稳态噪声与非稳态噪声所致工人听力损害的对比研究

目的对稳态噪声和非稳态噪声导致的工人听力损害进行对比分析。方法随机选择同一企业,稳态噪声下工作工人50例为A组稳态组,并选择非稳态噪声下工作工人35例为B组非稳态组,分别给予A、B两组研究对象为期14个月的稳态噪声和非稳态噪声工作环境,对患者听力受损程度进行检测。结果经统计,A组对象听力损伤率低于B组,患病率低于B组,职业性耳聋率低于B组,对象听力损害程度相对于B组对象较低。结论非稳态噪声与稳态噪声相比,对工人听力损害程度较高,职业性耳聋率高。     

Effects of unsteady fixation on multifocal electroretinogram (mfERG)

Purpose To investigate the effect of unsteady fixation on the multifocal electroretinogram (mfERG) measurement in normal subjects.Methods The mfERGs of 20 subjects with normal vision (mean age=23.5 years) were recorded with different levels of voluntary eye movements made to mimic unsteady fixation. Subjects were required to move their fixation regularly every 2 s between the center and the ends of a fixation cross, so that 51.2% of the time fixation was at the center and 12.2% of the time it was at each end of the fixation cross. Four different conditions were performed: central fixation (without voluntary eye movements) and with 2°, 4° and 6° magnitude of unsteady fixation. First-order kernel mfERG findings are presented.Results Analysis of the ring responses indicated that the central mfERG amplitude was most affected by unsteady fixation. There was significantly reduced amplitude for 4° unsteady fixation and as expected, this reduction became larger with 6° unstable fixation. However, there was no significant effect on the center hexagon amplitude for 2° unsteady fixation. The amplitudes of the ring-2 responses were only affected in the 6° unsteady fixation condition. No significant change in implicit time was found for any level of unsteady fixation.Conclusion These results suggest that mfERG amplitude is not substantially affected if fixation is maintained within the central stimulus hexagon. We conclude that, for patients with poor fixation, the accuracy of mfERG results may be difficult to interpret and the use of a fixation-monitoring system is desirable for ideal measurement. The depth of depression at the blind spot area may be another useful parameter to interpret the accuracy of mfERG results in patients with poor fixation.     

A high precision dual feedback pump for unsteady perfusion of small organs

A dynamic pump system is described for perfusion of small organs with whole blood. The pump system was designed with the following aims: Very low flowrates to perfuse single organs in small rodents; high dynamic response for pressure or flow to permit experimenting with a harmonic signal at frequencies up to 20 Hz or by way of sharp step transients in less than 10 msec; high precision to allow detection of fine physiological details, and minimum blood cell trauma or cell activation by use of a piston principle. Representative pressure-flow curves are shown for the rat gracilis muscle after vasodilation. The curves are highly reproducible and serve as a complimentary dataset for microvascular observations in the same organ.     

组合压气机中尾迹与势流同频/异频干涉的叠加特性

为揭示多级压气机中上下游叶轮对中间叶片叠加气动影响特性,阐述不同叠加干涉情况下下游叶轮进气角度变化,采用数值方法模拟了一级轴流和一级离心组成的组合压气机非定常流场。详细讨论了上游动叶尾迹和下游动叶势流对中间导流叶栅段气流非定常流动的异频和同频叠加干涉特性,依据计算结果,直观地展示了静叶通道中两种干涉间相互激励和抑制作用的位置和时间,与数学公式的推导结果相互印证。研究结果表明:当上下游动叶对中间静叶段异频干涉时,干涉的激励、抑制区域的轴向位置随时间发生变化；当上下游动叶对中间静叶干涉频率相同时,干涉的相互激励、抑制区域的轴向位置不随时间发生变化,但干涉的激励、抑制区域的轴向位置受时序位置影响。另外,上游动叶尾迹与下游离心叶轮势流的不同叠加情况,决定着下游离心叶轮进口相对气流角的大小及波动幅值。 