Metal Oxide Nanosheets as 2D Building Blocks for the Design of Novel Materials

Research into 2-dimensional materials has soared during the last couple of years. Next to van der Waals type 2D materials such as graphene and h-BN, less well-known oxidic 2D equivalents also exist. Most 2D oxide nanosheets are derived from layered metal oxide phases, although few 2D oxide phases can be also made by bottom-up solution syntheses. Owing to the strong electrostatic interactions within layered metal oxide crystals, a chemical process is usually needed to delaminate them into their 2D constituents. This Review article provides an overview of the synthesis of oxide nanosheets, and methods to assemble them into nanocomposites, mono- or multilayer films. In particular, the use of Langmuir–Blodgett methods to form monolayer films over large surface areas, and the emerging use of ink jet printing to form patterned functional films is emphasized. The utilization of nanosheets in various areas of technology, for example, electronics, energy storage and tribology, is illustrated, with special focus on their use as seed layers for epitaxial growth of thin films, and as electrochemically active electrodes for supercapacitors and Li ion batteries.     

Amorphous iron-chromium oxide nanoparticles prepared by sonochemistry

Amorphous Fe₂O₃ and Fe_1.9Cr_0.1O₃ materials have been prepared by sonochemical method. X-ray diffraction patterns, transmission electron microscopy, Raman and infrared spectra, differential scanning calorimetry, Mössbauer and magnetic measurements revealed many interesting behaviors of the samples. Reaction to form the materials only occurred at the preparation temperatures of 70 °C or above. Upon heating, the sample prepared at 70°C presented a strong ferromagnetic behavior due to the presence of the magnetite phase coexisting with the hematite phase whereas the samples prepared at higher temperatures presented only the existence of the hematite phase. Thermal analyses of the sample prepared at 80°C revealed three exothermic peaks which were corresponding to the phase changes of dehydroxylation, crystallization of the maghemite phase and maghemite–hematite transition, respectively. The activation energies of the phase changes deduced from the thermal analyses showed that the presence of Cr enhanced the activation energy which can slow down the ageing effect of the amorphous state when being used in practice.     

Instance Segmentation of Multiple Myeloma Cells Using Deep-Wise Data Augmentation and Mask R-CNN

Multiple myeloma is a condition of cancer in the bone marrow that can lead to dysfunction of the body and fatal expression in the patient. Manual microscopic analysis of abnormal plasma cells, also known as multiple myeloma cells, is one of the most commonly used diagnostic methods for multiple myeloma. However, as it is a manual process, it consumes too much effort and time. Besides, it has a higher chance of human errors. This paper presents a computer-aided detection and segmentation of myeloma cells from microscopic images of the bone marrow aspiration. Two major contributions are presented in this paper. First, different Mask R-CNN models using different images, including original microscopic images, contrast-enhanced images and stained cell images, are developed to perform instance segmentation of multiple myeloma cells. As a second contribution, a deep-wise augmentation, a deep learning-based data augmentation method, is applied to increase the performance of Mask R-CNN models. Based on the experimental findings, the Mask R-CNN model using contrast-enhanced images combined with the proposed deep-wise data augmentation provides a superior performance compared to other models. It achieves a mean precision of 0.9973, mean recall of 0.8631, and mean intersection over union (IOU) of 0.9062.     

Pulse broadening of enhanced backscattering from rough surfaces

Recently, we presented a study of pulse scattering by rough surfaces based on the first-order Kirchhoff approximation which is applicable to rough surfaces with RMS slope less than 0.5 and correlation distance l≳λ. However, there has been an increased interest in enhanced backscattering from rough surfaces, study of which requires inclusion of the second-order Kirchhoff approximation with shadowing corrections. This paper presents a theory for the two-frequency mutual coherence function in this region and shows that the multiple scattering on the surface gives rise to an additional pulse tail in the direction of enhanced backscattering. The theory predicts pulse broadening approximately 20% greater than that caused by single scattering alone for a delta-function incident pulse and typical surface parameters. Analytical results are compared with Monte Carlo simulations and millimetre-wave experiments for the one-dimensional rough surface with RMS height 1λ and correlation distance 1λ, showing good agreement.     

Electronic and nuclear contributions to the third-order nonlinear optical susceptibilities of new p-N, N'-dimethylaniline tetrathiafulvalene derivatives

We report large third-order nonlinear optical susceptibilities (?3?)(ijkl) of new tetrathiafulvalene derivatives, using the degenerate four-wave mixing (DFWM) method. To understand the physical nature of the optical nonlinearities, we separate their electronic and nuclear contributions. The electronic contribution to the third-order nonlinear optical susceptibilities of the molecules turns out to be dominant. From DFWM measurements we also deduce the values of the second-order hyperpolarizabilities gamma, which are ~10(5) greater than the gamma value of CS(2).     

γ-Subdifferential and γ-convexity of functions on a normed space

In this paper, the -subdifferential is introduced for investigating the global behavior of real-valued functions on a normed spaceX. Iff: DX attains its global minimum onD atx ^*, then 0 f(x ^*). This necessary condition always holds, even iff is not continuous orx ^* is at the boundary of its domain. Nevertheless, it is useful because, by choosing a suitable ₊, many local minima cannot satisfy this necessary condition. For the sufficient conditions, the so-called -convex functions are defined. The class of these functions is rather large. For example, every periodic function on the real line is a -convex function. There are -convex functions which are not continuous everywhere. Every function of bounded variation can be represented as the difference of two -convex functions. For all that, -convex functions still have properties similar to those of convex functions. For instance, each -local minimizer off is at the same time a global one. Iff attains its global minimum onD, then it does so at least at one point of its -boundary.This research was supported by the Alexander von Humboldt Foundation. The author thanks Professors R. Bulirsch, K. H. Hoffmann, and H. G. Bock for inviting him to Munich and Augsburg where this research was done.     

Global and local definition of the Monge–Ampère operator on compact Kähler manifolds

The aim of this Note is to give a sufficient condition in order for a function in the global domain of definition of the Monge–Ampère operator not to belong to the local domain of the former in the sense of Cegrell, when one looks at the n-dimensional complex projective space. Using this result, we show that the subsolution theorem is false for functions in the local domain of definition of the Monge–Ampère operator on such a projective space.     

Some Analytical Properties of γ-Convex Functions in Normed Linear Spaces

For a fixed positive number γ, a real-valued function f defined on a convex subset D of a normed space X is said to be γ-convex if it satisfies the inequality