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2.2 Principle of direct torque control of induction motor:
In DTC motor drive, it is possible to control directly the stator flux linkage (s?) or the rotor flux (r?) or the magnetizing flux (m?) and the electromagnetic torque by the selection of an optimal inverter voltage vector. The selection of the voltage vector of the voltage source inverter is made to restrict the flux and torque error within their respective flux and torque hysteresis bands and to get the fastest torque response and highest efficiency at every instant. DTC enables both quick torque response in the transient operation and reduction of the harmonic losses and acoustic noise.
The Benefits of using DTC include the following:
1 No need for motor speed or position feedback in 95% of applications. Thus, installation of costly encoders or other feedback devices can be avoided.
2DTC control is available for different types of motor including permanent magnet and synchronous reluctance motors.
3Accurate torque and speed control down to low speeds, as well as full startup torque down to zero speed.
4 Excellent torque linearity.
5 High static and dynamic speed accuracy.
6 No preset switching frequency optimal transistor switching is determined
2.2.1 Voltage Source Inverter
A six step voltage source inverter provides the variable frequency AC voltage input to the induction motor in DTC method. The DC supply to the inverter is provided either by a DC source like a battery, or a rectifier supplied from a three phase or single phase AC source. Fig. 2.2 shows a six step voltage source inverter. The inductor L is inserted to limit short circuit through fault current. A large electrolytic capacitor C is inserted to stiffen the DC link voltage.
The switching devices in the voltage source inverter bridge must be capable of being turned OFF and ON. Insulated gate bipolar transistors (IGBT) are used because they can offer high switching speed with enough power rating. Each IGBT has an inverse parallel-connected diode. This diode provide alternate path for the motor current after the IGBT, is turned off.

Figure 2.2 Voltage Source Inverter
Each leg of the inverter has two switches one connected to the high side (+) of the DC link and the other to the low side (-); only one of the two can be ON at any moment. When the high side gate signal is ON the phase is assigned the binary number 1, and assigned the binary number 0 when the low side gate signal is ON. Considering the combinations of status of phases a, b and c the inverter has eight switching modes(Va,Vb,Vc=000-111) V2 (000) are zero voltage vectors V0 (000) and V7 (111) where the motor terminals are short circuited and the others are nonzero voltage vectors V1 to V6
The six nonzero voltages space vectors will have the orientation, and also shows the possible dynamic locus of the stator flux, and its different variation depending on the VSI states chosen. The possible global locus is divided into six different sectors signaled by the discontinuous line. Each vector lies in the center of a sector of width named S1 to S6 according to the voltage vector it contains.
It can be seen that the inverter voltage directly force the stator flux, the required stator flux locus will be obtained by choosing the appropriate inverter switching state. Thus the stator flux linkage move in space in the direction of the stator voltage space vector at a speed that is proportional to the magnitude of the stator voltage space vector. By selecting one after another the appropriate stator voltage vector, is then possible to change the stator flux in the required method. If an increase of the torque is required then the torque is controlled by applying voltage vectors that advance the
same sector depending on the stator flux position.

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2.6 GENOME PLASTICITY AND EVOLUTION OF ESCHERICHIA COLI
Like all life forms, new strains of E. coli evolve through the natural biological processes of mutation, gene duplication, and horizontal gene transfer; in particular, 18% of the genome of the laboratory strain MG1655 was horizontally acquired since the divergence from Salmonella. E. coli K-12 and E. coli B strains are the most frequently used varieties for laboratory purposes. Some strains develop traits that can be harmful to a host animal. These virulent strains typically cause a bout of diarrhea that is often self-limiting in healthy adults but is frequently lethal to children in the developing world. (Futadar et al., 2005). More virulent strains, such as O157:H7, cause serious illness or death in the elderly, the very young, or the immunocompromised.
The genera Escherichia and Salmonella diverged around 102 million years ago (credibility interval: 57–176 mya), which coincides with the divergence of their hosts: the former being found in mammals and the latter in birds and reptiles. (Wang et al., 2009). This was followed by a split of an Escherichia ancestor into five species (E. albertii, E. coli, E. fergusonii, E. hermannii, and E. vulneris). The last E. coli ancestor split between 20 and 30 million years ago.
The long-term evolution experiments using E. coli, begun by Richard Lenski in 1988, have allowed direct observation of genome evolution over more than 65,000 generations in the laboratory. For instance, E. coli typically do not have the ability to grow aerobically with citrate as a carbon source, which is used as a diagnostic criterion with which to differentiate E. coli from other, closely, related bacteria such as Salmonella. In this experiment, one population of E. coli unexpectedly evolved the ability to aerobically metabolize citrate, a major evolutionary shift with some hallmarks of microbial speciation.
2.7 INCUBATION PERIOD
The time between ingesting the STEC bacteria and feeling sick is called the “incubation period”. The incubation period is usually 3–4 days after the exposure, but may be as short as 1 day or as long as 10 days. The symptoms often begin slowly with mild belly pain or non-bloody diarrhea that worsens over several days. HUS, if it occurs, develops an average of 7 days after the first symptoms, when the diarrhea is improving.

2.7.1 DISCOVERY OF ANTIBIOTICS
• History of antibiotics – 1
19th century:Louis Pasteur & Robert Koch
• History of antibiotics – 2
Plant extracts
– Quinine (against malaria)
– Ipecacuanha root (emetic, e.g. in dysentery)
Toxic metals
– Mercury (against syphilis)
– Arsenic (Atoxyl, against Trypanosoma)
• Dyes
– Trypan Blue (Ehrlich)
– Prontosil (azo-dye, Domagk, 1936)
• History of antibiotics – 3
Paul Ehrlich
• started science of chemotherapy
• Systematic chemical modifications
(“Magic Bullet”) no. 606 compound = Salvarsan (1910)
• Selective toxicity.
• Developed the Chemotherapeutic Index
• History of antibiotics – 4
Penicillin- the first antibiotic – 1928• Alexander Fleming observed the
killing of staphylococci by a fungus (Penicillium notatum)
• observed by others – never exploited
• Florey & Chain purified it by freeze-drying (1940) – Nobel prize 1945
• First used in a patient: 1942
• World War II: penicillin saved 12-15% of lives
• History of antibiotics – 5
Selman Waksman – Streptomycin (1943), was the first scientist who discovered antibiotic active against all Gram-negatives for examples; Mycobacterium tuberculosis
– Most severe infections were caused by Gram-negatives and Mycobacterium
tuberculosis, extracted from Streptomyces – extracted from Streptomyces
– 20 other antibiotics include. neomycin, actinomycin
2.8 CHARACTERISTICS OF ANTIBIOTICS
According to the Oxford Dictionary, the term Antibiotics encompasses medicines (such as penicillin or its derivatives) that inhibit the growth of or destroys microorganisms. Antibiotics are naturally occurring substances that exhibit inhibitory properties towards microbial growth at high concentrations. (Zaffiri, et al., 2012).
-Antibiotics are selective in their effect on different microorganisms, being specific in their action not only against genera and species but even against strains and individual cells. Some of these agents act mainly on gram-positive bacteria, while others inhibit only gram-negative ones.
-Some antibiotics are produced by some organism, from different strains of penicillin.
-Bacteria are sensitive to the antibiotic which enable them to developed resistance after contact, for several periods.

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2.9 ROLE OF ANTIBIOTICS
Based on the clinical use of antibiotics, it may appear that these compounds play a similar role as microbial weapons in nature, yet this seems unlikely due to the fact that the concentrations used in the clinical setting are significantly higher than that produced in nature (Fajardo et al., 2008). Due to experimental evidence, it makes more sense to see antibiotics as small, secreted molecules involved in cell-to-cell communication within microbial communities.
(Martinez, 2008). Diverse Studies have been conducted in which different antibiotics and antibiotic-like structures were administered to different bacterial species at levels below the compounds minimum inhibitory concentrations (MIC). (Fajardo et al., 2008). that was

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2.3.1 Informed Consent
M.J Myers identifies that informed consent is used by a medical practitioner to treat a patient under risky circumstances. Moreover, he specifies that the doctor must disclose the actual and real risk of the operation, or any other treatment or otherwise the consent given without knowing real risk is not fair at all. This kind of a scenario seems not to be the real product of the informed consent. According to him, the disclosure of real facts is a custom of the society. The majority of the society accept that the doctor should be imposed liability for violating that custom. Disclosing the real facts of the risk is related to the standard of care of the doctor, and the adoption of this is linked to the self-determination right of the patient.
In the Martin v. Lowney case it was held that the doctor has got a duty to disclose every fact and risks of the medical proceedings and the patient should have a chance to get an intelligence decision whether to proceed on or not. If the doctor is unable reveal, all the facts the doctor can be held liable for breach of that duty.
According to the Aceto v. Dougherty case if the physician hides the real situation and the risk of the treatment to the patient and the doctor is liable for any injury whether he acts negligent or not.
Alan H Crede introduces “Average qualified Surgeon” should have the ability to assume the risk and reveal the real risk of the treatment and the patient can take the decision on the basis of his recommendation.
Nijahwan points out that informed consent has been inherited from history and legislated in some statutes. He states that in Nuremberg Code 1947, Declaration of Helsinki 1964, The Belmont Report 1979, CIOMS Guidelines 1982, The Guidelines for GCP originated in International Conference on Harmonisation 1996 the concept of informed consent had been established.
Moreover, Nijahwan identifies that, the informed consent faces some challenges and issues like language barriers, religious influence, false expectations, patients’ perceptions and some other considerable issues.
In the decision of Darviris v. Petros it was discussed that, if the doctor does not estimate the actual financial cost of the treatment or therapy it is also reached amount to a medical malpractice.
In the Chatterton v. Gerson decision it was identified that the consent given by a patient may not be the real consent as the detailed procedures are not been revealed and the broad terms are not understood by the patient.
Dr. Perera says even though the comprehensive consent form is the best option to take the real consent illiteracy, the doctor patient relationship and attitudes which are paternalistically measured, and the faith towards the doctor is not given the real consent in Sri Lankan context.
Conversely, in the Castell v. De Greef case the informed consent has been held as a standard and valid defence against the medical malpractice occurred in South Africa.
Dr. Perera emphasizes that the assumption of risk by the patient or the “volenti non fit injuria” also goes hand in hand with informed consent and in those circumstances the doctor can be excluded himself from the liability. The Nigerian case Okonkwo v. Medical and Dental Practitioners Disciplinary Tribunal the doctor was not liable for breach of the duty of disclosure the risk where an aneamic patient who had been a Jehovah’s witness refused for a blood transfusion was considered to be voluntarily assumed the risk.
She furthermore takes the attention of the reader that the courts have followed the reasonable doctor’s test and a new approach called “prudent patient’s test” which stands on what a reasonable patient need to know in his position.
2.4 Litigation Against Medical practitioners in Sri Lanka
Dr. Fernando reports that until 2002 there had been only about 10 cases about medical negligence claims in Sri Lanka. Priyani Soyza case is the landmark in that history.
Dr. Perera is in the view that, the Traditional Sri Lankan does not try to file an action against a doctor as it depends on many more factors as cost, respect, unawareness etc.
Dr. Ruwanpura categorizes the patients who have been undergone a medical negligence into three. They are Compensative mode , Punitive and Deterrent Mode and Corrective Deterrent Mode .
According to Dr. Ruwanpura Sri Lankan patients have four options after facing a medical negligence.
• Complain to the Health Authorities.
• Lodge a complaint in a police station.
• Forward an affidavit to the SLMC or Human Rights Commission.
• File a Civil Action in a District Court.
According to him, the present litigation system is basically build upon the tort liability system, similarly as in the USA. He furthermore states that earlier patients had tried to file criminal cases under Criminal Procedure Code and Police Act and failed resulting another civil case. The undue arrest of doctors on medical malpractice is known to have ruled to limit by the Indian Supreme Court.

2.5 Compensation Mechanisms
2.5.1 Judicial Compensation
The judicial compensation is awarded under the tort based liability and it seems to have a lot of inconsistencies. It is basically upon the balance of probabilities.
The IMO Committee in the USA has concluded its report with the intention of “replacing tort liability with a system of patient-centered and safety focused non-judicial compensation” as per the recognized inconsistencies.
Considering the UK context, the tort based liability system is known to enrich the legal practitioners and impoverish the medical practitioners while the victims are getting a very little portion of the compensation. This is due to the high attorney fees and the duration of the case.
Dr. Ruwanpura suggests the Consumer Protection Legislation and the “No-fault Liability System” to avoid the inconsistencies in tort based litigation.
2.5.2 Consumer Protection Legislation
Singh assures that the Consumer Protection Legislation is used to compensate in medical negligence in India and in the Middle East.
According to him it is very difficult to implement in India as the government medical service is fully served freely. At the same time, it does not cover the unavoidable medical mishaps.
Anita and Madhuri has conducted their study to link the medical negligence and the consumer protection under Consumer Protection Act 1986. According to their view, the definition given for the consumer and the service is wider enough to cover the patient as a consumer and the medical service given as a service given under the act.
Nevertheless, this concept is unable to be used where the medical service given free of charge. This view was uprooted in the judgement of Indian Medical Association v. VP Shantha and Others case.

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2.5.3 No-fault Liability System
Bismark identifies that in the tort based liability both patients and doctors are victims. This system has been successfully implemented in Canada and New Zealand whom considered to be the top ranked nations in humanitarian development for nearly 25 years.
This system is very efficient taking only 6-9 months to complete the process of compensation. This takes only 10 percent of a cost while the tort based liability takes 50-60 percent amount for cost of action. In New Zealand the Accident Compensation Cooperation (ACC) handles the system.
Moreover, Bismark summarizes how the system works. The system is funded by taxation and the employer levy. The patient must inform the negligence or the mishap to the ACC and the doctor in written form. The doctor must write a detailed submission to the ACC about the incident and ACC takes the necessary steps to compensate the patient adequately and introduce the necessary systematic and procedural developments to the healthcare system. No judicial intervention is made.
Dr. Ruwanpura is in the opinion that the system would help to console the patient while developing the healthcare system. He furthermore, reveals the Agrahara Medical Insurance could be restructured to reach that level.

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