• 한국추진공학회지
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• 제18권4호
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• pp.18-25
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• 2014

본 연구에서는 다이아프램(diaphragm)을 설치한 하이브리드 로켓에서 발생하는 연소불안정의 발생 메커니즘을 알아보고, 고체연료의 연소율은 증가하면서 연소불안정은 줄일 수 있는 그레인 설계를 제안하였다. 고체연료의 연소율을 증진시키기 위해 다이아프램을 설치한 하이브리드 로켓 모터에서 관찰되는 큰 연소불안정의 가진 요인은 전방 연소실에서 생성된 와류가 후방의 다이아프램에 부딪치면서 나타나는 Hole-tone으로 판단된다. 또한 다이아프램의 고연소율 발생 메카니즘을 적용하면서 연소불안정은 줄일 수 있는 'Stepped Grain'을 제안하였다.

• Parasites, Hosts and Diseases
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• 제57권6호
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• pp.587-593
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• 2019

Excavation (2008-2014) carried out under the Uffizi Gallery (Florence, Italy) led to the discovery of 75 individuals, mostly buried in multiple graves. Based on Roman minted coins, the graves were preliminarily dated between the second half of the 4th and the beginning of the 5th centuries CE. Taphonomy showed that this was an emergency burial site associated with a catastrophic event, possibly an epidemic of unknown etiology with high mortality rates. In this perspective, paleoparasitological investigations were performed on 18 individuals exhumed from 9 multiple graves to assess the burden of gastrointestinal parasitism. Five out of eighteen individuals (27.7%) tested positive for ascarid-type remains; these are considered as "decorticated" Ascaris eggs, which have lost their outer mammillated coat. Roundworms (genus Ascaris) commonly infest human populations under dire sanitary conditions. Archaeological and historical evidence indicates that Florentia suffered a period of economic crisis between the end of 4th and the beginning of the 5th centuries CE, and that the aqueduct was severely damaged at the beginning of the 4th century CE, possibly during the siege of the Goths (406 CE). It is more than plausible that the epidemic, possibly coupled with the disruption of the aqueduct, deeply affected the living conditions of these individuals. A 27.7% frequency suggests that ascariasis was widespread in this population. This investigation exemplifies how paleoparasitological information can be retrieved from the analysis of sediments sampled in cemeteries, thus allowing a better assessment of the varying frequency of parasitic infections among ancient populations.

• Journal of Forest and Environmental Science
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• 제26권2호
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• pp.83-94
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• 2010

Chinese fir (Latin name: Cunninghaimia lanceolata) is one of the major commercial coniferous trees. Most of Chinese fir forests are managed in successive rotation sites, which lead productivity to decline. Autotoxicity is the important reason for soil degradation of Chinese fir plantation, especially, phenolic acids are considered as the major allelopathic toxins which induce autotoxicity in Chinese fir rotation stands. We performed here proteomic approach to investigate the response of proteins in Chinese fir leaves to salicylic acid. The tube plantlets of Chinese fir clone were treated with 120 mg/L salicylic acid for 1, 3 and 5th day. 2-DE, coupled with MALDI-TOF-TOF/MS, was used to separate and identify the responsive proteins. We found 12, 7, and 12 candidate protein spots that were up- or down-regulated by at least 2.5 fold after 1, 3, and 5th day of the stress, respectively. Of these protein spots, 16 spots were identified successfully. According to the putative physiological functions, these proteins were categorized into five classes (1) the proteins involved in protein stability and folding, including 26S proteome, Grp78, Hsp70, Hsp90 and PPIase; (2) the protein involved in photosynthesis and respiration, including OEC 33 kDa subunit, GAPDH; (3) the protein related to cell endurance to acid, F-ATPase; (4) the protein related to cytoskeleton, tubulin; (5) the protein related to protein translation: prolyl-tRNA synthetase. These results give new insights into autotoxic substance stress response in Chinese fir leaves and provide preliminary footprints for further studies on the molecular signal mechanisms induced by the stress.

• Journal of Microbiology and Biotechnology
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• 제24권6호
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• pp.748-755
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• 2014

In the genome annotation of Escherichia coli MG1655, the orf382 (1,149 bp) is designated as a gene encoding an alcohol dehydrogenase that may be Fe-dependent. In this study, the gene was amplified from the genome by PCR and overexpressed in Escherichia coli BL21(DE3). The recombinant $6{\times}$His-tag protein was then purified and characterized. In an enzymatic assay using different hydroxyl-containing substrates (n-butanol, $\small{L}$-threonine, ethanol, isopropanol, glucose, glycerol, $\small{L}$-serine, lactic acid, citric acid, methanol, or $\small{D}$-threonine), the enzyme showed the highest activity on $\small{L}$-threonine. Characterization of the mutant constructed using gene knockout of the orf382 also implied the function of the enzyme in the metabolism of $\small{L}$-threonine into glycine. Considering the presence of tested substrates in living E. coli cel ls and previous literature, we believed that the suitable nomenclature for the enzyme should be an $\small{L}$-threonine dehydrogenase (LTDH). When using $\small{L}$-threonine as the substrate, the enzyme exhibited the best catalytic performance at $39^{\circ}C$ and pH 9.8 with $NAD^+$ as the cofactor. The determination of the Km values towards $\small{L}$-threonine (Km = $11.29{\mu}M$), ethanol ($222.5{\mu}M$), and n-butanol ($8.02{\mu}M$) also confirmed the enzyme as an LTDH. Furthermore, the LTDH was shown to be an ion-containing protein based on inductively coupled plasma-atomic emission spectrometry with an isoelectronic point of pH 5.4. Moreover, a circular dichroism analysis revealed that the metal ion was structurally and enzymatically essential, as its deprivation remarkably changed the ${\alpha}$-helix percentage (from 12.6% to 6.3%).