Impurity induced enhancement of perpendicular magnetic anisotropy in Fe/MgO tunnel junctions

Using first-principles calculations, we investigated the impact of chromium (Cr) and vanadium (V) impurities on the magnetic anisotropy and spin polarization in Fe/MgO magnetic tunnel junctions. It is demonstrated using layer resolved anisotropy calculation technique, that while the impurity near the interface has a drastic effect in decreasing the perpendicular magnetic anisotropy (PMA), its position within the bulk allows maintaining high surface PMA. Moreover, the effective magnetic anisotropy has a strong tendency to go from in-plane to out-of-plane character as a function of Cr and V concentration favoring out-of-plane magnetization direction for ~1.5 nm thick Fe layers at impurity concentrations above 20 %. At the same time, spin polarization is not affected and even enhanced in most situations favoring an increase of tunnel magnetoresistance (TMR) values.Comment: 6 pages, 3 figure

Anatomy of perpendicular magnetic anisotropy in Fe/MgO magnetic tunnel junctions: First principles insight

Using first-principles calculations, we elucidate microscopic mechanisms of perpendicular magnetic anisotropy (PMA)in Fe/MgO magnetic tunnel junctions through evaluation of orbital and layer resolved contributions into the total anisotropy value. It is demonstrated that the origin of the large PMA values is far beyond simply considering the hybridization between Fe-3d$and O-2p orbitals at the interface between the metal and the insulator. On-site projected analysis show that the anisotropy energy is not localized at the interface but it rather propagates into the bulk showing an attenuating oscillatory behavior which depends on orbital character of contributing states and interfacial conditions. Furthermore, it is found in most situations that states with$d_{yz(xz)}$and$d_{z^2}$character tend always to maintain the PMA while those with$d_{xy}$and$d_{x^2-y^2}$character tend to favor the in-plane anisotropy. It is also found that while MgO thickness has no influence on PMA, the calculated perpendicular magnetic anisotropy oscillates as a function of Fe thickness with a period of 2ML and reaches a maximum value of 3.6 mJ/m$^2$.Comment: 5 pages, 5 figure

Characterisation of the zinc fingers of Erythroid Kruppel-Like Factor

Gene expression is known to be regulated at the level of transcription. Recently, however, there has been a growing realisation of the importance of gene regulation at the post-transcriptional level, namely at the level of pre-mRNA processing (5’ capping, splicing and polyadenylation), nuclear export, mRNA localisation and translation. Erythroid krüppel-like factor (Eklf) is the founding member of the Krüppel-like factor (Klf) family of transcription factors and plays an important role in erythropoiesis. In addition to its nuclear presence, Eklf was recently found to localise to the cytoplasm and this observation prompted us to examine whether this protein has a role as an RNA-binding protein, in addition to its well-characterised DNA-binding function. In this thesis we demonstrate that Eklf displays RNA-binding activity in an in vitro and in vivo context through the use of its classical zinc finger (ZF) domains. Furthermore, using two independent in vitro assays, we show that Eklf has a preference for A and U RNA homoribopolymers. These results represent the first description of RNA-binding by a member of the Klf family. We developed a dominant negative mutant of Eklf by expressing its ZF region in murine erythroleukaemia (MEL) cells. We used this to investigate the importance of this protein in haematopoietic lineage decisions by examining its effect on the multipotent K562 cell line. We provide evidence that Eklf appears to be critical not only for the promotion of erythropoiesis, but also for the inhibition of megakaryopoiesis

Diferenças nas taxas de mortalidade por COVID-19 ao redor do mundo

Background: COVID-19 was declared pandemic on March 11. By April 18, over 150,000 people had died around the world. Here we compare mortality statistics due to COVID-19 worldwide, by adjusting for the size of the population and the stage of the pandemic. Methods: Data from the European Centre for Disease Control and Prevention, and Our World in Data websites were used. Analyses are based on number of deaths per one million inhabitants. In order to account for the stage of the pandemic, the baseline date was defined as the day in which the 10th death was reported. The analyses included 78 countries and territories which reported 10 or more deaths by April 9. Results: Mortality statistics varied remarkably worldwide. On day 10, India had 0.06 deaths per million, Belgium had 30.46 and San Marino 618.78. On day 20, India had 0.27 deaths per million, China had 0.71 and Spain 139.62. On day 30, four Asian countries had the lowest mortality figures, whereas eight European countries had the highest ones. In Italy and Spain, mortality on day 40 was greater than 250 per million, whereas in China and South Korea, mortality was below 4 per million.  Mortality on day 10 was moderately correlated with life expectancy (rho 0.53; P<0.001), but not with population density (rho 0.12; P=0.31). Conclusions: Asian countries presented much lower mortality figures as compared to European ones. Life expectancy was found to be correlated with mortality.  Introdução: A COVID-19 foi declarada uma pandemia em 11 de março. Até o dia 18 de abril, há haviam falecido mais de 150.000 pessoas ao redor do mundo. Neste artigo, são comparadas as estatísticas de mortalidade por COVID-19 no mundo, ajustando-se para o tamanho da população e para o estágio da pandemia em cada país. Métodos: Dados dos websites do Centro para o Controle e Prevenção de Doenças da Europa e do Our World in Data foram utilizados. As análises são baseadas no número de mortes por um milhão de habitantes. Para levar em consideração o estágio da pandemia, definiu-se como linha de base a data da décima morte em cada país. As análises incluíram 78 países e territórios com 10 ou mais mortes relatadas até o dia 09 de abril. Resultados: As taxas de mortalidade variaram consideravelmente ao redor do mundo.No dia 10, a Índia tinha 0,06 mortes por um milhão, a Bélgica tinha 30,46 e San Marino tinha 618,78. No dia 20, a Índia tinha 0,27 mortes por um milhão, a China 0,71 e a Espanha 139,62. No dia 30, quatro países da Ásia tinham as menores taxas de mortalidade, enquanto oito países europeus tinham as maiores. Na Itália e na Espanha, a mortalidade no dia 40 era maior do que 250 por um milhão, enquanto na China e na Coréia do Sul, era abaixo de 4 por um milhão. A mortalidade no dia 10 correlacionou-se moderadamente com a expectativa de vida (rho 0,53; P<0,001), mas não mostrou correlação com a densidade populacional (rho 0,12; P=0,31). Conclusões: Os países asiáticos apresentaram taxas de mortalidade muito menores do que aquelas observadas nos países europeus. A expectativa de vida correlacionou-se com a mortalidade

Safe sex practices: Identity style, sexual communication, and HIV/AIDS knowledge

The focus of this research was to gain a better understanding of the factors that potentially enhance safe sex practices, given the aggressive spread of sexually transmitted infections (STIs), including the human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS) namely in the adolescent population. Despite the substantial amount of research that has been done in this area, no findings seem substantive enough in nature to satisfactorily shape effective programs for the prevention of STIs, including HIV/AIDS. Two Ontarian Universities were sampled and a total of 264 students between the ages of 18 and 22 (inclusively) were subsequently included in the study. Respondents completed and returned the questionnaire measuring identity style, sexual practices, sexual communication and HIV/AIDS knowledge and beliefs. There are a few main reasons for concurrently including these four measures. First, identity formation is a major life task of adolescence—as important as the discovery of one\u27s sexuality and sexual experimentation. Since the literature suggests that identity developmental issues affect decisions to engage in sexually risk-taking behaviour, it is appropriate to examine these relationships. Second, sexual communication seems to emerge as a promising area for education around STIs and HIV/AIDS. Finally, knowledge and beliefs about HIV/AIDS is measured because without accurate knowledge of the mode of transmission of this deadly disease, sexual communication would seem ineffective. Given the salience of identity formation and sexuality, and the promising emergence of sexual communication (based in accurate HIV/AIDS knowledge) as a preventive tool to STIs, including HIV/AIDS, the relationship between identity style, sexual practices, sexual communication, and HIV/AIDS knowledge and beliefs were examined. High levels of sexual activity—unprotected sexual activity—were reported by both genders. Little to no relationship was found between sexual practices and the variables of identity style, sexual communication and HIV/AIDS knowledge. Age, however, emerged as an important determinant of safe sex, with younger individuals practicing safer sex. A negative relationship also emerged between sexual communication and safe sex practices. In addition getting oneself medically checked for STIs, including HIV/AIDS was related to lower rates of sexual protection, indicating that it is used as a safe sex mechanism. Implications of findings are discussed

Identification of a Potential Mitotic Function for the Mammalian Nup50

Mitosis is a conserved process in which the genetic material, DNA, is equally segregated between two daughter cells. DNA is contained in the nucleus of the eukaryotic cell and surrounded by the nuclear envelope. Multi protein complexes known as the Nuclear Pore Complexes (NPCs) embed within the nuclear envelope and regulate the transport of molecules in and out of the nucleus. Surprisingly, in Aspergillus nidulans, the model system used in my study, a nuclear pore complex protein Nup2 undergoes a unique translocation to chromatin during mitosis and is essential for proper mitotic progression. Interestingly, the Nup2 homolog in higher eukaryotes, Nup50, undergoes the same translocation. Therefore, the purpose of this study is to test whether Nup50 can translocate onto chromatin in Aspergillus nidulans and complement the mitotic function of Nup2. In order to test this hypothesis, the Nup50 gene was integrated into A. nidulans using homologous recombination. Four way fusion PCR was used to generate a DNA cassette that contains the Nup50 gene fused to EGFP2 marker and its expression under control of the inducible promoter alcA. Once Nup50 was introduced into A. nidulans, Nup2 was deleted in the background. So far, we have discovered that Nup50 is present in the nucleus at interphase and disperses throughout the cell during mitosis in the absence or presence of the Aspergillus nidulans Nup2. Results showed that Nup50 cannot complement Nup2’s function perhaps because it is not located at either the NPCs of mitotic chromatin. Furthermore, mmNup50 is a much smaller protein than Nup2 and it lacks a specific domain which is present in Nup2, termed domain 4. Domain 4 has been shown to be sufficient and necessary for Nup2’s location to the pore and DNA. This suggests that introducing domain 4 into mmNup50 might tether it to the pore at interphase and mitotic chromatin. We plan to create a version of Nup50 that carries domain 4 and replace the endogenous An-Nup2 with this version. We can then ask whether this version of Nup50 can complement Nup2’s function. This study may provide evidence that the novel essential mitotic function of the A. nidulans Nup2 is conserved in humans. Knowledge gained from these experiments might help us identify a potentially novel essential function of the mammalian Nucleoporin 50 in mitosis, which is important to understanding the initiation and progression of human diseases that can arise from defective mitosis such as cancer.A one-year embargo was granted for this item

Sexual consent in a gay, lesbian, and bisexual population: An exploratory study

Recently, researchers have begun to study how consent to sexual activity is negotiated between men and women in romantic relationships. Much of this research has focused on heterosexual relationships where factors affecting the process of consent include differential socialization between men and women. Consequently, the literature to date is arguably heterosexist in nature and evidently indirectly oppressive to individuals not identifying as heterosexual. Further, clinicians addressing issues of sexual consent have no literature to draw upon when working with gay males, lesbian women, or bisexual (GLB) individuals, potentially assuming heterosexist dynamics. Conducting research within a GLB population on sexual consent will not only render the sexual consent literature more inclusive, but also legitimize lifestyles other than heterosexual. This research therefore specifically explored sexual consent issues within a GLB sample and compare results to heterosexual males and females previously described in the literature. As such, 63 questionnaires were collected from GLB women and men (N = 63), including 32 lesbians, 25 gay males, 7 bisexual individuals, and 2 individuals who were questioning their sexuality. A number of measuring tools were used and include the sexual consent attitudes scale, the sexual consent behaviours scale, the tactic scale, token resistance, a relationship power scale, and a sex role scale (BSRI). Findings indicate that gay males and lesbian females did not differ on any aspect of sexual consent, suggesting that this population might be more homogenous as compared to reported sexual consent differences between heterosexual males and females. Implications are discussed

Band edge noise spectroscopy of a magnetic tunnel junction

We propose a conceptually new way to gather information on the electron bands of buried metal(semiconductor)/insulator interfaces. The bias dependence of low frequency noise in Fe$_{1-x}$V$_{x}$/MgO/Fe (0 $<$ x $<$ 0.25) tunnel junctions show clear anomalies at specific applied voltages, reflecting electron tunneling to the band edges of the magnetic electrodes. The change in magnitude of these noise anomalies with the magnetic state allows evaluating the degree of spin mixing between the spin polarized bands at the ferromagnet/insulator interface. Our results are in qualitative agreement with numerical calculations

Bruit des lasers dans la génération optique d'ondes submillimétriques pour la spectroscopie

National audienceLe photomélange de deux porteuses optiques sur une photodiode UTC peut fournir une source très accordable. Nous montrons la stabilisation de deux diodes fibrées sur un résonateur optique lui-même fibré, en polarisations orthogonales, avec une électronique dédiée pour contrôler le bruit de fréquence important. Avec les diodes choisies, la source millimétrique/submillimétrique est accordable de 0 à 500 GHz. Nous montrons la densité spectrale des battements de 2 à 92 GHz, correspondant à une excursion de fréquence quadratique moyenne de 100 kHz et une largeur de raie de 30 Hz. Nous montrons par des simulations des mesures peu perturbées par le bruit de phase en spectrométrie moléculaire entre 100 GHz et 1 THz de raies de largeur de 100 kHz, ordre de grandeur de la largeur Doppler de molécules de masse d’une centaine de g/mol lorsqu’elles sont à pression réduite