Characterisation of K, Na, and Li birnessites prepared by oxidation with H2O2 in a basic medium. Ion exchange properties and study of the calcined products

Birnessites containing Na, K or Li in the interlayer have been prepared by oxidation of Mn(II) cations with H₂O₂ in a basic medium with different alkaline cation/Mn molar ratios. The solids prepared have been characterised by elemental chemical analysis, powder X-ray diffraction, thermal analyses (differential thermal analysis and thermogravimetric analysis), FT-IR spectroscopy and surface texture assessment by adsorption of N₂ at –196°C. Crystalline birnessites are obtained for A/Mn ratios (A = K, Li) larger than 3.4, but MnO(OH) has been also identificed when such a ratio is smaller than 3.4. Ion exchange is topotactic, but is not complete for exchanging Na, K, or Mg for pre-existing Li. The solids are stable up to 400°C, and formation of spinels and solids with tunnel structures is observed at this temperature. Li-containing birnessites are transformed to LiMn₂O₄ spinel at 400°C, and co-crystallization of bixbyte (Mn₂O₃) is observed at higher temperatures. Bixbyte and cryptomelane are formed at 500°C for the K-containing birnessites.     

Microstructural and textural characterization of a hot-rolled IF steel

The present paper reports the experimental results on the microstructural and textural characterization of a hot-rolled IF steel. The IF steel was hot-rolled in multiple passes in the austenitic field (1,070 °C) followed by air-cooling. SEM, TEM, and LOM were used to image the microstructure of the material. The global texture was determined by X-ray diffraction (XRD) technique. The mesotexture of selected regions was investigated by electron backscatter diffraction (EBSD). Results show the presence of a diffuse (nearly random) and weak texture in the hot-band that consists of recrystallized polygonal grains and subgrains. The fraction of boundaries with misorientations comprised in the interval 2° ≤ ψ < 15° was found to be lower than 5%. It can be concluded that these low angle boundaries and the presence of subgrains can be associated to the existence of a few areas softened by recovery during or after hot rolling in austenitic field.     

Eutectic bonding of Al-based high aspect ratio microscale structures

Metal-based microelectromechanical systems (MEMS) have important advantages over Si-based MEMS. To form any functional metal-based microdevice from metallic high-aspect-ratio microscale structures (HARMS), proper assembly and packaging are required. In this paper, we report successful eutectic bonding of Al-based HARMS using Al–Ge intermediate layers. A series of Al–Ge composite thin films were vapor deposited. Their composition and micro-/nano-scale structure were characterized. The morphology of bonded Al structures was examined, including the morphology of separated surfaces.     

Temperature variation of the morphology of nanocluster ensembles in the Ge/Si(100) system

The morphological characteristics of hut-cluster ensembles formed in a Ge/Si(100) heteroepitaxial system have been studied as functions of the substrate surface temperature by theoretical methods and by atomic force microscopy. As the temperature increases from 420 to 500°C, the lateral size of nanoclusters with a square base (grown at the same rate of 0.0345 ML/s to a total coverage of 6.2 ML) grows from 12 to 20 nm, while their number density on the substrate surface drops from 5.6×10¹⁰ to 1.5×10¹⁰ cm⁻². Predictions of a kinetic model are in sufficiently good agreement with the experimental data.     

Effect of hydrogen charging on dislocation behavior in Ni-Cr and Ni<Subscript>2</Subscript>Cr alloys

The effects of hydrogen charging on the dislocation behaviour in Ni-Cr binary alloys have been investigated by means of transmission electron microscope (TEM) observations using single-crystalline specimens. The deformation mode of Ni-Cr alloys in the absence of hydrogen is characterized by planar dislocations. However, hydrogen charging changed the dislocation configurations to promote curved dislocations, such as dislocation loops and dipoles. The hydrogen-affected dislocation configurations are enhanced with increasing Ni content and reducing Cr content. Weak-beam images show that the Shockley partials of the hydrogen-affected dislocations frequently constrict to make kinks and cross-slip, as if the dislocations were generated by a thermally activated process. The effect of hydrogen charging on superdislocations of a Ni₂Cr superstructure has been also investigated using an aged 70Ni-30Cr alloy. While the deformation mode in the Ni₂Cr superlattice is classified as five variants of superdislocation triplets and one variant of ordinary dislocations, the hydrogen charging has preferred the ordinary dislocations to the superdislocation triplets. The results suggest that the charged hydrogen changes the local plasticity to affect the deformation dynamics in Ni-Cr alloys, where the influence of hydrogen on the plasticity is sensitive to the Ni/Cr concentration and the symmetry of atomic arrangement.     

Bayesian and Dempster-Shafer fusion

The Kalman Filter is traditionally viewed as a prediction-correction filtering algorithm. In this work we show that it can be viewed as a Bayesian fusion algorithm and derive it using Bayesian arguments. We begin with an outline of Bayes theory, using it to discuss well-known quantities such as priors, likelihood and posteriors, and we provide the basic Bayesian fusion equation. We derive the Kalman Filter from this equation using a novel method to evaluate the Chapman-Kolmogorov prediction integral. We then use the theory to fuse data from multiple sensors. Vying with this approach is the Dempster-Shafer theory, which deals with measures of “belief”, and is based on the nonclassical idea of “mass” as opposed to probability. Although these two measures look very similar, there are some differences. We point them out through outlining the ideas of the Dempster-Shafer theory and presenting the basic Dempster-Shafer fusion equation. Finally we compare the two methods, and discuss the relative merits and demerits using an illustrative example.     

The effects of glycol methacrylate as a dehydrating agent on the dimensional changes of liver tissue

The dimensional changes of liver sections during the course of processing with glycol methacrylate (GMA) or with ethanol are described. Tissue processing with ethanol served as a control. During prolonged processing steps (24 h each), linear shrinkage of tissue specimens dehydrated with GMA at room temperature was 13.2%. Subsequent infiltration with GMA resulted in trivial swelling, and polymerization in slight shrinkage (2.3%). In comparison, processing with cold GMA resulted in shrinkage during dehydration (about 10.8%), a slight swelling in pure GMA, followed by shrinkage during polymerization (2.2%). Short routine processing schedules resulted in similar shrinkage/swelling patterns, although precise values differed slightly. In all experiments, ethanolic dehydration resulted in smaller dimensional tissue changes than did GMA dehydration. The dimensional changes of tissue sections during stretching on water, mounting and drying compensated for the major part of the shrinkage manifested during processing.     

Significance of DNA ploidy in the treatment of T1 glottic carcinoma

OBJECTIVE: To assess the role of DNA ploidy as a predictor of radioresistance in T1 glottic carcinoma. DESIGN: Case-control study. Flow cytometric DNA ploidy measurements were performed on formalin-fixed paraffin-embedded tumor specimens from 15 patients with T1 glottic laryngeal carcinomas in whom radiotherapy had failed and from a matched group of 15 patients in whom an identical radiotherapy regimen was curative. Analysis of DNA content was performed blind to outcome of treatment. SETTING: Academic tertiary referral medical center. PARTICIPANTS: Thirty patients with clinically staged T1, N0, M0 glottic carcinoma. INTERVENTION: All patients received radiation to the larynx through opposed lateral ports at a total dose of 64 to 70 Gy. RESULTS: Ten diploid and five aneuploid histograms were found in the resistant group, and six diploid and nine aneuploid histograms were found in the radiosensitive group. This difference was not statistically significant. A trend toward a higher relapse rate after radiotherapy (62.5%) among patients with diploid tumor compared with those with aneuploid tumor (35.7%) was noted. CONCLUSIONS: DNA ploidy did not predict response to radiotherapy in patients with T1 glottic cancer, probably because of the small number of patients. A trend toward lower risk of local recurrence after radiotherapy in aneuploid tumors was noted. A larger prospective study is needed to assess the value of DNA ploidy in the treatment of early laryngeal cancer.     

Effect of precyclic loading on stress-corrosion-cracking initiation in an X-65 pipeline steel exposed to near-neutral pH soil environment

A study was carried out to understand the effect of precyclic loading on stress-corrosion-crack initiation in an X-65 pipeline steel exposed to a near-neutral-pH soil environment. The test specimens were precyclically loaded before corrosion exposure to represent a service history of up to about 20 years, depending on the severity of pressure fluctuation. Microcracks had initiated on the polished surface of the X-65 pipeline steel after long-time exposure at open-circuit potential (OCP) in a near-neutral-pH synthetic soil solution. These microcracks were mostly initiated from pits at metallurgical discontinuities such as grain boundaries, pearlitic colonies, and banded phases in the steel. Strong preferential dissolution was observed along planes of the banded structures in the steel. The selective corrosion attack at these metallurgical discontinuities is attributed to the galvanic nature of those areas to their neighbors. Cyclic loading prior to corrosion exposure had significant effects on microcrack initiation and propagation during subsequent corrosion exposure. Cyclic loading prior to corrosion exposure either reduced or increased the probability of crack initiation and the rate of crack propagation, depending upon the magnitude of the stress cycles. The largest reduction was seen at a peak cyclic stress of about 0.8 of the yield strength. This cyclic-loading-dependent cracking behavior might be related to the alteration of the substructures and the residual stress in the steel as a result of precyclic loading.