• Journal of the Korean Wood Science and Technology
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• v.22 no.1
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• pp.66-71
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• 1994

To increase drying rate and reduce drying degradation, pretreatments such as prefreezing and presteaming have been widely used in wood industries. Presteaming lumbers prior to kiln drying is known positively to improve its permeability, to increase diffusion coefficient and to reduce discoloration, but negatively to increase collapse. Prefreezing lumbers prior to kiln drying is also known to reduce significantly its drying defects and its shrinkages. Thus it is no doubt that the pretreated lumbers shrink diversely from the untreated. In this study the shrinkage behaviors of the pretreated specimens are investigated by drying two tropical hardwoods (Apitong and Taun) in three different dying conditions: high temperature and slow drying rate (drying in a closed cylinder), high temperature and rapid drying rate (drying in an oven) and low temperature and slow drying rate(drying at room temperature). The prefrozen specimens show the least volumetric shrinkages in most drying conditions. The specimens dried in cylinders shrink most among all drying conditions. In general the pretreated specimens reached the 30 % moisture content faster than the untreated by about 30 %.

• Journal of Embryo Transfer
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• v.10 no.3
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• pp.193-202
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• 1995

In order to improve the cryopreservatory techniques of livestock embryos, the quick freezing method which is directly plunged in liquid nitrogen via prefreezing procedure without freezing machine was carried out for mouse embryos treated with permeable and nonpermeable cryoprotectants. The viability of frozen-thawed embryos were evaluated by FDA vital dye test. The results obtained was summaried as follows: 1. A total of 720 embryos were recovered from frozen embryos for viability test. Evalution of the fluorescein diacetate(FDA) vital dye test with mice embryos were resulted of 2.3 total mean score - evaluted in orderly higher mean grade of P3 453 (63%), P2 133(18%), P1 51(7%) and P0 83(12%). 2. An all-round evalution of these combination, the highest viability was showed in 3M ethylene glycol + 0. 25M trehalose treated with the copper prefreezing. 3. Effects of permeable and nonpermeable cryoprotectants combination were evaluated by means FDA score. 3M ethylene glycol + 0.25M trehalose showed the highest survival rates of 2.8 mean FDA score. 4. Effects of permeable cryoprotectants were evaluated by mean FDA score but the results were not significantly different each other. 5. In evalution of the nonpermeable cryoprotectants, 0. 25M trehalose obtalned higher mean FDA score than of 0.25M sucrose and it was significantly different(P<0.05). 6. There was no significantly difference between copper and stainless-steel in prefreezing procedures.

• Journal of Plant Biotechnology
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• v.30 no.1
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• pp.109-113
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• 2003

Cryopreservation of embryogenic callus derived from apical meristem culture was attempted by slow prefreezing method (two-step method) with various cryoprotectants in sweetpotato cv. 'Yulmi' Precultured embryogenic calli on medium containing 10 mg/L ABA prior to slow prefreezing in liquid nitrogen indicated higher survival rate than 1.0 mg/L ABA preteatment. The cryoprotectant comprising 1.28 M DMSO in 0.4 M sucrose solution gave the best survival (over 46%) of sweetpotato cells exposed to liquid nitrogen as determined by TTC reduction and FDA staining method. Cryopreserved calli cultured on MS medium with 1.0 mg/L 2,4-D were grown for 4 weeks in the dark and induced embryos after another 4 weeks. They were subcultured on MS medium supplemented with 0.1 mg/L 2,4-D＋0.1 mg/L kinetin for 2 weeks and regenerated into normal plantlets in MS basal medium.

• Korean Journal of Agricultural Science
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• v.31 no.1
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• pp.9-14
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• 2004

This study was carried out for deresinning the larch boards dried in a conventional kiln. Prior to heat treatment they were steamed in an autoclave for 5 hours or frozen for 24 hours at a temperature of $-35^{\circ}C$. The velocities of ultrasound transmitted through the specimens were measured to examine the correlation with their resin contents. It was found that the specimens heated at $100^{\circ}C$ for 5 hours contained less resin that those heated at $200^{\circ}C$ for an hour. Both treatments of steaming and freezing were effective for deresinning and the former was better than the latter. The ultrasonic velocities measured before the heat treatment showed a negative correlation to the resin contents of the specimens, but those measured after the heat treatment a positive correlation. This difference may be attributed to the viscosity of resin.

• Journal of the Korean Wood Science and Technology
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• v.23 no.3
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• pp.28-32
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• 1995

The presteamed or prefrozen persimmon blocks of 10cm ${\times}$ 10cm ${\times}$ 15cm were air-dried at room temperature until about 30% moisture content, and then were dried in a MW oven. During drying their internal temperatures were monitored with thermo-couple probes. The presteamed and prefrozen blocks didn't show any improvement in drying rate and moisture gradient when compared with the controls. Checks appeared on the surfaces of most presteamed blocks during air-drying. It has been clearly revealed that the maximum weight, loss must, be less than 2g/min during MW drying to prevent internal checking and that MW drying reduced moisture gradients inside blocks. MW dried the persimmon blocks 440 times faster than conventional kiln.

• Journal of the Korean Wood Science and Technology
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• v.25 no.3
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• pp.66-74
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• 1997

Liquid permeabilities of red oak and several softwoods were measured by the pressure bomb method and a modified liquid permeability method in order to investigate their efficacy. The effect of preboiling and prefreezing on wood permeability were also examined for both green and resaturated specimens. Regardless of some disadvantages these two methods were revealed as a handy tool for quick evaluation of the permeability of an unknown species. The permeabilities of the resaturated specimens increased when preboiled. but decreased when prefrozen. For green specimens, however, pre freezing increased permeability. The discrepancy of the pre freezing effect on two specimens partially attributes to their difference of initial permeabilities. For all species except radiata pine heartwood, the radii of the effective capillary pores, derived from the water potential equation, distribute from $0.42{\mu}m$ to $7.2{\mu}m$. Those of radiata pine heartwood are below $0.46{\mu}m$.

• Journal of the Korean Wood Science and Technology
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• v.23 no.1
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• pp.35-41
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• 1995

Persimmon boards of 30mm thick were dried, their temperatures were monitored during drying with 490 and 200watt microwave, and the drying efficacy and problems were investigated. The effects of pretreatments such as presteaming and prefreezing were also examined. The persimmon green lumbers of 80% moisture content were dried to 10% for only 50~60 and 110 minutes with 49watt and 200watt microwave, respectively. Severe internal checks were, however, found in all boards. The presteamed boards collapsed on their surfaces earlier than the controls. It may attribute to the high temperature inside boards during microwave drying and the decrease of their internal tensile strength caused by the presteaming treatment. To increase the internal tensile strength of the pretreated boards and to reduce their internal checks, they were air-dried at room temperature. The air-dried boards could be dried to 10% moisture content clearly and free from defects with 200watt microwave. The heating efficiency were also calculated with the maximum weight loss per minute of 490watt and 200watt.

• Clinical and Experimental Reproductive Medicine
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• v.25 no.3
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• pp.261-268
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• 1998

The present study was to assess the effect of ultrarapid freezing on the development of 1-cell mouse zygote using cryoprotectants, DMSO (dimethyl sulfoxide) or PROH (1,2-propanediol). We investigated the effect of the type and concentration of cryoprotectant, and of the temperature and time of prefreezing equilibration on their capacity to develop to the blastocyst stage in vitro. The concenration, the equilibration temperature, and the exposure time seemed to serve as an important factor in ultrarapid freezing of 1-cell mouse zygotes. In addition to the exposure time and the concentration of cryoprotectant appeared to playa key role in the development of the embryo. In general, the development of the embryo was more effective at $3^{\circ}C$ than $23^{\circ}C$ and 4.5 M than 3 M for 3 to 5 minutes. At $23^{\circ}C$ the development of the embryo was stimulated by DMSO while at $3^{\circ}C$ it was stimulated by PROH. Thus it has been suggested that there exists a correlation between the concentration of cryoprotectants and exposure time in the development of the embryo. In conclusion, we found that for ultrarapid freezing of mouse 1-cell embryos in DMSO, or PROH-based solution, viability shown optimum depending on the cryoprotectant, the concentration of the cryoprotectant and on the temperature and the duration of equilibration.