Determination of immobilized heparin The amount of immobilized heparin was determined by toluidine blue assay.15,16 Cubic collagen matrices (size, 5 5 5 mm; weight, 3.8–4.2 mg) were incubated with 5 mL of an aqueous solution of toluidine blue (0.1 M HCl, NaCl [2 mg/mL], and toluidine...
浓度单位ppm、ppb等的含义（The units of concentration, ppm,ppb, etc.）The units of concentration, ppm, PPb, etc.PPb is the abbreviation of part per billion, a unit symbol that indicates the concentration of a liquid. Generally read as "1/10 million", "1/1000000000", or "10 negative", ...
在SQLServer 2008中,设有数据库应用系统中有商品类别表(商品类别号,类别名称,类别描述信息) 和商品表(商品号,商品类别号,商品名称,生产日期,单价,库存量)。该系统要求增加每种商品在入库的时候自动检查其类别,禁止未归类商品入库的约朿。下列实现此约束的语句中正确的是( )。