X-ray diffraction and electron microscopy studies on the morphology of the Cu0.96CO2.04O4 spinel prepared by thermal decomposition of copper (II)-cobalt (II) hydroxonitrates

Polycrystalline samples of Cu_x. Co_2-x(OH)₃NO₃ with a Cu/Co atomic ratio equal to 0.47 have been thermally decomposed in air at temperatures in the range 180–450 C. The morphology of the final cu_o.96Co_2.04O₄ spinel products has been studied by means of X-ray diffraction line profile analyses and electron microscopy observations. It has been found that in the temperature interval 180–325°C the size and form of the spinel crystallites do not depend on the temperature or on the reaction rate. It has been assumed that the oxide formation is associated with a diffusionless transformation similar to that established with a number of hydroxonitrate and hydroxide precursors having layered crystal structures.     

Protein Crystals Nucleated and Grown by Means of Porous Materials Display Improved X-ray Diffraction Quality

Well-diffracting protein crystals are indispensable for X-ray diffraction analysis, which is still the most powerful method for structure-function studies of biomolecules. A promising approach to growing such crystals is the use of porous nucleation-inducing materials. However, while protein crystal nucleation in pores has been thoroughly considered, little attention has been paid to the subsequent growth of crystals. Although the nucleation stage is decisive, it is the subsequent growth of crystals outside the pore that determines their diffraction quality. The molecular-scale mechanism of growth of protein crystals in and outside pores is theoretically considered. Due to the low degree of metastability, the crystals that emerge from the pores grow slowly, which is a prerequisite for better diffraction. This expectation has been corroborated by experiments carried out with several types of porous material, such as bioglass (“Naomi’s Nucleant”), buckypaper, porous gold and porous silicon. Protein crystals grown with the aid of bioglass and buckypaper yield significantly better diffraction quality compared with crystals grown conventionally. In all cases, visually superior crystals are usually obtained. Our theoretical conclusion is that heterogeneous nucleation of a crystal outside the pore is an exceptional case. Rather, the protein crystals nucleating inside the pores continue growing outside them.     

Lidar monitoring of regions of intense backscatter with poorly defined boundaries

The upper height of a region of intense backscatter with a poorly defined boundary between this region and a region of clear air above it is found as the maximal height where aerosol heterogeneity is detectable, that is, where it can be discriminated from noise. The theoretical basis behind the retrieval technique and the corresponding lidar-data-processing procedures are discussed. We also show how such a technique can be applied to one-directional measurements. Examples of typical results obtained with a scanning lidar in smoke-polluted atmospheres and experimental data obtained in an urban atmosphere with a vertically pointing lidar are presented.     

An improved model for surround suppression by steerable filters and multilevel inhibition with application to contour detection

Psychophysical and neurophysiological evidence about the human visual system shows the existence of a mechanism, called surround suppression, which inhibits the response of an edge in the presence of other similar edges in the surroundings. A simple computational model of this phenomenon has been previously proposed by us, by introducing an inhibition term that is supposed to be high on texture and low on isolated edges. While such an approach leads to better discrimination between object contours and texture edges w.r.t. methods based on the sole gradient magnitude, it has two drawbacks: first, a phenomenon called self-inhibition occurs, so that the inhibition term is quite high on isolated contours too; previous attempts to overcome self-inhibition result in slow and inelegant algorithms. Second, an input parameter called “inhibition level” needs to be introduced, whose value is left to heuristics. The contribution of this paper is two-fold: on one hand, we propose a new model for the inhibition term, based on the theory of steerable filters, to reduce self-inhibition. On the other hand, we introduce a simple method to combine the binary edge maps obtained by different inhibition levels, so that the inhibition level is no longer specified by the user. The proposed approach is validated by a broad range of experimental results.     

Morphology rearrangement of PEO and PG blocks of amphiphilic copolymer particles in solution affected by FeCl<Subscript>3</Subscript>/acidified water addition

The present contribution describes the preparation of nanosized aggregates by dissolving diblock copolymers consisting of hydrophobic polystyrene (PS) with randomly distributed short diene (D) moieties and hydrophilic polyether (polyethylene oxide (PEO) or polyglycidol (PG)) blocks in selective solvents. Inducing structural and/or size changes of the aggregates by addition of FeCl₃/acidified H₂O to the system is experimented. Dynamic light scattering (DLS) and size exclusion chromatography (SEC) measurements reveal resizing of the particles whilst adding FeCl₃/acidified H₂O. Further the structure and size of P(SD-EO/G) block copolymer corе-shell particles are determined by Diffusion Ordered NMR Spectroscopy (DOSY) which indicates a partial reversal of the core-shell structure upon the addition of FeCl₃/acidified H₂O. Transmission electron microscopy provides a more detailed insight on the morphology, shape and size distribution of the aggregates. For comparison, the change in the particle size under identical conditions for species of preliminary stabilized core-shell morphology is monitored as well.     

The structural and electrical properties of the SrTa2O6/In0.53Ga0.47As/InP system

The structural and electrical properties of SrTa₂O₆(SrTaO)/n-In_0.53GaAs_0.47(InGaAs)/InP structures where the SrTaO was grown by atomic vapor deposition, were investigated. Transmission electron microscopy revealed a uniform, amorphous SrTaO film having an atomically flat interface with the InGaAs substrate with a SrTaO film thickness of 11.2 nm. The amorphous SrTaO films (11.2 nm) exhibit a dielectric constant of ∼20, and a breakdown field of >8 MV/cm. A capacitance equivalent thickness of ∼1 nm is obtained for a SrTaO thickness of 3.4 nm, demonstrating the scaling potential of the SrTaO/InGaAs MOS system. Thinner SrTaO films (3.4 nm) exhibited increased non-uniformity in thickness. From the capacitance-voltage response of the SrTaO (3.4 nm)/n-InGaAs/InP structure, prior to any post deposition annealing, a peak interface state density of ∼2.3 × 10¹³ cm⁻² eV⁻¹ is obtained located at ∼0.28 eV (±0.05 eV) above the valence band energy (E_v) and the integrated interface state density in range E_v + 0.2 to E_v + 0.7 eV is 6.8 × 10¹² cm⁻². The peak energy position (0.28 ± 0.05 eV) and the energy distribution of the interface states are similar to other high-k layers on InGaAs, such as Al₂O₃ and LaAlO₃, providing further evidence that the interface defects in the high-k/InGaAs system are intrinsic defects related to the InGaAs surface.     

A Two-Fluid Simulation of Tailings Dam Breaching

Mine Water and the Environment - This paper presents the development and application of a dam breach model, EMBREA-MUD, which is suitable for tailings dams. One of the common failure modes for...