Magnetic phase diagram of the antiferromagnetic pyrochlore Gd2Ti2O7

Gd2Ti2O7 is a highly frustrated antiferromagnet on a pyrochlore lattice, where apart from the Heisenberg exchange the spins also interact via dipole-dipole forces. We report on low-temperature specific heat measurements performed on single crystals of Gd2Ti2O7 for three different directions of an applied magnetic field. The measurements reveal the strongly anisotropic behaviour of Gd2Ti2O7 in a magnetic field despite the apparent absence of a significant single-ion anisotropy for Gd3+. The H-T phase diagrams are constructed for H//111], H//[110] and H//[112]. The results indicate that further theoretical work beyond a simple mean-field model is required.Comment: 4 figure

Stray field signatures of N\'eel textured skyrmions in Ir/Fe/Co/Pt multilayer films

Skyrmions are nanoscale spin configurations with topological properties that hold great promise for spintronic devices. Here, we establish their N\'eel texture, helicity, and size in Ir/Fe/Co/Pt multilayer films by constructing a multipole expansion to model their stray field signatures and applying it to magnetic force microscopy (MFM) images. Furthermore, the demonstrated sensitivity to inhomogeneity in skyrmion properties, coupled with a unique capability to estimate the pinning force governing dynamics, portends broad applicability in the burgeoning field of topological spin textures.Comment: 6 pages, 4 figures, significantly revised and upgraded. For the updated supplementary material please contact one of the corresponding author

Maintenance, Repair, and Overhaul Performance Indicators for Military Aircraft

Modern day military and commercial aircraft systems are an integration of a large number of sub-systems and components. Each of these systems has different reliability characteristics and different probability distributions governing their failure rates. Space constraints and structural layout of the aircraft govern the position of each component. The accessibility, reliability, and snag diagnostic-ability determines the maintainability of the aircraft. The peculiarities involved in aircraft maintenance are discussed and performance measurement indices for O, I and D level maintenance are presented in this paper. These performance measurement indices are intended for use by aircraft maintenance managers for instituting process improvements for achieving best flight and maintenance safety records, improve operational availability of the aircraft and reduce costs.Defence Science Journal, 2012, 62(2), pp.83-89, DOI:http://dx.doi.org/10.14429/dsj.62.88

Chiral magnetic textures in Ir/Fe/Co/Pt multilayers: Evolution and topological Hall signature

Skyrmions are topologically protected, two-dimensional, localized hedgehogs and whorls of spin. Originally invented as a concept in field theory for nuclear interactions, skyrmions are central to a wide range of phenomena in condensed matter. Their realization at room temperature (RT) in magnetic multilayers has generated considerable interest, fueled by technological prospects and the access granted to fundamental questions. The interaction of skyrmions with charge carriers gives rise to exotic electrodynamics, such as the topological Hall effect (THE), the Hall response to an emergent magnetic field, a manifestation of the skyrmion Berry-phase. The proposal that THE can be used to detect skyrmions needs to be tested quantitatively. For that it is imperative to develop comprehensive understanding of skyrmions and other chiral textures, and their electrical fingerprint. Here, using Hall transport and magnetic imaging, we track the evolution of magnetic textures and their THE signature in a technologically viable multilayer film as a function of temperature ($T$) and out-of-plane applied magnetic field ($H$). We show that topological Hall resistivity ($\rho_\mathrm{TH}$) scales with the density of isolated skyrmions ($n_\mathrm{sk}$) over a wide range of $T$, confirming the impact of the skyrmion Berry-phase on electronic transport. We find that at higher $n_\mathrm{sk}$ skyrmions cluster into worms which carry considerable topological charge, unlike topologically-trivial spin spirals. While we establish a qualitative agreement between $\rho_\mathrm{TH}(H,T)$ and areal density of topological charge $n_\mathrm{T}(H,T)$, our detailed quantitative analysis shows a much larger $\rho_\mathrm{TH}$ than the prevailing theory predicts for observed $n_\mathrm{T}$.Comment: Major revision of the original version. The extensive Supplementary Information is available upon reques

Anti-microbial and anti-corrosive poly (ester amide urethane) siloxane modified ZnO hybrid coatings from Thevetia peruviana seed oil

The utilization of renewable resources for the development of organic coatings is a viable means of creating alternatives to petroleum-based chemicals which are not eco-friendly. This paper reports the synthesis of polyesteramide– urethane–silica–zinc oxide hybrid coatings from Thevetia peruviana seed oil (TPSO). The periphery of ZnO nano-particles is modified with 3-aminopropyltrimethoxysilane to prepare silica grafted ZnO composite particles. The TPSO based polyesteramide was reacted with 4,40- diisocyanatodicyclohexylmethane in presence of siloxane modified ZnO to obtain –NCO terminated polyesteramide– urethane–silica ZnO prepolymer. These hybrid pre-polymers were casted on tin foil and cured under atmospheric moisture to obtain eco-friendly, moisture cured polyesteramide– urethanes–silica–zinc oxide hybrid coating films. The synthesized polyester and polyurethane formation was confirmed by using FT-IR and NMR spectroscopic techniques.The resultant hybrid coating films were characterized by using FT-IR, TGA, DSC, SEM, corrosion resistance and microbial resistance. Results confirm that with increase of siloxane modified ZnO content in the polyurethane matrix thermal stability, glass transition temperature and corrosion resistance improved. The antibacterial activity shows that the hybrid films exhibit excellent resistance towards Escherichia coli and Staphylococcus aureus. The salt spray test on coated panel samples show good corrosion resistance properties

Upaya Meningkatkan Hasil Belajar Matematika Siswa Kelas Vii3 SMP Negeri 32 Pekanbaru melalui Penerapan Pembelajaran Kooperatif dengan Pendekatan Think Pair Square (Tps)

This research aims to improve the learning process and improve the student's mathematics learning outcomes through the implementation of Cooperative Learning with Think Pair Square Approach. The type of research is the Classroom Action Research with two cycles. The research was conducted in studentof grade VII3 SMP N 32 Pekanbaru in the second semester of the 2015/2016 academic year with the subject of as many as 41 students. The research instrument are consists of learning devices and instrument data collectors. Learning device used in this research are consists of the Syllabus, Lesson plan and Student work sheet. The instrument data collector used in this research is consists of the observation sheet and math test. Technique of data analysis is analysis of narrative descriptive and analysis of statistical descriptive. Based on the result of the research show that, the learning process has improved and the student's mathematics learning outcomes have improved after applying the Cooperative Learning with Think Pair Square Approach. The Cooperative Learning with Think Pair Square Approach can be used as an alternative in learning, because it can improve the learning process and improve the students learning outcomes

SYNTHESIS, CHARACTERIZATION AND ANTIBACTERIAL EVALUATIONS OF NOVEL HYBRID POLYESTERAMIDEURETHANES PREPARED FROM YELLOW OLEANDA SEED OIL

Air drying polyesteramide-urethanes resins were synthesized from Thevetia peruviana seed oil commonly known as Yellow oleanda (a tropical ornamental shrub) having about 68.8% unsaturated and 30.9% saturated fatty acids. The physico- chemical characterization of the optimized unsaturated FAME such as hydroxyl value, iodine value, saponification value, refractive index, inherent viscosity were carried out using standard methods. Through condensation reaction the N,N'- bis(2-hydroxyethyl) Thevetia peruviana (HETA) prepared from the FAME reacted with isophthalic acid to form polyesteramide. The latter undergo urethanation with H1 ' 2MDI. The structural elucidation of the moisture cured polyesteramide-urethane coating was based on FTIR, 1H-NMR and 13C-NMR spectroscopic methods. The coatings films were evaluated for its antihacterial activity and thermal stability properties on TGA and DSC. The SEM of the --uating films was also examined

Impacts of Mercury Exposure on Human Health, Safety and Environment: Literature Review and Bibliometric Analysis (1995 to 2021)

Introduction: Mercury is a highly toxic and persistent contaminant found in food and parts of the environment. Over the years, global research on mercury poison has soared owing to concerns about its effects on human health, occupational safety, and environmental sustainability. Although numerous studies have identified and examined the various types, sources, toxicity, exposure, and impacts of mercury, comprehensive studies on the research landscape and scientific developments on the subject areas are currently lacking. Therefore, this paper shows a bibliometric analysis (BA) and literature review (LR) of the top publications, funders, organisations, and countries working on Mercury research worldwide. Methods: The research landscape on the subject area was examined by BA from 1995 to 2021, whereas the scientific developments were highlighted through LR. Results: Results showed that mercury research has gained global prominence since the discovery of the Minamata disease in 1956. The most prolific mercury researchers, institutions, and funders are from the United States, Japan, Brazil, Canada, and China, whereas the publications on Mercury research doubled over the period. The top source titles for publications on Mercury are Neurotoxicology, Science of the Total Environment, and Environmental Health Perspectives. However, Micheal Aschner (US) and Takashi Yorifuji (Japan) are the most prolific researchers. Co-occurrence analysis revealed that mercury, methyl mercury, fish, toxicity, and Minamata disease are the most cited keywords, which shows the correlation nexus between fish consumption and mercury poisoning. Conclusion: The LR showed that mercury research is widely investigated due to global concerns about its impact on human health, safety, and the environment

Indices for Superconformal Field Theories in 3,5 and 6 Dimensions

We present a trace formula for a Witten type Index for superconformal field theories in d=3,5 and 6 dimensions, generalizing a similar recent construction in d=4. We perform a detailed study of the decomposition of long representations into sums of short representations at the unitarity bound to demonstrate that our trace formula yields the most general index (i.e. quantity that is guaranteed to be protected by superconformal symmetry alone) for the corresponding superalgebras. Using the dual gravitational description, we compute our index for the theory on the world volume of N M2 and M5 branes in the large N limit. We also compute our index for recently constructed Chern Simons theories in three dimensions in the large N limit, and find that, in certain cases, this index undergoes a large N phase transition as a function of chemical potentials.Comment: a small typo corrected, 46 page

Renewable resource based novel antimicrobial polyesteramide-urethenehybrid coatings

The use of renewable resources for the development of coating materials is a viable means to reduce environmental impact and support sustainability efforts. This paper describes a novel antimicrobial polyesteramide-urethane-silica- Zinc Oxide (ZnO) hybrid coatings based on milk bush seed oil as renewable resource. Initially ZnO nanoparticles were modified with aminopropyltrimethoxysilane to get silica grafted ZnO composite particles. The milk bush oil based polyesteramide were reacted with excess H12MDI to get NCO terminated polyesteramide-urethanes and the excess NCO was reacted with silica grafted ZnO composite particles to get the reactive hybrid prepolymers. These prepolymers were casted on tin foil and cured under atmospheric moisture to get eco-friendly moisture curing polyesteramide-urethane-silica- Zinc Oxide (ZnO) hybrid coatings films. The coatings films were evaluated for its antimicrobial and thermo mechanical properties while coated steel specimen were used for corrosion studies. The techniques such as FTIR, TGA, DSC, DMTA, SEM and XRD have been used in this study. The hybrid coating films has shown very good antibacterial and antifungal propertie$, higher thermal stability and better thermo mechanical properties. The improvement in the properties was dependent" on the concentration of ZnO composite particles in the coating films. The antibacterial experiments show that the ZnO doped films exhibit excellent antibacterial activity, especially for E.coli. The salt spray test on coated specimen show good corrosion resistance properties for hybrid coating