长白山金沟岭杨桦次生林下幼树生物量模型

为了对杨桦次生林下生物量模型进行补充研究,以长白山金沟岭林场杨桦次生林固定样地为研究对象,采用样地抽样的方法对林下主要树种幼树进行抽样,运用异速生长方程对幼树生物量模型进行拟合。结果表明,林下主要树种幼树生物量模型呈异速生长关系,自变量以地径D0,树高H最为紧密。其中,仅以地径D0作为单一自变量的模型精度明显低于以地径D0和树高H为自变量的模型精度;调整系数Radj2均在0.9以上,平均预测误差MPE范围在5%～49%之间,椴树的枝、叶、根和地上生物量,色木的枝生物量模型相对较差,平均预测误差均达到了40%以上;其次,根茎比与地径D0呈明显负相关关系,与树高H相关性不显著,调整系数Radj2较低,范围仅为0.053～0.507之间。最后,主要树种幼树生物量随着郁闭度的增大,表现依次下降的趋势,即W(0.6)>W(0.8)>W(1.0)。     

Effect of combined heat and high-pressure treatments on the texture of chicken breast muscle (pectoralis fundus)

Commercially supplied chicken breast muscle was subjected to simultaneous heat and pressure treatments. Treatment conditions ranged from ambient temperature to 70 degrees C and from 0.1 to 800 MPa, respectively, in various combinations. Texture profile analysis (TPA) of the treated samples was performed to determine changes in muscle hardness. At treatment temperatures up to and including 50 degrees C, heat and pressure acted synergistically to increase muscle hardness. However, at 60 and 70 degrees C, hardness decreased following treatments in excess of 200 MPa. TPA was performed on extracted myofibrillar protein gels that after treatment under similar conditions revealed similar effects of heat and pressure. Differential scanning calorimetry analysis of whole muscle samples revealed that at ambient pressure the unfolding of myosin was completed at 60 degrees C, unlike actin, which completely denatured only above 70 degrees C. With simultaneous pressure treatment at >200 MPa, myosin and actin unfolded at 20 degrees C. Unfolding of myosin and actin could be induced in extracted myofibrillar protein with simultaneous treatment at 200 MPa and 40 degrees C. Electrophoretic analysis indicated high pressure/temperature regimens induced disulfide bonding between myosin chains.