Emergence of physiological rhythmicity in term and preterm neonates in a neonatal intensive care unit

Background  

Biological rhythmicity, particularly circadian rhythmicity, is considered to be a key mechanism in the maintenance of physiological function. Very little is known, however, about biological rhythmicity pattern in preterm and term neonates in neonatal intensive care units (NICU). In this study, we investigated whether term and preterm neonates admitted to NICU exhibit biological rhythmicity during the neonatal period.     

Development of binderless fiberboard from kenaf core

Binderless fiberboards with densities of 0.3 and 0.5 g/cm³ were developed from kenaf core material using the conventional dry-manufacturing process. The effects of steam pressure (0.4–0.8 MPa) and cooking time (10–30 min) in the refining process, fiber moisture content (MC) (10%, 30%), and hot-pressing time (3–10 min) on the board properties were investigated. The results showed that kenaf core binderless fiberboards manufactured with high steam pressure and long cooking time during the refining process had high internal bond (IB) strength, low thickness swelling (TS), but low bending strength values. The binderless fiberboards made from 30% MC fibers showed better mechanical and dimensional properties than those from air-dried fibers. Hot-pressing time was found to have little effect on the IB value of the binderless board at the refining conditions of 0.8 MPa/20 min, but longer pressing time resulted in lower TS. At a density of 0.5 g/cm³, binderless fiberboard with the refining conditions of 0.8 MPa/20 min recorded a modulus of rupture (MOR) of 12 MPa, modulus of elasticity (MOE) of 1.7 GPa, IB of 0.43 MPa, and 12% TS under the optimum board manufacturing conditions. Part of this article was presented at the 54th Annual Meeting of the Japan Wood Research Society, Hokkaido, August 3–5, 2004     

Durability of isocyanate resin adhesives for wood IV: degradation under constant steam heating

The durability of isocyanate resins consisting of emulsion-type polymeric diphenylmethane diisocyanate (EMDI) was investigated under constant steam heating. Two kinds of resin, water only-added resin and polyol/water-added resin, were used in this study. The degradation of the resins under steam heating was observed using Fourier transform infrared spectroscopy (FT-IR), weight changes, and thermogravimetric analysis (TGA). FT-IR analysis showed that the degradation reaction of the resins scarcely proceeded for a few hours and then increased significantly. The weights of the resins decreased linearly during steam heating. The thermal stability of steam-treated resins was made clear by TGA. The bond strength reductions of the specimens bonded with the resins were also observed. The best fitting regression function for the behavior of bond strength reduction was determined statistically. The apparent activation energy of each resin was calculated from the regression function, for the half-life period. Considering the calculated values, the adhesion durability of using polyol-added resin was superior to that of using water only-added resin. It was clarified that the durability of the isocyanate resins under steam heating was markedly inferior to that under dry heating.Part of this paper was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, 2000     

Characterization of new thioacidolysis products of sinapyl aldehyde and coniferyl aldehyde

To elucidate the chemical structure ofp-hydroxycinnamyl aldehyde moieties of abnormal angiosperm lignins of cinnamyl alcohol dehydrogenase down-regulated plants, sinapyl and coniferyl aldehydes were subjected to thioacidolysis. and the products were analyzed by gas chromatograph-mass spectrometer (GC-MS). The chromatograms indicated that two pairs of new isomeric compounds were released during thioacidolysis of sinapyl and coniferyl aldehydes, respectively, together with the previously found products. These products were also found in the thioacidolysis products of dehydrogenation polymer incorporatingp-hydroxycinnamyl aldehydes. The new compounds had the novel indane structure in that they position of the side chain was linked to an aromatic ring. In the case of sinapyl aldehyde, these isomer compounds were the main products, which indicated different reactivities of sinapyl and coniferyl aldehydes during thioacidolysis.Part of this paper was presented at the TAPPI Pulping Conference. Nashville, October 1996; and the 41st Lignin Symposium, Nagoya. October 1996     

Elastic moduli and stiffness optimization in four-point bending of wood-based sandwich panel for use as structural insulated walls and floors

Several wood-based sandwich panels with low-density fiberboard core were developed for structural insulated walls and floors, with different face material, panel thickness, and core density. The elastic moduli with and without shear effect (E _L, E ₀) and shear modulus (G_b) were evaluated in four-point bending. Generally, the stiffer face, thicker panel, and higher core density were advantageous in flexural and shear rigidity for structural use, but the weight control was critical for insulation. Therefore, optimum designs of some virtual sandwich structures were analyzed for bending stiffness in relation to weight for fixed core densities, considering the manufactured-panel designs. As a result, the plywood-faced sandwich panel with a panel thickness of 95 mm (PSW-T100), with insulation performance that had been previously confirmed, was most advantageous at a panel density of 430 kg/m³, showing the highest flexural rigidity (E _L I = 13 × 10⁻⁶ GNm²) among these panels, where E _L, E ₀, and G _b were 3.5, 5.5, and 0.038 GN/m², respectively. The panel was found to be closest to the optimum design, which meant that its core and face thickness were optimum for stiffness with minimum density. The panel also provided enough internal bond strength and an excellent dimensional stability. The panel was the most feasible for structural insulation use with the weight-saving structure.     

Hybrid drying with high-frequency heating and hot air under atmospheric pressure IV: water movement in <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> wood during high-frequency heating

 The relations among internal temperature, internal pressure, and moisture content distribution in sugi square lumber during high-frequency (HF) heating were determined to clarify the mechanism of water movement during the combination of HF heating and hot air exposure. Green sugi square lumbers were subjected to HF heating under atmospheric pressure. The water movement and pathways in the lumber during HF heating were also investigated. Results showed that internal pressure is the driving force of water movement. HF heating causes a rise in the internal temperature and internal pressure in sugi square lumber. Ordinarily, water in lumber evaporates from the surfaces of lumber during hot air drying. However, with HF heating the internal pressure is generated by the increased temperature, and liquid water is driven not only parallel to the grain but also perpendicular to the grain of the lumber. The ratio of the amount of liquid flow in the parallel and perpendicular directions ranged from 2 : 3 to 1 : 3. When the movement of water in the lumber was traced with a 0.5% aqueous solution of acid fuchsin, water was found to move through the lumber in the longitudinal direction and then flow in a direction perpendicular to the grain or in the radial and tangential directions. Received: June 15, 2001 / Accepted: February 8, 2002 Acknowledgment The authors thank Dr. O.R. Pulido, Institute of Wood Technology, Akita Prefectural University, for discussions and for proofreading this paper. Part of this research was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 2001 Correspondence to:Y. Kawai     

Effect of polyol on thermo-oxidative degradation of isocyanate resin for wood adhesives

The thermo-oxidative degradation of various polyol-added isocyanate resins for wood adhesives was studied using differential scanning calorimetry and thermogravimetry. The degradation of the resin cured with water began at 150°C. When a certain polyol was added to the resin at an NCO/OH ratio of 25 in addition to water, the cured resin began to degrade at 200°C. To clarify the cause of the good thermal stability in polyol-added resins, the effect of various polyols on the reactivity of isocyanate was investigated. It was found that the reactivity of isocyanate was enhanced by the addition of a dipropylene glycol and glycerin-type polyols. In addition, the effect of the NCO/ polyol-OH ratio was investigated using dipropylene glycoltype polyol. The reactivity of isocyanate increased with increasing polyol content. The thermal stability of the resin was improved to a certain degree by addition of a small amount of the polyol but deteriorated when a large amount of the polyol was added.Part of this paper was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998     

Self-bonding characteristics of binderless kenaf core composites

We investigated optimum self-bonding conditions of kenaf core composites manufactured by steam treatment, and discussed on the roles of cinnamic acids in the self-bonding mechanism. The presence of cinnamic acids in the kenaf core and its composites were analyzed by pyrolysis gas chromatography-mass spectrophotometry in the presence of tetramethyl ammonium hydroxide (TMAH/Py-GC-MS). The results showed that the optimum bonding properties of kenaf core composites were achieved under these conditions: steam pressure of 0.8–1.0 MPa and pressing time of 10–15 min were able to provide shear strength of 0.40–0.42 MPa while having 2–5% of weight loss. Lignin analysis showed that steam-treated kenaf core composites had a lower proportion of syringyl- to guaiacyl-derived moieties and also cinnamic acids to guaiacyl-derived moieties than its native counterpart. The results indicated that some parts of the ester-linked cinnamic acids were also cleaved due to the degradation of hemicelluloses and lignin during steam treatment. Based on these results, it was concluded that in addition to three main components, the cinnamic acid was also suggested to participate in the self-bonding mechanism of non-wood lignocellulosic binderless boards.     

Strength,decay and termite resistance of oriented kenaf fiberboards

The development of oriented fiberboards made from kenaf (Hibiscus cannabinus L.) and their suitability as a construction material has been investigated. Three different types of boards consisting of five layers with individual orientations were prepared using a combination of low molecular weight and high molecular weight phenol-formaldehyde (PF) resin for impregnation and adhesion purposes. Additional boards with the same structure were prepared using high molecular weight PF resin only. The mechanical properties of the boards have been examined as well as their resistance against fungal decay and termite attack. All kenaf fiberboards showed elevated mechanical properties compared with medium-density fiberboard made from wood fibers, and showed increased decay and termite resistance. Differences in the decay and termite resistance between the board types were caused by the presence of the low molecular weight PF resin for the impregnation of the fibers. No significant difference was found for the mechanical properties. The effect of the PF resin for impregnation was much clearer in fungal decay resistance than for termite resistance; however, fiber orientation had no effect on both decay and termite resistance of the specimens.