• Journal of The Korean Association For Science Education
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• v.20 no.2
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• pp.221-233
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• 2000

Many investigators have reported difficulties in changing the high school students' misconceptions on mechanics. By one possible solution to this problem, some researchers suggested that the students should be taught mechanics at a younger age to make conceptual changes possible. because as they get older they become less willing to change their ideas. The purpose of this study was to compare the patterns of students' conceptual changes on force by age, to find out whether older students were less ready to change their conceptions than younger students. Individual interviews were carried out with 35 students (average ages 13) in middle school class and 50 students (average ages 17) in high school class near by the middle school. Those students who held the misconcetpion that "motion-implies-force (Impetus conception)" were asked to read a student-centered refutational text (anomalous data). In the immediate and delayed posttest, the types of responses of the students were analyzed to find out the patterns of student's conceptual changes on force by age. In result, first, most of students had impetus conception. Some of the students aged 13 understood the force as terminologies related with everyday experiences, while the students aged 17 understood the force as scientific terminologies. Second, there was no evidence to suggest that conceptual change is more difficult for the students aged 17 than aged 13. Third, the students aged 13 showed diverse responses (plain acceptance, critical acceptance, plain rejection, critical rejection) to the refutational text, while the students aged 17 showed restricted responses (critical acceptance, critical rejection). A month later those students who showed the plain acceptance retrogressed unscientific conceptions, while those students who showed critical acceptance maintained scientific conceptions. We did not find out any evidence to suggest that conceptual change is more difficult for older students. These results need deeper investigation on the nature of the loss of plasticity in comparison with other important variables.

• Korean Journal of Organic Agriculture
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• v.23 no.4
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• pp.781-796
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• 2015

This study was carried out to investigate the effect of no-tillage and split irrigation on the growth of pepper plant under green house condition in Jeonnam province. Moisture content of soil at whole quantity irrigation in tillage was increased rapidly regardless of soil depth for initial irrigation and then was decreased continuously until next irrigation. Deviation of moisture content in soil was decreased with increasing depth of soil. Moisture contents of top soil and subsoil (20 cm) at whole quantity irrigation in no-tillage were increased with sunrise, and then decreased with sunset. Moisture contents of top soil in tillage, and top soil and subsoil (20 cm) in no-tillage at half quantity irrigation indicated a cyclic diurnal variation by evapotranspiration. Salinity of soil was increased after initial irrigation and then was decreased continuously until next irrigation. With increasing depth of soil, increases of salinity in soil was delayed. Salinity of top soil in no-tillage was increased between AM 11:00 and AM 12:00, and then showed the highest level between PM 2:00 and PM 6:00 on a cyclic diurnal variation by evapotranspiration. Salinity of subsoil (30 cm) in no-tillage was not measured a cyclic diurnal variation. Moisture content and salinity of soil was positive correlation regardless of tillage and no-tillage cultivation. Growth of pepper in no-tillage cultivation was higher than that in tillage cultivation. Main branch Length and stem diameter of half quantity irrigation plot was higher than that of whole quantity irrigation plot regardless of tillage and no-tillage cultivation. After harvesting, the number of pepper fruits of half quantity irrigation plot was increased remarkably by 49% and 47%, in tillage and no-tillage cultivation, respectively. Pepper yield of no-tillage cultivation plot was higher by 8% than that of tillage cultivation plot. Pepper yield of half quantity irrigation plot was increased remarkably by 36% and 39%, in tillage and no-tillage cultivation, respectively.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.11 no.2
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• pp.116-121
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• 2008

Purpose: Cricopharyngeal incoordination is a rare cause of swallowing difficulties in newborns and infants; it is characterized by delayed pharyngeal contractions related to cricopharyngeal relaxation. Dysphagia and repeated aspiration are common findings despite normal sucking. We conducted this study to assess the clinical features of cricopharyngeal incoordination in newborns and infants. Methods: An analysis of the clinical data from 17 patients with cricopharyngeal incoordination who were admitted to the Department of Pediatrics, Pusan National University Hospital, between 2000 and 2006 was conducted retrospectively. The diagnosis of cricopharyngeal incoordination was established by the clinical characteristics and the videofluoroscopic swallowing studies. Results: The male to female ratio was 1:1.1 (males 8, females 9) the age range 1 to 60 days. The body weight of 11 patients (64.7%) was less than the $10^{th}$ percentile at diagnosis. Six patients (35.3%) were born prematurely. The associated anomalies or diseases were chromosomal anomaly (2 cases), congenital heart disease (3 cases), and laryngomalacia, hypoxic brain damage or neonatal seizures (1 case each). The chief complaints of patients were recurrent aspiration pneumonia (10 cases), feeding difficulty (9 cases), dyspnea (4 cases), and chocking (4 cases). The severity of aspiration on the videoesophagogram or esophagogram was mild in 12 cases. The correlation between the severity of aspiration and the duration of tube feeding after the diagnosis was significant (p<0.05). Conclusion: Cricopharyngeal incoordination should be considered in the differential diagnosis of newborns and infants, without known risk factors associated with swallowing dysfunction, when they present with unexplained respiratory problems. Although the prognosis of cricopharyngeal incoordination is good, early diagnosis and tube feeding are recommended to prevent the complications associated with this disorder.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.197-208
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• 2020

This study was carried out to analyze spatial and temporal incidence characteristics of scrub typhus and predict the future incidence of scrub typhus since the incidences of scrub typhus have been rapidly increased among vector-borne diseases. A maximum entropy (MaxEnt) ecological model was implemented to predict spatial distribution and incidence rate of scrub typhus using spatial data sets on environmental and social variables. Additionally, relationships between the incidence of scrub typhus and critical spatial data were analyzed. Elevation and temperature were analyzed as dominant spatial factors which influenced the growth environment of Leptotrombidium scutellare (L. scutellare) which is the primary vector of scrub typhus. A temporal number of diseases by scrub typhus was predicted by a deep neural network (DNN). The model considered the time-lagged effect of scrub typhus. The DNN-based prediction model showed that temperature, precipitation, and humidity in summer had significant influence factors on the activity of L. scutellare and the number of diseases at fall. Moreover, the DNN-based prediction model had superior performance compared to a conventional statistical prediction model. Finally, the spatial and temporal models were used under climate change scenario. The future characteristics of scrub typhus showed that the maximum incidence rate would increase by 8%, areas of the high potential of incidence rate would increase by 9%, and disease occurrence duration would expand by 2 months. The results would contribute to the disease management and prediction for the health of residents in terms of public health.

• Korean Journal of Food Science and Technology
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• v.42 no.4
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• pp.383-389
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• 2010

The aim of this study was to determine the methylmercury (MeHg) levels in abyssal fish species. The MeHg in the fishes was extracted with hydrochloric acid and toluene and then purified using an L-cysteine solution. The extract was analyzed with a gas chromatography-electron capture detector (GC-${\mu}ECD$) with a thermon Hg-capillary column. The detection limit and the recovery of the method were 0.002 and 84.2-98.5% (mean, 93.4%), respectively. The MeHg content in 492 abyssal fishes ranged from 0.037 to 2.009 mg/kg. The levels of MeHg [range, mg/kg (mean)] were significantly dependent on fish species and presented as the following; 0.157-2.009 (0.546) in Scalloped hammerhead shark, 0.211-0.878 (0.501) in Blue shark, 0.121-0.993 (0.482) in Spiny dogfish, 0.243-0.658 (0.397) in Salmon shark, 0.074-1.958 (0.353) in Blacktip shark, 0.038-0.807 (0.302) in Southern hake, 0.099-0.511 (0.300) in Scorpion fish, and 0.037-0.133 (0.067) in Ling. The monitoring results showed that the estimated weekly intake of MeHg from sharks, Southern hake, and Ling were lower than the provisional tolerable weekly intake recommended by the Joint FAO/WHO expert committee on food additives.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 1999.06a
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• pp.97-117
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• 1999

This study was performed to investigate the effect of pork on the cadmium detoxification in rats. Ninety male Sprague-Dawley rats weighing $125.3{\pm}1.4g$ were divided into five groups based on cadmium treatment(0, 25, 50, 100, 250ppm) and five levels of Cd in AIN-76 purified diet had been fed for 8 weeks. Cadmium was supplemented with a form of $CdCl_2$.. During following 8 weeks of intoxication, casein was replaced by pork and the effect of pork on cadmium- detoxification was compared with casein. After 8 weeks of Cd intake had resulted in apparent cadmium intoxication; reduced growth rate, enlarged kidney and testis, decreased hematocrit value and hemoglobin content in response to the supplemented Cd levels in the diets. Discontinuing cadmium feeding, the body weights were relieved. Pork-fed groups seemed to have higher body weight than casein-fed groups. Hemoglobin content and hematocrit value became normal range at detoxification stage. The weights of liver, kidney, and testis were decreased along with cadmium intake. However, organ weight ratio was not affected by cadmium. Cadmium accumulation in liver and kidney showed a tendency to increase in the cadmium-exposed groups. The levels of metallothionein were also significantly elevated in the tissues of liver in response to the levels of Cd supplemented(p<0.05). Cadmium concentration in kidney was two times higher than that in liver. Cadmium removal rate of liver was higher than that of kidney. Cadmium accumulation of the pork-fed group was lower than that of casein. Especially, the factors which affected the cadmium contents in kidney were $Cd^{***}$ and $Cd{\times}pork^{***}$. Metallothionein(MT) was increased with cadmium, and MT was not likely to be affected by pork. Based on the findings from gross lesion, rats fed 250ppm of Cd were externally emaciated, had exposed penis and observed atrophies of kidney and testis. Histopathological observation seemed that the liver of groups feeding Cd supplemented diets showed cellular degeneration and accumulation of eosinophilic materials in the capillaries. In kidney, rats fed Cd diets had shown tubular epithelium degeneration and lesions of basophilic materials, while testis were weakened in numbers of spermatid and sporadically enlarged of giant cells. But the rats administered cadmium-detoxified diet supplemented pork for 7 weeks were shown individually decreased lesions compared with the rats supplied with casein diet.

• Journal of Food Hygiene and Safety
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• v.33 no.5
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• pp.361-368
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• 2018

N-nitrosamines are probable or possible human carcinogens, which are produced by the reaction between secondary amines and nitrogen oxide in the acidic environment or by heating. Common risk assessment procedure involves the comparison between exposures expressed in the unit, mg/kg body weight/day and the Health-Based Reference dose expressed in the same unit. This procedure is suitable for the policy decision-making and is considered as inappropriate for the consumers to get information about their dietary decision-making. Therefore, the distributions of NDMA (N-nitrosodimethylamine), NDBA (N-nitrosodibutylamine), the six N-nitrosamines (NDMA, NDBA, NDEA (N-nitrosodiethylamine), NPYR (N-nitrosopyrrolidine), NPIP (N-nitrosopiperidine), and NMOR (N-nitrosomorpholine) in the menus grouped based on the presence of main ingredients and cooking methods were analyzed to generate consumer-friendly information regarding food contaminants. Recipes and intakes were taken from 2014 to 2016 KNHANES (The Korean National Health and Nutrition Examination Survey) and only the data from ages of 7 years or older were used. The contamination data were collected from the 2014~2016 Total Diet Study and all the analysis were performed using R software. Rockfish, eel, anchovy broth and pollock were mainly exposed to N-nitrosamines. In terms of cooking methods, soups and stews appeared to contain the highest amount of N-nitrosamines. Cereals, fruits, and dairy products in the ingredient categories, and rice dishes and rice combined with others in recipe categories had the lowest level exposure to N-nitrosamines. In case of N-nitrosamines, unlike other cooking related food contaminants, boiled dishes such as soups and stews and dishes mainly consisting of fishes and shellfishes had highest level of exposure, showing a large discrepancy with the previous thought of processed meat is the main source of N-nitrosamines.

• Journal of Food Hygiene and Safety
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• v.35 no.1
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• pp.51-59
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• 2020

This study evalutated the risk of foodborne illness from Vibrio spp. (Vibrio vulnificus and Vibrio cholerae) through sea squirt consumption. The prevalence of V. vulnificus and V. cholerae in sea squirt was evaluated, and the predictive models to describe the kinetic behavior of the Vibrio in sea squirt were developed. Distribution temperatures and times were collected, and they were fitted to probabilistic distributions to determine the appropriate distributions. The raw data from the Korea National Health and Nutrition Examination Survey 2016 were used to estimate the consumption rates and amount of sea squirt. In the hazard characterization, the Beta-Poisson model for V. vulnificus and V. cholerae infection was used. With the collected data, a simulation model was prepared and it was run with @RISK to estimate probabilities of foodborne illness by pathogenic Vibrio spp. through sea squirt consumption. Among 101 sea squirt samples, there were no V. vulnificus positive samples, but V. cholerae was detected in one sample. The developed predictive models described the fates of Vibrio spp. in sea squirt during distribution and storage, appropriately shown as 0.815-0.907 of R² and 0.28 of RMSE. The consumption rate of sea squirt was 0.26%, and the daily consumption amount was 68.84 g per person. The Beta-Poisson model [P=1-(1+Dose/β)^-α] was selected as a dose-response model. With these data, a simulation model was developed, and the risks of V. vulnificus and V. cholerae foodborne illness from sea squirt consumption were 2.66×10^-15, and 1.02×10^-12, respectively. These results suggest that the risk of pathogenic Vibrio spp. in sea squirt could be considered low in Korea.

• Korean journal of food and cookery science
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• v.23 no.5
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• pp.626-634
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• 2007

This study investigated the effects of 3% ground fresh paprika (FP) and 5% freeze-dried paprika powder (FDP) on lipid oxidation inhibition and warmed-over flavor (WOF) development in cooked ground pork (CGP; meat:fat = 70:30), using two packaging methods (atmosphere packaging and vacuum packaging) during 8 days at $4^{\circ}C$ and 4 months at $-26^{\circ}C$. In the CGP containing FP with atmosphere packaging, at both $4^{\circ}C\;and\;-26^{\circ}C$, peroxide formation increased sharply, and was similar to that of the CGP without paprika. Peroxide formation, in both the CGP without paprika and with FP and packaged with vacuum packaging, repectively, was much lower than that found with atmosphere packaging. Vacuum packaging was superior to atmosphere packaging for lipid oxidation inhibition. In the CGP containing FP with vacuum packaging and stored at $-26^{\circ}C$, peroxide formation almost didn't occur, which was similar to the CGP containing FDP. The peroxide value and thiobarbituric acid (TBA) value did not increase in the CGP containing FDP over the storage periods ($4^{\circ}C\;and\;-26^{\circ}C$) for both the atmosphere and vacuum packaging. Therefore, FDP was the most effective for lipid oxidation inhibition during refrigerated storage, regardless of the packaging method. Both FP and FDP with vacuum packaging during frozen storage showed similar antioxidant activities. The development of WOF in the CGP containing FDP with vacuum packaging was delayed until 7 days at $4^{\circ}C$ and 3 months at $-26^{\circ}C$, respectively. WOF was highly correlated with TBA value in the CGP stored at $-26^{\circ}C$ with vacuum packaging (r = 0.88, p<0.05). The oxidative stability of the lipid in the CGP containing FDP with vacuum packaging was excellent.

• The Korean Journal of Mycology
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• v.35 no.2
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• pp.81-84
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• 2007

In some cases, the problem with the mycelium of Tricholoma giganteum is delayed mycelial growth or non-regeneration. Therefore, this study was conducted to understand the mycelial storage condition of T. giganteum and to investigate the regeneration ratio of mycelial growth. T. giganteum obtained from KACC in RDA was evaluated for its simple preservation at $10^{\circ}C$ and subcultured on different media. Mycelium of T. giganteum was cultured on the PBA (potato bamboo extract medium) for seven days at $30^{\circ}C$. Using simple preservation method, the mycelium of T. giganteum (MKACC 50852) and Pleurotus ostreatus (Chunchu No. 2) were stored on six different media in two kinds of storage vessels (tube and vial) for a period of 1-12 months at $4^{\circ}C,\;15^{\circ}C$, and $25^{\circ}C$ storage temperatures. At $4^{\circ}C$ storage condition, mycelial regeneration was failed in all agar media, but was successful in the sawdust medium for 3 months. At $15^{\circ}C$ storage, mycelial activity was maintained up to six months. On the other hand, P. ostreatus produced well-regenerated mycelia both at $4^{\circ}C$ and $15^{\circ}C$ storage up to 12 months. In conclusion, it is estimated that the mycelia storage condition of T. giganteum must be done at $15^{\circ}C$ and subcultured within six months.