• Progress in Medical Physics
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• v.25 no.4
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• pp.205-209
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• 2014

Medical polymers require sterilization and must be able to maintain material properties for a specified shelf life. Sterilization can be achieved by using gamma or e-beam exposure. In this study, accelerated aging tests of poly(ether-block-amide) (PEBA) copolymer samples is presented. PEBA copolymer samples with different polyether content that result in Shore hardness of 35D to 72D, were sterilized using e-beam radiation followed by accelerated aging at $55^{\circ}C$. E-beam sterilization effect on molecular weight and mechanical property has performed and analyzed. The average molecular weight significantly reduced as a result of ageing. The enlarged proportion of low molecular weight chains in the aged samples is consistent with the generation of degradation products produced by oxidative chain scission. Also E-beam materials have shown decreased tensile strength and elongation. Overall, this study demonstrated that the medical grade PEBA was significantly affected by radiation exposure over aging time, particularly at high irradiation doses. For medical use in case of radiation sterilization required, it is recommended to avoid Pebax material. If Pebax material must be in use for medical device, recommend to use alternate sterilization method such as Ethylene Oxide sterilization.

• Journal of fish pathology
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• v.20 no.3
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• pp.281-289
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• 2007

We have investigated lysozyme activity and protectivity of starry flounder, Platichthys stellatus against olive flounder pathogenic bacteria, Edwardsiella tarda, Vibrio ichthyoenteri and Streptococcus iniae in varying salinities, water temperatures and stocking density. Starry flounders were susceptible to E. tarda but not V. ichthyoenteri and S. iniae. Under low salinity condition, the lysozyme activity was decreased a little compared to the control but not significant. The physiological and immune activities were normal up to 26 ℃ culture temperature and 100% stocking density; they were compromised from 29℃ and 200%, respectively.

• Korean Journal of Microbiology
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• v.45 no.2
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• pp.177-184
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• 2009

Three hundred lactic acid bacteria isolated from human feces were studied their probiotic characters to develop potential probiotics. The properties were tested on the basis of guideline for probiotic selection protocol such as tolerance for acid or bile salt, thermal stability, antimicrobial, anticancer cell, and antiviral activity. Strain Miny-148 was selected as a potential probiotic bacterium which showed resistance to low pH, bile salts and thermal stability. On the basis of fatty acid profiles and 16S rDNA sequences analysis, the strain was identified as Lactobacillus pentosus (similarity 99.9%). The strain, L. pentosus Miny-148, showed broad antimicrobial spectrum against E. coli O157:H7, Shigella flexneri, Bacillus anthracis, Staphylococcus aureus, E. coli, Vibrio cholerae, V. vulnificus, Salmonella typhimurium, and Methicillin-resistant S. aureus (MRSA). Cell-free culture supernatant of the strain also inhibited against the growth of HT-29 colon cancer cell and transmissible gastroenterits virus.

• Biomolecules & Therapeutics
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• v.22 no.4
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• pp.347-354
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• 2014

Larrea nitida is a plant that belongs to the Zygophyllaceae family and is widely used in South America to treat inflammatory diseases, tumors and menstrual pain. However, its pharmacological activity remains unclear. In this study we evaluated the property of selective estrogen receptor modulator (SERM) of Larrea nitida extracts (LNE) as a phytoestrogen that can mimic, modulate or disrupt the actions of endogenous estrogens, depending on the tissue and relative amount of other SERMs. To investigate the property of SERM of LNE, we performed MCF-7 cell proliferation assays, estrogen response element (ERE)-luciferase reporter gene assay, human estrogen receptor (hER) binding assays and in vivo uterotrophic assay. To gain insight into the active principles, we performed a bioassay-guided analysis of LNE employing solvents of various polarities and using classical column chromatography, which yielded 16 fractions (LNs). LNE showed high binding affinities for $hER{\alpha}$ and $hER{\beta}$ with $IC_{50}$ values of $1.20{\times}10^{-7}$ g/ml and $1.00{\times}10^{-7}$ g/ml, respectively. LNE induced $17{\beta}$-estradiol (E2)-induced MCF-7 cell proliferation, however, it reduced the proliferation in the presence of E2. Furthermore, LNE had an atrophic effect in the uterus of immature rats through reducing the expression level of progesterone receptor (PR) proteins. LN08 and LN10 had more potent affinities for binding on $hER{\alpha}$ and ${\beta}$ than other fractions. Our results indicate that LNE had higher binding affinities for $hER{\beta}$ than $hER{\alpha}$, and showed SERM properties in MCF-7 breast cancer cells and the rat uterus. LNE may be useful for the treatment of estrogen-related conditions, such as female cancers and menopause.

• Journal of Digital Convergence
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• v.13 no.7
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• pp.23-31
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• 2015

With the expiration of main patent of printing method, public interest now has shifted to 3D printing. In this, it needs to shine a light on the negative effects, particularly in the socio-economic aspect of 3D printing. By analyzing the existing research findings, policy reports and press releases, the negative effects of 3D printing and its countermeasures were derived. The main drawbacks of 3D printing includes the following: It might cause 3D printing-related crimes(e.g. printed weapons, intellectual property infringement, etc.) and it poses a big threat to other related business sectors.(e.g. potential job loss in molding and medical equipments manufacturing industries) What's more, the nature of 3D printing that it is easy to operate attracts lots of people, which then leads to serious social and environmental problems-product liability, ethical issues, environmental pollution, and finally government's blindly excessive investment in 3D printing. To avoid such potential risks, the government should establish and enforce the institutional law, and guidelines. Government's rational investment decision is also inevitable for the short-term and long-term sustainability of 3D printing.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2001.06a
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• pp.77-80
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• 2001

A variety of different methods to generate diverse proteins, including random mutagenesis and recombination, are currently available, and most of them accumulate the mutations on the target gene of a protein, whose sequence space remains unchanged. On the other hand, a pool of diverse genes, which is generated by random insertions, deletions, and exchange of the homologous domains with different lengths in the target gene, would present the protein lineages resulting in new fitness landscapes. Here we report a method to generate a pool of protein variants with different sequence spaces by employing green fluorescent protein (GFP) as a model protein. This process, designated functional salvage screen (FSS), comprises the following procedures： a defective GFP template expressing no fluorescence is firstly constructed by genetically disrupting a predetermined region(s) of the protein, and a library of GFP variants is generated from the defective template by incorporating the randomly fragmented genomic DNA from E. coli into the defined region(s) of the target gene, followed by screening of the functionally salvaged, fluorescence-emitting GFPs. Two approaches, sequence-directed and PCR-coupled methods, were attempted to generate the library of GFP variants with new sequences derived from the genomic segments of E. coli. The functionally salvaged GFPs were selected and analyzed in terms of the sequence space and functional property. The results demonstrate that the functional salvage process not only can be a simple and effective method to create protein lineages with new sequence spaces, but also can be useful in elucidating the involvement of a specific region(s) or domain(s) in the structure and function of protein.

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.109-116
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• 2008

This study was performed to get information of self-healing mechanism in cement system and the influence of waterproofing admixtures for concrete on self-healing property. For testing, cement paste specimens cured for 7, 14 and 28 days were prepared and crushed into plate-shape pieces. Screened specimens with thickness not more than 1mm were covered with wet rags and cured in a plastic container for 7 and 28 days. After stopping hydration process of the specimens by treatment with acetone, the surfaces of specimens have been contacted with wet rags were analyzed by XRD, DSC, SEM and EDX. The analysis results showed that cement paste has self-healing property and this property is mainly affected by water. Self-healing in cement system is more effective and faster at an early stage of hydration as there is enough content of unreacted cement to make an additional hydration in this period. The results of this study also showed that waterproofing admixtures for concrete have a considerable effect on self-healing of cement pastes; i.e., they improved self-healing effect of cement and, especially, the specimen using admixture C has shown a lot of needle-like or fibrous hydration products which are estimated as ettringite. It is supposed that these ettringite products are effective to enhance self-healing in cement system.

• Cross-Cultural Studies
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• v.29
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• pp.25-53
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• 2012

The attitude of observer in the painting of history is to exclude a prejudice and a subjective view of an artist and to introduce a photograph, which is a record of objectivity, in the process of painting. Its ultimate intent is to redescribe the fact of an event's image intactly without any prejudice and to represent the event as a proven evidence that it was. The representation of history based on fact had already been conceived in imagination of renowned artists such as Francisco Goya or $Th{\acute{e}}odore$ $G{\acute{e}}ricault$ even before cameras were invented. What they portrayed was their own truth of reality which is gained through their observation, not a history that have corresponded to political ideologies, for all reliance on a limited tool of representation, painting. Furthermore, history was necessary for 19th century impressionism artists to be represented under proven fact in a neutral perspective excluding all subjective prejudice, not based on the representation with imagination. Edouard Manet in particular reconstited an instant moment on the basis of real proof of photograph without personal prejudice or opinion as if today's photojournalism. The catastrophic series by Andy Warhol and the photographic painting by Gerhard Richter show another role of painting in the realm of art, each of them implying information distortion and abuse by current media and intentional deformation toward history as Manet's painting of history. Today, the representation of an historical event that we experience in the era of the Internet and social networks having a great deal of information already came to be the exclusive property of the cutting edge mass media. Nevertheless, the attitude of observer which is realistic and contemplative in the realm of art is the crucial point in terms of artists' act as ever.

• Advances in nano research
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• v.17 no.2
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• pp.181-195
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• 2024

This study introduces a novel functionally graded material model, termed the "Coated Functionally Graded Graphene-Reinforced Composite (FG GRC)" model, for investigating the free vibration response of plates, highlighting its potential to advance the understanding and application of material property variations in structural engineering. Two types of coated FG GRC plates are examined: Hardcore and Softcore, and five distribution patterns are proposed, namely FG-A, FG-B, FG-C, FG-D, and FG-E. A modified displacement field is proposed based on the higher-order shear deformation theory, effectively reducing the number of variables from five to four while accurately accounting for shear deformation effects. To solve the equations of motion, an analytical solution based on the Galerkin approach was developed for FG GRC plates resting on a viscoelastic Winkler/Pasternak foundation, applicable to various boundary conditions. A comprehensive parametric analysis elucidates the impact of multiple factors on the fundamental frequencies. These factors encompass the types and distribution patterns of the coated FG GRC plates, gradient material distribution, porosities, nonlocal length scale parameter, gradient material scale parameter, nanoplate geometry, and variations in the elastic foundation. Our theoretical research aims to overcome the inherent challenges in modeling structures, providing a robust alternative to experimental analyses of the mechanical behavior of complex structures.

• Journal of applied mathematics & informatics
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• v.27 no.5_6
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• pp.1493-1499
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• 2009

Let $A_1$ and $A_2$ be nonzero complex idempotent and tripotent matrix, respectively. Denote a linear combination of the two matrices by A = $c_1A_1$ + $c_2A_2$, where $c_1,\;c_2$ are nonzero complex scalars. In this paper, under an assumption of $A_1A_2$ = $A_2A_1$, we characterize all situations in which the linear combination is tripotent. A statistical interpretation of this tripotent problem is also pointed out. Moreover, In [2], Baksalary characterized all situations in which the above linear combination is idem-potent by using the property of decomposition of a tripotent matrix, i.e. if $A_2$ is tripotent, then $A_2$ = $B_1-B_2$, where $B^2_i=B_i$, i = 1, 2 and $B_1B_2=B_2B_1=0$. While in this paper, by utilizing a method different from the one used by Baksalary in [2], we prove the theorem 1 in [2] again.