Surface checking of wood is increased by photodegradation caused by ultraviolet and visible light
The aim of this research was to test the hypothesis that exposure to solar radiation increases the checking of wood exposed to the weather, and to examine the causes and spectral dependency of such an effect. Lodgepole pine decking samples were exposed outdoors under filters, which blocked selected regions of the solar spectrum while allowing other weathering factors to act on samples. Surface checking in samples was quantified after 12, 24 and 36 weeks of exposure, and the chemical and micro-structural changes occurring at weathered wood surfaces were examined. Check numbers and dimensions were greater in samples exposed under a filter to the full solar spectrum than in samples exposed under filters that blocked the transmission of UV, visible or infrared radiation. Samples that were shielded from more energetic wavelengths developed less checking and also showed less delignification at the exposed wood surfaces. Checks developed at the margins of rays and propagated at the interface between adjacent tracheids, close to the middle lamella. We conclude that exposure to UV and visible light increases the tendency of wood to check during exterior exposure. Our findings point to a link between changes in cell micro-structure as a result of photodegradation of lignin and the development of visible checks in wood exposed outdoors.
Effects of chemical modification with glutaraldehyde on the weathering performance of Scots pine sapwood
Scots pine sapwood was treated with glutaraldehyde (GA) in aqueous solution using magnesium chloride as a catalyst in order to evaluate the durability towards weathering. Infrared spectroscopy suggested that GA treatment increased the photo-stability of lignin during artificial weathering of micro-veneers in a QUV over 168 h; photo-protection increased with increasing GA concentration. In comparison with the unmodified controls, GA-modified pine micro-veneer strips exhibited a lower tensile strength loss measured in a zero-span mode in the course of weathering. During 18 months of outdoor exposure, GA-modified pine wood boards exhibited a lower moisture content and water uptake than the unmodified ones. GA treatment also clearly restricted the penetration of blue stain fungi into deeper layers of wood. On the macroscopic scale, the surface of the GA-modified boards was significantly smoother due to less erosion, cracking and minor peeling of tracheids. Scanning electron microscopy further revealed that individual tracheids were detached from the cell compound and then washed away from the unmodified wood surface, whereas tracheids on surfaces of GA-modified wood remained in the tissue compound but displayed many axial and transversal cracks.
The Role of Information Retrieval in the Diagnostic/Decision making Process within the Medical Appointment: A Review of the Literature
ABSTRACT Information retrieval/memory recall by patients/carers within the medical appointment is reported to be of paramount importance to the diagnostic/decision-making process within the medical appointment and hence to the outcome of the medical encounter itself. The rationale behind this paper (second in a series of papers) is to delve into the current literature to ascertain the pervasiveness of long-term information retrieval/memory recall concepts within this intricate environment, including the disease states in which patient information retrieval/memory recall research has been conducted, affording an analysis of research activities in order to identify the gaps in knowledge that currently exist. A rigorous systematic process detected 49 papers that clearly consider information retrieval/memory recall events within the medical appointment. Content analysis was conducted using a Concept-Centric Matrix in conjunction with open-coding techniques, giving rise to the detection of 227 concepts, which were subsequently assembled into 63 categories. Our analysis reveals the prevalence of long-term information retrieval/memory recall concepts, and the disease states that have conducted patient information retrieval/memory recall research (within the medical appointment) reported in writings over the past 43 years. Additionally, we have advanced our conceptual model of memory recall/information retrieval within the elicitation phase of the medical appointment, which we first presented in an earlier paper . The current paper is of significance as it facilitates an augmented understanding of information retrieval/memory recall (and the importance of same to the diagnostic/decision-making process and to patient outcomes, within the medical appointment. Furthermore, the exploration serves to highlight a number of IS research opportunities.