Evaluation of Mold and Termite Resistance of Included Sapwood in Eastern Redcedar

The heartwood of eastern redcedar (Juniperus virginiana) frequently contains areas of light-colored wood. This "included sapwood" is considered to be a defect by some manufacturers. In this study, sapwood, included sapwood, and heartwood samples from five eastern redcedar trees were exposed to mold fungi or subterranean termites in a no-choice feeding test. Specific gravity, extractives content, and total volumetric shrinkage were also measured. The extractive content, specific gravity, and volumetric shrinkage values of sapwood and included sapwood were equivalent. Greater extractive content in heartwood blocks was associated with less volumetric shrinkage and greater specific gravity. Included sapwood showed the same resistance to mold growth as heartwood, which was more mold-resistant that the sapwood. Included sapwood, heartwood, and sapwood of redcedar all exhibited resistance to termite attack compared with pine wood controls

Facing hierarchy: a qualitative study of residents\u27 experiences in an obstetrical simulation scenario

BACKGROUND: Residents in surgical specialties face a steep hierarchy when managing medical crises. Hierarchy can negatively impact patient safety when team members are reluctant to speak up. Yet, simulation has scarcely been previously utilized to qualitatively explore the way residents in surgical specialities navigate this challenge. The study aimed to explore the experiences of residents in one surgical specialty, obstetrics and gynecology (Ob/Gyn), when challenging hierarchy, with the goal of informing future interventions to optimize resident learning and patient safety. METHODS: Eight 3rd- and 4th-year Ob/Gyn residents participated in a simulation scenario in which their supervising physician made an erroneous medical decision that jeopardized the wellbeing of the labouring mother and her foetus. Residents participated in 30-45 min semi-structured interviews that explored their approach to managing this scenario. Transcribed interviews were analysed using qualitative thematic inquiry by three research team members, finalizing the identified themes once consensus was reached. RESULTS: Study results show that the simulated scenario did create an experience of hierarchy that challenged residents. In response, residents adopted three distinct communication strategies while confronting hierarchy: (1) messaging - a mere reporting of existing clinical information; (2) interpretive - a deliberate construction of clinical facts aimed at swaying supervising physician\u27s clinical decision; and (3) advocative - a readiness to confront the staff physician\u27s clinical decision. Furthermore, residents utilized coping mechanisms to mitigate challenges related to confronting hierarchy, namely deflecting responsibility, diminishing urgency, and drafting allies. Both these communication strategies and coping mechanisms shaped their practice when challenging hierarchy to preserve patient safety. CONCLUSIONS: Understanding the complex processes in which residents engage when confronting hierarchy can serve to inform the development and study of curricular innovations. Informed by these processes, we must move beyond solely teaching residents to speak up and consider a broader curriculum that targets not only residents but also faculty physicians and the learning environment within the organization

Technical Note: Effect of Epoxy Embedment on Micromechanical Properties of Brown-Rot-Decayed Wood Cell Walls Assessed with Nanoindentation

Mechanical properties of brown-rot-decayed wood cell walls were evaluated using a nanoindentation technique. Epoxy resin is a typical medium for the sample embedding process in nanoindentation. It is assumed that the embedding process does not affect cell wall properties or that any effects are similar for different samples. As part of an investigation of microscale mechanical effects of brown-rot in wood, we applied nanoindentation to cell walls of decayed and nondecayed pine wood samples. For epoxy-embedded samples, there were no differences in modulus and hardness for control and decayed samples. However, for unembedded samples, significant differences were found between control and decayed samples. These results indicate that the epoxy-embedding process may confound micromechanical testing results. We speculate that in this case, epoxy resin penetrated and reinforced the cell wall of decayed samples

Heartwood Formation and Natural Durability—A Review

This paper reviews recent literature on the formation of heartwood and on the components that affect natural durability. It includes discussion about the function of heartwood in living trees, factors influencing the natural durability of heartwood, the process of heartwood formation, and variations in heartwood quantity and quality. Heartwood formation is a regular occurrence in tree stems, and heartwood may have many different properties from sapwood, including natural decay resistance. A greater understanding of the heartwood formation process could allow control of heartwood production. Recent research involving enzymatic analyses have provided valuable insight into the biochemical processes involved in heartwood formation. Further study of the role natural durability plays in living trees would help to bring together many of the disparate strands of research relating to heartwood

Effect of Wood Species on Water Sorption and Durability of Wood-Plastic Composites

Wood-plastic composites (WPCs) were made from isotactic polypropylene and 10 wood species (8 hardwoods and 2 softwoods). Water sorption and durability of the composites were evaluated. WPCs made with eastern redcedar and Osage orange had low moisture sorption characteristics, lower levels of fungal decay, and increased resistance to mold compared with composites made from other species. The color of the composites was initially quite different, reflecting the differences in color of the various wood species, but after outdoor exposure, the samples were similar in appearance. Metals in contact with WPCs corroded during accelerated exposure and the corrosion of galvanized steel was greatest when in contact with WPCs made from southern pine and black walnut. WPCs made from hickory, sweet gum, black cherry, and red oak corroded ordinary steel more than composites containing other species. These results demonstrate that the inherent characteristics of the wood filler can affect the properties of WPCs. The use of durable wood species in WPCs could result in products with improved durability performance

Effect of Extractives on Water Sorption and Durability of Wood-Plastic Composites

Wood—plastic composites (WPCs) were made from isotactic polypropylene and extracted and unextracted flours of one of four different wood species. WPCs made with extracted wood flour had lower mechanical properties than unextracted WPCs with the exception of pine WPCs. For all of the species except pine, WPCs made with extracted wood flours showed higher moisture sorption and thickness swelling characteristics. Higher levels of fungal decay were observed for the WPCs made with extracted wood, except for the pine WPCs, in which there was lower fungal decay from brown rot in the extracted wood samples. These results demonstrate that wood extractives affect the mechanical properties, water sorption, and fungal decay resistance of WPCs

Shared neural substrates of emotionally enhanced perceptual and mnemonic vividness

It is well known that emotionally salient events are remembered more vividly than mundane ones. Our recent research has demonstrated that such memory vividness is due in part to the subjective experience of emotional events as more perceptually vivid, an effect we call emotion-enhanced vividness, or EEV. The present study built on previously reported research in which fMRI data were collected while participants rated relative levels of visual noise overlaid on emotionally salient and neutral images. Ratings of greater EEV were associated with greater activation in the amygdala, visual cortex, and posterior insula. In the present study, we measured BOLD activation that predicted recognition memory vividness for these same images one week later. Results showed that, after controlling for differences between scenes in low-level objective features, hippocampus activation uniquely predicted subsequent memory vividness. In contrast, amygdala and visual cortex regions that were sensitive to EEV were also modulated by subsequent ratings of memory vividness. These findings suggest shared neural substrates for the influence of emotional salience on perceptual and mnemonic vividness, with amygdala and visual cortex activation at encoding contributing to the experience of both perception and subsequent memory. © 2013 Todd, Schmitz, Susskind and Anderson

Nonlinear interaction between electromagnetic fields at high temperature

The electron-positron `box' diagram produces an effective action which is fourth order in the electromagnetic field. We examine the behaviour of this effective action at high-temperature (in analytically continued imaginary-time thermal perturbation theory). We argue that there is a finite, nonzero limit as $T\rightarrow \infty$ (where $T$ is the temperature). We calculate this limit in the nonrelativistic static case, and in the long-wavelength limit. We also briefly discuss the self-energy in 2-dimensional QED, which is similar in some respects.Comment: 13 pages, DAMTP 94/3

Sequence-Specific Recognition and Cooperative Dimerization of N-Terminal Aromatic Peptides in Aqueous Solution by a Synthetic Host

This article describes the selective recognition and noncovalent dimerization of N-terminal aromatic peptides in aqueous solution by the synthetic host compound, cucurbit[8]uril (Q8). Q8 is known to bind two aromatic guests simultaneously and, in the presence of methyl viologen, to recognize N-terminal tryptophan over internal and C-terminal sequence isomers. Here, the binding of Q8 to aromatic peptides in the absence of methyl viologen was studied by isothermal titration calorimetry (ITC), 1H NMR spectroscopy, and X-ray crystallography. The peptides studied were of sequence X-Gly-Gly, Gly-X-Gly, and Gly-Gly-X (X = Trp, Phe, Tyr, and His). Q8 selectively binds and dimerizes Trp-Gly-Gly (1) and Phe-Gly-Gly (4) with high affinity (ternary K = 109−1011 M-2); binding constants for the other 10 peptides were too small to be measured by ITC. Both peptides bound in a stepwise manner, and peptide 4 bound with positive cooperativity. Crystal structures of Q8·1 and Q8·42 reveal the basis for selective recognition as simultaneous inclusion of the hydrophobic aromatic side chain into the cavity of Q8 and chelation of the proximal N-terminal ammonium group by carbonyl groups of Q8. The peptide sequence selectivity and positively cooperative dimerization reported here are, to the best of our knowledge, unprecedented for synthetic hosts in aqueous solution. Specific peptide recognition and dimerization by synthetic hosts such as Q8 should be important in the study of dimer-mediated biochemical processes and for the separation of peptides and proteins