• Journal of The Korean Association For Science Education
• /
• v.23 no.5
• /
• pp.470-483
• /
• 2003

This study analyzed the evolutionary content in 13 textbooks developed from the first to the 6th high school biology curriculum, The content analysis of textbooks, which were delineated nine component, was performed on the 80 evolutionary categories, According to the result, the proportion of the total evolutionary content in textbook increased from the textbooks developed by the Ist curriculum to the textbooks developed by the 6th curriculum, but the proportion of 'main narrative' in total evolutionary content was gradually decreased. It also showed that biology curriculum and points of view of textbook writers influenced on the proportion of evolutionary contents. On the whole, the topics of analysed textbooks exhibit insufficient diversity, Any categories- 'group selection', 'gene selection', 'gaps in fossil record', 'co-evolution', 'punctuated equilibrium', 'mosaic evolution', 'place of labor in human evolution', 'human race differentiation', 'criticism of "ontogeny recapitulates phylogeny", and 'human activities affecting evolution' - were not treated and others - 'theory of neutralism', 'theories of major episodes(excepting extinctions) found in the geologic time scale', 'sympatric speciation', 'clinal and area-effect speciation', 'polyploidy and evolution', 'gradualism' and 'evolution and origin of mammals' - were treated very lightly, the most emphasized topic was 'phylogeny in general' and 'formation of precells', 'miscellaneous' in the order of emphasis. 'Theory of natural selection' was lightly treated as just one of evolutionary theory though it should be emphasized as major theme of evolution. Also, the law of recapitulation, of which biologists doubt the validity, was discussed as an evidence of evolution in some textbooks. And the agents of genetic equilibrium disruption like genetic drift and migration were treated as of little importance. On the basis of above result, it was suggested that the textbook writers introduced the more meaningful evolutionary topics focused the theory of natural selection in explanation of evolution and evolution theory.

• Economic and Environmental Geology
• /
• v.49 no.2
• /
• pp.77-88
• /
• 2016

Chrysotile is a 1:1 sheet silicate mineral belonging to serpentine group. It has been highlighted studies because of uses, shapes and structural characteristics of the fibrous chrysotile. However, it was designated as Class 1 carcinogen, so high attentions were being placed on detoxification studies of chrysotile. The objectives of this study were to investigate changes of mineralogical characteristics of chrysotile and to suggest detoxification mechanism of chrysotile by thermal decomposition. Samples for this study were obtained from LAB Chrysotile mine in Canada. The samples were heated in air in the range of 600 to $1,300^{\circ}C$. Changes of mineralogical characteristics such as crystal structure, shape, and chemical composition of the chrysotile fibers were examined by TG-DTA, XRD, FT-IR, TEM-EDS and SEM-EDS analyses. As a result of thermal decomposition, the fibrous chrysotile having hollow tube structure was dehydroxylated at $600-650^{\circ}C$ and transformed to disordered chrysotile by removal of OH at the octahedral sheet (MgOH) (Dehydroxylation 1). Upon increasing temperature, it was transformed to forsterite ($Mg_2SiO_4$) at $820^{\circ}C$ by rearrangement of Mg, Si and O (Dehydroxylation 2). In addition, crystal structure of forsterite had begun to transform at $800^{\circ}C$, and gradually grown 3-dimensionally to enstatite ($MgSiO_3$) by recrystallization after the heating above $1,100^{\circ}C$. And then finally transformed to spherical minerals. This study showed chrysotile structure was collapsed about $600-700^{\circ}C$ by dehydroxylation. And then the fibrous chrysotile was transformed to forsterite and enstatite, as non-hazardous minerals. Therefore, this study indicates heat treatment can be used to detoxification of chrysotile.

• Korean Journal of Environmental Biology
• /
• v.40 no.3
• /
• pp.267-274
• /
• 2022

Excess nitrogen (N) flowing from livestock manure to water systems poses a serious threat to the natural environment. Thus, livestock wastewater management has recently drawn attention to this related field. This study first attempted to obtain the optimal conditions for the further volatilization of NH₃ gas generated from pig wastewater by adjusting the amount of injected magnesia (MgO). At 0.8 wt.% of MgO (by pig wastewater weight), the volatility rate of NH₃ increased to 75.5% after a day of aeration compared to untreated samples (pig wastewater itself). This phenomenon was attributed to increases in the pH of pig wastewater as MgO dissolved in it, increasing the volatilization efficiency of NH₃. The initial pH of pig wastewater was 8.4, and the pH was 9.2 when MgO was added up to 0.8 wt.%. Second, the residual ammonia nitrogen (NH₄⁺-N) in pig wastewater was removed by precipitation in the form of struvite (NH₄MgPO₄·6H₂O) by adjusting the pH after adding MgO and H₃PO₄. Struvite produced in the pig wastewater was identified by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis. White precipitates began to form at pH 6, and the higher the pH, the lower the concentration of NH₄⁺-N in pig wastewater. Of the total 86.1% of NH₄⁺-N removed, 62.4% was achieved at pH 6, which was the highest removal rate. Furthermore, how struvite changes with pH was investigated. Under conditions of pH 11 or higher, the synthesized struvite was completely decomposed. The yield of struvite in the precipitate was determined to be between 68% and 84% through a variety of analyses.

• The Korean Journal of Petroleum Geology
• /
• v.10 no.1_2 s.11
• /
• pp.23-33
• /
• 2004

The Lago Sofia conglomerate in southern Chile is a lenticular unit encased within mudstone-dominated, deep-sea successions (Cerro Toro Formation, upper Cretaceous), extending from north to south for more than $120{\cal}km$. The Lago Sofia conglomerate is a unique example of long, gravelly deep-sea channels, which are rare in the modern environments. In the northern part (areas of Lago Pehoe and Laguna Goic), the conglomerate unit consists of 3-5 conglomerate bodies intervened by mudstone sequences. Paleocurrent data from these bodies indicate sediment transport to the east, south, and southeart. The conglomerate bodies in the northern Part are interpreted as the tributary channels that drained down the Paleoslope and converged to form N-S-trending trunk channels. In the southern part (Lago Sofia section), the conglomerate unit comprises a thick (> 300 m) conglomerate body, which probably formed in axial trunk channels of the N-5-trending foredeep trough. The well-exposed Lago Sofia section allowed for detailed investigation of sedimentary facies and large-scale architecture of the deepsea channel conglomerate. The conglomerate in Lago Sofia section comprises stratified conglomerate, massive-to-graded conglomerate, and diamictite, which represent bedload deposition under turbidity currents, deposition by high-density turbidity currents, and muddy debris flows, respectively. Paleocurrent data suggest that the debris flows originated from the failure of nearby channel banks or slopes flanking the channel system, whereas the turbidity currents flowed parallel to the orientation of the overall channel system. Architectural elements produced by turbidity currents represent vertical stacking of gravel sheets, lateral accretion of gravel bars, migration of gravel dunes, and filling of channel thalwegs and scoured hollows, similar to those in terrestrial gravel-bed braided rivers. Observations of large-scale stratal pattern reveal that the channel bodies are offset stacked toward the east, suggestive of an eastward migration of the axial trunk channel. The eastward channel migration is probably due to tectonic tilting related to the uplift of the Andean protocordillera just west of the Lago Sofia deep-sea channel system.