2 mutant subclones, established from type-1 lymphomas, was impaired by the treatment with an Ezh1/2 small molecule inhibitor, identifying the Ezh2 paralog, Ezh1, as a determinant of resistance of tumor cells to Ezh2 inactivation. Ezh2 inhibition led to genome wide loss of H3K27me3, which was comparable between lymphoma types. However, while the loss of H3K27me3 at target genes in type-1 lymphomas failed to alter their expression, in type-2 lymphomas Ezh2 targets were in most cases deregulated following the loss of the histone mark. Based on these results, we propose that Ezh2 mutant subclones from type-1 lymphomas select an H3K27me3-independent mechanism to ensure correct regulation of Ezh2 target genes, which is needed for tumor growth. We also find that residual H3K27me3 is deposited at the promoter of new genes by a non-canonical PRC2/Ezh1, in Ezh2 mutant subclones from type-1 lymphomas. This activity alters the expression of target genes contributing to tumor growth. We finally report the isolation of clonal variants from type-1 lymphomas that acquire secondary resistance to pharmacological Ezh1/2 inhibition. The latter tumors (together with type-2 lymphomas) will be instrumental to unravel the genetic bases of resistance of MYC-driven lymphomas to PRC2 inhibition. Anti-Ezh2 inhibitors are currently being tested in phase-1 and -2 clinical trials for the treatment of both solid and blood cancers including B cell lymphomas. Our studies highlight the importance of understanding in more detail the mechanisms of action of Ezh2/PRC2 in tumors, in order to identify those that may benefit from anti-Ezh2 therapies. Our results also provide evidence for mechanisms of lymphoma resistance to Ezh2 inhibition and suggest strategies to circumvent such resistance

A summary of research in auditory and visual discrimination

Thesis (Ed.M.)--Boston Universit

Pitfalls of counterfactual thinking in medical practice: preventing errors by using more functional reference points

Background. Counterfactual thinking involves mentally simulating alternatives to reality. The current article reviews literature pertaining to the relevance counterfactual thinking has for the quality of medical decision making. Although earlier counterfactual thought research concluded that counterfactuals have important benefits for the individual, there are reasons to believe that counterfactual thinking is also associated with dysfunctional consequences. Of particular focus is whether or not medical experience, and its influence on counterfactual thinking, actually informs or improves medical practice. It is hypothesized that relatively more probable decision alternatives, followed by undesirable outcomes and counterfactual thought responses, can be abandoned for relatively less probable decision alternatives.Design and Methods. Building on earlier research demonstrating that counterfactual thinking can impede memory and learning in a decision paradigm with undergraduate students, the current study examines the extent to which earlier findings can be generalized to practicing physicians (N=10). Participants were asked to complete 60 trials of a computerized Monty Hall Problem simulation. Learning by experience was operationalized as the frequency of switch-decisions.Results. Although some learning was evidenced by a general increase in switch-decision frequency across block trials, the extent of learning demonstrated was not ideal, nor practical.Conclusions. A simple, multiple-trial, decision paradigm demonstrated that doctors fail to learn basic decision-outcome associations through experience. An agenda for future research, which tests the functionality of reference points (other than counterfactual alternatives) for the purposes of medical decision making, is proposed