叶绿素计SPAD-502在林业上应用

叶绿素是植物光合作用的色素,传统方法测定叶绿素一般采用分光光度法.本研究采用便携式叶绿素计SPAD-502测定落叶松人工林下4个主要阔叶树种绿色度（SPAD值）的季节变化,并与分光光度法测定的叶绿素含量进行相关性分析.结果表明,SPAD值与叶绿素含量具有显著的相关性,SPAD值能较好地反映树木叶绿素含量的变化.因此,使用叶绿素计测定树木的叶绿素含量是完全可行的,在一定条件下可代替叶绿素含量的直接测定.由于叶绿素计SPAD-502携带方便、测定简便、迅速,且不损坏叶片,应在林业研究中积极推广使用.     

数字式磁控脊髓夹损仪

在原磁控机械夹断装置的基础上,研制出一种新型的、定量的数字式磁控脊髓夹损仪。该仪器是根据电磁理论和力学平衡原理设计的,由定时器、电流调节器和电流表、控制电路及电磁夹具所组成。电磁夹具左、右两臂间的距离、其单或双臂作用力,运动方向和持续时间均可根据实验要求预先设置和调整。流经电磁夹具单臂或双臂的电流可在数字显示屏上显示并保持。本仪器操作简便可靠,还可直读,适用于复制不同种系动物的不同类型和程度的脊髓损伤。     

不同类型益生菌制剂在胃肠道中耐受程度的对比

目的 对市场销售的几种不同类型益生菌制剂进行胃、肠液耐受程度比较,评价各益生菌制剂活菌数量,为临床选择益生菌制剂提供参考。 方法 选择7种菌粉及某颗粒益生菌、国产某晶球、日本产某晶球、某胶囊益生菌、圣邦步步佳肠释益生菌共12种口服益生菌产品,在崩解时限仪中加入人工胃液进行崩解试验,在0.0 h、0.5 h、1.0 h、1.5 h和2.0 h时吸取上述样品并进行浓度梯度稀释,并在MRS固体培养基上培养后进行活菌计数。在上述5个时间点吸取部分益生菌-胃液混合物(针对益生菌粉末)或取出益生菌产品(针对晶球、肠溶胶囊、肠释益生菌)换人工肠液再进行40 min崩解,在MRS固体培养基上培养后进行活菌计数。 结果 粉末状益生菌制剂对人工胃液的耐受能力普遍较差。某颗粒益生菌、国产某晶球、日本产某晶球、某胶囊益生菌、圣邦步步佳肠释益生菌在人工胃液中不崩解。圣邦步步佳肠释益生菌在人工肠液中40 min完全崩解且活菌数峰值较高。 结论 圣邦步步佳肠释益生菌对人工胃、肠液耐受能力较强,且活菌数较高。     

The Multicenter Aerobic Iron Respiratory Chain of Acidithiobacillus ferrooxidans Functions as an Ensemble with a Single Macroscopic Rate Constant

Electron transfer reactions among three prominent colored proteins in intact cells of Acidithiobacillus ferrooxidans were monitored using an integrating cavity absorption meter that permitted the acquisition of accurate absorbance data in suspensions of cells that scattered light. The concentrations of proteins in the periplasmic space were estimated to be 350 and 25 mg/ml for rusticyanin and cytochrome c, respectively; cytochrome a was present as one molecule for every 91 nm² in the cytoplasmic membrane. All three proteins were rapidly reduced to the same relative extent when suspensions of live bacteria were mixed with different concentrations of ferrous ions at pH 1.5. The subsequent molecular oxygen-dependent oxidation of the multicenter respiratory chain occurred with a single macroscopic rate constant, regardless of the proteins'' in vitro redox potentials or their putative positions in the aerobic iron respiratory chain. The crowded electron transport proteins in the periplasm of the organism constituted an electron conductive medium where the network of protein interactions functioned in a concerted fashion as a single ensemble with a standard reduction potential of 650 mV. The appearance of product ferric ions was correlated with the reduction levels of the periplasmic electron transfer proteins; the limiting first-order catalytic rate constant for aerobic respiration on iron was 7,400 s⁻¹. The ability to conduct direct spectrophotometric studies under noninvasive physiological conditions represents a new and powerful approach to examine the extent and rates of biological events in situ without disrupting the complexity of the live cellular environment.     

Portuguese Physical Education Instructors’ Exposure to Noise and Perception of Associated Risk

The purpose of this study was to quantify noise exposure of professional physical education instructors in Portugal, understand how they perceive risk and the effects associated with this exposure as well as examine the existence of health complaints potentially related to the exposure to noise. Quantification of sound level exposure comprised 200 measurements of different sport activities in state schools and private health clubs. Characterization of risk perception as well as symptomatology was performed by a three-part survey that provided to a sample of 48 physical education professionals and a comparison group of 52 non-professionals. Results showed the existence of high noise levels that may endanger physical education teachers’ health. These levels are significantly higher in health clubs. Health complaints were significantly higher in the group of professionals, especially concerning hearing difficulties, muffled hearing, intolerance to loud sounds, constant headaches, and irritability. The majority of the physical education instructors are exposed to high levels of sound pressure on a daily basis, which depending on their working hours may compromise their health. This study also reveals the importance of training as well as organizational and structural measures to reduce exposure to harmful noise levels during the performance of sports activities.