Sterilization by Saturated Steam Experiment

Sterilization by Saturated Steam Experiment Nurul Aisha Zainal Abidin Introduction Microorganisms are tiny living cells that inhabit our environment. Most of these microorganisms are harmless, where they do not cause any diseases, hence they are known as non-pathogens (Benowit-West et al., 2009). However, there are some that can cause infections which are termed pathogenic. Certain environments make them necessary that the population of these microorganisms are controlled especially health care facilities, laboratories, food industries, pharmaceutical industries, and more (Hoffman et al., 2004). Sterilisation is an important method to control the microbial population, where it is the process of removing or killing viable microorganisms from equipment or substances. Sterilisation process can be done via several means including heat sterilisation, filtration, chemical sterilisation and radiation sterilisation (Schlegel and Zaborosch, 1993). Among these methods, the most commonly used is heat sterilisation in moist (steam) and dry form as others each have their own disadvantages such as toxic residues, risk of radiation, high cost, and capability of causing physical damage to equipment (Rogers, 2005). Other than heat being used as physical agents for sterilisation, ionising radiation and filtration can also be used. Moist heat (steam) sterilisation uses liquid, heat and pressure to form steam which will kill the microorganisms. This process is recognised for its speed of operation, effectiveness, low risk and cost because steam is only pressurised water in gas phase (Block, 1983). It is known that vegetative cells of most bacteria can be killed within 5-10 minutes at a temperature of 60oC however bacterial spores are thermoduric, where they can survive long exposure to high temperature (Bonewit-West et al., 2009). Thus, steam sterilisation is considered to be effective as it destroys viable microorganisms at 121oC for 15 minutes and prevents them from germinating into bacteria. The high temperature applied denatures the proteins within the bacterial endospores, destroying them (Jha and Ghosha, 2005). Dry heat sterilisation also uses heat to denature the proteins of the bacterial cells. This process involves exposing heat stable solid equipment to a temperature of 160oC for 1-2 hours. However, moist heat is more effective in destroying microorganisms compared to dry heat because water vapour can penetrate into microorganisms more readily than dry air. This heat sterilisation method is done in a metal vessel known as autoclave (Jha and Ghosha, 2005). Another method for sterilisation is tyndallisation which is usually for materials that cannot withstand high temperatures in the autoclave. They are exposed to 100oC heat for 30 minutes to inactivate vegetative cells but not the spores. These spores that survive will germinate to form bacterial cells during incubation at 37oC and then the material being sterilised is again subjected to steam at 100 oC for 30 minutes to kill these bacteria. This cycle is repeated for the next 3 days (Talaro and Talaro, 1993). This experiment was done to determine whether there is a difference between efficacy of heat sterilisation (moist heat and dry) and the requirements necessary for this sterilisation process to be adequate. Aims The aims of this experiment were to understand how a steam sterilizer operates, the role and the importance of having to implement moist heat sterilization process, as well as to identify the basic requirements needed for successful steam sterilization. Materials and Methods As per practical manual from page 56-57 Results Two Thermalog strips were each placed in two Schott bottles; one bottle was tightly capped with no water and the other was loosely capped with water present. Five bottles were prepared and spore strips impregnated with B. Stearothermophilus were placed in bottles 1-4. Some water and paraffin oil was added in bottle 2 and 4 respectively. Schott bottles, bottles 2-4 and a Sterikon plus Bioindicator were sterilised in the autoclave. Thermalog strips were observed after the sterilisation process. 3ml of TSB was added into bottles 1, 2, 3, 5 and the spore strip from bottle 4 was transferred to bottle 5. All the bottles were then incubated. The tables below show the observation made from the experiment. Table 1. The observation of the â€Å"Thermalog† strips in the two Schott bottles with different conditions Table 2. The observation of Sterikon vials with one being sterilized and one without being sterilized Table 3. B. Stearothermophilus spore strips in TSB with different conditions after sterilization and incubation Discussion In the first part of the experiment, steam sterilisation indicator, Thermalog strips are placed in two Schott bottles under different conditions. The tightly capped Schott bottle without any water only had a change of colour within the â€Å"unsafe† zone. This is due to the steam from the steriliser that was not able to enter through the tight cap and reach the Thermalog strip. With no water present in the bottle either, steam could not be produced, giving exposure to dry heat. Hence, complete sterilisation was not achieved as direct contact between the steam and the bottle is needed, alongside its temperature and time parameters (121oC and 15 minutes respectively). In comparison, the loosely capped Schott bottle with added water had a change of colour until the â€Å"safe† zone. Because the Thermalog strip was exposed to moist heat in the form of steam during the sterilisation process, complete sterilisation is achieved. In the second part of the experiment, two Sterikon plus Bioindicator vials are used, which could determine the effectiveness of steam sterilisation. These vials have B. stearothermophilus spores along with a pH indicator in a nutrient-filled broth. Both vials were pink at the beginning of the experiment and incubated for several days. The Bioindicator vial that was put in the steriliser showed no colour change while the vial that was not sterilised turned yellow and only slightly turbid. The sterilised vial had no bacterial growth because the spores did not undergo germination to form bacteria due to successful sterilisation which have completely destroyed all bacterial spores. Therefore, the vial retained its pink colour after incubation. However, the colour change from pink to yellow in the other vial indicates that the spores had germinated into bacteria. This is because the vial was not sterilised, thus the spores were able to grow in a favourable condition, whereby they take up nutrients and produce acid which causes the colour change. These findings show that they are vital for monitoring steam steriliser, ensuring that all spores are properly destroyed. If they are not exposed to its temperature and time parameters, some spores might still survive and germinate. In order to determine that sterilisation process is successful, incubation process is implemented to observe whether these spores could still form new bacteria or whether they really have been destroyed. In the experiment which used strips impregnated with spores of B. stearothermophilus in tryptone soy broth (TSB), bottle 1 appeared to be the most turbid among other bottles, which suggests bacterial growth is sustained. Because bottle 1 was not autoclaved, it did not go through proper sterilisation process prior incubation, thus allowing the spores to germinate from the spore strip. Culturing this unexposed spore strip in bottle 1 therefore acts as a control, as it would not have demonstrated that steam sterilisation was actually successful if bacterial growth was not observed because they could have not been able to germinate at all. Bottle 2, however, shows that steam sterilisation was done successfully as the TSB media does not show any turbidity, thus bacterial spore activity was not there. As mentioned, water was added to bottle 2 before it was tightly capped and put into the autoclave, which evaporated into steam (or moist heat) at a 121oC within the steriliser. The steam formed will then kill the spores directly. Apart from that, bottle 3 was tightly capped and had no water added before it was placed in the autoclave. As a consequence, the moist heat could not possibly have direct contact with the spores to be able to kill them. This meant that the spores were only subjected to dry heat sterilization within the bottle, which clearly showed to be a less effective of a method compared to moist heat sterilisation. Because these spores survived the dry heat sterilisation process, they were able to germinate and form bacterial growth under the favourable conditions during incubation, making the TSB media turbid. If dry heat sterilisation was to be implemented to eradicate spores, a higher temperature would suffice. Furthermore, bottle 5 also showed turbidity to almost the same degree as bottle 3. The spore strip in bottle 5 was initially immersed in paraffin oil in bottle 4, before it was transferred into bottle 5. Other than the tightly capped bottle preventing the moist heat from entering, the o il somewhat acts as a protective barrier for the spores, not even allowing dry heat to have direct contact with the spore strip. Based on these findings, it demonstrates to a certain extent to how the biocidal action of moist and dry heat is different and can be compared. Most importantly, the role and the significance of the requirements needed for each sterilisation method. For moist heat sterilisation, a holding time of 121oC for 15 minutes under a pressure of 101kPa is required. In contrast, dry heat sterilisation needs a holding time of 1-2 hours at a temperature of 160oC (Arora, 2003). Therefore, it can be said that moist heat (steam) can perform faster sterilisation, with higher penetrating power as compared to dry heat (Vasanthakumari, 2007). Furthermore, sterilisation using moist heat is more efficient as it uses a lower temperature for the denaturation of protein and the heat in water is also transferred to substances easily (Greenwood et al., 2007). Hence, it is important to note that for steam to be an ideal sterilant, it must be able to have direct contact with the object (external and internal surface) or substance being sterilised. The reason for this is for its stored energy to be transferred to the object through condensation onto all the surfaces which releases its latent heat. As a result, microorganisms are destroyed. Without this direct steam contact, the sterilisation process would be inadequate (Slatter, 1985). Even so, moist heat sterilisation still has a limitation, where it is not capable of destroying prions in the same way as bacteria and spores. Prions, which are stable self-replicating proteins, are highly infective in the central nervous system tissue and they are highly resistant to heat (Hanlon and Hodges, 2013). Therefore, in order to destroy these prions, dry heat sterilisation may be implemented with a temperature of 200oC. Conclusion Successful and complete steam sterilisation can only be achieved if the material being sterilised have physical contact with moist heat (steam) either from the steriliser or from the water inside the material being vaporised. Without the steam, sterilisation process will not be effective because the dry heat cannot destroy the heat-resistant spores. Furthermore, barriers like oils or fats would also prevent the steam from penetrating. Because there are many interruptions or factors that could influence the efficacy of sterilisation, it is necessary to monitor the process. Thermalog strips can be used to determine if the sterilisation process has met its criteria where the material has been exposed to conditions to be safely sterilised. Sterikon plus Bioindicator vials are also used to monitor whether steam sterilisation has occurred. References Arora, D. R. 2003.Textbook of microbiology. New Delhi: CBS Publishers. Block, S. S. 1983.Disinfection, sterilization, and preservation. Philadelphia: Lea Febiger. Bonewit-West, K., Hunt, S. A. and Applegate, E. J. 2009.Todays medical assistant. St. Louis, Mo.: Saunders/Elsevier. Dunn, C. E. and Chennell, S. 2012.Australian master work health and safety guide. North Ryde, N.S.W.: CCH Australia. Greenwood, M., Seymour, R. A. and Meechan, J. G. 2009.Textbook of human disease in dentistry. Chichester, U.K.: Wiley-Blackwell. Hanlon, G. and Hodges, N. A. 2013.Essential microbiology for pharmacy and pharmaceutical science. Chichester, West Sussex, UK: John Wiley Sons. Hoffman, P. N., Bradley, C., Ayliffe, G. A. J. and Ayliffe, G. A. J. 2004.Disinfection in healthcare. Malden, Mass: Blackwell Pub. Jha, T. B. and Ghosha, B. 2005.Plant tissue culture. Hyderabad: Universities Press. Rogers, W. J. 2005.Sterilisation of polymer healthcare products. Shawbury, Shrewsbury, Shropshire, UK: Rapra Technology. Schlegel, H. G. and Zaborosch, C. 1993.General microbiology. Cambridge [England]: Cambridge University Press. Slatter, D. H. 1985.Textbook of small animal surgery. Philadelphia: W.B. Saunders. Talaro, K. P. and Talaro, A. 1993.Foundations in microbiology. Dubuque, Iowa: W.C. Brown. Vasanthakumari, R. 2007.Textbook of Microbiology. New Delhi: BI Publications Pvt Ltd.

Police and Corruption Essay -- Civil Law Criminal Police Law Enforceme

Police and Corruption The police. Twenty-four hours a day, three hundred sixty-five days a year, this division of our government has a mandate to enforce the criminal law and preserve public peace. Understood in this mandate is an obligation to police everyday life matters that originate in the daily lives and activities of citizens within their community. Police interact in some form with the average citizen more often than any other government official. In society today the police play a key role in maintaining a civil society. This role assumes a substantial amount of power and authority over the general public. With power comes corruption and/or misuse of power. The question that is presented is, how and why do the police exceed the parameters of their power and authority?   Ã‚  Ã‚  Ã‚  Ã‚  This is an issue that is predominant in urban settings, but not exclusive to these settings. This is an important issue because it affects all people. The police is a government service to all people, but all people do not feel they are being serviced. Not everyone is satisfied with the conduct of the police. Why do people feel that police are crossing boundaries that they should not be? This will be observed from four different aspects in which police are capable of exceeding the parameters of their power and authority: police and use of discretionary enforcement, â€Å"Police justice†, police harassment, and the unwarranted use of police authority.   Ã‚  Ã‚  Ã‚  Ã‚  Police are allowed to and must use personal discretion in their determination of law enforcement. Unlike a judge or lawyer a police officer can not gather information and take time to make a prognosis to make a decision affecting the fate of a person. He must make a quick decision based on his discretion to determine the fate of a person.. â€Å"...a quick decision is required to protect the interests of the public and to satisfy requirements of operating efficiency† (Reiss, p.130) Now we are telling officer to not enforce the law, but to determine the law. A policeman's discretionary decision may then be evaluated by others both inside and outside of the department. This is the cause for a further complication in the processes because in order to avoid criticism the police officer then might use his own sense of justice. This â€Å"police justice† is basically having the officer conduct his own trial. Th... ...spect they received from citizens. Thirty percent felt that the average citizen in their patrol held the police in some degree of contempt. Nineteen percent felt that most people in the precinct generally look at the police as enemies. Also one third of the police in the study frequently stop people to question or frisk them, which is seen by most citizens as suspicion of crime. This may have something to do with why so many of the police officers felt the citizens resented them.(More, p.120)   Ã‚  Ã‚  Ã‚  Ã‚  The best way to study these issues of whether the police exceed the parameters of their power and authority would be to conduct a survey of citizens, because the general population is who the police have power and authority over. Who else would know better if the police were servicing their communities in the manner in which is expected. When police take too much power of the criminal justice system into their own hands they are damaging society. They are splitting society into the people who are policed for, and the people who are policed against. The police that abuse their power and authority are no longer enforcing justice, but are making it just to obey force.

Hvac Tube

Tube in tube condensers Small tube in tube condensers Straight tube in tube condensers Shell and water cooled condensers Vertical shell and coil water cooled condensers Shell and tube water cooled condensers Vertical shell and tube condensers Surface condenser Counter flow in condensers Cross flow in condensers Air cooled condensers Cooling Tower Re circulated water system Condenser control Condenser capacity Condensing temperature control Expansion valve Objectives Expansion device Superheat sensor on dry expansion circuit Thermostatic expansion valve Automatic expansion valveThermal electric expansion valve Capillary tube High pressure float valve Low pressure float valve TWO Control Operation of thermostatic expansion valve TWO Operation Evaporator Evaporator Control Splitting finned – tube evaporator coils Row – split coil configuration Refrigeration accessories and their locations Superconductivity. Webby. Com Filtering and drying Pressure controls and their applic ation Window air conditioners The refrigeration system of the window air conditioner Parts of the window air conditioners The reiteration system to the window air conditioner :The refrigeration system of the window air conditioner: Types of Split A/c Parts of a split air – conditioning system Air filter Outdoor unit Refrigerant piping or tubing Working of split AC Pressure sides Air Conditioning schematic system : The various steps involved in this method are: 1. Select suitable velocities in the main and branch ducts. 2. Find the diameters of main and branch ducts from airflow rates and velocities for circular ducts. For rectangular ducts, find the cross – sectional area from flow rate and velocity, and then y fixing the aspect ratio, find the two sides of the rectangular duct. . From the velocities and duct dimensions obtained in the previous step, find the frictional pressure drop for main and branch ducts using friction chart or equation

The End Of World War I - 1329 Words

Before World War I, the countries of Europe competed with one another in a race to colonize the world. The end of World War I brought national sovereignty, and an end to colonization to the forefront of the Allies’ concerns as they drew up plans for peace, and as a result, the Allied countries received former enemy colonies to watch over and guide to independence1. As a result of this mandate system, among other colonies, France received Syria. Instead of guiding Syria to independence, however, as the conflict dragged on, France forgot its mission and attempted to subdue Syrian resistance to her humanitarian efforts. This paper will address the following questions: Who is more to blame for the violence, the Syrians or the French? What did†¦show more content†¦Without the assistance of France or any other European power, Syria proved it was ready for independence. However, France ignored the objective of the mandate system and hounded Feisal and his government. Franceà ¢â‚¬â„¢s Prime Minister at the time, Alexandre Millerand refused to negotiate with Feisal, the man a majority of Syrians wanted as their ruler, and did anything he could to oust him from power5. The mandate system put the colony in the charge of a European nation with the intention that it would be helped along to independence, but France did the opposite of this, despite her leaders’ insistence that France’s mission â€Å"was not imperialistic.†6 Even before Syria became France’s under the mandate system, France asserted a degree of influence over the region while it still sat under the Ottoman Empire. While the Ottomans ruled over Syria, France had established a protectorate for Catholics and even had ties to the Uniate churches in that area7. In addition to having religious ties to the region, the French government before the First World War also had invested in Syria financially, and one company formed by the Comte de Perthius built the railroad that ran from Beirut to Aleppo and Damascus8. France put a lot of money into assisting the development Syria and the surrounding areas, so it seems to be only natural that France would want to mandate over Syria after World War I. The French occupation of Syria parallels much of what happened with the French