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Evaluating liquid crystal properties for use in terahertz devices.
Park, Hongkyu,Parrott, Edward P J,Fan, Fan,Lim, Meehyun,Han, Haewook,Chigrinov, Vladimir G,Pickwell-MacPherson, Emma Optical Society of America 2012 Optics express Vol.20 No.11
<P>Despite the wide application of liquid crystals (LCs) in the visible frequency range, their properties in the terahertz range have not yet been extensively investigated. In this paper we have investigated the terahertz properties of LCs E7, BL037, RDP-94990 and RDP-97304 using terahertz time-domain-spectroscopy. We find that RDP-94990 has the largest birefringence and smallest absorption in the terahertz range compared to E7 and BL037. We highlight the importance of investigating all parameters, not just the birefringence, when designing fast, efficient and transmissive terahertz LC devices.</P>
Lee, Dong-Keun,Parrott, David L.,Adhikari, Emma,Fraser, Nisa,Sieburth, Leslie E. American Society of Plant Biologists 2016 Plant Physiology Vol.171 No.3
<P>The bypass1 (bps1) mutant of Arabidopsis (Arabidopsis thaliana) produces a root-sourced compound (the bps signal) that moves to the shoot and is sufficient to arrest growth of a wild-type shoot; however, the mechanism of growth arrest is not understood. Here, we show that the earliest shoot defect arises during germination and is a failure of bps1 mutants to maintain their shoot apical meristem (SAM). This finding suggested that the bps signal might affect expression or function of SAM regulatory genes, and we found WUSCHEL (WUS) expression to be repressed in bps1 mutants. Repression appears to arise from the mobile bps signal, as the bps1 root was sufficient to rapidly down-regulate WUS expression in wild-type shoots. Normally, WUS is regulated by a balance between positive regulation by cytokinin (CK) and negative regulation by CLAVATA (CLV). In bps1, repression of WUS was independent of CLV, and, instead, the bps signal down-regulates CK responses. Cytokinin treatment of bps1 mutants restored both WUS expression and activity, but only in the rib meristem. How the bps signal down-regulates CK remains unknown, though the bps signal was sufficient to repress expression of one CK receptor (AHK4) and one response regulator (AHP6). Together, these data suggest that the bps signal pathway has the potential for long-distance regulation through modification of CK signaling and altering gene expression.</P>
Learning Contracts in Residential Design Classes
Eunju Hwang,Kathleen Parrott,Hyun Joo Kwon 한국주거학회 2015 한국주거학회 국제학술대회논문집 Vol.2015 No.4
The purpose of this study was to reflect on teaching methods in the context of residential design students’ design process and assessment with learning contracts. We used Grow’s (1991) Staged Self-Directed Learning Model which has four stages starting from understanding a teacher as authority coach to the self-directed phase, understanding the teacher as consultant or delegator. This model fostered collective and experiential learning for design students. The learning contract methodology was developed as t he basis of course assignments and evaluation for two residential design studio classes. After the initial meeting with the instructor, students developed and implemented a learning contract including specific tasks, timelines, and outcomes to proceed with their design implementation. Students had to meet with the instructor and shared their progress regularly in class. Overall, the learning contract increased students’ responsibility, and improved their inter-personal communication skills.
Development and Evaluation of an Oral Controlled Release Delivery System for Melatonin
Lee,Beom Jin,Keith A Parrott,Robert L Sack,James W Ayres 한국약제학회 1993 Journal of Pharmaceutical Investigation Vol.23 No.3
Sugar spheres loaded with melatonin (MT) were coated with Aquacoat^ⓡ to control the release rate of MT over 8 hours. A zero-order release pattern over 8 hours was obtained with 20% coating on 8-10 mesh beads in USP basket dissolution studies. MT in 20% coated beads was quite stable at room temperature with less than 5% MT degraded during 6 months' storage. Dissolution profiles were also unchanged after 6 months. An oral preparation containing MT-loaded uncoated beads for immediate release and 20% coated beads with Aquacoat^ⓡ for controlled release over 8 hours was evaluated in six human subjects. When total 0.5 ㎎ MT as low dose (immediate release portion of MT, 0.1 ㎎) was administered to four subjects, average peak plasma MT concentration was reached at about 600 pg/㎖ and maintained at about 10 pg/㎖ over 8 hours. Plasma MT concentration-time profiles were similar in shape to computer-simulated profiles. However, maximal plasma MT concentrations were three times greater compared to computer simulated curve. These results suggest that MT dose, ratio of immediate and controlled release MT, and pharmacokinetic parameters selected are adjusted to mimic endogenous MT concentration-time curve. In another study, 0.2 ㎎ MT having 10% of immediate release portion and 80% controlled release portion produced plasma MT concentration-time curve which is more similar to endogenous profiles. A low bioavailability (<20%) may result from extensive first pass metabolism and remaining amounts of MT from controlled beads. A good correlation between plasma MT concentration and urinary excretion rate of 6-sulphatoxymelatonin (6-STMT), a major metabolite of MT was observed. As plasma MT concentration increased, urinary excretion rate of 6-STMT increased concomitantly. The linear relation between plasma MT and urinary excretion rate of 6-STMT was statistically significant. This result suggests that urinary 6-STMT may be used as an index of circadian rhythms of MT in humans.
AGEING IN THE UNITED STATES AT THE END OF THE CENTURY
BENGTSON, VERN L.,MILLS, TEHERAN L.,PARROTT, TONYA M. Institute for Social Development and Policy Resear 1995 Korea Journal of Population and Development Vol.24 No.2
The belief that America is a “young” nation is widely held by many individuals in the United States. Historically, individualism, self-reliance, and an orientation towards youth have been cherished values reflecting of our national heritage and tradition dating from the 18th through the mid-20th Century. However, America is no longer a “young” nation. Rather, we are an “aging” population, as we show in our analysis of demographic transitions reviewed in this paper. The phenomenon of “cultural (or structural) lag” is discussed in two different contexts: first-the context of the aging family; and second-the context of ethnic/racial minority groups. Finally, some of the relevant public policy responses to aging are described. We look at government programs in four major categories, namely, 1) income; 2) health care; 3) social services; and 4) housing.
Lee, Beom-Jin,Ryu, Seung-Goo,Choi, Han-Gon,Kim, Chong-Kook,Parrott, Keith-A.,Ayres, James-W.,Sack, Robert-L. The Pharmaceutical Society of Korea 1997 Archives of Pharmacal Research Vol.20 No.6
The three different batches of an oral sustained release melatonin (MT) delivery system were prepared by aqueous-based fluid-bed coating of the sugar spheres for the evaluation of in vitro release characteristics and plasma concentration profiles in human subjects. The MT contents in 20% coated sugar spheres of three batches (B1, B2 and B3) were $3.3{\pm}0.08$, $2.4{\pm}0.1$ and $2.5{\pm}0.13$ mg per gram of coated sugar spheres, respectively. The release profiles of three different batches had a very similar fashion. However, the release profiles of three different batches had a very similar fashion. However, the release half-lives $(T_{50%})$ of MT from B1, B2 and B3 was $3.70{\pm}0.2$, $5.2{\pm}0.2$ and $4.9{\pm}0.07h$, respectively. Plasma concentration profiles of sustained release 0.2mg melatonin-loaded sugar spheres containing 10% immediate release melatonin in gelatin capsules (B1 and B2) were then evaluated in human subjects. The in vivo plasma concentration profies of the two batches (B1 and B2) were very similar each other and located between the physiological endogenous ranges. The time to reach the peak concentration $(T_max)$ was more advanced in case of B1 when compared to B2. However, there was no statistically significant difference in the maximum concentration $(C_max)$ and the area under the curve (AUC) between B1 and B2. The AUC of melatonin-loaded sugar spheres containing 10% and 20% immediate release MT in human subjects had a good linearity between dose and AUC, regardless of the fraction of immediate release MT, indicating the first order elimination process of MT within these doses. The current oral sustained release MT delivery system may be utilized to treat circadian rhythm disorders if it is proven to be more clinically useful when compared to immediate release MT.
Lee, Beom-Jin,Choi, Han-Gon,Kim, Chong-Kook,Parrott, Keith-A.,Ayres, James-W.,Sack, Robert-L. The Pharmaceutical Society of Korea 1997 Archives of Pharmacal Research Vol.20 No.6
The physicochemical properties of melatonin (MT) in propylene glycol (PG) and 2-hydroxypropyl-.betha.-cyclodextrin $(2-HP{\beta}CD)$ vehicles were characterized. MT was endothermally decomposed as determined by differential scanning calorimetry (DSC). Melting point and heat of fusion obtained were $116.9{\pm}0.24^{\circ}C $.and $7249{\pm}217 cal/mol$., respectively. MT as received from a manufacture was very pure, at least 99.9%. The solubility of MT in PG solution increased slowly until reaching 40% PG and then steeply increased. Solubility of MT increased linearly as concentration of $2-HP{\beta}CD$ without PG INCREASED$(R^2=0.993)$. MT solubility in the mixtures of pg and $2-HP{\beta}CD$ also increased linearly but was less than the sum of its solubility in $2-HP{\beta}CD$ and PG individually. The MT solubility was low in water, simulated gastric or intestinal fluid but the highest in the mixture of PG(40v/v%) and $2-HP{\beta}CD$ (30w/v%) although efficiency of MT solubilization in $2-HP{\beta}CD$ decreased as the concentration of PG increased. MT was degraded in a fashion of the first order kinetics $(r^2>0.90)$. MT was unstable in strong acidic solution (HCl-NaCl buffer, pH 1.4) but relatively stable in other pH values of 4-10 at $70^{\circ}C$. In HCl-NaCl buffer, MT in 10% PG was more quickly degraded and then slowed dpwm at a higher concentration. However, the degradation rate constant of MT in 2-HP.betha.CD was not changed significantly when compared to the water. The current studies can be applied to the dosage formulations for the purpose of enhancing percutaneous absorption or bioavailability of MT.