Comparison of Hysteresis Based PWM Schemes ΔΣ-PWM and Direct Torque Control

This paper presents the differences and similarities of ΔΣ-PWM as a hysteresis-based PWM scheme with direct torque control (DTC) using simulation models. The variable switching frequency caused by the hysteresis element is examined with regard to its instantaneous values. The comparison is based on an equal maximum switching frequency as a design criterion. With this first assumption, the variation of the instantaneous switching frequency is higher when using DTC because of the temporary prioritization of one inverter leg. Besides the lower variation, ΔΣ-PWM shows a higher average switching frequency. Because the switching frequency is related to the torque ripple, the usage of ΔΣ-PWM results in a smaller torque ripple. Due to the dependence of torque ripple on switching frequency, a second comparison is carried out based on the same average switching frequency. In this comparison the ΔΣ-PWM shows higher torque ripple than DTC

Impact of Nano- and Micro-Sized Chromium(III) Particles on Cytotoxicity and Gene Expression Profiles Related to Genomic Stability in Human Keratinocytes and Alveolar Epithelial Cells

Exposure to Cr(VI) compounds has been consistently associated with genotoxicity and carcinogenicity, whereas Cr(III) is far less toxic, due to its poor cellular uptake. However, contradictory results have been published in relation to particulate Cr$_2$O_3$. The aim of the present study was to investigate whether Cr(III) particles exerted properties comparable to water soluble Cr(III) or to Cr(VI), including two nano-sized and one micro-sized particles. The morphology and size distribution were determined by TEM, while the oxidation state was analyzed by XPS. Chromium release was quantified via AAS, and colorimetrically differentiated between Cr(VI) and Cr(III). Furthermore, the toxicological fingerprints of the Cr$_2$O_3$ particles were established using high-throughput RT-qPCR and then compared to water-soluble Cr(VI) and Cr(III) in A549 and HaCaT cells. Regarding the Cr$_2$O_3$ particles, two out of three exerted only minor or no toxicity, and the gene expression profiles were comparable to Cr(III). However, one particle under investigation released considerable amounts of Cr(VI), and also resembled the toxicity profiles of Cr(VI); this was also evident in the altered gene expression related to DNA damage signaling, oxidative stress response, inflammation, and cell death pathways. Even though the highest toxicity was found in the case of the smallest particle, size did not appear to be the decisive parameter, but rather the purity of the Cr(III) particles with respect to Cr(VI) content

Stadt.Geschichte.Basel: Gesamtkonzept für eine neue Basler Stadtgeschichte

Die neue, fundierte Gesamtdarstellung ist ein Kompass für alle, die Basel tagtäglich beleben und mitgestalten – als Einwohnerin und Pendler, als Arbeitnehmer und Unternehmerin, als Fasnächtler, Durchreisende oder Rheinschwimmerin. Die Stadt.Geschichte.Basel schliesst eine Lücke für die vielen Geschichtsinteressierten und Mitglieder der historischen Vereinigungen, für Lehrerinnen, Kulturschaffende und Politiker. Und sie ist ein unentbehrliches Arbeitsinstrument für alle, die sich genauer mit der Stadt und ihrer Vergangenheit befassen und ihr Wissen weitergeben wollen: für Frauen und Männer in Archiven, Museen, Bibliotheken und Universitäten