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박상준,한민희 한국경영과학회 2000 韓國經營科學會誌 Vol.25 No.2
Consumers facing a large number of brands to choose from are known to use simplified heuristic to screen a set of relevant brands called the consideration set from the whole alternatives. Purchase decisions are then made from the brands in the consideration set. Two approaches have been suggested to model the two-stage choice process. One is to treat the consideration set as a crisp set (e.g, Roberts and Lattin 1991). The other is to treat the set as a fuzzy set (e.g, Fortheringham 1988). The paper empirically compares the two types of models using data for soft drinks, sneakers, and departments. The results show that a model employing the crisp set approach fits the data better than that with the fuzzy set approach and better than a single-stage choice logit model.
Involvement of Spontaneously Formed Cyclic Nucleotides in Cat Gastric Muscle Relaxation
Sang-Soo Sim,Hye-Jung Baek,Duck-Joo Rhie,Shin-Hee Yoon,Sang June Hahn,Yang-Hyeok Jo,Myung-Suk Kim 대한생리학회-대한약리학회 1999 The Korean Journal of Physiology & Pharmacology Vol.3 No.3
<P> Muscle strips and muscle cells from cat stomach were used to investigate whether spontaneously formed cyclic nucleotides were involved in the inhibition of gastric smooth muscle contraction. A phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX), increased the levels of both cyclic GMP (cGMP) and cyclic AMP (cAMP) in resting state cells, while decreasing acetylcholine-induced muscle contraction. Under the influence of IBMX, SQ22536, an adenylyl cyclase inhibitor and methylene blue, a guanylyl cyclase inhibitor completely blocked increases in cAMP and cGMP respectively, without any effect on contraction. However, the combination of SQ22536 and methylene blue completely blocked increases in both cAMP and cGMP levels and stimulated contractions markedly even in the presence of IBMX. Muscle contraction inhibitors such as isoprenaline, vasoactive intestinal polypeptide and sodium nitroprusside also appeared to increase cyclic nucleotide levels which decreased contraction. Which nucleotide increased the most was dependent on the agonist used. Therefore, irrespective of the cyclic nucleotide class, the spontaneous formation of cyclic nucleotides should be considered in evaluating the mechanism of gastric smooth muscle relaxation.
Open Channel Block of Kv3.1 Currents by Fluoxetine
Sung, Min Ji,Ahn, Hye Sook,Hahn, Sang June,Choi, Bok Hee The Japanese Pharmacological Society 2008 Journal of pharmacological sciences Vol.106 No.1
<P>The action of fluoxetine, a serotonin reuptake inhibitor, on the cloned neuronal rat Kv3.1 channels stably expressed in Chinese hamster ovary cells was investigated using the whole-cell patch-clamp technique. Fluoxetine reduced Kv3.1 whole-cell currents in a reversible, concentration-dependent manner, with an IC<SUB>50</SUB> value and a Hill coefficient of 13.4 μM and 1.4, respectively. Fluoxetine accelerated the decay rate of inactivation of Kv3.1 currents without modifying the kinetics of current activation. The inhibition increased steeply between 0 and +30 mV, which corresponded with the voltage range for channel opening. In the voltage range positive to +30 mV, inhibition displayed a weak voltage dependence, consistent with an electrical distance δ of 0.38. The binding (k<SUB>+1</SUB>) and dissociation (k<SUB>−</SUB><SUB>1</SUB>) rate constants for fluoxetine-induced block of Kv3.1 were 5.7 μM<SUP>−</SUP><SUP>1</SUP>s<SUP>−</SUP><SUP>1</SUP> and 53.5 s<SUP>−</SUP><SUP>1</SUP>, respectively. The theoretical K<SUB>D</SUB> value derived by k<SUB>−</SUB><SUB>1</SUB>/k<SUB>+1</SUB> yielded 9.3 μM. Fluoxetine did not affect the ion selectivity of Kv3.1. Fluoxetine slowed the deactivation time course, resulting in a tail crossover phenomenon when the tail currents, recorded in the presence and absence of fluoxetine, were superimposed. Inhibition of Kv3.1 by fluoxetine was use-dependent. The present results suggest that fluoxetine acts on Kv3.1 currents as an open-channel blocker.</P>
자기증폭자발방사에서의 Coherent bunched beam효과
한상준 中央大學校 基礎科學硏究所 1995 基礎科學硏究所 論文集 Vol.9 No.-
A general formalism of Self-Amplified-Spontaneous-Emission(SASE) in the linear regime is developed by deriving the coupled Maxwell-Klimontovich equations for an arbitrary density profile and including the effects of the energy spread, diffraction, and the betatron oscillation. The temporal and the spectral intensity profiles of SASE depend linearly on the initial electron correlation function. The correlation function consists of two terms, a term giving rise to the usual spontaneous radiation and its amplification to SASE, and a term representing the coherent bunched beam effect. The latter term has been neglected so far in the treatments of SASE, but it could be significant when there is a variation in the electron density at a length scale comparable to the wavelength. By the extensive numerical calculation, the comparison with the recent SASE experiment at Stanford University will be made.
Sim. Sang-Soo,Yoon. Shin-Hee,Hahn. Sang-June,Rhie. Duck-Joo,Jo. Yang-Hyeok,Kim. Myung-Suk 대한생리학회 1995 대한생리학회지 Vol.29 No.1
Gastric smooth muscle of guinea pigs was used to investigate whether the inhibitory effect of calcium antagonists on tonic contraction was accompanied by inhibition of phospholipase C activity. Tonic contraction and [<sup>3</sup>H] inositol phosphate (IP) formation in response to acetylcholine were measured after pretreatment with verapamil, nifedipine, 8-(N,N-diethylamino)octyl 3,4,5-trimethoxy-benzoate (TMB-8) or EGTA. Verapamil (10 μM), TMB-8 (10 μM) or EGTA (2 mM) significantly inhibited acetylcholine (1 μM)-stimulated tonic contraction but nifedipine (100 nM) did not. Acetylcholine dose-dependently increased the formation of [<sup>3</sup>H]IP. This effect was not observed in the presence of 2 mM EGTA. Both verapamil and TMB-8 significantly inhibited [<sup>3</sup>H]IP formation induced by 10 μM acetylcholine, whereas nifedipine did not. In a subsequent study, we measured phospholipase C activity in gastric muscle cell homogenate and in permeabilized cells to determine whether calcium antagonists could inhibit the activity directly. The calcium antagonists did not change the phospholipase C activity of the cell homogenate or the permeabilized cells. But EGTA decreased phospholipase C activity by 50%. These results suggest that the inhibitory effects of verapamil and TMB-8 on acetylcholine-stimulated tonic contraction may be accompanied by inhibition of phospholipase C activity.