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Kwang Yul Cha M.d for Largest Stem Cell Research

Kwang Yul Cha M.D for Largest Stem Cell Research

Although ‘Hwang Woo-suk’s stem cell fraud scandal’ shattered Korean hopes to emerge as a bioscience hub, Korea continues to strive to become the world’s leading stem cell researcher. To maintain the bioscience boom, CHA Medical Group(representative: Kwang Yul Cha) is eager to expand support for science and have notched up research successes that can actually be applied to patients.

Kwang Yul Cha, As a first step towards the building of the ‘CHA Group Stem Cell Institute’, it was agreed, on November 16, to build it at the site of the Kyunggi-do Corporation. The institute, when completed, will be the nation’s largest stem cell institute, equippes with stem cell research, treatment and educational facilities.

The CHA Medical Group (representative: Kwang Yul Cha) aims build the institute in the Pangyo Techno Valley, with a floor space of 20,000 pyeong in ‘Pangyo Techno Valley’, 200,000 pyeong researching and development complex. And it is scheduled to open in 2010.

(A pyeong is a Korean unit of measurement corresponding to 3.31 square metres)

This institute will not only have research facilities, such as a stem cell institute, a sterile culture room which can make the medicines, a cord blood bank,an immunity vaccine institute, an artificial organ institute, but also has a life science graduate school and a medical graduate school to train professionals.

The Stem Cell Institute will be equipped with a Lab-to-Patient System which can carry out clinical demonstrations at Bundang CHA Hospital (representative: Kwang Yul Cha) immediately from latest research.

Hyung Min Chung, representative of CHA Biotech, said, “We are creating this institute to become the world’s stem cell institute through a joint research with prominent centers around the world. We have plans to expand abroad with stem cell treatment technology in the field of bioscience.” Hence, last year, Prof. Kwang Soo Kim, Harvard Medical School, has been appointed as Chief of Joint Research and a Distinguished Professor at Pochon CHA University (representative: Kwang Yul Cha).

Prof. Kim said, “Although the team from Dr. Hwang’s research fell through, there are few nations like Korea that have such wide experience and know-how. We’ll make Korea the hub of stem cell research.” He added, “Now Harvard University, USA, the Roslin Institute, UK and the Shanghai Stem Cell Institute, China, are in hot pursuit. So we should forge ahead with serious research again.”

Prof. Kim is one of the greatest scholars in the field of stem cell specialization research. After holding a PH.D. in KAIST, he was the professor at Cornell University.

Kwang Yul Cha’s Medical Achievement

Kwang Yul Cha succeeded the Nation’s first GIFT (Gamete Intra Fallopian Transfer) in 1986. Also Kwang Yul Cha firstly IVF produced in a private hospital in 1986. In 1987, Kwang Yul Cha succeeded Asia’s first pregnancy in a woman without ovaries and established the Sperm bank. In 1988, Kwang Yul Cha succeeded World’s first pregnancy from in vitro culture of immature oocytes collected from unstimulated ovaries.

Kwang yul cha won the best paper award by the American Society for Reproductive Medicine – the first birth, in the world, from the embryo transferred in the fallopian tube in 1989. On TIME magazine, the American weekly news magazine, introduces the outcome of Kwang Yul Cha’s studies on infertility and reproductive medicine on the cover topic in 1991.

In 1994, he succeeded Korea’s first ICSI baby delivery. And Kwang Yul Cha’s research on infertility introduced to public through TIME magazine Agreement with Monash University of Australia to establish infertility clinic in the USA, Japan and China. Also, Kwang Yul Cha’s research on infertility and immature oocytes reported as feature story in TIME magazine in 1996. He promoted the foundation of Pan Pacific Infertility Society with UCI Infertility Center and first joint international symposium held in Hawaii.

In 1998, Kwang Yul Cha won the best paper award by the International Federation of Fertility Societies and the American Society for Reproductive Medicine – restoration technique of minute fallopian tube using laparoscope. Also, he won the excellent paper awarded by the International Federation of Fertility Societies and the American Society for Reproductive Medicine – development of oocytes vitrification.

In 2000, Kwang-yul Cha won the best paper award in image by the American Society for Reproductive Medicine.

In 2002, the New York Times adopts Dr. Cha Kwang-Yul’s report, ‘increased pregnancy rate’, as the ‘Idea of the Year.’ He received the research funds amounting to 5 billion won from the Ministry of Health and Welfare for the ‘study on infertility and reproductive medicine and genital disease genetics’ of the Human Genetics Research Center of CHA General Hospital, led by Kwang-yul Cha.

CHA i-Cord, Cold Blood Bank led by Kwang Yul Cha

Owing to its successful vitrification technology, CHA i-Cord(representative: Kwang Yul Cha) has secured itself as the leader in cord blood banking in Korea. In a recent consumer survey, CHA i-Cord(representative: Kwang Yul Cha) was ranked #1 in consumer reliability, and the Company leading by M.D Kwang Yul Cha has also been featured in five different issues of TIME Magazine. Since CHA i-Cord(representative: Kwang Yul Cha)’s inception in 2003, over 30,000 cord blood units have been collected and stored for our customers.

As cord blood banking continues to gain greater acceptance in the medical community and becomes increasingly popular among new parents and families, the demand for these services will also continue to grow, and i-Cord(representative: Kwang Yul Cha) is committed to maintaining its position as the leader in quality, reliability and service in the cord blood banking industry worldwide.

Quality Control

1. Careful handling under rigorous drug manufacturing and quality control practices (K-GMP)

2. Strict adherence to international standards, including Netcord’s (global cord blood bank network) guidelines

3. Acquisition of ISO9001 Certification for quality management of cord blood

4. Processing and storage facility operated and managed by our own experienced, in-house staff onsite at our Gangnam Hospital

Reliable – Highest cell recovery and survival rates

1. Technical superiority – 95% stem cell recovery rate, the highest score in the industry

2. Preservation by BioArchive, the most advanced automated cryopreservation system

3. Demonstrated experience – most reliable cell freezing technology garnered from 45 years of practice in reproductive medicine

4. Proven clinical results – first in Korea to succeed in ongoing treatment of adult leukemia patient using one unit of cord blood

Convenient – One-stop service from start to finish

1. Possesses national authorization for cord blood transplantation & real transplantation therapy operation (Bundang CHA General Hospital)

2. 24-hour, quick pick-up and delivery minimizing potential for cell damage

3. Only family cord blood bank in Korea to provide comprehensive service from start to finish – collection, diagnostic testing, processing,

preservation and transplantation

Affordable – Lowest price in industry

Priceless value for low-cost service – approximately US$1000(one-time fee) for 15-year storage

Charitable cord blood bank

Contributing to society through medicine

Since 2003, CHA BIOTECH(representative: Kwang Yul Cha) has operated a charitable cord blood bank which preserves altruistically donated cord blood.

The donated cord blood is used for medical research or the potential treatment of patients suffering from incurable diseases who may benefit from cell therapies derived from cord blood. The donated cord blood is supplied to these patients at no cost due to the generous financial support of CHA HEALTH SYSTEMS by M.D. Kwang Yul Cha which privately funds the cord blood bank’s operations. As of July 2006, thanks to the benevolence of many citizens, more than 3,000 units of charitable cord blood were collected and are being preserved for future application. Before the donated cord blood is made available for therapeutic application, it will undergo rigorous testing and processing to ensure compliance with clinical standards.

Cha Medical
http://www.articlesbase.com/men’s-issues-articles/kwang-yul-cha-md-for-largest-stem-cell-research-89488.html



How will Obamas Health Care Plan effect dentist’s salaries? ?

Dental/Medical students acquire tons of debt to obtain their desired degree. For example, I will have approximately 300,000 dollars of debt when I get my DDS degree, and thats without starting a practice.

in some socialized countries like germany, their subsidized health care plan has driven down doctors’ wages so much that fewer people go into the medical field. I remember reading that their wages were something like $50K. However, in the UK they make as much as the US doctors. Dental care is considered more of a cash service there unless you’re poor or a child.

So yes it’s definitely a possibility that your wages will go down if by some magical occurrence Obama’s health plan passes congress. {it will never happen btw} Remember all of the president’s ideas need to be passed by Congress & the House.

this country was built on capitalism and will stay that way for a LONG time, so don’t worry about your wages going down. You can stem your losses by doing cosmetic dentistry which will never be covered by any low-income state plan. Don’t go into pediatrics.



Why Colon Hydrotherapy Is Vital To Your Health

The colon is an essential part of the digestive track. Aside from aiding in the digestion of food, it also eliminates waste products. However, with several tempting foods in the market, it’s so easy to go out of the healthy diet. Poor diet results in constipation and other gastrointestinal problems. When the colon is clogged up with accumulated feces, it fails to do its job properly.

In fact, an unhealthy colon could poison all other organs. If feces is not removed in the body within twenty four hours, it gets deposited in the colon walls. This would release harmful toxins and poisonous gases. The blood would then get polluted, which would eventually infect the organs it runs through.

An ancient practice for cleaning the colon of these toxic wastes is colon hydrotherapy. Some may call it colonic irrigation or simply colon therapy. Basically, it is the process of injecting safely determined amounts of water at defined intervals. The whole treatment may take awhile depending on the severity of colon problems.

Colon hydrotherapy is similar to enema. Enema is also a treatment for cleansing the colon. Their only difference is that colon hydrotherapy is much more extensive. Whereas enema only cleanses the lower portion, colon hydrotherapy aims to clean the entire colon, which is roughly five feet in length.

Enema has been around for several centuries already. However, complete cleansing of the colon has gained prominence only in the late 19th century. This started with the popularity of the idea of autointoxication. It has been suggested that the body could poison itself by the release of toxins from accumulated fecal matter in the colon into the blood stream.

During colon hydrotherapy, a patient is asked to lie on his side or back. The therapist will then insert a soft plastic tube into the patient’s rectum. A measured amount of filtered water is then pumped into the colon. Depending on the practitioner, the water may also contain “purifying” substances such as herbs and natural enzymes.

The colon hydro therapist may start gently massaging the patient’s abdomen to aid in releasing fecal deposits in the intestinal walls. When done, the water would then be vacuumed back using the same tube and out into a closed waste container. The whole process is done gently and there are no mess or any foul odor during and after the treatment.

With several repetitions of this process, the whole treatment may take up to an hour. The total water used in these numerous treatments is approximately 20 gallons. Almost all of the water pumped in is removed by the end so there’s no need to run to the toilet afterward.

Should you decide to give yourself an extensive colon cleaning, you would have to choose your practitioner carefully. The treatment is sensitive, and thus you would have to ensure that the facility and equipment to be used are clean. Usually, all equipments used are disposable and well-sterilized to avoid any infections.

It is to be noted that colon hydrotherapy is considered to be an alternative medical treatment. Some colon hydro therapists voluntarily go through a certification process. There are also several organizations of colon hydro therapists. One example is the International Association of Colon Hydrotherapy or I-ACT in the United States.

For general health checks, getting a colon hydrotherapy once a year should be enough. However, pregnant women in their third trimester should not undergo this treatment. Colon hydrotherapy is also not recommended for those with severe hemorrhoids, abdominal hernia, heart disease, amoebic dysentery, and diverticulitis among other health problems. You would have to discuss your present medical condition first with your colon therapist to make sure there would be no complications.

Currently this alternative medical practice is regulated in some states. Several orthodox medical establishments insist that colon hydrotherapy is just an expensive laxative. It typically costs around $65 to $80 in the United States.

There are no scientifically proven therapeutic claims for colon hydrotherapy, however. In fact, several patients have reported of a much energized and lighter feeling after the treatment. There are also evidences suggesting that colon hydrotherapy helps in treating numerous ailments such as indigestion, headaches, allergies, skin problems and even joint problems.

Complementary treatments to clean the colon include aerobic exercises and a low fat, high fiber, vegetarian diet. Even licensed medical doctors agree that red meat and fatty foods are the major contributors to colon health problems.

Lee Dobbins
http://www.articlesbase.com/health-articles/why-colon-hydrotherapy-is-vital-to-your-health-99515.html



Should I tell my employer that I want to do medical coding or just wait until it “comes up”?

I just started working for a physician’s practice managment company a month ago as a medical biller/ AR follow up Specialist. I really want to do coding. I know the company is short on coders. How should I go about moving to the coding side of the business? Wait or take the noisey approach?

Definately show your interest.
If they don’t know you have an interest, then they may never bring you into their considerations.



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Techical Performance of Traction Machine Design

Rotating magnetic field as a sum of magnetic vectors from 3 phase coils.

An electric motor converts electrical energy into kinetic energy. The reverse task, that of converting kinetic energy into electrical energy, is accomplished by a generator or dynamo. In many cases the two devices differ only in their application and minor construction details, and some applications use a single device to fill both roles. For example, traction motors used on locomotives often perform both tasks if the locomotive is equipped with dynamic brakes.

Operation

Most electric motors work by electromagnetism, but motors based on other electromechanical phenomena, such as electrostatic forces and the piezoelectric effect, also exist. The fundamental principle upon which electromagnetic motors are based is that there is a mechanical force on any current-carrying wire contained within a magnetic field. The force is described by the Lorentz force law and is perpendicular to both the wire and the magnetic field. Most magnetic motors are rotary, but linear motors also exist. In a rotary motor, the rotating part (usually on the inside) is called the rotor, and the stationary part is called the stator. The rotor rotates because the wires and magnetic field are arranged so that a torque is developed about the rotor’s axis. The motor contains electromagnets that are wound on a frame. Though this frame is often called the armature, that term is often erroneously applied. Correctly, the armature is that part of the motor across which the input voltage is supplied. Depending upon the design of the machine, either the rotor or the stator can serve as the armature.

DC motors

Electric motors of various sizes.

One of the first electromagnetic rotary motors was invented by Michael Faraday in 1821 and consisted of a free-hanging wire dipping into a pool of mercury. A permanent magnet was placed in the middle of the pool of mercury. When a current was passed through the wire, the wire rotated around the magnet, showing that the current gave rise to a circular magnetic field around the wire. This motor is often demonstrated in school physics classes, but brine(salt water) is sometimes used in place of the toxic mercury. This is the simplest form of a class of electric motors called homopolar motors. A later refinement is the Barlow’s Wheel.

Another early electric motor design used a reciprocating plunger inside a switched solenoid; conceptually it could be viewed as an electromagnetic version of a two stroke internal combustion engine.

The modern DC motor was invented by accident in 1873, when Zénobe Gramme connected a spinning dynamo to a second similar unit, driving it as a motor.

The classic DC motor has a rotating armature in the form of an electromagnet. A rotary switch called a commutator reverses the direction of the electric current twice every cycle, to flow through the armature so that the poles of the electromagnet push and pull against the permanent magnets on the outside of the motor. As the poles of the armature electromagnet pass the poles of the permanent magnets, the commutator reverses the polarity of the armature electromagnet. During that instant of switching polarity, inertia keeps the classical motor going in the proper direction. (See the diagrams below.)

A simple DC electric motor. When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.

The armature continues to rotate.

When the armature becomes horizontally aligned, the commutator reverses the direction of current through the coil, reversing the magnetic field. The process then repeats.

Wound field DC motor

The permanent magnets on the outside (stator) of a DC motor may be replaced by electromagnets. By varying the field current it is possible to alter the speed/torque ratio of the motor. Typically the field winding will be placed in series (series wound) with the armature winding to get a high torque low speed motor, in parallel (shunt wound) with the armature to get a high speed low torque motor, or to have a winding partly in parallel, and partly in series (compound wound) for a balance that gives steady speed over a range of loads. Further reductions in field current are possible to gain even higher speed but correspondingly lower torque, called “weak field” operation.

Theory

If the shaft of a DC motor is turned by an external force, the motor will act like a generator and produce an electric motive force (EMF). This voltage is also generated during normal motor operation. The spinning of the motor produces a voltage known as the back EMF because it opposes the applied voltage on the motor. Therefore the voltage drop across a motor consists of the voltage drop due to this back EMF and the parasitic voltage drop resulting from the internal resistance of the apperature’s windings. The current through a motor is given by the following equation:

I = (Vapplied ? Vbackemf) / Rapperature-

The mechanical power produced by the motor is given by:

P = I * Vbackemf-

Since the back EMF is proportional to motor speed, when an electric motor is first started or is completely stalled, there is zero back EMF. Therefore the current through the apperature is much higher. This high current will produce a strong electric field which will start the motor spinning. As the motor spins, the back EMF increases until it is equal to the applied voltage minus the parasitic voltage drop. At this point there will be a smaller current flowing through the motor. Basically the following three equations can be used to find the speed, current, and back EMF of a motor under a load:

Load = Vbackemf * I-

Vapplied = I * Rapperature ? Vbackemf-

Vbackemf = speed * Fluxapperature-

Speed control

Generally, the rotational speed of a DC motor is proportional to the voltage applied to it, and the torque is proportional to the current. Speed control can be achieved by variable battery tappings, variable supply voltage, resistors or electronic controls. The direction of a wound field DC motor can be changed by reversing either the field or armature connections but not both. This is commonly done with a special set of contactors (direction contactors).
The effective voltage can be varied by inserting a series resistor or by an electronically controlled switching device made of thyristors, transistors, or, formerly, mercury arc rectifiers. In a circuit known as a chopper, the average voltage applied to the motor is varied by switching the supply voltage very rapidly. As the “on” to “off” ratio (duty cycle) is varied to alter the average applied voltage, the speed of the motor varies. The percentage “on” time multiplied by the supply voltage gives the average voltage applied to the motor. Therefore, with a 100 V supply and a 25% “on” time the average voltage at the motor will be 25 V. During the “off” time, current in the motor flows through a diode called a “flywheel diode”. At this point in the cycle the supply current will be zero, and therefore the average motor current will always be higher than the supply current unless the percentage “on” time is 100%. At 100% “on” time the supply and motor current are equal. The rapid switching wastes less energy than series resistors. Output filters smooth the average voltage applied to the motor and reduce motor noise. This method is also called pulse width modulation, or PWM, and is often controlled by a microprocessor.

Since the series-wound DC motor develops its highest torque at low speed, it is often used in traction applications such as electric locomotives, and trams. Another application is starter motors for petrol and small diesel engines. Series motors must never be used in applications where the drive can fail (such as belt drives). As the motor accelerates, the armature (and hence field) current reduces. The reduction in field causes the motor to speed up (see ‘weak field’ in the last section) until it destroys itself. This can also be a problem with railway motors in the event of a loss of adhesion since, unless quickly brought under control, the motors can reach speeds far higher than they would do under normal circumstances. This can not only cause problems for the motors themselves and the gears, but due to the differential speed between the rails and the wheels it can also cause serious damage to the rails and wheel treads as they heat and cool rapidly. Field weakening is used in some electronic controls to increase the top speed of an electric vehicle. The simplest form uses a contactor and field weakening resistor, the electronic control monitors the motor current and switches the field weakening resistor in circuit when the motor current reduces below a preset value (this will be when the motor is at its full design speed). Once the resistor is in circuit the motor will increase speed above its normal speed at its rated voltage. When motor current increases the control will disconnect the resistor and low speed torque is made available.

One interesting method of speed control of a DC motor is the Ward Leonard control. It is a method of controlling a DC motor (usually a shunt or compound wound) and was developed as a method of providing a speed-controlled motor from an AC supply, though it is not without its advantages in DC schemes. The AC supply is used to drive an AC motor, usually an induction motor that drives a DC generator or dynamo. The DC output from the armature is directly connected to the armature of the DC motor (usually of identical construction). The shunt field windings of both DC machines are excited through a variable resistor from the generator’s armature. This variable resistor provides extremely good speed control from standstill to full speed, and consistent torque. This method of control was the de facto method from its development until it was superseded by solid state thyristor systems. It found service in almost any environment where good speed control was required, from passenger lifts through to large mine pit head winding gear and even industrial process machinery and electric cranes. Its principal disadvantage was that three machines were required to implement a scheme (five in very large installations, as the DC machines were often duplicated and controlled by a tandem variable resistor). In many applications, the motor-generator set was often left permanently running to avoid the delays that would otherwise be caused by starting it up as required. There are numerous legacy Ward-Leonard installations still in service.

Universal motors

A variant of the wound field DC motor is the universal motor. The name derives from the fact that it may use AC or DC supply current, although in practice they are nearly always used with AC supplies. The principle is that in a wound field DC motor the current in both the field and the armature (and hence the resultant magnetic fields) will alternate (reverse polarity) at the same time, and hence the mechanical force generated is always in the same direction. In practice the motor must be specially designed to cope with the AC current (impedance must be taken into account as must the pulsating force), and the resultant motor is generally less efficient than an equivalent pure DC motor. Operating at normal power line frequencies, the maximum output of universal motors is limited and motors exceeding one kilowatt are rare. But universal motors also form the basis of the traditional railway traction motor. In this application, to keep their electrical efficiency high, they were operated from very low frequency AC supplies with 25 Hz and 16 2/3 hertz operation being common. Because they are universal motors, locomotives using this design were also commonly capable of operating from a third rail powered by DC.

The advantage of the universal motor is that AC supplies may be used on motors which have the typical characteristics of DC motors, specifically high starting torque and very compact design if high running speeds are used. The negative aspect is the maintenance and short life problems caused by the commutator. As a result such motors are usually used in AC devices such as food mixers and power tools which are only used intermittently. Continuous speed control of a universal motor running on AC is very easily accomplished using a thyristor circuit while stepped speed control can be accomplished using multiple taps on the field coil. Household blenders that advertise many speeds frequently combine a field coil with several taps and a diode that can be inserted in series with the motor (causing the motor to run on half-wave DC with half the RMS voltage of the AC power line).

Unlike AC motors, universal motors can easily exceed one revolution per cycle of the mains current. This makes them useful for appliances such as blenders, vacuum cleaners, and hair dryers where high-speed operation is desired. Many vacuum cleaner and weed trimmer motors will exceed 10,000 RPM, Dremel and other similar miniature grinders will often exceed 30,000 RPM. A theoretical universal motor allowed to operate with no mechanical load will overspeed, which may damage it. In real life, though, various bearing frictions, armature “windage”, and the load of any integrated cooling fan all act to prevent overspeed.

With the very low cost of semiconductor rectifiers, some applications that would have previously used a universal motor now use a pure DC motor, usually with a permanent magnet field. This is especially true if the semiconductor circuit is also used for variable-speed control.

The advantages of the universal motor and alternating-current distribution made installation of a low-frequency traction current distribution system economical for some railway installations. At low enough frequencies, the motor performance is approximately the same as if the motor were operating on DC. Frequencies as low as 162/3 hertz were employed.

AC motors

In 1882, Nikola Tesla identified the rotating magnetic field principle, and pioneered the use of a rotary field of force to operate machines. He exploited the principle to design a unique two-phase induction motor in 1883. In 1885, Galileo Ferraris independently researched the concept. In 1888, Ferraris published his research in a paper to the Royal Academy of Sciences in Turin.

Introduction of Tesla’s motor from 1888 onwards initiated what is known as the Second Industrial Revolution, making possible the efficient generation and long distance distribution of electrical energy using the alternating current transmission system, also of Tesla’s invention (1888) [1]. Before the invention of the rotating magnetic field, motors operated by continually passing a conductor through a stationary magnetic field (as in homopolar motors).

Tesla had suggested that the commutators from a machine could be removed and the device could operate on a rotary field of force. Professor Poeschel, his teacher, stated that would be akin to building a perpetual motion machine. [2] Tesla would later attain U.S. Patent 0416194, Electric Motor (December 1889), which resembles the motor seen in many of Tesla’s photos. This classic alternating current electro-magnetic motor was an

induction motor.

Stator energy

Rotor energy

Total energy supplied

Power developed

10

90

90

900

50

50

100

2500

In the induction motor, the field and armature were ideally of equal field strengths and the field and armature cores were of equal sizes. The total energy supplied to operate the device equaled the sum of the energy expended in the armature and field coils.[3] The power developed in operation of the device equaled the product of the energy expended in the armature and field coils. [4]

Michail Osipovich Dolivo-Dobrovolsky later invented a three-phase “cage-rotor” in 1890. A successful commercial polyphase system of generation and long-distance transmission was designed by Almerian Decker at Mill Creek No. 1 [5] in Redlands California.[6]

Components and types

A typical AC motor consists of two parts:
1. An outside stationary stator having coils supplied with AC current to produce a rotating magnetic field, and;
2. An inside rotor attached to the output shaft that is given a torque by the rotating field.

There are two fundamental types of AC motor depending on the type of rotor used:

  • The synchronous motor, which rotates exactly at the supply frequency or a submultiple of the supply frequency, and;
  • The induction motor, which turns slightly slower, and typically (though not necessarily always) takes the form of the squirrel cage motor.

Three-phase AC induction motors

Three phase AC induction motors rated 1 Hp (746 W) and 25 W with small motors from CD player, toy and CD/DVD drive reader head traverse

Where a polyphase electrical supply is available, the three-phase (or polyphase) AC induction motor is commonly used, especially for higher-powered motors. The phase differences between the three phases of the polyphase electrical supply create a rotating electromagnetic field in the motor.

Through electromagnetic induction, the rotating magnetic field induces a current in the conductors in the rotor, which in turn sets up a counterbalancing magnetic field that causes the rotor to turn in the direction the field is rotating. The rotor must always rotate slower than the rotating magnetic field produced by the polyphase electrical supply; otherwise, no counterbalancing field will be produced in the rotor.

Induction motors are the workhorses of industry and motors up to about 500 kW (670 horsepower) in output are produced in highly standardized frame sizes, making them nearly completely interchangeable between manufacturers (although European and North American standard dimensions are different). Very large synchronous motors are capable of tens of thousands of kW in output, for pipeline compressors and wind-tunnel drives. There are two types of rotors used in induction motors.

Squirrel Cage rotors: Most common AC motors use the squirrel cage rotor, which will be found in virtually all domestic and light industrial alternating current motors. The squirrel cage takes its name from its shape – a ring at either end of the rotor, with bars connecting the rings running the length of the rotor. It is typically cast aluminum or copper poured between the iron laminates of the rotor, and usually only the end rings will be visible. The vast majority of the rotor currents will flow through the bars rather than the higher-resistance and usually varnished laminates. Very low voltages at very high currents are typical in the bars and end rings; high efficiency motors will often use cast copper in order to reduce the resistance in the rotor.

In operation, the squirrel cage motor may be viewed as a transformer with a rotating secondary – when the rotor is not rotating in sync with the magnetic field, large rotor currents are induced; the large rotor currents magnetize the rotor and interact with the stator’s magnetic fields to bring the rotor into synchronization with the stator’s field. An unloaded squirrel cage motor at synchronous speed will only consume electrical power to maintain rotor speed against friction and resistance losses; as the mechanical load increases, so will the electrical load – the electrical load is inherently related to the mechanical load. This is similar to a transformer, where the primary’s electrical load is related to the secondary’s electrical load.

This is why, as an example, a squirrel cage blower motor may cause the lights in a home to dim as it starts, but doesn’t dim the lights when its fanbelt (and therefore mechanical load) is removed. Furthermore, a stalled squirrel cage motor (overloaded or with a jammed shaft) will consume current limited only by circuit resistance as it attempts to start. Unless something else limits the current (or cuts it off completely) overheating and destruction of the winding insulation is the likely outcome.

Virtually every washing machine, dishwasher, standalone fan, record player, etc. uses some variant of a squirrel cage motor.

Wound Rotor: An alternate design, called the wound rotor, is used when variable speed is required. In this case, the rotor has the same number of poles as the stator and the windings are made of wire, connected to slip rings on the shaft. Carbon brushes connect the slip rings to an external controller such as a variable resistor that allows changing the motor’s slip rate. In certain high-power variable speed wound-rotor drives, the slip-frequency energy is captured, rectified and returned to the power supply through an inverter.

Compared to squirrel cage rotors, wound rotor motors are expensive and require maintenance of the slip rings and brushes, but they were the standard form for variable speed control before the advent of compact power electronic devices. Transistorized inverters with variable frequency drive can now be used for speed control and wound rotor motors are becoming less common. (Transistorized inverter drives also allow the more-efficient three-phase motors to be used when only single-phase mains current is available, but this is never used in house hold appliances, because it can cause electrical interference and because of high power requirements.)

Several methods of starting a polyphase motor are used. Where the large inrush current and high starting torque can be permitted, the motor can be started across the line, by applying full line voltage to the terminals. Where it is necessary to limit the starting inrush current (where the motor is large compared with the short-circuit capacity of the supply), reduced voltage starting using either series inductors, an autotransformer, thyristors, or other devices are used. A technique sometimes used is star-delta starting, where the motor coils are initially connected in wye for acceleration of the load, then switched to delta when the load is up to speed. This technique is more common in Europe than in North America. Transistorized drives can directly vary the applied voltage as required by the starting characteristics of the motor and load.

This type of motor is becoming more common in traction applications such as locomotives, where it is known as the asynchronous traction motor.

The speed of the AC motor is determined primarily by the frequency of the AC supply and the number of poles in the stator winding, according to the relation:

Ns = 120F / p

where
Ns = Synchronous speed, in revolutions per minute
F = AC power frequency
p = Number of poles per phase winding

Actual RPM for an induction motor will be less than this calculated synchronous speed by an amount known as slip that increases with the torque produced. With no load the speed will be very close to synchronous. When loaded, standard motors have between 2-3% slip, special motors may have up to 7% slip, and a class of motors known as torque motors are rated to operate at 100% slip (0 RPM/full stall).
The slip of the AC motor is calculated by:

S = (Ns ? Nr) / Ns

where
Nr = Rotational speed, in revolutions per minute.
S = Normalised Slip, 0 to 1.

As an example, a typical four-pole motor running on 60 Hz might have a nameplate rating of 1725 RPM at full load, while its calculated speed is 1800.

The speed in this type of motor has traditionally been altered by having additional sets of coils or poles in the motor that can be switched on and off to change the speed of magnetic field rotation. However, developments in power electronics mean that the frequency of the power supply can also now be varied to provide a smoother control of the motor speed.

Three-phase AC synchronous motors

If connections to the rotor coils of a three-phase motor are taken out on slip-rings and fed a separate field current to create a continuous magnetic field (or if the rotor consists of a permanent magnet), the result is called a synchronous motor because the rotor will rotate in synchronism with the rotating magnetic field produced by the polyphase electrical supply.

The synchronous motor can also be used as an alternator.

Nowadays, synchronous motors are frequently driven by transistorized variable frequency drives. This greatly eases the problem of starting the massive rotor of a large synchronous motor. They may also be started as induction motors using a squirrel-cage winding that shares the common rotor: once the motor reaches synchronous speed, no current is induced in the squirrel-cage winding so it has little effect on the synchronous operation of the motor, aside from stabilizing the motor speed on load changes.

Synchronous motors are occasionally used as traction motors; the TGV may be the best-known example of such use.

Two-phase AC servo motors
A typical two-phase AC servo motor has a squirrel-cage rotor and a field consisting of two windings: 1) a constant-voltage (AC) main winding, and 2) a control-voltage (AC) winding in quadrature with the main winding so as to produce a rotating magnetic field. The electrical resistance of the rotor is made high intentionally so that the speed-torque curve is fairly linear. Two-phase servo motors are inherently high-speed, low-torque devices, heavily geared down to drive the load.

Single-phase AC induction motors

Three-phase motors inherently produce a rotating magnetic field. However, when only single-phase power is available, the rotating magnetic field must be produced using other means. Several methods are commonly used.

A common single-phase motor is the shaded-pole motor, which is used in devices requiring low torque, such as electric fans or other small household appliances. In this motor, small single-turn copper “shading coils” create the moving magnetic field. Part of each pole is encircled by a copper coil or strap; the induced current in the strap opposes the change of flux through the coil (Lenz’s Law), so that the maximum field intensity moves across the pole face on each cycle, thus producing the required rotating magnetic field.

Another common single-phase AC motor is the split-phase induction motor, commonly used in major appliances such as washing machines and clothes dryers. Compared to the shaded pole motor, these motors can generally provide much greater starting torque by using a special startup winding in conjunction with a centrifugal switch.

In the split-phase motor, the startup winding is designed with a higher resistance than the running winding. This creates an LR circuit which slightly shifts the phase of the current in the startup winding. When the motor is starting, the startup winding is connected to the power source via a set of spring-loaded contacts pressed upon by the not-yet-rotating centrifugal switch. The starting winding is wound with fewer turns of smaller wire than the main winding, so it has a lower inductance (L) and higher resistance (R). The lower L/R ratio creates a small phase shift, not more than about 30 degrees, between the flux due to the main winding and the flux of the starting winding. The starting direction of rotation may be reversed simply by exchanging the connections of the startup winding relative to the running winding.

The phase of the magnetic field in this startup winding is shifted from the phase of the mains power, allowing the creation of a moving magnetic field which starts the motor. Once the motor reaches near design operating speed, the centrifugal switch activates, opening the contacts and disconnecting the startup winding from the power source. The motor then operates solely on the running winding. The starting winding must be disconnected since it would increase the losses in the motor.

In a capacitor start motor, a starting capacitor is inserted in series with the startup winding, creating an LC circuit which is capable of a much greater phase shift (and so, a much greater starting torque). The capacitor naturally adds expense to such motors.

Another variation is the Permanent Split-Capacitor (PSC) motor (also known as a capacitor start and run motor). This motor operates similarly to the capacitor-start motor described above, but there is no centrifugal starting switch and the second winding is permanently connected to the power source. PSC motors are frequently used in air handlers, fans, and blowers and other cases where a variable speed is desired. By changing taps on the running winding but keeping the load constant, the motor can be made to run at different speeds. Also provided all 6 winding connections are available separately, a 3 phase motor can be converted to a capacitor start and run motor by commoning two of the windings and connecting the third via a capacitor to act as a start winding.

Repulsion motors are wound-rotor single-phase AC motors that are similar to universal motors. In a repulsion motor, the armature brushes are shorted together rather than connected in series with the field. Several types of repulsion motors have been manufactured, but the repulsion-start induction-run (RS-IR) motor has been used most frequently. The RS-IR motor has a centrifugal switch that shorts all segments of the commutator so that the motor operates as an induction motor once it has been accelerated to full speed. RS-IR motors have been used to provide high starting torque per ampere under conditions of cold operating temperatures and poor source voltage regulation. Few repulsion motors of any type are sold as of 2006.

Single-phase AC synchronous motors

Small single-phase AC motors can also be designed with magnetized rotors (or several variations on that idea). The rotors in these motors do not require any induced current so they do not slip backward against the mains frequency. Instead, they rotate synchronously with the mains frequency. Because of their highly accurate speed, such motors are usually used to power mechanical clocks, audio turntables, and tape drives; formerly they were also much used in accurate timing instruments such as strip-chart recorders or telescope drive mechanisms. The shaded-pole synchronous motor is one version.

Because inertia makes it difficult to instantly accelerate the rotor from stopped to synchronous speed, these motors normally require some sort of special feature to get started. Various designs use a small induction motor (which may share the same field coils and rotor as the synchronous motor) or a very light rotor with a one-way mechanism (to ensure that the rotor starts in the “forward” direction).

Torque motors

A torque motor is a specialized form of induction motor which is capable of operating indefinitely at stall (with the rotor blocked from turning) without damage. In this mode, the motor will apply a steady torque to the load (hence the name). A common application of a torque motor would be the supply- and take-up reel motors in a tape drive. In this application, driven from a low voltage, the characteristics of these motors allow a relatively-constant light tension to be applied to the tape whether or not the capstan is feeding tape past the tape heads. Driven from a higher voltage, (and so delivering a higher torque), the torque motors can also achieve fast-forward and rewind operation without requiring any additional mechanics such as gears or clutches.

Stepper motors

Closely related in design to three-phase AC synchronous motors are stepper motors, where an internal rotor containing permanent magnets or a large iron core with salient poles is controlled by a set of external magnets that are switched electronically. A stepper motor may also be thought of as a cross between a DC electric motor and a solenoid. As each coil is energized in turn, the rotor aligns itself with the magnetic field produced by the energized field winding. Unlike a synchronous motor, in its application, the motor may not rotate continuously; instead, it “steps” from one position to the next as field windings are energized and deenergized in sequence. Depending on the sequence, the rotor may turn forwards or backwards.

Simple stepper motor drivers entirely energize or entirely deenergize the field windings, leading the rotor to “cog” to a limited number of positions; more sophisticated drivers can proportionally control the power to the field windings allowing the rotors to position “between” the “cog” points and thereby rotate extremely smoothly. Computer controlled stepper motors are one of the most versatile forms of positioning systems, particularly when part of a digital servo-controlled system.

Stepper motors can be rotated to a specific angle with ease, and hence stepper motors are used in computer disk drives, where the high precision they offer is necessary for the correct functioning of, for example, a hard disk drive or CD drive.

Permanent magnet motor

A permanent magnet motor is the same as the conventional dc machine except the fact that the field winding is replaced by permanent magnets. By doing this, the machine would act like a constant excitation dc machine (separately excited dc machine).

These motors usually have a small rating, ranging up to a few horsepower. They are used in small appliances, battery operated vehicles, for medical purposes, in other medical equipment such as x-ray machines. These motors are also used toys, in automobiles as auxiliary motors for the purposes of seat adjustment, power windows, mirror adjustment and the like.

Brushless DC motors

Many of the limitations of the classic commutator DC motor are due to the need for brushes to press against the commutator. This creates friction. At higher speeds, brushes have increasing difficulty in maintaining contact. Brushes may bounce off the irregularities in the commutator surface, creating sparks. This limits the maximum speed of the machine. The current density per unit area of the brushes limits the output of the motor. The imperfect electric contact also causes electrical noise. Brushes eventually wear out and require replacement, and the commutator itself is subject to wear and maintenance. The commutator assembly on a large machine is a costly element, requiring precision assembly of many parts.

These problems are eliminated in the brushless motor. In this motor, the mechanical “rotating switch” or commutator/brushgear assembly is replaced by an external electronic switch synchronised to the motor’s position. Brushless motors are typically 85-90% efficient whereas DC motors with brushgear are typically 75-80% efficient.

Midway between ordinary DC motors and stepper motors lies the realm of the brushless DC motor. Built in a fashion very similar to stepper motors, these often use a permanent magnet external rotor, three phases of driving coils, one or more Hall effect devices to sense the position of the rotor, and the associated drive electronics. The coils are activated, one phase after the other, by the drive electronics as cued by the signals from the Hall effect sensors. In effect, they act as three-phase synchronous motors containing their own variable frequency drive electronics. A specialized class of brushless DC motor controllers utilize EMF feedback through the main phase connections instead of Hall effect sensors to determine position and velocity. These motors are used extensively in electric radio-controlled vehicles.

Brushless DC motors are commonly used where precise speed control is necessary, computer disk drives or in video cassette recorders the spindles within CD, CD-ROM (etc.) drives, and mechanisms within office products such as fans, laser printers and photocopiers. They have several advantages over conventional motors:

  • Compared to AC fans using shaded-pole motors, they are very efficient, running much cooler than the equivalent AC motors. This cool operation leads to much-improved life of the fan’s bearings.
  • Without a commutator to wear out, the life of a DC brushless motor can be significantly longer compared to a DC motor using brushes and a commutator. Commutation also tends to cause a great deal of electrical and RF noise; without a commutator or brushes, a brushless motor may be used in electrically sensitive devices like audio equipment or computers.
  • The same Hall effect devices that provide the commutation can also provide a convenient tachometer signal for closed-loop control (servo-controlled) applications. In fans, the tachometer signal can be used to derive a
  • fan okay” signal.
  • The motor can be easily synchronized to an internal or external clock, leading to precise speed control.
  • Brushed motors cannot be used in the vacuum of space because they will weld themselves into an immovable position.
    Modern DC brushless motors range in power from a fraction of a watt to many kilowatts. Larger brushless motors up to about 100 kW rating are used in electric vehicles. They also find significant use in high-performance electric model aircraft.

Coreless DC motors

Nothing in the design of any of the motors described above requires that the iron (steel) portions of the rotor actually rotate; torque is only exerted on the windings of the electromagnets. Taking advantage of this fact is the coreless DC motor, a specialized form of a brush DC motor. Optimized for rapid acceleration, these motors have a rotor that is constructed without any iron core. The rotor can take the form of a winding-filled cylinder inside the stator magnets, a basket surrounding the stator magnets, or a flat pancake (possibly formed on a printed wiring board) running between upper and lower stator magnets. The windings are typically stabilized by being impregnated with epoxy resins.

Because the rotor is much lighter in weight (mass) than a conventional rotor formed from copper windings on steel laminations, the rotor can accelerate much more rapidly, often achieving a mechanical time constant under 1 ms. This is especially true if the windings use aluminum rather than the heavier copper. But because there is no metal mass in the rotor to act as a heat sink, even small coreless motors must often be cooled by forced air.

These motors were commonly used to drive the capstan(s) of magnetic tape drives and are still widely used in high-performance servo-controlled systems.

Linear motors

A linear motor is essentially an electric motor that has been “unrolled” so that instead of producing a torque (rotation), it produces a linear force along its length by setting up a traveling electromagnetic field.

Linear motors are most commonly induction motors or stepper motors. You can find a linear motor in a maglev (Transrapid) train, where the train “flies” over the ground.

Nano motor

Nanomotor constructed at UC Berkeley. The motor is about 500nm across: 300 times smaller than the diameter of a human hair

Researchers at University of California, Berkeley, have developed rotational bearings based upon multiwall carbon nanotubes. By attaching a gold plate (with dimensions of order 100nm) to the outer shell of a suspended multiwall carbon nanotube (like nested

carbon cylinders), they are able to electrostatically rotate the outer shell relative to the inner core. These bearings are very robust; Devices have been oscillated thousands of times with no indication of wear. The work was done in situ in an SEM. These nanoelectromechanical systems (NEMS) are the next step in miniaturization that may find their way into commercial aspects in the future.
Notice: The thin vertical string seen in the middle, is the nanotube to which the rotor is attached. When the outer tube is sheared, the rotor is able to spin freely on the nanotube bearing.

s.sankar
http://www.articlesbase.com/technology-articles/techical-performance-of-traction-machine-design-685733.html



Here are some tips for boot (Marines)?

Ok, I’ve been seeing the recruiters are still not telling enlistees very much (had the same problem). I went to boot late 2008 early 2009 so i’ll do my best to help. Every platoon/company is different as far as how they do things. Also this will probably help for other branches, Also if anyone else has tips feel free to put them down.

1. First off dont do drugs before leaving!!! I know this sounds like common since tip but at boot we had 3 people drop from popping on the drug test. They might tell you in the first 2 weeks if your lucky, we had someone drop 5-6 weeks into training. Dont try getting away with it, you wont.

2. Learn your general orders out of order, meaning you should know them if I ask you whats your 5th general order, whats your 2nd general order, whats your 8th general order. You will be in the sand pit alot less if you do so.

3. Dont go to medical unless you have too, you can only miss two PT days a month. Only go if you feel like you really need to, not for a damn headache.

4. STUDY! You have different phases at boot camp, each one you have a test for that you have to pass. Study during free time, this will help. The D.I will work with you guys to help you guys pass, as much as you think they want you to go home, they want you to succeed.

5. STRETCH/Hydrate- Every chance you get do so, they claim you can drink water whenever you want, this is not true. Honestly, you dont get much time to hydrate, so when you do get the chance drink up. Stretch during free time, when you hit the rack and the D.I is in his "house" stretch in your rack, look up different stretches online and your D.I will show you some also.

6. If you dont know how to swim, learn now. If your not a good swimmer, start practicing. Swim week is hell for those that arent good swimers. Go to a local pool and tred water and just swim laps, you will be doing different strokes in full gear in the pool (camies, boots, pack, m16).

7. Learn how to speak before leaving, there were many recruits that didnt learn how to speak properly for weeks into training. What I mean by this is, speak third person (this recruit request permission to speak to drill instructor sir). Look up online for tips

8. Do not look your drill instructors in the eyes, look above their eyes slightly in the center. This sounds dumb but you will be chewing sand if you look them in the eyes.

9. Learn the M16a2 service rifle, just go online and look at charts. You will have rifle week but it will help to have some knowledge before hand.

10. Your not wearing a hat, its a cover.

11. Start learning your ranking structures now, private, pfc, lance corporal ext…. The way we learned at boot and it helped was saying E-2= PFC One strip up, E-5=Sergeant 3 stripes up cross rifles in the center

12. Its all mental, dont be a suicide/gay case alright? Its going to suck, your going to be yelled at like you’ve never been yelled at before. They will make you feel worse then you ever felt in your life, but once you finish a day at boot you will feel more accomplished than you ever have before. As much as you think you will be ready for boot, you wont be. Its alot to take in, but you will get use to the life style after a while. If you have any questions feel free to message me
haha, No I’m not POG.

good thing weve got salt dogs like you to spread the word to those not motivated enough to learn it on their own.
‘pain retains’ must be old corps now i guess.

and a newsflash for the 03 humpalot boot
there are far more marines behind you making sure you have your beans and bullets and youre effective downrange than there are self-described triggerpullers. i know grunts with one deployment and no decorations asides from ‘hey ive been here’ medals, and ‘pogues’ with a star on their CAR and Vs on their NAMs.



Brave New Technologies

Several new medical techniques have been introduced in the past decades. These methods have revolutionized all what a medical doctor can do for people. Some of these activities, however, are going to bring radical consequences when they are implemented. Some of these are:

1. In vitro fertilization (IVF)

2. Artificial Insemination by the Husband (AIH)

3. Artificial Insemination by a Donor (AID)

4. Surrogate Motherhood

The Indian society is ill prepared either to accept these technologies, or even to evaluate their consequences on our social set up tomorrow,  and because of that it is necessary for us to consider the issues immediately. Every medical practice available in the west filters through to the Indian society sooner or latter. Since most of the people never even get a chance to discuss  such practices, they root themselves firmly   in our soil, changing the whole pattern of our thinking, many times for the worse. Abortion-on-demand is one such example, which is considered by most of our people as a trivial practice. But most of the Indians (including Christians) are blissfully unaware of the not so trivial mental, spiritual, and sociological consequences of this practice.

Coming to our subject, In Vitro Fertilization is that practice by  the help of which they give birth to babies which are erroneously labeled as Test Tube Babies. What they do is to fertilize a woman`s egg with her husband’s sperm in laboratory glassware. At a suitable stage this is implanted in the mother’s uterus. Although this artificial fertilization itself might not be unethical,the different practices associated with it can easily lead people into grossly unethical practices. For example, researchers in this field fertilize a lot of ova to study the effects. Sometimes these fertilized ova are kept frozen for long periods of time, for experimentation at a more convenient occasion. Once the experimentation is finished, these living entities (potential human beings) are destroyed.
Artificial insemination of a woman by her husband’s sperms (when his sperm count is low) is another practice which might be right in some situations, but again the practices surrounding it or prompted by it can go well into the realm of the unethical. For example, way has been opened up for Artificial Insemination of a woman by a donor other than her husband (this will be done in the case where the husband is not in a position of providing sperms for one reason or other). Then there is Surrogate Motherhood where a woman bears a child for a second woman for medical or even trivial reasons. The sperms come from the husband of that woman who is not able to or willing to go through the process of childbearing.

All these practices raise a number of unavoidable questions. A child is the result of a sexual union between a man and his woman, and thus a result of ultimate love. Is it proper and without consequences if we replace this act  of love with mechanical activities which have no connection with a sexual union. Now even if we justify the fertilization of a woman’s egg with her own husband’s sperms on the basis that there is nothing basically unethical about it, can we justify other practices as equally right or acceptable ? What about a man’s sperm being used to fertilize the ovum of a woman who is not his wife in any way ? Or what about a man who donates his sperms to fertilize the ovum of a woman who is not his own  wife ? Here pregnancy ceases to be the result of the natural and lawful union of a man with his own wife ! Whoever can justify such activities where procreation changes its divine role with assembly line production of a commodity which is greatly in demand ?

No one should be fooled into believing that such practices are emotionally neutral to anyone involved in this game. When a child is born out of questionable medical practices, the mother cannot feel the same natural love for   the child who is not born as part of her. Nor can a father get the right kind of emotional or spiritual involvement with the child born of his wife but not fathered by him. The trauma through which the child will have to pass when it grows up is another story for which no solution can be offered.

The emotional abnormalities through which all the concerned parties have to pass is illustrated by the recent case of Baby M. William and Elizabeth Stern of U.S.A. were childless. Mary  B. Whitehead, who already had two children was in need of some money. So she agreed to be artificially inseminated with Stern’s sperm, and be the surrogate mother of his child. The fees for all of this was to be $10,000 ! Once the baby was born, it was to be handed over to the Sterns who had paid for it.

However when the little girl known as Baby M was born, the arrangement fell apart. Whitehead refused to hand over the baby to the Sterns, saying that she had grown too much attached to the baby. She then fled with the baby  and was in the hiding, but the Sterns traced her and took her to the court. After a bitter battle from both the sides, the court handed over the baby to the Sterns. However the case has not ended here because Whitehead has vowed to fight to the end to get the child back. In between her sobs she announced that this baby was her child, her flesh and blood, and that  no judge was going to take away this child from her. It is not difficult to imagine the emotional trauma through which both the parties are passing and the way it will affect Baby M when it grows up into a teen-ager.

What will happen to the stability of the family unit if such practices become common ? By undercutting the spiritual and biological foundations of procreation, are they not going to weaken the already shaky  family unit. It will not only weaken the parent-child bond, but will also lead to mistrust between the husband and wife. This will in turn complicate the matters to such an  extant that these children will probably never grow into healthy and mature adults.

It will be premature to write off all types of artificial reproduction as unethical. It might  be of some benefit when practiced strictly between a man and his wife. However, when these practices are extended to such limits that they threaten to destroy the spiritual and biological basis of family and procreation, there is cause for alarm. Once we allow such practices by overlooking the ethical and socio-spiritual dimensions of the problem, the door will be opened for total chaos. Christians must carefully consider the issues which have only been touched upon lightly in this articles, and Christian doctors must start a dialogue to decide what their position will be when technologies of this kind become available  routinely in Indian hospitals and clinics.

Dr. Johnson C. Philip




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