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Definition 3 Disinfection is the process of inactivation of a fraction of the total microorganisms existing on the treated object. If the desired effect is the total disinfection of an object, then the process will be called sterilization [7, 8, 10]. Under these terms, the sterilization can be defined under two different aspects: a theoretical, as well as a practical (operational) one. Definition 4 (Theoretical) Sterilization is the process of inactivation of all the microorganisms existent on the treated object. In practice, the assessment of the effectiveness of an inactivation experiment is realized by counting the surviving microorganisms [10-12]. This experimental procedure makes use of the following operational definitions: Definition 5 Disinfection is the process at the end of which the number of surviving microorganisms is at least one. Definition 6 Sterilization is the process at the end of which the number of surviving microorganisms is less than one. These definitions are also illustrated by the schematically representation from the Fig. 1.1. Usually, the standard number of microorganisms infecting an object is chosen to be 10 6 [13-18]. Then, in accord with the above definitions, at the end of the experiment, the treated object (surface) is said to be "sterilized" if the final 3
Figure 1.1: Schematic representation of disinfection and sterilization operative definitions. The number of microorganisms is represented by N, whereN0 is the initial number of microorganisms on the treated object at the beginning of disinfection or/and sterilization process. number of surviving microorganisms is less than 10 −6 of their initial number [17, 18]. With other words, the sterilization is achieved if the employed technique is able to decrease the number of viable microorganisms with 6 (six)ordersof magnitude. For microbial decontamination processes, two particular microorganism struc- tures have a major importance: the bacterial vegetative state and its sporu- lated form [15, 17-26]. The vegetative or the natural living state is the bacterial form which can be found in the natural habitat. When the natural habitat has no nourishment resources then the vegetative cell will produce, through the sporu- lation process, one spore which represents a defensive and resistant structural adaptation of bacterium to hard living conditions, as shown in Fig. 1.2 [15, 21- 26]. Hence, it is believed that the spore formation is a mechanism of bacterial 4
Page 1 and 2: PLASMA STERILIZATION USING LOW PRES
Page 3 and 4: my appreciation especially for the
Page 5 and 6: Iis ion saturation current [µA] t
Page 7 and 8: CONTENTS 1 PRINCIPLES OF SURFACE DI
Page 9 and 10: 4 EFFECTS OF LOW TEMPERATURE PULSED
Page 11: and intuited to bring new important
Page 15 and 16: Table 1.1: Common disinfection and
Page 17 and 18: the radiation energy is resonantly
Page 19 and 20: ers of heat, optical radiation and
Page 21 and 22: Table 1.2: Main plasma sources used
Page 23 and 24: microorganism population as a respo
Page 25 and 26: UV Photon Before After DNA Figure 1
Page 27 and 28: to sterilize medical tools, but the
Page 29 and 30: sented by both theoretical and expe
Page 31 and 32: Plasma Sterilization Using Low Pres
Page 33 and 34: Figure 2.1: Experimental set-up. MB
Page 35 and 36: Figure 2.3: Electronic circuit of t
Page 37 and 38: such circumstances, the inactivatio
Page 39 and 40: ment time t is N = N0e −αt ≡ N
Page 41 and 42: shows the number of the viable micr
Page 43 and 44: has n −1 0 > 281.25 µm 2 availab
Page 45 and 46: 1 st 2 nd ( I) TNTC (II) TNTC (III)
Page 47 and 48: U LC blocking filter 19.74 pF 20.24
Page 49 and 50: Figure 2.8: Experimental set-up use
Page 51 and 52: the reactive species from plasma ar
Page 53 and 54: Temperature measurement Relative in
Page 55 and 56: MR MP SH Figure 3.2: Experimental a
Page 57 and 58: a fast temperature increasing rate.
Page 59 and 60: D h (min) 10 3 10 2 10 1 10 0 100 2
Page 61 and 62: MR QP SH Figure 3.6: Experimental a
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The contribution of photons and hea
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D (min) 10 3 10 2 10 1 10 0 Dν D h
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N/N 0 (%) 10 2 10 2 10 2 10 2 10 2
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D (min) 10 2 10 1 10 0 D h+ν+p D h
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holder is mainly given by particle
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3.5 Power sensitivity of spore inac
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If for a reference treatment temper
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of the sample was achieved. Moreove
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microorganisms were disposed in mon
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The pulse period covered a wide int
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in chapter 2. The treatment time of
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4.2.2 Injected RF power In order to
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ton =500µs, and the duty cycle was
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T ( 0 C) 120 100 80 60 40 20 I 0 5
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N/N 0 (%) 10 2 10 2 10 2 10 1 10 1
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elow 70 ◦ C. 3. Increasing the in
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the second phase of the inactivatio
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k 1, 2 (min -1 ) 1.2 1.0 0.8 0.6 0.
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I (arb. unit) 140 120 100 80 60 40
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I (arb. unit) 5 4 3 2 1 0 0.000 0.0
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I > (arb.unit) 1.0 0.9 0.8 0.7 0.6
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shown in Fig. 4.14. It can be seen
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I is (mA) 0.25 0.20 0.15 0.10 0.05
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value. When ton has been kept const
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survival curve characteristics were
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of the effects produced by differen
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solutely necessary for a profound u
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Conferences 1. Bacillus spores ster
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[9] W. A. Rutala, D. J. Weber, J. H
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[34] J. H. Young: Sterilization wit
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[57] M. K. Boudam, M. Moisan, B. Sa
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[79] J. Schneider, K. M. Baumgartne
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[100] S. Villeger, S. Cousty, A. Ri
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