• 천문학회보
• /
• 제39권1호
• /
• pp.67.2-67.2
• /
• 2014

Comet nucleus is a solid body consisting of dark dust grains and ice. Cometary volatiles sublimate from subsurface layer by solar heating, leaving behind large dust grains on the surface. Eventually, the appearance could turn into asteroidal rather than cometary. It is, therefore, expected that there would be "dormant comets" in the list of known asteroids. Our research group has undertaken the research on the population of dormant comets. We applied a brand-new asteroidal catalog compiled from data garnered by three infrared astronomical observatories, AKARI, IRAS and WISE. We extracted objects which have comet-like orbits on the basis of their orbital properties (Tisserand parameters with respect to Jupiter, TJ, and aphelion distance, Q). We found that (1) there are a considerable number (>100) of asteroids in comet-like orbits, and (2) 80% of them have low albedo consistent with comets. This result suggest that these low albedo objects could be dormant comets. One unanticipated finding is that 20% of asteroids in comet-like orbit have high albedo similar to S-type asteroids. It is difficult to explain the population of S-type asteroids in comet-like orbits by the classical mechanics theory. We further found that these high-albedo objects are small (D < 2 km) bodies distributed in near-Earth space. We suggest that such high-albedo, small, near-Earth asteroids are susceptible to Yarkovsky effect and injected into comet-like orbits.

• 한국표면공학회지
• /
• 제29권5호
• /
• pp.549-555
• /
• 1996

Diamond Like Carbon film is amorphous film which is considered to consist of three coordinate graphite structure and tetrahedron coordinate diamond structure. Its hardness, thermal conductivity and chemical stability are nearly to one of diamond. It is well known to become semi-conductor by doping of inpurity. In this study Diamond Like Carbon film was synthesized by Microwave Plasma CVD in the gas mixture of hydrogen-methan-nitrogen and doped of nitrogen on the single-crystal silicon or silica glass. The temperature of substrate and nitrogen concentration in the gas mixture had an effect on the bonding state, structural properties and conduction mechanism. The surface morphology was observed by Scanning Electron Microscope. The strucure was analyzed by laser Raman spectrometry. The bonding state was evaluated by electron spectroscopy. Diamond Like Carbon film synthesized was amorphous carbon containing the $sp^2$ and $sp^3$ carbon cluster. The number of $sp^2$ bonding increased as nitrogen concentration increased from 0 to 40 vol% in the feed gas at 1233K substrate temperature and at $7.4\times10^3$ Pa. Increase of nitrogen concentration made Diamond Like Carbon to be amorphous and the doze of nitragen could be controlled by nitrogen concentration of feed gas.

• Earthquakes and Structures
• /
• 제10권1호
• /
• pp.239-260
• /
• 2016

Tuned mass dampers (TMDs) have been frequently proposed to mitigate the detrimental effects of dynamic loadings in structural systems. The effectiveness of this protection strategy has been demonstrated for wind-induced vibrations and, to some extent, for seismic loadings. Within this framework, recent numerical studies have shown that beneficial effects can be achieved by placing a linear TMD on the roof of linear elastic structural systems subjected to pulse-like ground motions. Motivated by these positive outcomes, closed-form design formulations have been also proposed to optimize the device's parameters. For structural systems that undergo a near-fault pulse-like ground motion, however, it is unlikely that their dynamic response be linear elastic. Hence, it is very important to understand whether such strategy is effective for inelastic structural systems. In order to provide new useful insights about this issue, the paper presents statistical results obtained from a numerical study conducted for three shear-type hysteretic (softening-type) systems having 4, 8 and 16 stories equipped with a linear elastic TMD. The effectiveness of two design procedures is discussed by examining the performances of the protected systems subjected to 124 natural pulse-like earthquakes.

• International Journal of Molecular Medicine
• /
• 제43권5호
• /
• pp.2230-2240
• /
• 2019

Hair follicles (HFs) are a well-characterized niche for adult stem cells (SCs), and include epithelial and melanocytic SCs. HF cells are an accessible source of multipotent adult SCs for the generation of the interfollicular epidermis, HF structures and sebaceous glands in addition to the reconstitution of novel HFs in vivo. In the present study, it was demonstrated that HF cells are able to be induced to differentiate into cardiomyocyte-like cells in vitro under specific conditions. It was determined that HF cells cultured on OP9 feeder cells in KnockOut-Dulbecco's modified Eagle's medium/B27 in the presence of vascular endothelial growth factors differentiated into cardiomyocyte-like cells that express markers specific to cardiac lineage, but do not express non-cardiac lineage markers including neural stem/progenitor cell, HF bulge cells or undifferentiated spermatogonia markers. These cardiomyocyte-like cells exhibited a spindle- and filament-shaped morphology similar to that presented by cardiac muscles and exhibited spontaneous beating that persisted for over 3 months. These results demonstrate that SC reprogramming and differentiation may be induced without resulting in any genetic modification, which is important for the clinical applications of SCs including tissue and organ regeneration.

• Environmental Engineering Research
• /
• 제11권3호
• /
• pp.127-133
• /
• 2006

Aerobic floc-like sludge was formed in a batch reactor and the effect of cations on the formation of aerobic floc-like sludge was studied. In order to enhance the formation (rate) of aerobic floc-like sludge, cations such as $K^+$, $Na^+$, $Ca^{2+}$, and $Mg^{2+}$ were added to the seed sludge. It was found that $Ca^{2+}$ had positive effect on the formation of floc-like sludge, as measured by sludge volume index (SVI) for settle ability. The formation of floc-like sludge was confirmed by the microscopic observation after DAPI staining. The scattered forms of sludge samples at the initial stage became aggregated to form floes after $Ca^{2+}$ addition. To ensure the functions of sludge floes in a treatment plant, the gradient of ionic species around the surfaces of floc-like sludge was monitored by ion selective microelectrodes for ${NH_4}^+,\;{NO_3}^-$, and pH. The effective concentration of $Ca^{2+}$ ion to form floc-like sludge was determined to be 750 mg/L (0.15 mg $Ca^{2+}/mg$ MLSS). Under the effective $Ca^{2+}$ condition, the SVI value was the lowest and large distribution of nitrifying bacteria at the outer surface was observed in the aerobic floc-like sludge. From the results, it was found that the calcium ion functioned as an agent for the formation of aerobic floc-like sludge, resulting in the enhanced nitrification.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제10권2호
• /
• pp.131-136
• /
• 2005

Beauveria bassiana F-101, which has high toxicity toward Acantholyda parki as well as Thecodiplosis japonensis, was an isolate to develop an alternative control system against the major forest pests. Up to now, in B. bassiana, only one pr1 gene has been isolated and characterized. Therefore, we here reported the identification of a pr1-like gene, which would be a factor of toxicity from B. bassiana F-101. The oligonucleotides for the amplification of the pr1-like gene, were chosen based on the conserved regions of the subtilisin family enzymes, pr1 genes of B. bassiana and Metarhizium anisopliae, and proteinase K of Tritirachium album. The cloned PCR fragment had 1111 bp including 52 bp intron. The deduced Pr1-like peptide showed a low identity with Pr1s of entomopathogenic fungi such as B. bassiana Pr1 (BbPr1) and M. anisopliae Pr1 (MaPr1) as well as the proteinase K of T. album (TaPrK). Instead, the deduced peptide had a substantially high amino acid sequence identity $(>65\%)$ with the serine proteases of Magnaporthe grisea (MgSPM1) and Podospora anserina (PaPspA). These results, therefore, appear to suggest that the putative Pr1-like peptide of B. bassiana F-101 belongs to the subtilisin-like serine protease family and may be a novel gene.

• Asian Pacific Journal of Cancer Prevention
• /
• 제16권18호
• /
• pp.8365-8370
• /
• 2016

Background: Shammah is a traditional form of snuff dipping tobacco (a smokeless tobacco form) that is commonly used in Yemen. Oral mucosal changes due to the use of shammah can usually be observed in the mucosal surfaces that the product touches. The aim of this study was to determine the association between shammah use and oral leukoplakia-like lesions. Other associated factors were also determined. Materials and Methods: A cross sectional study was conducted on 346 randomly selected adult males. Multi-stage random sampling was used to select the study location. After completing the structured questionnaire interviews, all the participants underwent clinical exanimation for screening of oral leukoplakia-like lesions Clinical features of oral leukoplakia-like lesion were characterized based on the grades of $Ax{\acute{e}}ll$ et al (1976). Univariable logistic regression and multivariable logistic regression were used to assess the potential associated factors. Results: Out of 346 male participants aged 18 years and older, 68 (19.7%) reported being current shammah users. The multivariable analysis revealed that age, non-formal or primary level of education, former shammah user, current shammah user, and frequency of shammah use per day were statistically associated with the presence of oral leukoplakia-like lesions [Adjusted odds ratio (AOR) = 1.03; 95% confidence interval (CI) : 1.01, 1.06; P=0.006], (AOR=8.65; 95% CI: 2.81, 26.57; P=0.001), (AOR=3.65; 95% CI: 1.40, 9.50; P=0.008), (AOR=12.99; 95% CI: 6.34, 26.59; P=0.001), and (AOR=1.17; 95% CI: 1.02, 1.36; P=0.026), respectively. Conclusions: The results revealed oral leukoplakia-like lesions to be significantly associated with shammah use. Therefore, it is important to develop comprehensive shammah prevention programs in Yemen.

• 대한화장품학회:학술대회논문집
• /
• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book I
• /
• pp.98-141
• /
• 2003

Lip chapping is a serious cosmetics problem, though remedies other than moisturizing have not been proposed. We investigated changes in the surface configurations of lip corneocytes and increased CD activity and improved chapping severity. Our results suggest that lip chapping can be activities of desquamation-regulating proteinases associated with lip chapping. Using scanning electron microscopy, villus-like projections were observed on the inner surfaces of most corneocytes from normal lips, whereas those with flatter surface were predominant in chapped lips. Further, cell surface area increased with the severity of lip chapping. Cathepsin D (CD)-like and chymotrypsin-like proteinase, which are also present in skin as desquamation-regulating proteinases, were detected in lip corneocytes, though only CD activity was found to decrease in severely chapped lips. Hydration was also lower in areas of lip chapping. Sequential topical application of apricot extract essence characterized as similar to senile xerosis rather than dry skin such as winter xerosis, as it shows a delayed transition of corneocytes through the stratum corneum, and the reduced CD activity may be one of the mechanisms that is further decreased by low hydration. We propose that an enhancement of both CD activity and lip moisture may be effective to improve lip chapping.

• 천문학회보
• /
• 제43권1호
• /
• pp.55.1-55.1
• /
• 2018

Studies on rotation-powered pulsars with strong surface magnetic field may help us clarify the unclear link between magnetars and canonical radio pulsars because the magnetar-like emission is expected to be observed. PSR J1119-6127 associated with SNR G292.2-0.5 has a high magnetic field of $4.1{\times}1013$ gauss, and a young characteristic age of ~1700 years can be served as the good candidate to compare with magnetars and rotation-powered pulsars. The glitch accompanied by the radiative changes detected in 2007 is the first case we observed for a rotationally powered radio pulsar. This pulsar experienced magnetar-like outbursts in mid. 2016, similar to the 2006 transition occurred on the other radio-quiet rotation-powered pulsar with strong surface magnetic field, PSR J1846-0258. In this talk, I'll report the investigation with X-ray and gamma-ray data of this magnetar-like pulsar. A sudden decrease in the gamma-ray emission at the GeV band was detected immediately after the X-ray outburst. Accompanying with the disappearance of the radio pulsation, the gamma-ray pulsation cannot be resolved as well after the outburst. We tried to derive the timing behavior and some intriguing features of this pulsar in this work corresponding to the outburst using the Swift data, NuSTAR and XMM observations.

• 방사성폐기물학회지
• /
• 제18권3호
• /
• pp.363-372
• /
• 2020

Anionic radionuclides pose one of the highest risks to the long-term safety assessments of disposal repositories. Therefore, techniques to immobilize and separate such anionic radionuclides are of crucial importance from the viewpoints of safety and waste volume reduction. The main objective of this study is to design a separator with minimum pressure disturbance, based on the concept of a conventional cyclone separator. We hypothesize that the anionic radionuclides can be immobilized onto a nanomaterial-based substrate and that the particles generated in the process can flow via water. These particles are denser than water; hence, they can be trapped within the cyclone-type separator because of its design. We conducted particle tracking analysis using computational fluid dynamics (CFD) for the conventional cyclone separator and studied the effects due to the morphology of the separator. The proposed sandglass-like design of the separator shows promising results (i.e., only one out of 10,000 particles escaped to the outlet from the separation zone). To validate the design, we manufactured a laboratory-scale prototype separator and tested it for iron particles; the efficiency was ca. 99%. Furthermore, using an additional magnetic effect with the separator, we could effectively separate particles with ~100% efficiency. The proposed sandglass-like separator can thus be used for effective separation and recovery of immobilized anionic radionuclides.