Technical note: Development of a closed-tube isothermal multiple self-matching-initiated amplification assay for visual detection of Staphylococcus aureus in milk samples

Staphylococcus aureus is one of the most common mastitis-causing bacteria in dairy cows. It is associated with reduced production performance in animals and with huge financial losses for the dairy industry worldwide. An accurate and sensitive method for the early diagnosis and identification of Staph. aureus in milk samples is essential. The present study aimed to establish a closed-tube isothermal multiple self-matching-initiated amplification (IMSA) technique for visual confirmation of the presence of Staph. aureus targeting the nuc conserved sequence gene. The specific primers successfully amplified the target sequence within 45 min at 63°C reaction temperature and using the optimal components of the reaction system. The positive amplicon showed bright green fluorescence under UV light when mixed with the chromogenic substrate SYBR Green I, and the negative samples remained orange in color. We observed fluorescence and a ladder-like pattern in the IMSA amplicon for all Staph. aureus strains, and we observed no significant change for the non–Staph. aureus strains. The IMSA assay had high specificity compared with loop-mediated isothermal amplification (LAMP): it confirmed the presence of all 7 Staph. aureus strains, and we found no false-positive results for the 12 non–Staph. aureus strains. The lower limit of detection for the IMSA assay was 1 × 10² cfu/mL, 10-fold more sensitive than the results obtained using LAMP. We also successfully applied the IMSA assay to confirm the presence of Staph. aureus in milk samples of cows with mastitis, and the results were consistent with those of LAMP and real-time PCR. The present study reports the use of IMSA to confirm the presence of Staph. aureus and provides a potentially useful method for rapid preliminary screening for Staph. aureus.     

富汞热处理对碲镉汞电学性能的影响

对用液相外延(Liquid Phase Epitaxy,LPE)方法生长的碲镉汞(HgCdTe)材料进行了闭管富汞热处理,并研究了不同的热处理时间和热处理温度对其电学性能的影响。通过对HgCdTe材料进行富汞热处理可以有效降低材料内的缺陷尺寸、密度以及位错密度,并可完成材料由p型到n型的转变。工艺中,低温热处理对HgCdTe材料的电学性能有较大影响。研究发现,随着低温热处理时间的持续增加,HgCdTe材料的载流子浓度会明显增加。而当低温热处理温度在210℃~250℃范围内变化时,保持低温热处理时间不变,热处理后HgCdTe材料的载流子浓度会在一定范围内波动(无明显变化)。通过对HgCdTe器件进行I--V曲线测试以及最终的组件测试发现,热处理后载流子浓度在1×1013~1×1014 cm-3范围内的HgCdTe芯片具有很好的测试结果。     

Determination of Binary Diffusion Coefficients of Gases Using Holographic Interferometry in a Loschmidt Cell

A measuring system for the determination of binary diffusion coefficients of gases has been developed. The lower and upper half cells of the Loschmidt diffusion cell are fixed, one upon the other, contrary to the usual shearing cells. A sliding component between the half cells is moved to connect them and to start the diffusion. The concentration changes due to diffusion are determined by the optical method of real-time holographic interferometry. In this way the concentration is obtained as a function of time and location resulting from the analysis of the interference pattern. The data are evaluated by using the integrated diffusion equation for the closed-tube technique. First, measurements on the system argon-propane have been successfully performed at 1 bar and at room temperature. The results show an uncertainty of 1 per cent and are in good agreement with data by Wakeham and Slater (1974). Furthermore, refractive index measurements on the pure gases, argon and propane, as a function of gas density have been performed and evaluated to derive values of the first refractivity virial coefficient.     

富汞热处理对碲镉汞电学性能的影响

对液相外延方法(LPE)生长的碲镉汞(HgCdTe)材料进行了闭管富汞热处理,并研究了不同的热处理时间和热处理温度对碲镉汞材料电学性能的影响。HgCdTe材料经过富汞热处理后可以有效降低材料内的缺陷尺寸和密度。该方法不仅可以降低材料内的位错密度,而且还可以完成材料P型到N型的转变。工艺中的低温热处理对HgCdTe材料的电学性能有较大影响。研究发现,随着低温热处理时间的持续增加,HgCdTe材料的载流子浓度会明显增加。而当低温热处理温度在210℃~250℃范围内变化时,若保持低温热处理时间不变,则热处理后HgCdTe材料的载流子浓度在一定范围内波动,且无明显变化。通过对HgCdTe器件进行I-V曲线测试以及最终的组件测试,发现热处理后载流子浓度在1E13~1E14cm^-3范围内的HgCdTe芯片就可以得到很好的测试结果。