缅甸翡翠

缅甸所产的玉石,有红、绿、青、蓝、黄、紫、白、黑等色彩。红绿二色,鲜艳夺目,人们称红者为翡,绿者为翠,统称翡翠。 翡翠的化学成份是硅酸铝钠,晶体结构致密,质坚硬,为摩氏七级,比重3.3。翡翠颜色天然鲜艳,有不透明、半透明和近乎透明等。目前世界上以翡翠玉为最优,产地仅在缅甸。 翡翠产于缅甸北部的勐拱、密支那等地。勐拱元代叫蒙光路,明洪武年间改为柔远路,置孟养府,永乐二年(公元1404年)改为军民宣慰使司,治所在今缅甸孟养。

Effects of tissue absorption on calculation of mean photon path length using modified Beer-Lambert law

The mean path length(MPL)of photons is a critical parameter to calculate tissue absorption coefficient as well as blood oxygenation using modified Beer-Lambert law,where in the differential path factor(DPF)is often assumed as constant over range of tissue absorption.By utilizing the Monte Carlo(MC)simulation of photon migrations in the leg,this study used four approaches to estimate MPL,and compared them with that determined by the MPL definition.The simulation results indicate that the DPF is remarkably affected by tissue absorption,at approximate 10% variation.A linear model is suggested to calculate MPL for measurements of tissue absorption as well as blood oxygenation using modified Beer-Lambert law.

永恒的守望

神奇又神秘的琥珀历来受到世界各民族的顶礼膜拜,作为世界上最古老的琥珀、宝石级存量最稀少的琥珀、最具科研价值的琥珀、色彩最绚烂的琥珀——缅甸琥珀蕴藏着巨大的投资价值。缅甸琥珀的历史近几年,具有天然宝石品质的缅甸琥珀越来越被全国琥珀玩家所关注,喜欢缅甸琥珀的人在不断增多。