203 research outputs found
Interplay of antiferromagnetism, ferromagnetism, and superconductivity in EuFe2(As1-xPx)2 single crystals
No full textWe report a systematic study of the influence of antiferromagnetic and ferromagnetic phases of Eu2+ moments on the superconducting phase upon doping the As site by isovalent P, which essentially acts like chemical pressure on EuFe2As2. Bulk superconductivity with transition temperatures of 22 and 28 K are observed for x = 0.16 and 0.20 samples, respectively. The Eu ions order antiferromagnetically for x = 0.22 whereupon the Eu ions order ferromagnetically and superconductivity is fully suppressed. Density-functional-theory-based calculations reproduce the observed experimental findings consistently. We discuss in detail the coexistence of superconductivity and magnetism in a tiny region of the phase space and comment on the competition of ferromagnetism and superconductivity in the title compound.DFG [SPP-1458
Electrical resistivity and specific heat of single-crystalline EuFe2As2: A magnetic homologue of SrFe2As2
No full textWe have grown single crystals of EuFe(2)As(2), and investigated its electrical transport and thermodynamic properties. Electrical resistivity and specific-heat measurements clearly establish the intrinsic nature of magnetic phase transitions at 20 and 195 K. While the high-temperature phase transition is associated with the itinerant moment of Fe, the low-temperature phase transition is due to magnetic order of localized Eu moments. Band-structure calculations point out a very close similarity of the electronic structure with SrFe(2)As(2). Magnetically, the Eu and Fe(2)As(2) sublattices are nearly decoupled.DFG Research Unit 960 and BRNS [2007/37/28
High-temperature superconductivity in Eu0.5K0.5Fe2As2
No full textEuFe(2)As(2) shows a spin-density wave (SDW) type transition at 190 K and antiferromagnetic (AF) order below 20 K. Here, we have studied the effect of K substitution on the SDW transition at high temperature and AF Eu order at low temperature. 50% K substitution suppresses the SDW transition and in turn gives rise to high-temperature superconductivity below T(c) = 32 K, as observed in the electrical resistivity, AC susceptibility, as well as magnetization. A well defined anomaly in the specific heat provides additional evidence for bulk superconductivity. Below 10 K, short-range magnetic order of the Eu moments is suggested by a broad feature in the specific-heat data. Electronic structure calculations reveal very close similarity with the nonmagnetic superconductor Sr(0.5)K(0.5)Fe(2)As(2), but yield localized 4f magnetic moments for the remaining Eu atoms.DFG Research Unit 960; BRNS [2007/37/28
Evidence for a reentrant superconducting state in EuFe2As2 under pressure
No full textWe studied the temperature-pressure phase diagram of EuFe2As2 by electrical resistivity measurements. The spin-density-wave transition at T-0 associated with the FeAs-layers is continuously suppressed with increasing pressure, while the antiferromagnetic ordering temperature of the Eu2+ moments seems to be nearly pressure independent up to 2.6 GPa. Above 2 GPa a sharp drop of the resistivity, rho(T), indicates the onset of superconductivity at T-c approximate to 29.5 K. Surprisingly, on further reducing the temperature, rho(T) is increasing again and exhibiting a maximum caused by the ordering of the Eu2+ moments, a behavior which is reminiscent of reentrant superconductivity as it is observed in the ternary Chevrel phases or in the rare-earth nickel borocarbides
Computational chemistry and molecular modeling : principles and applications / K.I. Ramachandran, G. Deepa, K. Namboori.
No full text"An exclusive URL (http://www.amrita.edu/cen/ccmm/) for this book with the required support materials has been provided for readers ..."--Preface.pharmacy bookfair2015Includes bibliographical references and index.xxi, 397 pages
Micro-raman spectroscopy of caries lesion formation in dental enamel
No full textCaries lesions form by a complex process of chemical interactions between dental enamel and its environment. They can cause cavities and pain, and are expensive to fix. Lesions form by slow demineralization over many months, even years. It is hard to characterize in vivo as a result of environmental factors and remineralization by ions in the oral cavity. In this thesis the process of demineralization was carried out in vitro and micro-Raman spectroscopy used to investigate and characterize the lesion's chemistry. Demineralization occurs by diffusion across the depth of the lesion of mineral ions via interstitial spaces in the dental enamel. Hydroxyl ions are initially lost by acidic attack, which increases the interstitial space. The demineralization is retarded by diffusion processes in the opposite direction, and a balance in the charges of the ions must be maintained. Having multiple ions diffusing simultaneously is termed “coupled diffusion”. A subsurface highly demineralized region is formed, but this can be remineralized.
Micro-Raman spectroscopy is a powerful tool for studying material composition by exciting chemical bonds in the sample. Using micro-Raman to characterize the chemical composition of lesions may help in developing preventative measures to stop their formation. Raman (λ=785 nm) was used to characterize lesions grown over 5, 7, 9, 11 and 14 days. The amide I peak at ~1605 cm-1, which has not been observed previously, was seen in the maturing lesions. The extreme demineralization in these lesions enables the organic peaks to be seen rather than the normally stronger mineral peaks. Analysis of crystallinity shows that there is always a reduction in mineral content with distance below the enamel surface, but this becomes magnified as the lesion matures. Type B carbonate substitution for phosphate ions can also be examined with Raman. Correcting for crystallinity shows that both carbonate and phosphate ions are lost at the same rate during demineralization.
In summary, micro-Raman is an effective and relatively easy tool to use in lesion characterization. It also has the advantage that it can be used to identify changes in both the mineral and protein phases of enamel.M.S.Includes bibliographical references (p. 53-55)
CeRu4Sn6 a strongly correlated material with nontrivial topology
No full textTopological insulators form a novel state of matter that provides new opportunities to create unique quantum phenomena. While the materials used so far are based on semiconductors, recent theoretical studies predict that also strongly correlated systems can show non trivial topological properties, thereby allowing even the emergence of surface phenomena that are not possible with topological band insulators. From a practical point of view, it is also expected that strong correlations will reduce the disturbing impact of defects or mpurities, and at the same increase the Fermi velocities of the topological surface states. The challenge is now to discover such correlated materials. Here, using advanced x ray spectroscopies in combination with band structure calculations, we infer that CeRu4Sn6 is a strongly correlated material with non trivial topolog
Corrections to “An Improved Harmonics Mitigation Scheme for a Modular Multilevel Converter” [2019 147244-147255]
No full textIn the above-named work, T. Deepa should have been listed as the second co-author of the article with the affiliation of (1): School of Electrical Engineering, Vellore Institute of Technology, Chennai 600127, India. The author's biography is also provided within this correction. Additionally, the correct zip code of affiliation (1) should be 600127, and the correct statement on financial support acknowledgement should be as follows: "This work was funded by the Renewable Energy Laboratory, Department of Communications and Networks Engineering, Prince Sultan University, Riyadh, Saudi Arabia." It is necessary to mention the nature of funding provided by Prince Sultan University and to note the correction in the spelling of the university in the same statement in the published manuscript
Creating Value Through Design: Company and Country Perspectives from East Asia
No full textFor the final Y.B. Min lecture of the semester, the Center for Asian Business welcomed Deepa Prahalad, an author and business strategist specializing in opportunities at the intersection of consumer experience, technology and strategy. In her presentation, titled “Creating Value through Design: Company and Country Perspectives from East Asia,” Prahalad discussed the role of design in creating value, the ingredients of good design and how this applies to Asian countries in particular.
Prahalad discussed the success of great brands such as Apple, Nike, Coca-Cola and Samsung and how they have created awareness of the value of design to business. Design today is an important source of strategic advantage for entrepreneurs, established companies and countries. Her talk focused on case studies of how companies and countries have used design to build brands and create a sphere of influence.
According to Prahalad, strategic challenges such as co-creation, customer experience, globalization, innovation and new business model creation all require design. Today, we’re seeing a convergence of brand and design. Leading brands such as Nike, Apple, McDonald’s and Mercedes are all identifiable by their logo alone. These brands have a distinct look, feel and experience, and the experience must be valued by the consumers. Prahalad went on to address how emotional connections often lead to business results.
At the conclusion of her lecture, she highlighted the following points: Behavior is as important as income There is a convergence of quantitative and qualitative data Looking at emotions creates obligations for companies A great design still needs a great business model
Passionate about emerging markets and innovation, Prahalad has worked as a management consultant with firms from start-ups to large multinationals. She researched and co-authored the book, Predictable Magic: Unleash the Power of Design Strategy to Transform Your Business. Prahalad speaks on design strategy and emerging markets at business schools and at global and government forums on the importance of design as a competitive innovation. Prahalad received a B.A. in Economics and Political Science from the University of Michigan and an MBA from the Tuck School of Business at Dartmouth.https://digitalcommons.lmu.edu/ybminlectureseries/1003/thumbnail.jp
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