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Influence of humidity on total sterilisation effect of dielectric barrier discharge
Kramárová, Petra ; Bartlová, Milada (referee) ; Kozáková, Zdenka (advisor)
The main subject of this diploma thesis is the study of the effect of humidity on the total sterilization effect of the dielectric barrier discharge. Sterilization is a process which can eliminate all forms of life. The plasma sterilization is one of the methods that are suitable for sterilization of temperature and chemical sensitive materials. This sterilization method was proved to be effective on the wide spectrum of procaryotic and eucaryotic microorganisms. Basically, the main inactivation factors for cells exposed to plasma are heat, UV radiation and various reactive species. Dielectric barrier discharge (DBD) operating at atmospheric pressure was used for the sterilization of the samples. The discharge was generated in dry air and in humid air. The plasma power densities were 2 160 mW.cm-3, 2 279 mW.cm-3 and 2 760 mW.cm-3 (dry air) or 2 326 mW.cm-3 and 2 850 mW.cm-3 (humid air). Humidity of air was achieved using a wash bottle filled with water through which air flowed into the DBD reactor. Fungi spores of Aspergillus niger were used as model microorganisms. Whatman paper No. 1 was used as the carrying medium. When comparing sterilization efficiency of humid and dry air operating at the same conditions, the higher sterilization effect was observed in humid air. The sterilization effect of the DBD generated in air was compared with results obtained during plasma generation in argon and nitrogen. At the same conditions, the highest sterilization effect was observed in argon, followed by humid air, nitrogen and dry air. It was found out that in our experimental setup the active species are probably the main inactivation mechanism. The influence of temperature on the inactivation of microorganisms was completely negligible. The discharge parameters were studied by means of the optical emission spectroscopy (OES). Plasma treated samples were analyzed employing scanning electron microscopy (SEM). Damage of the microorganisms due to the effect of plasma as well as plasma effect on the structure of the carrying medium was evaluated.
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Study of the sterilization effect of temperature and UV light present in dielectric barrier discharge
Kramárová, Petra ; Grossmannová, Hana (referee) ; Kozáková, Zdenka (advisor)
The main theme of this bachelor thesis is to study the effect of temperature and UV radiation to the total sterilizing effect of dielectric barrier discharge. Sterilization is a process, which can eliminate all forms of life. The presented bachelor thesis discusses plasma sterilization, which is one of the method, which are suitable for sterilization of heat and chemical sensitive materials. This sterilization method is effective on the wide spektrum of procaryotic and eucaryotic microorganisms. Basically, the main inactivation factors for cells exposed to plasma are heat, UV radiation and various reactive species. In my thesis a dielectric barrier discharge (DBD) operating at atmospheric pressure was used for the sterilization of the samples. Plasma was generated in argon and nitrogen. According to the previous measurement the best sterilization results were observed using plasma power input 2 562,96 mW•cm-3 (argon) a 2 044,44 mW•cm-3 (nitrogen), therefore the same plasma power input was applied during our measurement. Fungi spores of Aspergillus niger were used as model organisms. Whatman paper No. 1st was used as the carrying medium. Each sample series was exposed to plasma for 5, 10, 20, 40, 60, 120 and 180 s. In order to separate the effect of UV radiation generated by DBD the quartz glass transmitting UV radiation was used. During the plasma exposition one of the sample was covered with the quartz window and the other sample was directly exposed to the plasma, afterwards the results were compared. The microbial abatement observed for the samples covered by quartz window was much lower than for the the samples directly exposed to the plasma. In first case the UV radiation and temperature is the main inactivation mechanism, while in the latter one the synergistic effect of UV radiation, temperature and active species is employed. Furthermore the effect of plasma sterilization increases with increasing the plasma exposition time. While comparing results observed for the argon and nitrogen, better results were achieved in argon. Effects of UV radiation and temperature were studied separately. The temperature between the DBD electrodes was measured by means of thermocouple. Afterwards the samples were placed in an oven and exposed to the same temperature as was measured between the electrodes. By comparing the results of heat treated samples and plasma treated samples it can be assumed that the influence of the temperature during the sterilization process in DBD was negligeable. The discharge parameters were studied by means of the optical emission spectroscopy.
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Influence of humidity on total sterilisation effect of dielectric barrier discharge
Kramárová, Petra ; Bartlová, Milada (referee) ; Kozáková, Zdenka (advisor)
The main subject of this diploma thesis is the study of the effect of humidity on the total sterilization effect of the dielectric barrier discharge. Sterilization is a process which can eliminate all forms of life. The plasma sterilization is one of the methods that are suitable for sterilization of temperature and chemical sensitive materials. This sterilization method was proved to be effective on the wide spectrum of procaryotic and eucaryotic microorganisms. Basically, the main inactivation factors for cells exposed to plasma are heat, UV radiation and various reactive species. Dielectric barrier discharge (DBD) operating at atmospheric pressure was used for the sterilization of the samples. The discharge was generated in dry air and in humid air. The plasma power densities were 2 160 mW.cm-3, 2 279 mW.cm-3 and 2 760 mW.cm-3 (dry air) or 2 326 mW.cm-3 and 2 850 mW.cm-3 (humid air). Humidity of air was achieved using a wash bottle filled with water through which air flowed into the DBD reactor. Fungi spores of Aspergillus niger were used as model microorganisms. Whatman paper No. 1 was used as the carrying medium. When comparing sterilization efficiency of humid and dry air operating at the same conditions, the higher sterilization effect was observed in humid air. The sterilization effect of the DBD generated in air was compared with results obtained during plasma generation in argon and nitrogen. At the same conditions, the highest sterilization effect was observed in argon, followed by humid air, nitrogen and dry air. It was found out that in our experimental setup the active species are probably the main inactivation mechanism. The influence of temperature on the inactivation of microorganisms was completely negligible. The discharge parameters were studied by means of the optical emission spectroscopy (OES). Plasma treated samples were analyzed employing scanning electron microscopy (SEM). Damage of the microorganisms due to the effect of plasma as well as plasma effect on the structure of the carrying medium was evaluated.
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Study of the sterilization effect of temperature and UV light present in dielectric barrier discharge
Kramárová, Petra ; Grossmannová, Hana (referee) ; Kozáková, Zdenka (advisor)
The main theme of this bachelor thesis is to study the effect of temperature and UV radiation to the total sterilizing effect of dielectric barrier discharge. Sterilization is a process, which can eliminate all forms of life. The presented bachelor thesis discusses plasma sterilization, which is one of the method, which are suitable for sterilization of heat and chemical sensitive materials. This sterilization method is effective on the wide spektrum of procaryotic and eucaryotic microorganisms. Basically, the main inactivation factors for cells exposed to plasma are heat, UV radiation and various reactive species. In my thesis a dielectric barrier discharge (DBD) operating at atmospheric pressure was used for the sterilization of the samples. Plasma was generated in argon and nitrogen. According to the previous measurement the best sterilization results were observed using plasma power input 2 562,96 mW•cm-3 (argon) a 2 044,44 mW•cm-3 (nitrogen), therefore the same plasma power input was applied during our measurement. Fungi spores of Aspergillus niger were used as model organisms. Whatman paper No. 1st was used as the carrying medium. Each sample series was exposed to plasma for 5, 10, 20, 40, 60, 120 and 180 s. In order to separate the effect of UV radiation generated by DBD the quartz glass transmitting UV radiation was used. During the plasma exposition one of the sample was covered with the quartz window and the other sample was directly exposed to the plasma, afterwards the results were compared. The microbial abatement observed for the samples covered by quartz window was much lower than for the the samples directly exposed to the plasma. In first case the UV radiation and temperature is the main inactivation mechanism, while in the latter one the synergistic effect of UV radiation, temperature and active species is employed. Furthermore the effect of plasma sterilization increases with increasing the plasma exposition time. While comparing results observed for the argon and nitrogen, better results were achieved in argon. Effects of UV radiation and temperature were studied separately. The temperature between the DBD electrodes was measured by means of thermocouple. Afterwards the samples were placed in an oven and exposed to the same temperature as was measured between the electrodes. By comparing the results of heat treated samples and plasma treated samples it can be assumed that the influence of the temperature during the sterilization process in DBD was negligeable. The discharge parameters were studied by means of the optical emission spectroscopy.
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