Magnetic properties of the iron sublattice in the YFe12-xMx compounds (M = Ti, Mo or V; x = 1-3.5)

International audienceThe magnetic properties of the YFe12-xMx compounds (M = Ti, Mo or V; x = 1-3.5) have been determined in the ordered ferromagnetic state as well as in the paramagnetic state. The iron magnetic moment has been determined from 4 K up to the Curie temperature whereas the analysis of the paramagnetic region has led to the determination of the effective iron magnetic moment. The number of spins has been calculated below and above the Curie temperature in order to discuss the degree of itinerancy of the Fe magnetic behavior in the YFe12-xMx compounds. All the YFe12-xMx compounds (M = Ti, Mo or V; x = 1-3.5) have very similar crystalline properties: they crystallize in the same crystal structure and all the M elements used here are known to substitute for iron on the same crystal site. In contrast, they exhibit a wide range of magnetic behavior; the Curie temperature varies from 63 to 539 K and the mean magnetic moment per iron atom is also very dependent upon the M element used and its concentration. Furthermore the degree of itinerancy of the iron is not preserved along YFe12-xMx compounds but is found to depend significantly upon the nature of the substituting element M and its concentration. The results are discussed and compared to earlier published results obtained on binary R-Fe and ternary R-Fe-B compounds

Enhanced iron magnetic moment in the ThFe11C2 intermetallic compound

International audienceDetailed theoretical investigations on the electronic and magnetic properties of the ThFe11C2 compound have been performed using both the linear muffin-tin orbital and Korringa-Kohn-Rostocker methods of band structure calculation. The structure of the ThFe11C2 compound has three inequivalent iron sites with different local environment. A strongly enhanced magnetic moment is observed on certain Fe positions, coexisting with much lower magnetic moments on other iron positions of the lattice. Band structure calculations indeed show that the Fe magnetic moments depend strongly on the local environment. The average Fe magnetic moment obtained from these calculations is in good agreement with the experimental average Fe moment obtained from magnetization measurements. The orbital contribution to the magnetic moment is found to be especially large on the Fe 4b position. Comparing calculated hyperfine fields with experimental results, it is found that the calculated and experimental hyperfine fields are correlated. However, similarly to the results reported before for elemental Fe, the magnitude of all calculated Fe hyperfine fields is about 25% smaller. The agreement with the Mössbauer measurements is improved by scaling the core polarization contribution and by estimating the orbital valence d-electrons contribution to the magnetic hyperfine fields using the local spin density approximation + dynamical mean field theory calculated orbital moments

Traitement de texte et stratégies rédactionnelles

The objective of this experimental observation is to show how the use of a standard word processor changes the writing strategies devised by advanced users during the production of short texts. Empirical research has indicated that word processors, in fact, have a negative impact on writing strategies. Analysis of the conditions under which "man-machine" dialogue takes place, has shown that screen size and linear management both have an effect on writing. Before determining the ways in which a word processor can disrupt common writing practices, we must gain a better understanding of how a text is actually composed in real time, with or without a computer. Although the various writing processes have been clearly identified, the functional scenario describing the succession of writing phases and accompagnying activities is still poorly defined. The marks produced by writers on paper, whether linguistic (words, sentence fragments, sentences) or non-linguistic (arrows, underlining, indexation, diagrams, etc.), reflect the planning, translating, and revising processes being carried out by the writer. Sharples and Pemberton (1990) describe the exact functions of these marks in the elaboration of the ideas to be translated into text form (levels of organization). However, more knowledge about their frequency of use at the different stages of text composition is required. This is one of the goals of the present experimental observation. For the most part, such marks cannot be displayed and manipulated on the screen of a standard word processor as they can on paper. It is therefore crucial that we observe the means employed by writers to adapt their use of these necessary devices to word processing. The main results indicate that writers who use a word processor still resort to "pencil and paper" for the initial planning. The small amount of text preparation done by computer users (manifested by chronological and hierarchical organization marks) compared to writers who produce without a word processor is compensated by extensive revision on the screen. However, while writing strategies are highly dependent on production conditions, the quality of the texts produced does not vary significantly. The possibility of eliminating one of the important drawbacks of computer-assisted writing i. e. the fact that the information must be displayed linearly on the screen, is currently being studied by designers of planning aids that accompagny word processors. Before such aids can actually be developed, however, more knowledge is needed of the phases of writing and the marks used by writers throughout the production process

Origin of the metamagnetic transitions in Y1-xErxFe2(H,D)4.2 compounds

The structural and magnetic properties of Y1-xErxFe2 intermetallic compounds and their hydrides and deuterides Y1-xErxFe2H(D)4.2 have been investigated using X-ray diffraction and magnetic measurements under static and pulsed magnetic field up to 60 T. The intermetallics crystallize in the C15 cubic structure , whereas corresponding hydrides and deuterides crystallize in a monoclinic structure. All compounds display a linear decrease of the unit cell volume versus Er concentration; the hydrides have a 0.8% larger cell volume compared to the deuterides with same Er content. They are ferrimagnetic at low field and temperature with a compensation point at x = 0.33 for the intermetallics and x = 0.57 for the hydrides and deuterides. A sharp first order ferromagnetic-antiferromagnetic (FM-AFM) transition is observed upon heating at TFM-AFM for both hydrides and deuterides. These compounds show two different types of field induced transitions, which have different physical origin. At low temperature (T < 50 K), a forced ferri-ferromagnetic metamagnetic transition with Btrans1 = 8 T, related to the change of the Er moments orientation from antiparallel to parallel Fe moment, is observed. Btrans1 is not sensitive to Er concentration, temperature and isotope effect. A second metamagnetic transition resulting from antiferromagnetic to ferrimagnetic state is also observed. The transition field Btrans2 increases linearly versus temperature and relates to the itinerant electron metamagnetic behavior of the Fe sublattice. An onset temperature TM0 is obtained by extrapolating TFM-AFM (B) at zero field. TM0 decreases linearly versus the Er content and is 45(5) K higher for the hydrides compared to the corresponding deuteride. The evolution of TM0 versus cell volume shows that it cannot be attributed exclusively to a pure volume effect and that electronic effects should also be considered.Comment: 22 pages, 10 figure

USING THE INTERNET IN THE ACTIVITIES OF ENVIRONMENTAL SCANNING IN SMALL AND MEDIUM ENTERPRISES DOI:10.5773/rai.v1i1.526

Este artigo tem como proposta compreender a importância da sistematização do monitoramento ambiental em PMEs (pequenas e médias empresas), considerando que o entendimento de como as empresas buscam e utilizam informações da Internet é de grande relevância para esse processo, mantendo-as mais competitivas no seu mercado. Foi realizada uma revisão bibliográfica sobre monitoramento ambiental, avaliando que vários modelos genéricos são descritos na literatura, apesar de que muitos não direcionam seus esforços para empresas de pequeno ou médio porte. A metodologia utilizada foi descritiva com estudo de caso único, de forma a apresentar os procedimentos realizados por uma empresa ao utilizar dados da Internet em seu monitoramento ambiental, comparando a prática utilizada com as etapas do modelo descrito na literatura. Os resultados demonstraram que a Internet é utilizada como uma importante fonte para o monitoramento ambiental dessa empresa, mas a busca por informações on-line ocorre sem sistematização, intuitivamente e de forma reativa. Este artigo contribui para que PMEs vislumbrem a importância de monitorar o ambiente e passem a adotar um modelo formal que sistematize a obtenção e o uso da informação on-line, tornando-as mais estratégicas para o seu negócio.This article aims to understand the importance of systematic environmental scanning in SMEs (small and medium enterprises), whereas the understanding of how companies seek and use information from the Internet is of great relevance to this process, keeping them more competitive in their market. For this was a literature review of environmental scanning, evaluating that several generic models are described in the literature, although many don’t direct their efforts for small and medium enterprises. The methodology used was a descriptive single case study to present the procedures performed by a company that uses data from the Internet in its environmental scanning, comparing the practice used with the steps of the model described in the literature. The results showed that the Internet is used as an important source for environmental scanning of this company, but the search for on-line information happens without systematic, intuitively and reactively. This article contributes to help SMEs to perceive the importance of scanning the environment and begin to adopt a formal model that systematizes the search and use of on-line information, making them more strategic to their business

USING THE INTERNET IN THE ACTIVITIES OF ENVIRONMENTAL SCANNING IN SMALL AND MEDIUM ENTERPRISES DOI:10.5773/rai.v1i1.526

Este artigo tem como proposta compreender a importância da sistematização do monitoramento ambiental em PMEs (pequenas e médias empresas), considerando que o entendimento de como as empresas buscam e utilizam informações da Internet é de grande relevância para esse processo, mantendo-as mais competitivas no seu mercado. Foi realizada uma revisão bibliográfica sobre monitoramento ambiental, avaliando que vários modelos genéricos são descritos na literatura, apesar de que muitos não direcionam seus esforços para empresas de pequeno ou médio porte. A metodologia utilizada foi descritiva com estudo de caso único, de forma a apresentar os procedimentos realizados por uma empresa ao utilizar dados da Internet em seu monitoramento ambiental, comparando a prática utilizada com as etapas do modelo descrito na literatura. Os resultados demonstraram que a Internet é utilizada como uma importante fonte para o monitoramento ambiental dessa empresa, mas a busca por informações on-line ocorre sem sistematização, intuitivamente e de forma reativa. Este artigo contribui para que PMEs vislumbrem a importância de monitorar o ambiente e passem a adotar um modelo formal que sistematize a obtenção e o uso da informação on-line, tornando-as mais estratégicas para o seu negócio.This article aims to understand the importance of systematic environmental scanning in SMEs (small and medium enterprises), whereas the understanding of how companies seek and use information from the Internet is of great relevance to this process, keeping them more competitive in their market. For this was a literature review of environmental scanning, evaluating that several generic models are described in the literature, although many don’t direct their efforts for small and medium enterprises. The methodology used was a descriptive single case study to present the procedures performed by a company that uses data from the Internet in its environmental scanning, comparing the practice used with the steps of the model described in the literature. The results showed that the Internet is used as an important source for environmental scanning of this company, but the search for on-line information happens without systematic, intuitively and reactively. This article contributes to help SMEs to perceive the importance of scanning the environment and begin to adopt a formal model that systematizes the search and use of on-line information, making them more strategic to their business

Magnetic order and spin fluctuations in the spin liquid Tb2_2Sn2_2O7_7.

We have studied the spin liquid Tb$_2$Sn$_2$O$_7$ by neutron diffraction and specific heat measurements. Below about 2 K, the magnetic correlations change from antiferromagnetic to ferromagnetic. Magnetic order settles in two steps, with a smeared transition at 1.3(1) K then an abrupt transition at 0.87(2) K. A new magnetic structure is observed, not predicted by current models, with both ferromagnetic and antiferromagnetic character. It suggests that the spin liquid degeneracy is lifted by dipolar interactions combined with a finite anisotropy along $$ axes. In the ground state, the Tb$^{3+}$ ordered moment is reduced with respect to the free ion moment (9 $\mu_{\rm B}$). The moment value of 3.3(3) $\mu_{\rm B}$ deduced from the specific heat is much smaller than derived from neutron diffraction of 5.9(1) $\mu_{\rm B}$. This difference is interpreted by the persistence of slow collective magnetic fluctuations down to the lowest temperatures

Repurposing Metformin in Nondiabetic People With HIV:Influence on Weight and Gut Microbiota

Background. People with HIV (PWH) taking antiretroviral therapy (ART) may experience weight gain, dyslipidemia, increased risk of non-AIDS comorbidities, and long-term alteration of the gut microbiota. Both low CD4/CD8 ratio and chronic inflammation have been associated with changes in the gut microbiota of PWH. The antidiabetic drug metformin has been shown to improve gut microbiota composition while decreasing weight and inflammation in diabetes and polycystic ovary syndrome. Nevertheless, it remains unknown whether metformin may benefit PWH receiving ART, especially those with a low CD4/CD8 ratio. Methods. In the Lilac pilot trial, we recruited 23 nondiabetic PWI I receiving ART for more than 2 years with a low CD4/CD8 ratio ( Results. Metformin decreased weight in PWH, and weight loss was inversely correlated with plasma levels of the satiety factor GDF-15. Furthermore, metformin changed the gut microbiota composition by increasing the abundance of anti-inflammatory bacteria such as butyrate-producing species and the protective Akkermansia muciniphila. Conclusions. Our study provides the first evidence that a 12-week metformin treatment decreased weight and favored anti-inflammatory bacteria abundance in the microbiota of nondiabetic ART-treated PWH. Larger randomized placebo-controlled clinical trials with longer metformin treatment will be needed to further investigate the role of metformin in reducing inflammation and the risk of non-AIDS comorbidities in ART-treated PWH

Expression and Localization of CLC Chloride Transport Proteins in the Avian Retina

Members of the ubiquitously expressed CLC protein family of chloride channels and transporters play important roles in regulating cellular chloride and pH. The CLCs that function as Cl−/H+ antiporters, ClCs 3–7, are essential in particular for the acidification of endosomal compartments and protein degradation. These proteins are broadly expressed in the nervous system, and mutations that disrupt their expression are responsible for several human genetic diseases. Furthermore, knock-out of ClC3 and ClC7 in the mouse result in the degeneration of the hippocampus and the retina. Despite this evidence of their importance in retinal function, the expression patterns of different CLC transporters in different retinal cell types are as yet undescribed. Previous work in our lab has shown that in chicken amacrine cells, internal Cl− can be dynamic. To determine whether CLCs have the potential to participate, we used PCR and immunohistochemical techniques to examine CLC transporter expression in the chicken retina. We observed a high level of variation in the retinal expression levels and patterns among the different CLC proteins examined. These findings, which represent the first systematic investigation of CLC transporter expression in the retina, support diverse functions for the different CLCs in this tissue