The impact of drying and steaming processes on surface color changes of tension and normal beech wood

Abstract

Beech wood has a high frequency of defects such as red heartwood, reaction wood (tension wood). For the experimental measurements four logs without visible defects like red heartwood, which can noticeably affects the measurements' results were qualified. The drying medium temperature in the first phase of the process before the moisture content of the specimens fell below the FSP was maintained at 45?°C. Then, the temperature was gradually increased to the maximum value 65?°C. The results showed that different initial wood moisture content does not affect to final value of tension and normal wood. The colorimetric parameter L* was much higher for tension wood. After steaming, there were greater differences in the colorimetric parameters, respectively, a* and b*. After drying the difference of all colorimetric parameters between tension and normal wood was significantly less. The color changes were only noticed in the surface layers of specimens. Differences were small, and thus, the impact of the tension wood on the color changes was not confirmed. However, since the lightness of tension wood plays a key role for its visual detection, it may be adequate to only measure the lightness parameter (L*).     

Characterization and dielectric properties of β-SiC nanofibres

SiC nanofibres produced by chemical vapour reaction technique are investigated using scanning and transmission electron microscopy. The nanofibres have been found to have a crystalline core of β-SiC sheathed with thorn-like turbostratic carbon or amorphous Si/O/C, respectively. For this material, real and imaginary part of relative permittivity is measured in a frequency range of 1–18 GHz at room temperature. The results reveal that the permittivity and dielectric loss in the SiC nanofibres are a magnitude higher compared with sub-microcrystalline SiC powder. Composition and nanostructure are held responsible for the difference in dielectric properties. The mechanisms of dielectric loss in the SiC nanofibres are discussed based on interfacial polarization, lattice defects in the SiC nanofibre cores and conduction loss of turbostratic carbon in the thorn-like sheath of SiC nanofibres.     

Variation of the adsorption properties of porous silicon in the course of natural and high-temperature aging

The photo-and thermostimulated adsorption-desorption processes on the surface of porous silicon (por-Si) were studied in the course of natural and high-temperature degradation of the samples. The results of IR absorption, luminescence, and Auger electron spectroscopy measurements indicate that an active stage in the sample morphology variation under the natural aging conditions lasts for a prolonged time (exceeding 74 days) upon the por-Si layer formation and is accompanied by redistribution of the adsorbed molecules. The surface properties vary so as to favor the adsorption of oxygen, carbon, and, probably, OH groups. The high-temperature (1149 K) treatment of the por-Si surface in acetone vapor favors the formation of a carbonized layer possessing a characteristic photoluminescence spectrum with a maximum intensity at 458 nm. The IR spectra indicate the presence of a silicon carbide phase, identified as the cubic β-SiC, with a characteristic absorption at 800–833 cm⁻¹. A strong shift of the high-frequency wing of the IR absorption spectrum is explained by the carbon substitution for one oxygen in the O-Si-O groups.     

Aberrant methylation of p16INK4a and deletion of p15INK4b are frequent events in human esophageal cancer in Linxian, China

Esophageal transit scintigraphy seems to be a valid methodology to assess impaired esophageal motility in early stages of disease. The purpose of this study was to discriminate patients with primary Raynaud's phenomenon (RP) and patients with systemic sclerosis (SSc) from healthy subjects by esophageal scintigraphy with a semisolid meal. METHODS: We studied 32 patients with primary RP, 18 with SSc and 13 healthy subjects. Dysphagia, acid regurgitation and heartburn were scored. After an overnight fast, all subjects underwent esophageal scintigraphy, using a semisolid orally ingested bolus (10 mL apple puree) labeled with 99mTc-sulfur colloid. Esophageal transit and emptying time and integral value were evaluated with the subjects in the upright (sitting) and supine positions. Transit time was defined as the time from the entry of 50% of radioactivity into the upper esophagus until the clearance of 50% of the bolus from the whole esophagus. Emptying time was defined as the time from the entry of 50% of radioactivity into the upper esophagus, until the clearance of 100% of the bolus from the whole esophagus. Integral value was defined as the total counts under the time-activity curve normalized to the maximum. RESULTS: Esophageal transit and emptying time and integral value, evaluated in both positions, were significantly higher in patients with SSc than in healthy subjects and than in patients with RP. Moreover, patients with RP had all three parameters, assessed in supine position, significantly longer compared to healthy subjects. Clinical scores regarding dysphagia, acid regurgitation and heartburn were not significantly different between patients with RP and SSc. CONCLUSION: Esophageal transit and emptying time and integral value appear to be able to discriminate patients with primary RP from patients with SSc and patients with RP from healthy subjects, suggesting an early mild esophageal dysfunction in RP.     

Microstructure and Porosity of Laser Welds in Cast Ti-6Al-4V with Addition of Boron

Metallurgical and Materials Transactions A - Addition of small amounts of boron to cast Ti-6Al-4V alloy has shown to render a finer microstructure and improved mechanical properties. For such an...     

Comparison of the microstructures in continuous-cooled and quench-tempered pre-hardened mould steels

The increased demand for plastic mould steels in pre-hardened condition has drawn the attention to this specific type of steel. As a result, more investigations are performed to understand microstructure and properties. In this work, the microstructures of two pre-hardened plastic mould steels, one quench-tempered (Uddeholm Impax HH) and the other continuously cooled (Uddeholm Nimax), are studied in delivery condition by means of different microscopy techniques and are linked to their production procedure. The results show that the quench-tempered material contains large amounts of M₃C carbides formed within the martensite plates as well as at the lath- and prior austenite grain boundaries. A few coarser Cr-rich M₇C₃ carbides have also been found. In comparison, the microstructure of the continuously cooled material consists of mainly bainite with much lower density and finer cementite particles. The hardness is with ∼40 HRC more or less constant over the cross section of both materials.