X-ray holographic imaging of magnetic surface spirals in FeGe lamellae

Isotropic helimagnets are known to host a diverse range of chiral magnetic states. In 2016, Rybakov et al., theorized the presence of a surface-pinned stacked spin spiral phase [F. N. Rybakov et al., New J. Phys. 18, 045002 (2016)], which has yet to be observed experimentally. The phase is characterized by surface spiral periods exceeding the host material's fundamental winding period L D . Here, we present experimental evidence for the observation of this state in lamellae of FeGe using resonant x-ray holographic imaging data and micromagnetic simulations. We find images of FeGe lamellae, exceeding a critical thickness of 300 nm ( 4.3 L D ), exhibit contrast modulations with a field-dependent periodicity of λ ≥ 1.4 L D , consistent with theoretical predictions of the stacked spiral state. The identification of this spiral state has significant implications for the stability of other coexisting spin textures, and will help complete our understanding of helimagnetic systems

Heat Transfer Characteristics of Conventional Fluids and Nanofluids in Micro-Channels with Vortex Generators: A Review

An effective way to enhance the heat transfer in mini and micro electronic devices is to use different shapes of micro-channels containing vortex generators (VGs). This attracts researchers due to the reduced volume of the electronic micro-chips and increase in the heat generated from the devices. Another way to enhance the heat transfer is using nanofluids, which are considered to have great potential for heat transfer enhancement and are highly suited to application in practical heat transfer processes. Recently, several important studies have been carried out to understand and explain the causes of the enhancement or control of heat transfer using nanofluids. The main aim upon which the present work is based is to give a comprehensive review on the research progress on the heat transfer and fluid flow characteristics of nanofluids for both single- and two- phase models in different types of micro-channels. Both experimental and numerical studies have been reviewed for traditional and nanofluids in different types and shapes of micro-channels with vortex generators. It was found that the optimization of heat transfer enhancement should consider the pumping power reduction when evaluating the improvement of heat transfer

Towards routine refinement of hydrogenous materials by neutron powder diffraction

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Stability and metastability of skyrmions in thin lamellae of Cu2OSeO3

We report small-angle x-ray scattering measurements of the skyrmion lattice in two 200-nm-thick Cu2OSeO3 lamellae aligned with the applied magnetic field parallel to the out of plane [110] or [100] crystallographic directions. Our measurements show that the equilibrium skyrmion phase in both samples is expanded significantly compared to bulk crystals, existing between approximately 30 and 50 K over a wide region of magnetic field. This skyrmion state is elliptically distorted at low fields for the [110] sample, and symmetric for the [100] sample, possibly due to crystalline anisotropy becoming more important at this sample thickness than it is in bulk samples. Furthermore, we find that a metastable skyrmion state can be observed at low temperature by field cooling through the equilibrium skyrmion pocket in both samples. In contrast to the behavior in bulk samples, the volume fraction of metastable skyrmions does not significantly depend on cooling rate. We show that a possible explanation for this is the change in the lowest temperature of the skyrmion state in this lamellae compared to bulk, without requiring different energetics of the skyrmion state

Toda Soliton Mass Corrections and the Particle--Soliton Duality Conjecture

We compute quantum corrections to soliton masses in affine Toda theories with imaginary exponentials based on the nonsimply-laced Lie algebras $c_n^{(1)}$. We find that the soliton mass ratios renormalize nontrivially, in the same manner as those of the fundamental particles of the theories with real exponentials based on the nonsimply-laced algebras $b_n^{(1)}$. This gives evidence that the conjectured relation between solitons in one Toda theory and fundamental particles in a dual Toda theory holds also at the quantum level. This duality can be seen as a toy model for S-duality.Comment: LATEX, 17 pages, no figures Note added at end of discussio

Correlações entre médias de híbridos F1 e medias parentais em tomate

In a six parent tomato (Lycopersicon esculentum Mill) diallel cross, specific heterosis was more important for marketable yield (PFC) than for its components - average weight (PMFC) and number of marketable fruit (NFC). Correlation coefficients between F1 hybrid means and parental means were larger for PMFC and NFC than for PFC. The product of PMFC by NFC parental means can be used more efficiently as an estimate of F1 hybrid PFC's than PFC parental means themselves.Em cruzamento dialélico de seis cultivares de tomate (Lycopersicon esculentum Mill), a heterose específica foi mais importante para produção de frutos comerciáveis (PFC) do que para suas componentes peso médio (PMFC) e número de frutos comerciáveis (NFC). Os coeficientes de correlação entre médias de híbridos F1 e médias parentais foram maiores para PMFC e NFC do que para PFC. O produto das médias parentais de PMFC e NFC pode ser utilizado para estimar a PFC dos híbridos com mais eficiência do que a PFC média parental propriamente dita

Position-dependent stability and lifetime of the skyrmion state in nickel-substituted Cu2OSeO3

We report spatially resolved small-angle neutron-scattering measurements of the conical and skyrmion states of a bulk single crystal of nickel-substituted Cu2OSeO3, with a nominal concentration of Ni of 14%. We observe a significant spatial dependence of the structure of these magnetic states, characterized by increased disorder and misalignment with respect to the applied field as we approach the edge of the sample. Remarkably, the edge skyrmion state is also characterized by an extended stability towards lower temperatures. Surprisingly, in the same region of the sample, the metastable skyrmion state did not show simple decay. Instead, only a fraction of the scattered intensity appeared to decay, and the intensity therefore did not approach zero during our measurements. We suggest that the increased local disorder and the coexistence of conical and skyrmion states, induced by demagnetization effects at the edge of the sample, are responsible for the increased stability of this skyrmion state. We also infer that the unclear metastable behavior of the skyrmion lattice at the edge of the sample is due to the local geometry of the sample, which induces coexistence of different skyrmion states whose lifetimes are superimposed and difficult to separate in the data

Assessment of patient-derived tumour xenografts (PDXs) as a discovery tool for cancer epigenomics

Background: The use of tumour xenografts is a well-established research tool in cancer genomics but has not yet been comprehensively evaluated for cancer epigenomics. Methods: In this study, we assessed the suitability of patient-derived tumour xenografts (PDXs) for methylome analysis using Infinium 450 K Beadchips and MeDIP-seq. Results: Controlled for confounding host (mouse) sequences, comparison of primary PDXs and matching patient tumours in a rare (osteosarcoma) and common (colon) cancer revealed that an average 2.7% of the assayed CpG sites undergo major (Δβ ≥ 0.51) methylation changes in a cancer-specific manner as a result of the xenografting procedure. No significant subsequent methylation changes were observed after a second round of xenografting between primary and secondary PDXs. Based on computational simulation using publically available methylation data, we additionally show that future studies comparing two groups of PDXs should use 15 or more samples in each group to minimise the impact of xenografting-associated changes in methylation on comparison results. Conclusions: Our results from rare and common cancers indicate that PDXs are a suitable discovery tool for cancer epigenomics and we provide guidance on how to overcome the observed limitations

A study of smoke formation from wood combustion

Aerosol time of flight mass spectrometry (ATOFMS) was used to analyse the particles emitted during the flaming and smouldering phases of the combustion of samples of hard and soft woods. Eugenol and furfural were also burned and using results from previous work of the authors, they have been shown to be useful proxies for initial wood combustion products. The ratios of elementary carbon to total carbon in the particles were similar for both the woods and for eugenol. The ATOFMS spectra of most of the particles were consistent with the presence of soot precursor constituents along with oxygen containing fragments. Most particle diameters were less than 2.5. μm, with the greatest concentration of <. 0.12. μm

Neutron powder diffraction:New opportunities in hydrogen location in molecular and materials structure

The potential of neutron powder diffraction in the location of hydrogen atoms in molecular materials and inorganic-molecular complexes is reviewed. Advances in instrumentation and data collection techniques that have made this field accessible are reviewed, along with a wide range of applications carried out by our collaboration investigating functional materials, hydrogen-containing minerals and molecular compounds. Some of the limitations in this area, particularly for molecular systems, are also addressed