Current-perpendicular-to-plane giant magnetoresistance of a spin valve using Co2MnSi Heusler alloy electrodes

We report the current-perpendicular-to-plane giant magnetoresistance of a spin valve with Co2MnSi (CMS) Heusler alloy ferromagnetic electrodes. A multilayer stack of Cr/Ag/Cr/CMS/Cu/CMS/Fe25Co75/Ir28Mn72/Ru was deposited on a MgO (001) single crystal substrate. The bottom CMS layer was epitaxially grown on the Cr/Ag/Cr buffer layers and was ordered to the L21 structure after annealing at 673 K. The upper CMS layer was found to grow epitaxially on the Cu spacer layer despite the large lattice mismatch between Cu and CMS. The highest MR ratios of 8.6% and 30.7% for CPP-GMR were recorded at room temperature and 6 K, respectively. The high spin polarization of the epitaxial CMS layers is the most likely origin of the high MR ratio.Comment: 14 pages, 3 figures, presented at the 53rd Annual Conference on Magnetism and Magnetic Materials, to be published in J. Appl. Phy

Real-space observation of current-driven domain wall motion in submicron magnetic wires

Spintronic devices, whose operation is based on the motion of a magnetic domain wall (DW), have been proposed recently. If a DW could be driven directly by flowing an electric current instead of a magnetic field, the performance and functions of such device would be drastically improved. Here we report real-space observation of the current-driven DW motion by using a well-defined single DW in a micro-fabricated magnetic wire with submicron width. Magnetic force microscopy (MFM) visualizes that a single DW introduced in the wire is displaced back and forth by positive and negative pulsed-current, respectively. We can control the DW position in the wire by tuning the intensity, the duration and the polarity of the pulsed-current. It is, thus, demonstrated that spintronic device operation by the current-driven DW motion is possible.Comment: Accepted and published in PR

Extracellular Electron Transfer: Respiratory or Nutrient Homeostasis?

Exoelectrogens are able to transfer electrons extracellularly, enabling them to respire on insoluble terminal electron acceptors. Extensively studied exoelectrogens, such as Geobacter sulfurreducens and Shewanella oneidensis, are Gram negative. More recently, it has been reported that Gram-positive bacteria, such as Listeria monocytogenes and Enterococcus faecalis, also exhibit the ability to transfer electrons extracellularly, although it is still unclear whether this has a function in respiration or in redox control of the environment, for instance, by reducing ferric iron for iron uptake. In this issue of Journal of Bacteriology, Hederstedt and colleagues report on experiments that directly compare extracellular electron transfer (EET) pathways for ferric iron reduction and respiration and find a clear difference (L. Hederstedt, L. Gorton, and G. Pankratova, J Bacteriol 202:e00725-19, 2020, https://doi.org/10.1128/JB.00725-19), providing further insights and new questions into the function and metabolic pathways of EET in Gram-positive bacteria

Variabilidade genética de Xanthomonas axonopodis pv. passiflorae

A mancha bacteriana, causada por Xanthomonas axonopodis pv. passiflorae, é uma das mais importantes doenças do maracujazeiro, podendo limitar a produção dessa frutífera em algumas regiões do País. O uso de resistência genética e controle químico, juntamente com o emprego de medidas de exclusão, são as práticas de controle da doença mais recomendadas. Para o desenvolvimento de variedades resistentes é necessário conhecer tanto a variabilidade genética do hospedeiro quanto do patógeno. Nesse trabalho foi estudada a variabilidade de cinqüenta isolados patogênicos de Xanthomonas axonopodis pv. passiflorae, coletados em quatro diferentes locais no estado de São Paulo. No estudo da variabilidade genética foram usados dados de marcadores moleculares RAPD (Random Amplified Polymorphic DNA), os quais foram usados para o cálculo do coeficiente de similaridade de Dice entre os isolados, análise de variância molecular (AMOVA) entre e dentro das populações e agrupamento dos isolados pelo método UPGMA. Para análise da agressividade foram usados cinco isolados, mais divergentes, baseado no dendrograma. O coeficiente de similaridade variou entre 0,6887 e 0,9688. Na análise de agrupamento, os isolados foram separados em sete grupos e não houve relação evidente entre local de coleta com a composição dos grupos. Na análise da variância molecular (AMOVA) verificou-se que a maior parte da variabilidade genética está dentro das populações (89,4%) e apenas 10,6%, entre populações. Os resultados da análise de agrupamento e da AMOVA indicam que existe grande fluxo gênico entre isolados bacterianos nas regiões analisadas. No teste de patogenicidade verificou-se diferença significativa de agressividade entre os isolados. Os resultados demonstram a importância do conhecimento da variabilidade genética e da agressividade na seleção dos isolados para serem utilizados em testes de resistência genética no desenvolvimento de variedades resistentes.The bacterial spot, caused by Xanthomonas axonopodis pv. passiflorae , is one of the most important diseases of passion fruit, which can drastically limit the production in some regions of Brazil. The use of genetic resistance, chemical control and the adoption of exclusion measures are the more recommended practices for the control of this disease. To produce the resistant varieties knowledge about the variability of both host and pathogen is needed. In this study, we investigated the variability of 50 pathogenic isolates of X. axonopodis pv. passiflorae, collected from four production areas in São Paulo State. We used RAPD markers (Random Amplified Polymorphic DNA) for identification of the degree of genetic similarities through dice coefficient, analysis of molecular variance (AMOVA), among as well as within populations and clustering by the UPGMA method. Based on the clustering, the five more divergent isolates were selected for agressiveness trials. The similarity coefficient ranged from 0.6887 to 0.9688. Clustering analysis grouped the isolates in seven categories and neither apparent correlation was identified among their geographical origin no clustering pattern. The AMOVA data showed that the variability within and among populations were 89.4% and 10.6% respectively. The clustering analysis indicated genic flow among the different production areas. The results highlights the importance of taking into consideration the bacterial genetic variability of this bacterium as well as its agressiveness during the selection of resistant varieties

Photon-Working SwitchesProperties and Applications of Indolinooxazolidines as Photo-, Electro-, and Acidochromic Units

The aim of this chapter was to introduce the readers to indolinooxazolidines (IndOxa), a new family of molecular switches. First, in a short historical account their evolution is followed from their first appearance in the 1970s until today. The second section concentrates on the general structural features of the indolinooxazolidine motif, which are closely related to those of the spiropyrans. In the core of their chemistry lies the oxazolidine ring opening that is discussed in the following. Owing to the facility of the very same ring opening, they show chromophoric properties and can be addressed using different stimuli, such as light irradiation, change in electrical potential and pH. For this reason, the last three sections are devoted to provide a general understanding on their photo-, electro-, and acidochromic properties