• Journal of the Korean Mathematical Society
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• v.55 no.1
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• pp.43-58
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• 2018

In this paper, we study a delayed predator-prey system with Holling type IV functional response incorporating the effect of habitat complexity. The results show that there exist stability switches and Hopf bifurcation occurs while the delay crosses a set of critical values. The explicit formulas which determine the direction and stability of Hopf bifurcation are obtained by the normal form theory and the center manifold theorem.

• Communications of the Korean Mathematical Society
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• v.21 no.4
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• pp.701-717
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• 2006

The positive coexistence of a simple food chain model with ratio-dependent functional response and cross-diffusion is discussed. Especially, when a cross-diffusion is small enough, the existence of positive solutions of the system concerned can be expected. The extinction conditions for all three interacting species and for one or two of three species are studied. Moreover, when a cross-diffusion is sufficiently large, the extinction of prey species with cross-diffusion interaction to predator occurs. The method employed is the comparison argument for elliptic problem and fixed point theory in a positive cone on a Banach space.

• Journal of the Korean Mathematical Society
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• v.50 no.4
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• pp.695-713
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• 2013

We formulate and study a predator-prey model with non-monotonic functional response type and weak Allee effects on the prey, which extends the system studied by Ruan and Xiao in [Global analysis in a predator-prey system with nonmonotonic functional response, SIAM J. Appl. Math. 61 (2001), no. 4, 1445-1472] but containing an extra term describing weak Allee effects on the prey. We obtain the global dynamics of the model by combining the global qualitative and bifurcation analysis. Our bifurcation analysis of the model indicates that it exhibits numerous kinds of bifurcation phenomena, including the saddle-node bifurcation, the supercritical and the subcritical Hopf bifurcations, and the homoclinic bifurcation, as the values of parameters vary. In the generic case, the model has the bifurcation of cusp type of codimension 2 (i.e., Bogdanov-Takens bifurcation).

• BMB Reports
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• v.53 no.4
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• pp.181-190
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• 2020

Protein phosphatase 4 (PP4), one of serine/threonine phosphatases, is involved in many critical cellular pathways, including DNA damage response (DNA repair, cell cycle regulation, and apoptosis), tumorigenesis, cell migration, immune response, stem cell development, glucose metabolism, and diabetes. PP4 has been steadily studied over the past decade about wide spectrum of physiological activities in cells. Given the many vital functions in cells, PP4 has great potential to develop into the finding of key working mechanisms and effective treatments for related diseases such as cancer and diabetes. In this review, we provide an overview of the cellular and molecular mechanisms by which PP4 impacts and also discuss the functional significance of it in cell health.

• Kyungpook Mathematical Journal
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• v.50 no.2
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• pp.255-266
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• 2010

We consider a delayed predator-prey system with Holling II functional response. Firstly, the paper considers the stability and local Hopf bifurcation for a delayed prey-predator model using the basic theorem on zeros of general transcendental function, which was established by Cook etc.. Secondly, special attention is paid to the global existence of periodic solutions bifurcating from Hopf bifurcations. By using a global Hopf bifurcation result due to Wu, we show that the local Hopf bifurcation implies the global Hopf bifurcation after the second critical value of delay. Finally, several numerical simulations supporting the theoretical analysis are given.

• The Pure and Applied Mathematics
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• v.15 no.3
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• pp.329-342
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• 2008

There have been many experimental and observational evidences which indicate the predator response to prey density needs not always monotone increasing as in the classical predator-prey models in population dynamics. Holling type functional response depicts situations in which sufficiently large number of the prey species increases their ability to defend or disguise themselves from the predator. In this paper we investigated the stability and instability property for a Holling type predator-prey system of a generalized form. Hopf type bifurcation properties of the non-diffusive system and the diffusion effects on instability and bifurcation values are studied.

• Journal of the Korean Dietetic Association
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• v.11 no.2
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• pp.216-222
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• 2005

In Korea, there are many kinds of functional foods to manage diabetes, however, they have not been evaluated or investigated systematically. The purpose of this study was to investigate the status of recognition and intake of functional foods among diabetic patients. The study subjects were 307 patients(male 135, female 172), who diagnosed with type 2 diabetes at Seoul National University of Bundang Hospital. Questionnaire survey was done from July to October, 2004 for the characteristics of patients and factors related to the use of functional foods. The mean age of the subjects was 64$\pm$10.2 years, and the mean duration of disease was 9.5$\pm$8.90 years. Approximately 49.8% of the subjects had experience to use functional foods at least once in past. Total number of functional foods used were 56 types. Red ginseng was used most frequently(27.9%), then followed by Silkworm powder(13.6%), Vitamin supplements(10.4%), Mulberry tree(7.1%), Cordyceps sinensis(6.8%) and Ginseng(4.2%). Functional foods were introduced by their friends.relatives(38.4%), family(29.1%), internet(13.9%), and the mass media(10.6%). Among respondents, 94.7% took functional foods with conventional diet therapies(diet, exercise and medication). The purpose of functional food use was to control blood glucose level(49.0%), to relieve fatigue and improve stamina(19.9%), to treat and prevent a disease(17.2%) and to help blood circulation(7.9%). Upon the question of further recommendation of functional foods to others, 74.8% of the subjects answered negative response. However, 12.6% of the subjects showed the further intention of using new product. Therefore, to guide the appropriate use of functional foods for diabetic patients, diabetic educator should provide the knowledge of the efficacy of functional foods and the desirable guidelines.

• Food Science and Biotechnology
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• v.17 no.2
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• pp.379-383
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• 2008

Extraction characteristics of garlic and functional properties of corresponding extract were monitored by response surface methodology (RSM). Maximum extraction yield of 26.41% was obtained at microwave power of 146.29 W, ethanol concentration of 63.31 %, and extraction time of 5.88 min. At microwave power, ethanol concentration, and extraction time of 114.84 W, 58.83%, and 1.42 min, respectively, maximum electron-donating ability (EDA) was 72.86%. Maximum nitrite-scavenging ability was 94.62% at microwave power, ethanol concentration, and extraction time of 81.83 W, 2.65%, and 3.83 min, respectively. Superoxide dismutase (SOD) showed maximum pseudo-activity of 49.12% at microwave power of 34.23 W, ethanol concentration of 33.11 %, and extraction time of 4.40 min. Based on superimposition of 4-dimensional RSM with respect to extraction yield, electron-donating ability, nitrite-scavenging ability, and pseudo-activity of SOD, optimum ranges of extraction conditions were microwave power of 0-100 W, ethanol concentration of 40-70%, and extraction time of 2-8 min.

• Earthquakes and Structures
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• v.8 no.5
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• pp.957-976
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• 2015

Recently, two energy-based response parameters, i.e., the absolute and the relative elastic input energy equivalent velocity, have been receiving a lot of research attention. Several studies, in fact, have demonstrated the potential of these intensity measures in the prediction of the seismic structural response. Although some ground motion prediction equations have been developed for these parameters, they only provide marginal distributions without information about the joint occurrence of the spectral values at different periods. In order to build new prediction models for the two equivalent velocities, a large set of ground motion records is used to calculate the correlation coefficients between the response spectral values corresponding to different periods and components of the ground motion. Then, functional forms adopted in models from the literature are calibrated to fit the obtained data. A new functional form is proposed to improve the predictions of the considered models from the literature. The components of the ground motion considered in this study are the two horizontal ones only. Potential uses of the proposed equations in addition to the prediction of the correlation coefficients of the equivalent velocity spectral values are shown, such as the prediction of derived intensity measures and the development of conditional mean spectra.

• Journal of Chest Surgery
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• v.23 no.4
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• pp.676-682
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• 1990

From August, 1978, to August, 1989, 22 patients underwent pericardiectomy for chronic constrictive pericarditis on the Department of Thoracic and Cardiovascular Surgery, School of Medicine, Keimyung University. There were 14 male and 6 female patients ranging from 11 years to 70 years old[mean age, 44. 1 years]. All patients underwent radical pericardiectomy through a median sternotomy. There was 1 postoperative death[4.s%]. This patient died of low cardiac output 7 days after pericardiectomy. Postoperative complications were hemothorax[2 patients], low cardiac output[2 patients], generalized seizure[1 patient], wound infection[1 patient] and pneumonia[1 patient]. Clinical and pathological findings showed tuberculous origin in 12 patients[54.6%], unknown etiology in 8 patients[36.4%] pyogenic pericarditis in 2 patients[9.1%]. Three hemodynamic responses to pericardiectomy were observed: [1] rapid response, where central venous pressure[CUP] fell below 10 cmH2O by 24 hours in 6 patients; [2] delayed response. Where CVP fell below 10 cmH2O by 48 hours in 12 patients; and [3] no response of CVP in 4 patients. Follow-up ranged from 6 to 62 months with an average of 35.3 months. Postoperative Functional Class was obtained for 21 surviving patients and showed 18 patients[81.8%] to be New York Heart Association functional class I or II.