Influence of argon modified atmosphere packaging on the growth potential of strains of Listeria monocytogenes and Escherichia coli

Modified atmosphere packaging (MAP) based on carbon dioxide (CO₂) – nitrogen (N₂) gas mixtures has been applied to maintain the safety and quality of ready-to-eat (RTE) meat products. The use of argon (Ar) gas as a supplement to CO₂–N₂ mixtures or as substitute for N₂ is a current approach to enhance the effectiveness of MAP. As there is limited information on the effect of Ar MAP on the growth behaviour or the survival of pathogenic bacteria in RTE foods, the aim of the present study was to assess the influence of Ar in MAP on the growth of Listeria monocytogenes and Escherichia coli strains under different conditions. For this purpose, a CO₂–N₂ (20:80) atmosphere was compared with a CO₂–N₂–Ar (30:30:40) and CO₂–Ar (30:70) atmosphere based on the assessment of bacterial growth (δ) on a gelatin-agar medium and ham. Additionally, a shelf life monitoring study was performed to evaluate the effect of these treatments on the background microflora of ham. The findings suggest that under the CO₂–N₂ MAP the product matrices supported the growth (δ > 0.5 log CFU g⁻¹) of L. monocytogenes throughout an observation period of 21 days at 4 ± 2 °C. On the contrary, both MAP containing Ar were equally able to reduce the δ below 0.5 log CFU g⁻¹. In this regard it was irrelevant whether L. monocytogenes was inoculated in depth (per slice) or at the surface (top slice) of the ham. Regarding the influence of the different gas atmospheres on E. coli all gas mixtures applied had the capacity to reduce the δ of E. coli below −0.5 log CFU g⁻¹. Further, shelf-life extension could not be managed with the gas atmospheres considered.     

The structure and adhesion of hydrogenated amorphous carbon (a-C:H) films synthesized on CoCrMo alloy by plasma immersion ion implantation and deposition at different flow ratios of acetylene to argon

Hydrogenated amorphous carbon (a-C:H) film is deposited on CoCrMo alloy by plasma immersion ion implantation and deposition (PIII-D) at different flow ratios of acetylene to argon (C₂H₂/Ar). The results show that Ar fraction in the C₂H₂-Ar gas mixture has an important effect on the structure and the adhesion of the a-C:H films. When Ar fraction in the C₂H₂-Ar gas mixture is less than 50%, the fabricated a-C:H film composition transfer from graphite-like to diamond-like which contains higher sp³ binding thanks to Ar ion bombardment, and the adhesion strength decreased with the increment of Ar fraction. But when Ar fraction in the C₂H₂-Ar gas mixture is beyond 50%, the fabricated film contains more sp² bonding for thermally driven and exhibits higher adhesion strength with the increment of the Ar fraction.     

循环粗氩泵轴封处漏液故障分析与处理

在24000 m3/h空分设备运行过程中,突然发生循环粗氩泵轴封处异常漏液故障,切换至备用泵运行,不久也出现类似的漏液现象。介绍故障现象及相关参数,详细分析了故障原因和采取的处理,最后提出了工艺设计上的一些建议。     

20000m~3/h空分设备氩馏分组分异常的分析和处理

舞钢20000 m3/h空分设备在建成投产后出现氩馏分组分异常现象,在各项工艺调整措施无效后,进行上塔吊出检查并实施改进处理,使氩馏分组分恢复正常。介绍上塔拆除检查和处理方案,分析上塔的杂质堵塞、填料及分布器安装等影响因素。     

43000m~3/h空分设备制氩系统的调试及操作优化

详细叙述兴化43000 m3/h空分设备制氩系统的调试过程。根据空分设备运行数据,结合其内在设计结构,采用边调试、边分析、边优化的方法,完成了制氩系统的调试,并提出了从设计上需对空分设备采取的改进措施。     

浅议高纯氩气的生产

简述了贵冶 4 # 制氧机氩系统的工艺流程及分析了影响高纯氩生产的一些因素。     

磁控溅射沉积NiCrAlY涂层中的氩及其对氧化行为的影响

用直流磁控溅射沉积NiCrAlY涂层。发现使用较高的负偏压时,涂层中掺有氩,其含量与负偏压的立方成正比。用SEM和TEM观察,发现高偏压下沉积的涂层中有微孔和微裂纹。因此,过高的负偏压导致涂层的氩含量激增,以至严重降低涂层的周期氧化性能。     

Effects of argon and oxygen addition to the CH4-H2 feed gas on diamond synthesis by microwave plasma enhanced chemical vapor deposition

In order to investigate the effects of argon and oxygen on diamond synthesis, the behaviors of diamond deposition using microwave plasma chemical vapor deposition method have been studied by varying the concentrations of argon and oxygen in the methane-hydrogen gas mixture. Diamond films were deposited on silicon wafer under the conditions of substrate temperatures: 1073 1173 K, total reaction pressure: 5333 Pa (40 Torr), methane concentrations: 0.5 5.0%, and they were characterized by scanning electron microscopy, Raman spectroscopy and optical emission spectroscopy. The deposition rates of diamond films were enhanced by adding argon into the methane-hydrogen system, but nondiamond carbon phases in the films also increased. It resulted from the increase of hydrocarbon radicals in the plasma. As oxygen was added, the quality of deposited diamond films was improved due to the decrease of C₂ radicals and increase of OH radicals in the plasma. Simultaneous addition of 0.3% oxygen and 20% argon has been able to effectively suppress the formation of nondiamond carbon components and increase the deposition rate of diamond films. It appears that the ionized argon (Ar⁺) and excited argon atoms (Ar*) may activate the various chemical species and promote the reactions between the gas phase species and oxygen in the plasma.     

太钢730t/d空分设备氩系统的快复车操作

太钢 730t/d空分设备全精馏制氩系统在临时停车后冷态启动 ,由于采用了 7点措施 ,使氩系统恢复时间从最初 2 0多个小时缩短到目前平均 13小时 ,最快 8 5小时 ,效果明显