Chiral Magnetism and High-Temperature Skyrmions in B20-Ordered Co-Si.

Magnets with chiral crystal structures and helical spin structures have recently attracted much attention as potential spin-electronics materials, but their relatively low magnetic-ordering temperatures are a disadvantage. While cobalt has long been recognized as an element that promotes high-temperature magnetic ordering, most Co-rich alloys are achiral and exhibit collinear rather than helimagnetic order. Crystallographically, the B20-ordered compound CoSi is an exception due to its chiral structure, but it does not exhibit any kind of magnetic order. Here, we use nonequilibrium processing to produce B20-ordered Co_{1+x}Si_{1-x} with a maximum Co solubility of x=0.043. Above a critical excess-Co content (x_{c}=0.028), the alloys are magnetically ordered, and for x=0.043, a critical temperature T_{c}=328 K is obtained, the highest among all B20-type magnets. The crystal structure of the alloy supports spin spirals caused by Dzyaloshinskii-Moriya interactions, and from magnetic measurements we estimate that the spirals have a periodicity of about 17 nm. Our density-functional calculations explain the combination of high magnetic-ordering temperature and short periodicity in terms of a quantum phase transition where excess-cobalt spins are coupled through the host matrix.

Structural and magnetic evolution of bimetallic MnAu clusters driven by asymmetric atomic migration.

The nanoscale structural, compositional, and magnetic properties are examined for annealed MnAu nanoclusters. The MnAu clusters order into the L1(0) structure, and monotonic size-dependences develop for the composition and lattice parameters, which are well reproduced by our density functional theory calculations. Simultaneously, Mn diffusion forms 5 Å nanoshells on larger clusters inducing significant magnetization in an otherwise antiferromagnetic system. The differing atomic mobilities yield new cluster nanostructures that can be employed generally to create novel physical properties.

Revisiting calculation of tilt angles for double-tilt sample holders in transmission electron microscopes.

We revisited the formula related to the overall tilt angle of a specimen using a side-entry double-tilt sample holder in a transmission electron microscope. Initially, we examined existing formulas in the literature for calculating the overall tilt angle. Subsequently, a new formula was derived, proven to better account for the actions of the double-tilt holder, thereby providing improved accuracy in the calculation. This newly derived formula has been implemented in the Landyne software suite. Furthermore, we demonstrated the accuracy of the new formula through examples. RESEARCH HIGHLIGHTS: A new formula has been derived to calculate overall tilt angles for side-entry double-tilt holders in TEM.

Sensitization of Europium Oxide Nanoparticles Enhances Signal-to-Noise over Autofluorescence with Time-Gated Luminescence Detection.

Clinical translation of nanoparticle-based therapeutics has been limited, and a lack of preclinical delivery characterization is partly to blame, limiting our understanding of the mechanisms of failure. The improvement of the preclinical delivery assessment requires nanoparticles with higher detectability. This work focused on the exploration of several aromatic carboxylic ligands (terephthalic acid, quinaldic acid, and kynurenic acid) for the sensitization of europium oxide nanoparticles with a long emission lifetime to overcome cellular autofluorescence, a key confounder of detection in luminescence-based bioimaging. A facile one-pot synthesis and ligand exchange process generated and sensitized ultrasmall Eu2O3 cores. As reflected in the emission spectra and lifetimes, ligand binding yielded unique coordination environments around Eu3+. Then, the efficacy of sensitization was tested against the autofluorescence provided by tissue lysate. Normal (simultaneous excite-read) measurements showed integrated signal improvements over autofluorescence of 2.2-, 3.9-, and 14.0-fold for EuTA, EuQA, and EuKA, respectively. In time-gated mode, the improvements over autofluorescence were more dramatic with fold differences of 75-, 89-, and 108-fold for EuTA, EuQA, and EuKA, respectively. The investigation of novel sensitizers expands the breadth of the field of sensitized lanthanide oxide nanoparticles, and the signal enhancement observed with sensitization and time-gating supports the utility of the generated samples for future bioimaging applications.

Systematic and meta-based evaluation of the relationship between the built environment and physical activity behaviors among older adults.

Objectives: Existing assertions about the relationship between various factors of the built environment and physical activity behaviors are inconsistent and warrant further exploration and analysis. Methods: This study systematically searched PubMed, Embase, Web of Science, Scopus, the Cochrane Library and Google Scholar for the effect of the built environment on the physical activity behaviors of older adults. R software was used to calculate the meta-estimated odds ratio with a 95% confidence interval. Simultaneously, the quality of included studies was evaluated using an observational study quality evaluation standard recommended by American health care quality and research institutions. Results: A total of 16 original researches were included in this meta-analysis and eight factors of the built environment were evaluated. These factors which ranked from high to low according to their impact were traffic safety (OR = 1.58, 95% CI [1.14-2.20]), destination accessibility (OR = 1.24, 95% CI [1.06-1.44]), aesthetics of sports venues (OR = 1.21, 95% CI [1.07-1.37]), virescence of sports venues (OR = 1.14, 95% CI [1.06-1.23]), building density (OR = 1.07, 95% CI [1.02-1.13]). Additionally, it seemed that there was no potential association between mixed land use (OR = 1.01, 95% CI [0.92-1.10]), the quality of pedestrian facilities (OR = 1.00, 95% CI [0.92-1.08]) or commercial facilities (OR = 0.94, 95% CI [0.88-1.00]) and physical activity behaviors of older adults. Conclusions: The built environment has been found to exhibit a significant relationship with the physical activity behaviors of older adults. It is proposed that factors such as traffic safety, destination accessibility, aesthetics of sports venues, virescence of sports venues, and building density be given more consideration when aiming to promote physical activity levels among older adults.

Cluster synthesis and direct ordering of rare-earth transition-metal nanomagnets.

Rare-earth transition-metal (R-TM) alloys show superior permanent magnetic properties in the bulk, but the synthesis and application of R-TM nanoparticles remains a challenge due to the requirement of high-temperature annealing above about 800 °C for alloy formation and subsequent crystalline ordering. Here we report a single-step method to produce highly ordered R-TM nanoparticles such as YCo(5) and Y(2)Co(17), without high-temperature thermal annealing by employing a cluster-deposition system and investigate their structural and magnetic properties. The direct ordering is highly desirable to create and assemble R-TM nanoparticle building blocks for future permanent-magnet and other significant applications.

[Correlation between highest point of greater trochanter and the ideal entry point for antegrade femoral nailing by three-dimensional images].

OBJECTIVE: To provide reference of the ideal entry point for antegrade femoral nailing according to analysis correlation between highest point of greater trochanter and the middle line of the medullary cavity in adults by three-dimensional images. METHODS: From January 2016 to January 2017, 107 adults who underwent continuous computed tomography (CT) scans were ultimately enrolled, including 64 males and 43 females with an average age of (51.7±16.4) years old;54 patients on the left side and 53 patients on the right side. Three-dimensional images were built by using image-processing software (Volume Viewer) to reconstruct geometry of cortex and medullary canal. All people weregrouped according to different femoral greater trochanter morphology, such as anterior apex (AA), posterior apex (PA), middle apex (MA) and none apex (NA). Forwards inclination was adjusted to apparent neck shaft angle (ANSA) and true neck shaft angle (TNSA) on the coronal and saggittal view, recorded as C-ANSA, C-TNSA, S-ANSA, S-TNSA respectively, vertical distance from the middle line of femur medullary cavity to the highest point of greater trochanter of femur on the 4 positions were measured and performed statistical analysis, multiple linear regression was applied to analysis relationship between clinical data and VD value. RESULTS: (1)Comparison of VD value among 4 groups on the 4 positions, there were no difference in VD value between AA and MA groups on the S-ANSA position;and no differences in VD value among AA, MA and NA groups on the C-ANSA and C-TNSA position. (2)There were differences in VD value among AA, MA and NA groups on the sagittal plane;while had difference in VD value between PA and NA group on the coronal plane. (3)Prediction equation of VD value on S-ANSA and S-TNSA position by multiple linear regression showed R=0.343, F=3.409, P=0.012 on the S-ANSA position;R=0.317, F=2.846, P=0.028 on the S-TNSA position; neck shaft angle and sex were risk factors of VD value on the sagittal plane, while no difference in VD value on the coronal position. CONCLUSION: (1)When indentify insertion point in adult femoral nail according to the highest point of greater trochanter as anatomic landmark, the morphology of greater trochanter of femur should be distinguished to certain observation position, then evaluate migration before and after on the sagttial plane and lateral offset on the coronal plane. (2)Migration before and after on the sagttial plane is increase with increase of neck shaft angle, and the degree of migration of female before and after is less than that of male.

Magnetism of new metastable cobalt-nitride compounds.

The search for new magnetic materials with high magnetization and magnetocrystalline anisotropy is important for a wide range of applications including information and energy processing. There is only a limited number of naturally occurring magnetic compounds that are suitable. This situation stimulates an exploration of new phases that occur far from thermal-equilibrium conditions, but their stabilization is generally inhibited due to high positive formation energies. Here a nanocluster-deposition method has enabled the discovery of a set of new non-equilibrium Co-N intermetallic compounds. The experimental search was assisted by computational methods including adaptive-genetic-algorithm and electronic-structure calculations. Conventional wisdom is that the interstitial or substitutional solubility of N in Co is much lower than that in Fe and that N in Co in equilibrium alloys does not produce materials with significant magnetization and anisotropy. By contrast, our experiments identify new Co-N compounds with favorable magnetic properties including hexagonal Co3N nanoparticles with a high saturation magnetic polarization (Js = 1.28 T or 12.8 kG) and an appreciable uniaxial magnetocrystalline anisotropy (K1 = 1.01 MJ m-3 or 10.1 Mergs per cm3). This research provides a pathway for uncovering new magnetic compounds with computational efficiency beyond the existing materials database, which is significant for future technologies.

New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy.

A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description.