Formation and Radiative Feedback of First Objects and First Galaxies

First, the formation of first objects driven by dark matter is revisited by high-resolution hydrodynamic simulations. It is revealed that dark matter haloes of ~10^4M_sun can produce first luminous objects with the aid of dark matter cusps. Therefore, the mass of first objects is smaller by roughly two orders of magnitude than in the previous prediction. This implies that the number of Pop III stars formed in the early universe could be significantly larger than hitherto thought. Secondly, the feedback by photo-ionization and photo-dissociation photons in the first objects is explored with radiation hydrodynamic simulations, and it is demonstrated that multiple stars can form in a 10^5M_sun halo. Thirdly, the fragmentation of an accretion disk around a primordial protostar is explored with photo-dissociation feedback. As a result, it is found that the photo-dissociation can reduce the mass accretion rate onto protostars. Also, protostars as small as 0.8M_sun may be ejected and evolve with keeping their mass, which might be detected as "real first stars" in the Galactic halo. Finally, state-of-the-art radiation hydrodynamic simulations are performed to investigate the internal ionization of first galaxies and the escape of ionizing photons. We find that UV feedback by forming massive stars enhances the escape fraction even in a halo as massive as > 6* 10^9M_sun, while it reduces the star formation rate significantly. This may have a momentous impact on the cosmic reionization.Comment: 26 pages, 14 figure

Decay Resistance of Medium Density Fibreboard (MDF) Made from Pineapple Leaf Fiber

Medium density fiberboard (MDF) production is increasing due to the development of manufacturing technologies. MDF products are utilized for traditional wood applications that require fungal resistance. This study investigated some of the important biodegradation properties of MDF composite board made from renewable biomass from pineapple leaf fiber (Ananas comosus). The variable factors were type of board and type of resin. Two different types of board with a target density of 0.8 g/cm3 were manufactured. The boards were prepared in three layers of about 1:1:1 weight ratio in crossoriented and unidirectional pattern, using low molecular weight (LM) phenol formaldehyde (PF) resin type PL-3725 and high molecular weight (HM) PF resin type PL-2818 for impregnation and adhesive purposes. Decay resistance (white and brown rot fungi) of the MDF was evaluated to assess its biological performance. In this study, fiber orientation had no effect on the decay resistance to white and brown rot fungi of the specimens. However, a slight increase was found for the mass loss of the low molecular weight PF resin board specimens compared with the mixed low and high molecular PF resin board specimens. The total resin content of 20% of the type I boards prohibits degradation by decay

Molding of wood powder with a natural binder

International Conference on the Technology of Plasticity, ICTP 2017, 17-22 September 2017, Cambridge, United KingdomThis paper describes the molding of wood powder using sucrose as a natural binder, as a means of fabricating products based on natural resources. The conditions, such as the temperature and binder content of the wood powder, were optimized in order to produce compacts successfully in the molding process. In experiments, the plasticization temperature of sucrose was initially investigated by thermogravimetric/differential thermal analysis for the prediction of the thermal flow temperature of the wood powder combined with sucrose. In addition, flow behavior of the mixture was evaluated for the temperature and the binder content by capillary flow tests. Based on these data, molding test of wood powder with sucrose was conducted to evaluate the injection moldabilty. As a result, the plasticization point of sucrose was found to be approximately 176 ºC, with a mass reduction onset at 200 ºC due to decomposition to volatile products. Wood powder mixed with sucrose flowed at temperatures above 180 ºC, although flow was restricted above 220 ºC due to the effect of gases evolved from the sucrose. The minimum sucrose content required for flow was 30 wt% within the temperature range of 180 to 200 ºC. The mixture was found to fill a mold under optimized conditions, forming compacts with good surface texture at a sucrose content of 30 wt% and 200 ºC. This method allows the fabrication of products from naturally occurring materials with minimal environmental impact

Influence of pulsive pressure waves on liquid penetration into wood in semi-opened container

The purpose of this paper was to confirm the influence of pulsive pressure waves on the liquid penetration into wood in the semi-opened container. Wood block sample was irradiated by the pulsive pressure waves in the semi-opened container filled with water used as a liquid. The irradiation was also performed in the closed container for the comparison. The water penetration into the sample was promoted by the pressure-wave irradiation. There was little difference in the degree of the penetration between the closed and the semi-opened containers. It was presumed from the measured hydraulic pressure that the pressure-wave energy irradiated on the sample in the closed container was higher than that in the semi-opened container. It was also presumed that the cavitation generation was promoted in the semi-opened container. This indicates that the cavitation as well as the pressure waves themselves affected the liquid penetration into wood. The compressive deformation of the sample irradiated in the semi-opened container was slightly smaller than that in the closed container. This indicates that the pulsive pressure-wave irradiation in the semi-opened container promoted the liquid penetration into wood with less compressive deformation

Evaluation of termite resistance of medium density fiberboard (MDF) manufacture from agricultural fiber bonded with citric acid

The 5th Sustainable Future for Human Security (SustaiN 2014)Nowadays, the use of agricultural fibers for panel composite materials attracts great intention. Further, it is desirable to develop of natural adhesive derived from non fossil resources to be safe adhesive without using harmful chemical substances. In this study, citric acid application as natural adhesive was investigated for medium density fiberboard (MDF) manufacture from pineapple leaf fiber. The ratio of citric acid and sucrose and adhesive content was 25–75 and 20 wt%, respectively. Two different types of board consisting of three layers with target density of 0.8 gr/cm³ were prepared. The board was hot pressed at 200 °C and 4.5 MPa for 10 min.Additionalboards with same structure were prepared using citric acid only. The biological properties of the boards such as their resistance against subterranean termite attack have been examined. The results indicate that generally, there was a significant effect of impregnation with mixture of citric acid and sucrose and citric acid only on the susceptibility of the MDF board specimens. With regards to the percentage of specimen mass losses, fiber orientation had no significant effect on the termite resistance against Coptotermes formosanus Shiraki. Utilization of natural adhesive, citric acid was promising to be used for MDF manufacturing. Our findings show that the total adhesive content of 20% of the type a board could be used for agricultural fiber product applications to protect structures from degradation by termites