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Metabolism of Rabbit Masseter Muscle Measured with ^31P Magnetic Resonance Spectroscopy
Chang, Chongon,Chew, Will,Alcantara, Moses,McNeill, Charles,DeCrespigny, Alex J.,Miller, Arthur J. Korean Academy of Oral Biology and the UCLA Dental 1997 International Journal of Oral Biology Vol.22 No.1
^31P NMR spectroscopy was used to study the metabolic characteristics of a jaw-closing muscle. The masseter was stimulated electrically to evoke repeated twitches (5 Hz), tetany (50 Hz) and periodic contracions in 15 anesthetized New Zealand adult male rabbits in 22 recording sessions. NMR spectra consisting of 5 peaks related to unbound phosphate were obtained during rest and contraction using a 2×3㎝, double-turn, copper transmit/receive coil while the animal was placed in a small bore Bruker 4.7 Tesla superconducting magnet. Stimulation at frequencies below 20-30 Hz evoked a significant increase in inorganic phosphate (Pi) and a marked decrease in phosphocreatine (PCr); both exhibited a steady state plateau during a three-minute stimulation trial. In contrast, stimulating at frequencies above 20-30 Hz developed a peak change in Pi and PCr that rapidly declined during the three-minute contraction. Electrically stimulating the masseter at 50 Hz while varying the periodicity of the stimulus with train durations of 200 to 800 msec indicated that the Pi and PCr changes switched between that of twitching to tetany with train durations exceeding 200 msec. These findings suggest that Pi/PCr changes demonstrate two types of responses during contraction that relate to the frequency of contraction.
A study of fracture loads and fracture characteristics of teeth
Sheen, Chang-Yong,Dong, Jin-Keun,Brantley, William Arthur,Han, David Seungho The Korean Academy of Prosthodonitics 2019 The Journal of Advanced Prosthodontics Vol.11 No.3
PURPOSE. The purpose of this in vitro study was to investigate the fracture loads and modes of failure for the full range of natural teeth under simulated occlusal loading. MATERIALS AND METHODS. One hundred and forty natural teeth were taken from mandibles and maxillas of patients. There were 14 groups of teeth with 10 teeth in each group (5 males and 5 females). Each specimen was embedded in resin and mounted on a positioning jig, with the long axis of the tooth at an inclined angle of 30 degrees. A universal testing machine was used to measure the compression load at which fracture of the tooth specimen occurred; loads were applied on the incisal edge and/or functional cusp. RESULTS. The mean fracture load for the mandibular first premolar was the highest (2002 N) of all the types of teeth, while the mean fracture load for the maxillary first premolar was the lowest (525 N). Mean fracture loads for the mandibular and maxillary incisors, and the first and second maxillary premolars, had significantly lower values compared to the other types of teeth. The mean fracture load for the teeth from males was significantly greater than that for the teeth from females. There was an inverse relationship between age and mean fracture load, in which older teeth had lower fracture loads compared to younger teeth. CONCLUSION. The mean fracture loads for natural teeth were significantly different, with dependence on tooth position and the sex and age of the individual.
An Economic Evaluation of Swine Waste Management Systems under Environmental Regulations
Kim, Chang-Gil,Stoecker, Arthur,Williams, Joseph 한국농업경제학회 2002 農業經濟硏究 Vol.43 No.4
The objectives of this study are to evaluate the economics of alternative swine waste management systems and to determine the optimal waste management strategy that maximized a representative swine producer's profitability from production while managing swine waste in a manner that meets environmental regulations. The objectives are accomplished through the use of a mixed integer programming model. The analytical model is to determine the most profitable swine production and waste management system for representative producers in Texas and Seminole counties in Oklahoma. The major finding is that there is no single best or optimal waste management system for all sizes and types of swine operations. In general, and use of the lagoon to store and the use of an irrigation system to spread swine waste require less energy and labor and is more cost effective than other systems such as tank-hauling, pit-hauling, or lagoon-hauling systems.
Approaches to the Syntheses of Partially Reduced Imidazo[1,2-a]pyridines
신준화,Young Chang Nho,Arthur S. Howard 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.10
Two synthetic pathways to substituted hexahydroimidazo[1,2-a]pyridines, which may serve as precursors of aza-alkaloids, were investigated. The first involves the condensation of a bisnucleophilic enediaminoester and a biselectrophile. The second involves attachment to nitrogen of the carbon chain skeleton required to form the six-memberd ring, before formation of the enediaminoester. Several substituted hexahydroimidazo[1,2- a]pyridines were synthesized via these two approaches.