Covariate-adjusted generalized pairwise comparisons in small samples

Semiparametric probabilistic index models allow for the comparison of two groups of observations, whilst adjusting for covariates, thereby fitting nicely within the framework of generalized pairwise comparisons (GPC). As with most regression approaches in this setting, the limited amount of data results in invalid inference as the asymptotic normality assumption is not met. In addition, separation issues might arise when considering small samples. In this article, we show that the parameters of the probabilistic index model can be estimated using generalized estimating equations, for which adjustments exist that lead to estimators of the sandwich variance-covariance matrix with improved finite sample properties and that can deal with bias due to separation. In this way, appropriate inference can be performed as is shown through extensive simulation studies. The known relationships between the probabilistic index and other GPC statistics allow to also provide valid inference for example, the net treatment benefit or the success odds

DataSheet1_Asymmetric Interfacial Intermixing Associated Magnetic Coupling in LaMnO3/LaFeO3 Heterostructures.docx

The structural and magnetic properties of LaMnO3/LaFeO3 (LMO/LFO) heterostructures are characterized using a combination of scanning transmission electron microscopy, electron energy-loss spectroscopy, bulk magnetometry, and resonant x-ray reflectivity. Unlike the relatively abrupt interface when LMO is deposited on top of LFO, the interface with reversed growth order shows significant cation intermixing of Mn3+ and Fe3+, spreading ∼8 unit cells across the interface. The asymmetric interfacial chemical profiles result in distinct magnetic properties. The bilayer with abrupt interface shows a single magnetic hysteresis loop with strongly enhanced coercivity, as compared to the LMO plain film. However, the bilayer with intermixed interface shows a step-like hysteresis loop, associated with the separate switching of the “clean” and intermixed LMO sublayers. Our study illustrates the key role of interfacial chemical profile in determining the functional properties of oxide heterostructures.</p

Secondary electron induced current in scanning transmission electron microscopy: an alternative way to visualize the morphology of nanoparticles

Electron tomography (ET) is a powerful tool to determine the three-dimensional (3D) structure of nanomaterials in a transmission electron microscope. However, the acquisition of a conventional tilt series for ET is a time-consuming process and can therefore not provide 3D structural information in a time-efficient manner. Here, we propose surface-sensitive secondary electron (SE) imaging as an alternative to ET for the investigation of the morphology of nanomaterials. We use the SE electron beam induced current (SEEBIC) technique that maps the electrical current arising from holes generated by the emission of SEs from the sample. SEEBIC imaging can provide valuable information on the sample morphology with high spatial resolution and significantly shorter throughput times compared with ET. In addition, we discuss the contrast formation mechanisms that aid in the interpretation of SEEBIC data

Cation Ordering and Flexibility of the BO₄^2– Tetrahedra in Incommensurately Modulated CaEu₂(BO₄)₄ (B = Mo, W) Scheelites

The factors mediating cation ordering in the scheelite-based molybdates and tungstates are discussed on the basis of the incommensurately modulated crystal structures of the CaEu₂(BO₄)₄ (B = Mo, W) red phosphors solved from high-resolution synchrotron powder X-ray diffraction data. Monoclinic CaEu₂(WO₄)₄ adopts a (3 + 1)-dimensionally modulated structure [superspace group <i>I</i>2<i>/b</i>(αβ0)­00, <i>a</i> = 5.238 73(1)­Å, <i>b</i> = 5.266 35(1) Å, <i>c</i> = 11.463 19(9) Å, γ = 91.1511(2)°, <b>q</b> = 0.56153(6)<b>a</b>* + 0.7708(9)<b>b</b>*, <i>R</i>_F = 0.050, <i>R</i>_P = 0.069], whereas tetragonal CaEu₂(MoO₄)₄ is (3 + 2)-dimensionally modulated [superspace group <i>I</i>4₁/<i>a</i>(αβ0)­00(−βα0)­00, <i>a</i> = 5.238 672(7) Å, <i>c</i> = 11.548 43(2) Å, <b>q</b>_<b>1</b> = 0.55331(8)<b>a</b>* + 0.82068(9)<b>b</b>*, <b>q</b>_<b>2</b> = −0.82068(9)<b>a</b>* + 0.55331(8)<b>b</b>*, <i>R</i>_F = 0.061, <i>R</i>_P = 0.082]. In both cases the modulation arises from the ordering of the Ca/Eu cations and the cation vacancies at the A-sublattice of the parent scheelite ABO₄ structure. The cation ordering is incomplete and better described with harmonic rather than with steplike occupational modulation functions. The structures respond to the variation of the effective charge and cation size at the A-position through the flexible geometry of the MoO₄^2– and WO₄^2– tetrahedra demonstrating an alternation of stretching the B–O bond lengths and bending the O–B–O bond angles. The tendency towards A-site cation ordering in scheelites is rationalized using the difference in ionic radii and concentration of the A-site vacancies as parameters and presented in the form of a structure map

Secondary electron induced current in scanning transmission electron microscopy: an alternative way to visualize the morphology of nanoparticles

Electron tomography (ET) is a powerful tool to determine the three-dimensional (3D) structure of nanomaterials in a transmission electron microscope. However, the acquisition of a conventional tilt series for ET is a time-consuming process and can therefore not provide 3D structural information in a time-efficient manner. Here, we propose surface-sensitive secondary electron (SE) imaging as an alternative to ET for the investigation of the morphology of nanomaterials. We use the SE electron beam induced current (SEEBIC) technique that maps the electrical current arising from holes generated by the emission of SEs from the sample. SEEBIC imaging can provide valuable information on the sample morphology with high spatial resolution and significantly shorter throughput times compared with ET. In addition, we discuss the contrast formation mechanisms that aid in the interpretation of SEEBIC data

Unbiasedness and efficiency of non-parametric and UMVUE estimators of the probabilistic index and related statistics

In reliability theory, diagnostic accuracy, and clinical trials, the quantity (Formula presented.), also known as the Probabilistic Index (PI), is a common treatment effect measure when comparing two groups of observations. The quantity (Formula presented.), a linear transformation of PI known as the net benefit, has also been advocated as an intuitively appealing treatment effect measure. Parametric estimation of PI has received a lot of attention in the past 40 years, with the formulation of the Uniformly Minimum-Variance Unbiased Estimator (UMVUE) for many distributions. However, the non-parametric Mann–Whitney estimator of the PI is also known to be UMVUE in some situations. To understand this seeming contradiction, in this paper a systematic comparison is performed between the non-parametric estimator for the PI and parametric UMVUE estimators in various settings. We show that the Mann–Whitney estimator is always an unbiased estimator of the PI with univariate, completely observed data, while the parametric UMVUE is not when the distribution is misspecified. Additionally, the Mann–Whitney estimator is the UMVUE when observations belong to an unrestricted family. When observations come from a more restrictive family of distributions, the loss in efficiency for the non-parametric estimator is limited in realistic clinical scenarios. In conclusion, the Mann–Whitney estimator is simple to use and is a reliable estimator for the PI and net benefit in realistic clinical scenarios

Stabilizing Perovskite Pb(Mg_0.33Nb_0.67)O₃–PbTiO₃ Thin Films by Fast Deposition and Tensile Mismatched Growth Template

Because of its low hysteresis, high dielectric constant, and strong piezoelectric response, Pb­(Mg1/3Nb2/3)­O3–PbTiO3 (PMN–PT) thin films have attracted considerable attention for the application in PiezoMEMS, field-effect transistors, and energy harvesting and storage devices. However, it remains a great challenge to fabricate phase-pure, pyrochlore-free PMN–PT thin films. In this study, we demonstrate that a high deposition rate, combined with a tensile mismatched template layer can stabilize the perovskite phase of PMN–PT films and prevent the nucleation of passive pyrochlore phases. We observed that an accelerated deposition rate promoted mixing of the B-site cation and facilitated relaxation of the compressively strained PMN–PT on the SrTiO3 (STO) substrate in the initial growth layer, which apparently suppressed the initial formation of pyrochlore phases. By employing La-doped-BaSnO3 (LBSO) as the tensile mismatched buffer layer, 750 nm thick phase-pure perovskite PMN–PT films were synthesized. The resulting PMN–PT films exhibited excellent crystalline quality close to that of the STO substrate

High-Throughput Morphological Chirality Quantification of Twisted and Wrinkled Gold Nanorods

Chirality in gold nanostructures offers an exciting opportunity to tune their differential optical response to left- and right-handed circularly polarized light, as well as their interactions with biomolecules and living matter. However, tuning and understanding such interactions demands quantification of the structural features that are responsible for the chiral behavior. Electron tomography (ET) enables structural characterization at the single-particle level and has been used to quantify the helicity of complex chiral nanorods. However, the technique is time-consuming and consequently lacks statistical value. To address this issue, we introduce herein a high-throughput methodology that combines images acquired by secondary electron-based electron beam-induced current (SEEBIC) with quantitative image analysis. As a result, the geometric chirality of hundreds of nanoparticles can be quantified in less than 1 h. When combining the drastic gain in data collection efficiency of SEEBIC with a limited number of ET data sets, a better understanding of how the chiral structure of individual chiral nanoparticles translates into the ensemble chiroptical response can be reached

Low-Dose 4D-STEM Tomography for Beam-Sensitive Nanocomposites

Electron tomography is essential for investigating the three-dimensional (3D) structure of nanomaterials. However, many of these materials, such as metal–organic frameworks (MOFs), are extremely sensitive to electron radiation, making it difficult to acquire a series of projection images for electron tomography without inducing electron-beam damage. Another significant challenge is the high contrast in high-angle annular dark field scanning transmission electron microscopy that can be expected for nanocomposites composed of a metal nanoparticle and an MOF. This strong contrast leads to so-called metal artifacts in the 3D reconstruction. To overcome these limitations, we here present low-dose electron tomography based on four-dimensional scanning transmission electron microscopy (4D-STEM) data sets, collected using an ultrafast and highly sensitive direct electron detector. As a proof of concept, we demonstrate the applicability of the method for an Au nanostar embedded in a ZIF-8 MOF, which is of great interest for applications in various fields, including drug delivery

Low-Dose 4D-STEM Tomography for Beam-Sensitive Nanocomposites

Electron tomography is essential for investigating the three-dimensional (3D) structure of nanomaterials. However, many of these materials, such as metal–organic frameworks (MOFs), are extremely sensitive to electron radiation, making it difficult to acquire a series of projection images for electron tomography without inducing electron-beam damage. Another significant challenge is the high contrast in high-angle annular dark field scanning transmission electron microscopy that can be expected for nanocomposites composed of a metal nanoparticle and an MOF. This strong contrast leads to so-called metal artifacts in the 3D reconstruction. To overcome these limitations, we here present low-dose electron tomography based on four-dimensional scanning transmission electron microscopy (4D-STEM) data sets, collected using an ultrafast and highly sensitive direct electron detector. As a proof of concept, we demonstrate the applicability of the method for an Au nanostar embedded in a ZIF-8 MOF, which is of great interest for applications in various fields, including drug delivery